656 research outputs found
A tidal disruption event in the nearby ultra-luminous infrared galaxy F01004-2237
Tidal disruption events (TDEs), in which stars are gravitationally disrupted
as they pass close to the supermassive black holes in the centres of galaxies,
are potentially important probes of strong gravity and accretion physics. Most
TDEs have been discovered in large-area monitoring surveys of many 1000s of
galaxies, and the rate deduced for such events is relatively low: one event
every 10 - 10 years per galaxy. However, given the selection effects
inherent in such surveys, considerable uncertainties remain about the
conditions that favour TDEs. Here we report the detection of unusually strong
and broad helium emission lines following a luminous optical flare (Mv < -20.1
mag) in the nucleus of the nearby ultra-luminous infrared galaxy F01004-2237.
The particular combination of variability and post-flare emission line spectrum
observed in F01004-2237 is unlike any known supernova or active galactic
nucleus. Therefore, the most plausible explanation for this phenomenon is a TDE
-- the first detected in a galaxy with an ongoing massive starburst. The fact
that this event has been detected in repeat spectroscopic observations of a
sample of 15 ultra-luminous infrared galaxies over a period of just 10 years
suggests that the rate of TDEs is much higher in such objects than in the
general galaxy population.Comment: 17 pages, 4 figures, accepted for publication in Nature Astronom
Does High Medial Elbow Stress During Pitching Compromise the Dynamic Stabilizers of The Elbow?
# Background
The flexor carpi ulnaris (FCU) and flexor digitorum superficialis (FDS) are thought to provide dynamic stability to the medial elbow, with a lesser contribution from the pronator teres (PT).
# Hypothesis/Purpose
The purpose of this study was to determine if baseball pitchers with higher valgus elbow torque experience greater FCU and FDS strength loss.
# Study Design
Controlled Laboratory Study
# Methods
A pilot study was performed to determine if middle and ring finger flexion strength tests preferentially activated the FCU and FDS versus the PT (10 men age 36Ā±12 yr). EMG amplitudes, expressed as percent of maximal voluntary contraction (MVC) were compared between tests and muscles. In a field study of college baseball pitchers, middle finger, ring finger and grip strength were tested prior to, immediately after, and one day after 14 pitching performances in 10 pitchers (21Ā±2 yr). Elbow valgus torque was measured from an inertial measurement unit, housed in a compression sleeve and pitchers were categorized as having high or low valgus torque.
# Results
For the pilot study EMG activations were 74% FDS, 66% FCU and 35% PT for the middle finger test (muscle effect p=0.032) and 93% FCU, 61% FDS and 23% PT for the ring finger test (muscle effect p=0.005). In the field study, pitchers with high valgus torque showed marked post-game middle finger fatigue (88% of baseline) and incomplete recovery the following day (95%), while pitchers with low valgus torque showed no strength loss (107% post game, 106% a day later; group x time p=0.022). Results were similar for ring finger strength (high torque: 94% post game 96% a day later; low torque: 114% post game 107% a day later; group x time p=0.048). By contrast, grip strength was not different between pitchers with high versus low valgus torque (p=0.143).
# Conclusion
High medial elbow stress during pitching fatigues the dynamic stabilizers of the medial elbow.
