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Dirac semimetals show nontrivial physical properties and can host exotic quantum states like Weyl semimetals and topological insulators under suitable external conditions. Here, by combining angle-resolved photoemission spectroscopy measurements (ARPES) and first-principle calculations, we demonstrate that Zintl-phase compound SmMg$_2$Bi$_2$ belongs to the close proximity to a topological Dirac semimetallic state. ARPES results show a Dirac-like band crossing at the zone-center near the Fermi level ($E_\mathrm {F}$) which is further confirmed by first-principle calculations. Theoretical studies also reveal that SmMg$_2$Bi$_2$ belongs to a $Z_2$ topological class and hosts spin-polarized states around the $E_\mathrm {F}$. Zintl's theory predicts that the valence state of Sm in this material should be Sm$^{2+}$, however we detect many Sm-4$f$ multiplet states (flat-bands) whose energy positions suggest the presence of both Sm$^{2+}$ and Sm$^{3+}$. It is also evident that these flat-bands and other dispersive states are strongly hybridized when they cross each other. Due to the presence of Sm$^{3+}$ ions, the temperature dependence of magnetic susceptibility $\chi(T)$ shows Curie-Weiss-like contribution in the low temperature region, in addition to the Van Vleck-like behaviour expected for the Sm$^{2+}$ ions. The present study will help in better understanding of the electronic structure, magnetism and transport properties of related materials., Comment: 11 pages, 7 figures

Spin-polarized electrons confined in low-dimensional structures are of high interest for spintronics applications. Here, we investigate the electronic structure of an ordered array of Bi monomer and dimer chains on the Ag(110) surface. By means of spin-resolved photoemission spectroscopy, we find Rashba-Bychkov split bands crossing the Fermi level with one-dimensional constant energy contours. These bands are up-spin polarized for positive wave vectors and down-spin polarized for negative wave vectors, at variance with the Rashba-Bychkov model that predicts a pair of states with opposite spin in each half of the surface Brillouin zone. Density functional theory shows that spin-selective hybridization with the Ag bulk bands originates this unconventional spin texture.

A quasi periodic elliptical undulator (QP-EPU105) has been recently put in operation at the Electron Spectro Microscopy beamline at NSLS-II. Commissioning results pertaining to its initial characterization are presented. The spectral and angular distributions of the light have been probed and compared with emission calculations based on the measured magnetic field. The light polarization produced in parallel and anti-parallel operation modes is also quantitatively analyzed.

Rationale & Objective Clinical practice guidelines for dietary intake in hemodialysis focus on individual nutrients. Little is known about associations of dietary patterns with survival. We evaluated the associations of dietary patterns with cardiovascular and all-cause mortality among adults treated by hemodialysis. Study Design Prospective cohort study. Setting & Participants 8,110 of 9,757 consecutive adults on hemodialysis (January 2014 to June 2017) treated in a multinational private dialysis network and with analyzable dietary data. Exposures Data-driven dietary patterns based on the GA2LEN food frequency questionnaire. Participants received a score for each identified pattern, with higher scores indicating closer resemblance of their diet to the identified pattern. Quartiles of standardized pattern scores were used as primary exposures. Outcomes Cardiovascular and all-cause mortality. Analytical Approach Principal components analysis with varimax rotation to identify common dietary patterns. Adjusted proportional hazards regression analyses with country as a random effect to estimate the associations between dietary pattern scores and mortality. Associations were expressed as adjusted HRs with 95% CIs, using the lowest quartile score as reference. Results During a median follow-up of 2.7 years (18,666 person-years), there were 2,087 deaths (958 cardiovascular). 2 dietary patterns, “fruit and vegetable” and “Western,” were identified. For the fruit and vegetable dietary pattern score, adjusted HRs, in ascending quartiles, were 0.94 (95% CI, 0.76-1.15), 0.83 (95% CI, 0.66-1.06), and 0.91 (95% CI, 0.69-1.21) for cardiovascular mortality and 0.95 (95% CI, 0.83-1.09), 0.84 (95% CI, 0.71-0.99), and 0.87 (95% CI, 0.72-1.05) for all-cause mortality. For the Western dietary pattern score, the corresponding estimates were 1.10 (95% CI, 0.90-1.35), 1.11 (95% CI, 0.87-1.41), and 1.09 (95% CI, 0.80-1.49) for cardiovascular mortality and 1.01 (95% CI, 0.88-1.16), 1.00 (95% CI, 0.85-1.18), and 1.14 (95% CI, 0.93-1.41) for all-cause mortality. Limitations Self-reported food frequency questionnaire, data-driven approach. Conclusions These findings did not confirm an association between mortality among patients receiving long-term hemodialysis and the extent to which dietary patterns were either high in fruit and vegetables or consistent with a Western diet.

