bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reflux–recycle–reactor for high yield and selectivity in TAME and TAEE production
Authors: Boz Nezahat , Dogu Timur 
Published: January 2005

AbstractThe batch reflux–recycle–reactor (RRR) proposed here was shown to give high product yields and selectivities in the production of tert‐ethers. Because the vapor pressures of product ethers are lower than those of the reactants, vapor‐phase reactor inlet stream is always rich in reactants in this batch RRR. A first‐order reversible reaction rate model was shown to give good prediction of experimental results. The apparent activation energy of the rate constant was evaluated as 24.8 kJ mol−1. This low value of activation energy for vapor‐phase synthesis of tert‐amyl methyl ether (TAME) was concluded to be primarily attributed to the significance of transport resistances in the macropores of Amberlyst‐15 and also through the thin liquid film covering catalyst particles. In the case of TAME production fractional conversion values reaching 0.91 were obtained at 82°C with almost 100% selectivity. Comparison of the results obtained for TAME and tert‐amyl ethyl ether (TAEE) synthesis showed that reactivity of methanol was much higher than that of ethanol in the etherification reaction of isoamylene, over Amberlyst‐15. © 2005 American Institute of Chemical Engineers AIChE J, 51:631–640, 2005
Microporous membrane blood oxygenators
Authors: Wickramasinghe S. R. , Han B. , Garcia J. D. , Specht R. 
Published: January 2005

AbstractExtracorporeal blood oxygenators are used to oxygenate blood during open‐heart surgery. Hydrophobic microporous flat‐sheet or hollow‐fiber membranes are used to separate blood and gas phases. Oxygen diffuses from the gas phase through the gas‐filled membrane pores into the blood. Mass‐transfer and friction‐factor correlations have been developed for flat‐sheet and hollow‐fiber blood oxygenators. Generalized Graetz, Reynolds, and Schmidt numbers are used in these correlations to account for the shear‐thinning behavior of blood. Because oxygen not only dissolves in plasma but also binds to hemoglobin, a mass‐transfer enhancement factor based on film theory has been developed to account for oxygen binding to hemoglobin. Experimental results for oxygen transfer to bovine blood and both non‐Newtonian and Newtonian blood analogue fluids indicate that the correlations developed may be used to predict the performance of a blood oxygenator based on results for an experimentally simple system such as the oxygenation of deionized water. © 2005 American Institute of Chemical Engineers AIChE J, 51: 656–670, 2005
Electrochemical self‐assembly of porous alumina templates
Authors: Sadasivan V. , Richter C. P. , Menon L. , Williams P. F. 
Published: January 2005

AbstractPorous alumina templates are fabricated by anodization of Al in an acid. The characteristics of the template, such as the pore diameter, interpore separation, and the periodicity of the porous structure depend on the conditions of anodization and the acid that is used as electrolyte. The variation of pore diameter and interpore separation as a function of anodization parameters are described. The use of porous alumina templates as masks to assemble nanoarrays is an important application and the deposition of Au nanodots on a surface of silicon is discussed. © 2005 American Institute of Chemical Engineers AIChE J, 51: 649–655, 2005
Interrogation of a precipitation reaction by electrical resistance tomography (ERT)
Authors: Stanley S. J. , Mann R. , Primrose K. 
Published: January 2005

