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In order to further improve the stability of the composite axis aviation photoelectric stabilization platform, a control method of negative effect compensation of disturbance (NECOD) is proposed and applied to the voice-coil fast steering mirror adjusting the optical path of the platform. The experimental results show that the control accuracy and closed-loop bandwidth of the voice-coil fast steering mirror based on NECOD have been greatly improved, while its advantages of large stroke are not possessed by piezoelectric fast mirror. The experimental results of high-frequency turntable and vibration table show that NECOD proposed in this paper has better antidisturbance performance than DOB and ARC, and its parameters are less and easy to adjust. It is proved that the robustness of NECOD is very strong in the presence of 20% parameter perturbation. The final LOS stabilization accuracy experiment shows that the NECOD voice-coil fast steering mirror proposed in this paper fully meets the performance requirements of high-precision aviation photoelectric stabilization platform, and has high practical value for improving the antidisturbance performance of the control system of aviation photoelectric stabilization platform. [ABSTRACT FROM AUTHOR]

We present a derivation of a coarse-grained description, in the form of a generalized Langevin equation, from the Langevin dynamics model that describes the dynamics of bio-molecules. The focus is placed on the form of the memory kernel function, the colored noise, and the second fluctuation-dissipation theorem that connects them. Also presented is a hierarchy of approximations for the memory and random noise terms, using rational approximations in the Laplace domain. These approximations offer increasing accuracy. More importantly, they eliminate the need to evaluate the integral associated with the memory term at each time step. Direct sampling of the colored noise can also be avoided within this framework. Therefore, the numerical implementation of the generalized Langevin equation is much more efficient. [ABSTRACT FROM AUTHOR]

We present the reduction of generalized Langevin equations to a coordinate-only stochastic model, which in its exact form involves a forcing term with memory and a general Gaussian noise. It will be shown that a similar fluctuation-dissipation theorem still holds at this level. We study the approximation by the typical Brownian dynamics as a first approximation. Our numerical test indicates how the intrinsic frequency of the kernel function influences the accuracy of this approximation. In the case when such an approximate is inadequate, further approximations can be derived by embedding the nonlocal model into an extended dynamics without memory. By imposing noises in the auxiliary variables, we show how the second fluctuation-dissipation theorem is still exactly satisfied. [ABSTRACT FROM AUTHOR]

We present a numerical method to approximate the memory functions in the generalized Langevin models for the collective dynamics of macromolecules. We first derive the exact expressions of the memory functions, obtained from projection to subspaces that correspond to the selection of coarsegrain variables. In particular, the memory functions are expressed in the forms of matrix functions, which will then be approximated by Krylov-subspace methods. It will also be demonstrated that the random noise can be approximated under the same framework, and the second fluctuation-dissipation theorem is automatically satisfied. The accuracy of the method is examined through several numerical examples. [ABSTRACT FROM AUTHOR]

We present a first-principle based approach that leads from a many-particle description to a nonlinear, stochastic constitutive relation for the modeling of transient heat conduction processes at the nano-mechanical scale. By enforcing statistical consistency, in that the statistics of local energy is consistent with that from an all-atom description, we identify the driving force as well as the model parameters in these generalized constitutive models. The connections to established generalized constitutive relations, including Cattaneo-Vernotte-type models, will be demonstrated. [ABSTRACT FROM AUTHOR]

We derive a coarse-grained model for heat conduction in nanoscale mechanical systems. Starting with an all-atom description, this approach yields a reduced model, in the form of conservation laws of momentum and energy. The model closure is accomplished by introducing a quasilocal thermodynamic equilibrium, followed by a linear response approximation. Of particular interest is the constitutive relation for the heat flux, which is expressed nonlocally in terms of the spatial and temporal variation of the temperature. Nanowires made of copper and silicon are presented as examples. [ABSTRACT FROM AUTHOR]

