A differential equation model of HIV infection of CD4T-cells with cure rate

A differential equation model of HIV infection of CD4⁺T-cells with cure rate is studied. We prove that if the basic reproduction number R₀<1, the HIV infection is cleared from the T-cell population and the disease dies out; if R₀>1, the HIV infection persists in the host. We find that the chronic disease steady state is globally asymptotically stable if R₀>1. Furthermore, we also obtain the conditions for which the system exists an orbitally asymptotically stable periodic solution. Numerical simulations are presented to illustrate the results.     

序半群的一类正则同余

设S是有向序半群,本文给出了S上的一类正则同余,称为强序同余的定义及性质.证明了S的强序同余是强正则同余,但反之不成立.同时证明了强序同余格SOC(S)是S的同余格C(S)关于通常集合的交和传递积的V-完备的分配子格.     

Theoretical design and experimental study of hydrothermal synthesis of KNbO3

In the framework of the Lencka-Riman thermodynamic model, we give a theoretical design for the hydrothermal synthesis of pure KNbO₃ powder in a K-Nb-O tri-component system, where the stability yield diagrams and the optimum conditions (i.e., synthesis temperature, precursor concentrations, solution pH) are provided. Additionally, a hydrothermal experiment is carried out to synthesize KNbO₃ powder by reacting niobium pentoxide with potassium hydroxide at a temperature above 523 K and highly alkaline conditions. It is found that the experiment is in great agreement with the theoretical design. This research shows that the newly developed Lencka-Riman model is a powerful theoretical tool for designing hydrothermal synthesis of new materials.     

Oscillatory Behavior during the Partial Oxidation of Methane

A simplified Monte Carlo model was proposed to simulate the oscillatory behavior during catalytic partial oxidation of methane. Using the Langmuir-Hinshelwood mechanism, the oscillatory behavior was observed in both reaction rates and coverages of adsorbed species. The influence of oxidation and reduction of the catalyst surface on the oscillations was investigated, and the analysis showed that the fast oxidation and slow reduction of the catalyst surface resulted in the oscillatory behavior.     

Density perturbation of unparticle dark matter in the flat Universe

The unparticle has been suggested as a candidate of dark matter. We investigated the growth rate of the density perturbation for unparticle dark matter in the flat Universe. First, we consider the model in which the unparticle is the sole dark matter and find that the growth factor can be approximated well by f=(1+3ω _u )Ω _u ^γ , where ω _u is the equation of state of unparticle. Our results show that the presence of ω _u modifies the behavior of the growth factor f. For the second model where the unparticle co-exists with cold dark matter, the growth factor has a new approximation f=(1+3ω _u )Ω _u ^γ +α Ω _m and α is a function of ω _u . Thus the growth factor of the unparticle is quite different from that of the usual dark matter. This information can help us know more about unparticle and the early evolution of the Universe.     

金属团簇在单晶表面的稳定性和扩散行为的Monte Carlo研究

The stability and diffusion behaviors of 1.3 MPa Pt, Pd, Ni and Cu clusters supported on Pd(001) surface were studied by the Monte Carlo method. The support surface can strongly influence the stability and diffusion behaviors of the supported clusters. The structure transition temperatures of the supported clusters are much lower than the melting temperatures of their corresponding free clusters due to the vibration coupling between the support and the clusters. The stability of the supported clusters depends on not only the strength of metal support interaction but also the strength of the metal metal interaction. The diffusion constants of supported 1.3 MPa clusters are similar to those of corresponding metal atoms. Combining the diffusion parameters with the critical temperature of the supported clusters, the thermal stability is closely related to the diffusion behaviors of the metal clusters.     

