bluuebunny/crossref_metadata_2025_split huggingface dataset:
Micromechanical analysis of failure propagation in frictional granular materials
Authors: Tordesillas Antoinette , Shi Jingyu 
Published: April 2009

AbstractThe extent to which the evolution of instabilities and failure across multiple length scales can be reproduced with the aid of a bifurcation analysis is examined. We adopt an elastoplastic micropolar constitutive model, recently developed for dense cohesionless granular materials within the framework of thermomicromechanics. The internal variables and their evolution laws are conceived from a direct consideration of the dissipative mechanism of force chain buckling. The resulting constitutive law is cast entirely in terms of the particle scale properties. It thus presents a unique opportunity to test the potential of micromechanical continuum formulations to reproduce key stages in the deformation history: the development of material instabilities and failure following an initially homogeneous deformation. Progression of failure, initiating from frictional sliding and rolling at contacts, followed by the buckling of force chains, through to macroscopic strain softening and shear banding, is reproduced. Bifurcation point, marking the onset of shear banding, occurred shortly after the peak stress ratio. A wide range of material parameters was examined to show the effect of particle scale properties on the progression of failure. Model predictions on the thickness and angle of inclination of the shear band and the structural evolution inside the band, namely the latitudinal distribution of particle rotations and the angular distributions of contacts and the normal contact forces, are consistent with observations from numerical simulations and experiments. Copyright © 2009 John Wiley & Sons, Ltd.
An evaluation of nurse engagement in emancipatory practice development: The diary of a critical companion
Authors: Newman Claire , Cashin Andrew , Downie Amanda 
Published: April 2009

AbstractThere is a paucity of research in the area of nurse engagement in the process of practice development. Little is published about the sequencing of engagement with consent and pre‐measures in a research project. It has, however, been recognized that without engagement, development of one's practice, and subsequently health service change, would be minimal. This article reports on nurse engagement in the first six weeks of the implementation of a new model of care in two correctional service health care settings. Copyright © 2009 John Wiley & Sons, Ltd.
‘Teaching an old dog new tricks’: A practice development approach to organizational change in mental health
Authors: Lamont Scott , Walker Peter , Brunero Scott 
Published: April 2009

AbstractPractice development is widely described as: ‘ways in which knowledge and skills development is used to provide better patient care’. This article will outline a mental health units approach and experience of implementing collaborative practice development processes which identify values and beliefs and enable the development of a framework of action to effect positive change. A qualitative participatory action research design was used to engage participants in exploring and critiquing relevant workplace culture issues. The project was divided into four chronological stages: values clarification; claims, concerns and issues; barriers, enablers and actions; and action planning. The results of this project highlight a number of issues for practice development approaches. We believe that these processes are easily transferable to other organizations within health care. Copyright © 2009 John Wiley & Sons, Ltd.
Synthesis and characterization of novel thermoplastic poly(oligophosphazene‐urethane)s
Authors: Zhou Yubo , Huang Xiaobin , Tang Xiaozhen 
Published: April 2009

AbstractBACKGROUND: Polyurethanes are some of the most popular polymers used in a variety of products, such as coatings, adhesives, flexible and rigid foams, elastomers, etc. Despite the possibility of tailoring their properties, polyurethanes suffer a serious disadvantage of poor thermal stability. Many attempts have been made in order to improve the thermal stability of polyurethanes.RESULTS: A new hydroxyl‐terminated oligomer containing sulfone groups, 2,2‐bis(4‐hydroxy‐4,4‐sulfonyldiphoneloxy)tetraphenoxyoligocyclotriphosphazene (HSPPZ), was synthesized. HSPPZ was characterized using Fourier transform infrared (FTIR), NMR and gel permeation chromatography analyses. A series of novel thermoplastic poly(oligophosphazene‐urethane)s were then synthesized via the reaction of NCO‐terminated polyurethane prepolymer with HSPPZ containing chain‐extender diols. Their structure and properties were investigated using FTIR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X‐ray diffraction, water contact angle measurement and tensile measurements.CONCLUSION: Compared to conventional thermoplastic polyurethanes, poly(oligophosphazene‐urethane)s exhibit better thermal stability, low‐temperature resistance and hydrophobicity, but their mechanical properties are slightly poorer. Copyright © 2009 Society of Chemical Industry
Transmission of polar substituent effects across the cubane ring system: 19F substituent chemical shifts (SCS) of 4‐substituted (X) cub‐1‐yl fluorides revisited
Authors: Adcock William 
Published: April 2009

