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71.
SL Cheng SF Zhang S Mohan F Lecanda A Fausto AH Hunt E Canalis LV Avioli 《Canadian Metallurgical Quarterly》1998,71(3):449-458
Müller cells are highly permeable to potassium ions and play a major role in maintaining potassium homeostasis in the vertebrate retina during light-evoked neuronal activity. Potassium fluxes across the Müller cell's membrane are believed to underlie the light-evoked responses of these cells. We studied the potassium currents of turtle Müller cells in the retinal slice and in dissociated cell preparations and their role in the genesis of the light-evoked responses of these cells. In either preparation, the I-V curve, measured under voltage-clamp conditions, consisted of inward and outward currents. A mixture of cesium ions, TEA, and 4-AP blocked the inward current but had no effect on the outward current. Extracellular cesium ions alone blocked the inward current but exerted no effect on the photoresponses. Extracellular barium ions blocked both inward and outward currents, induced substantial depolarization, and augmented the light-evoked responses, especially the OFF component. Exposing isolated Müller cells to a high potassium concentration did not cause any current or voltage responses when barium ions were present. In contrast, application of glutamate in the presence of barium ions induced a small inward current that was associated with a substantially augmented depolarizing wave relative to that observed under control conditions. This observation suggests a role for an electrogenic glutamate transporter in generating the OFF component of the turtle Müller cell photoresponse. 相似文献
72.
73.
P Mamunes PE Prince NH Thornton PA Hunt ES Hitchcock 《Canadian Metallurgical Quarterly》1976,57(5):675-680
An analysis was made of the obstetric history of 1,360 patients who were delivered in 1971. It involved 3,185 pregnancies. The aim of the study was to evaluate the risk of spontaneous termination of the pregnancy, worked out from its demographic aspect. Several ideas are worthy of consideration. The risk of spontaneous intra-uterine death is cumulative, sharply increased by a repetition of such cessation of pregnancy. The same patients often undergo intentional abortion repeatedly. The respective risks of spontaneous and provoked interruption of pregnancy have been studied in greater detail as a function of parity. 相似文献
74.
P. A. Thornton 《Journal of Materials Science》1971,6(4):347-356
The literature regarding the influence of nonmetallic inclusions on the mechanical properties of steel is reviewed, with critical
comments on various studies. A brief discussion of inclusion rating methods and a synopsis of the effects of applied stress
on inclusions in an isotropic, elastic matrix are presented. The parameters considered are tensile strength, impact strength,
reduction of area, fatigue properties and fracture toughness. It is concluded that in many applications, the type of inclusions
are more important than the total content and as matrix strength increases, the notch effect of inclusions becomes more significant.
Also, mechanical properties can be influenced by any one or a combination of the following inclusion parameters; shape, size,
quantity, interspacing, distribution, orientation, interfacial strength, and physical properties relative to the matrix. 相似文献
75.
SF Abraham JR Blair-West JP Coghlan DA Denton DR Mouw BA Scoggins 《Canadian Metallurgical Quarterly》1976,81(1):120-132
Conscious sheep with permanent indwelling cannulae in the lateral ventricles and the cisterna magna were Na depleted and then perfused for 9 h with an artificial CSF solution. There were 3 experimental groups: Group I (n=5) received perfusion with aritifical CSF containing NA 170 MEq./1, Group II (n=7) received perfusion with artificial CSF containing Na 145 mEq./1, Group III (n=7) received no perfusion. In Group I the blood aldosterone level fell from 26.4 +/- 7.4 to 8.6 +/- 2.3 ng/100 ml by 9 h after perfusion. There was no significant change in plasma [Na] or [K], blood angiotensin II or plasma renin concentration. Blood cortisol and corticosterone levels rose. There was also a fall in post-perfusion. Group III showed no significant change in blood aldosterone concentration. Multivariate statistical analysis showed that the fall in aldosterone levels during 170 mEq./l Na perfusion could not be accounted for by changes, either alone or together, of ACTH as evidenced by alteration in blood cortisol or corticosterone, or by change of plasma [Na], [K] or renin concentrations. This data supports the hypothesis of an additional factor which may be of CNS origin being involved in the control of aldosterone secretion. 相似文献
76.
M. A. Thornton 《Automation and Remote Control》2004,65(6):1007-1017
Discrete finite-valued functions are increasingly important in applications involving automation and control. In particular, it is evident that industry is focusing on Systems-on-a-Chip (SoC) where the integration of analog (infinite-valued) and digital (binary-valued) circuits must co-exist. As designers struggle with these interfacing issues, it is natural to consider the intermediate circuits that can be modeled as multi-valued, discrete logic-level circuits. This viewpoint is not unprecedented as such principles have been used for at least the past twenty years in telecommunications protocols. If an analogous approach is considered in control systems implemented in Integrated Circuit (IC) designs, it is proposed that spectral analysis may provide an important role and efficient methods for computing such mixed-radix function spectra are described here. These methods are formulated as transformations of word-level decision diagrams representing the underlying arithmetic expressions and can be implemented as graph traversal algorithms. The theoretical foundation of the spectral transform of a mixed-radix function is presented and the equivalence of the resulting spectrum and the spectrum of a Cayley graph is shown. 相似文献
77.
78.
A linearised pixel-swapping method for mapping rural linear land cover features from fine spatial resolution remotely sensed imagery 总被引:1,自引:0,他引:1
Accurate maps of rural linear land cover features, such as paths and hedgerows, would be useful to ecologists, conservation managers and land planning agencies. Such information might be used in a variety of applications (e.g., ecological, conservation and land management applications). Based on the phenomenon of spatial dependence, sub-pixel mapping techniques can be used to increase the spatial resolution of land cover maps produced from satellite sensor imagery and map such features with increased accuracy. Aerial photography with a spatial resolution of 0.25 m was acquired of the Christchurch area of Dorset, UK. The imagery was hard classified using a simple Mahalanobis distance classifier and the classification degraded to simulate land cover proportion images with spatial resolutions of 2.5 and 5 m. A simple pixel-swapping algorithm was then applied to each of the proportion images. Sub-pixels within pixels were swapped iteratively until the spatial correlation between neighbouring sub-pixels for the entire image was maximised. Visual inspection of the super-resolved output showed that prediction of the position and dimensions of hedgerows was comparable with the original imagery. The maps displayed an accuracy of 87%. To enhance the prediction of linear features within the super-resolved output, an anisotropic modelling component was added. The direction of the largest sums of proportions was calculated within a moving window at the pixel level. The orthogonal sum of proportions was used in estimating the anisotropy ratio. The direction and anisotropy ratio were then used to modify the pixel-swapping algorithm so as to increase the likelihood of creating linear features in the output map. The new linear pixel-swapping method led to an increase in the accuracy of mapping fine linear features of approximately 5% compared with the conventional pixel-swapping method. 相似文献
79.
80.
A variant of the hemispherical microwave lens antenna is reported where the ground plane region is modified through use of a frequency selective surface. This allows discrimination of frequencies by two closely spaced primary feeds. A scale model is reported operating at 12 and 30 GHz 相似文献