5,917 research outputs found

    Human interleukin-1 receptor antagonist is expressed in liver

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    AbstractUsing PCR and Northern blot analysis, an IL-1 receptor antagonist specific transcript was amplified from HepG2- and liver mRNA, cDNA clones coding for IL-1 receptor antagonist were isolated from a liver cDNA library and sequence comparison revealed complete identity with the secreted, monocytic form of IL-1 receptor antagonist

    Phonon emission and arrival times of electrons from a single-electron source

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    In recent charge-pump experiments, single electrons are injected into quantum Hall edge channels at energies significantly above the Fermi level. We consider here the relaxation of these hot edge-channel electrons through longitudinal-optical-phonon emission. Our results show that the probability for an electron in the outermost edge channel to emit one or more phonons en route to a detector some microns distant along the edge channel suffers a double-exponential suppression with increasing magnetic field. This explains recent experimental observations. We also describe how the shape of the arrival-time distribution of electrons at the detector reflects the velocities of the electronic states post phonon emission. We show how this can give rise to pronounced oscillations in the arrival-time-distribution width as a function of magnetic field or electron energy

    The reverberation signatures of rotating disc winds in active galactic nuclei

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    The broad emission lines (BELs) in active galactic nuclei (AGN) respond to ionizing continuum variations. The time and velocity dependence of their response depends on the structure of the broad-line region: its geometry, kinematics and ionization state. Here, we predict the reverberation signatures of BELs formed in rotating accretion disc winds. We use a Monte Carlo radiative transfer and ionization code to predict velocity-delay maps for representative high- (C IV~IV) and low-ionization (Hα\alpha) emission lines in both high- and moderate-luminosity AGN. Self-shielding, multiple scattering and the ionization structure of the outflows are all self-consistently taken into account, while small-scale structure in the outflow is modelled in the micro-clumping approximation. Our main findings are: (1) The velocity-delay maps of smooth/micro-clumped outflows often contain significant negative responses. (2)~The reverberation signatures of disc wind models tend to be rotation dominated and can even resemble the classic "red-leads-blue" inflow signature. (3) Traditional "blue-leads-red" outflow signatures can usually only be observed in the long-delay limit. (4) Our models predict lag-luminosity relationships similar to those inferred from observations, but systematically underpredict the observed centroid delays. (5) The ratio between "virial product" and black hole mass predicted by our models depends on viewing angle. Our results imply that considerable care needs to be taken in interpreting data obtained by observational reverberation mapping campaigns. In particular, basic signatures such as "red-leads-blue", "blue-leads-red" and "blue and red vary jointly" are not always reliable indicators of inflow, outflow or rotation. This may help to explain the perplexing diversity of such signatures seen in observational campaigns to date.Comment: 15 pages, 17 figures, 2 tables. Accepted by MNRAS 20/7/201

    A Simulation Model for Electron Irradiation Induced Specimen Charging in a Scanning Electron Microscope

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    A numerical model has been formulated to simulate the dynamics of specimen charging in a scanning electron microscope. In this model, the electric field due to imposed boundary conditions and fixed charges is solved by the finite element method. The empirical electron yield data are stored in Universal Yield Curves (UYC) . These UYCs control the generation of secondary and backscattered electrons from various materials. The electrons emitted from electron-solid interactions are tracked using a leapfrog integration scheme. Excess charges generated on the surface of electrically floating solids are assigned to numerical grids using a linear charge redistribution scheme. The validity of the simulation model was verified by measurements in a special setup which consisted of several isolated electrodes in the SEM chamber. Excess currents generated inside each electrode due to electron irradiation were measured simultaneously. Measurements and simulation results are in broad agreement and show that electrically floating electrodes, not directly irradiated by the primary beam, can charge-up if they are irradiated by secondary electrons and backscattered electrons emitted from a nearby electrode. The polarity of charge generation on the electrically floating solid depends on its own material property, and also strongly on the potential distribution in the space surrounding the floating electrode

    MPIFA: A Modified Protocol Independent Fairness Algorithm for Community Wireless Mesh Networks

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    Community Wireless Mesh Networks (WMN) is a paradigm in wireless communication of 21st centuary as means of providing high speed braodband access. Un-cooperative nodes, both selfish and malicious proves to be a significant threat in Community WMN that require a solution independent of routing protocols being used. We propose to implement Modified PIFA (MPIFA), an Improved version of Protocol Independent Fairness Algorithm (PIFA) proposed by Younghwan Yoo, Sanghyun and P. Agrawal [6] with ability to cater specific requirements in Community WMN. MPIFA has malicious nodes detection rate improvement of 50% when nodes demonstrate low probabilistic malicious behavior of 10% to circumvent the security measures in place. Improvements were also made to reduce false malicious node detections to 4% when node-to-node link failures occur in Community WMN.Comment: Innovative Technologies in Intelligent Systems and Industrial Applications(CITISIA) 200

