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Thermal Effects (thermal + effects)
Selected AbstractsThermal Effects on Fast Skeletal Myosins from Alaska Pollock, White Croaker, and Rabbit in Relation to Gel FormationJOURNAL OF FOOD SCIENCE, Issue 5 2003H. Fukushima ABSTRACT Thermodynamic properties in differential scanning calorimetry (DSC) and changes in viscoelasticity upon heating of myosins from white croaker, Alaska pollock, and rabbit fast muscles were investigated in relation to their thermal gel formation abilities. Alaska pollock myosin unfolded in a wide temperature range of 19 to 69°C as revealed by DSC, whereas rabbit myosin unfolded in very narrow range of 32 to 56°C. Thermal unfolding of white croaker myosin occurred in an intermediate temperature range of 30 to 60°C. Viscoelastic properties determined as storage modulus, G,, and loss modulus, G,, reflected differences observed in DSC for the 3 myosins. [source] Biochemical Studies of the Thermal Effects on DNA Modifications by the Antitumor Cisplatin and Their RepairCHEMBIOCHEM, Issue 16 2007Anna Halamikova Mgr. Abstract Using biochemical methods, we have examined the effect of two factors that might play a role in the mechanism of the biological activity of cisplatin at elevated temperatures (>37°C). We show that increased temperatures result in distinct alterations in the modification of the target DNA by cisplatin, and in the repair of these modifications. Our in vitro results support the view that the enhanced DNA-cross-linking efficiency of cisplatin and the lower efficiency of native DNA repair mechanisms at higher temperature play at least a partial role in the potentiation of the antitumor effects of cisplatin under conditions of mild hyperthermia. [source] ChemInform Abstract: Calorimetry and Thermal Effects in CatalysisCHEMINFORM, Issue 3 2002several authors several authors Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] Thermal Effects and Vibrational Corrections to Transition Metal NMR Chemical ShiftsCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2004Sonja Grigoleit Dr. Abstract Both zero-point and classical thermal effects on the chemical shift of transition metals have been calculated at appropriate levels of density functional theory for a number of complexes of titanium, vanadium, manganese and iron. The zero-point effects were computed by applying a perturbational approach, whereas classical thermal effects were probed by Car,Parrinello molecular dynamics simulations. The systematic investigation shows that both procedures lead to a deshielding of the magnetic shielding constants evaluated at the GIAO-B3,LYP level, which in general also leads to a downfield shift in the relative chemical shifts, ,. The effect is small for the titanium and vanadium complexes, where it is typically on the order of a few dozen ppm, and is larger for the manganese and iron complexes, where it can amount to several hundred ppm. Zero-point corrections are usually smaller than the classical thermal effect. The pronounced downfield shift is due to the sensitivity of the shielding of the metal centre with regard to the metal,ligand bond length, which increase upon vibrational averaging. Both applied methods improve the accuracy of the chemical shifts in some cases, but not in general. [source] Thermal effects in partially saturated soils: a constitutive modelINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 9 2005Gabriella Bolzon Abstract The present paper is centred on the assessment of an elastic,plastic model for partially saturated soils, earlier proposed by the authors, for its predictive capability with respect to temperature changes, on the light of available experimental results. The model is cast within a constitutive framework that uses Bishop's stress and suction as main variables governing the volumetric response of the material. Some enhancement to the original temperature-independent formulation is proposed. In particular, functions describing the yield surface and the compressibility modulus are modified to account for the shrinking of the elastic domain and for the increase of irreversible volumetric strain with heating. Some examples illustrate the main features of the present proposal. Comparison with some experimental results is also included. Copyright © 2005 John Wiley & Sons, Ltd. [source] Modeling Thermal and Mechanical Effects on Retention of Thiamin in Extruded FoodsJOURNAL OF FOOD SCIENCE, Issue 8 2003J.Y. Cha ABSTRACT: A model was proposed to predict separate thermal and mechanical effects of extrusion cooking on thiamin retention. Thermal effects were determined by heating small samples of wheat flour mixed with 0.30% (wt/ wt) thiamin hydrochloride isothermally at 140 °C, 151 °C, and 161 °C for different times. The calculated activation energy and