bluuebunny/crossref_metadata_2025_split huggingface dataset:
A study of fluid dispersion in oscillatory flow through a baffled tube
Authors: Ni Xiongewei 
Published: May 2005

AbstractPrevious studies show that axial dispersion in steady laminar flow can be substantially reduced by superimposing fluid oscillation in a baffled tube. In this paper, experimental observations on fluid dispersion for oscillatory flow in a baffled tube are obtained in a series of concentration measurements using high spatial resolution local conductivity probes, and two models—the continuous stirred tank (CST) with feedback and the plug flow with axial dispersion—are used to analyse the concentration curves and determine the fluid dispersion for such a system. The CST with feedback model combines the algorithms from Mecklenburgh and Hartland with the evaluations of unbiased moments from Anderssen and White to determine the dimensionless dispersion coefficient, D/uL, and the backmixing coefficient, F. The plug flow with axial dispersion model, on the other hand, utilises the axial diffusion model by replacing the molecular diffusion coefficient to the axial dispersion coefficient. This model uses an upstream concentration measurement together with an imperfect pulse technique to predict a downstream concentration profile, and thereby determine a best fit value for the dispersion coefficient D/uL. The axial dispersion results show that there is generally more dispersion predicted using the plug flow with axial dispersion model than when using the CST with feedback model for all the oscillatory Reynolds numbers and Strouhal numbers tested. The difference in the calculated D/uL between the two models is discussed.
Immobilization of glucose oxidase in the regenerated silk fibroin membrane: Characterization of the membrane structure and its application to an amperometric glucose sensor employing ferrocene as electron shuttle
Authors: Liu Yongcheng , Yu Tongyin , Liu Haiying , Qian Jianghong , Deng Jiaqi 
Published: May 2005

AbstractThe structural changes of the regenerated silk fibroin membranes for immobilizing glucose oxidase were characterized with FT‐IR spectra. The results of electronic absorption spectra and scanning electron microscopy illustrated that the glucose oxidase in the membranes existed in aggregates. The blend membranes exhibited an island‐like structure, attributable to the incompatible and weak intermolecular interactions between regenerated silk fibroin and glucose oxidase. The glucose sensor was constructed by combining glucose oxidase immobilized in regenerated silk fibroin membrane with an Eastman‐AQ‐ferrocene modified electrode. The advantages of the mediator include high stability and the ability to use a less positive potential for increased selectivity.
Kinetics of formation of diphenoxymethane from phenol and dichloromethane using phase‐transfer catalysis
Authors: Wu Ho‐Shing , Jou Sung‐Hauh 
Published: May 2005

AbstractThe reactions of phenol with dichloromethane using quaternary ammonium salts as a liquid–liquid phase‐transfer catalyst in an organic solvent/alkaline solution were investigated. The technique of phase‐transfer catalysis had a dramatic accelerating effect on the reaction and increased the yield of diphenoxymethane by more than 95%. The effects of catalysts, temperature, and basic concentration on reaction rate were studied in order to find the optimum operating conditions for this reaction. Experimental results indicated that a potassium hydroxide was preferred over sodium hydroxide in order to enhance the reactivity of the reaction. The reaction rate constant and the distribution coefficient of the intermediate product were obtained. During the reaction, the concentration of the intermediate product was also measured in order to study its behavior in the liquid–liquid system.
Production of salicylate hydroxylase fromPseudomonas putidaUUC‐1 and its application in the construction of a biosensor
Authors: Zhou Dao‐Min , Nigam Poonam , Jones John , Marchant Roger 
Published: May 2005

AbstractThe enzyme salicylate hydroxylase was produced fromPseudomonas putidaUUC‐1 in an 80 dm316 h batch fermentation process yielding, ∼ 9 K units per 60 dm3. This enzyme preparation has been studied for its application in the construction of biosensor systems, e.g. carbon past electrodes, screen‐printed carbon electrodes, and disposable carbon enzyme electrodes, which will be used for the rapid estimation of salicylate in blood sample. The linear range of the disposable carbon enzyme electrode in response to salicylate was achieved to 1·8 mmol dm−3.
Stabilization of cell biocatalyst with β‐galactosidase activity by glutaradehyde treatment
Authors: Flores María V. , Voget Claudio E. , Ertola Rodolfo J. J. 
Published: May 2005

