bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparation of Nanowells on a PS‐b‐PMMA Copolymer Thin Film by CO2 Treatment
Authors: Taki Kentaro , Waratani Yusuke , Ohshima Masahiro 
Published: May 2008

AbstractOrdered nanowells with diameters of ca. 40 nm and depth of 1–2 nm were prepared on a poly(methyl methacrylate) (PMMA) spherical domain, which was exposed on the polystyrene‐block‐poly(methyl methacrylate) (PS‐b‐PMMA) copolymer thin film. The PS‐b‐PMMA film formed spherical PMMA domains after the film was annealed above the order–disorder transition temperature. CO2 was dissolved into the PS‐b‐PMMA thin film at 8.6 MPa and at a temperature of 20 °C. The release of CO2‐pressure at the same temperature created the nanowell on the PMMA domain. The temperature and pressure to create nanowells in the PMMA domain affected the possibility of nanowell's formation.magnified image
Liquid Crystalline Orientation of Semiconducting Nanorods in a Semiconducting Matrix
Authors: Zorn Matthias , Zentel Rudolf 
Published: May 2008

AbstractThis paper describes the synthesis of narrowly distributed block copolymers consisting of a hole conducting triarylamine block and an anchor block via RAFT polymerization. The anchor block is thereby introduced via a reactive ester approach. Block copolymers with dopamine anchor groups bind to oxidic semiconductors like TiO2, SnO2, and ZnO. Thus, it becomes possible to cover inorganic electron conducting (acceptor) nanomaterials with a corona of an organic hole conducting (donor) polymer like poly(triphenylamine), giving new hybrid materials. The poly(triphenylamine) grafted to inorganic nanorods allows the preparation of stable nanorod dispersions in appropriate solvents. At higher concentration the nanorods form liquid crystalline phases in various solvents and in a low Tg oligotriphenylamine matrix. This offers the potential to orient semiconducting inorganic nanorods in a hole conducting polymer matrix by self‐assembly.magnified image
Supported (nBuCp)2ZrCl2 Catalysts: Effects of Selected Lewis Acid Organotin Silica Surface Modifiers on Ethylene Polymerization
Authors: Akhtar Muhammad N. , Atiqullah Muhammad , Moman Akhlaq A. , Abu‐Raqabah Atieh H. , Ahmed Neaz 
Published: May 2008

AbstractThis study investigated the effects of several organotin silica surface modifiers on the ethylene polymerization performance of (nBuCp)2ZrCl2‐based supported catalysts in which MAO and metallocene were sequentially loaded. Each organotin compound acted as a spacer, increasing the catalyst activity. However, the catalyst activity and $\overline M _{\rm w}$ of the resulting polyethylenes varied as follows:Activity and fractional Sn+ charge: nBuSn(OH)2Cl > MeSnCl3 > nBuSnCl3 > Reference catalyst; and,$\overline M _{\rm w}$: Reference catalyst > nBuSnCl3 > MeSnCl3 > nBuSn(OH)2Cl.The above catalyst activity rating was explained considering the influence of the Lewis acidity, that is, the fractional Sn+ charge of the organotin modifiers on the generation, concentration, and electron density at the active [(nBuCp)2ZrMe]+ cation. All the catalysts showed fairly stable kinetic profiles and produced narrow molecular weight distribution resins; 2.8 ≤ PDI ≤ 3.magnified image
Occupational therapy students' perceptions of their cultural awareness and competency
Authors: Murden Ravyn , Norman Ayana , Ross Julissa , Sturdivant Erin , Kedia Margaret , Shah Surya 
Published: May 2008

AbstractOccupational therapy students' perceptions of cultural awareness and their self‐rated level of cultural competence were investigated. Seventy‐two participants at four stages of education (on entry, on completion of university‐based studies, on completion of fieldwork and one year following graduation) completed the Cultural Awareness and Sensitivity Questionnaire. The findings indicate that occupational therapy students graduated with an understanding of cultural diversity and the realization that cultural awareness and sensitivity are essential to culturally competent practice. The findings suggest that there is not enough exposure to cultural issues in both university‐based education and in fieldwork. This study was limited to one state university and to most students aged ≤24 years and predominantly female. It did not explore the factors that influence the development of cultural competence and the methods to develop it. Future studies should monitor actual culture‐related exposures to determine how learning experiences are organized and the ways culture influences the learning process and clinical competence. Copyright © 2008 John Wiley & Sons, Ltd.
Elderly persons with disabilities in Sweden: their experiences of everyday life
Authors: Tollén Anita , Fredriksson Carin , Kamwendo Kitty 
Published: May 2008

