M2高速钢中相组态的背散射穆斯堡尔法研究

用背散射X光穆斯堡尔法研究了M2高速钢中相的组态结构,从实验上得到:(1)M2高速钢中最近邻两层上各配位合金元素对铁磁有效场的影响可以近似认为相等,相应其马氏体相可简化为只有四种不同环境的铁位,即铁原子最近邻两层上无配位合金元素和有1,2,3个配位合金元素等四种;(2)M2高速钢的残留奥氏体相中的碳原子处于八面体间隙位置,并且在高温淬火过程中,间隙碳原子会发生向残留奥氏体相中偏聚的现象.

Bi-modal microstructure in a powder metallurgical ferritic steel

Ferritic steel with a nominal composition of Fe-14Cr-3W-0.42Ti-0.32Y was prepared by mixing gas-atomized prealloyed powder and mechanically alloyed powder. The microstructure is much different fxom other ferritic steels with the same composition and prepared via only mechanically alloyed powder. A bi-modal structure, which consists of pure ferritic grains and martensitic grains, was obtained after hot forging and air cooling. A phase transformation of αbcc→γfcc→α＇bcc was also discovered in microstructural observation. The bi-modal microstructure shows a good combination of high strength and high ductility.

A Global ab initio Potential Energy Surface for F+H_(2)→HF+H

A global three dimensional potential energy surface for the F＋H2→HF＋H reaction has been developed by spline interpolation of about 15,000 symmetry-unique ab initio points, obtained from the multi-reference configuration interaction level with Davidson correction using the aug-cc-pV5Z basis set. In the entrance channel the spin-orbit coupling energy is also included.

Polymorphism of Exon 3 of MHC Class Ⅱ B Gene in Chinese Alligator(Alligator sinensis)

The polymorphism of MHC class II B gene in 14 Chinese alligators was analyzed, which came from three different areas： a wild population from Xuancheng, Anhui, a captive population from Changxing, Zhejiang, and a captive population from Anhui Research Center for Reproduction of Chinese Alligators. The gene fragment was amplified using a pair of specific primers designed from the MHC gene sequence of the spectacled caiman. A total of 34 sequence haplotypes of exon 3 were detected in the sampled Chinese alligators. The numbers of haplotypes of the 3 Chinese alligator populations were 15, 10, and 9, respectively. The overall estimation of the MHC polymorphism in the Chinese alligator population was higher than those in mammals and in cypdnid fish, The rates of nonsynonymous substitutions （dN） occurred at a significantly lower frequency than that of synonymous substitutions （ds）, which were not consistent with the common rule. This result might suggest that the polymorphism of exon 3 seemed not to be maintained by the balancing selection. The neutrality test of Tajima excluded the null hypothesis that the polymorphism of exon 3 was generated by a random drift, and the fact that D = -0.401 indicated an excess of rare mutations in the Chinese alligator. The nucleotide diversity of the sequences and the phylogenetic relations were also analyzed, and the results suggested that there was no significant difference in genetic diversity among the 3 populations of Chinese alligator.

Influence of I-phase and W-phase on microstructure and mechanical properties of Mg-8Li-3Zn alloy

Microstructures and mechanical properties of LZ83?xY alloys containingI-phase andW-phase were investigated by XRD, OM, SEM and EDS. The experimental results show that the content ofI-phase andW-phase changes by varying Zn/Y mass ratio in the LZ83?xY alloys. The cohesion ofI-phase/α-Mg eutectic pockets can enhance the strength in the as-cast LZ83?0.5Y and LZ83?1.0Y alloys, while theW-phase has no obvious strengthening effect on the LZ83?1.5Y alloy. In the extruded alloys, the I-phase andW-phase were extruded into the particles with nanoscale size in theβ-Li matrix phase. The dispersion strengthening of W-phase was more obvious because of the higher volume fraction. The ultimate tensile strength of extruded LZ83?1.5Y alloy is up to 238 MPa while the elongation is up to 20%.

Time-dependent Wave Packet Quantum Scattering Study of Reaction S（3p）＋H2→HS＋H on a New ab initio Potential Energy Surface 3A’

A new potential energy surface is presented for the triplet state 3At of the chemical reaction S（3P）＋H2 from a set of accurate ab initio data. The single point energies are computed using highly correlated complete active space self-consistent-field and multi-reference configuration interaction wave functions with a basis set of aug-cc-pV5Z. We have fitted the full set of energy values using many-body expansion method with an Aguado-Paniagua function. Based on the new potential energy surface, we carry out the time-dependent wave packet scattering calculations over the collision energy range of 0.8-2.2 eV. Both the centrifugalsudden approximation and Coriolis Coupling cross sections are obtained. In addition, the total reaction probabilities are calculated for the reactant H2 initially in the vibrational states v=0-3 （j=0）. It is found that initial vibrational excitation enhances the title reaction.

