Alcohol Dehydrogenases with anti-Prelog Stereopreference in Synthesis of Enantiopure Alcohols

Biocatalytic production of both enantiomers of optically active alcohols with high enantiopurities is of great interest in industry. Alcohol dehydrogenases (ADHs) represent an important class of enzymes that could be used as catalysts to produce optically active alcohols from their corresponding prochiral ketones. This review covers examples of the synthesis of optically active alcohols using ADHs that exhibit anti-Prelog stereopreference. Both wild-type and engineered ADHs that exhibit anti-Prelog stereopreference are highlighted.     

Miscibility between PS and PSAN Affected by Solvent and Temperature of the System

The influence of solvent on the miscibility of polystyrene（PS） and poly（styrene-co-acrylonitrile）（PSAN） blends has been investigated viscometrically. The miscibility of different PS/PSAN blend（30/70, 50/50 and 70/30） compositions in acetone and benzene at 20, 30, and 40 °C was investigated on the basis of the sign of Chee（ΔB and ）, and Sun’s（α） criteria. The values of these parameters were evaluated from the analyses of reduced viscosity data of binary（solvent/polymer） and ternary（solvent/polymer1/polymer2） polymer systems. These investigations indicated partial miscibility for both the blend systems. However, PS/PSAN/acetone blend system showed somewhat higher partial miscibility than the PS/PSAN/Benzene blend system highlighting the impact of solvent over the polymer-polymer interactions and hence their miscibility. The results obtained through viscometry were also corroborated by the refractive index and density results for the blends under study. The effect of temperature on miscibility in both the cases was almost negligible.     

The Ã1B2-X̃1A1 two-photon fluorescence excitation spectrum of 1,3-difluorobenzene

The $\text{A}\text{?}{}^1\text{B}{}_2\text{-}\text{X}\text{?}{}^1\text{A}{}_1$ system of 1,3-difluorobenzene has been observed using the technique of two-photon fluorescence excitation obtained with a pulsed dye laser. Calibration was achieved by a combination of the neon optogalvanic spectrum and etalon fringes. In circular, compared to linear, polarization the bands divide into two groups, those which are B₂-A₁ and which retain their intensity with circular polarization, and those which are A₁-A₁ and lose about 60% of their intensity under the same conditions. These two kinds of bands also show characteristic rotational contours. All of the A₁-A₁ bands whose assignments are established obtain their intensity through vibronic interaction in which the vibration ν′₂₅ (ν′₁₄ in the Wilson numbering) mixes the $\text{A}\text{?}$ with, presumably, the $\text{X}\text{?}$ state. There is an important Fermi resonance between the 9¹ and 10¹11¹ levels. Parts of the one-photon absorption spectrum have been photographed to identify sequences associated with the 0₀⁰ band for comparison with those observed in the two-photon spectrum, and to search for bands involving odd quanta of b₂ vibrations, including ν′₂₅ (ν′₁₄); none was found.     

Global Geometry of 3-Body Motions with Vanishing Angular Momentum Ⅰ

Following Jacobi＇s geometrization of Lagrange＇s least action principle, trajectories of classical mechanics can be characterized as geodesics on the configuration space M with respect to a suitable metric which is the conformal modification of the kinematic metric by the factor （U ＋ h）, where U and h are the potential function and the total energy, respectively. In the special case of 3-body motions with zero angular momentum, the global geometry of such trajectories can be reduced to that of their moduli curves, which record the change of size and shape, in the moduli space of oriented m-triangles, whose kinematic metric is, in fact, a Riemannian cone over the shape space M^＊≌S^2 （1/2）.
In this paper, it is shown that the moduli curve of such a motion is uniquely determined by its shape curve （which only records the change of shape） in the case of h≠0, while in the special case of h = 0 it is uniquely determined up to scaling. Thus, the study of the global geometry of such motions can be further reduced to that of the shape curves, which are time-parametrized curves on the 2-sphere characterized by a third order ODE. Moreover, these curves have two remarkable properties, namely the uniqueness of parametrization and the monotonieity, that constitute a solid foundation for a systematic study of their global geometry and naturally lead to the formulation of some pertinent problems.     

Crystalline and random “diamond-like” boron–carbon structures

The bulk properties and relative stabilities of B–C structures are studied using both first-principles and molecular dynamics simulations that employ Tersoff potentials. The elastic properties of the B–C structures are deduced and some properties of random structures compared with possible crystalline counterparts.     