AbstractThe aim of this study was to describe the everyday life experiences of 22 elderly persons with physical disabilities in Sweden. The participants were aged between 65 and 91 years. Interviews were conducted and analysed according to a qualitative research approach. Disengagement in activities and social contacts resulted in feelings of resignation and dejection for some participants, while others delegated tasks as a satisfactory alternative. Participants also described how activities and social contacts continued, albeit in a different way, and being active and socializing gave feelings of pleasure and a sense of belonging. While receiving help was experienced as valuable, it also increased the fear of becoming dependent. Occupational therapy intervention should be directed at increasing social contacts and engagements in meaningful activities, as well as strengthening the individual's autonomy. The transferability of the study can be questioned as the sample only included elderly persons with physical disabilities from urban areas. Further research is needed to address the impact of occupational therapy interventions on life satisfaction. Copyright © 2008 John Wiley & Sons, Ltd.
A new family of low wear, low coefficient of friction polymer blend based on polytetrafluoroethylene and an aromatic thermosetting polyester
Authors: Zhang Jing , Demas Nicholaos G. , Polycarpou Andreas A. , Economy James 
Published: May 2008

AbstractTo improve the wear resistance of polytetrafluoroethylene (PTFE), a crosslinked aromatic thermosetting polyester (ATSP) has been blended directly with PTFE. Cured ATSP powder which was directly synthesized as a cured powder form was used for this application. Because of the similar processing temperature range of cured ATSP and PTFE, composites within the entire composition range were successfully prepared by blending these two powders using a hot press. Tribological pin‐on‐disk tests (composite pins sliding against gray cast iron disks) showed improvement on friction coefficient of all composites and much less wear than pure PTFE. The composites survived at contact pressures of 7 MPa, which is higher than either pure PTFE or pure ATSP could sustain. With an increase in the amount of ATSP in the composites, storage modulus, and glass transition temperature were higher, and the wear resistance was enhanced. SEM images helped provide explanations for the unusually low mean wear rates that were observed for these composite samples. Copyright © 2008 John Wiley & Sons, Ltd.
Study on a novel and efficient flame retardant synergist–nanoporous nickel phosphates VSB‐1 with intumescent flame retardants in polypropylene
Authors: Nie Shibin , Hu Yuan , Song Lei , He Shuqing , Yang Dandan 
Published: May 2008

AbstractNanoporous nickel phosphate VSB‐1 was synthesized by hydrothermal method and its structure was characterized. Then VSB‐1 was added to the ammonium polyphosphate (APP) and pentaerythritol (petol) system in a polypropylene (PP) matrix for the first time, and the synergistic effect of VSB‐1 with intumescent flame retardants (IFR) was studied. With the addition of 2 wt% VSB‐1 and 23 wt% IFR, the LOI value of PP/IFR composites increased from 28.0 to 35.5. The UL‐94 test showed that PP with 20% IFR burned and had no rating, but with the addition of 2 wt% of VSB‐1 and 18% of IFR, it could reach V‐0 rating. The results of the X‐ray photoelectron spectroscopy (XPS) showed that the ratios of P/C and N/C of PP/IFR/VSB‐1 systems changed significantly from 0.133 to 0.205 (54% increase) and from 0.0328 to 0.047 (45.4% increase), respectively under 800°C for 10 min. Compared with the organophilic montmorillonite (OMT), 4 Å zeolite, and zinc tetraborate (ZB), VSB‐1 showed better synergistic effect at the same loading. Copyright © 2008 John Wiley & Sons, Ltd.
Fabrication of highly ordered polymer/graphite flake composite with eminent anisotropic electrical property
Authors: Chen Guohua , Wang Haiquan , Zhao Weifeng 
Published: May 2008

AbstractHighly ordered polyester/graphite flake composite has been fabricated via orienting the graphite flakes within a polymer matrix. The randomly dispersed graphite flakes in a polyester prepolymer were induced twice along the electric field direction, followed by the cross‐linking of the prepolymer. Scanning electron microscopy (SEM), X‐ray diffraction (XRD) analysis showed that the graphite flakes in the resulting composites were aligned parallel to each other. This structure anisotropy of the composite appeared to be a significant electrical anisotropic property with five to six orders of magnitude. Analysis showed that field‐induced torque caused by the polarization of graphite flakes undergone at electric field was a main force inducing the orientation of the graphite flakes. Copyright © 2008 John Wiley & Sons, Ltd.
Synthesis of poly(cystine bisamide)‐PEG block copolymers grafted with 1‐(3‐aminopropyl)imidazole and their phase transition behaviors
Authors: Jin Byung Suk , Kang Han Chang , Kim Dongin , Lee Kwang Hee , Bae You Han 
Published: May 2008

