Journal articles on the topic 'Conductance theories'
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1
Mahdi, Loauy Abd Al-Azez, Wahid S. Mohammad, and Samir Akram Mahmood. "Exergy Analysis of a Domestic Refrigerator." Journal of Engineering 24, no. 9 (August 29, 2018): 1. http://dx.doi.org/10.31026/j.eng.2018.09.01.
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An energy and exergy thermodynamic analysis using EES program was done for a domestic refrigerator working with R-134a using vapor compression refrigeration cycle. The analysis deals with the system component, i.e. compressor, condenser, evaporator and the expansion device. The analysis depends on the entropy generation minimization approach to improve the refrigerator performance by exploring the optimum design points. These design points were derived from three different theories governing the entropy generation minimization using exergy analyzing method. These theories were first applied to find the optimum balance between the hot inner condenser area and the cold inner evaporator area of the refrigerator and between its hot and cold thermal conductances. Nine types of condensers were used according to its internal surface area and thermal conductance, in order to reach the minimum entropy generation in the refrigerator. The results showed that the compressor has the lowest exergy efficiency of 25%. The expansion device was the second component after the compressor with exergy efficiency of 92%, followed by the condenser with an efficiency of 93%. The evaporator was found to have an exergy efficiency of 98 %. The experimental tests were repeated for the nine condensers sizes with three different ambient temperatures 25℃, 30℃ and 35℃. The exergy analysis showed that the design of the refrigerator mainly depends on thermal conductance calculations rather than the surface inner area estimation.
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Anderegg, William R. L. "Quantifying seasonal and diurnal variation of stomatal behavior in a hydraulic-based stomatal optimization model." Journal of Plant Hydraulics 5 (December 22, 2018): e001. http://dx.doi.org/10.20870/jph.2018.e001.
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Plant responses to drought occur across many time-scales, with stomatal closure typically considered to be a critical short-term response. Recent theories of optimal stomatal conductance linked to plant hydraulic transport have shown promise, but it is not known if stomata update their hydraulic “shadow price” of water use (marginal increase in carbon cost with a marginal drop in water potential) over days, seasons, or in response to recent drought. Here, I estimate the hydraulic shadow price in five species – two semi-arid gymnosperms, one temperate and two tropical angiosperms – at daily timescales and in wet and dry periods. I tested whether the shadow prices varies predictably as a function of current and/or lagged drought conditions. Diurnal estimates of the hydraulic shadow price estimated from observed stomatal conductance, while variable, did not vary predictably with environmental variables. Seasonal variation in shadow price was observed in the gymnosperm species, but not the angiosperm species, and did not meaningfully influence prediction accuracy of stomatal conductance. The lack of systematic variation in shadow price and high predictive ability of stomatal conductance when using a single set of parameters further emphasizes the potential of hydraulic-based stomatal optimization theories.
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OVCHINNIKOV, A. A. "NON-RENORMALIZATION THEOREM IN CHERN-SIMONS THEORIES AND FRACTIONAL QUANTUM HALL EFFECT." Modern Physics Letters A 07, no. 07 (March 7, 1992): 611–17. http://dx.doi.org/10.1142/s0217732392000586.
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We prove the non-renormalization theorem resulting in the exact cancellation of Chern-Simons term (and superconductivity) in systems of both free and interacting anyons with the statistical parameter 1/N. The theorem is used to prove the quantization of transverse conductance in the proposed second-quantized fermionic description of fractional quantum Hall effect.
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Castro-Alvaredo, O. A., and A. Fring. "Rational sequences for the conductance in quantum wires from affine Toda field theories." Journal of Physics A: Mathematical and General 36, no. 26 (June 17, 2003): L425—L432. http://dx.doi.org/10.1088/0305-4470/36/26/101.
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Yevtushenko, Oleg M., and Vladimir I. Yudson. "Protection of edge transport in quantum spin Hall samples: spin-symmetry based general approach and examples." New Journal of Physics 24, no. 2 (February 1, 2022): 023040. http://dx.doi.org/10.1088/1367-2630/ac50e9.
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Abstract Understanding possible mechanisms, which can lead to suppression of helical edge transport in quantum spin Hall (QSH) systems, attracted huge attention right after the first experiments revealing the fragility of the ballistic conductance. Despite the very intensive research and the abundance of theoretical models, the fully consistent explanation of the experimental results is still lacking. We systematize various theories of helical transport with the help of the spin conservation analysis which allows one to single out setups with the ballistic conductance being robustly protected regardless of the electron backscattering. First, we briefly review different theories of edge transport in the QSH samples with and without the spin axial symmetry of the electrons including those theoretical predictions which are not consistent with the spin conservation analysis and, thus, call for a deeper study. Next, we illustrate the general approach by a detailed study of representative examples. One of them addresses the helical edge coupled to an array of Heisenberg-interacting magnetic impurities (MIs) and demonstrates that the conductance remains ballistic even if the time-reversal symmetry on the edge is (locally) broken but the total spin is conserved. Another example focuses on the effects of the space-fluctuating spin–orbit interaction on the QSH edge. It reveals weakness of the protection in several cases, including, e.g. the presence of either the U(1)-symmetric, though not fully isotropic, MIs or generic electron–electron interactions.
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Lambert, M. A., and L. S. Fletcher. "Thermal Contact Conductance of Non-Flat, Rough, Metallic Coated Metals." Journal of Heat Transfer 124, no. 3 (May 10, 2002): 405–12. http://dx.doi.org/10.1115/1.1464565.
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Thermal contact conductance is an important consideration in such applications as nuclear reactor cooling, electronics packaging, spacecraft thermal control, and gas turbine and internal combustion engine cooling. In many instances, the highest possible thermal contact conductance is desired. For this reason, soft, high conductivity, metallic coatings are sometimes applied to contacting surfaces (often metallic) to increase thermal contact conductance. O’Callaghan et al. (1981) as well as Antonetti and Yovanovich (1985, 1988) developed theoretical models for thermal contact conductance of metallic coated metals, both of which have proven accurate for flat, rough surfaces. However, these theories often substantially overpredict the conductance of non-flat, rough, metallic coated metals. In the present investigation, a semi-empirical model for flat and non-flat, rough, uncoated metals, previously developed by Lambert and Fletcher (1996), is employed in predicting the conductance of flat and non-flat, rough, metallic coated metals. The models of Antonetti and Yovanovich (1985, 1988) and Lambert and Fletcher (1996) are compared to experimental data from a number of investigations in the literature. This entailed analyzing the results for a number of metallic coating/substrate combinations on surfaces with widely varying flatness and roughness. Both models agree well with experimental results for flat, rough, metallic coated metals. However, the semi-empirical model by Lambert and Fletcher (1996) is more conservative than the theoretical model by Antonetti and Yovanovich (1985, 1988) when compared to the majority of experimental results for non-flat, rough, metallic coated metals.
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Wojtczak, Lech, and Mariusz R. Więckowski. "From mitochondrial large amplitude swelling to the permeability transition – a short historic overview." Postępy Biochemii 62, no. 3 (November 18, 2016): 298–302. http://dx.doi.org/10.18388/pb.2016_29.
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An outline of studies on the mitochondrial large conductance permeability pore is presented starting from the early observations in the 1950s on the large amplitude mitochondrial swelling, through the concept of the permeability transition and various theories on the structure of the related permeability transition pore, up to its present identification as a part of mitochondrial (F1 FO) ATPase/ATP synthase.
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Mazzone, A. M. "The conductance of SnO2 small nanowires: A study based on density functional and scattering theories." Solid State Communications 143, no. 10 (September 2007): 481–86. http://dx.doi.org/10.1016/j.ssc.2007.06.023.
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Gao, Jun Li, Yan Hong Que, Dong Ying Feng, and Wei Chen. "Research of the Model and MPPT Algorithm of Solar Cells." Advanced Materials Research 724-725 (August 2013): 67–73. http://dx.doi.org/10.4028/www.scientific.net/amr.724-725.67.
