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Low Fraction (low + fraction)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Spitzer IRAC infrared colours of submillimetre-bright galaxies

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008
Min S. Yun
ABSTRACT High-redshift submillimetre-bright galaxies identified by blank field surveys at millimetre and submillimetre wavelengths appear in the region of the Infra Red Array Camera (IRAC) colour,colour diagrams previously identified as the domain of luminous active galactic nuclei (AGNs). Our analysis using a set of empirical and theoretical dusty starburst spectral energy distribution (SED) models shows that power-law continuum sources associated with hot dust heated by young (,100 Myr old), extreme starbursts at z > 2 also occupy the same general area as AGNs in the IRAC colour,colour plots. A detailed comparison of the IRAC colours and SEDs demonstrates that the two populations are distinct from each other, with submillimetre-bright galaxies having a systematically flatter IRAC spectrum (,1 mag bluer in the observed [4.5],[8.0] colour). Only about 20 per cent of the objects overlap in the colour,colour plots, and this low fraction suggests that submillimetre galaxies powered by a dust-obscured AGN are not common. The red infrared colours of the submillimetre galaxies are distinct from those of the ubiquitous foreground IRAC sources, and we propose a set of infrared colour selection criteria for identifying SMG counterparts that can be used even in the absence of radio or Multiband Imaging Photometer for Spitzer (MIPS) 24 ,m data. [source]

Exercise-induced wheeze: Fraction of exhaled nitric oxide-directed management

RESPIROLOGY, Issue 4 2010
Douglas C. COWAN
ABSTRACT Background and objective: Exercise-induced wheeze (EIW) is common. Several treatment options exist. Patients with low fraction of exhaled nitric oxide (FENO) are unlikely to be steroid-responsive and might benefit from non-steroidal therapies. We assessed: the efficacy of cromoglycate, formoterol and montelukast in patients with EIW and low FENO (<35 ppb) in a randomized cross-over trial, and the efficacy of inhaled corticosteroid in a high FENO (>35 ppb) group. Methods: Patients had EIW and airway hyperresponsiveness (AHR) to mannitol and/or exercise. Those with low FENO (n = 19) received cromoglycate (20 mg inh. bd + before challenge tests), formoterol (12 µg inh. bd + before challenge tests) and montelukast (10 mg p.o. od), each for 2 weeks. Those with high FENO (n = 20) took inhaled fluticasone (500 µg) daily for 4 weeks. Primary end-points were: 50% reduction in maximum FEV1 %fall (clinical protection) and decrease in AHR to mannitol. Results: In patients with low FENO, cromoglycate, formoterol and montelukast significantly decreased AHR to mannitol in 63%, 61% and 47% of patients, respectively. In this group, the magnitude of exercise-induced bronchoconstriction (EIB) was significantly reduced with montelukast and formoterol; between-treatment differences were not significant. Of 6/19 with low FENO and EIB, protection occurred in 67% (cromoglycate), 83% (formoterol) and 50% (montelukast), respectively. In the high FENO group, AHR to mannitol and EIB decreased significantly with fluticasone (P < 0.001, P = 0.005, respectively), and protection occurred in 7/8 (88%) with EIB. Conclusions: In patients with EIW and low FENO, the number of ,responders' to cromoglycate, formoterol and montelukast was similar. In a high FENO population the response to inhaled corticosteroid was highly significant and comparable to previous studies. [source]

Binding of GTP,[35S] is regulated by GDP and receptor activation.

BRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2010
Studies with the nociceptin/orphanin FQ receptor
Background and purpose:, We have examined the effects of ligand efficacy and receptor density on the binding of guanosine 5,-[,-thio]triphosphate (GTP,S) and GDP to the nociceptin/orphanin FQ (N/OFQ) peptide receptor (NOP)-coupled G-proteins. Experimental approach:, In GTP,[35S] binding experiments, using stable (CHOhNOP) and inducible (CHOINDhNOP) recombinant human and rat NOP we have measured: (i) ligand-specific GDP requirements; (ii) the effects of receptor density on guanine nucleotide affinity/capacity; and (iii) the effect of ligand efficacy on GTP,S association kinetics. Key results:, GTP,S competition curves were shallow and modelled by high- and low-affinity components that were relatively consistent between cell types and tissue preparations. In the presence of 1 µM N/OFQ a high-affinity GDP binding site was also present, but the fraction of total binding was reduced. In an efficacy-dependent manner, the partial agonists [F/G]N/OFQ(1-13)NH2 ([Phe1,(CH2 -NH)Gly2]-nociceptin(1-13)NH2) and naloxone benzoylhydrazone both reduced the fraction of high-affinity sites for GDP (relative to basal). While the pIC50 for high-affinity GDP binding site did not decrease in the presence of 1 µM N/OFQ, N/OFQ produced a significant reduction in pIC50 for the low-affinity site. Agonist-mediated decrease in affinity for GDP binding was efficacy-dependent. GDP displayed three affinities: high, conserved in the presence and absence of ligand; intermediate, present as a low fraction under basal conditions; low (efficacy-dependent), present during receptor activation representing the majority of binding. Conclusions and implications:, The affinity of GTP,[35S] was regulated by GDP and receptor activation caused increased binding of GTP,[35S] through a reduction in GDP affinity. [source]

Dynamics of stream nitrate sources and flow pathways during stormflows on urban, forest and agricultural watersheds in central Pennsylvania, USA

HYDROLOGICAL PROCESSES, Issue 23 2009
Anthony R. Buda
Abstract Understanding the influence of storm events on nitrate (NO3,) dynamics is important for efficiently managing NO3, pollution. In this study, five sites representing a downstream progression of forested uplands underlain by resistant sandstone to karst lowlands with agricultural, urban and mixed land-use were established in Spring Creek, a 201 km2 mixed land-use watershed in central Pennsylvania, USA. At each site, stream water was monitored during six storm events in 2005 to assess changes in stable isotopes of NO3, (,15N-NO3, and ,18O-NO3,) and water (,18O-H2O) from baseflow to peakflow. Peakflow fractions of event NO3, and event water were then computed using two-component mixing models to elucidate NO3, flow pathway differences among the five sites. For the forested upland site, storm size appeared to affect NO3, sources and flow pathways. During small storms (<35 mm rainfall), greater event NO3, fractions than event water fractions indicated the prevalence of atmospheric NO3, source contributions at peakflow. During larger storms (>35 mm rainfall), event NO3, fractions were less than event water fractions at peakflow suggesting that NO3, was flushed from stored sources via shallow subsurface flow pathways. For the urbanized site, wash-off of atmospheric NO3, was an important NO3, source at peakflow, especially during short-duration storms where event water contributions indicated the prevalence of overland flow. In the karst lowlands, very low fractions of event water and even lower fractions of event NO3, at peakflow suggested the dominance of ground water flow pathways during storms. These ground water flow pathways likely flushed stored NO3, sources into the stream, while deep soils in the karst lowlands also may have promoted NO3, assimilation. The results of this study illustrated how NO3, isotopes and ,18O-H2O could be combined to show key differences in water and NO3, delivery between forested uplands, karst valleys and fully urbanized watersheds. Copyright © 2009 John Wiley & Sons, Ltd. [source]