气相反应76/70C_(70)=C_(76)(D_2)热力学函数的计算

采用统计热力学方法计算了气相C76（D2）的标准热力学函数，在此基础上计算了不同温度下气相反应76／70C70＝C76（D2）的热力学函数，讨论了C70与C76（D2）之间相互转化的热力学条件．结果表明，气相中温度低于536K时C70转化为C76（D2），温度高于536K时气相中C76（D2）转化为C70。     

Analysis of the basis set and correlation effects on the computation of molecular polarizabilities using molecular polarization maps

In the present report, we analyze the effect of augmenting the basis set and the level of the theory in the computation of the molecular polarization potential and it is used as a tool to understand their spatial effects in the calculation of molecular polarizabilities. This is analyzed in the present report through the results obtained for three reference molecules: hydrogen cyanide, formaldehyde and urea. Accordingly, different basis sets were used for the calculations, including: 6-31G(D), 6-31G(D,P), 6-31G(2D,2P) and 6-31++G(2D,2P). On the other hand, calculations at different levels of the theory were considered, including: Hartree–Fock, Moller–Plesset second order (MP2) and fourth order (MP4) as well as the functionals BLYP and B3LYP at the density functional theory. The results of the polarization maps reveal similar trends observed with the calculation of the different components of the polarizability tensor. However, the use of the maps permits to understand spatial effects specific for each level of calculation and each basis set.     

高有机硫炼焦煤分选组分中硫的赋存形态及其热变迁行为研究

利用重介质分选法分别将两种高有机硫炼焦煤分选为密度范围不同的五个组分。采用X射线光电子能谱仪（XPS）、核磁共振波谱仪（¹³C NMR）和热解质谱联用技术（Py-MS）探究不同分选组分中硫的赋存形态及其热变迁行为。结果表明,不同分选组分中硫的分布、赋存形态及其所处化学环境存在显著差异。有机硫主要分布在低密度组分（D1）中,且以噻吩硫的形式存在;无机硫作为矿物质组分主要分布于高密度组分（D5）中。随着分选组分密度的增大,其脂肪碳的比例降低,芳香碳的比例增加,D1中硫醇、硫醚等硫化物的含量明显增加。热解过程中脂肪碳结构裂解生成的挥发分促进含硫气体的释放,进而提高了D1的脱硫效率,D5中硫的热变迁行为则主要受煤中矿物质的影响。     

Deriving the colloidal synthesis of crystalline nanosheets to create self-assembly monolayers of nanoclusters

Two-dimensional (2D) nanomaterials with the thickness at atomic level are promising candidates for a wide range of applications, and now reach the point to create diversified 2D architectures. The colloidal synthesis route is powerful to produce crystalline nanosheets, nanoribbons and nanoplatelets, and the self-assembly strategy is robust to integrate the functionalities of different nano-objects. In this review, we bridge the colloidal synthesis of nanosheets and the 2D self-assembly of nanoclusters (NCs) with the aim to further optimize the physical and chemical properties of 2D nanomaterials. Ultrasmall NCs, the intermediate for synthesizing nanosheets, are highlighted to show the similarity of 2D crystallization and 2D self-assembly. The modification of conventional 2D colloidal synthesis route greatly permits the controlled self-assembly of NCs into free-standing monolayers in colloidal solutions.     

Towards the complete experiment: measurement of S((1)D2) polarization in correlation with single rotational states of CO(J) from the photodissociation of oriented OCS(v2 = 1|JlM = 111)

In this paper we report slice imaging polarization experiments on the state-to-state photodissociation at 42,594 cm(-1) of spatially oriented OCS(v(2) = 1|JlM = 111) → CO(J) + S((1)D(2)). Slice images were measured of the three-dimensional recoil distribution of the S((1)D(2)) photofragment for different polarization geometries of the photolysis and probe laser. The high resolution slice images show well separated velocity rings in the S((1)D(2)) velocity distribution. The velocity rings of the S((1)D(2)) photofragment correlate with individual rotational states of the CO(J) cofragment in the J(CO) = 57-65 region. The angular distribution of the S((1)D(2)) velocity rings are extracted and analyzed using two different polarization models. The first model assumes the nonaxial dynamics evolves after excitation to a single potential energy surface of an oriented OCS(v(2) = 1|JlM = 111) molecule. The second model assumes the excitation is to two potential energy surfaces, and the OCS molecule is randomly oriented. In the high J region (J(CO) = 62-65) it appears that both models fit the polarization very well, in the region J(CO) = 57-61 both models seem to fit the data less well. From the molecular frame alignment moments the m-state distribution of S((1)D(2)) is calculated as a function of the CO(J) channel. A comparison is made with the theoretical m-state distribution calculated from the long-range electrostatic dipole-dipole plus quadrupole interaction model. The S((1)D(2)) photofragment velocity distribution shows a very pronounced strong peak for S((1)D(2)) fragments born in coincidence with CO(J = 61).     

