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Flux Ratio (flux + ratio)
Selected AbstractsEffectiveness of very thin soil layers in chemical release from bed sedimentENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2001Bryan Talbert The chemical containment effectiveness of both the natural recovery and the "particle broadcasting" processes for remediating contaminated bed-sediments depend upon very thin soil and/or sand layers millimeters in depth. Conventional capping for in situ chemical containment of bed-sediment or dredged material typically involves thick layers of 30 to 90 centimeters in depth. Few studies have been conducted with thin layers of candidate natural materials. A steady-state benzoic acid dissolution test apparatus and procedure, devised to realistically simulate bed-sediment chemo-dynamic conditions, was used to measure chemical flux through thin layers (1 to 8 mm) of soil, sand, and ideal porous media. The thin layers were found to be very effective. Flux reductions ranged from 81 to 96%, with fine sand being slightly better than top soil. Design algorithms developed for the thick layers used in conventional capping design will under predict the flux through very thin layers. Advective flow induced by surface roughness is proposed to explain the higher average measure d-to-predicted flux ratio of 1.67. [source] The XMM,Newton Needles in the Haystack Survey: the local X-ray luminosity function of ,normal' galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2005I. Georgantopoulos ABSTRACT In this paper we estimate the local (z < 0.22) X-ray luminosity function of ,normal' galaxies derived from the XMM,Newton Needles in the Haystack Survey. This is an on-going project that aims to identify X-ray-selected normal galaxies (i.e. non-AGN dominated) in the local Universe. We are using a total of 70 XMM,Newton fields covering an area of 11 deg2 which overlap with the Sloan Digital Sky Survey Data Release 2. Normal galaxies are selected on the basis of their resolved optical light profile, their low X-ray-to-optical flux ratio [log (fx/fo) < , 2] and soft X-ray colours. We find a total of 28 candidate normal galaxies to the 0.5,8 keV band flux limit of ,2 × 10,15 erg cm,2 s,1. Optical spectra are available for most sources in our sample (82 per cent). These provide additional evidence that our sources are bona fide normal galaxies with X-ray emission coming from diffuse hot gas emission and/or X-ray binaries rather than a supermassive black hole. 16 of our galaxies have narrow emission lines or a late-type spectral energy distribution (SED) while the remaining 12 present only absorption lines or an early-type SED. Combining our XMM,Newton sample with 18 local (z < 0.22) galaxies from the Chandra Deep Field North and South surveys, we construct the local X-ray luminosity function of normal galaxies. This can be represented with a Schechter form with a break at L,, 3+1.4,1.0× 1041 erg s,1 and a slope of ,, 1.78 ± 0.12. Using this luminosity function and assuming pure luminosity evolution of the form ,(1 +z)3.3 we estimate a contribution to the X-ray background from normal galaxies of ,10,20 per cent (0.5,8 keV). Finally, we derive, for the first time, the luminosity functions for early- and late-type systems separately. [source] The SCUBA Local Universe Galaxy Survey , II.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2001m data: evidence for cold dust in bright IRAS galaxies This is the second in a series of papers presenting results from the SCUBA Local Universe Galaxy Survey. In our first paper we provided 850-,m flux densities for 104 galaxies selected from the IRAS Bright Galaxy Sample and we found that the 60-, 100-,m (IRAS) and 850-,m (SCUBA) fluxes could be adequately fitted by emission from dust at a single temperature. In this paper we present 450-,m data for the galaxies. With the new data, the spectral energy distributions of the galaxies can no longer be fitted with an isothermal dust model , two temperature components are now required. Using our 450-,m data and fluxes from the literature, we find that the 450/850-,m flux ratio for the galaxies is remarkably constant, and this holds from objects in which the star formation rate is similar to our own Galaxy, to ultraluminous infrared galaxies (ULIRGs) such as Arp 220. The only possible explanation for this is if the dust emissivity index for all of the galaxies is ,2 and the cold dust component has a similar temperature in all galaxies . The 60-,m luminosities of the galaxies were found to depend on both the dust mass and the relative amount of energy in the warm component, with a tendency for the temperature effects to dominate at the highest L60. The dust masses estimated using the new temperatures are higher by a factor of ,2 than those determined previously using a single temperature. This brings the gas-to-dust ratios of the IRAS galaxies into agreement with those of the Milky Way and other spiral galaxies which have been intensively studied in the submm. [source] Structural evolution of ZnO films