Brave New World: Can We Engineer a Better Start for Freshers?

Abstract - The crucial importance of first experiences in shaping future success has been widely acknowledged. Creating the best foundations in large cohorts of students from diverse backgrounds presents special problems of its own. But a secure foundation can enhance student achievement and improve retention – and the students may even have fun too. Research has suggested that building learning communities can enhance student engagement and achievement. This paper examines how introducing non-technical activities can establish sound foundations for a university career by a) addressing objectives in the wider curriculum and b) promoting non-technical skills and experience of group working. A set of changes introduced to five degree cohorts in our academic school were designed to complement enhancements to our technical curriculum introduced during many years of debate and consideration. The changes have impacted upon generic and technical educational experiences. The paper presents an evaluation of the programme of changes through two iterations from the perspective of both faculty and student

Competition Between Stripes and Pairing in a t-t'-J Model

As the number of legs n of an n-leg, t-J ladder increases, density matrix renormalization group calculations have shown that the doped state tends to be characterized by a static array of domain walls and that pairing correlations are suppressed. Here we present results for a t-t'-J model in which a diagonal, single particle, next-near-neighbor hopping t' is introduced. We find that this can suppress the formation of stripes and, for t' positive, enhance the d_{x^2-y^2}-like pairing correlations. The effect of t' > 0 is to cause the stripes to evaporate into pairs and for t' < 0 to evaporate into quasi-particles. Results for n=4 and 6-leg ladders are discussed.Comment: Four pages, four encapsulated figure

Usability evaluation of a virtual museum interface

The Augmented Representation of Cultural Objects (ARCO) system provides software and interface tools to museum curators to develop virtual museum exhibitions, as well as a virtual environment for museum visitors over the World Wide Web or in informative kiosks. The main purpose of the system is to offer an enhanced educative and entertaining experience to virtual museum visitors. In order to assess the usability of the system, two approaches have been employed: a questionnaire based survey and a Cognitive Walkthrough session. Both approaches employed expert evaluators, such as domain experts and usability experts. The result of this study shows a fair performance of the followed approach, as regards the consumed time, financial and other resources, as a great deal of usability problems has been uncovered and many aspects of the system have been investigated. The knowledge gathered aims at creating a conceptual framework for diagnose usability problems in systems in the area of Virtual Cultural Heritage

Cosmology of the Next-to-Minimal Supersymmetric Standard Model

We discuss the domain wall problem in the Next-to-Minimal Supersymmetric Standard Model, with particular attention to the usual solution of explicit breaking of the discrete symmetry by non-renormalisable operators. This ``solution'' leads to a contradiction between the requirements of cosmology and those of avoiding the destabilisation of the hierarchy.Comment: 6 pages LaTeX, needs sprocl.sty (included at end) Talk presented by P.L. White at Valencia 9

ROSAT PSPC observations of the outer regions of the Perseus cluster of galaxies

We present an analysis of four off-axis ROSAT PSPC observations of the Perseus cluster of galaxies (Abell~426). We detect the surface brightness profile to a radius of 80 arcmin ($\sim 2.4 h_{50}^{-1}$ Mpc) from the X-ray peak. The profile is measured in various sectors and in three different energy bands. Firstly, a colour analysis highlights a slight variation of $N_{H}$ over the region, and cool components in the core and in the eastern sector. We apply the $\beta$-model to the profiles from different sectors and present a solution to the, so-called, $\beta$-problem. The residuals from an azimuthally-averaged profile highlight extended emission both in the East and in the West, with estimated luminosities of about 8 and 1 $\times 10^{43} erg/s$, respectively. We fit several models to the surface brightness profile, including the one obtained from the Navarro, Frenk and White (1995) potential. We obtain the best fit with the gas distribution described by a power law in the inner, cooling region and a $\beta$-model for the extended emission. Through the best-fit results and the constraints from the deprojection of the surface brightness profiles, we define the radius where the overdensity inside the cluster is 200 times the critical value, $r_{200}$, at $2.7 h_{50}^{-1}$ Mpc. Within $2.3 h_{50}^{-1}$ Mpc ($0.85 r_{200}$), the total mass in the Perseus cluster is $1.2 \times 10^{15} M_{\odot}$ and its gas fraction is about 30 per cent.Comment: 21 pages, 23 figures; accepted for publication in MNRAS; also available at http://www-xray.ast.cam.ac.uk/~settori/paper.htm

