DRUG AND ALCOHOL REVIEW, Issue 5 2006
MAHMUD MAZLAN MD
Abstract Until recently, Malaysia has lagged behind in the treatment of drug addiction and related disorders, despite experiencing severe drug problems. By the end of 2004, 234 000 heroin users or heroin-dependent individuals had been registered in the official government registry, but other estimates exceed 500 000 for heroin abusers in the country. Amphetamine-type stimulant abuse is also increasing and of considerable public and government concern. Among the population of drug users, HIV and other infectious diseases rates are very high. In the Western Pacific regions, Malaysia has the second highest HIV prevalence (after Vietnam) among adult populations (0.62%) and the highest proportion of HIV cases resulting from injection drug use (76.3%). Drug use and related disorders exert a heavy burden on the country's health care and legal systems. Historically, drug abusers were rehabilitated involuntarily in correctional, rather than health-care, facilities. This primarily criminal treatment approach had limited effectiveness which led to widespread public dissatisfaction and the recent introduction of medical treatments for addiction. Naltrexone was introduced in 1999; buprenorphine was introduced in 2001 and methadone in 2003. Agonist maintenance programmes were embraced rapidly by the medical community in Malaysia. Currently, over 30 000 opiate-dependent patients are treated with agonist maintenance treatments by more than 500 medical practitioners in Malaysia. Despite these recent advances, treatments for amphetamine-type stimulant abuse or dependence are underdeveloped, and diversion of agonist medications is an emerging concern. [source]

DETERMINATION OF AFLATOXIN CONTAMINATION IN OLIVES BY IMMUNOAFFINITY COLUMN USING HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

JOURNAL OF FOOD QUALITY, Issue 2 2006
CAVIT BIRCAN
ABSTRACT Eighty-two whole black olive samples gathered from six different olive oil processing facilities were surveyed to determine levels of aflatoxins using immunoaffinity column extraction and reversed-phase high-performance liquid chromatography. Two different analytical procedures adopted for the analysis of aflatoxins were investigated for their suitability by spiking the blank olive samples with five different known levels of aflatoxins to determine which one had higher recovery rates. Although some of the olive samples had been exposed to adverse conditions, such as rain and high temperatures, none were found to contain aflatoxins at the determined detection limit. Although the samples were kept in high relative humidity (75%) and high temperature (30C) for 3 months and were tested at 1-month intervals, no aflatoxins were detected. In addition, the olives were inoculated on a potato dextrose agar medium and incubated for 7 days at 25C to characterize the microflora. Because there is no evidence of aflatoxins in fresh whole olives, the next step of processing the contaminated olives into olive oils and testing them for the aflatoxins was not pursued. [source]

Collapse of Reinforced Concrete Column by Vehicle Impact

COMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 6 2008
Hing-Ho Tsang
The column slenderness ratio can be in the order of 6,9. Some of these buildings are right next to busy streets and hence continuously exposed to the potential hazard of a vehicle impacting on a column in an accident. In the early part of this study, the ultimate energy absorption capacity of a reinforced concrete column is compared to the kinetic energy embodied in the moving vehicle. The energy-absorption capacity is calculated from the force-displacement curve of the column as determined from a nonlinear static (push-over) analysis. The ultimate displacement of the column is defined at the point when the column fails to continue carrying the full gravitational loading. Results obtained from the nonlinear static analysis have been evaluated by computer simulations of the dynamic behavior of the column following the impact. Limitations in the static analysis procedure have been demonstrated. The effects of strain rate have been discussed and the sensitivity of the result to changes in the velocity function and stiffness of the impacting vehicle has also been studied. [source]

Solid-Phase Reactive Chromatography (SPRC): A New Methodology for Wittig and Horner,Emmons Reactions on a Column under Microwave Irradiation

