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  • 1
    Electronic Resource
    Electronic Resource
    Effect of pressure on the oxidative coupling of methane in the absence of catalyst (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 521-535 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The oxidative coupling of methane was carried out in the absence of catalyst in a continuous flow setup at total pressures up to 1,000 kPa, temperatures from 950 to 1,230 K, and inlet molar ratios of CH4/O2 down to 2.5. At constant temperature and residence time, the conversions of methane and oxygen increase drastically with increasing pressure. At oxygen conversions higher than 80%, product selectivities are comparable at different pressures. The space-time yield of the C2 products reaches a level comparable to that required for industrial operations from 400 kPa on. A radical-reaction network consisting of 38 elementary reactions allows to describe the experimental data. To describe adequately the effect of total pressure, the pressure fall-off behavior of the rate coefficients for the unimolecular reactions in the network has to be taken into account explicitly.General features of the reaction mechanism do not depend on the total pressure. Methyl and hydrogen peroxy radicals are the most abundant radicals. The total pressure increase results in a drastic increase of the concentrations of the chain carriers, particularly the hydrogen peroxy radical. Higher pressure favor the oxidative route from ethane to ethylene compared to the pyrolytic route. Increasing the total pressure leads to an increase of the primary and a decrease of the consecutive CO formation relative to the coupling. The balance between these nonselective routes determines the effect of the total pressure on the integral selectivity to C2 products at different conversions. The major contribution to the integral CO selectivity comes from the oxidation of methyl radicals.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400313
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  • 2
    Electronic Resource
    Electronic Resource
    Mechanisms of carbon dioxide laser stereolithography in epoxy-based materials (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 62 (1996), S. 491-500 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We present in this article the use of infrared laser radiation to achieve localized curing in thermosensitive epoxy resin compounds. In stereolithography, the objective is to cure a localized region in a material by precisely confining the laser energy to the area that is to be cured. Industry already uses ultraviolet laser radiation at 352 nm to fabricate three-dimensional structures. Via infrared laser curing, we demonstrate the viability of a completely thermal localized curing process. In our experiment, we have focused the beam from a carbon dioxide (CO2) laser onto a sample composed of epoxy resin, diethylene triamine, and silica powder. Such resins typically cure, or solidify, when heated to moderately high temperatures, and our results show that we can confine the heating of the material, and, therefore, its curing in all three dimensions. We present a physical and a chemical model to describe the process and measure the curing rate as a function of temperature. In order to model the flow of heat in our sample as a result of infrared laser irradiation, we solved the time-dependent heat equation in cylindrical coordinates using the Crank-Nicholson finite-difference method. The results allow us to predict the curing behavior of the sample as a function of laser irradiation conditions, and we find good agreement with our preliminary experimental observations. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 3
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    Optimization of Methanol Yield from a Lurgi Reactor (2011)
    Wiley-Blackwell
    Details
    Publication Date: 2011-03-22
    Description: Methanol is an important chemical with the potential to become an alternative fuel. An optimization study was performed for a Lurgi methanol synthesis reactor using the commercial process simulator Aspen Plus. The optimization routine is coupled with a steady-state model of the methanol synthesis reactor. Syngas inlet temperature, steam drum pressure, and cooling water volumetric flow rate were optimized so that methanol production in the reactor outlet was maximized. The methanol yield increased by 7.04 %. Optimization of a Lurgi methanol synthesis reactor was performed using the commercial simulator Aspen Plus. Syngas inlet temperature, steam drum pressure, and cooling water volumetric flow rate were optimized so that methanol production at the reactor outlet could be maximized. The methanol yield thus increased by 7.04 %.
