Isolation of glutathione biosynthesis-deficient mutants of Saccharomyces cerevisiae and their use in baker's yeast production

 Glutathione biosynthesis-deficient mutants of Saccharomyces cerevisiae 0511 were obtained by mutation under specific conditions. A total of 3388 strains were isolated and among them were found 46 mutants sensitive to methylglyoxal. The intracellular glutathione concentration of mutant strain S. cerevisiae 3033 was 0.0172 g/g dry weight, which was a decrease of >76% compared to that of the parent. The growth of mutant strains S. cerevisiae 3033 and S. cerevisiae 1116 in the medium with glutathione present and absent was compared to that of the parent strain. The sensibility of the baker's yeast strains studied to antifoaming agents, butanol and acetic acid was also investigated. The relationship between glutathione presence in the cell and the sensitivity of strain S. cerevisiae 3033 to antifoaming agents and butanol was ascertained, while such a connection with the presence of acetic acid in the molasses medium used for baker's yeast cultivation was not observed. The higher sensitivity of strain S. cerevisiae 3033 to some chemical compounds in the molasses nutrition medium was shown. Received: 2 November 1999 / Revised version: 15 February 2000     

Line width of single-crystal Mössbauer absorption

The Mössbauer line broadening method for the determination of Lamb–Mössbauer factors f_LM cannot be applied directly in the determination of the probability of the resonant absorption f_LM for single-crystalline absorbers with quadrupole splitted Mössbauer spectra. The line width Γ_exp for single crystals with quadrupole splitted Mössbauer spectra has been computed for various absorber thicknesses. The polarization effects are important and have been taken into account. The linear dependence has been adapted for Lamb–Mössbauer factor measurements by introducing a polarization-dependent coefficient. This method has been tested on measurements of guanidinium nitroprusside (GNP) (CN₃H₆)₂[Fe(CN)₅NO] single crystals.     

In-depth element analysis of weld no. 4 of RPV of unit no. 1 of KzNPP (atomic emission spectroscopy)

Two micro boat samples cut from weld no. 4 of RPV of unit 1 of Kozloduy Nuclear Power Plant (NNP) were studied by atomic emission spectroscopy for the content of phosphorus. The analysis was performed at several depths on flat surfaces, machined by a cutter. Special procedures were developed for the accounting of the dark current generated by the radioactivity of the samples. The final results for phosphorus for 0.1 mm depth is 0.0485–0.0515 wt%, for depths 2.4–6.2 mm the content is 0.0449±0.0022 wt% and for 6.6 mm the content is 0.0423±0.0022 wt%. The results are in good agreement with independent analysis performed at the Institute I.V. Kurchatov in Moscow and also with the results from wet chemical analysis performed at the Institute of Metal Science in Sofia.     

Stampede: a cluster programming middleware for interactive stream-oriented applications

Emerging application domains such as interactive vision, animation, and multimedia collaboration display dynamic scalable parallelism and high-computational requirements, making them good candidates for executing on parallel architectures such as SMPs and clusters of SMPs. Stampede is a programming system that has many of the needed functionalities such as high-level data sharing, dynamic cluster-wide threads and their synchronization, support for task and data parallelism, handling of time-sequenced data items, and automatic buffer management. We present an overview of Stampede, the primary data abstractions, the algorithmic basis of garbage collection, and the issues in implementing these abstractions on a cluster of SMPs. We also present a set of micromeasurements along with two multimedia applications implemented on top of Stampede, through which we demonstrate the low overhead of this runtime and that it is suitable for the streaming multimedia applications.     

Effect of layered silicates on fibril formation and properties of PCL/PLA microfibrillar composites

The study deals with improvement of poly(?‐caprolactone) (PCL) parameters by in situ forming of poly(lactic acid) (PLA) fibrils. This structure is achieved by preparation of the melt‐drawn microfibrillar composite (MFC) from the PCL/PLA 80/20 blend containing the organophilized montmorillonite (oMMT) added using various mixing protocols. Improved mechanical behavior corresponds to the micron‐sized fibrils formation and reinforcement of both polymer components by oMMT, and to increased crystalline phase content in the fibrillar PLA phase. Effective melt drawing is only possible after the rheological parameters of the polymer components have been modified by oMMT where the clay addition method and content are of primary importance. From the results obtained, it follows that the role of oMMT in MFC is quite complex, numerous clay‐induced effects may be contradictory and must be harmonized to achieve PCL‐based biodegradable MFCs with improved parameters. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43061.     