AbstractNew biodegradable and pH‐sensitive block copolymers were prepared by grafting 1‐(3‐aminopropyl) imidazole onto a backbone polymer formed via condensation polymerization between l‐cystine and EDTA‐dianhydride. The copolymer with a graft ratio of 79% exhibited a good buffering capacity and pH sensitivity. These are attributed to protonation–deprotonation of the imidazole ring at around pH 7. The copolymers with less imidazole content did not show any apparent responses to changes in pH. The particle size of the copolymer aggregate formed under basic conditions was around 200 nm and increased with decreasing pH. The critical aggregation values at pH 6.0 and 8.0, derived from the changes of intensity ratios (I1/I3) in the emission spectrums of pyrene, were approximately 0.17 and 0.05 mg/ml, respectively. The surface charge of the aggregates increased with the decreasing pH as a result of the increase in protonation of imidazole and the tertiary amine in the polymer chain. The microviscosity of hydrophobic domains was estimated using 1,6‐diphenyl‐1,3,5‐hexatriene. The decrease of the anisotropy value under acidic conditions reflects a disruption of hydrophobic interaction. Copyright © 2008 John Wiley & Sons, Ltd.
Fine dispersion of carbon black in fluorene‐based resin
Authors: Kawasaki Shinichi , Yamada Masahiro , Kobori Kana , Jin Fengzhe , Takata Toshikazu 
Published: May 2008

AbstractThe dispersion ability of fluorene‐based epoxy resin (FBE), bisphenol A based epoxy resin (PBE), fluorene‐based polyester (FBP), and polycarbonate (PC) in carbon black (CB) was evaluated. CB/FBE composite had a lower L value (reflectance, blackness) than that of CB/PBE composite, for the same CB content. Aggregations of CB in CB/FBE composites were much smaller than those in CB/PBE composites. The strong interaction between fluorene with cardo structure and CB resulted in a fine dispersion of CB in FBE. FBP had much higher dispersion ability of CB than PC. CB (50 wt%) was dispersed into FBP compared with the 10 wt% of CB dispersed in PC by melt blending. The effect of CB on the mechanical properties of FBP was much higher than that on PC due to fine dispersion of CB in FBP. The effect of CB addition on the Tg of FBP was also higher than that of CB on the Tg of PC. Computational simulation indicates that most stable energy between fluorene with a cardo structure and graphite structure was smaller than the energy between bisphenol A and graphite. It was also shown that the minimum energy appeared when the fluorene structure was almost parallel to the graphite plane. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Physical properties of poly(trimethylene terephthalate)/organoclay nanocomposites obtained via melt compounding and in situ polymerization
Authors: Cho H.W. , Lee J.S. , Prabu A.A. , Kim K.J. 
Published: May 2008

AbstractTwo series of poly(trimethylene terephthalate) (PTT) nanocomposites, containing an organically modified montmorillonite (MMT) clay (1,2‐aminododecanoic acid (ADA)–intercalated MMT) were prepared via melt compounding and in situ polymerization methods using dimethyl terephthalate (DMT) and 1,3‐propanediol (PDO). The effect of different methods of preparation and varying organoclay contents (1−5 wt%) on the structural, morphological, thermal, and mechanical properties were investigated. The results of wide‐angle X‐ray diffraction (WAXD) and transmission electron microscope (TEM) suggested the possible existence of intercalation morphology between ADA‐MMT and the PTT matrix obtained from melt compounding, and mostly exfoliation state from in situ polymerization depending on the amount of organoclay. From DSC studies, in melt compounding case, the addition of ADA‐MMT in PTT increases melt‐crystallization (Tcm) peak temperature by 14−15°C irrespective of the clay content. However, the melting temperature (Tm) of pristine PTT remains unchanged with increasing clay content. In the case of in situ polymerization, the Tcm and Tm peaks are shifted towards lower temperature with increasing clay content. Dynamic mechanical thermal analysis (DMTA) studies on melt compounded samples revealed a marginal lowering of glass transition temperature (Tg) irrespective of clay content, and a noticeable decrease in Tg with increasing clay content for in situ polymerized samples. The PTT/ADA‐MMT nanocomposites via melt compounding showed higher initial modulus and yield stress, and lower strain at break compared with in situ polymerization with increasing clay content. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Study and comparison of interaction parameters and phase behavior of epoxy/polystyrene and epoxies copolymer polystyrene‐b‐poly(methyl methacrylate) blends
Authors: Torrens Francisco , Monzó Isidro S. , Gómez‐Clarí Clara M. , Abad Concepción , Campos Agustín 
Published: May 2008

