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We investigated the electronic structure of the vacancy-ordered $4d$-transition-metal monoxide $\mathrm{NbO}\phantom{\rule{0.28em}{0ex}}({\mathrm{Nb}}_{3}{\mathrm{O}}_{3})$ using angle-integrated soft- and hard-x-ray photoelectron spectroscopies as well as ultraviolet angle-resolved photoelectron spectroscopy. We found that density-functional-based band-structure calculations can describe the spectral features accurately provided that self-interaction effects are taken into account. In the angle-resolved spectra we were able to identify the so-called `vacancy' band that characterizes the ordering of the vacancies. This together with the band-structure results indicate the important role of the very large inter-Nb-$4d$ hybridization for the formation of the ordered vacancies and the high thermal stability of the ordered structure of niobium monoxide.

Polar catastrophe at the interface of oxide materials with strongly correlated electrons has triggered a flurry of new research activities. The expectations are that the design of such advanced interfaces will become a powerful route to engineer devices with novel functionalities. Here, we investigate the initial stages of growth and the electronic structure of the spintronic Fe3O4/MgO(001) interface. Using soft x-ray absorption spectroscopy, we have discovered that the so-called A-sites are ompletely missing in the first Fe3O4 monolayer. This discovery allows us to develop an unexpected but elegant growth principle in which, during deposition, the Fe atoms are constantly on the move to solve the divergent electrostatic potential problem, thereby ensuring epitaxy and stoichiometry at the same time. This growth principle provides a new perspective for the design of interfaces.

Two distinct ferromagnetic phases are present in LaMn0.5Co0.5O3 for which the spin-only magnetic moment calculated from the high temperature dc susceptibility is found to be unusually high. Such a high moment can only be accounted for by assigning the valence state of the cations to Mn2+-Co4+. This is unrealistic as the earlier report based on X-ray absorption spectroscopy (XAS) has suggested the valence state to be mainly Mn4+-Co2+ with traces of Co3+. Also from our studies using XAS, it is found that the valence state is mainly Mn4+-Co2+. In addition, no notable difference is observed in the minor Co3+ present in both phases. Our results based on X-ray magnetic circular dichroism studies (XMCD) reveal the presence of ``distinct'' high orbital moment associated with Co2+ for both phases. Thus it is found that the distinctness of the orbital moment also plays a vital role in determining the magnetic moment and T-c of both phases of LaMn0.5Co0.5O3. By considering the orbital moment obtained from XMCD, the anomaly in the paramagnetic susceptibility is resolved and thus we are able to assign the valence state to Mn4+-Co2+ configuration. The difference in the magnitude of orbital moment in both phases is believed to be due to the crystal field effects.

We have studied the far-infrared (far-IR) charge dynamics of an equilibrated pure oxygen doped La2CuO4+0.0315 under slow-cooled and fast-cooled conditions. The superconducting transition temperature (Tc) for the slow-cooled and that for the fast-cooled processes were respectively found to be close to the two intrinsic Tc's: One at 30 K and the other at 15 K. Direct comparison with our previous results and other far-IR and Raman studies on single crystalline La2-xSrxCuO4, we conclude that the topology of the pristine electronic phases that are responsible for the two intrinsic Tc's is holes arranged into two-dimensional (2D) square lattices., Submitted to PRB

The yield of secondary electrons emitted from an epitaxial three monolayer (3 ML) NiO(1 0 0)/Ag(1 0 0) film excited by soft X-ray linearly polarized synchrotron radiation at the Ni L 2,3 absorption threshold has been measured for different values of the thickness of a MgO(1 0 0) capping layer. Compared with the as grown 3 ML NiO(1 0 0)/Ag(1 0 0) film, we observe a significant enhancement by about a factor 1.2 of the secondary electron emission for the capped 8 ML MgO(1 0 0)/3 ML NiO(1 0 0)/Ag(1 0 0) sample. A further substantial yield enhancement by a factor 1.6 with respect to the uncapped NiO sample is observed after deposition of an additional 8 ML MgO(1 0 0) film, for a total capping layer thickness of 16 ML. The observed secondary electron yield enhancement is discussed in terms of modified electronic structure, surface work function changes, and characteristic electron propagation lengths.

