Magnetic properties of TCNQ complex salts with polycations containing sulfur atoms in the main chain

The magnetic properties of TCNQ anion salts with polycations containing sulfur atoms in the main chain were investigated using ESR and magnetostatic methods. For the majority of these complex salts asymmetric ESR lines were recorded and characterized by g_⊥, g_∥, and ΔH_max values as well as by an asymmetry parameter δ′. An analysis of symmetrical ESR lines was carried out by the linear anamorphose technique. The temperature dependence of magnetic susceptibility χ_p was studied for the K_s [x, y] complex salts obtained. A correlation was found between the magnetic properties (ΔH_max, δ′, and χ_p) and the electrical properties ([sgrave]₂₅, E_a) studied in our previous works.     

Organosilane modified silica/polydimethylsiloxane mixed matrix membranes for enhanced propylene/nitrogen separation

Gas transport behaviors of oxygen (O₂), nitrogen (N₂) and propylene (C₃H₆) in polydimethylsiloxane (PDMS) mixed matrix membranes (MMM) containing modified silica (SiO₂) nanoparticles are presented. Two surface modified SiO₂ nanoparticles, silica dimethyloctyl silane (Si-DMOS) and silica dimethylphenyl silane (Si-DMPS), were used as fillers. Surface modification was carried out through silanization, which was confirmed via Fourier transform infrared spectroscopy. From elemental analysis, degrees of modifications on Si-DMOS and Si-DMPS were estimated to be 29.64% and 79.89%, respectively. Field emission scanning electron microscopy showed uniform distribution of the modified SiO₂ fillers in MMMs. Both MMMs exhibited reduced O₂ and N₂ permeabilities as compared to pure PDMS, while enhanced C₃H₆ permeabilities were observed. Consequently, C₃H₆/N₂ permselectivities were increased by 35 and 44% in MMMs filled with Si-DMOS and Si-DMPS, respectively. Results revealed that permeability was dependent on penetrant diffusivities, a parameter related to the structure of MMMs. Density measurements and differential scanning calorimetry were performed to elucidate the changes in MMM properties which affected the permeation behaviors of O₂, N₂ and C₃H₆. Overall, both Si-DMOS and Si-DMPS show potential as fillers for the enhancement of PDMS permeation performance.     

Prediction of ortho substituent effect in alkaline hydrolysis of substituted phenyl benzoates in aqueous acetonitrile

The second‐order rate constants k (dm³mol^?1s^?1) for alkaline hydrolysis of meta‐, para‐ and ortho‐substituted phenyl esters of benzoic acid, C₆H₅CO₂C₆H₄‐X, in aqueous 50.9% (v/v) acetonitrile have been measured spectrophotometrically at 25 °C. In substituted phenyl benzoates, C₆H₅CO₂C₆H₄‐X, the substituent effects log k_X ? log k_H in aqueous 50.9% acetonitrile at 25 °C for para, meta and ortho derivatives showed good correlations with the Taft and Charton equations, respectively. Using the log k values for various media at 25 °C, the variation of the ortho substituent effect with solvent was found to be precisely described with the following equation: Δlog k_ortho = log k_ortho ? log k_H = 1.57σ_I + 0.93σ°_R + 1.08E_s^B ? 0.030ΔEσ_I ? 0.069ΔEσ°_R, where ΔE is the solvent electrophilicity, ΔE = E_S ? E_H20, characterizing the hydrogen‐bond donating power of the solvent. We found that the experimental log k values for ortho‐, para‐ and meta‐substituted phenyl benzoates in aqueous 50.9% acetonitrile at 25 °C, determined in the present work, precisely coincided with the log k values predicted with the equation (log k^X)_calc = (log k^H_AN)_exp + (Δlog k^X)_calc where the substituent effect (Δlog k^X)_calc was calculated from equation describing the variation of the substituent effect with the solvent electrophilicity parameter, using for aqueous 50.9% CH₃CN the solvent electrophilicity parameter, ΔE = ?5.84. In going from water to aqueous 50.9% CH₃CN, the ortho inductive term grows twice less as compared with the para polar effect. Copyright © 2013 John Wiley & Sons, Ltd.     

