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Filling Factor (filling + factor)
Selected AbstractsESR detection of irradiated broad bean (Vicia faba L.) and kinetics of the radiation induced free radical and Mn2+ signalsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 6 2003Mustafa Polat Summary An ESR (Electron Spin Resonance) investigation on irradiated dry broad bean gave a spectrum which was composed of an equally spaced sextet and a single resonance line. These lines appeared at g = 2.0045 (±0.0005) and originated from Mn2+ ions and radiation induced radicals, respectively. Ground broad bean was used throughout the work to avoid any artefacts arising from a microwave cavity filling factor. Free radical signal intensity was observed to increase exponentially in relation to the increase in absorbed dose over the dose range 1.25,15 kGy. Although the Mn2+ signal increases below room temperature, the signal due to the natural and radiation induced radicals decreases. Above room temperature, they both decreased and these decreases were irreversible. The kinetics of these decreases were studied in detail over a temperature range of 308,373 K by annealing samples at different temperatures for various times. [source] Determination of twin-screw extruder operational conditions for the preparation of thermoplastic vulcanizates on the basis of batch-mixer resultsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008F. Goharpey Abstract In this study, we attempted to prepare a thermoplastic vulcanizate in a twin-screw extruder by determining the screw configuration on the basis of batch-mixer results. In this regard, two sets of information were used: (1) the time length, power consumption, and filling factor of different stages of the reactive blending process in the internal mixer and (2) the mean residence time and power consumption of the twin-screw extruder. Morphological features of the samples taken from the melt-mixing and dynamic vulcanization zones of the extruder with the selected screw configuration were found to be comparable with corresponding samples taken from an internal mixer reported in our previous study. The rheological and mechanical properties could provide valuable information to support the reliability of this study. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Evidence of Nearest-Neighbor Ordering in Wet-Processed Zirconia,Nickel CompositesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2001Carlos Pecharromán Monolithic zirconia,nickel (ZrO2/Ni) cermets have been prepared by a wet-processing method with nickel volume concentrations of 16%,40%. Microstructural analysis performed on scanning electron microscopy images has revealed evidence of a partial ordering of metallic particles inside the ceramic matrix. This ordering does not appear in mullite/molybdenum cermets. Complex impedance measurements have shown that the percolation threshold of ZrO2/Ni cermets appears at a filling factor (fc) of 0.34, exceeding the theoretical value (fc= 0.16), as a consequence of its microstructural order. Electrical measurements display the expected increase of capacity near the percolation threshold. These results open the possibility to design new devices with the appealing electric, magnetic, and mechanical properties that are predicted by the percolation theory. [source] Particle energies and filling fractions of radio bubbles in cluster coresMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2004R. J. H. Dunn ABSTRACT Using Chandra images of cluster cores with clear radio bubbles, we have determined k, which is the ratio of the total particle energy to that of the electrons radiating between 10 MHz and 10 GHz. Radiative and dynamical constraints on the bubbles indicate that the ratio of the energy factor, k, to the volume filling factor, f, lies within the range 1 ,k/f, 1000. Assuming pressure equilibrium between the radio-emitting plasma and the surrounding X-ray gas, none of the lobes has equipartition between relativistic particles and magnetic field. There is no evidence for any dependence of the upper limit of the k/f ratio on any physical parameter of the cluster or the radio source. The distribution of the upper limit on k/f appears to be bimodal, the value being ,3 for some clusters and ,300 for the others. We show that this may be due to the composition of the jet which forms the bubbles, the variation in the volume filling fraction or variation in the amount of reacceleration occurring in the bubble. [source] Spin-dependent electron tunnelling and spin relaxation in quantum dots in regime with filling factor of around twoPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 8 2007S. Tarucha Abstract Spin-dependent electron tunnelling and spin relaxation were studied for a quantum dot in the regime with a filling factor between two and four. In this regime, the electronic configuration of a quantum dot undergoes transitions between a spin singlet and triplet states for an even number of electrons, and between two doublet states for an odd number of electrons. These transitions were clearly distinguished by using quantum wires as spin filtering contact leads to the dot. In addition, the temporal behaviour of electron tunnelling was studied for a quantum dot in a similar filling factor regime, using a quantum point contact as a charge sensor. Electron tunnelling through the dot in a spin singlet state could be well distinguished from that in a triplet state using the fact that the tunnelling rate was much larger for the triplet state. The difference in the tunnelling rate was also used to derive a triplet-to-singlet-state relaxation time. The obtained relaxation time agreed fairly well with that predicted by the theory of spin-orbit interaction. