Chapter7StandardPartsandCommonlyUsedParts
听力-chapter 7
Unit Three American TrademarksChapter 7 Multiculturalism PRELISTENINGB.V ocabulary and Key Concepts1. I understand why a foreigner might react skeptically to U. S. culture, especially if the person comes from a more ethnically and racially homogeneous society.2. It seems naive or even perverse to deny the existence of a culture that has such great impact on other cultures, for better or worse.3. A melting pot, literally a pot in which metals like aluminum and copper are melted in order to blend them, is the traditional metaphor for the way the different groups of immigrants came together in the United States.4. Some people feel that the monoculturalist view of many nationalities blending together into an alloy of all the parts in it is a myth.5. Opponents point out that many groups have at times been excluded from participating in U.S.society through segregation and discrimination.6. U. S. society probably did not assimilate new cultural input until the new immigrants were viewed with less prejudice.7. The metaphor the multiculturalists use is the patchwork quilt, a mosaic of separate, autonomous subcultures.8. Intermarriage and the adoption of children of another race make a difference in how people in a family look at themselves.9. The point here is that the ethnically and racially pure individuals implied by the multiculturalist view are more the.exception than the rule.10. We inherit some of our culture from our families and absorb some of our culture unconsciously.11. If assimilation does not take place in the first generation, it most certainly does by the second or third.12. Monoculturalists fear a fragmentation, or even destmction, of U. S. culture, whereas proponents of the pluralistic view disagree.13. It would be wrong to assume that the dominant culture we’ve been speaking about reflects the culture of only one group.14. Opponents of the pluralistic view of culture cite Latinos, especially Mexican immigrants, the single largest immigrant group since the 1990s.LISTENINGLECTURE：MulticulturalismForeigners from older cultures with traditions dating back hundreds and hundreds of years sometimes react with surprise and skepticism when the topic of U. S. culture comes up. Commenting on the United States, they sometimes say things like “But the United Stateshas no culture.” People in the United States find comments such as this one amusing at best, and sometimes downright infuriating. In a way, I understand why a foreigner might react skeptically to the United States, especially if the person comes from a more ethnically and racially homogeneous society. Or if the person comes from a society whose culture is reinforced by state institutions—govemment, church, and schools, for instance. It would be hard for this foreigner to understand a multiracial, ethnically diverse country like the United States, whose institutions do not strongly reinforce the culture. However, it seems naive or even perverse to deny the existence of a culture that has such great impact on other cultures, for better or worse. The clothes that Americans wear the food they eat, the music, films, and books they produce, and even to some extent the religions they practice influence how many people in other countries live and think. One may easily disapprove of the influence that mass American culture has on the world, but one cannot objectively deny that influence.In all fairness, I have to say that it’s understandable that foreigners have trouble identifying an American culture because not even the best minds in the country—writers, educators, and politicians—agree on the basic nature of U.S. culture. Today I’ll try to contrast three ways that U.S. culture has been perceived over the years. Then perhaps you can decide which point of view seems the most logicalto you. We’ll take a look at the older monoculturalist view；a newer, multiculturalist view; and finally a third view, which I’ll call the pluralistic view.First in, our discussion is the monoculturalist view of the United States as a melting pot. A melting pot, literally a pot in which metals like aluminum and copper are melted in order to blend them, is the traditional metaphor for the way the different groups of immigrants came together in the United States. Now, theoretically, the result of many nationalities blending together is one big unified common culture, an alloy of all the parts in it. In other words, the result is a combination of all the different parts, which have mixed together and are no longer recognizable as separate parts. However, many people today feel that the idea of one common U.S. culture is a myth and has always been a myth. To support their view, opponents point out that many groups, notably, African, Asian, and Native Americans, have at times been excluded from participating fully in society through segregation and discrimination. Furthermore, a trademark of U.S. immigration has been that the most recently arrived group, whether Irish or Italian or Chinese or Jewish, typically faced strong discrimination from those already in the United States. We know that all these groups haye made important contributions to the culture, that is not the point. The point is, given the climate of discrimination at different times in the past (and even now), U.S. society does notassimilate new cultural input until much later—after the new imrnigrants are viewed with less prejudice. Let’s move on to another view of U.S. culture.The second view of U.S. culture that we’ll look at today is the multiculturalist view. The multiculturalist view focuses on the many subcultures that make up the U.S. population—all the different ethnic and racial groups we talked about in a previous lecture. Now, each group brought its own distinct culture when it immigrated to the United States. The multiculturalist view does not see U.S. culture as a melting pot; rather, the metaphor that multiculturalists often employ is the patchwork quilt, a bedcover made of numerous pieces of different-colored material. (Have you seen quilts like these on beds?) The metaphor of the patchwork quilt is appropriate in that the multiculturalists see the United States as a mosaic of separate, autonomous subcultures, each one distinct from the other. U.S. culture, in this view, is a sum of the distinct parts, with little or no mixing of subculture. Opponents of this view, those who disagree with it (and there are many wno do) say that the multiculturalist view ignores the characteristic mixing of groups, both ethnic and racial, that has been common in the United States. Americans of European background have always intermarried. Many people are a combination of four or more ethnic backgrounds—and often of more backgrounds than they can keep track of. I do not want to imply thatthe United States has overcome it’s race problems—far from it. But recent census statistics give two indications of somewhat more mixing than previously. First, one in fifteen U.S. marriages is now interracial. An interracial marriage would be any combination of white, black, Asian, and Native American spouses. Admittedly, there are many more marriages between Asians or Native Americans and whites than between blacks and whites. Second, of the 1.6 million children who are adopted, l7 percent make their families multiracial because of the adoption of local children of another race or of children from abroad, especially from Asia or Latin America. Intermarriage and adoption of children of another race make a difference in how people in a family look at themselves. The point here is, the ethnically and racially pure individuals implied by the multiculturalist view are more the exception than the rule. Take, for instance, an African American man married to a Filipina, whose two sons married white woman. Where in the patchwork quilt do the grandchildren of the African American former Supreme Court Justice Thurgood Marshall belong? This is an extreme example, but I think it shows that Marshall’s grandchildren share many subcultures；they do not represent just one square on the quilt. For this reason, many people prefer anotherr more satisfactory, view of U.S. culture.The last cultural view we’ll discuss today, the pluralistic view, is acombination of the first two views. The pluralistic view says that individuals have a number of cultural influences, some of which they share with others and some of which fire different from one person to another. These cultural influences have three distinct sources：we inherit some of our culture from our families；we absorb some of our culture unconsciously from living in the culture (television figures importantly in this unconscious absorption)；And third, we choose some cultural influences that we find attractive from the many subcultures in the United States. In this way, the population shares a large portion of common culture. But people also have individual cultural characteristic that make them different from others. The pluralistic view of culture recognizes the strong role of assimilation, becoming part of the larger group. In assimilation, one becomes part of a larger, dominant culture by accepting much, if not all, of the culture. The pluralistic view differs from the monocultural view in that pluralistic assimilation does not mean that immigrants must deny, their original cultures or that they must forget them. But in all likelihood, immigrants become a little less Mexican, Chinese, or Arab as they assimilate parts of the new culture. Assimilation is not required by the dominant culture, but we do know that it occurs regularly among immigrant groups. If assimilation does not take place in the