45,853 research outputs found
On the Asymptotic Capacity of -Secure -Private Information Retrieval with Graph Based Replicated Storage
The problem of private information retrieval with graph-based replicated
storage was recently introduced by Raviv, Tamo and Yaakobi. Its capacity
remains open in almost all cases. In this work the asymptotic (large number of
messages) capacity of this problem is studied along with its generalizations to
include arbitrary -privacy and -security constraints, where the privacy
of the user must be protected against any set of up to colluding servers
and the security of the stored data must be protected against any set of up to
colluding servers. A general achievable scheme for arbitrary storage
patterns is presented that achieves the rate , where
is the total number of servers, and each message is replicated at least
times. Notably, the scheme makes use of a special structure
inspired by dual Generalized Reed Solomon (GRS) codes. A general converse is
also presented. The two bounds are shown to match for many settings, including
symmetric storage patterns. Finally, the asymptotic capacity is fully
characterized for the case without security constraints for arbitrary
storage patterns provided that each message is replicated no more than
times. As an example of this result, consider PIR with arbitrary graph based
storage () where every message is replicated at exactly servers.
For this -replicated storage setting, the asymptotic capacity is equal to
where is the maximum size of a -matching in a
storage graph . In this undirected graph, the vertices correspond
to the set of servers, and there is an edge between vertices
only if a subset of messages is replicated at both servers and
Measurement of the rapidity-even dipolar flow in Pb-Pb collisions with the ATLAS detector
The rapidity-even dipolar flow v1 associated with dipole asymmetry in the
initial geometry is measured over a broad range in transverse momentum 0.5
GeV<pT<9 GeV, and centrality (0-50)% in Pb-Pb collisions at sqrt(s_NN)=2.76
TeV, recorded by the ATLAS experiment at the LHC. The v1 coefficient is
determined via a two-component fit of the first order Fourier coefficient,
v_{1,1}= cos \Delta\phi, of two-particle correlations in azimuthal angle
\Delta\phi=\phi_a-\phi_b as a function of pT^a and pT^b. This fit is motivated
by the finding that the pT dependence of v_{1,1}(pT^a,pT^b) data are consistent
with the combined contributions from a rapidity-even v1 and global momentum
conservation. The magnitude of the extracted momentum conservation component
suggests that the system conserving momentum involves only a subset of the
event (spanning about 3 units in \eta in central collisions). The extracted v1
is observed to cross zero at pT~1.0 GeV, reaches a maximum at 4-5 GeV with a
value comparable to that for v3, and decreases at higher pT. Interestingly, the
magnitude of v1 at high pT exceeds the value of the v3 in all centrality
interval and exceeds the value of v2 in central collisions. This behavior
suggests that the path-length dependence of energy loss and initial dipole
asymmetry from fluctuations corroborate to produce a large dipolar anisotropy
for high pT hadrons, making the v1 a valuable probe for studying the jet
quenching phenomena.Comment: 9 pages, 6 figures. Proceedings for the 28th Winter Workshop on
Nuclear Dynamics, Dorado Del Mar, Puerto Rico, United States Of America, 7 -
14 Apr 201
A study of the correlations between jet quenching observables at RHIC
Focusing on four types of correlation plots, vs. , vs. , vs. and vs.\
, we demonstrate how the centrality dependence of
\emph{correlations} between multiple jet quenching observables provide valuable
insight into the energy loss mechanism in a quark-gluon plasma. In particular
we find that a qualitative energy loss model gives a good description of
vs.\ only when we take and a medium
geometry generated by a model of the Color Glass Condensate. This same model also qualitatively describes the trigger dependence of
vs.\ data and makes novel predictions for the
centrality dependence for this vs.\ correlation.
