bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparative study on effect of aromatic polyimide chain conformation on reinforcement of carbon nanotube/polyimide nanocomposites
Authors: Zhang Baode , Chakoli Ali Nabipour , Zang Wanchen , Tian Yanqing , Zhang Ke , Chen Chunhai , Li Yao 
Published: February 2014

ABSTRACTTwo kinds of polyimides (PIs) were selected as matrices for multiwalled carbon nanotubes (CNTs)‐based nanocomposites. The two PIs were initially synthesized through reactions of a same benzoxazole‐containing diamine with two different dianhydrids. A linear PI was formed from the ether bond‐containing dianhydride, while a nonlinear PI was formed from the C(CF3)2− groups containing dianhydride. Optimized dispersion of nanotubes in both kinds of PIs was found to be at a concentration with 0.5 wt % COOH‐CNT, where great enhancement was achieved for both PIs. It was also found that introducing nanotubes into PI matrices aroused more significant increase of Young's modulus and break stress in linear PI than that in nonlinear PI. To determine the key parameters involved in design of PIs for maximum reinforcement efficiency using CNT as the nanofiller, the nanoscopic dispersion state of the nanotubes in diamine solution and their reaction were investigated via morphological and spectroscopic studies. The interfacial interactions between nanotubes and two PI chains were characterized by FT‐IR and Raman spectroscopy. The fracture surface characteristics of two series of CNT/PI nanocomposites were further investigated using SEM. Our findings show that the diamine plays a double role for the in‐situ polymerization, a dispersant to disentangle the CNT agglomerates and a monomer for PI synthesis with dianhydrides. It was also found that geometry and flexibility of PI chains are crucial to determine the interfacial interactions between nanotubes and PI chains. For elucidating the different interfacial characteristics of the two PIs on the surface of CNT, we proposed a model for preferred conformation adopted by a single PI chain on a single CNT. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40479.
Critical Evaluation of Adsorption–Desorption Hysteresis of Heavy Metal Ions from Carbon Nanotubes: Influence of Wall Number and Surface Functionalization
Authors: Li Jie , Chen Changlun , Zhang Shouwei , Ren Xuemei , Tan Xiaoli , Wang Xiangke 
Published: February 2014

AbstractSingle‐, double‐, and multi‐walled carbon nanotubes (SWCNTs, DWCNTs, and MWCNTs), and two oxidized MWCNTs with different oxygen contents (2.51 wt % and 3.5 wt %) were used to study the effect of the wall number and surface functionalization of CNTs on their adsorption capacity and adsorption–desorption hysteresis for heavy metal ions (NiII, CdII, and PbII). Metal ions adsorbed on CNTs could be desorbed by lowering the solution pH. Adsoprtion of heavy metal ions was not completely reversible when the supernatant was replaced with metal ion‐free electrolyte solution. With increasing wall number and amount of surface functional groups, CNTs had more surface defects and exhibited higher adsorption capacity and higher adsorption–desorption hysteresis index (HI) values. The coverage of heavy metal ions on the surface of CNTs, solution pH, and temperature affect the metal ion adsorption–desorption hysteresis. A possible shift in the adsorption mechanism from mainly irreversible to largely reversible processes may take place, as the amount of metal ions adsorbed on CNTs increases. Heavy metal ions may be irreversibly adsorbed on defect sites.
Enhancement of Host–Guest Interactions Using Rationally Designed Macrocyclic Boronic Esters with a Naphthalene Core
Authors: Kikuchi Yuji , Takahagi Hiroki , Ono Kosuke , Iwasawa Nobuharu 
Published: February 2014

