459 research outputs found

    Small for Gestational Age Babies After 37 Weeks: An Impact Study of a Risk Stratification Protocol.

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    OBJECTIVES: Although no clear evidence exists, many international guidelines advocate early term delivery of small for gestational age (SGA) fetuses. The aim of this study was to determine whether a protocol that included monitoring SGA fetuses beyond 37 weeks affected perinatal and maternal outcomes. METHODS: The impact of the introduction in 2014 of a protocol for management of SGA, which included risk stratification with surveillance and expectant management after 37 weeks for lower risk babies (Group 2), was compared with the previous strategy, which recommended delivery at around 37 weeks (Group 1). Data from all referred SGA babies over a 39 month period were analyzed. RESULTS: In group 1 there were 138 SGA babies; in group 2 there were 143. The mean gestation at delivery was 37 + 4 and 38 + 2 weeks respectively (p = 0.04). The incidence of neonatal composite adverse outcomes was lower in Group 2 (9% v 22% v; p < 0.01) as was neonatal NNU admission (13% v 42%; p < 0.01). Induction of labour and caesarean section rates were lower, and vaginal delivery (83% v 60%; p < 0.01) was higher in group 2. Most of the differences were due to delayed delivery of SGA babies that were stratified as low risk. CONCLUSIONS: This study suggests that protocol-based management of SGA babies may improve outcomes and that identification of moderate SGA should not alone prompt delivery. Larger numbers are required to assess any impact on perinatal mortality

    Line versus Flux Statistics -- Considerations for the Low Redshift Lyman-alpha Forest

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    The flux/transmission power spectrum has become a popular statistical tool in studies of the high redshift (z>2z > 2) Lyman-alpha forest. At low redshifts, where the forest has thinned out into a series of well-isolated absorption lines, the motivation for flux statistics is less obvious. Here, we study the relative merits of flux versus line correlations, and derive a simple condition under which one is favored over the other on purely statistical grounds. Systematic errors probably play an important role in this discussion, and they are outlined as well.Comment: 6 pages, to appear in "The IGM/Galaxy Connection: The Distribution of Baryons at z=0", eds. J. L. Rosenberg and M. E. Putma

    PMN J1838-3427: A new gravitationally lensed quasar

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    We report the discovery of a new double-image quasar that was found during a search for gravitational lenses in the southern sky. Radio source PMN J1838-3427 is composed of two flat-spectrum components with separation 1", flux density ratio 14:1 and matching spectral indices, in VLA and VLBA images. Ground-based BRI images show the optical counterpart (total I=18.6) is also double with the same separation and position angle as the radio components. An HST/WFPC2 image reveals the lens galaxy. The optical flux ratio (27:1) is higher than the radio value probably due to differential extinction of the components by the lens galaxy. An optical spectrum of the bright component contains quasar emission lines at z=2.78 and several absorption features, including prominent Ly-alpha absorption. The lens galaxy redshift could not be measured but is estimated to be z=0.36 +/- 0.08. The image configuration is consistent with the simplest plausible models for the lens potential. The flat radio spectrum and observed variability of PMN J1838-3427 suggest the time delay between flux variations of the components is measurable, and could thus provide an independent measurement of H_0.Comment: 23 pages, incl. 6 figures, to appear in A.J.; replaced with accepted version; minor changes to text, improved figure

    The Quasar Pair Q 1634+267 A, B and the Binary QSO vs. Dark Lens Hypotheses

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    Deep HST/NICMOS H (F160W) band observations of the z=1.96 quasar pair Q 1634+267A,B reveal no signs of a lens galaxy to a 1 sigma threshold of approximately 22.5 mag. The minimum luminosity for a normal lens galaxy would be a 6L_* galaxy at z > 0.5, which is 650 times greater than our detection threshold. Our observation constrains the infrared mass-to-light ratio of any putative, early-type, lens galaxy to (M/L)_H > 690h_65 (1200h_65) for Omega_0=0.1 (1.0) and H_0=65h_65 km/s/Mpc. We would expect to detect a galaxy somewhere in the field because of the very strong Mg II absorption lines at z=1.1262 in the Q 1634+267 A spectrum, but the HST H-band, I-band (F785LP) and V-band (F555W) images require that any associated galaxy be very under-luminous less than 0.1 L^*_H (1.0 L^*_I) if it lies within less than 40 h^{-1} (100 h^{-1}) kpc from Q 1634+267 A,B. While the large image separation (3.86 arcsec) and the lack of a lens galaxy strongly favor interpreting Q 1634+267A,B as a binary quasar system, the spectral similarity remains a puzzle. We estimate that at most 0.06% of randomly selected quasar pairs would have spectra as similar to each other as the spectra of Q 1634+267 A and B. Moreover, spectral similarities observed for the 14 quasar pairs are significantly greater than would be expected for an equivalent sample of randomly selected field quasars. Depending on how strictly we define similarity, we estimate that only 0.01--3% of randomly drawn samples of 14 quasar pairs would have as many similar pairs as the observational sample.Comment: 24 pages, including 4 figures, LaTex, ApJ accepted, comments from the editor included, minor editorial change

    Function and Safety of SlowflowHD Ultrasound Doppler in Obstetrics.

