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Maximum Capacity (maximum + capacity)

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Chemistry	50%

Selected Abstracts

Red Cell Pulmonary Transit Times Through the Healthy Human Lung

EXPERIMENTAL PHYSIOLOGY, Issue 2 2003
G. S. Zavorsky
It has previously been postulated that rapid red cell capillary transit through the human lung plays a role in the mechanism of diffusion limitation in some endurance athletes. Methodological limitations currently prevent researchers from directly measuring pulmonary capillary transit times in humans during exercise; however, first pass radionuclide cardiography allows direct measurement of red blood cell (RBC) transit times through the whole lung at various exercise intensities. We examined the relationship between mean whole lung red cell pulmonary transit times (cardiopulmonary transit times or CPTT) and different levels of flow in 88 healthy humans (76 males, 12 females) from several studies (mean age 31 years). The pooled data suggest that the relationship between CPTT and cardiac index (CI), beginning at rest and progressing through to maximum exercise demonstrates that CPTT reaches its minimum value when CI is about 8.1 l m2 min,1 (2.5-3 times the CI value at rest), and does not significantly change with further increases in CI. Cardiopulmonary blood volume (CPBV) index also does not change significantly until CI reaches 2.5 to 3 times the CI value at rest and then increases roughly linearly after that point. Consequently, the systematic increase in CPBV index with increasing pulmonary blood flow between 8.1 and 20 l m2 min,1 displays an adaptive response of the cardiopulmonary system by augmenting CPBV (and perhaps pulmonary capillary blood volume through distension and recruitment) to offset the reduction in CPTT, as no significant difference in mean CPTT is observed between these levels of flow (P > 0.05). Therefore, these data demonstrate that CPBV does not reach maximum capacity during strenuous or maximum exercise. This does not support the principle of quarter-power allometric scaling for flow when explaining modifications during exercise. Therefore, we speculate that the observed relationships between CPTT, CBPV index and flow may prevent mean CPTT (and perhaps mean pulmonary capillary transit times) from decreasing below the threshold time required for oxygenation. [source]

Improvement of the hydrological component of an urban soil,vegetation,atmosphere,transfer model

HYDROLOGICAL PROCESSES, Issue 16 2007
A. Lemonsu
Abstract A numerical study was conducted on the Rezé suburban catchment (Nantes, France) to evaluate the hydrological component of the town energy balance (TEB) scheme, which simulates in a coupled way the water and energy balances for the urban covers. The catchment is a residential area where hydrological data were continuously collected from 1993 to 1998 by the Laboratoire Central des Ponts et Chaussées (LCPC), notably the runoff in the stormwater drainage network. A 6-year simulation with the TEB and interaction soil,biosphere,atmosphere (ISBA) schemes in off-line mode enabled the comparison of modelled and observed runoff. Some weaknesses of the TEB were uncovered and led to improved parameterization of water exchanges: (1) calibration of the maximum capacity of the rainfall interception reservoir on roads and roofs and (2) inclusion of water infiltration through the roads, according to a simple formulation. The calibration of this water flux gives results that are consistent with direct measurements of water infiltration performed on the Rezé site and from the literature. The new parameterization produces better runoff in terms of timing and magnitude, which are comparable to those obtained by the LCPC with other hydrological models. It shows also the impact of the water infiltration through the roads, corresponding to a water transfer from the TEB to ISBA, on the water balance: the water contents of road, roof and soil reservoirs being modified, the evaporation from artificial surfaces decreases, while the evapotranspiration from natural covers increases. Through the evaporative flux, such a modification of the water balance induces large repercussions on the surface energy balance. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Optimization of a model IV fluidized catalytic cracking unit

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2001
Rein Luus
Abstract Maximization of a profit function related to a fluidized catalytic cracking unit model was carried out by Luus-jaakola optimization procedure. A 7-dimensional search is carried out on a FCC unit described by 113 nonlinear algebraic equations and 9 differential equations. Despite the low sensitivity and the existence of several local optima, the global optimum was obtained with reasonable amount of computational effort. At the optimum, the profit function is 1% higher than when the air blowers are constrained to operate at their maximum capacity. On a réalisé par la méthode d'optimisation de Luus-jaakola la maximisation d'une fonction de profit relativement à un modèle d'unité de craquage catarytique fluidisé (FCC). Une recherche en sept dimensions est menée sur une unité FCC décrite par 113 équations algébriques non linéaires et 9 équations différentielles. Malgré la faible sensibilité et l'existence de plusieurs optimums locaux, l'optimum global a été atteint avec des efforts raisonnables en termes de calcul. À l'optimum, la fonction de profit est de 1% supérieure à celle obtenue lorsqu'on force les ventilateurs soufflants à fonctionner à leur capacité maximum. [source]

Dynamic binding capacity of plasmid DNA in histidine,agarose chromatography

BIOMEDICAL CHROMATOGRAPHY, Issue 9 2007
F. Sousa
Abstract The use of histidine,agarose chromatography in the purification of supercoiled (sc) plasmid DNA (pDNA) from Escherichia coli lysates has been reported recently. In the current work we describe a set of breakthrough experiments which were designed to study the effect of parameters such as flow-rate, temperature, concentration and conformation on the dynamic binding capacity of pDNA to the histidine support. One of the most striking results shows that the dynamic binding capacity for sc pDNA decreases linearly from 250.8 to 192.0 µg sc pDNA/mL when the temperature is varied from 5 to 24°C. This behaviour was attributed to temperature-induced, pre-denaturation conformational changes which promote the removal of negative superhelical turns in sc pDNA molecules and decrease the interaction of DNA bases with the histidine ligands. The capacity for sc pDNA was highly improved when using feeds with higher pDNA concentrations, a phenomenon which was attributed to the fact that pDNA molecules in more concentrated solutions are significantly compressed. A maximum capacity of 530.0 µg pDNA/mL gel was obtained when using a 125 µg/mL pDNA feed at 1 mL/min and 5°C, a figure which is comparable to the plasmid capacity values published for other chromatographic supports. Finally, a more than 2-fold increase in capacity was obtained when changing from open circular to sc pDNA solutions. Overall, the results obtained provide valuable information for the future development and implementation of histidine chromatography in the process scale purification of pDNA. Copyright © 2007 John Wiley & Sons, Ltd. [source]