Comparison of the structure and the transport properties of low-set and high-set curdlan hydrogels

Curdlan, a bacterial polysaccharide, can form different types of thermogels, having the very same chemical composition, but whose structures depend on the incubation temperature. Structural characterization of 10% (w/v) low-set and high-set curdlan gels was carried out by Fourier transformed infrared (FT-IR) imaging and environmental scanning electron microscopy (eSEM) in the hydrated state. Considerable differences were observed between the two gels, the high-set one being overall more homogeneous. The self-diffusion coefficients of a series of analytes of different sizes (water, phosphate, glucose-6-phosphate, polyphosphate, polyethylene glycol, and dextran labelled with rhodamine B) were measured in aqueous solution (D(s)(sln)) and in both types of curdlan gels (D(s)(gel)) using (1)H and (31)P pulsed field gradient nuclear magnetic resonance (PFG NMR) spectroscopy. The mutual-diffusion coefficients (D(m)(gel)) of dextran in the curdlan gels were determined from release experiments based on fluorescence spectroscopy. The dependence of the relative diffusion coefficient (D(s)(gel)D(s)(sln)) on the size of the analyte, expressed by its hydrodynamic radius (R(h)), could be expressed by D(s)(gel)D(s)(sln) ∝ exp(-R(h)(0.46)), valid for both types of gels. The self-diffusion measurements for the largest investigated analytes were not compatible with a single diffusion coefficient and, therefore, were analysed using an approach based on a normal distribution of self-diffusion coefficients. In the hydrogels, broadening of the self-diffusion coefficient distribution increased as a function of the analyte size. This phenomenon was associated with the limited distance travelled by the analytes during the measurements, and it is inferred that the distribution of diffusion coefficients is representative of the distribution of local environments of the individual analyte. It was found that the structural differences observed between both types of curdlan gels are not correlated with the gel transport properties, highlighting the complexity of the relationship between structural details and transport properties in gels.     

UV emission of I2 from the ion-pair state following amplified spontaneous emission

This paper reports the results of processes resulting in D0(u) (+)-X (1)Sigma(g) (+) emission when a single rovibrational level of the E0(g) (+) state is prepared. Our study reveals that two kinds of processes populate the D0(u) (+) state; which one occurs depends on the experimental conditions. One process involves amplified spontaneous emission from the E0(g) (+) state. The other is collision-induced energy transfer in self-quenching. We distinguish these two processes from the time profiles of fluorescence signals. These processes give completely different vibrational distributions in the D0(u) (+) state from a given rovibrational level of the E0(g) (+) state. The discrepancy between our results and previous results for the E0(g) (+)-->D0(u) (+) relaxation is briefly discussed.     

Application of two-dimensional near-infrared correlation spectroscopy to the discrimination of Chinese herbal medicine of different geographic regions

Fructus Lycii is a traditional Chinese medicinal herb. The objective of this paper was to apply two-dimensional (2D) near-infrared (NIR) correlation spectroscopy to the discrimination of Fructus Lycii of four different geographic regions. Generalized 2D-NIR correlation spectroscopy was able to enhance spectral resolution, simplify the spectrum with overlapped bands, and provide information about temperature-induced spectral intensity variations that was hard to obtain from one-dimensional NIR spectroscopy. The 2D synchronous and asynchronous spectra showed remarkable differences within the range of 4950-5700cm(-1) between samples of different geographic regions. Using NIR instead of IR made the 2D approach more convenient and fast, and it can be applied to more area like process control. This approach can also be applied analogously to the discrimination of other Chinese herbal medicine of different geographic regions.     