We study three quasi-continuum approximations of a lattice model for crack propagation. The influence of the approximation on the bifurcation patterns is investigated. The estimate of the modeling error is applicable to near and beyond bifurcation points, which enables us to evaluate the approximation over a finite range of loading and multiple mechanical equilibria. [ABSTRACT FROM AUTHOR]

Outer hair cells (OHC) function as both receptors and effectors in providing a boost to auditory reception. Amplification is driven by the motor protein prestin, which is under anionic control. Interestingly, we now find that the major, 4-AP-sensitive, outward K+ current of the OHC (IK) is also sensitive to Cl-, although, in contrast to prestin, extracellularly. IK is inhibited by reducing extracellular Cl- levels, with a linear dependence of 0.4%/mM. Other voltage-dependent K+ (Kv) channel conductances in supporting cells, such as Hensen and Deiters' cells, are not affected by reduced extracellular Cl-. To elucidate the molecular basis of this Cl--sensitive IK, we looked at potential molecular candidates based on Cl- sensitivity and/or similarities in kinetics. For IK, we identified three different Ca2+-independent components of IK based on the time constant of inactivation: a fast, transient outward current, a rapidly activating, slowly inactivating current (Ik1), and a slowly inactivating current (Ik2). Extracellular Cl- differentially affects these components. Because the inactivation time constants of Ik1 and Ik2 are similar to those of Kv1.5 and Kv2.1, we transiently transfected these constructs into CHO cells and found that low extracellular Cl- inhibited both channels with linear current reductions of 0.38%/mM and 0.49%/mM, respectively. We also tested heterologously expressed Slick and Slack conductances, two intracellularly Cl--sensitive K+ channels, but found no extracellular Cl- sensitivity. The Cl- sensitivity of Kv2.1 and its robust expression within OHCs verified by single-cell RT-PCR indicate that these channels underlie the OHC's extracellular Cl- sensitivity. [ABSTRACT FROM AUTHOR]

We present a multiscale model for numerical simulation of dynamics of crystalline solids. The method couples nonlinear elastodynamics as the continuum description and molecular dynamics as another component at the atomic scale. The governing equations on the macroscale are solved by the discontinuous Galerkin method, which is built up with an appropriate local curl-free space to produce a coherent displacement field. The constitutive data are based on the underlying atomistic model: it is either calibrated prior to the computation or obtained from molecular dynamics as the computation proceeds. The decision to use either the former or the latter is made locally for each cell based on suitable criteria. [ABSTRACT FROM AUTHOR]

We present a class of exponential integrators to compute solutions of the stochastic Schrödinger equations arising from the modeling of open quantum systems. To be able to implement the methods within the same framework as the deterministic counterpart, we express the solution using Kunita's representation. With appropriate truncations, the solution operator can be written as matrix exponentials, which can be efficiently implemented by the Krylov subspace projection. The accuracy is examined in terms of the strong convergence by comparing trajectories, and in terms of the weak convergence by comparing the density-matrix operators. We show that the local accuracy can be further improved by introducing third-order commutators in the exponential. The effectiveness of the proposed methods is tested using the example from Di Ventra et al. [J. Phys.: Condens. Matter 16, 8025 (2004)]. [ABSTRACT FROM AUTHOR]

Absorbing boundary conditions are presented for three-dimensional time-dependent Schrödinger-type of equations as a means to reduce the cost of the quantum-mechanical calculations. The boundary condition is first derived from a semidiscrete approximation of the Schrödinger equation with the advantage that the resulting formulas are automatically compatible with the finite-difference scheme and no further discretization is needed in space. The absorbing boundary condition is expressed as a discrete Dirichlet-to-Neumann map, which can be further approximated in time by using rational approximations of the Laplace transform to enable a more efficient implementation. This approach can be applied to domains with arbitrary geometry. The stability of the zeroth-order and first-order absorbing boundary conditions is proved. We tested the boundary conditions on benchmark problems. The effectiveness is further verified by a time-dependent Hartree-Fock model with Skyrme interactions. The accuracy in terms of energy and nucleon density is examined as well. [ABSTRACT FROM AUTHOR]

