bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applicability of continuous membrane bioreactor in production of phenylacetylcarbinol
Authors: Liew Michelle K. H. , Fane Anthony G. , Rogers Peter L. 
Published: May 2005

AbstractA continuous membrane bioreactor (CMB) with Ceraflo ceramic microfilter was evaluated for the production of phenylacetylcarbinol (PAC) using 12–15 g dm−3 Candida utilis. Compared with the classical continuous fermentation, the CMB process was shown to have higher biomass concentration (from 40% to 400% increase) and greater growth rate (from 3‐ to 9‐fold) at dilution rates varying from 0·03 h−1. These advantages were partially offset by the reduced permeate flux caused by the increased biomass. Furthermore, an addition of only 3·0 cm3 h−1 benzaldehyde for 17 h (a typical bioconversion protocol) was found to kill the yeast, resulting in 27% dead organisms and 35% lysed organisms and their associated species. This led to a 100% flux decline during the course of PAC production over the above period.
Penicillin G extraction by amberlite LA‐2—a study of interfacial reaction kinetics by interfacial tension measurements
Authors: Lee Chau Jen , Wang Shih Sheng 
Published: May 2005

AbstractThe concentration of reactants at an interface cannot be determined directly. The concentration at the interface has been estimated by measuring the interfacial tension at the interface between two immiscible solutions. An aqueous phase, de‐ionised water containing penicillin G, and an organic phase containing amberlite LA‐2 were used as a typical system to study the kinetics of interfacial reaction. The interfacial tension was measured by a spinning‐drop tensiometer at 25 ± 0·1°C. The interfacial tension was found to correlate well with the concentrations of penicillin G, Amberlite, LA‐2 and proton in each respective phase.
Multi‐substrate analysis of carbon oxidation and nitrification in an upflow packed‐bed biofilm reactor
Authors: Beg Shafkat A. , Hassan Mirza M. , Chaudhary Muhammad A. S. 
Published: May 2005

AbstractThe performance of an upflow packed‐bed biofilm reactor (UPBR) was analysed under multi‐substrate limitation by considering simultaneous carbon oxidation and nitrification reactions. Numerical solutions of the proposed model defining the system were obtained for a wide range of operating conditions of illustrate individual substrate limitation behavior. For an inlet concentrating of 75 mg dm −3 of NH4‐N and 25 mg dm −3 of methanol., the organic substrate was consumed rapidly near the inlet of the reactor while most of the NH‐N was converted in the central region. The concentration profiles within the biofilm indicated that oxygen was limiting near the inlet of the reactor while organic substrate was laminating at the middle of the reactor. Both NH‐N and methanol became limiting near the reactor exit. Detailed analyses were carried out for a wide range NH‐N concentration and for a given concentration of methanol which showed that oxygen could also become limiting even at the middle of the reactor.
Lignocaine ion‐selective electrodes based on its ion‐associates with cobalt thiocyanate, phosphomolybdate and reineckate complex ions
Authors: Issa Yousry M. , Shoukry Adel F. , Rizk Mahmoud S. , Atia Ehab M. 
Published: May 2005

AbstractLignocaine (Lg) selective PVC membrane electrodes based on the ionassociates lignocaine‐cobalt thiocynate (I), lignocaine–phosphomolybdate (II) and lingnocaine–reinckate (III) were constructed. The electrodes exhibited linear response over the concentration ranges 0.02–100, 0.01–100 and 0.01–10 mM for I, II and III, respectively. pH did not effect the electrodes performance within the ranges 3–6, 3–7 and 3–6·5 for 10−2, 10−3 and 10−4 M LgHCl, respectively. Interferences are negligible for many inorganic cation, sugars and amino acids. The isothermal coefficients were found to be 0·000459, 0·000698 and 0·000404 V °C−1 for I, II and III, respectively. The life spans of the electrodes are more than 2 months of continuous work. Potentiometric titration and the standard addition method were used to determine LgGCl in pure solutions and in pharmaceutical preparations with high accuracy and precision.
Liquid and gas chromatographic separation of isomeric methylated dibenzothiophenes
Authors: Berthou F. , Dreano Y. , Sandra P. 
Published: May 2005