rate constants at each temperature were 67.28 kJ/g mol and 0.00869/min, 0.0145/min, and 0.0224/min, respectively. The "extruder constant" was estimated as 27.7/rev, based on a matching-viscosity method. Wheat flour with 0.30% (wt/wt) thiamin was extruded at different screw speeds. Mechanical effects caused 89.7% to 94.4% of total thiamin loss. This research provides a generalized method to "fingerprint" the extrusion process. [source] Pilot clinical study of a novel minimally invasive bipolar microneedle radiofrequency device,LASERS IN SURGERY AND MEDICINE, Issue 2 2009Basil M. Hantash MD Abstract Background and Objectives Noninvasive bipolar and monopolar radiofrequency (RF) deep dermal heating devices have previously been described. A novel minimally invasive RF device employing a bipolar microneedle electrode system is introduced and its resultant thermal effects on human skin in vivo were characterized for the first time. Study Design/Materials and Methods An investigational 35 W RF device was configured to operate in bipolar mode delivering energy directly within the dermis using 5 microneedle electrode pairs with real-time feedback of tissue temperature for treatment control. Superficial cooling was achieved using a Peltier device. A range of pulse durations between 1 and 25 seconds, and lesion temperatures between 60 and 80°C were tested in vivo on 15 human subjects. Thermal effects were assessed histologically using either hematoxylin & eosin (H&E) or nitroblue-tetrazoliumchloride (NBTC) staining. Treatment effects and adverse events were also monitored clinically. Results The investigational bipolar RF device delivered controlled heating within dermal tissue. Histological staining with H&E revealed the presence of zones of denatured collagen within the reticular dermis. Lesions were generated at preselected temperatures between 60 and 80°C. Fractional lesions separated by zones of sparing as well as contiguous lesion patterns were demonstrated. Histological staining with H&E and NBTC revealed sparing of adnexal structures and adipose tissue. No major adverse events were observed. Conclusions A novel fractional RF device utilizing a minimally invasive bipolar microneedle delivery system for the treatment of human tissue was developed. Treatment of 15 human subjects illustrated the controlled creation of dermally located thermal coagulation zones, herein known as radiofrequency thermal zones. We discovered that varying the pulse length allowed for fractional sparing of dermal tissue. To our knowledge, this is the first report to describe use of a direct real-time temperature and impedance feedback system to control energy delivery during deep dermal heating. Lasers Surg. Med. 41:87,95, 2009. © 2009 Wiley-Liss, Inc. [source] Influence of cylinder-on-plate or block-on-ring sliding configurations on friction and wear of pure and filled engineering polymersLUBRICATION SCIENCE, Issue 2 2007P. Samyn Abstract Polyamides, polyesters and polyacetals are often used in line contacts under reciprocating or continuous sliding. These contacts are simulated on cylinder-on-plate (COP) or block-on-ring (BOR) tribotests. Comparative tests for pure, oil-filled and solid lubricated polymers at 100N and 0.3m/s are presented for relative material classification. Differences are discussed according to the sliding geometries. Thermal effects dominate friction and wear behaviour: the polymer glass transition temperature is exceeded in COP tests while the temperature is lower in BOR tests. Thick and brittle films are observed for pure polymers in BOR tests, promoting higher friction. The test configuration is mainly important for evaluation of internal lubricants. The efficiency of oil-lubricated polymers is not demonstrated in COP tests, while solid lubricants are not efficient in BOR tests. Deformation restricts the diffusion of oil lubricants in COP tests while solid lubricants are deposited on the polymer surface rather than being incorporated in the transfer film in BOR tests. Copyright © 2007 John Wiley & Sons, Ltd. [source] Thermal effects and contact conductivity under boundaryZ lZuZbricationLUBRICATION SCIENCE, Issue 2 2000V. V. Konchits Abstract This paper considers the use of contact electrical conductivity to analyse boundary lubrication at various temperatures. The main mechanisms of contact conductivity within the temperature range typical of lubricated tribosystems are discussed. Special equipment is described for temperature investigation and experimental data are presented on electrophysical methods. Model experiments with static nominal point contacts bring to light some peculiarities of the behaviour of boundary films when heated. Analysis of electrical and frictional characteristics under sliding shows the contact resistance method to be promising in the