AbstractEfficient inclusion of electron‐deficient aromatic guest molecules in an organic solvent utilizing π‐stacking interactions was achieved by using two kinds of macrocyclic boronic esters, 1,4‐naph‐[2+2] and 1,5‐naph‐[2+2], which were easily prepared by self‐assembly of 1,4‐naphthalenediboronic acid (3) or 1,5‐naphthalenediboronic acid (4) and racemic tetrol 1 with an indacene framework in a protic solvent. The X‐ray crystallographic analyses revealed that the tilt angles of the two naphthalene rings are different: that of 1,4‐naph‐[2+2] is about 15° and that of 1,5‐naph‐[2+2] is about 0°. Owing to the parallel alignment of two aromatic rings, 1,5‐naph‐[2+2] has a much higher binding ability than 1,4‐naph‐[2+2]. This knowledge could be useful for the design of the new host molecules in organic solvents.
Switchable Dielectric Phase Transition Induced by a Twisting Transformation in Diglycine Methanesulfonate
Authors: Zhou Pan , Sun Zhihua , Zhang Shuquan , Chen Tianliang , Ji Chengmin , Zhao Sangen , Luo Junhua 
Published: February 2014

AbstractA new glycine‐based reversible phase transition compound diglycine methanesulfonate (1) has been successfully synthesized. Differential scanning calorimetry (DSC) measurements of 1 showed a pair of broad peaks around 134 K (Tc=phase transition temperature) with a slight thermal hysteresis during the heating/cooling cycle, thereby indicating that this compound undergoes a reversible second‐order phase transition. Dielectric measurements further confirmed the phase transition and revealed a switchable response to the ambient temperature change for the dielectric constants of 1, namely, the dielectric constants have a distinctive step‐like anomaly switching between a high dielectric state in the room temperature phase (RTP) and a low state in the low temperature phase (LTP). Variable‐temperature single‐crystal X‐ray diffraction analyses show that 1 undergoes an atypical transition from the space group P21/m in the RTP to P21/c in the LTP. The origin of the switchable dielectric phase transition is ascribed to the movement of the moieties in 1 from the equilibrium position, and this stems from the twisting of the molecules in the compound. We believe that these findings will be useful in exploring switchable dielectric phase transition materials.
Vehicle trajectory reconstruction using automatic vehicle identification and traffic count data
Authors: Feng Yu , Sun Jian , Chen Peng 
Published: February 2014

SummaryThe origin–destination (OD) matrix and the vehicle trajectory data are critical to transportation planning, design, and operation management. On the basis of the deployment of automatic vehicle identification (AVI) technology in urban traffic networks in China, this study proposed a vehicle trajectory reconstruction method for a large‐scale network by using AVI and traditional detector data. Particle filter theory was employed as the framework for this method that combines five spatial‐temporal trajectory correction factors (i.e., the path consistency, the AVI measurability criterion, the travel time consistency, the gravity flow model, and the path‐link flow matching model) to estimate the trajectory of a vehicle. The probabilities of the most likely trajectories are updated by the Bayesian method to approximate the ‘true’ trajectory. The traffic network in the Beijing Olympic Park was selected as the test bed and was simulated by using VISSIM to create a complete set of vehicle trajectories. The accuracy of the resulting trajectory reconstruction exceeds 90% when the AVI coverage is only 50%, assuming an AVI detection error of 5% for a closed network and an open network. The average relative error of a static OD matrix is 11.05%. Although the accuracy of reconstruction exceeds 80% when the AVI coverage is between 50% and 40%, the accuracy of a defective product‐OD matrix decreases rapidly. The proposed method yields high estimation accuracy for the full trajectories of individual vehicles and the OD matrix, which demonstrates significant potential for traffic‐related applications. Copyright © 2014 John Wiley & Sons, Ltd.
Entwicklung verschleißarmer Fahrbahnübergangskonstruktionen
Authors: Zimmermann Thomas , Friedrich Henriette Pauline , Strauss Alfred , Lachinger Stefan , Binder Fritz , Gabl Thomas , Zlatarits Jakob , Schön Andreas , Hoffmann Simon 
Published: February 2014

