244 research outputs found
Lowdin Atornic Charges for Modeling Long Range Deuteriurn Isotope Shifts in C-13 NMR Spectra of Binuclear Arornatic Compounđs
An approach for modeling long range deuterium isotope effects on
C-13 chemical shifts, based on ab initio calculations of the differences of atomic charges between parent and deuterated molecules, is proposed. The total atomic charges were calculated for a series of molecules consisting of two benzene rings linked direct1yor via different groups, the so called binudear aromatic molecules: biphenyl, trans-stilbene, cis-stilbene, diphenylacetylene, diphenylbutadiene and their 4-deuterated derivatives. The basis sets used were: STO-3G, 6-31G, 6-31G** and MIDI. The deuteration site, i.e. C-D bond was simulated by the shortening of the corresponding C-H bond length by 0.012 A or by the reduction of CCH in-plane or out-of-plane bending angle by 1.3° and 2°, respectively. Calculations were performed
both for the X-ray geometries and 6-31G fully optimized geometries. The charge differences from Lčwdin but not from Mulliken population analysis, calculated with 6-31G, 6-31G**and MIDI basis sets, showed good correlaation with the measured longrange deuterium isotope effects on C-13 chemical shifts of C-atoms, five, six, seven, eight, ten and twelve bonds away from the site of deuteration. This correlation holds only for bond shortening but not for bending angle changes, which corresponds to the predominance of stretching over bending mode contributions to isotope effects. The vibrational analysis (6-31G) revealed no coupling of C-D stretching with the vibrations
of remote C-atoms. Therefore, we assume that the symmetry
breaking due to unsymmetrical deuterium substitution produces a small electric dipole moment by an unbalance in the normal vibrations which in turn polarizes n-electrons, giving rise to charge changes throughout the molecule. Calculated charge redistribution due to deuterium, experimentally also observed by microwave spectroscopy, might induce long-range deuterium isotope effects on C-13 chemical shifts in agreement with the postulated C-C n-bond polarization contribution to C-13 chemical shif
SDSS J115517.35+634622.0: A Newly Discovered Gravitationally Lensed Quasar
We report the discovery of SDSSJ115517.35+634622.0, a previously unknown
gravitationally lensed quasar. The lens system exhibits two images of a quasar, with an image separation of 1{\farcs}832 \pm 0.007 . Near-IR
imaging of the system reveals the presence of the lensing galaxy between the
two quasar images. Based on absorption features seen in the Sloan Digital Sky
Survey (SDSS) spectrum, we determine a lens galaxy redshift of .
The lens is rather unusual in that one of the quasar images is only
0{\farcs}22\pm0{\farcs}07 () from the center of the
lens galaxy and photometric modeling indicates that this image is significantly
brighter than predicted by a SIS model. This system was discovered in the
course of an ongoing search for strongly lensed quasars in the dataset from the
SDSS.Comment: 18 pages, 6 figures. Accepted for publication in A
Health and lifestyle of Nepalese migrants in the UK
Background: The health status and lifestyle of migrants is often poorer than that of the general
population of their host countries. The Nepalese represent a relatively small, but growing,
immigrant community in the UK, about whom very little is known in term of public health.
Therefore, our study examined the health and lifestyle of Nepalese migrants in the UK.
Methods: A cross-sectional survey of Nepalese migrants in UK was conducted in early 2007 using
a postal, self-administered questionnaire in England and Scotland (n = 312), and telephone
interviews in Wales (n = 15). The total response rate was 68% (327 out of 480). Data were analyzed
to establish whether there are associations between socio-economic and lifestyle factors. A
multivariate binary logistic regression was applied to find out independent effect of personal factors
on health status.
