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Selected AbstractsSelf-Assembled Multilayers of Polyethylenimine and DNA: Spectrophotometric and Electrochemical Characterization and Application for the Determination of Acridine Orange InteractionELECTROANALYSIS, Issue 15 2009F. Ferreyra Abstract This work deals with the study of the interaction between acridine orange (AO) and calf-thymus double stranded DNA (dsDNA) present in supramolecular architectures built on gold electrodes modified with mercapto-1-propanesulfonic acid (MPS) by self-assembling of polyethylenimine and dsDNA. The optimal conditions for building the supramolecular architecture were obtained from UV-vis spectrophotometric experiments. The electrochemical studies were performed by adsorptive transfer square wave voltammetry from the evaluation of the oxidation signal of AO accumulated within the multistructure. The effect of the number of PEI-dsDNA bilayers (Au/MPS/(PEI-dsDNA)n) on the accumulation and electrooxidation of AO is also discussed. [source] Enantioseparation of amino acids, ,-hydroxy acids, and dipeptides by ligand-exchange CEC using silica-based chiral stationary phasesELECTROPHORESIS, Issue 16 2009Elfriede Pittler Abstract This work deals with the application of silica-based ligand-exchange chiral stationary phases (CSPs) for the enantioseparation of underivatised amino acids, ,-hydroxy acids, and dipeptides with packed CEC. Two different possibilities of preparing silica-based CSPs are presented. One phase contains L -4-hydroxyproline chemically bonded via a spacer to 3,,m silica material. The other approach makes use of N -decyl- L -4-hydroxyproline dynamically coated on a reversed-phase packed capillary. Dynamical coating of reversed-phase material represents a simple alternative to prepare CSP. A comparison of the chemically bonded phase with the dynamically coated CSP by means of resolution of complex-forming analytes is presented. The chemically bonded phase was found to be superior to the dynamically coated phase in terms of resolution of amino acids and dipeptides. However, the dynamically coated CSP was found to be especially suitable for the separation of ,-hydroxy acids. Both techniques are applicable for enantiomer purity tests. [source] Iron availability affects mcyD expression and microcystin-LR synthesis in Microcystis aeruginosa PCC7806ENVIRONMENTAL MICROBIOLOGY, Issue 10 2008Emma Sevilla Summary Microcystins are toxins produced by cyanobacteria that entail serious health and environmental problems. They are cyclic heptapeptides synthesized via a mixed polyketide synthase/non-ribosomal peptide synthetase system called microcystin synthetase. Environmental and nutritional factors that trigger microcystin synthesis are still debated and this work deals with the study of the influence of iron nutritional status on the microcystin synthesis. The results indicate that iron deficiency could be one of the inducing factors of the microcystin synthesis. For the first time, increased transcription of an essential mcy gene and correlative microcystin synthesis has been established. Real-time PCR analysis of mcyD, and microcystin-LR synthesis were studied on Microcystis aeruginosa PCC7806 grown in iron-replete and iron-deplete media. Iron starvation causes an increase of mcyD transcription, correlative to the increase of microcystin-LR levels. Four transcription start points were identified for mcyD and two for mcyA, and they are not changed as a consequence of iron deficiency. [source] Enhanced Strength and Ductility of Ultrafine-Grained Ti Processed by Severe Plastic Deformation,ADVANCED ENGINEERING MATERIALS, Issue 8 2010Irina Semenova This work deals with the study of strength and ductility in ultrafine-grained (UFG) Ti Grade 4 produced by equal channel angular pressing (ECAP) in combination with subsequent thermomechanical treatments. We found that additional annealing of UFG Ti resulted in unusual enhancement of strength and ductility, which is associated with not only small grain size but also with a grain boundary structure. The origin of this phenomenon is investigated using the results of transmission electron microscopy and atom probe tomography. The innovation potential of UFG Ti for medical use is considered. [source] Operational and structural optimization of multi-carrier energy systemsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2006Martin Geidl Abstract This paper presents an approach for the combined optimization of energy systems including multiple energy carriers such as electricity, natural gas, and district heat. Power flow and conversion between the different energy infrastructures are described as multi-input multi-output coupling, what enables simple analysis and optimization of the flows. While previous work deals with operational optimization (multi-carrier optimal dispatch and power flow), this paper focuses on optimization of the couplings between the different networks, that is the structure of the system. Copyright © 2006 John Wiley & Sons, Ltd. [source] Fatigue crack initiation life estimation in a steel welded joint by the use of a two-scale damage modelFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 