AbstractTrace amounts of a dibenzothiophene (DBT) series in complex matrices were detected by gas chromatography with flame photometric detection (FPD) after purification and isolation by normal‐phase high performance liquid chromatography. The gas chromatographic behavior of eleven methylated DBTs was studied on six common stationary phases. Complete resolution of the four monomethyl DBT isomers was only achieved on a capillary column coated with a methylphenylsilicone phase gummified in situ by heat‐curing.The determination of the relative distribution of the four monomethylated isomers is proposed as a powerful method for monitoring oil pollution in marine environment.
Influence of temperature on FTIR spectra of various organic compounds analyzed by on‐line carbon dioxide SFC/FTIR
Authors: Morin Ph. , Beccard B. , Caude M. , Rosset R. 
Published: May 2005

AbstractThe development of an on‐line SFC‐FTIR method with supercritical carbon dioxide as mobile phase requires information about the nature of the FTIR spectrum of a solute dissolved in supercritical or liquid CO2. The wavenumber of maximum absorbance of the carbonyl stretching vibration was quantitatively studied versus temperature and CO2 density. FTIR spectra recorded in supercritical or liquid CO2 have been compared to their vapor‐phase and condensed‐phase spectra for various solutes.
Quantitative analysis of polymer additives in low density polyethylene using supercritical fluid extraction/supercritical fluid chromatography
Authors: Ashraf‐Khorassani Mehdi , Levy Joseph M. 
Published: May 2005

AbstractAnalysis of low concentration polymer additives has been a challenging problem. The commonly used methods of analysis involve the initial extraction of polymer additives with solvents, often in a Soxhlet apparatus, followed by liquid, size exclusion, or gas chromatography. This paper describes the on‐line super‐critical fluid extraction (SFE)‐supercritical fluid chromatographic (SFC) determination of different additives from low density polyethylene. Cryogenic collection was used as an interface between SFE and SFC to focus the extraction eluate before transfer to an analytical SFC column for quantitative analysis.
New on‐line concentrator for LC‐GC: Analysis of PAHs with LC‐GC
Authors: Heo Gwi Suk , Suh Jung Kee 
Published: May 2005

AbstractA new, versatile, and low cost on‐line LC‐GC interface has been devloped for the fast and reliable introduction of large volume samples into a cappillary GC column without using the conventional retention gap. PAHs in soot were analyzed by on‐line normal phase HPLC‐capillary GC. A glass, vial‐shaped on‐line concentrator provides a zone for solvent evaporation and sample concentration. Large volumes of HPLC eluate can be concentrated with the on‐line concentrator and then transferred directly into the cappillary column. Trace levels (< 10 ppb) of PAH compounds can be efficiently concentrated with the on‐line concentrator and determined without loss or contamination.
Selectivity tuning of serially coupled columns in high performance liquid chromatography
Authors: Welsch Thomas , Dornberger Uwe , Lerche Dietmar 
Published: May 2005

AbstractThe tuning of selectivity by changing the flow rate has been investigated in HPLC: two columns with different retention characteristics were coupled in series via a T‐piece and the relative retention of components chromatographed on the system were changed by varying the individual flow rates in the coupled columns. The flow rate alteration was performed by adding a second flow after the first column. The flow rate ratio necessary for optimum resolution can be easily calculated on the basis of the capacity factors measured on the individual columns. The performance of this method for adjusting selectivity has been demonstrated by using different column combinations to separate several mixtures containing chlorophenols, nitroaromatic compounds, and aromatic hydrocarbons.
Adjusting the selectivity of inorganic anion separation by capillary electrophoresis
Authors: François C. , Morin Ph. , Dreux M. 
Published: May 2005

