bluuebunny/crossref_metadata_2025_split huggingface dataset:
Die Alzheimer‐Demenz: von der Pathologie zu therapeutischen Ansätzen
Authors: Jakob‐Roetne Roland , Jacobsen Helmut 
Published: March 2009

AbstractDie gegenwärtigen Strategien zur Entwicklung von Alzheimer‐Therapien sind breit gefächert. Ein verstärktes Augenmerk gilt der Suche nach Hemmstoffen (siehe Bild für zwei Beispiele) der proteolytischen Enzyme β‐ und γ‐Secretase, die die Spaltung des Amyloid‐Vorläuferproteins in Amyloid‐β‐Peptide inhibieren, aus denen die krankheitstypischen Plaque‐Ablagerungen im Gehirn von Alzheimer‐Patienten entstehen.magnified imageDie Forschungen über Altersdemenz und die Alzheimersche Krankheit umfassen ein sehr breites Feld wissenschaftlicher Aktivitäten. So wurden etwa bei der letztjährigen internationalen Tagung der Alzheimer‐Gesellschaft (ICAD 2008 in Chicago) mehr als 2200 Einzelbeiträge präsentiert. Ziel dieses Aufsatzes ist es, einen zusammenhängenden Überblick über das Gebiet zu präsentieren und die wichtigsten Themen und Forschungstrends aufzuzeigen. Die Ausführungen beginnen mit einer Diskussion von Verhaltensabweichungen und sichtbaren pathologischen Befunden, bevor dann auf die molekularen Details der Pathologie eingegangen wird. Besonderes Augenmerk gilt der “Amyloidhypothese” der Alzheimer‐Krankheit, da sie das theoretische Fundament für die meisten der in der Entwicklung befindlichen therapeutischen Konzepte bildet.
The Colloidal Suprastructure of Smart Microgels at Oil–Water Interfaces
Authors: Brugger Bastian , Rütten Stephan , Phan Kim‐Ho , Möller Martin , Richtering Walter 
Published: March 2009

AbstractOrdnung im Ölfilm: Mithilfe von reizempfindlichen Emulsionen wurden temperatur‐ und pH‐responsive Mikrogele entwickelt. Die Emulsionsstabilität an den Öl‐Wasser‐Grenzflächen wird nicht durch die Packungsdichte der Partikel bestimmt. Durch die Grenzfläche ausgelöste Strukturänderungen führen zur Verknüpfung der Mikrogele (siehe Bild; Maßstab 1 μm), die sich in ihrem Verhalten deutlich von Festpartikel‐stabilisierten Emulsionen unterscheiden.magnified image
Electrospun nanocomposites from polystyrene loaded with cellulose nanowhiskers
Authors: Rojas Orlando J. , Montero Gerardo A. , Habibi Youssef 
Published: March 2009

AbstractComposite microfibers from polystyrene and cellulose nanowhiskers were produced by electrospinning. The morphology of the microfibers was examined by using scanning and transmission electron microscopies. Surface porosity, unique ribbon‐shapes, and the presence of twists along the fiber axis were observed in the composite microfibers. Thermomechanical properties of processed nanocomposites were studied by differential scanning calorimetry and dynamical mechanical analyses. The reinforcing effect of cellulose nanowhiskers was confirmed as the glassy modulus of electrospun microfibers increased with nanowhisker load. This effect is explained to be the result of mechanical percolation of cellulose nanowhiskers forming a stiff and continuous network held by hydrogen bonding. It is demonstrated that cellulose nanoparticles can be used effectively to reinforce hydrophobic matrices and to produce unique structural properties, enabling new functionalities and properties. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Differential Photoluminescent and Electrochemiluminescent Detection of Anions with a Modified Ruthenium(II)–Bipyridyl Complex
Authors: Berni Emanuela , Gosse Isabelle , Badocco Denis , Pastore Paolo , Sojic Neso , Pinet Sandra 
Published: March 2009

