Gas-Induced Osmosis as a Factor Influencing the Distribution of Body Water

1971 ◽  
Vol 40 (2) ◽  
pp. 175-191 ◽  
Author(s):  
B. A. Hills
Keyword(s):  
Nitrous Oxide ◽  
Steady State ◽  
Molecular Size ◽  
Concentration Gradients ◽  
Gas Concentration ◽  
Quantitative Correlation ◽  
Tissue Sections ◽  
A Value ◽  
Partial Pressures ◽  
Excised Tissues

1. Two methods have been used to determine whether differences in gas concentrations between adjacent regions of tissue can induce osmosis. 2. In a steady-state experiment water has been shown to move in the direction of increasing gas concentration across gross sections of excised tissues such as bladder and peritoneum. 3. In a second experiment it was found that more water was retained in subcutaneous pockets of saline saturated with a soluble gas (nitrous oxide or ethylene) than was retained in a control pocket saturated with nitrogen and simultaneously monitored in the same rabbit. 4. A value of the reflexion coefficient for nitrous oxide has been estimated from the results of the experiments with the gross tissue sections and shown to be compatible with those known for non-gaseous solutes by extrapolation with respect to molecular size. 5. The significance of possible osmotic effects due to transient gas concentration gradients are discussed in connection with dry joints, aseptic bone necrosis in caisson workers and inert gas narcosis, the approach offering a quantitative correlation of narcotic potency by a simple physical mechanism. 6. The steady-state gas concentration gradients which arise in tissue as a result of metabolism are suggested as a third driving force in homeostasis but, unless larger reflexion coefficients can be demonstrated, this effect would only appear to be significant for inspired oxygen partial pressures appreciably greater than normal.

A System for Individualized Dosing of Intravenous Aminophylline Using a Programmable Calculator

PEDIATRICS ◽  
1984 ◽  
Vol 73 (1) ◽  
pp. 64-67
Author(s):  
J. Chris Mitsuoka ◽  
Richard J. Fleck
Keyword(s):  
Steady State ◽  
Serum Sample ◽  
Drug Exposure ◽  
Plasma Concentrations ◽  
Dose Administration ◽  
Programmable Calculator ◽  
Concentration Determination ◽  
A Value ◽  
Individualized Dosing ◽  
History Of

A program that calculates a value of clearance for an individual patient prior to reaching steady state in the early stages of aminophylline therapy is presented. The program is written for the Texas Instruments TI-59 programmable calculator and may be used with or without the PC-100C printer. The program can provide clinically useful information concerning projected plasma concentrations prior to reaching steady state with an accurate history of the dose administration and serum concentration determination. If the patient has not received xanthene therapy prior to admission, only one serum sample is required. If there has been prior drug exposure, a second serum sample is required. An iterative technique, which would be impractical to use without calculator assistance, is employed to make these determinations.

Super-Fine Structure in the Critical Flow-Rate of Critical Flow Venturi Nozzles

2002 ◽  
Author(s):  
Masahiro Ishibashi
Keyword(s):  
Fine Structure ◽  
Steady State ◽  
Discharge Coefficient ◽  
Constant Pressure ◽  
Pressure Ratio ◽  
Critical Flow ◽  
Time Intervals ◽  
Critical Flow Rate ◽  
A Value ◽  
Long Time

It is shown that critical flow Venturi nozzles need time intervals, i.e., more than five hours, to achieve steady state conditions. During these intervals, the discharge coefficient varies gradually to reach a value inherent to the pressure ratio applied. When a nozzle is suddenly put in the critical condition, its discharge coefficient is trapped at a certain value then afterwards approaches gradually to the inherent value. Primary calibrations are considered to have measured the trapped discharge coefficient, whereas nozzles in applications, where a constant pressure ratio is applied for a long time, have a discharge coefficient inherent to the pressure ratio; inherent and trapped coefficients can differ by 0.03–0.04%.

scholarly journals Updating the steady state model of C4 photosynthesis

2021 ◽  
Author(s):  
Susanne von Caemmerer
Keyword(s):  
Steady State ◽  
Electron Transport ◽  
Electron Transport Rate ◽  
Transport Rate ◽  
Initial Slope ◽  
Carboxylase Activity ◽  
Quantitative Correlation ◽  
Steady State Model ◽  
State Models

