What quantity of limestone, upon heating, will give 56 kg of CaO?

Limestone (Chemical formula: CaCO3), upon heating, produces lime or calcium oxide (chemical formula: CaO) and carbon dioxide. The reaction can be represented by the following chemical equation:

`CaCO_3 (s) + heat -> CaO (s) + CO_2 (g)`

Here, 1 mole of limestone produces 1 mole of carbon dioxide and 1 mole of lime or calcium oxide. 

The molar mass of limestone is 100 g (= mass of Ca + mass of C + 3 x mass of O = 40 + 12 + 3 x 16). Similarly, the molar mass of lime is 56 g.

Thus, we can also say that 100 g of limestone produces 56 g of lime.

Or, 1 g of lime is produced by 100/56 g limestone.

Thus, 56 kg of lime will be produced by 100/56 x 56 kg = 100 kg.

So, in order to obtain 56 kg of lime, we need to heat 100 kg of limestone.

What are three lessons taught by the characters in The Chrysalids?

From David we can learn to be open-minded about the world and the people in it, and not blindly follow the will of our parents.  Children are definitely impacted by their parents’ beliefs.  Parents raise their children with a moral code.  However, sometimes children grow up to question that code. 

This was the case with David.  His father was strongly religious, but he realized that just because someone is different does not make them a mutant, ungodly, or worthy of rejection.  He befriended Sophie despite her extra toes, even though not turning her in was a crime.

I certainly did not feel unusual. I was a normal little boy, growing up in a normal way, taking the ways of the world about me for granted.  And I kept on like that until the day I met Sophie. Even then, the difference was not immediate. It is hind-sight that enables me to fix that as the day when my first small doubts started to germinate. (Ch. 1) 

David’s relationship with Sophie helps him to better understand himself.  Both of them are mutants, even though David is certified.  His difference is not visible.  He is a telepath, meaning he is one of a small group who can read minds.  This would make him blasphemous too if anyone knew. 

Another person we can learn from is Anne.  Anne’s story is truly tragic.  She marries Alan, a man who is not only not telepathic but also strictly religious.  He is the one who turns Sophie in.  She knows that he would turn anyone in easily and not think twice about it, but she fell in love with him.  You can’t control who you love.  Yet Anne teaches us that we should take care in who we choose.  Things do not just work out because we want them to. 

I'm not a fool. Of course I've thought. I've thought more than you have. I'm a woman — I've a right to marry and have children. There are three of you and five of us. Are you saying that two of us must never marry? Never have any lives or homes of our own? If not, then two of us have got to marry norms. (Ch. 10) 

Anne makes a bold choice, with disastrous consequences.  She ends up killing herself.  Sometimes we take chance on love and it doesn’t work out.  When she finds Alan dead, she blames the telepaths.  She kills herself and leaves a note renouncing all of the telepaths. 

Sophie’s parents are the last characters we can learn from.  They hide their daughter and protect her, even though it is dangerous for all of them.  They do not care, because she is their child.  From them we can learn the value of protecting people you love, no matter the consequences.  If someone hadn’t spotted the extra toes, how would anyone know she was different?

David ponders the extent of a mother's love.

And Aunt Harriet had been more than ready to break the Purity Laws. So had Sophie's mother. It made one wonder how many mothers there might be who were turning a blind eye towards matters that did not actually infringe the Definition of the True Image — and perhaps to things that did infringe it, if the inspector could be dodged. (Ch. 12)

David's Aunt Harriet had tried to hide her baby when it did not conform.  She wanted David's mother to lend her Petra so she could get a certificate.  David's mother turned her away.  David wonders if she would given up David and Petra if she knew, or how she will feel when they are caught.

What are two quotes from the novel To Kill a Mockingbird that show how Jem Finch matures throughout the book?

In Chapter 4, Dill arrives from Meridian and the children begin to bicker about the Radley Place. Jem says, "Yawl hush...you act like you believe in Hot Steams" (Lee 48). Scout rebuttals by saying, "You act like you don't" (Lee 49). When Dill asks what a Hot Steam is, Jem explains by saying,

"A Hot Steam's somebody who can't get to heaven, just wallows around on lonesome roads an' if you walk through him, when you die you'll be one too, an' you'll go around at night suckin' people's breath---" (Lee 49).

Jem continues to elaborate on how to avoid passing through a Hot Steam by reciting an incantation, and Scout tells Dill not to believe a word that Jem says. Jem's superstitious beliefs are typical childhood fantasies. Jem's over active imagination and obsession with mysterious phenomena is depicted by his childhood belief in Hot Steams.

Towards then end of the novel in Chapter 28, Jem and Scout are walking to the Maycomb Halloween festival. As they pass the Radley place, Jem teases Scout by saying, "That yard's a mighty long place for little girls to cross at night...Ain't you scared of haints?" (Lee 341). They both laugh and Scout mentions, "Haints, Hot Steams, incantations, secret signs, had vanished with our years as mist with the sunrise" (Lee 341). Jem then says,

"What was that old thing...Angel bright, life-in-death; get off the road, don't suck my breath" (Lee 341).

Clearly, both Jem and Scout have matured from their childhood beliefs in mysterious phenomena and are able to laugh at themselves when they reminisce.

What shows that Scout has a new respect for Aunt Alexandra?

When Aunt Alexandra is hosting the missionary circle, Atticus comes to the house and calls her to the kitchen. Scout sees how Aunt Alexandra reacts to the news of Tom Robinson's death. Aunt Alexandra is obviously distressed by the horrible shooting. She puts her hands to her face, her voice shakes, and Scout thinks she may be crying. Aunt Alexandra then shows her disgust with the town--that they have let Atticus "do what they're too afraid to do themselves," namely, to stand up for the rights of the black residents in the town. This gives Scout an understanding that Aunt Alexandra is a compassionate woman after all. When Aunt Alexandra is able to pull herself together, despite how upset she is, and go out to graciously serve the women she has just railed against, Scout sees how strong her aunt is. Aunt Alexandra nods toward Scout and the tray of cookies. Scout mimics her aunt's manners and poise as she passes around the tray of cookies "with my very best company manners." Scout concludes, "If Aunty could be a lady at a time like this, so could I." She begins to see the value of her aunt's constantly insisting that she behave like a lady. 

How was the early Massachusetts colony different from all the other colonies?

The first European settlers in Massachusetts were the Pilgrims, who were Separatists.  They held Christian beliefs, but they separated themselves from the Church of England.  They were persecuted for their beliefs in England, so they decided to seek religious freedom in the New World.  Their reason for settling in Massachusetts was one motivated by religion.  Other colonies were settled for mainly economic reasons.

Religion continued to be important in the Massachusetts Bay Colony.  The Puritans had a strong presence in the colony.  They established churches and schools throughout Massachusetts.  Puritan beliefs governed many laws in the Massachusetts Bay Colony.  Religion did not permeate the other colonies as it did in Massachusetts.

The Massachusetts Bay Colony was farther north than other colonies.  They had a shorter growing season than many of the other colonies due to the long winter months.  They were unable to rely as heavily on farming as an industry because of this.  The soil in Massachusetts was also not as rich as in the colonies further south.  It was rocky and not as fertile.  The Massachusetts Bay Colony had to rely on the industries of trade, shipbuilding, and lumber.

Why do you think Shakespeare has Macbeth stand alone on stage when he speaks about what he can see?

Of the three scenes in which Macbeth sees apparitions or hallucinations, he's actually only alone on stage in one of them. When he's visited by the bloodied corpse of Banquo at the banquet, he is accompanied by his wife and several lords. In Act IV, the witches share the stage with him as he receives the series of visions and prophecies which guide his actions through the remainder of the play. So I assume you're referring to his hallucination of the "air-drawn dagger" shortly before the murder of Duncan. Perhaps the most straightforward reason for why Macbeth receives this portent alone is to create a degree of ambiguity as to whether the dagger is a "false creation," an illusion emanating from Macbeth's own mind and desires, or a genuine supernatural manifestation. This in turn reflects one of the play's largest thematic questions, which is the uncertain relationship between human will and predestination, unknown and possibly malevolent forces which guide our actions and fates. We know that supernatural phenomena occur in this play, because the witches' prophecies are accurate (though deliberately misleading), but we also see that apparently paranormal happenings (like the march of Birnam wood toward Dunsinane) can have more rational explanations. We're also given reason to believe that Macbeth suffers from some non-specific neurological affliction which causes visual and auditory hallucinations; upon his rapt reaction to the ghost of Banquo, Lady Macbeth anxiously tells the guests "my lord is often thus, and hath been since his youth... the fit is momentary." She could arguably be lying about his medical history, of course, but it tracks with what Shakespeare has shown us, since Macbeth has had two prior hallucinations in the play, immediately before Duncan's death (the dagger) and immediately after (when he hears a disembodied voice cry "Sleep no more!").

So by placing Macbeth alone on stage when he sees the bloody dagger pointing his path to Duncan, Shakespeare achieves several functions at once. By creating an atmosphere of ambiguity about the objective reality of this uncanny event, he presents a visual metaphor for the play's central, haunting question, regarding Macbeth's degree of control over his own actions. He also preserves for later (the banquet scene) the spectacle of Macbeth terrified by a vision that no one else can see. Finally, he reinforces Macbeth's extreme degree of isolation and feeling of imprisonment within his own haunted thoughts in this decisive moment; this dagger vision is the very last scene prior to the murder of Duncan, which strengthens our uncomfortable sense of identification with Macbeth and our awareness that it is ultimately he alone, and not his wife, who takes the final murderous step; although agreeing to commit the act is their moment of greatest unity as husband and wife, the reality of the deed itself begins to drive them apart and to divide Macbeth from the rest of humanity.

What are lipids?

Structure and Functions

Lipids are a class of bio-organic compounds that are typically insoluble in water and relatively soluble in organic solvents such as alcohols, ethers, and hydrocarbons. Unlike the other classes of organic molecules found in biological systems (carbohydrates, proteins, and nucleic acids), lipids possess a unifying physical property—solubility behavior—rather than a unifying structural feature. Fats, oils, some vitamins and hormones, and most of the nonprotein components of cell membranes are lipids.

There are two categories of lipids—those that undergo saponification and those that are nonsaponifiable. The saponifiable lipids can be divided into simple and complex lipids. Simple lipids, which are composed of carbon, hydrogen, and oxygen, yield fatty acids and an alcohol upon saponification. Complex lipids contain one or more additional elements, such as phosphorus, nitrogen, and sulfur, yielding fatty acids, alcohol, and other compounds on saponification.