thermal testing of boundary films. [source] Subtraction of scattering parameters for adiabatic intrinsic responses of semiconductor lasersMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2008S. J. Zhang Abstract Thermal effects will make chip temperature change with bias current of semiconductor lasers, which results in inaccurate intrinsic response by the conventional subtraction method. In this article, an extended subtraction method of scattering parameters for characterizing adiabatic responses of laser diode is proposed. The pulsed injection operation is used to determine the chip temperature of packaged semiconductor laser, and an optimal injection condition is obtained by investigating the dependence of the lasing wavelength on the width and period of the injection pulse in a relatively wide temperature range. In this case, the scattering parameters of laser diode are measured on adiabatic condition and the adiabatic intrinsic responses of packaged laser diode are first extracted. It is found that the adiabatic intrinsic responses are evidently superior to those without thermal consideration. The analysis results indicate that inclusion of thermal effects is necessary to acquire accurate intrinsic responses of semiconductor lasers. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 992,995, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23278 [source] Thermal effects of circumplanetary disc formation around proto-gas giant planetsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2009M. N. Machida ABSTRACT The formation of a circumplanetary disc and accretion of angular momentum on to a protoplanetary system are investigated using three-dimensional hydrodynamical simulations. The local region around a protoplanet in a protoplanetary disc is considered with sufficient spatial resolution: the region from outside the Hill sphere to the Jovian radius is covered by the nested-grid method. To investigate the thermal effects of the circumplanetary disc, various equations of state are adopted. Large thermal energy around the protoplanet slightly changes the structure of the circumplanetary disc. Compared with a model adopting an isothermal equation of state, in a model with an adiabatic equation of state, the protoplanet's gas envelope extends farther, and a slightly thick disc appears near the protoplanet. However, different equations of state do not affect the acquisition process of angular momentum for the protoplanetary system. Thus, the specific angular momentum acquired by the system is fitted as a function only of the protoplanet's mass. A large fraction of the total angular momentum contributes to the formation of the circumplanetary disc. The disc forms only in a compact region in very close proximity to the protoplanet. Adapting the results to the Solar system, the proto-Jupiter and Saturn have compact discs in the region of r < 21rJup(r < 0.028 rH,Jup) and r < 66rSat(r < 0.061rH,Sat), respectively, where rJup(rH,Jup) and rSat(rH,Sat) are the Jovian and Saturnian (Hill) radius, respectively. The surface density has a peak in these regions due to the balance between centrifugal force and gravity of the protoplanet. The size of these discs corresponds well to the outermost orbit of regular satellites around Jupiter and Saturn. Regular satellites may form in such compact discs around proto-gas giant planets. [source] A method to predict triaxial residual stresses in plastic pipesPOLYMER ENGINEERING & SCIENCE, Issue 10 2004Z. W. Guan Significant hoop and longitudinal stresses are present in medium-density polyethylene (MDPE) pipe, arising from differential cooling from the inner and the outer surfaces of a pipe during production. Owing to the difficulty of directly measuring deformations, these stresses have hitherto been almost exclusively estimated indirectly from deflection measurements on large samples cut from the pipe wall. Furthermore, because of procedural problems, only uniaxial hoop or longitudinal stresses are normally attempted, and these are known to be specimen size,dependent. Similar problems are experienced with other polymeric pipes. In this paper, based on direct biaxial strain measurements on small samples cut from the pipe wall, a method to predict triaxial residual stress distributions through the pipe wall is presented. Thermal effects that generate residual stresses in plastic pipe were considered in the theory. The analytical solutions satisfy the self-equilibrating conditions for both the hoop and the longitudinal stresses. Also, the radial stress is shown to be insignificant through the wall thickness of a mildly thick pipe. Polym. Eng. Sci. 44:1828,1838, 2004. © 2004 Society of Plastics Engineers. [source] Thermal effects on reptile reproduction: adaptation and phenotypic plasticity in a montane lizardBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2010RORY S. TELEMECO Interspecific comparisons suggest a strong association between cool climates and viviparity in reptiles. However, intraspecific comparisons, which provide an opportunity to identify causal pathways and to distinguish facultative (phenotypically plastic) effects from canalized (genetically fixed) responses, are lacking. We documented the reproductive traits in an alpine oviparous lizard, and manipulated thermal regimes of gravid females and their eggs to identify proximate causes of life-history variation. Embryonic development at oviposition was more advanced in eggs laid by females from high-elevation populations than in eggs produced by females from lower elevations. In the laboratory, experimentally imposed low maternal body temperatures delayed oviposition and resulted in more advanced embryonic development at oviposition. Warm conditions both in utero and in the nest increased hatching success and offspring body size. Our intraspecific comparisons support the hypothesis that viviparity has evolved in cold-climate squamates because of the direct fitness advantages that warm temperatures provide developing offspring. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 642,655. [source] Contribution to the stability analysis of the dewetted Bridgman growth under microgravity conditionsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 6 2004L. Bizet Abstract Experimental observations show that the gap between the sample and the crucible, commonly obtained after solidification in microgravity, is remarkably stable. With the aim to understand the reason of this stability, the dewetting phenomenon is studied by Lyapunov's method. After a short review of the existing mechanisms leading to dewetting, the open smooth crucible configuration is chosen as the most representative. The analytical stability analysis, taking into account geometrical and thermal effects, performed under some boundary heat transfer approximations, shows that, in most cases, the dewetting process is intrinsically stable. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Cover Picture: Electrophoresis 5'09ELECTROPHORESIS, Issue 5 2009Article first published online: 3 MAR 200 Issue no. 5 is a special issue on "Fundamentals of Electrophoresis" containing 21 papers including 3 Fast Track papers. The first Fast Track paper deals with imaged CE technology for measuring charge variants of monoclonal antibodies, the second paper is on the dispersion of protein bands in a horseshoe microchannel during IEF while the third Fast Track paper reports a theoretical and experimental study on the irreversible deposition of colloidal particles from electrokinetic microfluidic flow. The remaining 18 papers of this special issue are distributed into seven parts pertaining to various fundamental topics, e.g., electromigration and dielectrophoresis in microchip channels, computer simulation of electromigration, stacking, interaction in electrophoretic systems, thermal effects, electroosmotic flow, etc. [source] THE ADAPTIVE SIGNIFICANCE OF TEMPERATURE-DEPENDENT SEX DETERMINATION: EXPERIMENTAL TESTS WITH A SHORT-LIVED LIZARDEVOLUTION, Issue 10 2005Daniel A. Warner Abstract Why is the sex of many reptiles determined by the temperatures that these animals experience during embryogenesis, rather than by their genes? The Charnov-Bull model suggests that temperature-dependent sex determination (TSD) can enhance maternal fitness relative to genotypic sex determination (GSD) if offspring traits affect fitness differently for sons versus daughters and nest temperatures either determine or predict those offspring traits. Although potential pathways for such effects have attracted much speculation, empirical tests largely have been precluded by logistical constraints (i.e., long life spans and late maturation of most TSD reptiles). We experimentally tested four differential fitness models within the Charnov-Bull framework, using a short-lived, early-maturing Australian lizard (Amphibolurus muricatus) with TSD. Eggs from wild-caught females were incubated at a range of thermal regimes, and the resultant hatchlings raised in large outdoor enclosures. We applied an aromatase inhibitor to half the eggs to override thermal effects on sex determination, thus decoupling sex and incubation temperature. Based on relationships between incubation temperatures, hatching dates, morphology, growth, and survival of hatchlings in their first season, we were able to reject three of the four differential fitness models. First, matching offspring sex to egg size was not plausible because the relationship between egg (offspring) size and fitness was similar in the two sexes. Second, sex differences in optimal incubation temperatures were not evident, because (1) although