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According to the mathematic model of solar cells, builds its general simulation model based on the S-function designed under the Matlab/Simulink environment. Presents the incremental conductance algorithm based on the optimal gradient to simulate and verify the theories about the maximum power point tracking (MPPT) of photovoltaic power generation. Give the in-depth contrast analysis on the power, output voltage characteristics of photovoltaic power generation, which lays a solid foundation for engineering practice.
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Chung, Tien Tung, Chih Kang Lu, and Yi Ting Tu. "Design, Manufacturing and Pump-down Curve Simulation of High Vacuum Systems." Applied Mechanics and Materials 220-223 (November 2012): 575–79. http://dx.doi.org/10.4028/www.scientific.net/amm.220-223.575.
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This paper presents a vacuum system design for extreme ultraviolet lithography (EUV) and studies the prediction of pump-down curves for vacuum chambers. Related basic theories include gas laws, conductance for several kinds of flow regimes, equivalent length for pipes, outgassing, diffusion, and permeation etc. The simulation program consists of a MFC module and a MATLAB module. The MFC module is used to input necessary parameters, including start and target pressure for pumping, volume and inner surface area of vacuum chambers, configuration of pumping lines, performance of vacuum pumps, and gas loads. The MATLAB module deals with the pump-down curve calculation based on related theories. The governing equation of the conservation of mass in a pumped vacuum chamber is derived from extended Temkin isotherm. The pump-down curve of vacuum chamber is predicted by four steps, including calculation of equivalent length for pipes, conductance of pipes, and effective pumping speed of pumps, and pump-down time. An empty vacuum chamber is used to test the developed program. The pump-down curve reaches 6.5E-8 torr with 42 hours pump-down time in experiment measurement, and the simulated curve reaches 5.79E-8 torr at the same time point. The developed program can predict pump-down curve with a good accuracy in the range from low vacuum pressure to high vacuum pressure.
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Muller, Eilif, Lars Buesing, Johannes Schemmel, and Karlheinz Meier. "Spike-Frequency Adapting Neural Ensembles: Beyond Mean Adaptation and Renewal Theories." Neural Computation 19, no. 11 (November 2007): 2958–3010. http://dx.doi.org/10.1162/neco.2007.19.11.2958.
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We propose a Markov process model for spike-frequency adapting neural ensembles that synthesizes existing mean-adaptation approaches, population density methods, and inhomogeneous renewal theory, resulting in a unified and tractable framework that goes beyond renewal and mean-adaptation theories by accounting for correlations between subsequent interspike intervals. A method for efficiently generating inhomogeneous realizations of the proposed Markov process is given, numerical methods for solving the population equation are presented, and an expression for the first-order interspike interval correlation is derived. Further, we show that the full five-dimensional master equation for a conductance-based integrate-and-fire neuron with spike-frequency adaptation and a relative refractory mechanism driven by Poisson spike trains can be reduced to a two-dimensional generalization of the proposed Markov process by an adiabatic elimination of fast variables. For static and dynamic stimulation, negative serial interspike interval correlations and transient population responses, respectively, of Monte Carlo simulations of the full five-dimensional system can be accurately described by the proposed two-dimensional Markov process.
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Ansari, Aijaz Ahmad, and M. R. Islam. "Conductivity and ionic association of tetraalkylammonium halides in tert-butanol–water mixture at 25 °C." Canadian Journal of Chemistry 66, no. 5 (May 1, 1988): 1223–28. http://dx.doi.org/10.1139/v88-200.
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The molar conductivities of Pr4NBr, Bu4NBr, Pr4NI, and BU4NI have been measured in tert-butanol–water (t-BuOH–H2O) mixtures (61.30 ≥ D ≥ 16.50) over the maximum concentration range (2 × D3 × 10−7 mol dm−3) along with the densities and viscosities of the solvent mixtures at 25 °C. The conductance data have been analysed by using the Fuoss-1978 (F78) conductance equation and the results compared with the values obtained from the Justice (J), Pitt's (P), and Fuoss–Onsager–Skinner (FOS) equations. Molar conductivities at infinite dilution (Λ0), the thermodynamic ion association constants (KA) and the distance or ion-size parameters (R0 or a0) are evaluated from these data. The F78 equation fitted the data better and yielded KA and R values which are in accord with the ion-association theories. The interpretation of these parameters is discussed to provide some insight on the magnitude of the ionic association and the ion–solvent interaction.
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Weingärtner, Hermann, Volker C. Weiss, and Wolffram Schröer. "Ion association and electrical conductance minimum in Debye–Hückel-based theories of the hard sphere ionic fluid." Journal of Chemical Physics 113, no. 2 (July 8, 2000): 762–70. http://dx.doi.org/10.1063/1.481822.
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CASTRO-ALVAREDO, O. A., and A. FRING. "APPLICATIONS OF QUANTUM INTEGRABLE SYSTEMS." International Journal of Modern Physics A 19, supp02 (May 2004): 92–116. http://dx.doi.org/10.1142/s0217751x04020336.
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We present two applications of quantum integrable systems. First, we predict that it is possible to generate high harmonics from solid state devices by demonstrating that the emission spectrum of a minimally coupled laser field of frequency ω to an impurity system of a quantum wire, contains multiples of the incoming frequency. Second, by evaluating expressions for the conductance in the high temperature regime we show that multiples of the characteristic filling fractions of the Jain sequence, which occur in the fractional quantum Hall effect, can be obtained from quantum wires which are described by minimal affine Toda field theories.
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XIONG, YONG-JIAN, and SHI-JIE XIONG. "BROADENING OF FANO RESONANCE IN ELECTRONIC CURRENT THROUGH A QUANTUM DOT BY DEPHASING." International Journal of Modern Physics B 16, no. 10 (April 20, 2002): 1479–87. http://dx.doi.org/10.1142/s0217979202011032.
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We investigate the Fano line shape in electron transport through a quantum dot in presence of dephasing. The dephasing effect is introduced by the Büttiker model. We derive a generalized Fano formula for the conductance that includes the components of the standard Fano line shape and the Breit–Wigner line shape. According to this formula the Fano parameter |q| decreases when the dephasing strength increases by increasing the temperature. The increase of the half width of the resonance peak by increasing the temperature measured by Zacharia et al. [Phys. Rev.B64, 155311 (2001)] which is more rapid than expected from the ordinary theories is possibly attributed to the dephasing.
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Li, Rui-Hao, Jun-Yang Liu, and Wen-Jing Hong. "Regulation strategies based on quantum interference in electrical transport of single-molecule devices." Acta Physica Sinica 71, no. 6 (2022): 067303. http://dx.doi.org/10.7498/aps.71.20211819.
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The quantum interference effect in single-molecule devices is a phenomenon in which electrons are coherently transported through different frontier molecular orbitals with multiple energy levels, and the interference will occur between different energy levels. This phenomenon results in the increase or decrease of the probability of electron transmission in the electrical transport of the single-molecule device, and it is manifested in the experiment when the conductance value of the single-molecule device increases or decreases. In recent years, the use of quantum interference effects to control the electron transport in single-molecule device has proved to be an effective method, such as single-molecule switches, single-molecule thermoelectric devices, and single-molecule spintronic devices. In this work, we introduce the related theories of quantum interference effects, early experimental observations, and their regulatory role in single-molecule devices.
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RUBINSTEIN, I., and B. ZALTZMAN. "ELECTRO-OSMOTIC SLIP OF THE SECOND KIND AND INSTABILITY IN CONCENTRATION POLARIZATION AT ELECTRODIALYSIS MEMBRANES." Mathematical Models and Methods in Applied Sciences 11, no. 02 (March 2001): 263–300. http://dx.doi.org/10.1142/s0218202501000866.
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Theories of electro-osmotic slip, of either the equilibrium (first) or nonequilibrium (second) kind at a permselective conductive surface (ion exchange electrodialysis membrane, electrode) are reviewed. A slip condition for electro-osmosis of the second kind, relevant for a developed concentration polarization at an electrodialysis membrane, is derived through a boundary layer analysis of the appropriate convective electrodiffusion problem. Linear hydrodynamic stability of the quiescent concentration polarization in a diffusion layer at a cation exchange electrodialysis membrane is studied. It is shown that electro-osmotic slip of the second kind, as opposed to that of the first kind, yields instability for realistic conditions. Numerical calculations for the resulting nonlinear convection show that the latter provides an efficient mixing mechanism for the diffusion layer, capable of accounting for the overlimiting conductance in concentration polarization at a cation exchange membrane.
