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  • 1
    ISSN: 1662-0356
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Natural Sciences in General , Technology
    Notes: CuTCNQ is a charge transfer complex displaying resistive electrical switching whensandwiched between Cu and Al contacts. Corresponding memory cells switch from a native highresistive OFF state (HRS) to a low resistive ON state (LRS) by applying a negative voltage to theAl with respect to the Cu. Inversion of the signal polarity leads to switching from the LRS to theHRS. Typical CuTCNQ preparation occurs by a chemical reaction of a Cu substrate with TCNQ,involving (partial) corrosion of the metal. In this contribution we present electrodeposition ofCuTCNQ on Au and Pt substrates, leading – in contrast to previously published dendritically crystalgrowth – to relatively smooth, micrometer thick layers. Corresponding large area cross-bar memoryarrays (200€m by 200€m, with Al top contacts) exhibited up to several thousand write/erase cycleswith an ON/OFF current ratio of 5-10. Furthermore preliminary growth experiments with blankettungsten bottom contact Metal–Oxide–Semiconductor (CMOS) wafers with 250 nm diametercontact holes showed that electrodeposition is a suitable method for CuTCNQ integration
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature genetics 2 (1992), S. 5-8 
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] “Nature is nowhere accustomed more openly to display her secret mysteries than in cases where she shows traces of her workings apart from the beaten path; nor is there any better way to advance the proper practice of medicine than to give our minds to the discovery of the usual law of nature ...
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  • 3
    ISSN: 1573-6830
    Keywords: uridine ; cerebrospinal fluid ; ischemia ; hypoglycemia ; hypoxia ; subarachnoid hemorrhage ; hypoxanthine ; xanthine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Rats which survived hypoglycemia by insulin, hypoxia by 10% O2, or ischemia by carotid ligation and hypotension to 40 mm Hg, evidenced no changes in cerebrospinal fluid (CSF) uridine. Animals which died soon after the above interventions or as a result of KCl-induced cardiac arrest had elevated CSF uridine concentrations. 2. Injection of whole blood or the soluble contents of lysed blood cells into the lateral ventricle of rats reduced CSF uridine to less than one-half normal at 24 hrs but values returned to normal 3 days later. Changes in hypoxanthine resembled those of uridine, but were less dramatic, whereas xanthine concentrations were largely unaltered. Intraventricular injection of plasma or saline did not alter CSF uridine. 3. It seems most likely that low CSF uridine concentrations previously reported in head injury patients may be secondary to the effects of blood cell contents in the cerebrospinal fluid, rather than responses to altered metabolism in neurons or glia cells.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 1161-1170 
    ISSN: 0006-3592
    Keywords: bacterial colonization ; kinetic rates ; solidwater interfaces ; Pseudomonas aeruginosa ; Pseudomonas fluorescens ; image analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The processes leading to bacterial colonization on solidwater interfaces are adsorption, desorption, growth, and erosion. These processes have been measured individually in situ in a flowing system in real time using image analysis. Four different substrata (copper, silicon, 316 stainless-steel and glass) and 2 different bacterial species (Pseudomonas aeruginosa and Pseudomonas fluorescens) were used in the experiments. The flow was laminar (Re = 1.4) and the shear stress was kept constant during all experiments at 0.75 N m-2. The surface roughness varied among the substrata from 0.002 μm (for silicon) to 0.015 μm (for copper). Surface free energies varied from 25.1 dynes cm-1 for silicon to 31.2 dynes cm-1 for copper. Cell curface hydrophobicity, reported as hydrocarbon partitioning values, ranged from 0.67 for Ps. fluorescens to 0.97 for Ps. aeruginosa.The adsorption rate coefficient varried by as much as a factor of 10 among the combinations of bacterial strain and substratum material, and was positively correlated with surface free energy, the surface roughness of the substratum, and the hydrophobicity of the cells. The probability of desorption decreased with increasing surface free energy and surface roughness of the substratum. Cell growth was inhibited on copper, but replication of cells overlying an initial cell layer was observed with increased exposure time to the cell-containing bulk water. A mathematical model describing cell accumulation on a substratum is presented.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 263-269 
    ISSN: 0006-3592
