5,067 research outputs found
Bisphosphonates and evidence for association with esophageal and gastric cancer:A systematic review and metaanalysis
OBJECTIVES: Concerns have been raised about a possible link between bisphosphonate use, and in particular alendronate, and upper gastrointestinal (UGI) cancer. A number of epidemiological studies have been published with conflicting results. We conducted a systematic review and meta-analysis of observational studies, to determine the risk of esophageal and gastric cancer in users of bisphosphonates compared with non-users. DESIGN: We searched PubMed, MEDLINE, EMBASE, Web of Knowledge and Cochrane Database of Systematic Reviews for studies investigating bisphosphonates and esophageal or gastric cancer. We calculated pooled ORs and 95% CIs for the risk of esophageal or gastric cancer in bisphosphonate users compared with non-users. We performed a sensitivity analysis of alendronate as this was the most common single drug studied and is also the most widely used in clinical practice. RESULTS: 11 studies (from 10 papers) examining bisphosphonate exposure and UGI cancer (gastric and esophageal), met our inclusion criteria. All studies were retrospective, 6/11 (55%) case–control and 5/11(45%) cohort, and carried out using data from 5 longitudinal clinical databases. Combining 5 studies (1 from each database), we found no increased risk, OR 1.11 (95% CI 0.97 to 1.27) of esophageal cancer in bisphosphonate users compared with non-users and no increased risk of gastric cancer in bisphosphonate users, OR 0.96 (95% CI 0.82 to 1.12). CONCLUSION: This is the fourth and most detailed meta-analysis on this topic. We have not identified any compelling evidence for a significantly raised risk of esophageal cancer or gastric cancer in male and female patients prescribed bisphosphonates
The detection and photometric redshift determination of distant galaxies using SIRTF's Infrared Array Camera
We investigate the ability of the Space Infrared Telescope Facility's
Infrared Array Camera to detect distant (z ~ 3)galaxies and measure their
photometric redshifts. Our analysis shows that changing the original long
wavelength filter specifications provides significant improvements in
performance in this and other areas.Comment: 28 pages incl 12 figures; to appear in June 1999 PASP. Fig.12
replaced with corrected versio
A platform for the discovery of new macrolide antibiotics.
The chemical modification of structurally complex fermentation products, a process known as semisynthesis, has been an important tool in the discovery and manufacture of antibiotics for the treatment of various infectious diseases. However, many of the therapeutics obtained in this way are no longer effective, because bacterial resistance to these compounds has developed. Here we present a practical, fully synthetic route to macrolide antibiotics by the convergent assembly of simple chemical building blocks, enabling the synthesis of diverse structures not accessible by traditional semisynthetic approaches. More than 300 new macrolide antibiotic candidates, as well as the clinical candidate solithromycin, have been synthesized using our convergent approach. Evaluation of these compounds against a panel of pathogenic bacteria revealed that the majority of these structures had antibiotic activity, some efficacious against strains resistant to macrolides in current use. The chemistry we describe here provides a platform for the discovery of new macrolide antibiotics and may also serve as the basis for their manufacture
Probing dark matter substructure in the gravitational lens HE0435-1223 with the WFC3 grism
Strong gravitational lensing provides a powerful test of Cold Dark Matter
(CDM) as it enables the detection and mass measurement of low mass haloes even
if they do not contain baryons. Compact lensed sources such as Active Galactic
Nuclei (AGN) are particularly sensitive to perturbing subhalos, but their use
as a test of CDM has been limited by the small number of systems which have
significant radio emission which is extended enough avoid significant lensing
by stars in the plane of the lens galaxy, and red enough to be minimally
affected by differential dust extinction. Narrow-line emission is a promising
alternative as it is also extended and, unlike radio, detectable in virtually
all optically selected AGN lenses. We present first results from a WFC3 grism
narrow-line survey of lensed quasars, for the quadruply lensed AGN HE0435-1223.
Using a forward modelling pipeline which enables us to robustly account for
spatial blending, we measure the [OIII] 5007 \AA~ flux ratios of the four
images. We find that the [OIII] fluxes and positions are well fit by a simple
smooth mass model for the main lens. Our data rule out a NFW perturber projected within 1\farcs0 (0\farcs1)
arcseconds of each of the lensed images, where is the perturber mass
within its central 600 pc. The non-detection is broadly consistent with the
expectations of CDM for a single system. The sensitivity achieved
demonstrates that powerful limits on the nature of dark matter can be obtained
with the analysis of narrow-line lenses.Comment: Accepted for publication in MNRAS, 15 pages, 8 figure
Retired A Stars and Their Companions: Exoplanets Orbiting Three Intermediate-Mass Subgiants
We report precision Doppler measurements of three intermediate-mass subgiants
from Lick and Keck Observatories. All three stars show variability in their
radial velocities consistent with planet-mass companions in Keplerian orbits.
