bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Dissipation Rate in Stirred Vessels Through Direct Measurement of Fluctuating Velocity Gradients
Authors: Baldi S. , Ducci A. , Yianneskis M. 
Published: February 2004

Abstract2‐D and 3‐D PIV and 4‐channel LDA techniques were employed to measure the turbulence energy dissipation rate in vessels stirred by Rushton impellers. The measurements were made in vessels of diameter T = 100 mm and 294 mm and stirred by impellers of diameter D = T/3. The impellers were rotated at speeds corresponding to Reynolds number of 40,000 to ensure fully‐turbulent flow in the vessels. ϵ was determined directly from measurements of the Reynolds stress gradients by analyzing the PIV images over interrogation areas down to 0.1 mm. Similar LDA data were obtained in the larger 294 mm vessel, with a resolution of around 50 μm. The fluctuating gradient results obtained with the two techniques compare well and show that direct measurement of the ϵ distribution is feasible with both PIV and LDA methods.
Hydrodynamics in a Stirred Square Tank Investigated Using a 3‐D PIV LES Decomposition Approach and LDA Measurements
Authors: Kilander J. , Rasmuson A. 
Published: February 2004

AbstractIn this study, the hydrodynamics and turbulence in a square tank stirred with the hydrofoil impeller Lightnin A310 is investigated using a large eddy particle image velocimetry approach. Particle image velocimetry data are used as the large scale part of a large eddy simulation and the small scales are modelled by direct calculation of the turbulent stress tensor using filtered particle image velocimetry data. The spatial distribution of the calculated dissipation rate showed agreement with previous work. The macro instabilities of the flow structure were investigated by means of spectral analysis. Low frequency phenomena separated from the mean flow were detected. The cause of these could partly be explained by the circulation time for the tank.
Modeling of Mixing and Precipitation Using CFD and Population Balances
Authors: Paschedag A.R. 
Published: February 2004

AbstractSimulations of particle size distributions in technical precipitation reactors require the consideration of turbulent mixing and precipitation kinetics. For that, spatially resolved population balances have to be evaluated. In turbulent flows these balances cannot be solved directly, instead either Reynolds averaging or Large Eddy Simulations have to be applied, while unresolved fluctuations need to be modeled. Reynolds averaging of the population balance leads to a turbulent growth dispersion term which has to be modeled. As no theoretically founded approach is available, an assumption was made in analogy to the turbulent diffusion, which improves the prediction of the size distribution shape compared to experiments.
CFD Modelling of Mixing Effects on the Course of Parallel Chemical Reactions Carried out in a Stirred Tank
Authors: Bałdyga J. , Makowski Ł. 
Published: February 2004

AbstractEffects of turbulent mixing on the course of two fast parallel chemical reactions (neutralization of sodium hydroxide and hydrolysis of ethyl chloroacetate) carried out in a semibatch stirred tank reactor are experimentally investigated and numerically simulated. The flow pattern in the stirred tank is predicted using CFD and experimentally validated using Laser Doppler Anemometry. Mixing effects are modelled using three CFD based models. In the first and the second model the Beta probability distribution and the spiked distribution are used respectively; in the third model concentration fluctuations are neglected.
Large Eddy Simulation of Turbulent Flow in a Rushton Impeller Stirred Reactor with Sliding‐Deforming Mesh Methodology
Authors: Yeoh S.L. , Papadakis G. , Lee K.C. , Yianneskis M. 
Published: February 2004

AbstractThe unsteady turbulent flow in a mixing vessel stirred by a Rushton impeller is predicted using the Large Eddy Simulation technique. The interaction between the moving impeller and the static baffles is accounted for explicitly through a sliding‐deforming mesh methodology, thus, eliminating approximations used to account for the effect of the moving impeller. Large‐scale structures associated with the trailing vortices are assessed via the vorticity and the turbulent kinetic energy distributions. The phase‐resolved predictions are compared with measurement data obtained by laser‐Doppler anemometry and favourable agreement is reported both for mean as well as turbulence quantities.
Steering of Liquid Mixing Speed in Interdigital Micro Mixers – From Very Fast to Deliberately Slow Mixing
Authors: Löb P. , Drese Klaus S. , Hessel V. , Hardt S. , Hofmann C. , Löwe H. , Schenk R. , Schönfeld F. , Werner B. 
Published: February 2004

