南极普里兹湾关键物理海洋学问题研究进展及未来趋势

南极普里兹湾及其邻近海域关键物理海洋学问题包括水团特性、环流特征和冰架 海洋 海冰相互作用过程等。该海域水团可以分为南极表层水、绕极深层水、南极底层水、南极陆架水和南极冰架水等,受外部条件影响,这些水团时空变化显著。普里兹湾区域的环流以普里兹湾流涡,西向的沿岸流和东向的绕极流,以及两者之间的南极辐散带的环流为主要特征,地形是环流特征的关键影响因素。埃默里冰架 海洋的相互作用过程显著影响普里兹湾海域的水团特性和环流状况。冰泵机制,是埃默里冰架外海水进入冰穴,并引起冰架底部消融和冻结的重要原因。冰架 海洋 海冰相互作用形成的低温高盐水,是普里兹湾形成南极底层水的潜在因素之一。加强现场观测,并建立高分辨率的冰架 海洋 海冰耦合模型系统是研究普里兹湾海域物理海洋学关键过程和变化机制的重要手段,是南极研究的发展趋势。     

A fine-scale map of recombination rates and hotspots across the human genome

Genetic maps, which document the way in which recombination rates vary over a genome, are an essential tool for many genetic analyses. We present a high-resolution genetic map of the human genome, based on statistical analyses of genetic variation data, and identify more than 25,000 recombination hotspots, together with motifs and sequence contexts that play a role in hotspot activity. Differences between the behavior of recombination rates over large (megabase) and small (kilobase) scales lead us to suggest a two-stage model for recombination in which hotspots are stochastic features, within a framework in which large-scale rates are constrained.     

Photochemical air pollution in the northeast United States

Statistical analyses of meteorological and contaminant data and chemical kinetic modeling demonstrate that (i) the concentrations of ozone in the New Jersey-New York City metropolitan area are regional in character; (ii) ozone concentrations in Connecticut are increased by approximately 20 percent as a consequence of primary emissions in the New Jersey-New York City metropolitan region and subsequent transport; and (iii) the concentrations of a variety of products of smog chemistry in the New Jersey area are markedly increased by an increase in NO emissions, but are minimally affected by a change in hydrocarbon emissions.     

Small molecule-induced allosteric activation of the Vibrio cholerae RTX cysteine protease domain

Vibrio cholerae RTX (repeats in toxin) is an actin-disrupting toxin that is autoprocessed by an internal cysteine protease domain (CPD). The RTX CPD is efficiently activated by the eukaryote-specific small molecule inositol hexakisphosphate (InsP6), and we present the 2.1 angstrom structure of the RTX CPD in complex with InsP6. InsP6 binds to a conserved basic cleft that is distant from the protease active site. Biochemical and kinetic analyses of CPD mutants indicate that InsP6 binding induces an allosteric switch that leads to the autoprocessing and intracellular release of toxin-effector domains.     

Molecular evidence for the early colonization of land by fungi and plants

The colonization of land by eukaryotes probably was facilitated by a partnership (symbiosis) between a photosynthesizing organism (phototroph) and a fungus. However, the time when colonization occurred remains speculative. The first fossil land plants and fungi appeared 480 to 460 million years ago (Ma), whereas molecular clock estimates suggest an earlier colonization of land, about 600 Ma. Our protein sequence analyses indicate that green algae and major lineages of fungi were present 1000 Ma and that land plants appeared by 700 Ma, possibly affecting Earth's atmosphere, climate, and evolution of animals in the Precambrian.     

Direct observations of North Pacific ventilation: brine rejection in the Okhotsk Sea

Brine rejection that accompanies ice formation in coastal polynyas is responsible for ventilating several globally important water masses in the Arctic and Antarctic. However, most previous studies of this process have been indirect, based on heat budget analyses or on warm-season water column inventories. Here, we present direct measurements of brine rejection and formation of North Pacific Intermediate Water in the Okhotsk Sea from moored winter observations. A steady, nearly linear salinity increase unambiguously caused by local ice formation was observed for more than a month.     

