The role of intermolecular potential well depths in collision‐induced state changes

L-type Ca2+ channel currents were recorded from myocytes isolated from bovine pial and porcine coronary arteries to study the influence of changes in intracellular pH (pHi). Whole cell ICa fell when pHi was made more acidic by substituting HEPES/NaOH with CO2/bicarbonate buffer (pHo 7.4, 36 degrees C), and increased when pHi was made more alkaline by addition of 20 mM NH4Cl. Peak ICa was less pHi sensitive than late ICa (170 ms after depolarization to 0 mV). pHi-effects on single Ca2+ channel currents were studied with 110 mM BaCl2 as the charge carrier (22 degrees C, pHo 7.4). In cell-attached patches pHi was changed by extracellular NH4Cl or through the opened cell. In inside-out patches pHi was controlled through the bath. Independent of the method used the following results were obtained: (a) Single channel conductance (24 pS) and life time of the open state were not influenced by pHi (between pHi 6 and 8.4). (b) Alkaline pHi increased and acidic pHi reduced the channel availability (frequency of nonblank sweeps). (c) Alkaline pHi increased and acidic pHi reduced the frequency of late channel re-openings. The effects are discussed in terms of a deprotonation (protonation) of cytosolic binding sites that favor (prevent) the shift of the channels from a sleepy to an available state. Changes of bath pHo mimicked the pHi effects within 20 s, suggesting that protons can rapidly permeate through the surface membrane of vascular smooth muscle cells. The role of pHi in Ca2+ homeostases and vasotonus is discussed.

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On Thresholds and Trigger Mechanisms

Governing Complex Systems ◽

10.7551/mitpress/9780262035934.003.0004 ◽

2017 ◽

Author(s):

Oran R. Young

Keyword(s):

Economic Growth ◽

Complex Systems ◽

Social Systems ◽

Tipping Points ◽

Political Systems ◽

Socioecological Systems ◽

Governance Systems ◽

State Changes ◽

Trigger Mechanisms

Complex systems are subject to changes that are nonlinear, commonly hard to anticipate, often abrupt, and sometimes transformative. In recent years, these phenomena have become a focus of considerable interest among natural scientists who speak about thresholds or boundaries (often characterized as tipping points), trigger mechanisms, and state changes. Similar phenomena occur in social systems involving shifts from peace to war and back, the collapse and replacement of political systems, and fluctuations between periods of economic growth and depression. In this context, it is helpful to differentiate among explosions, cascades, and inflections. The dynamics of such transitions are determined by the fragility of the relevant systems and the intensity of the trigger mechanisms. Building on analyses of tipping points and trigger mechanisms in biophysical systems and socioeconomic systems leads to a consideration of similar phenomena in socioecological systems of the sort that are central to the pursuit of sustainability in the Anthropocene. In considering the role of governance in such settings, it is important to bear in mind that governance systems, too, are complex and dynamic.

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The role of short range interaction in molecular collision broadening

Canadian Journal of Physics ◽

10.1139/p77-074 ◽

1977 ◽

Vol 55 (6) ◽

pp. 533-541 ◽

Cited By ~ 3

Author(s):

R. P. Srivastava ◽

H. R. Zaidi

Keyword(s):

Short Range ◽

Intermolecular Potential ◽

Short Range Interaction ◽

Range Interaction ◽

Multipole Interaction ◽

Molecular Collision ◽

Core Potential ◽

Classical Path ◽

Collision Broadening

The effect of a short range interaction on collision broadening is investigated for molecular transitions. Expressions for the collision width are derived for an intermolecular potential consisting of a multipole term together with a core potential of the form r−n. Impact and straight classical path approximations are used. The short range interaction is included to all orders, but contributions up to second order are retained for the multipole interaction. This approach eliminates the need for a cutoff at small impact parameters. Our results represent the proper generalizations, which reduce to the results of the Anderson theory, in the limit as n → ∞. This work suggests that some information about the effective core potential can be obtained from a comparison of the theory and the experiment.

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The Role of High Excitations in Constructing Sub-spectroscopic Accuracy Intermolecular Potential of He-HCN: Critically Examined by the High-Resolution Spectra with Resonance States

Chinese Journal of Chemical Physics ◽

10.1063/1674-0068/30/cjcp1712231 ◽

2017 ◽

Vol 30 (6) ◽

pp. 776-788 ◽

Cited By ~ 3

Author(s):

Dan Hou ◽

Xiao-Long Zhang ◽

Yu Zhai ◽

Hui Li

Keyword(s):

High Resolution ◽

Intermolecular Potential ◽

Resonance States

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Role of parametric resonance in the inhibition of chaotic escape from a potential well

Physics Letters A ◽

10.1016/s0375-9601(97)00614-2 ◽

1997 ◽

Vol 235 (2) ◽

pp. 153-158 ◽

Cited By ~ 10

Author(s):

R. Chacón ◽

F. Balibrea ◽

M.A. López

Keyword(s):

Parametric Resonance ◽

Potential Well

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Circular orbits in the Taub–NUT and massless Taub–NUT spacetime

International Journal of Geometric Methods in Modern Physics ◽

10.1142/s0219887817501018 ◽

2017 ◽

Vol 14 (07) ◽

pp. 1750101

Author(s):

Parthapratim Pradhan

Keyword(s):

Black Hole ◽

Circular Orbit ◽

Center Of Mass ◽

Null Geodesic ◽

Spherically Symmetric ◽

Potential Well ◽

Killing Horizon ◽

Stable Circular Orbit ◽

Innermost Stable Circular Orbit

In this work, we study the equatorial causal geodesics of the Taub–NUT (TN) spacetime in comparison with massless TN spacetime. We emphasized both on the null circular geodesics and time-like circular geodesics. From the effective potential diagram of null and time-like geodesics, we differentiate the geodesics structure between TN spacetime and massless TN spacetime. It has been shown that there is a key role of the NUT parameter to changes the shape of pattern of the potential well in the NUT spacetime in comparison with massless NUT spacetime. We compared the innermost stable circular orbit (ISCO), marginally bound circular orbit (MBCO) and circular photon orbit (CPO) of the said spacetime with graphically in comparison with massless cases. Moreover, we compute the radius of ISCO, MBCO and CPO for extreme TN black hole (BH). Interestingly, we show that these three radii coincides with the Killing horizon, i.e. the null geodesic generators of the horizon. Finally in Appendix A, we compute the center-of-mass (CM) energy for TN BH and massless TN BH. We show that in both cases, the CM energy is finite. For extreme NUT BH, we found that the diverging nature of CM energy. First, we have observed that a non-asymptotic flat, spherically symmetric and stationary extreme BH showing such feature.

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