ASTRONOMY: Enhanced: Water's Role in Making Stars

Water has long been believed to play an important role in star-forming regions as an oxygen reservoir and by cooling the circumstellar gas cloud, but observational evidence has been hard to come by. In her Perspective, Nisini explains how recent satellite missions have provided the first observational evidence that allows chemical models of star formation to be tested. Water is found to be initially low in abundance but to increase in abundance once a protostar has formed. The observations include protostars that are the precursors of sunlike stars, thus shedding light on water production in solar-type systems.     

Energy Conditions in the Epoch of Galaxy Formation

The energy conditions of Einsteinian gravity (classical general relativity) do not require one to fix a specific equation of state. In a Friedmann-Robertson-Walker universe where the equation of state for the cosmological fluid is uncertain, the energy conditions provide simple, model-independent, and robust bounds on the behavior of the density and look-back time as a function of red shift. Current observations suggest that the "strong energy condition" was violated sometime between the epoch of galaxy formation and the present. This implies that no possible combination of "normal" matter is capable of fitting the observational data.     

ASTRONOMY: The Distance to the Large Magellanic Cloud

The Large Magellanic Cloud (LMC), a satellite of the Milky Way, is an important yardstick by which most intergalactic distances are measured. But as Cole explains in this Perspective, how far away the LMC is remains a matter of dispute, with far reaching implications in cosmology. But observations of Cepheids and of eclipsing binaries, two types of stars that allow absolute luminosity and thus absolute distances to be determined, are promising to resolve this important issue in the not too distant future.     

ASTRONOMY: A New Source of Gamma Rays

Relativistic outflows or "jets" are collimated streams of high-energy electrons that emit synchrotron radiation at radio wavelengths and have bulk velocities that are a substantial fraction of the speed of light. They trace the outflow of enormous amounts of energy and matter from a central supermassive black hole in distant radio galaxies. As Fender explains in this Perspective, much smaller, more local sources may also produce such jets. Data presented by Paredes et al. point toward association of one such source, a relatively faint x-ray binary, with a gamma-ray source. This and similar pairs may contribute substantially to the production of high-energy particles and photons within our galaxy.     

Genesis of the heaviest elements in the Milky Way Galaxy

We review the origin and evolution of the heavy elements, those with atomic numbers greater than 30, in the early history of the Milky Way. There is a large star-to-star bulk scatter in the concentrations of heavy elements with respect to the lighter metals, which suggests an early chemically unmixed and inhomogeneous Galaxy. The relative abundance patterns among the heavy elements are often very different from the solar system mix, revealing the characteristics of the first element donors in the Galaxy. Abundance comparisons among several halo stars show that the heaviest neutron-capture elements (including barium and heavier) are consistent with a scaled solar system rapid neutron-capture abundance distribution, whereas the lighter such elements do not conform to the solar pattern. The stellar abundances indicate an increasing contribution from the slow neutron-capture process (s-process) at higher metallicities in the Galaxy. The detection of thorium in halo and globular cluster stars offers a promising, independent age-dating technique that can put lower limits on the age of the Galaxy.     

全氟丙烷白蛋白微球注射剂左心声学造影的初步临床观察

目的:评价全氟丙烷白蛋白微球注射剂经静脉注射后增强左室内膜边界识别的效果。方法:50例研究对象分别经静脉注射稀释的全氟丙烷白蛋白微球注射剂0.01 mL/kg,采用自身前后对照方法,评价左室显影和左室内膜边界识别的效果。结果:50例研究对象注射全氟丙烷白蛋白微球注射剂后,左室内膜边界可清晰识别节段数明显增多,两独立研究者间结果无统计学差异。A研究者评价结果:左心室显影II级占2%,III级占98%;B研究者评价结果:左心室显影II级占4%,III级占96%。两组研究者分别独立评价的造影有效率均为100%,差异无统计学意义。结论:全氟丙烷白蛋白微球注射剂经静脉注射后左心显影效果显著。     

Enhanced metabolism of Leishmania donovani amastigotes at acid pH: an adaptation for intracellular growth

Amastigotes (tissue forms) of Leishmania donovani isolated from infected hamster spleens carried out several physiological activities (respiration, catabolism of energy substrates, and incorporation of precursors into macromolecules) optimally at pH 4.0 to 5.5. All metabolic activities that were examined decreased sharply above the optimal pH. Promastigotes (culture forms), on the other hand, carried out the same metabolic activities optimally at or near neutral pH. This adaptation to an acid environment may account in part for the unusual ability of amastigotes to survive and multiply within the acidic environment of the phagolysosomes in vivo.     