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    SlowflowHD is a new ultrasound Doppler imaging technology that allows visualization of flow within small blood vessels. In this mode, a proprietary algorithm differentiates between low-speed flow and signals attributed to tissue motion so that microvessel vasculature can be examined. Our objectives were to describe the low-velocity Doppler mode principles, to assess the bone thermal index (TIb) safety parameter in obstetric ultrasound scans and to evaluate adherence to professional guidelines. To achieve the latter goals, we retrospectively reviewed prospectively collected ultrasound images and video clips from pregnancy ultrasound scans at >10 wk of gestation over 4 mo. We used a custom-built optical character recognition-based software to automatically identify all images and video clips using this technology and extract the TIb. Overall, a total of 185 ultrasound scans performed by three fetal medicine physicians were included, of which 60, 54 and 71 scans were first-, second- and third-trimester scans, respectively. The mean (highest recorded) TIb values were 0.32 (0.70), 0.23 (0.70) and 0.32 (0.60) in the first, second, and third trimesters, respectively. Thermal index values were within recommended values set by the World Federation for Ultrasound in Medicine and Biology American Institute of Ultrasound in Medicine and British Medical Ultrasound Society in all scans

    HST Imaging of the BL Lacertae Object OJ 287

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    Hubble Space Telescope WFPC-2 I-band (F814W) images of the BL Lacertae object OJ 287 and the surrounding field are presented. We find evidence of associated extended nebulosity near OJ 287, as well as a small nebulosity to the West, which may be spatially coincident with the position of previously observed radio emission. The brightness of a host galaxy is difficult to determine due to the brightness of the active nucleus, but it lies in the range -21.5 > M_R > -23.1 (H_0 = 100 km s^{-1} Mpc^{-1}, q_0 = 0). No evidence is seen for the previously reported optical ``jet'' at position angle 220 degrees to a surface brightness limit of I = 24.3 mag arcsec^{-2}. There are several resolved and unresolved objects within 17'' of OJ~287 in the field to limits of I=25 (point source 5\sigma detections). The magnitudes and relative positions of these objects are reported. An offset in the centroid position between the OJ 287 point source and the underlying nebulosity reported by Wurtz, Stocke and Yee is confirmed and measured to be about 0.4 (1.2h^{-1} kpc at the redshift of OJ~287). This offset is tentatively interpreted as evidence for recent merger activity rather than a sign of gravitational microlensing.Comment: To appear in ApJ Letters, 3 jpg figure

    The FIRST Bright Quasar Survey. II. 60 Nights and 1200 Spectra Later

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    We have used the VLA FIRST survey and the APM catalog of the POSS-I plates as the basis for constructing a new radio-selected sample of optically bright quasars. This is the first radio-selected sample that is competitive in size with current optically selected quasar surveys. Using only two basic criteria, radio-optical positional coincidence and optical morphology, quasars and BL Lacs can be identified with 60% selection efficiency; the efficiency increases to 70% for objects fainter than magnitude 17. We show that a more sophisticated selection scheme can predict with better than 85% reliability which candidates will turn out to be quasars. This paper presents the second installment of the FIRST Bright Quasar Survey with a catalog of 636 quasars distributed over 2682 square degrees. The quasar sample is characterized and all spectra are displayed. The FBQS detects both radio-loud and radio-quiet quasars out to a redshift z>3. We find a large population of objects of intermediate radio-loudness; there is no evidence in our sample for a bimodal distribution of radio characteristics. The sample includes ~29 broad absorption line quasars, both high and low ionization, and a number of new objects with remarkable optical spectra.Comment: 41 pages plus 39 gifs which contain all quasar spectra. Accepted for publication in the Astrophysical Journal Supplement Serie

    EGRET Spectral Index and the Low-Energy Peak Position in the Spectral Energy Distribution of EGRET-Detected Blazars

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    In current theoretical models of the blazar subclass of active galaxies, the broadband emission consists of two components: a low-frequency synchrotron component with a peak in the IR to X-ray band, and a high-frequency inverse Compton component with a peak in the gamma-ray band. In such models, the gamma-ray spectral index should be correlated with the location of the low-energy peak, with flatter gamma-ray spectra expected for blazars with synchrotron peaks at higher photon energies and vice versa. Using the EGRET-detected blazars as a sample, we examine this correlation and possible uncertainties in its construction.Comment: 17 pages including 1 figure, accepted for publication in The Astrophysical Journa

    Randomized Interventional Study on Prediction of Preeclampsia/Eclampsia in Women With Suspected Preeclampsia: INSPIRE.