AbstractVery fast mixing in the range of milliseconds as well as deliberately slow mixing was realized by specially adjusted interdigital micro mixers made of glass or stainless steel. The corresponding micro mixers are presented including experimental and theoretical investigations of the respective mixing process. Fast mixing was realized by combination of flow multilamination by interdigital microstructured feeding structures with geometric focusing. Details on the microfabrication, achievable throughputs and hydrodynamics are discussed. To prevent clogging of microsized feeding structures in the case of precipitation reactions, mixing was deliberately slowed down by separating the reactant solutions at the outlet by additional layers of inert liquids.
Coaxial Mixer Hydrodynamics with Newtonian and non‐Newtonian Fluids
Authors: Foucault S. , Ascanio G. , Tanguy P.A. 
Published: February 2004

AbstractThe performance of several combinations of a wall scraping impeller and dispersing impellers in a coaxial mixer operated in counter‐ and co‐rotating mode were assessed with Newtonian and non‐Newtonian fluids. Using the power consumption and the mixing time as the efficiency criteria, impellers in co‐rotating mode were found to be a better choice for Newtonian and non‐Newtonian fluids. The hybrid impeller‐anchor combination was found to be the most efficient for mixing in counter‐rotating or co‐rotating mode regardless of the fluid rheology. For both rotating modes, it was shown that the anchor speed does not have any effect on the power draw of the dispersing turbines. However, the impeller speed was shown to affect the anchor power consumption. The determination of the minimum agitation conditions to achieve the just suspended state of solid particles (Njs) was also determined. It was found that Njs had lower values with the impellers having the best axial pumping capabilities.
Macro‐ and Micromixing in a Taylor‐Couette Reactor with Axial Flow and their Influence on the Precipitation of Barium Sulfate
Authors: Judat B. , Racina A. , Kind M. 
Published: February 2004

AbstractA new set‐up for precipitation experiments capable of independent adjustment of micromixing and macromixing conditions is presented. The setup consists of a Taylor‐Couette (TC) reactor serving as the reaction zone and an external loop where the slower stages of precipitation processes take place. Micromixing in the TC reactor has been investigated with a chemical reaction system and with PIV‐measurements. Micromixing times range between 6·10–3 and 8·10–2 s. Tracer experiments reveal the macromixing performance of the whole set‐up which has been compared with the behavior of ideal reactors. Precipitation experiments with barium sulfate show some influence of micromixing intensity on the particle size and of macromixing on particle morphology.
The Mixing Efficiency of an Eccentric‐Disc Kneading Zone in Intermeshing Co‐ and Counter‐Rotating Twin‐Screw Extruders
Authors: Brod H. , Liesenfelder U. 
Published: February 2004

AbstractThe distributive mixing efficiency of a twin‐screw extruder kneading zone consisting of eccentric disc elements was measured using an online video technique. Both co‐ and counter‐rotation were examined. Viscous Newtonian silicone oil was used as model liquid and black iron oxide pigment served as tracer substance. Under isoviscous, creeping flow and non‐diffusive conditions and for a fixed flow rate ratio of the colored and uncolored feed streams, the intensity of segregation S is only a function of the kinematic parameter Λ (the ratio of the imposed extruder throughput and the throughput at zero axial pressure gradient). The measured dependency of S on Λ is in qualitative agreement with the results of Pawlowski for a single screw extruder. The data was also plotted against the dimensionless speed of rotation, i.e. the product of the screw speed and the average residence time within the mixing section. This brings the abscissa ranges for mixers with different conveying capacity closer together, and differences in mixing efficiency between the tested configurations can be better interpreted. The energetic efficiency of the mixers investigated is compared by applying the concept of specific action. This helps to decide which mixer geometry and operating conditions produce a given homogeneity with the lowest amount of work done by viscous forces.
State of the Art and Future Trends in CFD Simulation of Stirred Vessel Hydrodynamics
Authors: Sommerfeld M. , Decker S. 
Published: February 2004

AbstractComputational fluid dynamics (CFD) has become a widely used tool for analysing, optimising and supporting the design of mixing processes in stirred vessels. The present contribution gives a brief summary of the methods applied for numerically treating the power input by the impeller, such as empirical methods, the multiple frame of reference approach and unsteady methods using sliding or clicking meshes. Thereafter, recent developments and trends in the numerical computation of single phase flows in stirred vessels on the basis of DNS (direct numerical simulations), LES (large eddy simulations) and RANS (Reynolds‐averaged Navier‐Stokes) approaches are summarised. Since many operations in stirred vessels involve at least two phases, also the methods for modelling these flows, such as the two‐fluid method and the Euler/Lagrange approach are briefly described and recent applications are reviewed. Finally, also own calculations for single‐phase mixing and particle dispersion in a stirred vessel using the Euler/Lagrange approach are introduced emphasising some recent developments.
Auslegung und Optimierung von hybriden Trennverfahren
Authors: Franke M. , Górak A. , Strube J. 
Published: February 2004

