bluuebunny/crossref_metadata_2025_split huggingface dataset:
Entdeckung und Strukturbestimmung eines ungewöhnlichen Sulfidtellurids mithilfe einer effektiven Kombination von TEM und Synchrotron‐Mikrodiffraktion
Authors: Fahrnbauer Felix , Rosenthal Tobias , Schmutzler Tilo , Wagner Gerald , Vaughan Gavin B. M. , Wright Jonathan P. , Oeckler Oliver 
Published: July 2015

AbstractAnhand der Strukturanalyse des neuartigen Sulfidtellurids Pb8Sb8S15Te5 wird eine neue, vielseitig anwendbare Vorgehensweise vorgestellt, die den Synergismus von Elektronenmikroskopie und Beugungsexperimenten mit Synchrotronstrahlung für genaue Strukturanalysen von Nebenphasen in heterogenen mikrokristallinen Proben nutzt. Geeignete Kristallite unbekannter Phasen können mittels Transmissionselektronenmikroskopie identifiziert und mithilfe von Röntgenfluoreszenz‐Scans in einem mikrofokussierten Synchrotronstrahl wiedergefunden und zentriert werden. Das verfeinerte Strukturmodell wird anschließend durch Simulation von HRTEM‐Abbildungen desselben Kristallits bestätigt. Pb8Sb8S15Te5 besteht aus Ketten heterocubanartiger Einheiten. Die Kationenkoordinationspolyeder bilden ungewöhnlich verschlungene Ketten kanten‐ und flächenverknüpfter doppelt überkappter trigonaler Prismen. Die Strukturdaten sind ausreichend präzise für Bindungsvalenzrechnungen, die die fehlgeordnete Atomverteilung überzeugend bestätigen. Diese Methode ermöglicht die Optimierung der physikalischen Eigenschaften.
A Crystal Structure of a Functional RNA Molecule Containing an Artificial Nucleobase Pair
Authors: Hernandez Armando R. , Shao Yaming , Hoshika Shuichi , Yang Zunyi , Shelke Sandip A. , Herrou Julien , Kim Hyo‐Joong , Kim Myong‐Jung , Piccirilli Joseph A. , Benner Steven A. 
Published: July 2015

AbstractAs one of its goals, synthetic biology seeks to increase the number of building blocks in nucleic acids. While efforts towards this goal are well advanced for DNA, they have hardly begun for RNA. Herein, we present a crystal structure for an RNA riboswitch where a stem C:G pair has been replaced by a pair between two components of an artificially expanded genetic‐information system (AEGIS), Z and P, (6‐amino‐5‐nitro‐2(1H)‐pyridone and 2‐amino‐imidazo[1,2‐a]‐1,3,5‐triazin‐4‐(8H)‐one). The structure shows that the Z:P pair does not greatly change the conformation of the RNA molecule nor the details of its interaction with a hypoxanthine ligand. This was confirmed in solution by in‐line probing, which also measured a 3.7 nM affinity of the riboswitch for guanine. These data show that the Z:P pair mimics the natural Watson–Crick geometry in RNA in the first example of a crystal structure of an RNA molecule that contains an orthogonal added nucleobase pair.
Synthetische Oligosaccharide belegen die immunologische Bedeutung der Pyruvatmodifikation im Kapselpolysaccharid von Serotyp 4 Streptococcus pneumoniae
Authors: Pereira Claney L. , Geissner Andreas , Anish Chakkumkal , Seeberger Peter H. 
Published: July 2015

AbstractNach allgemeiner Annahme wird die Immunogenität von Kohlenhydraten stark von deren Modifikationen beeinflusst. Kapselpolysaccharide (KPS) von pathogenen Bakterien enthalten häufig ein Pyruvat, das als Acetal die 4,6‐, 3,4‐ oder 2,3‐Positionen überbrücken kann. Das KPS von Serotyp 4 Streptococcus pneumoniae (ST4) ist mit einem trans‐2,3‐verknüpften Pyruvat modifiziert. Um die immunologische Bedeutung dieser Modifikation zu untersuchen, wurde die Wiederholungseinheit dieses Polysaccharids erstmals chemisch synthetisiert. Bei der Analyse von Antikörpern gegen ST4‐KPS mithilfe eines Kohlenhydratmikroarrays, der verschiedene Substrukturen des KPS enthält, konnte eine exklusive Bindung an die Wiederholungseinheit mit Pyruvat festgestellt werden. Das Pyruvatacetal ist somit ein Schlüsselmotiv für die Entwicklung minimaler synthetischer Kohlenhydratimpfstoffe gegen ST4.
Pinensins: The First Antifungal Lantibiotics
Authors: Mohr Kathrin I. , Volz Carsten , Jansen Rolf , Wray Victor , Hoffmann Judith , Bernecker Steffen , Wink Joachim , Gerth Klaus , Stadler Marc , Müller Rolf 
Published: July 2015