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    The ratio of maternal serum sFlt-1 (soluble fms-like tyrosine kinase 1) to PlGF (placental growth factor) has been used retrospectively to rule out the occurrence of preeclampsia, a pregnancy hypertensive disorder, within 7 days in women presenting with clinical suspicion of preeclampsia. A prospective, interventional, parallel-group, randomized clinical trial evaluated the use of sFlt-1/PlGF ratio in women presenting with suspected preeclampsia. Women were assigned to reveal (sFlt-1/PlGF result known to clinicians) or nonreveal (result unknown) arms. A ratio cutoff of 38 was used to define low (≤38) and elevated risk (>38) of developing the condition in the subsequent week. The primary end point was hospitalization within 24 hours of the test. Secondary end points were development of preeclampsia and other adverse maternal-fetal outcomes. We recruited 370 women (186 reveal versus 184 nonreveal). Preeclampsia occurred in 85 women (23%). The number of admissions was not significantly different between groups (n=48 nonreveal versus n=60 reveal; P=0.192). The reveal trial arm admitted 100% of the cases that developed preeclampsia within 7 days, whereas the nonreveal admitted 83% (P=0.038). Use of the test yielded a sensitivity of 100% (95% CI, 85.8-100) and a negative predictive value of 100% (95% CI, 97.1-100) compared with a sensitivity of 83.3 (95% CI, 58.6-96.4) and negative predictive value of 97.8 (95% CI, 93.7-99.5) with clinical practice alone. Use of the sFlt-1/PlGF ratio significantly improved clinical precision without changing the admission rate. Clinical Trial Registration- URL: http://www.isrctn.com. Unique identifier: ISRCTN87470468

    Inter-comparison of Radio-Loudness Criteria for Type 1 AGNs in the XMM-COSMOS Survey

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    Limited studies have been performed on the radio-loud fraction in X-ray selected type 1 AGN samples. The consistency between various radio-loudness definitions also needs to be checked. We measure the radio-loudness of the 407 type 1 AGNs in the XMM-COSMOS quasar sample using nine criteria from the literature (six defined in the rest-frame and three defined in the observed frame): RL=log(L5GHz/LB)R_L=\log(L_{5GHz}/L_B), q24=log(L24μm/L1.4GHz)q_{24}=\log(L_{24\mu m}/L_{1.4GHz}), Ruv=log(L5GHz/L2500A˚)R_{uv}=\log(L_{5GHz}/L_{2500\AA}), Ri=log(L1.4GHz/Li)R_{i}=\log(L_{1.4GHz}/L_i), RX=log(νLν(5GHz)/LX)R_X=\log(\nu L_{\nu}(5GHz)/L_X), P5GHz=log(P5GHz(W/Hz/Sr))P_{5GHz}=\log(P_{5GHz}(W/Hz/Sr)), RL,obs=log(f1.4GHz/fB)R_{L,obs}=\log(f_{1.4GHz}/f_B) (observed frame), Ri,obs=log(f1.4GHz/fi)R_{i,obs}=\log(f_{1.4GHz}/f_i) (observed frame), and q24,obs=log(f24μm/f1.4GHz)q_{24, obs}=\log(f_{24\mu m}/f_{1.4GHz}) (observed frame). Using any single criterion defined in the rest-frame, we find a low radio-loud fraction of 5%\lesssim 5\% in the XMM-COSMOS type 1 AGN sample, except for RuvR_{uv}. Requiring that any two criteria agree reduces the radio-loud fraction to 2%\lesssim 2\% for about 3/4 of the cases. The low radio-loud fraction cannot be simply explained by the contribution of the host galaxy luminosity and reddening. The P5GHz=log(P5GHz(W/Hz/Sr))P_{5GHz}=\log(P_{5GHz}(W/Hz/Sr)) gives the smallest radio-loud fraction. Two of the three radio-loud fractions from the criteria defined in the observed frame without k-correction (RL,obsR_{L,obs} and Ri,obsR_{i,obs}) are much larger than the radio-loud fractions from other criteria.Comment: 12 pages, 7 figures, MNRAS submitte
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