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Transfer Theory (transfer + theory)
Selected AbstractsSituational and Demographic Influences on Transfer System Characteristics in OrganizationsPERFORMANCE IMPROVEMENT QUARTERLY, Issue 3 2006Hsin-Chih Chen Transfer theories, which are closely related to evaluation theory, have been developed from a holistic perspective, but most of empirical transfer research has not effectively utilized holistic models to investigate transfer of learning until the late 1990s. Additionally, little has been done in examining the relationship between situational variables, demographic variables, and transfer system characteristics. This study contributes to transfer research by examining the combined effects of situational and demographic variables on a holistic model of perceived organizational transfer systems. A key finding was that demographic variables make only a marginal contribution to predicting transfer system characteristics when compared to situational variables. It seems clear that the differences in transfer system characteristics depend on diverse situational influences, primarily due to types of training programs and types of organizational cultures. This finding does not support one-size-fits-all transfer interventions. Future research may focus on investigating benchmark transfer practices in certain types of organizations or industries to empirically identify the true leverage points of a diagnosing instrument of transfer,the Learning Transfer System Inventory,for interventions and change. [source] Theoretical design study on multifunctional triphenyl amino-based derivatives for OLEDsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2009Lu-Yi Zou Abstract The use of triphenyl amino-based derivatives in organic light-emitting diodes (OLEDs) can significantly improve their efficiency and stability and especially their electroluminescence characteristics , most of the new hole-transport materials have this feature. In this study, a series of triphenyl amino-based compounds were computed, including two newly designed molecules. They can function as charge transport materials and emitters with high efficiency and stability. To reveal the relationship between the properties and structures of these bifunctional and multifunctional electroluminescent materials, the ground and excited state geometries were optimized at the B3LYP/6-31G(d), HF/6-31G(d), TD-B3LYP/6-31G(d), and CIS/6-31G(d) levels, respectively. The ionization potentials (IPs) and electron affinities (EAs) were computed. The lowest excitation energies, the maximum absorption, and emission wavelengths of these compounds were calculated by employing the time-dependent density functional theory (TD-DFT) method. Also, the mobilities of holes and electrons were studied computationally based on the Marcus electron transfer theory. The CH2Cl2 solvent effect on the absorption spectra of N,N,-di-1-naphthyl- N,N,-diphenylbenzidine (NPB) was considered by polarizable continuum model (PCM). The results obtained for these compounds are in good agreement with the experimental values. These data show that the proposed compounds 1 and 2 (N,B-di-1-naphthyl-N,B-diphenylbenzidine and Mes2N[p-4,4,-biphenyl-NPh(1-naphthyl)]), are multifunctional and bifunctional materials similar to Mes2B[p -4,4,-biphenyl-NPh(1-naphthyl)] (BNPB) and NPB, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] Sequence, Structure and Energy Transfer in DNA,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2007Thomas M. Nordlund Excitation energy transfer in DNA has similarities to charge transfer, but the transport is of an excited state, not of mass or charge. Use of the fluorescent, modified adenine base 2-aminopurine (2AP) as an energy trap in short (3- to 20-base) single- and double-stranded DNA oligomers is reviewed. Variation of 2AP's neighboring sequence shows (1) relatively efficient transfer from adenine compared to that from cytosine and thymine, (2) efficient transfer from guanine, but only when 2AP is at the 3, end, (3) approximate equality of efficiencies for 3, to 5, and 5, to 3, directional transfer in adenine tracks. The overall, average transfer distance at room temperature is about four adenine bases or less before de-excitation. The transfer fluorescence excitation spectral shape is similar to that of the absorption spectrum of the neighboring normal bases, confirming that initial excitation of the normal bases, followed by emission from 2AP (i.e. energy transfer), is occurring. Transfer apparently may take place both along one strand and cross-strand, depending on the oligomer sequence. Efficiency increases when the temperature is decreased, rising above 50% (overall efficiency) in decamers of adenine below ,60°C (frozen media). Modeling of the efficiencies of transfer from the nearest several adenine neighbors of 2AP in these oligomers suggests that the nearest two neighbors transfer with near 100% efficiency. As bases in B DNA, as well as in single-stranded DNA, are separated by less than 5 Å (less than the size of a base), standard Förster transfer theory should not apply. Indeed, while both theory and experiment show efficiency decreasing with donor,acceptor distance, the experimental dependence clearly disagrees with Förster 1/r6 dependence. It is not yet clear what the best theoretical approach is, but any calculation must deal accurately with the excited states of bases, including strong base,base interactions and structural fluctuations, and should reflect the increase of efficiency with temperature decrease and the relative insensitivity to strandedness (single, double). Attempts to use DNA as a molecular "fiber optic" face three primary challenges. First, reasonable efficiency over more than a base or two occurs only in adenine stretches at temperatures well below freezing. Second, transfer in these adenine tracks is efficient in both directions. Third, absorption of UV light occurs randomly, making excitation at a specific site on this "fiber optic" a challenge. [source] Microwave-assisted extraction of total bioactive saponin fraction from Gymnema sylvestre with reference to gymnemagenin: a potential biomarkerPHYTOCHEMICAL ANALYSIS, Issue 6 2009Vivekananda Mandal Abstract Objective , To develop a fast and ecofriendly microwave assisted extraction (MAE) technique for the effective and exhaustive extraction of gymnemagenin as an indicative biomarker for the quality control of Gymnema sylvestre. Methodology , Several extraction parameters such as microwave power, extraction time, solvent composition, pre-leaching time, loading ratio and extraction cycle were studied for the determination of the optimum extraction condition. Scanning electron micrographs were obtained to elucidate the mechanism of extraction Results , The final optimum extraction conditions as obtained from the study were: 40% microwave power, 6,min irradiation time, 85% v/v methanol as the extraction solvent, 15,min pre-leaching time and 25,:,1 (mL/g) as the solvent-to-material loading ratio. The proposed extraction technique produced a maximum yield of 4.3% w/w gymnemagenin in 6,min which was 1.3, 2.5 and 1.95 times more efficient than 6,h of heat reflux, 24,h of maceration and stirring extraction, respectively. A synergistic heat and mass transfer theory was also proposed to support the extraction mechanism Conclusion , Comparison with conventional extraction methods revealed that MAE could save considerable amounts of time and energy, whilst the reduction of volume of organic solvent consumed provides an ecofriendly feature. Copyright © 2009 John Wiley & Sons, Ltd. [source] Study on the Interaction of Ketoconazole with Human and Bovine Serum Albumins by Fluorescence SpectroscopyCHINESE JOURNAL OF CHEMISTRY, Issue 12 2008Qing-Lian GUO Abstract The binding of ketoconazole to human serum albumin and bovine serum albumin was studied by using fluorescence and ultraviolet spectroscopy. The measurements were performed in 0.1 mol·L,1 phosphate buffer solution at pH=7.40±0.1. Decreasing of quenching constant was observed in association with temperature increase. Our findings show that the quenching mechanism of fluorescence of serum albumins by ketoconazole was static quenching because of compound formation. The thermodynamic parameters ,G, ,H, and ,S at different temperatures were calculated, showing that the electrostatic interactions and hydrophobic interaction are the main forces for the binding of ketoconazole to serum albumins. The distance r between the donor (Trp-214) and acceptor (ketoconazole) was obtained according to fluorescence resonance energy transfer theory. [source] | ||||||||||