bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polymeric alkenoxy amino acid surfactants: II. Chiral separations of β‐blockers with multiple stereogenic centers
Authors: Rizvi Syed A. A. , Akbay Cevdet , Shamsi Shahab A. 
Published: March 2004

AbstractTwo amino acid‐based (leucine and isoleucine) alkenoxy micelle polymers were employed in this study for the separation of multichiral center‐bearing β‐blockers, nadolol and labetalol. These polymers include polysodium N‐undecenoxy carbonyl‐L‐leucinate (poly‐L‐SUCL) and polysodium N‐undecenoxy carbonyl‐L‐isoleucinate (poly‐L‐SUCIL). Detailed synthesis and characterization were reported in our previous paper [26]. It was found that poly‐L‐SUCIL gives better chiral separation than poly‐L‐SUCL for both nadolol and labetalol isomers. The use of 50–100 mM poly‐L‐SUCIL as a single chiral selector provided separation of four and three isomers of labetalol and nadolol, respectively. Further optimization in separation of both enantiomeric pairs of nadolol and labetalol was achieved by evaluation of type and concentration of organic solvents, capillary temperature as well type and concentration of cyclodextrins. A synergistic approach, using a combination of poly‐L‐SUCIL and sulfated β‐CD (S‐β‐CD) was evaluated and it showed dramatic separation for enantiomeric pairs of nadolol. On the other hand for labetalol enantiomers, separation was slightly decreased or remain unaffected using the dual chiral selector system. Finally, simultaneous separation of both nadolol and labetalol enantiomers was achieved in a single run using 25 mM poly‐L‐SUCIL and 5% w/v of S‐β‐CD in less then 35 min highlighting the importance of high‐throughput chiral analysis.
Polyelectrolyte‐modified short microchannel for cation separation
Authors: Bai Xiaoxia , Roussel Christophe , Jensen Henrik , Girault Hubert H. 
Published: March 2004

AbstractThree alkali cations, potassium, sodium, and lithium, have been separated within 15 s in a 1 cm long polymer microchip. The separation microchannel is modified by a polycation, poly(allylammonium chloride), which makes the channel surfaces positively charged leading to a reversed electroosmotic flow (EOF) when compared to bare channels. Due to the decreased apparent mobility of the cations, the separation resolution is improved allowing the use of shorter channels.
A promotor polymorphism in the Interleukin 11 gene is associated with chronic obstructive pulmonary disease
Authors: Klein Wolfram , Rohde Gernot , Arinir Umut , Hagedorn Michaela , Dürig Natascha , Schultze‐Werninghaus Gerhard , Epplen Jörg T. 
Published: March 2004

AbstractChronic obstructive pulmonary disease (COPD) is a multifactorial disorder characterized by irreversible airflow obstruction due to chronic inflammation. Hence, the gene encoding the anti‐inflammatory cytokine IL 11 is a good candidate for being involved in the genetic predisposition to COPD. In order to evaluate the role of the Interleukin 11 (IL 11) gene in the genetic predisposition for COPD, a dinucleotide microsatellite polymorphism in the promoter region has been genotyped in 153 patients with COPD (including 25 non‐smokers) and 463 healthy controls. Frequencies of the IL 11.A2 microsatellite allele and of IL 11.A2 homozygous individuals were significantly decreased among the patients with COPD (p < 0.012 and p < 0.022, respectively) as compared to controls. Both frequencies were even more drastically reduced among the nonsmoking patients. Tight linkage of this microsatellite allele with another polymorphism in the promotor region was established. Altered expression of IL 11 may be involved in the genetic predisposition to COPD.
Separation of thiol and cyanide hydrolysis products of chemical warfare agents by capillary electrophoresis
Authors: Copper Christine L. , Collins Greg E. 
Published: March 2004

