163 research outputs found

    Graphical sequences of some family of induced subgraphs

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    The subdivision graph S(G)S(G) of a graph GG is the graph obtained by inserting a new vertex into every edge of GG. The SvertexS_{vertex} or SverS_{ver} join of the graph G1G_{1} with the graph G2G_{2}, denoted by G1˙G2G_{1}\dot{\vee}G_{2}, is obtained from S(G1)S(G_{1}) and G2G_{2} by joining all vertices of G1G_{1} with all vertices of G2G_{2}. The SedgeS_{edge} or SedS_{ed} join of G1G_{1} and G2G_{2}, denoted by G1ˉG2G_{1}\bar{\vee}G_{2}, is obtained from S(G1)S(G_{1}) and G2G_{2} by joining all vertices of S(G1)S(G_{1}) corresponding to the edges of G1G_{1} with all vertices of G2G_{2}. In this paper, we obtain graphical sequences of the family of induced subgraphs of SJ=G1G2S_{J} = G_{1}\vee G_{2}, Sver=G1˙G2S_{ver} = G_{1}\dot{\vee}G_{2} and Sed=G1ˉG2S_{ed} = G_{1}\bar{\vee}G_{2}. Also we prove that the graphic sequence of SedS_{ed} is potentially K4eK_{4}-e-graphical

    Spitzer Space Telescope Observations of the Magnetic Cataclysmic Variable AE Aqr

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    The magnetic cataclysmic variable AE Aquarii hosts a rapidly rotating white dwarf which is thought to expel most of the material streaming onto it. Observations of AE Aqr have been obtained in the wavelength range of 5 - 70 microns with the IRS, IRAC, and MIPS instruments on board the Spitzer Space Telescope. The spectral energy distribution reveals a significant excess above the K4V spectrum of the donor star with the flux increasing with wavelength above 12.5 microns. Superposed on the energy distribution are several hydrogen emission lines, identified as Pf alpha and Hu alpha, beta, gamma. The infrared spectrum above 12.5 microns can be interpreted as synchrotron emission from electrons accelerated to a power-law distribution dN=E^{-2.4}dE in expanding clouds with an initial evolution timescale in seconds. However, too many components must then be superposed to explain satisfactorily both the mid-infrared continuum and the observed radio variability. Thermal emission from cold circumbinary material can contribute, but it requires a disk temperature profile intermediate between that produced by local viscous dissipation in the disk and that characteristic of a passively irradiated disk. Future high-time resolution observations spanning the optical to radio regime could shed light on the acceleration process and the subsequent particle evolution.Comment: 15 pages, 3 figures, accepted for publication in Ap

    POTENTIALLY GRAPHIC SEQUENCES OF SPLIT GRAPHS

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    Abstract. A sequence π = (d 1 , d 2 , . . . , d n ) of non-negative integers is said to be graphic if it is the degree sequence of a simple G on n vertices, and such a graph G is referred to as a realization of π. The set of all non-increasing non-negative integer sequences π = (d 1 , d 2 , . . . , d n ) is denoted by N S n . A sequence π ∈ N S n is said to be graphic if it is the degree sequence of a graph G on n vertices, and such a graph G is called a realization of π. The set of all graphic sequences in N S n is denoted by GS n . A split graph K r + K s on r + s vertices is denoted by S r,s . A graphic sequence π is potentially H-graphic if there is a realizaton of π containing H as a subgraph. In this paper, we determine the graphic sequences of subgraphs H, where H is S r1,s1 + S r2,s2 + S r3,s3 + . . . + S rm,sm , S r1,s1 ∨ S r2,s2 ∨ . . . ∨ S rm,sm and S r1,s1 × S r2,s2 × . . . × S rm,sm and +, V and × denotes the standard join operation, the normal join operation and the cartesian product in these graphs respectively

