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Now showing items 1 - 8 of 8

  • Pressure influence on unsteady film boiling of water-ethanol mixtures

    Zabirov, Arslan   Yagov, Victor   Kanin, Pavel   Ryzantcev, Vladislav   Vinogradov, Michael   Molotova, Irina  

    Film boiling of subcooled liquid is a process important for many technologies. However, there exists the specific film boiling regime accompanied by an enormous heat transfer coefficients, which has no common physical explanation. This paper presents the new experimental results on influence of a liquid properties and its sub-cooling on this high intensive boiling regime. The quenching a stainless steel sphere in subcooled water-ethanol mixtures of different compositions at different liquid temperatures and pressures up to 0.5 MPa was an object for study. The cooling process considerably intensifies with increase of pressure and of water mass fraction in the mixture. At some conditions, the transition temperature corresponding to incipience of the intensive boiling regime noticeably exceeded the critical temperature of the liquid; as direct liquid-solid contact is impossible in this case, micro-bubble boiling regime obviously occurred. All results obtained are in qualitative agreement with the model of incipience of the intensive film-boiling regime of subcooled liquid published previously by the authors.
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  • Letters

    Vinogradov, Michael   Ryabikhin, Leonid   Miller, Bruce   Wales, Jane   Petnuch, Mark   McAdams, Rich   Ikeda, Daisaku   Gunter, Paul   Smith, William Wharton  

    Several letters to the editor are presented in response to the articles published in the March to April 2008 issue including "Consensual Security" by John Steinbruner, "A Nuclear-Weapon-Free Arctic" by Michael D. Wallace, and "Making Nuclear Energy Work" by Robert Roser.
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  • METHOD AND DEVICE FOR MEASURING FORCES

    The device of the invention is intended for measuring a loading force and a friction force in a tribological system. The device includes an assembly of two deformation sensitive sensors (200, 300) for simultaneous equal deformation in two opposite directions for eliminating misbalance created in the measurement system (100) when a single sensor is used. Each sensor (200, 300) comprises a deformable beam (212, 312) having through longitudinal slots (218, 220) extending in different and non-parallel directions and overlapped within the body of the beam (212, 312). Each sensor (200, 300) deforms in one direction under the effect of a loading force beam in another direction under the effect of a friction force measured by another two pairs of strain gauges (R1-2 and R3-2) located on opposite sides of the beam (212, 312) near the other end of the beam (212, 312). Two aforementioned sensors (200, 300) are sandwiched between two plates (102, 104) in diagonally symmetrical positions, so as to transmit forces between both plates (102, 104) and at the same time to ensure limited freedom of movement between both plates (102, 104) to allow deformations caused by the applied forces. One plate (102) is attached to the loading unit of the tribological system and another (104) supports an upper sample for engagement with the lower sample of the system.
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  • Sulfhydryl-specific PEGylation of phosphotriesterase cysteine mutants for organophosphate detoxification.

    Daffu, Gurdip K   Lopez, Patricia   Katz, Francine   Vinogradov, Michael   Zhan, Chang-Guo   Landry, Donald W   Macdonald, Joanne  

    The catalytic bioscavenger phosphotriesterase (PTE) is experimentally an effective antidote for organophosphate poisoning. We are interested in the molecular engineering of this enzyme to confer additional functionality, such as improved in vivo longevity. To this aim, we developed PTE cysteine mutants with free sulfhydryls to allow macromolecular attachments to the protein. A library of PTE cysteine mutants were assessed for efficiency in hydrolysing the toxic pesticide metabolite paraoxon, and screened for attachment with a sulfhydryl-reactive small molecule, fluorescein 5-maleimide (F5M), to examine cysteine availability. We established that the newly incorporated cysteines were readily available for labelling, with R90C, E116C and S291C displaying the highest affinity for binding with F5M. Next, we screened for efficiency in attaching a large macromolecule, a 30 000 Da polyethylene glycol (PEG) molecule. Using a solid-phase PEGylation strategy, we found the E116C mutant to be the best single-mutant candidate for attachment with PEG30. Kinetic activity of PEGylated E116C, with paraoxon as substrate, displayed activity approaching that of the unPEGylated wild-type. Our findings demonstrate, for the first time, an efficient cysteine mutation and subsequent method for sulfhydryl-specific macromolecule attachment to PTE. =C2=A9 The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.
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  • Cloning and characterization of acetohydroxyacid synthase from Bacillus stearothermophilus.