AbstractDifferent lights, different selectivies: Luminescence of a new guanidinium 3,3′‐functionalized bipyridyl–RuII complex has been studied for sensing of several anions. L‐Glutamate and dihydrogenphosphate are both detected by photoluminescence and electrochemiluminescence. However, the complex displays differential selectivities for these anions depending on the sensing channels (see scheme).magnified imageA new guanidinium 3,3′‐functionalized bipyridylruthenium(II) complex has been prepared for the differential sensing of L‐glutamate and dihydrogenphosphate anions depending on the luminescent detection scheme. The effects of such anions on the photoluminescent (PL) and electrochemiluminescent (ECL) properties of the complex have been investigated and compared. The PL intensity increases up to fourfold in the presence of L‐glutamate. The increase of intensity in the presence of dihydrogenphosphate is weaker and no change in PL intensity is observed in presence of acetate, iodide, or chloride anions. With n‐tripropylamine, ECL emission of the RuII complex is initiated at 1.45 V versus Ag/AgCl/KCl and the ECL intensity increases only in the presence of dihydrogenphosphate. Indeed, L‐glutamate is already oxidized at the relatively high potential required for ECL generation and thus it does not affect the ECL signal. The comparison of the competitive ECL and PL assays in a mixture of anions confirms the differential detection of L‐glutamate and of dihydrogenphosphate. Thus, both sensing channels (i.e., PL and ECL) show different selectivities depending on the nature and on the electroactivity of the target anions. Multianion analysis is demonstrated in competitive assays using complementary detection methods.
Methane‐Propylene homologation and reactivity of surface carbon on modified Ni‐Al2O3 catalysts
Authors: Liu Qingdong , Smith Kevin J. 
Published: March 2009

AbstractModified Ni catalysts supported on alumina and reduced in CH4 have been investigated for the synthesis of C4 hydrocarbons from CH4 and C3H6. Addition of K or P to the Ni/Al2O3 catalyst increased C4 selectivity and C3H6 conversion. A maximum selectivity to the desired C4 product of 9 mol % was obtained at 350°C and 101 kPa with a feed gas composition of 90 mol% CH4/10 mol% C3H6, but the catalyst activity declined rapidly with time‐on‐stream. Large amounts of unreactive carbon were deposited on the catalyst surface following reduction in CH4 and reaction in CH4/C3H6. However, the relative amount of a much more reactive species identified from Temperature‐Programmed‐Surface‐Reaction that was formed in the presence of CH4 and C3H6, is shown to correlate with the catalyst C4 yield. Both the C4 yield and the relative amount of this low temperature carbonaceous species increased in the order Ni<Ni/P<Ni/K.
A combined model of mass transfer coefficients for contaminated drop liquid‐liquid systems
Authors: Slater M. J. 
Published: March 2009

AbstractMass transfer rates to and from drops in liquid‐liquid extraction equipment are often likely to be reduced by the presence of surface active contaminants. For industrial column design circumstances it is ideally required to account for the extent of contamination in a quantitative manner yet existing design procedures do not allow this to be done for the typical intermediate Reynolds number region of 10 to 100. A method is proposed for correcting continuous phase and drop mass transfer coefficients for the deleterious effects of contamination using only one contamination parameter which needs to be determined experimentally.
On the timing of primary fragmentation during bituminous coal particle devolatilisation in a fluidized bed combustor
Authors: Stubington John F. , Moss Brendan 
Published: March 2009

AbstractThe times at which devolatilising coal particles fragmented were compared with their devolatilisation times in a fluidized bed combustor. Whereas the devolatilisation times were similar, the time to first fragmentation varied markedly from coal to coal. Immediate fragmentation was attributed to thermal shock. Fragmentation during the first 1/3 of the devolatilisation time was attributed to the internal pressure generated from restricted transport of volatiles through the pores in the coal structure. Fragmentation near the end of devolatilisation may occur due to weakening of the coal structure by loss of volatiles. Primary fragmentation did not affect the devolatilisation time, even for coals which fragmented early in their devolatilisation time.
Drag on chains and agglomerates of spheres in viscous newtonian and power law fluids
Authors: Chhabra R. P. , Singh Tushar , Nandrajog S. 
Published: March 2009

AbstractNew experimental data on the free settling velocity of straight chains (up to twenty spheres) and planar clusters of touching spheres in Newionian and power law media are reported. The results embrace the following ranges of conditions: 0.65 ≤ n ≤ 1; Re < ‐ 2.5 and 1.22 < m < 48.87 Pa·sn. The straight chain drag measurements are in line with theoretical predictions for Newtonian fluids. The present results in power law fluids seem to suggest that it is possible to express the drag on a straight chain of spheres in terms of that on a single sphere of equal volume. Limited results with planar clusters are satisfactorily correlated using a volume equivalent sphere diameter.
Hydrodynamics of circulating fluidized bed risers: A review
Authors: Berruti F. , Pugsley T. S. , Godfroy L. , Chaouki J. , Patience G. S. 
Published: March 2009

