bluuebunny/crossref_metadata_2025_split huggingface dataset:
When it hurts, a positive attitude may help: association of positive affect with daily walking in knee osteoarthritis. Results from a multicenter longitudinal cohort study
Authors: White Daniel K. , Keysor Julie J. , Neogi Tuhina , Felson David T. , LaValley Michael , Gross K. Doug , Niu Jingbo , Nevitt Michael , Lewis Cora E. , Torner Jim , Fredman Lisa 
Published: April 2012

AbstractObjectiveWhile depressive symptoms and knee pain are independently known to impede daily walking in older adults, it is unknown whether positive affect promotes daily walking. This study investigated this association among adults with knee osteoarthritis (OA) and examined whether knee pain modified this association.MethodsThis study is a cross‐sectional analysis of the Multicenter Osteoarthritis Study. We included 1,018 participants (mean ± SD age 63.1 ± 7.8 years, 60% women) who had radiographic knee OA and had worn a StepWatch monitor to record their number of steps per day. High and low positive affect and depressive symptoms were based on the Center for Epidemiologic Studies Depression Scale. Knee pain was categorized as present in respondents who reported pain on most days at both a clinic visit and a telephone screening.ResultsCompared to respondents with low positive affect (27% of all respondents), those with high positive affect (63%) walked a similar number of steps per day, while those with depressive symptoms (10%) walked less (adjusted β −32.6 [95% confidence interval (95% CI) −458.9, 393.8] and −579.1 [95% CI −1,274.9, 116.7], respectively). There was a statistically significant interaction of positive affect by knee pain (P = 0.0045). Among the respondents with knee pain (39%), those with high positive affect walked significantly more steps per day (adjusted β 711.0 [95% CI 55.1, 1,366.9]) than those with low positive affect.ConclusionHigh positive affect was associated with more daily walking among adults with painful knee OA. Positive affect may be an important psychological factor to consider for promoting physical activity among people with painful knee OA.
Chiral Phosphoric Acid‐Catalyzed Asymmetric Oxidation of Aryl Alkyl Sulfides and Aldehyde‐Derived 1,3‐Dithianes: Using Aqueous Hydrogen Peroxide as the Terminal Oxidant
Authors: Liu Zhao‐Min , Zhao Hua , Li Mei‐Qiu , Lan Yu‐Bao , Yao Qi‐Bo , Tao Jing‐Chao , Wang Xing‐Wang 
Published: April 2012

Abstract(R)‐1,1′‐Binaphthyl‐2,2′‐diol (R‐BINOL) derived chiral phosphoric acids have been explored as organocatalysts for the asymmetric oxidation of a series of aryl alkyl sulfides and 1,3‐dithianes derived from aldehydes with aqueous hydrogen peroxide (H2O2) as the terminal oxidant. The enantiomerically enriched sulfoxides are obtained in moderate to excellent yield (up to 99%) with excellent diastereoselectivity (up to >99:1 dr) and moderate to good enantioselectivity (up to 91:9 er). In particular, the present protocol stereoselectively provides an efficient access to enantiomerically enriched aryl alkyl sulfoxides and dithioacetal mono‐sulfoxides, which strictly restrains the formation of the undesirable by‐products: sulfones or disulfoxides. The tracking experiments also verify that this approach proceeds via a direct sulfoxidation process, instead of a kinetic resolution route by overoxidation of the resulting sulfoxides.
Olefin Metathesis on a TLC Plate as a Tool for a High‐Throughput Screening of Catalyst‐Substrate Sets
Authors: Cabrera José , Padilla Robin , Dehn Richard , Deuerlein Stephan , Gułajski Łukasz , Chomiszczak Ewa , Teles J. Henrique , Limbach Michael , Grela Karol 
Published: April 2012

AbstractA methodology for screening either various catalysts for a given metathesis reaction, i.e., ring opening‐ring closing alkene metathesis (RO‐RCM) and cross‐metathesis (CM), or various substrates for a given pre‐catalyst on a thin layer chromatography (TLC) plate has been developed. As the substrates elute with the solvent, this TLC‐based system acts as a heterogeneous catalyst bed (“TLC reactor”). Selected promising catalyst candidates were screened on a TLC plate and their initial catalytic potential as observed in the TLC test was later fully confirmed in a classical heterogeneous reaction set‐up using standard commercially available silica (D11‐10). Reacting polyfunctional, natural product‐like substrates in our TLC reactor allows the simultaneous screening of various substrates and the convenient micro‐scale preparation and isolation of potentially biologically active products.
Bioinspirierte künstliche funktionelle Nanokanäle: von der symmetrischen zur unsymmetrischen Modifikation
Authors: Hou Xu , Zhang Huacheng , Jiang Lei 
Published: April 2012

