Adjacent Fe-Vacancy Interactions as the Origin of Room Temperature Ferromagnetism in (In(1-x)Fe(x))2O3.

Dilute magnetic semiconductors (DMSs) show great promise for applications in spin-based electronics, but in most cases continue to elude explanations of their magnetic behavior. Here, we combine quantitative x-ray spectroscopy and Anderson impurity model calculations to study ferromagnetic Fe-substituted In2O3 films, and we identify a subset of Fe atoms adjacent to oxygen vacancies in the crystal lattice which are responsible for the observed room temperature ferromagnetism. Using resonant inelastic x-ray scattering, we map out the near gap electronic structure and provide further support for this conclusion. Serving as a concrete verification of recent theoretical results and indirect experimental evidence, these results solidify the role of impurity-vacancy coupling in oxide-based DMSs.

Electronic structure and spin trapping in LiMnAs and LiFeAs:Mn.

The electronic structure of insulating antiferromagnetic LiMnAs is investigated using soft x-ray spectroscopy and compared to the electronic structure of metallic LiFeAs. Our calculations support the experimentally observed insulating antiferromagnetic order in LiMnAs. The x-ray absorption and resonant inelastic x-ray scattering spectra in LiFeAs and LiMnAs are adequately explained by the electronic structure alone, although it is possible that LiMnAs has significant electronic correlations driven by Hund's J coupling. Finally, we show evidence of a possible spin trap in Li(Fe0.95Mn0.05)As.

Effect of 3d doping on the electronic structure of BaFe2As2.

The electronic structure of BaFe(2)As(2) doped with Co, Ni and Cu has been studied by a variety of experimental and theoretical methods, but a clear picture of the dopant 3d states has not yet emerged. Herein we provide experimental evidence of the distribution of Co, Ni and Cu 3d states in the valence band. We conclude that the Co and Ni 3d states provide additional free carriers to the Fermi level, while the Cu 3d states are found at the bottom of the valence band in a localized 3d(10) shell. These findings help shed light on why superconductivity can occur in BaFe(2)As(2) doped with Co and Ni but not Cu.

The electronic structure of lithium metagallate.

Herein we present a study of the electronic structure of lithium metagallate (LiGaO(2)), a material of interest in the field of optoelectronics. We use soft x-ray spectroscopy to probe the electronic structure of both the valence and conduction bands and compare our measurements to ab initio density functional theory calculations. We use several different exchange-correlation functionals, but find that no single theoretical approach used herein accurately quantifies both the band gap and the Ga 3d(10) states in LiGaO(2). We derive a band gap of 5.6 eV, and characterize electron hybridization in both the valence and conduction bands. Our study of the x-ray spectra may prove useful in analysing spectra from more complicated LiGaO(2) heterostructures.

Structural models of FeSe(x).

Two different structural models for non-stoichiometric FeSe(x) are examined and compared with soft x-ray spectroscopy findings for FeSe(x) (x = 0.85, 0.50). A structural model of tetragonal FeSe with excess interstitial Fe gives better agreement with experiment than a structural model of tetragonal FeSe with Se vacancies. This interstitial Fe increases the number of 3d states at the Fermi level. We find evidence that large non-stoichiometric ratios of Fe:Se, such as that of FeSe(0.50), yield clusters of pure Fe in the crystal structure.

Identifying valence structure in LiFeAs and NaFeAs with core-level spectroscopy.

Resonant x-ray emission spectroscopy (XES) measurements at Fe L(2,3) edges and electronic structure calculations for LiFeAs and NaFeAs are presented. Experiment and theory show that in the vicinity of the Fermi energy, the density of states is dominated by contributions from Fe 3d states. The comparison of Fe L(2,3) XES with spectra of related FeAs compounds reveals similar trends in energy and the ratio of intensities of the L(2) and L(3) peaks (I(L(2))/I(L(3)) ratio). The I(L(2))/I(L(3)) ratio for all FeAs-based superconductors is found to be closer to that of metallic Fe than that of the strongly correlated FeO. We conclude that iron-based superconductors are weakly or, at most, moderately correlated systems.

An outbreak of methicillin resistant Staphylococcus aureus on a burn unit: potential role of contaminated hydrotherapy equipment.

