Ecological importance of trichromatic vision to primates

Trichromatic colour vision, characterized by three retinal photopigments tuned to peak wavelengths of approximately 430 nm, approximately 535 nm and approximately 562 nm (refs 1, 2), has evolved convergently in catarrhine primates and one genus of New World monkey, the howlers (genus Alouatta). This uniform capacity to discriminate red-green colours, which is not found in other mammals, has been proposed as advantageous for the long-range detection of either ripe fruits or young leaves (which frequently flush red in the tropics) against a background of mature foliage. Here we show that four trichromatic primate species in Kibale Forest, Uganda, eat leaves that are colour discriminated only by red-greenness, a colour axis correlated with high protein levels and low toughness. Despite their divergent digestive systems, these primates have no significant interspecific differences in leaf colour selection. In contrast, eaten fruits were generally discriminated from mature leaves on both red-green and yellow-blue channels and also by their luminance, with a significant difference between chimpanzees and monkeys in fruit colour choice. Our results implicate leaf consumption, a critical food resource when fruit is scarce, as having unique value in maintaining trichromacy in catarrhines.     

Effect of nluminants on the Colour Appearance of Reactive - dyed Cotton

The colour appearance of dyed textile materials changes with the viewing condition, especially with a change in the light source or Illuminant. The attitude and magnitude of the change vary with the hue of the colour, the light absorbance nature of the dye and the colour depth to which it is dyed. This paper examines the change in colour appearance of reactive - dyed cotton when the light source is changed from CIE Uluminant D65 to CIE illuminant A. Reactive dyes of primary hues were selected and applied at various depths and the dyed colours were assessed with reference to changing the illuminant.     

Parallel processing of motion and colour information

When the two eyes are confronted with sufficiently different versions of the visual environment, one or the other eye dominates perception in alternation. A similar situation may be created in the laboratory by presenting images to the left and right eyes which differ in orientation or colour. Although perception is dominated by one eye during rivalry, there are a number of instances in which visual processes nevertheless continue to integrate information from the suppressed eye. For example the interocular transfer of the motion after-effect is undiminished when induced during binocular rivalry. Thus motion information processing may occur in parallel with the rivalry process. Here we describe a novel example in which the visual system simultaneously exhibits binocular rivalry and vision that integrates signals from both eyes. This apparent contradiction is resolved by postulating parallel visual processes devoted to the analyses of colour and motion information. Counterphased gratings are viewed dichoptically such that for one eye the grating is composed of alternating yellow and black stripes (luminance) while for the other it is composed of alternating red and green stripes (chrominance). When the gratings are fused, a moving grating is perceived. A consistent direction of motion can only be achieved if left and right monocular signals are integrated by the nervous system. Yet the apparent colour of the binocular percept alternates between red-green and yellow-black. These observations demonstrate the segregation of processing by the early motion system from that affording the perception of colour. Although, in this stimulus, colour information in itself can play no part in the cyclopean perception of motion direction, colour is carried along perceptually (filled in) by the moving pattern which is integrated from both eyes.     

半数值解析法计算高弹粘流在狭缝流道中的流动

文章在二维非牛顿流体流动分析的基础上，根据高弹粘流在狭缝流道中流动的特点，通过将沿流道高度方向流速分布用级数模拟，建立了一种半数值解析法。该法可将三维流动问题化为平面问题处理．且有节约内存及机时，使用方便等优点。通过与理论解的比较，精度是令人满意的。     

基于像素流的视频彩色化

针对利用传统光流传递关键帧颜色信息的视频彩色化方法计算耗时问题,以及全局传递颜色的视频彩色化方法导致欠饱和度问题,提出基于像素流的视频彩色化方法.首先,将参考帧与目标帧转换到Lab颜色空间中,利用其亮度通道通过一个深度学习网络得到像素流,该像素流中的数值指示了目标帧的颜色在参考帧中的位置;然后,利用该像素流对参考帧颜色...     

The correlation of multi-channel thermal infrared remote sensing information and its effect on retrieval of land surface temperature

The informational correlation among seven thermal infrared channels of MODIS is simulated. Results show that they have high correlation coefficient, which becomes one of the main obstacles to raise accuracy of LST retrieved by the remote sensing method. By means of principal component analysis we have proven 14 independent equations for retrieval of LST at most having five independent informative components, if seven bands are chosen for retrieval of LST, only three independent informative components exist. Therefore the property of retrieval of LST belongs to the underdetermined inverse problem. We cannot expect to get a stable and high accurate LST retrieved by various currently used remote sensing methods based on determined equations. From now on it is a main research topic to retrieve LST by underdetermined equations.     