Results: The majority of respondents was male (75%), aged between 30 and 45 (66%), married or
had a civil partner (83%), had university education (47%) and an annual family income (69%) ranging
from £5,035 to £33,300. More than one third (39%) of the respondents have lived in the UK for 1
to 5 years and approximately half (46%) were longer-term residents. Most (95%) were registered
with a family doctor, but only 38% with a dentist. A low proportion (14%) of respondents smoked
but more than half (61%) consumed alcohol. More than half (57%) did not do regular exercises and
nearly one fourth (23%) of respondents rated their health as poor. Self reported 'good' health
status of the respondents was independently associated with immigration status and doing regular exercise
Conclusion: The self reported health status and lifestyle, health seeking behaviour of Nepalese
people who are residing in UK appears to be good. However, the overall regular exercise and dentist registration was rather poor. Health promotion, especially aimed at Nepalese migrants could help encourage them to exercise regularly and assist them to register with a dentist
The Sloan Digital Sky Survey Quasar Lens Search. II. Statistical lens sample from the third data release
We report the first results of our systematic search for strongly lensed quasars using the spectroscopically confirmed quasars in the Sloan Digital Sky Survey (SDSS). Among 46,420 quasars from the SDSS Data Release 3 (~4188 deg^2), we select a subsample of 22,683 quasars that are located at redshifts between 0.6 and 2.2 and are brighter than the Galactic extinction-corrected i-band magnitude of 19.1. We identify 220 lens candidates from the quasar subsample, for which we conduct extensive and systematic follow-up observations in optical and near-infrared wavebands, in order to construct a complete lensed quasar sample at image separations between 1" and 20" and flux ratios of faint to bright lensed images larger than 10^(−0.5). We construct a statistical sample of 11 lensed quasars. Ten of these are galaxy-scale lenses with small image separations (~ 1"-2") and one is a large separation (15") system which is produced by a massive cluster of galaxies, representing the first statistical sample of lensed quasars including both galaxy- and cluster-scale lenses. The Data Release 3 spectroscopic quasars contain an additional 11 lensed quasars outside the statistical sample
Smoking, Cardiac Symptoms, and an Emergency Care Visit: A Mixed Methods Exploration of Cognitive and Emotional Reactions
Emergency departments and hospitals are being urged to implement onsite interventions to promote smoking cessation, yet little is known about the theoretical underpinnings of behavior change after a healthcare visit. This observational pilot study evaluated three factors that may predict smoking cessation after an acute health emergency: perceived illness severity, event-related emotions, and causal attribution. Fifty smokers who presented to a hospital because of suspected cardiac symptoms were interviewed, either in the emergency department (ED) or, for those who were admitted, on the cardiac inpatient units. Their data were analyzed using both qualitative and quantitative methodologies to capture the individual, first-hand experience and to evaluate trends over the illness chronology. Reported perceptions of the event during semistructured interview varied widely and related to the individual's intentions regarding smoking cessation. No significant differences were found between those interviewed in the ED versus the inpatient unit. Although the typical profile was characterized by a peak in perceived illness severity and negative emotions at the time the patient presented in the ED, considerable pattern variation occurred. Our results suggest that future studies of eventrelated perceptions and emotional reactions should consider using multi-item and multidimensional assessment methods rated serially over the event chronology
Observations and Theoretical Implications of the Large Separation Lensed Quasar SDSS J1004+4112
We study the recently discovered gravitational lens SDSS J1004+4112, the
first quasar lensed by a cluster of galaxies. It consists of four images with a
maximum separation of 14.62''. The system has been confirmed as a lensed quasar
at z=1.734 on the basis of deep imaging and spectroscopic follow-up
observations. We present color-magnitude relations for galaxies near the lens
plus spectroscopy of three central cluster members, which unambiguously confirm
that a cluster at z=0.68 is responsible for the large image separation. We find
a wide range of lens models consistent with the data, but they suggest four
general conclusions: (1) the brightest cluster galaxy and the center of the
cluster potential well appear to be offset by several kpc; (2) the cluster mass
distribution must be elongated in the North--South direction, which is
consistent with the observed distribution of cluster galaxies; (3) the
inference of a large tidal shear (~0.2) suggests significant substructure in
the cluster; and (4) enormous uncertainty in the predicted time delays between
the images means that measuring the delays would greatly improve constraints on
the models. We also compute the probability of such large separation lensing in
the SDSS quasar sample, on the basis of the CDM model. The lack of large
separation lenses in previous surveys and the discovery of one in SDSS together
imply a mass fluctuation normalization \sigma_8=1.0^{+0.4}_{-0.2} (95% CL), if
cluster dark matter halos have an inner slope -1.5. Shallower profiles would
require higher values of \sigma_8. Although the statistical conclusion might be
somewhat dependent on the degree of the complexity of the lens potential, the
discovery is consistent with the predictions of the abundance of cluster-scale
halos in the CDM scenario. (Abridged)Comment: 21 pages, 24 figures, 5 tables, accepted for publication in Ap
The Sloan Digital Sky Survey Quasar Lens Search. III. Constraints on Dark Energy from the Third Data Release Quasar Lens Catalog
We present cosmological results from the statistics of lensed quasars in the
Sloan Digital Sky Survey (SDSS) Quasar Lens Search. By taking proper account of
the selection function, we compute the expected number of quasars lensed by
early-type galaxies and their image separation distribution assuming a flat
universe, which is then compared with 7 lenses found in the SDSS Data Release 3
to derive constraints on dark energy under strictly controlled criteria. For a
cosmological constant model (w=-1) we obtain
\Omega_\Lambda=0.74^{+0.11}_{-0.15}(stat.)^{+0.13}_{-0.06}(syst.). Allowing w
to be a free parameter we find
\Omega_M=0.26^{+0.07}_{-0.06}(stat.)^{+0.03}_{-0.05}(syst.) and
w=-1.1\pm0.6(stat.)^{+0.3}_{-0.5}(syst.) when combined with the constraint from
the measurement of baryon acoustic oscillations in the SDSS luminous red galaxy
sample. Our results are in good agreement with earlier lensing constraints
obtained using radio lenses, and provide additional confirmation of the
presence of dark energy consistent with a cosmological constant, derived
independently of type Ia supernovae.Comment: 9 pages, 3 figures, 2 tables, accepted for publication in A
Systematic review and meta-analysis of the diagnostic accuracy of ultrasonography for deep vein thrombosis
Background
Ultrasound (US) has largely replaced contrast venography as the definitive diagnostic test for deep vein thrombosis (DVT). We aimed to derive a definitive estimate of the diagnostic accuracy of US for clinically suspected DVT and identify study-level factors that might predict accuracy.