AbstractAny vessel in which solids are transported upward by a gas stream and then recycled to the bottom may be classified as a Circulating Fluidized Bed (CFB). We describe possible CFB operating regimes in the context of this broad classification and highlight commercial processes that employ CFB technology and potential applications. Process design and development require a fundamental understanding of gas and solids hydrodynamics — solids hold‐up, mixing and velocity distribution. We discuss techniques used to measure solids mass flux, which is a critical parameter for both design and control. In the last decade, significant research efforts have been devoted to new experimental techniques to measure both gas and solids spatial and temporal distribution. We list these techniques and detail the different modelling approaches that have emerged based on the new data. Characterization of the data is still incomplete and the available models require further refinement to reliably predict the effect of scale, operating conditions and particle characteristics on hydrodynamics.
The characteristics of cluster in a high density circulating fluidized bed
Authors: Wei Fei , Yang Guo‐Qiang , Jin Yong , Yu Zhi‐Qing 
Published: March 2009

AbstractThe cluster images in a high density circulating fluidized bed (HDCFB) measured by a one‐dimensional optical fiber image analysis system are studied. The experimental results show that the characteristics of cluster in the riser vary greatly at different operating conditions. The radial cluster size, the cluster interception time and the probability of cluster appearance increase with bed density and decrease with gas velocity. Based on the analysis of the cluster image at various operating conditions, correlations of the radial cluster size, the cluster interception time and the probability of cluster appearance in a HDCFB are proposed. It is found that they are related to local solids concentration and gas velocity.
Modelling of induced aeration in turbine aerators by use of radial basis function neural networks
Authors: Aldrich C. , Van Deventer J. S. J. 
Published: March 2009

AbstractGas induction in agitated vessels with turbine impellers can be modelled accurately by means of radial basis function neural nets. The results obtained with the radial basis neural net were significantly better than those obtained by multivariate regression models or standard back propagation neural nets. Moreover, by using the radial basis function neural net model, it was possible to conduct a sensitivity analysis of the variables affecting aeration. Increased medium density showed a strong adverse effect, while variation of the viscosity can cause an increase or a decrease in the rate of aeration, depending on the prevailing process conditions.
Gas‐liquid mass transfer in two and three‐phase upflows through a vertical tube
Authors: Ishida Kazuhiko , Enda Shigeyuki , Kikuchi Ken‐Ichi , Takahashi Hiroshi 
Published: March 2009

AbstractOxygen absorption rates were measured to determine volumetric coefficients of gas‐liquid mass transfer coefficients kLa in gas‐liquid and gas‐liquid‐solid upward flows through a vertical tube. The liquid was deionized water or aqueous glycerol solution, and the solids were glass beads or polystyrene beads. The dependencies of kLa on gas velocity, liquid velocity, temperature, solid material, and solid concentration were examined. The experimental results were correlated with empirical equations. The mechanisms of the solid loading effect are discussed.
An LDA study of the turbulent flow field in a baffled vessel agitated by an axial, down‐pumping hydrofoil impeller
Authors: Jaworski Z. , Nienow A. W. , Dyster K. N. 
Published: March 2009

AbstractThe turbulent flow of water in a cylindrical, baffled vessel with an axial flow hydrofoil impeller, either a Chemineer HE3 (CHE3) or a Prochem Maxflo T (PMT), has been studied using a laser Doppler anemometer. Using ensemble averaging, the mean axial and radial flow and the associated fluctuating components were obtained for the whole of the vessel; plus similar data for the tangential component close to the impeller. Assuming axial symmetry, flow rates were calculated as were flow numbers and circulation flow numbers. Power numbers were also determined. All the data obtained were used to compare the circulation efficiency of the two hydrofoils plus a pitched blade and a Rushton turbine. This comparison showed that the CHE3 required a power input of about 2/3 of that for the PMT and about 1/3 of that for the pitched blade and Rushton turbine to obtain the same axial‐radial circulation in the tankz.
Statistical assessment of gas/liquid mass transfer in slurry‐phase propylene polymerization process
Authors: Li J. , Tekie Z. , Mohammad A. , Morsi B. I. 
Published: March 2009

