bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrical bistability of organic devices with a polymeric thin film for nonvolatile data storage
Authors: Park Jae‐Eun , Eom Jae‐Hoon , Lim Taehoon , Hwang Do‐Hoon , Pyo Seungmoon 
Published: February 2012

AbstractIn this study, organic memory devices with a single active layer between the two external electrodes were fabricated using an electron‐donor type conjugated polymer and an electron‐acceptor type small organic molecule. The active layer of the memory device was prepared by blending polystyrene, poly[10‐(2′‐ethylhexyl)phenothiazine‐3,7‐diyl], and tetracyanoquinodimethane in 1,2‐dichlorobenzene. The device initially showed a low‐conductance state (OFF state) in the low‐voltage range, and an abrupt current increase, corresponding to the transition to a high‐conductance state (ON state), occurred at a certain voltage (Vth). The ON state could be reverted to the OFF state by applying a voltage higher than Vth. The current ratio between the two states was about 103 (up to 105). After this transition, the device remained in the ON state even after the applied voltage was removed, and this indicated the nonvolatile characteristics of the device. There was no sharp current degradation in the OFF or ON states for 4500 s of continuous bias. The device‐to‐device performance fluctuation was measured, and the conduction mechanisms in the ON and OFF states were examined by fitting the data to well‐known theoretical models. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Synthesis of amphiphilic tadpole‐shaped copolymers by combination of glaser coupling with living anionic polymerization and ring‐opening polymerization
Authors: Wang Guowei , Hu Bin , Fan Xiaoshan , Zhang Yannan , Huang Junlian 
Published: February 2012

AbstractThe tadpole‐shaped copolymers polystyrene (PS)‐b‐[cyclic poly(ethylene oxide) (PEO)] [PS‐b‐(c‐PEO)] contained linear tail chains of PS and cyclic head chains of PEO were synthesized by combination of Glaser coupling with living anionic polymerization (LAP) and ring‐opening polymerization (ROP). First, the functionalized polystyrene‐glycerol (PS‐Gly) with two active hydroxyl groups at ω end was synthesized by LAP of St and the subsequent capping with 1‐ethoxyethyl glycidyl ether and then deprotection of protected hydroxyl group in acid condition. Then, using PS‐Gly as macroinitiator, the ROP of EO was performed using diphenylmethylpotassium as cocatalyst for AB2 star‐shaped copolymers PS‐b‐(PEO‐OH)2, and the alkyne group was introduced onto PEO arm end for PS‐b‐(PEO‐Alkyne)2. Finally, the intramolecular cyclization was performed by Glaser coupling reaction in pyridine/Cu(I)Br/N,N,N′,N″,N″‐pentamethyldiethylenetriamine system under room temperature, and tadpole‐shaped PS‐b‐(c‐PEO) was formed. The target copolymers and their intermediates were well characterized by size‐exclusion chromatography, proton nuclear magnetic resonance spectroscopy, and fourier transform infrared spectroscopy in details. The thermal properties was also determined and compared to investigate the influence of architecture on properties. The results showed that tadpole‐shaped copolymers had lower Tm, Tc, and Xc than that of their precursors of AB2 star‐shaped copolymers. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012
Effects of carbon nanotubes on polymer physics
Authors: Grady Brian P. 
Published: February 2012

AbstractA single carbon nanotube has many similarities with an individual polymer chain including the fact that the end‐to‐end length of both are often about the same and the diameter of the chain is about the same (for single‐walled nanotubes) or only ∼10 to 20 times larger (for multiwalled nanotubes). The combination of the solid surface and the similarity of the two materials means that polymer physics are altered in manners not seen with any other type of commonly used filler. The purpose of this review is to update a chapter that appears in a recent tome by Grady (2011) and describe how polymer physics is altered in composites that contain carbon nanotubes. Subjects that will be discussed include chain configuration, glass transition, polymer diffusion, unit cells and crystalline superstructure (lamellae, spherulites and shish‐kebabs), and crystallization kinetics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Organic transistors in the new decade: Toward n‐channel, printed, and stabilized devices
Authors: Kola Srinivas , Sinha Jasmine , Katz Howard E. 
Published: February 2012

