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A four-component model of the action potential in mouse detrusor smooth muscle cell
No full textBackground and hypothesis Detrusor smooth muscle cells (DSMCs) of the urinary bladder are electrically connected to one another via gap junctions and form a three dimensional syncytium. DSMCs exhibit spontaneous electrical activity, including passive depolarizations and action potentials. The shapes of spontaneous action potentials (sAPs) observed from a single DSM cell can vary widely. The biophysical origins of this variability, and the precise components which contribute to the complex shapes observed are not known. To address these questions, the basic components which constitute the sAPs were investigated. We hypothesized that linear combinations of scaled versions of these basic components can produce sAP shapes observed in the syncytium. Methods and results The basic components were identified as spontaneous evoked junction potentials (sEJP), native AP (nAP), slow after hyperpolarization (sAHP) and very slow after hyperpolarization (vsAHP). The experimental recordings were grouped into two sets: a training data set and a testing data set. A training set was used to estimate the components, and a test set to evaluate the efficiency of the estimated components. We found that a linear combination of the identified components when appropriately amplified and time shifted replicated various AP shapes to a high degree of similarity, as quantified by the root mean square error (RMSE) measure. Conclusions We conclude that the four basic components D sEJP, nAP, sAHP, and vsAHP D identified and isolated in this work are necessary and sufficient to replicate all varieties of the sAPs recorded experimentally in DSMCs. This model has the potential to generate testable hypotheses that can help identify the physiological processes underlying various features of the sAPs. Further, this model also provides a means to classify the sAPs into various shape classes
Entrainment and mixing in lock-exchange gravity currents using simultaneous velocity-density measurements
No full textGravity currents modify their flow characteristics by entraining ambient fluid, which depends on a variety of governing parameters such as the initial density, Delta rho, the total initial height of the fluid, H, and the slope of the terrain, alpha, from where it is released. It is imperative to study the entrainment dynamics of a gravity current in order to have a clear understanding of mixing transitions that govern the flow physics, the velocity mixing layer thickness, delta(u), and the density mixing layer thickness, delta(rho). Experiments were conducted in a lock-exchange facility in which the dense fluid was separated from the ambient lighter fluid using a gate. As the gate is released instantaneously, an energy conserving gravity current is formed, for which the only governing parameter is the Reynolds number defined as Re = Uh /nu, where U is the front velocity of the gravity current and h is the height of the current. In our study, the bulk Richardson number (inverse of Froude number, Fr), Ri(b) = g'H/U-b(2) = 1, takes a constant value for all the experiments, with U-b being the bulk velocity of the current defined as Ub = root g'H. Simultaneous particle image velocimetry and planar laser induced fluorescence measurement techniques are employed to get the velocity and density statistics. Using the buoyancy conservation equation, a new flux-based method was formulated for calculating the entrainment coefficient, E-F, near the front and head of the propagating gravity current for a Reynolds number range of Re approximate to 485-12 270 used in our experiments. At the head of the current, the results show a mixing transition at Re approximate to 2700 that is attributed to the flowtransitioning from weak Holmboewaves toKelvin-Helmholtz instabilities, in the form of Kelvin-Helmholtz vortex rolls. Following this mixing transition, the entrainment coefficient continued to increase with increasing Reynolds number owing to the occurrence of three-dimensional Kelvin-Helmholtz billows that promote further small-scale local mixing. Such a mixing transition indicates that a fully turbulent state is not reached even at Re = 12 270 and the amount of entrainment and ensuing mixing depends on the type of flow instability and presence of small-scale secondary structures. The entrainment dynamics were further substantiated using the ratio of delta(u) and delta(rho). It was observed that delta(u)/delta(rho) decreases with increasing Re and reaches a constant value of delta(u)/delta(rho) approximate to 1 at high values of Re. This trend is in contrast to the entrainment coefficient E-F, which never