AbstractThermodynamic studies in terms of phase separation behavior and interaction parameters, in mixtures of epoxy resins (thermoset materials) with thermoplastic additives, consisting of polystyrene (PS) or polystyrene‐b‐poly(methyl methacrylate) P(S‐MMA) (with small proportion of MMA), have been carried out. It can be confirmed that the solubility of P(S‐MMA) is an improvement on that of PS, with the prepolymer epoxy resins. Moreover, the interaction parameters are positive at temperatures in which phase separation is observed, but negative at temperatures in which the phase separation window disappears, in the corresponding phase diagram. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
The effect of polyoxypropylene‐montmorillonite intercalates on polymethylmethacrylate
Authors: Salahuddin Nehal 
Published: May 2008

AbstractPolymethylmethacrylate (PMMA)‐layered silicate nanocomposites have been prepared by in situ polymerization of commercial type of methylmethacrylate monomer (MMA), for denture base material, into organoclay. Organoclay was prepared through an ion exchange process between sodium cations in montmorillonite and NH3+ groups in polyethertriamine hydrochloride and polyoxypropylene triamine hydrochloride with different molecular weight (5000, 440). X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) have been used to investigate the structure of the resulting composites. Both intercalated and exfoliated nanocomposites were obtained depending on the type and amount of organoclay. The thermal decomposition temperatures of the nanocomposites were found to be higher than that of pristine polymer. PMMA was strongly fixed to inorganic surfaces, due to cooperative formation of electrostatic bonding between NH3+ group and negatively charged surface of layered silicate and amide linkage between PMMA and polyethertriamine or polyoxypropylene triamine. The effect of the organoclay on the hardness, toughness, tensile stress, and elongation at break of the polymer was studied and was compared with pristine polymer. The hardness and Izod impact strength of PMMA‐organoclay nanocomposites were enhanced with the inclusion of clay. Tensile properties appear to be enhanced at certain organoclay content. However, the water absorption is slightly higher than the pristine PMMA. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Preparation of a fibrous catalyst containing palladium nanoparticles and its application in hydrogenation of olefins
Authors: Yu Jianxiang , Liu Taiqi 
Published: May 2008

AbstractA novel fibrous catalyst containing palladium nanoparticles was produced via electrospinning technique. The fibrous catalyst was characterized by scanning electron microscopy and transmission electron microscopy respectively, the results show that the diameter of fiber was about 200 nm and the palladium (Pd) nanoparticles was in the range of 30–40 nm. The size and shape of Pd particles on the fiber can be adjusted by changing the concentration of polymer or amount of PdCl2 in the electrospun solution. The catalyst was tested in hydrogenation of α‐hexene and α‐octene in ethanol at room temperature. The catalytic experimental results show that the activity of the titled catalyst was 4.7 times higher than that of PdCl2/γ‐Al2O3 and higher than that of PdCl2 on poly(styrene‐divinylbenzene) resin catalyst (Zharmagambetov et al., J Mol Catal A: Chemical, 177, 165 (2001)). POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Mechanisms of the homogeneous, unimolecular gas‐phase elimination kinetics of triethyl orthoacetate and triethyl orthopropionate
Authors: Marquez Edgar , Tosta Maria , Domínguez Rosa M. , Herize Armando , Chuchani Gabriel 
Published: May 2008