deposited by rf magnetron sputtering on glass substratePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2010Yan-Ping Liao Abstract Influences of O2/Ar flux ratio (R) on surface morphology and structural evolution have been studied in the case of ZnO films deposited on glass substrates by radio-frequency (rf) magnetron sputtering. Results of atomic force microscopy (AFM), X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) clearly indicate that the surface root-mean-square (rms) roughness, crystallinity, stress, and defects strongly depend on the R. At R,=,1/2, the crystallized ZnO film with highly c -axis orientation and highly smooth surface has been obtained. The implication of these results is that a moderate R is needed to realize high-quality ZnO film. [source] High-quality ZnO epilayers grown on Zn-polar ZnO substrates by plasma-assisted molecular beam epitaxyPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2004Hiroyuki Kato Abstract High-quality ZnO epilayers have been grown on Zn-polar ZnO substrates by plasma-assisted molecular beam epitaxy. With increasing O/Zn flux ratio from the stoichiometric to the O-rich, the growth mode changed from three- to two-dimensional growth and the line widths of (0002) and (10,10) ,-rocking curves showed dramatic narrowing from 471 to 42 arsec and from 1635 to 46 arcsec, respectively. These values are narrower compared to those of ZnO on sapphire and also those of device-grade MOCVD-grown GaN. Moreover, A-, B-excitons (FEA, FEB), and the n = 2 state of FEA at 3.378, 3.393, and 3.424 eV, respectively, were clearly observed in the low-temperature (4.2 K) photoluminescence spectrum of ZnO grown under O-rich flux conditions. Our results show that growth under high O-rich flux conditions is required to produce high-quality Zn-polar ZnO films. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Comparison of deep level incorporation in ammonia and rf-plasma assisted molecular beam epitaxy n-GaN filmsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2008A. R. Arehart Abstract The use of rf-plasma and ammonia nitrogen sources for growth of GaN films by molecular beam epitaxy (MBE) are compared in terms of defect incorporation using deep level optical spectroscopy (DLOS) and deep level transient spectroscopy (DLTS). To better improve the understanding of ammonia-based MBE growth of GaN and potential defect sources as opposed to the more studied plasma source-based MBE-grown material several V/III ratios were also investigated, which were generated via systematic adjustment of the ammonia flow rates during growth. The DLOS spectra, comparing deep traps within the n-GaN grown using N-plasma and ammonia sources, reveal the presence of the same deep levels due to background carbon and gallium vacancies, with energy levels at EC -3.28, EC -2.62, and EC -1.28. The DLTS results of the N-plasma and ammonia-based MBE samples show two similarly dominant electron traps at EC -0.60, and EC -0.24 in each sample. Measurements made as a function of V/III flux ratio for ammonia-based MBE growth indicate a large dependence of the EC -0.24 eV trap concentration on growth flux ratio, which is significant for guiding continued optimization of this promising MBE growth method for GaN devices. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterization of MBE grown ZnO on GaAs(111) substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2006Takashi Matsumoto Abstract ZnO epitaxial layers grown on GaAs(111)B substrates by plasma assisted MBE with different O/Zn flux ratios are characterized by photoluminescence (PL), X-ray diffraction (XRD) , ,2, scan, , scan, and reciprocal lattice mapping. Low temperature PL spectra are dominated by bound exciton bands at 3.360 eV and 3.330 eV. The 3.360 eV band is strong in samples grown under Zn-rich cindition and the 3.330 eV band is strong in samples grown under O-rich condition. The epitaxial orientation relationship is ZnO(0001)//GaAs(111) and ZnO[11-20]//GaAs [01-1] irrespective of the O/Zn flux ratio. The ZnO c-axis tilts by 0.2° , 0.3° from the GaAs [111] axis toward ,1-10, or ,2-1-1, direction. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Effects of V/III flux ratio on AlInGaN/AlGaN quantum wells grown by atmospheric pressure MOCVDPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7 2005R. J. Choi Abstract We investigated the structural and optical properties of AlInGaN/AlGaN quantum wells (QWs) and the quaternary AlInGaN epilayers as a function of V/III flux ratio (flow rate of NH3). From the photoluminescence and cathodoluminescence (CL) measurements, the emission wavelengths of the AlInGaN/AlGaN QWs linearly became blueshifted and the intensities decreased with increasing the flow rate of NH3. In the X-ray rocking curve, a pattern of the sample grown at lower NH3 flow rate gives an indication of the good crystalline quality of the films. The monochromated scanning CL image of the AlInGaN epilayers measured at around 80 K showed that more densely and uniformly distributed bright spot densities, indicating In segregation regions, increased at lower NH3 flow rate. Therefore, these results suggest that the relatively decrease of NH3 flow rate results in the increase of In composition fluctuations into the AlInGaN alloys, which generate exciton localized states, and thereby enhances the emission. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Surface Modification of Poly(propylene) Microporous Membrane to Improve Its Antifouling Characteristics in an SMBR: O2 Plasma TreatmentPLASMA PROCESSES AND POLYMERS, Issue 1 2008Hai-Yin Yu Abstract Fouling is the major obstacle in membrane processes applied in water and wastewater treatment. To improve the antifouling characteristics of PPHFMMs in an SMBR for wastewater treatment, the PPHFMMs were surface-modified by O2 low temperature plasma treatment. Structural and morphological changes on the membrane surface were characterized by XPS and FE-SEM. The change of surface wettability was monitored by contact angle measurements. Results of XPS clearly indicated that the plasma treatment introduced oxygen containing polar groups on the membrane surface. The static water contact angle of the modified membrane reduced obviously with the increase of plasma treatment time. The relative pure water flux for the modified membranes increased with plasma treatment time up to 1 min, then it decreased with further increase of plasma treatment time. Decreases in the tensile strength and the tensile elongation at break of the modified membranes were also observed. To assess the relation between the plasma treatment and the membrane fouling in an SMBR, filtration for activated sludge was carried out by using synthetic wastewater. After continuous operation in the SMBR for about 75 h, flux recovery were 8.7 and 12.3%, reduction of flux were 91.6 and 87.4% for the nascent and O2 plasma treated PPHFMM for 1 min, relative flux ratio for O2 plasma treated PPHFMM for 1 min was 49.9% higher than that of the nascent PPHFMM. [source] Dual isotope and isotopomer ratios of N2O emitted from a temperate grassland soil after fertiliser applicationRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 22 2003R. Bol The N2O and N2 fluxes emitted from a temperate UK grassland soil after fertiliser application (equivalent to 25 and 75,kg N ha,1) were simultaneously measured, using a new automated soil incubation system, which replaces soil atmosphere (N2 dominated) with a He+O2 mixture. Dual isotope and isotopomer ratios of the emitted N2O were also determined. Total N2O and N2 fluxes were significantly lower (P,<,0.001) in the control (0,kg N) than in the 25 and 75,kg N treatments. The total N2O flux was significantly higher (P,<,0.001) in the 75,kg N than in the 25,kg N treatment. The general patterns of N2O and N2 fluxes were similar for both fertiliser treatments. The total gaseous N loss in the control treatment was nearly all N2, whereas in the fertiliser treatment more N2O than N2 was emitted from the soil. The ratio N2O/N2 fluxes as measured during the experiment suggested three phases in N2O production, in phase 1 nitrification > denitrification, in phase 2 denitrification,>,nitrification, and in phase 3 denitrification (and total denitrification),,,nitrification. Dual ,15N and ,18O isotope and isotopomer (,15N, and ,15N,) value ratios of emitted N2O also pointed towards an increasing dominance of the production of N2O by denitrification and total denitrification. The site preference value from the soil-emitted N2O was lower than the troposphere value. This confirmed that the enhanced troposphere N2O site preference could result from back injection of N2O from the stratosphere. The measurements of N2O/N2 flux ratio and the isotopic content of emitted N2O pointed, independently, to similar temporal trends in N2O production processes after fertiliser application to grassland soil. This confirmed that both measurements are suitable diagnostic tools to study the N2O production process in soils. Copyright © 2003 John Wiley & Sons, Ltd. [source] Metabolic Control Analysis of Monoclonal Antibody SynthesisBIOTECHNOLOGY PROGRESS, Issue 2 2001Ramon Gonzalez A general route for protein synthesis in eukaryotic cells has been proposed and applied to monoclonal antibody (MAb) synthesis. It takes into account transcription of the gene, binding of ribosomes to mRNA, and polypeptide elongation including binding to SRP (signal recognition particles) and SRP-receptor, competing translocation, folding and glycosylation, assembly of the heavy and light chains in a tetrameric protein and Golgi processing and secretion. A comprehensive model was built on the basis of the proposed pathway. The model takes into account the mechanism of each step. Metabolic control analysis (MCA) principles were applied to the general pathway using the proposed model, and control coefficients were calculated. The results show a shared flux control (of both pathway flux and flux ratio at the branch) among different steps, i.e., transcription, folding, glycosylation, translocation and building blocks synthesis. The steps sharing the control