Detection of a large-scale mass redistribution in the terrestrial system since 1998

Earth's dynamic oblateness (J2) had been undergoing a decrease, according to space geodetic observations over the past 25 years, until around 1998, when it switched quite suddenly to an increasing trend that has continued to the present. The secular decrease in J2 resulted primarily from the postglacial rebound in the mantle. The present increase, whose geophysical cause(s) are uncertain, thus signifies a large change in global mass distribution with a J2 effect that considerably overshadows that of mantle rebound.     

Binding of the human Prp31 Nop domain to a composite RNA-protein platform in U4 snRNP

Although highly homologous, the spliceosomal hPrp31 and the nucleolar Nop56 and Nop58 (Nop56/58) proteins recognize different ribonucleoprotein (RNP) particles. hPrp31 interacts with complexes containing the 15.5K protein and U4 or U4atac small nuclear RNA (snRNA), whereas Nop56/58 associate with 15.5K-box C/D small nucleolar RNA complexes. We present structural and biochemical analyses of hPrp31-15.5K-U4 snRNA complexes that show how the conserved Nop domain in hPrp31 maintains high RNP binding selectivity despite relaxed RNA sequence requirements. The Nop domain is a genuine RNP binding module, exhibiting RNA and protein binding surfaces. Yeast two-hybrid analyses suggest a link between retinitis pigmentosa and an aberrant hPrp31-hPrp6 interaction that blocks U4/U6-U5 tri-snRNP formation.     

驻马店市粮食生产核心区建设中存在的问题与对策

阐述了驻马店市粮食生产现状和粮食生产核心区建设过程中存在的问题,提出了强力推进＂三化＂协调发展,科学制定粮食生产核心区建设规划,加快完善农业基础设施建设,加速推进农村土地流转,充分调动农民种粮和政府抓粮的积极性,努力提高农业科技含量等一系列对策建议。     

Activated expression of the N-myc gene in human neuroblastomas and related tumors

In neuroblastoma lines in which the N-myc gene is present as a single copy, the expression of N-myc as messenger RNA is increased relative to that in nonneuroblastoma cell lines and tumors. The increase of expression in neuroblastomas with amplified N-myc genes is the result of (i) an increase in the absolute amount of expression of each N-myc gene and (ii) an increase in the copy number of the N-myc gene. A second gene--which is amplified in many of the same lines as N-myc--is expressed to about the same degree in most human cell lines and primary tumors regardless of origin (when normalized to gene copy number). Thus, a change in the regulation of N-myc expression in neuroblastomas and certain other tumors results in greatly increased expression of each N-myc gene copy.     

Banded corals: changes in oceanic carbon-14 during the little ice age

Radiocarbon analyses and stable isotope measurements are presented foro recent cores of banded corals from the Florida Straits. These values provide a record of variations in the ratio of carbon-14 to carbon-12 in the dissolved inorganic carbon in the surface waters of the Gulf Stream from A.D. 1642 to 1800. An increase in the carbon-14/carbon-12 ratio of 7 per mil for coral growth during the early 1700's was most likely induced by an increase in the carbon-14/carbon-12 ratio of 20 per mil in the atmospheric carbon dioxide that occurred at about 1700. The ratios of oxygen 18 to oxygen-16 in these coral bands show a small decrease of a water temperature ( approximately 1 degrees C) during the latter part of the Little Ice Age (1700 to 1725). These results support the hypothesis that the increase in atmospheric carbon-14 at about 1700, and possibly the temperature change as well, was caused by a decrease in solar activity (Maunder sunspot minimum).     

小麦根高亲和NO_3~-转运体全长基因(TaNRT2.1)的克隆和鉴定

 在前期获得的 pTaAF 的工作基础上,采用 RACE 方法进一步克隆和鉴定了小麦根 NO3 转运体全长基因-(TaNRT2.1)。将TaNRT2.1和已知的硝态氮转运体基因家族进行同源性比较,指出TaNRT2.1属于HATS中的NRT2家族。Southern　印迹揭示小麦基因组中有1个TaNRT2.1拷贝。Northern　分析示出硝态氮可瞬时诱导TaNRT2.1　mRNA积累,NO 处理 1 h　TaNRT2.1　mRNA很快增加,4　h 达到最大,24　h恢复至诱导前水平,具根专一表达特点。 - 3     

Visualization of the molecular Jahn-Teller effect in an insulating K4C60 monolayer