The Mori-Zwanzig formalism for coarse-graining a complex dynamical system typically introduces memory effects. The Markovian assumption of delta-correlated fluctuating forces is often employed to simplify the formulation of coarse-grained (CG) models and numerical implementations. However, when the time scales of a system are not clearly separated, the memory effects become strong and the Markovian assumption becomes inaccurate. To this end, we incorporate memory effects into CG modeling by preserving non-Markovian interactions between CG variables, and the memory kernel is evaluated directly from microscopic dynamics. For a specific example, molecular dynamics (MD) simulations of star polymer melts are performed while the corresponding CG system is defined by grouping many bonded atoms into single clusters. Then, the effective interactions between CG clusters as well as the memory kernel are obtained from the MD simulations. The constructed CG force field with a memory kernel leads to a non-Markovian dissipative particle dynamics (NM-DPD). Quantitative comparisons between the CG models with Markovian and non-Markovian approximations indicate that including the memory effects using NM-DPD yields similar results as the Markovian-based DPD if the system has clear time scale separation. However, for systems with small separation of time scales, NM-DPD can reproduce correct short-time properties that are related to how the system responds to high-frequency disturbances, which cannot be captured by the Markovian-based DPD model. [ABSTRACT FROM AUTHOR]

A new formulation of a boundary element method (BEM) is proposed in this paper to simulate cracks at the micron scale. The main departure from the traditional BEMs is that the current model is derived from the underlying atomistic model, which involves the interactions of atoms at the scale of Angstroms. By using the lattice Green’s function, the new BEM formulation eliminates the excessive atomic degrees of freedom away from crack tips, and directly couples the process zones with the physical boundary conditions. We show that with such a drastic reduction, one can simulate brittle fracture process on the scale of microns, for which the entire system consists of a few billion atoms. We discuss several numerical issues to make the implementation more efficient. Examples will be presented for cracks in the bcc iron system. [ABSTRACT FROM AUTHOR]

Results from molecular dynamics simulations often need to be further processed to understand the physics on a larger scale. This paper considers the definitions of momentum and energy fluxes obtained from a control-volume approach. To assess the validity of these defined quantities, two consistency criteria are proposed. As examples, the embedded atom potential and the Tersoff potential are considered. The consistency is verified using analytical and numerical methods. [ABSTRACT FROM AUTHOR]

We present a data-driven approach to determine the memory kernel and random noise in generalized Langevin equations. To facilitate practical implementations, we parameterize the kernel function in the Laplace domain by a rational function, with coefficients directly linked to the equilibrium statistics of the coarse-grain variables. We show that such an approximation can be constructed to arbitrarily high order and the resulting generalized Langevin dynamics can be embedded in an extended stochastic model without explicit memory. We demonstrate how to introduce the stochastic noise so that the second fluctuation-dissipation theorem is exactly satisfied. Results from several numerical tests are presented to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Two systems of hyperbolic equations, arising in the multiphase semiclassical limit of the linear Schrödinger equations, are investigated. One stems from a Wigner measure analysis and uses a closure by the Delta functions, whereas the other relies on the classical WKB expansion and uses the Heaviside functions for closure. The two resulting moment systems are weakly and non-strictly hyperbolic respectively. They provide two different Eulerian methods able to reproduce superimposed signals with a finite number of phases. Analytical properties of these moment systems are investigated and compared. Efficient numerical discretizations and test-cases with increasing difficulty are presented. [ABSTRACT FROM AUTHOR]

Studies several kinetic approximations-based schemes of first- or second-order accuracy to solve pressureless and isothermal gas dynamics equations. Godunov method; Riemann solver; Discrete entropy inequalities.

