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Transport Experiments (transport + experiment)

Distribution by Scientific Domains

Chemistry	53%
Medical Sciences	20%
Engineering	13%

Selected Abstracts

Eulerian backtracking of atmospheric tracers.

THE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 615 2006
II: Numerical aspects
Abstract In Part I of this paper, a mathematical equivalence was established between Eulerian backtracking or retro- transport, on the one hand, and adjoint transport with respect to an air-mass-weighted scalar product, on the other. The time symmetry which lies at the basis of this mathematical equivalence can however be lost through discretization. That question is studied, and conditions are explicitly identified under which discretization schemes possess the property of time symmetry. Particular consideration is given to the case of the LMDZ model. The linear schemes used for turbulent diffusion and subgrid-scale convection are symmetric. For the Van Leer advection scheme used in LMDZ, which is nonlinear, the question of time symmetry does not even make sense. Those facts are illustrated by numerical simulations performed in the conditions of the European Transport EXperiment (ETEX). For a model that is not time-symmetric, the question arises as to whether it is preferable, in practical applications, to use the exact numerical adjoint, or the retro-transport model. Numerical results obtained in the context of one-dimensional advection show that the presence of slope limiters in the Van Leer advection scheme can produce in some circumstances unrealistic (in particular, negative) adjoint sensitivities. The retro-transport equation, on the other hand, generally produces robust and realistic results, and always preserves the positivity of sensitivities. Retro-transport may therefore be preferable in sensitivity computations, even in the context of variational assimilation. Copyright © 2006 Royal Meteorological Society [source]

Lysosomal trapping of amodiaquine: impact on transport across intestinal epithelia models

BIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 6 2008
Rose Hayeshi
Abstract The lipophilic weak base amodiaquine is an antimalarial drug that has been in use for over 40 years. Little is known of amodiaquine's mechanism of transport across membranes. Transport experiments of amodiaquine in Caco-2 cells showed a low recovery of 30% and rapid disappearance from the apical chamber. Compounds structurally similar to amodiaquine, and those affecting non-specific binding of amodiaquine or the pH of the system, were tested to unravel the mechanism behind these observations. Chloroquine and ammonium chloride increased the transmonolayer permeability of amodiaquine and decreased its accumulation in Caco-2 cells, whereas BSA had no effect. Chloroquine and BSA decreased plastic binding whereas ammonium chloride had no effect. This suggests that amodiaquine is trapped in acidic cell compartments such as lysosomes. Amodiaquine was also trapped in rat intestinal tissue. In addition, permeability from the apical to basolateral direction was significantly higher, suggesting an active uptake over the apical membrane of the rat tissue. It can be concluded that amodiaquine is trapped in acidic cell compartments due to its base properties and recovery may be improved by the use of ammonium chloride rather than BSA in transport experiments. Further studies are required to confirm whether amodiaquine is actively absorbed in the intestine. Copyright © 2008 John Wiley & Sons, Ltd. [source]

A Modular Injection System, Multilevel Sampler, and Manifold for Tracer Tests

GROUND WATER, Issue 6 2003
Brian J. Mailloux
Ground water injection and sampling systems were developed for bacterial transport experiments in both homogenous and heterogeneous unconsolidated, surficial aquifers. Two types of injection systems, a large single tank and a dynamic mixing tank, were designed to deliver more than 800 L of amended ground water to the aquifer over 12 hours, without altering the ground water temperature, pH, Eh, or dissolved gas composition. Two types of multilevel samplers (MLSs) were designed and installed. Permanent MLSs performed well for the homogenous surficial aquifer, but their installation procedure promoted vertical mixing, which could obfuscate experimental data obtained from vertically stratified, heterogeneous aquifers. A novel, removable MLS was designed to fit in 2- and 4-inch wells. Expandable O-rings between each sampling port hydraulically isolated each port for sample collection when a nut was tightened at the land surface. A low-cost vacuum manifold system designed to work with both MLS designs used 50 mL centrifuge tubes to efficiently sample 12 MLS ports with one peristaltic pump head. The integrated system was developed and used during four field campaigns over a period of three years. During each campaign, more than 3000 ground water samples were collected in less than one week. This system should prove particularly useful for ground water tracer, injection, and push-pull experiments that require high-frequency and/or high-density sampling. [source]

Synthesis, Structure, and Optical Properties of Terminally Sulfur-Functionalized Core-Substituted Naphthalene-Bisimide Dyes

