International Nuclear Information System (INIS)
Erpenbeck, J.J.
1987-01-01
We apply the so-called ''synthetic'' nonequilibrium molecular-dynamics method to the calculation of the self-diffusion constant of a Lennard-Jones fluid at a number density of 0.85/σ 3 and a temperature of 1.08 epsilon-c/k/sub B/ (where epsilon-c and σ are the energy and length parameters of the potential and k/sub B/ is the Boltzmann constant). By comparing with the Green-Kubo calculation for the same state of the system and for the same number of particles, N, we find the latter calculation to yield more precise values of the self-diffusion constant for a given number of molecular-dynamics time steps. Even at small values of the diffusion current, a nontrivial time is needed for the nonequilibrium calculation to reach the steady state. For larger values of the driving force, the steady-state flow appears to become unstable and evidence of a secondary flow pattern is presented. The presence of these instabilities acts as a limit to the range of the driving force for which the steady-state method can be applied. With increasing N the range of stable values of the diffusion current density decreases. For the Green-Kubo calculations, the N dependence of the self-diffusion constant is found to be anomalous for N = 108, with the 1/N dependence only exhibited for at least 500 particles. The nonequilibrium results, while approximately independent of N for 108 and 500 particles, are found to have a similar anomalous N dependence when we extend the calculations to 1372 particles, thereby bringing the Green-Kubo and nonequilibrium results into agreement in the large-system limit
Green--Kubo formula for collisional relaxation
International Nuclear Information System (INIS)
Visscher, P.B.
1988-01-01
In this paper we generalize the Green--Kubo method (usually used for obtaining formulas for transport coefficients involving conserved densities) to relaxation processes occurring during collisions, such as the transfer of energy from vibrational to translational modes in a molecular fluid. We show that the relaxation rate can be calculated without evaluating time correlation functions over long times, and can in fact be written as a sum over collisions which makes the relation between the Green--Kubo method and approximate independent-collision models much clearer
The Green-Kubo formula for locally interacting fermionic open systems
Jaksic, V; Pillet, C A
2006-01-01
We consider a model describing finitely many free Fermi gas reservoirs coupled by local interactions and prove the Green-Kubo formulas and the Onsager reciprocity relations for heat and charge fluxes generated by temperature and chemical potential differentials.
The Green-Kubo formula for general Markov processes with a continuous time parameter
International Nuclear Information System (INIS)
Yang Fengxia; Liu Yong; Chen Yong
2010-01-01
For general Markov processes, the Green-Kubo formula is shown to be valid under a mild condition. A class of stochastic evolution equations on a separable Hilbert space and three typical infinite systems of locally interacting diffusions on Z d (irreversible in most cases) are shown to satisfy the Green-Kubo formula, and the Einstein relations for these stochastic evolution equations are shown explicitly as a corollary.
Shear viscosity of the Lennard-Jones fluid near the triple point: Green-Kubo results
International Nuclear Information System (INIS)
Erpenbeck, J.J.
1988-01-01
The long-standing disagreement over the shear viscosity coefficient of the Lennard-Jones fluid near the triple point is reexamined through a series of very extensive Monte Carlo molecular-dynamics calculations of this transport coefficient based on the Green-Kubo theory. The stress autocorrelation function is shown to exhibit a slow decay, principally in the kinetic-potential and the potential-potential terms, which is large compared with the kinetic-kinetic long-time tail predicted by simple mode-coupling theory. Nonetheless, the viscosity coefficient, exclusive of any correction for this tail for times greater than are accessible numerically, is found to agree with that of Schoen and Hoheisel (who discounted the existence of such a tail) as well as nonequilibrium molecular-dynamics calculations. The large value of the viscosity coefficient found by Levesque and co-workers for 864 particles is brought into statistical agreement with the present results by a modest, but not unrealistic, increase in its statistical uncertainty. The pressure is found to exhibit an anomalous dependence on the size of the system, but the viscosity as well as the self-diffusion constant appear to be linear in the inverse of the number of particles, within the precision of our calculations. The viscosity coefficient, including a long-time-tail contribution based on the extended mode-coupling theory is (3.796 +- 0.068)σepsilon-c/m)/sup 1/2/ for the Lennard-Jones potential, fitted to a cubic spline, and (3.345 +- 0.068)σepsilon-c/m)/sup 1/2/ for the potential truncated at 2.5σ
International Nuclear Information System (INIS)
Hoover, W.G.; Evans, D.J.; Hickman, R.B.; Ladd, A.J.C.; Ashurst, W.T.; Moran, B.
1980-01-01
A new Hamiltonian method for deformation simulations is related to the Green-Kubo fluctuation theory through perturbation theory and linear-response theory. Numerical results for the bulk and shear viscosity coefficients are compared to corresponding Green-Kubo calculations. Both viscosity coefficients depend similarly on frequency, in a way consistent with enhanced ''long-time tails.''
Danel, J.-F.; Kazandjian, L.; Zérah, G.
2012-06-01
Computations of the self-diffusion coefficient and viscosity in warm dense matter are presented with an emphasis on obtaining numerical convergence and a careful evaluation of the standard deviation. The transport coefficients are computed with the Green-Kubo relation and orbital-free molecular dynamics at the Thomas-Fermi-Dirac level. The numerical parameters are varied until the Green-Kubo integral is equal to a constant in the t→+∞ limit; the transport coefficients are deduced from this constant and not by extrapolation of the Green-Kubo integral. The latter method, which gives rise to an unknown error, is tested for the computation of viscosity; it appears that it should be used with caution. In the large domain of coupling constant considered, both the self-diffusion coefficient and viscosity turn out to be well approximated by simple analytical laws using a single effective atomic number calculated in the average-atom model.
Scaling Green-Kubo Relation and Application to Three Aging Systems
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A. Dechant
2014-02-01
Full Text Available The Green-Kubo formula relates the spatial diffusion coefficient to the stationary velocity autocorrelation function. We derive a generalization of the Green-Kubo formula that is valid for systems with long-range or nonstationary correlations for which the standard approach is no longer valid. For the systems under consideration, the velocity autocorrelation function ⟨v(t+τv(t⟩ asymptotically exhibits a certain scaling behavior and the diffusion is anomalous, ⟨x^{2}(t⟩≃2D_{ν}t^{ν}. We show how both the anomalous diffusion coefficient D_{ν} and the exponent ν can be extracted from this scaling form. Our scaling Green-Kubo relation thus extends an important relation between transport properties and correlation functions to generic systems with scale-invariant dynamics. This includes stationary systems with slowly decaying power-law correlations, as well as aging systems, systems whose properties depend on the age of the system. Even for systems that are stationary in the long-time limit, we find that the long-time diffusive behavior can strongly depend on the initial preparation of the system. In these cases, the diffusivity D_{ν} is not unique, and we determine its values, respectively, for a stationary or nonstationary initial state. We discuss three applications of the scaling Green-Kubo relation: free diffusion with nonlinear friction corresponding to cold atoms diffusing in optical lattices, the fractional Langevin equation with external noise recently suggested to model active transport in cells, and the Lévy walk with numerous applications, in particular, blinking quantum dots. These examples underline the wide applicability of our approach, which is able to treat very different mechanisms of anomalous diffusion.
Jones, Reese E.; Mandadapu, Kranthi K.
2012-04-01
We present a rigorous Green-Kubo methodology for calculating transport coefficients based on on-the-fly estimates of: (a) statistical stationarity of the relevant process, and (b) error in the resulting coefficient. The methodology uses time samples efficiently across an ensemble of parallel replicas to yield accurate estimates, which is particularly useful for estimating the thermal conductivity of semi-conductors near their Debye temperatures where the characteristic decay times of the heat flux correlation functions are large. Employing and extending the error analysis of Zwanzig and Ailawadi [Phys. Rev. 182, 280 (1969)], 10.1103/PhysRev.182.280 and Frenkel [in Proceedings of the International School of Physics "Enrico Fermi", Course LXXV (North-Holland Publishing Company, Amsterdam, 1980)] to the integral of correlation, we are able to provide tight theoretical bounds for the error in the estimate of the transport coefficient. To demonstrate the performance of the method, four test cases of increasing computational cost and complexity are presented: the viscosity of Ar and water, and the thermal conductivity of Si and GaN. In addition to producing accurate estimates of the transport coefficients for these materials, this work demonstrates precise agreement of the computed variances in the estimates of the correlation and the transport coefficient with the extended theory based on the assumption that fluctuations follow a Gaussian process. The proposed algorithm in conjunction with the extended theory enables the calculation of transport coefficients with the Green-Kubo method accurately and efficiently.
Spatial resolution of the electrical conductance of ionic fluids using a Green-Kubo method
Jones, R. E.; Ward, D. K.; Templeton, J. A.
2014-11-01
We present a Green-Kubo method to spatially resolve transport coefficients in compositionally heterogeneous mixtures. We develop the underlying theory based on well-known results from mixture theory, Irving-Kirkwood field estimation, and linear response theory. Then, using standard molecular dynamics techniques, we apply the methodology to representative systems. With a homogeneous salt water system, where the expectation of the distribution of conductivity is clear, we demonstrate the sensitivities of the method to system size, and other physical and algorithmic parameters. Then we present a simple model of an electrochemical double layer where we explore the resolution limit of the method. In this system, we observe significant anisotropy in the wall-normal vs. transverse ionic conductances, as well as near wall effects. Finally, we discuss extensions and applications to more realistic systems such as batteries where detailed understanding of the transport properties in the vicinity of the electrodes is of technological importance.
Spatial resolution of the electrical conductance of ionic fluids using a Green-Kubo method.
Jones, R E; Ward, D K; Templeton, J A
2014-11-14
We present a Green-Kubo method to spatially resolve transport coefficients in compositionally heterogeneous mixtures. We develop the underlying theory based on well-known results from mixture theory, Irving-Kirkwood field estimation, and linear response theory. Then, using standard molecular dynamics techniques, we apply the methodology to representative systems. With a homogeneous salt water system, where the expectation of the distribution of conductivity is clear, we demonstrate the sensitivities of the method to system size, and other physical and algorithmic parameters. Then we present a simple model of an electrochemical double layer where we explore the resolution limit of the method. In this system, we observe significant anisotropy in the wall-normal vs. transverse ionic conductances, as well as near wall effects. Finally, we discuss extensions and applications to more realistic systems such as batteries where detailed understanding of the transport properties in the vicinity of the electrodes is of technological importance.
Systematic errors in transport calculations of shear viscosity using the Green-Kubo formalism
Rose, J. B.; Torres-Rincon, J. M.; Oliinychenko, D.; Schäfer, A.; Petersen, H.
2018-05-01
The purpose of this study is to provide a reproducible framework in the use of the Green-Kubo formalism to extract transport coefficients. More specifically, in the case of shear viscosity, we investigate the limitations and technical details of fitting the auto-correlation function to a decaying exponential. This fitting procedure is found to be applicable for systems interacting both through constant and energy-dependent cross-sections, although this is only true for sufficiently dilute systems in the latter case. We find that the optimal fit technique consists in simultaneously fixing the intercept of the correlation function and use a fitting interval constrained by the relative error on the correlation function. The formalism is then applied to the full hadron gas, for which we obtain the shear viscosity to entropy ratio.
Hydrodynamic modes, Green-Kubo relations, and velocity correlations in dilute granular gases
International Nuclear Information System (INIS)
Brey, J Javier; Ruiz-Montero, M J; Maynar, P; Garcia de Soria, M I
2005-01-01
It is shown that the hydrodynamic modes of a dilute granular gas of inelastic hard spheres can be identified, and calculated in the long wavelength limit. Assuming they dominate at long times, formal expressions for the Navier-Stokes transport coefficients are derived. They can be expressed in a form that generalizes the Green-Kubo relations for molecular systems, and it is shown that they can also be evaluated by means of N-particle simulation methods. The form of the hydrodynamic modes to zeroth order in the gradients is used to detect the presence of inherent velocity correlations in the homogeneous cooling state, even in the low density limit. They manifest themselves in the fluctuations of the total energy of the system. The theoretical predictions are shown to be in agreement with molecular dynamics simulations. Relevant related questions deserving further attention are pointed out
Green-Kubo relations for the viscosity of biaxial nematic liquid crystals
Sarman, Sten
1996-09-01
We derive Green-Kubo relations for the viscosities of a biaxial nematic liquid crystal. In this system there are seven shear viscosities, three twist viscosities, and three cross coupling coefficients between the antisymmetric strain rate and the symmetric traceless pressure tensor. According to the Onsager reciprocity relations these couplings are equal to the cross couplings between the symmetric traceless strain rate and the antisymmetric pressure. Our method is based on a comparison of the microscopic linear response generated by the SLLOD equations of motion for planar Couette flow (so named because of their close connection to the Doll's tensor Hamiltonian) and the macroscopic linear phenomenological relations between the pressure tensor and the strain rate. In order to obtain simple Green-Kubo relations we employ an equilibrium ensemble where the angular velocities of the directors are identically zero. This is achieved by adding constraint torques to the equations for the molecular angular accelerations. One finds that all the viscosity coefficients can be expressed as linear combinations of time correlation function integrals (TCFIs). This is much simpler compared to the expressions in the conventional canonical ensemble, where the viscosities are complicated rational functions of the TCFIs. The reason for this is, that in the constrained angular velocity ensemble, the thermodynamic forces are given external parameters whereas the thermodynamic fluxes are ensemble averages of phase functions. This is not the case in the canonical ensemble. The simplest way of obtaining numerical estimates of viscosity coefficients of a particular molecular model system is to evaluate these fluctuation relations by equilibrium molecular dynamics simulations.
The calculation of viscosity of liquid n-decane and n-hexadecane by the Green-Kubo method
Cui, S. T.; Cummings, P. T.; Cochran, H. D.
This short commentary presents the result of long molecular dynamics simulation calculations of the shear viscosity of liquid n-decane and n-hexadecane using the Green-Kubo integration method. The relaxation time of the stress-stress correlation function is compared with those of rotation and diffusion. The rotational and diffusional relaxation times, which are easy to calculate, provide useful guides for the required simulation time in viscosity calculations. Also, the computational time required for viscosity calculations of these systems by the Green-Kubo method is compared with the time required for previous non-equilibrium molecular dynamics calculations of the same systems. The method of choice for a particular calculation is determined largely by the properties of interest, since the efficiencies of the two methods are comparable for calculation of the zero strain rate viscosity.
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Chen Yong; Chen Xi; Qian Minping [School of Mathematical Sciences, Peking University, Beijing 100871 (China)
2006-03-17
A general form of the Green-Kubo formula, which describes the fluctuations pertaining to all the steady states whether equilibrium or non-equilibrium, for a system driven by a finite Markov chain with continuous time (briefly, MC) {l_brace}{xi}{sub t}{r_brace}, is shown. The equivalence of different forms of the Green-Kubo formula is exploited. We also look at the differences in terms of the autocorrelation function and the fluctuation spectrum between the equilibrium state and the non-equilibrium steady state. Also, if the MC is in the non-equilibrium steady state, we can always find a complex function {psi}, such that the fluctuation spectrum of {l_brace}{phi}({xi}{sub t}){r_brace} is non-monotonous in [0, + {infinity})
Lin, Neil Y. C.; Bierbaum, Matthew; Cohen, Itai
2017-09-01
By combining confocal microscopy and stress assessment from local structural anisotropy, we directly measure stresses in 3D quiescent colloidal liquids. Our noninvasive and nonperturbative method allows us to measure forces ≲50 fN with a small and tunable probing volume, enabling us to resolve the stress fluctuations arising from particle thermal motions. We use the Green-Kubo relation to relate these measured stress fluctuations to the bulk Brownian viscosity at different volume fractions, comparing against simulations and conventional rheometry measurements. We find that the Green-Kubo analysis gives excellent agreement with these prior results, suggesting that similar methods could be applied to investigations of local flow properties in many poorly understood far-from-equilibrium systems, including suspensions that are glassy, strongly sheared, or highly confined.
International Nuclear Information System (INIS)
Chen Yong; Chen Xi; Qian Minping
2006-01-01
A general form of the Green-Kubo formula, which describes the fluctuations pertaining to all the steady states whether equilibrium or non-equilibrium, for a system driven by a finite Markov chain with continuous time (briefly, MC) {ξ t }, is shown. The equivalence of different forms of the Green-Kubo formula is exploited. We also look at the differences in terms of the autocorrelation function and the fluctuation spectrum between the equilibrium state and the non-equilibrium steady state. Also, if the MC is in the non-equilibrium steady state, we can always find a complex function ψ, such that the fluctuation spectrum of {φ(ξ t )} is non-monotonous in [0, + ∞)
Colloidal electrophoresis: scaling analysis, Green-Kubo relation, and numerical results
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Duenweg, B; Lobaskin, V; Seethalakshmy-Hariharan, K; Holm, C
2008-01-01
We consider electrophoresis of a single charged colloidal particle in a finite box with periodic boundary conditions, where added counterions and salt ions ensure charge neutrality. A systematic rescaling of the electrokinetic equations allows us to identify a minimum set of suitable dimensionless parameters, which, within this theoretical framework, determine the reduced electrophoretic mobility. It turns out that the salt-free case can, on the mean field level, be described in terms of just three parameters. A fourth parameter, which had previously been identified on the basis of straightforward dimensional analysis, can only be important beyond mean field. More complicated behavior is expected to arise when further ionic species are added. However, for a certain parameter regime, we can demonstrate that the salt-free case can be mapped onto a corresponding system containing additional salt. The Green-Kubo formula for the electrophoretic mobility is derived, and its usefulness demonstrated by simulation data. Finally, we report on finite-element solutions of the electrokinetic equations, using the commercial software package COMSOL
Scale-invariant Green-Kubo relation for time-averaged diffusivity
Meyer, Philipp; Barkai, Eli; Kantz, Holger
2017-12-01
In recent years it was shown both theoretically and experimentally that in certain systems exhibiting anomalous diffusion the time- and ensemble-averaged mean-squared displacement are remarkably different. The ensemble-averaged diffusivity is obtained from a scaling Green-Kubo relation, which connects the scale-invariant nonstationary velocity correlation function with the transport coefficient. Here we obtain the relation between time-averaged diffusivity, usually recorded in single-particle tracking experiments, and the underlying scale-invariant velocity correlation function. The time-averaged mean-squared displacement is given by 〈δ2¯〉 ˜2 DνtβΔν -β , where t is the total measurement time and Δ is the lag time. Here ν is the anomalous diffusion exponent obtained from ensemble-averaged measurements 〈x2〉 ˜tν , while β ≥-1 marks the growth or decline of the kinetic energy 〈v2〉 ˜tβ . Thus, we establish a connection between exponents that can be read off the asymptotic properties of the velocity correlation function and similarly for the transport constant Dν. We demonstrate our results with nonstationary scale-invariant stochastic and deterministic models, thereby highlighting that systems with equivalent behavior in the ensemble average can differ strongly in their time average. If the averaged kinetic energy is finite, β =0 , the time scaling of 〈δ2¯〉 and 〈x2〉 are identical; however, the time-averaged transport coefficient Dν is not identical to the corresponding ensemble-averaged diffusion constant.
Green-Kubo relation for viscosity tested using experimental data for a two-dimensional dusty plasma
Feng, Yan; Goree, J.; Liu, Bin; Cohen, E. G. D.
2011-10-01
The theoretical Green-Kubo relation for viscosity is tested using experimentally obtained data. In a dusty plasma experiment, micron-sized dust particles are introduced into a partially ionized argon plasma, where they become negatively charged. They are electrically levitated to form a single-layer Wigner crystal, which is subsequently melted using laser heating. In the liquid phase, these dust particles experience interparticle electric repulsion, laser heating, and friction from the ambient neutral argon gas, and they can be considered to be in a nonequilibrium steady state. Direct measurements of the positions and velocities of individual dust particles are then used to obtain a time series for an off-diagonal element of the stress tensor and its time autocorrelation function. This calculation also requires the interparticle potential, which was not measured experimentally but was obtained using a Debye-Hückel-type model with experimentally determined parameters. Integrating the autocorrelation function over time yields the viscosity for shearing motion among dust particles. The viscosity so obtained is found to agree with results from a previous experiment using a hydrodynamical Navier-Stokes equation. This comparison serves as a test of the Green-Kubo relation for viscosity. Our result is also compared to the predictions of several simulations.
Experimental Measurement of Self-Diffusion in a Strongly Coupled Plasma
2016-08-04
the calculation of the self-diffusion constant through the Green- Kubo integral of hΔvxðtÞiþ=hΔvxð0Þiþ over the scaled time. Overall, the estimate of... Kubo relation D ¼ Z ∞ 0 ZðtÞdt; which describes the long-time mean-square displacement of a given particle through D ¼ limt→∞hjrðtÞ − rð0Þj2i=6t [25...ion VAF, the self-diffusion coefficient D may be calculated from our measurements. As is normally the case with calculations of this type, proper
Levashov, V. A.
2017-11-01
We studied the connection between the structural relaxation and viscosity for a binary model of repulsive particles in the supercooled liquid regime. The used approach is based on the decomposition of the macroscopic Green-Kubo stress correlation function into the correlation functions between the atomic level stresses. Previously we used the approach to study an iron-like single component system of particles. The role of vibrational motion has been addressed through the demonstration of the relationship between viscosity and the shear waves propagating over large distances. In our previous considerations, however, we did not discuss the role of the structural relaxation. Here we suggest that the contribution to viscosity from the structural relaxation can be taken into account through the consideration of the contribution from the atomic stress auto-correlation term only. This conclusion, however, does not mean that only the auto-correlation term represents the contribution to viscosity from the structural relaxation. Previously the role of the structural relaxation for viscosity has been addressed through the considerations of the transitions between inherent structures and within the mode-coupling theory by other authors. In the present work, we study the structural relaxation through the considerations of the parent liquid and the atomic level stress correlations in it. The comparison with the results obtained on the inherent structures also is made. Our current results suggest, as our previous observations, that in the supercooled liquid regime, the vibrational contribution to viscosity extends over the times that are much larger than the Einstein's vibrational period and much larger than the times that it takes for the shear waves to propagate over the model systems. Besides addressing the atomic level shear stress correlations, we also studied correlations between the atomic level pressure elements.
International Nuclear Information System (INIS)
Mundy, J.N.; Rothman, S.J.; Lam, N.Q.; Nowicki, L.J.; Hoff, H.A.
1978-01-01
The lack of understanding of self-diffusion in Group VI metals together with the wide scatter in the measured values of tungsten self-diffusion has prompted the present measurements to be made over a wide temperature range (1/2Tsub(m) to Tsub(m)). The diffusion coefficients have been measured in the temperature range 1430-2630 0 C. The present measurements show non-linear Arrhenius behavior but a reliable two-exponential fit of the data should await further measurements. (Auth.)
Self diffusion in isotopic fluid
International Nuclear Information System (INIS)
Tankeshwar, K.
1991-01-01
Expressions for the second and fourth frequency sum rules of the velocity auto-correlation function have been obtained for an isotopic fluid. These expressions and Mori memory function formalism have been used to study the influence of the particle mass and mole fraction on the self diffusion coefficient. Our results confirm the weak mass dependence of the self diffusion. The influence of the mole fraction of the light particles on the self diffusion constant has been found to increase for the larger particle mass. (author). 17 refs, 1 fig., 2 tabs
Multi-charge-state molecular dynamics and self-diffusion coefficient in the warm dense matter regime
Fu, Yongsheng; Hou, Yong; Kang, Dongdong; Gao, Cheng; Jin, Fengtao; Yuan, Jianmin
2018-01-01
We present a multi-ion molecular dynamics (MIMD) simulation and apply it to calculating the self-diffusion coefficients of ions with different charge-states in the warm dense matter (WDM) regime. First, the method is used for the self-consistent calculation of electron structures of different charge-state ions in the ion sphere, with the ion-sphere radii being determined by the plasma density and the ion charges. The ionic fraction is then obtained by solving the Saha equation, taking account of interactions among different charge-state ions in the system, and ion-ion pair potentials are computed using the modified Gordon-Kim method in the framework of temperature-dependent density functional theory on the basis of the electron structures. Finally, MIMD is used to calculate ionic self-diffusion coefficients from the velocity correlation function according to the Green-Kubo relation. A comparison with the results of the average-atom model shows that different statistical processes will influence the ionic diffusion coefficient in the WDM regime.
Counterion self-diffusion in polyelectrolyte solutions
Schipper, F. J. M.; Hollander, J. G.; Leyte, J. C.
1997-12-01
The self-diffusion coefficient of 0953-8984/9/50/019/img1, tetra-methylammonium 0953-8984/9/50/019/img2, tetra-ethylammonium 0953-8984/9/50/019/img3, tetra-propylammonium 0953-8984/9/50/019/img4 and tetra-butylammonium 0953-8984/9/50/019/img5 in solutions of the weak polymethacrylic acid (PMA) were measured with PFG NMR. No additional salt was present in any of the experiments. The polyion concentration and degree of neutralization were varied. The maximum relative counterion self-diffusion coefficient against polyion concentration, that was reported earlier, was observed for both alkali and tetra-alkylammonium 0953-8984/9/50/019/img6 counterions. We propose that the maximum is due to the combination of the obstruction by the polyion and the changing counterion distribution at increasing polyion concentration. An explanation of this proposal is offered in terms of the Poisson - Boltzmann - Smoluchowski (PBS) model for polyelectrolytes. Qualitative agreement of this model with experiment was found for the dependence of the counterion self-diffusion coefficient on the degree of neutralization of the polyion, on counterion radius and on polyion concentration, over a concentration range from 0.01 to 1 0953-8984/9/50/019/img7. Adaption of the theoretical obstruction, to fit the self-diffusion data of the solvent, also greatly improves the model predictions on the counterion self-diffusion.
Self-diffusion in remodeling and growth
Epstein, Marcelo
2011-07-16
Self-diffusion, or the flux of mass of a single species within itself, is viewed as an independent phenomenon amenable to treatment by the introduction of an auxiliary field of diffusion velocities. The theory is shown to be heuristically derivable as a limiting case of that of an ordinary binary mixture. © 2011 Springer Basel AG.
Self-diffusion in remodeling and growth
Epstein, Marcelo; Goriely, Alain
2011-01-01
Self-diffusion, or the flux of mass of a single species within itself, is viewed as an independent phenomenon amenable to treatment by the introduction of an auxiliary field of diffusion velocities. The theory is shown to be heuristically derivable
Tellurium self-diffusion and point defects in lead telluride
International Nuclear Information System (INIS)
Simirskij, Yu.N.; Firsova, L.P.
1982-01-01
Method of radioactive indicators was used to determine factors of tellurium self-diffusion in lead telluride with different deviation of the composition from stoichiometric in the range of enrichment by tellurium. It was found that at 973 K factors of tellurium self-diffusion in lead telluride depend slightly on the vapor pressure of tellurium equilibrium with solid phase
Estimating the basic reproduction rate of HFMD using the time series SIR model in Guangdong, China.
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Zhicheng Du
Full Text Available Hand, foot, and mouth disease (HFMD has caused a substantial burden of disease in China, especially in Guangdong Province. Based on notifiable cases, we use the time series Susceptible-Infected-Recovered model to estimate the basic reproduction rate (R0 and the herd immunity threshold, understanding the transmission and persistence of HFMD more completely for efficient intervention in this province. The standardized difference between the reported and fitted time series of HFMD was 0.009 (<0.2. The median basic reproduction rate of total, enterovirus 71, and coxsackievirus 16 cases in Guangdong were 4.621 (IQR: 3.907-5.823, 3.023 (IQR: 2.289-4.292 and 7.767 (IQR: 6.903-10.353, respectively. The heatmap of R0 showed semiannual peaks of activity, including a major peak in spring and early summer (about the 12th week followed by a smaller peak in autumn (about the 36th week. The county-level model showed that Longchuan (R0 = 33, Gaozhou (R0 = 24, Huazhou (R0 = 23 and Qingxin (R0 = 19 counties have higher basic reproduction rate than other counties in the province. The epidemic of HFMD in Guangdong Province is still grim, and strategies like the World Health Organization's expanded program on immunization need to be implemented. An elimination of HFMD in Guangdong might need a Herd Immunity Threshold of 78%.
Single atom self-diffusion on nickel surfaces
International Nuclear Information System (INIS)
Tung, R.T.; Graham, W.R.
1980-01-01
Results of a field ion microscope study of single atom self-diffusion on Ni(311), (331), (110), (111) and (100) planes are presented, including detailed information on the self-diffusion parameters on (311), (331), and (110) surfaces, and activation energies for diffusion on the (111), and (100) surfaces. Evidence is presented for the existence of two types of adsorption site and surface site geometry for single nickel atoms on the (111) surface. The presence of adsorbed hydrogen on the (110), (311), and (331) surfaces is shown to lower the onset temperature for self-diffusion on these planes. (orig.)
Li, Xiuhui; Li, Qin; Li, Junhong; Li, Ying; Chen, Yuping; Lv, Aiping; Zhang, Jian; Ding, Jianbo; Von Maltzan, Kristine; Wen, Tao
2014-12-01
Hand, foot, and mouth disease (HFMD) is a common infectious disease in children, characterized by acute viral infection accompanying acute inflammatory responses. Circulating histones are leading mediators of the inflammatory processes. This study aimed to elucidate whether circulating histones play a contributory role during HFMD. We measured plasma levels of histones, myeloperoxidase (MPO), lactate dehydrogenase (LDH), and cytokines in HFMD patients (n = 126) and compared the results with those of a control group (n = 30). Circulating histone levels were significantly increased in HFMD patients (3.794 ± 0.156 μg/ml) compared with healthy controls (0.238 ± 0.023 μg/ml, p histones correlated positively with plasma IL-6 and IL-10, whereas in severe HFMD, histones were associated with elevated IL-6 and TNF-ɑ levels. These data demonstrate that circulating histones are excessively released in patients with HFMD, which may indicate disease severity and contribute to systemic inflammation by promoting cytokine production (e.g. IL-6). We suggest that in mild HFMD, circulating histones may originate largely from neutrophil activation, whereas in severe HFMD, dying tissue cells and neutrophil activation may be synergistically involved in the increased levels of histones.
Self-diffusion in single crystalline silicon nanowires
Südkamp, T.; Hamdana, G.; Descoins, M.; Mangelinck, D.; Wasisto, H. S.; Peiner, E.; Bracht, H.
2018-04-01
Self-diffusion experiments in single crystalline isotopically controlled silicon nanowires with diameters of 70 and 400 nm at 850 and 1000 °C are reported. The isotope structures were first epitaxially grown on top of silicon substrate wafers. Nanowires were subsequently fabricated using a nanosphere lithography process in combination with inductively coupled plasma dry reactive ion etching. Three-dimensional profiling of the nanosized structure before and after diffusion annealing was performed by means of atom probe tomography (APT). Self-diffusion profiles obtained from APT analyses are accurately described by Fick's law for self-diffusion. Data obtained for silicon self-diffusion in nanowires are equal to the results reported for bulk silicon crystals, i.e., finite size effects and high surface-to-volume ratios do not significantly affect silicon self-diffusion. This shows that the properties of native point defects determined from self-diffusion in bulk crystals also hold for nanosized silicon structures with diameters down to 70 nm.
Mao, Qunying; Wang, Yiping; Bian, Lianlian; Xu, Miao; Liang, Zhenglun
2016-07-20
Enteroviruses (EVs) are the most common viral agents in humans. Although most infections are mild or asymptomatic, there is a wide spectrum of clinical manifestations that may be caused by EV infections with varying degrees of severity. Among these viruses, EV-A71 and coxsackievirus (CV) CV-A16 from group A EVs attract the most attention because they are responsible for hand, foot and mouth disease (HFMD). Other EV-A viruses such as CV-A6 and CV-A10 were also reported to cause HFMD outbreaks in several countries or regions. Group B EVs such as CV-B3, CV-B5 and echovirus 30 were reported to be the main pathogens responsible for myocarditis and encephalitis epidemics and were also detected in HFMD patients. Vaccines are the best tools to control infectious diseases. In December 2015, China's Food and Drug Administration approved two inactivated EV-A71 vaccines for preventing severe HFMD.The CV-A16 vaccine and the EV-A71-CV-A16 bivalent vaccine showed substantial efficacy against HFMD in pre-clinical animal models. Previously, research on EV-B group vaccines was mainly focused on CV-B3 vaccine development. Because the HFMD pathogen spectrum has changed, and the threat from EV-B virus-associated severe diseases has gradually increased, it is necessary to develop multivalent HFMD vaccines. This study summarizes the clinical symptoms of diseases caused by EVs, such as HFMD, myocarditis and encephalitis, and the related EV vaccine development progress. In conclusion, developing multivalent EV vaccines should be strongly recommended to prevent HFMD, myocarditis, encephalitis and other severe diseases.
On self-diffusion in silicon and germanium
International Nuclear Information System (INIS)
Bourgoin, J.C.; Lannoo, M.
1980-01-01
The experimental results concerning self-diffusion in Si and Ge are discussed. It is noted, using recent direct experimental data, that there is no temperature variation of the activation energy for self-diffusion, as it was postulated by Seeger and coworkers. A calculation is made of the sum of the formation and migration vibrational entropies for a vacancy, versus the lattice distortion which occurs around this vacancy. Using a Morse potential to obtain force constants, a lower limit is obtained for the value of this entropy at high temperature which is in correct agreement with the large (10 to 15 k) experimental value. It is concluded that the model, proposed by Seeger and coworkers, that self-diffusion occurs through extended defects (vacancies or interstitials), can be definitively ruled out. (author)
Calculation of self-diffusion coefficients in iron
Directory of Open Access Journals (Sweden)
Baohua Zhang
2014-01-01
Full Text Available On the basis of available P-V-T equation of state of iron, the temperature and pressure dependence of self-diffusion coefficients in iron polymorphs (α, δ, γ and ɛ phases have been successfully reproduced in terms of the bulk elastic and expansivity data by means of a thermodynamical model that interconnects point defects parameters with bulk properties. The calculated diffusion parameters, such as self-diffusion coefficient, activation energy and activation volume over a broad temperature range (500-2500 K and pressure range (0-100 GPa, compare favorably well with experimental or theoretical ones when the uncertainties are considered.
EV71 vaccine, a new tool to control outbreaks of hand, foot and mouth disease (HFMD).
Mao, Qun-ying; Wang, Yiping; Bian, Lianlian; Xu, Miao; Liang, Zhenglun
2016-05-01
On December 3rd 2015, the China Food and Drug Administration (CFDA) approved the first inactivated Enterovirus 71 (EV71) whole virus vaccine for preventing severe hand, foot and mouth disease (HFMD). As one of the few preventive vaccines for children's infectious diseases generated by the developing countries in recent years, EV71 vaccine is a blessing to children's health in China and worldwide. However, there are still a few challenges facing the worldwide use of EV71 vaccine, including the applicability against various EV71 pandemic strains in other countries, international requirements on vaccine production and quality control, standardization and harmonization on different pathogen monitoring and detecting methods, etc. In addition, the affordability of EV71 vaccine in other countries is a factor to be considered in HFMD prevention. Therefore, with EV71 vaccine commercially available, there is still a long way to go before reaching effective protection against severe HFMD after EV71 vaccines enter the market. In this paper, the bottlenecks and prospects for the wide use of EV71 vaccine after its approval are evaluated.
Mechanisms of self-diffusion on Pt(110)
DEFF Research Database (Denmark)
Lorensen, Henrik Qvist; Nørskov, Jens Kehlet; Jacobsen, Karsten Wedel
1999-01-01
The self-diffusion of Pt on the missing row reconstructed Pt(110) surface is discussed based on density functional calculations of activation energy barriers. Different competing diffusion mechanisms are considered and we show that several different diffusion paths along the reconstruction troughs...
Temperature dependence of Self-diffusion coefficient (SDC) of liquid ...
African Journals Online (AJOL)
PROF HORSFALL
2018-04-09
Apr 9, 2018 ... inverse square relationship between the natural logarithm of self-diffusion ... using the Equilibrium Molecular Dynamics (MD) and ..... Density, and Viscosity of Liquid Aluminum and. Iron. J. Phys. Chem. Ref. Data 35 ... Atomic Diffusion in Condensed Matter. Nature. 381: 137. Einstein, A (1905). Annalen der ...
The development and application of the two real-time RT-PCR assays to detect the pathogen of HFMD.
Directory of Open Access Journals (Sweden)
Aili Cui
Full Text Available Large-scale Hand, Foot, and Mouth Disease (HFMD outbreaks have frequently occurred in China since 2008, affecting more than one million children and causing several hundred children deaths every year. The pathogens of HFMD are mainly human enteroviruses (HEVs. Among them, human enterovirus 71 (HEV71 and coxsackievirus A16 (CVA16 are the most common pathogens of HFMD. However, other HEVs could also cause HFMD. To rapidly detect HEV71 and CVA16, and ensure detection of all HEVs causing HFMD, two real-time hybridization probe-based RT-PCR assays were developed in this study. One is a multiplex real-time RT-PCR assay, which was developed to detect and differentiate HEV71 specifically from CVA16 directly from clinical specimens within 1-2 h, and the other is a broad-spectrum real-time RT-PCR assay, which targeted almost all HEVs. The experiments confirmed that the two assays have high sensitivity and specificity, and the sensitivity was up to 0.1 TCID50/ml for detection of HEVs, HEV71, and CVA16, respectively. A total of 213 clinical specimens were simultaneously detected by three kinds of assays, including the two real-time RT-PCR assays, direct conventional RT-PCR assay, and virus isolation assay on human rhabdomyosarcoma cells (RD cells. The total positive rate of both HEV71 and CVA16 was 69.48% with real-time RT-PCR assay, 47.42% with RT-PCR assay, and 34.58% with virus isolation assay. One HFMD clinical specimen was positive for HEV, but negative for HEV71 or CVA16, which was identified as Echovirus 11 (Echo11 by virus isolation, RT-PCR, and sequencing for the VP1 gene. The two real-time RT-PCR assays had been applied in 31 provincial HFMD labs to detect the pathogens of HFMD, which has contributed to the rapid identification of the pathogens in the early stages of HFMD outbreaks, and helped to clarify the etiologic agents of HFMD in China.
Zheng, Yaming; Jit, Mark; Wu, Joseph T; Yang, Juan; Leung, Kathy; Liao, Qiaohong; Yu, Hongjie
2017-01-01
Hand, foot and mouth disease (HFMD) is a common illness in China that mainly affects infants and children. The objective of this study is to assess the economic cost and health-related quality of life associated with HFMD in China. A telephone survey of caregivers were conducted in 31 provinces across China. Caregivers of laboratory-confirmed HFMD patients who were registered in the national HFMD enhanced surveillance database during 2012-2013 were invited to participate in the survey. Total costs included direct medical costs (outpatient care, inpatient care and self-medication), direct non-medical costs (transportation, nutrition, accommodation and nursery), and indirect costs for lost income associated with caregiving. Health utility weights elicited using EuroQol EQ-5D-3L and EQ-Visual Analogue Scale (VAS) were used to calculate associated loss in quality adjusted life years (QALYs). The subjects comprised 1136 mild outpatients, 1124 mild inpatients, 1170 severe cases and 61 fatal cases. The mean total costs for mild outpatients, mild inpatients, severe cases and fatal cases were $201 (95%CI $187, $215), $1072 (95%CI $999, $1144), $3051 (95%CI $2905, $3197) and $2819 (95%CI $2068, $3571) respectively. The mean QALY losses per HFMD episode for mild outpatients, mild inpatients and severe cases were 3.6 (95%CI 3.4, 3,9), 6.9 (95%CI 6.4, 7.4) and 13.7 (95%CI 12.9, 14.5) per 1000 persons. Cases who were diagnosed with EV-A71 infection and had longer duration of illness were associated with higher total cost and QALY loss. HFMD poses a high economic and health burden in China. Our results provide economic and health utility data for cost-effectiveness analysis for HFMD vaccination in China.
Directory of Open Access Journals (Sweden)
Yaming Zheng
Full Text Available Hand, foot and mouth disease (HFMD is a common illness in China that mainly affects infants and children. The objective of this study is to assess the economic cost and health-related quality of life associated with HFMD in China.A telephone survey of caregivers were conducted in 31 provinces across China. Caregivers of laboratory-confirmed HFMD patients who were registered in the national HFMD enhanced surveillance database during 2012-2013 were invited to participate in the survey. Total costs included direct medical costs (outpatient care, inpatient care and self-medication, direct non-medical costs (transportation, nutrition, accommodation and nursery, and indirect costs for lost income associated with caregiving. Health utility weights elicited using EuroQol EQ-5D-3L and EQ-Visual Analogue Scale (VAS were used to calculate associated loss in quality adjusted life years (QALYs.The subjects comprised 1136 mild outpatients, 1124 mild inpatients, 1170 severe cases and 61 fatal cases. The mean total costs for mild outpatients, mild inpatients, severe cases and fatal cases were $201 (95%CI $187, $215, $1072 (95%CI $999, $1144, $3051 (95%CI $2905, $3197 and $2819 (95%CI $2068, $3571 respectively. The mean QALY losses per HFMD episode for mild outpatients, mild inpatients and severe cases were 3.6 (95%CI 3.4, 3,9, 6.9 (95%CI 6.4, 7.4 and 13.7 (95%CI 12.9, 14.5 per 1000 persons. Cases who were diagnosed with EV-A71 infection and had longer duration of illness were associated with higher total cost and QALY loss.HFMD poses a high economic and health burden in China. Our results provide economic and health utility data for cost-effectiveness analysis for HFMD vaccination in China.
Green-Kubo relations for dynamic interfacial excess properties
Sagis, L.M.C.
2012-01-01
In this paper we analyze the fluctuations of the in-plane interfacial excess fluxes in multiphase systems, in the context of the extended irreversible thermodynamics formalism. We derive expressions for the time correlation functions of the surface extra stress tensor, the surface mass flux vector,
The anomalous self-diffusion in α-Zr
International Nuclear Information System (INIS)
Hood, G.M.
1985-01-01
In a very recent publication, Horvath, Dyment and Mehrer, henceforth HDM, presented measurements of the self-diffusion coefficient Dsub(m) 0 for α-Zr as a function of temperature. The results of that study, done on a single crystal sample, were anomalous in the sense that a plot of log Dsub(m) 0 vs. 1/T(K -1 ) was not only non-linear, but exhibited two regions of downward curvature with increasing 1/T. HDM indicated that they were unable to see any explanation of their anomalous self-diffusion results. It is the purpose of this letter to indicate a means whereby these anomalous results may be ''explained'' and to suggest some experiments which might be undertaken to test the proposal. (orig./RK)
Spatio-Temporal Distribution and Hotspots of Hand, Foot and Mouth Disease (HFMD in Northern Thailand
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Ratchaphon Samphutthanon
2013-12-01
Full Text Available Hand, Foot and Mouth Disease (HFMD is an emerging viral disease, and at present, there are no antiviral drugs or vaccines available to control it. Outbreaks have persisted for the past 10 years, particularly in northern Thailand. This study aimed to elucidate the phenomenon of HFMD outbreaks from 2003 to 2012 using general statistics and spatial-temporal analysis employing a GIS-based method. The spatial analysis examined data at the village level to create a map representing the distribution pattern, mean center, standard deviation ellipse and hotspots for each outbreak. A temporal analysis was used to analyze the correlation between monthly case data and meteorological factors. The results indicate that the disease can occur at any time of the year, but appears to peak in the rainy and cold seasons. The distribution of outbreaks exhibited a clustered pattern. Most mean centers and standard deviation ellipses occurred in similar areas. The linear directional mean values of the outbreaks were oriented toward the south. When separated by season, it was found that there was a significant correlation with the direction of the southwest monsoon at the same time. An autocorrelation analysis revealed that hotspots tended to increase even when patient cases subsided. In particular, a new hotspot was found in the recent year in Mae Hong Son province.
Increased self-diffusion of brain water in normal aging
DEFF Research Database (Denmark)
Gideon, P; Thomsen, C; Henriksen, O
1994-01-01
With magnetic resonance (MR) imaging, brain water self-diffusion was measured in 17 healthy volunteers 22-76 (mean, 44.6) years old. The calculated values for the apparent diffusion coefficients (ADCs) ranged from 0.58 x 10(-9) to 1.23 x 10(-9) m2/sec in cerebral white matter. A significant...... by an increase in the extracellular volume due to age-dependent neuronal degeneration or to changes in myelination. These findings have implications for future clinical investigations with diffusion MR imaging techniques in patients with neurologic diseases, and stress the importance of having an age...
Self-diffusion in zirconium-α. A calculation
International Nuclear Information System (INIS)
Monti, A.M.
1991-01-01
After controversial discussions about normal and abnormal nature of self-diffusion in phase α in zirconium, the work of Horvath and co-authors has demonstrated the existence of an important negative curvature in the Arrhenius graph. Different reasons have been proposed to explain such unusual behaviour. Such interpretations of experimental results indicate that different effects and mechanisms could be masking thermal diffusion process by vacancy mechanism. The present work aims to determine the diffusion constants corresponding to a vacancy mechanism from computer simulation of this process. (Author) [es
Self diffusion of sodium ion in sodium chloride
International Nuclear Information System (INIS)
Haridasan, T.M.; Lawrence, N.
1985-09-01
The problem of cation self diffusion in NaCl for a single vacancy mechanism is attempted using a reaction coordinate approach employing the phonons in the system. The vacancy is given an active role by estimating the displacements of its nearest neighbour Cl - ions in the environment of the vacancy through the lattice Green's functions and the t matrix formalism. The jump frequency, the isotope effect and diffusion coefficients estimated by this approach agree well with the experimentally deduced values. These results support the experimental conclusion of about 30% of vacancy pairs in the cation diffusion in NaCl. (author)
Directory of Open Access Journals (Sweden)
Wei Li
Full Text Available BACKGROUND: Human Enterovirus 71 and Coxsackie A16 have caused many outbreaks in the last decade in mainland China, resulting in thousands of fatal cases. Seroepidemiology which provides important information to document population immunity is rare in China. METHODOLOGY/PRINCIPAL FINDINGS: A cross sectional study of Enterovirus 71 (EV71 and Coxsackie A16 (CA16 seroprevalence was carried out in Guangdong, China, pre- and post- the 2010 hand, foot and mouth disease (HFMD epidemic period. The levels of EV71 and CA16 specific antibodies were evaluated by a microneutralization test and the geometric mean titer (GMT was calculated and compared. Our results indicated frequent infection by EV71 and CA16 in Guangdong before the 2010 epidemic. Only EV71 neutralizing antibody but not CA16 seroprevalence was significantly increased after the 2010 HFMD epidemic. Children less than 3 years old especially those aged 2 years showed the lowest positive rates for EV71 and CA16 NA before epidemic and the most significantly increased EV71 seroprevalence after epidemic. CA16 GMT values declined after the 2010 epidemic. CONCLUSIONS: These results indicate EV71 was the major pathogen of HFMD in Guangdong during the 2010 epidemic. The infection occurs largely in children less than 3 years, who should have first priority to receive an EV71 vaccine.
Self-diffusion in dense granular shear flows.
Utter, Brian; Behringer, R P
2004-03-01
Diffusivity is a key quantity in describing velocity fluctuations in granular materials. These fluctuations are the basis of many thermodynamic and hydrodynamic models which aim to provide a statistical description of granular systems. We present experimental results on diffusivity in dense, granular shear flows in a two-dimensional Couette geometry. We find that self-diffusivities D are proportional to the local shear rate gamma; with diffusivities along the direction of the mean flow approximately twice as large as those in the perpendicular direction. The magnitude of the diffusivity is D approximately gamma;a(2), where a is the particle radius. However, the gradient in shear rate, coupling to the mean flow, and strong drag at the moving boundary lead to particle displacements that can appear subdiffusive or superdiffusive. In particular, diffusion appears to be superdiffusive along the mean flow direction due to Taylor dispersion effects and subdiffusive along the perpendicular direction due to the gradient in shear rate. The anisotropic force network leads to an additional anisotropy in the diffusivity that is a property of dense systems and has no obvious analog in rapid flows. Specifically, the diffusivity is suppressed along the direction of the strong force network. A simple random walk simulation reproduces the key features of the data, such as the apparent superdiffusive and subdiffusive behavior arising from the mean velocity field, confirming the underlying diffusive motion. The additional anisotropy is not observed in the simulation since the strong force network is not included. Examples of correlated motion, such as transient vortices, and Lévy flights are also observed. Although correlated motion creates velocity fields which are qualitatively different from collisional Brownian motion and can introduce nondiffusive effects, on average the system appears simply diffusive.
Water self-diffusion through narrow oxygenated carbon nanotubes
Energy Technology Data Exchange (ETDEWEB)
Striolo, Alberto [School of Chemical Biological and Materials Engineering, University of Oklahoma, Norman, OK 73019 (United States)
2007-11-28
The hydrophobic interior of carbon nanotubes, which is reminiscent of ion channels in cellular membranes, has inspired scientific research directed towards the production of, for example, membranes for water desalination, drug-delivery devices, and nanosyringes. To develop these technologies it is crucial to understand and predict the equilibrium and transport properties of confined water. We present here a series of molecular dynamics simulation results conducted to understand the extent to which the presence of a few oxygenated active sites, modeled as carbonyls, affects the transport properties of confined water. The model for the carbon nanotube is not intended to be realistic. Its only purpose is to allow us to understand the effect of a few oxygenated sites on the transport properties of water confined in a narrow cylindrical pore, which is otherwise hydrophobic. At low hydration levels we found little, if any, water diffusion. The diffusion, which appears to be of the Fickian type for sufficiently large hydration levels, becomes faster as the number of confined water molecules increases, reaches a maximum, and slows as water fills the carbon nanotubes. We explain our findings on the basis of two collective motion mechanisms observed from the analysis of sequences of simulation snapshots. We term the two mechanisms 'cluster-breakage' and 'cluster-libration' mechanisms. We observe that the cluster-breakage mechanism produces longer displacements for the confined water molecules than the cluster-libration one, but deactivates as water fills the carbon nanotube. From a practical point of view, our results are particularly important for two reasons: (1) at low hydration levels the presence of only eight carbonyl groups can prevent the diffusion of water through (8, 8) carbon nanotubes; and (2) the extremely fast self-diffusion coefficients observed for water within narrow carbon nanotubes are significantly decreased in the presence of only a
Water self-diffusion through narrow oxygenated carbon nanotubes
International Nuclear Information System (INIS)
Striolo, Alberto
2007-01-01
The hydrophobic interior of carbon nanotubes, which is reminiscent of ion channels in cellular membranes, has inspired scientific research directed towards the production of, for example, membranes for water desalination, drug-delivery devices, and nanosyringes. To develop these technologies it is crucial to understand and predict the equilibrium and transport properties of confined water. We present here a series of molecular dynamics simulation results conducted to understand the extent to which the presence of a few oxygenated active sites, modeled as carbonyls, affects the transport properties of confined water. The model for the carbon nanotube is not intended to be realistic. Its only purpose is to allow us to understand the effect of a few oxygenated sites on the transport properties of water confined in a narrow cylindrical pore, which is otherwise hydrophobic. At low hydration levels we found little, if any, water diffusion. The diffusion, which appears to be of the Fickian type for sufficiently large hydration levels, becomes faster as the number of confined water molecules increases, reaches a maximum, and slows as water fills the carbon nanotubes. We explain our findings on the basis of two collective motion mechanisms observed from the analysis of sequences of simulation snapshots. We term the two mechanisms 'cluster-breakage' and 'cluster-libration' mechanisms. We observe that the cluster-breakage mechanism produces longer displacements for the confined water molecules than the cluster-libration one, but deactivates as water fills the carbon nanotube. From a practical point of view, our results are particularly important for two reasons: (1) at low hydration levels the presence of only eight carbonyl groups can prevent the diffusion of water through (8, 8) carbon nanotubes; and (2) the extremely fast self-diffusion coefficients observed for water within narrow carbon nanotubes are significantly decreased in the presence of only a few oxygenated active
Self-diffusion coefficients of the metastable Lennard-Jones vapor
International Nuclear Information System (INIS)
Nie Chu; Zhou Youhua; Marlow, W H; Hassan, Y A
2008-01-01
Self-diffusion coefficients of a metastable Lennard-Jones vapor were obtained using the memory function formalism and the frequency moments of the velocity autocorrelation function at reduced temperatures from 0.75 to 1.0. The radial density distribution functions used to evaluate the second, fourth and sixth frequency moments of the velocity autocorrelation function were obtained from the restricted canonical ensemble Monte Carlo simulation (Corti and Debenedetti 1994 Chem. Eng. Sci. 49 2717). The self-diffusion coefficients at reduced temperature 0.75 do not vary monotonically as the density increases, and for the other three temperatures the self-diffusion coefficients vary normally
Self-diffusion coefficients of the metastable Lennard-Jones vapor
Energy Technology Data Exchange (ETDEWEB)
Nie Chu; Zhou Youhua [School of Physics and Information Engineering, Jianghan University, Wuhan 430056 (China); Marlow, W H; Hassan, Y A [Department of Nuclear Engineering, Texas A and M University, College Station, TX 77843 (United States)], E-mail: yhzhou@jhun.edu.cn
2008-10-15
Self-diffusion coefficients of a metastable Lennard-Jones vapor were obtained using the memory function formalism and the frequency moments of the velocity autocorrelation function at reduced temperatures from 0.75 to 1.0. The radial density distribution functions used to evaluate the second, fourth and sixth frequency moments of the velocity autocorrelation function were obtained from the restricted canonical ensemble Monte Carlo simulation (Corti and Debenedetti 1994 Chem. Eng. Sci. 49 2717). The self-diffusion coefficients at reduced temperature 0.75 do not vary monotonically as the density increases, and for the other three temperatures the self-diffusion coefficients vary normally.
Directory of Open Access Journals (Sweden)
Feng-Cai Zhu
Full Text Available Hand, foot, and mouth disease (HFMD has been emerging as an important public problem over the past few decades, especially in Asian and Pacific regions. A national program on EV71 vaccine development against HFMD was initiated in China, in 2008, which called for a need for seroepidemiological study for the target population.This was a retrospective study conducted in Jiangsu Province, in October, 2010. We measured the neutralizing antibodies against EV71 and CoxA16 in a cohort of infants aged of 2, 7, 12, and 27-38 months and their mothers just before delivery. Series sera samples from 975 infants and 555 mothers were collected and analyzed. Questionnaires on the history of HFMD were completed in the survey. A total of 143 HFMD cases were collected, but only 11.2% were reported to the National Infectious Disease Information Management System. The level of maternal antibody titers decreased dramatically during the first 7 month and remained at a relatively low level thereafter. But it increased significantly from month 12 to months 27-38. The accumulate incidence density of HFMD demonstrated a significant increase after 14 months of age, resulting in a accumulate incidence density of 50.8/1000 person-years in survey period. Seropositivity of EV71 antibody in infants at the age of 2 months seems to demonstrate a protective effect against HFMD.High seropositive rate of EV71 and CoxA16 antibody was found in prenatal women in mainland China, and there is a need to enhance the HFMD case management and the current surveillance system. We suggest that infants aged between 6 to 14 months should have the first priority to receive EV71 vaccine.
Anisotropy of self-diffusion and α-zirconium radiation growth problems
International Nuclear Information System (INIS)
Smirnov, E.A.; Subbotin, A.V.
1996-01-01
Temperature dependence of α-zirconium seft-diffusion anisotropy coefficients is obtained within the framework of linear extrapolation of self-diffusion anisotropy characteristics for metal HCP with c/a ration of [ru
In vivo measurement of water self diffusion in the human brain by magnetic resonance imaging
DEFF Research Database (Denmark)
Thomsen, C; Henriksen, O; Ring, P
1987-01-01
A new pulse sequence for in vivo diffusion measurements by magnetic resonance imaging (MRI) is introduced. The pulse sequence was tested on phantoms to evaluate the accuracy, reproducibility and inplane variations. The sensitivity of the sequence was tested by measuring the self diffusion...... coefficient of water with different temperatures. This phantom study showed that the water self diffusion could be measured accurately and that the inplane deviation was less than +/- 10 per cent. Seven healthy volunteers were studied with a 10 mm thick slice through the lateral ventricles, clear differences...... between grey and white matter as well as regional differences within the white matter were seen. In two patients with infarction, alternations in water self diffusion were seen in the region of the infarct. Likewise, pronounced changes in brain water self diffusion were observed in a patient with benign...
On the self-diffusion process in liquid metals and alloys by the radioactive tracer method
International Nuclear Information System (INIS)
Ganovici, L.
1978-01-01
A theoretical and experimental study of self-diffusion process in liquid metals and alloys is presented. There are only a few pure metals for which diffusion coefficients in a liquid state are known. The thesis aims at increasing the number of liquid metals for which diffusion coefficients are available, by determining these values for liquids: Cd, Tl, Sb and Te. The self-diffusion coefficients of Te in some tellurium based liquid alloys such as Tl 2 Te, PbTe and Bi 90 Te 10 were also determined. Self-diffusion coefficients have been measured using two radioactive tracer methods: a) the capillary-reservoir method; b) the semi-infinite capillary method. The self-diffusion coefficients were derived from the measured radioactive concentration profile, using the solutions of Fick's second law for appropriate initial and limit conditions. The temperature dependence study of self-diffusion coefficients in liquids Cd, Tl, Sb and Te, was used to check some theoretical models on the diffusion mechanism in metallic melts. The experimental diffusion data interpreted in terms of the Arrhenius type temperature dependence, was used to propose two simple empiric relations for determining self diffusion coefficients of group I liquid metals and for liquid semi-metals. It was established a marked decrease of self-diffusion coefficients of liquid Te close to the solidification temperature. The diffusivity of Te in liquid Tl 2 Te points to an important decrease close to the solidification temperature. A simplified model was proposed for the diffusion structural unit in this alloy and the hard sphere model for liquid metals was checked by comparing the theoretical and experimental self-diffusion coefficients. (author)
Self-diffusion in monodisperse three-dimensional magnetic fluids by molecular dynamics simulations
Energy Technology Data Exchange (ETDEWEB)
Dobroserdova, A.B. [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); Kantorovich, S.S., E-mail: alla.dobroserdova@urfu.ru [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); University of Vienna, Sensengasse 8, Vienna (Austria)
2017-06-01
In the present work we study the self-diffusion behaviour in the three-dimensional monodisperse magnetic fluids using the Molecular Dynamics Simulation and Density Functional Theory. The peculiarity of computer simulation is to study two different systems: dipolar and soft sphere ones. In the theoretical method, it is important to choose the approximation for the main structures, which are chains. We compare the theoretical results and the computer simulation data for the self-diffusion coefficient as a function of the particle volume fraction and magnetic dipole-dipole interaction parameter and find the qualitative and quantitative agreement to be good. - Highlights: • The paper deals with the study of the self-diffusion in monodisperse three-dimensional magnetic fluids. • The theoretical approach contains the free energy density functional minimization. • Computer simulations are performed by the molecular dynamics method. • We have a good qualitative and quantitative agreement between the theoretical results and computer simulation data.
Dense fluid self-diffusion coefficient calculations using perturbation theory and molecular dynamics
Directory of Open Access Journals (Sweden)
COELHO L. A. F.
1999-01-01
Full Text Available A procedure to correlate self-diffusion coefficients in dense fluids by using the perturbation theory (WCA coupled with the smooth-hard-sphere theory is presented and tested against molecular simulations and experimental data. This simple algebraic expression correlates well the self-diffusion coefficients of carbon dioxide, ethane, propane, ethylene, and sulfur hexafluoride. We have also performed canonical ensemble molecular dynamics simulations by using the Hoover-Nosé thermostat and the mean-square displacement formula to compute self-diffusion coefficients for the reference WCA intermolecular potential. The good agreement obtained from both methods, when compared with experimental data, suggests that the smooth-effective-sphere theory is a useful procedure to correlate diffusivity of pure substances.
Self-diffusion at the melting point: From H2 and N2 to liquid metals
International Nuclear Information System (INIS)
Armstrong, B.H.
1992-01-01
A nominal lower bound to the mean free diffusion time at the melting point T m was obtained earlier which provided a factor-two type estimate for self-diffusion coefficients of the alkali halides, alkali metals, eight other metals, and Ar. The argument was based on the classical Uncertainty Principle applied to the solid crystal, whereby maximum-frequency phonons lose validity as collective excitations and degenerate into aperiodic, single-particle diffusive motion at the melting point. Because of the short time scale of this motion, the perfect-gas diffusion equation and true mass can be used to obtain the self-diffusion coefficient in the Debye approximation to the phonon spectrum. This result for the self-diffusion coefficient also yields the scale factor that determines the order of magnitude of liquid self-diffusion coefficients, which has long been an open question. The earlier theory is summarized and clarified, and the results extended to the more complex molecular liquids H 2 and N 2 . It is also demonstrated that combining Lindemann's melting law with the perfect-gas diffusion equation estimate yields a well-known empirical expression for liquid-metal self-diffusion at T m . Validity of the self-diffusion estimate over a melting temperature range from 14 to more than 1,300 K and over a wide variety of crystals provides strong confirmation for the existence of the specialized diffusive motion at the melting point, as well as confirmation of a relation between the phonon spectrum of the solid crystal and diffusive motion in the melt. 21 refs., 2 tabs
Wen, Tao; Xu, Wenjun; Liang, Lianchun; Li, Junhong; Ding, Xiaorong; Chen, Xiao; Hu, Jianhua; Lv, Aiping; Li, Xiuhui
2015-08-01
Andrographolide sulfonate treatment has been shown to improve clinical severe hand, foot, and mouth disease (HFMD) efficacies when combined with conventional therapy. However, the mechanisms for its therapeutic effects remain elusive. In this study, we aimed to investigate whether andrographolide sulfonate exerts its efficacy by acting on neutrophil activation. We obtained serial plasma samples at two time points (before and after 5 days of therapy) from 28 HFMD patients who received conventional therapy and 18 patients who received combination therapy (andrographolide sulfonate plus conventional therapy). Then, we measured plasma myeloperoxidase (MPO), S100A8/A9, histone, and inflammatory cytokine levels. Furthermore, we examined if andrographolide sulfonate had direct effects on neutrophil activation in vitro. We observed that MPO and S100A8/A9 levels were markedly elevated in the HFMD patients before clinical treatment. At 5 days post-medication, the MPO, S100A8/A9, histone, and interleukin-6 levels were markedly lower in the combination therapy group compared with the conventional therapy group. In vitro studies showed that andrographolide sulfonate inhibited lipopolysaccharide-stimulated neutrophil activation, demonstrated by the decreased production of reactive oxygen species and cytokines. These data indicate that neutrophil activation modulation by andrographolide sulfonate may be a critical determinant for its clinical HFMD treatment efficacy. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.
Samphutthanon, R.; Tripathi, N. K.; Ninsawat, S.; Duboz, R.
2014-12-01
The main objective of this research was the development of an HFMD hazard zonation (HFMD-HZ) model by applying AHP and Fuzzy Logic AHP methodologies for weighting each spatial factor such as disease incidence, socio-economic and physical factors. The outputs of AHP and FAHP were input into a Geographic Information Systems (GIS) process for spatial analysis. 14 criteria were selected for analysis as important factors: disease incidence over 10 years from 2003 to 2012, population density, road density, land use and physical features. The results showed a consistency ratio (CR) value for these main criteria of 0.075427 for AHP, the CR for FAHP results was 0.092436. As both remained below the threshold of 0.1, the CR value were acceptable. After linking to actual geospatial data (disease incidence 2013) through spatial analysis by GIS for validation, the results of the FAHP approach were found to match more accurately than those of the AHP approach. The zones with the highest hazard of HFMD outbreaks were located in two main areas in central Muang Chiang Mai district including suburbs and Muang Chiang Rai district including the vicinity. The produced hazardous maps may be useful for organizing HFMD protection plans.
Self-diffusion coefficient of iron as affected by chelating agents using tracer technique
Energy Technology Data Exchange (ETDEWEB)
Massoud, M.A.; Abd-El-Sabour, M.F. (Agriculture Dept. for Soil and Water Research, Nuclear Research Centre, A.E.A., Cairo (Egypt)); Omar, M.A. (Ain Shams Univ., Cairo (Egypt). Faculty of Agriculture)
1983-01-01
The effect of Fe/sub 2/(So/sub 4/)/sub 3/, Fe-DTPA, and Fe-EDDHA on the self-diffusion coefficient of Fe in some soils of Egypt was studied. The effect of chelating compounds on the ratio between solid phase fraction of the labile Fe and its concentration in the soil solution (capacity factor) was also studied. The data reveals the following items of more interesting: 1) The use of chelating agents, i.e., DTPA and EDDHA increased the amount of Fe in soil solution, hence the capacity factor was decreased using these compounds. It seems that as the addition of Fe was in the chelated form in soil solution, the slight loss of 59Fe from solution when 59Fe - chelate was used could be attributed to the isotopic exchange with soil Fe. 2) It was found that the addition of either Fe-DTPA or Fe-EDDHA significantly increased the self-diffusion of Fe in soil as compared with Fe/sub 2/(So/sub 4/)/sub 3/. It was also noticed that the self-diffusion for Fe in the alluvial soil was greater than in the calcareous one due to the instance competition between Ca and Fe for the chelating ligands in the calcareous soil. It was also seen that soil texture affects Fe self-diffusion.
Self-diffusion coefficient of iron as affected by chelating agents using tracer technique
International Nuclear Information System (INIS)
Massoud, M.A.; Abd-El-Sabour, M.F.; Omar, M.A.
1983-01-01
The effect of Fe 2 (So 4 ) 3 , Fe-DTPA, and Fe-EDDHA on the self-diffusion coefficient of Fe in some soils of Egypt was studied. The effect of chelating compounds on the ratio between solid phase fraction of the labile Fe and its concentration in the soil solution (capacity factor) was also studied. The data reveals the following items of more interesting: 1) The use of chelating agents, i.e., DTPA and EDDHA increased the amount of Fe in soil solution, hence the capacity factor was decreased using these compounds. It seems that as the addition of Fe was in the chelated form in soil solution, the slight loss of 59Fe from solution when 59Fe - chelate was used could be attributed to the isotopic exchange with soil Fe. 2) It was found that the addition of either Fe-DTPA or Fe-EDDHA significantly increased the self-diffusion of Fe in soil as compared with Fe 2 (So 4 ) 3 . It was also noticed that the self-diffusion for Fe in the alluvial soil was greater than in the calcareous one due to the instance competition between Ca and Fe for the chelating ligands in the calcareous soil. It was also seen that soil texture affects Fe self-diffusion
Molecular dynamics simulation of self-diffusion coefficients for liquid metals
International Nuclear Information System (INIS)
Ju Yuan-Yuan; Zhang Qing-Ming; Gong Zi-Zheng; Ji Guang-Fu
2013-01-01
The temperature-dependent coefficients of self-diffusion for liquid metals are simulated by molecular dynamics methods based on the embedded-atom-method (EAM) potential function. The simulated results show that a good inverse linear relation exists between the natural logarithm of self-diffusion coefficients and temperature, though the results in the literature vary somewhat, due to the employment of different potential functions. The estimated activation energy of liquid metals obtained by fitting the Arrhenius formula is close to the experimental data. The temperature-dependent shear-viscosities obtained from the Stokes—Einstein relation in conjunction with the results of molecular dynamics simulation are generally consistent with other values in the literature. (atomic and molecular physics)
Contribution to the study of zirconium self-diffusion in zirconium carbide
International Nuclear Information System (INIS)
An, Chul
1972-01-01
The objective of this research thesis is to determine experimental conditions allowing the measurement of the self-diffusion coefficient of zirconium in zirconium carbide. The author reports the development of a method of preparation of zirconium carbide samples. He reports the use of ion implantation as technique to obtain a radio-tracer coating. The obtained results give evidence of the impossibility to use sintered samples with small grains because of the demonstrated importance of intergranular diffusion. The self-diffusion coefficient is obtained in the case of zirconium carbide with grains having a diameter of few millimetres. The presence of 95 Nb from the disintegration of 95 Zr indicates that these both metallic elements have very close diffusion coefficients at 2.600 C [fr
Self-diffusion in Zr-Cr and Zr-Fe alloys
International Nuclear Information System (INIS)
Patil, R.V.; Tiwari, G.P.; Sharma, B.D.
1981-01-01
Self-diffusion studies in a series of zirconium-rich alloys containing 2.05, 3.49, 4.08 and 7.86 at %Cr and 0.98, 1.35, 1.64, 3.54 and 6.37 at.%Fe have been carried out in the temperature range 1173-1518 K, using standard serial-sectioning technique. The temperature dependence of self-diffusion coefficients in all these alloys could be described by Arrhenius expressions of the type D = D 0 exp (- Q/RT). The data have been analysed on the basis of current concepts of alloy diffusion. An analysis based on the vacancy mechanism leads to negative values of the correlation factors. The possibility of interstitial-vacancy pair and ω-phase embryos being rate-controlling mechanisms is also discussed. (author)
International Nuclear Information System (INIS)
Goel, Gaurav; Krekelberg, William P; Pond, Mark J; Truskett, Thomas M; Mittal, Jeetain; Shen, Vincent K; Errington, Jeffrey R
2009-01-01
Although classical density functional theory provides reliable predictions for the static properties of simple equilibrium fluids under confinement, a theory of comparative accuracy for the transport coefficients has yet to emerge. Nonetheless, there is evidence that knowledge of how confinement modifies static behavior can aid in forecasting dynamics. Specifically, recent molecular simulation studies have shown that the relationship between excess entropy and self-diffusivity of a bulk equilibrium fluid changes only modestly when the fluid is isothermally confined, indicating that knowledge of the former might allow semi-quantitative predictions of the latter. Do other static measures, such as those that characterize free or available volume, also strongly correlate with single-particle dynamics of confined fluids? Here, we investigate this question for both the single-component hard-sphere fluid and hard-sphere mixtures. Specifically, we use molecular simulations and fundamental measure theory to study these systems at approximately 10 3 equilibrium state points. We examine three different confining geometries (slit pore, square channel, and cylindrical pore) and the effects of particle packing fraction and particle–boundary interactions. Although average density fails to predict some key qualitative trends for the self-diffusivity of confined fluids, we provide strong empirical evidence that a new generalized measure of available volume for inhomogeneous fluids correlates excellently with self-diffusivity across a wide parameter space in these systems, approximately independently of the degree of confinement. An important consequence, which we demonstrate here, is that density functional theory predictions of this static property can be used together with knowledge of bulk fluid behavior to semi-quantitatively estimate the self-diffusion coefficient of confined fluids under equilibrium conditions
Expanding the calculation of activation volumes: Self-diffusion in liquid water
Piskulich, Zeke A.; Mesele, Oluwaseun O.; Thompson, Ward H.
