Color adaptation of spatial frequency detectors in the human visual system

Observers exposed alternately to a vertical grating of one spatial frequency in red light and a vertical grating of different spatial frequency in green light subsequently report frequency-specific color aftereffects when shown gratings in white light. Aftereffects occur, however, only when inspection gratings differ in spatial frequency by one octave or more and the frequency of at least one grating is above 3 cycles per degree. This spatial selectivity of the aftereffect is considered in terms of a neural adaptation model incorporating evidence on the tuning of spatial frequency detectors in the human visual system.     

A neural effect of partial visual deprivation in humans

Certain human subjects have considerable sensitivity differences in the visual resolution of vertical gratings as compared to horizontal gratings. Although only subjects with pronounced ocular astigmatism exhibit this effect, the differences are of neural, rather than optical, origin. It is argued that the resolution anisotropies result from early abnormal visual input caused by astigmatism. This abnormal input permanently modifies the brain.     

Hyperacuity in cat retinal ganglion cells

Cat X retinal ganglion cells that can resolve sine gratings of only 2.5 cycles per degree can nevertheless respond reliably to displacements of a grating of approximately 1 minute of arc. This is a form of hyperacuity comparable in magnitude to that seen in human vision. A theoretical analysis of this form of hyperacuity reveals it to be a result of the high gain and low noise of ganglion cells. The hyperacuity expected for the best retinal ganglion cells is substantially better than that observed in behavioral experiments. Thus the brain, rather than improving on the retinal signal-to-noise ratio by pooling signals from many ganglion cells, is unable to make use of all the hyperacuity information present in single ganglion cell responses.     

Goldfish retina: sign of the rod input in opponent color ganglion cells

After light adaptation, all "on-center" ganglion cells in the dark became "red on-center," and all "off-center" cells turned into "red off-center" cells. On a chance basis, this similitude of effect between the rods and the red cones in opponent color cells was not expected. These findings indicate that in the goldfish there is some similarity between the connections of the rods and of the long-wavelength cones.     

Chiral fiber gratings

Chiral gratings with double helix symmetry were produced by twisting glass optical fiber with a noncircular core cross section as it passed through a miniature oven. We observed polarization-selective transmission in chiral fibers with pitches of tens of micrometers. Two modes of optical interaction were differentiated. In chirallong-period gratings, dips in transmission were observed at wavelengths associated with scattering into distinct cladding modes mediated by the chiral grating. In chiral intermediateperiod gratings, a broad scattering band was observed. These gratings can be used to produce sharp or broad polarization-selective filters.     

Neural integration of information specifying structure from stereopsis and motion

When one views a two-dimensional parallel projection of dots on the surface of a rotating globe, the direction of rotation is ambiguous, and the perceived direction of rotation of the two-dimensional figure is unstable over time. Stability can be temporarily induced by adaptation to a three-dimensional globe with a direction of rotation unambiguously specified by stereo disparity; adaptation causes the two-dimensional figure to appear to rotate in the direction opposite that experienced during stereoscopic adaptation. This adaptation effect is selective for axis of rotation but is not shape-specific. It does depend on simultaneous stimulation by multiple depth planes defined by elements moving in different directions. Evidently information about stereopsis and information about structure from motion are integrated within a common neural site in the brain.     

自信与青少年社会适应的关系:清晰度的中介作用

以社会适应双功能模型为理论基础,考察自信与社会适应之间的关系,以及自信清晰度的中介作用.采用总体自信问卷、自信清晰度问卷和青少年社会适应状况量表对333名青少年进行测查,结果显示:自信能够预测青少年的积极/消极适应状况,但是自信对2种社会适应的预测力不同,表明自信与2种社会适应的关系紧密度不同;自信清晰度在自信与积极/消极适应之间的中介效应显著,但是对消极适应的中介效应大于积极适应,说明自信清晰度的中介功能也有差异.     

Disruptive Coloration in Butterflies: Lack of Support in Anartia fatima

Experimental obliteration of high-contrast wing stripes of the neotropical butterfly Anartia fatima affected neither survival nor wing damage in a natural population over a 5-month period. There is no direct evidence supporting the hypothesis that so-called disruptive wing patterns function as protective coloration in butterflies.     