Dynamics of fluids near the consolute critical point: a molecular-dynamics study of the Widom-Rowlinson mixture

Molecular-dynamics simulations are presented for the dynamic behavior of the Widom-Rowlinson mixture [B. Widom, and J. S. Rowlinson, J. Chem. Phys. 52, 1670 (1970)] at its critical point. This model consists of two components where like species do not interact and unlike species interact via a hard-core potential. Critical exponents are obtained from a finite-size scaling analysis. The self-diffusion coefficient shows no anomalous behavior near the critical point. The shear viscosity and thermal conductivity show no divergent behavior for the system sizes considered, although there is a significant critical enhancement. The mutual diffusion coefficient, D(AB), vanishes as D(AB) approximately xi(-1.26 +/- 0.08), where xi is the correlation length. This is different from the renormalization-group (D(AB) approximately xi(-1.065)) mode coupling theory (D(AB) approximately xi(-1)) predictions. The theories and simulations can be reconciled if we assume that logarithmic corrections to scaling are important.     

Studies of translational diffusion in the smectic A phase of a Gay-Berne mesogen using molecular dynamics computer simulation

Molecular dynamics computer simulations are used to determine the self-diffusion coefficients for a Gay-Berne model mesogen GB (4.4,20,1,1) in the isotropic, nematic and smectic A phases along two isobars. The values of the parallel and perpendicular diffusion coefficients, D(parallel) and D(perpendicular), are calculated and compared in the different phases. For the phase sequence isotropic-smectic A, D(perpendicular)*> or =D(parallel)* over the whole smectic A range with the ratio D(parallel)*/D(perpendicular)* decreasing with decreasing temperature. At a higher pressure, a nematic phase is observed between these two phases and we find that D(parallel)*>D(perpendicular)* throughout the nematic region and the inequality D(parallel)*>D(perpendicular)* remains on entering the smectic A phase. However, the ratio D(parallel)*/D(perpendicular)* decreases with decreasing temperature within the smectic A range and eventually this ratio inverts such that D(perpendicular)*>D(parallel)* at low temperatures. The temperature dependence of the parallel diffusion coefficient in the smectic A phase for this model mesogen is compared to that predicted by a theoretical model for diffusion subject to a cosine potential.     

Mechanistic insights into the hydrolysis of a nucleoside triphosphate model in neutral and acidic solution

Nucleoside triphosphate hydrolysis is an essential component of all living systems. Despite extensive research, the exact modus and mechanism of this ubiquitous reaction still remain elusive. In this work, we examined the detailed hydrolysis mechanisms of a model nucleoside triphosphate in acidic and neutral solution by means of ab initio simulations. The timescale of the reaction was accessed through use of an accelerated sampling method, metadynamics. Both hydrolyses were found to proceed via different mechanisms; the acidic system reacted by means of concerted general acid catalysis (found to be a so-called D(N)A(N)A(H)D(xh) mechanism), whereas the neutral system reacted by way of a different mechanism (namely, D(N)*A(N)D(xh)A(H)). A neighboring water molecule took on the role of a general base in both systems, which has not been seen before but is a highly plausible reaction path, meaning that substrate-assisted catalysis was not observed in the bulk water environment.     

Establishing an alternative method for the quantitative analysis of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans by comprehensive two dimensional gas chromatography-time-of-flight mass spectrometry for developing countries

Comprehensive Gas Chromatography-Time-of-Flight Mass Spectrometry (GC×GC-TOFMS) methodology has been refined for the analysis of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in samples with different matrices. This is specifically for application in developing countries where access to gas chromatography-high resolution mass spectrometry (GC-HRMS) and highly skilled personnel is limited. The method, using an Rxi-5 Sil MS column in the first dimension ((1)D) coupled with an Rtx-200 column in the second dimension ((2)D), was used to quantify PCDDs and PCDFs in different environmental sample matrices. The results were compared with those obtained using GC-HRMS and good agreement was observed. The limit of detection (LOD) for the method (300fg on column for spiked soil samples) was determined using an Rxi-XLB ((1)D) column coupled with an Rtx-200 column ((2)D). Preliminary South African sample results are also discussed. Isomer specificity for different tetrachloro dibenzo-p-dioxins (TCDDs) and tetrachloro dibenzofurans (TCDFs) was investigated using a commercial standard. Adequate resolution was achieved. The method as described has great attraction for developing countries being both financially and operationally favourable.     