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2010
Saada C. Dakdouki
Abstract A new methodology named solid-phase reactive chromatography (SPRC), which combines reaction, separation, and purification into a single unit for the preparation of small samples, is described. This method was illustrated in the synthesis of some natural bioactive compounds, namely, methoxylated analogues of resveratrol, alkylresorcinols, and 5-aryl-2,4-pentadienoates, over a column of alumina-KF under microwave irradiation by using the Wittig and Horner,Emmons reactions. This approach permitted the preparation of the target olefins with high purity and good to excellent yields in short reaction times. [source]

Rapid simulated hydrologic response within the variably saturated near surface

HYDROLOGICAL PROCESSES, Issue 3 2008
Brian A. Ebel
Abstract Column and field experiments have shown that the hydrologic response to increases in rainfall rates can be more rapid than expected from simple estimates. Physics-based hydrologic response simulation, with the Integrated Hydrology Model (InHM), is used here to investigate rapid hydrologic response, within the variably saturated near surface, to temporal variations in applied flux at the surface boundary. The factors controlling the speed of wetting front propagation are discussed within the Darcy,Buckingham conceptual framework, including kinematic wave approximations. The Coos Bay boundary-value problem is employed to examine simulated discharge, pressure head, and saturation responses to a large increase in applied surface flux. The results presented here suggest that physics-based simulations are capable of representing rapid hydrologic response within the variably saturated near surface. The new InHM simulations indicate that the temporal discretization and measurement precision needed to capture the rapid subsurface response to a spike increase in surface flux, necessary for both data-based analyses and evaluation of physics-based models, are smaller than the capabilities of the instrumentation deployed at the Coos Bay experimental catchment. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Column: Food Science Education Publications and Websites

JOURNAL OF FOOD SCIENCE EDUCATION, Issue 3 2010
Jim Bird
No abstract is available for this article. [source]

Qualitative analysis and HPLC isolation and identification of procyanidins from vicia faba

PHYTOCHEMICAL ANALYSIS, Issue 2 2004
Rachid Merghem
Abstract The soluble proanthocyanidins of the coloured seed coats of Vicia faba L. were isolated and separated by solvent partition. The chemical characteristics of the proanthocyanidins were elucidated by total oxidation and partial degradation in the presence of phloroglucinol followed by HPLC analysis. The native extract of proanthocyanidins contained (+)-gallocatechin, (,)-epigallocatechin, (+)-catechin and (,)-epicatechin units. Oligomeric procyanidins were puri,ed by chromatography on Sephadex LH-20 and the accessible compounds were isolated by RP-HPLC using a Licrospher Li 100 Column. The structures of the puri,ed oligomeric procyanidins were elucidated using a procedure involving TLC, UV spectroscopy, ESI-MS and HPLC analysis of the products from the phloroglucinol reaction. The major condensed tannins of Vicia faba comprise six compounds identi,ed as two A-type procyanidin dimers, the procyanidin dimers B1, B2 and B3, and a procyanidin trimer. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Energy Efficiency of Two-Phase Mixing in a Modified Bubble Column

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2007
Subrata Kumar Majumder
Abstract Energy efficiency for gas liquid mixing in a modified downflow bubble column reactor has been analyzed in this paper. Efficiencies of the different parts of the bubble column have been assessed on the basis of energy dissipation. Prediction of the energy dissipation coefficient as well as energy utilization efficiency due to gas-liquid mixing as a function of different physical, geometric and dynamic variables of the system has been done by correlation method. The distribution of energy utilization in the different zones of the column has also been analyzed. Experiments were carried out with air-water and air-aqueous solutions of carboxy methyl cellulose with different concentrations. Dans cet article on a analysé l'efficacité énergétique pour le mélange gaz-liquide dans un réacteur à colonne à bulles à écoulement descendant modifié. Les efficacités des différentes régions de la colonne à bulles ont été évaluées sur la base de la dissipation d'énergie. On a utilisé une méthode de corrélation pour prédire le coefficient de dissipation d'énergie ainsi que l'efficacité d'utilisation de l'énergie due au mélange gaz-liquide en fonction des différentes variables physiques, géométriques et dynamiques du système. La distribution de l'utilisation de l'énergie dans les différentes régions de la colonne a également été analysée. Des expériences ont été menées avec des solutions air-eau et air-solutions aqueuses de carboxyméthylcellulose à différentes concentrations. [source]

