行星轧制—联拉紫铜管坯的“黑纹”缺陷研究

＂黑纹＂是行星轧制法生产紫铜管时常常出现的一种产品缺陷,对铜管的质量造成严重影响.笔者通过现场跟踪、塑性变形计算、显微组织显现与观察、试验验证等研究手段,对＂黑纹＂的形貌、特征、分布等方面进行了充分研究,此外分析了其产生的原因,提出措施来有效减少甚至避免＂黑纹＂的产生.     

冷轧板条痕缺陷的特征及形成原因探讨

对冷轧板中发现的条痕缺陷特征进行了分析，探讨了该缺陷的形成原因，通过对热轧板中发现的条状缺陷特征分析，以及对条状缺陷热轧板的冷轧试验和热轧板酸洗出口处进行的缺陷跟踪，认为热轧板中的条状缺陷可以形成冷轧板中的条痕缺陷，综合分析认为连铸坯中的气泡是形成冷轧板表面条痕缺陷的主要原因。     

基于特征量和神经网络的钢管缺陷预测模型

分析了钢管缺陷几何大小与缺陷漏磁信号(MFL)特征量之间关系，建立了一组全方位的钢管缺陷信号特征量，并将人工神经网络理论和算法应用于钢管缺陷预测。通过实验取得样本，在对网络进行训练的基础上，建立了基于钢管缺陷漏磁信号特征量和神经网络的缺陷预测模型，继而根据漏磁信号对缺陷进行定量预测。给出了实验结果，结果表明采用这种方法能够较好地实现管道缺陷的定量识别。     

线材缺陷探测和处理新技术

线材缺陷探测和处理新技术近年来，对线材表面质量的要求日益严格，一直在寻求一种表面缺陷检查精度高、缺陷修磨处理能力大的技术。为解决这一问题，新日本制铁所开发了采用涡流探伤机对线材表面缺陷进行检测，并使用了缺陷修磨自动化的新技术。过去，为保证对表面缺陷要...     

冷轧薄板表面缺陷研究

介绍了冷轧薄板表面主要缺陷的形貌、形成原因及预防措施。研究表明：冷轧薄板表面缺陷主要分为常规缺陷和非常规缺陷两大类。常规缺陷的产生与冷轧工艺质量密切相关，而非常规缺陷的形成机理则比较复杂，可能在炼钢工序也可能在轧钢工序形成，需具体情况具体分析。     

钢管缺陷漏磁场及影响漏磁信号因素的分析

介绍了钢管检测中常见的缺陷漏磁场模型和漏磁场分布，以及对凹坑缺陷漏磁场进行的模拟研究。比较了两种缺陷漏磁检测信号的时频特性，讨论了缺陷深度、励磁电流、检测探头纵向旋转速度等对矩形槽缺陷漏磁感应电压信号的影响。研究发现，缺陷深度和漏磁感应信号峰值约呈线性关系，这可作为钢管缺陷检测的应用基础。     

矢量光点运动示迹用于缺陷定性与外折的检出

采用观察矢量光点运动示迹对缺陷定性与检出，发现缺陷的相位与标准人工通孔有差异恶性缺陷外面积状缺陷相位，幅度不一，就此方面工作进行探讨。     

SWRM6鱼鳞状缺陷成因分析

分析了SWRM6高速线材鱼鳞状缺陷的主要形态特征及其成因，指出这些缺陷并非折叠缺陷，而是由铸坯本身的皮下气泡引起的。改进脱氧工艺后，消除了鱼鳞状缺陷。     

钢轨裂缝缺陷产生原因分析

钢轨在线路焊接时，发现钢轨端面轨底脚部位有一严重裂缝缺陷。经过缺陷的形貌特征，及缺陷中夹杂物成分分析，结果为钢轨中的裂缝缺陷是因铸锭时保护渣卷入钢水中所造成。     

熔盐炉内盘管缺陷检测与分析

针对熔盐炉内盘管的主要缺陷形式，应用脉动直流磁粉探伤技术和超声波测厚技术，对内盘管裂纹及厚壁减薄缺陷进行检测，并结合实际工况，对检测的缺陷结果进行计算分析，为熔盐炉的安全运行及缺陷处理提供科学依据。     

