Collapse of Classic Maya civilization related to modest reduction in precipitation

The disintegration of the Classic Maya civilization in the Yucatán Peninsula and Central America was a complex process that occurred over an approximately 200-year interval and involved a catastrophic depopulation of the region. Although it is well established that the civilization collapse coincided with widespread episodes of drought, their nature and severity remain enigmatic. We present a quantitative analysis that offers a coherent interpretation of four of the most detailed paleoclimate records of the event. We conclude that the droughts occurring during the disintegration of the Maya civilization represented up to a 40% reduction in annual precipitation, probably due to a reduction in summer season tropical storm frequency and intensity.     

ARCHAEOLOGY: Arizona to Take High Road to Preservation?

State transportation officials have agreed to weigh a proposal to set aside a scientifically valuable parcel of a federal highway project for future research rather than excavating it and selling it to the highest bidder. Should it proceed, Arizona could set a new standard of stewardship for government agencies that determine the fate of ancient relics.     

Landsat, computers, and development projects

Data provided by earth-orbiting satellites and analyzed through specific computer techniques are rapidly providing policy-makers around the world with new information on the location and extent of their countries' renewable and nonrenewable resources. Development projects utilizing remote sensing technology are being supported, for example, by the Inter-American Development Bank, the World Bank, and other international funding agencies. The Inter-American Development Bank is financing a natural resources inventory of five countries in Central America, and this will require the application of remote sensing in the analysis of 33 Landsat images covering the area. Although the Landsat program remains experimental in nature, studies pertaining to its follow-on aspects will ensure continuation of the program so that developed and developing countries will be able to maintain better control of the management of their natural resources.     

On the fringes of conquest: maya-spanish contact in colonial belize

The defeat of the Aztecs of Mexico by Hernán Cortés in 1521 was but the beginning of a long and torturous conquest of Central America that did not always result in the mastery of people and production for which the Spanish had hoped. The Maya of the resource-poor Yucatán peninsula were spared the heavy colonial hand that held fast to central Mexico and its riches. In addition, the dense forests of the peninsula served as a haven for refugees fleeing oppressive conditions in colonial towns. Despite the paucity of documentary information on Maya communities of the frontier, knowledge of Maya-Spanish relations in the 16th and 17th centuries has advanced in recent years through archeological and ethnohistorical research. Work in one region of the Maya lowlands has brought us closer to an understanding of the early interaction of the rulers and the ruled.     

Hail suppression and society

An interdisciplinary assessment of hail suppression in the past, present, and future has shown it to be currently scientifically uncertain but a potentially beneficial future technology. An established suppression technology would be widely adopted in the Great Plains, providing benefits to agriculture and secondarily to the American consumer. Development of a reliable technology will require a sizable longterm federal commitment to atmospheric and social research. Subcritical funding would be a mistake. Orderly future usage of hail suppression, with its scientific complexities and regional character, will necessitate development of governmental regulations, evaluation procedures, interstate arrangements, and means for compensating those who lose from modification.     

The process values of university research. A new research funding system is needed for federal support of the process values of university research

The process values of university research are important in the context of several significant social and economic trends in American life. These values are being taken into account in the design and administration of federal programs. Federal programs to support these values should be distinguished from programs to support the product values of research. Failure to distinguish between these two types of programs will lead to a further dilution of quality in programs designed to advance science as a legitimate end in itself. The scientific community can best protect its own interests by helping federal agencies and universities and colleges develop a funding system to support the process values of university research on a cooperative, regional basis.     

Reporting of faculty time: an accounting perspective

Controversial federal regulations requiring universities to report 100 percent of the activities performed by faculty members encounter severe theoretical difficulties of allocation that pervade accounting and that at present are insoluble. Yet it is only natural for universities and government agencies to desire that such allocations be made. Accounting practitioners have faced such reporting dilemmas for generations; their experiences suggest ways of palliating the federal requirements.     

Photovoltaics

The federal government has sponsored a program of research and development on terrestrial photovoltaic systems that is designed to reduce the costs of such systems through technological advances. There are many potential paths to lower system costs, and successful developments have led to increased private investment in photovoltaics. The prices for photovoltaic collectors and systems that appear to be achievable within this decade offer hope that the systems will soon be attractive in utility applications within the United States. Most of the advances achieved will also be directly applicable to the remote markets in which photovoltaic systems are now commercially successful.     