Current data suggests, albeit with extremely large uncertainty, that
, a correlation that is difficult to reproduce in
current energy loss models.Comment: 6 pages, 6 figure
Mapping of the \u3cem\u3eSaccharomyces cerevisiae\u3c/em\u3e Oxa1-Mitochondrial Ribosome Interface and Identification of MrpL40, a Ribosomal Protein in Close Proximity to Oxa1 and Critical for Oxidative Phosphorylation Complex Assembly
The Oxa1 protein plays a central role in facilitating the cotranslational insertion of the nascent polypeptide chains into the mitochondrial inner membrane. Mitochondrially encoded proteins are synthesized on matrix-localized ribosomes which are tethered to the inner membrane and in physical association with the Oxa1 protein. In the present study we used a chemical cross-linking approach to map the Saccharomyces cerevisiae Oxa1-ribosome interface, and we demonstrate here a close association of Oxa1 and the large ribosomal subunit protein, MrpL40. Evidence to indicate that a close physical and functional relationship exists between MrpL40 and another large ribosomal protein, the Mrp20/L23 protein, is also provided. MrpL40 shares sequence features with the bacterial ribosomal protein L24, which like Mrp20/L23 is known to be located adjacent to the ribosomal polypeptide exit site. We propose therefore that MrpL40 represents the Saccharomyces cerevisiae L24 homolog. MrpL40, like many mitochondrial ribosomal proteins, contains a C-terminal extension region that bears no similarity to the bacterial counterpart. We show that this C-terminal mitochondria-specific region is important for MrpL40\u27s ability to support the synthesis of the correct complement of mitochondrially encoded proteins and their subsequent assembly into oxidative phosphorylation complexes
Mapping of the saccharomyces cerevisiae oxa1-mitochondrial ribosome interface and identification of MrpL40, a ribosomal protein in close proximity to oxal and critical for oxidative phosphorylation complex assembly
The Oxa1 protein plays a central role in facilitating the cotranslational insertion of the nascent polypeptide chains into the mitochondrial inner membrane. Mitochondrially encoded proteins are synthesized on matrix-localized ribosomes which are tethered to the inner membrane and in physical association with the Oxa1 protein. In the present study we used a chemical cross-linking approach to map the Saccharomyces cerevisiae Oxa1-ribosome interface, and we demonstrate here a close association of Oxa1 and the large ribosomal subunit protein, MrpL40. Evidence to indicate that a close physical and functional relationship exists between MrpL40 and another large ribosomal protein, the Mrp20/L23 protein, is also provided. MrpL40 shares sequence features with the bacterial ribosomal protein L24, which like Mrp20/L23 is known to be located adjacent to the ribosomal polypeptide exit site. We propose therefore that MrpL40 represents the Saccharomyces cerevisiae L24 homolog. MrpL40, like many mitochondrial ribosomal proteins, contains a C-terminal extension region that bears no similarity to the bacterial counterpart. We show that this C-terminal mitochondria-specific region is important for MrpL40's ability to support the synthesis of the correct complement of mitochondrially encoded proteins and their subsequent assembly into oxidative phosphorylation complexes
Oxa1 Directly Interacts with Atp9 and Mediates Its Assembly into the Mitochondrial F\u3csub\u3e1\u3c/sub\u3eF\u3csub\u3eo\u3c/sub\u3e-ATP Synthase Complex
The yeast Oxa1 protein is involved in the biogenesis of the mitochondrial oxidative phosphorylation (OXPHOS) machinery. The involvement of Oxa1 in the assembly of the cytochrome oxidase (COX) complex, where it facilitates the cotranslational membrane insertion of mitochondrially encoded COX subunits, is well documented. In this study we have addressed the role of Oxa1, and its sequence-related protein Cox18/Oxa2, in the biogenesis of the F1Fo-ATP synthase complex. We demonstrate that Oxa1, but not Cox18/Oxa2, directly supports the assembly of the membrane embedded Fo-sector of the ATP synthase. Oxa1 was found to physically interact with newly synthesized mitochondrially encoded Atp9 protein in a posttranslational manner and in a manner that is not dependent on the C-terminal, matrix-localized region of Oxa1. The stable manner of the Atp9-Oxa1 interaction is in contrast to the cotranslational and transient interaction previously observed for the mitochondrially encoded COX subunits with Oxa1. In the absence of Oxa1, Atp9 was observed to assemble into an oligomeric complex containing F1-subunits, but its further assembly with subunit 6 (Atp6) of the Fo-sector was perturbed. We propose that by directly interacting with newly synthesized Atp9 in a posttranslational manner, Oxa1 is required to maintain the assembly competence of the Atp9-F1-subcomplex for its association with Atp6
Transport through the intertube link between two parallel carbon nanotubes
Quantum transport through the junction between two metallic carbon nanotubes
connected by intertube links has been studied within the TB method and Landauer
formula. It is found that the conductance oscillates with both of the coupling
strength and length. The corresponding local density of states (LDOS) is
clearly shown and can be used to explain the reason why there are such kinds of
oscillations of the conductances, which should be noted in the design of
nanotube-based devices.Comment: 6 pages, 4 figure
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