bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of a Novel Low‐Bandgap Polymer Based on a Ladder‐Type Heptacyclic Arene Consisting of Outer Thieno[3,2‐b]thiophene Units for Efficient Photovoltaic Application
Authors: Xu Xiaofeng , Cai Ping , Lu Yong , Choon Ng Siu , Chen Junwu , Ong Beng S. , Hu Xiao 
Published: March 2013

AbstractA novel conjugated polymer PIDTT‐quinoxaline (Qx) based on the coplanar thieno[3,2‐b]thiophene‐phenylene‐thieno[3,2‐b]thiophene structure is synthesized and evaluated as an electron‐donor material for bulk‐heterojunction polymer solar cells (BHJ PSCs). The absorption spectra, electrochemical, charge transport, and film morphology properties as well as theoretical modeling of PIDTT‐Qx are investigated to understand its intrinsic structure–property relationship. As expected, this polymer with an extended π‐conjugated backbone exhibits a narrow‐bandgap and board absorption spectrum for enhanced light harvesting. BHJ PSCs (ITO/PEDOT:PSS/polymer:PC71BM/interlayer/Al) afford a maximum power conversion efficiency of 5.05% with an open‐circuit voltage of 0.84 V, a short‐circuit current density of 11.26 mA cm−2, and a fill factor of 53.4%. These results demonstrate the potential of PIDTT‐Qx as an efficient electron‐donor material for BHJ PSCs.magnified image
Cationic Salt‐Responsive Bottle‐Brush Polymers
Authors: Yao Kejian , Chen Ying , Zhang Jun , Bunyard Clay , Tang Chuanbing 
Published: March 2013

AbstractA class of cationic bottle‐brush polymers that show ionic strength‐dependent stimuli responsiveness is prepared. Brush polymers with norbornene as backbone and quaternary ammonium (QA)‐containing polycaprolactone copolymers as side chains are synthesized by a combination of ring‐opening metathesis polymerization, ring‐opening polymerization, and click reaction. In water with low ionic strength, brush polymers are soluble due to the strong electrostatic repulsion between cationic QA groups. As the addition of salt to increase ionic strength, single brush polymers undergo a transition from extended conformation to collapsed state and finally become insoluble in solution due to the screening effect of salts that yield the once‐dominant electrostatic interactions among QA species to hydrophobic–hydrophobic interactions.magnified image
Tunneling characteristics of superconducting junctions with inhomogeneous tunnel barriers
Authors: Shaternik V. , Shapovalov A. , Belogolovskii M. , Döring S. , Schmidt S. , Seidel P. 
Published: March 2013

AbstractThe increasing interest in charge transport across amorphous nanometer‐thick oxide layers is motivated by their promising applications in semiconductor and superconductor electronics. But usually, electrical characteristics of corresponding devices strongly differ from those following from a conventional theory of tunneling processes. In this work we discuss a possible reason of the anomalous behavior, namely, the presence of an universal bimodal distribution of transparencies across ultra‐thin insulating films. We present low‐temperature current‐voltage characteristics of tunnel junctions with superconducting MoRe alloy electrodes separated by an inhomogeneous nano‐scaled interlayer and found a good agreement between experimental data and numerical results of our theoretical approach.
Ordering kinetics of dopant atoms in graphene lattice with stoichiometric compositions of 1/3 and 1/6
Authors: Radchenko T.M. , Tatarenko V.A. 
Published: March 2013

AbstractPossible ordered distributions of carbon (C) and substituting dopant (A) atoms over the sites in a graphene‐type lattice are considered for C2A‐ and C5A‐type (super)structures (corresponding to stoichiometries of 1/3 and 1/6, respectively). Relaxation model of atomic long‐range order (LRO) in a graphene‐based lattice is developed, and kinetic curves of the long‐range order parameters are calculated for a wide range of values of temperature and energy parameters. The long‐range order parameters of C2A and C5A structures, described by three long‐range order parameters, can relax nonmonotonically. It is caused by the ‘competition’ of intra‐ and intersublattice interaction energies: the first ones predominate only at the early relaxation stage opposing the ordering, while the second ones predominate at the later relaxation stage and in the equilibrium contributing to the ordering.
Influence of the substrate bias on the stoichiometry and structure of RF‐magnetron sputter‐deposited silver‐containing calcium phosphate coatings
Authors: Ivanova A. A. , Surmeneva M. A. , Grubova I. Y. , Sharonova A. A. , Pichugin V. F. , Chaikina M. V. , Buck V. , Prymak O. , Epple M. , Surmenev R. A. 
Published: March 2013

