A Bayesian Approach to Calibrating Period-Luminosity Relations of RR Lyrae Stars in the Mid-Infrared

A Bayesian approach to calibrating period-luminosity (PL) relations has substantial benefits over generic least-squares fits. In particular, the Bayesian approach takes into account the full prior distribution of the model parameters, such as the a priori distances, and refits these parameters as part of the process of settling on the most highly-constrained final fit. Additionally, the Bayesian approach can naturally ingest data from multiple wavebands and simultaneously fit the parameters of PL relations for each waveband in a procedure that constrains the parameter posterior distributions so as to minimize the scatter of the final fits appropriately in all wavebands. Here we describe the generalized approach to Bayesian model fitting and then specialize to a detailed description of applying Bayesian linear model fitting to the mid-infrared PL relations of RR Lyrae variable stars. For this example application we quantify the improvement afforded by using a Bayesian model fit. We also compare distances previously predicted in our example application to recently published parallax distances measured with the Hubble Space Telescope and find their agreement to be a vindication of our methodology. Our intent with this article is to spread awareness of the benefits and applicability of this Bayesian approach and encourage future PL relation investigations to consider employing this powerful analysis method.Comment: 6 pages, 1 figure. Accepted for publication in Astrophysics & Space Science. Following a presentation at the conference The Fundamental Cosmic Distance Scale: State of the Art and the Gaia Perspective, Naples, May 201

The metallicity dependence of the Cepheid PL-relation

A sample of 37 Galactic, 10 LMC and 6 SMC cepheids is compiled for which individual metallicity estimates exist and BVIK photometry in almost all cases. The Galactic cepheids all have an individual distance estimate available. For the MC objects different sources of photometry are combined to obtain improved periods and mean magnitudes. A multi-parameter Period-Luminosity relation is fitted to the data which also solves for the distance to the LMC and SMC. When all three galaxies are considered, without metallicity effect, a significant quadratic term in log P is found, as previously observed and also predicted in some theoretical calculations. For the present sample it is empirically determined that for log P < 1.65 linear PL-relations may be adopted, but this restricts the sample to only 4 LMC and 1 SMC cepheid. Considering the Galactic sample a metallicity effect is found in the zero point in the VIWK PL-relation (-0.6 \pm 0.4 or -0.8 \pm 0.3 mag/dex depending on the in- or exclusion of one object), in the sense that metal-rich cepheids are brighter. The small significance is mostly due to the fact that the Galactic sample spans a narrow metallicity range. The error is to a significant part due to the error in the metallicity determinations and not to the error in the fit. Including the 5 MC cepheids broadens the observed metallicity range and a metallity effect of about -0.27 \pm 0.08 mag/dex in the zero point is found in VIWK, in agreement with some previous empirical estimates, but now derived using direct metallicity determinations for the cepheids themselves.Comment: Accepted Astronomy and Astrophysics, February 20, 200

Direct Distances to Cepheids in the Large Magellanic Cloud: Evidence for a Universal Slope of the Period-Luminosity Relation up to Solar Abundance

We have applied the infrared surface brightness (ISB) technique to derive distances to 13 Cepheids in the LMC which span a period range from 3 to 42 days. From the absolute magnitudes of the variables calculated from these distances, we find that the LMC Cepheids define tight period-luminosity relations in the V, I, W, J and K bands which agree exceedingly well with the corresponding Galactic PL relations derived from the same technique, and are significantly steeper than the LMC PL relations in these bands observed by the OGLE-II Project in V, I and W, and by Persson et al. in J and K. We find that the tilt-corrected true distance moduli of the LMC Cepheids show a significant dependence on period, which hints at a systematic error in the ISB technique related to the period of the stars. We identify as the most likely culprit the p-factor which converts the radial into pulsational velocities; our data imply a much steeper period dependence of the p-factor than previously thought, and we derive p=1.58 (+/-0.02) -0.15 (+/-0.05) logP as the best fit from our data, with a zero point tied to the Milky Way open cluster Cepheids. Using this revised p-factor law, the period dependence of the LMC Cepheid distance moduli disappears, and at the same time the Milky Way and LMC PL relations agree among themselves, and with the directly observed LMC PL relations, within the 1 sigma uncertainties. Our main conclusion is that the previous, steeper Galactic PL relations were caused by an erroneous calibration of the p-factor law, and that there is now evidence that the slope of the Cepheid PL relation is independent of metallicity up to solar metallicity, in both optical, and near-infrared bands.Comment: ApJ accepte

