共查询到20条相似文献,搜索用时 15 毫秒
1.
It is a widely held belief that the products of axonal degeneration in the CNS are transitory and are caused by metabolic and phagocytic processes. However, recent light microscopic examinations of human and primate brains using the paraphenylene diamine staining method (PPD), which stains degenerating axons, have confirmed that the products of degeneration persist for years in visual pathways. The routine utilization of the PPD method for delineating human visual pathways requires further confirmation of axonal degeneration. Optic nerves, optic tracts, and lateral geniculate nuclei were collected from human brains that had clinical documentation of optic nerve damage prior to death. Optic nerves, optic tracts, and lateral geniculate nuclei taken from the brains of cynomolgus monkeys that had undergone enucleation 3 months to 1 year prior to sacrifice were also examined. All tissue was processed for electron microscopy; ultrathin sections were cut for electron microscopy, and consecutive sections were cut for light microscopy. In all cases, the homology of the degenerated processes was confirmed between the light microscopic (PPD) and the electron microscopic sections. Such ultrastructural examination demonstrates that the products of axonal degeneration remain in the primate visual system longer than previously supposed. 相似文献
2.
The neuroanatomy of experimental animals has been investigated through a variety of histological and physiological techniques. Recently, more sophisticated methods have permitted a better understanding of the complex connections of animal brains. In contrast, the methods available for the direct examination of the human brain have remained relatively primitive. We have developed a staining method (paraphenylene-diamine method: PPD) which bridges the techniques of light and electron microscopy. The method permits the tracing of degenerated fibers in the human brain even after very long survival periods. With this method we have documented several visual pathways not previously described in man. We have also demonstrated, in several species, that products of axonal degeneration remain far longer than previously supposed. The PPD technique is relatively simple, reliable, provides high resolution, works in human brains, and can be used in conjunction with TEM. 相似文献
3.
Shahzad Akbar Muhammad Sharif Muhammad Usman Akram Tanzila Saba Toqeer Mahmood Mahyar Kolivand 《Microscopy research and technique》2019,82(2):153-170
Retina is the interior part of human's eye, has a vital role in vision. The digital image captured by fundus camera is very useful to analyze the abnormalities in retina especially in retinal blood vessels. To get information of blood vessels through fundus retinal image, a precise and accurate vessels segmentation image is required. This segmented blood vessel image is most beneficial to detect retinal diseases. Many automated techniques are widely used for retinal vessels segmentation which is a primary element of computerized diagnostic systems for retinal diseases. The automatic vessels segmentation may lead to more challenging task in the presence of lesions and abnormalities. This paper briefly describes the various publicly available retinal image databases and various machine learning techniques. State of the art exhibited that researchers have proposed several vessel segmentation methods based on supervised and supervised techniques and evaluated their results mostly on publicly datasets such as digital retinal images for vessel extraction and structured analysis of the retina. A comprehensive review of existing supervised and unsupervised vessel segmentation techniques or algorithms is presented which describes the philosophy of each algorithm. This review will be useful for readers in their future research. 相似文献
4.
Nonlinear ultrasonic techniques for nondestructive assessment of micro damage in material: A review 总被引:2,自引:0,他引:2
Kyung-Young Jhang 《International Journal of Precision Engineering and Manufacturing》2009,10(1):123-135
The nondestructive assessment of the damage that occurs in components during service plays a key role for condition monitoring
and residual life estimation of in-service components/structures. Ultrasound has been widely utilized for this; however most
of these conventional methods using ultrasonic characteristics in the linear elastic region are only sensitive to gross defects
but much less sensitive to micro-damage. Recently, the nonlinear ultrasonic technique, which uses nonlinear ultrasonic behavior
such as higher-harmonic generation, subharmonic generation, nonlinear resonance, or mixed frequency response, has been studied
as a positive method for overcoming this limitation. In this paper, overall progress in this technique is reviewed with the
brief introduction of basic principle in the application of each nonlinear ultrasonic phenomenon. 相似文献
5.