AbstractSignificant progress has been made in designing organic semiconducting materials (OSCs) for the past few decades for organic field‐effect transistors (OFETs). Much attention has been paid to the development of p‐channel OSCs, with less but highly significant progress on n‐channel OSCs. In this review, we focus on the advances made with OFETs in the last few years to achieve high performance in n‐channel modes, air stability, and solution processability, leading to printable active electronics. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012
Atmospheric Pressure Plasma Surface Modification of Poly(D,L‐lactic acid) Increases Fibroblast, Osteoblast and Keratinocyte Adhesion and Proliferation
Authors: Renò Filippo , D'Angelo Domenico , Gottardi Gloria , Rizzi Manuela , Aragno Davide , Piacenza Giacomo , Cartasegna Federico , Biasizzo Miriam , Trotta Francesco , Cannas Mario 
Published: February 2012

AbstractAn atmospheric pressure plasma deposition for P(d,L)LA (PLA) film was used to modify polymer surface properties using 1,2‐diaminopropane and acrylic acid as precursors. These two different plasma coatings result in a high density of amino groups (PLA‐NH2) and carboxylic groups (PLA‐COOH) onto PLA surface as demonstrated by Fourier transform infra‐red (FTIR) spectroscopy and X‐ray photoelectron spectroscopy (XPS). Plasma coatings modified PLA surface wettability and proteins adsorption from fetal bovine serum (FBS), influencing cell adhesion and proliferation of 3T3 mouse fibroblast, MC‐3T3 E1 mouse pre‐osteoblast, and HaCaT cells (human keratinocytes). In particular both coatings increased pre‐osteoblast and keratinocyte adhesion while no effect was observed on fibroblast. Moreover, cell proliferation assessed after 48 h by Tox‐8 assay was significantly higher for osteoblast cells and keratinocyte seeded onto both PLA‐NH2 and PLA‐COOH compared to cells seeded onto normal PLA. On the basis of the obtained data, the atmospheric pressure plasma deposition described might represent an innovative and useful tool for bone and skin tissue engineering. magnified image
The conformational preferences of acylphloroglucinols—a promising class of biologically active compounds
Authors: Kabanda Mwadham M. , Mammino Liliana 
Published: February 2012

AbstractAcylphloroglucinols are a broad class of phloroglucinol derivatives characterized by the presence of a COR group, where R is more often an alkyl chain. They are largely present in natural sources and exhibit a variety of biological activities, including antibacterial, antiviral, antifungal, antitumor, antioxidant, and antimalarial. This work reports the results of a systematic conformational study (in vacuo, chloroform, acetonitrile, and water) of a representative number (118) of actual and model acylphloroglucinol structures, considering the most common R chains and investigating conformational preferences and relative energies as well as the influence of specific structural features characterizing significant subsets of compounds. The study aimed at identifying patterns for conformational preferences and at singling out the conformational aspects more closely related to the individuality of different structures, as these are expected to be more closely linked to the differences in the biological activities of different compounds. The results highlight patterns enabling reliable predictions of the conformational preferences of acylphloroglucinol molecules. © 2012 Wiley Periodicals, Inc.
A natural orbital functional based on an explicit approach of the two‐electron cumulant
Authors: Piris M. 
Published: February 2012

AbstractThe cumulant expansion gives rise to an useful decomposition of the two‐matrix in which the pair correlated matrix (cumulant) is disconnected from the antisymmetric product of the one‐matrices. The cumulant can be approximated in terms of two matrices, Δ and Π, which are explicit functions of the occupation numbers of the natural orbitals. It produces a natural orbital functional (NOF) that reduces to the exact expression for the total energy in two‐electron systems. The N‐representability positivity necessary conditions of the two‐matrix impose several bounds on the matrices Δ and Π. Appropriate forms of these matrices lead to different implementations of the NOF known in the literature as PNOFi (i = 1–5). The basic features of these functionals are reviewed here. The strengths and weaknesses of the different PNOFs are assessed. © 2012 Wiley Periodicals, Inc.
Assessing structural bonding aspects of multiband superconductors through impurity‐induced local lattice distortions: A case study on MgB2
Authors: Pishtshev Aleksandr , Klopov Mihhail 
Published: February 2012