first generation, it most certainly does by the second or third generation. Opponents of the pluralistic view of culture citeLatinos especially Mexican immigrants, the single largest immigrant group since the 1990s. These opponents say that instead of assimilating as other goups have, Mexicans maintain strong ties to neighboring Mexico through frequent visits home. As a result, opponents fear a fragmentation, or even destruction, of U.S. culture as we know it. On the other hand, proponents of the pluralistic view point out that even Latinos follow the pattern of previous immigrants; indeed, a fifth of Latinos in the United States intermarry. If this seems like a small number, I think we could safely predict higher intermarriage rates in future generations. It would be wrong to assume that the dominant, or common, culture we’ve been speaking about reflects the culture of only one ethnic or racial group that makes up the United States. At the same time, if U. S. society is an open one, as Americans like to believe, it would be hard to deny the changing nature of U.S. culture. It has always reflected the cultures of its immigrants and will likely continue to do so. If we accept this premise, the continuation and possible increase in Latino immigration will change the character of the U.S. culture somewhat. Not as drastically as monoculturalists fear, I think, but a change no doubt will occur. I suspect U.S. culture, to use another metaphor, will continue to seem like the same dish—but it will be a dish with a somewhat Latino flavor in the future. The real test of the future of the United States as a culture may well be whether its cultural idealof tolerance is a reality. Well, I really have taken much more of your time than I should have. Good-bye for now.1.Is the United States an ethnically and racially homogeneoussociety?2.Does the lecturer think U.S. culture is easier or harder tounderstand than the cultures of some other countries?3.Which of the three views of culture is the oldest one?4.In the first subtopic, which groups suffered from discrimination?5.What metaphor for the culture do the multiculturalists use?6.Does the multiculturalist view support the idea of one commonU.S. culture?7.Of the l6 million adopted children, what percentage makes theirfamilies multiracial?8.In what three ways do we get our culture, according to thepluralistic view?9.What do some people fear will result if the large Hispanicimmigration continues in the future？Does the lecturer see the United States as a culture that is open to change or one that is closed to change?。
chapter 7 Pigments and colors(
Chapter 8 Pigments8.1 IntroductionTo understand colorants in foods some terms need to be defined. Color refers to human perception of colored materials---red, green, blue, etc. A colorant is any chemical, either natural or synthetic, that imparts color. Foods have color because of their ability to reflect or emit different quantities of energy at wavelengths able to stimulate the retina in the eye. The energy range to which the eye is sensitive is referred to as visible light. Visible light, depending on an individual’s sensitivity, encompasses wavelengths of approximately 380-370 nm. This range makes up a very small portion of the electromagnetic spectrum. In addition to obvious colors (hues), black, white, and intermediate grays are also regarded as colors.Pigments are natural substances in cells and tissues of plants and animals that impart color. Dyes are any substances that lend color to materials. The term dye is commonly used in the textile industrial. In the U .S. food industry, a dye is a fetid-grade water-soluble colorant certified by the U.S. Food and Drug Administration (FDA). These specific dyes are referred to as “certified colors,” and each one is assigned an FD&C number. The FD&C designation means that the dye may be used in foods, drugs, and cosmetics. Added to the approved list of certified colors are the FD&C lakes. Lakes are dyes extended on a substratum and they are oil dispersible. The dye/substratum combination is achieved by adsorption, coprecipitation, or chemical reaction. The complex involves a salt of a water-soluble primary dye and an approved insoluble base stratum. Alumina is the only approved substratum for preparing FD&C lakes. In addition, there are other dyes or lakes approved for use in other countries, where specifications are established by the European Economic Community (EEC) or the World Health Organization (WHO). Colorants exempt from certification may also be used. These are natural pigments or sunbatance synthesized, but identical to the natural pigment.Color and appearance are major, if not the most important, quality, attributes of foods. It is because of our ability to easily perceive these factors that they are the first to be evaluate by the consumer when purchasing foods. One can provide consumers the most nutrition, safest, and most economical foods, but if they are not attractive, purchase will not occur. The consumer also relates specific colors of foods to quality. Specific colors of fruits are often associated maturity---while redness of raw meat is associated with freshness, a green apple may be judge immature (although some are green when ripe), and brownish-red meat as not fresh.Color also influences flavor perception. The consumer expects red drinks to be strawberry, raspberry, or cherry flavored, yellow to be lemon, and green to be lime flavored. The impact of color on sweetness perception has also been demonstrated. It should also be noted that some substances such as β-carotene or riboflavin are not only colorants but nutrients as well. It is clear therefore that color of foods has multiple effects on consumers, and it is wrong to regard color as being purely' cosmetic.Many food pigments are, unfortunately, unstable during processing and storage. Prevention of undesirable changes is usually difficult or impossible. Depending on the pigment, stability isimpacted by factors such as the presence or absence of light, oxygen, heavy metals, and oxidizing or reducing agents, temperature and water activity, and pH. Because of the instability of pigments, colorants are sometimes added to foods.The purpose of this chapter is to provide an understanding of colorant chemistry---an essential prerequisite for controlling the color and color stability of foods.8.2 Chlorophyll8.2.1 Structure of ChlorophyllsChlorophylls are the major fight harvesting pigments in green plants, algae, and photosynthetic bacteria. Several chlorophylls are found in nature. Their structures differ in the substituents around the pborbin nucleus. Chlorophyll a and b are found in green plants in an approximate ratio of 3:1. They differ in the carbon C-3 substituent. Chlorophyll a contains a methyl group while chlorophyll b contains a formyl groups (Fig. 1). Both chlorophylls have a vinyl and an ethyl group at the C-2 and C 4 position, respectively; a carbomethoxy group at the C- l0 position of the isocylic rings, and a phytol group esterfied to pmpionate at the C-7 position. Phytol is a 20-carbon monounsaturated isoprenoid alcohol. Chlorophyll c is found in association with chlorophyll a in marine algae, dinoflagellates, and diatoms. Chlorophyll d is a minor constituent accompanying chlorophyll a in red algae. Bacteriochlorophylls and chlorobium chlorophylls are principal chlorophylls found in purple photosynthetic bacteria and green sulfur bacteria, respectively.Figure 1 Structure of chlorophyll.8.2.2 Physical CharacteristicsChlorophyll are located in the lamellae of intercellular organelles of green plants known as chloroplasts. They are associated with carotenoids, lipids, and lipoproteins. Weak linkages (noncovalent bonds) exist between these molecules. The bonds are easily broken; hence chlorophylls can be extracted by macerating plant tissue in organic solvents. Various solvents have been used. Polar solvents such as acetone, methanol ethanol, ethyl acetate, pyridine, and dimethylformamide are most effective for complete extraction of chlorophylls. Nonpolar solvents such as hexane or petrolleum ether are less effective. High-performance liquid chromatography (HPLC) today is the method of choice for separating individual chlorophylls and their derivatives. In the case of chlorophyll a and b, for example, the increase in polarity contributed by the C-3 formyl substituent of chlorophyll b causes it to be more strongly adsorbed on a normal-phase column and more weakly absorbed on a reverse-phase column than chlorophyll a.8.2.3 Color Loss during Thermal ProcessingLoss of green color in thermally processed vegetables results from formation of pheophytin and pyropheophytin. Blanching and commercial heat sterilization can reduce chlorophyll content by as much as 80-100%. The greater amount of pheophytin detected in frozen spinach as compared to spinach blanched for canning is most likely attributable to the greater severity of the blanch treatment that is generally applied to vegetables intended for freezing. One of the major reason for blanching of spinach prior to canning is to wilt the tissue and facilitate packaging, whereas blanching prior to freezing must be sufficient not only to wilt the tissue but also to inactivate enzymes. The pigment composition shown for the canned sample indicated that total conversion of chlorophylls to pheophytins and pyropheophytins has occurred.Degradation of chlorophyll within plant tissues postharvest is initiated by heat-reduced decompartmentalization of cellular acids as well as the synthesis of new acids. In vegetables several acids have been identified, including oxalic, malic, citric, acetic, succinic, and pyrrolidone