A Short Note on Steady State Behaviour of a Petlyuk Distillation Column by Using a Non-Equilibrium Stage Model

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2006
Erika Fabiola Abad-Zarate
Abstract A Petlyuk distillation column, considering equilibrium and non-equilibrium stage models, was studied. Rigorous simulations were conducted using Aspen PlusÔ RATEFRAC Module for the separation of ternary mixtures. According to the equilibrium model, the energy-efficient design of the Petlyuk column requires that the intermediate component be extracted from the maximum point in the composition profile in the main column. It was found that, for the intermediate component, mass transfer occurs from the vapour to the liquid phase from the top of the column to the stage where the side stream is extracted, from this point mass transfer occurs in the opposite direction. This point, considering the non-equilibrium model, corresponds to the stage in which the net mass transfer rate is zero. For the case of two segments per stage, it was found that the heat duties predicted by the equilibrium model are significantly lower than those obtained by using the non-equilibrium model, which is consistent with previous reported results. However, it is important to say that despite the higher energy duty predicted by the non-equilibrium model; both models predict significant energy savings. On a étudié une colonne de distillation de Petlyuk en considérant des modèles d'étage en équilibre et hors équilibre. Des simulations rigoureuses ont été menées au moyen du module RATEFRAC d'Aspen PlusÔ pour la séparation de mélanges ternaires. Selon le modèle en équilibre, une conception énergétiquement efficace de la colonne Petlyuk nécessite que le composant intermédiaire soit extrait du point maximum du profil de composition dans la colonne principale. On a trouvé que, pour le composant intermédiaire, le transfert de masse se produisait de la vapeur vers le liquide de la tête de la colonne jusqu'à l'étage où le courant secondaire est extrait; à partir de ce point le transfert de masse se produit dans la direction opposée. Ce point, en considérant le modèle hors équilibre, correspond à l'étage où le taux de transfert de masse net est nul. Dans le cas où il y a deux segments par étage, on a trouvé que les rendements thermiques prédits par le modèle en équilibre étaient significativement plus faibles que ceux obtenus à l'aide du modèle hors équilibre, ce qui est cohérent avec les résultats existants. Cependant, il est important de préciser que malgré le rendement énergétique plus élevé prédit par le modèle hors équilibre, les deux modèles fournissent des économies d'énergie significatives. [source]

Mixing Time in a Short Bubble Column

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2003
M Ravinath
Abstract Mixing time measurements have been carried out in a 0.2m I.D. short bubble column (Hc/D , 5) with different spargers and for different clear liquid height to diameter (HC/D) ratios. Superficial gas velocity has been varied in the range of 0.01m/s to 0.1m/s. Effect of bulk fluid viscosity on the mixing time has also been studied. The circulation cell model, with two fitted parameters viz. number of circulation cells, S and the inter-cell exchange velocity, Ve, has been used to predict and explain the variation in mixing time and the flow pattern in the short bubble column for different types of spargers. On a effectué des mesures de temps de mélange dans une colonne à bulles courte de 0,2 m de diamètre intérieur (Hc/D , 5) munie de différents aérateurs et pour différents rapports entre la hauteur de liquide clair et le diamètre (HC/D). On a fait varier la vitesse de gaz superficielle dans la gamme de 0,01-0,1 m/s. L'effet de la viscosité en masse du fluide sur le temps de mélange est également étudié. On a utilisé le modèle de zones de circulation, comprenant deux paramètres calés, à savoir le nombre de zones de circulation, S, et la vitesse d'échange entre les zones, Ve, pour prédire et expliquer la variation du temps de mélange et le profil d'écoulement dans la colonne à bulles courte pour différents types d'aérateurs. [source]