AbstractElectrical resistance tomography (ERT) provides a noninvasive and nonintrusive technique for the full 3‐D interrogation of a typical stirred vessel reactor up to a spatial discrimination of approximately 2,500 derived data points. Some recent ERT results are presented for a newly refurbished 8 ring 16‐sensor 2.3 m3 pilot scale vessel, detecting the conductivity changes throughout the whole volume of the vessel during the semi‐batch precipitation of barium sulfate. Fast timewise acquisition at video frame rates provides an augmented‐reality visualization of the precipitation process. Time evolving images created by solid‐body iso‐surfaces, which use color to denote conductivity, are presented during the proceeding reaction. These images provide a 5‐D representation of the conductivity fields within the stirred vessel reactor. The conductivity (or pixel) distributions during the precipitation process provide a real‐time measurement of the homogeneity within the vessel. The timewise conductivity profiles, over the whole of the vessel during the precipitation, indicate three very distinctive regions reflecting the complex reaction kinetics. The ERT system also highlights the very different conductivity profiles during precipitation when the stirred vessel is operated without agitation. This application is believed to be the first example of ERT applied to a precipitation process. ERT offers new possibilities for control action linked to spatio‐temporal distributions of phases and components for industrial applications. © 2005 American Institute of Chemical Engineers AIChE J, 51: 607–614, 2005
Reaction kinetics of polybutylene terephthalate polycondensation reaction
Authors: Darda P. J. , Hogendoorn J. A. , Versteeg G. F. , Souren F. 
Published: January 2005

AbstractThe kinetics of the forward polycondensation reaction of polybutylene terephthalate (PBT) has been investigated using thermogravimetric analysis (TGA). PBT ‐ prepolymer with an initial degree of polymerization of 5.5 was used as starting material. The PBT prepolymer was prepared from dimethyl terephthalate (DMT), and 1,4 ‐ butanediol with 470 ppm wt (with respect to DMT) of tetrabutoxytitanate as catalyst. The process conditions in the TGA were such that the weight loss curves obtained from the TGA could be correlated uniquely and directly to the forward polycondensation reaction kinetics due to the absence of (1) mass transfer limitations in the removal of 1,4 butanediol from the melt, and (2) degradation reactions. It is shown that in the temperature range of 230–270°C, the forward polycondensation reaction can be expressed using second‐order kinetics in terms of the hydroxyl end group concentration of the PBT polymer. © 2005 American Institute of Chemical Engineers AIChE J, 51: 622–630, 2005
Human brain derived neurotrophic factor (BDNF) genes, splicing patterns, and assessments of associations with substance abuse and Parkinson's Disease
Authors: Liu Qing‐Rong , Walther Donna , Drgon Tomas , Polesskaya Oxana , Lesnick Timothy G. , Strain Kari J. , de Andrade Mariza , Bower James H. , Maraganore Demetrius M. , Uhl George R. 
Published: January 2005

AbstractPotential roles for variants in the human BDNF gene in human brain disorders are supported by findings that include: (a) influences that this trophic factor can exert on important neurons, brain regions, and neurotransmitter systems, (b) changes in BDNF expression that follow altered neuronal activity and drug treatments, and (c) linkages or associations between genetic markers in or near BDNF and human traits and disorders that include depression, schizophrenia, addictions, and Parkinson's disease. We now report assembly of more than 70 kb of BDNF genomic sequence, delineation of 7 noncoding and 1 coding human BDNF exons, elucidation of BDNF transcripts that are initiated at several alternative promoters, identification of BDNF mRNA splicing patterns, elucidation of novel sequences that could contribute to activity‐dependent BDNF mRNA transcription, targeting and/or translation, elucidation of tissue‐specific and brain‐region‐specific use of the alternative human BDNF promoters and splicing patterns, identification of single nucleotide polymorphism (SNP), and simple sequence length polymorphism (SSLP) BDNF genomic variants and identification of patterns of restricted haplotype diversity at the BDNF locus. We also identified type 2 BDNF‐locus transcripts that are coded by a novel gene that is overlapped with type 1 BDNF gene and transcribed in reverse orientation with several alternative splicing isoforms. Association studies of BDNF variants reveal no associations with Parkinson's disease. Comparisons between substance abusers and controls reveal modest associations. These findings increase interest in this diverse human gene. Published 2005 Wiley‐Liss, Inc.
Dithiolproteine als Hüter des intrazellulären Redoxmilieus bei Parasiten: alte und neue Wirkstoff‐Targets bei Trypanosomiasis und Malaria
Authors: Krauth‐Siegel R. Luise , Bauer Holger , Schirmer R. Heiner 
Published: January 2005