AbstractC4 plants play a key role in world agriculture. For example, C4 crops such as maize and sorghum are major contributors to both first and third world food production and the C4 grasses sugarcane; miscanthus and switchgrass are major plant sources of bioenergy. In the challenge to manipulate and enhance C4 photosynthesis, steady state models of leaf photosynthesis provide and important tool for gas exchange analysis and thought experiments that can explore photosynthetic pathway changes. Here the C4 photosynthetic model by von Caemmerer and Furbank (1999) has been updated with new kinetic parameterisation and temperature dependencies added. The parameterisation was derived from experiments on the C4 monocot, Setaria viridis, which for the first time provides a cohesive parametrisation. Mesophyll conductance and its temperature dependence have also been included, as this is an important step in the quantitative correlation between the initial slope of the CO2 response curve of CO2 assimilation and in vitro PEP carboxylase activity. Furthermore, the equations for chloroplast electron transport have been updated to include cyclic electron transport flow and equations have been added to calculate electron transport rate from measured CO2 assimilation rates.HighlightThe C4 photosynthesis model by von Caemmerer and Furbank (1999) has been updated. It now includes temperature dependencies and equations to calculate electron transport rate from measured CO2 assimilation rates.

scholarly journals Analysis of CO2 Facilitation Transport Effect through a Hybrid Poly(Allyl Amine) Membrane: Pathways for Further Improvement

Membranes ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 367
Author(s):  
Bouchra Belaissaoui ◽  
Elsa Lasseuguette ◽  
Saravanan Janakiram ◽  
Liyuan Deng ◽  
Maria-Chiara Ferrari
Keyword(s):  
Facilitated Transport ◽  
Transport Parameters ◽  
Material Synthesis ◽  
Transport Models ◽  
Transport Modelling ◽  
Selective Layer ◽  
Membrane Performance ◽  
A Value ◽  
Partial Pressures ◽  
Good Agreement

Numerous studies have been reported on CO2 facilitated transport membrane synthesis, but few works have dealt with the interaction between material synthesis and transport modelling aspects for optimization purposes. In this work, a hybrid fixed-site carrier membrane was prepared using polyallylamine with 10 wt% polyvinyl alcohol and 0.2 wt% graphene oxide. The membrane was tested using the feed gases with different relative humidity and at different CO2 partial pressures. Selected facilitated transport models reported in the literature were used to fit the experimental data with good agreement. The key dimensionless facilitated transport parameters were obtained from the modelling and data fitting. Based on the values of these parameters, it was shown that the diffusion of the amine-CO2 reaction product was the rate-controlling step of the overall CO2 transport through the membrane. It was shown theoretically that by decreasing the membrane selective layer thickness below the actual value of 1 µm to a value of 0.1 µm, a CO2 permeance as high as 2500 GPU can be attained while maintaining the selectivity at a value of about 19. Furthermore, improving the carrier concentration by a factor of two might shift the performances above the Robeson upper bound. These potential paths for membrane performance improvement have to be confirmed by targeted experimental work.

Non-steady state behaviour of heavy metals in contaminated freshwater sediments

1998 ◽  
Vol 37 (6-7) ◽  
pp. 39-46 ◽  
Author(s):  
Gerard A. van den Berg ◽  
J. P. Gustav Loch ◽  
John J. G. Zwolsman ◽  
Lambertus M. van der Heijdt
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Steady State ◽  
Surface Water ◽  
Metal Mobility ◽  
Pore Waters ◽  
Concentration Gradients ◽  
River Meuse ◽  
State Behaviour ◽  
Diffusive Fluxes

The behaviour of heavy metals has been investigated in contaminated sediments of the river Meuse, The Netherlands. Due to temporal changes in temperature and degradability of organic matter, the depths of the redox boundaries fluctuate. This contributes to a non-steady state. As a result of oxidation processes, a distinct peak in heavy metal concentrations in pore water is measured at the sediment-water interface. Because the studied anoxic sediments contain low levels of sulphide, other solid phases are expected to be of importance in the binding of heavy metals. Furthermore, heterogeneity of the sediment and complexation with dissolved organic compounds may result in supersaturation of the anoxic pore waters with respect to discrete heavy metal sulphides, thus influencing heavy metal mobility. Calculations using concentration gradients of heavy metals indicate that diffusive fluxes between the sediment and the surface water contribute to concentrations in the surface water, although significant effects may be confined to specific locations.

