bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparing Language Learning Attitudes in England, Germany and the Netherlands: Some Methodological Considerations
Authors: Bartram Brendan
Published: January 2006

The following article examines the methodological considerations involved in carrying out a trinational comparative survey of pupils' attitudes to learning French, German and English (as foreign languages) at comprehensive schools in England, Germany and the Netherlands. The research was conducted as part of a Ph.D. study aiming to describe the nature of the pupils' attitudes and to examine and compare the pupils' perceptions of educational and socio-cultural influences in the different contexts. A discussion of the broader theoretical framework in which the study is located is followed by an analysis of research design and decision-making. This includes a detailed review of country, sample and instrument selection, along with an examination of the practicalities of access, piloting and analysis. Finally, a number of ethical issues are considered.
Theories of Intelligence, Goal Orientation and Attribution in Malawi's MESA Schools
Authors: Chauncey Kate
Published: January 2006

This article suggests that, as the Malawian Ministry of Education, Science, and Technology continues to advocate for educational access, equity and quality, aspects of educational psychology may be particularly important to consider in context. It presents and discusses research conducted in June and July 2004. The key research concepts (theories of intelligence, goal orientation, attribution to setback, and confidence) are briefly introduced, and then, the study's objectives, methods and findings are each discussed in turn. The research objectives included: (i) examination of the relation between particular Malawian students' theories of intelligence and their goals and attributions in response to academic setback; (ii) examination of gender differences in students' theories of intelligence, goals, setback attributions, and confidence levels; and (iii) exploration of the variables mentioned as possible predictors of students' 2004 examination scores (controlling for student demographics and prior academic performance). In order to reach these aims, a survey was administered to 284 Malawian students attending Malawi Education Support Activity (MESA) schools. Test scores were collected from ‘progress books,’ and quantitative data were supplemented by semi-structured interviews with key informants. Students' theories of intelligence were found to be associated with their goals and setback attributions, but not with their confidence levels. Females were significantly more likely than males to hold entity theories of intelligence, to have dominant performance goals, and to attribute academic setback to lack of intelligence. Male students reported moderately higher confidence than females. Regression analysis revealed ‘learning goal’ to significantly predict test scores. The findings suggest that student theories, goals, and attributions warrant further research and school community attention. In addition, the findings encourage questions concerning the cross-cultural applicability of certain educational psychology theories. In conclusion, this article recognises the need to understand cross-cultural differences in educational psychology, yet raises questions by identifying potential similarities between previous findings from the United States, United Kingdom, and Hong Kong and the study at hand.
Cover Picture: A Two‐Dimensional Porphyrin‐Based Porous Network Featuring Communicating Cavities for the Templated Complexation of Fullerenes (Adv. Mater. 3/2006)
Authors: Spillmann H. , Kiebele A. , Stöhr M. , Jung T. A. , Bonifazi D. , Cheng F. , Diederich F.
Published: January 2006

A 2D porous network has been realized by self‐assembly of porphyrin modules on a silver surface, as reported by Diederich and co‐workers on p. 275. The so‐formed pores are able to host single fullerene molecules and mediate long‐range interactions between such carbon guests, resulting in the formation of large supramolecular chains and islands. The cover shows a scanning tunnelling microscopy image of several single C60 molecules (large green protrusions) hosted in the 2D porous network. As indicated by the molecular model, each pore is formed by the symmetric arrangement of three porphyrin molecules and the fullerene guest is located exactly in the center of the cavity.
Inside Front Cover: Electronic Transport through Electron‐Doped Metal Phthalocyanine Materials (Adv. Mater. 3/2006)
Authors: Craciun M. F. , Rogge S. , den Boer M.‐J. L. , Margadonna S. , Prassides K. , Iwasa Y. , Morpurgo A. F.
Published: January 2006