Activity Dependent Changes In Functional And Morphological Characteristics Among Presympathetic Neurons Of The Rostral Ventrolateral Medulla

A sedentary lifestyle is a major risk factor for the development of cardiovascular disease (CVD), the leading cause of death among Americans. Increasing evidence implicates increased sympathetic nerve activity (SNA) as the link between a sedentary lifestyle and CVD. The research presented in this dissertation examines the region of the brainstem known as the rostral ventrolateral medulla (RVLM) and how its regulation of SNA changes as a result of sedentary conditions. Our group has previously reported that sedentary conditions enhance splanchnic SNA in response to pharmacologically induced decreases in blood pressure or by direct activation of the RVLM via microinjection of the amino acid glutamate. More recently, our group has published the first evidence of overt structural differences in phenotypically identified RVLM neurons from sedentary versus physically active rats. Although collectively these studies suggest that a sedentary lifestyle results in increased activity and sensitivity of presympathetic RVLM neurons involved in blood pressure regulation, direct evidence of this proposed mechanism for the observed increased splanchnic SNA is lacking. The studies presented in this dissertation use in vivo characterization and juxtacellular labeling of RVLM neurons to examine the potential mechanistic connection and physiological relevance of overt changes in their structure and function and how they relate to enhanced SNA in sedentary versus physically active rats. These cross sectional studies are complemented by longitudinally based studies of in vivo neuronal activity in the RVLM utilizing manganese-enhanced magnetic resonance imaging (MEMRI). The information gained from these studies will contribute to our understanding of how a sedentary lifestyle contributes to the development of CVD and may provide information on new therapeutic targets in the brain to prevent or slow the progression of CVD

In Situ Resource Utilization (ISRU II) Technical Interchange Meeting

This volume contains extended abstracts that have been accepted for presentation at the In Situ Resource Utilization (ISRU II) Technical Interchange Meeting, November 18-19, 1997, at the Lunar and Planetary Institute, Houston, Texas. Included are topics which include: Extraterrestrial resources, in situ propellant production, sampling of planetary surfaces, oxygen production, water vapor extraction from the Martian atmosphere, gas generation, cryogenic refrigeration, and propellant transport and storage

The first case of botulism in a donkey

open8noBotulism, a severe neuroparalytic disease that can affect humans, all warm-blooded animals, and some fishes, is caused by exotoxins produced by ubiquitous, obligate anaerobic, spore-forming bacteria belonging to the genus Clostridium and named botulinum neurotoxin (BoNT)-producing clostridia. This report presents the case of a 3-year-old donkey mare referred for progressive and worsening dysphagia of four days' duration. Her voluntary effort in eating and drinking was conserved, and she was able to slow chew without swallowing. A complete neurological examination was performed, and botulism was strongly suspected. The ability to swallow feed and water returned on the tenth day of hospitalization and improved progressively. The jenny was discharged from the hospital after fifteen days. During the hospitalization, the Italian National Reference Centre for Botulism confirmed the diagnosis: mare's feces were positive for BoNT/B and Clostridium botulinum type B.openLanci A.; Rinnovati R.; Anniballi F.; Auricchio B.; Scalfaro C.; Menchetti M.; Spadari A.; Mariella J.Lanci A.; Rinnovati R.; Anniballi F.; Auricchio B.; Scalfaro C.; Menchetti M.; Spadari A.; Mariella J

