Shape and nature of small sedimentary quartz particles

Quartz particles in sediments become flatter with decreasing size; a cleavage mechanism may operate below the critical size of about 100 microns. Flat particles would tend to form a more open packing than spherical particles, and this may contribute to the collapse of loess and similar soils and the sudden loss of strength observed in "sensitive" clay soils.     

Morphology and related chemistry of small lunar particles from tranquillity base

Glass spherules show multiple high-velocity impact craters and are coated with small particles including glass, plagioclase, clinopyroxene, ilmenite, olivine, chromite, rock fragments, and frozen droplets of iron, nickel-iron, and troilite. These spherules passed through an impact cloud of hot fragmental material, condensing iron-rich vapor and high-velocity projectiles. Breccia contains concentric, accretionary lapilli units and appears to be a sintered deposit from a hot lunar base surge generated by impact.     

Structural rearrangements that govern flow in colloidal glasses

Structural rearrangements are an essential property of atomic and molecular glasses; they are critical in controlling resistance to flow and are central to the evolution of many properties of glasses, such as their heat capacity and dielectric constant. Despite their importance, these rearrangements cannot directly be visualized in atomic glasses. We used a colloidal glass to obtain direct three-dimensional images of thermally induced structural rearrangements in the presence of an applied shear. We identified localized irreversible shear transformation zones and determined their formation energy and topology. A transformation favored successive ones in its vicinity. Using continuum models, we elucidated the interplay between applied strain and thermal fluctuations that governs the formation of these zones in both colloidal and molecular glasses.     

以金磁微球为载体的H5N1 AIV免疫PCR检测方法的建立

【目的】将高特异性的抗原-抗体反应与高灵敏性的PCR扩增技术相结合,建立快速检测低浓度H5N1禽流感病毒(Avianinfluenzavirus,AIV)的免疫PCR方法。【方法】以pUC19为模板,采用5′端标记有生物素的引物进行PCR扩增,制备含有生物素的报告DNA分子。以金磁微球为固相吸附载体,通过亲和素-生物素的桥联作用,将含有生物素的报告DNA分子与生物素标记的抗AIVH5N1血凝素蛋白的检测抗体分子连接,H5N1AIV与检测抗体结合后,体外扩增报告DNA,间接放大低含量病毒信号,建立可有效检测微量H5N1AIV的免疫PCR方法。对建立的免疫PCR方法的最适报告DNA浓度、最适链亲和素工作浓度、灵敏度和特异性进行确定和评价。【结果】建立的免疫PCR方法最适报告DNA质量浓度为1ng/mL,最适链亲和素工作质量浓度为20ng/mL,该方法可成功检测到10-4EID50/mL的H5N1AIV,而且特异性良好。【结论】建立的以金磁微球为吸附载体的免疫PCR是一种灵敏度高、特异性好的检测微量H5N1AIV的方法。     

Energetics of hydrogen bond network rearrangements in liquid water

A strong temperature dependence of oxygen K-edge x-ray absorption fine structure features was observed for supercooled and normal liquid water droplets prepared from the breakup of a liquid microjet. Analysis of the data over the temperature range 251 to 288 kelvin (-22 degrees to +15 degrees C) yields a value of 1.5 +/- 0.5 kilocalories per mole for the average thermal energy required to effect an observable rearrangement between the fully coordinated ("ice-like") and distorted ("broken-donor") local hydrogen-bonding configurations responsible for the pre-edge and post-edge features, respectively. This energy equals the latent heat of melting of ice with hexagonal symmetry (ice Ih) and is consistent with the distribution of hydrogen bond strengths obtained for the "overstructured" ST2 model of water.     

Site-specific X-chromosome rearrangements from hybrid dysgenesis in Drosophila melanogaster

When the germ line of Drosophila males is destabilized by a syndrome known as hybrid dysgenesis, X-chromosome rearrangements are found in up to 10 percent of the gametes produced. Some of these aberrations are simple inversions, but many are complex multibreak rearrangements. Furthermore, most of the breakpoints fall into a few highly localized positions on the chromosome. These positions are mostly at points of intercalary heterochromatin and may vary from one strain to the next. the results suggest that they may represent points of insertion of mobile DNA sequences.     

Droplet Chondrules: Jetting on high-velocity collision of small meteoritie particles may have produced droplet chondrules

I have proposed that droplet chondrules were formed by jetting during collision of meteoritic particles with diameters ranging in order of magnitude from 0.5 mm to 20 cm. This conclusion, based on a dynamic model for the collision process, supports the hypotheses of Wasson (2) (based on geochemical considerations) and Whipple (35) and Cameron (36) (based on dynamic model considerations) that chondrules were formed from objects less than 1 m in radius. In this model, the formation of chondrules is viewed as a textural, but not substantial chemical, change in the material of the early solar system. Droplets of melt produced by jetting are mixtures of material derived from two parent grains. Jets are probably not appreciably fractionated (except in volatile elements) either in the short duration of the shock events (several microseconds) or in subsequent cooling. This model for the formation of droplet chondrules implies that they were formed at a time in the history of the solar system when particle sizes were small. The most likely time for this condition is early in the process of accretion of nebular dust to planetary matter. Since velocities less than approximately 1.5 km/sec are required for the agglomeration and accretion of particles (37), the relatively higher velocities indicated for droplet chondrule-forming collisions indicate an early high-velocity destructive epoch amidst the general trend toward accretion of material.     