5 2009N. LAUTROU ABSTRACT This work deals with the fatigue behaviour of S355NL steel welded joints classically used in naval structures. The approach suggested here, in order to estimate the fatigue crack initiation life, can be split into two stages. First, stabilized stress,strain cycles are obtained in all points of the welded joint by a finite element analysis, taking constant or variable amplitude loadings into account. This calculation takes account of: base metal elastic,plastic behaviour, variable yield stress based on hardness measurements in various zones of the weld, local geometry at the weld toe and residual stresses if any. Second, if a fast elastic shakedown occurs, a two-scale damage model based on Lemaitre et al.'s work is used as a post-processor in order to estimate the fatigue crack initiation life. Material parameters for this model were identified from two Wöhler curves established for base metal. As a validation, four-point bending fatigue tests were carried out on welded specimens supplied by ,DCNS company'. Two load ratios were considered: 0.1 and 0.3. Residual stress measurements by X-ray diffraction completed this analysis. Comparisons between experimental and calculated fatigue lives are promising for the considered loadings. An exploitation of this method is planned for another welding process. [source] Specific aspects on crack advance during J -test method for structural materials at cryogenic temperaturesFATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 2 2006K. WEISS ABSTRACT Cryogenic elastic plastic, J -integral investigations on metallic materials often show negative crack extension values with respect to resistance curve J - R. According to the present ASTM standard, the use of unloading compliance technique relies on the estimation procedure of the crack lengths during the unloading sequences of the test. The current standard, however, does not give any specific procedure for treating such negative data. To date, the applied procedure uses the shifting of the negative crack extension values either to the onset of the blunting line or to the offset of the resistance curve. The present paper represents a solution of the negative crack length problem on the basis of a mechanical evaluation procedure of the unloading slopes. The achieved progress using this evaluation technique is demonstrated on different materials such as cryogenic high toughness stainless steels, low carbon ferritic steel and aluminum alloys from the series of 7000 and 5000. In addition, this work deals with the crack tunnelling phenomenon, observed for high toughness materials, and shows the reduction of this crack extension appearance by using electro discharge machining (EDM) side groove technique. The differences between EDM processed side grooves and standard V-notch machining have been investigated within these test series. [source] Responses of leaf nitrogen concentration and specific leaf area to atmospheric CO2 enrichment: a retrospective synthesis across 62 speciesGLOBAL CHANGE BIOLOGY, Issue 7 2002Xiwei Yin Abstract Knowledge of leaf responses to elevated atmospheric [CO2] (CO2 concentration) is integral to understanding interactions between vegetation and global change. This work deals with responses of leaf mass-based nitrogen concentration (Nm) and specific leaf area (SLA). It assesses the statistical significance of factors perceived as influential on the responses, and quantifies how the responses vary with the significant factors identified, based on 170 data cases of 62 species compiled from the literature. Resultant equations capture about 41% of the variance in the data for percent responses of Nm and SLA, or about 95% of the variance for Nm and SLA at 57,320% normal [CO2]; these performance statistics also hold for leaf area-based N concentration and specific leaf weight. The equations generalize that: (i) both Nm and SLA decline as [CO2] increases; (ii) proportional decline of Nm is greater with deciduous woody species and with plants of normally low Nm, increases with pot size in growth chamber and greenhouse settings and with temperature and photosynthetic photon flux density (PPFD), and is mitigated by N fertilization; and (iii) proportional decline of SLA depends on pot size and PPFD similarly to Nm, increases with leaf life span and water vapour pressure deficit in enclosed experiments, and decreases with prolonged exposure to elevated [CO2] among broadleaf woody species in field conditions. The results highlight great uncertainty in the percent-response data and reveal the potential feasibility to estimate Nm and SLA at various magnitudes of elevated [CO2] from a few key plant and environmental factors of broad data bases. [source] Stress and strain-driven algorithmic formulations for finite strain viscoplasticity for hybrid and standard finite elementsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 7 2009C. S. Jog Abstract This work deals with the formulation and implementation of finite deformation viscoplasticity within the framework of stress-based hybrid finite element methods. Hybrid elements, which are based on a two-field variational