carboxylic acid (PCA). Thermal degradation of glutamine to form PCA is believed to be the major cause of the increase in acidity of vegetables during heating. Other contributors to increased acidity may be fatty acids formed by lipid hydrolysis, hydrogen sulfide liberated from proteins or amino acids, and carbon dioxide from browning reactions.8.2.4 Technology of Color PreservationEfforts to preserve green color in canned vegetables have concentrated on retaining chlorophyll, forming or retaining green derivatives of chlorophyll, that is, chlorophyllides, or creating a more acceptable green color through the formation of metallo complexes.Acid Neutralization to Retain ChlorophyllThe addition of alkalizing agents to canned green vegetables can result in improved retention of chlorophylls during processing. Techniques have involved the addition of calcium oxide andsodium dihydrogen phosphate in blanch water to maintain product pH or to raise the pH to 7.0. Magnesium carbonate or sodium carbonate in combination with sodium phosphate has been tested for this purpose. However, all of these treatments result in softening of the tissue and an alkaline flavor.Blair in 1940 recognized the toughening effect of calcium and magnesium when added to vegetables. This observation led to the use of calcium or magnesium hydroxide for the purpose of raising pH and maintaining texture, This combination of treatments became known as the “Blair process”. Commercial application of these processes has not been successful because of the inability of the alkalizing agents to effectively neutralize interior tissue acids over a long period of time, resulting in substantial color loss after less than 2 months of storage.Another technique involved coating the can interior with ethycellulose and 5% magnesium hydroxide. It was claimed that slow leaching of magnesium oxide from the lining would maintain the pH at or near 8.0 for a longer time and would therefore help stabilize the green color. These efforts were only partially successful, because increasing the pH of canned vegetables can also cause hydrolysis of amides such as glutamine or asparagine with formation of undesirable ammonia-like odors. In addition, fatty acids formed by lipid hydrolysis during high pH blanching may oxidize to form rancid flavors. In peas an elevated pH (8.0 or above) can cause formation of struvite, a glass-like crystals consisting of a magnesium and ammonium phosphate complex. Struvite is believed to result from the reaction of magnesium with ammonium generated from the protein in peas during heating.High-Temperature Short-Time processingCommercially sterilized foods processed at a higher than normal temperature for a relatively short time (HTST) often exhibit better retention of vitamins, flavor and color than do conventionally processed foods. The greater retention of these constituents in HTST foods results because their destruction is more temperature dependent than that for inactivation of Clostridium botulinum spores. Temperature dependence can be expressed in terms of z value or activation energy. The z-value is the change in ºC required to effect a tenfold change in the destruction rate. The large values for both as compared to that for Clostridium botulinum spores (z =10ºC), result in greater color retention when HTST processing is used. However, this advantage of HTST processing is lost after about 2 months of storage, apparently because of a decrease in product pH during storage.Other studies of vegetable tissue have combined HTST processing with pH adjustment. Samples treated in this manner were initially greener and contained more chlorophyll than control samples (typical processing and pH). However, the improvement in color was generally lost during storage.Enzymatic Conversion of Chlorophyll to Chlorophyllides to Retain Green ColorBlanching at lower temperatures than conventionally used to inactivate enzymes has been suggested as a means of achieving better retention of color in green vegetables, in tile belief that the chlorophyllides produced have greater thermal stability than their parent compounds. Early studies showed that when spinach was blanched for canning at 71 ºC (168ºF) for a total of 20 minbetter color retention resulted. This occurred as long as the blanch temperature was maintained between 54ºC (130ºF) and 76ºC (168ºF). It was concluded that the better color of processed spinach blanched under low temperature conditions (65ºC for up to 45 min) was caused by heat-induced conversion of chlorophyll to chlorophyllides by the enzyme chlorophyllase. However, the improvement in color retention achieved by this approach was insufficient to warrant commercialization of the process.Commercial Application of Metallo ComplexCurrent efforts to improve the color of green processed vegetables and to prepare chlorophylls that might be used as food colorants have involved the use of either zinc or copper complexes of chlorophyll derivatives. Copper complexes of pheophytin and pheophorbide are available commercially under the names copper chlorophyll and copper chlorophyllin, respectively. The chlorophyll derivatives cannot be used in foods in the United States. Their use in canned foods, soups, candy, and dairy products is permitted in most European countries under regulatory control of the European Economic Community. The Food and Agriculture Organization (FAO) of the United Nations has certified their use as safe in foods, provided no more than 200 ppm of free ionizable copper is present.Commercial production of the Cu pigments was described by Humphry. Chlorophyll is exacted from dried grass or alfalfa with acetone or chlorinated hydrocarbons. Sufficient water is added, depending on the moisture content of the plant material, to aid penetration of the solvent while avoiding activation of chlorophyllase. Some pheophytin romps spontaneously during extraction. Copper acetate is added to form oil-soluble copper chlorophyll. Alternatively, pheophytin can be acid hydrolyzed before copper ion is added, resulting in formation of water-soluble copper chlorophyllin. The copper complexes have greater stability than comparable Mg complexes; for example, after 25 hr at 25ºC, 97% of the chlorophyll degrades while only 44% of the copper chlorophyll degrades.Regreening of Thermal Processed VegetablesIt has been observed that when vegetables purees ale commercially sterilized, small bright-green areas occasionally appear. It was determined that pigments in the bright green areas contained zinc and copper. This formation of bright-green areas in vegetable purees was termed “regree n ing.” Regreening of commercially processed vegetables has bee n observed when zinc and/or copper ions are present in process solutions. Okra when processed in brine solution containing zinc chloride retains its bright green color, and this is attributed to the formation of zinc complexes of chlorophyll derivatives.8.3 Myoglobin/hemoglobinStructure of Heme CompoundsMyoglobin is a globular protein consisting of a single polypeptide chain. Its molecular mass is 16.8 kD and it is comprised of 153 amino acids. This protein portion of the molecule is known as globin. The chromophore component responsible for light absorption and color is a porphyrin known as heme. Within the porphyrin ring, a centrally located iron atom is complexed with fourtetrapyrrole nitrogen atoms. Thus, myoglobin is a complex of globin and heme. The heme porphyrin is present within a hydrophobic pocket of the globin protein and bound to a histidine residue (Fig. 2). The centrally located iron atom shown possesses six coordination sites, four of which are occupied by the nitrogen atoms within the tetrapyrrole ring. The fifth coordination site is bound by the histidine residue of globin, leaving the sixth site available to complex with electronegative atoms donated by various ligands.Hemoglobin consists of four myoglobins linked together as a tetramer. Hemoglobin, a component of red blood cells, forms reversible complexes with oxygen in the lung. This complex is distributed via the blood to various tissues thv3ughout the animal where oxygen is absorbed. It is the heme group that binds molecular oxygen. Myoglobin within the cellular tissue acts in a similar fashion, accepting the oxygen carried b7 hemoglobin. Myoglobln thus stores oxygen within the tissues, making it available for metabolism.Chemistry and Color—DiscolorationTwo different reactions can cause green discoloration of myoglobin. Hydrogen peroxide can react with either the ferrous or ferric site of heme, resulting in choleglobin, a green-colored pigment. Also, in the presence of hydrogen sulfide and oxygen, green sulfomyoglobin can form. It is thought that hydrogen peroxide and/or hydrogen sulfide arise from bacterial growth. A third mechanisms forr green pigmentation occurs in cured meals and is mentioned later.8.3.1 Cured Meat PigmentsDuring the curing process, specific reactions occur that are responsible for the stable pink color of cured meal products. These reactions are outlined in Fig. 2.Figure 2Myoglobin reactions in fresh and cured meats. ChMb = cholemyglobin (oxidized porphyrin ring); O2Mb = oxymyoglobin (Fe2+); MMb = metmyoglobin (Fe3+); Mb = myoglobin (Fe2+); MMb-NO2= metmyoglobin nitrite; NOMMb = nitrosylmetmyoglobin; NOMb = nitrosylmyoglobin; NMMb = ndrometmyoglobin; NMb = nitromyoglobin, the latter two being reaction products of nitrous acid and the heme portion of the molecule; R = reductant; O = strong oxidizing conditions.The first reaction occurs between nitric oxide (NO) and myoglobin to produce nitric oxide myoglobin (MbNO2). also know as nitrosylmyoglobin MbNO2 is bright