bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrologic variability and the onset of modern El Niño–Southern Oscillation: a 19 250‐year record from Lake Elsinore, southern California
Authors: Kirby Matthew E. , Lund Steve P. , Poulsen Christopher J. 
Published: March 2005

AbstractThere are very few terrestrial palaeoclimate archives spanning the Last Glacial Maximum through the Holocene from coastal southern California. Yet, knowledge of past climate dynamics is critical for assessing present and future constraints on the region's dwindling freshwater resources. We present initial results from two drill cores extracted from the present‐day edge of Lake Elsinore, southern California's largest natural lake. Using a multiproxy approach including lithologic description, mass magnetic susceptibility, LOI 550°C (total organic matter), and LOI 950°C (total carbonate), we infer first‐order, long‐term climate change over the past 19 250 calendar years. Furthermore, we suggest possible first‐order forcing mechanisms that drive this change, which include presence/absence of continental ice sheets, insolation, and complex ocean–atmosphere interactions. Our results indicate four distinct millennial‐scale climate modes over the past 19 250 calendar years. These modes include a wet Last Glacial Maximum (19 250–17 120 cal. yr BP), a relatively dry late‐Glacial/Holocene transition (17 120–9450 cal. yr BP), a wet early Holocene (9450–7670 cal. yr BP), and a highly variable mid‐to‐late Holocene climate (i.e., alternating wet/dry cycles; 7670 cal. yr BP–present). We attribute the mid‐to‐late Holocene climate interval to the onset of El Niño–Southern Oscillation ca. 7000 cal. yr BP and a more vigorous hydrologic system. These results are supported by a variety of regional terrestrial and marine palaeoclimate archives. Copyright © 2005 John Wiley & Sons, Ltd.
A new early Holocene cryptotephra from northwest Scotland
Authors: Ranner Patricia H. , Allen Judy R. M. , Huntley Brian 
Published: March 2005

AbstractClarification of the temporal relationships amongst records of environmental change is dependent on accurate timescales. Event markers such as tephra layers are extremely important for constraining chronologies and providing tie points. In this report we present evidence of a previously unknown early Holocene Icelandic cryptotephra from a lake in northern Scotland—the ‘An Druim Tephra’. The calibrated radiocarbon age of 9560 cal. yr BP for this new cryptotephra makes it an important addition to the suite of cryptotephras now recorded from the last glacial termination and early Holocene in northwest Europe. In addition we report evidence in support of a ‘Younger Borrobol Tephra’ from Lateglacial sediments of Allerød age. Copyright © 2005 John Wiley & Sons, Ltd.
Thermo‐ and pH‐Responsive Micelles of Poly(acrylic acid)‐block‐Poly(N,N‐diethylacrylamide)
Authors: André Xavier , Zhang Mingfu , Müller Axel H. E. 
Published: March 2005

AbstractSummary: The bis‐hydrophilic block copolymer, poly(acrylic acid)45‐block‐poly(N,N‐diethylacrylamide)360, was obtained after hydrolysis of poly(tert‐butyl acrylate)45‐block‐poly(N,N‐diethylacrylamide)360, synthesized by sequential anionic polymerization of tert‐butyl acrylate (tBA) and N,N‐diethylacrylamide (DEAAm) in the presence of Et3Al. The polymer is stimuli‐sensitive with respect to both pH and temperature in aqueous solution, reversibly forming spherical crew‐cut micelles with PDEAAm‐core (〈Rh〉z = 21.5 nm) under alkaline conditions for T > 35 °C as well as inverse star‐like micelles with an expanded PAA‐core (〈Rh〉z = 43.8 nm) under acidic conditions for T < 35 °C, as indicated by dynamic light scattering.Modes of micelle formation for poly(acrylic acid)45‐block‐poly(N,N‐diethylacrylamide)360 in aqueous solution depending on the pH and temperature.imageModes of micelle formation for poly(acrylic acid)45‐block‐poly(N,N‐diethylacrylamide)360 in aqueous solution depending on the pH and temperature.
Effect of Polydispersity on the Phase Behavior of Polymer Blends
Authors: Lo Chieh‐Tsung , Seifert Soenke , Thiyagarajan Pappannan , Narasimhan Balaji 
Published: March 2005