incubation temperature influenced offspring phenotypes and growth, it did so in similar ways in sons versus daughters, and (2) the relationship between phenotypic traits and fitness was similar in the two sexes, at least during preadult life. We were unable to reject a fourth model, in which TSD enhances offspring fitness by generating seasonal shifts in offspring sex ratio: that is, TSD allows overproduction of daughters (the sex likely to benefit most from early hatching) early in the nesting season. In keeping with this model, hatching early in the season massively enhanced body size at the beginning of the first winter, albeit with a significant decline in probability of survival. Thus, the timing of hatching is likely to influence reproductive success in this short-lived, early maturing species; and this effect may well differ between the sexes. [source] ORIGINAL ARTICLE: Big dams and salmon evolution: changes in thermal regimes and their potential evolutionary consequencesEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 2 2008Michael J. Angilletta Jr Abstract Dams designed for hydropower and other purposes alter the environments of many economically important fishes, including Chinook salmon (Oncorhynchus tshawytscha). We estimated that dams on the Rogue River, the Willamette River, the Cowlitz River, and Fall Creek decreased water temperatures during summer and increased water temperatures during fall and winter. These thermal changes undoubtedly impact the behavior, physiology, and life histories of Chinook salmon. For example, relatively high temperatures during the fall and winter should speed growth and development, leading to early emergence of fry. Evolutionary theory provides tools to predict selective pressures and genetic responses caused by this environmental warming. Here, we illustrate this point by conducting a sensitivity analysis of the fitness consequences of thermal changes caused by dams, mediated by the thermal sensitivity of embryonic development. Based on our model, we predict Chinook salmon likely suffered a decrease in mean fitness after the construction of a dam in the Rogue River. Nevertheless, these demographic impacts might have resulted in strong selection for compensatory strategies, such as delayed spawning by adults or slowed development by embryos. Because the thermal effects of dams vary throughout the year, we predict dams impacted late spawners more than early spawners. Similar analyses could shed light on the evolutionary consequences of other environmental perturbations and their interactions. [source] A probabilistic two-scale model for high-cycle fatigue life predictionsFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 3 2005C. DOUDARD ABSTRACT It is proposed to develop and identify a probabilistic two-scale model for HCF that accounts for the failure of samples, but also for the thermal effects during cyclic loadings in a unified framework. The probabilistic model is based on a Poisson point process. Within the weakest link theory, the model corresponds to a Weibull law for the fatigue limits. The thermal effects can be described if one considers the same hypotheses apart from the weakest link assumption. A method of identification is proposed and uses temperature measurements to identify the scatter in an S/N curve. The validation of the model is obtained by predicting S/N curves for different effective volumes of a dual-phase steel. [source] Water temperature determines strength of top-down control in a stream food webFRESHWATER BIOLOGY, Issue 8 2005DAISUKE KISHI Summary 1. We examined effects of water temperature on the community structure of a three trophic level food chain (predatory fish, herbivorous caddisfly larvae and periphyton) in boreal streams. We used laboratory experiments to examine (i) the effects of water temperature on feeding activities of fish and caddisfly larvae and on periphyton productivity, to evaluate the thermal effects on each trophic level (species-level experiment), and (ii) the effects of water temperature on predation pressure of fish on abundance of the lower trophic levels, to evaluate how temperature affects top-down control by fish (community-level experiment). 2. In the species-level experiment, feeding activity of fish was high at 12 °C, which coincides with the mean summer temperature in forested streams of Hokkaido, Japan, but was depressed at 3 °C, which coincides with the mean winter temperature, and also above 18 °C, which coincides with the near maximum summer temperatures. Periphyton productivity increased over the range of water temperatures. 3. In the community-level experiments, a top-down effect of fish on the abundance of caddisfly larvae and periphyton was clear at 12 °C. This effect was not observed at 3 and 21 °C because of low predation pressure of fish at these temperatures. 