15,760 research outputs found
Towards a Model of Understanding Social Search
Search engine researchers typically depict search as the solitary activity of
an individual searcher. In contrast, results from our critical-incident survey
of 150 users on Amazon's Mechanical Turk service suggest that social
interactions play an important role throughout the search process. Our main
contribution is that we have integrated models from previous work in
sensemaking and information seeking behavior to present a canonical social
model of user activities before, during, and after search, suggesting where in
the search process even implicitly shared information may be valuable to
individual searchers.Comment: Presented at 1st Intl Workshop on Collaborative Information Seeking,
2008 (arXiv:0908.0583
Anomaly Inflow and Membrane Dynamics in the QCD Vacuum
Large and holographic arguments, as well as Monte Carlo results,
suggest that the topological structure of the QCD vacuum is dominated by
codimension-one membranes which appear as thin dipole layers of topological
charge. Such membranes arise naturally as branes in the holographic
formulation of QCD based on IIA string theory. The polarizability of these
membranes leads to a vacuum energy , providing the origin of
nonzero topological susceptibility. Here we show that the axial U(1) anomaly
can be formulated as anomaly inflow on the brane surfaces. A 4D gauge
transformation at the brane surface separates into a 3D gauge transformation of
components within the brane and the transformation of the transverse component.
The in-brane gauge transformation induces currents of an effective Chern-Simons
theory on the brane surface, while the transformation of the transverse
component describes the transverse motion of the brane and is related to the
Ramond-Ramond closed string field in the holographic formulation of QCD. The
relation between the surface currents and the transverse motion of the brane is
dictated by the descent equations of Yang-Mills theory.Comment: 22 pages, 3 figure
cAMP Pulsing of Denuded Mouse Oocytes Increases Meiotic Resumption Via Activation of AMP-activated Protein Kinase
cAMP plays a critical role in the control of oocyte maturation, as a high level of cAMP maintains oocyte arrest at the first meiotic prophase. Yet this study shows that pulsing meiotically arrested denuded oocytes (DO) with cAMP induces oocyte maturation through the activation of AMP-activated protein kinase (PRKA). Short-term (3 h) pulsing of meiotically arrested oocytes with forskolin, an adenyl cyclase (AC) activator, increased oocyte cAMP, led to elevated AMP, and induced oocyte meiotic resumption compared to oocytes continuously cultured in the control medium with or without forskolin. Western analysis showed that germinal vesicle (GV)-stage oocytes after forskolin pulsing contained increased levels of phospho-acetyl CoA carboxylase (pACACA), a primary substrate of PRKA. Pulsing oocytes with the phosphodiesterase (PDE)-sensitive cAMP analog, 8-bromo-cAMP (8-Br-cAMP), also increased pACACA and pPRKA levels in GV-stage oocytes and induced oocyte meiotic resumption. Moreover, the PRKA inhibitors, compound C and araA, prevented 8-Br-cAMP pulsing-induced maturation. The lack of effect on meiotic induction and PRKA activation when oocytes were pulsed with the PDE-resistant activators of cAMP-dependent protein kinase, Sp-cAMP-AM and Sp-5,6-DCI-cBIMPS, suggests that cAMP degradation is required for pulsing-induced maturation. Pulsing oocytes with the exchange protein directly activated by cAMP (Epac)-specific activator, 8-CPT-2′-O-Me-cAMP, had no stimulatory effect on oocyte maturation, suggesting Epac is not involved in the pulsing-induced maturation. Taken together, these data support the idea that a transient increase in oocyte cAMP can induce meiotic resumption via activation of PRKA
Entanglement transformation between sets of bipartite pure quantum states using local operations
Alice and Bob are given an unknown initial state chosen from a set of pure
quantum states. Their task is to transform the initial state to a corresponding
final pure state using local operations only. We prove necessary and sufficient
conditions on the existence of such a transformation. We also provide efficient
algorithms that can quickly rule out the possibility of transforming a set of
initial states to a set of final states.Comment: 19 pages, 1 figure, minor revision, to appear in J.Math.Phy
Discrimination between pure states and mixed states
In this paper, we discuss the problem of determining whether a quantum system
is in a pure state, or in a mixed state. We apply two strategies to settle this
problem: the unambiguous discrimination and the maximum confidence
discrimination. We also proved that the optimal versions of both strategies are
equivalent. The efficiency of the discrimination is also analyzed. This scheme
also provides a method to estimate purity of quantum states, and Schmidt
numbers of composed systems
Destruction of Neel order and appearance of superconductivity in electron-doped cuprates by oxygen annealing process
We use thermodynamic and neutron scattering measurements to study the effect
of oxygen annealing on the superconductivity and magnetism in
PrLaCeCuO. Although the transition temperature
measured by susceptibility and superconducting coherence length increase
smoothly with gradual oxygen removal from the annealing process, bulk
superconductivity, marked by a specific heat anomaly at and the presence
of a neutron magnetic resonance, only appears abruptly when is close to
the largest value. These results suggest that the effect of oxygen annealing
must be first determined in order to establish a Ce-doping dependence of
antiferromagnetism and superconductivity phase diagram for electron-doped
copper oxides.Comment: 5 pages, 4 figures, accepted by Phys. Rev.
