Clusters in the inner spiral arms of M51: the cluster IMF and the formation history

We study the cluster population in a region of 3.2x3.2 kpc^2 in the inner spiral arms of the intergacting galaxy M51, at a distance of about 1 to 3 kpc from the nucleus, based on HST--WFPC2 images taken through five broadband and two narrowband filters. We found 877 cluster candidates and we derived their ages, initial masses and extinctions by comparing their energy distribution with the Starburst99 cluster models. We describe the 3 and 2-dimensional least-square energy fitting method that was used (3DEF, 2DEF). The lack of [OIII] emission in even the youngest clusters with strong H-alpha emission, indicates the absence of the most massive stars and suggests a mass upper limit of about 25 to 30 solar masses. The mass versus age distribution of the clusters shows a drastic decrease in the number of clusters with age, which indicates that cluster disruption is occurring on a timescale of about 10 Myr for low mass clusters. The cluster initial mass function for clusters younger than 10 Myr has an exponent of alpha = 2.0 (+- 0.05) We derived the cluster formation history from clusters with an initial mass larger than 10^4 solar masses. There is no evidence for a peak in the cluster formation rate within a factor two at about 200 to 400 Myr ago, i.e. at the time of the interaction with the companion galaxy NGC 5194.Comment: 15 pages, 15 figures. Accepted for publication by Astronomy and Astrophysic

Impacts of zero tillage on soil enzyme activities, microbial characteristics and organic matter functional chemistry in temperate soils

Zero tillage management of agricultural soils has potential for enhancing soil carbon (C) storage and reducing greenhouse gas emissions. However, the mechanisms which control carbon (C) sequestration in soil in response to zero tillage are not well understood. The aim of this study was to investigate the links between zero tillage practices and the functioning of the soil microbial community with regards to C cycling, testing the hypothesis that zero tillage enhances biological functioning in soil with positive implications for C sequestration. Specifically, we determined microbial respiration rates, enzyme activities, carbon source utilization and the functional chemistry of the soil organic matter in temperate well drained soils that had been zero tilled for seven years against annually tilled soils. Zero tilled soils contained 9% more soil C, 30% higher microbial biomass C than tilled soil and an increased presence of aromatic functional groups indicating greater preservation of recalcitrant C. Greater CO2 emission and higher respirational quotients were observed from tilled soils compared to zero tilled soils while microbial biomass was 30% greater in zero tilled soils indicating a more efficient functioning of the microbial community under zero tillage practice. Furthermore, microbial enzyme activities of dehydrogenase, cellulase, xylanase, β-glucosidase, phenol oxidase and peroxidase were higher in zero tilled soils. Considering zero tillage enhanced both microbial functioning and C storage in soil, we suggest that it offers significant promise to improve soil health and support mitigation measures against climate change

Remarks on the Concept of Critique in Habermasian Thought

The main purpose of this paper is to examine the concept of critique in Habermasian thought. Given that the concept of critique is a central theoretical category in the work of the Frankfurt School, it comes as a surprise that little in the way of a systematic account which sheds light on the multifaceted meanings of the concept of critique in Habermas’s oeuvre can be found in the literature. This paper aims to fill this gap by exploring the various meanings that Habermas attributes to the concept of critique in 10 key thematic areas of his writings: (1) the public sphere, (2) knowledge, (3) language, (4) morality, (5) ethics, (6) evolution, (7) legitimation, (8) democracy, (9) religion, and (10) modernity. On the basis of a detailed analysis of Habermas’s multifaceted concerns with the nature and function of critique, the study seeks to demonstrate that the concept of critique can be considered not only as a constitutive element but also as a normative cornerstone of Habermasian thought. The paper draws to a close by reflecting on some of the limitations of Habermas’s conception of critique, arguing that in order to be truly critical in the Habermasian sense we need to turn the subject of critique into an object of critique

Growth of fluoroform (CHF, HFC-23) in the background atmosphere

There is growing concern over the emission and accumulation of very long-lived fluorinated trace gases in the atmosphere, due to their large global warming potentials (GWPs). Unlike CFCs and other ozone-depleting, chlorinated and brominated chemicals, consumption of these fluorinated compounds is not controlled by the Montreal Protocol or any other international agreement. Of all the known and potential trace 'greenhouse' gases, the two with the highest GWPs are sulfur hexafluoride (SF) and fluoroform (CHF, HFC-23). Whereas several studies have reported the detection and accumulation of SF in the atmosphere, the presence of HFC-23 has remained unreported. We have found that present-day HFC-23 concentrations (c. 11 pptv in late 1995) exceed those of SF by a factor of three. Concentrations have steadily increased in the atmosphere since at least 1978, and are continuing to do so at a present rate of 5% per year. Furthermore, HFC-23 appears to be long-lived in the atmosphere, with a stratospheric lifetime of at least 1000 years, and a modelled tropospheric lifetime of 230 years. In terms of global warming, the cumulative emissions of HFC-23 up to, and including, 1995 are equivalent to 1.6 billion tonnes of CO

Detecting proteins in microfluidic channels decorated with liquid crystal sensing dots

10.1021/la303213hLangmuir285017571-17577LANG