752 research outputs found
Goserelin, as an ovarian protector during (neo)adjuvant breast cancer chemotherapy, prevents long term altered bone turnover
Background: The Ovarian Protection Trial In Premenopausal Breast Cancer Patients “OPTION” trial
(NCT00427245) was a prospective, multicenter, randomised, open label study evaluating the frequency of
primary ovarian insufficiency (POI) at 12 months in women randomised to 6–8 cycles of (neo)adjuvant
chemotherapy (CT) þ/ goserelin (G). Here we report the results of a secondary endpoint analysis of the
effects of CTþ/-G on markers of bone turnover.
Methods: Serum for bone alkaline phosphatase (BALP) and urine for N-terminal telopeptide (NTX) were
collected at baseline, 6, 12, 18, 24 and 36 months. Changes in median levels of bone turnover markers
were evaluated for the overall population, according to age stratification at randomisation (r40 vs 440
years) and with exploratory analysis according to POI rates at 12 months.
Results: In the overall population, there was a significant increase in NTX at 6 months compared to
baseline in patients treated with CTþG (40.81 vs 57.82 p¼0.0074) with normalisation of levels thereafter.
BALP was significantly increased compared to baseline at 6 months and 12 months in those receiving
CTþG, but normalised thereafter. BALP remained significantly higher compared to baseline at 12, 24 and
36 months in patients receiving CT, resulting in a significant difference between treatment groups at 36
months (CTþG 5.845 vs CT 8.5 p¼0.0006). These changes were predominantly seen in women 440
years. Women with POI at 12 months showed altered bone formation compared to baseline levels for a
longer duration than women who maintained menses.
Conclusion: Addition of G to CT increases bone turnover during treatment with normalisation after
cessation of treatment suggesting G may offer sufficient ovarian protection against CT induced POI to
negate longstanding altered bone turnover associated with POI
On the Progenitors of Core-Collapse Supernovae
Theory holds that a star born with an initial mass between about 8 and 140
times the mass of the Sun will end its life through the catastrophic
gravitational collapse of its iron core to a neutron star or black hole. This
core collapse process is thought to usually be accompanied by the ejection of
the star's envelope as a supernova. This established theory is now being tested
observationally, with over three dozen core-collapse supernovae having had the
properties of their progenitor stars directly measured through the examination
of high-resolution images taken prior to the explosion. Here I review what has
been learned from these studies and briefly examine the potential impact on
stellar evolution theory, the existence of "failed supernovae", and our
understanding of the core-collapse explosion mechanism.Comment: 7 Pages, invited review accepted for publication by Astrophysics and
Space Science (special HEDLA 2010 issue
Circumstellar interaction in supernovae in dense environments - an observational perspective
In a supernova explosion, the ejecta interacting with the surrounding
circumstellar medium (CSM) give rise to variety of radiation. Since CSM is
created from the mass lost from the progenitor star, it carries footprints of
the late time evolution of the star. This is one of the unique ways to get a
handle on the nature of the progenitor star system. Here, I will focus mainly
on the supernovae (SNe) exploding in dense environments, a.k.a. Type IIn SNe.
Radio and X-ray emission from this class of SNe have revealed important
modifications in their radiation properties, due to the presence of high
density CSM. Forward shock dominance of the X-ray emission, internal free-free
absorption of the radio emission, episodic or non-steady mass loss rate,
asymmetry in the explosion seem to be common properties of this class of SNe.Comment: Fixed minor typos. 31 pages, 9 figures, accepted for publication in
Space Science Reviews. Chapter in International Space Science Institute
(ISSI) Book on "Supernovae" to be published in Space Science Reviews by
Springe
Inhomogeneous Neutrino Degeneracy and Big Bang Nucleosynthesis
We examine Big Bang nucleosynthesis (BBN) in the case of inhomogenous
neutrino degeneracy, in the limit where the fluctuations are sufficiently small
on large length scales that the present-day element abundances are homogeneous.
