bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geometric variation of the frontal squama in the genus homo: Frontal bulging and the origin of modern human morphology
Authors: Bruner Emiliano , Athreya Sheela , de la Cuétara José Manuel , Marks Tarah 
Published: January 2013

AbstractThe majority of studies of frontal bone morphology in paleoanthropology have analyzed the frontal squama and the browridge as a single unit, mixing information from different functional elements. Taking into account that the bulging of the frontal bone is often described as a species‐specific trait of Homo sapiens, in this article we analyze variation in the midsagittal profile of the genus Homo, focusing on the frontal squama alone, using landmark‐based superimpositions and principal components analysis. Our results demonstrate that anatomically modern humans are definitely separated from extinct human taxa on the basis of frontal bulging. However, there is minor overlap among these groups, indicating that it is necessary to exercise caution when using this trait alone to make taxonomic inferences on individual specimens. Early modern humans do not show differences with recent modern humans, and “transitional” individuals such as Jebel Irhoud 1, Maba, and Florisbad, show modern‐like frontal squama morphology. The bulging of the frontal squama in modern humans may represent a structural consequence of more general cranial changes, or it could be a response to changes in the morphology of the underlying prefrontal brain elements. A subtle difference between Neandertals and the Afro‐European Middle Pleistocene Homo sample is associated with flattening at bregma in the former group, a result that merits further investigation. Am J Phys Anthropol, 2013. © 2013 Wiley Periodicals, Inc
Antibacterial and anticoagulation properties of polyethylene/geneO‐MPC nanocomposites
Authors: Jin Suxing , Xu Dong , Zhou Ninglin , Yuan Jiang , Shen Jian 
Published: January 2013

AbstractNanocomposite technology has been utilized to improve biocompatibility and mechanical property of biomedical catheter materials. In this study, graphene oxide (GeneO), graphene oxide complexes with 2‐(methacryloyloxy)ethyl phosphorylcholine (GeneO‐MPC), and modified polyethylene (PE/GeneO‐MPC) nanocomposites applied in biomedical catheter materials field were synthesized and their bacteriostasis to E. coli and S. aureus was studied. According to the results of bacterial adhesion, PE/GeneO‐MPC nanocomposites inhibited the growth of the mass of predominant bacteria. PE/GeneO‐MPC could reduce platelet adhesion greatly as compared to PE, which displayed the improved anticoagulant property. The tensile strength and elongation of PE/GeneO‐MPC nanocomposites were enhanced by 15.5 and 97.3%, respectively. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Silicone rubber films modified by ethylenoxy moieties: Characterization and drug delivery properties
Authors: Soulas Dimitrios N. , Papadokostaki Kyriaki G. , Sanopoulou Merope 
Published: January 2013

AbstractWe present a comparative study between two different types of modification applied on a highly hydrophobic, yet biocompatible polymer, aiming to increase its hydrophilicity. More specifically, silicone rubber (SR) was modified by the introduction of low‐molecular weight poly(ethylene glycol), through either (a) blending or (b) addition‐grafting reaction. The modifications were first evaluated in neat films with respect to their water sorption capacity, stability of ethylenoxy groups' embedment, mechanical and thermal properties. The results from this series of tests showed that blending offered better results in terms of hydrophilicity, both surficial and in the bulk, while the films maintained better mechanical properties. Subsequently, the release kinetics of a relatively hydrophilic drug (theophylline) along with the concurrent water uptake was examined in drug‐loaded, pure and modified SR films. As in the case of the drug‐free films, blending appeared to offer better possibilities in controlling the drug's release rate through increased water sorption. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Selective recognition of beta‐cypermethrin by molecularly imprinted polymers based on magnetite yeast composites
Authors: Guan Wei‐Sheng , Lei Jun‐Ru , Wang Xu , Zhou Ya , Lu Chen‐Chen , Sun Shao‐Fang 
Published: January 2013