    Print ISSN: 0930-7516
    Electronic ISSN: 1521-4125
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley-Blackwell
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  • 4
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    Comparative Transcriptome Analysis Reveals the Mechanism Underlying 3,5-Dibromo-4-Hydroxybenzoate Catabolism via a New Oxidative Decarboxylation Pathway [Biodegradation] (2018)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2018-03-06
    Description: The compound 3,5-dibromo-4-hydroxybenzoate (DBHB) is both anthropogenically released into and naturally produced in the environment, and its environmental fate is of great concern. Aerobic and anaerobic reductive dehalogenations are the only two reported pathways for DBHB catabolism. In this study, a new oxidative decarboxylation pathway for DBHB catabolism was identified in a DBHB-utilizing strain, Pigmentiphaga sp. strain H8. The genetic determinants underlying this pathway were elucidated based on comparative transcriptome analysis and subsequent experimental validation. A gene cluster comprising orf420 to orf426 , with transcripts that were about 33- to 4,400-fold upregulated in DBHB-induced cells compared with those in uninduced cells, was suspected to be involved in DBHB catabolism. The gene odcA ( orf420 ), which is essential for the initial catabolism of DBHB, encodes a novel NAD(P)H-dependent flavin monooxygenase that mediates the oxidative decarboxylation of DBHB to 2,6-dibromohydroquinone (2,6-DBHQ). The substrate specificity of the purified OdcA indicated that the 4-hydroxyl group and its ortho -halogen(s) are important for hydroxylation of the C-1 site carboxyl group by OdcA. 2,6-DBHQ is then ring cleaved by the dioxygenase OdcB (Orf425) to 2-bromomaleylacetate, which is finally transformed to β-ketoadipate by the maleylacetate reductase OdcC (Orf426). These results provide a better understanding of the molecular mechanism underlying the catabolic diversity of halogenated para -hydroxybenzoates. IMPORTANCE Halogenated hydroxybenzoates (HBs), which are widely used synthetic precursors for chemical products and common metabolic intermediates from halogenated aromatics, exert considerable adverse effects on human health and ecological security. Microbial catabolism plays key roles in the dissipation of halogenated HBs in the environment. In this study, the discovery of a new catabolic pathway for 3,5-dibromo-4-hydroxybenzoate (DBHB) and clarification of the genetic determinants underlying the pathway broaden our knowledge of the catabolic diversity of halogenated HBs in microorganisms. Furthermore, the NAD(P)H-dependent flavin monooxygenase OdcA identified in Pigmentiphaga sp. strain H8 represents a novel 1-monooxygenase for halogenated para -HBs found in prokaryotes and enhances our knowledge of the decarboxylative hydroxylation of (halogenated) para -HBs.
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
    Published by The American Society for Microbiology (ASM)
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  • 5
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    Complete Genome Sequences of Two Chinese Virulent Avian Coronavirus Infectious Bronchitis Virus Variants [Genome Announcements] (2012)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2012-09-11
    Description: Avian coronavirus infectious bronchitis virus (IBV) is variable, which causes many serotypes. Here we reported the complete genome sequences of two virulent IBV variants from China, GX-YL5 and GX-YL9, belonging to different serotypes. Differences between GX-YL5 and GX-YL9 were found mainly in stem-loop structure I in the predicted RNA secondary structure of open reading frame (ORF) 1b and the S protein gene fusion region, which will help us understand the molecular evolutionary mechanism of IBV and the disconcordance between the genotypes and serotypes of coronavirus.
    Print ISSN: 0022-538X
    Electronic ISSN: 1098-5514
    Topics: Medicine
    Published by The American Society for Microbiology (ASM)
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  • 6
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    Oncogenic Activity of Retinoic Acid Receptor {gamma} Is Exhibited through Activation of the Akt/NF-{kappa}B and Wnt/{beta}-Catenin Pathways in Cholangiocarcinoma [Articles] (2013)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2013-08-08
    Description: Aberrant expression and function of retinoic acid receptor (RAR) are often involved in the progression of several cancers. However, the role of RAR in cholangiocarcinoma (CCA), chemoresistant bile duct carcinoma with a poor prognosis, remains unclear. In the present study, we found that RAR was frequently overexpressed in human CCA specimens. Its overexpression was associated with poor differentiation, lymph node metastasis, high serum carbohydrate antigen 19-9 level, and poor prognosis of CCA. Downregulation of RAR reduced CCA cell proliferation, migration, invasion, and colony formation ability in vitro and tumorigenic potential in nude mice. RAR knockdown resulted in upregulation of cell cycle inhibitor P21, as well as downregulation of cyclin D1, proliferating cell nuclear antigen, and matrix metallopeptidase 9, in parallel with suppression of the Akt/NF-B pathway. Furthermore, overexpression of RAR contributed to the multidrug chemoresistance of CCA cells, at least in part due to upregulation of P glycoprotein via activation of the Wnt/β-catenin pathway. Molecular mechanism studies revealed that RAR interacted with β-catenin and led to β-catenin nuclear translocation. Taken together, our results suggested that RAR plays an important role in the proliferation, metastasis, and chemoresistance of CCA through simultaneous activation of the Akt/NF-B and Wnt/β-catenin pathways, serving as a potential molecular target for CCA treatment.