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Magnetoresistance in dilute p-Si/SiGe in parallel and tilted magnetic fieldsANNALEN DER PHYSIK, Issue 12 2009I.L. Drichko Abstract We report the results of an experimental study of the magnetoresistance ,xx and ,xy in two samples of p-Si/SiGe with low carrier concentrations p = 8.2 × 1010 cm -2 and p = 2 × 1011 cm -2. The research was performed in the temperature range of 0.3,2 K and in the magnetic fields of up to 18 T, parallel or tilted with respect to the two-dimensional (2D) channel plane. The large in-plane magnetoresistance can be explained by the influence of the in-plane magnetic field on the orbital motion of the charge carriers in the quasi-2D system. The measurements of ,xx and ,xy in the tilted magnetic field showed that the anomaly in ,xx, observed at filling factor , = 3/2 is practically nonexistent in the conductivity ,xx. The anomaly in ,xx at , = 2 might be explained by overlapping of the levels with different spins 0 , and 1 , when the tilt angle of the applied magnetic field is changed. The dependence of g-factor g*(,)/g*(00) on the tilt angle , was determined. [source] Localised magneto-optical collective excitations of impure grapheneANNALEN DER PHYSIK, Issue 12 2009A.M. Fischer Abstract We study optically-induced collective excitations of graphene in the presence of a strong perpendicular magnetic field and a single impurity. We determine the energies and absorption strengths of these excitations, which become localised on the impurity. Two different types of impurity are considered i. the long-range Coulomb impurity, ii. a ,-function impurity located at either an A or B graphene sublattice site. Both impurity types result in some bound states appearing both above and below the magnetoplasmon continuum, although the effect of the short-range impurity is less pronounced. The dependence of the energies and oscillator strengths of the bound states on the filling factor is investigated. [source] Chandra ACIS Imaging Spectroscopy of Sgr A EastASTRONOMISCHE NACHRICHTEN, Issue S1 2003Y. Maeda Abstract We report on the X-ray emission from the shell-like, non-thermal radio source Sgr A East located in the inner few parsecs of the Galaxy based on observations made with the ACIS detector on board the Chandra X-ray Observatory. The X-ray emission from Sgr A East is concentrated within the central ,2 pc of the larger radio shell. The spectrum shows strong K, lines from highly ionized ions of S, Ar, Ca, and Fe. A simple isothermal plasma model gives electron temperature ,2 keV, absorption column ,1 × 1023 H cm,2, luminosity ,8 × 1034 ergs s,1 in the 2,10 keV band, and gas mass ,2,˝ M, with a filling factor ,. The plasma appears to be rich in heavy elements, over-abundant by roughly a factor of four with respect to solar abundances. Accompanied with filamentary or blob-like structures, the plasma shows a spatial gradient of elemental abundance: the spatial distribution of iron is more compact than that of the lighter elements. These Chandra results strongly support the long-standing hypothesis that Sgr A East is a supernova remnant (SNR). Since Sgr A East surrounds Sgr A* in projection, it is possible that the dust ridge compressed by the forward shock of Sgr A East hit Sgr A* in the past, and the passage of the ridge may have supplied material to accrete onto the black hole in the past, and may have removed material from the black hole vicinity, leading to its present quiescent state. [source] Radio constraints on the volume filling factors of AGN windsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2009A. J. Blustin ABSTRACT The calculation of mass outflow rates of active galactic nuclei (AGN) winds is of great importance in understanding the role that such winds play in AGN-galaxy feedback processes. The mass outflow rates are, however, difficult to estimate since the volume filling factors of the winds are unknown. In this paper, we use constraints imposed by the observed radio emission to obtain upper limits to the volume filling factors of wind components in certain nearby AGN. We do this by predicting the 1.4 GHz radio flux densities emitted by those components, assuming a uniform wind, and then comparing these with the observed flux densities for each AGN at this frequency. We find that the upper limits to the volume filling factors are in the range of 10,4,0.5. [source] Cosmological simulations of intergalactic medium enrichment from galactic outflowsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Benjamin D. Oppenheimer ABSTRACT We investigate models of self-consistent chemical enrichment of the intergalactic medium (IGM) from z= 6.0 , 1.5, based on hydrodynamic simulations of structure formation that explicitly incorporate outflows from star-forming galaxies. Our main result is that outflow parametrizations derived from observations of local starburst galaxies, in particular momentum-driven wind scenarios, provide the best agreement with observations of C iv absorption at z, 2,5. Such models sufficiently enrich the high- z IGM to produce a global mass density of C iv absorbers that is relatively invariant from z= 5.5 , 1.5, in agreement with observations. This occurs despite continual IGM enrichment causing an increase in volume-averaged metallicity by ,× 5,10 over this redshift range, because energy input accompanying the enriching outflows causes a drop in the global ionization fraction of C iv. Comparisons to observed C iv column density and linewidth distributions and C iv -based pixel optical depth ratios provide significant constraints on wind models. Our best-fitting outflow models show mean IGM temperatures only slightly above our no-outflow case, metal filling factors of just a few per cent with volume-weighted metallicities around 10,3 at z, 3, significant amounts of collisionally ionized C iv absorption and a metallicity,density relationship that rises rapidly at low overdensities and flattens at higher ones. In general, we find that outflow speeds must be high enough to enrich the low-density IGM at early times but low enough not to overheat it, and concurrently must significantly suppress early star formation while still producing enough early metals. It is therefore non-trivial that locally calibrated momentum-driven wind scenarios naturally yield the desired strength and evolution of outflows, and suggest that such models represent a significant step towards understanding the impact of galactic outflows on galaxies and the IGM across cosmic time. [source] Transport mechanism in the quantum well