bluuebunny/crossref_metadata_2025_split huggingface dataset:
Highly Enantioselective Michael Addition of α‐Substituted Cyano Ketones to β,γ‐Unsaturated α‐Keto Esters using Bifunctional Thiourea‐Tertiary Amine Catalysts: An Easy Access to Chiral Dihydropyrans
Authors: Zhao Sheng‐Li , Zheng Chang‐Wu , Wang Hai‐Feng , Zhao Gang 
Published: November 2009

AbstractAn asymmetric Michael addition of α‐substituted cyano ketones to β,γ‐unsaturated α‐keto esters to form chiral dihydropyrans catalyzed by a series of α‐amino acid‐derived thiourea‐tertiary amines is presented. A novel tyrosine‐derived thiourea catalyst was identified as the optimal catalyst providing the desired product in 91–95% yields and with 90–96% ee at a low catalyst loading of 2.0 mol%. The utility of the reaction was exemplified by facile conversion of the dihydropyran product into pharmaceutically useful dihydropyridine.
Intramolecular Photochemical Cross‐Coupling Reactions of 3‐Acyl‐2‐haloindoles and 2‐Chloropyrrole‐3‐carbaldehydes with Substituted Benzenes
Authors: Lu Shen‐Ci , Zhang Xi‐Xia , Shi Zong‐Jun , Ren Yu‐Wei , Li Bing , Zhang Wei 
Published: November 2009

AbstractHighly efficient syntheses of indolo[2,1‐a]isoquinolines, indolo[2,1‐a][2]benzazepines, pyrrolo[2,1‐a]isoquinolines and pyrrolo[1,2‐a]benzazepines in excellent yields have been achieved by the intramolecular photochemical cross‐coupling reactions of 3‐acyl‐2‐halo‐N‐(ω‐arylalkyl)indoles and 2‐chloro‐N‐(ω‐arylalkyl)pyrrole‐3‐carbaldehydes in acetone. A new heterocyclic ring system – pyrrolo[1,2‐d][1,4]benzoxazepine – has also been constructed for the first time in this work by the photocyclization of 2‐chloro‐N‐(2‐phenoxyethyl)pyrrole‐3‐carbaldehyde.
Effect of Long Chain Fatty Acids on Organocatalytic Aqueous Direct Aldol Reactions
Authors: Mase Nobuyuki , Noshiro Naoyasu , Mokuya Asuka , Takabe Kunihiko 
Published: November 2009

AbstractIn an organocatalyzed, aqueous direct aldol reaction, the addition of a long chain fatty acid (1 mol%) such as stearic acid or erucic acid improved the aldol product yield and the enantioselectivity with low catalyst loading (1 mol%). The small particle size of the emulsion (less than 1 μm) was a key to the enhanced reactivity as shown by dynamic light scattering (DLS) analyses.
Facile Synthesis of Polycyclic Fluorene Derivatives via a Palladium‐Catalyzed Coupling, Propargyl‐Allenyl Isomerization and Schmittel Cyclization Sequence
Authors: Shen Ruwei , Chen Linzhu , Huang Xian 
Published: November 2009

AbstractA stepwise process involving Sonogashira coupling, propargyl‐allenyl isomerization and Schmittel cyclization has been realized, leading to an efficient synthesis of polycyclic fluorene derivatives from readily available starting materials. The reaction features the formation of three new carbon‐carbon bonds to construct the benzene unit together with an efficient assembly of three or four rings in a single operative step.
Gold Catalysis: Anellated Heterocycles and Dependency of the Reaction Pathway on the Tether Length
Authors: Hashmi A. Stephen K. , Pankajakshan Sreekumar , Rudolph Matthias , Enns Elisabeth , Bander Thomas , Rominger Frank , Frey Wolfgang 
Published: November 2009

