bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusion constant in gel electrophoresis at high fields
Authors: Krawczyk Małgorzata J. , Dulak Józef , Paściak Paweł , Kułakowski Krzysztof
Published: March 2004

We present new measurements of the diffusion constant D in standard (slab‐gel) electrophoresis of DNA at fields up to 10 V/cm. Molecules investigated are bacteriophages: T4 of length 173 kbp and λ of length 48.5 kbp cut by restriction enzyme HindIII. We show, that D increases with the molecule length for electric field E above 5 V/cm. The results are interpreted within the geometration model.
Precision and accuracy in fluorescent short tandem repeat DNA typing: Assessment of benefits imparted by the use of allelic ladders with the AmpFlSTR®Profiler Plus™ kit
Authors: Leclair Benoît , Frégeau Chantal J. , Bowen Kathy L. , Fourney Ron M.
Published: March 2004

Base‐calling precision of short tandem repeat (STR) allelic bands on dynamic slab‐gel electrophoresis systems was evaluated. Data was collected from over 6000 population database allele peaks generated from 468 population database samples amplified with the AmpFlSTR®Profiler Plus™ (PP) kit and electrophoresed on ABD 377 DNA sequencers. Precision was measured by way of standard deviations and was shown to be essentially the same, whether using fixed or floating bin genotyping. However, the allelic ladders have proven more sensitive to electrophoretic variations than database samples, which have caused some floating bins of D18S51 to shift on occasion. This observation prompted the investigation of polyacrylamide gel formulations in order to stabilize allelic ladder migration. The results demonstrate that, although alleles comprised in allelic ladders and questioned samples run on the same gel should migrate in an identical manner, this premise needs to be verified for any given electrophoresis platform and gel formulation. We show that the compilation of base‐calling data is a very informative and useful tool for assessing the performance stability of dynamic gel electrophoresis systems, stability on which depends genotyping result quality.
Monomer surface modifications for rapid peptide analysis by capillary electrophoresis and capillary electrochromatography coupled to electrospray ionization‐mass spectrometry
Authors: Johannesson Nina , Wetterhall Magnus , Markides Karin E. , Bergquist Jonas
Published: March 2004

In this study, positively charged alkylaminosilyl monomers were used to modify the inner surface of fused silica capillaries, which subsequently were employed in capillary electrophoresis (CE) and capillary electrochromatography (CEC). The obtained surfaces yield a reversed electroosmotic flow (EOF) and have varying carbon chain lengths, that interact with the analytes and give chromatographic retention. The coating procedure is very simple and fast. The performance of the modified capillaries was evaluated regarding pH influence on EOF and chromatographic interactions. The experiments were conducted with UV and mass spectrometry (MS) and applied to the separation of various neuropeptides. The derivatized surfaces showed a linear (R2 ∼0.99) pH dependence with isoelectric points (pI) at 8.6–8.8. Rapid separations of peptide standards and a protein digest with efficiencies as high as 5×105 plates/m were performed.
Efficient and reproducible analysis of peptides by capillary electrophoresis using noncovalently bilayer‐coated capillaries
Authors: Catai Jonatan R. , Somsen Govert W. , de Jong Gerhardus J.
Published: March 2004

The usefulness of a noncovalent capillary coating consisting of two layers of oppositely charged polymers for the separation of peptides with capillary electrophoresis (CE) was studied. Capillaries were coated simply by subsequently flushing with solutions of 1% m/v Polybrene and 1% v/v poly(vinylsulfonate) (PVS) forming a bilayer, which showed to produce a strong and highly reproducible electroosmotic flow (EOF) at low pH. Using this coating in combination with a background electrolyte (BGE) containing sodium phosphate (pH 2.5) and 0.01% v/v PVS, initially broadened and overlapping peaks were obtained for some test peptides. By omitting the PVS from the BGE, the peak width and shape of the peptides improved resulting in baseline separation. A systematic study of the influence of the BGE composition showed that considerable further enhancement of the separation efficiency was achieved by increasing the ionic strength of the BGE. Using a BGE of 200 mM tris(hydroxymethyl)aminomethane (Tris)‐phosphate (pH 2.5) plate numbers for the peptides were in the 300 000–600 000 range and the relative standard deviation of the peptide migration times was less then 0.3% (n = 5). The use of Tris‐phosphate instead of sodium phosphate allowed the current to stay within acceptable limits when 30 kV was used as separation voltage. Overall, the bilayer coating showed a remarkable EOF repeatability, as well as long‐term stability. Compared to bare fused‐silica capillaries the intraday and interday repeatability of migration times was very favorable and coated capillaries could be used for over a month performing analyses with low and high ionic strength BGEs without any performance deterioration. The usefulness of the bilayer‐coated capillaries for the analysis of positively charged peptides was demonstrated by the fast and efficient separation of various closely related enkephalins and the baseline separation of an isomeric peptide/peptoid couple exhibiting efficiencies of over 550 000 plates.
Immobilized pH gradients as a first dimension in shotgun proteomics and analysis of the accuracy of pI predictability of peptides
Authors: Cargile Benjamin J. , Talley Dana L. , Stephenson James L.
Published: March 2004

