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Optimal Pressure (optimal + pressure)

Distribution by Scientific Domains

Chemistry	75%

Selected Abstracts

Haemodynamic effects of ,75 mmHg negative pressure therapy in a porcine sternotomy wound model

INTERNATIONAL WOUND JOURNAL, Issue 1 2009
Arash Mokhtari
Abstract Previous research has shown ,125 mmHg to be the optimal negative pressure for creating an environment that promotes wound healing, and this has therefore been adopted as a standard pressure for patients with deep sternal wound infection. However, it has not yet been clearly shown that ,125 mmHg is the optimal pressure from a haemodynamic point of view. Furthermore, there have been reports of cardiac rupture during ,125 mmHg negative pressure therapy. We therefore studied the effects of a lower pressure: ,75 mmHg. Twelve pigs were used. After median sternotomy, sealed negative pressure therapy of ,75 mmHg was applied. Baseline measurements were made and continuous recording of the cardiac output, end-tidal CO2 production, mean arterial pressure, mean pulmonary pressure (pulmonary artery pressure), systemic vascular resistance, pulmonary vascular resistance, left atrial pressure and central venous pressure was started. Six pigs served as controls. No statistically significant difference was observed in any of the haemodynamic parameters studied, compared with the controls. The present study shows that, with a suitable foam application technique, ,75 mmHg can be applied without compromising the central haemodynamics. [source]

Pressure and gas composition effects on the operation of the pulsed flame photometric detector

ISRAEL JOURNAL OF CHEMISTRY, Issue 2 2001
Gad Frishman
The effect of pressure and hydrogen/oxygen ratio of a burning gas mixture on pulsed flame emission time-dependence was investigated in the range of 0.1,5 atm using a specially designed pulsed flame photometric detector (PFPD). We studied the pressure and gas composition effect on the pulsed flame delayed light emission of sulfur, phosphorus, and nitrogen-containing organic compounds. The optimal pressure conditions for nitrogen detection, intensity, and emission time delay was found to be 0.4 bar, at which the detection sensitivity could be improved by a factor of 2. For phosphorus, the optimal pressure obtained was 1.3 bar with 40% sensitivity improvement (compared with 1 bar). In the case of sulfur detection, two emission maxima were obtained, at 1.1 and 0.6 bar, at H/O ratio of 5. Increasing the H/O ratio resulted in the appearance of only one peak at 1 bar, and enhancement of the sensitivity by a factor of 2.4 at H/O ratio of 10.3. From the analytical point of view, we found that emission intensity is practically unchanged by the pressure and the H/O ratio for all three elements investigated in the range of 0.8,1.1 bar and H/O of 5,6. Thus, in addition to excellent sensitivity and improved selectivity, the PFPD can be applied under a variety of atmospheric pressure conditions in field environmental applications. [source]

Designing supercritical carbon dioxide extraction of rice bran oil that contain oryzanols using response surface methodology

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 8 2008
Chih-Hung Wang
Abstract This study examines the supercritical carbon dioxide (SC-CO2) extraction of oryzanols contained rice bran oil from powdered rice bran. The extraction efficiencies and concentration factors of oryzanols, free fatty acids and triglycerides in the SC-CO2 extracts were determined. With top-flow type SC-CO2 extraction the total oil yield was 18.1% and the extraction efficiencies of oryzanols and triglycerides were 88.5 and 91.3% respectively, when 2750 g CO2 was consumed during the extraction of 35 g rice bran powder. The concentration factors of oryzanols and triglycerides in SC-CO2 -extracted oil were higher than in the Soxhlet n -hexane extracted oil. SC-CO2 extractions indicated that pressure can be used more effectively than temperature to enhance the extraction efficiency and concentration factor of oryzanols. A two-factor central composite scheme of response surface methodology was employed to determine the optimal pressure (300 bar) and temperature (313 K) for increasing the concentration of oryzanols in the SC-CO2 extracted oil. [source]

Optimal pressure conditions for unbiased external ion accumulation in a two-dimensional radio-frequency quadrupole for Fourier transform ion cyclotron resonance mass spectrometry

RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 21 2001
Mikhail E. Belov
When combined with on-line separations (e.g., capillary liquid chromatography (LC)), Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) provides a powerful tool for biological applications, and particularly proteomic studies. The sensitivity, dynamic range, and duty cycle provided by FTICR-MS have been shown to be increased by ion trapping and accumulation in a two-dimensional (2D) radio-frequency (rf)-only multipole positioned externally to an FTICR cell. However, it is important that ions be detected across the desired m/z range without a significant bias. In this work we found that pressure inside the accumulation rf-quadrupole plays an important role in obtaining ,unbiased' ion accumulation. Pressure optimization was performed in both pulsed and continuous modes. It was found that unbiased accumulation in a 2D rf-only quadrupole could be achieved in the pressure range of 5,×,10,4 to 5,×,10,3 Torr. External ion accumulation performed at the optimal pressure resulted in an increase in both the spectrum acquisition rates and dynamic range. Copyright © 2001 John Wiley & Sons, Ltd. [source]