The reaction 13C(alpha,n)16O: a background for the observation of geo-neutrinos

The absolute cross section of the $^{13}$C($\alpha$,n)$^{16}$O reaction has been measured at E$_{\alpha}$ = 0.8 to 8.0 MeV with an overall accuracy of 4%. The precision is needed to subtract reliably a background in the observation of geo-neutrinos, e.g. in the KamLAND detector.Comment: LaTex file, 13 pages including 3 ps figures. Any request to [email protected]. Phys. Rev . C, to appea

Polytopality and Cartesian products of graphs

We study the question of polytopality of graphs: when is a given graph the graph of a polytope? We first review the known necessary conditions for a graph to be polytopal, and we provide several families of graphs which satisfy all these conditions, but which nonetheless are not graphs of polytopes. Our main contribution concerns the polytopality of Cartesian products of non-polytopal graphs. On the one hand, we show that products of simple polytopes are the only simple polytopes whose graph is a product. On the other hand, we provide a general method to construct (non-simple) polytopal products whose factors are not polytopal.Comment: 21 pages, 10 figure

Origin of magnetic moments in defective TiO2 single crystals

In this paper we show that ferromagnetism can be induced in pure TiO2 single crystals by oxygen ion irradiation. By combining x-ray diffraction, Raman-scattering, and electron spin resonance spectroscopy, a defect complex, \emph{i.e.} Ti$^{3+}$ ions on the substitutional sites accompanied by oxygen vacancies, has been identified in irradiated TiO2. This kind of defect complex results in a local (TiO$_{6-x}$) stretching Raman mode. We elucidate that Ti$^{3+}$ ions with one unpaired 3d electron provide the local magnetic moments.Comment: 4 pages, 4 figures, to be published at Phys. Rev.

Quantum Phase Diagram of Bosons in Optical Lattices

We work out two different analytical methods for calculating the boundary of the Mott-insulator-superfluid (MI-SF) quantum phase transition for scalar bosons in cubic optical lattices of arbitrary dimension at zero temperature which improve upon the seminal mean-field result. The first one is a variational method, which is inspired by variational perturbation theory, whereas the second one is based on the field-theoretic concept of effective potential. Within both analytical approaches we achieve a considerable improvement of the location of the MI-SF quantum phase transition for the first Mott lobe in excellent agreement with recent numerical results from Quantum Monte-Carlo simulations in two and three dimensions. Thus, our analytical results for the whole quantum phase diagram can be regarded as being essentially exact for all practical purposes

The Star-Forming Dwarf Galaxy Populations of two z ~ 0.4 Clusters: MS1512.4+3647 and Abell 851

We present the results of a deep narrow-band [OII] 3727 \AA emission-line search for faint ($g <$ 27), star-forming galaxies in the field of the $z=0.37$ MS1512.4+3647 cluster. We find no evidence for an over-density of emission-line sources relative to the field at $z \sim$ 0.4 (Hogg et al. 1998), and therefore conclude that the MS1512.4+3647 sample is dominated by field [OII] emission-line galaxies which lie along the $\sim$ 180 Mpc line of sight immediately in front and behind the cluster. This is surprising, given that the previously surveyed $z=0.41$ cluster Abell 851 has 3-4 times the field emission-line galaxy density (Martin et al. 2000). We find that the MS1512.4+3647 sample is deficient in galaxies with intermediate colors (1.0 $< g-i <$ 2.0) and implied star-formation exponential decay timescales $\tau \sim$ 100 Myr - 1 Gyr that dominate the Abell 851 emission-line galaxy population. Instead, the majority of [OII] emission-line galaxies surrounding the MS1512.4+3647 cluster are blue ($g-i \leq 1.0$) and forming stars in bursts with $\tau <$ 100 Myr. In both samples, galaxies with the shortest star-formation timescales are preferentially among the faintest star-forming objects. Their i luminosities are consistent with young stellar populations \sim 10^8 - 10^9 \Msun, although an additional factor of ten in stellar mass could be hiding in underlying old stellar populations. We discuss the implications for the star-formation histories of dwarf galaxies in the field and rich clusters.Comment: 26 pages, including 5 tables and 13 figures; accepted for publication in the Astrophysical Journa

Breast cancer worry in higher-risk women offered preventive therapy: a UK multicentre prospective study

PURPOSE: Women's worry about developing breast cancer may influence their decision to use preventive therapy. However, the direction of this relationship has been questioned. We prospectively investigated the relationship between breast cancer worry and uptake of preventive therapy. The socio-demographic and clinical factors associated with high breast cancer worry were also investigated. METHODS: Women at increased risk of developing breast cancer were recruited from clinics across England (n = 408). Participants completed a survey on their breast cancer worry, socio-demographic and clinical factors. Uptake of tamoxifen was recorded at 3 months (n = 258 women, 63.2%). Both primary and sensitivity analyses were conducted using different classifications of low, medium and high worry. RESULTS: 39.5% of respondents reported medium breast cancer worry at baseline and 21.2% reported high worry. Ethnic minority women were more likely to report high worry than white women (OR = 3.02, 95%CI 1.02, 8.91, p = 0.046). Women educated below degree level were more likely to report high worry than those with higher education (OR = 2.29, 95%CI 1.28, 4.09, p = 0.005). No statistically significant association was observed between worry and uptake. In the primary analysis, fewer respondents with medium worry at baseline initiated tamoxifen (low worry = 15.5%, medium = 13.5%, high = 15.7%). In the sensitivity analysis, participants with medium worry reported the highest uptake of tamoxifen (19.7%). CONCLUSIONS: No association was observed between worry and uptake, although the relationship was affected by the categorisation of worry. Standardised reporting of the classification of worry is warranted to allow transparent comparisons across cohorts

Bose-Einstein Condensation in a Trap: the Case of a Dense Condensate

We consider the Bose-Einstein condensation of atoms in a trap where the density of particles is so high that the low density approach of Gross and Pitaevskii will not be applicable. For this purpose we use the slave boson representation which is valid for hard-core bosons at any density. This description leads to the same results as the Gross-Pitaevskii approach in the low density limit, but for higher densities, it predicts the depletion of the order parameter field condensate in the regions where the density of the atomic cloud is high.Comment: 6 pages RevTeX, 3 eps-figure

The Casimir Force in Randall Sundrum Models

We discuss and compare the effects of one extra dimension in the Randall Sundrum models on the evaluation of the Casimir force between two parallel plates. We impose the condition that the result reproduce the experimental measurements within the known uncertainties in the force and the plate separation, and get an upper bound kR < 20 if the curvature parameter k of AdS_5 is equal to the Planck scale. Although the upper bound decreases as k decreases, kR ~ 12, which is the required value for solving the hierarchy problem, is consistent with the Casimir force measurements. For the case where the 5th dimension is infinite, the correction to the Casimir force is very small and negligible.Comment: 16 pages, 2 figures, references added, text improved, accepted for publication in PR