417 research outputs found
Solving the stellar 62Ni problem with AMS
An accurate knowledge of the neutron capture cross sections of 62,63Ni is
crucial since both isotopes take key positions which affect the whole reaction
flow in the weak s process up to A=90. No experimental value for the
63Ni(n,gamma) cross section exists so far, and until recently the experimental
values for 62Ni(n,gamma) at stellar temperatures (kT=30 keV) ranged between 12
and 37 mb. This latter discrepancy could now be solved by two activations with
following AMS using the GAMS setup at the Munich tandem accelerator which are
also in perfect agreement with a recent time-of-flight measurement. The
resulting (preliminary) Maxwellian cross section at kT=30 keV was determined to
be 30keV = 23.4 +/- 4.6 mb. Additionally, we have measured the
64Ni(gamma,n)63Ni cross section close to threshold. Photoactivations at 13.5
MeV, 11.4 MeV and 10.3 MeV were carried out with the ELBE accelerator at
Forschungszentrum Dresden-Rossendorf. A first AMS measurement of the sample
activated at 13.5 MeV revealed a cross section smaller by more than a factor of
2 compared to NON-SMOKER predictions.Comment: Proceedings of the 11th International Conference on Accelerator Mass
Spectrometry in Rome, Sept. 14-19, 2008; to be published in Nucl. Instr.
Meth.
Determination of time delay from the gravitational lens B1422+231
We present the radio light curves of lensed images of the gravitational lens
B1422+231. The observations have been carried out using the VLA at 8.4 and 15
GHz over a period of 197 days. We describe a method to estimate the time delay
from the observed light curves. Using this method, our cross-correlation
analysis shows that the time delay between images B and A is 1.51.4d,
between A and C is 7.62.5d, between B and C is 8.22.0d. When applied
to other lensed systems with measured time delays our new method gives
comparable results.Comment: 10 pages, 9 figures, accepted in MNRA
Sedimentation record in the Konkan-Kerala Basin: implications for the evolution of the Western Ghats and the Western Indian passive margin
The Konkan and Kerala Basins constitute a major depocentre for sediment from the onshore hinterland of Western India and as such provide a valuable record of the timing and magnitude of Cenozoic denudation along the continental margin. This paper presents an analysis of sedimentation in the Konkan-Kerala Basin, coupledwith a mass balance study, and numerical modelling of flexural responses to onshore denudational unloading and o¡shore sediment loading in order to test competing conceptual models for the development of high-elevation passive margins. The Konkan-Kerala Basin contains an estimated 109,000 km<sup>3</sup>; of Cenozoic clastic sediment, a volume difficult to reconcile with the denudation of a downwarped rift flank onshore, and more consistent with denudation of an elevated rift flank. We infer from modelling of the isostatic response of the lithosphere to sediment loading offshore and denudation onshore that flexure is an important component in the development of the Western Indian Margin.There is evidence for two major pulses in sedimentation: an early phase in the Palaeocene, and a second beginning in the Pliocene. The Palaeocene increase in sedimentation can be interpreted in terms of a denudational response to the rifting between India and the Seychelles, whereas the mechanism responsible for the Pliocene pulse is more enigmatic
Estimated GFR Trajectories in Pediatric and Adult Nephrotic Syndrome: Results From the Nephrotic Syndrome Study Network (NEPTUNE)
56% and 16% had PNL 50%, respectively. In both adults and pediatric patients, higher baseline eGFR was associated with higher PNL, whereas longer follow-up time was associated with lower PNL. Higher urine protein-creatinine ratio and steroid use were also associated with higher PNL in adults. Higher percentages of tubular atrophy and foot-process effacement were associated with lower and higher PNLs, respectively, in adults. Limitations: Relatively short follow-up time, inability to assess acute kidney injury events, and variable eGFR measurement frequency across patients. Conclusions: Although increasing follow-up time resulted in more linear trajectories, nonlinear eGFR trajectories were common in this cohort. Future studies in nephrotic syndrome should consider novel outcomes that do not rely on linearity assumptions.Rationale & Objective: Surrogate outcomes for end-stage kidney disease often assume linear changes, which may not reflect true estimated glomerular filtration rate (eGFR) trajectories. This study's objective was to characterize nonlinear eGFR trajectories in nephrotic syndrome. Study Design: Observational cohort study. Setting & Participants: Nephrotic Syndrome Study Network (NEPTUNE) is a multicenter study of adult and pediatric patients with proteinuria enrolled at clinically indicated kidney biopsy or initial presentation of disease (pediatric only). Predictors: Patient demographic, clinical, and pathology variables at study enrollment and follow-up time. Outcome: eGFR was calculated using the Chronic Kidney Disease Epidemiology Collaboration (patients ≥ 18 years old) or modified Chronic Kidney Disease in Children Study–Schwartz (patients < 18 years) formulas. The probability of nonlinearity (PNL) was calculated for individual eGFR trajectories. Analytical Approach: Associations between predictors and PNL were assessed using multivariable linear regression. Results: 453 patients with ≥3 eGFR measurements and 1 or more year of follow-up were included (median follow-up, 3.6 years). Median PNL was 0.05