Currently, there is very limited ability to measure the temperature of the brain, but a direct technique for its estimation in vivo could improve the detection of patients at risk of temperature-related brain damage, help in the diagnosis of stroke and tumour, and provide useful information on the mechanisms of thermoregulation of the brain. In this article, new calibrations in vitro of MRS thermometry using temperature-stabilised reference phantoms are reported. The phantoms comprise two concentric glass spheres: the inner sphere contains the phantom material to be measured by MRS, and the outer sphere contains a substance with a known temperature stable to within 0.2 °C. The substances were freezing organic fixed-point compounds (diphenyl ether and ethylene carbonate, freezing at 26.3 and 35.8 °C, respectively) or temperature-controlled circulating water. The phantom temperature was continuously monitored with a fluoroptic probe calibrated at the National Physical Laboratory with traceability to the International Temperature Scale 1990 (ITS-90). The MRS temperature calibration was obtained by measuring the chemical shift of water relative to N-acetylaspartate (NAA) in a single voxel as a function of temperature using a 1.5-T Philips Intera scanner. Measurements were made for several phantom materials to assess the effect of tissue composition on the water-NAA chemical shift against temperature calibration. The phantom mixtures contained 25 mm of NAA buffered to pH 6.5 or 7.5 and several ionic salts or bovine serum albumin (BSA). Spectra were acquired from 25 to 45 °C. The correlation between frequency differences and phantom temperature was very linear with small residuals. However, the linear fitting parameters varied with ionic composition and BSA concentration. The 'apparent' temperature (calibrated using the water-NAA frequency differences) decreased by approximately 1 °C for every 100 mm increase in ionic concentration and increased proportionally to the concentration of BSA.

We report the present status of a newly installed low-energy electron microscopy and photoelectron microscopy end station at beamline U5UA at the National Synchrotron Light Source. In first test experiments on sub-monolayer Au coverages deposited on Ru(0 0 0 1) we demonstrate core-level and valence band photoelectron imaging with a lateral resolution of about 65 nm at a field of view of 10 μm. In contrast to other installations for photoelectron microscopy, the new NSLS end station uses illumination under normal incidence. The implications of this geometry for different applications are discussed.

Background Dental disease is more extensive in adults with chronic kidney disease, but whether dental health and behaviors are associated with survival in the setting of hemodialysis is unknown. Study Design Prospective multinational cohort. Setting & Participants 4,205 adults treated with long-term hemodialysis, 2010 to 2012 (Oral Diseases in Hemodialysis [ORAL-D] Study). Predictors Dental health as assessed by a standardized dental examination using World Health Organization guidelines and personal oral care, including edentulousness; decayed, missing, and filled teeth index; teeth brushing and flossing; and dental health consultation. Outcomes All-cause and cardiovascular mortality at 12 months after dental assessment. Measurements Multivariable-adjusted Cox proportional hazards regression models fitted with shared frailty to account for clustering of mortality risk within countries. Results During a mean follow-up of 22.1 months, 942 deaths occurred, including 477 cardiovascular deaths. Edentulousness (adjusted HR, 1.29; 95% CI, 1.10-1.51) and decayed, missing, or filled teeth score ≥ 14 (adjusted HR, 1.70; 95% CI, 1.33-2.17) were associated with early all-cause mortality, while dental flossing, using mouthwash, brushing teeth daily, spending at least 2 minutes on oral hygiene daily, changing a toothbrush at least every 3 months, and visiting a dentist within the past 6 months (adjusted HRs of 0.52 [95% CI, 0.32-0.85], 0.79 [95% CI, 0.64-0.97], 0.76 [95% CI, 0.58-0.99], 0.84 [95% CI, 0.71-0.99], 0.79 [95% CI, 0.65-0.95], and 0.79 [95% CI, 0.65-0.96], respectively) were associated with better survival. Results for cardiovascular mortality were similar. Limitations Convenience sample of clinics. Conclusions In adults treated with hemodialysis, poorer dental health was associated with early death, whereas preventive dental health practices were associated with longer survival.

