New pH-sensitive aminoxyls: application to the study of biomembrane transport processes

1993 ◽  
pp. 2157 ◽  
Author(s):  
Maxim Balakirev ◽  
Valery Khramtsov
Keyword(s):  
Ph Sensitive ◽  
Transport Processes ◽  
Biomembrane Transport

Proximal duodenal enterocyte transport: evidence for Na(+)-H+ and Cl(-)-HCO3- exchange and NaHCO3 cotransport

1993 ◽  
Vol 265 (4) ◽  
pp. G677-G685 ◽  
Author(s):  
J. I. Isenberg ◽  
M. Ljungstrom ◽  
B. Safsten ◽  
G. Flemstrom
Keyword(s):  
Intracellular Ph ◽  
Collagen Matrix ◽  
Ph Sensitive ◽  
Transport Processes ◽  
High Rate ◽  
Disulfonic Acid ◽  
Acid Base ◽  
Acetoxymethyl Ester ◽  
Addition And Subtraction ◽  
Ethanesulfonic Acid

The duodenum, in contrast to the jejunum, actively secretes HCO3- at a high rate, a process that protects the mucosa from acid/peptic injury. Our purpose was to define the mechanisms involved in HCO3- transport by studying the acid-base transport processes in isolated duodenal enterocytes. Individual rat duodenocytes, isolated by a combination of Ca2+ chelation and collagenase, attached to a collagen matrix were loaded with the pH-sensitive fluoroprobe 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein acetoxymethyl ester (BCECF-AM), and intracellular pH was monitored by microfluorospectrophotometry. To identify Na(+)-H+ transport, cells in N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid 1) were pulsed with NH4Cl (40 mM) in the absence and presence of amiloride and 2) were removed of Na+. To examine Cl(-)-HCO3- exchange, Cl- was removed from Ringer-HCO3- superfusate in the presence and absence of dihydro-4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (H2DIDS). The NaHCO3 cotransporter was studied by addition and subtraction of Na+ to amiloride-treated and Cl(-)-depleted enterocytes perfused with Na(+)- and Cl(-)-free Ringer-HCO3- buffer with and without H2DIDS. Mammalian duodenocytes contain at least three acid-base transporters: an amiloride-sensitive Na(+)-H+ exchanger that extrudes acid, a DIDS-sensitive Cl(-)-HCO3- exchanger that extrudes base, and a NaHCO3 cotransporter, also DIDS sensitive, that functions as a base loader. These acid-base transporters likely play a key role in duodenal mucosal HCO3- secretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Saturn's E, G and F rings: modulated by the plasma sheet

1984 ◽  
Vol 75 ◽  
pp. 597
Author(s):  
E. Grün ◽  
G.E. Morfill ◽  
T.V. Johnson ◽  
G.H. Schwehm
Keyword(s):  
Solar Wind ◽  
Direct Contact ◽  
Transport Processes ◽  
Time Variable ◽  
Dust Particles ◽  
Spatial Diffusion ◽  
Drag Forces ◽  
Orbit Perturbation ◽  
Time Variations ◽  
F Ring

ABSTRACTSaturn's broad E ring, the narrow G ring and the structured and apparently time variable F ring(s), contain many micron and sub-micron sized particles, which make up the “visible” component. These rings (or ring systems) are in direct contact with magnetospheric plasma. Fluctuations in the plasma density and/or mean energy, due to magnetospheric and solar wind processes, may induce stochastic charge variations on the dust particles, which in turn lead to an orbit perturbation and spatial diffusion. It is suggested that the extent of the E ring and the braided, kinky structure of certain portions of the F rings as well as possible time variations are a result of plasma induced electromagnetic perturbations and drag forces. The G ring, in this scenario, requires some form of shepherding and should be akin to the F ring in structure. Sputtering of micron-sized dust particles in the E ring by magnetospheric ions yields lifetimes of 102to 104years. This effect as well as the plasma induced transport processes require an active source for the E ring, probably Enceladus.