OBJECTIVE: To report a multi-institution outbreak caused by a single strain of methicillin-resistant Staphylococcus aureus (MRSA). OUTBREAK: Between September 19 and November 20, 1996 an index case and five secondary cases of nosocomial MRSA occurred on a 26 bed adult plastic surgery/burn unit (PSBU) at a tertiary care teaching hospital. Between November 11 and December 23, 1996, six additional cases were identified at a community hospital. One of the community hospital cases was transferred from the PSBU. All strains were identical by pulsed-field gel electrophoresis. MRSA may have contributed to skin graft breakdown in one case, and delayed wound healing in others. Patients required 2 to 226 isolation days. CONTROL MEASURES: A hand held shower and stretcher for showering in the hydrotherapy room of the PSBU were culture positive for the outbreak strain, and the presumed means of transmission. Replacement of stretcher showering with bedside sterile burn wound compresses terminated the outbreak. The PSBU was closed to new admissions and transfers out for 11 days during the investigation. Seven of 12 patients had effective decolonization therapy. CONCLUSION: Environmental contamination is a potential source of nosocomial MRSA transmission on a burn unit. Notification among institutions and community care providers of shared patients infected or colonized with an antimicrobial resistant microorganism is necessary.

Domiciliary oxygen: a survey and clinical assessment of patients in Christchurch.

A clinical review of the 50 patients with severe respiratory disease using domiciliary oxygen, was conducted in Christchurch where there had been no specified assessment of patients prior to commencement of therapy. It was found that uncontrolled growth of this expensive domiciliary service had resulted in its inappropriate and non-cost effective use. Thirty-seven (74 percent) of the patients die not require oxygen according to scientific indications, including 22 (44 percent) who had a resting arterial oxygen tension (PaO2) greater than 70 mmHg (9.31 kPa). This situation is believed to be widespread and reflects a lack of informed medical supervision. It is recommended that prior to commencement of therapy, patients be assessed according to specific domiciliary oxygen criteria with investigations including arterial blood gas tensions.

Immunoperoxidase localization of keratin in human neoplasms: a preliminary survey.

The distribution of intracellular keratin was studied in a variety of human tumors using a previously described immunoperoxidase technique employing antikeratin antibodies. Squamous cell carcinomas, transitional cell tumors, and mesotheliomas exhibited strong reactivity with antikeratin antibodies. Mammary adenocarcinomas were either negative or weakly positive. In the lung, an organ which can give rise to several morphologically distinct forms of carcinoma, only the squamous cell type stained strongly for keratin; undifferentiated lung carcinomas were negative, and adenocarcinomas were either negative or weakly positive. Colonic, renal, and prostatic adenocarcinomas were negative. Sarcomas, lymphomas, and neural tumors were uniformly negative. The analysis of intracellular keratin by the immunoperoxidase technique appears helpful in establishing the epithelial nature of primary or metastatic poorly differentiated neoplasms.

alpha-Naphthyl acetate esterase activity--a cytochemical marker for T lymphocytees. Correlation with immunologic studies of normal tissues, lymphocytic leukemias, non-Hodgkin's lymphomas, Hodgkin's disease, and other lymphoproliferative disorders.

Cytochemical identification of T lymphocytes on the basis of alpha-naphthyl acetate esterase (NAE) activity was compared with immunologic markers for cell suspensions and/or cryostat sections of 113 specimens. Nonneoplastic tissues (peripheral blood, lymph nodes, spleens, tonsils, thymus, and pleural fluid) and specimens from various lymphoproliferative disorders, including acute and chronic lymphocytic leukemia, lymphosarcoma cell leukemia, hairy cell leukemia, non-Hodgkin's lymphomas of B-and T-cell types, and Hodgkin's disease, were evaluated. T (E-rosetting) cells demonstrated several patterns of NAE reactivity: 1) a strong globular reaction product, the most specific pattern for T-cell identification, 2) granular cytoplasmic staining, or 3) no reactivity. B lymphocytes revealed a granular pattern of NAE staining, were devoid of enzyme, or, in rare instances, exhibited strong NAE activity. Percentages of lymphoid cells with strong (globular) NAE activity closely paralleled T-cell (E-rosette) values in the majority of cases, with the best correlations observed for peripheral blood studies. However, discordant results were noted for some neoplastic and nonneoplastic tissues, including cases of T-cell lymphoma or leukemia. Markedly discrepant results were noted for thymic lymphocytes, most of which revealed E-rosette formation and weak or absent NAE activity. Lymph nodes involved by Hodgkin's disease demonstrated a heterogeneous pattern of staining in E-rosetting cells and in Reed-Sternberg variants. Cryostat section studies of reactive lymph nodes and nodular lymphomas demonstrated strong NAE staining in lymphoid cells of T-cell (interfollicular, internodular) areas, with little or no positivity in follicles or nodules (B-cell areas). NAE staining patterns further suggested that T cells comprise part of the follicular cuff and possibly represent a minor population of some neoplastic nodules. Although NAE determinations do not represent a consistently reliable alternative to immunologic methods for T-cell identification, this easily applicable cytochemical marker is complementary to other techniques in assessing neoplastic or nonneoplastic tissues, particularly cryostat sections. (Am J Pathol 97:17--42, 1979).