Equivalence of conservation laws and equivalence of potential systems

We study conservation laws and potential symmetries of (systems of) differential equations applying equivalence relations generated by point transformations between the equations. A Fokker-Planck equation and the Burgers equation are considered as examples. Using reducibility of them to the one-dimensional linear heat equation, we construct complete hierarchies of local and potential conservation laws for them and describe, in some sense, all their potential symmetries. Known results on the subject are interpreted in the proposed framework. This paper is an extended comment on the paper of J.-q. Mei and H.-q. Zhang [Internat. J. Theoret. Phys., 2006, in press].Comment: 10 page

A one-dimensional model for the growth of CdTe quantum dots on Si substrates

Recent experiments involving CdTe films grown on Si(111) substrates by hot wall epitaxy revealed features not previously observed [S. O. Ferreira \textit{et al.}, J. Appl. Phys. \textbf{93}, 1195 (2003)]. This system, which follows the Volmer-Weber growth mode with nucleation of isolated 3D islands for less than one monolayer of evaporated material, was described by a peculiar behavior of the quantum dot (QD) size distributions. In this work, we proposed a kinetic deposition model to reproduce these new features. The model, which includes thermally activated diffusion and evaporation of CdTe, qualitatively reproduced the experimental QD size distributions. Moreover, the model predicts a transition from Stranski-Krastanow growth mode at lower temperatures to Volmer-Weber growth mode at higher ones characterized through the QD width distributions.Comment: to appear in Physics Letters

Evolution of the infrared luminosity density and star formation history up to z~1: preliminary results from MIPS

Using deep observations of the Chandra Deep Field South obtained with MIPS at 24mic, we present our preliminary estimates on the evolution of the infrared (IR) luminosity density of the Universe from z=0 to z~1. We find that a pure density evolution of the IR luminosity function is clearly excluded by the data. The characteristic luminosity L_IR* evolves at least by (1+z)^3.5 with lookback time, but our monochromatic approach does not allow us to break the degeneracy between a pure evolution in luminosity or an evolution in both density and luminosity. Our results imply that IR luminous systems (L_IR > 10^11 L_sol) become the dominant population contributing to the comoving IR energy density beyond z~0.5-0.6. The uncertainties affecting our measurements are largely dominated by the poor constraints on the spectral energy distributions that are used to translate the observed 24mic flux into luminosities.Comment: 4 pages, 2 figures. To be published in "Starbursts: From 30 Doradus to Lyman Break Galaxies", held in Cambridge, 6-10 September 2004, Ed. R. de Grijs & R. M. Gonzalez Delgad

Nanosized superparamagnetic precipitates in cobalt-doped ZnO

The existence of semiconductors exhibiting long-range ferromagnetic ordering at room temperature still is controversial. One particularly important issue is the presence of secondary magnetic phases such as clusters, segregations, etc... These are often tedious to detect, leading to contradictory interpretations. We show that in our cobalt doped ZnO films grown homoepitaxially on single crystalline ZnO substrates the magnetism unambiguously stems from metallic cobalt nano-inclusions. The magnetic behavior was investigated by SQUID magnetometry, x-ray magnetic circular dichroism, and AC susceptibility measurements. The results were correlated to a detailed microstructural analysis based on high resolution x-ray diffraction, transmission electron microscopy, and electron-spectroscopic imaging. No evidence for carrier mediated ferromagnetic exchange between diluted cobalt moments was found. In contrast, the combined data provide clear evidence that the observed room temperature ferromagnetic-like behavior originates from nanometer sized superparamagnetic metallic cobalt precipitates.Comment: 20 pages, 6 figures; details about background subtraction added to section III. (XMCD

Non-Markovian dynamics for an open two-level system without rotating wave approximation: Indivisibility versus backflow of information

By use of the two measures presented recently, the indivisibility and the backflow of information, we study the non-Markovianity of the dynamics for a two-level system interacting with a zero-temperature structured environment without using rotating wave approximation (RWA). In the limit of weak coupling between the system and the reservoir, and by expanding the time-convolutionless (TCL) generator to the forth order with respect to the coupling strength, the time-local non-Markovian master equation for the reduced state of the system is derived. Under the secular approximation, the exact analytic solution is obtained and the sufficient and necessary conditions for the indivisibility and the backflow of information for the system dynamics are presented. In the more general case, we investigate numerically the properties of the two measures for the case of Lorentzian reservoir. Our results show the importance of the counter-rotating terms to the short-time-scale non-Markovian behavior of the system dynamics, further expose the relations between the two measures and their rationality as non-Markovian measures. Finally, the complete positivity of the dynamics of the considered system is discussed

Effects of estimated community-level health literacy on treatment initiation and preventive care among older adults with newly diagnosed diabetes

Purpose: Individual measures of health literacy are not feasible for administration on a large scale, yet estimates of community-level health literacy in the US recently became available. We sought to investigate whether community-level health literacy estimates are associated with the initiation of oral antihyperglycemic agents (OHA) and the use of standard preventive care services among older adults with newly diagnosed diabetes. Patients and methods: We conducted a retrospective cohort study of 169,758 patients, ≥65 years old with hypertension and newly diagnosed type 2 diabetes using 2007–2011 data from the Center for Medicare and Medicaid Services Chronic Conditions Warehouse. We examined the relationship between community-level health literacy estimates and initiation of OHA, receipt of flu shots, eye exams, Hemoglobin A1c tests, and lipid tests within 12 months post diabetes diagnosis. Results: Patients living in communities with above basic health literacy (vs. basic/below basic) were 15% more likely to initiate OHA (Hazard Ratio=1.15; 95% CI 1.12 to 1.18). After classifying the health literacy distribution as quintiles, the analysis revealed a dose– response relationship with OHA initiation that plateaued at the third and fourth quintiles and declined at the fifth quintile. Individuals residing in communities with higher health literacy were more likely to participate in preventive care services (relative risk ranged from 1.09 for lipid test [95% CI 1.07–1.11] to 1.43 for flu shot [95% CI 1.41–1.46]). Conclusion: Community-level health literacy estimates were associated with the initiation of OHA and uptake of standard preventive care services in older adults. Community-level health literacy may help to inform targeted diabetes education and support efforts

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

The Labour of Love: Seasonal Migration from Jharkhand to the Brick Kilns of Other States in India

Seasonal casual labour migration in India has conventionally been understood as the result of extreme poverty whereby villagers are forced to become migrants for the dry six months to subsist or merely survive. This article draws on fieldwork in a village in Jharkhand and a brick kiln in West Bengal to argue that migrants do not understand their movement in economic terms alone. Many see the brick kilns as a temporary space of freedom to escape problems back home, explore a new country, gain independence from parents or live out prohibited amorous relationships. It is suggested that Jharkhandi activists and policy-makers’ construction of such migration as a ‘problem’ is as much about their vision of how the new tribal state ought to be as about exploitation. Migration to the kilns is seen by them as a threat to the purity and regulation of the social and sexual tribal citizen. This moralising perspective creates a climate that paradoxically encourages many young people to flee to the brick kilns where they can live ‘freely’. In this way, the new puritanism at home helps to reproduce the conditions for capitalist exploitation and the extraction of surplus value

Measurement of charged-particle multiplicity distributions and their H_q moments in hadronic Z decays at LEP

The charged-particle multiplicity distribution is measured for all hadronic events as well as for light-quark and b-quark events produced in e+e- collisions at the Z pole. Moments of the charged-particle multiplicity distributions are calculated. The H moments of the multiplicity distributions are studied, and their quasi-oscillations as a function of the rank of the moment are investigated.Comment: Matches published versio