Preserved figure-ground segregation and symmetry perception in visual neglect.

A central controversy in current research on visual attention is whether figures are segregated from their background preattentively, or whether attention is first directed to unstructured regions of the image. Here we present neurological evidence for the former view from studies of a brain-injured patient with visual neglect. His attentional impairment arises after normal segmentation of the image into figures and background has taken place. Our results indicate that information which is neglected and unavailable to higher levels of visual processing can nevertheless be processed by earlier stages in the visual system concerned with segmentation.     

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.     

Polymorphism in red photopigment underlies variation in colour matching.

Genetic variation of human senses within the normal range probably exists but usually cannot be investigated in detail for lack of appropriate methods. The study of subtle perceptual differences in red-green colour vision is feasible since both photopigment genotypes and psychophysical phenotypes can be assessed by sophisticated techniques. Red-green colour vision in humans is mediated by two different visual pigments: red (long-wavelength sensitive) and green (middle-wavelength sensitive). The apoproteins of these highly homologous photopigments are encoded by genes on the X chromosome. Colour matches of males with normal colour vision fall into two main groups that appear to be transmitted by X-linked inheritance. This difference in colour matching is likely to reflect small variations in the absorption maxima of visual pigments, suggesting the presence of two common variants of the red and/or green visual pigments that differ in spectral positioning. We report that a common single amino-acid polymorphism (62% Ser, 38% Ala) at residue 180 of the X-linked red visual pigment explains the finding of two major groups in the distribution of colour matching among males with normal colour vision.     

Perceptual learning without perception.

The brain is able to adapt rapidly and continually to the surrounding environment, becoming increasingly sensitive to important and frequently encountered stimuli. It is often claimed that this adaptive learning is highly task-specific, that is, we become more sensitive to the critical signals in the tasks we attend to. Here, we show a new type of perceptual learning, which occurs without attention, without awareness and without any task relevance. Subjects were repeatedly presented with a background motion signal so weak that its direction was not visible; the invisible motion was an irrelevant background to the central task that engaged the subject's attention. Despite being below the threshold of visibility and being irrelevant to the central task, the repetitive exposure improved performance specifically for the direction of the exposed motion when tested in a subsequent suprathreshold test. These results suggest that a frequently presented feature sensitizes the visual system merely owing to its frequency, not its relevance or salience.     

Sensory adaptation. Tunable colour vision in a mantis shrimp

Systems of colour vision are normally identical in all members of a species, but a single design may not be adequate for species living in a diverse range of light environments. Here we show that in the mantis shrimp Haptosquilla trispinosa, which occupies a range of depths in the ocean, long-wavelength colour receptors are individually tuned to the local light environment. The spectral sensitivity of specific classes of photoreceptor is adjusted by filters that vary between individuals.     

寺河二号井15号煤层的回采实践

结合寺河二号井煤层赋存条件,对15号层煤的工作面布置方案及回采实践进行了详细分析,总结了回采经验,以期对类似煤层的开采提供借鉴。     

金融数学第一人--访山东省科学技术最高奖获得者彭实戈

采访彭实戈,记者颇费了一些周折,全省科技大会结束后第三天,竟想不到他已身在威海,千里之遥,采访一事只好暂时搁浅。一个月后,当记者得知彭实戈教授已返回山大的消息,欣喜之余,拨通了他的电话…… 秋天,因了这份采访而更加充满了诗意;秋天,期盼缤纷中收获季节的完美。 就是在这样的一个初秋里,彭实戈把话数学,把话数学之于艺术…… 彭实戈,1947年生于滨县。1971-1974年就读于山东大学物理系;1983-1986年,在巴黎九大、普鲁旺斯大学读博士,获“数学与自动化”三阶段博士、“应用数学”博士;1988-1989年,在复旦大学做博士后研究;1992年获法国“领导研究资格”证书(即国家博士)。现为山东大学数学与系统科学学院博士生导师,教育部“长江学者奖励计划”首批特聘教授。 “平和、自然、谦逊”当记者初次见到彭实戈,脑海中便跳出这样几个词。在他身上没有丝毫成名后的霸气,所有的只是他对于数学的那份强烈的爱与无止尽的追求…… 走近这样一位学者,可深深感受到他那股超越常人的内在力量,可谛听到他对数学美的诠释……     

化学中双轨道重叠对称性判据方法综述

综述了双轨道对称性是否匹配的各种方法，并给出了最新的理论判据公式和完善的判别方法。