广州(珠江三角洲)数字遥测地震台网建设回顾

广州（珠江三角洲）数字无线遥测地震台网是我国第一个全套引进的数字无线遥测地震系统的数字地震台网,采用２４位数字地震采集、无线数据传输、地震数据处理等先进技术,对增强广东省特别是珠江三角洲地区的地震监测能力发挥了重要作用,为发展和推动我国数字地震观测技术进行了有益的探索和实践。系统介绍了广州台网的建设过程和技术特色。     

Abrupt climate change and transient climates during the Paleogene: a marine perspective

Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.     

Thermal synthesis of amino acids and the origin of life

The recent review by Marshall (1994) of the production of amino acids from the interstellar components, formaldehyde and ammonia, is placed in the larger context of the origin of life. Thermal energy, being ubiquitous in the Earth, emerges as the sole necessary form of energy. To appreciate the overview of the natural evolutionary sequence it is necessary to recognize stepwiseness in evolution, a principle that has however been often ignored. Since self organization of thermal protein to cells is instantaneous, but only one step in a geochemical ladder, individual steps may be regarded as instantaneous, while the sequence requires measurable time. Two steps indicated are extrusion of a hot, dry organic magma of amino acids --> peptides into an aqueous environment in which occurs a second step of self organization. In this paper, spinoffs of the defensible theory for the origin of life have been briefly reviewed as a fundamental consequence of nonrandom thermal copolymerization of amino acids.     

Distribution of petroleum hydrocarbons and organochlorinated contaminants in marine biota and coastal sediments from the ROPME Sea Area during 2005

The composition and spatial distribution of various petroleum hydrocarbons (PHs), comprising both aliphatic and polycyclic aromatic hydrocarbons (PAHs), and selected chlorinated pesticides and PCBs were measured in biota and coastal sediments from seven countries in the Persian Gulf and the Gulf of Oman (Bahrain, Iran, Kuwait, Oman, Qatar, Saudi Arabia and the United Arab Emirates). Evidence of extensive marine contamination with respect to organochlorinated compounds and PHs was not observed. Only one site, namely the BAPCO oil refinery in Bahrain, was considered to be chronically contaminated. Comparison of the results from this survey for Σ DDTs and Σ PCBs in rock oysters from the Gulf of Oman with similar measurements made at the same locations over the past two decades indicates a temporal trend of overall decreasing Σ PCB concentrations in oysters, whereas Σ DDTs levels have little changed during that period.