bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of additives, catalyst residues, and confining substrates on the fractionated crystallization of polypropylene droplets
Authors: Langhe Deepak S. , Hiltner Anne , Baer Eric 
Published: January 2012

AbstractFractionated crystallization of Ziegler‐Natta PP (ZN‐PP) droplets produced from ZN‐PP/polystyrene (PS) multilayered films resulted in four crystallization exotherms at 40, 64, 90, and 103°C. The origins of these crystallization peaks were investigated in this article. The nucleation of ZN‐PP droplets at various crystallization exotherms was attributed to (1) various additives in ZN‐PP and PS, (2) catalyst residues present in ZN‐PP, or (3) substrate nucleation by confining matrix. Effect of various additives on the fractionated crystallization an additive‐free grade of ZN‐PP (cPP) was investigated. Crystallization of cPP droplets from 200‐nm layers showed that Irganox was responsible for crystallization of droplets at 103°C. Irgafos and ZnS did not affect the crystallization of cPP droplets. We also investigated three grades of PP, which were synthesized using different catalysts. The PP grades were ZN‐PP, developmental PP (D‐PP) and metallocene PP (M‐PP). D‐PP droplets from 200‐nm layers showed crystallization at 100°C, while ZN‐PP resulted in crystallization at 90 and 103°C. It was suggested that the 90°C peak for ZN‐PP droplets was most likely due to the presence of Ziegler‐Natta catalyst residues. Crystallization of M‐PP droplets produced from 200 nm showed multiple crystallization exotherms (60 to 90°C). The effect of confining substrates on the fractionated crystallization of ZN‐PP droplets revealed heterogeneous nucleation by polycarbonate (PC) substrate. When the confining matrix was changed from polystyrene (PS) to polymethyl methacrylate (PMMA), the crystallization thermograms of ZN‐PP droplets were unaffected. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Study on the changing regularity of structure and properties of PC aged outdoor in western areas of China
Authors: Yonghao Pan , Mingjiao Yang , Shimin Han , Weibin Gao , Yi Dan 
Published: January 2012

AbstractAs an important engineering material, polycarbonate (PC) has been used widely. When exposed to the environment, PC will have aging process, which will reduce its performance and efficiency. This article studies the changing regularities of PCs structure and properties of ageing in western areas of China by measuring the change of intrinsic viscosity (IV), thermal decomposition temperature, glass transition temperature, and the groups within PC. The analysis of its IV, DSC, and thermo gravimetric analysis exhibited the same changing regularity, i.e., the aged PC (in Lasa, Yuli, and Jiangjin) experienced degradation and crosslinking, while degradation occurred earlier in the process of ageing, crosslinking predominated in later period. In addition, the results of UV absorption spectra and infrared absorption spectra showed the evidence of decomposition of the ester groups, resulting in the production of alcohol and phenol. And the results of mechanical tests indicated that the ductility disappeared mainly in the first year of outdoor aging. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Interrelation between preparation conditions, structure, and mechanical reinforcement in isoprene rubber filled with in situ generated silica
Authors: Bignotti F. , Borsacchi S. , de Santis R. , Geppi M. , Messori M. , Sudhakaran U. P. 
Published: January 2012

AbstractThe sol–gel technique was used to reinforce isoprene rubber (IR) by generating silica in situ from tetraethoxysilane (TEOS). The aim of the research was to elucidate the effect of the preparation conditions on the structural and morphological characteristics of silica and the resulting mechanical reinforcement. The structure of the in situ generated silica was analyzed by 29Si high‐resolution solid‐state NMR spectroscopy, which evidenced a high condensation degree of TEOS that decreased with increasing the sol–gel reaction time. The silica dispersion became less homogeneous as the TEOS content and the reaction time were increased. The incorporation of a coupling agent (OTES, octyltriethoxysilane) in the reaction mixture promoted full conversion of TEOS. Lower particle size, better silica dispersion, and higher filler‐matrix adhesion were noticed if the incorporation of OTES was delayed compared to TEOS. Uniaxial tensile tests evidenced that the tensile strength typically increased in the first 60 min of reaction and then leveled off. A similar behavior was observed for the high deformation stiffness, whereas at low deformations, the stiffness increased monotonically with the reaction time. In the vulcanizates with silica contents higher than 25 wt %, a drastic stiffness decrement was observed passing from low to high deformations. This reduction was ascribed to the disruption of the secondary filler network occurring in these materials when severely stretched. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Rheological properties and melt strength of LDPE during coextrusion process
Authors: Keawkanoksilp Chetporn , Apimonsiri Weerapol , Patcharaphun Somjate , Sombatsompop Narongrit 
Published: January 2012