A Transient Radio Source near the Center of the Milky Way Galaxy

In late December 1990, a new radio source appeared near the center of our galaxy rivaling the intensity of Sgr A(*) (the compact radio source at the galactic center). Following its first detection, the flux density of the galactic center transient (GCT) increased rapidly to a maximum 1 month later, and then declined gradually with a time scale of about 3 months. Surprisingly, the GCT maintained a steep radio spectrum during both its rising and decay phases. The neutral hydrogen (HI) absorption shows similar absorption to that in front of Sgr A(*); this indicates that the GCT lies near the galactic center. Furthermore, both HI and OH observations show an additional deep absorption at +20 kilometers per second with respect to the local standard of rest. Thus, the GCT is either embedded in or located behind a molecular cloud moving with that velocity. The cloud can be seen on infrared images. Its opacity is shown to be inadequate to conceal a supernova near the galactic center. It is argued that the GCT was probably transient radio emission from synchrotron-radiating plasma associated with an x-ray binary system.     

Formation of Chiral Interdigitated Multilayers at the Air-Liquid Interface Through Acid-Base Interactions

Thin interdigitated films composed of a long-chain, water-insoluble chiral acid (p-pentadecylmandelic acid of absolute configuration R) and a water-soluble chiral base (phenylethylamine, R') were constructed at the air-solution interface. The (R, R') structure was characterized to near-atomic resolution by grazing-incidence x-ray diffraction (GIXD). The two diastereomeric systems, (R, R') and (R, S'), demonstrate similar surface pressure-molecular area isotherms, but their structures are completely different on the molecular level, as monitored by GIXD. Complementary data on these two architectures were provided by atomic force microscopy.     

阿克苏红富士苹果冰糖心形成的影响因素调查分析

为了解影响阿克苏红富士苹果冰糖心形成的因素,开展了红富士冰糖心形成因素调查研究。结果表明,采收时间、负载量、树势、树龄、土壤质地、品种、方位、套袋、乔矮化栽培等因素都会对阿克苏红富士苹果冰糖心的形成产生影响。红富士在阿克苏10月上旬已开始形成糖心,10月26日糖心果率和糖心指数达到较高值,此后变化平缓;负载量高不利于糖心的形成;树势弱、树龄较小、树势旺都易于糖心的产生;沙质土壤栽培、不套袋管理、矮化栽培也有利于冰糖心的形成;条红品种较片红品种更易形成糖心。     

QUANTUM MECHANICS: Enhanced: Schrodinger's Cat Is Out of the Hat

In 1935, Erwin Schr?dinger suggested his famous gedanken experiment of the cat that is simultaneously "dead" and "alive" inside its box until the box is opened. But as Tesche explains in her Perspective, such a macroscopic manifestation of quantum mechanics has remained elusive until recently. The experiments by van der Wal et al. are an important step toward demonstrating that quantum mechanics can describe macroscopic phenomena. The approach may be exploited in quantum computing and quantum cryptography.     

Formation of glaciers on Mars by atmospheric precipitation at high obliquity

Surface conditions on Mars are currently cold and dry, with water ice unstable on the surface except near the poles. However, geologically recent glacierlike landforms have been identified in the tropics and the midlatitudes of Mars. The ice has been proposed to originate from either a subsurface reservoir or the atmosphere. We present high-resolution climate simulations performed with a model designed to simulate the present-day Mars water cycle but assuming a 45 degrees obliquity as experienced by Mars a few million years ago. The model predicts ice accumulation in regions where glacier landforms are observed, on the western flanks of the great volcanoes and in the eastern Hellas region. This agreement points to an atmospheric origin for the ice and reveals how precipitation could have formed glaciers on Mars.     

