1,411 research outputs found
Optimal scheduling of real-time traffic in wireless networks with delayed feedback
In this paper we consider a wireless network composed of a base station and a number of clients, with the goal of scheduling real-time traffic. Even though this problem has been extensively studied in the literature, the impact of delayed acknowledgment has not been assessed. Delayed feedback is of increasing importance in systems where the round trip delay is much greater than the packet transmission time, and it has a significant effect on the scheduling decisions and network performance. Previous work considered the problem of scheduling real-time traffic with instantaneous feedback and without feedback. In this work, we address the general case of delayed feedback and use Dynamic Programming to characterize the optimal scheduling policy. An optimal algorithm that fulfills any feasible minimum delivery ratio requirements is proposed. Moreover, we develop a low-complexity suboptimal heuristic algorithm which is suitable for platforms with low computational power. Both algorithms are evaluated through simulations.National Science Foundation (U.S.) (CNS-1217048)United States. Office of Naval Research (Grant N00014-12-1-00640Coordenação de Aperfeiçoamento de Pessoal de NĂvel Superio
Parameterizing the Power Spectrum: Beyond the Truncated Taylor Expansion
The power spectrum is traditionally parameterized by a truncated Taylor
series: . It is
reasonable to truncate the Taylor series if , but
it is not if . We argue that there is no good
theoretical reason to prefer , and show that current
observations are consistent with even for
. Thus, there are regions of parameter space, which are both
theoretically and observationally relevant, for which the traditional truncated
Taylor series parameterization is inconsistent, and hence it can lead to
incorrect parameter estimations. Motivated by this, we propose a simple
extension of the traditional parameterization, which uses no extra parameters,
but that, unlike the traditional approach, covers well motivated inflationary
spectra with . Our parameterization therefore covers not only
standard-slow-roll inflation models but also a much wider class of inflation
models. We use this parameterization to perform a likelihood analysis for the
cosmological parameters.Comment: References added. Typo correcte
The Earliest Optical Observations of GRB 030329
We present the earliest optical imaging observations of GRB 030329 related to
SN 2003dh. The burst was detected by the HETE-2 satellite at 2003 March 29,
11:37:14.67 UT. Our wide-field monitoring started 97 minutes before the trigger
and the burst position was continuously observed. We found no precursor or
contemporaneous flare brighter than () in 32 s (64 s) timescale
between 10:00 and 13:00 UT. Follow-up time series photometries started at
12:51:39 UT (75 s after position notice through the GCN) and continued for more
than 5 hours. The afterglow was at min after burst.
Its fading between 1.2 and 6.3 hours is well characterized by a single
power-law of the form in -band. No significant flux variation was
detected and upper limits are derived as % in
minutes to hours timescales and % in seconds to
minutes timescales. Such a featureless lightcurve is explained by the smooth
distribution of circumburst medium. Another explanation is that the optical
band was above the synchrotron cooling frequency where emergent flux is
insensitive to the ambient density contrasts. Extrapolation of the afterglow
lightcurve to the burst epoch excludes the presence of an additional flare
component at minutes as seen in GRB 990123 and GRB 021211.Comment: ApJL, in pres
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Neurotrophic factor expression after CNS viral injury produces enhanced sensitivity to psychostimulants : potential mechanism for addiction vulnerability
Hypothesized risk factors for psychostimulant, amphetamine, and cocaine abuse include dopamine (DA) receptor polymorphisms, HIV infection, schizophrenia, drug-induced paranoias, and movement disorders; however, the molecular, cellular, and biochemical mechanisms that predispose to drug sensitivity or drive the development of addiction are incompletely understood. Using the Borna disease rat, an animal model of viralinduced encephalopathy wherein sensitivity to the locomotor and stereotypic behavioral effects of D-amphetamine and cocaine is enhanced (Solbrig et al., 1994, 1998), we identify a specific neurotrophin expression pattern triggered by striatal viral injury that increases tyrosine hydroxylase activity, an early step in DA synthesis, to produce a phenotype of enhanced amphetamine sensitivity. The reactive neurotrophin pattern provides a molecular framework for understanding how CNS viral injury, as well as other CNS adaptations producing similar growth factor activation profiles, may influence psychostimulant sensitivity
Fingerprints of spin-orbital physics in cubic Mott insulators: Magnetic exchange interactions and optical spectral weights
The temperature dependence and anisotropy of optical spectral weights
associated with different multiplet transitions is determined by the spin and
orbital correlations. To provide a systematic basis to exploit this close
relationship between magnetism and optical spectra, we present and analyze the
spin-orbital superexchange models for a series of representative
orbital-degenerate transition metal oxides with different multiplet structure.