Application of Modern Colour Measurement Dervices in Coloration Industries

In colour measurement ralated industry, reflectance spectrophotometer is the one of the popular measuring machine for measuring colour and quality control. Colour communications is frequently confusing. This is because the colour appearance is subject to the influence of at least three different phenomena: the light source, the object and the visual system. The variation in either the radiant quantity or the spectral distribution of the source can alter the observed colour. Because of this reason, the objective quantitative tool, colour measurement equipment and communication method; become more important in evaluating of the colour. In fact, based on the advanced in computer system and electronic device, the colour measurement becomes more and more accuracy, especially in spectrophotometer measurement. In this paper, we will focus on the review of modern spectrophotometers in coloration industries.     

声学多孔材料的孔结构优化

介绍了一种基于微结构的声学模型,可用来对多孔材料的微组织结构进行优化,从而使多孔材料具备最佳的声学性能.该模型是一种适用于低雷诺数的非稳态线性声学模型,主要微结构考虑平行排列的柱形杆件或圆球列阵,包括3个子模型:①声波传播方向平行于圆柱形杆件的子模型;②声波传播方向垂直于圆柱形杆件的子模型;③声波在圆球列阵中传播和吸收的子模型.前2个子模型通过考虑多边形周期边界条件的影响,计及了相邻圆柱形杆件间的交互作用.由于模型是线性的,因此可以结合起来描述任意角度入射声波的传播特性.第3个子模型可用于描述胞状多孔材料中节点处的情形.文中利用这3个子模型来扩大吸声材料的设计空间,根据不同用途所要求的声学特性计算最优的胞元结构,并对这种模型的应用领域进行了分析讨论.     

基于改进k-均值聚类的纸币冠字号图像分割算法

针对传统彩色图像分割方法的局限性,提出了基于HSI色彩空间和改进K-均值聚类的图像分割方法,通过将彩色图像分解成三个相互独立的H、S、I分量,利用各个分量特点及其直方图确定聚类类别和初始聚类中心,在高饱和度区和低饱和度区分别聚类,并将聚类结果合并取交集,从而分割出目标区域.将该方法用于纸币冠字号码图像分割,经仿真验证,结果不受噪声和局部边缘变化的影响,分割效果得到明显提升,为后续冠字号准确识别提供了良好的基础.     

Accelerated speciation in colour-polymorphic birds

Colour polymorphism exemplifies extreme morphological diversity within populations. It is taxonomically widespread but generally rare. Theory suggests that where colour polymorphism does occur, processes generating and maintaining it can promote speciation but the generality of this claim is unclear. Here we confirm, using species-level molecular phylogenies for five families of non-passerine birds, that colour polymorphism is associated with accelerated speciation rates in the three groups in which polymorphism is most prevalent. In all five groups, colour polymorphism is lost at a significantly greater rate than it is gained. Thus, the general rarity and phylogenetic dispersion of colour polymorphism is accounted for by a combination of higher speciation rate and higher transition rate from polymorphism to monomorphism, consistent with theoretical models where speciation is driven by fixation of one or more morphs. This is corroborated by evidence from a species-level molecular phylogeny of passerines, incorporating 4,128 (66.5%) extant species, that polymorphic species tend to be younger than monomorphic species. Our results provide empirical support for the general proposition, dating from classical evolutionary theory, that colour polymorphism can increase speciation rates.     

Gaze direction controls response gain in primary visual-cortex neurons

To localize objects in space, the brain needs to combine information about the position of the stimulus on the retinae with information about the location of the eyes in their orbits. Interaction between these two types of information occurs in several cortical areas, but the role of the primary visual cortex (area V1) in this process has remained unclear. Here we show that, for half the cells recorded in area V1 of behaving monkeys, the classically described visual responses are strongly modulated by gaze direction. Specifically, we find that selectivity for horizontal retinal disparity-the difference in the position of a stimulus on each retina which relates to relative object distance-and for stimulus orientation may be present at a given gaze direction, but be absent or poorly expressed at another direction. Shifts in preferred disparity also occurred in several neurons. These neural changes were most often present at the beginning of the visual response, suggesting a feedforward gain control by eye position signals. Cortical neural processes for encoding information about the three-dimensional position of a stimulus in space therefore start as early as area V1.     