AbstractParasitäre Erkrankungen wie Schlafkrankheit, Chagas‐Krankheit oder Malaria gehören zu den Hauptursachen weltweiter Armut. Dringend benötigt werden antiparasitäre Medikamente, die nicht nur wirksam, sondern für die Betroffenen auch erschwinglich und verfügbar sind. Ein Ansatz bei der Suche nach neuen Wirkstoffen (und der Wiederentdeckung alter) basiert auf dem Einsatz von Enzyminhibitoren, die die antioxidativen Systeme in den Pathogenen blockieren. Für Parasiten sind die antioxidativen Netzwerke essentiell, da sie vom menschlichen Wirt durch starke Oxidantien wie Peroxynitrit, Hypochlorit und Wasserstoffperoxid bekämpft werden. Das pathogeneigene Schutzsystem besteht aus etwa zwanzig Thiol‐ und Dithiolproteinen, die das intrazelluläre Redoxmilieu bei einem Potential von etwa −250 mV puffern. Im Zentrum dieses Redoxgefüges steht bei Trypanosomen und Leishmanien das parasitenspezifische Dithiol Trypanothion (N1,N8‐Bis(glutathionyl)spermidin). Malariaparasiten hingegen besitzen ein konservativeres System, das auf Glutathion und Thioredoxin basiert. Inhibitoren von antioxidativen Enzymen wie der Trypanothionreduktase sind per se parasitizid, darüber hinaus können sie aber auch die Entwicklung von Resistenz gegen andere antiparasitäre Wirkstoffe verzögern.
Crystal structure of cyclic (APGVGV)2, an analog of elastin, and a suggested mechanism for elongation/contraction of the molecule
Authors: Karle Isabella L. , Urry Dan W. 
Published: January 2005

AbstractTropoelastin is a complex polymeric protein composed primarily of repeating segments of Val‐Pro‐Gly‐Gly, Val‐Pro‐Gly‐Val‐Gly, and Ala‐Pro‐Gly‐Val‐Gly‐Val that occurs in connective tissue and arteries. It has rubber‐like extensible properties. A synthetic cyclic dodecapeptide, with a double repeat of the hexapeptide sequence, has been shown to undergo a reversible inverse temperature transition; that is, crystals grow at 60°C and dissolve in the mother liquor upon cooling. An x‐ray crystal structure analysis established that the cyclic backbone formed an elongated loop with a Pro‐Gly, type II beta turn at both ends. Six internal cross strand NH···OC hydrogen bonds form between six NH donors and four OC acceptors where two of the carbonyl O atoms are bifurcated acceptors. As a result, the molecule is pulled up into a corrugated profile. The corrugated loops form extended β‐sheets by additional intermolecular hydrogen bonds. An analysis of the dome region in a corrugated sheet suggests a reversible mechanism for extending and contracting the length of the whole molecule, akin to the motion of opening and closing an umbrella, caused by the motion of a water molecule with its associated hydrogen bonds acting as spokes. Crystal parameters: C44H72N12O12˙3H2O, sp. gr. P212121, a = 9.212 Å, b = 19.055 Å, c = 32.247 Å, d = 1.157 g/cm3. © 2005 Wiley Periodicals, Inc. Biopolymers, 2005
Receptor fragment approach to the binding between CCK8 peptide and cholecystokinin receptors: A fluorescence study on type B receptor fragment CCKB‐R (352–379)
Authors: De Luca Stefania , Sanseverino Marina , Zocchi Ivana , Pedone Carlo , Morelli Giancarlo , Ragone Raffaele 
Published: January 2005