The heats of formation of the haloacetylenes XCCY [X,Y = H,F, Cl]: basis set limit ab initio results and thermochemical analysis

The heats of formation of haloacetylenes are evaluated using the recent W1 and W2 ab initio computational thermochemistry methods. These calculations involve CCSD and CCSD(T) coupled cluster methods, basis sets of up to spdfgh quality, extrapolations to the one-particle basis set limit, and contributions of inner-shell correlation, scalar relativistic effects. and (where relevant) first-order spin-orbit coupling. The heats of formation determined using W2 theory are: δH₁ ²⁹⁸(HCCH) = 54.48 kcal mol^?1, δH_f ²⁹⁸(HCCH) = 25.15 kcal mol, δH_f ²⁹⁸(FCCF) = 1.38 kcal mol^?1, δH_f ²⁹⁸(HCCC1) = 54.83 kcal mol^?1, δH_f ²⁹⁸(CICCC1) = 56.21 kcal mol^?1, and δH_f ²⁹⁸(FCCC1) = 28.47 kcal mo1^?1. Enthalpies of hydrogenation and destabilization energies relative to acetylene were obtained at the WI level of theory. So doing we find the following destabilization order for acetylenes: FCCF > ClCCF > HCCF > ClCCCl > HCCCI > HCCH. By a combination of WI theory and isodesmic reactions. we show that the generally accepted heat of formation of 1,2-dichloroethane should be revised to ?31.8 ± 0.6 kcal mol^?1, in excellent agreement with a very recent critically evaluated review. The performance of compound thermochemistry schemes, such as G2, G3, G3X and CBS-QB3 theories, has been analysed.     

Determination of the Solubility Parameter of Epoxidized Soybean Oil by Inverse Gas Chromatography

The thermodynamic parameters of epoxidized soybean oil (ESO) were determined by means of inverse gas chromatography (IGC) in the temperature range of 303.15 K-343.15 K. Two groups of probe solvents with different chemical natures and polarities were used to obtain information about ESO. The thermodynamic parameters—such as molar heat of sorption, weight fraction activity coefficient, Flory–Huggins interaction parameter, and partial molar heat of mixing—were obtained to judge the interactions between ESO and solvents at the studied temperatures. Also, the solubility parameters of ESO were found by plotting the graph of δ₁ ²/(RT) – χ^∞ ₁₂/V₁ vs. solubility parameters, δ₁, of the probes. The results showed that the selected solvent ethyl acetate was a moderate solvent for ESO; n-hexane was a moderate (but close to a better) solvent; while the probes n-heptane, n-octane, n-nonane, and chloroform were excellent solvents. From the extrapolation to 298 K, the solubility parameter value of ESO was 16.70 (J/cm³)^0.5.     

SOFC-anodes,proof for a finite-length type Gerischer impedance?

The impedance of a symmetric cell with Ni/Ti-doped YSZ cermet anodes was measured as function of ambient (P_H2, P_H2O) and temperature. The impedances showed identical shapes with a minor dispersive contribution in the high frequency region and a dominating dispersion down to 0.01 Hz. The characteristic shape of this dispersion was clearly in between a finite-length Warburg (FLW) and a Gerischer impedance. Analysis of the dispersion in the Bode representation, after subtraction of the high frequency contribution, showed a clear relation with the Gerischer impedance. Assuming a finite-length constraint led to quite reasonable modelling of the data. The parameter set of this finite-length Gerischer showed a consistent dependence on P_H2, P_H2O. A qualitative interpretation of this modified Gerischer is presented.     