Compartments within human primary auditory cortex: evidence from cytochrome oxidase and acetylcholinesterase staining

The human primary auditory area (AI) corresponds to granular cortex located on Heschl's gyrus. We studied its pattern of cytochrome oxidase and acetylcholinesterase activity in 10 normal human hemispheres. In cytochrome-oxidase-stained coronal sections layer IV was prominent by its dark staining. The overall staining intensity varied along the medio-lateral extent of Al; a 2.0-2.5-mm-wide antero-posterior dark band was present at mid-AI. In acetylcholinesterase-stained coronal sections a dark antero-posterior band appeared at the same location, corresponding to the highly granular part of Al. In cytochrome-oxidase-stained tangential sections of flattened Al, approximately 500-microm thick alternating dark and light cytochrome oxidase stripes were present in layers III and IV. These stripes were perpendicular to the dark band. Comparison with tonotopic maps of human Al obtained by activation studies suggests that the cytochrome oxidase and acetylcholinesterase dark band is most likely parallel to isofrequency lines and may correspond to the representation of frequencies critical for speech comprehension. The narrow stripes may be related to particular binaural or ampliotopic domains, whose presence is suggested by evidence from electrophysiological recordings in cat Al and from magnetoencephalographic studies in humans.     

Circadian rhythms in the incorporation and secretion of 3H-proline by odontoblasts in relation to incremental lines in rat dentin

Circadian incremental lines are universally found in the dentin of animals. They are believed to be caused by functional changes in odontoblasts over 24 hrs. However, the mechanism of rhythmic dentin formation has not yet been elucidated. In the present study, we investigated whether there is a 24-hour rhythm in the collagen-synthetic and secretory activities of odontoblasts by radioautography with 3H-proline as a tracer. Six different groups of rats were injected with 3H-proline at 0000, 0400, 0800, 1200, 1600, or 2000 after the animals had become acclimated to a 12/12-hour light-dark illumination cycle for 2 wks. One hour after the injection, the maxillary incisors were removed and processed for radioautographic study. The silver grains of 3H-proline were most intense over odontoblasts and predentin during the environmental light period, while the nadir occurred during the dark period. The peak value was approximately two-fold higher than the minimum value. Moreover, in the dentin from rats that had been infused with 3H-proline continuously for 10 days by means of osmotic minipumps, silver grains of 3H-proline were heavily distributed over the dark hematoxylin-stained incremental lines. Thus, we demonstrated that odontoblasts show circadian rhythm with regard to collagen synthesis and secretion. These rhythms in odontoblastic function may be responsible for circadian incremental lines in dentin.     

UV- and gamma-radiation sensitive mutants of Arabidopsis thaliana

Arabidopsis seedlings repair UV-induced DNA damage via light-dependent and independent pathways. The mechanism of the "dark repair" pathway is still unknown. To determine the number of genes required for dark repair and to investigate the substrate-specificity of this process we isolated mutants with enhanced sensitivity to UV radiation in the absence of photoreactivating light. Seven independently derived UV sensitive mutants were isolated from an EMS-mutagenized population. These fell into six complementation groups, two of which (UVR1 and UVH1) have previously been defined. Four of these mutants are defective in the dark repair of UV-induced pyrimidine [6-4]pyrimidinone dimers. These four mutant lines are sensitive to the growth-inhibitory effects of gamma radiation, suggesting that this repair pathway is also involved in the repair of some type of gamma-induced DNA damage product. The requirement for the coordinate action of several different gene products for effective repair of pyrimidine dimers, as well as the nonspecific nature of the repair activity, is consistent with nucleotide excision repair mechanisms previously described in Saccharomyces cerevisiae and nonplant higher eukaryotes and inconsistent with substrate-specific base excision repair mechanisms found in some bacteria, bacteriophage, and fungi.     