reaches a constant value even at high enough Re. This disparity could be explained by the fact that E-F accounts for small-scale scalar mixing, which is not captured by the ratio of mixing layer thicknesses. Experimentally, it was also observed that the E-F value near the front of gravity current was 2-9 times higher than the head value depending on the value of the Reynolds numbers. At low Reynolds numbers, the entrainment near the front is an order of magnitude higher than the head and the value decreases with increasing Re. This could be attributed to different modes of entrainment near the front (dominated by vortical structures) and the head (dominated by turbulent flux exchange triggered by the nature of the flow instability). The results from this study improve our understanding of entrainment dynamics and would be useful in developing empirical parameterizations for mixing in stratified flows. Published by AIP Publishing
Investigating the performance of snowmelt runoff model using temporally varying near-surface lapse rate in Western Himalayas
No full textThe present study assesses the effect of accounting the temporal variation of near-surface lapse rate in the conceptual, degree-day snowmelt runoff model simulations in a cold-desert region of Himalayas. The nearsurface lapse rate over Spiti basin shows seasonal variation during a year. The results obtained show that the inclusion of monthly variation of lapse rate in the hydrological modelling is able to capture the observed hydrograph more efficiently than when an annually constant value of lapse rate is employed. Based on our results and considering the available data, a monthly representation of near-surface lapse rates in the temperature index based models is recommended for Himalayan basins
Uncertainty quantification of Kinetic Monte Carlo models constructed on-the-fly using molecular dynamics
No full textKinetic Monte Carlo (KMC) models of complex materials and biomolecules are increasingly being constructed using molecular dynamics (MD). A KMC model contains a catalog of states and kinetic pathways, which enables study of the dynamics. The completeness of the catalog is crucial to the model accuracy and is linked to the quality of the MD data used for model construction. Therefore, quantifying the uncertainty clue to missing states and pathways is important. A review on computational procedures available for on-the-fly KMC model construction using MD, uncertainty measurement, and algorithms for guiding further MD sampling in an accelerated manner is presented
Plasma-assisted As implants for effective work function modulation of TiN/HfO2 gate stacks on germanium
No full textThe plasma assisted As doping (PLAD) technique is used to demonstrate multiple flatband voltages (multi-V-fb) on TiN/HfO2 Ge gate stacks for n-FinFET applications. Through detailed studies with varying doses, implant energies, and TiN cap thicknesses, we show that the PLAD As technique can be used to obtain effective work function (EWF) modulation from the near midgap to the conduction band edge (up to 280 meV) of Ge, a key technological requirement for multi-threshold voltage (V-T) Ge n-FinFETs. Furthermore, there is no deterioration of key gate stack parameters such as gate leakage, effective oxide thickness, and gate/channel interface trap densities. From secondary ion mass spectroscopy data, we attribute the tuning of EWF to As accumulation and interfacial dipole formation at the TiN/HfO2 interface. The experimental observations are reinforced by ab initio simulations of near-interface As substitutions at the TiN/HfO2 interface. As substitution at N sites near the interface reduces the EWF, making it more suitable for n-MOS applications. Published by AIP Publishing
Herring-Flicker coupling and thermal quantum correlations in bipartite system
No full textIn this paper, we study thermal quantum correlations as quantum discord and entanglement in bipartite system imposed by external magnetic field with Herring-Flicker coupling, i.e., J (R) = 1.642e(-2R) R-5/2 + O(R(2)e(-2R)). The Herring-Flicker coupling strength is the function of R, which is the distance between spins and systems carry XXX Heisenberg interaction. By tuning the coupling distance R, temperature and magnetic field quantum correlations can be scaled in the bipartite system. We find the long sustainable behavior of quantum discord in comparison with entanglement over the coupling distance R. We also investigate the situations, where entanglement totally dies but quantum discord exists in the system
Schematic Harder-Narasimhan stratification for families of principal bundles in higher dimensions