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Mucha, R. F., P. Pauli, and A. Angrilli. "Conditioned responses elicited by experimentally produced cues for smoking." Canadian Journal of Physiology and Pharmacology 76, no. 3 (March 1, 1998): 259–68. http://dx.doi.org/10.1139/y98-022.
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Several theories of drug-craving postulate that a signal for drug elicits conditioned responses. However, depending on the theory, a drug cue is said to elicit drug similar, drug compensatory, positive motivational, and negative motivational effects. Since animal data alone cannot tease apart the relative importance of different cue-related processes in the addict, we developed and examined a model of drug cues in the human based on a two-sound, differential conditioning procedure using smoking as the reinforcer. After multiple pairings of a sound with smoking, there was a preference for the smoking cue on a conditioned preference test. The acute effects of smoking (increased heart rate, respiration rate, skin conductance level, skin conductance fluctuations, EEG beta power and trapezius EMG, decreased alpha power) were not affected by the smoking cue, although subjects drew more on their cigarette in the presence of the smoking cue than in the presence of a control cue. Moreover, the cue did not change baseline behaviour except for a possible increase in EEG beta power and an increase in trapezius EMG at about the time when smoking should have occurred. The findings confirm the value of experimental models of drug cues in the human for comparing different cue phenomena in the dependent individual. They indicate that an acquired signal for drug in the human may elicit incentive motivational effects and associated preparatory motor responses in addition to possible conditioned tolerance.Key words: drug cues, conditioning, smoking, tolerance, human.
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Mäkelä, Annikki, Leila Grönlund, Pauliina Schiestl-Aalto, Tuomo Kalliokoski, and Teemu Hölttä. "Current-year shoot hydraulic structure in two boreal conifers—implications of growth habit on water potential." Tree Physiology 39, no. 12 (November 14, 2019): 1995–2007. http://dx.doi.org/10.1093/treephys/tpz107.
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Abstract Metabolic scaling theory allows us to link plant hydraulic structure with metabolic rates in a quantitative framework. In this theoretical framework, we considered the hydraulic structure of current-year shoots in Pinus sylvestris and Picea abies, focusing on two properties unaccounted for by metabolic scaling theories: conifer needles are attached to the entire length of shoots, and the shoot as a terminal element does not display invariant properties. We measured shoot length and diameter as well as conduit diameter and density in two locations of 14 current-year non-leader shoots of pine and spruce saplings, and calculated conductivities of shoots from measured conduit properties. We evaluated scaling exponents for the hydraulic structure of shoots at the end of the water transport pathway from the data and applied the results to simulate water potential of shoots in the crown. Shoot shape was intermediate between cylindrical and paraboloid. Contrary to previous findings, we found that conduit diameter scaled with relative, not absolute, distance from the apex and absolute under-bark shoot diameter independently of species within the first-year shoots. Shoot hydraulic conductivity scaled with shoot diameter and hydraulic diameter. Larger shoots had higher hydraulic conductance. We further demonstrate by novel model calculations that ignoring foliage distribution along the hydraulic pathway overestimates water potential loss in shoots and branches and therefore overestimates related water stress effects. Scaling of hydraulic properties with shoot size enhances apical dominance and may contribute to the decline of whole-tree conductance in large trees.
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Riedl, René, Harald Kindermann, Andreas Auinger, and Andrija Javor. "Computer Breakdown as a Stress Factor during Task Completion under Time Pressure: Identifying Gender Differences Based on Skin Conductance." Advances in Human-Computer Interaction 2013 (2013): 1–8. http://dx.doi.org/10.1155/2013/420169.
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In today’s society, as computers, the Internet, and mobile phones pervade almost every corner of life, the impact of Information and Communication Technologies (ICT) on humans is dramatic. The use of ICT, however, may also have a negative side. Human interaction with technology may lead to notable stress perceptions, a phenomenon referred to as technostress. An investigation of the literature reveals that computer users’ gender has largely been ignored in technostress research, treating users as “gender-neutral.” To close this significant research gap, we conducted a laboratory experiment in which we investigated users’ physiological reaction to the malfunctioning of technology. Based on theories which explain that men, in contrast to women, are more sensitive to “achievement stress,” we predicted that male users would exhibit higher levels of stress than women in cases of system breakdown during the execution of a human-computer interaction task under time pressure, if compared to a breakdown situation without time pressure. Using skin conductance as a stress indicator, the hypothesis was confirmed. Thus, this study shows that user gender is crucial to better understanding the influence of stress factors such as computer malfunctions on physiological stress reactions.
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Kyvelidis, S., G. M. Maistros, P. Rattray, H. Block, J. Akhavan, and G. Tsangaris. "The Place of Dielectric Spectroscopy in Probing Electrorheology." International Journal of Modern Physics B 13, no. 14n16 (June 30, 1999): 1829–36. http://dx.doi.org/10.1142/s0217979299001855.
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The measurement of the dielectric spectra of PAnQR based ER fluids under shear and electric fields is discussed and results presented. Data in which either but not both shear or electric fields are present are submitted to analysis in terms of known theories. For flow alone, that analysis provides information on the attenuation of polarization by the uniform shear fields whilst the polarization of quiescent fluids by electric fields may lead to estimates of particles packing within the columns. Permittivity data when both fields are acting is presented, but in the absence of suitable theory, not modelled quantitatively. Empirical correlations are discussed and the conclusion drawn that fibrillation is readily suppressed by even moderate shear rates, although long range dipolar forces still persist to high shear rates. The dc conductance of these fluids have also been measured. This together with permittivity data under ER fluid working conditions has importance in establishing the electrical parameters for any ER fluid.
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Weingärtner, Hermann. "Corresponding states for electrolyte solutions." Pure and Applied Chemistry 73, no. 11 (January 1, 2001): 1733–48. http://dx.doi.org/10.1351/pac200173111733.
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The equilibrium properties of electrolyte solutions over wide ranges of concentration, temperature, and solvent dielectric constant are discussed on a corresponding-states basis. If low-melting salts are used, these properties can be studied up to the pure fused salt. We mainly focus on systems at low reduced temperature, where the depth of the interaction potential is large compared with the thermal energy. Examples are singly charged ions in solvents of low dielectric constant and of highly charged ions in water. The state of the ions is discussed on the basis of thermodynamic, electrical conductance and dielectric constant data. Special attention is given to the transition to the fused salt, where ion clusters have to redissociate to form the dissociated structure of the salt. This transition can lead to liquidliquid phase separations. The resulting critical points serve as important targets for testing theories. Examples are given for large deviations from corresponding-states behavior caused by specific short-range interactions.
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Groschner, Lukas N., Jonatan G. Malis, Birte Zuidinga, and Alexander Borst. "A biophysical account of multiplication by a single neuron." Nature 603, no. 7899 (February 23, 2022): 119–23. http://dx.doi.org/10.1038/s41586-022-04428-3.
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AbstractNonlinear, multiplication-like operations carried out by individual nerve cells greatly enhance the computational power of a neural system1–3, but our understanding of their biophysical implementation is scant. Here we pursue this problem in the Drosophila melanogaster ON motion vision circuit4,5, in which we record the membrane potentials of direction-selective T4 neurons and of their columnar input elements6,7 in response to visual and pharmacological stimuli in vivo. Our electrophysiological measurements and conductance-based simulations provide evidence for a passive supralinear interaction between two distinct types of synapse on T4 dendrites. We show that this multiplication-like nonlinearity arises from the coincidence of cholinergic excitation and release from glutamatergic inhibition. The latter depends on the expression of the glutamate-gated chloride channel GluClα8,9 in T4 neurons, which sharpens the directional tuning of the cells and shapes the optomotor behaviour of the animals. Interacting pairs of shunting inhibitory and excitatory synapses have long been postulated as an analogue approximation of a multiplication, which is integral to theories of motion detection10,11, sound localization12 and sensorimotor control13.