A “source-to-sam ple” w avefront propagation analysis of the E lectron S pectro-M icroscopy (E S M ) U V / soft X -ray beam line, w hich is under construction at the N ational Synchrotron L ight S ource II (N S L S -II) in the B rookhaven N ational L aboratory, has been conducted. A ll elem ents of the beam line - insertion device, m irrors, variable-line-spacing gratings and slits - are included in the sim ulations. R adiation intensity distributions at the sam ple position are displayed for representative photon energies in the U V range (20 - 100 eV ) w here diffraction effects are strong. T he finite acceptance of the refocusing m irrors is the dom inating factor lim iting the spatial resolution at the sam ple (by ~ 3 P m at 20 eV ). A bsolute estim ates of the radiation flux and energy resolution at the sam ple are also obtained from the electrom agnetic calculations. T he analysis of the propagated U V range undulator radiation at different deflection param eter values dem onstrates that w ithin the beam line angular acceptance a slightly “red-shifted” radiation provides higher flux at the sam ple and better energy resolution com pared to the on-axis resonant radiation of the fundam ental harm onic. K eyw ord s: physical optics, w avefront propagation, soft X -ray beam line

Thick Fe(1 1 0) films (>50 ML) have been epitaxially grown on W(1 1 0) and studied by spin- and angle-resolved photoemission spectroscopy utilizing linearly polarized synchrotron radiation. The photoemission spectra display two surface sensitive 3d-derived features. The first, located at Γ , consists of an exchange-split pair (Δ ex =2.3 eV ) with a sharp minority peak at about 0.25 eV below EF and a broader majority counterpart; the second, located midway along the Γ – S symmetry line of the surface Brillouin zone, is a majority peak close to EF. A comparison of the experimental results with first-principle slab calculations reveals that both features are surface resonances, with a substantial charge density distribution on both the surface and the subsurface Fe(1 1 0) layer.

The third international workshop on hard X-ray photoelectron spectroscopy (HAXPES 2009) was held at Brookhaven National Laboratory, Upton, New York, from May 20–22, 2009. This three-day workshop brought together approximately 100 scientists from 14 countries to discuss progress and future prospects for this rapidly developing field of research. The conference was sponsored by the National Synchrotron Light Source, the National Synchrotron Light Source-II Project, Brookhaven National Laboratory Condensed Matter Physics and Materials Science Department, and the National Institute of Standards and Technology.

The oxygen adsorption on the Fe(110) surface has been studied by spin- and angular-resolved photoemission and low-energy electron diffraction techniques. At very low coverage, oxygen adsorbs in a sequence of well-defined ordered structures: a c(2{times}2) followed by a c(3{times}1). For the c(2{times}2) overlayer the oxygen bands show hardly any dispersion along the [1{bar 1}0] direction of the surface Brillouin zone. A slightly larger dispersion is instead detected for the c(3{times}1) overlayer. In both cases, the two-dimensional models for the oxygen 2p-derived bands do not seem to be appropriate. The spin-resolved data suggest a considerable interaction with the Fe substrate. A relatively large exchange splitting ({Delta}{sub ex}=0.3thinspeV) is induced on the oxygen 2p bands, indicating a local magnetic moment on the oxygen sites. The considerably different line shape of the O 2p emission in the two spin channels is also an indication of strong interaction of the oxygen adatoms with the spin-dependent electronic structure of the ferromagnetic substrate. {copyright} {ital 1998} {ital The American Physical Society}

Photoelectron spectra of the ordered surface alloy c(2 × 2) CuMn/ Cu(100) show distinct valence band spectral features at higher binding energy, which are most pronounced for the optimal CuMnc(2 × 2) superstructure at half-monolayer Mn deposition. Our analysis comprising resonant photoemission, core level photoemission, inverse photoemission, first-principles local-density calculations, and configuration-interaction cluster-model calculations shows that the data represent the first observation of a valence band satellite caused by the increased electron correlation in an ultrathin metal film.