# Level of Evidence
Level 3
Ā©The Author(s
Mimotopes and Proteome Analyses Using Human Genomic and cDNA Epitope Phage Display
In the post-genomic era, validation of candidate gene targets frequently requires proteinbased
strategies. Phage display is a powerful tool to define protein-protein interactions by
generating peptide binders against target antigens. Epitope phage display libraries have the
potential to enrich coding exon sequences from human genomic loci. We evaluated genomic
and cDNA phage display strategies to identify genes in the 5q31 Interleukin gene cluster
and to enrich cell surface receptor tyrosine kinase genes from a breast cancer cDNA
library. A genomic display library containing 2 Ć
10
6
clones with exon-sized inserts was
selected with antibodies specific for human Interleukin-4 (IL-4) and Interleukin-13. The
library was enriched significantly after two selection rounds and DNA sequencing revealed
unique clones. One clone matched a cognate IL-4 epitope; however, the majority of clone
insert sequences corresponded to E. coli genomic DNA. These bacterial sequences act as
āmimotopesā (mimetic sequences of the true epitope), correspond to open reading frames,
generate displayed peptides, and compete for binding during phage selection. The specificity
of these mimotopes for IL-4 was confirmed by competition ELISA. Other E. coli
mimotopes were generated using additional antibodies. Mimotopes for a receptor tyrosine
kinase gene were also selected using a breast cancer SKBR-3 cDNA phage display library,
screened against an anti-erbB2 monoclonal antibody. Identification of mimotopes in
genomic and cDNA phage libraries is essential for phage display-based protein validation
assays and two-hybrid phage approaches that examine protein-protein interactions. The
predominance of E. coli mimotopes suggests that the E. coli genome may be useful to
generate peptide diversity biased towards protein coding sequences
The Spitzer discovery of a galaxy with infrared emission solely due to AGN activity
We present a galaxy (SAGE1CJ053634.78-722658.5) at a redshift of 0.14 of
which the IR is entirely dominated by emission associated with the AGN. We
present the 5-37 um Spitzer/IRS spectrum and broad wavelength SED of
SAGE1CJ053634, an IR point-source detected by Spitzer/SAGE (Meixner et al
2006). The source was observed in the SAGE-Spec program (Kemper et al., 2010)
and was included to determine the nature of sources with deviant IR colours.
The spectrum shows a redshifted (z=0.14+-0.005) silicate emission feature with
an exceptionally high feature-to-continuum ratio and weak polycyclic aromatic
hydrocarbon (PAH) bands. We compare the source with models of emission from
dusty tori around AGNs from Nenkova et al. (2008). We present a diagnostic
diagram that will help to identify similar sources based on Spitzer/MIPS and
Herschel/PACS photometry. The SED of SAGE1CJ053634 is peculiar because it lacks
far-IR emission and a clear stellar counterpart. We find that the SED and the
IR spectrum can be understood as emission originating from the inner ~10 pc
around an accreting black hole. There is no need to invoke emission from the
host galaxy, either from the stars or from the interstellar medium, although a
possible early-type host galaxy cannot be excluded based on the SED analysis.
The hot dust around the accretion disk gives rise to a continuum, which peaks
at 4 um, whereas the strong silicate features may arise from optically thin
emission of dusty clouds within ~10 pc around the black hole. The weak PAH
emission does not appear to be linked to star formation, as star formation
templates strongly over-predict the measured far-IR flux levels. The SED of
SAGE1CJ053634 is rare in the local universe but may be more common in the more
distant universe. The conspicuous absence of host-galaxy IR emission places
limits on the far-IR emission arising from the dusty torus alone.Comment: Accepted for publication in A&A, 7 pages, 6 figure
The forbidden high ionisation line region of the type 2 quasar Q1131+16: a clear view of the inner face of the torus?