AbstractUnter hybriden Trennverfahren versteht man die Verschaltung von mindestens zwei verschiedenen, apparativ getrennten Grundoperationen, die zur Trennaufgabe beitragen. Hybride Trennverfahren werden bei schwierigen Trennungen, wie bei engsiedenden oder azeotropen Gemischen, eingesetzt, wenn eine einzelne Grundoperation, z. B. Rektifikation, Extraktion, Kristallisation, Membranverfahren oder Chromatographie, gar nicht oder nur mit sehr großem Aufwand zum Ziel führt. Aufgrund der Struktur des Hybridprozesses, die das Vorhandensein mindestens zwei verschiedener Grundoperationen und eine entsprechende Anzahl von Rückführungen impliziert, ist die Auslegung komplex, sie wird deshalb z. Z. systematisch in der Forschung untersucht. In dieser Arbeit werden die Anforderungen an eine Auslegungsmethodik für hybride Trennverfahren dargestellt. Es wird eine Methodik vorgestellt, die auf einer detaillierten Modellierung der Grundoperationen und einer simultanen Mehrvariablen‐Optimierung beruht. Die Anwendbarkeit dieser Methodik wird anhand einer Isomerentrennung gezeigt.
Der Einfluss der Biotechnologie auf Produktionsverfahren in der Chemieindustrie
Authors: Festel G. , Knöll J. , Götz H. , Zinke H. 
Published: February 2004

AbstractEine aktuelle Marktstudie von Festel Capital zeigt, dass der Einfluss der Biotechnologie auf die industriellen Produktionsverfahren in der Chemieindustrie weiter wachsen wird. Von besonderem Interesse ist dabei die Herstellung von Feinchemikalien, insbesondere von enantiomerenreinen Wirkstoffen für die Agro‐ und Pharmaindustrie. Die Produktionskosten sind die entscheidende Triebkraft für einen Wechsel zu biotechnologischen Produktionsverfahren. Ziel sind Einsparungen durch Prozessvereinfachungen sowie bei den Roh‐, Neben‐ und Abfallprodukten. Andere Faktoren spielen bei der Wahl des Produktionsverfahrens in der Regel keine Rolle. Ein wichtiger Aspekt ist allerdings die Zugänglichkeit von neuen Biotech‐Produkten, die durch herkömmliche Verfahren nicht hergestellt werden können.
Immunohistochemical localization of Ih channel subunits, HCN1–4, in the rat brain
Authors: Notomi Takuya , Shigemoto Ryuichi 
Published: February 2004

AbstractHyperpolarization‐activated cation currents (Ih) contribute to various physiological properties and functions in the brain, including neuronal pacemaker activity, setting of resting membrane potential, and dendritic integration of synaptic input. Four subunits of the Hyperpolarization‐activated and Cyclic‐Nucleotide‐gated nonselective cation channels (HCN1–4), which generate Ih, have been cloned recently. To better understand the functional diversity of Ih in the brain, we examined precise immunohistochemical localization of four HCNs in the rat brain. Immunoreactivity for HCN1 showed predominantly cortical distribution, being intense in the neocortex, hippocampus, superior colliculus, and cerebellum, whereas those for HCN3 and HCN4 exhibited subcortical distribution mainly concentrated in the hypothalamus and thalamus, respectively. Immunoreactivity for HCN2 had a widespread distribution throughout the brain. Double immunofluorescence revealed colocalization of immunoreactivity for HCN1 and HCN2 in distal dendrites of pyramidal cells in the hippocampus and neocortex. At the electron microscopic level, immunogold particles for HCN1 and HCN2 had similar distribution patterns along plasma membrane of dendritic shafts in layer I of the neocortex and stratum lacunosum moleculare of the hippocampal CA1 area, suggesting that these subunits could form heteromeric channels. Our results further indicate that HCNs are localized not only in somato‐dendritic compartments but also in axonal compartments of neurons. Immunoreactivity for HCNs often occurred in preterminal rather than terminal portions of axons and in specific populations of myelinated axons. We also found HCN2‐immunopositive oligodendrocytes including perineuronal oligodendrocytes throughout the brain. These results support previous electrophysiological findings and further suggest unexpected roles of Ih channels in the brain. J. Comp. Neurol. 471:241–276, 2004. © 2004 Wiley‐Liss, Inc.
Demonstration of an orexinergic central innervation of the pineal gland of the pig
Authors: Fabris Chiara , Cozzi Bruno , Hay‐Schmidt Anders , Naver Bjarke , Møller Morten 
Published: February 2004