2018-04-01
A general method for calculating the dependence of dynamical time scales on macroscopic thermodynamic variables from a single set of simulations is presented. The approach is applied to the pressure dependence of the self-diffusion coefficient of liquid water as a particularly useful illustration. It is shown how the activation volume associated with diffusion can be obtained directly from simulations at a single pressure, avoiding approximations that are typically invoked.
International Nuclear Information System (INIS)
Gupta, Ajay; Chakravarty, Sajoy; Gupta, Mukul; Horisberger, M.; Rueffer, Rudolf; Wille, Hans-Christian; Leupold, Olaf
2005-01-01
It is demonstrated that nuclear resonance reflectivity from isotopic multilayers can be used to do accurate measurements of self diffusion of iron in thin film samples. Diffusion lengths down to ∼ 1A 0 can be measured. The technique has been used to measure the self-diffusion of iron in FeNZr nanocrystalline alloys. The activation energy for self-diffusion of iron is found to be 0.8% ± 0.01 eV while the pre-exponential factor is 3.54 x 10 13 m 2 /s. (author)
Self-diffusion measurements in heterogeneous systems using NMR pulsed field gradient technique
International Nuclear Information System (INIS)
Heink, W.; Kaerger, J.; Walter, A.
1978-01-01
The experimental pecularities of the NMR pulsed field gradient technique are critical surveyed in its application to zeolite adsorbate adsorbent systems. After a presentation of the different transport parameters accessible by this technique, the consequences of the existence of inner field gradients being inherent to heterogeneous systems are analyzed. Experimental conditions and consequences of an application of pulsed field gradients of high intensity which are necessary for the measurement of small intracrystalline self-diffusion coefficients, are discussed. Gradient pulses of 0.15 Tcm -1 with pulse widths of 2 ms maximum and relative deviations of less than 0.01 per mille can be realized. Since for a number of adsorbate adsorbent systems a distinct dependence of the intracrystalline self-diffusion coeffcients on adsorbate concentration is observed, determination of zeolite pore fiiling factor is of considerable importance for the interpretation of the diffusivities obtained. It is demonstrated that also this information can be obtained by NMR technique in a straightforward way with a mean error of less than 5 to 10 %. Applying this new method and using an optimum experimental device as described, pore filling factor dependences of the self-diffusion coefficients of alkanes in NaX zeolites can be followed over more than two orders of magnitude. (author)
Semenycheva, Alexandra V.; Chuvil'deev, Vladimir N.; Nokhrin, Aleksey V.
2018-05-01
The paper offers a model describing the process of grain boundary self-diffusion in metals with phase transitions in the solid state. The model is based on ideas and approaches found in the theory of non-equilibrium grain boundaries. The range of application of basic relations contained in this theory is shown to expand, as they can be used to calculate the parameters of grain boundary self-diffusion in high-temperature and low-temperature phases of metals with a phase transition. The model constructed is used to calculate grain boundary self-diffusion activation energy in titanium and zirconium and an explanation is provided as to their abnormally low values in the low-temperature phase. The values of grain boundary self-diffusion activation energy are in good agreement with the experiment.
International Nuclear Information System (INIS)
McKee, R.A.
1981-01-01
It is shown that the Nernst-Einstein equation can be generalized for a high defect concentration solid to relate the mobility or conductivity to the self-diffusion coefficient. This relationship is derived assuming that the diffusing particles interact strongly and that the mobility is concentration-dependent. It is derived for interstitial disordered structures, but it is perfectly general to any mechanism of self diffusion as long as diffusion in a pure system is considered
Self-thermophoresis and thermal self-diffusion in liquids and gases.
Brenner, Howard
2010-09-01
This paper demonstrates the existence of self-thermophoresis, a phenomenon whereby a virtual thermophoretic force arising from a temperature gradient in a quiescent single-component liquid or gas acts upon an individual molecule of that fluid in much the same manner as a "real" thermophoretic force acts upon a macroscopic, non-Brownian body immersed in that same fluid. In turn, self-thermophoresis acting in concert with Brownian self-diffusion gives rise to the phenomenon of thermal self-diffusion in single-component fluids. The latter furnishes quantitative explanations of both thermophoresis in pure fluids and thermal diffusion in binary mixtures (the latter composed of a dilute solution of a physicochemically inert solute whose molecules are large compared with those of the solvent continuum). Explicitly, the self-thermophoretic theory furnishes a simple expression for both the thermophoretic velocity U of a macroscopic body in a single-component fluid subjected to a temperature gradient ∇T , and the intimately related binary thermal diffusion coefficient D{T} for a two-component colloidal or macromolecular mixture. The predicted expressions U=-D{T}∇T≡-βD{S}∇T and D{T}=βD{S} (with β and D{S} the pure solvent's respective thermal expansion and isothermal self-diffusion coefficients) are each noted to accord reasonably well with experimental data for both liquids and gases. The likely source of systematic deviations of the predicted values of D{T} from these data is discussed. This appears to be the first successful thermodiffusion theory applicable to both liquids and gases, a not insignificant achievement considering that the respective thermal diffusivities and thermophoretic velocities of these two classes of fluids differ by as much as six orders of magnitude.
Self-diffusion in electrolyte solutions a critical examination of data compiled from the literature
Mills, R
1989-01-01
This compilation - the first of its kind - fills a real gap in the field of electrolyte data. Virtually all self-diffusion data in electrolyte solutions as reported in the literature have been examined and the book contains over 400 tables covering diffusion in binary and ternary aqueous solutions, in mixed solvents, and of non-electrolytes in various solvents.An important feature of the compilation is that all data have been critically examined and their accuracy assessed. Other features are an introductory chapter in which the methods of measurement are reviewed; appendices containing tables
Self-diffusion in 69Ga121Sb/71Ga123Sb isotope heterostructures
Bracht, H.; Nicols, S. P.; Haller, E. E.; Silveira, Juan Pedro; Briones Fernández-Pola, Fernando
2001-01-01
Gallium and antimony self-diffusion experiments have been performed in undoped 69Ga121Sb/71Ga123Sb isotope heterostructures at temperatures between 571 and 708 °C under Sb- and Ga-rich ambients. Ga and Sb profiles measured with secondary ion mass spectrometry reveal that Ga diffuses faster than Sb by several orders of magnitude. This strongly suggests that the two self-atom species diffuse independently on their own sublattices. Experimental results lead us to conclude that Ga and Sb diffusio...
A model for self-diffusion of guanidinium-based ionic liquids: a molecular simulation study.
Klähn, Marco; Seduraman, Abirami; Wu, Ping
2008-11-06
We propose a novel self-diffusion model for ionic liquids on an atomic level of detail. The model is derived from molecular dynamics simulations of guanidinium-based ionic liquids (GILs) as a model case. The simulations are based on an empirical molecular mechanical force field, which has been developed in our preceding work, and it relies on the charge distribution in the actual liquid. The simulated GILs consist of acyclic and cyclic cations that were paired with nitrate and perchlorate anions. Self-diffusion coefficients are calculated at different temperatures from which diffusive activation energies between 32-40 kJ/mol are derived. Vaporization enthalpies between 174-212 kJ/mol are calculated, and their strong connection with diffusive activation energies is demonstrated. An observed formation of cavities in GILs of up to 6.5% of the total volume does not facilitate self-diffusion. Instead, the diffusion of ions is found to be determined primarily by interactions with their immediate environment via electrostatic attraction between cation hydrogen and anion oxygen atoms. The calculated average time between single diffusive transitions varies between 58-107 ps and determines the speed of diffusion, in contrast to diffusive displacement distances, which were found to be similar in all simulated GILs. All simulations indicate that ions diffuse by using a brachiation type of movement: a diffusive transition is initiated by cleaving close contacts to a coordinated counterion, after which the ion diffuses only about 2 A until new close contacts are formed with another counterion in its vicinity. The proposed diffusion model links all calculated energetic and dynamic properties of GILs consistently and explains their molecular origin. The validity of the model is confirmed by providing an explanation for the variation of measured ratios of self-diffusion coefficients of cations and paired anions over a wide range of values, encompassing various ionic liquid classes
Self-Diffusion and Heteroassociation in an Acetone-Chloroform Mixture at 298 K
Golubev, V. A.; Gurina, D. L.; Kumeev, R. S.
2018-01-01
The self-diffusion coefficients of acetone and chloroform in a binary acetone-chloroform mixture at 298 K are determined via pulsed field gradient NMR spectroscopy. It is estimated that the hydrodynamic radii of the mixture's components, calculated using the Stokes-Einstein equation, grow as the concentrations of the components fall. It is shown that such behavior of hydrodynamic radii is due to acetone-chloroform heteroassociation. The hydrodynamic radii of monomers and heteroassociates in a 1: 1 ratio are determined along with the constant of heteroassociation, using the proposed model of an associated solution.
Applicability of the Taylor-Green-Kubo formula in particle diffusion theory
International Nuclear Information System (INIS)
Shalchi, A.
2011-01-01
Diffusion coefficients of particles can be defined as time integrals over velocity correlation functions, or as mean square displacements divided by time. In the present paper it is demonstrated that these two definitions are not equivalent. An exact relation between mean square displacements and velocity correlations is derived. As an example of the applicability of these results so-called drift coefficients of energetic particles are discussed. It is explained why different previous approaches in drift theory provided contradicting results.
Self-diffusion in MgO--a density functional study.
Runevall, Odd; Sandberg, Nils
2011-08-31
Density functional theory calculations have been performed to study self-diffusion in magnesium oxide, a model material for a wide range of ionic compounds. Formation energies and entropies of Schottky defects and divacancies were obtained by means of total energy and phonon calculations in supercell configurations. Transition state theory was used to estimate defect migration rates, with migration energies taken from static calculations, and the corresponding frequency factors estimated from the phonon spectrum. In all static calculations we corrected for image effects using either a multipole expansion or an extrapolation to the low concentration limit. It is shown that both methods give similar results. The results for self-diffusion of Mg and O confirm the previously established picture, namely that in materials of nominal purity, Mg diffuses extrinsically by a single vacancy mechanism, while O diffuses intrinsically by a divacancy mechanism. Quantitatively, the current results are in very good agreement with experiments concerning O diffusion, while for Mg the absolute diffusion rate is generally underestimated by a factor of 5-10. The reason for this discrepancy is discussed.
Self-diffusion in isotopically enriched silicon carbide and its correlation with dopant diffusion
International Nuclear Information System (INIS)
Rueschenschmidt, K.; Bracht, H.; Stolwijk, N.A.; Laube, M.; Pensl, G.; Brandes, G.R.
2004-01-01
Diffusion of 13 C and 30 Si in silicon carbide was performed with isotopically enriched 4H- 28 Si 12 C/ nat SiC heterostructures which were grown by chemical vapor phase epitaxy. After diffusion annealing at temperatures between 2000 deg. C and 2200 deg. C the 30 Si and 13 C profiles were measured by means of secondary ion mass spectrometry. We found that the Si and C diffusivity is of the same order of magnitude but several orders of magnitude lower than earlier data reported in the literature. Both Si and C tracer diffusion coefficients are in satisfactory agreement with the native point defect contribution to self-diffusion deduced from B diffusion in SiC. This reveals that the native defect which mediates B diffusion also controls self-diffusion. Assuming that B atoms within the extended tail region of B profiles are mainly dissolved on C sites, we propose that B diffuses via the kick-out mechanism involving C interstitials. Accordingly, C diffusion should proceed mainly via C interstitials. The mechanism of Si diffusion remains unsolved but Si may diffuse via both Si vacancies and interstitials, with the preference for either species depending on the doping level
Self-diffusion of Er and Hf inpure and HfO2-doped polycrystalline Er2O3
International Nuclear Information System (INIS)
Scheidecker, R.W.
1979-01-01
Using a tracer technique, self-diffusion of Er and Hf was measured over the approximate temperature interval of 1600 to 1970 0 C in pure and HfO 2 -doped polycryatalline Er 2 O 3 . Up to about 10 m/o HfO 2 dopant level, the Er self-diffusion coefficients followed a relationship based on cation vacancies. Above 10 m/o HfO 2 , deviation from this relationship occurred, apparently due to clustering of cation vacancies and oxygen interstitials around the dopant hafnia ion. The activation energy for the self-diffusion of Er in pure Er 2 O 3 was 82.2 Kcal/mole and increased with the HfO 2 dopant level present. Self-diffusion of Hf was measured in pure Er 2 O 3 having two impurity levels, and a separation of the grain boundary. The volume diffusion of Hf showed both extrinsic and intrinsic behavior with the transition temperature increasing with the impurity level present in Er 2 O 3 . The activation energy for Hf volume diffusion in the intrinsic region was high, i.e. 235 -+ 9.5 Kcal/mole. The grain boundary diffusion was apparently extrinsic over the entire temperature interval Very low Hf self diffusion rates were found in both pure and HfO 2 doped Er 2 O 3 compositions. Despite a clustering effect, the HfO 2 dopant increased the Hf volume diffusion coefficients
Energy Technology Data Exchange (ETDEWEB)
Isoda, Taiga; Uematsu, Masashi; Itoh, Kohei M., E-mail: kitoh@appi.keio.ac.jp [School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan)
2015-09-21
Si self-diffusion in the presence of end-of-range (EOR) defects is investigated using {sup nat}Si/{sup 28}Si isotope multilayers. The isotope multilayers were amorphized by Ge ion implantation, and then annealed at 800–950 °C. The behavior of Si self-interstitials is investigated through the {sup 30}Si self-diffusion. The experimental {sup 30}Si profiles show further enhancement of Si self-diffusion at the EOR defect region, in addition to the transient enhanced diffusion via excess Si self-interstitials by EOR defects. To explain this additional enhanced diffusion, we propose a model which takes into account enhanced diffusion by tensile strain originated from EOR defects. The calculation results based on this model have well reproduced the experimental {sup 30}Si profiles.
Effect of EDTA and gypsum on self diffusion coefficient of zinc in alkali soil
International Nuclear Information System (INIS)
Gupta, G.N.; Deb, D.L.
1981-01-01
The effect of EDTA and gypsum application on the rate of zinc diffusion was studied in an alkali soil. Gypsum application at the rate of half gypsum requirement (GR) increased the apparent self diffusion coefficient of zinc (DaZn) and decreased the capacity factor (B) of soil. The higher rates (full GR and double GR) depressed the rate of zinc diffusion and increased the B value. Application of EDTA at the rate of 0.77 μeg -1 of soil produced 1600 and 24 fold increase in DaZn and DpZn values respectively and 100 times drop in B value. Addition of 55 ppm Zn to the soil significantly increased the DaZn and DpZn values. (author)
Transport tensors in perfectly aligned low-density fluids: Self-diffusion and thermal conductivity
International Nuclear Information System (INIS)
Singh, G. S.; Kumar, B.
2001-01-01
The modified Taxman equation for the kinetic theory of low-density fluids composed of rigid aspherical molecules possessing internal degrees of freedom is generalized to obtain the transport tensors in a fluid of aligned molecules. The theory takes care of the shape of the particles exactly but the solution has been obtained only for the case of perfectly aligned hard spheroids within the framework of the first Sonine polynomial approximation. The expressions for the thermal-conductivity components have been obtained for the first time whereas the self-diffusion components obtained here turn out to be exactly the same as those derived by Kumar and Masters [Mol. Phys. >81, 491 (1994)] through the solution of the Lorentz-Boltzmann equation. All our expressions yield correct results in the hard-sphere limit
Diffusion in the uranium - plutonium system and self-diffusion of plutonium in epsilon phase
International Nuclear Information System (INIS)
Dupuy, M.
1967-07-01
A survey of uranium-plutonium phase diagram leads to confirm anglo-saxon results about the plutonium solubility in α uranium (15 per cent at 565 C) and the uranium one in ζ phase (74 per cent at 565 C). Interdiffusion coefficients, for concentration lower than 15 per cent had been determined in a temperature range from 410 C to 640 C. They vary between 0.2 and 6 10 12 cm 2 s -1 , and the activation energy between 13 and 20 kcal/mole. Grain boundary, diffusion of plutonium in a uranium had been pointed out by micrography, X-ray microanalysis and α autoradiography. Self-diffusion of plutonium in ε phase (bcc) obeys Arrhenius law: D = 2. 10 -2 exp -(18500)/RT. But this activation energy does not follow empirical laws generally accepted for other metals. It has analogies with 'anomalous' bcc metals (βZr, βTi, βHf, U γ ). (author) [fr
Increased self-diffusion of brain water in hydrocephalus measured by MR imaging
DEFF Research Database (Denmark)
Gideon, P; Thomsen, C; Gjerris, F
1994-01-01
We used MR imaging to measure the apparent brain water self-diffusion in 5 patients with normal pressure hydrocephalus (NPH), in 2 patients with high pressure hydrocephalus (HPH), and in 8 age-matched controls. In all patients with NPH significant elevations of the apparent diffusion coefficients...... white matter, and in one patient reexamined one year after surgery, ADCs were unchanged in nearly all brain regions. The increased ADC values in hydrocephalus patients may be caused by factors such as changes in myelin-associated bound water, increased Virchow-Robin spaces, and increased extracellular...... brain water fraction. For further studies of brain water diffusion in hydrocephalus patients, echo-planar imaging techniques with imaging times of a few seconds may be valuable....
First-principles study on mono-vacancy self diffusion and recovery in tungsten crystal
Energy Technology Data Exchange (ETDEWEB)
Wen, Shu long [Key Laboratory of Advanced Technology of Materials (Ministry of Education), Superconductivity and New Energy R& D Ceter, Southwest JiaoTong University, Chengdu, Sichuan 610031 (China); Chen, Ji ming; Liu, Xiang [Fusion Science of Southwestern Institute of Physics, Chengdu, Sichuan 610041 (China); Zhu, Hao; Chang, Hong yan [Key Laboratory of Advanced Technology of Materials (Ministry of Education), Superconductivity and New Energy R& D Ceter, Southwest JiaoTong University, Chengdu, Sichuan 610031 (China); Huang, Zheng, E-mail: zhhuang@swjtu.edu.cn [Key Laboratory of Advanced Technology of Materials (Ministry of Education), Superconductivity and New Energy R& D Ceter, Southwest JiaoTong University, Chengdu, Sichuan 610031 (China); Pan, Min, E-mail: mpan@swjtu.edu.cn [Key Laboratory of Advanced Technology of Materials (Ministry of Education), Superconductivity and New Energy R& D Ceter, Southwest JiaoTong University, Chengdu, Sichuan 610031 (China); Western Superconducting Technologies Co., Ltd., Xi’an, Shanxi 710018 (China); Zhao, Yong [Key Laboratory of Advanced Technology of Materials (Ministry of Education), Superconductivity and New Energy R& D Ceter, Southwest JiaoTong University, Chengdu, Sichuan 610031 (China)
2016-11-01
Highlights: • The migration barrier energy E{sub m} of vacancy indicated that the optimum diffusion paths would exist in the diffusion process. • The Frenkel pair’s recovery had a close correlation with the “I–V” distance and within a range of 1.86–2.08 eV. • The self-recovery region has an ellipsoid profile with the semiminor axis of 2.7 Å and the semimajor axis of 5.5 Å. • The probability for the vacancy migration was closely assosiated with the E{sub m} and the working temperature. - Abstract: The point defects behavior becomes one of the most basic issues under the challenge of fusion environment. The recovery mechanisms of Frenkel pair defects and the self-diffusion coefficient of mono-vacancy in bulk bcc tungsten were researched by the first principle calculations. The calculation of migration energy curves for <111> SIAs indicated that the process of the Frenkel pair recovery had a close correlation with the “I–V” distance, and the migration barrier energies E{sub m} was within a limit range of 1.86–2.08 eV. It was found that the self-recovery region had an ellipsoid profile with the semiminor axis of 2.7 Å and the semimajor axis of 5.5 Å. The self-diffusion coefficients of the mono-vacancy were calculated and the results showed that the probability for the vacancy migration was not only associated with the E{sub m} but also the temperature being challenged.
First-principles study on mono-vacancy self diffusion and recovery in tungsten crystal
International Nuclear Information System (INIS)
Wen, Shu long; Chen, Ji ming; Liu, Xiang; Zhu, Hao; Chang, Hong yan; Huang, Zheng; Pan, Min; Zhao, Yong
2016-01-01
Highlights: • The migration barrier energy E_m of vacancy indicated that the optimum diffusion paths would exist in the diffusion process. • The Frenkel pair’s recovery had a close correlation with the “I–V” distance and within a range of 1.86–2.08 eV. • The self-recovery region has an ellipsoid profile with the semiminor axis of 2.7 Å and the semimajor axis of 5.5 Å. • The probability for the vacancy migration was closely assosiated with the E_m and the working temperature. - Abstract: The point defects behavior becomes one of the most basic issues under the challenge of fusion environment. The recovery mechanisms of Frenkel pair defects and the self-diffusion coefficient of mono-vacancy in bulk bcc tungsten were researched by the first principle calculations. The calculation of migration energy curves for SIAs indicated that the process of the Frenkel pair recovery had a close correlation with the “I–V” distance, and the migration barrier energies E_m was within a limit range of 1.86–2.08 eV. It was found that the self-recovery region had an ellipsoid profile with the semiminor axis of 2.7 Å and the semimajor axis of 5.5 Å. The self-diffusion coefficients of the mono-vacancy were calculated and the results showed that the probability for the vacancy migration was not only associated with the E_m but also the temperature being challenged.
Krishna, R.; van Baten, J.M.
2011-01-01
Kärger and Pfeifer (1987) [1] have listed five different types of dependencies of the self-diffusivities, Di,self, on the loading, Θi, of guest molecules in zeolites. Of these five types, the Type IV dependence is particularly intriguing because it displays a maximum in the Di,self − Θi dependence
PFG-NMR self-diffusion in casein dispersions: effect of probe size and protein aggregate size
Salami, S.; Rondeau, C.; Duynhoven, van J.P.M.; Mariette, F.
2013-01-01
The self-diffusion coefficients of different molecular weight PEGs (Polyethylene glycol) and casein particles were measured, using a pulsed-gradient nuclear magnetic resonance technique (PFG-NMR), in native phosphocaseinate (NPC) and sodium caseinate (SC) dispersions where caseins are not structured
Nasrabad, Afshin Eskandari; Laghaei, Rozita; Eu, Byung Chan
2005-04-28
In previous work on the density fluctuation theory of transport coefficients of liquids, it was necessary to use empirical self-diffusion coefficients to calculate the transport coefficients (e.g., shear viscosity of carbon dioxide). In this work, the necessity of empirical input of the self-diffusion coefficients in the calculation of shear viscosity is removed, and the theory is thus made a self-contained molecular theory of transport coefficients of liquids, albeit it contains an empirical parameter in the subcritical regime. The required self-diffusion coefficients of liquid carbon dioxide are calculated by using the modified free volume theory for which the generic van der Waals equation of state and Monte Carlo simulations are combined to accurately compute the mean free volume by means of statistical mechanics. They have been computed as a function of density along four different isotherms and isobars. A Lennard-Jones site-site interaction potential was used to model the molecular carbon dioxide interaction. The density and temperature dependence of the theoretical self-diffusion coefficients are shown to be in excellent agreement with experimental data when the minimum critical free volume is identified with the molecular volume. The self-diffusion coefficients thus computed are then used to compute the density and temperature dependence of the shear viscosity of liquid carbon dioxide by employing the density fluctuation theory formula for shear viscosity as reported in an earlier paper (J. Chem. Phys. 2000, 112, 7118). The theoretical shear viscosity is shown to be robust and yields excellent density and temperature dependence for carbon dioxide. The pair correlation function appearing in the theory has been computed by Monte Carlo simulations.
Ganorkar, Nital N; Patil, Pooja R; Tikute, Sanjay S; Gopalkrishna, Varanasi
2017-10-01
Hand, Foot and Mouth disease (HFMD) is a common childhood disease and caused due to Enterovirus-A (EV-A), EV-B and EV-C species worldwide. Cases of HFMD were reported from, Ahmedabad (Gujarat, 2012) and Pune (Maharashtra, 2013-2014) in India. The present study highlights the identification of EV strains (CVA16, CVA6, CVA4 and Echo12), characterization of subgenotypes of CVA16, CVA6 strains during 2012-14 and CVA16, CVA6, EV71 strains reported from the earlier study (2009-10) in HFMD cases from India. A total 158 clinical specimens collected from 64 HFMD cases (2012-2014) were included in the study. EV detection was carried out by 5'NCR based RT-PCR, molecular typing and subgenotyping was by VP1/2A junction or VP1, full VP1 gene amplification respectively followed by phylogenetic analysis. The present study reports 63.92% (101/158) EV positivity by RT-PCR. Ninety four of the 101 (93.06%) EV positive strains were amplified by VP1/2A junction or VP1 regions. Sequence analysis revealed the presence of CVA16 (61.7%), CVA6 (34.04%), CVA4 and Echo12 (4.3%). A total of 114 EV positive strains were genotyped using full and partial VP1 region. All CVA16 Indian strains (n=70) clustered with rarely reported B1c subgenotype, CVA6 (n=43) and EV71 (n=1) strains clustered with sub-lineage E2 and C1 subgenotypes respectively. In summary, the study reports genetic characterization of CVA16, CVA6, CVA4 and Echo12 strains in HFMD cases from India. Circulation of B1c subgenotype of CVA16, E2 sub-lineage of CVA6 and C1 subgenotype of EV 71 strains in HFMD cases were reported for the first time from India. This study helps to understand the genotype distribution, genetic diversity of EV strains associated with HFMD from Eastern, Western and Southern regions in India. Copyright © 2017 Elsevier B.V. All rights reserved.
Self-diffusion in 69Ga121Sb/71Ga123Sb isotope heterostructures
Bracht, H.; Nicols, S. P.; Haller, E. E.; Silveira, J. P.; Briones, F.
2001-05-01
Gallium and antimony self-diffusion experiments have been performed in undoped 69Ga121Sb/71Ga123Sb isotope heterostructures at temperatures between 571 and 708 °C under Sb- and Ga-rich ambients. Ga and Sb profiles measured with secondary ion mass spectrometry reveal that Ga diffuses faster than Sb by several orders of magnitude. This strongly suggests that the two self-atom species diffuse independently on their own sublattices. Experimental results lead us to conclude that Ga and Sb diffusion are mediated by Ga vacancies and Sb interstitials, respectively, and not by the formation of a triple defect proposed earlier by Weiler and Mehrer [Philos. Mag. A 49, 309 (1984)]. The extremely slow diffusion of Sb up to the melting temperature of GaSb is proposed to be a consequence of amphoteric transformations between native point defects which suppress the formation of those native defects which control Sb diffusion. Preliminary experiments exploring the effect of Zn indiffusion at 550 °C on Ga and Sb diffusion reveal an enhanced intermixing of the Ga isotope layers compared to undoped GaSb. However, under the same conditions the diffusion of Sb was not significantly affected.
Self-diffusion and solute diffusion in alloys under irradiation: Influence of ballistic jumps
International Nuclear Information System (INIS)
Roussel, Jean-Marc; Bellon, Pascal
2002-01-01
We have studied the influence of ballistic jumps on thermal and total diffusion of solvent and solute atoms in dilute fcc alloys under irradiation. For the diffusion components that result from vacancy migration, we introduce generalized five-frequency models, and show that ballistic jumps produce decorrelation effects that have a moderate impact on self-diffusion but that can enhance or suppress solute diffusion by several orders of magnitude. These could lead to new irradiation-induced transformations, especially in the case of subthreshold irradiation conditions. We also show that the mutual influence of thermal and ballistic jumps results in a nonadditivity of partial diffusion coefficients: the total diffusion coefficient under irradiation may be less than the sum of the thermal and ballistic diffusion coefficients. These predictions are confirmed by kinetic Monte Carlo simulations. Finally, it is shown that the method introduced here can be extended to take into account the effect of ballistic jumps on the diffusion of dumbbell interstitials in dilute alloys
Increased self-diffusion of brain water in hydrocephalus measured by MR imaging
International Nuclear Information System (INIS)
Gideon, P.; Thomsen, C.; Gjerris, F.; Soerensen, P.S.; Henriksen, O.
1994-01-01
We used MR imaging to measure the apparent brain water self-diffusion in 5 patients with normal pressure hydrocephalus (NPH), in 2 patients with high pressure hydrocephalus (HPH), and in 8 agematched controls. In all patients with NPH significant elevations of the apparent diffusion coefficients (ADC) of brain water were found within periventricular white matter, in the corpus callosum, in the internal capsule, within cortical gray matter, and in cerebrospinal fluid, whereas normal ADCs were found within the basal ganglia. In 2 patients with HPH elevated ADCs were found most prominently within white matter and in one patient reexamined one year after surgery. ADCs were unchanged in nearly all brain regions. The increased ADC values in hydrocephalus patients may be caused by factors such as changes in myelin-associated bound water, increased Virchow-Robin spaces, and increased extracellular brain water fraction. For further studies of brain water diffusion in hydrocephalus patients, echo-planar imaging techniques with imaging times of a few seconds may be valuable. (orig.)
Lü, Yongjun; Cheng, Hao; Chen, Min
2012-06-01
The self-diffusion coefficients D and the viscosities η of elemental Ni, Cu, and Ni-Si alloys have been calculated over a wide temperature range by molecular dynamics simulations. For elemental Ni and Cu, Arrhenius-law variations of D and η with temperature dominate. The temperature dependence of Dη can be approximated by a linear relation, whereas the Stokes-Einstein relation is violated. The calculations of D and η are extended to the regions close to the crystallization of Ni95Si5, Ni90Si10, and the glass transitions of Ni80Si20 and Ni75Si25. The results show that both D and η strongly deviate from the Arrhenius law in the vicinity of phase transitions, exhibiting a power-law divergence. We find a decoupling of diffusion and viscous flow just above the crystallization of Ni95Si5 and Ni90Si10. For the two glass-forming alloys, Ni80Si20 and Ni75Si25, the relation Dη = const is obeyed as the glass transition is approached, indicating a dynamic coupling as predicted by the mode-coupling theory. This coupling is enhanced with increasing Si composition and at 25%, Si spans a wide temperature range through the melting point. The decoupling is found to be related to the distribution of local ordered structure in the melts. The power-law governing the growth of solid-like clusters prior to crystallization creates a dynamic heterogeneity responsible for decoupling.
Long-time self-diffusion of charged spherical colloidal particles in parallel planar layers.
Contreras-Aburto, Claudio; Báez, César A; Méndez-Alcaraz, José M; Castañeda-Priego, Ramón
2014-06-28
The long-time self-diffusion coefficient, D(L), of charged spherical colloidal particles in parallel planar layers is studied by means of Brownian dynamics computer simulations and mode-coupling theory. All particles (regardless which layer they are located on) interact with each other via the screened Coulomb potential and there is no particle transfer between layers. As a result of the geometrical constraint on particle positions, the simulation results show that D(L) is strongly controlled by the separation between layers. On the basis of the so-called contraction of the description formalism [C. Contreras-Aburto, J. M. Méndez-Alcaraz, and R. Castañeda-Priego, J. Chem. Phys. 132, 174111 (2010)], the effective potential between particles in a layer (the so-called observed layer) is obtained from integrating out the degrees of freedom of particles in the remaining layers. We have shown in a previous work that the effective potential performs well in describing the static structure of the observed layer (loc. cit.). In this work, we find that the D(L) values determined from the simulations of the observed layer, where the particles interact via the effective potential, do not agree with the exact values of D(L). Our findings confirm that even when an effective potential can perform well in describing the static properties, there is no guarantee that it will correctly describe the dynamic properties of colloidal systems.
Self-diffusion dynamic behavior of atomic clusters on Re(0 0 0 1) surface
Energy Technology Data Exchange (ETDEWEB)
Liu Fusheng [Department of Applied Physics, Hunan University, Changsha 410082 (China); Hu Wangyu, E-mail: wangyuhu2001cn@yahoo.com.cn [Department of Applied Physics, Hunan University, Changsha 410082 (China); Deng Huiqiu; Luo Wenhua; Xiao Shifang [Department of Applied Physics, Hunan University, Changsha 410082 (China); Yang Jianyu [Department of Maths and Physics, Hunan Institute of Engineering, Xiangtan 411104 (China)
2009-08-15
Using molecular dynamics simulations and a modified analytic embedded atom potential, the self-diffusion dynamics of rhenium atomic clusters up to seven atoms on Re(0 0 0 1) surface have been studied in the temperature ranges from 600 K to 1900 K. The simulation time varies from 20 ns to 200 ns according to the cluster sizes and the temperature. The heptamer and trimer are more stable comparing to other neighboring non-compact clusters. The diffusion coefficients of clusters are derived from the mean square displacement of cluster's mass-center, and diffusion prefactors D{sub 0} and activation energies E{sub a} are derived from the Arrhenius relation. It is found that the Arrhenius relation of the adatom can be divided into two parts at different temperature range. The activation energy of clusters increases with the increasing of the atom number in clusters. The prefactor of the heptamer is 2-3 orders of magnitude higher than a usual prefactor because of a large number of nonequivalent diffusion processes. The trimer and heptamer are the nuclei at different temperature range according to the nucleation theory.
Retardation of grain boundary self-diffusion in nickel doped with antimony and tin
International Nuclear Information System (INIS)
Padgett, R.A.; White, C.L.
1984-01-01
Many important metallurgical phenomena are strongly influenced or controlled by grain boundary mass transport. There is also much evidence that the composition of grain boundaries is often significantly different from the overall composition of metals and alloys, owing to strong segregation of residual (and often undetected) impurities. This segregation, which does not always advertise its presence through grain boundary brittleness, may vary markedly from heat to heat, and occasionally from specimen to specimen within a given heat. Unfortunately, there are relatively few experimental observations of how such segregation affects grain boundary mass transport, and even less fundamental understanding of how these effects occur. In this paper we present autoradiographic results on self-diffusion of 63 Ni in nickel and nickel doped with antimony and tin. While these results do not permit a quantitative evaluation of the grain boundary diffusivity, D, they qualitatively illustrate the dramatic effect that these solute elements have on the ability of nickel grain boundaries to act as preferential paths for mass transport
Determination of the cationic self-diffusion coefficient in ThO2-5%UO2 nuclear fuel
International Nuclear Information System (INIS)
Sabioni, A.C.S.
1984-01-01
The cation self-diffusion coefficient for the ThO 2 -5%UO 2 by means of the densification model developed by Assmann and Stehle was determined. The experimental data of the fuel densification, used in the calculations, were obtained from thermal resinter tests. Our result is comparable to previously published values for U and Th diffusion in polycrystalline ThO 2 and (Th, U)O 2 . (Author) [pt
Fluids in micropores. II. Self-diffusion in a simple classical fluid in a slit pore
International Nuclear Information System (INIS)
Schoen, M.; Cushman, J.H.; Diestler, D.J.; Rhykerd, C.L. Jr.
1988-01-01
Self-diffusion coefficients D are computed for a model slit pore consisting of a rare-gas fluid confined between two parallel face-centered cubic (100) planes (walls) of rigidly fixed rare-gas atoms. By means of an optimally vectorized molecular-dynamics program for the CYBER 205, the dependence of D on the thermodynamic state (specified by the chemical potential μ, temperature T, and the pore width h) of the pore fluid has been explored. Diffusion is governed by Fick's law, even in pores as narrow as 2 or 3 atomic diameters. The diffusion coefficient oscillates as a function of h with fixed μ and T, vanishing at critical values of h, where fluid--solid phase transitions occur. A shift of the pore walls relative to one another in directions parallel with the walls can radically alter the structure of the pore fluid and consequently the magnitude of D. Since the pore fluid forms distinct layers parallel to the walls, a local diffusion coefficient D/sup (//sup i//sup )//sub parallel/ associated with a given layer i can be defined. D/sup (//sup i//sup )//sub parallel/ is least for the contact layer, even for pores as wide as 30 atomic diameters (∼100 A). Moreover, D/sup (//sup i//sup )//sub parallel/ increases with increasing distance of the fluid layer from the wall and, for pore widths between 16 and 30 atomic diameters, D/sup (//sup i//sup )//sub parallel/ is larger in the center of the pore than in the bulk fluid that is in equilibrium with the pore fluid. The opposite behavior is observed in corresponding smooth-wall pores, in which the discrete fluid--wall interactions have been averaged by smearing the wall atoms over the plane of the wall
Molecular dynamics simulations of self-diffusion near a symmetrical tilt grain boundary in UO{sub 2}
Energy Technology Data Exchange (ETDEWEB)
Vincent-Aublant, E.; Delaye, J.M. [CEA-Marcoule, DEN/DTCD/SECM, B.P. 17171, 30207 Bagnols sur Ceze cedex (France); Van Brutzel, L. [CEA-Saclay, DEN-DANS/DPC/SCP/LM2T, 91191 Gif-sur-Yvette (France)
2008-07-01
Molecular dynamics (MD) simulations have been used to study the influence of symmetrical tilt grain boundaries (GBs) in stoichiometric UO{sub 2} on uranium and oxygen self-diffusions. The study was performed on a large range of temperature varying from 300 K to 2100 K. First, the effect of the temperature on the structure and the formation energies of 6 relaxed tilt GBs was investigated. The {sigma}5 and {sigma}41 GBs geometries were chosen to study the diffusion. O and U diffusion coefficients have been calculated and compared to those obtained in a perfect stoichiometric UO{sub 2} as well as in over and under-stoichiometric matrices. (authors)
Self-diffusion of protons in H{sub 2}O ice VII at high pressures: Anomaly around 10 GPa
Energy Technology Data Exchange (ETDEWEB)
Noguchi, Naoki, E-mail: noguchi-n@okayama-u.ac.jp; Okuchi, Takuo [Institute for Planetary Materials, Okayama University, Misasa, Tottori 682-0193 (Japan)
2016-06-21
The self-diffusion of ice VII in the pressure range of 5.5–17 GPa and temperature range of 400–425 K was studied using micro Raman spectroscopy and a diamond anvil cell. The diffusion was monitored by observing the distribution of isotope tracers: D{sub 2}O and H{sub 2}{sup 18}O. The diffusion coefficient of hydrogen reached a maximum value around 10 GPa. It was two orders of magnitude greater at 10 GPa than at 6 GPa. Hydrogen diffusion was much faster than oxygen diffusion, which indicates that protonic diffusion is the dominant mechanism for the diffusion of hydrogen in ice VII. This mechanism is in remarkable contrast to the self-diffusion in ice I{sub h} that is dominated by an interstitial mechanism for the whole water molecule. An anomaly around 10 GPa in ice VII indicates that the rate-determining process for the proton diffusion changes from the diffusion of ionic defects to the diffusion of rotational defects, which was suggested by proton conductivity measurements and molecular dynamics simulations.
Hughes, Eric; Maan, Abid Aslam; Acquistapace, Simone; Burbidge, Adam; Johns, Michael L; Gunes, Deniz Z; Clausen, Pascal; Syrbe, Axel; Hugo, Julien; Schroen, Karin; Miralles, Vincent; Atkins, Tim; Gray, Richard; Homewood, Philip; Zick, Klaus
2013-01-01
Monodisperse water-in-oil-in-water (WOW) double emulsions have been prepared using microfluidic glass devices designed and built primarily from off the shelf components. The systems were easy to assemble and use. They were capable of producing double emulsions with an outer droplet size from 100 to 40 μm. Depending on how the devices were operated, double emulsions containing either single or multiple water droplets could be produced. Pulsed-field gradient self-diffusion NMR experiments have been performed on the monodisperse water-in-oil-in-water double emulsions to obtain information on the inner water droplet diameter and the distribution of the water in the different phases of the double emulsion. This has been achieved by applying regularization methods to the self-diffusion data. Using these methods the stability of the double emulsions to osmotic pressure imbalance has been followed by observing the change in the size of the inner water droplets over time. Copyright © 2012 Elsevier Inc. All rights reserved.
International Nuclear Information System (INIS)
Slade, R.C.; Pressman, H.A.; Barker, J.; Strange, J.H.
1988-01-01
Temperature dependent protonic conductivities σ and 1/H self-diffusion coefficients, D, are reported for polycrystalline hydrates of 12-tungstophosphoric acid (TPA). Conductivities were measured using ac admittane spectrometry and diffusion coefficients by the pulsed field gradient NMR technique. Conductivities for the hydrates TPA.nH 2 O (n=6, 14, 21) increase with n. Examination of σ and D values and of activation techniques shows self-diffusion and conduction to occur by different mechanisms in the higher hydrates. 25 refs.; 14 figs.; 1 table
International Nuclear Information System (INIS)
Shah, Syed Islamuddin; Nandipati, Giridhar; Rahman, Talat S; Karim, Altaf
2016-01-01
We studied self-diffusion of small two-dimensional Ag islands, containing up to ten atoms, on the Ag(111) surface using self-learning kinetic Monte Carlo (SLKMC) simulations. Activation barriers are calculated using the semi-empirical embedded atom method (EAM) potential. We find that two- to seven-atom islands primarily diffuse via concerted translation processes with small contributions from multi-atom and single-atom processes, while eight- to ten-atom islands diffuse via single-atom processes, especially edge diffusion, corner rounding and kink detachment, along with a minimal contribution from concerted processes. For each island size, we give a detailed description of the important processes, and their activation barriers, responsible for its diffusion. (paper)
Sushko, Gennady B; Verkhovtsev, Alexey V; Yakubovich, Alexander V; Schramm, Stefan; Solov'yov, Andrey V
2014-08-21
The process of self-diffusion of titanium atoms in a bulk material, on grain junctions and on surface is explored numerically in a broad temperature range by means of classical molecular dynamics simulation. The analysis is carried out for a nanoscale cylindrical sample consisting of three adjacent sectors and various junctions between nanocrystals. The calculated diffusion coefficient varies by several orders of magnitude for different regions of the sample. The calculated values of the bulk diffusion coefficient correspond reasonably well to the experimental data obtained for solid and molten states of titanium. Investigation of diffusion in the nanocrystalline titanium is of a significant importance because of its numerous technological applications. This paper aims to reduce the lack of data on diffusion in titanium and describe the processes occurring in bulk, at different interfaces and on surface of the crystalline titanium.
Energy Technology Data Exchange (ETDEWEB)
Villaine, P [Commissariat a l' Energie Atomique, 38 - Grenoble (France). Centre d' Etudes Nucleaires
1967-10-01
Uranium self diffusion in near-stoichiometric stabilized uranium monocarbide has been investigated in the temperature range 1450-2000 deg. C. A thin layer of {sup 235}UC was deposited onto the samples and the diffusion profiles were analyzed by both sectioning and alpha-spectrometry techniques. The variation with temperature of the self-diffusion coefficient can be expressed by the equation: D = 7.5 x 10{sup -5} exp [-(81 {+-} 10) kcal/mole / RT] Cm{sup 2} s{sup -1} The coefficient D decreases with increasing carbon content. Autoradiographs and profile analysis have evidenced a preferential grain-boundary diffusion at all temperatures and compositions investigated. This phenomenon was used for a study of grain-boundary migration and for the evaluation of grain-boundary diffusion coefficients. The activation energy thus derived is close to the volume diffusion activation energy. (author) [French] L'autodiffusion de l'uranium dans le monocarbure d'uranium de composition voisine de la stoechiometrie et stabilise par recuit prealable, a ete etudiee entre 1450 et 2000 deg. C par la methode du depot mince de traceur, suivie des techniques d'abrasion comptage et de spectrometrie alpha. La variation avec la temperature du coefficient d'autodiffusion peut s'ecrire: D = 7.5 x 10{sup -5} exp [-(81 {+-} 10) kcal/mole / RT] Cm{sup 2} s{sup -1} Le coefficient D decroit avec une augmentation de la teneur en carbone. L'observation d'autoradiographies et l'analyse de profils de diffusion ont mis en evidence l'importance d'une diffusion intergranulaire preferentielle pour toutes les compositions etudiees et a toutes les temperatures. Cette diffusion a egalement ete utilisee pour l'etude de la migration des joints de grains et pour le calcul approche du coefficient de diffusion mtergranulaire. L'energie d'activation ainsi determinee est voisine de celle correspondant a la diffusion volumique. (auteur)
DEFF Research Database (Denmark)
Rittig, F.; Karger, J.; Papadakis, C.M.
1999-01-01
We report on temperature-dependent self-diffusion measurements of compositionally different and non-entangled poly(ethylene-co-propylene)-b-poly(dimethylsiloxane) PEP-PDMS diblock copolymers in the melt above and below the order-to-disorder transition temperature. Depending on the dimensionality...
Self-diffusion of 60Co and 72Ga in the ordered electronic compound CoGa
International Nuclear Information System (INIS)
Bose, A.; Frohberg, G.; Wever, H.
1979-01-01
The investigation of the self-diffusion of 60 Co and 72 Ga in the ordered B2-compound CoGa containing 48.6, 52.4, 54.3, and 57.2 at% Co results in a ratio G of the diffusion coefficients of both components between 1.45 and 1.87 which is nearly temperature-independent for one composition. This suggests that the diffusion process is governed by a six-jump-ring-mechanism. Two kinds of rings have to be distinguished: ring I begins with a vacancy at a Co lattice site, ring II with a vacancy on a Ga lattice site. The contribution from each ring can be calculated from the ratio G. The activation enthalpies of diffusion for both rings can then be separated into formation and migration enthalpies, the latter being determined by the rate controlling steps, which are step 3 for ring I and step 2 for ring II. From the resulting migration enthalpies, the measured formation enthalpy of the triple defect, the formation enthalpy of the compound and their concentration dependences the energy changes during the six-jump-ring-mechanism are calculated. (author)
Self-diffusion of calcium and yttrium in pure and YF3-doped CaF2 single crystals
International Nuclear Information System (INIS)
Kucheria, C.S.
1979-07-01
Self-diffusion coefficients for Ca and Y were measured in pure and YF 3 -doped CaF 2 crystals for dopant levels ranging from 2 to 10 mole %. Diffusion data were analyzed as a function of temperature and as a function of composition. Comparison of Arrhenius relationships for both Ca and Y showed that the activation energy for cation diffusion decreased approximately linearly as the YF 3 dopant level increased. Atomic jump pathways were considered and the decrease in the activation energy was explained by an increase in the constriction sizes due to Willis cluster formation. Diffusion coefficients for both cations were found to increase approximately linearly with square of the mole percent YF 3 . A comparison of activation energies and diffusion coefficients for both cations in doped crystals indicated that Y required lower activation energy for diffusion than Ca but the diffusion coefficient was also lower for Y compared to Ca. The smaller activation energy for Y was explained by the smaller ionic size of Y, whereas the smaller diffusion coefficient for Y was explained on the basis of highly correlated jumps of Y ions because of interaction between Y/sub Ca/ and V/sub Ca/
Kluijtmans, Sebastiaan G. J. M.; de Hoog, Els H. A.; Philipse, Albert P.
1998-05-01
The influence of charge on diffusion in porous media was studied for fluorescent colloidal silica spheres diffusing in a porous glass medium. The bicontinuous porous silica glasses were optically matched with an organic solvent mixture in which both glass and tracers are negatively charged. Using fluorescence recovery after photobleaching, the long-time self-diffusion coefficient DSL of the confined silica particles was monitored in situ as a function of the ionic strength and particle to pore size ratio. At high salt concentration DSL reaches a relatively high plateau value, which depends on the particle to pore size ratio. This plateau value is unexpectedly higher than the value found for uncharged silica spheres in these porous glasses, but still significantly smaller than the free particle bulk diffusion coefficient of the silica spheres. At low salt concentration DSL reduces markedly, up to the point where colloids are nearly immobilized. This peculiar retardation probably originates from potential traps and barriers at pore intersections due to deviations from cylinder symmetry in the double layer interactions between tracers and pore walls. This indicates that diffusion of charged particles in tortuous porous media may be very different from transport in long capillaries without such intersections.
International Nuclear Information System (INIS)
Guenza, M.; Schweizer, K.S.
1998-01-01
The predictions of polymer-mode-coupling theory for self-diffusion in entangled structurally and interaction symmetric diblock copolymer fluids are illustrated by explicit numerical calculations. We find that retardation of translational motion emerges near and somewhat below the order endash disorder transition (ODT) in an approximately exponential and/or thermally activated manner. At fixed reduced temperature, suppression of diffusion is enhanced with increasing diblock molecular weight, compositional symmetry, and/or copolymer concentration. At very low temperatures, a new entropic-like regime of mobility suppression is predicted based on an isotropic supercooled liquid description of the copolymer structure. Preliminary generalization of the theory to treat diblock tracer diffusion is also presented. Quantitative applications to recent self and tracer diffusion measurements on compositionally symmetric polyolefin diblock materials have been carried out, and very good agreement between theory and experiment is found. Asymmetry in block local friction constants is predicted to significantly influence mobility suppression, with the largest effects occurring when the minority block is also the high friction species. New experiments to further test the predictions of the theory are suggested. copyright 1998 American Institute of Physics
Energetics and self-diffusion behavior of Zr atomic clusters on a Zr(0 0 0 1) surface
Energy Technology Data Exchange (ETDEWEB)
Liu Fusheng [Department of Applied Physics, Hunan University, Changsha 410082 (China); Hu Wangyu [Department of Applied Physics, Hunan University, Changsha 410082 (China)], E-mail: wangyuhu2001cn@yahoo.com.cn; Deng Huiqiu; Luo Wenhua; Xiao Shifang [Department of Applied Physics, Hunan University, Changsha 410082 (China); Yang Jianyu [Department of Maths and Physics, Hunan Institute of Engineering, Xiangtan 411104 (China)
2009-09-15
Using a molecular dynamics method and a modified analytic embedded atom potential, the energetic and the self-diffusion dynamics of Zr atomic clusters up to eight atoms on {alpha}-Zr(0 0 0 1) surface have been studied. The simulation temperature ranges from 300 to 1100 K and the simulation time varies from 20 to 40 ns. It's found that the heptamer and trimer are more stable comparing to other neighboring non-compact clusters. The diffusion coefficients of clusters are derived from the mean square displacement of cluster's mass-center and the present diffusion coefficients for clusters exhibit an Arrhenius behavior. The Arrhenius relation of the single adatom can be divided into two parts in different temperature range because of their different diffusion mechanisms. The migration energies of clusters increase with increasing the number of atoms in cluster. The differences of the prefactors also come from the diverse diffusion mechanisms. On the facet of 60 nm, the heptamer can be the nuclei in the crystal growth below 370 K.
International Nuclear Information System (INIS)
Gopala Rao, R.V.; Das, R.
1988-01-01
The three partial structure factors S/sub 11/(K), S/sub 22/(K), and S/sub 12/(K) defined by Ashcroft and Langreth are computed with a square-well potential as a perturbation over a hard-sphere potential for different atomic fractions or concentrations of cadmium for Cd-Ga melt at 296 0 C. Also, the number-number, concentration-concentration, and the cross-term number-concentration structure factors due to Bhatia-Thornton have been calculated for the seven concentrations of Cd-Ga melt at that temperature. From these partial structure factors total structure factors are computed and are compared with the experimental results. The total structure factors so computed are found to be in excellent agreement with the measured values except in the long-wavelength limit of S(0). Using the partial structure factors in the long-wavelength limit the isothermal compressibilities have been calculated. From these partial structure factors and by using the linear-trajectory approximation of Helfand, the self-diffusion coefficients D/sub i/'s have also been calculated for various atomic fractions of Cd for Cd-Ga alloy at 296 0 C. From these D/sub i/'s, an estimate of the mutual diffusion coefficients has been made to a good approximation
Yang, Jing; Youssef, Mostafa; Yildiz, Bilge
2018-01-01
In this work, we quantify oxygen self-diffusion in monoclinic-phase zirconium oxide as a function of temperature and oxygen partial pressure. A migration barrier of each type of oxygen defect was obtained by first-principles calculations. Random walk theory was used to quantify the diffusivities of oxygen interstitials by using the calculated migration barriers. Kinetic Monte Carlo simulations were used to calculate diffusivities of oxygen vacancies by distinguishing the threefold- and fourfold-coordinated lattice oxygen. By combining the equilibrium defect concentrations obtained in our previous work together with the herein calculated diffusivity of each defect species, we present the resulting oxygen self-diffusion coefficients and the corresponding atomistically resolved transport mechanisms. The predicted effective migration barriers and diffusion prefactors are in reasonable agreement with the experimentally reported values. This work provides insights into oxygen diffusion engineering in Zr O2 -related devices and parametrization for continuum transport modeling.
Golubev, V. A.; Kumeev, R. S.; Gurina, D. L.; Nikiforov, M. Yu.
2017-05-01
The effect of concentration on the self-diffusion coefficients of acetylsalicylic acid and methyl salicylate in methanol- d4 is investigated in the temperature range of 278-318 K using NMR. It is found that the self-diffusion coefficients increase along with temperature and fall as concentration rises. Within the limit of an infinitely dilute solution, the effective radii of solute molecules, calculated using the Stokes-Einstein equation shrink as the temperature grows. It is shown that the observed reduction of effective radii is associated with an increase in the fraction of solute monomers as the temperature rises. The physicochemical parameters of heteroassociation of acetylsalicylic acid and methyl salicylate with methanol are determined.
Tsapis, N; Reiss-Husson, F; Ober, R; Genest, M; Hodges, R S; Urbach, W
2001-01-01
The light-harvesting complex LH2 from a purple bacterium, Rubrivivax gelatinosus, has been incorporated into the Q230 cubic phase of monoolein. We measured the self-diffusion of LH2 in detergent solution and in the cubic phase by fluorescence recovery after photobleaching. We investigated also the absorption and fluorescence properties of this oligomeric membrane protein in the cubic phase, in comparison with its beta-octyl glucoside solution. In these experiments, native LH2 and LH2 labeled ...
International Nuclear Information System (INIS)
Ferraz, Wilmar Barbosa
1998-01-01
This study of uranium self-diffusion in UO 2 presents a great technological interest because its knowledge is necessary to interpret the mechanism of many important processes like, for example, sintering, creep, grain growth, in-reactor densification and others. The present work deals with new measurements of uranium diffusion in UO 2 single crystals and polycrystals through an original mythology based on the utilization of 235 U as tracer and depth profiling by secondary ions mass spectrometry (SIMS). The diffusion experiments were performed between 1498 and 1697 deg C, in H 2 atmosphere. In our experimental conditions, the uranium volume diffusion coefficients measured in UO 2 single crystals can be described by the following Arrhenius relation: D(cm 2 /s) = 8.54x10 -7 exp[-4.4(eV)/K T]. The uranium grain-boundary diffusion experiments performed in UO 2 polycrystals corresponded to the type-B diffusion. In this case, it was possible to determine the product D'δ, where D is the grain-boundary diffusion and is the width of the grain-boundary. In our experimental conditions, the product D'δ can be described by the following relation: D'δ (cm 3 /s) = 1.62x10 -5 exp[-5.6(eV)/K T]. These results that the uranium volume diffusion coefficients, measured in UO 2 single crystals, are 5 orders of magnitude lower than the uranium grain boundary diffusion coefficients measured in UO 2 polycrystalline pellets, in the same experimental conditions. This large difference between these two types of diffusivities indicates that the grain boundary is a preferential via for uranium diffusion in UO 2 polycrystalline pellet. (author)
Self-diffusion coefficients and shear viscosity of inverse power fluids: from hard- to soft-spheres.
Heyes, D M; Brańka, A C
2008-07-21
Molecular dynamics computer simulation has been used to compute the self-diffusion coefficient, D, and shear viscosity, eta(s), of soft-sphere fluids, in which the particles interact through the soft-sphere or inverse power pair potential, phi(r) = epsilon(sigma/r)(n), where n measures the steepness or stiffness of the potential, and epsilon and sigma are a characteristic energy and distance, respectively. The simulations were carried out on monodisperse systems for a range of n values from the hard-sphere (n --> infinity) limit down to n = 4, and up to densities in excess of the fluid-solid co-existence value. A new analytical procedure is proposed which reproduces the transport coefficients at high densities, and can be used to extrapolate the data to densities higher than accurately accessible by simulation or experiment, and tending to the glass transition. This formula, DX(c-1) proportional, variant A/X + B, where c is an adjustable parameter, and X is either the packing fraction or the pressure, is a development of one proposed by Dymond. In the expression, -A/B is the value of X at the ideal glass transition (i.e., where D and eta(s)(-1) --> 0). Estimated values are presented for the packing fraction and the pressure at the glass transition for n values between the hard and soft particle limits. The above expression is also shown to reproduce the high density viscosity data of supercritical argon, krypton and nitrogen. Fits to the soft-sphere simulation transport coefficients close to solid-fluid co-existence are also made using the analytic form, ln(D) = alpha(X)X, and n-dependence of the alpha(X) is presented (X is either the packing fraction or the pressure).
International Nuclear Information System (INIS)
Posselt, M.; Gao, F.; Bracht, H.
2008-01-01
The migration of point defects in silicon and the corresponding atomic mobility are investigated by comprehensive classical molecular-dynamics simulations using the Stillinger-Weber potential and the Tersoff potential. In contrast to most of the previous studies both the point defect diffusivity and the self-diffusion coefficient per defect are calculated separately so that the diffusion-correlation factor can be determined. Simulations with both the Stillinger-Weber and the Tersoff potential show that vacancy migration is characterized by the transformation of the tetrahedral vacancy to the split vacancy and vice versa and the diffusion-correlation factor f V is about 0.5. This value was also derived by the statistical diffusion theory under the assumption of the same migration mechanism. The mechanisms of self-interstitial migration are more complex. The detailed study, including a visual analysis and investigations with the nudged elastic band method, reveals a variety of transformations between different self-interstitial configurations. Molecular-dynamics simulations using the Stillinger-Weber potential show that the self-interstitial migration is dominated by a dumbbell mechanism, whereas in the case of the Tersoff potential the interstitialcy mechanism prevails. The corresponding values of the correlation factor f I are different, namely, 0.59 and 0.69 for the dumbbell and the interstitialcy mechanisms, respectively. The latter value is nearly equal to that obtained by the statistical theory which assumes the interstitialcy mechanism. Recent analysis of experimental results demonstrated that in the framework of state-of-the-art diffusion and reaction models the best interpretation of point defect data can be given by assuming f I ≅0.6. The comparison with the present atomistic study leads to the conclusion that the self-interstitial migration in Si should be governed by a dumbbell mechanism
Self-diffusion dynamics processes relevant to 2D homoepitaxy growth of Ni adatom on Ni(111) surface
Energy Technology Data Exchange (ETDEWEB)
Liu, Fusheng [College of Metallurgical Engineering, Hunan University of Technology, Zhuzhou 412007 (China); Chen, Yifeng, E-mail: yefengc63@sina.com [College of Metallurgical Engineering, Hunan University of Technology, Zhuzhou 412007 (China); Wang, Yufei, E-mail: yejin802@126.com [College of Metallurgical Engineering, Hunan University of Technology, Zhuzhou 412007 (China); Liu, Zhulin; Hu, Zhongliang [College of Metallurgical Engineering, Hunan University of Technology, Zhuzhou 412007 (China); Yang, Xiyuan [Department of Physics, Hunan University of Arts and Science, Changde 415000 (China); Luo, Wenhua [Department of Physics and Electronic Information Science, Hunan Institute of Science and Technology, Yueyang 414006 (China)
2014-07-01
Using molecular dynamics and modified analytic embedded atom methods, the atomic self-diffusion dynamics behaviors relevant to 2D crystal growth on Ni(111) surface have been studied between 150 and 600 K. On perfect Ni(111) surface, the activation energy and prefactor are 0.058±0.001 eV and 4.2×10{sup −4} cm{sup 2}/s between 150 and 350 K, and 0.082±0.003 eV and 7.8×10{sup −4} cm{sup 2}/s from 400 to 600 K. Ni adatom just hops along the directions of close-packed steps on stepped Ni(111) surface, the corresponding activation energies and prefactors are 0.188±0.002 eV and (3.8–4.4)×10{sup −3} cm{sup 2}/s along the direction of A-type step, 0.140±0.001 eV and (1.1–1.2)×10{sup −3} cm{sup 2}/s along the direction of B-type step, and both fitting lines of Arrhenius law intersect at T{sub c}=420–440 K. Our results show that the atomic growth dynamics under nonequilibrium conditions is gradually dominated by the prefactor with increasing temperature. In addition, the shape-change of the 2D nanometer-size island has been discussed on stepped Ni(111) surface in different temperature range.
International Nuclear Information System (INIS)
Matzke, H.; Bradbury, M.H.
1978-01-01
Self-diffusion measurements of Pu-238 and U-233 have been carried out in a wide range of advanced nuclear fuels in the temperature region from 1200 to 2300 0 C. The materials studied varied in composition from carbides through carbonitrides to nitrides. In particular the effect on self-diffusion rates of factors such as non-metal/metal ratio, oxygen content increasing nitrogen contents, metallic impurity additions, the presence of second phases and fission products simulating 16, 10 and 3 a /o burn up has been established. Grain boundary diffusion rates were evaluated where possible. Carbon diffusion in stoichiometric and off-stoichiometric UC and in a series of uranium carbonitride samples was also measured. The RADIF experiments (radiation induced diffusion) have provided results upon the effect of irradiation on the self-diffusion rates in the temperature range 150 to 1300 0 C. Each of the factors mentioned above is discussed in detail with special attention being given to the effects of non-metal/metal ratio, impurities and increasing the nitrogen content in carbonitride materials
Energy Technology Data Exchange (ETDEWEB)
Sarman, Sten, E-mail: sarman@ownit.nu; Wang, Yong-Lei; Laaksonen, Aatto [Arrhenius Laboratory, Department of Materials and Environmental Chemistry, Stockholm University, 106 91 Stockholm (Sweden)
2016-02-07
The self-diffusion coefficients of nematic phases of various model systems consisting of regular convex calamitic and discotic ellipsoids and non-convex bodies such as bent-core molecules and soft ellipsoid strings have been obtained as functions of the shear rate in a shear flow. Then the self-diffusion coefficient is a second rank tensor with three different diagonal components and two off-diagonal components. These coefficients were found to be determined by a combination of two mechanisms, which previously have been found to govern the self-diffusion of shearing isotropic liquids, namely, (i) shear alignment enhancing the diffusion in the direction parallel to the streamlines and hindering the diffusion in the perpendicular directions and (ii) the distortion of the shell structure in the liquid whereby a molecule more readily can escape from a surrounding shell of nearest neighbors, so that the mobility increases in every direction. Thus, the diffusion parallel to the streamlines always increases with the shear rate since these mechanisms cooperate in this direction. In the perpendicular directions, these mechanisms counteract each other so that the behaviour becomes less regular. In the case of the nematic phases of the calamitic and discotic ellipsoids and of the bent core molecules, mechanism (ii) prevails so that the diffusion coefficients increase. However, the diffusion coefficients of the soft ellipsoid strings decrease in the direction of the velocity gradient because the broadsides of these molecules are oriented perpendicularly to this direction due the shear alignment (i). The cross coupling coefficient relating a gradient of tracer particles in the direction of the velocity gradient and their flow in the direction of the streamlines is negative and rather large, whereas the other coupling coefficient relating a gradient in the direction of the streamlines and a flow in the direction of the velocity gradient is very small.
Sarman, Sten; Wang, Yong-Lei; Laaksonen, Aatto
2016-02-01
The self-diffusion coefficients of nematic phases of various model systems consisting of regular convex calamitic and discotic ellipsoids and non-convex bodies such as bent-core molecules and soft ellipsoid strings have been obtained as functions of the shear rate in a shear flow. Then the self-diffusion coefficient is a second rank tensor with three different diagonal components and two off-diagonal components. These coefficients were found to be determined by a combination of two mechanisms, which previously have been found to govern the self-diffusion of shearing isotropic liquids, namely, (i) shear alignment enhancing the diffusion in the direction parallel to the streamlines and hindering the diffusion in the perpendicular directions and (ii) the distortion of the shell structure in the liquid whereby a molecule more readily can escape from a surrounding shell of nearest neighbors, so that the mobility increases in every direction. Thus, the diffusion parallel to the streamlines always increases with the shear rate since these mechanisms cooperate in this direction. In the perpendicular directions, these mechanisms counteract each other so that the behaviour becomes less regular. In the case of the nematic phases of the calamitic and discotic ellipsoids and of the bent core molecules, mechanism (ii) prevails so that the diffusion coefficients increase. However, the diffusion coefficients of the soft ellipsoid strings decrease in the direction of the velocity gradient because the broadsides of these molecules are oriented perpendicularly to this direction due the shear alignment (i). The cross coupling coefficient relating a gradient of tracer particles in the direction of the velocity gradient and their flow in the direction of the streamlines is negative and rather large, whereas the other coupling coefficient relating a gradient in the direction of the streamlines and a flow in the direction of the velocity gradient is very small.
International Nuclear Information System (INIS)
Taherkhani, Farid; Akbarzadeh, Hamed; Feyzi, Mostafa; Rafiee, Hamid Reza
2015-01-01
Molecular dynamics simulation has been implemented for doping effect on melting temperature, heat capacity, self-diffusion coefficient of gold–copper bimetallic nanostructure with 55 total gold and copper atom numbers and its bulk alloy. Trend of melting temperature for gold–copper bimetallic nanocluster is not same as melting temperature copper–gold bulk alloy. Molecular dynamics simulation of our result regarding bulk melting temperature is consistence with available experimental data. Molecular dynamics simulation shows that melting temperature of gold–copper bimetallic nanocluster increases with copper atom fraction. Semi-empirical potential model and quantum Sutton–Chen potential models do not change melting temperature trend with copper doping of gold–copper bimetallic nanocluster. Self-diffusion coefficient of copper atom is greater than gold atom in gold–copper bimetallic nanocluster. Semi-empirical potential within the tight-binding second moment approximation as new application potential model for melting temperature of gold–copper bulk structure shows better result in comparison with EAM, Sutton–Chen potential, and quantum Sutton–Chen potential models
Nylandsted larsen, A; Voss, T L; Strohm, A
2002-01-01
An invaluable method for studying diffusion in solids is the radiotracer technique. However, its applicability had been restricted to radiotracer atoms with half-lives $t_{1/2}$ of about 1~d or longer. Within the framework of IS372 a facility was developed in which short-lived radiotracer atoms ( 5min $\\scriptstyle{\\lesssim}$ $t_{1/2}\\scriptstyle{\\lesssim}$1 d ) can be used. For the implantation of the short-lived tracers the facility is flanged to the ISOLDE beamline, and all post-implantation steps required in the radiotracer technique are done in situ.\\\\ After successful application of this novel technique in diffusion studies of $^{11}$C ($t_{1/2}$ = 20.3 min), this experiment aims at performing self-diffusion studies of $^{31}$Si ($t_{1/2}$ = 2.6~h) in Si--Ge alloys and in amorphous Si--(B--)C--N ceramics.\\\\ Our motivation for measuring diffusion in Si--Ge alloys is their recent technological renaissance as well as the purpose to test the prediction that in these alloys the self-diffusion mechanism chang...
Energy Technology Data Exchange (ETDEWEB)
Taherkhani, Farid, E-mail: faridtaherkhani@gmail.com, E-mail: f.taherkhani@razi.ac.ir [Razi University, Department of Physical Chemistry (Iran, Islamic Republic of); Akbarzadeh, Hamed [Hakim Sabzevari University, Department of Chemistry (Iran, Islamic Republic of); Feyzi, Mostafa; Rafiee, Hamid Reza [Razi University, Department of Physical Chemistry (Iran, Islamic Republic of)
2015-01-15
Molecular dynamics simulation has been implemented for doping effect on melting temperature, heat capacity, self-diffusion coefficient of gold–copper bimetallic nanostructure with 55 total gold and copper atom numbers and its bulk alloy. Trend of melting temperature for gold–copper bimetallic nanocluster is not same as melting temperature copper–gold bulk alloy. Molecular dynamics simulation of our result regarding bulk melting temperature is consistence with available experimental data. Molecular dynamics simulation shows that melting temperature of gold–copper bimetallic nanocluster increases with copper atom fraction. Semi-empirical potential model and quantum Sutton–Chen potential models do not change melting temperature trend with copper doping of gold–copper bimetallic nanocluster. Self-diffusion coefficient of copper atom is greater than gold atom in gold–copper bimetallic nanocluster. Semi-empirical potential within the tight-binding second moment approximation as new application potential model for melting temperature of gold–copper bulk structure shows better result in comparison with EAM, Sutton–Chen potential, and quantum Sutton–Chen potential models.
Smith, R. Scott; Matthiesen, Jesper; Kay, Bruce D.
2010-03-01
Molecular beam techniques, temperature-programmed desorption (TPD), and reflection absorption infrared spectroscopy (RAIRS) are used to explore the relationship between krypton permeation through and the self-diffusivity of supercooled liquid methanol at temperatures (100-115 K) near the glass transition temperature, Tg (103 K). Layered films, consisting of CH3OH and CD3OH, are deposited on top of a monolayer of Kr on a graphene covered Pt(111) substrate at 25 K. Concurrent Kr TPD and RAIRS spectra are acquired during the heating of the composite film to temperatures above Tg. The CO vibrational stretch is sensitive to the local molecular environment and is used to determine the supercooled liquid diffusivity from the intermixing of the isotopic layers. We find that the Kr permeation and the diffusivity of the supercooled liquid are directly and quantitatively correlated. These results validate the rare-gas permeation technique as a tool for probing the diffusivity of supercooled liquids.
International Nuclear Information System (INIS)
Loon, L.R. van; Mueller, W.; Iijima, K.
2005-01-01
The temperature dependence of the self-diffusion of HTO, 22 Na + and 36 Cl - in Opalinus Clay (OPA) was studied using a through-diffusion technique, in which the temperature was gradually increased in the steady state phase of the diffusion. The measurements were done on samples from two different geological locations. The dependence of the effective diffusion coefficient on temperature was found to be of an Arrhenius type in the temperature range between 0 and 70 deg. C. A slight difference between the two locations could be observed. The average value of the activation energy of the self-diffusion of HTO in OPA was 21.1 ± 1.6 kJ mol -1 , and 21.0 ± 3.5 and 19.4 ± 1.5 kJ mol -1 for 22 Na + and 36 Cl - , respectively. The measured values for HTO are slightly higher than the values found for the bulk liquid water (HTO: 18.8 ± 0.4 kJ mol -1 ). This indicates that the structure of the confined water in OPA might be slightly different from that of bulk liquid water. Also for Na + and Cl - , slightly higher values than in bulk liquid water (Na + : 18.4 kJ mol -1 ; Cl - : 17.4 kJ mol -1 ) were observed. The Stokes-Einstein relationship, based on the temperature dependency of the viscosity of bulk water, could not be used to describe the temperature dependence of the diffusion of HTO in OPA. This additionally indicates the slightly different structure of the pore water in OPA
Hand, Foot, and Mouth Disease (HFMD)
... feature story, podcast, and other CDC resources about personal hygiene... Prevention People infected with hand, foot, and mouth ... these countries can protect themselves by practicing good personal hygiene. Learn more . To learn more about outbreaks occurring ...
