scholarly journals Control of electron transfer in the cytochrome system of mitochondria by pH, transmembrane pH gradient and electrical potential. The cytochromes b-c segment

1981 ◽  
Vol 194 (2) ◽  
pp. 395-406 ◽  
Author(s):  
S Papa ◽  
M Lorusso ◽  
G Izzo ◽  
F Capuano
Keyword(s):  
Steady State ◽  
Electron Flow ◽  
Ph Dependence ◽  
Electrical Potential ◽  
The Other ◽  
Ph Gradient ◽  
Preferential Oxidation ◽  
Submitochondrial Particles ◽  
Cytochrome B562 ◽  
Other Hand

1. A study is presented of the effects of pH, transmembrane pH gradient and electrical potential on oxidoreductions of b and c cytochromes in ox heart mitochondria and ‘inside-out’ submitochondrial particles. 2. Kinetic analysis shows that, in mitochondria at neutral pH, there is a restraint on the aerobic oxidation of cytochrome b566 with respect to cytochrome b562. Valinomycin plus K+ accelerates cytochrome b566 oxidation and retards net oxidation of cytochrome b562. At alkaline pH the rate of cytochrome b566 oxidation approaches that of cytochrome b562 and the effects of valinomycin on b cytochromes are impaired. 3. At slightly acidic pH, oxygenation of antimycin-supplemented mitochondria causes rapid reduction of cytochrome b566 and small delayed reduction of cytochrome b562. Valinomycin or a pH increase in the medium promote reduction of cytochrome b562 and decrease net reduction of cytochrome b566. 4. Addition of valinomycin to mitochondria and submitochondrial particles in the respiring steady state causes, at pH values around neutrality, preferential oxidation of cytochrome b566 with respect to cytochrome b562. The differential effect of valinomycin on oxidation of cytochromes b566 and b562 is enhanced by substitution of 1H2O of the medium with 2H2O and tends to disappear as the pH of the medium is raised to alkaline values. 5. Nigericin addition in the aerobic steady state causes, both in mitochondria and submitochondrial particles, preferential oxidation of cytochrome b562 with respect to cytochrome b566. This is accompanied by c cytochrome oxidation in mitochondria but c cytochrome reduction in submitochondrial particles. 6. In mitochondria as well as in submitochondrial particles, the aerobic transmembrane potential (delta psi) does not change by raising the pH of the external medium from neutrality to alkalinity. The transmembrane pH gradient (delta pH) on the other hand, decrease slightly. 7. The results presented provide evidence that the delta psi component of the aerobic delta microH+ (the sum of the proton chemical and electrical activities) exerts a pH-dependent constraint on forward electron flow from cytochrome b566 to cytochrome b562. This effect is explained as a consequence of anisotropic location of cytochromes b566 and b562 in the membrane and the pH-dependence of the redox function of these cytochromes. Transmembrane delta pH, on the other hand, exerts control on electron flow from cytochrome b562 to c cytochromes.

TRANSMITTING BIPARTITE AND MULTIPARTITE CORRELATIONS VIA SPIN CHAINS UNDER PHASE DECOHERENCE

2012 ◽  
Vol 10 (06) ◽  
pp. 1250073
Author(s):  
JIAN-FENG AI ◽  
JIAN-SONG ZHANG ◽  
AI-XI CHEN
Keyword(s):  
Steady State ◽  
Anisotropy Parameter ◽  
Quantum Correlations ◽  
Spin Chains ◽  
The Other ◽  
Bipartite Entanglement ◽  
Other Hand ◽  
Long Time ◽  
Phase Decoherence ◽  
The One

We investigate the transfer of bipartite (measured by cocurrence) and multipartite (measured by global discord) quantum correlations though spin chains under phase decoherence. The influence of phase decoherence and anisotropy parameter upon quantum correlations transfer is investigated. On the one hand, in the case of no phase decoherence, there is no steady state quantum correlations between spins. On the other hand, if the phase decoherence is larger than zero, the bipartite quantum correlations can be transferred through a Heisenberg XXX chain for a long time and there is steady state bipartite entanglement. For a Heisenberg XX chain, bipartite entanglement between two spins is destroyed completely after a long time. Multipartite quantum correlations of all spins are more robust than bipartite quantum correlations. Thus, one can store multipartite quantum correlations in spin chains for a long time under phase decoherence.