embedded with quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2009E. S. Kannan Abstract Electron transport in single and double quantum well system embedded with InAs quantum dots is investigated by carrying out magnetoresistance measurements at 1.2 K. At low carrier densities, the electrons are strongly localized due to disorder and undergo magnetic field induced insulator to quantum Hall liquid transitions characterized by temperature independent crossing points. At higher carrier densities no such magnetic field induced transition are observed. The potential induced by the electrons in the quantum dots were found to enhance the scattering between the edge states resulting in the substantial reduction of the width of the Hall plateau in the single quantum well system. In the double quantum well system, instead of plateaus abrupt increase in the Hall resistance is observed at integer filling factors. On sweeping the gate bias at fixed magnetic field, hysteresis effect was observed in the double quantum well system due to the charge trapping in the defect levels. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Epitaxial lateral overgrowth of GaN on 4 inch Si(111) by MOVPEPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008Kai Cheng Abstract Epitaxial Lateral Overgrowth (ELOG) of GaN on 4 inch silicon(111) substrates by MOVPE was investigated in this study. ELOG was performed on a GaN template with a couple of AlGaN intermediate layers (IL) on an AlN nucleation layer. The AlGaN ILs supply compressive stress to the top GaN template and thereafter to the ELOG layer. Consequently, layer cracking is minimized. Two masks were used in this work: a 2 inch wagon wheel mask and a 4 inch mask with parallel stripes of various filling factors and periods. The filling factor is varied from 0.33 to 0.7. The periodic spacing is in the range of 6 ,m to 10 ,m. Temperature, V/III ratio, pressure and stripe orientation were optimized to achieve fastest lateral growth rate. The highest lateral to vertical ratio can be more than 4. A fully coalesced layer within the critical thickness for a crack-free layer was achieved on 4 inch silicon substrates. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hopping magnetoresistance in two-dimensional arrays of Ge/Si quantum dotsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 2 2006A. I. Yakimov Abstract The temperature and magnetic field dependences of the conductivity associated with hopping transport of holes over 2D arrays of Ge/Si quantum dots with various filling factors are studied experimentally. A transition from the Efros-Shklovskii law for the temperature dependence of hopping conductivity to the Arrhenius law with an activation energy equal to 1.0-1.2 meV is observed upon a decrease in temperature. The activation energy for the low-temperature conductivity increases with the magnetic field and attains saturation in fields exceeding 4 T. It is found that the magnetoresistance in layers of quantum dots is essentially anisotropic: the conductivity decreases in magnetic fields oriented perpendicular to a dot layer and increases in a field whose vector lies in the plane of the sample. The absolute values of magnetoresistance for transverse and longitudinal field orientations differ by two orders of magnitude. Effect of spin correlations on the hopping magnetoresistance is discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Light-curve inversions with truncated least-squares principal components: Tests and application to HD 291095 = V1355 OrionisASTRONOMISCHE NACHRICHTEN, Issue 4 2008I.S. Savanov Abstract We present a new inversion code that reconstructs the stellar surface spot configuration from the light curve of a rotating star. Our code employs a method that uses the truncated least-squares estimation of the inverse problem's objects principal components. We use spot filling factors as the unknown objects. Various test cases that represent a rapidly-rotating K subgiant are used for the forward problem. Tests are then performed to recover the artificial input map and include data errors and input-parameter errors. We demonstrate the robustness of the solution to false input parameters like photospheric temperature, spot temperature, gravity, inclination, unspotted brightness and different spot distributions and we also demonstrate the insensitivity of the solution to spot latitude. Tests with spots peppered over the entire stellar surface or with phase gaps do not produce fake active longitudes. The code is then applied to ten years of V and I -band light curve data of the spotted sub-giant HD291095. A total of 22 light curves is presented. We find that for most of the time its spots were grouped around two active longitudes separated on average by 180°. Switches of the dominant active region between these two longitudes likely occurred about every 3.15±0.23 years while the amplitude modulation of the brightness occurred with a possible period of 3.0±0.15 years. For the first time, we found evidence that the times of the activity flips coincide with times of minimum light as well as minimum photometric amplitude, i.e. maximum spottedness. From a comparison with simultaneous Doppler images we conclude that the activity flips likely take place near the rotational pole of the star. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Calculation of the Evolution of Surface Area and Free Volume During the Infiltration of Fiber Felts,CHEMICAL VAPOR DEPOSITION, Issue 12 2007A. Pfrang Abstract The evolution of surface area and free volume during the infiltration of fiber felts is calculated quantitatively and compared with experimental data. For overlapping fibers the evolution is approximated by a Boolean model, where the ratio of surface area to free volume increases linearly with the radius of the fibers. For randomly distributed fibers which do not overlap in the initial state, the evolution of surface area and free volume is calculated numerically. The surface area/free volume ratio increases nearly linearly for all initial filling factors and for all degrees of orientation anisotropy of the fibers. [source] | |||||||||||||||||||||||||