Petroleum drilling and production in the United States: yield per effort and net energy analysis

For the past three decades the quantity of petroleum (both oil and oil plus gas) found per foot of drilling effort in the United States for any given year can be expressed as a secular decrease of about 2 percent per year combined with an inverse function of drilling effort for that year. Extrapolation of energy costs and gains from petroleum drilling and extraction indicates that drilling for domestic petroleum could cease to be a net source of energy by about 2004 at low drilling rates and by 2000 or sooner at high drilling rates, and that the net yield will be less at higher drilling rates.     

Pleistocene climates in the atlantic and pacific oceans: a comparison based on deep-sea sediments

Comparison of Pleistocene climatic records defined by variations in abundance of planktonic Foraminifera in three cores from the southeastern Pacific with similar records in cores from the Atlantic suggests that times of warm surface water in this region of the Pacific were at least partly synchronous with times of cool water in the Altantic. This conclusion opposes the Milankovitch theory of the causation of ice ages, but it harmonizes with a modified form of Simpson's hypothesis.     

North atlantic ice-rafting: a major change at 75,000 years before the present

During the last interglacial-to-glacial climatic cycle [127,000 to 10,000 years before the present (B.P.)], the fundamental geographic shift in the main axis of ice-rafting deposition occurred at 75,000 years B.P. An earlier meridional depositional maximum along the Greenland-Newfoundland coasts was superseded by a nearly zonal and much stronger axis some 1500 kilometers to the south along 40 degrees N to 50 degrees N. Both depositional patterns are best explained by cyclonic flow in the subpolor gyre, with the depositional shift related to the retreat of warm, ice-melting North Atlantic drift water from the northwestern half of the gyre. Similar shifts must have characterized preceding interglacial-glacial cycles.     

Nitrogen fixation by floating diatom mats: a source of new nitrogen to oligotrophic ocean waters

Nitrogen fixation, apparently by bacterial endosymbionts, is associated with intertwining chains of two species of the diatom Rhizosolenia. In situ fixation rates were enhanced by incubation in the dark, whereas concurrent shipboard experiments either underestimated or did not detect nitrogen fixation. This is the first example of nitrogen fixation associated with a bacteria-diatom symbiosis in the pelagic zone, and it indicates that these systems may contribute a significant amount of "new" nitrogen to oligotrophic waters.     

Dust concentration in the atmosphere of the equatorial north atlantic: possible relationship to the sahelian drought

The concentration of insoluble mineral aerosol in the lower troposphere of the western equatorial North Atlantic Ocean has increased by a factor of 3 over the last decade. This increase may be related to the drought in the Sahelian zone of North Africa.     

Evolution of Petroleum Hydrocarbons in Soil Polluted with Crude Oil Treated with a Natural Product

Bioremediation of petroleum hydrocarbons contaminated/polluted soils has been recognized as an efficient, economic, versatile and environmentally good treatment. This method is limited by the microorganisms activity in degrading the spills hydrocarbons. Low solubility of the hydrocarbons involves low bioavailability to microorganisms. The main objective of this research is to increase biodegradation of petroleum hydrocarbons by treating the crude oil polluted soil with the natural biodegradable product and bacterial inoculum. Biodegradation was quantified by total petroleum hydrocarbons （TPH） analyses. The paper presents data obtained in biodegradation process of an artificial polluted soil with 5% and 10% crude oil, treated with a natural biodegradable product and bacterial inoculum during two years of experiment. Biodegradation process takes time to rehabilitate and reuse of the soil in agricultural scopes.     

Evaluating the grassland net primary productivity of southern China from 2000 to 2011 using a new climate productivity model

Grassland is the important component of the terrestrial ecosystems. Estimating net primary productivity(NPP) of grassland ecosystem has been a central focus in global climate change researches. To simulate the grassland NPP in southern China, we built a new climate productivity model, and validated the model with the measured data from different years in the past. The results showed that there was a logarithmic correlation between the grassland NPP and the mean annual temperature, and there was a linear positive correlation between the grassland NPP and the annual precipitation in southern China. All these results reached a very significant level(P0.01). There was a good correlation between the simulated and the measured NPP, with R2 of 0.8027, reaching the very significant level. Meanwhile, both root mean square errors(RMSE) and relative root-mean-square errors(RRMSE) stayed at a relatively low level, showing that the simulation results of the model were reliable. The NPP values in the study area had a decreasing trend from east to west and from south to north, and the mean NPP was 471.62 g C m~(-2) from 2000 to 2011. Additionally, there was a rising trend year by year for the mean annual NPP of southern grassland and the tilt rate of the mean annual NPP was 3.49 g C m~(-2) yr~(-1) in recent 12 years. The above results provided a new method for grassland NPP estimation in southern China.     