AbstractOrexins/hypocretins, two isoforms of the same prepropeptide, are widely distributed throughout the brain and are involved in several physiological and neuroendocrine regulatory patterns, mostly related to feeding, sleep, arousal, and cyclic sleep‐wake behaviors. Orexin‐A and orexin‐B bind with different affinities to two G‐protein‐coupled transmembrane receptors, orexin‐1 and orexin‐2 receptors (OR‐R1 and OR‐R2, respectively). Because of the similarities between the human and the swine brain, we have studied the pig to investigate the orexinergic system in the diencephalon, with special emphasis on the neuroanatomical projections to the epithalamic region. By using antibodies against orexin‐A and orexin‐B, immunoreactive large multipolar perikarya were detected in the hypothalamic periventricular and perifornical areas at the light and electron microscopic levels. In the region of the paraventricular nucleus, the orexinergic neurons extended all the way to the lateral hypothalamic area. Immunoreactive nerve fibers, often endowed with large varicosities, were found throughout the hypothalamus and the epithalamus. Some periventricular immunoreactive nerve fibers entered the epithalamic region and continued into the pineal stalk and parenchyma to disperse among the pinealocytes. Immunoelectron microscopy confirmed the presence of orexinergic nerve fibers in the pig pineal gland. After extraction of total mRNA from the hypothalamus and pineal gland, we performed RT‐PCR and nested PCR using primers specific for porcine orexin receptors. PCR products were sequenced, verifying the presence of both OR‐R1 and OR‐R2 in the tissues investigated. These findings, supported by previous studies on rodents, suggest a hypothalamic regulation of the pineal gland via central orexinergic nervous inputs. J. Comp. Neurol. 471:113–127, 2004. © 2004 Wiley‐Liss, Inc.
Localization of the mRNA encoding prolyl endopeptidase in the rat brain and pituitary
Authors: Bellemère Gaelle , Vaudry Hubert , Mounien Lourdes , Boutelet Isabelle , Jégou Sylvie 
Published: February 2004

AbstractProlyl endopeptidase (EC 3.4.21.26, PEP), a serine protease that hydrolyzes peptides at the carboxyl side of proline residues, is involved in the breakdown of several proline‐containing neuropeptides and, thus, may contribute to the regulation of behavioral activities. In this study, the distribution of PEP mRNA was investigated in the central nervous system and pituitary of rat by means of quantitative reverse transcriptase‐polymerase chain reaction analysis and in situ hybridization histochemistry. High densities of PEP transcripts were found in cerebellar Purkinje and granule cells, within most hypothalamic nuclei, in pyramidal neurons of the Ammon's horn, in granule cells of the dentate gyrus, and within the basolateral complex of the amygdala. Moderate levels of PEP mRNA were observed in layers 3–5 of the cerebral cortex, the anterior thalamic group, the septal region, the substantia nigra, the magnocellular neurons of the red nucleus, and the motor nuclei of the cranial nerves. Low concentrations of PEP mRNA were detected in the deep mesencephalic nuclei, the reticular formation, the pretectum, and the tectum. A high density of PEP mRNA was found in the intermediate and the anterior lobes of the pituitary, while the neural lobe was devoid of labeling. In several brain regions, the distribution pattern of PEP mRNA overlapped that of various neuropeptide receptors, suggesting that PEP is actually involved in the inactivation of regulatory neuropeptides. J. Comp. Neurol. 471:128–143, 2004. © 2004 Wiley‐Liss, Inc.
The single neurofilament subunit of lamprey may need another element for filament assembly
Authors: Zhang Guixin , Spencer Paula H. , Jin Li‐Qing , Cohlberg Jeffrey A. , Beaulieu Jean Martin , Julien Jean‐Pierre , Selzer Michael E. 
Published: February 2004

