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Thermal Heating (thermal + heating)
Selected AbstractsClosure of the Greater Saphenous Vein with Endoluminal Radiofrequency Thermal Heating of the Vein Wall in Combination with Ambulatory Phlebectomy: Preliminary 6-Month Follow-upDERMATOLOGIC SURGERY, Issue 5 2000Mitchel P. Goldman MD Background. Incompetence of the saphenofemoral junction with reflux into the greater saphenous vein is one cause of chronic venous hypertension which may lead to the development of varicose and telangiectatic leg veins. Therefore treatment is necessary. Objective. To evaluate a novel method for closing the incompetent greater saphenous vein at its junction with the femoral vein through an endoluminal approach. Methods. Ten patients with reflux at the saphenofemoral junction into the greater saphenous vein were treated with radiofrequency heating of the vein wall through an endoluminal catheter. Patients were evaluated at 3 and 6 months to determine treatment efficacy as well as adverse sequelae. Results. All treated patients achieved complete closure of the saphenofemoral junction and greater saphenous vein. Complete treatment took an average of 20 minutes. Adverse sequelae were minimal, with 2 of 12 patients having mild erythema for 2,3 days. Conclusion. Endoluminal radiofrequency thermal heating of an incompetent greater saphenous vein has been shown to be easily accomplished and efficacious throughout the 6-month follow-up period. [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] Effect of phase change material on passive thermal heating of a greenhouseINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2006Nisha Kumari Abstract In this study, a periodic analysis of a greenhouse with combination of phase change material (PCM) and insulation as a north wall has been developed for thermal heating. The thermal model is based on Fourier analysis. Effect of distribution of PCM thickness on plant and room air temperature has been studied in detail. The plant and room air temperature have been evaluated with and without north wall. Numerical computations have been carried out for a typical winter day of New Delhi. On the basis of numerical results, it is inferred that (i) there is a significant effect of PCM north wall and heat capacity of plant temperature during off-sunshine hour due to storage effect and (ii) the rate of heat flux inside greenhouse from north wall is maximum for least thickness of PCM. Copyright © 2005 John Wiley & Sons, Ltd. [source] Transformations of phenylhydrazones of 5-acyl-1,2,4-triazines to pyrazolo[4,3- e][1,2,4]triazines or 4-cyanopyrazole,JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2007Mariusz Mojzych A simple and high yielding preparation of pyrazolo[4,3- e][1,2,4]triazines and 4-cyano-3-methyl-1-phenylpyrazole derivatives from corresponding phenylhydrazones of 5-acyl-1,2,4-triazines by melt under acidic medium and by thermal heating, respectively. [source] Microwave-Accelerated Polymerization of 2-Phenoxymethyl-1,4,6-trioxaspiro[4,4]nonane with Diglycidyl Ether of Bisphenol AMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 18 2007Judit Canadell Abstract The cationic copolymerization of 2-phenoxymethyl-1,4,6-trioxaspiro[4,4]nonane with DGEBA under microwave irradiation using ytterbium and lanthanum triflates as initiators is described. A comparison with thermal heating showed a great enhancement in the reaction rates and a higher SOE incorporation in the network. The double ring opening of SOE reduces the usual shrinkage of epoxy resins on curing, and it was lower under microwave irradiation. Moreover, the ytterbium triflate initiator lead to a higher incorporation of linear ester moieties in the network than lanthanum triflate. [source] Influence of Microwave Irradiation on the Lipase-Catalyzed Ring-Opening Polymerization of , -CaprolactoneMACROMOLECULAR RAPID COMMUNICATIONS, Issue 9 2006Patrick Kerep Abstract Summary: The microwave (MW)-assisted lipase-catalyzed ring-opening polymerization of , -caprolactone in boiling solvents was investigated for the first time. In case of boiling toluene or benzene the MW-assisted reaction proceeded significantly slower compared to oil bath heating. On the other hand, using boiling diethyl ether as solvent, an increase of the polymerization rate due to MW irradiation was found. Yield, molecular weight measurements, and MALDI-TOF analysis supported the results. Reactivity of the MW-assisted ring-opening polymerization of , -caprolactone compared with conventional thermal heating in different solvents. [source] Removal of N -methylpyrrolidone hydrogen-bonded to polyaniline free-standing films by protonation,deprotonation cycles or thermal heatingPOLYMER INTERNATIONAL, Issue 11 2001Eduardo A Ponzio Abstract Free-standing films of polyaniline (PANI), in an emeraldine base state, prepared by evaporation of polymer solutions in N -methylpyrrolidone (NMP) retain solvent even under dynamic vacuum drying as indicated by transmission Fourier transform infrared (FTIR) spectroscopy, where a band at 1670,cm,1 is clearly observed. Upon protonation,deprotonation cycles in aqueous media the weight of the dry base film decreases indicating gradual loss of NMP. Transmission FTIR spectra shows also the washing out of NMP with a clear decrease in intensity of the hydrogen-bonded >CO stretching band (1670,cm,1) of NMP. During this process the bands between 3500 and 3200,cm,1, assigned to >NH stretching in the PANI backbone, change intensity suggesting that intermolecular hydrogen-bonded >NH, with carbonyl oxygen of NMP, is replaced by free >NH. This is clear evidence of specific interaction of NMP with the emeraldine base. A similar loss of NMP is observed during heating but evidence of polymer degradation is also present. A mechanism is proposed to account for the loss of hydrogen-bonding ability upon protonation which requires delocalization of the radical cations in the protonated films. © 2001 Society of Chemical Industry [source] Microwave-Assisted Cross-Coupling and Hydrogenation Chemistry by Using Heterogeneous Transition-Metal Catalysts: An Evaluation of the Role of Selective Catalyst HeatingCHEMISTRY - A EUROPEAN JOURNAL, Issue 43 2009Muhammed Irfan Abstract The concept of specific microwave effects in solid/liquid catalytic processes resulting from the selective heating of a microwave-absorbing heterogeneous transition-metal catalyst by using 2.45,GHz microwave irradiation was evaluated. As model transformations Ni/C-, Cu/C-, Pd/C-, and Pd/Al2O3 -catalyzed carbon,carbon/carbon,heteroatom cross-couplings and hydrogenation reactions were investigated. To probe the existence of specific microwave effects by means of selective catalyst heating in these transformations, control experiments comparing microwave dielectric heating and conventional thermal heating at the same reaction temperature were performed. Although the supported metal catalysts were experimentally found to be strongly microwave absorbing, for all chemistry examples investigated herein no differences in reaction rate or selectivity between microwave and conventional heating experiments under carefully controlled conditions were observed. This was true also for reactions that use low-absorbing or microwave transparent solvents, and was independent of the microwave absorbtivity of the catalyst support material. In the case of hydrogenation reactions, the stirring speed was found to be a critical factor on the mass transfer between gas and liquid phase, influencing the rate of the hydrogenation in both microwave and conventionally heated experiments. 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