AbstractFahrbahnübergangskonstruktionen an Brücken sind aufgrund ihrer Position hochdynamisch belastete Strukturelemente. Fahrbahnübergänge zählen nach Eurocode 0 zu den erneuerbaren strukturellen Komponenten und sollten somit für eine Lebensdauer von zehn bis 25 Jahren und mehr ausgelegt werden. Unabhängig von der Entwurfslebensdauer besteht ein Bedarf, den Erhaltungsaufwand von Fahrbahnübergängen zu minimieren. Das Forschungsprojekt “Entwicklung verschleißarmer Fahrbahnübergangskonstruktionen” (EVAF) hat daher die Zielsetzung, auf Basis umfangreicher Schadenserhebungen, Literaturstudien und numerischer Beanspruchungsanalysen die Ursachen für frühzeitige Schäden zu ermitteln und in Folge für einzelne Typen von Fahrbahnübergangskonstruktionen innovative Lösungen zur Verringerung des Erhaltungsaufwandes und zur Schadensvermeidung zu entwickeln. Es sollen robuste, wartungsarme und mit geringem Aufwand instand zu setzende Fahrbahnübergangskonstruktionen (FÜK) entwickelt werden. Dieser Beitrag zeigt die Erkenntnisse, welche in den beiden ersten Arbeitspaketen (AP1 und AP2) aus den Erhebungen und numerischen Analysen, welche durch das intensive Zusammenwirken der Auftraggeber BMViT, ASFINAG, ÖBB, dem industriellen Partner Mageba und den Forschungspartnern AIT (Austrian Institute of Technology) und der Universität für Bodenkultur im Zuge der Forschungsinitiative vif2012 gewonnen werden konnten.Development of low‐wear road expansion joints – Research project EVAFRoadway expansion joints for bridges are highly dynamically loaded structural elements due to their position. Expansion joints are renewable structural components according to Eurocode 0 and should therefore be designed for a service life of ten to 25 and more years. Regardless of the design life there is a need to minimize effort of conservation of such expansion joints. The research project “Development of wear‐resistant expansion joints for bridges” (EVAF) therefore has the objective on the basis of a comprehensive damage surveys, literature studies and numerical stress analysis to determine the causes of early damage patterns and to develop innovative solutions to reduce the maintenance effort and further to avoid the damage with respect to the individual types of expansion joints for bridges. Thereby robust, low‐maintenance, with low cost serviced expansion joints for bridges should be developed. This paper shows the outcomes of the first two work packages from the surveys and numerical analyzes which have been carried out due to the intense interaction between the customer bmvit, ASFINAG and ÖBB as well as the industrial partner Mageba and the research partners AIT (Austrian Institute of Technology) and University of Natural Resources and Life Sciences Vienna within the research initiative vif2012.
Der König ist tot. Lang lebe der König.
Authors: Bluhm Ján 
Published: February 2014

AbstractIm Zuge des Ersatzneubaus der Sinntalbrücke auf der Bundesautobahn A7 bei Bad Brückenau wurde am 22. Juni 2013 die alte Sinntalbrücke mit einer Länge von 770 m durch Sprengen abgerissen. Aufgrund der fehlenden Erfahrungen in Deutschland mit dem Sprengabbruch von Brückenbauwerken dieser Größenordnung wurde dem Auftraggeber ein entsprechendes Abbruchkonzept inklusive statischer Berechnungen vorgelegt, welches auch die Wirkung von Erschütterungen auf benachbarte bauliche Anlagen beurteilte. Da beide Brückenbauwerke nur wenige Meter voneinander entfernt standen, waren eine fachliche Überprüfung dieser Planungsunterlagen, eine umfassende Beweissicherung ausgewählter baulicher und technischer Anlagen sowie vergleichende Erschütterungsprognosen und ‐messungen nach DIN 4150 notwendig. Diese Aufgabe übernahm die Bluhm Partner AG im März 2013. Der vorliegende Beitrag gibt einen Überblick zum Abbruchkonzept, zur Beweissicherung sowie zu den Erschütterungsprognosen und ‐messungen.The king is dead. Long live the king. The demolition of the old Sinntal Bridge near Bad Brückenau (Germany)As part of the new construction replacement of the Sinntal bridge on the A7 motorway at Bad Brückenau on 22 June 2013 the old Sinntal bridge with a length of 770 m was demolished by blasting. Due to the lack of experience in Germany with the blasting demolition of bridges of this size an appropriate demolition concept including static calculations was presented to the client, which also evaluated the effect of vibrations on adjacent buildings and structures. Since both bridges were only a few meters apart, a technical review of the planning documents, a comprehensive preservation of evidence of selected structural and technical facilities as well as comparative vibration predictions and measurements according to DIN 4150 were necessary. This task was given to the Bluhm Partner AG in March 2013. This article gives an overview of the demolition concept, the preservation of evidence and the vibration predictions and measurements.
Zuverlässigkeitsanalyse von Massivbrücken für außergewöhnliche Bedrohungsszenarien
Authors: Boros Vazul , Novák Balthasar 
Published: February 2014

