The Optical-Geometrical Characteristics and Thresholds of Perception of Fragmented Outline Figures

Measurements were made of the threshold of recognition of cumulatively forming line figures. The threshold value of the outline, expressed in pixels, depended on the length of the outline of the whole unfragmented figure. Relative threshold values were constant, and for the measures of figure fragments used in the present study, averaged 12.5%. A spatial frequency analysis of the test images was performed. Variation of the amplitude-frequency parameters of the spectra of the images of various figures with threshold fragmentation was minimal as compared with the variation of these parameters in figures with subthreshold or suprathreshold levels of fragmentation.     

Estimating Effect Sizes in Genome-Wide Association Studies

Knowledge about the proportion of markers without effects (p ₀ ) and the effect sizes in large scale genetic studies is important to understand the basic properties of the data and for applications such as the control of false discoveries and designing adequately powered replication studies. Many p ₀ estimators have been proposed. However, high dimensional data sets typically comprise a large range of effect sizes and it is unclear whether the estimated p ₀ is related to the whole range, including markers with very small effects, or just the markers with large effects. In this article we develop an estimation procedure that can be used in all scenarios where the test statistic distribution under the alternative can be characterized by a single parameter (e.g. non-centrality parameter of the non-central chi-square or F distribution). The estimation procedure starts with estimating the largest effect in the data set, then the second largest effect, then the third largest effect, etc. We stop when the effect sizes become so small that they cannot be estimated precisely anymore for the given sample size. Once the individual effect sizes are estimated, they can be used to calculate an interpretable estimate of p ₀. Thus, our method results in both an interpretable estimate of p ₀ as well as estimates of the effect sizes present in the whole marker set by repeatedly estimating a single parameter. Simulations suggest that the effects are estimated precisely with only a small upward bias. The R codes that compute the effect estimates are freely downloadable from the website: .     

Perception of Fragmented Images of Three-Dimensional Objects as the Observation Angle Changes

Recognition thresholds for incomplete two-dimensional images of three-dimensional objects were measured as the observation angle was changed. A new experimental psychophysical method was developed and programmed for this purpose, this being a modification of the Gollin test, which measures perception thresholds of incomplete outline images. After training to a stimulus alphabet, observers’ responses were found to be invariant to changes in the observation angles of three-dimensional objects from 15° to 60°. It is suggested that possible algorithms for the formation of models of three-dimensional images in the human visual system do not operate on the basis of simple section, but involve invariance mechanisms.     

Studies of Chemoreceptor Perception in Mollusks

The formation and operation of the peripheral nervous system can be observed and studied in mollusks using as an example the primitive chemoreceptor organ, the osphradium, which is connected to the visceral arch of the CNS and analyzes the physicochemical properties of water in the mantle cavity. Nerve recordings showed that the osphradium is sensitive to excess osmotic pressure, sodium chloride, and amino acids. In addition, the osphradium responds to the quality of the water in which the animal is living. The osphradium of the pond snail retains its ancient multisensory function, uniting the perception of various chemical and physical stimuli. Patch clamp recordings at fixed potential or current were used to study membrane currents in identified ganglion and receptor cells, associated with increases in the concentrations of Na⁺ and L-aspartate in the solution bathing the osphradium. The influx current appears to be a sodium and/or calcium current, and is not blocked by tetraethylammonium, while the efflux current is a potassium current, as has been shown for the taste cells of vertebrates.     

不同粒径银粒子的体外细胞毒性比较

目的 比较纳米银粉末与微米银粉末体外细胞毒性的差异,并初步探讨毒性机制与粒径大小的相关性.方法 四种不同粒径银粒子通过扫描电镜确定其粒径分布后,制备成不同浓度的含银培养液与L929细胞接触培养,通过倒置相差显微镜观察其形态,采取MTT（四唑盐）比色法量化细胞毒性,计算相对增值率（RGR）,并进行毒性评价.结果 当银浓度在一定范围内（2.5～25）μg//mL,纳米银粒子呈现轻微细胞毒性（0～1）级,RGR与含银量呈量-效关系;随着浓度增高到大于50μg/mL时,与之共培养的细胞,形态上发生较大改变,显示明显的细胞毒性,量-效相关性也随之消失.粒径较小的微米银在银浓度达到250μg/mL时显示明显的细胞毒性.而粒径较大的两组微米银粒子在所有试验浓度下,共培养的细胞生长良好,未见明显的细胞毒性.结论 粒径不同的银粒子的体外细胞毒性有较大差异.同等剂量下,纳米级的银粒子和粒径较小的微米级银粒子,比粒径较大的微米级银粒子的体外细胞毒性更大.     

Intestinal Absorption of Botulinum Toxins of Different Molecular Sizes in Rats

During a period of 10 to 12 h after injection of type B 16S (L) toxin into the ligated duodenum of rats, 0.01 to 0.1% of the total toxicity administered was found in the lymph drawn by cannulation of the thoracic duct. The recovery was 50 to 100 times higher than that of the rat given type B 12S (M) or 7S (S) toxin. During the same period, 0.6 to 1.5% of the specific antigens were recovered, regardless of the molecular size of the toxin that had been administered. In lymph of the B-L or B-M toxin recipient, the toxic and nontoxic components were detected in comparable quantities, indicating that the undissociated progenitor toxin molecule is absorbed through the intestinal wall. Although the toxic component had lost its toxic activity, the two components of B-M toxin appearing in lymph reassembled to reconstruct the 12S molecule, whereas those of B-L toxin did not, although the toxic component was still active. Type B-L, B-M, and B-S toxins showed similar stabilities to in vitro exposure to rat lymph (pH 8.2), but B-L toxin showed a considerably higher stability to intestinal juice (pH 7.0) than did B-M toxin. Thus, the toxicity of lymph of rats administered botulinum toxin intraduodenally depends not upon the rate of absorption, but largely upon the stability in the intestine.     