Abstract19F NMR shieldings of 4‐substituted (X) cub‐1‐yl fluorides (4) for a set of substituents (XH, NO2, CN, NC, CF3, COOH, F, Cl, HO, NH2, CH3, Si(CH3)3, Li, O− and NH) covering a wide range of electronic substituent effects were calculated using the DFT‐GIAO theoretical model. The level of theory, B3LYP/6‐311+G(2d,p), provided 19F substituent chemical shifts (SCS) in good agreement with experimental values where known. By means of NBO analysis, various molecular parameters were obtained from the optimized geometries. Linear regression analysis was employed to explore the relationship between the calculated 19F SCS and polar field, resonance and group electronegativity substituent constants (σF, σR and σx, respectively) and also the NBO derived molecular parameters (fluorine natural charges (Qn), electron occupancies on fluorine of lone pairs (nF) and occupation number of the CF antibonding orbital (σCF*)). The key determining parameters appear to be nF and σCF*(occup). Both factors are a function of the electrostatic field influence of the substituent (σF effect) but are counteractive in their influence on the shifts. No evidence for a significant resonance effect influence on the shifts could be identified. Copyright © 2009 John Wiley & Sons, Ltd.
PMMA‐based core‐shell nanoparticles with various PTFE cores
Authors: Kapeliouchko Valerj , Palamone Giovanna , Poggio Tiziana , Zuccheri Giampaolo , Passeri Rosita , Sparnacci Katia , Antonioli Diego , Deregibus Simone , Laus Michele 
Published: April 2009

AbstractPolytetrafluoroethylene (PTFE) latices with spherical and rod‐like particles in the submicrometer size range, were employed as seeds in the emulsifier‐free methylmethacrylate (MMA) emulsion polymerization to obtain PTFE‐polymethylmethacrylate (PMMA) core‐shell nanoparticles. Stable latices were generally obtained. No residual PTFE was found at the end of the reaction. By appropriately choosing the ratio between MMA and PTFE in the reaction mixture, particles with predetermined size and monodisperse or narrow size distribution were prepared. The high structural regularity of the core‐shell samples allows the preparation of film with a periodic distribution of the cores thus ultimately leading to a well structured 2D colloidal crystal. A very peculiar crystallization behavior was observed because of the PTFE compartmentalization in the composite. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2928–2937, 2009
Preparation of monodisperse nanoparticles containing poly(propylene imine)(NH2)32‐polystyrene
Authors: Liu Hu , Hu Xiaoxi , Wang Yingxi , Li Xiaoqin , Yi Changfeng , Xu Zushun 
Published: April 2009

AbstractPolypropylenimine dendrimer (DAB‐Am‐32, generation 4.0) was converted into a macroinitiator DAB‐Am‐32‐Cl via reaction with 2‐chloropropionyl chloride. Monodisperse nanoparticles containing poly(propylene imine)(NH2)32‐polystyrene were prepared by emulsion atom transfer radical polymerization (ATRP) of styrene (St), using the DAB‐Am‐32‐Cl/CuCl/bpy as initiating system. The structure of macroinitiator was characterized by FTIR spectrum, 1H NMR, and 13C NMR. The structure of poly(propylene imine)(NH2)32‐polystyrene was characterized by FT‐IR spectrum and 1H NMR; the molecular weight and molecular weight distribution of poly(propylene imine)(NH2)32‐polystyrene were characterized by gel permeation chromatograph (GPC). The morphology, size and size distribution of the nanoparticles were characterized by photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The effects of monomer/macroinitiator ratio and surfactant concentration on the size and size distribution of the nanoparticles were investigated. It was found that the diameters of the nanoparticles were smaller than 100 nm (30–80 nm) and monodisperse; moreover, the particle size could be controlled by monomer/macroinitiator ratios and surfactant concentration. With the increasing of the ratio of St/DAB‐Am‐32‐Cl, the number‐average diameter (Dn), weight‐average diameter (Dw) were both increased gradually. With enhancing the surfactant concentration, the measured Dh of the nanoparticles decreased, while the polydispersity increased. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2892–2904, 2009
Synthesis and characterization of novel resorcinarene‐centered amphiphilic star‐block copolymers consisting of eight ABA triblock arms by combination of ROP, ATRP, and click chemistry
Authors: Gou Peng‐Fei , Zhu Wei‐Pu , Zhu Ning , Shen Zhi‐Quan 
Published: April 2009