Mohammad Rezazadeh Mehrjou Norman Mariun Mohammad Hamiruce Marhaban Norhisam Misron 《Mechanical Systems and Signal Processing》2011,25(8):2827-2848
Nowadays, manufacturing companies are making great efforts to implement an effective machinery maintenance program, which provides incipient fault detection. The machine problem and its irregularity can be detected at an early stage by employing a suitable condition monitoring accompanied with powerful signal processing technique. Among various defects occurred in machines, rotor faults are of significant importance as they cause secondary failures that lead to a serious motor malfunction. Diagnosis of rotor failures has long been an important but complicated task in the area of motor faults detection. This paper intends to review and summarize the recent researches and developments performed in condition monitoring of the induction machine with the purpose of rotor faults detection. The aim of this article is to provide a broad outlook on rotor fault monitoring techniques for the researchers and engineers. 相似文献
6.
The simultaneous flow of gas, oil, and water forms various flow patterns due to the complex interfacial relationships. Three-phase flow patterns are classified as the gas-liquid and liquid-liquid flow patterns. Pressure drop, void fraction, liquid holdup, and phase distribution are important characteristics of the three-phase flow. These characteristics are generally associated with the three-phase flow patterns. Hence, the knowledge about flow patterns can help to predict the overall behavior of the three-phase flow. Studies have been conducted to identify three-phase flow pattern and their characteristics at various superficial velocities of gas, oil, and water. The major purpose of the studies is to gather information about the three-phase co-current flow and use it for improvement of the efficiency of the flow systems. Therefore, the accuracy of the measurement technique is critical. Several types of flow pattern identification and measurement techniques have been developed to improve accuracy and provide high-quality results. In this article, classical and advanced techniques used for the three-phase flow identification and measurement have been reviewed. The survey will help the researchers working in the area of multiphase flow to choose the right technique based on the objectives of the studies. 相似文献
7.
Tianfeng Zhou Yupeng He Tianxing Wang Zhanchen Zhu Ruzhen Xu Qian Yu Bin Zhao Wenxiang Zhao Peng Liu Xibin Wang 《极端制造(英文)》2021,3(4):23-55
Micro/nanostructured components play an important role in micro-optics and optical engineering, tribology and surface engineering, and biological and biomedical engineering, among other fields. Precision glass molding technology is the most efficient method of manufacturing micro/nanostructured glass components, the premise of which is meld manufacturing with complementary micro/nanostructures. Numerous mold manufacturing methods have been developed to fabricate extremely small and high-quality micro/nanostructures to satisfy the demands of functional micro/nanostructured glass components for various applications. Moreover, the service performance of the mold should also be carefully considered. This paper reviews a variety of technologies for manufacturing micro/nanostructured molds. The authors begin with an introduction of the extreme requirements of mold materials. The following section provides a detailed survey of the existing micro/nanostructured mold manufacturing techniques and their corresponding mold materials, including nonmechanical and mechanical methods. This paper concludes with a detailed discussion of the authors recent research on nickel-phosphorus (Ni-P) mold manufacturing and its service performance. 相似文献
8.
9.
C.M. Cheah C.K. Chua C.W. Lee C. Feng K. Totong 《The International Journal of Advanced Manufacturing Technology》2005,25(3-4):308-320
Investment casting (IC) has benefited numerous industries as an economical means for mass producing quality near net shape metal parts with high geometric complexity and acceptable tolerances. The economic benefits of IC are limited to mass production. The high costs and long lead-time associated with the development of hard tooling for wax pattern moulding renders IC uneconomical for low-volume production. The outstanding manufacturing capabilities of rapid prototyping (RP) and rapid tooling (RT) technologies (RP&T) are exploited to provide cost-effective solutions for low-volume IC runs. RP parts substitute traditional wax patterns for IC or serve as production moulds for wax injection moulding. This paper reviews the application and potential application of state-of-the-art RP&T techniques in IC. The techniques are examined by introducing their concepts, strengths and weaknesses. Related research carried out worldwide by different organisations and academic institutions are discussed. 相似文献
10.
11.
