Toward a High-Resolution Monitoring of Continental Surface Water Extent and Dynamics, at Global Scale: from GIEMS (Global Inundation Extent from Multi-Satellites) to SWOT (Surface Water Ocean Topography)

Up to now, high-resolution mapping of surface water extent from satellites has only been available for a few regions, over limited time periods. The extension of the temporal and spatial coverage was difficult, due to the limitation of the remote sensing technique e.g., the interaction of the radiation with vegetation or cloud for visible observations or the temporal sampling with the synthetic aperture radar (SAR)]. The advantages and the limitations of the various satellite techniques are reviewed. The need to have a global and consistent estimate of the water surfaces over long time periods triggered the development of a multi-satellite methodology to obtain consistent surface water all over the globe, regardless of the environments. The Global Inundation Extent from Multi-satellites (GIEMS) combines the complementary strengths of satellite observations from the visible to the microwave, to produce a low-resolution monthly dataset () of surface water extent and dynamics. Downscaling algorithms are now developed and applied to GIEMS, using high-spatial-resolution information from visible, near-infrared, and synthetic aperture radar (SAR) satellite images, or from digital elevation models. Preliminary products are available down to 500-m spatial resolution. This work bridges the gaps and prepares for the future NASA/CNES Surface Water Ocean Topography (SWOT) mission to be launched in 2020. SWOT will delineate surface water extent estimates and their water storage with an unprecedented spatial resolution and accuracy, thanks to a SAR in an interferometry mode. When available, the SWOT data will be adopted to downscale GIEMS, to produce a long time series of water surfaces at global scale, consistent with the SWOT observations.

Chemical kinetics and self-ignition in a model supersonic hydrogen-air combustor

Self-ignition tests of a model scramjet combustor were conducted by using parallel sonic injection of gaseous hydrogen from the base of a blade-like strut into a supersonic vitiated airstream. The range of stagnation pressure and temperature studied varied from 1.0 to 4.5 MPa and from 1300 to 2200 K, respectively. Experimental results show that the self-ignition limit, in terms of either global or local quantities of pressure and temperature, exhibits a nonmonotonic behavior resembling the classical homogeneous explosion limit of the hydrogen-oxygen system. Specifically, for a given temperature, increasing pressure from a low value can render a nonignitable mixture to first become ignitable, then nonignitable again, This correspondence shows that, despite the globally supersonic nonpremixed configuration studied herein, ignition is strongly influenced by the intricate chemical reaction mechanism and thereby exhibits the homogeneous explosion character. Consequently, self-ignition criteria based on a global reaction rate approximating the complex chemistry are inadequate. An auxiliary computational study on counterflow ignition was also conducted to systematically investigate the contamination effects of vitiated air. Results indicate that the net contamination effects for the present experimental data are expected to be substantially smaller than contributions from the individual contamination species because of the counterbalancing influences of the H2O-inhibition and NO-promotion reactions in effecting ignition.

NSTL与CSDL全文传递服务的比较与分析

简要介绍了NSTL和CSDL的概况,并结合中国科学院力学研究所图书馆开展的全文传递服务工作,对NSTL和CSDL提供的全文传递服务进行了比较、分析,得出其服务具有较大的互补性。

第十四届国际材料强度大会简介

2006年6月5—9日，第十四届国际材料强度大会（14th International Conferenceon the Strength of Materials，IC-SMA14）在西安古都新世界大酒店举行，会议正式代表322人（其中境外代表200多人），这是该系列国际材料强度大会第一次在中国举办．大会由中国国家自然科学基金委员会、国家教育部、中国材料研究学会、西安交通大学、中国科学院沈阳金属研究所和西安市科技局等单位共同支持．大会主席为J．L．Martin教授，会议组织委员会主席由西安交通大学的孙军教授与中国科学院金属研究所的李守新研究员共同担任．

液池中大Pr数流体的热流体波

数值研究零重力条件下浅液池中大Pr数流体（Pr=105．6）的热流体波．液池的两侧有不同的温度，形成一定的温度差．当温度差增加并超过临界温度差时，在液池中会出现从冷端向热端传播的行波．扰动温度，扰动速度和扰动压强的相位关系表明这种行波为扰动温度所驱动，为热流体波．热流体波很弱，在热流体波出现时，在液池中几乎观测不到振荡的流场和温度分布．对热流体波的形成机理进行了分析和讨论．

蒸发液层对流稳定性理论与实验研究进展

综述了蒸发液层稳定性理论分析和蒸发对流实验研究方面的最新进展．首先回顾历史上经典的单层流Marangoni不稳定性分析．利用经典的单层流模型可以很好解释无蒸发液层的稳定性特性，但是由于经典的单层流模型没有考虑蒸汽层与液层之间的动力学耦合关系，所以不能完全解释蒸发液层的Marangoni不稳定性特性．有的学者建立了考虑蒸汽层与液层的热耦合与动力学耦合关系的两层流模型，并采用了界面温度连续这样的假设．而在实验的观测中，蒸发界面处的温度是不连续的，特别是在蒸发量比较大的情况下，汽／液界面处温度跳跃很明显．由于界面温度连续假设在处于非平衡状态的系统中是不成立的，所以这些模型虽然能给出一些新的有关系统稳定性的特性，但还是不能完全解释蒸发液层的Marangoni不稳定性的特性，特别是为什么从底部冷却液层的时候，在实验中仍然能够观察到Marangoni对流涡胞的出现的原因．本文总结了前人的研究成果，同时给出了蒸发系统的动力学建模过程和实验研究方法，并对各种模型的稳定性特性进行了总结．最后，指出了现有理论中存在的问题和有待进一步研究的问题．