We report x-ray absorption spectra at the Cr ${\mathit{L}}_{2,3}$ and oxygen K edges from ${\mathrm{La}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{CrO}}_{3}$ for several values of x. Various spectral features observed are interpreted in terms of transitions to states with different symmetries. The results show that the doped holes are localized with primarily Cr d character, suggesting the formation of local ${\mathrm{Cr}}^{4+}$-like configurations, arising from the Mott-Hubbard insulating nature of the parent stoichiometric compound. These results are discussed in relation to the transport properties. \textcopyright{} 1996 The American Physical Society.

Currently, there is very limited ability to measure the temperature of the brain, but a direct technique for its estimation in vivo could improve the detection of patients at risk of temperature-related brain damage, help in the diagnosis of stroke and tumour, and provide useful information on the mechanisms of thermoregulation of the brain. In this article, new calibrations in vitro of MRS thermometry using temperature-stabilised reference phantoms are reported. The phantoms comprise two concentric glass spheres: the inner sphere contains the phantom material to be measured by MRS, and the outer sphere contains a substance with a known temperature stable to within 0.2 °C. The substances were freezing organic fixed-point compounds (diphenyl ether and ethylene carbonate, freezing at 26.3 and 35.8 °C, respectively) or temperature-controlled circulating water. The phantom temperature was continuously monitored with a fluoroptic probe calibrated at the National Physical Laboratory with traceability to the International Temperature Scale 1990 (ITS-90). The MRS temperature calibration was obtained by measuring the chemical shift of water relative to N-acetylaspartate (NAA) in a single voxel as a function of temperature using a 1.5-T Philips Intera scanner. Measurements were made for several phantom materials to assess the effect of tissue composition on the water-NAA chemical shift against temperature calibration. The phantom mixtures contained 25 mm of NAA buffered to pH 6.5 or 7.5 and several ionic salts or bovine serum albumin (BSA). Spectra were acquired from 25 to 45 °C. The correlation between frequency differences and phantom temperature was very linear with small residuals. However, the linear fitting parameters varied with ionic composition and BSA concentration. The 'apparent' temperature (calibrated using the water-NAA frequency differences) decreased by approximately 1 °C for every 100 mm increase in ionic concentration and increased proportionally to the concentration of BSA.

The magnetic properties of Fe-Pd multilayers are strongly affected by the high magnetic polarization of Pd. The origin of the magnetization of Pd in contact with Fe is examined. We found that a surface Pd(100) photoemission structure persists upon preparation of 1 and 2 monolayers Fe. Comparison with an ab initio calculation identifies this structure as a state distributed equally between the Fe and the adjacent Pd layer. Spin analysis of the photoelectrons shows that this state is magnetic, and the calculation reveals that it contributes to the large Pd moment at the interface of 0.32${\mathrm{\ensuremath{\mu}}}_{\mathit{B}}$.

We performed high-resolution spin- and angle-resolved photoemission spectroscopy studies of the electronic structure and the spin texture on the surface of Bi2Se3, a model TI. By tuning the photon energy, we found that the topological surface state is well separated from the bulk states in the vicinity of kz = Z plane of the bulk Brillouin zone. The spin-resolved measurements in that region indicate a very high degree of spin polarization of the surface state, ~0.75, much higher than previously reported. Our results demonstrate that the topological surface state on Bi2Se3 is highly spin polarized and that the dominant factors limiting the polarization are mainly extrinsic.