AbstractNovel amphiphilic eight‐arm star triblock copolymers, star poly(ε‐caprolactone)‐block‐poly(acrylic acid)‐block‐poly(ε‐caprolactone)s (SPCL‐PAA‐PCL) with resorcinarene as core moiety were prepared by combination of ROP, ATRP, and “click” reaction strategy. First, the hydroxyl end groups of the predefined eight‐arm SPCLs synthesized by ROP were converted to 2‐bromoesters which permitted ATRP of tert‐butyl acrylate (tBA) to form star diblock copolymers: SPCL‐PtBA. Next, the bromide end groups of SPCL‐PtBA were quantitatively converted to terminal azides by NaN3, which were combined with presynthesized alkyne‐terminated poly(ε‐caprolactone) (A‐PCL) in the presence of Cu(I)/N,N,N′,N″,N″‐pentamethyldiethylenetriamine in DMF to give the star triblock copolymers: SPCL‐PtBA‐PCL. 1H NMR, FTIR, and SEC analyses confirmed the expected star triblock architecture. The hydrolysis of tert‐butyl ester groups of the poly(tert‐butyl acrylate) blocks gave the amphiphilic star triblock copolymers: SPCL‐PAA‐PCL. These amphiphilic star triblock copolymers could self‐assemble into spherical micelles in aqueous solution with the particle size ranging from 20 to 60 nm. Their micellization behaviors were characterized by dynamic light scattering and transmission electron microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2905–2916, 2009
Prepolymerization and postpolymerization functionalization approaches to fluorescent conjugated carbazole‐based glycopolymers via “click chemistry”
Authors: Chen Qi , Han Bao‐Hang 
Published: April 2009

AbstractFacile prepolymerization and postpolymerization functionalization approaches to prepare well‐defined fluorescent conjugated glycopolymers through Cu(I)‐catalyzed azide/alkyne “Click” ligation were explored. Two well‐defined carbazole‐based fluorescent conjugated glycopolymers were readily synthesized based on these strategies and characterized by 1H NMR, 13C NMR, IR spectra, and UV‐vis spectra. The “Click” ligation offers a very effective conjugation method to covalently attach carbohydrate residues to fluorescent conjugated polymers. In addition, the studies of carbohydrate–lectin interactions were performed by titration of concanavalin A (Con A) to D‐glucose‐bearing poly(anthracene‐alt‐carbazole) copolymer P‐2 resulting in significant fluorescence quenching of the polymer due to carbohydrate–lectin interactions. When peanut agglutinin (PNA) was added, no distinct change in the fluorescent properties of P‐2 was observed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2948–2957, 2009
Spin probe mobility in relation to free volume and relaxation dynamics of glass‐formers: A series of spin probes in poly(isobutylene)
Authors: Švajdlenková Helena , Bartoš Josef 
Published: April 2009

