Hard discs in circular cavities: density functional theory versus simulation

Three different density functional approaches, namely the Rickayzen, Takamiya-Nakanishi and Rosenfeld approximations, have been employed to study the equilibrium particle density distributions of hard-disc fluids in hard circular cavities. Also, Monte Carlo simulations have been performed to test the theoretical results. The comparison with the simulation data shows that the Rosenfeld approximation, which is based on the fundamental geometrical measures of the particles, is better than the Takamiya-Nakanishi and Rickayzen approximations and yields good agreement with the computer simulation data even for higher densities.     

On transmission problem for viscoelastic wave equation with a localized a nonlinear dissipation

In this article, we consider the global existence and decay rates of solutions for the transmission problem of Kirchhoff type wave equations consisting of two physically different types of materials, one component being a Kirchhoff type wave equation with time dependent localized dissipation which is effective only on a neighborhood of certain part of boundary, while the other being a Kirchhoff type viscoelastic wave equation with nonlinear memory.     

Evaluation study on properties of isohexyl-BTP/SiO2-P resin for direct separation of trivalent minor actinides from HLLW

In order to develop a direct separation process for trivalent minor actinides from fission products in high level liquid waste (HLLW) by extraction chromatography, a novel macroporous silica-based 2,6-bis(5,6-diisohexyl)-1,2,4-triazin-3-yl)pyridine resin (isohexyl-BTP/SiO₂-P resin) was prepared. The content of isohexyl-BTP extractant in the resin was as high as 33.3 wt%. The resin exhibited much higher adsorption affinity for Am(III) in 2–3 M (mol/L) HNO₃ solution over U and FP which are contained in HLLW. The kinetic data were analyzed using pseudo-second-order equation. The results suggested that the Eu(III), Gd(III), and Dy(III) adsorption was well explained by the pseudo-second-order equation. Quantitative desorption for adsorbed elements was achieved by using H₂O or thiourea as eluting agents. However, the kinetics of adsorption and desorption were rather slow and this drawback needs to be resolved. Stability of the resin against HNO₃ was also examined. It was found that the resin was considerably stable against ≤4 M HNO₃ solution for the reasons of an extremely small leakage of the extractant into the solution from the resin and the adsorption performance keeping for rare earths in 3 M HNO₃ solution.     

SBA-15介孔分子筛表面的磺酸基改性及其催化性能

 采用后合成方法，将含有巯基的化合物3－巯丙基三甲氧基硅烷（MPTMS）键合在大孔径、厚孔壁的新型纯硅介孔分子筛SBA－15表面上，经氧化和酸化后得到含有强酸性的磺酸基团的固体酸催化剂SBA－15－SO3H．用X射线衍射、红外光谱、固体核磁共振及热失重等方法对改性前后的SBA－15样品进行了表征．结果表明，改性后SBA－15分子筛的结构未发生变化，MPTMS键合于分子筛的表面，改性后的分子筛具有质子酸中心．SBA－15－SO3H催化剂对十八碳烯酸与甲醇的酯化反应具有较高的活性，催化剂上的磺酸基团在反应过程中具有较好的稳定性．     

若干简单Plakoric acid类似物的合成及体外抗疟活性

Several simple analogues of peroxyplakoric acid were synthesized by using Kobayashi＇s method to construct the key 1,2-dioxane core and tested in vitro for antimalarial activity. The scope and limitation of the method was also briefly examined.     

PORPHYRIN-SENSITIZED PHOTOREACTIONS IN THE PRESENCE OF ASCORBATE: OXIDATION OF CELL MEMBRANE LIPIDS AND HYDROXYL RADICAL TRAPS