High-precision molecular dynamics simulation of UO2–PuO2: Anion self-diffusion in UO2
International Nuclear Information System (INIS)
Potashnikov, S.I.; Boyarchenkov, A.S.; Nekrasov, K.A.; Kupryazhkin, A.Ya.
2013-01-01
Highlights: ► We perform MD simulation of oxygen diffusion in UO2 (up to 50 000 ions and 1 μs time). ► We reached 1400 K and 10 −12 cm 2 /sec, which allowed direct comparison to experiments. ► S-shaped T-dependence of activation energy and λ-peak of its derivative were obtained. ► Continual superionic phase transition (rather than first or second order) was proved. ► Activation energy of exchange diffusion equals anti-Frenkel defect formation energy. -- Abstract: Our series of articles is devoted to high-precision molecular dynamics simulation of mixed actinide-oxide (MOX) fuel in the approximation of rigid ions and pair interactions (RIPI) using high-performance graphics processors (GPU). In this article we study self-diffusion mechanisms of oxygen anions in uranium dioxide (UO 2 ) with the 10 recent and widely used sets of interatomic pair potentials (SPP) under periodic (PBC) and isolated (IBC) boundary conditions. Wide range of measured diffusion coefficients (from 10 −3 cm 2 /s at melting point down to 10 −12 cm 2 /s at 1400 K) made possible a direct comparison (without extrapolation) of the simulation results with the experimental data, which have been known only at low temperatures (T < 1500 K). A highly detailed (with the temperature step of 1 K) calculation of the diffusion coefficient allowed us to plot temperature dependences of the diffusion activation energy and its derivative, both of which show a wide (∼1000 K) superionic transition region confirming the broad λ-peaks of heat capacity obtained by us earlier. It is shown that regardless of SPP the anion self-diffusion in model crystals without surface or artificially embedded defects goes on via exchange mechanism, rather than interstitial or vacancy mechanisms suggested by the previous works. The activation energy of exchange diffusion turned out to coincide with the anti-Frenkel defect formation energy calculated by the lattice statics
Self-diffusion of calcium and yttrium in pure and YF/sub 3/-doped CaF/sub 2/ single crystals
Energy Technology Data Exchange (ETDEWEB)
Kucheria, C.S.
1979-07-01
Self-diffusion coefficients for Ca and Y were measured in pure and YF/sub 3/-doped CaF/sub 2/ crystals for dopant levels ranging from 2 to 10 mole %. Diffusion data were analyzed as a function of temperature and as a function of composition. Comparison of Arrhenius relationships for both Ca and Y showed that the activation energy for cation diffusion decreased approximately linearly as the YF/sub 3/ dopant level increased. Atomic jump pathways were considered and the decrease in the activation energy was explained by an increase in the constriction sizes due to Willis cluster formation. Diffusion coefficients for both cations were found to increase approximately linearly with square of the mole percent YF/sub 3/. A comparison of activation energies and diffusion coefficients for both cations in doped crystals indicated that Y required lower activation energy for diffusion than Ca but the diffusion coefficient was also lower for Y compared to Ca. The smaller activation energy for Y was explained by the smaller ionic size of Y, whereas the smaller diffusion coefficient for Y was explained on the basis of highly correlated jumps of Y ions because of interaction between Y/sub Ca/ and V/sub Ca/.
Energy Technology Data Exchange (ETDEWEB)
Moultos, Othonas A.; Economou, Ioannis G. [Chemical Engineering Program, Texas A& M University at Qatar, P.O. Box 23847, Doha (Qatar); Zhang, Yong; Maginn, Edward J., E-mail: ed@nd.edu [Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Tsimpanogiannis, Ioannis N. [Chemical Engineering Program, Texas A& M University at Qatar, P.O. Box 23847, Doha (Qatar); Environmental Research Laboratory, National Center for Scientific Research “Demokritos,” 15310 Aghia Paraskevi Attikis (Greece)
2016-08-21
Molecular dynamics simulations were carried out to study the self-diffusion coefficients of CO{sub 2}, methane, propane, n-hexane, n-hexadecane, and various poly(ethylene glycol) dimethyl ethers (glymes in short, CH{sub 3}O–(CH{sub 2}CH{sub 2}O){sub n}–CH{sub 3} with n = 1, 2, 3, and 4, labeled as G1, G2, G3, and G4, respectively) at different conditions. Various system sizes were examined. The widely used Yeh and Hummer [J. Phys. Chem. B 108, 15873 (2004)] correction for the prediction of diffusion coefficient at the thermodynamic limit was applied and shown to be accurate in all cases compared to extrapolated values at infinite system size. The magnitude of correction, in all cases examined, is significant, with the smallest systems examined giving for some cases a self-diffusion coefficient approximately 15% lower than the infinite system-size extrapolated value. The results suggest that finite size corrections to computed self-diffusivities must be used in order to obtain accurate results.
Energy Technology Data Exchange (ETDEWEB)
Dupuy, M [Commissariat a l' Energie Atomique, Fontenay-Aux-Roses (France). Centre d' Etudes Nucleaires
1967-07-01
A survey of uranium-plutonium phase diagram leads to confirm anglo-saxon results about the plutonium solubility in {alpha} uranium (15 per cent at 565 C) and the uranium one in {zeta} phase (74 per cent at 565 C). Interdiffusion coefficients, for concentration lower than 15 per cent had been determined in a temperature range from 410 C to 640 C. They vary between 0.2 and 6 10{sup 12} cm{sup 2} s{sup -1}, and the activation energy between 13 and 20 kcal/mole. Grain boundary, diffusion of plutonium in a uranium had been pointed out by micrography, X-ray microanalysis and {alpha} autoradiography. Self-diffusion of plutonium in {epsilon} phase (bcc) obeys Arrhenius law: D = 2. 10{sup -2} exp -(18500)/RT. But this activation energy does not follow empirical laws generally accepted for other metals. It has analogies with 'anomalous' bcc metals ({beta}Zr, {beta}Ti, {beta}Hf, U{sub {gamma}}). (author) [French] Une etude du diagramme d'equilibre uranium-plutonium conduit a confirmer les resultats anglo-saxons relatifs a la solubilite du plutonium dans l'uranium {alpha} (15 pour cent a 565 C) et de l'uranium dans la phase {zeta} (74 pour cent a 565 C). Les coefficients de diffusion chimique, pour des concentrations inferieures a 15 pour cent ont ete determines a des temperatures comprises entre 410 et 640 C. Ils se situent entre 0.2 et 6. 10{sup 12} cm{sup 2} s{sup -1}. L'energie d'activation varie entre 13 et 20 kcal/mole. La diffusion intergranulaire du plutonium dans l'uranium a a ete mise en evidence par micrographie, microanalyse X et autoradiographie {alpha}. L' autodiffusion du plutonium {beta} cubique centree obeit a la loi d'Arrhenius D = 2. 10{sup -2} exp - (18500)/RT. Son energie d'activation n'obeit pas aux lois empiriques generalement admises pour les autres metaux. Elle possede des analogies avec les cubiques centres ''anormaux'' (Zr{beta}, Ti{beta}, Hf{beta}, U{gamma}). (auteur)
Sun, Liyuan; Morales-Collazo, Oscar; Xia, Han; Brennecke, Joan F
2015-12-03
A series of room temperature ionic liquids (RTILs) based on 1-ethyl-3-methylimidazolium ([emim](+)) with different aprotic heterocyclic anions (AHAs) were synthesized and characterized as potential electrolyte candidates for lithium ion batteries. The density and transport properties of these ILs were measured over the temperature range between 283.15 and 343.15 K at ambient pressure. The temperature dependence of the transport properties (viscosity, ionic conductivity, self-diffusion coefficient, and molar conductivity) is fit well by the Vogel-Fulcher-Tamman (VFT) equation. The best-fit VFT parameters, as well as linear fits to the density, are reported. The ionicity of these ILs was quantified by the ratio of the molar conductivity obtained from the ionic conductivity and molar concentration to that calculated from the self-diffusion coefficients using the Nernst-Einstein equation. The results of this study, which is based on ILs composed of both a planar cation and planar anions, show that many of the [emim][AHA] ILs exhibit very good conductivity for their viscosities and provide insight into the design of ILs with enhanced dynamics that may be suitable for electrolyte applications.
Energy Technology Data Exchange (ETDEWEB)
Mulkay, P. [Université Lovanium, Kinshasa (Congo, The Democratic Republic of the); Roels, J. [Centre nucléaire TRICO, Kinshasa (Congo, The Democratic Republic of the)
1970-01-15
The authors measured cobalt, manganese and nickel in 13X zeolite and studied self-diffusion of cobalt in 5A zeolite. Ion exchange revealed the following order of selectivity: Co≥Mn>Ni. The metals were labelled in situ. For the self-diffusion study, cobalt activated by neutron bombardment was adsorbed in suitable quantities on the zeolite, which had been previously charged with natural cobalt by ion exchange. The measurements were carried out by gamma spectrometry. The activation energy for self-diffusion was determined from the linear plot of log{sub 10} D versus l/T °K, using the Arrhenius equation. A value of 13.4 kcal/deg/Lon g was found. The values obtained are compared with those for other divalent cations. (author) [French] Les auteurs ont réalisé le dosage du cobalt, du manganese et du nickel dans le zéolithe 13X et ont suivi l'auto-diffusion du cobalt dans le zéolithe 5A. L’échange ionique présentait la sélectivité suivante: Co≥Mn>Ni. Les métaux étaient marqués in situ. Pour I'auto-diffusion, le cobalt activé par bombardement neutronique a été fixé en quantité convenable sur le zéolithe, qui a été préalablement chargé de cobalt naturel par échange. Les mesures ont été réalisées par spectrométrie gamma- L’énergie d’activation pour le phénomène d'auto-diffusion est obtenue à partir du tracé linéaire de log{sub 10} D en fonction de l/T °K en se basant sur l’équation d’Arrhénius. Les auteurs ont trouvé une valeur de 13,4 kcal/degré/ion g. Les valeurs obtenues sont comparées à celles obtenues pour d'autres cations divalents. (author)
Energy Technology Data Exchange (ETDEWEB)
Martin, L.; Colomer, S
2004-11-15
SiO{sub 2} and silica based compounds are key materials in a variety of scientific and technological fields as, for instance, in microelectronics or nuclear technology. In all these fields, one of the still open questions is their long term aging in a radioactive environment. Due to the complexity of the effects of radiations upon matter, the understanding of the long term aging needs the knowledge of diffusion mechanisms at the atomic scale. In that context, numerical modelling appears as a way to access this scale. We present a first principles study on self-defects and self-diffusion in a silica model. As expected, at variance with SiO{sub 2} crystalline phases, the defects formation energies are distributed, due to the non-equivalence of defects sites. We prove that the formation energy dispersion is correlated to the local stress. Concerning the equilibrium concentrations and oxygen diffusion mechanism, we discuss how the shape of the distribution, as well as impurity levels within the gap, play a main role in the dominance of defect types. Finally we present the main oxygen diffusion mechanism in homogeneous and heterogeneous defect formation regime. (author)
Energy Technology Data Exchange (ETDEWEB)
Yang, Ji-Hui; Yin, Wan-Jian; Park, Ji-Sang; Wei, Su-Huai
2016-01-01
The stability of organic-inorganic halide perovskites is a major challenge for their applications and has been extensively studied. Among the possible underlying reasons, ion self-diffusion has been inferred to play important roles. While theoretical studies congruously support that iodine is more mobile, experimental studies only observe the direct diffusion of the MA ion and possible diffusion of iodine. The discrepancy may result from the incomplete understanding of ion diffusion mechanisms. With the help of first-principles calculations, we studied ion diffusion in CH3NH3PbI3 (MAPbI3) through not only the vacancy-assisted mechanisms presumed in previous theoretical studies, but also the neglected interstiticaly mechanisms. We found that compared to the diffusion through the vacancy-assisted mechanism, MA ion diffusion through the interstiticaly mechanism has a much smaller barrier which could explain experimental observations. For iodine diffusion, both mechanisms can yield relatively small barriers. Depending on the growth conditions, defect densities of vacancies and interstitials can vary and so do the diffusion species as well as diffusion mechanisms. Our work thus supports that both MA and iodine ion diffusion could contribute to the performance instability of MAPbI3. While being congruous with experimental results, our work fills the research gap by providing a full understanding of ion diffusion in halide perovskites.
Self-diffusion on copper surfaces
DEFF Research Database (Denmark)
Hansen, L.; Stoltze, Per; Jacobsen, Karsten Wedel
1991-01-01
The diffusion paths and activation energies of a Cu adatom on Cu(100), Cu(111), and Cu(110) are studied using the effective-medium theory to calculate the energetics. For the (100) and (110) faces, diffusion via an exchange mechanism is found to be important. The transition state for these paths ...
Bazhenov, Alexiev M.; Heyes, David M.
1990-01-01
The thermodynamics, structure, and transport coefficients, as defined by the Green-Kubo integrals, of the one-dimensional Lennard-Jones fluid are evaluated for a wide range of state points by molecular dynamics computer simulation. These calculations are performed for the first time for thermal conductivity and the viscosity. We observe a transition from hard-rod behavior at low number density to harmonic-spring fluid behavior in the close-packed limit. The self-diffusion coefficient decays with increasing density to a finite limiting value. The thermal conductivity increases with density, tending to ∞ in the close-packed limit. The viscosity in contrast maximizes at intermediate density, tending to zero in the zero density and close-packed limits.
Calculation of Transport Coefficients in Dense Plasma Mixtures
Haxhimali, T.; Cabot, W. H.; Caspersen, K. J.; Greenough, J.; Miller, P. L.; Rudd, R. E.; Schwegler, E. R.
2011-10-01
We use classical molecular dynamics (MD) to estimate species diffusivity and viscosity in mixed dense plasmas. The Yukawa potential is used to describe the screened Coulomb interaction between the ions. This potential has been used widely, providing the basis for models of dense stellar materials, inertial confined plasmas, and colloidal particles in electrolytes. We calculate transport coefficients in equilibrium simulations using the Green- Kubo relation over a range of thermodynamic conditions including the viscosity and the self - diffusivity for each component of the mixture. The interdiffusivity (or mutual diffusivity) can then be related to the self-diffusivities by using a generalization of the Darken equation. We have also employed non-equilibrium MD to estimate interdiffusivity during the broadening of the interface between two regions each with a high concentration of either species. Here we present results for an asymmetric mixture between Ar and H. These can easily be extended to other plasma mixtures. A main motivation for this study is to develop accurate transport models that can be incorporated into the hydrodynamic codes to study hydrodynamic instabilities. We use classical molecular dynamics (MD) to estimate species diffusivity and viscosity in mixed dense plasmas. The Yukawa potential is used to describe the screened Coulomb interaction between the ions. This potential has been used widely, providing the basis for models of dense stellar materials, inertial confined plasmas, and colloidal particles in electrolytes. We calculate transport coefficients in equilibrium simulations using the Green- Kubo relation over a range of thermodynamic conditions including the viscosity and the self - diffusivity for each component of the mixture. The interdiffusivity (or mutual diffusivity) can then be related to the self-diffusivities by using a generalization of the Darken equation. We have also employed non-equilibrium MD to estimate interdiffusivity during
Self-diffusion in silicon - Change of a paradigm
Energy Technology Data Exchange (ETDEWEB)
Seeger, Alfred [Universitaet Stuttgart, Institut fuer Theoretische und Angewandte Physik, Pfaffenwaldring 57, 70569 Stuttgart (Germany); Max-Planck-Institut fuer Metallforschung, Heisenbergstr. 3, 70569 Stuttgart (Germany)
2011-12-15
Diffusion processes play a key role in the fabrication of semiconductor devices. For a long time the underlying mechanisms were thought to be analogous to those in metals, based on vacancies as thc dominant lattice defects in thermal equilibrium. From the mid-sixties onwards it became clear that this picture is invalid for Si, where strongly relaxed self-interstitials are dominant and responsible for self- and Group-III- diffusion. Inter alia, this change of a paradigm led to novel concepts and to the quantitative explanation of the diffusion of so-called hybrids such as Au, Pt, and Zn in Si by the so-called kick-out mechanism. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Self-diffusion of plutonium in uranium-plutonium mononitride
International Nuclear Information System (INIS)
Bradbury, M.H.; Matzke, H.
1978-01-01
In the following, first data on the tracer diffusion of Pu-238 in (Usub(0.8)Pusub(0.2)N are reported and some aspects of the diffusion mechanism are discussed. Two sets of specimens with different non-metal to metal ratios were used, and on one of the materials the Pu diffusion rates were measured as a function of nitrogen partial pressure at three different temperatures
Energy Technology Data Exchange (ETDEWEB)
Lacombe, P; Guiraldenq, P; Leymonie, C [Centre de Recherches Metallurgiques, Ecole Nationale Superieure des Mines, Paris (France)
1962-01-15
In view of the difficulty of measuring accurately self-diffusion coefficients, whether in the mass or at grain boundaries, within a given temperature range in which the two phenomena co-exist, the authors decided to reconsider the classical cutting method. The authors establish that, in the case of a semi-infinite solid, the post-diffusion concentration C(x{sub n}) of radioactive atoms at distance x{sub n} from the initial radioactive deposit is a simple function of the overall activity remaining in the sample after abrasion to depth x{sub n}. This conclusion is reached as a result of the general application of the GRUZIN formula which up to now had been applied only to diffusion in volume. The authors show that by measuring the remaining overall activity as a function of the depth of penetration they can distinguish the part of the activity due to self-diffusion in volume from that due to intergranular self-diffusion. The advantage of this method is, therefore, that it enables one to follow continuously on the same sample the passage from self-diffusion in volume to intergranular self-diffusion. The authors use this new method for measuring the self-diffusion constants in gamma iron in volume between 1260 and 918 Degree-Sign C and at grain boundaries between 1020 and 918 Degree-Sign C. (author) [French] En raison des difficultes rencontrees dans la mesure precise des coefficients d'autodiffusion, soit massique, soit intergranulaire dans certains intervalles de temperature ou les deux phenomenes coexistent, les auteurs ont ete conduits a reconsiderer la methode classique de sectionnement. Ils ont en effet constate que pour un solide semi-infini, la concentration apres diffusion en atomes radioactifs C (x{sub n}) a la distance x{sub n} du depot radioactif initial est une fonction simple de l'activite globale restant dans l'echantillon apres son abrasion, jusqu'a la profondeur x{sub n}. Cette conclusion resulte de la generalisation de la formule de Gruzin, qui jusqu
Energy Technology Data Exchange (ETDEWEB)
Guevara-Carrion, Gabriela; Janzen, Tatjana; Muñoz-Muñoz, Y. Mauricio; Vrabec, Jadran, E-mail: jadran.vrabec@uni-paderborn.de [Thermodynamics and Energy Technology, University of Paderborn, 33098 Paderborn (Germany)
2016-03-28
Mutual diffusion coefficients of all 20 binary liquid mixtures that can be formed out of methanol, ethanol, acetone, benzene, cyclohexane, toluene, and carbon tetrachloride without a miscibility gap are studied at ambient conditions of temperature and pressure in the entire composition range. The considered mixtures show a varying mixing behavior from almost ideal to strongly non-ideal. Predictive molecular dynamics simulations employing the Green-Kubo formalism are carried out. Radial distribution functions are analyzed to gain an understanding of the liquid structure influencing the diffusion processes. It is shown that cluster formation in mixtures containing one alcoholic component has a significant impact on the diffusion process. The estimation of the thermodynamic factor from experimental vapor-liquid equilibrium data is investigated, considering three excess Gibbs energy models, i.e., Wilson, NRTL, and UNIQUAC. It is found that the Wilson model yields the thermodynamic factor that best suits the simulation results for the prediction of the Fick diffusion coefficient. Four semi-empirical methods for the prediction of the self-diffusion coefficients and nine predictive equations for the Fick diffusion coefficient are assessed and it is found that methods based on local composition models are more reliable. Finally, the shear viscosity and thermal conductivity are predicted and in most cases favorably compared with experimental literature values.
Song, Jie; Hu, Yajie; Hu, Yunguang; Wang, Jingjing; Zhang, Xiaolong; Wang, Lichun; Guo, Lei; Wang, Yancui; Ning, Ruotong; Liao, Yun; Zhang, Ying; Zheng, Huiwen; Shi, Haijing; He, Zhanlong; Li, Qihan; Liu, Longding
2016-03-02
Coxsackievirus A16 (CA16) is a dominant pathogen that results in hand, foot, and mouth disease and causes outbreaks worldwide, particularly in the Asia-Pacific region. However, the underlying molecular mechanisms remain unclear. Our previous study has demonstrated that the basic CA16 pathogenic process was successfully mimicked in rhesus monkey infant. The present study focused on the global gene expression changes in peripheral blood mononuclear cells of rhesus monkey infants with hand, foot, and mouth disease induced by CA16 infection at different time points. Genome-wide expression analysis was performed with Agilent whole-genome microarrays and established bioinformatics tools. Nine hundred and forty-eight significant differentially expressed genes that were associated with 5 gene ontology categories, including cell communication, cell cycle, immune system process, regulation of transcription and metabolic process were identified. Subsequently, the mapping of genes related to the immune system process by PANTHER pathway analysis revealed the predominance of inflammation mediated by chemokine and cytokine signaling pathways and the interleukin signaling pathway. Ultimately, co-expressed genes and their networks were analyzed. The results revealed the gene expression profile of the immune system in response to CA16 in rhesus monkey infants and suggested that such an immune response was generated as a result of the positive mobilization of the immune system. This initial microarray study will provide insights into the molecular mechanism of CA16 infection and will facilitate the identification of biomarkers for the evaluation of vaccines against this virus. Copyright © 2016 Elsevier B.V. All rights reserved.
1989-01-01
scale separation, the small scales would provide a diffusivity given by the Green - Kubo formula D = >dt: ( 1 ) 246 where V is the velocity followed by...the Green - Kubo convergence time can be considerably larger than the eddy under consideration. It is the nature of diffusion that if there isn’t any...adopt an eddy viscosity parameterization based on SCM or even a lower level parameterization, then one does find that, by integrating the mean
One-dimensional classical many-body system having a normal thermal conductivity
International Nuclear Information System (INIS)
Casati, G.; Ford, J.; Vivaldi, F.; Visscher, W.M.
1984-01-01
By numerically computing orbits for a chaotic, one-dimensional, many-body system placed between two thermal reservoirs, we verify directly that its energy transport obeys the Fourier heat law and we determine its thermal conductivity K. The same value of K is independently obtained by use of the Green-Kubo formalism. These numerical studies verify that chaos is the essential ingredient of diffusive energy transport, and they validate the Green-Kubo formalism
Atomistic study of self-diffusion in Cu-Ag immiscible alloy system
International Nuclear Information System (INIS)
Zhang Jianmin; Chen Gouxiang; Xu Kewei
2006-01-01
Combining molecular dynamic (MD) simulation with modified analytic embedded-atom method (MAEAM) potential, the formation, migration and activation energies have been calculated for four-kind migrations of Cu vacancy and three-kind migrations of Ag vacancy in Cu-Ag immiscible alloy system. The equilibrium concentration of Cu vacancies is greater than that of Ag vacancies owing to the formation energy of Cu vacancy (1.012 eV) is lower than that of Ag vacancy (1.169 eV). Comparing the migration or activation energy needed for four-kind migrations of Cu vacancy and three-kind migrations of Ag vacancy show that the favorable migration mechanism is the nearest-neighbor (NN) jump for Cu vacancy, while the straight [0 1 0] six-jump cycle (6JC) for Ag vacancy. Furthermore, the activation energy of the NN jump of Cu vacancy (2.164 eV) is lower than that of straight [0 1 0] 6JC of Ag vacancy (2.404 eV) also show that the former is more favorable. We conclude accordingly that the primary migration mechanism is the NN jump of an abundance of Cu vacancies
Self-diffusion of particles interacting through a square-well or square-shoulder potential
Wilbertz, H.; Michels, J.; Beijeren, H. van; Leegwater, J.A.
1988-01-01
The diffusion coefficient and velocity autocorrelation function for a fluid of particles interacting through a square-well or square-shoulder potential are calculated from a kinetic theory similar to the Davis-Rice-Sengers theory and the results are compared to those of computer simulations. At low
Increased brain water self-diffusion in patients with idiopathic intracranial hypertension
DEFF Research Database (Denmark)
Gideon, P; Sørensen, P S; Thomsen, C
1995-01-01
PURPOSE: To investigate changes in brain water diffusion in patients with idiopathic intracranial hypertension. METHODS: A motion-compensated MR pulse sequence was used to create diffusion maps of the apparent diffusion coefficient (ADC) in 12 patients fulfilling conventional diagnostic criteria...... for idiopathic intracranial hypertension and in 12 healthy volunteers. RESULTS: A significantly larger ADC was found within subcortical white matter in the patient group (mean, 1.16 x 10(-9) m2/s) than in the control group (mean, 0.75 x 10(-9) m2/s), whereas no significant differences were found within cortical...
Schwartz, L M; Bergman, D J; Dunn, K J; Mitra, P P
1996-01-01
Random walk computer simulations are an important tool in understanding magnetic resonance measurements in porous media. In this paper we focus on the description of pulsed field gradient spin echo (PGSE) experiments that measure the probability, P(R,t), that a diffusing water molecule will travel a distance R in a time t. Because PGSE simulations are often limited by statistical considerations, we will see that valuable insight can be gained by working with simple periodic geometries and comparing simulation data to the results of exact eigenvalue expansions. In this connection, our attention will be focused on (1) the wavevector, k, and time dependent magnetization, M(k, t); and (2) the normalized probability, Ps(delta R, t), that a diffusing particle will return to within delta R of the origin after time t.
Mechanism of anisotropic surface self-diffusivity at the prismatic ice-vapor interface
Czech Academy of Sciences Publication Activity Database
Gladich, I.; Oswald, A.; Bowens, N.; Naatz, S.; Rowe, P.; Roeselová, Martina; Neshyba, S.
2015-01-01
Roč. 17, č. 35 (2015), s. 22947-22958 ISSN 1463-9076 R&D Projects: GA ČR GA13-06181S Institutional support: RVO:61388963 Keywords : molecular dynamics simulations * water models * melting point Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.449, year: 2015
Hedin, Niklas; DeMartin, Gregory J.; Reyes, Sebastián C.
2006-03-01
In studies of gas diffusion in porous solids with nuclear magnetic resonance (NMR) spectroscopy the sample preparation procedure becomes very important. An apparatus is presented here that pretreats the sample ex situ and accurately sets the desired pressure and temperature within the NMR tube prior to its introduction in the spectrometer. The gas manifold that supplies the NMR tube is also connected to a microbalance containing another portion of the same sample, which is kept at the same temperature as the sample in the NMR tube. This arrangement permits the simultaneous measurement of the adsorption loading on the sample, which is required for the interpretation of the NMR diffusion experiments. Furthermore, to ensure a good seal of the NMR tube, a hybrid valve design composed of titanium, a Teflon® seat, and Kalrez® O-rings is utilized. A computer controlled algorithm ensures the accuracy and reproducibility of all the procedures, enabling the NMR diffusion experiments to be performed at well controlled conditions of pressure, temperature, and amount of gas adsorbed on the porous sample.
Self-diffusion of zinc in Egyptian soils as affected by chelating agents
International Nuclear Information System (INIS)
Massoud, M.A.; El-Nennah, M.E.; El-Kholi, A.F.; Gad-Allah, A.M.
1981-01-01
Haematological data are, on the average, greater in normal juvenile than in adult fish. No significant difference in such haematological data have been recorded between adult males and females. Total-body gamma irradiation at the dose levels of 100, 200 and 400 rad caused in juvenile fish, decreased haematological data. The decrease was more intensive after the higher radiation dose. In adult fish, such decrease in haematological data was not well pronounced. However, males, on the average, were slightly more affected than females. The creatinine level in blood was, on the average, slightly higher in adult than in juvenile animals. In adult fish, however, the males showed slightly higher level than did the females. Total-body gamma irradiation at the tested dose levels, did not show significant changes in blood creatinine level apart from a slight rise recorded in the blood of adult males after the higher dose of 400 rad. (author)
Direct measurement of Cu surface self-diffusion on a checked surface
International Nuclear Information System (INIS)
Cousty, Jacques; Peix, Roger; Perraillon, Bernard.
1976-01-01
A radiotracer technique ( 64 Cu) was developed to measure surface diffusion on copper surfaces of total impurity concentration not exceeding some 10 -3 monolayers. The apparatus used consists of a slow electron diffraction device, an Auger analysis spectrometer (CMA), an ion gun and an evaporation device assembled in an ultra-vacuum chamber holding a residual pressure below 10 -10 Torr. A sample handler enables the surface studied to be positioned in front of each of these instruments. During the diffusion treatment the chemical composition of the surface is checked intermittently, and afterwards the spread of the deposit is measured outside the ultravacuum chamber. Slices several microns thick are removed and dissolved separately in dishes containing HNO 3 . The activity is then measured with a flow counter [fr
Self-diffusion imaging by spin echo in Earth's magnetic field.
Mohoric, A; Stepisnik, J; Kos, M; Planinsi
1999-01-01
The NMR of the Earth's magnetic field is used for diffusion-weighted imaging of phantoms. Due to a weak Larmor field, care needs to be taken regarding the use of the usual high field assumption in calculating the effect of the applied inhomogeneous magnetic field. The usual definition of the magnetic field gradient must be replaced by a generalized formula valid when the strength of a nonuniform magnetic field and a Larmor field are comparable (J. Stepisnik, Z. Phys. Chem. 190, 51-62 (1995)). It turns out that the expression for spin echo attenuation is identical to the well-known Torrey formula only when the applied nonuniform field has a proper symmetry. This kind of problem may occur in a strong Larmor field as well as when the slow diffusion rate of particles needs an extremely strong gradient to be applied. The measurements of the geomagnetic field NMR demonstrate the usefulness of the method for diffusion and flow-weighted imaging. Copyright 1999 Academic Press.
Ordering of Self-Diffusion Barrier Energies on Pt(110)-1x2
International Nuclear Information System (INIS)
Feibelman, Peter J.
1999-01-01
Bond-counting arguments, supported by ab-initio calculations, predict a lower barrier for ''leapfrog'' diffusion of Pt addimers on Pt(llO)-lx2 than for adatom dif- fusion or addimer dissociation. This conflicts with experiment, possibly signaling contaminant influence
Surface self-diffusion of adatom on Pt cluster with truncated octahedron structure
Energy Technology Data Exchange (ETDEWEB)
Yang Jianyu, E-mail: wuliyangjianyu@yahoo.com.c [Department of Maths and Physics, Hunan Institute of Engineering, Xiangtan 411104 (China); Hu Wangyu, E-mail: wangyuhu2001@yahoo.com.c [Department of Applied Physics, Hunan University, Changsha 410082 (China); Chen Shuguang [Department of Applied Physics, Hunan University, Changsha 410082 (China)
2010-05-03
Surface diffusion of single Pt adatom on Pt cluster with truncated octahedron structure is investigated through a combination of molecular dynamics and nudged elastic band method. Using an embedded atom method to describe the atomic interactions, the minimum energy paths are determined and the energy barriers for adatom diffusion across and along step are evaluated. The diffusion of adatom crossing step edge between {l_brace}111{r_brace} and {l_brace}100{r_brace} facets has a surprisingly low barrier of 0.03 eV, which is 0.12 eV lower than the barrier for adatom diffusion from {l_brace}111{r_brace} to neighboring {l_brace}111{r_brace} facet. Owing to the small barrier of adatom diffusion across the step edge between {l_brace}111{r_brace} and {l_brace}100{r_brace} facets, the diffusion of adatom along the step edge cannot occur. The molecular dynamics simulations at low temperatures also support these results. Our results show that mass transport will prefer step with {l_brace}100{r_brace} microfacet and the Pt clusters can have only {l_brace}111{r_brace} facets in epitaxial growth.
Surface self-diffusion of adatom on Pt cluster with truncated octahedron structure
International Nuclear Information System (INIS)
Yang Jianyu; Hu Wangyu; Chen Shuguang
2010-01-01
Surface diffusion of single Pt adatom on Pt cluster with truncated octahedron structure is investigated through a combination of molecular dynamics and nudged elastic band method. Using an embedded atom method to describe the atomic interactions, the minimum energy paths are determined and the energy barriers for adatom diffusion across and along step are evaluated. The diffusion of adatom crossing step edge between {111} and {100} facets has a surprisingly low barrier of 0.03 eV, which is 0.12 eV lower than the barrier for adatom diffusion from {111} to neighboring {111} facet. Owing to the small barrier of adatom diffusion across the step edge between {111} and {100} facets, the diffusion of adatom along the step edge cannot occur. The molecular dynamics simulations at low temperatures also support these results. Our results show that mass transport will prefer step with {100} microfacet and the Pt clusters can have only {111} facets in epitaxial growth.
Surface self-diffusion behavior of individual tungsten adatoms on rhombohedral clusters
International Nuclear Information System (INIS)
Yang Jianyu; Hu Wangyu; Tang Jianfeng
2011-01-01
The diffusion of single tungsten adatoms on the surfaces of rhombohedral clusters is studied by means of molecular dynamics and the embedded atom method. The energy barriers for the adatom diffusing across and along the step edge between a {110} facet and a neighboring {110} facet are calculated using the nudged elastic band method. We notice that the tungsten adatom diffusion across the step edge has a much higher barrier than that for face-centered cubic metal clusters. The result shows that diffusion from the {110} facet to a neighboring {110} facet could not take place at low temperatures. In addition, the calculated energy barrier for an adatom diffusing along the step edge is lower than that for an adatom on the flat (110) surface. The results show that the adatom could diffuse easily along the step edge, and could be trapped by the facet corner. Taking all of this evidence together, we infer that the {110} facet starts to grow from the facet corner, and then along the step edge, and finally toward the {110} facet center. So the tungsten rhombohedron can grow epitaxially along the {110} facet one facet at a time and the rhombohedron should be the stable structure for both large and small tungsten clusters. (paper)
Potassium self-diffusion in a K-rich single-crystal alkali feldspar
Hergemöller, Fabian; Deicher, Manfred; Wolf, Herbert; Brenner, Florian; Hutter, Herbert; Abart, Rainer; Stolwijk, Nicolaas A.
The paper reports potassium diffusion measurements performed on gem-quality single-crystal alkali feldspar in the temperature range from 1169 to 1021 K. Natural sanidine from Volkesfeld, Germany was implanted with {}^{43}K at the ISOLDE/CERN radioactive ion-beam facility normal to the (001) crystallographic plane. Diffusion coefficients are well described by the Arrhenius equation with an activation energy of 2.4 eV and a pre-exponential factor of 5×10^{-6}m^{2}/s, which is more than three orders of magnitude lower than the {}^{22}Na diffusivity in the same feldspar and the same crystallographic direction. State-of-the-art considerations including ionic conductivity data on the same crystal and Monte Carlo simulations of diffusion in random binary alloy structures point to a correlated motion of K and Na through the interstitialcy mechanism.
Molecular dynamics studies of transport properties and equation of state of supercritical fluids
Nwobi, Obika C.
Many chemical propulsion systems operate with one or more of the reactants above the critical point in order to enhance their performance. Most of the computational fluid dynamics (CFD) methods used to predict these flows require accurate information on the transport properties and equation of state at these supercritical conditions. This work involves the determination of transport coefficients and equation of state of supercritical fluids by equilibrium molecular dynamics (MD) simulations on parallel computers using the Green-Kubo formulae and the virial equation of state, respectively. MD involves the solution of equations of motion of a system of molecules that interact with each other through an intermolecular potential. Provided that an accurate potential can be found for the system of interest, MD can be used regardless of the phase and thermodynamic conditions of the substances involved. The MD program uses the effective Lennard-Jones potential, with system sizes of 1000-1200 molecules and, simulations of 2,000,000 time-steps for computing transport coefficients and 200,000 time-steps for pressures. The computer code also uses linked cell lists for efficient sorting of molecules, periodic boundary conditions, and a modified velocity Verlet algorithm for particle displacement. Particle decomposition is used for distributing the molecules to different processors of a parallel computer. Simulations have been carried out on pure argon, nitrogen, oxygen and ethylene at various supercritical conditions, with self-diffusion coefficients, shear viscosity coefficients, thermal conductivity coefficients and pressures computed for most of the conditions. Results compare well with experimental and the National Institute of Standards and Technology (NIST) values. The results show that the number of molecules and the potential cut-off radius have no significant effect on the computed coefficients, while long-time integration is necessary for accurate determination of the
Tica, Christian D.; Galapon, Eric A.
2018-02-01
The paper addresses the exact evaluation of the generalized Stieltjes transform Sn[f ] =∫0∞f (x ) (ω+x ) -nd x of integral order n = 1, 2, 3, … about ω = 0 from which the asymptotic behavior of Sn[f] for small parameters ω is directly extracted. An attempt to evaluate the integral by expanding the integrand (ω + x)-n about ω = 0 and then naively integrating the resulting infinite series term by term leads to an infinite series whose terms are divergent integrals. Assigning values to the divergent integrals, say, by analytic continuation or by Hadamard's finite part is known to reproduce only some of the correct terms of the expansion but completely misses out a group of terms. Here we evaluate explicitly the generalized Stieltjes transform by means of finite-part integration recently introduced in Galapon [Proc. R. Soc. A 473, 20160567 (2017)]. It is shown that, when f(x) does not vanish or has zero of order m at the origin such that (n - m) ≥ 1, the dominant terms of Sn[f] as ω → 0 come from contributions arising from the poles and branch points of the complex valued function f(z)(ω + z)-n. These dominant terms are precisely the terms missed out by naive term by term integration. Furthermore, it is demonstrated how finite-part integration leads to new series representations of special functions by exploiting their known Stieltjes integral representations. Finally, the application of finite part integration in obtaining asymptotic expansions of the effective diffusivity in the limit of high Peclet number, the Green-Kubo formula for the self-diffusion coefficient, and the antisymmetric part of the diffusion tensor in the weak noise limit is discussed.
Empirical molecular-dynamics study of diffusion in liquid semiconductors
Yu, W.; Wang, Z. Q.; Stroud, D.
1996-11-01
We report the results of an extensive molecular-dynamics study of diffusion in liquid Si and Ge (l-Si and l-Ge) and of impurities in l-Ge, using empirical Stillinger-Weber (SW) potentials with several choices of parameters. We use a numerical algorithm in which the three-body part of the SW potential is decomposed into products of two-body potentials, thereby permitting the study of large systems. One choice of SW parameters agrees very well with the observed l-Ge structure factors. The diffusion coefficients D(T) at melting are found to be approximately 6.4×10-5 cm2/s for l-Si, in good agreement with previous calculations, and about 4.2×10-5 and 4.6×10-5 cm2/s for two models of l-Ge. In all cases, D(T) can be fitted to an activated temperature dependence, with activation energies Ed of about 0.42 eV for l-Si, and 0.32 or 0.26 eV for two models of l-Ge, as calculated from either the Einstein relation or from a Green-Kubo-type integration of the velocity autocorrelation function. D(T) for Si impurities in l-Ge is found to be very similar to the self-diffusion coefficient of l-Ge. We briefly discuss possible reasons why the SW potentials give D(T)'s substantially lower than ab initio predictions.
Kowsari, Mohammad H; Ebrahimi, Soraya
2018-05-16
Comprehensive molecular dynamics simulations are performed to study the average single-particle dynamics and the transport properties of 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], and 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [bmim][FAP], ionic liquids (ILs) at 400 K. We applied one of the most widely used nonpolarizable all-atom force fields for ILs, both with the original unit (±1) charges on each ion and with the partial charges uniformly scaled to 80-85%, taking into account the average polarizability and tracing the experimentally compatible transport properties. In all simulations, [bmim]+ was considered to be flexible, while the effect of a flexible vs. rigid structure of the anions and the effect of two applied charge sets on the calculated properties were separately investigated in detail. The simulation results showed that replacing [PF6]- with [FAP]-, considering anion flexibility, and applying the charge-scaled model significantly enhanced the ionic self-diffusion, ionic conductivity, inverse viscosity, and hyper anion preference (HAP). Both of the calculated self-diffusion coefficients from the long-time linear slope of the mean-square displacement (MSD) and from the integration of the velocity autocorrelation function (VACF) for the centers of mass of the ions were used for evaluation of the ionic transference number, HAP, ideal Nernst-Einstein ionic conductivity (σNE), and the Stokes-Einstein viscosity. In addition, for quantification of the degree of complicated ionic association (known as the Nernst-Einstein deviation parameter, Δ) and ionicity phenomena in the two studied ILs, the ionic conductivity was determined more rigorously by the Green-Kubo integral of the electric-current autocorrelation function (ECACF), and then the σGK/σNE ratio was evaluated. It was found that the correlated motion of the (cationanion) neighbors in [bmim][FAP] is smaller than in [bmim][PF6]. The relaxation times of
International Nuclear Information System (INIS)
Ahmed, N.; Khan, G.
1990-09-01
In this report the author used of a very useful technique of simulation and applied it to successfully for determining the various properties of sodium, both in liquid and solid phase near transition point. As a first step the determination of specific heat and diffusion coefficient have been carried out. In liquid state the molecular dynamics (MD) values calculated matched the experimental data. But in solid state the diffusion coefficient obtained were not consistent with the one expected for a solid, rather the values obtained suggested that sodium remained in liquid state even below the melting point. (A.B.)
Noguchi, Naoki; Kubo, Tomoaki; Durham, William B.; Kagi, Hiroyuki; Shimizu, Ichiko
2016-08-01
We have developed a high-resolution technique based on micro Raman spectroscopy to measure hydrogen isotope diffusion profiles in ice Ih. The calibration curve for quantitative analysis of deuterium in ice Ih was constructed using micro Raman spectroscopy. Diffusion experiments using diffusion couples composed of dense polycrystalline H2O and D2O ice were carried out under a gas confining pressure of 100 MPa (to suppress micro-fracturing and pore formation) at temperatures from 235 K to 245 K and diffusion times from 0.2 to 94 hours. Two-dimensional deuterium profiles across the diffusion couples were determined by Raman imaging. The location of small spots of frost from room air could be detected from the shapes of the Raman bands of OH and OD stretching modes, which change because of the effect of the molar ratio of deuterium on the molecular coupling interaction. We emphasize the validity for screening the impurities utilizing the coupling interaction. Some recrystallization and grain boundary migration occurred in recovered diffusion couples, but analysis of two-dimensional diffusion profiles of regions not affected by grain boundary migration allowed us to measure a volume diffusivity for ice at 100 MPa of (2.8 ± 0.4) ×10-3exp[ -57.0 ± 15.4kJ /mol RT ] m2 /s (R is the gas constant, T is temperature). Based on ambient pressure diffusivity measurements by others, this value indicates a high (negative) activation volume for volume diffusivity of -29.5 cm3/mol or more. We can also constrain the value of grain boundary diffusivity in ice at 100 MPa to be volume diffusivity.
PFG NMR Study of Liquid n-Hexane Self-Diffusion in the Bed of Porous Glass Beads
Czech Academy of Sciences Publication Activity Database
Peksa, M.; Lang, J.; Kočiřík, Milan
2009-01-01
Roč. 11, č. 36 (2009), s. 1-2 ISSN 1862-4138 R&D Projects: GA ČR GA203/09/1353 Institutional research plan: CEZ:AV0Z40400503 Keywords : PFG NMR Study * porous glass beads Subject RIV: CF - Physical ; Theoretical Chemistry http://www.uni-leipzig.de/diffusion/journal/index.html
Harmon, Jennifer; Coffman, Cierra; Villarrial, Spring; Chabolla, Steven; Heisel, Kurt A.; Krishnan, Viswanathan V.
2012-01-01
NMR spectroscopy has become one of the primary tools that chemists utilize to characterize a range of chemical species in the solution phase, from small organic molecules to medium-sized proteins. A discussion of NMR spectroscopy is an essential component of physical and biophysical chemistry lecture courses, and a number of instructional…
Shin, Hyun Kyung; Choi, Bongsik; Talkner, Peter; Lee, Eok Kyun
2014-12-01
Based on the generalized Langevin equation for the momentum of a Brownian particle a generalized asymptotic Einstein relation is derived. It agrees with the well-known Einstein relation in the case of normal diffusion but continues to hold for sub- and super-diffusive spreading of the Brownian particle's mean square displacement. The generalized asymptotic Einstein relation is used to analyze data obtained from molecular dynamics simulations of a two-dimensional soft disk fluid. We mainly concentrated on medium densities for which we found super-diffusive behavior of a tagged fluid particle. At higher densities a range of normal diffusion can be identified. The motion presumably changes to sub-diffusion for even higher densities.
DEFF Research Database (Denmark)
Boned, C.; Allal, A.; Baylaucq, A.
2004-01-01
applied to dynamic viscosity, has been considered and generalized. In this generalized model the compound is characterized by only four parameters. But if the quadratic length is known, the number of adjustable parameters is three. The compounds considered in this work are benzene, carbon tetrachloride...
Collective dynamics and self-diffusion in a diblock copolymer melt in the body-centered cubic phase
DEFF Research Database (Denmark)
Papadakis, C.M.; Rittig, F.; Almdal, K.
2004-01-01
The structure and dynamics of a strongly asymmetric poly(ethylene propylene)poly (dimethylsiloxane) (PEP-PDMS) diblock copolymer in the melt have been studied over a wide temperature range. Small-angle neutron scattering reveals that the sample exhibits two stable phases in this temperature range......: Above the order-to-disorder transition temperature, it is disordered, whereas the domain structure is body-centered cubic (bcc) below, being stable down to the lowest temperatures measured. In the disordered state, dynamic light scattering (DLS) in the polarized geometry reveals the heterogeneity mode...
Hydrodynamic limit of a nongradient interacting particle process
International Nuclear Information System (INIS)
Wick, W.D.
1989-01-01
A simple example of a nongradient stochastic interacting particle system is analyzed. In this model, symmetric simple exclusion in one dimension in a periodic environment, the dynamical term in the Green-Kubo formula contributes to the bulk diffusion constant. The law of large numbers for the density field and the central limit theorem for the density fluctuation field are proven, and the Green-Kubo expression for the diffusion constant is computed exactly. The hydrodynamic equation for the model turns out to be linear
Journal of Chemical Sciences | Indian Academy of Sciences
Indian Academy of Sciences (India)
Ionic melts; molecular dynamics; viscosity; ionic conductivity. ... The Green-Kubo formalism has been applied to compute viscosities and ionic ... The computational parameters critical for reliably estimating these collective transport properties ... will display persistent oscillatory behaviour of the integral of the charge-flux ACF.
Ion diffusion related to structure in molten salts
International Nuclear Information System (INIS)
Tosi, M.P.
1996-08-01
A model first developed by Zwanzig to derive transport coefficients in cold dense fluids directly from the Green-Kubo time correlation formulae allows one to relate macroscopic diffusion coefficients to the local fluid structure. Applications to various ionic diffusion processes in molten salts are reviewed. Consequences of partial structural quenching are also discussed. (author). 28 refs, 3 tabs
Gluon gas viscosity in nonperturbative region
International Nuclear Information System (INIS)
Il'in, S.V.; Mogilevskij, O.A.; Smolyanskij, S.A.; Zinov'ev, G.M.
1992-01-01
Using the Green-Kubo-type formulae and the cutoff model motivated by Monte Carlo lattice gluodynamics simulations we find the temperature behaviour of shear viscosity of gluon gas in the region of deconfinement phase transition. 22 refs.; 1 fig. (author)
Dissipative electromagnetism from a nonequilibrium thermodynamics perspective
Jelic, A.; Hütter, M.; Öttinger, H.C.
2006-01-01
Dissipative effects in electromagnetism on macroscopic scales are examined by coarse-graining the microscopic Maxwell equations with respect to time. We illustrate a procedure to derive the dissipative effects on the macroscopic scale by using a Green-Kubo type expression in terms of the microscopic
Anomalous heat conduction in a one-dimensional ideal gas.
Casati, Giulio; Prosen, Tomaz
2003-01-01
We provide firm convincing evidence that the energy transport in a one-dimensional gas of elastically colliding free particles of unequal masses is anomalous, i.e., the Fourier law does not hold. Our conclusions are confirmed by a theoretical and numerical analysis based on a Green-Kubo-type approach specialized to momentum-conserving lattices.
Suttorp, L.G.
1990-01-01
Mode-coupling theory is used to determine the long-time behaviour of the Green-Kubo integrands for the heat conductivity and the diffusion coefficients of an ionic mixture in a magnetic field. It is shown that the presence of several species of particles with a different ratio of charges and masses
Time correlation functions and transport coefficients in a dilute superfluid
International Nuclear Information System (INIS)
Kirkpatrick, T.R.; Dorfman, J.R.
1985-01-01
Time correlation functions for the transport coefficients in the linear Landau-Khalatnikov equations are derived on the basis of a formal theory. These Green--Kubo expressions are then explicitly evaluated for a dilute superfluid and the resulting transport coefficiencts are shown to be identical to those obtained previously by using a distribution function method
Transport properties of quasi-free Fermions
Aschbacher, W; Pautrat, Y; Pillet, C A
2006-01-01
Using the scattering approach to the construction of Non-Equilibrium Steady States proposed by Ruelle we study the transport properties of systems of independent electrons. We show that Landauer-Buttiker and Green-Kubo formulas hold under very general conditions.
Zhang, Yong; Otani, Akihito; Maginn, Edward J
2015-08-11
Equilibrium molecular dynamics is often used in conjunction with a Green-Kubo integral of the pressure tensor autocorrelation function to compute the shear viscosity of fluids. This approach is computationally expensive and is subject to a large amount of variability because the plateau region of the Green-Kubo integral is difficult to identify unambiguously. Here, we propose a time decomposition approach for computing the shear viscosity using the Green-Kubo formalism. Instead of one long trajectory, multiple independent trajectories are run and the Green-Kubo relation is applied to each trajectory. The averaged running integral as a function of time is fit to a double-exponential function with a weighting function derived from the standard deviation of the running integrals. Such a weighting function minimizes the uncertainty of the estimated shear viscosity and provides an objective means of estimating the viscosity. While the formal Green-Kubo integral requires an integration to infinite time, we suggest an integration cutoff time tcut, which can be determined by the relative values of the running integral and the corresponding standard deviation. This approach for computing the shear viscosity can be easily automated and used in computational screening studies where human judgment and intervention in the data analysis are impractical. The method has been applied to the calculation of the shear viscosity of a relatively low-viscosity liquid, ethanol, and relatively high-viscosity ionic liquid, 1-n-butyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide ([BMIM][Tf2N]), over a range of temperatures. These test cases show that the method is robust and yields reproducible and reliable shear viscosity values.
... protection) to the viruses that cause HFMD. However, older children and adults can also get HFMD. In the United States it is more common for people to get HFMD during spring, summer, and fall. What Are the Symptoms of HFMD? Symptoms of ...
DEFF Research Database (Denmark)
Spernath, Aviram; Yaghmur, Anan; Aserin, Abraham
2003-01-01
Microemulsions are of growing interest to the food industry as vehicles for delivering and enhancing solubilization of natural food supplements with nutritional and health benefits. The incorporation of molecular phytosterols, cholesterol-lowering agents, in food products is of great interest...... to the food industry. In this work is demonstrated the use of water dilutable food-grade microemulsions consisting of ethoxylated sorbitan ester (Tween 60), water, R-(+)-limonene, ethanol, and propylene glycol as vehicles for enhancing the phytosterols solubilization. Phytosterols were solubilized up to 12...... times more than the dissolution capacity of the oil [R-(+)-limonene] for the same compounds. The solubilization capacity of phytosterols and cholesterol along a dilution line in a pseudo-ternary phase diagram [on this dilution line the weight ratio of R-(+)-limonene/ethanol/Tween 60 is constant at 1...
Czech Academy of Sciences Publication Activity Database
Veselý, M.; Bultreys, T.; Peksa, M.; Lang, J.; Cnudde, V.; van Hoorebeke, L.; Kočiřík, Milan; Hejtmánek, Vladimír; Šolcová, Olga; Soukup, Karel; Gerke, K.; Stallmach, F.; Čapek, P.
2015-01-01
Roč. 110, č. 1 (2015), s. 81-111 ISSN 0169-3913 R&D Projects: GA ČR(CZ) GAP204/11/1206 Institutional support: RVO:61388955 ; RVO:67985858 Keywords : Isobaric counter-current diffusion * Knudsen flow * Pulsed field gradient NMR Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.653, year: 2015
International Nuclear Information System (INIS)
Iribarren, M.J.; Dyment, F.
1991-01-01
Conventional radioactive tracer section techniques were used to make an experimental determination of diffusion parameters for Zr, Nb and Ni along the α/β boundary interfaces of Zr-2.5%Nb and comparing them with those for Zr, Nb and Co in α-Zr grain boundaries. Both determinations were made for a wide range of temperatures, including reactor working temperatures. Different materials were used for this purpose, both specially prepared alloys for diffusion experiments and part of the material from the actual pressure tubes. Different stabilizing thermal treatments were performed and results were analyzed based on the different morphologies obtained. (Author) [es
International Nuclear Information System (INIS)
Ku'rpick, Ulrike
2001-01-01
We calculate activation barriers and prefactors for diffusion via hopping on (100), (110), and (111) surfaces of Ni and Cu. The calculations reveal that, when activation barriers decrease there is also a decrease in the prefactors such that the changes in both quantities partly compensate for each other with respect to the diffusivities. Thermodynamic functions which contribute to the prefactors are calculated from local vibrational density of states, showing that mainly entropy contributions control the prefactors. Our method allows one to trace the obtained values back to vibrational properties of the adatoms in both the minimum-energy and transition-state configurations, and enables a physical understanding of why prefactors have certain values
Molecular Simulation Studies of Covalently and Ionically Grafted Nanoparticles
Hong, Bingbing
Solvent-free covalently- or ionically-grafted nanoparticles (CGNs and IGNs) are a new class of organic-inorganic hybrid composite materials exhibiting fluid-like behaviors around room temperature. With similar structures to prior systems, e.g. nanocomposites, neutral or charged colloids, ionic liquids, etc, CGNs and IGNs inherit the functionality of inorganic nanopariticles, the facile processibility of polymers, as well as conductivity and nonvolatility from their constituent materials. In spite of the extensive prior experimental research having covered synthesis and measurements of thermal and dynamic properties, little progress in understanding of these new materials at the molecular level has been achieved, because of the lack of simulation work in this new area. Atomistic and coarse-grained molecular dynamics simulations have been performed in this thesis to investigate the thermodynamics, structure, and dynamics of these systems and to seek predictive methods predictable for their properties. Starting from poly(ethylene oxide) oligomers (PEO) melts, we established atomistic models based on united-atom representations of methylene. The Green-Kubo and Einstein-Helfand formulas were used to calculate the transport properties. The simulations generate densities, viscosities, diffusivities, in good agreement with experimental data. The chain-length dependence of the transport properties suggests that neither Rouse nor reptation models are applicable in the short-chain regime investigated. Coupled with thermodynamic integration methods, the models give good predictions of pressure-composition-density relations for CO 2 + PEO oligomers. Water effects on the Henry's constant of CO 2 in PEO have also been investigated. The dependence of the calculated Henry's constants on the weight percentage of water falls on a temperature-dependent master curve, irrespective of PEO chain length. CGNs are modeled by the inclusion of solid-sphere nanoparticles into the atomistic
Molecular dynamics of liquid crystals
Sarman, Sten
1997-02-01
We derive Green-Kubo relations for the viscosities of a nematic liquid crystal. The derivation is based on the application of a Gaussian constraint algorithm that makes the director angular velocity of a liquid crystal a constant of motion. Setting this velocity equal to zero means that a director-based coordinate system becomes an inertial frame and that the constraint torques do not do any work on the system. The system consequently remains in equilibrium. However, one generates a different equilibrium ensemble. The great advantage of this ensemble is that the Green-Kubo relations for the viscosities become linear combinations of time correlation function integrals, whereas they are complicated rational functions in the conventional canonical ensemble. This facilitates the numerical evaluation of the viscosities by molecular dynamics simulations.
Calculation of the mutual diffusion coefficient by equilibrium and nonequilibrium molecular dynamics
International Nuclear Information System (INIS)
Erpenbeck, J.J.; Kincaid, J.M.
1985-01-01
A nonequilibrium molecular dynamics method for the calculation of the mutual diffusion coefficient for a mixture of hard spheres is described. The method is applied to a 50-50 mixture of equidiameter particles having a mass ratio of 0.1 for the two species, at a volume of three times close-packing. By extrapolating the results to the limit of vanishing concentration gradient and infinite system size, we obtain a value in statistical agreement with the result obtained using a Green-Kubo molecular dynamics procedure which is also described. The nonequilibrium calculation yields a mutual diffusion coefficient which decreases slightly with increasing concentration gradient. The Green-Kubo time correlation function for mutual diffusion displays a slow decay with time, qualitatively similar to the long-time tail which has been predicted by the hydrodynamic theory of Pomeau
Calculation of the mutual diffusion coefficient by equilibrium and nonequilibrium molecular dynamics
International Nuclear Information System (INIS)
Erpenbeck, J.J.; Kincaid, J.M.
1986-01-01
A nonequilibrium molecular dynamics method for the calculation of the mutual diffusion coefficient for a mixture of hard spheres is described. The method is applied to a 50-50 mixture of equidiameter particles having a mass ratio of 0.1 for the two species, at a volume of three times close-packing. By extrapolating the results to the limit of vanishing concentration gradient and infinite system size, we obtain a value in statistical agreement with the result obtained using a Green-Kubo molecular dynamics procedure, which is also described. The nonequilibrium calculation yields a mutual diffusion coefficient which decreases slightly with increasing concentration gradient. The Green-Kubo timecorrelation function for mutual diffusion displays a slow decay with time, qualitatively similar to the long-time tail which has been predicted by the hydrodynamic theory of Pomeau
International Nuclear Information System (INIS)
Chattaraj, D.; Dash, Smruti
2013-01-01
The thermal conductivity and coefficient of shear viscosity of molten sodium fluoride were calculated using Green-Kubo equilibrium molecular dynamics (EMD) simulation. The Green-Kubo method is an equilibrium technique based on the fluctuation-dissipation theorem of statistical thermodynamics. The canonical ensemble (N, V, T) was used in the MD simulation to obtain the transport properties of molten NaF. In this simulation, several state points were investigated using the Born-Meyer-Huggins-Tosi-Fumi interionic potential model. The electrostatic interactions present in this ionic fluid were calculated through the Ewald method. The results obtained in this study were found to be in good agreement with the reported experimental data. (author)
Rheology of liquid n-triacontane: Molecular dynamics simulation
International Nuclear Information System (INIS)
Kondratyuk, N D; Norman, G E; Stegailov, V V
2016-01-01
Molecular dynamics is applied to calculate diffusion coefficients of n-triacontane C 30 H 62 using Einstein-Smoluchowski and Green-Kubo relations. The displacement 〈Δr 2 〉( t ) has a subdiffusive part 〈Δr 2 〉 ∼ t α , caused by molecular crowding at low temperatures. Longtime asymptotes of 〈v(0)v(t)〉 are collated with the hydrodynamic tail t -3/2 demonstrated for atomic liquids. The influence of these asymptotes on the compliance of Einstein-Smoluchowski and Green-Kubo methods is analyzed. The effects of the force field parameters on the diffusion process are treated. The results are compared with experimental data. (paper)
FY06 NRL DoD High Performance Computing Modernization Program Annual Reports
2007-10-31
nonequilibrium MD with isokinetic thermostatting. We have explored both the Green - Kubo and the mean-square displacement approaches to transport...codes. The flow solver was combined with adaptive re-meshing techniques for these transient problems with moving grids and was also integrated with the...simple one-dimensional eddy viscosity to a fully three-dimensional direct numerical simulation. Coupling between fluid and sediment phases varies from
Lawson, John W.; Murray, Daw S.; Bauschlicher, Charles W., Jr.
2011-01-01
Atomistic Green-Kubo simulations are performed to evaluate the lattice thermal conductivity for single crystals of the ultra high temperature ceramics ZrB2 and HfB2 for a range of temperatures. Recently developed interatomic potentials are used for these simulations. Heat current correlation functions show rapid oscillations which can be identified with mixed metal-Boron optical phonon modes. Agreement with available experimental data is good.
Thermal conductivity of ZnTe investigated by molecular dynamics
International Nuclear Information System (INIS)
Wang Hanfu; Chu Weiguo
2009-01-01
The thermal conductivity of ZnTe with zinc-blende structure has been computed by equilibrium molecular dynamics method based on Green-Kubo formalism. A Tersoff's potential is adopted in the simulation to model the atomic interactions. The calculations are performed as a function of temperature up to 800 K. The calculated thermal conductivities are in agreement with the experimental values between 150 K and 300 K, while the results above the room temperature are comparable with the Slack's equation.
The properties of tagged lattice fluids: II. Velocity correlation functions
International Nuclear Information System (INIS)
Binder, P.M.; d'Humieres, D.; Poujol, L.
1988-01-01
We report preliminary measurements of the velocity autocorrelation function for a tagged particle in a lattice gas. These measurements agree with the Boltzmann-level theory. The Green-Kubo integration of these measurements agrees with theoretical predictions for the diffusion coefficient. To within the error bars of the simulations (3 /times/ 10/sup /minus/3/) we observe no long-time tails. 9 refs., 1 fig., 1 tab
Statistical mechanics of nonequilibrium liquids
Evans, Denis J; Craig, D P; McWeeny, R
1990-01-01
Statistical Mechanics of Nonequilibrium Liquids deals with theoretical rheology. The book discusses nonlinear response of systems and outlines the statistical mechanical theory. In discussing the framework of nonequilibrium statistical mechanics, the book explains the derivation of a nonequilibrium analogue of the Gibbsian basis for equilibrium statistical mechanics. The book reviews the linear irreversible thermodynamics, the Liouville equation, and the Irving-Kirkwood procedure. The text then explains the Green-Kubo relations used in linear transport coefficients, the linear response theory,
Collisional Thermalization in Strongly Coupled Ultracold Neutral Plasmas
2017-01-25
calculated collisions rates in a strongly coupled plasma. From Bannasch et al., PRL 109, 185008 (2012). DISTRIBUTION A: Distribution approved for public...applicability to other plasmas.) We use a Green- Kubo relation to extract the diffusion constant from our measurements of the relaxation towards...strongly coupled systems. Our measurements (data symbols) agree with numerical calculations (solid lines) from J. Daligault, PRL 108, 225004 (2012
Shear flow simulations of biaxial nematic liquid crystals
Sarman, Sten
1997-08-01
We have calculated the viscosities of a biaxial nematic liquid crystal phase of a variant of the Gay-Berne fluid [J. G. Gay and B. J. Berne, J. Chem. Phys. 74, 3316 (1981)] by performing molecular dynamics simulations. The equations of motion have been augmented by a director constraint torque that fixes the orientation of the directors. This makes it possible to fix them at different angles relative to the stream lines in shear flow simulations. In equilibrium simulations the constraints generate a new ensemble. One finds that the Green-Kubo relations for the viscosities become linear combinations of time correlation function integrals in this ensemble whereas they are complicated rational functions in the conventional canonical ensemble. We have evaluated these Green-Kubo relations for all the shear viscosities and all the twist viscosities. We have also calculated the alignment angles, which are functions of the viscosity coefficients. We find that there are three real alignment angles but a linear stability analysis shows that only one of them corresponds to a stable director orientation. The Green-Kubo results have been cross checked by nonequilibrium shear flow simulations. The results from the different methods agree very well. Finally, we have evaluated the Miesowicz viscosities [D. Baalss, Z. Naturforsch. Teil A 45, 7 (1990)]. They vary by more than 2 orders of magnitude. The viscosity is consequently highly orientation dependent.
International Nuclear Information System (INIS)
Chialvo, A.A.; Debenedetti, P.G.
1991-01-01
To date, the calculation of shear viscosity for soft-core fluids via equilibrium molecular dynamics has been done almost exclusively using the Green-Kubo formalism. The alternative mean-squared displacement approach has not been used, except for hard-sphere fluids, in which case the expression proposed by Helfand [Phys. Rev. 119, 1 (1960)] has invariably been selected. When written in the form given by McQuarrie [Statistical Mechanics (Harper ampersand Row, New York, 1976), Chap. 21], however, the mean-squared displacement approach offers significant computational advantages over both its Green-Kubo and Helfand counterparts. In order to achieve comparable statistical significance, the number of experiments needed when using the Green-Kubo or Helfand formalisms is more than an order of magnitude higher than for the McQuarrie expression. For pairwise-additive systems with zero linear momentum, the McQuarrie method yields frame-independent shear viscosities. The hitherto unexplored McQuarrie implementation of the mean-squared displacement approach to shear-viscosity calculation thus appears superior to alternative methods currently in use
Shear viscosity of the quark-gluon plasma in a kinetic theory approach
International Nuclear Information System (INIS)
Puglisi, A.; Plumari, S.; Scardina, F.; Greco, V.
2014-01-01
One of the main results of heavy ions collision (HIC) at relativistic energy experiments is the very small shear viscosity to entropy density ratio of the Quark-Gluon Plasma, close to the conjectured lower bound η/s=1/4π for systems in the infinite coupling limit. Transport coefficients like shear viscosity are responsible of non-equilibrium properties of a system: Green-Kubo relations give us an exact expression to compute these coefficients. We compute shear viscosity numerically using Green-Kubo relation in the framework of Kinetic Theory solving the relativistic transport Boltzmann equation in a finite box with periodic boundary conditions. We investigate a system of particles interacting via anisotropic and energy dependent cross-section in the range of temperature of interest for HIC. Green-Kubo results are in agreement with Chapman-Enskog approximation while Relaxation Time approximation can underestimates the viscosity of a factor 2. The correct analytic formula for shear viscosity can be used to develop a transport theory with a fixed η/s and have a comparison with physical observables like elliptic flow
Transport coefficients of Quark-Gluon Plasma in a Kinetic Theory approach
International Nuclear Information System (INIS)
Puglisi, A; Plumari, S; Scardina, F; Greco, V
2014-01-01
One of the main results of heavy ions collision at relativistic energy experiments is the very small shear viscosity to entropy density ratio of the Quark-Gluon Plasma, close to the conjectured lower bound η/s = 1/4π for systems in the infinite coupling limit. Transport coefficients like shear viscosity are responsible of non-equilibrium properties of a system: Green- Kubo relations give us an exact expression to compute these coefficients. We computed shear viscosity numerically using Green-Kubo relation in the framework of Kinetic Theory solving the relativistic transport Boltzmann equation in a finite box with periodic boundary conditions. We investigated different cases of particles, for one component system (gluon matter), interacting via isotropic or anisotropic cross-section in the range of temperature of interest for HIC. Green-Kubo results are in agreement with Chapman-Enskog approximation while Relaxation Time approximation can underestimates the viscosity of a factor 2. Another transport coefficient of interest is the electric conductivity σ el which determines the response of QGP to the electromagnetic fields present in the early stage of the collision. We study the σ el dependence on microscopic details of interaction and we find also in this case that Relaxation Time Approximation is a good approximation only for isotropic cross-section.
International Nuclear Information System (INIS)
Erpenbeck, J.J.
1989-01-01
The thermal transport properties of mixtures can be formulated in a number of ways, depending on the choice of driving forces for the transport of heat and matter, without violating the Onsager conditions. Here we treat transport in mixtures based on the driving forces -del ln T and -T del(μ/sub a//T), with T the temperature and μ/sub a/ the specific chemical potential, to obtain the Green-Kubo expressions and the Enskog theory for the corresponding transport coefficients which seem most amenable to molecular-dynamics evaluation. The transport properties of a hard-sphere mixture (mass ratio of 0.1, diameter ratio of 1.0, at a volume of three times close-packed volume), calculated by a Monte Carlo, molecular-dynamics method based on the Green-Kubo formulas, are compared with the predictions of the Enskog theory. The long-time behavior of the Green-Kubo time-correlation functions for shear viscosity, thermal conductivity, thermal diffusion, and mutual diffusion are found to be in good agreement with the predictions of mode-coupling theory. Except for viscosity, the contribution of the long-time tails to the transport coefficients is found to be significant. We obtain values, relative to Enskog, of 1.016 +- 0.007 for shear viscosity, 1.218 +- 0.009 for thermal conductivity, 1.267 +- 0.026 for thermal diffusion, and 1.117 +- 0.008 for mutual diffusion
Coxsackievirus A6 and enterovirus 71 causing hand, foot and mouth disease in Cuba, 2011-2013.
Fonseca, Magilé C; Sarmiento, Luis; Resik, Sonia; Martínez, Yenisleidys; Hung, Lai Heng; Morier, Luis; Piñón, Alexander; Valdéz, Odalys; Kourí, Vivian; González, Guelsys
2014-09-01
Hand, foot and mouth disease (HFMD) is usually caused by coxsackievirus A16 or enterovirus 71 (EV71). Between 2011 and 2013, HFMD cases were reported from different Cuban provinces. A total of 42 clinical specimens were obtained from 23 patients. Detection, identification and phylogenetic analysis of enterovirus-associated HFMD were carried out by virus isolation, specific enterovirus PCR and partial VP1 sequences. HEV was detected in 11 HFMD cases. Emerging genetic variants of coxsackievirus A6 and EV71 were identified as the causative agents of the Cuban HFMD cases.