We present spectroscopic observations of the type 2 quasar SDSS
J11311.05+162739.5 (Q1131+16 hereafter; z=0.1732), which has the richest
spectrum of forbidden high ionisation lines (FHIL, e.g. [Fe \textsc{vii}], [Fe
\textsc{x}], [Fe \textsc{xi}] and [Ne \textsc{v}]) yet reported for an AGN, as
well as unusually strong [O \textsc{iii}]4363 emission. The study of
this object provides a rare opportunity to investigate the physical conditions
and kinematics of the region(s) emitting the FHILs. By comparison with
photoionisation model results, we find that the FHIL region has high densities
(10 cm\textsuperscript{-3}) and ionisation
parameters (-1.5 log[U] 0), yet its kinematics are similar to those of
the low ionisation emission line region detected in the same object (FWHM
36030 km/s), with no evidence for a significant shift between the
velocity centroid of the FHILs and the rest frame of the host galaxy. The
deduced physical conditions lie between those of the Broad-Line (n
cm\textsuperscript{-3}) and Narrow-Line Regions (
cm\textsuperscript{-3}) of active galactic nuclei (AGN), and we demonstrate
that the FHIL regions must be situated relatively close to the illuminating AGN
(0.32 50pc). We suggest that the inner torus wall is the
most likely location for the FHIL region, and that the unusual strength of the
FHILs in this object is due to a specific viewing angle of the far wall of the
torus, coupled with a lack of dust on larger scales that might otherwise
obscure our view of the torus.Comment: Accepted for publication in the Monthly Notices of the Royal
Astronomical Society (3rd of March 2011). 23 Pages (including tables 5 and 6
in the source file), 21 figure
A wide search for obscured active galactic nuclei using XMM-Newton and WISE
Heavily obscured and Compton-thick active galactic nuclei (AGNs) are missing even in the deepest X-ray surveys, and indirect methods are required to detect them. Here we use a combination of the XMMāNewton serendipitous X-ray survey with the optical Sloan Digital Sky Survey (SDSS), and the infrared WISE all-sky survey in order to check the efficiency of the low X-ray-to-infrared luminosity selection method in finding heavily obscured AGNs. We select the sources which are detected in the hard X-ray band (2ā8ākeV), and also have a redshift determination (photometric or spectroscopic) in the SDSS catalogue. We match this sample with the WISE catalogue, and fit the spectral energy distributions of the 2844 sources which have three, or more, photometric data points in the infrared. We then select the heavily obscured AGN candidates by comparing their 12āĪ¼m luminosity to the observed 2ā10ākeV X-ray luminosity and the intrinsic relation between the X-ray and the mid-infrared luminosities. With this approach, we find 20 candidate heavily obscured AGNs and we then examine their X-ray and optical spectra. Of the 20 initial candidates, we find nine (64āperācent; out of the 14, for which X-ray spectra could be fitted) based on the X-ray spectra, and seven (78āperācent; out of the nine detected spectroscopically in the SDSS) based on the [OāIII] line fluxes. Combining all criteria, we determine the final number of heavily obscured AGNs to be 12ā19, and the number of Compton-thick AGNs to be 2ā5, showing that the method is reliable in finding obscured AGNs, but not Compton thick. However, those numbers are smaller than what would be expected from X-ray background population synthesis models, which demonstrates how the opticalāinfrared selection and the scatter of the Lx-LMIR relation limit the efficiency of the method. Finally, we test popular obscured AGN selection methods based on mid-infrared colours, and find that the probability of an AGN to be selected by its mid-infrared colours increases with the X-ray luminosity. The (observed) X-ray luminosities of heavily obscured AGNs are relatively low (L2ā10keV<1044ergsā1), even though most of them are located in the āquasi stellar object (QSO) locusā. However, a selection scheme based on a relatively low X-ray luminosity and mid-infrared colours characteristic of QSOs would not select ā¼25āperācent of the heavily obscured AGNs of our sample
Learning radiation oncology in Europe: Results of the ESTRO multidisciplinary survey
Introduction: Radiotherapy education can be very different across Europe, despite the publication of the ESTRO core curricula in 2011. The purpose of the current study is to map the different RO European education systems, to report their perceived quality and to understand what could be improved to better teach RO. Methods: An online survey consisting of 30 questions was sent to RO professionals under 40 years of age via email and social media. Clinicians, radiobiologists, physicists and radiation therapists (RTTs) were invited to answer questions regarding (1) demographics data, (2) duration, (3) organization, (4) content, (5) quality and potential improvements of national education programs. Results: Four hundred and sixty three questionnaires were received from 34 European countries. All disciplines were represented: 