AbstractSummary: The effect of polydispersity on polymer blend phase behavior is studied by in situ small‐angle X‐ray scattering. In a polydisperse polyethylene (PE)/isotactic poly(propylene) (iPP) blend, the enthalpic portion of the interaction parameter is greater than that of a corresponding blend with lower polydispersity. This is attributed to the presence of long chains, which provide a higher interaction energy and packing constraint, reducing the system miscibility. As expected, the radius of gyration is higher in the system with higher polydispersity.Comparison of phase diagrams of the iPP/PE system used in this study (thin lines) with that obtained from the literature (thick lines). The solid lines represent binodals and the dashed lines are spinodals.imageComparison of phase diagrams of the iPP/PE system used in this study (thin lines) with that obtained from the literature (thick lines). The solid lines represent binodals and the dashed lines are spinodals.
Three‐Dimensional Structure of Olefinic Thermoplastic Elastomer Blends Using Electron Tomography
Authors: Sengupta Pratip , Noordermeer Jacques W. M. 
Published: March 2005

AbstractSummary: The present communication reports the first use of electron tomography in reconstructing the three‐dimensional morphology in thermoplastic elastomer blends. The blends investigated were dynamically vulcanized blends of ethylene‐propylene‐diene (EPDM) rubber/poly(propylene)/oil and polystyrene‐block‐(ethylene‐co‐butylene)‐block‐polystyrene (SEBS)/poly(propylene)/oil. An easy identification of blend morphology could be carried out at blend compositions, where conventional transmission electron microscopic imaging gives misleading information. This technique gives a higher resolution than any other microscopic technique, and is applicable to blends with dispersed as well as co‐continuous morphologies.Example of a tomographic model of partially co‐continuous SEBS phases in a SEBS/PP/oil thermoplastic blend. Only the contours of the SEBS phase are shown.imageExample of a tomographic model of partially co‐continuous SEBS phases in a SEBS/PP/oil thermoplastic blend. Only the contours of the SEBS phase are shown.
NMR Analysis and Regiochemical Structure of Some Selectively 13C‐Enriched Poly(propylene)s
Authors: Zambelli Adolfo , Csok Zsolt , Sessa Irene 
Published: March 2005

AbstractSummary: The regiochemical structures of poly(propylene)s obtained in the presence of three single‐site catalysts, Cp*Ti(CH3)3 + B(C6F5)3 (I + III), CpTi(CH3)3 + B(C6F5)3 (II + III), and VCl4 + anisole + Al(C2H5)2Cl (V + A), are investigated by 13C NMR analysis. Polymer 1, obtained in the presence of I + III is, seemingly, fully regioregular, while, surprisingly, polymer 2, obtained in the presence of II + III, appears to be alternating sequence of primary and secondary regioblocks, very much like polymer 3, obtained in the presence of V + A. The stereochemical structure of the polymer obtained in the presence of I + III is in excellent agreement with a Bernoullian statistical model of the stereoselective propagation, while those of the other two polymers possibly require a Coleman‐Fox model.13C NMR spectra of 10%‐enriched poly[(2‐13C)propylene], 1′ and 2′, prepared under the conditions reported in Table 1 for the corresponding poly(propylene)s, 1 and 2. The resonances of the tertiary carbons are diagnostic of the regioblock structure of sample 2′.image13C NMR spectra of 10%‐enriched poly[(2‐13C)propylene], 1′ and 2′, prepared under the conditions reported in Table 1 for the corresponding poly(propylene)s, 1 and 2. The resonances of the tertiary carbons are diagnostic of the regioblock structure of sample 2′.
Highly‐Ordered Hybrid Organic‐Inorganic Isoporous Membranes from Polymer Modified Nanoparticles
Authors: Nyström Daniel , Antoni Per , Malmström Eva , Johansson Mats , Whittaker Michael , Hult Anders 
Published: March 2005

AbstractSummary: Organic‐inorganic hybrid materials consisting of nanosized silica particles with surface grafted PS or PS‐b‐PMMA were synthesized using ATRP. These hybrid materials were used in the fabrication of highly‐ordered isoporous membranes. Optical characterization revealed that the membranes consisted of hexagonally ordered pores of uniform size. The combination of an open pore structure and high surface area makes isoporous membranes into materials of high interest in fields as biotechnology and photonics.Image from optical microscope of hybrid nanoparticle membrane of SiO2‐g‐PS with hexagonally‐ordered pores.imageImage from optical microscope of hybrid nanoparticle membrane of SiO2‐g‐PS with hexagonally‐ordered pores.
Gelation Studies, 3
Authors: Richter Sven , Brand Torsten , Berger Stefan 
Published: March 2005