Magic angle spinning NMR on single crystals as a new aid in characterizing phase transitions: application to squaric acid

Accurate measurement of δ_ISO, the isotropic part of the NMR chemical shift tensor, is usually difficult for solids. This study suggests that the technique of magic angle sample spinning (MAS), employing single crystals, might be suitable for this purpose. In our ¹³C CP(cross polarization)/MAS measurements on squaric acid (H₂C₄O₄), single crystals yielded about five-fold narrower line widths than powder samples. The resolution enhancement thus obtained enabled us to measure δ_ISO for all four carbons of squaric acid, and to show that the average O-H distance can serve as an order parameter for the phase transition at 373 K. Additionally, the ¹³C δ_ISO data suggest that the transition mechanism involves a significant displacive component, in addition to the known order-disorder behavior, thus demonstrating the high potential of the single crystal MAS-NMR methodology for studying the microscopic mechanism of phase transitions.     

用双点源δ-P1近似光学模型反演生物组织的光学参量

根据空间分辨漫反射的双点源δ-P₁近似理论模型,采用非线性最小二乘法,从反射率的测量数据中反演得到了生物组织的吸收系数μ_a、有效散射系数μ' _s和二阶参量γ.研究表明,在光源与探测器之间距离大于一个输运平均自由程的情况下,双点源δ-P₁近似能较好地描述光源附近的光辐射分布,而且能够根据参量γ与μ' _s的关系得到组织的各向异性因子g.这些研究对于生物组织的光学性质测量以及漫反射光谱技术的应用具有重要意义. 关键词： 组织光学 P₁近似')" href="#">δ-P₁近似 光学参量 双点源     

Effect of Hall current and chemical reaction on MHD flow along a fluctuating porous flat plate with internal heat absorption/generation

Effect of Hall current on the unsteady free convection flow of a viscous incompressible and electrically conducting fluid past a fluctuating porous flat plate with internal heat absorption/generation in the presence of foreign gasses (such as H₂, CO₂, H₂O, NH₃) was investigated. The results are discussed with the effect of the parameters m, the Hall current, Mt, the hydromagnetic parameter, G _r the Grashoff number for heat transfer, G _c , the Grashoff number for mass transfer, S, the internal heat absorption/generation parameter, α, the transpiration parameter, S _c , the Schmidt parameter, and K _c the chemical reaction parameter for Prandtl number P _r = 0.71, which represents air. Further, the present study accounts for the 1st order chemical reaction affecting the flow characteristics. The governing equations are solved in closed form applying Hh _n (x) function. The effects of pertinent parameters characterizing the flow field are discussed with the help of graphs and tables. The important observation of the present study is that heat generation/absorption modifies the flow of current simultaneously to a magnetic force and thermal bouncy force. Heat generation combined with blowing leads to a sharp fall of temperature.     

Deexcitation of Cd 53P1 atoms in collisions with ground state atoms and molecules

Collisions of excited Cd 5³P₁ atoms were investigated using atomic fluorescence spectroscopy. Cadmium vapor, together with a quenching gas, was irradiated in a quartz fluorescence vessel with Cd 3261 Å resonance radiation and the intensity of the resulting resonance fluorescence was monitored in relation to the gas pressures. The experiments yielded the following cross sections Q₁₀ (in A²) for collisional transfer 5³P₁→5³P₀: CdAr=2×10^?3, CdN₂=8.0, CdH₂=7.0, CdCO=15.6. The cross sections Q for collisional deexcitation to the ground state (quenching) in A² are CdN₂ = 2.6×10^?2, CdH₂ = 11.0, CdCO = 3.4, CdCO₂ = 26.     