Numerical solutions of population balance models in preferential crystallization

This article focuses on the implementation of numerical schemes to solve model equations describing preferential crystallization for enantiomers. Two types of numerical methods are proposed for this purpose. The first method uses high resolution finite volume schemes, while the second method is the so-called method of characteristics (MOC). On the one hand, the finite volume schemes which were derived for general system in divergence form are computationally efficient, give desired accuracy on coarse grids, and are robust. On the other hand, the MOC offers a technique which is in general a powerful tool for solving growth processes, has capability to overcome numerical diffusion and dispersion, gives highly resolved solutions, as well as being computationally efficient. Several numerical test examples for a preferential crystallization model with and without fines dissolution under isothermal and non-isothermal conditions are considered. The comparison of the numerical schemes demonstrates clear advantages of the finite volume schemes and the MOC for the current model.     

Variational and numerical approach to a steady-state rolling problem

A steady-state rolling problem with rigid–plastic, incompressible material and nonlocal Coulomb-contact friction condition is considered. The corresponding primal, penalty and regularized penalty variational formulations are presented and studied. It is shown that the solutions of the penalty and regularized penalty variational problems converge to the solutions of the primal and penalty variational problems, when the penalty and regularization parameters tend to zero. The finite-element approximation of the regularized penalty problem is presented and analysed. An algorithm, combining the finite-element method with convergent successive iterations method of secant-modulus is proposed and applied to solve an illustrative example.     

Sol-gel synthesis,surface and magnetic properties of nanocrystalline SmAlO3

Nanocrystals of single-phase samarium monoaluminate (SmAlO3) were synthesized and studied for the first time. Malic acid was employed as a new complexing agent in the sol-gel process. The material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDS), specific surface area and density. The lowest size of the nanoparticles was about 50–60 nm and some of them formed agglomerates. The binding energies of core-level electrons of Sm (3d, 4d, 4f, ...     

Structure and properties of microfibrillar‐reinforced composites based on thermoplastic PET/LDPE blends after manufacturing by means of pultrusion

In situ microfibrillar‐reinforced composites (MFC) based on blends from poly(ethyleneterephthalate) (PET) and low‐density polyethylene (LDPE) were prepared under industrial relevant conditions by melt extrusion, followed by continuous cold drawing in weight ratios of PET/LDPE equal to 50/50. Test specimens were prepared by pultrusion (Pult) of the drawn blend at a processing temperature below the melting temperature of PET. This was the first attempt to pultrude such a material. By varying the Pult parameters, rectangular cross‐sectional profiles have been successfully produced using a self‐designed Pult line. For comparison, plates were also prepared by compression (CM) and injection molding (IM). Samples of each stage of MFC manufacturing and processing were characterized by means of scanning electron microscopy (SEM), wide‐angle X‐ray scattering (WAXS), and mechanical testing. SEM and WAXS showed that the highly oriented blends are converted into MFC‐structured polymer–polymer composites during the Pult, CM, and IM process. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Investigation of antioxidant activity and lipophilicity parameters of some preservatives

The preservatives have been widely used in food, drugs and cosmetic products to prevent their aging and decay. Antioxidant and antimicrobial activities of some preservatives, such as benzoic acid, sorbic acid and alkyl-parabens, were considered in this work. Study of antioxidant properties of these compounds was carried out by differential pulse voltammetry together with evaluation of their influence on the kinetics of the electrochemical oxygen reduction. Mathematical models of the processes were obtained and their adequacy was estimated using design of experiment methods. As a result, the kinetic parameters of interaction between reactive oxygen species and preservatives were evaluation. Finally, the use of these substances as antimicrobials and antioxidants ensured product stability and safety has been recommended.