Large Interarcuate Spaces in the Cervical Vertebral Column of the Tyrolean Mountain Sheep

ANATOMIA, HISTOLOGIA, EMBRYOLOGIA, Issue 1 2003
E. Turkof
Summary Large interarcual spaces have been described between the arcus vertebrae C5/C6 and C6/C7 in the cervical vertebral column of Nubian goats. This aperture enables direct access to spinal cord and rootlets without the need to perform a hemilaminectomy. The present study was performed in order to determine whether these large interarcual spaces can also be found in the vertebral column of the Tyrolean mountain sheep, as this small ruminant, which is anatomically very similar to the Nubian goat, is frequently used for experimental purposes at the Surgical University Clinic in Austria. The carcasses of 10 sheep (six females, four males; range of age: 2.5,6 years, range of weight: 52,89 kg) were dissected and the vertebral column was exposed. All 10 sheep showed elliptic openings between the fourth cervical and the first thoracal vertebrae. Three sheep had additional openings between the first and the second thoracal vertebrae. All openings were covered solitarily by the ligamentum flavum and under this ligamentum lay the spinal cord without any further osseous or ligamentous protection. These findings are not mentioned in the common textbooks of veterinary anatomy and deserve attention, as they can be a step forward towards non-traumatic experimental surgery on the spinal cord. [source]

Arresting Dialysis-Related Amyloidosis: A Prospective Multicenter Controlled Trial of Direct Hemoperfusion with a ,2 -Microglobulin Adsorption Column

ARTIFICIAL ORGANS, Issue 4 2004
Fumitake Gejyo
Abstract:, We investigated the clinical efficacy of direct hemoperfusion with a ,2 -microglobulin (,2 -m) adsorption column for the treatment of patients with dialysis-related amyloidosis. A 2-year prospective controlled study was performed to compare the effects of passaging blood through a (,2 -m) adsorption column (Lixelle) before it is passaged through the dialysis polysulfone membrane on the severity of amyloidosis in these individuals. Patients (n = 22) whose blood went through the Lixelle column prior to dialysis had a higher ,2 -m removal rate compared to an equal number of controls, and they showed earlier improvement in their symptoms which included impaired daily ,activities, ,joint ,stiffness, ,and ,pain. ,The ,appearance of additional bone cysts was prevented in pre-adsorbed patients but not in the controls. Thus, the Lixelle column is useful in preventing the progression of dialysis-related amyloidosis and in ameliorating or arresting the progression of the ,symptoms ,of ,this ,disorder. [source]

A Study on Increasing Separation Efficiency of an Industrial, Compound Distillation Column

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2002
Shengjing Mu
Simulation of a multistage distillation column is often required for its design and operation A debottieneck study for an acetic acid (HAc) dehydration column is presented in this paper. The column is consists of 4 structured packing sections at the top, a sieve tray section with smaller diameter in the middle, and a sieve tray section with larger diameter at the bottom By using steady-state simulation, the bottleneck to increasing the efficiency of separation is identified to be the middle sieve tray section with smaller diameter and smaller tray spacing Renovation schemes without any additional investment on equipment are proposed [source]

Operational Optimization of Ideal Internal Thermally Coupled Distillation Columns

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1-2 2001
Xing-Gao Liu
Lack of the optimal operation parameters in operation is one of major difficulties associated with the use of advanced energy saving distillation methods. In this paper, the operational optimization of the ideal Internal Thermally Coupled Distillation Column (ITCDIC) is considered. An optimization model and the related simulation algorithm are proposed. An optimization and the related result analysis are carried out, which pave the way for further design studies and its practical application. [source]