AbstractFluorescence titrations in a membrane mimetic solvent system allowed us to estimate that the dissociation constant of the bimolecular complex between CCK8 peptide and cholecystokinin type B receptor fragment CCKB‐R (352–379) is in the micromolar range. When considered in the context of the full receptor/ligand model, these experiments demonstrate that the receptor fragment chosen on the basis of previous structural studies represents a reliable model system to monitor the ability of CCK8 or CCK8 analogs to bind the cholecystokinin receptor. Together with previous studies, this confirms that the receptor fragment approach adopted to define the binding mode of the CCK8 fragment of cholecystokinin with its two receptors, CCKA and CCKB, can be used to characterize the binding from the equilibrium standpoint. In this context, fluorescence spectroscopy proves to be the favored technique to measure dissociation constants in the nanomolar to micromolar range. © 2005 Wiley Periodicals, Inc. Biopolymers, 2005
Helix–helix interconversion rates of short 13C‐labeled helical peptides as measured by dynamic NMR spectroscopy
Authors: Kubasik Matthew , Kotz James , Szabo Christopher , Furlong Theresa , Stace Justin 
Published: January 2005

AbstractThe rates at which a peptide hexamer and a peptide octamer interconvert between left‐ and right‐handed helical forms in CD2Cl2 solution have been characterized by 13C dynamic NMR (DNMR) spectroscopy. The peptide esters studied are Fmoc–(Aib)n–OtBu (n = 6 and 8), where Fmoc is 9‐fluorenylmethyoxycarbonyl and Aib is the strongly helix‐forming residue α‐aminoisobutyric acid. Because the Aib residue is itself achiral, homooligomers of this residue form a 50/50 mixture of enantiomeric 310‐helices in solution. It has been demonstrated (R.‐P. Hummel, C. Toniolo, and G. Jung, Angewandte Chemie International Edition, 1987, Vol. 26, pp. 1150–1152) that oligomers of Aib interconvert on the millisecond timescale. We have performed lineshape analysis of 13C‐NMR spectra collected for our peptides enriched with 13C at a single residue. Rate constants for the octamer range from 6 s−1 at 196 K to about 56,500 s−1 at 320 K. At all temperatures, the hexamer interconverts about three times faster than the octamer. Eyring plots of the data reveal experimentally indistinguishable ΔH‡ values for the hexamer and octamer of 37.8 ± 0.6 and 37.6 ± 0.4 kJ mol−1 respectively. The difference in the rates of interconversion is dictated by entropic factors. The hexamer and octamer exhibit negative ΔS‡ values of −29.0−1 ± 2.5 and −37.3 ± 1.7 J K−1 mol−1, respectively. A mechanism for the helix–helix interconversion is proposed. and calculated ΔG‡ values are compared to the estimate for a decamer undergoing a helix–helix interconversion. © 2005 Wiley Periodicals, Inc. Biopolymers 78: 87–95, 2005
Differential susceptibility of C2C12 myoblasts and myotubes to group II phospholipase A2 myotoxins from crotalid snake venoms
Authors: Angulo Yamileth , Lomonte Bruno 
Published: January 2005

AbstractGroup II phospholipase A2 (PLA2) myotoxins isolated from Viperidae/Crotalidae snake venoms induce a rapid cytolytic effect upon diverse cell types in vitro. Previous studies suggested that this effect could be more pronounced on skeletal muscle myotubes than on other cell types, including undifferentiated myoblasts. This study utilized the murine skeletal muscle C2C12 cell line to investigate whether differentiated myotubes are more susceptible than myoblasts, and if this characteristic is specific for the group II myotoxic PLA2s. The release of lactic dehydrogenase was quantified as a measure of cytolysis, 3 h after cell exposure to different group II PLA2s purified from Bothrops asper, Atropoides nummifer, Cerrophidion godmani, and Bothriechis schlegelii venoms. In addition, susceptibility to lysis induced by synthetic melittin and group III PLA2 from bee (Apis mellifera) venom, as well as by anionic, cationic, and neutral detergents, was comparatively evaluated on the two cultures. Myotubes were significantly more susceptible to group II PLA2 myotoxins, but not to the other agents tested, under the same conditions. Moreover, the increased susceptibility of myotubes over myoblasts was also demonstrated with two cytolytic synthetic peptides, derived from the C‐terminal region of Lys49 PLA2 myotoxins, that reproduce the action of their parent proteins. These results indicate that fusion and differentiation of myoblasts into myotubes induce changes that render these cells more susceptible to the toxic mechanism of group II PLA2 myotoxins, but not to general perturbations of membrane homeostasis. Such changes are likely to involve myotoxin acceptor site(s), which remain(s) to be identified. Copyright © 2005 John Wiley & Sons, Ltd.
Analysis of video images from a gas–liquid transfer experiment: a comparison of PCA and PARAFAC for multivariate image analysis
Authors: Gurden Stephen P. , Lage Euler M. , de Faria Cristiano G. , Joekes Inés , Ferreira Márcia M. C. 
Published: January 2005

