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Corresponding Experimental Data (corresponding + experimental_data)
Selected AbstractsNumerical simulation of DNA sample preconcentration in microdevice electrophoresisELECTROPHORESIS, Issue 6 2005Alok Srivastava Abstract A numerical model is presented for the accurate and efficient prediction of preconcentration and transport of DNA during sample introduction and injection in microcapillary electrophoresis. The model incorporates conservation laws for the different buffer ions, salt ions, and DNA sample, coupled through a Gaussian electric field to account for the field modifications that cause electromigration. The accuracy and efficiency required to capture the physics associated with such a complex transient problem are realized by the use of the finite element-flux corrected transport (FE-FCT) algorithm in two dimensions. The model has been employed for the prediction of DNA sample preconcentration and transport during electrophoresis in a double-T injector microdevice. To test its validity, the numerical results have been compared with the corresponding experimental data under similar conditions, and excellent agreement has been found. Finally, detailed results from a simulation of DNA sample preconcentration in electrophoretic microdevices are presented using as parameters the electric field strength and the other species concentrations. The effect of the Tris concentration on sample stacking is also investigated. These results demonstrate the great potential offered by the model for future optimization of such microchip devices with respect to significantly enhanced speed and resolution of sample separation. [source] Estimation of elongational viscosity of polymers from entrance loss data using individual parameter optimizationADVANCES IN POLYMER TECHNOLOGY, Issue 2 2002Mahesh Gupta The elongational viscosity model proposed by Sarkar and Gupta (Journal of Reinforced Plastics and Composites 2001, 20, 1473), along with the Carreau model for shear viscosity is used for a finite element simulation of the flow in a capillary rheometer. The entrance pressure loss predicted by the finite element flow simulation is matched with the corresponding experimental data to predict the parameters in the elongational viscosity model. To improve the computational efficiency, various elongational viscosity parameters are optimized individually. Estimated elongational viscosity for a Low Density Polyethylene (Dow 132i) is reported for two different temperatures. © 2002 Wiley Periodicals, Inc. Adv Polym Techn 21: 98,107, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/adv.10017 [source] Accurate evaluation of the absorption maxima of retinal proteins based on a hybrid QM/MM methodJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 14 2006Azuma Matsuura Abstract Here we improved our hybrid QM/MM methodology (Houjou et al. J Phys Chem B 2001, 105, 867) for evaluating the absorption maxima of photoreceptor proteins. The renewed method was applied to evaluation of the absorption maxima of several retinal proteins and photoactive yellow protein. The calculated absorption maxima were in good agreement with the corresponding experimental data with a computational error of <10 nm. In addition, our calculations reproduced the experimental gas-phase absorption maxima of model chromophores (protonated all-trans retinal Schiff base and deprotonated thiophenyl- p -coumarate) with the same accuracy. It is expected that our methodology allows for definitive interpretation of the spectral tuning mechanism of retinal proteins. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2006 [source] TDDFT investigation on nucleic acid bases: Comparison with experiments and standard approachJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2004M.K. Shukla Abstract A comprehensive theoretical study of electronic transitions of canonical nucleic acid bases, namely guanine, adenine, cytosine, uracil, and thymine, was performed. Ground state geometries were optimized at the MP2/6-311G(d,p) level. The nature of respective potential energy surfaces was determined using the harmonic vibrational frequency analysis. The MP2 optimized geometries were used to compute electronic vertical singlet transition energies at the time-dependent density functional theory (TDDFT) level using the B3LYP functional. The 6-311++G(d,p), 6-311(2+,2+)G(d,p), 6-311(3+,3+)G(df,pd), and 6-311(5+,5+)G(df,pd) basis sets were used for the transition energy calculations. Computed transition energies were found in good agreement with the corresponding experimental data. However, in higher transitions, the Rydberg contaminations were also obtained. The existence of ,,* type Rydberg transition was found near the lowest singlet ,,* state of all bases, which may be responsible for the ultrafast deactivation process in nucleic acid bases. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 768,778, 2004 [source] Numerical and experimental investigation of shrinkage behavior of precision injection molded articles.POLYMER ENGINEERING & SCIENCE, Issue 8 2008In the accompanying paper, Part I, presented are the physical modeling and numerical formulation of new lateral motion modelings. In Part II, new models developed in Part I are validated by the successful comparison of calculated residual stress profile with the literature data. The predicted results of the birefringence, residual stress distribution, and shrinkage from new lateral motion modeling are in better agreement with corresponding experimental data than those from the conventional ones. The new model prediction falls between those of two extreme cases corresponding to conventional models. As a result of extensive parametric study of processing conditions, the developed analysis system is found to be capable of successfully predicting the tendency of shrinkage behavior varying with most of processing conditions. In this regard, the new model enables better analysis based design and optimization of precision injection-molded products. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Elongational viscosity of LDPEs and polystyrenes using entrance loss dataPOLYMER ENGINEERING & SCIENCE, Issue 2 2008K. Walczak For two low-density polyethylenes and two polystyrenes, axisymmetric and planar elongational viscosities are estimated using entrance loss data from capillary and slit rheometers, respectively. The elongational viscosity is estimated by optimizing the values of various parameters in the Sarkar,Gupta elongational viscosity model such that the entrance loss predicted by a finite element simulation agrees with the corresponding experimental data. The predicted entrance loss is in good agreement with the experimental data at high flow rates. The difference in the experimental and predicted entrance loss at lower flow rates might have been caused by large error in the experimental data in this range. POLYM. ENG. SCI., 2008. © 2007 Society of Plastics Engineers [source] A comprehensive experimental study and numerical modeling of parison formation in extrusion blow molding,POLYMER ENGINEERING & SCIENCE, Issue 1 2007Azizeh-Mitra Yousefi Parison dimensions in extrusion blow molding are affected by two phenomena, swell due to stress relaxation and sag drawdown due to gravity. It is well established that the parison swell and sag are strongly dependent on the die geometry and the operating conditions. The availability of a modeling technique ensures a more accurate prediction of the entire blow molding process, as the proper prediction of the parison formation is the input for the remaining process phases. This study considers both the simulated and the experimental effects of the die geometry, the operating conditions, and the resin properties on the parison dimensions using high density polyethylene. Parison programming with a moving mandrel and the flow rate evolution in intermittent extrusion are also considered. The parison dimensions are measured experimentally by using the pinch-off mold technique on two industrial scale machines. The finite element software BlowParison® developed at IMI is used to predict the parison formation, taking into account the swell, sag, and nonisothermal effects. The comparison between the predicted parison/part dimensions and the corresponding experimental data demonstrates the efficiency of numerical tools in the prediction of the final part thickness and weight distributions. POLYM. ENG. SCI., 47:1,13, 2007. © 2006 Society of Plastics Engineers [source] | ||||||||||