Magnesium Isotopes in Halo Stars

We have determined Mg isotope ratios in halo field dwarfs and giants in the globular cluster M71 based on high S/N high spectral resolution (R = 10$^5$) Keck HIRES spectra. Unlike previous claims of an important contribution from intermediate-mass AGB stars to the Galactic halo, we find that our $^{26}$Mg/$^{24}$Mg ratios can be explained by massive stars.Comment: Proceedings, First Stars III, July 16-20, 2007, Santa F

PREFERENTIAL TRADING ARRANGEMENTS IN THE WESTERN HEMISPHERE

The first half of this decade has witnessed an explosion in the creation and rejuvenation of preferential trading arrangements. Indeed, since 1990, 33 regional agreements have been notified to the GATT. An understanding of the basic structure of these agreements within the Western Hemisphere is critical to the ex ante assessment of the potential impacts of a Western Hemisphere Free Trade Agreement (WHFTA) on individual countries and groups, as well as specific sectors such as agriculture and food processing.International Relations/Trade,

Revisiting the axion bounds from the Galactic white dwarf luminosity function

It has been shown that the shape of the luminosity function of white dwarfs (WDLF) is a powerful tool to check for the possible existence of DFSZ-axions, a proposed but not yet detected type of weakly interacting particles. With the aim of deriving new constraints on the axion mass, we compute in this paper new theoretical WDLFs on the basis of WD evolving models that incorporate for the feedback of axions on the thermal structure of the white dwarf. We find that the impact of the axion emission into the neutrino emission can not be neglected at high luminosities ($M_{\rm Bol}\lesssim 8$) and that the axion emission needs to be incorporated self-consistently into the evolution of the white dwarfs when dealing with axion masses larger than $m_a\cos^2\beta\gtrsim 5$ meV (i.e. axion-electron coupling constant $g_{ae}\gtrsim 1.4\times 10^{-13}$). We went beyond previous works by including 5 different derivations of the WDLF in our analysis. Then we have performed $\chi^2$-tests to have a quantitative measure of the assessment between the theoretical WDLFs ---computed under the assumptions of different axion masses and normalization methods--- and the observed WDLFs of the Galactic disk. While all the WDLF studied in this work disfavour axion masses in the range suggested by asteroseismology ($m_a\cos^2\beta\gtrsim 10$ meV; $g_{ae}\gtrsim 2.8\times 10^{-13}$) lower axion masses can not be discarded from our current knowledge of the WDLF of the Galactic Disk. A larger set of completely independent derivations of the WDLF of the galactic disk as well as a detailed study of the uncertainties of the theoretical WDLFs is needed before quantitative constraints on the axion-electron coupling constant can be made.Comment: 17 pages, 6 figures, accepted for publication in the Journal of Cosmology and Astroparticle Physic

Data reduction in the ITMS system through a data acquisition model with self-adaptive sampling rate

Long pulse or steady state operation of fusion experiments require data acquisition and processing systems that reduce the volume of data involved. The availability of self-adaptive sampling rate systems and the use of real-time lossless data compression techniques can help solve these problems. The former is important for continuous adaptation of sampling frequency for experimental requirements. The latter allows the maintenance of continuous digitization under limited memory conditions. This can be achieved by permanent transmission of compressed data to other systems. The compacted transfer ensures the use of minimum bandwidth. This paper presents an implementation based on intelligent test and measurement system (ITMS), a data acquisition system architecture with multiprocessing capabilities that permits it to adapt the system’s sampling frequency throughout the experiment. The sampling rate can be controlled depending on the experiment’s specific requirements by using an external dc voltage signal or by defining user events through software. The system takes advantage of the high processing capabilities of the ITMS platform to implement a data reduction mechanism based in lossless data compression algorithms which are themselves based in periodic deltas

AIDS-defining illnesses at initial diagnosis of HIV in a large Guatemalan cohort

AbstractBackgroundAnecdotal evidence suggests that a high proportion of patients diagnosed with HIV in Guatemala present with AIDS. There remain limited data on the epidemiology of AIDS-defining illnesses (ADIs) in Central America.MethodsWe conducted a retrospective cohort study of all patients living with HIV at the largest HIV clinic in Guatemala. Charts were analyzed for clinical and demographic data. Presence of an ADI was assessed by US Centers for Disease Control definitions; patients who presented with an ADI were compared with those without ADI using descriptive statistics.ResultsOf 3686 patients living with HIV, 931 (25.3%) had an ADI at HIV diagnosis, 748 (80.3%) of whom had CD4 counts lower than 200 cells/mm3. Those with ADIs were more likely to be male (67.5% vs 54.6%; P &amp;lt; .0001) and heterosexual (89.4% vs 85.0%; P = .005). The most common ADIs were Mycobacterium tuberculosis (55.0%), Pneumocystis jirovecii pneumonia (13.7%), esophageal candidiasis (13.4%), and histoplasmosis (11.4%). Histoplasmosis and HIV wasting syndrome were both more common among rural patients.ConclusionsIn this large Guatemalan cohort of patients currently living with HIV, a significant portion presented with an ADI. These data inform the most common ADIs diagnosed among survivors, show that histoplasmosis is more commonly diagnosed in rural patients, and suggest that HIV wasting syndrome may reflect missed histoplasmosis diagnoses.</jats:sec

A Puzzle Involving Galactic Bulge Microlensing Events

We study a sample of 16 microlensed Galactic bulge main sequence turnoff region stars for which high dispersion spectra have been obtained with detailed abundance analyses. We demonstrate that there is a very strong and highly statistically significant correlation between the maximum magnification of the microlensed bulge star and the value of the [Fe/H] deduced from the high resolution spectrum of each object. Physics demands that this correlation, assuming it to be real, be the result of some sample bias. We suggest several possible explanations, but are forced to reject them all,and are left puzzled. To obtain a reliable metallicity distribution in the Galactic bulge based on microlensed dwarf stars it will be necessary to resolve this issue through the course of additional observations.Comment: Submitted to ApJL, table 2 (quite long) will only appear in the on-line version of ApJ