Long-lasting sensitization to a given colour after visual search

Visual attention enables an observer to select specific visual information for processing. In an ambiguous motion task in which a coloured grating can be perceived as moving in either of two opposite directions depending on the relative salience of two colours in the display, attending to one of the colours influences the direction in which the grating appears to move. Here, we use this secondary effect of attention in a motion task to measure the effect of attending to a specific colour in a search task. Observers performed a search task in which they searched for a target letter in a 4 x 4 coloured matrix. Each of the 16 squares within a matrix was assigned one of four colours, and observers knew that the target letter would appear on only one of these colours throughout the experiment. Observers performed the ambiguous motion task before and after the search task. Attending to a particular colour for a brief period in the search task profoundly influenced the perceived direction of motion. This effect lasted for up to one month and in some cases had to be reversed by practising searches for the complementary colour, indicating a much longer-persisting effect of attention than has been observed previously.     

Interaction between colour and motion in human vision

There is a wealth of anatomical and psychological evidence which suggests that when people look at an object in the visual world, its various attributes such as colour, 'form', motion and depth are analysed by separate channels in the visual system. If so, how are these attributes put back together again to create a unified picture of the object? And if the object moves rapidly, how is perfect perceptual synchrony maintained between different features on its surface, if it is indeed true that they are being processed separately? Our evidence suggests that the visual system extracts certain conspicuous image features based on luminance contrast, and that the signals derived from these are then attributed to other features on the object, a process that we call 'capture'. Specifically, we find that when either illusory contours or random-dot patterns are moved in the vicinity of a colour-border, the colour border will also seem to move in the same direction even though it is physically stationary.     

Structure of the gating domain of a Ca2+-activated K+ channel complexed with Ca2+/calmodulin

Small-conductance Ca2+-activated K+ channels (SK channels) are independent of voltage and gated solely by intracellular Ca2+. These membrane channels are heteromeric complexes that comprise pore-forming alpha-subunits and the Ca2+-binding protein calmodulin (CaM). CaM binds to the SK channel through the CaM-binding domain (CaMBD), which is located in an intracellular region of the alpha-subunit immediately carboxy-terminal to the pore. Channel opening is triggered when Ca2+ binds the EF hands in the N-lobe of CaM. Here we report the 1.60 A crystal structure of the SK channel CaMBD/Ca2+/CaM complex. The CaMBD forms an elongated dimer with a CaM molecule bound at each end; each CaM wraps around three alpha-helices, two from one CaMBD subunit and one from the other. As only the CaM N-lobe has bound Ca2+, the structure provides a view of both calcium-dependent and -independent CaM/protein interactions. Together with biochemical data, the structure suggests a possible gating mechanism for the SK channel.     

基于多目标遗传算法的起重机吊装路径规划

采用改进遗传算子操作策略的遗传算法以解决起重机三维空间多目标吊装路径的规划问题.首先建立起重机作业场景和位姿空间的数学模型,将起重机的空间多自由度路径规划问题转化成平面路径点的求解问题.然后确定以吊装路径最短、安全性最好和运动形式变化最少为优化目标,通过添加记忆算子为插入算子和变异算子选取合适的方向和步长进行多目标优化操作.实验证明该算法能综合考虑多种因素,并能同时提供不同特点的路径供决策者选择.     

一种数字信道化接收机参数编码方法

研究一种基于多波束比幅测角的数字信道化接收机参数编码方法.描述了数字信道化接收机的参数编码流程,详细论述编码过程中通道间幅度测量同步和脉冲到达角(DOA)测量方法.采用该方法的数字信道化接收机的脉冲描述字(PDW)编码与典型接收机的一致.实践证明,该方法可以满足复杂电磁环境下雷达信号处理实时性的要求.     