AbstractA series of furan‐yne substrates with an arylalkynylamide substructure were prepared and subjected to catalytic amounts of phosphanegold(I) complexes. With two carbon atoms in the tether between the arylalkynylamide and the furan subunits, the formation of benzoanellated heterocycles was observed, a number of interesting heterocyclic framworks could be accessed in this way. With three carbon atoms in the tether, the outcome was quite different, cyclopentadiene derivatives anellated to tetrahydropyridine rings were isolated. The two different pathways suggested are supported by calculations regarding the selectivity‐determining step.
Prediction of flammability characteristics of pure hydrocarbons from molecular structures
Authors: Pan Yong , Jiang Juncheng , Ding Xiaoye , Wang Rui , Jiang Jiajia 
Published: November 2009

AbstractA quantitative structure‐property relationship study is performed to develop mathematical models for predicting the flammability characteristics of pure hydrocarbons. The molecular structures of the compounds are numerically represented by various kinds of molecular descriptors. Genetic algorithm based multiple linear regression is used to select most statistically effective descriptors on the flash point, the autoignition temperature, and the lower and upper flammability limits of hydrocarbons, respectively. The resulted models are four multilinear equations. These models are very simple and can predict the flash point, the autoignition temperature, and the lower and upper flammability limits for the test set with average absolute errors of 5.41 K, 28.00 K, 0.044 vol %, and 0.503 vol %, respectively. The models are further compared with other published method and are shown to be more superior. The proposed method can be used to predict the flammability characteristics of hydrocarbons from the knowledge of only the molecular structures. © 2009 American Institute of Chemical Engineers AIChE J, 2010
DFT Study on Tautomerism of Dihydro‐2H‐1,5‐benzodiazepin‐2‐ones and Dihydro‐2H‐1,5‐benzodiazepine‐2‐thiones
Authors: Okovytyy Sergiy I. , Sviatenko Liudmyla K. , Gaponov Alexandr A. , Kasyan Liliya I. , Tarabara Igor N. , Leszczynski Jerzy 
Published: November 2009

AbstractDFT calculations were performed to study the tautomeric rearrangements in the isolated, monoethanol‐ and diethanol‐solvated, and dimeric forms of 4‐methyl‐1,3‐dihydro‐2H‐1,5‐benzodiazepin‐2‐one and 4‐methyl‐1,3‐dihydro‐2H‐1,5‐benzodiazepine‐2‐thione. Molecular geometries of the tautomers and transition state structures were optimized at the B3LYP/6‐31G(d) and B3LYP/6‐311++G(d,p) levels of theory. The long‐range solvent effects on the geometrical and energy parameters of tautomerization were also analyzed by use of the PCM model. The calculated relative Gibbs free energies were used to estimate the equilibrium constants. It was shown that the keto forms are more stable than the enol tautomers both in the gas phase and in solution. The activation energies of tautomerization increase in the following order: lactim–lactam, keto–enol, and imine–enamine transformations. Proton transfer in the solvated complexes and dimers is virtually effortless in relation to that in the isolated tautomers. The bulk of solvent does not substantially affect either the activation energies or the equilibrium constants. The differences between the tautomerism in 4‐methyl‐1,3‐dihydro‐2H‐1,5‐benzodiazepin‐2‐one and in 4‐methyl‐1,3‐dihydro‐2H‐1,5‐benzodiazepine‐2‐thione are discussed.
Cyclopentadienyl‐Free Rare‐Earth Metal Amides [{(CH2SiMe2){(2,6‐iPr2C6H3)N}2}Ln{N(SiMe3)2}(THF)] as Highly Efficient Versatile Catalysts for C–C and C–N Bond Formation
Authors: Wu Yunjun , Wang Shaowu , Zhang Lijun , Yang Gaosheng , Zhu Xiancui , Zhou Zhihong , Zhu Hong , Wu Shihong 
Published: November 2009