formulation, are much less susceptible to locking than conventional displacement-based elements. The conventional return-mapping scheme cannot be used in the context of hybrid stress methods since the stress is known, and the strain and the internal plastic variables have to be recovered using this known stress field. We discuss the formulation and implementation of the consistent tangent tensor, and the return-mapping algorithm within the context of the hybrid method. We demonstrate the efficacy of the algorithm on a wide range of problems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Batch cooling crystallization of xylitol produced by biotechnological routeJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2009Ernesto Acosta Martínez Abstract BACKGROUND: This work deals with the xylitol production by biotechnological routes emphasizing the purification process using crystallization. RESULTS: Xylitol volumetric productivity of 0.665 g L,1 h,1 and yield of 0.7024 g g,1 were obtained after 92 h fermentation. The fermented broth (61.3 g L,1 xylitol) was centrifuged, treated and concentrated obtain a syrup (745.3 g L,1 xylitol) which was crystallized twice, xylitol crystals with 98.5,99.2% purity being obtained. CONCLUSION: The hypothetical distribution obtained permits the determination of modeling parameters, which make possible the estimation of crystal dominant size from different initial experimental conditions. Copyright © 2008 Society of Chemical Industry [source] On the efficient evaluation of Fourier patterns for nanoparticles and clustersJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 9 2006Antonio Cervellino Abstract Samples made of an isotropically oriented ensemble of atomic clusters or structures that are not large crystals (i.e. extended less than 10 periods in each direction) are at the frontier of today's material science and chemistry. Examples are nanoparticles, nanotubes, amorphous matter, polymers, and macromolecules in suspension. For such systems the computation of powder diffraction patterns (which may provide an efficient characterization) is to be performed the hard way, by summing contributions from each atom pair. This work deals with performing such computation in the most practical and efficient way. Three main points are developed: how to encode the enormous array of interatomic distances (which increase as the square or higher powers of the cluster diameter) to a much smaller array of equispaced values on a coarse grid (whose size increases linearly with the diameter); how to perform a fast computation of the diffraction pattern from this equispaced grid; how to optimize the grid step to obtain an arbitrarily small error on the computed diffraction pattern. Theory and examples are jointly developed and presented. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 995,1008, 2006 [source] The Effect of Electric Field on Important Food-processing Enzymes: Comparison of Inactivation Kinetics under Conventional and Ohmic HeatingJOURNAL OF FOOD SCIENCE, Issue 9 2004I. Castro ABSTRACT: This work deals with the determination of the inactivation kinetics of several enzymes, most of them used as time-temperature integrators in the food industry. The tested enzymes were polyphenoloxidase, lipoxygenase, pectinase, alkaline phosphatase, and p-galactosidase, and the inactivation assays were performed under conventional and ohmic heating conditions. The thermal history of the samples (conventional and ohmically processed) was made equal to determine if there was an additional inactivation caused by the presence of an electric field, thus eliminating temperature as a variable. All the enzymes followed 1st-order inactivation kinetics for both conventional and ohmic heating treatments. The presence of an electric field does not cause an enhanced inactivation to alkaline phosphatase, pectinase, and ,- galactosidase. However, lipoxygenase and polyphenoloxidase kinetics were significantly affected by the electric field, reducing the time needed for inactivation. The results of the present work can be used industrially to determine processing effectiveness when ohmic heating technology is applied. [source] Estimation of Kinetic Parameters for Nonisothermal Food ProcessesJOURNAL OF FOOD SCIENCE, Issue 3 2003K.D. Dolan ABSTRACT This work deals with the hypothesis that kinetic parameters for nonisothermal processes can be reliably obtained using a 1-step method. Parameters were estimated for 3 typical processes: (1) no residence time distribution (RTD), (2) first-order reaction with RTD, and (3) nth-order reaction with RTD. When nonisothermal processes were approximated isothermally, k and ,E were underestimated 80% to 3 orders of magnitude, and 30% to 1 order of magnitude, respectively. Reaction order was overestimated by up to 0.81. Therefore, accounting for thermal history and RTD is critical to obtain accurate estimates of kinetic parameters. The 1-step method was also used to solve for equivalent isothermal temperatures and times for an arbitrary nonisothermal process. [source] Terminal and transient drop rise velocity of single toluene droplets in waterAICHE JOURNAL, Issue 1 2010Mirco Wegener