bluuebunny/crossref_metadata_2025_split huggingface dataset:
ATNRC and SET‐NRC synthesis of PtBA‐g‐PEO well‐defined amphiphilic graft copolymers
Authors: Li Yaogong , Du Ming , Zhang Yaqin , Li Yongjun , Sui Long , Lu Guolin , Huang Xiaoyu 
Published: February 2012

AbstractA series of new well‐defined amphiphilic graft copolymers containing hydrophobic poly(tert‐butyl acrylate) backbone and hydrophilic poly(ethylene oxide) side chains were reported. Reversible addition‐fragmentation chain transfer homopolymerization of tert‐butyl 2‐((2‐bromopropanoyloxy)methyl)acrylate was first performed to afford a well‐defined backbone with a narrow molecular weight distribution (Mw/Mn = 1.07). The target poly(tert‐butyl acrylate)‐g‐poly(ethylene oxide) (PtBA‐g‐PEO) graft copolymers with low polydispersities (Mw/Mn = 1.18–1.26) were then synthesized by atom transfer nitroxide radical coupling or single electron transfer‐nitroxide radical coupling reaction using CuBr(Cu)/PMDETA as catalytic system. Fluorescence probe technique was employed to determine the critical micelle concentrations (cmc) of the obtained amphiphilic graft copolymers in aqueous media. Furthermore, PAA‐g‐PEO graft copolymers were obtained by selective acidic hydrolysis of hydrophobic PtBA backbone while PEO side chains kept inert. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Preparation and optical characterization of two photoactive poly(bisphenol a ethoxylate diacrylate) copolymers containing designed amino‐nitro‐substituted azobenzene units, obtained via classical and frontal polymerization, using novel ionic liquids as initiators
Authors: Illescas Javier , Ortíz‐Palacios Jesús , Esquivel‐Guzmán Jair , Ramirez‐Fuentes Yessica S. , Rivera Ernesto , Morales‐Saavedra Omar G. , Rodríguez‐Rosales Antonio A. , Alzari Valeria , Nuvoli Daniele , Scognamillo Sergio , Mariani Alberto 
Published: February 2012

AbstractThe frontal polymerization (FP) of bisphenol A ethoxylate diacrylate (BPAEDA) was carried with and without the presence of two different azobenzene comonomers by means of an external heating source. The first azomonomer (MDR‐1) is a derivative of disperse red‐1, N‐ethyl‐N‐(2‐hydroxyethyl)‐4‐(4‐nitrophenylazo)aniline, whereas the second (E)‐2‐(4‐((4‐nitrophenyl)diazenyl)phenyl)‐5,8,11‐trioxa‐2‐azatridecan‐13‐yl methacrylate (4PEGMAN) comes from the azo‐dye N‐methyl‐N‐{4‐[(E)‐(4‐nitrophenyl)diazenyl]phenyl}‐N‐(11‐hydroxy‐3,6,9‐trioxaundecas‐1‐yl) amine. In this work, an ionic liquid trihexyltetradecylphosphonium persulfate was used as initiator. This compound produced stable propagating polymerization fronts with good velocities and moderate maximum temperature values. Moreover, this initiator prevented bubble formation and was found to be the most efficient when it was used in lower amounts with respect to other initiators, such as benzoyl peroxide, 2,2′‐azobisisobutyronitrile, aliquat persulfate®, and tetrabutylphosphonium persulfate. The thermal properties of the obtained polymers and copolymers were determined by thermogravimetric analysis and differential scanning calorimetry. The nonlinear optical (NLO) characterizations of the developed BPAEDA/MDR‐1 and BPAEDA/4PEGMAN copolymers were performed according to the Z‐Scan technique in film samples prepared by classical polymerization. It has been proven that samples with higher 4PEGMAN content (0.26 mol %) exhibited outstanding cubic NLO‐activity with positive NLO‐refractive coefficients in the promising range of n2 = +3.2 × 10−4 esu. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Click synthesis and reversible electrochromic behaviors of novel polystyrenes bearing aromatic amine units
Authors: Li Yongrong , Michinobu Tsuyoshi 
Published: February 2012