AbstractIn the present study the stabilization with glutaraldehyde of permeabilized, non‐viable Kluvernomyces lactis cells with β‐galactosidas (β‐D‐galactosidase galactohydrolase, EC 3.21.23) activity has been investigated. The influence of various factors in relation to the glutaradehyde treatment, such as reaction time, temperature and glutaraldehyde and cell concentration, has been considered. The cell biocatalysts showed a good storage and operational stability. The kinetic properties of the biocatalyst in concentration with lactose hydrolysis were found to be comparable to the cell‐free enzyme.
Surface properties of magnesium oxide obtained from basic magnesium carbonate: Influence of preparation conditions of magnesium carbonate
Authors: Choudhary Vasant R. , Pataskar Suryakant G. , Zope Ganesh B. , Chaudhari Pravin N. 
Published: May 2005

AbstractSurface area, total basicity and base strength distribution (weak, strong and intermediate strength basic sites) of magnesium oxide obtained from basic magnesium carbonate (by its decomposition at 873 K) prepared by precipitation using different magnesium slats, precipitating agents and precipitating conditions (viz. concentration of magnesium salt. pH, temperature, mode of mixing and ageing period) have been thoroughly investigated. The total basicity and base strength distribution of the different magnesium oxide samples have been determined by step‐wise thermal desorption of carbon dioxide from 323 to 1253 K. The chemical composition of basic magnesium carbonate and the surface properties and carbon dioxide content of magnesium oxide are found to be strongly influenced by the aforementioned preparation conditions of basic magnesium carbonate.
Capillary gas chromatography based on a capsule‐insertion technique. 1. General aspects and comparison with split‐injection systems
Authors: Buser H. U. , Widmer H. M. 
Published: May 2005

AbstractA capsule‐insertion system tailored to the needs of capillary gas chromatography is described. It provides the basis for a truly quantitative and improved qualitative approach to open tubular capillary GLC. The advantages of the system lie in its simplicity of handling and in the possibility of using relatively low injection temperatures, thus reducing the risks to thermally unstable samples.The observed high efficiencies characterizing this capillary GLC capsule technique allow full advantage to be taken of the operating capacity of the superior capillary columns to give a performance competitive with the best known split‐injection systems.
Supercritical fluid chromatography and some of its applications: A review
Authors: White C. M. , Houck R. K. 
Published: May 2005

AbstractThe general topic of supercritical fluid chromatography (SFC) is introduced, and historical aspects of its development are discussed. The physical properties of supercritical fluids, gases and liquids are tabulated. SFC is compared and contrasted with the classical forms of chromatography ‐ gas chromatography (GC) and high performance liquid chromatography (HPLC). The selectivity of SFC, GC, and HPLC are discussed and compared. Instrumentation employed for supercritical fluid chromatography is depicted. A wide variety of SFC applications are introduced. New examples of the use of SFC for analysis of a variety of complex oligomeric mixtures indcluding polypropylene glycol, polysiloxanes, fluorocarbon oligomers (i.e. ‐3M's fluoro‐chemical surfactant Fluorad 171, and Kel‐F) and high molecular weight normal alcohols are shown. The use of SFC for separation of mono‐, di‐, and triglycerides at low operating temperatures is described. Lastly, the use of SFC for separations of complex hydrocarbon mixtures from liquid fuels, polycyclic aromatic hydrocarbons, synthetic alpha‐olefins, and petroleum functional group separations are depicted.
Some aspects of quantification of neutral steroid metabolites in body fluids of healthy and uremic subjects by capillary gas chromatography
Authors: Ludwig‐Koehn H. , Henning H. V. 
Published: May 2005

AbstractNeutral steroid metabolites enriched from urine and hemofiltrate were identified by gas chromatography/mass spectrometry and quantified by capillary gas chromatography. This study included 20 healthy controls and 37 uremic patients. Before enrichment of steroids from biological material, the standard deviation of the workup procedure and subsequent derivatization into the trimethylsilyl‐enol‐trimethylsilyl ethers was tested and found to be 2–5% in urine and 12–17% in the more complicated workup procedure of hemofiltrate, but essentially smaller than the biological standard deviation. Compared to the 24 h urinary excretion rates of controls, the excretion rates of androsterone, etiocholanolone, and corticoid metabolites were significantly lower in uremic body fluids, while those of 11‐oxygenated androstanolones, degradation products of corticoids, were enhanced in uremic urine. The ratio of corticoid metabolites to 11‐oxygenated androstanolones in urine of nondialyzed uremics correlated significantly with their plasma creatinine levels.
Acceleration of free release static coating of capillary columns by the presence of polar solvents in the coating solution – a theoretical study
Authors: Xu B. , Vermeulen N. P. E. 
Published: May 2005