AbstractThe fluorescence derivatizing agent, o‐phthalaldehyde (OPA), has been applied to the separation and detection of cyanide and several structurally similar thiols by capillary electrophoresis (CE)‐laser induced fluorescence (LIF). Of particular interest to this investigation was the separation of 2‐dimethylaminoethanethiol, 2‐diethylaminoethanethiol, and cyanide, each of which are hydrolysis products or hydrolysis product simulants of the chemical warfare (CW) agents O‐ethyl S‐2‐diisopropylaminoethyl methylphosphonothiolate (VX), O‐isobutyl S‐2‐diethylaminoethyl methylphosphonothiolate (R‐VX), and tabun (GA). Other structurally similar thiols simultaneously resolved by this method include 1‐pentanethiol and 2‐mercaptoethanol. Instrumental parameters were probed and optimum values for capillary length (50 cm) and inner diameter (75 μm), injection time (30 s) and field strength (15 kV) were determined. Sample stacking methods enabled detection limits of 9.3 μg/L for cyanide, 1.8 μg/L for 2‐diethylaminoethanethiol, 35 μg/L for 2‐dimethylaminoethanethiol, 15 μg/L for 2‐mercaptoethanol, and 89 μg/L for 1‐pentanethiol. The linearity of the method was verified over an order of magnitude and the reproducibility was found to be 3.0%.
Contagion in banking due to BCCI's failure: evidence from national equity indices
Authors: Kanas Angelos 
Published: March 2004

AbstractWe examine whether the failure of the multinational banking group BCCI caused contagion effects in the banking sectors of four countries where BCCI had established operations, namely the UK, the US, Spain and Switzerland. We find evidence of contagion effects in the UK and Spain which appear to have registered several months before the eventual closure announcement. There is no evidence of contagion effects in the US and Switzerland. Our results have implications for the stability of the European banking sector, as banks licensed anywhere in the EU will be able to set up branches in other EU countries without needing to obtain further authorization. Copyright © 2004 John Wiley & Sons, Ltd.
A new interpretation of the exchange rate–yield differential nexus
Authors: Coakley Jerry , Fuertes Ana‐Maria , Wood Andrew 
Published: March 2004

AbstractEmpirical studies have had difficulty in establishing the long‐run relationship between real exchange rates and real yield differentials predicted by sticky price exchange rate models. We revisit this issue in a nonstationary panel regression framework. This facilitates estimation of a long‐run parameter even when the underlying relation‐ship is subject to permanent shocks or the variables do not cointegrate. The slope coefficient estimate from a sample of 23 industrialized countries 1973M1–1998M12 has the correct sign and is statistically significant for both short and long‐term yields. These results support fundamentals‐based models of exchange rate behaviour while permitting real factors to play a role. Moreover, they indicate that capital markets integration is more advanced than hitherto believed. Copyright © 2004 John Wiley & Sons, Ltd.
Inducible superoxide dismutase 1 aggregation in transgenic amyotrophic lateral sclerosis mouse fibroblasts
Authors: Turner Bradley J. , Lopes Elizabeth C. , Cheema Surindar S. 
Published: March 2004

AbstractHigh molecular weight detergent‐insoluble complexes of superoxide dismutase 1 (SOD1) enzyme are a biochemical abnormality associated with mutant SOD1‐linked familial amyotrophic lateral sclerosis (FALS). In the present study, SOD1 protein from spinal cords of transgenic FALS mice was fractionated according to solubility in saline, zwitterionic, non‐ionic or anionic detergents. Both endogenous mouse SOD1 and mutant human SOD1 were least soluble in SDS, followed by NP‐40 and CHAPS, with an eight‐fold greater detergent resistance of mutant protein overall. Importantly, high molecular weight mutant SOD1 complexes were isolated with SDS‐extraction only. To reproduce SOD1 aggregate pathology in vitro, primary fibroblasts were isolated and cultured from neonatal transgenic FALS mice. Fibroblasts expressed abundant mutant SOD1 without spontaneous aggregation over time with passage. Proteasomal inhibition of cultures using lactacystin induced dose‐dependent aggregation and increased the SDS‐insoluble fraction of mutant SOD1, but not endogenous SOD1. In contrast, paraquat‐mediated superoxide stress in fibroblasts promoted aggregation of endogenous SOD1, but not mutant SOD1. Treatment of cultures with peroxynitrite or the copper chelator diethyldithiocarbamate (DDC) alone did not modulate aggregation. However, DDC inhibited lactacystin‐induced mutant SOD1 aggregation in transgenic fibroblasts, while exogenous copper slightly augmented aggregation. These data suggest that SOD1 aggregates may derive from proteasomal or oxidation‐mediated oligomerisation pathways from mutant and endogenous subunits respectively. Furthermore, these pathways may be affected by copper availability. We propose that non‐neural cultures such as these transgenic fibroblasts with inducible SOD1 aggregation may be useful for rapid screening of compounds with anti‐aggregation potential in FALS. © 2004 Wiley‐Liss, Inc.
Reduction kinetics of ceria surface by hydrogen
Authors: Al‐Madfa H. A. , Khader M. M. , Morris M. A. 
Published: March 2004

