沼虾体色调节之初探

实验通过单色光、明暗环境变化、虾的眼柄提取液、虾的肌肉提取液、蟹的眼柄提取液、海水、肾上腺素以及不同浓度的乙醇溶液对沼虾体色变化的影响，发现了沼虾体色调节的部分机制，眼柄提取液的无种间特异性，以及乙醇对虾的体色的抑制作用．本实验还通过认真观察对比发现了沼虾色素细胞分布的规律和一些特殊的色素细胞．     

Adaptive divergence in pigment composition promotes phytoplankton biodiversity

The dazzling diversity of the phytoplankton has puzzled biologists for decades. The puzzle has been enlarged rather than solved by the progressive discovery of new phototrophic microorganisms in the oceans, including picocyanobacteria, pico-eukaryotes, and bacteriochlorophyll-based and rhodopsin-based phototrophic bacteria. Physiological and genomic studies suggest that natural selection promotes niche differentiation among these phototrophic microorganisms, particularly with respect to their photosynthetic characteristics. We have analysed competition for light between two closely related picocyanobacteria of the Synechococcus group that we isolated from the Baltic Sea. One of these two has a red colour because it contains the pigment phycoerythrin, whereas the other is blue-green because it contains high contents of the pigment phycocyanin. Here we report theory and competition experiments that reveal stable coexistence of the two picocyanobacteria, owing to partitioning of the light spectrum. Further competition experiments with a third marine cyanobacterium, capable of adapting its pigment composition, show that this species persists by investing in the pigment that absorbs the colour not used by its competitors. These results demonstrate the adaptive significance of divergence in pigment composition of phototrophic microorganisms, which allows an efficient utilization of light energy and favours species coexistence.     

Chloroplast avoidance movement reduces photodamage in plants

When plants are exposed to light levels higher than those required for photosynthesis, reactive oxygen species are generated in the chloroplasts and cause photodamage. This can occur even under natural growth conditions. To mitigate photodamage, plants have developed several protective mechanisms. One is chloroplast avoidance movement, in which chloroplasts move from the cell surface to the side walls of cells under high light conditions, although experimental support is still awaited. Here, using different classes of mutant defective in chloroplast avoidance movement, we show that these mutants are more susceptible to damage in high light than wild-type plants. Damage of the photosynthetic apparatus and subsequent bleaching of leaf colour and necrosis occur faster under high light conditions in the mutants than in wild-type plants. We conclude that chloroplast avoidance movement actually decreases the amount of light absorption by chloroplasts, and might therefore be important to the survival of plants under natural growth conditions.     

Perception of three-dimensional shape influences colour perception through mutual illumination

Objects in the natural world possess different visual attributes, including shape, colour, surface texture and motion. Previous perceptual studies have assumed that the brain analyses the colour of a surface independently of its three-dimensional shape and viewing geometry, although there are neural connections between colour and two-dimensional form processing early in the visual pathway. Here we show that colour perception is strongly influenced by three-dimensional shape perception in a novel, chromatic version of the Mach Card--a concave folded card with one side made of magenta paper and the other of white paper. The light reflected from the magenta paper casts a pinkish glow on the white side. The perceived colour of the white side changes from pale pink to deep magenta when the perceived shape of the card flips from concave to convex. The effect demonstrates that the human visual system incorporates knowledge of mutual illumination-the physics of light reflection between surfaces--at an early stage in colour perception.     

Photonic structures in biology

Millions of years before we began to manipulate the flow of light using synthetic structures, biological systems were using nanometre-scale architectures to produce striking optical effects. An astonishing variety of natural photonic structures exists: a species of Brittlestar uses photonic elements composed of calcite to collect light, Morpho butterflies use multiple layers of cuticle and air to produce their striking blue colour and some insects use arrays of elements, known as nipple arrays, to reduce reflectivity in their compound eyes. Natural photonic structures are providing inspiration for technological applications.     

双谱假彩色微光电视系统原理与技术研究

该文对双谱假彩色微光电视系统的原理进行论述，探讨了实现双谱假彩色微光电视系统的有关技术。双探测技术是这种彩色微光技术的重要组成部分和理论基础，其关键是根据夜天光辐射以及景物夜晚光谱反射特性，选择合适的对比度转换点位置，分割有效光谱两部分；彩色最佳逼近技术，就是研究如何选择这一对比度转换眯位置和适当算法，才能使双谱彩色图象具有最佳的分辩率和图象探测率，最后给出系统实现方法、实验结果及分析。     

