Ising models on power-law random graphs

We study a ferromagnetic Ising model on random graphs with a power-law degree distribution and compute the thermodynamic limit of the pressure when the mean degree is finite (degree exponent $\tau>2$), for which the random graph has a tree-like structure. For this, we adapt and simplify an analysis by Dembo and Montanari, which assumes finite variance degrees ($\tau>3$). We further identify the thermodynamic limits of various physical quantities, such as the magnetization and the internal energy

A New SX Phe Star in the Globular Cluster M15

A new SX Phe star (labelled SXP1) found from $BV$ CCD photometry is the first to be discovered in the globular cluster M15. It is a blue straggler and is located 102\arcsec.8 north and 285\arcsec.6 west of the center of M15 \citep{har96}. Mean magnitudes of SXP1 are = 18$\fm$671 and = 18\fm445. The amplitude of variability of SXP1 is measured to be $\Delta V \approx 0.15$. From multiple-frequency analysis based on the Fourier decomposition method, we detect two very closely separated pulsating frequencies: the primary frequency at $f_1=24.630$ c/d for both $B$- and $V$-bands, and the secondary frequency at $f_2=24.338$ c/d for the $B$-band and 24.343 c/d for the $V$-band. This star is the second among known SX Phe stars found to pulsate with very closely separated frequencies ($f_2/f_1\ge0.95$). These frequencies may be explained by excitation of nonradial modes; however, we have an incomplete understanding of this phenomenon in the case of SX Phe stars with relatively high amplitudes. The metallicity-period and the variability amplitude-period relations for SXP1 in M15 are found to be consistent with those for SX Phe stars in other globular clusters.Comment: 15 pages with 6 figures, accepted by the Astronomical Journal (scheduled May 2001

On the correlation between fragility and stretching in glassforming liquids

We study the pressure and temperature dependences of the dielectric relaxation of two molecular glassforming liquids, dibutyl phtalate and m-toluidine. We focus on two characteristics of the slowing down of relaxation, the fragility associated with the temperature dependence and the stretching characterizing the relaxation function. We combine our data with data from the literature to revisit the proposed correlation between these two quantities. We do this in light of constraints that we suggest to put on the search for empirical correlations among properties of glassformers. In particular, argue that a meaningful correlation is to be looked for between stretching and isochoric fragility, as both seem to be constant under isochronic conditions and thereby reflect the intrinsic effect of temperature

Approximate square-root-time relaxation in glass-forming liquids

We present data for the dielectric relaxation of 43 glass-forming organic liquids, showing that the primary (alpha) relaxation is often close to square-root-time relaxation. The better an inverse power-law description of the high-frequency loss applies, the more accurately is square-root-time relaxation obeyed. These findings suggest that square-root-time relaxation is generic to the alpha process, once a common view, but since long believed to be incorrect. Only liquids with very large dielectric losses deviate from this picture by having consistently narrower loss peaks. As a further challenge to the prevailing opinion, we find that liquids with accurate square-root-time relaxation cover a wide range of fragilities

Harmonization Of Interprofessional Collaboration To Improve The Quality Of Health Care

Cooperation among health workers need to be increased in order to provide better health services in Indonesia as well as develop good cooperating skills among professions. Collaborative services given by health workers will give positive impacts to patient outcome. Good collaboration among health workers can be prepared starting from education level through IPE (Interprofessional Education). IPE is applied to undergraduate students such as medical students, dentistry students, pharmacy students, nutritionist students, public health students, and midwifery students. For literature review and condition analysis, the writer applied a method that requires collecting and analyzing sources such as research articles and other literatures on IPE. IPE itself is an education process with two or more different disciplines used to apply interactive learning process in increasing collaboration and quality of health services and practices of each discipline. By applying IPE on students, it aims to make them learn how to give contribution in a team interprofession through knowledge, skills, and cooperation among teams in providing patients with satisfying health services. Students’ ability to handle conflict and good attitudes in problem solving indicates whether the application of IPE succeeds or not. There are several obstacles in applying IPE on institutions, such as difficulties in time management among health professional students due to differences of the schedule; the lack of academic regulation regulating aligned IPE application; problems in communication among professions; and the lack of interdisciplinary teachers. In conclusion, IPE is an important method that needs to be applied on health students in order to improve collaboration skills among professions and health workers. The methods that can be used in applying IPE are classic lectures, Problem-Based Learning (PBL), and Team Collaboration Health Care (TCHC)