AbstractThe separation of the principal inorganic anions (bromide, carbonate, chlorate, chloride, fluoride, nitrate, nitrite, sulfate, phosphate) has been achieved using a capillary electrophoresis system with indirect UV detection at 260 nm. Several types of cationic surfactants (quaternary ammonium, phosphonium or methonium) were tested as electroosmotic flow modifiers and added to a chromatebased buffer prepared from potassium dichromate. The influence of many physicochemical parameters such as nature and concentration of cationic surfactant, buffer pH, dichromate concentration buffer, voltage and temperature upon the migration time of an analyte anion, peak efficiency, asymmetry factor, and finally resolution has been investigated. A linear relationship between the corrected area and the anion concentration in the 2.5–50 ppm range was obtained, thus allowing the quantitative analysis of anions in mineral water. Finally, by increasing the hydrodynamic injection time, the separation of inorganic anions at a low concentration level of 50 ng/ml was achieved without any loss of resolution.
Development and evaluation of an interface for coupled capillary supercritical fluid chromatography/magnetic sector mass spectrometry. Application to thermally unstable and high molecular mass compounds
Authors: Mertens Manuel A. A. , Janssen Hans‐Gerd M. , Cramers Carel A. , Genuit Wim J. L. , van Velzen Ger J. , Dirkzwager Henk , van Binsbergen Herman 
Published: May 2005

AbstractAn interface for coupling supercritical fluid chromatography to a magnetic sector mass spectrometer was developed and evaluated. The interface is based on direct introduction of the mobile phase, carbon dioxide, into the ion‐source of the mass spectrometer. The SFC‐MS system was optimized with respect to the signal‐to‐noise ratio. Under optimized conditions, the estimated detection limit for n‐pentadecane is approximately 30 ppm. Spectra obtained in the electron‐impact ionization mode show a very good similarity with library spectra. The performance of the SFC‐MS system was evaluated by the analysis of a number of test mixtures. A sample containing several low molecular mass, thermally unstable compounds, which could neither be analyzed by GC‐MS nor by LC‐MS, was analyzed. Also for the analysis of high molecular mass compounds, the coupled system showed a good performance.
Testing the polarity and adsorptivity of nondeactivated GC capillary surfaces
Authors: Grob Konrad , Vorburger Thomas 
Published: May 2005

AbstractSplit injection of 1‐pentanol headspace on to raw or treated fused silica tubing yields information on the characteristics of its surface (silanol concentration, polarity, adsorptivity). Fused silica tubing from three sources was compared. The effect of various leaching and etching procedures used for column preparation was studied, as was the stability of uncoated fused silica precolumns towards water and some organic solvents.
A new look at light hydrocarbon separations on commercial alumina PLOT columns: Column selectivity and separation
Authors: Ji Zhenghua , Chang Imogene L. 
Published: May 2005

AbstractAlumina‐coated porous layer open tubular (PLOT) columns are widely used for analyses of light hydrocarbons (C1 to C6). There is, however, a need for improved selectivity for complex analyses such as the determination of impurities in high purity petrochemical products. Some commercial alumina PLOT columns do not have sufficient selectivity for such analyses. The selectivity of four commercial alumina PLOT columns is evaluated for analyses of propylene and ethylene, and differences in column selectivity discussed. Requirements of column selectivity and retention are presented for several applications including the analysis of refinery gas, transformer oil gas, and fuel gas.
Simultaneous capillary GC of acids and sugars as their silyl(oxime) derivatives: Quantitation of chlorogenic acid, raffinose, and pectin substances
Authors: Tisza Sándor , Molnár‐Perl Ibolya , Friedman Mendel , Sass Pál 
Published: May 2005

AbstractOur GC‐MS method for the simultaneous quantitation of sugars and acids as their silyl(oxime) derivatives, from one solution by one injection, has been extended to the reproducible determination of high molecular weight compounds sensitive to decomposition yet requiring a high evaporation temperature (e.g. chlorogenic acid and rffinose) and for the quantitation of the decomposition products of pectin (i.e., for the determination of galacturonic acid at low ng levels in the presence of a 10–100 fold excess of glucose eluting just before the acid). The optimized GC procedure has been used for quantitation of the sugar and acid (including chlorogenic acid) composition of potato samples, and for the determination of the increasing amount of the decomposition products of pectin substances in apple pulp after different storage times.
Solid phase extraction GC/ECD method for the analysis of organochlorine pesticides in wildlife plasma
Authors: Johnstone John J. , Petty Eric E. , Volz Stephanie A. 
Published: May 2005