AbstractThe cause of an observed acceleration in the free release static coating process of a capillary when more polar solvents are added to alkanes as stationary phase solvents has been studied. By using a computer program, 9 of the relevant physical parameers were calculated in relation to the composition of the solvent hixtures. Curves of these parameters vs composition of the mixures were drawn. From the results it can be deduced that the change of these parameters with the increase of polar solvents in the solution, is probably insufficient to explain the drastic increase of the free release static coating speed. A physical model is proposed to calculate the depth of the meniscus around which sufficient heat can be transferred into the evaporating surface per unit time, to evaporate the solvent at a rate that the coating speed indicates. It is demonstrated that when pentane‐acetone mixtures are used to coat a capillary, the depth of the meniscus indeed is greater than when pure pentane is used. The proposed model may lead to a better understanding of phenomena involved in the static coating process.
Considerations for analytical supercritical fluid extraction of sulfonyl ureas employing a modified fluid
Authors: Howard Angela L. , Taylor Larry T. 
Published: May 2005

AbstractImportant considerations are discussed for analytical SFE method development employing methanol–modified carbon dioxide and solid‐phase trapping. The focus of this study was to break the method development procedure into distinct steps so that the origins of low recoveries could be determined conclusively. Sulfonyl urea herbicides were used as probe analytes. Analyte solubility, analyte trapping, analyte trap removal (solid‐phase), and extract analysis were all shown to be equally important in achieving quantitative SFE recoveries.
Prediction of retention values in linear temperature programming of narrow and mega‐bore capillary columns
Authors: Gerbino Tomaso C. , Castello Gianrico 
Published: May 2005

AbstractRetention times in linear temperature programmed gas chromatography on narrow bore and megabore capillary columns have been calculated from experimental retention times measured at three isothermal temperatures: an iterative procedure performed by BASIC programs was used to obtain the values of the constants enabling the calculation of the programmed temperature retention times. Different methods of calculation have been compared.
Supercritical fluid extraction of atrazine and its metabolites from soil
Authors: Alzaga Roberto , Bayona Josep M. , Barceló Damià 
Published: May 2005

AbstractSoxhlet (methanol) and SFE extraction with carbon dioxide in the presence of modifiers at different temperatures (100–200°C) for the extraction of atrazine and its main metabolites from a soil sample were compared. The most effective extraction conditions for both atrazine and its metabolites (i.e.deethylatrazine and deisopropylatrazine) were Co2modified with 20% molar methanol‐trifluoroacetic acid (MeOH‐TFA) (TFA 0.65M in MeOH) at 100°C, leading to an extraction efficiency comparable with that of Soxhlet extraction with MeOH for atrazine andca.20% higher for its main metabolites. The relative standard deviation (RSD) of SFE was lower than that obtained by Soxhlet extraction, probably because of less interference in the cGC‐NPD determination. All the other modifiers evaluated (acetone, triethylamine, and methanol) were less effective than MeOH‐TFA for the extraction of atrazine and its metabolites from a soil sample, even at high molar concentrations (20%) and use of higher extraction temperatures (200°C). These results indicate the importance of matrix effects and the need of the selection of an appropriate modifier in order to obtain quantitative extractions by SFE.
Comparison of different heptakis(6‐O‐alkyldimethylsilyl‐2‐3‐di‐O‐ethyl)‐β‐cyclodextrins as chiral stationary phases in capillary GC
Authors: Kim Byoung Eog , Lee Kwang‐Pill , Park Keung‐Shik , Lee (deceased) Sun Haing , Park Jung Hag 
Published: May 2005

