bluuebunny/crossref_metadata_2025_split huggingface dataset:
Anion Coordination Effect on the Nuclearity of CoII, NiII, CuII, and ZnII Complexes with a Benzimidazole Pendant‐Armed Crown
Authors: Vaiana Lea , Esteban‐Gómez David , Mato‐Iglesias Marta , Platas‐Iglesias Carlos , de Blas Andrés , Rodríguez‐Blas Teresa 
Published: December 2008

AbstractThe study presented in this paper provides a rare example of a macrocyclic receptor allowing the formation of mono‐ or binuclear complexes on the same first‐row transition‐metal guest cation depending on the nature of the counterion present. Reaction of N,N′‐bis(benzimidazol‐2‐ylmethyl)‐4,13‐diaza‐18‐crown‐6 (L4) with CoII, NiII, CuII, or ZnII perchlorates leads to the formation of the expected mononuclear complexes with the metal ion showing a distorted octahedral coordination environment. In these complexes, the metal ion is placed at one end of the macrocyclic cavity, and two of the oxygen atoms of the crown ether moiety remain uncoordinated. 1H and 13C NMR spectroscopic studies on the diamagnetic [Zn(L4)]2+ complex indicate that the asymmetric coordination of the metal ion inside the macrocyclic cavity is maintained in acetonitrile solution, but translocation of the ZnII ion from one end of the macrobicyclic cavity to the second one occurs. However, reaction of L4 with CoII, NiII, or CuII perchlorates in the presence of chloride anions results in the formation of binuclear complexes where the metal ion is either five‐coordinate in a distorted trigonal bipyramidal coordination environment (Co or Cu) or six‐coordinate in a distorted octahedral geometry (Ni), and a chloride anion coordinates to each of the two metal ions in all cases. The ZnII ion behaves in a different way, and addition of chloride anions to the ZnII perchlorate in the presence of L4 does not lead to the formation of a binuclear complex. The formation of these binuclear systems was followed by spectrophotometric titrations of the mononuclear [M(L4)](ClO4)2 complexes with [nBu4N]Cl in acetonitrile solution indicating the formation of a [M2(L4)(Cl)]2+ intermediate species, followed by the formation of the binuclear complex [M2(L4)(Cl)2]2+ (M = Co, Ni, or Cu). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Ligand Effects on the Mechanisms of Thermal Bond Activation in the Gas‐Phase Reactions NiX+/CH4→Ni(CH3)+/HX (X=H, CH3, OH, F). Short Communication
Authors: Schlangen Maria , Schwarz Helmut 
Published: December 2008

AbstractThe thermal ion‐molecule reactions NiX++CH4→Ni(CH3)++HX (X=H, CH3, OH, F) have been studied by mass spectrometric methods, and the experimental data are complemented by density functional theory (DFT)‐based computations. With regard to mechanistic aspects, a rather coherent picture emerges such that, for none of the systems studied, oxidative addition/reductive elimination pathways are involved. Rather, the energetically most favored variant corresponds to a σ‐complex‐assisted metathesis (σ‐CAM). For X=H and CH3, the ligand exchange follows a ‘two‐state reactivity (TSR)’ scenario such that, in the course of the thermal reaction, a twofold spin inversion, i.e., triplet→singlet→triplet, is involved. This TSR feature bypasses the energetically high‐lying transition state of the adiabatic ground‐state triplet surface. In contrast, for X=F, the exothermic ligand exchange proceeds adiabatically on the triplet ground state, and some arguments are proposed to account for the different behavior of NiX+/Ni(CH3)+ (X=H, CH3) vs. NiF+. While the couple Ni(OH)+/CH4 does not undergo a thermal ligand switch, the DFT computations suggest a potential‐energy surface that is mechanistically comparable to the NiF+/CH4 system. Obviously, the ligands X act as a mechanistic distributor to switch between single vs. two‐state reactivity patterns.
Photocycloaddition Reactions of 2‐(Alk‐3‐en‐1‐ynyl)cyclohex‐2‐enones
Authors: Möbius Janne , Margaretha Paul 
Published: December 2008