An analytical model of the heat of chemisorption: A perturbation LCAO MO approach

An analytical LCAO MO perturbation model has been developed for treating the heat of chemisorption Q of an adsorbate A monolayer on a transition metal M film. The model combines parameters of the metal band (the Fermi level E_F, band width W = W^occ + W^vac, the d occupancy N_d, density of states n(?), etc.) with those of the local A-M interactions (the adorbital energy ?_A, off-diagonal matrix elements β_AM, etc.). The major cases of A's having lone pair, singly occupied, and vacant adorbitals have been considered, and the analytical expressions for Q as well as some numerical estimations are presented. The relative values of Q seem to be crucially dependent on the ratio β/(?_A ? E_F). The Q vs. N_d plots for the donor and radical A's are rather flat, typically Q decreasing monotonically as N_d increases, but for the acceptor A's the plots are very parameter dependent and show a variety of trends. The results obtained agree with straightforward computations and (scarce) experimental data.     

The hydrostatic pressure derivatives of the elastic constants of indium and an indium cadmium alloy

The hydrostatic pressure derivatives of the elastic stiffness constants of indium and indium-3.4 at.% cadmium alloy single crystals have been obtained from pulse echo overlap measurements of the dependence of ultrasonic wave velocities upon pressure. The softest zone centre acoustic phonon mode in indium is a shear mode propagating k along the [101] direction rather than that (k[110], e[11?0]) which drives the ferroelastic phase transition in the indium-cadmium alloys. The derivative δ((C₁₁ – C₁₂)/2)/δP is positive, accounting for the stability of the fct structure of indium under high pressure. Using the quasiharmonic, anisotropic continuum model the acoustic mode Grüneisen parameters have been calculated and are discussed in terms of mode softening. The high temperature limiting value$\text{\$}\text{?}$γ_H (= 2.56) of the mean acoustic mode Grüneisen parameter is found to be close to the thermodynamic Grüneisen parameter γ^th (=2.5).     

Compatibility of Thermally Reduced Graphene with Polyesters

The compatibility of thermally reduced graphene (TRG) with multiblock copolyesters, composed of poly(butylene terephthalate) (PBT) segments and poly(tetramethylene ether) glycol segments, was examined in detail. The morphology observed by optical microscopy and scanning electron microscopy showed that the compatibility was enhanced with increasing content of the PBT segment in the polyester. This compatibility behavior was analyzed quantitatively, by using the percolation threshold of electrical conductivity, and then further analyzed by using the Hansen solubility parameters to provide a general quantitative guideline to predict the compatibility of TRG with various polymers. The results suggest that the total solubility parameter, δ_T, value of TRG is larger than 24.0 (MPa)^½, and thus that the compatibility with polymer is enhanced as the δ_T value of a polymer increases toward 24.0 (MPa)^½. However, this prediction does not fit well in the presence of a comonomer such as acrylic acid, which has a high tendency to hydrogen bond with itself.     

Effect of high pressures on exchange and hyperfine interactions in rare-earth orthoferrites

The effect of high pressures P on the Néel temperature T _N , the crystal lattice parameters, and the magnitude of the hyperfine magnetic field H ^Sn at a nucleus of a diamagnetic tin atom was studied in pure and tin-doped orthoferrites RFeO₃ (R = Nd, Lu). The dependence of these quantities on the geometry of the exchange bonds, specifically, the angle and length of the chemical bond Fe-O-Fe(Sn), was analyzed. It was established that under pressure the angular contribution decreases and the radial contribution increases T _N and H ^Sn, the radial contribution being greater than the angular contribution in absolute magnitude. Numerical estimates were obtained for the angular and radial contributions to T _N and H ^Sn. In lutecium orthoferrite, at P > 30 GPa anomalies indicating a possible phase transition were observed in the behavior of the lattice parameters and the value of H ^Sn.     

