bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enzymes, Directed Evolution
Authors: Reetz Manfred T. 
Published: October 2009

AbstractDirected evolution has emerged as a powerful method for engineering the catalytic profile of enzymes. It is based on repetitive cycles of random gene mutagenesis and expression coupled with efficient high‐throughput screening or selection for a given catalytic property such as thermostability, substrate acceptance, and/or enantioselectivity. In the 1990s, directed evolution was established on a broad front by applying standard mutagenesis methods such aserror‐prone polymerase chain reaction(epPCR), saturation mutagenesis, and DNA shuffling. The current challenge is to devise optimal strategies for probing protein sequence space, thereby allowing for fast directed evolution. This article covers the progress of the last few years.
Neurite Outgrowth on Nanocomposite Scaffolds Synthesized from PLGA and Carboxylated Carbon Nanotubes
Authors: Lee Hyun Jung , Yoon Ok Ja , Kim Do Hee , Jang Yeong Mi , Kim Hyun Woo , Lee Won Bok , Lee Nae‐Eung , Kim Sung Su 
Published: October 2009

AbstractCarbon nanotubes (CNTs) have been suggested as suitable materials for biomedical applications, especially in the neural area. It is essential not only to investigate the biocompatibility of CNTs with the neural system but also to determine proper methods for applying CNTs to neuronal growth. This work represents the first application of CNTs by electrospun poly(D,L‐lactic‐co‐glycolic acid) (PLGA) scaffolds for a neural system. We synthesized electrospun nanocomposites of PLGA and single‐walled carbon nanotubes functionalized by carboxylic acid groups (c‐SWNTs), and investigated neurite outgrowth from SH‐SY5Y cells on these nanocomposites as compared to that on fibrous PLGA alone. Cells on our PLGA/c‐SWNT nanocomposite showed significantly enhanced mitochondrial function and neurite outgrowth compared to cells on PLGA alone. We concluded that c‐SWNTs incorporated into fibrous PLGA scaffolds exerted a positive role on the health of neural cells.
Swelling of superabsorbents polymers in an aqueous medium
Authors: Bahaj H. , Benaddi R. , Bakass M. , Bayane C. 
Published: October 2009

AbstractThe polymers studied are superabsorbents materials. They were synthesized by inverse suspension polymerisation of acrylic acid. The polymers studied, X10 and X5, are different in their degree of ionisation. In fact, our objective was to increase the amount of water that may be stored by the polymer. In this article, we investigated not only the effect of temperature and pH on the satured water absorbency of polymers X10 and X5, but also various swelling behaviours of polymer X10 in different saline solutions. The results show that for temperature ranging from 10 to 90°C, the effect of temperature on the satured water absorbency is rather limited when the superabsorbent is swelled by distilled water. Further, water absorbency of X10 and X5 is strongly affected by the pH value. The results also indicate that saline solutions can weaken the swelling abilities of the polymer X10. Water absorbency of polymer X10 in aqueous chloride salt solutions has the following order: Na+ = K+= NH > Ca2+ = Mg2+ all through the range of investigated concentration. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Post sulfonation of bisphenol A poly(arylene ethers)
Authors: Guhathakurta Soma , Min Kyonsuku 
Published: October 2009

AbstractIn this study, bisphenol A polyetherimide (PEI) was sulfonated by a novel postsulfonation route using trimethylsilylchlorosulfonate. Different degrees of sulfonation were achieved by varying the mole ratio of the sulfonating agent to the PEI repeat unit and the reaction time. Comparison was made with respect to bisphenol A polysulfone (PSU) to study the influence of electron withdrawing group in the sulfonated poly(arylene ethers) (SPAE) backbone on sulfonation. Structural characterization of SPAE was conducted by 1H‐NMR and FTIR spectroscopy. The enhanced reaction rate with PSU compared to PEI was attributed to the deactivation of bisphenol A unit due to the stronger electron withdrawing effect of imide group. The sulfonation of PEI was also carried out with chlorosulfonic acid for comparative study. The effects of degree of sulfonation on thermal and mechanical properties of SPAE‐s were studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and a tensile testing machine. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Needle and needleless electrospinning for nanofibers
Authors: Zhou Feng‐Lei , Gong Rong‐Hua , Porat Isaac 
Published: October 2009