AbstractSummary:The sol‐gel transition of one thermoreversible gelling mixture made of xanthan gum and locust bean gum has been studied by using in situ time‐resolved dynamic light scattering (DLS) and measuring the spin‐lattice relaxation timeT1of several protons. A critical dynamical behavior was observed near the sol‐gel transition, which is characterized by the presence of power‐law spectra over four decades of the delay time in the time‐intensity correlation functiong2(t)−1 ∼ t−μat 48 °C. The increase inT1with increasing temperature becomes steeper at 50 °C indicating a significant change in the local mobility of one anomeric proton of the xanthan side chain and the anomeric protons of the locust bean gum mannose backbone.Temperature dependence of the spin‐lattice relaxation timeT1for the equatorial anomeric proton of the mannopyranosic unit located next to the main chain of the xanthan.imageTemperature dependence of the spin‐lattice relaxation timeT1for the equatorial anomeric proton of the mannopyranosic unit located next to the main chain of the xanthan.
Combining Atom Transfer Radical Polymerization and Click Chemistry: A Versatile Method for the Preparation of End‐Functional Polymers
Authors: Lutz Jean‐François , Börner Hans G. , Weichenhan Katja 
Published: March 2005

AbstractSummary: The bromine chain ends of well‐defined polystyrene ($\overline M _{\rm n}$ = 2 700 g · mol−1, $\overline M _{\rm w} /\overline M _{\rm n}$ = 1.11) prepared using ATRP were successfully transformed into various functional end groups (ω‐hydroxy, ω‐carboxyl and ω‐methyl‐vinyl) by a two‐step pathway: (1) substitution of the bromine terminal atom by an azide function and (2) 1,3‐dipolar cycloaddition of the terminal azide and functional alkynes (propargyl alcohol, propiolic acid and 2‐methyl‐1‐buten‐3‐yne). The “click” cycloaddition was catalyzed efficiently by the system copper bromide/4,4′‐di‐(5‐nonyl)‐2,2′‐bipyridine. In all cases, 1H NMR spectra indicated quantitative transformation of the chain ends of polystyrene into the desired function.Preparation of well‐defined functional polymers possessing diverse chain‐end functionalities by the combination of atom transfer radical polymerization and click chemistry.imagePreparation of well‐defined functional polymers possessing diverse chain‐end functionalities by the combination of atom transfer radical polymerization and click chemistry.
Monte Carlo Technique to Simulate Amide Interchange Reactions, 3
Authors: Liu Zhen Hong , Wang Chao Sheng , Wang Xia Qin , Huang Nan Xun , Filippini‐Fantoni Roberto 
Published: March 2005

AbstractSummary: Influence of amide interchange reactions of polyamide 6 (PA6) on its molecular weight distribution (MWD) was analyzed using a kinetic Monte Carlo simulation method, by which two reaction systems with different types of initial non‐equilibrium distributions, monodisperse and bimodal distribution, were investigated. The simulation results indicate that initial deviations from equilibrium MWD are rapidly relaxed to an equilibrium one, which approaches the most probable MWD proposed by Flory. The reaction time to reach the equilibrium MWD decreases with an increase in reaction temperature. The simulated polydispersity index data suggest that about 0.3 interchanges per segment are sufficient to equilibrate the non‐equilibrium systems, consistent with the results reported by Jo et al. on ester interchange reactions of poly(ethylene terephthalate) (PET).Variation of polydispersity index Q with interchange reaction time at different reaction temperatures for an initial monodisperse distribution.imageVariation of polydispersity index Q with interchange reaction time at different reaction temperatures for an initial monodisperse distribution.
A Mathematical Model for the Longest Ethylene Sequence Distribution of Random Ethylene Copolymers
Authors: Gemoets Frederik , Hagen Henk 
Published: March 2005

AbstractSummary: In the first step to model Crystaf® curves, a mathematical expression ψ has been derived to describe the longest ethylene sequence (LES) distribution of random binary (e.g., ethylene/α‐olefin) copolymer chains. Based on this expression, a method Ψpolymer has been developed to describe the LES‐distribution of random copolymers. Comparisons of the LES‐distribution of a random copolymer with polydispersity of 2, as calculated by Ψpolymer, with Monte Carlo simulation and with a method previously described in literature show that the derived mathematical expression ψ is correct. This model allows for the description of the crystallizing temperature‐distribution of polymers using the reported relation between crystallizing temperature and LES. It will also hold if the crystallizing temperature of a chain would depend on other chain properties next to its LES. Exactly this latter prospect will favor the use of the mathematical expression derived in this report, above the ones from the literature.LES weight‐distribution of a random copolymer, calculated by Ψpolymer and by a Monte Carlo simulation.imageLES weight‐distribution of a random copolymer, calculated by Ψpolymer and by a Monte Carlo simulation.
Model Bridging Effects of Asymmetrical Triblock Copolymers
Authors: Peng Changjun , Li Jiankang , Liu Honglai , Hu Ying 
Published: March 2005

