337 research outputs found
Low-dimensional dynamics embedded in a plane Poiseuille flow turbulence : Traveling-wave solution is a saddle point ?
The instability of a streak and its nonlinear evolution are investigated by
direct numerical simulation (DNS) for plane Poiseuille flow at Re=3000. It is
suggested that there exists a traveling-wave solution (TWS). The TWS is
localized around one of the two walls and notably resemble to the coherent
structures observed in experiments and DNS so far. The phase space structure
around this TWS is similar to a saddle point. Since the stable manifold of this
TWS is extended close to the quasi two dimensional (Q2D) energy axis, the
approaching process toward the TWS along the stable manifold is approximately
described as the instability of the streak (Q2D flow) and the succeeding
nonlinear evolution. Bursting corresponds to the escape from the TWS along the
unstable manifold. These manifolds constitute part of basin boundary of the
turbulent state.Comment: 5 pages, 6 figure
Panchromatic Imaging of a Transitional Disk: The Disk of GM Aur in Optical and FUV Scattered Light
We have imaged GM Aur with HST, detected its disk in scattered light at 1400A
and 1650A, and compared these with observations at 3300A, 5550A, 1.1 microns,
and 1.6 microns. The scattered light increases at shorter wavelengths. The
radial surface brightness profile at 3300A shows no evidence of the 24AU radius
cavity that has been previously observed in sub-mm observations. Comparison
with dust grain opacity models indicates the surface of the entire disk is
populated with sub-micron grains. We have compiled an SED from 0.1 microns to 1
mm, and used it to constrain a model of the star+disk system that includes the
sub-mm cavity using the Monte Carlo Radiative Transfer code by Barbara Whitney.
The best-fit model image indicates that the cavity should be detectable in the
F330W bandpass if the cavity has been cleared of both large and small dust
grains, but we do not detect it. The lack of an observed cavity can be
explained by the presence of sub-microns grains interior to the sub-mm cavity
wall. We suggest one explanation for this which could be due to a planet of
mass <9 Jupiter masses interior to 24 AU. A unique cylindrical structure is
detected in the FUV data from the Advanced Camera for Surveys/Solar Blind
Channel. It is aligned along the system semi-minor axis, but does not resemble
an accretion-driven jet. The structure is limb-brightened and extends 190 +/-
35 AU above the disk midplane. The inner radius of the limb-brightening is 40
+/- 10 AU, just beyond the sub-millimeter cavity wall.Comment: 40 pages, 11 figures, 4 tables, accepted to Ap
Resolving the gap and AU-scale asymmetries in pre-transitional disks of V1247 ORIONIS
adsurl: http://adsabs.harvard.edu/abs/2013prpl.conf2B051K adsnote: Provided by the SAO/NASA Astrophysics Data SystemPre-transitional disks are protoplanetary disks with a gapped disk structure, potentially indicating the presence of
young planets in these systems. In order to explore the structure of these objects and their gap-opening mechanism,
we observed the pre-transitional disk V1247 Orionis using the Very Large Telescope Interferometer, the Keck
Interferometer, Keck-II, Gemini South, and IRTF. This allows us to spatially resolve the AU-scale disk structure
from near- to mid-infrared wavelengths (1.5–13µm), tracing material at different temperatures and over a wide
range of stellocentric radii. Our observations reveal a narrow, optically thick inner-disk component (located at
0.18 AU from the star) that is separated from the optically thick outer disk (radii !46 AU), providing unambiguous
evidence for the existence of a gap in this pre-transitional disk. Surprisingly, we find that the gap region is filled
with significant amounts of optically thin material with a carbon-dominated dust mineralogy. The presence of this
optically thin gap material cannot be deduced solely from the spectral energy distribution, yet it is the dominant
contributor at mid-infrared wavelengths. Furthermore, using Keck/NIRC2 aperture masking observations in the
H, K′
, and L′ bands, we detect asymmetries in the brightness distribution on scales of ∼15–40 AU, i.e., within
the gap region. The detected asymmetries are highly significant, yet their amplitude and direction changes with
wavelength, which is not consistent with a companion interpretation but indicates an inhomogeneous distribution
of the gap material. We interpret this as strong evidence for the presence of complex density structures, possibly
reflecting the dynamical interaction of the disk material with sub-stellar mass bodies that are responsible for the