Dynamic Simulation and Control of an MTBE Catalytic Distillation Column

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2000
H. Lin
A dynamic model of an MTBE (methyl tert butyl ether) catalytic distillation column was developed using the SpeedUp simulation package. Experimental kinetic rate data, rigorous thermodynamics, vapour-liquid nonidealities and tray hydraulics were incorporated in the simulation. The steady state results from the dynamic model were compared with the steady state results from a steady state model developed using the AspenPlus simulation package. The steady state results from the two simulations were in perfect agreement with each other. Open hop step tests were performed on the dynamic model of this process and the process model indicated a non-linear, self-regulating behaviour and did not exhibit any multiplicities. Multiloop linear control systems were designed and PI, PID and Dynamic Matrix Control (DMC) controllers were tested on the simulation for load disturbances and setpoint changes. All controllers performed adequately; the DMC controller consistently resulted in better dynamic control performance than the other two controllers. [source]

Gas-Liquid Mass Transfer Approach applied to the Modeling of Flotation in a Bubble Column

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2008
J. Chahed
Abstract A kinetic model developed to describe flotation in a bubble column is presented. This model, developed on the basis of the theory of mass transfer in gas-liquid flows, makes explicit in its formulation the effect of the superficial saturation of bubbles on the kinetics of flotation. The model is applied to the simulation of flotation column experiments for which the classical first-order models, commonly used in flotation modeling, are insufficient to represent the flotation kinetics. The results of the simulations obtained under different hypotheses of simplification and compared to experimental data show that the model succeeds in representing the flotation kinetics in these cases. [source]

New Predictive Correlations for the Drop Size in a Rotating Disc Contactor Liquid-Liquid Extraction Column

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 2 2007
M. Ismail Al-Rahawi
Abstract Sauter mean drop sizes (d32) generated from a hole distributor in liquid extraction RDC columns were studied under various conditions. Experiments were designed to generate data required to determine the main variables that control the drop sizes in RDCs. Two precise correlations were proposed for predicting d32 in a RDC extraction column. The first was based on operating variables, hole-distributor diameter, disc speed, column geometry, and system physical properties. The second one considered the same variables, except the column geometry. This model can be used for design purposes. The two correlations are the first of their type to consider the distributor hole inlet diameter in a RDC column. This diameter has been neglected by previous investigators. The maximum standard deviation for all data is 0.75,%, with a maximum absolute error of 6.8,%. [source]

Effect of Suspended Liposomes on Hydrodynamic and Oxygen Transfer Properties in a Mini-Scale External Loop Airlift Bubble Column

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2006
M. Yoshimoto
Abstract The circulating liquid velocity, gas holdup, bubble size distribution, and liquid phase oxygen transfer coefficient were measured in a mini-scale external loop airlift bubble column (MELBC) with the liquid volume suspending enzyme-free liposomes of varying diameters. These values were compared to those for liposome-free MELBC, normal bubble column (NBC), and a larger scale airlift column. The liposomes suspended in the MELBC are incorporated into the liquid film around the bubbles, leading to the development of a foam layer, where the incorporated liposomes exert negligible effect on the oxygen transfer in the film. [source]

Template Refolding by Use of an Antibody-Coupled Affinity Column

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2005
S. Katoh
Abstract To improve the efficiency and throughput, the biointeraction between an antigen and antibody was used for refolding in a packed column, in which an antibody against carbonic anhydrase coupled on a gel support was used as a template ligand. A denatured solution of CAB was mixed with a refolding buffer in a mixing chamber, and was supplied to the antibody-coupled column for refolding. Higher refolding efficiencies were obtained in the column than by the batch dilution method at relatively low concentrations of denaturant. By increasing the adsorption capacity of the column, the efficiency of refolding, as well as the throughput, could be increased. [source]

Gas-Liquid Mass Transfer in a Slurry Bubble Column at High Slurry Concentrations and High Gas Velocities

