663 research outputs found
Doping-Dependent Raman Resonance in the Model High-Temperature Superconductor HgBa2CuO4+d
We study the model high-temperature superconductor HgBa2CuO4+d with
electronic Raman scattering and optical ellipsometry over a wide doping range.
The resonant Raman condition which enhances the scattering cross section of
"two-magnon" excitations is found to change strongly with doping, and it
corresponds to a rearrangement of inter-band optical transitions in the 1-3 eV
range seen by ellipsometry. This unexpected change of the resonance condition
allows us to reconcile the apparent discrepancy between Raman and x-ray
detection of magnetic fluctuations in superconducting cuprates. Intriguingly,
the strongest variation occurs across the doping level where the antinodal
superconducting gap reaches its maximum.Comment: 4 pages, 4 figures, contact authors for Supplemental Materia
Large single crystal growth of BaFe1.87Co0.13As2 using a nucleation pole
Co-doped iron arsenic single crystal of BaFe1.87Co0.13As2 with dimension up
to 20 x 10 x 2 mm3 were grown by a nucleation pole: an alumina stick served as
nucleation center during growth. The high quality of crystalline was
illustrated by the measurements of neutron rocking curve and X-ray diffraction
pattern. A very sharp superconducting transition temperature Tc~25 K was
revealed by both resistivity and susceptibility measurements. A nearly 100%
shielding fraction and bulk nature of the superconductivity for the single
crystal were confirmed using magnetic susceptibility data.Comment: 4 pages, 5 figure
Retrospective analysis of protein kinase C-beta (PKC-β) expression in lymphoid malignancies and its association with survival in diffuse large B-cell lymphomas
BACKGROUND: Both mechanistic features and recent correlative findings suggest a potential role for protein kinase C-beta (PKC-β) in tumor pathogenesis, particularly in B-cell malignancies. To evaluate the role of this gene in lymphoid malignancies, we analyzed global gene expression data to quantify PKC-β expression across diagnostic groups and, when possible, determined correlations between PKC-β expression and survival. RESULTS: Our analysis showed that the level of PKC-β expression was highest in chronic lymphocytic leukemia and follicular lymphoma. Within diffuse large-B cell lymphoma (DLBCL), PKC-β expression was significantly higher in activated B-cell- like subtype than germinal center B-cell- like subtype (P < 0.0001). Elevated PKC-β appeared to be associated with worse survival in both of these subtypes. When analyzed within clinically defined risk groups established by the International Prognostic Index (IPI), PKC-β expression was lowest in patients with low IPI scores (0–1). Within intermediate- and high-risk IPI groups, elevated PKC-β expression was associated with worse survival, suggesting that PKC-β may expand the prognostic value of the IPI. Results of global gene expression analyses of DLBCL samples corroborate previous observations that anti-apoptosis, cell proliferation, and B-cell proliferation signaling pathways are functionally related to PKC-β. CONCLUSION: We present a first detailed pharmacogenomics report comparing PKC-β mRNA expression across different lymphoid malignancies and evaluating it as an outcome predictor. Our findings suggest that DLBCL patients with elevated PKC-β have a worse prognosis, indicating that further evaluation of PKC-β as a chemotherapeutic target for lymphoid malignancies is warranted. REVIEWERS: This article was reviewed by Dr. Pierre Pontarotti, Dr. Kateryna Makova, and Dr. Matthew Coleman (nominated by Dr. Sandrine Dudoit)
Deflection of coronal rays by remote CMEs: shock wave or magnetic pressure?
We analyze five events of the interaction of coronal mass ejections (CMEs)
with the remote coronal rays located up to 90^\circ away from the CME as
observed by the SOHO/LASCO C2 coronagraph. Using sequences of SOHO/LASCO C2
images, we estimate the kink propagation in the coronal rays during their
interaction with the corresponding CMEs ranging from 180 to 920 km/s within the
interval of radial distances form 3 R. to 6 R. . We conclude that all studied
events do not correspond to the expected pattern of shock wave propagation in
the corona. Coronal ray deflection can be interpreted as the influence of the
magnetic field of a moving flux rope related to a CME. The motion of a
large-scale flux rope away from the Sun creates changes in the structure of
surrounding field lines, which are similar to the kink propagation along
coronal rays. The retardation of the potential should be taken into account
since the flux rope moves at high speed comparable with the Alfven speed.Comment: Accepted for Publication in Solar Physic
Strong pairing at iron orbitals in hole-doped BaFeAs
Among numerous hypotheses, recently proposed to explain superconductivity in
iron-based superconductors [1-9], many consider Fermi surface (FS) nesting [2,
4, 8, 10] and dimensionality [4, 9] as important contributors. Precise
determination of the electronic spectrum and its modification by
superconductivity, crucial for further theoretical advance, were hindered by a
rich structure of the FS [11-17]. Here, using the angle-resolved photoemission
spectroscopy (ARPES) with resolution of all three components of electron
momentum and electronic states symmetry, we disentangle the electronic
structure of hole-doped BaFe2As2, and show that nesting and dimensionality of
FS sheets have no immediate relation to the superconducting pairing.