AbstractThree new β‐cyclodextrin derivatives, heptakis(6‐O‐isopropyldi‐methylsilyl‐2,3‐di‐O‐ethyl)‐β‐cyclodextrin, heptakis(6‐O‐thexyldi‐methylsilyl‐2,3‐di‐O‐ethyl)‐β‐cyclodextrin, and heptakis(6‐O‐cy‐clohexyldimethyl‐2,3‐di‐O‐ethyl)‐β‐cyclodextrin (IPDE‐β‐CD, TXDE‐β‐CD, and CHDE‐β‐CD), were synthesized and the enan‐tioselectivities of these three CD derivatives and heptakis(6‐O‐tert‐butyldimethylsilyl‐2,3‐di‐O‐ethyl)‐β‐cyclodextrin (TBDE‐β‐CD) were compared for GC separation of a range of chiral test com‐pounds. In particular TXDE‐β‐CD showed much higher enentio‐selectivity than TBDE‐β‐CD. Enentioselectivities of IPDE‐β‐CD and CHDE‐β‐CD are somewhat lower than that of TXDE‐β‐CD and CHDE‐β‐Cd are somewhat lower than that of TXDE‐β‐CD. These observations are indicative of significant effects of subtle changes in the structure of the 6‐O‐substituent on the enantioselec‐tivity of the β‐CD derivatives. The difference in enantioselectivities of the 6‐O‐substituted CD derivatives were explained in terms of relative contributions of the effects of hydrophobicity and steric hindrance of the substituent to the inclusion process. CHDE‐β‐CD showed the lowest enantioselectivity among the threederivatives. It is likely that the unfavorable steric hindrance of the bulky cyclo‐hexyl group plays a greater role than the favorable hydrophobicity effect of the cyclohexyl group in the inclusion process in CHDE‐β‐CD. IPDE‐β‐CD showed lower selectivity than TXDE‐β‐CD and TBDE‐β‐CD. In the case of these CD derivatives having acyclic substituents the relative hydrophobicity of the substituent seems to be a dominant factor affecting the inclusion process. Isopropyl groups factor affecting the inclusion process. Isopropyl groups are less hydrophobic than thexyl and tert‐butyl groups.
Proposed interaction between insulin and retinoblastoma protein
Authors: Radulescu Razvan T. , Wendtner Clemens M. 
Published: May 2005

AbstractRetinoblastoma protein (RB) is a tumor suppressor gene product involved in embryogenesis and cell cycle progression. One of the major mechanisms leading to RB dysfunction is complex formation with viral oncoproteins using the common RB binding motif Leu × Cys × Glu (LXCXE) which has also been identified in cellular ligands, e.g., RBP‐1 and RBP‐2. p107, a cellular protein with RB sequence homology, has been shown to bind to the same viral oncoproteins associating with RB and is therefore thought to contribute to cell cycle regulation. It has recently been suggested that insulin stimulates gene transcription through direct association with an, as yet, unidentified intracellular transcription factor. Due to the central roles of RB and p107 in coupling external growth signals with the progression of the cell cycle clock, we have hypothesized that these two proteins might be candidates for mediating the effects of insulin of DNA. We report here the identification of a region in the B‐chain of human insulin that has the sequence LXCXE. Based on this finding we predict that the insulin B‐chain may interact with RB and/or p107. Since we have also identified sequences hydropathically related to LXCXE in insulin‐like growth factor I (IGF‐I) and II (IGF‐II), but not in relaxin, nerve growth factor, epidermal growth factor, glucagon or β‐endorphin, we further proposed that both IGF‐I and ‐II may assemble with RB and / or p107, too. Moreover, binding sites on RB and p107 identical with those suggested for viral oncoproteins and cellular ligands are predicted for insulin/IGF‐I/IGF‐II by using the hydropathic complementarity approach. Our proposal of associations between insulin/IGF‐I/IGF‐II and RB/p107 might be important for the understanding of cell growth regulation.
Plasticity of the serotonergic innervation of the dorsal horn of the rat spinal cord following neonatal capsaicin treatment
Authors: Marlier L. , Poulat P. , Rajaofetra N. , Sandillon F. , Privat A. 
Published: May 2005