The initiation and termination steps of the anionic polymerization of P=C bonds have been modeled. The initiation step was investigated through the stoichiometric reaction of MesP=CPh2 (1) with RLi (R = Me or n-Bu). In each case, the addition was highly regioselective with the formal attack of R– at phosphorus to give the carbanion Li[Mes(R)P–CPh2] (3a, R = Me; 3b, R = n-Bu). To simulate the termination step in the anionic polymerization of 1, carbanions 3a and 3b were quenched in situ with various electrophiles. Through these reactions, several new tertiary phosphines have been prepared, namely, Mes(Me)P–CPh2H (4a), Mes(n-Bu)P–CPh2H (4b), Mes(Me)P–CPh2Me (6a), Mes(Me)P–CPh2–P(NEt2)2 (7a), Mes(Me)P–CPh2–SiMe2H (8a), and Mes(Me)P–CPh2–SiMe3 (9a). In addition, compounds 4a, 7a, 8a, and 9a were characterized by X-ray crystallography. Most of the metrical parameters are typical of tertiary phosphines; however, the P–CPh2H bonds were elongated in all cases reflecting the considerable steric bulk surrounding this bond. Unexpectedly, an unusually large 31P–31P coupling constant (2JPP > 200 Hz) was observed for 7a both in solution and the solid state. This observation may be rationalized by a through space P···P interaction. This rationale is further supported by the short P···P distance [P(1)—P(2) = 2.966(1) Å; cf. Σ rvdw = 3.7 Å] and a small P–C–P bond angle for 7a [P(1)–C(11)–P(1) = 99.17(9)°].Key words: phosphaalkenes, phosphorus polymers, phosphines, anionic polymerization.

The oxidation behavior of an Fe48Cr15C15Mo14B6Er2 bulk metallic glass (Fe-BMG) was studied over the temperature range of 600–725 � C in dry air. The oxidation kinetics of the glassy alloy followed a two-stage parabolic rate law at T � 650� C, while the single-stage linear rate was observed at higher temperatures (T � 675 � C). The oxidation rates of the Fe-BMG at T � 625 � C were much lower than those of the commercial 304 stainless steel (304 SS), revealing the excellent oxidation resistance of the amorphous alloy. A continuous, thin layer of chromium oxide (Cr2O3) containing some iron was formed at T � 650 � C, while typical hump iron oxides intermixed with minor amounts of Cr2O3 and MoO2 were observed at T � 675 � C. In addition, a substrate phase transformation from the amorphous structure to Fe-Cr and FeCrMo crystalline phases was detected after the oxidation. Very likely, the formation of the non-protective Fe3O4 and MoO2 breaks the scale integrity and allows the rapid cation/anion transportation, resulting in the fast linear-kinetics behavior of the Fe-BMG at T � 675 � C.

This study measures X-ray absorption spectra of crystalline (c)-Si–C–N thin film at the C and Si K-edge using the sample drain current mode, and at the N K-edge using the fluorescent mode. A resonance peak resembling the C 1s core exciton in CVD-diamond/Si is observed, and a broad feature occurring in the energy range between ∼290 and 300 eV can be assigned to the antibonding C 2p–Si 3sp hybridized states and the C 2p–N 2sp hybridized states as well. Analysis of the N K-edge near edge absorption spectra reveals a similar feature in c-Si–C–N and a-Si3N4, suggesting that nitrogen atoms generally have similar local environment in these two materials. Moreover, results obtained from Si K-edge absorption spectra for c-Si–C–N demonstrate a proportional combination of local Si–N and Si–C bonds, associated with the local tetrahedral C–Si–N3 as well as the long-range ordered atomic structure around Si atoms.

Physical review / B 85, 235106 (2012). doi:10.1103/PhysRevB.85.235106, Published by APS, College Park, Md.

A type of GaAs-based ferromagnetic semiconductor, (Ga, Cr)As, was successfully prepared by low-temperature molecular-beam epitaxy. The (Ga, Cr)As thin film shows a flat surface up to the Cr content x=0.18. However, when Cr content x exceeded 0.20, the roughness of the film became larger. The ferromagnetic ordering of the semiconductor sample with the Cr content of x=0.11 was observed. The electronic structures of (Ga, Cr)As were characterized by x-ray absorption spectroscopy (XAS). The XAS spectra show different line shapes in different Cr content.

Zinc-blende CrAs/GaAs multilayers were grown by molecular beam epitaxy. It was certified that each CrAs layer maintains an epitaxial relationship with the zinc-blende GaAs structure judging from the reflection high-energy electron diffraction observation. The film contains thicker zinc- blende CrAs layers in total than the CrAs thin film directly grown on the GaAs substrate which has the critical thickness of 3 nm. It was clarified that the optimum thicknesses of CrAs and GaAs to keep a good epitaxial relationship are 2 ML and 2 ML, respectively. The electronic structure of the multilayer is thought to be close to that of the (Ga, Cr)As thin film which has 50% of Cr content judging from x-ray absorption spectroscopy measurements.

Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ∼16.4 hr. Starting in 2010 August the period changed from 16.6 hr to near 19 hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO2-driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production. Fil: Meech, K. J.. Institute for Astronomy; Estados Unidos Fil: A’Hearn, M. F.. University of Maryland; Estados Unidos Fil: Adams, J. A.. Cornell University; Estados Unidos Fil: Bacci, P.. Centro Astronomico di Libbiano; Italia Fil: Bai, J.. Chinese Academy of Sciences; China Fil: Barrera, L.. Universidad Metropolitana de Ciencias de la Educacion; Chile Fil: Battelino, M.. Swedish Space Corporation; Suecia Fil: Bauer, J. M.. Jet Propulsion Laboratory; Estados Unidos Fil: Becklin, E.. Stratospheric Observatory for Infrared Astronomy; Estados Unidos Fil: Bhatt, B.. Indian Institute of Astrophysics; India Fil: Biver, N.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia Fil: Bockelee Morvan, D.. Centre National de la Recherche Scientifique. Observatoire de Paris; Francia Fil: Bodewits, D.. University of Maryland; Estados Unidos Fil: Bohnhardt, H.. Gobierno de la Republica Federal de Alemania. Max Planck Institut Fur Astrophysik; Alemania Fil: Boissier, J.. Inst. di Radioastronomia; Italia Fil: Bonev, B. P.. Catholic University of America; Estados Unidos Fil: Borghini, W.. Osservatorio Astronomico Naturalistico di Casasco; Italia Fil: Brucato, J. R.. Osservatorio Astrofisico di Arcetri; Italia Fil: Bryssinck, E.. Brixiis Observatory; Bélgica Fil: Buie. M. W.. Southwest Research Institute; Estados Unidos Fil: Canovas, H.. Utrecht University; Países Bajos Fil: Castellano, D.. Unione Astrofili Italiani; Italia Fil: Charnley, S. B.. National Aeronautics And Space Administration; Estados Unidos Fil: Chen, W. P.. National Taiwan Normal University; Corea del Sur Fil: Chiang, P.. Korea Astronomy and Space Science Institute; Corea del Sur Fil: Choi, Y. J.. Korea Astronomy and Space Science Institute; Corea del Sur Fil: Christian, D. J.. California State University; Estados Unidos Fil: Chuang, Y. L.. National Taiwan Normal University; Corea del Sur Fil: Cochran, A. L.. University of Texas; Estados Unidos Fil: Melita, Mario Daniel. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina

Soft x-ray absorption experiments on the transition-metal ${L}_{2,3}$ edge of multiferroic ${\text{MnWO}}_{4}$ and antiferromagnetic ${\text{CoWO}}_{4}$ are presented. The observed linear polarization dependence, analyzed by full-multiplet calculations, is used to determine the ground-state wave function of the magnetic ${\text{Mn}}^{2+}$ and ${\text{Co}}^{2+}$ ions. The impact of the local structure and the spin-orbit coupling on the orbital moment is discussed in terms of the single-ion anisotropy. It is shown that the orbital moment in ${\text{CoWO}}_{4}$ is responsible for the collinear antiferromagnetism, while the small size of spin-orbit coupling effects make spiral magnetic order in ${\text{MnWO}}_{4}$ possible, enabling the material to be multiferroic.

We report on the local electronic structure of Fe impurities in MgO thin films. Using soft x-ray absorption spectroscopy, we verified that the Fe impurities are all in the $2+$ valence state. The fine details in the line shape of the $\text{Fe}\text{ }{L}_{2,3}$ edges provide direct evidence for the presence of a dynamical Jahn-Teller distortion. We are able to determine the magnitude of the effective ${D}_{4h}$ crystal field energies. We also observed a strong temperature dependence in the spectra which we can attribute to the thermal population of low-lying excited states that are present due to the spin-orbit coupling in the $\text{Fe}\text{ }3d$. Using this ${\text{Fe}}^{2+}$ impurity system as an example, we show that an accurate measurement of the orbital moment in ${\text{Fe}}_{3}{\text{O}}_{4}$ will provide a direct estimate for the effective local low-symmetry crystal fields on the ${\text{Fe}}^{2+}$ sites, important for the theoretical modeling of the formation of orbital ordering.

Linear-polarized soft-x-ray absorption (XAS) and inelastic neutron scattering (INS) experiments have been performed on $\text{Ce}M{\text{In}}_{5}$ with $M=\text{Rh}$, Ir, and Co to determine the crystal-field scheme and characteristic Kondo temperatures ${T}^{\ensuremath{\ast}}$ for the hybridization between $4f$ and conduction electrons. The ground-state wave functions are determined from the polarization-dependent soft-XAS data at the cerium ${M}_{4,5}$ edge and the crystal-field splittings from INS. The characteristic temperature ${T}^{\ensuremath{\ast}}$ has been determined from the line widths of the neutron scattering data. We find that the quasielastic linewidths of the superconducting compounds ${\text{CeCoIn}}_{5}$ and ${\text{CeIrIn}}_{5}$ are comparable with the low-energy crystal-field splitting.