AbstractNovel electrochromic polymers were prepared by the click postfunctionalization of poly(4‐azidomethylstyrene) with alkyne‐containing aromatic amine units in the presence of Cu(I) catalysts. Two kinds of aromatic amine units, tris(4‐alkoxyphenyl)amine and N,N,N′,N′‐tetraphenyl‐p‐phenylenediamine, were introduced into polystyrene side chains, which were completely characterized by gel permeation chromatography–multiangle light scattering, nuclear magnetic resonance, and infrared spectroscopies, and elemental analysis. Thermal analyses demonstrated the high stability with the decomposition temperatures exceeding 300 °C even after postfunctionalization. The UV–vis absorption spectra of the polymer thin films revealed negligible absorption in the visible region, as reasonably confirmed by visual observation. The polymer thin films were prepared by spray‐coating on an indium tin oxide‐coated glass plate. Cyclic voltammograms of these films exhibited anodic peaks ascribed to the oxidation of the side‐chain aromatic amine moieties. The tris(4‐alkoxyphenyl)amine unit displayed one‐step oxidation at 0.287 V (vs. Ag/AgCl), while the N,N,N′,N′‐tetraphenyl‐p‐phenylenediamine unit showed two‐step oxidations at 0.297 and 0.641 V. These oxidation processes produced new colors of the polymer films. The former triarylamine‐based chromophore provided a blue color after the oxidation, while the latter phenylenediamine‐based chromophore showed a potentially controlled green and dark blue colors. The reversibility and switching behaviors of these color changes were also comprehensively investigated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Polymeric temperature and pH fluorescent sensor synthesized by reversible addition–fragmentation chain transfer polymerization
Authors: Liu Guofeng , Zhou Wei , Zhang Jiaqi , Zhao Ping 
Published: February 2012

AbstractSimple‐structured copolymer, poly(NIPMAM‐co‐CPMA), consisting of N‐isopropylmethacrylamide (NIPMAM) and (Z)‐4‐(1‐cyano‐2‐(4‐(dimethylamino) phenyl)vinyl)phenylmethylacrylate (CPMA) units as thermo‐ and pH‐responsive fluorescent signaling parts, respectively, has been synthesized by reversible addition–fragmentation chain transfer polymerization. The copolymer PCN250 (m/n = 250) shows absorbance enhancement or decrease at different pH value. However, the fluorescence intensity of this copolymer shows enhancement with a rise in temperature regardless of pH value in the range of pH = 4–10. In addition, fluorescence suppression of copolymer (PCN250) was observed with high proton concentration. Moreover, the lower critical solution temperature of the copolymers, poly‐(NIPMAM‐co‐CPMA), with different component was also investigated. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Inositol phosphate‐induced stabilization of inositol 1,3,4,5,6‐pentakisphosphate 2‐kinase and its role in substrate specificity
Authors: Gosein Varin , Leung Ting‐Fung , Krajden Oren , Miller Gregory J. 
Published: February 2012

AbstractInositol phosphate kinases (IPKs) sequentially phosphorylate inositol phosphates (IPs) on their inositol rings to yield an array of signaling molecules. IPKs must possess the ability to recognize their physiological substrates from among a pool of over 30 cellular IPs that differ in numbers and positions of phosphates. Crystal structures from IPK subfamilies have revealed structural determinants for IP discrimination, which vary considerably between IPKs. However, recent structures of inositol 1,3,4,5,6‐pentakisphosphate 2‐kinase (IPK1) did not reveal how IPK1 selectively recognizes its physiological substrate, IP5, while excluding others. Here, we report that limited proteolysis has revealed the presence of multiple conformational states in the IPK1 catalytic cycle, with notable protection from protease only in the presence of IP. Further, a 3.1‐Å crystal structure of IPK1 bound to ADP in the absence of IP revealed decreased order in residues 110–140 within the N‐lobe of the kinase compared with structures in which IP is bound. Using this solution and crystallographic data, we propose a model for recognition of IP substrate by IPK1 wherein phosphate groups at the 4‐, 5‐, and 6‐positions are recognized initially by the C‐lobe with subsequent interaction of the 1‐position phosphate by Arg130 that stabilizes this residue and the N‐lobe. This model explains how IPK1 can be highly specific for a single IP substrate by linking its interactions with substrate phosphate groups to the stabilization of the N‐ and C‐lobes and kinase activation.
Excited and core‐ionized state calculations with a local potential expressed in terms of the external potential
Authors: Glushkov V. N. 
Published: February 2012

