Evolution of nano-pores during annealing of technically pure molybdenum sheet produced from different sintered formats

Molybdenum is a refractory metal with no phase transformation in the solid state and a high melting point. It is therefore an excellent structural material for various high temperature applications. Especially in this field of operation, significant creep resistance is essential. To achieve this, a microstructure with grains in the range of millimeters is desired. However, as demonstrated in the present study, the onset temperature for secondary recrystallization, which would lead to a beneficial grain size, is among other things dependent on the initial dimensions of the sintered part. One possible reason for the different microstructural evolutions is the influence of residual pores in sub-micrometer size. Sheets were thus fabricated via three different production routes employing the same initial Mo powder to exclude chemical variation as an influencing factor. The samples were investigated by in-situ small-angle X-ray scattering at a synchrotron radiation source with two different heating rates. Additionally, selected annealed samples were studied ex-situ with high energy X-rays. The apparent volume fraction of pores is compared to a volatilization model for the vaporization of typical accompanying elements and the induced thermal expansion

Spectroscopy of 19^{19}Ne for the thermonuclear 15^{15}O(α,γ\alpha,\gamma)19^{19}Ne and 18^{18}F(p,αp,\alpha)15^{15}O reaction rates

Uncertainties in the thermonuclear rates of the $^{15}$O($\alpha,\gamma$)$^{19}$Ne and $^{18}$F($p,\alpha$)$^{15}$O reactions affect model predictions of light curves from type I X-ray bursts and the amount of the observable radioisotope $^{18}$F produced in classical novae, respectively. To address these uncertainties, we have studied the nuclear structure of $^{19}$Ne over $E_{x} = 4.0 - 5.1$ MeV and $6.1 - 7.3$ MeV using the $^{19}$F($^{3}$He,t)$^{19}$Ne reaction. We find the $J^{\pi}$ values of the 4.14 and 4.20 MeV levels to be consistent with $9/2^{-}$ and $7/2^{-}$ respectively, in contrast to previous assumptions. We confirm the recently observed triplet of states around 6.4 MeV, and find evidence that the state at 6.29 MeV, just below the proton threshold, is either broad or a doublet. Our data also suggest that predicted but yet unobserved levels may exist near the 6.86 MeV state. Higher resolution experiments are urgently needed to further clarify the structure of $^{19}$Ne around the proton threshold before a reliable $^{18}$F($p,\alpha$)$^{15}$O rate for nova models can be determined.Comment: 5 pages, 3 figures, Phys. Rev. C (in press

Gamma ray production cross sections in proton induced reactions on natural Mg, Si and Fe targets over the proton energy range 30 up to 66 MeV

Gamma-ray excitation functions have been measured for 30, 42, 54 and 66 MeV proton beams accelerated onto C + O (Mylar), Mg, Si, and Fe targets of astrophysical interest at the separate-sector cyclotron of iThemba LABS in Somerset West (Cape Town, South Africa). A large solid angle, high energy resolution detection system of the Eurogam type was used to record Gamma-ray energy spectra. Derived preliminary results of Gamma-ray line production cross sections for the Mg, Si and Fe target nuclei are reported and discussed. The current cross section data for known, intense Gamma-ray lines from these nuclei consistently extend to higher proton energies previous experimental data measured up to Ep ~ 25 MeV at the Orsay and Washington tandem accelerators. Data for new Gamma-ray lines observed for the first time in this work are also reported.Comment: 11 pages, 6 figures. IOP Institute of Physics Conference Nuclear Physics in Astrophysics VII, 28th EPF Nuclear Physics Divisional Conference, May 18-22 2015, York, U

E1−E2E1-E2 interference in the Coulomb dissociation of 8^8B

We investigate the effects arising out of the $E1 - E2$ interference in the Coulomb dissociation of $^8$B at beam energies below and around 50 MeV/nucleon. The theory has been formulated within a first order semiclassical scheme of Coulomb excitation, in which both the ground state and the continuum state wave functions of $^8$B enter as inputs. We find that the magnitude of the interference could be large in some cases. However, there are some specific observables which are free from the effects of the $E1 - E2$ interference, which is independent of the models used to describe the structure of $^8$B. This will be useful for the analysis of the breakup data in relation to the extraction of the astrophysical factor $S_{17}(0)$.Comment: Revised version to appear in Physical Review

Low energy measurement of the 7Be(p,gamma)8B cross section

We have measured the cross section of the 7Be(p,gamma)8B reaction for E_cm = 185.8 keV, 134.7 keV and 111.7 keV using a radioactive 7Be target (132 mCi). Single and coincidence spectra of beta^+ and alpha particles from 8B and 8Be^* decay, respectively, were measured using a large acceptance spectrometer. The zero energy S factor inferred from these data is 18.5 +/- 2.4 eV b and a weighted mean value of 18.8 +/- 1.7 eV b (theoretical uncertainty included) is deduced when combining this value with our previous results at higher energies.Comment: Accepted for publication in Phys. Rev. Let

S17(0) Determined from the Coulomb Breakup of 83 MeV/nucleon 8B

A kinematically complete measurement was made of the Coulomb dissociation of 8B nuclei on a Pb target at 83 MeV/nucleon. The cross section was measured at low relative energies in order to infer the astrophysical S factor for the 7Be(p,gamma)8B reaction. A first-order perturbation theory analysis of the reaction dynamics including E1, E2, and M1 transitions was employed to extract the E1 strength relevant to neutrino-producing reactions in the solar interior. By fitting the measured cross section from Erel = 130 keV to 400 keV, we find S17(0) = 17.8 (+1.4, -1.2) eV b

PU.1 controls fibroblast polarization and tissue fibrosis

Fibroblasts are polymorphic cells with pleiotropic roles in organ morphogenesis, tissue homeostasis and immune responses. In fibrotic diseases, fibroblasts synthesize abundant amounts of extracellular matrix, which induces scarring and organ failure. By contrast, a hallmark feature of fibroblasts in arthritis is degradation of the extracellular matrix because of the release of metalloproteinases and degrading enzymes, and subsequent tissue destruction. The mechanisms that drive these functionally opposing pro-fibrotic and pro-inflammatory phenotypes of fibroblasts remain unknown. Here we identify the transcription factor PU.1 as an essential regulator of the pro-fibrotic gene expression program. The interplay between transcriptional and post-transcriptional mechanisms that normally control the expression of PU.1 expression is perturbed in various fibrotic diseases, resulting in the upregulation of PU.1, induction of fibrosis-associated gene sets and a phenotypic switch in extracellular matrix-producing pro-fibrotic fibroblasts. By contrast, pharmacological and genetic inactivation of PU.1 disrupts the fibrotic network and enables reprogramming of fibrotic fibroblasts into resting fibroblasts, leading to regression of fibrosis in several organs

Polymorphisms in the interleukin 4, interleukin 13 and corresponding receptor genes are not associated with Systemic Sclerosis and do not influence gene expression

1 página.-- Póster presentado al 5º European Workshop on Immune-Mediated Inflammatory Diseases celebrado en Sitges (Barcelona, Españ) del 1 al 3 de Diciembre de 2010.-- et al.Peer reviewe