    Print ISSN: 0270-7306
    Electronic ISSN: 1098-5549
    Topics: Biology , Medicine
    Published by The American Society for Microbiology (ASM)
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  • 7
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    A Novel Angular Dioxygenase Gene Cluster Encoding 3-Phenoxybenzoate 1',2'-Dioxygenase in Sphingobium wenxiniae JZ-1 [Biodegradation] (2014)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2014-06-06
    Description: Sphingobium wenxiniae JZ-1 utilizes a wide range of pyrethroids and their metabolic product, 3-phenoxybenzoate, as sources of carbon and energy. A mutant JZ-1 strain, MJZ-1, defective in the degradation of 3-phenoxybenzoate was obtained by successive streaking on LB agar. Comparison of the draft genomes of strains JZ-1 and MJZ-1 revealed that a 29,366-bp DNA fragment containing a putative angular dioxygenase gene cluster ( pbaA1A2B ) is missing in strain MJZ-1. PbaA1, PbaA2, and PbaB share 65%, 52%, and 10% identity with the corresponding α and β subunits and the ferredoxin component of dioxin dioxygenase from Sphingomonas wittichii RW1, respectively. Complementation of pbaA1A2B in strain MJZ-1 resulted in the active 3-phenoxybenzoate 1',2'-dioxygenase, but the enzyme activity in Escherichia coli was achieved only through the coexpression of pbaA1A2B and a glutathione reductase (GR)-type reductase gene, pbaC , indicating that the 3-phenoxybenzoate 1',2'-dioxygenase belongs to a type IV Rieske non-heme iron aromatic ring-hydroxylating oxygenase system consisting of a hetero-oligomeric oxygenase, a [2Fe-2S]-type ferredoxin, and a GR-type reductase. The pbaC gene is not located in the immediate vicinity of pbaA1A2B . 3-Phenoxybenzoate 1',2'-dioxygenase catalyzes the hydroxylation in the 1' and 2' positions of the benzene moiety of 3-phenoxybenzoate, yielding 3-hydroxybenzoate and catechol. Transcription of pbaA1A2B and pbaC was induced by 3-phenoxybenzoate, but the transcriptional level of pbaC was far less than that of pbaA1A2B , implying the possibility that PbaC may not be the only reductase that can physiologically transfer electrons to PbaA1A2B in strain JZ-1. Some GR-type reductases from other sphingomonad strains could also transfer electrons to PbaA1A2B, suggesting that PbaA1A2B has a low specificity for reductase.