AbstractSummary: We have performed Monte Carlo simulations to study the bridging of symmetrical or asymmetrical triblock copolymers confined between two similar or different solid surfaces based on a simple lattice model. The influence of the molecular structure, surface separation, adsorption energy, chain composition, and the chain concentration on the fractions of chains with bridge, loop and dangling configurations are reported in detail. The results show that the largest bridging fraction is given only when symmetrical triblock copolymers are confined between two parallel surfaces with the same adsorption energy. The bridge fraction is decreased so long as the asymmetry of the copolymers or the difference between the two surfaces is enhanced. It was found also that the bridging fraction increases as the adsorption energy increases. The bridging fraction Ωbridge under different separations, Lz, can be expressed as $\Omega _{{\rm bridge}} = A(1 - L_z /L_{z.\max } )^\alpha $ in various situations. On the other hand, by introducing a symmetry index ν, the influence of molecular structure of copolymers on the bridges can be illustrated approximately by a relation $(1 - \Omega _{{\rm b,asym}} /\Omega _{{\rm b,symm}} ) = B(1 - \nu )^\zeta $ when the two surfaces are similar and the adsorption energy is not too high. Combining the two expressions, data of the bridge fractions for copolymers of different symmetries confined between surfaces with different separations can be described with a single equation, which, in some occasion, can be used for prediction.Influence of molecular structure on the bridging fraction for ${\rm A}_{r_{{\rm A1}} } {\rm B}_{{\rm 40}} {\rm A}_{r_{{\rm A2}} }$.imageInfluence of molecular structure on the bridging fraction for ${\rm A}_{r_{{\rm A1}} } {\rm B}_{{\rm 40}} {\rm A}_{r_{{\rm A2}} }$.
Diagnosis of Impurity Levels in a Copolymerization Process
Authors: Lou Shijin , Duever Thomas A. , Budman Hector M. 
Published: March 2005

AbstractSummary: This work investigates a fault diagnosis problem in the copolymerization process of styrene and methyl methacrylate (STY/MMA). Two topics are discussed in this paper: the system observability and optimal experimental design (OED) to reduce fault misclassification. Lack of observability has been found to be one of the major causes of misclassification in fault diagnosis, which is not remediable by any means other than including the right measurements necessary for the observability. In this work, the system observability has been studied through simulation analysis. Then, two new experimental design methods are proposed to train the projection pursuit regression (PPR) algorithm for fault diagnosis purpose. The new design methods, referred to as Gaussian probability design and Fuzzy boundary design, are compared to a conventional factorial design, to evaluate their performance for the problem under study. The Gaussian probability design is based on the calculation of the probability of an experimental data point near a class boundary belonging to a specific class. The Fuzzy boundary design is based on a bootstrapping technique used in part for the learning process in developing neural network models. It investigates the insufficiency of training data based on the identification of class boundaries by a group of models, such as PPR models. Both Gaussian probability design and Fuzzy boundary design methods automatically search for the sparseness of the training data, and provide guidelines to include pairs of training data on two sides of a class boundary in the areas where the data density is the lowest. The proposed design methods outperform a conventional factorial design by reducing the fault misclassification more effectively with the same amount of additional training data.Testing data in the process measurement space of temperature vs. conversion.imageTesting data in the process measurement space of temperature vs. conversion.
Advanced Computational Strategies for Modelling the Evolution of Full Molecular Weight Distributions Formed During Multiarmed (Star) Polymerisations
Authors: Chaffey‐Millar Hugh , Busch Markus , Davis Thomas P. , Stenzel Martina H. , Barner‐Kowollik Christopher 
Published: March 2005