AbstractRheological properties and mechanical strength of coextruded low‐density polyethyelene (LDPE) were studied in this work. The influences of die temperature, shear rate at skin and core layers, and number of extrusion passes at the core layer were of interest. The experimental results suggested that the viscosity and swelling behavior of LDPE coextrudate were more dependent on the shear rate of skin layer as compared with that of core layer. Increasing die temperature resulted in decreases in viscosity and die swell ratio. The reductions in viscosity and die swell ratio of the coextrudate for the reprocessing numbers 1 and 2 at the core layer arose from the disentanglement of long chain branching of LDPE molecules, while the increase of viscosity and die swell ratio for the reprocessing numbers 3 and 4 mainly involved an occurrence of crosslinking structure. For mechanical strength results, the changes in elongational stress for different shear rates, die temperature, and number of extrusion passes were in line well with the rheological measurements. That was, the higher the stored energies in polymer melts due to higher shear rates, the greater the amount of force required to conquer the elastic resistance. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
Estimating local and regional population sizes for an endangered minnow, redside dace (Clinostomus elongatus), in Canada
Authors: Poos Mark , Lawrie David , TU Christine , Jackson Donald A. , Mandrak Nicholas E. 
Published: January 2012

ABSTRACTThe Laurentian Great Lakes have undergone drastic declines in freshwater fishes, with 22 species having become extinct in the past century and many more currently at risk. One such species is the endangered minnow, the redside dace (Clinostomus elongatus), which is undergoing severe declines across its entire range.Depletion and mark–recapture surveys were used to quantify population estimates of redside dace at several spatial scales (pool, reach and catchment) across several Great Lakes tributaries in Canada.There was large variation in the local population estimates and the rate of occurrence of redside dace populations. In some cases, such as Gully Creek, a Lake Huron tributary, redside dace were widespread (9/10 of pools) but in low abundances (13.5 individuals per pool ± 5.09 ). In other cases, such as in the Don River, redside dace were highly localized (2/27 pools) but in relatively high abundance (99.2 individuals/pool ± 18.1).Extrapolated population estimates at the catchment scale showed that three of the five study populations were below conservative estimates needed for long‐term population viability.Differences in redside dace populations were driven by adjacent land‐use. Post‐hoc analyses revealed strong negative associations between population estimates and impervious land‐use (i.e. urbanization) at both the pool and sub‐catchment level.Immediate recovery actions that will focus on eliminating chronic and episodic impacts of adjacent land‐use and improve connectivity are needed to help ensure redside dace, like many freshwater species in the Laurentian Great Lakes, remain a species at risk of – rather than facing – extinction.Copyright © 2012 John Wiley & Sons, Ltd.
Morphology of the Distal Radius in Extant Hominoids and Fossil Hominins: Implications for the Evolution of Bipedalism
Authors: Tallman Melissa 
Published: January 2012

AbstractOne of the long‐standing arguments about the evolution of bipedality centers on the locomotor pattern used by the last common ancestor (LCA) of apes and humans. In particular, knuckle‐walking has been suggested as this locomotor pattern on the basis of shared morphology in the upper limb between African apes and humans and phylogenetic parsimony. Using three‐dimensional geometric morphometrics, this study tests whether the distal radius of extant hominoids is sufficient for determining locomotor pattern and the affiliations of Plio‐Pleistocene hominins to the extant taxa. Results indicate that while the entire radius differentiates the extant taxa very well by locomotor pattern, the distal radius fails to clearly differentiate the extant taxa. The sigmoid notch of the distal radius is the anatomical feature that differs most among the extant taxa, and its variability broadly correlates with necessary mobility at the wrist joint. Principal components and discriminant function analyses indicate that early hominins are affiliated with a variety of extant taxa with different locomotor patterns. Overall, the bony anatomy of the distal radius of early hominins points towards something adapted for a wide variety of locomotor postures. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.
Morphological Studies of the Pineal Gland in the Common Gull (Larus canus) Reveal Uncommon Features of Pinealocytes
Authors: Przybylska‐Gornowicz Barbara , Lewczuk Bogdan , Prusik Magdalena , Kalicki Miroslaw , Ziólkowska Natalia 
Published: January 2012