The site of visual adaptation

In response to background illumination, the adaptation properties of the b-wave are similar to those observed in the human eye with psychophysical methods. With increasing background luminance the b-wave sensitivity is diminished; except at the lowest background intensity the elevation of the log threshold is linearly related to the increase of background intensity, the relation having a slope of almost 1. The a-wave, however, behaves quite differently. At low background luminances it shows little adaptation. With higher background luminances the awave saturates, and no a-wave potential can be elicited with any stimulus intensity. The L-type S-potentials respond to background light in much the same way as the a-wave does. Thus, the b-wave is the first of the known responses in the visual system to show typical adaptation properties. This suggests that the site of visual adaptation may be in the bi-polarcell layer, the presumed locus of b-wave generation. Recent electron microscopic studies have demonstrated reciprocal synapses between the bipolar terminals and amacrine processes, and it is suggested that such a synaptic arrangement could account for visual adaptation by a mechanism of inhibitory feedback on the bipolar cells.     

Electrophysiological evidence for binocular disparity detectors in human visual system

Evoked potentials have been recorded from humans in response to two moving gratings presented stereoscopically to both eyes. The amplitude of the evoked potential is greater when the two gratings have slightly different spatial frequencies, which produces an apparent inclination of the binocularly fused image. The amplitude of the response is correlated with the degree of the perceived inclination.     

套种的气候生态适应性研究

本文概述了我国套种的发展及类型,着重论述了套种的小气候效应即边行效应、共生期的作物互利与竞争及套种作物的生态适应性,对小麦玉米套种的优势和问题,作出较全面的评定,并提出在生产上的应用。套种(Relaycropping)系指在第一种作物生长的后期,在其间播种(或移栽)生育季节不同的另一作物,两种作物共生期小于各作物生育期的二分之一。     

Molecular imaging using a targeted magnetic resonance hyperpolarized biosensor

A magnetic resonance approach is presented that enables high-sensitivity, high-contrast molecular imaging by exploiting xenon biosensors. These sensors link xenon atoms to specific biomolecular targets, coupling the high sensitivity of hyperpolarized nuclei with the specificity of biochemical interactions. We demonstrated spatial resolution of a specific target protein in vitro at micromolar concentration, with a readout scheme that reduces the required acquisition time by >3300-fold relative to direct detection. This technique uses the signal of free hyperpolarized xenon to dramatically amplify the sensor signal via chemical exchange saturation transfer (CEST). Because it is approximately 10,000 times more sensitive than previous CEST methods and other molecular magnetic resonance imaging techniques, it marks a critical step toward the application of xenon biosensors as selective contrast agents in biomedical applications.     

兴安落叶松（Larix gmelinii Rupr）针叶解剖结构变化体现其光合能力对气候变化的适应性

叶片易受环境因子影响，其形态解剖结构特征不但与叶片的生理功能密切相关，而且反映树木对环境变化的响应和适应。叶片结构的改变势必会改变树木的生理功能。同一树种长期生长在异质环境条件下，经过自然选择和适应，会在形态和生理特性等方面产生变异，形成特定的地理种群。另外，母体所经受的环境胁迫也会影响到其子代的生长、发育和生理等特征。因此，了解植物叶片形态结构对环境变化的响应与适应是探索植物对环境变化的响应适应机制的基础。兴安落叶松(Larix gmelinii Rupr.)是我国北方森林的优势树种，主要分布在我国东北地区，但日益加剧的气候变化可能会改变其现有的分布区。为了区分叶片对气候变化的可塑性和适应性，本研究采用同质园法比较测定了6个不同气候条件下的兴安落叶松种源的32年生树木的针叶解剖结构和光合生理相关因子，利用石蜡切片方法分析了针叶的解剖结构特征、光合能力（Pmax-a）、水分利用效率（WUE）之间的关系及其对气候变化的适应性。结果表明：表皮细胞厚度、叶肉细胞厚度、传输组织厚度、维管束厚度、内皮层厚度以及叶片总厚度均存在显著的种源间差异（P < 0.05）。叶肉细胞厚度与Pmax-a、气孔导度和WUE之间均存在显著的正相关关系（P < 0.05）。叶肉细胞厚度、表皮细胞厚度、叶片总厚度以及叶肉细胞厚度和表皮细胞厚度在叶片总厚度中所占比例均与种源地的干燥度指数（即年蒸发量与年降水量之比）呈正线性关系。这些结果说明：不同种源兴安落叶松针叶解剖结构因对种源原地气候条件的长期适应而产生显著的差异，从而引起其针叶光合作用、水分利用等生理功能发生相应的变化,从而有利于该树种在气候变化的情景下得以生存和繁衍。     

新型城镇化进程中农村人力资源开发生态环境研究

党的十八大报告提出了坚持走中国特色的新型城镇化战略。新型城镇化的核心是实现‘人’的城镇化,‘人’的城镇化的关键在于实现‘农民’向‘市民’的转化。这种转化的进程取决于农村人力资源与人力资源所处开发环境之间的五个适配性：区域文化环境适配性、技术环境适配性、教育环境适配性、自然环境适配性和开发政策环境适配性。     

