The hospitality phenomenon: philosophical enlightenment?

The emergent paradigm of hospitality studies does not have a coherent philosophical foundation. In seeking to identify a philosophy of hospitality this paper explores Derrida's contribution, along with other writers in philosophy and postcolonial theory, who are either writing in the field or have developed his works. Derrida and others are often cited within the context of the emerging paradigm of hospitality studies. In order to examine and critically evaluate the possibility of the construct of a philosophy of the phenomenon of hospitality, the review of the philosophical concepts is set within three perspectives: individual moral philosophy; hospitality and the nation states, and hospitality and language. Although examining the writings of Derrida and others provides an insight into the phenomenon of hospitality, a coherent philosophy of hospitality seems to be an enigma; possibly because hospitality is not a matter of objective knowledge

Ytterbium divalency and lattice disorder in near-zero thermal expansion YbGaGe

While near-zero thermal expansion (NZTE) in YbGaGe is sensitive to stoichiometry and defect concentration, the NZTE mechanism remains elusive. We present x-ray absorption spectra that show unequivocally that Yb is nearly divalent in YbGaGe and the valence does not change with temperature or with nominally 1% B or 5% C impurities, ruling out a valence-fluctuation mechanism. Moreover, substantial changes occur in the local structure around Yb with B and C inclusion. Together with inelastic neutron scattering measurements, these data indicate a strong tendency for the lattice to disorder, providing a possible explanation for NZTE in YbGaGe.Comment: 4 pages, 4 figure, supplementary inf

Elastic and thermodynamic properties of the shape-memory alloy AuZn

The current work reports on the elastic shear moduli, internal friction, and the specific heat of the B2 cubic ordered alloy AuZn as a function of temperature. Measurements were made on single-crystal and polycrystalline samples using Resonant Ultrasound Spectroscopy (RUS), semi-adiabatic calorimetry and stress-strain measurements. Our results confirm that this alloy exhibits the shape-memory effect and a phase transition at 64.75 K that appears to be continuous (second-order) from the specific heat data. It is argued that the combination of equiatomic composition and a low transformation temperature constrain the chemical potential and its derivatives to exhibit behavior that lies at the borderline between that of a first-order (discontinuous) and a continuous phase transition. The acoustic dissipation does not peak at the transtion temperature as expected, but shows a maximum well into the low-temperature phase. The Debye temeprature value of 219 K, obtained from the low-temperature specific heat data is in favorable agreement with that determined from the acoustic data (207 K) above the transition.Comment: 25 pages, 6 figures, submitted to Phys. Rev.

Multiconfigurational nature of 5f orbitals in uranium and plutonium intermetallics

Uranium and plutonium's 5f electrons are tenuously poised between strongly bonding with ligand spd-states and residing close to the nucleus. The unusual properties of these elements and their compounds (eg. the six different allotropes of elemental plutonium) are widely believed to depend on the related attributes of f-orbital occupancy and delocalization, for which a quantitative measure is lacking. By employing resonant x-ray emission spectroscopy (RXES) and x-ray absorption near-edge structure (XANES) spectroscopy and making comparisons to specific heat measurements, we demonstrate the presence of multiconfigurational f-orbital states in the actinide elements U and Pu, and in a wide range of uranium and plutonium intermetallic compounds. These results provide a robust experimental basis for a new framework for understanding the strongly-correlated behavior of actinide materials.Comment: 30 pages, concatenated article and supporting information, 10 figure

Magnetic phase transition in the itinerant helimagnet MnSi: Thermodynamic and transport properties

A careful study of thermodynamic and transport properties of a high-quality single crystal of MnSi at ambient pressure suggests that its transition to a helical magnetic state near 29 K is weakly first order. The heat capacity, temperature derivative of resistivity, thermal expansion, and magnetic susceptibility exhibit a specific structure around the phase transition point, interpreted as a combination of first- and second-order features. Striking mirror symmetry between the temperature derivative of resistivity and the thermal expansion coefficient is observed. Conclusions drawn from these experiments question prevailing views on the phase diagram of MnSi

Fermi Surface of Alpha-Uranium at Ambient Pressure

We have performed de Haas-van Alphen measurements of the Fermi surface of alpha-uranium single crystals at ambient pressure within the alpha-3 charge density wave (CDW) state from 0.020 K - 10 K and magnetic fields to 35 T using torque magnetometry. The angular dependence of the resulting frequencies is described. Effective masses were measured and the Dingle temperature was determined to be 0.74 K +/- 0.04 K. The observation of quantum oscillations within the alpha-3 CDW state gives new insight into the effect of the charge density waves on the Fermi surface. In addition we observed no signature of superconductivity in either transport or magnetization down to 0.020 K indicating the possibility of a pressure-induced quantum critical point that separates the superconducting dome from the normal CDW phase.Comment: 11 pages, 4 figures, 3 table