We have succeeded in preparing high-quality Gd-doped single-crystalline EuO films. Using Eu-distillation-assisted molecular beam epitaxy and a systematic variation in the Gd and oxygen deposition rates, we have been able to observe sustained layer-by-layer epitaxial growth on yttria-stabilized cubic zirconia (001). The presence of Gd helps to stabilize the layer-by-layer growth mode. We used soft x-ray absorption spectroscopy at the Eu and Gd M4,5 edges to confirm the absence of Eu3+ contaminants and to determine the actual Gd concentration. The distillation process ensures the absence of oxygen vacancies in the films. From magnetization measurements we found the Curie temperature to increase smoothly as a function of doping from 70 K up to a maximum of 125 K. A threshold behavior was not observed for concentrations as low as 0.2%., 8 pages, 9 figures

We present a combined study of the electronic structure of the superconducting skutterudite derivative SrPt4Ge12 by means of x-ray photoelectron spectroscopy and full-potential band structure calculations including an analysis of the chemical bonding. We establish that the states at the Fermi level originate predominantly from the Ge 4p electrons and that the Pt 5d shell is effectively full. We find excellent agreement between the measured and the calculated valence-band spectra, thereby validating that band structure calculations in combination with photoelectron spectroscopy can provide a solid basis for the modeling of superconductivity in the compound series MPt4Ge12 M=Sr,Ba,La,Pr.

We have tested the concept of image charge screening as a new approach to restore magnetic ordering temperatures and superexchange interactions in correlated oxide ultrathin films. Using a three-monolayer NiO(100) film grown on Ag(100) and an identically thin film on MgO(100) as model systems, we observed that the N\'eel temperature of the NiO film on the highly polarizable metal substrate is 390 K while that of the film on the poorly polarizable insulator substrate is below 40 K. This demonstrates that screening by highly polarizable media may point to a practical way toward designing strongly correlated oxide nanostructures with greatly improved magnetic properties.

Using $\mathrm{Co}\mathrm{\text{\ensuremath{-}}}{L}_{2,3}$ and $\mathrm{O}\mathrm{\text{\ensuremath{-}}}K$ x-ray absorption spectroscopy, we reveal that the charge ordering in ${\mathrm{La}}_{1.5}{\mathrm{Sr}}_{0.5}{\mathrm{CoO}}_{4}$ involves high spin ($S=3/2$) ${\mathrm{Co}}^{2+}$ and low spin ($S=0$) ${\mathrm{Co}}^{3+}$ ions. This provides evidence for the spin-blockade phenomenon as a source for the extremely insulating nature of the ${\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CoO}}_{4}$ series. The associated ${e}_{g}^{2}$ and ${e}_{g}^{0}$ orbital occupation accounts for the large contrast in the Co-O bond lengths and, in turn, the high charge ordering temperature. Yet, the low magnetic ordering temperature is naturally explained by the presence of the nonmagnetic ($S=0$) ${\mathrm{Co}}^{3+}$ ions. From the identification of the bands we infer that ${\mathrm{La}}_{1.5}{\mathrm{Sr}}_{0.5}{\mathrm{CoO}}_{4}$ is a narrow band material.

We have succeeded in growing epitaxial and highly stoichiometric films of EuO on yttria-stabilized cubic zirconia (YSZ) (001). The use of the Eu-distillation process during the molecular beam epitaxy assisted growth enables the consistent achievement of stoichiometry. We have also succeeded in growing the films in a layer-by-layer fashion by fine tuning the Eu vs. oxygen deposition rates. The initial stages of growth involve the limited supply of oxygen from the YSZ substrate, but the EuO stoichiometry can still be well maintained. The films grown were sufficiently smooth so that the capping with a thin layer of aluminum was leak tight and enabled ex situ experiments free from trivalent Eu species. The findings were used to obtain recipes for better epitaxial growth of EuO on MgO (001)., 10 pages, 15 figures