Methods
We undertook a systematic review, meta-analysis and meta-regression of diagnostic cohort studies that compared US to contrast venography in patients with suspected DVT. We searched Medline, EMBASE, CINAHL, Web of Science, Cochrane Database of Systematic Reviews, Cochrane Controlled Trials Register, Database of Reviews of Effectiveness, the ACP Journal Club, and citation lists (1966 to April 2004). Random effects meta-analysis was used to derive pooled estimates of sensitivity and specificity. Random effects meta-regression was used to identify study-level covariates that predicted diagnostic performance.
Results
We identified 100 cohorts comparing US to venography in patients with suspected DVT. Overall sensitivity for proximal DVT (95% confidence interval) was 94.2% (93.2 to 95.0), for distal DVT was 63.5% (59.8 to 67.0), and specificity was 93.8% (93.1 to 94.4). Duplex US had pooled sensitivity of 96.5% (95.1 to 97.6) for proximal DVT, 71.2% (64.6 to 77.2) for distal DVT and specificity of 94.0% (92.8 to 95.1). Triplex US had pooled sensitivity of 96.4% (94.4 to 97.1%) for proximal DVT, 75.2% (67.7 to 81.6) for distal DVT and specificity of 94.3% (92.5 to 95.8). Compression US alone had pooled sensitivity of 93.8 % (92.0 to 95.3%) for proximal DVT, 56.8% (49.0 to 66.4) for distal DVT and specificity of 97.8% (97.0 to 98.4). Sensitivity was higher in more recently published studies and in cohorts with higher prevalence of DVT and more proximal DVT, and was lower in cohorts that reported interpretation by a radiologist. Specificity was higher in cohorts that excluded patients with previous DVT. No studies were identified that compared repeat US to venography in all patients. Repeat US appears to have a positive yield of 1.3%, with 89% of these being confirmed by venography.
Conclusion
Combined colour-doppler US techniques have optimal sensitivity, while compression US has optimal specificity for DVT. However, all estimates are subject to substantial unexplained heterogeneity. The role of repeat scanning is very uncertain and based upon limited data
MicroRNAs in Renal Cell Carcinoma: Diagnostic Implications of Serum miR-1233 Levels
BACKGROUND: MicroRNA expression is altered in cancer cells, and microRNAs could serve as diagnostic/prognostic biomarker for cancer patients. Our study was designed to analyze circulating serum microRNAs in patients with renal cell carcinoma (RCC). METHODOLOGY/PRINCIPAL FINDINGS: We first explored microrna expression profiles in tissue and serum using taqman low density arrays in each six malignant and benign samples: Although 109 microRNAs were circulating at higher levels in cancer patients' serum, we identified only 36 microRNAs with up-regulation in RCC tissue and serum of RCC patients. Seven candidate microRNAs were selected for verification based on the finding of up-regulation in serum and tissue of RCC patients: miR-7-1*, miR-93, miR-106b*, miR-210, miR-320b, miR-1233 and miR-1290 levels in serum of healthy controls (n = 30) and RCC (n = 33) patients were determined using quantitative real-time PCR (TaqMan MicroRNA Assays). miR-1233 was increased in RCC patients, and thus validated in a multicentre cohort of 84 RCC patients and 93 healthy controls using quantitative real-time PCR (sensitivity 77.4%, specificity 37.6%, AUC 0.588). We also studied 13 samples of patients with angiomyolipoma or oncocytoma, whose serum miR-1233 levels were similar to RCC patients. Circulating microRNAs were not correlated with clinical-pathological parameters. CONCLUSIONS/SIGNIFICANCE: MicroRNA levels are distinctly increased in cancer patients, although only a small subset of circulating microRNAs has a tumor-specific origin. We identify circulating miR-1233 as a potential biomarker for RCC patients. Larger-scaled studies are warranted to fully explore the role of circulating microRNAs in RCC
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