Evolution of a polyphenism by genetic accommodation

Polyphenisms are adaptations in which a genome is associated with discrete alternative phenotypes in different environments. Little is known about the mechanism by which polyphenisms originate. We show that a mutation in the juvenile hormone-regulatory pathway in Manduca sexta enables heat stress to reveal a hidden reaction norm of larval coloration. Selection for increased color change in response to heat stress resulted in the evolution of a larval color polyphenism and a corresponding change in hormonal titers through genetic accommodation. Evidently, mechanisms that regulate developmental hormones can mask genetic variation and act as evolutionary capacitors, facilitating the origin of novel adaptive phenotypes.     

SQL Server数据库"置疑"的原因及解决方法

SQL Server数据库因为软件,硬件或人为因素,常常被标记为"置疑",而导致数据库不能正常访问.文中给出了SQL Server数据库"置疑"的几种原因,以及由这些原因引起而采用相应的解决方法.这些解决方法均通过实践证明,简便可行,安全可靠,能够达到恢复数据库的目的.     

Auditory spatial receptive fields created by multiplication

Examples of multiplication by neurons or neural circuits are scarce, although many computational models use this basic operation. The owl's auditory system computes interaural time (ITD) and level (ILD) differences to create a two-dimensional map of auditory space. Space-specific neurons are selective for combinations of ITD and ILD, which define, respectively, the horizontal and vertical dimensions of their receptive fields. A multiplication of separate postsynaptic potentials tuned to ITD and ILD, rather than an addition, can account for the subthreshold responses of these neurons to ITD-ILD pairs. Other nonlinear processes improve the spatial tuning of the spike output and reduce the fit to the multiplicative model.     

Encoding of spatial location by posterior parietal neurons

The cortex of the inferior parietal lobule in primates is important for spatial perception and spatially oriented behavior. Recordings of single neurons in this area in behaving monkeys showed that the visual sensitivity of the retinotopic receptive fields changes systematically with the angle of gaze. The activity of many of the neurons can be largely described by the product of a gain factor that is a function of the eye position and the response profile of the visual receptive field. This operation produces an eye position-dependent tuning for locations in head-centered coordinate space.     

黄土丘陵区人工林土壤微生物PLFA标记多样性分析

为研究不同植被下土壤微生物群落结构多样性的差异,采用磷脂脂肪酸(PLFA)生物标记法,对山西吉县黄土丘陵区典型人工林刺槐、油松以及荒草地的土壤微生物群落结构多样性进行分析研究。结果表明:不同植被下土壤微生物PLFA标记含量存在显著差异,刺槐人工林的土壤微生物PLFA总量最大,细菌、真菌、放线菌的PLFA含量均大于油松人工林和荒草地;细菌PLFA含量在3种样地中的差异显著;2种人工林的真菌PLFA含量接近,而与荒草地差异显著,与荒草地相比,人工林的种植可明显提高土壤中真菌的比例;革兰氏阳性菌与革兰氏阴性菌呈现相同的变化趋势,油松人工林与荒草地2种菌群的PLFA含量接近,而与刺槐人工林差异显著。通过相关性分析发现,不同植被下土壤细菌、真菌、革兰氏阳性菌与革兰氏阴性菌各总PLFA与土壤养分因子之间密切相关;不同植被下土壤微生物群落多样性差异显著,刺槐人工林更为丰富,且各个菌群分布更为均匀,油松人工林土壤的微生物群落多样性及菌群分布均匀度与刺槐人工林土壤较为接近,荒草地土壤微生物群落多样性和均匀程度较2种人工林明显偏低。因此从微生物群落结构多样性的角度看,人工林的种植能够明显改善微生物群落结构,改善土壤质量;刺槐人工林是黄土丘陵区人工植被恢复的较好选择。      

Collagen defect induced by penicillamine

Collagen synthesis, as judged by the accumulation of collagen in a subcutaneous, induced granuloma, was significantly decreased by penicillamine. Penicillamine also caused a marked increase in the amount of soluble collagen in skin and a sharp drop in insoluble material. These findings, which reflect an abnormal pattern of collagen metdbolism, are accompanied by an inhibition of wound-healing and by skin fragility.     

Interferon induced by Plasmodium berghei

An inhibitor of virus is demonstrable in the serums of mice infected with Plasmodium berghei. The titer of the inhibitor, detectable within 10 hours after injection of parasitized blood, increases rapidly until 30 to 40 hours when it levels off or decreases slightly before reaching a plateau. The factor that induces production of the antiviral substance is not present in the plasma of the infected blood, and the inhibitor is not detectable in serums of mice injected with nonparasitized mouse erythrocytes. The inhibitor fulfills the essential require ments of an interferon.     