This work investigates the charge transfer and A1 (Ga) p-Ni d hybridization effects in the intermetallic Ni3Al (Ni3Ga) alloy using the Ni L3~- and K-edge and Al (Ga) K x-ray absorption near edge structure (XANES) measurements. We find that the intensity of white-line features at the Ni L3~-edge in the Ni3Al (Ni3Ga) alloy decreased in comparison with that of pure Ni, which can be attributed to the enhancement of Ni 3d states filling and the depletion of the density of Ni 3d unoccupied states in the Ni3A1 (Ni3Ga) alloy. Two clear features are also observed in the Ni3Al (Ni3Ga) XANES spectrum at the Al (Ga) K-edge, which can be assigned to the Al (Ga) unoccupied 3p (4p) states and their hybridized states with the Ni 3d/4sp states above the Fermi level in Ni3Al (Ni3Ga). The threshold at Al K-edge XANES for Ni3Al clearly shifts towards higher photon energies relative to that of pure Al, indicating that Al loses charges upon forming Ni3AI. On the other hand, the Ni K-edge shifts towards lower photon energies in Ni3Al (Ni3Ga) relative to that of pure Ni, which is consistent with the results of the Al K-edge XANES spectrum and is indicative of a charge transfer from Al to Ni sites. Our data support that no significant net charge flow occurs on and off sites in Ni3AI 0Nli3Ga ).

We have studied the local electronic structure of $\mathrm{La}{\mathrm{Mn}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{O}}_{3}$ using soft-x-ray absorption spectroscopy at the $\mathrm{Co}\text{\ensuremath{-}}{L}_{3,2}$ and $\mathrm{Mn}\text{\ensuremath{-}}{L}_{3,2}$ edges. We found a high-spin ${\mathrm{Co}}^{2+}\text{\ensuremath{-}}{\mathrm{Mn}}^{4+}$ valence state for samples with the optimal Curie temperature. We discovered that samples with lower Curie temperatures contain low-spin nonmagnetic ${\mathrm{Co}}^{3+}$ ions. Using soft-x-ray magnetic circular dichroism, we established that the ${\mathrm{Co}}^{2+}$ and ${\mathrm{Mn}}^{4+}$ ions are ferromagnetically aligned. We also revealed that the ${\mathrm{Co}}^{2+}$ ions have a large orbital moment: ${m}_{\mathrm{orb}}∕{m}_{\text{spin}}\ensuremath{\approx}0.47$. Together with model calculations, this suggests the presence of a large magnetocrystalline anisotropy in the material and predicts a nontrivial temperature dependence for the magnetic susceptibility.

We infer that soft-x-ray absorption spectroscopy is a versatile method for the determination of the crystal-field ground state symmetry of rare earth heavy fermion systems, complementing neutron scattering. Using realistic and universal parameters, we provide a theoretical mapping between the polarization dependence of Ce ${M}_{4,5}$ spectra and the charge distribution of the Ce $4f$ states. The experimental resolution can be orders of magnitude larger than the $4f$ crystal-field splitting itself. To demonstrate the experimental feasibility of the method, we investigated ${\mathrm{CePd}}_{2}{\mathrm{Si}}_{2}$, thereby settling an existing disagreement about its crystal-field ground state.

We have investigated the valence, spin, and orbital state of the Co ions in the one-dimensional cobaltate Ca3Co2O6 using x-ray absorption and x-ray magnetic circular dichroism at the Co-L2,3 edges. The Co ions at both the octahedral Cooct and trigonal Cotrig sites are found to be in a 3+ state. From the analysis of the dichroism we established a low-spin state for the Cooct and a high-spin state with an anomalously large orbital moment of 1.7B at the Co trig ions. This large orbital moment along the c-axis chain and the unusually large magnetocrystalline anisotropy can be traced back to the double occupancy of the d2 orbital in trigonal crystal field.

We report on the growth and characterization of ferromagnetic Gd-doped EuO thin films. We prepared samples with Gd concentrations up to 11% by means of molecular beam epitaxy under distillation conditions, which allows a very precise control of the doping concentration and oxygen stoichiometry. Using soft x-ray magnetic circular dichroism at the Eu and Gd M4,5 edges, we found that the Curie temperature ranged from 69 K for pure stoichiometric EuO to about 170 K for the film with the optimal Gd doping of around 4%. We also show that the Gd magnetic moment couples ferromagnetically to that of Eu., Comment: 4 pages, 4 figures

We found direct experimental evidence for an orbital switching in the V $3d$ states across the metal-insulator transition in ${\mathrm{VO}}_{2}$. We have used soft-x-ray absorption spectroscopy at the V ${L}_{2,3}$ edges as a sensitive local probe and have determined quantitatively the orbital polarizations. These results strongly suggest that, in going from the metallic to the insulating state, the orbital occupation changes in a manner that charge fluctuations and effective bandwidths are reduced, that the system becomes more one dimensional and more susceptible to a Peierls-like transition, and that the required massive orbital switching can only be made if the system is close to a Mott insulating regime.