AbstractBrücken spielen eine zentrale Rolle im Straßenverkehrsnetz, sind jedoch zugleich zahlreichen Gefahren ausgesetzt. Um den erforderlich Schutz für diese wichtigen Infrastrukturbauwerke gewährleisten zu können, müssen potenzielle Bedrohungen identifiziert, die Kritikalität von Brücken beurteilt und die Wirksamkeit von Schutzmaßnahmen bewertet werden. Es wird eine Methodik aufgezeigt, mit der eine quantitative Beurteilung der Tragwerkszuverlässigkeit für verschiedene Bauwerke und Szenarien erfolgen kann, damit solche Analysen vorgenommen werden können. An Beispielszenarien werden zudem die Ergebnisse einer Risikoanalyse vorgestellt und bewertet. Schließlich wird ein neuer Indikator für die Zuverlässigkeit von Massivbrücken eingeführt, der eine vereinfachte Abschätzung der Tragwerkssicherheit ermöglicht.Reliability analysis of concrete bridges for hazard scenariosBridges play a vital role in the highway network, yet are also subject to numerous hazards. In order to protect these important elements of the infrastructure, potential hazards have to be identified, the criticality of bridges needs to be assessed and the efficiency of protection measures has to be evaluated. To achieve this, a methodology is shown, how for different structures and scenarios the reliability can be quantified. Furthermore on sample scenarios the results of a risk analysis are displayed and evaluated. Finally a new indicator of reliability for reinforced concrete bridges is introduced, enabling a simplified estimation of structural safety.
Planung und Bau einer semiintegralen Eisenbahnüberführung in Walzträger‐in‐Beton (WiB)‐Bauweise
Authors: Brunner Andreas , Frühauf Wolfgang , Kotz Peter , Schantz Torsten , Windisch Daniel 
Published: February 2014

AbstractDie aus dem Jahr 1898/99 stammende Eisenbahnüberführung Großenhainer Straße in Dresden entspricht nicht mehr den gestellten Anforderungen. Sie wird als moderne semiintegrale Dreifeldbrücke in Walzträger‐in‐Beton (WiB)‐Bauweise mit zwei zweigleisigen Überbauten unter laufendem Eisenbahnverkehr und unter innerstädtischem Fahrzeug‐ und Straßenbahnverkehr erneuert. Unter den vorgegebenen schwierigen Randbedingungen stellt sie eine innovative und äußerst anspruchsvolle Ingenieuraufgabe dar. Dem sensiblen innerstädtischen Raum geschuldet waren besondere gestalterische Vorgaben zu erfüllen. Mit der neuen Eisenbahnüberführung Großenhainer Straße wird ein gestalterisch, konstruktiv und funktional hervorragendes Bauwerk geschaffen.Design and construction of a semi‐integral railway overpass using the “rolled steel girders in concrete” (WiB) construction methodThe existing railway overpass “Großenhainer Straße” in Dresden, built in 1898/99, does not comply to the latest requirements. The structure will be replaced by a modern three‐span‐bridge in “rolled steel girders in concrete” (WiB) construction method with two superstructures with double track lines. During construction the rail traffic, motor vehicles and tramway will be continuously in service. With respect to the present boundary conditions, the structure represents an innovative and extremely ambitious engineering task. Due to the sensitive urban environment, ambitious visual design requirements have to be fulfilled. The new railway bridge “Großenhainer Straße” is an outstanding structure in respect of architectural and technical design as well as functionality.
In vitro response to functionalized self‐assembled peptide scaffolds for three‐dimensional cell culture
Authors: Modepalli Vengama N. , Rodriguez Alexandra L. , Li Rui , Pavuluri Sivapriya , Nicholas Kevin R. , Barrow Colin J. , Nisbet David R. , Williams Richard J. 
Published: February 2014