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Iafusco, Fernanda, Giovanna Maione, Francesco Maria Rosanio, Enza Mozzillo, Adriana Franzese, and Nadia Tinto. "Cystic Fibrosis-Related Diabetes (CFRD): Overview of Associated Genetic Factors." Diagnostics 11, no. 3 (March 22, 2021): 572. http://dx.doi.org/10.3390/diagnostics11030572.
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Cystic fibrosis (CF) is the most common autosomal recessive disease in the Caucasian population and is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene that encodes for a chloride/bicarbonate channel expressed on the membrane of epithelial cells of the airways and of the intestine, as well as in cells with exocrine and endocrine functions. A common nonpulmonary complication of CF is cystic fibrosis-related diabetes (CFRD), a distinct form of diabetes due to insulin insufficiency or malfunction secondary to destruction/derangement of pancreatic betacells, as well as to other factors that affect their function. The prevalence of CFRD increases with age, and 40–50% of CF adults develop the disease. Several proposed hypotheses on how CFRD develops have emerged, including exocrine-driven fibrosis and destruction of the entire pancreas, as well as contrasting theories on the direct or indirect impact of CFTR mutation on islet function. Among contributors to the development of CFRD, in addition to CFTR genotype, there are other genetic factors related and not related to type 2 diabetes. This review presents an overview of the current understanding on genetic factors associated with glucose metabolism abnormalities in CF.
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Merckelbach, Harald, Arie Dijkstra, Peter J. de Jong, and Peter Muris. "No Effects of Verbal Versus Imaginal Cognitive Strategies on Emotional Responses to Aversive Slides." Behavioural and Cognitive Psychotherapy 22, no. 3 (July 1994): 199–209. http://dx.doi.org/10.1017/s1352465800013072.
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A number of studies have indicated that the right hemisphere is specialized for (negative) emotions. Some authors have suggested that this specialization stems from the cognitive characteristics of this hemisphere. More specifically, the verbal and analytic approach that characterizes left hemisphere functioning would inhibit emotional reactions, whereas the imaginal and global approach that characterizes right hemisphere functioning would facilitate emotional reactivity. The present study examined whether these two cognitive strategies have, indeed, different effects on emotional responsivity. Subjects were exposed to a series of aversive slides. One group (n = 14) was instructed to process the slides in a verbal/analytic manner. The second group (n = 14) employed an imaginal/global strategy while viewing the slides. The third group (n = 14) was a control group that received no explicit instructions. Self-reported emotions, skin conductance responses, heart rate frequency, and eye blink startles were recorded. There were no differences between the three groups with regard to any of these variables. Thus, no evidence was obtained to support the idea that processing modes (i.e., verbal/analytic versus imaginal/global) have a differential impact on emotional reactivity. The implications for theories about lateralization of emotions and for cognitive therapy are discussed.
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Schröer, W., and H. Weingärtner. "Structure and criticality of ionic fluids." Pure and Applied Chemistry 76, no. 1 (January 1, 2004): 19–27. http://dx.doi.org/10.1351/pac200476010019.
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Two properties render electrolyte theories difficult, namely the long-range nature of the Coulomb interactions and the high figures of the Coulomb energy at small ion separations. In solvents of low dielectric constant, where the Coulomb interactions are particularly strong, electrical conductance and dielectric spectra suggest that the ion distribution involves dipolar ion pairs, which then interact with the free ions and with other dipolar pairs. The dipole-dipole interactions between ion pairs lead to an increase of the dielectric constant, which in turn stabilizes the free ions, thus leading to redissociation at high salt concentrations. An equation of state that accounts for ion pairing, ion-ion pair, and ion pair-ion pair interactions rationalizes the basic features of the ion distribution. It also predicts a fluid-phase transition at low reduced temperatures, which closely corresponds to simulation results and to experimentally observed liquid-liquid phase transitions. The long-range nature of the Coulomb potential driving these transitions raises questions concerning their universality class. Experiments suggest that the Ising universality class applies, but there is cross-over to mean-field behavior rather close to the critical, not yet well explained by theory.
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Elsysy, Mokhles A., Michael V. Mickelbart, and Peter M. Hirst. "Effect of Fruiting and Biennial Bearing Potential on Spur Quality and Leaf Gas Exchange in Apple." Journal of the American Society for Horticultural Science 144, no. 1 (January 2019): 31–37. http://dx.doi.org/10.21273/jashs04524-18.
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Uniform annual apple (Malus ×domestica) fruit production is highly dependent on consistent flower formation from year to year, as inconsistent flowering can lead to the biennial bearing observed in some high-value cultivars. The presence of fruit on a spur has been considered the main cause of the expression of biennial bearing and the inhibition of flower initiation, with a number of theories being introduced to explain the phenomenon. In the current experiment, individual spurs of annual bearing cultivars (Gala, Ruby Jon, and Pink Lady) and biennial bearing cultivars (Honeycrisp, Fuji, and Golden Delicious) were thinned to a single fruit or completely defruited at petal fall. Spurs were sampled at the end of the growing season. Effects of fruiting on spur characteristics such as spur and bourse leaf area, stomatal density, leaf gas exchange, and flower formation were determined. Across all cultivars, the presence of fruit on a spur did not affect spur characteristics or flower formation compared with nonfruiting spurs. Similarly, flowering was unaffected by those factors associated with greater spur carbohydrate status, such as bourse leaf area and assimilation rate. Cultivars with greater transpiration and stomatal conductance (gs) rates had lower rates of flower formation. Future studies should focus on xylem flow and expression of genes regulating flowering and plant growth regulators in annual and biennial bearing cultivars.
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Kelsey, Ryan, Fiona N. Manderson Koivula, Neville H. McClenaghan, and Catriona Kelly. "Cystic Fibrosis–Related Diabetes: Pathophysiology and Therapeutic Challenges." Clinical Medicine Insights: Endocrinology and Diabetes 12 (January 2019): 117955141985177. http://dx.doi.org/10.1177/1179551419851770.
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Cystic fibrosis–related diabetes (CFRD) is among the most common extrapulmonary co-morbidity associated with cystic fibrosis (CF), affecting an estimated 50% of adults with the condition. Cystic fibrosis is prevalent in 1 in every 2500 Caucasian live births and is caused by a mutation in the cystic fibrosis transmembrane conductance regulator ( CFTR) gene. Mutated CFTR leads to dehydrated epithelial surfaces and a build-up of mucus in a variety of tissues including the lungs and pancreas. The leading cause of mortality in CF is repeated respiratory bacterial infections, which prompts a decline in lung function. Co-morbid diabetes promotes bacterial colonisation of the airways and exacerbates the deterioration in respiratory health. Cystic fibrosis–related diabetes is associated with a 6-fold higher mortality rate compared with those with CF alone. The management of CFRD adds a further burden for the patient and creates new therapeutic challenges for the clinical team. Several proposed hypotheses on how CFRD develops have emerged, including exocrine-driven fibrosis and destruction of the entire pancreas and contrasting theories on the direct or indirect impact of CFTR mutation on islet function. The current review outlines recent data on the impact of CFTR on endocrine pancreatic function and discusses the use of conventional diabetic therapies and new CFTR-correcting drugs on the treatment of CFRD.
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Adams, Mark Andrew, Tarryn L. Turnbull, Janet I. Sprent, and Nina Buchmann. "Legumes are different: Leaf nitrogen, photosynthesis, and water use efficiency." Proceedings of the National Academy of Sciences 113, no. 15 (March 30, 2016): 4098–103. http://dx.doi.org/10.1073/pnas.1523936113.
