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Absolute Temperature (absolute + temperature)
Selected AbstractsTwo variable semi-empirical and artificial neural-network-based modeling of peptide mobilities in CZE: The effect of temperature and organic modifier concentrationELECTROPHORESIS, Issue 5 2009Stefan Mittermayr Abstract This work was focused on investigating the effects of two separation influencing parameters in CZE, namely temperature and organic additive concentration upon the electrophoretic migration properties of model tripeptides. Two variable semi-empirical (TVSE) models and back-propagation artificial neural networks (ANN) were applied to predict the electrophoretic mobilities of the tripeptides with non-polar, polar, positively charged, negatively charged and aromatic R group characteristics. Previously published work on the subject did not account for the effect of temperature and buffer organic modifier concentration on peptide mobility, in spite of the fact that both were considered to be influential factors in peptide analysis. In this work, a substantial data set was generated consisting of actual electrophoretic mobilities of the model tripeptides in 30,mM phosphate buffer at pH 7.5, at 20, 25, 30, 35 and 40°C and at four different organic additive containing running buffers (0, 5, 10 and 15% MeOH) applying two electric field strengths (12 and 16,kV) to assess our mobility predicting models. Based on the Arrhenius plots of natural logarithm of mobility versus reciprocal absolute temperature of the various experimental setups, the corresponding activation energy values were derived and evaluated. Calculated mobilities by TVSE and back-propagation ANN models were compared with each other and to the experimental data, respectively. Neural network approaches were able to model the complex impact of both temperature and organic additive concentrations and resulted in considerably higher predictive power over the TVSE models, justifying that the effect of these two factors should not be neglected. [source] Using measured octanol-air partition coefficients to explain environmental partitioning of organochlorine pesticidesENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2002Mahiba Shoeib Abstract Octanol-air partition coefficients (Koa) were measured directly for 19 organochlorine (OC) pesticides over the temperature range of 5 to 35°C. Values of log Koa at 25°C ranged over three orders of magnitude, from 7.4 for hexachlorobenzene to 10.1 for 1,1-dichloro-2,2-bis (p-chlorophenyl) ethane. Measured values were compared to values calculated as KowRT/H (where R is the ideal gas constant [8.314 J mol,1 K,1], T is absolute temperature, and H is Henry's law constant) were, in general, larger. Discrepancies of up to three orders of magnitude were observed, highlighting the need for direct measurements of Koa. Plots of Koa versus inverse absolute temperature exhibited a log-linear correlation. Enthalpies of phase transition between octanol and air (,Hoa) were determined from the temperature slopes and were in the range of 56 to 105 kJ mol,1 K,1. Activity coefficients in octanol (,o) were determined from Koa and reported supercooled liquid vapor pressures (p), and these were in the range of 0.3 to 12, indicating near-ideal solution behavior. Differences in Koa values for structural isomers of hexachlorocyclohexane were also explored. A Koa -based model was described for predicting the partitioning of OC pesticides to aerosols and used to calculate particulate fractions at 25 and ,10°C. The model also agreed well with experimental results for several OC pesticides that were equilibrated with urban aerosols in the laboratory. A log-log regression of the particle-gas partition coefficient versus Koa had a slope near unity, indicating that octanol is a good surrogate for the aerosol organic matter. [source] Geometrical isomerisation of eicosapentaenoic and docosahexaenoic acid at high temperaturesEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 7 2006Svein A. Mjøs Abstract Concentrates of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were heated at 140,240,°C for 2,8,h under nitrogen. The trans isomers were analysed by gas chromatography-mass spectrometry on a BPX-70 cyanopropyl column. All geometrical isomers of EPA and DHA with one trans double bond were observed. The rate constants (k) for the isomerisation of the all- cis isomers were calculated and found to be higher than previously reported for linoleic acid and ,-linolenic acid. Arrhenius plots showed a linear relationship between ln,k and the reciprocal absolute temperature above 180,°C. The distribution patterns of isomers with one trans double bond are approximately constant up to a degree of isomerisation of 25%. The degree of isomerisation can therefore be estimated from selected trans peaks. [source] Temperature dependence of stress,lifetime fatigue curvesFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 12 2000J. Kohout By analysing