    Nearwork-induced transient myopia in preadolescent Hong Kong Chinese

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    PURPOSE. To compare the magnitude and time course of nearwork-induced transient myopia (NITM) in preadolescent Hong Kong Chinese myopes and emmetropes. METHOD. Forty-five Hong Kong Chinese children, 35 myopes and 10 emmetropes aged 6 to 12 years (median, 7.5), monocularly viewed a letter target through a Badal lens for 5 minutes at either 5.00- or 2.50-D accommodative demand, followed by 3 minutes of viewing the equivalent target at optical infinity. Accommodative responses were measured continuously with a modified, infrared, objective open-field autorefractor. Accommodative responses were also measured for a countercondition: viewing of a letter target for 5 minutes at optical infinity, followed by 3 minutes of viewing the target at a 5.00-D accommodative demand. The results were compared with tonic accommodation and both subject and family history of refractive error. RESULTS. Retinal-blur-driven NITM was significantly greater in Hong Kong Chinese children with myopic vision than in the emmetropes after both near tasks, but showed no significant dose effect. The NITM was still evident 3 minutes after viewing the 5.00-D near task for 5 minutes. The magnitude of NITM correlated with the accommodative drift after viewing a distant target for more than 4 minutes, but was unrelated to the subjects' or family history of refractive error. CONCLUSIONS. In a preadolescent ethnic population with known predisposition to myopia, there is a significant posttask blur-driven accommodative NITM, which is sustained for longer than has previously been found in white adults

    The impact of the molecular weight on the nonequilibrium glass transition dynamics of poly(phenylmethyl siloxane) in cylindrical nanopores

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    Changes in the glass transition dynamics caused by nanoconfinement reveal pronounced out-of-equilibrium features. Therefore, the confinement effects weaken with time. Using dielectric spectroscopy, we have investigated the impact of molecular weight on the equilibration kinetics of the studied polymer embedded within anodic aluminum oxide nanoporous templates. For our research, we have used poly(phenylmethyl siloxane) (PMPS) with low (Mw = 2530 g/mol) and high (Mw = 27,800 g/mol) molecular weight. We have found that the observed faster dynamics of the nanopore-confined systems weakens with time, and ultimately it is possible to regain the bulk-like mobility. The equilibration time increases by reducing the pore size and lowering the annealing temperature much below the glass transition temperature of the interfacial layer, Tg_interface. The experimental data analysis has also revealed that the molecular weight of the nanopore-confined polymer influences the recovery of the bulk segmental relaxation time, τα. Low-molecular-weight PMPS rearrange and reach denser packing of the polymer chains with greater ease than the high-molecular-weight one. Finally, we have also demonstrated that the molecular weight affects the relationship between the time constant characterizing the equilibration kinetics and the characteristic time of viscous flow in cylindrical channels of nanometer size

    Nanodust detection near 1 AU from spectral analysis of Cassini/RPWS radio data

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    Nanodust grains of a few nanometer in size are produced near the Sun by collisional break-up of larger grains and picked-up by the magnetized solar wind. They have so far been detected at 1 AU by only the two STEREO spacecraft. Here we analyze the spectra measured by the radio and plasma wave instrument onboard Cassini during the cruise phase close to Earth orbit; they exhibit bursty signatures similar to those observed by the same instrument in association to nanodust stream impacts on Cassini near Jupiter. The observed wave level and spectral shape reveal impacts of nanoparticles at about 300 km/s, with an average flux compatible with that observed by the radio and plasma wave instrument onboard STEREO and with the interplanetary flux models

    Study of High Viscous Multiphase Flow Using OLGA Flow Simulator

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    The continuous depletion of conventional reserves of the world oil and gas has spurred investigation towards the exploration and production from unconventional sources of hydrocarbons such as heavy oil. However, heavy oils are known for their high liquid viscosities making them even more difficult and expensive to produce and transport in pipelines at ambient temperatures. As a consequence of this, a critical understanding of multiphase flow characteristics is vital to aid engineering design it has become imperative to investigate the rheology of high viscosity oils and ways of enhancing its production and transportation. In this study, the characteristics of high viscous oil flows were studied using OLGA flow simulator. A comparison between simulation results from the flow simulator and those of data acquired for high oil-gas viscosity experiments (i.e. for oil viscosity ranging from 0.7-5.0 Pa.s) for two phase flow parameters such liquid holdup and pressure gradient exhibited huge discrepancies and under prediction