AbstractMagnetic nanoparticles were attached to yeast by co‐precipitation reaction of FeCl3·6H2O and FeCl2·4H2O. Then, based on magnetite yeast composites (M@Y), the magnetic molecularly imprinted polymers (MMIPs) were synthesized for the selective recognition of beta‐cypermethrin (PP321). MMIPs were characterized by scanning electron microscopy, X‐ray diffraction, vibrating sample magnetometer, Fourier transform infrared analysis, thermogravimetric analysis, and elemental analysis. MMIPs exhibited uniform morphology and magnetic property (Ms = 17.87 emu/g) and thermal stability. Batch mode adsorption studies were carried out to investigate the specific adsorption equilibrium, kinetics, and selective recognition. The Langmuir isotherm model was fitted to the equilibrium data slightly better than the Freundlich model, and the adsorption capacity of MMIPs was 39.64 mg/g at 298 K. The kinetic properties of MMIPs were well described by the pseudo‐second‐order equation. Hydrogen bonds between methacrylic acid and PP321 were mainly responsible for the adsorption mechanism. The MMIPs prepared were applied to the separation of PP321 from experimental samples successfully. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Characterization of shear stress at the tool‐part interface during autoclave processing of prepreg composites
Authors: Joven Ronald , Tavakol Behrouz , Rodriguez Alejandro , Guzman Mauricio , Minaie Bob 
Published: January 2013

AbstractIn this article, shear stress between an aluminum tool and a carbon fiber‐epoxy prepreg is characterized during cure using polymeric release agent and release film at the tool‐part interface. The effects of surface roughness, release materials, pull‐out speed, temperature, and normal force (autoclave pressure) on the shear stress are investigated using a customized friction rig. Results show that the interfacial shear stress decreases as the temperature increases and it increases as the normal force increases when using either the release film or the release agent. Additionally, changes in surface roughness from 1.35 to 0.18 μm decrease the shear stress 10–27% while the use of release agent shows a decrease between 23% and 51% in the shear stress. Furthermore, strong adhesion between the tool and the part is observed when using release agent and pull‐out speeds of 0.05 mm/min (static/dynamic friction ratio of 5.29 ± 0.19). Using the experimental data, a mathematical approach based on the Coulomb's friction model is proposed to predict the friction force at the tool‐part interface. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Synthesis, characterization, and swelling behavior of superabsorbent hydrogel from sodium salt of partially carboxymethylated tamarind kernel powder‐g‐PAN
Authors: Trivedi Jignesh H. 
Published: January 2013

AbstractPolyacrylonitrile (PAN)‐grafted sodium salt of partially carboxymethylated tamarind kernel powder (Na‐PCMTKP‐g‐PAN, %G = 413.76 and %GE = 96.48) was prepared using the established optimal reaction conditions for ceric‐initiated graft copolymerization of acrylonitrile onto Na‐PCMTKP (DS = 0.15) in a homogeneous medium. The graft copolymer was hydrolyzed by 0.7N KOH solution at 90–95°C to yield the superabsorbent hydrogel H‐Na‐PCMTKP‐g‐PAN. The nitrile groups of Na‐PCMTKP‐g‐PAN were completely converted into a mixture of hydrophilic carboxamide and carboxylate groups during alkaline hydrolysis, followed by in situ crosslinking of the grafted PAN chains. The products were characterized spectroscopically and morphologically. The swelling behavior of the unreported superabsorbent hydrogel, H‐Na‐PCMTKP‐g‐PAN, was studied by carrying out its absorbency measurements in low‐conductivity water, 0.15M salt (NaCl, CaCl2, and AlCl3) solutions, and simulated urine (SU) at different timings. The swelling behavior of the hydrogel in different swelling media followed the second‐order kinetics. The values of the various swelling characteristics were reported. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Sorption properties of polymers based on N‐substituted maleimides
Authors: Batueva Tatiana D. , Gorbunova Marina N. , Scherban M. G. 
Published: January 2013

