Active state estimation for nonlinear systems: a neural approximation approach.

In this paper, we consider the problem of actively providing an estimate of the state of a stochastic dynamic system over a (possibly long) finite time horizon. The active estimation problem (AEP) is formulated as a stochastic optimal control one, in which the minimization of a suitable uncertainty measure is carried out. Toward this end, the use of the Renyi entropy as an information measure is proposed and motivated. A neural control scheme, based on the application of the extended Ritz method (ERIM) and on the use of a Gaussian sum filter (GSF), is then presented. Simulation results show the effectiveness of the proposed approach.     

Influence of Threshold Stress on the Estimation of the Weibull Statistics

The influence of threshold stress on the estimation of the Weibull statistics is discussed in terms of the Akaike information criterion. Numerical simulations show that, if sample data are limited in number and threshold stress is not too large, the two-parameter Weibull distribution is still a preferred choice. For example, the fit of strength data of glass and ceramics to the two- and three-parameter Weibull distributions is compared.     

Two-Way Protocol with Imperfect Devices

The security of a deterministic quantum scheme for communication, namely the LM05 [1], is studied in presence of a lossy channel under the assumption of imperfect generation and detection of single photons. It is shown that the scheme allows for a rate of distillable secure bits higher than that pertaining to BB84 [2]. We report on a first implementation of LM05 with weak pulses.     

Does Physiological Blood Glucose Control Require an Adaptive Control Strategy?

To test the hypothesis that only an adaptive algorithm would guarantee optimal feedback control of glycemia in insulin-dependent diabetes, fasting chronically diabetic dogs at rest were subjected to short-term artificial beta cell treatment. Insulin was applied intravenously and an oral glucose load was given during the experiment. Employing the same dosing algorithm, three different control strategies were employed in a random order on different days: adaptive control (minimum variance controller, Test A), fixed command control using on-line parameter estimates (Test B), and fixed command control using off-line individually optimized dosage constants (Test C). Comparison was made to nondiabetic control animals. The glycemic profiles were entirely normal in Test A and C, but were distinctly elevated in Test B. The peripheral hyperinsulinaemia could, however, not be avoided by adaptive control. It is concluded that the restoration of physiological blood glucose control in insulin-dependent diabetes requires dosage parameters which are either continually adapted to the actual situation (adaptive control) or are optimized to meet the individual's needs. In the latter case, fixed command control may be employed. Peripheral hyperinsulinaemia cannot be avoided as long as insulin is administered by a posthepatic route.     

Culture and characterization of sinusoidal endothelial cells isolated from human liver

BACKGROUND: Epidemiologic data concerning skin diseases in many rural areas in sub-Saharan Africa are not available. Little is known about the effect of regular treatment schedules by paramedical staff (especially community health workers) in the primary healthcare system on the severity and prevalence of dermatoses. METHODS: 5780 school and pre-school children from 13 primary schools in four sublocations in rural western Kenya (Kisumu District) were examined for dermatoses by the author, together with community health workers in 1993. On-the-spot training and weekend seminars about important and common dermatoses were also given. In 1994 a dermatology program was started within the primary healthcare system. Twelve trained community health workers carried out regular school visits once a week and diagnosed and treated pupils with dermatoses. Treatment was performed with gentian violet 1% solution for bacterial skin infections, Whitfield's ointment for dermatophytoses, benzylbenzoate emulsion 25% for scabies, and hydrocortisone acetate 1% cream for eczemas. All schools were visited again in 1995 to evaluate the long-term effects of the program. RESULTS: In 1993, the prevalence rate for dermatoses was 32.4%. Most of the skin diseases found were of infective origin (27.1% were caused by bacteria, 21.6% by fungi, and 17.6% by arthropods, mainly scabies mites). Dermatitis accounted for 3.5%. In 1995, the prevalence of dermatoses declined to 29.6% (p<0.05), and this reduction was most strongly observed for tropical ulcers and tinea capitis. Additionally, there was an improvement in the extent and severity of skin diseases. CONCLUSIONS: This study defines, for the first time, the number and extent of skin diseases in children in rural Kisumu District; most dermatoses were of infective origin. The study demonstrates that community health workers in the primary healthcare system are capable of dealing successfully with the most common dermatoses in children following a short training period.     

Does carbohydrate-deficient transferrin predict the severity of alcohol withdrawal syndrome?

