Substrate Conformations Set the Rate of Enzymatic Acrylation by Lipases

Acrylates represent a class of α,β‐unsaturated compounds of high industrial importance. We investigated the influence of substrate conformations on the experimentally determined reaction rates of the enzyme‐catalysed transacylation of methyl acrylate and derivatives by ab initio DFT B3LYP calculations and molecular dynamics simulations. The results supported a least‐motion mechanism upon the sp² to sp³ substrate transition to reach the transition state in the enzyme active site. This was in accordance with our hypothesis that acrylates form productive transition states from their low‐energy s‐sis/s‐trans conformations. Apparent k_cat values were measured for Candida antarctica lipase B (CALB), Humicola insolens cutinase and Rhizomucor miehei lipase and were compared to results from computer simulations. More potent enzymes for acryltransfer, such as the CALB mutant V190A and acrylates with higher turnover numbers, showed elevated populations of productive transition states.     

Recent Progress in the Molecular Imaging of Nonalcoholic Fatty Liver Disease

Pathological fibrosis of the liver is a landmark feature in chronic liver diseases, including nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Diagnosis and assessment of progress or treatment efficacy today requires biopsy of the liver, which is a challenge in, e.g., longitudinal interventional studies. Molecular imaging techniques such as positron emission tomography (PET) have the potential to enable minimally invasive assessment of liver fibrosis. This review will summarize and discuss the current status of the development of innovative imaging markers for processes relevant for fibrogenesis in liver, e.g., certain immune cells, activated fibroblasts, and collagen depositions.     

WISC–III index score profiles of 520 Swedish children with pervasive developmental disorders.

WISC–III (Wechsler, 1991) index score profiles and their characteristics were examined with traditional statistics in a large Swedish sample consisting of children with autistic disorder (n = 85), Asperger's disorder (n = 341), or pervasive developmental disorders not otherwise specified (PDD-NOS; n = 94). There was a clear and significant difference in level between children with Asperger's disorder, who performed in the average range according to the Swedish standardization, and children with either autistic disorder or PDD-NOS, who performed below the average range (almost 2 standard deviations below the mean), but few other differences between the diagnostic groups were found. The variation in this sample, compared with the Swedish standardization, was generally larger in regard to the size of standard deviations and to the proportion of individuals who exhibited significant differences between indices. The result implied that a WISC–III profile could not be used to discriminate between the different PDDs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quantification of Birch and Grass Pollen Allergens in Indoor Air

Abstract Birch and grass pollen grains as well as pollen-derived small particles appear as potent allergens in the outdoor air during spring and summer. The occurrence of pollen allergens in indoor air, however, has not been studied in depth due to lack of suitable sampling and analytical methods. Herein, a recently reported “direct on sampling filter estimation” (DOSAFE) technique ( Acevedo et al., 1998 ) has been validated for quantification of pollen allergens in indoor air using two school rooms and two office rooms as experimental models. Using DOSAFE and polyclonal antibodies against water extracts of pollen from Betula pendula and Phleum pratense L, we found that indoor air of school and office rooms carried substantial amounts of pollen allergens, expressed as SQ units, predominantly occurring as particles with smaller diameters than the pollen grains. In one school room the indoor air birch pollen allergen concentrations increased from 242 to 403 SQ units/m³ over the sampling period although the corresponding outdoor air concentrations decreased from 350 to 90 SQ units/m³. Electrostatic air cleaning in one office room reduced its grass pollen allergen concentrations by more than 95% to 0.02–0.34 SQ units/m³ as compared to the control room.     

Asymmetric Synthesis of Substituted Thiolanes through Domino Thia‐Michael–Henry Dynamic Covalent Systemic Resolution using Lipase Catalysis

Dynamic systems based on consecutive thia‐Michael and Henry reactions were generated and transformed using lipase‐catalyzed asymmetric transformation. Substituted thiolane structures with three contiguous stereocenters were resolved in the process in high yields and high enantiomeric excesses.

     

ADAPTIVE COORDINATED DECENTRALIZED CONTROL OF STATE DELAYED SYSTEMS WITH ACTUATOR FAILURES

This paper develops an adaptive state feedback coordinated decentralized control scheme for a class of dynamic systems with state delay in subsystems and in the interconnections and in the presence of unknown actuator failures in each subsystem. The main contributions of this paper are the development of a new controller parametrization which attempt to anticipate the future states and failures, the introduction of an appropriate Lyapunov‐Krasovskii type functional to design the adaptation algorithms, and a stability proof.     

Some aspects on the optimum repository plug design with respect to the escape of gas

BfS is in the progress of developing a closure concept for the repository for low and intermediate level radioactive waste in Morsleben (ERAM). In the course of this work, the optimal design of the plug is currently being evaluated with respect to gas escape and the exchange of potentially contaminated brine through the plug. For the sealing to behave well in the long term, it is important that the gas formation processes do not disrupt the plug or enhance the radionuclide release, e.g. by means of excessive pressure build-up. The object has been to study different scenarios for gas and brine transport for two alternative plug concepts, by using the multi-phase flow model TOUGH. Rock convergence due to creep has been included in the modelling. The results of the calculations indicate that the closure concepts restrict he exchange of brine and allow escape of gas; an excavation-damaged zone around tunnels is a potential pathway for gas and brine, and the effect of the rock convergence is small. The results also indicate that a very dense plug results in excessive pressurisation of the repository, whereas a permeable plug results in an increased exchange of brine.     

A continuum model for cracked UO2 fuel

This paper presents a constitutive model for uranium dioxide fuel pellets in light water reactor fuel rods. The proposed model accounts for the fuel mechanical behaviour under pellet cracking, fragment relocation and pellet-clad mechanical interaction. Moreover, the detrimental effect of cracking on the fuel thermal conductivity is considered in the model. An essential part of the model is the representation of pellet cracks, which significantly affect both the mechanical and thermal behaviour of nuclear fuel under operation. Cracking is modelled in a continuum context, where cracks are represented by nonelastic strains in the material. The continuum representation is particularly suitable for finite element computer codes, since cracking can be treated in the same manner as plasticity and creep. The model is derived in the form of a nonlinear constitutive relation for the fuel material, that may be implemented in either two- or three-dimensional finite element fuel performance computer codes. The fundamentals of the model are presented, and issues concerning its numerical implementation are discussed. The model's ability to capture important aspects of the cracked fuel behaviour is also illustrated by comparisons with in-reactor experiments.     

Rational Approximations of Transfer Functions of Some Viscoelastic Rods with Applications to Robust Control

We study rational approximations of the transfer function of a uniform or nonuniform viscoelastic rod undergoing torsional vibrations that are excited and measured at the same end. The approximation is to be carried out in a way that is appropriate, with respect to stability and performance, for the construction of suboptimal rational stabilizing compensators for the rod. The function can be expressed as , where g is an infinite product of fractional linear transformations and is a (generally transcendental) function that characterizes a particular viscoelastic material. First, g(²) is approximated by its partial products g _N(²). For relevant values of ², convergence rates for g _N are analyzed in detail. Convergence suitable for our problem requires the introduction of a new irrational convergence factor, which must be approximated separately. In addition, the fractional linear factors in ²(s) that appear in g _N(²(s)) must be replaced by something rational. When the damping is weak it is possible to do this by separating the oscillatory modes from the creep modes and ignoring the latter; in general, this step remains incomplete. Some numerical data illustrating all the stages of the process as well as the final results for various viscoelastic constitutive relations are presented.