red and unstable. Upon heating, the more stable nitric oxide myohemochromogen (nitrosylhemochrome) forms. This product yields the desirable pink color of cured meats. Heating of this pigment denatures globin, but the pink color persists. If metmyogthbin is present, it has been postulated that reducing agents are required to convert metmyoglobin to myoglobin before the reaction with nitric oxide can take place Alternatively, nitrite can interact directly with metmyoglobin, in the presence of excess nitrous acid, nitrimyoglobin (NMb) will form. Upon heating in a reducing environment, NMb is converted to nitrihemin, a green pigment. This series of reactions causes a defect known as “nitrite burn.”In the absence of oxygen, nitric oxide complexes of myoglobin are relatively stable. However, especially under aerobic conditions, these pigments are sensitive to light. If reductants are added, such as ascorbate or sulftlydryl compounds, the reductive conversion of nitrite to nitric oxide is favored. Thus, under these conditions, formation of nitric oxide myoglobin occurs more readily.8.3.2 Stability of Meat PigmentsMany factors operative in a complex food system can influence the stability of meat pigments. In addition, interactions between these factors are critical and make it difficult to determine cause and effect relationships. Some environmental conditions that have important effects on meal color and pigment stability include exposure lo light, temperature, relative humidity, pH, and the presence of specific bacteria.Specific reactions, such as lipid oxidation, are known 1o increase the rate of pigment oxidation. Similarly, color stability can be improved by the addition of antioxidants such as ascorbic acid, vitamin E, butytated hydroxyanisole (BHA), or propyl gallate. These compounds have been shown to delay lipid oxidation and improve retention of color in tissues. Other biochemical factors, such as the rate of oxygen consumption prior to slaughter and activity of metmyoglobin reductase, can influence the color stability of fresh meat.8.4 CarotenoidsCarotenoids are nature's most widespread pigments, with the earth's annual biomass production estimated at 100 million tons. A large majority of these pigments are biosynthesized by the ocean algae population. In higher plants, carotenoids in chloroplasts are often masked by the more dominant chlorophyll pigments. In the autumn season when chloroplasts decompose during plant senescene, the yellow-orange color of carotenoids becomes evident.8.4.1 Structures of CarotenoidsCarotenoids are comprised of two structural groups: the hydrocarbon carotenes and the oxygenated xanthophylls. Oxygenated carotenoids (xanthophylls) consist of a variety ofderivatives frequently containing hydroxyl, epoxy, aldehyde, and keto groups. In addition, fatty acid esters of hydroxylated carotenoids are also widely found in nature. Thus, over 5613 carotenoid structures have been identified and compiled. Furthermore, when geometric isomers of cis (Z) or tranns (E) forms ate considered, a great many more configurations are possible.The basic carotenoid structural backbone consists of isoprene units linked covalently in either a bead-to tail or a tail-to-tail fashion to create a symmetrical molecule (Fig. 4). Other carotenoids are derived from this primary structure of forty carbons. Some structures contain cyclic end groups (β-carotene. Fig. 3) while others possess either one or no cyclization (lycopene, the prominent red pigment in tomatoes) (Fig. 4). Other carotenoids may have shorter carbon skeletons and an known as apocarotenals. Although rules exist for naming and numbering all carotenoids the trivial names ate commonly used and presented in this chapter.Figure 3 Structures of commonly occurring carotenoids. Lutein (yellow) from green leaves, corn, and marigold; zeaxanthin (yellow) from corn and saffron; β-crygtoxanthin (yellow) from corn; β-carotene (yellow) from carrots; β-carotene (yellow) from carrots and sweet potatoes; neoxanthin (yellow) from green leaves; capsanthin (red) from red peppers; violaxanthin (yellow) from green leaveS; and bixin (yellow) from annatto seeds.Figure 4 Joining of isoprenoid units to form lycopene (primary red pigment of tomatoes).8.4.2 Physical PropertiesAll classes of carotenoids (hydrocarbons: carotenes and lycopene, and oxygenated xanthophylls) are lipophilic compounds and thus are soluble in oils and organic solvents. They are moderately heat stable and are subject to loss of color by oxidation. Carotenoids can be easily isomerized by heat, acid, or light. Since they range in color from yellow to red, detection wavelengths for monitoring carotenoids typically range from approximately 430 to 480 nm. The higher wavelengths are usually used for some xanthophylls to prevent interference from chlorophylls, Many carotenoids exhibit spectral shifts after reaction with various reagents, and these spectral changes are useful to assist in identification.8.4.3 Stability during ProcessingCarotenoids are relatively stable during typical storage and handling of most fruits and vegetables. Freezing causes little change in carotene content. However, blanching is known to influence the level of carotenoids. Often blanched plant products exhibit an apparent increase in carotenoids content relative to raw tissues. This is caused by inactivation of lipoxygenase, which is known to catalyze oxidative decomposition of carotenoids, the loss of soluble constituents into the blanch water, or the mild heat treatments traditionally used during blanching may enhance the efficiency of extraction of the pigments relative to fresh tissue. Lye peeling, which is commonly used for sweet potatoes, causes little destruction or isomerization of carotenoids.Although carotene historically has been regarded as fairly stable during heating, it is now known that heat sterilization induces cis/trans isomerization reactions as shown in Figure 5. To lessen excessive isomerization, the severity of thermal treatments should be minimized whenpossible. In the case of extrusion cooking and high-temperature heating in oils, not only will carotenoids isomerize but thermal de gradation will also occur. Very high temperatures can yield fr agmentation products that are volatile. Prod0cts arising from severe heating of β-carotene in the presence of air are similar to those arising from severe heating of β-carotene oxidation (Fig. 5). In contrast, air dehydration exposes carotenoids to oxygen, which can cause extensive degradation of carotenoids. Dehydrated products that have large surface to-mass ratios, such as camel or sweet potato flakes, are especially susceptible to oxidative decomposition during drying and storage in air.Figure 5 Degradation of all-trans-β-carotene.8.5 Flavonoids and Other Phenols8.5.1 AnthocyaninsPhenolic compounds comprise a large group of organic substances, and flavonoids are an important subgroup. The flavonoid subgroup contains the anthocyanins, one of the most broadly distributed pigment groups in the plant world. Anthocyanins are responsible for a wide range of colors in plants, including blue, purple, violet, magenta, red, and orange.Anthocyanins are considered flavonoids because of the characteristic C6C3C6 carbon skeleton. The basic chemical structure of the flavonoid group and the relationship to antbocyanin are shown in Figure 6. Within each group there are many different compounds with their color depending on the substituents on rings A and B.When the sugar moiety of an antbocyanin is hydrolyzed, the aglycone (the nonsugar hydrolysis product) is referred to as an antbocyanidin. The color of antbocyanins and antbocyanidins results from excitation of a molecule by visible light. The ease with which aFigure 6 Carbon skeleton of the flavonoid group.Figure 7 Most common anthocyanidins in foods, arranged in increasing redness and blueness.molecule is excited depends on the relative electron mobility in the structure. Double bonds, which are abundant in anthocyanins and anthocyanidins, are excited very easily, and their presence is essential for color. Antbocyanins occurring in nature contain several anthocyanidins, but only six occur commonly in foods (Figure 7). It should be noted that increasing substitution on tile molecule results in a deeper hue. The deepening of hue is the result of a bathochromic change (longer wavelength), which means that the light absorption band in the visible spectrum shifts from violet through red to blue. An opposite change is referred to as a hypsochromic shift. Bathochromic effects are caused by auxochrome groups, groups that by themselves have no chromophoric properties but cause deepening in the hue when attached to the molecule. Auxochmme groups are electron-donating groups, and in the case of anthocyanidins they are the hydroxyl and methoxy groups. The methoxy groups, because their electron-donating capacity is greater than that of hydroxyl groups, cause a greater bathochromic shift than do hydroxyl groups. The effect of the number of methoxy groups on redness is illustrated in Figure 7. In anthocyanin, several other factors, such as change in pH, metal complex formation, and copigmentation, cause changes in hue.Metal complexes of anthocyanin are common in the plant world and they extend the colorspectrum of flowers. Coated metal cans have long beenfound to be essential for retaining typical colors of anthocyanins of fruits and vegetables during sterilization in metal cans. Anthocyanins with vicinal, phenolic hydroxyl groups can sequester several multivalent metals. Complexation produces a bathochromic shift toward the blue. Addition of AlCl3to anthocyanin solutions has been used