In this work, we demonstrate the potential use of immobilized pH gradient isoelectric focusing as a first dimension in shotgun proteomics. The high resolving power and resulting reduction in matrix ionization effects due to analyzing peptides with almost the exact same physiochemical properties, represents a significant improvement in performance over traditional strong cation‐exchange first‐dimensional analysis associated with the shotgun proteomics approach. For example, using this technology, we were able to identify more than 6000 peptides and > 1200 proteins from the cytosolic fraction of Escherichia coli from approximately 10 μg of material analyzed in the second‐dimensional liquid chromatography‐tandem mass spectrometry experiment. Sample loads on the order of 1 mg can be resolved to 0.25 isoelectric point (pI) units, which make it possible to analyze organisms with significantly larger genomes/proteomes. Accurate pI prediction can then be employed using currently available algorithms to very effectively filter data for peptide/protein identification, and thus lowering the false‐positive rate for cross‐correlation‐based peptide identification algorithms. By simplifying the protein mixture problem to tryptic peptides, the effect of specific amino acids on pI prediction can be evaluated as a function of their position in the peptide chain.
Analysis of proteins stained by Alexa dyes
Authors: Huang Shijun , Wang Houyi , Carroll Christopher A. , Hayes Shirley J. , Weintraub Susan T. , Serwer Philip
Published: March 2004

Alexa dye staining of proteins is used for the fluorescence microscopy of single particles that are sometimes multimolecular protein complexes. To characterize the staining, post‐staining determination must be made of which protein(s) in a complex have been Alexa‐stained. The present communication describes the use of sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) for performing this determination. The Alexa‐stained proteins are observed directly in gels by illumination with an ultraviolet transilluminator. The test multimolecular particle is bacteriophage T7. The protein capsid of T7 is a multimolecular complex that has both external and internal proteins. SDS‐PAGE of Alexa‐stained bacteriophage T7 produces fluorescent capsid proteins each of which usually comigrates with an unstained protein. However, one Alexa‐induced modification of protein migration was observed by SDS‐PAGE. Mass spectrometry shows that the protein with modified migration is the major protein of the outer shell of the T7 capsid. The procedures used are generally applicable. The distribution of Alexa staining among T7 capsid proteins depends on the size of the dye molecule used. The larger the dye molecule is, the greater the preference for external proteins.
Capillary zone electrophoresis investigation of the interaction between heparin and granulocyte‐colony stimulating factor
Authors: Liang Aiye , He Xinya , Du Yuguang , Wang Keyi , Fung Yingsing , Lin Bingcheng
Published: March 2004

The interaction between standard heparin, low‐molecular‐weight heparin (LMWH), and granulocyte‐colony stimulating factor (G‐CSF) was studied by capillary zone electrophoresis. Both qualitative and quantitative characterizations of the heparin‐protein binding were determined. The binding constants of the two different groups of heparins with G‐CSF, calculated from the Scatchard plot by regression, were 4.805×105 M−1 and 4.579×105 M−1, respectively. The two binding constants measured are of the same order of magnitude at 105 M−1, indicating that LMWH contains most of the functional groups bound to G‐CSF by standard heparin.
Renal prothrombin: Quantification of mRNA using reverse transcription‐polymerase chain reaction in a rat model
Authors: Grover Phulwinder K. , Miyazawa Katsuhito , Ryall Rosemary Lyons
Published: March 2004