HELVETICA CHIMICA ACTA, Issue 9 2006
Alfred B, aszczyk
Abstract The synthesis, characterization, and optical properties of a series of new 2,6-disubstituted naphthalene-bisimide dyes as molecular rods comprising terminal AcS groups is reported. The first series of dyes (1,3), comprising phenylhetero (Ph-X) core substituents, cover a broad range of the VIS spectrum, ranging from yellow (2) over red (3) to blue (1). The second series of dyes contains benzylhetero (Bn-X) core substituents (4,7). For the same heteroatom connecting the substituent to the naphthalene core, both series were found to display comparable colors. For the second series, the colors were blue (4), red (5), and violet (6, 7). The Ph-X-substituted dyes 1,3 are nonfluorescent, in contrast to the Bn-X-substituted compounds 4,7. This rich variety of optical features that can be adjusted by rather small alterations of the core substituents makes these structurally very comparable molecular rods ideal candidates for optically triggered molecular-transport investigations. Also, thanks to the terminal AcS groups, these compounds can be placed between nobel-metal electrodes for optically triggered transport experiments. [source]

Modulation of sinusoidal and canalicular elimination of bilirubin-glucuronides by rifampicin and other cholestatic drugs in a sandwich culture of rat hepatocytes

HEPATOLOGY RESEARCH, Issue 3 2008
György Lengyel
Aim:, Drug-induced hyperbilirubinemia has been shown to often be derived from modulation of the expression and activity of hepatobiliary transporters. In this study we examined the interactions of some therapeutic agents, which have been shown to cause cholestasis, with the elimination of bilirubin-glucuronides, in order to clarify whether these drugs modify the activity of Mrp2 and Mrp3 directly. Methods:, The modulation of bilirubin-glucuronide elimination with rifampicin, probenecid, indomethacin and benzbromarone was assayed in sandwich cultured rat hepatocytes. Results:, All the drugs studied decreased the canalicular transport, but modified the sinusoidal efflux differently. Rifampicin and probenecid stimulated the sinusoidal efflux, shifting the elimination of bilirubin-glucuronides to the sinusoidal domain (biliary excretion index: 3.9 ± 1.2; 22.7 ± 7.4 vs. 56.6 ± 1.5 and 56.8 ± 5.5). However, the overall elimination of bilirubin-glucuronides did not change significantly. In contrast, indomethacin and benzbromarone inhibited bothtransport processes, resulting in the decrease of the overall bilirubin-glucuronide elimination (61 ± 22; 56 ± 5% of the control). Rifampicin, indomethacin and benzbromarone decreased 5,(6)-carboxy-2,,7,-dichlorofluorescein transport by multidrug resistance-associated protein (Mrp)2 as visualized by confocal laser microscopy and in vesicular transport experiments. Interestingly, rifampicin decreased the MRP3 activity in vesicular transport experiments using 17-beta-estradiol-17-beta-D-glucuronide as substrate, in contrast to that observed in bilirubin-glucuronide transport experiments. Conclusion:, Here we show that the interactions of drugs on hepatobiliary transporter proteins may be identified in vitro in a sandwich culture of hepatocytes, in which canalicular and sinusoidal transport can be studied separately. [source]

Mechanistic study of electroosmotic transport across hydrated nail plates: Effects of pH and ionic strength

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2008
Jinsong Hao
Abstract The objective of this study was to investigate the effects of pH and ionic strength on electroosmotic transport in transungual iontophoresis. Transungual iontophoretic transport of model neutral permeants mannitol (MA) and urea (UR) across fully hydrated human nail plates in phosphate-buffered saline of different pH and ionic strengths were investigated in vitro. Two protocols were involved in the transport experiments with each protocol divided into stages including passive and iontophoresis transport at 0.1 and/or 0.3 mA. Nail plate electrical resistance and water uptake of nail clippings were measured at various pH and ionic strengths. In the pH study, electroosmosis enhanced the anodal transport of MA at pH 9 and cathodal transport at pH 3. The Peclet numbers of MA were more than two times higher than those of UR under these conditions. No significant electroosmosis enhancement was observed for MA and UR at pH 5. In the ionic strength study, a decrease in solution ionic strength from 0.7 to 0.04 M enhanced electroosmotic transport. Nail electrical resistance increased with decreasing the ionic strength of the equilibrating solution, but reached a plateau when the ionic strength was less than approximately 0.07 M. Solution pH and ionic strength had no significant effect on nail hydration. Under the studied pH and ionic strength conditions, the effects of electroosmosis were small compared to the direct-field effects in transungual iontophoretic transport of small to moderate size permeants. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:5186,5197, 2008 [source]

Transungual iontophoretic transport of polar neutral and positively charged model permeants: Effects of electrophoresis and electroosmosis