For each case we derive the magnetic exchange constants, which determine the
spin wave dispersions, as well as the partial optical sum rules. The magnetic
and optical properties of early transition metal oxides with degenerate
orbitals (titanates and vanadates with perovskite structure) are shown
to depend only on two parameters, viz. the superexchange energy and the
ratio of Hund's exchange to the intraorbital Coulomb interaction, and on
the actual orbital state. In systems important corrections follow from
charge transfer excitations, and we show that KCuF can be classified as a
charge transfer insulator, while LaMnO is a Mott insulator with moderate
charge transfer contributions. In some cases orbital fluctuations are quenched
and decoupling of spin and orbital degrees of freedom with static orbital order
gives satisfactory results for the optical weights. On the example of cubic
vanadates we describe a case where the full quantum spin-orbital physics must
be considered. Thus information on optical excitations, their energies,
temperature dependence and anisotropy, combined with the results of magnetic
neutron scattering experiments, provides an important consistency test of the
spin-orbital models, and indicates whether orbital and/or spin fluctuations are
important in a given compound.Comment: 34 pages, 16 figure
Spontaneous Basal Cell Carcinoma of the Submandibular Gland in a Rat
At necropsy, a white nodule (about 5 Ă 3 mm in size) was observed in the right
submandibular gland of a 10-week-old female GALAS rat. Histopathologically, oval
to spindle-shaped and pale basophilic tumor cells proliferated closely, and
formed variably sized foci. The nodule partially spread into or invaded the
surrounding normal tissue, and necrotic foci were recognized in the tumor.
Immunohistochemically, the nuclei of the tumor cells showed a diffusely positive
reaction for p63, and the cytoplasm showed a diffusely positive reaction for
cytokeratin and negative reaction for αSMA, vimentin, desmin and S-100. Many
tumor cells were positive for PCNA. Ultrastructurally, the tumor cells contained
many tonofilaments in the cytoplasm and a few desmosomes at the intercellular
portion. Based on these findings, the tumor was diagnosed as a basal cell
carcinoma originating from the duct in the rat submandibular gland
The phagocytosis oxidase/Bem1p domain-containing protein PB1CP negatively regulates the NADPH oxidase RBOHD in plant immunity
Perception of pathogen-associated molecular patterns (PAMPs) by surface-localized pattern recognition receptors activates RESPIRATORY BURST OXIDASE HOMOLOG D (RBOHD) through direct phosphorylation by BOTRYTIS-INDUCED KINASE 1 (BIK1) and induces the production of reactive oxygen species (ROS). RBOHD activity must be tightly controlled to avoid the detrimental effects of ROS, but little is known about RBOHD downregulation. To understand the regulation of RBOHD, we used co-immunoprecipitation of RBOHD with mass spectrometry analysis and identified PHAGOCYTOSIS OXIDASE/BEM1P (PB1) DOMAIN-CONTAINING PROTEIN (PB1CP). PB1CP negatively regulates RBOHD and the resistance against the fungal pathogen Colletotrichum higginsianum. PB1CP competes with BIK1 for binding to RBOHD in vitro. Furthermore, PAMP treatment enhances the PB1CP-RBOHD interaction, thereby leading to the dissociation of phosphorylated BIK1 from RBOHD in vivo. PB1CP localizes at the cell periphery and PAMP treatment induces relocalization of PB1CP and RBOHD to the same small endomembrane compartments. Additionally, overexpression of PB1CP in Arabidopsis leads to a reduction in the abundance of RBOHD protein, suggesting the possible involvement of PB1CP in RBOHD endocytosis. We found PB1CP, a novel negative regulator of RBOHD, and revealed its possible regulatory mechanisms involving the removal of phosphorylated BIK1 from RBOHD and the promotion of RBOHD endocytosis
Allele-Specific Chromatin Immunoprecipitation Studies Show Genetic Influence on Chromatin State in Human Genome
Several recent studies have shown a genetic influence on gene expression variation, including variation between the two chromosomes within an individual and variation between individuals at the population level. We hypothesized that genetic inheritance may also affect variation in chromatin states. To test this hypothesis, we analyzed chromatin states in 12 lymphoblastoid cells derived from two Centre d'Etude du Polymorphisme Humain families using an allele-specific chromatin immunoprecipitation (ChIP-on-chip) assay with Affymetrix 10K SNP chip. We performed the allele-specific ChIP-on-chip assays for the 12 lymphoblastoid cells using antibodies targeting at RNA polymerase II and five post-translation modified forms of the histone H3 protein. The use of multiple cell lines from the Centre d'Etude du Polymorphisme Humain families allowed us to evaluate variation of chromatin states across pedigrees. These studies demonstrated that chromatin state clustered by family. Our results support the idea that genetic inheritance can determine the epigenetic state of the chromatin as shown previously in model organisms. To our knowledge, this is the first demonstration in humans that genetics may be an important factor that influences global chromatin state mediated by histone modification, the hallmark of the epigenetic phenomena
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