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Using robust, pairwise comparisons and a global dataset, we show that nitrogen concentration per unit leaf mass for nitrogen-fixing plants (N2FP; mainly legumes plus some actinorhizal species) in nonagricultural ecosystems is universally greater (43–100%) than that for other plants (OP). This difference is maintained across Koppen climate zones and growth forms and strongest in the wet tropics and within deciduous angiosperms. N2FP mostly show a similar advantage over OP in nitrogen per leaf area (Narea), even in arid climates, despite diazotrophy being sensitive to drought. We also show that, for most N2FP, carbon fixation by photosynthesis (Asat) and stomatal conductance (gs) are not related to Narea—in distinct challenge to current theories that place the leaf nitrogen–Asat relationship at the center of explanations of plant fitness and competitive ability. Among N2FP, only forbs displayed an Narea–gs relationship similar to that for OP, whereas intrinsic water use efficiency (WUEi; Asat/gs) was positively related to Narea for woody N2FP. Enhanced foliar nitrogen (relative to OP) contributes strongly to other evolutionarily advantageous attributes of legumes, such as seed nitrogen and herbivore defense. These alternate explanations of clear differences in leaf N between N2FP and OP have significant implications (e.g., for global models of carbon fluxes based on relationships between leaf N and Asat). Combined, greater WUE and leaf nitrogen—in a variety of forms—enhance fitness and survival of genomes of N2FP, particularly in arid and semiarid climates.
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Hultman, C., S. Vadlin, M. Rehn, K. Nilsson, and C. Åslund. "Autonomic responses during gambling: the effect of outcome type and sex in a large community sample of young adults." European Psychiatry 65, S1 (June 2022): S299—S300. http://dx.doi.org/10.1192/j.eurpsy.2022.764.
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Introduction Autonomic arousal is believed to be an underlying reinforcer for problematic gambling behavior. Theories suggests that near-misses (outcomes falling just short of a true win) are structural characteristics affecting emotion and motivation while increasing gambling persistence. Objectives Psychophysiological responses to different outcomes in gambling were investigated in a community-based sample of young adults. Furthermore, sex differences in responses to different gambling outcomes were investigated. Methods Young adults (n=270) performed a simplified virtual slot machine producing wins, two types of near-misses (before/after payline) and full-misses, with simultaneous measurements of heart rate (HR) and skin conductance responses (SCR). Self-reports of perceived chance of winning, pleasure and motivation to play were given by the participants on each trial. Results Near-misses were associated with the largest HR acceleration compared to wins and full-misses, and larger HR deceleration and SCRs compared to full-misses. Differential autonomic and subjective reports were observed for near-misses subtypes, suggesting that near-misses are processed differently depending on their position before or after payline. Females showed larger SCR responses and increased motivation following wins compared to males. Conclusions Slot machine gambling outcomes elicit differential physiological and subjective responses in young adults. Specifically, near-misses produce larger autonomic responses compared to regular full-misses. However, near-misses are complex, multifaceted events producing various emotional responses depending on their characterization. Males and females respond differently to wins, highlighting the importance of considering sex differences in experimental research on autonomic responses in gambling. Disclosure No significant relationships.
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Roux, Benoît, Toby Allen, Simon Bernèche, and Wonpil Im. "Theoretical and computational models of biological ion channels." Quarterly Reviews of Biophysics 37, no. 1 (February 2004): 15–103. http://dx.doi.org/10.1017/s0033583504003968.
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1. Introduction 172. Dynamics of many-body systems 192.1 Effective dynamics of reduced systems 212.2 The constraint of thermodynamic equilibrium 242.3 Mean-field theories 253. Solvation free energy and electrostatics 273.1 Microscopic view of the Born model 273.2 Ion–Ion interactions in bulk solution 293.3 Continuum electrostatics and the PB equation 293.4 Limitations of continuum dielectric models 323.5 The dielectric barrier 333.6 The transmembrane potential and the PB-V equation 354. Statistical mechanical equilibrium theory 404.1 Multi-ion PMF 404.2 Equilibrium probabilities of occupancy 434.3 Coupling to the membrane potential 444.4 Ionic selectivity 484.5 Reduction to a one-dimensional (1D) free-energy profile 495. From MD toI–V: a practical guide 505.1 Extracting the essential ingredients from MD 515.1.1 Channel conductance from equilibrium and non-equilibrium MD 515.1.2 PMF techniques 525.1.3 Friction and diffusion coefficient techniques 535.1.4 About computational times 555.2 Ion permeation models 565.2.1 The 1D-NP electrodiffusion theory 565.2.2 Discrete-state Markov chains 575.2.3 The GCMC/BD algorithm 585.2.4 PNP electrodiffusion theory 626. Computational studies of ion channels 636.1 Computational studies of gA 656.1.1 Free-energy surface for K+ permeation 666.1.2 Mean-force decomposition 696.1.3 Cation-binding sites 696.1.4 Channel conductance 706.1.5 Selectivity 726.2 Computational studies of KcsA 726.2.1 Multi-ion free-energy surface and cation-binding sites 736.2.2 Channel conductance 746.2.3 Mechanism of ion conduction 776.2.4 Selectivity 786.3 Computational studies of OmpF 796.3.1 The need to compare the different level of approximations 796.3.2 Equilibrium protein fluctuations and ion distribution 806.3.3 Non-equilibrium ion fluxes 806.3.4 Reversal potential and selectivity 846.4 Successes and limitations 876.4.1 Channel structure 876.4.2 Ion-binding sites 876.4.3 Ion conduction 886.4.4 Ion selectivity 897. Conclusion 908. Acknowledgments 939. References 93The goal of this review is to establish a broad and rigorous theoretical framework to describe ion permeation through biological channels. This framework is developed in the context of atomic models on the basis of the statistical mechanical projection-operator formalism of Mori and Zwanzig. The review is divided into two main parts. The first part introduces the fundamental concepts needed to construct a hierarchy of dynamical models at different level of approximation. In particular, the potential of mean force (PMF) as a configuration-dependent free energy is introduced, and its significance concerning equilibrium and non-equilibrium phenomena is discussed. In addition, fundamental aspects of membrane electrostatics, with a particular emphasis on the influence of the transmembrane potential, as well as important computational techniques for extracting essential information from all-atom molecular dynamics (MD) simulations are described and discussed. The first part of the review provides a theoretical formalism to ‘translate’ the information from the atomic structure into the familiar language of phenomenological models of ion permeation. The second part is aimed at reviewing and contrasting results obtained in recent computational studies of three very different channels; the gramicidin A (gA) channel, which is a narrow one-ion pore (at moderate concentration), the KcsA channel from Streptomyces lividans, which is a narrow multi-ion pore, and the outer membrane matrix porin F (OmpF) from Escherichia coli, which is a trimer of three β-barrel subunits each forming wide aqueous multi-ion pores. Comparison with experiments demonstrates that current computational models are approaching semi-quantitative accuracy and are able to provide significant insight into the microscopic mechanisms of ion conduction and selectivity. We conclude that all-atom MD with explicit water molecules can represent important structural features of complex biological channels accurately, including such features as the location of ion-binding sites along the permeation pathway. We finally discuss the broader issue of the validity of ion permeation models and an outlook to the future.
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Soiné, Anna, Alessandra Flöck, and Peter Walla. "Electroencephalography (EEG) Reveals Increased Frontal Activity in Social Presence." Brain Sciences 11, no. 6 (May 31, 2021): 731. http://dx.doi.org/10.3390/brainsci11060731.
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It remains an unsolved conundrum how social presence affects the neural processes involved in adaptive situation-specific decision-making mechanisms. To investigate this question, brain potential changes via electroencephalography (EEG) and skin conductance responses (SCR) were taken within this study, while participants were exposed to pre-rated pleasant, neutral, and unpleasant pictures, which they had to rate in terms of their perceived arousal. Crucially, they had to—in respective runs—do this alone and in the presence of a significant other. Contrasting respective event-related potentials (ERPs) revealed significantly more negative going potentials peaking at 708 ms post stimulus onset at mid-frontal electrode locations (around FPz and AFz), when participants were exposed to neutral pictures while in the presence of a significant other. SCR results demonstrate higher states of arousal in the presence of a significant other regardless of picture emotion category. Self-reported arousal turned out to be highest in response to neutral pictures within the significant other condition, whereas in the alone condition in response to the pleasant pictures. In light of existing literature on social aspects and the anterior cingulate cortex (ACC), the ERP finding in the significant other condition, while rating emotionally neutral pictures, is interpreted as reflecting heightened ACC activation, which is supported by electrode locations showing significant brain activity differences as well as by source localization results. Neutral pictures are inherently ambiguous, and the current results indicate the presence of another person to change the way one processes, perceives, and acts on them. This is in support for theories proposing the ACC to be part of a larger signal-specification network that gauges relevant stimuli for adequate execution of control.
