2,224 research outputs found
Tools for computing the AGN feedback: radio-loudness distribution and the kinetic luminosity function
We studied the Active Galactic Nuclei (AGN) radio emission from a compilation
of hard X-ray selected samples, all observed in the 1.4 GHz band. A total of
more than 1600 AGN with 2-10 keV de-absorbed luminosities higher than 10^42
erg/s were used. For a sub-sample of about 50 z\lsim 0.1 AGN it was possible to
reach a ~80% fraction of radio detections and therefore, for the first time, it
was possible to almost completely measure the probability distribution function
of the ratio between the radio and the X-ray luminosity Rx=log[L(1.4)/Lx]. The
probability distribution function of Rx was functionally fitted as dependent on
the X-ray luminosity and redshift, P(Rx|Lx,z). It roughly spans over 6 decades
(-7<Rx<-1), and does not show any sign of bi-modality. It resulted that the
probability of finding large values of the Rx ratio increases with decreasing
X-ray luminosities and (possibly) with increasing redshift. No statistical
significant difference was found between the radio properties of the X-ray
absorbed and unabsorbed AGN. The measure of the probability distribution
function of Rx allowed us to compute the kinetic luminosity function and the
kinetic energy density which, at variance with what assumed in many galaxy
evolution models, is observed to decrease of about a factor of five at redshift
below 0.5. About half of the kinetic energy density results to be produced by
the more radio quiet (Rx<-4) AGN. In agreement with previous estimates, the AGN
efficiency in converting the accreted mass energy into kinetic power is, on
average, ~5x10-3.Comment: 13 pages, ApJsty; ApJ in pres
Iron(III)-catalyzed chlorination of activated arenes
A general and regioselective method for the chlorination of activated arenes has been developed. The transformation uses iron(III) triflimide as a powerful Lewis acid for the activation of N-chlorosuccinimide and the subsequent chlorination of a wide range of anisole, aniline, acetanilide and phenol derivatives. The reaction was utilized for the late-stage mono- and di-chlorination of a range of target compounds such as the natural product nitrofungin, the antibacterial agent chloroxylenol and the herbicide chloroxynil. The facile nature of this transformation was demonstrated with the development of one-pot tandem iron-catalyzed dihalogenation processes allowing highly regioselective formation of different carbon-halogen bonds. The synthetic utility of the resulting dihalogenated aryl compounds as building blocks was established with the synthesis of natural products and pharmaceutically relevant targets
Commentary: Unravelling the mechanisms linking climate change, agriculture and avian population declines
Dynamic changes in the brain protein interaction network correlates with progression of Aβ42 pathology in Drosophila
Alzheimer’s disease (AD), the most prevalent form of dementia, is a progressive and devastating neurodegenerative condition for which there are no effective treatments. Understanding the molecular pathology of AD during disease progression may identify new ways to reduce neuronal damage. Here, we present a longitudinal study tracking dynamic proteomic alterations in the brains of an inducible Drosophila melanogaster model of AD expressing the Arctic mutant Aβ42 gene. We identified 3093 proteins from flies that were induced to express Aβ42 and age-matched healthy controls using label-free quantitative ion-mobility data independent analysis mass spectrometry. Of these, 228 proteins were significantly altered by Aβ42 accumulation and were enriched for AD-associated processes. Network analyses further revealed that these proteins have distinct hub and bottleneck properties in the brain protein interaction network, suggesting that several may have significant effects on brain function. Our unbiased analysis provides useful insights into the key processes governing the progression of amyloid toxicity and forms a basis for further functional analyses in model organisms and translation to mammalian systems
Tomographic weak lensing shear spectra from large N-body and hydrodynamical simulations
Forthcoming experiments will enable us to determine tomographic shear spectra
at a high precision level. Most predictions about them have until now been
biased on algorithms yielding the expected linear and non-linear spectrum of
density fluctuations. Even when simulations have been used, so-called Halofit
(Smith et al 2003) predictions on fairly large scales have been needed. We wish
to go beyond this limitation. We perform N-body and hydrodynamical simulations
within a sufficiently large cosmological volume to allow a direct connection
between simulations and linear spectra. While covering large length-scales, the