AbstractA statistical approach was developed to investigate the effects of pressure, temperature, mixing speed and solid concentration on kLa for gaseous hydrogen, ethylene, and propylene in liquid n‐hexane containing solid polypropylene powder in a 4‐litre agitated reactor. The solubilities of the gases appeared to follow Henry's Law. Statistical correlations to predict kLa were proposed and response surfaces were constructed. kLa values appeared to reach a maximum around 15 mass% and sharply decrease above 30 mass%. The effects of pressure and temperature on kLa were found to depend on the gas‐liquid system and operating conditions used.
Mixing of a lateral gas stream in a two‐dimensional riser of a circulating fluidized bed
Authors: Marzocchella Antonio , Arena Umberto 
Published: March 2009

AbstractA cold model of a circulating fluidized bed having a two‐dimensional riser, with a 12 × 120 mm section and a 6.4 m height, was equipped with a device to inject a lateral gas stream along the riser. The apparatus was operated under conditions ranging from those characteristic of combustors to those of gas‐conversion processes. Flow structures in the interaction region between the rising gas—solids suspension and the lateral gas stream were studied by means of a motion analysis system. Three main configurations were identified. The ratio between the momentum of the lateral gas stream and that of the rising suspension was found to be the parameter able to discriminate among the three configurations. A satisfactory agreement was found with mixing data obtained using a cylindrical riser.
Experimental study of the fluidic mixing in a cylindrical reactor
Authors: Orfaniotis A. , Fonade C. , Lalane M. , Doubrovine N. 
Published: March 2009

AbstractAn experimental study of fluidic mixing in a cylindrical reactor was conducted in order to determine the effects of jet position and liquid viscosity. The tests were carried out in a tank of 0.09 m3 liquid volume using eight conductimetric probes to measure the mixing time. Relative jet positions leading to an impinging flow structure have been found to be less efficient than shear flow configurations. Mixing time and inhomogeneity correlations extending the previous results of Simon and Fonade (1993) are put forward for mixing by steady or unsteady jets.
Gas and particle flow patterns in cyclones at room and elevated temperatures
Authors: Patterson P. A. , Munz R. J. 
Published: March 2009

AbstractExperimental results are presented for a study of gas and particle flows in a 102 mm diameter conventional cyclone operated at temperatures between 300 and 2000 K. Inlet gas velocities ranged from 3 to 42 m/s. Particle deposition patterns and the measurements of local pressures were used to determine the flow patterns and velocity profiles within the cyclone. A “Reynolds Number” has been defined based on the mean inlet velocity and the hydraulic diameter of the annulus between the cyclone wall and the gas outlet duct. An empirical equation was derived to correlate the ratio of the wall tangential velocity to the mean inlet velocity with this Reynolds Number.
Relationship between solids formation, residuum conversion, liquid yields and losses during athabasca bitumen processing in the presence of a variety of chemicals
Authors: Sanford Emerson C. , Xu Chun Ming 
Published: March 2009

AbstractConditions were chosen for the batch processing of Athabasca bitumen such that approximately 8% of the feed was converted to solids under an atmosphere of nitrogen. When hydrogen or tetralin was used, the amount of solids formed was cut in half. The combination of hydrogen and tetralin decreased the amount of solids formed by one‐half again. These conditions were used to study radical trapping reactions and hydrogen transfer under a variety of conditions using solids formation as a measure of reaction. None of the reagents used decreased solids formation significantly, and many increased the retrograde reaction. Correlations between solids formation (2–25% of feed) and yields and conversions showed that CCR conversion and sulfur conversion were not correlated with solids formation but nitrogen and vanadium conversions were. Most significant was the finding that losses (yields of gases) were constant for the 29 runs, at constant residuum conversion. Gases must be formed as a result of the initial thermally induced carbon‐to‐carbon bond breaking step in order for the yield to be independent of solids formation. Distillate yields decreased as solids formation increased.
A new policy for the estimation of the course of supersaturation in batch crystallization
Authors: Fevotte G. , Klein J. P. 
Published: March 2009

