bluuebunny/crossref_metadata_2025_split huggingface dataset:
A methodology for screening hydrocracking catalysts
Authors: Prasad Rameshwar , Dabral Rameshwar P. , Wadehra Brij M. L. , Moolchandra R. , Mittal Krishan G. 
Published: May 2005

AbstractHydroconversion of n‐heptane and toluene has been studied over a commercially proven Ni–W/SiO2–Al2O3 amorphous base hydrocracking catalyst (suitable for maximizing middle distillates production from heavier feedstocks) under a wide range of operating conditions (pressure: 400–1200 psig; temperature: 315–360°C, liquid hourly space velocity (LHSV) ≃ 1 h−1 and molar hydrogen/hydrocarbon feed ratio: 6–8) to assess the hydrogenation and cracking activities of the catalyst screening. Hydroisomerization followed by hydrocracking, ad hydrogenation followed by isomerization have been found to be the major reaction with n‐heptane and toluene respectively as the feeds. The hydroconversion of toluene gives a very high selectivity of hydrogenated product. With n‐heptane, a very high selectivity of hydroisomerized product, together with a high ratio of hydroisomerized to hydrocracked product, is obtained.
Kinetic behavior of yeast alcohol dehydrogenase in AOT/isooctane reverse micelles
Authors: Chen Dong‐Hwang , Chen Hsien‐Hsin , Huang Ting‐Chia 
Published: May 2005

AbstractThe kinetic behavior of yeast alcohol dehydrogenase (YADH) in sodium di‐2‐ethylhexylsulfosuccinate (AOT) isooctane reverse micelles has been studied using methyl ethyl ketone (MEK), NADH and Tris as the substrate, coenzyme and buffer, respectively. The solubility diagrams of aqueous buffer in the isooctane solution of AOT were established as a function of temperature and molar ratio of water of surfactant (ω0) at various Tris and AOT concentrations. The dependence of enzyme activity on enzyme concentration, pH, ω0 and Tris concentration was determined. The optimal ω0 was at 10–15, increasing slightly with an increase in Tris concentration. The YADH entrapped in reverse micelles exhibited minimum activity at a Tris concentration of 0·1 mol dm−3, while in aqueous buffer enzyme activity was not significantly affected by Tris concentration. Comparing the rate equation of the reduction of MEK by YADH in reverse micelles with that in aqueous buffer, the association of YADH and NADH could apparently have proceeded with an irreversible reaction before the substrate was bound, when performed in a reverse micellar system. Although the YADH entrapped in reverse micelles was less stable than when dissolved in aqueous buffer, the enzyme retained at least 20% activity after 21 h at 25°C and ω0 = 20. This result was an improvement over previously reported data.
Influence of the organic volumetric loading rate on soluble chemical oxygen demand removal in a down‐flow fixed‐bed reactor treating abattoir wastewater
Authors: Borja Rafael , Banks Charles J. , Martín Antonio 
Published: May 2005

AbstractA laboratory‐scale anaerobic down‐flow fixed‐bed reactor, operating at 35°C, was used to treat abattoir wastewater at input soluble chemical oxygen demand (COD) levels ranging from 4·7 to 28·7 g sm−3 and volumetric organic loading rates ranging from 2·5 to 25 g COD dm −3 day −1. Start up of the reactor was achieved within 35 days using a regime that include stepped increases in input COD and methanol substitution. The effects of the organic volumetric loading rates on soluble (COD) (SCOD) removal were studied at four feed SCOD concentrations between 4·7 and 28‐7 g dm−3. An exponential dependency of the organic volumetric loading rate with the SCOD removal was observed in the range of loading studied, with variation between 1 and 12 g COD sm−3 day −1 Further increases of the organic loading rates has smaller effects on SCOD removal. A pseudo first‐order kinetic model was used to obtain the gross removal coefficients, the values of which were virtually independent of the feed COD concentration at 6·9 to 7·3 g COD dm −3 day −1. The methane yield coefficient decreased slightly from 0·34 to 0·31 dm 3 g −1 COD when the feed SCOD concentration was increased from 4·7 to 28·7 g dm −3.
Separation of (3S, 3′S)‐, (3R 3′R)‐ and (3S, 3′R)‐astaxanthin via (−)‐camphanic acid esters
Authors: Vecchi Max , Müller Robert K. 
Published: May 2005