as an analytical tool to differentiate cyanidin, petunidin, and delphinidin from pelargonidin, peonidin, and malvidin. The latter group of anthocyanidins does not possess vicinal phenolic hydroxyls and will not react with Al3+(Fig. 7). Some studies have shown that metal complexation stabilizes the color of anthocyanin-containing folds. Ca, Fe, Al, and Sn have been shown to offer some protection to anthocyanins in cranberry juice; however, the blue and brown discoloration produced by tannin-metal complexes negates any beneficial effect.A fruit discoloration problem referred to a s “pink in g” has been a ttributed to formation of metal anthocynin complexes. This type of discoloration has been reported in pears peaches, and lychees. It is generally believed that pinking is caused by heat induced conversion of colorless proanthocyanidins to anthocyanins under acid conditions, followed by complex formation with metals.8.5.2 Other FlavonoidsAnthocyanins, as previously mentioned, are the most prevalent flavonoids. Although most yellow colors in food are attributable to the presence of carotenoids, some are attributable to the presence of nonanthocyanin-type flavonoids, in addition, flavonoids also account for some of the whiteness of plant materials, and the oxidation products of those containing phenolic groups contribute to the browns and blacks found in nature. The term anthoxanthin is also sometimes used to designate certain groups of yellow flavonoids. Differences among classes of flavonoids relate to the state of oxidation of the 3-carbon link. Structures commonly found in nature vary from flavan-3-ols (catechin) to flavonols (3-hydroxyflavones) and anthocyanins. The flavonoids also include flavanone, flavononols or fiihydroflavonol, and flavan-3,4-diols (proanthocyanidin). In addition, there are five classes of compounds that do not possess the basic flavonoid skeleton, but are chemically related, and therefore are generally included in the flavonoid group. These are the dihydrochalcones, chalcones, isoflavones, neoflavones, and aurones. Individual compounds within this group are distinguished, as with anthocyanins, by the number of hydroxyl, methoxyl, and other subslituents on the two benzene rings. Many flavonoid compounds carry a name related to the first source from which they were isolated, rather than being named according to the substiluems of the respective aglycone. This inconsistent nomenclature has brought about confusion in assigning compounds to various classes.Physical PropertiesThe light absorption characteristics of flavonoid classes clearly demonstrates the relationship of color and unsaturation within a molecule and the impact of auxochromes (groups present in a molecule which deepens the color). In the hydroxyl-substituted flavons catechin and proanthocyanin, the unsaturation is interrupted between the two benzene rings, and therefore, the light absorption is similar to that of phenols, which exhibit maximum light absorption between 275 and 230 nm (Fig. 8a). In the flavanone naringenin, the hydroxyl groups only occur in conjunction with the carbonyl group at C-4 and therefore do not exert their auxochromic。
专业英语
questions
How
do you distinguish steel from cast iron? How do you distinguish low alloy steel from high alloy steel?
1.1.1 Iron and Steel
The earth contains a large number of metals which are useful to man. One of the most important of these is iron. Modern industry needs considerable quantities of this metal, either in the form of iron or in the form of steel.
Mechanical Engineering materials
Organic polymer materials Inorganic non-metallic materials
plastic rubber Synthetic Fibers Traditional ceramics Special Ceramics Metal Matrix Composites
1.1.1 Iron and Steel
The ore becomes molten, and its oxides combine with carbon from the coke. The non-metallic constituents of the ore combine with the limestone to form a liquid slag. This floats on top of the molten iron, and passed out of the furnace through a tap. The metal which remains is pig iron.
专业英语
Definition of polymers A simple understanding of polymers can be gained by imaging them to be like a chain or, perhaps, a string of pearls, where the individual pearl represent small molecules that are chemically bonded together. Therefore, a polymer is a molecule made up of smaller molecules that are joined together by chemical bonds. The word polymer means „many parts or units.‟ The parts or units are the small molecules that combine. The result of the combination is, of course, a chainlike molecule (polymer). Usually the polymer chains are long, often consisting of hundreds of units, but polymers consisting of only a few units linked together are also known and can be commercially valuable.
Figure 1.1 Diagram illustrating the definition of plastics.
As Figure 1.1 shows, all materials can be classified as gases, simple liquids, or solids, with the understanding that most materials can be converted from one state to another through heating or cooling. If only materials that are structural solids at normal temperatures are examined, three major types of materials are encountered: metals, polymers, and ceramics. The polymer materials can be further divided into synthetic polymers and natural polymers. Most synthetic polymers are those that do not occur naturally and are represented by materials such as nylon, polyethylene, and polyester. Some synthetic polymers could be manufactured copies of naturally occurring materials (such as
Unit 7
Unit 7Long-term Assets7.1 plant and equipmentThe term plant and equipment is used to describe long-term assets acquired for use in the operation of the business and not intended for resale to customers.Among the more common examples are land,buildings,machinery,furniture and fixtures,office equipment,and automobiles.1.The term of plant and equipmentThe term fixed assets or plant assets has been used in accounting literature to describe all types of plant and equipment.This term,however,has virtually disappeared from the published financial statements of large corporations.Plant and equipment appear to be a more descriptive term. Another alternative term used on many corporation balance sheets is property,plant,and equipment.It is convenient to think of a plant and equipment as a stream of services to be received by the owner over a period of years.2.Major categories of plant and equipmentPlant and equipment items are often classified into the following groups:Tangible plant assetsThe term tangible plant assets denote physical substances,as exemplified by land,a buiding,ora machine.This category may be subdivided into two distinct classifications:(1)Plant property subject to depreciation.Assets are plant assets of limited useful life suchas buildings and office equipment.(2)Land.The only plant asset not subject to depreciation is land,which has an unlimited termof existence.Natural ResourcesTimber,fossil,mineral deposits,and other natural resources are different form depreciable assets because they are physically extracted during company operations and they are replaceable only through natural processes.Intangible AssetsThe term intangible assets are used to describe assets which are used in the operation of the business but no physical substance,and are non-current.Current assets such as accounts receivable or prepaid rent are not included in the intangible classification,even though they are lacking in physical substance.The intangible assets will be separately discussed in the later part.3.The cost of plant and equipmentThe cost of plant and equipment includes all expenditures reasonable and necessary in acquiring the asset and placing it in a position and condition for use in operation of the business.Assets Purchased for cashCost is most easily determined when an asset is purchased for cash.The cost of the asset is then equal to the cash outlay necessary in acquiring the asset plus any expenditure for freight,insurance while in transit,installation,and any other cost necessary to make the asset ready for use.Assets Acquired by exchangeAssets are frequently acquired by trading in an existing asset as partial or complete payment for a new asset.The cost amount of the new asset is the money amount of the resourcesgiven up to acquire it.The resources “given up”in this case include s non-monetary asset.Determination of the cost of the new asset depends upon the measurement of the money amount of the asset traded in.The AICPA in Opinion NO.29 recommended that “Acco unting for non-monetary transactions should be based upon the fair values of the assets (or services)involved,which is the same as that used in monetary transactions.”This recommendation is based upon an assumption that where a non-monetary asset is exchanged for another,two separate transactions occur.The traded asset is realized for cash at its fair market price and the proceeds are used to acquire the new asset.The Opinion thus interprets the money amount of the traded asset as the price for which it could be sold in a normal arm’s-length transaction.This amount is referred to as the asset’s fair market value.Donated AssetsIn some circumstances,assets may be donated to a firm.For example,to stimulate investment in a depressed area,a local council may donate land to firms which commence operations in the area.Under these circumstances,the donated assets belong to the firm’s assets.When the plant and equipment is acquired as a donation,the cost of the plant and equipment is equal to its fair market value.Self-constructed AssetsMany assets are constructed by the owner rather than acquired by purchase or exchange.The cost of self-constructed assets is the money amounts of resources