AbstractLantibiotics (lanthionine‐containing antibiotics) from Gram‐positive bacteria typically exhibit activity against Gram‐positive bacteria. The activity and structure of pinensin A (1) and B (2), lantibiotics isolated from a native Gram‐negative producer Chitinophaga pinensis are described. Surprisingly, the pinensins were found to be highly active against many filamentous fungi and yeasts but show only weak antibacterial activity. To the best of our knowledge, lantibiotic fungicides have not been described before. An in‐depth bioinformatic analysis of the biosynthetic gene cluster established the ribosomal origin of these compounds and identified candidate genes encoding all of the enzymes required for post‐translational modification. Additional encoded functions enabled us to build up a hypothesis for the biosynthesis, export, sensing, and import of this intriguing lantibiotic.
Gold(I)‐Catalyzed Tandem Transformation with Diynes: Rapid Access to Linear Cyclopentenone‐Fused Polycyclic Molecules
Authors: Yu Congjun , Chen Bin , Zhou Tian , Tian Qingshan , Zhang Guozhu 
Published: July 2015

AbstractAn efficient and convenient synthesis of useful linear cyclopentenone‐fused polycyclic compounds has been achieved through a novel gold(I)‐catalyzed transformation of diynes. The method demonstrates high product yields and tolerates of a wide variety of important functional groups. Gold‐vinylidene formation, methoxy group migration, and Nazarov‐type cyclization are proposed to be the key steps in the reaction pathway. The synthetic utility of this method is demonstrated by converting the product to eight‐membered‐ring‐fused compound.
Cooperative Gold Nanoparticle Stabilization by Acetylenic Phosphaalkenes
Authors: Orthaber Andreas , Löfås Henrik , Öberg Elisabet , Grigoriev Anton , Wallner Andreas , Jafri S. Hassan M. , Santoni Marie‐Pierre , Ahuja Rajeev , Leifer Klaus , Ottosson Henrik , Ott Sascha 
Published: July 2015

AbstractAcetylenic phosphaalkenes (APAs) are used as a novel type of ligands for the stabilization of gold nanoparticles (AuNP). As demonstrated by a variety of experimental and analytical methods, both structural features of the APA, that is, the PC as well as the CC units are essential for NP stabilization. The presence of intact APAs on the AuNP is demonstrated by surface‐enhanced Raman spectroscopy (SERS), and first principle calculations indicate that bonding occurs most likely at defect sites on the Au surface. AuNP‐bound APAs are in chemical equilibrium with free APAs in solution, leading to a dynamic behavior that can be explored for facile place‐exchange reactions with other types of anchor groups such as thiols or more weakly binding phosphine ligands.
Chemical Synthesis Elucidates the Immunological Importance of a Pyruvate Modification in the Capsular Polysaccharide of Streptococcus pneumoniae Serotype 4
Authors: Pereira Claney L. , Geissner Andreas , Anish Chakkumkal , Seeberger Peter H. 
Published: July 2015

AbstractCarbohydrate modifications are believed to strongly affect the immunogenicity of glycans. Capsular polysaccharides (CPS) from bacterial pathogens are frequently equipped with a pyruvate that can be placed across the 4,6‐, 3,4‐, or 2,3‐positions. A trans‐2,3‐linked pyruvate is present on the CPS of the Gram‐positive bacterium Streptococcus pneumoniae serotype 4 (ST4), a pathogen responsible for pneumococcal infections. To assess the immunological importance of this modification within the CPS repeating unit, the first total synthesis of the glycan was carried out. Glycan microarrays containing a series of synthetic antigens demonstrated how antibodies raised against natural ST4 CPS specifically recognize the pyruvate within the context of the tetrasaccharide repeating unit. The pyruvate modification is a key motif for designing minimal synthetic carbohydrate vaccines for ST4.
Structure Elucidation and Characterization of Different Thyroxine Polymorphs
Authors: Mondal Santanu , Mugesh Govindasamy 
Published: July 2015