Liao, Jiaqiang; Yu, Shicheng; Yang, Fang; Yang, Min; Hu, Yuehua; Zhang, Juying
2016-01-01
Hand, Foot, and Mouth Disease (HFMD) is a worldwide infectious disease. In China, many provinces have reported HFMD cases, especially the south and southwest provinces. Many studies have found a strong association between the incidence of HFMD and climatic factors such as temperature, rainfall, and relative humidity. However, few studies have analyzed cluster effects between various geographical units. The nonlinear relationships and lag effects between weekly HFMD cases and climatic variables were estimated for the period of 2008-2013 using a polynomial distributed lag model. The extra-Poisson multilevel spatial polynomial model was used to model the exact relationship between weekly HFMD incidence and climatic variables after considering cluster effects, provincial correlated structure of HFMD incidence and overdispersion. The smoothing spline methods were used to detect threshold effects between climatic factors and HFMD incidence. The HFMD incidence spatial heterogeneity distributed among provinces, and the scale measurement of overdispersion was 548.077. After controlling for long-term trends, spatial heterogeneity and overdispersion, temperature was highly associated with HFMD incidence. Weekly average temperature and weekly temperature difference approximate inverse "V" shape and "V" shape relationships associated with HFMD incidence. The lag effects for weekly average temperature and weekly temperature difference were 3 weeks and 2 weeks. High spatial correlated HFMD incidence were detected in northern, central and southern province. Temperature can be used to explain most of variation of HFMD incidence in southern and northeastern provinces. After adjustment for temperature, eastern and Northern provinces still had high variation HFMD incidence. We found a relatively strong association between weekly HFMD incidence and weekly average temperature. The association between the HFMD incidence and climatic variables spatial heterogeneity distributed across
Yang, Fang; Yang, Min; Hu, Yuehua; Zhang, Juying
2016-01-01
Background Hand, Foot, and Mouth Disease (HFMD) is a worldwide infectious disease. In China, many provinces have reported HFMD cases, especially the south and southwest provinces. Many studies have found a strong association between the incidence of HFMD and climatic factors such as temperature, rainfall, and relative humidity. However, few studies have analyzed cluster effects between various geographical units. Methods The nonlinear relationships and lag effects between weekly HFMD cases and climatic variables were estimated for the period of 2008–2013 using a polynomial distributed lag model. The extra-Poisson multilevel spatial polynomial model was used to model the exact relationship between weekly HFMD incidence and climatic variables after considering cluster effects, provincial correlated structure of HFMD incidence and overdispersion. The smoothing spline methods were used to detect threshold effects between climatic factors and HFMD incidence. Results The HFMD incidence spatial heterogeneity distributed among provinces, and the scale measurement of overdispersion was 548.077. After controlling for long-term trends, spatial heterogeneity and overdispersion, temperature was highly associated with HFMD incidence. Weekly average temperature and weekly temperature difference approximate inverse “V” shape and “V” shape relationships associated with HFMD incidence. The lag effects for weekly average temperature and weekly temperature difference were 3 weeks and 2 weeks. High spatial correlated HFMD incidence were detected in northern, central and southern province. Temperature can be used to explain most of variation of HFMD incidence in southern and northeastern provinces. After adjustment for temperature, eastern and Northern provinces still had high variation HFMD incidence. Conclusion We found a relatively strong association between weekly HFMD incidence and weekly average temperature. The association between the HFMD incidence and climatic
International Nuclear Information System (INIS)
Bresme, F.; Armstrong, J.
2014-01-01
We report non-equilibrium molecular dynamics simulations of heat transport in models of molecular fluids. We show that the “local” thermal conductivities obtained from non-equilibrium molecular dynamics simulations agree within numerical accuracy with equilibrium Green-Kubo computations. Our results support the local equilibrium hypothesis for transport properties. We show how to use the local dependence of the thermal gradients to quantify the thermal conductivity of molecular fluids for a wide range of thermodynamic states using a single simulation
Eggenberger, Rolf; Gerber, Stefan; Huber, Hanspeter; Searles, Debra; Welker, Marc
1992-08-01
The shear viscosity is calculated ab initio for the liquid and hypercritical state, i.e. a previously published potential for Ne 2, obtained from ab initio calculations including electron correlation, is used in classical equilibrium molecular dynamics simulations to obtain the shear viscosity from a Green-Kubo integral. The quality of the results is quite uniform over a large pressure range up to 1000 MPa and a wide temperature range from 26 to 600 K. In most cases the calculated shear viscosity deviates by less than 10% from the experimental value, in general the error being only a few percent.
Aerospace Materials for Extreme Environments
2013-03-07
6.0% 8.0% 35.0 45.0 55.0 Zr [at%] Icosahedron Fraction • Chosen Method: Green - Kubo = t B t dstPstP Tk V 0 00 )()(lim Zr Al Ni...1 DISTRIBUTION STATEMENT A – Unclassified, Unlimited Distribution 15 February 2013 Integrity Service Excellence Dr. Ali Sayir Program Officer...Liquid Crystal Crystallization inhibitors: 1. Driving Force: Icosahedra 2. Kinetics: Viscosity (fragility) Direct Measurement: Critical Cooling
Correlations and the Ring-Kinetic Equation in Dense Sheared Granular Flows
Kumaran, V.
A formal way of deriving fluctuation-correlation relations in densesheared granular media, starting with the Enskog approximation for the collision integral in the Chapman-Enskog theory, is discussed. The correlation correction to the viscosity is obtained using the ring-kinetic equation, in terms of the correlations in the hydrodynamic modes of the linearised Enskog equation. It is shown that the Green-Kubo formula for the shear viscosity emerges from the two-body correlation function obtained from the ring-kinetic equation.
International Nuclear Information System (INIS)
Palmer, B.J.
1994-01-01
A method to calculate the thermal diffusivity D T from spontaneous fluctuations in the local heat energy density is presented. Calculations of the thermal diffusivity are performed for the Lennard-Jones fluid, carbon dioxide, and water. The results for the Lennard-Jones fluid are in agreement with calculations of the thermal conductivity using Green-Kubo relations and nonequilibrium molecular-dynamics techniques. The results for carbon dioxide and water give thermal diffusivities within a factor of 2 of the experimental values
Viscosity calculated in simulations of strongly coupled dusty plasmas with gas friction
International Nuclear Information System (INIS)
Feng Yan; Goree, J.; Liu Bin
2011-01-01
A two-dimensional strongly coupled dusty plasma is modeled using Langevin and frictionless molecular dynamical simulations. The static viscosity η and the wave-number-dependent viscosity η(k) are calculated from the microscopic shear in the random motion of particles. A recently developed method of calculating the wave-number-dependent viscosity η(k) is validated by comparing the results of η(k) from the two simulations. It is also verified that the Green-Kubo relation can still yield an accurate measure of the static viscosity η in the presence of a modest level of friction as in dusty plasma experiments.
Theory of the Chemla effect in molten (Li,K)Cl
International Nuclear Information System (INIS)
Tankeshwar, K.; Tosi, M.P.
1991-12-01
We treat ionic diffusion in liquid (Li,K)Cl mixtures by an approach originally due to Zwanzig, which evaluates the Green-Kubo time correlation formula by a jump-diffusion model involving an average vibrational frequency and an average residence time for each ionic species. These model parameters are calculated from the pair structure of the melt and from pair potentials. The diffusion coefficients of K + ions is found to overtake that of Li + ions with increasing content of KCl, in agreement with the experimental reversal of the electrical mobilities of the two cations discovered by Chemla. (author). 20 refs, 2 tabs
Numerical simulations of thermal conductivity in dissipative two-dimensional Yukawa systems.
Khrustalyov, Yu V; Vaulina, O S
2012-04-01
Numerical data on the heat transfer constants in two-dimensional Yukawa systems were obtained. Numerical study of the thermal conductivity and diffusivity was carried out for the equilibrium systems with parameters close to conditions of laboratory experiments with dusty plasma. For calculations of heat transfer constants the Green-Kubo formulas were used. The influence of dissipation (friction) on the heat transfer processes in nonideal systems was investigated. The approximation of the coefficient of thermal conductivity is proposed. Comparison of the obtained results to the existing experimental and numerical data is discussed.
Diffusion in Deterministic Interacting Lattice Systems
Medenjak, Marko; Klobas, Katja; Prosen, Tomaž
2017-09-01
We study reversible deterministic dynamics of classical charged particles on a lattice with hard-core interaction. It is rigorously shown that the system exhibits three types of transport phenomena, ranging from ballistic, through diffusive to insulating. By obtaining an exact expressions for the current time-autocorrelation function we are able to calculate the linear response transport coefficients, such as the diffusion constant and the Drude weight. Additionally, we calculate the long-time charge profile after an inhomogeneous quench and obtain diffusive profilewith the Green-Kubo diffusion constant. Exact analytical results are corroborated by Monte Carlo simulations.
Linear and nonlinear viscous flow in two-dimensional fluids
International Nuclear Information System (INIS)
Gravina, D.; Ciccotti, G.; Holian, B.L.
1995-01-01
We report on molecular dynamics simulations of shear viscosity η of a dense two-dimensional fluid as a function of the shear rate γ. We find an analytic dependence of η on γ, and do not find any evidence whatsoever of divergence in the Green-Kubo (GK) value that would be caused by the well-known long-time tail for the shear-stress autocorrelation function, as predicted by the mode-coupling theory. In accordance with the linear response theory, the GK value of η agrees remarkably well with nonequilibrium values at small shear rates. (c) 1995 The American Physical Society
2015-04-28
conductivity The Green- Kubo method uses the auto-correlation of equilibrium heat flux J to calculate the conductivity κ from the expression (2) where V...specific experiments are discussed here, specifically, sensitivity calculations of our measurements to the thermal conductivity of the TCNQ@Cu3(BTC)2...where x denotes κMOF, CMOF, hK,Al/MOF or hK,MOF/SiO2. This TDTR sensitivity, Sx, is calculated by ]ln[ )( )( ln )( x tV tV tS out in x
Viscosity calculations at molecular dynamics simulations
International Nuclear Information System (INIS)
Kirova, E M; Norman, G E
2015-01-01
Viscosity and diffusion are chosen as an example to demonstrate the universality of diagnostics methods in the molecular dynamics method. To emphasize the universality, three diverse systems are investigated, which differ from each other drastically: liquids with embedded atom method and pairwise interatomic interaction potentials and dusty plasma with a unique multiparametric interparticle interaction potential. Both the Einstein-Helfand and Green-Kubo relations are used. Such a particular process as glass transition is analysed at the simulation of the aluminium melt. The effect of the dust particle charge fluctuation is considered. The results are compared with the experimental data. (paper)
Wang, Pin; Zhao, Han; You, Fangxin; Zhou, Hailong; Goggins, William B.
2017-08-01
Hand, foot, and mouth disease (HFMD) is an enterovirus-induced infectious disease, mainly affecting children under 5 years old. Outbreaks of HFMD in recent years indicate the disease interacts with both the weather and season. This study aimed to investigate the seasonal association between HFMD and weather variation in Chongqing, China. Generalized additive models and distributed lag non-linear models based on a maximum lag of 14 days, with negative binomial distribution assumed to account for overdispersion, were constructed to model the association between reporting HFMD cases from 2009 to 2014 and daily mean temperature, relative humidity, total rainfall and sun duration, adjusting for trend, season, and day of the week. The year-round temperature and relative humidity, rainfall in summer, and sun duration in winter were all significantly associated with HFMD. An inverted-U relationship was found between mean temperature and HFMD above 19 °C in summer, with a maximum morbidity at 27 °C, while the risk increased linearly with the temperature in winter. A hockey-stick association was found for relative humidity in summer with increasing risks over 60%. Heavy rainfall, relative to no rain, was found to be associated with reduced HFMD risk in summer and 2 h of sunshine could decrease the risk by 21% in winter. The present study showed meteorological variables were differentially associated with HFMD incidence in two seasons. Short-term weather variation surveillance and forecasting could be employed as an early indicator for potential HFMD outbreaks.
Zhang, Shu-Yan; Xu, Mei-Yan; Xu, Hong-Mei; Li, Xiu-Jun; Ding, Shu-Jun; Wang, Xian-Jun; Li, Ting-Yu; Lu, Qing-Bin
2015-07-01
Viral encephalitis is a serious complication of hand, foot, and mouth disease (HFMD), but characteristics of cytokines response in enterovirus 71 (EV-71) and/or coxsackievirus A16 (CV-A16) associated HFMD with or without viral encephalitis remained unclear.We performed a multigroup retrospective study and compared the serum cytokines concentrations among 16 encephalitis patients infected with EV-71 and CV-A16, 24 encephalitis patients with single EV-71 infection, 34 mild HFMD patients with EV-71 infection, 18 mild HFMD patients with CV-A16 infection, and 39 healthy control subjects.Serum levels of interleukin (IL)-4, IL-5, IL-22, and IL-23 were significantly higher in encephalitis patients than in HFMD-alone patients when adjusting for age and sex; IL-2, tumor necrosis factor (TNF)-α, IL-4, IL-22, and IL-1β were significantly higher in HFMD-alone patients of EV-71 infection than in CV-A16 infected HFMD patients; cerebrospinal fluid level of IL-6 was lower in the EV-71/CV-A16 associated encephalitis than that in the EV-71 alone associated encephalitis patients.Over or low expression of the cytokines cascade in HFMD patients appears to play an important role in the elicitation of the immune response to EV-71 and CV-A16. These data will be used to define a cytokine profile, which might help to recognize HFMD patients with the high risk of developing encephalitis.
Numerical Test of Different Approximations Used in the Transport Theory of Energetic Particles
Qin, G.; Shalchi, A.
2016-05-01
Recently developed theories for perpendicular diffusion work remarkably well. The diffusion coefficients they provide agree with test-particle simulations performed for different turbulence setups ranging from slab and slab-like models to two-dimensional and noisy reduced MHD turbulence. However, such theories are still based on different analytical approximations. In the current paper we use a test-particle code to explore the different approximations used in diffusion theory. We benchmark different guiding center approximations, simplifications of higher-order correlations, and the Taylor-Green-Kubo formula. We demonstrate that guiding center approximations work very well as long as the particle's unperturbed Larmor radius is smaller than the perpendicular correlation length of the turbulence. Furthermore, the Taylor-Green-Kubo formula and the definition of perpendicular diffusion coefficients via mean square displacements provide the same results. The only approximation that was used in the past in nonlinear diffusion theory that fails is to replace fourth-order correlations by a product of two second-order correlation functions. In more advanced nonlinear theories, however, this type of approximation is no longer used. Therefore, we confirm the validity of modern diffusion theories as a result of the work presented in the current paper.
Shear viscosity coefficient from microscopic models
International Nuclear Information System (INIS)
Muronga, Azwinndini
2004-01-01
The transport coefficient of shear viscosity is studied for a hadron matter through microscopic transport model, the ultrarelativistic quantum molecular dynamics (UrQMD), using the Green-Kubo formulas. Molecular-dynamical simulations are performed for a system of light mesons in a box with periodic boundary conditions. Starting from an initial state composed of π,η,ω,ρ,φ with a uniform phase-space distribution, the evolution takes place through elastic collisions, production, and annihilation. The system approaches a stationary state of mesons and their resonances, which is characterized by common temperature. After equilibration, thermodynamic quantities such as the energy density, particle density, and pressure are calculated. From such an equilibrated state the shear viscosity coefficient is calculated from the fluctuations of stress tensor around equilibrium using Green-Kubo relations. We do our simulations here at zero net baryon density so that the equilibration times depend on the energy density. We do not include hadron strings as degrees of freedom so as to maintain detailed balance. Hence we do not get the saturation of temperature but this leads to longer equilibration times
Dong, Haikuan; Fan, Zheyong; Shi, Libin; Harju, Ari; Ala-Nissila, Tapio
2018-03-01
Molecular dynamics (MD) simulations play an important role in studying heat transport in complex materials. The lattice thermal conductivity can be computed either using the Green-Kubo formula in equilibrium MD (EMD) simulations or using Fourier's law in nonequilibrium MD (NEMD) simulations. These two methods have not been systematically compared for materials with different dimensions and inconsistencies between them have been occasionally reported in the literature. Here we give an in-depth comparison of them in terms of heat transport in three allotropes of Si: three-dimensional bulk silicon, two-dimensional silicene, and quasi-one-dimensional silicon nanowire. By multiplying the correlation time in the Green-Kubo formula with an appropriate effective group velocity, we can express the running thermal conductivity in the EMD method as a function of an effective length and directly compare it to the length-dependent thermal conductivity in the NEMD method. We find that the two methods quantitatively agree with each other for all the systems studied, firmly establishing their equivalence in computing thermal conductivity.
Bulk diffusion in a kinetically constrained lattice gas
Arita, Chikashi; Krapivsky, P. L.; Mallick, Kirone
2018-03-01
In the hydrodynamic regime, the evolution of a stochastic lattice gas with symmetric hopping rules is described by a diffusion equation with density-dependent diffusion coefficient encapsulating all microscopic details of the dynamics. This diffusion coefficient is, in principle, determined by a Green-Kubo formula. In practice, even when the equilibrium properties of a lattice gas are analytically known, the diffusion coefficient cannot be computed except when a lattice gas additionally satisfies the gradient condition. We develop a procedure to systematically obtain analytical approximations for the diffusion coefficient for non-gradient lattice gases with known equilibrium. The method relies on a variational formula found by Varadhan and Spohn which is a version of the Green-Kubo formula particularly suitable for diffusive lattice gases. Restricting the variational formula to finite-dimensional sub-spaces allows one to perform the minimization and gives upper bounds for the diffusion coefficient. We apply this approach to a kinetically constrained non-gradient lattice gas in two dimensions, viz. to the Kob-Andersen model on the square lattice.
Huang, Jiao; Chen, Shi; Wu, Yang; Tong, Yeqing; Wang, Lei; Zhu, Min; Hu, Shuhua; Guan, Xuhua; Wei, Sheng
2018-01-31
Hand, foot and mouth disease (HFMD) is a substantial burden throughout Asia, but the effects of temperature pattern on HFMD risk are inconsistent. To quantify the effect of temperature on HFMD incidence, Wuhan was chosen as the study site because of its high temperature variability and high HFMD incidence. Daily series of HFMD counts and meteorological variables during 2010-2015 were obtained. Distributed lag non-linear models were applied to characterize the temperature-HFMD relationship and to assess its variability across different ages, genders, and types of child care. Totally, 80,219 patients of 0-5 years experienced HFMD in 2010-2015 in Wuhan. The cumulative relative risk of HFMD increased linearly with temperature over 7 days (lag0-7), while it presented as an approximately inverted V-shape over 14 days (lag0-14). The cumulative relative risk at lag0-14 peaked at 26.4 °C with value of 2.78 (95%CI: 2.08-3.72) compared with the 5 th percentile temperature (1.7 °C). Subgroup analyses revealed that children attended daycare were more vulnerable to temperature variation than those cared for at home. This study suggests that public health actions should take into consideration local weather conditions and demographic characteristics.
Survey of enterovirus infections from hand, foot and mouth disease outbreak in china, 2009
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Yang Fan
2011-11-01
Full Text Available Abstract Background In China, a rapid expansion of Hand, foot, and mouth disease (HFMD outbreaks has occurred since 2004 and HFMD has become an important issue for China. However, people are still only concerned with human enterovirus 71(HEV-71 and coxsackie virus A16 (CV-A16. Much of what is known about the other enterovirus infections relies on fractional evidence and old epidemic data, with little knowledge concerning their distribution. To alert potential threatens of the other enteroviruses, our study genetically characterized specimens from different regions of China and yielded novel information concerning the circulating and phylogenetic characteristics of enteroviral strains from HFMD cases. Findings A total of 301 clinical throat swabs were randomly obtained from patients suffering from HFMD from the southern, northern and central regions of China during outbreaks in 2009. 266 of 301 (88.4% HFMD cases were found positive for HEV and seven genotypes, HEV-71, CV-A16, -B5, -A4, -A6, -A10, and -A12, were detected. Conclusions The HFMD pathogen compositions in the different regions of China were significantly different. HFMD epidemics might persist for a long time in China due to the multiple pathogen compositions, the enteroviral characteristic of recombination and co-infection, the ever-increasing travel and migration and the deficiency of effective vaccine. Our study deserves the attention on HFMD control and vaccine development.
Directory of Open Access Journals (Sweden)
Xueyong Huang
Full Text Available A rapid expansion of HFMD with enterovirus 71 infection outbreaks has occurred and caused deaths in recent years in China, but no vaccine or antiviral drug is currently available for EV71 infection. This study aims to provide treatment programs for HFMD patients. We conducted a randomized, double-blind, controlled trial and evaluated clinical efficacy of therapy with rHuIFN-α1b in HFMD patients with EV71 infection. There were statistical differences in outcomes including the fever clearance time, healing time of typical skin or oral mucosa lesions, and EV71 viral load of the HFMD patients among ultrasonic aerosol inhalation group, intramuscular injection group and control group. rHuIFN-α1b therapy reduced the fever clearance time, healing time of typical skin or oral mucosa lesions, and EV71 viral load in children with HFMD.Chinese Clinical Trial Registry ChiCTR-TRC-14005153.
Enterovirus co-infections and onychomadesis after hand, foot, and mouth disease, Spain, 2008.
Bracho, Maria A; González-Candelas, Fernando; Valero, Ana; Córdoba, Juan; Salazar, Antonio
2011-12-01
Hand, foot, and mouth disease (HFMD), a common disease caused by enteroviruses (EVs), usually affects children. Clustered and sporadic HFMD cases, followed by onychomadesis (nail shedding), occurred during summer and fall 2008 in Valencia, Spain. Fecal samples from onychomadesis patients, who did or did not have previous HFMD, and from healthy children exposed to onychomadesis patients tested positive for EV. The complete viral protein 1 capsid gene sequence was obtained for typing and phylogenetic analysis. Two EV serotypes, coxsackievirus A10 and coxsackievirus B1 (CVB1), were mainly detected as a monoinfection or co-infection in a childcare center where an onychomadesis outbreak occurred. On the basis of our results, and detection of CVB1 in 2 other contemporary onychomadesis outbreaks in childcare centers in Spain, we propose that mixed infection of an EV serotype that causes HFMD, plus the serotype CVB1, could explain the emergence after HFMD of onychomadesis, a rare and late complication.
Li, Jing; Shan, Ruo-Bing; Liu, Rui-Hai; Xu, Ying-Jun; Qu, Ni-Yan; Pan, Gui-Mei; Zhang, Na; Yang, Na; Chen, Zhen-Zhen; Zhang, Wen-Xiang; Li, Zi-Pu
2017-08-01
To investigate the association between rs9722 polymorphisms in the S100B gene and hand, foot and mouth disease (HFMD) caused by enterovirus 71. A total of 124 HFMD children with enterovirus 71 infection were enrolled as subjects, and 56 healthy children were enrolled as control group. The rs9722 polymorphisms in the S100B gene were detected for both groups, and the serum level of S100B protein was measured for 74 HFMD children. The rs9722 locus of the S100B gene had three genotypes, CC, CT, and TT, and the genotype frequencies were in accordance with Hardy-Weinberg equilibrium. Compared with the control group, the HFMD group had significant increases in the frequencies of TT genotype and T allele (Penterovirus 71 infection had significantly higher frequencies of TT genotype and T allele than those with moderate or mild HFMD (Penterovirus 71 infection.
Size Effect on Transport Properties of Gaseous Argon: A Molecular Dynamics Simulation Study
International Nuclear Information System (INIS)
Lee, Songhi
2014-01-01
We have carried out a series of equilibrium molecular dynamics (EMD) simulations of gaseous argon at 273.15 K and 1.00 atm for the calculation of transport properties as a function of the number of argon molecules (N). While the diffusion coefficients (D) of gaseous argon approach to the experimental measure with increasing N, the viscosities (η) and thermal conductivities (λ) obtained for N = 432 are unreliable due to the high fluctuation of the time correlation functions and those for N = 1728 are rather acceptable. Increasing further to N = 6912 has improved the MD results a little closer to the experimental measures for η and λ. Both the EMD results for η and λ for N = 6912 underestimate the experimental measures and it is not expected that the more increasing N makes the closer results to the experimental measures. One possible explanation for the large disagreement between MD results and the experimental measures for η and λ may be due to the use of LJ parameters which were used for liquid argon. In a recent study, we have examined the Green-Kubo formula for the calculation of transport properties (diffusion coefficient, viscosity, and thermal conductivity) of noble gases (He, Ne, Ar, Kr, and Xe) by carrying out a series of equilibrium molecular dynamics (EMD) simulations for the system of N=1728 at 273.15 K and 1.00 atm.1 While the diffusion coefficients (D) of noble gases were obtained through the original Green-Kubo formula, the viscosities (η) and thermal conductivities (λ) were obtained by utilizing the revised Green-Kubo formulas. The structural and dynamic properties of gaseous argon are completely different from those of liquid argon at 94.4 K and 1.374 g/cm 3 . The results for transport properties (D, η, and λ) at 273.15 K and 1.00 atm obtained from our EMD simulations are in general agreement with the experimental data and superior to the rigorous results of the kinetic theory
Du, Zhicheng; Xu, Lin; Zhang, Wangjian; Zhang, Dingmei; Yu, Shicheng; Hao, Yuantao
2017-10-06
Hand, foot, and mouth disease (HFMD) has caused a substantial burden in China, especially in Guangdong Province. Based on the enhanced surveillance system, we aimed to explore whether the addition of temperate and search engine query data improves the risk prediction of HFMD. Ecological study. Information on the confirmed cases of HFMD, climate parameters and search engine query logs was collected. A total of 1.36 million HFMD cases were identified from the surveillance system during 2011-2014. Analyses were conducted at aggregate level and no confidential information was involved. A seasonal autoregressive integrated moving average (ARIMA) model with external variables (ARIMAX) was used to predict the HFMD incidence from 2011 to 2014, taking into account temperature and search engine query data (Baidu Index, BDI). Statistics of goodness-of-fit and precision of prediction were used to compare models (1) based on surveillance data only, and with the addition of (2) temperature, (3) BDI, and (4) both temperature and BDI. A high correlation between HFMD incidence and BDI ( r =0.794, pengine query data significantly improved the prediction of HFMD. Further studies are warranted to examine whether including search engine query data also improves the prediction of other infectious diseases in other settings. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2017. All rights reserved. No commercial use is permitted unless otherwise expressly granted.
Wang, J X; Hu, M G; Yu, S C; Xiao, G X
2017-09-10
Objective: To understand the spatial distribution of incidence of hand foot and mouth disease (HFMD) at scale of township and provide evidence for the better prevention and control of HFMD and allocation of medical resources. Methods: The incidence data of HFMD in 108 counties (district) in Shandong province in 2010 were collected. Downscaling interpolation was conducted by using area-to-area Poisson Kriging method. The interpolation results were visualized by using geographic information system (GIS). The county (district) incidence was interpolated into township incidence to get the distribution of spatial distribution of incidence of township. Results: In the downscaling interpolation, the range of the fitting semi-variance equation was 20.38 km. Within the range, the incidence had correlation with each other. The fitting function of scatter diagram of estimated and actual incidence of HFMD at country level was y =1.053 1 x , R (2)=0.99. The incidences at different scale were consistent. Conclusions: The incidence of HFMD had spatial autocorrelation within 20.38 km. When HFMD occurs in one place, it is necessary to strengthen the surveillance and allocation of medical resource in the surrounding area within 20.38 km. Area to area Poisson Kriging method based downscaling research can be used in spatial visualization of HFMD incidence.
Gou, Faxiang; Liu, Xinfeng; Ren, Xiaowei; Liu, Dongpeng; Liu, Haixia; Wei, Kongfu; Yang, Xiaoting; Cheng, Yao; Zheng, Yunhe; Jiang, Xiaojuan; Li, Juansheng; Meng, Lei; Hu, Wenbiao
2017-01-01
The influence of socio-ecological factors on hand, foot and mouth disease (HFMD) were explored in this study using Bayesian spatial modeling and spatial patterns identified in dry regions of Gansu, China. Notified HFMD cases and socio-ecological data were obtained from the China Information System for Disease Control and Prevention, Gansu Yearbook and Gansu Meteorological Bureau. A Bayesian spatial conditional autoregressive model was used to quantify the effects of socio-ecological factors on the HFMD and explore spatial patterns, with the consideration of its socio-ecological effects. Our non-spatial model suggests temperature (relative risk (RR) 1.15, 95 % CI 1.01-1.31), GDP per capita (RR 1.19, 95 % CI 1.01-1.39) and population density (RR 1.98, 95 % CI 1.19-3.17) to have a significant effect on HFMD transmission. However, after controlling for spatial random effects, only temperature (RR 1.25, 95 % CI 1.04-1.53) showed significant association with HFMD. The spatial model demonstrates temperature to play a major role in the transmission of HFMD in dry regions. Estimated residual variation after taking into account the socio-ecological variables indicated that high incidences of HFMD were mainly clustered in the northwest of Gansu. And, spatial structure showed a unique distribution after taking account of socio-ecological effects.
Hand, foot and mouth disease: spatiotemporal transmission and climate.
Wang, Jin-feng; Guo, Yan-Sha; Christakos, George; Yang, Wei-Zhong; Liao, Yi-Lan; Li, Zhong-Jie; Li, Xiao-Zhou; Lai, Sheng-Jie; Chen, Hong-Yan
2011-04-05
The Hand-Foot-Mouth Disease (HFMD) is the most common infectious disease in China, its total incidence being around 500,000~1,000,000 cases per year. The composite space-time disease variation is the result of underlining attribute mechanisms that could provide clues about the physiologic and demographic determinants of disease transmission and also guide the appropriate allocation of medical resources to control the disease. HFMD cases were aggregated into 1456 counties and during a period of 11 months. Suspected climate attributes to HFMD were recorded monthly at 674 stations throughout the country and subsequently interpolated within 1456 × 11 cells across space-time (same as the number of HFMD cases) using the Bayesian Maximum Entropy (BME) method while taking into consideration the relevant uncertainty sources. The dimensionalities of the two datasets together with the integrated dataset combining the two previous ones are very high when the topologies of the space-time relationships between cells are taken into account. Using a self-organizing map (SOM) algorithm the dataset dimensionality was effectively reduced into 2 dimensions, while the spatiotemporal attribute structure was maintained. 16 types of spatiotemporal HFMD transmission were identified, and 3-4 high spatial incidence clusters of the HFMD types were found throughout China, which are basically within the scope of the monthly climate (precipitation) types. HFMD propagates in a composite space-time domain rather than showing a purely spatial and purely temporal variation. There is a clear relationship between HFMD occurrence and climate. HFMD cases are geographically clustered and closely linked to the monthly precipitation types of the region. The occurrence of the former depends on the later.
Zhang, Wangjian; Du, Zhicheng; Zhang, Dingmei; Yu, Shicheng; Hao, Yuantao
2016-01-15
Hand, foot and mouth disease (HFMD) is a common childhood infection and has become a major public health issue in China. Considerable research has focused on the role of meteorological factors such as temperature and relative humidity in HFMD development. However, no studies have specifically quantified the impact of another major environmental agent, excessive heat, on HFMD. The current study was designed to help address this research gap. Case-based HFMD surveillance data and daily meteorological data collected between 2010 and 2012 was obtained from China CDC and the National Meteorological Information Center, respectively. Distributed lag nonlinear models were applied to assess the impact of excessive heat on HFMD and its variability across social-economic status and age groups. After controlling the effects of several potential confounders, the commonly hot days were found to positively affect the HFMD burdens with the relative risk (RR) peaking at around 6 days of lag. The RR of HFMD in the Pearl-River Delta Region was generally higher and persisted longer than that in the remaining developing areas. Regarding the inter-age group discrepancy, children aged 3-6 years old had the highest risk of HFMD under conditions of excessive heat whereas those greater than 6 years old had the lowest. The lag structure of the impact of the extremely hot days was quite similar to that of the commonly hot days, although the relative effect of these two kinds of conditions of excessive heat might vary across regions. This study indicated significantly facilitating effects of excessive heat on HFMD especially among those aged 3-6 and from developed areas. Results from the current study were particularly practical and important for developing area-and-age-targeted control programs in the context of climate change and urbanization. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.
Hand, foot and mouth disease: spatiotemporal transmission and climate
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Li Xiao-Zhou
2011-04-01
Full Text Available Abstract Background The Hand-Foot-Mouth Disease (HFMD is the most common infectious disease in China, its total incidence being around 500,000 ~1,000,000 cases per year. The composite space-time disease variation is the result of underlining attribute mechanisms that could provide clues about the physiologic and demographic determinants of disease transmission and also guide the appropriate allocation of medical resources to control the disease. Methods and Findings HFMD cases were aggregated into 1456 counties and during a period of 11 months. Suspected climate attributes to HFMD were recorded monthly at 674 stations throughout the country and subsequently interpolated within 1456 × 11 cells across space-time (same as the number of HFMD cases using the Bayesian Maximum Entropy (BME method while taking into consideration the relevant uncertainty sources. The dimensionalities of the two datasets together with the integrated dataset combining the two previous ones are very high when the topologies of the space-time relationships between cells are taken into account. Using a self-organizing map (SOM algorithm the dataset dimensionality was effectively reduced into 2 dimensions, while the spatiotemporal attribute structure was maintained. 16 types of spatiotemporal HFMD transmission were identified, and 3-4 high spatial incidence clusters of the HFMD types were found throughout China, which are basically within the scope of the monthly climate (precipitation types. Conclusions HFMD propagates in a composite space-time domain rather than showing a purely spatial and purely temporal variation. There is a clear relationship between HFMD occurrence and climate. HFMD cases are geographically clustered and closely linked to the monthly precipitation types of the region. The occurrence of the former depends on the later.
Virological investigation of hand, foot, and mouth disease in a tertiary care center in South India
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Pavithra M Vijayaraghavan
2012-01-01
Full Text Available Context: Hand, foot, and mouth disease (HFMD remains a common problem in India, yet its etiology is largely unknown as diagnosis is based on clinical characteristics. There are very few laboratory-based molecular studies on HFMD outbreaks. Aim: The aim of this study was to characterize HFMD-related isolates by molecular techniques. Settings and Design: Between 2005 and 2008, during two documented HFMD outbreaks, 30 suspected HFMD cases presented at the Outpatient Unit of the Department of Dermatology, Christian Medical College (CMC, Vellore. Seventy-eight clinical specimens (swabs from throat, mouth, rectum, anus, buttocks, tongue, forearm, sole, and foot were received from these patients at the Department of Clinical Virology, CMC, for routine diagnosis of hand, foot, and mouth disease. Materials and Methods: Samples from these patients were cultured in Vero and rhabdomyosarcoma (RD cell lines. Isolates producing enterovirus-like cytopathogenic effect (CPE in cell culture were identified by a nested reverse transcription-based polymerase chain reaction (RT-PCR and sequenced. The nucleotide sequences were analyzed using the BioEdit sequence program. Homology searches were performed using the Basic Local Alignment Search Tool (BLAST algorithm. Statistical Analysis used: The statistical analysis was performed using Epi Info version 6.04b and Microsoft Excel 2002 (Microsoft Office XP. Results: Of the 30 suspected HFMD cases, only 17 (57% were laboratory confirmed and Coxsackievirus A16 (CVA16 was identified as the etiological agent in all these cases. Conclusions: Coxsackievirus A16 (CVA16 was identified as the virus that caused the HFMD outbreaks in Vellore between 2005 and 2008. Early confirmation of HFMD helps to initiate control measures to interrupt virus transmission. In the laboratory, classical diagnostic methods, culture and serological tests are being replaced by molecular techniques. Routine surveillance systems will help understand the
Xu, C D; Xiao, G X
2017-10-01
Hand, foot and mouth disease (HFMD) risk has become an increasing concern in the Beijing-Tianjin-Hebei region, which is the biggest urban agglomeration in north-eastern Asia. In the study, spatiotemporal epidemiological features of HFMD were analysed, and a Bayesian space-time hierarchy model was used to detect local spatial relative risk (RR) and to assess the effect of meteorological factors. From 2009 to 2013, there was an obvious seasonal pattern of HFMD risk. The highest risk period was in the summer, with an average monthly incidence of 4·17/103, whereas the index in wintertime was 0·16/103. Meteorological variables influenced temporal changes in HFMD. A 1 °C rise in air temperature was associated with an 11·5% increase in HFMD (corresponding RR 1·122). A 1% rise in relative humidity was related to a 9·51% increase in the number of HFMD cases (corresponding RR 1·100). A 1 hPa increment in air pressure was related to a 0·11% decrease in HFMD (corresponding RR 0·999). A 1 h increase in sunshine was associated with a 0·28% rise in HFMD cases (corresponding RR 1·003). A 1 m/s rise in wind speed was related to a 6·2% increase in HFMD (corresponding RR 1·064). High-risk areas were mainly large cities, such as Beijing, Tianjin, Shijiazhuang and their neighbouring areas. These findings can contribute to risk control and implementation of disease-prevention policies.
The Epidemiology of Hand, Foot and Mouth Disease in Asia
Koh, Wee Ming; Bogich, Tiffany; Siegel, Karen; Jin, Jing; Chong, Elizabeth Y.; Tan, Chong Yew; Chen, Mark IC; Horby, Peter
2016-01-01
Context: Hand, foot and mouth disease (HFMD) is a widespread pediatric disease caused primarily by human enterovirus 71 (EV-A71) and Coxsackievirus A16 (CV-A16). Objective: This study reports a systematic review of the epidemiology of HFMD in Asia. Data Sources: PubMed, Web of Science and Google Scholar were searched up to December 2014. Study Selection: Two reviewers independently assessed studies for epidemiologic and serologic information about prevalence and incidence of HFMD against predetermined inclusion/exclusion criteria. Data Extraction: Two reviewers extracted answers for 8 specific research questions on HFMD epidemiology. The results are checked by 3 others. Results: HFMD is found to be seasonal in temperate Asia with a summer peak and in subtropical Asia with spring and fall peaks, but not in tropical Asia; evidence of a climatic role was identified for temperate Japan. Risk factors for HFMD include hygiene, age, gender and social contacts, but most studies were underpowered to adjust rigorously for confounding variables. Both community-level and school-level transmission have been implicated, but their relative importance for HFMD is inconclusive. Epidemiologic indices are poorly understood: No supporting quantitative evidence was found for the incubation period of EV-A71; the symptomatic rate of EV-A71/Coxsackievirus A16 infection was from 10% to 71% in 4 studies; while the basic reproduction number was between 1.1 and 5.5 in 3 studies. The uncertainty in these estimates inhibits their use for further analysis. Limitations: Diversity of study designs complicates attempts to identify features of HFMD epidemiology. Conclusions: Knowledge on HFMD remains insufficient to guide interventions such as the incorporation of an EV-A71 vaccine in pediatric vaccination schedules. Research is urgently needed to fill these gaps. PMID:27273688
Temporal and spatial mapping of hand, foot and mouth disease in Sarawak, Malaysia.
Sham, Noraishah M; Krishnarajah, Isthrinayagy; Ibrahim, Noor Akma; Lye, Munn-Sann
2014-05-01
Hand, foot and mouth disease (HFMD) is endemic in Sarawak, Malaysia. In this study, a geographical information system (GIS) was used to investigate the relationship between the reported HFMD cases and the spatial patterns in 11 districts of Sarawak from 2006 to 2012. Within this 7-years period, the highest number of reported HFMD cases occurred in 2006, followed by 2012, 2008, 2009, 2007, 2010 and 2011, in descending order. However, while there was no significant distribution pattern or clustering in the first part of the study period (2006 to 2011) based on Moran's I statistic, spatial autocorrelation (P = 0.068) was observed in 2012.
Hoheisel, C.
1988-09-01
Equilibrium molecular dynamics calculations with constraints have been performed for model liquids SF6 and CF4. The computations were carried out with four- and six-center Lennard-Jones potentials and up to 2×105 integration steps. Shear, bulk viscosity and the thermal conductivity have been calculated with use of Green-Kubo relations in the formulation of ``molecule variables.'' Various thermodynamic states were investigated. For SF6, a detailed comparison with experimental data was possible. For CF4, the MD results could only be compared with experiment for one liquid state. For the latter liquid, a complementary comparison was performed using MD results obtained with a one-center Lennard-Jones potential. A limited test of the particle number dependence of the results is presented. Partial and total correlations functions are shown and discussed with respect to findings obtained for the one-center Lennard-Jones liquid.
Cui, S. T.
The stress-stress correlation function and the viscosity of a united-atom model of liquid decane are studied by equilibrium molecular dynamics simulation using two different formalisms for the stress tensor: the atomic and the molecular formalisms. The atomic and molecular correlation functions show dramatic difference in short-time behaviour. The integrals of the two correlation functions, however, become identical after a short transient period whichis significantly shorter than the rotational relaxation time of the molecule. Both reach the same plateau value in a time period corresponding to this relaxation time. These results provide a convenient guide for the choice of the upper integral time limit in calculating the viscosity by the Green-Kubo formula.
Hoheisel, C.
1989-01-01
For several liquid states of CF4 and SF4, the shear and the bulk viscosity as well as the thermal conductivity were determined by equilibrium molecular dynamics (MD) calculations. Lennard-Jones four- and six-center pair potentials were applied, and the method of constraints was chosen for the MD. The computed Green-Kubo integrands show a steep time decay, and no particular longtime behavior occurs. The molecule number dependence of the results is found to be small, and 3×105 integration steps allow an accuracy of about 10% for the shear viscosity and the thermal conductivity coefficient. Comparison with experimental data shows a fair agreement for CF4, while for SF6 the transport coefficients fall below the experimental ones by about 30%.
Adiabatic Hamiltonian deformation, linear response theory, and nonequilibrium molecular dynamics
International Nuclear Information System (INIS)
Hoover, W.G.
1980-01-01
Although Hamiltonians of various kinds have previously been used to derive Green-Kubo relations for the transport coefficients, the particular choice described is uniquely related to thermodynamics. This nonequilibrium Hamiltonian formulation of fluid flow provides pedagogically simple routes to nonequilibrium fluxes and distribution functions, to theoretical understanding of long-time effects, and to new numerical methods for simulating systems far from equilibrium. The same methods are now being applied to solid-phase problems. At the relatively high frequencies used in the viscous fluid calculations described, solids typically behave elastically. Lower frequencies lead to the formation of dislocations and other defects, making it possible to study plastic flow. A property of the nonequilibrium equations of motion which might be profitably explored is their effective irreversibility. Because only a few particles are necessary to generate irreversible behavior, simulations using adiabatic deformations of the kind described here could perhaps elucidate the instability in the equations of motion responsible for irreversibility
International Nuclear Information System (INIS)
Hoheisel, C.
1989-01-01
For several liquid states of CF 4 and SF 6 , the shear and the bulk viscosity as well as the thermal conductivity were determined by equilibrium molecular dynamics (MD) calculations. Lennard-Jones four- and six-center pair potentials were applied, and the method of constraints were chosen for the MD. The computed Green-Kubo integrands show a steep time decay, and no particular longtime behavior occurs. The molecule number dependence of the results is found to be small, and 3 x 10 5 integration steps allow an accuracy of about 10% for the shear viscosity and the thermal conductivity coefficient. Comparison with experimental data shows a fair agreement for CF 4 , while for SF 6 the transport coefficients fall below the experimental ones by about 30%
Vogelsang, R.; Hoheisel, C.
1987-02-01
Molecular-dynamics (MD) calculations are reported for three thermodynamic states of a Lennard-Jones fluid. Systems of 2048 particles and 105 integration steps were used. The transverse current autocorrelation function, Ct(k,t), has been determined for wave vectors of the range 0.5viscosities which showed a systematic behavior as a function of k. Extrapolation to the hydrodynamic region at k=0 gave shear viscosity coefficients in good agreement with direct Green-Kubo results obtained in previous work. The two-exponential model fit for the memory function proposed by other authors does not provide a reasonable description of the MD results, as the fit parameters show no systematic wave-vector dependence, although the Ct(k,t) functions are somewhat better fitted. Similarly, the semiempirical interpolation formula for the decay time based on the viscoelastic concept proposed by Akcasu and Daniels fails to reproduce the correct k dependence for the wavelength range investigated herein.
Relaxation and transport properties of liquid n-triacontane
International Nuclear Information System (INIS)
Kondratyuk, N D; Lankin, A V; Norman, G E; Stegailov, V V
2015-01-01
Molecular modelling is used to calculate transport properties and to study relaxation of liquid n-triacontane (C 30 H 62 ). The problem is important in connection with the behavior of liquid isolators in a pre-breakdown state. Two all-atom models and a united-atom model are used. Shear viscosity is calculated using the Green-Kubo formula. The force fields are compared with each other using the following criteria: the required time for one molecular dynamics step, the compliance of the main physical and transport properties with experimental values. The problem of the system equilibration is considered. The united-atom potential is used to model the n-triacontane liquid with an initial directional orientation. The time of relaxation to the disordered state, when all molecules orientations are randomized, are obtained. The influence of the molecules orientations on the shear viscosity value and the shear viscosity relaxation are treated. (paper)
Self-consistent molecular dynamics calculation of diffusion in higher n-alkanes.
Kondratyuk, Nikolay D; Norman, Genri E; Stegailov, Vladimir V
2016-11-28
Diffusion is one of the key subjects of molecular modeling and simulation studies. However, there is an unresolved lack of consistency between Einstein-Smoluchowski (E-S) and Green-Kubo (G-K) methods for diffusion coefficient calculations in systems of complex molecules. In this paper, we analyze this problem for the case of liquid n-triacontane. The non-conventional long-time tails of the velocity autocorrelation function (VACF) are found for this system. Temperature dependence of the VACF tail decay exponent is defined. The proper inclusion of the long-time tail contributions to the diffusion coefficient calculation results in the consistency between G-K and E-S methods. Having considered the major factors influencing the precision of the diffusion rate calculations in comparison with experimental data (system size effects and force field parameters), we point to hydrogen nuclear quantum effects as, presumably, the last obstacle to fully consistent n-alkane description.
Deterministic diffusion in flower-shaped billiards.
Harayama, Takahisa; Klages, Rainer; Gaspard, Pierre
2002-08-01
We propose a flower-shaped billiard in order to study the irregular parameter dependence of chaotic normal diffusion. Our model is an open system consisting of periodically distributed obstacles in the shape of a flower, and it is strongly chaotic for almost all parameter values. We compute the parameter dependent diffusion coefficient of this model from computer simulations and analyze its functional form using different schemes, all generalizing the simple random walk approximation of Machta and Zwanzig. The improved methods we use are based either on heuristic higher-order corrections to the simple random walk model, on lattice gas simulation methods, or they start from a suitable Green-Kubo formula for diffusion. We show that dynamical correlations, or memory effects, are of crucial importance in reproducing the precise parameter dependence of the diffusion coefficent.
Torres-Carbajal, Alexis; Castañeda-Priego, Ramón
2018-03-07
We report on the friction and diffusion of a single mobile nano-colloidal disk, whose size and mass are one and two orders of magnitude, respectively, greater than the molecules of the host solvent; all particles are restricted to move in a two-dimensional space. Using molecular dynamics simulations, the variation of the transport coefficients as a function of the thermodynamic state of the supporting fluid, in particular, around those states in the neighbourhood of the liquid-liquid phase coexistence, is investigated. The diffusion coefficient is determined through the fit of the mean-square displacement at long times and with the Green-Kubo relationship for the velocity autocorrelation function, whereas the friction coefficient is computed from the correlation of the fluctuating force. From the determination of the transport properties, the applicability of the Stokes-Einstein relation in two dimensions around the second critical point is discussed.
Transport Coefficients from Large Deviation Functions
Gao, Chloe; Limmer, David
2017-10-01
We describe a method for computing transport coefficients from the direct evaluation of large deviation function. This method is general, relying on only equilibrium fluctuations, and is statistically efficient, employing trajectory based importance sampling. Equilibrium fluctuations of molecular currents are characterized by their large deviation functions, which is a scaled cumulant generating function analogous to the free energy. A diffusion Monte Carlo algorithm is used to evaluate the large deviation functions, from which arbitrary transport coefficients are derivable. We find significant statistical improvement over traditional Green-Kubo based calculations. The systematic and statistical errors of this method are analyzed in the context of specific transport coefficient calculations, including the shear viscosity, interfacial friction coefficient, and thermal conductivity.
Understanding deterministic diffusion by correlated random walks
International Nuclear Information System (INIS)
Klages, R.; Korabel, N.
2002-01-01
Low-dimensional periodic arrays of scatterers with a moving point particle are ideal models for studying deterministic diffusion. For such systems the diffusion coefficient is typically an irregular function under variation of a control parameter. Here we propose a systematic scheme of how to approximate deterministic diffusion coefficients of this kind in terms of correlated random walks. We apply this approach to two simple examples which are a one-dimensional map on the line and the periodic Lorentz gas. Starting from suitable Green-Kubo formulae we evaluate hierarchies of approximations for their parameter-dependent diffusion coefficients. These approximations converge exactly yielding a straightforward interpretation of the structure of these irregular diffusion coefficients in terms of dynamical correlations. (author)
Linear response approach to active Brownian particles in time-varying activity fields
Merlitz, Holger; Vuijk, Hidde D.; Brader, Joseph; Sharma, Abhinav; Sommer, Jens-Uwe
2018-05-01
In a theoretical and simulation study, active Brownian particles (ABPs) in three-dimensional bulk systems are exposed to time-varying sinusoidal activity waves that are running through the system. A linear response (Green-Kubo) formalism is applied to derive fully analytical expressions for the torque-free polarization profiles of non-interacting particles. The activity waves induce fluxes that strongly depend on the particle size and may be employed to de-mix mixtures of ABPs or to drive the particles into selected areas of the system. Three-dimensional Langevin dynamics simulations are carried out to verify the accuracy of the linear response formalism, which is shown to work best when the particles are small (i.e., highly Brownian) or operating at low activity levels.
Energy Technology Data Exchange (ETDEWEB)
Jung, Gerhard, E-mail: jungge@uni-mainz.de; Schmid, Friederike, E-mail: friederike.schmid@uni-mainz.de [Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 9, D-55099 Mainz (Germany)
2016-05-28
Exact values for bulk and shear viscosity are important to characterize a fluid, and they are a necessary input for a continuum description. Here we present two novel methods to compute bulk viscosities by non-equilibrium molecular dynamics simulations of steady-state systems with periodic boundary conditions — one based on frequent particle displacements and one based on the application of external bulk forces with an inhomogeneous force profile. In equilibrium simulations, viscosities can be determined from the stress tensor fluctuations via Green-Kubo relations; however, the correct incorporation of random and dissipative forces is not obvious. We discuss different expressions proposed in the literature and test them at the example of a dissipative particle dynamics fluid.
Asymptotic neutron scattering laws for anomalously diffusing quantum particles
Energy Technology Data Exchange (ETDEWEB)
Kneller, Gerald R. [Centre de Biophysique Moléculaire, CNRS, Rue Charles Sadron, 45071 Orléans (France); Université d’Orléans, Chateau de la Source-Ave. du Parc Floral, 45067 Orléans (France); Synchrotron-SOLEIL, L’Orme de Merisiers, 91192 Gif-sur-Yvette (France)
2016-07-28
The paper deals with a model-free approach to the analysis of quasielastic neutron scattering intensities from anomalously diffusing quantum particles. All quantities are inferred from the asymptotic form of their time-dependent mean square displacements which grow ∝t{sup α}, with 0 ≤ α < 2. Confined diffusion (α = 0) is here explicitly included. We discuss in particular the intermediate scattering function for long times and the Fourier spectrum of the velocity autocorrelation function for small frequencies. Quantum effects enter in both cases through the general symmetry properties of quantum time correlation functions. It is shown that the fractional diffusion constant can be expressed by a Green-Kubo type relation involving the real part of the velocity autocorrelation function. The theory is exact in the diffusive regime and at moderate momentum transfers.
Diffusion of test particles in stochastic magnetic fields in the percolative regime
International Nuclear Information System (INIS)
Neuer, Marcus; Spatschek, Karl H.
2006-01-01
For stochastic magnetic flux functions with percolative contours the test particle transport is investigated. The calculations make use of the stochastic Liouville approach. They start from the so-called A-Langevin equations, including stochastic magnetic field components and binary collisions. Using the decorrelation trajectory method, a relation between the Lagrangian velocity correlation function and the Eulerian magnetic field correlation is derived and introduced into the Green-Kubo formalism. Finite Larmor radius effects are included. Interesting results are presented in the percolation regime corresponding to high Kubo numbers. Previous results are found to be limiting cases for small Kubo numbers. For different percolative scenarios the diffusion is analyzed and strong influences of the percolative structures on the transport scaling are found. The finite Larmor radius effects are discussed in detail. Numerical simulations of the A-Langevin equation confirm the semianalytical predictions
Time reversibility, computer simulation, algorithms, chaos
Hoover, William Graham
2012-01-01
A small army of physicists, chemists, mathematicians, and engineers has joined forces to attack a classic problem, the "reversibility paradox", with modern tools. This book describes their work from the perspective of computer simulation, emphasizing the author's approach to the problem of understanding the compatibility, and even inevitability, of the irreversible second law of thermodynamics with an underlying time-reversible mechanics. Computer simulation has made it possible to probe reversibility from a variety of directions and "chaos theory" or "nonlinear dynamics" has supplied a useful vocabulary and a set of concepts, which allow a fuller explanation of irreversibility than that available to Boltzmann or to Green, Kubo and Onsager. Clear illustration of concepts is emphasized throughout, and reinforced with a glossary of technical terms from the specialized fields which have been combined here to focus on a common theme. The book begins with a discussion, contrasting the idealized reversibility of ba...
Feng, Yan; Lin, Wei; Murillo, M. S.
2017-11-01
Transport properties of two-dimensional (2D) strongly coupled dusty plasmas have been investigated in detail, but never for viscosity with a strong perpendicular magnetic field; here, we examine this scenario using Langevin dynamics simulations of 2D liquids with a binary Yukawa interparticle interaction. The shear viscosity η of 2D liquid dusty plasma is estimated from the simulation data using the Green-Kubo relation, which is the integration of the shear stress autocorrelation function. It is found that, when a perpendicular magnetic field is applied, the shear viscosity of 2D liquid dusty plasma is modified substantially. When the magnetic field is increased, its viscosity increases at low temperatures, while at high temperatures its viscosity diminishes. It is determined that these different variational trends of η arise from the different behaviors of the kinetic and potential parts of the shear stress under external magnetic fields.
International Nuclear Information System (INIS)
Zanjani, Mehdi B.; Lukes, Jennifer R.
2014-01-01
A computational study of thermal conductivity and phonon dispersion of gold nanocrystal superlattices is presented. Phonon dispersion curves, reported here for the first time from combined molecular dynamics and lattice dynamics calculations, show multiple phononic band gaps and consist of many more dispersion branches than simple atomic crystals. Fully atomistic three dimensional molecular dynamics calculations of thermal conductivity using the Green Kubo method are also performed for the first time on these materials. Thermal conductivity is observed to increase for increasing nanocrystal core size and decrease for increasing surface ligand density. Our calculations predict values in the range 0.1–1 W/m K that are consistent with reported experimental results
Shear Viscosity of Benzene, Toluene, and p-Xylene by Non-equilibrium Molecular Dynamics Simulations
International Nuclear Information System (INIS)
Lee, Song Hi
2004-01-01
Green and Kubo showed that the phenomenological coefficients describing many transport processes and time dependent phenomena in general could be written as integrals over a certain type of function called a time correlation function. The Green-Kubo formulas are the formal expressions for hydrodynamic field variables and some of the thermodynamic properties in terms of the microscopic variables of an N-particle system. The identification of microscopic expressions for macroscopic variables is made by a process of comparison of the conservation equations of hydrodynamics with the microscopic equations of change for conserved densities. The importance of these formulas is three-fold: they provide an obvious method for calculating transport coefficients using computer simulation, a convenient starting point for constructing analytic theories for non-equilibrium processes, and an essential information for designing non-equilibrium molecular dynamics (NEMD) algorithm.
Nonequilibrium molecular dynamics: The first 25 years
International Nuclear Information System (INIS)
Hoover, W.G.
1992-08-01
Equilibrium Molecular Dynamics has been generalized to simulate Nonequilibrium systems by adding sources of thermodynamic heat and work. This generalization incorporates microscopic mechanical definitions of macroscopic thermodynamic and hydrodynamic variables, such as temperature and stress, and augments atomistic forces with special boundary, constraint, and driving forces capable of doing work on, and exchanging heat with, an otherwise Newtonian system. The underlying Lyapunov instability of these nonequilibrium equations of motion links microscopic time-reversible deterministic trajectories to macroscopic time-irreversible hydrodynamic behavior as described by the Second Law of Thermodynamics. Green-Kubo linear-response theory has been checked. Nonlinear plastic deformation, intense heat conduction, shockwave propagation, and nonequilibrium phase transformation have all been simulated. The nonequilibrium techniques, coupled with qualitative improvements in parallel computer hardware, are enabling simulations to approximate real-world microscale and nanoscale experiments
Computational study of heat transport in compositionally disordered binary crystals
International Nuclear Information System (INIS)
Lyver, John W.; Blaisten-Barojas, Estela
2006-01-01
The thermal conductivity of compositionally disordered binary crystals with atoms interacting through Lennard-Jones potentials has been studied as a function of temperature. The two species in the crystal differ in mass, hard-core atomic diameter, well depth and relative concentration. The isobaric Monte Carlo was used to equilibrate the samples at near-zero pressure. The isoenergy molecular dynamics combined with the Green-Kubo approach was taken to calculate the heat current time-dependent autocorrelation function and determine the lattice thermal conductivity of the sample. The inverse temperature dependence of the lattice thermal conductivity was shown to fail at low temperatures when the atomic diameters of the two species differ. Instead, the thermal conductivity was nearly a constant across temperatures for species with different atomic diameters. Overall, it is shown that there is a dramatic decrease of the lattice thermal conductivity with increasing atomic radii ratio between species and a moderate decrease due to mass disorder
Diffusivities and Viscosities of Poly(ethylene oxide) Oligomers †
Hong, Bingbing
2010-10-14
Diffusivities and viscosities of poly(ethylene oxide) (PEO) oligomer melts with 1 to 12 repeat units have been obtained from equilibrium molecular dynamics simulations using the TraPPE-UA force field. The simulations generated diffusion coefficients with high accuracy for all of the molar masses studied, but the statistical uncertainties in the viscosity calculations were significantly larger for longer chains. There is good agreement of the calculated viscosities and densities with available experimental data, and thus, the simulations can be used to bridge gaps in the data and for extrapolations with respect to chain length, temperature, and pressure. We explored the convergence characteristics of the Green-Kubo formulas for different chain lengths and propose minimal production times required for convergence of the transport properties. The chain-length dependence of the transport properties suggests that neither Rouse nor reptation models are applicable in the short-chain regime investigated. © 2010 American Chemical Society.
Strain-induced friction anisotropy between graphene and molecular liquids
Liao, Meng; To, Quy-Dong; Léonard, Céline; Monchiet, Vincent; Vo, Van-Hoang
2017-01-01
In this paper, we study the friction behavior of molecular liquids with anisotropically strained graphene. Due to the changes of lattice and the potential energy surface, the friction is orientation dependent and can be computed by tensorial Green-Kubo formula. Simple quantitative estimations are also proposed for the zero-time response and agree reasonably well with the molecular dynamics results. From simulations, we can obtain the information of structures, dynamics of the system, and study the influence of strain and molecular shapes on the anisotropy degree. It is found that unilateral strain can increase friction in all directions but the strain direction is privileged. Numerical evidences also show that nonspherical molecules are more sensitive to strain and give rise to more pronounced anisotropy effects.
International Nuclear Information System (INIS)
Levashov, V. A.
2016-01-01
It is possible to associate with every atom or molecule in a liquid its own atomic stress tensor. These atomic stress tensors can be used to describe liquids’ structures and to investigate the connection between structural and dynamic properties. In particular, atomic stresses allow to address atomic scale correlations relevant to the Green-Kubo expression for viscosity. Previously correlations between the atomic stresses of different atoms were studied using the Cartesian representation of the stress tensors or the representation based on spherical harmonics. In this paper we address structural correlations in a 3D model binary liquid using the eigenvalues and eigenvectors of the atomic stress tensors. This approach allows to interpret correlations relevant to the Green-Kubo expression for viscosity in a simple geometric way. On decrease of temperature the changes in the relevant stress correlation function between different atoms are significantly more pronounced than the changes in the pair density function. We demonstrate that this behaviour originates from the orientational correlations between the eigenvectors of the atomic stress tensors. We also found correlations between the eigenvalues of the same atomic stress tensor. For the studied system, with purely repulsive interactions between the particles, the eigenvalues of every atomic stress tensor are positive and they can be ordered: λ 1 ≥ λ 2 ≥ λ 3 ≥ 0. We found that, for the particles of a given type, the probability distributions of the ratios (λ 2 /λ 1 ) and (λ 3 /λ 2 ) are essentially identical to each other in the liquids state. We also found that λ 2 tends to be equal to the geometric average of λ 1 and λ 3 . In our view, correlations between the eigenvalues may represent “the Poisson ratio effect” at the atomic scale.
Energy Technology Data Exchange (ETDEWEB)
Levashov, V. A. [Technological Design Institute of Scientific Instrument Engineering, Novosibirsk 630058 (Russian Federation)
2016-03-07
It is possible to associate with every atom or molecule in a liquid its own atomic stress tensor. These atomic stress tensors can be used to describe liquids’ structures and to investigate the connection between structural and dynamic properties. In particular, atomic stresses allow to address atomic scale correlations relevant to the Green-Kubo expression for viscosity. Previously correlations between the atomic stresses of different atoms were studied using the Cartesian representation of the stress tensors or the representation based on spherical harmonics. In this paper we address structural correlations in a 3D model binary liquid using the eigenvalues and eigenvectors of the atomic stress tensors. This approach allows to interpret correlations relevant to the Green-Kubo expression for viscosity in a simple geometric way. On decrease of temperature the changes in the relevant stress correlation function between different atoms are significantly more pronounced than the changes in the pair density function. We demonstrate that this behaviour originates from the orientational correlations between the eigenvectors of the atomic stress tensors. We also found correlations between the eigenvalues of the same atomic stress tensor. For the studied system, with purely repulsive interactions between the particles, the eigenvalues of every atomic stress tensor are positive and they can be ordered: λ{sub 1} ≥ λ{sub 2} ≥ λ{sub 3} ≥ 0. We found that, for the particles of a given type, the probability distributions of the ratios (λ{sub 2}/λ{sub 1}) and (λ{sub 3}/λ{sub 2}) are essentially identical to each other in the liquids state. We also found that λ{sub 2} tends to be equal to the geometric average of λ{sub 1} and λ{sub 3}. In our view, correlations between the eigenvalues may represent “the Poisson ratio effect” at the atomic scale.
Directory of Open Access Journals (Sweden)
Jing-Fang Chen
2014-11-01
Conclusions: Our results demonstrate that EV-71 was the primary causative agent responsible for the HFMD outbreak in Changsha in 2012, and the co-circulation of other coxsackievirus A strains posed a potential risk to public health.
Atypical Hand, Foot, and Mouth Disease Caused by Coxsackievirus A6 in Denmark:
DEFF Research Database (Denmark)
Horsten, Hans-Henrik; Kemp, Michael; Fischer, Thea K
2018-01-01
, vasculitis, syphilis, dermatophytid, erythema multiforme and Stevens-Johnson syndrome. Three adults and 3 children required hospitalization due to extensive skin involvement and fever. All reported patients had laboratory confirmed enterovirus infection. This study demonstrated an upsurge in atypical HFMD...
Directory of Open Access Journals (Sweden)
Lianfa Li
2018-02-01
Full Text Available Abstract Background As a common infectious disease, hand, foot and mouth disease (HFMD is affected by multiple environmental and socioeconomic factors, and its pathogenesis is complex. Furthermore, the transmission of HFMD is characterized by strong spatial clustering and autocorrelation, and the classical statistical approach may be biased without consideration of spatial autocorrelation. In this paper, we propose to embed spatial characteristics into a spatiotemporal additive model to improve HFMD incidence assessment. Methods Using incidence data (6439 samples from 137 monitoring district for Shandong Province, China, along with meteorological, environmental and socioeconomic spatial and spatiotemporal covariate data, we proposed a spatiotemporal mixed model to estimate HFMD incidence. Geo-additive regression was used to model the non-linear effects of the covariates on the incidence risk of HFMD in univariate and multivariate models. Furthermore, the spatial effect was constructed to capture spatial autocorrelation at the sub-regional scale, and clusters (hotspots of high risk were generated using spatiotemporal scanning statistics as a predictor. Linear and non-linear effects were compared to illustrate the usefulness of non-linear associations. Patterns of spatial effects and clusters were explored to illustrate the variation of the HFMD incidence across geographical sub-regions. To validate our approach, 10-fold cross-validation was conducted. Results The results showed that there were significant non-linear associations of the temporal index, spatiotemporal meteorological factors and spatial environmental and socioeconomic factors with HFMD incidence. Furthermore, there were strong spatial autocorrelation and clusters for the HFMD incidence. Spatiotemporal meteorological parameters, the normalized difference vegetation index (NDVI, the temporal index, spatiotemporal clustering and spatial effects played important roles as predictors in
Geographical Detector-Based Risk Factors Assessment of the Hand-Foot-Mouth Disease in China
Huang, J.
2017-12-01
Background: Hand, foot and mouth disease(HFMD) is a common infectious disease, causing thousands of deaths among children in China. This study focused on analyzing the impacts of different populations and different industry structures on HFMD incidence in China. Methods: We collected HFMD cases from 2307 counties during May 2008 in China. The potential risk factors included: monthly mean temperature, monthly mean relative humidity, monthly precipitation, different population density, different industry structures. Geographical detector technique was used to analyze the main and interactive effect of potential risk factors on HFMD incidence. Result: Using risk detector, we found the most serious HFMD incidence mainly located in the Yangtze River delta and the Pearl River delta. When the temperature was high, the incidence of HFMD was also high. This finding indicates that there is a correlation between monthly mean temperature and the incidence of HFMD. Similar analysis was undertaken to analyze the correlation between other variables and the incidence of HFMD using the risk detector. Using factor detector, we found the effect of risk factors on the incidence of HFMD, and this was ranked by PD value as follows: density of children aged 0-9 years (0.25) > tertiary industry (0.23) > GDP (0.20) >middle school student density (0.13) > relative humidity (0.12) >average temperature (0.11) >first industry (0.05). Using ecological detector, we found that child density, tertiary industry, and GDP had a strong effect on the incidence of HFMD. Using interactive detector, we found that the interactive PD value of tertiary industry and child population density was 0.42, which of GDP and tertiary industry was 0.34, that of child population density and GDP was 0.35, and that of average temperature and relative humidity was 0.28. All of these interactive PD values appeared to be higher than any PD value of sole risk factors. The combinations of the above-mentioned risk factors
The correlation between the chest X-ray classifications and the pathogens of hand–foot–mouth disease
Directory of Open Access Journals (Sweden)
Huan-guo Li
2015-12-01
Conclusions: There was some relativity between clinical grade and pathogens. The severe and critical HFMD were caused mainly by EV71, and the mild HFMD was caused mainly by other pathogens except EV71. There was no significant correlation between chest X-ray classification and pathogens, but in the same chest X-ray classification, the distribution of pathogens was not identical. For the limitations of this study, we will do more research in the future work.
Song, Jae-Hyoung; Park, Kwisung; Shim, Aeri; Kwon, Bo-Eun; Ahn, Jae-Hee; Choi, Young Jin; Kim, Jae Kyung; Yeo, Sang-Gu; Yoon, Kyungah; Ko, Hyun-Jeong
2015-01-01
Objectives Coxsackievirus A group 16 strain (CVA16) is one of the predominant causative agents of hand, foot, and mouth disease (HFMD). Methods Using a specimen from a male patient with HFMD, we isolated and performed sequencing of the Korean CVA16 strain and compared it with a G10 reference strain. Also, we were investigated the effects of medicinal plant extract on the cytopathic effects (CPE) by CPE reduction assay against Korean CVA16. Results Phylogenetic analysis showed that the Korean ...
An, Qingyu; Wu, Jun; Fan, Xuesong; Pan, Liyang; Sun, Wei
2016-01-01
The hand foot and mouth disease (HFMD) is a human syndrome caused by intestinal viruses like that coxsackie A virus 16, enterovirus 71 and easily developed into outbreak in kindergarten and school. Scientifically and accurately early detection of the start time of HFMD epidemic is a key principle in planning of control measures and minimizing the impact of HFMD. The objective of this study was to establish a reliable early detection model for start timing of hand foot mouth disease epidemic in Dalian and to evaluate the performance of model by analyzing the sensitivity in detectability. The negative binomial regression model was used to estimate the weekly baseline case number of HFMD and identified the optimal alerting threshold between tested difference threshold values during the epidemic and non-epidemic year. Circular distribution method was used to calculate the gold standard of start timing of HFMD epidemic. From 2009 to 2014, a total of 62022 HFMD cases were reported (36879 males and 25143 females) in Dalian, Liaoning Province, China, including 15 fatal cases. The median age of the patients was 3 years. The incidence rate of epidemic year ranged from 137.54 per 100,000 population to 231.44 per 100,000population, the incidence rate of non-epidemic year was lower than 112 per 100,000 population. The negative binomial regression model with AIC value 147.28 was finally selected to construct the baseline level. The threshold value was 100 for the epidemic year and 50 for the non- epidemic year had the highest sensitivity(100%) both in retrospective and prospective early warning and the detection time-consuming was 2 weeks before the actual starting of HFMD epidemic. The negative binomial regression model could early warning the start of a HFMD epidemic with good sensitivity and appropriate detection time in Dalian.
Hand-foot-and-mouth disease and weather factors in Guangzhou, southern China.
Li, T; Yang, Z; DI, B; Wang, M
2014-08-01
Hand-foot-and-mouth disease (HFMD) is becoming one of the common airborne and contact transmission diseases in Guangzhou, southern China, leading public health authorities to be concerned about its increased incidence. In this study, we aimed to examine the effect of weather patterns on the incidence of HFMD in the subtropical city of Guangzhou for the period 2009-2012, and assist public health prevention and control measures. A negative binomial multivariable regression was used to identify the relationship between meteorological variables and HFMD. During the study period, a total of 166,770 HFMD-confirmed cases were reported, of which 11 died, yielding a fatality rate of 0·66/10,000. Annual incidence rates from 2009 to 2012 were 132·44, 311·40, 402·76, and 468·59/100,000 respectively. Each 1°C rise in temperature corresponded to an increase of 9·38% (95% CI 8·17-10·51) in the weekly number of HFMD cases, while a 1 hPa rise in atmospheric pressure corresponded to a decrease in the number of cases by 6·80% (95% CI -6·99 to -6·65), having an opposite effect. Similarly, a 1% rise in relative humidity corresponded to an increase of 0·67% or 0·51%, a 1 m/h rise in wind velocity corresponded to an increase of 4·01% or 2·65%, and a 1 day addition in the number of windy days corresponded to an increase of 24·73% or 25·87%, in the weekly number of HFMD cases, depending on the variables considered in the model. Our findings revealed that the epidemic status of HFMD in Guangzhou is characterized by high morbidity but low fatality. Weather factors had a significant influence on occurrence and transmission of HFMD.
