Towards genetic genome projects: genomic library screening and gene-targeting vector construction in a single step.

We have developed technologies that simplify genomic library construction and screening, substantially reducing both the time and the cost associated with traditional library screening methods and facilitating the generation of gene-targeting constructs. By taking advantage of homologous recombination in Escherichia coli, we were able to use as little as 80 bp of total sequence homology to screen for a specific gene from a genomic library in plasmid or phage form. This method, called recombination cloning (REC), takes only a few days instead of the several weeks required for traditional plaque-lift methods. In addition, because every clone in the mouse genomic library we have constructed has a negative selection marker adjacent to the genomic insert, REC screening can generate gene-targeting vectors in one step, from library screening to finished construct. Conditional targeting constructs can be generated easily with minimal additional manipulation.     

The extent of linkage disequilibrium in Arabidopsis thaliana.

Linkage disequilibrium (LD), the nonrandom occurrence of alleles in haplotypes, has long been of interest to population geneticists. Recently, the rapidly increasing availability of genomic polymorphism data has fueled interest in LD as a tool for fine-scale mapping, in particular for human disease loci. The chromosomal extent of LD is crucial in this context, because it determines how dense a map must be for associations to be detected and, conversely, limits how finely loci may be mapped. Arabidopsis thaliana is expected to harbor unusually extensive LD because of its high degree of selfing. Several polymorphism studies have found very strong LD within individual loci, but also evidence of some recombination. Here we investigate the pattern of LD on a genomic scale and show that in global samples, LD decays within approximately 1 cM, or 250 kb. We also show that LD in local populations may be much stronger than that of global populations, presumably as a result of founder events. The combination of a relatively high level of polymorphism and extensive haplotype structure bodes well for developing a genome-wide LD map in A. thaliana.     

重载流多芯电缆周围的磁场 Ⅰ. 理论模型

多芯电力电缆在低压配电系统中常被用作配电干线，这种重载流电缆周围的极低频磁场可能干扰附近敏感电子设备的正常运行，甚至影响暴露于该场下的人体的健康，为分析这种磁场的分布特性，建立了多芯电缆周围磁场的载流平行螺旋线模型，并推导了周围磁场的简化计算公式，基于所提出的理想模型对电缆周围电磁的特性进行了分析，发现在电缆的半径方向上磁场随距离衰减的速度大于指数衰减速度，在平行于电缆轴线的直线上和在电缆抽轴圆周线上，磁场的幅值和相角都随观测点的位置周期变化，理论计算结果表明，常用规格的多芯电力电缆在载额定电流的情况下，距电缆2m外空间中的磁场已小于有关国际标准的限值。     

长白山采集的中国东北新记录苔藓植物

在对中国和加拿大苔藓学者联合于中国东北最高的长白山采集的2千余份标本鉴定的基础上。认定有苔藓植物59科，152属，300种。报道了中国大陆新记录1属－小曲柄藓属（Campylostelium）。中国东北新记录2属－直蓑衣藓属（Macrocoma）和同叶藓属（Isopterygium）。中国东北新记录5种－褶叶裂叶苔（Lophozia incisa）。假狗牙藓（Cynodontium fallax）。细枝牛毛藓（Ditrichum gracile）。散叶牛毛藓（Ditrichum divarcatum）和细叶棉藓（Plagiothecium latebricola）。     

Palaeolake and palaeoenvironment between 42 and 18 kaBP in tengger desert, NW China

Comprehensive field investigations and laboratory analyses show that palaeolakes, including fresh- mesohaline water Megalake Tengger and other semi-con- nected, isolated water bodies, during late Pleistocene covered an area of more than 20000 km², which is more than half of the Tengger Desert in NW China. Stratigraphic correlation and chronological evidence indicate that before ca. 42000 aBP the area was more arid. The palaeolakes started to develop around 40000 uncal. ¹⁴C aBP but until 37000 ¹⁴C aBP their scope was limited. High water levels established from 35000 ¹⁴C aBP lasted until 22000 ¹⁴CaBP. Lake levels regressed between 22000 and 20000 ¹⁴C aBP but transgressed from 20000 to 18600 ¹⁴C aBP. Subsequently, water level declined further and the Megalake Tengger finally desiccated at around 18000 ¹⁴C aBP. Megalake Tengger possessed a fresh-mesohaline water property, implying that the regional precipitation increased significantly. During the period of Megalake Tengger, the climate was warmer-humid than present. The annual rainfall was 250 to 350 mm more than that of today and the temperature was 1.5 to 3.0℃ higher.     

