6,306 research outputs found
Getting research findings into practice : when to act on the evidence.
There is increasing interest in providing evidence based health care—that is, care in which healthcare professionals, provider managers, those who commission health care, the public, and policymakers consistently consider research evidence when making decisions. Purchasers, for example, should be able to influence the organisation and delivery of care (such as for cancer and stroke services) and the type and content of services (such as using chiropractic for back pain or dilatation and curettage and drug treatment for menorrhagia). Policymakers should ensure that policies on treatment reflect and are consistent with research evidence, and that the incentive structure within the health system promotes cost effective practice. They must also ensure that there is an adequate infrastructure for monitoring changes in practice and for producing, gathering, summarising, and disseminating evidence. Clinicians determine the day to day care patients receive in healthcare systems, and user groups (for example, patients, their families, and their representatives) are also beginning to play an important role in influencing healthcare decisions
Testing the Modern Merger Hypothesis via the Assembly of Massive Blue Elliptical Galaxies in the Local Universe
The modern merger hypothesis offers a method of forming a new elliptical
galaxy through merging two equal-mass, gas-rich disk galaxies fuelling a
nuclear starburst followed by efficient quenching and dynamical stabilization.
A key prediction of this scenario is a central concentration of young stars
during the brief phase of morphological transformation from highly-disturbed
remnant to new elliptical galaxy. To test this aspect of the merger hypothesis,
we use integral field spectroscopy to track the stellar Balmer absorption and
4000\AA\ break strength indices as a function of galactic radius for 12 massive
(), nearby (),
visually-selected plausible new ellipticals with blue-cloud optical colours and
varying degrees of morphological peculiarities. We find that these index values
and their radial dependence correlate with specific morphological features such
that the most disturbed galaxies have the smallest 4000\AA\ break strengths and
the largest Balmer absorption values. Overall, two-thirds of our sample are
inconsistent with the predictions of the modern merger hypothesis. Of these
eight, half exhibit signatures consistent with recent minor merger
interactions. The other half have star formation histories similar to local,
quiescent early-type galaxies. Of the remaining four galaxies, three have the
strong morphological disturbances and star-forming optical colours consistent
with being remnants of recent, gas-rich major mergers, but exhibit a weak,
central burst consistent with forming of their stars. The final
galaxy possesses spectroscopic signatures of a strong, centrally-concentrated
starburst and quiescent core optical colours indicative of recent quenching
(i.e., a post-starburst signature) as prescribed by the modern merger
hypothesis.Comment: 25 pages, 37 figures, accepted to MNRA
A Herschel Study of 24 micron-Selected AGNs and Their Host Galaxies
We present a sample of 290 24-micron-selected active galactic nuclei (AGNs)
mostly at z ~ 0.3 -- 2.5, within 5.2 square degrees distributed as 25' X 25'
fields around each of 30 galaxy clusters in the Local Cluster Substructure
Survey (LoCuSS). The sample is nearly complete to 1 mJy at 24 microns, and has
a rich multi-wavelength set of ancillary data; 162 are detected by Herschel. We
use spectral templates for AGNs, stellar populations, and infrared emission by
star forming galaxies to decompose the spectral energy distributions (SEDs) of
these AGNs and their host galaxies, and estimate their star formation rates
(SFRs), AGN luminosities, and host galaxy stellar masses. The set of templates
is relatively simple: a standard Type-1 quasar template; another for the
photospheric output of the stellar population; and a far infrared star-forming
template. For the Type-2 AGN SEDs, we substitute templates including internal
obscuration, and some Type-1 objects require a warm component (T > 50 K). The
individually Herschel- detected Type-1 AGNs and a subset of 17 Type-2 ones
typically have luminosities > 10^{45} ergs/s, and supermassive black holes of ~
3 X 10^8 Msun emitting at ~ 10% of the Eddington rate. We find them in about