AbstractThe newly synthesized 2‐(alk‐3‐en‐1‐ynyl)cyclohex‐2‐enones 4 undergo photodimerization (chemo‐ and regio‐)selectively at the exocyclic CC bond to give diastereoisomeric mixtures of 1,2‐dialkynyl‐1,2‐dimethylcyclobutanes. On irradiation of 4 in the presence of 2‐chloroacrylonitrile, cyclobutane formation occurs again (chemo‐ and regio‐)selectively at the exocyclic CC bond to afford diastereoisomeric mixtures of 2‐alkynyl‐1‐chloro‐2‐methylcyclobutanecarbonitriles. Similarly, compounds 4 undergo photoaddition to 2,3‐dimethylbuta‐1,3‐diene exclusively at the exocyclic CC bond to afford mixtures of [2+2] and [4+2] cycloadducts.
Dimeric Diterpenes from the Roots of the Mangrove Plant Ceriops tagal
Authors: Chen Jun‐De , Qiu Yan , Yang Zhi‐Wei , Lin Peng , Lin Yi‐Ming 
Published: December 2008

AbstractThree new dimeric diterpenes, tagalsin L (1), tagalsin M (2), and tagalsin N (3) were isolated from the roots of the mangrove plant Ceriops tagal. Their structures and relative configurations were elucidated by means of extensive IR, NMR, and MS analyses.
New Verticillane‐Type Diterpenoids from the Taiwanese Soft Coral Cespitularia hypotentaculata
Authors: Cheng Yuan‐Bin , Lo Kuang‐Liang , Chen Ching‐Yeu , Khalil Ashraf Taha , Shen Ya‐Ching 
Published: December 2008

AbstractInvestigation of the MeOH/CH2Cl2 extract of the soft coral Cespitularia hypotentaculata collected in Taiwan has resulted in the isolation of four new verticillane‐type diterpenoids, cespihypotins M–P (1–4). Compounds 2 and 3 are C(20)‐epimers. Compound 4 with a CO group at C(10) and a methoxycarbonyl group at C(12) may be an important precursor of cespitularins and cespihypotins. The structures of these compounds were determined on the basis of spectroscopic analyses.
The Late Pleistocene clastic deposits in the Romito Cave, southern Italy: a proxy record of environmental changes and human presence
Authors: Ghinassi Massimiliano , Colonese Andrè C. , Giuseppe Zelia Di , Govoni Lisa , Vetro Domenico Lo , Malavasi Giulia , Martini Fabio , Ricciardi Silvia , Sala Benedetto 
Published: December 2008

AbstractClastic sediments deposited in caves and rock shelters bear peculiar sedimentological characteristics and have seldom been considered as a high‐resolution proxy record of climatic or environmental changes. The Romito Cave has its entrance at 275 m above sea level, about 25 km from the Tyrrhenian coast of Calabria, southern Italy. New archaeological excavation performed since 2000 has revealed a sedimentary succession spanning the record of Gravettian to Late Epigravettian cultures (Late Pleistocene). The present study focuses on the lower part (2.5 m thick) of the succession, where three main unconformity‐bounded stratigraphic units have been recognised (labelled RM1–3). Each unit consists of water‐lain deposits indicating high‐ to low‐competence flow, capped with anthropogenic deposits. The gradual deactivation and reactivation of the water drainage between 23 475 ± 190 and 16 250 ± 500 cal. a BP is correlated with regional precipitation changes due to the onset of dry climatic conditions of the Last Glacial Maximum. However, the deactivation of cave drainage after the deposition of unit RM3, around 15 400 ± 500 cal. a BP, deviates from the regional hydrological trend of progressively increasing water discharges and is attributed to the drainage cut‐off by probable cave wall collapses. Copyright © 2008 John Wiley & Sons, Ltd.
Core Crosslinking of Biodegradable Block Copolymer Micelles Based on Poly(ester carbonate)
Authors: Hu Xiuli , Chen Xuesi , Wei Jizheng , Liu Shi , Jing Xiabin 
Published: December 2008

AbstractA biodegradable amphiphilic block copolymer, PEG‐b‐P(LA‐co‐MAC), was used to prepare spherical micelles consisting of a hydrophobic P(LA‐co‐MAC) core and a hydrophilic PEG shell. To improve their stability, the micelles were crosslinked by radical polymerization of the double bonds in the hydrophobic blocks. The crosslinked micelles had similar sizes and a narrow size distribution compared to their uncrosslinked precursor. The improved stability of the crosslinked micelles was confirmed by measurements of the CMC and a thermodynamic investigation. These micelles can internalize into Hela cells in vitro as demonstrated by inverted fluorescence microscopy and CLSM. These stabilized nanoscale micelles have potential use in biomedical applications such as drug delivery and disease diagnosis.magnified image
Polyelectrolyte Coated PLGA Nanoparticles: Templation and Release Behavior
Authors: Zhou Jie , Moya Sergio , Ma Lie , Gao Changyou , Shen Jiacong 
Published: December 2008

