1,113 research outputs found
A comparison of cardiovascular magnetic resonance and single photon emission computed tomography (SPECT) perfusion imaging in left main stem or equivalent coronary artery disease: a CE-MARC substudy
Background: Assessment of left main stem (LMS) stenosis has prognostic and therapeutic implications. Data on assessment of LMS disease by cardiovascular magnetic resonance (CMR) and single photon emission computed tomography (SPECT) are limited. CE-MARC is the largest prospective comparison of CMR and SPECT against quantitative invasive coronary angiography (QCA) for detection of coronary artery disease (CAD), and provided the framework for this evaluation. The aims of this study were to compare diagnostic accuracy of visual and quantitative perfusion CMR to SPECT in patients with LMS stable CAD. Methods: Fifty-four patients from the CE-MARC study were included: 27 (4%) with significant LMS or LMS-equivalent disease on QCA, and 27 age/sex-matched patients with no flow-limiting CAD. All patients underwent multi-parametric CMR, SPECT and QCA. Performance of visual and quantitative perfusion CMR by Fermi-constrained deconvolution to detect LMS disease was compared with SPECT. Results: Of 27 patients in the LMS group, 22 (81%) had abnormal CMR and 16 (59%) had abnormal SPECT. All patients with abnormal CMR had abnormal perfusion by visual analysis. CMR demonstrated significantly higher area under the curve (AUC) for detection of disease (0.95; 0.85–0.99) over SPECT (0.63; 0.49–0.76) (p = 0.0001). Global mean stress myocardial blood flow (MBF) by CMR in LMS patients was significantly lower than controls (1.77 ± 0.72 ml/g/min vs. 3.28 ± 1.20 ml/g/min, p < 0.001). MBF of <2.08 ml/g/min had sensitivity of 78% and specificity of 85% for diagnosis of LMS disease, with an AUC (0.87; 0.75–0.94) not significantly different to visual CMR analysis (p = 0.18), and more accurate than SPECT (p = 0.003). Conclusion: Visual stress perfusion CMR had higher diagnostic accuracy than SPECT to detect LMS disease. Quantitative perfusion CMR had similar performance to visual CMR perfusion analysis
The Galaxy Structure-Redshift Relationship
There exists a gradual, but persistent, evolutionary effect in the galaxy
population such that galaxy structure and morphology change with redshift. This
galaxy structure-redshift relationship is such that an increasingly large
fraction of all bright and massive galaxies at redshifts 2 < z < 3 are
morphologically peculiar at wavelengths from rest-frame ultraviolet to
rest-frame optical. There are however examples of morphologically selected
spirals and ellipticals at all redshifts up to z ~ 3. At lower redshift, the
bright galaxy population smoothly transforms into normal ellipticals and
spirals. The rate of this transformation strongly depends on redshift, with the
swiftest evolution occurring between 1 < z < 2. This review characterizes the
galaxy structure-redshift relationship, discusses its various physical causes,
and how these are revealing the mechanisms responsible for galaxy formation.Comment: 20 pages, 8 figures. Invited Review to appear in "Penetrating Bars
Through Masks of Cosmic Dust: The Hubble Tuning Fork Strikes A New Note", ed.
D. Block et a
VLT/FORS2 view at z ∼ 6: Lyman-α emitter fraction and galaxy physical properties at the edge of the epoch of cosmic reionization
The fraction of Lyman- emitters among the galaxy population has been
found to increase from to and drop dramatically at .
This drop has been interpreted as an effect of an increasingly neutral
intergalactic medium with increasing redshift, while a LyC escape fraction
evolving with redshift. We report the result of a large VLT/FORS2 program
aiming to confirm spectroscopically a large galaxy sample at that has
been selected in several independent fields through the Lyman Break technique.