Overview of Impacts of Climate Change and Adaptation in China's Agriculture

The purpose of this paper is to document the likely impacts of climate change on China’s agriculture and the current adaptation efforts made by government and farmers.The review of literature shows that climate change will have a significant impact on agriculture,primarily through its effect on crop yields.The extent of predicted impacts highly depends on the crop,the CO2 fertilization effect assumption and adaptation abilities.Market response to the production shocks resulting from climate change will lessen the impacts on agricultural production predicted by natural scientists.On adaptation,the government’s major efforts have been in the developing new technologies,reforming extension system and enhancing institutional capacity.Farmers do adapt to climate change,but their adaptation measures cannot fully offset the negative impacts of climate change.The paper concludes and makes implications for future studies.     

Climate change and agriculture: Impacts and adaptive responses in Iran

The impacts of climate change on agriculture are still shadowed with uncertainty. However, climate change is expected to adversely affect Iran's agricultural practices through changes in precipitation, temperature and carbon dioxide fertilization. Therefore, adaptation of this sector to the increasing weather events is imperative. This study is aimed to document the likely impacts of climate change on Iran's agriculture and the current adaptation efforts made by government and farmers. The review of literature shows that changes in rainfall and water endowments will have significant impacts on crop yield, crops' water requirements and income and welfare of farm families. The extent of the changes in yield depends on the crop type, assumptions related to the CO₂ fertilization effect, climate scenarios and adaptation abilities. On adaptation, the government's efforts have been distinguished in the improving agricultural productivity and irrigation development based on current technology, developing new technologies and policy reforms. Farmers' adaptive responses have also been identified. Some conclusions and recommendations are offered to increase the adaptive capacity of farmers and reduce negative impacts of climate change.     

保加利亚乳杆菌的冷适应性与冷应激蛋白的研究

几乎所有单细胞生物在外界环境急剧降温的条件下都会发生应激反应,产生的一系列蛋白质被称为冷应激蛋白。冷应激蛋白在乳酸菌适应低温环境和增强抗冻能力方面发挥着重要作用。本研究从冷应激蛋白着手,研究了保加利亚乳杆菌低温适应性及冷应激蛋白的抗冻保护作用。在冷冻前进行20℃预处理可以使保加利亚乳杆菌的存活率增加100倍,而低于最低生长温度时,与对照组的存活率相差不大。通过SDS-PAGE电泳,冷处理样泳道出现了两种7ku的冷应激蛋白。利用PCR技术进一步获得保加利亚乳杆菌中冷休克蛋白的基因片断,与L.delbrueckii subsp.bulgaricus ATCC11842中CspA序列同源性达到100%。低温预处理可以增强菌体抗冻能力,且可以产生3条6.3、6.7、7.0ku的冷应激蛋白,初步推测低温诱导冷应激蛋白的表达抵御了冷冻对保加利亚乳杆菌的伤害。     

富稀土猴头菇抗疲劳的试验研究

本文以小鼠为对象，研究了富稀土猴头菇的抗疲劳效应，结果显示，饲料中添加一定量的富稀土猴头菇．小鼠的游泳时间比添加等量的硝酸稀土与不加稀土的对照组显著延长，泳后血乳酸水平显著降低，血糖含量明显增加．说明富稀土猴头菇对提高机体对运动负荷的适应能力和抵抗疲劳产生具有明显的作用。     

Picosecond holographic-grating spectroscopy

Interfering light waves produce an optical interference pattern in any medium that interacts with light. This modulation of some physical parameter of the system acts as a classical holographic grating for optical radiation. When such a grating is produced through interaction of pulsed light waves with an optical transition, a transient grating is formed whose decay is a measure of the relaxation time of the excited state. Transient gratings can be formed in real space or in frequency space depending on the time ordering of the interfering light waves. The two gratings are related by a space-time transformation and contain complementary information on the optical dynamics of a system. The status of a grating can be probed by a delayed third pulse, which diffracts off this grating in a direction determined by the wave vector difference of the interfering light beams. This generalized concept of a transient grating can be used to interpret many picosecond-pulse optical experiments on condensed-phase systems. Examples of some low-temperature experiments will be presented. In principle, many of these experiments could also be performed by using stochastic broad-band excitation. In these nonlinear photon-interference experiments the time resolution is determined by the correlation time of the light source rather than its pulse width.