AbstractPoly[(D,L‐lactide)‐co‐glycolide] nanoparticles coated with polyethyleneimine on their surface were prepared by an emulsification‐solvent evaporation method and subsequently surface modified by LBL assembly. The assembly of poly(acrylic acid) and polyethyleneimine on a planar substrate and on the PLGA nanoparticles was monitored by QCM‐D,ζ‐potential, flow cytometry and TEM. Carboxylic and amino groups in the multilayers were crosslinked by carbodiimide condensation, which was also later used to graft poly(ethylene glycol) (PEG). Rhodamine 6G, 5(6)‐carboxyfluorescein and fluorescein were incorporated into the nanoparticles and their release profiles were recorded at 60 °C and at 37 °C for rhodamine 6G, for nanoparticles with a multilayer coating, and those that were crosslinked and grafted with PEG.magnified image
Hybrid Microgels with Antibacterial Properties
Authors: Häntzschel Nadine , Hund Rolf‐Dieter , Hund Heike , Schrinner Marc , Lück Christian , Pich Andrij 
Published: December 2008

AbstractIn the present work, we have used aqueous microgels as containers for the deposition of silver nanoparticles (AgNPs). It has been shown that AgNPs can be effectively incorporated in the microgel interior during the in situ reduction of silver ions. Obtained hybrid microgels with variable AgNPs loading (from 1 to 12 wt.‐%) have been used as antibacterial agents for two bacteria types. The experimental results indicate that porous microgel structure allows the release of the silver ions from the AgNPs surface into an aqueous phase. This ensures effective reduction in the number of bacterial colonies in test plates and complete bacteria killing. The antibacterial efficiency of the microgel particles increases with AgNPs loading.magnified image
Cellulose Derivatives Carrying Triphenylamine (TPA) Moieties: Synthesis and Electro‐Optical Properties
Authors: Qu Jinqing , Liao Wenbo , Chen Huanqin , Masuda Toshio 
Published: December 2008

AbstractA novel ethyl cellulose derivative [poly(1)] that carries triphenylamine moieties is synthesized with a moderate number‐average molecular weight up to 78 200 in 85% yield by the reaction of 4‐(diphenylamino)benzoic acid with the residual hydroxy group of ethyl cellulose. Poly(1) is soluble in common organic solvents including toluene, CHCl3, CH2Cl2, and tetrahydrofuran while insoluble in hexane, diethyl ether, and methanol. The polymer emits blue–green fluorescence with quantum yields up to 65% in CHCl3 and displays unique solvatochromism. The cyclic voltammograms of poly(1) indicate that the polymer carrying TPA moieties is electrochemically redox active. The onset temperature of weight loss of the poly(1) is about 177 °C according to thermogravimetric analysis in air.magnified image
Phenolic Hydroxy Groups Incorporated for the Peroxidase‐Catalyzed Gelation of a Carboxymethylcellulose Support: Cellular Adhesion and Proliferation
Authors: Ogushi Yuko , Sakai Shinji , Kawakami Koei 
Published: December 2008

AbstractThe effect of Ph‐OH group content on gelation time, mechanical properties, hydrophobicity, and cellular adhesiveness of hydrogels produced from carboxymethylcellulose derivatives is investigated. A higher Ph‐OH group content induces faster gelation and yields more brittle and hydrophobic gels. After 4 h of seeding, a larger number of L929 fibroblasts adhere to the hydrogel of the CMC‐Ph that contains 15.4 Ph‐OH groups per 100 repeat units of uronic acid (97% adhesion rate) than to the gel of CMC‐Ph with only 8.4 Ph‐OH groups (62% adhesion rate). The results demonstrate that controlling the Ph‐OH group content is an effective and useful way to control cellular adhesion and proliferation on the hydrogels, as well as gelation time and mechanical properties of the gels.magnified image
Metal dusting in CCR platforming unit
Authors: Dampc J. , Grzesik Z. , Hucińska J. 
Published: December 2008