AbstractDie Natur hat über die Jahrmillionen komplexe Prozesse hervorgebracht, die über ausgeklügelte Kontrollmechanismen verfügen. Das Prinzip, von der Natur zu lernen, spielt bei der Entwicklung “intelligenter” Materialien und Systeme seit langem eine tragende Rolle. Biologische Nanokanäle, typischerweise Ionenkanäle, spielen zum Beispiel eine gewichtige Rolle bei den grundlegenden biochemischen Prozessen in der Zelle. Die Entwicklung biomimetischer Nanokanäle wurde durch Ionenkanäle angeregt, deren Komponenten unsymmetrisch über die Membran verteilt sind, und präsentiert sich gegenwärtig als ein vielseitiges Forschungsgebiet. Die Gestaltung neuer biomimetischer Kanäle umfasst den Einsatz von unterschiedlich geformten Kanälen, von Molekülen, die auf unterschiedliche Stimuli reagieren, und von unterschiedlichen Methoden zur symmetrischen oder unsymmetrischen Modifikation.
Building Bio‐Inspired Artificial Functional Nanochannels: From Symmetric to Asymmetric Modification
Authors: Hou Xu , Zhang Huacheng , Jiang Lei 
Published: April 2012

AbstractOver millions of years, complex processes of intelligent control have evolved in nature. Learning from nature is a continuing theme in the development of smart materials and intelligent systems. For example, biological nanochannels, which are typically ion channels, play a very important role in basic biochemical processes in cells. Inspired by ion channels, in which the components are asymmetrically distributed between the membrane surfaces, the generation of biomimetic smart nanochannels is a broad and varied scientific research field. The design and development of new biomimetic channels includes the use of different shapes of channels, different stimuli‐responsive molecules, and different symmetric/asymmetric modification methods. In this Minireview, we summarize recent developments in building functional nanochannels by applying various symmetric and asymmetric modifications.
Effects of long chain branching on melt fractures in capillary extrusion of metallocene‐catalyzed linear low‐density polyethylene melts
Authors: Yoo Taehyun , Kim Dong Hak , Son Younggon 
Published: April 2012

AbstractTo investigate the effect of long chain branching (LCB) on melt fractures of metallocene‐catalyzed linear low‐density polyethylene (mLLDPE), we prepared a series of sparsely long‐chain‐branched mLLDPEs with well‐defined degrees of LCB. Gross melt fractures were observed to decrease as the degree of LCB increases. This is in accordance with a prediction based on the observation that LCB enhances chain entanglement and consequently increases the melt strength of a polymer. However, sharkskin melt fracture (SMF) was observed to be more severe with the degree of LCB. There have been debates over the effect of LCB on SMF. According to a well‐known mechanism of SMF, SMF is expected to decrease with the degree of LCB. Therefore, the majority of research groups believe that SMF decreases with the degree of LCB. This study clearly shows that the SMF becomes more severe with an increase of the degree of LCB and suggests another possible mechanism for the SMF. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Cellulose‐nanowhisker‐templated synthesis of titanium dioxide/cellulose nanomaterials with promising photocatalytic abilities
Authors: Liu Shilin , Tao Dandan , Bai Huiyu , Liu Xiaoya 
Published: April 2012

AbstractBy using native cellulose nanowhiskers as green templates, we prepared TiO2/cellulose nanomaterials via a sol–gel process from the hydrolysis of Ti(OC2H5)4. The structures and properties of the composite nanoparticles were characterized with X‐ray diffraction, transmission electron microscopy, thermogravimetric analysis, ultraviolet–visible spectroscopy, and photocatalytic degradation tests. The TiO2/cellulose nanoparticles with low loadings of TiO2 nanoparticles exhibited obvious quantum size effects and lower band gaps. The composite nanoparticles had promising photocatalytic activity for the photodegradation of a methyl orange solution under weak UV light irradiation. Furthermore, they exhibited good stability against photocorrosion, so it is possible that they could be used in the photodegradation of organic pollutants. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Electrical and thermal properties of kraft paper reinforced with montmorillonite
Authors: Liao Ruijin , Zhang Fuzhou , Yang Lijun 
Published: April 2012