Abstract The knowledge of the drop rise velocity in dispersed systems is of fundamental importance. Especially, the residence time is needed for calculation of mass transfer rates in extraction columns. This work deals with fluid dynamic measurements of toluene droplets rising in water ranging from 1.0 to 7.0 mm, with the premise of high purity of the used chemicals. The toluene/water-system is widely used as a test system with high interfacial tension. A semiempirical correlation for pure systems to predict the terminal velocity of single rising/falling droplets based on experimental data is presented. Results show that a distinction between maximum and characteristic mean values of the drop rise velocity is necessary, especially in the diameter range 2.4,3.0 mm where unexpected velocity fluctuations occur. Two distinct terminal rise velocities were observed for 3 mm droplets. Furthermore, comparisons of the Weber-Reynolds-correlation and the drag coefficient with correlations from literature show good agreement. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] An example of the complementarity of laser-induced breakdown spectroscopy and Raman microscopy for wall painting pigments analysisJOURNAL OF RAMAN SPECTROSCOPY, Issue 7 2007Romain Bruder Abstract Laser-induced breakdown spectroscopy (LIBS) and Raman microscopy were used for the identification of pigments in wall painting. Raman spectroscopy, which provides the molecular ,fingerprint' of the compound, is nowadays widely used by the archaeometry community, especially for pigment analysis. LIBS, which provides the elementary composition of samples, is a rapid noncontact method, enabling layer-by-layer analysis through a precise laser ablation of the sample. This work deals with the behavior of pigments after a LIBS analysis, by trying to identify the compounds before and after the laser shot. Six commercial pigments prepared with the fresco technique were investigated: ultramarine blue, red lead, charcoal, a yellow and a red ochre, and a green earth. Raman spectra, acquired on the sample surface and in the crater induced by LIBS analysis, were compared. The results show that these pigments are well recognized after a LIBS measurement. The analysis of green earth illustrates that the combination of these two techniques gives complete information from a sample. Copyright © 2007 John Wiley & Sons, Ltd. [source] Use of evaporative light scattering detector in the detection and quantification of enantiomeric mixtures by HPLCJOURNAL OF SEPARATION SCIENCE, JSS, Issue 10 2006Tong Zhang Abstract Routinely used in our laboratories at analytical scale, an evaporative light scattering detector (ELSD) has proved to be versatile in the detection of enantiomeric resolution using chiral stationary phases by HPLC. Though this kind of detector has been widely used in various domains, its application in enantiomeric resolution has not been discussed in the literature and is found to have very specific features especially in the quantitative perspective. In contrast with the UV detection, the peak area from ELSD for both enantiomers of a racemic mixture may not be the same. This complicates the assessment of the enantiomeric purity of unknown samples. This current work deals with some practical aspects in the detection of enantiomers and in accurate quantitative determination of enantiomeric purity by ELSD. Effects of analyte nature (more precisely molecular weight and volatility), peak shape and peak shape difference between enantiomers on the quantitative integration by ELSD are discussed in connection with the UV-detection results. The calibration for quantitative enantiomeric analysis and its effectiveness are demonstrated. [source] New tribometer designed for the characterisation of the friction properties at the tool/chip/workpiece interfaces in machiningLUBRICATION SCIENCE, Issue 1 2008F. Zemzemi Abstract This work deals with the development of a new tribometer designed for the characterisation of the frictional properties at the tool/chip/workpiece interfaces in cutting processes. Based on a plane,sphere contact configuration, the experimental set-up enables a continuous regeneration of the pin,workmaterial contact. The average contact pressure can be selected up to 3,GPa under sliding velocities reaching 16,m/s. Under such severe conditions, which are not reachable with conventional tribometers, the apparent friction coefficient is quantified in parallel to the heat flux transmitted to the pin. This new system has been applied to the characterisation of the frictional properties during the dry machining of a 27MnCr5 annealed steel with a carbide cutting tool. The influence of the sliding velocity and of an additional TiN layer deposited by PVD on the carbide pins has been investigated in dry conditions. It has been shown that the sliding velocity is the more influential parameter, followed by the coating. Copyright © 2007 John Wiley & Sons, Ltd. [source] Design of Blends with an Extremely Low Viscosity Ratio between the Dispersed and Continuous Phases.MACROMOLECULAR SYMPOSIA, Issue 1 2007Dependence of the Dispersed Phase Size on the Processing Parameters Abstract