AbstractWe present the dynamics of a series of three paramagnetic molecules of different volume, mass, and shape in amorphous glass‐forming polymer poly(isobutylene) (PIB) as investigated by means of electron spin resonance (ESR) technique. The reorientation behavior of spin probes is related to the ortho‐positronium (o‐Ps) annihilation in PIB from positron annihilation lifetime spectroscopy (PALS) and the extracted free volume information. It is also related to the dynamic data of PIB from broadband dielectric spectroscopy (BDS), neutron scattering (NS), and nuclear magnetic resonance (NMR) spectroscopy from literature. In the case of the smallest spin probe, 2,2,6,6‐tetramethyl‐1‐piperidinyloxy (TEMPO), a discontinuous course of the spectral parameter 2Azz′ versus T dependence was observed and the subsequent phenomenological model‐free analyses of the spectral parameter, 2Azz′ versus T, as well as of the correlation time, τc, versus 1/T plots provided the characteristic ESR temperatures ($T_{X1}^{2A_{zz}}$, T50G, $T_{X2}^{2A_{zz}}$) and (T, T, T). These characteristic ESR temperatures were found to be consistent with the characteristic PALS temperatures: T, T = T from temperature dependences of the mean o‐Ps lifetime, τ3, or the width of o‐Ps lifetime distribution, σ3, respectively. In addition, the relationships between the spin probe size, V, and the free volume hole size distributions gn(Vh) at the characteristic ESR temperatures indicate the significant influence of the free volume fluctuation at the crossover from slow to rapid regime as well as within the rapid motional regime. On the other hand, the two larger spin probes exhibit a rather continuous 2Azz′–T plots with the respective T50G's lying in the vicinity of T independently of their volume, mass and shape, suggesting the common origin of underlying process controlling this T50G transition. Finally, these mutual PALS and ESR findings were compared with the known dynamic behavior of PIB which suggest that the dynamics of the TEMPO and the larger spin probes are related to free volume fluctuation associated with primary α ‐ and secondary β processes, respectively. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1058–1068, 2009
Agglomerates Structure Characterization Using 3D‐Image Reconstruction
Authors: Turchiuli Christelle , Castillo‐Castaneda Eduardo 
Published: April 2009

AbstractInstant properties of agglomerated powders are linked to the size and structure of agglomerates. In this study, agglomerates structure was investigated through the measurement of their porosity. An image analysis method for 3D re‐construction of particle shape from silhouette was developed to measure the envelope volume of dehydrated milk agglomerates (1–2 mm). With known true density of the powder, the intra‐particular porosity of agglomerates could be estimated. It was found that intra‐particular porosity increases with agglomerates diameter indicating a fractal structure with a fractal dimension of 2.64. This allowed understanding the different behavior of large agglomerates settling and dissolving rapidly in water whilst small ones settle and dissolve slowly and must be avoided in a good instant powder.
Comparison of Nanometric Particle Size Distributions as Determined by SAXS, TEM and Analytical Ultracentrifuge
Authors: Goertz Verena , Dingenouts Nico , Nirschl Hermann 
Published: April 2009

AbstractIn this paper the particle size distribution of SiO2 spherical nanoparticles is determined by small angle X‐ray scattering (SAXS). The experimental scattering intensity data were compared with theoretical intensities based on different numeric procedures and different assumptions for the distribution of the particles. Hereby two fixed shapes of distribution, Gauss and log normal, were used and compared to a free particle distribution which is determined with the maximum entropy method (MEM). The results were further compared with the particle size distributions obtained from the transmission electron microscopy (TEM) and analytical ultracentrifuge (AUC). The comparison demonstrated SAXS to be a generally reliable method for determining size distributions of spherical particles in the nanometer range. Assuming a fixed distribution in the SAXS method, reliable data can be obtained even in the case of bad statistical data or higher concentrations. The MEM procedure allows shape determination but is restricted to scattering data of dilute samples and high statistical quality if one wishes to avoid artefacts in the resulting size distribution.
A New Approach to Model the Re‐Entrainment of Settled Particles Based on Film Theory of Fluid Mass Transfer Processes
Authors: Nitschke Dirk , Schmidt Eberhard 
Published: April 2009

AbstractThis work presents a model that calculates re‐entrainment in analogy to transport processes between fluid phases, which are well known in chemical engineering. Mass transfer processes for fluid phases are described, among other models, by film theory. Re‐entrainment was computed according to the film theory with a mass transfer coefficient. The mass transfer coefficient is just one parameter that determines the re‐entrainment rate. To show that this parameter was accessible by physical principles, outcomes of this model were compared with experimental data published by Ibrahim et al. [1–2]. The mass transfer coefficients for these calculations were determined by a microscopic view of the forces acting on one single particle. This comparison shows that this one parameter model was able to reproduce experimental data of the re‐entrainment of single particles.
A Neural Network Model for Estimating the Particle Size Distribution of Dilute Latex from Multiangle Dynamic Light Scattering Measurements
Authors: Gugliotta Luis M. , Stegmayer Georgina S. , Clementi Luis A. , Gonzalez Verónica D. G. , Minari Roque J. , Leiza José R. , Vega Jorge R. 
Published: April 2009

