The effect of magnetic dipolar interactions on the interchain spin wave dispersion in CsNiF_3

Inelastic neutron scattering measurements were performed on the ferromagnetic chain system CsNiF_3 in the collinear antiferromagnetic ordered state below T_N = 2.67K. The measured spin wave dispersion was found to be in good agreement with linear spin wave theory including dipolar interactions. The additional dipole tensor in the Hamiltonian was essential to explain some striking phenomena in the measured spin wave spectrum: a peculiar feature of the dispersion relation is a jump at the zone center, caused by strong dipolar interactions in this system. The interchain exchange coupling constant and the planar anisotropy energy were determined within the present model to be J'/k_B = -0.0247(12)K and A/k_B = 3.3(1)K. This gives a ratio J/J' \approx 500, using the previously determined intrachain coupling constant J/k_B = 11.8$. The small exchange energy J' is of the same order as the dipolar energy, which implies a strong competition between the both interactions.Comment: 18 pages, TeX type, 7 Postscript figures included. To be published in Phys. Rev.

Continued Progress: Promising Evidence on Personalized Learning

The findings are grouped into four sections. The first section on student achievement finds that there were positive effects on student mathematics and reading performance and that the lowest-performing students made substantial gains relative to their peers. The second section on implementation and the perceptions of stakeholders finds that adoption of personalized learning practices varied considerably. Personalized learning practices that are direct extensions of current practice were more common, but implementation of some of the more challenging personalized learning strategies was less common. The third section relates implementation features to outcomes and identifies three elements of personalized learning that were being implemented in tandem in the schools with the largest achievement effects. Finally, the fourth section compares teachers' and students' survey responses to a national sample and finds some differences, such as teachers' greater use of practices that support competency-based learning and greater use of technology for personalization in the schools in this study with implementation data

WR 7a: a V Sagittae or a qWR star?

The star WR 7a, also known as SPH 2, has a spectrum that resembles that of V Sagittae stars although no O VI emission has been reported. The Temporal Variance Spectrum - TVS - analysis of our data shows weak but strongly variable emission of O VI lines which is below the noise level in the intensity spectrum. Contrary to what is seen in V Sagittae stars, optical photometric monitoring shows very little, if any, flickering. We found evidence of periodic variability. The most likely photometric period is P(phot) = 0.227(14) d, while radial velocities suggest a period of P(spec) = 0.204(13) d. One-day aliases of these periods can not be ruled out. We call attention to similarities with HD 45166 and DI Cru (= WR 46), where multiple periods are present. They may be associated to the binary motion or to non-radial oscillations. In contrast to a previous conclusion by Pereira et al. (1998), we show that WR 7a contains hydrogen. The spectrum of the primary star seems to be detectable as the N V 4604A absorption line is visible. If so, it means that the wind is optically thin in the continuum and that it is likely to be a helium main sequence star. Given the similarity to HD 45166, we suggests that WR 7a may be a qWR - quasi Wolf-Rayet - star. Its classification is WN4h/CE in the Smith et al. (1996) three dimensional classification system.Comment: 6 pages, 6 figures, preprint of an article accepted for publication in Monthly Notices of The Royal Astronomical Societ

Excessive alcohol consumption in young men: is there an association with their earlier family situation? A baseline-analysis of the C-SURF-study (Cohort Study on Substance Use Risk Factors).

AIMS: To determine whether parental factors earlier in life (parenting, single parent family, parental substance use problem) are associated with patterns of alcohol consumption among young men in Switzerland. METHODS: This analysis of a population based sample from the Cohort Study on Substance Use Risk Factors (C-SURF) included 5,990 young men (mean age 19.51 years), all attending a mandatory recruitment process for the army. These conscripts reported on parental monitoring and rule-setting, parental behaviour and family structure. The alcohol use pattern was assessed through abstention, risky single occasion drinking (RSOD), volume drinking and dependence. Furthermore, the impact of age, family socio-economic status, educational level of the parents, language region and civil status was analysed. RESULTS: A parental substance use problem was positively associated with volume drinking and alcohol dependence in young Swiss men. Active parenting corresponded negatively with RSOD, volume drinking and alcohol dependence. Single parent family was not associated with a different alcohol consumption pattern compared to standard family. CONCLUSION: Parental influences earlier in life such as active parenting (monitoring, rule-setting and knowing the whereabouts) and perceived parental substance use problem are associated with alcohol drinking behaviour in young male adults. Therefore, health professionals should stress the importance of active parenting and parental substance use prevention in alcohol prevention strategies