4. These experiments revealed that trophic cascading effects may vary with temperature even in the presence of abundant predators. Physiological depression of predators because of thermal stress can alter top-down control and lead to changes in community structure. 5. We suggest that thermal habitat alteration can change food web structure via combinations of direct and indirect trophic interactions. [source] Experimental and numerical investigations of the behaviour of a heat exchanger pileINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 8 2006Lyesse Laloui Abstract The geothermal use of concrete geostructures (piles, walls and slabs) is an environmentally friendly way of cooling and heating buildings. With such geothermal structures, it is possible to transfer energy from the ground to fluid-filled pipes cast in concrete and then to building environments. To improve the knowledge in the field of geothermal structures, the behaviour of a pile subjected to thermo-mechanical loads is studied in situ. The aim is to study the increased loads on pile due to thermal effects. The maximum thermal increment applied to the pile is on the order of 21°C and the mechanical load reached 1300 kN. Coupled multi-physical finite element modelling is carried out to simulate the observed experimental results. It is shown that the numerical model is able to reproduce the most significant thermo-mechanical effects. Copyright © 2006 John Wiley & Sons, Ltd. [source] Experimental study of thermal effects on the mechanical behaviour of a clayINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 3 2004Cane Cekerevac Abstract The paper presents the results of an experimental study of thermal effects on the mechanical behaviour of a saturated clay. The study was performed on CM clay (Kaolin) using a temperature-controlled triaxial apparatus. Applied temperatures were between 22 and 90°C. A comprehensive experimental program was carried out, including: (i) triaxial shear tests at ambient and high temperatures for different initial overconsolidation ratios; (ii) consolidation tests at ambient and high temperatures; and (iii) drained thermal heating for different initial overconsolidation ratios. The obtained results provide observations concerning a wide scope of the thermo-mechanical behaviour of clays. Test results obtained at 90°C were compared with tests performed at ambient temperature. Based on these comparisons, thermal effects on a variety of features of behaviour are presented and discussed. Focus is made on: (i) induced thermal volume change during drained heating; (ii) experimental evidence of temperature influence on preconsolidation pressure and on compressibility index; (iii) thermal effects on shear strength and critical state; and (iv) thermal effects on elastic modulus. Thermal yielding is discussed and yield limit evolution with temperature is presented. The directions of the induced plastic strains are also discussed. Several remarks on the difference in the mechanical behaviour at ambient and high temperatures conclude the paper. Copyright © 2004 John Wiley & Sons, Ltd. [source] Finite element and finite volume simulation and error assessment of polymer melt flow in closed channelsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 11 2006M. Vaz Jr. Abstract This work aims at evaluating the discretization errors associated to the finite volume and finite element methods of polymer melt flow in closed channels. Two strategies are discussed: (i) Richardson extrapolation and (ii) a posteriori error estimation based on projection/smoothing techniques. The numerical model accounts for the full interaction between the thermal effects caused by viscous heating and the momentum diffusion effects dictated by a shear rate and temperature-dependent constitutive model. The simulations have been performed for the commercial polymer Polyacetal POM-M90-44. Copyright © 2006 John Wiley & Sons, Ltd. [source] Two-scale method for shear bands: thermal effects and variable bandwidthINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2007Pedro M. A. Areias Abstract A method for the analysis of shear bands using local partition of unity is developed in the framework of the extended finite element method (XFEM). Enrichments are introduced for both the displacement field and the thermal field. The shear band width is determined by minimizing the plastic work. A coupled finite strain thermo-elastoplastic constitutive law is used. The enrichment is injected into the mesh when the material law becomes unstable. The criterion based on a complete stability analysis for materials in the finite strain regime including heat conduction, strain hardening, strain rate hardening and thermal softening is presented. A mixed continuous quadrilateral element is employed. The