AbstractThe particle size distribution (PSD) of dilute latex was estimated through a general regression neural network (GRNN) that was supplied with PSD average diameters derived from multiangle dynamic light scattering (MDLS) measurements. The GRNN was trained with a large set of measurements that were simulated from unimodal normal‐logarithmic distributions representing the PSDs of polystyrene (PS) latexes. The proposed method was first tested through three simulated examples involving different PSD shapes, widths, and diameter ranges. Then the GRNN was employed to estimate the PSD of two PS samples; a latex standard of narrow PSD and known nominal diameter, and a latex synthesized in our laboratory. Both samples were also characterized through independent techniques (capillary hydrodynamic fractionation, transmission electron microscopy, and disc centrifugation). For comparison, all examples were solved by numerical inversion of MDLS measurements through a Tikhonov regularization technique. The PSDs estimated by the GRNN gave more accurate results than those obtained through other conventional techniques. The proposed method is a simple, effective, and robust tool for characterizing unimodal PSDs.
Diamond and Oxidized Disordered Graphite on the Surface of Gallium Phosphide Nanoparticles
Authors: Zhang Zhao‐Chun , Wang Bao‐Ping 
Published: April 2009

AbstractThe X‐ray diffraction (XRD) pattern from gallium phosphide (GaP) nanoparticles showed the presence of the diamond (111) diffraction peak. Analysis of the Raman scattering of GaP nanoparticles revealed that disordered graphite displayed a wide band at 1572 cm–1 assigned to the E2g mode, and diamond displayed a wide band at 1324 cm–1 assigned to the F2g mode. By means of Gaussian fitting, the X‐ray photoelectron spectroscopy (XPS) spectrum of the C 1s core level was deconvoluted into two components centered at 284.2 and 287.2 eV binding energy, respectively. The binding energy peaks were indicative of the presence of oxidized disordered graphite and diamond phases.
The effect of K‐ fluorescence reabsorption of selenium on the performance of an imaging detector for protein crystallography
Authors: Sultana Afrin , Karim K. S. , Rowlands J. A. 
Published: April 2009

AbstractProtein crystallography is an important technique in the determination of three dimensional atomic structures of proteins. In order to reconstruct the atomic structure of protein from experimental diffraction data, both the magnitude and phase of the atomic scattering factor should be known. The phase can be calculated using the Multiple Wavelength Anomalous Dispersion (MAD) method. Selenium (Se) is commonly used as an anomalous scatterer in the MAD method since the K ‐edge of Se (12.6 keV) is readily accessible on most synchrotron X‐ray sources. Recently, we proposed a novel direct X‐ray conversion imager for protein crystallography which employs amorphous Se for the X‐ray to charge conversion and an amorphous silicon flat panel thin film transistor array as the charge image readout method. For the protein crystallography X‐ray energy range (6‐20 keV), X‐ray interaction in Se is due to the photoelectric effect. Therefore there is a possibility of generation and reabsorption of K ‐fluorescence at or above the K ‐edge. The reabsorption of a fraction of the generated K ‐fluorescence is a random process which leads to fluctuations in conversion gain and hence addition of image noise. In this paper, the physics of K ‐fluorescence is explained and the probability of K ‐fluorescence reabsorption of Se for the useful X‐ray energy of protein crystallography is calculated. Finally, the possible consequences from K ‐fluorescence reabsorption of Se on the performance of a protein crystallography imager where Se is used both as an anomalous scatterer and a photoconductor is elucidated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of In2O3 thin films prepared by rf helicon magnetron sputtering
Authors: Miao L. , Tanemura S. , Cao Y.G. , Xu G. 
Published: April 2009

AbstractPolycrystalline In2O3 films with cubic crystal structure and film thicknesses of 239, 472, 579 and 745 nm respectively were grown on quartz substrates at substrate temperature 450 °C by rf helicon magnetron sputtering. The preferred crystal growth orientation is varied from <111> to <211> with increasing film thickness as confirmed by X‐ray diffractometry. The photon energy dependent optical properties such as complex dielectric functions and absorption coefficient, optical band gap, and Urbach energy width of the samples have been obtained from spectroscopic ellipsometry analysis in the energy range from 1.5 eV to 5.0 eV. The relation between those optical properties and crystal structure and/or crystallinity of the films was discussed. The band gap value, which is averaged over two typical samples with good crystallinity, is 3.765 eV and agrees satisfactorily with reported value on that of single crystal. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)