AbstractThe use of chemical imaging is a developing area which has potential benefits for chemical systems where spatial distribution is important. Examples include processes in which homogeneity is critical, such as polymerizations, pharmaceutical powder blending and surface catalysis, and dynamic processes such as the study of diffusion rates or the transport of environmental pollutants. Whilst single images can be used to determine chemical distribution patterns at a given point in time, dynamic processes can be studied using a sequence of images measured at regular time intervals, i.e. a movie. Multivariate modeling of image data can help to provide insight into the important chemical factors present. However, many issues of how best to apply these models remain unclear, especially when the data arrays involved have four or five different dimensions (height, width, wavelength, time, experiment number, etc.). In this paper we describe the analysis of video images recorded during an experiment to investigate the uptake of CO2 across a free air–water interface. The use of PCA and PARAFAC for the analysis of both single images and movies is described and some differences and similarities are highlighted. Some other image transformation techniques, such as chemical mapping and histograms, are found to be useful both for pretreatment of the raw data and for dimensionality reduction of the data arrays prior to further modeling. Copyright © 2003 John Wiley & Sons, Ltd.
From Discrete Particles to Spherical Aggregates: A Simple Approach to the Self‐Assembly of Au Colloids
Authors: Zhong Ziyi , Subramanian Alamelu Suriya , Highfield James , Carpenter Keith , Gedanken Aharon 
Published: January 2005

AbstractHere we demonstrate a simple, template‐free approach to the formation of spherical gold aggregates through the reduction of HAuCl4 by NaBH4, in the presence of cysteine (Cys) as a capping agent. The resulting aggregates are quite stable in solution. The pH of the solution and the molar ratio of Au:Cys are two key empirical factors in the formation of such highly ordered aggregates. At slightly alkaline pH (7–10) and with Au:Cys ratios ranging from 1:0.5 to 1:2, spherical Au aggregates of 30–80 nm are formed. At lower Cys ratios (Au:Cys≥1:0.5) very loosely linked aggregates are formed; however, at very high Cys ratios (Au:Cys≤1:3), highly dispersed Au particles of 2–4 nm are obtained, which are virtually indistinguishable from the original colloidal form. Aggregate size is influenced markedly by component concentration; a 3‐fold increase in standard levels resulted in Au spherical aggregates of a larger size, 200–500 nm. In addition, we used a combination of Cys and lysine (Lys) as a capping agent/cross‐linker and found that the morphology of the Au colloid aggregates can be easily manipulated from a linear to a spherical form by adjusting the proportions of Cys and Lys in the capping agent/cross‐linker mixture. The introduction of mercapto (SH)‐containing organic acids reduced the cross‐linking ability of Cys, especially in the case of long‐chain acids. Complete disruption of the spherical aggregates highlights the importance of Cys per se. An explanation of this ordered self‐assembly process is proposed, in the context of the known surface chemistry of Au colloids.
The Rich Stereochemistry of Eight‐Vertex Polyhedra: A Continuous Shape Measures Study
Authors: Casanova David , Llunell Miquel , Alemany Pere , Alvarez Santiago 
Published: January 2005