Topological Change in Mean Convex Mean Curvature Flow

Consider the mean curvature flow of an (n+1)-dimensional, compact, mean convex region in Euclidean space (or, if n<7, in a Riemannian manifold). We prove that elements of the m-th homotopy group of the complementary region can die only if there is a shrinking S^k x R^(n-k) singularity for some k less than or equal to m. We also prove that for each m from 1 to n, there is a nonempty open set of compact, mean convex regions K in R^(n+1) with smooth boundary for which the resulting mean curvature flow has a shrinking S^m x R^(n-m) singularity.Comment: 19 pages. This version includes a new section proving that certain kinds of mean curvature flow singularities persist under arbitrary small perturbations of the initial surface. Newest update (Oct 2013) fixes some bibliographic reference

A Two-dimensional Infinte System Density Matrix Renormalization Group Algorithm

It has proved difficult to extend the density matrix renormalization group technique to large two-dimensional systems. In this Communication I present a novel approach where the calculation is done directly in two dimensions. This makes it possible to use an infinite system method, and for the first time the fixed point in two dimensions is studied. By analyzing several related blocking schemes I find that there exists an algorithm for which the local energy decreases monotonically as the system size increases, thereby showing the potential feasibility of this method.Comment: 5 pages, 6 figure

Deconvolution of ASCA X-ray data: II. Radial temperature and metallicity profiles for 106 galaxy clusters

In Paper-I we presented a methodology to recover the spatial variations of properties of the intracluster gas from ASCA X-ray satellite observations of galaxy clusters. We verified the correctness of this procedure by applying it to simulated cluster datasets which we had subjected to the various contaminants common in ASCA data. In this paper we present the results which we obtain when we apply this method to real galaxy cluster observations. We determine broad-band temperature and cooling-flow mass-deposition rates for the 106 clusters in our sample, and obtain temperature, abundance and emissivity profiles (i.e. at least two annular bins) for 98 of these clusters. We find that 90 percent of these temperature profiles are consistent with isothermality at the 3-sigma confidence level. This conflicts with the prevalence of steeply-declining cluster temperature profiles found by Markevitch et al. (1998) from a sample of 30 clusters. In Paper-III (in preparation) we utilise our temperature and emissivity profiles to determine radial hydrostatic-mass properties for a subsample of the clusters presented in this paper.Comment: MNRAS, accpeted. Postscript copy of paper and individual postscript files for plots in Appendix B can be obtained from: http://www-xray.ast.cam.ac.uk/~da

Detection of coherent beam-beam modes with digitized beam position monitor signals

A system for bunch-by-bunch detection of transverse proton and antiproton coherent oscillations in the Fermilab Tevatron collider is described. It is based on the signal from a single beam-position monitor located in a region of the ring with large amplitude functions. The signal is digitized over a large number of turns and Fourier-analyzed offline with a dedicated algorithm. To enhance the signal, band-limited noise is applied to the beam for about 1 s. This excitation does not adversely affect the circulating beams even at high luminosities. The device has a response time of a few seconds, a frequency resolution of $1.6\times 10^{-5}$ in fractional tune, and it is sensitive to oscillation amplitudes of 60 nm. It complements Schottky detectors as a diagnostic tool for tunes, tune spreads, and beam-beam effects. Measurements of coherent mode spectra are presented and compared with models of beam-beam oscillations.Comment: 7 pages, 4 figures. Submitted to the Proceedings of the ICFA Mini-Workshop on Beam-beam Effects in Hadron Colliders (BB2013), Geneva, Switzerland, 18-22 March 201

Oxygen Absorption in Cooling Flows

The inhomogeneous cooling flow scenario predicts the existence of large quantities of gas in massive elliptical galaxies, groups, and clusters that have cooled and dropped out of the flow. Using spatially resolved, deprojected X-ray spectra from the ROSAT PSPC we have detected strong absorption over energies ~0.4-0.8 keV intrinsic to the central ~1 arcmin of the galaxy, NGC 1399, the group, NGC 5044, and the cluster, A1795. These systems have amongst the largest nearby cooling flows in their respective classes and low Galactic columns. Since no excess absorption is indicated for energies below ~0.4 keV the most reasonable model for the absorber is warm, collisionally ionized gas with T=10^{5-6} K where ionized states of oxygen provide most of the absorption. Attributing the absorption only to ionized gas reconciles the large columns of cold H and He inferred from Einstein and ASCA with the lack of such columns inferred from ROSAT, and also is consistent with the negligible atomic and molecular H inferred from HI, and CO observations of cooling flows. The prediction of warm ionized gas as the product of mass drop-out in these and other cooling flows can be verified by Chandra, XMM, and ASTRO-E.Comment: 4 pages (2 figures), Accepted for publication in ApJ Letters, no significant changes from previous submitted versio