MaryAnn Foote 《Journal of microscopy》1982,128(2):199-201
A number of techniques are given for preparing permanent slides of freshly collected algae. The methods reviewed are suitable for phytoplankton, delicate species, filamentous algae and marine samples. Included are traditional techniques using corn syrup or glycerin and also a new technique with a commercial histological product. 相似文献
12.
Gan Y 《The Review of scientific instruments》2007,78(8):081101
Cantilevers with single micro- or nanoparticle probes have been widely used for atomic force microscopy surface force measurements and apertureless scanning near-field optical microscopy applications. In this article, I critically review the particle attachment and modification techniques currently available, to help researchers choose the appropriate techniques for specific applications. 相似文献
13.
A method is described for scanning electron microscope (SEM) autoradiography whereby preservation of high resolution cell surface details is retained together with degelatination of the emulsion without gross loss or redistribution of silver grains. This method should provide a convenient medium-sized marker for SEM (using secondary, backscattered electron and X-ray imaging) topographic studies of biosynthesized molecules, and of cell surface receptors and antigens, using indirect or direct labelling procedures with radio-labelled ligands. 相似文献
14.
K.L. MCDONALD 《Journal of microscopy》2009,235(3):273-281
In this paper, we review some published studies using correlative light and electron microscopy methods. We further refined our criteria to include only those studies using live cells for light microscope and where high-pressure freezing was the method of specimen preparation for electron microscopy. High-pressure freezing is especially important for some difficult-to-fix samples, and for optimal preservation of ultrastructure in samples larger than a few micrometres. How the light microscope observations are done is completely sample dependent, but the choice of high-pressure freezer depends on the speed required to capture (freeze) the biological event of interest. For events requiring high time resolution (in the 4–5 s range) the Leica EM PACT2 with rapid transfer system works well. For correlative work on structures of interest that are either non-motile or moving slowly (minutes rather than seconds), any make of high-pressure freezer will work. We also report on some efforts to improve the capabilities of the Leica EM PACT2 rapid transfer system. 相似文献
15.
16.
A review of the experimental techniques for the measurement of heat and temperatures generated in some manufacturing processes and tribology 总被引:1,自引:0,他引:1
Several techniques have been developed over time for the measurement of heat and the temperatures generated in various manufacturing processes and tribological applications. They include: (1) thermocouples — the embedded thermocouple and the dynamic thermocouple (or the chip–tool thermocouple in the case of cutting), (2) infra-red photography; (3) infrared optical pyrometers, (4) thermal paints, (5) materials of known melting temperatures, either in the powder form, or, as a thin film, and (6) change in microstructure with temperature in the case of high-speed steel tools, to name some. Each technique has its own advantages and disadvantages. The appropriate technique for a given thermal problem depends on the situation under consideration, such as the ease of accessibility, spot size, dynamics of the situation, accuracy needed, cost of instrumentation, advancements in technology. In this paper, these techniques are briefly reviewed with pros and cons on their application for a given situation. 相似文献
17.
Thirty years since their invention, laser trackers are now recognized as the measurement tool of choice in the manufacture and assembly of large components. The general design of laser trackers, i.e., a ranging unit on a two-axis gimbal, has not changed significantly over the years. However, innovations in ranging technology, for example, the emergence of increasingly accurate absolute distance meters (ADMs), are providing users with an alternative to interferometers (IFMs). Hand-held accessories such as touch probes and line scanners are expanding the scope and applicability of laser trackers. In this paper, we survey the literature in all areas of laser trackers as applied to large-scale dimensional metrology (LSDM), with emphasis on error modeling, measurement uncertainty, performance evaluation and standardization. 相似文献
18.
19.
Gillian R. Bullock 《Journal of microscopy》1984,133(1):1-15
Chemical fixation of cells has been used extensively in different fields of electron microscopy. The type of fixation can be selected to maximize retention of different cell constituents where morphology is of prime interest. For techniques such as immunocytochemistry and autoradiography, a compromise between morphology and retention of antigenicity or radiolabel has to be reached. By careful choice of fixative, buffer and other physical parameters, optimum results can be obtained for both animal and plant tissues. Emphasis has been put on more recent developments in technique. 相似文献