method is applied to the Nesterenko experiments, which exhibit multiple propagating shear bands and other problems. Copyright © 2007 John Wiley & Sons, Ltd. [source] Chemical effects of CO2 addition to oxidizer and fuel streams on flame structure in H2,O2 counterflow diffusion flamesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2003Jeong Park Abstract Numerical simulation of CO2 addition effects to fuel and oxidizer streams on flame structure has been conducted with detailed chemistry in H2,O2 diffusion flames of a counterflow configuration. An artificial species, which displaces added CO2 in the fuel- and oxidizer-sides and has the same thermochemical, transport, and radiation properties to that of added CO2, is introduced to extract pure chemical effects in flame structure. Chemical effects due to thermal dissociation of added CO2 causes the reduction flame temperature in addition to some thermal effects. The reason why flame temperature due to chemical effects is larger in cases of CO2 addition to oxidizer stream is well explained though a defined characteristic strain rate. The produced CO is responsible for the reaction, CO2+H=CO+OH and takes its origin from chemical effects due to thermal dissociation. It is also found that the behavior of produced CO mole fraction is closely related to added CO2 mole fraction, maximum H mole fraction and its position, and maximum flame temperature and its position. Copyright © 2003 John Wiley & Sons, Ltd. [source] Numerical study on flame structure in H2,O2/CO2 laminar flamesINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 7 2003Jeong Park Abstract Numerical study, aimed at the understanding of the flame structure in O2/CO2 recycling combustion system, has been conducted with detailed chemistry. Special concern is focused on addition effect of carbon dioxide on flame structure in H2,O2 counterflow diffusion flame as a simulating configuration. To clarify chemical and thermal effects on flame structure, the comparison between predicted results with a virtual species X to displace the real carbon dioxide and with added carbon dioxide in oxidizer stream is made according to strain rate and the concentration of added CO2. From the systematical comparison of a dominant radical producing reaction with a chain termination reaction the effects of strain rate and composition control of oxidizer stream on flame structure are estimated. It is found that the behaviours of C1 - and C2 -branch species are a direct outcome of that of produced CO due to the breakdown of added CO2. There exists a temperature dependency in the behaviour of produced CO and this competes for the behaviour of the produced CO with chemical effects due to the backward reaction of CO+OH=CO2+H. Copyright © 2003 John Wiley & Sons, Ltd. [source] Thermal and chemical contributions of added H2O and CO2 to major flame structures and NO emission characteristics in H2/N2 laminar diffusion flameINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 12 2002Seung-Gon Kim Abstract Numerical simulation with detailed chemistry has been carried out to clearly discriminate the thermal and chemical contributions of added diluents (H2O and CO2) to major flame structures and NO emission characteristics in H2/N2 counterflow diffusion flame. The pertinence of GRI, Miller,Bowman, and their recent modified mechanisms are estimated for the combined fuel of H2, CO2, and N2. A virtual species X, which displaces the individual CO2 and H2O in the fuel sides, is introduced to separate chemical effects from thermal effects. In the case of H2O addition the chain branching reaction, H + O2 , O + OH is considerably augmented in comparison with that in the case of CO2 addition. It is also seen that there exists a chemically super-adiabatic effect in flame temperature due to the breakdown of H2O. The reaction path of CH2O,CH2OH,CH3 and the C1-branch reactions become predominant due to the breakdown of CO2. In NO emission behaviour super-equilibrium effects caused by the surplus chain carrier radicals due to the breakdown of added H2O are more superior to the enhanced effects of prompt NO with the breakdown of added CO2. Especially, it is noted that thermal NO emission is directly influenced by the chemical super-equilibrium effects of chain carrier radicals in the case of H2O addition. As a result the overall NO emission in the case of the addition of H2O is higher than that in the case of CO2 addition. Copyright © 2002 John Wiley & Sons, Ltd. [source] Optical techniques to determine thermal effects on proteinsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 11 2008Teepakorn Kongraksawech Summary Optical rotation (OR) and transmitted light (TL) measurements were conducted on 1%, 2.5% and 5% (w/v) bovine serum albumin (BSA) in 0.01 m phosphate buffer at pH 7 and ionic