AbstractThyroid hormones regulate almost every process in the body, including body temperature, growth, and heart rate. They influence carbohydrate metabolism, protein synthesis and breakdown, and cardiovascular, renal, and brain function. Two new polymorphs of synthetic L‐thyroxine (T4) are reported and the effect of polymorphism on the solubility of this important hormone is shown. Conformational changes were also discovered to have a remarkable effect on the strength of halogen bonding and the reactivity of the CI bonds, which could have a significant effect on the hormone activity.
Modification of poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) properties by reactive blending with a monoterpene derivative
Authors: Pilon Laura , Kelly Catherine 
Published: July 2015

ABSTRACTA one‐step reactive blending approach is reported for modification of the thermal and mechanical properties of poly (3‐hydroxybutyrate‐co‐3‐hydroxyvalerate). A free‐radical initiated reaction of the monoterpene derivative, linalool, was carried out with PHBV in the melt. This processing led to a reduction in the material melt temperature and increase in the tensile strength and elongation at break. Reduced embrittlement over time was also evident in the reactive blended materials in an ambient temperature ageing study, suggestive of reduced secondary crystallization. The nature of the structural changes within the materials could not be fully elucidated, but evidence pointed to free radical cross‐linking, mediated by the linalool, as a major component of the changes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42588.
Synthesis of chitosan derivative with dual‐antibacterial functional groups and its antibacterial activity
Authors: Li Zhihan , Yang Fei , Yang Rendang 
Published: July 2015

ABSTRACTThe O‐fumaryl ester (OFTMCS) of N,N,N‐trimethyl chitosan (TMCS) has been synthesized as a water‐soluble chitosan (CS) derivative bearing dual‐functional groups, with the aim of discovering novel CS derivatives with good water solubility and enhanced the antibacterial activity compared with unmodified CS. OFTMCS was characterized by FT‐IR, 13C NMR, XPS, XRD and Zeta potential analyses. The XPS results indicated that the degree of substitution (DS) on the C2‐NH2 group of the CS was 0.78, and that the DS on its C6‐OH group was 0.31. The TGA results showed that the thermal stability of OFTMCS was lower than that of unmodified CS. The antibacterial activities of OFTMCS were investigated by assessing the mortality rates of the representative Gram‐positive and Gram‐negative bacteria Staphylococcus aureus and Escherichia coli, respectively. The results indicated that OFTMCS exhibited superior antibacterial activity to CS at a lower dosage. The synthesis of CS derivatives bearing dual‐functional groups could therefore be used as a promising strategy to enhance the antibacterial activity of CS. The antimicrobial mechanism of action of OFTMCS was discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42663.
Improving electrical conductivity of poly methyl methacrylate by utilization of carbon nanotube and CO2 laser
Authors: Ghavidel Ayub Karimzad , Azdast Taher , Shabgard Mohammadreza , Navidfar Amir , Sadighikia Sina 
Published: July 2015

ABSTRACTIn this work, the electrical surface conductivity enhancement of injection‐molded multiwalled carbon nanotube (MWCNT)/poly(methyl methacrylate) (PMMA) nanocomposite by using CO2 laser processing was studied. Variable input factors are considered as MWCNT concentration (in three levels 0.5, 1, and 1.5 wt %), the laser feed angle with the flow direction (in five levels 0°, 30°, 45°, 75°, and 90°), and the cavity machining method that were produced by electrodischarge machining and computer numerical control milling with finishing process. The studies show that the irradiation of laser and utilization of covering gas could enhance the CNT–CNT contacts and the surface electrical conductivity. The morphology of laser‐irradiated surface by using scanning electron microscope certified that the conductive network generated from CNT–CNT contacts can transfer the electrical current. The findings clearly show that the laser feed angle with the flow direction influenced the electrical conductivity. The maximum conductivity (∼ 5.310 × 10−4 S) was observed at 75°. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42671.
In‐situ formation of metal nanoparticle/acrylic polymer hybrid and its application to miniemulsion polymerization
Authors: Tamai Toshiyuki , Watanabe Mitsuru , Matsukawa Kimihiro 
Published: July 2015

ABSTRACTWe present in‐situ formation of metal nanoparticle/acrylic polymer hybrid and its application to prepare hybrid latex particles by miniemulsion polymerization. On the surface of a silver nanoparticle/silica nanoparticle/acrylic polymer hybrid layer formed in‐situ on a polyethylene terephthalate (PET) substrate, a copper film is deposited using electroless copper deposition. Silver nanoparticles, which are formed in‐situ via the reduction of silver ion by radical species and subsequent annealing, work as a catalyst for the electroless deposition. Miniemulsion polymerization via the in‐situ formation of nanoparticles affords nanoparticle/acrylic polymer hybrid latex particles and polymer particles. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42675.
Length scale dependent deformation in natural rubber
Authors: Chandrashekar Gurudutt , Alisafaei Farid , Han Chung‐Souk 
Published: July 2015