No full textLet G be a connected split reductive group over a field k of characteristic zero. Let be a smooth projective morphism of k-schemes, with geometrically connected fibers. We formulate a natural definition of a relative canonical reduction, under which principal G-bundles of any given Harder-Narasimhan type on fibers of X / S form an Artin algebraic stack over S, and as varies, these stacks define a stratification of the stack by locally closed substacks. This result extends to principal bundles in higher dimensions the earlier such result for principal bundles on families of curves. The result is new even for vector bundles, that is, for G = GL(n,k)
A note on the weight spectrum of the Schubert code C-alpha(2, m)
No full textWe consider the Schubert code Ca(2, m) associated to the Fq -rational points of the Schubert variety Qa(2, m) in the Grassmannian G2, m. A correspondence between codewords of Ca(2, m) and skew-symmetric matrices of certain special form is given. Using this correspondence, we give a formula for all possible weights of codewords in Ca(2, m). It is shown that the weight of each codeword is divisible by certain power of q. Further, a formula for the weight spectrum of the Schubert code Ca(2, m) is given
Substituted versus Naked Thiourea Ligand Containing Pseudotetrahedral Cobalt(II) Complexes: A Comparative Study on Its Magnetization Relaxation Dynamics Phenomenon
No full textA series of mononuclear tetrahedral cobalt(II) complexes with the general molecular formula [Co(L-1)(2)X-2] [where L-1 = tetramethylthiourea ([(CH3)(2)N](2)C=S) and X = Cl (1), Br (2), and I (3)] were isolated, and their structures were characterized by single-crystal X-ray diffraction. The experimental direct-current magnetic data are excellently " reproduced by fitting both chi T-M(T) and M(H) simultaneously using the spin Hamiltonian (SH) parameters D-1 = 18.1 cm(-1) and g(1,iso) = 2.26, D-2 = 16.4 cm(-1) and g(2,iso) = 2.33, and D-3 = -22 cm(-1) and g(3,iso) 2.4 for 1-3, respectively, and the sign of D was unambiguously confirmed from X-band electron paramagnetic resonance measurements. The effective energy barrier extracted for the magnetically diluted complexes 1-3 (10%) is larger than the barrier observed for the pure samples and implies a nonzero contribution of dipolar interaction to the magnetization relaxation dynamics. The SH parameters extracted for the three complexes drastically differ from their respective parent complexes that possess the general molecular formula [Co(L)(2)X-2] [where L = thiourea [(NH2)(2)C=S] and X = Cl (la), Br (2a), and I (3a)], which is rationalized by detailed ab initio calculations. An exhaustive theoretical study reveals that both the ground and excited states are not pure but rather multideterminental in nature (1-3). Noticeably, the substitution of L by L, induces structural distortion in 1-3 on the level of the secondary coordination sphere compared to 1a-3a. This distortion leads to an overall reduction in vertical bar E/D vertical bar of 1-3 compared to 1a-3a. This may be one of the reasons for the origin of the slower relaxation times of 1-3 compared to 1a-3a
Design and Characterization of a Soft Dielectric Elastomer Peristaltic Pump Driven by Electromechanical Load
No full textPumps are widely used in nature and engineering to transport fluids, particles, and mixtures. Compared to those in engineering, most natural pumps are soft, highly efficient, and reliable. In this paper, we design a soft dielectric elastomer peristaltic pump (DEPP) inspired by the human heart. The DEPP is composed of two pump modules and each module consists of four layers of dielectric elastomer membrane and three layers of carbon grease as electrodes. The two pump modules are driven by two complementary signals with different waveforms including square, sine, sawtooth, and triangular waves. We build a measuring system including pressure and flow rate sensors to characterize the DEPP's performance. The experimental results reveal that the square wave voltage provides the highest flow rate and pressure difference compared to the other three waveforms. The mechanical resonance of DEPP is observed and the optimal frequency with square wave voltage is about 1.5 Hz, which falls in the range of the human heart rate. The optimal frequency decreases with the increase of electromechanical loads. In the experiment, compared with the existing dielectric elastomer pump, we obtain the highest average flow rate and the highest instant flow rate as 2.5 L/min and 3.2 L/min, respectively. The maximum pump volume per cycle for the DEPP is 0.09 L. It takes about 1 s for the DEPP to reach a new equilibrium state when the working frequency of the voltage is switched from 1 to 1.5 Hz. It is hoped that this study will guide the development of new artificial hearts and other soft industrial pumps