美国MEDICA公司Easylyte电解质分析仪常见故障的排除

目前美国MEDICA公司生产的Easylyte电解质分析仪在很多医院的门诊化验室使用 ,这里对它的一些常见故障的排除作一介绍     

美国小学教师教育体系的基本特点与思考

美国小学教师的培养在几十年的发展过程中形成了一个具有特色的教师教育体系,在招生和专业选择上,能够录取那些乐意当教师的学生;在课程体系方面,前两年的通识教育课程具有较大的选择性,后两年的专业教育课程重视结合小学的教学实际,很少有选修课程,同时教学实习长达四个学期;在教学方法上,呈现多样化特征,以小组讨论为主。这些特点对于我国当下小学教育专业的建设与发展具有参考价值。     

美国汽车车体装配与焊接研究现状

介绍美国近年来在车体装配、焊接等领域的研究现状，并介绍一些相关技术的发展趋势。     

A rapid and simple technique for correlating light microscopy,transmission and scanning electron microscopy of fixed tissues in Epon blocks

A simplified and standardized technique for close correlation between light microscopy (LM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) is described. Perfusion and immersion fixed tissue specimens were embedded in Epon 812 and cut for conventional LM and TEM. The Epon blocks with remaining tissue were thereafter treated with epoxy solvent (ethanol-NaOH solution) for partial epoxy resin removal only (dissolving rate approx 33μm/h). The blocks with partially blotted tissue specimens were then critically point dried and gold coated for SEM. This method, in an easy way, allows repeated observations with LM, TEM and SEM with preserved fine structure and exact correlation. Since the technique is so simple and there is no need for special equipment the method can easily be adopted in all laboratories with basic SEM standards.     

美国教育博士与教育哲学博士之争的缘起和发展

美国教育博士（Ed．D．）学位与教育哲学博士（Ph．D．）学位之争由来已久。这既有复杂的历史原因,也与美国高等教育多样性、不同利益诉求、对学位教育质量关切等因素有关。从历史角度分析两种学位之争的缘起、演变及成因,并探讨其对发展我国教育博士专业学位教育的启示,具有积极的现实意义。     

A study of control strategy for the bin system with tube mill in the coal fired power station

The pulverized coal systems with tube mills are widely used in coal fired power plants. As there are many controlled variables and disturbances in this system, and startup and shutdown of the system is frequent and the dynamic characteristic of the controlled plant is also extraordinary, the automatic control system for this kind of pulverized coal system is not ideally implemented for long. The authors of this paper investigated and tested a pulverized coal system with tube mill in Nanjing Thermal Power Station, and based on various different controlled plants and control objectives, proposed rather independent control subsystems. These subsystems can organize a whole automatic control system of pulverized coal system that can be used in different conditions. The control system presented in this paper has worked well since it was put into operation in May 1998, and good economic benefits have been acquired.     

Moderated histogram equalization, an automatic means of enhancing the contrast in digital light micrographs reversibly

A means for improving the contrast in the images produced from digital light micrographs is described that requires no intervention by the experimenter: zero‐order, scaling, tonally independent, moderated histogram equalization. It is based upon histogram equalization, which often results in digital light micrographs that contain regions that appear to be saturated, negatively biased or very grainy. Here a non‐decreasing monotonic function is introduced into the process, which moderates the changes in contrast that are generated. This method is highly effective for all three of the main types of contrast found in digital light micrography: bright objects viewed against a dark background, e.g. fluorescence and dark‐ground or dark‐field image data sets; bright and dark objects sets against a grey background, e.g. image data sets collected with phase or Nomarski differential interference contrast optics; and darker objects set against a light background, e.g. views of absorbing specimens. Moreover, it is demonstrated that there is a single fixed moderating function, whose actions are independent of the number of elements of image data, which works well with all types of digital light micrographs, including multimodal or multidimensional image data sets. The use of this fixed function is very robust as the appearance of the final image is not altered discernibly when it is applied repeatedly to an image data set. Consequently, moderated histogram equalization can be applied to digital light micrographs as a push‐button solution, thereby eliminating biases that those undertaking the processing might have introduced during manual processing. Finally, moderated histogram equalization yields a mapping function and so, through the use of look‐up tables, indexes or palettes, the information present in the original data file can be preserved while an image with the improved contrast is displayed on the monitor screen.     