Attempts to quantify renal prothrombin (PT) have failed due to interference of its hepatic counterpart. In order to gauge PT synthesized by the kidney, the expression of PT mRNA was compared in renal and hepatic tissues of rats. PT mRNAs were quantified, using quantitative competitive reverse transcription‐polymerase chain reaction (RT‐PCR), from RNA extracts of kidneys and livers of ten hooded Wistar rats. To control variations in sample preparation, the amount of PT transcript in each sample was normalized to the amount of its β‐actin transcript. The median ratio of PT to β‐actin transcript of 0.0011 (with a mean ± standard deviation (SD) of 0.0010 ± 0.0002, range 0.0007–0.0014) in the renal tissues was significantly (p ≤ 0.001) lower than its corresponding value of 0.3669 (with a mean ± SD of 0.3729 ± 0.0716, range 0.2718–0.4675) in the hepatic tissues. Thus, expression of PT mRNA in the rat kidney was almost 300‐fold less as compared with its expression in hepatic tissue.
Contactless conductivity detection of selected organic ions in on‐chip electrophoresis
Authors: Tanyanyiwa Jatisai , Abad‐Villar Eva M. , Hauser Peter C.
Published: March 2004

The detection of underivatized anionic sulfonates, carboxylates, amino acids, sugars, and artificial sweeteners, and of cationic dopamine, ephedrine, and metanephrine in microfabricated electrophoresis devices is demonstrated. This was achieved by high‐voltage contactless conductivity measurements with external electrodes. Poly(methyl methacrylate) chips with thin covers to enable sensitive contactless detection were used for most determinations but glass microchips had to be employed for amino acids and sugars. The plastic chips were found not be stable in the alkaline media required to render those two classes of species in the ionic form amenable for separation and detection. The reproducibility of peak area measurements was about 1% or better and the detection limits ranged between 1 and 30 μM for the different compounds examined.
On‐chip potential gradient detection with a portable capillary electrophoresis system
Authors: Feng Hua‐Tao , Wei Hong‐Ping , Y. Li Sam F.
Published: March 2004

A portable chip‐CE system with potential gradient detection (PGD) was developed and applied to the determinations of alkali metals and alkaloids. The separation efficiency appeared to be satisfactory and nonaqueous capillary electrophoresis (NACE) proved to be applicable to PGD or conductivity detection. The power supplies, separation and detection were built on a device of 3 kg in weight. A branch channel near the end of the separation channel was designed to perform PGD and make the application of relatively high field strength possible. The study is the first report on the application of PGD on the microchip platform. The design of the chip‐CE system shows several advantages, such as simplicity, miniaturization and wide applicability.
Determination of oxidized and reduced glutathione, by capillary zone electrophoresis, in Brassica juncea plants treated with copper and cadmium
Authors: Mendoza Jorge , Soto Paula , Ahumada Inés , Garrido Tatiana
Published: March 2004

A rapid method of capillary zone electrophoresis is described to determine the oxidized (GSSG) and reduced (GSH) form of glutathione in plant tissue. In order to separate both analytes in a fused‐silica capillary, the pH and composition of the electrolyte solution were optimized. The electrolyte composition was 100 mmol/L, borate 25 mmol/L Tris, and 0.2% w/v metaphosphoric acid (MPA), pH 8.2. Some instrumental conditions used to run the samples were hydrostatic injection for 30 s, 30 kV applied voltage, and UV detection (185 nm) at 25°C. Linearity and useful range obtained for the calibration curves were optimum, with correlation coefficients about 0.999 in the 0–120 μmol/L range. The migration time was highly reproducible, less than 5 min being afforded to run a sample. Electrolyte buffer and samples required a careful pH control for optimal separation of both analytes. This aspect constitutes a critical analytical step when acids are used in the procedure for sample preparation. Simultaneous analysis of GSH and GSSG may provide a useful tool for comparative studies of plants in order to select those species with a potential capacity for detoxification from toxic elements or those appearing promising from phytoremediation for these elements.
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

Two 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

Three 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

Chronic 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

The 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%.
Book Review: Eectrokinetec Phenomena: Principles and Applications in Analytical Chemistry and Microchip Technology. By A.S. Rathore and A. Guttman (Eds.)
Authors: Foret Frantisek
Published: March 2004

No abstracts.
Contagion in banking due to BCCI's failure: evidence from national equity indices
Authors: Kanas Angelos
Published: March 2004

We 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

Empirical 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

High 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

Powdered 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

The 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

The 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

The 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

Gitterkonstruktionen 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

Großtechnisch 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

Aluminiumdruckgussteile 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

Mineralische 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

Nach 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

An 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

Two 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
Discovery of semaphorin receptors, neuropilin and plexin, and their functions in neural development
Authors: Fujisawa Hajime
Published: March 2004