Alcohol withdrawal often causes severe complications. However, many addicts deny any abuse. Thus, the diagnosis of alcohol abuse frequently becomes difficult. Laboratory parameters are often used to support the diagnosis of alcohol abuse. Furthermore, laboratory parameters should facilitate the prediction of the severity of alcohol withdrawal syndrome (AWS). The most promising laboratory parameter indicating a recent elevated alcohol consumption is carbohydrate-deficient transferrin (CDT). The aim of this study was to examine whether the measurement of CDT at admission can indicate a higher risk for the development of a complicated AWS. The severity of AWS was assessed by the AWS scale, consisting of two subscales for somatic and mental symptoms. CDT was measured by different methods (radioimmunoassay and HPLC). The radioimmunoassay for CDT (CDTect) yielded the best prediction. Our results showed a weak correlation between CDTect and the severity of AWS. However, there were great gender differences. In men, CDTect had the highest positive predictive value for a severe AWS (86.7%), whereas in women mean corpuscular volume was the best predictor (77.8%). However, the sensitivity of CDTect in men (25.5%), as well as mean corpuscular volume in females (29.2%), was too low for a screening test in a general hospital.     

Mechanisms involved in the intrinsic isoniazid resistance of Mycobacterium avium

Isoniazid (INH), which acts by inhibiting mycolic acid biosynthesis, is very potent against the tuberculous mycobacteria. It is about 100-fold less effective against Mycobacterium avium. This difference has often been attributed to a decreased permeability of the cell wall. We measured the rate of conversion of radiolabelled INH to 4-pyridylmethanol by whole cells and cell-free extracts and estimated the permeability barrier imposed by the cell wall to INH influx in Mycobacterium tuberculosis and M. avium. There was no significant difference in the relative permeability to INH between these two species. However, the total conversion rate in M. tuberculosis was found to be four times greater. Examination of in vitro-generated mutants revealed that the major resistance mechanism for both species is loss of the catalase-peroxidase KatG. Analysis of lipid and protein biosynthetic profiles demonstrated that the molecular target of activated INH was identical for both species. M. avium, however, formed colonies at INH concentrations inhibitory for mycolic acid biosynthesis. These mycolate-deficient M. avium exhibited altered colony morphologies, modified cell wall ultrastructure and were 10-fold more sensitive to treatment with hydrophobic antibiotics, such as rifampin. These findings may significantly impact the design of new therapeutic regimens for the treatment of infections with atypical mycobacteria.     

Prognosis in endoscopic perforans vein excision in postphlebitic syndrome

In the presence of leg ulcer endoscopic treatment is particularly indicated as it permits reliable diagnosis and treatment of incompetent perforator veins from a small incision away from the contaminated zone. Lately 3 surgeons have developed special instruments for this type of endoscopy. Hauer was the 1st to develop a specialized technique with the Wolf Company. He uses an angulated optic system and a double cautery clamp. It permits excellent vision. Sattler works with a Storz thoracoscope and specially built instruments controlled by a monitor. This means agreeable and motivating handling. Fischer uses direct vision through a Wolf or similar endoscope shaft and a set of instruments produced by Storz and Ulrich Co for him for swift, simple and reasonable treatment. Each surgeon will chose his method on the ground of his education, his special liking and his set up.     

Significance of tissue polypeptide specific antigen (TPS) in diagnosis and monitoring of treatment in ovarian cancer

BACKGROUND AND STUDY AIMS: It has recently been reported that in developed countries gastric outlet obstruction now predicts gastric malignancy. The aim of this study was to find out if this is the case in a developing country like India. PATIENTS AND METHODS: Seventy-four patients with gastric outlet obstruction underwent upper gastrointestinal endoscopy and biopsy specimens were obtained from any suspicious looking lesions or from the most distal point at which the endoscope could be positioned. RESULTS: In 56 patients (76%) the cause of the gastric outlet obstruction was malignant. On clinical and endoscopic appearance three patients were wrongly diagnosed as having malignancy when the cause, on endoscopic biopsy, was benign (tuberculosis n = 2, and immunoproliferative small intestinal disease n = 1). Twelve of the 18 patients with benign gastric outlet obstruction were managed conservatively with drugs and endoscopic balloon dilatation. CONCLUSION: Even in a developing country like India, malignancy is the commonest cause of gastric outlet obstruction and endoscopic biopsy specimens should be obtained in all patients with gastric outlet obstruction because the occasional benign lesions can be managed conservatively.