AbstractThe avian pineal is a directly photosensory organ taking part in the organization of the circadian and seasonal rhythms. It plays an important role in regulation of many behavior and physiological phenomena including migration. The aim of the study was to investigate morphology of the pineal organ in the common gull (Larus canus). The light and electron microscopic studies were performed on the pineals of juvenile birds living in natural conditions of the Baltic Sea coast, which have been untreatably injured during strong storms in autumn and qualified for euthanasia. The investigated pineals consisted of a wide, triangular, superficially localized distal part and a narrow, elongated proximal part, attached via the choroid plexus to the intercommissural region of the diencephalon. The accessory pineal tissue was localized caudally to the choroid plexus. Based on the histological criteria, the organ was classified as the solid‐follicular type. Two types of cells of fotoreceptory line were distinguished: rudimentary–receptor pinealocytes and secretory pinealocytes. Both types of cells were characterized by unusual features, which have been not previously described in avian pinealocytes: the presence of paracrystalline structures in the basal processes and their endings, the storage of glycogen in the form of large accumulations and the arrangement of mitochondria in clusters. Further studies on other species of wild water birds dwelling in condition of cold seas are necessary to explain if the described features of pinealocytes are specific for genus Larus, family Laridae or a larger group of water birds living in similar environmental conditions. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.
The Expression of Neuronal Nitric Oxide Synthase in the Brain of the Mouse During Embryogenesis
Authors: Ling Shucai , Zhou Jing , Rudd John A. , Hu Zhiying , Fang Marong 
Published: January 2012

AbstractThe distribution of neuronal nitric oxide synthase (nNOS) in the process of normal mouse brain growth from embryonic (E) Day 11 to postnatal (P) Day 1 was investigated by means of immunohistochemical and immunofluorescent methods. Our results demonstrated that nNOS positive neurons appeared early in superficial cortex at E11. At E13, nNOS positive neurons were located in lateral hypothalamus and amygdala, and temporarily in medullar and ventral hypothalamic neuroepithelia. From E15 to P0, nNOS positive neurons were distributed in superior and inferior colliculi, positive staining could also be seen in superior and inferior tectal neuroepithelium at E15. From E17 to birth, the medial geniculate nucleus had a high density of nNOS labeling. The distribution of nNOS gradually increased and extended laterally in embryo brain, which in turn implies that NO might be involved in the development of mouse brain. Anat Rec, 2012. © 2012 Wiley Periodicals, Inc.
Covalent Immobilization of Imidazolium Cations Inside a Silica Support: Palladium‐Catalyzed Olefin Hydrogenation
Authors: Wang Lei , Shylesh Sankaranarayanapillai , Dehe Daniel , Philippi Thomas , Dörr Gunder , Seifert Andreas , Zhou Zhou , Hartmann Martin , Klupp Taylor Robin N. , Jia Mingjun , Ernst Stefan , Thiel Werner R. 
Published: January 2012

AbstractMesoporous organosilica materials with different contents of bistrialkoxysilyl imidazolium salts in the framework were synthesized by a one‐step synthesis. Textural characterization of the materials confirmed that the morphology and surface properties of the imidazolium‐bridged organosilicas depended critically on the amount of organic groups in the framework, whereas solid‐state NMR characterization showed that the imidazolium fragments were integrated covalently into the framework. Further reaction of these materials with Pd(OAc)2, followed by reduction with NaBH4 yielded palladium nanoparticles stabilized in the mesoporous organosilicas. The stabilizing effect of the imidazolium cations and the mesostructure contributed to the high activity, selectivity, and stability of the palladium nanoparticles and allowed olefin hydrogenation under mild reaction conditions.
Synthetic and Mechanistic Aspects of the Immortal Ring‐Opening Polymerization of Lactide and Trimethylene Carbonate with New Homo‐ and Heteroleptic Tin(II)‐Phenolate Catalysts
Authors: Poirier Valentin , Roisnel Thierry , Sinbandhit Sourisak , Bochmann Manfred , Carpentier Jean‐François , Sarazin Yann 
Published: January 2012