AbstractA stereochemical study of polyhedral eight‐vertex structures is presented, based on continuous shape measures (CShM). Reference polyhedra, shape maps, and minimal‐distortion interconversion paths are presented for eight‐vertex polyhedral and polygonal structures within the CShM framework. The application of these stereochemical tools is analyzed for several families of experimental structures: 1) coordination polyhedra of molecular transition‐metal coordination compounds, classified by electron configuration and ligands; 2) edge‐bonded polyhedra, including cubane structures, realgar, and metal clusters; 3) octanuclear transition‐metal supramolecular architectures; and 4) coordination polyhedra in extended structures in inorganic solids. Structural classification is shown to be greatly facilitated by these tools, and the detection of less common structures, such as the gyrobifastigium, is straightforward.
7Li, 31P, and 1H Pulsed Gradient Spin‐Echo (PGSE) Diffusion NMR Spectroscopy and Ion Pairing: On the Temperature Dependence of the Ion Pairing in Li(CPh3), Fluorenyllithium, and Li[N(SiMe3)2] amongst Other Salts
Authors: Fernández Ignacio , Martínez‐Viviente Eloísa , Breher Frank , Pregosin Paul S. 
Published: January 2005

Abstract7Li, 31P, and 1H variable‐temperature pulsed gradient spin‐echo (PGSE) diffusion methods have been used to study ion pairing and aggregation states for a range of lithium salts such as lithium halides, lithium carbanions, and a lithium amide in THF solutions. For trityllithium (2) and fluorenyllithium (9), it is shown that ion pairing is favored at 299 K but the ions are well separated at 155 K. For 2‐lithio‐1,3‐dithiane (13) and lithium hexamethyldisilazane (LiHMDS 16), low‐temperature data show that the ions remain together. For the dithio anion 13, a mononuclear species has been established, whereas for the lithium amide 16, the PGSE results allow two different aggregation states to be readily recognized. For the lithium halides LiX (X = Br, Cl, I) in THF, the 7Li PGSE data show that all three salts can be described as well‐separated ions at ambient temperature. The solid state structure of trityllithium (2) is described and reveals a solvent‐separated ion pair formed by a [Li(thf)4]+ ion and a bare triphenylmethide anion.
High‐Pressure Synthesis and Crystal Structure of the Structurally New Orthorhombic Rare‐Earth meta‐Oxoborates γ‐Ln(BO2)3 (Ln: La—Nd).
Authors: Emme Holger , Despotopoulou Christina , Huppertz Hubert 
Published: January 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.
Fluoromanganate(III) Anions with New Tetrameric and Chain Structures in (pipzH2)3 [Mn4F18(H2O)]×(H2O) and (pipzH2)4[Mn2F9]2 [MnF4(H2O)2] [MnF4(HF)2].
Authors: Stief Ronald , Massa Werner 
Published: January 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.
Indolizines, Triazolo[4,3‐a]pyridines, Benzimidazo[1,2‐d]oxadiazoles, and Pyrazolo[1,5‐c]triazoles via Nitrogen and Sulfur Ylides.
Authors: Dawood Kamal M. 
Published: January 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.
2‐Arylhydrazono‐3‐oxopropanals in Heterocyclic Synthesis: Synthesis of Arylazopyrazole, Arylazoisoxazole and Dialkylpyridazine‐5,6‐dicarboxylate Derivatives. New One‐Step Synthesis of Arylazopyrimidines.
Authors: Al‐Shiekh Mariam A. , El‐Din Abdellatif M. Salah , Hafez Ebtisam A. , Elnagdi Mohamed H. 
Published: January 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.
Preparation of New N‐Heterocyclic Carbene Metal—Alkyne Complexes and Application to a Stereocontrolled Pauson—Khand Reaction.
Authors: Poulton Andrew M. , Christie Steven D. R. , Fryatt Ross , Dale Sophie H. , Elsegood Mark R. J. , Andrews David M. 
Published: January 2005

AbstractFor Abstract see ChemInform Abstract in Full Text.