    Porat, Iris   Vinogradov, Michael   Vyazmensky, Maria   Lu, Chung-Dar   Chipman, David M.   Abdelal, Ahmed T.  

    Five genes from the ilv-leu operon from Bacillus stearothermophilus have been sequenced. Acetohydroxyacid synthase (AHAS) and its subunits were separately cloned, purified, and characterized. This thermophilic enzyme resembles AHAS III of Escherichia coli, and regulatory subunits of AHAS III complement the catalytic subunit of the AHAS of B. stearothermophilus, suggesting that AHAS III is functionally and evolutionally related to the single AHAS of gram-positive bacteria.
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  • Wear behavior and wear debris distribution of UHMWPE against Si3N4 ball in bi-directional sliding

    Ge, Shirong   Wang, Shibo   Gitis, Norm   Vinogradov, Michael   Xiao, Jun  

    Four kinds of wear tracks possibly occurred in the wear of artificial hip joints, including uni-directional sliding, oval curvilinear sliding, double-elliptical sliding, triple-elliptical sliding, were simulated on the UNIT wear tester by using of a Si3N4 ball sliding on the UHMWPE disc under bi-directional sliding motion. The wear behavior and wear particle distribution of UHMWPE in plasma solution lubrication were studied for these sliding motions. The experimental results indicate that the wear mass loss in uni-directional reciprocating sliding is much smaller than those in bi-directional sliding modes. The wear rates of UHMWPE in bi-directional sliding modes are linearly inverse proportional to the defined frequency factor, as agreed with the cross-shear theory. This result suggests that cross-shear movement with larger intersection angles is a significant factor influencing the wear rate of UHMWPE, and the bi-directional sliding path at direction reversals will play an important role on the increasing of UHMWPE wear compared to uni-directional sliding motion. In bi-directional sliding modes, the wear particle distribution range decreases when direction reversal path increases in the sliding motions. So, the complex wear tracks are harmful to the implant joint due to the higher wear and more active wear particles. The particles sizes follow a lognormal distribution. The central size and the peak accumulation of UHMWPE particles decreases and increases against the frequency ratio, respectively, besides the uni-directional reciprocating sliding. These suggest that the intersection angle increasing on sliding path will contribute to the size decreasing of UHMWPE wear particle. Also, cross-points on sliding track will produce wear particles in smaller size. The radius of curvature of the curvilinear paths may be dictating the size reducing of UHMWPE wear particles. The main wear mechanisms are ploughing in uni-directional reciprocation, while plastic deformation, adhesion and fatigue in the bi-directional sliding modes. (c) 2007 Elsevier B.V. All rights reserved.
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  • Comment on “Central Bank announcements: Big news for little people?” by Michael Lamla and Dmitri Vinogradov

    Binder, Carola Conces  

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  • Monitoring the acetohydroxy acid synthase reaction and related carboligations by circular dichroism spectroscopy

    Vinogradov, Michael   Kaplun, Alexander   Vyazmensky, Maria   Engel, Stanislav   Golbik, Ralph   Tittmann, Kai   Uhlemann, Kathrin   Meshalkina, Ludmilla   Barak, Ze'ev   Hubner, Gerhard  

    Acetohydroxy acid synthase (AHAS) and related enzymes catalyze the production of chiral compounds [(S)-acetolactate, (S)-acetohydroxybutyrate, or (R)-phenylacetylcarbinol] from achiral substrates (pyruvate, 2-ketobutyrate, or benzaldehyde). The common methods for the determination of AHAS activity have shortcomings. The colorimetric method for detection of acyloins formed from the products is tedious and does not allow time-resolved measurements. The continuous assay for consumption of pyruvate based on its absorbance at 333 rim, though convenient.. is limited by the extremely small extinction coefficient of pyruvate, which results in a low signal-to-noise ratio and sensitivity to interfering absorbing compounds. Here, we report the use of circular dichroism spectroscopy for monitoring AHAS activity. This method, which exploits the optical activity of reaction products, displays a high signal-to-noise ratio and is easy to perform both in time-resolved and in commercial modes. In addition to AHAS, we examined the determination of activity of glyoxylate carboligase. This enzyme catalyzes the condensation of two molecules of glyoxylate to chiral tartronic acid semialdehyde. The use of circular dichroism also identifies the product of glyoxylate carboligase as being in the (R) configuration. (c) 2005 Elsevier Inc. All rights reserved.
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