Normarski differential interference microscopy study of the ferroelastic domains in NaCN,RbCN and KCN

Photomicrographs of the ferroelastic domains present in the low temperature, intermediate phase of NaCN, RbCN and KCN are presented with their linear dimensions and angular orientations. The Normarski optical technique used to display the domain surfaces in colour and used to determine the small out-of-plane angular orientations is discussed in detail. Figures and the construction details are presented of the cold stage that allowed microscopic examination of the crystal surfaces by either reflected or transmitted light down to liquid nitrogen temperatures.     

An electron microscopic analysis on the ultra structural abnormalities in sperm of the common carp Cyprinus carpio L. inhabiting a polluted lake, Umiam (Meghalaya, India)

The present communication reports the ultra structural abnormalities in sperm of a fish species Cyprinus carpio inhabiting a polluted lake, Umiam in North‐East India. Transmission electron microscopy (TEM) revealed absence of differentiation between head and midpiece (neck) of some sperm while scanning electron microscopy (SEM) showed some sperm tails with highly reduced length and some sperm with folded tail. Abnormal shape of some sperm head was also revealed by Scanning electron microscopy. Detachment of membrane from some parts of the sperm head and an outward expansion of the same was observed from Transmission electron micrographs of transverse section of sperm head. The well developed mitochondria surrounding the cytoplasmic channel in the sperm tail, as observed in control were found to be drastically disorganized in fish inhabiting the polluted lake. The study suggests that the fish C. carpio inhabiting the polluted lake Umiam is under severe stress as far as its male reproductive system is concerned. The study further suggests that Electron microscopic approach is extremely important in the assessment of adverse effects of environmental pollution on fish tissue. Microsc. Res. Tech. 2011. © 2011 Wiley Periodicals, Inc.     

Morphological specializations of the epidermis of an angler catfish Chaca chaca (Siluriformes,Chacidae) in relation to its ecological niche: A scanning electron microscopic investigation

The present work was undertaken with the aim to deduce morphological adaptations in skin of an angler catfish Chaca chaca by means of scanning electron microscopy. The fish is nocturnal, bottom dwelling, sluggish, ambush predator, lives in sand, mud, or soft substrates often buried and camouflaged for protection and to feed. The surface of the epidermis is covered with polygonal epithelial cells, each having surface relief of microridges forming intricate patterns. In between epithelial cells irregularly distributed mucous cell openings, randomly distributed epidermal specialized structures, taste buds, and neuromasts are discernible. The epidermal specialized structures are keratinized. These are either irregularly the rounded elevated plaque like or the cone shaped structures. The superficial keratinized cells could frequently be discernible exfoliated at the surface. At intervals, characteristic epidermal projections could be observed. Surface of these projections at intervals is differentiated into short stumpy protuberances, each bearing a taste bud at its summit. Further, near the basal portion of these epidermal projections, conical, or rounded plaque like epidermal specialized structures are also discernible. The surface sculpture of the skin of Chaca chaca is associated with the structural and functional significance and physiological adaptations of the epidermis with respect to its ecological niche.     

Synaptic structure, distribution, and circuitry in the central nervous system of the locust and related insects.

