Search results for " ATO"
showing 10 items of 1592 documents
Effect of electron-withdrawing substituents on the electrophilicity of carbonyl carbons
2005
Indexación: Scopus The substituent effects on the carbonyl carbon atom for a series of twelve substituted phenyl acetates have been rationalized using a global electrophilicity index. This index is linearly correlated with the experimental reaction rate coefficients. We found that, in contrast to the proposed interpretation based on experimental 13C NMR chemical shifts and ground state destabilization calculations, the electrophilicity of carbonyl compounds increases due to the effect promoted by electron-withdrawing groups in these systems. https://www.sciencedirect.com/science/article/pii/S0040402004018046?via%3Dihub
Stanislao Cannizzaro and the Development of Chemistry in Palermo from 1862 to 1871
2009
Stanislao Cannizzaro worked at Palermo University for about ten years. There he managed to establish a modern and well-equipped chemical laboratory. His international fame attracted co-workers even from abroad: Naquet, Lieben, and Körner came to Palermo to work with him. This greatly improved the quality of teaching and of research in Palermo, which became a worldwide acknowledged center of chemical culture. In Palermo, atomic-molecular theory was extensively taught and research was carried out on chemical atomicity (valence) and spatial structures of both aliphatic and aromatic organic molecules: Körner found the relative positions of substituent groups on the benzene ring, Paternò proved …
Calix[4]arenes with alkylidene bridges, synthesis and conformational properties
1994
Abstract Calix[4]arenes with one or two alkylidene bridges were synthesized by “2+2” fragment condensation. As predicted by molecular mechanics calculations aliphatic residues at the bridging carbon atom(s) prefer the equatorial position.
MTA HP Repair stimulates in vitro an homogeneous calcium phosphate phase coating deposition
2019
Background To study the mineralization capacity in vitro of the bioceramic endodontic material MTA HP Repair. Material and methods Bioactivity evaluation in vitro was carried out, by soaking processed cement disk in simulated body fluid (SBF) during 168 h. The cement surface was studied by Fourier transform infrared spectroscopy (FT-IR), field emission gun scanning electron microscopy (FEG-SEM) and energy dispersive X-ray analysis (EDX). Release to the SBF media of ionic degradation products was monitored using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Results FT-IR showed increasing formation of phosphate phase bands at 1097, 960, 607 and 570 cm-1 with prolonged SB…
Nanoscale Chemical Interaction Enhances the Physical Properties of Bioglass Composites
2013
Bioglasses are favorable biomaterials for bone tissue engineering; however, their applications are limited due to their brittleness. In addition, the early failure in the interface is a common problem of composites of bioglass and a polymer with high mechanical strength. This effect is due to the phase separation, nonhomogeneous mixture, nonuniform mechanical strength, and different degradation properties of two compounds. To address these issues, in this study a nanoscale interaction between poly(methyl methacrylate) (PMMA) and bioactive glass was formed via silane coupling agent (3-trimethoxysilyl)propyl methacrylate (MPMA). A monolith was produced at optimum composition from this hybrid …
Validated fast procedure for trace element determination in basil powder
2011
Abstract An inductively coupled plasma optical emission spectroscopic (ICP-OES) method has been developed and fully validated for trace element determination in basil samples. The method involves the previous sample digestion, under pressure, with a mixture of HNO 3 , HCl and H 2 O 2 inside a microwave oven, 42 elements were studied and 33 elements (Al, As, Ba, Ca, Cr, Co, Cu, Fe, Pb, Li, Mg, Mn, Mo, Ni, K, Se, Na, Sr, Tl, Ti, V, Zn, Sc, Y, La, Ce, Nd, Tb, Ho, Er, Tm, Yb, Lu) were determined quantitatively in basil leaves obtained from Morocco and Spain. The method provided recovery percentages from 89% to 113% for spiked concentrations at mg kg −1 and μg kg −1 . Accurate results were found…
Plasmonic Resonant Nanoantennas Induce Changes in the Shape and the Intensity of Infrared Spectra of Phospholipids.
2021
Surface enhanced infrared absorption spectroscopic studies (SEIRAS) as a technique to study biological molecules in extremely low concentrations is greatly evolving. In order to use the technique for identification of the structure and interactions of such biological molecules, it is necessary to identify the effects of the plasmonic electric-field enhancement on the spectral signature. In this study the spectral properties of 1,2-Dipalmitoyl-sn-glycero-3 phosphothioethanol (DPPTE) phospholipid immobilized on gold nanoantennas, specifically designed to enhance the vibrational fingerprints of lipid molecules were studied. An AFM study demonstrates an organization of the DPPTE phospholipid in…
Fourier transform spectroscopy and coupled-channel deperturbation treatment of the A1Sigma+ ~ b3Pi complex of KCs molecule
2009
The laser induced fluorescence (LIF) spectra A1Sigma ~ b3Pi --> X1Sigma+ of KCs dimer were recorded in near infrared region by Fourier Transform Spectrometer with a resolution of 0.03 cm-1. Overall more than 200 LIF spectra were rotationally assigned to 39K133Cs and 41K133Cs isotopomers yielding with the uncertainty of 0.003-0.01 cm-1 more than 3400 rovibronic term values of the strongly mixed singlet A1Sigma+ and triplet b3Pi states. Experimental data massive starts from the lowest vibrational level v_A=0 of the singlet and nonuniformly cover the energy range from 10040 to 13250 cm-1 with rotational quantum numbers J from 7 to 225. Besides of the dominating regular A1Sigma+ ~ b3P Omega=…
On Oscillation Theorem for Two-Component Schrodinger Equation
2009
Conventional one-dimensional oscillation theorem is found to be violated for multi-component Schr\"{o}dinger equations in a general case while for two-component eigenstates coupled by the sign-constant potential operator the following statements are valid: (1) the ground state ($v = 0$) is not degenerate; and (2) the arithmetic mean of nodes $n_1$, $n_2$ for the two-component wavefunction never exceeds the ordering number $v$ of eigenstate: $(n_1 + n_2)/2\leq v$.
Setting the photoelectron clock through molecular alignment
2020
The interaction of strong laser fields with matter intrinsically provides a powerful tool for imaging transient dynamics with an extremely high spatiotemporal resolution. Here, we study strong-field ionisation of laser-aligned molecules, and show a full real-time picture of the photoelectron dynamics in the combined action of the laser field and the molecular interaction. We demonstrate that the molecule has a dramatic impact on the overall strong-field dynamics: it sets the clock for the emission of electrons with a given rescattering kinetic energy. This result represents a benchmark for the seminal statements of molecular-frame strong-field physics and has strong impact on the interpreta…