AbstractA so‐called constrained optimized effective potential (COEP) method for excited states (ESs) is briefly reviewed. In contrast to known density functional theory and OEP‐based approaches for ESs, the COEP method explicitly introduces orthogonality of the Kohn–Sham (KS) ES function to the lower states of the same symmetry. This makes it possible to solve the KS‐like equation so that, “variational collapsing” is avoided and any appropriate local potential can be handled. In particular, we implemented a local effective
${V_{{\rm{eff}}}}(\vec r)$
expressed as a direct mapping of the external potential, that is,
${V_{{\rm{eff}}}}(\vec r)$=
${V_{{\rm{eff}}}}[{V_{{\rm{ext}}}}(\vec r)]$. It is shown that excited and core‐ionized states can be treated within the framework of a unified computational approach. Our practical calculations demonstrate that the exchange‐only implementation of the COEP method in conjunction with
${V_{{\rm{eff}}}}(\vec r)$
expressed in terms of the external potential is capable of delivering reasonable results on the energies of singly excited as well as core‐ionized states and can be easily applied to both atoms and molecules. © 2012 Wiley Periodicals, Inc.
Functional dependence of excitation energy for pentacene/C60 model complex in the nonempirically tuned long‐range corrected density functional theory
Authors: Minami Takuya , Ito Soichi , Nakano Masayoshi 
Published: February 2012

AbstractFunctional dependence of excitation energy has been investigated for pentacene/C60 model complex in the time‐dependent long‐range corrected (LC) density functional theory (TD‐DFT). We especially evaluate the performance of nonempirically tuned LC‐DFT, in which the range‐separating parameter is optimized so as to satisfy the exact condition of DFT. In addition, the effect of short‐range Hartree–Fock (HF) exchange term is also examined based on the Coulomb‐attenuating method (CAM). We have shown that the nonempirical tuning scheme improves the excitation energies by the LC‐DFT (LC‐BLYP, LC‐ωPBE, and ωB97), as well as by the CAM‐DFT (CAM‐BLYP, CAM‐ωPBE, and CAM‐ωB97), independent of the existence of short‐range HF exchange term. We have also found that the functional dependence of excitation energy is very small when the nonempirically tuned parameter is applied. This indicates that the tuning of the range‐separating parameter is essential for improving the excitation energy within the framework of the TD‐LC‐DFT. © 2012 Wiley Periodicals, Inc.
Quantum Monte Carlo simulation of carbon monoxide reactivity when adsorbed at metal and oxide catalyst surfaces: Trial wave‐functions with exponential type basis and quasi‐exact three‐body correlation
Authors: Hoggan Philip E. 
Published: February 2012

AbstractReview publications show the advantages of using quantum Monte Carlo (QMC) methods when bonding interactions are modified and consequently, where the electron correlation energy varies and needs to be evaluated accurately. This article considers a model efficient metal catalyst for reactions of carbon monoxide. The ultimate aim is to help design industrially useful catalysts, since the reaction with water produces hydrogen gas selectively, that is, a clean fuel and a sustainable energy source. To narrow the gap between the industrial process and calculation, a model of platinum/oxide is studied. It is mimicked here by copper with and without adsorbed oxygen. Periodicity as well as a validated pseudo‐potential are used to limit the number of active electrons considered. A suitable code to carry out this task is CASINO. Furthermore, this code scales linearly to 100,000 processors and possesses a shared memory facility so that it is well‐suited to runs on the Blugene/P. It has been in production on such computers since early in 2011. A mixed plane‐wave/exponential type orbitals (ETO) basis is used for the systems studied. Plane waves are well‐suited to periodic solid substrates and a linear combination of ETOs for molecules. The atomic orbitals have direct physical interpretation, i.e., Coulomb Sturmians and hydrogen‐like orbitals. Their radial nodes are shown to be essential in obtaining the vitally important accurate QMC trial wave‐functions. Until 2008, ETO products on different atoms were difficult to manipulate for the evaluation of two‐electron integrals. Coulomb resolutions provide an excellent approximation that reduces these integrals to a sum of one‐electron overlap‐like integral products that each involve orbitals on at most two centers. They are thus readily evaluated. Only these integrals need to be re‐evaluated to change basis functions. In this article, QMC‐VMC variational optimisation is used with a quasi analytic two‐electron and nucleus correlation factor. The QMC diffusion Monte Carlo methodology is applied to adsorbed carbon monoxide and some of its reactions. © 2012 Wiley Periodicals, Inc.
Theoretical DFT karplus equations: Amino acid side‐chain torsion angle χ1
Authors: García De La Vega J. M. , San Fabián J. , Crespo‐Otero R. , Suardíaz R. , Pérez C. 
Published: February 2012

