Common Fermi-liquid origin of T-squared resistivity and superconductivity in n-type SrTiO3

A detailed analysis is given of the T^2 term in the resistivity observed in electron-doped SrTiO3. Novel bandstructure data are presented, which provide values for the bare mass, density of states, and plasma frequency of the quasiparticles as a function of doping. It is shown that these values are renormalized by approximately a factor 2 due to electron-phonon interaction. It is argued that the quasiparticles are in the anti-adiabatic limit with respect to electron-phonon interaction. The condition of anti-adiabatic coupling renders the interaction mediated through phonons effectively non-retarded. We apply Fermi-liquid theory developed in the 70's for the T^2 term in the resistivity of common metals, and combine this with expressions for Tc and with the Brinkman-Platzman-Rice (BPR) sum-rule to obtain Landau parameters of n-type SrTiO3. These parameters are comparable to those of liquid 3He, indicating interesting parallels between these Fermi-liquids despite the differences between the composite fermions from which they are formed.Comment: 12 pages, 9 figure

Stratified dispersive model for material characterization using terahertz time-domain spectroscopy

We propose a novel THz material analysis approach which provides highly accurate material parameters and can be used for industrial quality control. The method treats the inspected material within its environment locally as a stratified system and describes the light-matter interaction of each layer in a realistic way. The approach is illustrated in the time-domain and frequency-domain for two potential fields of implementation of THz technology: quality control of (coated) paper sheets and car paint multilayers, both measured in humid air.Comment: 4 pages, 4 figure

Spin resonance in EuTiO3 probed by time-domain GHz ellipsometry

We show an example of a purely magnetic spin resonance in EuTiO3 and the resulting new record high Faraday rotation of 590 deg/mm at 1.6 T for 1 cm wavelengths probed by a novel technique of magneto-optical GHz time-domain ellipsometry. From our transmission measurements of linear polarized light we map out the complex index of refraction in the GHz to THz range. We observe a strong resonant absorption by magnetic dipole transitions involving the Zeeman split S=7/2 magnetic energy levels of the Eu 2+ ions, which causes a very large dichroism for circular polarized radiation.Comment: 4 pages, 4 figure

Mg-Ni-H films as selective coatings: tunable reflectance by layered hydrogenation

Unlike other switchable mirrors, Mg2NiHx films show large changes in reflection that yield very low reflectance (high absorptance) at different hydrogen contents, far before reaching the semiconducting state. The resulting reflectance patterns are of interference origin, due to a self-organized layered hydrogenation mechanism that starts at the substrate interface, and can therefore be tuned by varying the film thickness. This tunability, together with the high absorptance contrast observed between the solar and the thermal energies, strongly suggests the use of these films in smart coatings for solar applications.Comment: Three two-column pages with 3 figures embedded; RevTE

Design of a randomized controlled trial on the effects of Counseling of mental health problems by Occupational Physicians on return to work: the CO-OP-study

Mental health problems often lead to prolonged sick leave. In primary care, the usual approach towards these patients was the advice to take rest and not return to work before all complaints had disappeared. When complaints persist, these patients are often referred to psychologists from primary and specialized secondary care. As an alternative, ways have been sought to activate the Dutch occupational physician (OP) in primary care. Early 2000, the Dutch Association of Occupational Physicians (NVAB) published a guideline concerning the management by OPs of employees with mental health problems. The guideline received positive reactions from employees, employers and Dutch OPs. This manuscript describes the design of a study, which aims to assess the effects of the guideline, compared with usual care. In a randomized controlled trial (RCT), subjects in the intervention group were treated according to the guideline. The control group received usual care, with minimal involvement of the OP and easy access to a psychologist. Subjects were recruited from two Dutch police departments. The primary outcomes of the study are return to work and treatment satisfaction by the employee, employer, and OP. A secondary outcome is cost-effectiveness of the intervention, compared with usual care. Furthermore, prognostic measures are taken into account as potential confounders. A process evaluation will be done by means of performance indicators, based on the guideline. In this pragmatic trial, effectiveness instead of efficacy is studied. We will evaluate what is possible in real clinical practice, rather than under ideal circumstances. Many requirements for a high quality trial are being met. Results of this study will contribute to treatment options in occupational health practice for employees on sick leave due to mental health problems. Additionally, they may contribute to new and better-suited guidelines and stepped care. Results will become available during 2007. Current Controlled Trials ISRCTN3488734

The positive effect on determinants of physical activity of a tailored, general practice-based physical activity intervention

PACE (Physician-based Assessment and Counseling for Exercise) is an individualized theory-based minimal intervention strategy aimed at the enhancement of regular physical activity. The aim of this study was to evaluate the effectiveness of a PACE intervention applied by general practitioners (GPs) on potential determinants of physical activity. A randomized controlled trial was conducted in 29 general practices with the following inclusion criteria for patients: aged between 18 and 70 years, diagnosed with hypertension, hypercholesterolemia and/or non-insulin-dependent diabetes mellitus, and not in maintenance stage for regular physical activity. The intervention consisted of two visits with the GP and two telephone booster calls by a physical activity counselor. Determinants of physical activity were assessed with questionnaires at baseline, and at 8-week (short), 6-month (medium) and 1-year (long) follow-up. A significant positive effect was observed on self-efficacy, and on the use of cognitive and behavioral processes of change, at both short- and medium-term follow-up. The intervention respondents also perceived fewer barriers for regular physical activity at short-term and used behavioral processes of change more at long-term follow-up. No intervention effect was observed for perceived benefits of physical activity. In conclusion, this GP-based PACE intervention resulted in positive changes in potential determinants of physical activit