新疆南疆籽棉超高产机理研究

为探寻新疆南疆地区籽棉9000 kg·hm-2超高产机理以及相关的指标,对南疆地区生态条件下超高产田、高产田、中高产田进行了调查研究与数据采集。研究发现:要获得超高产,首先要有良好的基础地力,有机质含量超10 g·kg-1,种植密度18×104~21×104株·hm-2为宜;其次,塑造良好株型,株高65~75 cm,茎粗接近10 mm,果枝9~10台,棉铃空间分布均匀,纵向上、中、下果枝棉铃比例3.2∶4.7∶2.1,横向第一、二果节比例7∶3,初花至盛铃LAI、SPAD、Pn一直维持较高水平,盛铃前后达到最大,后期下降缓慢;最后,氮磷钾分配上,前期差异不大,进入花铃期生殖生长明显增强,蕾花铃氮磷钾比例明显增大,一直维持到见絮,超高产处理的蕾花铃干物质量比例明显高于其它处理8%以上,见絮时蕾花铃干物质量达到了6 402 kg·hm-2。以指标数据作参考,塑造良好株型,协调棉铃空间分布,维持较高较长的光合速率,减缓LAI、SPAD下降速度,促进生殖生长,合理养分分配,便能实现产量目标。     

兰州市尘暴过程中降尘粒度特征探析

通过对兰州市两次强度上有较大差异的尘暴样的采集、粒度分析及其与自然降尘样的对比研究,揭示出兰州市尘暴降尘粒度特性的一些细微特征。不论是自然降尘样还是尘暴样,皆以4～63μm的粉砂为主,说明粉砂粒级的颗粒是兰州地区自然降尘与沙尘暴所携带的主要组分;虽然含量甚微,但是尘暴样中存在近源低空气流所搬运的粒径(181.97～724.44μm)较大的粗颗粒物质。在粒径-体积百分含量曲线上,尘暴样基本上为三峰分布模式,区别于自然降尘样的双峰模式。同时,尘暴样具有向粗、细颗粒区间(尤其是细颗粒区间)延伸并富集的特点,尘暴强度越大,其延伸富集的程度也越明显,而且,随着尘暴强度的增大,其主峰的众数粒径呈减小趋势。     

Aetiology and histopathology of bovine mastitis of espontaneous occurrence

Infectious bovine mastitis is responsible for serious economic losses in dairy cattle breeding. Information about the damages caused by micro-organisms is of great interest and importance. The purpose of the present study was to report on the microbiological and histopathological aspects of the mammary parenchymas of slaughtered dairy cows. A total of 184 mammary glands were examined and samples of mammary parenchyma were collected for microbiological and histopathological examinations. Micro-organisms were isolated from 69.6% samples; 23 (12.5%) of the 184 samples did not show histological changes; inflammatory response was observed in 56 (30.4%) samples; inflammatory response and repair were present in 82 (44.6%) samples; repair process was verified in 23 (12.5%) of the mammary glands. Coagulase-negative Staphylococci were observed in 53.8% of the samples followed by coagulase-positive Staphylococci (7.6%), Prototheca sp. (2.2%) and Streptococcus dysgalactiae (1.6%). Coagulase-negative Staphylococci and coagulase-positive Staphylococci were associated mainly to chronic inflammatory response and chronic inflammatory response and repair. Samples from which no micro-organisms were isolated (n = 56) had no histological changes in 82.6% of the cases. These results were higher (P < 0.05) when compared to the samples with micro-organisms and without histological changes (17.4%).     

GONG Observations of Solar Surface Flows

Doppler velocity observations obtained by the Global Oscillation Network Group (GONG) instruments directly measure the nearly steady flows in the solar photosphere. The sun's differential rotation is accurately determined from single observations. The rotation profile with respect to latitude agrees well with previous measures, but it also shows a slight north-south asymmetry. Rotation profiles averaged over 27-day rotations of the sun reveal the torsional oscillation signal-weak, jetlike features, with amplitudes of 5 meters per second, that are associated with the sunspot latitude activity belts. A meridional circulation with a poleward flow of about 20 meters per second is also evident. Several characteristics of the surface flows suggest the presence of large convection cells.     

Domain dynamics during ferroelectric switching

The utility of ferroelectric materials stems from the ability to nucleate and move polarized domains using an electric field. To understand the mechanisms of polarization switching, structural characterization at the nanoscale is required. We used aberration-corrected transmission electron microscopy to follow the kinetics and dynamics of ferroelectric switching at millisecond temporal and subangstrom spatial resolution in an epitaxial bilayer of an antiferromagnetic ferroelectric (BiFeO(3)) on a ferromagnetic electrode (La(0.7)Sr(0.3)MnO(3)). We observed localized nucleation events at the electrode interface, domain wall pinning on point defects, and the formation of ferroelectric domains localized to the ferroelectric and ferromagnetic interface. These results show how defects and interfaces impede full ferroelectric switching of a thin film.