AbstractA metallic needle is most often used in conventional electrospinning, where a point‐plate electric field with nonuniform distribution is formed in single‐needle electrospinning (SNE). Low flow rate in SNE has restricted the application of electrospinning on an industrial scale. Multiple needles have been introduced to enhance the flow rate. However, multiple needles make the electric field distribution much more complex. To resolve this problem, alternative electrospinning setups with more uniform electric field have to be developed. Flat spinnerets have been demonstrated to replace the needle in SNE setups. The operating diagrams for flat spinneret electrospinning (FSE) were determined and differed significantly from those for SNE. Nanofibers produced by FSE were more uniform than those from SNE. These differences were explained by the differences in electric fields simulated using finite element analysis (FEA). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Analysis of ordered categorical data to develop control charts for monitoring customer loyalty
Authors: Samimi Y. , Aghaie A. , Tarokh M. J. 
Published: October 2009

AbstractIn the highly competitive business environment of today, the cost to attract new customers is much higher than the cost required to maintain the existing ones. To keep the balance between the acquisition rate and defection rate through executing offensive and defensive marketing policies, it is required to have real time information using an efficient method to monitor customer loyalty. The relationship between customer loyalty and customer satisfaction should be kept in mind when one develops a method for loyalty monitoring. This paper presents several control charts classified in two groups based on the scale used to assess customer loyalty. In the first group of control charts, customer loyalty is considered as a binary random variable modeled by Bernoulli distribution whilst in the second group, an ordinal scale is considered to report loyalty level. Performance comparison of the proposed techniques using ARL criterion indicates that chi‐square and likelihood‐ratio control charts developed based on Pearson chi‐square statistic and ordinal logistic regression model respectively are able to rapidly detect the significant changes in loyalty behavior. To show how to apply the procedures and how to interpret their results, two illustrative synthetic cases are also explained. Copyright © 2009 John Wiley & Sons, Ltd.
System availability in a shock model under preventive repair and phase‐type distributions
Authors: Montoro‐Cazorla Delia , Pérez‐Ocón Rafael 
Published: October 2009

AbstractA device that can fail by shocks or ageing under policy N of maintenance is presented. The interarrival times between shocks follow phase‐type distributions depending on the number of cumulated shocks. The successive shocks deteriorate the system, and some of them can be fatal. After a prefixed number k of nonfatal shocks, the device is preventively repaired. After a fatal shock the device is correctively repaired. Repairs are as good as new, and follow phase‐type distributions. The system is governed by a Markov process whose infinitesimal generator, stationary probability vector, and availability are calculated, obtaining well‐structured expressions due to the use of phase‐type distributions. The availability is optimized in terms of the number k of preventive repairs. Copyright © 2009 John Wiley & Sons, Ltd.
Erfahrungen bei der Anwendung der neuen DIN 1052 mit Vergleichen zur Vorgängernorm
Authors: Kneidl Rupert , Seiler Christian 
Published: October 2009

AbstractMit Einführung der neuen DIN 1052 kommen nun auch im Holzbau das semiprobabilistische Sicherheitskonzept sowie neue Bemessungsregeln und zum Teil erheblich abgeminderte Festigkeitswerte im Vergleich zur alten Norm zur Anwendung. Um die Auswirkungen der niedrigeren Querdruckfestigkeiten aufzuzeigen, werden Vergleichsrechnungen am Beispiel einer eingespannten Stütze und eines Einfeldträgers durchgeführt und einige kritische Anmerkungen zu den in vielen Fällen erforderlichen Verstärkungsmaßnahmen gemacht. Bei Holzbalkendecken wird dargestellt, dass die neu aufgenommenen Empfehlungen zum Schwingungsnachweis die erforderliche Konstruktionshöhe bestimmen und damit Holzbalkendecken für größere Spannweiten unwirtschaftlich werden. Insgesamt zeigt sich bei Anwendung der neuen DIN 1052, dass der Planungsaufwand gegenüber der alten Norm erheblich anwächst.Experience in application of the new German code DIN 1052 in comparison with the previous standard.With the new German code DIN 1052 the semi‐probabilistic safety concept has been introduced for timber constructions as well as new design procedures and to some extent considerably reduced strength properties in comparison to the previous standard. For illustration of the impact of the low lateral pressure strength comparative calculations are performed using a clamped column and a simply supported beam and some critical comments are given for strengthening measurements required in many cases. For timber beam ceilings it is shown that the new recommendations for vibration control govern the required construction height und make such constructions inefficient for longer span lengths. In general, the complexity applying the new DIN 1052 is considerably higher than designing on the basis of the previous standard.
Die neue Schneelastnorm DIN 1055‐5, kritisch hinterfragt
Authors: Schwind Wolfgang 
Published: October 2009

