1,496 research outputs found
Biomimetic bluff body drag reduction by self-adaptive porous flaps
The performances of an original passive control system based on a biomimetic
approach are assessed by investigating the flow over a bluff-body. This control
device consists in a couple of flaps made from the combination of a rigid
plastic skeleton coated with a porous fabric mimicking the shaft and the vane
of the bird's feathers, respectively. The sides of a square cylinder have been
fitted with this system so as to enable the flaps to freely rotate around their
leading edge. This feature allows the movable flaps to self-adapt to the flow
conditions. Comparing both the uncontrolled and the controlled flow, a
significant drag reduction (up to 22%) has been obtained over a broad range of
Reynolds number. The investigation of the mean flow reveals a noticeable
modification of the flow topology at large scale in the vicinity of the
controlled cylinder accounting for the increase of the pressure base in
comparison with the natural flow. Meanwhile, the study of the relative motion
of both flaps points out that their dynamics is sensitive to the Reynolds
number. Furthermore, the comparative study of the flow dynamics at large scale
suggest a lock-in coupling of the flap motion and the vortex shedding.Comment: 19 pages, 17 figures, submitted to Comptes-Rendus de l' Acad\'emie
des Sciences (M\'ecanique
Luces en una crisis global
El segundo semestre de 2008 fue especialmente difĂcil, en donde destacaron diversos puntos que se recogen en este nĂșmero de AnĂĄlisis Plural, como: los secuestros y el âya bastaâ; los efectos de la crisis en MĂ©xico; el narcotrĂĄfico, terrorismo y corrupciĂłn; la âinacabadaâ reforma energĂ©tica; el âavionazoâ de Mouriño; la crisis en el Partido de la RevoluciĂłn DemocrĂĄtica; el estallido bursĂĄtil estadounidense, de resonancia mundial, y los problemas energĂ©ticos agudizados por la globalizaciĂłn
The histone chaperone Vps75 forms multiple oligomeric assemblies capable of mediating exchange between histone H3âH4 tetramers and Asf1âH3âH4 complexes
Wellcome Trust [094090, 097945, 099149]; Medical Research Council [G1100021]. Funding for open access charge: Wellcome Trust.Vps75 is a histone chaperone that has been historically characterized as homodimer by X-ray crystallography. In this study, we present a crystal structure containing two related tetrameric forms of Vps75 within the crystal lattice. We show Vps75 associates with histones in multiple oligomers. In the presence of equimolar H3-H4 and Vps75, the major species is a reconfigured Vps75 tetramer bound to a histone H3-H4 tetramer. However, in the presence of excess histones, a Vps75 dimer bound to a histone H3-H4 tetramer predominates. We show the Vps75-H3-H4 interaction is compatible with the histone chaperone Asf1 and deduce a structural model of the Vps75-Asf1-H3-H4 (VAH) co-chaperone complex using the Pulsed Electron-electron Double Resonance (PELDOR) technique and cross-linking MS/MS distance restraints. The model provides a molecular basis for the involvement of both Vps75 and Asf1 in Rtt109 catalysed histone H3 K9 acetylation. In the absence of Asf1 this model can be used to generate a complex consisting of a reconfigured Vps75 tetramer bound to a H3-H4 tetramer. This provides a structural explanation for many of the complexes detected biochemically and illustrates the ability of Vps75 to interact with dimeric or tetrameric H3-H4 using the same interaction surface.Publisher PDFPeer reviewe
Stronger security notions for decentralized traceable attribute-based signatures and more efficient constructions
We revisit the notion of Decentralized Traceable Attribute-Based Signatures (DTABS) introduced by El Kaafarani et al. (CT-RSA 2014) and improve the state-of-the-art in three dimensions: Firstly, we provide a new stronger security model which circumvents some shortcomings in existing models. Our model minimizes the trust placed in attribute authorities and hence provides, among other things, a stronger definition for non-frameability. In addition, our model captures the notion of tracing soundness which is important for many applications of the primitive. Secondly, we provide a generic construction that is secure w.r.t. our strong security model and show two example instantiations in the standard model which are more efficient than existing constructions (secure under weaker security definitions). Finally, we dispense with the need for the expensive zero-knowledge proofs required for proving tracing correctness by the tracing authority. As a result, tracing a signature in our constructions is significantly more efficient than existing constructions, both in terms of the size of the tracing proof and the computational cost required to generate and verify it. For instance, verifying tracing correctness in our constructions requires only 4 pairings compared to 34 pairings in the most efficient existing construction
Depletion of Kinesin 5B Affects Lysosomal Distribution and Stability and Induces Peri-Nuclear Accumulation of Autophagosomes in Cancer Cells
Background: Enhanced lysosomal trafficking is associated with metastatic cancer. In an attempt to discover cancer relevant
lysosomal motor proteins, we compared the lysosomal proteomes from parental MCF-7 breast cancer cells with those from
highly invasive MCF-7 cells that express an active form of the ErbB2 (DN-ErbB2).
