Drawn gelatin films with improved mechanical properties

Chain anisotropic distribution in gelatin films has been obtained by uniaxial stretching at constant relative humidity, followed by air drying and successive cross-linking with glutaraldehyde. The drawn samples have been characterized by mechanical tests, differential scanning calorimetry and scanning electron microscopy. The Young’s modulus, E, and the stress at break, σ_b, increase linearly with the draw ratio and reach values which are about five times those characteristic of undrawn samples. Furthermore, on stretching the alignment of the gelatin strands along the direction of deformation increases while the thickness of the layers decreases significantly. The renaturation level, that is the fraction of gelatin in a collagen-like structure, has been calculated as the ratio between the melting enthalpy of gelatin samples and that of tendon collagen. The results indicate that the improvement of mechanical properties achieved by drawn gelatin is closely related to the renaturation level. The experimental approach utilized to induce segmental orientation in gelatin films, allows to obtain anisotropic materials with improved mechanical properties in the direction of deformation, and can be usefully applied in the preparation of biomaterials.     

Interaction of sensory and cognitive processes during visual recognition: The role of the associative areas of the cerebral cortex

The first part of the present study used a model of Alzheimers disease in two groups of animals (three monkeys in each), given injections of neurotoxins (monkeys of group I) and physiological saline (monkeys of group II). Before injections, all monkeys were trained to discriminate stimuli containing different types of information (spatial frequency grids and geometrical figures of different colors and with different spatial relationships between objects) and to perform spatial selection. The dynamics of impairments in the characteristics of working memory were identified using delayed differentiation tasks in monkeys of both groups before injections and every two months after injections. Quantitative measures of impairments were made using the entropy of visual recognition, which characterizes uncertainty in decision-taking. The development of Alzheimers disease in rhesus macaques was characterized by a deficit of working memory, resulting from lesions to the two component processes of memory. Impairments of the first of these in monkeys of group I were manifest as a significant increase in entropy, which is associated with correct decision-taking. The magnitude of the increase depended on the type of visual information. Impairments of the second component were characterized by increases in entropy associated with refusals to take decisions and were independent of the delay duration and the type of visual information. Monkeys given injections of physiological saline showed no significant changes in these characteristics. The features of working memory were also studied in the second part of the investigation, using four groups of Rhesus macaques: intact, those with bilateral extirpation of the sulcus principalis or field 7 or both: degradation again identified two components. Entropy associated with this was increased significantly for most of the stimuli tested on monkeys of all extirpation groups as compared with intact animals. Significant differences were found in these characteristics for a number of stimuli, which depended on the location of the structures removed. The characteristics of impairments of the components of working memory resulting in the development of Alzheimers disease showed that the cholinergic mechanisms responsible for sensory processing differ from those involved in decision-taking. The structural-functional organization of the interaction of sensory and cognitive processes controlled by the motivation and attention systems is discussed, as is the role of the associative areas of the cortex.Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 89, No. 10, pp. 1226–1239, October, 2003.     

图、词回忆中的序列位置效应及其年龄变化规律

目的：探讨图、词回忆中的首因和近因效应及其年龄变化规律。方法：采用多维记忆评估量表中的汉词回忆和图画回忆分测验对947人的连续年龄组的大样本进行测试，分析不同通道首因和近因效应的差异和年龄变化规律。结果：受试在汉词和图画自由回忆中，均呈现明显的系列位置效应；受试的首因和近因效应均随年龄的增长而增大。当发展到高峰后则随年龄的增长而减弱，各年龄组间比较有显著差异；首因和近因效应随年龄增长是不平行的，首因效应随年龄的增长变化较大。而近因效应的变化则相对较为平缓；两种不同呈现途径的比较发现，图画回忆的首因和近因效应均高于汉词回忆。结论：视觉和听觉呈现途径均呈现明显的系列位置效应，首因效应和近因效应的发展变化规律与记忆的发展变化规律是一致的。首因效应受年龄的影响较大，在有意义的图画回忆中首因效应和近因效应均高于汉词回忆。     

大学生身体意识量表的修订

目的:在Mckinley和Hyde的身体意识客体化量表(OBCS)基础上,进行量表的修订。方法:对432名大学生进行原始量表的测量,其中212名被试的结果作探索性因素分析,其余220名被试的结果作信、效度检验。结果:量表包含20个项目,三个分量表,分别是身体监视、身体羞耻感和控制信念。因素分析表明,三个分量表解释总方差的60.25%,各个项目载荷在0.623~0.824之间。重测信度为0.764~0.802,同质信度为0.861~0.875。与OBSC原量表相比,修订的大学生身体意识量表删减了4个项目。结论:经修订后,大学生身体意识量表具有较为满意的信、效度,可以在大学生中使用。     

Response properties of neurons in the visual cortex of the rat

Summary Response properties of neurons in the visual cortex, area 17, of Long Evans pigmented rats were investigated quantitatively with computer-controlled stimuli. Ninety percent of the cells recorded (296/327) were responsive to visual stimulation. The majority (95%, 281/296) responded to moving images and were classified as complex (44%), simple (27%), hypercomplex (13%) and non-oriented (16%) according to criteria previously established for cortical cells in the cat and monkey. The remaining 5% of the neurons responded only to stationary stimuli flashed on-off in their receptive field. Results of this study indicate that neurons of the rat visual cortex have properties similar to those of cells in the striate cortex of more visual mammals.Supported by grant EY02964, the Biological Humanics Foundation and the Bendix Corporation     