AbstractKraft‐montmorillonite composites (K‐MMT) with different weight percent of MMT and different stirring time were prepared successfully. The electrical properties and thermal stability of K‐MMT were investigated. The breakdown voltage of K‐MMT (9 wt % MMT, stirring 12 min) was increased to 60 kV/mm from 50.3 kV/mm of blank Kraft. With the increase of MMT, the relative permittivity had a corresponding reduction. The relative permittivity was in the range of 2.29–2.42 at 50 Hz. The thermal stability of K‐MMT, Kraft, and MMT were also measured. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Poly(trimethylene terephthalate‐block‐tetramethylene oxide) elastomer/single‐walled carbon nanotubes nanocomposites: Synthesis, structure, and properties
Authors: Szymczyk Anna 
Published: April 2012

AbstractNanocomposites based on poly(trimethylene terephthalate)‐block‐poly(tetramethylene oxide) (PTT‐PTMO)‐segmented copolymer and COOH‐functionalized single‐walled carbon nanotubes (SWCNTs) were prepared by in situ polymerization method. The obtained nanocomposites were characterized by thermogravimetric analysis, scanning electron microscopy, differential scanning calorimetry (DSC), DMTA, wide‐angle x‐ray scattering (WAXS), small‐angle X‐ray scattering, and tensile testing. The nanocomposites with low SWCNTs loading (<0.5 wt %) shows uniform dispersion of CNT in polymer matrix. As the SWCNTs loading in the nanocomposites increase, the significant improvement of thermo‐oxidative stability was observed. It was found that the nanocomposites have slightly higher degree of crystallinity (determined by DSC and WAXS) of poly(trimethylene terephthalate) (PTT) hard phase than neat PTT‐PTMO copolymer. The melting point of PTT hard phase and glass transition temperature of poly(tetramethylene oxide)‐rich phase were not affected by the presence of CNTs in polymer matrix. The SWCNTs played a role as nucleating agent in PTT‐PTMO matrix, which led to increase in the crystallization rate. Tensile tests showed that the tensile strength of the nanocomposites with 0.05–0.3 wt % loading of SWCNTs have improved tensile strength in comparison to the neat PTT‐PTMO copolymer without reduction elongation at break. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Are They Linear, Bent, or Cyclic? Quantum Chemical Investigation of the Heavier Group 14 and Group 15 Homologues of HCN and HNC
Authors: Devarajan Deepa , Frenking Gernot 
Published: April 2012

AbstractThe singlet potential‐energy surface (PES) of the system involving the atoms H, X, and E (the (H, X, E) system) in which X=N–Bi and E=C–Pb has been explored at the CCSD(T)/TZVPP and BP86/TZ2P+ levels of theory. The nature of the XE bonding has been analyzed with charge‐ and energy‐partitioning methods. The calculations show that the linear isomers of the nitrogen systemslin‐HENandlin‐HNEare minima on the singlet PES. The carbon compoundlin‐HCN(HCN=hydrogen cyanide) is 14.9 kcal mol−1lower in energy thanlin‐HNCbut the heavier group 14 homologueslin‐HEN(E=Si–Pb) are between 64.8 and 71.5 kcal mol−1less stable than thelin‐HNEisomers. The phosphorous system (H, P, E) exhibits significant differences concerning the geometry and stability of the equilibrium structures compared with the nitrogen system. The linear formlin‐HEPof the former system is much more stable thanlin‐HPE. The moleculelin‐HCPis the only minimum on the singlet PES. It is 78.5 kcal mol−1lower in energy thanlin‐HPC, which is a second‐order saddle point. The heavier homologueslin‐HPE, in which E=Si–Pb, are also second‐order saddle points, whereas thebent‐HPEstructures are the global minima on the PES. They are between 10.3 (E=Si) and 36.5 kcal mol−1(E=Pb) lower in energy thanlin‐HEP. Thebent‐HPEstructures possess rather acute bending angles H‐P‐E between 60.1 (E=Si) and 79.7° (E=Pb). The energy differences between the heavier group 15 isomerslin‐HEX(X=P–Bi) and the bent structuresbent‐HXEbecome continuously smaller. The silicon specieslin‐HSiBiis even 3.1 kcal mol−1lower in energy thanbent‐HBiSi. The bending angle H‐X‐E becomes more acute when X becomes heavier. The drastic energy differences between the isomers of the system (H, X, E) are explained with three factors that determine the relative stabilities of the energy minima: 1) The different bond strength between the hydrogen bonds HX and HE. 2) The electronic excitation energy of the fragment HE from the X2Π ground state to the4Σ−excited state, which is required to establish a E≡X triple bond in the moleculeslin‐HEX. 3) The strength of the intrinsic XE interactions in the molecules. The trends of the geometries and relative energies of the linear, bent, and cyclic isomers are explained with an energy‐decomposition analysis that provides deep insight into the nature of the bonding situation.
Diaminoterephthalate Turn‐On Fluorescence Probes for Thiols—Tagging of Recoverin and Tracking of its Conformational Change
Authors: Wache Nina , Schröder Claudia , Koch Karl‐Wilhelm , Christoffers Jens 
Published: April 2012