The semaphorin receptors neuropilin and plexin were initially identified as antigens for monoclonal antibodies MAb‐A5 and MAb‐B2, which bind to specific neuropiles and plexiform layers within the Xenopus tadpole nervous systems, several years before the discovery of the first semaphorin. This article provides an overview of how neuropilin and plexin were discovered. In addition, it describes the functions of neuropilin in the signaling of chemorepulsive activities of class 3 semaphorins and roles of neuropilin‐mediated semaphorin activities in the directional guidance of the peripheral nervous system (PNS) and integration of the peripheral ganglia. © 2004 Wiley Periodicals, Inc. J Neurobiol 59: 24–33, 2004
Insights into activity‐dependent map formation from the retinotectal system: A middle‐of‐the‐brain perspective
Authors: Ruthazer Edward S. , Cline Hollis T.
Published: March 2004

The development of orderly topographic maps in the central nervous system (CNS) results from a collaboration of chemoaffinity cues that establish the coarse organization of the projection and activity‐dependent mechanisms that fine‐tune the map. Using the retinotectal projection as a model system, we describe evidence that biochemical tags and patterned neural activity work in parallel to produce topographically ordered axonal projections. Finally, we review recent experiments in other CNS projections that support the proposition that cooperation between molecular guidance cues and activity‐dependent processes constitutes a general paradigm for CNS map formation. © 2004 Wiley Periodicals, Inc. J Neurobiol 59: 134–146, 2004
Multiple roles of ephrins during the formation of thalamocortical projections: Maps and more
Authors: Bolz Jürgen , Uziel Daniela , Mühlfriedel Sven , Güllmar André , Peuckert Christiane , Zarbalis Konstantionos , Wurst Wolfgang , Torii Masaaki , Levitt Pat
Published: March 2004

The functional architecture of the cerebral cortex is based on intrinsic connections that precisely link neurons from distinct cortical laminae as well as layer‐specific afferent and efferent projections. Experimental strategies using in vitro assays originally developed by Friedrich Bonhoeffer have suggested that positional cues confined to individual layers regulate the assembly of local cortical circuits and the formation of thalamocortical projections. One of these wiring molecules is ephrinA5, a ligand for Eph receptor tyrosine kinases. EphrinA5 and Eph receptors exhibit highly dynamic expression patterns in distinct regions of the cortex and thalamus during early and late stages of thalamocortical and cortical circuit formation. In vitro assays suggest that ephrinA5 is a multifunctional wiring molecule for different populations of cortical and thalamic axons. Additionally, the expression patterns of ephrinA5 during cortical development are consistent with this molecule regulating, in alternative ways, specific components of thalamic and cortical connectivity. To test this directly, the organization of thalamocortical projections was examined in mice lacking ephrinA5 gene expression. The anatomical studies in ephrinA5 knockout animals revealed a miswiring of limbic thalamic projections and changes in neocortical circuits that were predicted from the expression pattern and the in vitro analysis of ephrinA5 function. © 2004 Wiley Periodicals, Inc. J Neurobiol 59: 82–94, 2004
Potential role of Pax‐2 in retinal axon navigation through the chick optic nerve stalk and optic chiasm
Authors: Thanos Solon , Püttmann Sylvia , Naskar Rita , Rose Karin , Langkamp‐Flock Mechthild , Paulus Werner
Published: March 2004

The degree of fiber decussation at the optic chiasm differs between species, ranging from complete crossing in lower vertebrates to highly complex patterns of intermingling of the fibers from the two eyes seen in mammals and birds. Understanding the genetic control of fiber guidance through the chiasm is therefore important to unravel the developmental mechanisms within the visual system. Here we first report on early stages of chiasm formation, with pioneering axons from the left eye consistently arriving earlier than their counterparts from the right eye. This initial left–right asymmetry is transient and no functional significance is assigned to it yet. Secondly, we examined formation of the chiasm in relation with the expression of the transcription factor Pax‐2 along the ventral eye cup and optic nerve stalk. Finally, in order to examine causal involvement of Pax‐2 in chiasm formation, the gene was overexpressed along the neuraxis and in the eye cup at embryonic stages preceding the exit of axons from the eye, and hence arrival of axons at the chiasm. When studied with neuroanatomical tracing, Pax‐2 overexpression resulted in visibly anomalous decussation of axons at the chiasm. A likely consequence of this perturbation was erroneous arrival of axons at the tectum, as observed by anterograde staining from the retina. These data suggest that balanced expression of Pax‐2 results in the correct formation of the chick chiasm at early stages by imposing accurate pathfinding within the optic stalk and the midline. © 2004 Wiley Periodicals, Inc. J Neurobiol 59: 8–23, 2004
Numerical approximation of a thermoviscoelastic problem to the contact of two rods by a penalty method
Authors: Copetti M. I. M.
Published: March 2004

In this article we analyze a numerical approximation by the finite element method of a system modeling the thermoviscoelastic contact of two rods. The numerical scheme is based on an auxiliary penalized problem. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2004
Posttraumatic stress symptoms in adult survivors of childhood cancer
Authors: Langeveld N.E. , Grootenhuis M.A. , Voûte P.A. , de Haan R.J.
Published: March 2004

Background

Previous research suggests that posttraumatic stress disorder (PTSD) is present in survivors of childhood cancer. The aim of the current study was to explore posttraumatic stress symptoms in a sample of young adult survivors of childhood cancer. In addition, the impact of demographic, medical and treatment factors on survivors' posttraumatic stress symptoms was studied.