不同粒径活性炭对中,小分子物质吸附平衡的差异与分析

本文研究了不同粒径活性炭对中、小分子物质吸附平衡的差异，结果表明，粒径对小分子物质吸附平衡的影响较小，而对中分子物质影响较大。据此结果建议，在保证血液相容性的前提下，对同一种活性炭，宜选用孔道发达的小颗粒炭进行血液灌流。     

Toxicities of Clostridium botulinum Type C Toxins of Different Molecular Sizes in Geese

Clostridium botulinum type C toxin of 16S was more potent as an oral toxin to geese than that of 12S.     

不同尺寸参数对双极高频电刀热应力场的影响

目的分析不同尺寸参数对双极高频电刀热应力场的影响规律。方法基于有限元分析软件ANSYS,对双极高频电刀工作过程中的热应力场进行系统的电热耦合仿真分析,研究3种不同绝缘层厚度(0.5、1.0、1.5 mm)、电极厚度(0.5、1.0、1.5 mm)以及涂层厚度(3、6、9μm)对高频电刀各部分热应力场的影响。结果绝缘层厚度越大,心肌组织由于热应力产生的变形量越小,即高频电刀工作过程中绝缘层厚度与心肌组织的热变形量成反比;对于3种电极厚度而言,选取1.0 mm更为合适;对于3种涂层厚度而言,选取6μm更为合适。结论高频电刀各组成部件的尺寸参数对其工作过程中的热应力场有重要的影响,研究结果可为高频电刀的设计开发提供指导。     

不同粒径纳米二氧化硅的体外细胞膜毒性作用

探讨不同粒径纳米二氧化硅对体外培养细胞膜的损伤作用及其机制。20nm、60nmSiO2及微米SiO2对RAW264.7巨噬细胞染毒后,分别采用MTT法、显微镜及透射电镜、能谱分析、荧光漂白恢复技术(FRAP)、丙酮酸法、荧光探针2′,7′-二乙酰二氯荧光素(DCFH-DA),测定染毒细胞的活性、形态及超微结构,细胞内外Si元素分布、膜流动性,细胞外液中乳酸脱氢酶(LDH)含量和细胞内活性氧生成。试验结果显示:20nm、60nmSiO2及微米SiO2粒子的细胞半数抑制浓度(IC50)分别为2.07、6.82和14.71mg/mL;染毒后细胞数量减少,呈气球样变,线粒体肿胀、破坏;细胞内吞噬泡和细胞间隙颗粒均含Si元素;31.25、125、500μg/mL的20nm、60nmSiO2组及500μg/mL微米SiO2组细胞膜荧光恢复率降低(P0.05);125、500μg/mL两种粒径纳米SiO2组及500μg/mL微米SiO2组细胞膜扩散系数降低(P0.05);两种粒径纳米SiO2组细胞外液中LDH活性升高(P0.05),500μg/mL的20nmSiO2较60nmSiO2和微米SiO2致细胞荧光恢复率降低,LDH活性升高(P0.05);两种粒径纳米SiO2及微米SiO2可致染毒细胞内活性氧水平升高(P0.05)。结果表明,20nm、60nmSiO2可通过诱导脂质过氧化引起细胞生长抑制、形态异常、超微结构改变和细胞膜损伤,相同剂量20nmSiO2产生的毒性效应较60nmSiO2明显,说明纳米SiO2的尺寸效应是一个值得关注的问题。     

Model Studies of the Mechanisms of Tuning of Visual Cortex Neurons to Incomplete Cross-Shaped Figures

Numerical simulation modeling of the receptive fields of visual cortex neurons able to detect cross-shaped figures with masked central or peripheral areas was performed. Receptive field models of two types were considered: those with antagonistic and cooperative interactions between the center and the periphery. Model neurons with receptive fields with reciprocal (antagonistic) interactions produced greater responses to peripheral or central crosses than to complete crosses. Studies using the model showed that the basis of this type of tuning could be provided by a disinhibition mechanism: blockade of the inhibitory zones in the center or periphery of the receptive field by activation of a lateral disinhibitory zone. A model with cooperative interactions between the center and periphery of the receptive field was also studied, in which responses to complete crosses were summed from the responses to the peripheral and central parts. Tuning of these model receptive fields was comparable to the sensitivity of real visual cortex neurons to the shape, size, and orientation of figures. The properties of model receptive fields (configuration, localization, and weightings of the various zones) allowing simulation of the properties of cat visual cortex field 17 neurons sensitive to the orientation and configuration of incomplete cross-shaped figures were identified.     

不同长度疟原虫环子孢子蛋白重复序列DNA免疫的实验分析

本实验利用DNA免疫技术 ,将PCR得到的疟原虫环子孢子蛋白 (CSP )不同长度的重复序列基因克隆到pcDNA3质粒中 ,对小鼠进行肌肉注射 ,经过免疫检测 ,结果证明不同长度CSP的重复序列能够单独诱发机体全面的细胞免疫和体液免疫 ,这为今后疟疾疫苗的发展提供了新的思路。     

不同滤波方法对超声图像分割的影响

采用各向异性滤波方法以及Gabor滤波方法对乳腺肿瘤超声图像进行处理,再使用snake方法以及level set方法在设置相同参数的条件下,对过滤的图像分别进行分割.试验结果表明,不同的滤波方法在分割目标图像的收敛度,边缘圆滑度及整体轮廓提取效果都有较大影响,为分割图像选取适当的滤波器提供了参考.