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Tracer Technique (tracer + technique)
Selected AbstractsPrecise matching of olivo-cortical divergence and cortico-nuclear convergence between somatotopically corresponding areas in the medial C1 and medial C3 zones of the paravermal cerebellumEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2000R. Apps Abstract The paravermal cerebellar cortex contains three spatially separate zones (the C1, C3 and Y zones) which form a functionally coupled system involved in the control of voluntary limb movements. A series of ,modules' has been postulated, each defined by a set of olivary neurons with similar receptive fields, the cortical microzones innervated by these neurons and the group of deep cerebellar nuclear neurons upon which the microzones converge. A key feature of this modular organization is a correspondence between cortical input and output, irrespective of the zonal identity of the microzone. This was tested directly using a combined electrophysiological and bi-directional tracer technique in barbiturate-anaesthetized cats. During an initial operation, small injections of a mix of retrograde and anterograde tracer material (red beads combined with Fluoro-Ruby or green beads combined with biotinylated dextran amine or Fluoro-Emerald) were made into areas of the medial C1 and medial C3 zones in cerebellar lobule V characterized by olivo-cerebellar input from the ventral forelimb. The inferior olive and the deep cerebellar nuclei were then scrutinized for retrogradely labelled cells and anterogradely labelled axon terminals, respectively. For individual experiments, the degree of C1,C3 zone terminal field overlap in the nucleus interpositus anterior was plotted as a function of either the regional overlap of single-labelled cells or the proportion of double-labelled cells in the dorsal accessory olive. The results were highly positively correlated, indicating that cortico-nuclear convergence between parts of the two zones is in close proportion to the corresponding olivo-cerebellar divergence, entirely consistent with the modular hypothesis. [source] Kinetics of Lysine and Other Amino Acids Loss During Extrusion Cooking of Maize GritsJOURNAL OF FOOD SCIENCE, Issue 2 2003S. Ilo ABSTRACT: Maize grits were extrusion-cooked in a conical, counter-rotating twin-screw extruder at different barrel temperatures, feed moistures, and screw speeds. Residence time distribution was measured by a dye tracer technique. Experiments with lysine-fortified maize grits showed a 1st order reaction for lysine loss. A detailed kinetic study has been performed for the losses during extrusion cooking of lysine, cystine, and arginine. The 1st-order rate constants were dependent mainly on product temperature and feed moisture, whereas screw speed had no influence. Activation energy of lysine, arginine, and cystine loss was 127, 68, and 76 kJ/mol, respectively. Shear stress significantly affected the rate constants of amino acids loss in extrusion cooking. [source] Fluid dynamics in coal liquefaction reactors using neutron absorption tracer techniqueAICHE JOURNAL, Issue 8 2000Naohide Sakai Hydrodynamic properties in the coal liquefaction reactors at the Kashima pilot plant, which was constructed based on the NEDOL process, were investigated using the neutron absorption tracer technique. The reactor system is composed of three vessels, each with 1.0 m ID and 11.8 m in height. The gas velocity in the reactors under coal liquefaction conditions was estimated using a reaction simulator that contained reaction rates and vapor,liquid equilibrium. The axial dispersion coefficients in the first and third reactors at superficial gas velocities of 0.06,0.07 m/s were much smaller than those reported for air,water systems under ambient conditions. This suggests that the pilot-plant reactors operated fundamentally in the homogeneous bubble flow regime. [source] In situ determination of sulfate turnover in peatlands: A down-scaled push,pull tracer technique,JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 5 2008Tobias Goldhammer Abstract Bacterial sulfate reduction (BSR) is a key process in anaerobic respiration in wetlands and may have considerable impacts on methane emissions. A method to determine sulfate production and consumption in situ is lacking to date. We applied a single-well, injection-withdrawal tracer test for the in situ determination of potential sulfate turnover in a northern temperate peatland. Piezometers were installed in three peat depth levels (20, 30, and 50,cm) during summer 2004, and three series of injection-withdrawal cycles were carried out over a period of several days. Turnover rates of sulfate, calculated from first-order-reaction constant k (,0.097 to 0.053 h,1) and pore-water sulfate concentrations (approx. 10 µmol L,1), ranged from ,1.3 to ,9.0 nmol cm,3 d,1 for reduction and from +0.7 to +25.4 nmol cm,2 d,1 for production, which occurred after infiltration of water following a heavy rainstorm. Analysis of stable isotopes in peat-water sulfate revealed slightly increasing ,34S values and decreasing sulfate concentrations indicating the presence of BSR. The calculated low sulfur-fractionation factors of <2, are in line with high sulfate-reduction rates during BSR. Routine application will require technical optimization, but the method seems a promising addition to common ex situ techniques, as the investigated soil is not structurally altered. The method can furthermore be applied at low expense even in remote locations. [source] Advances in protein turnover analysis at the global level and biological insightsMASS SPECTROMETRY REVIEWS, Issue 5 2010Qingbo Li Abstract The concept of a dynamic state of body constituents, a precursor of the modern term of proteome dynamics, was conceived over a century ago. But, not until recently can we examine the dynamics of