Proximity of chromosomal loci that participate in radiation-induced rearrangements in human cells

Rearrangements involving the RET gene are common in radiation-associated papillary thyroid cancer (PTC). The RET/PTC1 type of rearrangement is an inversion of chromosome 10 mediated by illegitimate recombination between the RET and the H4 genes, which are 30 megabases apart. Here we ask whether despite the great linear distance between them, RET and H4 recombination might be promoted by their proximity in the nucleus. We used two-color fluorescence in situ hybridization and three-dimensional microscopy to map the positions of the RET and H4 loci within interphase nuclei. At least one pair of RET and H4 was juxtaposed in 35% of normal human thyroid cells and in 21% of peripheral blood lymphocytes, but only in 6% of normal mammary epithelial cells. Spatial contiguity of RET and H4 may provide a structural basis for generation of RET/PTC1 rearrangement by allowing a single radiation track to produce a double-strand break in each gene at the same site in the nucleus.     

小型收割机切割机构运动学和动力学分析及惯性力平衡

把小型收割机切割机构简化为曲柄滑块机构，指出传统分析中存在的问题，对切割机构运动学和动力学分析及惯性力平衡进行了探索，建立了计算机模型     

Translocation and rearrangements of the c-myc oncogene locus in human undifferentiated B-cell lymphomas

The locus for the cellular myc (c-myc) oncogene in humans is located on the region of chromosome 8 that is translocated to chromosome 14 in cells from most undifferentiated B-cell lymphomas. It is shown in this study that the c-myc locus is rearranged in 5 out of 15 cell lines from patients with undifferentiated B-cell lymphomas, and that the rearrangement involves a region at the 5' side of an apparently intact c-myc gene. In at least three patients, this rearranged region appears to contain immunoglobulin heavy chain mu sequences that are located on chromosome 14. The data indicate that this region contains the crossover point between chromosomes 8 and 14. The break point can occur at different positions on both chromosomes among individual cell lines.     

Energetic particles in the jovian magnetotail

When the solar wind hits Jupiter's magnetic field, it creates a long magnetotail trailing behind the planet that channels material out of the Jupiter system. The New Horizons spacecraft traversed the length of the jovian magnetotail to >2500 jovian radii (RJ; 1 RJ identical with 71,400 kilometers), observing a high-temperature, multispecies population of energetic particles. Velocity dispersions, anisotropies, and compositional variation seen in the deep-tail (greater, similar 500 RJ) with a approximately 3-day periodicity are similar to variations seen closer to Jupiter in Galileo data. The signatures suggest plasma streaming away from the planet and injection sites in the near-tail region (approximately 200 to 400 RJ) that could be related to magnetic reconnection events. The tail structure remains coherent at least until it reaches the magnetosheath at 1655 RJ.     

Chains of particles in shear flow

Interesting physical models of threads, rouleaux of red blood cells, and other flexible structures (including macromolecules) have been prepared with chains of spheres and discs. When suspended in a viscous liquid undergoing shear flow, the aggregates rotate as nearly rigid bodies, even though they have no tensile strength or stiffness until shear rates high enough to cause bending and then breaking are reached. By adding a second liquid phase which causes a meniscus to bridge adjacent particles, sufficient tensile strength can be provided to cause bending without breakage.     

黔西南红土型金矿与云南东川拖布卡-播卡金矿苔藓植物比较研究

对黔西南红土型金矿苔藓植物的调查结果显示,黔西南红土型金矿苔藓植物共14科53属124种,其中苔类植物1科2属2种分别为叶苔科叶苔属拟卵叶叶苔和细茎叶苔;藓类植物13科52属122种。与云南东川拖布卡-播卡金矿苔藓植物比较发现,黔西南红土型金矿苔藓植物丰富度大于云南东川拖布卡-播卡金矿,生活型以丛集型为主,两矿区共有科为3科,共有属为10属,相同种为10种,种的相似性较小,种的相似性系数为6.99%,属的相似性指数为15.87%,科的相似性指数为17.6%,其相同种中土生对齿藓Didymodon vinealis(Brid.)Zander、云南墙藓Tortula yunnanensis P.C.Chen和硬叶小金发藓Pogonatum neesii(C.Muell.)Dozy.分布较广泛,可进一步作为生态修复研究的材料。