PREANNOUNCED OPTIMAL TAX REFORM

2005 ◽  
Vol 9 (2) ◽  
pp. 150-169 ◽  
Author(s):  
DAVID DOMEIJ ◽  
PAUL KLEIN
Keyword(s):  
Steady State ◽  
Fiscal Policy ◽  
Tax Reform ◽  
The Other ◽  
Welfare Gain ◽  
Welfare Gains ◽  
Optimal Tax ◽  
Other Hand ◽  
Optimal Fiscal Policy ◽  
Implementation Lag

In constitutional democracies, laws take time to be deliberated upon, to be passed, and to be implemented. Motivated by this observation, we study the properties of optimal tax reform when it has to be announced in advance of its implementation. We find that a delay between announcement and implementation has large effects on the optimal fiscal policy during the transition to the new steady state. On the other hand, we find that the welfare gains from optimal tax reform are fairly robust to the introduction of an implementation lag. Increasing the lag from zero to four years reduces the welfare gains by less than a quarter. Moreover, it turns out that this reduction of the welfare gain is mainly due to the delay itself rather than the effect of preannouncement on the character of the optimal tax reform.

scholarly journals A note on dynamical compensation and its relation to parameter identifiability

2017 ◽  
Author(s):  
Omer Karin ◽  
Uri Alon ◽  
Eduardo Sontag
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
The Other ◽  
Apparent Discrepancy ◽  
Parameter Identifiability ◽  
Other Hand ◽  
The Face ◽  
System Variables

AbstractWe recently identified a motif for dynamical compensation (DC) – a property where a system maintains the dynamics and steady-state of a regulated variable robust in the face of fluctuations in key parameters. Such parameters are therefore unidentifiable from measurements of the regulated variable at steady-state. On the other hand, since the models showing dynamical compensation are typically non-redundant, their parameters are identifiable from experimental data. We clarify this apparent discrepancy by requiring that the parameters of DC circuits be identifiable both away from steady-state and when measuring other system variables. We use this observation to provide a definition for DC in terms of parameter identifiability and discuss its relevance for the examples provided in Karin et al.

P6303Developmental origin of cardiac macrophages in steady state and myocardial infarction

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
T Weinberger ◽  
R Thaler ◽  
V Schneider ◽  
D Messerer ◽  
S Massberg ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Bone Marrow ◽  
Steady State ◽  
Acute Phase ◽  
Cardiac Remodeling ◽  
The Other ◽  
Bone Marrow Chimera ◽  
Resident Macrophage ◽  
Developmental Origin ◽  
Other Hand