The fatty acid building blocks of saponifiable lipids may be either saturated, which means that as many hydrogen atoms as possible are attached to the carbon chain, or unsaturated, which means that at least two hydrogen atoms are missing. Saturated fatty acids are white solids at room temperature, while unsaturated ones are liquids at room temperature, because of a geometrical difference in the long carbon chains. The carbon atoms of a saturated fatty acid are arranged in a zigzag or accordion configuration. These chains are stacked on top of one another in a very orderly and efficient fashion, making it difficult to separate the chains from one another. When carbons in the chain are missing hydrogen atoms, the regular zigzag of the chain is disrupted, leading to less efficient packing, which allows the chains to be separated more easily. Saturated fatty acids have a higher melting temperature because they require more energy to separate their chains than do unsaturated fatty acids. Unsaturated fatty acids can be converted into saturated ones by adding hydrogen atoms through a process called hydrogenation.

Simple lipids can be divided into triglycerides and waxes. Waxes such as beeswax, lanolin (from lamb’s wool), and carnauba wax (from a palm tree) are esters formed from an alcohol with a long carbon chain and a fatty acid. These compounds, which are solids at room temperature, serve as protective coatings. Most plant leaves are coated with a wax film to prevent attack by microorganisms and loss of water through evaporation. Animal fur and bird feathers have a wax coating. For example, the wax coating on their feathers is what allows ducks to stay afloat.

Edible fats and oils such as lard (pig fat), tallow (beef fat), corn oil, and butter are triglycerides. Triglyceride molecules are fatty acid esters in which three fatty acids (all saturated, all unsaturated, or mixed) combine with one molecule of the alcohol glycerol. Oils are triglycerides that are liquid at room temperature, while fats are solid at room temperature. The fluidity of a triglyceride is dependent on the nature of its fatty acid chains; the more unsaturated the triglyceride, the more fluid its structure. The triglycerides found in animals tend to have more saturated fatty acids than do those found in plants. Vegetable oils and fish oils are frequently polyunsaturated.

Complex lipids are classified as phospholipids or glycolipids. Structurally, phospholipids are composed of fatty acids and a phosphate group. Glycerol-based lipids called phosphoglycerides contain glycerol, two fatty acids, and a phosphate group. The phosphoglyceride structure contains a hydrophilic (polar) head, the phosphate unit, and two hydrophobic (nonpolar) fatty acid tails. The polar head can interact strongly with water, while the nonpolar tails interact strongly with organic solvents and avoid water. Egg yolks contain a large amount of the phosphoglyceride phosphatidylcholine (also called lecithin). This lipid is used to form the emulsion mayonnaise from oil and vinegar. Normally, oil and water do not mix. The hydrophobic oil forms a separate layer on top of the water. Since lecithin’s structure contains both a hydrophobic and a hydrophilic region, it can attach to the water with its polar head and the oil with its nonpolar tail, preventing the two materials from separating. Lipids derived from the alcohol sphingosine are called sphingolipids. They contain one fatty acid, one long hydrocarbon chain and a phosphate group. Like the phosphoglycerides, sphingolipids have a head-and-two-tail structure. Sphingolipids are important components in the protective and insulating coating that surrounds nerves.

Glycolipids differ from phospholipids in that they possess a sugar group in place of the phosphate group. Their structure is again the polar head and dual tail arrangement in which the sugar is the hydrophilic unit. Cerebrosides, which are sphingosine-based glycolipids containing a simple sugar such as galactose or glucose, are found in large amounts in the white matter of the brain and in the myelin sheath. Gangliosides, which are found in the gray matter of the brain, in neural tissue, and in the receptor sites for neurotransmitters, contain a more complex sugar component.

Nonsaponifiable lipids do not contain esters of fatty acids as their basic structural feature. Steroids are an important class of nonsaponifiable lipids. All steroids possess an identical four-ring framework called the steroid nucleus, but they differ in the groups that are attached to their ring systems. Examples of steroids are sterols such as cholesterol, the bile acids secreted by the liver, the sex hormones, corticosteroids secreted by the adrenal cortex, and digitoxin from the digitalis plant, which is used to treat heart disease.

Lipids constitute about 50 percent of the mass of most animal cell membranes. Biological membranes control the chemical environment of the space they enclose. They are selective filters controlling what substances enter and exit the cell, since they constitute a relatively impermeable barrier against most water-soluble molecules. The three types of lipids involved are phospholipids (most abundant), glycolipids, and cholesterol. Phospholipids, when surrounded by an aqueous environment, tend to organize into a double layer of lipid molecules, a bilayer, allowing their hydrophobic tails to be buried internally and their hydrophilic heads to be exposed to the water. These phospholipids have one saturated and one unsaturated tail. Differences in tail length and saturation influence the packing efficiency of the molecules and affect the fluidity of the membrane. Short, unsaturated tails increase the fluidity of the membrane. Cholesterol is important in maintaining the mechanical stability of the lipid bilayer, thereby preventing a change from the fluid state to a rigid crystalline state. It also decreases the permeability of small water-soluble molecules.

The lipid bilayer provides the basic structure of the membrane and serves as a two-dimensional solvent for protein molecules. Protein molecules are responsible for most membrane functions; for example, they can provide receptor sites, catalyze reactions, or transport molecules across the membrane. These proteins may extend across the bilayer (transmembrane proteins) or be associated with only one face of the bilayer. Cell membranes also have carbohydrates attached to the outer face of the bilayer. These carbohydrates are bound to membrane proteins or part of a glycolipid. Typically, 2 to 10 percent of a membrane’s total weight is carbohydrate. Evidence exists that cell-surface carbohydrates are used as recognition sites for chemical processes.

Lipids play an important role in health and well-being. The body acquires lipids directly from dietary lipids and indirectly by converting other nutrients into lipids. There are two fatty acids, linoleic and linolenic acids, which are called essential fatty acids. Since these fatty acids cannot be synthesized in the body in sufficient amounts, their supply must come directly from dietary sources. Fortunately, these acids are widely found in foodstuffs, so deficiency is rarely observed in adults.

About 95 percent of the lipids in foods are triglycerides, which provide 30 to 50 percent of the calories in an average diet. Triglycerides produce 4,000 calories of energy per pound, compared to the 1,800 calories per pound produced by carbohydrates or proteins. Since the triglyceride is such an efficient energy source, the body converts carbohydrates and proteins into adipose (reserve fatty) tissue for storage to be used when extra fuel is required.

While carbohydrates and proteins undergo major degradation in the stomach, triglycerides remain intact, forming large globules that float to the top of the mixture. Fats spend a longer time than other nutrients in the stomach, slowing molecular activity before continuing into the intestines. Thus, a fat-laden meal gives longer satiety than a low-fat one.

In the small intestine, bile salts split fat globules into smaller droplets, allowing enzymes called lipases to saponify the triglycerides. In some instances, the fatty acids at the two ends are removed, leaving one attached as a monoglyceride. About 97 percent of dietary triglycerides are absorbed into the bloodstream; the remainder are excreted. Although glycerol and fatty acids with short carbon chains are water-soluble enough to dissolve in the blood, the long-chain fatty acids and monoglycerides are not. These insoluble materials recombine to form new triglycerides. Since these hydrophobic triglycerides would form large globules if they were dumped directly into the blood, small triglyceride droplets are surrounded with a protective protein coat that can dissolve in water, taking the encapsulated triglyceride with it. This structure is an example of a lipoprotein.

Cholesterol is found in relatively small (milligram) quantities in foods, compared to triglycerides. Cholesterol supplies raw materials for the production of bile salts and to be used as a structural constituent of brain and nerve tissue. Since these functions are important to animals but serve no purpose in plants, cholesterol is found only in animals. Only about 50 percent of dietary cholesterol is absorbed into the blood; the rest is excreted. Much of the body’s supply of cholesterol is produced in the liver. For most individuals, the amount of cholesterol synthesized in the body is larger than the amount absorbed directly from the diet.

Digested lipids released from the intestine and those synthesized in the liver compose the lipid content of the blood. The fatty acids required by the liver are obtained directly from the bloodstream or by synthesis from sources such as glucose, amino acids, and alcohol. Liver-synthesized triglycerides are incorporated into lipoprotein packages before entering the bloodstream. There are three types of lipoprotein packages that transport lipids to and from the liver. Very-low-density lipoproteins (VLDLs) transport triglycerides to tissues;
low-density lipoproteins (LDLs) transport the cholesterol from the liver to other cells; and high-density lipoproteins (HDLs) transport cholesterol from other tissues to the liver for destruction.

Disorders and Diseases

Lipid consumption is an important dietary concern. Lipid deficiency is rarely observed in adults but can occur in infants who are fed nonfat formulas. Since fatty acids are essential for growth, lipid consumption should not be restricted in individuals under two years of age. Excess lipid consumption is associated with health problems such as obesity and cardiovascular disease. Although excess calories from any dietary source can lead to obesity, the body must expend less energy to store dietary fat than to store dietary carbohydrate as body fat. Thus, high-fat diets produce more body fat than do high-carbohydrate, low-fat diets.

Atherosclerosis, or “hardening of the arteries,” is the leading cause of cardiovascular disease. A strong correlation exists between diets high in saturated fats and the incidence of atherosclerosis. In this condition, deposits called plaques, which have a high cholesterol content, form on artery walls. Over time, these deposits narrow the artery and decrease its elasticity, resulting in reduced blood flow. Blockages can occur, resulting in heart attack or stroke. High serum cholesterol levels (total blood cholesterol content) often result in increased plaque formation. Since dietary cholesterol is not efficiently absorbed into the bloodstream and the serum cholesterol level is largely determined by the amount of cholesterol synthesized in the liver, high serum cholesterol levels are frequently related to high saturated fat intake.

Since the measurement of the serum cholesterol level gives the total cholesterol concentration of the blood, it can be a somewhat misleading predictor of atherosclerosis risk; cholesterol is not free in blood, but is encapsulated in lipoproteins. Since the cholesterol packaged in the LDL, cholesterol that can be deposited in plaques (“bad” cholesterol), has a very different fate from that in the HDL, which is transporting cholesterol for destruction (“good” cholesterol), measuring the ratio of LDL cholesterol to HDL cholesterol has been found to be a better indicator of atherosclerosis risk. Decreasing dietary intake of cholesterol and saturated fats, increasing water-soluble fibers in the diet, removing excess body weight, and increasing the amount of aerobic exercise will all serve to improve the LDL-C/HDL-C ratio.