AbstractPhysicochemical and functional properties of 2,2‐diallyl‐1,1,3,3‐tetraethylguanidinium chloride copolymers with N‐(n‐carboxyphenyl)maleimide, of N‐vinylpyrrolidone with N‐(n‐carboxyphenyl)maleimide, and of N‐vinylpyrrolidone with N‐phenylmaleimide have been investigated. Specific surface area and porosity of the copolymers under investigation have been determined by using the low‐temperature adsorption method. Electron microscope investigations in surfaces of the polymers have evinced that all of them have a spongy microstructure, the N‐vinylpyrrolidone copolymer with N‐(n‐carboxyphenyl)maleimide being the most homogeneous of these. Sorption capacity of the copolymers toward Re(VII) ions has been investigated. The process is described by the Langmuir isotherm. The pH is the most important parameter for sorption process of Re(VII). In the conjoint presence of Re(VII) and Mo(VI) in a solution of acid and ammoniac mediums, rhenium can be separated from molybdenum by using the sorbents under investigation at pH > 4.5 or at hydrochloric acid concentrations 0.1 mol L−1 and more. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013
Parametric Absolute Stabilization for Interconnected Lurie Time‐Delay Systems with Polytopic Uncertainty
Authors: Chen Ning , Liu Yutian , Liu Bo , Gui Weihua 
Published: January 2013

AbstractThe paper considers the parametric absolute stabilization for interconnected Lurie time‐delay systems with polytopic uncertainty. The concept of parametric absolute stabilization characterizes both the existence and the stability of equilibrium in the case of uncertain parameters and reference input shift. First, the existing conditions of parametric stability and the stable region are studied by the change of the uncertain parameters and reference input based on decentralized state feedback. Then, a delay‐dependent absolute stability condition in parametric stabilization region for interconnected Lurie time‐delay systems with polytopic uncertainties is obtained through a linear matrix inequality method. Finally, an example is given to illustrate the effectiveness of the proposed method.
Organic Photovoltaic Devices Based on a New Class of Oligothienylenevinylene Derivatives as Donor Materials
Authors: Kwok Eric Chi‐Ho , Tsang Daniel Ping‐Kuen , Chan Mei‐Yee , Yam Vivian Wing‐Wah 
Published: January 2013

AbstractA new class of donor–acceptor‐containing oligothienylenevinylenes with a triphenylamine donor and a dicyanovinyl group as acceptor has been synthesized and characterized. By extending the oligothiophene backbone, both the optical bandgaps and the charge‐transport properties can be tuned. These oligothienylenevinylene derivatives show intense charge‐transfer absorption bands that cover the entire visible spectrum, with low optical bandgaps of approximately 1.64 eV. In addition, electrochemical studies reveal that these compounds possess relatively large ionization potentials of approximately 5.5 eV. On the basis of these newly developed dicyanovinyl‐substituted chromophores as donor materials and C60 as acceptor material, bilayer organic photovoltaic devices have been fabricated, with the best device showing a high power conversion efficiency (PCE) of 2.0 %, with an open‐circuit voltage of 0.68 V and a fill factor of 0.60 after thermal annealing. The obvious morphology change with the formation of small domains in thin films and the reduction of series resistance are believed to be responsible for the dramatic performance improvement upon thermal annealing.
Chemoenzymatic Synthesis of All Four Diastereomers of 2,6‐Disubstituted Piperidines through Stereoselective Monoamination of 1,5‐Diketones
Authors: Simon Robert C. , Zepeck Ferdinand , Kroutil Wolfgang 
Published: January 2013