Iterative Multireference Configuration Interaction

Iterative multireference configuration interaction (IMRCI) is proposed. It is exploited to compute the electronic energies of H2O and CH2(singlet and triplet states) at equilibrium and non-equilibrium geometries. The potential energy curves of H2O, CH2(singlet and triplet states) and N2 have also been calculated with IMRCI as well as the M?ller Plesset perturbation theory (MP2, MP3, and MP4), the coupled cluster method with single and double substitutions (CCSD), and CCSD with perturbative triples correction (CCSD(T)).These calculations demonstrate that IMRCI results are independent of the initial guess of configuration functions in the reference space and converge quickly to the results of the full configuration interaction. The IMRCI errors relative to the full configuration interaction results are at the order of magnitude of 10-5 hartree within just 2-4 iterations. Further,IMRCI provides an efficient way to find on the potential energy surface the leading electron configurations which, as correct reference states, will be very helpful for the single-reference and multireference theoretical models to obtain accurate results.

Microstructure evolution of isothermal holding treatment during melt solidification of Ti-6Al-4V alloy

Effect of isothermal holding treatment in the solidification process on the microstructure of Ti-6Al-4V alloy was studied by temperature controlled induced melting apparatus. The result shows that with isothermal holding treatment above the β transus temperature during solidification, the colony structure consisting of parallel lamellae was obtained. While the isothermal holding treatment was set at 960 °C, a unique bi-modal microstructure consisting of coarse primary α and fine secondary lamellar α was obtained. The primary lamellar α tended to break into several pieces, globularize and present equiaxed morphology. The formation mechanism of the equiaxed α can be explained with the atom immigration, high density dislocations, combined action with the interface tension of formed α phase during the isothermal holding treatment. After the isothermal holding, the retained β matrix transformed into fine lamellar α, thus, bi-modal microstructure was acquired. Compared with the lamellar structure, the grain boundary α presented discontinuously and cannot be distinguished from the primary α lamellae easily. The size of colonies α was greatly decreased. The microstructure tended to be much more homogeneous in the whole section of the samples.

Vibrational Spectra and Quantum Calculations of Ethylbenzene

Normal vibrations of ethylbenzene in the first excited state have been studied using resonant two-photon ionization spectroscopy. The band origin of ethylbenzene of S1-S0 transition appeared at 37586 cm-1. A vibrational spectrum of 2000 cm-1 above the band origin in the first excited state has been obtained. Several chain torsions and normal vibrations are obtained in the spectrum. The energies of the first excited state are calculated by the time- dependent density function theory and configuration interaction singles （CIS） methods with various basis sets. The optimized structures and vibrational frequencies of the So and S1 states are calculated using Hartree-Fock and CIS methods with 6-311＋＋G（2d,2p） basis set. The calculated geometric structures in the So and $1 states are gauche conformations that the symmetric plane of ethyl group is perpendicular to the ring plane. All the observed spectral bands have been successfully assigned with the help of our calculations.

Effect of ECAP process on liquid distribution of AZ80M alloy during semi-solid isothermal heat treatment

Two kinds of semi-solid samples of AZ80−0.2Y−0.15Ca(wt.%)(AZ80M)magnesium alloy were prepared by semi-solid isothermal heat treatment of materials with and without equal channel angular pressing(ECAP)process.The microstructures of initial and semi-solid treated samples were compared and analyzed.The results showed a significant difference in the liquid phase distribution between three-pass ECAP processed(3P)and as-received samples during the isothermal heating process.The semi-solid 3P sample showed a more uniform liquid distribution due to its smaller dihedral angle.Besides,the coarsening processes of solid grains of as-received and 3P samples were dominated by the coalescence and Ostwald ripening mechanism,respectively.The difference of coarsening processes was mainly related to the proportion of the high-angle grain boundaries in materials,which further affected the evolution behavior of the liquid pools.

Theoretical Calculation on Isotope Shifts of N(I)

The special mass shift coefficient and field parameter factor of four multiples,3s^4P→3p4P°,3s^4P→3p^4D°,3s^2D→5p^2D°,and 3s^2P→3p^2P°,of ^14N and ^15N were studied using the multi-configuration Dirac-Hartree-Fock method and the relativistic configuration interaction approach.The normal mass shifts,special mass shifts,field shifts,and isotope shifts of N(I)were derived from the theoretical calculated normal mass shift parameter,special mass shift parameter and field parameter factor,and compared with the reported experimental measurements and theoretical results.

