Enzymatic and genetic bases on assimilation, depolymerization, and transport of heteropolysaccharides in bacteria

When microorganisms utilize macromolecules for their growth, they commonly produce extracellular depolymerization enzymes and then incorporate the depolymerized low-molecular-weight products. Assimilation of heteropolysaccharides (gellan and xanthan) by Bacillus sp. GL1 depends on this generally accepted mechanism. On the other hand, Sphingomonas sp. A1 represents an unexplored specific and interesting system for macromolecule assimilation. In the presence of heteropolysaccharide (alginate), the bacterium forms a mouthlike pit on its cell surface and directly incorporates the macromolecule using a novel ATP-binding cassette transporter (ABC transporter). In this review, we discuss enzymatic and genetic bases on the depolymerization and assimilation routes of heteropolysaccharides in bacteria, with particular emphasis on the novel incorporation system for macromolecules, characteristic post-translational modification processes of polysaccharide lyases and on the mouthlike pit structure on the bacterial cell surface.     

Immobilization of P450 monooxygenase and chloroplast for use in light-driven bioreactors

P450 monooxygenases exhibit great potential for application to bioreactors for the decomposition of various hydrophobic chemicals including pollutant compounds. P450-containing microsomes were immobilized in spinach chloroplasts for use in light-driven bioreactors. We tested three methods (entrapment, adsorption and cross-linking) to immobilize chloroplasts and yeast microsomes containing a genetically engineered fusion enzyme between rat P450 1A1 and yeast P450 reductase. Entrapment in agarose gave the best activity for the conversion of 7-ethoxycoumarin to 7-hydroxycoumarin under illumination of 6200 lx. We then tested three light-driven bioreactors (two column-type and one batch-type reactors developed) using the immobilized gels. A two-phase column-type reactor with separately immobilized microsomes and chloroplasts showed a higher conversion rate than a reactor with co-immobilization of both components. The reactor showed a turnover rate of 6.32 mol product/mol P450/min after a 40-min run, and 2.49 after a 180-min run. These turnover rates are higher than the values reported by others using immobilized microsomal P450s.     

Epitaxial p-type SiC as a self-driven photocathode for water splitting

Solar-to-hydrogen conversion efficiencies of water-splitting photochathodes using epitaxially grown p-type 4H-, 6H- and 3C-SiC were estimated in a two-electrode system without applying any external bias. By using electrode materials with small oxygen overpotentials as counter electrodes, the photocurrent became comparable to that observed in a three-electrode system with a suitable bias. Estimated efficiencies seem to depend on the bandgap of the SiC polytypes. For the 3C-SiC, the obtained efficiency was 0.38%, which is so far the highest value reported for SiC. We confirmed that the hydrogen volumes estimated from the photocurrent were almost the same as actual volumes observed by gas chromatography.     

On the natural structure of thermodynamic potentials and fluxes in the theory of chemically non-reacting binary mixtures

A theory describing the behavior of chemically non-reacting binary mixtures can be based on a detailed formulation of the governing equations for the individual components of the mixture or on treating the mixture as a single homogenized continuous medium. We argue that if we accept that both approaches can be used to describe the behavior of the given mixture, then the requirement on the equivalence of these approaches places restrictions on the possible structure of the internal energy, entropy, Helmholtz potential, and also of the diffusive, energy, and entropy fluxes. (The equivalence of the approaches is understood in the sense that the quantities used in one approach can be interpreted in terms of the quantities used in the other approach and vice versa. Further, both approaches must lead to the same predictions concerning the evolution of the physical system under consideration). In the case of a general chemically non-reacting binary mixture of components at the same temperature, we show that these restrictions can indeed be obtained by purely algebraic manipulations. An important outcome of this analysis is, for example, a general form of the evolution equation for the diffusive flux. The restrictions can be further exploited in the specification of thermodynamically consistent constitutive relations for quantities such as the interaction (drag) force or the Cauchy stress tensor. As an example of the application of the current framework, we derive, among others, a generalization of Fick’s law and we recover several non-trivial results obtained by other techniques. The qualitative features of the derived generalization of Fick’s law are demonstrated by a numerical experiment.     

Hemophagocytic syndrome in five patients with Epstein-Barr virus negative B-cell lymphoma