Gravitational Lensing at Millimeter Wavelengths
With today's millimeter and submillimeter instruments observers use
gravitational lensing mostly as a tool to boost the sensitivity when observing
distant objects. This is evident through the dominance of gravitationally
lensed objects among those detected in CO rotational lines at z>1. It is also
evident in the use of lensing magnification by galaxy clusters in order to
reach faint submm/mm continuum sources. There are, however, a few cases where
millimeter lines have been directly involved in understanding lensing
configurations. Future mm/submm instruments, such as the ALMA interferometer,
will have both the sensitivity and the angular resolution to allow detailed
observations of gravitational lenses. The almost constant sensitivity to dust
emission over the redshift range z=1-10 means that the likelihood for strong
lensing of dust continuum sources is much higher than for optically selected
sources. A large number of new strong lenses are therefore likely to be
discovered with ALMA, allowing a direct assessment of cosmological parameters
through lens statistics. Combined with an angular resolution <0.1", ALMA will
also be efficient for probing the gravitational potential of galaxy clusters,
where we will be able to study both the sources and the lenses themselves, free
of obscuration and extinction corrections, derive rotation curves for the
lenses, their orientation and, thus, greatly constrain lens models.Comment: 69 pages, Review on quasar lensing. Part of a LNP Topical Volume on
"Dark matter and gravitational lensing", eds. F. Courbin, D. Minniti. To be
published by Springer-Verlag 2002. Paper with full resolution figures can be
found at ftp://oden.oso.chalmers.se/pub/tommy/mmviews.ps.g
An Integrated TCGA Pan-Cancer Clinical Data Resource to Drive High-Quality Survival Outcome Analytics
For a decade, The Cancer Genome Atlas (TCGA) program collected clinicopathologic annotation data along with multi-platform molecular profiles of more than 11,000 human tumors across 33 different cancer types. TCGA clinical data contain key features representing the democratized nature of the data collection process. To ensure proper use of this large clinical dataset associated with genomic features, we developed a standardized dataset named the TCGA Pan-Cancer Clinical Data Resource (TCGA-CDR), which includes four major clinical outcome endpoints. In addition to detailing major challenges and statistical limitations encountered during the effort of integrating the acquired clinical data, we present a summary that includes endpoint usage recommendations for each cancer type. These TCGA-CDR findings appear to be consistent with cancer genomics studies independent of the TCGA effort and provide opportunities for investigating cancer biology using clinical correlates at an unprecedented scale. Analysis of clinicopathologic annotations for over 11,000 cancer patients in the TCGA program leads to the generation of TCGA Clinical Data Resource, which provides recommendations of clinical outcome endpoint usage for 33 cancer types
Measuring the metric: a parametrized post-Friedmanian approach to the cosmic dark energy problem
We argue for a ``parametrized post-Friedmanian'' approach to linear
cosmology, where the history of expansion and perturbation growth is measured
without assuming that the Einstein Field Equations hold. As an illustration, a
model-independent analysis of 92 type Ia supernovae demonstrates that the curve
giving the expansion history has the wrong shape to be explained without some
form of dark energy or modified gravity. We discuss how upcoming lensing,
galaxy clustering, cosmic microwave background and Lyman alpha forest
observations can be combined to pursue this program, which generalizes the
quest for a dark energy equation of state, and forecast the accuracy that the
proposed SNAP satellite can attain.Comment: Replaced to match accepted PRD version. References and another
example added, section III omitted since superceded by astro-ph/0207047. 11
PRD pages, 7 figs. Color figs and links at
http://www.hep.upenn.edu/~max/gravity.html or from [email protected]
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