Transport measurements for different electron‐doped metal–phthalocyanine (MPc) materials are reported by Morpurgo and co‐workers on p. 320. It is experimentally demonstrated that for these doped MPc materials, increasing the doping level results first in a metallic state and, subsequently, in the re‐entrance of an insulating state. The artist's impression on the inside cover shows an MPc film situated between two electrodes and exposed to a flux of alkali atoms in vacuum. The alkali atoms intercalate and donate electrons to the molecular material.
One step synthesis and rapid ring‐opening polymerization of macrocyclic (arylene thioether ketone) oligomers
Authors: Yan H. , Li X. H. , Wang S. J. , Meng Y. Z.
Published: January 2006

Well‐crystal macrocyclic (arylene thioether ketone) oligomers were synthesized under high dilution condition by the reaction of Na2S with bis(4‐fluoro‐phenyl)‐methanone in 1‐methyl‐pyrrolidone (NMP). The oligomers were fully characterized by Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra (MALDI‐TOF‐MS), high‐pressure liquid chromatography (HPLC), gel permeation chromatography (GPC), 1H NMR, 13C‐NMR, and differential scanning calorimetry (DSC). According to DSC studies, uncatalyzed and rapid ring‐opening polymerization (ROP) of the oligomers took place instantly when they were heated to melting point. Extracted by dichloro‐methane, the obtained polymer neither loses any weight nor dissolves in boiling 1‐chloro‐ naphthalene. These facts indicated that there are no residual oligomers within the resultant polymer. The as‐prepared oligomers could be potentially used as high‐temperature hot‐melt adhesive at a high temperature > 350°C, and matrices for high‐performance composites and nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 161–166, 2006
Properties of fullerene‐containing natural rubber
Authors: Jurkowska B. , Jurkowski B. , Kamrowski P. , Pesetskii S. S. , Koval V. N. , Pinchuk L. S. , Olkhov Y. A.
Published: January 2006

Addition of fullerene in concentration between 0.065 and 0.75 phr increases Schob elasticity, hardness, and modulus of NR‐based rubber. There is no substantial influence of fullerene on Tg, tan δ, and G‐modulus all evaluated by DMA at twisting within a temperature range −150 to −50°C (glassy state). At temperatures between 0 and 150°C (rubbery state) it is different, namely an increase in modulus and some changes in the slope of segments in G(T) curves were observed. It could be resulted from additional strong physical junctions of the rubber network. This suggests the growth of degradation energies of the branching junctions and related rise in the aging resistance as concentration of fullerene increases. Simultaneously, it could be expected some reduction of tire temperature at service. Because of this, introduction of fullerene could be reasonable for tread rubbers in case of reduction of its price. Permittivity and dielectric loss angle are correlated with fullerene concentration. Compounding technology when fullerene dispersed within carbon black is mixed with raw rubber on available machines could be easily implemented in the industry. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 390–398, 2006
Studies on LDPE—Cyanoethylated lignocellulosics blends using epoxy functionalized LDPE as compatibilizer
Authors: Sailaja R. R. N.
Published: January 2006

Rubberwood flour and cellulose have been plasticized by cyanoethylation and then blended with low‐density polyethylene (LDPE). A small quantity of epoxy functionalized polyethylene i.e., polyethylene‐co‐glycidyl methacrylate (PEGMA) has been added to further enhance the mechanical properties. The mechanical properties were measured according to the standard ASTM methods. SEM analysis was performed for both fractured and unfractured blend specimens. The mechanical properties were improved by the addition of PEGMA compatibilizer. LDPE blends with cyanoethylated wood flour (CYWF) showed higher tensile strength and modulus than cyanoethylated cellulose CYC‐LDPE blends. However CYC‐LDPE blends exhibited higher relative elongation at break values as compared with the former. The TGA analysis showed lowering of thermal stability as the filler content is increased and degradation temperature of LDPE is shifted slightly to lower temperature. DSC analysis showed loss of crystallinity for the LDPE phase as the filler content is increased for both types of blends. Dielectric properties of the blends were similar to LDPE, but were lowered on adding PEGMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 219–237, 2006
Destabilization mechanism of polyethylene‐modified bitumen
Authors: Pérez‐Lepe A. , Martínez‐Boza F. J. , Attané P. , Gallegos C.
Published: January 2006