Abstract Background Macrophages are the most abundant immune cells in the myocardial tissue in steady state. The sterile inflammation caused by myocardial infarction triggers a massive immune reaction, which leads to a profound influx of neutrophils and monocytes. In the postacute phase of infarction macrophages play an essential role in reparative processes. Recently, it has become clear that macrophages in the heart have a dual developmental origin from embryonic and bone marrow (BM) hematopoiesis. In this study, we sought to investigate the contribution of embryonic derived macrophages to the cardiac macrophage pool in steady state as well as the acute and chronic phase after ischemia/reperfusion injury. Methods/Results To address the origin of macrophages in steady state we used different models of lineage tracing to determine the developmental origin of cardiac macrophages. Using FLT3-Cre mice and radiation-independent CD45.1/.2 bone marrow chimera, we found that the resident macrophage population in the heart is mainly independent of definitive hematopoiesis (approximately 70–80% of cardiac macrophages). The BM-dependent population on the other hand is replenished by blood-derived monocytes. Further we used the radiation-independent CD45.1/.2 bone marrow chimera to characterize the origin of macrophages at different time points after I/R-injury. In the acute phase after myocardial infarction we observed a profound influx of BM-derived macrophages in the infarct region and also in the remote area. 30 days after I/R-injury the composition of the resident macrophage pool was mainly comprised of BM-independent macrophages, similar to steady state conditions. To address the role of BM-derived macrophages we used CCR2-ko mice, which have low numbers of inflammatory monocytes in peripheral blood. CCR2-ko mice showed reduced macrophage numbers in the acute phase after myocardial infarction. Using positron emission tomography we investigated the influence of CCR2-deficiency on cardiac function after I/R-injury. In comparison to WT mice, CCR2-ko mice showed a significantly increased infarct size. Cardiac remodeling, determined by end-diastolic volume, on the other hand was improved in CCR2-ko mice. The ejection fraction was similar in both groups. Conclusion The cardiac macrophage pool is mainly comprised of BM-independent macrophages. In response to I/R-injury monocyte-derived macrophages transiently enter the myocardium but do not persist in significant numbers over time. The influx of BM-derived macrophages after I/R-injury was reduced using CCR2-ko mice, which led to improved cardiac remodeling. Our findings are of potential importance for understanding the cardiac immune response and for the therapeutic targeting of macrophages in inflammatory conditions. Acknowledgement/Funding German Society of Cardiology, German Centre for Cardiovascular Research, LMU Excellence, SFB 914

scholarly journals Electrical Potential Difference Measurements in Perfused Single Proximal Tubules of Necturus Kidney

1961 ◽  
Vol 44 (4) ◽  
pp. 679-687 ◽  
Author(s):  
Guillermo Whittembury ◽  
Erich E. Windhager
Keyword(s):  
Electrical Potential ◽  
Proximal Tubules ◽  
The Other ◽  
Potential Difference ◽  
Stopped Flow ◽  
Electrical Potential Difference ◽  
Necturus Maculosus ◽  
Other Hand ◽  
Glomerular Filtrate

Transtubular and peritubular face electrical potential differences (P.D.) of the proximal tubules of the kidney of the amphibian Necturus maculosus have been measured in situ. These measurements have been carried out both under normal conditions, when the tubular fluid originates in the glomerular filtrate, and under conditions when the composition of the tubular fluid has been altered using the stopped flow microperfusion technique. Under normal conditions the transtubular potential difference is 20 mv. (lumen-negative) and the P.D. across the peritubular face is 74 mv. (cell-negative). The P.D. across the luminal face is thus 54 mv. (cell-negative). This electrical asymmetry is not influenced by replacing the normal tubular fluid by NaCl, NaCl + mannitol, or by alteration in the intraluminal pH from 7 to 4. On the other hand, replacement of Na by K or choline and the addition of small amounts of DNP to the perfusate diminish this asymmetry.

Influence of the location of production wells in unconfined groundwater basins: an analysis by numerical simulation

1990 ◽  
Vol 27 (5) ◽  
pp. 657-668 ◽  
Author(s):  
Duke Ophori ◽  
József Tóth
Keyword(s):  
Numerical Simulation ◽  
Steady State ◽  
Groundwater Resources ◽  
The Other ◽  
Recharge Area ◽  
Development Potential ◽  
Discharge Area ◽  
Other Hand ◽  
Well Yield ◽  
Production Wells

