3,360 research outputs found
On the origin of the hump structure in the in-plane optical conductivity of high Tc cuprates based on a SU(2) slave-boson theory
An improved version of SU(2) slave-boson approach is applied to study the
in-plane optical conductivity of the two dimensional systems of high Tc
cuprates. We investigate the role of fluctuations of both the phase and
amplitude of order parameters on the (Drude) peak-dip-hump structure in the
in-plane conductivity as a function of hole doping concentration and
temperature. The mid-infrared(MIR) hump in the in-plane optical conductivity is
shown to originate from the antiferromagnetic spin fluctuations of short
range(the amplitude fluctuations of spin singlet pairing order parameters),
which is consistent with our previous U(1) study. However the inclusion of both
the phase and amplitude fluctuations is shown to substantially improve the
qualitative feature of the optical conductivity by showing substantially
reduced Drude peak widths for entire doping range. Both the shift of the hump
position to lower frequency and the growth of the hump peak height with
increasing hole concentration is shown to be consistent with observations.Comment: 7 pages, 6 figure
Enhanced cardiac expression of two isoforms of matrix metalloproteinase-2 in experimental diabetes mellitus.
BackgroundDiabetic cardiomyopathy (DM CMP) is defined as cardiomyocyte damage and ventricular dysfunction directly associated with diabetes independent of concomitant coronary artery disease or hypertension. Matrix metalloproteinases (MMPs), especially MMP-2, have been reported to underlie the pathogenesis of DM CMP by increasing extracellular collagen content.PurposeWe hypothesized that two discrete MMP-2 isoforms (full length MMP-2, FL-MMP-2; N-terminal truncated MMP-2, NTT-MMP-2) are induced by high glucose stimulation in vitro and in an experimental diabetic heart model.MethodsRat cardiomyoblasts (H9C2 cells) were examined to determine whether high glucose can induce the expression of the two isoforms of MMP-2. For the in vivo study, we used the streptozotocin-induced DM mouse heart model and age-matched controls. The changes of each MMP-2 isoform expression in the diabetic mice hearts were determined using quantitative real-time polymerase chain reaction (qRT-PCR). Immunohistochemical stains were conducted to identify the location and patterns of MMP-2 isoform expression. Echocardiography was performed to compare and analyze the changes in cardiac function induced by diabetes.ResultsQuantitative RT-PCR and immunofluorescence staining showed that the two MMP-2 isoforms were strongly induced by high glucose stimulation in H9C2 cells. Although no definite histologic features of diabetic cardiomyopathy were observed in diabetic mice hearts, left ventricular systolic dysfunction was determined by echocardiography. Quantitative RT-PCR and IHC staining showed this abnormal cardiac function was accompanied with the increases in the mRNA levels of the two isoforms of MMP-2 and related to intracellular localization.ConclusionTwo isoforms of MMP-2 were induced by high glucose stimulation in vitro and in a Type 1 DM mouse heart model. Further study is required to examine the role of these isoforms in DM CMP
The Bell Laboratories (13)CO Survey: Longitude-Velocity Maps
A survey is presented of the Galactic plane in the J=1-0 transition of
(13)CO. About 73,000 spectra were obtained with the 7 m telescope at Bell
Laboratories over a ten-year period. The coverage of survey is (l, b) = (-5 to
117, -1 to +1), or 244 square degrees, with a grid spacing of 3' for |b| < 0.5,
and a grid spacing of 6' for |b| > 0.5. The data presented here have been
resampled onto a 3' grid. For 0.68 km/s channels, the rms noise level of the
survey is 0.1 K on the scale. The raw data have been transformed into
FITS format, and all the reduction processes, such as correcting for emission
in the reference positions, baseline removal and interpolation were conducted
within IRAF using the FCRAO task package and additional programs. The reduced
data are presented here in the form of longitude-velocity color maps at each
latitude. These data allow identification and classification of molecular
clouds with masses in excess of ~ 1,000 solar masses throughout the first
quadrant of the Galaxy. Spiral structure is manifested by the locations of the
largest and brightest molecular clouds.Comment: 23 pages, 7 figures, ApJS submitted (out of 41 frames of Figure4,
only one is included becaue of size limit
[Fe II] and H2 filaments in the Supernova Remnant G11.2-0.3: Supernova Ejecta and Presupernova Circumstellar Wind
We present the results of near-infrared imaging and spectroscopic
observations of the young, core-collapse supernova remnant (SNR) G11.2-0.3. In
the [Fe II] 1.644 um image, we first discover long, clumpy [Fe II] filaments
within the radio shell of the SNR, together with some faint, knotty features in
