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F Thiel

Publications and source records attributed to F Thiel.

10 recordsLinked to original sources
PubMed2001

Impedance analyser module for EIT and spectroscopy using undersampling.

In this paper we present the concept, the design and the test procedure for a DSP-based high-precision and high-performance wide-band (up to 10 MHz) bioimpedance analyser module for application in EIT or bioimpedance spectroscopy. The module implements a digital concept with appropriate signal conditioning hardware for voltage and current measurement, early signal digitization and subsequent digital signal processing in order to calculate the components of impedance (or admittance). At low frequencies, the module utilizes the conventional direct conversion method, whereas at high frequencies the undersampling technique is used. The advantages of the described system are the following: (a) the frequency range is extended to higher frequencies, (b) the number of data sampled per time interval is significantly reduced, and (c) the current consumption and the costs of the ADCs can be significantly reduced. The validation procedure is performed by comparing the measured and theoretical values of the magnitude and the phase of the impedance for a commonly used tissue model. The module offers an accuracy of better than 0.012% for the magnitude of impedance and better than 0.02 degrees for the phase.

Electric Impedance↗
PubMed2001

Quantitative evaluation of the performance of different electrical tomography devices.

Two widely used electrical tomography systems, the Sheffield Mark I and the DAS-01P, were quantitatively evaluated and compared to the newly developed Goe-MF system. The performance was quantified using a hardware phantom which closely matches the real input and transfer impedances of the human thorax and allows measurements equivalent to different states of lung inflation. Our results demonstrate that adequate averaging is necessary for noise reduction for the Mark I and especially for the DAS-01P system to get meaningful results even in visualizing maximal respiratory manoeuvres. The Goe-MF system showed a notably improved signal-to-noise ratio which allows also dynamic measurements at low levels of lung volume changes, e.g., in intensive care lung injury patients.

Calibration↗
PubMed2001

Barriers to providing diabetes care in community health centers.

OBJECTIVE: We aimed to identify barriers to improving care for individuals with diabetes in community health centers. These findings are important because many such patients, as in most other practice settings, receive care that does not meet evidence-based standards. RESEARCH DESIGN AND METHODS: In 42 Midwestern health centers, we surveyed 389 health providers and administrators about the barriers they faced delivering diabetes care. We report on home blood glucose monitoring, HbA1c tests, dilated eye examinations, foot examinations, diet, and exercise, all of which are a subset of the larger clinical practice recommendations of the American Diabetes Association (ADA). RESULTS: Among the 279 (72%) respondents, providers perceived that patients were significantly less likely than providers to believe that key processes of care were important (overall mean on 30-point scale: providers 26.8, patients 18.2, P = 0.0001). Providers were more confident in their ability to instruct patients on diet and exercise than on their ability to help them make changes in these areas. Ratings of the importance of access to care and finances as barriers varied widely; however, >25% of the providers and administrators agreed that significant barriers included affordability of home blood glucose monitoring, HbA1c testing, dilated eye examination, and special diets; nonproximity of ophthalmologist; forgetting to order eye examinations and to examine patients' feet; time required to teach home blood glucose monitoring; and language or cultural barriers. CONCLUSIONS: Providers in health centers indicate a need to enhance behavioral change in diabetic patients. In addition, better health care delivery systems and reforms that improve the affordability, accessibility, and efficiency of care are also likely to help health centers meet ADA standards of care.

Blood Glucose Self-Monitoring↗
PubMed2000

Quality of diabetes care in community health centers.

OBJECTIVES: This study assessed the quality of diabetes care in community health centers. METHODS: In 55 midwestern community health centers, we reviewed the charts of 2865 diabetic adults for American Diabetes Association measures of quality. RESULTS: On average, 70% of the patients in each community health center had measurements of glycosylated hemoglobin, 26% had dilated eye examinations, 66% had diet intervention, and 51% received foot care. The average glycosylated hemoglobin value per community health center was 8.6%. Practice guidelines were independently associated with higher quality of care. CONCLUSIONS: Rates of adherence to process measures of quality were relatively low among community health centers, compared with the targets established by the American Diabetes Association.

Adult↗
PubMed1995

Molecular basis of glycoalkaloid induced membrane disruption.

In this study the interaction between the glycoalkaloids alpha-chaconine, alpha-solanine and alpha-tomatine and sterols in model membranes was analysed systematically using techniques like membrane leakage, binding experiments, detergent extraction, electron microscopy, NMR and molecular modelling. The most important properties for sterols to interact with glycoalkaloids turned out to be a planer ring structure and a 3 beta-OH group, whereas for alpha-chaconine the 5-6 double bond and the 10-methyl group were also of importance. The importance of sugar-sugar interactions was illustrated by the high synergistic effect between alpha-chaconine and alpha-solanine, the leakage enhancing effect of glycolipids, and the almost complete loss of activity after deleting one or more mono-saccharides from the glycoalkaloids. The formed complexes which were resistant against detergent extraction existed of glycoalkaloid/sterol in a 1:1 ratio and formed tubular structures (alpha-chaconine) with an inner monolayer of phospholipids, whereas with alpha-tomatine also spherical structures were formed. Based on the results a molecular model for glycoalkaloid induced membrane disruption is presented.

Carbohydrate Sequence↗
PubMed1977

Structural and functional studies on the transformation of the intestinal mucosa in rats with experimental diabetes.

Twenty days after the onset of alloxan-induced diabetes, a villous hyperplasia has developed in the intestines of rats having free access to food. The transformation is characterised by a considerable increase in the area of the villous surface, caused by an enhanced mitotic activity in the crypts. The absorption of glucose or methionine by jejunal loops, whether expressed in terms of serosal area or villous area, is unchanged at this stage. On the other hand, the specific activity of certain disaccharidases and dipeptidases in crude mucosal homogenates is greater in diabetic animals, but quantitative histochemistry revealed no changes in the activities of alkaline phosphatase, leucine amino-peptidase and non-specific esterase in the individual enterocytes. Thus the biochemical changes may simply reflect the hyperplasia of the mucosa. The blood sugar level does not appear to be directly responsible for the mucosal transformation; however, the positive correlation between the daily food intake and the villus height suggests a role of hyperphagia and consequent increased luminal nutrition in the development of the hyperplasia.

Animals↗
PubMedDate not supplied

Low-temperature scanning electron microscopy in fungus-nematode interaction.

A comparative study has been made of different preparation techniques used for the scanning electron microscope (SEM), with regard to their application to fungus-nematode interaction. The preparation of frozen-hydrated specimens of both healthy and Arthrobotrys-oligospora-infected second-stage larvae of the root-knot nematode (Meloidogyne sp.) is described, and the results are compared with those obtained by critical point-drying and freeze-drying. In all cases the frozen-hydrated specimens consistently showed the best preservation.

Animals↗