AbstractSeveral new heteroleptic SnII complexes supported by amino‐ether phenolate ligands [Sn{LOn}(Nu)] (LO1=2‐[(1,4,7,10‐tetraoxa‐13‐azacyclopentadecan‐13‐yl)methyl]‐4,6‐di‐tert‐butylphenolate, Nu=NMe2 (1), N(SiMe3)2 (3), OSiPh3 (6); LO2=2,4‐di‐tert‐butyl‐6‐(morpholinomethyl)phenolate, Nu=N(SiMe3)2 (7), OSiPh3 (8)) and the homoleptic Sn{LO1}2 (2) have been synthesized. The alkoxy derivatives [Sn{LO1}(OR)] (OR=OiPr (4), (S)‐OCH(CH3)CO2iPr (5)), which were generated by alcoholysis of the parent amido precursor, were stable in solution but could not be isolated. [Sn{LO1}]+[H2N{B(C6F5)3}2]− (9), a rare well‐defined, solvent‐free tin cation, was prepared in high yield. The X‐ray crystal structures of compounds 3, 6, and 8 were elucidated, and compounds 3, 6, 8, and 9 were further characterized by 119Sn Mössbauer spectroscopy. In the presence of iPrOH, compounds 1–5, 7, and 9 catalyzed the well‐controlled, immortal ring‐opening polymerization (iROP) of L‐lactide (L‐LA) with high activities (ca. 150–550 molL−LA molSn−1 h−1) for tin(II) complexes. The cationic compound 9 required a higher temperature (100 °C) than the neutral species (60 °C); monodisperse poly(L‐LA)s were obtained in all cases. The activities of the heteroleptic pre‐catalysts 1, 3, and 7 were virtually independent of the nature of the ancillary ligand, and, most strikingly, the homoleptic complex 2 was equally competent as a pre‐catalyst. Polymerization of trimethylene carbonate (TMC) occurs much more slowly, and not at all in the presence of LA; therefore, the generation of PLA‐PTMC copolymers is only possible if TMC is polymerized first. Mechanistic studies based on 1H and 119Sn{1H} NMR spectroscopy showed that the addition of an excess of iPrOH to compound 3 yielded a mixture of compound 4, compound [Sn(OiPr)2]n 10, and free {LO1}H in a dynamic temperature‐dependent and concentration‐dependent equilibrium. Upon further addition of L‐LA, two active species were detected, [Sn{LO1}(OPLLA)] (12) and [Sn(OPLLA)2] (14), which were also in fast equilibrium. Based on assignment of the 119Sn{1H} NMR spectrum, all of the species present in the ROP reaction were identified; starting from either the heteroleptic (1, 3, 7) or homoleptic (2) pre‐catalysts, both types of pre‐catalysts yielded the same active species. The catalytic inactivity of the siloxy derivative 6 confirmed that ROP catalysts of the type 1–5 could not operate according to an activated‐monomer mechanism. These mechanistic studies removed a number of ambiguities regarding the mechanism of the (i)ROPs of L‐LA and TMC promoted by industrially relevant homoleptic or heteroleptic SnII species.
Ferrocenes with Perfluorinated Side Chains and Ferrocenophanes with Fluorinated Handles
Authors: Roemer Max , Kang Youn Kyung , Chung Young Keun , Lentz Dieter 
Published: January 2012

AbstractTrifluorovinyl groups are introduced onto the cyclopentadienyl ligands of ferrocene at the 1‐, 1,1′‐, and 1,2‐positions by Negishi‐type and Stille‐type coupling reactions of trifluorovinylzinc chloride and tri‐n‐butyltrifluorovinyl stannane with several iodoferrocenes. Modification of the trifluorovinyl group by nucleophilic substitution and [2+2] cycloaddition make them versatile building blocks for synthetic transformations. 1,1′‐Bis(trifluorovinyl) ferrocene reacts upon contact with silica or oxidizing agents and in the presence of a suitable nucleophile through a redox autocatalytic mechanism to afford ferrocenophanes with fluorinated handles. C(F)(H) and C(F)(OMe) moieties in α‐positions allowed further modifications to be performed by nucleophilic substitution of the fluorine atoms. A series of ferrocenes with fluorinated side chains and ferrocenophanes with fluorinated handles were isolated and characterized. Several molecular structures were determined by single‐crystal X‐ray diffraction. The influence of the fluorine substituents on the redox properties of the iron center were studied by cyclic voltammetry.
Controlled Synthesis and Enhanced Catalytic and Gas‐Sensing Properties of Tin Dioxide Nanoparticles with Exposed High‐Energy Facets
Authors: Wang Xue , Han Xiguang , Xie Shuifen , Kuang Qin , Jiang Yaqi , Zhang Subing , Mu Xiaoliang , Chen Guangxu , Xie Zhaoxiong , Zheng Lansun 
Published: January 2012