We consider two representive cases: degeneracy of the electron neutrino alone,
and equal chemical potentials for all three neutrinos. We use a linear
programming method to constrain an arbitrary distribution of the chemical
potentials. For the current set of (highly-restrictive) limits on the
primordial element abundances, homogeneous neutrino degeneracy barely changes
the allowed range of the baryon-to-photon ratio. Inhomogeneous degeneracy
allows for little change in the lower bound on the baryon-to-photon ratio, but
the upper bound in this case can be as large as 1.1 \times 10^{-8} (only
electron neutrino degeneracy) or 1.0 \times 10^{-9} (equal degeneracies for all
three neutrinos). For the case of inhomogeneous neutrino degeneracy, we show
that there is no BBN upper bound on the neutrino energy density, which is
bounded in this case only by limits from structure formation and the cosmic
microwave background.Comment: 6 pages, no figure
The Aharonov-Bohm effect for an exciton
We study theoretically the exciton absorption on a ring shreded by a magnetic
flux. For the case when the attraction between electron and hole is
short-ranged we get an exact solution of the problem. We demonstrate that,
despite the electrical neutrality of the exciton, both the spectral position of
the exciton peak in the absorption, and the corresponding oscillator strength
oscillate with magnetic flux with a period ---the universal flux
quantum. The origin of the effect is the finite probability for electron and
hole, created by a photon at the same point, to tunnel in the opposite
directions and meet each other on the opposite side of the ring.Comment: 13 RevTeX 3.0 pages plus 4 EPS-figures, changes include updated
references and an improved chapter on possible experimental realization
Supernova Interaction with a Circumstellar Medium
The explosion of a core collapse supernova drives a powerful shock front into
the wind from the progenitor star. A layer of shocked circumstellar gas and
ejecta develops that is subject to hydrodynamic instabilities. The hot gas can
be observed directly by its X-ray emission, some of which is absorbed and
re-radiated at lower frequencies by the ejecta and the circumstellar gas.
Synchrotron radiation from relativistic electrons accelerated at the shock
fronts provides information on the mass loss density if free-free absorption
dominates at early times or the size of the emitting region if synchrotron
self-absorption dominates. Analysis of the interaction leads to information on
the density and structure of the ejecta and the circumstellar medium, and the
abundances in these media. The emphasis here is on the physical processes
related to the interaction.Comment: 22 pages, 7 figures, to appear as a Chapter in "Supernovae and
Gamma-Ray Bursts," edited by K. W. Weiler (Springer-Verlag
The utility of anti-Müllerian hormone in the diagnosis and prediction of loss of ovarian function following chemotherapy for early breast cancer
Experimental/Theoretical Comparisons of the Turbulence in the Scrape-Off-Layers of Alcator C-Mod, DIII-D, AND NSTX
Towards Machine Wald
The past century has seen a steady increase in the need of estimating and
predicting complex systems and making (possibly critical) decisions with
limited information. Although computers have made possible the numerical
evaluation of sophisticated statistical models, these models are still designed
\emph{by humans} because there is currently no known recipe or algorithm for
dividing the design of a statistical model into a sequence of arithmetic
operations. Indeed enabling computers to \emph{think} as \emph{humans} have the
ability to do when faced with uncertainty is challenging in several major ways:
(1) Finding optimal statistical models remains to be formulated as a well posed
problem when information on the system of interest is incomplete and comes in
the form of a complex combination of sample data, partial knowledge of
constitutive relations and a limited description of the distribution of input
random variables. (2) The space of admissible scenarios along with the space of
relevant information, assumptions, and/or beliefs, tend to be infinite
dimensional, whereas calculus on a computer is necessarily discrete and finite.
With this purpose, this paper explores the foundations of a rigorous framework
for the scientific computation of optimal statistical estimators/models and
reviews their connections with Decision Theory, Machine Learning, Bayesian
Inference, Stochastic Optimization, Robust Optimization, Optimal Uncertainty
Quantification and Information Based Complexity.Comment: 37 page
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