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Clear Dependence (clear + dependence)
Selected AbstractsBacterial community structure of glacier forefields on siliceous and calcareous bedrockEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2009A. Lazzaro Summary Forefields of retreating glaciers represent unique opportunities to investigate the initial phases of soil formation and microbial interactions with mineral surfaces. An open question concerns the physical and chemical driving-factors affecting the establishment of microbial communities in these young ecosystems. In this study we compared the bacterial community structure of six glacier forefield soils belonging to two contrasting bedrock categories (calcareous and siliceous) through T-RFLP profiling of the 16S rRNA gene. The community profiles were correlated with an array of physical (soil texture, water holding capacity, hours of sunshine, temperature, rainfall and exposure) and chemical (TC, TN, DOC, extractable nutrients and pH) factors using canonical correspondence analysis (CCA). A first comparison of the T-RFLP profiles suggested that the degree of operational taxonomic unit (OTU) diversity of these soils was similar, and that community structure was dominated by ubiquitous taxa. CCA showed that both physical (e.g. hours of sunshine or rainfall) and chemical factors (e.g. SO2,4 or PO3,4) played an equal role in shaping the soil bacterial communities. OTUs unique to specific sites appeared to be strongly influenced by the climatic regime and by texture. Overall, the community structure of the six glacial forefields showed no clear dependence on the bedrock categories. [source] Characterization of the combustion products in large-scale fire tests: comparison of three experimental configurationsFIRE AND MATERIALS, Issue 2 2001Per Blomqvist The storage of large amounts of polymers and other bulk chemicals is a potential hazard in the case of fire. There is at present a lack of knowledge about the implications of such fires. In particular the role of the ventilation conditions on fire chemistry has warranted investigation. A set of indoor, large-scale combustion experiments, conducted on five different materials is described in this article. The main test series was conducted using the ISO 9705 room, where both well-ventilated and under-ventilated conditions were attained by restricting the opening of the room. The degree of ventilation was determined using a phi meter. Furthermore, in addition to measuring the traditional fire-related parameters, extensive chemical characterization of the combustion products was made. Two additional series of experiments were also performed. In one series of tests the size of the enclosure was increased and the fuel was placed in a storage configuration to simulate a real storage situation. In the other test series, three of the materials were tested as large-scale open pool fires. The results from the three configurations are compared regarding yields of combustion products as a function of the degree of ventilation. For a number of toxic combustion products a clear dependence of the production on the equivalence ratio was found. Further, placing the fuel in a storage configuration did not significantly change the outcome of the combustion. Thus, the ISO 9705 room is of a size and scale that can be taken as a model for representing real-scale fires. Additionally it has been demonstrated that an advantage of the ISO 9705 room is the ability to alter the ventilation conditions. Copyright © 2001 John Wiley & Sons, Ltd. [source] Air temperature effect on spray evaporation in sprinkler irrigation,IRRIGATION AND DRAINAGE, Issue 4 2002Dr Giulio Lorenzini évaporation aérienne; irrigation par arroseur; équipement expérimental Abstract The temperature effect of the surrounding environment on mean steady aerial water evaporation in sprinkler irrigation is investigated. An experimental set-up was designed and built to work at opportune operating conditions holding all the other variables constant to minimise the experimental error. One hundred and thirty-seven tests were performed for this work, of which 81 were considered valid for a statistical analysis of the data measured. Evaporation ranged from 4.15 to 7.73% as the air temperature varied from 21.0 to 27.0° C. Results show a clear dependence of sprinkler water evaporation on air temperature with a logarithmic relation. Further investigations will examine broader temperature intervals to improve the assessment and will consider the effects due to other parameters affecting the phenomenon. Copyright © 2002 John Wiley & Sons, Ltd. Résumé Les effets de la température de l'environnement sur l'irrigation par arroseur ont été examinés. Un eq,uipement expérimental a été conçu et créé pour fonctionner dans des conditions d'emploi propices, et on a travaillé aussi pour tenir les autres variables le plus possible constantes pour minimiser l'erreur expérimentale. On a réalisé 137 tests et seulement 81 ont été considérés bons pour l'analyse statistique. On a vu que l'évaporation change de 4.15 à 7.73 pour cent avec le changement de température de 21.0 à 27.0° C. Les résultats montrent une claire dépendance logarithmique de l'évaporation avec la température de l'air. On propose dans le futur d'étendre l'intervalle des températures pour confirmer les résultats déjà vus et aussi de tester les influences d'autres variables d'intérêt pour ce phénomène. Copyright © 2002 John Wiley & Sons, Ltd. [source] Mesomixing in semi-batch reaction crystallization and influence of reactor sizeAICHE JOURNAL, Issue 12 2004Marika Torbacke Abstract Experiments on semibatch reaction crystallization of benzoic acid are reported, in which hydrochloric acid was fed into an