SIPS - Screening-Instrument für prämenstruelle Symptome*: Die deutsche Version des Premenstrual Symptoms Screening Tool zur Erfassung klinisch relevanter Beschwerden

Zusammenfassung: Hintergrund: Prämenstruelle dysphorische Störungen (PMDS) und schwere prämenstruelle Syndrome (PMS) treten häufig auf, bleiben jedoch oft unerkannt und unbehandelt. Begünstigt wird dies durch das Fehlen eines entsprechenden deutschsprachigen Screening-Instruments. Ziel dieser Studie war es, das englischsprachige Premenstrual Symptoms Screening Tool (PSST) ins Deutsche zu übertragen und seine Anwendung zu prüfen. Material und Methoden: Die deutschsprachige Version des PSST wurde als "Screening-Instrument für prämenstruelle Symptome" (SIPS) erstellt und ihre Güte an 47 Frauen mit und ohne PMDS/schwerem PMS internetbasiert mittels täglichen Symptomeinschätzungen bestimmt. Ergebnisse: Die Retest-Reliabilität des SIPS betrug r=0,69, das Cronbachsα 0,924. Als Validitätsmaß des SIPS zeigten sich signifikante Unterschiede zwischen Frauen mit und ohne PMDS/schwerem PMS, bestimmt durch das SIPS, bezüglich prospektiv erfasster prämenstrueller Symptomatik (F[2,44]=4,52, p<0,001) und Symptomveränderung (F[2,44]=25,23, p<0,001). Schlussfolgerung: Das SIPS ist reliabel und valide und kann helfen, Frauen mit behandlungsbedürftigen prämenstruellen Beschwerden zu identifiziere

X-ray Spectral Analysis of the Steady States of GRS 1915+105

We report on the X-ray spectral behavior within the steady states of GRS 1915+105. Our work is based on the full data set on the source obtained using the Proportional Counter Array on the Rossi X-ray Timing Explorer and 15 GHz radio data obtained using the Ryle Telescope. The steady observations within the X-ray data set naturally separated into two regions in the color-color diagram and we refer to them as steady-soft and steady-hard. GRS 1915+105 displays significant curvature in the coronal component in both the soft and hard data within the {\it RXTE}/PCA bandpass. A majority of the steady-soft observations displays a roughly constant inner disk radius (R_in), while the steady-hard observations display an evolving disk truncation which is correlated to the mass accretion rate through the disk. The disk flux and coronal flux are strongly correlated in steady-hard observations and very weakly correlated in the steady-soft observations. Within the steady-hard observations we observe two particular circumstances when there are correlations between the coronal X-ray flux and the radio flux with log slopes \eta~0.68 +/- 0.35 and \eta ~ 1.12 +/- 0.13. They are consistent with the upper and lower tracks of Gallo et al. (2012), respectively. A comparison of model parameters to the state definitions show that almost all steady-soft observations match the criteria of either thermal or steep power law state, while a large portion of the steady-hard observations match the hard state criteria when the disk fraction constraint is neglected.Comment: 21 pages, 15 figures, 2 tables. Accepted for publication in Ap

Device-spectroscopy of magnetic field effects in a polyfluorene organic light-emitting diode

We perform charge-induced absorption and electroluminescence spectroscopy in a polyfluorene organic magnetoresistive device. Our experiments allow us to measure the singlet exciton, triplet exciton and polaron densities in a live device under an applied magnetic field, and to distinguish between three different models that were proposed to explain organic magnetoresistance. These models are based on different spin-dependent interactions, namely exciton formation, triplet exciton-polaron quenching and bipolaron formation. We show that the singlet exciton, triplet exciton and polaron densities and conductivity all increase with increasing magnetic field. Our data are inconsistent with the exciton formation and triplet-exciton polaron quenching models.Comment: 4 pages, two figure