Maslach倦怠量表-服务行业版在警察中的修订及应用分析

目的对Maslach倦怠量表-服务行业版(MBI-HSS)进行修订,并了解我国警察工作倦怠现状。方法采用MBI-HSS对4855名警察进行测试并对量表作出信、效度分析。结果修订后的量表保持原有的三维度结构,具有良好的结构效度(CFI=0.945,TLI=0.936,GFI=0.947,AGFI=0.930,NFI=0.942,IFI=0.945,RM-SEA=0.060),总量表和分量表的内部一致性信度、重测信度均大于0.70。综合三个维度的结果发现,男性警察的倦怠程度高于女性警察,警龄在6-15年的警察倦怠程度最严重,离异警察的倦怠程度高于已婚和未婚警察,学历低的警察倦怠程度较高。结论修订后的MBI-HSS可作为测量我国警察工作倦怠的有效工具。警察的工作倦怠在性别、警龄、婚姻状况、受教育程度方面存在差异。     

骨水泥性能及其对人工关节柄固定强度的影响

本文研究了骨水泥三种不同临床使用方法所形成的内部气泡结构状态,测定了骨水泥的抗压强度、收缩率、疲劳强度、变形积累量等物理机械性能,以及关节固定强度,用气泡状态解释了不同临床使用方法对骨水泥性能及固定强度所带来的各种影响。     

Morphology and Thermal Properties of MCPA6/ABS by in situ Polymerization of ε‐Caprolactam

Summary: In this work, blends of monomer casting polyamide 6 (MCPA6) and acrylonitrile‐butadiene‐styrene (ABS) were successfully prepared by in situ polymerization via the application of ε‐caprolactam as a reactive solvent. The morphology and thermal properties of MCPA6/ABS were investigated by means of wide angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), respectively. The domain sizes of the ABS phase in MCPA6/ABS blends were much finer than those in corresponding polyamide 6 (PA6)/ABS blends prepared by simple melt blending. With an increased amount of ABS in MCPA6, the melt enthalpy (ΔH_f), the rate of crystallization (T_c) and the degree of crystallinity (X_c(DSC)) of MCPA6 in MCPA6/ABS blends were all decreased. The degree of supercooling (ΔT_d) showed a contrary trend. However, the melting temperatures of these blends were almost unchanged. All the results could be attributed to in situ polymerization and the hydrolysis reaction of ABS that occurred during the polymerization process. Furthermore, WAXD results showed that only α‐form crystals existed in the MCPA6/ABS blends, despite the ABS content and heat treatment.

SEM micrograph of the fractured surface of an MCPA6/ABS blend with an ABS content of 20 wt.‐% (×10 000).     

人体体温下UHMWPE人工髋臼材料压缩性能的试验研究

模拟人体体温下对超高分子量聚乙烯（UHMWPE）人工髋臼材料进行了压缩力学性能的试验研究,并与室温下的试验结果进行了对比.当由室温22℃升高到体温37℃和40℃时,其屈服应力呈明显的下降趋势,分别下降了23.1%和31.9%,由体温37℃升高到40℃时,二者仅差3℃,其屈服应力亦下降了11.5%.同时还对不同加载速度下UHMWPE试件压缩变形过程进行了红外辐射温度的监测与分析.不同加载速度下试件压缩变形过程中的红外辐射温度均有明显升高,加载时间越长,试件平均红外辐射温度越高.试验结果分析表明,不能忽视植入人体后UHMWPE人工髋臼局部受压时温度的升高,特别不能忽视植入人体后在人体体温作用下其力学性能的改变和下降,人体体温的作用是UHMWPE人工髋臼出现过早失效的原因之一.本试验研究为UHMWPE材料在人体环境中的应用研究提供了参考.     

Acrylic‐Based Polyurethane/Silica Hybrids Prepared by Acid‐Catalyzed Sol–Gel Process: Structure and Mechanical Properties

Summary: Silica sols were first prepared based on different ratios of tetraethoxysilane (TEOS) and methyltriethoxysilane (MTES) by an acid‐catalyzed sol–gel process, and then incorporated into acrylic‐based polyurethanes. The structures and morphologies of silicone‐oxo clusters were studied by ²⁹Si NMR, SAXS, and scanning electron microscopy (SEM), whereas the mechanical properties of polyurethane/silica hybrids were characterized by DMA and tensile tests. The silicone‐oxo clusters in both silica sol and polyurethane hybrids became denser and larger at a higher molar ratio of TEOS/MTES and higher silica content, and the silica‐oxo clusters of polyurethane/silica hybrids even became more compact and larger than those of silica sols, increasing the elastic modulus and tensile strength of polyurethane/silica hybrids.

Typical structure of silica sol prepared from the hydrolysis and condensation of TEOS and MTES with acid as the catalyst.