AbstractDie neue Schneelastnorm DIN 1055‐5:7/2005 brachte vor allem in den höhergelegenen Orten der Zone 3 erhebliche Erhöhungen der Schneelast, die bis zum Zweifachen der bisher anzusetzenden Belastung reicht. Auch die neuen Formeln für die Belastung von aneinandergereihten Dächern, von Shed‐ und Tonnendächern sowie die Behandlung von Höhensprüngen und Trauflasten erscheint problematisch. In diesem Beitrag wird versucht, Unstimmigkeiten der Norm aufzuzeigen.The current snow load standard DIN 1055‐5 – a critical review.The current snow load standard DIN 1055‐5:7/2005 caused a considerable increase of snow load, particularly in more elevated areas located in zone 3. It doubles the amount of snow load capacity – compared to the old standard. The new equations for calculating snow loads for adjacent roofs, shed roofs and arched roofs as well as the handling differences in altitude and gutter load seems problematic. This paper tries to show the inconsistencies of current standard.
Betongelenke aus selbstverdichtendem und hochfestem Beton bei der neuen Elbebrücke Mühlberg
Authors: Tue Nguyen Viet , Jankowiak Holger 
Published: October 2009

AbstractNeben der architektonisch ansprechenden Form weist die neue Elbebrücke Mühlberg mit Betongelenken aus selbstverdichtendem und hochfestem Beton technische Neuheiten auf. Für die Bemessung der Betongelenke sind Ergänzungen und Modifikationen der vorhandenen Bemessungsregeln gemäß [1] erforderlich. Weiterhin ist die umfängliche Erstanwendung von selbstverdichtendem und hochfestem Beton im Brückenbau eine weitere Herausforderung für die Beteiligten. In diesem Beitrag werden die neu aufgestellten Bemessungsregeln für die Betongelenke zusammenfassend erläutert und über die Erfahrungen im Zusammenhang mit der Anwendung von selbstverdichtendem und hochfestem Beton im Brückenbau berichtet.Concrete Hinge made of self compacting and high strength concrete for the new Elbe‐Bridge Mühlberg.Additional to a sophisticated architectural design the new Elbe‐Bridge Mühlberg shows technical novelty with concrete hinges made of self compacting and high strength concrete. For the design of concrete hinge in this construction few modifications and additions to the available design rules according to [1] are necessary. Furthermore the use of self compacting and high strength concrete in great volume is a challenge. In this paper the new design rules for concrete hinge are explained and the know how regarding on the use of self compacting and high strength in bridge construction are reported.
Einheit von Wissenschaft und Kunst im Brückenbau: Hellmut Homberg (1909–1990) – Leben und Wirken (Teil I)
Authors: Kurrer Karl‐Eugen , Pelke Eberhard , Stiglat Klaus 
Published: October 2009

AbstractAm 5. September 2009 wäre Hellmut Homberg einhundert Jahre alt geworden. Dies ist Anlass, an sein vor allem den Brückenbau bereicherndes Wirken zu erinnern und ein, wenn auch nicht vollständiges, Werkverzeichnis zu erstellen. Das gilt sowohl für die unter seiner maßgebenden Mitwirkung entworfenen Brücken als auch für seine völlig neuartigen, die statischen Berechnungen in der Praxis erleichternden, streng theoretisch hergeleiteten und eine zutreffende Bemessung der Kreuzwerke und orthotropen Fahrbahnplatten ermöglichenden Tafel‐ und Tabellenwerke.Teil I schildert Homberg s beruflichen Weg und versucht, ein Porträt zu zeichnen; Teil II ist seinen theoretischen Untersuchungen gewidmet, und Teil III geht auf besondere Brücken ein, und.Harmony between science and art in bridge‐building: Hellmut Homberg (1909–90) – life and work (part I).Hellmut Homberg would have been 100 years old on 5 September 2009. This is an opportunity to look back on his work which so enriched the world of bridge‐building in particular, and also a chance to compile a catalogue of his work, albeit incomplete.This applies to the bridges in which he played an influential role in their design and also to his books of mathematical and design tables that enabled the accurate design of beam grids and orthotropic bridge decks. The tables with their rigorous theoretical background were at the time quite new and eased structural calculations in everyday practice.Part I describes Homberg's professional career and attempts to draw a portrait of the man; part II is devoted to his theoretical studies, and part III deals with particular bridges.
The genetic background of thecurly tailstrain confers susceptibility to folate‐deficiency‐induced exencephaly
Authors: Burren Katie A. , Scott John M. , Copp Andrew J. , Greene Nicholas D. E. 
Published: October 2009