Polymer‐modified binders are widely used for pavement construction. Among different polymers used to modify bitumen, polyolefins have shown to impart beneficial effects on the bitumen, especially to prevent some of the pavement shortcomings at high temperatures, such as rutting. The phase separation problems of these polymers from the bitumen may affect the final properties of the pavement. The determination of the polymer phase destabilization mechanism and rate are crucial to defer or delay the polymer separation from the matrix. With this aim, several HDPE‐modified binders were manufactured by using a high‐shear mixing device. The binders were stored in tubes at temperatures as high as 180°C. During the storage, the unstable polymer phase creamed up to the surface. The destabilization process was followed by means of optical microscopy observations through time, as the separation process proceeded. The segregation of the polymer phase is shown to be preceded by a coalescence mechanism. Enhanced mechanical properties have been obtained by HDPE modification. However, such binders may not be efficient for the pavement application, since phase separation may occur during the application of the binder on the road. Functionalized reactive polymers are envisaged to hinder the separation problems in bituminous binders. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 260–267, 2006
Surface grafting polymerization of N‐vinyl‐2‐pyrrolidone onto a poly(ethylene terephthalate) nonwoven by plasma pretreatment and its antibacterial activities
Authors: Chen Ko‐Shao , Ku Yuan‐An , Lin Hong‐Ru , Yan Tsong‐Rong , Sheu Dey‐Chyi , Chen Tim‐Mo
Published: January 2006

The objective of this research was the surface grafting polymerization of biocompatible monomer N‐vinyl‐2‐pyrrolidone (NVP) onto a plasma‐treated nonwoven poly(ethylene terephthalate) (PET) substrate with ultraviolet (UV)‐induced methods. The effects of various parameters, such as the monomer concentration, reaction time, initiator (ammonium peroxodisulfate) concentration, and crosslinking agent (N,N′‐methylene bisacrylamide) concentration, on the grafting percentage were studied. The grafting efficiency of the modified nonwoven PET surfaces reached a maximum at 50 min of UV irradiation and with a 30 wt % aqueous NVP solution. After the plasma activation and/or grafting, the hydrophobic surface of the nonwoven was modified into a hydrophilic surface. NVP was successfully grafted onto nonwoven PET surfaces. The surface wettability showed that the water absorption of NVP‐grafted nonwoven PET (NVP‐g‐nonwoven PET) increased with increasing grafting time. NVP‐g‐nonwoven PET was verified by Fourier transform infrared spectra and scanning electron microscopy measurements. An antibacterial assessment using an anti‐Staphylococcus aureus test indicated that S. aureus was restrained from growing in NVP‐g‐nonwoven PET. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 803–809, 2006
Effect of polymerization time on the molecular weight and molecular weight distribution of polypropylene
Authors: Abedi S. , Hosseinzadeh M. , Kazemzadeh M. A. , Daftari‐Besheli M.
Published: January 2006

The influence of the polymerization time on the molecular weight (Mw, Mn, Mp, and Mz), molecular weight distribution (MWD) and relative MWD of polypropylene (PP) in the propylene polymerization with a Mg(OEt)2/DIBP/TiCl4/PTES/AlEt3 catalyst system in the slurry phase has been studied by using gel permeation chromatography (GPC), where Mg(OEt)2, DIBP (diisobutyl phthalate), TiCl4, PTES (phenyl triethoxy silane), and triethyl aluminum (TEA) are support, internal donor, catalyst, external donor, and cocatalyst, respectively. It has been found that the increase of the polymerization time increases the molecular weight and MWD of PP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 368–371, 2006
Synthesis of poly(ferrocenylsilanes) with different molecular weight and their electrochemical behavior
Authors: Wang Jian Jun , Wang Li , Wang Xue Jie , Chen Tao , Chen Ying
Published: January 2006