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Gu, W. Y., W. M. Lai, and V. C. Mow. "A Mixture Theory for Charged-Hydrated Soft Tissues Containing Multi-electrolytes: Passive Transport and Swelling Behaviors." Journal of Biomechanical Engineering 120, no. 2 (April 1, 1998): 169–80. http://dx.doi.org/10.1115/1.2798299.
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A new mixture theory was developed to model the mechano-electrochemical behaviors of charged-hydrated soft tissues containing multi-electrolytes. The mixture is composed of n + 2 constituents (1 charged solid phase, 1 noncharged solvent phase, and n ion species). Results from this theory show that three types of force are involved in the transport of ions and solvent through such materials: (1) a mechanochemical force (including hydraulic and osmotic pressures); (2) an electrochemical force; and (3) an electrical force. Our results also show that three types of material coefficients are required to characterize the transport rates of these ions and solvent: (1) a hydraulic permeability; (2) mechano-electrochemical coupling coefficients; and (3) an ionic conductance matrix. Specifically, we derived the fundamental governing relationships between these forces and material coefficients to describe such mechano-electrochemical transduction effects as streaming potential, streaming current, diffusion (membrane) potential, electro-osmosis, and anomalous (negative) osmosis. As an example, we showed that the well-known formula for the resting cell membrane potential (Hodgkin and Huxley, 1952a, b) could be derived using our new n + 2 mixture model (a generalized triphasic theory). In general, the n + 2 mixture theory is consistent with and subsumes all previous theories pertaining to specific aspects of charged-hydrated tissues. In addition, our results provided the stress, strain, and fluid velocity fields within a tissue of finite thickness during a one-dimensional steady diffusion process. Numerical results were provided for the exchange of Na+ and Ca++ through the tissue. These numerical results support our hypothesis that tissue fixed charge density (cF) plays a significant role in modulating kinetics of ions and solvent transport through charged-hydrated soft tissues.
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Marinos, Julia, Olivia Simioni, and Andrea R. Ashbaugh. "Verbal manipulations of learning expectancy do not enhance reconsolidation." PLOS ONE 17, no. 8 (August 18, 2022): e0241943. http://dx.doi.org/10.1371/journal.pone.0241943.
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Objectives Pharmacological studies using propranolol suggest that if reactivation signals that new information will be learned (i.e., there is an expectation for learning) reconsolidation can be enhanced. We examined if the verbal instructions to expect new learning will enhance reconsolidation of fear memories using the post-retrieval extinction paradigm. Methods On day one, participants (n = 48) underwent differential fear conditioning to two images (CS+ and CS-). On day two, participants were randomly assigned to one of three groups; groups one and two had their memory for the CS+ reactivated (i.e., a single presentation of the CS+) 10 minutes prior to extinction, whereas group three did not have their memory reactivated but went right to extinction (no reactivation group). One reactivation group was told that they would learn something new about the images (expectation for learning group), and the other group was told that they would not learn anything new (no expectation for learning group). On day three, return of fear was measured following reinstatement (i.e., four shocks). Fear potentiated startle (FPS) and skin conductance response (SCR) were measured throughout. Results There was evidence of fear acquisition for participants for SCR but not FPS. With regards to reconsolidation, SCR increased for the CS+ and CS-in all groups from the end of extinction to the beginning of re-extinction (i.e., return of fear). For FPS, post-hoc tests conducted on the sub-group of participants showing fear learning showed that FPS remained stable in the two reactivation groups, but increased to the CS+, but not the CS- in the no reactivation group. Implications These findings suggest that a verbal manipulation of the expectation for learning may not be salient enough to enhance reconsolidation. Results are discussed in relation to theories on differences in between SCR, as a measure of cognitive awareness, and FPS, as a measure of fear.
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Choi, Bum-Rak, and Guy Salama. "Optical mapping of atrioventricular node reveals a conduction barrier between atrial and nodal cells." American Journal of Physiology-Heart and Circulatory Physiology 274, no. 3 (March 1, 1998): H829—H845. http://dx.doi.org/10.1152/ajpheart.1998.274.3.h829.
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The mechanisms responsible for atrioventricular (AV) delay remain unclear, in part due to the inability to map electrical activity by conventional microelectrode techniques. In this study, voltage-sensitive dyes and imaging techniques were refined to detect action potentials (APs) from the small cells comprising the AV node and to map activation from the “compact” node. Optical APs (124) were recorded from 5 × 5 mm (∼0.5-mm depth) AV zones of perfused rabbit hearts stained with a voltage-sensitive dye. Signals from the node exhibited a set of three spikes; the first and third ( peaks I and III) were coincident with atrial (A) and ventricular (V) electrograms, respectively. The second spike ( peak II) represented the firing of midnodal (N) and/or lower nodal (NH) cell APs as indicated by their small amplitude, propagation pattern, location determined from superimposition of activation maps and histological sections of the node region, dependence on depth of focus, and insensitivity to tetrodotoxin (TTX). AV delays consisted of τ1 (49.5 ± 6.59 ms, 300-ms cycle length), the interval between peaks I and II (perhaps AN to N cells), and τ2 (57.57 ± 5.15 ms), the interval between peaks II and III (N to V cells). The conductance time across the node was 10.33 ± 3.21 ms, indicating an apparent conduction velocity (ΘN) of 0.162 ± 0.02 m/s ( n = 9) that was insensitive to TTX. In contrast, τ1 correlated with changes in AV node delays (measured with surface electrodes) caused by changes in heart rate or perfusion with acetylcholine. The data provide the first maps of activation across the AV node and demonstrate that ΘN is faster than previously presumed. These findings are inconsistent with theories of decremental conduction and prove the existence of a conduction barrier between the atrium and the AV node that is an important determinant of AV node delay.
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Fukasawa, Masaaki. "Limit theorems for random walks under irregular conductance." Proceedings of the Japan Academy, Series A, Mathematical Sciences 89, no. 8 (August 2013): 87–91. http://dx.doi.org/10.3792/pjaa.89.87.
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Efimov, Igor R. "Letters to the Editor." American Journal of Physiology-Heart and Circulatory Physiology 275, no. 5 (November 1, 1998): H1905—H1909. http://dx.doi.org/10.1152/ajpheart.1998.275.5.h1905.
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The following is an abstract of the article discussed in the subsequent letter: Choi, Bum-Rak, and Guy Salama. Optical mapping of atrioventricular node reveals a conduction barrier between atrial and nodal cells. Am. J. Physiol. 274 ( Heart Circ. Physiol. 43): H829–H845, 1998.—The mechanisms responsible for atrioventricular (AV) delay remain unclear, in part due to the inability to map electrical activity by conventional microelectrode techniques. In this study, voltage-sensitive dyes and imaging techniques were refined to detect action potentials (APs) from the small cells comprising the AV node and to map activation from the “compact” node. Optical APs (124) were recorded from 5 × 5 mm (∼0.5-mm depth) AV zones of perfused rabbit hearts stained with a voltage-sensitive dye. Signals from the node exhibited a set of three spikes; the first and third ( peaks Iand III) were coincident with atrial (A) and ventricular (V) electrograms, respectively. The second spike ( peak II)represented the firing of midnodal (N) and/or lower nodal (NH) cell APs as indicated by their small amplitude, propagation pattern, location determined from superimposition of activation maps and histological sections of the node region, dependence on depth of focus, and insensitivity to tetrodotoxin (TTX). AV delays consisted of τ1 (49.5 ± 6.59 ms, 300-ms cycle length), the interval between peaks I and II (perhaps AN to N cells), and τ2 (57.57 ± 5.15 ms), the interval between peaks II and III (N to V cells). The conductance time across the node was 10.33 ± 3.21 ms, indicating an apparent conduction velocity (ΘN) of 0.162 ± 0.02 m/s ( n = 9) that was insensitive to TTX. In contrast, τ1 correlated with changes in AV node delays (measured with surface electrodes) caused by changes in heart rate or perfusion with acetylcholine. The data provide the first maps of activation across the AV node and demonstrate that ΘN is faster than previously presumed. These findings are inconsistent with theories of decremental conduction and prove the existence of a conduction barrier between the atrium and the AV node that is an important determinant of AV node delay.
