Physically and chemically bound H2O in the α-C2S hydrate structure

In this paper, a fundamental practical unit, namely the wedge-shaped enclosure, is proposed as a novel and efficient latent heat storage unit for thermal energy storage. The enthalpy–porosity method that treats the solid and liquid zones as a single domain is employed. Effect of the mushy zone constant C on melting is analyzed and a suitable value is obtained by comparing the numerical results with experimental data in the literature. A series of simulations are conducted to analyze the transient melting coupled with natural convection as well as the heat transfer process. Fourteen units those have different length ratios between top and bottom of the enclosures are investigated and compared by the analysis of transient temperature fields, vertical velocity distributions, and evolution of the melting fronts. It is found that the length ratio n dramatically affects the full melting time and heat transfer intensity. An enclosure of n = 5.5, which has the shortest completion time and the highest heat transfer intensity, is determined as the optimal unit. Compared with the base geometry (n = 1), charging time of the optimal unit (n = 5.5) decreased by 32.8 %, while the heat transfer intensity increased by 45.7 %. This is a significant improvement in the field of latent heat storage.     

General excitations in time-dependent density functional theory

A general framework within time-dependent density functional theory is presented for the calculation of excitations to states of arbitrary multiplicity in molecular systems with a non-singlet ground state. The proposed approach combines generalized orbital excitation operators designed to generate excited states which have well-defined multiplicities and the noncollinear formulation of density functional theory and it can be straightforwardly implemented in currently existing density functional programs.     

Microcirculatory, mitochondrial, and histological changes following cerebral ischemia in swine

Background

Although cerebral palsy (CP) is usually defined as a group of permanent motor disorders due to non-progressive disturbances in the developing fetal or infant brain, recent research has shown that CP individuals are also characterized by altered somatosensory perception, increased pain and abnormal activation of cortical somatosensory areas. The present study was aimed to examine hemispheric differences on somatosensory brain processing in individuals with bilateral CP and lateralized motor impairments compared with healthy controls. Nine CP individuals with left-dominant motor impairments (LMI) (age range 5–28 yrs), nine CP individuals with right-dominant motor impairments (RMI) (age range 7–29 yrs), and 12 healthy controls (age range 5–30 yrs) participated in the study. Proprioception, touch and pain thresholds, as well as somatosensory evoked potentials (SEP) elicited by tactile stimulation of right and left lips and thumbs were compared.

Results

Pain sensitivity was higher, and lip stimulation elicited greater beta power and more symmetrical SEP amplitudes in individuals with CP than in healthy controls. In addition, although there was no significant differences between individuals with RMI and LMI on pain or touch sensitivity, lip and thumb stimulation elicited smaller beta power and more symmetrical SEP amplitudes in individuals with LMI than with RMI.

Conclusions

Our data revealed that brain processing of somatosensory stimulation was abnormal in CP individuals. Moreover, this processing was different depending if they presented right- or left-dominant motor impairments, suggesting that different mechanisms of sensorimotor reorganization should be involved in CP depending on dominant side of motor impairment.     

The influence of different additives on the early-stage hydration of calcium aluminate cement

The thermal decomposition behaviors of 2,4,6-Trinitrotoluene (TNT) and 1-methoxy-2,4-dinitro-benzene (DNAN) were studied by using a NETSCH company accelerating rate calorimetry. Hazard indicators such as onset temperature, adiabatic temperature rise, initial self-heat temperature, maximum self-heating rate, and time-to-maximum temperature rise rate have been determined directly. The kinetic parameters, such as the activation energy (E _a) and the pre-exponential factor (A) were studied from the measured self-heating rate data by assuming order reaction.     