simulation resolution is good enough to allow us to explore the high-l
harmonics of the cosmic shear (up to l ~ 50000), well into the domain where
baryon physics becomes important. We then compare shear spectra in the absence
and in presence of various kinds of baryon physics, such as radiative cooling,
star formation, and supernova feedback in the form of galactic winds. We
distinguish several typical properties of matter fluctuation spectra in the
different simulations and test their impact on shear spectra. We compare our
outputs with those obtainable using approximate expressions for non--linear
spectra, and identify substantial discrepancies even between our results and
those of purely N-body results. Our simulations and the treatment of their
outputs however enable us, for the first time, to obtain shear results taht are
fully independent of any approximate expression, also in the high-l range,
where we need to incorporate a non-linear power spectrum of density
perturbations, and the effects of baryon physics. This will allow us to fully
exploit the cosmological information contained in future high--sensitivity
cosmic shear surveys, exploring the physics of cosmic shears via weak lensing
measurements.Comment: 13 pages, 19 figures, A&A in pres
Photoionized OVI absorbers toward the bright QSO HE 0515-4414
We report on detailed Monte Carlo inversion analysis of five OVI systems from
the spectrum of the bright quasar HE 0515-4414 (z_e = 1.71). The associated
system at z_a = 1.697 with the neutral hydrogen column density N(HI)= 4.4
10^{13} cm^{-2} shows pronounced absorption from highly ionized transitions of
CIII, CIV, NV, OVI, SiIV, and probably SVI. We found that only a power law type
ionizing spectrum (J_nu propto nu^{-1.5}) is consistent with the observed
sample of the line profiles, i.e. the system is definitely intrinsic. The
relative metal abundances give almost the solar pattern and the metallicity of
about 5 times solar. The system originates in a thin shell of the line-of-sight
thickness L <= 16 pc. Two OVI systems at z_a = 1.674 ([C/H] = -1.6) and 1.602
([O/H] = -1.1), arising in intervening halos, have linear sizes of L = 3-14 kpc
and 17 kpc, respectively. Absorption systems at z_a = 1.385 ([C/H] = -0.3, L =
1.7-2.5 kpc) and z_a = 1.667 ([C/H] = -0.5, L = 1 kpc) exhibit characteristics
very similar to that observed in metal-enriched high velocity clouds in the
Milky Way.These systems are probably embedded in extremely metal-poor halos
with [C/H] < -2.4 (z_a = 1.667) and [C/H] < -3.7 (z_a = 1.385). We also found
two additional extremely metal-poor Ly-alpha systems at z_a = 1.500 and 1.681
with, respectively, N(HI) = 1.7 10^{15} and 1.8 10^{15} cm^{-2} and [C/H] <
-4.0 and <-3.0, - an indication that the distribution of metals in the
metagalactic medium is utterly patchy. Our results show that the ionization
states in the analyzed OVI absorbers, ranging from z = 1.4 to 1.7, can be
maintained by photoionization only and that the fraction of the shock-heated
hot gas with temperature T > 10^5 K is negligible in these systems.Comment: 16 pages, including 11 PostScript figures. Accepted for publication
in A&
How do you say ‘hello’? Personality impressions from brief novel voices
On hearing a novel voice, listeners readily form personality impressions of that speaker. Accurate or not, these impressions are known to affect subsequent interactions; yet the underlying psychological and acoustical bases remain poorly understood. Furthermore, hitherto studies have focussed on extended speech as opposed to analysing the instantaneous impressions we obtain from first experience. In this paper, through a mass online rating experiment, 320 participants rated 64 sub-second vocal utterances of the word ‘hello’ on one of 10 personality traits. We show that: (1) personality judgements of brief utterances from unfamiliar speakers are consistent across listeners; (2) a two-dimensional ‘social voice space’ with axes mapping Valence (Trust, Likeability) and Dominance, each driven by differing combinations of vocal acoustics, adequately summarises ratings in both male and female voices; and (3) a positive combination of Valence and Dominance results in increased perceived male vocal Attractiveness, whereas perceived female vocal Attractiveness is largely controlled by increasing Valence. Results are discussed in relation to the rapid evaluation of personality and, in turn, the intent of others, as being driven by survival mechanisms via approach or avoidance behaviours. These findings provide empirical bases for predicting personality impressions from acoustical analyses of short utterances and for generating desired personality impressions in artificial voices
X-ray selected Infrared Excess AGN in the Chandra Deep Fields: a moderate fraction of Compton-thick sources
We examine the properties of the X-ray detected, Infrared Excess AGN or Dust
