Vanishing Fe 3d orbital moments in single-crystalline magnetite

We show detailed magnetic absorption spectroscopy results of an in situ cleaved high quality single crystal of magnetite. In addition the experimental setup was carefully optimized to reduce drift, self absorption, and offset phenomena as far as possible. In strong contradiction to recently published data, our observed orbital moments are nearly vanishing and the spin moments are quite close to the integer values proposed by theory. This very important issue supports the half metallic full spin polarized picture of magnetite.Comment: 7 pages, 4 figure

Magnetic coupling in highly-ordered NiO/Fe3O4(110): Ultrasharp magnetic interfaces vs. long-range magnetoelastic interactions

We present a laterally resolved X-ray magnetic dichroism study of the magnetic proximity effect in a highly ordered oxide system, i.e. NiO films on Fe3O4(110). We found that the magnetic interface shows an ultrasharp electronic, magnetic and structural transition from the ferrimagnet to the antiferromagnet. The monolayer which forms the interface reconstructs to NiFe2O4 and exhibits an enhanced Fe and Ni orbital moment, possibly caused by bonding anisotropy or electronic interaction between Fe and Ni cations. The absence of spin-flop coupling for this crystallographic orientation can be explained by a structurally uncompensated interface and additional magnetoelastic effects

Emergence of Oxacillin Resistance in Stealth Methicillin-Resistant \u3cem\u3eStaphylococcus aureus \u3c/em\u3eDue to \u3cem\u3emecA \u3c/em\u3eSequence Instability

Staphylococcus aureus strains that possess a mecA gene but are phenotypically susceptible to oxacillin and cefoxitin (OS-MRSA) have been recognized for over a decade and are a challenge for diagnostic laboratories. The mechanisms underlying the discrepancy vary from isolate to isolate. We characterized seven OS-MRSA clinical isolates of six different spa types from six different states by whole-genome sequencing to identify the nucleotide sequence changes leading to the OS-MRSA phenotype. The results demonstrated that oxacillin susceptibility was associated with mutations in regions of nucleotide repeats within mecA. Subinhibitory antibiotic exposure selected for secondary mecA mutations that restored oxacillin resistance. Thus, strains of S. aureus that contain mecA but are phenotypically susceptible can become resistant after antibiotic exposure, which may result in treatment failure. OS-MRSA warrant follow-up susceptibility testing to ensure detection of resistant revertants

Angular Dependent Soft X-ray Absorption Spectroscopy of V2O5 and V6O13

We have measured the V 2p3/2 and O 1s x-ray absorption spectra of single crystal V2O5 and V6O13 and compared to linear combinations of atomic orbitals (LCAO) density of states (DOS) calculations. The spectra change dramatically with incident angle. The use of polarized light and a single crystal limits the number of transitions possible, revealing spectral features that cannot be resolved on polycrystals (angle-integrated). The measured O 1s and V 2p3/2 spectra agree with the projected unoccupied O 2p and V 3d DOS respectively, indicating that atomic and solid state effects, including V-O hybridization, must be included to adequately describe the spectra.Comment: PostScript, 9 pages, 3 figure

Element-Specific Depth Profile of Magnetism and Stoichiometry at the La0.67Sr0.33MnO3/BiFeO3 Interface

Depth-sensitive magnetic, structural and chemical characterization is important in the understanding and optimization of novel physical phenomena emerging at interfaces of transition metal oxide heterostructures. In a simultaneous approach we have used polarized neutron and resonant X-ray reflectometry to determine the magnetic profile across atomically sharp interfaces of ferromagnetic La0.67Sr0.33MnO3 / multiferroic BiFeO3 bi-layers with sub-nanometer resolution. In particular, the X-ray resonant magnetic reflectivity measurements at the Fe and Mn resonance edges allowed us to determine the element specific depth profile of the ferromagnetic moments in both the La0.67Sr0.33MnO3 and BiFeO3 layers. Our measurements indicate a magnetically diluted interface layer within the La0.67Sr0.33MnO3 layer, in contrast to previous observations on inversely deposited layers. Additional resonant X-ray reflection measurements indicate a region of an altered Mn- and O-content at the interface, with a thickness matching that of the magnetic diluted layer, as origin of the reduction of the magnetic moment.Comment: 13 pages, 4 figures, supplemental material include