H2S对NiW/Al2O3和CoMo/Al2O3上二苯并噻吩和4,6-二甲基二苯并噻吩加氢脱硫反应的影响

 考察了H2S对NiW/Al2O3和CoMo/Al2O3上二苯并噻吩(DBT)和4,6-二甲基二苯并噻吩(DMDBT)加氢脱硫反应的影响. 结果表明,H2S同时抑制DBT和DMDBT两种硫化物的加氢脱硫反应,并且对DBT的抑制作用更为明显. 对于NiW/Al2O3和CoMo/Al2O3两种催化剂,H2S抑制了DBT和DMDBT的直接脱硫路径活性; 对于CoMo/Al2O3催化剂上DBT转化中的加氢反应也有抑制作用,但促进了DMDBT转化中加氢反应的进行. NiW/Al2O3催化剂更易受H2S的影响.     

Spectra and dissociation properties of Freon 31 under electric field

Freon 31 is a carcinogenic substance. It is of great significance for studying its degradation under external electric field. The bond length, energy, dipole moment, orbital energy lever distribution, infrared spectra, and dissociation properties of Freon 31 molecule under the external field are investigated using the density functional theory on basis set level of B3LYP/6-311++G(d, p). In addition, the effects of electric field on ultraviolet–visible absorption spectra of the molecule are studied with CIS/6-311G++(d, p) method. The results indicate that spectra and dissociated properties under electric field have changed significantly. As the electric field (0–0.04 atomic units) along negative direction of y-axis increases, the bond length of carbon–chlorine bond gradually increases and tends to break; the bond length of carbon–fluorine bond gradually decreases. The energy gap first increases and then decreases changing with electric field. The infrared spectra and ultraviolet–visible absorption spectra exhibit blue shift or bathochromic shift under electric field. Moreover, the potential energy surface of Freon 31 about Carbon–Chlorine bond is scanned by the same basis set with configuration interaction - single excitation (CIS) method. The result shows the barrier of dissociation gradually decreases with the electric field. When the intensity of electric field is equal to 0.04 atomic units, the barrier has disappeared. In addition, the molecule is induced to fragmentation due to carbon–chlorine bond breaking. The results offer important reference to the degradation of contaminants.     

Synthesis and biodistribution of the 99mTc nitrido complex with 2-(4-nitro-1H-imidazolyl)ethyl dithiocarbamate (NIET)

Sodium and chlorine measurements were made by instrumental neutron activation analysis (INAA) on stratigraphically dated ice core samples from Byrd Station, Antarctica, for the last three centuries. The time period between 1969 and 1989 showed an enhanced impact on the Antarctic ice sheets from oceans in the form of marine aerosols. A disturbed ocean-atmosphere interface due to El Niño Southern Oscillation (ENSO) events seems to be a candidate for this observation in Antarctica.     

Stereoselective determination of famoxadone enantiomers with HPLC-MS/MS and evaluation of their dissipation process in spinach

A simple and enantioselective method for the determination of famoxadone enantiomers in spinach using reversed-phase HPLC-MS/MS is presented. Famoxadone residues in spinach were extracted with acetonitrile and an aliquot was cleaned up with PSA (primary and secondary amine, Si-(CH(2))(3)-NH-(CH(2))(2)-NH(2)) and C(18) sorbent, which were powder material. Chiral stationary phase (CSP), cellulose tris(3,5-dimethylphenylcarbamate), was successfully applied to separate two enantiomers using methanol/formic acid-ammonium acetate buffer as mobile phase. The MS/MS fragmentation pathway of ammonium adduct famoxadone molecules ion at m/z 392 was analyzed and an odd electron fragment ion at m/z 238 was observed. Excellent linearity was achieved for each enantiomer over a range of concentrations from 0.5 to 1500 μg/L with coefficients more than 0.99. Average recoveries at five different levels (1, 2.5, 12.5, 250 and 1250 μg/kg, for each enantiomer) ranged from 80.8 to 96.5% with RSD of 4.8-13.4%. The famoxadone enantiomers LODs in spinach were determined to be both 0.3 μg/kg with LOQs of 1 μg/kg. Based on this method, the dissipation process of famoxadone enantiomers in spinach under open field and greenhouse conditions was characterized, providing guidance to the proper and safe use of this fungicide in agriculture.