AbstractThe mechanism of metal dusting of 9Cr‐1Mo steel in CCR platforming unit, based on examinations of a charge heater tube, is presented. The tube operated for 10 years, and the metal skin temperature was about 600 °C. The feed was composed of hydrotreated naphtha and hydrogen gas. The mechanism of the corrosion was elucidated using scanning electron microscopy, electron probe microanalysis and X‐ray diffraction technique. It has been found that the carbon deposition on the steel surface and its inward diffusion into the steel is accompanied by the outward diffusion of carbide forming elements, i.e. chromium and molybdenum. At an advanced stage of the metal dusting process a thin layer of fine chromium‐rich carbides beneath the steel surface exists. The layer is followed by a porous zone composed of big degraded primary carbides and fine carbides instead of alloy ferrite, with chromium and molybdenum content higher than the ferrite inside the tube wall. On the steel surface, a layer of coke composed of graphite, iron and M7C3 carbides is formed and the uniform wastage of the steel takes place. Possible influence of some sulphur additions to the CCR platformer feed during the future service on degradation of the subsurface material has been considered.
Exfoliation corrosion of 7150 Al alloy with various tempers and its electrochemical impedance spectroscopy in EXCO solution
Authors: Li J. F. , Jia Z. Q. , Li C. X. , Birbilis N. , Cai C. 
Published: December 2008

AbstractThe exfoliation corrosion susceptibility and electrochemical impedance spectroscopy (EIS) of 7150 Al alloys with T6, T73, and RRA (retrogression at 175 °C for 3 h) tempers in EXCO solution were investigated. The anodic equilibrium precipitate η(MgZn2) is continuous or closely spaced at the grain boundaries in the 7150‐T6 Al alloy, resulting in its greatest susceptibility to exfoliation corrosion. The grain boundary η precipitates in the RRA and T73 treated 7150 Al alloys are coarsened and show a clear discontinuous nature; they possess similar exfoliation corrosion sensitivity and their exfoliation corrosion resistance is greatly increased. At the beginning of immersion in EXCO solution, the EIS plot of the 7150 Al alloys is composed of a capacitive arc in the high to medium frequency range and an inductive component in the medium to low frequency range. As immersion time is increased, exfoliation corrosion with different corrosion ratings occurs on the surface of the 7150 Al alloy with various tempers, two capacitive arcs appear in the high to medium and medium to low frequency ranges, respectively. The fitted medium to low frequency capacitance C2 of 7150‐T6 Al alloy, corresponding to the new surface caused by the exfoliation corrosion, is much greater than that of the T73 and RRA treated 7150 Al alloy, which is consistent with the greatest exfoliation corrosion susceptibility of the 7150‐T6 Al alloy.
Influence of turbulent flow on the corrosion of Al‐Zn‐Mg galvanic anode in artificial seawater media
Authors: Quevedo M. C. , Genesca J. 
Published: December 2008

AbstractThe effect of hydrodynamics on the corrosion of Al(14 wt%)‐Zn(8 wt%)‐Mg alloy in artificial seawater media at room temperature was studied in a rotating cylinder electrode (RCE) system under turbulent flow conditions. Five different rotation rates were studied: 100, 1000, 3000, 5000, and 7000 rpm. The corrosion rates were measured by electrochemical impedance spectroscopy (EIS). For the system studied, the steady‐state corrosion potential increased with increase in rotation rate. The effect of increasing the rotation rate is to increase the availability of oxygen at the surface, which in turn will polarize the corrosion reaction in the more noble direction. The corrosion rate also increases with increase in RCE rotation rate. This reflects the fact that the rate of corrosion is controlled, at least in part, by the rate of mass transfer. In this case, the effect of increase in the rotation rate on the corrosion rate is to increase the interfacial concentration of the reactant (oxygen).
Polytriarylamines with On‐Chain Crystal Violet Moieties
Authors: Dumsch Ines , Kudla Christof J. , Scherf Ullrich 
Published: December 2008

AbstractA novel polytriarylamine (PTAA)‐type alternating copolymer with on‐chain crystal violet moieties has been generated which shows the expected strong dependence of its UV‐Vis absorption spectrum from the pH value of the surrounding medium. Starting from the colorless leucocrystal violet form subsequent protonation/water elimination (by trifluoroacetic acid) leads to the formation of a blue colored, cationic copolymer with on‐chain crystal violet units that displays a characteristic Vis absorption band peaking at 627 nm. Further protonation leads to the generation of the corresponding dicationic species which is accompanied by a red shift of the long wavelength absorption maximum to 713 nm. The novel pH‐sensitive polytriarylamine derivatives will be investigated as potential p‐type semiconductors for OFET (gas) sensors.magnified image
Functionalization of Macroporous Organic Polymer Monolith Based on Succinimide Ester Reactivity for Chiral Capillary Chromatography: A Cyclodextrin Click Approach
Authors: Guerrouache Mohamed , Millot Marie‐Claude , Carbonnier Benjamin 
Published: December 2008