AbstractTo examine how a change in the host cation affects the structural and bonding properties of the local ionic environment, we have performed a series of ab initio simulations of substitutional impurities such as zinc, copper, and zirconium ions incorporated into the magnesium sublattice of MgB2. It was shown that at a low doping level, the induced lattice distortions and additional forces are noticeable small. For the given set of substituents, it was also determined how the impurity ion modifies the initial charge distribution around the host cation position and therefore, affects both the overall picture of the electronic states involved in the chemical bonding and the intrinsic charge‐transfer channels. In the context of the cation properties, by analyzing specific changes in local charge structures caused by the presence of the impurity, the existence of two different trends in the Mg‐site substitution effect was found and discussed. © 2012 Wiley Periodicals, Inc.
Embedding scaling relations in Padé approximants: Detours to tame divergent perturbation series
Authors: Dhatt Sharmistha , Bhattacharyya Kamal 
Published: February 2012

AbstractA divergent perturbation series is known to yield very unreliable results for observables even at moderate coupling strengths. One of the most popular techniques in handling such series is to express them as rational functions, but it is often faithful only for small coupling. We outline here how one can gain considerable advantages in the large‐coupling regime by properly embedding known asymptotic scaling relations for selected observables during construction of the aforesaid Padé approximants. Three new bypass routes are explored in this context. The first approach involves a weighted geometric mean of two neighboring PA. The second idea is to consider series for specific ratios of observables. The third strategy is to express observables as functionals of the total energy in the form of series expansions. Symanzik's scaling relation, and the virial and Hellmann–Feynman theorems, are used at appropriate places to aid each of the strategies. Pilot calculations on the ground‐state perturbation series of certain observables for the quartic anharmonic oscillator problem reveal readily the benefit and novelty. © 2012 Wiley Periodicals, Inc.
A DFT‐based potential energy surface for the H cluster
Authors: Barragán Patricia , Prosmiti Rita 
Published: February 2012

AbstractA global potential energy surface (PES) for the H complex is presented based on density functional theory (DFT) calculations. We used the B3(H) hybrid functional, a specifically parameterized B3LYP functional for hydrogen‐only systems, and we first characterize the equilibrium H structure. In turn, by comparing with coupled clusterwith single, double and perturbative triples excitations (CCSD(T)) results, we show that the B3(H) predictions are in overall satisfactory and quantitative good agreement with these higher accurate ab initio data for all aspects of the potential, including the correct estimates asymptotic behavior at long H + H2 distances. Moreover, using the present surface we compute dissociation energies and dissociation enthalpies for the equilibrium H ⇋ H + H2 reaction, and compare them with the data available from experimental measurements. In general, a very good accord is found, with the theoretical values from both DFT/B3(H) and CCSD(T) computations to predict somehow a less bound H cluster than the experimental estimates. Such realistic representations of the potential surfaces of polyatomic systems are of particular interest for studying spectroscopy, collision, and/or fragmentation dynamics, and this is the first attempt for a reasonable description of the H PES suitable for future direct dynamics simulations. © 2012 Wiley Periodicals, Inc.
Excitation energy transfer in GFP‐X‐CFP model peptides (X = amino acids): Direct Versus through‐bridge energy transfers
Authors: Kawatsu Tsutomu , Hasegawa Jun‐ya 
Published: February 2012

AbstractThe excitation energy transfer (EET) between a fluorescent resonance energy transfer (FRET) pair, cyan fluorescent protein chromophore (CFPc)/ green fluorescent protein chromophore (GFPc), is used for measuring molecular proximity in experimental studies. In this article, the role of the bridging protein media has been investigated using the quantum chemical calculations for the EET electronic coupling. We adopted a model peptide connecting GFPc and CFPc, a GFPc‐X‐CFPc model, and examined the X (amino acids) dependence. The major part of the EET coupling element arises from the direct interaction between GFPc and CFPc via the Förster mechanism. The magnitude of the through‐X interactions vary for the type of residues. The contribution of the X was, however, at most 10% of the total value. Together with the contributions from through‐peptide and charge‐transfer types, X gives minor modifications to the total coupling via the super‐exchange mechanism. © 2012 Wiley Periodicals, Inc.
Study on the noncovalent interactions of saikosaponins and cytochrome c by electrospray ionization mass spectrometry
Authors: Liu Yingzhi , Su Bo , Wang Xian 
Published: February 2012