AbstractNeonatal capsaicin treatments (25 or 50 mg/kg, 12, 24, or 48 hr after birth given subcutaneously) were applied in order to follow by immunocytochemical techniques the postnatal development and plasticity of the Serotonergic system in the dorsal horn of the rat spinal cord. Two markers of the lesions of C primary afferents induced by capsaicin were tested by immunocytochemical detection: substance P and cal‐citonin gene‐related peptide (CGRP). We show that the internal part of substantia gelatinosa (lamina Ili) which does not contain Serotonergic fibers in intact or vehicle‐treated rats is invaded within a few days after capsaicin treatment by Serotonergic fibers apparently sprouting from the deepest laminae. Moreover, these fibers often establish axodendritic synapses while synapses are rare in intact animals in the whole dorsal horn. This reorganization is stable whatever the dose of capsaicin used or the moment chosen for its injection. On the other hand, while lesions of substance P‐ergic fibers appeared quite stable, partial recovery of CGRP innervation was found after 3 to 6 months, especially with the low dose of capsaicin. We discuss the ability of the Serotonergic system innervating the dorsal cord either to find new targets or to fill vacated sites when one of its putative targets is removed.
Axonal regeneration of an identified Helisoma neuron depends on the site of axotomy
Authors: Kruk P. J. , Bulloch A. G. M. 
Published: May 2005

AbstractAxotomy or molluscan neurons usually results in axonal regeneration. In this study, we tested the axotomy response of an identified neuron of the pond snail Helisoma trivolvis (buccal neuron 4, B4). This neuron has two primary axonal branches, the ipsilateral axon and the contralateral axon, each innervating one of the paired salivary glands. The ipsilateral axon projects via the ipsilateral esophageal nerve trunk whereas the contralateral axon crosses both buccal ganglia and projects via the contralateral esophageal nerve trunk. We tested various procedures of axotomy: injury to one axon or both axons, close to the ganglion or more distal. Surprisingly, we found that proximal axotomy of the ipsilateral axon was not usually followed by axonal regeneration. By contrast, all other procedures of axotomy (e.g., distal ipsilateral, or proximal bilateral) resulted in robust axonal regeneration and target reinnervation. Thus, in this preparation, axotomy may or may not result in axonal regeneration, depending on the site(s) of axotomy. To the best of our knowledge, such a differential result has not yet been found in any other preparation. We conclude that axotomy is not always a sufficient condition for axonal regeneration of molluscan neurons. We hypothesize that a damaged axonal stump may be a necessary condition for the initiation of regeneration. An alternative hypothesis is that neurite outgrowth is inhibited in normal mature neurons by a target‐derived factor. This hypothetical factor would be transported retrogradely, but not anterogradely, along axons.
Alterations of 45Ca accumulation and [3H] inositol 1,4,5‐trisphosphate binding using autoradiography in the exo‐focal postischemic brain areas of the rat
Authors: Nagasawa H. , Kogure K. 
Published: May 2005

AbstractWe studied the alterations of calcium accumulation and intracellular signal transduction using autoradiography of the second messenger system in order to clarify the mechanisms of the delayed neuronal changes in the remote areas of rat brain after transient focal ischemia. Chronological changes of 45Ca accumulation and [3H] inositol 1,4,5‐trisphosphate (IP3) binding sites were determined after 90 min of right middle cerebral artery (MCA) occlusion and after such occlusion followed by different periods of recirculation. After the ischemic insult, 45Ca accumulation extended to the lateral segment of the caudate putamen and to the cerebral cortex, both supplied by the occluded MCA. One day after the ischemia, [3H]IP binding sites decreased significantly compared with the control values in these ischemic areas. Moreover, 3 days after the ischemia, 45 Ca accumulation was first detected in the ipsilateral thalamus and the substantia nigra, which lay outside the ischemic areas. In the substantia nigra, a significant decrease of [3H]IP3 binding sites and concurrent 45Ca accumulation were observed. In the thalamus, however, there was no alteration until 1 week after the ischemia, and then [3H]IP3 binding sites increased significantly 2 weeks (P < 0.05) and 4 weeks (P < 0.01) after the ischemia. Based on the present study, we speculate that different mechanisms associated with signal transduction systems may be responsible for exo‐focal postischemic delayed neuronal changes in the thalamus and the substantia nigra. The increase of [3H]IP3 binding sites of the thalamus in the chronic stage may be new evidence of plasticity related to neurotransmission.