State-selective predissociation dynamics of methylamines: the vibronic and HD effects on the conical intersection dynamics

The photodissociation dynamics of methylamines (CH(3)NH(2) and CD(3)ND(2)) on the first electronically excited state has been investigated using the velocity map ion imaging technique probing the H or D fragment. Two distinct velocity components are found in the H(D) translational energy distribution, implying the existence of two different reaction pathways for the bond dissociation. The high H(D) velocity component with the small internal energy of the radical fragment is ascribed to the N-H(D) fragmentation via the coupling of S(1) to the upper-lying S(2) repulsive potential energy surface along the N-H(D) bond elongation axis. Dissociation on the ground S(0) state prepared via the nonadiabatic dynamics at the conical intersection should be responsible for the slow H(D) fragment. Several S(1) vibronic states of methylamines including the zero-point level and nnu(9) states (n=1, 2, or 3) are exclusively chosen in order to explore the effect of the initial quantum content on the chemical reaction dynamics. The branching ratio of the fast and slow components is found to be sensitive to the initial vibronic state for the N-H bond dissociation of CH(3)NH(2), whereas it is little affected in the N-D dissociation event of CD(3)ND(2). The fast component is found to be more dominant in the translational distribution of D from CD(3)ND(2) than it is in that of H from CH(3)NH(2). The experimental result is discussed with a plausible mechanism of the conical intersection dynamics.     

Exploring the sources of the magnetic anisotropy in a family of cyanide-bridged Ni9Mo6 and Ni9W6 systems: a density functional theory study

A density functional theory (DFT) study of the magnetic coupling interactions and magnetic anisotropy in a family of experimentally synthesized Ni(9)Mo(V) and Ni(9)W(V) systems is presented. Our calculations show that for all of our selected Ni(9)M(6) systems, the intramolecular magnetic coupling interactions are ferromagnetic, and the ground-state spins are 12. All of the D values of Ni(9)W(6) systems come mainly from the contribution of the D(i) of W(6)(CN)(48)Ni extracted from Ni(9)W(6), and the influence of the eight surrounding Ni including the ligands on their magnetic anisotropy is very small. Although the surrounding Ni bounded by different ligands have a small influence on all D values for our selected complexes, they decide on the core structures of W(6)(CN)(48)Ni, which dominate their magnetic anisotropy. Thus, to obtain a Ni(9)W(6) system having a large negative D, we can use different ligands bound to Ni to obtain a good core structure of W(6)(CN)(48)Ni with a large negative D value. All D values of Ni(9)Mo(6) systems also come mainly from the contribution of D(i) of the Mo(6)(CN)(48)Ni, which is positive or negative but very small; most of these systems do not behave as single-molecule magnets.     

pK(a) coupling at the intein active site: implications for the coordination mechanism of protein splicing with a conserved aspartate

Protein splicing is a robust multistep posttranslational process catalyzed by inteins. In the Mtu RecA intein, a conserved block-F aspartate (D422) coordinates different steps in protein splicing, but the precise mechanism is unclear. Solution NMR shows that D422 has a strikingly high pK(a) of 6.1, two units above the normal pK(a) of aspartate. The elevated pK(a) of D422 is coupled to the depressed pK(a) of another active-site residue, the block-A cysteine (C1). A C1A mutation lowers the D422 pK(a) to normal, while a D422G mutation increases the C1 pK(a) from 7.5 to 8.5. The pK(a) coupling and NMR structure determination demonstrate that protonated D422 serves as a hydrogen bond donor to stabilize the C1 thiolate and promote the N-S acyl shift, the first step of protein splicing. Additionally, in vivo splicing assays with mutations of D422 to Glu, Cys, and Ser show that the deprotonated aspartate is essential for splicing, most likely by deprotonating and activating the downstream nucleophile in transesterification, the second step of protein splicing. We propose that the sequential protonation and deprotonation of the D422 side chain is the coordination mechanism for the first two steps of protein splicing.     