    Keywords: microbial souring ; sulfate reduction ; porous media ; kinetics ; biotransformation ; oil reservoir ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Microbial souring (H2S production) in porous media was investigated in an anaerobic upflow porous media reactor at 60°C using microbial consortia obtained from oil reservoirs. Multiple carbon sources (formate, acetate, propionate, iso- and n-butyrates) found in reservoir waters as well as sulfate as the electron acceptor was used. Kinetics and rates of souring in the reactor system were analyzed. Higher volumetric substrate consumption rates (organic acids and sulfate) and a higher volumetric H2S production rate were found at the from part of the reactor column after H2S production had stabilized. Concentration gradients for the substrates (organic acids and sulfate) and H2S were generated along the column. Biomass accumulation throughout the entire column was observed. The average specific sulfate reduction rate (H2S production rate) in the present reactor after H2S production had stabilized was calculated to be 11062 ±2.22 mg sulfate-S/day g biomass. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 267-274 
    ISSN: 0006-3592
    Keywords: microbial souring ; sulfate reduction ; porous media ; kinetics ; stoichiometry ; transport phenomena ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An anaerobic upflow porous media biofilm reactor was designed to study the kinetics and stoichiometry of hydrogen sulfide production by the sulfate-reducing bacterium (SRB) Desulfovibrio desulfuricans (ATCC 5575) as the first step for the modeling and control of formation souring (H2S) in oil field porous media. The reactor was a packed bed (50 × 5.5 cm) tubular reactor. Sea sand (140 to 375 μm) was used as the porous media. The initial indication of souring was the appearance of well-separated black spots (precipitates of iron sulfide) in the sand bed. The blackened zones expanded radially and upward through the column. New spots also appeared and expanded into the cone shapes. Lactate (substrate) was depleted and hydrogen sulfide appeared in the effluent.Analysis of the pseudo-steady state column shows that there were concentration gradients for lactate and hydrogen sulfide along the column. The results indicate that most of the lactate was consumed at the front part of the column. Measurements of SRB biomass on the solid phase (sand) and in the liquid phase indicate that the maximum concentration of SRB biomass resided at the front part of the column while the maximum in the liquid phase occurred further downstream. The stoichiometry regarding lactate consumption and hydrogen sulfide production observed in the porous media reactor was different from that in a chemostat. After analyzing the radial dispersion coefficient for the SRB in porous media and kinetics of microbial growth, it was deduced that transport phenomena dominate the souring process in our porous media reactor system. © 1994 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 7
    ISSN: 1573-904X
    Keywords: prostaglandin E1 α-cyclodextrin ; 1H nuclear magnetic resonance (NMR) ; nuclear Overhauser effect (NOE) difference measurement ; complex formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Prostaglandin El is currently marketed as a freeze-dried injectable inclusion complex with α-cyclodextrin for the treatment of peripheral arterial diseases. α-Cyclodextrin is used as a stabilizing agent and to improve the dissolution characteristics of prostaglandin El. Upon dilution with the infusion medium, the inclusion complex dissociates almost completely as shown by NMR chemical shift measurements of the complexed and uncomplexed prostaglandin E1 Nuclear Overhauser effect (NOE) measurements of the interacting atoms of α-cyclodextrin and prostaglandin El provide insight into the structure of the complex.
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  • 8
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Incubation of the synthetic 18O-labelled phytyl-hydroquinone (O4-18O)-2 with the tocopherol cyclase from Anabaena variabilis KÜTZING (Cyanobacteria) in D2O furnished the doubly labelled γ-tocopherol, (2R,3S,4′R,8′R)-(1-18O,3-2H)-1. The chirality at C(3) was determined by two independent routes providing interlocking evidence that the enzyme-catalyzed ring closure proceeds by si-protonation of the double bond of 2 and concomitant re-attack of the phenolic O-atom.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A New Method for the Stereochemical Analysis of Acyclic Terpenoid Carbonyl CompoundsA new method for the determination of the enantiomeric and diastereoisomeric composition of terpenoid carbonyl compounds is presented. Separation of the diastereoisomeric (+)-L-diisopropyl-tartrate acetals derived from dihydrocitronellal (6), hexahydropseudoionone (3), hexahydrofarnesal (7), and hexahydro far nesy lace tone (4), the C10, C13, C15, and C18 intermediates in various syntheses of naturally occurring tocopherols and vitamin K1, can be achieved by capillary GC on a cyanopropylsilicon-coated glass column under standardized conditions. This technique, presenting a significant improvement over existing methodologies, is considered to be particularly useful for the analysis of highly enriched samples, typically obtained by present-day asymmetric synthesis. With reproducibilities of ± 0.3%, and, therefore, safe for routine analysis, the complete Stereochemical characterization of terpenoids with 15 and 18 C-atoms bearing two stereogenic centres is performed in a single operation for the first time.
    Additional Material: 6 Tab.
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  • 10
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