PubMed Health⌕ Search

Biomedical subjects

Gautam Kumar

Publications and source records attributed to Gautam Kumar.

6 recordsLinked to original sources
PubMed2006

Giant coronary artery aneurysm causing superior vena cava syndrome and congestive heart failure.

Coronary artery aneurysms are defined as localized coronary artery dilations >1.5 times the diameter of the adjacent segments. In adults, they are commonly of atherosclerotic origin and are usually asymptomatic. This is the first case report of a coronary artery aneurysm causing superior vena cava syndrome and heart failure. Chest x-ray showed cardiomegaly, and transthoracic echocardiography showed a mass that was confirmed by transesophageal echocardiography, computed tomography, and coronary angiography. In conclusion, giant coronary artery aneurysms can cause superior vena cava syndrome.

Aged↗
PubMed2006

A modeling approach to describe the adhesion of rough, asymmetric particles to surfaces.

A combined theoretical and experimental study of the adhesion of alumina particles and polystyrene latex spheres to silicon dioxide surfaces was performed. A boundary element technique was used to model electrostatic interactions between micron-scale particles and planar surfaces when the particles and surfaces were in contact. This method allows quantitative evaluation of the effects of particle geometry and surface roughness on the electrostatic interaction. The electrostatic interactions are combined with a previously developed model for van der Waals forces in particle adhesion. The combined model accounts for the effects of particle and substrate geometry, surface roughness and asperity deformation on the adhesion force. Predictions from the combined model are compared with experimental measurements made with an atomic force microscope. Measurements are made in aqueous solutions of varying ionic strength and solution pH. While van der Waals forces are generally dominant when particles are in contact with surfaces, results obtained here indicate that electrostatic interactions contribute to the overall adhesion force in certain cases. Specifically, alumina particles with complex geometries were found to adhere to surfaces due to both electrostatic and van der Waals interactions, while polystyrene latex spheres were not affected by electrostatic forces when in contact with various surfaces.

Journal Article↗
PubMedDate not supplied

Correlation of capillary and venous blood glucometry with laboratory determination.

BACKGROUND: During resuscitation in the Singapore Armed Forces, blood glucose samples are often obtained for analysis using the capillary glucometer. A drop of venous blood from the intravenous cannula is sometimes used to ascertain the patient's blood glucose level. Venous samples may be sent to a commercial laboratory, but this does not allow immediate results. OBJECTIVE: To establish the correlation between the glucose levels of the capillary fingerprick sample analyzed by the glucometer (Cap), the venous sample analyzed by the glucometer (Ven), and the venous sample tested by the commercial laboratory (Lab). METHODS: This multicenter, prospective study enrolled subjects from Selarang, Clementi, and Maju Camp Medical Centers in the Singapore Armed Forces from November 2002 to January 2003. All subjects provided at least two samples; because provision of the capillary blood glucose sample was voluntary, only some gave consent for capillary fingerprick and provided three samples. There were no exclusion criteria. Bland-Altman plots were then constructed to compare the capillary and venous-on-capillary values with the laboratory results. RESULTS: A total of 270 subjects were recruited. One hundred seventy subjects (63.0%) gave consent for capillary glucose measurement and, thus, had three readings for comparison. There was a mean difference of 0.97 mmol/L (17.46 mg/dL) between the Ven and Lab results. There was an insignificant mean difference of 0.01 mmol/L (0.18 mg/dL) between the Cap and Lab results. CONCLUSION: Capillary whole-blood glucose values best approximated venous plasma glucose values from the laboratory. Measuring the venous whole-blood glucose using the glucometer resulted in an overestimation of the venous plasma glucose compared with the laboratory result by about 0.97 mmol/L (17.46 mg/dL). This may result in the withholding of intravenous glucose for patients who are actually hypoglycemic.

Adult↗
PubMedDate not supplied

Visual exploration of complex time-varying graphs.

Many graph drawing and visualization algorithms, such as force-directed layout and line-dot rendering, work very well on relatively small and sparse graphs. However, they often produce extremely tangled results and exhibit impractical running times for highly non-planar graphs with large edge density. And very few graph layout algorithms support dynamic time-varying graphs; applying them independently to each frame produces distracting temporally incoherent visualizations. We have developed a new visualization technique based on a novel approach to hierarchically structuring dense graphs via stratification. Using this structure, we formulate a hierarchical force-directed layout algorithm that is both efficient and produces quality graph layouts. The stratification of the graph also allows us to present views of the data that abstract away many small details of its structure. Rather than displaying all edges and nodes at once, resulting in a convoluted rendering, we present an interactive tool that filters edges and nodes using the graph hierarchy and allows users to drill down into the graph for details. Our layout algorithm also accommodates time-varying graphs in a natural way, producing a temporally coherent animation that can be used to analyze and extract trends from dynamic graph data. For example, we demonstrate the use of our method to explore financial correlation data for the U.S. stock market in the period from 1990 to 2005. The user can easily analyze the time-varying correlation graph of the market, uncovering information such as market sector trends, representative stocks for portfolio construction, and the interrelationship of stocks over time.

Journal Article↗