agitated solution of sodium benzoate. The influence of mixing and the influence of reactor size are examined on the product crystal mean size. The product mean size increases with increasing stirring rate and with decreasing feed rate. At low feed rates, the mean size increases at decreasing feed pipe diameter. At high feed rates the influence of the feed pipe diameter is more complex. Micromixing is of some importance in most experiments, but the rate of mesomixing especially governs the process. Mesomixing seems to be adequately described by the inertial-convective disintegration mechanism. In many aspects experimental results cannot be described by the turbulent-dispersion mechanism. The product mean size does not exhibit a clear dependence on reactor size, but depends more strongly on other parameters. Results from experiments from 1 L scale to 200 L scale can be correlated fairly well against a dimensionless number defined as the ratio of the total time of reactant feeding to the time constant of mixing. The best representation of the mixing time constant is obtained by making it directly proportional to the ratio of the feed pipe diameter and the linear velocity of the bulk flow passing the feed pipe. The proportionality constant can be calculated from turbulence data over the bulk flow at the feed point. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3107,3119, 2004 [source] Dose dependence of radiation damage for protein crystals studied at various X-ray energiesJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2007Nobutaka Shimizu Radiation damage to protein crystals is the most serious problem in obtaining accurate structures from protein crystallography. In order to examine the photon energy dependence of radiation damage, 12 to 15 data sets from each of nine tetragonal lysozyme crystals were collected at nine different X-ray energies (6.5, 7.1, 8.3, 9.9, 12.4, 16.5, 20.0, 24.8 and 33.0,keV) using beamline BL41XU at SPring-8. All results were compared on the basis of absorbed dose, expressed in Gray (Gy). Crystallographic statistics, such as the values of lattice constants, Rmerge and I/,(I), for each data set degraded at all nine energies as the exposure time for each crystal increased. In all data sets, radiation damage was observed after the absorbed dose exceeded 106,Gy. However, from the point of view of crystallographic statistics normalized to the absorbed dose, no clear dependence on photon energy was observed in these results. Structural refinement showed that the average B -factor for the last data set was larger than that for the first data set at all energies tested. However, no energy dependence of radiation damage on B -factor was found. Furthermore, disruption of disulfide bonds due to radiation damage was observed in electron density maps even at the highest photon energy (33,keV) used in this study. Therefore, these results suggest that radiation damage in the energy range investigated could be evaluated based on absorbed dose without energy dependence, and that it is important to minimize the absorbed dose in a crystal sample for obtaining an accurate protein structure. [source] Yodel: A Yield Stress Model for SuspensionsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 4 2006Robert J. Flatt A model for the yield stress of particulate suspensions is presented that incorporates microstructural parameters taking into account volume fraction of solids, particle size, particle size distribution, maximum packing, percolation threshold, and interparticle forces. The model relates the interparticle forces between particles of dissimilar size and the statistical distribution of particle pairs expected for measured or log-normal size distributions. The model is tested on published data of sub-micron ceramic suspensions and represents the measured data very well, over a wide range of volume fractions of solids. The model shows the variation of the yield stress of particulate suspensions to be inversely proportional to the particle diameter. Not all the parameters in the model could be directly evaluated; thus, two were used as adjustable variables: the maximum packing fraction and the minimum interparticle separation distance. The values for these two adjustable variables provided by the model are in good agreement with separate determinations of these parameters. This indicates that the model and the approximations used in its derivation capture the main parameters that influence the yield stress of particulate suspensions and should help us to better predict changes in the rheological properties of complex suspensions. The model predicts the variation of the yield stress of particulate suspensions to be inversely proportional to the particle diameter, but the experimental results do not show a clear dependence on diameter. This result is consistent with previous evaluations, which have shown significant variations in this dependence, and the reasons behind the yield stress dependence on particle size are discussed in the context of the radius of curvature of particles at contact. [source] Low-temperature single crystal reflection spectra of forsteriteMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006H. Suto ABSTRACT The infrared reflectivities of crystalline forsterite (Mg2SiO4) were measured for the temperature range 295,50 K for each crystal axis, between wavenumber 5000 and 100 cm,1. The reflection spectra show clear dependence of temperature; most of the bands become more intense, sharper and their peak positions shift to higher wavenumber with decreasing temperature. Reflection spectra were fitted with dispersion formula of damped oscillator model of the dielectric constants and the oscillator parameters in the model were derived. The absorption