Dust Abundance Variations in the Magellanic Clouds: Probing the Lifecycle of Metals with All-Sky Surveys

Observations and modeling suggest that the dust abundance (gas-to-dust ratio, G/D) depends on (surface) density. The variations of the G/D provide constraints on the timescales for the different processes involved in the lifecycle of metals in galaxies. Recent G/D measurements based on Herschel data suggest a factor 5---10 decrease in the dust abundance between the dense and diffuse interstellar medium (ISM) in the Magellanic Clouds. However, the relative nature of the Herschel measurements precludes definitive conclusions on the magnitude of those variations. We investigate the variations of the dust abundance in the LMC and SMC using all-sky far-infrared surveys, which do not suffer from the limitations of Herschel on their zero-point calibration. We stack the dust spectral energy distribution (SED) at 100, 350, 550, and 850 microns from IRAS and Planck in intervals of gas surface density, model the stacked SEDs to derive the dust surface density, and constrain the relation between G/D and gas surface density in the range 10---100 \Msu pc$^{-2}$ on $\sim$ 80 pc scales. We find that G/D decreases by factors of 3 (from 1500 to 500) in the LMC and 7 (from 1.5$\times 10^4$ to 2000) in the SMC between the diffuse and dense ISM. The surface density dependence of G/D is consistent with elemental depletions and with simple modeling of the accretion of gas-phase metals onto dust grains. This result has important implications for the sub-grid modeling of galaxy evolution, and for the calibration of dust-based gas mass estimates, both locally and at high-redshift.Comment: 20 pages, 14 figure

Forty Years of Arctic: The Journal of the Arctic Institute of North America

When the Arctic Institute of North America was established in 1945 as a membership institution, it was understood that the membership expected the Institute to publish a journal. It appeared for the first time in 1948, as Arctic, The Journal of the Arctic Institute of North America, and has been published continuously for 40 years since then. It is now a leading academic journal publishing research papers from a variety of disciplines on a wide range of subjects dealing with the Arctic. Over the 40 years it published 40 volumes comprising 1231 research papers and other related material. The present study reports a content analysis of the 1231 papers revealing that trends over the last 40 years of research in the North were guided by the economic and academic pressures of the day for northern research. The bulk of papers in the 40 years involved three major areas: biological sciences, earth sciences and social sciences. The proportion of research papers in earth sciences showed a decline, accompanied by a strong growth in biological science papers and a modest growth in social science papers. Over the 40 years, subjects sited in the Canadian Arctic always dominated, with a steady growth from 23% of the total papers per volume to 42%. In particular, significant increases in the numbers of papers in the last 10 years came from resource-related work in the North, as well as from political, educational, cultural and sovereignty-related research. Research in the North leading to publication in Arctic was conducted largely by biologists and earth scientists. Canadian and American authors accounted for most of the papers, with the proportion being roughly equal. ... Numbers of manuscripts received by Arctic increased steadily over the years .... Acceptance rates declined slightly over the years to the present rate of 60%. ...Key words: Arctic Institute of North America, Arctic, content analysis, trends, subject matter, location of study area, author’s discipline, author’s nationality Quand l'Institut arctique de l'Amérique du Nord fut établi en 1945, en tant qu'organisme composé de membres, il était entendu que l'Institut devait publier un journal. Il parut pour la première fois en 1948 sous le nom de Arctic, The Journal of the Arctic Institute of North America, et il a été publié sans interruption depuis 40 ans. C'est maintenant un journal académique de premier plan, qui publie des articles de recherche dans diverses disciplines sur des sujets très variés se rapportant à l'Arctique. Au cours de ces 40 années, le journal a publié 40 volumes comprenant 1231 articles de recherche et d'autres documents connexes. La présente étude offre une analyse du contenu des 1231 articles, qui révèle qu'au cours des 40 dernières années, les sujets de recherche dans le Nord ont été influencés par les pressions économiques et académiques de l'heure. La majorité des articles publiés au cours de ces 40 ans couvrent trois domaines principaux : les sciences biologiques, les sciences de la terre et les sciences sociales. L'analyse montre une diminution de la proportion des articles de recherche sur les sciences de la terre, accompagnée d'une forte augmentation du nombre d'articles sur les sciences biologiques et d'une augmentation modeste de ceux sur les sciences sociales. Pendant ces 40 ans, les sujets situés dans l'Arctique canadien ont toujours dominé, avec une croissance soutenue de 23% à 42% des articles par volume. En particulier, l'augmentation importante du nombre d'articles dans les 10 dernières années est due aux travaux reliés aux ressources naturelles dans le Nord, ainsi qu'aux recherches sur les questions de politique, d'éducation, de culture et de souveraineté. La recherche dans le Nord qui a donné lieu à des publications dans Arctic a été menée en grande partie par des biologistes et des spécialistes en sciences de la terre. Les auteurs canadiens et américains ont été responsables de la majorité des articles, en proportions à peu près égales. Le nombre d'auteurs américains est resté presque constant au cours des 40 années, tandis que celui des auteurs canadiens a légèrement augmenté. Pendant la même période, le nombre de pages et le nombre d'articles par volume ont augmenté et ils atteignent maintenant respectivement environ 400 et 45. Les articles sont devenus plus courts durant ces 40 années, et le nombre d'auteurs part article s'est accru continuellement pour atteindre 1,8 vers la fin de cette période. Le nombre de manuscrits reçus par Arctic a augmenté de façon continue au cours des années, sauf lors d'une interruption causée par le déménagement de l'Institut de Montréal à Calgary. Le taux d'acceptation a diminué légèrement pendant cette période jusqu'au taux actuel de 60%. La plupart des auteurs ayant publié dans Arctic n'ont écrit qu'un seul article et 14 auteurs en ont écrit plus de 5. On peut considérer Arctic comme une publication viable car elle est un véhicule unique en son genre qui permet de faire circuler des informations multidisciplinaires sur un grand nombre de sujets reliés au Nord. Mots clés : Institut arctique de l'Amérique du Nord, Arctic, analyse du contenu, tendances, sujet, emplacement de la zone d'étude, discipline de l'auteur, nationalité de l'auteu