An industry picture of u.s. Science policy

With regard to promoting the competitiveness of U.S. industry, federal science policy is performing unevenly. Federally supported basic research is not well aligned with industrial needs, although the National Science Foundation's Engineering Research Centers and similar programs are improving matters. Large-scale federal undertakings in science and technology, such as the Apollo program and now the Strategic Defense Initiative, actually tend to divert resources away from commercial research and development. Needed are federal and industrial leaders who will work together to serve the interests of both competitive industry and efficient government in the United States.     

Technology utilization: incentives and solar energy

If the federal government is not going to be the major market for the application of federally funded R & D results, then the responsibility for bringing about technology utilization cannot be borne alone by the federal agency funding the R & D. That this problem is now being recognized is shown by the number of bills that were introduced in Congress in 1974, culminating in the Solar Heating and Cooling Act of 1974 (7). An examination of the incentives for technology utilization in the conceptual framework of TDS (as shown in Fig. 4) reveals the following: 1) Incentives must be applied to each component of the TDS. 2) Different components in the TDS require different incentives. 3) Although information exists concerning a wide variety of incentives that are currently being used by various federal agencies to stimulate technology utilization, most of this information is in the form of raw data compiled by the respective agencies and a substantial effort will be required to collect, compile, and evaluate them. 4) All the components of a TDS must be activated if technology utilization is to occur on a self-sustaining basis. This makes experimental verification of a particular incentive on a particular component difficult. 5) A federal agency concerned with technology utilization can and should assume the responsibility for identifying all the components of the required TDS, devising incentives for each component and testing them to ensure their effectiveness. Where a TDS does not exist, the federal agency may have to assume the responsibility of creating one. The scope of this effort in many cases may transcend the present authority of the agency, and congressional action may be required to remedy this shortcoming.     

基于CALIOP资料的中国及周边地区云出现概率时空分布特征分析

云垂直结构是影响大气辐射的重要参数,其时空分布是影响全球气候变化的关键组成部分.本文利用星载激光雷达CALIOP的1km云层产品,计算了中国及周边地区(0-55°N,70-140°E)云的出现概率,对不同地区、不同季节、不同高度单层云的出现概率做了对比分析.结果表明:云的出现概率表现出明显的地区差异,蒙古高原和印度半岛北部少云,热带海域和中国南方多云,多数地区夜间云出现概率略高于白天;除蒙古高原和印度半岛北部以外,多数地区单层云比多层云更常见;多数地区高云占单层云的比例最大,而中国大陆南部单层的中云较常见,西太平洋北部海域常被单层的低云覆盖;夏秋两季云出现概率普遍大于春冬两季,尤其印度半岛北部的云主要出现在夏季;蒙古高原和印度半岛北部单层云少于多层云,冬季尤其明显,而中国西南地区东部全年单层云更常见;夏季单层的高云占全年单层云的比例最大,青藏高原部分地区超过35%,这与其地形特征和夏季对流活动旺盛有关.     

试论新政时期美国联邦政府的西部农业政策

新政时期美国联邦政府的西部农业政策是联邦政府应对西部的农业经济危机和自然灾害而采取的应急改革和措施,同时也体现了联邦政府对西部农业长远发展的规划.这一政策总体来说较为成功,它有效地帮助了西部地区的农民,维护了西部地区社会的稳定,为西部地区农业的长远发展打下了坚实的基础,因而赢得了西部地区农民的充分肯定和支持.     

Coeval 40Ar/39Ar Ages of 65.0 Million Years Ago from Chicxulub Crater Melt Rock and Cretaceous-Tertiary Boundary Tektites

(40)Ar/(39)Ar dating of drill core samples of a glassy melt rock recovered from beneath a massive impact breccia contained within the 180-kilometer subsurface Chicxulub crater in Yucatán, Mexico, has yielded well-behaved incremental heating spectra with a mean plateau age of 64.98 +/- 0.05 million years ago (Ma). The glassy melt rock of andesitic composition was obtained from core 9 (1390 to 1393 meters) in the Chicxulub 1 well. The age of the melt rock is virtually indistinguishable from (40)Ar/(39)Ar ages obtained on tektite glass from Beloc, Haiti, and Arroyo el Mimbral, northeastern Mexico, of 65.01 +/- 0.08 Ma (mean plateau age for Beloc) and 65.07 +/- 0.10 Ma (mean total fusion age for both sites). The (40)Ar/(39)Ar ages, in conjunction with geochemical and petrological similarities, strengthen the recent suggestion that the Chicxulub structure is the source for the Haitian and Mexican tektites and is a viable candidate for the Cretaceous-Tertiary boundary impact site.     

