Search results for "absorption."
showing 10 items of 2682 documents
Hexasubstituted Benzenes with Ultrastrong Dipole Moments
2015
Hexasubstituted benzenes have been synthesized with the highest known dipole moments, as determined by dielectric spectroscopy and DFT methods. Based on the preparation of 4,5-diamino-3,6-dibromophthalonitrile, combined with a novel method to synthesize dihydrobenzimidazoles, these benzene derivatives have dipole moments in excess of 10 debye. Such dipole moments are desirable in ferroelectrics, nonlinear optics, and in organic photovoltaics. Structure determination was achieved through single-crystal X-ray crystallography, and the optical properties were determined by UV/Vis absorption and fluorescence spectroscopy.
Utrecht Work Engagement Scale in Dominican Teachers: Dimensionality, Reliability, and Validity
2018
Work engagement is described by dedication, vigor, and absorption. The most widely used measure of engagement is the Utrecht Work Engagement Scale (UWES), intended to measure engagement for any occupational group. This research aims to study psychometric properties of the UWES for its use in the Dominican Republic and other Caribbean Spanish-speaking countries. The Composite Reliability Index (CRI) as well as alphas were calculated, indicating good internal consistency. Confirmatory factor analyses were carried out to test its dimensionality. Both tested models showed extremely good fit to the data, which called for model comparison. The three-factor solution was retained as the one showing…
The role of partners for employees' recovery during the weekend
2012
Abstract We examined the effects of positive and negative experiences with the partner (absorption in joint activities and conflict with the partner) during the weekend on affective states at the beginning of the following work week and tested whether recovery experiences (psychological detachment, relaxation, and mastery experiences) mediated these effects. In total, 269 university faculty members completed online surveys before and after the weekend. Hierarchical regression analyses revealed that absorption in joint activities with the partner predicted recovery experiences during the weekend and increased positive affective states (vigor, joviality, serenity) at the beginning of the foll…
Effect of cusp coverage and water storage on compressive strength of composite restorations of premolars
2018
Background The aim of this study was to assess the effect of cusp coverage and water storage on compressive strength of composite restorations. Material and Methods This in vitro experimental study was conducted on 40 extracted human maxillary premolar teeth, which were randomly divided into four groups of 10. Mesio-occluso-distal (MOD) cavities were prepared in all teeth. The thickness of composite for cusp coverage was 1.5 mm in groups 1 and 3 and 2.5 mm in groups 2 and 4. Compressive strength (CS) was measured after 24 hours in groups 1 and 2 and after six months of water storage in groups 3 and 4. Two-way ANOVA was used to statistically analyze the data. Results The mean and standard er…
On the hexagonal ice-like model of structured water: Theoretical analysis of the low-lying excited states
2014
Abstract The basic molecular unit ( BMU ) of the hexameric ice-like model has been identified as the negatively charged radical species [H 19 O 10 ] − . On the basis of high-level ab initio computations, by means of using the CASPT2 methodology, the low-lying excited states of BMU and its π-stacked dimer are analysed. It is concluded that the BMU constitutes certainly a versatile unit having two spectroscopic features in the near infrared region, two in the visible range and two in the near ultraviolet zone. The main absorption feature is found however for the π-stacked dimer formed by two BMUs , the H 38 O 20 system, which has a pronounced stabilization in the ground state with respect to …
Iontophoretic Transdermal Delivery of Sumatriptan: Effect of Current Density and Ionic Strength
2005
ABSTRACT: Iontophoretic transdermal delivery of sumatriptan was investigated in vitro . Among the conditions tested, 0.25 mA/cm 2 and low ionic strength (NaCl 25 mM) was the best experimental condition to increase its transport across the skin. The flux increased 385-fold respective to passive diffusion, thus resulting in a transdermal flux of sumatriptan of 1273 ± 83 nmol/cm 2 h. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association
OH/OD-IR absorption bands in SrxBa1−xNb2O6
1995
Single crystals of Sr x Ba 1−x Nb 2 O 6 (SBN) with congruent composition (x = 0.61) and Sr 0.61 Ba 0.39 Nb 2 O 6 crystals doped with various concentrations of cerium are grown with the Czochralski method. A subsequent doping of the crystals with protons and deuterons is performed either by hydrothermal high temperature treatment or by field supported hydrogen diffusion at elevated temperatures in humid atmosphere. The presence of the protons is revealed by the infrared absorption of the OH stretching vibration. This broad OH absorption band is essentially the same for Sr 0.61 Ba 0.39 Nb 2 O 6 and Sr 0.61 Ba 0.39 Nb 2 O 6 :Ce (0.025 wt% CeO 2 ). It shows a polarization dependence with respec…
Oxidative C-N fusion of pyridinyl-substituted porphyrins.
2018
International audience; The mild (electro) chemical oxidation of pyridin-2-ylthio-meso substituted Ni(II) porphyrins affords C-N fused cationic and dicationic pyridinium-based derivatives. These porphyrins are fully characterized and the molecular structure of one of them was confirmed by X-ray crystallography. A mechanism for the intramolecular oxidative C-N coupling is proposed based on theoretical calculations and cyclic voltammetry analyses.
Measurements of total ozone amount over Badajoz (Southwestern Spain) by means of a GUV multiband radiometer
2012
This paper presents the first measurements of total ozone amount performed at the radiometric station of Badajoz (Spain) by means of a multichannel radiometer GUV-2511. The retrieval of total ozone amount from GUV measurements of solar ultraviolet irradiance is performed with the support of look-up tables calculated using the SBDART radiation transfer code. This methodology is based on the different absorption by ozone suffered by the radiation at two certain near wavelengths. In this case the pair 305, 340 nm was chosen because of its better performance than the pair 305, 320 nm. The look-up table contains the ratio between irradiances at the mentioned wavelengths calculated under differen…
Stoichiometry-related Auger lineshapes in titanium oxides: Influence of valence-band profile and of Coster-Kronig processes
2004
International audience; The ability to determine the nature and the occurrence of defects is a central need of ceramic surface chemistry. In titanium oxides, the Ti-LMV Auger decays line shape is very sensitive to the titanium degree of oxidation, and has long been empirically used as a qualitative probe of the stoichiometry. In the present work, resonant Auger and resonant valence-band measurements at the Ti-L2,3 edges in TiO2, TiO2–x and metallic titanium provide a clear evidence that the evolutions of the Ti-LMV Auger line shape are due to drastic changes in the valence-band profile and in the probability of L2L3V Coster-Kronig decay processes when a fraction of titanium ions is reduced.…