embodied in asset.The amount of direct materials,direct labor,and variable overhead is clearly part of the cost of constructing assets and there is no dispute about their inclusion in the amount.Interest cost incurred during the construction period is viewed as part of the cost of the asset.4.Capital Expenditures and revenue expendituresExpenditures for the purchase or expansion of long-term are called capital expenditures and are recorded in asset accounts.Expenditures for ordinary repairs,maintenance,fuel,and other items necessary to the ownership and use of plant and equipment are called revenue expenditures and recorded by debits to expense accounts.The charge to an expense account is based on the assumption that the benefits from the expenditures will be used up in the current period,and the cost should therefore be deducted from the revenue of the current period in determining the net income.A careful distinction between capital and revenue expenditures is essential to attainment ofone of the most fundamental objectives of accounting-the determination of net income for each year of operation of a business.A capital expenditure is recorded by debiting an asset account;the transaction has no immediate effect upon net income.Revenue expenditures,on the other hand,are recorded by debiting an expense account and therefore represent an immediate deduction from earnings in the current period.7.2 DepreciationA business entity will often incur expenditures to acquire long-term assets for operationalpurposes.These expenditures can be viewed as long-term prepayments of expenses.As the assets are used for used for their intended purposes,utility decreases.There should be a systematic and periodic allocation of the cost associated with the acquisition of assets that corresponds to the decrease in untility and matches expenses with revenues.This cost allocation process is depreciation of capital assets the periodic revenue earned.1.Nature of depreciationIt is important to understand that depreciation is a method of cost allocation,not asset valuation.The cost of a capital asset less estimated salvage value is allocated over its estimated useful life.In accordance with the matching principle,the recording of depreciation allocates the cost of the asset to the accounting periods that benefit from the asset’s use.The total amount of depreciation expense is recorede in the contra-asset account called Accumulated Depreciation.Because the pattern by which a firm uses up its depreciable assets is not readily observable,any allocation method can be defended so long as it is rational and systematic.2.Factors Affecting DepreciationFour factors that influence depreciation are cost of the asset,estimated residual value(or salvage value),estimated service life,and depreciation methods.The cost of the asset is determined by the cash or cash-equivalent price paid to acquire the asset.There may be many cost components incurred to acquire and prepare the asset for its inended useThe estimated esidual value of the asset is an estimate of the net realizable value of the asset to an enterpri se at the end of the asset’s estimated service life.The estimated service life of the asset is the number of years that the asset economically capable of performing its intended service.3.Depreciation MethodsThe most common methods of depreciation are the straight-line method;the units-of-production method and accelerated methods.Straight-line MethodThe straight-line method of depreciation allocates equal amounts of the cost of an asset to each accounting period during its estimated life.This method is most common method used to allocate the cost of property,plant and equipment among accounting periods because it is easy and simple to calculate.A typical example would be depreciation for a building or for office furniture.The depreciation is computed as follows:Depreciation per year=(Cost-Estimated Residual Value)/(Service Life in Years)Annual rate of depreciation=1/Service Life in YearsOn the balance sheet,accumulated depreciation is deducted from the cost of property,plant,and the difference called the book value(property,plant,and equipment)is in total assets.Units-of-production MethodThe units-of-production method allocates the cost of an asset to usage rather than years.This method amortizes the cost of the asset over the estimated service life as measured by estimated untis of production,not by estimated years.If the use of the asset varies and the contribution to revenue differs from period,the units-of-production method may be appropriate.The depreciation per unit of production is determined as follows:Depreciation cost per unit=(Cost-Residual Value)/(Estimated units of production)Depreciation expense for period=( Depreciation cost per unit*Actual productionamount during current period)Note that the strainght-line method provides a constant depreciation amount per year,but the units-of-production method provides a constant amount per unit of production.Accelerated MethodsAccelerated methods charge higher amounts of depreciation to the earlier years of an asset’slife.As an asset has greater economic benefit in the earlier years of its life than in the later years,depreciation should be allocated more in the early years of the asset’s life,and the amount of depreciation charged period declines with time.An increase in repairs and maintenance costs and a decrease in revenue-producing ability in the later years of an asset’s useful life suggest that accelerated methods better match revenues and expenses.Two common methods for allocating depreciation on an accelerated basis are declining-balance method and sum-of-the-year’s-digits method.1)Declining-balance MethodThe declining-balance method should be used for assets that are expected to benefit earlier periods of the asset’s useful life more than later periods.The most common v ersion of the declining-balance method is the double-declining-balance(DDB)method.The DDB rate is twice the rate used for the strdight-line method and is calculated as:DDB rate=2/NN=useful life in yearsDepreciation expense is calculated as follows:Depreciation expense=DDB rate*Book values=DDB rate*(cost of asset-accumulated depreciation)Book value represents the cost of the asset minus the accumulated depreciation.It declines at a faster rate during the early years of the asset when using the double-declining-balance method than it does using the straight-line method in each accounting period.It ignores estimated salvage when computing depreciation.The amount of depreciation calculated(twice the straight-line rate book value)may have to be adjusted in the last two periods so as not to amortize the asset beyond its residual value.2)Sum-of-the-year’s-digits Method (SYD)The sum-of-the-year’s-digits method results in a decreasing depreciation expense based on a decreasing fraction of depreciable cost (original cost less residual value).Each fraction uses the sum of the years as a denominator and the number of years of estimated life remaining as of the beginning of the year as a numerator.It calculates depreciation expense by applying a rate to the asset’s depreciable amount.The rate is determined by using the following formulas:Annual depreciation expense=(cost-residual amount)*SYD rateSYD rate=(Number of Year of Useful Life at Beginning of Year)/(The Su m of the Year’s Digits)It this method,the numerator decreases year by year and the denominator remain constant.At the end of the asset’s useful life,the balance remaining should be equal to the residual value.7.3 Intangible AssetsIntangible assets are assets that are used in the operation of the business but have no physical substance.Intangible assets with indefinite useful lives.Various intangible assets are described as follows:(1)PatentsPatents are granted by the government,and convey the exclusive right to use a product or process for a period of certain years.(2)CopyrightsCopyrights are also granted by the government,and convey the exclusive right to use artistic or literary works for a period of certain years beyond the author’s mon examples of works that can be copyrighted include books,songs,and movies.The economic life of a copyrightmay be considerably shorter than its legal life.(3)TrademarksTrademarks are works,symbols,or other distinctive elements used to identify a particular firm’s products.