Hu, Ya-Qian; Xie, Guang-Cheng; Li, Dan-Di; Pang, Li-Li; Xie, Jing; Wang, Peng; Chen, Ying; Yang, Jing; Cheng, Wei-Xia; Zhang, Qing; Jin, Yu; Duan, Zhao-Jun
2015-09-01
Although hand, foot and mouth disease (HFMD) has been strongly associated with enterovirus 71 (EV71), coxsackievirus A16 (CVA16) and other enteroviruses, studies regarding coxsackievirus A6 (CVA6) infection in HFMD are limited. The aim of this study was to identify the major etiological agents causing HFMD in Nanjing in 2013 and explore the clinical and genetic characteristics of the prevalent enterovirus (EV) types in HFMD. A total of 394 throat swabs were collected from hospitalized children diagnosed with HFMD from April to July 2013. EVs were detected by reverse transcription polymerase chain reaction of 5' UTR sequences. Genotyping and phylogenetic analysis were based on VP4 sequences. Demographic and clinical data were obtained. Of the specimens, 68.5% (270/394) were positive for EVs. The genotypes and detection rates were CVA6, 30.00% (81/270); EV71, 17.41% (47/270); HRV, 11.11% (30/270); CVA10, 3.33% (9/270); CVA2, 1.11% (3/270); CVA16, 0.74% (2/270); EV68, 0.37% (1/270); echovirus 6, 0.37% (1/270); echovirus 9, 0.37% (1/270), respectively. Patients infected with CVA6 displayed symptoms atypical of HFMD, including larger vesicles on their limbs and buttocks. Phylogenetic analysis revealed 2 genetically distinct CVA6 strains that circulated independently within the region. Patients infected with CVA6 were more likely to have abnormal periphery blood white blood cell and C-reactive protein levels, while EV71 was more likely to infect the central nervous system, as indicated by clinical manifestations and white blood cell analysis of cerebrospinal fluid. Multiple EV genotypes contributed to HFMD in Nanjing in 2013, and CVA6 was the dominant genotype. The clinical presentation of CVA6 infection differs from that of EV71 infection in HFMD.
The Effects of Weather Factors on Hand, Foot and Mouth Disease in Beijing
Dong, Weihua; Li, Xian'En; Yang, Peng; Liao, Hua; Wang, Xiaoli; Wang, Quanyi
2016-01-01
The morbidity and mortality of hand, foot and mouth disease (HFMD) are increasing in Beijing, China. Previous studies have indicated an association between incidents of HFMD and weather factors. However, the seasonal influence of these factors on the disease is not yet understood, and their relationship with the enterovirus 71 (EV71) and Coxsackie virus A16 (CV-A16) viruses are not well documented. We analysed 84,502 HFMD cases from 2008 to 2011 in Beijing to explore the seasonal influence of weather factors (average temperature [AT], average relative humidity [ARH], total precipitation [TP] and average wind speed [AWS]) on incidents of HFMD by using a geographically weighted regression (GWR) model. The results indicated that weather factors differ significantly in their influence on HFMD depending on the season. AT had the greatest effect among the four weather factors, and while the influence of AT and AWS was greater in the summer than in the winter, the influence of TP was positive in the summer and negative in the winter. ARH was negatively correlated with HFMD. Also, we observed more EV71-associated cases than CV-A16 but there is no convincing evidence to show significant differences between the influences of the weather factors on EV71 and CV-A16.
Is a multivalent hand, foot, and mouth disease vaccine feasible?
Klein, Michel; Chong, Pele
2015-01-01
Enterovirus A infections are the primary cause of hand, foot and mouth disease (HFMD) in infants and young children. Although enterovirus 71 (EV-A71) and coxsackievirus A16 (CV-A16) are the predominant causes of HFMD epidemics worldwide, EV-A71 has emerged as a major neurovirulent virus responsible for severe neurological complications and fatal outcomes. HFMD is a serious health threat and economic burden across the Asia-Pacific region. Inactivated EV-A71 vaccines have elicited protection against EV-A71 but not against CV-A16 infections in large efficacy trials. The current development of a bivalent inactivated EV-A71/CV-A16 vaccine is the next step toward that of multivalent HFMD vaccines. These vaccines should ultimately include other prevalent pathogenic coxsackieviruses A (CV-A6 and CV-A10), coxsackieviruses B (B3 and B5) and echovirus 30 that often co-circulate during HFMD epidemics and can cause severe HFMD, aseptic meningitis and acute viral myocarditis. The prospect and challenges for the development of such multivalent vaccines are discussed. PMID:26009802
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Qiang Wu
Full Text Available Etiological carriers and the excretion of the pathogens causing hand, foot, and mouth disease (HFMD in healthy persons, patients, and asymptomatic persons infected with HFMD as ongoing infection sources may play an important role in perpetuating and spreading epidemics of HFMD. The aims of this study were to determine the carrier status of EV-A71 and CV-A16 in healthy populations, as well as the duration of EV-A71 and CV-A16 shedding in the stools of HFMD patients in an epidemic area of southwest China. A cross-sectional study and a follow-up study were conducted in three HFMD endemic counties of Yunnan Province. Six hundred sixty-seven healthy subjects were recruited to participate in the cross-sectional study, and two stool specimens were collected from each subject. Among the healthy subjects, 90 (13.5% tested positive for viral isolation, but neither EV-A71 nor CV-A16 was detected in healthy individuals. Of the 150 patients with probable HFMD, 55.3% (83/150 tested positive for viral isolation with presented serotypes such as EV-A71 (51.81%, 43/83, CV-A16 (32.53%, 27/83, other EVs (13.25%, 11/83, and mixed EV-A71 and CV-A16 (2.41%, 2/83. The longest duration of EV-A71 and CV-A16 shedding in stool specimens from patients with HFMD was >46 days after onset. The positive rate of EV-A71 in the stool specimens of confirmed patients dropped to 50% by the end of the third week, and the same occurred with CV-A16 by the end of approximately the seventh week after onset. Although carriers of major causative agents of HFMD in healthy populations are fewer in number, the prolonged shedding of pathogens in patients with HFMD may serve as an important factor in perpetuating and spreading HFMD epidemics.
Chen, Chun; Lin, Hualiang; Li, Xiaoquan; Lang, Lingling; Xiao, Xincai; Ding, Peng; He, Peng; Zhang, Ying; Wang, Ming; Liu, Qiyong
2014-09-01
Hand, foot and mouth disease (HFMD) is a contagious viral illness that commonly affects infants and children. The underlying risk factors have not yet been systematically examined. This study analyzed the short-term effects of meteorological factors on children HFMD in Guangzhou, China. Daily count of HFMD among children younger than 15 years and meteorological variables from 2009 to 2011 were collected to construct the time series. A generalized additive model was applied to estimate the effects of meteorological factors on HFMD occurrence, after adjusting for long-term trend, seasonal trend, day of week, and public holidays. A negative association between temperature and children HFMD occurrence was observed at lag days 1-3, with the relative risk (RR) for a 1 °C increase on lag day 2 being 0.983 (95 % confidence intervals (CI) 0.977 to 0.989); positive effect was found for temperature at lag days 5-9, with the highest effect at lag day 6 (RR = 1.014, 95 % CI 1.006 to 1.023). Higher humidity was associated with increased HFMD at lag days 3-10, with the highest effect at lag day 8 (RR = 1.009 for 1 % increase in relative humidity, 95 % CI 1.007 to 1.010). And we also observed significant positive effect for rainfall at lag days 4 and 8 (RR = 1.001, 95 % CI 1.000 to 1.002) for 1-mm increase. Subgroup analyses showed that the positive effects of temperature were more pronounced among younger children. This study suggests that meteorological factors might be important predictors of children HFMD occurrence in Guangzhou.
Liu, Sijun; Chen, Jiaping; Wang, Jianming; Wu, Zhuchao; Wu, Weihua; Xu, Zhiwei; Hu, Wenbiao; Xu, Fei; Tong, Shilu; Shen, Hongbing
2017-10-01
Hand, foot, and mouth disease (HFMD) is a significant public health issue in China and an accurate prediction of epidemic can improve the effectiveness of HFMD control. This study aims to develop a weather-based forecasting model for HFMD using the information on climatic variables and HFMD surveillance in Nanjing, China. Daily data on HFMD cases and meteorological variables between 2010 and 2015 were acquired from the Nanjing Center for Disease Control and Prevention, and China Meteorological Data Sharing Service System, respectively. A multivariate seasonal autoregressive integrated moving average (SARIMA) model was developed and validated by dividing HFMD infection data into two datasets: the data from 2010 to 2013 were used to construct a model and those from 2014 to 2015 were used to validate it. Moreover, we used weekly prediction for the data between 1 January 2014 and 31 December 2015 and leave-1-week-out prediction was used to validate the performance of model prediction. SARIMA (2,0,0)52 associated with the average temperature at lag of 1 week appeared to be the best model (R 2 = 0.936, BIC = 8.465), which also showed non-significant autocorrelations in the residuals of the model. In the validation of the constructed model, the predicted values matched the observed values reasonably well between 2014 and 2015. There was a high agreement rate between the predicted values and the observed values (sensitivity 80%, specificity 96.63%). This study suggests that the SARIMA model with average temperature could be used as an important tool for early detection and prediction of HFMD outbreaks in Nanjing, China.
Li, Yang; Bao, Honghong; Zhang, Xiangping; Zhai, Mingqiang; Bao, Xiaobing; Wang, Demin; Zhang, Shuanhu
2017-10-01
Enterovirus 71 (EV-A71) and coxsackievirus A16 (CV-A16) are major pathogens of hand, foot, and mouth disease (HFMD) and have been associated with consecutive outbreaks of HFMD in China over the past years. Although several other human enteroviruses (HEVs) have also acted as causative agents of HFMD, published information on their roles in the prevalence of HFMD is limited. This study was conducted to reveal the characteristics of the pathogenic spectrum and molecular epidemiology of the non-EV-71 and -CV-A16 HEVs in Anyang City, which is located in north-central China and has a population of five million. From 2011 to 2015, 2270 samples were collected from HFMD patients (3.89 ± 1.06 years of age), and 1863 HEV-positive samples, including 524 samples with 23 non-EV-71 and non-CV-A16 serotypes, were identified. Based on the nucleotide sequence of the VP1 gene, 6 common non-EV-71 and non-CV-A16 HEVs, including coxsackievirus A2, A6, A10, A14, B2, and B5, were studied to determine their phylogenies and selective pressures. Phylogenetic analyses revealed a high level of genetic divergence and a pattern of lineage replacement over time in Mainland China. Selective pressure analyses showed that purifying selection was predominant in the evolution of the VP1 gene, whereas positive selection acted on individual codons. Overall, non-EV-71 and non-CV-A16 HEVs were important constituents of the pathogenic spectrum of HFMD in Anyang City during 2011-2015. Some of these HEVs with complex and active phylogenies represent a potential threat to public health, suggesting that long-term monitoring of these pathogens should be implemented to prevent HFMD outbreaks. © 2017 Wiley Periodicals, Inc.
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Tiegang Li
2014-12-01
Full Text Available Hand-foot-and-mouth disease (HFMD is becoming one of the extremely common airborne and contact transmission diseases in Guangzhou, southern China, leading public health authorities to be concerned about its increased incidence. In this study, it was used an ecological study plus the negative binomial regression to identify the epidemic status of HFMD and its relationship with meteorological variables. During 2008-2012, a total of 173,524 HFMD confirmed cases were reported, 12 cases of death, yielding a fatality rate of 0.69 per 10,000. The annual incidence rates from 2008 to 2012 were 60.56, 132.44, 311.40, 402.76, and 468.59 (per 100,000, respectively, showing a rapid increasing trend. Each 1 °C rise in temperature corresponded to an increase of 9.47% (95% CI 9.36% to 9.58% in the weekly number of HFMD cases, while a one hPa rise in atmospheric pressure corresponded to a decrease in the number of cases by 7.53% (95% CI -7.60% to -7.45%. Similarly, each one percent rise in relative humidity corresponded to an increase of 1.48% or 3.3%, and a one meter per hour rise in wind speed corresponded to an increase of 2.18% or 4.57%, in the weekly number of HFMD cases, depending on the variables considered in the model. These findings revealed that epidemic status of HFMD in Guangzhou is characterized by high morbidity but low fatality. Weather factors had a significant influence on the incidence of HFMD.
Du, Zhicheng; Xu, Lin; Zhang, Wangjian; Zhang, Dingmei; Yu, Shicheng; Hao, Yuantao
2017-01-01
Objectives Hand, foot, and mouth disease (HFMD) has caused a substantial burden in China, especially in Guangdong Province. Based on the enhanced surveillance system, we aimed to explore whether the addition of temperate and search engine query data improves the risk prediction of HFMD. Design Ecological study. Setting and participants Information on the confirmed cases of HFMD, climate parameters and search engine query logs was collected. A total of 1.36 million HFMD cases were identified from the surveillance system during 2011–2014. Analyses were conducted at aggregate level and no confidential information was involved. Outcome measures A seasonal autoregressive integrated moving average (ARIMA) model with external variables (ARIMAX) was used to predict the HFMD incidence from 2011 to 2014, taking into account temperature and search engine query data (Baidu Index, BDI). Statistics of goodness-of-fit and precision of prediction were used to compare models (1) based on surveillance data only, and with the addition of (2) temperature, (3) BDI, and (4) both temperature and BDI. Results A high correlation between HFMD incidence and BDI (r=0.794, pmodel. Compared with the model based on surveillance data only, the ARIMAX model including BDI reached the best goodness-of-fit with an Akaike information criterion (AIC) value of −345.332, whereas the model including both BDI and temperature had the most accurate prediction in terms of the mean absolute percentage error (MAPE) of 101.745%. Conclusions An ARIMAX model incorporating search engine query data significantly improved the prediction of HFMD. Further studies are warranted to examine whether including search engine query data also improves the prediction of other infectious diseases in other settings. PMID:28988169
Li, Tiegang; Yang, Zhicong; Liu, Xiangyi; Kang, Yan; Wang, Ming
2014-01-01
Hand-foot-and-mouth disease (HFMD) is becoming one of the extremely common airborne and contact transmission diseases in Guangzhou, southern China, leading public health authorities to be concerned about its increased incidence. In this study, it was used an ecological study plus the negative binomial regression to identify the epidemic status of HFMD and its relationship with meteorological variables. During 2008-2012, a total of 173,524 HFMD confirmed cases were reported, 12 cases of death, yielding a fatality rate of 0.69 per 10,000. The annual incidence rates from 2008 to 2012 were 60.56, 132.44, 311.40, 402.76, and 468.59 (per 100,000), respectively, showing a rapid increasing trend. Each 1 °C rise in temperature corresponded to an increase of 9.47% (95% CI 9.36% to 9.58%) in the weekly number of HFMD cases, while a one hPa rise in atmospheric pressure corresponded to a decrease in the number of cases by 7.53% (95% CI -7.60% to -7.45%). Similarly, each one percent rise in relative humidity corresponded to an increase of 1.48% or 3.3%, and a one meter per hour rise in wind speed corresponded to an increase of 2.18% or 4.57%, in the weekly number of HFMD cases, depending on the variables considered in the model. These findings revealed that epidemic status of HFMD in Guangzhou is characterized by high morbidity but low fatality. Weather factors had a significant influence on the incidence of HFMD.
Cheng, Qiang; Bai, Lijun; Zhang, Yanwu; Zhang, Heng; Wang, Shusi; Xie, Mingyu; Zhao, Desheng; Su, Hong
2018-06-01
The relationship between ambient temperature, humidity and hand, foot, and mouth disease (HFMD) has been highlighted in East and Southeast Asia, which showed multiple different results. Therefore, our goal is to conduct a meta-analysis to further clarify this relationship and to quantify the size of these effects as well as the susceptible populations. PubMed, Web of science, and Cochrane library were searched up to November 22, 2017 for articles analyzing the relationships between ambient temperature, humidity and incidence of HFMD. We assessed sources of heterogeneity by study design (temperature measure and exposed time resolution), population vulnerability (national income level and regional climate) and evaluated pooled effect estimates for the subgroups identified in the heterogeneity analysis. We identified 11 studies with 19 estimates of the relationship between ambient temperature, humidity and incidence of HFMD. It was found that per 1°C increase in the temperature and per 1% increase in the relative humidity were both significantly associated with increased incidence of HFMD (temperature: IRR, 1.05; 95% CI, 1.02-1.08; relative humidity: IRR, 1.01; 95% CI, 1.00-1.02). Subgroup analysis showed that people living in subtropical and middle income areas had a higher risk of incidence of HFMD. Ambient temperature and humidity may increase the incidence of HFMD in Asia-Pacific regions. Further studies are needed to clarify the relationship between ambient temperature, humidity and incidence of HFMD in various settings with distinct climate, socioeconomic, and demographic features. Copyright © 2018. Published by Elsevier B.V.
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Shiyin Zhang
Full Text Available The recent, ongoing epidemic of hand, foot, and mouth disease (HFMD, which is caused by enterovirus infection, has affected millions of children and resulted in thousands of deaths in China. Enterovirus 71 (EV71 and coxsackie A16 (CA16 are the two major distinct pathogens for HFMD. However, EV71 is more commonly associated with neurologic complications and even fatalities. Therefore, simultaneously detecting and differentiating EV71 and CA16 specifically from other enteroviruses for diagnosing HFMD is important. Here, we developed a one-step, triplex, real-time RT-PCR assay for the simultaneous detection of EV71, CA16, and pan-enterovirus (EVs in a single tube with an internal amplification control. The detection results for the serially diluted viruses indicate that the lower limit of detection for this assay is 0.001-0.04 TCID50/ml, 0.02 TCID50/ml, and 0.001 TCID50/ml for EVs, EV71, and CA16, respectively. After evaluating known HFMD virus stocks of 17 strains of 16 different serotypes, this assay showed a favorable detection spectrum and no obvious cross-reactivity. The results for 141 clinical throat swabs from HFMD-suspected patients demonstrated sensitivities of 98.4%, 98.7%, and 100% for EVs, EV71, and CA16, respectively, and 100% specificity for each virus. The application of this one-step, triplex, real-time RT-PCR assay in clinical units will contribute to HFMD surveillance and help to identify causative pathogen in patients with suspected HFMD.
Li, Yaping; Zhai, Song; Li, Mei; Wang, Yuan; Lu, Tong; Deng, Huiling; Zhang, Xin; Dang, Shuangsuo
2017-07-01
Objective To investigate whether the polymorphisms of TLR7/MyD88 signaling pathway is associated with the susceptibility to and severity of hand, foot and mouth disease (HFMD) caused by enterovirus 71 (EV71) in children. Methods We collected 180 EV71 HFMD cases and 201 healthy controls from both the Second Affiliated Hospital of Xi'an Jiaotong University and Xi'an Children's Hospital. The genotypes including rs3853839, rs179010 of TLR7, and rs7744 of MyD88 were detected in the 381 samples by SNPscan kit. Results The susceptibility risk (OR=2.343, 95%CI:1.516-3.621) and severity risk (OR=1.939, 95%CI: 1.064-3.521) of TLR7 rs3853839 allele C significantly increased in the male children with EV71 HFMD. Also, the susceptibility risk (OR=1.701, 95%CI: 1.142-2.535) and severity risk (OR=1.852, 95%CI: 1.038-3.305) of TLR7 rs179010 allele T significantly increased in the male children with EV71 HFMD. But there was no significant difference in the distribution of TLR7 rs179010 and rs3853839 genes between female children with EV71 HFMD and female controls. There was no correlation between the genetic polymorphisms of MyD88 rs7744 and the susceptibility to and severity of EV71 HFMD in the children. Conclusion Polymorphisms of TLR7 rs3853839 and rs179010 are correlated to the susceptibility to and severity of EV71 HFMD in male children.
Zhang, Shiyin; Wang, Jin; Yan, Qiang; He, Shuizhen; Zhou, Wenbin; Ge, Shengxiang; Xia, Ningshao
2014-01-01
The recent, ongoing epidemic of hand, foot, and mouth disease (HFMD), which is caused by enterovirus infection, has affected millions of children and resulted in thousands of deaths in China. Enterovirus 71 (EV71) and coxsackie A16 (CA16) are the two major distinct pathogens for HFMD. However, EV71 is more commonly associated with neurologic complications and even fatalities. Therefore, simultaneously detecting and differentiating EV71 and CA16 specifically from other enteroviruses for diagnosing HFMD is important. Here, we developed a one-step, triplex, real-time RT-PCR assay for the simultaneous detection of EV71, CA16, and pan-enterovirus (EVs) in a single tube with an internal amplification control. The detection results for the serially diluted viruses indicate that the lower limit of detection for this assay is 0.001-0.04 TCID50/ml, 0.02 TCID50/ml, and 0.001 TCID50/ml for EVs, EV71, and CA16, respectively. After evaluating known HFMD virus stocks of 17 strains of 16 different serotypes, this assay showed a favorable detection spectrum and no obvious cross-reactivity. The results for 141 clinical throat swabs from HFMD-suspected patients demonstrated sensitivities of 98.4%, 98.7%, and 100% for EVs, EV71, and CA16, respectively, and 100% specificity for each virus. The application of this one-step, triplex, real-time RT-PCR assay in clinical units will contribute to HFMD surveillance and help to identify causative pathogen in patients with suspected HFMD.
Cabrerizo, M; Tarragó, D; Muñoz-Almagro, C; Del Amo, E; Domínguez-Gil, M; Eiros, J M; López-Miragaya, I; Pérez, C; Reina, J; Otero, A; González, I; Echevarría, J E; Trallero, G
2014-03-01
Hand, foot and mouth disease (HFMD) is a childhood illness frequently caused by genotypes belonging to the enterovirus A species, including coxsackievirus (CV)-A16 and enterovirus (EV)-71. Between 2010 and 2012, several outbreaks and sporadic cases of HFMD occurred in different regions of Spain. The objective of the present study was to describe the enterovirus epidemiology associated with HFMD in the country. A total of 80 patients with HFMD or atypical rash were included. Detection and typing of the enteroviruses were performed directly in clinical samples using molecular methods. Enteroviruses were detected in 53 of the patients (66%). CV-A6 was the most frequent genotype, followed by CV-A16 and EV-71, but other minority types were also identified. Interestingly, during almost all of 2010, CV-A16 was the only causative agent of HFMD but by the end of the year and during 2011, CV-A6 became predominant, while CV-A16 was not detected. In 2012, however, both CV-A6 and CV-A16 circulated. EV-71 was associated with HFMD symptoms only in three cases during 2012. All Spanish CV-A6 sequences segregated into one major genetic cluster together with other European and Asian strains isolated between 2008 and 2011, most forming a particular clade. Spanish EV-71 strains belonged to subgenogroup C2, as did most of the European sequences circulated. In conclusion, the recent increase of HFMD cases in Spain and other European countries has been due to a larger incidence of circulating species A enteroviruses, mainly CV-A6 and CV-A16, and the emergence of new genetic variants of these viruses. © 2013 The Authors Clinical Microbiology and Infection © 2013 European Society of Clinical Microbiology and Infectious Diseases.
Yang, Lisheng; Liu, Yajing; Li, Shuxuan; Zhao, Huan; Lin, Qiaona; Yu, Hai; Huang, Xiumin; Zheng, Qingbing; Cheng, Tong; Xia, Ningshao
2016-11-21
Hand, foot, and mouth disease (HFMD) is a highly contagious disease that mainly affects infants and children. Enterovirus 71 (EV71) and coxsackievirus A16 (CA16) are the major pathogens of HFMD. Two EV71 vaccines were recently licensed in China and the administration of the EV71 vaccines is believed to significantly reduce the number of HFMD-related severe or fatal cases. However, a monovalent EV71 vaccine cannot cross-protect against CA16 infection, this may result in that it cannot effectively control the overall HFMD epidemic. In this study, a chimeric EV71, whose VP1/210-225 epitope was replaced by that of CA16, was constructed using a reverse genetics technique to produce a candidate EV71/CA16 bivalent vaccine strain. The chimeric EV71 was infectious and showed similar growth characteristics as its parental strain. The replacement of the VP1/210-225 epitope did not significantly affect the antigenicity and immunogenicity of EV71. More importantly, the chimeric EV71 could induce protective immunity against both EV71 and CA16, and protect neonatal mice against either EV71 or CA16 lethal infections, the chimeric EV71 constructed in this study was shown to be a feasible and promising candidate bivalent vaccine against both EV71 and CA16. The construction of a chimeric enterovirus also provides an alternative platform for broad-spectrum HFMD vaccines development. Copyright © 2016 Elsevier Ltd. All rights reserved.
Excretion of enterovirus 71 in persons infected with hand, foot and mouth disease
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Li Jie
2013-01-01
Full Text Available Abstract Background Hand, foot and mouth disease (HFMD is a common illness in young children. It also can be seen in adults occasionally. Enterovirus 71 (EV71, a pathogen that causes not only HFMD but also neurological complications and even death, has caused many HFMD outbreaks in China. However, till now the data about the duration of EV71 shedding is very limited. Results A total of 136 throat swabs and fecal samples were collected from 27 children and 3 adults, which includs 7 close contacts, 9 mild cases and 14 severe cases,. The participants were divided into three groups namely, severe case group, mild case group and close contact group. All the samples were assayed with real-time polymerase chain reaction (PCR. Kruskal-Wallis Test was employed to compare the difference in duration of viral RNA shedding among three groups. The results showed that significant difference in duration of EV71 shedding was found among three groups (P Conclusions HFMD is characterized by extended excretion of EV71. Our results suggest that the duration of EV71 shedding is correlated with the severity of the disease. EV71 shedding through feces can persist more than 54 days. Prolonged virus shedding is a potential risk factor of proliferating HFMD epidemic.
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Li-Dong Gao
Full Text Available An increase in the incidence of hand, foot and mouth disease (HFMD cases has been observed in the Hunan province of mainland China since 2009 with a particularly higher level of severe cases in 2010-2012. Intestinal viruses of the picornaviridae family are responsible for the human syndrome associated with HFMD with enterovirus 71 (EV71 and Coxsackievirus A16 (Cox A16 being the most common causative strains. HFMD cases associated with EV71 are generally more severe with an increased association of morbidity and mortality. In this study, the etiology surveillance data of HFMD cases in Hunan province from March 2010 to October 2012 were analyzed to determine if there is a statistically relevant linear correlation exists between the detection rate of EV71 in mild cases and the proportion of severe cases among all HFMD patients. As the cases progressed from mild to severe to fatal, the likelihood of EV71 detection increased (25.78%, 52.20% and 84.18%, respectively. For all cases in the timeframe evaluated in this study, the presence of virus was detected in 63.21% of cases; among cases showing positivity for virus, EV71 infection accounted for 50.14%. These results provide evidence to support the observed higher morbidity and mortality associated with this outbreak and emphasizes the importance of early detection in order to implement necessary prevention measures to mitigate disease progression.
He, Si-Jie; Han, Jian-Feng; Ding, Xi-Xia; Wang, Ya-Di; Qin, Cheng-Feng
2013-11-01
Hand, foot, and mouth disease (HFMD) is an acute viral disease caused by human enteroviruses, especially human enterovirus 71 (HEV71) and coxsackievirus A16 (CVA16), and mainly affects infants and young children. After the outbreak in 2008 in Fuyang, China, HFMD was classified as a category C notifiable infectious disease by the Ministry of Health of China. In this study, we report the epidemiologic and clinical manifestations of HFMD in Guangdong Province, China in 2010, and characterize HEV71 and CVA16 isolated from clinical specimens. Among the 542 HFMD patients, 495 (91.3%) were positive for enterovirus as detected by real-time reverse transcriptase PCR; 243 were positive for HEV71 (49.1%, 243/495) and 114 were positive for CVA16 (23.0%, 114/495). Most of the affected children were aged 5 years or under (93.7%, 508/542). Phylogenetic analyses of VP1 gene sequences showed that the HEV71 isolates belonged to C4a subgenotype, and CVA16 isolates belonged to B1 genotype. Our results demonstrate that HEV71 and CVA16 are the primary causative agents responsible for HFMD in Guangdong Province, and their co-circulation poses a potential risk to public health. Copyright © 2013 International Society for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.
Zarkova, L.; Hohm, U.
2002-03-01
We present results on self-consistent calculations of second pVT-virial coefficients B(T), viscosity data η(T), and diffusion coefficients ρD(T) for eleven heavy globular gases: boron trifluoride (BF3), carbon tetrafluoride (CF4), silicon tetrafluoride (SiF4), carbon tetrachloride (CCl4), silicon tetrachloride (SiCl4), sulfur hexafluoride (SF6), molybdenum hexafluoride (MoF6), tungsten hexafluoride (WF6), uranium hexafluoride (UF6), tetramethyl methane (C(CH3)4, TMM), and tetramethyl silane (Si(CH3)4, TMS). The calculations are performed mainly in the temperature range between 200 and 900 K by means of isotropic n-6 potentials with temperature-dependent separation rm(T) and potential well depth ɛ(T). The potential parameters at T=0 K (ɛ, rm, n) and the enlargement of the first level radii δ are obtained solving an ill-posed problem of minimizing the squared deviations between experimental and calculated values normalized to their relative experimental error. The temperature dependence of the potential is obtained as a result of the influence of vibrational excitation on binary interactions. This concept of the isotropic temperature-dependent potential (ITDP) is presented in detail where gaseous SF6 will serve as an example. The ITDP is subsequently applied to all other gases. This approach and the main part of the results presented here have already been published during 1996-2000. However, in some cases the data are upgraded due to the recently improved software (CF4, SF6) and newly found experimental data (CF4, SiF4, CCl4, SF6).
der, R.
1987-01-01
The various approaches to nonequilibrium statistical mechanics may be subdivided into convolution and convolutionless (time-local) ones. While the former, put forward by Zwanzig, Mori, and others, are used most commonly, the latter are less well developed, but have proven very useful in recent applications. The aim of the present series of papers is to develop the time-local picture (TLP) of nonequilibrium statistical mechanics on a new footing and to consider its physical implications for topics such as the formulation of irreversible thermodynamics. The most natural approach to TLP is seen to derive from the Fourier-Laplace transformwidetilde{C}(z)) of pertinent time correlation functions, which on the physical sheet typically displays an essential singularity at z=∞ and a number of macroscopic and microscopic poles in the lower half-plane corresponding to long- and short-lived modes, respectively, the former giving rise to the autonomous macrodynamics, whereas the latter are interpreted as doorway modes mediating the transfer of information from relevant to irrelevant channels. Possible implications of this doorway mode concept for socalled extended irreversible thermodynamics are briefly discussed. The pole structure is used for deriving new kinds of generalized Green-Kubo relations expressing macroscopic quantities, transport coefficients, e.g., by contour integrals over current-current correlation functions obeying Hamiltonian dynamics, the contour integration replacing projection. The conventional Green-Kubo relations valid for conserved quantities only are rederived for illustration. Moreover,widetilde{C}(z) may be expressed by a Laurent series expansion in positive and negative powers of z, from which a rigorous, general, and straightforward method is developed for extracting all macroscopic quantities from so-called secularly divergent expansions ofwidetilde{C}(z) as obtained from the application of conventional many-body techniques to the calculation
Guo, Wen-Ping; Lin, Xian-Dan; Chen, Yi-Ping; Liu, Qi; Wang, Wen; Wang, Cai-Qiao; Li, Ming-Hui; Sun, Xiao-Yu; Shi, Mang; Holmes, Edward C; Zhang, Yong-Zhen
2015-09-01
Although hand, foot, and mouth disease (HFMD) is a major public concern in China, the prevalence and clinical symptoms associated with the different agents of HFMD in this country remain poorly understood. We investigated the clinical and molecular characteristics of enteroviruses in patients with HFMD from Wenzhou, China. Patients with laboratory-confirmed HFMD admitted to the Yuying Children's Hospital in Wenzhou, China during 2013 were included in this study. Viral RNA sequences were amplified using RT-PCR, determined by sequencing, and compared by phylogenetic analysis. A total of 955 clinically diagnosed HFMD cases were determined using PCR, with whole viral genomes obtained for each enterovirus type. 14 types of enterovirus belonging to two viral species were identified. Notably, Coxsackievirus A6 (CV-A6) was the most common species detected (77.8%), followed by EV-A71 (8.2%) and CV-A10 (8.1%). Phylogenetic analysis revealed multiple independent introductions of these viruses into Wenzhou. In addition, the enterovirus observed in Wenzhou had a recombinant history, with two or three recombination breakpoints. Although the illness associated with CV-A6 was milder than that of EV-A71, CV-A6 infection caused more widespread rash, larger blisters, and subsequent skin peeling and/or nail shedding. Our study revealed the co-circulation of 14 types of enteroviruses in a single location - Wenzhou, China - with CV-A6 virus the predominant agent of HFMD. This work highlights the need to perform larger-scale surveillance to fully understand the epidemiology of enteroviruses in China and the wider Asia-Pacific region. Copyright © 2015 Elsevier B.V. All rights reserved.
Characterization of severe hand, foot, and mouth disease in Shenzhen, China, 2009-2013.
Huang, Yun; Zhou, Yuanping; Lu, Hong; Yang, Hong; Feng, Qianjin; Dai, Yingchun; Chen, Long; Yu, Shouyi; Yao, Xiangjie; Zhang, Hailong; Jiang, Ming; Wang, Yujie; Han, Ning; Hu, Guifang; He, Yaqing
2015-09-01
Hand, foot, and mouth disease (HFMD) is caused by human enteroviruses, especially by enterovirus 71 (EV71) and coxsackievirus A16 (CA16). Patients infected with different enteroviruses show varied clinical symptoms. The aim of this study was to determine whether the etiological spectrum of mild and severe HFMD changed, and the association between pathogens and clinical features. From 2009 to 2013, a total of 2,299 stool or rectal specimens were collected with corresponding patient data. A dynamic view of the etiological spectrum of mild and severe HFMD in Shenzhen city of China was provided. EV71 accounted for the majority proportion of severe HFMD cases and fatalities during 2009-2013. CA16 and EV71 were gradually replaced by coxsackievirus A6 (CA6) as the most common serotype for mild HFMD since 2010. Myoclonic jerk and vomiting were the most frequent severe symptoms. Nervous system complications, including aseptic encephalitis and aseptic meningitis were observed mainly in patients infected by EV71. Among EV71, CA16, CA6, and CA10 infection, fever and pharyngalgia were more likely to develop, vesicles on the hand, foot, elbow, knee and buttock were less likely to develop in patients infected with CA10. Vesicles on the mouth more frequently occurred in the patients with CA6, but less in the patient with EV71. Associations between diverse enterovirus serotypes and various clinical features were discovered in the present study, which may offer further insight into early detection, diagnosis and treatment of HFMD. © 2015 Wiley Periodicals, Inc.
Epidemiology of hand foot mouth disease in Northern Thailand in 2016: A prospective cohort study
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Panupong Upala
2017-06-01
Full Text Available Objective: To determine the correlations between the meteorological data and the number of hand foot mouth disease (HFMD cases in 2016 in Northern Thailand, and to estimate the medical costs. Methods: A prospective cohort study was conducted. Data on numbers of HFMD cases were collected from 49 hospitals in three different provinces in Northern Thailand: 16 hospitals from Chiang Rai Province, 7 hospitals from Pha Yao Province, and 26 hospitals from Chiang Mai Province. A questionnaire had been developed and tested for validity and reliability before used. The specific form for collecting meteorological data was developed and used in the field. All information was recorded in the same data spread sheet before analysis. Chi-square and correlation tests were used for explaining the epidemiology of HFMD in the areas. An alpha error at 0.05 was used to determine the statistical significance level. Results: A total of 8 261 cases were analyzed in the study. 56.0% were males, 97.5% aged less than 6 years, 82.6% were out-patient department (OPD cases, 75.5% were reported in raining season, and 43.2% were from Chiang Mai Province. The number of HFMD cases had statistically significant correlations with temperature, air pressure, relative humidity, and rainfall amount. Averagely, 216 baht and 3 678 baht per case per visit had to be expended for medical cost in OPD and IPD cases, respectively. Most of the cases had been reported in the border areas: Thai-Myanmar, and Thai-Lao. Conclusions: Thailand health care system should provide a concrete schedule for taking care of HFMD patients during raining season, and should develop an effective preventive and control program for HFMD particularly among children less than 6 years.
Thao, Nguyen Thi Thanh; Ngoc, Nguyen Thi Kim; Tú, Phan Văn; Thúy, Trần Thi; Cardosa, Mary Jane; McMinn, Peter Charles; Phuektes, Patchara
2010-01-01
Human enterovirus 71 (HEV71) and coxsackievirus A16 (CVA16) are two major aetiological agents of hand, foot and mouth disease (HFMD) in children. Recently there have been several large outbreaks of HFMD in Vietnam and the Asia-Pacific region. In this study, a multiplex RT-PCR assay was developed in order to detect simultaneously HEV71, CVA16 and other human enteroviruses. Enterovirus detection was performed with a mixture of three pairs of oligonucleotide primers: one pair of published primers for amplifying all known enterovirus genomes and two new primer pairs specific for detection of the VP1 genes of HEV71 and CVA16. Enterovirus isolates, CVA16 and HEV71 strains identified previously from patients with HFMD were examined to evaluate the sensitivity and specificity of the multiplex RT-PCR assay. The assay was then applied to the direct detection of these viruses in clinical specimens obtained from HFMD cases identified at Children's Hospital Number 2, Ho Chi Minh City, Vietnam. The multiplex RT-PCR assay showed 100% specificity in screening for enteroviruses and in identifying HEV71 and CVA16. Similar results were obtained when using the multiplex RT-PCR assay to screen for enteroviruses and to identify HEV71 and CVA16 in clinical specimens obtained from HFMD cases identified at the hospital. This multiplex RT-PCR assay is a rapid, sensitive and specific assay for the diagnosis of HEV71 or CVA16 infection in cases of HFMD and is also potentially useful for molecular epidemiological investigations. PMID:20863857
Zhao, Hui; Li, Hao-Yang; Han, Jian-Feng; Deng, Yong-Qiang; Zhu, Shun-Ya; Li, Xiao-Feng; Yang, Hui-Qin; Li, Yue-Xiang; Zhang, Yu; Qin, E-De; Chen, Rong; Qin, Cheng-Feng
2015-01-19
Hand-foot-and-mouth disease (HFMD) has been recognized as an important global public health issue, which is predominantly caused by enterovirus 71 (EV-A71) and coxsackievirus A16 (CVA16). There is no available vaccine against HFMD. An ideal HFMD vaccine should be bivalent against both EV-A71 and CVA16. Here, a novel strategy to produce bivalent HFMD vaccine based on chimeric EV-A71 virus-like particles (ChiEV-A71 VLPs) was proposed and illustrated. The neutralizing epitope SP70 within the capsid protein VP1 of EV-A71 was replaced with that of CVA16 in ChiEV-A71 VLPs. Structural modeling revealed that the replaced CVA16-SP70 epitope is well exposed on the surface of ChiEV-A71 VLPs. These VLPs produced in Saccharomyces cerevisiae exhibited similarity in both protein composition and morphology as naive EV-A71 VLPs. Immunization with ChiEV-A71 VLPs in mice elicited robust Th1/Th2 dependent immune responses against EV-A71 and CVA16. Furthermore, passive immunization with anti-ChiEV-A71 VLPs sera conferred full protection against lethal challenge of both EV-A71 and CVA16 infection in neonatal mice. These results suggested that this chimeric vaccine, ChiEV-A71 might have the potential to be further developed as a bivalent HFMD vaccine in the near future. Such chimeric enterovirus VLPs provide an alternative platform for bivalent HFMD vaccine development.
Circulation of Coxsackievirus A10 and A6 in hand-foot-mouth disease in China, 2009-2011.
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Qing-Bin Lu
Full Text Available Coxsackieviruses A10 (CV-A10 and A6 (CV-A6 have been associated with increasingly occurred sporadic hand-foot-mouth disease (HFMD cases and outbreak events globally. However, our understanding of epidemiological and genetic characteristics of these new agents remains far from complete. This study was to explore the circulation of CV-A10 and CV-A6 in HFMD and their genetic characteristics in China. A hospital based surveillance was performed in three heavily inflicted regions with HFMD from March 2009 to August 2011. Feces samples were collected from children with clinical diagnosis of HFMD. The detection and genotyping of enteroviruses was performed by real-time PCR and sequencing of 5'UTR/VP1 regions. Phylogenetic analysis and selection pressure were performed based on the VP1 sequences. Logistic regression model was used to identify the effect of predominant enterovirus serotypes in causing severe HFMD. The results showed 92.0% of 1748 feces samples were detected positive for enterovirus, with the most frequently presented serotypes as EV-71 (944, 54.0% and CV-A16 (451, 25.8%. CV-A10 and CV-A6 were detected as a sole pathogen in 82 (4.7% and 44 (2.5% cases, respectively. Infection with CV-A10 and EV-71 were independently associated with high risk of severe HFMD (OR = 2.66, 95% CI: 1.40-5.06; OR = 4.81, 95% CI: 3.07-7.53, when adjusted for age and sex. Phylogenetic analysis revealed that distinct geographic and temporal origins correlated with the gene clusters based on VP1 sequences. An overall ω value of the VP1 was 0.046 for CV-A10 and 0.047 for CV-A6, and no positively selected site was detected in VP1 of both CV-A10 and CV-A6, indicating that purifying selection shaped the evolution of CV-A10 and CV-A6. Our study demonstrates variety of enterovirus genotypes as viral pathogens in causing HFMD in China. CV-A10 and CV-A6 were co-circulating together with EV-71 and CV-A16 in recent years. CV-A10 infection might also be independently
A novel Enterovirus 96 circulating in China causes hand, foot, and mouth disease.
Xu, Yi; Sun, Yisuo; Ma, Jinmin; Zhou, Shuru; Fang, Wei; Ye, Jiawei; Tan, Limei; Ji, Jingkai; Luo, Dan; Li, Liqiang; Li, Jiandong; Fang, Chunxiao; Pei, Na; Shi, Shuo; Liu, Xin; Jiang, Hui; Gong, Sitang; Xu, Xun
2017-06-01
Enterovirus 96 (EV-96) is a recently described member of the species Enterovirus C and is associated with paralysis and myelitis. In this study, using metagenomic sequencing, we identified a new enterovirus 96 strain (EV-96-SZ/GD/CHN/2014) as the sole pathogen causing hand, foot, and mouth disease (HFMD). A genomic comparison showed that EV-96-SZ/GD/CHN/2014 is most similar to the EV-96-05517 strain (85% identity), which has also been detected in Guangdong Province. This is the first time that metagenomic sequencing has been used to identify an EV-96 strain shown to be associated with HFMD.
Evaluation of uranium dioxide thermal conductivity using molecular dynamics simulations
International Nuclear Information System (INIS)
Kim, Woongkee; Kaviany, Massoud; Shim, J. H.
2014-01-01
It can be extended to larger space, time scale and even real reactor situation with fission product as multi-scale formalism. Uranium dioxide is a fluorite structure with Fm3m space group. Since it is insulator, dominant heat carrier is phonon, rather than electrons. So, using equilibrium molecular dynamics (MD) simulation, we present the appropriate calculation parameters in MD simulation by calculating thermal conductivity and application of it to the thermal conductivity of polycrystal. In this work, we investigate thermal conductivity of uranium dioxide and optimize the parameters related to its process. In this process, called Green Kubo formula, there are two parameters i.e correlation length and sampling interval, which effect on ensemble integration in order to obtain thermal conductivity. Through several comparisons, long correlation length and short sampling interval give better results. Using this strategy, thermal conductivity of poly crystal is obtained and comparison with that of pure crystal is made. Thermal conductivity of poly crystal show lower value that that of pure crystal. In further study, we broaden the study to transport coefficient of radiation damaged structures using molecular dynamics. Although molecular dynamics is tools for treating microscopic scale, most macroscopic issues related to nuclear materials such as voids in fuel materials and weakened mechanical properties by radiation are based on microscopic basis. Thus, research on microscopic scale would be expanded in this field and many hidden mechanism in atomic scales will be revealed via both atomic scale simulations and experiments
Longitudinal and bulk viscosities of Lennard-Jones fluids
Tankeshwar, K.; Pathak, K. N.; Ranganathan, S.
1996-12-01
Expressions for the longitudinal and bulk viscosities have been derived using Green Kubo formulae involving the time integral of the longitudinal and bulk stress autocorrelation functions. The time evolution of stress autocorrelation functions are determined using the Mori formalism and a memory function which is obtained from the Mori equation of motion. The memory function is of hyperbolic secant form and involves two parameters which are related to the microscopic sum rules of the respective autocorrelation function. We have derived expressions for the zeroth-, second-and fourth- order sum rules of the longitudinal and bulk stress autocorrelation functions. These involve static correlation functions up to four particles. The final expressions for these have been put in a form suitable for numerical calculations using low- order decoupling approximations. The numerical results have been obtained for the sum rules of longitudinal and bulk stress autocorrelation functions. These have been used to calculate the longitudinal and bulk viscosities and time evolution of the longitudinal stress autocorrelation function of the Lennard-Jones fluids over wide ranges of densities and temperatures. We have compared our results with the available computer simulation data and found reasonable agreement.
Velocity and stress autocorrelation decay in isothermal dissipative particle dynamics
Chaudhri, Anuj; Lukes, Jennifer R.
2010-02-01
The velocity and stress autocorrelation decay in a dissipative particle dynamics ideal fluid model is analyzed in this paper. The autocorrelation functions are calculated at three different friction parameters and three different time steps using the well-known Groot/Warren algorithm and newer algorithms including self-consistent leap-frog, self-consistent velocity Verlet and Shardlow first and second order integrators. At low friction values, the velocity autocorrelation function decays exponentially at short times, shows slower-than exponential decay at intermediate times, and approaches zero at long times for all five integrators. As friction value increases, the deviation from exponential behavior occurs earlier and is more pronounced. At small time steps, all the integrators give identical decay profiles. As time step increases, there are qualitative and quantitative differences between the integrators. The stress correlation behavior is markedly different for the algorithms. The self-consistent velocity Verlet and the Shardlow algorithms show very similar stress autocorrelation decay with change in friction parameter, whereas the Groot/Warren and leap-frog schemes show variations at higher friction factors. Diffusion coefficients and shear viscosities are calculated using Green-Kubo integration of the velocity and stress autocorrelation functions. The diffusion coefficients match well-known theoretical results at low friction limits. Although the stress autocorrelation function is different for each integrator, fluctuates rapidly, and gives poor statistics for most of the cases, the calculated shear viscosities still fall within range of theoretical predictions and nonequilibrium studies.
International Nuclear Information System (INIS)
Adebayo, G.A.; Anusionwu, B.C.; Njah, A.N.; Adeniran, O.J.; Mathew, B.; Sunmonu, R.S.
2009-01-01
Arising from the inability of theoretical calculations to give accurate descriptions of (shear) viscosity in rare gases at high densities, we investigated the likely cause of discrepancy between theory and experiments. Molecular Dynamics simulations were performed to calculate transport coefficients and collision frequency of rare gases at high densities and different temperatures using a Lennard-Jones modelled pair potential. The results, when compared with experiments show an underestimation of the viscosity calculated through the Green-Kubo formalism, but in agreement with some other calculations performed by other groups. In the present work the origin of the underestimation is considered. Analyses of the transport coefficients show a very high collision frequency which suggests an atom may spend much less time in the neighbourhood of the fields of force of another atom and that the distribution in the systems studied adjusts itself to a nearly Maxwellian type which resulted in a locally and temporarily slowly varying temperature. We show that the time spent in the fields of force is so small compared with relaxation time thereby leading to a possible reduction in local velocity auto-correlation between atoms. (author)
International Nuclear Information System (INIS)
Bocquet, L.; Hansen, J.P.; Piasecki, J.
1997-01-01
In this work, we show that in any finite system, the binary friction tenser for two Brownian particles cannot be directly estimated from an evaluation of the microscopic Green Kubo formula, involving the time integral of force-force autocorrelation functions. This pitfall is associated with a subtle inversion of the thermodynamic and long-time limits and leads to spurious results for the estimates of the friction matrix based on molecular dynamics simulations. Starting from a careful analysis of the coupled Langevin equations for two interacting Brownian particles, we derive a method to circumvent these effects and extract the binary friction tenser from the correlation function matrix of the instantaneous forces exerted by the bath particles on the fixed Brownian particles, and from the relaxation of the total momentum of the bath in a finite system. The general methodology is applied to the case of two hard or soft Brownian spheres in a bath of light particles. Numerical estimates of the relevant correlation functions and of the resulting self and mutual components of the matrix of friction tensors are obtained by molecular dynamics simulations for various spacings between the Brownian particles
Haxhimali, Tomorr; Rudd, Robert E.; Cabot, William H.; Graziani, Frank R.
2015-11-01
We present molecular dynamics (MD) calculations of shear viscosity for asymmetric mixed plasma for thermodynamic conditions relevant to astrophysical and inertial confinement fusion plasmas. Specifically, we consider mixtures of deuterium and argon at temperatures of 100-500 eV and a number density of 1025 ions/cc. The motion of 30 000-120 000 ions is simulated in which the ions interact via the Yukawa (screened Coulomb) potential. The electric field of the electrons is included in this effective interaction; the electrons are not simulated explicitly. Shear viscosity is calculated using the Green-Kubo approach with an integral of the shear stress autocorrelation function, a quantity calculated in the equilibrium MD simulations. We systematically study different mixtures through a series of simulations with increasing fraction of the minority high-Z element (Ar) in the D-Ar plasma mixture. In the more weakly coupled plasmas, at 500 eV and low Ar fractions, results from MD compare very well with Chapman-Enskog kinetic results. In the more strongly coupled plasmas, the kinetic theory does not agree well with the MD results. We develop a simple model that interpolates between classical kinetic theories at weak coupling and the Murillo Yukawa viscosity model at higher coupling. This hybrid kinetics-MD viscosity model agrees well with the MD results over the conditions simulated, ranging from moderately weakly coupled to moderately strongly coupled asymmetric plasma mixtures.
Molecular dynamics simulations for transport coefficients of liquid argon: new approaches
International Nuclear Information System (INIS)
Lee, Song Hi; Park, Dong Kue; Kang, Dae Bok
2003-01-01
The stress and the heat-flux auto-correlation functions in the Green-Kubo formulas for shear viscosity and thermal conductivity have non-decaying long-time tails. This problem can be overcome by improving the statistical accuracy by N (number of particles)times, considering the stress and the heat-flux of the system as properties of each particle. The mean square stress and the heat-flux displacements in the Einstein formulas for shear viscosity and thermal conductivity are non linear functions of time since the quantities in the mean square stress and the heat-flux displacements are not continuous under periodic boundary conditions. An alternative to these quantities is to integrate the stress and the heat-flux with respect to time, but the resulting mean square stress and heat-flux displacements are still not linear versus time. This problem can be also overcome by improving the statistical accuracy. The results for transport coefficients of liquid argon obtained are discussed
Levashov, Valentin A.; Morris, James R.; Egami, Takeshi
2012-02-01
Temporal and spatial correlations among the local atomic level shear stresses were studied for a model liquid iron by molecular dynamics simulation [PRL 106,115703]. Integration over time and space of the shear stress correlation function F(r,t) yields viscosity via Green-Kubo relation. The stress correlation function in time and space F(r,t) was Fourier transformed to study the dependence on frequency, E, and wave vector, Q. The results, F(Q,E), showed damped shear stress waves propagating in the liquid for small Q at high and low temperatures. We also observed additional diffuse feature that appears as temperature is reduced below crossover temperature of potential energy landscape at relatively low frequencies at small Q. We suggest that this additional feature might be related to dynamic heterogeneity and boson peaks. We also discuss a relation between the time-scale of the stress-stress correlation function and the alpha-relaxation time of the intermediate self-scattering function S(Q,E).
Equation of State and Viscosity of Tantalum and Iron from First Principles
Miljacic, Ljubomir; Demers, Steven; van de Walle, Axel
2011-03-01
To understand and model at continuum level the high-energy-density dynamic response in transition metals like Tantalum and Iron, as it arises in hypervelocity impact experiments, an accurate prediction of the underlying thermodynamic and kinetic properties for a range of temperatures and pressures is of critical importance. The relevant time scale of atomic motion in a dense gas, liquid, and solid is accessible with ab-initio Molecular Dynamics (MD) simulations. We calculate EoS for Ta and Fe via Thermodynamical Integration in 2D (V,T) phase space throughout different single and two-component phases. To reduce the ab-initio demand in selected regions of the space, we fit available gas-liquid data to the Peng-Robinson model and treat the solid phase within the Boxed-quasi-harmonic approximation. In the fluid part of the 2D phase space, we calculate shear viscosity via Green-Kubo relations, as time integration of the stress autocorrelation function.
Chapman-Enskog expansion for the Vicsek model of self-propelled particles
Ihle, Thomas
2016-08-01
Using the standard Vicsek model, I show how the macroscopic transport equations can be systematically derived from microscopic collision rules. The approach starts with the exact evolution equation for the N-particle probability distribution and, after making the mean-field assumption of molecular chaos, leads to a multi-particle Enskog-type equation. This equation is treated by a non-standard Chapman-Enskog expansion to extract the macroscopic behavior. The expansion includes terms up to third order in a formal expansion parameter ɛ, and involves a fast time scale. A self-consistent closure of the moment equations is presented that leads to a continuity equation for the particle density and a Navier-Stokes-like equation for the momentum density. Expressions for all transport coefficients in these macroscopic equations are given explicitly in terms of microscopic parameters of the model. The transport coefficients depend on specific angular integrals which are evaluated asymptotically in the limit of infinitely many collision partners, using an analogy to a random walk. The consistency of the Chapman-Enskog approach is checked by an independent calculation of the shear viscosity using a Green-Kubo relation.
A molecular dynamics simulation study of chloroform
Tironi, Ilario G.; van Gunsteren, Wilfred F.
Three different chloroform models have been investigated using molecular dynamics computer simulation. The thermodynamic, structural and dynamic properties of the various models were investigated in detail. In particular, the potential energies, diffusion coefficients and rotational correlation times obtained for each model are compared with experiment. It is found that the theory of rotational Brownian motion fails in describing the rotational diffusion of chloroform. The force field of Dietz and Heinzinger was found to give good overall agreement with experiment. An extended investigation of this chloroform model has been performed. Values are reported for the isothermal compressibility, the thermal expansion coefficient and the constant volume heat capacity. The values agree well with experiment. The static and frequency dependent dielectric permittivity were computed from a 1·2 ns simulation conducted under reaction field boundary conditions. Considering the fact that the model is rigid with fixed partial charges, the static dielectric constant and Debye relaxation time compare well with experiment. From the same simulation the shear viscosity was computed using the off-diagonal elements of the pressure tensor, both via an Einstein type relation and via a Green-Kubo equation. The calculated viscosities show good agreement with experimental values. The excess Helmholtz energy is calculated using the thermodynamic integration technique and simulations of 50 and 80 ps. The value obtained for the excess Helmholtz energy matches the theoretical value within a few per cent.
Haxhimali, Tomorr; Rudd, Robert; Cabot, William; Graziani, Frank
2015-11-01
We present molecular dynamics (MD) calculations of shear viscosity for asymmetric mixed plasma for thermodynamic conditions relevant to astrophysical and Inertial Confinement Fusion plasmas. Specifically, we consider mixtures of deuterium and argon at temperatures of 100-500 eV and a number density of 1025 ions/cc. The motion of 30000-120000 ions is simulated in which the ions interact via the Yukawa (screened Coulomb) potential. The electric field of the electrons is included in this effective interaction. Shear viscosity is calculated using the Green-Kubo approach with an integral of the shear stress autocorrelation function, a quantity calculated in the equilibrium MD simulations. We study different mixtures with increasing fraction of the minority high-Z element (Ar) in the D-Ar plasma mixture. In the more weakly coupled plasmas, at 500 eV and low Ar fractions, results from MD compare very well with Chapman-Enskog kinetic results. We introduce a model that interpolates between a screened-plasma kinetic theory at weak coupling and the Murillo Yukawa viscosity model at higher coupling. This hybrid kinetics-MD viscosity model agrees well with the MD results over the conditions simulated. This work was performed under the auspices of the US Dept. of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344.
Thermodynamics of Micro- and Nano-Systems Driven by Periodic Temperature Variations
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Kay Brandner
2015-08-01
Full Text Available We introduce a general framework for analyzing the thermodynamics of small systems that are driven by both a periodic temperature variation and some external parameter modulating their energy. This setup covers, in particular, periodic micro- and nano-heat engines. In a first step, we show how to express total entropy production by properly identified time-independent affinities and currents without making a linear response assumption. In linear response, kinetic coefficients akin to Onsager coefficients can be identified. Specializing to a Fokker-Planck-type dynamics, we show that these coefficients can be expressed as a sum of an adiabatic contribution and one reminiscent of a Green-Kubo expression that contains deviations from adiabaticity. Furthermore, we show that the generalized kinetic coefficients fulfill an Onsager-Casimir-type symmetry tracing back to microscopic reversibility. This symmetry allows for nonidentical off-diagonal coefficients if the driving protocols are not symmetric under time reversal. We then derive a novel constraint on the kinetic coefficients that is sharper than the second law and provides an efficiency-dependent bound on power. As one consequence, we can prove that the power vanishes at least linearly when approaching Carnot efficiency. We illustrate our general framework by explicitly working out the paradigmatic case of a Brownian heat engine realized by a colloidal particle in a time-dependent harmonic trap subject to a periodic temperature profile. This case study reveals inter alia that our new general bound on power is asymptotically tight.
Wei, Xingfei; Zhang, Teng; Luo, Tengfei
2017-10-04
Thermal transport across hard-soft interfaces is critical to many modern applications, such as composite materials, thermal management in microelectronics, solar-thermal phase transition, and nanoparticle-assisted hyperthermia therapeutics. In this study, we use equilibrium molecular dynamics (EMD) simulations combined with the Green-Kubo method to study how molecularly heterogeneous structures of the self-assembled monolayer (SAM) affect the thermal transport across the interfaces between the SAM-functionalized gold and organic liquids (hexylamine, propylamine and hexane). We focus on a practically synthesizable heterogeneous SAM featuring alternating short and long molecular chains. Such a structure is found to improve the thermal conductance across the hard-soft interface by 46-68% compared to a homogeneous nonpolar SAM. Through a series of further simulations and analyses, it is found that the root reason for this enhancement is the penetration of the liquid molecules into the spaces between the long SAM molecule chains, which increase the effective contact area. Such an effect is similar to the fins used in macroscopic heat exchanger. This "molecular fin" structure from the heterogeneous SAM studied in this work provides a new general route for enhancing thermal transport across hard-soft material interfaces.
Thermal conductivity of nanocrystalline SiGe alloys using molecular dynamics simulations
Abs da Cruz, Carolina; Katcho, Nebil A.; Mingo, Natalio; Veiga, Roberto G. A.
2013-10-01
We have studied the effect of nanocrystalline microstructure on the thermal conductivity of SiGe alloys using molecular dynamics simulations. Nanograins are modeled using both the coincidence site lattice and the Voronoi tessellation methods, and the thermal conductivity is computed using the Green-Kubo formalism. We analyze the dependence of the thermal conductivity with temperature, grain size L, and misorientation angle. We find a power dependence of L1/4 of the thermal conductivity with the grain size, instead of the linear dependence shown by non-alloyed nanograined systems. This dependence can be derived analytically underlines the important role that disorder scattering plays even when the grains are of the order of a few nm. This is in contrast to non-alloyed systems, where phonon transport is governed mainly by the boundary scattering. The temperature dependence is weak, in agreement with experimental measurements. The effect of angle misorientation is also small, which stresses the main role played by the disorder scattering.
Thermal conductivity and heat transport properties of nitrogen-doped graphene.
Goharshadi, Elaheh K; Mahdizadeh, Sayyed Jalil
2015-11-01
In the present study, the thermal conductivity (TC) and heat transport properties of nitrogen doped graphene (N-graphene) were investigated as a function of temperature (107-400K) and N-doped concentration (0.0-7.0%) using equilibrium molecular dynamics simulation based on Green-Kubo method. According to the results, a drastic decline in TC of graphene observed at very low N-doped concentration (0.5 and 1.0%). Substitution of just 1.0% of carbon atoms with nitrogens causes a 77.2, 65.4, 59.2, and 53.7% reduction in TC at 107, 200, 300, and 400K, respectively. The values of TC of N-graphene at different temperatures approach to each other as N-doped concentration increases. The results also indicate that TC of N-graphene is much less sensitive to temperature compared with pristine graphene and the sensitivity decreases as N-doped concentration increases. The phonon-phonon scattering relaxation times and the phonon mean free path of phonons were also calculated. The contribution of high frequency optical phonons for pristine graphene and N-graphene with 7.0% N-doped concentration is 0-2% and 4-8%, respectively. These findings imply that it is potentially feasible to control heat transfer on the nanoscale when designing N-graphene based thermal devices. Copyright © 2015 Elsevier Inc. All rights reserved.
Natural approach to quantum dissipation
Taj, David; Öttinger, Hans Christian
2015-12-01
The dissipative dynamics of a quantum system weakly coupled to one or several reservoirs is usually described in terms of a Lindblad generator. The popularity of this approach is certainly due to the linear character of the latter. However, while such linearity finds justification from an underlying Hamiltonian evolution in some scaling limit, it does not rely on solid physical motivations at small but finite values of the coupling constants, where the generator is typically used for applications. The Markovian quantum master equations we propose are instead supported by very natural thermodynamic arguments. They themselves arise from Markovian master equations for the system and the environment which preserve factorized states and mean energy and generate entropy at a non-negative rate. The dissipative structure is driven by an entropic map, called modular, which introduces nonlinearity. The generated modular dynamical semigroup (MDS) guarantees for the positivity of the time evolved state the correct steady state properties, the positivity of the entropy production, and a positive Onsager matrix with symmetry relations arising from Green-Kubo formulas. We show that the celebrated Davies Lindblad generator, obtained through the Born and the secular approximations, generates a MDS. In doing so we also provide a nonlinear MDS which is supported by a weak coupling argument and is free from the limitations of the Davies generator.
Anharmonicity Rise the Thermal Conductivity in Amorphous Silicon
Lv, Wei; Henry, Asegun
We recently proposed a new method called Direct Green-Kubo Modal Analysis (GKMA) method, which has been shown to calculate the thermal conductivity (TC) of several amorphous materials accurately. A-F method has been widely used for amorphous materials. However, researchers have found out that it failed on several different materials. The missing component of A-F method is the harmonic approximation and considering only the interactions of modes with similar frequencies, which neglect interactions of modes with large frequency difference. On the contrary, GKMA method, which is based on molecular dynamics, intrinsically includes all types of phonon interactions. In GKMA method, each mode's TC comes from both mode self-correlations (autocorrelations) and mode-mode correlations (crosscorrelations). We have demonstrated that the GKMA predicted TC of a-Si from Tersoff potential is in excellent agreement with one of experimental results. In this work, we will present the GKMA applications on a-Si using multiple potentials and gives us more insight of the effect of anharmonicity on the TC of amorphous silicon. This research was supported Intel grant AGMT DTD 1-15-13 and computational resources by NSF supported XSEDE resources under allocations DMR130105 and TG- PHY130049.
Spectral functions and transport coefficients from the functional renormalization group
Energy Technology Data Exchange (ETDEWEB)
Tripolt, Ralf-Arno
2015-06-03
In this thesis we present a new method to obtain real-time quantities like spectral functions and transport coefficients at finite temperature and density using the Functional Renormalization Group approach. Our non-perturbative method is thermodynamically consistent, symmetry preserving and based on an analytic continuation from imaginary to real time on the level of the flow equations. We demonstrate the applicability of this method by calculating mesonic spectral functions as well as the shear viscosity for the quark-meson model. In particular, results are presented for the pion and sigma spectral function at finite temperature and chemical potential, with a focus on the regime near the critical endpoint in the phase diagram of the quark-meson model. Moreover, the different time-like and space-like processes, which give rise to a complex structure of the spectral functions, are discussed. Finally, based on the momentum dependence of the spectral functions, we calculate the shear viscosity and the shear viscosity to entropy density ratio using the corresponding Green-Kubo formula.
Thermal Conductivities in Solids from First Principles: Accurate Computations and Rapid Estimates
Carbogno, Christian; Scheffler, Matthias
In spite of significant research efforts, a first-principles determination of the thermal conductivity κ at high temperatures has remained elusive. Boltzmann transport techniques that account for anharmonicity perturbatively become inaccurate under such conditions. Ab initio molecular dynamics (MD) techniques using the Green-Kubo (GK) formalism capture the full anharmonicity, but can become prohibitively costly to converge in time and size. We developed a formalism that accelerates such GK simulations by several orders of magnitude and that thus enables its application within the limited time and length scales accessible in ab initio MD. For this purpose, we determine the effective harmonic potential occurring during the MD, the associated temperature-dependent phonon properties and lifetimes. Interpolation in reciprocal and frequency space then allows to extrapolate to the macroscopic scale. For both force-field and ab initio MD, we validate this approach by computing κ for Si and ZrO2, two materials known for their particularly harmonic and anharmonic character. Eventually, we demonstrate how these techniques facilitate reasonable estimates of κ from existing MD calculations at virtually no additional computational cost.
Haskins, Justin; Kinaci, Alper; Sevik, Cem; Cagin, Tahir
2012-01-01
It is widely known that graphene and many of its derivative nanostructures have exceedingly high reported thermal conductivities (up to 4000 W/mK at 300 K). Such attractive thermal properties beg the use of these structures in practical devices; however, to implement these materials while preserving transport quality, the influence of structure on thermal conductivity should be thoroughly understood. For graphene nanostructures, having average phonon mean free paths on the order of one micron, a primary concern is how size influences the potential for heat conduction. To investigate this, we employ a novel technique to evaluate the lattice thermal conductivity from the Green-Kubo relations and equilibrium molecular dynamics in systems where phonon-boundary scattering dominates heat flow. Specifically, the thermal conductivities of graphene nanoribbons and carbon nanotubes are calculated in sizes up to 3 microns, and the relative influence of boundary scattering on thermal transport is determined to be dominant at sizes less than 1 micron, after which the thermal transport largely depends on the quality of the nanostructure interface. The method is also extended to carbon nanostructures (fullerenes) where phonon confinement, as opposed to boundary scattering, dominates, and general trends related to the influence of curvature on thermal transport in these materials are discussed.
Perspective: Maximum caliber is a general variational principle for dynamical systems.
Dixit, Purushottam D; Wagoner, Jason; Weistuch, Corey; Pressé, Steve; Ghosh, Kingshuk; Dill, Ken A
2018-01-07
We review here Maximum Caliber (Max Cal), a general variational principle for inferring distributions of paths in dynamical processes and networks. Max Cal is to dynamical trajectories what the principle of maximum entropy is to equilibrium states or stationary populations. In Max Cal, you maximize a path entropy over all possible pathways, subject to dynamical constraints, in order to predict relative path weights. Many well-known relationships of non-equilibrium statistical physics-such as the Green-Kubo fluctuation-dissipation relations, Onsager's reciprocal relations, and Prigogine's minimum entropy production-are limited to near-equilibrium processes. Max Cal is more general. While it can readily derive these results under those limits, Max Cal is also applicable far from equilibrium. We give examples of Max Cal as a method of inference about trajectory distributions from limited data, finding reaction coordinates in bio-molecular simulations, and modeling the complex dynamics of non-thermal systems such as gene regulatory networks or the collective firing of neurons. We also survey its basis in principle and some limitations.
Lawson, John W.; Daw, Murray S.; Bauschlicher, Charles W.
2012-01-01
Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 have a number of properties that make them attractive for applications in extreme environments. One such property is their high thermal conductivity. Computational modeling of these materials will facilitate understanding of fundamental mechanisms, elucidate structure-property relationships, and ultimately accelerate the materials design cycle. Progress in computational modeling of UHTCs however has been limited in part due to the absence of suitable interatomic potentials. Recently, we developed Tersoff style parameterizations of such potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current, in contrast to the more typical monotonic decay seen in monoatomic materials such as Silicon, for example. Results at room temperature and at elevated temperatures will be reported.
Lattice Thermal Conductivity from Atomistic Simulations: ZrB2 and HfB2
Lawson, John W.; Daw, Murray S.; Bauschlicher, Charles W.
2012-01-01
Ultra high temperature ceramics (UHTC) including ZrB2 and HfB2 have a number of properties that make them attractive for applications in extreme environments. One such property is their high thermal conductivity. Computational modeling of these materials will facilitate understanding of fundamental mechanisms, elucidate structure-property relationships, and ultimately accelerate the materials design cycle. Progress in computational modeling of UHTCs however has been limited in part due to the absence of suitable interatomic potentials. Recently, we developed Tersoff style parameterizations of such potentials for both ZrB2 and HfB2 appropriate for atomistic simulations. As an application, Green-Kubo molecular dynamics simulations were performed to evaluate the lattice thermal conductivity for single crystals of ZrB2 and HfB2. The atomic mass difference in these binary compounds leads to oscillations in the time correlation function of the heat current, in contrast to the more typical monotonic decay seen in monoatomic materials such as Silicon, for example. Results at room temperature and at elevated temperatures will be reported.
International Nuclear Information System (INIS)
Barra, F.; Gaspard, P.
2001-01-01
We consider the classical evolution of a particle on a graph by using a time-continuous Frobenius-Perron operator that generalizes previous propositions. In this way, the relaxation rates as well as the chaotic properties can be defined for the time-continuous classical dynamics on graphs. These properties are given as the zeros of some periodic-orbit zeta functions. We consider in detail the case of infinite periodic graphs where the particle undergoes a diffusion process. The infinite spatial extension is taken into account by Fourier transforms that decompose the observables and probability densities into sectors corresponding to different values of the wave number. The hydrodynamic modes of diffusion are studied by an eigenvalue problem of a Frobenius-Perron operator corresponding to a given sector. The diffusion coefficient is obtained from the hydrodynamic modes of diffusion and has the Green-Kubo form. Moreover, we study finite but large open graphs that converge to the infinite periodic graph when their size goes to infinity. The lifetime of the particle on the open graph is shown to correspond to the lifetime of a system that undergoes a diffusion process before it escapes
Paul, J.; Madhu, A. K.; Jayadeep, U. B.; Sobhan, C. B.; Peterson, G. P.
2018-03-01
Liquid layering is considered to be one of the factors contributing to the often anomalous enhancement in thermal conductivity of nanoparticle suspensions. The extent of this layering was found to be significant at lower particle sizes, as reported in an earlier work by the authors. In continuation to that work, an investigation was conducted to better understand the fundamental parameters impacting the reported anomalous enhancement in thermal conductivity of nanoparticle suspensions (nanofluids), utilizing equilibrium molecular dynamics simulations in a copper-argon system. Nanofluids containing nanoparticles of size less than 6 nm were investigated and studied analytically. The heat current auto-correlation function in the Green-Kubo formulation for thermal conductivity was decomposed into self-correlations and cross-correlations of different species and the kinetic, potential, collision and enthalpy terms of the dominant portion of the heat current vector. The presence of liquid layering around the nanoparticle was firmly established through simulations that show the dominant contribution of Ar-Ar self-correlation and the trend displayed by the kinetic-potential cross-correlation within the argon species.
Einstein-Kubo-Helfand and McQuarrie relations for transport coefficients
International Nuclear Information System (INIS)
Erpenbeck, J.J.