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2008
Jinsong Hao
Abstract Transungual iontophoretic transport of model neutral permeants mannitol (MA), urea (UR), and positively charged permeant tetraethylammonium ion (TEA) across fully hydrated human nail plates at pH 7.4 were investigated in vitro. Four protocols were involved in the transport experiments with each protocol divided into stages including passive and iontophoresis transport of 0.1 and 0.3 mA. Water and permeant uptake experiments of nail clippings were also conducted to characterize the hydration and binding effects of the permeants to the nails. Iontophoresis enhanced the transport of MA and UR from anode to cathode, but this effect (electroosmosis) was marginal. The transport of TEA was significantly enhanced by anodal iontophoresis and the experimental enhancement factors were consistent with the Nernst,Planck theory predictions. Hindered transport was also observed and believed to be critical in transungual delivery. The barrier of the nail plates was stable over the time course of the study, and no significant electric field-induced alteration of the barrier was observed. The present results with hydrated nail plates are consistent with electrophoresis-dominant (the direct field effect) transungual iontophoretic transport of small ionic permeants with small contribution from electroosmosis. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:893,905, 2008 [source]

Biological, pharmaceutical, and analytical considerations with respect to the transport media used in the absorption screening system, Caco-2

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 8 2003
Françoise M. Ingels
Abstract During the evaluation and selection of drug candidates, the Caco-2 cell culture system is commonly used for the determination of intestinal transport characteristics and to anticipate permeability limited drug absorption. Although classic HBSS-like buffered salt solutions are commonly used to perform Caco-2 transport experiments, different shortcomings (e.g., adsorption and low solubility) have been associated with the use of plain aqueous buffers. As transport experiments performed with unoptimized conditions may compromize the value of the Caco-2 model as a permeation screening tool, many efforts have been made to optimize the experimental conditions of Caco-2 transport assays. In this minireview, the hurdles associated with the use of saline aqueous buffers in Caco-2 transport experiments are summarized and the different options, which have been proposed to overcome these issues, are reviewed and discussed. Biologically, pharmaceutically, as well as analytically relevant media affecting the outcome of the transport experiments are described. Unfortunately, up to now, no systematic studies comparing the different experimental conditions have been performed, jeopardizing the possibility to define a (single) optimal solution to overcome the different issues associated with the use of saline aqueous buffers. Based on the reported options it can be proposed to use DMSO (,1%) in standard screening procedures for the ranking of compounds based on their apical to basolateral transport. If compounds are not soluble in DMSO 1%, dimethylacetamide (3%) or N -1-methyl-pyrrolidone (2.5%) are good alternatives. However, these options do not imitate the in vivo situation. If one wants to take into account the physiological relevance of the media, the use of a biologically relevant apical medium (e.g., FASSIF) in combination with an analytically friendly, sink condition creating basolateral solvent (e.g., containing a micelle forming agent) can be suggested. © 2003 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 92:1545,1558, 2003 [source]

Changes in calcium absorption and subsequent tissue distribution induced by Maillard reaction products: in vitro and in vivo assays,

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 2 2006
Cristina Delgado-Andrade
Abstract The effects of Maillard reaction products (MRP) from glucose,lysine and glucose,methionine on calcium bioavailability were studied by in vivo (rats) and in vitro (Caco-2 cells) assays. Equimolar glucose/lysine and glucose/methionine mixtures (40% moisture) were heated (150 °C, 30 min) to prepare samples (GL30 and GM30, respectively). For 21 days, rats were fed a control diet (control group) or diets containing separately 3% of the heated mixtures (GL30 and GM30 groups, respectively). In the last week a calcium balance was performed, after which the animals were sacrificed and some organs and serum were removed to analyze calcium levels. A second balance was carried out throughout the experimental period to calculate global calcium retention (retained calcium during the entire 21 days). Unheated and heated samples were used for calcium transport experiments in Caco-2 cells. Food intake and final body weight were lower in the GM30 group. Calcium fecal excretion decreased and digestibility increased in this group. Accordingly, increased calcium transport in Caco-2 cells was found in the presence of the GM30 sample, when compared with the unheated sample. However, global calcium retention tended to decrease in the GM30 group, mainly owing to the lower food intake. Bone calcium concentrations decreased in the animals fed the MRP diets. The possible long-term effects of MRP intake on calcium digestibility and bone calcium should be taken into account to avoid related diseases. Copyright © 2005 Society of Chemical Industry [source]

Purely electronic transport and localization in the Bose glass

ANNALEN DER PHYSIK, Issue 12 2009
M. Müller
Abstract We discuss transport and localization properties on the insulating side of the disorder dominated superconductor-insulator transition, described in terms of the dirty boson model. Analyzing the spectral properties of the interacting bosons in the absence of phonons, we argue that the Bose glass phase admits three distinct regimes. For strongest disorder the boson system is a fully localized, perfect insulator at any temperature. At smaller disorder, only the low temperature phase exhibits perfect insulation while delocalization takes place above a finite temperature. We argue that a third phase must intervene between these perfect insulators and the superconductor. This conducting Bose glass phase is characterized by a mobility edge in the many body spectrum, located at finite energy above the ground state. In this insulating regime purely electronically activated transport occurs, with a conductivity following an Arrhenius law at asymptotically low temperatures, while a tendency to superactivation is predicted at higher T. These predictions are in good agreement with recent transport experiments in highly disordered films of superconducting materials. [source]