We have observed that CoO films grown on different substrates show dramatic differences in their magnetic properties. Using polarization dependent x-ray absorption spectroscopy at the Co L-2,L-3 edges, we revealed that the magnitude and orientation of the magnetic moments strongly depend on the strain in the films induced by the substrate. We presented a quantitative model to explain how strain together with the spin-orbit interaction determine the 3d orbital occupation, the magnetic anisotropy, as well as the spin and orbital contributions to the magnetic moments. Control over the sign and direction of the strain may, therefore, open new opportunities for applications in the field of exchange bias in multilayered magnetic films.

Utilizing a sum rule in a spin-resolved photoelectron spectroscopic experiment with circularly polarized light, we show that the orbital moment in ${\mathrm{L}\mathrm{a}\mathrm{T}\mathrm{i}\mathrm{O}}_{3}$ is strongly reduced from its ionic value, both below and above the N\'eel temperature. Using Ti ${L}_{2,3}$ x-ray absorption spectroscopy as a local probe, we found that the crystal-field splitting in the ${t}_{2g}$ subshell is about 0.12--0.30 eV. This large splitting does not facilitate the formation of an orbital liquid.

Using soft-x-ray absorption spectroscopy at the Co ${L}_{2,3}$ and O $K$ edges, we demonstrate that the ${\mathrm{Co}}^{3+}$ ions with the ${\mathrm{CoO}}_{5}$ pyramidal coordination in the layered ${\mathrm{Sr}}_{2}{\mathrm{CoO}}_{3}\mathrm{Cl}$ compound are unambiguously in the high spin state. Our result questions the reliability of the spin state assignments made so far for the recently synthesized layered cobalt perovskites and calls for a reexamination of the modeling for the complex and fascinating properties of these new materials.

We have succeeded in growing epitaxial films of rocksalt VOx on MgO(001) substrates. The oxygen content as a function of oxygen flux was determined using O-18(2)-Rutherford backscattering spectrometry and the vanadium valence using x-ray-absorption spectroscopy. The upper and lower stoichiometry limits found are similar to those known for bulk material (0.8

We have detected strong dichroism in the Ni ${L}_{2,3}$ x-ray absorption spectra of a monolayer NiO film. The dichroic signal appears to be very similar to the magnetic linear dichroism observed for thicker antiferromagnetic NiO films. Detailed analysis reveals, however, that the dichroism is caused by crystal-field effects in the monolayer film, which is a nontrivial effect because the high spin Ni ${3d}^{8}$ ground state is not split by low-symmetry crystal fields. We present a practical method for identifying the independent magnetic and crystal-field contributions to the linear dichroic signal in spectra of NiO films with arbitrary thicknesses and lattice strains. Our findings are also relevant for ${3d}^{5}$ and ${3d}^{3}$ systems such as ${\mathrm{LaFeO}}_{3},$ ${\mathrm{Fe}}_{2}{\mathrm{O}}_{3},$ VO, ${\mathrm{LaCrO}}_{3},$ ${\mathrm{Cr}}_{2}{\mathrm{O}}_{3},$ and ${\mathrm{Mn}}^{4+}$ thin films.

We report an x-ray absorption spectroscopic (XAS) study on thin films of ${\mathrm{La}}_{0.7}{\mathrm{Ce}}_{0.3}{\mathrm{MnO}}_{3}.$ The measurements clearly show that the cerium is in the Ce(IV) valence state, and that the manganese is present in a mixture of ${\mathrm{Mn}}^{2+}$ and ${\mathrm{Mn}}^{3+}$ valence states. These data demonstrate that ${\mathrm{La}}_{0.7}{\mathrm{Ce}}_{0.3}{\mathrm{MnO}}_{3}$ is an electron-doped colossal magnetoresistive manganite, a finding that may open up opportunities for device applications as well as for further research on the colossal magnetoresistance phenomenon in these materials.

We investigated ferromagnetism of a newly discovered ferromagnetic semiconductor Co-doped anatase ${\mathrm{T}\mathrm{i}\mathrm{O}}_{2}$ thin film, using the magnetic circular dichroism (MCD) at the Co ${L}_{2,3}$ absorption edges. The magnetic moment was observed to be $\ensuremath{\sim}0.1{\ensuremath{\mu}}_{B}/\mathrm{C}\mathrm{o}$ in the measurements, but the MCD spectral line shape is nearly identical to that of Co metal, showing that the ferromagnetism is induced by a small amount of clustered Co. With thermal treatments at $\ensuremath{\sim}400\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, the MCD signal increases, and the moment reaches up to $\ensuremath{\sim}1.55{\ensuremath{\mu}}_{B}/\mathrm{C}\mathrm{o}$, which is $\ensuremath{\sim}90%$ of the moment in Co metal. In the latter case, the cluster size was observed to be 20--60 nm.

