Search results for "Valence"
showing 10 items of 2732 documents
Linear and nonlinear optical properties of some organoxenon derivatives
2007
We employ a series of state-of-the-art computational techniques to study the effect of inserting one or more Xe atoms in HC2H and HC4H, on the linear and nonlinear optical (L&NLO) properties of the resulting compounds. It has been found that the inserted Xe has a great effect on the L&NLO properties of the organoxenon derivatives. We analyze the bonding in HXeC2H, and the change of the electronic structure, which is induced by inserting Xe, in order to rationalize the observed extraordinary L&NLO properties. The derivatives, which are of interest in this work, have been synthesized in a Xe matrix. Thus the effect of the local field (LF), due to the Xe environment, on the properties of HXeC2…
Optimal shakedown design of beam structures
1994
The optimal design of plane beam structures made of elastic perfectly plastic material is studied according to the shakedown criterion. The design problem is formulated by means of a statical approach on the grounds of the shakedown lower bound theorem, and by means of a kinematical approach on the grounds of the shakedown upper bound theorem. In both cases two different types of design problems are formulated: one searches for the minimum volume design whose shakedown limit load is assigned; the other searches for the design of the assigned volume whose shakedown limit load is maximum. The optimality conditions of the four problems above are found by the use of a variational approach; such…
Theoretical determination of the geometric and electronic structures of oligorylenes and poli(peri‐naphthalene)
1992
We present a theoretical investigation of the electronic structure of oligorylenes (from perylene to heptarylene, including also the naphthalene molecule) and their corresponding polymer poly(peri‐naphthalene) (PPN) using the nonempirical valence effective (VEH) method. The geometry of the unit cell used to generate the polymer is extrapolated from the PM3‐optimized molecular geometries of the longest oligorylenes. That geometry shows some bond alternation along the perimeter carbon chains and a bond length of ≊1.46 Å is calculated for the peri bonds connecting the naphthalene units. The VEH one‐electron energy level distributions calculated for oligorylenes are used to interpret the experi…
Prevalence of tooth erosion and associated factors in 13-16-year old adolescents in Greece
2012
Objectives: The aim of this study was to estimate the prevalence of dental erosion and to investigate possible associations among dental erosion and medical history, dietary and lifestyle habits in a sample of adolescents in Greece. Study design: The study sample consisted of 770 adolescents, 374 boys and 396 girls aged 13 to 16 years. All individuals were clinically examined and answered questions regarding their medical history, rate and frequency of drinks and food consumption and lifestyle habits. Statistical analysis of the questionnaire items was performed by using the multiple logistic regression analysis model. Results: Two hundreds and sixty adolescents were diagnosed as having den…
Three-Way Interactions Among Interruptions/Multitasking Demands, Occupational Age, and Alertness: A Diary Study
2015
In this study, we examined the within-person relationships between workday “cognitive” stressors (multitasking demands and workflow interruptions) and strain (situational well-being throughout the day and irritation in the evening). We hypothesized that occupational age, in terms of job tenure and an indicator of functional age (alertness), would moderate these relationships in that employees with low experience and low alertness would suffer most from the stressors. We conducted a 5-day diary study in a sample of 123 nurses, with 4 measurements per day (3 taken during the work shift and 1 taken in the evening), and 1 survey (occupational age) and computer-based cognitive performance test b…
Testing invariance between web and paper students satisfaction surveys. A case study
2017
[EN] Purpose: This paper studied the measurement invariance (MI) across web-based and paper-based surveys to evidence if both techniques of data collection can be regarded as equivalent. Design/methodology: We develop a multigroup confirmatory factor analysis (MGCFA) with Maximum Likelihood Estimation to asses measurement invariance of the Job Diagnostic Survey (JDS) adapted to teaching, with data collected from paper and web surveys. Sample from paper surveys was constituted by 294 student of a Spanish public university in the academic years 2007-08, 2008-09 and 2009-10. Internet surveys were administered through an open source survey application called Lime Survey. We received 241 complet…
The Worst Record in Europe?: A Comparative Analysis of Industrial Conflict in Spain
2001
Since the transition to democracy, Spain has recorded the highest strike rate of EU countries. Drawing on a comparison with Franzosi's analysis of strikes in Italy, this article seeks to explain the high number of working days lost in Spain by reference to the role of sectoral bargaining, the instability of corporatist relations, solidaristic features of worker representation and Spanish society, and the development of industrial action by unions outside the main confederations. It is suggested that the pattern of industrial conflict reflects the limited strategic options available to Spanish trade unions and Spanish employers' ambivalence toward industrial relations institutions. The arti…
New light on an old debate: Does the RCN-PtCl2 bond include any back-donation? RCN←PtCl2 backbonding: Vs. the IR ν CN blue-shift dichotomy in organon…
2019
For a series of organonitrile [RCN (R = Me, CF3, Ph, CH3Ph, CF3Ph)] ligands, the nature of the N-Pt bond in the related cis-/trans-(RCN)2PtCl2 complexes has been computationally investigated by Density Functional Theory. A fragment based bond analysis has been performed in the canonical Kohn-Sham molecular orbitals framework, and it has been ultimately assessed that this bond is characterized both by N→Pt σ and by N←Pt π contributions. Voronoi Deformation Density charges further confirms the occurrence of N←Pt π interactions. Moreover, the Energy Decomposition Analysis-Natural Orbital for Chemical Valence (EDA-NOCV) method shows that the strength of the N←Pt π interaction is not negligible …
Prevalence of elongation and calcification patterns of elongated styloid process in south india
2012
Objective: Very few studies have been reported in the literature classifying the elongation and calcification patterns of styloid process. The present study was done to investigate the prevalence of elongation and calcification patterns of styloid process in patients attending a dental institution in south India. Study design: 600 digital panoramic radiographs of patients with dental problems were obtained from the outpatient department of the Dental institution. The apparent length of the styloid process was measured by a single experienced oral radiologist, with the help of the measuring tools on the accompanying software. The type of elongation and calcification patterns of each elongate…
Lower Rydberg series of methane: a combined coupled cluster linear response and molecular quantum defect orbital calculation.
2006
Vertical excitation energies as well as related absolute photoabsorption oscillator strength data are very scarce in the literature for methane. In this study, we have characterized the three existing series of low-lying Rydberg states of CH4 by computing coupled cluster linear response (CCLR) vertical excitation energies together with oscillator strengths in the molecular-adapted quantum defect orbital formalism from a distorted Cs geometry selected on the basis of outer valence green function calculations. The present work provides a wide range of data of excitation energies and absolute oscillator strengths which correspond to the Rydberg series converging to the three lower ionization p…