AbstractA method is described for the qualitative and quantitative determination of configurational isomers of astaxanthin. It is based on the esterification of astaxanthin with (—)‐camphanic acid chloride and analysis of the corresponding diesters by HPLC.
A study of the effects of temperature and pressure on the retention time in series‐coupled columns under conditions of constant mass flow rate
Authors: Buys T. S. , Smuts T. W. 
Published: May 2005

AbstractThe technique of controlling chromatographic selectivity by the adjustment of column temperatures in systems of series‐coupled columns is investigated by means of a general model incorporating the effects of temperature and mobile phase compressibility. In a previous article the performance of series‐coupled columns was investigated under conditions of constant overall pressure drop. The present paper, on the other hand, considers systems in which a constant mass flow rate is maintained at all temperatures. The expressions derived for the effective partition coefficient and the retention time are compared with those of the previous paper. The numerical results for two‐column systems exhibit the same major trends as those for constant pressure drop. It is shown that the effective partition coefficient is slightly dependent on the mass flow rate.
Quantitative evaluation of thin‐layer chromatograms. 4. Calculation of fluorescence using Bodó equations
Authors: Pršsek M. , Medja A. , Kučan E. , Katifč M. , Bano M. 
Published: May 2005

AbstractChanges in fluorescence intensity at the far and near side for various spot locations in a sorbent are calculated using a multilayer model and Bodó equations for each sublayer. Flow charts are given for evaluation of reflectance transmission, and fluorescence.
Separation of isomers of nitro‐polycyclic aromatic hydrocarbons
Authors: Greibrokk T. , Iversen B. , Johansen E. J. , Rønningsen H.‐P. , Svendsen H. 
Published: May 2005

AbstractSince positional isomers of several nitro‐polycyclic aromatic hydrocarbons (nitro‐PAH) contain widely different mutagenic properties, methods for separating the isomers were investigated. High performance liquid chromatography with dichloromethane in hexane on silica gave the best resolution for the majority of the compounds. A few groups of isomers were better resolved with other modifiers or with reversed phases. Of the reversed phase systems, methanol‐water gave better resolution than acetonitrile‐water. With dichloromethane/hexane on silica, the retention was found to depend on the presence of a bay nitro group (first), the number of H atoms peri to the nitro group (second), and the length/breadth ratio of the molecule (third).Front electron density calculations were combined with the structure‐retention relations in making tentative structure assignments of minor isomers of nitro‐PAH.
Two‐dimensional gas chromatography for determination of volatile compounds in ambient air
Authors: Berg S. , Jonsson A. 
Published: May 2005

AbstractA two‐dimensional gas chromatograph is described for the analysis of volatile compounds. The chromatographic system consists of two separate chromatographs linked together with an interface containing an intermediate trap. The trap is cooled with nitrogen (−150°C) and a cryogradient is created inside the trap enclosure. The sample is reinjected during controlled (chromatographic) conditions, using thermostated air. The sample components are eluted from the trap as narrow symmetrical peaks; the shape and width of the peaks eluted do not noticeably affect the subsequent chromatography. The enrichment of n‐butane in the trap is quantitative in the range 10−10 – 10−5 g.
Deactivation, coating and performance of nickel capillary columns for GLC
Authors: Rohwer E. R. , Pretorius V. , Hulse G. A. 
Published: May 2005

AbstractElectroformed nickel tubing was deactivated by chemical vapor deposition of silicon from silane gas and subsequent treatment with cyclooctamethyltetrasiloxane (D4). Standard activity tests performed on the uncoated tube and also on columns coated with crosslinked and uncrosslinked, nonpolar stationary phase, show that good quality flexible columns can be prepared from nickel tubing. The inner surface of the silicon coated tube was characterized by Auger depth profile analysis.
Advances in the liquid chromatography of hop bitter compounds
Authors: Verzele M. , Steenbeke G. , Dewaele C. , Verhagen L. C. , Strating J. 
Published: May 2005

AbstractHigh efficiency liquid chromatography (LC) on both coupled conventional columns and long micro‐LC columns, both with diode array detection, has revealed the presence of some hitherto unknown compounds in hop extracts. Proof is advanced that ethanol extracts of hops contain iso‐alpha acids.The elution order of the cis‐trans pairs of the iso‐alpha acids, and the separation of the alpha acids from the deoxyalpha acids, is reversed by switching from methanol to acetonitrile in the reversed phase solvent system.An LC solvent system giving higher resolution (higher selectivity factor) of the iso‐alpha acid cis and trans stereoisomers is obtained by adding magnesium salts to the eluent.
A water trap for static cryo‐headspace gas chromatography
Authors: Kolb Bruno , Zwick Gerhard , Auer Maria 
Published: May 2005