(4)Franchises and licensesFranchises and licenses are rights to market a particular product or service or to engage in a particular activity.For example,Pizza Hut sells franchises to various individuals and businesses.A franchise permits the holder to operate a Pizza Hut restaurant at a specified location.This right has economic value to the holder and would be reflected as an asset.1.Acquisition of Intangible AssetsIntangible assets may be acquired from others or by the compa ny’s own research and development.If purchased externally,intangible assets should be initially recorded at their historical cost.The cost includes the acquisition cost (purchase price)and any legal fee.Many firms internally develop new products,as opposed to purchasing patents from others.Because large expenditures can be made without the assurance of ultimate success,this strategy is more risky,substantial uncertainty exists regarding future economic benefits.So GAAP requires that all research and development costs be expensed immediately.Research and development costs are those incurred to generate new knowledge or to translate knowledge into a new product or process.Most countries follow the practive of immediately expensing these costs.Special accounting rules exist for software development costs.For a given project,these costs are expensed until technological feasibility is demonstrated,and costs incurred after that point are capitalized.2.Amortization of Intangible AssetsThe term amortization is used to describe the write-off expense of the cost of an intangible asset over its useful life.The amortization of limited-useful-life intangible assets is essentially are same process as the depreciation of tangible assets.It also needs to consider the useful life of assets and amortization method.If the useful life is limited by agreement or by law(e.g.17 years for a patent),the amortization period cannot be longer.It may be shorter if company believes that because of technological advances or other reasons,the practical life will be shorter than the legal life.The method of amortization should reflect the pattern in which the economic benefits of the intangible asset are consumed or otherwise used up.However,if that pattern cannot be reliably determined,a straight-line amortization method will be used.Also,amortization of an intangible asset is usually credited directly to the intangible asset account rather than being accumulated in a separate contra-asset account,as is the case with accumulated depreciation.Intangibles assets with indefinite useful lives,such as a renewable broadcasting license,are not amortized.Rather,they are subjected to periodic impairment tests.If it is determined that sure an intangible asset is impaired,its carrying value is written down to its realizable value and a charge equal to the write-down is made to income.3.GoodwillAccording to accounting guidelines,intangible assets are not owned or controlled enterprises kindidentifiable non-monetary assets.Therefore,the goodwill cannot be identified because of its nature,the new guidelines will be separated from and independent of intangible assets is recognized as an asset.When one company buys another company,the purchasing company may pay more for the acquired company than the fair value of its net identifiable assets.The amount by which the purchase price exceeds the fair value of the net assets is recorded as an asset of the acquiring company.It is important to note that goodwill arises only as part of a purchase transaction.The buying company may be willing to pay more than the fair value of the acquired net assets other than goodwill because the acquired company has a strong management team,a favorable reputation in the marketplace,superior production methods,or other unidentifiable intangible things.The acquisition cost of the recognized assets other than goodwill is their fair value at the time of ually,these values are determined by appraisal.Goodwill cannot be amortized under any circumstances.It must be subjected to an annual impairment test.Any write-down due to impairment is charged to income.单元7长期资产7.1 工厂和设备词厂房和设备用来描述长期资产收购业务的运作在使用和不拟转售给客户。
Part 1 Chapter 7_3
Part 1 Chapter 7THE OFFICIALS OF THE COURT.At last Matthew Nikitich also arrived, and the usher, a thin man, with a long neck and a kind of sideways walk, his nether lip protruding to one side, which made him resemble a turkey, came into the jurymen's room.This usher was an honest man, and had a university education, but could not keep a place for any length of time, as he was subject to fits of drunkenness. Three months before a certain countess, who patronised his wife, had found him this place, and he was very pleased to have kept it so long."Well, sirs, is everybody here?" he asked, putting his pince-nez on his nose, and looking round."Everybody, I think," said the jolly merchant."All right; we'll soon see." And, taking a list from his pocket, he began calling out the names, looking at the men, sometimes through and sometimes over his pince-nez."Councillor of State, [grades such as this are common in Russia, and mean very little] J. M. Nikiforoff!""I am he," said the dignified-looking man, well versed in the habits of the law court."Ivan Semionovitch Ivanoff, retired colonel!""Here!" replied a thin man, in the uniform of a retired officer."Merchant of the Second Guild, Peter Baklasheff!""Here we are, ready!" said the good-humoured merchant, with a broad smile."Lieutenant of the Guards, Prince Dmitri Nekhludoff!" "I am he," answered Nekhludoff.The usher bowed to him, looking over his pince-nez, politely and pleasantly, as if wishing to distinguish him from the others."Captain Youri Demitrievitch-Dantchenko, merchant; Grigori Euphimitch Kouleshoff," etc. All but two were present. "Now please to come to the court, gentlemen," said the usher, pointing to the door, with an amiable wave of his hand.All moved towards the door, pausing to let each other pass. Then they went through the corridor into the court.The court was a large, long room. At one end there was a raised platform, with three steps leading up to it, on which stood a table, covered with a green cloth trimmed with a fringe of a darker shade. At the table were placed three arm-chairs, with high-carved oak backs; on the wall behind them hung a full-length, brightly-coloured portrait of the Emperor inuniform and ribbon, with one foot in advance, and holding a sword. In the right corner hung a case, with an image of Christ crowned with thorns, and beneath it stood a lectern, and on the same side the prosecuting attorney's desk. On the left, opposite the desk, was the secretary's table, and in front of it, nearer the public, an oak grating, with the prisoners' bench, as yet unoccupied, behind it. Besides all this, there were on the right side of the platform high-backed ashwood chairs for the jury, and on the floor below tables for the advocates. All this was in the front part of the court, divided from the back by a grating.The back was all taken up by seats in tiers. Sitting on the front seats were four women, either servant or factory girls, and two working men, evidently overawed by the grandeur of the room, and not venturing to speak above a whisper.Soon after the jury had come in the usher entered, with his sideward gait, and stepping to the front, called out in a loud voice, as if he meant to frighten those present, "The Court is coming!" Every one got up as the members stepped on to the platform. Among them the president, with his muscles and fine whiskers. Next came the gloomy member of the Court, who was now more gloomy than ever, having met his brother-in-law, who informed him that he had just called in to see his sister (the member's wife), and that she had told him that there would be no dinner there."So that, evidently, we shall have to call in at a cook shop," the brother-in-law added, laughing."It is not at all funny," said the gloomy member, and became gloomier still.Then at last came the third member of the Court, the sameMatthew Nikitich, who was always late. He was a bearded man, with large, round, kindly eyes. He was suffering from a catarrh of the stomach, and, according to his doctor's advice, he had begun trying a new treatment, and this had kept him at home longer than usual. Now, as he was ascending the platform, he had a pensive air. He was in the habit of making guesses in answer to all sorts of self-put questions by different curious means. Just now he had asked whether the new treatment would be beneficial, and had decided that it would cure his catarrh if the number of steps from the door to his chair would divide by three. He made 26 steps, but managed to get in a 27th just by his chair.The figures of the president and the members in their uniforms, with gold-embroidered collars, looked very imposing. They seemed to feel this themselves, and, as if overpowered bytheir own grandeur, hurriedly sat down on the high backed chairs behind the table with the green cloth, on which were a triangular article with an eagle at the top, two glass vases--something like those in which sweetmeats are kept in refreshment rooms--an inkstand, pens, clean paper, and good, newly-cut pencils of different kinds.The public prosecutor came in with the judges. With his portfolio under one arm, and swinging the other, he hurriedly walked to his seat near the window, and was instantly absorbed in reading and looking through the papers, not wasting a single moment, in hope of being ready when the business commenced. He had been public prosecutor but a short time, and had only prosecuted four times before this. He was very ambitious, and had firmly made up his mind to get on, and therefore thought it necessary to get a conviction whenever he prosecuted. He knewthe chief facts of the poisoning case, and had already formed a plan of action. He only wanted to copy out a few points which he required.The secretary sat on the opposite side of the platform, and, having got ready all the papers he might want, was looking through an article, prohibited by the censor, which he had procured and read the day before. He was anxious to have a talk about this article with the bearded member, who shared his views, but wanted to look through it once more before doing so.玛特维终于来了。
商务英语chapter 7
Quantity
9
Could you cite some closest examples of pure competition? Suppose you are a manager of a firm in an purely competitive market, what measures will you take to compete with other competitors?
Many
Many Homogeneous Free entry Perfect 25 Information
3. Products No close substitute nature 4. Ease of entry
availability Forbidden
5. Information Restricted
Chapter 7
Market Structure
1
Concept Tour
Market
Market Structure
Perfect/Pure Competition Imperfey
Monopolistic Competition
2
What is a “MARKET” ?
10
Four Features: 1. Large No. of Buyers & Sellers 2. Differentiated Products 3. Free Entry & Exit 4. Imperfect Market Information
11
Product Differentiation A firm can use product differentiation to promote sales.
