Analytical solution of a model for complex food webs

We investigate numerically and analytically a recently proposed model for food webs [Nature {\bf 404}, 180 (2000)] in the limit of large web sizes and sparse interaction matrices. We obtain analytical expressions for several quantities with ecological interest, in particular the probability distributions for the number of prey and the number of predators. We find that these distributions have fast-decaying exponential and Gaussian tails, respectively. We also find that our analytical expressions are robust to changes in the details of the model.Comment: 4 pages (RevTeX). Final versio

Diminished temperature and vegetation seasonality over northern high latitudes

Global temperature is increasing, especially over northern lands (>50° N), owing to positive feedbacks1. As this increase is most pronounced in winter, temperature seasonality (ST)—conventionally defined as the difference between summer and winter temperatures—is diminishing over time2, a phenomenon that is analogous to its equatorward decline at an annual scale. The initiation, termination and performance of vegetation photosynthetic activity are tied to threshold temperatures3. Trends in the timing of these thresholds and cumulative temperatures above them may alter vegetation productivity, or modify vegetation seasonality (SV), over time. The relationship between ST and SV is critically examined here with newly improved ground and satellite data sets. The observed diminishment of ST and SV is equivalent to 4° and 7° (5° and 6°) latitudinal shift equatorward during the past 30 years in the Arctic (boreal) region. Analysis of simulations from 17 state-of-the-art climate models4 indicates an additional STdiminishment equivalent to a 20° equatorward shift could occur this century. How SV will change in response to such large projected ST declines and the impact this will have on ecosystem services5 are not well understood. Hence the need for continued monitoring6 of northern lands as their seasonal temperature profiles evolve to resemble thosefurther south.Lopullinen vertaisarvioitu käsikirjoitu

Early respiratory viral infections in infants with cystic fibrosis

This article is made available for unrestricted research re-use and secondary analysis in any form or by any means with acknowledgement of the original source. These permissions are granted for the duration of the World Health Organization (WHO) declaration of COVID-19 as a global pandemic.Background Viral infections contribute to morbidity in cystic fibrosis (CF), but the impact of respiratory viruses on the development of airway disease is poorly understood. Methods Infants with CF identified by newborn screening were enrolled prior to 4 months of age to participate in a prospective observational study at 4 centers. Clinical data were collected at clinic visits and weekly phone calls. Multiplex PCR assays were performed on nasopharyngeal swabs to detect respiratory viruses during routine visits and when symptomatic. Participants underwent bronchoscopy with bronchoalveolar lavage (BAL) and a subset underwent pulmonary function testing. We present findings through 8.5 months of life. Results Seventy infants were enrolled, mean age 3.1 ± 0.8 months. Rhinovirus was the most prevalent virus (66%), followed by parainfluenza (19%), and coronavirus (16%). Participants had a median of 1.5 viral positive swabs (range 0–10). Past viral infection was associated with elevated neutrophil concentrations and bacterial isolates in BAL fluid, including recovery of classic CF bacterial pathogens. When antibiotics were prescribed for respiratory-related indications, viruses were identified in 52% of those instances. Conclusions Early viral infections were associated with greater neutrophilic inflammation and bacterial pathogens. Early viral infections appear to contribute to initiation of lower airway inflammation in infants with CF. Antibiotics were commonly prescribed in the setting of a viral infection. Future investigations examining longitudinal relationships between viral infections, airway microbiome, and antibiotic use will allow us to elucidate the interplay between these factors in young children with CF

A Sample of Intermediate-Mass Star-Forming Regions: Making Stars at Mass Column Densities <1 g/cm^2