AbstractThe regioselectivity of various enantiocomplementary ω‐transaminases was evaluated for the stereoselective monoamination of designated 1,5‐diketones; excellent conversions, enantio‐ and regioselectivities were observed. The resulting amino‐ketones underwent spontaneous intramolecular ring closure to afford Δ1‐piperideines, which served as precursors for the cis‐ and anti‐piperidine scaffold as demonstrated for the synthesis of the alkaloids dihydropinidine and epi‐dihydropinidine. Key to the success of accessing the trans‐piperidines was a Lewis acid mediated conformational change of the Δ1‐piperideines in the reduction step. Thus, all four diastereomers of 2,6‐disubstituted piperidines could successfully be prepared.
Three‐Coordinate Nickel(I) Complexes Stabilised by Six‐, Seven‐ and Eight‐Membered Ring N‐Heterocyclic Carbenes: Synthesis, EPR/DFT Studies and Catalytic Activity
Authors: Page Michael J. , Lu Wei Y. , Poulten Rebecca C. , Carter Emma , Algarra Andrés G. , Kariuki Benson M. , Macgregor Stuart A. , Mahon Mary F. , Cavell Kingsley J. , Murphy Damien M. , Whittlesey Michael K. 
Published: January 2013

AbstractComproportionation of [Ni(cod)2] (cod=cyclooctadiene) and [Ni(PPh3)2X2] (X=Br, Cl) in the presence of six‐, seven‐ and eight‐membered ring N‐aryl‐substituted heterocyclic carbenes (NHCs) provides a route to a series of isostructural three‐coordinate NiI complexes [Ni(NHC)(PPh3)X] (X=Br, Cl; NHC=6‐Mes 1, 6‐Anis 2, 6‐AnisMes 3, 7‐o‐Tol 4, 8‐Mes 5, 8‐o‐Tol 6, O‐8‐o‐Tol 7). Continuous wave (CW) and pulsed EPR measurements on 1, 4, 5, 6 and 7 reveal that the spin Hamiltonian parameters are particularly sensitive to changes in NHC ring size, N substituents and halide. In combination with DFT calculations, a mixed SOMO of ∣3d〉 and ∣3d〉 character, which was found to be dependent on the complex geometry, was observed and this was compared to the experimental g values obtained from the EPR spectra. A pronounced 31P superhyperfine coupling to the PPh3 group was also identified, consistent with the large spin density on the phosphorus, along with partially resolved bromine couplings. The use of 1, 4, 5 and 6 as pre‐catalysts for the Kumada coupling of aryl chlorides and fluorides with ArMgY (Ar=Ph, Mes) showed the highest activity for the smaller ring systems and/or smaller substituents (i.e., 1>4≈6≫5).
A Modular Synthesis of Teraryl‐Based α‐Helix Mimetics, Part 1: Synthesis of Core Fragments with Two Electronically Differentiated Leaving Groups
Authors: Peters Martin , Trobe Melanie , Tan Hao , Kleineweischede Rolf , Breinbauer Rolf 
Published: January 2013

AbstractTeraryl‐based α‐helix mimetics have proven to be useful compounds for the inhibition of protein–protein interactions (PPI). We have developed a modular and flexible approach for the synthesis of teraryl‐based α‐helix mimetics. Central to our strategy is the use of a benzene core unit featuring two leaving groups of differentiated reactivity in the Pd‐catalyzed cross‐coupling used for terphenyl assembly. With the halogen/diazonium route and the halogen/triflate route, two strategies have successfully been established. The synthesis of core building blocks with aliphatic (Ala, Val, Leu, Ile), aromatic (Phe), polar (Cys, Lys), hydrophilic (Ser, Gln), and acidic (Glu) amino acid side chains are reported.
Hydride Reactivity of NiIIXNiII Entities: Mixed‐Valent Hydrido Complexes and Reversible Metal Reduction
Authors: Gehring Henrike , Metzinger Ramona , Herwig Christian , Intemann Julia , Harder Sjoerd , Limberg Christian 
Published: January 2013

