해커스 GRE 버벌 송종옥 선생님의 특급 자료

Saturn’s moon Enceladus shows signs of geological activity concentrated in the south polar terrain, where surface fractures emit plumes of water vapor and large amounts of heat. Tides influenced by orbital eccentricity might explain this phenomenon given the correlation between observed plume brightness and Enceladus’ Orbital position. However, there is a significant delay between apocenter (maximum distance from Saturn) and peak brightness. In order to explain this, one must invoke the unknown viscosity of Enceladus’ crust. Even then we don’t know why geysers occur only at the south pole or how so small a body can lose all that heat into space without freezing and thus ending the activity. Existing models predict that heat would be lost faster than it is produced by tidal friction.

Calculating hydroelectric plants’ environmental impact is not simple. Dam building requires steel and cement, the manufacture of which entails greenhouse gas emissions. Estimates for these emissions are relatively straightforward to make and show that the consequences are small compared to the benefits of generating greenhouse gas-free hydroelectric power. But more difficult-to-estimate greenhouse gas contributions occur during the plants operation. The submerging of large areas behind dams results in the microbial decomposition of vegetation, which produces substantial quantities of methane-a potent greenhouse gas. Furthermore, eradicating vegetation eliminates the consumption of the greenhouse gas

1. by that vegetation. Estimating amounts of these gases is difficult, and amounts vary depending upon the specific location, terrain, and power intensity of the dam with its associated lake.

It makes sense for large grazing animals to leave the Serengeti Plain in the dry season. The grass there stops growing soon after the rains cease. The wildebeests and zebras then head northwest, to the region of higher rainfall where there is still plenty of grass amid the acacia woodlands. But why do they ever leave those woodlands, especially after the rains have started and the amount of green forage is increasing? Recent studies have shown that grass on the Serengeti Plain contains higher concentrations of protein. This difference could be important to a lactating wildebeest or zebra. Even more striking, however, are the differences in the amounts of calcium and phosphorus available to grazers in the two habitats. Concentrations of calcium in grass samples from the Serengeti Plain are, on average, 40 percent greater than in samples from the northwestern woodlands; phosphorus concentrations are double. The calcium difference may not be very significant, as even the levels found in the woodlands should be adequate. But the concentration of phosphorus in the woodland forage appears to be below the level a lactating female wildebeest requires. In domestic livestock, phosphorus deficiencies have been linked to reduced fertility and milk yield and to other problems; similar problems presumably would affect wild grazers too.

African American musicians in the 1950s faced a dilemma regarding classical music. A cosmopolitan display of knowledge about modern classical music enabled artists such as Duke Ellington to counter misconceptions that jazz musicians were untutored. Yet jazz musicians’ interest in classical music was often taken as an admission that jazz innovations were derived from European sources. After Charlie Parker expressed admiration for Bartók, an interviewer asked if Parker’s musical innovations were adaptations of classical predecessors’ ideas. Often, comparisons with modern European composers connected jazz to the presumed superior standards of classical music without recognizing that jazz articulated its own musical vision-by developing expressive and improvisational principles rooted in a wide variety of African American musics-that challenged the hegemony of European standards in American music.

A longstanding scholarly neglect of the subject of cooking is partly attributable to the antiquated “separate spheres” schema that differentiated a private female sphere, which included food preparation and consumption, from a public male sphere, which included food production. While this concept never reflected most women’s daily realities-women are major food producers worldwide the ideological polarization certainly influenced the development of academia: it effectively segregated women into working in low-status “domestic” disciplines such as dietetics and home economics, while the male-dominated realms of industrial agriculture, food technology, mass retailing, and corporate management enjoyed public respect and academic prestige. This institutionalized bias delayed serious attention to cooking even after feminists in the 1960s obliterated the notion of separate spheres and more women entered all areas of academia.

It must be acknowledged that data on ceramic artifacts do not provide the complete picture of regional economic interactions in the ancient Basin of Mexico. First, patterns of exchange between settlements cannot be understood purely through chemical compositional analysis , even when pottery provenance can be securely determined: compositional data do not indicate exactly how pots moved from one place to another or how many times a vessel was exchanged. In addition, ceramics are not the only kind of material that was exchanged between settlements. The transport of bulky and breakable ceramic pots was costly, and clay resources were widely available. Therefore, the orbits within which most ceramics circulated are likely to have been smaller than those of artifacts made from more durable materials, such as obsidian.

In the late 1920s, the noted writer Lu Xun, who was also the primary figure behind the modern Chinese woodcut movement, began to introduce modern Western woodcuts into China. Lu Xun believed that Western artists’ emphasis on linearity and sharp black-and-white contrasts gave their art a distinctly serious quality, very different from the largely decorative nature of the traditional, richly colored Chinese woodcut. But he also believed that the most important ingredient in the Western woodcut was its close link to the broader society, an element missing in the Chinese woodcut tradition. It is true that Lu Xun was deeply impressed by the Western artists” techniques, which enabled them to evoke human emotions through gestures and facial expressions, but his decision to introduce their works was prompted more by his admiration of the works’ role in the struggle for social and political justice than by his interest in technique and craftsmanship. Lu Xun realized that woodcuts could do more than evoke emotions; they could be used as an educational tool to reshape public consciousness.

In the United States, studying the territoriality of nonnative ants such as the red fire ant, a species native to South America, may seem unlikely to yield generalizable results-but it does have distinct advantages. Most importantly, whereas the fire ant shares habitat with many ant competitors in South America, its communities in the United States are much simpler. Colonizable landscape is blanketed almost continuously with fire ant territories, so all territorial boundaries are with other fire ant colonies. We can study the complexities of territoriality in almost pure, continuous populations of a single species, without the complicating influences of other competitors. Furthermore, the high densities of many fire ant populations ensure that interactions among competing colonies will be intense and obvious.

Ten years ago off Garnea Island, large numbers of sea turtles were being trapped and drowned in commercial shrimping nets, and the sea-turtle population was rapidly declining. A law was passed requiring shrimping nets to have special flaps that enable trapped turtles to escape. Initially, compliance was strictly monitored, and sea-turtle deaths fell dramatically. In recent years, however, boats are monitored less frequently, and sea-turtle deaths have significantly increased. Clearly, therefore, compliance has decreased.

Why does so much of our coal and petroleum date from the Carboniferous period? The orthodox view is that Carboniferous swamps provided optimal conditions for fossil fuel formation. After the Carboniferous, the world became drier, and conditions became less favorable. But is that all there is to it? Forests didn’t disappear after the Carboniferous. If anything, there were even more trees, growing ever more widely at higher elevations, and growing to greater heights over the Mesozoic and Cenozoic. After the Carboniferous, the continents may have been drier inland, but they still had lots of streams, rivers, and coastal wetlands. Trees from dry highlands could easily have washed into rivers and accumulated in lowland marshes. Something other than a change in climate must have occurred.