AbstractA coating on the basis of silver‐containing hydroxyapatite (silver‐hydroxyapatite) was deposited by radio frequency (RF) magnetron sputtering. X‐ray diffractometry, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and ellipsometry were used to analyse the change in structure and stoichiometry of the coatings upon the change of the negative electrical bias (–50 V and –100 V) on the substrate. The chemical composition of the sputter‐deposited coating was identical to the target. However, an increase in the negative electrical bias on the substrate led to a decrease of the coating thickness. In addition, the average size of the grains decreased from 55 ± 15 nm (grounded substrate) up to 30 ± 10 nm when an electrical bias of –100 V was applied.
Impact of single‐walled carbon nanotubes on the medullary neurons in spontaneously hypertensive rats
Authors: Radchenko N.V. , Prylutskyy Yu.I. , Shapoval L.M. , Sagach V.F. , Davydovska T.L. , Dmitrenko O.V. , Stepanenko L.G. , Pobigailo L.S. , Schütze Ch. , Ritter U. 
Published: March 2013

AbstractThe effect of single‐walled carbon nanotubes (SWCNTs) on the nervous cardiovascular control in normotensive (NTR) and spontaneously hypertensive rats (SHR) was studied. SWCNTs were injected into the medullary nuclei involved in the neural control of the cardiovascular system (nucleus of tractus solitarius (NTS); nucleus ambiguus (AMB), paramedian reticular nucleus (PMn), and lateral reticular nucleus (LRN)). It was found that SWCNT microinjections into all the studied medullary nuclei of both NTR and SHR resulted in a lowering of the arterial pressure more essential in SHR compared to those in NTR.
Effect of adsorbed magnetic and non‐magnetic atoms on electronic transport through surfaces with strong spin‐orbit coupling
Authors: Lükermann D. , Sologub S. , Pfnür H. , Klein C. , Horn‐von‐Hoegen M. , Tegenkamp C. 
Published: March 2013

AbstractAdsorption‐induced reduction of the surface state conductivity in epitaxial Bi(111) films, a prototype system with a large Rashba‐induced surface state splitting by adsorbed atoms of Bi, Fe and Co was investigated by macroscopic surface magneto‐transport measurements at a temperature of 10 K. A detailed analysis of magneto‐transport, DC‐transport and Hall data reveals that the scattering efficiencies for Co and Fe are by a factor of two larger than for Bi. While for the latter, charge transfer and change of band filling near the Fermi level is negligible, we found an increase of hole concentration upon Co and Fe adsorption. These atoms act as acceptors and retract roughly 0.5 electrons from the surface per adsorbed atom. Besides the dominant classical magneto‐conductance signal the films show signatures of weak anti‐localization (WAL) reflecting the strong spin‐orbit coupling in Bi(111) surface states. Our measurements show that the control of hybridization is important in order to make use of local spin‐moments and to increase the backscattering rate in strongly spin‐orbit coupled systems, e. g., topological insulators.
Electrical conductivity of epoxy resin filled with graphite nanoplatelets and boron nitride
Authors: Matzui L. Y. , Vovchenko L. L. , Perets Y. S. , Lazarenko O. A. 
Published: March 2013

AbstractThe electrical conductivity of polymer composites with mixture of fillers, i. e. graphite nanoplatelets and hexagonal boron nitride (BN), was investigated. The content of graphite nanoplatelets (prepared by ultrasonication of thermoexfoliated graphite) in composite materials varied from 2 to 10 wt%. The DC conductivity was measured by the two‐ or four‐probe methods in the temperature range of 77–293 K. A model of the electrical conductivity of composite materials was proposed. It takes into account the conductivity of the graphite particles, the contact resistance between particles, and the number of electrically conducting chains from graphite particles. In the framework of this model the number of graphite chains and the contact resistance of investigated composite materials were calculated. It was shown that the addition of boron nitride increases the number of electrically conducting chains from the graphite particles, decreases the value of contact resistance Rk between graphite particles that leads to smaller changes of contact resistance with increasing temperature, and weakens the temperature dependence of electrical conductivity of composite materials.
Resveratrol metabolites inhibit human metastatic colon cancer cells progression and synergize with chemotherapeutic drugs to induce cell death
Authors: Aires Virginie , Limagne Emeric , Cotte Alexia K. , Latruffe Norbert , Ghiringhelli François , Delmas Dominique 
Published: March 2013