Seeing with a new light: synchrotron radiation

The special properties of synchrotron light are leading to a rapid increase in its utilization for both research and technology. At wavelength in the ultraviolet region of the broad spectrum in these beams a number of atomic, molecular, and solid-state spectroscopies are being pursued; soft x-rays are being used for spectroscopy, lithography, microscopy, and topography; at still shorter wavelengths, advantage is taken of scattering properties to probe the structure of matter. Characteristics of synchrotron radiation and of the sources which produce it are described, and some typical investigations and applications are presented to suggest the versatility of these sources.     

Cell polarity: quantitative modeling as a tool in cell biology

Among a number of innovative approaches that have modernized cell biology, modeling has a prominent yet unusual place. One popular view is that we progress linearly, from conceptual to ever more detailed models. We review recent discoveries of cell polarity mechanisms, in which modeling played an important role, to demonstrate that the experiment-theory feedback loop requires diverse models characterized by varying levels of biological detail and mathematical complexity. We argue that a quantitative model is a tool that has to fit an experimental study, and the model's value should be judged not by how complex and detailed it is, but by what could be learned from it.     

Chemistry with a thousand faces: new ways to play with clay

Like a species that has moved into open niches, evolved, and diversified, chemistry can no longer be seen as a discrete scientific field. Its methods, concepts, and practitioners are penetrating virtually every nook and cranny of science and technology. That message came through clearly 2 weeks ago in New York City at the Fourth Chemical Congress of North America-a week-long conference organized by the American Chemical Society, the Chemical Institute of Canada, and the Chemical Society of Mexico and attended by some 10,000 scientists, engineers, and entrepreneurs. In roughly 4200 papers, participants explored such topics as borrowing from nature to improve industrial processes and electronic devices, and controlling the molecular architecture of clays and polymers.     

Free radicals in the stratosphere: a new observational technique

A new approach to in situ observations of trace reactive species in the stratosphere is described. A balloon-borne system, floating 40 kilometers above the earth's surface, successfully lowered and then retracted a cluster of instruments a distance of 12 kilometers on a filament of Kevlar. This instrument cluster is capable of detecting gas-phase free radicals at the part-per-trillion level. The suspended instrument array has excellent stability and has been used to measure atomic oxygen concentrations in the stratosphere.     

Regional myocardial substrate uptake in hypertensive rats: a quantitative autoradiographic measurement

Severe hypertension causes global and regional changes in myocardial perfusion and substrate utilization. Regional perfusion and fatty acid utilization were evaluated by dual-tracer autoradiography in normotensive and hypertensive rats of the Dahl strain. The regional distributions of perfusion and fatty acid utilization were homogeneous in normotensive rats. Severe hypertension was associated with a homogeneous pattern of regional perfusion, but fatty acid utilization was focally decreased in the free wall of the left ventricle. The decrease in fatty acid uptake was associated with a concomitant increase in glucose utilization. These findings suggest that severe hypertension is associated with uniform myocardial perfusion and focal alterations in the substrates used for the performance of myocardial work.     

中国1新记录属--刺蛛属(蜘蛛目:圆颚蛛科)及1新种的记述

记述中国圆颚蛛科1新记录属——刺蛛属Echinax Deeleman—Reinhold 2001。其中包括2新记录种：拟猫刺蛛Echinax oxyopoides(Deeleman—Reinhold,1995)和羽状刺蛛Echinax panache Deeleman—Reinhold．2001．和1新种：安龙刺蛛,新种Echinax anlongensis sp．nov．。描述标本保存在河北大学博物馆。文中测量单位：mm。目前,刺蛛属全球已知5种,中国已知3种。