AbstractTheoretical Karplus equations for determining the conformation in proteins is applied to phenylalanine and tyrosine residues of Desulfovibrio vulgaris flavodoxin using density functional theory (DFT) calculations. The accuracy of different Karplus equations is evaluated showing that S2 Fourier coefficient is not negligible and C1 adopts positive values for some couplings. These two points should be considered in future empirical parameterizations. The dihedral angles χ1 calculated in this study using the full set of Fourier coefficients present a root mean square deviation of 6° against those obtained from X‐ray structures. © 2012 Wiley Periodicals, Inc.
Diradicalology in third‐order nonlinear optical systems: Second hyperpolarizabilities of acetylene‐linked phenalenyl‐based superpolyenes
Authors: Nakano Masayoshi , Kishi Ryohei , Fukui Hitoshi , Minami Takuya , Yoneda Kyohei , Minamide Shu , Inoue Yudai , Yamada Taishi , Ito Soichi , Muhammad Shabbir , Shigeta Yasuteru , Kubo Takashi , Champagne Benoît 
Published: February 2012

AbstractFrom the viewpoint of “diradical character,” referred to as “diradicalology,” we investigate the second hyperpolarizability γ—the molecular third‐order nonlinear optical (NLO) property—of one‐dimensional supermolecular systems composed of acetylene‐linked phenalenyl/pyrene rings using long‐range corrected spin‐unrestricted density functional theory. It turns out that the pyrene‐based superpolyenes (Py‐n) behave like closed‐shell systems, whereas phenalenyl‐based superpolyenes (Ph1‐nand Ph2‐n) have different diradical characters depending on the linked form, that is, Ph1‐nand Ph2‐nhave intermediate and pure diradical characters, respectively. In comparison with Py‐nand Ph2‐n, the longitudinal γ of Ph1‐nis significantly larger, and it displays larger enhancement as a function of system size. Substitutions to the terminal rings by donor (NH2) and acceptor (NO2) groups further enhance γ in Ph1‐n, more than in Ph2‐nand Py‐n. These results are in agreement with the structure–property relationships derived for open‐shell NLO systems with symmetric and asymmetric charge distributions (Nakano et al.,J. Chem. Phys. 2010,133, 154302). © 2012 Wiley Periodicals, Inc.
Study of fragmentation pathways of metastable negative ions in aliphatic dipeptides using the statistical theory
Authors: Shchukin P. V. , Muftakhov M. V. , Pogulay A. V. 
Published: February 2012

RATIONALEDipeptide molecules are good model systems for investigation of resonant reactions of low‐energy electrons with proteins. The present work is devoted to the study of the processes of formation and fragmentation of negative ions in aliphatic dipeptides glycyl‐glycine and glycyl‐alanine. The metastable decays of negative ions were detected in these objects, and have been investigated with the aim of clarification of the mechanisms of fragmentation.METHODSThe effective yield curves for negative ions as functions of electron energy were obtained using a magnetic sector mass spectrometer rebuilt for generation and detection of negative ions. For analysis of the observed metastable decays statistical and thermochemical approaches have been used.RESULTSThe ions structures, the enthalpies of formation of neutral and charged particles, and the rate constants of dissociative reactions have been found.CONCLUSIONSComparison of the experimental results with theoretical data leads to the conclusion that metastable ion decay proceeds with minimal structural changes avoiding complicated rearrangements and isomerization processes. Copyright © 2012 John Wiley & Sons, Ltd.
A new method to determine carbon isotopic composition of dissolved inorganic carbon in seawater and pore waters by CO2‐water equilibrium
Authors: Yang Tao , Jiang Shao‐Yong 
Published: February 2012