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2005
C. O. Vandu
Abstract The volumetric mass transfer coefficient kLa in a 0.1,m-diameter bubble column was studied for an air-slurry system. A C9 -C11n -paraffin oil was employed as the liquid phase with fine alumina catalyst carrier particles used as the solid phase. The n -paraffin oil had properties similar to those of the liquid phase in a commercial Fischer-Tropsch reactor under reaction conditions. The superficial gas velocity UG was varied in the range of 0.01 to 0.8,m/s, spanning both the homogeneous and heterogeneous flow regimes. The slurry concentration ,S ranged from 0 to 0.5. The experimental results obtained show that the gas hold-up ,G decreases with an increase in slurry concentration, with this decrease being most significant when ,S < 0.2. kLa/,G was found to be practically independent of the superficial gas velocity when UG > 0.1,m/s is taking on values predominantly between 0.4 and 0.6,s,1 when ,S = 0.1 to 0.4, and 0.29,s,1, when ,S = 0.5. This study provides a practical means for estimating the volumetric mass transfer coefficient kLa in an industrial-size bubble column slurry reactor, with a particular focus on the Fischer-Tropsch process as well as high gas velocities and high slurry concentrations. [source]

A Column-Based "Flush and Flow" System for the Asymmetric ,-Chlorination of Acid Halides.

CHEMINFORM, Issue 14 2006
Daniel Bernstein
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source]

A Two-Dimensional KTiOPO4 Photonic Crystal Grown Using a Macroporous Silicon Template,

ADVANCED MATERIALS, Issue 17 2006
A. Peña
2D KTiOPO4 photonic crystals are fabricated using a silicon membrane of air holes as a template. Columns of KTiOPO4 are grown by liquid-phase epitaxy from a substrate into such air holes. The crystallographic orientation of the columns is the same as that of the substrate. The photonic-crystal properties of the fabricated structures and their capability to generate second-harmonic light are experimentally demonstrated. [source]

Peptide Nanotubes: Simple Separation Using Size-Exclusion Columns and Use as Templates for Fabricating One-Dimensional Single Chains of Au Nanoparticles,

ADVANCED MATERIALS, Issue 14 2005
X. Gao
Straight single chains of Au nanoparticles have been synthesized using 10,nm diameter peptide nanotubes as templates (see Figure). The 6,nm Au nanoparticles grow in the gaps between the synthetic peptide coating the nanotubes which regulates the size, dispersity, interparticle distance, and crystallinity of the nanoparticles. The use of longer nanotubes results in longer chains. [source]

Heavy-metal displacement in chelate-treated soil with sludge during phytoremediation

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2006
Stanley Liphadzi
Abstract Heavy metals (HMs) in domestic sewage sludge, applied to land, contaminate soils. Phytoremediation is the use of plants to clean-up toxic HMs from soil. Chelating agents are added to soil to solubilize the metals for enhanced uptake. Yet no studies report the displacement of HMs in soil with sludge following solubilization with chelates. The objective of this work was to determine the uptake or leaching of HMs due to a chelate added to a soil from a sludge farm that had received sludge for 25 y. The soil was placed in long columns (105,cm long; , 39,cm) in a greenhouse. Columns either had a plant (hybrid poplar; Populus deltoides Marsh. × P. nigra L.) or no plant. After the poplar seedlings had grown for 144 d, the tetrasodium salt of the chelating agent EDTA was irrigated onto the surface of the soil at a rate of 1 g per,kg of soil. Drainage water, soil, and plants were analyzed for three toxic HMs (Cd, Ni, Pb) and four essential HMs (Cu, Fe, Mn, Zn). At harvest, extractable and total concentrations of each HM in the soil with EDTA were similar to those in soil without EDTA. The chelate did not affect the concentrations of HMs in the roots or leaves. With or without plants, EDTA mobilized all seven HMs and increased their concentrations in drainage water. Lower concentrations of Cd, Cu, Fe, Ni, and Zn in leachate from columns with EDTA and plants compared to columns with EDTA and no plants showed that poplars can reduce groundwater contamination by intercepting these HMs in the soil. But the poplar plants did not reduce Pb and Mn in the leachate from columns with EDTA. Concentrations of Cd and Pb in the leachate mobilized by EDTA remained above drinking-water standards with or without plants. The results showed that a chelate (EDTA) should not be added to a soil at a sludge farm to enhance phytoremediation. The chelate mobilized HMs that leached to drainage water and contaminated it. [source]