Intellectual property. Enhanced: intellectual property landscape of the human genome

The impact of gene patents on downstream research and innovation are unknown, in part because of a lack of empirical data on the extent and nature of gene patenting. In this Policy Forum, the authors show that 20% of human gene DNA sequences are patented and that some genes are patented as many as 20 times. Unsurprisingly, genes associated with health and disease are more patented than the genome at large. The intellectual property rights for some genes can become highly fragmented between many owners, which suggests that downstream innovators may face considerable costs to gain access to gene-oriented technologies.     

Enhanced upper tropical tropospheric COS: impact on the stratospheric aerosol layer

Carbonyl sulfide (COS) is considered to be a major source of the stratospheric sulfate aerosol during periods of volcanic quiescence. We measured COS at the tropical tropopause and find mixing ratios to be 20 to 50% larger than are assumed in models. The enhanced COS levels are correlated with high concentrations of biomass-burning pollutants like carbon monoxide (CO) and hydrogen cyanide (HCN). The analysis of backward trajectories and global maps of fire statistics suggest that biomass-burning emissions transported upward by deep convection are the source of the enhanced COS in the upper tropical troposphere.     

不同浓度的生根粉对纹瓣悬铃花生根的影响

本文通过三种生根粉不同浓度对纹瓣悬铃花不同茎段的生根情况进行试验,结果表明浓度为5g／1000ml的“根旺”生根粉效果最佳。     

2012年7月我国中东部持续性强降水形成机制分析

利用NCEP/NCAR再分析资料,通过对2012年7月中旬我国中东部地区持续性强降水过程中东亚夏季风系统中主要成员的时空变化特征进行分析.结果表明,此次持续性强降水期间,副高北界、南亚高压脊线及中纬度锋区位置相对稳定,长江中下游地区一直处于南亚高压反气旋环流东侧偏北风与西风槽前偏南风之间的风向开口辐散区中;副高南撤时,强降水主要位于584 dagpm线北侧,副高北抬时,强降水主要位于584 dagpm线南侧;此次持续性强降水发生前期,大气为上干下湿不稳定层结,当西风带低槽频频携带冷空气南下影响,同时低空西南急流反复加强,其出口区左侧较强的风速梯度为暴雨的发生发展提供了动力条件;低层干空气的不断侵入,低槽和低涡间的垂直正反环流促使垂直上升运动维持或发展,进而造成持续性强降水;高空西风急流加强(减弱)超前低空西南急流加强(减弱)2～5 d,对持续性强降水有超前指示意义.     

真实收益学说的形成、发展与影响

公允价值和资产负债观已成为现阶段各国会计准则和国际会计准则的显著特征,本次金融危机中各方的指责也未能动摇这一局面,这就表明公允价值与资产负债观必然具有理论上的合理性.而要明确公允价值与资产负债观到底具有怎样的理论合理性,并理清公允价值、资产负债观、全面收益、资本保全观念以及会计准则管制之间存在的关系,就必须对真实收益学说的发展背景、发展阶段和主要观点进行考察.通过这一考察,我们不难发现公允价值、资产负债观与全面收益实际上是一个同一体,且这个同一体与资本保全观念统一于真实收益学说,而会计准则管制的产生则在相当大程度上是受到了真实收益学说的支持.     

真实收益学说的形成、发展与影响

公允价值和资产负债观已成为现阶段各国会计准则和国际会计准则的显著特征,本次金融危机中各方的指责也未能动摇这一局面,这就表明公允价值与资产负债观必然具有理论上的合理性。而要明确公允价值与资产负债观到底具有怎样的理论合理性,并理清公允价值、资产负债观、全面收益、资本保全观念以及会计准则管制之间存在的关系,就必须对真实收益学说的发展背景、发展阶段和主要观点进行考察。通过这一考察,我们不难发现公允价值、资产负债观与全面收益实际上是一个同一体,且这个同一体与资本保全观念统一于真实收益学说,而会计准则管制的产生则在相当大程度上是受到了真实收益学说的支持。