The Orthopteran central nervous system has proved a fertile substrate for combined morphological and physiological studies of identified neurons. Electron microscopy reveals two major types of synaptic contacts between nerve fibres: chemical synapses (which predominate) and electrotonic (gap) junctions. The chemical synapses are characterized by a structural asymmetry between the pre- and postsynaptic electron dense paramembranous structures. The postsynaptic paramembranous density defines the extent of a synaptic contact that varies according to synaptic type and location in single identified neurons. Synaptic bars are the most prominent presynaptic element at both monadic and dyadic (divergent) synapses. These are associated with small electron lucent synaptic vesicles in neurons that are cholinergic or glutamatergic (round vesicles) or GABAergic (pleomorphic vesicles). Dense core vesicles of different sizes are indicative of the presence of peptide or amine transmitters. Synapses are mostly found on small-diameter neuropilar branches and the number of synaptic contacts constituting a single physiological synapse ranges from a few tens to several thousand depending on the neurones involved. Some principles of synaptic circuitry can be deduced from the analysis of highly ordered brain neuropiles. With the light microscope, synaptic location can be inferred from the distribution of the presynaptic protein synapsin I. In the ventral nerve cord, identified neurons that are components of circuits subserving known behaviours, have been studied using electrophysiology in combination with light and electron microscopy and immunocytochemistry of neuroactive compounds. This has allowed the synaptic distribution of the major classes of neurone in the ventral nerve cord to be analysed within a functional context.     

A quantitative evaluation of the glomerular capillary endothelium in rat and human kidneys: Utilization of vascular perfusion,freeze-cracking of tissue,and scanning electron microscopy

Modern morphological investigation requires the use of a variety of technological approaches and the employment of rigorous morphometric analysis for an adequate evaluation of the structural and ultrastructural features of a tissue or organ. The introduction of the technique of freeze-cracking of tissue to expose new surfaces has made it possible to quantitate the normal surface characteristics of the glomerular capillaries of the mammalian kidney. This report describes the techniques used for the preparation and quantitative assessment of normal glomerular endothelial morphology. The techniques of in vivo and in vitro vascular perfusion of kidneys as a method of fixation and the freeze-cracking of tissue are outlined in detail. In addition, a morphometric analysis of the endothelial surface characteristics are described and values are reported for the control rat and human kidneys from transplant donors.     

Recent advances in insect olfaction, specifically regarding the morphology and sensory physiology of antennal sensilla of the female sphinx moth Manduca sexta.

The antennal flagellum of female Manduca sexta bears eight sensillum types: two trichoid, two basiconic, one auriculate, two coeloconic, and one styliform complex sensilla. The first type of trichoid sensillum averages 34 microm in length and is innervated by two sensory cells. The second type averages 26 microm in length and is innervated by either one or three sensory cells. The first type of basiconic sensillum averages 22 microm in length, while the second type averages 15 microm in length. Both types are innervated by three bipolar sensory cells. The auriculate sensillum averages 4 microm in length and is innervated by two bipolar sensory cells. The coeloconic type-A and type-B both average 2 microm in length. The former type is innervated by five bipolar sensory cells, while the latter type, by three bipolar sensory cells. The styliform complex sensillum occurs singly on each annulus and averages 38-40 microm in length. It is formed by several contiguous sensilla. Each unit is innervated by three bipolar sensory cells. A total of 2,216 sensilla were found on a single annulus (annulus 21) of the flagellum. Electrophysiological responses from type-A trichoid sensilla to a large panel of volatile odorants revealed three different subsets of olfactory receptor cells (ORCs). Two subsets responded strongly to only a narrow range of odorants, while the third responded strongly to a broad range of odorants. Anterograde labeling of ORCs from type-A trichoid sensilla revealed that their axons projected mainly to two large female glomeruli of the antennal lobe.     

A study on the deposit formation in the cylinder and intake valve of a S. I. Engine

A spark ignition engine with port fuel injection (P.F.I.) system was used to accumulate cylinder head deposit (C.H.D.), intake valve deposit (I.V.D.), and piston top deposit (P.T.D.) on an engine dynamometer. In this study, the effect of base gasoline on I.V.D. was examined. The deposit forming tendency and the influence of the fuel component for decreasing deposits have been experimentally examined. The amount of I.V.D. has been observed to increase linearly with the engine operating time. It is also observed that the amount of valve deposit with newly blended gasoline is less than that with base gasoline.