1995-01-01
Monte Carlo molecular dynamics calculations of η E (C) (t;N) for an equimolar binary mixture of hard spheres (diameter ratio of 0.4 and mass ratio of 0.03) confirm these large differences at a few mean free times, but suggest a long-time plateau value having the magnitude of the Green-Kubo result, but the values at 70 mean free times do not approach η(t;N) with increasing N. Finally, we consider the one-particle, EKH-like, McQuarrie expression for shear viscosity, showing that the Chialvo-Cummings-Evans [Phys. Rev. E 47, 1702 (1993)] ''proof'' is defective. Moreover, we demonstrate through molecular dynamics calculations for the same hard-sphere mixture that the two-particle contribution to the time-dependent viscosity, which must vanish at long times for the McQuarrie formula to be valid, in fact contributes roughly 40% of the shear viscosity at a volume of (5 √2 /2)tsum a N a σ a 3 , where N a is the number of particles of species a having diameter σ a
Perspective: Maximum caliber is a general variational principle for dynamical systems
Dixit, Purushottam D.; Wagoner, Jason; Weistuch, Corey; Pressé, Steve; Ghosh, Kingshuk; Dill, Ken A.
2018-01-01
We review here Maximum Caliber (Max Cal), a general variational principle for inferring distributions of paths in dynamical processes and networks. Max Cal is to dynamical trajectories what the principle of maximum entropy is to equilibrium states or stationary populations. In Max Cal, you maximize a path entropy over all possible pathways, subject to dynamical constraints, in order to predict relative path weights. Many well-known relationships of non-equilibrium statistical physics—such as the Green-Kubo fluctuation-dissipation relations, Onsager's reciprocal relations, and Prigogine's minimum entropy production—are limited to near-equilibrium processes. Max Cal is more general. While it can readily derive these results under those limits, Max Cal is also applicable far from equilibrium. We give examples of Max Cal as a method of inference about trajectory distributions from limited data, finding reaction coordinates in bio-molecular simulations, and modeling the complex dynamics of non-thermal systems such as gene regulatory networks or the collective firing of neurons. We also survey its basis in principle and some limitations.
Directory of Open Access Journals (Sweden)
Ahmad Ehsan Mohd Tamidi
2016-01-01
Full Text Available We have used a molecular dynamics technique to simulate the relationship between nanocluster precipitation and thermal conductivity in Si/Ge amorphous multilayer films, with and without Cu addition. In the study, the Green-Kubo equation was used to calculate thermal conductivity in these materials. Five specimens were prepared: Si/Ge layers, Si/(Ge + Cu layers, (Si + Cu/(Ge + Cu layers, Si/Cu/Ge/Cu layers, and Si/Cu/Ge layers. The number of precipitated nanoclusters in these specimens, which is defined as the number of four-coordinate atoms, was counted along the lateral direction of the specimens. The observed results of precipitate formation were considered in relation to the thermal conductivity results. Enhancement of precipitation of nanoclusters by Cu addition, that is, densification of four-coordinate atoms, can prevent the increment of thermal conductivity. Cu dopant increases the thermal conductivity of these materials. Combining these two points, we concluded that Si/Cu/Ge is the best structure to improve the conversion efficiency of the Si/Ge amorphous multilayer films.
Summability of Connected Correlation Functions of Coupled Lattice Fields
Lukkarinen, Jani; Marcozzi, Matteo; Nota, Alessia
2018-04-01
We consider two nonindependent random fields ψ and φ defined on a countable set Z. For instance, Z=Z^d or Z=Z^d× I, where I denotes a finite set of possible "internal degrees of freedom" such as spin. We prove that, if the cumulants of ψ and φ enjoy a certain decay property, then all joint cumulants between ψ and φ are ℓ _2-summable in the precise sense described in the text. The decay assumption for the cumulants of ψ and φ is a restricted ℓ _1 summability condition called ℓ _1-clustering property. One immediate application of the results is given by a stochastic process ψ _t(x) whose state is ℓ _1-clustering at any time t: then the above estimates can be applied with ψ =ψ _t and φ =ψ _0 and we obtain uniform in t estimates for the summability of time-correlations of the field. The above clustering assumption is obviously satisfied by any ℓ _1-clustering stationary state of the process, and our original motivation for the control of the summability of time-correlations comes from a quest for a rigorous control of the Green-Kubo correlation function in such a system. A key role in the proof is played by the properties of non-Gaussian Wick polynomials and their connection to cumulants
Bulk viscosity of molecular fluids
Jaeger, Frederike; Matar, Omar K.; Müller, Erich A.
2018-05-01
The bulk viscosity of molecular models of gases and liquids is determined by molecular simulations as a combination of a dilute gas contribution, arising due to the relaxation of internal degrees of freedom, and a configurational contribution, due to the presence of intermolecular interactions. The dilute gas contribution is evaluated using experimental data for the relaxation times of vibrational and rotational degrees of freedom. The configurational part is calculated using Green-Kubo relations for the fluctuations of the pressure tensor obtained from equilibrium microcanonical molecular dynamics simulations. As a benchmark, the Lennard-Jones fluid is studied. Both atomistic and coarse-grained force fields for water, CO2, and n-decane are considered and tested for their accuracy, and where possible, compared to experimental data. The dilute gas contribution to the bulk viscosity is seen to be significant only in the cases when intramolecular relaxation times are in the μs range, and for low vibrational wave numbers (<1000 cm-1); This explains the abnormally high values of bulk viscosity reported for CO2. In all other cases studied, the dilute gas contribution is negligible and the configurational contribution dominates the overall behavior. In particular, the configurational term is responsible for the enhancement of the bulk viscosity near the critical point.
Influence of defects on the thermal conductivity of compressed LiF
Jones, R. E.; Ward, D. K.
2018-02-01
Defect formation in LiF, which is used as an observation window in ramp and shock experiments, has significant effects on its transmission properties. Given the extreme conditions of the experiments it is hard to measure the change in transmission directly. Using molecular dynamics, we estimate the change in conductivity as a function of the concentration of likely point and extended defects using a Green-Kubo technique with careful treatment of size effects. With this data, we form a model of the mean behavior and its estimated error; then, we use this model to predict the conductivity of a large sample of defective LiF resulting from a direct simulation of ramp compression as a demonstration of the accuracy of its predictions. Given estimates of defect densities in a LiF window used in an experiment, the model can be used to correct the observations of thermal energy through the window. In addition, the methodology we develop is extensible to modeling, with quantified uncertainty, the effects of a variety of defects on the thermal conductivity of solid materials.
Effect of Ion Streaming on Diffusion of Dust Grains in Dissipative System
Begum, M.; Das, N.
2018-01-01
The presence of strong electric fields in the sheath region of laboratory complex plasma induces an ion drift and perturbs the field around dust grains. The downstream focusing of ions leads to the formation of oscillatory kind of attractive wake potential which superimpose with the normal Debye-Hückel (DH) potential. The structural properties of complex plasma and diffusion coefficient of dust grains in the presence of such a wake potential have been investigated using Langevin dynamics simulation in the subsonic regime of ion flow. The study reveals that the diffusion of dust grains is strongly affected by the ion flow, so that the diffusion changes its character in the wake potential to the DH potential dominant regimes. The dependence of the diffusion coefficient on the parameters, such as the neutral pressure, dust grain size, ion flow velocity, and Coulomb coupling parameter, have been calculated for the subsonic regime by using the Green-Kubo expression, which is based on the integrated velocity autocorrelation function. It is found that the diffusion and the structural property of the system is intimately connected with the interaction potential and significantly get affected in the presence of ion flow in the subsonic regime.
Stresses in non-equilibrium fluids: Exact formulation and coarse-grained theory
Krüger, Matthias; Solon, Alexandre; Démery, Vincent; Rohwer, Christian M.; Dean, David S.
2018-02-01
Starting from the stochastic equation for the density operator, we formulate the exact (instantaneous) stress tensor for interacting Brownian particles and show that its average value agrees with expressions derived previously. We analyze the relation between the stress tensor and forces due to external potentials and observe that, out of equilibrium, particle currents give rise to extra forces. Next, we derive the stress tensor for a Landau-Ginzburg theory in generic, non-equilibrium situations, finding an expression analogous to that of the exact microscopic stress tensor, and discuss the computation of out-of-equilibrium (classical) Casimir forces. Subsequently, we give a general form for the stress tensor which is valid for a large variety of energy functionals and which reproduces the two mentioned cases. We then use these relations to study the spatio-temporal correlations of the stress tensor in a Brownian fluid, which we compute to leading order in the interaction potential strength. We observe that, after integration over time, the spatial correlations generally decay as power laws in space. These are expected to be of importance for driven confined systems. We also show that divergence-free parts of the stress tensor do not contribute to the Green-Kubo relation for the viscosity.
Giri, Ashutosh; Hopkins, Patrick E.
2017-12-01
Fullerene condensed-matter solids can possess thermal conductivities below their minimum glassy limit while theorized to be stiffer than diamond when crystallized under pressure. These seemingly disparate extremes in thermal and mechanical properties raise questions into the pressure dependence on the thermal conductivity of C60 fullerite crystals, and how the spectral contributions to vibrational thermal conductivity changes under applied pressure. To answer these questions, we investigate the effect of strain on the thermal conductivity of C60 fullerite crystals via pressure-dependent molecular dynamics simulations under the Green-Kubo formalism. We show that the thermal conductivity increases rapidly with compressive strain, which demonstrates a power-law relationship similar to their stress-strain relationship for the C60 crystals. Calculations of the density of states for the crystals under compressive strains reveal that the librational modes characteristic in the unstrained case are diminished due to densification of the molecular crystal. Over a large compression range (0-20 GPa), the Leibfried-Schlömann equation is shown to adequately describe the pressure dependence of thermal conductivity, suggesting that low-frequency intermolecular vibrations dictate heat flow in the C60 crystals. A spectral decomposition of the thermal conductivity supports this hypothesis.
Obeidat, Abdalla; Abu-Ghazleh, Hind
2018-06-01
Two intermolecular potential models of methanol (TraPPE-UA and OPLS-AA) have been used in order to examine their validity in reproducing the selected structural, dynamical, and thermodynamic properties in the unary and binary systems. These two models are combined with two water models (SPC/E and TIP4P). The temperature dependence of density, surface tension, diffusion and structural properties for the unary system has been computed over specific range of temperatures (200-300K). The very good performance of the TraPPE-UA potential model in predicting surface tension, diffusion, structure, and density of the unary system led us to examine its accuracy and performance in its aqueous solution. In the binary system the same properties were examined, using different mole fractions of methanol. The TraPPE-UA model combined with TIP4P-water shows a very good agreement with the experimental results for density and surface tension properties; whereas the OPLS-AA combined with SPCE-water shows a very agreement with experimental results regarding the diffusion coefficients. Two different approaches have been used in calculating the diffusion coefficient in the mixture, namely the Einstein equation (EE) and Green-Kubo (GK) method. Our results show the advantageous of applying GK over EE in reproducing the experimental results and in saving computer time.
A molecular dynamics study of nuclear quantum effect on the diffusion of hydrogen in condensed phase
International Nuclear Information System (INIS)
Nagashima, Hiroki; Tokumasu, Takashi; Tsuda, Shin-ichi; Tsuboi, Nobuyuki; Koshi, Mitsuo; Hayashie, A. Koichi
2014-01-01
In this paper, the quantum effect of hydrogen molecule on its diffusivity is analyzed using Molecular Dynamics (MD) method. The path integral centroid MD (CMD) method is applied for the reproduction method of time evolution of the molecules. The diffusion coefficient of liquid hydrogen is calculated using the Green-Kubo method. The simulation is performed at wide temperature region and the temperature dependence of the quantum effect of hydrogen molecule is addressed. The calculation results are compared with those of classical MD results. As a result, it is confirmed that the diffusivity of hydrogen molecule is changed depending on temperature by the quantum effect. It is clarified that this result can be explained that the dominant factor by quantum effect on the diffusivity of hydrogen changes from the swollening the potential to the shallowing the potential well around 30 K. Moreover, it is found that this tendency is related to the temperature dependency of the ratio of the quantum kinetic energy and classical kinetic energy
Directory of Open Access Journals (Sweden)
Asir Intisar Khan
2015-12-01
Full Text Available The thermal conductivity of graphene nanoribbons (GNRs has been investigated using equilibrium molecular dynamics (EMD simulation based on Green-Kubo (GK method to compare two interatomic potentials namely optimized Tersoff and 2nd generation Reactive Empirical Bond Order (REBO. Our comparative study includes the estimation of thermal conductivity as a function of temperature, length and width of GNR for both the potentials. The thermal conductivity of graphene nanoribbon decreases with the increase of temperature. Quantum correction has been introduced for thermal conductivity as a function of temperature to include quantum effect below Debye temperature. Our results show that for temperatures up to Debye temperature, thermal conductivity increases, attains its peak and then falls off monotonically. Thermal conductivity is found to decrease with the increasing length for optimized Tersoff potential. However, thermal conductivity has been reported to increase with length using 2nd generation REBO potential for the GNRs of same size. Thermal conductivity, for the specified range of width, demonstrates an increasing trend with the increase of width for both the concerned potentials. In comparison with 2nd generation REBO potential, optimized Tersoff potential demonstrates a better modeling of thermal conductivity as well as provides a more appropriate description of phonon thermal transport in graphene nanoribbon. Such comparative study would provide a good insight for the optimization of the thermal conductivity of graphene nanoribbons under diverse conditions.
Puenpa, Jiratchaya; Mauleekoonphairoj, John; Linsuwanon, Piyada; Suwannakarn, Kamol; Chieochansin, Thaweesak; Korkong, Sumeth; Theamboonlers, Apiradee; Poovorawan, Yong
2014-01-01
Hand, foot, and mouth disease (HFMD) and herpangina are common infectious diseases caused by several genotypes of human enterovirus species A and frequently occurring in young children. This study was aimed at analyzing enteroviruses from patients with these diseases in Thailand in 2012. Detection and genotype determination of enteroviruses were accomplished by reverse transcription-polymerase chain reaction and sequencing of the VP1 region. Enterovirus-positive samples were differentiated into 17 genotypes (coxsackievirus A4 (CAV4), A5, A6, A8, A9, A10, A12, A16, A21, B1, B2, B4, B5, echovirus 7, 16, 25 and Enterovirus 71). The result showed CAV6 (33.5%), followed by CAV16 (9.4%) and EV71 (8.8%) as the most frequent genotypes in HFMD, CAV8 (19.3%) in herpangina and CAV6 (1.5%) in influenza like illness. Enterovirus infections were most prevalent during July with 34.4% in HFMD, 39.8% in herpangina and 1.6% in ILI. The higher enterovirus infection associated with HFMD and herpangina occurred in infants over one year-old. This represents the first report describing the circulation of multiple enteroviruses in Thailand.
Xu, Menghua; Su, Liyun; Cao, Lingfeng; Zhong, Huaqing; Dong, Niuniu; Xu, Jin
2013-10-22
A rapid expansion of hand, foot, and mouth disease (HFMD) outbreaks has occurred and caused deaths in China in recent years, but little is known about the other etiologic agents except enterovirus 71 (EV71) and coxsackievirus A 16 (CA16). The objective of this study is to determine the genotype compositions of enterovirus causing HFMD in Shanghai and identify any associations between enterovirus types and clinical manifestations. Stool specimens were collected from patients hospitalized for treatment of HFMD, from May 2010 to April 2011. Enterovirus was detected by reverse transcription PCR and directly genotyped by sequencing the PCR products. Phylogenetic analysis was based on the VP1 partial gene. Of 290 specimens, 277 (95.5%) tested positive for enterovirus. The major genotypes were EV71 (63.8%), CA10 (9.0%), CA6 (8.3%), CA16 (6.9%), CA12 (2.4%), and CA4 (1.4%). The EV71 strains belonged to the C4a subtype and CA16 belonged to the B subtype. CA6 was closely related to strains detected in Japan, Taiwan and China, and CA10, CA12 and CA4 were phylogenetically similar to other strains circulating in China. Mean hospital stays and the prevalence of complications in patients with EV71 infection were higher than those in patients in CA6, CA10 or CA16 infection (P treatment of HFMD patients.
Quality control for laboratory diagnosis for hand, foot and mouth ...
African Journals Online (AJOL)
McRoy
the system for laboratory diagnosis in HFMD. Despite using molecular based technique, some laboratories can still not possibly detect the pathogen.[11] For sure, this can cause the problem in disease control during the outbreak. It is noted that using internal control help improve diagnostic property of laboratory test.[12].
Directory of Open Access Journals (Sweden)
Hye Kyung Cho
2010-05-01
Full Text Available Purpose : Hand-foot-mouth disease (HFMD is a common viral illness in children, which is usually mild and self-limiting. However, in recent epidemics of HFMD in Asia, enterovirus 71 (EV71 has been recognized as a causative agent with severe neurological symptoms with or without cardiopulmonary involvement. HFMD was epidemic in Korea in the spring of 2009. Severe cases with complications including death have been reported. The clinical characteristics in children with neurologic manifestations of EV71 were studied in Ewha Womans University Mokdong Hospital. Methods : Examinations for EV71 were performed from the stools, respiratory secretion or CSF of children who presented neurologic symptoms associated with HFMD by realtime PCR. Clinical and radiologic data of the patients were collected and analyzed. Results : EV71 was isolated from the stool of 16 patients but not from respiratory secretion or CSF. Among the 16 patients, meningitis (n=10 was the most common manifestation, followed by Guillain-Barré syndrome (n=3, meningoencephalitis (n=2, poliomyelitis-like paralytic disease (n=1, and myoclonus (n=1. Gene analysis showed that most of them were caused by EV71 subgenotype C4a, which was prevalent in China in 2008. Conclusion : Because EV71 causes severe complications and death in children, a surveillance system to predict upcoming outbreaks should be established and maintained and adequate public health measures are needed to control disease.
Puenpa, Jiratchaya; Mauleekoonphairoj, John; Linsuwanon, Piyada; Suwannakarn, Kamol; Chieochansin, Thaweesak; Korkong, Sumeth; Theamboonlers, Apiradee; Poovorawan, Yong
2014-01-01
Hand, foot, and mouth disease (HFMD) and herpangina are common infectious diseases caused by several genotypes of human enterovirus species A and frequently occurring in young children. This study was aimed at analyzing enteroviruses from patients with these diseases in Thailand in 2012. Detection and genotype determination of enteroviruses were accomplished by reverse transcription-polymerase chain reaction and sequencing of the VP1 region. Enterovirus-positive samples were differentiated into 17 genotypes (coxsackievirus A4 (CAV4), A5, A6, A8, A9, A10, A12, A16, A21, B1, B2, B4, B5, echovirus 7, 16, 25 and Enterovirus 71). The result showed CAV6 (33.5%), followed by CAV16 (9.4%) and EV71 (8.8%) as the most frequent genotypes in HFMD, CAV8 (19.3%) in herpangina and CAV6 (1.5%) in influenza like illness. Enterovirus infections were most prevalent during July with 34.4% in HFMD, 39.8% in herpangina and 1.6% in ILI. The higher enterovirus infection associated with HFMD and herpangina occurred in infants over one year-old. This represents the first report describing the circulation of multiple enteroviruses in Thailand. PMID:24887237
Studies on Inhibition of Proliferation of Enterovirus-71 by Compound YZ-LY-0.
Yang, Qingzhan; Jie, Qing; Shaw, Neil; Li, Lei; Rao, Zihe; Yin, Zheng; Lou, Zhiyong
2015-01-01
In recent years, hand-foot-and-mouth disease (HFMD), which is caused by Enteroviruses, has emerged as a serious illness. It affects mainly children under the age of five and results in high fatality rates. Enterovirus 71 (EV71) is the main causative agent of HFMD in China and currently there are no effective anti-viral drugs available to treat HFMD. In the present study, we screened compounds for inhibition of proliferation of EV71. Compound YZ-LY-0 stalled the life cycle of EV71. The inhibitor exhibited EC50 value of 0.29 μm against SK-EV006 strain of EV71. Notably, YZ-LY-0 had low cytotoxicity (CC50 > 100 μM) and a high selectivity index (over 300) in Vero and RD cells. YZ-LY-0 in combination with an EV71 RdRp inhibitor or an entry inhibitor showed an antagonistic effect at very low concentrations. However, at higher concentrations the inhibitors exhibited a synergistic effect in inhibiting viral replication. Preliminary results on investigation of the mechanism of inhibition indicate that YZ-LY-0 does not block the entry of the virus in the host cell, but instead inhibits an early stage of EV71 replication. Our studies provide a potential clinical therapeutic option against EV71 infections and suggest that a combined application of YZ-LY-0 with other inhibitors could be more effective in the treatment of HFMD.
Yao, Xin; Bian, Lian-Lian; Lu, Wei-Wei; Li, Jing-Xin; Mao, Qun-Ying; Wang, Yi-Ping; Gao, Fan; Wu, Xing; Ye, Qiang; Xu, Miao; Li, Xiu-Ling; Zhu, Feng-Cai; Liang, Zheng-Lun
2015-12-01
Epidemiological data from active surveillance on human enterovirus, which could cause hand, foot, and mouth disease, were limited. An active surveillance system was used to investigate the enterovirus spectrum and the incidence of different enteroviruses in infants aged 6-35 months in Jiangsu Province from 2012 to 2013. Fifty-nine infants were randomly selected from 522 non-EV-A71/CV-A16 HFMD patients. We collected 173 throat swabs and 174 rectal swabs from these infants. RT-PCR was used to amplify 5'-UTR and VP1 regions of enteroviruses and the serotypes were determined by the sequence comparison using BLAST. Twenty-one non-EV-A71/CA16 enterovirus serotypes were detected in those infants. E16, E18 were firstly reported in HFMD patients. The four top common non-EV-A71/CV-A enteroviruses among infants were CV-B3, CV-A10, CV-A6, and E9 with the HFMD incidence rates at 1.4%, 0.84%, 0.56%, and 0.47%, respectively. Over 20.8% patients were co-infected with multiple enteroviruses. Neither the course of sickness nor clinical symptoms of the co-infected patients was more severe than those infected with single enterovirus. Two patients were infected different enterovirus successively within 2 months. Several new enterovirus serotypes and multiple models of infection associated with HFMD were discovered through the active surveillance system. These data provide a better understanding of the viral etiology of HFMD. © 2015 Wiley Periodicals, Inc.
Zhou, Hong-Tao; Yi, Hai-Su; Guo, Yong-Hui; Pan, Yu-Xian; Tao, Shao-Hua; Wang, Bin; Chen, Man-Jun; Yang, Mei; Yu, Nan
2016-03-16
A series of complications caused by enteroviruses, including meningitis, encephalitis, acute flaccid paralysis, acute cardiopulmonary failure, respiratory infection, and myocardial injury have been reported in hand, foot and mouth disease/herpangina (HFMD/HA). However, the complication of diarrhoea caused by enteroviruses has been neglected, and a summary of its clinical features and impact on HFMD/HA is unavailable. We included inpatients with HFMD/HA admitted to the Paediatric Department of Zhujiang Hospital during 2009-2012. We summarised and compared clinical data for cases with and without diarrhoea, and determined enterovirus serotypes by reverse transcriptase polymerase chain reaction and genotyping based on a partial-length fragment of viral protein 1 or the 5'-untranslated region. There were 804 inpatients with HFMD/HA and 28 (3.5%) presented with diarrhoea. Gastrointestinal symptoms were mild in most cases of diarrhoea (82.1%), with high prevalence of no dehydration (82.1%), short duration of diarrhoea (78.6%) and watery stools (75.0%). The prevalence of multi-organ dysfunction syndrome (10.7 vs 0.40%) (p = 0.001), hepatic injury (14.3 vs 3.4%) (p = 0.019), myocardial injury (21.4 vs 6.1%) (p = 0.002) and convulsion (21.4 vs 7.2%) (p = 0.016) was significantly higher in the diarrhoea than no diarrhoea group. There was no significant difference between the two groups regarding prevalence of death, altered consciousness, paralysis, central nervous system involvement, or acute respiratory infection. Most patients with diarrhoea caused by enteroviruses circulating in Guangdong Province in 2009-2012 had mild or moderate gastrointestinal symptoms. Although enterovirus-related diarrhoea caused additional multi-organ dysfunction syndrome, hepatic injury and myocardial injury in children with HFMD/HA, timely intervention efficiently reduced disease severity and improved outcome.
Ang, Lei Yin Emily; Too, Horng Khit Issac; Tan, Eng Lee; Chow, Tak-Kwong Vincent; Shek, Lynette Pei-Chi; Tham, Elizabeth Huiwen; Alonso, Sylvie
2016-06-24
Recurrence of hand, foot and mouth disease (HFMD) pandemics continues to threaten public health. Despite increasing awareness and efforts, effective vaccine and drug treatment have yet to be available. Probiotics have gained recognition in the field of healthcare worldwide, and have been extensively prescribed to babies and young children to relieve gastrointestinal (GI) disturbances and diseases, associated or not with microbial infections. Since the faecal-oral axis represents the major route of HFMD transmission, transient persistence of probiotic bacteria in the GI tract may confer some protection against HFMD and limit transmission among children. In this work, the antiviral activity of two commercially available probiotics, namely Lactobacillus reuteri Protectis (L. reuteri Protectis) and Lactobacillus casei Shirota (L. casei Shirota), was assayed against Coxsackieviruses and Enterovirus 71 (EV71), the main agents responsible for HFMD. In vitro infection set-ups using human skeletal muscle and colon cell lines were designed to assess the antiviral effect of the probiotic bacteria during entry and post-entry steps of the infection cycle. Our findings indicate that L. reuteri Protectis displays a significant dose-dependent antiviral activity against Coxsackievirus type A (CA) strain 6 (CA6), CA16 and EV71, but not against Coxsackievirus type B strain 2. Our data support that the antiviral effect is likely achieved through direct physical interaction between bacteria and virus particles, which impairs virus entry into its mammalian host cell. In contrast, no significant antiviral effect was observed with L. casei Shirota. Should the antiviral activity of L. reuteri Protectis observed in vitro be translated in vivo, such probiotics-based therapeutic approach may have the potential to address the urgent need for a safe and effective means to protect against HFMD and limit its transmission among children.
Directory of Open Access Journals (Sweden)
Huifang Tian
Full Text Available Hand, foot, and mouth disease (HFMD has been one of the most common infectious diseases in Shijiazhuang City, as is the situation in China overall. In the National HFMD surveillance system, the pathogen detection was focused on EV-A71 and CVA16, and therefore, information on the other EVs is very limited. In order to identify the circulating EV serotypes in the HFMD outbreaks in Shijiazhuang City during 2010-2012, 4045 patients presented with HFMD were recruited in the study, and clinical samples were investigated. Typing of EV serotypes was performed using the molecular typing methods, and phylogenetic analyses based on entire VP1 sequences of human enterovirus 71 (EV-A71, coxsackievirus A16 (CVA16, CVA10 and CVB3 was performed. The results revealed that EV-A71 and CVA16 were the 2 most important pathogens but the circulating trends of the 2 viruses showed a shift, the spread of EV-A71 became increasingly weak, whereas the spread of CVA16 became increasingly stronger. CVA10 and CVB3 were the third and fourth most prevalent pathogens, respectively. Co-infection of two viruses at the same time was not found in these samples. Based on entire VP1 region sequences, the phylogenetic analysis revealed that C4a subgenotype EV-A71, B1a and B1b subgenotype CVA16 continued to evolve. The CVA10 strains were assigned to 4 genotypes (A-D, whereas the CVB3 strains were assigned to 5 genotypes (A-E, with clear geographical and temporal-specific distributions. The Shijiazhuang CVA10 sequences belonged to 4 epidemic lineages within genotype C, whereas the Shijiazhuang CVB3 sequences belonged to 2 epidemic lineages within genotype E, which may have the same origins as the strains reported in other part of China. CVA10 and CVB3, 2 pathogens that were previously infrequently detected, were identified as pathogens causing the HFMD outbreaks. This study underscores the need for detailed laboratory-based surveillances of HFMD in mainland China.
Zhou, Hong-Tao; Guo, Yong-Hui; Chen, Man-Jun; Pan, Yu-Xian; Xue, Lin; Wang, Bin; Tao, Shao-Hua; Yu, Nan
2016-08-09
Enterovirus (EV)-related hand, foot, and mouth disease/herpangina (HFMD/HA) has been prevalent in Guangdong Province, China, since 2010. Clinical data for EV-related HFMD/HA inpatients admitted to the Department of Paediatrics of Zhujiang Hospital from 2010 to 2013 were retrospectively reviewed. The corresponding EV serotypes were also determined by reverse transcription-polymerase chain reaction or BLAST analysis of the sequenced partial lengths of the viral protein1/5'-untranslated region. A total of 867 eligible inpatients admitted during 2010-2013 were included in the study. Of these, the serotype of the responsible EV was successfully identified in 824 cases. The incidence of enterovirus 71 (EV71) infection amongst pediatric HFMD/HA inpatients decreased dramatically from 55.5 % in 2010 to 8.1 % in 2013, with a similar decrease recorded for coxsackievirus A16 (CVA16). However, the incidence of non-EV71/CVA16 infection increased from 30.0 % in 2010 to 83.8 % in 2013. We noted that the types of infection caused by different EV serotypes varied: EV71 was responsible for 100 % of the paralysis cases (26/26), 84.6 % of the deaths (11/13), and 84.1 % of cases with severe central nervous system involvement (SCNSI) (74/88); echovirus contributed to 16.4 % of the deaths (2/13) and 4.4 % of the SCNSI cases; and coxsackievirus accounted for only 2.2 % of the SCNSI cases (2/90). The clinical features of HFMD/HA cases varied greatly during the time period examined, with drastic changes in the hospitalization rates (45.1, 63.7, 36.4, and 19.1 % for 2010, 2011, 2012, and 21013, respectively), mortality rates (2.3, 0.9, 2.5, and 0.0 %, respectively), paralysis (5.1, 1.2, 5.4, and 0.0 %, respectively), SCNSI (16.8, 7.1, 12.7, and 2.2 %, respectively), and acute respiratory infection (21.1, 22.0, 45.9, and 59.0 %, respectively). The incidences of infection caused by different EV serotypes, along with the clinical features of HFMD/HA cases, changed drastically in
Age patterns and transmission characteristics of hand, foot and mouth disease in China
Directory of Open Access Journals (Sweden)
Jijun Zhao
2016-11-01
Full Text Available Abstract Background Hand, foot and mouth disease (HFMD has circulated in China and caused yearly outbreak. To understand the transmission of the disease and to assess the spatial variation in cases reported, we examined age-specific transmission characteristics and reporting rates of HFMD for 31 provinces in mainland China. Methods We first analyzed incidence spatial patterns and age-specific incidence patterns using dataset from 2008 to 2012. Transmission characteristics were estimated based on catalytic model. Reporting rates were estimated using a simple mass action model from “Time Series Susceptible Infectious Recovered” (TSIR modeling. Results We found age-specific spatial incidence patterns: age-specific proportions of HFMD cases varied geographically in China; larger case percentage was among children of 3–5 years old in the northern part of China and was among children of 0–2 years old in the southern part of China. Our analysis results revealed that: 1 reporting rates and transmission characteristics including the average age at infection, the force of infection and the basic reproduction number varied geographically in China; 2 patterns of the age-specific force of infection for 30 provinces were similar to that of childhood infections in developed countries; the age group that had the highest infection risk was 3–5 years old in 30 provinces, and 10–14 years old in Tibet; 3 a large difference in HFMD transmission existed between northwest region and southeast region; 4 transmission characteristics determined incidence patterns: the higher the disease transmission in a province, the earlier the annual seasonality started and the more case percentage was among children 0–2 years old and less among 3–5 years old. Conclusion Because HFMD has higher transmission than most childhood infections reported, high effective vaccine coverage is needed to substantially reduce HFMD incidence. Control measures before the vaccine
Determination of the vacancy formation enthalpy in chromium by positron annihilation
International Nuclear Information System (INIS)
Loper, G.D.; Smedskjaer, L.C.; Chason, M.K.; Siegel, R.W.
1985-01-01
Doppler broadening of the positron annihilation lineshape in 99.99 at. % pure chromium was measured over the temperature range 296 to 2049 0 K. The chromium sample was encapsulated in sapphire owing to its high vapor pressure near melting. Saturation-like behavior of the lineshape was observed near the melting temperature (2130 0 K). A two-state trapping model fit to the data yielded a vacancy formation enthalpy of 2.0 +- 0.2 eV. This result is discussed in relation to extant empirical relations for vacancy migration and self-diffusion in metals and to data from previous self-diffusion and annealing experiments in chromium. It is concluded that the observed vacancy ensemble is unlikely to be responsible for the measured self-diffusion behavior. The implications of the present results in terms of our understanding of mechanisms for self-diffusion in chromium and other refractory bcc metals are discussed
Theory and experiments on surface diffusion
Energy Technology Data Exchange (ETDEWEB)
Silvestri, W.L.
1998-11-01
The following topics were dealt with: adatom formation and self-diffusion on the Ni(100) surface, helium atom scattering measurements, surface-diffusion parameter measurements, embedded atom method calculations.
Mass transport in polyelectrolyte solutions
Schipper, F. J. M.; Leyte, J. C.
1999-02-01
The self-diffusion coefficients of the three components of a salt-free heavy-water solution of polymethacrylic acid, completely neutralized with tetra-methylammonium hydroxide, were measured over a broad concentration range. Three concentration regions were observed for the self-diffusion of both the polyions and the counterions. At polyion concentrations below 0.01 mol monomer kg-1, the dilute concentration regime for the polymer, the polyion self-diffusion coefficient approaches the self-diffusion coefficient of a freely diffusing rod upon dilution. At polyelectrolyte concentrations above 0.1 mol monomer kg-1, the self-diffusion coefficients of the solvent, the counterions and the polymer decreased with concentration, suggesting that this decrease is due to a topological constraint on the motions of the components. In the intermediate-concentration region, the self-diffusion coefficients of the polyions and the counterions are independent of the concentration. The polyion dynamic behaviour is, in the intermediate- and high-concentration regions, reasonably well described by that of a hard sphere, with a radius of 3.7 nm. A correct prediction for the solvent dynamics is given by the obstruction effect of this hard sphere on the solvent. The relative counterion self-diffusion coefficient is predicted almost quantitatively over the entire concentration range with the Poisson-Boltzmann-Smoluchowski model for the spherical cell, provided that the sphere radius and the number of charges are chosen appropriately (approximately the number of charges in a persistence length). Using this model, the dependence of the counterion self-diffusion coefficient on the ionic strength, polyion concentration and counterion radius is calculated quantitatively over a large concentration range.
International Nuclear Information System (INIS)
Dianoux, A.J.; Volino, F.; Heidemann, A.; Hervet, H.
1975-01-01
Neutron quasi-elastic scattering experiments in the smectic H, C and A phases of TBBA are presented, using the high resolution backscattering technique. The data are analyzed in terms of translational motion and are characterized by an apparent self diffusion coefficient Dsub(ap). The physical meaning of Dsub(ap) is discussed in terms of the true bulk self diffusion tensor and other kinds of translational motions [fr
Routine Pediatric Enterovirus 71 Vaccination in China: a Cost-Effectiveness Analysis.
Wu, Joseph T; Jit, Mark; Zheng, Yaming; Leung, Kathy; Xing, Weijia; Yang, Juan; Liao, Qiaohong; Cowling, Benjamin J; Yang, Bingyi; Lau, Eric H Y; Takahashi, Saki; Farrar, Jeremy J; Grenfell, Bryan T; Leung, Gabriel M; Yu, Hongjie
2016-03-01
China accounted for 87% (9.8 million/11.3 million) of all hand, foot, and mouth disease (HFMD) cases reported to WHO during 2010-2014. Enterovirus 71 (EV71) is responsible for most of the severe HFMD cases. Three EV71 vaccines recently demonstrated good efficacy in children aged 6-71 mo. Here we assessed the cost-effectiveness of routine pediatric EV71 vaccination in China. We characterized the economic and health burden of EV71-associated HFMD (EV71-HFMD) in China using (i) the national surveillance database, (ii) virological surveillance records from all provinces, and (iii) a caregiver survey on the household costs and health utility loss for 1,787 laboratory-confirmed pediatric cases. Using a static model parameterized with these data, we estimated the effective vaccine cost (EVC, defined as cost/efficacy or simply the cost of a 100% efficacious vaccine) below which routine pediatric vaccination would be considered cost-effective. We performed the base-case analysis from the societal perspective with a willingness-to-pay threshold of one times the gross domestic product per capita (GDPpc) and an annual discount rate of 3%. We performed uncertainty analysis by (i) accounting for the uncertainty in the risk of EV71-HFMD due to missing laboratory data in the national database, (ii) excluding productivity loss of parents and caregivers, (iii) increasing the willingness-to-pay threshold to three times GDPpc, (iv) increasing the discount rate to 6%, and (v) accounting for the proportion of EV71-HFMD cases not registered by national surveillance. In each of these scenarios, we performed probabilistic sensitivity analysis to account for parametric uncertainty in our estimates of the risk of EV71-HFMD and the expected costs and health utility loss due to EV71-HFMD. Routine pediatric EV71 vaccination would be cost-saving if the all-inclusive EVC is below US$10.6 (95% CI US$9.7-US$11.5) and would remain cost-effective if EVC is below US$17.9 (95% CI US$16.9-US$18.8) in
Routine Pediatric Enterovirus 71 Vaccination in China: a Cost-Effectiveness Analysis
Leung, Kathy; Xing, Weijia; Yang, Juan; Liao, Qiaohong; Cowling, Benjamin J.; Yang, Bingyi; Lau, Eric H. Y.; Takahashi, Saki; Farrar, Jeremy J.; Grenfell, Bryan T.; Leung, Gabriel M.; Yu, Hongjie
2016-01-01
Background China accounted for 87% (9.8 million/11.3 million) of all hand, foot, and mouth disease (HFMD) cases reported to WHO during 2010–2014. Enterovirus 71 (EV71) is responsible for most of the severe HFMD cases. Three EV71 vaccines recently demonstrated good efficacy in children aged 6–71 mo. Here we assessed the cost-effectiveness of routine pediatric EV71 vaccination in China. Methods and Findings We characterized the economic and health burden of EV71-associated HFMD (EV71-HFMD) in China using (i) the national surveillance database, (ii) virological surveillance records from all provinces, and (iii) a caregiver survey on the household costs and health utility loss for 1,787 laboratory-confirmed pediatric cases. Using a static model parameterized with these data, we estimated the effective vaccine cost (EVC, defined as cost/efficacy or simply the cost of a 100% efficacious vaccine) below which routine pediatric vaccination would be considered cost-effective. We performed the base-case analysis from the societal perspective with a willingness-to-pay threshold of one times the gross domestic product per capita (GDPpc) and an annual discount rate of 3%. We performed uncertainty analysis by (i) accounting for the uncertainty in the risk of EV71-HFMD due to missing laboratory data in the national database, (ii) excluding productivity loss of parents and caregivers, (iii) increasing the willingness-to-pay threshold to three times GDPpc, (iv) increasing the discount rate to 6%, and (v) accounting for the proportion of EV71-HFMD cases not registered by national surveillance. In each of these scenarios, we performed probabilistic sensitivity analysis to account for parametric uncertainty in our estimates of the risk of EV71-HFMD and the expected costs and health utility loss due to EV71-HFMD. Routine pediatric EV71 vaccination would be cost-saving if the all-inclusive EVC is below US$10.6 (95% CI US$9.7–US$11.5) and would remain cost-effective if EVC is below
Routine Pediatric Enterovirus 71 Vaccination in China: a Cost-Effectiveness Analysis.
Directory of Open Access Journals (Sweden)
Joseph T Wu
2016-03-01
Full Text Available China accounted for 87% (9.8 million/11.3 million of all hand, foot, and mouth disease (HFMD cases reported to WHO during 2010-2014. Enterovirus 71 (EV71 is responsible for most of the severe HFMD cases. Three EV71 vaccines recently demonstrated good efficacy in children aged 6-71 mo. Here we assessed the cost-effectiveness of routine pediatric EV71 vaccination in China.We characterized the economic and health burden of EV71-associated HFMD (EV71-HFMD in China using (i the national surveillance database, (ii virological surveillance records from all provinces, and (iii a caregiver survey on the household costs and health utility loss for 1,787 laboratory-confirmed pediatric cases. Using a static model parameterized with these data, we estimated the effective vaccine cost (EVC, defined as cost/efficacy or simply the cost of a 100% efficacious vaccine below which routine pediatric vaccination would be considered cost-effective. We performed the base-case analysis from the societal perspective with a willingness-to-pay threshold of one times the gross domestic product per capita (GDPpc and an annual discount rate of 3%. We performed uncertainty analysis by (i accounting for the uncertainty in the risk of EV71-HFMD due to missing laboratory data in the national database, (ii excluding productivity loss of parents and caregivers, (iii increasing the willingness-to-pay threshold to three times GDPpc, (iv increasing the discount rate to 6%, and (v accounting for the proportion of EV71-HFMD cases not registered by national surveillance. In each of these scenarios, we performed probabilistic sensitivity analysis to account for parametric uncertainty in our estimates of the risk of EV71-HFMD and the expected costs and health utility loss due to EV71-HFMD. Routine pediatric EV71 vaccination would be cost-saving if the all-inclusive EVC is below US$10.6 (95% CI US$9.7-US$11.5 and would remain cost-effective if EVC is below US$17.9 (95% CI US$16.9-US$18.8 in
Energy Technology Data Exchange (ETDEWEB)
Español, Pep [Dept. Física Fundamental, Universidad Nacional de Educación a Distancia, Aptdo. 60141, E-28080 Madrid (Spain); Donev, Aleksandar [Dept. Física Fundamental, Universidad Nacional de Educación a Distancia, Aptdo. 60141, E-28080 Madrid (Spain); Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, New York 10012 (United States)
2015-12-21
We derive a coarse-grained description of the dynamics of a nanoparticle immersed in an isothermal simple fluid by performing a systematic coarse graining of the underlying microscopic dynamics. As coarse-grained or relevant variables, we select the position of the nanoparticle and the total mass and momentum density field of the fluid, which are locally conserved slow variables because they are defined to include the contribution of the nanoparticle. The theory of coarse graining based on the Zwanzing projection operator leads us to a system of stochastic ordinary differential equations that are closed in the relevant variables. We demonstrate that our discrete coarse-grained equations are consistent with a Petrov-Galerkin finite-element discretization of a system of formal stochastic partial differential equations which resemble previously used phenomenological models based on fluctuating hydrodynamics. Key to this connection between our “bottom-up” and previous “top-down” approaches is the use of the same dual orthogonal set of linear basis functions familiar from finite element methods (FEMs), both as a way to coarse-grain the microscopic degrees of freedom and as a way to discretize the equations of fluctuating hydrodynamics. Another key ingredient is the use of a “linear for spiky” weak approximation which replaces microscopic “fields” with a linear FE interpolant inside expectation values. For the irreversible or dissipative dynamics, we approximate the constrained Green-Kubo expressions for the dissipation coefficients with their equilibrium averages. Under suitable approximations, we obtain closed approximations of the coarse-grained dynamics in a manner which gives them a clear physical interpretation and provides explicit microscopic expressions for all of the coefficients appearing in the closure. Our work leads to a model for dilute nanocolloidal suspensions that can be simulated effectively using feasibly short molecular dynamics
Shim, Youngseon; Kim, Hyung J; Jung, Younjoon
2012-01-01
Supercapacitors with two single-sheet graphene electrodes in the parallel plate geometry are studied via molecular dynamics (MD) computer simulations. Pure 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI+BF4-) and a 1.1 M solution of EMI+BF4- in acetonitrile are considered as prototypes of room-temperature ionic liquids (RTILs) and organic electrolytes. Electrolyte structure, charge density and associated electric potential are investigated by varying the charges and separation of the two electrodes. Multiple charge layers formed in the electrolytes in the vicinity of the electrodes are found to screen the electrode surface charge almost completely. As a result, the supercapacitors show nearly an ideal electric double layer behavior, i.e., the electric potential exhibits essentially a plateau behavior in the entire electrolyte region except for sharp changes in screening zones very close to the electrodes. Due to its small size and large charge separation, BF4- is considerably more efficient in shielding electrode charges than EMI+. In the case of the acetonitrile solution, acetonitrile also plays an important role by aligning its dipoles near the electrodes; however, the overall screening mainly arises from ions. Because of the disparity of shielding efficiency between cations and anions, the capacitance of the positively-charged anode is significantly larger than that of the negatively-charged cathode. Therefore, the total cell capacitance in the parallel plate configuration is primarily governed by the cathode. Ion conductivity obtained via the Green-Kubo (GK) method is found to be largely independent of the electrode surface charge. Interestingly, EMI+BF4- shows higher GK ion conductivity than the 1.1 M acetonitrile solution between two parallel plate electrodes.
Rovibrational coupling in molecular nitrogen at high temperature: An atomic-level study
Energy Technology Data Exchange (ETDEWEB)
Valentini, Paolo, E-mail: vale0142@umn.edu; Norman, Paul, E-mail: norma198@umn.edu; Zhang, Chonglin, E-mail: zhang993@umn.edu; Schwartzentruber, Thomas E., E-mail: schwart@aem.umn.edu [Department of Aerospace Engineering and Mechanics, College of Science and Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
2014-05-15
This article contains an atomic-level numerical investigation of rovibrational relaxation in molecular nitrogen at high temperature (>4000 K), neglecting dissociation. We conduct our study with the use of pure Molecular Dynamics (MD) and Classical Trajectory Calculations (CTC) Direct Simulation Monte Carlo (DSMC), verified to produce statistically identical results at the conditions of interest here. MD and CTC DSMC solely rely on the specification of a potential energy surface: in this work, the site-site Ling-Rigby potential. Additionally, dissociation is prevented by modeling the N–N bond either as a harmonic or an anharmonic spring. The selected molecular model was shown to (i) recover the shear viscosity (obtained from equilibrium pure MD Green-Kubo calculations) of molecular nitrogen over a wide range of temperatures, up to dissociation; (ii) predict well the near-equilibrium rotational relaxation behavior of N{sub 2}; (iii) reproduce vibrational relaxation times in excellent accordance with the Millikan-White correlation and previous semi-classical trajectory calculations in the low temperature range, i.e., between 4000 K and 10 000 K. By simulating isothermal relaxations in a periodic box, we found that the traditional two-temperature model assumptions become invalid at high temperatures (>10 000 K), due to a significant coupling between rotational and vibrational modes for bound states. This led us to add a modification to both the Jeans and the Landau-Teller equations to include a coupling term, essentially described by an additional relaxation time for internal energy equilibration. The degree of anharmonicity of the N{sub 2} bond determines the strength of the rovibrational coupling. Although neglecting N{sub 2} dissociation only provides a partial description of a nitrogen system at very high temperatures, high-energy trends for bound-bound transitions are essential to understand nonequilibrium gas flows, with possible implications on rovibration
Rovibrational coupling in molecular nitrogen at high temperature: An atomic-level study
International Nuclear Information System (INIS)
Valentini, Paolo; Norman, Paul; Zhang, Chonglin; Schwartzentruber, Thomas E.
2014-01-01
This article contains an atomic-level numerical investigation of rovibrational relaxation in molecular nitrogen at high temperature (>4000 K), neglecting dissociation. We conduct our study with the use of pure Molecular Dynamics (MD) and Classical Trajectory Calculations (CTC) Direct Simulation Monte Carlo (DSMC), verified to produce statistically identical results at the conditions of interest here. MD and CTC DSMC solely rely on the specification of a potential energy surface: in this work, the site-site Ling-Rigby potential. Additionally, dissociation is prevented by modeling the N–N bond either as a harmonic or an anharmonic spring. The selected molecular model was shown to (i) recover the shear viscosity (obtained from equilibrium pure MD Green-Kubo calculations) of molecular nitrogen over a wide range of temperatures, up to dissociation; (ii) predict well the near-equilibrium rotational relaxation behavior of N 2 ; (iii) reproduce vibrational relaxation times in excellent accordance with the Millikan-White correlation and previous semi-classical trajectory calculations in the low temperature range, i.e., between 4000 K and 10 000 K. By simulating isothermal relaxations in a periodic box, we found that the traditional two-temperature model assumptions become invalid at high temperatures (>10 000 K), due to a significant coupling between rotational and vibrational modes for bound states. This led us to add a modification to both the Jeans and the Landau-Teller equations to include a coupling term, essentially described by an additional relaxation time for internal energy equilibration. The degree of anharmonicity of the N 2 bond determines the strength of the rovibrational coupling. Although neglecting N 2 dissociation only provides a partial description of a nitrogen system at very high temperatures, high-energy trends for bound-bound transitions are essential to understand nonequilibrium gas flows, with possible implications on rovibration
Thermal parameter identification for non-Fourier heat transfer from molecular dynamics
Singh, Amit; Tadmor, Ellad B.
2015-10-01
Fourier's law leads to a diffusive model of heat transfer in which a thermal signal propagates infinitely fast and the only material parameter is the thermal conductivity. In micro- and nano-scale systems, non-Fourier effects involving coupled diffusion and wavelike propagation of heat can become important. An extension of Fourier's law to account for such effects leads to a Jeffreys-type model for heat transfer with two relaxation times. We propose a new Thermal Parameter Identification (TPI) method for obtaining the Jeffreys-type thermal parameters from molecular dynamics simulations. The TPI method makes use of a nonlinear regression-based approach for obtaining the coefficients in analytical expressions for cosine and sine-weighted averages of temperature and heat flux over the length of the system. The method is applied to argon nanobeams over a range of temperature and system sizes. The results for thermal conductivity are found to be in good agreement with standard Green-Kubo and direct method calculations. The TPI method is more efficient for systems with high diffusivity and has the advantage, that unlike the direct method, it is free from the influence of thermostats. In addition, the method provides the thermal relaxation times for argon. Using the determined parameters, the Jeffreys-type model is able to reproduce the molecular dynamics results for a short-duration heat pulse where wavelike propagation of heat is observed thereby confirming the existence of second sound in argon. An implementation of the TPI method in MATLAB is available as part of the online supplementary material.
Phonon optimized interatomic potential for aluminum
Directory of Open Access Journals (Sweden)
Murali Gopal Muraleedharan
2017-12-01
Full Text Available We address the problem of generating a phonon optimized interatomic potential (POP for aluminum. The POP methodology, which has already been shown to work for semiconductors such as silicon and germanium, uses an evolutionary strategy based on a genetic algorithm (GA to optimize the free parameters in an empirical interatomic potential (EIP. For aluminum, we used the Vashishta functional form. The training data set was generated ab initio, consisting of forces, energy vs. volume, stresses, and harmonic and cubic force constants obtained from density functional theory (DFT calculations. Existing potentials for aluminum, such as the embedded atom method (EAM and charge-optimized many-body (COMB3 potential, show larger errors when the EIP forces are compared with those predicted by DFT, and thus they are not particularly well suited for reproducing phonon properties. Using a comprehensive Vashishta functional form, which involves short and long-ranged interactions, as well as three-body terms, we were able to better capture interactions that reproduce phonon properties accurately. Furthermore, the Vashishta potential is flexible enough to be extended to Al2O3 and the interface between Al-Al2O3, which is technologically important for combustion of solid Al nano powders. The POP developed here is tested for accuracy by comparing phonon thermal conductivity accumulation plots, density of states, and dispersion relations with DFT results. It is shown to perform well in molecular dynamics (MD simulations as well, where the phonon thermal conductivity is calculated via the Green-Kubo relation. The results are within 10% of the values obtained by solving the Boltzmann transport equation (BTE, employing Fermi’s Golden Rule to predict the phonon-phonon relaxation times.
Atomistic Modeling of Thermal Conductivity of Epoxy Nanotube Composites
Fasanella, Nicholas A.; Sundararaghavan, Veera
2016-05-01
The Green-Kubo method was used to investigate the thermal conductivity as a function of temperature for epoxy/single wall carbon nanotube (SWNT) nanocomposites. An epoxy network of DGEBA-DDS was built using the `dendrimer' growth approach, and conductivity was computed by taking into account long-range Coulombic forces via a k-space approach. Thermal conductivity was calculated in the direction perpendicular to, and along the SWNT axis for functionalized and pristine SWNT/epoxy nanocomposites. Inefficient phonon transport at the ends of nanotubes is an important factor in the thermal conductivity of the nanocomposites, and for this reason discontinuous nanotubes were modeled in addition to long nanotubes. The thermal conductivity of the long, pristine SWNT/epoxy system is equivalent to that of an isolated SWNT along its axis, but there was a 27% reduction perpendicular to the nanotube axis. The functionalized, long SWNT/epoxy system had a very large increase in thermal conductivity along the nanotube axis (~700%), as well as the directions perpendicular to the nanotube (64%). The discontinuous nanotubes displayed an increased thermal conductivity along the SWNT axis compared to neat epoxy (103-115% for the pristine SWNT/epoxy, and 91-103% for functionalized SWNT/epoxy system). The functionalized system also showed a 42% improvement perpendicular to the nanotube, while the pristine SWNT/epoxy system had no improvement over epoxy. The thermal conductivity tensor is averaged over all possible orientations to see the effects of randomly orientated nanotubes, and allow for experimental comparison. Excellent agreement is seen for the discontinuous, pristine SWNT/epoxy nanocomposite. These simulations demonstrate there exists a threshold of the SWNT length where the best improvement for a composite system with randomly oriented nanotubes would transition from pristine SWNTs to functionalized SWNTs.
Energy Technology Data Exchange (ETDEWEB)
Kim, Woong Kee; Shim, Ji Hoon [Pohang University of Science and Technology, Pohang (Korea, Republic of); Kaviany Massoud [University of Michigan, Ann Arbor (United States)
2016-10-15
The analysis of such accidents (fate of the melt), requires accurate corium thermophysical properties data up to 5000 K. In addition, the initial corium melt superheat melt, determined from such properties, are key in predicting the fuel-coolant interactions (FCIs) and convection and retention of corium in accident scenarios, e.g., core-melt down corium discharge from reactor pressure vessels and spreading in external core-catcher. Due to the high temperatures, data on molten corium and its constituents are limited, so there are much data scatters and mostly extrapolations (even from solid state) have been used. Here we predict the thermophysical properties of molten UO{sub 2} and ZrO{sub 2} using classical molecular dynamics (MD) simulations (properties of corium are predicted using the mixture theories and UO{sub 2} and ZrO{sub 2} properties). The thermophysical properties (density, compressibility, heat capacity, viscosity and surface tension) of liquid UO{sub 2} and ZrO{sub 2} are predicted using classical molecular dynamics simulations, up to 5000 K. For atomic interactions, the CRG and the Teter potential models are found most appropriate. The liquid behavior is verified with the random motion of the constituent atoms and the pair-distribution functions, starting with the solid phase and raising the temperature to realize liquid phase. The viscosity and thermal conductivity are calculated with the Green-Kubo autocorrelation decay formulae and compared with the predictive models of Andrade and Bridgman. For liquid UO{sub 2}, the CRG model gives satisfactory MD predictions. For ZrO{sub 2}, the density is reliably predicted with the CRG potential model, while the compressibility and viscosity are more accurately predicted by the Teter model.
Energy Technology Data Exchange (ETDEWEB)
Kumagai, Tomohisa, E-mail: kumagai@criepi.denken.or.jp; Nakamura, Kaoru; Yamada, Susumu; Ohnuma, Toshiharu [Materials Science Research Laboratory, Central Research Institute of Electric Power Industry, 2-6-1 Nagasaka, Yokosuka, Kanagawa 240-0196 (Japan)
2016-08-14
The effects of guest atomic species in Si clathrates on the lattice thermal conductivity were studied using classical molecular dynamics calculations. The interaction between a host atom and a guest atom was described by the Morse potential function while that between host atoms was described by the Tersoff potential. The parameters of the potentials were newly determined for this study such that the potential curves obtained from first-principles calculations for the insertion of a guest atom into a Si cage were successfully reproduced. The lattice thermal conductivities were calculated by using the Green-Kubo method. The experimental lattice thermal conductivity of Ba{sub 8}Ga{sub 16}Si{sub 30} can be successfully reproduced using the method. As a result, the lattice thermal conductivities of type-I Si clathrates, M{sub 8}Si{sub 46} (M = Na, Mg, K, Ca Rb, Sr, Cs, or Ba), were obtained. It is found that the lattice thermal conductivities of M{sub 8}Si{sub 46}, where M is IIA elements (i.e., M = Mg, Ca, Sr, or Ba) tend to be lower than those of M{sub 8}Si{sub 46}, where M is IA elements (i.e., M = Na, K, Rb, or Cs). Those of {sup m}M{sub 8}Si{sub 46}, where m was artificially modified atomic weight were also obtained. The obtained lattice thermal conductivity can be regarded as a function of a characteristic frequency, f{sub c}. That indicates minimum values around f{sub c}=2-4 THz, which corresponds to the center of the frequencies of the transverse acoustic phonon modes associated with Si cages.
Si, Chao; Li, Liang; Lu, Gui; Cao, Bing-Yang; Wang, Xiao-Dong; Fan, Zhen; Feng, Zhi-Hai
2018-04-01
Graphene has received great attention due to its fascinating thermal properties. The inevitable defects in graphene, such as single vacancy, doping, and functional group, greatly affect the thermal conductivity. The sole effect of these defects on the thermal conductivity has been widely studied, while the mechanisms of the coupling effects are still open. We studied the combined effect of defects with N-doping, the -CH3 group, and single vacancy on the thermal conductivity of multi-layer graphene at various temperatures using equilibrium molecular dynamics with the Green-Kubo theory. The Taguchi orthogonal algorithm is used to evaluate the sensitivity of N-doping, the -CH3 group, and single vacancy. Sole factor analysis shows that the effect of single vacancy on thermal conductivity is always the strongest at 300 K, 700 K, and 1500 K. However, for the graphene with three defects, the single vacancy defect only plays a significant role in the thermal conductivity modification at 300 K and 700 K, while the -CH3 group dominates the thermal conductivity reduction at 1500 K. The phonon dispersion is calculated using a spectral energy density approach to explain such a temperature dependence. The combined effect of the three defects further decreases the thermal conductivity compared to any sole defect at both 300 K and 700 K. The weaker single vacancy effect is due to the stronger Umklapp scattering at 1500 K, at which the combined effect seriously covers almost all the energy gaps in the phonon dispersion relation, significantly reducing the phonon lifetimes. Therefore, the temperature dependence only appears on the multi-layer graphene with combined defects.
Kinetic evolution and correlation of fluctuations in an expanding quark gluon plasma
Sarwar, Golam; Alam, Jan-E.
2018-03-01
Evolution of spatially anisotropic perturbation created in the system formed after Relativistic Heavy Ion Collisions has been studied. The microscopic evolution of the fluctuations has been examined within the ambit of Boltzmann Transport Equation (BTE) in a hydrodynamically expanding background. The expansion of the background composed of quark gluon plasma (QGP) is treated within the framework of relativistic hydrodynamics. Spatial anisotropic fluctuations with different geometries have been evolved through Boltzmann equation. It is observed that the trace of such fluctuation survives the evolution. Within the relaxation time approximation, analytical results have been obtained for the evolution of these anisotropies. Explicit relations between fluctuations and transport coefficients have been derived. The mixing of various Fourier (or k) modes of the perturbations during the evolution of the system has been explicitly demonstrated. This study is very useful in understanding the presumption that the measured anisotropies in the data from heavy ion collisions at relativistic energies imitate the initial state effects. The evolution of correlation function for the perturbation in pressure has been studied and shows that the initial correlation between two neighbouring points in real space evolves to a constant value at later time which gives rise to Dirac delta function for the correlation function in Fourier space. The power spectrum of the fluctuation in thermodynamic quantities (like temperature estimated in this work) can be connected to the fluctuation in transverse momentum of the thermal hadrons measured experimentally. The bulk viscous coefficient of the QGP has been estimated by using correlations of pressure fluctuation with the help of Green-Kubo relation. Angular power spectrum of the anisotropies has been estimated in the appendix.
Phonon optimized interatomic potential for aluminum
Muraleedharan, Murali Gopal; Rohskopf, Andrew; Yang, Vigor; Henry, Asegun
2017-12-01
We address the problem of generating a phonon optimized interatomic potential (POP) for aluminum. The POP methodology, which has already been shown to work for semiconductors such as silicon and germanium, uses an evolutionary strategy based on a genetic algorithm (GA) to optimize the free parameters in an empirical interatomic potential (EIP). For aluminum, we used the Vashishta functional form. The training data set was generated ab initio, consisting of forces, energy vs. volume, stresses, and harmonic and cubic force constants obtained from density functional theory (DFT) calculations. Existing potentials for aluminum, such as the embedded atom method (EAM) and charge-optimized many-body (COMB3) potential, show larger errors when the EIP forces are compared with those predicted by DFT, and thus they are not particularly well suited for reproducing phonon properties. Using a comprehensive Vashishta functional form, which involves short and long-ranged interactions, as well as three-body terms, we were able to better capture interactions that reproduce phonon properties accurately. Furthermore, the Vashishta potential is flexible enough to be extended to Al2O3 and the interface between Al-Al2O3, which is technologically important for combustion of solid Al nano powders. The POP developed here is tested for accuracy by comparing phonon thermal conductivity accumulation plots, density of states, and dispersion relations with DFT results. It is shown to perform well in molecular dynamics (MD) simulations as well, where the phonon thermal conductivity is calculated via the Green-Kubo relation. The results are within 10% of the values obtained by solving the Boltzmann transport equation (BTE), employing Fermi's Golden Rule to predict the phonon-phonon relaxation times.
Thermophysical properties of liquid UO2, ZrO2 and corium by molecular dynamics and predictive models
International Nuclear Information System (INIS)
Kim, Woong Kee; Shim, Ji Hoon; Kaviany Massoud
2016-01-01
The analysis of such accidents (fate of the melt), requires accurate corium thermophysical properties data up to 5000 K. In addition, the initial corium melt superheat melt, determined from such properties, are key in predicting the fuel-coolant interactions (FCIs) and convection and retention of corium in accident scenarios, e.g., core-melt down corium discharge from reactor pressure vessels and spreading in external core-catcher. Due to the high temperatures, data on molten corium and its constituents are limited, so there are much data scatters and mostly extrapolations (even from solid state) have been used. Here we predict the thermophysical properties of molten UO 2 and ZrO 2 using classical molecular dynamics (MD) simulations (properties of corium are predicted using the mixture theories and UO 2 and ZrO 2 properties). The thermophysical properties (density, compressibility, heat capacity, viscosity and surface tension) of liquid UO 2 and ZrO 2 are predicted using classical molecular dynamics simulations, up to 5000 K. For atomic interactions, the CRG and the Teter potential models are found most appropriate. The liquid behavior is verified with the random motion of the constituent atoms and the pair-distribution functions, starting with the solid phase and raising the temperature to realize liquid phase. The viscosity and thermal conductivity are calculated with the Green-Kubo autocorrelation decay formulae and compared with the predictive models of Andrade and Bridgman. For liquid UO 2 , the CRG model gives satisfactory MD predictions. For ZrO 2 , the density is reliably predicted with the CRG potential model, while the compressibility and viscosity are more accurately predicted by the Teter model
Hong, Bingbing
2012-03-01
A molecular model of silica nanoparticles grafted with poly(ethylene oxide) oligomers has been developed for predicting the transport properties of nanoparticle organic-hybrid materials (NOHMs). Ungrafted silica nanoparticles in a medium of poly(ethylene oxide) oligomers were also simulated to clarify the effect of grafting on the dynamics of nanoparticles and chains. The model approximates nanoparticles as solid spheres and uses a united-atom representation for chains, including torsional and bond-bending interactions. The calculated viscosities from Green-Kubo relationships and temperature extrapolation are of the same order of magnitude as experimental data but show a smaller activation energy relative to real NOHMs systems. Grafted systems have higher viscosities, smaller diffusion coefficients, and slower chain dynamics than the ungrafted ones at high temperatures. At lower temperatures, grafted systems exhibit faster dynamics for both nanoparticles and chains relative to ungrafted systems, because of lower aggregation of particles and enhanced correlations between nanoparticles and chains. This agrees with the experimental observation that NOHMs have liquidlike behavior in the absence of a solvent. For both grafted and ungrafted systems at low temperatures, increasing chain length reduces the volume fraction of nanoparticles and accelerates the dynamics. However, at high temperatures, longer chains slow down nanoparticle diffusion. From the Stokes-Einstein relationship, it was determined that the coarse-grained treatment of nanoparticles leads to slip on the nanoparticle surfaces. Grafted systems obey the Stokes-Einstein relationship over the temperature range simulated, but ungrafted systems display deviations from it. © 2012 American Chemical Society.
Krekelberg, William P; Siderius, Daniel W; Shen, Vincent K; Truskett, Thomas M; Errington, Jeffrey R
2017-12-12
Using molecular simulations, we investigate the relationship between the pore-averaged and position-dependent self-diffusivity of a fluid adsorbed in a strongly attractive pore as a function of loading. Previous work (Krekelberg, W. P.; Siderius, D. W.; Shen, V. K.; Truskett, T. M.; Errington, J. R. Connection between thermodynamics and dynamics of simple fluids in highly attractive pores. Langmuir 2013, 29, 14527-14535, doi: 10.1021/la4037327) established that pore-averaged self-diffusivity in the multilayer adsorption regime, where the fluid exhibits a dense film at the pore surface and a lower density interior pore region, is nearly constant as a function of loading. Here we show that this puzzling behavior can be understood in terms of how loading affects the fraction of particles that reside in the film and interior pore regions as well as their distinct dynamics. Specifically, the insensitivity of pore-averaged diffusivity to loading arises from the approximate cancellation of two factors: an increase in the fraction of particles in the higher diffusivity interior pore region with loading and a corresponding decrease in the particle diffusivity in that region. We also find that the position-dependent self-diffusivities scale with the position-dependent density. We present a model for predicting the pore-average self-diffusivity based on the position-dependent self-diffusivity, which captures the unusual characteristics of pore-averaged self-diffusivity in strongly attractive pores over several orders of magnitude.
Schipper, F. J. M.; Hollander, J. G.; Leyte, J. C.
1998-10-01
The self-diffusion coefficient of tetra-methylammonium counterion in solutions of polymethacrylic acid in 0953-8984/10/41/004/img1 has been measured over a broad polyion concentration range at a constant degree of neutralization and at different ratios of added monovalent or bivalent salt to polyions. A maximum counterion self-diffusion coefficient was observed as a function of polyion concentration. The value of the self-diffusion coefficient at the maximum did not depend on the valency of the added salt. The maximum was found at lower polymer concentrations and with a higher value, when the ratio of added salt to polyions was increased, as predicted by the Poisson-Boltzmann-Smoluchowski equation in the cylindrical cell model for polyelectrolytes. At higher polyion concentrations a maximum counterion self-diffusion coefficient against the ratio of added salt and polyions was observed, which has not been reported before. Upon increasing this ratio the electrostatic potential of the polyelectrolyte gets screened, leading to an increase of the counterion self-diffusion coefficient. Concentration effects of the added salt on the other hand ultimately lead to a decrease of the counterion self-diffusion coefficient, which explains the occurrence of a maximum.
Energy Technology Data Exchange (ETDEWEB)
Park, Byung Sa; Yu, In Kyu; Lee, Byung Hee [Eulji University Hospital, Daejeon (Korea, Republic of)
2011-02-15
We report here on the MR findings of the first Korean case of hand-foot-mouth disease (HFMD) complicated by acute enterovirus 71 (EV 71) encephalitis in a 33-month old girl. Conventional MR images of the patient showed the increased signal intensity (SI) on a T2-weighted image (WI) at the posterior aspect of the medulla, the pontine tegmen, the bilateral dentate nuclei of the cerebellum and the midbrain. There was no evidence of abnormal SI or contrast enhancement at the same areas of the brain on the pre- and post-contrast T1-WI. The diffusion weighted images (DWI) also revealed the bilateral symmetrical strong high SI at the posterior aspect of the medulla and pontine tegmen and there was low SI at the same areas on the apparent diffusion coefficient (ADC) map. DWI in addition to the conventional MR imaging may be helpful for the early detection of acute EV 71 encephalitis in a patient with HFMD
Directory of Open Access Journals (Sweden)
Zhu Liye
2011-06-01
Full Text Available Abstract Enterovirus 71 (EV71 has emerged as a significant pathogen causing large outbreaks in China for the past 3 years. Developing an EV71 vaccine is urgently needed to stop the spread of the disease; however, the adaptive immune response of humans to EV71 infection remains unclear. We examined the neutralizing antibody titers in HFMD patients and compared them to those of asymptomatic healthy children and young adults. We found that 80% of HFMD patients became positive for neutralizing antibodies against EV71 (GMT = 24.3 one day after the onset of illness. The antibody titers in the patients peaked two days (GMT = 79.5 after the illness appeared and were comparable to the level of adults (GMT = 45.2. Noticeably, the antibody response was not correlated with disease severity, suggesting that cellular immune response, besides neutralizing antibodies, could play critical role in controlling the outcome of EV71 infection in humans.