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YAN, YI JING, and HOUYU ZHANG. "TOWARD THE MECHANISM OF LONG-RANGE CHARGE TRANSFER IN DNA: THEORIES AND MODELS." Journal of Theoretical and Computational Chemistry 01, no. 01 (July 2002): 225–44. http://dx.doi.org/10.1142/s0219633602000154.
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This article reviews our recent theoretical development toward understanding the interplay of electronic structure and dephasing effects on charge transfer/transport through molecular donor-bridge-acceptor systems. Both the generalized scattering matrix and Green's function formalisms for partially incoherent tunneling processes are summarized. Presented is also an exact mapping between the kinetic rate constants and the electric conductances in evaluation of chemical yields of sequential charge transfer in the presence of competing branching reactions. As an important example, the mechanism of long-range charge transfer in DNA in aqueous solution is investigated with a quantum chemistry implementation of the generalized Green's function formalism. A time scale of about 5 ps is found for the partially incoherent tunneling through a thymine/adenine π-stack in DNA. Numerical results further show that while the carrier oxidative charge does hop sequentially over all guanine sites in a DNA duplex, its tunneling over thymine/adenine bridge base pairs deviates substantially from the superexchange regime. Presented are also evidences for the involvement of both intrastrand and interstrand pathways in the ground state hole charge transfer in DNA.
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Goldberg, Joshua A., Chris A. Deister, and Charles J. Wilson. "Response Properties and Synchronization of Rhythmically Firing Dendritic Neurons." Journal of Neurophysiology 97, no. 1 (January 2007): 208–19. http://dx.doi.org/10.1152/jn.00810.2006.
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The responsiveness of rhythmically firing neurons to synaptic inputs is characterized by their phase-response curve (PRC), which relates how weak somatic perturbations affect the timing of the next action potential. The shape of the somatic PRC is an important determinant of collective network dynamics. Here we study theoretically and experimentally the impact of distally located synapses and dendritic nonlinearities on the synchronization properties of rhythmically firing neurons. By combining the theories of quasi-active cables and phase-coupled oscillators we derive an approximation for the dendritic responsiveness, captured by the neuron's dendritic PRC (dPRC). This closed-form expression indicates that the dPRCs are linearly filtered versions of the somatic PRC and that the filter characteristics are determined by the passive and active properties of the dendrite. The passive properties induce leftward shifts in the dPRCs and attenuate them. Our analysis yields a single dimensionless parameter that classifies active dendritic conductances as either regenerative conductances that counter the passive properties by boosting the dPRCs or restorative conductances that high-pass filter the dPRCs. Thus dendritic properties can generate a qualitative difference between the somatic and dendritic PRCs. As a result collective dynamics can be qualitatively different depending on the location of the synapse, the neuronal firing rates, and the dendritic nonlinearities. Finally, we use dual whole cell recordings from the soma and apical dendrite of cortical pyramidal neurons to test these predictions and find that empirical dPRCs are shifted leftward, as predicted, but may also display high-pass characteristics resulting from the restorative dendritic HCN (h) current.
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Mazzone, Anna. "Monoatomic Chains Deposited onto Silicon Steps Studied by Density Functional and Scattering Theories." MRS Proceedings 959 (2006). http://dx.doi.org/10.1557/proc-0959-m03-12.
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ABSTRACTThe purpose of this study is the assessment of the properties of deposited atomic chains. Therefore linear chains of covalent and metallic atoms, i.e. As and Ag,deposited onto monolayer SA steps onto Si(100) have been considered. Their study is based on a semi-empirical Hamiltonian, used for the evaluation of both the electronic structure and the conductance, and the calaculations analyze the binding energy of chains of variable length deposited onto steps in the light of the analogous energy of free-standing chains and of chains deposited onto the Si(100) surface. This comparison shows that the stability of the chains has a primary dependence on the type of the substrate, rather than on the chain length and composition, and increases in the order: free standing,deposited onto SA,deposited onto Si(100). The central result of the calculations of the conductance is that the dependence on the type of the substrate and on the chain composition parallels the one of the binding energy.
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"Evaluation of the physical parameters of nano-sized tetrachlorosilane as an inorganic material a mixed solvent using Fuoss-Shedlovsky and Fuoss-Hsia-Fernández-Prini techniques." Biointerface Research in Applied Chemistry 10, no. 4 (March 29, 2020): 5741–46. http://dx.doi.org/10.33263/briac104.741746.
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The electrical conductance of nano-sized tetrachlorosilane is measured in 50% mixed solvent of (absolute ethanol-H2O) at various temperatures. The Λ0 (limiting molar conductance) and the KA (association constant) are evaluated via using Fuoss-Shedlovsky (F-SH) and Fuoss-Hsia-Fernández-Prini (FHFP) theories. The standard thermodynamic parameters for association (ΔS°A, ΔH°A& ΔG°A), energy of activation (Ea), hydrodynamic radii (RH) and Walden product (Λ0 η0) are calculated for tetrachlorosilane. These various physical parameters for tetrachlorosilane are evaluated and discussed.
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Cheng, Zhe, Ruiyang Li, Xingxu Yan, Glenn Jernigan, Jingjing Shi, Michael E. Liao, Nicholas J. Hines, et al. "Experimental observation of localized interfacial phonon modes." Nature Communications 12, no. 1 (November 25, 2021). http://dx.doi.org/10.1038/s41467-021-27250-3.
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AbstractInterfaces impede heat flow in micro/nanostructured systems. Conventional theories for interfacial thermal transport were derived based on bulk phonon properties of the materials making up the interface without explicitly considering the atomistic interfacial details, which are found critical to correctly describing thermal boundary conductance. Recent theoretical studies predicted the existence of localized phonon modes at the interface which can play an important role in understanding interfacial thermal transport. However, experimental validation is still lacking. Through a combination of Raman spectroscopy and high-energy-resolution electron energy-loss spectroscopy in a scanning transmission electron microscope, we report the experimental observation of localized interfacial phonon modes at ~12 THz at a high-quality epitaxial Si-Ge interface. These modes are further confirmed using molecular dynamics simulations with a high-fidelity neural network interatomic potential, which also yield thermal boundary conductance agreeing well with that measured in time-domain thermoreflectance experiments. Simulations find that the interfacial phonon modes have an obvious contribution to the total thermal boundary conductance. Our findings significantly contribute to the understanding of interfacial thermal transport physics and have impact on engineering thermal boundary conductance at interfaces in applications such as electronics thermal management and thermoelectric energy conversion.
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Klein, Louis, Frances L. Doyle, Jaimie C. Northam, Valsamma Eapen, Paul J. Frick, Eva R. Kimonis, David J. Hawes, et al. "Sympathetic nervous system functioning during the face-to-face still-face paradigm in the first year of life." Development and Psychopathology, December 20, 2021, 1–10. http://dx.doi.org/10.1017/s0954579421001553.
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Abstract Contemporary theories of early development and emerging child psychopathology all posit a major, if not central role for physiological responsiveness. To understand infants’ potential risk for emergent psychopathology, consideration is needed to both autonomic reactivity and environmental contexts (e.g., parent–child interactions). The current study maps infants’ arousal during the face-to-face still-face paradigm using skin conductance (n = 255 ethnically-diverse mother–infant dyads; 52.5% girls, mean infant age = 7.4 months; SD = 0.9 months). A novel statistical approach was designed to model the potential build-up of nonlinear counter electromotive force over the course of the task. Results showed a significant increase in infants’ skin conductance between the Baseline Free-play and the Still-Face phase, and a significant decrease in skin conductance during the Reunion Play when compared to the Still-Face phase. Skin conductance during the Reunion Play phase remained significantly higher than during the Baseline Play phase; indicating that infants had not fully recovered from the mild social stressor. These results further our understanding of infant arousal during dyadic interactions, and the role of caregivers in the development of emotion regulation during infancy.