We present a low-temperature scanning tunneling microscopy (STM) study of K(x)C60 monolayers on Au(111) for 3 < or = x < or = 4. The STM spectrum evolves from one that is characteristic of a metal at x = 3 to one that is characteristic of an insulator at x = 4. This electronic transition is accompanied by a dramatic structural rearrangement of the C60 molecules. The Jahn-Teller effect, a charge-induced mechanical deformation of molecular structure, is directly visualized in the K4C60 monolayer at the single-molecule level. These results, along with theoretical analyses, provide strong evidence that the transition from metal to insulator in K(x)C60 monolayers is caused by the Jahn-Teller effect.     

农业产业结构调整与产业化经营策略

回顾了我国农业产业结构调整的历史,论述了当前农业产业结构调整的必要性,提出了农业产业结构调整的原则对策和经营方式的转变。指出新时期农业产业结构调整较之过去的结构调整具有明显的特点和本质的不同。决不是多种点什么,少种点什么的问题,而是一次面向市场经济的全面调整,具有全局性、高层次性、长期性和深刻性。     

Oxygen isotopes: experimental vapor fractionation and variations in tektites

High-temperature (about 2800 degrees C) vapor fractionation of a silicate glass that originally contained 82 percent by weight of SiO(2) resulted in a decrease of the silica content to 45 percent. Oxygen isotope analyses show that the O(18)/O(16) ratio increased from 13.80 per mil in the starting material to 14.47 and 15.03 per mil in the residuum. This suggests that bediasites, which also exhibit an increase in this ratio with decreasing content of silica, have been subjected to a process of vapor fractionation.     

Biochemical Anomaly in Flower Extracts of Interspecific Hybrids between Lotus Specoes

Chromatographic analyses of unhydrolyzed flower extracts of two Lotus hybrids and of two individuals from an F(2) population have revealed the presence of a substance which was not present in the extracts of the parental species. This hybrid substance has not been identified, but its occurrence might be explained as the result of gene interaction in heterozygous individuals.     

发展证券代理业，促进天津证券市场发展

证券代理在证券市场的发展中占有重要地位。本文在深入分析天津证券市场发展中存在问题的基础上，阐述了发展天津证券代理业务的对策。     

农村公共服务效率及其影响因素的实证研究

以苏北地区为例,对农村公共服务效率及其影响因素进行了实证分析。结果表明,苏北农村公共服务效率呈现波动上升趋势;农村公共服务效率与公平之间存在非线性关系;城镇化水平和市场化水平对农村公共服务效率的影响为正,但后者的影响不显著,这可能与目前的市场机制不完善有关。政府在农村公共服务供给过程中应正确处理公平与效率、政府供给与市场供给两种关系,建立完善的多元化供给体制。     

多效唑对大豆生长发育中碳氮代谢动态变化的影响及其与产量形成关系的研究

本文阐述了多效唑对大豆初花期、盛花期、结荚期、鼓粒期的净光合速率,叶绿素含量,还原糖、蔗糖、粗淀粉含量,全氮含量,硝酸还原酶活性的作用。根据测定的结果,分析并讨论了多效唑对于大豆不同生长发育时期C—N代谢动态变化的影响及其与产量形成的关系,我们的研究结果表明,多效唑由于能够有效地影响大豆的上述生理效应,调节好大豆植株内的C—N代谢,减少大豆花、荚的脱落,增加籽粒数和单株粒重,从而促进了大豆产量的提高。     

Nuclear genomic sequences reveal that polar bears are an old and distinct bear lineage

Recent studies have shown that the polar bear matriline (mitochondrial DNA) evolved from a brown bear lineage since the late Pleistocene, potentially indicating rapid speciation and adaption to arctic conditions. Here, we present a high-resolution data set from multiple independent loci across the nuclear genomes of a broad sample of polar, brown, and black bears. Bayesian coalescent analyses place polar bears outside the brown bear clade and date the divergence much earlier, in the middle Pleistocene, about 600 (338 to 934) thousand years ago. This provides more time for polar bear evolution and confirms previous suggestions that polar bears carry introgressed brown bear mitochondrial DNA due to past hybridization. Our results highlight that multilocus genomic analyses are crucial for an accurate understanding of evolutionary history.