Procedure

Participants were 500 long‐term survivors of childhood cancer. The median age at follow‐up was 24 years (age range, 16– 49 years, 47% female). To assess symptoms of posttraumatic stress, all participants completed the Impact of Event Scale (IES), a self‐report instrument consisting of two subscales, intrusion and avoidance.

Results

Twelve percent of this sample of adult survivors of childhood cancer had scores in the severe range, indicating they are unable to cope with the impact of their disease and need professional help. Twenty percent of the female survivors had scores in the severe range as compared with 6% of the male survivors. Linear regression models revealed that being female, unemployed, a lower educational level, type of diagnosis and severe late effects/health problems were associated with posttraumatic stress symptoms.

Conclusions

The results indicate that, although the proportion of survivors reporting symptoms is well within the proportions found in the general population, a substantial subset of survivors report symptoms of posttraumatic stress. This finding supports the outcomes reported previously that diagnosis and treatment for childhood cancer may have significant long‐term effects, which are manifested in symptoms of posttraumatic stress. The investigated factors could explain posttraumatic stress symptoms only to a limited extent. Further research exploring symptoms of posttraumatic stress in childhood cancer survivors in more detail is clearly warranted. From a clinical perspective, health care providers must pay attention to these symptoms during evaluations in the follow‐up clinic. Early identification and treatment of PTSD symptoms can enhance the quality of life for survivors of childhood cancer. © 2004 Wiley‐Liss, Inc.
Intensive cisplatin and cyclophosphamide‐based chemotherapy without radiotherapy for intracranial germinomas: Failure of a primary chemotherapy approach
Authors: Kellie Stewart J. , Boyce Hayden , Dunkel Ira J. , Diez Blanca , Rosenblum Marc , Brualdi Lynette , Finlay Jonathan L.
Published: March 2004

Purpose

High rates of overall and event‐free survival have been reported in patients with intracranial germinomas treated with craniospinal radiotherapy. More recently, similar results have been reported with chemotherapy combined with radiotherapy to more localized treatment volumes. Our interest in exploring chemotherapy without radiotherapy in patients with CNS germinomas was based on concerns about the late sequelae of radiotherapy to the brain or neuraxis and also the well documented success of chemotherapy alone in patients with disseminated extracranial germinomas. The primary objective of this study was to determine whether intensive cisplatin and cyclophosphamide‐based combination chemotherapy, without radiotherapy, was effective in patients with CNS germinomas.

Patients and Methods

Nineteen patients were enrolled, ranging in age from 1 to 24 years (median, 14 years). Thirteen were male. Nine had diabetes insipidus. Therapy comprised two courses of Regimen ‘A’ (cisplatin, etoposide, cyclophosphamide, and bleomycin) followed by MRI evaluation. Patients achieving a complete remission (CR) completed all planned therapy with two courses of regimen ‘B’ (carboplatin, etoposide, and bleomycin). Patients achieving less than a CR received two courses of Regimen ‘B’ followed by another evaluation. Those in CR after four courses of treatment received one additional course of Regimen ‘A’ and Regimen ‘B’, while those not in CR after four treatment courses underwent second look surgery and/or radiation therapy.

Results

Eleven of 11 patients with residual postoperative disease assessable for response achieved a CR. With a median follow‐up of 6.5 years, eight out of 19 (0.42) patients remain in CR 1 without radiotherapy and another three patients are in stable second or subsequent remissions. Three patients died from treatment‐related toxicity and another died in CR 1 from an uncharacterized leukoencephalopathy. The 5‐year event‐free survival (EFS) was 0.47 ± 0.23 and 5‐year overall survival (OS) was 0.68 ± 0.22.

Conclusions

Intensive cisplatin and cyclophosphamide‐based chemotherapy was effective in achieving remissions, however, the long‐term outcome using this treatment program was unsatisfactory and associated with unacceptable morbidity and mortality, particularly in patients with diabetes insipidus. © 2004 Wiley‐Liss, Inc.