Development potential of groundwater resources under continuous production is calculated by numerical simulation for models of unit basins for the plains regions of Alberta, Canada, in order to analyze the relations between the location of water wells on the one hand, and well yield and basin stability, on the other. These relations are expressed in terms of two basin hydrologic parameters, namely the transitional basin yield (TBY) and the sustainable basin yield (SBY). TBY is the net cumulative inflow of water into the system, induced by and during development at a particular site, from an initial to a final steady-state condition. SBY, on the other hand, is the amount of water captured from precipitation due to production at a particular site under the newly established steady-state conditions. TBY is highest for well locations in the discharge area and decreases gradually as the sites are moved toward the recharge area. This is so because more of the naturally discharging, and thus otherwise lost, water is captured by wells located in discharge areas than by wells in recharge areas. On the other hand, SBY is greater if the wells are located in recharge areas than if they are in the discharge areas because an increasing percentage of precipitation is converted to infiltration by production wells as their locations are moved upslope in the basin. From a regional hydrological viewpoint, these are key relations in optimizing the development potential of the groundwater resources in extensive unconfined basins. Precipitation rate, simulated as maximum potential infiltration rate, is assumed to be constant over time. It is shown also that under conditions of restricted rainfall, a recharge-area development results in unstable basin-hydrological conditions sooner than when development takes place in the discharge area. Regional groundwater exploitation should, therefore, be initiated in discharge areas and moved towards recharge regions gradually, and only for compelling reasons. Factors such as precipitation rates and positions of aquifers within a basin affect TBY and SBY to various degrees, thereby influencing the optimal location of well sites in the basin.

A Study of the Development of an Analytical Wall Function for LES

2014 ◽  
Author(s):  
R. S. Amano ◽  
Takahiko Hasegawa ◽  
Shaohua Shen
Keyword(s):  
Boundary Layer ◽  
Steady State ◽  
Cfd Simulation ◽  
The Other ◽  
Unsteady State ◽  
Wall Function ◽  
Other Hand ◽  
Log Law ◽  
Complicated Geometry ◽  
Steady State Simulation

In order to invent a new near-wall treatment for turbulence in Computational Fluid Dynamics (CFD) simulation, an Analytical Wall Function (AWF) has been studied and shown that it is possible to work accurately with Reynolds Averaged Navier-Stokes (RANS) Simulation even for complicated geometry such as impinging jet flow or separation and reattachment flow. One of the most common wall functions is the Standard Wall Function (SWF) which assumes log-law inside the boundary layer. However, there is a problem that SWF has been used for industrial applications even though it is difficult to analyze the turbulence phenomenon in a complicated geometry accurately because log-law is not applicable in that geometry. On the other hand, since AWF derives the boundary condition on the wall by integrating analytically the boundary layer equation in wall adjacent cells, it can analyze the turbulence accurately even in complicated geometry. AWF has an advantage over SWF from this point of view. In this study, AWF was improved and optimized for Large Eddy Simulation (LES) by changing the way of modeling of eddy viscosity inside the boundary layer for steady state simulation to that for unsteady state simulation. This is because RANS is a steady state simulation; on the other hand, LES is unsteady state simulation, which is one of the largest differences between them. The accuracy of the new AWF for LES (LES-AWF) was validated by both of experimental results and CFD simulation results. Both of the experiment and CFD simulation are conducted in the wind tunnel.

scholarly journals The effect of methanol and dioxan on the rates of the β-galactosidase-catalysed hydrolyses of some β-d-galactopyranosides: rate-limiting degalactosylation. The pH-dependence of galactosylation and degalactosylation

1973 ◽  
Vol 133 (1) ◽  
pp. 81-87 ◽  
Author(s):  
Michael L. Sinnott ◽  
Odile M. Viratelle
Keyword(s):  
Steady State ◽  
Ph Dependence ◽  
Methanol Concentration ◽  
The Other ◽  
Fractional Rate ◽  
Rate Of Increase ◽  
Rate Limiting ◽  
Hydrolysis Of

1. The effect of methanol on the β-galactosidase-catalysed hydrolysis of some nitrophenyl β-d-galactopyranosides has been studied under steady-state conditions. 2. The initial fractional rate of increase of kcat. as a function of methanol concentration with 2,4- and 3,5-dinitrophenyl β-d-galactopyranosides, but not with the other substrates studied, indicated that degalactosylation of the enzyme was rate-limiting. 3. The decrease in kcat. at high methanol concentrations for these substrates is considered to arise from causes other than galactosylation becoming rate-limiting. 4. Both galactosylation and degalactosylation of the enzyme require protonation of a group of pKa approx. 9.