AbstractPowdered cerium dioxide (ceria, CeO2) as compressed, sintered pellets, of porosity 16.4% and density 5.99 g cm−3, were treated in hydrogen flow at 1 atm and various temperatures to effect reduction. The electrical conductivity was measured in situ during the reduction process. The conductivity increased continuously during the hydrogen treatment because of the creation of anion vacancies and accompanying small polaron electrons. The conductivity–time relationship exhibits three distinct regions indicated as I, II, and III. For each of steps I and II, the conductivity increases exponentially with the reduction. It is suggested from the kinetic analysis of the data that region I is due to desorption of adsorbed oxygen states. Region II appears to be the reduction of surface lattice oxygen. The kinetics of the reactions in both regions I and II obey first‐order rate laws with similar activation energies of 86 and 115 kJ mol−1, respectively. Thermogravimetric experiments were used to determine the time needed to remove one monolayer of adsorbed oxygen from the surface. This could be used to estimate the activation energy of the desorption process at 95 kJ mol−1—close to the value measured by conductivity measurements. After completing the surface reduction the electrical conductivity subsequently increased slowly during region III. This step is assigned to a diffusion‐controlled process during which the bulk of the pellets are reduced. 1H MASNMR and in situ PXRD experiments confirmed the chemical nature of each of the three steps. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 293–301, 2004
Kinetics and mechanism of the thermal decomposition reaction of acetone cyclic diperoxide in methyl tert‐butyl ether solution
Authors: Leiva Laura C. , Jorge Nelly L. , Romero Jorge M. , Cafferata Lázaro F. R. , Vara Manuel E. Gómez 
Published: March 2004

AbstractThe thermal decomposition reaction of acetone cyclic diperoxide (3,3,6,6‐tetramethyl‐1,2,4,5‐tetroxane, ACDP), in the temperature range of 130.0–166.0°C and initial concentrations range of 0.4–3.1 × 10−2 mol kg−1 has been studied in methyl t‐butyl ether solution. The thermolysis follows first‐order kinetic laws up to at least ca 60% ACDP conversion. Under the experimental conditions, the activation parameters of the initial step of the reaction (ΔH# = 33.6 ± 1.1 kcal mol−1; ΔS# = −4.1 ± 0.7 cal mol−1 K−1; ΔG# = 35.0 ± 1.1 kcal mol−1) and acetone, as the only organic product, support a stepwise reaction mechanism with the homolytic rupture of one of its peroxidic bond. Also, participation of solvent molecules in the reaction is postulated given an intermediate diradical, which further decomposes by CO bond ruptures, yielding a stoichiometric amount of acetone (2 mol per mole of ACDP decomposed). The results are compared with those obtained for the above diperoxide thermolysis in other solvents. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 302–307, 2004
Kinetic study of the nitrosation of 1,3‐dialkylureas in aqueous‐perchloric acid medium
Authors: González‐Alatorre Guillermo , Guzmán‐Maldonado Salvador H. , Escamilla‐Silva Eleazar M. , Loarca‐Piña Guadalupe , Benítez Carlos Hernández 
Published: March 2004