AbstractA gas chromatographic method for the analysis of nine organo‐chlorine pesticides in wildlife plasma is described. Reversed‐phase solid phase extraction is utilized to extract the organochlorine pesticides from plasma. This is followed by a normal phase solid phase extraction clean‐up as the pesticides are recovered by elution with hexane:ethyl ether (1:1) and quantified by gas chromatogra‐phy/electron capture detection. Method limits of detection range from 7.0–25 μg/L. The mean recovery for all pesticides is 81%.
Identification of migratable substances in recycled high density polyethylene collected from household waste
Authors: Huber Monika , Franz Roland 
Published: May 2005

AbstractHigh Density polyethylene regranules reprocessed from separated household waste collection were investigated for migratable con‐taminants which were not present in virgin material. Although the material originated from different European reprocessors, the de‐tected recycling‐specific compounds were similar in most of the investigated samples. At a chosen threshold concentration of 0.5 μg/g more than 70 compounds were tentatively identified. Aroma compounds and preservatives were found in the range of 0.5 to 10 μg/g. Limonene, di(ethylhexyl) phthalate, and the isopropyl esters of myristic and palmitic acids were detected in concentrations up to 200 μg/g. These compounds were found in almost all the regranules. Most of the substances identified are constituents of personal hygiene products and cleaning agents and are therefore absorbed by the package during the storage. Owing to European food legislation and German cosmetics regulations, the use of such recycling packaging material appears suitable only for filling with technical products.
Flow of the carrier gas in open‐tubular capillary columns in temperature‐programmed gas chromatography
Authors: Hevesi Tibor , Krupcík Ján 
Published: May 2005

AbstractA second‐order non‐linear partial different equation was derived to describe the dependence of carrier gas pressure in the column on the column distance and the time under temperature programmed conditions. This equation was solved numerically by the modified finite difference method for various column parameters. Constant inlet and outlet pressures were used as boundary conditions. The retention times calculated on assumption of a constant pressure profile along the column. Significant differences between retention times of corresponding solutes calculated by the two methods were found, especially when relatively long columns(L>50m) with small internal diameter(d<0.3mm)and high temperature program rates (r>5°/min)are used.
Drug—DNA sequence‐dependent interactions analysed by electric linear dichroism
Authors: Bailly Christian , Hénichart Jean‐Pierre , Colson Pierre , Houssier Claude 
Published: May 2005

AbstractThe interactions between 20 drugs and a variety of synthetic DNA polymers and natural DNAs were studied by electric linear dischroism (ELD). All compounds tested, including several clinically used antitumour agents, are thought to exert their biological activities mainly by virtue of their abilities to bind to DNA. The selected drugs include intercalating agents with fused and unfused aromatic structures and several groove binders. To examine the role of base composition and base sequence in the binding of these drugs to DNA, ELD experiments were carried out with natural DNAs of widely differing base composition as well as with polynucleotides containing defined alternating and non‐alternating repeating sequences, poly(dA).poly(dT),poly(dA‐dT).poly(dA‐dT),poly(dG).poly(dC) and poly(dG‐dC).poly(dG‐dC). Among intercalating agents, actinomycin D was found to be by far the most GC‐selective. GC selectivity was also observed with an amsacrine‐4‐carboxamidederivative and to a laser extent with methylene blue. In contrast, the binding of amsacrine and 9‐aminoacridine was practically unaffected by varying the GC content of the DNAs. Ethidium bromide, proflavine, mitoxantrone, daunomycin and an ellipticine derivative were found to bind best to alternating purine‐pyrimidine sequences regardless of their nature. ELD measurements provided evidence for non‐specific intercalation of amiloride. A significant AT selectivity was observed with hycanthone and lucanthone. The triphenyl methane dye methyl green was found to exhibit positive and negative dichroism signals at AT and GC sites, respectively, showing that the mode of binding of a drug can change markedly with the DNA base composition. Among minor groove binders, the N‐methylpyrrole carboxamide‐containing antibiotics netropsin and distamycin bound to DNA with very pronounced AT specificity, as expected. More interestingly the dye Hoechst 33258, berenil and a thiazole‐containing lexitropsin elicited negative reduced dichroism in the presence of GC‐rich DNA which is totally inconsistent with a groove binding process. We postulate that these three drugs share with the trypanocide 4′, 6‐diamidino‐2‐phenylindole (DAPI) the property of intercalating at GC‐rich sites and binding to the minor groove of DNA at other sites. Replacement of guanines by inosines (i.e., removal of the protruding exocyclic C‐2 amino group of guanine) restored minor groove binding of DAPI, Hoechst 33258 and berenil. Thus there are several cases where the mode of binding to DNA is directly dependent on the base composition of the polymer. Consequently the ELD technique appears uniquely valuable as a means of investigating the possibility of sequence‐dependent recognition of DNA by drugs.
Structure and expression of proteolipid protein in the peripheral nervous system
Authors: Kamholz J. , Sessa M. , Scherer S. , Vogelbacker H. , Mokuno K. , Baron P. , Wrabetz L. , Shy M. , Pleasure D. 
Published: May 2005