Cyclical Patterns of Hand, Foot and Mouth Disease Caused by Enterovirus A71 in Malaysia
NikNadia, NMN; Sam, I-Ching; Rampal, Sanjay; WanNorAmalina, WMZ; NurAtifah, Ghazali; Verasahib, Khebir; Ong, Chia Ching; MohdAdib, MohdAidinniza; Chan, Yoke Fun
2016-01-01
Enterovirus A71 (EV-A71) is an important emerging pathogen causing large epidemics of hand, foot and mouth disease (HFMD) in children. In Malaysia, since the first EV-A71 epidemic in 1997, recurrent cyclical epidemics have occurred every 2–3 years for reasons that remain unclear. We hypothesize that this cyclical pattern is due to changes in population immunity in children (measured as seroprevalence). Neutralizing antibody titers against EV-A71 were measured in 2,141 residual serum samples collected from children ≤12 years old between 1995 and 2012 to determine the seroprevalence of EV-A71. Reported national HFMD incidence was highest in children Malaysia is mainly due to the fall of population immunity accompanying the accumulation of susceptible children between epidemics. This study will impact the future planning, timing and target populations for vaccine programs. PMID:27010319
Takahashi, Saki; Liao, Qiaohong; Van Boeckel, Thomas P; Xing, Weijia; Sun, Junling; Hsiao, Victor Y; Metcalf, C Jessica E; Chang, Zhaorui; Liu, Fengfeng; Zhang, Jing; Wu, Joseph T; Cowling, Benjamin J; Leung, Gabriel M; Farrar, Jeremy J; van Doorn, H Rogier; Grenfell, Bryan T; Yu, Hongjie
2016-02-01
Hand, foot, and mouth disease (HFMD) is a common childhood illness caused by serotypes of the Enterovirus A species in the genus Enterovirus of the Picornaviridae family. The disease has had a substantial burden throughout East and Southeast Asia over the past 15 y. China reported 9 million cases of HFMD between 2008 and 2013, with the two serotypes Enterovirus A71 (EV-A71) and Coxsackievirus A16 (CV-A16) being responsible for the majority of these cases. Three recent phase 3 clinical trials showed that inactivated monovalent EV-A71 vaccines manufactured in China were highly efficacious against HFMD associated with EV-A71, but offered no protection against HFMD caused by CV-A16. To better inform vaccination policy, we used mathematical models to evaluate the effect of prospective vaccination against EV-A71-associated HFMD and the potential risk of serotype replacement by CV-A16. We also extended the model to address the co-circulation, and implications for vaccination, of additional non-EV-A71, non-CV-A16 serotypes of enterovirus. Weekly reports of HFMD incidence from 31 provinces in Mainland China from 1 January 2009 to 31 December 2013 were used to fit multi-serotype time series susceptible-infected-recovered (TSIR) epidemic models. We obtained good model fit for the two-serotype TSIR with cross-protection, capturing the seasonality and geographic heterogeneity of province-level transmission, with strong correlation between the observed and simulated epidemic series. The national estimate of the basic reproduction number, R0, weighted by provincial population size, was 26.63 for EV-A71 (interquartile range [IQR]: 23.14, 30.40) and 27.13 for CV-A16 (IQR: 23.15, 31.34), with considerable variation between provinces (however, predictions about the overall impact of vaccination were robust to this variation). EV-A71 incidence was projected to decrease monotonically with higher coverage rates of EV-A71 vaccination. Across provinces, CV-A16 incidence in the post-EV-A71
International Nuclear Information System (INIS)
Park, Byung Sa; Yu, In Kyu; Lee, Byung Hee
2011-01-01
We report here on the MR findings of the first Korean case of hand-foot-mouth disease (HFMD) complicated by acute enterovirus 71 (EV 71) encephalitis in a 33-month old girl. Conventional MR images of the patient showed the increased signal intensity (SI) on a T2-weighted image (WI) at the posterior aspect of the medulla, the pontine tegmen, the bilateral dentate nuclei of the cerebellum and the midbrain. There was no evidence of abnormal SI or contrast enhancement at the same areas of the brain on the pre- and post-contrast T1-WI. The diffusion weighted images (DWI) also revealed the bilateral symmetrical strong high SI at the posterior aspect of the medulla and pontine tegmen and there was low SI at the same areas on the apparent diffusion coefficient (ADC) map. DWI in addition to the conventional MR imaging may be helpful for the early detection of acute EV 71 encephalitis in a patient with HFMD
Directory of Open Access Journals (Sweden)
Saki Takahashi
2016-02-01
Full Text Available Hand, foot, and mouth disease (HFMD is a common childhood illness caused by serotypes of the Enterovirus A species in the genus Enterovirus of the Picornaviridae family. The disease has had a substantial burden throughout East and Southeast Asia over the past 15 y. China reported 9 million cases of HFMD between 2008 and 2013, with the two serotypes Enterovirus A71 (EV-A71 and Coxsackievirus A16 (CV-A16 being responsible for the majority of these cases. Three recent phase 3 clinical trials showed that inactivated monovalent EV-A71 vaccines manufactured in China were highly efficacious against HFMD associated with EV-A71, but offered no protection against HFMD caused by CV-A16. To better inform vaccination policy, we used mathematical models to evaluate the effect of prospective vaccination against EV-A71-associated HFMD and the potential risk of serotype replacement by CV-A16. We also extended the model to address the co-circulation, and implications for vaccination, of additional non-EV-A71, non-CV-A16 serotypes of enterovirus.Weekly reports of HFMD incidence from 31 provinces in Mainland China from 1 January 2009 to 31 December 2013 were used to fit multi-serotype time series susceptible-infected-recovered (TSIR epidemic models. We obtained good model fit for the two-serotype TSIR with cross-protection, capturing the seasonality and geographic heterogeneity of province-level transmission, with strong correlation between the observed and simulated epidemic series. The national estimate of the basic reproduction number, R0, weighted by provincial population size, was 26.63 for EV-A71 (interquartile range [IQR]: 23.14, 30.40 and 27.13 for CV-A16 (IQR: 23.15, 31.34, with considerable variation between provinces (however, predictions about the overall impact of vaccination were robust to this variation. EV-A71 incidence was projected to decrease monotonically with higher coverage rates of EV-A71 vaccination. Across provinces, CV-A16 incidence in the
Zhang, Xiao; Sun, Chunyun; Xiao, Xiangqian; Pang, Lin; Shen, Sisi; Zhang, Jie; Cen, Shan; Yang, Burton B; Huang, Yuming; Sheng, Wang; Zeng, Yi
2016-01-01
Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) are members of the Picornaviridae family and are considered the main causative agents of hand, foot and mouth disease (HFMD). In recent decades large HFMD outbreaks caused by EV71 and CVA16 have become significant public health concerns in the Asia-Pacific region. Vaccines and antiviral drugs are unavailable to prevent EV71 and CVA16 infection. In the current study, a chimeric antibody targeting a highly conserved peptide in the EV71 VP4 protein was isolated by using a phage display technique. The antibody showed cross-neutralizing capability against EV71 and CVA16 in vitro. The results suggest that this phage display-derived antibody will have great potential as a broad neutralizing antibody against EV71 and CVA16 after affinity maturation and humanization.
Wu, Yidong; Chen, Dong; Zhou, Jun; Wang, Jie; Zhao, Shiyong; Shao, Qimin; Wei, Yi
2015-05-01
To detect the anti-enterovirus 71 (EV71) IgM level in cerebrospinal fluid (CSF) of children with severe hand, foot and mouth disease (HFMD) induced by EV71 and then analyze the relationships among the IgM antibody levels, CSF routine examination and patients' clinical features, and thus to evaluate the clinical significance of anti-EV71 IgM as a new indicator for early diagnosis of children with severe HFMD induced by EV71. A total of 294 laboratory-confirmed cases of children with severe HFMD infected with EV71 were enrolled into the research group from March 2014 to June 2014, consisting of 53 fatal cases and 241 severe cases, and their CSF samples underwent enzyme-linked immunosorbent assay (ELISA) for anti-EV71 IgM levels, CSF routine and biochemical tests. Forty-one cases of children with severe HFMD induced by other enteroviruses were collected as antibody-testing control group during the same period. In the research group, the total positive rate of anti-EV71 IgM in 294 CSF samples of children with severe HFMD infected by EV71 was 60.2% (177/294); the positive rate of anti-EV71 IgM in the fatal HFMD subgroup was 62.3% (33/53); the positive rate of anti-EV71 IgM in the severe HFMD subgroup was 59.8% (144/241). In the control group, the results of CSF anti-EV71 IgM tests were all negative (0/41). In the research group, patients in antibody-positive subgroup (2.5±1.2) years old were younger than those in antibody-negative subgroup (2.9±1.1) years old (t=2.595, P=0.010). And within the antibody-positive subgroup, the patients ((1.9±0.7) years old) with fatal type disease were younger than those ((2.6±1.2) years old) with severe type disease (t=3.150, P=0.002). The CSF nucleated cells count and positive rates (105 (56,180) ×10(6) /L; 97.7% (173/177)) in antibody-positive subgroup were higher than those (62(30,150) ×10(6) /L; 83.8% (98/117)) in antibody-negative subgroup (Z=3.663, P=0.000; χ(2)=19.089, P=0.000). In antibody-positive subgroup, the percentage
Directory of Open Access Journals (Sweden)
del Sel Sylvia
2009-01-01
Full Text Available Abstract Background Human enterovirus 71 (HEV71 can cause Hand, foot, and mouth disease (HFMD with neurological complications, which may rapidly progress to fulminant cardiorespiratory failure, and death. Early recognition of children at risk is the key to reduce acute mortality and morbidity. Methods We examined data collected through a prospective clinical study of HFMD conducted between 2000 and 2006 that included 3 distinct outbreaks of HEV71 to identify risk factors associated with neurological involvement in children with HFMD. Results Total duration of fever ≥ 3 days, peak temperature ≥ 38.5°C and history of lethargy were identified as independent risk factors for neurological involvement (evident by CSF pleocytosis in the analysis of 725 children admitted during the first phase of the study. When they were validated in the second phase of the study, two or more (≥ 2 risk factors were present in 162 (65% of 250 children with CSF pleocytosis compared with 56 (30% of 186 children with no CSF pleocytosis (OR 4.27, 95% CI2.79–6.56, p rd or later day of febrile illness, the sensitivity, specificity, PPV and NPV of ≥ 2 risk factors predictive of CSF pleocytosis were 75%(57/76, 59%(27/46, 75%(57/76 and 59%(27/46, respectively. Conclusion Three readily elicited clinical risk factors were identified to help detect children at risk of neurological involvement. These risk factors may serve as a guide to clinicians to decide the need for hospitalization and further investigation, including cerebrospinal fluid examination, and close monitoring for disease progression in children with HFMD.
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Elizabeth A. Caine
2015-11-01
Full Text Available Hand, foot, and mouth disease (HFMD has recently emerged as a major public health concern across the Asian-Pacific region. Enterovirus 71 (EV71 and Coxsackievirus A16 (CVA16 are the primary causative agents of HFMD, but other members of the Enterovirus A species, including Coxsackievirus A6 (CVA6, can cause disease. The lack of small animal models for these viruses have hampered the development of a licensed HFMD vaccine or antivirals. We have previously reported on the development of a mouse model for EV71 and demonstrated the protective efficacy of an inactivated EV71 vaccine candidate. Here, mouse-adapted strains of CVA16 and CVA6 were produced by sequential passage of the viruses through mice deficient in interferon (IFN α/β (A129 and α/β and γ (AG129 receptors. Adapted viruses were capable of infecting 3 week-old A129 (CVA6 and 12 week-old AG129 (CVA16 mice. Accordingly, these models were used in active and passive immunization studies to test the efficacy of a trivalent vaccine candidate containing inactivated EV71, CVA16, and CVA6. Full protection from lethal challenge against EV71 and CVA16 was observed in trivalent vaccinated groups. In contrast, monovalent vaccinated groups with non-homologous challenges failed to cross protect. Protection from CVA6 challenge was accomplished through a passive transfer study involving serum raised against the trivalent vaccine. These animal models will be useful for future studies on HFMD related pathogenesis and the efficacy of vaccine candidates.
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Dawei Guan
Full Text Available BACKGROUND: Since 1997, several countries within the Asian Pacific region have been affected by one or more massive outbreaks of Hand Foot and Mouth Disease (HFMD. Virus typing experiments revealed that these outbreaks were caused by strains of human enterovirus 71 (EV71 belonging to several different, recently emerged subgenogroups. In mainland China, a different situation was observed. The first outbreak, localized in Shangdong Province, was reported in 2007, and was followed by a wide-spread outbreak in mainland China in 2008. Since then, numbers of reported HFMD cases have been persistently high. METHODOLOGY/PRINCIPAL FINDINGS: To gain insight in the epidemiological behavior of EV71 in China, we studied genetic diversity and EV71 population dynamics to address whether the increase in number of reported EV71 infections reflects a real increase in viral spread or is just the result of increased awareness and surveillance. We used systematically collected VP1 gene sequences of 257 EV71 strains collected in Guangdong province from 2008 to 2010 as part of HFMD surveillance activities, and supplemented them with 305 GenBank EV71 reference stains collected in China from 1998 to 2010. All isolates from Guangdong Province belonged to subgenogroup C4. Viral population dynamics indicated that the increased reporting of HFMD in China since 2007 reflects a real increase in viral spread and continued replacement of viral lineages through time. Amino acid sequence comparisons revealed substitution of amino acid in residues 22, 145 and 289 through time regularly with the VP1 gene of EV71 strains isolated in mainland China from 1998 to 2010. CONCLUSIONS: EV71 strains isolated in mainland China mainly belonged to subgenogroup C4. There was exponential growth of the EV71 virus population in 2007 and 2008. There was amino acid substitution through time regularly with the VP1 gene which possibly increased viral spread and/or ability of the virus to circulate
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Jiahua Pan
2012-01-01
Full Text Available Objectives: This study sought to determine the high risk factors for severe hand, foot, and mouth disease (HFMD. Materials and Methods: Retrospective 229 severe HFMD cases from four hospitals in FuYang, HeFei, and BoZhou (Anhui Provincial Hospital, Fuyang City People′s Hospital, No. 2 People′s Hospital of Fuyang and Bozhou city People′s Hospital in 2008-2009 were studied, with 140 mild HFMD cases in the same area. Using univariate and multivariate logistic regression analyses, the high risk factors of HFMD were identified by comparing clinical and laboratory findings between severe cases and mild cases. Results: There was a significant difference in age, total duration of fever, rate of respiratory and heart, shake of limbs, white blood cell count, blood sugar, and CK-MB between the two groups. Univariate logistic regression analysis showed that severe cases were associated with age (<3 years, withdrawnness and lethargy, shake of limbs, tachycardia, total leukocyte count (≥17×10 9 /l, blood sugar (≥7 mmol/l, and CK-MB (≥16 mmol/l. Furthermore, age (<3 years, withdrawnness, and lethargy, shake of limbs, WBC (≥17×10 9 /l, and CK-MB (≥16 mmol/l were found to be high risk factors for severe cases after multivariate logistic regression analysis. Conclusions: Clinicians should give importance to these risk factors. Early recognition of children at risk and timely intervention is the key to reduce acute mortality and morbidity.
Lim, C T K; Jiang, L; Ma, S; James, L; Ang, L W
2016-04-01
Coxsackievirus A6 (CV-A6), coxsackievirus A16 (CV-A16) and enterovirus 71 (EV-A71) were the major enteroviruses causing nationwide hand, foot and mouth disease (HFMD) epidemics in Singapore in the last decade. We estimated the basic reproduction number (R 0) of these enteroviruses to obtain a better understanding of their transmission dynamics. We merged records of cases from HFMD outbreaks reported between 2007 and 2012 with laboratory results from virological surveillance. R 0 was estimated based on the cumulative number of reported cases in the initial growth phase of each outbreak associated with the particular enterovirus type. A total of 33 HFMD outbreaks were selected based on the inclusion criteria specified for our study, of which five were associated with CV-A6, 13 with CV-A16, and 15 with EV-A71. The median R 0 was estimated to be 5·04 [interquartile range (IQR) 3·57-5·16] for CV-A6, 2·42 (IQR 1·85-3·36) for CV-A16, and 3·50 (IQR 2·36-4·53) for EV-A71. R 0 was not significantly associated with number of infected children (P = 0·86), number of exposed children (P = 0·94), and duration of the outbreak (P = 0·05). These enterovirus-specific R 0 estimates will be helpful in providing insights into the potential growth of future HFMD epidemics and outbreaks for timely implementation of disease control measures, together with disease dynamics such as severity of the cases.
Puenpa, Jiratchaya; Suwannakarn, Kamol; Chansaenroj, Jira; Vongpunsawad, Sompong; Poovorawan, Yong
2017-10-01
Real-time reverse-transcription polymerase chain reaction (rRT-PCR) to detect enterovirus 71 (EV-A71) and coxsackievirus A16 (CV-A16) has facilitated the rapid and accurate identification of the two most common etiological agents underlying hand, foot, and mouth disease (HFMD). However, the worldwide emergence of CV-A6 infection in HFMD necessitates development of an improved multiplex rRT-PCR method. To rapidly determine the etiology of HFMD, two rRT-PCR assays using TaqMan probes were developed to differentiate among three selected common enteroviruses (EV-A71, CV-A16 and CV-A6) and to enable broad detection of enteroviruses (pan-enterovirus assay). No cross-reactions were observed with other RNA viruses examined. The detection limits of both assays were 10 copies per microliter for EV-A71, CV-A6 and CV-A16, and pan-enterovirus. The methods showed high accuracy (EV-A71, 90.6%; CV-A6, 92.0%; CV-A16, 100%), sensitivity (EV-A71, 96.5%; CV-A6, 95.8%; CV-A16, 99.0%), and specificity (EV-A71, 100%; CV-A6, 99.9%; CV-A16, 99.9%) in testing clinical specimens (n=1049) during 2014-2016, superior to those of conventional RT-PCR. Overall, the multiplex rRT-PCR assays enabled highly sensitive detection and rapid simultaneous typing of EV-A71, CV-A6 and CV-A16, and enteroviruses, rendering them feasible and attractive methods for large-scale surveillance of enteroviruses associated with HFMD outbreaks. Copyright © 2017 Elsevier B.V. All rights reserved.
Caine, Elizabeth A; Fuchs, Jeremy; Das, Subash C; Partidos, Charalambos D; Osorio, Jorge E
2015-11-17
Hand, foot, and mouth disease (HFMD) has recently emerged as a major public health concern across the Asian-Pacific region. Enterovirus 71 (EV71) and Coxsackievirus A16 (CVA16) are the primary causative agents of HFMD, but other members of the Enterovirus A species, including Coxsackievirus A6 (CVA6), can cause disease. The lack of small animal models for these viruses have hampered the development of a licensed HFMD vaccine or antivirals. We have previously reported on the development of a mouse model for EV71 and demonstrated the protective efficacy of an inactivated EV71 vaccine candidate. Here, mouse-adapted strains of CVA16 and CVA6 were produced by sequential passage of the viruses through mice deficient in interferon (IFN) α/β (A129) and α/β and γ (AG129) receptors. Adapted viruses were capable of infecting 3 week-old A129 (CVA6) and 12 week-old AG129 (CVA16) mice. Accordingly, these models were used in active and passive immunization studies to test the efficacy of a trivalent vaccine candidate containing inactivated EV71, CVA16, and CVA6. Full protection from lethal challenge against EV71 and CVA16 was observed in trivalent vaccinated groups. In contrast, monovalent vaccinated groups with non-homologous challenges failed to cross protect. Protection from CVA6 challenge was accomplished through a passive transfer study involving serum raised against the trivalent vaccine. These animal models will be useful for future studies on HFMD related pathogenesis and the efficacy of vaccine candidates.
New coxsackievirus B4 genotype circulating in Inner Mongolia Autonomous Region, China.
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Xiaoling Tian
Full Text Available Hand, foot, and mouth disease (HFMD surveillance was initiated in the Inner Mongolia Autonomous Region of China in 2007, a crucial scrutiny for monitoring the prevalence of enterovirus serotypes associated with HFMD patients. However, this surveillance mostly focused on enterovirus 71 (EV-A71 and coxsackievirus A16; therefore, information on other enterovirus serotypes is limited. To identify the other circulating enterovirus serotypes in the HFMD outbreaks in Inner Mongolia in 2010, clinical samples from HFMD patients were investigated. Six coxsackievirus B4 (CVB4 strains were isolated and phylogenetic analyses of VP1 sequences were performed. Full-length genome sequences of two representative CVB4 isolates were acquired and similarity plot and bootscanning analyses were performed. The phylogenetic dendrogram indicated that all CVB4 strains could be divided into 5 genotypes (Genotypes I-V with high bootstrap support (90-100%. The CVB4 prototype strain (JVB was the sole member of genotype I. CVB4 strains belonging to genotype II, which were once common in Europe and the Americas, seemingly disappeared and gave way to genotype III and IV strains, which appear to be the dominant circulating strains in the world. All Chinese CVB4 strains belonged to Genotype V, a newly identified genotype supported by a high bootstrap value (100%, and are circulating only in mainland of China. Intertypic recombination occurred in the Chinese CVB4 strains with novel unknown serotype EV-B donor sequences. Two Chinese CVB4 strains had a virulent residue at position 129 of VP1, and one strain also had a virulent residue at position 16 of VP4. Increased surveillance is needed to monitor the emergence of new genetic lineages of enteroviruses in areas that are often associated with large-scale outbreaks. In addition, continued monitoring of enteroviruses by clinical surveillance and genetic characterization should be enhanced.
2013-01-01
Background A rapid expansion of hand, foot, and mouth disease (HFMD) outbreaks has occurred and caused deaths in China in recent years, but little is known about the other etiologic agents except enterovirus 71 (EV71) and coxsackievirus A 16 (CA16). The objective of this study is to determine the genotype compositions of enterovirus causing HFMD in Shanghai and identify any associations between enterovirus types and clinical manifestations. Methods Stool specimens were collected from patients hospitalized for treatment of HFMD, from May 2010 to April 2011. Enterovirus was detected by reverse transcription PCR and directly genotyped by sequencing the PCR products. Phylogenetic analysis was based on the VP1 partial gene. Results Of 290 specimens, 277 (95.5%) tested positive for enterovirus. The major genotypes were EV71 (63.8%), CA10 (9.0%), CA6 (8.3%), CA16 (6.9%), CA12 (2.4%), and CA4 (1.4%). The EV71 strains belonged to the C4a subtype and CA16 belonged to the B subtype. CA6 was closely related to strains detected in Japan, Taiwan and China, and CA10, CA12 and CA4 were phylogenetically similar to other strains circulating in China. Mean hospital stays and the prevalence of complications in patients with EV71 infection were higher than those in patients in CA6, CA10 or CA16 infection (P enterovirus genotypes. It deserves our attention as early identification of enterovirus genotypes is important for diagnosis and treatment of HFMD patients. PMID:24148902
Ogi, Miki; Yano, Yoshihiko; Chikahira, Masatsugu; Takai, Denshi; Oshibe, Tomohiro; Arashiro, Takeshi; Hanaoka, Nozomu; Fujimoto, Tsuguto; Hayashi, Yoshitake
2017-08-01
Coxsackievirus A6 (CV-A6) is an enterovirus, which is known to cause herpangina. However, since 2009 it has frequently been isolated from children with hand, foot, and mouth disease (HFMD). In Japan, CV-A6 has been linked to HFMD outbreaks in 2011 and 2013. In this study, the full-length genome sequencing of CV-A6 strains were analyzed to identify the association with clinical manifestations. Five thousand six hundred and twelve children with suspected enterovirus infection (0-17 years old) between 1999 and 2013 in Hyogo Prefecture, Japan, were enrolled. Enterovirus infection was confirmed with reverse transcriptase-PCR in 753 children (791 samples), 127 of whom (133 samples) were positive for CV-A6 based on the direct sequencing of the VP4 region. The complete genomes of CV-A6 from 22 positive patients with different clinical manifestations were investigated. A phylogenetic analysis divided these 22 strains into two clusters based on the VP1 region; cluster I contained strains collected in 1999-2009 and mostly related to herpangina, and cluster II contained strains collected in 2011-2013 and related to HFMD outbreak. Based on the full-length polyprotein analysis, the amino acid differences between the strains in cluster I and II were 97.7 ± 0.28%. Amino acid differences were detected in 17 positions within the polyprotein. Strains collected in 1999-2009 and those in 2011-2013 were separately clustered by phylogenetic analysis based on 5'UTR and 3Dpol region, as well as VP1 region. In conclusion, HFMD outbreaks by CV-A6 were recently frequent in Japan and the accumulation of genomic change might be associated with the clinical course. © 2017 Wiley Periodicals, Inc.
Circadian rhythm disruption was observed in hand, foot, and mouth disease patients.
Zhu, Yu; Jiang, Zhou; Xiao, Guoguang; Cheng, Suting; Wen, Yang; Wan, Chaomin
2015-03-01
Hand, foot, and mouth disease (HFMD) with central nerve system complications may rapidly progress to fulminated cardiorespiratory failure, with higher mortality and worse prognosis. It has been reported that circadian rhythms of heart rate (HR) and respiratory rate are useful in predicting prognosis of severe cardiovascular and neurological diseases. The present study aims to investigate the characteristics of the circadian rhythms of HR, respiratory rate, and temperature in HFMD patients with neurological complications. Hospitalized HFMD patients including 33 common cases (common group), 61 severe cases (severe group), and 9 critical cases (critical group) were contrasted retrospectively. Their HR, respiratory rate, and temperatures were measured every 4 hours during the first 48-hour in the hospital. Data were analyzed with the least-squares fit of a 24-hour cosine function by the single cosinor and population-mean cosinor method. Results of population-mean cosinor analysis demonstrated that the circadian rhythm of HR, respiratory rate, and temperature was present in the common and severe group, but absent in the critical group. The midline-estimating statistic of rhythm (MESOR) (P = 0.016) and acrophase (P circadian characteristics of HR among 3 groups. Compared with the common group, the MESOR of temperature and respiratory rate was significantly higher, and acrophase of temperature and respiratory rate was 2 hours ahead in the severe group, critical HFMD patients lost their population-circadian rhythm of temperature, HR, and respiratory rate. The high values of temperature and respiratory rate for the common group were concentrated between 3 and 9 PM, whereas those for the severe group were more dispersive. And the high values for the critical group were equally distributed in 24 hours of the day. Circadian rhythm of patients' temperature in the common group was the same as the normal rhythm of human body temperature. Circadian rhythm of patients
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Yan Zhang
Full Text Available BACKGROUND: Enterovirus 71 (EV71 infection can lead to a rapidly progressing, life-threatening, and severe neurological disease in young children, including the development of human hand, foot, and mouth disease (HFMD. This study aims to further characterize the specific immunological features in EV71-mediated HFMD patients presenting with differing degrees of disease severity. METHODOLOGY: Comprehensive cytokine and chemokine expression were broadly evaluated by cytokine antibody array in EV71-infected patients hospitalized for HFMD compared to Coxsackievirus A16-infected patients and age-matched healthy controls. More detailed analysis using Luminex-based cytokine bead array was performed in EV71-infected patients stratified into diverse clinic outcomes. Additionally, immune cell frequencies in peripheral blood and EV71-specific antibodies in plasma were also examined. PRINCIPAL FINDINGS: Expression of several cytokines and chemokines were significantly increased in plasma from EV71-infected patients compared to healthy controls, which further indicated that: (1 GM-CSF, MIP-1β, IL-2, IL-33, and IL-23 secretion was elevated in patients who rapidly developed disease and presented with uncomplicated neurological damage; (2 G-CSF and MCP-1 were distinguishably secreted in EV71 infected very severe patients presenting with acute respiratory failure; (3 IP-10, MCP-1, IL-6, IL-8, and G-CSF levels were much higher in cerebrospinal fluid than in plasma from patients with neurological damage; (4 FACS analysis revealed that the frequency of CD19(+HLADR(+ mature B cells dynamically changed over time during the course of hospitalization and was accompanied by dramatically increased EV71-specific antibodies. Our data provide a panoramic view of specific immune mediator and cellular immune responses of HFMD and may provide useful immunological profiles for monitoring the progress of EV71-induced fatal neurological symptoms with acute respiratory failure.
Huang, Xueyong; Liu, Guohua; Hu, Xiaoning; Du, Yanhua; Li, Xingle; Xu, Yuling; Chen, Haomin; Xu, Bianli
2014-04-01
To clone and express the recombinant capsid protein VP2 of enterovirus type 71 (EV71) and to identify the immune activity of expressed protein in order to build a basis for the investigation work of vaccine and diagnostic antigen. VP2 gene of EV71 was amplified by PCR, and then was cut by restriction enzyme and inserted into expression vector pMAL-c2X. The positive recombinants were transferred into E.coli TB1, the genetically engineered bacteria including pMAL-c2X-VP2 plasmids were induced by isopropyl thiogalactoside ( IPTG) , and the expression products were analyzed by SDS-PAGE and western blotting method. EV71 IgM antibody detection method by ELISA was set up, and the sensitivity and specificity of this method was assessed; 60 neutralizing antibody positive serum samples from hand foot and mouth disease (HFMD) patients were determined, of which 52 samples were positive and 8 samples were negative; a total of 88 acute phase serum samples of HFMD patients diagnosed in clinical were also detected. VP2 gene of 762 bp was obtained by PCR, the gene segment inserted into the recombinant vector was identified using restriction enzyme digestion. The recombinant vector could express a specific about 71 500 fusion protein in E.coli by SDS-PAGE. The purified recombinant protein of EV71-VP2 can react with the serum of HFMD patients to produce a specific band by western blotting. The sensitivity and specificity of ELISA was 87% and 83%, respectively. Of the 88 acute phase serum samples from children with HFMD, 48 samples (55%) were positive by the ELISA assay. VP2 gene of EV71 has been cloned and a prokaryotic high expression system for VP2 gene was successfully constructed in the present study. The recombination EV71-VP2 has well antigenicity, which could be useful for developing diagnose reagent or vaccine of EV71.
D Wang; X Wang; Y Geng; C An
2014-01-01
Purpose : The objective of this study was to develop a sensitive, specific and rapid approach to diagnose hand foot and mouth disease (HFMD) for an early treatment by using loop-mediated isothermal amplification (LAMP) technique. Materials and Methods : A reverse-transcription loop-mediated isothermal amplification (RT-LAMP) for detecting EV71 virus was developed, the specificity and sensitivity of RT-LAMP was tested, and the clinical specimens was assayed by the RT-LAMP comparing with conven...
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Xiuhui Li
2013-01-01
Full Text Available Background. Herb-derived compound andrographolide sulfonate (called Xiyanping injection recommended control measure for severe hand, foot, and mouth disease (HFMD by the Ministry of Health (China during the 2010 epidemic. However, there is a lack of good quality evidence directly comparing the efficacy of Andrographolide Sulfonate combination therapy with conventional therapy. Methods. 230 patients were randomly assigned to 7–10 days of Andrographolide Sulfonate 5–10 mg/Kg/day and conventional therapy, or conventional therapy alone. Results. The major complications occurred less often after Andrographolide Sulfonate (2.6% versus 12.1%; risk difference [RD], 0.94; 95% CI, 0.28–1.61; P=0.006. Median fever clearance times were 96 hours (CI, 80 to 126 for conventional therapy recipients and 48 hours (CI, 36 to 54 for Andrographolide Sulfonate combination-treated patients (χ2=16.57, P<0.001. The two groups did not differ in terms of HFMD-cause mortality (P=1.00 and duration of hospitalization (P=0.70. There was one death in conventional therapy group. No important adverse event was found in Andrographolide Sulfonate combination therapy group. Conclusions. The addition of Andrographolide Sulfonate to conventional therapy reduced the occurrence of major complications, fever clearance time, and the healing time of typical skin or oral mucosa lesions in children with severe HFMD.
A dominant EV71-specific CD4+ T cell epitope is highly conserved among human enteroviruses.
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Ruicheng Wei
Full Text Available CD4+ T cell-mediated immunity plays a central role in determining the immunopathogenesis of viral infections. However, the role of CD4+ T cells in EV71 infection, which causes hand, foot and mouth disease (HFMD, has yet to be elucidated. We applied a sophisticated method to identify promiscuous CD4+ T cell epitopes contained within the sequence of the EV71 polyprotein. Fifteen epitopes were identified, and three of them are dominant ones. The most dominant epitope is highly conserved among enterovirus species, including HFMD-related coxsackieviruses, HFMD-unrelated echoviruses and polioviruses. Furthermore, the CD4+ T cells specific to the epitope indeed cross-reacted with the homolog of poliovirus 3 Sabin. Our findings imply that CD4+ T cell responses to poliovirus following vaccination, or to other enteroviruses to which individuals may be exposed in early childhood, may have a modulating effect on subsequent CD4+ T cell response to EV71 infection or vaccine.
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Shih-Min Wang
Full Text Available Brainstem encephalitis (BE and pulmonary edema (PE are notable complications of enterovirus 71 (EV71 infection.This study investigated the immunoregulatory characterizations of EV71 neurological complications by disease severity and milrinone treatment.Patients <18 years with virologically confirmed EV71 infections were enrolled and divided into 2 groups: the hand, foot, and mouth disease (HFMD or BE group, and the autonomic nervous system (ANS dysregulation or PE group. Cytokine and cyclic adenosine monophosphate (cAMP levels, and the regulatory T cell (Tregs profiles of the patients were determined.Patients with ANS dysregulation or PE exhibited significantly low frequency of CD4(+CD25(+Foxp3+ and CD4(+Foxp3(+ T cells compared with patients with HFMD or BE. The expression frequency of CD4-CD8- was also significantly decreased in patients with ANS dysregulation or PE. Among patients with ANS dysregulation or PE, the expression frequency of CD4+Foxp3+ increased markedly after milrinone treatment, and was associated with reduction of plasma levels IL-6, IL-8 and IL-10. Plasma concentrations of cAMP were significantly decreased in patients with ANS dysregulation or PE compared with patients with HFMD or BE; however, cAMP levels increased after milrinone treatment.These findings suggested decreased different regulatory T populations and cAMP expression correlate with increased EV71 disease severity. Improved outcome after milrinone treatment may associate with increased regulatory T populations, cAMP expression and modulation of cytokines levels.
Expression and immunogenicity of novel subunit enterovirus 71 VP1 antigens
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Xu, Juan [China-US Vaccine Research Center, The First Affiliated Hospital, Nanjing Medical University (China); Department of Microbiology and Immunology, Nanjing Medical University (China); Wang, Shixia [China-US Vaccine Research Center, The First Affiliated Hospital, Nanjing Medical University (China); Department of Medicine, University of Massachusetts Medical School (United States); Gan, Weihua [Department of Pediatrics, The Second Affiliated Hospital, Nanjing Medical University (China); Zhang, Wenhong [Department of Infectious Diseases, Huashan Hospital, Fudan University (China); Ju, Liwen [School of Public Health, Fudan University (China); Huang, Zuhu [Department of Infectious Diseases, The First Affiliated Hospital, Nanjing Medical University (China); China-US Vaccine Research Center, The First Affiliated Hospital, Nanjing Medical University (China); Lu, Shan, E-mail: shan.lu@umassmed.edu [Department of Infectious Diseases, The First Affiliated Hospital, Nanjing Medical University (China); China-US Vaccine Research Center, The First Affiliated Hospital, Nanjing Medical University (China); Department of Medicine, University of Massachusetts Medical School (United States)
2012-04-20
Highlights: Black-Right-Pointing-Pointer EV71 is a major emerging infectious disease in many Asian countries. Black-Right-Pointing-Pointer Inactivated EV71 vaccines are in clinical studies but their safety and efficacy are unknown. Black-Right-Pointing-Pointer Developing subunit based EV71 vaccines is significant and novel antigen design is needed. Black-Right-Pointing-Pointer DNA immunization is an efficient tool to test the immunogenicity of VP1 based EV71 vaccines. Black-Right-Pointing-Pointer Multiple VP1 antigens are developed showing immunogenic potential. -- Abstract: Hand, foot, and mouth disease (HFMD) is a common viral illness in young children. HFMD is caused by viruses belonging to the enterovirus genus of the picornavirus family. Recently, enterovirus 71 (EV71) has emerged as a virulent agent for HFMD with severe clinical outcomes. In the current report, we conducted a pilot antigen engineering study to optimize the expression and immunogenicity of subunit VP1 antigen for the design of EV71 vaccines. DNA immunization was adopted as a simple technical approach to test different designs of VP1 antigens without the need to express VP1 protein in vitro first. Our studies indicated that the expression and immunogenicity of VP1 protein can be improved with alternated VP1 antigen designs. Data presented in the current report revealed novel pathways to optimize the design of VP1 antigen-based EV71 vaccines.
Clinical features for 89 deaths of hand, foot and mouth disease in Guangxi, China, 2014
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Wei Lin
2017-11-01
Full Text Available Objectives: The aim of this study is to summarize the risk factors of severe Hand, foot and mouth disease (HFMD and explore the clinical characteristics of pulmonary edema (PE and non-PE in the deceased patients with HFMD. Methods: We identified 89 HFMD deaths which were separated into the PE group or non-PE group. Next, patients were divided based on their initial admission to hospitals as stage 1, 2, 3, or 4; at this point, their clinical manifestations were compared. Results: There were 87 cases in the PE group, and 2 cases in the non-PE group. In the PE group, the difference in median time for patients at different stages from onset to symptoms, showed no significant difference (p > 0.05. The etiology was detected as a positive rate for enterovirus 71 (EV71 of 89.19%, which showed a more severe course than other etiologies. The white blood cell (WBC counts, lymphocyte (LYM counts and creatine kinase MB (CK-MB counts of patients admitted in different stages increased significantly with severity (p < 0.05. Conclusions: There may be two clinical subtypes, mostly PE and rarely non-PE, in the deceased patients with HMFD. EV71 and risk factors such as an increased WBC count are associated with a severe course of HMFD. Keywords: Hand, foot, and mouth disease, Pulmonary edema, Non-pulmonary edema, Death cases
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Luan-Yin Chang
2007-01-01
Full Text Available Sixteen cases from the 1980-1981 Taiwan outbreak of hand, foot and mouth disease (HFMD associated with central nervous system involvement were identified: nine had polio-like syndrome, four had encephalitis or encephalomyelitis, one had cerebellitis, and two had aseptic meningitis. They all had fever, five (31% had documented myoclonic jerk, and 15 (93% had HFMD. Their mean blood leukocyte count was 12,490/mL, and five (31% had leukocytosis (> 15,000/mL; mean cerebrospinal fluid (CSF leukocyte count was 156/mL, CSF protein was 57 mg/dL and CSF glucose was 57 mg/dL. Two patients with HFMD plus encephalitis died within 1 day of hospitalization, and one of them had acute cardiopulmonary failure mimicking myocarditis. Twenty years later, at least one male patient had sequelae of polio-like syndrome and was therefore exempted from military service. Clinical severity was comparable to the 1998 EV71 epidemic. [J Formos Med Assoc 2007;106(2:173-176
Short-term impacts of floods on enteric infectious disease in Qingdao, China, 2005-2011.
Zhang, F; Liu, Z; Gao, L; Zhang, C; Jiang, B
2016-11-01
The current study aimed to examine the relationship between floods and the three enteric infectious diseases, namely bacillary dysentery (BD), hand-foot-mouth disease (HFMD) and other infectious diarrhoea (OID) in Qingdao, China. Relative risks (RRs) and 95% confidence intervals (CIs) of floods on BD, HFMD and OID were calculated using a quasi-Poisson generalized linear model, adjusting for daily average temperature, daily average relative humidity, and seasonal and long-term temporal trends. Two separate models within two different periods were designed. Model 1 for the summer period showed that floods were positively associated with BD for 4- to 12-day lags, with the greatest effects for 7-day (RR 1·41, 95% CI 1·22-1·62) and 11-day (RR 1·42, 95% CI 1·22-1·64) lags. Similar findings were found in model 2 for the whole study period for 5- to 12-day lags. However, HFMD and OID were not significantly associated with floods in both models. Results from this study will provide insight into the health risks associated with floods and may help inform public health precautionary measures for such disasters.
Liu, L; Luan, R S; Yin, F; Zhu, X P; Lü, Q
2016-01-01
Hand, foot and mouth disease (HFMD) is an infectious disease caused by enteroviruses, which usually occurs in children aged ARIMA) model to forecast HFMD incidence in Sichuan province, China. HFMD infection data from January 2010 to June 2014 were used to fit the ARIMA model. The coefficient of determination (R 2), normalized Bayesian Information Criterion (BIC) and mean absolute percentage of error (MAPE) were used to evaluate the goodness-of-fit of the constructed models. The fitted ARIMA model was applied to forecast the incidence of HMFD from April to June 2014. The goodness-of-fit test generated the optimum general multiplicative seasonal ARIMA (1,0,1) × (0,1,0)12 model (R 2 = 0·692, MAPE = 15·982, BIC = 5·265), which also showed non-significant autocorrelations in the residuals of the model (P = 0·893). The forecast incidence values of the ARIMA (1,0,1) × (0,1,0)12 model from July to December 2014 were 4103-9987, which were proximate forecasts. The ARIMA model could be applied to forecast HMFD incidence trend and provide support for HMFD prevention and control. Further observations should be carried out continually into the time sequence, and the parameters of the models could be adjusted because HMFD incidence will not be absolutely stationary in the future.
Mauleekoonphairoj, John; Puenpa, Jiratchaya; Korkong, Sumeth; Vongpunsawad, Sompong; Poovorawan, Yong
2015-11-01
Human enterovirus (EV) infection causes hand, foot, and mouth disease (HFMD) and herpangina (HA). We studied the prevalence of enterovirus (EV) among patients with HFMD and HA in Thailand during 2013. We conducted a study in archived specimens of patients sent for screening for enterovirus. A total of 203 clinical specimens from 184 individuals with painful blister in the oropharynx and on the palms, soles, knees, elbows or buttock were examined by semi-nested polymerase chain reaction (PCR) for the 5'UTR and VP1 genes of EV. Eighty-six samples were positive: EV71 was detected in 14 (30%), CV-A8 in 12 (26%) and CV-A16 in 10 (21%). Classification of EV species detected revealed that 46 specimens were EV-A, 14 specimens were EV-B, 1 specimen was EV-D, and 16 specimens were positive for unclassified enterovirus. The majority of individuals with EV infection were aged 2-6 years. Multiple EV-A serotypes were detected among HFMD and HA patients in our study.
Expression and immunogenicity of novel subunit enterovirus 71 VP1 antigens
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Xu, Juan; Wang, Shixia; Gan, Weihua; Zhang, Wenhong; Ju, Liwen; Huang, Zuhu; Lu, Shan
2012-01-01
Highlights: ► EV71 is a major emerging infectious disease in many Asian countries. ► Inactivated EV71 vaccines are in clinical studies but their safety and efficacy are unknown. ► Developing subunit based EV71 vaccines is significant and novel antigen design is needed. ► DNA immunization is an efficient tool to test the immunogenicity of VP1 based EV71 vaccines. ► Multiple VP1 antigens are developed showing immunogenic potential. -- Abstract: Hand, foot, and mouth disease (HFMD) is a common viral illness in young children. HFMD is caused by viruses belonging to the enterovirus genus of the picornavirus family. Recently, enterovirus 71 (EV71) has emerged as a virulent agent for HFMD with severe clinical outcomes. In the current report, we conducted a pilot antigen engineering study to optimize the expression and immunogenicity of subunit VP1 antigen for the design of EV71 vaccines. DNA immunization was adopted as a simple technical approach to test different designs of VP1 antigens without the need to express VP1 protein in vitro first. Our studies indicated that the expression and immunogenicity of VP1 protein can be improved with alternated VP1 antigen designs. Data presented in the current report revealed novel pathways to optimize the design of VP1 antigen-based EV71 vaccines.
Impact of genetic changes, pathogenicity and antigenicity on Enterovirus- A71 vaccine development.
Yee, Pinn Tsin Isabel; Laa Poh, Chit
2017-06-01
Enterovirus-A71 (EV-A71) is an etiological agent of the hand, foot and mouth disease (HFMD). EV-A71 infection produces high fever and ulcers in children. Some EV-A71 strains produce severe infections leading to pulmonary edema and death. Although the protective efficacy of the inactivated vaccine (IV) was ≥90% against mild HFMD, there was approximately 80% protection against severe HFMD. The monovalent EV-A71 IV elicits humoral immunity but lacks long-term immunogenicity. Spontaneous mutations of the EV-A71 genome could lead to antigenicity changes and the virus may not be neutralized by antibodies elicited by the IV. A better alternative would be the live attenuated vaccine (LAV) that elicits cellular and humoral immunity. The LAV induces excellent antigenicity and chances of reversion is reduced by presence of multiple mutations which could reduce pathogenicity. Besides CV-A16, outbreaks have been caused by CV-A6 and CV-A10, hence the development of bivalent and trivalent vaccines is required. Copyright © 2017 Elsevier Inc. All rights reserved.
Directory of Open Access Journals (Sweden)
Sun Junling
2010-05-01
Full Text Available Abstract Hand, foot and mouth disease (HFMD, a common contagious disease that usually affects children, is normally mild but can have life-threatening manifestations. It can be caused by enteroviruses, particularly Coxsackieviruses and human enterovirus 71 (HEV71 with highly variable clinical manifestations. In the spring of 2008, a large, unprecedented HFMD outbreak in Fuyang city of Anhui province in the central part of southeastern China resulted in a high aggregation of fatal cases. In this study, epidemiologic and clinical investigations, laboratory testing, and genetic analyses were performed to identify the causal pathogen of the outbreak. Of the 6,049 cases reported between 1 March and 9 May of 2008, 3023 (50% were hospitalized, 353 (5.8% were severe and 22 (0.36% were fatal. HEV71 was confirmed as the etiological pathogen of the outbreak. Phylogenetic analyses of entire VP1 capsid protein sequence of 45 Fuyang HEV71 isolates showed that they belong to C4a cluster of the C4 subgenotype. In addition, genetic recombinations were found in the 3D region (RNA-dependent RNA polymerase, a major component of the viral replication complex of the genome between the Fuyang HEV71 strain and Coxsackievirus A16 (CV-A16, resulting in a recombination virus. In conclusion, an emerging recombinant HEV71 was responsible for the HFMD outbreak in Fuyang City of China, 2008.
Song, Jae-Hyoung; Park, Kwisung; Shim, Aeri; Kwon, Bo-Eun; Ahn, Jae-Hee; Choi, Young Jin; Kim, Jae Kyung; Yeo, Sang-Gu; Yoon, Kyungah; Ko, Hyun-Jeong
2015-02-01
Coxsackievirus A group 16 strain (CVA16) is one of the predominant causative agents of hand, foot, and mouth disease (HFMD). Using a specimen from a male patient with HFMD, we isolated and performed sequencing of the Korean CVA16 strain and compared it with a G10 reference strain. Also, we were investigated the effects of medicinal plant extract on the cytopathic effects (CPE) by CPE reduction assay against Korean CVA16. Phylogenetic analysis showed that the Korean CVA16 isolate belonged to cluster B-1 and was closely related to the strain PM-15765-00 isolated in Malaysia in 2000. The Korean CVA16 isolate showed 73.2% nucleotide identity to the G10 prototype strain and 98.7% nucleotide identity to PM-15765-00. Next, we assessed whether the Korean CVA16 isolate could be used for in vitro screening of antiviral agents to treat HFMD infection. Vero cells infected with the Korean CVA16 isolate showed a cytopathic effect 2 days after the infection, and the treatment of cells with Cornus officinalis, Acer triflorum, Pulsatilla koreana, and Clematis heracleifolia var. davidiana Hemsl extracts exhibited strong antiviral activity against CVA16. Collectively, our work provides potential candidates for the development of vaccine and novel drugs to treat the CVA16 strain isolated from a Korean patient.
Chest imaging characteristics of hand-foot-mouth disease in children
International Nuclear Information System (INIS)
Ma Bo; Chen Ruigang; Dou Shewei; Zhu Xiaonian; Shi Dapeng
2010-01-01
Objective: To study radiological characteristics of hand-foot-mouth disease (HFMD) in children. Methods: The chest X-ray films of 1295 children patients of HFMD were analyzed, for the general X-ray manifestations and the evolution. Results: A total of 1427 films was obtained from all patients, in which 1203 cases were normal and 224 cases were abnormal. The interstitial changes characterized the abnormal group, mainly as increased and vague lung markings, increased hilar shadows (137 cases). The parenchyma changes appeared as patchy exudative shadows(49 cases). Short-term dynamic observation was applied in 62 cases, 38 cases pulmonary disease progression manifested as normal and the interstitial type changing into the parenchyma type and the mixed type, the localized type changing into the diffuse type. Conclusions: Most children patients of' HFMD showed normal chest films, while the abnormal patients were characterized by interstitial and parenchyma pulmonary edema. Serial chest X-ray examination and short-term dynamic observation were important to identify the severe cases and assess patients' condition. (authors)
Changes in the EV-A71 Genome through Recombination and Spontaneous Mutations: Impact on Virulence
Directory of Open Access Journals (Sweden)
Madiiha Bibi Mandary
2018-06-01
Full Text Available Enterovirus 71 (EV-A71 is a major etiological agent of hand, foot and mouth disease (HFMD that mainly affects young children less than five years old. The onset of severe HFMD is due to neurological complications bringing about acute flaccid paralysis and pulmonary oedema. In this review, we address how genetic events such as recombination and spontaneous mutations could change the genomic organization of EV-A71, leading to an impact on viral virulence. An understanding of the recombination mechanism of the poliovirus and non-polio enteroviruses will provide further evidence of the emergence of novel strains responsible for fatal HFMD outbreaks. We aim to see if the virulence of EV-A71 is contributed solely by the presence of fatal strains or is due to the co-operation of quasispecies within a viral population. The phenomenon of quasispecies within the poliovirus is discussed to reflect viral fitness, virulence and its implications for EV-A71. Ultimately, this review gives an insight into the evolution patterns of EV-A71 by looking into its recombination history and how spontaneous mutations would affect its virulence.
Challenges to Licensure of Enterovirus 71 Vaccines
Wang, Jen-Ren; Chi, Chia-Yu; Chong, Pele; Su, Ih-Jen
2012-01-01
Human enteroviruses usually cause self-limited infections except polioviruses and enterovirus 71 (EV71), which frequently involve neurological complications. EV71 vaccines are being evaluated in humans. However, several challenges to licensure of EV71 vaccines need to be addressed. Firstly, EV71 and coxsackievirus A (CA) are frequently found to co-circulate and cause hand-foot-mouth disease (HFMD). A polyvalent vaccine that can provide protection against EV71 and prevalent CA are desirable. Secondly, infants are the target population of HFMD vaccines and it would need multi-national efficacy trials to prove clinical protection and speed up the licensure and usage of HFMD vaccines in children. An international network for enterovirus surveillance and clinical trials is urgently needed. Thirdly, EV71 is found to evolve quickly in the past 15 years. Prospective cohort studies are warranted to clarify clinical and epidemiological significances of the antigenic and genetic variations between different EV71 genogroups, which is critical for vaccine design. PMID:22953003
Challenges to licensure of enterovirus 71 vaccines.
Directory of Open Access Journals (Sweden)
Min-Shi Lee
Full Text Available Human enteroviruses usually cause self-limited infections except polioviruses and enterovirus 71 (EV71, which frequently involve neurological complications. EV71 vaccines are being evaluated in humans. However, several challenges to licensure of EV71 vaccines need to be addressed. Firstly, EV71 and coxsackievirus A (CA are frequently found to co-circulate and cause hand-foot-mouth disease (HFMD. A polyvalent vaccine that can provide protection against EV71 and prevalent CA are desirable. Secondly, infants are the target population of HFMD vaccines and it would need multi-national efficacy trials to prove clinical protection and speed up the licensure and usage of HFMD vaccines in children. An international network for enterovirus surveillance and clinical trials is urgently needed. Thirdly, EV71 is found to evolve quickly in the past 15 years. Prospective cohort studies are warranted to clarify clinical and epidemiological significances of the antigenic and genetic variations between different EV71 genogroups, which is critical for vaccine design.
Fan, Xingliang; Jiang, Jun; Liu, Yanjing; Huang, Xueyong; Wang, Pengzhi; Liu, Licheng; Wang, Junzhi; Chen, Weijun; Wu, Weili; Xu, Bianli
2013-02-01
During 2009, an outbreak of hand, foot, and mouth disease (HFMD) enrolled 490 people in Henan Province, causing the death of two children. In order to investigate the pathogens responsible for this outbreak and characterize their genetic characteristics, a total of 508 clinical specimens (stool, throat swab, and vesicle fluid) were collected from the Center for Disease Control and Prevention of Henan Province. Virological investigations (virus isolation, conventional reverse transcription PCR, and real-time reverse transcription PCR) and phylogenetic analysis were performed. It was found that human enterovirus 71 (EV71) was the main pathogen causing this outbreak, while Coxsackievirus A16 (CoxA16) played only a subsidiary role. Phylogenetic analysis of 24 EV71 isolates collected during the period from March 11 to July 24, 2009 showed that they belonged to subgenotypes C4 and C5. Our study for the first time characterizes the epidemiology of HFMD and EV71 infection in Henan Province in 2009 and provides the first direct evidence of the genotype of EV71 circulating in Henan Province at that time. Our study should facilitate the development of public health measures for the control and prevention of HFMD and EV71 infection in at-risk individuals in China.
Directory of Open Access Journals (Sweden)
Ting Zhang
Full Text Available The epidemiology and molecular characteristics of human enterovirus B (HEV-B associated with hand, foot and mouth disease (HFMD outbreaks in China are not well known. In the present study, we tested 201 HEV isolates from 233 clinical specimens from patients with severe HFMD during 2010-2011 in Linyi, Shandong, China. Of the 201 isolates, 189 were fully typed and 18 corresponded to HEV-B species (six serotypes CVA9, CVB1, CVB4, Echo 6, Echo 25 and Echo 30 using sensitive semi-nested polymerase chain reaction analysis of VP1 gene sequences. Phylogenetic analysis based on the VP1 region showed that eight E30SD belonged to a novel sub-genogroup D2; E25SD belonged to a novel sub-genogroup D6; E6SD belonged to sub-lineage C6 and five CVB1SD belonged to subgroup 4C; and B4SD belonged sub-lineage D2. The full viral genomes of the CVB1SD, E6SD, E25SD and E30SD isolates were sequenced. Analysis of phylogenetic and similarity plots indicated that E25SD recombined with E25-HN-2, E30FDJS03 and E4AUS250 at noncontiguous P2A-P3D regions, while E30SD, E30FDJ03, E25-HN-2 and E9 DM had shared sequences in discrete regions of P2 and P3. Both E6SD and B1SD shared sequences with E1-HN, B4/GX/10, B5-HN, and A9-Alberta in contiguous regions of most of P2 and P3. Genetic algorithm recombination detection analysis further confirmed the existence of multiple potential recombination points. In conclusion, analysis of the complete genomes of E25SD, E30SD, CVB1SD and E6SD isolated from HFMD patients revealed that they formed novel subgenogroup. Given the prevalence and recombination of these viruses in outbreaks of HFMD, persistent surveillance of HFMD-associated HEV-B pathogens is required to predict potential emerging viruses and related disease outbreaks.
[Genetic evidence for recombination and mutation in the emergence of human enterovirus 71].
Liu, Ai-Ping; Tan, Hui; Xie, Qun; Chen, Bai-Tang; Liu, Xiao-Feng; Zhang, Yong
2014-09-01
We wished to understand the genetic recombination and phylogenetic characteristics of human en- terovirus A71 (EV-A71) and to explore its potential virulence-related sites. Full-length genomes of three EV-A71 strains isolated from patients in Chenzhou City (China) were sequenced and analyzed. Possible re- combination events and crossover sites were analyzed with Recombination Detection Program v4. 1. 6 by comparison with the complete genome sequences of 231 strains of EV-A71. Similarly, plot and bootscanning analyses were undertaken with SimPlot v3. 5. 1. Phylogenetic trees based on the sequences of VP1 regions were constructed with MEGA v5. 2 using the Kimura two-parameter model and neighbor-joining method. Results suggested that recombination events were detected among the three EV-A71 isolates from Chenzhou City. The common main parent sequence was from JF799986 isolated from samples in Guang- zhou City (China) in 2009, and the minor parent sequence was TW/70516/08. Intertypic recombination e- vents were found in the C4b strain (strain SHZH98 isolated in 1998) and C4a strain (Fuyang strain isola- ted in 2008) with the prototype strains of CVA4 and CVA14 in the 3D region. The chi-square test was used to screen-out potential virulence-related sites with nucleotide substitutions of different types of hand, foot, and mouth disease (HFMD) cases using SPSS v19.0. Results suggested that there were no significant nucleotide substitutions between death cases and severe-HFMD cases. Eighteen significant nucleotide substitutions were found between death/severe-HFMD cases and mild-HFMD cases, and all these 18 substitutions were distributed only in P2 and P3 regions. Intertypic recombination among the predominant circulating EV-A71 strains in the Chinese mainland and other EV-A strains probably dates before 1998, and intratypic recombination might have occurred frequently in the HFMD outbreak from 2008 to 2012. Substitutions in the non-capsid region may be correlated with the
Phylodynamics of Enterovirus A71-Associated Hand, Foot, and Mouth Disease in Viet Nam.
Geoghegan, Jemma L; Tan, Le Van; Kühnert, Denise; Halpin, Rebecca A; Lin, Xudong; Simenauer, Ari; Akopov, Asmik; Das, Suman R; Stockwell, Timothy B; Shrivastava, Susmita; Ngoc, Nghiem My; Uyen, Le Thi Tam; Tuyen, Nguyen Thi Kim; Thanh, Tran Tan; Hang, Vu Thi Ty; Qui, Phan Tu; Hung, Nguyen Thanh; Khanh, Truong Huu; Thinh, Le Quoc; Nhan, Le Nguyen Thanh; Van, Hoang Minh Tu; Viet, Do Chau; Tuan, Ha Manh; Viet, Ho Lu; Hien, Tran Tinh; Chau, Nguyen Van Vinh; Thwaites, Guy; Grenfell, Bryan T; Stadler, Tanja; Wentworth, David E; Holmes, Edward C; Van Doorn, H Rogier
2015-09-01
Enterovirus A71 (EV-A71) is a major cause of hand, foot, and mouth disease (HFMD) and is particularly prevalent in parts of Southeast Asia, affecting thousands of children and infants each year. Revealing the evolutionary and epidemiological dynamics of EV-A71 through time and space is central to understanding its outbreak potential. We generated the full genome sequences of 200 EV-A71 strains sampled from various locations in Viet Nam between 2011 and 2013 and used these sequence data to determine the evolutionary history and phylodynamics of EV-A71 in Viet Nam, providing estimates of the effective reproduction number (Re) of the infection through time. In addition, we described the phylogeography of EV-A71 throughout Southeast Asia, documenting patterns of viral gene flow. Accordingly, our analysis reveals that a rapid genogroup switch from C4 to B5 likely took place during 2012 in Viet Nam. We show that the Re of subgenogroup C4 decreased during the time frame of sampling, whereas that of B5 increased and remained >1 at the end of 2013, corresponding to a rise in B5 prevalence. Our study reveals that the subgenogroup B5 virus that emerged into Viet Nam is closely related to variants that were responsible for large epidemics in Malaysia and Taiwan and therefore extends our knowledge regarding its associated area of endemicity. Subgenogroup B5 evidently has the potential to cause more widespread outbreaks across Southeast Asia. EV-A71 is one of many viruses that cause HFMD, a common syndrome that largely affects infants and children. HFMD usually causes only mild illness with no long-term consequences. Occasionally, however, severe infection may arise, especially in very young children, causing neurological complications and even death. EV-A71 is highly contagious and is associated with the most severe HFMD cases, with large and frequent epidemics of the virus recorded worldwide. Although major advances have been made in the development of a potential EV-A71
Song, Qinwei; Huang, Hui; Deng, Jie; Zhao, Linqing; Deng, Li; Sun, Yu; Wang, Fang; Oian, Yuan; Zhu, Runan
2015-08-01
To analyze the genotype, epidemic pattern and the characteristics of the disease of enteroviruses during the epidemic season of hand, foot and mouth disease (HMFD) in children from 2013 to 2014 in Beijing to provide the scientific evidence for prevention and treatment of HFMD. During April to September in 2013 and March to October in 2014, a total of 977 throat swabs were collected from children who visited the Children's Hospital Affiliated to Capital Institute of Pediatrics, including 147 from patients with HFMD in 2013, 343 with HFMD, 201 with atypical HFMD, 83 with herpangina, 25 with fever with convulsions, 64 fever with rash and 114 with rash in 2014. Enteroviruses universal type (EV), Enteroviruses type 71 (EV71) and Coxsackievirus group A 16 (CA16) were detected by real-time RT-PCR respectively. The nucleic acid of specimens which were identified with non-EV71, non-CA16 was tested by nested PCR and analyzed by VP1 sequencing. The detection rate and epidemic pattern of different genotypes of enterovirus were analyzed among different age groups and between 2013 and 2014. Of 977 throat swabs, 80. 1% samples were detected positive for enteroviruses. The positive rates of CA16, EV71, CA6, CA10, CA4 and other EVs were 25. 6% (250/977), 18. 9% (185/977), 20. 0% (195/977), 5. 0% (49/977), 1.5% (15/977) and 9.1% (89/977), respectively. Twenty six of the 89 other EVs included CA2, CA5, CA8, CA9, CA12, CA14, CB2, CB5, E6, E9 and E25, each genotype of which was no more than 3. The nucleotide homologies shared among CA6, CA10 and CA4 strains between 2013 and 2014 were 94. 3% - 100%, 93. 8% - 99. 1% and 92.7% - 99. 8%, respectively. The positive rates of ≤1 year group were 71. 1% (106/149), which was lower than that of other age groups (all P 5 year group (χ2 =1. 181,P = 0. 277). In 2013, the positive rate of EV was 85. 7% (126/147) and the predominant genotype was CA6 54. 8% (69/126), followed by CA16 20. 6% (26/126) and EV71 11. 9% (15/126). In 2014, the positive
Contribution to the study of diffusion in rare earth metals and actinides
International Nuclear Information System (INIS)
Marbach, Gabriel.
1978-07-01
This work describes several experiments carried out in order to understand the process of self diffusion in rare earth and actinides (self diffusion of body centered cubic γ neptunium, diffusion of gadolinium in body centered delta cerium, measurement of the activation volume of face centered cubic γ cerium). The unstable electronic structure of some elements cannot be correlate with anomalous diffusion properties. In fact the diffusion parameters of neptunium and plutonium are similar (high diffusivity and low activation energy) whereas the electronic structure of neptunium is stable and that of plutonium is temperature dependent. The negative activation volume of the body centered cubic phases of plutonium and cerium does not indicate a particular diffusion mechanism since self diffusion is faster under pressure in face centered cubic γ cerium where a vacancy mechanism is assumed according to earlier results. The vacancy mechanism is the most probable diffusion process in the body centered cubic and compact phases of rare earths and actinides [fr
In vivo magnetic resonance diffusion measurement in the brain of patients with multiple sclerosis
DEFF Research Database (Denmark)
Larsson, H B; Thomsen, C; Frederiksen, J
1992-01-01
Measurement of water self-diffusion in the brain in 25 patients with multiple sclerosis was performed by magnetic resonance imaging. Quantitative diffusion measurements were obtained using single spin-echo pulse sequences with pulsed magnetic field gradients of different magnitude. Twenty......-two of these patients also underwent measurement of the transverse relaxation time (T2). Only one plaque was evaluated in each patient. Based on prior knowledge, 12 plaques were classified as being 3 mo or less in age, and 7 plaques were classified as being more than 3 mo old. In all 25 plaques, water self......-diffusion was found to be higher than in apparently normal white matter. Furthermore, water self-diffusion was found to be higher in acute plaques compared with chronic plaques. Finally, a slight tendency toward a relationship between the diffusion capability and T2 was found. We believe that an increased diffusion...
Coefficients of tracer transfer through membranes. Pt. 7
Energy Technology Data Exchange (ETDEWEB)
Dorabialska, A; Hawlicka, E; Plonka, A [Politechnika Lodzka (Poland)
1974-01-01
The doubled value of the tracer transfer coefficient in the self-diffusion process is equal to the sum of tracer transfer coefficients in the diffusion and interfusion processes. The fundamental phenomenological relation can be deduced for the coefficients of tracer transfer between two phases of electrolyte solutions spearated by a virtual boundary. Indeed, the doubled value of the tracer mobility in the self-diffusion experiment (no concentration gradient of the traced substance) is equal to the sum of the tracer mobilities in the diffusion (tracer movement along with the concentration gradient of the traced substance) and interfusion experiments (tracer movement against the concentration gradient of the traced substance). Thus the doubled value of the tracer transfer coefficient in the self-diffusion process should be equal to the sum of tracer transfer coefficients in the diffusion and interfusion processes. The experimental verification of that fundamental relation is presented.
Radionuclides in diffusion probing of inorganic materials based on chalcogenides
International Nuclear Information System (INIS)
Firsova, L.P.
1994-01-01
Migration of tellurium-125m, selenium-75, sulfur-35 radionuclides in solid solutions Pb 1-y (Se 0.08 Te 0.92 ) y and (Pb 1-x Sn x ) y Te 1-y , where x=0.1 and 0.2, has been studied, the results are presented. Data on dependence of selenium and tellurium self-diffusion coefficients on temperature in the range of 600-750 deg C are given. The results of the study of self-diffusion coefficient isothermal dependences on lead and tellurium vapour pressure in equilibrium with solid phases have been considered. It is ascertained that a change in the temperature and p-n transitions initiate the change in self-diffusion mechanisms of chalcogenide atoms. 8 refs., 3 tabs
Atomic defects and diffusion in metals
International Nuclear Information System (INIS)
Siegel, R.W.
1981-11-01
The tracer self-diffusion data for fcc and refractory bcc metals are briefly reviewed with respect to (i) the available monovacancy formation and migration properties and (ii) the high-temperature diffusion enhancement above that expected for mass transport via atomic exchange with monovacancies. While the atomic-defect mechanism for low-temperature self-diffusion can be reliably attributed to monovacancies, the mechanisms responsible for high-temperature mass transport are not so easily defined at this time; both divacancies and interstitials must be seriously considered. Possibilities for improving our understanding in this area are discussed. 68 references, 7 figures
Anomalous diffusion in niobium. Study of solute diffusion mechanism of iron in niobium
International Nuclear Information System (INIS)
Ablitzer, D.
1977-01-01
In order to explain anomalously high diffusion velocities observed for iron diffusion in niobium, the following parameters were measured: isotope effect, b factor (which expresses the effect of iron on niobium self-diffusion), self-diffusion coefficient of niobium, solute diffusion coefficient of iron in niobium. The results obtained show that neither pure vacancy models, nor diffusion in the lattice defects (dislocations, sub-boundaries, grain boundaries), nor pure interstitialy mechanisms, nor simple or cyclic exchange mechanisms agree with experiments. A mechanism is proposed which considers an equilibrium between substitution iron atoms and interstitial iron atoms. The diffusion of iron then occurs through interstitial vancancy pairs [fr
The melting-diffusion correlation in the plutonium-zirconium alloys
International Nuclear Information System (INIS)
Zanghi, J.-P.; Calais, Daniel.
1975-01-01
The activation volumes for self-diffusion of Pu in b.c.c. PuZr alloys (10 and 40at%Zr) have been determined, the validity of Nachtrieb's melting-diffusion correlation was checked. Indeed, in the Pu-40at%Zr alloy, which has a pressure temperature phase diagram whose liquidus has a positive slope, the activation volume is positive, whereas in pure epsilon Pu where the slope is negative, the activation volume is negative. A self-diffusion mechanism in PuZr alloys is proposed [fr
Theoretical study of carbon dioxide adsorption and diffusion in MIL-127(Fe) metal organic framework
Pongsajanukul, Pavee; Parasuk, Vudhichai; Fritzsche, Siegfried; Assabumrungrat, Suttichai; Wongsakulphasatch, Suwimol; Bovornratanaraks, Thiti; Chokbunpiam, Tatiya
2017-07-01
The UFF force field is found to reproduce the adsorption isotherm of carbon dioxide in MIL-127(Fe) well. It has therefore been used to investigate the structure and self-diffusion of carbon dioxide molecules in the MIL which is a candidate for membrane or adsorption application. The structure of the adsorbed phase shows different regions of high concentration. The highest particle concentration was found in the central regions of the channels. The self-diffusion coefficient slightly increases with the loading for low concentration of guest molecules while for higher concentrations it decreases because of mutual hindrance of guest molecules.
Mohoric; Stepisnik
2000-11-01
This paper describes the influence of natural convection on NMR measurement of a self-diffusion constant of fluid in the earth's magnetic field. To get an estimation of the effect, the Lorenz model of natural convection in a horizontally oriented cylinder, heated from below, is derived. Since the Lorenz model of natural convection is derived for the free boundary condition, its validity is of a limited value for the natural no-slip boundary condition. We point out that even a slight temperature gradient can cause significant misinterpretation of measurements. The chaotic nature of convection enhances the apparent self-diffusion constant of the liquid.
Thermal conductivity of water: Molecular dynamics and generalized hydrodynamics results
Bertolini, Davide; Tani, Alessandro
1997-10-01
Equilibrium molecular dynamics simulations have been carried out in the microcanonical ensemble at 300 and 255 K on the extended simple point charge (SPC/E) model of water [Berendsen et al., J. Phys. Chem. 91, 6269 (1987)]. In addition to a number of static and dynamic properties, thermal conductivity λ has been calculated via Green-Kubo integration of the heat current time correlation functions (CF's) in the atomic and molecular formalism, at wave number k=0. The calculated values (0.67+/-0.04 W/mK at 300 K and 0.52+/-0.03 W/mK at 255 K) are in good agreement with the experimental data (0.61 W/mK at 300 K and 0.49 W/mK at 255 K). A negative long-time tail of the heat current CF, more apparent at 255 K, is responsible for the anomalous decrease of λ with temperature. An analysis of the dynamical modes contributing to λ has shown that its value is due to two low-frequency exponential-like modes, a faster collisional mode, with positive contribution, and a slower one, which determines the negative long-time tail. A comparison of the molecular and atomic spectra of the heat current CF has suggested that higher-frequency modes should not contribute to λ in this temperature range. Generalized thermal diffusivity DT(k) decreases as a function of k, after an initial minor increase at k=kmin. The k dependence of the generalized thermodynamic properties has been calculated in the atomic and molecular formalisms. The observed differences have been traced back to intramolecular or intermolecular rotational effects and related to the partial structure functions. Finally, from the results we calculated it appears that the SPC/E model gives results in better agreement with experimental data than the transferable intermolecular potential with four points TIP4P water model [Jorgensen et al., J. Chem. Phys. 79, 926 (1983)], with a larger improvement for, e.g., diffusion, viscosities, and dielectric properties and a smaller one for thermal conductivity. The SPC/E model shares
Stress tensor and viscosity of water: Molecular dynamics and generalized hydrodynamics results
Bertolini, Davide; Tani, Alessandro
1995-08-01
The time correlation functions (CF's) of diagonal and off-diagonal components of the stress tensor of water have been calculated at 245 and 298 K in a molecular dynamics (MD) study on 343 molecules in the microcanonical ensemble. We present results obtained at wave number k=0 and at a few finite values of k, in the atomic and molecular formalism. In all cases, more than 98% of these functions are due to the potential term of the stress tensor. At k=0, their main features are a fast oscillatory initial decay, followed by a long-time tail more apparent in the supercooled region. Bulk and shear viscosities, calculated via Green-Kubo integration of the relevant CF at k=0, are underestimated with respect to experimental data, mainly at low temperature, but their ratio (~=2) is correctly reproduced. Both shear and bulk viscosity decrease as a function of k, the latter more rapidly, so that they become almost equal at ~=1 Å-1. Also, both viscosities drop rapidly from their maximum at ω=0. This behavior has been related to the large narrowing observed in the acoustic band, mainly in the supercooled region. The infinite frequency bulk and shear rigidity moduli have been shown to be in fair agreement with the experimental data, provided the MD value used for comparison is that corresponding to the frequency range relevant to ultrasonic measurements. The MD results of stress-stress CF's compare well with those predicted by Bertolini and Tani [Phys. Rev. E 51, 1091 (1995)] at k=0, by an application of generalized hydrodynamics [de Schepper et al., Phys. Rev. A 38, 271 (1988)] in the molecular formalism, to the same model of water (TIP4P) [Jorgensen et al., J. Chem. Phys. 79, 926 (1983)]. These CF's are essentially equal in the atomic and molecular formalism, the only minor difference being restricted to the high frequency librational region of the shear function. By a comparison of atomic and molecular results, we show here that neglecting libration has no effect on the
Multiscale Modeling of Carbon Nanotube-Epoxy Nanocomposites
Fasanella, Nicholas A.