AbstractThe kinetics of the nitrosation of 1,3‐dimethyl (DMU), 1,3‐diethyl (DEU), 1,3‐dipropylurea (DPU), 1,3‐dibuthyl (DBU), and 1,3‐diallylurea (DAU) were studied in a conventional UV/vis spectrophotometer in aqueous‐perchloric acid media. The kinetic study was carried out using the initial rate method. The reaction rate observed was

equation image

where Ka is the acidity constant of nitrous acid. The diureas exhibited the reactivity order DMU ≫ DEU > DPU > DAU, which can be interpreted as a function of the steric impediment generated by the R alkyl group in the rate controlling step. A probable relationship between both the chemical reactivity and structure of the nitrosable substrate with the biological activity of the N‐nitroso compounds generated is proposed. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 273–279, 2004
Long term corrosion behaviour of copper in soil: A study of archaeological analogues
Authors: Balasubramaniam R. , Laha T. , Srivastava A. 
Published: March 2004

AbstractThe long term corrosion behaviour of copper in soil environment has been addressed by studying two archaeological copper samples. The microstructures of the material of construction of a Chalcolithic (2350BC‐1800BC) copper chisel from Balathal and an OCP period (2650BC‐800BC) Cu anthropomorphic object have been first characterized by microscopy and the features understood by stereological methods. The equiaxed grain size, coring effects in the grains and the relatively soft matrix of the OCP copper object indicated that it was manufactured by casting. The deformed grains near the surfaces and variation in the microhardness of the sample at different points suggests that the Chalcolithic copper chisel was processed by cold deformation after casting of the square cross section chisel. The surface patina on the two archaelogical copper objects has been characterized by X‐ray diffraction. In the case of OCP copper, the green surface patina was analyzed as a mixture composed mainly of cuprite, and minor amounts of malachite and brochantite. In the case of Chalcolithic copper, the patina was composed of sulfates and oxysulfates in the outer layers while the inner layers were rich in copper oxides. The electrochemical behaviour of both the archaeololgical coppers has been characterized and compared with that of a modern Cu sample by potentiodynamic polarization studies. The corrosion rate, determined by Tafel extrapolation technique in 3.5% NaCl solution, of Chalcolithic Cu was only marginally higher than that of modern and OCP Cu. The higher rates of corrosion in case of archaeological coppers have been attributed to the presence of second phase sulfide inclusions.
Korrosionsverhalten wetterfester Baustähle unter Berücksichtigung konstruktionsbedingter Spalte
Authors: Friedrich S. 
Published: March 2004

AbstractGitterkonstruktionen aus den Stählen WT St 37‐2, COR‐TEN A, KT 62/St 37‐2 und WT Neu unterlagen einer 8‐jährigen Freibewitterung in Zinnwald/Erzgebirge. Während sich auf den freien Oberflächen stationäre korrosionshemmende Deckschichten ausgebildet haben, die aus einer inneren, amorphen Sperrschicht und einer teilweise kristallinen äußeren Schicht bestehen, ist dieser Schichtaufbau in Spalten unterschiedlicher Geometrie nicht oder nur teilweise zu finden.In der vorliegenden Arbeit wird der Wanddickenverlust in Abhängigkeit von der konstruktiven Gestaltung des Spaltes bewertet sowie der morphologische und chemische Aufbau der Rostschichten beschrieben und hinsichtlich einer für das Abrostungsverhalten günstigen oder ungünstigen Spaltkonstruktion bewertet.Aus den Untersuchungsergebnissen werden Hinweise für die konstruktive Gestaltung spaltbildender Verbindungen abgeleitet.
Einfluss höchster Reinheitsgrade auf die Lochkorrosionseigenschaften austenitischer Stähle
Authors: Hochörtler G. , Kriszt K. , Huber R. 
Published: March 2004