45% clinicians (n = 210), 29% physicists (n = 135), 24% RTTs (n = 108) and 2% radiobiologists (n = 10). Male and female participants were well-balanced in each speciality, except for radiobiologists (80% males). Median age was 31.5 years old (range 21ā40). A large range of the duration of the National RO education programs was observed: median = 9 years (range: 3ā15). In half of the surveyed countries the European Credit Transfer System (ECTS), that facilitates mobility for trainees, has been implemented. Participants declared only a minority of countries have implemented the ESTRO Core Curriculum (n = 5). A quarter of participants indicated that their national education program is insufficient. Conclusion: This is the first study to examine the different RO education systems in Europe. Large differences in organization and duration of national education programs have been found, along with perceived quality across Europe within each speciality. These results show the necessity of a discussion on how to move forward in this diversity of education programs and the potential contribution that the ESTRO may fulfil
The X-Ray Star Formation Story as Told by Lyman Break Galaxies in the 4 Ms CDF-S
We present results from deep X-ray stacking of {gt}4000 high-redshift galaxies from z {ap} 1 to 8 using the 4 Ms Chandra Deep Field-South data, the deepest X-ray survey of the extragalactic sky to date. The galaxy samples were selected using the Lyman break technique based primarily on recent Hubble Space Telescope ACS and WFC3 observations. Based on such high specific star formation rates (sSFRs): log SFR/M {gt} -8.7, we expect that the observed properties of these Lyman break galaxies (LBGs) are dominated by young stellar populations. The X-ray emission in LBGs, eliminating individually detected X-ray sources (potential active galactic nucleus), is expected to be powered by X-ray binaries and hot gas. We find, for the first time, evidence of evolution in the X-ray/SFR relation. Based on X-ray stacking analyses for z {lt} 4 LBGs (covering ~{}90% of the universe's history), we find that the 2-10 keV X-ray luminosity evolves weakly with redshift (z) and SFR as log L = 0.93log (1 + z) + 0.65log SFR + 39.80. By comparing our observations with sophisticated X-ray binary population synthesis models, we interpret that the redshift evolution of L /SFR is driven by metallicity evolution in high mass X-ray binaries, likely the dominant population in these high sSFR galaxies. We also compare these models with our observations of X-ray luminosity density (total 2-10 keV luminosity per Mpc) and find excellent agreement. While there are no significant stacked detections at z {gt}~{} 5, we use our upper limits from 5 {lt}~{} z {lt}~{} 8 LBGs to constrain the supermassive black hole accretion history of the universe around the epoch of reionization
The XMM deep survey in the CDF-S: IV. Compton-thick AGN candidates
The Chandra Deep Field is the region of the sky with the highest concentration of X-ray data available: 4 Ms of Chandra and 3 Ms of XMM-Newton data, allowing excellent quality spectra to be extracted even for faint sources. We took advantage of this to compile a sample of heavily obscured active galactic nuclei (AGN) using X-ray spectroscopy. We selected our sample among the 176 brightest XMM-Newton sources, searching for either flat X-ray spectra (Ī < 1.4 at the 90% confidence level) suggestive of a reflection dominated continuum or an absorption turn-over suggestive of a column density higher than ā 1024 cm-2. We found a sample of nine heavily-obscured sources satisfying the above criteria. Four of these show statistically significant FeKĪ± lines with large equivalent widths (three out of four have equivalent widths consistent with 1 keV) suggesting that these are the most certain Compton-thick AGN candidates. Two of these sources are transmission dominated while the other two are most probably reflection dominated Compton-thick AGN. Although this sample of four sources is by no means statistically complete, it represents the best example of Compton-thick sources found at moderate-to-high redshift with three sources at z = 1.2ā1.5 and one source at z = 3.7. Using Spitzer and Herschel observations, we estimate with good accuracy the X-ray to mid-IR (12 Ī¼m) luminosity ratio of our sources. These are well below the average AGN relation, independently suggesting that these four sources are heavily obscured.I.G. and A.C. acknowledge the Marie Curie fellowship FP7-PEOPLE-IEF-2008 Prop. 235285. We acknowledge financial contribution from the agreement ASI-INAF I/009/10/0. P.R. acknowledges the receipt of a fellowship (proposal no. P9-3493) from the Greek Secretariat of Research and Technology in the framework of the project āSupport to postdoctoral researchersā. N.C. acknowledges financial support from the Della Riccia foundation. F.J.C. acknowledges partial financial support by the Spanish Ministry of Economy and Competitiveness through the grant AYA2010-21490-C02-01.Peer Reviewe
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