687 research outputs found
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 ), 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 (). 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 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 . From multiple-frequency analysis based on the Fourier
decomposition method, we detect two very closely separated pulsating
frequencies: the primary frequency at c/d for both - and
-bands, and the secondary frequency at c/d for the -band and
24.343 c/d for the -band. This star is the second among known SX Phe stars
found to pulsate with very closely separated frequencies ().
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. Studentsâ 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
Dynamic Assessment (DA) in a university clinic for Danish children with Developmental Communicative Disorders (DCD) â problem-based practice as a means for training psychology students how to intervene with SLI-children.
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: where
and 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 :
with an rms scatter of 0.038,
corresponding to for an adopted distance modulus
of (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
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