RATIONALEPrecise measurement of the carbon isotopic compositions of dissolved inorganic carbon (DIC) in water samples is very important for earth and environmental sciences, and the H3PO4 acidification method has long been applied for this purpose. Due to the large variation in DIC concentration in various types of water samples, however, it is difficult to sample the optimized amount of water for high‐precision mass spectrometry analysis and in many cases this has led to poor data quality. In addition, when the amount of water sample is very limited or when the water has a complicated composition such as seawater and saline marine pore waters, it is often difficult to obtain high‐quality data using the conventional method.METHODSHere we report a new method of obtaining CO2‐water equilibrium for high‐precision carbon isotope analysis of DIC in water samples. The instrument used was a Delta Plus XP stable isotope mass spectrometer coupled with an on‐line a Gas Bench II sample preparation device. In general, 0.5 mL of water is sampled and equilibrated with CO2 in headspace. The CO2 is then transferred into the mass spectrometer and δ13C values are obtained.RESULTSThe δ13C values for four marine pore water samples determined by this new method are only slightly different (<0.15‰) from those determined using the conventional H3PO4 method. The new method of obtaining CO2‐water equilibrium also allows a constant amount of CO2 for every sample to finally enter the mass spectrometer and hence better precision can be achieved.CONCLUSIONSThis new method is suitable for the measurement of both oxygen isotopic composition in water and carbon isotopic composition of DIC for seawater and pore water samples. Another benefit of this new method is that the water sample can be re‐used for other further analyses and this is critical when the amount of sample is limited. Copyright © 2012 John Wiley & Sons, Ltd.
Inferring occurrence of growth checks in pike (Esox lucius) scales by using sequential isotopic analysis of otoliths
Authors: Gerdeaux Daniel , Dufour Elise 
Published: February 2012

RATIONALESequential analysis of otolith oxygen isotope (δ18Ooto) values was performed by classical mechanical microdrilling and dual inlet mass spectrometry to infer the timing of growth checks in pike (Esox lucius) scales from Lake Annecy (France). It indicated that the first check on scales occurs before the first winter of life of the fish.METHODSEleven fish caught in February and June 2008 were studied. Intra‐individual isotopic profiles exhibit cyclic variations that are consistent with that of modeled δ18Ooto values using variations in epilimnion temperature and otolith‐specific isotope fractionation equations. The positions of growth checks on scales were compared with the periodic variations of δ18Ooto values on otolith radii using an allometric relationship.RESULTSAll individuals presented at least one check deposited before the first winter. Deposition of some checks might be linked to a shift in fish diet or habitat or to catch‐and‐release induced stress.CONCLUSIONSAlthough coupling between sequential analysis of δ18Ooto values and observation of scale growth features has been shown to be useful, there are limitations in the methodology, especially for the growth‐attenuated region of otoliths associated with older ages. Copyright © 2012 John Wiley & Sons, Ltd.
There is no evidence that the forest service's goshawk recommendations improve goshawk nest productivity
Authors: Beier Paul , Ingraldi Michael F. 
Published: February 2012

AbstractSeveral years ago we tested whether goshawk (accipiter genitilis) productivity increased with increasing similarity of goshawk breeding areas to Forest Service recommendations for the northern goshawk in the southwestern United States. Surprisingly, we found that nest productivity declined as similarity to the recommendations increased from 21% to 57% (Beier et al. 2008). Reynolds et al. (2012) argued that this pattern may have been the result of flawed measurements and analyses, and suggested alternative methods and analyses. Although their suggestions have merit, it is unlikely such changes would have altered the negative trend we observed. Reynolds et al. (2012) also argued that goshawk reproduction might increase as similarity with Forest Service recommendations increases from 57% to 100%. We agree that a larger sample of breeding areas, spanning the full spectrum of similarity to the recommendations, would provide a more powerful evaluation of the recommendations. We suggest that the Forest Service conduct such an evaluation using data for all or some of the 121 breeding areas they have monitored for 8–19 years each. © 2012 The Wildlife Society.