Digitalis for treatment of heart failure in patients in sinus rhythm

<b>Background</b><p></p> Digitalis glycosides have been in clinical use for the treatment of heart failure (HF) for longer than 200 years. In recent years, several trials have been conducted to address concerns about their efficacy and toxicity.<p></p> <b>Objectives</b><p></p> To examine the effectiveness of digitalis glycosides in treating HF in patients with normal sinus rhythm. To examine the effects of digitalis in patients taking diuretics and angiotensin-converting enzyme inhibitors; in patients with varying severity and duration of disease; in patients with prior exposure to digitalis versus no prior exposure; and in patients with "HF due to systolic dysfunction" versus "HF with preserved ejection fraction."<p></p> <b>Search methods</b><p></p> Searches on the following databases were updated in May 2013: The Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, and Dissertation Abstracts. Annual meeting abstracts of the American Heart Association, the American College of Cardiology, and the European Society of Cardiology were searched from 1996 to March 2013. In addition, reference lists provided by the pharmaceutical industry (GlaxoSmithKline and Covis Pharma) were searched.<p></p> <b>Selection criteria</b><p></p> Included were randomized placebo-controlled trials of 20 or more adult participants of either sex with symptomatic HF who were studied for seven weeks or longer. Excluded were trials in which the prevalence of atrial fibrillation was 2% or greater, or in which any arrhythmia that might compromise cardiac function or any potentially reversible cause of HF such as acute ischemic heart disease or myocarditis was present.<p></p> <b>Data collection and analysis</b><p></p> Articles selected from the searches described above were evaluated in a joint effort of the review authors. The staff of the Cochrane Heart Group ran searches on the Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE.<p></p> <b>Main results</b><p></p> No new studies were identified in the updated searches. Thirteen studies (7896 participants) are included, and major endpoints of mortality, hospitalization, and clinical status, based respectively on 8, 4, and 12 of these selected studies, were recorded and analyzed. The data show no evidence of a difference in mortality between treatment and control groups, whereas digitalis therapy is associated with lower rates of both hospitalization and clinical deterioration. The largest study, in which most participants were taking angiotensin-converting enzyme inhibitors, showed a significant rise in “other cardiac” deaths, possibly due to arrhythmias. However collectively, these findings were based on studies done before beta-blockers, as well as angiotensin receptor blockers and aldosterone antagonists, became widely used to treat HF.<p></p> <b>Authors' conclusions</b><p></p> The literature indicates that digitalis may have a useful role in the treatment of patients with HF who are in normal sinus rhythm. New trials are needed to elucidate the importance of the dosage of digitalis and its usefulness in the era of beta-blockers and other agents shown to be effective in treating HF.<p></p&gt

TRX: A Formally Verified Parser Interpreter

Parsing is an important problem in computer science and yet surprisingly little attention has been devoted to its formal verification. In this paper, we present TRX: a parser interpreter formally developed in the proof assistant Coq, capable of producing formally correct parsers. We are using parsing expression grammars (PEGs), a formalism essentially representing recursive descent parsing, which we consider an attractive alternative to context-free grammars (CFGs). From this formalization we can extract a parser for an arbitrary PEG grammar with the warranty of total correctness, i.e., the resulting parser is terminating and correct with respect to its grammar and the semantics of PEGs; both properties formally proven in Coq.Comment: 26 pages, LMC

Mechanosensing of shear by Pseudomonas aeruginosa leads to increased levels of the cyclic-di-GMP signal initiating biofilm development

Biofilms are communities of sessile microbes that are phenotypically distinct from their genetically identical, free-swimming counterparts. Biofilms initiate when bacteria attach to a solid surface. Attachment triggers intracellular signaling to change gene expression from the planktonic to the biofilm phenotype. For Pseudomonas aeruginosa, it has long been known that intracellular levels of the signal cyclic-di-GMP increase upon surface adhesion and that this is required to begin biofilm development. However, what cue is sensed to notify bacteria that they are attached to the surface has not been known. Here, we show that mechanical shear acts as a cue for surface adhesion and activates cyclic-di-GMP signaling. The magnitude of the shear force, and thereby the corresponding activation of cyclic-di-GMP signaling, can be adjusted both by varying the strength of the adhesion that binds bacteria to the surface and by varying the rate of fluid flow over surface-bound bacteria. We show that the envelope protein PilY1 and functional type IV pili are required mechanosensory elements. An analytic model that accounts for the feedback between mechanosensors, cyclic-di-GMP signaling, and production of adhesive polysaccharides describes our data well