Methodology/Principal Findings: Mass spectrometry analysis identified kinesin heavy chain protein KIF5B as the only
microtubule motor associated with the lysosomes in MCF-7 cells, and ectopic DN-ErbB2 enhanced its lysosomal association.
KIF5B associated with lysosomes also in HeLa cervix carcinoma cells as analyzed by subcellular fractionation. The depletion
of KIF5B triggered peripheral aggregations of lysosomes followed by lysosomal destabilization, and cell death in HeLa cells.
Lysosomal exocytosis in response to plasma membrane damage as well as fluid phase endocytosis functioned, however,
normally in these cells. Both HeLa and MCF-7 cells appeared to express similar levels of the KIF5B isoform but the death
phenotype was weaker in KIF5B-depleted MCF-7 cells. Surprisingly, KIF5B depletion inhibited the rapamycin-induced
accumulation of autophagosomes in MCF-7 cells. In KIF5B-depleted cells the autophagosomes formed and accumulated in
the close proximity to the Golgi apparatus, whereas in the control cells they appeared uniformly distributed in the
cytoplasm.
Conclusions/Significance: Our data identify KIF5B as a cancer relevant lysosomal motor protein with additional functions in
autophagosome formatio
Effects of Aliskiren on Stroke in Rats Expressing Human Renin and Angiotensinogen Genes
OBJECTIVE: Pre-treatment with angiotensin receptor blockers is known to improve neurological outcome after stroke. This study investigated for the first time, whether the renin inhibitor aliskiren has similar neuroprotective effects. METHODS: Since aliskiren specifically blocks human renin, double transgenic rats expressing human renin and angiotensinogen genes were used. To achieve a systolic blood pressure of 150 or 130 mmHg animals were treated with aliskiren (7.5 or 12.5 mg/kg*d) or candesartan (1.5 or 10 mg/kg*d) via osmotic minipump starting five days before middle cerebral artery occlusion with reperfusion. Infarct size was determined by magnetic resonance imaging. mRNA of inflammatory marker genes was studied in different brain regions. RESULTS: The mortality of 33.3% (7 of 21 animals) in the vehicle group was reduced to below 10% by treatment with candesartan or aliskiren (p<0.05). Aliskiren-treated animals had a better neurological outcome 7 days post-ischemia, compared to candesartan (Garcia scale: 9.9±0.7 vs. 7.3±0.7; p<0.05). The reduction of infarct size in the aliskiren group did not reach statistical significance compared to candesartan and vehicle (24 h post-ischemia: 314±81 vs. 377±70 and 403±70 mm(3) respectively). Only aliskiren was able to significantly reduce stroke-induced gene expression of CXC chemokine ligand 1, interleukin-6 and tumor necrosis factor-alpha in the ischemic core. CONCLUSIONS: Head-to-head comparison suggests that treatment with aliskiren before and during cerebral ischemia is at least as effective as candesartan in double transgenic rats. The improved neurological outcome in the aliskiren group was blood pressure independent. Whether this effect is due to primary anti-inflammatory mechanisms has to be investigated further
Identification and characterisation of ten microsatellite loci in the Noisy Scrub-bird Atrichornis clamosus using next-generation sequencing technology
The Noisy Scrub-bird is an endangered species of songbird endemic to the south coast of Western Australia that has undergone a major and prolonged population bottleneck. Using shotgun 454 next-generation DNA sequencing we have identified and characterised ten polymorphic microsatellite loci in this species. Observed allelic diversity was relatively low (2â5 alleles per locus) and significant deviations from Hardyâweinberg Equilibrium observed, although the presence of null alleles was onlypostulated for two loci. The microsatellite loci characterised in this study will be useful in a future population genetics studies in this endangered species
Further Lower Bounds for Structure-Preserving Signatures in Asymmetric Bilinear Groups
Structure-Preserving Signatures (SPSs) are a useful tool for the design of modular cryptographic protocols. Recent series of works have shown that by limiting the message space of those schemes to the set of Diffie-Hellman (DH) pairs, it is possible to circumvent the known lower bounds in the Type-3 bilinear group setting thus obtaining the shortest signatures consisting of only 2 elements from the shorter source group. It has been shown that such a variant yields efficiency gains for some cryptographic constructions, including attribute-based signatures and direct anonymous attestation. Only the cases of signing a single DH pair or a DH pair and a vector from have been considered. Signing a vector of group elements is required for various applications of SPSs, especially if the aim is to forgo relying on heuristic assumptions.