AbstractBACKGROUND: Suboptimal maternal folate status is considered a risk factor for neural tube defects (NTDs). However, the relationship between dietary folate status and risk of NTDs appears complex, as experimentally induced folate deficiency is insufficient to cause NTDs in nonmutant mice. In contrast, folate deficiency can exacerbate the effect of an NTD‐causing mutation, as insplotchmice. The purpose of the present study was to determine whether folate deficiency can induce NTDs in mice with a permissive genetic background which do not normally exhibit defects.METHODS: Folate deficiency was induced incurly tailand genetically matched wild‐type mice, and we analyzed the effect on maternal folate status, embryonic growth and development, and frequency of NTDs.RESULTS: Folate‐deficient diets resulted in reduced maternal blood folate, elevated homocysteine, and a diminished embryonic folate content. Folate deficiency had a deleterious effect on reproductive success, resulting in smaller litter sizes and an increased rate of resorption. Notably, folate deficiency caused a similar‐sized, statistically significant increase in the frequency of cranial NTDs among bothcurly tail(Grhl3mutant) embryos and background‐matched embryos that are wild type forGrhl3. The latter do not exhibit NTDs under normal dietary conditions. Maternal supplementation withmyo‐inositol reduced the incidence of NTDs in the folate‐deficient wild‐type strain.CONCLUSIONS: Dietary folate deficiency can induce cranial NTDs in nonmutant mice with a permissive genetic background, a situation that likely parallels gene‐nutrient interactions in human NTDs. Our findings suggest that inositol supplementation may ameliorate NTDs resulting from insufficient dietary folate. Birth Defects Research (Part A), 2010. © 2009 Wiley‐Liss, Inc.
Designed RNAs with Two Peptide‐Binding Units as Artificial Templates for Native Chemical Ligation of RNA‐Binding Peptides
Authors: Kashiwagi Norimasa , Yamashita Kohei , Furuta Hiroyuki , Ikawa Yoshiya 
Published: October 2009

AbstractThe template effect plays important roles not only in modern synthetic and enzymatic catalysis but also in the ancient “RNA‐polypeptide (RNP) world,” which has been postulated to be a crucial stage in the origin of life. To mimic primitive template catalysis of peptide ligations by RNAs, we previously reported the design and synthesis of a ternary RNP complex in which the ligation of two peptides was significantly facilitated by a template RNA with two peptide‐binding units. However, RNA molecules also promoted the ligation reaction in a nonspecific manner through electrostatic interactions between RNA and basic peptides. In this study, we suppressed this effect by reducing the length of the original template derived from the Tetrahymena intron RNA. This modification, however, decreased the template ability for the specific reaction. As an alternative RNA that was as effective as the original template, we found that a self‐dimerizing RNA was a promising template for peptide ligation without a nonspecific effect.
An Investigation into the Transient Behavior of a Microreactor System for Reforming of Diesel Fuel in the kW Range
Authors: O'Connell M. , Kolb G. , Schelhaas K.‐P. , Schürer J. , Tiemann D. , Ziogas A. , Hessel V. 
Published: October 2009

AbstractA diesel reformer based on microreaction technology was developed for application in an auxiliary power unit (APU) system. The transient characteristics of this reactor for reforming of diesel fuel are reported. Diesel steam reforming was performed at various S/C ratios with load changes ranging from 30 % LL to 80 % LL, i.e., a 1.5 kW to a 4 kW electrical equivalent. The reactor itself was based on an integrated reformer/burner heat exchange reactor concept. The reforming was performed at temperatures above 750 °C and at various S/C ratios, down to a minimum of 3.17. Variation of experimental parameters, such as O/C and S/C ratios, are critical for optimum and efficient operation of the reformer.
Development of a Micro‐Structured Methanol Fuel Processor Coupled to a High‐Temperature Proton Exchange Membrane Fuel Cell
Authors: Kolb G. , Schelhaas K.‐P. , Wichert M. , Burfeind J. , Heßke C. , Bandlamudi G. 
Published: October 2009

AbstractThe aim of the work presented in the current paper was the development of a portable power generation device applying methanol as fuel and fuel cell technology with an electrical net power output of 100 W. At the Institut für Mikrotechnik Mainz (IMM), Germany, an integrated micro‐structured methanol fuel processor based on oxidative steam reforming was developed. The fuel processor was tested separately and then coupled to a high‐temperature fuel cell that had been developed in parallel by the Zentrum für Brennstoffzellentechnik GmbH (ZBT).
Charge‐Transfer Mechanism in Pt/KTa(Zr)O3 Photocatalysts Modified with Porphyrinoids for Water Splitting
Authors: Hagiwara Hidehisa , Inoue Takanori , Kaneko Kenji , Ishihara Tatsumi 
Published: October 2009