Abstract— Photooxidation reactions in ascorbate (AH)-containing erythrocyte membrane suspensions have been studied in broad perspective by simultaneously monitoring lipid peroxidation in the membrane compartment and formation of hydrogen peroxide (H₂O₂) and hydroxyl radical (OH) in the aqueous compartment. Non-bound uroporphyrin (UP) and membrane-bound protoporphyrin (PP) were used as sensitizers. Photoreduction of UP to the radical anion (UP^-) was detected by electron spin resonance when UP/AH/membrane mixtures were irradiated anaerobically. Aerobic irradiation resulted in a strong AH^--stimulation of lipid peroxidation, H₂O₂ formation, and OH^- generation (detected with 2-deoxyribose (DOR) and the spin trap 5,5-dimethyl-l-pyrroline-N-oxide). Use of diagnostic agents (e.g. catalase, desferrioxamine, mannitol) revealed that OH^- is involved in light-stimulated DOR oxidation, but not in lipid peroxidation. Similar irradiation in the presence of PP resulted in far greater lipid peroxidation than observed with UP, but less DOR oxidation, and insignificant accumulation of H₂O₂. This suggests that photoreduction of membrane-bound PP is less efficient, possibly due to hindered access of AH^-.     

A model for the value of a business, some optimization problems in its operating procedures and the valuation of its debt

Corresponding author, email pw{at}oxfordfinancial.co.uk; also at: Imperial College, London In this paper we present a model for the value of a firm basedon observable variables and parameters: the annual turnover,the expenses, interest rates. This value is the solution ofa parabolic partial differential equation. We show how the valueof the company depends on its legal status such as its liability(that is, whether it is a Limited Company or a sole trader/partnership).We give examples of how the operating procedures can be optimized(for example, whether the firm should close down, relocate etc.).Finally, we show how the model can be used to value the debtissued by the firm.     

Graham’s pebbling conjecture on product of complete bipartite graphs

The pebbling number of a graph G, f(G), is the least n such that, no matter how n pebbles are placed on the vertices of G, we can move a pebble to any vertex by a sequence of moves, each move taking two pebbles off one vertex and placing one on an adjacent vertex. Graham conjectured that for any connected graphs G and H, f( G x H) ⩽ f( G) f( H). We show that Graham’s conjecture holds true of a complete bipartite graph by a graph with the two-pebbling property. As a corollary, Graham’s conjecture holds when G and H are complete bipartite graphs.     

微生物酶催化制备人参皂苷20(S)-Rg2,20(S)-Rh1和20(S)-PPT

摘要 人参次级皂苷具有较强的抗癌、抗癌转移等药理活性,但由于在人参中含量少或不存在,因此以人参中含量较高的主要人参皂苷制备药效更高的人参次级皂苷不仅有必要,而且很有意义．本文以微生物Microbacterium esteraromaticum GS514的培养液中分离的粗酶为催化剂水解人参皂苷Re和Rg1,并通过1H NMR和13C NMR谱进行了水解产物的结构表征．实验结果表明,反应体系中无机盐NaCl的存在与否直接影响人参皂苷Re,Rg1与粗酶液的反应结果.人参皂苷与粗酶液直接反应,人参皂苷Re不发生反应,人参皂苷Rg1通过C6所连β-D-吡喃葡萄糖的选择性水解转化成人参皂苷F1.如果该反应是在无机盐NaCl存在下进行,人参皂苷Re通过对C20 所连β-D-吡喃葡萄糖的选择性水解定向转化为20(S)-人参皂苷Rg2;人参皂苷Rg1定向转化成20(S)-人参皂苷Rh1以及20(S)-原人参三醇（PPT）.这说明NaCl的加入激活了C20β-D-吡喃葡萄糖苷酶的活性,这对定向合成不同次级人参皂苷具有重要意义.     

疏水石墨烯水相分散液的制备及电化学性能

通过未添加表面活性剂和稳定剂而得到均匀的石墨烯水相分散液的方法,近来来成为研究的一大热点.本工作通过提高水合肼的用量,来替代表面活性剂或者其它稳定剂的作用,得到了良好的均匀的水相石墨烯分散液,可长期稳定存放,6个月内未发生团聚现象.其Zeta电位低于-32.5 mV(pH值为5.89),原子力显微镜和透射电子显微镜图像表明产物为具有褶皱结构的、六方晶系的单层石墨烯结构,厚度为0.38 nm.XPS分析显示这种方法对于除去羟基和环氧基团起到了有效的作用.利用这种分散液所制备的石墨烯-玻碳电极(GE-GCE)在检测抗坏血酸(AA)和尿酸(UA)时,比普通玻碳电极(GCE)显示出更良好的电化学响应.