twice the numbers of AGN identified in SDSS data in the same fields, i.e., they
represent typical high luminosity AGN, not an infrared-selected minority. These
AGNs and their host galaxies are studied further in an accompanying paper
Shapley Supercluster Survey: Ram-Pressure Stripping vs. Tidal Interactions in the Shapley Supercluster
We present two new examples of galaxies undergoing transformation in the
Shapley supercluster core. These low-mass (stellar mass from 0.4E10 to 1E10
Msun) galaxies are members of the two clusters SC-1329-313 (z=0.045) and
SC-1327-312 (z=0.049). Integral-field spectroscopy complemented by imaging in
ugriK bands and in Halpha narrow-band are used to disentangle the effects of
tidal interaction (TI) and ram-pressure stripping (RPS). In both galaxies,
SOS-61086 and SOS-90630, we observe one-sided extraplanar ionized gas extending
respectively 30kpc and 41kpc in projection from their disks. The galaxies'
gaseous disks are truncated and the kinematics of the stellar and gas
components are decoupled, supporting the RPS scenario. The emission of the
ionized gas extends in the direction of a possible companion for both galaxies
suggesting a TI. The overall gas velocity field of SOS-61086 is reproduced by
ad hoc N-body/hydrodynamical simulations of RPS acting almost face-on and
starting about 250Myr ago, consistent with the age of the young stellar
populations. A link between the observed gas stripping and the cluster-cluster
interaction experienced by SC-1329-313 and A3562 is suggested. Simulations of
ram pressure acting almost edge-on are able to fully reproduce the gas velocity
field of SOS-90630, but cannot at the same time reproduce the extended tail of
outflowing gas. This suggests that an additional disturbance from a TI is
required. This study adds a piece of evidence that RPS may take place in
different environments with different impacts and witnesses the possible effect
of cluster-cluster merger on RPS.Comment: 27 pages, 28 figures, MNRAS accepte
Peculiar Velocities of Nonlinear Structure: Voids in McVittie Spacetime
As a study of peculiar velocities of nonlinear structure, we analyze the
model of a relativistic thin-shell void in the expanding universe. (1) Adopting
McVittie (MV) spacetime as a background universe, we investigate the dynamics
of an uncompensated void with negative MV mass. Although the motion itself is
quite different from that of a compensated void, as shown by Haines & Harris
(1993), the present peculiar velocities are not affected by MV mass. (2) We
discuss how precisely the formula in the linear perturbation theory applies to
nonlinear relativistic voids, using the results in (1) as well as the previous
results for the homogeneous background (Sakai, Maeda, & Sato 1993). (3) We
re-examine the effect of the cosmic microwave background radiation. Contrary to
the results of Pim & Lake (1986, 1988), we find that the effect is negligible.
We show that their results are due to inappropriate initial conditions. Our
results (1)-(3) suggest that the formula in the linear perturbation theory is
approximately valid even for nonlinear voids.Comment: 12 pages, aastex, 4 ps figures separate, Fig.2 added, to appear in
Ap
Star formation in the massive cluster merger Abell 2744
We present a comprehensive study of star-forming (SF) galaxies in the HST
Frontier Field recent cluster merger A2744 (z=0.308). Wide-field,
ultraviolet-infrared (UV-IR) imaging enables a direct constraint of the total
star formation rate (SFR) for 53 cluster galaxies, with SFR{UV+IR}=343+/-10
Msun/yr. Within the central 4 arcmin (1.1 Mpc) radius, the integrated SFR is
complete, yielding a total SFR{UV+IR}=201+/-9 Msun/yr. Focussing on obscured
star formation, this core region exhibits a total SFR{IR}=138+/-8 Msun/yr, a
mass-normalised SFR{IR} of Sigma{SFR}=11.2+/-0.7 Msun/yr per 10^14 Msun and a
fraction of IR-detected SF galaxies f{SF}=0.080(+0.010,-0.037). Overall, the
cluster population at z~0.3 exhibits significant intrinsic scatter in IR
properties (total SFR{IR}, Tdust distribution) apparently unrelated to the
dynamical state: A2744 is noticeably different to the merging Bullet cluster,
but similar to several relaxed clusters. However, in A2744 we identify a trail
of SF sources including jellyfish galaxies with substantial unobscured SF due
to extreme stripping (SFR{UV}/SFR{IR} up to 3.3). The orientation of the trail,
