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Moderate Pressures (moderate + pressure)
Selected AbstractsChemInform Abstract: Magnetism, Magnetotransport and Magnetic Structure of ThCu3Mn4O12, Prepared at Moderate Pressures.CHEMINFORM, Issue 36 2008Javier Sanchez-Benitez Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] INACTIVATION OF BACTERIAL SPORES BY COMBINED ACTION OF HYDROSTATIC PRESSURE AND BACTERIOCINS IN ROAST BEEFJOURNAL OF FOOD SAFETY, Issue 4 2003N. KALCHAYANAND ABSTRACT Foodborne bacterial spores are normally resistant to high hydrostatic pressure; however, at moderate pressure, they can be induced to germinate and outgrow. At this stage, they can be killed by bacteriocin-based biopreservatives (BP-containing pediocin and nisin at 3:7 ratio; BPX, BP + 100 ,g/mL lysozyme; BPY, BPX+ 500 ,g/mL Na-EDTA). Based on this principle, spores of the meat spoilage organism, Clostridium laramie (1,2 × 102 spores/bag) alone or a mixture of four clostridial spores (5 × 103 spores/bag), Clostridium sporogenes, Clostridium perfringens, Clostridium tertium, and Clostridium laramie, were inoculated in roast beef in the presence of 5000 AU/g of bacteriocin-based biopreservatives. The roast beef samples were subjected to hydrostatic pressure (HP) at 345 MPa for 5 min at 60C and stored at 4 or 12C for 84 days or at 25C for 7 days. The HP treatment of roast beef samples inoculated with a mixture of clostridial spores could be stored for 42 days at 4C. The HP in combination with either BPX or BPY extended the shelf-life of roast beef up to 7 days at 25C. The combined treatment of HP and BP controlled the growth of C. laramie spores and extended the shelf-life of roast beef for 84 days when stored at 4C. [source] Field-free molecular alignment of CO2 mixtures in presence of collisional relaxationJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2008T. Vieillard Abstract The present work explores the extension of the concept of short-pulse-induced alignment to dissipative environments within quantum mechanical density matrix formalism (Liouville equation) from the weak to the strong field regime. This is illustrated within the example of the CO2 molecule in mixture with Ar and He, at room temperature, for which a steep decrease of the alignment is observed at moderate pressure because of the collisional relaxation. The field-free alignment is measured by a polarization technique where the degree of alignment is monitored in the time domain by measuring the resulting transient birefringence with a probe pulse Raman induced polarization spectroscopy (RIPS) Copyright © 2008 John Wiley & Sons, Ltd. [source] Extending the Pressure,Temperature State Diagram of MyoglobinHELVETICA CHIMICA ACTA, Issue 3 2005Filip Meersman The pressure,temperature (P,T) diagram of proteins proposed by Hawley concerns the equilibrium between native and denatured forms. However, the importance of protein aggregation is increasingly recognized, and it has been suggested that certain aggregated states represent alternative folds of the polypeptide chain. Here, we present a P,T -diagram for myoglobin in which we include the aggregated state and suggest to call it a P,T -state diagram, as not all boundaries are true equilibrium transitions. We observe by Fourier transform infrared spectroscopy that increasing temperature causes the protein to aggregate, but that a subsequent further temperature increase results in the dissociation of this aggregate. Moreover, we observe that moderate pressures stabilize myoglobin against thermal denaturation. We hypothesize that this effect originates from the volume changes associated with the aggregation transition. [source] Validation of a thermal decomposition mechanism of formaldehyde by detection of CH2O and HCO behind shock wavesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2004Gernot Friedrichs The thermal decomposition of formaldehyde was investigated behind shock waves at temperatures between 1675 and 2080 K. Quantitative concentration time profiles of formaldehyde and formyl radicals were measured by means of sensitive 174 nm VUV absorption (CH2O) and 614 nm FM spectroscopy (HCO), respectively. The rate constant of the radical forming channel (1a), CH2O + M , HCO + H + M, of the unimolecular decomposition of formaldehyde in argon was measured at temperatures from 1675 to 2080 K at an average total pressure of 1.2 bar, k1a = 5.0 × 1015 exp(-308 kJ mol,1/RT) cm3 mol,1 s,1. The pressure dependence, the rate of the competing molecular channel (1b), CH2O + M , H2 + CO + M, and the branching fraction , = k1a/(kA1a + k1b) was characterized by a two-channel RRKM/master equation analysis. With channel (1b) being the main channel at low pressures, the branching fraction was found to switch from channel (1b) to channel (1a) at moderate pressures of 1,50 bar. Taking advantage of the results of two preceding publications, a decomposition mechanism with six reactions is recommended, which was validated by measured formyl radical profiles and numerous literature experimental observations. The mechanism is capable of a reliable prediction of almost all formaldehyde pyrolysis literature data, including CH2O, CO, and H atom measurements at temperatures of 1200,3200 K, with mixtures of 7 ppm to 5% formaldehyde, and pressures up to 15 bar. Some evidence was found for a self-reaction of two CH2O molecules. At high initial CH2O mole fractions the reverse of reaction (6), CH2OH + HCO , CH2O + CH2O becomes noticeable. The rate of the forward reaction was roughly measured to be k6 = 1.5 × 1013 cm3 mol,1 s,1. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 157,169 2004 [source] Solubility islands for polymer blends , a new option to homogenize incompatible polymers?MACROMOLECULAR SYMPOSIA, Issue 1 2003Attila R. Imre Abstract Experimental results of liquid-liquid phase equilibrium in a polydisperse blend of two polyalkylsiloxane are presented here. The UCST has an unusual pressure dependence: pressure induced miscibility at moderate pressures and pressure induced immiscibility at higher pressures, above a double critical point. The cloud point curve has two maxima in (concentration, temperature) as well as in (concentration, pressure) space. Approaching the double critical point, the high and low pressure branches of the cloud point curve merge and in a certain stage of this merging, they form a miscibility island located inside the two-phase region. Islands of this kind can give us a new tool to mix virtually immiscible blends. [source] Kaolin polytypes revisited ab initioACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2008Patrick H. J. Mercier The well known 36 distinguishable transformations between adjacent kaolin layers are split into 20 energetically distinguishable transformations (EDT) and 16 enantiomorphic transformations, hereafter denoted EDT*. For infinitesimal energy contribution of interactions between non-adjacent layers, the lowest-energy models must result from either (a) repeated application of an EDT or (b) alternate application of an EDT and its EDT*. All modeling, quantum input preparation and interpretation was performed with Materials Toolkit, and quantum optimizations with VASP. Kaolinite and dickite are the lowest-energy models at zero temperature and pressure, whereas nacrite and HP-dickite are the lowest-enthalpy models under moderate pressures based on a rough enthalpy/pressure graph built from numbers given in the supplementary tables. Minor temperature dependence of this calculated 0,K graph would explain the bulk of the current observations regarding synthesis, diagenesis and transformation of kaolin minerals. Other stackings that we list have energies so competitive that they might crystallize at ambient pressure. A homometric pair of energetically distinguishable ideal models, one of them for nacrite, is exposed. The printed experimental structure of nacrite correctly corresponds to the stable member of the pair. In our opinion, all recent literature measurements of the free energy of bulk kaolinite are too negative by ,,15,kJ,mol,1 for some unknown reason. [source] | ||||||||||