A number of hereditary diseases are known that result from abnormal accumulation of the complex lipids utilized in membranes. These diseases are called lipid (or lysosomal) storage diseases, or lipidoses. In normal individuals, the amount of each complex lipid present in the body is relatively constant; in other words, the rate of formation equals the rate of destruction. The lipids are broken down by enzymes that attack specific bonds in the lipid structure. Lipid storage diseases occur when a lipid-degrading enzyme is defective or absent. In these cases, the lipid synthesis proceeds normally, but the degradation is impaired, causing the lipid or a partial degradation product to accumulate, with consequences such as an enlarged liver and spleen, mental disability, blindness, and death.

Niemann-Pick, Gaucher’s, and Tay-Sachs diseases are examples of lipidoses. Niemann-Pick disease is caused by a defect in an enzyme that breaks down sphingomyelin. The disease becomes apparent in infancy, causing mental retardation and death normally by age four. Gaucher’s disease, a more common disease involving the accumulation of a glycolipid, produces two different syndromes. The acute cerebral form affects infants, causing severe nervous system abnormalities, retardation, and death before age one. The chronic form, which may become evident at any age, causes enlargement of the spleen, anemia, and erosion of the bones. In Tay-Sachs disease, a partially degraded lipid accumulates in the tissues of the central nervous system. Symptoms include progressive loss of vision, paralysis, and death at three or four years of age. Although Tay-Sachs disease is relatively rare (1 in 300,000
births), it has a high incidence in individuals of Eastern European Jewish descent (1 in 3,600 births). This defect is a recessive genetic trait that is found in one of every twenty-eight members of this population. For two parents who are both carriers of this trait, there is a one in four chance that their child will develop Tay-Sachs disease. Tests have been developed to detect the presence of the defective gene in the parent, and the amniotic fluid of a developing fetus can be sampled using a technique called amniocentesis to detect Tay-Sachs disease. Lipid storage diseases have no known cures; however, they can be prevented through genetic counseling.

Perspective and Prospects

The ability of a cell to discriminate in its chemical exchanges with the environment is fundamental to life. How the cell membrane accomplishes this feat has been a subject of intense biochemical research since the beginning of the twentieth century.

In 1895, Ernst Overton observed that substances that are lipid-soluble enter cells more quickly than those that are lipid-insoluble. He reasoned that the membrane must be composed of lipids. About twenty years later, chemical analysis showed that membranes also contain proteins. Irwin Langmuir prepared the first artificial membrane in 1917 by mixing a phospholipid-containing hydrocarbon solution with water. Evaporation of the hydrocarbon left a phospholipid film on the surface of the water, which showed that only the hydrophilic heads contacted the water. When the Dutch biologists E. Gorter and F. Grendel deposited the lipids from red blood cell membranes on a water surface and decreased the occupied surface area with a movable barrier, a continuous film resulted that occupied an area approximately twice the surface area of the original red blood cells. In 1935, all these observations, along with the fact that the surfaces of artificial membranes containing only phospholipids are less water-absorbent than the surfaces of true biological membranes, were combined by Hugh Davson and James Danielli into a membrane model in which a phospholipid bilayer was sandwiched between two water-absorbent protein layers.

The technological advances of the 1950s in x-ray diffraction and electron
microscopy allowed the structures of membranes to be probed directly. Such studies revealed that membranes are indeed composed of parallel orderly arrays of lipids, although many of the proteins are attached to one of the faces of the bilayer: The Davson-Danielli model was too simplistic. The freeze-fracture technique of preparing cells for electron microscopy has provided the most information about the nature of membrane proteins. In this technique, the two layers are separated so that the inner topography can be studied. Instead of the smooth surface predicted by the Davson-Danielli model, a cobblestone-like surface was observed that resulted from proteins penetrating into the interior of the membrane. All experimental evidence supports the fluid mosaic model for biological membranes, a model first proposed by Seymour Singer and Garth Nicholson in 1972. In this model, proteins are dispersed and embedded in a phospholipid bilayer that is in a fluid state. How membranes function was the next question to be considered.

Although most of the small molecules needed by cells cross the barrier via protein channels, some essential nutrients, such as cholesterol in its LDL package, are too large to pass through a small channel. In 1986, Michael Brown and Joseph Goldstein received the Nobel Prize for their discovery of specific protein receptors on the membranes of liver cells to which LDL molecules attach. These receptors move across the surface until they encounter a shallow indentation or pit. As the pit deepens, the membrane closes behind the LDL, forming a coating allowing transport across the hydrophobic membrane interior. The presence of insufficient numbers of these receptors causes abnormal LDL-cholesterol buildup in the blood.

Many questions remain unanswered concerning the roles of proteins and glycolipids in membranes. Membranes are involved in the movement, growth, and development of cells. How the membrane is involved in the uncontrolled multiplication and migration in cancer is one medically important question. Experiments that will answer questions about how membrane structure affects functioning should lead to the development of new medical treatments.

Bibliography

Bettelheim, Frederick A., et al. Introduction to General, Organic, and Biochemistry. 10th ed. Belmont, Calif: Brooks/Cole Cengage Learning, 2013.

Bloomfield, Molly M., and Lawrence J. Stephens. Chemistry and the Living Organism. 6th ed. New York: John Wiley, 1996.

Brown, Michael S., and Joseph L. Goldstein. “How LDL Receptors Influence Cholesterol and Atherosclerosis.” Scientific American 251 (November, 1984): 58–66.

Carlson, Emily. "The Big, Fat World of Lipids." NIH National Institute of General Medical Sciences: Inside Life Science, August 9, 2012.

Christian, Janet L., and Janet L. Greger. Nutrition for Living. 4th ed. Redwood City, Calif.: Benjamin/Cummings, 1994.

Cornatzer, W. E. Role of Nutrition in Health and Disease. Springfield, Ill.: Thomas, 1989.

MedlinePlus. "Dietary Fats." MedlinePlus, June 28, 2013.

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Sikorski, Zdzisław E., and Anna Kołakowska, eds. Chemical and Functional Properties of Food Lipids. Boca Raton, Fla.: CRC Press, 2002.

Vance, Dennis E., and Jean E. Vance, eds. Biochemistry of Lipids, Lipoproteins, and Membranes. 5th ed. Boston: Elsevier, 2008.

What were the principles of the Renaissance?

The defining principle of the Renaissance is usually identified as humanism. By humanism, historians mean a return among intellectuals, especially in Italy, to classical knowledge. This was understood at the time as a rejection of the medieval scholasticism associated with such philosophers as Thomas Aquinas. Humanists studied ancient Greek, Roman, and Hellenistic texts in the belief that the classical wisdom they contained had something to offer in their own time. But for many writers and intellectuals like Petrarch, the seminal Italian poet whose works are often seen as foundation to the Italian Renaissance, humanism meant something more. It meant focusing on the secular as well as the divine. In his essay "Oration on the Dignity of Man," Pico Della Mirandola extolled the divine nature of man:

Imagine! The great generosity of God! The happiness of man! To man it is allowed to be whatever he chooses to be!

This new secularism, derived from humanism, was another of the defining principles of the Renaissance. For Machiavelli, it meant divorcing politics from religious or even moral principles, as he did most famously in The Prince. For a whole bevy of artists like Leonardo da Vinci, Raphael, Michelangelo, and many others, secularism meant portraying the human form in all its natural (albeit usually idealized) beauty. These new artists also embraced another principle important to the Renaissance--individualism. If people were divine, and one's humanity was not something to be ashamed of, then striving for individual greatness was a valid goal. Renaissance-era artists became something like celebrities, competing publicly with each other for patronage and fame. They sought to glorify God with their works, many of which were strongly religious in theme, but they also sought to glorify themselves. 

What can you infer about Bruno's father from the information presented in Chapter 1 of The Boy in the Striped Pajamas? Discuss his character...

In Chapter 1, Bruno comes home to find Maria packing his belongings into wooden crates. He politely asks Maria what she is doing because his mother told him to treat her respectfully and not "imitate the way Father spoke to her." The previous statement suggests that Bruno's father is rather disrespectful to Maria and talks down to her. Bruno's mother then explains to him that they will be moving because of his father's job. She mentions that her husband's job is very important which suggests that he holds a prestigious position or rank. Bruno also says that there were always many visitors in his home who wore fancy uniforms and were friendly to his father. Bruno's mother goes on to say, "Well, sometimes when someone is very important...the man who employs him asks him to go somewhere else because there's a very special job that needs doing there" (Boyne 4). One can infer that Bruno's father is a high-ranking officer who is both valued and talented.

When Bruno tells his mother that he doesn't want to go, she mentions that his father would miss him terribly. She also tells Bruno that his father loves him and Gretel equally which suggests that Bruno's father has compassion for his family. When Bruno asks his mother who is going to take care of their house, she sighs and looks around at the beautiful, five-floor home. Their massive home also suggests that Bruno's father is a very successful man who gets paid well.

As Bruno laments about leaving his friends, he overhears his father and mother arguing in his father's office which is "Out Of Bounds At All Times And No Exceptions." Bruno mentions that his father's voice rose until he could no longer hear his mother talk. One can infer that Bruno's father is also a strict disciplinarian who does not shy away from confrontation. The fact that he is choosing to move his family, against their wishes, indicates that he values his position and does not take into consideration his wife's feelings. As the novel progresses, it is revealed that Bruno's father is a Commandant in the Third Reich who is responsible for overseeing the day-to-day operations of the Auschwitz concentration camp.

Why is the word "Traveller" written with a capital letter in "The Listeners" by Walter de la Mare?

This is a good question. Of course, we can't go back in time and ask de la Mare why he capitalized it, but there are two possible explanations. 

The first reason is that "The Traveller" functions as a proper name. He is the protagonist of the poem and is given no other name, and so within the context of the poem, this is his name, and proper names are normally capitalized in English.

A second reason has to do with genre and intertextuality. The poem is echoing the tradition of early English literature in which characters were named by their characteristics. One finds this sort of naming convention in morality plays such as "Everyman" or Bunyan's Pilgrim's Progress (an early modern allegory that derives from the morality play tradition in certain ways). Thus the capitalization, in evoking the older tradition of characters named by their characteristics, suggests that we should not read this as a narrative about the personal experiences of "The Traveller" but rather as a reflection on the way all people relate to things in their past. 

What is the valence of sodium?

Na is the symbol for the element sodium. Sodium has an atomic number of 11 and an atomic mass of 23 atomic mass units.

The number 11 indicates the number of protons in the nucleus, which in turn indicates the number of electrons in orbitals around the nucleus. The first level can hold 2 electrons; the next can hold 8. The valence electrons are in the unfilled orbital, which will be 1 electron.

