Electron-vibration coupling constants in positively charged fullerene

Recent experiments have shown that C60 can be positively field-doped. In that state, fullerene exhibits a higher resistivity and a higher superconducting temperature than the corresponding negatively doped state. A strong intramolecular hole-phonon coupling, connected with the Jahn-Teller effect of the isolated positive ion, is expected to be important for both properties, but the actual coupling strengths are so far unknown. Based on density functional calculations, we determine the linear couplings of the two a_g, six g_g, and eight h_g vibrational modes to the H_u HOMO level of the C60 molecule. The couplings predict a D_5 distortion, and an H_u vibronic ground state for C60^+. They are also used to generate the dimensionless coupling constant which controls the superconductivity and the phonon contribution to the electrical resistivity in the crystalline phase. We find that is 1.4 times larger in positively-charged C60 than in the negatively-doped case. These results are discussed in the context of the available transport data and superconducting temperatures. The role of higher orbital degeneracy in superconductivity is also addressed.Comment: 22 pages - 3 figures. This revision includes few punctuation corrections from proofreadin

One perception, two perspectives: measuring psychological contract dimensionality through the Psychological Contract Content Questionnaire

The present study aims to contribute to the validity strengthening of a psychological contract measure, assessing the dimensionality of the item structure of the Psychological Contract Content Questionnaire (PCCQ). According to the authors (De Vos, Buyens, & Schalk, 2003), the scale consists of two theoretical dimensions, one to measure perceived employer inducement (PEI) and the other to measure perceived employee contributions (PEC), both from the employee's perception, each divided into five content areas. Different structure models were tested in newcomers (police officers working in the Penitentiary Administration attending a one-year training) in two different stages of their entry: at their early entrance (three weeks, TI; 436 respondents) and after their encounter with the operative environment (eight months, T2; 519 respondents). Analyses were carried out using nonparametric item response theory (IRT) approach and multidimensional IRT approach. Results showed that psychological contract is a single latent construct that describes the general perception that the employee has about his/her relationship with the organization and reciprocal obligations fulfilment

An Opportunity to Grow or a Label? Performance Appraisal Justice and Performance Appraisal Satisfaction to Increase Teachers\u2019 Well-Being

Performance management is a key factor to enhance professional development and improve teaching quality. This process is successful only if teachers perceive it as fair, clear, and effective: namely, if it is satisfying. Carefully considering teachers\u2019 attributions in the performance appraisal process is fundamental to better clarify the relations between performance management and positive individual outcomes. Therefore, this study aims to investigate the effects of perceived performance appraisal justice on teachers\u2019 well-being, in terms of job performance, job satisfaction, and life satisfaction, hypothesizing the mediation role of performance appraisal satisfaction. Data from a sample of Italian teachers were analyzed through structural equation modeling. Results confirm the mediation role of performance appraisal satisfaction. In particular, perceived performance appraisal justice was positively associated to performance appraisal satisfaction, which, in turn, was positively associated with job performance, job satisfaction, life satisfaction. Consequently, performance appraisal satisfaction totally mediated the relations between performance appraisal justice and the outcomes considered. Findings are relevant for two reasons. First, they contribute to better understanding the performance management process in educational settings \u2013 an issue requiring further attention. Second, they contribute to highlighting the importance of performance management efficacy, which is essential not only to improve individual well-being but also to enhance teaching quality

Is workaholism associated with inflammatory response? The moderating role of work engagement

The aim of this study was to investigate the association between two different forms of heavy work investment, namely workaholism and work engagement, and serum levels of the proinflammatory cytokine interleukin-17 (IL-17), a possible biomarker of stress. Given the different motivational underpinnings and outcomes of workaholism and work engagement and drawing on the allostatic load and the effort-recovery models, we hypothesized that workaholism is positively associated with IL-17, and that work engagement buffers this association. Workers in an Italian healthcare organization (88 females and 31 males) completed a self-report questionnaire, and then underwent blood sample collection. Data were analysed using moderated multiple regression. Results showed that workaholism was positively associated with IL-17, controlling for the effect of gender, age, and body mass index. Work engagement buffered this association, which was nonsignificant when work engagement was high. To reduce the risk of future health complaints, interventions should be aimed at preventing workaholism and promoting work engagement

First-principles study of lattice instabilities in the ferromagnetic martensite Ni2_2MnGa

