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

Leiomyosarcoma of the inferior vena cava: Radical surgery and vascular reconstruction

<p>Abstract</p> <p>Background</p> <p>Vascular leiomyosarcoma are rare tumors typically originating from the inferior vena cava (IVC). Due to nonspecific clinical signs most tumors are diagnosed at advanced stages. Complete surgical resection remains the only potential curative therapeutic option. Surgical strategy is particularly influenced by the level of the IVC affected. Due to the topographic relation to the renal veins level-II involvement of the IVC raises special surgical challenges with respect to the maintenance of venous outflow.</p> <p>Case presentation</p> <p>We herein report two cases of leiomyosarcoma of the IVC with successful en bloc resection and individualized caval reconstruction. One patient presented with a large intramural and intraluminal mass and received a complete circumferential resection. Reconstruction was performed by graft replacement of the caval segment affected. The other patient displayed a predominantly extraluminal tumor growth and underwent semicircumferential resection of the IVC including the confluence of the left renal vein. In this case vascular reconstruction was performed by cavoplasty and reinsertion of the left renal vein into the proximal portion of the IVC. Resection margins of both patients were tumor free and no clinical signs of venous insufficiency of the lower extremity occurred.</p> <p>Conclusion</p> <p>This paper presents two cases of successfully managed leiomyosarcomas of the vena cava and exemplifies two different options for vascular reconstruction in level II sarcomas and includes a thorough review of the literature.</p

Resolving the Ellsberg Paradox by Assuming that People Evaluate Repetitive Sampling

Ellsberg (1961) designed a decision experiment where most people violated the axioms of rational choice. He asked people to bet on the outcome of certain random events with known and with unknown probabilities. They usually preferred to bet on events with known probabilities. It is shown that this behavior is reasonable and in accordance with the axioms of rational decision making if it is assumed that people consider bets on events that are repeatedly sampled instead of just sampled once

Compton scattering beyond the impulse approximation

We treat the non-relativistic Compton scattering process in which an incoming photon scatters from an N-electron many-body state to yield an outgoing photon and a recoil electron, without invoking the commonly used frameworks of either the impulse approximation (IA) or the independent particle model (IPM). An expression for the associated triple differential scattering cross section is obtained in terms of Dyson orbitals, which give the overlap amplitudes between the N-electron initial state and the (N-1) electron singly ionized quantum states of the target. We show how in the high energy transfer regime, one can recover from our general formalism the standard IA based formula for the cross section which involves the ground state electron momentum density (EMD) of the initial state. Our formalism will permit the analysis and interpretation of electronic transitions in correlated electron systems via inelastic x-ray scattering (IXS) spectroscopy beyond the constraints of the IA and the IPM.Comment: 7 pages, 1 figur

Local lattice disorder in the geometrically-frustrated spin glass pyrochlore Y2Mo2O7

The geometrically-frustrated spin glass Y2Mo2O7 has been considered widely to be crystallographically ordered with a unique nearest neighbor magnetic exchange interaction, J. To test this assertion, we present x-ray-absorption fine-structure results for the Mo and Y K edges as a function of temperature and compare them to results from a well-ordered pyrochlore, Tl2Mn2O7. We find that the Mo-Mo pair distances are significantly disordered at approximately right angles to the Y-Mo pairs. These results strongly suggest that lattice disorder nucleates the spin-glass phase in this material.Comment: 9 pages, 2 Postscript figures, Phys. Rev. B: Rapid, in pres