Signature inversion in axially deformed 160,162^{160,162}Tm

The microscopic analysis of experimental data in $^{160,162}$Tm is presented within the two-quasiparticle-phonon model. The model includes the interaction between odd quasiparticles and their coupling with core vibrations. The coupling explains naturally the attenuation of the Coriolis interaction in rotating odd-odd nuclei. It is shown that the competition between the Coriolis and neutron-proton interactions is responsible for the signature inversion phenomenon.Comment: 10 pages, 1 figure, corrected some typo

Observations of Low Frequency Solar Radio Bursts from the Rosse Solar-Terrestrial Observatory

The Rosse Solar-Terrestrial Observatory (RSTO; www.rosseobservatory.ie) was established at Birr Castle, Co. Offaly, Ireland (53 05'38.9", 7 55'12.7") in 2010 to study solar radio bursts and the response of the Earth's ionosphere and geomagnetic field. To date, three Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometers have been installed, with the capability of observing in the frequency range 10-870 MHz. The receivers are fed simultaneously by biconical and log-periodic antennas. Nominally, frequency spectra in the range 10-400 MHz are obtained with 4 sweeps per second over 600 channels. Here, we describe the RSTO solar radio spectrometer set-up, and present dynamic spectra of a sample of Type II, III and IV radio bursts. In particular, we describe fine-scale structure observed in Type II bursts, including band splitting and rapidly varying herringbone features

Energy Release During Slow Long Duration Flares Observed by RHESSI

Slow Long Duration Events (SLDEs) are flares characterized by long duration of rising phase. In many such cases impulsive phase is weak with lack of typical short-lasting pulses. Instead of that smooth, long-lasting Hard X-ray (HXR) emission is observed. We analysed hard X-ray emission and morphology of six selected SLDEs. In our analysis we utilized data from RHESSI and GOES satellites. Physical parameters of HXR sources were obtained from imaging spectroscopy and were used for the energy balance analysis. Characteristic time of heating rate decrease, after reaching its maximum value, is very long, which explains long rising phase of these flares.Comment: Accepted for publication in Solar Physic

Novae Ejecta as Colliding Shells

Following on our initial absorption-line analysis of fifteen novae spectra we present additional evidence for the existence of two distinct components of novae ejecta having different origins. As argued in Paper I one component is the rapidly expanding gas ejected from the outer layers of the white dwarf by the outburst. The second component is pre-existing outer, more slowly expanding circumbinary gas that represents ejecta from the secondary star or accretion disk. We present measurements of the emission-line widths that show them to be significantly narrower than the broad P Cygni profiles that immediately precede them. The emission profiles of novae in the nebular phase are distinctly rectangular, i.e., strongly suggestive of emission from a relatively thin, roughly spherical shell. We thus interpret novae spectral evolution in terms of the collision between the two components of ejecta, which converts the early absorption spectrum to an emission-line spectrum within weeks of the outburst. The narrow emission widths require the outer circumbinary gas to be much more massive than the white dwarf ejecta, thereby slowing the latter's expansion upon collision. The presence of a large reservoir of circumbinary gas at the time of outburst is suggestive that novae outbursts may sometime be triggered by collapse of gas onto the white dwarf, as occurs for dwarf novae, rather than steady mass transfer through the inner Lagrangian point.Comment: 12 pages, 3 figures; Revised manuscript; Accepted for publication in Astrophysics & Space Scienc

Hall-conductivity sign change and fluctuations in amorphous Nbx_{x}Ge1−x_{1-x} films

The sign change in the Hall conductivity has been studied in thin amorphous Nb$_{1-x}$Ge$_x (x\approx$0.3) films. By changing the film thickness it is shown that the field at which the sign reversal occurs shifts to lower values (from above to below the mean-field transition field $H_{c2}$) with increasing film thickness. This effect can be understood in terms of a competition between a positive normal and a negative fluctuation contribution to the Hall conductivity.Comment: 5 pages, 4 figures, to appear in Phys. Rev.

Search for the Proton Decay Mode proton to neutrino K+ in Soudan 2

We have searched for the proton decay mode proton to neutrino K+ using the one-kiloton Soudan 2 high resolution calorimeter. Contained events obtained from a 3.56 kiloton-year fiducial exposure through June 1997 are examined for occurrence of a visible K+ track which decays at rest into mu+ nu or pi+ pi0. We found one candidate event consistent with background, yielding a limit, tau/B > 4.3 10^{31} years at 90% CL with no background subtraction.Comment: 13 pages, Latex, 3 tables and 3 figures, Accepted by Physics Letters

Powder production, FAST processing and properties of a Nb-silicide based alloy for high temperature aerospace applications

A Nb-silicide based alloy with nominal composition Nb–18Ti–22Si–6Mo-1.5Cr–2Sn-1Hf (at. %), designed for high temperature aerospace applications, was produced via a powder metallurgy (PM) route. The raw elements were arc melted, crushed, and milled to powder, then consolidated using Field Assisted Sintering Technology (FAST). The compressive creep of the alloy was evaluated using electro-thermal mechanical testing (ETMT). The study demonstrated the production of larger 60 mm diameter samples, with potential for further scale up. The microstructure of the FAST alloy, which is comprised of bcc Nbss and tetragonal αNb5Si3 was more homogenous compared with the cast alloy, with some interstitial contamination that occurred during powder production. The FAST alloy had lower density than state of the art Ni-based superalloys and refractory metal complex concentrated alloys (RCCAs) and high entropy alloys (RHEAs), and its yield strength and specific yield strength was higher than those of the latter metallic Ultra high temperature materials (UHTMs) and comparable to those of Nb-silicide based alloys with B addition. The stress exponent n in compressive creep was in the range 1.7–2.6, similar to that of binary Nb–10Si and Nb–16Si alloys and its creep rate at 1200 °C and 100 MPa was similar to that of the MASC alloy (Nb–25Ti–16Si-8Hf-2Al–2Cr (at.%)). Like the latter, the creep of the FAST alloy did not meet the creep goal

An Observational Overview of Solar Flares

We present an overview of solar flares and associated phenomena, drawing upon a wide range of observational data primarily from the RHESSI era. Following an introductory discussion and overview of the status of observational capabilities, the article is split into topical sections which deal with different areas of flare phenomena (footpoints and ribbons, coronal sources, relationship to coronal mass ejections) and their interconnections. We also discuss flare soft X-ray spectroscopy and the energetics of the process. The emphasis is to describe the observations from multiple points of view, while bearing in mind the models that link them to each other and to theory. The present theoretical and observational understanding of solar flares is far from complete, so we conclude with a brief discussion of models, and a list of missing but important observations.Comment: This is an article for a monograph on the physics of solar flares, inspired by RHESSI observations. The individual articles are to appear in Space Science Reviews (2011