several finite-life fatigue curves obtained at various temperatures, a relation describing the temperature dependence of fatigue strength is proposed, based on the Basquin equation. Accordingly, an approximate inverse law between fatigue strength and the square root of absolute temperature is demonstrated. Moreover, a boundary temperature above which creep begins to play a significant role is estimated. A simple extension of the relationship to the low-cycle fatigue region, allows one to determine predictive curves describing fatigue behaviour at various temperatures, even in cases where only a single fatigue curve at a given temperature plus the temperature dependence of tensile strength are known. [source] The Effect of Weather on HeadacheHEADACHE, Issue 6 2004Patricia B. Prince MD Objectives.,To assess headache patients' beliefs about how strongly weather affects their headaches; To objectively investigate the influence of multiple weather variables on headache. Design and Methods.,Our sample consisted of 77 migraineurs seen in a headache clinic, who provided headache calendars for a period ranging from 2 to 24 months. Our study was divided into two phases. First, each patient was given a questionnaire assessing their beliefs about how strongly (if so) weather affected their headaches. Second, weather data were collected from the National Weather Service, from three reporting stations central to the residences of the study participants. Analysis was performed on 43 variables to generate three meteorological factors. Linear regression was used to assess the relationship between headache and these three factors. Factor 1 represents a function of absolute temperature and humidity. Factor 2 represents a changing weather pattern. Factor 3 represents barometric pressure. Results.,Of the 77 subjects in the study, 39 (50.6%), were found to be sensitive to weather, but 48 (62.3%) thought they were sensitive to weather conditions (P < 0.05). Thirty (38.9%) were sensitive to one weather factor and 9 (11.7%) to two factors. Twenty-six (33.7%) were sensitive to factor 1; 11 (14.3%) to factor 2; 10 (12.9%) to factor 3. Conclusions.,Our study supports the influence of weather variables on headache. We showed that patients are susceptible to multiple weather variables and that more patients thought weather was a trigger than was the case. [source] Gaseous diffusion coefficients of methyl bromide and methyl iodide into air, nitrogen, and oxygenHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 6 2009Naoki Matsunaga Abstract The gaseous diffusion coefficients of methyl bromide (CH3Br) and methyl iodide (CH3I) into dry air, nitrogen, and oxygen have been measured in the temperature range 303,453 K and at atmospheric pressure via the Taylor dispersion method. Both for methyl bromide and methyl iodide, the diffusion coefficients do not vary in practice on substituting pure nitrogen or oxygen for dry air. The diffusion coefficients for methyl iodide are systematically smaller than those for methyl bromide by about 11%. For the methyl iodide-oxygen system, the effect of the thermal decomposition of methyl iodide has been observed at 453 K. The present results can be reproduced well by the functional form D = ATB, where D (cm2s,1) is the diffusion coefficient at 101 325 Pa (1 atm) and T (K) is the absolute temperature. The constants A and B are as follows: methyl bromide-(air, nitrogen, oxygen), A = 5.57 × 10,6, B = 1.76; methyl iodide-(air, nitrogen, oxygen), A = 5.26 × 10,6, B = 1.75. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20255 [source] Teratogenicity of elevated egg incubation temperature and egg vitamin A status in Atlantic salmon, Salmo salar L.JOURNAL OF FISH DISEASES, Issue 4 2004R Ørnsrud Abstract The present study was undertaken to investigate the possibility that high egg vitamin A (VA) status in combination with elevated egg incubation temperatures may cause deformities in Atlantic salmon, Salmo salar L. Egg batches selected for their total VA concentration were exposed to low (normal, 8 °C) or elevated (14 °C) egg incubation temperatures. Temperature was the main factor causing bone deformities such as warped gill opercula, fin and jaw deformities, but not for the development of spinal deformities where all groups displayed a ,baseline' occurrence of mild deformity (decreased vertebral size in the cephalic region) and no systematic variation in the occurrence of serious spinal deformities (fused vertebrae). A possible effect of egg incubation temperature fluctuation was found for the groups reared at low temperatures. An indication of a negative effect of elevated egg VA status for the development of organ deformities such as missing septum transversum and situs inversus was found in addition to temperature effects, however, no firm conclusions could be drawn from the present data. The phenotypes for temperature-induced deformities resembled the phenotype of VA-induced deformities, but no clear conclusions on the causality