AbstractThe mechanism of photocatalytic splitting of H2O into H2 and O2 on Pt/KTa(Zr)O3 modified with various porphyrinoids was investigated. The photocatalytic activity of KTaO3 catalysts is improved by dye modification. Cyanocobalamin (vitamin B12) is the most effective for improving water‐splitting activity, and the formation rates of H2 and O2 achieved values of 575 and 280 μmol gcat.−1 h−1, respectively. X‐ray photoelectron spectroscopy spectra of KTa(Zr)O3 photocatalysts showed that Pt loaded onto dye‐modified KTaO3 was slightly oxidized and had low catalytic activity for the H2 oxidation reaction. Photoluminescence (PL) spectra of KTaO3 catalysts suggested that excitation energy was transferred between KTaO3, tetraphenylporphyrinatochromium(III) (Cr–TPP), and the Pt cocatalyst. The wavelength dependence of the activity of dye‐modified KTa(Zr)O3 photocatalysts indicated that excitation of both KTa(Zr)O3 and the dye was essential for achieving increased photocatalytic activity. This result suggests that two‐step excitation occurred in the dye‐modified KTa(Zr)O3 photocatalysts. Because the lifetime of the charge‐separated state increased, this study reveals that modification with porphyrinoids is effective for increasing water‐splitting activity.
Chiral 2‐endo‐Substituted 9‐Oxabispidines: Novel Ligands for Enantioselective Copper(II)‐Catalyzed Henry Reactions
Authors: Breuning Matthias , Hein David , Steiner Melanie , Gessner Viktoria H. , Strohmann Carsten 
Published: October 2009

AbstractA flexible approach, applicable on a gram scale, to chiral 2‐endo‐substituted 9‐oxabispidines was developed. The key intermediate, a cis‐configured 6‐aminomethylmorpholine‐2‐carbonitrile, was prepared from (R)‐3‐aminopropane‐1,2‐diol and 2‐chloroacrylonitrile. The 2‐endo substituent was introduced by Grignard addition, cyclization, and exo‐selective reduction, thus furnishing the enantiomerically pure bi‐ and tricyclic 9‐oxabispidines in 19–59 % yield. The CuCl2 complex of the tricyclic 9‐oxabispidine, which carries an 2‐endo,N‐anellated piperidine ring, is an excellent catalyst for enantioselective Henry reactions giving the S‐configured β‐nitro alcohols in 91–98 % ee (13 examples). Surprisingly, the analogous copper complexes of the bicyclic 9‐oxabispidines delivered the enantiocomplementary R‐configured products in 33–57 % ee. The respective transition states were discussed.
Layer‐by‐Layer Assembly of Polyelectrolyte and Nanoparticles, Monitored by Capillary Electrophoresis
Authors: Liu Qian , Yao Lihua , Shen Qinpeng , Nie Zhou , Guo Manli , Yao Shouzhuo 
Published: October 2009

AbstractLayer‐by‐layer (LBL) assembly is a versatile nanofabrication technique, and investigation of its kinetics is essential for understanding the assembly mechanism and optimizing the assembly procedure. In this work, the LBL assembly of polyelectrolyte and nanoparticles were monitored in situ by capillary electrophoresis (CE) for the first time. The assembly of poly(diallyldimethylammonium chloride) (PDDA), and gold nanoparticles (AuNPs) on capillary walls causes surface‐charge neutralization and resaturation, and thus yields synchronous changes in the electroosmotic flow (EOF). The EOF data show that formation of multilayers follows first‐order adsorption kinetics. On the basis of the fit results, influencing factors, including number of layers, concentration of materials, flow rate, and size of AuNPs, were investigated. The stability and robustness of the assembled coatings were also characterized by CE. It was found that degradation of PDDA layers follows first‐order chemical kinetics, while desorption of AuNPs takes place in a disorderly manner. The substrate strongly affects assembly of the underlying layer, while this effect is rapidly screened with increasing number of layers. Furthermore, we demonstrate that the EOF measuring step does not disturb LBL assembly, and the proposed method is reliable and rugged. This work not only studies in detail the LBL adsorption/desorption process of polyelectrolyte and nanoparticles, but also offers an alternative tool for monitoring multilayer buildup. It may also reveal the potential of CE in fields other than analytical separation.