AbstractDiaminoterephthalates with a maleimide moiety were synthesized and used as fluorescence dyes for sensing thiols. Whereas these “NiWa Blue” dyes showed no emission, the conjugate addition of a thiol to the maleimide group turned on a fluorescence at about 400 nm when irradiating the dye at 338 nm. The neuronal‐calcium sensor protein recoverin possesses a single cysteine residue at position 39, which reacts with NiWa Blue, and is therefore labeled by a fluorophore with an emission at about 440 nm. In the absence of Ca2+, irradiation at 280 nm of a tryptophan residue in close proximity to Cys‐bound NiWa Blue lead to strong FRET, which was detected by emission of the dye at 440 nm. In the presence of Ca2+, the protein holds a conformation with distal Trp and Cys residues, thus FRET of irradiated Trp to Cys‐bound NiWa Blue was significantly weakened.
Pivaloylmetals (tBu‐COM: M=Li, MgX, K) as Equilibrium Components
Authors: Knorr R. , Böhrer G. , Schubert B. , Böhrer P. 
Published: April 2012

AbstractShort‐lived pivaloylmetals, (H3C)3C‐COM, were established as the reactive intermediates arising through thermal heterolytic expulsion of O=CtBu2 from the overcrowded metal alkoxides tBuC(=O)‐C(‐OM)tBu2 (M=MgX, Li, K). In all three cases, this fission step is counteracted by a faster return process, as shown through the trapping of tBu‐COM by O=C(tBu)‐C(CD3)3 with formation of the deuterated starting alkoxides. If generated in the absence of trapping agents, all three tBu‐COM species “dimerize” to give the enediolates MO‐C(tBu)=C(tBu)‐OM along with O=CtBu2 (2 equiv). A common‐component rate depression by surplus O=CtBu2 proves the existence of some free tBu‐COM (separated from O=CtBu2); but companion intermediates with the traits of an undissociated complex such as tBu‐COM & O=CtBu2 had to be postulated. The slow fission step generating tBu‐COMgX in THF levels the overall rates of dimerization, ketone addition, and deuterium incorporation. Formed by much faster fission steps, both tBu‐COLi and tBu‐COK add very rapidly to ketones and dimerize somewhat slower (but still fairly fast, as shown through trapping of the emerging O=CtBu2 by H3CLi or PhCH2K, respectively). At first sight surprisingly, the rapid fission, return, and dimerization steps combine to very slow overall decay rates of the precursor Li and K alkoxides in the absence of trapping agents: A detailed study revealed that the fast fission step, generating tBu‐COLi in THF, is followed by a kinetic partitioning that is heavily biased toward return and against the product‐forming dimerization. Both tBu‐COLi and tBu‐COK form tBu‐CH=O with HN(SiMe3)3, but only tBu‐COK is basic enough for being protonated by the precursor acyloin tBuC(=O)‐C(‐OH)tBu2.
Strong Lewis Acids of Air‐Stable Metallocene Bis(perfluorooctanesulfonate)s as High‐Efficiency Catalysts for Carbonyl‐Group Transformation Reactions
Authors: Qiu Renhua , Xu Xinhua , Peng Lifeng , Zhao Yalei , Li Ningbo , Yin Shuangfeng 
Published: April 2012