the interior of the remnant. We have detected several [Fe II] lines and HI Br-G
line toward the peak position of the bright southeastern [Fe II] filament. The
derived extinction is large (Av=13 mag) and it is the brightest [Fe II]
filament detected toward SNRs to date. By analyzing two [Fe II] 1.644 um images
obtained in 2.2 yrs apart, we detect a proper motion corresponding to an
expansion rate of 0.''035 (0.''013) /yr [or 830 (310) km/s]. We also discover
two small H2 filaments. One is bright and along the SE boundary of the radio
shell, while the other is faint and just outside of its NE boundary. We have
detected H2 (2-1) S(3) line toward the former filament and derive an excitation
temperature of 2,100 K. We suggest that the H2 filaments are dense clumps in a
presupernova circumstellar wind swept up by the SNR shock while the [Fe II]
filaments are probably composed of both shocked wind material and shocked
supernova (SN) ejecta. The distribution of [Fe II] filaments may indicate that
the SN explosion in G11.2-0.3 was asymmetric as in Cassiopeia A. Our results
support the suggestion that G11.2-0.3 is a remnant of a SN IIL/b interacting
with a dense red supergiant wind.Comment: 30 pages with 10 figures, To appear in the Astrophysical Journa
Higgs Boson Sector of the Next-to-MSSM with CP Violation
We perform a comprehensive study of the Higgs sector in the framework of the
next-to-minimal supersymmetric standard model with CP-violating parameters in
the superpotential and in the soft-supersymmetry-breaking sector. Since the CP
is no longer a good symmetry, the two CP-odd and the three CP-even Higgs bosons
of the next-to-minimal supersymmetric standard model in the CP-conserving limit
will mix. We show explicitly how the mass spectrum and couplings to gauge
bosons of the various Higgs bosons change when the CP-violating phases take on
nonzero values. We include full one-loop and the logarithmically enhanced
two-loop effects employing the renormalization-group (RG) improved approach. In
addition, the LEP limits, the global minimum condition, and the positivity of
the square of the Higgs-boson mass have been imposed. We demonstrate the
effects on the Higgs-mass spectrum and the couplings to gauge bosons with and
without the RG-improved corrections. Substantial modifications to the allowed
parameter space happen because of the changes to the Higgs-boson spectrum and
their couplings with the RG-improved corrections. Finally, we calculate the
mass spectrum and couplings of the few selected scenarios and compare to the
previous results in literature where possible; in particular, we illustrate a
scenario motivated by electroweak baryogenesis.Comment: 40 pages, 49 figures; v2: typos corrected and references added; v3:
some clarification and new figures added, version published in PR
Obstructed D-Branes in Landau-Ginzburg Orbifolds
We study deformations of Landau-Ginzburg D-branes corresponding to obstructed
rational curves on Calabi-Yau threefolds. We determine D-brane moduli spaces
and D-brane superpotentials by evaluating higher products up to homotopy in the
Landau-Ginzburg orbifold category. For concreteness we work out the details for
lines on a perturbed Fermat quintic. In this case we show that our results
reproduce the local analytic structure of the Hilbert scheme of curves on the
threefold.Comment: 44 pages; v3: typos correcte
SAP HANA distributed in-memory database system: Transaction, session, and metadata management
One of the core principles of the SAP HANA database system is the comprehensive support of distributed query facility. Supporting scale-out scenarios was one of the major design principles of the system from the very beginning. Within this paper, we first give an overview of the overall functionality with respect to data allocation, metadata caching and query routing. We then dive into some level of detail for specific topics and explain features and methods not common in traditional disk-based database systems. In summary, the paper provides a comprehensive overview of distributed query processing in SAP HANA database to achieve scalability to handle large databases and heterogeneous types of workloads
Lanczos exact diagonalization study of field-induced phase transition for Ising and Heisenberg antiferromagnets
Using an exact diagonalization treatment of Ising and Heisenberg model
Hamiltonians, we study field-induced phase transition for two-dimensional
antiferromagnets. For the system of Ising antiferromagnet the predicted
field-induced phase transition is of first order, while for the system of
Heisenberg antiferromagnet it is the second-order transition. We find from the
exact diagonalization calculations that the second-order phase transition
(metamagnetism) occurs through a spin-flop process as an intermediate step.Comment: 4 pages, 4 figure
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