840 research outputs found
Stripe structure, spectral feature and soliton gap in high Tc cuprates
We show that the lightly doped La_{2-x}Sr_{x}CuO_{4} can be described in
terms of a stripe magnetic structure or soliton picture. The internal
relationship between the recent neutron observation of the diagonal (x=0.05) to
vertical (x >= 0.06) stripe transition, which was predicted, and the
concomitant metal-insulator transition is clarified by this solitonic physics.
The phase diagram with the unidentified transition lines between
antiferromagnetic to stripe phases, the doping dependence of the modulation
period, the origin of the mid-infrared optical absorption are investigated
comparatively with other single layer systems: La_{2-x}Sr_{x}NiO_{4} and
(La,Nd)_{2-x}Sr_{x}CuO_{4}. The novel type of quasi-particles and holes is
fully responsible for metallic conduction and ultimately superconductivity.Comment: 4 pages RevTex, 5 figure
AN OBLIGATORY ROLE OF MIND BOMB-1 IN NOTCH SIGNALING OF MAMMALIAN DEVELOPMENT
Background. The Notch signaling pathway is an evolutionarily conserved intercellular signaling module essential for cell fate specification that requires endocytosis of Notch ligands. Structurally distinct E3 ubiquitin ligases, Neuralized (Neur) and Mind bomb (Mib), cooperatively regulate the endocytosis of Notch ligands in Drosophila. However, the respective roles of the mammalian E3 ubiquitin ligases, Neur1, Neur2, Mib1, and Mib2, in mammalian development are poorly understood. Methodology/Principal Findings. Through extensive use of mammalian genetics, here we show that Neur1 and Neur2 double mutants and Mib2 2/2 mice were viable and grossly normal. In contrast, conditional inactivation of Mib1 in various tissues revealed the representative Notch phenotypes: defects of arterial specification as deltalike4 mutants, abnormal cerebellum and skin development as jagged1 conditional mutants, and syndactylism as jagged2 mutants. Conclusions/Significance. Our data provide the first evidence that Mib1 is essential for Jagged as well as Deltalike ligand-mediated Notch signaling in mammalian development, while Neur1, Neur2, and Mib2 are dispensable.open117978Nsciescopu
Searching for Exoplanets Using a Microresonator Astrocomb
Detection of weak radial velocity shifts of host stars induced by orbiting
planets is an important technique for discovering and characterizing planets
beyond our solar system. Optical frequency combs enable calibration of stellar
radial velocity shifts at levels required for detection of Earth analogs. A new
chip-based device, the Kerr soliton microcomb, has properties ideal for
ubiquitous application outside the lab and even in future space-borne
instruments. Moreover, microcomb spectra are ideally suited for astronomical
spectrograph calibration and eliminate filtering steps required by conventional
mode-locked-laser frequency combs. Here, for the calibration of astronomical
spectrographs, we demonstrate an atomic/molecular line-referenced,
near-infrared soliton microcomb. Efforts to search for the known exoplanet HD
187123b were conducted at the Keck-II telescope as a first in-the-field
demonstration of microcombs
Cluster Spin Glass Distribution Functions in LaSrCuO
Signatures of the cluster spin glass have been found in a variety of
experiments, with an effective onset temperature that is frequency
dependent. We reanalyze the experimental results and find that they are
characterized by a distribution of activation energies, with a nonzero glass
transition temperature . While the distribution of activation
energies is the same, the distribution of weights depends on the process.
Remarkably, the weights are essentially doping independent.Comment: 5 pages, 5 ps figure
Rethinking the red wolf disease: does Protein S suppress systemic lupus erythematosus clinical activity?