A custom pulse discriminator designed to reduce interchannel crosstalk effects in an inverse photoemission spectrograph is presented. The design and performances are reported. The circuit is based on an IC TTL voltage comparator, the sensitivity of which is extended to nanosecond input pulses by means of a simple additional input stage.

We have studied the growth of Pd on Fe(100) using LEED and Auger electron spectroscopy. We find that Pd grows on Fe(100) epitaxially and without interdiffusion up to 2 monolayers (ML) while layer by layer growth continues up to at least 5 ML. Spin-resolved photoemission spectra show that 1 ML Pd is ferromagnetically ordered in agreement with our ab initio FLAPW band structure calculation.

A spin‐polarized electron gun for electron spectroscopies is described in detail. The gun consists of an electron source based on a negative electron affinity GaAs photocathode coupled to an appropriate transport electron optics. The gun has been designed with the aid of ray‐tracing analysis and then accurately tested. It produces a transversely polarized (P0∼27%) electron beam at variable energy with a small spot size and angular spread (less than 2 mm and 5°, respectively). Such performances are attained up to sample currents as high as 10 μA for the whole beam energy range (8–50 eV). As an application we present data on spin‐dependent absorbed current spectroscopy from bcc Fe films epitaxially grown on Ag(100).

The valence electron states of a ZrFe getter having Zr2Fe as majority component (80% of the total volume) and their evolution upon oxidation at room temperature are studied with direct photoemission (hv = 21.2 and 40.8 eV) and inverse photoemission (isochromats in the range 12–21 eV). In the clean getter direct photoemission is mostly sensitive to Fe-derived states and inverse photoemission to Zr-derived states. Direct photoemission shows the modification of oxygen-p-derived states in the suboxide-oxide transition and the effect of Fe-oxygen interaction with a depletion of Fe d states near the Fermi level. Inverse photoemission shows a progressive localization of the Zr d states upon oxidation.

Photoemission spectra of pseudobinary Yb1−xMxAl2 (M = Sc, Ca) compounds derived from YbAl2 are given (hν = 40.8, 65, 181.5 and 1253.6 eV) at various stoichiometries corresponding to compressed (with Sc) and decompressed compounds (with Ca). The surface divalent Yb 4f signal depends on the chemical substitution and is stronger in the compressed compounds (2.9 times with respect to YbAl2 in the case of 80% Sc measured at 40.8 eV). Auger results are also reported. The effect is discussed in connection with the release of compression energy in the surface region.

We present inverse photoemission results in the ultraviolet (11.3–23eV) from YFe2. The photon energy dependence of k-integrated isochromat spectra gives direct access to the Fe and Y contributions to the density of empty electron states. The measurements are compared with published calculations; it is shown that the position of the mixed Fe(3d)−Y(4d) peak around 2 eV above the Fermi level is particularly critical.

The unoccupied electronic structure of an opend-shell transition metal oxide, namely Fe3O4, has been addressed by measuring ultraviolet angle-integrated inverse photoemission (IP) spectra acquired in the isochromat mode (hv=10.2-24 eV). Exploitation of photon energy dependence of symmetry-projected IP cross-sections and comparison with the O 1s X-ray absorption spectrum allow us to recognize a strong covalent admixture of Fe [3d; 4 (sp)]-and O (2p)-derived states in this compound.

We present photoemission results with uv and with x rays from a family of pseudobinary compounds obtained by partial substitution of Yb, with Ca or Sc, in the reference compound YbAl{sub 2}. The substitution with Ca gives rise to a decompression and the one with Sc a compression of the lattice. Ultraviolet photoemission shows the perturbation of the electron states due to chemical substitution; Sc introduces a {ital d} character extending up to about 3 eV below the Fermi level. The weights of the Yb{sup 3+} and Yb{sup 2+} multiplets given by x-ray photoemission are compared with the results from x-ray absorption; the two spectroscopies agree in YbAl{sub 2} while the relative weights Yb{sup 3+} versus Yb{sup 2+} from x-ray photoemission are definitely below the x-ray-absorption values in the compounds heavily substituted with Sc; this is interpreted as a photoemission final-state effect connected with the {ital d} character introduced by the substitution.

