An expert aid to fault diagnosis and trouble-shooting in satellitecommunications

Presents the Satellite Communications Network Expert (SaNE), a knowledge-based aid designed to provide engineering support for fault diagnosis. The SaNE is composed of two elements: a satcom network model, which simulates the structure and functionality of a system based loosely upon a large military satcom network, and a diagnostic component, which uses knowledge- and model-based reasoning techniques to analyse system anomalies and diagnose possible causes for the alarms such networks generate. The development cycle is described, emphasising lessons learnt during development and testing and the advantages and disadvantages of the techniques applied. The goal of the SaNE project is primarily commercial acceptance rather than innovation. The authors illustrate how novel concepts can be implemented in a practical system without compromising this goal     

Dissolved organic carbon dynamics in the upper rhone: The influence of side-arms?

Dissolved organic carbon (DOC) dynamics were investigated over a two year period in the Upper Rhǒne River to examine the role of side-arms in providing DOC to the main channel in relation to discharge fluctuations, especially floods. Concentrations of DOC are shown to remain low in space and in time (average 1.5 mg ^?1) and to be more related to global hydrological events (precipitation) than to any local flushing for backwaters during floods. The results do not support the general assumption that side-arms are the providers of DOC to the main channel.     

Effect of postoperative mydriatics on the iris

PURPOSE: To assess the role postoperative mydriatics play after extracapsular cataract extraction (ECCE) and posterior chamber intraocular lens (IOL) implantation in causing iris modifications and in controlling inflammation. SETTING: Outpatients Department, Ninewells Hospital, Dundee, Scotland. METHODS: The prospective study comprised 136 patients who had standardized ECCE. Half the patients used a mydriatic for 2 weeks postoperatively. Anterior chamber activity, pain, and eye redness were evaluated at 2 weeks postoperatively; pupil shape, peripheral anterior synechias, IOL position, and iris adhesions, at 6 weeks. RESULTS: Iris-lens adhesions were significantly more common in the group using a mydriatic. There was no difference between the two groups in postoperative inflammation. CONCLUSION: Mydriatics should not be used routinely after ECCE with posterior chamber IOL implantation.     

The effects of cholecystokinin A and B receptor antagonists, devazepide and L 365260, on citalopram-induced decrease of exploratory behaviour in rat

The present study has been divided into two sets. In the first set, the aim of the experiments was to investigate the dose-response effect of selective serotonin re-uptake inhibitor (SSRI) citalopram on rat exploratory behaviour in the elevated plus-maze. In the second set of experiments, the effect of cholecystokinin (CCK) CCKA and CCKB receptor antagonists, devazepide and L 365260, on citalopram-induced decrease of exploratory behaviour in the elevated plus-maze was studied. Citalopram (5 and 10 mg/kg) decreased the number of open and total arm entries, line crossings on open arms, and percentage of time spent exploring in open arm. Dose 15 mg/kg was without any effect on rat exploratory behaviour. Devazepide (0.01 and 1.0 mg/kg) failed to modify any of the citalopram-induced changes observed. L 365260 (1.0 mg/kg) reversed most of the effects of citalopram: the numbers of open and total arm entries, the number of line crossings, and the percentage of time spent exploring in open arms. L 365260 at dose level 0.01 mg/kg was ineffective. These results support the involvement of the CCKB receptor subtype in SSRI-induced anxiogenic-like effects in rodents.     

Thermal expansion of semiconductor materials

The thermal expansion of tellurides of germanium, bismuth, and intermetallic compounds is investigated over the temperature range 293-973 K.Belarusian Agricultural Technical University, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 5, pp. 612–616, May 1994.     