Biotech policy draws flood of comments

The federal government's draft plan to regulate the biotechnology industry has elicited dozens of letters from researchers, industry, environmental groups, and others in response to the Environmental Protection Agency's (EPA) proposed role. Many commentators took issue with the EPA's intention to subject the products of genetic engineering to more rigorous scrutiny than conventionally manufactured products, a policy that the agency defends on the premise that genetically manipulated substances may pose more risks. Several respondents also claimed that products produced by genetic techniques not involving recombinant DNA are not "new," and therefore not subject to EPA's authority. Questions were asked as well about the need for the Biotechnology Science Board that the government plans to establish to oversee review committees in federal agencies involved with biotechnology research.     

地域语境下的衙署园林场所特征探析——以罨画池为例

以四川省成都市西部的罨画池为例,以之作为西蜀园林中衙署园林的典范,从山水布局、园林建筑、植物环境以及园林品题方面,对罨画池的造园特征加以分析,提炼并总结出罨画池在西蜀地域语境下所体现的衙署园林的场所特征,认为罨画池作为衙署园林的典型代表,印证了中国古代衙署园林引水造园,因水得景的特征。以期为今后的地区园林创作提供借鉴。     

Larger public sector role sought on biotech

Increasing opposition to field tests of genetically altered organisms is causing the biotechnology industry to look to some form of government regulation as a way to calm the public's fears. Industry leaders are concerned that future developments will be subject to costly legal delays unless an efficient regulatory system is in place, although neither the federal government nor industry has been able to determine what standards are needed or what classes of products should be regulated. The two biotechnology trade associations have begun to work on their positions, regulatory legislation has been introduced in Congress, and the roles of the Environmental Protection Agency and the Department of Agriculture are about to be defined. There is a divergence of opinion about federally-supported intermediate test facilities, which some industry spokesmen believe would be unnecessary.     

进一步完善政府信息公开的思考

现阶段,政府信息公开是政治研究中的一个热门话题。完善政府信息公开制度,有利于遏制政府机关的腐败问题,有利于调动公众参与政治活动的积极性,密切政府与人民之间的关系,进而实现构建社会主义和谐社会的伟大构想。     

海峡西岸经济区江西区域供水保障方案与对策研究

分析了海峡西岸经济区江西区域的供用水现状及存在问题,并结合区域发展规划,分析了区域产业发展布局及供用水需求态势,提出了未来中长期供水保障的总体思路、工程布局以及相应的对策和措施。     

北方村镇生态景观的设计思考

针对北方村镇生态景观中农田生态景观和居住区生态景观中存在的一系列问题,以及北方村镇中废物再回收利用率不高,生态景观评价指标不确定、管理者意识不强、组织管理不到位等多方面问题,提出了相应的规划建议,阐述了科学种田,发展生态农业,完善生态化廊道系统对农田生态景观的重要意义;论述了合理生态建构,充分利用可再生能源,统一规划,提高土地利用率,突出生态景观地方特色对于居住区建设的重要意义。强调发展观光农业,加强生态景观理论研究,完善管理机构,开展合理生态评价,尊重生态学原则,充分挖掘地方特色,加强政府引导,考虑村民意愿,以期建立人与自然和谐相处的社会。     

新农村建设中农业区域规划问题的思考——以拜泉县为例

2006年中央一号文件提出建设社会主义新农村的战略目标,农业区域规划对于发展生态农业,特色农业以及农业结构的调整方面具有重大的意义。文章从分析农业区域规对新农村建设意义入手,以黑龙江省拜泉县为例,从经济生态学、比较优势以及区域分工方面提出了农业区域规划的理论依据,最后提出对其他地区发展农业的启示。