Photodynamic effects of hypericin on lipid peroxidation and antioxidant status in melanoma cells

Photodynamic-induced cytotoxicity by hypericin (HYP) was studied on three human melanoma cell lines: one pigmented cell line (G361) and two amelanotic cell lines (M18 and M6). No significant variation in the rate of uptake and in the maximum level of HYP incorporation for the different cells was observed. In the dark, no cytotoxicity was observed in the range 0-10-6 M HYP for the three cell lines. Amelanotic cells were found to be more sensitive than pigmented cells to irradiation of HYP with visible light (lambda > 590 nm). In addition, for the three cell lines HYP-induced photocytotoxicity was found to be drug-dose and light-dose dependent. Under the conditions used, thiobarbituric acid-reacting substances (TBARs) were significantly increased in amelanotic cells after irradiation (P < 0.0001). By contrast, the amount of TBARS remained unchanged in pigmented cells. Antioxidant defenses including enzymes and glutathione (GSH) were assayed before and after HYP photosensitization. Significantly increased total SOD activity was observed after photosensitizaton for amelanotic cells (P < 0.05), while glutathione peroxidase (GSHPx) and catalase (Cat) activities but also GSH levels were significantly decreased (P < 0.01). In pigmented cells a significantly increased Cat activity was found (P < 0.05), whereas GSHPx was unaffected after irradiation. It can be inferred that (a) HYP may be an effective PDT agent for melanoma and (b) there is a relationship between melanin content and sensitivity to HYP phototoxicity in human melanoma cells.     

Membrane glycoprotein PC-1 and insulin resistance

The photosensitizing ability of the second generation photosensitizer 5,10,15,20-tetra-(3-carboxymethoxyphenyl)-chlorin (m-TCMPC), a derivative of m-THPC, was tested on both three-dimensional multicellular spheroids of varying sizes and on monolayer cultures. These experiments were carried out on two spheroid-forming cell lines, A2780 (a human ovarian adenocarcinoma) and CHO (Chinese hamster ovarian cells). For both cell lines, photodynamic therapy (sensitizer plus visible light) treatments were carried out. The chlorin m-TCMPC was shown to have considerable promise as a photosensitizing agent. Cell kill was achieved for all situations tested, i.e. monolayer, 100, 500 and 750 microm spheroids. In addition no significant dark toxicity was observed.     

Expression of transforming growth factor-alpha (TGF-alpha) in cholesteatoma

BACKGROUND: This report describes the measurement of convergent eye movements and calculation of the spatial convergence point from the angular eye position data. These measurements were made in the dark while the subject experienced inertial motion aboard a centrifuge. This was an exploratory experiment with the goal of evaluating the eyes' convergence in the dark, and to see if this convergence point is dependent on inertial motion. METHODS: The subject was rotated in the dark on NAMRL's Coriolis Acceleration Platform in Pensacola, FL. The pupil positions were tracked by two helmet-mounted infrared cameras connected to a computer-controlled data acquisition system. We used the position data to calculate the angles through which the eyes rotated, and then applied trigonometric principles to construct the line of sight for each eye for any instant in time. The intersection of these two lines of sight was the convergence point. RESULTS: With the binocular eye-tracking system, we could accurately determine an accelerating subject's convergence point to within 10%, if the point was less than 1.5 m away from the subject. At convergence distances greater than 1.5 m, the angular movements of the two eyes became so small that determining a convergence point was difficult.     