Epoxy-composites are widely used in the aerospace industry. In order to improve upon stiffness and thermal conductivity; carbon nanotube additives to epoxies are being explored. This dissertation presents multiscale modeling techniques to study the engineering properties of single walled carbon nanotube (SWNT)-epoxy nanocomposites, consisting of pristine and covalently functionalized systems. Using Molecular Dynamics (MD), thermomechanical properties were calculated for a representative polymer unit cell. Finite Element (FE) and orientation distribution function (ODF) based methods were used in a multiscale framework to obtain macroscale properties. An epoxy network was built using the dendrimer growth approach. The epoxy model was verified by matching the experimental glass transition temperature, density, and dilatation. MD, via the constant valence force field (CVFF), was used to explore the mechanical and dilatometric effects of adding pristine and functionalized SWNTs to epoxy. Full stiffness matrices and linear coefficient of thermal expansion vectors were obtained. The Green-Kubo method was used to investigate the thermal conductivity as a function of temperature for the various nanocomposites. Inefficient phonon transport at the ends of nanotubes is an important factor in the thermal conductivity of the nanocomposites, and for this reason discontinuous nanotubes were modeled in addition to long nanotubes. To obtain continuum-scale elastic properties from the MD data, multiscale modeling was considered to give better control over the volume fraction of nanotubes, and investigate the effects of nanotube alignment. Two methods were considered; an FE based method, and an ODF based method. The FE method probabilistically assigned elastic properties of elements from the MD lattice results based on the desired volume fraction and alignment of the nanotubes. For the ODF method, a distribution function was generated based on the desired amount of nanotube alignment
Fundamental aspects of steady-state conversion of heat to work at the nanoscale
Benenti, Giuliano; Casati, Giulio; Saito, Keiji; Whitney, Robert S.
2017-06-01
In recent years, the study of heat to work conversion has been re-invigorated by nanotechnology. Steady-state devices do this conversion without any macroscopic moving parts, through steady-state flows of microscopic particles such as electrons, photons, phonons, etc. This review aims to introduce some of the theories used to describe these steady-state flows in a variety of mesoscopic or nanoscale systems. These theories are introduced in the context of idealized machines which convert heat into electrical power (heat-engines) or convert electrical power into a heat flow (refrigerators). In this sense, the machines could be categorized as thermoelectrics, although this should be understood to include photovoltaics when the heat source is the sun. As quantum mechanics is important for most such machines, they fall into the field of quantum thermodynamics. In many cases, the machines we consider have few degrees of freedom, however the reservoirs of heat and work that they interact with are assumed to be macroscopic. This review discusses different theories which can take into account different aspects of mesoscopic and nanoscale physics, such as coherent quantum transport, magnetic-field induced effects (including topological ones such as the quantum Hall effect), and single electron charging effects. It discusses the efficiency of thermoelectric conversion, and the thermoelectric figure of merit. More specifically, the theories presented are (i) linear response theory with or without magnetic fields, (ii) Landauer scattering theory in the linear response regime and far from equilibrium, (iii) Green-Kubo formula for strongly interacting systems within the linear response regime, (iv) rate equation analysis for small quantum machines with or without interaction effects, (v) stochastic thermodynamic for fluctuating small systems. In all cases, we place particular emphasis on the fundamental questions about the bounds on ideal machines. Can magnetic-fields change the
Summary report on UO_{2} thermal conductivity model refinement and assessment studies
Energy Technology Data Exchange (ETDEWEB)
Liu, Xiang-Yang [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Cooper, Michael William Donald [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mcclellan, Kenneth James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lashley, Jason Charles [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Byler, Darrin David [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bell, B. D.C. [Imperial College, London (United Kingdom); Grimes, R. W. [Imperial College, London (United Kingdom); Stanek, Christopher Richard [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Andersson, David Ragnar [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-02-03
-temperature model typically used in fuel performance codes. The model is validated by comparison to low-temperature experimental measurements on single crystal hyper-stoichiometric UO_{2+x} samples and high-temperature literature data. Ongoing works include investigation of the effect of phase separation to UO_{2}+U_{4}O_{9} on the low temperature thermal conductivity of UO_{2+x}, and modeling of thermal conductivity using the Green-Kubo method. Ultimately, this work will enable more accurate fuel performance simulations as well as extension to new fuel types and operating conditions, all of which improve the fuel economics of nuclear energy and maintain high fuel reliability and safety.
Energy Technology Data Exchange (ETDEWEB)
Zeng, Hongwu; Gan, Yungen [Shenzhen Children' s Hospital, Department of Radiology, Shenzhen (China); Wen, Feiqiu [Shenzhen Children' s Hospital, Department of Neurology, Shenzhen (China); Huang, Wenxian [Shenzhen Children' s Hospital, Department of Respiratory, Shenzhen (China)
2012-06-15
This study was conducted to investigate MRI and associated clinical characteristics of brainstem encephalitis induced by enterovirus 71 (EV71) in children with hand-foot-mouth disease (HFMD). We analyzed clinical and imaging data from 42 HFMD cases with EV71-induced brainstem encephalitis. All patients underwent plain and enhanced MRI cranial scans and were placed into one of two groups according to MRI enhancement results, an enhanced group or a nonenhanced group. Thirty-two cases were positive on MRI exam. The primary location of the lesion for brainstem encephalitis was the dorsal pons and medulla oblongata (32 cases), followed by the cerebellar dentate nucleus (8 cases), midbrain (5 cases), and thalamus (2 cases). Plain T1-weighted images showed isointense or hypointense signals, and T2-weighted images showed isointense and hyperintense signals. Enhanced MRI scans showed that 12 cases had slight to moderate enhancement; 4 of these were normal on plain scan. The time from MRI examination to disease onset was statistically different between the enhanced (n = 12) and nonenhanced (n = 21) groups with a mean of 7.67 days (SD = 1.07) vs 11.95 days (SD = 5.33), respectively. The most common neurological symptoms for brainstem encephalitis were myoclonus and tremor. The greater the area of affected brain, the more severe the clinical symptoms were. The locations of EV71-induced HFMD-associated brainstem encephalitis lesions are relatively specific. Enhanced MRI scans could also identify the lesions missed by early plain scans. MRI scans can provide important information for clinical evaluation and treatment. (orig.)
International Nuclear Information System (INIS)
Zeng, Hongwu; Gan, Yungen; Wen, Feiqiu; Huang, Wenxian
2012-01-01
This study was conducted to investigate MRI and associated clinical characteristics of brainstem encephalitis induced by enterovirus 71 (EV71) in children with hand-foot-mouth disease (HFMD). We analyzed clinical and imaging data from 42 HFMD cases with EV71-induced brainstem encephalitis. All patients underwent plain and enhanced MRI cranial scans and were placed into one of two groups according to MRI enhancement results, an enhanced group or a nonenhanced group. Thirty-two cases were positive on MRI exam. The primary location of the lesion for brainstem encephalitis was the dorsal pons and medulla oblongata (32 cases), followed by the cerebellar dentate nucleus (8 cases), midbrain (5 cases), and thalamus (2 cases). Plain T1-weighted images showed isointense or hypointense signals, and T2-weighted images showed isointense and hyperintense signals. Enhanced MRI scans showed that 12 cases had slight to moderate enhancement; 4 of these were normal on plain scan. The time from MRI examination to disease onset was statistically different between the enhanced (n = 12) and nonenhanced (n = 21) groups with a mean of 7.67 days (SD = 1.07) vs 11.95 days (SD = 5.33), respectively. The most common neurological symptoms for brainstem encephalitis were myoclonus and tremor. The greater the area of affected brain, the more severe the clinical symptoms were. The locations of EV71-induced HFMD-associated brainstem encephalitis lesions are relatively specific. Enhanced MRI scans could also identify the lesions missed by early plain scans. MRI scans can provide important information for clinical evaluation and treatment. (orig.)
Somasundaram, Balaji; Chang, Cindy; Fan, Yuan Y; Lim, Pei-Yin; Cardosa, Jane; Lua, Linda
2016-02-15
Enterovirus 71 (EV71) and Coxsackievirus A16 (CVA16) are two viruses commonly responsible for hand, foot and mouth disease (HFMD) in children. The lack of prophylactic or therapeutic measures against HFMD is a major public health concern. Insect cell-based EV71 and CVA16 virus-like particles (VLPs) are promising vaccine candidates against HFMD and are currently under development. In this paper, the influence of insect cell line, incubation temperature, and serial passaging effect and stability of budded virus (BV) stocks on EV71 and CVA16 VLP production was investigated. Enhanced EV71 and CVA16 VLP production was observed in Sf9 cells compared to High Five™ cells. Lowering the incubation temperature from the standard 27°C to 21°C increased the production of both VLPs in Sf9 cells. Serial passaging of CVA16 BV stocks in cell culture had a detrimental effect on the productivity of the structural proteins and the effect was observed with only 5 passages of BV stocks. A 2.7× higher production yield was achieved with EV71 compared to CVA16. High-resolution asymmetric flow field-flow fractionation couple with multi-angle light scattering (AF4-MALS) was used for the first time to characterize EV71 and CVA16 VLPs, displaying an average root mean square radius of 15±1nm and 15.3±5.8 nm respectively. This study highlights the need for different approaches in the design of production process to develop a bivalent EV71 and CVA16 vaccine. Copyright © 2015 Elsevier Inc. All rights reserved.
Zhang, Chao; Yang, Yong; Chi, Yudan; Yin, Jieyun; Yan, Lijun; Ku, Zhiqiang; Liu, Qingwei; Huang, Zhong; Zhou, Dongming
2015-09-22
Hand, foot and mouth disease (HFMD) is a major public health concern in Asia; more efficient vaccines against HFMD are urgently required. Adenoviral (Ad) capsids have been used widely for the presentation of foreign antigens to induce specific immune responses in the host. Here, we describe a novel bivalent vaccine for HFMD based on the hexon-modified, E1-deleted chimpanzee adenovirus serotype 68 (AdC68). The novel vaccine candidate was generated by incorporating the neutralising epitope of Coxsackievirus A16 (CA16), PEP71, into hypervariable region 1 (HVR1), and a shortened neutralising epitope of Enterovirus 71 (EV71), sSP70, into HVR2 of the AdC68 hexon. In order to enhance the immunogenicity of EV71, VP1 of EV71 was cloned into the E1-region of the AdC68 vectors. The results demonstrated that these two epitopes were well presented on the virion surface and had high affinity towards specific antibodies, and VP1 of EV71 was also significantly expressed. In pre-clinical mouse models, the hexon-modified AdC68 elicited neutralising antibodies against both CA16 and EV71, which conferred protection to suckling mice against a lethal challenge of CA16 and EV71. In summary, this study demonstrates that the hexon-modified AdC68 may represent a promising bivalent vaccine carrier against EV71 and CA16 and an epitope-display platform for other pathogens. Copyright © 2015 Elsevier Ltd. All rights reserved.
Niu, Peihua; Qi, Shunxiang; Yu, Benzhang; Zhang, Chen; Wang, Ji; Li, Qi; Ma, Xuejun
2016-11-01
Enterovirus 71 (EV71) is one of the major causative agents of outbreaks of hand, foot, and mouth disease (HFMD). A commercial TaqMan probe-based real-time PCR assay has been widely used for the differential detection of EV71 despite its relatively high cost and failure to detect samples with a low viral load (Ct value > 35). In this study, a highly sensitive real-time nested RT-PCR (RTN RT-PCR) assay in a single closed tube for detection of EV71 in HFMD was developed. The sensitivity and specificity of this assay were evaluated using a reference EV71 stock and a panel of controls consisting of coxsackievirus A16 (CVA16) and common respiratory viruses, respectively. The clinical performance of this assay was evaluated and compared with those of a commercial TaqMan probe-based real-time PCR (qRT-PCR) assay and a traditional two-step nested RT-PCR assay. The limit of detection for the RTN RT-PCR assay was 0.01 TCID50/ml, with a Ct value of 38.3, which was the same as that of the traditional two-step nested RT-PCR assay and approximately tenfold lower than that of the qRT-PCR assay. When testing the reference strain EV71, this assay showed favorable detection reproducibility and no obvious cross-reactivity. The testing results of 100 clinical throat swabs from HFMD-suspected patients revealed that 41 samples were positive for EV71 by both RTN RT-PCR and traditional two-step nested RT-PCR assays, whereas only 29 were EV71 positive by qRT-PCR assay.
Li, Pengyuan; Li, Tao; Gu, Qiuyun; Chen, Xiaomin; Li, Jiahui; Chen, Xiashi; Chen, Yan; Zhang, Danwei; Gao, Rong; He, Zhenjian; Zhu, Xun; Zhang, Wangjian; Hao, Yuantao; Zhang, Dingmei
2016-11-01
Hand-foot-and-mouth disease (HFMD) is a common infectious disease, which has led to millions of clinical cases and hundreds of deaths every year in China. This study aimed to exploring the effects on HFMD transmission of children’s caregivers and public area, as well as trying to locate the potential reservoirs of infections in primary cases. Total children’s 257 samples (98 children’s caregivers and 159 environmental samples) were tested for the presence of universal enterovirus, enterovirus 71, coxsackie virus A6 and A16 by real-time fluorescence quantitative polymerase chain reaction (qPCR). 5.84% (15/257, 95% confidence interval [CI]: 2.98%, 8.70%) of total samples had positive results of enterovirus. The enterovirus positive rates of children’s caregiver samples and environmental samples were respectively 7.14% (7/98, 95% CI: 2.04%, 12.24%), and 5.03% (8/159, 95% CI: 1.63%, 8.43%); 7.61% (7/92, 95% CI: 2.21%, 13.01%) of wiping samples from playgrounds and 1.49% (1/67, 95% CI: 0, 7.00%) of air samples in indoor market places had positive result of enterovirus. High positive rates of enterovirus in children’s caregivers and from playgrounds indicated that they would be potential reservoirs of HFMD infection, as children might be infected via contacting with asymptomatic-infected individuals or exposure of contaminated surface of public facilities.
Chen, Jing-Fang; Zhang, Ru-Sheng; Ou, Xin-Hua; Chen, Fa-Ming; Sun, Bian-Cheng
2014-11-01
During 2012, Changsha experienced a large outbreak of hand, foot, and mouth disease (HFMD), resulting in 25,438 cases, including 42 severe cases and eight deaths. Seven hundred and forty-six clinical specimens were collected from hospital-based surveillance for HFMD in 2012. The detection and genotyping of enterovirus were performed by real-time RT-PCR and sequencing of the VP1 regions; phylogenetic analysis was performed based on the VP1 sequences. A total of 545 (73.1%) enterovirus-positive samples were identified, with the most frequently presenting serotype being enterovirus 71 (EV-71; n=364, 66.8%), followed by coxsackievirus A16 (CV-A16; n=84, 15.4%), CV-A6 (n=22, 4.0%), and CV-A10 (n=19, 3.5%). Most of the affected patients were children aged ≤5 years (n=524, 96.1%). EV-71 was the major pathogen in the severe and fatal cases (n=22, 78.6%). Phylogenetic analysis of VP1 gene sequences showed the EV-71 isolates to belong to subgenotype C4a, and the CV-A16 isolates to belong to subgenotype B1. The Changsha CV-A6 and CV-A10 circulating strains were homologous to strains circulating in other areas of mainland China. Our results demonstrate that EV-71 was the primary causative agent responsible for the HFMD outbreak in Changsha in 2012, and the co-circulation of other coxsackievirus A strains posed a potential risk to public health.
Shen, Jun; Zhao, Chao; Cao, Ping; Shi, Peng; Cao, Lingfeng; Zhu, Qirong
2015-01-01
This study aimed to explore the correlation between clinical symptoms, including rash and fever, and serum antibody reaction to enterovirus 71 (EV71) infection in children hospitalized due to hand-foot-mouth disease (HFMD). From May 2014 to July 2014, a total of 547 children hospitalized due to HFMD in Children's Hospital of Fudan University were enrolled retrospectively. RNA levels of EV71 and CA16 in fecal, serum, and cerebrospinal fluid specimens were measured using quantitative real-time RT-PCR, and EV71-IgM antibody in the serum was detected using immune colloidal gold assays. Of the 547 fecal specimens, 296 were EV71 RNA positive, 109 were CA16 RNA positive, and 8 were positive for both EV71 RNA and CA16 RNA. The total positive rate for either EV71 or CA16 in feces was 72.58% (397/547). Additionally, 544 serum specimens were collected, and 409 were EV71-IgM positive (75.18%). The duration of rash and fever was found to be correlated to the positive rate of serum EV71-IgM, and the positive rate of serum EV71-IgM plus EV71 RNA in feces. The positive rates of serum EV71-IgM and serum EV71-IgM plus EV71 RNA in fecal collected at day 3 of fever were 79.7% and 52.8%, respectively. In conclusion, EV71 and CA16 were found to be the major pathogens responsible for the epidemics of HFMD in children during May to July 2014 in Shanghai, China. There is a close relationship between the positive rate of serum EV71-IgM and the duration of fever and rash.
Su, Weiheng; Li, Xue; Chen, Meili; Dai, Wenwen; Sun, Shiyang; Wang, Shuai; Sheng, Xin; Sun, Shixiang; Gao, Chen; Hou, Ali; Zhou, Yan; Sun, Bo; Gao, Feng; Xiao, Jingfa; Zhang, Zhewen; Jiang, Chunlai
2017-09-01
Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) have been considered major pathogens of hand, foot and mouth disease (HFMD) throughout the world for decades. In recent years, coxsackievirus A6 (CVA6) and coxsackievirus A10 (CVA10) have raised attention as two other serious pathogens of HFMD. The present study focused on the synonymous codon usage of four viruses isolated from 2008 to 2015, with particular attention on P1 (encoding capsid proteins) and P2-P3 regions (both encoding non-structural proteins) in the genomic RNA. Relative synonymous codon usage, effective number of codons, neutrality and correspondence were analyzed. The results indicated that these viruses prefer A/T at the third position in codons rather than G/C. The most frequent codons of 4 essential and 2 semi-essential amino acids, as well as a key amino acid of metabolic junctions (Glu) used in the four viruses are also the most frequently used in humans. Effective number of codons (ENC) values indicated weak codon usage bias in all the viruses. Relatively, the force of mutation pressure in the P1 region was found to be stronger than that in the P2-P3 region, and this force in the P1 region of CVA6 and EV71 was stronger than that of CVA10 and A16. The neutrality analysis results implied that mutation pressure plays a minor role in shaping codon bias of these viruses. Correspondence analysis indicated that the codon usage of EV71 strains varied much more than that of other viruses. In conclusion, the present study provides novel and comparative insight into the evolution of HFMD pathogens at the codon level. Copyright © 2017. Published by Elsevier B.V.
Chen, Qian; Hu, Zheng; Zhang, Qihua; Yu, Minghui
2016-05-01
Hand, foot, and mouth disease (HFMD) is a common infectious disease caused by a group of the human enteroviruses (HEV), including coxsackievirus A16 (CA16) and enterovirus 71 (EV71). In recent years, another HEV-A serotype, CA6 or CA10, has emerged to be one of the major etiologic agents that can induce HFMD worldwide. The objective of this study is to develop specific, sensitive, and rapid methods to help diagnose HEV and CA16 specifically by using simultaneous amplification testing (SAT) based on isothermal amplification of RNA and real-time detection of fluorescence technique, which were named as SAT-HEV and SAT-CA16, respectively (SAT-HEV/SAT-CA16). The specificity and sensitivity of SAT were tested here. SAT-HEV/SAT-CA16 could measure viral titers that were at least 10-fold lower than those measured by real-time PCR. Non-false cross-reactive amplification indicated that SAT-HEV/SAT-CA16 were highly specific with the addition of internal control (IC) RNA (5000 copies/reaction). A total of 198 clinical specimens were assayed by SAT comparing with real-time PCR. The statistically robust assessment of SAT-HEV and HEV-specific real-time PCR plus sequencing reached 99.0% (196/198), with a kappa value of 0.97, and 99.5% (197/198) and a kappa value of 0.99 for CA16, respectively. Additionally, IC prevented false-negative readings and assured the SAT-HEV/SAT-CA16 method's accuracy. Overall, SAT-HEV/SAT-CA16 method may serve as a platform for the simple and rapid detection of HEV/CA16 in time of HFMD outbreak. Copyright © 2016 Elsevier Inc. All rights reserved.
Liu, Weiyong; Wu, Shimin; Xiong, Ying; Li, Tongya; Wen, Zhou; Yan, Mingzhe; Qin, Kai; Liu, Yingle; Wu, Jianguo
2014-01-01
A total of 1844 patients with hand, foot, and mouth disease (HFMD), most of them were children of age 1–3-year-old, in Central China were hospitalized from 2011 to 2012. Among them, 422 were infected with coxsackievirus A16 (CVA16), 334 were infected with enterovirus 71 (EV71), 38 were co-infected with EV71 and CVA16, and 35 were infected with other enteroviruses. Molecular epidemiology analysis revealed that EV71 and CVA16 were detected year-round, but EV71 circulated mainly in July and CVA16 circulated predominantly in November, and incidence of HFMD was reduced in January and February and increased in March. Clinical data showed that hyperglycemia and neurologic complications were significantly higher in EV71-infected patients, while upper respiratory tract infection and C-reactive protein were significantly higher in CVA16-associated patients. 124 EV71 and 80 CVA16 strains were isolated, among them 56 and 68 EV71 strains were C4a and C4b, while 25 and 55 CVA16 strains were B1a and B1b, respectively. Similarity plots and bootscan analyses based on entire genomic sequences revealed that the three C4a sub-genotype EV71 strains were recombinant with C4b sub-genotype EV71 in 2B–2C region, and the three CVA16 strains were recombinant with EV71 in 2A–2B region. Thus, CVA16 and EV71 were the major causative agents in a large HFMD outbreak in Central China. HFMD incidence was high for children among household contact and was detected year-round, but outbreak was seasonal dependent. CVA16 B1b and EV71 C4b reemerged and caused a large epidemic in China after a quiet period of many years. Moreover, EV71 and CVA16 were co-circulated during the outbreak, which may have contributed to the genomic recombination between the pathogens. It should gain more attention as there may be an upward trend in co-circulation of the two pathogens globally and the new role recombination plays in the emergence of new enterovirus variants. PMID:24776922
Directory of Open Access Journals (Sweden)
Weiyong Liu
Full Text Available A total of 1844 patients with hand, foot, and mouth disease (HFMD, most of them were children of age 1-3-year-old, in Central China were hospitalized from 2011 to 2012. Among them, 422 were infected with coxsackievirus A16 (CVA16, 334 were infected with enterovirus 71 (EV71, 38 were co-infected with EV71 and CVA16, and 35 were infected with other enteroviruses. Molecular epidemiology analysis revealed that EV71 and CVA16 were detected year-round, but EV71 circulated mainly in July and CVA16 circulated predominantly in November, and incidence of HFMD was reduced in January and February and increased in March. Clinical data showed that hyperglycemia and neurologic complications were significantly higher in EV71-infected patients, while upper respiratory tract infection and C-reactive protein were significantly higher in CVA16-associated patients. 124 EV71 and 80 CVA16 strains were isolated, among them 56 and 68 EV71 strains were C4a and C4b, while 25 and 55 CVA16 strains were B1a and B1b, respectively. Similarity plots and bootscan analyses based on entire genomic sequences revealed that the three C4a sub-genotype EV71 strains were recombinant with C4b sub-genotype EV71 in 2B-2C region, and the three CVA16 strains were recombinant with EV71 in 2A-2B region. Thus, CVA16 and EV71 were the major causative agents in a large HFMD outbreak in Central China. HFMD incidence was high for children among household contact and was detected year-round, but outbreak was seasonal dependent. CVA16 B1b and EV71 C4b reemerged and caused a large epidemic in China after a quiet period of many years. Moreover, EV71 and CVA16 were co-circulated during the outbreak, which may have contributed to the genomic recombination between the pathogens. It should gain more attention as there may be an upward trend in co-circulation of the two pathogens globally and the new role recombination plays in the emergence of new enterovirus variants.
Kim, Hye-Jin; Hyeon, Ji-Yeon; Hwang, Seoyeon; Lee, Yong-Pyo; Lee, Sang Won; Yoo, Jung Sik; Kang, Byunghak; Ahn, Jeong-Bae; Jeong, Yong-Seok; Lee, June-Woo
2016-08-18
Enterovirus (EV) 71 is the main pathogen associated with hand, foot and mouth disease (HFMD) or herpangina. Outbreaks of HFMD caused by EV71 infection are associated severe neurological disease and high mortality rates in children. Several sporadic cases of EV71 infection occurred in the Republic of Korea (ROK) in 2000, and EV71 infections were not reported thereafter until 2006. In this prospective study, we report the epidemic and virologic characteristics of the EV71 endemic from 2007 to 2012 in the Republic of Korea. We analyzed characteristics of the EV71 infection-associated epidemic from collected specimens and clinical information from 9987 patients with suspected EV infection from the National EV Surveillance System in ROK. To identify the EV71 subgenotype, the homology of viral protein 1 sequences obtained using reverse transcription polymerase chain reaction was compared with the sequences on other countries available from GenBank database. EV71 was detected in 585 (16.7 %) specimens (cerebrospinal fluid, stool or rectal swabs, throat swabs and blood) during study period and was most frequently observed during epidemic seasons in 2009-2012. Major manifestations due to EV71 infection were HFMD (62.2 %) and HFMD with severe neurological complications (28.4 %). Five deaths (0.9 %) due to EV71 infection occurred, with an increased mortality rate during the period after 2009. Most patients (476; 81.4 %) were less than 5 years of age. Analysis of the monthly distribution showed that there was an obvious seasonal pattern to the epidemics, with infections appearing from June to August. The major subgenotype of EV71 isolates circulating in ROK was the C4a strain, which has also appeared in China, Japan and Vietnam. This surveillance provided valuable data on the epidemic characteristics of EV71 infections in ROK during a 6-year period. Our findings provide data to assist during future outbreaks of EV71 and associated acute neurologic disease.
International Nuclear Information System (INIS)
Yurlov, I.S.; Ushakova, Yu.N.; Medvedeva, O.V.; Kalinina, L.A.; Shirokova, G.I.; Ananchenko, B.A.
2007-01-01
Coefficients of self-diffusion and coefficients of diffusion of the sulfur ion in solid electrolytes BaSm 2 S 4 and CaGd 2 S 4 are determined with recourse to methods of conductometry and potentiostatic chronoamperometry. A vacancy mechanism for the defect formation in solid solutions on the basis of barium thiosamarate and calcium thiogadolynate is proposed [ru
An effective pair potential for liquid semiconductor, Se: Structure and ...
Indian Academy of Sciences (India)
This model potential is then used to describe through low-order perturbation theory, the structure and related dynamical properties like self-diffusion coefficient and shear viscosity of this complex liquid over a wide range of temperatures. Keywords. Liquid semiconductor; pair potential; structure and dynamical properties.
International Nuclear Information System (INIS)
Wasserburg, G.J.
1991-01-01
This report consists of sections entitled resonance ionization mass spectrometry of Os, Mg self-diffusion in spinel and silicate melts, neotectonics: U-Th ages of solitary corals from the California coast, uranium-series evidence on diagenesis and hydrology of carbonates of Barbados, diffusion of H 2 O molecules in silicate glasses, and development of an extremely high abundance sensitivity mass spectrometer
Connecting diffusion and entropy of bulk water at the single particle ...
Indian Academy of Sciences (India)
DEBASIS SAHA
Sex. The excess entropy denotes the difference between the actual entropy of the system and the system's entropy if it behaves as ... as viscosity or self-diffusion coefficient as well as the ..... modynamic determination of fragility in liquids and a.
An investigation on microwave sintering of Fe, Fe–Cu and Fe–Cu–C ...
Indian Academy of Sciences (India)
The current study examines the effect of heating mode on densifi- cation, microstructure ..... ing mechanisms. It increases the self diffusion coefficient of .... Lide D R (ed) 1998 CRC handbook of chemistry and physics (Boca. Raton, FL: CRC ... MPIF Standard 46 1991 Determination of tap density of metal powder. Standard ...
Intraparticle diffusion of rare earths in porous ion exchanger rounding by EDTA solution
International Nuclear Information System (INIS)
Ling Daren; Xie Weije
1991-01-01
The self-diffusion of rate earth (RE) isotopes in porous cation exchangers with various radii or different pore structures rounding by EDTA solution was studied. The intraparticle effective diffusivity De was calculated by Boyd's method and Kataoka's bi-disperse pore model, and through further calculation the solid phase diffusivity Dg and macropore diffusivity Dp were also obtained. (author)
Diffusion Mechanisms and Lattice Locations of Thermal-Equilibrium Defects in Si-Ge Alloys
Lyutovich, K; Touboltsev, V; Laitinen, P O; Strohm, A
2002-01-01
It is generally accepted that Ge and Si differ considerably with respect to intrinsic-point-defect-mediated diffusion. In Ge, the native point defects dominating under thermal-equilibium conditions at all solid-state temperatures accessible in diffusion experiments are vacancies, and therefore Ge self-diffusion is vacancy-controlled. In Si, by contrast, self-interstitials and vacancies co-exist in thermal equilibrium. Whereas in the most thoroughly investigated temperature regime above about 1000$^\\circ$C Si self-diffusion is self-interstitial-controlled, it is vacancy-controlled at lower temperatures. According to the scenario displayed above, self-diffusion in Si-Ge alloys is expected to change from an interstitialcy mechanism on the Si side to a vacancy mechanism on the Ge side. Therefore, $^{71}$Ge self-diffusion experiments in Si$_{1- \\it y}$Ge$_{\\it y}$ as a function of composition Y are highly interesting. In a first series of experiments the diffusion of Ge in 0.4 to 10 $\\mu$m thick, relaxed, low-disl...
International Nuclear Information System (INIS)
Cousty, J.P.
1981-12-01
In this work, we have studied the influence of atomic structure of crystal surface on surface self-diffusion in the medium temperature range. Two ways are followed. First, we have measured, using a radiotracer method, the self-diffusion coefficient at 820 K (0.6 T melting) on copper surfaces both the structure and the cleanliness of which were stable during the experiment. We have shown that the interaction between mobile surface defects and steps can be studied through measurements of the anisotropy of surface self diffusion. Second, the behavior of an adatom and a surface vacancy is simulated via a molecular dynamics method, on several surfaces of a Lennard Jones crystal. An inventory of possible migration mechanisms of these surface defects has been drawn between 0.35 and 0.45 Tsub(m). The results obtained with both the methods point out the influence of the surface atomic structure in surface self-diffusion in the medium temperature range [fr
Structure and thermal stability of nanocrystalline materials
Indian Academy of Sciences (India)
R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22
, ... Advances in nanoscience and nanotechnology are expected to have major impact on human .... faces, Baloghet al(2000) have reported that the grain boundary of ..... volume self-diffusion (Lu 1996; Krill et al 2001; Lu et al 1995) implies that ...
Optimization for sinusoidal profiles in surface relief gratings ...
Indian Academy of Sciences (India)
2014-02-07
Feb 7, 2014 ... filometry [7–9] and monitoring of surface self-diffusion of solids under ultrahigh vacuum conditions [10]. In the present work, recording parameters, i.e. exposure time and deve- lopment time for fabrication of such holographic gratings have been optimized to obtain nearly perfect sinusoidal profiles in the ...
On creep of directionally solidified eutectic Co-Cr-C-base superalloys
International Nuclear Information System (INIS)
Hildebrandt, U.W.
1981-01-01
It is shown in the present paper that the stress exponent and the activation energy of an Al-modified 73 C-alloy agree with the following mechanisms: diffusion controlled climbing of dislocation takes place and, the activation energy is in accordance with the self-diffusion energy of chromium, particularly that of Cr in Cr 7 C 3 . (orig.) [de
A Simple Molecular Dynamics Lab to Calculate Viscosity as a Function of Temperature
Eckler, Logan H.; Nee, Matthew J.
2016-01-01
A simple molecular dynamics experiment is described to demonstrate transport properties for the undergraduate physical chemistry laboratory. The AMBER package is used to monitor self-diffusion in "n"-hexane. Scripts (available in the Supporting Information) make the process considerably easier for students, allowing them to focus on the…
Non-local viscosity of polymer melts approaching their glassy state
DEFF Research Database (Denmark)
Puscasu, Ruslan; Todd, Billy; Daivis, Peter
2010-01-01
The nonlocal viscosity kernels of polymer melts have been determined by means of equilibrium molecular dynamics upon cooling toward the glass transition. Previous results for the temperature dependence of the self-diffusion coefficient and the value of the glass transition temperature are confirmed...
Scaling Behavior of Dendritic Nanoparticle Mobility in Semidilute Polymer Solutions
Kort, de D.W.; Rombouts, W.H.; Hoeben, F.J.M.; Janssen, H.M.; As, van H.; Duynhoven, van J.P.M.
2015-01-01
In our studies on particle mobility in polymer solutions, we have investigated and determined self-diffusion coefficients of nanoparticles in semidilute solutions of poly(ethylene glycol) (PEG, Mw = 6, 20, 35, and 100 kDa). Specially designed PEGylated dendrimers with well-defined sizes (dh =
Investigation of point defects diffusion in bcc uranium and U–Mo alloys
International Nuclear Information System (INIS)
Smirnova, D.E.; Kuksin, A.Yu.; Starikov, S.V.
2015-01-01
We present results of investigation of point defects formation and diffusion in pure γ-U and γ-U–Mo fuel alloys. The study was performed using molecular dynamics simulation with the different interatomic potentials. The point defects formation and migration energies were estimated for bcc γ-U and U–9 wt.%Mo alloy. The calculated diffusivities of atoms via defects are provided for pure γ-U and for the alloy components. Analysis of simulation results shows that self-interstitial atoms play a leading role in the self-diffusion processes in the materials studied. This fact can explain a remarkably high self-diffusion mobility observed experimentally for γ-U. The self-diffusion coefficients in γ-U calculated in this assumption agree with the data measured experimentally. It is shown that alloying of γ-U with Mo increase formation energy for self-interstitial atoms and decelerate their mobility. These changes lead to decrease of self-diffusion coefficients in U–Mo alloy compared to pure U
Transport properties of liquids
International Nuclear Information System (INIS)
Rajagopal, K.
1976-07-01
The transport coefficients, self diffusivity, dinamical viscosity,total viscosity (i.e., the first and second viscosity coefficient) and thermal conductivity, are calculated at several temperatures and saturation pressures for the Argon, Krypton and Xenon liquids, from the Mie otential and the hard sphere theory. (L.C.) [pt
An introduction to visualization of diffusion tensor imaging and its applications
Vilanova, A.; Zhang, S.; Kindlmann, G.; Laidlaw, D.H.; Weickert, J.; Hagen, H.
2005-01-01
Summary. Water diffusion is anisotropic in organized tissues such as white matter and muscle. Diffusion tensor imaging (DTI), a non-invasive MR technique, measures water self-diffusion rates and thus gives an indication of the underlying tissue microstructure. The diffusion rate is often expressed
Hendriks, Frank|info:eu-repo/dai/nl/412642697; Meirer, Florian; Kubarev, Alexey V.; Ristanovic, Zoran|info:eu-repo/dai/nl/328233005; Roeffaers, Maarten B J; Vogt, Eelco T. C.|info:eu-repo/dai/nl/073717398; Bruijnincx, Pieter C. A.|info:eu-repo/dai/nl/33799529X; Weckhuysen, Bert M.|info:eu-repo/dai/nl/285484397
2017-01-01
We used single-molecule fluorescence microscopy to study self-diffusion of a feedstock-like probe molecule with nanometer accuracy in the macropores of a micrometer-sized, real-life fluid catalytic cracking (FCC) particle. Movies of single fluorescent molecules allowed their movement through the
Czech Academy of Sciences Publication Activity Database
Svoboda, Martin; Brennan, J. K.; Lísal, Martin
2015-01-01
Roč. 113, 9-10 (2015), s. 1124-1136 ISSN 0026-8976 R&D Projects: GA ČR(CZ) GA13-02938S Institutional support: RVO:67985858 Keywords : carbon dioxide separation * density profiles * self-diffusion coefficients Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.837, year: 2015
Transport coefficients for dense hard-disk systems
García-Rojo, R.; Luding, S.; Brey, J.J.
2006-01-01
A study of the transport coefficients of a system of elastic hard disks based on the use of Helfand-Einstein expressions is reported. The self-diffusion, the viscosity, and the heat conductivity are examined with averaging techniques especially appropriate for event-driven molecular dynamics
Contribution of proton NMR relaxation to the investigation of ...
Indian Academy of Sciences (India)
dominant in the low frequency range, translational self-diffusion is dominant in .... geometry of the core (rod-like vs. disc-like) and the particular orientation of its main sym- .... out of the molecular disc plane are constrained by the piling up of the ...
Krekelberg, William P; Siderius, Daniel W; Shen, Vincent K; Truskett, Thomas M; Errington, Jeffrey R
2017-08-03
Using molecular simulations, we investigate how the range of fluid-fluid (adsorbate-adsorbate) interactions and the strength of fluid-solid (adsorbate-adsorbent) interactions impact the strong connection between distinct adsorptive regimes and distinct self-diffusivity regimes reported in [Krekelberg, W. P.; Siderius, D. W.; Shen, V. K.; Truskett, T. M.; Errington, J. R. Langmuir 2013 , 29 , 14527-14535]. Although increasing the fluid-fluid interaction range changes both the thermodynamics and the dynamic properties of adsorbed fluids, the previously reported connection between adsorptive filling regimes and self-diffusivity regimes remains. Increasing the fluid-fluid interaction range leads to enhanced layering and decreased self-diffusivity in the multilayer-formation regime but has little effect on the properties within film-formation and pore-filling regimes. We also find that weakly attractive adsorbents, which do not display distinct multilayer formation, are hard-sphere-like at super- and subcritical temperatures. In this case, the self-diffusivity of the confined and bulk fluid has a nearly identical scaling-relationship with effective density.
Crystallization in metglass: growth mechanism of crystals and radiation effects in Fe Ni P B
International Nuclear Information System (INIS)
Limoge, Y.; Barbu, A.
1981-08-01
Studying crystallization mechanisms and transport properties in amorphous metallic alloys we propose a model for systems wich are displaying eutectoid decomposition. Bringing together self diffusion, electron microscopy and electron irradiation experiments on a Fe Ni P B alloys we have shown that crystallization controlled by interfacial diffusion at the crystal surface can explain all the observed features of the experimental behaviour
Draft paper: On the analysis of diffusive mass transfer in ex-vessel corium pools
International Nuclear Information System (INIS)
Frolov, Kyrill N.
2003-01-01
In case of a severe accident at a nuclear power plant (NPP) involving the reactor pressure vessel (RPV) melt-through, confident solidification of ex-vessel corium is the imperative condition of its safe retention within the plant containment. The rate-determining process for solidification of ex-vessel coriums in the long-term is the chemical diffusion in the liquid phase at the solid-liquid interface. The process of chemical diffusion in the diffusive boundary layer can evolve taking on different rates, depending on the boundary conditions and the melt composition. Nonetheless, the chemical diffusion rates would entwine the self-diffusivities of corium constituents, which in turn would depend on the melt chemical composition. This work looks at some aspects of analytical and experimental determination of self-diffusivities of corium constituents. Following the corium-concrete interaction, an ex-vessel corium melt would contain several chemical components, including a fraction of silica. Accordingly, ex-vessel corium is considered in this paper as a silicate melts. In the realm of the geological and glass sciences, where silicate melts are most often discussed, the diffusive transport and viscous flow are conceived interrelated from a phenomenological point of view. Though the viscous and diffusive mass transfer mechanisms are not identical for different species even in the same melt, a combination of semi-empirical models can still provide an estimation of the diffusion thresholds in ex-vessel corium melts. Thus, the first part of this paper presents an analysis of the applicability of such empirical models for simple silicate melts based on the published data. This is followed by an estimation of diffusivities in melt compositions typical of ex-vessel coriums. Alternatively, although the general trend towards a coupled description of the viscous flow and diffusion for ex-vessel corium melts seems promising, it is limited to published data on self-diffusivities of
Producing infectious enterovirus type 71 in a rapid strategy
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Qin E-De
2010-06-01
Full Text Available Abstract Background Enterovirus 71 (EV71 is an etiologic agent of hand-foot-and-mouth disease (HFMD, and recent HFMD epidemics worldwide have been associated with a severe form of brainstem encephalitis associated with pulmonary edema and high case-fatality rates. EV71 contains a positive-sense single-stranded genome RNA of approximately 7400 bp in length which encodes a polyprotein with a single open reading frame (ORF, which is flanked by untranslated regions at both the 5' and 3' ends. Results A long distance RT-PCR assay was developed to amplify the full length genome cDNA of EV71 by using specific primes carrying a SP6 promoter. Then the in vitro synthesized RNA transcripts from the RT-PCR amplicons were then transfected into RD cells to produce the rescued virus. The rescued virus was further characterized by RT-PCR and indirect fluorescent-antibody (IFA assay in comparison with the wild type virus. The rescued viruses were infectious on RD cells and neurovirulent when intracerebrally injected into suckling mice. Conclusions Thus, we established a rapid method to produce the infectious full length cDNA of EV71 directly from RNA preparations and specific mutations can be easily engineered into the rescued enterovirus genome by this method.
Epidemiology of childhood enterovirus infections in Hangzhou, China.
Li, Wei; Zhang, Xiao; Chen, Xi; Cheng, Yu-Ping; Wu, Yi-Dong; Shu, Qiang; Chen, Xue-Jun; Shang, Shi-Qiang
2015-04-14
There are over 100 serotypes of enterovirus species A-D, which are the common cause of various symptoms in infants, such as meningitis, encephalitis and hand foot mouth disease (HFMD). This study aims to investigate the epidemiological characteristics of enteroviruses in Hangzhou, Zhejiang province, China, and to provide relevant information to guide public health responses and interventions. Systematic surveillance was conducted on enterovirus infections. Samples were collected from children admitted to the inpatient wards and outpatient departments between January 2010 and December 2012 in the Children's Hospital, Zhejiang University School of Medicine. Enteroviruses from all specimens were detected by RT-PCR using a commercialized detection kit. From 13026 samples collected and examined, 2673 (21.21%) were found positive for enteroviruses. The annual enterovirus-positive rate decreased from 32.78% in 2010 to 14.23% in 2012. Positivity rate for enteroviruses was highest among children aged less than 5 years. The monthly positivity rate for enterovirus infection ranged from 2.6% to 34.83%, with a peak in June and July. Serotypes causing severe symptoms such as HFMD including EV71 and CA16 were decreasing, while the proportion of unidentified EV serotypes causing herpangina and viral encephalitis were on the rise. EV infection is highly prevalent among young children in Hangzhou, as it is in the most other parts of the world. Further surveillance using methods that can subtype all EVs is warranted to better monitor these infections and their etiology.
Ji, Zheng; Wang, Xiaochang C; Xu, Limei; Zhang, Chongmiao; Funamizu, Naoyuki; Okabe, Satoshi; Sano, Daisuke
2014-06-01
A polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) method was employed to estimate the contamination sources of human enteroviruses and understand how their dominant strains vary in a wastewater treatment and reclamation system consisting of sewage collection, wastewater treatment with membrane bioreactor and open lakes for reclaimed water storage and reuse. After PCR-DGGE using a selected primer set targeting enteroviruses, phylogenetic analysis of acquired enterovirus gene sequences was performed. Enteroviruses identified from the septic tank were much more diverse than those from grey water and kitchen wastewater. Several unique types of enterovirus different from those in wastewater samples were dominant in a biological wastewater treatment unit. Membrane filtration followed by chlorination was proved effective for physically eliminating enteroviruses; however, secondary contamination likely occurred as the reclaimed water was stored in artificial lakes. Enterovirus 71 (EV71), a hand-foot-and-mouth disease (HFMD) viral pathogen, was detected mainly from the artificial lakes, implying that wastewater effluent was not the contamination source of EV71 and that there were unidentified non-point sources of the contamination with the HFMD viral pathogen in the reclaimed water stored in the artificial lakes. The PCR-DGGE targeting enteroviruses provided robust evidence about viral contamination sources in the wastewater treatment and reclamation system.
Inhibition of enterovirus 71 replication by an α-hydroxy-nitrile derivative NK-1.9k.
Wang, Yaxin; Cao, Lin; Zhai, Yangyang; Ma, Jiaming; Nie, Quandeng; Li, Ting; Yin, Zheng; Sun, Yuna; Shang, Luqing
2017-05-01
Enterovirus 71 (EV71) is one of the major etiological agents of human hand-foot-and-mouth disease (HFMD) worldwide. EV71 infection in young children and people with immunodeficiency causes severe symptoms with a high fatality rates. However, there is still no approved drugs to treat such infections. Based on our previous report of a peptide-aldehyde anti-EV71 protease, we present here a highly specific α-hydroxy-nitrile derivative NK-1.9k, which inhibited the proliferation of multiple EV71 strains and coxsackievirus A16 (CVA16) in various cells with EC 50 of 37.0 nM with low cytotoxicity (CC 50 > 200 μM). The hydroxy-nitrile covalent warhead conferred NK-1.9k high potency and selectivity to interact with the cysteine residue of the active site of the viral protease. We also documented the resistance to NK-1.9k with a N69S mutation in EV71 3C pro . The combination of NK-1.9k and EV71 polymerase or entry inhibitors produced strong synergistic antiviral effects. Collectively, our findings suggest our compounds can potentially be developed as drugs for the treatment of HFMD. Copyright © 2017. Published by Elsevier B.V.
Outbreak of Enterovirus - 71 Meningitis in Calicut
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CK Sasidharan
2016-04-01
Full Text Available Objective: Enterovirus 71(EV 71 causes wide spectrum of infections ranging from asymptomatic conditions to clinical syndromes like diarrhea, rash, hand-foot-and mouth disease (HFMD, herpangina, aseptic meningitis, encephalitis, myocarditis, acute flaccid paralysis, bulbar and brainstem encephalitis Guillain Barre syndrome, pulmonary haemorrhage. This study deals with an outbreak of aseptic meningitis in children caused by EV 71 virus. Methods: The authors report an outbreak of aseptic meningitis in children in and around Calicut in June 2008. Clinical and laboratory study was done in collaboration with National Centre for Disease Control, New Delhi. 149 children with aseptic meningitis were studied and followed up from June 2008 to May 2009. Result: All children had clinical features suggestive of aseptic meningitis and serology showed the rising antibody titre against EV 71 virus infection. CSF analysis also showed four fold rise in antibodies in one and ≥ 1:2 neutralising antibodies titer against EV- 71 in four samples indicating meningitis due to EV-71. Conclusion: EV 71 was identified as the causative agent of the outbreak of aseptic meningitis in the study and the fact that the EV 71 infection has evolved from minor illness like HFMD to major illness like aseptic meningitis from the same locality is truly alarming.
Directory of Open Access Journals (Sweden)
Hailong Lin
2016-01-01
Full Text Available This study aimed to evaluate the clinical efficacy and safety of using the traditional Chinese herbal medicine Scutellaria baicalensis for the treatment of severe HFMD in 725 patients aged >1 year in a multicenter, retrospective analysis. The patients were divided into the S. baicalensis and ribavirin groups, and the temperatures, presence or absence of skin rashes and oral lesions, nervous system (NS involvement, and viral loads of the patients, as well as the safety of the treatments, were evaluated. The median duration of fever, median time to NS involvement, and the number of patients with oral ulcers and/or vesicles, as well as skin rashes, were decreased in the S. baicalensis group compared with the ribavirin group. In addition, the EV71 viral loads were decreased in the S. baicalensis group, suggesting that S. baicalensis exerted more potent antiviral effects compared with ribavirin. The present study demonstrated that S. baicalensis was suitable for the treatment of severe HFMD in patients aged >1 year, since it was shown to rapidly relieve fever, attenuate oral lesions and rashes, and improve NS involvement. Furthermore, it was demonstrated to be relatively safe for topical application.
Wei, Mingwei; Meng, Fanyue; Wang, Shiyuan; Li, Jingxin; Zhang, Yuntao; Mao, Qunying; Hu, Yuemei; Liu, Pei; Shi, Nianmin; Tao, Hong; Chu, Kai; Wang, Yuxiao; Liang, Zhenglun; Li, Xiuling; Zhu, Fengcai
2017-01-01
This study evaluated the 2-year efficacy, immunogenicity, and safety of the Vigoo enterovirus 71 (EV71) vaccine. In an initial phase 3 study, we randomly assigned healthy infants and children aged 6-35 months (ratio, 1:1) to receive 2 doses of either EV71 vaccine (5120 participants) or placebo (5125 participants) at days 0 and 28, and followed them for 12 months after vaccination. In this extended follow-up study, we continued to evaluate the efficacy, immunogenicity, and safety of the EV71 vaccine for up to 2 years. Overall efficacy was 94.84% (95% confidence interval [CI], 83.53%-98.38%) during the 2-year follow-up period (P vaccine efficacy during the second year was 100.00% (95% CI, 84.15%-100.00%) against EV71-associated hand-foot-and-mouth disease (HFMD; P vaccine-related serious adverse events were recorded. Two doses of Vigoo EV71 vaccine could provide sustained protection against EV71-associated HFMD in healthy Chinese children. NCT01508247. © The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.
Chen, Xiaojin; Yan, Jun; Yu, Shuying; Wang, Pingping
2018-01-01
Enterovirus 71 (EV71) is a pathogenic factor of severe hand, foot, and mouth disease (HFMD). No vaccine or specific treatment is currently available for EV71 infection. Hence, we developed a buccal mucoadhesive gel containing matrine to protect against HFMD. Mucoadhesive gels were prepared by Carbopol 974P and were combined with Carbopol 971P, sodium carboxymethyl cellulose (CMC-Na), or hydroxypropylmethy cellulose (HPMC K100M). The formulations were characterized in terms of tensile testing and continuous flow techniques for mucoadhesion. The rheological studies and in vitro drug release characteristics were also investigated. The results showed that combinations of two polymers significantly improved mucoadhesion, especially Carbopol 974P blended with HPMC. Carbopol 974P to HPMC blend ratios of 1:1 and 2:1 induced better mucoadhesion in the tensile test and continuous flow method, respectively. The most sustained release was obtained at a Carbopol 974P to HPMC ratio of 2.5:1. A predominantly non-Fickian diffusion release mechanism was obtained. The gel containing 2.5% Carbopol 974P combined with 1% HPMC showed good mucoadhesion properties and sustained drug release.
Cai, Yicun; Ku, Zhiqiang; Liu, Qingwei; Leng, Qibin; Huang, Zhong
2014-05-01
Enterovirus 71 (EV71) and coxsackievirus A16 (CA16) are the two major causative agents of hand, foot and mouth disease (HFMD), which is an infectious disease frequently occurring in children. A bivalent vaccine against both EV71 and CA16 is highly desirable. In the present study, we compare monovalent inactivated EV71, monovalent inactivated CA16, and a combination vaccine candidate comprising of both inactivated EV71 and CA16, for their immunogenicity and in vivo protective efficacy. The two monovalent vaccines were found to elicit serum antibodies that potently neutralized the homologous virus but had no or weak neutralization activity against the heterologous one; in contrast, the bivalent vaccine immunized sera efficiently neutralized both EV71 and CA16. More importantly, passive immunization with the bivalent vaccine protected mice against either EV71 or CA16 lethal infections, whereas the monovalent vaccines only prevented the homologous but not the heterologous challenges. Together, our results demonstrate that the experimental bivalent vaccine comprising of inactivated EV71 and CA16 induces a balanced protective immunity against both EV71 and CA16, and thus provide proof-of-concept for further development of multivalent vaccines for broad protection against HFMD. Copyright © 2014 Elsevier Ltd. All rights reserved.
Xu, Lin; Su, Weiheng; Jin, Jun; Chen, Jiawen; Li, Xiaojun; Zhang, Xuyuan; Sun, Meiyan; Sun, Shiyang; Fan, Peihu; An, Dong; Zhang, Huafei; Zhang, Xiguang; Kong, Wei; Ma, Tonghui; Jiang, Chunlai
2014-07-17
Hand, foot and mouth disease (HFMD) is a common pediatric illness mainly caused by infection with enterovirus 71 (EV71) and coxsackievirus A16 (CA16). The frequent HFMD outbreaks have become a serious public health problem. Currently, no vaccine or antiviral drug for EV71/CA16 infections has been approved. In this study, a two-step screening platform consisting of reporter virus-based assays and cell viability‑based assays was developed to identify potential inhibitors of EV71/CA16 infection. Two types of reporter viruses, a pseudovirus containing luciferase-encoding RNA replicons encapsidated by viral capsid proteins and a full-length reporter virus containing enhanced green fluorescent protein, were used for primary screening of 400 highly purified natural compounds. Thereafter, a cell viability-based secondary screen was performed for the identified hits to confirm their antiviral activities. Three compounds (luteolin, galangin, and quercetin) were identified, among which luteolin exhibited the most potent inhibition of viral infection. In the cell viability assay and plaque reduction assay, luteolin showed similar 50% effective concentration (EC50) values of about 10 μM. Luteolin targeted the post-attachment stage of EV71 and CA16 infection by inhibiting viral RNA replication. This study suggests that luteolin may serve as a lead compound to develop potent anti-EV71 and CA16 drugs.
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Chih-Wei Lin
2014-01-01
Full Text Available We assessed two strategies for preparing candidate vaccines against hand, foot, and mouth disease (HFMD caused mainly by infections of enterovirus (EV 71 and coxsackievirus (CV A16. We firstly design and optimize the potency of adjuvant combinations of emulsion-based delivery systems, using EV71 candidate vaccine as a model. We then perform immunogenicity studies in mice of EV71/CVA16 antigen combinations formulated with PELC/CpG. A single dose of inactivated EV71 virion (0.2 μg emulsified in submicron particles was found (i to induce potent antigen-specific neutralizing antibody responses and (ii consistently to elicit broad antibody responses against EV71 neutralization epitopes. A single dose immunogenicity study of bivalent activated EV71/CVA16 virion formulated with either Alum or PELC/CpG adjuvant showed that CVA16 antigen failed to elicit CVA16 neutralizing antibody responses and did not affect EV71-specific neutralizing antibody responses. A boosting dose of emulsified EV71/CVA16 bivalent vaccine candidate was found to be necessary to achieve high seroconversion of CVA16-specific neutralizing antibody responses. The current results are important for the design and development of prophylactic vaccines against HFMD and other emerging infectious diseases.
Feng, Min; Guo, Sujie; Fan, Shengtao; Zeng, Xiaofeng; Zhang, Ying; Liao, Yun; Wang, Jianbin; Zhao, Ting; Wang, Lichun; Che, Yanchun; Wang, Jingjing; Ma, Na; Liu, Longding; Yue, Lei; Li, Qihan
2016-01-01
The pathological manifestations of fatal cases of human hand, foot, and mouth disease (HFMD) caused by enterovirus 71 (EV71) are characterized by inflammatory damage to the central nervous system (CNS). Here, the dynamic distribution of EV71 in the CNS and the subsequent pathological characteristics within different regions of neonatal rhesus macaque brain tissue were studied using a chimeric EV71 expressing green fluorescence protein. The results were compared with brain tissue obtained from the autopsies of deceased EV71-infected HFMD patients. These observations suggested that the virus was prevalent in areas around the blood vessels and nerve nuclei in the brain stem and showed a preference for astrocytes in the CNS. Interestingly, infected astrocytes within the in vivo and in vitro human and macaque systems exhibited increased expression of excitatory neurotransmitters and cytokines that also stimulated the neuronal secretion of the excitatory neurotransmitters noradrenalin and adrenalin, and this process most likely plays a role in the pathophysiological events that occur during EV71 infection.
Genetic characterization of Enterovirus 71 strains circulating in Vietnam in 2012.
Donato, Celeste; Hoi, Le Thi; Hoa, Nguyen Thi; Hoa, Tran Mai; Van Duyet, Le; Dieu Ngan, Ta Thi; Van Kinh, Nguyen; Vu Trung, Nguyen; Vijaykrishna, Dhanasekaran
2016-08-01
Enterovirus 71 subgenogroup C4 caused the largest outbreak of Hand, Foot and Mouth Disease (HFMD) in Vietnam during 2011-2012, resulting in over 200,000 hospitalisations and 207 fatalities. A total of 1917 samples with adequate volume for RT-PCR analysis were collected from patients hospitalised with HFMD throughout Vietnam and 637 were positive for EV71. VP1 gene (n=87) and complete genome (n=9) sequencing was performed. Maximum-likelihood phylogenetic analysis was performed to characterise the B5, C4 and C5 strains detected. Sequence analyses revealed that the dominant subgenogroup associated with the 2012 outbreak was C4, with B5 and C5 strains representing a small proportion of these cases. Numerous countries in the region including Malaysia, Taiwan and China have a large influence on strain diversity in Vietnam and understanding the transmission of EV71 throughout Southeast Asia is vital to inform preventative public health measures and vaccine development efforts. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.
Neutralizing Antibodies to Enterovirus 71 in Belém, Brazil
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Maria de Lourdes C Gomes
2002-01-01
Full Text Available Non-polio enteroviruses (Coxsackievirus A, Coxsackievirus B, Echovirus and EV 68-72 which belong to the enterovirus (EV genus, Picornaviridae family, may be responsible for acute flaccid paralysis, aseptic meningitis, myocarditis, hepatitis, pleurodinia, neonatal sepsis, hand, foot and mouth disease (HFMD even though 50-80% of infections are asymptomatic. EV 71 has been responsible for outbreaks and epidemics of HFMD and acute neurologic disease justifying its study in our country. The aim of this study was to detect neutralizing antibodies (NtAb to EV 71 in individuals up to 15 years of age living in Belém, State of Pará, northern Brazil. Serum samples from 238 patients attending the Virology Sector of Evandro Chagas Institute in Belém, Brazil, were analyzed using microneutralization tests that included RD cells and BrCr strain. Overall 40.8% (97/238 of tested samples had NtAb to EV 71. Regarding the distribution per age group, 85.2% (92/108 of patients aged 0-3 years had no NtAb to this virus and 69.2% of those 12 to15 years of age were seropositive. These results confirm that EV 71 infection occurs in the city of Belém; and that a high rate of individuals in this study were infected aged 3 years and over and, when aged 15 years nearly 70% had EV 71 NtAb.
Li, Huajun; Li, Shuxian; Zheng, Jianfeng; Cai, Chunyan; Ye, Bin; Yang, Jun; Chen, Zhimin
2015-03-01
Enterovirus 71 (EV71) infection can cause severe neurological complications including meningoencephalitis (ME) in some patients with hand, foot and mouth disease (HFMD). However, to date no studies have reported changes in cytokine concentrations and their correlations with clinical variables in patients with ME following EV71 infection. In this study, responses of Th1/Th2 cytokine, including IL-2, IL-4, IL-6, IL-10, TNF-α and IFN-γ, in cerebrospinal fluid (CSF) from patients with EV71-related HFMD with ME and patients with febrile convulsions (FC) were analyzed using cytometric bead array technology. It was found that CSF IL-6 and IFN-γ concentrations were significantly higher in patients with EV71-related ME than in those with FC. Additionally, both CSF IL-6 and IFN-γ concentrations were correlated with CSF cytology, fever duration and duration of hospital stay. More interestingly, a positive correlation between CSF IL-6 and IFN-γ concentrations was observed. Finally, receiver operating characteristic analysis revealed that when a cutoff value of 9.40 pg/mL was set for IL-6, the sensitivity and specificity were 84.5% and 85.5%, respectively, for discriminating EV71-related ME from FC. In conclusion, IL-6 and IFN-γ may be associated with EV71-induced neuropathology. © 2015 The Societies and Wiley Publishing Asia Pty Ltd.
Zhu, Zheng; Qi, Yuhua; Fan, Huan; Cui, Lunbiao; Shi, Zhiyang
2016-01-01
Hand, foot, and mouth disease (HFMD), mainly caused by coxsackievirus A16 (CVA16) and enterovirus 71 (EV71) infections, remains a serious public health issue with thousands of newly diagnostic cases each year since 2008 in China. The mechanisms underlying viral infection, however, are elusive to date. In the present study, we systematically investigated the host cellular microRNA (miRNA) expression patterns in response to CVA16 and EV71 infections. Through microarray examination, 27 miRNAs (15 upregulated and 12 downregulated) were found to be coassociated with the replication process of two viruses, while the expression levels of 15 and 5 miRNAs were significantly changed in CVA16- and EV71-infected cells, respectively. A great number of target genes of 27 common differentially expressed miRNAs were predicted by combined use of two computational target prediction algorithms, TargetScan and MiRanda. Comprehensive bioinformatic analysis of target genes in GO categories and KEGG pathways indicated the involvement of diverse biological functions and signaling pathways during viral infection. These results provide an overview of the roles of miRNAs in virus-host interaction, which will contribute to further understanding of HFMD pathological mechanisms.
Cellular receptors for human enterovirus species A
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Yorihiro eNishimura
2012-03-01
Full Text Available Human enterovirus species A (HEV-A is one of the four species of HEV in the genus Enterovirus in the family Picornaviridae. Among HEV-A, coxsackievirus A16 (CVA16 and enterovirus 71 (EV71 are the major causative agents of hand, foot, and mouth disease (HFMD. Some other types of HEV-A are commonly associated with herpangina. Although HFMD and herpangina due to HEV-A are common febrile diseases among infants and children, EV71 can cause various neurological diseases, such as aseptic meningitis and fatal encephalitis.Recently, two human transmembrane proteins, P-selectin glycoprotein ligand-1 (PSGL-1 and scavenger receptor class B, member 2 (SCARB2, were identified as functional receptors for EV71 and CVA16. In in vitro infection experiments using the prototype HEV-A strains, PSGL-1 and SCARB2 could be responsible for the specific receptors for EV71 and CVA16. However, the involvement of both receptors in the in vitro and in vivo infections of clinical isolates of HEV-A has not been clarified yet. To elucidate a diverse array of the clinical outcome of HEV-A-associated diseases, the identification and characterization of HEV-A receptors may provide useful information in understanding the HEV-A pathogenesis at a molecular level.
Recent developments in antiviral agents against enterovirus 71 infection.
Tan, Chee Wah; Lai, Jeffrey Kam Fatt; Sam, I-Ching; Chan, Yoke Fun
2014-02-12
Enterovirus 71 (EV-71) is the main etiological agent of hand, foot and mouth disease (HFMD). Recent EV-71 outbreaks in Asia-Pacific were not limited to mild HFMD, but were associated with severe neurological complications such as aseptic meningitis and brainstem encephalitis, which may lead to cardiopulmonary failure and death. The absence of licensed therapeutics for clinical use has intensified research into anti-EV-71 development. This review highlights the potential antiviral agents targeting EV-71 attachment, entry, uncoating, translation, polyprotein processing, virus-induced formation of membranous RNA replication complexes, and RNA-dependent RNA polymerase. The strategies for antiviral development include target-based synthetic compounds, anti-rhinovirus and poliovirus libraries screening, and natural compound libraries screening. Growing knowledge of the EV-71 life cycle will lead to successful development of antivirals. The continued effort to develop antiviral agents for treatment is crucial in the absence of a vaccine. The coupling of antivirals with an effective vaccine will accelerate eradication of the disease.
Wang, D; Wang, X; Geng, Y; An, C
2014-01-01
The objective of this study was to develop a sensitive, specific and rapid approach to diagnose hand foot and mouth disease (HFMD) for an early treatment by using loop-mediated isothermal amplification (LAMP) technique. A reverse-transcription loop-mediated isothermal amplification (RT-LAMP) for detecting EV71 virus was developed, the specificity and sensitivity of RT-LAMP was tested, and the clinical specimens was assayed by the RT-LAMP comparing with conventional reverse-transcription polymerase chain reaction (RT-PCR) and real-time PCR. A total of 116 clinical specimens from the suspected HFMD individual were detected with the RT-LAMP. The detection rate for EV71 was 56.89% by RT-LAMP, 41.38% by real-time PCR and 34.48% by RT-PCR. The minimum detection limit of RT-LAMP was 0.01 PFU, both of RT-PCR and real-time PCR was 0.1PFU. Non-cross-reactive amplification with other enteroviruses was detected in the survey reports. The effectiveness of RT-LAMP is higher than RT-PCR and real-time PCR. The protocol is easy to operate and time saving. It was not an expensive instrument, which was needed; it is an applicable method for rapid diagnosis of the disease, especially in resource-poor countries or in developing countries.
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D Wang
2014-01-01
Full Text Available Purpose : The objective of this study was to develop a sensitive, specific and rapid approach to diagnose hand foot and mouth disease (HFMD for an early treatment by using loop-mediated isothermal amplification (LAMP technique. Materials and Methods : A reverse-transcription loop-mediated isothermal amplification (RT-LAMP for detecting EV71 virus was developed, the specificity and sensitivity of RT-LAMP was tested, and the clinical specimens was assayed by the RT-LAMP comparing with conventional reverse-transcription polymerase chain reaction (RT-PCR and real-time PCR. Results : A total of 116 clinical specimens from the suspected HFMD individual were detected with the RT-LAMP. The detection rate for EV71 was 56.89% by RT-LAMP, 41.38% by real-time PCR and 34.48% by RT-PCR. The minimum detection limit of RT-LAMP was 0.01 PFU, both of RT-PCR and real-time PCR was 0.1PFU. Non-cross-reactive amplification with other enteroviruses was detected in the survey reports. Conclusions : The effectiveness of RT-LAMP is higher than RT-PCR and real-time PCR. The protocol is easy to operate and time saving. It was not an expensive instrument, which was needed; it is an applicable method for rapid diagnosis of the disease, especially in resource-poor countries or in developing countries.
Institute of Scientific and Technical Information of China (English)
叶贵诚; 彭建明; 官燕飞; 袁斌
2016-01-01
Objective To investigate the application value of procalcitonin (PCT ) ,C-reactive protein (CRP) ,prealbumi (PA ) and white blood cell count (WBC))in children with hand-foot-and-mouth disease (HFMD) .Methods A total of 209 children with HFMD were classified into ordinary group (171 patients) and severe group (38 patients) according to the condition of disease ,an-other 30 healthy children were selected as the control group .The levels of PCT ,CRP ,PA and WBC in the three groups were meas-ured and compared .Results The levels of PCT ,CRP ,PA and WBC of ordinary group were 0 .16(0 .08 - 0 .34)μg/L ,11 .7(5 .0 -19 .0)mg/L ,(142 .6 ± 38 .4)mg /L and (11 .3 ± 4 .6) × 129 /L respectively ,and those of severe group were 0 .26(0 .14 - 0 .92)μg /L , 18 .4(5 .3 - 41 .4) mg /L ,(125 .5 ± 32 .9)mg/L and (13 .0 ± 5 .6) × 129 /L respectively .The PCT ,CRP ,PA and WBC in ordinary group and severe group were significantly different with those in the control group (P < 0 .05) .The PCT ,CRP and PA in severe group had statistical differences compared with those in the ordinary group (P< 0 .05) .Conclusion PCT ,CRP ,PA and WBC could be used as reference indexes of inflammation in HFMD ,and could be used in the diagnosis of HFMD in children ,PCT and PA could be used to evaluate the severity of disease .%目的：探讨降钙素原（PCT）、C 反应蛋白（CRP）、前清蛋白（PA ）、白细胞（WBC）计数在儿童手足口病（HFMD）诊断中的应用价值。方法将209例 HFMD 患儿按病情分为普通病例组（171例）及重症病例组（38例），另外选择同期30例健康体检儿童纳入对照组，测定3组儿童 PCT 、CRP 、PA 及 WBC 水平，并进行比较。结果普通病例组的 PCT 、CRP 、PA 、WBC 水平分别为0．16（0．08～0．34）μg ／L 、11．7（5．0～19．0）mg／L 、（142．6±38．4）mg／L 、（11．3±4．6）×129／L ，重症病例组分别为0．26（0．14～0．92）μg／L 、18．4（5．3～41．4
Effect of liquid-phase sintering as a means of quality enhancement of pseudoalloys based on copper
Gordeev, Yu I.; Abkaryan, A. K.; Zeer, G. M.; Lepeshev, A. A.; Zelenkova, E. G.
2017-01-01
The effects of the liquid phase of a metal binder on the microstructure and properties of self-diffusion gradient composite (Cu - Al - ZnO) were investigated. For the compositions considered, it was revealed that at the temperature of about 550 °C, a liquid phase binder forms from nanoparticles Cu - Al. Applying a proper amount of a (Cu - Al) binder appeared to be beneficial for fabricating gradient composites with the desired self-diffusion process. It is also favorable for mass transfer of additives nanoparticles into the volume of a matrix during sintering and for the desired fine microstructure and mechanical properties. For the experimental conditions considered in this study, the best mechanical properties can be obtained when 6 mass % (Cu - Al) of ligature were used, which gave hardness HB at 120, electroerosion wear - 0.092 • 10-6 g / cycle, resistivity - 0.025 mcOm.
International Nuclear Information System (INIS)
Nestle, Nikolaus; Galvosas, Petrik; Geier, Oliver; Zimmermann, Christian; Dakkouri, Marwan; Karger, Jorg
2001-01-01
While the nuclear spin relaxation time changes in hydrating cement materials have been widely studied by various groups during the last 20 years, data on the self-diffusion behavior of the pore water during hydration of a cement paste are much scarcer. Taking advantage of improved spectrometer hardware for pulsed field gradient diffusometry and a specialized pulse sequence which is designed to compensate the detrimental effects of inner magnetic field gradients in the sample we have studied the water self-diffusion behavior in pastes prepared from white cement at various water/cement ratios. For the same mixtures, studies of the transverse spin relaxation behavior were also conducted. A comparison of the results from both techniques shows that the diffusion coefficient starts to decrease only much later than the relaxation times for all pastes studied. [copyright] 2001 American Institute of Physics
Diffusion phenomena of fluorine and cations in molten Li2BeF4, LiBeF3 and NaBeF3
International Nuclear Information System (INIS)
Ohno, Hideo
1984-03-01
Self-diffusion coefficients of fluorine and cations in molten LiF-BeF 2 and NaF-BeF 2 systems were summarized by the capillary reservoir technique. The diffusion coefficients and the activation energies of cations in these molten salts follow a similar behavior with those of cations in molten alkali halides. On the other hand, self-diffusion of fluorine have unusually high diffusion coefficients and activation energies. The characteristic diffusion phenomena of fluorine in these molten alkali fluoroberyllates are very similar to those of oxygen in molten CaO-SiO 2 and CaO-SiO 2 -Al 2 O 3 slag. The dynamical behavior of Li and F in molten Li 2 BeF 4 was also analyzed by NMR technique. According to both these experiments, most probable mechanism of characteristic diffusion of fluorine in these molten systems could be dissociation of F atom from complex anion and long distance diffusion. (author)