AbstractAfter the lithiation of PYR‐H2 (PYR2−=[{NC(Me)C(H)C(Me)NC6H3(iPr)2}2(C5H3N)]2−), which is the precursor of an expanded β‐diketiminato ligand system with two binding pockets, its reaction with [NiBr2(dme)] led to a dinuclear nickel(II)–bromide complex, [(PYR)Ni(μ‐Br)NiBr] (1). The bridging bromide ligand could be selectively exchanged for a thiolate ligand to yield [(PYR)Ni(μ‐SEt)NiBr] (3). In an attempt to introduce hydride ligands, both compounds were treated with KHBEt3. This treatment afforded [(PYR)Ni(μ‐H)Ni] (2), which is a mixed valent NiIμ‐HNiII complex, and [(PYR‐H)Ni(μ‐SEt)Ni] (4), in which two tricoordinated NiI moieties are strongly antiferromagnetically coupled. Compound 4 is the product of an initial salt metathesis, followed by an intramolecular redox process that separates the original hydride ligand into two electrons, which reduce the metal centres, and a proton, which is trapped by one of the binding pockets, thereby converting it into an olefin ligand on one of the NiI centres. The addition of a mild acid to complex 4 leads to the elimination of H2 and the formation of a NiIINiII compound, [(PYR)Ni(μ‐SEt)NiOTf] (5), so that the original NiII(μ‐SEt)NiIIX core of compound 3 is restored. All of these compounds were fully characterized, including by X‐ray diffraction, and their molecular structures, as well as their formation processes, are discussed.
Isomerization Energy Decomposition Analysis for Highly Ionic Systems: Case Study of Starlike E5Li7+ Clusters
Authors: Contreras Maryel , Osorio Edison , Ferraro Franklin , Puga Gustavo , Donald Kelling J. , Harrison Jason G. , Merino Gabriel , Tiznado William 
Published: January 2013

AbstractThe most stable forms of E5Li7+ (E=Ge, Sn, and Pb) have been explored by means of a stochastic search of their potential‐energy surfaces by using the gradient embedded genetic algorithm (GEGA). The preferred isomer of the Ge5Li7+ ion is a slightly distorted analogue of the D5h three‐dimensional seven‐pointed starlike structure adopted by the lighter C5Li7+ and Si5Li7+ clusters. In contrast, the preferred structures for Sn5Li7+ and Pb5Li7+ are quite different. By starting from the starlike arrangement, corresponding lowest‐energy structures are generated by migration of one of the E atoms out of the plane with the a corresponding rearrangement of the Li atoms. To understand these structural preferences, we propose a new energy decomposition analysis based on isomerizations (isomerization energy decomposition analysis (IEDA)), which enable us to extract energetic information from isomerization between structures, mainly from highly charged fragments.
Harnessing the Flexibility of Peptidic Scaffolds to Control their Copper(II)‐Coordination Properties: A Potentiometric and Spectroscopic Study
Authors: Fragoso Ana , Lamosa Pedro , Delgado Rita , Iranzo Olga 
Published: January 2013