AbstractThe headspace gas in static headspace gas chromatography contains mostly saturated water vapor. In the case of the cryofocusing enrichment technique this may cause baseline distortion in the early part of the chromatogram or may even lead to ice‐plugging of the capillary column. A water‐trap is described in which the water vapor is removed from the headspace gas before entering the cryo‐trap. The water trap is packed with lithium chloride on a porous support and is regenerated after each analysis by heating under backflush conditions. It therefore can be used for automatic operation. Data are given for the precision and accuracy, and some practical examples, for environmental and flavor analysis are shown.
Dimethylbenzothiophenes and methyldibenzothiophenes in crude oils from different sources
Authors: Andersson Jan T. , Sielex Klaus 
Published: May 2005

AbstractA method is presented for the identification and quantification of C2‐substituted benzothiophenes in crude oil. The method will enable analysis of the pattern of these compounds, for example as a basis for differentiating crude oils from one another (fingerprinting) and for investigation of their suitability as indicators of oil maturity. Here results are reported for five crudes from Iraq, Venezuela, Saudi Arabia, the former Soviet Union, and the North Sea. The aromatic fraction of the crudes was oxidized and the dioxides of the heterocycles separated according to the number of carbon atoms in the side chains. The final separation was by capillary GC with atomic emission or flame ionization detection. A fluorinated analog was synthesized and used as internal standard. The concentrations of 2,3‐, 2,4‐, 2,7‐, and 3,7‐dimethylbenzothiophene ranged between 11 and 272 ppm. Three other dimethylated benzothiophenes present in lower amounts were also identified.
Supramolecular selective transport of Ca2+/Na+ by dicarboxylic ligands across bulk liquid membranes
Authors: Biancardi Alberto , Marchelli Rosangela , Dossena Arnaldo 
Published: May 2005

AbstractBulk liquid membrane transport of Ca2+ and Na+ ions was performed with dicarboxylic type ligands containing (S)‐phenylalanine (Phe‐2‐O) and (S)‐benzyltyrosine (Bz‐Tyr‐2‐O) in pH gradients. With Bz‐Tyr‐2‐O, calcium was generally favoured at every pH, the transport rate strongly depending upon the ligand concentration. At pH 8, a reversal of selectivity (Na+/Ca2+) was observed for the first time at low ligand concentration, thus suggesting that a supramolecular‐type of transport occurs as a consequence of the different assemblages formed by the ligand according to pH and concentration. This is the first case of M2+/M+ selectivity induced by the carrier concentration.
Platelet‐derived growth factor and regulation of schwann cell proliferation in vivo
Authors: Hardy M. , Reddy U. R. , Pleasure D. 
Published: May 2005

AbstractTo examine the role of platelet‐derived growth factor (PDGF) in the in vivo regulation of Schwann cell proliferation, steady‐state levels of mRNAs encoding PDGF A and B chains, and PDGF α and β receptors were measured in immature and adult rat sciatic nerves and in cultured rat Schwann cells. PDGF B chain and PDGF β receptor mRNAs are present in immature rat sciatic nerves and to a lesser extent in adult rat nerves. Short‐term cultures of neonatal rat Schwann cells express PDGF β receptor mRNA, but not PDGF B chain mRNA, and are stimulated to synthesize DNA by addition of PDGF BB to the medium. These data indicate that PDGF BB is a developmenttally regulated paracrine growth factor for rat Schwann cells. Very long‐term cultures of rat Schwann cells, which have lost normal dependence on exogenous growth factors, express PDGF B chain mRNA as well as mRNAs encoding the PDGF α and β receptors, suggesting that, under these circumstances, PDGF BB also acts as an autocrine growth factor. PDGF A chain mRNA is present in both immature and adult rat sciatic nerves and is expressed by primary and secondary cultures of rat Schwann cells as well. However, because the abundance of PDGF α receptor mRNA is very low in rat Schwann cells, PDGF AA is not likely to be a significant autocrine growth factor for rat Schwann cells.
Spatial memory in aged rats: Population heterogeneity and effect of levocarnitine acetyl
Authors: Ghirardi O. , Giuliani A. , Caprioli A. , Ramacci M. T. , Angelucci L. 
Published: May 2005