Preparation and characterization of polymethacrylate monolithic capillary columns with dual hydrophilic interaction reversed-phase retention mechanism for polar compounds

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2009
í Urban
Abstract Monolithic columns for capillary hydrophilic interaction liquid chromatography (HILIC) were prepared in fused-silica capillaries by radical co-polymerization of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide and ethylene dimethacrylate in various binary and ternary porogen solvent mixtures with azobisisobutyronitrile as the initiator of the polymerization reaction. Columns showed mixed separation modes: reversed-phase (RP) in water-rich mobile phases and HILIC at high concentrations of acetonitrile (>60,80%) in aqueous,organic mobile phases. A continuous change in retention was observed at increasing concentration of water in acetonitrile, giving rise to characteristic U-turn plots of retention factors versus the concentration of water in the mobile phase, with minima corresponding to the transition between the mechanisms controlling the retention. The selectivity of organic polymer monolithic columns for HILIC separations can be varied by adjusting the concentration of sulfobetaine monomer and the composition of the porogen solvent in the polymerization mixture. Under HILIC conditions, the monolithic capillary sulfobetaine columns show separation selectivities for polar phenolic acids similar to those of a commercial silica-based sulfobetaine ZIC-HILIC column, which, however, has limited selectivity in the RP mode due to lower retention. [source]

Packing capillary electrochromatography columns using vacuum , A preliminary study

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 14 2004
Qishu Qu
Abstract This paper introduces a novel method for packing Capillary Electrochromatography Columns (CEC). Using vacuum packing methodology, silica particles as small as 1 ,m were successfully packed into the capillary columns with 75 ,m inner diameter. The columns are very stable and show no noticeable loss in efficiency after 200 sample injections. The performance of these vacuum packed capillary columns was evaluated with a mixture of aromatic and non-aromatic compounds. A 24 cm long capillary column can produce peak efficiencies of around 45 000 plates for benzene. [source]

Geochemical and Magnetic Provenancing of Roman Granite Columns from Andalucía and Extremadura, Spain

OXFORD JOURNAL OF ARCHAEOLOGY, Issue 2 2002
Olwen Williams-Thorpe
One hundred and fifty two granite columns were examined in eight towns and archaeological sites in Andalucía and Extremadura, Spain, in order to determine the geological provenance of the columns. Three non-destructive methods of characterization were used: mineralogical features, magnetic susceptibility, and concentrations of radioelements (K, U, Th) determined by portable gamma ray spectrometry. Columns were compared with potential sources within Spain and in the Mediterranean area using analogous data previously published and also new data obtained for this work. The majority of the columns are made of Spanish granites, some of which were probably quarried near Mérida. Different chemical types of Spanish granites were used in the northern part of the area studied (Extremadura) and in the southern part (Andalucía). Twenty five columns are not of Spanish granites, but were imported from other sources, namely the Troad and Kozak Da, areas of western Turkey, the Italian islands of Elba and/or Giglio, and Sardinia (confirming a column previously identified in the literature). The imported columns are found in Itálica, Hispalis (Seville) and Astigi (Écija), and were probably carried along the River Guadalquivir and its tributaries. [source]

Possibilities and Limits of Application of Electrical Resistance Tomography in Hydrodynamics of Bubble Columns