It is the valence electrons that make an element react with other elements. Atoms react together to create a valence shell that is complete. Since sodium has 1 valence electron, it can lose it to an element that needs one electron in an ionic bond. Chlorine, which has 7 valence electrons, can gain 1 electron from sodium and will form the compound sodium chloride or table salt.

The link I have provided has a diagram showing how sodium and chlorine form salt. It also shows the change in charge on each atom. Since sodium loses one electron, it gets a 1+ charge, and since chlorine gains an electron, it gets a 1- charge.

What is azathioprine? Does it cause cancer?

Exposure routes: Ingestion, intravenous injection, and inhalation

Where found: The drug is found in hospitals, used for transplant and autoimmune disease patients, and in manufacturing plants that make and package the drug.

At risk: Patients who take azathioprine and workers who manufacture it.

Etiology and symptoms of associated cancers: In the liver, azathioprine is converted to 6-mercaptopurine, which inhibits deoxyribonucleic acid (DNA) synthesis. This suppresses the immune system but can also cause a dangerous decrease in the number of white blood cells (leukopenia) and platelets (thrombocytopenia), increased risk of infection and bleeding, gastrointestinal disturbances, and liver damage. The substance 6-mercaptopurine also inserts between adjacent nucleotide bases in DNA molecules and causes mutations that lead to various types of cancer.

Azathioprine increases the risk of developing squamous cell carcinoma, a type of skin cancer that appears as persistent wartlike growths, scaly patches, or open sores that crust over and bleed; non-Hodgkin lymphoma, a blood-based cancer of white blood cells called T cells, the most common symptoms of which are painless swelling of the neck or underarm lymph nodes, unexplained fever, loss of weight and appetite, itchy skin with reddened patches, and constant fatigue; and cancer of the bile ducts or hepatobiliary carcinomas, whose symptoms include jaundice, itching, stomach pain, weight loss, and fever.

History: The pioneer of liver transplantation, Sir Roy Yorke Calne, first used azathioprine to prevent organ rejection in liver transplant patients. Azathioprine was the standard antirejection drug in the 1970s for organ transplants and was later enlisted to treat patients who suffer from diseases that result when the immune system attacks the patient’s own body (autoimmune diseases).

Several epidemiological studies have shown that transplant patients who took azathioprine were at a high risk for different types of tumors. Other patients who took azathioprine but were not transplant patients, including those with rheumatoid arthritis, systemic lupus, inflammatory bowel disease, and certain skin and renal diseases, have also shown higher incidences of such malignancies, but not as high as those observed in transplant patients, since the dosages to treat autoimmune diseases are lower than those used for transplant patients. Mycophenolate mofetil, which is not as carcinogenic, is gradually replacing azathioprine as the antirejection drug of choice.

Alldredge, Brian K., et al. Koda-Kimble and Young's Applied Therapeutics: The Clinical Use of Drugs.10th ed. Philadelphia: Lippincott, 2013. Print.

"Azathioprine." MedlinePlus. Natl. Lib. of Medicine, 15 May 2014. Web. 29 Aug. 2014.

"Imuran (Azathioprine) Tablets and Injection." US Food and Drug Administration. Dept. of Health and Human Services, 19 Mar. 2014. Web. 29 Aug. 2014.

"Skin Cancer Alert for Organ Drug." BBC News. BBC, 15 Sep. 2005. Web. 29 Aug. 2014.

United States. Dept. of Health and Human Services. Natl. Toxicology Program. Report on Carcinogens. 12th ed. Research Triangle Park: Dept. of Health and Human Services, 2011. Print.

Why does Beowulf contain so many references to Christianity?

In Anglo-Saxon culture, stories were often passed down orally. A poet or bard would sing/recite the stories without writing them down. By the time Beowulf was finally written down near the year 1000, many of the Anglo-Saxons had converted to Christianity, which is likely why so many Christian references were added to finalized text. 

Though Beowulf contains many pagan themes such as dragons and sea monsters, Christian references are prominent. In fact, Beowulf's triumph over Grendel and his success as a king is often attributed to God. For example, in lines 1270-1272, the text says, "but Beowulf was mindful of his mighty strength, the wondrous gifts God had showered on him; he relied for help on the Lord of All." Because Beowulf relies on God, God grants him victory. Christian themes like this one permeate the story of Beowulf because Anglo-Saxons were converting to Christianity during the time period in which Beowulf was written down. 

Find the wavelength of a train whistle heard by a fixed observer as the train moves toward the observer with a velocity of 40.0 m/s. A wind blows...

Hello!

The observed frequency of a train whistle may be different from its natural frequency when an observer moves relative to a train. This is called the Doppler effect. The cause of the Doppler effect is that each next maximum or minimum of a wave is emitted closer or farther from the observer then the previous. This way, wavelength shortens when an observer and a wave source are moving towards each other, and elongates otherwise.

The formula for the observed frequency if  `f_o=(v+v_o)/(v-v_s) f_n,` where  `v approx 344 m/s` is the speed of sound in air, `v_o` is the speed of an observer towards a source and `v_s` is the speed of a source towards an observer. This formula assumes no wind.

To take wind speed `v_w` into account, consider a frame of reference associated with air, it is an inertial one. There is no wind in this system and the speeds `v_o` and `v_s` become `v_s-v_w` and `v_s-v_w` (directions must be considered).

In our case `v_o=0` and the formula becomes `f_o=(v-v_w)/(v-(v_s-v_w)) f_n,` in numbers it is about `(344-7)/(344-33)*500 approx 541.8 (Hz).`

We are asked about the wavelength, it is of course `v/f_o approx 0.63 m.`

NH3 is very polar, whereas NF3 is almost nonpolar. Why?

What we are really talking about here is electronegativity.  Electronegativity is a measure of an element's ability to attract neighboring electron density.  When looking at the periodic table, electronegativity increases across a row and going up in a column.  That means that electronegativity increases as you move to the upper right of the table and decreases as you move to the lower left.  Polarity within a molecule increases when neighboring atoms within the molecule have large differences in electronegativity.  NH3 (ammonia) contains a central nitrogen flanked by three hydrogens.  Nitrogen and hydrogen are far apart from each other on the periodic table which means that they have very different electronegativity values which in turn means ammonia is a polar molecule.  NF3, on the other hand, contains nitrogen and fluorine which are close to one another on the periodic table and therefore have similar electronegativity values which in turn means that NF3 is a very non-polar compound.

What are some reasons that support the idea that Boo Radley has courage?

Throughout the novel, Boo Radley is a reclusive, shy individual who rarely leaves his house. He was raised in a home with religious radicals who refused to let him outside. At the beginning of the novel, Boo gives Scout and Jem several gifts in the knothole of the tree in his front yard. Scout describes two of Boo's gifts by saying, "Our biggest prize appeared four days later. It was a pocket watch that wouldn’t run, on a chain with an aluminum knife" (Lee 38). Despite his brother's strict rules to stay inside the house, Boo ventures out of his home in an attempt to form a friendship with the Finch children. Boo's actions are courageous because his brother is known to be a strict individual who doesn't shy away from confrontation. Boo knows that he will probably be punished for leaving his house, but decides to venture outside anyway.

At the end of the novel, Scout and Jem are walking home from a Halloween festival when Bob Ewell viciously attacks them. Boo Radley courageously leaves the comfort of his home to intervene and fight Bob Ewell off of the children. During the struggle Scout mentions,

"He slowly squeezed the breath out of me. I could not move. Suddenly, he was jerked backwards and flung on the ground, almost carrying me with him. I thought, Jem's up" (Lee 160).

Scout is unaware that Boo Radley was the individual who pulled Bob Ewell off of her during the struggle. Boo successfully wrestles Bob away from Jem and Scout and stabs Bob with his own knife, killing him.

Once Boo returns Jem to the safety of the Finch residence, Scout gives her description of the attack to Sheriff Tate. In Chapter 29, Scout mentions that someone pulled Bob Ewell off of her, and when Tate asks Scout who it was, she says, "Why there he is, Mr. Tate, he can tell you his name" (Lee 164). Scout then points to Boo Radley, who is quietly standing in the corner. Sheriff Tate then tells Atticus that Bob Ewell fell on his own knife, but Atticus refuses to believe him and thinks Jem stabbed Bob. Tate finally says to Atticus,

"I never heard tell that it’s against the law for a citizen to do his utmost to prevent a crime from being committed, which is exactly what he did, but maybe you’ll say it’s my duty to tell the town all about it and not hush it up. Know what’d happen then? All the ladies in Maycomb includin’ my wife’d be knocking on his door bringing angel food cakes. To my way of thinkin’, Mr. Finch, taking the one man who’s done you and this town a great service an’ draggin’ him with his shy ways into the limelight—to me, that’s a sin" (Lee 169).

Sheriff Tate indirectly says that he knows Boo Radley killed Bob Ewell out of self-defense but refuses to speak about Boo's heroics because it will draw unwanted attention to Boo. Boo saved the children's lives during a dangerous struggle with an armed man. Boo's actions are yet another reason to support the idea that he is courageous.

An elevator has to be designed for accidents. If it must withstand drops from a height of 48 m, what should be the tensile strength of the string...

A cable that is pulling an elevator should be able to withstand the maximum force that is exerted on it when the elevator is filled to its full capacity and its mass is at the maximum.

From the details provided in the problem, the maximum mass of the elevator can be 1080 kg. The cable supporting the elevator should be able to withstand the force exerted by this mass. This force is a constant; its value does not go up in the case of an accident. When the elevator is at its highest point, the force that is being exerted on the cable is equal to 1080*9.8 = 10584 N. This force remains the same irrespective of the height of the elevator.

The tensile strength of a material is given in terms of Pa, or force per unit area. For the same material a thicker cable can withstand a larger force without breaking. To determine the required tensile strength of the cable supporting the elevator, the diameter of the cable is required. A thinner cable would need a material with a higher tensile strength and vice versa.

Why did Maniac bring Mars Bar to the party in Maniac Magee by Jerry Spinelli? What did he achieve?

When Piper invited Maniac to his birthday party, he agrees on one condition.  He has a “zany” idea.  He tells them he will come if he can bring someone.  The someone he has in mind is Mars Bar.  The McNabs would never expect him to bring a black boy to the party, and they tell him to bring whoever he wants. 

Maniac has a plan.  He doesn’t understand the racial divide in Two Mills.  He wants people of both races to see that there is no difference between people. 