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
    Published by The American Society for Microbiology (ASM)
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  • 8
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    A MarR Family Transcriptional Regulator, DptR3, Activates Daptomycin Biosynthesis and Morphological Differentiation in Streptomyces roseosporus [Genetics and Molecular Biology] (2015)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2015-05-06
    Description: Daptomycin produced by Streptomyces roseosporus is an important lipopeptide antibiotic used to treat human infections caused by Gram-positive pathogenic bacteria, including drug-resistant strains. The genetic basis for regulatory mechanisms of daptomycin production is poorly known. Here, we characterized the dptR3 gene, which encodes a MarR family transcriptional regulator located adjacent to the known daptomycin biosynthetic ( dpt ) genes. Deletion of dptR3 reduced daptomycin production significantly and delayed aerial mycelium formation and sporulation on solid media. Dissection of the mechanism underlying the function of DptR3 in daptomycin production revealed that it stimulates daptomycin production indirectly by altering the transcription of dpt structural genes. DptR3 directly activated the transcription of its own gene, dptR3 , but repressed the transcription of the adjacent, divergent gene orf16 (which encodes a putative ABC transporter ATP-binding protein). A 66-nucleotide DptR3-binding site in the intergenic region of dptR3-orf16 was determined by DNase I footprinting, and the palindromic sequence TCATTGT TACCTATGCTC ACAATGA (underlining indicates inverted repeats) in the protected region was found to be essential for DptR3 binding. orf16 , the major target gene of DptR3, exerted a positive effect on daptomycin biosynthesis. Our findings indicate that DptR3 functions as a global regulator that positively controls daptomycin production and morphological development in S. roseosporus .
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
    Published by The American Society for Microbiology (ASM)
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  • 9
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    Development of a Functional Antibody by Using a Green Fluorescent Protein Frame as the Template [Enzymology and Protein Engineering] (2014)
    The American Society for Microbiology (ASM)
    Details
    Publication Date: 2014-06-25
    Description: Single-chain variable fragment (scFv) antibodies are widely used as diagnostic and therapeutic agents or biosensors for a majority of human disease. However, the limitations of the present scFv antibody in terms of stability, solubility, and affinity are challenging to produce by traditional antibody screening and expression formats. We describe here a feasible strategy for creating the green fluorescent protein (GFP)-based antibody. Complementarity-determining region 3 (CDR3), which retains the antigen binding activity, was introduced into the structural loops of superfolder GFP, and the result showed that CDR3-inserted GFP displayed almost the same fluorescence intensity as wild-type GFP, and the purified proteins of CDR3 insertion showed the similar binding activity to antigen as the corresponding scFv. Among of all of the CDRs, CDR3s are responsible for antigen recognition, and only the CDR3a insertion is the best format for producing GFP-based antibody binding to specific antigen. The wide versatility of this system was further verified by introducing CDR3 from other scFvs into loop 9 of GFP. We developed a feasible method for rapidly and effectively producing a high-affinity GFP-based antibody by inserting CDR3s into GFP loops. Further, the affinity can be enhanced by specific amino acids scanning and site-directed mutagenesis. Notably, this method had better versatility for creating antibodies to various antigens using GFP as the scaffold, suggesting that a GFP-based antibody with high affinity and specificity may be useful for disease diagnosis and therapy.
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
    Published by The American Society for Microbiology (ASM)
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  • 10
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    The Hemispheric Conjugate Observation of Postnoon “Bright Spots” / Auroral Spirals (2013)
    Wiley-Blackwell
    Details
    Publication Date: 2013-03-29
    Description: [1]  Using the Polar ultraviolet imager (UVI) above the Arctic and the all-sky camera (ASC) at Chinese Zhongshan Station (ZHS) in Antarctica, an outstanding hemispheric conjugate observation of postnoon “bright spots” in the Arctic and auroral spirals in Antarctica is presented. Multiple bright auroral spirals, which are counterclockwise rotation viewed along the direction of the magnetic field, in postnoon auroral arcs are seen on the filed of view (FOV) of ASC at ZHS in the southern hemisphere while multiple “bright spots” are seen at the conjugate FOV of ASC on postnoon auroral oval in the northern hemisphere by Polar UVI. We consider that the auroral spirals in postnoon arcs are the visible characteristic of postnoon UV " bright spots" on ground-based observation, and suggest that the current sheet instability above the parallel electric field region, which could produce the arcs, is the origin for “bright spots” occurring at the ionosphere, and the hemispheric symmetry/asymmetry of postnoon upward FACs, which is affected by the IMF By and season, can control the conjugacy/non-conjugacy of postnoon “bright spots”/auroral spirals between the two hemispheres.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley-Blackwell on behalf of American Geophysical Union (AGU).
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