AbstractProteolipid protein (PLP), the major myelin protein in the central nervous system (CNS), is also made by Schwann cells (SC) in the peripheral nervous system (PNS) but is not incorporated into the SC myelin sheath. We analyzed several PLP cDNA clones isolated from a rat sciatic nerve cDNA library and found that their coding sequences were identical to PLP cDNAs previously isolated from the CNS. In addition, we have discovered an unusual form of PLP message, present in both brain and sciatic nerve RNA, that is likely formed by alternative splicing within the 3′ untranslated region of the primary PLP transcript. The absence of PLP from the SC myelin sheath thus cannot be explained by an alteration in its amino acid sequence. Steady‐state levels of PLP mRNA in SC cultures treated with the cAMP analogue dibutyryl cAMP (dBcAMP) were not increased, whereas dBcAMP increased steady‐state levels of mRNA encoding the major myelin protein, PO. We have also shown that expression of PLP, unlike that of PO, is regulated in SC in vitro at a posttranscriptional level. Finally, the steady‐state levels of PO mRNA are much more dramatically reduced than those of PLP mRNA during Wallerian degeneration of the peripheral nerve. Thus PLP expression in the PNS is probably controlled by different molecular mechanisms from PO, and may not be part of the coordinate program of myelin gene expression. In contrast to its expression in the PNS, transcription of PLP in the CNS is coordinately regulated along with the other myelin protein genes, suggesting there may be differences in the cis‐acting elements and trans‐acting factors involved in the regulation of PLP transcription in SC and oligodendrocytes (OC). Consistent with this notion, we have found that most PLP transcripts are initiated at the more proximal of two start sites in the PNS, while in the CNS proportionally more PLP transcripts are initiated from the distal start site. We propose that the proximal site, utilized predominantly in SC, is responsible for maintenance expression of PLP and is not inducible, while the distal site is responsible for the rapid, inducible increase of PLP message during brain development.
Protection of neuro‐2a cells against calcium ionophore cytotoxicity by gangliosides
Authors: Nakamura K. , Wu G. , Ledeen R. W. 
Published: May 2005

AbstractGangliosides are known to assert both neuritogenic and neuroprotective effects when applied to a variety of neuroblastoma and primary neuronal cultures. We have developed a model employing Neuro‐2a Neuroblastoma cells with Ca2+ ionophore A23187 as neurotoxic agent causing neurite retraction and eventual cell death. Gangliosides attenuated the toxicity of this substance, increasing both cell survival and neurite stability. In one series of experiments, cells were exposed to A23187 for 24 hr and then incubated in fresh medium (washout) for 18 hr; gangliosides were present at varying times. The paradigm in which cells were only preincubated (2 hr) with ganglioside provided no benefit, nor did incubation of the cells in both ionophore and ganglioside during the 24‐hr exposure period. Significant protection was achieved by exposing the cells to ganglioside after washout of A23187, or continuously throughout the whole period. Bovine brain ganglioside mixture and the four major components (GM1, GDla, GDlb, GTlb) applied individually were all effective. By contrast, GM3 and GMl‐alcohol, a neutral derivative of GM1, provided little or no protection. Dichlorobenzamil an inhibitor of the Na+ −Ca2+ exchanger, tended to block the neurite stabilizing effect of gangliosides, suggesting that the mechanism might involve potentiation of this antiporter.