Whites never go inside blacks' homes. Much less inside their thoughts and feelings. And blacks are just as ignorant of whites. What white kid could hate blacks after spending five minutes in the Beales' house? And what black kid could hate whites after answering Mrs. Pickwell's dinner whistle? (Ch. 41) 

Maniac first brings Mars Bar to the Pickwell house so he can see “the best the West End had to offer.”  Mars Bar is a big hit there.  He is polite, and the Pickwell kids love having him. 

The little Pickwells made as much fuss over Mars Bar as over Maniac. They believed, as did all little kids in the West End, that he carried a hundred Mars Bars with him at all times. Not surprisingly, Mrs. Pickwell never batted an eye when she saw who was coming to dinner. (Ch. 41) 

On the way to the McNab house, Mars Bar demonstrates his feat of stopping traffic.  It is also a big hit.  Things are going well until they get to the McNab house.

The McNabs and Cobras are unrepentant racists.  George McNab demands to know what Mars Bar is doing at the party.  Piper breaks the tension when he asks for his birthday present, but the Cobras do not talk to Mars Bar and George says to tell him when "it" leaves. 

Despite George’s rudeness to Mars Bar, Mars Bar tolerates them until a fight breaks out when Mars Bar insults the McNab house's smell.  Maniac prevents them from fighting.   They leave, and Mars Bar demands to know why Maniac subjected him to the McNabs.

"You suckered me. You soften me up with them Pick-peoples, then bring me here.  Wha'd you think! I was gonna cry Okay, I come over. I did it. It's done. And don't YOU be comin' 'round no more, ya hear me, fish! 'Cause you ain't only seen me half bad yet." (Ch. 41) 

Maniac realizes that he should not have expected a miracle.  It would have been better to just bring Mars Bar to the Pickwells and leave it at that.  You can’t change deep-seated beliefs overnight.  So while Maniac might not have changed the McNabs, he did show the Pickwells that everyone is the same, and gave Mars Bar something to think about too.

What are flashbacks?

Acute Flashbacks

Acute flashbacks are sensory or emotional experiences in which a person relives a past event or experience. Most flashbacks are spontaneous and triggered by a particular sight, sound, or smell. The person undergoing a flashback recalls sounds, smells, images, and feelings often more vivid than they were during the original event or experience. Acute flashbacks are unexpected and short lasting. In most cases, they are benign, pleasant, even comforting. In some cases, however, they are disturbing and can lead to psychotic episodes, severe depression, or schizophrenia.

Chronic Flashbacks

Hallucinogen persisting perception disorder (HPPD) is a chronic condition in which recurring flashbacks interfere with a person’s daily life. In mild cases, flashbacks occur infrequently. In extreme cases, flashbacks occur regularly and begin to distort a person’s perception of reality. HPPD is associated with the use of hallucinogenic drugs. Flashbacks can occur any time, from a day to a year after taking a hallucinogen.

HPPD flashbacks cause visual disturbances. The person suffering HPPD may see flashes of intense color; auras around people’s heads; dancing geometric shapes; images trailing moving objects; positive afterimages, in which objects remain in the brain after they have left the field of vision; or distortions in which objects appear larger or smaller than they are in actuality.

Trauma-related Flashbacks

Trauma-related, or nondrug-related, flashbacks were first described medically by doctors treating World War I combat veterans. These types of flashbacks are seen not only in combat veterans but also in other people who have experienced severe trauma, such as witnessing violent death. Flashbacks affect many persons with post-traumatic stress disorder.

Drug-related Flashbacks

Hallucinogens are the drugs most associated with flashbacks. LSD (lysergic acid diethylamide, or acid); psilocybin in certain mushrooms; and PCP (phencyclidine, or angel dust), originally an anesthetic, are the main hallucinogenic, or psychedelic, drugs. By far, LSD is the most commonly used and studied psychedelic.

During LSD flashbacks, users experience an abbreviated version of an earlier drug trip, or experience, without taking the drug. Many users report that the flashbacks are even more intense than the original trips. The flashbacks can be isolated or recurring, brief or drawn-out, pleasant or disturbing, and benign or damaging. Because LSD flashbacks usually appear suddenly, without warning, they can disrupt a person’s daily routine and lead to unpredictable behavior.

Chronic LSD users are more prone to flashbacks than occasional users. People with an underlying emotional problem and people highly susceptible to suggestion also are more prone to flashbacks than healthy users. Even emotionally healthy people who have used LSD only once or twice can experience flashbacks more than one year after taking the drug.

Causes

Scientists do not fully understand the biochemical processes through which hallucinogens affect the mind and body, and they do not know the causes of LSD flashbacks and HPPD. Research suggests several theories for flashbacks.

First, drugs can remain stored in body fat and in some organs—lungs, kidneys, liver, brain—long after they are taken. When the body burns fat during strenuous activity, the drugs might enter the bloodstream, causing the person to experience some of the drug’s effects. Second, LSD might have damaged the brain, causing it to send incorrect signals. Third, LSD may have changed the way the brain functions and processes information, which may account for the accompanying visual disturbances. Another theory holds that flashbacks have nothing to do with psychedelic drugs, but that flashbacks are naturally occurring altered states of consciousness that are not understood and, consequently, mislabeled or misinterpreted by drug users.

Triggers

Although scientists do not know the causes of flashbacks, they are reasonably sure of certain triggers. Common flashback triggers include physical or mental stress; physical or mental fatigue; lack of sleep; marijuana or alcohol binging; the use of certain prescription drugs, including antidepressants; and mild sensory deprivation. People sometimes deliberately induce mild sensory deprivation to alter their consciousness or to deeply relax. To induce mild sensory deprivation, a person might focus intensely on one particular sound, blocking out all other background sound, or might stare at a solid-colored surface without blinking for an extended period.

Treatment

No specific treatment exists for flashbacks. Doctors have prescribed certain medications, such as antiseizure drugs, for people suffering HPPD. However, the effectiveness of these drugs remains debatable because of the unpredictability of flashbacks and because of the uncertainty of their cause. Treatment for trauma-related flashbacks generally follows the protocols for treating mild mental disorders: talk therapy or other forms of psychotherapy.

Bibliography

Baggott, Matthew, et al. “Abnormal Visual Experiences in Individuals with Histories of Hallucinogen Use: A Web-Based Questionnaire.” Drug and Alcohol Dependence 114 (2011): 61–67. Print.

“Hallucinogens: LSD, Peyote, Psilocybin, and PCP.” 18 Feb. 2012. Web. http://www.drugabuse.gov/infofacts/hallucinogens.html.

Heaton, Robert. “Subject Expectancy and Environmental Factors as Determinants of Psychedelic Flashback Experiences.” Journal of Nervous and Mental Disease 161 (1975): 157–65. Print.

Lerner, Arturo, et al. “Flashback and Hallucinogen Persisting Perception Disorder: Clinical Aspects and Pharmacological Treatment Approach.” Israel Journal of Psychiatry and Related Sciences 39 (2002): 92–99. Print.

Myers, Lin, Shelly Watkins, and Thomas Carter. “Flashbacks in Theory and Practice.” Heffter Review of Psychedelic Research 1 (1998): 51–57. Print.

What was Snowball's part in the battle in Animal Farm?

What is Snowball’s part in the “Battle of the Cowshed” in George Orwell’s Animal Farm?

Having expected Mr. Jones to attempt to recover control of Manor Farm, Snowball has been studying a book of Julius Caesar’s battle strategies and has trained the animals in a series of defense strategies.  We know the pigs are intelligent, having taught themselves to read, but it suggests a particular level of intellect that Snowball is able to understand and apply such military principles.  

On October 12 the animals see the men coming down the road, Mr. Jones leading the way with a menacing gun in his hands. Rather than panic, the animals get into position under the guidance of Snowball.  First he has the pigeons attack with excrement from overhead, while the geese bite at the men’s legs. Then the horses and sheep begin butting and kicking, “with Snowball at the head of them.”  His bravery encourages the others to continue the attack.

Next, at a pre-planned signal from Snowball, all the animals retreat, leading the men into an ambush in the cowshed, where they all attack at once. Snowball himself goes for Mr. Jones, who shoots at him.  In spite of bullet streaks wounding his back, the brave pig rushes at Jones, launching him into a pile of manure and knocking the gun out of his hands.  At this all the animals attack in a frenzy, chasing the intruders off the farm for good.  

When Boxer expresses sorrow, believing he has killed a stable boy, Snowball encourages them all to instead feel proud of their victory, stating that they should be willing to die for Animal Farm if necessary.  In response the animals declare Snowball an “‘Animal Hero, First Class.’”   Readers understand that Snowball is cunning and has his own agenda like the rest of the pigs, yet at this point in the story, he is clearly a leader willing to join ranks with his soldiers, not to merely give orders from a safe distance.  This is also likely a main reason that Napoleon runs him off the farm, out of jealousy and hunger for total power.  As a result, the animals will never get to know if life might have been better on Animal Farm under the leadership of Snowball.

How can the following passage from Sophocles' play Antigone be interpreted?Creon: But know that hard minds fall the hardest, and that iron, so...

Creon is implying that Antigone is too proud, and that her pride in her defenses, will be her tragic downfall. This also acts as a foreshadowing as her very pride results in her inescapable death, as both in her will and in her lineage of tragedy from Oedipus.

This further can be argued as ironic in relation to both Creon and Oedipus.

Creon's own statement is ironic to his own fate, as his stubbornness and pride is his own downfall as the tragic hero/antagonist. Because of his pride, he befalls his own tragedy in the end, as he loses his queen, Eurydice, and his son, Haemon, with their love and esteem for him.

This knowledge of forthcoming tragedy, however was made known to him by Tiresias, who stated:

" your own flesh and blood, a corpse for corpses given in return, since you have thrust to the world below a child sprung for the world above,"

From this, Creon resembles an ironic symbolism to Oedipus, who had befallen his tragic fate from ignorance to the truth, yet Creon, fully knowing of his consequences, pursues his distressing path, and accomplishes his fate from his tragic downfall, pride.

Battery acid is generally 3.00 M H2SO4. What is the volume of the solution in the battery, if it is known to contain 4.78 moles of solute?

The molarity of a solution is the ratio of the number of moles of solute to the volume of solution. In other words, 

molarity = moles/volume

The units of molarity are moles per liter or M (molar). Sometimes, millimoles or mM are also used as a unit for molarity.

In the given case, the molarity of the sulfuric acid solution is 3.00 M. The number of moles of solute are 4.78. 

Using the relationship for molarity (as described above),

3 = 4.78/volume

or, volume = 4.78/3 = 1.59 liters.

Thus, the volume of solution is 1.59 liters. 