    Study of High Viscous Multiphase Flow Using OLGA Flow Simulator

    Get PDF
    The continuous depletion of conventional reserves of the world oil and gas has spurred investigation towards the exploration and production from unconventional sources of hydrocarbons such as heavy oil. However, heavy oils are known for their high liquid viscosities making them even more difficult and expensive to produce and transport in pipelines at ambient temperatures. As a consequence of this, a critical understanding of multiphase flow characteristics is vital to aid engineering design it has become imperative to investigate the rheology of high viscosity oils and ways of enhancing its production and transportation. In this study, the characteristics of high viscous oil flows were studied using OLGA flow simulator. A comparison between simulation results from the flow simulator and those of data acquired for high oil-gas viscosity experiments (i.e. for oil viscosity ranging from 0.7-5.0 Pa.s) for two phase flow parameters such liquid holdup and pressure gradient exhibited huge discrepancies and under prediction.    Keywords— High viscosity oil, Liquid holdup, OLGA, Pressure gradien

    A programmed cell death pathway in the malaria parasite Plasmodium falciparum has general features of mammalian apoptosis but is mediated by clan CA cysteine proteases

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    Several recent discoveries of the hallmark features of programmed cell death (PCD) in Plasmodium falciparum have presented the possibility of revealing novel targets for antimalarial therapy. Using a combination of cell-based assays, flow cytometry and fluorescence microscopy, we detected features including mitochondrial dysregulation, activation of cysteine proteases and in situ DNA fragmentation in parasites induced with chloroquine (CQ) and staurosporine (ST). The use of the pan-caspase inhibitor, z-Val-Ala-Asp-fmk (zVAD), and the mitochondria outer membrane permeabilization (MOMP) inhibitor, 4-hydroxy-tamoxifen, enabled the characterization of a novel CQ-induced pathway linking cysteine protease activation to downstream mitochondrial dysregulation, amplified protease activity and DNA fragmentation. The PCD features were observed only at high (μM) concentrations of CQ. The use of a new synthetic coumarin-labeled chloroquine (CM-CQ) showed that these features may be associated with concentration-dependent differences in drug localization. By further using cysteine protease inhibitors z-Asp-Glu-Val-Asp-fmk (zDEVD), z-Phe-Ala-fmk (zFA), z-Phe-Phe-fmk (zFF), z-Leu-Leu-Leu-fmk (zLLL), E64d and CA-074, we were able to implicate clan CA cysteine proteases in CQ-mediated PCD. Finally, CQ induction of two CQ-resistant parasite strains, 7G8 and K1, reveals the existence of PCD features in these parasites, the extent of which was less than 3D7. The use of the chemoreversal agent verapamil implicates the parasite digestive vacuole in mediating CQ-induced PCD

    Biparental inheritance of plastidial and mitochondrial DNA and hybrid variegation in Pelargonium

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    Plastidial (pt) and mitochondrial (mt) genes usually show maternal inheritance. Non-Mendelian, biparental inheritance of plastids was first described by Baur (Z Indukt Abstamm Vererbungslehre 1:330–351, 1909) for crosses between Pelargonium cultivars. We have analyzed the inheritance of pt and mtDNA by examining the progeny from reciprocal crosses of Pelargoniumzonale and P. inquinans using nucleotide sequence polymorphisms of selected pt and mt genes. Sequence analysis of the progeny revealed biparental inheritance of both pt and mtDNA. Hybrid plants exhibited variegation: our data demonstrate that the inquinans chloroplasts, but not the zonale chloroplasts bleach out, presumably due to incompatibility of the former with the hybrid nuclear genome. Different distribution of maternal and paternal sequences could be observed in different sectors of the same leaf, in different leaves of the same plant, and in different plants indicating random segregation and sorting-out of maternal and paternal plastids and mitochondria in the hybrids. The substantial transmission of both maternal and paternal mitochondria to the progeny turns Pelargonium into a particular interesting subject for studies on the inheritance, segregation and recombination of mt genes
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