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2005
Dominique Toye
Abstract Knowing the hydrodynamic regime in which is working a bubble column is of great importance because the regime affects strongly the mass transfer between the phases. To this end, we examine the potentialities of an Electrical Resistance Tomography (ERT) device. We analyse cross correlation of electrode pair measurements, of neighbouring pixels and power spectra of averaged pixels within a single plane as well as cross correlations of averaged pixels between two planes, without finding a clear signature of the churn turbulent flow. Variable gas flow rate inputs are used to determine the time resolution of the ERT. L'objet du présent travail est de déterminer dans quelle mesure la Tomographie Électrique Résistive (ERT) peut être utilisée pour détecter le régime hydrodynamique dans lequel fonctionne une colonne à bulles. La connaissance de ce régime est extrêmement importante, en raison notamment de son influence sur les valeurs des paramètres de transfert. Dans ce but, nous avons analysé les spectres de puissance de la valeur moyenne des pixels dans un plan de mesure donné, ainsi que la corrélation temporelle existant entre les mesures de différence de potentiel, entre les pixels voisins d'un plan de mesure donné et entre les valeurs moyennes des pixels appartenant à deux plans de mesure différents. Nous n'avons trouvé aucune signature claire du régime hétérogène. La résolution temporelle de l'ERT a par ailleurs été évaluée en utilisant une alimentation de gaz variable. [source]

Local Bubble Dynamics and Macroscopic Flow Structure in Bubble Columns with Different Scales

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2003
Wei Chen
Abstract Local bubble behaviours were investigated in three bubble columns with different diameters of 200, 400 and 800 mm. By means of a novel single-tip optical fibre probe employing laser Doppler technique, the local gas holdup, bubble frequency, bubble size and velocity were measured simultaneously at different locations of the columns. Measurements were performed in air-water system at superficial gas velocities up to 90 mm/s. The averaged profiles and instantaneous measurements were analyzed and compared for different columns. The presence of a coherent gross circulation structure spanning the entire column diameter in the larger column rather than a pair of symmetrical circulation cells observed in the smaller columns has been confirmed. Les comportements locaux des bulles ont été étudiés dans trois colonnes à bulles de diamètres différents, soient 200, 400 et 800 mm. Au moyen d'une nouvelle sonde à fibre optique à embout unique employant la technique laser Doppler, des mesures locales de la rétention de gaz, de la fréquence des bulles, de la taille des bulles et de la vitesse ont été effectuées simultanément à différents endroits dans les colonnes. Ces mesures ont été effectuées pour un système air-eau à des vitesses de gaz superficielles atteignant 90 mm/s. Les profils moyennés et les mesures instantanées ont été analysés puis comparés pour différentes colonnes. La présence d'une structure de circulation unique cohérente occupant tout le diamètre de la colonne dans la colonne la plus large plutôt qu'une paire de cellules de circulation symétriques observées dans les colonnes plus petites est confirmée. [source]

Liquid Dispersion in Large Diameter Bubble Columns, with and without Internals

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2003
Ann Forret
Abstract Liquid mixing has been studied in a 1 m diameter bubble column, with and without internals (vertical cooling tubes). The presence of internals significantly affects both large scale recirculation and local dispersion. The most common approach to model liquid mixing is the one-dimensional axial dispersion model, validated many times in small bubble columns without internals. This paper shows that this model is still appropriate to large columns, but without internals. A two-dimensional model, taking into account a radially dependent axial velocity profile, and both axial and radial dispersion, is required to account for the internals on liquid mixing. Le mélange du liquide dans une colonne à bulles de 1 m de diamètre a été étudié, avec et sans internes (tubes verticaux simulant des échangeurs de chaleur). La présence d'internes affecte de manière significative à la fois la recirculation globale du liquide ainsi que la dispersion locale. L'approche la plus couramment employée pour modéliser le mélange du liquide est le modèle de dispersion axiale mono dimensionnel, validé maintes fois pour les petites colonnes à bulles sans internes. Cet article montre que ce modèle reste valable pour les colonnes de grande taille, sans internes. Par contre, la prise en compte des effets des internes sur le mélange liquide passe par l'utilisation d'un modèle bidimensionnel, prenant en compte le profile radiale de la vitesse axiale ainsi que les dispersions axiale et radiale. [source]