Spatial arrangements of responses by cells in the cat visual cortex to light and dark bars and edges

Detailed examination is made of the responses of visual cortical cells (area 17, border 17-18 and adjacent area 18) in the anaesthetized cat to stationary flashing bars and to bars (lines) and edges moving at their optimal velocities. Particular attention is given to the receptive field organization of cells in the simple family. While there is good general agreement between the main receptive field subregions revealed by stationary and moving stimuli, the responses to moving light and dark bars, supplemented by the responses to moving light and dark edges, provide a much more rapid, accurate and complete guide to the spatial organization of the receptive fields than do the response profiles to a stationary flashing bar. Moving light and dark bars between them generally reveal more subregions in the receptive fields of simple cells than is evident from the response profiles to a stationary flashing bar, particularly when the receptive fields have many subregions. In addition the responses to moving edges provide a rapid guide to spatial summation across the width of a subregion and the possible antagonistic effects of the next subregion in sequence. Two subclasses of cells in the simple family have been recognized: ordinary simple and fast simple cells. Two cell classes (A-cells and silent periodic cells) having properties intermediate between simple and complex types are discriminated and their properties described.     

Differential sensitivity of membrane-associated pyrophosphatases to inhibition by diphosphonates and fluoride delineates two classes of enzyme

The participation of GABAergic mechanisms in the regulation of circadian rhythmicity by the suprachiasmatic nuclei (SCN) has been suggested from different lines of evidence. Little is known, however, whether GABA synthesis, release, uptake or content within the SCN may show a circadian pattern. The present results show that the activity of the GABAergic system within the SCN region of the rat exhibits circadian rhythmicity, which is manifested by correlative changes of the GABA content and the glutamic acid decarboxylase activity under the light/dark cycle, and by changes in the GABA content in animals kept under constant darkness.     

Evaluation of preparation, staining and microscopic techniques for counting incremental lines in cementum of human teeth

Apposition of cementum occurs in phases resulting in two types of layers with different optical and staining properties that can be observed by light microscopy. Narrow, dark staining incremental lines are separated by wider bands of pale staining cementum. The distance from one line to the next represents a yearly increment deposit of cementum in many mammals, and counting these lines has been used routinely to estimate the age of the animals. Incremental lines in cementum have also been observed in sections of human teeth, and the object of the present investigation was to examine a number of methods for preparing and staining them for counting. Longitudinal and transverse sections, either ground or decalcified, were cut from formalin fixed human dental roots, paraffin embedded or frozen, and stained using several techniques. The cementum was investigated using conventional light, fluorescence, polarized light, confocal laser scanning, interference contrast, phase contrast, and scanning electron microscopy. Incremental lines in the cementum could be observed in ground sections and, following decalcification, in both frozen and paraffin embedded sections. Toluidine blue, cresyl violet, hematoxylin, or periodic acid Schiff (PAS) stained incremental lines allowing differentiation by conventional light microscopy. Contrast was best using fluorescence microscopy and excitation by green light since the stained cemental bands, but not the incremental lines, fluoresced after staining with cresyl violet, PAS or hematoxylin and eosin. The results with other microscopic techniques were unsatisfactory. Since incremental lines are not destroyed by acids and stain differently than the remaining cementum, it is likely that they possess an organic structure which differs from the cementum. Incremental lines in human dental cementum could be observed best using decalcified sections stained with cresyl violet excited by green light.     

Lattice Distortion Formations by Low-Energy Ar<Superscript>+</Superscript> Bombardment of Thin Silicon Films Grown on Silicon (100)

The transmission electron microscopy (TEM) and X-ray characterization of lattice distortion forms caused by low-energy Ar⁺ bombardment of grown thin silicon films on a silicon (001) substrate were studied. The isotropic case (of spherical distortions) takes place in epitaxial silicon “as grown” processes. The intensity distribution consists of two maxima—one from the distorted layer and the other from the original unaffected silicon lattice. Significant changes in the 2θ location, peak broadening, and integrated intensity from the (004)* reflections were obtained as functions of aging temperatures. First, aging heat treatment, affects the distribution of distortions obtained from local regions at the “as grown” layer, which changes to a special topography of continued distortions at higher aging temperatures. At aging temperatures above 923 K (650 °C), this extra diffraction peak disappears. The TEM observations reveal the appearance of dislocation lines with dark and bright contrasts around the lines and interdislocation strain contrasts and disorder of Ar atoms in Si matrix regions with coherent interfaces.