Lyman Alpha Blobs as an Observational Signature of Cold Accretion Streams into Galaxies

Recent hydrodynamic simulations of galaxy formation reveal streams of cold (T ~ 1e4 K) gas flowing into the centers of dark matter halos as massive as 1e12-1e13.5 M_sun at redshifts z~1-3. In this paper we show that if > 20% of the gravitational binding energy of the gas is radiated away, then the simulated cold flows are spatially extended Lyman Alpha (Lya) sources with luminosities, Lya line widths, and number densities that are comparable to those of observed Lya blobs. Furthermore, the filamentary structure of the cold flows can explain the wide range of observed Lya blob morphologies. Since the most massive halos form in dense environments, the association of Lya blobs with overdense regions arise naturally. We argue that Lya blobs - even those which are clearly associated with starburst galaxies or quasars - provide direct observational support for the cold accretion mode of galaxies. We discuss various testable predictions of this association.Comment: MNRAS in press. 13 pages, 6 figures. Discussion + references added. Main conclusions unaffecte

GeV Gamma-Ray Attenuation and the High-Redshift UV Background

We present new calculations of the evolving UV background out to the epoch of cosmological reionization and make predictions for the amount of GeV gamma-ray attenuation by electron-positron pair production. Our results are based on recent semi-analytic models of galaxy formation, which provide predictions of the dust-extinguished UV radiation field due to starlight, and empirical estimates of the contribution due to quasars. We account for the reprocessing of ionizing photons by the intergalactic medium. We test whether our models can reproduce estimates of the ionizing background at high redshift from flux decrement analysis and proximity effect measurements from quasar spectra, and identify a range of models that can satisfy these constraints. Pair-production against soft diffuse photons leads to a spectral cutoff feature for gamma rays observed between 10 and 100 GeV. This cutoff varies with redshift and the assumed star formation and quasar evolution models. We find only negligible amounts of absorption for gamma rays observed below 10 GeV for any emission redshift. With observations of high-redshift sources in sufficient numbers by the Fermi Gamma-ray Space Telescope and new ground-based instruments it should be possible to constrain the extragalactic background light in the UV and optical portion of the spectrum.Comment: 19 pages, 12 figures, Accepted for publication in MNRAS, this version includes minor correction

"I really should've gone to the doctor": older adults and family caregivers describe their experiences with community-acquired pneumonia

BACKGROUND: Responding to acute illness symptoms can often be challenging for older adults. The primary objective of this study was to describe how community-dwelling older adults and their family members responded to symptoms of community-acquired pneumonia (CAP). METHODS: A qualitative study that used face-to-face semi-structured interviews to collect data from a purposeful sample of seniors aged 60+ and their family members living in a mid-sized Canadian city. Data analysis began with descriptive and interpretive coding, then advanced as the research team repeatedly compared emerging thematic categories to the raw data. Searches for disconfirming evidence and member checking through focus groups provided additional data and helped ensure rigour. RESULTS: Community-acquired pneumonia symptoms varied greatly among older adults, making decisions to seek care difficult for them and their family members. Both groups took varying amounts of time as they attempted to sort out what was wrong and then determine how best to respond. Even after they concluded something was wrong, older adults with confirmed pneumonia continued to wait for days, to over a week, before seeking medical care. Participants provided diverse reasons for this delay, including fear, social obligations (work, family, leisure), and accessibility barriers (time, place, systemic). Several older adults and family members regretted their delays in seeking help. CONCLUSION: Treatment-seeking delay is a variable, multi-phased decision-making process that incorporates symptom assessment plus psychosocial and situational factors. Public health and health care professionals need to educate older adults about the potential causes and consequences of unnecessary waits. Such efforts may reduce the severity of community-acquired pneumonia upon presentation at clinics and hospitals, and that, in turn, could potentially improve health outcomes

Vaccine herd effect

Vaccination ideally protects susceptible populations at high risk for complications of the infection. However, vaccines for these subgroups do not always provide sufficient effectiveness. The herd effect or herd immunity is an attractive way to extend vaccine benefits beyond the directly targeted population. It refers to the indirect protection of unvaccinated persons, whereby an increase in the prevalence of immunity by the vaccine prevents circulation of infectious agents in susceptible populations. The herd effect has had a major impact in the eradication of smallpox, has reduced transmission of pertussis, and protects against influenza and pneumococcal disease. A high uptake of vaccines is generally needed for success. In this paper we aim to provide an update review on the herd effect, focusing on the clinical benefit, by reviewing data for specific vaccines

Mutation of HIV-1 Genomes in a Clinical Population Treated with the Mutagenic Nucleoside KP1461

The deoxycytidine analog KP1212, and its prodrug KP1461, are prototypes of a new class of antiretroviral drugs designed to increase viral mutation rates, with the goal of eventually causing the collapse of the viral population. Here we present an extensive analysis of viral sequences from HIV-1 infected volunteers from the first “mechanism validation” phase II clinical trial of a mutagenic base analog in which individuals previously treated with antiviral drugs received 1600 mg of KP1461 twice per day for 124 days. Plasma viral loads were not reduced, and overall levels of viral mutation were not increased during this short-term study, however, the mutation spectrum of HIV was altered. A large number (N = 105 per sample) of sequences were analyzed, each derived from individual HIV-1 RNA templates, after 0, 56 and 124 days of therapy from 10 treated and 10 untreated control individuals (>7.1 million base pairs of unique viral templates were sequenced). We found that private mutations, those not found in more than one viral sequence and likely to have occurred in the most recent rounds of replication, increased in treated individuals relative to controls after 56 (p = 0.038) and 124 (p = 0.002) days of drug treatment. The spectrum of mutations observed in the treated group showed an excess of A to G and G to A mutations (p = 0.01), and to a lesser extent T to C and C to T mutations (p = 0.09), as predicted by the mechanism of action of the drug. These results validate the proposed mechanism of action in humans and should spur development of this novel antiretroviral approach.Koronis Pharmaceutical