gap clearing.NASA through the Sagan Fellowship ProgramW. M. Keck FoundationAerospace Corporation’s Independent Research and Development (IR&D) programNASA AD
Myocardial Lipin 1 knockout in mice approximates cardiac effects of human LPIN1 mutations
Lipin 1 is a bifunctional protein that is a transcriptional regulator and has phosphatidic acid (PA) phosphohydrolase activity, which dephosphorylates PA to generate diacylglycerol. Human lipin 1 mutations lead to episodic rhabdomyolysis, and some affected patients exhibit cardiac abnormalities, including exercise-induced cardiac dysfunction and cardiac triglyceride accumulation. Furthermore, lipin 1 expression is deactivated in failing heart, but the effects of lipin 1 deactivation in myocardium are incompletely understood. We generated mice with cardiac-specific lipin 1 KO (cs-Lpin1-/-) to examine the intrinsic effects of lipin 1 in the myocardium. Cs-Lpin1-/- mice had normal systolic cardiac function but mild cardiac hypertrophy. Compared with littermate control mice, PA content was higher in cs-Lpin1-/- hearts, which also had an unexpected increase in diacylglycerol and triglyceride content. Cs-Lpin1-/- mice exhibited diminished cardiac cardiolipin content and impaired mitochondrial respiration rates when provided with pyruvate or succinate as metabolic substrates. After transverse aortic constriction-induced pressure overload, loss of lipin 1 did not exacerbate cardiac hypertrophy or dysfunction. However, loss of lipin 1 dampened the cardiac ionotropic response to dobutamine and exercise endurance in association with reduced protein kinase A signaling. These data suggest that loss of lipin 1 impairs cardiac functional reserve, likely due to effects on glycerolipid homeostasis, mitochondrial function, and protein kinase A signaling
Fission Fragment Isomers Populated Via \u3csup\u3e6\u3c/sup\u3eLi+\u3csup\u3e232\u3c/sup\u3eTh.
Short-lived isomers in fission fragments following bombardment of 45-MeV 6Li on 232Th were examined. Isomers in the A ~ 95,122, and 132 mass regions were observed. New isomeric decays were observed in 121In [T1/2=17(2) μs], 123In (T1/2≳100 μs), and 125Sb [T1/2=25(4) μs]. These isomers are suggested to arise from ν(h11/2⊗d3/2)7−and ν(h11/2⊗s1/2)5− neutron core excitations coupling with the valence proton
The disruption of GDP-fucose de novo biosynthesis suggests the presence of a novel fucose-containing glycoconjugate in <i>Plasmodium</i> asexual blood stages
Glycosylation is an important posttranslational protein
modification in all eukaryotes. Besides
glycosylphosphatidylinositol (GPI) anchors and N-glycosylation,
O-fucosylation has been recently reported in key sporozoite
proteins of the malaria parasite. Previous analyses showed the
presence of GDP-fucose (GDP-Fuc), the precursor for all
fucosylation reactions, in the blood stages of Plasmodium
falciparum. The GDP-Fuc de novo pathway, which requires the
action of GDP-mannose 4,6-dehydratase (GMD) and GDP-L-fucose
synthase (FS), is conserved in the parasite genome, but the
importance of fucose metabolism for the parasite is unknown. To
functionally characterize the pathway we generated a PfGMD
mutant and analyzed its phenotype. Although the labelling by the
fucose-binding Ulex europaeus agglutinin I (UEA-I) was
completely abrogated, GDP-Fuc was still detected in the mutant.
This unexpected result suggests the presence of an alternative
mechanism for maintaining GDP-Fuc in the parasite. Furthermore,
PfGMD null mutant exhibited normal growth and invasion rates,
revealing that the GDP-Fuc de novo metabolic pathway is not
essential for the development in culture of the malaria parasite
during the asexual blood stages. Nonetheless, the function of
this metabolic route and the GDP-Fuc pool that is generated
during this stage may be important for gametocytogenesis and
sporogonic development in the mosquito
Efficacy of Carboplatin Alone and in Combination with ABT888 in Intracranial Murine Models of BRCA-Mutated and BRCA-Wild-Type Triple-Negative Breast Cancer
Patients with breast cancer brain metastases have extremely limited survival and no approved systemic therapeutics. Triple negative breast cancer (TNBC) commonly metastasizes to the brain and predicts poor prognosis. TNBC frequently harbors BRCA mutations translating to platinum sensitivity potentially augmented by additional suppression of DNA repair mechanisms through poly(ADP-ribose)polymerase (PARP) inhibition. We evaluated brain penetrance and efficacy of Carboplatin +/− the PARP inhibitor ABT888, and investigated gene expression changes in murine intracranial (IC) TNBC models stratified by BRCA and molecular subtype status
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