A series of poly(ferrocenylsilanes) (PFS) with different molecular weight have been prepared via the thermal ring‐opening polymerization of the corresponding monomers. The electrochemical behavior of poly(ferrocenyldimethylsilane) (PFDMS) and poly(ferrocenylmethylphenylsilane) (PFMPS) in solutions were investigated by cyclic voltammetry (CV). It was found that PFS could be adsorbed and electrodeposited on the Pt electrode surface, and the electroactive multilayer films formed on the Pt electrode surface influenced the shape of the voltammogram. The redox potential varied with the molecular weight slightly, and ΔE1/2 became smaller with the increase in molecular weight. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 473–477, 2006
Determination of dynamic mechanical properties of engineering thermoplastics at wide frequency range using Havriliak–Negami model
Authors: Setua D. K. , Gupta Y. N. , Kumar S. , Awasthi R. , Mall A. , Sekhar K.
Published: January 2006

Using Havriliak–Negami (HN) model of time–temperature superposition, dynamic mechanical properties for two thermorheologically simple engineering thermoplastics, viz., polyether ether ketone (PEEK) and polycarbonate (PC) were determined. Calculations have been made with respect to (i) temperature‐independent HN parameters from dynamic mechanical analysis (DMA) and (ii) activation energies of the deformation processes involved. Viscoelastic properties, over a wide frequency range, were predicted from the HN model, which were further correlated with the experimentally determined quantities and chemical structure of the polymers. The mathematical calculations were done using Matlab® software. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 677–683, 2006
Polystyrene nanocomposite materials—Preparation, mechanical, electrical and thermal properties, and morphology
Authors: Ma Chen‐Chi M. , Chen Yi‐Jie , Kuan Hsu‐Chiang
Published: January 2006

This work prepared polystyrene resin nanocomposites with antistatic properties, by melt‐blending polystyrene with nanoscale zinc oxide. The effect of nanoscale zinc oxide on the electrical and physical characteristics of polystyrene nanocomposites was investigated. Two kinds of nanoscale powders, spherical zinc oxide (s‐ZnO) and zinc oxide whisker (w‐ZnO), were selected. The coupling agents, vinyltriethoxysilane and phenyltriethoxysilane, were utilized to improve the compatibility between nanopowders and polystyrene resin. Adding spherical zinc oxide and zinc oxide whisker improved the antistatic characteristic of materials. The surface resistivities of s‐ZnO and w‐ZnO nanocomposite were significantly reduced, by modification with vinyltriethoxysilane and phenyltriethoxysilane. Adding zinc oxide nanopowder increased the flexural modulus and reduces flexural strength. Silane coupling agent improved the flexural properties of nanocomposite. The glass transition temperature and thermal degradation temperature of zinc oxide/polystyrene nanocomposite increased with ZnO content. Treatment with silane increased the glass transition temperature and thermal degradation temperature of composite. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 508–515, 2006
Selectivity of shear rate on chains in polymer combination reaction
Authors: Liu Mengge , Yu Wei , Zhou Chixing
Published: January 2006

The combination reaction of linear low density polyethylene initiated by Dicumyl peroxide at elevated temperature was investigated under different steady shear rates. Gel‐permeation chromatography was used to determine the molecular weight distributions, and time–molecular weight superposition method was used to analyze the viscosity curves. The results showed that lower (or higher) shear rate increased the reaction possibility of shorter (or longer) chains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 839–842, 2006
Alkyd–epoxy blends as multipurpose coatings
Authors: Dutta N. , Karak N. , Dolui S. K.
Published: January 2006

The alkyd resins of three different compositions based on nahar seed oil (Mesua ferrea), phthalic anhydride, and maleic anhydride were synthesized by an alcoholysis method. These alkyd resins were blended with a commercially available epoxy resin (Araldite 250, Ciba Geigy, Mumbai, India) separately to study the performance of the blends as coatings. The morphology of the blends was studied with scanning electron microscopy. The drying time, gloss, flexibility, pencil hardness, adhesion, pressure test, and chemical resistance under different conditions were measured for this purpose. The thermal characteristics of the blends were also investigated by thermogravimetric analysis. The studies showed better performance of the blends with respect to the drying time, hardness, flexibility, gloss, pressure test, thermal stability, and chemical resistance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 516–521, 2006
Thermotropic liquid crystallinity, thermal decomposition behavior, and aggregated structure of poly(propylene carbonate)/ethyl cellulose blends
Authors: Zhang Zhihao , Zhang Huiliang , Zhang Qingxin , Zhou Qinghai , Zhang Hongfang , Mo Zhishen , Zhao Xiaojiang , Wang Xianhong
Published: January 2006