AbstractA continuing effort is being made in the development of on‐line sensors for the monitoring and control of crystallization processes. Applied on‐line calorimetry provides an estimate of the instantaneous heat release due to crystallization advancement. Two approaches to the implementation of such “soft sensors” are described and difficulties arising in the case of on‐line multipurpose non‐isothermal applications are outlined. Off‐line estimates of concentration and super‐saturation profiles during typical batch evaporative crystallizations are reported. Particular attention is paid to the detection of second, late nucleation bursts occurring in cases of poor crystal growth and rapid temperature decay.
An alternative method for evaluation of intrinsic viscosity
Authors: Kozicki W. , Kuang P. Q. 
Published: March 2009

AbstractAn alternative method for determination of intrinsic viscosities is described which evolves from the application of l'Hǒpital's rule to the expression defining the intrinsic viscosity. The method yields independent evaluations of the intrinsic viscosity and does not involve extrapolation beyond the range of experimental data or rely on a theoretical expression associated with such extrapolations. The application of the method is illustrated and comparisons are included with the results obtained by traditional approaches.
Simulation of airlift pumps for deep water wells
Authors: Nenes A. , Assimacopoulos D. , Markatos N. , Mitsoulis E. 
Published: March 2009

AbstractA mathematical model for the simulation of water airlift pumps is developed, based on the “interspersed continua” approximation for two‐phase flow systems, together with an algorithm that selects the appropriate friction correlation for specific flow regimes. The model presented can either predict the water or air flow rate for a given airlift system. Predictions obtained by the model were compared with a series of experiments performed by the Greek Institute of Geological and Mineral Exploration and were found to be in good agreement. The present predictions are far superior to those obtained by an existing simple model currently in general use.
Residence time distribution of the liquid in two‐phase cocurrent downflow in packed beds: Air/newtonian and non‐newtonian liquid systems
Authors: Iliuta I. , Thyrion F. C. , Muntean O. 
Published: March 2009

AbstractNew data on the liquid residence time distribution for two‐phase downflow of air‐Newtonian and non‐Newtonian liquids through packed beds of porous and non‐porous particles are presented. The piston‐dispersion‐exchange model is used to describe the liquid flow. With porous particles the dynamic evolution of the tracer concentration in the particles is described in terms of diffusion phenomena. The axial dispersion is very important in the case of two‐phase downflow of air‐water (trickle flow regime) and air‐CMC systems through fixed beds with porous particles, and is negligible in the case of non‐porous particles. With the porous particles, a key value is the effective diffusion coefficient of the tracer in the pores of the particles.
Degradation of alkanolamine blends by carbon dioxide
Authors: Dawodu Olukayode Fatai , Meisen Axel 
Published: March 2009

AbstractAqueous solutions of MDEA, MDEA + DEA and MDEA + MEA containing 4.2 kmol/m3 total amine, were contacted with CO2 at a partial pressure of 2.58 MPa and temperatures ranging from 120 to 180°C, in a stainless steel batch reactor. The reaction products include the known degradation compounds of the amines as well as products formed from secondary interactions in the amine blends. The rate of degradation was first order in the amines and, in magnitude, followed the sequence MDEA < MEA < DEA. Furthermore, the rate constant for MDEA was independent of amine substitution level and blend constituents. From a practical standpoint, MDEA + DEA blends would require frequent DEA make‐up to maintain treating efficiency.
Diffusion of lignin macromolecules within the fibre walls of kraft pulp. Part I: Determination of the diffusion coefficient under alkaline conditions
Authors: Li J. , Phoenix A. , Macleod J. M. 
Published: March 2009

AbstractThe intrinsic rate of diffusion of soluble lignin from fibre walls to bulk liquor has never been determined previously because of experimental difficulties; for example, the diffusion rate determined in a stirred cell is affected by the mechanical action of stirring. In our work, the intrinsic rate of diffusion of lignin macromolecules from the fibre walls of a softwood kraft pulp was determined under alkaline conditions using a displacement cell which eliminated external heat and mass transfer resistances and pulp fibre disturbances. The effects of such experimental conditions as pulp bed height and liquid flow rate were studied. The diffusion rate can be described by a diffusion model for a hollow cylinder with a very wide range of diffusion coefficients. The diffusion rate increased with increasing pH. Our results provide a new understanding of the lignin diffusion process in fibre walls, which is affected by the size of lignin molecules and the pores, and by the electrostatic interactions between intrafibre pore walls and lignin.