AbstractEfficient methods have been developed for the direct synthesis of amides from aldehydes and a straightforward route to propiolamidines using cyclopentadienyl‐free rare‐earth metal amides [{(CH2SiMe2){(2,6‐iPr2C6H3)N}2}Ln{N(SiMe3)2}(THF)] [Ln = Yb (1), Y (2), Dy (3), Sm (4), Nd (5)] as versatile catalysts. The results indicate that in the direct synthesis of amides from aldehydes the catalysts have the activity order 2 > 1  3  4  5. These methods have the advantage of easy preparation of the catalysts, low catalyst loading, high conversion of substrates to products, mild reaction conditions, and compatibility with a wide range of substrates.
Synthesis of Novel Substituted Phenanthrenes and Polycyclic Heteroarenes by Pd‐Catalyzed, Direct, Intramolecular Arylation/Heteroarylation
Authors: Yadav Ashok K. , Ila Hiriyakkanavar , Junjappa Hiriyakkanavar 
Published: November 2009

AbstractA novel route to substituted phenanthrenes and polycyclic heteroarenes by direct, Pd‐catalyzed, intramolecular arylation/heteroarylation of 2‐(2‐bromoaryl/heteroaryl)‐3‐(aryl/heteroaryl)‐3‐(methylthio)acrylonitriles has been reported.
Coloring plane graphs with independent crossings
Authors: Král' Daniel , Stacho Ladislav 
Published: November 2009

AbstractWe show that every plane graph with maximum face size four in which all faces of size four are vertex‐disjoint is cyclically 5‐colorable. This answers a question of Albertson whether graphs drawn in the plane with all crossings independent are 5‐colorable. © 2009 Wiley Periodicals, Inc. J Graph Theory 64: 184–205, 2010
The geometry oft‐spreads ink‐walk‐regular graphs
Authors: Dalfó C. , Fiol M. A. , Garriga E. 
Published: November 2009

AbstractA graph is walk‐regular if the number of closed walks of length ℓ rooted at a given vertex is a constant through all the vertices for all ℓ. For a walk‐regular graphGwithd+1 different eigenvalues and spectrally maximum diameterD=d, we study the geometry of itsd‐spreads, that is, the sets of vertices which are mutually at distanced. When these vertices are projected onto an eigenspace of its adjacency matrix, we show that they form a simplex (or tetrahedron in a three‐dimensional case) and we compute its parameters. Moreover, the results are generalized to the case ofk‐walk‐regular graphs, a family which includes both walk‐regular and distance‐regular graphs, and theirt‐spreads or vertices at distancetfrom each other. © 2009 Wiley Periodicals, Inc. J Graph Theory 64:312–322, 2010
Phonon properties of nanosized bismuth layered ferroelectric material—Bi2WO6
Authors: Ma̧czka M. , Macalik L. , Hermanowicz K. , Kȩpiński L. , Tomaszewski P. 
Published: November 2009

AbstractNanosized Bi2WO6 was synthesized by a mild hydrothermal crystallization process. This method allowed obtaining plate‐like crystallites of very small thickness (down to 3 nm). The effect of particle size on the structure and properties of Bi2WO6 was studied by X‐ray diffraction (XRD), transmission electron microscopy, and Raman and infrared spectroscopies. It has been shown that the orthorhombic distortion decreases with decreasing particle size, but the structure of the smallest crystallites is still orthorhombic. Raman studies have also revealed a very strong intensity decrease for those modes that appear mainly for incident and scattered light polarized perpendicular to the layers. This behavior has been attributed to a decrease in the orthorhombic distortion and a plate‐like shape of the nanocrystallites. Copyright © 2009 John Wiley & Sons, Ltd.
Peptide‐Functionalized Thermo‐Sensitive Hydrogels for Sustained Drug Delivery
Authors: Xun Wei , Wu De‐Qun , Li Ze‐Yong , Wang Hui‐Yuan , Huang Fu‐Wei , Cheng Si‐Xue , Zhang Xian‐Zheng , Zhuo Ren‐Xi 
Published: November 2009

