外汇期权交易 基础知识


Effects of Urban Land-Use Change on Biogeochemical Cycles 45-58

Urban land-use change, the conversion of agriculturaland natural ecosystems to human settlements, has be-come an important component of global change. Virtu-ally all of the projected increase in the world’s popula-tion is expected to occur in cities so that by the year 2007more than half of the global population is expected tolive in urban areas (United Nations 2004). Yet, urbansettlements and surrounding areas are complex ecologi-cal systems that have only recently been studied from arigorous ecological perspective (Pickett et al. 2001).Clearly, urban areas represent ecosystems with modifiedbiogeochemical cycles such that fluxes and pools of mat-ter, energy, and organisms differ greatly from the previ-ous ecosystem (Collins et al. 2000). Our knowledge ofthe magnitude and extent of these biogeochemical changesat local, regional, and global scales is a major area of un-certainty in our understanding of global change.

In the ecological sciences, the ecosystem approach has

Conceptual diagram of anurban ecosystem showing in-terrelationships between hu-man and biophysical compo-nents. Dashed line indicatesecosystem boundary if cityconsidered a “well-mixed re-actor” such that inputs andoutputs into and out of theecosystem can be measured.Model includes feedback loopfrom the human social compo-nent of the system to resourceacquisition, i.e., demand forresources dependent on popu-lation density, quality of lifeissues, and the ability of eco-

Effects of Urban Land-Use Change on Biogeochemical Cycles 45-58

system to assimilate waste

been used successfully in studying the effects of distur-bance and exogenous inputs of nutrients and pollutantson biogeochemical cycles (Likens 1992). To study biogeo-chemical cycles in urban areas, Grimm et al. (2003) rec-ommended the ecosystem approach where: (1) urbanecosystems are viewed as spatially homogenous, i.e.,“well-mixed reactors,” or (2) urban ecosystems are con-sidered a heterogeneous assemblage of 货币交易者的10大技巧 货币交易者的10大技巧 parts or “patches.”Indeed, cities have been viewed as well-mixed reactorsin answering questions about how they affect biogeo-chemical cycles at regional and global scales (Fig. 5.1).In so doing, mass balances have been constructed forentire cities to assess their “ecological footprint,” that is,the amount of land resources acquired from other eco-systems needed to sustain the urban population (Rees2003). Moreover, 货币交易者的10大技巧 the mass balance approach allows in-vestigations into the movement of nutrients and pollut-ants across ecosystem boundaries and the cycling of thesematerials within the system itself. For example, Bakeret al. (2001) constructed a nitrogen balance for the Phoe-nix metropolitan area and found that inputs (human and

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黑马股精析:股票投资入门致胜9大技巧 Paperback – 31 Oct. 2013

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Mothers have been warnedfor years that sleeping with their new born infant is a bad idea because it increases the risk that the baby might die unexpectedly during the night.But now Israeli researchers are reporting that even sleeping in the same room can have negative consequences, not for the child, but for the mother.Mothers who slept in the same 货币交易者的10大技巧 room with their infants, whether in the same bed or just the same room, have poor sleep the mother whose baby slept else where in the house. They woke up more frequently or awake approximately 20 minutes longer per night and have shorter period of uninterrupted sleep. These results how true even taking into account that many of the women in the study were breast-feeding their babies. Infants, on the other hand, didn’t appear to have worse sleep whether they slept in the same or different room from their mothers. The researchers acknowledge that since the families they studied were all middle classes Israelis. It is possible that the results will be different in different cultures. Lead author TTTT wrote in an email that the research team also didn’t measure father sleep. So it is possible that patterns could also be causing the sleep disruptions for mums. Right now, to reduce the risk of 货币交易者的10大技巧 sudden infant death in the room, the AmericanAcademy of PD recommends the mothers not sleep in the same bed with their babies, but sleep in the same room. The Israeli study suggests that doing so, may be best for the baby, but may take at all on mum.

9What is the long health view about the mother sleeping with 货币交易者的10大技巧 new-born babies?

10 What do Israeli researchers’ findings show?

11What does the American Academy’s PD recommend mothers do?


The US has already lost more than a third of the native languages that existed before European colonization and the remaining 192 are classed by the UNESCO as ranging between unsafe and extinct."We need more funding and more effort to return these languages to everyday use," says Fred Nowosky of the National museum of the American Indians, "we are making progress, but money needs to be spent on revitalizing languages, not just documenting them." Some reported languages mainly in California and Oklahoma where thousands of Indians were forced to relocate in the 19th century have fewer than 10 native speakers. Part of the issue is that tribal groups themselves don't always believe their languages are endangered until they are down to the last handful of speakers. "But progress is being made through emerging 货币交易者的10大技巧 schools, because if you teach children when they are young, it will stay with them as adults and that is the future." says Fred Nowosky. Such schools have become a model in Hawaii, but the islanders' native language are still classed by the UNESCO as critically endangered because only 1000 people speak it. The decline in the American African languages has historical roots. In the mid 19th century, the US government adopted a policy of Americanizing Indian children by removing them from their homes and cultures. Within a few generations, most have forgotten their native tongues. Another challenge to language survival is television. It has brought English into homes, and pushed out traditional storytelling and family time together, accelerating the extinction of native languages.

Questions 12-15 are based on the passage you just heard.

12. What can we learn from the report?

13. For what purpose does Fred Nowosky appeal from the funding?

14. What is the historical cause of the decline of the American Indian Languages?