新编英语教程7style and purpose randolph quirk
Part of the intricacy of co-ordination in using language lies, as we saw in the previous chapter, in the different constraints operating in speech and writing. But, as we know well, the constrains do not fall neatly into a twofold division, ‘speaking’versus ‘writing’. The stylistic range of English is wide and ultimately the gradations are infinite. When we are putting words together, we have to see that they are congruous with the expectations at some point on this scale and that they are arranged according to the conventions of collocation and grammar-with the reference to the same point on the scale.It may seem paradoxical to lay such stress on being conventional in the use of English when we may well fell that the big prizes to go to people who are so unconventional in their English. It is by no means certain that the big prize are so awarded, but whatever our opinion of this, there seems to be a general agreement that cries of ‘look, mother: no hands!’are especially unimpressive when we have still not properly mastered the art of cycling in the conventions manner. Before trying to write like Gertrude Stein, we have to school ourselves to observe and to use English within the strictest conventions – and we have support in this from the words of Mr Robert gravees6 quoted in the last chapter.Without a norm, it is difficult to recognize or practice originality. You may have sampled a variety of ice-cream which has little bits of crystallized ginger in it, and you may have come across it being marketed with the rather fetching gimmick, ‘fre ezing hot ice-cream’. Here is a case where a departure from conventional collocation is very effective. The title of noel coward’s play, bitter sweet, is a better known example, and most of us have at some time been amuses by hoary witticisms like ‘the hand that rocked the cradle has kicked the bucket’. In all these examples, we are recognize that ‘bitter’ and ‘sweet’ are mutually exclusive and not normally collocable that the junction of them can be effective,. The effectiveness of ‘freezing hot ice-cream’ depends on the tension that is set up between this and the normal collocations of ‘freezing’and ‘hot’(such as ‘freezing cold’ and ‘boiling hot’).The order of events in our strategy, then, must be first to observe the conventional arrangements and the points to which they belong in the stylistic range: again, it is necessary to insist on the central importance of keeping in line with actual usage. We observe that if people we expect begin a letter ‘dear Mr. Jones’, they will close it with ‘yours sincerely’, but that if they begin a letter with ‘dear sir’, they will end with ‘your faithfully’. Experienced and well-educated people will not mix these formulas-and they tend to think poor of those who do. And, of course, it is not merely the beginnings and endings that are not mixed: the type of the grammatical construction and selection of words- the whole style- will tend to be different (and consistently so) in the type of letter.It is true that many enlightened business firms have now give up the sillier, stiffer formalities that use to spoil commercial letter(expressions like ‘further to yours of the 23rd ult’): but a shapely sense of formality remains. The letter to or form a business firm or government department will now say (after the ‘dear sir’) something like ‘I n reply to you letter of 23rd June’ it will not begin with the informal and imprecise words, ‘thank you for your recent letter’, which are more suitable for one beginning with ‘dear Mr. Jones’. Needless to say, they are other expressions that are appropriate to other types of letters on the scale which runs from distant formality (especially in dealing with an organization, when personalities matter are kept in the background) to the completely familiar and intimate (where personalities matter as much as anything): ‘my dear frank, it was awfully nice to get your note the other day.’In each case, the experienced letter-writteradopts a style fitted to the degree of formality that his letter requires and maintains that style consistently throughout. He will not say, ‘my regards to your wife’ in a dear sir letter, and he will not end with ‘cheerio for now’ in a dear Mr. Jones letter.This must take us back to what was said in the previous chapter about expected collocations. Frequent and thoroughly expected collations (like ‘freezing cold’) are most apt to strike us as clichés when they are used on occasions which lead us to expect relatively high precision and low redundancy. As so often in mattes of language, it is not usually a question of whether a given expression out of context is or is not a cliché. If we are strolling during an interval at the theatre and our companion says, ‘I admired Pinter’s incredible insight in the act’, we may not feel any of that constitutes reaction to a cliché. Indeed, we can imagine many informal contexts of situation in which ‘incredible insight’, so far from being a cliché, might sound rather high-flown and technical: everything depends on what is expected at particular points in the stylistic range. But if ‘incredible insight’ is acceptable when used in criticism that is spoken on an informal occasion, it dose not mean that these words are equally acceptable in the written criticism of a formal kind.All too frequently we tend to pick up the collocations of the most commonly heard criticism and then to use them indiscriminately, without realizing how empty they seem in a setting where precision is expected. In a set of essays written by an undergraduate class recently, it appeared that the following are among the commonest collocations which must be branded as cliché in serious commentary on literature;Lofty flights of imagination; inimitable narrative technique; organic unity; consummate skill; consummate art; heights of majesty; heights of tragedy; inherent atmosphere; essential atmosphere; inherent appeal; essential appeal; essential characteristics.And this is to ignore expressions which descend from the hackneyed to the tautologous, like ‘basic fundamentals’! We must develop the critical awareness to recognize that such expressions, which may impress the inexperienced, are largely automatic, neither reflecting any precision in our judgment as we write them nor conveying any precise information to the reader. The reader may in fact conclude that the writer is incapable of judgment and is trying to deceive with a show of verbiage: a conclusion which may well be completely just in many cases. The use of cliché in essay-writing is often accompanied by a woolliness of expression which confirm the impression that no hard thinking has ever take place: ‘his verse is packed with special meaning’; ‘his poems have a character all their own’; ‘he paints the very body and soul of English industrial life’; ‘he decorative imagery always follow a structural line ’. do these reflect laziness or the will to deceive.。
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Secure link threads Threads
Buttress thread (B) threads for transmission Trapezoidal thread (Tr)
(2) Thread marks (a) marks of metric threads
Type symbol
(4) Representation of thread tooth profile
4. Types and marks of threads (1) Types and of threads
Coarse pitch thread Metric threads (M) Pipe threads Fine pitch thread Sealing pipe thread (Rc, Rp） Non Sealing pipe thread(G)
0.15d 45
×
2d
0.7d
l
d
2d
°
(3) Drawing methods of washers
0.15d 0.25d 1.5d 2.2d
70°
1.1d
(4) Drawing methods of screws
0.25d 0.25d 0.6d d 1.5d 0.2d 0.2d
0.5d
d
0.15d
Thread symbol ：
Type symbol Nominal diameter × Lead (Ｐpitch ) Revolving direction (blank for medium)
7.1.2 Screw fasteners
1. Types of screw fasteners
2. Symbol of screw fasteners
1. Drawing methods of bolt assembly (1) The assembly procedure of the bolt assembly
The bolt assembly is used when joint parts are not too thick to drill through holes.
(5) Drawing methods of studs
0.15d 45° ×
d
2d L1 L
0.15d 45° ×
7.1.3 Drawing methods of assembly of Screw fasteners
The contact surface of two parts is represented as a line, while the non- contact surface is represented as two lines. When two joint parts are cut, the directions of their section lines shall be reversed. when a section face cuts the bolts, nuts, screws and washer axes, these fastening parts are not drawn according to section drawing, but still following their outlines.
(3) Assembly of Internal and External threads
In the section view of a thread joint, the joint portion is drawn according to the description of the external thread, and the rest is drawn following their respective description. The major and minor diameter lines of Internal and External threads must be aligned accordingly.
(2) Thread diameter
Thread profile
Minor diameter Crest
Major diameter
Root
Root
Crest
The major diameter is the diameter of the column which passes the crest of the external thread or the root of the internal thread. External thread diameters are indicated with lowercase letter, while internal thread diameters are indicated with capital letter. The minor diameter is the diameter of the column which passes the root of the external thread or the crest of the internal thread, which is indicated with d1、D1.
Manufacturing Methods
2. Thread elements
(1)Thread tooth profile The outline of the thread section
cutting through the thread axis shows the Thread tooth profile.
120°
The thread depth The depth of the drilled hole 0nly 3/4 circle
Find out each errors in the following figures and draw the correct views .
Find out each errors in the following figures and draw the correct views .
1.Thread manufacturing
Threads are continuous protrusions or grooves found along a spiral line on a revolving component with the same cross section.
Threads on an external surface are called external Threads. Threads on an internal surface are called internal Threads.
2. Drawing methods of stud assembly
(1) The assembly procedure of the stud assembly
If one of the connected pieces is too thick, or in case the bolt fastening is not suitable or the connected pieces need be taken apart frequently, then the studs are used.
Nominal Pitch (blank for Revolving － Central diameter tol× coarse tooth) diameter direction erance zone symbol
Major diameter tol- －Symbol of joint length (blank for medium erance zone symbol
Major diame 3/4 circle The vanishing of thread
(2) Internal threads
The major diameter is drawn in thin solid lines The minor diameter is drawn in thin solid lines
A
Joint length
0.5d 0.5d
The thread depth
The depth of the drilled hole
When the section passes the axis of the solid pole, the thread is A not cut and only its outline is drawn.
3. Proportional drawing methods of screw fasteners
(1) Drawing methods of a hexagon nut
R Determining by construct 0.8D D 2D 30°
(2) Drawing methods of a hexagon head bolt
(5) Pitch (P) and Lead (S)
The axial distance between two points of adjacent teeth on the central diameter line is called thread pitch. The axial distance between two points of adjacent teeth of the same spiral line on the central diameter line is called lead.
(3) Revolving direction
(a) Thread to the left