Energetics of sugar transport by isolated intestinal epithelial cells: effects of cytochalasin B

1979 ◽  
Vol 237 (1) ◽  
pp. C56-C63 ◽  
Author(s):  
G. A. Kimmich ◽  
J. Randles
Keyword(s):  
Steady State ◽  
Epithelial Cells ◽  
Transport System ◽  
Cytochalasin B ◽  
Intestinal Epithelial Cells ◽  
Sugar Accumulation ◽  
Facilitated Diffusion ◽  
Intestinal Epithelial ◽  
Passive System ◽  
Concentration Gradients

The capability of isolated intestinal epithelial cells to establish concentration gradients of 3-O-methylglucose (3-OMG) by a Na+-dependent transport system is limited by concomitant function of a Na+-independent, facilitated diffusion transport system. Monosaccharides accumulated by the active system are continuously lost via the passive system, which acts to lower steady-state sugar gradients maintained by the cell. Cytochalasin B is a potent inhibitor of the passive system and allows the cells to establish a sugar gradient that is much higher than normal. When extracellular [3-;OMG] is 1 mM, cytochalasin induces sugar accumulation ratios of 30-;fold (+/- phlorizin) in contrast to control ratios of approximately 10-;fold. When [3-;OMG] is 0.1 mM, cytochalasin (0.1 mM) induces 40-;fold accumulation ratios. When changes in extracellular sugar concentration are considered, steady-state concentration gradients observed are 70-;fold. For a Na:sugar coupling stoichiometry of 1:1, gradients of this magnitude represent the approximate theoretical maximum for a transport system driven exclusively by the transmembrane electrochemical potential for Na+.

Evaluation of estimates of alveolar gas exchange by using a tidally ventilated nonhomogenous lung model

1997 ◽  
Vol 82 (6) ◽  
pp. 1963-1971 ◽  
Author(s):  
Thierry Busso ◽  
Peter A. Robbins
Keyword(s):  
Gas Exchange ◽  
Lung Model ◽  
Gas Composition ◽  
Breathing Patterns ◽  
Alveolar Volume ◽  
Gas Concentration ◽  
Pulmonary Capillaries ◽  
Partial Pressures ◽  
End Tidal ◽  
Alveolar Gas Exchange

Busso, Thierry, and Peter A. Robbins. Evaluation of estimates of alveolar gas exchange by using a tidally ventilated nonhomogenous lung model. J. Appl. Physiol. 82(6): 1963–1971, 1997.—The purpose of this study was to evaluate algorithms for estimating O2 and CO2 transfer at the pulmonary capillaries by use of a nine-compartment tidally ventilated lung model that incorporated inhomogeneities in ventilation-to-volume and ventilation-to-perfusion ratios. Breath-to-breath O2 and CO2 exchange at the capillary level and at the mouth were simulated by using realistic cyclical breathing patterns to drive the model, derived from 40-min recordings in six resting subjects. The SD of the breath-by-breath gas exchange at the mouth around the value at the pulmonary capillaries was 59.7 ± 25.5% for O2 and 22.3 ± 10.4% for CO2. Algorithms including corrections for changes in alveolar volume and for changes in alveolar gas composition improved the estimates of pulmonary exchange, reducing the SD to 20.8 ± 10.4% for O2 and 15.2 ± 5.8% for CO2. The remaining imprecision of the estimates arose almost entirely from using end-tidal measurements to estimate the breath-to-breath changes in end-expiratory alveolar gas concentration. The results led us to suggest an alternative method that does not use changes in end-tidal partial pressures as explicit estimates of the changes in alveolar gas concentration. The proposed method yielded significant improvements in estimation for the model data of this study.

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