An open question is whether such an improved lower bound also applies to signing a vector of messages. We answer this question negatively for schemes existentially unforgeable under an adaptive chosen-message attack (EUF-CMA) whereas we answer it positively for schemes existentially unforgeable under a random-message attack (EUF-RMA) and those which are existentially unforgeable under a combined chosen-random-message attack (EUF-CMA-RMA). The latter notion is a leeway between the two former notions where it allows the adversary to adaptively choose part of the message to be signed whereas the remaining part of the message is chosen uniformly at random by the signer.
Another open question is whether strongly existentially unforgeable under an adaptive chosen-message attack (sEUF-CMA) schemes with 2-element signatures exist. We answer this question negatively, proving it is impossible to construct sEUF-CMA schemes with 2-element signatures even if the signature consists of elements from both source groups. On the other hand, we prove that sEUF-RMA and sEUF-CMA-RMA schemes with 2-element (unilateral) signatures are possible by giving constructions for those notions.
Among other things, our findings show a gap between random-message/combined chosen-random-message security and chosen-message security in this setting
Measurement of the cross-section of high transverse momentum vector bosons reconstructed as single jets and studies of jet substructure in pp collisions at âs = 7 TeV with the ATLAS detector
This paper presents a measurement of the cross-section for high transverse momentum W and Z bosons produced in pp collisions and decaying to all-hadronic final states. The data used in the analysis were recorded by the ATLAS detector at the CERN Large Hadron Collider at a centre-of-mass energy of âs = 7 TeV;{\rm Te}{\rm V}4.6\;{\rm f}{{{\rm b}}^{-1}}{{p}_{{\rm T}}}\gt 320\;{\rm Ge}{\rm V}|\eta |\lt 1.9{{\sigma }_{W+Z}}=8.5\pm 1.7$ pb and is compared to next-to-leading-order calculations. The selected events are further used to study jet grooming techniques
Measurement of the inclusive and dijet cross-sections of b-jets in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector
The inclusive and dijet production cross-sections have been measured for jets
containing b-hadrons (b-jets) in proton-proton collisions at a centre-of-mass
energy of sqrt(s) = 7 TeV, using the ATLAS detector at the LHC. The
measurements use data corresponding to an integrated luminosity of 34 pb^-1.
The b-jets are identified using either a lifetime-based method, where secondary
decay vertices of b-hadrons in jets are reconstructed using information from
the tracking detectors, or a muon-based method where the presence of a muon is
used to identify semileptonic decays of b-hadrons inside jets. The inclusive
b-jet cross-section is measured as a function of transverse momentum in the
range 20 < pT < 400 GeV and rapidity in the range |y| < 2.1. The bbbar-dijet
cross-section is measured as a function of the dijet invariant mass in the
range 110 < m_jj < 760 GeV, the azimuthal angle difference between the two jets
and the angular variable chi in two dijet mass regions. The results are
compared with next-to-leading-order QCD predictions. Good agreement is observed
between the measured cross-sections and the predictions obtained using POWHEG +
Pythia. MC@NLO + Herwig shows good agreement with the measured bbbar-dijet
cross-section. However, it does not reproduce the measured inclusive
cross-section well, particularly for central b-jets with large transverse
momenta.Comment: 10 pages plus author list (21 pages total), 8 figures, 1 table, final
version published in European Physical Journal
- âŠ