Ein Trocknungskoeffizient für Baustoffe

BAUPHYSIK, Issue 3 2009
Gregor A. Scheffler Dr.-Ing.
Berechnungsverfahren; Feuchte Wärme; Versuche Abstract Ein wesentliches Element der hygrothermischen Charakterisierung von Baustoffen ist der Trocknungsversuch. Im Gegensatz zu anderen Feuchtetransportexperimenten wie dem Diffusionsversuch oder dem Wasseraufnahmeexperiment ist es bislang nicht möglich, aus der Trocknung einen einfachen Kennwert abzuleiten. In vielen Fällen, beispielsweise in der Interaktion von Forschung und Industrie, aber auch beim praktischen Vergleich bzw. der Auswahl geeigneter Baustoffe wäre ein solcher Kennwert jedoch wünschenswert. Im vorliegenden Artikel wird zunächst die Bedeutung des Trocknungsversuches für die hygrische Charakterisierung von Baustoffen herausgestellt, aus der sich das Bestreben ableitet, das Trocknungsverhalten zu standardisieren und einen Einzahlen-Materialkennwert zu definieren. Nach einer die verschiedenen Einflussfaktoren der Trocknung differenzierenden Einleitung werden bestehende Ansätze für die Standardisierung des Trocknungsverlaufes bzw. die Ableitung eines Trocknungskoeffizienten vorgestellt. Die einhergehenden Probleme werden diskutiert und weitere Möglichkeiten evaluiert. Ein einfacher Trocknungskoeffizient, der sich aus dem Trocknungsverlauf ableiten lässt, wird definiert. Die Korrelation dieses Koeffizienten mit dem Wasseraufnahmekoeffizienten und dem Dampfdiffusionswiderstand wird analysiert. Sein zusätzlicher Informationsgehalt wird in diesem Zusammenhang kritisch hinterfragt. Im Ergebnis steht die Definition des Trocknungskoeffizienten als ein neuer, unabhängiger Materialkennwert, der die Feuchtetransporteigenschaften im Übergang zwischen hygroskopischem und gesättigtem Transport beschreibt. Mit diesem Kennwert ist es möglich, Baustoffe einfach und schnell hinsichtlich ihres Trocknungsverhaltens zu unterscheiden und zu beurteilen, was insbesondere bei feuchtesensitiven Materialien von Bedeutung ist. A drying coefficient for building materials. The drying experiment is an important element of the hygrothermal characterisation of building materials. Contrary to other moisture transport experiments as the vapour diffusion and the water absorption test, it is until now not possible to derive a simple coefficient for the drying. However, in many cases such a coefficient would be highly appreciated, e.g. in interaction of industry and research or for the distinction and selection of suitable building materials throughout design and practise. This article first highlights the importance of drying experiments for hygrothermal characterisation of building materials on which the attempt is based to standardize the drying experiment as well as to derive a single number material coefficient. The drying itself is briefly reviewed and existing approaches are discussed. On this basis, possible definitions are evaluated. Finally, a drying coefficient is defined which can be determined based on measured drying data. The correlation of this coefficient with the water absorption and the vapour diffusion coefficient is analyzed and its additional information content is critically challenged. As result, a drying coefficient has been derived and defined as a new and independent material parameter. It contains information about the moisture transport properties throughout the wide range of moisture contents from hygroscopic up to saturation. With this new and valuable coefficient, it is now possible to distinguish and select building materials quickly and easily by means of their drying behaviour. This is particularly important for moisture sensitive materials. [source]

Lysosomal trapping of amodiaquine: impact on transport across intestinal epithelia models

Mass Transport in Multilayer Porous Metallic Membranes , Diagnosis, Identification and Validation

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2009
V. Edreva
Abstract For a reliable description of mass transfer in membrane reactors the multilayer structure of the membrane is essential. This paper discusses methods which are sufficient to distinguish between homogeneous and composite membranes, and some others which are not. Different mass transport experiments (single gas permeation, isobaric diffusion, transient diffusion) with a porous metallic membrane consisting of two layers and the dusty gas model were used for this purpose. Simultaneous identification of mass transport parameters of both layers was achieved by modern optimization techniques on single gas permeation data. These parameters were validated by isobaric or transient diffusion measurements. [source]

ChemInform Abstract: A Revision of the Central Part of the Cr,Ge Phase Diagram.

CHEMINFORM, Issue 36 2010
Isabella Jandl
Abstract The reinvestigation of the Cr,Ge phase diagram by XRD, DTA, and chemical vapor transport experiments does not show a polymorphic phase transformation for Cr5Ge3 as previously reported. [source]