Estimation of linear parametric models of nonGaussian discreterandom fields with application to texture synthesis

A general (possibly asymmetric noncausal and/or nonminimum phase) 2D autoregressive moving average random field model driven by an independent and identically distributed 2D nonGaussian sequence is considered. The model is restricted to be invertible, i.e., system zeros are not allowed to lie on the unit bicircle. Three performance criteria are investigated for parameter estimation of the system parameters given only the output measurements (image pixels). The proposed criteria are functions of the higher order cumulant statistics of an inverse filter output. One of these criteria is novel and the others have been considered in past only for moving average inverses and without any analysis of their consistency. In the paper strong consistency of the proposed methods under the assumption that the system order is known is proved. The convergence of the proposed parameter estimators under overparametrization is also analyzed. Experimental results involving synthesized as well as real life textures are presented to illustrate the performance of two of the considered approaches. Experimental results of synthesis of 128x128 textures visually resembling several real life textures in the Brodatz album (and other sources) are presented.     

Nonlinear protein binding and enzyme heterogeneity: effects on hepatic drug removal

The kinetics of substrate removal by the liver and the resulting nonlinear changes in unbound fraction along the flow path at varying input drug concentrations were examined by a model simulation study. Specifically, we varied the binding association constant, KA, and the Michaelis-Menten constants (Km and Vmax) to examine the steady state drug removal (expressed as hepatic extraction ratio E) and changes in drug binding for (i) unienzyme systems and (ii) simple, parallel metabolic pathways; zonal metabolic heterogeneity was also added as a variable. At low KA, E declined with increasing input drug concentration, due primarily to saturation of enzymes; only small differences in binding were present across the liver. At high KA, a parabolic profile for E with concentration was observed; changes in unbound fraction between the inlet and the outlet of the liver followed in parallel fashion. Protein binding was the rate-determining step at low input drug concentrations, whereas enzyme saturation was the rate-controlling factor at high input drug concentration. Heterogeneous enzymic distribution modulated changes in unbound fraction within the liver and at the outlet. Despite marked changes in unbound fraction occurring within the liver for different enzymic distributions, the overall transhepatic differences were relatively small. We then investigated the logarithmic average unbound concentration and the length averaged concentration as estimates of substrate concentration in liver in the presence of nonlinear drug binding. Fitting of simulated data, with and without assigned random error (10%), to the Michaelis-Menten equation was performed; fitting was repeated for simulated data obtained with presence of a specific inhibitor of the high-affinity, anteriorly distributed pathway. Results were similar for both concentration terms: accurate estimates were obtained for anterior, high affinity pathways; an overestimation of parameters was observed for the lower affinity posteriorly distributed pathways. Improved estimations were found for posteriorly distributed pathways upon inhibition with specific inhibitors; with added random error, however, the improvement was much decreased. We applied the method for fitting of several sets of metabolic data obtained from rat liver perfusion studies performed with salicylamide (SAM) (i) without and (ii) with the presence of 2,6-dichloro-4-nitrophenol (DCNP), a SAM sulfation inhibitor. The fitted results showed that SAM sulfation was a high-affinity high-capacity pathway; SAM glucuronidation was of lower affinity but comparable capacity as the sulfation pathway, whereas SAM hydroxylation was of lower affinity and lower capacity.     

An experimental and numerical investigation of ductile crack growth characteristics in surface cracked specimens under combined loading

Fracture mechanics tests have been performed in the upper shelf region of a steel on large surface cracked plate (SCT) specimens and on small compact tension (CT) specimens. Some of the SCT specimens were subjected to combined tension and bending in such a way that the loading was strongly non-proportional. Crack growth characteristics were compared between the specimens in order to assess possible influences of geometry and nonproportional loading. The differences observed could unambiguously be reduced to and correlated with differences in constraint. Constraint parameters were evaluated by detailed three-dimensional finite element computations and quantities for growing cracks were interpreted on the basis of deformation theory considerations, in analogy with the commonly used J _R-philosophy. It was noted that the initiation of ductile crack growth along a three-dimensional crack front appears to be independent of the degree of local constraint. However, the increase in toughness for a growing crack was markedly affected by the degree of local constraint. Some estimates of the constraints effects regarding stability considerations were also made.