ABSTRACTNanomaterials are rich in potential, particularly for the formation of scaffolds that mimic the landscape of the host environment of the cell. This niche arises from the spatial organization of a series of biochemical and biomechanical signals. Self‐assembling peptides have emerged as an important tool in the development of functional (bio‐)nanomaterials; these simple, easily synthesized subunits form structures which present the properties of these larger, more complex systems. Scaffolds based upon these nanofibrous matrices are promising materials for regenerative medicine as part of a new methodology in scaffold design where a “bottom‐up” approach is used in order to simulate the native cellular milieu. Importantly, SAPs hold the potential to be bioactive through the presentation of biochemical and biomechanical signals in a context similar to the natural extracellular matrix, making them ideal targets for providing structural and chemical support in a cellular context. Here, we discuss a new methodology for the presentation of biologically relevant epitopes through their effective presentation on the surface of the nanofibers. Here, we demonstrate that these signals have a direct effect on the viability of cells within a three‐dimensional matrix as compared with an unfunctionalized, yet mechanically and morphologically similar system. © 2014 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 102: 197–205, 2014.
Improved chemical synthesis of hydrophobic Aβ peptides using addition of C‐terminal lysines later removed by carboxypeptidase B
Authors: Chemuru Saketh , Kodali Ravindra , Wetzel Ronald 
Published: February 2014

ABSTRACTMany amyloidogenic peptides are highly hydrophobic, introducing significant challenges to obtaining high quality peptides by chemical synthesis. For example, while good yield and purity can be obtained in the solid‐phase synthesis of the Alzheimer's plaque peptide Aβ40, addition of a C‐terminal Ile‐Ala sequence to generate the more toxic Aβ42 molecule creates a much more difficult synthesis resulting in low yields and purities. We describe here a new method that significantly improves the Fmoc solid‐phase synthesis of Aβ peptides. In our method, Lys residues are linked to the desired peptide's C‐terminus through standard peptide bonds during the synthesis. These Lys residues are then removed post‐purification using immobilized carboxypeptidase B (CPB). With this method we obtained both Aβ42 and Aβ46 of superior quality that, for Aβ42, rivals that obtained by recombinant expression. Intriguingly, the method appears to provide independent beneficial effects on both the total synthetic yield and on purification yield and final purity. Reversible Lys addition with CPB removal should be a generally useful method for making hydrophobic peptides that is applicable to any sequence not ending in Arg or Lys. As expected from the additional hydrophobicity of Aβ46, which is extended from the sequence Aβ42 by a C‐terminal Thr‐Val‐Ile‐Val sequence, this peptide makes typical amyloid at rates significantly faster than for Aβ42 or Aβ40. The enhanced amyloidogenicity of Aβ46 suggests that, even though it is present in relatively low amounts in the human brain, it could play a significant role in helping to initiate Aβ amyloid formation. © 2014 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 102: 206–221, 2014.
Asymmetric Total Synthesis of Onoseriolide, Bolivianine, and Isobolivianine
Authors: Du Biao , Yuan Changchun , Yu Tianzi , Yang Li , Yang Yang , Liu Bo , Qin Song 
Published: February 2014