In other words, if we mix 4.78 moles of sulfuric acid in 1.59 liters of solvent, we will end up with a 3 molar (or 3 M) solution of the sulfuric acid. We can verify our answer.

Molarity of solution = moles/volume = 4.78/1.59 = 3 moles/l (approximately).

Why did Winnie's family feel as though "some part of her had slipped away" in Tuck Everlasting by Natalie Babbitt?

Winnie is different after her adventure with the Tucks, and has changed because of her new understanding of the world. 

It is clear to her parents that Winnie has changed when she returns from her adventure with the Tucks.  They do not know all of the details.  After all, the fact that the Tucks are immortal because they drank from a spring in the woods not far from the Fosters’ house is a big secret.  However, they know that there is something different about their daughter. 

Well, thought Winnie, crossing her arms on the windowsill, she was different. Things had happened to her that were hers alone, and had nothing to do with them. It was the first time. And no amount of telling about it could help them understand or share what she felt. (Ch. 21) 

You would be different too if you had been on such a grand adventure.  Winnie led a somewhat sheltered life.  She had not been far from home before, and was concerned that she was being smothered by her mother and grandmother.  After the Tucks “kidnapped” her, she learned about immortal people and then saw a man killed when Mae hit him with a shotgun. 

These experiences would definitely affect Winnie’s behavior, and make her seem to come back changed.  The Tucks were wonderful people and Winnie learned a lot about life from them.  With Mae being in prison,  Winnie faced some internal conflict due to her part of the plan to help her escape.  This was a big decision, and while it is not legal to bust someone out, Winnie felt it was the right thing to do. 

Winnie is definitely affected by both Mae’s upcoming jailbreak and the death of the man in the yellow suit.  She saw a man killed before her eyes, even if Mae did not intend it. 

She lay in the dark, propped up on the pillows, and stared at the lighter square of her window, at the heat lightning throbbing. It was like pain, she thought again, a dull pain on the fringes of the sky. Mae had killed the man in the yellow suit. And she had meant to kill him. (Ch. 21) 

Winnie’s plan is to sneak out and help Mae break out of prison so that no one finds out she is immortal.  If they tried to hang her, they would find out.  Winnie feels that the Tucks are good people, and she is trying to do her part, but the whole thing leaves her sad, conflicted, and scared.

What are the qualities described by Martin Luther King of the ''veteran of creative suffering?''

The line you are asking about is from one of the most powerful speeches ever delivered in the United States:  Martin Luther King's "I Have a Dream" speech. The chief quality that the "veteran of creative suffering" possesses is the experience of enduring great injustices in the United States, purely for being of a different race. The specific qualities mentioned by King are found in the sentences preceding his description of African-Americans as veterans of creative suffering.  

"I am not unmindful that some of you have come here out of great trials and tribulations. Some of you have come fresh from narrow jail cells. And some of you have come from areas where your quest -- quest for freedom left you battered by the storms of persecution and staggered by the winds of police brutality. You have been the veterans of creative suffering." --Martin Luther King

In this passage, King describes the violent treatment of black people at the hands of law enforcement.  He describes how his people are being jailed for protesting against their oppressive treatment.  King was jailed on numerous occasions and was a veteran of this suffering himself.  

The paragraph before this also describes the lack of economic and political opportunities for black Americans.  It speaks of segregation at hotels and the condition of the ghettos.  These are also qualities of "creative suffering."

"We can never be satisfied as long as our bodies, heavy with the fatigue of travel, cannot gain lodging in the motels of the highways and the hotels of the cities.  We cannot be satisfied as long as the negro's basic mobility is from a smaller ghetto to a larger one. We can never be satisfied as long as our children are stripped of their self-hood and robbed of their dignity by signs stating: "For Whites Only."  We cannot be satisfied as long as a Negro in Mississippi cannot vote and a Negro in New York believes he has nothing for which to vote. No, no, we are not satisfied, and we will not be satisfied until "justice rolls down like waters, and righteousness like a mighty stream." --Martin Luther King

How can the shape of a car be changed to reduce air resistance?

Air resistance is the resistance offered by air molecules as an object, such as a car, moves through them. There are a number of factors that affect air resistance. These include the shape of the car, the surface finish and the car's speed. 

The air resistance of a car can be reduced by providing lesser surface area that encounters air and providing smoother surfaces. To do this, we can make cars wedge-shaped and keep their heights very low (the car should be as close to the ground as possible). All the corners can be rounded and provided a smoother finish. This is exactly what is done with sports cars; you may want to check out the cars in Formula 1 racing. 

We can also keep the surfaces smooth by painting them with smooth, friction-reducing paint coats.

The lesser the number of corners that air encounters, the lesser the air resistance.

Note that lower air resistance is preferred in consumer vehicles to improve fuel efficiency.

Hope this helps. 

What made William Shakespeare come up with Romeo and Juliet?

Though William Shakespeare is the most famous author of the "Romeo and Juliet" story, he was not the first. He most likely based his play on an earlier work by the name of The Tragicall Historye of Romeus and Juliet, though French and Italian iterations predate even this English version. These earlier versions were poems or lyrical tales, though the earliest form of this story may have been a simple folk-tale or even a rumor!

A number of Shakespeare's works were based on earlier novellas, poems, or folklore. Hamlet was based on a Saxon legend called Amleth, though his favorite choice for source material seems to have been an Italian writer called Matteo Bandello. In addition to the novella which inspired Romeo and Juliet, Shakespeare adapted Bandello's work into Twelfth Night and Much Ado About Nothing. 

In short, Shakespeare didn't actually come up with the story of Romeo and Juliet, but he did write the most famous and fleshed-out version.

What are medulloblastomas?

Related conditions:
Supratentorial primitive neuroectodermal tumors, neurofibromatosis (von Recklinghausen disease), Gorlin syndrome

Definition:



Medulloblastomas are malignant (cancerous) or benign (noncancerous) tumors that form in the cerebellum of the brain. The cerebellum controls balance and movement, posture, and speech. These tumors occur more often in children but may rarely appear in adults.

Risk factors: There is no known cause of medulloblastomas, but, scientists are uncovering changes in genes and chromosomes that may influence the development of these tumors. A small percentage of tumors may tend to occur in families, particularly in families with neurofibromatosis (von Recklinghausen disease), an inherited disease that causes benign tumors to occur on peripheral nerves in the body. A few individuals with Gorlin syndrome, an inherited disease related to basal cell carcinoma and other conditions, also develop medulloblastoma.

Etiology and the disease process: Medulloblastoma is a relatively rare disease, with no known cause other than a familial tendency. The tumor is considered fast growing. Because of the location of the tumor, walking and talking disruptions are common as the disease progresses.

Incidence: The tumor occurs more often in boys than girls, and generally before the age of eight, with a peak incidence between five and ten years of age. In the United States, the incidence of medulloblastoma is 1.5 to 2 cases per 100,000 population (children). Approximately 1,000 cases are diagnosed annually, accounting for 18 percent of brain tumors in children, according to the American Brain Tumor Association.

Symptoms: The classic, initial symptoms of medulloblastoma are morning headaches, nausea, vomiting, and other flu-like symptoms. Because the symptoms mimic flu, the tumor may go undiagnosed until symptoms progress to balance problems. Older children may be more easily diagnosed than infants, as infants may initially exhibit an increase in head size and irritability, both common in infants as they grow and develop. Vomiting may make the person feel better, as the intracranial pressure is temporarily relieved. Symptoms increase as the tumor grows.

Screening and diagnosis: There is no screening test for medulloblastoma. Diagnosis begins with a history of symptoms and neurological examination. Radiology studies include magnetic resonance imaging (MRI), including the use of a contrast dye, to identify the presence of a brain tumor, and a positron emission tomography (PET) scan, used to determine if the tumor is active and growing. Other procedures, such as a lumbar puncture to take cerebrospinal fluid (CSF), a bone marrow aspiration and biopsy, and a bone scan, may be done to look for signs of cancer. A confirmed diagnosis is made during surgery, and pathologic examination of the tumor specimen removed determines if the tumor is benign or malignant.

Two risk groups are used in childhood medulloblastoma to determine treatment management, rather than the adult staging process. The average risk group and the poor risk group are differentiated based on the tumor remaining after surgery, spread of cancer cells within the brain and spinal cord, or distant spread of tumor cells to other parts of the body. Adults are staged based on the remaining tumor and whether the tumor has spread using the TNM (tumor/lymph node/metastasis) staging system.

Treatment and therapy: Treatment of medulloblastoma is with surgery, radiation therapy, chemotherapy, and, if necessary, mechanical diversion of cerebrospinal fluid with a shunt to carry blocked fluid out of the brain. Surgery is used to remove as much of the tumor as possible. Imaging studies may show that the tumor is inoperable. A biopsy will still be done to determine the type of tumor and whether it is malignant. If the tumor has grown into the brain stem, removal may not be an option, as the side effects of removal are life-threatening. Steroids are used to decrease swelling in the brain. A shunt, or tube to drain CSF away from the brain, usually to the abdomen, may be placed during surgery. Radiation therapy to the brain and the spinal cord is then used to kill any cells remaining. Radiation may be done with stereotactic radiosurgery, intensity-modulated radiation therapy, or external beam radiation. chemotherapy may be used in infants to postpone the use of radiation, as cranial radiation side effects may be severe. Chemotherapy may be given either intravenously (into a vein) or intrathecally (into the cerebrospinal fluid) by use of an Ommaya reservoir. In adults, chemotherapy effectiveness is less clear.

Prognosis, prevention, and outcomes: The prognosis for medulloblastoma varies with the patient’s age at diagnosis, the size of the tumor, the amount remaining after surgery, and the level of tumor cell spread to other sites in the brain, spinal cord, or elsewhere in the body (metastasis). Approximately 57 to 60 percent of adults are alive at five years after diagnosis, and up to 80 percent of children with average-risk classification can be expected to reach five years, according to the American Brain Tumor Association. With poor risk classification, up to 65 percent of children may survive to five years. The outcome for infants is poor, with a 30 to 50 percent survival. There is no prevention for medulloblastoma. Quality of life may be negatively affected by the side effects of therapy, including learning disabilities, hearing loss from drug therapy, obesity, thyroid deficiency, and other problems depending on treatment and site. Recurrence is always a risk as tumors may be difficult to remove completely.

Hargrave, D. R., and S. Zacharoulis. “Pediatric CNS Tumors: Current Treatment and Future Directions.” Expert Review of Neurotherapeutics 7.8 (2007): 1029–42. Print.