剪切水-气界面下湍流猝发特征的实验研究

利用氢气泡时间线-脉线组合示踪技术定量地考察剪切水-气界面下的湍流猝发现象,分析猝发事件的信号特征,重点探讨猝发与湍能产生之间的联系.在猝发过程中,水面近区的瞬时流速和Reynolds切应力出现较大幅度的脉动,它们在时间和空间垂直方向上表现出高度的相干性,这是猝发事件的一个显著特征.在猝发期,猝发事件涉及的空间区域内Reynolds切应力和湍流脉动强度明显比平均值和非猝发期的情况大.其结果表明:在所考察的实验条件下,猝发是剪切水-气界面附近湍流产生的主要过程.

Distribution and Abundance of Juvenile Salmonids off Oregon and Washington, 1981-1985

This report is a summary of the results of 883 purse seine sets made for juvenile salmonids during 15 cruises off the coasts of Oregon and Washington during the springs and summers of 1981-1985. Juvenile coho salmon (Oncorhynchus kisutch) occurred most frequently, followed by chinook salmon (0. tshawytscha). The juveniles of these two species co-occurred more frequently than expected. Juvenile chum, pink and sockeye salmon (0. keta, O. gorbuscha, and O. nerka), steelhead (0. mykiss) and cutthroat trout (0. clarki clarki) were caught much less frequently and in lower numbers than coho or chinook salmon. We found no evidence of large schools ofjuvenile salmonids. A northerly movement of juvenile coho salmon wa~ suggested by decreased catches off Oregon and increased catches off Washington between early and late summer. Highest catch per set of juvenile coho salmon was usually found inshore of 37.2 km. Juvenile chinook salmon were usually found within 27.9 km of the coast. Juvenile salmonids were found over a broad range of surface salinities and temperatures. High catches of juvenile coho salmon occurred in both the low salinity waters of the Columbia River plume and in adjacent higher salinity waters. Preferences for specific salinities or temperatures were not obvious for any species, although catch rates of juvenile coho salmon were highest in years when chlorophyll content was also high. Based on expansions of fish with coded wire tags, we estimated that hatchery coho salmon smolts comprised 74%, on average, of the juvenile coho salmon catches. The remaining 26% were presumably wild fish or hatchery fish released as fingerlings. Hatchery coho salmon were caught roughly in proportion to the numbers released. However, hatchery fish from the Columbia River and private coastal facilities were caught at slightly higher rates while those from coastal Washington and public coastal Oregon hatcheries were caught at slightly lower rates than expected from the numbers released. No juvenile coho salmon with coded wire tags were caught that had originated from either California or Puget Sound hatcheries. (PDF file contains 88 pages.)

Gene enrichment using antibodies to DNA/RNA hybrids : mapping the ribosomal DNA of slime mold and rat

A novel method for gene enrichment has been developed and applied to mapping the rRNA genes of two eucaryotic organisms. The method makes use of antibodies to DNA/RNA hybrids prepared by injecting rabbits with the synthetic hybrid poly(rA)•poly(dT). Antibodies which cross-react with non-hybrid nucleic acids were removed from the purified IgG fraction by adsorption on columns of DNA-Sepharose, oligo(dT)-cellulose, and poly(rA)-Sepharose. Subsequent purification of the specific DNA/RNA hybrid antibody was carried out on a column of oligo(dT)-cellulose to which poly(rA) was hybridized. Attachment of these antibodies to CNBr-activated Sepharose produced an affinity resin which specifically binds DNA/RNA hybrids.

In order to map the rDNA of the slime mold Dictyostelium discoideum, R-loops were formed using unsheared nuclear DNA and the 178 and 268 rRNAs of this organism. This mixture was passed through a column containing the affinity resin, and bound molecules containing R- loops were eluted by high salt. This purified rDN A was observed directly in the electron microscope. Evidence was obtained that there is a physical end to Dictyostelium rDN A molecules approximately 10 kilobase pairs (kbp) from the region which codes for the 268 rRNA. This finding is consistent with reports of other investigators that the rRNA genes exist as inverse repeats on extra-chromosomal molecules of DNA unattached to the remainder of the nuclear DNA in this organism.

The same general procedure was used to map the rRNA genes of the rat. Molecules of DNA which contained R-loops formed with the 188 and 288 rRNAs were enriched approximately 150- fold from total genomal rat DNA by two cycles of purification on the affinity column. Electron microscopic measurements of these molecules enabled the construction of an R-loop map of rat rDNA. Eleven of the observed molecules contained three or four R-loops or else two R-loops separated by a long spacer. These observations indicated that the rat rRNA genes are arranged as tandem repeats. The mean length of the repeating units was 37.2 kbp with a standard deviation of 1.3 kbp. These eleven molecules may represent repeating units of exactly the same length within the errors of the measurements, although a certain degree of length heterogeneity cannot be ruled out. If significantly shorter or longer repeating units exist, they are probably much less common than the 37.2 kbp unit.

The last section of the thesis describes the production of antibodies to non-histone chromosomal proteins which have been exposed to the ionic detergent sodium dodecyl sulfate (SDS). The presence of low concentrations of SDS did not seem to affect either production of antibodies or their general specificity. Also, a technique is described for the in situ immunofluorescent detection of protein antigens in polyacrylamide gels.