AbstractIn this article, we describe our efforts on the total synthesis of bolivianine (1) and isobolivianine (2), involving the synthesis of onoseriolide (3). The first generation synthesis of bolivianine was completed in 21 steps by following a chiral resolution strategy. Based on the potential biogenetic relationship between bolivianine (1), onoseriolide (3), and β‐(E)‐ocimene (8), the second generation synthesis of bolivianine was biomimetically achieved from commercially available (+)‐verbenone in 14 steps. The improved total synthesis features an unprecedented palladium‐catalyzed intramolecular cyclopropanation through an allylic metal carbene, for the construction of the ABC tricyclic system, and a Diels–Alder/intramolecular hetero‐Diels–Alder (DA/IMHDA) cascade for installation of the EFG tricyclic skeleton with the correct stereochemistry. Transformation from bolivianine to isobolivianine was facilitated in the presence of acid. The biosynthetic mechanism and the excellent regio‐ and endo selectivities in the cascade are well supported by theoretical chemistry based on the DFT calculations.
Cleavage of the CN Bond in Carbodiimides via Release of High Ring Strain: A New Strategy for the Selective Synthesis of 2‐Aminoaryl Alkynyl Imines
Authors: Zhou Yi , Chi Yue , Zhao Fei , Zhang Wen‐Xiong , Xi Zhenfeng 
Published: February 2014

AbstractA novel pattern of the cleavage and reorganization of CN bond in the multicomponent reaction (MCR) of terminal alkynes or haloalkynes, carbodiimides, and benzynes is achieved for the first time to construct efficiently 2‐aminoaryl alkynyl imines. The selective formation and ring‐opening of the azetine intermediate with the high ring strain is essential for this reaction. Further transformation of 2‐aminoaryl alkynyl imines via the Cu‐catalyzed cycloisomerization is explored to provide steroselectively the bi‐, tri‐, and tetracyclic fused pyrrolines.
Palladium‐Catalyzed Direct Thiolation of Aryl CH Bonds with Disulfides
Authors: Iwasaki Masayuki , Iyanaga Miki , Tsuchiya Yuta , Nishimura Yugo , Li Wenjuan , Li Zhiping , Nishihara Yasushi 
Published: February 2014

AbstractA catalytic variant of the direct thiolation of arenes, bearing directing groups, with disulfides or thiols has been developed under palladium and copper co‐catalysis. Both sulfenyl moieties of the disulfide could be incorporated into the thiolated products, therefore, the reactions reached completion with only half an equivalent of disulfide, with respect to the starting arene. Experimental evidence suggested that the reaction proceeds through a PdII/PdIV mechanism.
Electrocatalytically Switchable CO2 Capture: First Principle Computational Exploration of Carbon Nanotubes with Pyridinic Nitrogen
Authors: Jiao Yan , Zheng Yao , Smith Sean C. , Du Aijun , Zhu Zhonghua 
Published: February 2014

AbstractCarbon nanotubes with specific nitrogen doping are proposed for controllable, highly selective, and reversible CO2 capture. Using density functional theory incorporating long‐range dispersion corrections, we investigated the adsorption behavior of CO2 on (7,7) single‐walled carbon nanotubes (CNTs) with several nitrogen doping configurations and varying charge states. Pyridinic‐nitrogen incorporation in CNTs is found to induce an increasing CO2 adsorption strength with electron injecting, leading to a highly selective CO2 adsorption in comparison with N2. This functionality could induce intrinsically reversible CO2 adsorption as capture/release can be controlled by switching the charge carrying state of the system on/off. This phenomenon is verified for a number of different models and theoretical methods, with clear ramifications for the possibility of implementation with a broader class of graphene‐based materials. A scheme for the implementation of this remarkable reversible electrocatalytic CO2‐capture phenomenon is considered.