The Electronic and Superconducting Properties of Oxygen-Ordered MgB2 compounds of the form Mg2B3Ox

Possible candidates for the Mg2B3Ox nanostructures observed in bulk of polycrystalline MgB2 (Ref.1) have been studied using a combination of Z-contrast imaging, electron energy loss spectroscopy (EELS) and first-principles calculations. The electronic structures, phonon modes, and electron phonon coupling parameters are calculated for two oxygen-ordered MgB2 compounds of composition Mg2B3O and Mg2B3O2, and compared with those of MgB2. We find that the density of states for both Mg2B3Ox structures show very good agreement with EELS, indicating that they are excellent candidates to explain the observed coherent oxygen precipitates. Incorporation of oxygen reduces the transition temperature and gives calculated TC values of 18.3 K and 1.6 K for Mg2B3O and Mg2B3O2, respectively.Comment: Submitted to PR

Foreland Magmatism during the Arabia-Eurasia Collision: Pliocene-Quaternary Activity of the Karacadağ Volcanic Complex, SW Turkey

Pliocene to Quaternary magmatism in the Karacadağ Volcanic Complex in SE Turkey occurred in the foreland region of the Arabia-Eurasia collision and can be divided into two phases. The earlier Karacadağ phase formed a north-south-trending volcanic ridge that erupted three groups of lavas. The same range of mantle sources contributed to the younger Ovabağ phase lavas, which were erupted from monogenetic cones to the east of the Karacadağ fissure. As at several other intraplate localities across the northern Arabian Plate this magmatism represents mixtures of melt from shallow, isotopically enriched mantle and from deeper, more depleted mantle. The deep source is similar to the depleted mantle invoked for other northern Arabian intraplate volcanic fields but at Karacadağ this source contained phlogopite. This source could be located in the shallow convecting mantle or may represent a metasomatic layer in the base of the lithosphere. There is no evidence for a contribution from the Afar mantle plume, as has been proposed elsewhere in northern Arabia. Melting during the Karacadağ and Ovabağ phases could have resulted from a combination of upwelling beneath weak or thinned lithosphere and restricted local extension of that weakened lithosphere as it collided with Eurasia. Tension associated with the collision focused magma of the Karacadağ phase into the elongate shield volcano of Mt. Karacadağ. The northern end of the fissure accommodated more extensive differentiation of magma, with isolated cases of crustal contamination, consistent with greater stress in the lithosphere closest to the collision. Most magma batches of the Karacadağ and Ovabağ phases differentiated by fractional crystallization at ∼5 MPa, near the boundary between the upper and lower crust. Magma batches dominated by melt from garnet lherzolite show evidence for restricted amounts of differentiation at ∼22·5 MPa, which is close to the base of the lithospheric mantl

The role of repair strategy in warranty cost minimization: An investigation via quasi-renewal processes

Most companies seek efficient rectification strategies to keep their warranty related costs under control. This study develops and investigates different repair strategies for one- and two-dimensional warranties with the objective of minimizing manufacturer's expected warranty cost. Static, improved and dynamic repair strategies are proposed and analyzed under different warranty structures. Numerical experimentation with representative cost functions indicates that performance of the policies depend on various factors such as product reliability, structure of the cost function and type of the warranty contract. © 2008 Elsevier B.V. All rights reserved

Vancomycin-resistant enterococci colonization in patients with hematological malignancies: screening and its cost-effectiveness

Background and objective: We evaluated the rates of vancomycin-resistant enterococci (VRE) colonization and VRE related bacteremia in patients with hematological malignancies in terms of routine screening culture and its cost-effectiveness.Materials and Methods: All patients of the hematology department who were older than 14 years of age and who developed at least one febrile neutropenia episode during chemotherapy for hematological cancers between November 2010 and November 2012 were evaluated retrospectively.Results: We retrospectively analyzed 282 febrile episodes in 126 neutropenic patients during a two-year study period. The study included 65 cases in the first study-year and 78 cases in the second study-year. The numbers of colonization days and colonized patient were 748 days of colonization in 29 patients (44%) in the first study-year and 547 colonization days in 21 patients (26%) in the second study-year, respectively. Routine screening culture for VRE cost $4516,4 (427 cultures) in the first study-year,$5082,7 (504 cultures) in the second study-year depending on the number of patients and their length of stay.Conclusion: In line with our study results, routine screening of hematological patients for VRE colonization is not costeffective. Routine surveillance culture for VRE should be considered with respect to the conditions of health care setting.Keywords: Hematological patients, febrile neutropenia, vancomycin-resistant enterococci, vancomycin-sensitive enterococci, bacteremia, colonization

SpinWaves in the Frustrated Kagomé Lattice Antiferromagnet KFe\u3csub\u3e3\u3c/sub\u3e(OH)\u3csub\u3e6\u3c/sub\u3e(SO\u3csub\u3e4\u3c/sub\u3e)\u3csub\u3e2\u3c/sub\u3e

The spin wave excitations of the S = 5/2 kagomé lattice antiferromagnet KFe3(OH)6(SO4)2 have been measured using high-resolution inelastic neutron scattering. We directly observe a flat mode which corresponds to a lifted ‘‘zero energy mode,’’ verifying a fundamental prediction for the kagomé lattice. A simple Heisenberg spin Hamiltonian provides an excellent fit to our spin wave data. The antisymmetric Dzyaloshinskii-Moriya interaction is the primary source of anisotropy and explains the low-temperature magnetization and spin structure