The phonon dispersion relations and elastic constants for ferromagnetic Ni$_2$MnGa in the cubic and tetragonally distorted Heusler structures are computed using density-functional and density-functional perturbation theory within the spin-polarized generalized-gradient approximation. For $0.9<c/a<1.06$, the TA$_2$ tranverse acoustic branch along $[110]$ and symmetry-related directions displays a dynamical instability at a wavevector that depends on $c/a$. Through examination of the Fermi-surface nesting and electron-phonon coupling, this is identified as a Kohn anomaly. In the parent cubic phase the computed tetragonal shear elastic constant, C$^\prime$=(C$_{11}-$C$_{12}$)/2, is close to zero, indicating a marginal elastic instability towards a uniform tetragonal distortion. We conclude that the cubic Heusler structure is unstable against a family of energy-lowering distortions produced by the coupling between a uniform tetragonal distortion and the corresponding $[110]$ modulation. The computed relation between the $c/a$ ratio and the modulation wavevector is in excellent agreement with structural data on the premartensitic ($c/a$ = 1) and martensitic ($c/a$ = 0.94) phases of Ni$_2$MnGa.Comment: submitted to Phys. Rev.

Relationship between work rate and oxygen uptake in mitochondrial myopathy during ramp-incremental exercise

We determined the response characteristics and functional correlates of the dynamic relationship between the rate (&#916;) of oxygen consumption ( O2) and the applied power output (work rate = WR) during ramp-incremental exercise in patients with mitochondrial myopathy (MM). Fourteen patients (7 males, age 35.4 ± 10.8 years) with biopsy-proven MM and 10 sedentary controls (6 males, age 29.0 ± 7.8 years) took a ramp-incremental cycle ergometer test for the determination of the O2 on-exercise mean response time (MRT) and the gas exchange threshold (GET). The &#916;O2/&#916;WR slope was calculated up to GET (S1), above GET (S2) and over the entire linear portion of the response (S T). Knee muscle endurance was measured by isokinetic dynamometry. As expected, peak O2 and muscle performance were lower in patients than controls (P O2/&#916;WR than controls, especially the S2 component (6.8 ± 1.5 vs 10.3 ± 0.6 mL·min-1·W-1, respectively; P O2/&#916;WR (S T) and muscle endurance, MRT-O2, GET and peak O2 in MM patients (P O2/&#916;WR below 8 mL·min-1·W-1 had severely reduced peak O2 values (O2) had lower &#916;O2/&#916;WR (P O2/&#916;WR) is typically reduced in patients with MM, being related to increased functional impairment and higher cardiopulmonary stress

The OPERA magnetic spectrometer

The OPERA neutrino oscillation experiment foresees the construction of two magnetized iron spectrometers located after the lead-nuclear emulsion targets. The magnet is made up of two vertical walls of rectangular cross section connected by return yokes. The particle trajectories are measured by high precision drift tubes located before and after the arms of the magnet. Moreover, the magnet steel is instrumented with Resistive Plate Chambers that ease pattern recognition and allow a calorimetric measurement of the hadronic showers. In this paper we review the construction of the spectrometers. In particular, we describe the results obtained from the magnet and RPC prototypes and the installation of the final apparatus at the Gran Sasso laboratories. We discuss the mechanical and magnetic properties of the steel and the techniques employed to calibrate the field in the bulk of the magnet. Moreover, results of the tests and issues concerning the mass production of the Resistive Plate Chambers are reported. Finally, the expected physics performance of the detector is described; estimates rely on numerical simulations and the outcome of the tests described above.Comment: 6 pages, 10 figures, presented at the 2003 IEEE-NSS conference, Portland, OR, USA, October 20-24, 200

&#946;-Glucuronidase triggers extracellular MMAE release from an integrin-targeted conjugate

A non-internalizing \u3b1v\u3b23 integrin ligand was conjugated to the anticancer drug MMAE through a \u3b2-glucuronidase-responsive linker. In the presence of \u3b2-glucuronidase, only the conjugate bearing a PEG4 spacer inhibited the proliferation of integrin-expressing cancer cells at low nanomolar concentrations, indicating important structural requirements for the efficacy of these therapeutics

Non-linear optical susceptibilities, Raman efficiencies and electrooptic tensors from first-principles density functional perturbation theory

The non-linear response of infinite periodic solids to homogenous electric fields and collective atomic displacements is discussed in the framework of density functional perturbation theory. The approach is based on the 2n + 1 theorem applied to an electric-field-dependent energy functional. We report the expressions for the calculation of the non-linear optical susceptibilities, Raman scattering efficiencies and electrooptic coefficients. Different formulations of third-order energy derivatives are examined and their convergence with respect to the k-point sampling is discussed. We apply our method to a few simple cases and compare our results to those obtained with distinct techniques. Finally, we discuss the effect of a scissors correction on the EO coefficients and non-linear optical susceptibilities