AbstractGroßtechnisch hergestellte Stähle der Werkstoff Nr. 1.4401, welche zur Erreichung besonderer Reinheitskriterien bis zu drei Mal im Vakuum umgeschmolzen wurden, wurden auf das Korrosionsverhalten mit elektrochemischen Prüfungen untersucht. Dazu wurden potentiodynamische Stromdichte‐Potentialkurven auf Basis ASTM G 61‐86 aufgenommen.Es wird gezeigt, dass der Reinheitsgrad einen klaren, günstigen Einfluss auf das Lochkorrosionsverhalten ausübt. Das Umschmelzen mit selbstverzehrender Elektrode unter Vakuum bewirkt eine Erhöhung des Reinheitsgrades, indem die nichtmetallischen Einschlüsse in die Blockoberflächenzonen verdrängt werden – es kommt zu geringsten Gasgehalten und positiver Beeinflussung von Seigerungen im Block.
Einfluss der Porosität auf die Schwingfestigkeit von Proben und Bauteilen aus Aluminiumdruckguss
Authors: Zhang G. , Sonsino C. M. 
Published: March 2004

AbstractAluminiumdruckgussteile werden im Fahrzeugbau zur Erzielung eines Leichtbaus in großem Umfang eingesetzt. Als typische Beispiele sind unterschiedliche Halter, Motorblöcke, Räder und Lenker zu nennen.Durch die in der Gussschmelze enthaltenen Gase entstehen nach dem Erstarren überwiegend kugelförmigen Poren, die je nach Bauteilform und Abkühlbedingung statistisch verteilt sind. Im Bauteilinneren ist die Porenkonzentration in der Regel höher als am Bauteilrand.Für die rechnerische Schwingfestigkeitsuntersuchung von Druckgussteilen wird häufig der einfache Weg beschritten, indem die Schwingfestigkeitskennwerte an glatten Proben in Zug‐ und Druckversuchen ermittelt werden. Die Verwendung der auf diese Weise ermittelten Kennwerte auf Bauteile führt jedoch häufig zu Lebensdauerabschätzungen, die bei weitem zu konservativ sind [4,8].In der vorliegenden Arbeit wird versucht, die Kerbwirkung an den Poren anhand von einfachen Modellen abzuschätzen. Es wird dann gezeigt, wie diese Überlegung auf Bauteile übertragen werden kann, wobei den Tatsachen, dass die Spannungsverteilung in einem realen Bauteil in der Regel inhomogen ist und dass die Randschicht porenarm ist, eine zentrale Bedeutung zukommt. Damit lassen sich die Kerbunempfindlichkeit eines Aluminiumdruckgusses und die dadurch bedingten konservativen Lebensdauerabschätzungen in vielen Fällen erklären.
Eine Übergangsbedingung beim Strahlverschleiß von Gesteinen und Betonen
Authors: Momber A. W. 
Published: March 2004

AbstractMineralische Werkstoffe verhalten sich beim Verschleiß durch feste Strahlmittel je nach Beanspruchungsregime und Werkstofftyp elastisch oder elastisch‐plastisch. Eine einfache Verhältniskennzahl X, die Bruchzähigkeit und Druckfestigkeit kombiniert, gestattet jedoch bei vorgegebenem Beanspruchungsregime eine vorläufige Einordnung der Materialien. In herkömmlichem Sinne „harte”︁ Werkstoffe, wie Granit und Feldspate, weisen niedrige X‐Werte auf und verhalten sich elastisch, während in herkömmlichem Sinne „weiche”︁ Werkstoffe, wie Kalkstein, Mörtel und Schiefer, die elastisch‐plastisch reagieren, durch hohe X‐Werte charakterisiert werden können.
Vergleichende Untersuchungen zur Anrisslebensdauervorhersage gekerbter Proben mit dem Örtlichen Konzept und dem Nennspannungskonzept am Beispiel des Stahls Cm15
Authors: Laue S. , Bomas H. , Mayr P. 
Published: March 2004

