303 research outputs found
Electronic Structure of Cu_(1-x)Ni_xRh_2S_4 and CuRh_2Se_4: Band Structure Calculations, X-ray Photoemission and Fluorescence Measurements
The electronic structure of spinel-type Cu_(1-x)Ni_xRh_2S_4 (x = 0.0, 0.1,
0.3, 0.5, 1.0) and CuRh_2Se_4 compounds has been studied by means of X-ray
photoelectron and fluorescent spectroscopy. Cu L_3, Ni L_3, S L_(2,3) and Se
M_(2,3) X-ray emission spectra (XES) were measured near thresholds at Beamline
8.0 of the Lawrence Berkeley Laboratory's Advanced Light Source. XES
measurements of the constituent atoms of these compounds, reduced to the same
binding energy scale, are found to be in excellent agreement with XPS valence
bands. The calculated XES spectra which include dipole matrix elements show
that the partial density of states reproduce experimental spectra quite well.
States near the Fermi level (E_F) have strong Rh d and S(Se) p character in all
compounds. In NiRh_2S_4 the Ni 3d states contribute strongly at E_F, whereas in
both Cu compounds the Cu 3d bands are only ~1 eV wide and centered ~2.5 eV
below E_F, leaving very little 3d character at E_F. The density of states at
the Fermi level is less in NiRh_2S_4 than in CuRh_2S_4. This difference may
contribute to the observed decrease, as a function of Ni concentration, in the
superconducting transition temperature in Cu_(1-x)Ni_xRh_2S_4. The density of
states of the ordered alloy Cu_(1/2)Ni_(1/2)Rh_2S_4 shows behavior that is more
``split-band''-like than ``rigid band''-like.Comment: 7 pages of text, 11 trailing figures, updated to fix faulty
postscript in Fig.
Origin of ferroelectricity in the multiferroic barium fluorides BaMF4
We present a first principles study of the series of multiferroic barium
fluorides with the composition BaMF4, where M is Mn, Fe, Co, or Ni. We discuss
trends in the structural, electronic, and magnetic properties, and we show that
the ferroelectricity in these systems results from the "freezing in" of a
single unstable polar phonon mode. In contrast to the case of the standard
perovskite ferroelectrics, this structural distortion is not accompanied by
charge transfer between cations and anions. Thus, the ferroelectric instability
in the multiferroic barium fluorides arises solely due to size effects and the
special geometrical constraints of the underlying crystal structure.Comment: 8 pages, 6 figures, 3 table
Surface and bulk polaritons in a linear magnetoelectric multiferroic with canted spins: Transverse Electric polarisation
Some magnetoelectric multiferroics have a canted spin structure that can be
described by a Dzyaloshinkii-Moriya coupling. We calculate properties and
features expected for surface and bulk magnon polaritons in such media with a
linear magnetoelectric interaction for the case of transverse electric
polarisation. The dielectric polarisation and magnetisation of weak
ferromagnetism are constrained to lie in the plane parallel to the surface. We
examine a geometry with the polarisation oriented in the film plane and present
numerical results for the transverse electric polarisation. Particular
attention is given to non-reciprocal surface modes, which exist in frequency
between two bulk bands, and show how these modes can be modified by external
magnetic field. Results for attenuated total reflection are presented, and
discussed in relation to nonreciprocity. Example results are calculated for the
canted antiferromagnet BaMnF4.Comment: 14 pages, 6 figure
Angular-Distribution Of Fluorescence From Photoionization-Produced He+ (N=2)
We report the first measurement of the angular distribution of the 304-Å He + ( n = 2 ) radiation following photoionization. This distribution reflects the alignment of the ion, which is related to the fraction ξ = σ ( 2 p , k d ) [ σ ( 2 p , k s ) + σ ( 2 p , k d ) ] of d component in the electron wave. The experimental angular distributions correspond to alignments of -0.62 ± 0.03 and -0.62 ± 0.02 at photon energies of 65.5 and 66.5 eV, respectively. These translate into ratios ξ = 0.25 ± 0.04 and 0.25 ± 0.03 , in good agreement with close-coupling calculations