ScopeResveratrol (RSV) has been proposed to prevent tumor growth; nevertheless, these preventive effects are controversial since RSV pharmacokinetics studies show a low bioavailability. Recent clinical trials show that patients with colorectal cancer and receiving oral RSV have high levels of RSV conjugates in the colorectum, mainly RSV‐3‐O‐sulfate (R3S), RSV‐3‐O‐glucuronide, and RSV‐4′‐O‐glucuronide. However, their potential biological activity has not yet been established. This study thus investigated in human colorectal cancer cell lines whether RSV main metabolites retain anticarcinogenic properties as their parental molecule.Methods and resultsProliferation, apoptosis assays and cell cycle analysis were performed to study the effect of RSV, R3S, RSV‐3‐O‐glucuronide, or RSV‐4′‐O‐glucuronide alone or of a mixture of the three metabolites. R3S inhibits colon cancer cells proliferation and an accumulation of cells in S phase. Interestingly, the mixture induced a synergistic effect. This process was associated with an induction of DNA damages and apoptotic process, which allowed sensitization of colon cancer cells to the anticancer drugs.ConclusionAltogether, our data provide significant new insight into the molecular mechanism of RSV and support the notion that despite low bioavailability in vivo, RSV biological effects could be mediated by its metabolites.
Three‐dimensional ultrasound demonstration of the fetal palate in high‐risk patients: the accuracy of prenatal visualization
Authors: Gindes Liat , Weissmann‐Brenner Alina , Zajicek Michal , Weisz Boaz , Shrim Alon , Geffen Keren Tzadikevitch , Mendes David , Kuint Jaacov , Berkenstadt Michal , Achiron Reuven 
Published: March 2013

ABSTRACTObjectiveThe aim of this research was to evaluate the ability of three‐dimensional (3D) ultrasound for demonstrating the palate of fetuses at high risk for cleft palate.MethodFifty‐seven fetuses at high risk for cleft palate were referred for specialist ultrasound at 12–40 weeks' gestation. A detailed assessment of palate was made using both two‐dimensional and 3D ultrasounds on the axial plane. Antenatal diagnoses were compared with postnatal findings.ResultsCleft palate was suspected in 13 (22.8%); a normal palate was demonstrated in 38 (67%), and in six (10.2%), the palate view could not be obtained. Mean gestational age at the first visit was 27 weeks 6 days (range of 12–40 weeks 3 days). Examination after delivery revealed that one of the 38 fetuses with presumed normal palate had a cleft hard palate, and one had a cleft soft palate (false negative 5%). Among the 13 fetuses with suspected cleft palate, three had an intact palate (false‐positive 23%). Sensitivity, specificity, positive predictive value, and negative predictive value of detection of palatal clefts were 71.4%, 91.9%, 62.5%, and 94.4%, respectively.ConclusionUsing 3D technology, we diagnosed a cleft palate in 83% of high‐risk cases, with 5% false negative. 3D technology might produce some technical artifacts resulting in a 23% false‐positive rate. © 2013 John Wiley & Sons, Ltd.
Sulfonation of polystyrene: Toward the “ideal” polyelectrolyte
Authors: Coughlin Jessica E. , Reisch Andreas , Markarian Marie Z. , Schlenoff Joseph B. 
Published: March 2013

ABSTRACTSulfonation of narrow polydispersity polystyrene, PS, standards remains the method of choice for generating polystyrene sulfonate, PSS, samples with defined composition. Although a variety of sulfonation techniques have been described, relatively little is reported on the material obtained, which is used for so many studies on the fundamental behavior of polyelectrolytes. Here, we show that powdered polystyrene treated with concentrated sulfuric acid (96%) at 90 °C without catalyst yields fully sulfonated PSS. Extensive characterization with 1H and 13C NMR as well as size exclusion chromatography coupled with static and dynamic light scattering shows no evidence of sulfone crosslinking or chain degradation under the conditions used. Though mono‐sulfonated as soon as it dissolves in the acid, the PSS contains about 6% meta substitution. Sulfonation kinetics for this heterogeneous reaction depend strongly on particle size, sulfuric acid content and temperature. For preparing perdeuterated PSS from the corresponding PS it is essential to employ D2SO4, as about half of the aromatic units undergo H/D exchange during sulfonation. The remaining ortho H/D may be exchanged with extended exposure to the concentrated sulfuric acid, but the meta site is deactivated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2416–2624
Noncovalent linkage of telechelic oligo(dimethylsiloxanes) via end group attachment of host‐cyclodextrins and guest‐adamantanes or guest‐ferrocenes
Authors: Knudsen Berit , Kergl Beate E. , Paulsen Helene , Durnev Valerij , Ritter Helmut 
Published: March 2013