AbstractIn this study, a KRGDKK (Lys‐Arg‐Gly‐Asp‐Lys‐Lys) peptide with a RGD sequence is utilized as a functional group to synthesize a novel thermo‐sensitive hydrogel. The KRGDKK peptide prepared by a solid phase synthesis approach is coupled to the ends of a poly[(ε‐caprolactone)‐co‐lactide]‐poly(ethylene glycol)‐poly[(ε‐caprolactone)‐co‐lactide] (PCLA‐PEG‐PCLA) triblock copolymer to obtain peptide‐PCLA‐PEG‐PCLA‐peptide. The self‐assembly behavior of both PCLA‐PEG‐PCLA and peptide‐PCLA‐PEG‐PCLA‐peptide copolymers in aqueous solution is investigated, and hydrogels prepared from PCLA‐PEG‐PCLA and peptide‐PCLA‐PEG‐PCLA‐peptide are also prepared. An in vitro cell viability study demonstrated that the peptide‐PCLA‐PEG‐PCLA‐peptide hydrogels do not exhibit an apparent cytotoxicity, which suggests that the hydrogels have promising potential as injectable drug‐delivery systems. Furthermore, compared with the PCLA‐PEG‐PCLA hydrogels, the peptide‐PCLA‐PEG‐PCLA‐peptide hydrogels display improved mechanical properties because of hydrogen bonding between the amino groups of KRGDKK. An in vitro drug release study showed that the peptide‐PCLA‐PEG‐PCLA‐peptide hydrogels exhibit outstanding controlled release properties and the release of the drug could be sustained for more than a month without initial burst.magnified image
Decidability and Specker sequences in intuitionistic mathematics
Authors: Ardeshir Mohammad , Ramezanian Rasoul 
Published: November 2009

AbstractA bounded monotone sequence of reals without a limit is called a Specker sequence. In Russian constructive analysis, Church's Thesis permits the existence of a Specker sequence. In intuitionistic mathematics, Brouwer's Continuity Principle implies it is false that every bounded monotone sequence of real numbers has a limit. We claim that the existence of Specker sequences crucially depends on the properties of intuitionistic decidable sets. We propose a schema (which we call ED) about intuitionistic decidability that asserts “there exists an intuitionistic enumerable set that is not intuitionistic decidable” and show that the existence of a Specker sequence is equivalent to ED. We show that ED is consistent with some certain well known axioms of intuitionistic analysis as Weak Continuity Principle, bar induction, and Kripke Schema. Thus, the assumption of the existence of a Specker sequence is conceivable in intuitionistic analysis. We will also introduce the notion of double Specker sequence and study the existence of them (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Non‐isolated quasi‐degrees
Authors: Batyrshin Ilnur I. 
Published: November 2009

AbstractWe show that non‐isolated from below 2‐c.e. Q ‐degrees are dense in the structure of c.e. Q ‐degrees. We construct a 2‐c.e. Q ‐degree, which can't be isolated from below not only by c.e. Q ‐degrees, but by any Q ‐degree. We also prove that below any c.e. Q ‐degree there is a 2‐c.e. Q ‐degree, which is non‐isolated from below and from above (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some results in BL ‐algebras
Authors: Saeid Arsham Borumand , Motamed Somayeh 
Published: November 2009

AbstractWe define the set of double complemented elements in BL‐algebras and state and prove some theorems which determines properties of these sets. We introduce the notion of an almost top element and study the properties of these elements (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Definable group extensions in semi‐bounded o‐minimal structures
Authors: Edmundo Mário J. , Eleftheriou Pantelis E. 
Published: November 2009

AbstractIn this note we show: Let R = 〈R, <, +, 0, …〉 be a semi‐bounded (respectively, linear) o‐minimal expansion of an ordered group, and G a group definable in R of linear dimension m ([2]). Then G is a definable extension of a bounded (respectively, definably compact) definable group B by 〈Rm, +〉 (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transfer to Polymer and Long‐Chain Branching in PLP–SEC of Acrylates
Authors: Castignolles Patrice 
Published: November 2009

