Optimization of the fermentation conditions and partial characterization for acido-thermophilic <Emphasis Type=Italic>α</Emphasis>-amylase from <Emphasis Type=Italic>Aspergillus niger</Emphasis> NCIM 548

A high performance thermostable α-amylase at low pH values has been synthesized. Sugarcane bagasse was hydrolyzed in a dilute acid solution and utilized as carbon source for the growth of Aspergillus niger strain NCIM 548. Glucose, xylose and arabinose with the ratio of 1.0: 0.9: 0.3 (w/w/w) were detected in the hydrolyzate by HPLC analysis. Optimization of the fermentation conditions for α-amylase production was performed by varying four influential parameters such as Sugarcane bagasse hydrolyzate (SBH), NH₄Cl, pH and incubation time using a central composite design (CCD) under response surface methodology (RSM). The optimum values of SBH, NH₄Cl, pH and incubation time were 20.49, 2.34 g/l, 5.65 and 76.67 h, respectively. The acido-thermophilic enzyme showed maximum stability at 70°C and pH value of 4. The rate constant, K _m and maximum reaction rate, V _max were 18.79 g/l and 15.85 g/l·min, respectively.     

Bioreactors for heart valve tissue engineering: a review

Bioreactors have great potential in the successful development of tissue‐engineered heart valve replacements, both at the research stage and in commercial platforms. Their ability to mimick the chemical and physiological conditions of the body has allowed researchers to study in vitro cellular responses, and this has helped in the fabrication of better and more efficient tissues in vivo. Use of different bioreactors, such as, rotating, dynamic flexure, cyclic stretch and pulsatile bioreactors, in tissue engineering of heart valves has been widely investigated. However, this research is still at its early stage, and many critical issues need to be resolved to make tissue engineered heart valves sufficiently reliable for clinical applications. In the following article, after a brief introduction to the structure and role of heart valves, the efforts of tissue engineers in designing heart valves using different bioreactors is described. © 2015 Society of Chemical Industry     

Research issues in genomic signal processing

Genomic signal processing (GSP) concerns the processing of genomic signals. It may be defined as the analysis, processing, and use of genomic signals to gain biological knowledge and the translation of that knowledge into systems-based applications. In this article, the authors discuss the key research issues for GSP. It is important to recognize that "genomic signal processing" is not a name for genomic bioinformatics nor for the application of signal processing methods in genomics. We note that the research issues pertaining to GSP fit within the overall challenges confronting research in the area of multimodal biomedical systems.     

Extracellular breakdown of collagen by mice decidual cells. A cytochemical and ultrastructural study.

The interaction of antimesometrial decidual cells and collagen fibrils was studied by light microscopy and ultrastructural cytochemistry in fed and acutely fasted mice on days 9-11 of pregnancy. Fibrillar elements in the extracellular space consisted of collagen fibrils and filamentous aggregates (disintegrating collagen fibrils). Intracellular vacuoles exhibited typical collagen immersed in electron-translucent material (clear vacuoles) and faint cross-banded collagen immersed in electron-opaque material (dark vacuoles). Fibrillar elements showed extracellular acid phosphatase activity which was stronger in the region of mature decidua than in predecidual cells region in all animals; it was conspicuous in mature decidua of fasted animals. Intracellular acid phosphatase activity was observed in dark vacuoles and lysosomes, and was absent in clear vacuoles in all cells studied. Since acid phosphatase activity reflects the presence of lysosomal hydrolases in general, the results indicate that breakdown of extracellular collagen occurs by release of lysosomal enzymes by decidual cells and also by internalization of collagen for intracellular degradation in fed and fasted mice. Collagen breakdown may be part of the process of tissue remodeling in mature and predecidual regions, however, in mature decidua, collagen breakdown is enhanced and may therefore contribute to nutrition of the fetus, specially in acutely fasted mice.     

Fabrication of Strained-Si/Strained-Ge Heterostructures on Insulator

Ultrathin strained-Si/strained-Ge heterostructures on insulator have been fabricated using a bond and etch-back technique. The substrate consists of a trilayer of 9 nm strained-Si/4 nm strained-Ge/3 nm strained-Si on a 400-nm-thick buried oxide. The epitaxial trilayer structure was originally grown pseudomorphic to a relaxed Si_0.5Ge_0.5 layer on a donor substrate. Raman analysis of the as-grown and final transferred layer structures indicates that there is little change in the strain in the Si and Ge layers after layer transfer. These ultrathin Si and Ge films have very high levels of strain (∼1.8% biaxial tension and 1.4% compression, respectively), and are suitable for enhanced-mobility field-effect transistor applications.     