AbstractSummary: A novel computational strategy is described for the simulation of star polymerisations, allowing for the computation of full molecular weight distributions (MWDs). Whilst the strategy is applicable to a broad range of techniques for the synthesis of star polymers, the focus of the current study is the simulation of MWDs arising from a reversible addition fragmentation chain transfer (RAFT), R‐group approach star polymerisation. In this synthetic methodology, the arms of the star grow from a central, polyfunctional moiety, which is formed initially as the refragmenting R‐group of a polyfunctional RAFT agent. This synthetic methodology produces polymers with complex MWDs and the current simulation strategy is able to account for the features of such complex MWDs. The strategy involves a kinetic model which describes the reactions of a single arm of a star, the kinetics of which are implemented and simulated using the PREDICI® program package. The MWDs resulting from this simulation of single arms are then processed with an algorithm we describe, to generate a full MWD of stars. The algorithm is applicable to stars with an arbitrary number of arms. The kinetic model and subsequent algorithmic processing techniques are described in detail. A simulation has been parameterised using rate coefficients and densities for a 2,2′‐azoisobutyronitrile (AIBN) initiated, bulk polymerisation of styrene at 60 °C. A number of kinetic parameters have been varied over large ranges. Conversion normalised simulations were performed, leading to information regarding star arm length, polydispersity index (PDI) and the fraction of living arms. These screening processes provided a rigorous test for the kinetic model and also insight into the conditions, which lead to optimal star formation. Finally, full MWDs are simulated for several RAFT agent/initiator ratios as well as for stars with a varying number of arms.Full MWDs from a star with 1, 2, 4, 6 and 8 arms.imageFull MWDs from a star with 1, 2, 4, 6 and 8 arms.
A paracrine signal mediates the cell transformation response to low dose gamma radiation in JB6 cells
Authors: Weber Thomas J. , Siegel Robert W. , Markillie Lye M. , Chrisler William B. , Lei Xingye C. , Colburn Nancy H. 
Published: March 2005

AbstractThe carcinogenic response to radiation is complex and may involve adaptive cellular responses as well as a bystander effect mediated by paracrine or intercellular signaling activities. Using a newly developed co‐culture model we have examined whether low dose gamma radiation induces the transformation of JB6 mouse epidermal cells as well as non‐irradiated bystander cells. Cell transformation response is defined as the acquisition of anchorage‐independent growth properties and is quantified by counting colonies on soft agar. Exposure of JB6 cells to low dose (2–20 cGy) gamma radiation resulted in an approximate 1.9 ± 0.1 and 2.8 ± 0.5‐fold increase in cell transformation response when cells were seeded at 1 × 104 or 1 × 105 cells/dish, relative to respective sham exposed controls. We developed a co‐culture model where sham exposed or irradiated JB6 cells were mixed with non‐irradiated JB6 cells that had been stably transfected with the enhanced yellow fluorescent protein (EYFP) to enable the distinction of fluorescent bystander‐specific colonies. A significant increase in the number of bystander‐specific colonies was observed in co‐culture with 10 cGy irradiated JB6 cells (224 ± 9), relative to the number of bystander‐specific colonies arising in co‐culture with sham exposed JB6 cells (55 ± 16). Our results indicate that low dose radiation induces the transformation of JB6 cells and that a soluble paracrine factor that is secreted by irradiated cells induces the transformation of non‐irradiated bystander cells. © 2005 Wiley‐Liss, Inc.
Double‐blind, placebo‐controlled, unforced titration parallel trial of quetiapine for dopaminergic‐induced hallucinations in Parkinson's disease
Authors: Ondo William G. , Tintner Ron , Dat Voung Kevin , Lai Dejian , Ringholz George 
Published: March 2005

AbstractWe completed a single site, double‐blind, placebo‐controlled, parallel design study of quetiapine for hallucinations in PD. Thirty‐one subjects with PD and prominent visual hallucinations and Mini‐Mental State Examination score >21 were randomly assigned in a 2:1 drug to placebo ratio, up to 200 mg daily of quetiapine or matching placebo given in two doses. They were seen at 3 weeks (100 mg/day) and 12 weeks (200 mg/day, with optional dose reduction). Evaluation included the Unified Parkinson's Disease Rating Scale (UPDRS), the Baylor PD Hallucination Questionnaire, and a battery of neuropsychological tests. The demographics between subjects randomized to drug (n = 21) vs. placebo (n = 10) were similar. The final dose of active drug was 200 (n = 11), 150 (n = 2), 100 (n = 3), and 75 (n = 1) mg per day. All placebo subjects were on the equivalent of 200 mg per day. The UPDRS Activities of Daily Living and Motor scores did not significantly change compared to placebo. Compared to placebo, there were no significant changes in our hallucination questionnaire, the Brief Psychiatric Rating Scale (BPRS), or question 12 (hallucination item) of the BPRS. There were no significant changes on any of the neuropsychological measures. Adverse events on drug included sedation (n = 9), but no drug‐related adverse events precipitated discontinuation and none were rated as serious. Quetiapine, up to 200 mg daily, was well tolerated and did not worsen UPDRS scores; however, there was no significant improvement in psychosis rating scales compared to placebo. Larger doses of drug and greater sample sizes might be considered in future studies. © 2005 Movement Disorder Society