Electronic g-tensors of solvated molecules using the polarizable continuum model

We present the implementation of density functional response theory combined with the polarizable continuum model (PCM), enabling first principles calculations of molecular g-tensors of solvated molecules. The calculated g-tensor shifts are compared with experimental g-tensor shifts obtained from electron paramagnetic resonance spectra for a few solvated species. The results indicate qualitative agreement between the calculations and the experimental data for aprotic solvents, whereas PCM fails to reproduce the electronic g-tensor behavior for protic solvents. This failure of PCM for protic solvents can be resolved by including into the model those solvent molecules which are involved in hydrogen bonding with the solute. The results for the protic solvents show that the explicit inclusion of the solvent molecules of the first solvation sphere is not sufficient in order to reproduce the behavior of the electronic g-tensor in protic solvents, and that better agreement with experimental data can be obtained by including the long-range electrostatic effects accounted for by the PCM approach on top of the explicit hydrogen-bonded complexes.     

Nuclear magnetic shielding of the 113Cd(II) ion in aqua solution: a combined molecular dynamics/density functional theory study

We present a combined molecular dynamics simulation and density functional theory investigation of the nuclear magnetic shielding constant of the (113)Cd(II) ion solvated in aqueous solution. Molecular dynamics simulations are carried out for the cadmium-water system in order to produce instantaneous geometries for subsequent determination of the nuclear magnetic shielding constant at the density functional theory level. The nuclear magnetic shielding constant is computed using a perturbation theory formalism, which includes nonrelativistic and leading order relativistic contributions to the nuclear magnetic shielding tensor. Although the NMR shielding constant varies significantly with respect to simulation time, the value averaged over increasing number of snapshots remains almost constant. The paramagnetic nonrelativistic contribution is found to be most sensitive to dynamical changes in the system and is mainly responsible for the thermal and solvent effects in solution. The relativistic correction features very little sensitivity to the chemical environment, and can be disregarded in theoretical calculations when a Cd complex is used as reference compound in (113)Cd NMR experiments, due to the mutual cancelation between individual relativistic corrections.     

Time-dependent density functional theory for nonlinear properties of open-shell systems

This paper presents response theory based on a spin-restricted Kohn-Sham formalism for computation of time-dependent and time-independent nonlinear properties of molecules with a high spin ground state. The developed approach is capable to handle arbitrary perturbations and constitutes an efficient procedure for evaluation of electric, magnetic, and mixed properties. Apart from presenting the derivation of the proposed approach, we show results from illustrating calculations of static and dynamic hyperpolarizabilities of small Si(3n+1)H(6n+3) (n=0,1,2) clusters which mimic Si(111) surfaces with dangling bond defects. The results indicate that the first hyperpolarizability tensor components of Si(3n+1)H(6n+3) have an ordering compatible with the measurements of second harmonic generation in SiO2/Si(111) interfaces and, therefore, support the hypothesis that silicon surface defects with dangling bonds are responsible for this phenomenon. The results exhibit a strong dependence on the quality of basis set and exchange-correlation functional, showing that an appropriate set of diffuse functions is required for reliable predictions of the first hyperpolarizability of open-shell compounds.     

NMR spin-spin coupling constants in polymethine dyes as polarity indicators

Herein, we explore the use of spin-spin coupling constants (SSCCs) in merocyanine (MCYNE) dyes as indicators of polarity. For this purpose, we use Car-Parrinello hybrid quantum mechanics/molecular mechanics (QM/MM) to determine the structures of MCYNE in solvents of different polarity, followed by computations of the SSCCs by using QM/MM linear-response theory. The molecular geometry of MCYNE switches between neutral, cyanine-like, and zwitterionic depending on the polarity of the solvent. This structural variation is clearly reflected in the proton SSCCs in the polymethine backbone, which are highly sensitive to the dielectric nature of the environment; this mechanism can be used as a "polarity indicator" for different microenvironments. This result is highlighted by computing the SSCCs of the MCYNE probe in the cavity of the beta-lactoglobulin protein. The computed SSCCs clearly indicate a non-polar hydrophobic dielectric nature of this cavity.