AbstractRegenerating axon tips in transected lamprey spinal cord contain dense accumulations of neurofilaments (NFs), suggesting that NFs may play a role in the mechanism of axonal regeneration. Compared with heteropolymeric assemblies of NF triplet proteins in mammals, NF in lampreys has been thought to contain only a single subunit (NF180). This would imply that NF180 self‐assembles, which would be important for manipulating its expression in studies of axonal regeneration. In order to study the possible role of NF in process outgrowth and to determine whether NF180 can self‐assemble, its gene was transfected into mammalian and fish cell lines that either contain or lack vimentin. In transfected NIH3T3 cells, NF180 was poorly phosphorylated and its expression did not alter the length or number of cell processes. Nor did it appear to form typical intermediate filaments, suggesting that it may not self‐assemble. NF180 also did not form typical filaments in SW13cl cells that either possessed or lacked vimentin, nor in transfected fish cells that were cultured at 18°C. In vitro, NF180 could not self‐assemble but interacted with NF‐L to interrupt its self‐assembly. When cotransfected with rat NF‐L into SW13c1.2vim− cells, NF180 did form thick, rod‐like filamentous structures on immunofluorescence. More typical NFs were observed when NF180 was cotransfected with both NF‐L and NF‐M. Thus, NF180 cannot self‐assemble but appears to require one or more additional elements for incorporation into NFs. J. Comp. Neurol. 471:188–200, 2004. © 2004 Wiley‐Liss, Inc.
Characterization of projections from a sexually dimorphic motor nucleus in the spinal cord of adult green anoles
Authors: Holmes Melissa M. , Wade Juli 
Published: February 2004

AbstractMale green anoles possess two copulatory organs (hemipenes), which are independently controlled by bilateral muscles: the transversus penis (TPN) and retractor penis magnus (RPM). Adult females do not possess hemipenes or either of the two related muscles. Motoneurons projecting to the TPN lie in spinal segments trunk 17 and sacral 1 (T17–S1). Overall, motoneurons in this region are larger and more numerous in males than females. The present studies were designed to determine 1) whether motoneurons projecting to the RPM are located in the same sexually dimorphic nucleus, 2) other targets of T17–S1 motoneurons, and 3) the approximate proportion of motoneurons projecting to each muscle. In Study 1, unilateral injection of the retrograde tracer Fast Blue (FB) into RPMs and simultaneous unilateral injection of either Cholera Toxin‐fluorescein (CT‐FITC) or Diamidino Yellow into TPNs revealed that RPM and TPN motoneurons are indeed interdigitated in T17–S1. In Study 2, FB was used to characterize other targets of this nucleus in both males and females. In adult males, projections to four muscles accounted for 96% of the T17–S1 motoneurons: the TPN, RPM, caudifemoralis (CF), and cloacal sphincter (SC). In adult females, projections to the CF and SC comprised 70% of this nucleus. These data demonstrate that the T17–S1 nucleus is a mixed spinal nucleus that has projections to muscles present in both sexes, as well as those present only in males and specialized for male copulatory behavior. J. Comp. Neurol. 471:180–187, 2004. © 2004 Wiley‐Liss, Inc.
Rat intralaminar thalamic nuclei projections to the globus pallidus: A biotinylated dextran amine anterograde tracing study
Authors: Yasukawa T. , Kita T. , Xue Y. , Kita H. 
Published: February 2004

AbstractThe topographical organization and ultrastructural features of the intralaminar thalamic nuclei (ITN) projections to the globus pallidus (GP) were studied using the biotinylated dextran amine (BDA) anterograde tracing method in the rat. To assess the functional association of BDA injection sites in the ITN, the known topographical organization of the ITN‐neostriatal (Str) projections and calcium binding protein (CaBP) immunostaining patterns of the Str and GP were used. BDA injection in the lateral part of the lateral parafascicular nucleus and the caudal part of the central lateral nucleus labeled fibers and boutons mainly in the dorsolateral sensorimotor territory of the Str and the middle territories of the GP. BDA injection in the medial part of the lateral parafascicular nucleus and the central lateral nucleus labeled mainly the middle association territory of the Str and the border and the caudomedial territories of the GP. BDA injection in the medial parafascicular nucleus and the central medial nucleus labeled mainly the medial limbic territory of the Str. The medial parafascicular nucleus projected to the medial‐most region of the GP, while the central medial nucleus projection to the GP was very sparse. Electron microscopic observations indicated that BDA‐labeled boutons form asymmetric synapses mainly on 0.5–2.0 μm diameter dendritic shafts in the GP. The boutons were small but had a relatively long active zone. The present observations together with the known topographical organization of striatopallidal projections indicated that the ITN‐GP projections were topographically organized in parallel to the ITN‐Str projections. Thus, each part of the ITN projecting to the sensorimotor, the association, and the limbic territories of the Str also projects to the corresponding functional territories of the GP. J. Comp. Neurol. 471:153–167, 2004. © 2004 Wiley‐Liss, Inc.