strength 0.08. Denaturation temperatures (Td) obtained from OR measurements were consistent with reported differential scanning calorimetry values. Protein concentration did not affect Td in agreement with most reports. Changes in TL reflecting gel formation and protein aggregation were influenced by BSA concentration. Sugar concentration in the range used in this study (0,5%) did not affect the thermal stability of BSA. The lack of difference in sucrose, trehalose and sorbitol effects on the thermal stability of BSA was consistent with some but not all reports. The optical system used to study protein denaturation had acceptable accuracy (consistency with published Td values) and precision (coefficient of variation under 3.5%) levels. [source] Structure elucidation, conformational analysis and thermal effects on membrane bilayers of an antimicrobial myricetin ether derivativeJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2001C. Demetzos The membrane perturbing 3,7,4,,5,-tetramethyl ether of myricetin 1 was isolated from Cistus monspelien-sis L. Its structure was elucidated and its conformational properties were explored using a combination of 2D NMR spectroscopy and computational chemistry. The obtained results showed that compound 1 adopts four enantiomeric pairs of low energy conformers characterized: (a) by an aromatic ring B twisted through rotation about C2-C1, bond from the rigid isoflavone ring; (b) a 4,-O-CH3 bond oriented out of the plane with equal probability upwards or downwards the phenyl ring B, while all the other O-CH3 bonds are oriented in the plane of the aryl ring. Two of these enantiomeric pairs are lowest in energy. These possible bioactive con-formers are possibly stabilized by van Der Waals interactions. The 3,,5-diacetyl derivative 2 of compound 1 was synthesized and its structure elucidation was achieved based on the chemical shift assignment of the parent compound 1. The Differential Scanning Calorimetry (DSC) results revealed that the degree of the thermal effects exerted by the flavonoids at dipalmitoylphosphatidyl choline (DPPC) bilayers followed the order 1 > 2 > myricetin. Their antimicrobial activity against Gram positive bacteria followed the same order. [source] Kinetic modeling of catalytic conversion of methylcyclohexane over USY zeolites: Adsorption and reaction phenomenaAICHE JOURNAL, Issue 6 2009Mustafa Al-Sabawi Abstract Catalytic conversion of cycloparaffins is a complex process involving competing reaction steps. To understand this process, FCC experiments using methylcyclohexane (MCH) on USY zeolite catalysts were carried out in the mini-fluidized CREC riser simulator. Runs were developed under relevant FCC process conditions in terms of partial pressures of MCH, temperatures (450,550°C), contact times (3,7 s), catalyst-oil mass ratios (5), and using fluidized catalysts. MCH overall conversions ranged between 4 to 16 wt %, with slightly higher conversions obtained using the larger zeolite crystallites. Moreover, it was found that MCH undergoes ring opening, protolytic cracking, isomerization, hydrogen transfer and transalkylation. A heterogeneous kinetic model for MCH conversion including thermal effects, adsorption and intrinsic catalytic reaction phenomena was established. Adsorption and kinetic parameters were determined, including the heat of adsorption (,40 kJ/mol), as well as thermal and primary catalytic intrinsic activation energies, which were in the range of 43,69 kJ/mol, and 50,74 kJ/mol, respectively. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] Rapid contrasting of ultrathin sections using microwave irradiation with heat dissipationJOURNAL OF MICROSCOPY, Issue 2 2001F. Hernández-Chavarría The use of microwave irradiation (MWI) to accelerate fixation, dehydration and contrasting (staining) for electron microscopy has been applied to the development of rapid methods to process biological samples in electron microscopy. A simple explanation is that the reduced time in those procedures is due to heating. In this paper we propose a contrasting method for thin sections that avoids the thermal effects of MWI. Grids with thin sections of mouse kidney, the dinoflagellate Alexandrium monilatum, spermatophores of the fly Archicepsis diversiformis, the bacteria Acinetobacter calcoaceticum and Enterobacter cloacae were placed into Beem capsules and stained with uranyl acetate and lead citrate, while immersed in an ice-water bath, and irradiated for periods ranging from 30 s to 2 min. After each contrasting procedure, the Beem capsule was filled with distilled water to wash the grids under MWI with the same irradiation time as used to contrast. Good results were obtained on irradiating for 1 min and the temperature of the Beem capsule was maintained around 5 °C. [source] | ||||||||||||||||||||||||||||