Application of immobilized hydrogenase to h2 storage in concentrated solutions of methyl viologen

It has been found that immobilized cells ofC. pasteurianum possessing hydrogenase activity efficiently catalyze reversible reduction of concentrated (up to 0.5M) solutions of methyl viologen with H₂. A 0.5M aqueous solution of methyl viologen dissolves 240 times as much H₂ as pure water under the same pressure of hydrogen. The experimentally obtained levels of methyl viologen reduction and H₂ evolution are in satisfactory agreement with theoretical calculations. The potential of concentrated solutions of methyl viologen containing immobilized hydrogenase as a H₂ storage medium is discussed.     

Numerical identification of the leading coefficient of a parabolic equation

For a multidimensional parabolic equation, we study the problem of finding the leading coefficient, which is assumed to depend only on time, on the basis of additional information about the solution at an interior point of the computational domain. For the approximate solution of the nonlinear inverse problem, we construct linearized approximations in time with the use of ordinary finite-element approximations with respect to space. The numerical algorithm is based on a special decomposition of the approximate solution for which the transition to the next time level is carried out by solving two standard elliptic problems. The capabilities of the suggested numerical algorithm are illustrated by the results of numerical solution of a model inverse two-dimensional problem.     

Conjugation of proteins with chelating polymers via water-soluble carbodiimide andN-hydroxysulfosuccinimide

Water-soluble chelating polymers (CP) based on polylysine and diethylenetriaminepentaacetic acid (DTPA) have been prepared. The effect of the number of DTPA-groups in the polymer chain on the process of CP carbodiimide-mediated coupling to proteins has been studied. CP obtained were conjugated with proteins via carbodiimide andN-hydroxysulfosuccinimide (HSSI). The optimal conditions of CP activation were determined using model low-molecular-weight amine. It was shown that the addition of HSSI to an activation mixture increases the coupling efficiency of CP with immunoglobulins by 3‐4-fold compared with carbodiimide alone. Possible mechanisms of this phenomenon are discussed.     

Oxidation of Dibenzothiophene Catalyzed by Hemoglobin and Other Hemoproteins in Various Aqueous-Organic Media

Biocatalytic oxidation of dibenzothiophene (a model of organic sulfur in coal) with hydrogen peroxide was investigated. It was found that various hemoproteins, both enzymic (e.g., horseradish peroxidase) and nonenzymic (e.g., bovine blood hemoglobin), readily oxidized dibensothiophene to its S-oxide and, to a minor extent, further to its S-dioxide (sulfone). This process catalyzed by hemoglobin (a slaughterhouse waste protein) was studied in a number of monophasic aqueousorganic mixtures. Although hemoglobin was competent as an oxidation catalyst even in nearly dry organic solvents (with protic, acidic solvents being optimal), the highest conversions were observed in predominantly aqueous media. The hemoglobin-catalyzed oxidation of dibenzothiophene at low concentrations of the protein stopped long before all the substrate was oxidized. This phenomenon was caused by inactivation of hemoglobin by hydrogen peroxide that destroyed the heme moiety. The maximal degree of the hemoglobin-catalyzed dibenzothiophene oxidation was predicted, and found, to be strongly dependent on the reaction medium composition.     

Globally strictly convex cost functional for an inverse parabolic problem

A coefficient inverse problem for a parabolic equation is considered. Using a Carleman weight function, a globally strictly convex cost functional is constructed for this problem. Copyright © 2015 John Wiley & Sons, Ltd.     

Concerted and stepwise proton-coupled electron transfers in aquo/hydroxo complex couples in water: oxidative electrochemistry of [Os(II)(bpy)(2)(py)(OH(2))](2+)

Successive oxidation of transition metal(II) aqua complexes (M(II)OH(2) to M(III)OH) is a domain in which proton-coupled electron transfer reactions are extremely common. The mechanism of these PCET reactions-concerted or stepwise-is an important issue in the understanding and design of natural or artificial systems catalyzing the formation of dioxygen by four-electron oxidation of water. Concerted proton-coupled electron transfer from an aqua metal(II) to a hydroxo metal(III) complex requires the close proximity of a proton-accepting group with a pK value between those of the aqua complexes. Otherwise, stepwise electron-proton or proton-electron pathways involving high-energy intermediates are followed. Concerted proton-electron pathways involving water as proton-acceptor or proton-donor group are inefficient. Cyclic voltammetry of the title complex in buffered aqueous solution and re-examination of previous results for the same complex attached to an electrode surface are used to establish these conclusions, which provide a starting point on the route to higher degrees of oxidation, such as those involved in the catalysis of water oxidation.     

On the recovery of a 2-D function from the modulus of its Fourier transform

A uniqueness theorem is proven for the problem of the recovery of a complex valued compactly supported 2-D function from the modulus of its Fourier transform. An application to the phase problem in optics is discussed.     

Uniqueness of two phaseless non-overdetermined inverse acoustics problems in 3-d

Uniqueness is proven for two non-overdetermined 3-d inverse problems of the determination of the spatially distributed sound speed in the frequency dependent acoustic PDE. The main new point is the assumption that only the modulus of the scattered complex valued wave field is measured on a certain set. The phase is unknown.     

内埋炸药下超高韧性水泥基复合材料的抗爆性能

为研究超高韧性水泥基复合材料(ultra-high toughness cementitious composites, UHTCC)在内埋炸药爆炸下的抗爆性能和损伤破坏规律,对不同炸药埋深下的UHTCC和高强混凝土(high-strength concrete, HSC)进行了内埋炸药抗爆实验。得到了两种材料靶体的破坏状态,并利用接触爆炸的实验结果计算出了两种材料的抗爆性能参数。结果表明,在相同条件下,UHTCC抗爆性能优于高强混凝土。为了进一步探究UHTCC的抗压强度、抗拉强度以及拉伸韧性对靶体在内埋炸药下抗爆性能的影响,首先,采用改进的K&C模型对炸药埋深为40 mm的超高韧性水泥基复合材料靶体进行数值模拟,模拟结果与实验结果基本吻合,并根据数值模拟的结果得到了爆炸冲击波沿靶体径向衰减速度大于轴向衰减速度这一规律,验证了数值模型的有效性;然后,通过调整改进K&C模型中与抗压强度、抗拉强度以及拉伸韧性相关的参数,数值预测了不同抗压强度、抗拉强度以及拉伸韧性下UHTCC靶体的破坏状态,发现增强UHTCC的韧性可以有效防止靶体发生整体性破坏,增大UHTCC的抗拉强度可以减小靶体迎爆面的开坑直径,增大UHTCC的抗压强度对减小开坑直径效果不明显。     

Investigation of structural and electronic properties of β- HgS: Molecular dynamics simulations

The pressure induced phase transition of β-HgS is studied using an ab initio molecular dynamics simulation. The structural phase transformation from the zinc-blende structure to the NaCl-type structure (space group $Fm\overline{3}m$) and from this structure to CsCl-type structure ($Pm\overline{3}m$) with the application of hydrostatic pressure is predicted. Additionally, the electronic properties of HgS and various physical properties such as the lattice constants, the bulk modulus and the pressure derivative of the bulk modulus are revealed. Furthermore, these phase transitions are obtained using the total energy and enthalpy calculations. According to these calculations these transformations are occurring at about 20?GPa and 28?GPa for $F\overline{4}3m$ →$Fm\overline{3}m$ and $Fm\overline{3}m$ →$Pm\overline{3}m$, respectively.