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Biomedical subjects

C Pappas

Publications and source records attributed to C Pappas.

At least 19 recordsLinked to original sources
PubMed2002

Comparison of classical and ultrasound-assisted isolation procedures of cellulose from kenaf (Hibiscus cannabinus L.) and eucalyptus (Eucalyptus rodustrus Sm.).

A comparative study of classical and ultrasound-assisted extraction and purification of cellulose from kenaf (Hibiscus cannabinus L.) and eucalyptus (Eucalyptus rodustrus Sm.), has been conducted. The isolated cellulose samples were studied by diffuse reflectance infrared Fourier transform spectroscopy and 13C nuclear magnetic resonance (13C-NMR) spectroscopy and the crystallinity was also determined. The use of ultrasound decreased the total time of treatment, in addition the purity of the obtained cellulose was very high.

Cellulose↗
PubMed2001

Probing jump diffusion in crystalline solids with neutron spin-echo spectroscopy.

Neutron spin-echo spectroscopy has been applied to jump diffusion in a crystalline solid. Definite advantages of spin-echo spectroscopy over quasielastic neutron scattering are the direct visual discrimination of fast and slow diffusion processes and the high resolution in the time-energy domain. The potential of the method is demonstrated by way of Ni diffusion in the intermetallic alloy NiGa.

Journal Article↗
PubMed2001

Enzymatic acylation of hydroxypropyl cellulose in organic media and determination of ester formation by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy.

Esters were prepared by acylation of hydroxypropyl cellulose with fatty acid catalyzed by immobilized lipase from Candida antarctica in tert-butanol. The nature of the substrates used, the initial water activity of the system, and the molecular weight of the hydroxypropyl cellulose were investigated. Moreover, Fourier transform-infrared (FT-IR) spectroscopy was used for determination of ester content on hydroxypropyl cellulose. Specifically, a linear relationship was established between the peak height assigned to the absorption of the esterified carboxyl groups of the cellulose and the ester content. At optimum reaction conditions, the ester content on the hydroxypropyl cellulose was about 11%.

Acylation↗
PubMed2001

A neural network approach in diabetes management by insulin administration.

Diabetes management by insulin administration is based on medical experts' experience, intuition, and expertise. As there is very little information in medical literature concerning practical aspects of this issue, medical experts adopt their own rules for insulin regimen specification and dose adjustment. This paper investigates the application of a neural network approach for the development of a prototype system for knowledge classification in this domain. The system will further facilitate decision making for diabetic patient management by insulin administration. In particular, a generating algorithm for learning arbitrary classification is employed. The factors participating in the decision making were among other diabetes type, patient age, current treatment, glucose profile, physical activity, food intake, and desirable blood glucose control. The resulting system was trained with 100 cases and tested on 100 patient cases. The system proved to be applicable to this particular problem, classifying correctly 92% of the testing cases.

Adult↗
PubMed2001

Deconvolution and wavelet-based methods for membrane current estimation from simulated fractionated electrograms.

In infarcted myocardium, extracellular recordings exhibit multiple deflections due to irregular pathway of the electric impulse. In this work the problem of distinguishing local from distant deflections is tackled. In order to evaluate the proposed methods in a controlled setting, simulated data are used, following both Beeler-Reuter and Luo-Rudy kinetics. The input is an array of electrograms positioned on grid-points of a rectangular grid and the output is an array of estimates of the membrane current. First, deconvolution techniques are used in the form of spatial filtering for membrane current estimation from the extracellular recordings. Second, the extracellular recordings undergo wavelet based transformation, followed by a spatial filter which enhances local activity deflections and suppresses distant activity deflections. It is shown that wavelet filtering of the extracellular recordings acts as an evaluator of the efficiency of the deconvolution techniques for the membrane current estimation. Subsequently, activation times based on the results from the two methods are used for the reconstruction of the propagation pattern in a zig-zag case in two-dimensional grids. It is shown that the wavelet-based method is more robust, and can work well even in cases where the grid interval in the y direction is four times larger than the single cell size.

Algorithms↗
PubMed2001

Taxing issues.

Explore the source record for details and available documents.

Humans↗
PubMed2001

Mining association rules from clinical databases: an intelligent diagnostic process in healthcare.

Data mining is the process of discovering interesting knowledge, such as patterns, associations, changes, anomalies and significant structures, from large amounts of data stored in databases, data warehouses, or other information repositories. Mining Associations is one of the techniques involved in the process mentioned above and used in this paper. Association is the discovery of association relationships or correlations among a set of items. The algorithm that was implemented is a basic algorithm for mining association rules, known as a priori. In Healthcare, association rules are considered to be quite useful as they offer the possibility to conduct intelligent diagnosis and extract invaluable information and build important knowledge bases quickly and automatically. The problem of identifying new, unexpected and interesting patterns in medical databases in general, and diabetic data repositories in specific, is considered in this paper. We have applied the a priori algorithm to a database containing records of diabetic patients and attempted to extract association rules from the stored real parameters. The results indicate that the methodology followed may be of good value to the diagnostic procedure, especially when large data volumes are involved. The followed process and the implemented system offer an efficient and effective tool in the management of diabetes. Their clinical relevance and utility await the results of prospective clinical studies currently under investigation.