ABSTRACTStrong length scale dependent deformation has been previously observed in the elastomer polydimethylsiloxane by indentation type experiments at micro‐ to nanometer length scales with a sharp conical tip. To examine if other nonsilicone based elastomers exhibit similar length scale dependent deformation behavior, natural rubber has been chosen in this study. Performing indentation type tests with a nanoindentation system, the universal hardness and the elastic modulus are determined at different probing depths ranging from about 90 to 5 μm to characterize length scale dependent deformation behavior in natural rubber. The testing with a Berkovich tip resulted in an amazing increase in the universal hardness with decreasing probing depth indicating that the deformation mechanisms at the micrometer length scales are significantly different as compared to those at the macroscopic length scales. The observed length scale dependent deformation is associated with an increase in rotation gradients with decreasing probing depth. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42683.
Polyisoprene modified poly(alkyl acrylate) foam as oil sorbent material
Authors: Ratcha Arissara , Samart Chanatip , Yoosuk Boonyawan , Sawada Hideo , Reubroycharoen Prasert , Kongparakul Suwadee 
Published: July 2015

ABSTRACTBiorenewable polyisoprene latex obtained from natural rubber, Hevea brasiliensis, was used to prepare the reusable polyisoprene–poly(alkyl acrylate) foam for petroleum‐based liquid absorption. The foam was produced via latex vulcanization and cured by steaming. The effect of various types of poly(alkyl acrylate) such as poly(methyl methacrylate) (PMMA), poly(butyl methacrylate) (PBMA), and poly(butyl acrylate) (PBA) on oil sorption capacity of the foam were studied. Scanning electron microscope (SEM) images showed interconnected open‐cell macrostructure with the foam porosity greater than 75% and good compression set. The oil sorption capacity of the foam was in the range of 2.0–16.6 g g−1. The addition of poly(alkyl acrylate) enhanced hydrophobicity and oil sorption capacity of the foam. The absorbed oil was easily recovered by squeezing and the foam can be reused up to 30 sorption–desorption cycles and still preserve high quality sorption. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42688.
Fluorinated networks dynamics studied by means of broadband dielectric spectroscopy
Authors: Miccio Luis A. , Otegui Jon , Penoff Marcela E. , Montemartini Pablo E. , Schwartz Gustavo A. 
Published: July 2015

ABSTRACTThe influence of the surface chemical modification on the bulk behavior of epoxy based networks has been studied. In particular, the bulk dynamics of epoxy‐amine networks modified with fluorinated side chains has been characterized by means of broadband dielectric spectroscopy (BDS), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy. The fluorination effect on the structure and dynamics of the materials has been related with the observed changes in both segmental and secondary relaxations. An acceleration of the segmental dynamics as the fluorination degree increases has been clearly observed. As a result, a compromise between fluorine surface enrichment and bulk modification has been proposed for these materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42690.
Preparation and properties of porous polytetrafluoroethylene hollow fiber membrane through mechanical operations
Authors: Liu Guochang , Gao Congjie , Li Xiaoming , Guo Chungang , Chen Ying , Lv Jinglie 
Published: July 2015

ABSTRACTPorous polytetrafluoroethylene (PTFE) hollow fiber membranes were prepared from fine powder through a series of mechanical operations including paste extrusion, heat treatment, stretching and sintering. In contrast to conventional process, the heat treatment used in this study was performed at 200°C to 330°C (near the melting point) on the PTFE nascent hollow fiber (precursor of membrane). The results showed that the introduction of heat treatment step effectively improved the mechanical properties of precursors, the ultimate stress and strain increased observably with heat treatment temperature, which was beneficial to subsequently stretching precursors to make them porous. Furthermore, the morphological changes and improvement of membrane properties caused by stretching operation were investigated for porous PTFE hollow fiber membrane having finer pore size and higher porosity. The porous microstructure of nodes interconnected by fibrils varied depending on the stretching conditions, such as the stretching temperature, rate, and ratio. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42696.
Mixture design applied for the development of films based on starch, polyvinyl alcohol, and glycerol
Authors: Zanela Juliano , Olivato Juliana Bonametti , Dias Adriana Passos , Grossmann Maria Victória Eiras , Yamashita Fabio 
Published: July 2015