AbstractA morphology evolution of SnO2 nanoparticles from low‐energy facets (i.e., {101} and {110}) to high‐energy facets (i.e., {111}) was achieved in a basic environment. In the proposed synthetic method, octahedral SnO2 nanoparticles enclosed by high‐energy {111} facets were successfully synthesized for the first time, and tetramethylammonium hydroxide was found to be crucial for the control of exposed facets. Furthermore, our experiments demonstrated that the SnO2 nanoparticles with exposed high‐energy facets, such as {221} or {111}, exhibited enhanced catalytic activity for the oxidation of CO and enhanced gas‐sensing properties due to their high chemical activity, which results from unsaturated coordination of surface atoms, superior to that of low‐energy facets. These results effectively demonstrate the significance of research into improving the physical and chemical properties of materials by tailoring exposed facets of nanomaterials.
Pd‐Catalyzed Reaction of Allyl Carbonate with Polyols: The Role of CO2 in Transesterification versus Etherification of Glycerol
Authors: Gordillo Alvaro , Lloyd‐Jones Guy C. 
Published: January 2012

AbstractAn intermolecular Pd/PPh3‐catalyzed transesterification of diallyl carbonate with glycerol to generate glycerol carbonate has been developed. Analysis of the reaction kinetics in THF indicates a first‐order dependence on Pd and diallyl carbonate, that the Pd bears two phosphines during the turnover limiting event, and that increasing the glycerol concentration inhibits reaction, possibly via change in the polarity of the medium. 13C isotopic labeling studies demonstrate that the Pd‐catalyzed transesterification requires at least one allyl carbonate moiety and that there is rapid equilibrium of the allyl carbonate with CO2 in solution, even when present only at low concentrations. A mechanism that is consistent with these results involves oxidative addition of the allyl carbonate to Pd followed by reversible decarboxylation, with the intermediate η1‐ and η3‐allyl Pd alkoxides mediating direct and indirect transesterification reactions with the glycerol. Using this model, successful simulations of the kinetics of reactions conducted under atmospheres of N2 or CO2 could be achieved, including switching in selectivity between etherification and transesterification in the early stages of reaction. Reactions with the higher polyols threitol and erythritol are also efficient, generating the terminal (1,2) monocarbonates with high selectivity.
Pathway of Oxygen Incorporation from O2 in TiO2 Photocatalytic Hydroxylation of Aromatics: Oxygen Isotope Labeling Studies
Authors: Li Yue , Wen Bo , Yu Cailan , Chen Chuncheng , Ji Hongwei , Ma Wanhong , Zhao Jincai 
Published: January 2012

AbstractThe hydroxylation process is the primary, and even the rate‐determining step of the photocatalytic degradation of aromatic compounds. To make clear the hydroxylation pathway of aromatics, the TiO2 photocatalytic hydroxylation of several model substrates, such as benzoic acid, benzene, nitrobenzene, and benzonitrile, has been studied by an oxygen‐isotope‐labeling method, which can definitively assign the origin of the O atoms (from oxidant O2 or solvent H2O) in the hydroxyl groups of the hydroxylated products. It is found that the oxygen source of the hydroxylated products depends markedly on the reaction conditions. The percentage of the products with O2‐derived hydroxyl O atoms increases with the irradiation time, while it decreases with the increase of substrate concentration. More intriguingly, when photogenerated valence‐band holes (hvb+) are removed, nearly all the O atoms (>97 %) in the hydroxyl groups of the hydroxylated products of benzoic acid come from O2, whereas the scavenging of conduction‐band electrons (ecb−) makes almost all the hydroxyl O atoms (>95 %) originate from solvent H2O. In the photocatalytic oxidation system with benzoic acid and benzene coexisting in the same dispersion, the percentage of O2‐derived hydroxyl O atoms in the hydroxylated products of strongly adsorbed benzoic acid (ca. 30 %) is much less than in that of weakly adsorbed benzene (phenol) (>60 %). Such dependences provide unique clues to uncover the photocatalytic hydroxylation pathway. Our experiments show that the main O2‐incorporation pathway involves the reduction of O2 by ecb− and the subsequent formation of free .OH via H2O2, which was usually overlooked in the past photocatalytic studies. Moreover, in the hydroxylation initiated by hvb+, unlike the conventional mechanism, the O atom in O2 cannot incorporate into the product through the direct coupling between molecular O2 and the substrate‐based radicals.