Functions of the ON and OFF channels of the visual system

In the mammalian eye, the ON-centre and OFF-centre retinal ganglion cells form two major pathways projecting to central visual structures from the retina. These two pathways originate at the bipolar cell level: one class of bipolar cells becomes hyperpolarized in response to light, as do all photoreceptor cells, and the other class becomes depolarized on exposure to light, thereby inverting the receptor signal. It has recently become possible to examine the functional role of the ON-pathway in vision by selectively blocking it at the bipolar cell level using the glutamate neurotransmitter analogue 2-amino-4-phosphonobutyrate (APB)1. APB application to monkey, cat and rabbit retinas abolishes ON responses in retinal ganglion cells, the lateral geniculate nucleus and the visual cortex but has no effect on the centre-surround antagonism of OFF cells or the orientation and direction selectivities in the cortex2-5. These and related findings6-11 suggest that the ON and OFF pathways remain largely separate through the lateral geniculate nucleus and that in the cortex, contrary to some hypotheses, they are not directly involved in mechanisms giving rise to orientation and direction selectivities. We have examined the roles of the ON and OFF channels in vision in rhesus monkeys trained to do visual detection and discrimination tasks. We report here that the ON channel is reversibly blocked by injection of APB into the vitreous. Detection of light increment but not of light decrement is severely impaired, and there is a pronounced loss in contrast sensitivity. The perception of shape, colour, flicker, movement and stereo images is only mildly impaired, but longer times are required for their discrimination. Our results suggest that two reasons that the mammalian visual system has both ON and OFF channels is to yield equal sensitivity and rapid information transfer for both incremental and decremental light stimuli and to facilitate high contrast sensitivity.     

Repeat I of the dihydropyridine receptor is critical in determining calcium channel activation kinetics.

Membrane depolarization causes many kinds of ion channels to open, a process termed activation. For both Na+ channels and Ca2+ channels, kinetic analysis of current has suggested that during activation the channel undergoes several conformational changes before reaching the open state. Structurally, these channels share a common motif: the central element is a large polypeptide with four repeating units of homology (repeats I-IV), each containing a voltage-sensing region, the S4 segment. This suggests that the distinct conformational transitions inferred from kinetic analysis may be equated with conformational changes of the individual structural repeats. To investigate the molecular basis of channel activation, we constructed complementary DNAs encoding chimaeric Ca2+ channels in which one or more of the four repeats of the skeletal muscle dihydropyridine receptor are replaced by the corresponding repeats derived from the cardiac dihydropyridine receptor. We report here that repeat I determines whether the chimaeric Ca2+ channel shows slow (skeletal muscle-like) or rapid (cardiac-like) activation.     

Clustering of voltage-dependent sodium channels on axons depends on Schwann cell contact.

In myelinated nerves, segregation of voltage-dependent sodium channels to nodes of Ranvier is crucial for saltatory conduction along axons. As sodium channels associate and colocalize with ankyrin at nodes of Ranvier, one possibility is that sodium channels are recruited and immobilized at axonal sites which are specified by the subaxolemmal cytoskeleton, independent of glial cell contact. Alternatively, segregation of channels at distinct sites along the axon may depend on glial cell contact. To resolve this question, we have examined the distribution of sodium channels, ankyrin and spectrin in myelination-competent cocultures of sensory neurons and Schwann cells by immunofluorescence, using sodium channel-, ankyrin- and spectrin-specific antibodies. In the absence of Schwann cells, sodium channels, ankyrin and spectrin are homogeneously distributed on sensory axons. When Schwann cells are introduced into these cultures, the distribution of sodium channels dramatically changes so that channel clusters on axons are abundant, but ankyrin and spectrin remain homogeneously distributed. Addition of latex beads or Schwann cell membranes does not induce channel clustering. Our results suggest that segregation of sodium channels on axons is highly dependent on interactions with active Schwann cells and that continuing axon-glial interactions are necessary to organize and maintain channel distribution during differentiation of myelinated axons.     

Repeated morphological evolution through cis-regulatory changes in a pleiotropic gene

The independent evolution of morphological similarities is widespread. For simple traits, such as overall body colour, repeated transitions by means of mutations in the same gene may be common. However, for more complex traits, the possible genetic paths may be more numerous; the molecular mechanisms underlying their independent origins and the extent to which they are constrained to follow certain genetic paths are largely unknown. Here we show that a male wing pigmentation pattern involved in courtship display has been gained and lost multiple times in a Drosophila clade. Each of the cases we have analysed (two gains and two losses) involved regulatory changes at the pleiotropic pigmentation gene yellow. Losses involved the parallel inactivation of the same cis-regulatory element (CRE), with changes at a few nucleotides sufficient to account for the functional divergence of one element between two sibling species. Surprisingly, two independent gains of wing spots resulted from the co-option of distinct ancestral CREs. These results demonstrate how the functional diversification of the modular CREs of pleiotropic genes contributes to evolutionary novelty and the independent evolution of morphological similarities.