Combining those data with archival data, we create a large and homogeneous
sample of galaxies (), complete in terms of Ly
detection at for EW(Ly. We use this sample to derive
a new measurement of the LAE fraction at and derive the physical
properties of these galaxies through spectral energy distribution fitting. We
find a median LAE fraction at lower than in previous studies. The main
difference between LAEs and non-LAEs is that the latter are significantly
dustier. Using predictions of our SED fitting code accounting for nebular
emission, we find an effective Ly escape fraction
remarkably consistent with the
value derived by comparing UV luminosity function with Ly luminosity
function. We conclude that the drop in the LAE fraction from to
is less dramatic than previously found and the effect of an increasing IGM
neutral fraction is possibly observed at . Based on our derived
, we find that the IGM has a relatively small impact
on Ly photon visibility at , with a lower limit for the IGM
transmission to \lya\ photons, , likely due to the presence
of outflows. [abdridged
Assessing the influence of pig slurry pH on the degradation of selected antibiotic compounds
Veterinary medicines are routinely used in animal husbandry and the environment may consequently be exposed to them via manure applications. This presents potential environmental and societal risks such as toxicological effects to aquatic/terrestrial organisms and the spread of antimicrobial resistance. Regulatory studies that assess the degradability of veterinary antibiotics during manure storage currently permit the use of just one manure per animal type although we speculate that heterogenic properties such as pH could be driving significant variability within degradation rates. To bridge this knowledge gap and assess degradation variability with pH, laboratory degradation studies were performed on a broad range of antibiotics (ceftiofur, florfenicol, oxytetracycline, sulfamethoxazole and tylosin) at three different environmentally relevant pH levels (5.5, 7, and 8.5). The effect of pig slurry pH on degradation rates was found to be significant and compound specific. Usually, acidic slurries were found to inhibit degradation when compared to neutral pH, for florfenicol, tylosin, and ceftiofur; the associated changes in DT50 (half-life) values were 2–209 h, 35.28–234 h, and 0.98–2.13 h, respectively. In some circumstances alkaline slurries were observed to enhance the degradation rate when compared to those for neutral pH, for tylosin, the respective changes in DT50 values were from 3.52 to 35.28 h. Comparatively, the degradation of sulfamethoxazole was enhanced by acidic conditions compared to neutral (DT50 20.6–31.6 h). Tentative identification of unknown transformation products (TPs) was achieved for sulfamethoxazole and florfenicol for the first time in pig slurries. These results reveal the importance of considering slurry pH when assessing the degradation of antibiotic compounds, which has implications for the acidification of manures and the environmental risk assessment for veterinary medicines. Environmental relevance and significance: Given the significant effect of pig slurry pH on degradation rates, manure degradation studies need to be harmonised and standardized, taking into account the influence of pH
Do self-reported intentions predict clinicians behaviour: a systematic review.
Background: Implementation research is the scientific study of methods to promote the systematic uptake of
clinical research findings into routine clinical practice. Several interventions have been shown to be effective in
changing health care professionals' behaviour, but heterogeneity within interventions, targeted behaviours, and
study settings make generalisation difficult. Therefore, it is necessary to identify the 'active ingredients' in
professional behaviour change strategies. Theories of human behaviour that feature an individual's "intention" to
do something as the most immediate predictor of their behaviour have proved to be useful in non-clinical
populations. As clinical practice is a form of human behaviour such theories may offer a basis for developing a
scientific rationale for the choice of intervention to use in the implementation of new practice. The aim of this
review was to explore the relationship between intention and behaviour in clinicians and how this compares to
the intention-behaviour relationship in studies of non-clinicians.
Methods: We searched: PsycINFO, MEDLINE, EMBASE, CINAHL, Cochrane Central Register of Controlled
Trials, Science/Social science citation index, Current contents (social & behavioural med/clinical med), ISI
conference proceedings, and Index to Theses. The reference lists of all included papers were checked manually.
Studies were eligible for inclusion if they had: examined a clinical behaviour within a clinical context, included
measures of both intention and behaviour, measured behaviour after intention, and explored this relationship
quantitatively. All titles and abstracts retrieved by electronic searching were screened independently by two
reviewers, with disagreements resolved by discussion.
Discussion: Ten studies were found that examined the relationship between intention and clinical behaviours in
1623 health professionals. The proportion of variance in behaviour explained by intention was of a similar
magnitude to that found in the literature relating to non-health professionals. This was more consistently the case
for studies in which intention-behaviour correspondence was good and behaviour was self-reported. Though firm
conclusions are limited by a smaller literature, our findings are consistent with that of the non-health professional
literature. This review, viewed in the context of the larger populations of studies, provides encouragement for
the contention that there is a predictable relationship between the intentions of a health professional and their
subsequent behaviour. However, there remain significant methodological challenges
CANDELSz7: A large spectroscopic survey of CANDELS galaxies in the reionization epoch
We present the results of CANDELSz7, an ESO large program aimed at confirming
spectroscopically a homogeneous sample of z~6 and z~7 star forming galaxies.