Although cyclosporine (CsA) has been widely used in renal transplantation for more than 10 years, no large series of renal transplant patients has been studied in southern Taiwan. The purpose of this retrospective cohort study was to investigate the risk factors for graft survival in renal transplant recipients.From August 1987 to January 1998, 101 primary cadaveric renal transplantations were performed. The minimum follow-up period was 1 year. CsA and prednisolone were initially used as immunosuppressive agents in all patients. Use of lower doses of CsA to reduce CsA trough level (50-99 ng/mL) in hepatitis B surface antigen (HBsAg)-positive recipients was attempted at 6 months after transplantation.Graft actuarial survival rates at 1, 5, and 10 years posttransplantation were 89%, 75%, and 57%, respectively. Acute rejection and increased recipient age were found to be significant risk factors (p0.05) affecting graft survival, with hazard ratios of 5.20 and 1.74, respectively, by multivariate analysis using a Cox proportional hazards model. Hepatitis B and/or hepatitis C infection had no influence on graft survival.In this series of cadaveric renal allograft patients, the risk factors affecting allograft survival were acute rejection and recipient age.

We have performed Cr and Co K-edge x-ray-absorption measurements to investigate the dependence of local electronic and atomic structures on the Cr-layer thickness in epitaxial Co (40A)/Ct (t~) (t~ = 2, 3, 5, 7, and 9A) multilayers. The Cr K x-ray absorption near edge structure (XANES) spectra of Co/Cr multilayers indicate an abrupt transition of the Cr layer from a bcc structure to a hcp structure when the thickness of the Cr layer is decreased down to -5A or three atomic layers. The structural transition and bond-length distortion in Cr and Co layers observed in the extended x-ray absorption fine structure (EXAFS) measurements are consistent with the XANES results.

X-ray absorption near edges structure (XANES) spectra of the Diluted Magnetic Semiconductors (DMS) system Zn 1-x M x S (M=Mn, Co) have been measured at the Mn and Co L 3,2 -edge using sample current mode. Analysis of the M L 3,2 -edge XANES spectra for Zn 1-x M x S revealed the presence of a white line feature in each series, whose intensity increased linearly with concentration x. The white line feature is assigned to M 2p 3/2 and 2p 1/2 photoelectron excitations to nonbonding 3d(e) states and to the relatively broadened band of M 3d(t 2 ) - S 3p hybridized antibonding states. The rate of increase of L 3,2 white line intensity with is associated with the difference in the degree of p-d hybridization of states between M 3d and S 3p.

author, Room-temperature thermoelectric power S^290 as a function of hole concentration per planer Cu atom (P_pl) has been studied in a chain-free double-layer Y_1−_xCa_xBa_2Cu_3O_6. S^290(P_pl) of Y_1−_xCa_xBa_2Cu_3O_6 (P_pl=x/2) behaves identically to that of single-layer La_2−_xSr_xCuO_4 (P_pl=x). In order to show the validity of the present scale of S^290(P_pl), we demonstrate the phase diagram for bilayer Yba_2Cu_3O_y system and Bi_2Sr_2CaCu_2O_y system and discuss.

A cohort of 8436 men in Taiwan was recruited with personal interview and blood sample collection between 1984 and 1986. During the 5-year follow-up period, 50 incident cases of hepatocellular carcinoma (HCC) were identified. Retinol levels were measured for 35 HCC patients whose serum samples were available and 140 matched controls randomly selected from cohort members without HCC. Lower vegetable intake was significantly associated with an increased risk of HCC after adjustment for other HCC risk factors (P = 0.006). The effect of low vegetable intake on HCC risk was limited to hepatitis B virus chronic carriers and cigarette smokers. As compared with subjects who had a weekly vegetable consumption frequency of six or more meals, the multivariate-adjusted relative risk of HCC for subjects who had a frequency of less than six meals was 4.7 (95% confidence interval, 2.0-11.1; P = 0.0004) among chronic hepatitis B virus carriers and 3.8 (95% confidence interval, 1.7-8.5; P = 0.001) among cigarette smokers. There was an inverse dose-response relationship between the prediagnostic serum retinol level and the development of HCC (trend test, P = 0.003). The odds ratio of HCC for men with a retinol level in the lowest tertile was 9.0 (95% confidence interval, 2.1-39.1) compared with those with a level in the highest tertile. The relation remained after multivariate adjustment for cigarette smoking, habitual alcohol drinking, and either the seropositivity of hepatitis B virus surface antigen and/or anti-hepatitis C virus antibody or the past history of liver diseases through conditional logistic regression analysis. The association was more striking for men 55 years or younger and for those who smoked 10 or more cigarettes/day. There was a significant synergistic effect of hepatitis B virus surface antigen carrier status and low serum retinol level on the development of HCC. These data suggest a potential role of retinol in the chemoprevention of HCC.