Updating Molecular Diagnostics for Detecting Methicillin- Susceptible and Methicillin-Resistant \u3cem\u3eStaphylococcus aureus \u3c/em\u3eIsolates in Blood Culture Bottles

Molecular diagnostic tests can be used to provide rapid identification of staphylococcal species in blood culture bottles to help improve antimicrobial stewardship. However, alterations in the target nucleic acid sequences of the microorganisms or their antimicrobial resistance genes can lead to false-negative results. We determined the whole-genome sequences of 4 blood culture isolates of Staphylococcus aureus and 2 control organisms to understand the genetic basis of genotypephenotype discrepancies when using the Xpert MRSA/SA BC test (in vitro diagnostic medical device [IVD]). Three methicillin-resistant S. aureus (MRSA) isolates each had a different insertion of a genetic element in the staphylococcal cassette chromosome (SCCmec)-orfX junction region that led to a misclassification as methicillin-susceptible S. aureus (MSSA). One strain contained a deletion in spa, which produced a false S. aureus-negative result. A control strain of S. aureus that harbored an SCCmec element but no mecA (an empty cassette) was correctly called MSSA by the Xpert test. The second control contained an SCCM1 insertion. The updated Xpert MRSA/SA BC test successfully detected both spa and SCCmec variants of MRSA and correctly identified empty-cassette strains of S. aureus as MSSA. Among a sample of 252 MSSA isolates from the United States and Europe, 3.9% contained empty SCCmec cassettes, 1.6% carried SCCM1, \u3c1% had spa deletions, and \u3c1% contained SCCmec variants other than those with SCCM1. These data suggest that genetic variations that may interfere with Xpert MRSA/SA BC test results remain rare. Results for all the isolates were correct when tested with the updated assay

The method of calculating the group composition of a vacuum gas oil based on the results of determining its physical and chemical properties

The given paper proposes a method for calculating the group composition of vacuum gas which is used as catalytic cracking feedstock oil. This method describes the dependency of feedstock, density and viscosity on fractional composition. Absolute error of calculations for such indicators as the content of saturated hydrocarbons, aromatic hydrocarbons and resins does not exceed 5.0% wt. To increase adequacy of the method, it is necessary to expand the database by additional laboratory studies of samples

Complex-Orbital Order in Fe_3O_4 and Mechanism of the Verwey Transition

Electronic state and the Verwey transition in magnetite (Fe_3O_4) are studied using a spinless three-band Hubbard model for 3d electrons on the B sites with the Hartree-Fock approximation and the exact diagonalisation method. Complex-orbital, e.g., 1/sqrt(2)[|zx> + i |yz>], ordered (COO) states having noncollinear orbital moments ~ 0.4 mu_B on the B sites are obtained with the cubic lattice structure of the high-temperature phase. The COO state is a novel form of magnetic ordering within the orbital degree of freedom. It arises from the formation of Hund's second rule states of spinless pseudo-d molecular orbitals in the Fe_4 tetrahedral units of the B sites and ferromagnetic alignment of their fictitious orbital moments. A COO state with longer periodicity is obtained with pseudo-orthorhombic Pmca and Pmc2_1 structures for the low-temperature phase. The state spontaneously lowers the crystal symmetry to the monoclinic and explains experimentally observed rhombohedral cell deformation and Jahn-Teller like distortion. From these findings, we consider that at the Verwey transition temperature, the COO state remaining to be short-range order impeded by dynamical lattice distortion in high temperature is developed into that with long-range order coupled with the monoclinic lattice distortion.Comment: 16 pages, 13 figures, 6 tables, accepted for publication in J. Phys. Soc. Jp