spectra of forsterite particle are calculated with the derived dielectric constants to show that the forsterite features are good thermal indicator for cold temperature range below 295 K. [source] Improved luminescence efficiency of InAs quantum dots grown on atomic terraced GaAs surface prepared with in-situ chemical etchingPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 4 2009Yasuhiro Idutsu Abstract Observation of the enhanced luminescence efficiency of InAs quantum dots (QDs) grown on atomically controlled GaAs surfaces is reported. With the trisdimethylaminoarsenic (TDMAAs) in-situ surface etching process, formation of atomic steps and terraces on GaAs surfaces were clearly observed. InAs QDs grown on the processed GaAs surfaces showed the clear dependence of QDs size, density and optical characteristics on the surface properties, i.e., the increase of the QDs height and diameter the decrease of the QDs density. About 6-times enhancement of photoluminescence efficiency which has the peak around 1550-nm wavelength was observed by growing InAs QDs on atomically controlled GaAs surfaces. This is due to the migration enhancement of InAs during thegrowth the QDs. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical properties of silver nanoparticlesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2007A. L. González Abstract The optical response of embedded silver nanoparticles in terms of their morphology and dielectric environment is studied. Employing a discrete dipole approximation, the extinction efficiencies are calculated for nanoparticles of different shapes and in diverse ambient conditions. A clear dependence of the number, width and position of the surface plasmon resonances (SPRs) is identified for various nanoparticle shapes. For faceted particles, it is found that as the truncation of sides increases, the main resonance is always blue shifted, the SPRs at smaller wavelength are closer to the dominant mode, so, they overlap, and the width of the main resonance increases. The SPRs vanish as the number of faces increases, or when the symmetry of the NP becomes larger. As the vertices become sharper, the number of resonances increases significantly. By changing the refraction index of the environment, the number of SPRs is not affected, although their width and position are modified, so that, for larger the refraction indeces the resonances are red shifted. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Paired-pulse transcranial magnetic stimulation protocol applied to visual cortex of anaesthetized cat: effects on visually evoked single-unit activityTHE JOURNAL OF PHYSIOLOGY, Issue 3 2005Vera Moliadze In this study, we tested the paired-pulse transcranial magnetic stimulation (ppTMS) protocol , a conditioning stimulus (CS) given at variable intervals prior to a test stimulus (TS) , for visually evoked single-unit activity in cat primary visual cortex. We defined the TS as being supra-threshold when it caused a significant increase or decrease in the visually evoked activity. By systematically varying the interstimulus interval (ISI) between 2 and 30 ms and the strength of CS within the range 15,130% of TS, we found a clear dependence of the ppTMS effect on CS strength but little relation to ISI. The CS effect was strongest with an ISI of 3 ms and steadily declined for longer ISIs. A switch from enhancement of intracortical inhibition at short ISIs (2,5 ms, SICI) to intracortical facilitation (ICF) at longer ISIs (7,30 ms), as demonstrated for human motor cortex, was not evident. Whether the CS caused facilitation or suppression of the TS effect mainly depended on the strength of CS and the polarity of the TS effect: within a range of 60,130% a positive correlation between ppTMS and TS effect was evident, resulting in a stronger facilitation if the TS caused facilitation of visual activity, and more suppression if the TS was suppressive by itself. The correlation inverted when CS was reduced to 15,30%. The ppTMS effect was not simply the sum of the CS and TS effect, it was much smaller at weak CS strength (15,50%) but stronger than the sum of CS and TS effects at CS strength 60,100%. Differences in the physiological state between sensory and motor cortices and the interactions of paired synaptic inputs are discussed as possible reasons for the partly different effects of ppTMS in cat visual cortex and human motor cortex. [source] A Convergent Approach to Biocompatible Polyglycerol "Click" Dendrons for the Synthesis of Modular Core,Shell Architectures and Their Transport BehaviorCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2008Monika Wyszogrodzka Dipl.-Ing. Abstract Dendrimers are an important class of polymeric materials for a broad range of applications in which monodispersity and multivalency are of interest. Here we report on a highly efficient synthetic route towards bifunctional polyglycerol dendrons on a multigram scale. Commercially available triglycerol (1), which is highly biocompatible, was used as starting material. By applying Williamson ether synthesis followed by an ozonolysis/reduction procedure, glycerol-based dendrons up to the fourth generation were prepared. The obtained products have a reactive core, which was further functionalized to the corresponding monoazido derivatives. By applying copper(I)-catalyzed 1,3-dipolar cycloaddition, so-called "click" coupling, a library of core,shell architectures was prepared. After removal of the 1,2-diol protecting groups, water-soluble core,shell architectures 24,27 of different generations were obtained in high yields. In the structure,transport relationship with Nile red we observe a clear dependence on core size and generation of the polyglycerol dendrons. [source] | ||||||||||||||||