individual "constituents" for example, proteins at a truly global level. The path of advancement in our understanding of protein turnover at the global level is marked by the introduction of some key technological innovations. These methods include the isotopic tracer technique in the 1930s, the two-dimensional gel electrophoresis technique in the 1970s, the sector mass spectrometer that could analyze isotopomers of peptides in the early 1990s, the 2D gel/MALDI-TOF proteomics technology in the late 1990s, the booming liquid chromatography/mass spectrometry proteomics technology in this decade, and the recently emerging protein-tagging approaches that offer single-cell resolution for protein turnover measurements. The long-standing inquiry raised in the 1950s about the existence of a dynamic state in different organisms at different physiological conditions can now be answered with an individual "constituent" resolution on a truly global scale. Now it appears that protein degradation is not necessarily an end to the protein function. Rather, it can be the start of a new function because protein degradation clears the way for the action of other proteins. Protein turnover participates in a multi-layer complex regulatory network and shares equal importance with gene transcription and protein translation. The advances in technologies for protein turnover analysis and the improved understanding of the biological role of protein turnover will likely help to solve some long-standing biomedical problems such as the tuberculosis disease that at the present day still affects one-third of the world population. © 2009 Wiley Periodicals, Inc., Mass Spec Rev 29:717,736, 2010 [source] Positron Imaging Studies of Rotating DrumsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2005David J. Parker Abstract The potential of the radioisotope tracer technique of positron emission tomography (PET) and the related techniques of positron emission projection imaging (PEPI) and positron emission particle tracking (PEPT) is illustrated with reference to laboratory scale studies of particulate motion in rotating drums, operating either in batch or continuous flow modes. Sand grains, glass beads and TiO2 granules down to 0.5mm diameter were labelled. Using PEPT the transition between rolling and slumping modes has been identified and the velocity profile within the active layer has been determined for a range of drum diameters. PEPI has been used to measure and explain residence time distributions, while all three techniques have been used to study segregation based on particle size, both radially and axially within the drum. Data on particle motion within a novel baffled drum is also presented. Le potentiel de la technique de traçage par radio-isotopes en tomographie par émission de positrons (PET) et les techniques associées de l'imagerie par projection des émissions de positrons (PEPI) ou le traçage des particules par émission de positrons (PEPT), est illustré en référence à des études à l'échelle de laboratoire du déplacement de particules dans des tambours rotatifs, fonctionnant soit en mode d'écoulement discontinu ou continu. Des grains de sable, des billes de verre et des granules de TiO2 aussi petits que 0,5 mm de diamètre ont été marqués. À l'aide de la technique PEPT, la transition entre les modes roulant et glissant a été identifiée et le profil de vitesse à l'intérieur de la couche active a été déterminé pour une gamme de diamètres de tambours. La technique PEPI a été utilisée pour mesurer et expliquer les distributions de temps de séjour, tandis que les trois techniques ont servi pour l'analyse de la ségrégation d'après la taille des particules, à la fois radialement et axialement dans le tambour. Des données sur le déplacement des particules dans un nouveau tambour à chicanes sont également présentées. [source] Radioisotope tracer study in trickle bed reactorsTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2001Krishna Deo Prasad Nigam Abstract The residence time distribution (RTD) of liquid phase in trickle bed reactors has been measured for air-water system using radioisotope tracer technique. Experiments were carried out in a glass column of internal diameter of 0.152 m packed with glass beads and actual catalyst particles of two different shapes. From the measured RTD curves, mean residence time of liquid was calculated and used to estimate liquid holdup. The axial dispersion model was used to simulate the experimental data and estimate mixing index, ie. Peclet number. The effect of liquid and gas flow rates on total liquid holdup and Peclet number has been investigated. Results of the study indicated that shape of the packing has significant effect on holdup and axial dispersion. Bodenstein number has been correlated to Reynolds number, Galileo number, shape and size of the packing. La distribution de temps de séjour (DTS) de la phase dans des réacteurs a lits ruisselants a été measurée pour le système air-eau à d'une technique par traceurs radio-isotopes. Des expériences ont été menées dans une colonne de verre de 0,152 m de diamètre intérieur garnie de billes de verre et de particules de catalyseur réelles de deux formes différentes. à partir des courbes de DTS mesurées, ie temps de séjour moyen du liquide a été calculé puls utilisé pour l'estimation de la rétention de liquide. On a utilisé. On a utilisé le modèl de dispersion axiale afin de simuler les données expérimentales et d'estimer l'indice de mélange, soit le nombre de Peclet. On a étudié l'effet des débits de liquide et de gaz sur la rétention de liquide totale et le nombre de Peclet. Les résultats de l'étude indiquent que la forme du garnissage a un effet significatif sur la rétention et la dispersion axiale. Le nombre de Bodenstein a été corrélé au nombre de Reynolds, au nombre de Galilée, ainsi qu'à la forme et à la taille du garnissage. [source] | ||||||||||