Maleic anhydride end capped poly(propylene carbonate) (PPC‐MA) was blended with ethyl cellulose (EC) by casting from dichloromethane solutions. The thermotropic liquid crystallinity, thermal decomposition behavior, and aggregated structure were investigated by differential scanning calorimetry (DSC), thermogravimetry (TGA), and wide angle X‐ray diffraction (WAXD). DSC exhibits thermotropic liquid crystallinity in the rich EC composition range. TGA shows that thermal decomposition temperatures were elevated upon interfusing EC into PPC‐MA. WAXD corroborates that EC and PPC‐MA/EC blend films cast from dilute dichloromethane solution possessed cholesteric liquid crystalline structure in the rich EC composition range, and that dilution of PPC‐MA with EC increased the dimension of noncrystalline region, leading to a more ordered packed structure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 584–592, 2006
Mechanical, thermal, and morphological properties of bismaleimide/unsaturated polyester copolymers
Authors: Li Ying , Feng Lei , Zhang Liu‐Cheng
Published: January 2006

An unsaturated polyester (UP) resin was modified by the addition of a thermosetting bismaleimide (BMD) as a second coreactive monomer. The copolymers were characterized in terms of mechanical, thermal, and morphological properties by tensile, bend, and impact testing; thermogravimetric analysis; heat deforming temperature analysis; dynamic mechanical analysis; and scanning electron microscopy. In addition, Fourier transform infrared spectroscopy of modified resin indicated that crosslinking networks were formed between BMD and UP. The properties of the modified resins were compared with those of unmodified resins. The results indicate that the addition of BMD not only improved the thermal decomposition temperature and heat deforming temperature but also caused small changes in the mechanical properties. The effect of the construct of BMD and the reactions among BMD, UP, and styrene were analyzed. The results show that BMD has great potential to improve the properties of UP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 593–598, 2006
Preparation and characterization of novel pH‐sensitive binary grafted polymeric blends of gelatin and poly(vinyl alcohol): Water sorption and blood compatibility study
Authors: Bajpai A. K. , Sharma Manish
Published: January 2006

In this study, we attempted the synthesis and characterization of novel biocompatible hydrogels of binary polymeric blends of crosslinked poly(acrylic acid) grafted onto poly(vinyl alcohol) and gelatin by a redox polymerization technique. The end polymer was characterized by IR spectral analysis, differential scanning calorimetry measurements, and scanning electron microscopy. The prepared smart, environment‐responsive hydrogels, containing polyelectrolyte domains, were assessed for their water sorption potential under various experimental conditions and were further used to evaluate important network parameters such as the crosslink density, number of elastically effective chains, and molecular mass between crosslinks. The diffusion mechanism of the solvent–polymer interaction was also analyzed to predict the behavior of continuously relaxing chains containing several carboxylate ions. The blood compatibility of premeditated hydrogels was also judged by in vitro methods such as protein adsorption, blood clot formation, and hemolysis percentage assay measurement. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 599–617, 2006
Kenaf‐fiber‐reinforced poly(lactic acid) used for electronic products
Authors: Serizawa Shin , Inoue Kazuhiko , Iji Masatoshi
Published: January 2006