δ2H and δ18O of human body water: a GIS model to distinguish residents from non-residents in the contiguous USA

An understanding of the factors influencing the isotopic composition of body water is important to determine the isotopic composition of tissues that are used to reconstruct movement patterns of humans. The δ²H and δ¹⁸O values of body water (δ²H_bw and δ¹⁸O_bw) are related to the δ²H and δ¹⁸O values of drinking water (δ²H_dw and δ¹⁸O_dw), but clearly distinct because of other factors including the composition of food. Here, we develop a mechanistic geographical information system (GIS) model to produce spatial projections of δ²H_bw and δ¹⁸O_bw values for the USA. We investigate the influence of gender, food, and drinking water on the predicted values by comparing them with the published values. The strongest influence on the predicted values was related to the source of δ²H_dw and δ¹⁸O_dw values. We combine the model with equations that describe the rate of turnover to produce estimates for the time required for a non-resident to reach an isotopic equilibrium with a resident population.     

Generalized Ginzburg-Landau equation and the properties of superconductors with Ginzburg-Landau parameter κ close to 1

An expression is derived for the free energy of a superconductor near the critical temperature, taking account of the terms of next highest order in the parameter 1−T/T _c. These terms become important for Ginzburg-Landau parameter values |κ−1|≪1, and in this case, in an external magnetic field H ₀ close to H _c2, the structure of the order parameter is determined by the relative values of the three small parameters |κ−1|, 1−T/T _c, and (H _c2−H ₀)/H _c2. Three types of lattices are investigated: triangular with one and two flux quanta per cell and square with one flux quantum per cell. Zh. éksp. Teor. Fiz. 115, 726–739 (February 1999)     

Constraining the Parameters of New Variable Modified Chaplygin Gas Model

Assuming the flat FRW universe in Einstein’s gravity filled with New Variable Modified Chaplygin gas (NVMCG) dark energy and dark matter having negligible pressure. In this research work we analyze the viability on the basis of recent observation. Hubble parameter H is expressed in terms of the observable parameters H ₀, $\varOmega_{m}^{0}$ and the model parameters A ₀, B ₀, C ₀, m, n, α and the red shift parameter z. Here we find a best fitted parameter range of A ₀, B ₀ keeping 0≤α≤1 and using Stern data set (12 points) by minimizing the χ ² test at 66 %, 90 % and 99 % confidence levels. Next we do the joint analysis with BAO and CMB observations. Again evaluating the distance modulus μ(z) vs redshift (z) curve obtained in the model NVMCG with dark matter with the best fitted value of the parameters and comparing with that derived from the Union2 compilation data.     

Drying of heterogels swollen in organic vapor

Fast transient fluorescence technique (FTRF), which uses a Strobe Master System (SMS), is used to study swelling and drying of disc shape heterogels. Disc shape heterogels are prepared by free radical copolymerization (FCC) of methyl (methacrylate) (MMA) and styrene (S) with ethylene glycol dimethacrylate (EGDM). Pyrene (P_y) is introduced as a fluorescence probe during polymerization and lifetimes, τ, of P_y are measured during the in-situ swelling process. Chloroform was used as an organic vapor agent to induce gel swelling. It is observed that τ values decrease as swelling proceeds. The Li-Tanaka equation is used to determine the time constant, τ_c, and cooperative diffusion coefficients, D _c, for the swelling processes. Lifetimes of pyrene increase during drying. An empirical equation is introduced to determine the desorption coefficient, D, for drying. Heterogels with high S content swell and dry much more slowly than heterogels with low S content.     

Stability of the Meissner state in a 3D ordered Josephson medium

The stability of the Meissner state of a 3D Josephson medium against combinations of phase jump small fluctuations at contacts is considered. Expressions for the elements of the quadratic form matrix for the second variation of the Gibbs potential are derived. Overheat field values and forms of fluctuations causing instabilities are found. Ratio H _S1/H _S2, where H _S1 is the overheat field and H _S2 is the maximal field at which the Meissner state still exists, grows with increasing pinning parameter I, varying between 0.84 and 1. Almost at all pinning parameters, critical fluctuations represent rapidly decreasing (inward to the sample) periodic alternating-sign structures one cell wide. When the pinning parameter is very small (I < 0.1), such an instability is absent. In this range of I, ratio H _S1/H _S2 is close to unity.