RATIONALEThe study of interactions between protein and pharmaceutical molecules including natural extracts has become of increasing interest in biological and biomedical research. An investigation of the interaction between saikosaponins and cytochrome c (Cyt c) by electrospray ionization mass spectrometry (ESI‐MS) is described in this study. Saikosaponins are found in Bupleurum falcatum (a flowering plant), and they are glycosides that consist of saccharides and the sapogenins of triterpenoids.METHODSSeven model molecules of saccharides and triterpenes, namely maltose (Mal II), maltotriose (Mal III), raffinose (Raf), and stachyose (Sta), glycyrrhetinic acid (Gly), ursolic acid (Urs) and oleanic acid (Ole), were chosen to perform a series of ESI‐MS control experiments for the exploration of the interaction groups in saikosaponins with Cyt c. The dissociation constants of detected noncovalent complexes were determined by using a direct ESI‐MS assay.RESULTSWe have observed in the ESI mass spectra the formation of Cyt c complexes with saikosaponins a and c, and these saccharides, with 1:1 and 1:2 stoichiometry. Our results showed that no complex ions of triterpenes and Cyt c were detected in the ESI‐MS and similar Kd values were obtained for the Cyt c complexes of saikosaponins and saccharides. This demonstrates that the glycosyl moiety in the saikosaponins is the effective interaction group with Cyt c. We propose that saikosaponins and saccharides interact with Cyt c by hydrogen bonds. The binding affinity of these six ligands with Cyt c is shown to be in the order Ssa > Ssc > Raf, Mal III > Sta ≥ Mal II.CONCLUSIONSThe ESI‐MS methodology presented in this study enables us to investigate the interactions of saikosaponins with Cyt c, and allows the direct determination of binding constants. These results could guide further research for providing insights into the structure‐binding relationship of ligands with Cyt c. Copyright © 2012 John Wiley & Sons, Ltd.
Isotopic values of the Amazon headwaters in Peru: comparison of the wet upper Río Madre de Dios watershed with the dry Urubamba‐Apurimac river system
Authors: Lambs L. , Horwath A. , Otto T. , Julien F. , Antoine P.‐O. 
Published: February 2012

RATIONALEThe Amazon River is a huge network of long tributaries, and little is known about the headwaters. Here we present a study of one wet tropical Amazon forest side, and one dry and cold Atiplano plateau, originating from the same cordillera. The aim is to see how this difference affects the water characteristics.METHODSDifferent kind of water (spring, lake, river, rainfall) were sampled to determine their stable isotopes ratios (oxygen 18/16 and hydrogen 2/1) by continuous flow isotope ratio mass spectrometry (IRMS). These ratios coupled with chemical analysis enabled us to determine the origin of the water, the evaporation process and the water recycling over the Amazon plain forest and montane cloud forest.RESULTSOur study shows that the water flowing in the upper Madre de Dios basin comes mainly from the foothill humid forest, with a characteristic water recycling process signature, and not from higher glacier melt. On the contrary, the water flowing in the Altiplano Rivers is mainly from glacier melts, with a high evaporation process. This snow and glacier are fed mainly by Atlantic moisture which transits over the large Amazon forest.CONCLUSIONSThe Atlantic moisture and its recycling over this huge tropical forest display a progressive isotopic gradient, as a function of distance from the ocean. At the level of the montane cloud forest and on the altiplano, respectively, additional water recycling and evaporation occur, but they are insignificant in the total water discharge. Copyright © 2012 John Wiley & Sons, Ltd.
Tandem mass spectrometry of electrosprayed polyhedral oligomeric silsesquioxane compounds with different substituents
Authors: Fouquet Thierry , Phan Trang N. T. , Charles Laurence 
Published: February 2012

