An alternative polynomial approximation for the activation sigmoid function is developed here. It can considerably simplify the input/output operations of a neural network. The recursive algorithm is found for Chebyshev expansion of all constituting polynomials.
Transformation models for two samples of censored data are considered. Main examples are the proportional hazards and proportional odds model. The key assumption of these models is that the ratio of transformation rates (e. g., hazard rates or odds rates) is constant in time. A method of verification of this proportionality assumption is developed. The proposed procedure is based on the idea of Neyman's smooth test and its data-driven version. The method is suitable for detecting monotonic as well as nonmonotonic ratios of rates.
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Two 10-μm interplanetary dust particles collected in the stratosphere, have been analyzed with X-ray fluorescence excited by white synchrotron radiation (SYXFA) at the HASYLAB (DESY) in Hamburg. The measured abundances of the minor and trace elements with 16 < Z < 76 are in good agreement with abundances determined by PIXE analysis [1] of the same particles.
The results demonstrate that SYXFA is indeed a powerful
non-destructive technique for multi-element analysis of
micron-sized samples. Moreover we find that the combined
application of two such techniques, SYXFA and PIXE, to the same valuable particle lends high credibility to the results.
A possible influence of comets on the growth of heavy elements abundance suggested several years ago by Tinsley and Cameron is shortly reviewed. Such an effect would be significant if the formation of comets produce cometary material equivalent to 0.01 - 0.02 M per one solar mass. In the view of current hypothesis of the formation and structure of cometary nuclei the role of comets should be considered as one of the possible moderators of the Z value variation during the chemical evolution of our Galaxy.
Nitric oxide (NO) plays a crucial role not only in regulation of blood pressure but also in maintenance of cardiac autonomic tone and its deficiency induced hypertension is accompanied by cardiac autonomic dysfunction. However, underlying mechanisms are not clearly defined. We hypothesized that sympathetic activation mediates hemodynamic and cardiac autonomic changes consequent to deficient NO synthesis. We used chemical sympathectomy by 6-hydroxydopamine to examine the influence of sympathetic innervation on baroreflex sensitivity (BRS) and heart rate variability (HRV) of chronic NG-nitro-L-arginine methyl ester (L-NAME) treated adult Wistar rats. BRS was determined from heart rate responses to changes in systolic arterial pressure achieved by intravenous administration of phenylephrine and sodium nitroprusside. Time and frequency domain measures of HRV were calculated from 5-min electrocardiogram recordings. Chronic L-NAME administration (50 mg/kg per day for 7 days orally through gavage) in control rats produced significant elevation of blood pressure, tachycardia, attenuation of BRS for bradycardia and tachycardia reflex and fall in time as well as frequency domain parameters of HRV. Sympathectomy completely abolished the pressor as well as tachycardic effect of chronic L-NAME. In addition, BRS and HRV improved after removal of sympathetic influence in chronic L-NAME treated rats. These results support the concept that an exaggerated sympathetic activity is the principal mechanism of chronic L-NAME hypertension and associated autonomic dysfunction., M. Chaswal, S. Das, J. Prasad, A. Katyal, M. Fahim., and Obsahuje bibliografii
Results of radial velocity measurements from our spectrograms and orbital elements with elliptical orbit computed from them and published data are presented. It is suggested that light variations could be explained widths of some lines are interpreted by rotation.