The use of legume cover crops for livestock feeding in semi arid environments : Effects of Calopogonium mucunoïdes used as forage on weight maintenance of draught donkeys during the dry season

International audienceEn régions semi-arides, la saison sèche est une période difficile pour l'entretien des animaux, du fait de la rareté des ressources alimentaires. Les animaux sont maintenus sur des résidus de fourrage de pauvre qualité, nécessitant une complémentation protéique si l'on veut assurer leur productivité. Dans cette étude, Calopogonium mucunoides a été distribué à des ânes de trait au repos pendant la saison sèche pour tester son appétibilité et ses valeurs nutritionnelles: 12 ânes adultes ont été repartis en 3 groupes alimentés comme suit: Groupe A = tiges de maïs + 0.5 kg d'une provende domestique constituée d'un mélange de son de maïs et de tourteau de coton en quantités égales; Groupe B = C. mucunoides + 0.25 kg de provende; Groupe C = C. mucunoides + 0.5 kg de provende. La consommation de fourrage, d'eau et le poids vif des animaux ont été enregistrés. Des échantillons de fourrage et de fèces ont été analysés. Les résultats n'ont montré aucune différence significative dans la consommation de fourrage. Une différence hautement significative a été observée pour la digestibilité des rations proposées, la meilleure étant pour le groupe B. Quel que soit le groupe, la consommation d'eau augmente et l'ingestion de fourrage diminue lorsque la température ambiante s'élève. La forte digestibilité de C. mucunoides confirme sa qualité supérieure aux autres ressources alimentaires. En dépit de sa faible appétibilité ou acceptabilité par d'autres espèces, C. mucunoides présente un taux élevé de protéines brutes intéressant pour tous les animaux. Elle pourrait effectivement remplacer les sources agro-industrielles de compléments protéiques, difficiles d'accès pour les petits exploitants. (Résumé d'auteur

Pengaruh Latihan Fisik Aerobik terhadap Indeks Massa Tubuh, Rasio Lingkar Pinggang-Panggul dan Tekanan Darah Pasien Hipertensi di Palembang

Hipertensi merupakan salah satu faktor risiko penyakit kardiovaskular dengan prevalensi dan kematian yang cukup tinggi. Hipertensi dikaitkan dengan sejumlah penanda risiko kardiovaskular lainnya seperti obesitas, pola nutrisi yang tidak sehat dan aktivitas fisik yang rendah. Beberapa penelitian menunjukkan bahwa obesitas dan tekanan darah seseorang dapat dipengaruhi oleh aktifitas fisik. Tujuan: Mengetahui pengaruh latihan fisik aerobik terhadap IMT, RLPP dan tekanan darah pada pasien hipertensi di RS Pertamedika Palembang. Metode: Penelitian quasy experimental dengan one-group pretest-posttest. Data  adalah hasil pengukuran IMT, RLPP serta tekanan darah yang diukur sebelum dan setelah latihan fisik aerobik 3 kali seminggu selama 4 minggu dengan durasi 30 menit. Hasil: Sebanyak 21 sampel penelitian diambil dengan cara total sampling berdasarkan kriteria inklusi dan eksklusi. Hasil uji statistik didapatkan penurunan rerata IMT setelah latihan fisik aerobik yang signifikan menjadi 28,5 dengan P=0,023 (P<0,05), RLPP setelah latihan fisik aerobik yang signifikan menjadi 0,87 dengan P=0.002 (P<0,05), serta penurunan rerata sebesar 6,91 ± 1,008 mmHg untuk tekanan darah sistolik dan 7,39 ± 0,035 untuk tekanan darah diastolik sesudah latihan fisik dengan p value 0,000 (< 0,05). Kesimpulan:  Terdapat Pengaruh Latihan Fisik Aerobik terhadap Indeks Massa Tubuh, Rasio Lingkar Pinggang-Panggul dan tekanan darah pasien hipertensi di RS Pertamedika Palembang