    Electron interactions in an antidot in the integer quantum Hall regime

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    A quantum antidot, a submicron depletion region in a two-dimensional electron system, has been actively studied in the past two decades, providing a powerful tool for understanding quantum Hall systems. In a perpendicular magnetic field, electrons form bound states around the antidot. Aharonov-Bohm resonances through such bound states have been experimentally studied, showing interesting phenomena such as Coulomb charging, h/2e oscillations, spectator modes, signatures of electron interactions in the line shape, Kondo effect, etc. None of them can be explained by a simple noninteracting electron approach. Theoretical models for the above observations have been developed recently, such as a capacitive-interaction model for explaining the h/2e oscillations and the Kondo effect, numerical prediction of a hole maximum-density-droplet antidot ground state, and spin density-functional theory for investigating the compressibility of antidot edges. In this review, we summarize such experimental and theoretical works on electron interactions in antidots.Comment: 73 pages, 28 figures, to be published in Physics Reports. The resolution of some figures is reduced in this uploa

    Coulomb Blockade and Kondo Effect in a Quantum Hall Antidot

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    We propose a general capacitive model for an antidot, which has two localized edge states with different spins in the quantum Hall regime. The capacitive coupling of localized excess charges, which are generated around the antidot due to magnetic flux quantization, and their effective spin fluctuation can result in Coulomb blockade, h/(2e) Aharonov-Bohm oscillations, and the Kondo effect. The resultant conductance is in qualitative agreement with recent experimental data.Comment: 3 figures, to appear in Physical Review Letter

    Proteomic Analysis of Bacterial Expression Profiles Following Exposure to Organic Solvent Flower Extract of Melastoma candidum D Don (Melastomataceae)

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    Purpose: To identify potential antibacterial protein targets following exposure to Melastoma candidum extract.Methods: Plant extracts were prepared using sequential extraction method. Denaturing gel electrophoresis and MALDI TOF-TOF MS protein sequencing were used to identify differentialexpressed bacterial proteins. 96-well microplate method was used to determine the minimum inhibitory concentration (MIC) values. Thin layer chromatography (TLC) bio-autobiography and gaschromatography-mass spectrometry (GC-MS) were performed to determine the phytochemicals in the active fraction.Results: Five differentially expressed bacterial proteins (four from Escherichia coli and one from Staphylococcus aureus), were identified via proteomic approach. Among the bacterial proteins identified, glutamate decarboxylase, elongation factor-Tu and α-hemolysin are especially noteworthy, as they are implicated in critical bacterial pathways pertaining to survival in acidic environment, protein translation and virulence, respectively. Additionally, we tested and reported the minimum inhibition concentrations of different M. candidum fractions and gas chromatography-mass spectrometry GC-MS analysis of the active fraction.Conclusion: Glutamate decarboxylase, elongation factor-Tu and α-hemolysin represent potential antibacterial targets.Keywords: Escherichia coli, Staphylococcus aureus, Melastoma candidum, Glutamate decarboxylase, Elongation factor-Tu, α-Hemolysin, Protein expressio

    Interpreting filtration-based suffusion criteria using micro-Computed Tomography and laboratory filter tests

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    In a cohesionless soil containing a mixture of coarse and fine particles, suffusion is the erosion of the fine particles which can be transported through the void space between the coarse particles. Two commonly used criteria for suffusion are Kézdi (1979) and Kenney & Lau (1985), both of which were determined empirically and both include a limiting factor of 4 between fine and coarse particle sizes. This factor of 4 is often interpreted based on simple filter criteria, as the ratio between the size of coarse particles and the size of constrictions in the void space, with some factor of safety. To fully understand the suffusion mechanism it is necessary to consider the size of void constrictions, but also how far fine particles can move before they are retained and the potential for the fine material to self-filter. Several researchers have used empirical and numerical results to show that the criteria are conservative, however these studies could not clearly distinguish between the issues of constriction size, particle movement and self-filtration. This paper uses micro-Computed Tomography (microCT) images to examine the underlying filter criteria, by measuring constriction sizes relative to particle sizes for three materials. Laboratory filter tests, with minimal self-filtration, are then presented to observe particle movement. The results provide a new means to interpret the physical significance of the filter criteria, on which suffusion criteria are based
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