药剂诱导苎麻孤雌生殖效果初报

本试验于１９９４～１９９５年在江西农业大学进行，采用不同种类、浓度和配方的化学药剂诱导湘苎系列１～５号等１３个三麻品种弧雌生殖结实。对不同品种的平均诱导效果，以激动素最佳，二甲亚砜（ＤＭＳＯ）＋秋水仙素（Ｃｏｌ）混合液次之。从各个不同品种的反应来看，１％ＤＭＳＯ对资源１１号、１００μｇ／Ｌ激动素对湘苎４号、２％ＤＭＳＯ＋０．１％Ｃｏｌ对湘苎１号和５号、０．２％ＤＭＳＯ＋０．２％Ｃｏｌ对湘苎３号分别具有较好诱导单性结实作用。化学药剂的种类、浓度、配方均影响诱导效果。诱导产生的弧雌生殖体多为二倍体。     

Modulation of human visual cortex by crossmodal spatial attention

A sudden touch on one hand can improve vision near that hand, revealing crossmodal links in spatial attention. It is often assumed that such links involve only multimodal neural structures, but unimodal brain areas may also be affected. We tested the effect of simultaneous visuo-tactile stimulation on the activity of the human visual cortex. Tactile stimulation enhanced activity in the visual cortex, but only when it was on the same side as a visual target. Analysis of effective connectivity between brain areas suggests that touch influences unimodal visual cortex via back-projections from multimodal parietal areas. This provides a neural explanation for crossmodal links in spatial attention.     

Microfluidic adhesion induced by subsurface microstructures

Natural adhesives in the feet of different arthropods and vertebrates show strong adhesion as well as excellent reusability. Whereas the hierarchical structures on the surface are known to have a substantial effect on adhesion, the role of subsurface structures such as the network of microchannels has not been studied. Inspired by these bioadhesives, we generated elastomeric layers with embedded air- or oil-filled microchannels. These adhesives showed remarkable enhancement of adhesion ( approximately 30 times), which results from the crack-arresting properties of the microchannels, together with the surface stresses caused by the capillary force. The importance of the thickness of the adhesive layer, channel diameter, interchannel spacing, and vertical position within the adhesive has been examined for developing an optimal design of this microfluidic adhesive.     

ArcView在开发土壤养分空间分布图层中的应用

本文根据田间土壤采样数据，以“精确农业”为指导思想，以地统计学为基本原理，以GIS软件ArcView为工具，生成了土壤养分空间分布图，这是了解土壤养分空间变异性的重要手段，从而为以后的精确施肥奠定了基础。     

用极坐标矢量法设计空间凸轮廓线

针对空间凸轮廓线设计工作量大和设计精度较低的问题，以圆柱凸轮机构为例，提出用极坐标矢量解析法设计空间凸轮廓线。利用该方法推导出了空间凸轮廓线方程，采用Matlab软件编程计算，显示了凸轮廓线形状和凸轮压力角的变化情况。研究结果表明：当从动件运动规律一定时，随着从动件升程的增大，凸轮廓线变陡，有变尖的趋势，凸轮机构压力角也增大，动力性能变差；与传统图解法相比，极坐标矢量法设计空间凸轮廓线工作量减少了约50％，并有利于凸轮廓线的精确数控加工。     

Storage of spatial information by the maintenance mechanism of LTP

Analogous to learning and memory storage, long-term potentiation (LTP) is divided into induction and maintenance phases. Testing the hypothesis that the mechanism of LTP maintenance stores information requires reversing this mechanism in vivo and finding out whether long-term stored information is lost. This was not previously possible. Recently however, persistent phosphorylation by the atypical protein kinase C isoform, protein kinase Mzeta (PKMz), has been found to maintain late LTP in hippocampal slices. Here we show that a cell-permeable PKMz inhibitor, injected in the rat hippocampus, both reverses LTP maintenance in vivo and produces persistent loss of 1-day-old spatial information. Thus, the mechanism maintaining LTP sustains spatial memory.     

地塞米松诱导墟岗黄羽肉鸡免疫抑制的研究

将135只墟岗黄雏鸡随机分为3组,第1组为对照组,第2、第3组为处理组,10日龄开始,对照组胸肌注射0.5mL的生理盐水,第2、第3组分别按25mg·kg-1和50mg·kg-1的剂量,同部位注射用生理盐水稀释的地塞米松0.5mL;每天1次,连续注射3d.21、35、56日龄时每组分别随机抽取6只鸡进行屠宰取样,测定各组鸡的器官指数.另取3只鸡,测定各组鸡外周血液和脾脏淋巴细胞增殖转化率和脾脏的抗体形成细胞的数量.结果表明,注射地塞米松能显著降低墟岗黄鸡早期的体重,且与注射剂量呈依赖关系;降低鸡早期脾脏指数、法氏囊指数和胸腺指数;显著降低由ConA诱导的外周血液和脾脏淋巴细胞的增殖转化能力.     