New ab initio Potential Energy Surfaces for Cl（^2P3/2,^2P1/2）＋H2 Reaction

New global three dimensional potential energy surfaces for the Cl＋H2 reactive system have been constructed using accurate multireference configuration interaction calculations with a large basis set. The three lowest adiabatic potential energy surfaces correlating asymptotically with Cl（^2p）＋H2 have been transformed to adiabatic representation, which leads to a fourth coupling potential for non-linear geometries. In addition, the spin-orbit coupling surfaces have also been computed using the Breit-Pauli Hamiltonian. Properties of the new potential are described. Reaction dynamics based on the new potential agrees with the recent experimental results quite well.

Advantages and Drawbacks of Quantum Mechanical Static and Dynamic Approaches to Modelling Infrared Spectra

We present quantum mechanical vibrational computations beyond the harmonic approximation from effective second order perturbative and variation perturbation treatments defined as static approaches, as well as vibrational analysis from density functional theory molecular dynamics trajectories at 300 and 600 K. The four schemes are compared in terms of prediction of fundamental transitions, and simulation of the corresponding medium infrared spectrum at the same level of theory using the B3LYP/6-31＋G（d,p） description of the electronic structure. We summarize conclusions about advantages and drawbacks of these two approaches and report the main results obtained for semi-rigid and flexible molecules.

Spectroscopic Parameters of X^3∑^-, a^1△, and A^＇3△ Electronic States of SO Radical

The potential energy curves （PECs） of three low-lying electronic states （X^3∑, a^1△, and a^3△） of SO radical have been studied by ab initio quantum chemical method. The calcula- tions were carried out with the full valence complete active space self-consistent field method followed by the highly accurate valence internally contracted multireference configuration in- teraction （MRCI） approach in combination with correlation-consistent basis sets. Effects of the core-valence correlation and relativistic corrections on the PECs are taken into account. The core-valence correlation correction is carried out with the cc-pCVDZ basis set. The way to consider the relativistic correction is to use the second-order Douglas-Kroll Hamiltonian approximation, and the correction is performed at the level of cc-pV5Z basis set. To obtain more reliable results, the PECs determined by the MRCI calculations are also corrected for size-extensivity errors by means of the Davidson modification （MRCI＋Q）. These PECs are extrapolated to the complete basis set limit by the two-point energy extrapolation scheme. With these PECs, the spectroscopic parameters are determined.

Sequence polymorphism of two major histocompatibility(MH)classⅡB genes and their association with Vibrio anguillarum infection in half-smooth tongue sole(Cynoglossus semilaevis)

Major histocompatibility complex （MHC） class II B molecules play an important role in the adaptive immune response in fish. Previous study has reported that two highly polymorphic class II B genes, Cyse-DAB and Cyse-DBB exist in half-smooth tongue sole （Cynoglossus semilaevis）. In this study, the polymorphism within exon 2 of the class II B genes following bacterial challenge was evaluated. Two hundred C. semilaevis individuals were injected intraperitoneally with Vibrio anguillarum. Muscle tissue from the first 20 dead and 20 of the survivors was collected for genotyping. Sixty alleles from the 40 individuals were isolated, of which 32 belonged to Cyse-DAB and 28 belonged to Cyse-DBB. The rate of dN （non-synonymous substitution） was higher than that of ds （synonymous substitution） in the PBRs （peptide binding residues） of both class I1 B genes. Conversely, the rate of ds was higher than dy in the non-PBRs and the complete exon 2 sequence. Thus, the results suggest that positive selection has occurred in the PBRs and purifying selection in the non-PBRs and exon 2. Thirteen class II B alleles were used to study the association between alleles and resistance to infection. Though not significant, alleles Cyse-DAB＊ 0601, Cyse-DAB ＊ 0706, and Cyse-DBB＊O 101, Cyse-DBB＊ 1301 were only found in surviving individuals and may represent alleles that have resistance against V. anguillarum infection. Alleles Cyse-DAB＊0701 and Cyse-DAB＊1301 were significantly more prevalent in dead individuals than in surviving ones and may represent alleles that are associated with increased susceptibility to V. anguillarum infection.