ABSTRACTIn this article, we report the noncovalent linkage of terminal substituted oligo(dimethylsiloxanes) bearing cyclodextrins (CD) as host endgroups and adamantan or ferrocene, respectively, as guest endgroups. Structural characterization was performed by 1H NMR‐, IR‐, and mass spectroscopy. Electron microscopy studies show significant differences in the surface structure of the individual derivatives. In addition, the ferrocene‐terminated di‐and poly(dimethylsiloxanes) are distinguished by a red‐ox activity and reversibility, which also makes the complexes between the ferrocene‐ and CD functionalized siloxanes switchable via electrochemical stimuli. The evidence for a successful complexation of the end groups, and thus the successful supramolecular formation of the siloxane strands, was even performed by shift of the protons in the 1H NMR spectra. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2472–2482
Limitations of cyclodextrin‐mediated RAFT homopolymerization and block copolymer formation
Authors: Hetzer Martin , Schmidt Bernhard V. K. J. , Barner‐Kowollik Christopher , Ritter Helmut 
Published: March 2013

ABSTRACTThe design and synthesis of a new hydrophobic monomer, that is, 4‐(tert‐butyl)phenyl 6‐acrylamidohexanoate (TBP‐AA‐HO) and its ability to form supramolecular host/guest complexes with β‐cyclodextrin (CD) is described. The aqueous CD‐mediated reversible addition fragmentation chain transfer (RAFT) polymerization affords molecular masses up to 8600 g mol−1 with polydispersities between 1.2 and 1.4. The surprisingly low molecular weights for higher monomer/chain transfer agent (CTA) ratios are investigated by comparing results obtained from free radical and RAFT radical polymerization in aqueous and organic media. The results indicate a steric hindrance caused by attached CD molecules on the growing polymer chain leading to stagnation of the polymerization process due to a restricted accessibility of the reactive chain end. This hypothesis is supported by matrix‐assisted laser desorption/ionization time of flight mass spectrometry. Furthermore, the CD‐mediated synthesis of amphiphilic diblock copolymers in variable aqueous media is described. Hydrophilic poly(N,N‐dimethylacrylamide) macro‐CTAs with different molecular weights are used to polymerize TBP‐AA‐HO at 50 °C. The diblock copolymers are analyzed by 1H‐nuclear magnetic resonance spectroscopy and size exclusion chromatography. The results confirm the polymer structure and reveal similar limitations of chain growth as observed for the CD‐mediated homopolymerization with a limit of 7000 g mol−1 for efficient chain extension. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2504–2517
Plasma Etching of Silk Fibroin: Experiments and Models
Authors: Narayanamoorthy Jayasri , Tsioris Konstantinos , Omenetto Fiorenzo G. , Hopwood Jeffrey 
Published: March 2013

AbstractSilk fibroin biopolymer is anisotropically etched using oxygen and argon/oxygen plasma. At room temperature, silk removal rates are 0.25 µm min−1. Scanning electron micrographs show that silk fibroin is a heterogeneous material for which plasma etching reveals a silk backbone structure as the matrix is more quickly volatilized. A simple physical model of silk etching accurately predicts the etch rate without any fitting parameters. The model and experimental data show that atomic oxygen, in the absence of ion bombardment, only slowly etches silk (<0.017 µm min−1) and does not spontaneously etch silk fibroin backbone structures. Rather, the silk constituents must be removed by first covering the surface with adsorbed atomic oxygen which is then simultaneously desorbed through energetic ion bombardment. magnified image
Syngenetic Ice Wedges: Cyclical Formation, Radiocarbon Age and Stable Isotope Records by Yurij K. Vasil’chuk, Moscow University Press, Moscow, 2006. 404 pp. ISBN 5‐211‐05212‐9
Authors: Vasil'chuk Yurij K. 
Published: March 2013