Cancer cachexia is a life-threatening syndrome characterized by muscle atrophy. Cancer cachectic muscle atrophy (CCMA) is associated with mitochondrial injury. Mitochondrial calpains have been reported to induce mitochondrial injury in mouse cardiomyocytes and pulmonary smooth muscle. In the present study, the presence of calpain in the mitochondria of skeletal muscle and its potential role in CCMA were investigated. Transwell plates were used to develop a myotube-carcinoma cell co-culture model to simulate the cancer cachexia environment in vitro. The calpain inhibitors, calpastatin (CAST) and calpeptin (CAPT), were used to inhibit calpain activity in myotubes during co-culture. Calpain-1, calpain-2 and CAST were found to be present in mouse myotube mitochondria. Co-culture activated calpain in both cytoplasm and mitochondria, which caused myotube atrophy. CAST and CAPT treatment prevented calpain activation in both cytoplasm and mitochondria, which inhibited myotube atrophy during co-culture. Additionally, CAST and CAPT treatment increased mitochondrial complex I activity, decreased mitochondrial permeability transition pore opening and improved mitochondrial membrane potential in myotubes during co-culture. In addition, CAST and CAPT treatment increased AKT/mTOR activity, inhibited FoxO3a activity and decreased atrogin-1 content in myotubes during co-culture. The present findings provide new insights to understand the mechanism of CCMA and further help the development of focused approaches to treat CCMA by manipulating the mitochondrial and cytosolic calpain activity. [ABSTRACT FROM AUTHOR]

A necessity exists for the protection of people and their property against the unauthorized use of photoelectric devices. The retroreflection of optical systems can be utilized to detect and recognize photoelectric devices. The reduction of false alarms and processing speed are two crucial issues, particularly for interior applications involving complex scenes. Here, we propose a local texture criterion that determines the local maximum and local continuity of the reflections. A comprehensive evaluation method that combines a modified shape criterion and the local texture criterion to improve the recognition probability is also presented. A searching strategy for scanning and locating the target candidates with reduced time cost was used in laboratory experiments performed at operating distances of 2.2, 3.2, and 4.2 m with the presence of disturbing objects. The results demonstrated the practicability of the proposed method, its superior recognition probability over that of single-criterion methods, and its enhanced average processing speed in comparison with existing methods. [ABSTRACT FROM AUTHOR]

Background: Pre-diabetes is a growing health concern where a large percentage of these patients develop full type 2 diabetes. Effective interventions on pre-diabetes can prevent or delay the occurrence or development of diabetes. Pharmaco-dynamics and pre-clinical of JinQi-Jiangtang tablets (JQJT) suggest that it could be benefit for pre-diabetes. Methods/Design: Randomized controlled trial (RCT) is implemented in this study. The study term is 24 months (12 months for intervention and 12 months for follow up). Participants are recruited from four cities of China: Beijing, Tianjin, Xi'an and Nanning. Four hundred participants are randomized to treatment group (JQJT tablets) and control group (Placebo); two hundred participants each. People being included in this study must have been diagnosed as pre-diabetes via western medicine criteria and traditional Chinese medicine (TCM) criteria. The endpoint indexes include: incidence of diabetes mellitus and reversion rate. Primary outcome indexes include: oral glucose tolerance test; insulin releasing test; glycosylated hemoglobin (HA1c). Secondary outcome indexes include: score of the Short Form 36 Health Survey Questionnaire (SF-36); score of TCM symptoms; blood lipid test. Indexes of safety include: general medical examination; blood and urine regular test; electrocardiogram (ECG), liver function (ALT) and renal function (BUN, Creatinine) test; record of adverse event, such as headache, faint, etc. Qualitative control will be implemented and a number of standard operating processes (SOPs) will be formed throughout the study: laboratory quality control measures; compliance control for researchers and participants; researcher training before study; supervision; investigational drug management and others. Discussion: The aim of this study is to evaluate the effectiveness and safety of JinQi JiangTang (JQJT) tablets for the treatment of patients with pre-diabetes. Trial registration: Chinese clinical trials register ChiCTR-TRC-00000401 [ABSTRACT FROM AUTHOR]