Altered Blood Flow Response to Small Muscle Mass Exercise in Cancer Survivors Treated With Adjuvant Therapy
Citation: Didier, K. D., Ederer, A. K., Reiter, L. K., Brown, M., Hardy, R., Caldwell, J., . . . Ade, C. J. (2017). Altered Blood Flow Response to Small Muscle Mass Exercise in Cancer Survivors Treated With Adjuvant Therapy. Journal of the American Heart Association, 6(2), 9. doi:10.1161/jaha.116.004784Background-Adjuvant cancer treatments have been shown to decrease cardiac function. In addition to changes in cardiovascular risk, there are several additional functional consequences including decreases in exercise capacity and increased incidence of cancer-related fatigue. However, the effects of adjuvant cancer treatment on peripheral vascular function during exercise in cancer survivors have not been well documented. We investigated the vascular responses to exercise in cancer survivors previously treated with adjuvant cancer therapies. Methods and Results-Peripheral vascular responses were investigated in 11 cancer survivors previously treated with adjuvant cancer therapies (age 58 +/- 6 years, 34 +/- 30 months from diagnosis) and 9 healthy controls group matched for age, sex, and maximal voluntary contraction. A dynamic handgrip exercise test at 20% maximal voluntary contraction was performed with simultaneous measurements of forearm blood flow and mean arterial pressure. Forearm vascular conductance was calculated from forearm blood flow and mean arterial pressure. Left ventricular ejection time index (LVETi) was derived from the arterial pressure wave form. Forearm blood flow was attenuated in cancer therapies compared to control at 20% maximal voluntary contraction (189.8 +/- 53.8 vs 247.9 +/- 80.3 mL.min (1), respectively). Forearm vascular conductance was not different between groups at rest or during exercise. Mean arterial pressure response to exercise was attenuated in cancer therapies compared to controls (107.8 +/- 10.8 vs 119.2 +/- 16.2 mm Hg). LEVTi was lower in cancer therapies compared to controls. Conclusions-These data suggest an attenuated exercise blood flow response in cancer survivors approximate to 34 months following adjuvant cancer therapy that may be attributed to an attenuated increase in mean arterial pressure
Soft x-ray spectroscopy experiments on the near K-edge of B in MB2 (M=Mg, Al, Ta, and Nb)
Soft X-ray absorption and emission measurements are performed for the K- edge
of B in MB (M=Mg, Al, Ta and Nb). Unique feature of MgB with a high
density of B 2-state below and above the Fermi edge, which
extends to 1 eV above the edge, is confirmed. In contrast, the B 2 density
of states in AlB and TaB, both of occupied and unoccupied states,
decreased linearly towards the Fermi energy and showed a dip at the Fermi
energy. Furthermore, there is a broadening of the peaks with
-character in XES and XAS of AlB, which is due to the increase of
three dimensionality in the -band in AlB. The DOS of NbB has a
dip just below the Fermi energy. The present results indicate that the large
DOS of B-2 states near the Fermi energy are crucial for the
superconductivity of MgB.Comment: 3 pages text and 4 pages figures. accepted for publication to Phys.
Rev.
Soft-x-ray fluorescence study of the quasi-one-dimensional Heisenberg antiferromagnet tetraphenylverdazyl
Soft-x-ray fluorescence measurements have been performed on a single crystal of the organic antiferromagnet 2,4,6-triphenylverdazyl. Resonant and nonresonant C Kα and N Kα (2p → 1s transition) x-ray emission spectra (XES) were measured and compared with x-ray photoelectron valence band spectra and deMon density-functional theory calculations. It is shown that intramolecular interactions are much stronger than intermolecular ones and give the main contribution to the formation of C 2p density of states. We present evidence of a delocalization of unpaired N 2p electrons over the verdazyl ring. The excitation energy dependence of C Kα and N Kα XES observed below the C 1s and N 1s thresholds, respectively, is discussed in terms of symmetry selective resonant inelastic x-ray scattering
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