AbstractMacroporous cross‐linked organic polymer based on N‐acryloxysuccinimide (NAS) and ethylene dimethacrylate (EDMA) was prepared inside 75 µm id fused silica capillary as a functionalizable monolithic stationary phase for chromatographic applications. Succinimide groups on the monolith surface provide reactive sites able to react readily through standard electrophile–nucleophile chemistry. Propargylamine was used to prepare alkyne functionalized poly(NAS‐co‐EDMA). Onto this azido‐reactive polymer surface was grafted β‐cyclodextrin (CD) via a triazole ring utilizing the copper(I)‐catalyzed 1,3‐dipolar cyclo‐addition reaction. Chemical characterization was performed in situ after each synthetic step by means of Raman spectroscopy. Good enantioseparations of flavanone enantiomers, chosen as test chiral compound, were achieved under reversed phase conditions by both capillary electrochromatography and nano‐liquid chromatography (nano‐LC) techniques. These results demonstrate the potentiality and usefulness of click chemistry in the preparation of β‐CD containing chiral organic polymer monolith.magnified image
Swelling Behaviour of Isotropic Poly(n‐butyl acrylate) Networks in Isotropic and Anisotropic Solvents
Authors: Youcef Boumédiène Dali , Bouchaour Tewfik , Maschke Ulrich 
Published: December 2008

AbstractSummary: The swelling properties of photochemically crosslinked poly(n‐butyl acrylate) (PABu) networks in isotropic and anisotropic solvents were investigated experimentally. The purpose of this study was to examine the swelling kinetics of PABu networks in isotropic solvents and to compare the results obtained which those observed in the case of the low molecular weight liquid crystal 4‐cyano‐4′‐n‐pentyl‐biphenyl known as 5CB. The phase diagrams were established in terms of composition and temperature for isotropic solvents, as toluene, acetone, cyclohexane, and methanol, and 5CB, using the plateau values corresponding to equilibrium states of swelling. The polymer networks were prepared via free radical polymerization/crosslinking processes by ultraviolet (UV) radiation of initial mixtures made up from a monomer, a crosslinker, and a photoinitiator. PABu networks with several crosslinking densities were formed using different quantities of difunctional monomer hexanedioldiacrylate (HDDA). Immersion of these networks in excess solvent allows measuring the solvent uptake by determination of the weight in isotropic solvents and diameter in an anisotropic solvent (5CB). Swelling data were rationalized by calculating weight and diameter ratios considering swollen to dry network states of the samples.
pH‐Dependent Behavior of Hydrophobically Modified Polyelectrolyte Shells of Polymeric Nanoparticles
Authors: Procházka Karel , Matějíček Pavel , Uchman Mariusz , Štěpánek Miroslav , Humpolíčková Jana , Hof Martin , Špírková Milena 
Published: December 2008

AbstractSummary: The self‐assembled core‐shell nanoparticles based on fluorescently double‐tagged high‐molar‐mass polystyrene‐block‐poly(methacrylic acid), PS‐PMA, were prepared in aqueous buffers by dialysis from 1,4‐dioxane – water mixtures. The conformations of shell‐forming PMA chains were studied using nonradiative excitation energy transfer measurements. The study shows that two populations of distinctly different conformations (collapsed and stretched) coexist in the shell and their ratio depends on pH.
Effect of laser welding parameters on fusion zone morphological, mechanical and microstructural characteristics of AISI 304 stainless steel
Authors: Çelen S. , Karadeniz S. , Özden H. 
Published: December 2008

AbstractNowadays, the Nd:YAG laser has been a promising key tool for joining thin components. In this research, mechanical and microstructural properties of laser welded thin austenitic stainless steel sheets were investigated with experimental investigations, as a function of laser welding parameters. Butt welded joints were made using a Nd:YAG laser in the pulsed wave mode. The appropriate laser welding parameters were found in order to obtain quality and strong weld seam. The pulsed laser seam welding process is controlled by a variety of parameters. We focus on the effects of the several processing parameters on mechanical and microstructural characteristics of joint and weld quality. The aim of this research was to evaluate the influence of these processing parameters on joint strength and microstructure. And also we examined the weldability of stainless steels in butt joint configuration by a pulsed Nd:YAG laser beam.