AbstractThe existence in a population of aging rats of classes that display a different performance in the Morris water‐maze test was investigated by cluster analysis procedure. These classes identified at 18 months of age showed a different response to levocarnitinc acetyl and had a different behavioral profile when tested at 25 months of age. These findings demonstrate the need for an alternative interpretation of variability in animal populations as measured by the standard statistical analyses. The data analysis strategy we propose here will allow for the use of variability as a useful source of information.
Immunohistochemical localization of beta‐amyloid precursor protein sequences in Alzheimer and normal brain tissue by light and electron microscopy
Authors: McGeer P. L. , Akiyama H. , Kawamata T. , Yamada T. , Walker D. G. , Ishii T. 
Published: May 2005

AbstractImmunohistochemical staining with antibodies directed against four segments of the amyloid precursor protein (APP) was studied by light and electron microscopy in normal and Alzheimer (AD) brain tissue. The segments according to the Kang et al. sequence were:18–38 (T97); 527–540 (R36); 597–620 (1–24 of β‐amyloid protein [BAP], R17); and 681–695 (R37) (Kang et al. [1987]: Nature 325:733–736). The antibodies recognized full length APP in Western blots of extracts of APP transfected cells. They stained cytoplasmic granules in some pyramidal neurons in normal appearing tissue from control and AD cases. In AD affected tissue, the antibodies to amino terminal sections of APP stained tangled neurons and neuropil threads, and intensely stained dystrophic neurites in senile plaques. By electron microscopy, this staining was localized to abnormal filaments. The antibody to the carboxy terminal segment failed to stain neurofibrillary tangles or neuropil threads; it did stain some neurites with globular swellings. It also stained globular and elongated deposits in senile plaque areas. The antibody against the BAP intensely stained extracellular material in senile plaques and diffuse deposits. By electron microscopy, the antibodies all stained intramicroglial deposits. Some of the extracellular and intracellular BAP‐positive deposits were fibrillary. Communication between intramicroglial and extracellular fibrils was detected in plaque areas. These data suggest the following sequence of events. APP is normally concentrated in intraneuronal granules. In AD, it accumulates in damaged neuronal fibers. The amino terminal portion binds to abnormal neurofilaments. Major fragments of APP are phago‐cytosed and processed by microglia with the BAP portion being preserved. The preserved BAP is then extruded and accumulates in extracellular tissue.
Cytoskeletal elements regulate the distribution of nerve growth factor receptors in PC12 cells
Authors: Spoerri P. E. , Roisen F. J. 
Published: May 2005

AbstractNerve growth factor receptor (NGFR)‐like immunoreactivity (IR) was studied in PC12 cells treated for 96 hr with NGF (40 ng/ml), using immunogold labeling and electron microscopic morphomctric analysis. The cells were exposed to the anti‐NGFR antibody 192‐IgG, followed by immunoglobulin (IgG) conjugated with colloidal gold. PC12 cells exhibited occasional gold label (positive NGFR‐IR) on all surfaces. Cells treated with colcemid (0.05 μg/ml) or cytochalasin D (2 μg/ml), which limit microtubule (MT) and microfilament (MF) formation, respectively, displayed an increased NGFR‐IR in terms of gold labeling. NGFR‐IR was also seen on taxol (0.85 μg/ml)‐exposed cells, an agent that promotes MT assembly. Cells treated simultaneously with cytochalasin D and taxol had a dramatically augmented NGFR‐IR on their surfaces, which exceeded levels obtained with either agent alone. Prominent NGFR‐IR was localized frequently in coated endocytotic vesicles, in smooth endoplasmic reticulum, and in secondary multivesicular lysosomes, in both treated and untreated cells. The results suggest that a large number of NGFRs (positive NGFR‐IR) in PC12 cells are cryptic and not available for ligand binding. Changes in cytoskeletal organization that may affect mobility of integral membrane proteins can modulate the distribution of NGFR‐IR on neuronal surfaces.
Differential coupling of opioid binding sites to guanosine triphosphate binding regulatory proteins in subcellular fractions of rat brain
Authors: Szücs M. , Coscia C. J. 
Published: May 2005