AbstractNach wie vor konnte nicht eindeutig geklärt werden, ob das Örtliche Konzept oder das Nennspannungskonzept für die Lebensdauervorhersage gekerbter Proben bzw. Bauteile zu bevorzugen ist. In diesem Beitrag wird anhand kraftkontrollierter und dehnungskontrollierter einstufiger Ermüdungsversuche an gekerbten Flachproben zunächst gezeigt, dass beide Versuchführungen identische Anrissschwingspielzahlen liefern, wenn die Beanspruchung durch die zyklisch stabile örtliche Kerbgrunddehnungsamplitude beschrieben wird. Auf der Basis einer Analyse des elastisch‐plastischen Kerbgrundverhaltens wird aufgezeigt, wie die Dehnungswöhlerlinie in eine klassische Wöhlerlinie umgerechnet werden kann. Auf dieser Erkenntnis aufbauend, werden vergleichend für beide Konzepte Berechnungen der Lebensdauer von gekerbten Proben unter Random‐Belastungen durchgeführt, die nahezu zum gleichen Ergebnis führen, die experimentell bestimmte Lebensdauer jedoch deutlich überschätzen. Weiterhin wird aufgezeigt, dass die im Einstufenversuch ermittelte Ausgangswöhlerlinie nicht die geeignete Grundlage für eine Lebensdauerberechnung sein kann, da sie immer die Summe aus Rissinitiierungs‐ und Rissausbreitungsphase angibt. Bei Betriebsbelastung können hohe Belastungen aber frühzeitig zur Anrissbildung führen, was in der Folge dazu führt, dass die Schädigung von Schwingspielen im Übergangsgebiet zur Dauerfestigkeit bei Verwendung der Miner‐Regel unterschätzt wird.
Lesion therapy for Parkinson's disease and other movement disorders: Update and controversies
Authors: Okun Michael S. , Vitek Jerrold L. 
Published: March 2004

AbstractAn analysis of the international literature on lesioning for movement disorders was undertaken to review lesion therapy for Parkinson's disease (PD) and other movement disorders and to highlight important controversies surrounding this surgical technique. Lesions have been placed throughout the neuraxis with varying approaches and success. Our understanding of the pathophysiological basis underlying the development of PD and other movement disorders has led to a better understanding of why lesioning certain portions of the nervous system should improve motor function. Advances in imaging technology and electrophysiological techniques used for localization of brain structures, such as microelectrode mapping, have improved the ability to accurately identify and lesion target structures deep in the brain. This improvement has led to an increase in the degree and consistency of clinical benefit. The major controversies in lesion therapy include: (1) which target for which disorder; (2) determination of the optimal lesion site and whether the external globus pallidus (GPe) should be included in the pallidotomy lesion for PD; (3) determination of the size of the lesion; (4) whether bilateral lesions can be placed without the high incidence of side effects reported by some investigators; (5) whether microelectrodes aid in the ability to improve clinical outcomes or increase the risk of side effects by making multiple microelectrode penetrations; (6) whether the subthalamic nucleus (STN) should be explored further as a lesioning target; and (7) whether lesioning should be abandoned entirely in favor of deep brain stimulation (DBS). Many important questions and controversies regarding lesion therapy remain unanswered. It is unlikely given the pro‐DBS environment that these questions will be answered in the near future. We should, however, be careful not to abandon an effective therapy before fully exploring through randomized trials the relative effect of different surgical approaches for the treatment of patients with movement disorders. © 2004 Movement Disorder Society
Late‐onset presentation of pyruvate dehydrogenase deficiency
Authors: Mellick George , Price Lee , Boyle Richard 
Published: March 2004

AbstractTwo brothers presented in their mid‐forties with movement disorders including atypical parkinsonism, choreiform movements, stereotypies, ataxia and dysarthria. Both brothers showed putaminal lucencies on imaging and, in the proband, a deficiency of the pyruvate dehydrogenase complex (PDHC) was found on skin fibroblast assay. © 2004 Movement Disorder Society