AbstractPulsed laser polymerization (PLP) combined with size exclusion chromatography (SEC) is the method of choice for determining propagation rate coefficients. The influence of the long‐chain branching in PLP–SEC is investigated using multiple‐detection SEC and a recently developed method to detect long‐chain branching [P. Castignolles, R. Grab, M. Parkinson, M. Wilhelm, M. Gaborieau, Polymer 2009, 50, 2373.] While little or no long‐chain branching is detected in poly(n‐butyl acrylate), the error in relevant molecular weights of poly(2‐ethylhexyl acrylate) is large (30–100%) due to long‐chain branching. Possible variations of propagation rate coefficient with alkyl groups in alkyl acrylates or with the solvent have to be reconsidered.magnified image
Cross‐Linked Multilayers of Poly(vinyl amine) as a Single Component and Their Interaction with Proteins
Authors: Dragan Ecaterina S. , Bucatariu Florin 
Published: November 2009

AbstractNovel multilayer thin films that consist solely of cross‐linked single component layers are generated by a selective cross‐linking of the poly(vinyl amine) (PVAm) layers in [PVAm/poly(acrylic acid) (PAA)]n thin films constructed either on silica particles or silicon wafers, followed by the removal of PAA. The surface topography of the (PVAm)n multilayer thin films, before and after the adsorption of human serum albumin (HSA), has been studied by atomic force microscopy on the freeze‐dried films. The decrease of the average roughness of the film after the adsorption of HSA showed the protein was adsorbed into the (PVAm)n film making these films potential reservoirs for proteins.magnified image
Curing studies of epoxy resin by 4,4′‐diaminoazobenzene as curing agent reinforced with nanosilica and nanoclay particles along with impact resistance and thermal evaluation
Authors: Barghamadi Mohamad 
Published: November 2009

AbstractThe effects of nanosilica (NS) and nanoclay (NC) particles as catalyst on the mechanism and kinetic parameters of cure reaction of DGEBA/4,4′‐diaminoazobenzene (DAAB) systems were studied. The kinetics parameters were obtained from nonisothermal differential scanning calorimeter data using the Kissinger, Ozawa, and isoconversional equations. The exothermic peak was shifted toward lower temperatures in DGEBA/DAAB/nanoparticle (NP) systems with increasing amount of the NP. However, the existence of NS and NC particles with hydroxyl groups in the structure in the mixture of DGEBA/DAAB catalyzes the cure reaction and increases the rate constant. The activation energy of cure reaction of DGEBA/DAAB systems, obtained from three methods, was in good agreement and showed a decrease when NPs were present in the mixture. The morphology of nanocomposite and dispersion of NPs in the composites was also observed using scanning electron microscopy. The impact resistance and thermogravimetric analysis of cured epoxy systems were also reported. POLYM. COMPOS., 31:1465–1473, 2010. © 2009 Society of Plastics Engineers
Detection of a related difference in efficacy of azadirachtin treatments for the control of whiteflies on Gerbera jamesonii by testing for interactions in generalised linear models
Authors: Menke Sebastian , Gerhard Daniel 
Published: November 2009

AbstractBACKGROUND: Within a project cluster, systemical effects of two neem treatments (Neem Azal™ U and Neem Pellet) on the number of Trialeurodes vaporariorum (Westw.) in Gerbera jamesonii Flori Line Maxi were investigated. In order to minimise adverse ecological effects of a product, a new plant protection product can be declared as superior to a reference if it shows the same or a higher effect at a lower dosage.RESULTS: Based on a negative binomial model, the efficacy of the two treatments is compared by applying a user‐defined interaction contrast in a multiple‐contrast test framework. The corresponding calculation of simultaneous confidence intervals for the ratio of model parameters provides conclusions about statistical significance and biological relevance. The validity of the approach is shown by a small simulation study. As a result of the experiment, besides a significant difference between two negative control treatments, no significant difference between the efficiency of the two neem treatments (Neem Azal™ U and Neem Pellet) could be detected.CONCLUSIONS: Simultaneous confidence intervals for linear combinations of parameters of generalised linear models provide a useful way to compare the efficiency of two plant protection products. The results for the azadirachtin experiment indicate that large differences between any application effects of either Neem Azal™ U or Neem Pellet cannot be expected. Copyright © 2009 Society of Chemical Industry
New forms of gentrification: issues and debates
Authors: Rérat Patrick , Söderström Ola , Piguet Etienne 
Published: November 2009