Algorithms↗
PubMed2000

Effect of intracoronary gamma-radiation therapy on in-stent restenosis: An intravascular ultrasound analysis from the gamma-1 study.

BACKGROUND: The aim of this study was to use serial volumetric intravascular ultrasound to evaluate the effect of gamma-radiation on recurrent in-stent restenosis. METHODS AND RESULTS: After successful reintervention, patients were randomized to receive either (192)Ir or placebo. Intravascular ultrasound studies with motorized pullback (0.5 mm/s) were performed immediately after irradiation and at 8-month follow-up in 70 patients. Paired volumetric analysis of the stented segment and of 5-mm proximal and distal reference segments was performed; this included measurements of the external elastic membrane, lumen, plaque and media (external elastic membrane minus lumen), stent, and intimal hyperplasia (stent minus lumen). Baseline proximal reference, stent, and distal reference measurements were similar in both groups. The changes in proximal and distal reference measurements of the external elastic membrane, plaque and media, and lumen areas were similar in both groups. However, the decrease in stented segment lumen volume was less in the (192)Ir patients than the placebo patients (-25+/-34 mm(3) versus -48+/-42 mm(3); P:=0.0225), and the increase in the volume of intimal hyperplasia in the stented segment was less in the (192)Ir patients than in the placebo patients (28+/-37 mm(3) versus 50+/-40 mm(3); P:=0.0352). When averaged over the length of the stented segment (32+/-13 mm versus 33+/-14 mm; P:=0.9), the increase in mean area of intimal hyperplasia was 0.8+/-1.0 mm(2) in the (192)Ir group and 1.6+/-1.2 mm(2) in the control group (P:=0.0065). Late stent-vessel wall malapposition was noted in one placebo patient and no (192)Ir patients. CONCLUSIONS: gamma-Radiation therapy can effectively prevent recurrent in-stent restenosis by inhibiting neointimal formation within the stent. At the stent edge, there were no significant differences between (192)Ir and placebo patients.

Analysis of Variance↗
PubMed2000

Decay of methidathion on Greek soultanina grapes during storage and on the vines.

Decomposition of the pesticide methidathion on and in soultanina (Thomson seedless) grapes was studied. Vines, uncovered and covered were sprayed with the pesticide. Samples were collected and analyzed in regular time intervals. Two lots were collected, the first of them, 2 h after spraying and the second 20 days later, and were stored in a commercial refrigerated room. Degradation of the pesticide was studied for about 50 days for the grapes on the vines and 130 days for the grapes stored in the refrigerated room. The half-life of the pesticide methidathion was found to be 5 days for the uncovered vines, 7 days for the covered vines and 64 days for the grapes stored in the refrigerator.

Chromatography, Gas↗
PubMed2000

Evaluation of heterodimeric guanylyl cyclase genes as candidates for human hypertension.

OBJECTIVE: Both physiologic and pharmacological data have implicated the nitric oxide (NO) signaling cascade in the regulation of blood pressure in humans and its impairment in the pathogenesis of hypertension. In biological systems, the principal receptor for NO is NO-stimulated guanylyl cyclase. NO-stimulated guanylyl cyclases are obligate heterodimers (alpha/beta). The genes for guanylyl cyclase subunits alpha1, beta, and beta2 are likely candidates for causing hypertension in the Dahl rat as their expression is altered and their gene loci are closely linked to known quantitative trait loci for blood pressure in Dahl rat crosses. The objective of the current study was to test whether markers near guanylyl cyclase subunit genes were linked to hypertension in Caucasians. DESIGN: To test for linkage of genetic markers in or near the guanylyl cyclase genes to hypertension in Caucasians, a sample of 124 Utah hypertensive sib pairs was genotyped. RESULTS: Four highly polymorphic markers in or near the human guanylyl cyclase subunits homologous to the rat alpha1 (human chromosome 8), rat beta1 (human chromosome 4), and rat beta2 (human chromosome 13) genes showed no evidence of excess allele sharing in the set of hypertensive sibships. CONCLUSION: We conclude that the heterodimeric guanylyl cyclase subunit loci do not appear to be linked to hypertension in Caucasians.

Adult↗
PubMed2000

Spatial filtering methods for local activation determination in fractionated electrograms from simulated infarcted hearts.

The purpose of this work is the enhancement of local activation in multiphasic extracellular recordings coming from infarcted myocardial tissue and, consequently, the distinction of local from distal activation. Deconvolution procedures are applied, in the form of spatial filtering, in order to estimate transmembrane currents from the extracellular recordings. Simulated data are used in order to test the methods. The current source estimates are compared to the actual transmembrane currents and to Laplacian estimates.

Computer Simulation↗
PubMed2000

Prospects of medical informatics education in Greece: can we bridge the gap?

Medical Informatics education is a complex task,, since it aims in educating inhomogeneous groups of people coming from different disciplines. In Greece, recently considerable advancements in the medical informatics education field are made. These advancements aim in bridging gaps in various areas of MI users interactions. In particular, an overview of the strategy of the Greek ministry of education shall be given, some examples of MI related educational programs shall be referred to, and finally the MI educational structure used in the Aristotelian University shall be presented in detail, laying out the strategy of this University for bridging various types of gaps.

Curriculum↗