The candidates were selected in the GOODS-South, UDS and COSMOS fields using
the official CANDELS catalogs based on H160-band detections. Standard color
criteria, which were tailored depending on the ancillary multi-wavelength data
available for each field, were applied to select more than 160 candidate
galaxies at z~6 and z~7. Deep medium resolution FORS2 spectroscopic
observations were then conducted with integration times ranging from 12 to 20
hours, to reach a Lyalpha flux limit of approximately 1-3x 10-18 erg/s/cm^2 at
3sigma. For about 40% of the galaxies we could determine a spectroscopic
redshift, mainly through the detection of a single emission line that we
interpret as Lyalpha emission, or for some of the brightest objects (H160<
25.5) from the presence of faint continuum and sharp drop that we interpret as
a Lyman break. In this paper we present the redshifts and main properties of 65
newly confirmed high redshift galaxies. Adding previous proprietary and
archival data we assemble a sample of ~260 galaxies that we use to explore the
evolution of the Lyalpha fraction in Lyman break galaxies and the change in the
shape of the emission line between z~6 and z~7. We also discuss the accuracy of
the CANDELS photometric redshifts in this redshift range.STFC
ER
Rapid Evolution in the Most Luminous Galaxies During the First 900 Million Years
The first 900 million years (Myr) to redshift z~6 (the first seven per cent
of the age of the Universe) remains largely unexplored for the formation of
galaxies. Large samples of galaxies have been found at z~6, but detections at
earlier times are uncertain and unreliable. It is not at all clear how galaxies
built up from the first stars when the Universe was ~300 Myr old (z~12-15) to
z~6, just 600 Myr later. Here we report the results of a search for galaxies at
z~7-8, about 700 Myr after the Big Bang, using the deepest near-infrared and
optical images ever taken. Under conservative selection criteria we find only
one candidate galaxy at z~7-8, where ten would be expected if there were no
evolution in the galaxy population between z~7-8 and z~6. Using less
conservative criteria, there are four candidates, where 17 would be expected
with no evolution. This demonstrates that very luminous galaxies are quite rare
700 Myr after the Big Bang. The simplest explanation is that the Universe is
just too young to have built up many luminous galaxies at z~7-8 by the
hierarchical merging of small galaxies.Comment: Accepted for publication in Nature, 20 pages, 5 figures, 2 tables
(includes Supplementary Information), replaced to match version in pres
Financial considerations in the conduct of multi-centre randomised controlled trials: evidence from a qualitative study.
National Coordinating Centre for Research Methodology; Medical Research Council, UK Department of Health; Chief Scientist OfficeNot peer reviewedPublisher PD
Hepatopulmonary syndrome in patients with chronic liver disease: role of pulse oximetry
BACKGROUND: Hepatopulmonary syndrome (HPS) is a rare complication of liver diseases of different etiologies and may indicate a poor prognosis. Therefore, a simple non-invasive screening method to detect HPS would be highly desirable. In this study pulse oximetry was evaluated to identify patients with HPS. METHODS: In 316 consecutive patients with liver cirrhosis (n = 245), chronic hepatitis (n = 69) or non-cirrhotic portal hypertension (n = 2) arterial oxygen saturation (SaO(2)) was determined using a pulse oximeter. In patients with SaO(2 )≤92% in supine position and/or a decrease of ≥4% after change from supine to upright position further diagnostic procedures were performed, including contrast-enhanced echocardiography and perfusion lung scan. RESULTS: Seventeen patients (5.4%) had a pathological SaO(2). Four patients (1.3%) had HPS. HPS patients had a significant lower mean SaO(2 )in supine (89.7%, SD 5.4 vs. 96.0%, SD 2.3; p = 0.003) and upright position (84.3%, SD 5.0 vs. 96.0%, SD 2.4; p = 0.001) and had a lower mean PaO(2 )(56.2 mm Hg, SD 15.2 vs. 71.2 mm Hg, SD 20.2; p = 0.02) as compared to patients without HPS. The mean ΔSaO(2 )(difference between supine and upright position) was 5.50 (SD 7) in HPS patients compared to non-HPS patients who showed no change (p = 0.001). There was a strong correlation between shunt volume and the SaO(2 )values (R = -0.94). CONCLUSION: Arterial SaO(2 )determination in supine and upright position is a useful non-invasive screening test for HPS and correlates well with the intrapulmonary shunt volume
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