Influence of structure transition on plastic behaviors of iron based ordered alloys

The influence of ordered structure on the dislocation configuration,structure of anti-phase domain boundary,partial dislocation slips,etc.are analyzed in the background of promoting the plasticity of iron based ordered solid solutions with second-order phase transformation.The principles of deformation softening and annealing hardening in ordered solid solutions are discussed because of deformation induced structure disordering.It is concluded that the independent slip ability of the partial dislocations and the corresponding low temperature plasticity of ordered solid solutions could be promoted obviously by proper alloying effects,which reduces the anti-phase domain boundary energy,or by maintaining the disordering state into the low temperature range.The similar principles could be also used to modify the low temperature plasticity of other metal based ordered solid solutions.

Structural, Spectroscopic and Vibrational Properties for Low-Lying Electronic States of LiCl

A multireference configuration interaction （MRCI） study has been carried out on the LiCl molecule. The potential energy has been calculated over a wide range of internuclear separation for the 21 low-lying electronic states of the LiCl molecule dissociating into Li （^2S, ^2p, ^3S）＋Cl （^2p）. The （4）^1∑^＋, （3）∏, 1-3^3∑^＋, 1-3^3∏, 1,3Δ, ^1,3∑^-, （5）^1∑^＋,（4）^3∑^＋, （4）^3∏, （4）^3∏ excited states are studied for the first time in theory. Molecular spectroscopic constants .（Re, De,ωe, ωeΧe,Be and αe） have been derived for the 9 bound states （X^1∑^＋, （3）^1∑^＋, （2）^3∑^＋, ^1,3Δ, ^1,3∑^-, （4）^∏, （4）^3∏） with a regular shape, and the spectroscopic constants of ground states X^1 ∑^＋ are in good agreement with available experimental and theoretical values. The relative differences between experimental values and our values for Re, De, ωe, ωeΧe, Be and α3 are 1.02%, 0.60%, 1.72%, 9.46%, 2.0%, and 0.75%, respectively. Moreover, vibrational levels of 9 bound states, which have not been investigated experimentally, are computed.

An Accurate Calculation of Potential Energy Curves and Transition Dipole Moment for Low-Lying Electronic States of CO

In this paper, potential energy curves for the X1∑＋, a3П, a＇∑＋, da△, A1П and I∑- states of CO have been calculated using complete active space se1f-consistent field and multi-reference configuration interaction methods. The calculations have been performed at 108 nuclear separations from 0.7 to 4.0 A by the aug-cc-PVSZ basis set. Spectroscopic constants for the six low-lying electronic states are found in good agreement with experimental data. The vibrational states of the X1∑＋ and A1П states are also calculated, which are reliable and accurate by comparison with the experimental data and the other theoretical values. The transition dipole moment （TDM） shows that the TDM of the two states （X1∑＋→A1П）are reduced strongly with increase of bond length.

Potential energy curves crossing and low-energy charge transfer dynamics in (BeH_2O)^(2+) complex

The singlet rigid Be--O dissociation potential energy curves correlating to the first four molecular limits of （BeH2O）^2＋ com- plex were calculated using the multi-reference single and double excitation configuration interaction theory. The radial cou- plings of three low-lying IAl states were calculated and combined with adiabatic potential energy curves to investigate and charge- transfer collision dynamics by using quantum-mechanical molecular orbital close-coupling methods. It is found that the total charge-transfer cross sections are dominated by the Be^＋（^2S）＋H2O＋（A^2A1） channel. The rate coefficients in the range of 10^-17 - 10^-12 cm^3/s are very sensitive to temperature below 1000 K. The complexation energy without charge-transfer was determined to be 143.6 kcal/mol, including zero-point vibration energy corrections. This is in good agreement with the previous results.

Examining brain structures associated with attention networks in a large sample of young adults: a voxel-based morphometry study

Attention networks have three principal com- ponents supported by separate subprocesses, which include alerting, orienting, and executive control （EC） networks. Efficiently and accurately extracting useful information from the environment as the function of attention is pivotal to our survival. Previous brain imaging studies have examined activation patterns underlying the different attention networks in different cortical regions, yet focal differences in brain structures related to attention network components were not well understood. Therefore, in this study, voxel-based morphometry was used to investigate the relationship between gray matter volume （GMV） and different attention networks in a large young adult sample （n = 156）. As a result, multiple regression analysis revealed that higher alerting scores （stronger alerting ability） were negatively significantly correlated with region gray matter volume （rGMV） cingulate cortex/precuneus）, in the PCC/PreCu （posterior which might be associated with continuous maintenance of a vigilant state. Then, lower EC scores （stronger conflict resolution ability） were associated with larger rGMV in the dorsal anterior cingu- late cortex, which might be related to high-efficiency executive control processing. Together, findings of the present study provided a unique structural basis of GMV for individual differences in alerting and EC networks.