Probing the Epoch of Reionization with Milky Way Satellites

While the connection between high-redshift star formation and the local universe has recently been used to understand the observed population of faint dwarf galaxies in the Milky Way (MW) halo, we explore how well these nearby objects can probe the epoch of first light. We construct a detailed, physically motivated model for the MW satellites based on the state-of-the-art Via Lactea II dark-matter simulations. Our model incorporates molecular hydrogen (H_2) cooling in low-mass systems and inhomogeneous photo-heating feedback during the internal reionization of our own galaxy. We find that the existence of MW satellites fainter than M_V ~ -5 is strong evidence for H_2 cooling in low-mass halos, while satellites with -5 > M_V > -9 were affected by hydrogen cooling and photoheating feedback. The age of stars in very low-luminosity systems and the minimum luminosity of these satellites are key predictions of our model. Most of the stars populating the brightest MW satellites could have formed after the epoch of reionization. Our models also predict a significantly larger dispersion in M_300 values than observed and a number of luminous satellites with M_300 as low as 10^6 solar masses.Comment: 11 pages, 6 figures. Accepted by MNRAS. Updated to accepted versio

Urethral catheters: can we reduce use?

<p>Abstract</p> <p>Background</p> <p>Indwelling urinary catheters are the main cause of healthcare-associated urinary tract infections. It can be expected that reduction of the use of urinary catheters will lead to decreased numbers of urinary tract infection.</p> <p>Methods</p> <p>The efficacy of an intervention programme to improve adherence to recommendations to reduce the use of urethral catheters was studied in a before-after comparison in ten Dutch hospitals. The programme detected barriers and facilitators and each individual facility was supported with developing their own intervention strategy. Outcome was evaluated by the prevalence of catheters, alternatives such as diapers, numbers of urinary tract infections, the percentage of correct indications and the duration of catheterization. The costs of the implementation as well as the catheterization were evaluated.</p> <p>Results</p> <p>Of a population of 16,495 hospitalized patients 3335 patients of whom 2943 were evaluable for the study, had a urethral catheter. The prevalence of urethral catheters decreased insignificantly in neurology (OR 0.93; 95% CI 0.77 - 1.13) and internal medicine wards (OR 0.97; 95% CI 0.83 - 1.13), decreased significantly in surgical wards (OR 0.84; 95% CI 0.75 - 0.96), but increased significantly in intensive care (IC) and coronary care (CC) units (OR 1.48; 95% CI 1.01 - 2.17). The use of alternatives was limited and remained so after the intervention. Duration of catheterization decreased insignificantly in IC/CC units (ratio after/before 0.95; 95% CI 0.78 - 1.16) and neurology (ratio 0.97; 95% CI 0.80 - 1.18) and significantly in internal medicine (ratio 0.81; 95% CI 0.69 - 0.96) and surgery wards (ratio 0.80; 95% CI 0.71 - 0.90). The percentage of correct indications on the day of inclusion increased from 50 to 67% (p < 0.0001). The prevalence of urinary tract infections in catheterized patients did not change. The mean cost saved per 100 patients was € 537.</p> <p>Conclusion</p> <p>Targeted implementation of recommendations from an existing guideline can lead to better adherence and cost savings. Especially, hospitals which use a lot of urethral catheters or where catheterization is prolonged, can expect important improvements.</p

Reflections on Pandemic (H1N1) 2009 and the International Response

Gabriel Leung and Angus Nicoll provide their reflections on the international response to the 2009 H1N1 influenza pandemic, including what went well and what changes need to be made in anticipation of future flu pandemics

The ubiquitin-like molecule interferon-stimulated gene 15 (ISG15) is a potential prognostic marker in human breast cancer

INTRODUCTION: ISG15 is an ubiquitin-like molecule that is strongly upregulated by type I interferons as a primary response to diverse microbial and cellular stress stimuli. However, alterations in the ISG15 signalling pathway have also been found in several human tumour entities. To the best of our knowledge, in the current study we present for the first time a systematic characterisation of ISG15 expression in human breast cancer and normal breast tissue both at the mRNA and protein level. METHOD: Using semiquantitative real-time PCR, cDNA dot-blot hybridisation and immunohistochemistry, we systematically analysed ISG15 expression in invasive breast carcinomas (n = 910) and normal breast tissues (n = 135). ISG15 protein expression was analysed in two independent cohorts on tissue microarrays; in an initial evaluation set of 179 breast carcinomas and 51 normal breast tissues; and in a second large validation set of 646 breast carcinomas and 10 normal breast tissues. In addition, a collection of benign and malignant mammary cell lines (n = 9) were investigated for ISG15 expression. RESULTS: ISG15 was overexpressed in breast carcinoma cells compared with normal breast tissue, both at the RNA and protein level. Recurrence-free (p = 0.030), event-free (p = 0.001) and overall (p = 0.001) survival analyses showed a significant correlation between ISG15 overexpression and unfavourable prognosis. CONCLUSION: Therefore, ISG15 may represent a novel breast tumour marker with prognostic significance and may be helpful in selecting patients for and predicting response to the treatment of human breast cancer