AbstractTriethyl orthoacetate and triethyl orthopropionate were pyrolyzed in a static system over the temperature range of 291–351°C and pressure range of 80–170 Torr. The elimination reactions of these orthoesters in seasoned vessels are homogeneous, unimolecular, and follow a first‐order rate law. The reaction products are ethanol, ethylene and the corresponding ethyl ester. The Arrhenius expressions of these eliminations were found as follow: for triethyl orthoacetate, log k1 (s−1) = (13.76 ± 0.09) − (187.6 ± 1.1) kJ mol−1 (2.303 RT)−1 (r = 0.9993), and for triethyl orthopropionate, log k1 (s−1) = (13.63 ± 0.07) − (193.3 ± 1.8) kJ mol−1 (2.303 RT)−1 (r = 0.9992). A reasonable mechanism of these elimination is to consider that the COCH2CH3 bond, as Cδ+…δ− OCH2CH3 in the TS, is the rate‐determining step. The nucleophilicity of the oxygen atom of OCH2CH3 may abstract the hydrogen of the adjacent CH bond for a four‐membered cyclic structure to give the corresponding unsaturated ketal. The unstable ketal intermediate decomposes, in a six‐membered cyclic transition state, into ethylene and the corresponding ethyl ester. Copyright © 2008 John Wiley & Sons, Ltd.
Non‐oral contraceptive options: their efficacy and suitability
Authors: Everett Marian 
Published: May 2008

AbstractMany women are unaware of the wide variety of non‐oral contraceptives available and need advice on the range of options. Our Drug review considers the features and efficacy of non‐oral contraceptives, followed by sources of further information in Resources and the Datafile. Copyright © 2008 Wiley Interface Ltd
Reduction of buffer‐related current collapse in GaN FETs under favour of a field plate
Authors: Itagaki K. , Nakajima A. , Horio K. 
Published: May 2008

AbstractTwo‐dimensional transient analysis of GaN MESFETs with a semi‐insulating buffer layer is performed in which a deep donor and a deep acceptor are considered in the buffer layer, and the results are compared between the two cases with and without a field plate. It is shown that buffer‐related drain lag is reduced by introducing a field plate because trapping effects become smaller. It is also shown that current collapse and gate lag are also reduced in the field‐plate structure. The dependence on SiN passivation layer thickness is also studied, indicating that there is an optimum SiN thickness to minimize the buffer‐related current collapse and drain lag in GaN‐based FETs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Excess As in low‐temperature grown InAs
Authors: Takushima M. , Kajikawa Y. 
Published: May 2008

AbstractUsing secondary ion mass spectrometry, we have investigated the excess As concentration in InAs layers grown by molecular beam epitaxy at 150‐300 °C. A step‐like increase of the As/In ratio from the substrate to the epi layer was observed for the samples grown at lower temperatures than 250 °C. The excess As concentration averaged over the grown layer thickness reached 1.2×1020 cm–3 for the layer grown at 200 °C. Through the combination with the results of X‐ray diffraction, a proportional relation of Δa⊥/a = 2×10–24 δ [As] is deduced between the perpendicular lattice mismatch Δa⊥/a and the atomic density δ [As] of excess As in the unit of cm–3. Hall effect measurements at 77 K revealed that the electron concentration is much lower than the excess As concentration. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of the high‐energy proton irradiation on the properties of GaN ionizing radiation detectors
Authors: Kažukauskas V. , Kalendra V. , Jasiulionis R. , Vaitkus J.‐V. 
Published: May 2008

AbstractEffects of the irradiation by 24 GeV protons on the properties of GaN ionizing radiation detectors were investigated. Irradiation dozes ranged from 1×1014 up to 1×1016 p/cm2. In the γ‐spectra of the samples radiation of 7Be, 22Na and other long‐living radionuclides with A < 70 was identified. Their activities were proportional to the total irradiation doses. Device contact properties were analysed by IV dependencies. Created defects were revealed by the thermally stimulated spectroscopy. In the less irradiated samples the following values of the effective thermal activation energies were found: 0.12‐0.16 eV, 0.18‐0.22 eV, 0.35‐0.42 eV and 0.84‐0.94 eV. Meanwhile in the detectors irradiated with the highest dozes only current growth with the activation energy of about 0.8‐1.0 eV could be identified. Effects of percolation transport in disordered media were proved in the irradiated material. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microcavity structures in single GaAs nanowires
Authors: Hua B. , Motohisa J. , Hara S. , Fukui T. 
Published: May 2008

AbstractWe report the formation of Fabry‐Perot microcavity in single GaAs nanowire prepared by selective‐area metalorganic vapor phase epitaxy. The fabricated nanowires with hexagonal cross section are highly uniform and vertically oriented. Microphotoluminescence measurements of single GaAs nanowire exhibit several periodic peaks in the intensity, which are suggestive of the longitudinal modes of a Fabry‐Perot cavity. The cavity is formed along the length of the nanowire and the (111) facets of both ends act as reflecting mirrors in this case. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)