Divergent sexual selection enhances reproductive isolation in sticklebacks

Sexual selection may facilitate speciation because it can cause rapid evolutionary diversification of male mating signals and female preferences. Divergence in these traits can then contribute to reproductive isolation. The sensory drive hypothesis predicts that three mechanisms underlie divergence in sexually selected traits: (1) habitat-specific transmission of male signals; (2) adaptation of female perceptual sensitivity to local ecological conditions; and (3) matching of male signals to female perceptual sensitivity. I test these mechanisms in threespine sticklebacks (Gasterosteus spp.) that live in different light environments. Here I show that female perceptual sensitivity to red light varies with the extent of redshift in the light environment, and contributes to divergent preferences. Male nuptial colour varies with environment and is tuned to female perceptual sensitivity. The extent of divergence among populations in both male signal colour and female preference for red is correlated with the extent of reproductive isolation in these recently diverged species. These results demonstrate that divergent sexual selection generated by sensory drive contributes to speciation.     

Structural basis for the spectral difference in luciferase bioluminescence

Fireflies communicate with each other by emitting yellow-green to yellow-orange brilliant light. The bioluminescence reaction, which uses luciferin, Mg-ATP and molecular oxygen to yield an electronically excited oxyluciferin species, is carried out by the enzyme luciferase. Visible light is emitted during relaxation of excited oxyluciferin to its ground state. The high quantum yield of the luciferin/luciferase reaction and the change in bioluminescence colour caused by subtle structural differences in luciferase have attracted much research interest. In fact, a single amino acid substitution in luciferase changes the emission colour from yellow-green to red. Although the crystal structure of luciferase from the North American firefly (Photinus pyralis) has been described, the detailed mechanism for the bioluminescence colour change is still unclear. Here we report the crystal structures of wild-type and red mutant (S286N) luciferases from the Japanese Genji-botaru (Luciola cruciata) in complex with a high-energy intermediate analogue, 5'-O-[N-(dehydroluciferyl)-sulfamoyl]adenosine (DLSA). Comparing these structures to those of the wild-type luciferase complexed with AMP plus oxyluciferin (products) reveals a significant conformational change in the wild-type enzyme but not in the red mutant. This conformational change involves movement of the hydrophobic side chain of Ile 288 towards the benzothiazole ring of DLSA. Our results indicate that the degree of molecular rigidity of the excited state of oxyluciferin, which is controlled by a transient movement of Ile 288, determines the colour of bioluminescence during the emission reaction.     

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.     

一步真彩色彩虹全息术

本文提出不必先拍摄主全息图而只利用彩色照片或图片的分色片和单波长激光，根据加色法直接拍摄出能白光再现的真彩色彩虹全息图，这种一步法适宜批量生产出低噪声、彩色还原性好，高清晰度的真彩色彩虹全息图。     

Colour-contingent after-effects are really wavelength-contingent

McCollough reported that following adaptation to (say) a red and black pattern of vertical stripes, alternating every few seconds with a green and black pattern of horizontal stripes, an orientation-contingent colour after-effect is observed when black and white gratings are viewed. Vertical gratings are tinged with green and horizontal gratings with pink. We have exploited colour constancy, the tendency for objects to appear constant in hue despite large changes in the spectral composition of the illuminant, to examine whether the colours observed on the McCollough effect test gratings are determined by the wavelength composition of the adaptation patterns or by their perceived colour. The key to this approach can be illustrated by Edwin Land's elegant demonstrations of colour constancy using 'Mondrian' displays. By embedding the adapting grating that is used to induce the McCollough effect within a Mondrian we show that the effect depends upon the wavelength of light coming from the grating, rather than the perceived colour.     

彩色全息图的研究

通过使用Ronchi光栅和滤波片 ,把一张彩色透明片的红、绿、蓝信息编码记录在一张黑白胶片上并用单色激光制作彩色全息图。采用彩虹全息术 ,获得记录于同一块干版上的原彩色图由红、绿、蓝三色所成的三个基色彩虹全息象 ,用白光透射再现 ,得到原彩色图的真彩色全息象。     

Liquid crystal 'blue phases' with a wide temperature range

Liquid crystal 'blue phases' are highly fluid self-assembled three-dimensional cubic defect structures that exist over narrow temperature ranges in highly chiral liquid crystals. The characteristic period of these defects is of the order of the wavelength of visible light, and they give rise to vivid specular reflections that are controllable with external fields. Blue phases may be considered as examples of tuneable photonic crystals with many potential applications. The disadvantage of these materials, as predicted theoretically and proved experimentally, is that they have limited thermal stability: they exist over a small temperature range (0.5-2 degrees C) between isotropic and chiral nematic (N*) thermotropic phases, which limits their practical applicability. Here we report a generic family of liquid crystals that demonstrate an unusually broad body-centred cubic phase (BP I*) from 60 degrees C down to 16 degrees C. We prove this with optical texture analysis, selective reflection spectroscopy, K?ssel diagrams and differential scanning calorimetry, and show, using a simple polarizer-free electro-optic cell, that the reflected colour is switched reversibly in applied electric fields over a wide colour range in typically 10 ms. We propose that the unusual behaviour of these blue phase materials is due to their dimeric molecular structure and their very high flexoelectric coefficients. This in turn sets out new theoretical challenges and potentially opens up new photonic applications.     