Summary: This work deals with the development of the dispersed phase morphology in immiscible blends of poly(ethylene glycol)/polyamide 66 (PEG/PA) with an extremely low viscosity ratio. The blends were obtained, under different operating conditions, by melt blending in an internal mixer. The objective was to examine the influence of the main processing parameters on the particles size of the minor phase (PEG). A model was elaborated to describe the dependence of the particle size on interfacial tension, PEG concentration, shear rate and viscosity ratio between the two blend components. [source] Multi-scale modelling of two-phase,two-component processes in heterogeneous porous mediaNUMERICAL LINEAR ALGEBRA WITH APPLICATIONS, Issue 9 2006J. Niessner Abstract This work deals with flow and transport phenomena in porous media, which occur on different space and time scales. Additionally, the porous medium itself is heterogeneous where the heterogeneities occur on all spatial scales. We consider a large domain with randomly distributed heterogeneities where complex two-phase,two-component processes are relevant only in a small (local) subdomain. This subdomain needs fine resolution as the complex processes are governed by small-scale effects. For a comprehensive fine-scale model taking into account two-phase,two-component processes as well as heterogeneities in the whole (global) model domain, data collection is expensive and computational time is high. Therefore, we developed a multi-scale concept where on the one hand, the global flow field influences the local two-phase,two-component processes on the fine scale. On the other hand, a coarse-scale saturation equation is solved where the effects of the fine-scale two-phase,two-component processes in the subdomain are captured by source/sink terms and the effects of fine-scale heterogeneities by a macrodispersion term. Copyright © 2006 John Wiley & Sons, Ltd. [source] On-line Determination of Aggregate Size and Morphology in SuspensionsPARTICLE & PARTICLE SYSTEMS CHARACTERIZATION, Issue 3 2004Frédéric Gruy Abstract Information concerning the aggregation state of fine solid particles is an important element for process control and monitoring of product quality in many applications of industrial slurries. This work deals with the application of different in-line methods to the characterization of silica aggregate size and morphology. All of these methods exploit turbidity signals, obtained by various means including: from analysis of turbidity fluctuations in homogeneous suspension and from overall turbidity decrease during particle settling. This work also presents the opportunity to report progress in morphological and optical models of small aggregates. As a result of these models, the morphological characteristics of the aggregates along with the number of their constituting particles are derived from experimental results. Similarities between the different methods are examined and discussed. [source] Analysis of SR thermal load studied by FEAPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2007Abstract This work deals with analysis of the thermal effects and inherent mechanical deformations under absorption of the X-ray beam heat. The work is motivated by recent research concentrated on the development of optics for high-flux synchrotron radiation sources. We present the analyses of the static thermal load effects on the surface deformation field for a monocrystalline silicon target, which is the basic material for crystal X-ray optics. The surface and bulk thermal load induces the gradient of temperature and mechanical deformations of the target that are affecting the reflection and diffraction properties of the target. The paper presents the finite-element analyses (FEA) and simulation results of mechanical deformation of flat and slotted silicon targets. The hints for improved target geometry and physical limits for an actual cooling system can be obtained from the presented analyses. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Behavior of phonons in short period GaN-AlN superlatticesPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 11 2004C. Pinquier Abstract This work deals with short period GaN-AlN superlattices, studied by Raman spectroscopy using visible and ultraviolet excitations. The E2 (high) and E1(TO) phonons show a two-mode behavior. In contrast, we observed an unique spectral line in the A1(TO) spectrum: its dependence on the mean superlattice composition is in good agreement with recent theoretical results predicting its delocalized character. Two Raman lines strongly enhanced under ultraviolet excitations, were observed in the A1(LO) spectrum. Lattice dynamical simulations within the Rigid Ion Model have been performed to assign these Raman lines. The first one corresponds to an A1(LO) phonon confined in GaN wells. The second line is assigned to a dispersive B1 - like mode with an amplitude modulation similar to that of an interface mode. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Load Monitoring of Impacted Carbon-Fibre-Reinforced Plastic PlatesPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009Andy Ungethuem This work deals with a new wave migration model for the determination of an impact location for non-isotropic plates. The method is based on the wave propagation after the impact. The evaluation and processing of the signals of at least four sensors allow for the calculation of the impact location from the runtime of the signals. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Disturbance Propagation in the Melt Spinning ProcessPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2009Anthony McVeigh This work deals with the propagation of a disturbance acting on a fibre in the melt-spinning process, where molten polymer is ejected vertically downwards from an orifice before being drawn onto a wind-up spool. The disturbance may be produced by a sudden horizontal draught of air impinging on a part of the fibre. The flow is modeled as a wave propagating on a moving string under the influence of damping and variable tension. The amplitude of the disturbance is obtained in closed-form along the characteristics which emanate from the boundaries of the localised initial disturbance; the general solution of the damped disturbance is determined numerically. An important aspect of the model is the ability to predict the magnitude of this disturbance close to the orifice, where the extruded polymer is molten and therefore extremely sensitive to disturbances. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fatigue crack initiation in naval welded joints: experimental and numerical approachesPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2008D. Thevenet This work deals with the fatigue behavior of welded joints. The proposed strategy can be split into two stages: the structure shakedown study and the fatigue crack initiation study. Firstly, stabilized elastic stress,strain cycles are obtained in any point of the welded joint by a finite element analysis, taking constant or variable amplitude loadings into account. The second part of this work is the calculation of the fatigue crack initiation period. Under the assumption of a fast elastic shakedown, a recent approach, proposed by Lemaitre et al., based on damage mechanics, can be used to predict the fatigue crack initiation life in a structure subjected to variable and complex loadings. This strategy is used as a post,treatment of the shakedown finite element calculation for the studied welded specimen. As a validation, four,point bending fatigue tests under constant amplitude loading were carried out on welded specimens provided by DCNS group. Good correlations between experimental and calculated fatigue crack initiation lives have been established. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Separation of VOCs from N2 using poly(ether block amide) membranesTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2009Li Liu Abstract This work deals with the separation of volatile organic compounds (VOCs) from nitrogen streams for organic vapour emission control by poly(ether block amide) membranes. As representative air pollutant VOCs, n -pentane, n -hexane, cyclohexane, n -heptane, methanol, ethanol, n -propanol, n -butanol, acetone, dimethyl carbonate, and methyl tert -butyl ether were used in this study. The separation of both binary VOC/N2 and multicomponent VOCs/N2 gas mixtures was carried out, and the membranes exhibited good separation performance. A VOC concentration of more than 90 mol% was achieved at a feed VOC concentration of 5 mol%. It was found that the permeances of the VOCs were mainly dominated by their solubilities in the membrane, whereas the permeance of N2 was affected by the presence of the VOCs. The permeance of N2 in the VOC/N2 mixtures was shown to be higher than pure N2 permeance due to membrane swelling induced by the VOCs dissolved in the membrane. Nevertheless, theVOC/N2 selectivity increased with an increase in the feed VOC concentration. Among the VOCs studied, the membrane showed a higher permeance to alcohol VOCs than paraffin VOCs. The effects of feed VOC concentration, temperature, stage cut, and permeate pressure on the separation performance were investigated. Ce travail porte sur la séparation des composés organiques volatils (COV) présents dans des courants d'azote pour le contrôle des émissions de vapeur organique par des membranes de poly(éther amide bloc). Comme polluants atmosphériques représentatifs des COV, on a utilisé dans cette étude le n-pentane, le n-hexane, le cyclohexane, le n-heptane, le méthanol, l'éthanol, le n-propanol, le n-butanol, l'acétone, le carbonate de diméthyle et le méthyl tertio-butyl. On a procédé à la séparation du mélange de gaz de COV/N2 binaire et du mélange de gaz multicomposant COV/N2, et les membranes montrent une bonne performance de séparation. Une concentration de COV de plus de 90% en poids moléculaire a été obtenue à une concentration d'alimentation de COV de 5% en poids moléculaire. On a trouvé que les perméances de N2 était sensibles à la présence de COV. La perméance de N2 dans les mélanges de COV/N2 s'avère plus élevée que la perméance du N2 pur en raison du gonflement de la membrane provoqué par les COV dissous dans la membrane. Néanmoins, la sélectivité des COV/N2 augmente