Visual sensations induced by relativistic nitrogen nuclei

The ability of the human eye to detect nitrogen nuclei that enter the retina at speeds just above the Cerenkov threshold has been confirmed in an experiment at the Princeton Particle Accelerator. A system for beam transport and subject alignment delivered individual nitrogen nuclei onto a spot 3 millimeters in diameter on the retina at a visual angle of 7 degrees on the temporal side of the fovea. The beam particles entered the retina within 25 degrees of normal and induced visual sensations that had the appearance of streaks for three out of four subjects.     

Magnetosphere sawtooth oscillations induced by ionospheric outflow

The sawtooth mode of convection of Earth's magnetosphere is a 2- to 4-hour planetary-scale oscillation powered by the solar wind-magnetosphere-ionosphere (SW-M-I) interaction. Using global simulations of geospace, we have shown that ionospheric O(+) outflows can generate sawtooth oscillations. As the outflowing ions fill the inner magnetosphere, their pressure distends the nightside magnetic field. When the outflow fluence exceeds a threshold, magnetic field tension cannot confine the accumulating fluid; an O(+)-rich plasmoid is ejected, and the field dipolarizes. Below the threshold, the magnetosphere undergoes quasi-steady convection. Repetition and the sawtooth period are controlled by the strength of the SW-M-I interaction, which regulates the outflow fluence.     

稻飞虱诱导下水稻挥发物分析

【目的】明确稻飞虱诱导下不同抗性水稻材料挥发物的变化,为新型化学防虫剂研发及水稻抗稻飞虱机理研究提供理论依据。【方法】分别对高抗稻飞虱水稻材料YD1665和高感材料TN1进行稻飞虱取食胁迫,接虫后12 h利用固相微萃取法（SPME）提取褐飞虱取食前后抗感水稻材料的挥发物,并用气相色谱—质谱联用仪（GC-MS）对其化学成分进行鉴定分析。YD1665和TN1未接虫材料分别记为Y0和T0,接虫12 h后材料分别记为Y12和T12。【结果】水稻组成型挥发物鉴定结果表明,2-己烯醛、叶醇和β-紫罗兰酮等挥发物在Y0和T0中的含量均较高;挥发物主要组成成分在2种材料中存在明显差异,2-戊酮和2, 2, 4, 6, 6-五甲基庚烷仅在Y0中检测到,2-乙基呋喃和十六醛仅在T0中检测到。水稻诱导型挥发物鉴定结果表明,Y12以2-戊酮为代表的酮类物质为主,T12以2-己烯醛为代表的醛类物质为主;2-戊酮和2, 2, 4, 6, 6-五甲基庚烷等主要挥发物仅在Y12中检测到,2-乙基呋喃、十五醛、（E, E）-2, 4-己二烯醛和（E, E）-2, 4-庚二烯醛等主要挥发物仅在T12中检测到;2-己烯醛、β-紫罗兰酮为Y12和T12的主要共有挥发物成分。稻飞虱诱导前后水稻挥发物比较分析结果表明,稻飞虱诱导后2种材料的挥发物种类总数均有所增加;Y12的烷类、酮类和醇类相对含量变化最明显,但T12的挥发物种类相对含量变化不明显;2-戊酮、水杨酯甲酯、正己醇、十七烷、叶醇、（E）-2-己烯-1-醇和2, 6-二甲基-环己醇等物质在Y12中变化幅度较大,十五醛、BETA-环柠檬醛、十六醛、（E）-2-己烯-1-醇、叶醇、β-紫罗兰酮和肉豆蔻酸异丙酯等物质在T12中变化幅度较大。【结论】稻飞虱诱导后,水稻体内的水杨酯甲酯、肉豆蔻酸异丙酯、2-戊酮、β-紫罗兰酮、十五醛、十六醛、（E）-2-己烯-1-醇、叶醇、正己醇和2, 6-二甲基-环己醇等物质的变化幅度较大,推测这些挥发物与水稻抗稻飞虱有密切关系。     

Hyperphagia in ruminants induced by a depressant

Attempts at causing ventromedial hyperphagia in ruminants have been hitherto unsuccessful. In our experiments perfusion of the ventriculocisternal system with pentobarbital caused marked hyperphagia. This suggests that the ventromedial hypothalamic area is functioning in ruminants, probably as in monogastric animals, by inhibiting the lateral area.     

Chromosomal aberrations induced in barley by LSD

Seeds of hulled barley (Hordeum vulgare) were germinated and then treated with LSD. Preparations of squashed root tips stained with Feulgen revealed extensive chromosomal aberrations, most of which were chromosome breaks. Nearly half of the breaks occurred in the region of the primary constriction.