Microbial desulfurization of ground tire rubber by Thiobacillus ferrooxidans

This study focused on the microbial desulfurization of ground tire rubber (GTR) by Thiobacillus ferrooxidans, which selected from the soil of an iron mine had strong sulphur oxidizing capacity. GTR was desulfurizated in the modified Silverman medium during the cultivation of T. ferrooxidans for 30 days, and T. ferrooxidans was able to maintain a high biomass. The continuous increase of SO₄²⁻ in the medium indicated that the sulfur on the surface of GTR was oxidized. FTIR-ATR and XPS spectra revealed that a rupture of conjugated CC bonds and a reduction of sulfur content on the surface of GTR had occurred during desulfurization. The sol fraction of GTR increased from its original 4.69%-7.43%. Compared with GTR sheet, desulfurizated GTR (DGTR) sheets had much smoother surfaces, better physical properties, and higher swelling values. NR vulcanizates filled with DGTR (with 10-40 phr loading) had lower crosslink density and better mechanical properties than those filled with GTR at the same loading. The results determined by DMA suggested that NR vulcanizates filled with DGTR had a reduction of molecular chain friction resistance during glass transition and SEM photograph indicated a better interface coherence between DGTR and NR matrix.     

Continuous optimization methods for ground-state searches of spin clusters

Computational methods were developed for ground-state searches of Heisenberg model spin clusters in which spin sites were represented by classical spin vectors. Simulated annealing, continuous genetic algorithm, and particle swarm optimization methods were applied for solving the problems. Because the results of these calculations were influenced by the settings of optimization parameters, effective parameter settings were also investigated. The results indicated that a continuous genetic algorithm is the most effective method for ground-state searches of Heisenberg model spin clusters, and that a mutation operator plays an important role in this genetic algorithm. These results provide useful information for solving physically or chemically important continuous optimization problems.     

Front velocity and directed polymers in random medium

We consider a stochastic model of N$N$ evolving particles studied by Brunet and Derrida. This model can be seen as a directed polymer in random medium with N$N$ sites in the transverse direction. Cook and Derrida use heuristic arguments to obtain a formula for the ground state energy of the polymer. We formalize their argument and show that there is an additional term in the formula in the critical case. We also consider a generalization of the model, and show that in the noncritical case the behavior is basically the same, whereas in the critical case a new correction appears.     

Ab initio quantum mechanics of a cluster of SiH4 and two H2 molecules, together with its dimer and trimer

Recent experimental work by Strobel et al. [T.A. Strobel, M. Somayazulu, R.J. Hemley, Phys. Rev. Lett. 103 (2009) 065701] on a molecular solid subjected to high pressures has motivated the present study. We first investigate a molecular cluster containing one silane molecule plus two H₂ molecules, by ab initio quantum mechanics. Geometrical and electronic structures for the ground state of such a cluster are thereby proposed. The di-cluster is next examined, and the coming together of two H₂ molecules is predicted. Finally, the tri-cluster is studied and important aspects of the di-cluster bonding are found to remain largely intact.     

Multiplicity of ground states in quantum field models: applications of asymptotic fields

Ground states of Hamiltonian H of quantum field models are investigated. The infimum of the spectrum of H is in the edge of its essential spectrum. By means of the asymptotic field theory, we give a necessary and sufficient condition for that the expectation value of the number operator of ground states is finite, from which we give an upper bound of the multiplicity of ground states of H. Typical examples are massless GSB models and the Pauli-Fierz model with spin 1/2.     

类Li与类Be离子基态能量的简便计算公式

由双参数变分法导出类Ｌｉ与类Ｒｅ离子基态能量近似计算公式，该公式计算简便且具有很高精度。     

Uniqueness of the Ground State in Weak Perturbations of Non-Interacting Gapped Quantum Lattice Systems

We consider a general weak perturbation of a non-interacting quantum lattice system with a non-degenerate gapped ground state. We prove that in a finite volume the dependence of the ground state on the boundary condition exponentially decays with the distance to the boundary, which implies in particular that the infinite-volume ground state is unique. Also, equivalent forms of boundary conditions for ground states of general finite quantum systems are discussed.On leave from Institute for Information Transmission Problems, Moscow, Russia.     

New ground state constants of CH3Cl and CH3Cl from global polyad analysis

A global analysis of the infrared spectrum of chloromethane involving the ground state and the 13 vibrational states lying up to 2600 cm⁻¹ was recently achieved using high resolution Fourier transform spectra of pure isotopomers. More than 20 000 transitions (cold and hot bands) for each isotopomer ¹²CH₃³⁵Cl and ¹²CH₃³⁷Cl have been assigned and fitted with a standard deviation of about 3 × 10⁻⁴ cm⁻¹ close to the experimental precison. As part of this global effort, improved ground state constants up to sextic centrifugal distortion terms have been determined for each isotopomer taking advantage of the numerous allowed and perturtation-allowed transitions simultaneously fitted using our global model. The axial constants could be determined from ΔK ≠ 0 combinations arising from rovibrational local resonances within Polyads 3 and 5.     

外电场作用下三元环状水分子团簇的特性研究

采用了HartreeFork自洽场方法在321G水平上研究了0～0.01a.u.的外电场对三元环状水分子团(H2O)3基态能量和电偶极距的影响规律,分析了由外电场产生的HellmanFeynman(HF)力(内力和外力)和在这个力的平衡作用下的团簇的稳定结构,结果表明,外电场的大小对三元环状水分子团簇(H2O)3这些性质有明显的影响.通过高斯计算可以得出,在所加的电场范围内,随着外电场的增大总能量下降,电偶极距增大,结构相对更稳定;外电场引起团簇中各个原子的电荷密度改变,导致了各个原子所受的静电力随之变化.