We find a planet with a minimum mass of 2.5 Mjup in a 351.5 day orbit around HD
192699, a planet with a minimum mass of 2.0 Mjup in a 341.1 day orbit around HD
210702, and a planet with a minimum mass of 0.61 Mjup in a 297.3 day orbit
around HD 175541. Stellar mass estimates from evolutionary models indicate that
all of these stars were formerly A-type dwarfs with masses ranging from 1.65 to
1.85 Msun. These three long-period planets would not have been detectable
during their stars' main-sequence phases due to the large rotational velocities
and stellar jitter exhibited by early-type dwarfs. There are now 9 "retired"
(evolved) A-type stars (Mstar > 1.6 Msun) with known planets. All 9 planets
orbit at distances a \geq 0.78 AU, which is significantly different than the
semimajor axis distribution of planets around lower-mass stars. We examine the
possibility that the observed lack of close-in planets is due to engulfment by
their expanding host stars, but we find that this explanation is inadequate
given the relatively small stellar radii of K giants (Rstar < 32 Rsun = 0.15
AU) and subgiants (Rstar < 7 Rsun = 0.03 AU). Instead, we conclude that planets
around intermediate-mass stars reside preferentially beyond ~0.8 AU, which may
be a reflection of different formation and migration histories of planets
around A-type stars.Comment: 31 pages, 9 figures, 6 tables, ApJ accepted, corrected minor typo
Transient growth in Taylor-Couette flow
Transient growth due to non-normality is investigated for the Taylor-Couette
problem with counter-rotating cylinders as a function of aspect ratio eta and
Reynolds number Re. For all Re < 500, transient growth is enhanced by
curvature, i.e. is greater for eta < 1 than for eta = 1, the plane Couette
limit. For fixed Re < 130 it is found that the greatest transient growth is
achieved for eta between the Taylor-Couette linear stability boundary, if it
exists, and one, while for Re > 130 the greatest transient growth is achieved
for eta on the linear stability boundary. Transient growth is shown to be
approximately 20% higher near the linear stability boundary at Re = 310, eta =
0.986 than at Re = 310, eta = 1, near the threshold observed for transition in
plane Couette flow. The energy in the optimal inputs is primarily meridional;
that in the optimal outputs is primarily azimuthal. Pseudospectra are
calculated for two contrasting cases. For large curvature, eta = 0.5, the
pseudospectra adhere more closely to the spectrum than in a narrow gap case,
eta = 0.99
Noble gas signatures constrain oil-field water as the carrier phase of hydrocarbons occurring in shallow aquifers in the San Joaquin Basin, USA
© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Karolyte, R., Barry, P. H., Hunt, A. G., Kulongoski, J. T., Tyne, R. L., Davis, T. A., Wright, M. T., McMahon, P. B., & Ballentine, C. J. Noble gas signatures constrain oil-field water as the carrier phase of hydrocarbons occurring in shallow aquifers in the San Joaquin Basin, USA. Chemical Geology, 584, (2021): 120491, https://doi.org/10.1016/j.chemgeo.2021.120491.Noble gases record fluid interactions in multiphase subsurface environments through fractionation processes during fluid equilibration. Water in the presence of hydrocarbons at the subsurface acquires a distinct elemental signature due to the difference in solubility between these two fluids. We find the atmospheric noble gas signature in produced water is partially preserved after hydrocarbons production and water disposal to unlined ponds at the surface. This signature is distinct from meteoric water and can be used to trace oil-field water seepage into groundwater aquifers. We analyse groundwater (n = 30) and fluid disposal pond (n = 2) samples from areas overlying or adjacent to the Fruitvale, Lost Hills, and South Belridge Oil Fields in the San Joaquin Basin, California, USA. Methane (2.8 × 10−7 to 3 × 10−2 cm3 STP/cm3) was detected in 27 of 30 groundwater samples. Using atmospheric noble gas signatures, the presence of oil-field water was identified in 3 samples, which had equilibrated with thermogenic hydrocarbons in the reservoir. Two (of the three) samples also had a shallow microbial methane component, acquired when produced water was deposited in a disposal pond at the surface. An additional 6 samples contained benzene and toluene, indicative of interaction with oil-field water; however, the noble gas signatures of these samples are not anomalous. Based on low tritium and 14C contents (≤ 0.3 TU and 0.87–6.9 pcm, respectively), the source of oil-field water is likely deep, which could include both anthropogenic and natural processes. Incorporating noble gas analytical techniques into the groundwater monitoring programme allows us to 1) differentiate between thermogenic and microbial hydrocarbon gas sources in instances when methane isotope data are unavailable, 2) identify the carrier phase of oil-field constituents in the aquifer (gas, oil-field water, or a combination), and 3) differentiate between leakage from a surface source (disposal ponds) and from the hydrocarbon reservoir (either along natural or anthropogenic pathways such as faulty wells).This work was supported by the U.S. Geological Survey as part of the California State Water Resources Control Board's Oil and Gas Regional Monitoring Program
Five planets and an independent confirmation of HD 196885Ab from Lick Observatory
We present time series Doppler data from Lick Observatory that reveal the
presence of long-period planetary companions orbiting nearby stars. The typical
eccentricity of these massive planets are greater than the mean eccentricity of
known exoplanets. HD30562b has Msini = 1.29 Mjup, with semi-major axis of 2.3
AU and eccentricity 0.76. The host star has a spectral type F8V and is metal
rich. HD86264b has Msini = 7.0 Mjup, arel = 2.86 AU, an eccentricity, e = 0.7
and orbits a metal-rich, F7V star. HD87883b has Msini = 1.78 Mjup, arel = 3.6
AU, e = 0.53 and orbits a metal-rich K0V star. HD89307b has Msini = 1.78 Mjup,
arel = 3.3 AU, e = 0.24 and orbits a G0V star with slightly subsolar
metallicity. HD148427b has Msini = 0.96 Mjup, arel = 0.93 AU, eccentricity of
0.16 and orbits a metal rich K0 subgiant. We also present velocities for a
planet orbiting the F8V metal-rich binary star, HD196885A. The planet has Msini
= 2.58 Mjup, arel = 2.37 AU, and orbital eccentricity of 0.48, in agreement
with the independent discovery by Correia et al. 2008.Comment: 12 figures, 8 tables, accepted Ap
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