Search

Over the past decades, significant efforts have been made to understand the nature, dynamics and evolution of volcanic systems. In parallel, the continuous demographic expansion and extensive urbanization of volcanic areas have increased the exposure of our society to these natural phenomena. This increases the need to improve our capacities to accurately assess projected volcanic hazards and their potential socioeconomic and environmental impact, and Antarctica and the sub-Antarctic islands are no exception. More than a hundred volcanoes have been identified in Antarctica, some of which are entirely buried beneath the ice sheet and others as submarine volcanoes. Of these, at least eight large (basal diameters > c. 20-30 km) volcanoes are known to be active and pose a considerable threat to scientific and ever-increasing tourism activities being carried out in the region. Despite the scientific and socioeconomic interest, many aspects of the past volcanic activity and magmatic processes in Antarctica, and current volcanic hazards and risks, remain unknown. Moreover, many of Antarctica's volcanoes preserve a remarkable history of the eruptive environment, from which multiple parameters of past configurations of the Antarctic ice sheet (AIS) can be deduced. Given the critical role that the AIS plays in regulating Earth's climate, Antarctica's volcanoes therefore can be regarded as the ground truth for current models of past climates derived from modelling and studies of marine sediments. Here, we provide a succinct overview of the evolution of volcanism and magmatism in Antarctica and the sub-Antarctic region over the past 200 million years. Then, we briefly review the current state of knowledge of the most crucial aspects regarding Antarctica's volcanic and magmatic processes, and the contributions volcanic studies have made to our understanding of ice sheet history and evolution, geothermal heat flow, as well as present-day and future volcanic hazard and risk. A principal objective is to highlight the problems and critical limitations of the current state of knowledge and to provide suggestions for future potential directions of volcanic-driven investigations in Antarctica. Finally, we also discuss and assess the importance and scope of education and outreach activities specifically relating to Antarctic volcanism, and within the context of broader polar sciences. [Display omitted] • The state of knowledge of Antarctica's volcanic and magmatic processes is reviewed. • Volcanism and magmatism in Antarctica over the past 200 million years is summarized. • Recommendations for future research on Antarctic volcanism are provided. [ABSTRACT FROM AUTHOR]

Abstract: We provide new data for the stiffness, hardness, Debye temperatures and crystallization and glass transition temperatures for fourteen Ti–TL and Hf–TL amorphous alloys (TL=Ni,Cu) covering wide composition range (x(TL)≤70). These data increase linearly with x, as was previously observed for Zr–TL glassy alloys. Thus, the strength of interatomic bonding (reflected in stiffness) in all TE–TL amorphous alloys (TE=Ti,Zr,Hf) increases with x for x≤65. The actual variations of studied properties depend on TE, being feeble for TE=Ti. The approximately linear variation of mechanical, vibrational and thermal parameters with x enables one to estimate these parameters for pure amorphous TEs, but does not indicate compositions at which bulk metallic glasses (BMG) form in these alloy systems. The reduced glass transition temperature Trg is the property which roughly correlates with the formation of BMGs in glassy TE–TL alloys. [Copyright &y& Elsevier]

Abstract: Cross-section measurements were made of prompt γ-ray production as a function of incident neutron energy (E n =1–35MeV) on an enriched (95.6%) l50Sm sample. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the Los Alamos Neutron Science Center (LANSCE) facility. The prompt-reaction γ-rays were detected with the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The γ-ray excitation functions were converted to partial γ-ray cross-sections taking into account the dead-time correction, target thickness, detector efficiency and neutron flux (monitored with an in-line fission chamber). Partial γ-ray cross-sections were predicted using the Hauser–Feshbach statistical reaction code GNASH. Above E n ∼8MeV, the pre-equilibrium reaction process dominates the inelastic reaction. The spin-distribution transferred in pre-equilibrium neutron induced reactions was calculated using the quantum mechanical theory of Feshbach, Kerman and Koonin (FKK). These pre-equilibrium spin distributions were incorporated into a new version of GNASH and the γ-ray production cross-sections were calculated and compared with experimental data. The difference in the partial γ-ray cross-sections using spin-distributions with and without pre-equilibrium effects is discussed. [Copyright &y& Elsevier]

Abstract: Our understanding of the superconducting properties of MgB2 is strongly linked to our knowledge of its electronic structure. In this paper we review experimental measurements of the Fermi surface parameters of pure and Al-doped MgB2 using the de Haas–van Alphen (dHvA) effect. In general, the measurements are in excellent agreement with the theoretical predictions of the electronic structure, including the strength of the electron–phonon coupling on each Fermi surface sheet. For the Al doped samples, we are able to measure how the band structure changes with doping. These results are in excellent agreement with calculations based on the virtual crystal approximation. We also review work on the dHvA effect in the superconducting state. [Copyright &y& Elsevier]

We study the spin fluctuations of pure and Zn-substituted high temperature superconductors (HTS) using the muon spin relaxation (μSR) technique. Superconductivity is found to coexist with low frequency spin fluctuations over a large region of the superconducting phase diagram. The characteristic temperature of spin fluctuations detected by μSR decreases with increasing doping and vanishes above a critical doping pc≈0.19 where the normal state pseudogap vanishes. Furthermore, it is at pc that our penetration depth studies show an abrupt change in the doping dependence of the superfluid density, ρs. For p>pc the absolute value of ρs is large and nearly independent of carrier concentration whereas for p

B(E2;0+1→2+1) values for the unstable, neutron-rich nuclei 132,134Te were determined through Coulomb excitation, in inverse kinematics, of accelerated beams of these nuclei. The systematics of measured B(E2) values from the ground state to the first excited state have been extended to the N=82 shell closure in the Te nuclei and have been compared with the predictions of different theories. The measurements were performed at the Holifield Radioactive Ion Beam Facility (HRIBF) using the GRAFIK detector. The success of this approach, which couples a 5.7% efficient through-well NaI(Tl) γ-ray detector with thin foil microchannel plate beam detectors, also demonstrates the feasibility for Coulomb excitation studies of neutron-rich nuclei even further from the valley of beta stability, both at present-generation ISOL facilities and at the proposed Rare Isotope Accelerator. [Copyright &y& Elsevier]

Examines the fabrication of calcium-doped large grain Y-Ba-Cu-O superconductors. Temperature profile used for processing under isothermal conditions; Magnetic transitions of calcium-doped YBCO grains at different carrier concentrations; Critical current as a function of magnetic field.