In systemic lupus erythematosus, the forces responsible for disease initiation and self-perpetuation in these clinically heterogeneous populations remain poorly understood. Recent studies of the TAM (Tyro3, Axl and MerTK) family of receptor tyrosine kinases may lead to a better understanding of the fundamental control system responsible for the clearance of apoptotic cells and the regulation of inflammation. In a recent report, serum levels of the TAM ligand, Protein S, was found to correlate with certain disease manifestations and with C3 and C4 levels. Protein S levels could provide a quantitative clinical biomarker but it remains to be determined whether this factor directly affects disease activity
Similarity of slow stripe fluctations between Sr-doped cuprates and oxygen-doped nickelates
Stripe fluctuations in La2NiO4.17 have been studied by 139La NMR using the
field and temperature dependence of the linewidth and relaxation rates. In the
formation process of the stripes the NMR line intensity is maximal below 230K,
starts to diminish around 140K, disappears around 50K and recovers at 4K. These
results are shown to be consistent with, but completely complementary to
neutron measurements, and to be generic for oxygen doped nickelates and
underdoped cuprates.Comment: 4 pages including 4 figure
High angular resolution N-band observation of the silicate carbon star IRAS08002-3803 with the VLTI/MIDI instrument
We present the results of N-band spectro-interferometric observations of the
silicate carbon star IRAS08002-3803 with the MID-infrared Interferometric
instrument (MIDI) at the Very Large Telescope Interferometer (VLTI) of the
European Southern Observatory (ESO). The observations were carried out using
two unit telescopes (UT2 and UT3) with projected baseline lengths ranging from
39 to 47 m. Our observations of IRAS08002-3803 have spatially resolved the
dusty environment of a silicate carbon star for the first time and revealed an
unexpected wavelength dependence of the angular size in the N band: the
uniform-disk diameter is found to be constant and ~36 mas (72 Rstar) between 8
and 10 micron, while it steeply increases longward of 10 micron to reach ~53
mas (106 Rstar) at 13 micron. Model calculations with our Monte Carlo radiative
transfer code show that neither spherical shell models nor axisymmetric disk
models consisting of silicate grains alone can simultaneously explain the
observed wavelength dependence of the visibility and the spectral energy
distribution (SED). We propose that the circumstellar environment of
IRAS08002-3803 may consist of two grain species coexisting in the disk:
silicate and a second grain species, for which we consider amorphous carbon,
large silicate grains, and metallic iron grains. Comparison of the observed
visibilities and SED with our models shows that such disk models can fairly --
though not entirely satisfactorily -- reproduce the observed SED and N-band
visibilities. Our MIDI observations and the radiative transfer calculations
lend support to the picture where oxygen-rich material around IRAS08002-3803 is
stored in a circumbinary disk surrounding the carbon-rich primary star and its
putative low-luminosity companion.Comment: 15 pages, 8 figures, accepted for publication in A&
Adaptive transaction scheduling for transactional memory systems
Transactional memory systems are expected to enable parallel
programming at lower programming complexity, while delivering improved performance over traditional lock-based systems. Nonetheless, there are certain situations where transactional memory systems could actually perform worse. Transactional memory systems can outperform locks only
when the executing workloads contain sufficient parallelism. When the workload lacks inherent parallelism, launching excessive transactions can adversely degrade performance. These situations will actually become dominant in future workloads when large-scale transactions are frequently executed.
In this thesis, we propose a new paradigm called adaptive transaction scheduling to address this issue. Based on the parallelism feedback from applications, our adaptive transaction scheduler dynamically dispatches and controls the number of concurrently executing transactions. In our case study, we show that our low-cost mechanism not only guarantees that hardware transactional memory systems perform no worse than a single global lock, but also significantly improves performance for both hardware and software transactional memory systems.M.S.Committee Chair: Lee, Hsien-Hsin; Committee Member: Blough, Douglas; Committee Member: Yalamanchili, Sudhaka
Improved Culture-Based Isolation of Differentiating Endothelial Progenitor Cells from Mouse Bone Marrow Mononuclear Cells
Numerous endothelial progenitor cell (EPC)-related investigations have been performed in mouse experiments. However, defined characteristics of mouse cultured EPC have not been examined. We focused on fast versus slow adherent cell population in bone marrow mononuclear cells (BMMNCs) in culture and examined their characteristics. After 24 h-culture of BMMNCs, attached (AT) cells and floating (FL) cells were further cultured in endothelial differentiation medium separately. Immunological and molecular analyses exhibited more endothelial-like and less monocyte/macrophage-like characteristics in FL cells compared with AT cells. FL cells formed thick/stable tube and hypoxia or shear stress overload further enhanced these endothelial-like features with increased angiogenic cytokine/growth factor mRNA expressions. Finally, FL cells exhibited therapeutic potential in a mouse myocardial infarction model showing the specific local recruitment to ischemic border zone and tissue preservation. These findings suggest that slow adherent (FL) but not fast attached (AT) BMMNCs in culture are EPC-rich population in mouse
African-Caribbean cancer consortium for the study of viral, genetic and environmental cancer risk factors
This is a short summary of a meeting of the "African-Caribbean Cancer Consortium", jointly organized by the University of Pittsburgh, Department of Epidemiology and the University of Pittsburgh Cancer Institute, held in Montego Bay, Jamaica as a satellite meeting at the Caribbean Health Research Council, 52nd Annual Council and Scientific meeting on May 4, 2007
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