ABSTRACTThe monograph summarises radiocarbon and stable isotope research on syngenetic ice wedges. The southern boundary of active and inactive ice wedges in Russian permafrost is re‐evaluated and revised. A new model of cyclical growth of syngenetic ice wedges is proposed, involving three cycles in ice‐wedge development: micro‐, meso‐ and macrocycles. Direct dating of syngenetic ice wedges can be carried out by accelerator mass spectrometry (AMS) radiocarbon dating of organic microinclusions and pollen concentrates from ice‐wedge ice. Dating reveals vertical and lateral variation in the age of yedoma at Duvanny Yar (NE Yakutia), one of the key syngenetic permafrost exposures in Eurasia. Radiocarbon ages and oxygen and deuterium isotopic values of syngenetic ice wedges in northern Russia and North America provide insights into palaeoenvironmental history and palaeogeocryology. Syngenetic ice wedges sometimes show complex cryostratigraphic relationships with other types of ice, including massive ice, icing ice and pingo ice. Comparison of isotope records from syngenetic ice wedges with those from Greenland ice cores reveals evidence for Dansgaard‐Oeschger (D/O) events preserved in Siberian permafrost. Copyright © 2013 John Wiley & Sons, Ltd.
Biodegradable paclitaxel‐loaded microparticles prepared from novel block copolymers: influence of polymer composition on drug encapsulation and release
Authors: Sartori Susanna , Caporale Andrea , Rechichi Alfonsina , Cufari Domenico , Cristallini Caterina , Barbani Niccoletta , Giusti Paolo , Ciardelli Gianluca 
Published: March 2013

This study covers the preparation of microspheres for the controlled and targeted release of paclitaxel, using novel degradable polymers as carrier materials. Paclitaxel‐loaded microspheres were prepared by oil‐in‐water single‐emulsion solvent extraction/evaporation technique by using a series of polyurethanes and a block copolymer; the physicochemical properties of these polymers were modulated by changing nature and composition of their structural units. The obtained microparticles showed a regular morphology and properties (diameter: 1–100 µm; resuspension index: 18.8–100%; encapsulation efficiency: 26.6–97.2%) depending on polymer hydrophilicity and emulsifier used. In vitro release curves showed in all cases almost zero‐order kinetics after an initial low burst effect (from 1 to 8.4%), which is required to minimize the drug side effects.This work also proposes a novel strategy to combine a controlled and a targeted release through the functionalization of the polymer matrix with peptide sequences. An RGD‐functionalized polyurethane was used to successfully prepare paclitaxel‐loaded microparticles. Studies on the preparation of polymer microspheres are reported. Copyright © 2013 European Peptide Society and John Wiley & Sons, Ltd.
Electrospray ion source with a dynamic liquid flow splitter
Authors: Samokish V. A. , Muradymov M. Z. , Krasnov N. V. 
Published: March 2013

RATIONALEAlthough the electrospray method is widely used in biomedical mass spectrometry and ion‐drift spectrometry, the electrospray system can generate large drops that are the cause of electrical breakdowns, and of the fast clogging of the inlet diaphragm of the differential pumping first stage and system of ion transportation to the analyzer. Thus, a system free of such problems would be of benefit.METHODSTo drain the condensate away from the electrospraying zone and to maintain stability of spraying, a source was designed where the excessive non‐sprayed solution flowing down over the metal capillary outer wall is pumped away by an air micropump. An anti‐electrode is mounted opposite the metal capillary and is slightly tilted with respect to the horizon to make the condensed liquid flow down.RESULTSAn electrospray ion source allowing work with chromatographic flows of the solution under normal conditions was tested. The applicability of the operating modes of the electrospray ion source with dynamic liquid flow splitting for both ion‐drift and mass spectrometers was demonstrated. The flow rate range of liquid fed to the electrospray ion source with dynamic liquid flow splitting is such that it can be used in high performance liquid chromatography/Ion Mobility Spectrometry (HPLC/IMS) and HPLC/MS in the online mode.CONCLUSIONSAn electrospray ion source with a dynamic liquid flow splitter was developed and tested. Optimal operating modes of the electrospray ion source with dynamic liquid flow splitting were determined. Copyright © 2013 John Wiley & Sons, Ltd.