Alternatively a clear correlation between the orbital character of the
electronic states and their propensity to superconductivity is observed: the
magnitude of the superconducting gap maximizes at 10.5 meV exclusively for iron
3dxz;yz orbitals, while for others drops to 3.5 meV. Presented results reveal
similarities of electronic response to superconducting and magneto-structural
transitions [18, 19], implying that relation between these two phases is more
intimate than just competition for FS, and demonstrate importance of orbital
physics in iron superconductors.Comment: read m
Optimization of venous return tubing diameter for cardiopulmonary bypass
Objective: To determine the optimal venous tubing diameter for adult cardiopulmonary bypass (CPB) to improve gravity drainage and to reduce priming volume. Methods: (A) Maximum bovine blood flow rates by gravity drainage were assessed in vitro for four different tubing diameters (1/2, 3/8, 5/16,1/4 inch) with three different lengths and various pre- and afterloads. Based on the results of (A) and multiple regression analyses, we developed equations to predict tubing sizes as a function of target flows. (C) The equations obtained in (B) were validated by ex vivo bovine experiments. (D) The clinically required maximal flows were determined retrospectively by reviewing 119 perfusion records at Zurich University. (E) Based on our model (B), the clinical patient and hardware requirements, the optimal venous tubing diameter was calculated. (F) The optimized venous tubing was evaluated in a prospective clinical trial involving 312 patients in Hangzhou. Results: For a mean body surface area of 1.83±0.2 m2, the maximal perfusion flow rate (D) achieved with 1/2-inch (=1.27 cm2) venous tubing was 4.62±0.57 l/min (range: 2.50-6.24 l/min). Our validated model (B,C) predicted 1.0 cm2 as optimal cross-sectional area for the venous line. New tubing packs developed accordingly were used routinely thereafter. The maximal flow rate was 4.93±0.58 l/min (range: 3.9-7.0) in patients with a mean body surface area of 1.62±0.21 m2. Conclusion: The new venous tubing with 1.0-cm2 cross-sectional area improves the drainage in the vast majority of adult patients undergoing CPB and reduces the priming volume (−27 ml/m). Reduced hemodilution can prevent homologous transfusions if a predefined transfusion trigger level is not reache
Josephson Plasma in RuSr2GdCu2O8
Josephson plasma in RuSrGdCuO,
RuSrGdCuO (x = 0.3), and
RuSrEuCeCuO (x = 0.5) compounds is
investigated by the sphere resonance method. The Josephson plasma is observed
in a low-frequency region (around 8.5 cm at T ) for
ferromagnetic RuSrGdCuO, while it increases to 35 cm
for non-ferromagnetic RuSrGdCuO (x = 0.3), which
represents a large reduction in the Josephson coupling at ferromagnetic
RuO block layers. The temperature dependence of the plasma does not shift
to zero frequency ({\it i.e.} = 0) at low temperatures, indicating that
there is no transition from the 0-phase to the -phase in these compounds.
The temperature dependence and the oscillator strength of the peak are
different from those of other non-magnetic cuprates, and the origins of these
anomalies are discussed.Comment: to appear in Phys. Rev.B Rapid Com
Conformations of closed DNA
We examine the conformations of a model for a short segment of closed DNA.
The molecule is represented as a cylindrically symmetric elastic rod with a
constraint corresponding to a specification of the linking number. We obtain
analytic expressions leading to the spatial configuration of a family of
solutions representing distortions that interpolate between the circular form
of DNA and a figure-eight form that represents the onset of interwinding. We
are also able to generate knotted loops. We suggest ways to use our approach to
produce other configurations relevant to studies of DNA structure. The
stability of the distorted configurations is assessed, along with the effects
of fluctuations on the free energy of the various configurations.Comment: 39 pages in REVTEX with 14 eps figures. Submitted to Phys. Rev. E.
This manuscript updates, expands and revises, to a considerable extent, a
previously posted manuscript, entitled "Conformations of Circular DNA," which
appeared as cond-mat/970104
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