Kombogiorgas, Dimitris A. The Medulloblastoma Book. New York: Nova Biomedical, 2014. Print.

Nikitovic, Marina, and Ivana Golubicic. "Treatment Options for Childhood Medulloblastoma." Vojnosanitetski Pregled: Military Medical & Pharmaceutical Journal Of Serbia & Montenegro 70.8 (2013): 773–77. Print.

Parker, W., E. Filion, D. Roberge, and C. R. Freeman. “Intensity-Modulated Radiotherapy for Craniospinal Irradiation: Target Volume Considerations, Dose Constraints, and Competing Risks.” International Journal of Radiation Oncology, Biology, Physics 69.1 (2007): 251–57.

Wang, Jun. "The Rule of Stem Cells and Progenitors in the Genesis of Medulloblastoma." Experimental Neurology 260 (2014): 69–73. Print.

How could I start an argumentative essay about how racism still exists?

Evidence for the continued existence of racism can be found on a number of different levels. Examining racial differences in incarceration rates and rates of police brutality, contemporary racial hate groups, and representation in American media might be a good starting point for finding a variety of different types of racism.

Some evidence for the continued existence of racism can be found in Michelle Alexander's book, The New Jim Crow. In this book, Alexander uses statistics to prove that African Americans are incarcerated for drug crimes at much higher rates than  white Americans, despite the fact that white Americans are more likely to commit drug crimes. Alexander argues that differing incarceration rates have developed a "racial caste system" to deny opportunity to African Americans. African Americans are additionally more likely to be assaulted and even killed by police officers than non-black Americans.

Other evidence for the existence of racism includes the continued existence of hate groups such as the KKK, and the lack of representation of nonwhite people in American media. According to UCLA's 2015 Hollywood Diversity Report, people of color are greatly underrepresented in all media jobs; although minorities constitute 40% of the U.S. population, white lead actors in broadcast TV shows number nonwhite leads by a ratio of six to one.

In To Kill A Mockingbird, who helped Simon Finch create his homestead, Finch's Landing?

Scout's ancestor, Simon Finch, was from England. He left England and travelled to the United States. He eventually found himself in Alabama. It was there that he decided to abandon the religious teachings he had previously followed. Simon seemed to forget "his teacher’s dictum on the possession of human chattels" and "bought three slaves." It was "with their aid [that he] established a homestead on the banks of the Alabama River some forty miles above Saint Stephens" (To Kill a Mockingbird, Chapter 1).

The three slaves helped Simon to create a self-sufficient homestead. There was very little that the land did not produce. The items that did have to be brought in, such as blocks of ice and clothing, were shipped by river. These things would arrive by boat on the Alabama River. When they docked at Finch's Landing, the slaves would unload the items. If it were not for the hard work of slaves, Simon Finch would not have been able to build such a prosperous settlement along the Alabama River.

What is the ANC?

The ANC is the acronym for the African National Congress, the political party that has ruled South Africa since the end of Apartheid in 1994, when Nelson Mandela was elected president. Prior to the abolition of Apartheid, the ANC was a political and military resistance movement dedicated to combatting the violence and oppression of the white supremacist government that ruled South Africa and kept the black or so-called "colored population" in ghettos, living in substandard housing, unable to get good jobs or participate in politics. The all-white government, called the "National Party," (NP) officially banned the so-called "colored" population of South Africa from voting in 1969, and this complete disenfranchisement, along with brutal NP police tactics to suppress labor unrest and public dissent, as well the policy of forcibly removing black South Africans from Johannesburg to the all black shantytown of Sowetto, forced many leaders of the ANC to flee South Africa and set up their movement in the neighboring countries of Mozambique, Swaziland and Zimbabwe.

For much of the latter half of the 20th century, the African National Congress was an illegal opposition party to the all-white government. As a result of the fact that the United States and most other western nations recognized the legitimacy of the National Party Government and supported South African Apartheid, and because the ANC engaged in violent rebellion against the repressive and brutal Apartheid Government, the ANC was also listed as an international terrorist organization by the United States and its allies.

Today, and ever since 1994, however, when the South Africans held their first fully non-racially-based democratic elections, the ANC has continuously won the presidency and held a majority in the legislature (The National Assembly), by forming a governing coalition known as the Tripartite Alliance, comprised of the ANC, the Congress of South African Trade Unions (COSATU) and the South African Communist Party (SACP). Since Mandela left office as president in 1999, the ANC has had three more presidents: Thabo Mbeki, Kgalema Motlanthe and the current president, Jacob Zuma.

In "Winter Dreams" by F. Scott Fitzgerald, what do you learn about Dexter's family and social position?

In the very first paragraph of F. Scott Fitzgerald's short story "Winter Dreams," the third person narrator indicates that Dexter Green's father "owned the second best grocery store in Black Bear—the best one was the 'Hub' patronized by wealthy people from Sherry Island—and Dexter caddied only for pocket money." This snippet of information seems to reveal that Dexter comes from a middle class family but that the narrator, and Dexter himself, are keenly aware of the upper class.

Dexter comes from comfortable circumstances. His father, who is revealed at one point as "prospering now," offers to pay for Dexter's education at a state college, but Dexter strives for something else and attends a "more famous university in the east" (possibly Princeton, where Fitzgerald attended) where he is plagued by "scanty funds." Dexter has an obvious fascination for the rich and wants to become one of them. He directly parallels another Fitzgerald character, Jay Gatsby, who buys a giant mansion on West Egg (a symbol for the new rich) across from East Egg (established wealth). Dexter, too, becomes quite wealthy in the laundry business and eventually moves to New York. Like Gatsby, Dexter falls for a selfish and willful girl, Judy Jones (a forerunner of Daisy Buchanan), who comes from established wealth. And, just like Gatsby, Dexter is rejected in the end.   

Give a physical description of Arthur Radley from the novel To Kill a Mockingbird.

In Chapter 29, Scout finally meets Boo Radley after surviving Bob Ewell's vicious attack. Sheriff Tate tells Scout to recount her story of the attack and she mentions that someone yanked Mr. Ewell off of her. Scout says that she thought Atticus had come to save them, and Mr. Tate asks her who intervened. Scout says, "Why there he is, Mr. Tate, he can tell you his name" (Lee 362). Scout then points to Arthur "Boo" Radley, who is standing quietly in the corner. Scout proceeds to give a description of Boo by commenting on his sickly, white hands which had never been in the sunlight. Boo is a thin man, and Scout mentions that he was wearing khaki pants and a ripped denim shirt. She says that his face was as white as his hands and Boo had a "jutting" chin. Scout also mentions that his cheeks were so thin that they seemed hollow, and his mouth was wide. Boo had gray, colorless eyes, and his hair was dead and thin. When Scout finally realizes that she is standing face to face with Boo Radley, she tears up and says, "Hey, Boo" (Lee 362).

What is copper + magnesium sulfate?

You are asking what the reaction between copper and magnesium sulfate produces.  Actually, adding copper metal to an aqueous solution of magnesium sulfate will produce no reaction.  Nothing will change.  That is because magnesium is a more reactive metal than copper.  There is a metal reactivity series based on the naturally occurring reactivity potentials of the metals on the periodic table.  This series is referenced in the link below.  Copper is one of the least reactive metals and magnesium is one of the more reactive metals.  So adding magnesium metal to copper sulfate will produce a chemical reaction (the metal will slowly dissolve as it ionizes), but adding copper metal to magnesium sulfate will produce no reaction (the copper metal will simply sit in solution).

What is a cleft lip and palate?

Causes and Symptoms

Cleft palate is a congenital defect characterized by a fissure along the midline of the palate. It occurs when the two sides fail to fuse during embryonic development. The gap may be complete, extending through the hard and soft palates into the nasal cavities, or may be partial or incomplete. It is often associated with cleft lip or “harelip.” About one child in eight hundred live births is affected with some degree of clefting, and clefting is the most common of the craniofacial abnormalities.

Cleft palate is not generally a genetic disorder; rather, it is a result of defective cell migration. Embryonically, in the first month, the mouth and nose form one cavity destined to be separated by the hard and soft palates. In addition, there is no upper lip. Most of the upper jaw is lacking; only the part near the ears is present. In the next weeks, the upper lip and jaw are formed from structures growing in from the sides, fusing at the midline with a third portion growing downward from the nasal region. The palates develop in much the same way. The fusion of all these structures begins with the lip and moves posteriorly toward, and then includes the soft palate. The two cavities are separated by the palates by the end of the third month of gestation.

If, as embryonic development occurs, the cells that should grow together to form the lips and palate fail to move in the correct direction, the job is left unfinished. Clefting of the palate generally occurs between the thirty-fifth and thirty-seventh days of gestation. Fortunately, it is an isolated defect not usually associated with other disabilities or with developmental delays.

If the interference in normal growth and fusion begins early and lasts throughout the fusion period, the cleft that results will affect one or both sides of the top lip and may continue back through the upper jaw, the upper gum ridge, and both palates. If the disturbance lasts only part of the time that development is occurring, only the lip may be cleft, and the palate may be unaffected. If the problem begins a little into the fusion process, the lip is normally formed, but the palate is cleft. The cleft may divide only the soft palate or both the soft and the hard palate. Even the uvula may be affected; it can be split, unusually short, or even absent.

About 80 percent of cases of cleft lip are unilateral; of these, 70 percent occur on the left side. Of cleft palate cases, 25 percent are bilateral. The mildest manifestations of congenital cleft are mild scarring or notching of the upper lip. Beyond this, clefting is described by degrees. The first degree is incomplete, which is a small cleft in the uvula. The second degree is also incomplete, through the soft palate and into the hard palate. Another type of “second-degree incomplete” is a horseshoe type, in which there is a bilateral cleft proceeding almost to the front. Third-degree bilateral is a cleft through both palates but bilaterally through the gums; it results in a separate area where the teeth will erupt, and the teeth will show up in a very small segment. When the teeth appear, they may not be normally aligned. In addition to the lip, gum, and palate deviations, abnormalities of the nose may also occur.

Cleft palate may be inherited, probably as a result of the interaction of several genes. In addition, the effects of some environmental factors that affect embryonic development may be linked to this condition. They might include mechanical disturbances such as an enlarged tongue, which prevents the fusion of the palate and lip. Other disturbances may be caused by toxins introduced by the mother (drugs such as cortisone or alcohol) and defective blood. Other associated factors include deficiencies of vitamins or minerals in the mother’s diet, radiation from X-rays, and infectious diseases such as German measles. No definite cause has been identified, nor does it appear that one cause alone can be implicated. It is likely that there is an interplay between genetic and chromosomal abnormalities and environmental factors.