Web用户认证信息的安全性策略

文章重点讨论用户认证信息的安全性问题,分析了常用安全认证方法及其局限性,提出了一个用户认证安全性策略,即在信息交换前,进行计算机认证,保证对话双方能够同时且不受干扰(攻击者不能改动信息)地交换信息;采用随机算法,增加算法的复杂度,降低穷举攻击的可能性。     

Compositional analysis and rheological characterization of gum tragacanth exudates from six species of Iranian Astragalus

The sugar composition and viscoelastic behaviour of Iranian gum tragacanth exuded by six species of Astragalus was investigated at a concentration of 1.3% and varying ionic strength using a controlled shear-rate rheometer. Compositional analysis of the six species of gum tragacanth by high-performance anion-exchange chromatography with pulsed amperometric detection suggested the occurrence of arabinose, xylose, glucose, galactose, fucose, rhamnose and galacturonic acid residues in the gum structure; however, the proportions of each sugar varied significantly among the gums from the different species of Astragalus, and this variation led to interesting differences in functional properties. Rheological measurements performed on dispersions of the six species of gum tragacanth demonstrated viscoelastic properties. The mechanical spectra derived from strain sweep and frequency sweep measurements indicated that the different gum tragacanth dispersions had distinctive viscoelastic behaviours. Investigation of the viscoelastic properties of the different gum dispersions in the presence of NaCl revealed that the addition of NaCl could lead to slight to drastic decreases in the G′, G″ or η^∗ values of the various gums. In general, the results indicated that the six varieties of gum tragacanth studied exhibited significantly different rheological properties; therefore, these different gums may find use in a variety of applications as stabilisers, thickeners, emulsifiers and suspending agents depending on their rheological behaviour.     

Superscalar instruction issue

Clearly, instruction issue and execution are closely related: The more parallel the instruction execution, the higher the requirements for the parallelism of instruction issue. Thus, we see the continuous and harmonized increase of parallelism in instruction issue and execution. This article focuses on superscalar instruction issue, tracing the way parallel instruction execution and issue have increased performance. It also spans the design space of instruction issue, identifying important design aspects and available design choices. The article also demonstrates a concise way to represent the design space using DS trees, reviews the most frequently used issue schemes, and highlights trends for each design aspect of instruction issue     

Ordinary Gasoline Emissions Induce a Toxic Response in Bronchial Cells Grown at Air-Liquid Interface

Gasoline engine emissions have been classified as possibly carcinogenic to humans and represent a significant health risk. In this study, we used MucilAir™, a three-dimensional (3D) model of the human airway, and BEAS-2B, cells originating from the human bronchial epithelium, grown at the air-liquid interface to assess the toxicity of ordinary gasoline exhaust produced by a direct injection spark ignition engine. The transepithelial electrical resistance (TEER), production of mucin, and lactate dehydrogenase (LDH) and adenylate kinase (AK) activities were analyzed after one day and five days of exposure. The induction of double-stranded DNA breaks was measured by the detection of histone H2AX phosphorylation. Next-generation sequencing was used to analyze the modulation of expression of the relevant 370 genes. The exposure to gasoline emissions affected the integrity, as well as LDH and AK leakage in the 3D model, particularly after longer exposure periods. Mucin production was mostly decreased with the exception of longer BEAS-2B treatment, for which a significant increase was detected. DNA damage was detected after five days of exposure in the 3D model, but not in BEAS-2B cells. The expression of CYP1A1 and GSTA3 was modulated in MucilAir™ tissues after 5 days of treatment. In BEAS-2B cells, the expression of 39 mRNAs was affected after short exposure, most of them were upregulated. The five days of exposure modulated the expression of 11 genes in this cell line. In conclusion, the ordinary gasoline emissions induced a toxic response in MucilAir™. In BEAS-2B cells, the biological response was less pronounced, mostly limited to gene expression changes.