In an effort to understand the factors that govern the transition from low- to high-mass star formation, we identify for the first time a sample of intermediate-mass star-forming regions (IM SFRs) where stars up to - but not exceeding - 8 solar masses are being produced. We use IRAS colors and Spitzer Space Telescope mid-IR images, in conjunction with millimeter continuum and CO maps, to compile a sample of 50 IM SFRs in the inner Galaxy. These are likely to be precursors to Herbig AeBe stars and their associated clusters of low-mass stars. IM SFRs constitute embedded clusters at an early evolutionary stage akin to compact HII regions, but they lack the massive ionizing central star(s). The photodissociation regions that demarcate IM SFRs have typical diameters of ~1 pc and luminosities of ~10^4 solar luminosities, making them an order of magnitude less luminous than (ultra)compact HII regions. IM SFRs coincide with molecular clumps of mass ~10^3 solar masses which, in turn, lie within larger molecular clouds spanning the lower end of the giant molecular cloud mass range, 10^4-10^5 solar masses. The IR luminosity and associated molecular mass of IM SFRs are correlated, consistent with the known luminosity-mass relationship of compact HII regions. Peak mass column densities within IM SFRs are ~0.1-0.5 g/cm^2, a factor of several lower than ultra-compact HII regions, supporting the proposition that there is a threshold for massive star formation at ~1 g/cm^2.Comment: 61 pages, 6 tables, 20 figures. Accepted for publication in the Astronomical Journa

The source counts of submillimetre galaxies detected at 1.1 mm

The source counts of galaxies discovered at sub-millimetre and millimetre wavelengths provide important information on the evolution of infrared-bright galaxies. We combine the data from six blank-field surveys carried out at 1.1 mm with AzTEC, totalling 1.6 square degrees in area with root-mean-square depths ranging from 0.4 to 1.7 mJy, and derive the strongest constraints to date on the 1.1 mm source counts at flux densities S(1100) = 1-12 mJy. Using additional data from the AzTEC Cluster Environment Survey to extend the counts to S(1100) ~ 20 mJy, we see tentative evidence for an enhancement relative to the exponential drop in the counts at S(1100) ~ 13 mJy and a smooth connection to the bright source counts at >20 mJy measured by the South Pole Telescope; this excess may be due to strong lensing effects. We compare these counts to predictions from several semi-analytical and phenomenological models and find that for most the agreement is quite good at flux densities > 4 mJy; however, we find significant discrepancies (>3sigma) between the models and the observed 1.1 mm counts at lower flux densities, and none of them are consistent with the observed turnover in the Euclidean-normalised counts at S(1100) < 2 mJy. Our new results therefore may require modifications to existing evolutionary models for low luminosity galaxies. Alternatively, the discrepancy between the measured counts at the faint end and predictions from phenomenological models could arise from limited knowledge of the spectral energy distributions of faint galaxies in the local Universe.Comment: 16 pages, 3 figures, 4 tables; accepted for publication in MNRA

HerMES: point source catalogues from Herschel-SPIRE observations II

Key Programme on the Herschel Space Observatory. With a wedding cake survey strategy, it consists of nested fields with varying depth and area totalling ∼380 deg2. In this paper, we present deep point source catalogues extracted from Herschel-Spectral and Photometric Imaging Receiver (SPIRE) observations of all HerMES fields, except for the later addition of the 270 deg2 HerMES Large-Mode Survey (HeLMS) field. These catalogues constitute the second Data Release (DR2) made in 2013 October. A sub-set of these catalogues, which consists of bright sources extracted from Herschel-SPIRE observations completed by 2010 May 1 (covering ∼74 deg2) were released earlier in the first extensive data release in 2012 March. Two different methods are used to generate the point source catalogues, the SUSSEXTRACTOR point source extractor used in two earlier data releases (EDR and EDR2) and a new source detection and photometry method. The latter combines an iterative source detection algorithm, STARFINDER, and a De-blended SPIRE Photometry algorithm. We use end-to-end Herschel-SPIRE simulations with realistic number counts and clustering properties to characterize basic properties of the point source catalogues, such as the completeness, reliability, photometric and positional accuracy. Over 500 000 catalogue entries in HerMES fields (except HeLMS) are released to the public through the HeDAM (Herschel Database in Marseille) website (http://hedam.lam.fr/HerMES)

Prevalence of Trichomonas vaginalis and Coinfection with Chlamydia trachomatis and Neisseria gonorrhoeae in the United States as Determined by the Aptima Trichomonas vaginalis Nucleic Acid Amplification Assay