There are at least 150 syndromes involving oral and facial clefts. Four examples of cleft syndromes that illustrate these syndromes are EEC (ectrodactyly, ectodermal dysplasia, cleft lip/palate), popliteal pterygium syndrome, van der Woude’s syndrome, and trisomy 13 syndrome. EEC and trisomy 13 both result in intellectual and developmental disabilities as well as oral clefts. Popliteal pterygium has as its most common feature skin webbing (pterygium), along with clefts and skeletal abnormalities. Van der Woude’s syndrome usually shows syndactyly as well as clefting and lower-lip pitting.

Problems begin at birth for the infant born with a cleft palate. The most immediate problem is feeding the baby. If the cleft is small and the lip unaffected, nursing may proceed fairly easily. If the cleft is too large, however, the baby cannot build up enough suction to nurse efficiently. To remedy this, the hole in the nipple of the bottle can be enlarged, or a plastic obturator can be fitted to the bottle.

Babies with cleft palates are more susceptible to colds than other children. Since there is an open connection between the nose and mouth, an infection that starts in either location will easily and quickly spread to the other.
Frequently, the infection will spread to the middle ear via the Eustachian tube. One end of a muscle is affixed to the Eustachian tube opening, and the other end is attached to the middle of the roof of the mouth (palate). Normal contraction opens the tube so that air can travel through the tube and equalize air pressure on both sides of the eardrum. As long as the eardrum has flexibility of movement, the basics for good hearing are in place. Children with cleft palates, however, do not have good muscle contractions; therefore, air cannot travel through the tube. If the tube remains closed after swallowing, the air that is trapped is absorbed into the middle-ear tissue, resulting in a vacuum. This pulls the eardrum inward and decreases its flexibility, and hearing loss ensues. The cavity of the middle ear then fills with fluid, which can breed bacteria, causing infection. The infection may or may not be painful; if there is no pain, the infection may go unnoticed and untreated. The accumulated fluid can cause erosion of the tiny bones, which would decrease sound transmission to the auditory nerve. This conductive
hearing loss is permanent. Persistent and prolonged fluid buildup can also cause accumulation of dead matter, forming a tumorlike growth called a cholesteatoma.

Other problems associated with cleft palates are those related to dentition. In some children there may be extra teeth, while in others the cleft may prevent the formation of tooth buds so that teeth are missing. Teeth that are present may be malformed; those malformations include injury during development, fusion of teeth to form one large tooth, teeth lacking enamel, and teeth that have too little calcium in the enamel. If the teeth are misaligned, orthodontia may be undertaken. Another possible problem met by patients with a cleft palate is maxillary (upper jaw) arch collapse; this condition is also remedied with orthodontic treatment.

Treatment and Therapy

One of the first questions a parent of a child with a cleft palate will pose regards surgical repair. The purpose of surgically closing the cleft is not simply to close the hole—although that goal is important. The major purpose is to achieve a functional palate. Whether this can be accomplished depends on the size and shape of the cleft, the thickness of the available tissue, and other factors.

Cleft lip surgery is performed when the healthy baby weighs at least ten pounds; it is done under a general anesthetic. If the cleft is unilateral, one operation can accomplish the closure, but a bilateral cleft lip is often repaired in two steps at least a month apart. When the lip is repaired, normal lip pressure is restored, which may help in closing the cleft in the gum ridge. It may also reduce the gap in the hard palate, if one is present. Successive operations may be suggested when, even years after surgery, scars develop on the lip.

Surgery to close clefts of the hard and soft palate is typically done when the child is at least nine months of age, unless there is a medical reason not to do so. Different surgeons prefer different times for this surgery. The surgeon attempts to accomplish three goals in the repair procedure. The surgeon will first try to ensure that the palate is long enough to allow for function and movement (this is essential for proper speech patterns). Second, the musculature around the Eustachian tube should work properly in order to cut down the incidence of ear infections. Finally, the surgery should promote the development of the facial bones and, as much as possible, normal teeth. This goal aids in eating and appearance. All of this may be accomplished in one operation if the cleft is not too severe. For a cleft that requires more procedures, the surgeries are usually spaced at least six months apart so that complete healing can occur. This schedule decreases the potential for severe scarring.

At one time, it was thought that if surgery were performed before the child began talking, speech problems would be avoided. In reality, not only did the surgery not remedy that problem, but the early closure often resulted in a narrowing of the upper jaw and interference with facial growth as well. Thus, the trend to put off the surgery until the child was four or five years of age developed; by this age, more than 80 percent of the lateral growth of the upper jaw has occurred. However, most surgeons can perform the corrective surgery when the child is between one and two years of age without affecting facial growth.

Successful repair greatly improves speech and appearance, and the physiology of the oral and nasal cavities is also improved. Additional surgery may be necessary to improve appearance, breathing, and the function of the palate. Sometimes the palate may partially reopen, and surgery is needed to reclose it.

When the baby leaves the operating room, there are stitches in the repaired area. Sometimes a special device called a Logan’s bow is taped to the baby’s cheeks; this device not only protects the stitches but also relieves some of the tension on them. In addition, the baby’s arms may be restrained in order to keep the baby’s hands away from the affected area. (The child is fitted for elbow restraints before surgery; the elbows are encased in tubes that prevent them from bending.) A parent of a child that has just undergone cleft palate repair should not panic at the sight of bleeding from the mouth. To curb it, gauze may be packed into the repaired area and remain about five days after surgery. As mucus and other body fluids accumulate in the area, they may be suctioned out.

During the initial recovery, the child is kept in a moist, oxygen-rich environment (an oxygen tent) until respiration is normal. The patient will be observed for signs of airway obstruction or excessive bleeding. Feeding is done by syringe, eyedropper, or special nipples. Clear liquids and juices only are allowed. The child sits in a high chair to drink, when possible. After feeding, the mouth should be rinsed well with water to help keep the stitches clean. Peroxide mixed with the water may help, as well as ointment. Intake and output of fluids are measured. Hospitalization may last for about a week, or however long is dictated by speed of healing. At the end of this week, stitches are removed and the suture line covered and protected by a strip of paper tape.

An alternative to surgery is the use of an artificial palate known as an obturator. It is specially constructed by a dentist to fit into the child’s mouth. The appliance, or prosthesis, is carefully constructed to fit precisely and snugly, but it must be easily removable. There must be enough space at the back so the child can breathe through the nose. While speaking, the muscles move back over this opening so that speech is relatively unaffected.

Speech problems are the most likely residual problems in the cleft palate patient. The speech of the untreated, and sometimes the treated cleft palate patient is very nasal. If the soft palate is too short, the closure of the palate may leave a space between the nose and the throat, allowing air to escape through the nose. There is little penetrating quality to the patient’s voice, and it does not carry well. Some cleft palate speakers are difficult to understand because there are several faults in articulation. Certainly not all cleft lip or palate patients, however, will develop communication problems; modern surgical procedures ensure that most children will develop speech and language normally, without the help of a speech therapist.

Genetic counseling
may help answer some of the family’s questions about why the cleft palate occurred, whether it will happen with future children, and whether there is any way to prevent it. There are no universal answers to these questions. The answers depend on the degree and type of cleft, the presence of other problems, the family history, and the history of the pregnancy. Genetic counseling obtained at a hospital or medical clinic can determine whether the condition was heritable or a chance error and can establish the risk level for future pregnancies.

Perspective and Prospects

Oral clefts, as well as other facial clefts, have been a part of historical records for thousands of years. Perhaps the earliest recorded incidence is a Neolithic shrine with a two-headed figurine dated about 6500 BCE. The origination and causative agent of such clefts remain mysterious today.

Expectant parents are rarely alerted prior to birth that their child will be born with a cleft, so it is usually in the hospital, just after birth, that parents first learn of the birth defect. Even if it is suspected that a woman is at risk for producing a child with a cleft palate, there is no way to determine if the defect is indeed present, as neither amniocentesis nor chromosomal analysis reveals the condition. When the baby is delivered, the presence of the cleft can evoke a feeling of crisis in the delivery room.

The problems accompanying clefting may alter family morale and climate, increasing the complexity of the problem. A team of specialists usually works together to help the patient and the family cope with these problems. This team may include a pediatrician, a speech pathologist, a plastic surgeon, an orthodontist, a psychiatrist, an otologist, an audiologist, and perhaps others.

The cooperating team should monitor for the following situations: feeding problems, family and friends’ reactions to the baby’s appearance, how parents encourage the child to talk or how they respond to poor speech, and whether the parents are realistic about the long-term outcome for their child. The grief, guilt, and shock that the parents often feel can be positively altered by how the professional team tackles the problem and by communication with the parents. Usually the team does not begin functioning in the baby’s life until he or she is older than one month. Some parents have confronted their feelings, while others are still struggling with the negative feeling that the cleft brought to bear. Therefore, the first visit that the parents have with the team is important because it establishes the foundation of a support system that should last for years.

If the cleft were only a structural defect, the solution would simply be to close the cleft. Yet, problems concerning feeding and health, facial appearance, communication, speech, dental functioning, and hearing loss, as well as the potential for psychosocial difficulties, may necessitate additional surgical, orthodontic, speech, and otolaryngological interventions. In other words, after the closure has been made, attention is focused on aesthetic, functional, and other structural deficits.

Bibliography:

Berkowitz, Samuel, ed. Cleft Lip and Palate: Diagnosis and Management. 2d ed. New York: Springer, 2006.

"Cleft Lip and Palate" Medline Plus, May 4, 2012.

Clifford, Edward. The Cleft Palate Experience. Springfield, Ill.: Charles C. Thomas, 1987.

"Facts about Cleft Lip and Cleft Palate. Centers for Disease Control and Prevention, July 19, 2012.

Gruman-Trinker, Carrie T. Your Cleft-Affected Child: The Complete Book of Information, Resources, and Hope. Alameda, Calif.: Hunter House, 2001.

Kliegman, Robert, et al. "Cleft Lip and Palate." In Nelson Textbook of Pediatrics, edited by Robert Kliegman, et al. 19th ed. Philadelphia, Pa.: Elsevier, 2011.

Lorente, Christine, et al. “Tobacco and Alcohol Use During Pregnancy and Risk of Oral Clefts.” American Journal of Public Health 90, no. 3 (March, 2000): 415–419.

Stengelhofen, Jackie, ed. Cleft Palate. New York: Churchill Livingstone, 1988.

Wyszynski, Diego F., ed. Cleft Lip and Palate: From Origin to Treatment. New York: Oxford University Press, 2002.