BACKGROUND: The recent recognition of the association of Epstein-Barr virus (EBV) with T-cell/natural killer cell (T/NK-cell) lymphoma has documented that particular types of EBV-containing T/NK-cell lymphoma are frequently complicated by hemophagocytic syndrome (HPS). This observation suggests that both EBV and proliferating T/NK-lymphoma cells play significant roles in the development of HPS. Cytokines released from neoplastic T cells are presumed to account for the activation of macrophages, which is followed by a complex cascade of cytokine production, resulting in full-blown HPS. Five patients with B-cell lymphoma complicated by HPS were studied for elevated serum cytokines, the association of EBV, and CD25 expression of lymphoma cells; the aim of this study was to verify whether the mechanisms of HPS development hypothesized for T/NK-cell lymphoma also operate in B-cell lymphoma. METHODS: Sera were analyzed for the presence of inflammatory and immunoregulatory cytokines. Flow cytometry, immunohistology (IH), in situ hybridization (ISH), polymerase chain reaction (PCR), and Southern blot analysis were performed using bone marrow aspirates, biopsy specimens, and autopsy specimens. RESULTS: Immunophenotypic and Southern blot studies verified that the lymphoma cells of all five patients were of B-cell lineage. Bone marrow aspirates demonstrated histiocytosis with extensive hemophagocytic activity. Marked elevation of serum cytokines and expression of CD25 were observed in all five patients. However, the results of PCR, ISH using EBER1 probe, and IH for latent membrane protein indicated that these lymphoma cells were free of EBV infection. CONCLUSIONS: In patients with B-cell lymphoma, EBV infection is not necessarily required for the initiation of HPS. In this article, the pathogenesis of HPS assumed to be operative in B-cell lymphoma is discussed with reference to T/NK-cell lymphoma complicated by HPS.     

Multi-cyber framework for availability enhancement of cyber physical systems

With the rapid growth of wireless communication, the deployment of cyber-physical system (CPS) is increasing day by day. As a cyber physical system involves a tight coupling between the physical and computational components, it is critical to ensure that the system, apart from being secure, is available for both the cyber and physical processes. Traditional methods have generally been employed to defend an infrastructure system against physical threats. However, this does not guarantee that the availability of the system will always be high. In this paper, we propose a multi-cyber (computational unit) framework to improve the availability of CPS based on Markov model. We evaluate the effectiveness of our proposed framework in terms of availability, downtime, downtime cost and reliability of the CPS framework.     

Study of hybrid PVD–PECVD process of Ti sputtering in argon and acetylene

Hybrid PVD–PECVD process of target sputtering in hydrocarbon containing atmosphere combines aspects of both conventional reactive magnetron sputtering (PVD) and plasma enhanced chemical vapour deposition (PECVD). Such process is being typically used for deposition of metal carbides embedded in hydrogenated carbon matrix. Compared to the conventional co-sputtering of metal and carbon targets, in the hybrid deposition process the source of the carbon is dissociated hydrocarbon vapour in plasma. The aim of this paper is to study the extent of similarities or differences between this hybrid process and the conventional reactive magnetron sputtering. We have chosen the sputtering of titanium target in acetylene containing atmosphere as a representative of the hybrid processes. We focused on experimental measurements of the hybrid PVD–PECVD process behaviour, the time necessary for the process to achieve steady-state conditions and basic modelling of the process.     

Rapidly solidified thick stainless cast iron alloy deposit with niobium carbide particles produced by plasma spraying

In plasma spraying process, spray material is heated, melted and accelerated by a high temperature flame. Low-pressure plasma spraying can produce rapidly solidified thick materials because alloy droplets accumulate successively on the substrate, and solidify at a cooling rate in the range of 10⁵–10⁸ ks^?1. Depending on the cooling conditions of the substrate and on the alloy composition, deposits can be produced as metastable phases or extremely fine crystalline phases. Plasma spraying is an attractive method for the production of deposits with in-situ formed fine particles. In recent years, much attention has been paid to stainless cast iron with vanadium carbide, which is attractive for use in metal molds and pump parts, due to its high wear resistance and high corrosion resistance. In the present work, stainless cast iron alloy powder was low-pressure plasma sprayed to produce stainless cast iron base alloy deposits with finely dispersed niobium carbide particles. The as-sprayed deposit and deposits obtained by heat treatment of the as-sprayed deposit had niobium carbide particles. The carbide particles in the as-sprayed deposit produced on a water-cooled substrate were finer than that in the as-sprayed deposit produced on a non-cooled substrate. With increasing heat treatment temperature up to 1273 K, the carbide particles coarsened. The as-sprayed deposit produced on a non-cooled substrate had higher hardness than the heat-treated deposits.     

Partial oxidation of ethane to synthesis gas over Co-loaded catalysts

Attention has been increasingly paid to the partial oxidation of lower alkanes to synthesis gas, due to its intrinsic energy saving process. We studied the partial oxidation of ethane (POE) on Co loaded on various supports. The POE performance varied as follows: Y₂O₃, CeO₂, ZrO₂, La₂O₃  SiO₂, Al₂O₃, TiO₂ > MgO. Comparing Y₂O₃ and CeO₂, the carbon deposition during the POE was negligible on CeO₂ and therefore CeO₂ was the most preferable support. By changing space velocity and O₂ partial pressure, reaction mechanism of POE was studied and it was revealed that two-step mechanism was prevailing; combustion of ethane to H₂O and CO₂ and subsequent reforming of ethane with H₂O and CO₂ to synthesis gas. Co/CeO₂ catalyst exhibited high and stable catalytic activity for 10 h; high ethane conversion of 18% (maximum ethane conversion 20% at O₂/C₂H₆ = 0.2) with H₂ and CO selectivities of 93 and 84%, respectively.