Home About us Contact
|
Home About us Contact | ||
|
|
||
Easy Determination (easy + determination)
Selected AbstractsEigenvalue analysis of temperature distribution in composite wallsINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 13 2001Galip Oturanç Abstract The transient heat conduction problem in two-layer composite wall is solved analytically using spectral analysis. Eigenvalues and corresponding eigenfunctions of the spectral problem for the temperature distribution in composite walls are analysed using the Rouche Theorem. The number of eigenvalues is obtained and the temperature distribution of this complicated problem is given by a formula with calculated eigenvalues. The analytical solution obtained is in explicit form and provides easy determination of temperature rise in heating and thawing applications of composite materials. Copyright © 2001 John Wiley & Sons, Ltd. [source] 1H and 13C NMR study of a series of C-9-substituted 19-norsteroidsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2002Laurence Dallery Abstract The 1H and 13C NMR spectra of a series of 9-substituted 19-norsteroids were completely assigned using a series of 2D NMR experiments, which included 1H,1H COSY, NOESY and 1H,13C heteronuclear HETCOR and HMQC. For second-order spin systems, chemical shifts and coupling constants were obtained by simulation of the experimental spectrum. Criteria were deduced to characterize the stereochemistry of these different compounds (multiplet pattern of H-8, and variation of chemical shifts). The results allow the easy determination of the configuration at C-9. Conformational changes resulting from the substitution were studied by NMR and molecular modeling calculations (AM1). Copyright © 2001 John Wiley & Sons, Ltd. [source] Evaluation of lignans and free and linked hydroxy-tyrosol and tyrosol in extra virgin olive oil after hydrolysis processesJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 5 2006Nadia Mulinacci Abstract We describe chemical hydrolytic procedures to evaluate the total amount of tyrosol and hydroxy-tyrosol free and/or linked to secoiridoidic molecules (acid hydrolysis). At the same time a rapid determination of the lignans in complex minor polar compound (MPC) extracts is proposed (alkaline hydrolysis). High-performance liquid chromatography/diode array detection (HPLC/DAD) and HPLC/MS were applied as reference methods to evaluate the quantitative results from the hydrolysis experiments. The optimized acid hydrolysis procedures were first applied to an oleuropein standard and then to MPC fractions extracted from several commercial extra virgin olive oils. The results confirm the applicability of the method, consisting in the acid hydrolysis of complex mixtures of secoiridoidic derivatives, to determine the antioxidant potential in terms of MPC. These data can contribute to forecasting the potential ageing resistance of an extra virgin olive oil in terms of antioxidant potency. Finally, alkaline hydrolysis allows confirmation and easy determination of the amount of lignans, especially in those MPC fractions which are particularly complex. Copyright © 2006 Society of Chemical Industry [source] Measurement of the sign and the magnitude of heteronuclear coupling constants from spin-state-edited J -cross-polarization NMR experimentsMAGNETIC RESONANCE IN CHEMISTRY, Issue 10 2004Teodor Parella Abstract New spin-state-selective (S3) NMR pulse sequences exclusively applying cross-polarization schemes to achieve optimum homonuclear and heteronuclear 1HX coherence transfer are reported for the simple and accurate measurement of the magnitude and sign of heteronuclear coupling constants for samples at natural abundance. The proposed spin-edited HCP-TOCSY experiments are based on clean heteronuclear S3 excitation, generated by simultaneous co-addition of two independent in-phase and anti-phase components created during the mixing heteronuclear J -cross-polarization (HCP) step, which is finally transferred to other protons by a conventional homonuclear TOCSY mechanism. Selective 1D and non-selective 2D approaches for the easy determination of long-range proton,carbon and proton,nitrogen coupling constants on any protonated and non-protonated heteronuclei are presented and discussed for several organic molecules. Copyright © 2004 John Wiley & Sons, Ltd. [source] Optimised Plasma Absorption Probe for the Electron Density Determination in Reactive PlasmasPLASMA PROCESSES AND POLYMERS, Issue 1 2009Christian Scharwitz Abstract The plasma absorption probe (PAP) is a recently developed tool for the efficient determination of electron densities, especially in reactive plasmas. A dielectric cover protects this probe against the influences in reactive plasmas and it withstands conditions where Langmuir probes are easily damageable. The lack of adequate calibration constants and the occurrence of multiple absorption signals were two major drawbacks, which are successfully overcome in this work. Design variations are tested by numerical computation and the model-based achievements are established in experiment. In this work, a redesigned PAP is presented, which is optimised for the easy determination of electron densities. The developed tool works fast and efficiently, in particular in discharges in reactive gases. [source] | ||||||||||