ABSTRACTStarch and polyvinyl alcohol (PVA) are biodegradable materials with potentiality to replace the conventional polymers in some applications. The aim of this work was to produce biodegradable films of PVA, cassava starch, and glycerol by thermoplastic extrusion using a mixture design to evaluate the effects of each component in the blend properties. Six formulations were prepared using a twin‐screw extruder coupled with a calender. All the materials were visually homogeneous and presented good processability. Mechanical properties were dependent on both the relative humidity conditioning and the formulation; higher relative humidities detracted the mechanical properties, which was associated to plasticizer effect of the water. Furthermore, the mechanical properties were better when higher concentrations of PVA were used, resulting in films with lower opacity, lower water vapor permeability, and higher thermal stability, according to TGA. Biodegradable materials based on starch, PVA, and glycerol have adequate mechanical and processing properties for commercial production. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42697.
Probing small network differences in sulfur‐cured rubber compounds by combining nuclear magnetic resonance and swelling methods
Authors: Dibbanti Murali Krishna , Mauri Michele , Mauri Lucio , Medaglia Gabriele , Simonutti Roberto 
Published: July 2015

ABSTRACTWe studied the network structure of elastomers based on polyisoprene, polybutadiene, and their blends in the narrow range of formulations compatible with actual use in the automotive tyre industry. Cross‐link density (CLD) was quantified comparatively by low‐field 1H multiple quantum time domain nuclear magnetic resonance (MQ TD‐NMR) and by equilibrium swelling technique. The robustness and agreement of the two methods was demonstrated in measuring minute alterations of unfilled vulcanizates beyond the optimum cure time. Comparison with samples where polysulfidic bonds were selectively cleaved also demonstrates that the length of the sulfur chain constituting the cross‐link does not significantly affect residual dipolar coupling. Kraus, Lorenz, and Parks correction for filler restriction on swelling is validated by MQ TD‐NMR, which also allows extracting information on cross‐link distribution not provided by swelling measurement. Cross‐link distributions in the blends were demonstrated to be significantly different from the weighted average of the pure samples, while average proton–proton residual dipolar coupling values correspond. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42700.
Effects of maleic anhydride grafted polyethylene on rheological, thermal, and mechanical properties of ultra high molecular weight polyethylene/poly(ethylene glycol) blends
Authors: He Shuai , He Hui , Li Yingchun , Wang Dongqing 
Published: July 2015

ABSTRACTUltra‐high molecular weight polyethylene (UHMWPE) has gained considerable fame due to its excellent wear and mechanical properties, though the inferior processability has restricted its further extensive applications. In this study, a combination of UHMWPE and poly(ethylene glycol) (PEG) was considered based on the recent reports, and aiming to further exploit the potential of PEG that acts as processing aid, and also to obtain greater enhanced processability along with other properties, the effects of incorporating maleic anhydride grafted polyethylene (MAPE) was thoroughly investigated. Rheological tests revealed a further significant reduction in melt viscosity of UHMWPE/PEG blends after MAPE introduced, showing a potential of better processability, while the flexural strength and toughness of UHMWPE blends experienced a satisfying increase without any obvious compromises in other mechanical properties. A slight improvement of thermal stability in UHMWPE ternary blends along with an increase of vicat softening temperature were characterized by thermal tests, while the crystallinity of UHMWPE was diminished after the introduction of MAPE. Morphology analysis indicated that better dispersion and decreased size of PEG particles were achieved in UHMWPE matrix when MAPE was incorporated, which confirmed the improved interfacial interactions and other reinforcements obtained in UHMWPE/PEG/MAPE blends. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42701.
Fabrication of hierarchically crystallographic morphologies in isotactic polypropylene
Authors: Wang Ming , Yuan Jia , Luo Shi‐Hui , Zeng Jian‐Bing 
Published: July 2015

ABSTRACTThe hierarchically crystallographic morphologies were fabricated in isotactic polypropylene (iPP) by controlling the stratified distribution of the nucleating agents. The α‐ and β‐nucleating agents were chosen for preparing the different crystalline modifications. The transcrystals and spherulites were found in the stratified distribution samples by polar optical microscopy (POM) and scanning electron microscope (SEM). The transcrystals grew from the surfaces of the nucleating agents filled layers and occupied most space of the pure iPP layers. The crystalline modifications and crystallinity were analyzed by X‐ray diffraction (XRD) and differential scanning calorimeter (DSC) analysis. The mechanical and thermal degradation properties of these samples with hierarchically crystallographic morphologies were investigated by tensile testing machine and thermogravimetric analysis (TGA) respectively, and showed better than that of the samples with single crystallographic morphology (spherulites). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42703.