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Plasma Expansion (plasma + expansion)

Distribution by Scientific Domains

Polymers and Materials Science	50%

Selected Abstracts

Collisionless Plasma Expansion in the Presence of a Dipole Magnetic Field

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 6 2009
H. B. Nersisyan
Abstract The collisionless interaction of an expanding high,energy plasma cloud with a magnetized background plasma in the presence of a dipole magnetic field is examined in the framework of a 2D3V hybrid (kinetic ions and massless fluid electrons) model. The retardation of the plasma cloud and the dynamics of the perturbed electromagnetic fields and the background plasma are studied for high Alfvén,Mach numbers using the particle,in,cellmethod. It is shown that the plasma cloud expands excluding the ambient magnetic field and the background plasma to form a diamagnetic cavity which is accompanied by the generation of a collisionless shock wave. The energy exchange between the plasma cloud and the background plasma is also studied and qualitative agreement with the analytical model suggested previously is obtained (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Synthesis and in vitro degradation of poly(N -vinyl-2-pyrrolidone)-based graft copolymers for biomedical applications

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2002
Carl F. Brunius
Abstract This work is devoted to the design of a novel family of hydrosoluble biomaterials: poly(N -vinyl-2-pyrrolidone) (PVP)-based graft copolymers. A synthesis route has been elaborated in which ,-functionalized PVP is prepared via chain-transfer radical polymerization, end-group modified, and subsequently grafted onto a polyhydroxylated backbone, typically dextran or poly(vinyl alcohol). The resulting graft copolymer biomaterials are designed for use in various biomedical applications, particularly as materials with a stronger potential for plasma expansion than already existing products have. The graft copolymers are potentially degradable because the PVP grafts are connected to the polyol backbone via a hydrolytically labile carbonate or ester linkage. The degradation of the graft copolymers was performed in vitro over a period of 6 weeks. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3652,3661, 2002 [source]

Fluid challenge in patients at risk for fluid loading-induced pulmonary edema

ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 1 2004
M. Matejovic
Background:, This study evaluated the effects of protocol-guided fluid loading on extravascular lung water (EVLW) and hemodynamics in a group of patients at high risk for volume expansion-induced pulmonary and systemic edema. Methods:, Nine acutely admitted septic patients with acute lung injury (ALI) were prospectively studied. In addition to sepsis and ALI, the following criteria indicating increased risk for edema formation had to be fulfilled: increased vascular permeability defined as microalbuminuria greater than fivefold normal and hypoalbuminemia <30 g l,1. Two hundred-ml boluses of a 10% hydroxyethyl starch (HES) was titrated to obtain best filling pressure/stroke volume relation. Extravascular lung water and intrathoracic blood volume (ITBV) were measured using a transpulmonary double-indicator dilution technique. Baseline data were compared with data at the end of fluid loading and 3 h postchallenge. Results:, At study entry the mean EVLW was 13 ml kg,1, and the mean EVLW/ITBV ratio (indicator of pulmonary permeability) was 0.72 (normal range 0.20,0.30). To attain optimal preload/stroke volume relation 633 ± 240 ml of HES was needed. Fluid loading significantly increased preload (CVP, PAOP and ITBV), and stroke volume. Effective pulmonary capillary pressure (Pcap) rose only slightly. As a result, the Pcap,PAOP gradient decreased. Despite increased cardiac output, EVLW did not change by plasma expansion. Conclusion:, In this selected group of at-risk patients, the optimization of cardiac output guided by the concept of best individual filling pressure/stroke volume relationship did not worsen permeability pulmonary edema. [source]

Probe Diagnostics of Expanding Plasmas at Low Gas Pressure

PLASMA PROCESSES AND POLYMERS, Issue 2 2006
Mariya Dimitrova
Abstract Summary: Results from tandem-type probe diagnostics of a plasma source based on an inductive discharge are presented in this study. The driver region is in the classical form of a cylindrically shaped inductive discharge, with a coil positioned over a gas discharge tube, whereas a bigger metal chamber provides volume for plasma expansion. Low pressure argon discharges were studied. The axial profiles of the plasma parameters were measured in the discharge in the metal chamber. The results obtained show that decreasing electron temperature and plasma density with increasing distance from the driver characterizes the behavior of the expanding plasmas. Moreover, two regions with different rates of variation of the plasma parameters complete the plasma expansion volume: a faster drop close to the driver and slow axial changes away from it. The gas pressure and power applied for the discharge maintenance were the external parameters varied. Axial profiles of the electron concentration in the plasma expansion region of an inductive discharge. [source]