depend on the concentration of building blocks, pathway flux and levels of OST (oligosacharyl transferase), BiP (heavy chain binding protein) and PDI (protein disulfide isomerase). Model predictions compare well with experimental data for MAb synthesis, explaining the control structure of the route and the heterogeneity of the product and also addressing future targets for improvement of the production rate of MAbs. [source] Radial distribution and strong lensing statistics of satellite galaxies and substructure using high-resolution ,CDM hydrodynamical simulationsMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006Andrea V. Macciò ABSTRACT We analyse the number density and radial distribution of substructures and satellite galaxies using cosmological simulations that follow the gas dynamics of a baryonic component, including shock heating, radiative cooling and star formation within the hierarchical concordance Lambda cold dark matter model. We find that the dissipation of the baryons greatly enhances the survival of subhaloes, especially in the galaxy core, resulting in a radial distribution of satellite galaxies that closely follows the overall mass distribution. Hydrodynamical simulations are necessary to resolve the adiabatic contraction and dense cores of galaxies, resulting in a total number of satellites a factor of 2 larger than that found in pure dark matter simulation, in good agreement with the observed spatial distribution of satellite galaxies within galaxies and clusters. Convergence tests show that the cored distribution found by previous authors in pure N -body simulations was due to the physical overmerging of dark matter only structures. We proceed to use a ray-shooting technique in order to study the impact of these additional substructures on the number of violations of the cusp caustic magnification relation. We develop a new approach to try to disentangle the effect of substructures from the intrinsic discreteness of N -body simulations. Even with the increased number of substructures in the centres of galaxies, we are not able to reproduce the observed high numbers of discrepancies observed in the flux ratios of multiply lensed quasars. [source] Prospects for spectroscopic reflected-light planet searchesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2003Christopher Leigh ABSTRACT High-resolution spectroscopic searches for the starlight reflected from close-in extrasolar giant planets have the capability of determining the optical albedo spectra and scattering properties of these objects. When combined with radial velocity measurements they also yield the true mass of the planet. To date, only two such planets have been targeted for reflected-light signals, yielding upper limits on the optical albedos of the planets. Here we examine the prospects for future searches of this kind. We present Monte Carlo estimates of prior probability distributions for the orbital velocity amplitudes and planet/star flux ratios of six bright stars known to harbour giant planets in orbits with periods of less than 5 d. Using these estimates, we assess the viability of these targets for future reflected-light searches using 4- and 8-m class telescopes. [source] The dark halo of the main lens galaxy in QSO 0957 + 561MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2005L. J. Goicoechea ABSTRACT We present an analysis of infrared/optical/ultraviolet spectra of the two images of the first gravitationally lensed quasar Q0957 + 561A,B. The Hubble Space Telescope observations of Q0957 + 561A and Q0957 + 561B are separated in time by the known time delay in this system, so we can directly deduce the flux ratios. These flux ratios of images lead to important information on the dark halo of the main lens galaxy (a giant elliptical at redshift z= 0.36). Our measurements for the continuum are in good agreement with extinction in the elliptical galaxy and a small fraction of mass in collapsed objects (no need for gravitational microlensing). From the continuum and emission-line ratios, we also show evidence in favour of the existence of a network of compact dusty clouds. [source] Growth kinetics of AlxGa1,xN layers (0 < x < 1) in plasma-assisted molecular beam epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 7-8 2010A. M. Mizerov Abstract Comparative study of growth kinetics of the AlxGa1-xN (x = 0-1) layers of different polarity, grown by plasma assisted molecular beam epitaxy (PA MBE) under different growth conditions (substrate temperature, group III to activated nitrogen and Al to Ga flux ratios) and on different buffer layers, is presented. The 60 °C higher temperature stability of N-face AlGaN layers is detected. The strong influence of elastic stress on growth kinetics of metal-polar AlxGa1-xN (x > 0.2) layers is observed and discussed. It was found that two-dimensional growth of AlGaN films of the same composition on different buffer layers at TS = 700 °C can be achieved at different group III surface enrichment, the AlGaN(0001)/c-Al2O3 films exhibiting the atomically smooth