Scattering experiments on the structure of concentrated dispersions

 In this work the Couette cell is compared with a more recently constructed disk shear cell. There are distinct advantages of the disk over the Couette cell, in particular, when it comes to the determination of the intensity along certain Bragg rods. Received: 12 December 2000 Accepted: 31 January 2001     

Thermally degradable maleimides for reworkable adhesives

New thermosetting materials were developed for reworkable adhesive applications by introducing acetal ester groups as thermally degradable linkages into maleimide compounds. The synthesis of compounds containing maleimide functionality and acetal ester linkages was conducted by a one‐step neat reaction from commercially available materials. The polymerization process and thermal degradation of the synthesized materials were studied. It was found that the acetal ester linkage degraded rapidly above 225 °C, and introduction of this linkage into the adhesive formulation led to improved reworkability of adhesively bonded substrates. A mechanism for reworkability was proposed based on the insight provided by experimental and modeling work. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1073–1084, 2009     

Deep Task-Based Quantization

Quantizers play a critical role in digital signal processing systems. Recent works have shown that the performance of acquiring multiple analog signals using scalar analog-to-digital converters (ADCs) can be significantly improved by processing the signals prior to quantization. However, the design of such hybrid quantizers is quite complex, and their implementation requires complete knowledge of the statistical model of the analog signal. In this work we design data-driven task-oriented quantization systems with scalar ADCs, which determine their analog-to-digital mapping using deep learning tools. These mappings are designed to facilitate the task of recovering underlying information from the quantized signals. By using deep learning, we circumvent the need to explicitly recover the system model and to find the proper quantization rule for it. Our main target application is multiple-input multiple-output (MIMO) communication receivers, which simultaneously acquire a set of analog signals, and are commonly subject to constraints on the number of bits. Our results indicate that, in a MIMO channel estimation setup, the proposed deep task-bask quantizer is capable of approaching the optimal performance limits dictated by indirect rate-distortion theory, achievable using vector quantizers and requiring complete knowledge of the underlying statistical model. Furthermore, for a symbol detection scenario, it is demonstrated that the proposed approach can realize reliable bit-efficient hybrid MIMO receivers capable of setting their quantization rule in light of the task.     

Synthesis,structural, spectral,thermal and comparative biological activity studies of [V<Subscript>2</Subscript>O<Subscript>2</Subscript>(SO<Subscript>4</Subscript>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>6</Subscript>]

The hydrothermal reaction of a mixture of V₂O₅, VCl₃, 2,5-pyridinedicarboxylic acid and diluted H₂SO₄ for 68 h at 180°C gives a blue colored solution which yields prismatic blue crystals of IV ₂ ^IV O₂(SO₄)₂(H₂O)₆] (1) in 32% yield (based on V). Complex 1 was investigated by means of elemental analysis (C, H and S), TGA, FT-IR, manganometric titration, Single Crystal X-ray Diffraction Methods and also comparative antimicrobial activities. Crystal data for the compound: monoclinic space group P2₁/c and unit cell parameters are a = 7.3850(12) Å, b = 7.3990(7) Å, c = 12.229(2) Å, β = 108.976(12)° and Z = 2. Although structure of 1 as a natural mineral has been previously determined, this work covers new preparation method and full characterization of 1 along with comparison of antibacterial activity between 1 and the commercial vanadium(IV) oxide sulfate hydrate compounds, VOSO₄ · xH₂O (Riedel-de Haën and Alfa Aesar brand names). 1 was evaluated for the antimicrobial activity against gram-positive, gram-negative bacteria, yeasts and mould compared with the commercial VOSO₄ · xH₂O compounds. 1 showed weak activity against bacteria Bacillus cereus, Nocardia asteroides and yeast Candida albicans. A good antimicrobial activity was recorded against Cirtobacter freundii (15 mm). There are only a few reproducible well-defined vanadium(IV) starting materials to use for exploring the synthesis of new materials. VCl₄, VO(acac)₂, VOSO₄ · xH₂O and [V(IV)OSO₄(H₂O)₄] · SO₄ · [H₂N(C₂H₄)₂NH₂] are common starting materials for such applications. In addition to these compounds, 1 can be used as an oxovanadium precursor.