Obscured Galaxies (DOGs) in the Chandra Deep Fields (CDF). We find 26 X-ray
selected sources which obey the 24 micron to R-band flux ratio criterion
f_24/f_R>1000. These are at a median redshift of 2.3 while their IR
luminosities are above 10^12 solar. Their X-ray luminosities are all above a
few times 10^42 erg s-1 in the 2-10 keV band unambiguously arguing that these
host AGN. Nevertheless, their IR Spectral Energy Distributions are split
between AGN (Mrk231) and star-forming templates (Arp220). Our primary goal is
to examine their individual X-ray spectra in order to assess whether this X-ray
detected DOG population contains heavily obscured or even Compton-thick
sources. The X-ray spectroscopy reveals a mixed bag of objects. We find that
four out of the 12 sources with adequate photon statistics and hence reliable
X-ray spectra, show evidence for a hard X-ray spectral index (~1) or
harder,consistent with a Compton-thick spectrum. In total 12 out of the 26 DOGs
show evidence for flat spectral indices. However, owing to the limited photon
statistics we cannot differentiate whether these are flat because they are
reflection-dominated or because they show moderate amounts of absorption. Seven
DOGs show relatively steep spectra (>1.4) indicative of small column densities.
All the above suggest a fraction of Compton-thick sources that does not exceed
5%. The average X-ray spectrum of all 26 DOGs is hard (~1.1) or even harder
(~0.6) when we exclude the brightest sources. These spectral indices are well
in agreement with the stacked spectrum of X-ray undetected sources (~0.8 in the
CDFN). This could suggest (but not necessarily prove) that X-ray undetected
DOGs, in a similar fashion to the X-ray detected ones presented here, are
hosting a moderate fraction of Compton-thick sources.Comment: 16 pages To appear in A&
Maximising response to postal questionnaires – A systematic review of randomised trials in health research
Background
Postal self-completion questionnaires offer one of the least expensive modes of collecting patient based outcomes in health care research. The purpose of this review is to assess the efficacy of methods of increasing response to postal questionnaires in health care studies on patient populations.
Methods
The following databases were searched: Medline, Embase, CENTRAL, CDSR, PsycINFO, NRR and ZETOC. Reference lists of relevant reviews and relevant journals were hand searched. Inclusion criteria were randomised trials of strategies to improve questionnaire response in health care research on patient populations. Response rate was defined as the percentage of questionnaires returned after all follow-up efforts. Study quality was assessed by two independent reviewers. The Mantel-Haenszel method was used to calculate the pooled odds ratios.
Results
Thirteen studies reporting fifteen trials were included. Implementation of reminder letters and telephone contact had the most significant effect on response rates (odds ratio 3.7, 95% confidence interval 2.30 to 5.97 p = <0.00001). Shorter questionnaires also improved response rates to a lesser degree (odds ratio 1.4, 95% confidence interval 1.19 to 1.54). No evidence was found that incentives, re-ordering of questions or including an information brochure with the questionnaire confer any additional advantage.
Conclusion
Implementing repeat mailing strategies and/or telephone reminders may improve response to postal questionnaires in health care research. Making the questionnaire shorter may also improve response rates. There is a lack of evidence to suggest that incentives are useful. In the context of health care research all strategies to improve response to postal questionnaires require further evaluation
The ambivalent shadow of the pre-Wilsonian rise of international law
The generation of American international lawyers who founded the American Society of International Law in 1906 and nurtured the soil for what has been retrospectively called a “moralistic legalistic approach to international relations” remains little studied. A survey of the rise of international legal literature in the U.S. from the mid-19th century to the eve of the Great War serves as a backdrop to the examination of the boosting effect on international law of the Spanish American War in 1898. An examination of the Insular Cases before the US Supreme Court is then accompanied by the analysis of a number of influential factors behind the pre-war rise of international law in the U.S. The work concludes with an examination of the rise of natural law doctrines in international law during the interwar period and the critiques addressed.by the realist founders of the field of “international relations” to the “moralistic legalistic approach to international relation
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