surface at group III to activated nitrogen flux ratio FIII/FN *gradually increased from 1.3 to 2 with the x variation from 0.1 to 0.8. In this case the alloy composition is controlled by the variation of Al flux only (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Real time spectroscopic ellipsometry investigation of homoepitaxial GaN grown by plasma assisted molecular beam epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2006Tong-Ho Kim Abstract The growth of GaN by plasma assisted molecular beam epitaxy on GaN template substrates (GaN on sapphire) is investigated with in-situ multi-channel spectroscopic ellipsometry. Growth is performed under various Ga/N flux ratios at growth temperatures in the range 710,780 °C. The thermal roughening of the GaN template caused by decomposition of the surface is investigated through the termporal variation of the GaN pseudodielectric function over the temperature range of 650 °C to 850 °C. The structural, morphological, and optical properties are also discussed. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Characterization of MBE grown ZnO on GaAs(111) substratesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2006Takashi Matsumoto Abstract ZnO epitaxial layers grown on GaAs(111)B substrates by plasma assisted MBE with different O/Zn flux ratios are characterized by photoluminescence (PL), X-ray diffraction (XRD) , ,2, scan, , scan, and reciprocal lattice mapping. Low temperature PL spectra are dominated by bound exciton bands at 3.360 eV and 3.330 eV. The 3.360 eV band is strong in samples grown under Zn-rich cindition and the 3.330 eV band is strong in samples grown under O-rich condition. The epitaxial orientation relationship is ZnO(0001)//GaAs(111) and ZnO[11-20]//GaAs [01-1] irrespective of the O/Zn flux ratio. The ZnO c-axis tilts by 0.2° , 0.3° from the GaAs [111] axis toward ,1-10, or ,2-1-1, direction. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hard X,ray observations of Extremely Red ObjectsASTRONOMISCHE NACHRICHTEN, Issue 1-2 2003M. Brusa Abstract Extremely Red Objects (EROs, R,K>5) constitute a heterogeneous class of extragalactic sources including high redshift elliptical galaxies, dusty star,forming systems and heavily obscured AGNs. Hard X-ray observations provide an unique and powerful tool to uncover obscured nuclear or star,forming activity. We present the results of XMM,Newton observations of the largest sample of EROs available to date (about 450 objects over a contiguous area of 700 arcmin2). Five of the 46 hard X,ray selected sources brighter than 3 × 10,15 cgs in the 2,10 keV band, are associated with EROs. All of the X-ray detected EROs show rather extreme X,ray,to,optical flux ratios, suggesting the presence of highly obscured AGN activity. We also report on the X,ray stacking analysis of spectroscopically identified EROs in the Chandra Deep Field South. [source] Percutaneous permeation of enantiomers and racemates of chiral drugs and prediction of their flux ratios using thermal data: A pharmaceutical perspectiveCHIRALITY, Issue 5 2003Mohsen I. Afouna Abstract Albeit pharmacological, pharmacokinetic, and toxicological differences between enantiomeric pairs or between the pure enantiomers and racemate of chiral drugs are known to exist for decades, we are just beginning to realize that there are apparent differences between these species with respect to their percutaneous permeation as well. Such differences in permeation are likely to be enhanced when chiral drugs are formulated with chiral excipients, necessitating a careful assessment of the effect of formulation excipients on the permeation as well as the overall therapeutic outcomes. The in vitro transport data from the preclinical investigations, using laboratory animal models and/or in vitro cell culture systems, must be carefully validated in vivo as there are differences between these models and the human skin. Mathematical models such as MTMT that utilize the interdependence of certain physicochemical characteristics and percutaneous permeability have a predictive value in assessing the flux behavior of enantiomers and racemates. Chirality 15:456,465, 2003. © 2003 Wiley-Liss, Inc. [source] Flux growth of straw-like rutile monocrystalsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2008A. Bloise Abstract Millimetric straw-like rutile monocrystals were grown by the flux growth technique. A suitable mixture of flux (MoO3, V2O5, Li2CO3) and amorphous TiO2 gel was slowly cooled down to 750°C from 1250°C or 1350°C. The best yields of straw-like rutile were obtained with a nutrient/flux ratio and a cooling rate in the range 0.015-0.006 and 1.8-1.9 K h -1, respectively. The hollowed crystals were characterized by powder and single-crystal X-ray diffraction, scanning electron microscopy, microthermometry, and µ-Raman spectroscopy. As for skeletal crystal, the formation of axial canals in rutile is attributed to a lack of nutrient due to the viscosity of the melt and the high growth rate along [001]. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] |