Our aim was to determine Trichomonas vaginalis prevalence using the Aptima Trichomonas vaginalis assay (ATV; Gen-Probe) and the prevalence of Chlamydia trachomatis and Neisseria gonorrhoeae coinfections in U.S. women undergoing screening for C. trachomatis/N. gonorrhoeae. Discarded urogenital samples from 7,593 women (18 to 89 years old) undergoing C. trachomatis/N. gonorrhoeae screening using the Aptima Combo 2 assay (Gen-Probe) in various clinical settings were tested with ATV. Overall, T. vaginalis, C. trachomatis, and N. gonorrhoeae prevalences were 8.7%, 6.7%, and 1.7%, respectively. T. vaginalis was more prevalent than C. trachomatis or N. gonorrhoeae in all age groups except the 18- to 19-year-old group. The highest T. vaginalis prevalence was in women ≥40 years old (>11%), while the highest C. trachomatis prevalence (9.2%) and N. gonorrhoeae prevalence (2.2%) were in women C. trachomatis/T. vaginalis, 0.61% for C. trachomatis/N. gonorrhoeae and N. gonorrhoeae/T. vaginalis, and 0.24% for C. trachomatis/N. gonorrhoeae/T. vaginalis and highest in women T. vaginalis prevalence differed by race/ethnicity, with the highest prevalence in black women (20.2%). T. vaginalis prevalence ranged from 5.4% in family planning clinics to 22.3% in jails. Multivariate analysis determined that ages of ≥40 years, black race, and patient locations were significantly associated with T. vaginalis infection. T. vaginalis is the most common sexually transmitted infection (STI) in women of >40 years, while C. trachomatis and N. gonorrhoeae prevalence is lowest in that age group. Higher T. vaginalis prevalence in women of >40 years is probably attributed to the reason for testing, i.e., symptomatic status versus routine screening in younger women. Coinfections were relatively low. High T. vaginalis prevalence in all age groups suggests that women screened for C. trachomatis/N. gonorrhoeae, whether asymptomatic or symptomatic, should be screened for T. vaginalis

AzTEC half square degree survey of the SHADES fields — II. Identifications, redshifts and evidence for large-scale structure

This article has been accepted for publication in Monthly Notices Of The Royal Astronomical Society ©: 2012 Michał J. Michałowski et al. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.The Astronomical Thermal Emission Camera (AzTEC) 1.1 mm survey of the two SCUBA HAlf Degree Extragalactic Survey (SHADES) fields is the largest (0.7 deg(2)) blank-field millimetre-wavelength (mm-wavelength) survey undertaken to date at a resolution of ≃18 arcsec and a depth of ≃1 mJy. We have used the deep optical to radio multiwavelength data in the SHADES Lockman Hole East and SXDF/UDS fields to obtain galaxy identifications for ≃64 per cent (≃80 per cent including tentative identifications) of the 148 AzTEC-SHADES 1.1 mm sources reported by Austermann et al., exploiting deep radio and 24 μm data complemented by methods based on 8 μm flux density and red optical–infrared (i − K) colour. This unusually high identification rate can be attributed to the relatively bright mm-wavelength flux density threshold, combined with the relatively deep supporting multifrequency data now available in these two well-studied fields. We have further exploited the optical–mid-infrared–radio data to derive an ≃60 per cent (≃75 per cent including tentative identifications) complete redshift distribution for the AzTEC-SHADES sources, yielding a median redshift of z ≃ 2.2, with a high-redshift tail extending to at least z ≃ 4. Despite the larger area probed by the AzTEC survey relative to the original SCUBA-SHADES imaging, the redshift distribution of the AzTEC sources is consistent with that displayed by the SCUBA sources, and reinforces tentative evidence that the redshift distribution of mm/submm sources in the Lockman Hole field is significantly different from that found in the SXDF/UDS field. Comparison with simulated surveys of similar scale extracted from semi-analytic models based on the Millennium simulation indicates that this is as expected if the mm/submm sources are massive (M > 1011 M⊙) star-forming galaxies tracing large-scale structures over scales of 10–20 Mpc. This confirms the importance of surveys covering several deg2 (as now underway with SCUBA2) to obtain representative samples of bright (sub)mm-selected galaxies. This work provides a foundation for the further exploitation of the Spitzer and Herschel data in the SHADES fields in the study of the stellar masses and specific star formation rates of the most active star-forming galaxies in cosmic history