Mass march of termites into the deadly trap.

Carnivorous pitcher plants of the genus Nepenthes are not usually very selective about their prey, catching anything that is careless enough to walk on their slippery peristome, but Nepenthes albomarginata is an exception. We show here that this plant uses a fringe of edible white hairs to lure and then trap its prey, which consists exclusively of termites in enormous numbers. This singular feature accounts for the specialization of N. albomarginata for one prey taxon, unique so far among carnivorous plants.     

Superoxide activates mitochondrial uncoupling proteins.

Uncoupling protein 1 (UCP1) diverts energy from ATP synthesis to thermogenesis in the mitochondria of brown adipose tissue by catalysing a regulated leak of protons across the inner membrane. The functions of its homologues, UCP2 and UCP3, in other tissues are debated. UCP2 and UCP3 are present at much lower abundance than UCP1, and the uncoupling with which they are associated is not significantly thermogenic. Mild uncoupling would, however, decrease the mitochondrial production of reactive oxygen species, which are important mediators of oxidative damage. Here we show that superoxide increases mitochondrial proton conductance through effects on UCP1, UCP2 and UCP3. Superoxide-induced uncoupling requires fatty acids and is inhibited by purine nucleotides. It correlates with the tissue expression of UCPs, appears in mitochondria from yeast expressing UCP1, and is absent in skeletal muscle mitochondria from UCP3 knockout mice. Our findings indicate that the interaction of superoxide with UCPs may be a mechanism for decreasing the concentrations of reactive oxygen species inside mitochondria.     

Determination of the Altyn Tagh strike-slip fault basin and its relationship with mountains

A special extended basin topography is developed in the middle segment of the Altyn Tagh Fault Zone. The ratio of its length to width is over 50. The long boundaries at the two sides of the basin are controlled by the straight normal faults with strike-slip component. Within the basin, the Cenozoic strata are spread. The Altyn Tagh main fault goes through the basin, and a series of strike-slip topography was formed within the basin. The reverse thrust structures were formed at the two sides of the center of the basin, thus making the geological bodies composed of old metamorphic rocks at the two sides of the basin extrude vertically，and forming the extended massif (mountain) at the sides of the basin and parallel to the basin. This special topography was called the strike-slip fault basin. The giant extended strike-slip fault basin began to form during Pliocene, and its topography was basically formed during the late Pleistocene. It is the special topography formed during the strike-slip deformation process of the Altyn Tagh Fault Zone and under both transpression and uplifting.     

Summertime Subtropical Countercurrent on isopycnals in the western North Pacific

Circulations on isopycnals (σrθ) in the western North Pacific were investigated by using P-vector method;the data were taken from the U.S. Navy's climatological temperature and salinity dataset (public domain) with 1/2°×1/2° resolution. Results not only show the main circulation systems on isopycnals in the western North Pacific such as the North Equatorial Current (NEC), Kuroshio and Kuroshio Countercurrent, but also reveal the Subtropical Countercurrent (STCC) clearly. In this note we pay attention to discussing the distribution of STCC in summer (in June).The STCC flows eastward along a winding road; on shallow isopycnals, the STCC originates from the area east of Bashi Strait at about 122.5°E; with the isopycnals increasing, the origin and flow core of STCC move to north and east, but the main part of STCC is still between 18° and 23.5°N, i.e.near the Tropic of Cancer. There exists STCC on all isopycnals between the sea surface and 25.8 σθThe current vectors of STCC on isopycnais are shown for the first time, and the distribution of the potential vorticity indicates that STCC is just overlying the southern boundary of the Subtropical Mode Water (STMW).``     

Rutile U-Pb age for the ultra-high pressure eclogite from the dabie Mountains,central China:Evideence for rapid cooling

The U-Pb isotope compositions of rutile, omphacite and garnet in the eclogite from the Jinheqiao area in the Southern Dabie ultrahigh-pressure metamorphic zone were analyzed. The consistent high precision U-Pb age (218 ±(1.2) Ma of rutile in eclogite from the Dabie Mountains was obtained by two ways of isochron and common Pb correction based on the composition of omphacite. This proves that the omphacite in eclogite has a U/Pb ratio (μ = 2.8) low enough to be used for common Pb correction in the analyses of rutile. Under the rapid cooling condition (40℃/Ma) the closure temperature for U-Pb diffusion in rutile is about 470℃. Thus, this U-Pb age of rutile proves that 218 Ma should be the cooling age of eclogite at 470℃ instead of the peak metamorphic age.