RATIONALEPolyhedral oligomeric silsesquioxanes (POSSs), defined as [RSiO3/2]n with R designating an organic substituent, were considered here as models of highly cross‐linked polysiloxanes, to be further used as references in tandem mass spectrometric characterization of plasma polymers of hexamethyldisiloxane, expected to be composed of organic polydimethylsiloxane (PDMS) and inorganic (SiOx) silica‐based parts. The collision‐induced dissociation (CID) behavior of [RSiO3/2]8 compounds was then studied as a function of the R substituent.METHODSPOSS compounds were produced in the gas phase as ammonium adducts and the product ions generated upon CID, amongst which was the protonated precursor, were accurately mass measured in an orthogonal acceleration time‐of‐flight mass analyzer.RESULTSThe presence of eight propylamine substituents was shown to induce sequential dehydration of the protonated precursor, ultimately leading to a complete unfolding of the POSS cage. Similar opening of the octahedron structure in the protonated molecule substituted with OSi(CH3)3, OSiH(CH3)2 or OH (formed upon methanolysis of dimethylsiloxy substituents) was proposed to account for the product ions generated during their CID. Sequential charge‐remote transfers of a methyl group (and of H in the case of dimethylsiloxy substituents) from one substituent group to a neighboring one was shown to lead to a linear co‐oligomeric chain composed of randomly distributed siloxy‐based monomers.CONCLUSIONSAll the peaks observed in CID could be accounted for by applying dissociation reactions typically occurring in protonated polysiloxane‐like oligomers. The large number of product ions observed in MS/MS was found to result from the variety of possible structural rearrangements, producing numerous linear isomeric forms of the dissociating species. Copyright © 2012 John Wiley & Sons, Ltd.
Thermal decomposition of pyridoxine: an evolved gas analysis‐ion attachment mass spectrometry study
Authors: Juhász Márta , Takahashi Seiji , Kitahara Yuki , Fujii Toshihiro 
Published: February 2012

RATIONALEPyridoxine is an important vitamer in food and pharmaceutical products. Heat treatments applied during preparation or storage of the products cause the decomposition of pyridoxine. Identification and understanding of the degradation products of pyridoxine and studying its decomposition kinetics are essential in the preparation and preservation of pyridoxine‐containing foods and pharmaceuticals.METHODSReal‐time, non‐isothermal decomposition of pyridoxine was studied using evolved gas analysis‐Li+ ion attachment mass spectrometry (EGA‐Li+IAMS). Arrhenius parameters for the thermal decomposition of pyridoxine were obtained via the total ion monitoring (TIM) curve.RESULTSMost of the pyridoxine evaporated in molecular form, but the formation of pyridoxal and o‐quinone methide, both biologically important species, was also observed from the solid‐phase degradation of pyridoxine. The observation of o‐quinone methide, a species possessing anticancer activity, was particularly noteworthy due to its chemical instability. The activation energy (Ea) for pyridoxine decomposition determined by EGA‐IAMS was found to be 20.0 kcal mol–1, and the pre‐exponential factor (A) was 5.7 × 109 min–1.CONCLUSIONSThe calculated kinetic parameters are important for predicting the thermal stability of pyridoxine vitamer. The estimated lifetime (t90%,25°C) of 1.7 × 10–2 years in nitrogen was also obtained from the EGA‐IAMS experiment. Copyright © 2012 John Wiley & Sons, Ltd.
Molecular phylogenetics by direct comparison of tandem mass spectra
Authors: Palmblad Magnus , Deelder André M. 
Published: February 2012

RATIONALEMolecular phylogenetics is the study of evolution and relatedness of organisms or genes. Mass spectrometry is used routinely for bacterial identification and has also been used for phylogenetic analysis, for instance from bone material. Unfortunately, only a small fraction of the acquired tandem mass spectra allow direct interpretation.METHODSWe describe a new algorithm and software for molecular phylogenetics using pairwise comparisons of tandem mass spectra from enzymatically digested proteins. The spectra need not be annotated and all acquired data is used in the analysis. To demonstrate the method, we analyzed tryptic digests of sera from four great apes and two other primates.RESULTSThe distribution of spectra dot products for thousands of tandem mass spectra collected from two samples provides a measure on the fraction of shared peptides between the two samples. When inverted, this becomes a distance metric. By pairwise comparison between species and averaging over four individuals per species, it was possible to reconstruct the unique correct phylogenetic tree for the great apes and other primates.CONCLUSIONSThe new method described here has several attractive features compared with existing methods, among them simplicity, the unbiased use of all acquired data rather than a small subset of spectra, and the potential use of heavily degraded proteins or proteins with a priori unknown modifications. Copyright © 2012 John Wiley & Sons, Ltd.