AbstractDesigning small peptides that are capable of binding Cu2+ions mainly through the side‐chain functionalities is a hard task because the amide nitrogen atoms strongly compete for Cu2+ion coordination. However, the design of such peptides is important for obtaining biomimetic small systems of metalloenyzmes as well as for the development of artificial systems. With this in mind, a cyclic decapeptide, C‐Asp, which contained three His residues and one Asp residue, and its linear derivative, O‐Asp, were synthesized. The C‐Asp peptide has two ProGly β‐turn‐inducer units and, as a result of cyclization, and as shown by CD spectroscopy, its backbone is constrained into a more defined conformation than O‐Asp, which is linear and contains a single ProGly unit. A detailed potentiometric, mass spectrometric, and spectroscopic study (UV/Vis, CD, and EPR spectroscopy) showed that at a 1:1 Cu2+/peptide ratio, both peptides formed a major [CuHL]2+species in the pH range 5.0–7.5 (C‐Asp) and 5.5–7.0 (O‐Asp). The corrected stability constants of the protonated species (log K*CuH(O−Asp)=9.28 and log K*CuH(C−Asp)=10.79) indicate that the cyclic peptide binds Cu2+ions with higher affinity. In addition, the calculated value ofKeffshows that this higher affinity for Cu2+ions prevails at all pH values, not only for a 1:1 ratio but even for a 2:1 ratio. The spectroscopic data of both [CuHL]2+species are consistent with the exclusive coordination of Cu2+ions by the side‐chain functionalities of the three His residues and the Asp residue in a square‐planar or square‐pyramidal geometry. Nonetheless, although these data show that, upon metal coordination, both peptides adopt a similar fold, the larger conformational constraints that are present in the cyclic scaffold results in different behaviour for both [CuHL]2+species. CD and NMR analysis revealed the formation of a more rigid structure and a slower Cu2+‐exchange rate for [CuH(C‐Asp)]2+compared to [CuH(O‐Asp]2+. This detailed comparative study shows that cyclization has a remarkable effect on the Cu2+‐coordination properties of the C‐Asp peptide, which binds Cu2+ions with higher affinity at all pH values, stabilizes the [CuHL]2+species in a wider pH range, and has a slower Cu2+‐exchange rate compared to O‐Asp.
Development of Palladium Surface‐Enriched Heteronuclear Au–Pd Nanoparticle Dehalogenation Catalysts in an Ionic Liquid
Authors: Yuan Xiao , Sun Geng , Asakura Hiroyuki , Tanaka Tsunehiro , Chen Xi , Yuan Yuan , Laurenczy Gabor , Kou Yuan , Dyson Paul J. , Yan Ning 
Published: January 2013

AbstractHeteronuclear Au–Pd nanoparticles were prepared and immobilized in the functionalized ionic liquid [C2OHmim][NTf2]. The structural and electronic properties of the nanoparticles were characterized by a range of techniques and the surface of the nanoparticles was found to be enriched in Pd. Moreover, the extent of Pd enrichment is easily controlled by varying the ratio of Au and Pd salts used in the synthesis. The heteronuclear nanoparticles were found to be effective catalysts in dehalogenation reactions with no activity observed for the pure Au nanoparticles and only limited activity for the pure Pd nanoparticles. The activity of the heteronuclear nanoparticles may be attributed to charge transfer from Pd to Au and consequently to more efficient reductive elimination.
An Examination of the Palladium/Mor‐DalPhos Catalyst System in the Context of Selective Ammonia Monoarylation at Room Temperature
Authors: Alsabeh Pamela G. , Lundgren Rylan J. , McDonald Robert , Johansson Seechurn Carin C. C. , Colacot Thomas J. , Stradiotto Mark 
Published: January 2013

AbstractAn examination of the [{Pd(cinnamyl)Cl}2]/Mor‐DalPhos (Mor‐DalPhos=di(1‐adamantyl)‐2‐morpholinophenylphosphine) catalyst system in Buchwald–Hartwig aminations employing ammonia was conducted to better understand the catalyst formation process and to guide the development of precatalysts for otherwise challenging room‐temperature ammonia monoarylations. The combination of [{Pd(cinnamyl)Cl}2] and Mor‐DalPhos afforded [(κ2‐P,N‐Mor‐DalPhos)Pd(η1‐cinnamyl)Cl] (2), which, in the presence of a base and chlorobenzene, generated [(κ2‐P,N‐Mor‐DalPhos)Pd(Ph)Cl] (1 a). Halide abstraction from 1 a afforded [(κ3‐P,N,O‐Mor‐DalPhos)Pd(Ph)]OTf (5), bringing to light a potential stabilizing interaction that is offered by Mor‐DalPhos. An examination of [(κ2‐P,N‐Mor‐DalPhos)Pd(aryl)Cl] (1 b–f) and related precatalysts for the coupling of ammonia and chlorobenzene at room temperature established the suitability of 1 a in such challenging applications. The scope of reactivity for the use of 1 a (5 mol %) encompassed a range of (hetero)aryl (pseudo)halides (X=Cl, Br, I, OTs) with diverse substituents (alkyl, aryl, ether, thioether, ketone, amine, fluoro, trifluoromethyl, and nitrile), including chemoselective arylations.