AbstractStrong Lewis acids of air‐stable metallocene bis(perfluorooctanesulfonate)s [M(Cp)2][OSO2C8F17]2⋅nH2O⋅THF (M=Zr (2 a⋅3 H2O⋅THF), M=Ti (2 b⋅2 H2O⋅THF)) were synthesized by the reaction of [M(Cp)2]Cl2 (M=Zr (1 a), M=Ti (1 b)) with nBuLi and C8F17SO3H (2 equiv) or with C8F17SO3Ag (2 equiv). The hydrate numbers (n) of these complexes were variable, changing from 0 to 4 depending on conditions. In contrast to well‐known metallocene triflates, these complexes suffered no change in open air for a year. thermogravimetry–differential scanning calorimetry (TG‐DSC) analysis showed that 2 a and 2 b were thermally stable at 300 and 180 °C, respectively. These complexes exhibited unusually high solubility in polar organic solvents. Conductivity measurement showed that the complexes (2 a and 2 b) were ionic dissociation in CH3CN solution. X‐ray analysis result confirmed 2 a⋅3 H2O⋅THF was a cationic organometallic Lewis acid. UV/Vis spectra showed a significant red shift due to the strong complex formation between 10‐methylacridone and 2 a. Fluorescence spectra showed that the Lewis acidity of 2 a fell between those of Sc3+ (λem=474 nm) and Fe3+ (λem=478 nm). ESR spectra showed the Lewis acidity of 2 a (0.91 eV) was at the same level as that of Sc3+ (1.00 eV) and Y3+ (0.85 eV), while the Lewis acidity of 2 b (1.06 eV) was larger than that of Sc3+ (1.00 eV) and Y3+ (0.85 eV). They showed high catalytic ability in carbonyl‐compound transformation reactions, such as the Mannich reaction, the Mukaiyama aldol reaction, allylation of aldehydes, the Friedel–Crafts acylation of alkyl aromatic ethers, and cyclotrimerization of ketones. Moreover, the complexes possessed good reusability. On account of their excellent catalytic efficiency, stability, and reusability, the complexes will find broad catalytic applications in organic synthesis.
Rh‐Catalyzed [5+1] and [4+1] Cycloaddition Reactions of 1,4‐Enyne Esters with CO: A Shortcut to Functionalized Resorcinols and Cyclopentenones
Authors: Fukuyama Takahide , Ohta Yuko , Brancour Célia , Miyagawa Kazusa , Ryu Ilhyong , Dhimane Anne‐Lise , Fensterbank Louis , Malacria Max 
Published: April 2012

AbstractWe have developed novel Rh‐catalyzed [n+1]‐type cycloadditions of 1,4‐enyne esters, which involve an acyloxy migration as a key step. The efficient preparation of functionalized resorcinols, including biaryl derivatives, from readily available 1,4‐enyne esters and CO was achieved by Rh‐catalyzed [5+1] cycloaddition accompanied by 1,2‐acyloxy migration. When enyne esters had an internal alkyne moiety, the reaction proceeded by a [4+1]‐type cycloaddition involving 1,3‐acyloxy migration, leading to cyclopentenones.
Comparison of two views of maximum entropy in biodiversity: Frank (2011) and Pueyo et al. (2007)
Authors: Pueyo Salvador 
Published: April 2012

AbstractAn increasing number of authors agree in that the maximum entropy principle (MaxEnt) is essential for the understanding of macroecological patterns. However, there are subtle but crucial differences among the approaches by several of these authors. This poses a major obstacle for anyone interested in applying the methodology of MaxEnt in this context. In a recent publication, Frank (2011) gives some arguments why his own approach would represent an improvement as compared to the earlier paper by Pueyo et al. (2007) and also to the views by Edwin T. Jaynes, who first formulated MaxEnt in the context of statistical physics. Here I show that his criticisms are flawed and that there are fundamental reasons to prefer the original approach.
Phylogeography ofTibouchina papyrus(Pohl) Toledo (Melastomataceae), an endangered tree species from rocky savannas, suggests bidirectional expansion due to climate cooling in the Pleistocene
Authors: Collevatti Rosane Garcia , de Castro Thaís Guimarães , de Souza Lima Jacqueline , de Campos Telles Mariana Pires 
Published: April 2012

AbstractMany endemic species present disjunct geographical distribution; therefore, they are suitable models to test hypotheses about the ecological and evolutionary mechanisms involved in the origin of disjunct distributions in these habitats. We studied the genetic structure and phylogeography ofTibouchina papyrus(Melastomataceae), endemic to rocky savannas in Central Brazil, to test hypothesis of vicariance and dispersal in the origin of the disjunct geographical distribution. We sampled 474 individuals from the three localities where the species is reported: Serra dos Pirineus, Serra Dourada, and Serra de Natividade. Analyses were based on the polymorphisms at cpDNA and on nuclear microsatellite loci. To test for vicariance and dispersal we constructed a median‐joining network and performed an analysis of molecular variance (AMOVA). We also tested population bottleneck and estimated demographic parameters and time to most recent common ancestor (TMRCA) using coalescent analyses. A remarkable differentiation among populations was found. No significant effect of population expansion was detected and coalescent analyses showed a negligible gene flow among populations and an ancient coalescence time for chloroplast genome. Our results support that the disjunct distribution ofT. papyrusmay represent a climatic relict. With an estimated TMRCA dated from ∼836.491 ± 107.515 kyr BP (before present), we hypothesized that the disjunct distribution may be the outcome of bidirectional expansion of the geographical distribution favored by the drier and colder conditions that prevailed in much of Brazil during the Pre‐Illinoian glaciation, followed by the retraction as the climate became warmer and moister.