Landau Expansion for the Kugel-Khomskii t2gt_{2g} Hamiltonian

The Kugel-Khomskii (KK) Hamiltonian for the titanates describes spin and orbital superexchange interactions between $d^1$ ions in an ideal perovskite structure in which the three $t_{2g}$ orbitals are degenerate in energy and electron hopping is constrained by cubic site symmetry. In this paper we implement a variational approach to mean-field theory in which each site, $i$, has its own $n \times n$ single-site density matrix \rhov(i), where $n$, the number of allowed single-particle states, is 6 (3 orbital times 2 spin states). The variational free energy from this 35 parameter density matrix is shown to exhibit the unusual symmetries noted previously which lead to a wavevector-dependent susceptibility for spins in $\alpha$ orbitals which is dispersionless in the $q_\alpha$-direction. Thus, for the cubic KK model itself, mean-field theory does not provide wavevector `selection', in agreement with rigorous symmetry arguments. We consider the effect of including various perturbations. When spin-orbit interactions are introduced, the susceptibility has dispersion in all directions in ${\bf q}$-space, but the resulting antiferromagnetic mean-field state is degenerate with respect to global rotation of the staggered spin, implying that the spin-wave spectrum is gapless. This possibly surprising conclusion is also consistent with rigorous symmetry arguments. When next-nearest-neighbor hopping is included, staggered moments of all orbitals appear, but the sum of these moments is zero, yielding an exotic state with long-range order without long-range spin order. The effect of a Hund's rule coupling of sufficient strength is to produce a state with orbital order.Comment: 20 pages, 5 figures, submitted to Phys. Rev. B (2003

Quantum Dynamics of a Hydrogen Molecule Confined in a Cylindrical Potential

We study the coupled rotation-vibration levels of a hydrogen molecule in a confining potential with cylindrical symmetry. We include the coupling between rotations and translations and show how this interaction is essential to obtain the correct degeneracies of the energy level scheme. We applied our formalism to study the dynamics of H$_{2}$ molecules inside a "smooth" carbon nanotube as a function of tube radius. The results are obtained both by numerical solution of the ($2J+1$)-component radial Schrodinger equation and by developing an effective Hamiltonian to describe the splitting of a manifold of states of fixed angular momentum $J$ and number of phonons, $N$. For nanotube radius smaller than $\approx 3.5$ \AA, the confining potential has a parabolic shape and the results can be understood in terms of a simple toy model. For larger radius, the potential has the "Mexican hat" shape and therefore the H$_{2}$ molecule is off-centered, yielding radial and tangential translational dynamics in addition to rotational dynamics of H$_{2}$ molecule which we also describe by a simple model. Finally, we make several predictions for the the neutron scattering observation of various transitions between these levels.Comment: 36 pages, 8 figures, submitted to Phys. Rev. B on 12 December 200

Law of denial

Law’s claim of mastery over past political violence is frequently undermined by reversals of that relationship of mastery, so that the violence of the law, and especially its symbolic violence, becomes easily incorporated into longues durées of political violence, rather than mastering them, settling them, or providing closure. Doing justice to the past, therefore, requires a political and theoretical attunement to the ways in which law, in purportedly attempting to address past political violence, inscribes itself into contemporary contexts of violence. While this may be limited to an analysis of how law is an effect of and affects the political, theoretically this attunement can be further refined by means of a critique of dynamics that are internal to law itself and that have to do with how law understands its own historicity, as well as its relationship to history and historiography. This article aims to pursue such a critique, taking as its immediate focus the ECHR case of Perinçek v Switzerland, with occasional forays into debates around the criminalisation of Armenian genocide denialism in France. The Perinçek case concerned Switzerland's criminalisation of the denial of the Armenian genocide, and concluded in 2015 after producing two judgments, first by the Second Chamber, and then by the Grand Chamber of the ECHR. However, although they both found for the applicant, the two benches had very different lines of reasoning, and notably different conceptions regarding the relationship between law and history. I proceed by tracing the shifting status of 'history' and 'historians' in these two judgments, and paying attention to the deferrals, disclaimers and ellipses that structure law's relation to history. This close reading offers the opportunity for a critical reappraisal of the relationship between law, denial and violence: I propose that the symbolic violence of the law operative in memory laws is a product of that which remains unresolved in law's understanding of historicity (including its own), its self-understanding vis-à-vis the task of historiography, and its inability to respond to historical violence without inscribing itself into a history of violence, a process regarding which it remains in denial

HECTD2, a candidate susceptibility gene for Alzheimer's disease on 10q

Background: Late onset Alzheimer's disease (LOAD) is a neurodegenerative disorder characterised by the deposition of amyloid plaques and neurofibrillary tangles in the brain and is the major cause of dementia. Multiple genetic loci, including 10q, have been implicated in LOAD but to date, with the exception of APOE, the underlying genes have not been identified. HECTD2 maps to 10q and has been implicated in susceptibility to human prion diseases which are also neurodegenerative conditions associated with accumulation of misfolded host proteins. In this study we test whether the HECTD2 susceptibility allele seen in prion disease is also implicated in LOAD.Methods: DNA from 320 individuals with Alzheimer's disease and 601 controls were genotyped for a HECTD2 intronic tagging SNP, rs12249854 (A/T). Groups were further analysed following stratification by APOE genotype.Results: The rs12249854 minor allele (A) frequency was higher (5.8%) in the Alzheimer's disease group as compared to the controls (3.9%), however, this was not statistically significant (P = 0.0668). No significant difference was seen in minor allele frequency in the presence or absence of the APOE epsilon 4 allele.Conclusion: The common haplotypes of HECTD2, tagged by rs12249854, are not associated with susceptibility to LOAD