Wavelength sensitivity in blindsight

Blindsight--the residual visual functions observed in visualfield defects resulting from destruction of part of the primary visual cortex (striate cortex) even though visual stimuli presented in the field defect are not consciously perceived--has generated new insights into the nature of consciousness and the role of the extrastriate pathways in visual processing. Some patients can detect and localize unseen stimuli when they are required to guess. Discrimination of movement, flicker and orientation may also be present, but residual colour discrimination is controversial. Negative results imply that only the pathways from eye to striate cortex can transmit information about colour in primates. By measuring sensitivity to light of different wavelengths in patients with blindsight we show that spectral sensitivity in the blind fields is surprisingly high, with a reduction of only 1 log unit or less across the visible spectrum. It is also essentially normal in form, whether the patients are adapted to light or dark. The shift in peak sensitivity from medium to shorter wavelengths in adaptation to the dark (the Purkinje shift) and the presence of discontinuities in the light-adapted curve together show that blindsight involves both rod and cone contributions, and that some colour opponency remains. As colour opponency requires input from primate beta retinal ganglion cells, two-thirds of which degenerate transneurally after a striate cortical lesion in juvenile monkeys, our results show that the surviving subpopulation of primate beta cells is functional.     

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.     

Speciation by hybridization in Heliconius butterflies

Speciation is generally regarded to result from the splitting of a single lineage. An alternative is hybrid speciation, considered to be extremely rare, in which two distinct lineages contribute genes to a daughter species. Here we show that a hybrid trait in an animal species can directly cause reproductive isolation. The butterfly species Heliconius heurippa is known to have an intermediate morphology and a hybrid genome, and we have recreated its intermediate wing colour and pattern through laboratory crosses between H. melpomene, H. cydno and their F1 hybrids. We then used mate preference experiments to show that the phenotype of H. heurippa reproductively isolates it from both parental species. There is strong assortative mating between all three species, and in H. heurippa the wing pattern and colour elements derived from H. melpomene and H. cydno are both critical for mate recognition by males.     

Opsin expression: new mechanism for modulating colour vision

Each cone photoreceptor in the retina responds to light in a limited range of wavelengths, giving it a spectral phenotype. This phenotype is determined by the most prevalent of the photoreceptor's visual-pigment proteins (opsins) and is assumed to remain unchanged during an animal's lifetime. Here we show that in the Pacific pink salmon, Oncorhynchus gorbuscha, single cones can switch their spectral phenotype from ultraviolet to blue by regulating the production of the appropriate opsins as the fish grow older. This photoreceptor plasticity may operate to modulate colour vision as the salmon's lifestyle changes.     

Light emission: A temperature-tunable random laser.

Random lasers have fascinating emission properties that lie somewhere between those of a conventional laser and a common light-bulb. We have created a random laser that can be brought above and below its threshold for laser emission by small changes in its temperature, thereby creating a light source with a temperature-tunable colour spectrum. As a single random laser can be made as small as a grain of tens of micrometres in diameter, we expect our device to find application in photonics, temperature-sensitive displays and screens, and in remote temperature sensing. Lasers are now commonplace - for example, they are used in industry and in hospitals, in bar-code scanners and compact-disc players. Conventional lasers are based on an optically active material and some sort of laser cavity that traps light for long enough for laser action to occur. A new type of laser source, known as a random laser, has been discovered that does not require a regular cavity but instead depends on a diffusive material such as a fine powder. In a random laser, light waves are trapped by multiple light scattering (that is, light diffusion), which takes over the role of the cavity in a regular laser (Fig. 1). The emission of a random-laser source has a well defined colour spectrum and can be pulsed, just like a regular laser, although its emission is in several directions because of the intrinsic randomness of the system.     

用单波长激光制作真彩色全息图

研究将已有的彩色技术与彩色印刷术相结合,在无全色光致抗蚀剂的情况下,利用单一波长的激光光源和现有的蓝敏光致抗蚀剂,采用密度编码分区记录方法,在同一干版的不同区域记录三原色掩模的菲涅耳全息图,白光再现下,获得真彩色全息图.