of the deformities found in the present study could be drawn. Egg incubation temperatures, both absolute temperature and temperature variations, should therefore be strictly controlled. [source] Characterization of Thermorheological Behavior of Alaska Pollock and Pacific Whiting SurimiJOURNAL OF FOOD SCIENCE, Issue 7 2004W.B. Yoon ABSTRACT: Thermorheological behavior of Alaska pollock (AP) and Pacific whiting (PW) surimi was evaluated during gelation at different moisture contents (80% to 95%). The temperature sweep data (storage modulus, G,, compared with temperature) for both surimi clearly indicated G' minima. Unlike for the PW surimi, the minimum values of the AP surimi was moisture-content dependent and there was a linear relationship between logarithm of concentration and reciprocal absolute temperature at gelation. The activation energy (Ea) for aggregation after gelation temperature at each moisture content was calculated by a nonisothermal kinetic model for both AP and PW Surimi. The Ea values increased with moisture content of the system and ranged from 172.8 to 232.9 kJ/mol. Based on the assumption that melting temperature for a thermo-reversible gel may be considered equivalent to gelation temperature for thermo-irreversible gels, an Arrhenius-type model was used to estimate the enthalpy of cross-links formation for AP surimi to be 300.3 kJ/mol. [source] What can we learn on the thermal history of the Universe from future cosmic microwave background spectrum measurements at long wavelengths?MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2003C. Burigana ABSTRACT We analyse the implications of future observations of the cosmic microwave background (CMB) absolute temperature at centimetre and decimetre wavelengths, where both ground, balloon and space experiments are currently under way to complement the accurate COBE/FIRAS data available at ,, 1 cm. Our analysis shows that forthcoming ground and balloon measurements will allow a better understanding of free,free distortions but will not be able to significantly improve the constraints already provided by the FIRAS data on the possible energy exchanges in the primeval plasma. The same holds even for observations with sensitivities up to ,10 times better than those of forthcoming experiments. Thus, we have studied the impact of very high-quality data, such as those, in principle, achievable with a space experiment such as the Diffuse Microwave Emission Survey (DIMES) planned to measure the CMB absolute temperature at 0.5 ,,, 15 cm with a sensitivity of ,0.1 mK, close to that of FIRAS. We have demonstrated that such high-quality data would improve by a factor of ,50 the FIRAS results on the fractional energy exchanges, ,,/,i, associated with dissipation processes possibly occurred in a wide range of cosmic epochs, at intermediate and high redshifts (yh, 1), and that the energy dissipation epoch could also be significantly constrained. By jointly considering two dissipation processes occurring at different epochs, we demonstrated that the sensitivity and frequency coverage of a DIMES -like experiment would allow one to accurately recover the epoch and the amount of energy possibly injected into the radiation field at early and intermediate epochs even in the presence of a possible late distortion, while the constraints on the energy possibly dissipated at late epochs can be improved by a factor of ,2. In addition, such measurements can provide an independent and very accurate cross-check of FIRAS calibration. Finally, a DIMES -like experiment will be able to provide indicative independent estimates of the baryon density: the product ,bH20 can be recovered within a factor of ,2,5 even in the case of (very small) early distortions with ,,/,i, (5,2) × 10,6. On the other hand, for ,b (H0/50)2, 0.2, an independent baryon density determination with an accuracy at , per cent level, comparable to that achievable with CMB anisotropy experiments, would require an accuracy of ,1 mK or better in the measurement of possible early distortions but up to a wavelength from , few × dm to ,7 dm, according to the baryon density value. [source] New Zonal, Spectral Solutions for the Navier-Stokes Layer and Their ApplicationsPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003A. Nastase Prof. Dr.-Ing., Dr. Math. New zonal, spectral forms for the axial, lateral and vertical velocity's components, density function and absolute temperature inside of compressible three-dimensional Navier-Stokes layer (NSL) over flattened, flying configurations (FC), are here proposed. The inviscid flow over the FC, obtained after the solidification of the NSL, is here used as outer flow. If the spectral forms of the velocity's components are introduced in the partial differential equations of the NSL and the collocation method is used, the spectral coefficients are obtained by the iterative solving of an equivalent quadratical algebraic system with slightly variable coefficients. [source] | |||||||||||||