1,679 research outputs found
Search for supernova-produced 60Fe in a marine sediment
An 60Fe peak in a deep-sea FeMn crust has been interpreted as due to the
signature left by the ejecta of a supernova explosion close to the solar system
2.8 +/- 0.4 Myr ago [Knie et al., Phys. Rev. Lett. 93, 171103 (2004)]. To
confirm this interpretation with better time resolution and obtain a more
direct flux estimate, we measured 60Fe concentrations along a dated marine
sediment. We find no 60Fe peak at the expected level from 1.7 to 3.2 Myr ago.
However, applying the same chemistry used for the sediment, we confirm the 60Fe
signal in the FeMn crust. The cause of the discrepancy is discussed.Comment: 15 pages, 5 figures, submitted to PR
Introduction of the 2005 cardiopulmonary resuscitation guidelines did not increase return of spontaneous circulation in a physician-staffed prehospital emergency medical system
Settling the half-life of ⁶⁰Fe: fundamental for a versatile astrophysical chronometer
In order to resolve a recent discrepancy in the half-life of ⁶⁰Fe, we performed an independent measurement with a new method that determines the ⁶⁰Fe content of a material relative to Fe55 (t1/2=2.744yr) with accelerator mass spectrometry. Our result of (2.50±0.12)×10⁶yr clearly favors the recently reported value (2.62±0.04)×10⁶yr, and rules out the older result of (1.49±0.27)×10⁶yr. The present weighted mean half-life value of (2.60±0.05)×10⁶yr substantially improves the reliability as an important chronometer for astrophysical applications in the million-year time range. This includes its use as a sensitive probe for studying recent chemical evolution of our Galaxy, the formation of the early Solar System, nucleosynthesis processes in massive stars, and as an indicator of a recent nearby supernova.Part of this work was funded by the Austrian Science
Fund (FWF) Projects No. AP20434 and AI00428 (FWF
and CoDustMas, Eurogenesis via ESF)
Assessment of prognostic significance of cytoplasmic survivin expression in advanced oesophageal cancer.
Survivin is a member of the family of proteins, which inhibit apoptosis (inhibitor of apoptosis proteins - IAP). Expression of survivin was found in colorectal cancer, neuroblastoma, bladder cancer, non-small cell lung cancer, and breast cancer. There is some recent data indicating the correlation of poor prognosis and worse response to chemotherapy in patients with oesophageal squamous cell carcinoma (OSCC) expressing survivin. The aim of the present study was to assess survivin expression in cancerous tissue of patients with advanced OSCC and to test the potential correlation between survivin expression and clinicopathological data. Forty two patients (mean age 58.36+/-8.97 yrs), who were oesophagectomised due to squamous cell carcinoma of the thoracic oesophagus between 1998 and 2000, were retrospectively analysed. Cytoplasmic survivin expression, examined immunohistochemically, was found in 35 (83.33%) cases. No statistically significant correlation between survivin expression in the tumour and patients' gender, TNM stage, or vascular involvement was noted. The mean survival of patients with cytoplasmic survivin expression (17.81+/-5.51 months) was not statistically different to those with negative survivin staining (16+/-6.28 months) as assessed by Mantel-Cox test (p=0.49). Univariate regression analysis revealed UICC staging as the only predictor of survival in the analysed group (
The Ni(n,) cross section measured with DANCE
The neutron capture cross section of the s-process branch nucleus Ni
affects the abundances of other nuclei in its region, especially Cu and
Zn. In order to determine the energy dependent neutron capture cross
section in the astrophysical energy region, an experiment at the Los Alamos
National Laboratory has been performed using the calorimetric 4 BaF
array DANCE. The (n,) cross section of Ni has been determined
relative to the well known Au standard with uncertainties below 15%.
Various Ni resonances have been identified based on the Q-value.
Furthermore, the s-process sensitivity of the new values was analyzed with the
new network calculation tool NETZ.Comment: 11 pages, 13 page
Reality Conditions and Ashtekar Variables: a Different Perspective
We give in this paper a modified self-dual action that leads to the
-ADM formalism without having to face the difficult second class
constraints present in other approaches (for example if one starts from the
Hilbert-Palatini action). We use the new action principle to gain some new
insights into the problem of the reality conditions that must be imposed in
order to get real formulations from complex general relativity. We derive also
a real formulation for Lorentzian general relativity in the Ashtekar phase
space by using the modified action presented in the paper.Comment: 22 pages, LATEX, Preprint CGPG-94/10-
On the energy of homogeneous cosmologies
An energy for the homogeneous cosmological models is presented. More
specifically, using an appropriate natural prescription, we find the energy
within any region with any gravitational source for a large class of gravity
theories--namely those with a tetrad description--for all 9 Bianchi types. Our
energy is given by the value of the Hamiltonian with homogeneous boundary
conditions; this value vanishes for all regions in all Bianchi class A models,
and it does not vanish for any class B model. This is so not only for
Einstein's general relativity but, moreover, for the whole 3-parameter class of
tetrad-teleparallel theories. For the physically favored one parameter
subclass, which includes the teleparallel equivalent of Einstein's theory as an
important special case, the energy for all class B models is, contrary to
expectation, negative.Comment: 11 pages, reformated with minor change
Abundance of live ²⁴⁴Pu in deep-sea reservoirs on earth points to rarity of actinide nucleosynthesis
Measurement of the radiative capture cross section of the s-process branching points 204Tl and 171Tm at the n-TOF facility (CERN)
The neutron capture cross section of some unstable nuclei is especially relevant for s-process nucleosynthesis studies. This magnitude is crucial to determine the local abundance pattern, which can yield valuable information of the s-process stellar environment. In this work we describe the neutron capture (n,γ) measurement on two of these nuclei of interest, 204Tl and 171Tm, from target production to the final measurement, performed successfully at the n_TOF facility at CERN in 2014 and 2015. Preliminary results on the ongoing experimental data analysis will also be shown. These results include the first ever experimental observation of capture resonances for these two nuclei.The authors acknowledge financial support by the Spanish FPA2014-52823-C2-2-P project, by the EC
Marie Curie Action “NeutAndalus” (FP7-PEOPLE-2012-CIG- 334315), by the ARGOS scholarship of
the Spanish Nuclear Safety Council (CSN) and the Universitat Politècnica de Catalunya, and by the
University of Sevilla via the VI PPIT-US program
Pseudotensors and quasilocal energy-momentum
Early energy-momentum investigations for gravitating systems gave reference
frame dependent pseudotensors; later the quasilocal idea was developed.
Quasilocal energy-momentum can be determined by the Hamiltonian boundary term,
which also identifies the variables to be held fixed on the boundary. We show
that a pseudotensor corresponds to a Hamiltonian boundary term. Hence they are
quasilocal and acceptable; each is the energy-momentum density for a definite
physical situation with certain boundary conditions. These conditions are
identified for well-known pseudotensors.Comment: LaTeX (REVTex), 4 pages, no figures, revised Title, abstract,
introduction and conclusio
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