Search results for "Names"
showing 10 items of 6843 documents
Understanding the domino reactions of alkyne-tethered N-tosylhydrazones yielding fused polycyclic pyrazoles. An MEDT study
2019
Abstract The domino reactions of alkyne-tethered N-mesylhydrazones yielding fused polycyclic pyrazoles have been studied within the Molecular Electron Density Theory (MEDT). Analysis of the Gibbs free energies indicates that the more favourable reactive path is the one in which the elimination of mesylate anion takes place before the intramolecular [3 + 2] cycloaddition (IM32CA) reaction, which corresponds with the rate-determining step of these domino processes. ELF topological analysis of the bond formation along the IM32CA reaction indicates that in spite of the high activation energy associated to this intramolecular reaction, it shows a pmr-type mechanism characterised by the presence …
Tracer diffusion properties of core-shell latex films studied by photoinduced grating relaxation
2007
This article reports the application of the Photo-Induced Grating Relaxation technique (also known as Forced Rayleigh Scattering) to investigate the dynamics of films prepared from structured core–shell latex particles via the transport property of the photochromic tracer molecule Aberchrome 540®. The core–shell particles were prepared with a fluoropolymer core (immiscible and impenetrable to the tracer) and a poly(butyl methacrylate) shell. The incompletely dried films (with residual water) manifest their spatial heterogeneity via non-Fickian behavior (spatial scale- dependent apparent diffusion coefficient). The diffusion data was interpreted using the two-state diffusion model, previousl…
Rapid evaluation of oxidised fatty acid concentration in virgin olive oil using Fourier-transform infrared spectroscopy and multiple linear regression
2011
Abstract Fourier-transform infrared spectroscopy (FTIR), followed by multivariate treatment of spectral data, was used to evaluate the oxidised fatty acid (OFA) concentration in virgin olive oil samples characterised by different oxidative status. The entire FTIR spectra (4000–700 cm−1) of oils were divided in 25 wavelength regions. The normalised absorbances of the peak areas within these regions were used as predictors. In order to predict the OFA concentration, multiple linear regression (MLR) models were performed. After a cube root transformation of data, an MLR model constructed using eight predictors was able to predict OFA concentration with an average error of 17%. The main wavelen…
The chemistry of death--Adipocere degradation in modern graveyards.
2015
The formation of adipocere slows further decomposition and preserves corpses for decades or even centuries. This resistance to degradation is a serious problem, especially with regard to the reuse of graves after regular resting times. We present results from an exhumation series in modern graveyards where coffins from water-saturated earth graves contained adipocere embedded in black humic material after resting times of about 30 years. Based on the assumption that this humic material resulted from in situ degradation of adipocere, its presence contradicts the commonly held opinion that adipocere decomposition only occurs under aerobic conditions. To test our hypothesis, we collected black…
β-Relaxation and low-temperature specific heat in (KBr)1?x(KCN)x
1990
The specific heat in (KBr)1−x(KCN)x has been measured for concentrations 0.00≦x≦0.93 and for temperatures 2 K≦T≦50 K. In addition, the dipolar relaxation phenomena were studied using dielectric spectroscopy. The relaxation behaviour was parametrized assuming a Gaussian distribution of energy barriers and the mean activation energies, the distribution widths, and the attempt frequencies have been determined as a function of the CN− concentration. With these parameters the linear and the excess specific heat contributions were calculated and compared to the calorimetric results.
Disorder Classification of the Vibrational Spectra of Modern Glasses
2021
Using the coherent-potential approximation in heterogeneous-elasticity theory with a log-normal distribution of elastic constants for the description of the Raman spectrum and the temperature dependence of the specifi?c heat, we are able to reconstruct the vibrational density of states and characteristic descriptors of the elastic heterogeneity of a wide range of glassy materials. These descriptors are the non-affi?ne contribution to the shear modulus, the mean-square fluctuation of the local elasticity, and its correlation length. They enable a physical classification scheme for disorder in modern, industrially relevant glass materials. We apply our procedure to a broad range of real-world…
Quantifying the inverse spin-Hall effect in highly doped PEDOT:PSS
2020
The authors provide experimental results that show the onset of the Nernst effect, thermovoltages and an inverse spin-Hall effect in the polymer PEDOT:PSS. Specifically, the observed inverse spin-Hall effect appears to be smaller than other measurements, but in better agreement with theoretical calculations.
Affinity Distributions of a Molecularly Imprinted Polymer Calculated Numerically by the Expectation-Maximization Method
2003
Affinity distributions are calculated from adsorption isotherm data obtained for the enantiomers of L- and D-phenylalanine anilide (PA) on native and thermally annealed polymers molecularly imprinted with L-PA. The calculation is obtained with an iterative algorithm called expectation-maximization that does not require prior fit of the data to an isotherm model before inversion and thus yields a distribution indicative of the data only. The results show bimodal distributions, suggestive of a two-site model describing relatively selective and nonselective adsorption modes of the L-enantiomer and a corresponding unimodal/nonselective adsorption mode for the D-enantiomer. The nonselective adso…
Graphene related magnetic materials: micromechanical exfoliation of 2D layered magnets based on bimetallic anilate complexes with inserted [FeIII(aca…
2015
The syntheses, structures and magnetic properties of the coordination compounds of formula [FeIII(acac2-trien)][MnIICrIII(Cl2 An)3]·(CH3CN)2 (1), [FeIII(acac2-trien)][MnIICrIII(Br2An)3]·(CH3CN)2 (2) and [GaIII(acac2-trien)][MnIICrIII(Br2An)3]·(CH3CN)2 (3) are reported. They exhibit a 2D anionic network formed by Mn(II) and Cr(III) ions linked through anilate ligands, while the [FeIII(acac2-trien)]+ or [GaIII(acac2-trien)]+ charge-compensating cations are placed inside the hexagonal channels of the 2D network, instead of being inserted in the interlamellar spacing. Thus, these crystals are formed by hybrid layers assembled through van der Waals interactions. The magnetic properties indicate …
Spatial scale-dependent tracer diffusion in bulk polycarbonate studied by holographic relaxation.
2005
The diffusion of a photochromic dye tracer in polycarbonate was studied by a holographic relaxation technique (forced Rayleigh scattering) at temperatures close to the glass transition temperature. By varying the holographic grating period the results could be interpreted via the spatial scale dependence of apparent diffusion coefficients within a two-state diffusion model. This indicates inhomogeneities on the scale of a few micrometers in the polymer glass.