avec la concentration de COV d'alimentation. Parmi les COV étudiés, la membrane montre la plus haute perméance aux COV d'alcool qu'aux COVde paraffine. Les effets de la concentration de COV d'alimentation, de la température, la coupure de phase et la pression des perméats ont été étudiés. [source] TIN ISOTOPY,A NEW METHOD FOR SOLVING OLD QUESTIONSARCHAEOMETRY, Issue 5 2010M. HAUSTEIN Tin was a vital commodity in times past. In central Europe, the earliest finds of tin-bronze date to about 2200 bc, while in Greece they are c. 400,500 years earlier. While there is evidence for prehistoric copper mining,for example, in the Alps or mainland Greece, among other places,the provenance of the contemporary tin is still an unsolved problem. This work deals with a new approach for tracing the ancient tin via tin isotope signatures. The tin isotope ratios of 50 tin ores from the Erzgebirge region (D) and 30 tin ores from Cornwall (GB) were measured by MC,ICP,MS. Most ore deposits were found to be quite homogeneous regarding their tin isotope composition, but significant differences were observed between several deposits. This fact may be used to distinguish different tin deposits and thus form the basis for the investigation of the provenance of ancient tin that has been sought for more than a century. Furthermore, the tin-isotope ratio of the ,Himmelsscheibe von Nebra' will be presented: the value fits well with the bulk of investigated tin ores from Cornwall. [source] Construction and Performance of a Minibioreactor Suitable as Experimental Bioartificial LiverARTIFICIAL ORGANS, Issue 4 2008Joaquín V. Rodriguez Abstract:, This work deals with the construction and performance of a hollow fiber-based minibioreactor (MBR). Due to its simple design and the utilization of standard materials, it could serve as a suitable tool to evaluate the behavior and performance of cold preserved or cultured hepatocytes in bioartificial liver devices. The system consists of 140 fiber capillaries through which goat blood is pumped at a flow of 9 mL/min. The cell compartment contains 90 × 106 rat hepatocytes (volume 10 mL) and an internal oxygenator made of silicone tubing. To test the in vitro function of the system, 2-h perfusion experiments were performed, the evolution of hematocrit, plasma and extra-fiber fluid osmolality, and plasma urea and creatinine concentrations were evaluated. The detoxication efficiency of an ammonia overload was tested, showing that the system has enough capacity to remove ammonium. Also, the MBR oxygen transfer capacity to hepatocytes was tested, showing that the cells received an adequate oxygen supply. [source] Star formation in the LMC: Comparative CCD observations of young stellar populations in two giant molecular cloudsASTRONOMISCHE NACHRICHTEN, Issue 8 2009J. Ruppert Abstract This work deals with a CCD imaging study at optical and near-infrared wavelength oftwo giant molecular clouds (plus a control field) in the southern region of the Large Magellanic Cloud, one ofwhich shows multiple signs of star formation, whereas the other does not. The observational data from VLT FORS2 (R band) and NTT SOFI (Ks band) have been analyzed to derive luminosity functions and color-magnitude diagrams. The young stellar content of these two giant molecular clouds is compared and confirmed to be different, in the sense that the apparently "starless" cloud has so far formed only low-luminosity, low-mass stars (fainter than mKs , 16.5 mag, not seen by 2MASS), while the other cloud has formed both faint low-mass and luminous high-mass stars. The surface density excess oflow-luminosity stars (,2 per square arcmin) in the "starless" cloud with respect to the control field is about 20% whereas the excess is about a factor of 3 in the known star-forming cloud. The difference may be explained theoretically by the gravo-turbulent evolution of giant molecular clouds, one being younger and less centrally concentrated than the other (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Stability of fictitious Trojan planets in extrasolar systemsASTRONOMISCHE NACHRICHTEN, Issue 8 2007R. Schwarz Abstract Our work deals with the dynamical possibility that in extrasolar planetary systems a terrestrial planet may have stable orbits in a 1:1 mean motion resonance with a Jovian like planet. We studied the motion of fictitious Trojans around the Lagrangian points L4/L5 and checked the stability and/or chaoticity of their motion with the aid of the Lyapunov Indicators and the maximum eccentricity. The computations were carried out using the dynamical model of the elliptic restricted three-body problem that consists of a central star, a gas giant moving in the habitable zone, and a massless terrestrial planet. We found 3 new systems where the gas giant lies in the habitable zone, namely HD99109, HD101930, and HD33564. Additionally we investigated all known extrasolar planetary systems where the giant planet lies partly or fully in the habitable zone. The results show that the orbits around the Lagrangian points L4/L5 of all investigated systems are stable for long times (107 revolutions). (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||||||||