159 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
Resolving the gap and AU-scale asymmetries in the pre-transitional disk of V1247 Orionis
Pre-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 spatially resolve the AU-scale disk structure from near- to
mid-infrared wavelengths (1.5 to 13 {\mu}m), 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' band, we detect asymmetries in the
brightness distribution on scales of about 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.Comment: 16 pages, 17 Figures, accepted by Astrophysical Journa
A Tandem Mass Spectrometry Sequence Database Search Method for Identification of O-Fucosylated Proteins by Mass Spectrometry.
Thrombospondin type 1 repeats (TSRs), small adhesive protein domains with a wide range of functions, are usually modified with O-linked fucose, which may be extended to O-fucose-β1,3-glucose. Collision-induced dissociation (CID) spectra of O-fucosylated peptides cannot be sequenced by standard tandem mass spectrometry (MS/MS) sequence database search engines because O-linked glycans are highly labile in the gas phase and are effectively absent from the CID peptide fragment spectra, resulting in a large mass error. Electron transfer dissociation (ETD) preserves O-linked glycans on peptide fragments, but only a subset of tryptic peptides with low m/ z can be reliably sequenced from ETD spectra compared to CID. Accordingly, studies to date that have used MS to identify O-fucosylated TSRs have required manual interpretation of CID mass spectra even when ETD was also employed. In order to facilitate high-throughput, automatic identification of O-fucosylated peptides from CID spectra, we re-engineered the MS/MS sequence database search engine Comet and the MS data analysis suite Trans-Proteomic Pipeline to enable automated sequencing of peptides exhibiting the neutral losses characteristic of labile O-linked glycans. We used our approach to reanalyze published proteomics data from Plasmodium parasites and identified multiple glycoforms of TSR-containing proteins
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
Extreme Asymmetry in the Disk of V1247 Ori
We present the first near-infrared scattered-light detection of the
transitional disk around V1247 Ori, which was obtained using high-resolution
polarimetric differential imaging observations with Subaru/HiCIAO. Our imaging
in the H band reveals the disk morphology at separations of ~0.14"-0.86"
(54-330 au) from the central star. The polarized intensity (PI) image shows a
remarkable arc-like structure toward the southeast of the star, whereas the
fainter northwest region does not exhibit any notable features. The shape of
the arm is consistent with an arc of 0.28" 0.09" in radius (108 au from
the star), although the possibility of a spiral arm with a small pitch angle
cannot be excluded. V1247 Ori features an exceptionally large azimuthal
contrast in scattered, polarized light; the radial peak of the southeastern arc
is about three times brighter than the northwestern disk measured at the same
distance from the star. Combined with the previous indication of an
inhomogeneous density distribution in the gap at 46 au, the notable
asymmetry in the outer disk suggests the presence of unseen companions and/or
planet-forming processes ongoing in the arc.Comment: 21 pages, 5 figures, accepted for publication in PAS
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
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
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