Supersymmetric Runge-Lenz-Pauli vector for Dirac vortex in topological insulators and graphene
The Dirac mass-vortex at the surface of a topological insulator or in
graphene is considered. Within the linear approximation for the vortex
amplitude's radial dependence, the spectrum is a series of degenerate bound
states, which can be classified by a set of accidental SU(2) and supersymmetry
generators (I. F. Herbut and C.-K. Lu, Phys. Rev. B 83 125412 (2011)). Here we
discuss further the properties and manifestations of the supersymmetry of the
vortex Hamiltonian, and point out some interesting analogies to the
Runge-Lenz-Pauli vector in the non-relativistic hydrogen atom. Symmetry
breaking effects due to a finite chemical potential, and the Zeeman field are
also analyzed. We find that a residual accidental degeneracy remains only in
the special case of equal magnitudes of both terms, whereas otherwise it
becomes removed entirely.Comment: revised version with added reference and a new paragraph on
interpretation of two-velocity Weyl fermions realized in 2D optical lattice;
to appear in J Phys
AMPK Regulation of Mouse Oocyte Meiotic Resumption in Vitro
We have previously shown that the adenosine analog 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR), an activator of AMP-activated protein kinase (AMPK), stimulates an increase in AMPK activity and induces meiotic resumption in mouse oocytes [Downs, S.M., Hudson, E.R., Hardie, D.G., 2002. A potential role for AMP-activated protein kinase in meiotic induction in mouse oocytes. Dev. Biol, 245, 200–212]. The present study was carried out to better define a causative role for AMPK in oocyte meiotic maturation. When microinjected with a constitutively active AMPK, about 20% of mouse oocytes maintained in meiotic arrest with dibutyryl cAMP (dbcAMP) were stimulated to undergo germinal vesicle breakdown (GVB), while there was no effect of catalytically dead kinase. Western blot analysis revealed that germinal vesicle (GV)-stage oocytes cultured in dbcAMP-containing medium plus AICAR possessed elevated levels of active AMPK, and this was confirmed by AMPK assays using a peptide substrate of AMPK to directly measure AMPK activity. AICAR-induced meiotic resumption and AMPK activation were blocked by compound C or adenine 9-beta-d-arabinofuranoside (araA, a precursor of araATP), both inhibitors of AMPK. Compound C failed to suppress adenosine uptake and phosphorylation, indicating that it did not block AICAR action by preventing its metabolism to the AMP analog, ZMP. 2′-Deoxycoformycin (DCF), a potent adenosine deaminase inhibitor, reversed the inhibitory effect of adenosine on oocyte maturation by modulating intracellular AMP levels and activating AMPK. Rosiglitazone, an anti-diabetic agent, stimulated AMPK activation in oocytes and triggered meiotic resumption. In spontaneously maturing oocytes, GVB was preceded by AMPK activation and blocked by compound C. Collectively, these results support the proposition that active AMPK within mouse oocytes provides a potent meiosis-inducing signal in vitro
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