A simple and cost effective inverse photoemission spectrograph based on a spherical grating with very large optical acceptance ( f/2.8) is described. The system works in the 10–25 eV photon energy range. The dispersed photons are detected by a detector assembly based on a microchannelplate and consisting of twelve independent channels. Measurements are taken in the isochromat mode by sweeping the impinging electron energy, and the acquisition of the twelve channels is done in parallel. As an example of the apparatus performances data on polycrystalline Pt are presented.

A very compact electron gun devoted to inverse photoemission spectroscopy is described in detail. The gun has been designed with the aid of ray-tracing analysis and then accurately tested. It produces an electron beam at variable energy with a small spot size and angular spread (less than 2 mm and 5°, respectively). Such performances are attained up to currents as high as 15 μA for the whole beam energy range (8–50 eV). A BaO cathode operating at a relatively low temperature is used as the electron emitter providing a low thermal energy spread.

We present a set of angle integrated inverse photoemission data on LaPd3 taken in the u.v. region (10–25 eV) in the isochromat mode. The photon energy dependence of the spectra gives direct insight on the assignments of the spectral features. A strong solid state effect is found in transitions having as final states the La 4f and 5d-derived states; in particular the cross sections for the two channels become much more similar than in the atomic case. This effect is qualitatively discussed in terms of the modifications of the La 5d-states upon the formation of the solid.

In recent years great technological advance took place in preparation of single crystalline magnetic tunnel junctions (MTJs) with MgO(001) barriers. The theoretically predicted tunneling magnetoresistance (TMR) at room temperature of several hundred percent in Fe/MgO/Fe(001) was met by the experimental values of 180 -220%. The surface X-ray diffraction measurements on MgO/Fe(001) indicate the existence of the interface partial FeO layer which could strongly influence the performance of MTI. The spin polarized photoemission spectra in the photon energy range hv = 30 to 130 eV of up to 5 monolayers of MgO deposited on Fe(001) by electron beam evaporation. Experiments were performed at the beamline U5UE of the NSLS equipped with the retarding Mott polarimeter. Spectra are compared to ab initio electronic structure calculations of Fe(001) surface and MgO/Fe(001) interface. These results on electronic structure of the MgO/Fe(001) interface are related to the performance of the MTJs.

Investigating LaNi(1-x)M(x)O3 (M = Mn and Fe), we identify a characteristic evolution of the spectral function with increasing disorder in presence of strong interaction effects across the metal-insulator transition. We discuss these results vis-a-vis existing theories of electronic structure in simultaneous presence of disorder and interaction., Revtex, 4 pages, 3 postscript figures (To appear in Phys. Rev. Lett)

The software package jMRUI with Java-based graphical user interface enables user-friendly time-domain analysis of magnetic resonance spectroscopy (MRS) and spectroscopic imaging (MRSI) and HRMAS-NMR signals. Version 3.x has been distributed in more than 1200 groups or hospitals worldwide. The new version 4.x is a plug-in platform enabling the users to add their own algorithms. Moreover, it offers new functionalities compared to versions 3.x. The quantum-mechanical simulator based on NMR-SCOPE, the quantitation algorithm QUEST and the main MRSI functionalities are described. Quantitation results of signals obtained in vivo from a mouse and a human brain are given.

We present spin-resolved photoemission measurements from the 5p core levels of Gd and Tb metal. In contrast to the 3d transition-metal 3p spectra, the rare-earth 5p spin-resolved spectra show a detailed fine structure that cannot be explained within a one-electron model. The spin-orbit, Coulomb, and exchange interactions have to be treated on an equal footing. For the case of Gd, a remarkable agreement is obtained between experiment and theory when the spin polarization of the 5p emission is analyzed on the basis of atomic-multiplet calculations in intermediate coupling. For Tb, however, small discrepancies remain that cannot be analyzed in the absence of a more detailed magnetic characterization. The results emphasize strongly the potential of spin analysis in core-level studies. {copyright} {ital 1997} {ital The American Physical Society}