AbstractThis special issue addresses the questions of gentrification and new‐build gentrification, two processes of urban transformation that significantly contribute to the reconfiguration of the socio‐demographic profile of populations in contemporary cities. Whereas gentrification has long referred to the physical and social transformation of central areas through rehabilitation of existing housing stock and population displacement by more affluent households, the concept has recently been extended to include new high‐status developments (regeneration of brownfield sites or demolition/reconstruction of existing residential areas). Although these new developments do not always cause direct population displacement, the question of the possible indirect consequences has been critically raised while the densification of the built environment appears as a favourable outcome in a context of environmental sustainability concerns. The papers collected in this issue focus on the emerging debates surrounding the new forms of gentrification, the increased residential attractiveness of core cities, and the actors who are involved or affected by these processes. In so doing it discusses the geography of gentrification, expanding analysis towards a wide range of contexts. Copyright © 2009 John Wiley & Sons, Ltd.
Luminescent characteristics of praseodymium‐doped zinc aluminate powders
Authors: Hernández‐Pérez C. D. , García‐Hipólito M. , Álvarez‐Pérez M. A. , Álvarez‐Fregoso O. , Ramos‐Brito F. , Falcony C. 
Published: November 2009

AbstractIn this research, we report the cathodoluminescence (CL) and preliminary photoluminescence (PL) properties of praseodymium‐doped zinc aluminate powders. ZnAl2O4:Pr powders were synthesized by a very simple chemical process. X‐ray diffraction spectra indicated a cubic spinel crystalline structure with an average crystallite size of 15 nm. CL properties of the powders were studied as a function of the praseodymium concentration and electron‐accelerating potential. In this case, all the cathodoluminescent emission spectra showed main peaks located at 494, 535, 611, 646, and 733 nm, which were associated to the electronic transitions 3P0 → 3H4, 3P0 → 3H5, 3P0 → 3H6, 3P0 → 3F2, and 3P0 → 3F4 of the Pr3+ ions, respectively. A quenching of the CL, with increasing doping concentration, was observed. Also, an increment on cathodoluminescent emission intensity was observed as the accelerating voltage increased. The PL emission spectrum showed similar characteristics to those of the CL spectra. The chemical composition of the powders, as determined by energy dispersive spectroscopy, is also reported. In addition, the surface morphology characteristics of the powders are shown.
Identification of changes in the inorganic matrix of dye sensitized solar cells during preparation
Authors: Graaf Harald , Maedler Carsten , Kehr Mirko , Baumgaertel Thomas , Oekermann Torsten 
Published: November 2009

AbstractNanoporous zinc oxide films can be prepared by electrochemical co‐deposition with the dye eosin Y (EY) as template. A subsequent desorption of the dye with aqueous KOH is a key step for the increased efficiency of such dye sensitized solar cells (DSSC). In this contribution, the partial dissolving and reorganization of the zinc oxide film during the desorption step has been studied in detail by X‐ray diffraction, Kelvin probe force microscopy, and atomic force microscopy (AFM) as well as scanning electron microscopy. It is found that the reorganization leads to an enhancement of crystal orientation and a reduction of the defect concentration at the surface of zinc oxide, being a possible reason for suppressed recombination of electrons in these films. Also, an increased defect concentration in ZnO was found when co‐deposited with EY. For these co‐deposited films, AFM investigations showed a coverage of the surface with dye aggregates. High resolution AFM investigations revealed the nanocrystalline and highly porous structure of the inorganic matrix after desorption of the dye.magnified imagePhotographs of the organic/inorganic hybrid thin film material were investigated in this study. Left side: film directly after deposition, right side: after desorption of the organic dye.