TRANSPORT PROCESSES IN GLASS

1982 ◽  
Vol 43 (C9) ◽  
pp. C9-369-C9-380 ◽  
Author(s):  
A. R. Cooper ◽  
Jr
Keyword(s):  
Transport Processes

Revisiting the passivation of stainless steels and other passive CRAs

2018 ◽  
Vol 106 (1) ◽  
pp. 107 ◽  
Author(s):  
Jean- Louis Crolet
Keyword(s):  
Electrical Conductivity ◽  
Metal Ions ◽  
Base Metal ◽  
Stainless Steels ◽  
Electronic Conductivity ◽  
Transport Processes ◽  
General Knowledge ◽  
Inorganic Polymers ◽  
Faraday Cage

All that was said so far about passivity and passivation was indeed based on electrochemical prejudgments, and all based on unverified postulates. However, due the authors’ fame and for lack of anything better, the great many contradictions were carefully ignored. However, when resuming from raw experimental facts and the present general knowledge, it now appears that passivation always begins by the precipitation of a metallic hydroxide gel. Therefore, all the protectiveness mechanisms already known for porous corrosion layers apply, so that this outstanding protectiveness is indeed governed by the chemistry of transport processes throughout the entrapped water. For Al type passivation, the base metal ions only have deep and complete electronic shells, which precludes any electronic conductivity. Then protectiveness can only arise from gel thickening and densification. For Fe type passivation, an incomplete shell of superficial 3d electrons allows an early metallic or semimetallic conductivity in the gel skeleton, at the onset of the very first perfectly ordered inorganic polymers (- MII-O-MIII-O-)n. Then all depends on the acquisition, maintenance or loss of a sufficient electrical conductivity in this Faraday cage. But for both types of passive layers, all the known features can be explained by the chemistry of transport processes, with neither exception nor contradiction.

WET BURNING – THE MODERN TREND IN ENVIRONMENTAL BENIGN FUEL COMBUSTION AND IN SOLUTION TO THE PROBLEM OF SUSTAINABLE DEVELOPMENT OF THE POWER GENERATION

2018 ◽  
pp. 96-117 ◽  
Author(s):  
B. S. Soroka
Keyword(s):  
Numerical Simulation ◽  
Nitrogen Oxides ◽  
Chemical Kinetics ◽  
Fuel Combustion ◽  
Transport Processes ◽  
Cfd Modeling ◽  
Furnace Chamber ◽  
Modern Trend ◽  
Atmospheric Air ◽  
No Formation

The article considers the role and place of water and water vapor in combustion processes with the purpose of reduction the effluents of nitrogen oxides and carbon oxide. We have carried out the complex of theoretical and computational researches on reduction of harmful nitrogen and carbon oxides by gas fuel combustion in dependence on humidity of atmospheric air by two approaches: CFD modeling with attraction of DRM 19 chemical kinetics mechanism of combustion for 19 components along with Bowman’s mechanism used as “postprocessor” to determine the [NO] concentration; different thermodynamic models of predicting the nitrogen oxides NO formation. The numerical simulation of the transport processes for momentum, mass and heat being solved simultaneously in the united equations’ system with the chemical kinetics equations in frame of GRI methane combustion mechanism and NO formation calculated afterwards as “postprocessor” allow calculating the absolute actual [CO] and [NO] concentrations in dependence on combustion operative conditions and on design of furnace facilities. Prediction in frame of thermodynamic equilibrium state for combustion products ensures only evaluation of the relative value of [NO] concentration by wet combustion the gas with humid air regarding that in case of dry air – oxidant. We have developed the methodology and have revealed the results of numerical simulation of impact of the relative humidity of atmospheric air on harmful gases formation. Range of relative air humidity under calculations of atmospheric air under impact on [NO] and [CO] concentrations at the furnace chamber exit makes φ = 0 – 100%. The results of CFD modeling have been verified both by author’s experimental data and due comparing with the trends stated in world literature. We have carried out the complex of the experimental investigations regarding atmospheric air humidification impact on flame structure and environmental characteristics at natural gas combustion with premixed flame formation in open air. The article also proposes the methodology for evaluation of the nitrogen oxides formation in dependence on moisture content of burning mixture. The results of measurements have been used for verification the calculation data. Coincidence of relative change the NO (NOx) yield due humidification the combustion air revealed by means of CFD prediction has confirmed the qualitative and the quantitative correspondence of physical and chemical kinetics mechanisms and the CFD modeling procedures with the processes to be studied. A sharp, more than an order of reduction in NO emissions and simultaneously approximately a two-fold decrease in the CO concentration during combustion of the methane-air mixture under conditions of humidification of the combustion air to a saturation state at a temperature of 325 K.

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