and of material stripped from constituent galaxies, indicates that the passing
shock front of the cluster merger was the trigger. Constraints on star
formation from both IR and UV are crucial for understanding galaxy evolution
within the densest environments.Comment: Accepted by MNRAS. 12 pages, 7 figures (high resolution versions of
Figs. 1 & 2 are available in the published PDF
Auto-calibration of ultrasonic lubricant-film thickness measurements
The measurement of oil film thickness in a lubricated component is essential information for performance monitoring and design. It is well established that such measurements can be made ultrasonically if the lubricant film is modelled as a collection of small springs. The ultrasonic method requires that component faces are separated and a reference reflection recorded in order to obtain a reflection coefficient value from which film thickness is calculated. The novel and practically useful approach put forward in this paper and validated experimentally allows reflection coefficient measurement without the requirement for a reference. This involves simultaneously measuring the amplitude and phase of an ultrasonic pulse reflected from a layer. Provided that the acoustic properties of the substrate are known, the theoretical relationship between the two can be fitted to the data in order to yield reflection coefficient amplitude and phase for an infinitely thick layer. This is equivalent to measuring a reference signal directly, but importantly does not require the materials to be separated. The further valuable aspect of this approach, which is demonstrated experimentally, is its ability to be used as a self-calibrating routine, inherently compensating for temperature effects. This is due to the relationship between the amplitude and phase being unaffected by changes in temperature which cause unwanted changes to the incident pulse. Finally, error analysis is performed showing how the accuracy of the results can be optimized. A finding of particular significance is the strong dependence of the accuracy of the technique on the amplitude of reflection coefficient input data used. This places some limitations on the applicability of the technique. © 2008 IOP Publishing Ltd
ADAM‐10 is overexpressed in rheumatoid arthritis synovial tissue and mediates angiogenesis
Objective To examine the expression of ADAM‐10 in rheumatoid arthritis (RA) synovial tissue (ST) and the role it plays in angiogenesis. Methods ADAM‐10 expression was determined using immunohistology, Western blotting, and quantitative polymerase chain reaction. In order to examine the role of ADAM‐10 in angiogenesis, we performed in vitro Matrigel tube formation and chemotaxis assays using human microvascular endothelial cells (HMVECs) transfected with control or ADAM‐10 small interfering RNA (siRNA). To determine whether ADAM‐10 plays a role in angiogenesis in the context of RA, we performed Matrigel assays using a coculture system of HMVECs and RA synovial fibroblasts. Results Endothelial cells and lining cells within RA ST expressed high levels of ADAM‐10 compared with cells within osteoarthritis ST and normal ST. ADAM‐10 expression was significantly elevated at the protein and messenger RNA levels in HMVECs and RA synovial fibroblasts stimulated with proinflammatory mediators compared with unstimulated cells. ADAM‐10 siRNA–treated HMVECs had decreased endothelial cell tube formation and migration compared with control siRNA–treated HMVECs. In addition, ADAM‐10 siRNA–treated HMVECs from the RA synovial fibroblast coculture system had decreased endothelial cell tube formation compared with control siRNA–treated HMVECs. Conclusion These data show that ADAM‐10 is overexpressed in RA and suggest that ADAM‐10 may play a role in RA angiogenesis. ADAM‐10 may be a potential therapeutic target in inflammatory angiogenic diseases such as RA.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94711/1/37755_ftp.pd
Knot homology via derived categories of coherent sheaves II, sl(m) case
Using derived categories of equivariant coherent sheaves we construct a knot
homology theory which categorifies the quantum sl(m) knot polynomial. Our knot
homology naturally satisfies the categorified MOY relations and is
conjecturally isomorphic to Khovanov-Rozansky homology. Our construction is
motivated by the geometric Satake correspondence and is related to Manolescu's
by homological mirror symmetry.Comment: 51 pages, 9 figure
- …