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Duda, John C., Pamela M. Norris, and Patrick E. Hopkins. "On the Linear Temperature Dependence of Phonon Thermal Boundary Conductance in the Classical Limit." Journal of Heat Transfer 133, no. 7 (April 4, 2011). http://dx.doi.org/10.1115/1.4003575.
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We present a new model for predicting thermal boundary conductance in the classical limit. This model takes a different form than those of the traditionally used mismatch theories in the fact that the temperature dependence of thermal boundary conductance is driven by the phononic scattering mechanisms of the materials comprising the interface as opposed to the heat capacities of those materials. The model developed in this work assumes that a phonon on one side of an interface may not scatter at the interface itself but instead scatter with phonons in the adjacent material via the scattering processes intrinsic in the adjacent material. We find that this model is in good agreement with classical molecular dynamics simulations of phonon transport across a Si/Ge interface.
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Geuter, Stephan, Sabrina Boll, Falk Eippert, and Christian Büchel. "Functional dissociation of stimulus intensity encoding and predictive coding of pain in the insula." eLife 6 (May 19, 2017). http://dx.doi.org/10.7554/elife.24770.
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The computational principles by which the brain creates a painful experience from nociception are still unknown. Classic theories suggest that cortical regions either reflect stimulus intensity or additive effects of intensity and expectations, respectively. By contrast, predictive coding theories provide a unified framework explaining how perception is shaped by the integration of beliefs about the world with mismatches resulting from the comparison of these beliefs against sensory input. Using functional magnetic resonance imaging during a probabilistic heat pain paradigm, we investigated which computations underlie pain perception. Skin conductance, pupil dilation, and anterior insula responses to cued pain stimuli strictly followed the response patterns hypothesized by the predictive coding model, whereas posterior insula encoded stimulus intensity. This novel functional dissociation of pain processing within the insula together with previously observed alterations in chronic pain offer a novel interpretation of aberrant pain processing as disturbed weighting of predictions and prediction errors.
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Mazzone, Anna M., and V. Morandi. "A Computational Study on CO Adsorption onto SnO2 Small Grains." MRS Proceedings 900 (2005). http://dx.doi.org/10.1557/proc-0900-o03-15.
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ABSTRACTThe focus of this study is on the adsorption properties of the nanocrystalline materials and SnO2 has been chosen as the appropriate example. Therefore model structures consisting on SnO2 grains with a rutile lattice and a size comparable with the experimental ones have been considered and the adsorbed system is generated by depositing a CO molecule above a tin or oxygen atom on the grain surface. The calculations, based on semi-empirical Hartree-Fock and scattering theories, illustrate the dependence of the binding and adsorption energies of grains on their size and shape and show the effects of these energies on the grain conductance.
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Negrea, Adelina, and Natalia Pavlik. "Biological explanations on criminal behavior." Vector European, no. 1 (May 2022). http://dx.doi.org/10.52507/2345-1106.2022-1.27.
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The literature on the biological explanations for antisocial and criminal behavior is growing considerably. This scientific article will provide a selective analysis of three specific biological factors: psychophysiological (outlining heart rate and skin conductance), brain mechanisms (focusing on aberrations in structure and function of the prefrontal cortex, amygdala and striatum) and genetic factor (highlighting the gender-environment and gene-gene interaction). Therefore, the knowledge and correct perception of the role of biology in antisocial and criminal behavior can contribute to the development of the explanatory power of current research and theories, as well as to inform the authorities in the field and the various treatment options.
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Borys, Przemysław. "The role of passive calcium influx through the cell membrane in galvanotaxis." Cellular and Molecular Biology Letters 18, no. 2 (January 1, 2013). http://dx.doi.org/10.2478/s11658-013-0082-3.
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AbstractPassive calcium influx is one of the theories to explain the cathodal galvanotaxis of cells that utilize the electric field to guide their motion. When exposed to an electric field, the intracellular fluid becomes polarized, leading to positive charge accumulation on the cathodal side and negative charge accumulation on the anodal side. The negative charge on the anodal side attracts extracellular calcium ions, increasing the anodal calcium concentration, which is supposed to decrease the mobile properties of this side. Unfortunately, this model does not capture the Ca2+ dynamics after its presentation to the intracellular fluid. The ions cannot permanently accumulate on the anodal side because that would build a potential drop across the cytoplasm leading to an ionic current, which would carry positive ions (not only Ca2+) from the anodal to the cathodal part through the cytoplasm. If the cytoplasmic conductance for Ca2+ is low enough compared to the membrane conductance, the theory could correctly predict the actual behavior. If the ions move through the cytoplasm at a faster rate, compensating for the passive influx, this theory may fail. This paper contains a discussion of the regimes of validity for this theory.
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Norris, Pamela M., and Patrick E. Hopkins. "Examining Interfacial Diffuse Phonon Scattering Through Transient Thermoreflectance Measurements of Thermal Boundary Conductance." Journal of Heat Transfer 131, no. 4 (February 20, 2009). http://dx.doi.org/10.1115/1.3072928.
Full textAbstract:
Today’s electronic and optoelectronic devices are plagued by heat transfer issues. As device dimensions shrink and operating frequencies increase, ever-increasing amounts of thermal energy are being generated in smaller and smaller volumes. As devices shrink to length scales on the order of carrier mean free paths, thermal transport is no longer dictated by the thermal properties of the materials comprising the devices, but rather the transport of energy across the interfaces between adjacent materials in the devices. In this paper, current theories and experiments concerning phonon scattering processes driving thermal boundary conductance (hBD) are reviewed. Experimental studies of thermal boundary conductance conducted with the transient thermoreflectance technique challenging specific assumptions about phonon scattering during thermal boundary conductance are presented. To examine the effects of atomic mixing at the interface on hBD, a series of Cr/Si samples was fabricated subject to different deposition conditions. The varying degrees of atomic mixing were measured with Auger electron spectroscopy. Phonon scattering phenomena in the presence of interfacial mixing were observed with the trends in the Cr/Si hBD. The experimental results are reviewed and a virtual crystal diffuse mismatch model is presented to add insight into the effect of interatomic mixing at the interface. The assumption that phonons can only transmit energy across the interface by scattering with a phonon of the same frequency—i.e., elastic scattering, can lead to underpredictions of hBD by almost an order of magnitude. To examine the effects of inelastic scattering on hBD, a series of metal/dielectric interfaces with a wide range of vibrational similarity is studied at temperatures above and around materials’ Debye temperatures. Inelastic scattering is observed and new models are developed to predict hBD and its relative dependency on elastic and inelastic scattering events.
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AJ Rebelo, C Jarmain, KJ Esler, RM Cowling, and DC Le Maitre. "Water-use characteristics of Palmiet (Prionium serratum), an endemic South African wetland plant." Water SA 46, no. 4 October (October 27, 2020). http://dx.doi.org/10.17159/wsa/2020.v46.i4.9069.
Full textAbstract:
Palmiet, Prionium serratum, is an endemic wetland plant which dominates oligotrophic wetlands throughout the Cape Floristic Region, South Africa. Palmiet is often perceived as undesirable by landowners, in part because it is thought to have high water-use, although little is known about the water-use of this important wetland species. We estimated the water-use dynamics of Palmiet at the leaf scale, using stomatal conductance measurements, and at the wetland scale, by modelling evapotranspiration using remote sensing and an energy-balance model. Factors that influenced Palmiet water-use were also considered, and seasonal variations were analysed. The aim was to estimate Palmiet wetland water-use, and to develop a set of crop factors (Kc) for use in hydrological modelling of catchments containing Palmiet wetlands. Results show that Palmiet has a comparatively low stomatal conductance (11–152 mmol∙m-2∙s-1), which was lower in summer than winter, and moderate evapotranspiration for a riparian species (1 220 mm∙a-1 compared to a local reference evapotranspiration of 1 302 mm∙a-1 and A-Pan evaporation of 2 809 mm∙a-1), which was higher in summer (more energy to drive evapotranspiration and higher vapour pressure deficits). Morphological and physiological adaptations to nutrient poverty or periodic drought are suggested theories which may explain the controls on transpiration for Palmiet.