Composition Mixing during Blue Straggler Formation and Evolution

We use smoothed-particle hydrodynamics to examine differences between direct collisions of single stars and binary star mergers in their roles as possible blue straggler star formation mechanisms. We find in all cases that core helium in the progenitor stars is largely retained in the core of the remnant, almost independent of the type of interaction or the central concentration of the progenitor stars. We have also modelled the subsequent evolution of the hydrostatic remnants, including mass loss and energy input from the hydrodynamical interaction. The combination of the hydrodynamical and hydrostatic models enables us to predict that little mixing will occur during the merger of two globular cluster stars of equal mass. In contrast to the results of Proctor Sills, Bailyn, & Demarque (1995), we find that neither completely mixed nor unmixed models can match the absolute colors of observed blue stragglers in NGC 6397 at all luminosity levels. We also find that the color distribution is probably the crucial test for explanations of BSS formation - if stellar collisions or mergers are the correct mechanisms, a large fraction of the lifetime of the straggler must be spent away from the main sequence. This constraint appears to rule out the possibility of completely mixed models. For NGC 6397, unmixed models predict blue straggler lifetimes ranging from about 0.1 to 4 Gyr, while completely mixed models predict a range from about 0.6 to 4 Gyr.Comment: AASTeX, 28 pg., accepted for ApJ, also available at http://ucowww.ucsc.edu/~erics/bspaper.htm

New SX Phoenicis Stars in the Globular Cluster M53

Through time-series CCD photometry of the metal-poor globular cluster M53, we have discovered eight new SX Phoenicis type stars (labeled from SXP1 to SXP8). All the new SX Phoenicis stars are located in the blue straggler star region of a color-magnitude diagram of M53. One of these stars (SXP2) is found to have very closely separated pulsation frequencies: $f_1/f_2 = 0.9595$ where $f_1$ and $f_2$ are primary and secondary frequencies. This may be due to excitation of non-radial modes. Six of these SX Phoenicis stars are considered to be pulsating in the fundamental mode. They show a tight linear correlation between the period and luminosity. We derive a period - luminosity relation for the fundamental mode for the period range of $-1.36 < Log P[d]< -1.15$ : $=-3.010(\pm0.262)Log P + 15.310(\pm0.048)$ with an rms scatter of 0.038, corresponding to $=-3.010 Log P - 1.070$ for an adopted distance modulus of $(m-M)_V=16.38$ (Harris 1996).Comment: 31 pages with 7 figures, accepted by the Astronomical Journal (scheduled June 2003

Dielectric and thermal relaxation in the energy landscape

We derive an energy landscape interpretation of dielectric relaxation times in undercooled liquids, comparing it to the traditional Debye and Gemant-DiMarzio-Bishop pictures. The interaction between different local structural rearrangements in the energy landscape explains qualitatively the recently observed splitting of the flow process into an initial and a final stage. The initial mechanical relaxation stage is attributed to hopping processes, the final thermal or structural relaxation stage to the decay of the local double-well potentials. The energy landscape concept provides an explanation for the equality of thermal and dielectric relaxation times. The equality itself is once more demonstrated on the basis of literature data for salol.Comment: 7 pages, 3 figures, 41 references, Workshop Disordered Systems, Molveno 2006, submitted to Philosophical Magazin

A Blue Straggler Binary System with at least Three Progenitors in the Core of a Globular Cluster?

We show that the X-ray source W31 in the core of the globular cluster 47 Tucanae is physically associated with the bright blue straggler BSS-7. The two sources are astrometrically matched to 0.061\arcsec, with a chance coincidence probability of less than 1%. We then analyse optical time-series photometry obtained with the {\em Hubble Space Telescope} (HST) and find that BSS-7 displays a 1.56 day periodic signal in the I band. We also construct a broad-band (far-ultraviolet through far-red) spectral energy distribution for BSS-7 and fit this with single and binary models. The binary model is a better fit to the data, and we derive the corresponding stellar parameters. All of our findings are consistent with BSS-7 being a detached binary consisting of a blue straggler primary with an X-ray-active, upper-main-sequence companion. The formation of such a system would necessarily involve at least three stars, which is consistent with recent N-body models in which blue stragglers often form via multiple encounters that can involve both single and binary stars. However, we cannot yet entirely rule out the possibility that BSS-7 descended directly from a binary system via mass transfer. The system parameters needed to distinguish definitively between these scenarios may be obtainable from time-resolved spectroscopy.Comment: 19 pages, 3 figures, accepted for publication in ApJ; revised version includes a discussion of an alternative 2-progenitor binary evolution scenario, and an appendix discussing other probable/possible BSS/X-ray matches in globular clusters and related source