Choriocarcinoma of the kidney, either primary or metastatic, is rarely reported in the literature. We encountered a male patient with choriocarcinoma of the right kidney. The patient initially presented with fever, gross hematuria and flank pain. He had initially been unsuccessfully treated for bilateral renal stones for four months before an accurate diagnosis was made. The disease was verified only after a resection of the right kidney and meticulous examination of microscopic sections of the tumor. Further immunohistochemical study strongly supported the diagnosis of choriocarcinoma. The tumor responded briefly to Cisplatinum, Vinblastine and Bleomycin (PVB) treatment. The patient died of brain metastasis and respiratory failure four months after starting systemic chemotherapy.

After the introduction of methotrexate, vinblastine, adriamycin and cisplatin combination (M-VAC) chemotherapy for transitional cell carcinoma (TCC) of the urothelium, the reported response and survival rates improved when compared with the previous regimens. From July 1989 to March 1991, 43 consecutive cases of invasive or metastatic TCC that had received at least one course of M-VAC treatment were collected by a computer-assisted search and analyzed. The overall response rate, including complete response (CR) and partial response (PR), was 44% (CR, 16%; PR, 28%). Tumors originating from the renal pelvis or bladder responded better than those from the ureter (kidney, 57%; bladder, 42%; and ureter 30%). Lymph node, soft tissue, lung metastases and local recurrent tumors had a greater chance of response than bone or liver metastases. Although patients from the blackfoot disease endemic area seemed to respond better than those from the nonendemic area, there was no statistically significant survival benefit. The duration of follow-up ranged from nine to 38 months. The length of survival of nonresponders ranged from one month to 19 months (median, eight months; mean, seven months). Ten of the 19 responders relapsed, and the others were still responding. Three patients (7%) survived two years, disease-free. Although the response rate improved, the chance of long-term survival was still unsatisfactory in our study.

Hemodynamic and respiratory parameters were continuously monitored in 45 septic shock patients, 15 of whom developed adult respiratory distress syndrome (ARDS). Low oxygenation index (OI = PaO2/FIO2), pulmonary artery hypertension (high mean pulmonary artery pressure, MPAP) and elevated pulmonary vascular resistance (PVR) were observed in all ARDS, as well as in non-ARDS septic patients, as a baseline. These same pulmonary factors were compared between those who survived and those who died during the first few days (early fatalities) in both the ARDS group (5 patients) and the non-ARDS group (8 patients). The results showed that the early fatalities in the ARDS group had a significantly lower (p less than 0.001) OI than the survivors, as well as a lower MPAP (p less than 0.01). In the non-ARDS group, the MPAP of the early fatalities was significantly lower (p less than 0.01) than that of survivors, but their OI was not significantly lower. PVR, when compared between groups (ARDS versus non-ARDS) or between subgroups within each group, was elevated concurrently with the elevation of MPAP. It is concluded that patients with septic shock and ARDS who show a severely depressed OI and a modestly elevated MPAP and PVR during the first few days can be predicted to have a poor outcome.

Using soft x-ray absorption spectroscopy and magnetic circular dichroism at the Co-L(2,3) edge, we reveal that the spin state transition in LaCoO3 can be well described by a low-spin ground state and a triply degenerate high-spin first excited state. From the temperature dependence of the spectral line shapes, we find that LaCoO3 at finite temperatures is an inhomogeneous mixed-spin state system. It is crucial that the magnetic circular dichroism signal in the paramagnetic state carries a large orbital momentum. This directly shows that the currently accepted low- or intermediate-spin picture is at variance. Parameters derived from these spectroscopies fully explain existing magnetic susceptibility, electron spin resonance, and inelastic neutron data.

The electronic structure and magnetic properties of Al-doped Fe3O4 films at various Al concentrations were investigated by Al and OK-edge x-ray absorption near-edge structure (XANES) and FeL3,2-edge magnetic circular dichroism (MCD) measurements. The OK-edge XANES spectra reveal that the intensity of O2p–Fe3d hybridized states decreases linearly as the Al concentration increases, suggesting that nonmagnetic Al substitution reduces couplings of the O2p with Fe3d orbitals. The FeL3-edge MCD spectra show that the intensities of MCD features decrease as the Al concentration increases, which suggests that Al substitution reduces the magnetic moments of Fe ions. The FeL3,2 XANES spectra suggest the absence of mixed valence states in agreement with previous x-ray resonance scattering measurements.