Control of steady-state pH in rabbit proximal straight tubules

1987 ◽  
Vol 253 (2) ◽  
pp. F282-F289
Author(s):  
J. L. Atkins ◽  
M. B. Burg
Keyword(s):  
Steady State ◽  
Proximal Tubule ◽  
The Other ◽  
Slow Flow ◽  
Bicarbonate Concentration ◽  
Flow Rates ◽  
Other Hand ◽  
Straight Tubules

Steady-state pH (defined as the limiting pH reached at slow flow rates) was measured in isolated perfused rabbit proximal straight tubules (S2). With normal bath conditions (pH 7.4, bicarbonate 25 mM) the luminal steady-state pH was 6.85. Steady-state pH was directly related to bath pH and bicarbonate, but not to bath PCO2. Lowering of bath pH or bicarbonate consistently decreased luminal steady-state pH, and raising either caused steady-state pH to increase. When bath PCO2 was increased, on the other hand, steady-state pH either increased or decreased, depending on the concomitant changes in bicarbonate and pH. The changes in steady-state pH observed in the present studies following alterations in bath pH and bicarbonate concentration should, when extrapolated to the in vivo kidney, result in decreased delivery of bicarbonate from the proximal tubule in acidosis and increased delivery in alkalosis. The effects of potassium and chloride were also determined. Removal of potassium from the bath increased the steady-state pH, but removal of chloride from both the perfusate and bath had no significant effect.

scholarly journals Using pH dependence for understanding mechanisms in electrochemical CO reduction

2021 ◽  
Author(s):  
Georg Kastlunger ◽  
Lei Wang ◽  
Nitish Govindarajan ◽  
Hendrik H. Heenen ◽  
Stefan Ringe ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Ph Dependence ◽  
The Other ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Other Hand ◽  
Alkaline Conditions ◽  
Co Reduction ◽  
Rate Limiting ◽  
Electrolyte Ph

Utilizing electrochemical conversion of CO(2) into hydrocarbons and oxygenates is envisioned as a promising path towards closing the carbon cycle in modern technology. To this day, however, the exact reaction mechanisms towards the plethora of single and multi-carbon products on Cu electrodes are still disputed. This uncertainty even extends to the rate-limiting step of the respective reactions. Since multi-carbon products do not show a dependence on the electrolyte pH in neutral and alkaline media, CO dimerization on the Cu surface has been proposed as the rate-limiting step. However, other elementary steps would lead to the same pH dependence, namely the proton-electron transfer to *CO followed by subsequent coupling or the protonation of the *OCCO dimer. The pH dependence of methane production on the other hand suggests that the rate limiting step is located beyond the first proton-electron transfer to *CO. In order to conclusively identify the rate limiting steps in CO reduction, we analyzed the mechanisms on the basis of constant potential DFT calculations, CO reduction experiments on Cu at varying pH values (3 - 13) and fundamental rate theory. We find that, even in acidic media, the reaction rate towards multi-carbon products is nearly unchanged on an SHE potential scale, which indicates that its rate limiting step does not involve a proton donor. Hence, we deduce that the rate limiting step can indeed only consist of the coupling of two CO molecules on the surface, both in acidic and alkaline conditions. For methane, on the other hand, the rate-limiting step changes with the electrolyte pH from the first protonation step in acidic/neutral conditions to a later step in alkaline conditions. Finally, based on an in-depth kinetic analysis, we conclude that the pathway towards CH4 involving a surface combination of *CO and *H is unlikely, since it is unable to reproduce the measured current densities and Tafel slopes.

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