AbstractIn this study, we present evidence for the occurrence of μ, δ, and κ opioid binding sites in synaptic plasma membranes (SPM) and microsomes of rat brain. Binding to all three opioid classes was inhibited by 5′‐guanylylimidodiphosphate (Gpp[NH]p) in SPM, while microsomal sites proved to be insensitive to this GTP analog. Sensitivity was restored upon solubili‐zation of microsomes with digitonin, suggesting that opioid receptors are physically separated from G proteins in this fraction. Modulation of microsomal binding by Na+ and Mn++ was greater than that of SPM. Pertussis toxin‐catalyzed adenosine diphosphate (ADP) ribosylation revealed the presence of G proteins with α‐subunit molecular weights of 40 kDa in both subcellular fractions. Basal low Km GTPase activity in SPM was greater than in microsomes. Etorphine elicited a concentration‐dependent stimulation of guanosine triphosphatase (GTPase) activity in SPMs but not in microsomes, indicating functional coupling of opioid receptors to G protein in the former and an uncoupling in the latter. Microsomes from 3‐day‐old rat brain contained more μ opioid sites and they were more sensitive to Gpp(NH)p inhibition than those in adults. These results are consistent with the hypothesis that opioid binding sites in adult microsomes are internalized and G protein uncoupled, while those in neonates are newly synthesized, coupled receptors.
Neuronal origins of K+‐evoked amino acid release from cerebellar cultures
Authors: Simmons M. L. , Dutton G. R. 
Published: May 2005

AbstractNeuronal cultures from rat cerebellum consisting of approximately 90% glutamatergic granule neurons, 5–7% GABAergic inhibitory interneurons, and 3–5% glial cells, were treated for four days with 50 μM kainic acid (KA) to determine the cellular origin of released endogenous neuroactive substances. KA, known to be selectively toxic to GABAergic neurons, caused an estimated 80% decrease in glutamic acid decarboxylase (GAD) immunofluorescence. Furthermore, K+‐stimulated release of GABA decreased to 20% of control values, and did not return to control levels in cultures "recovered" two days in KA‐free media, suggesting the loss of inhibitory interneurons. Similarly, adenosine and taurine showed decreased K+‐stimulated release, which was unrecoverable when KA was removed from the medium. K+ stimulated release of glutamate and aspartate also decreased by 50% and 70%, respectively, after chronic KA treatment. In contrast, however, this release returned to control levels in recovered cultures. All decreases in K +‐stimulated release were Prevented concurrent treatment with KA and the KA antagonist 6‐cyano‐6‐nitroquinoxaline‐2,3‐dione (CNQX), indicating that a receptor‐mediated mechanism was involved. We conclude that, in these cultures, most of the K+‐stimulated release of adenosine and taurine originates from the GABAergic interneurons, the basket and stellate cells, which are selectively killed by the KA treatment. The data also strongly suggest that glutamate and aspartate, the levels of which recover after KA treatment, originate mainly from the granule neurons.
Dystrophin immunoreactivity in normal and duchenne human fetal neurons in culture
Authors: Torelli S. , Sogos V. , Ennas M. G. , Muntoni F. , Clerk A. , Strong P. N. , Gremo F. 
Published: May 2005

AbstractDystrophin, the protein product defective in Duchenne muscular dystrophy (DMD), is present in all types of muscle and in the brain. The function of the protein is unknown and its role in the brain is unclear, although 30% of DMD patients show nonprogressive mental retardation. We have therefore studied the localisation of dystrophin in cultures of normal and DMD human fetal neurons using antibodies raised to different regions of the protein. Dystrophin immunoreactivity was demonstrated in the soma and axon hillock of normal neurons and appeared to be associated with the inner part of the cell membrane, although some intracellular staining was also observed. Positive dystrophin staining was present only in cells with fully developed neuronal features, although not all the neurons were positive. Glial cells were always negative for the antigen. Immunostaining with antibodies to the brain spectrins indicate that the dystrophin antibodies did not cross‐react with these proteins. The possibility of cross‐reactivity with other proteins is discussed.Studies of cells cultured from a DMD fetus also showed specific dystrophin immunostaining in neurons, although the muscle was generally negative for dystrophin. However, the localisation of dystrophin immunostaining and that of the brain spectrins and neurofilaments appeared abnormal, as did the overall morphology of the cells. This suggests that dystrophin may play a role during brain development and dystrophin deficiency results in abnormal neuronal features. This would be consistent with the nonprogressive nature of the mental retardation observed in DMD patients. © 1992 Wiley‐Liss, Inc.