The application of sodium dodecyl sulphate-polyacrylamide gel electrophoresis to the taxonomic identification of the total body protein band profiles of Diplostomum spp. metacercariae (Digenea), parasites of fish eyes

Sodium dodecyl sulphate-polyacrylamide gel electrophoresis has been used to determine the metacercariae (Mc) total body protein band profiles of different Diplostomum spp. Four species of fish were investigated, roach (Rutilus rutilus) infected with D. spathaceum Mc, gywniad (Coregonus laveratus) infected with D. coregonus Mc, ruff (Gymnocephalus cernua) infected with a Diplostomum species related to D. gasterostei Mc, and perch (Perca fluviatilis) infected with D. gasterostei Mc. The four species of Diplostomum Mc were distinguished by three different bands of molecular weight, Mr 55,500, 53,500 and 52,000. A homology of polypeptide component distribution was evident for D. gasterostei Mc, from P. fluviatilis, and D. coregonus Mc, from C. laveratus, the latter showing reduced protein concentrations between bands Mr 32,000-40,000. Critical analysis of Mc polypeptide patterns showed no evidence of contamination with lens, retina or vitreous humour host eye protein. Gross morphological data for the parasites was also considered in relation to different band profiles obtained for the Diplostomum spp. Mc. Band profile analysis in conjunction with other taxonomic tests proved to be a useful tool in the identification of unknown species.     

Experimental measurement of the induced dipole moment of an isolated molecule in its ground and electronically excited states: indole and indole-H2O

Reported here are measurements of the magnitude and orientation of the induced dipole moment that is produced when an indole molecule in its ground S(0) and electronically excited S(1) states is polarized by the attachment of a hydrogen bonded water molecule in the gas phase complex indole-H(2)O. For the complex, we find the permanent dipole moment values mu(IW)(S(0)) = 4.4 D and mu(IW)(S(1)) = 4.0 D, values that are substantially different from calculated values based on vector sums of the dipole moments of the component parts. From this result, we derive the induced dipole moment values mu(I) (*)(S(0)) = 0.7 D and mu(I) (*)(S(1)) = 0.5 D. The orientation of the induced moment also is significantly different in the two electronic states. These results are quantitatively reproduced by a purely electrostatic calculation based on ab initio values of multipole moments.     

Full-dimensional quantum dynamics study of exchange processes for the D + H2O and D + HOD reactions

The exchange processes of D + H(2)O and D + HOD reactions are studied using initial state-selected time-dependent wave packet approach in full dimension. The total reaction probabilities for different partial waves, together with the integral cross sections, are obtained both by the centrifugal sudden (CS) approximation and exact coupled-channel (CC) calculations, for the H(2)O(HOD) reactant initially in the ground rovibrational state. In the CC calculations, small resonance peaks in the reaction probabilities and quick diminishing of the resonance peaks with the increase of total angular momenta J do not lead to clear step-like features just above the threshold in the cross sections for the title reactions, which are different in other isotopically substituted reactions where the hydrogen atom was included as the reactant instead of the deuterium atom [B. Fu, Y. Zhou, and D. H. Zhang, Chem. Sci. 3, 270 (2012); B. Fu and D. H. Zhang, J. Phys. Chem. A 116, 820 (2012)]. It is interesting that the shape resonance-induced features resulting from the reaction tunneling are significantly diminished accordingly in the reactions of the deuterium atom and H(2)O or HOD, owing to the weaker tunneling capability of the reagent deuterium atom in the title reactions than the reagent hydrogen atom in other reactions. In the CS calculations, the resonance peaks persist in many partial waves but cannot survive the partial-wave summations. The cross sections for the D(') + H(2)O → D(')OH + H and D(') + HOD → D(')OD + H reactions are substantially larger than those for the D(') + HOD → HOD(') + D reaction, indicating that the D(')/H exchange reactions are much more favored than the D(')/D exchange.     

Photoluminescence Properties of Two-dimensional Planar Layer and Three-dimensional Island Layer for ZnO Films Grown Using MOCVD

IntroductionOver the past few years, wide band gap semicon-ductors have attracted considerable attention because oftheir high commercial demand for the preparation ofblue and UV light emitters. The most promising amongall the known materials used for this…