We have developed high‐performance biomass‐based plastics that consist of poly(lactic acid) (PLA) and kenaf fiber, which fixates CO2 efficiently. Adding this fiber to PLA greatly increases its heat resistance (distortion temperature under load) and modulus and also enhances its crystallization, so the ease of molding this material is improved. Eliminating the short particles from the kenaf fiber improves its effect on the impact strength. Kenaf fiber without the particles exhibits effects on these characteristics of PLA practically comparable to the effects of glass fiber. Furthermore, adding a flexibilizer (a copolymer of lactic acid and aliphatic polyester) to the composites improves their strength. These composites (PLA/kenaf fiber and PLA/kenaf fiber/flexibilizer) show good practical characteristics for housing materials of electronic products in comparison with petroleum‐based plastics used in housing such as glass‐fiber‐reinforced acrylonitrile‐butadien‐styrene (ABS) resin. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 618–624, 2006
Comparison of the molecular properties and morphology of polypropylenes irradiated under different atmospheres and after annealing
Authors: Krause Beate , Häußler Liane , Voigt Dieter
Published: January 2006

Electron‐beam irradiation, a well‐known way of generating long‐chain branching, was used to modify polypropylene. Samples were investigated with differential scanning calorimetry, polarized light microscopy, and size exclusion chromatography. Independently of the atmosphere, postannealing led to the deactivation of residual radicals and to the reduction of the nucleus density. In comparison with the initial polypropylene, the crystallization temperatures increased for nonannealed samples but decreased for annealed samples. Stable products were obtained only by irradiation in nitrogen followed by annealing. A reaction including free radicals with oxygen in the ambient atmosphere led to increasing molar mass degradation and the formation of long‐chain branching after storage. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 634–639, 2006
Hydrogenation of natural rubber latex in the presence of OsHCl(CO)(O2)(PCy3)2
Authors: Mahittikul A. , Prasassarakich P. , Rempel G. L.
Published: January 2006

Hydrogenation is an important method of chemical modification, which improves the physical, chemical, and thermal properties of diene elastomers. Natural rubber latex (NRL) can be quantitatively hydrogenated to provide a strictly alternating ethylene–propylene copolymer using a homogeneous osmium catalyst OsHCl(CO)(O2)(PCy3)2. A detailed kinetic investigation was carried out by monitoring the amount of hydrogen consumption during the reaction using a gas‐uptake apparatus. The kinetic results of NRL hydrogenation indicated that this system had a second‐order dependence of the hydrogenation rate on hydrogen pressure and then decreased toward a zero‐order dependence for hydrogen pressures above 13.8 bar. The hydrogenation was also observed to be first‐order with respect to catalyst concentration and inverse first‐order on rubber concentration due to impurities present in the rubber latex. Additions of a controlled amount of acid demonstrated a beneficial effect on the hydrogenation rate of NRL. The temperature dependence of the hydrogenation rate was investigated and an apparent activation energy (over the range of 120–160°C) was calculated as 57.6 kJ/mol. Mechanistic aspects of this catalytic process are discussed on the basis of kinetic results. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 640–655, 2006
New polymer materials based on silicone‐acrylic copolymer to improve fastness properties of reactive dyes on cotton fabrics
Authors: Xie Kongliang , Hou Aiqin , Zhang Yuhao
Published: January 2006

New polymer materials, based on silicone‐acrylic copolymer containing cationic groups, were synthesized through radical mechanism and ring‐opening polymerization of cyclosiloxane. The polymers of polyacrylate/polysiloxane improved the fastness properties of reactive dyes on cotton. In comparison with those of polyacrylate‐containing cationic groups, the wash fastness and wet rubbing fastness of the dyed cotton fabric treated with the new polymer materials were better. The handle of the fabric with aftertreatment was also good. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 720–725, 2006
Self‐induced short chain branching in homopolymers and 1‐hexene copolymers of ethylene produced with amido functionalized ansa half‐sandwich complexes as catalysts
Authors: Alt Helmut G. , Reb Alexander , Bruce Welch M. , Jurkiewicz Antoni
Published: January 2006

Amido ansa 3‐substituted indenyl complex precursors can be activated with methylaluminoxane and used for prepolymerization with ethylene to give a heterogeneous catalyst for olefin polymerization. Homo polymerization of ethylene with 1‐(3‐pent‐4‐enylindenylidene) dimethylsilyl'butylamidotitaniumdichloride (1), 1‐(3‐hex‐5‐enylindenylidene)dimethylsilyl'butylamidotitanium‐dichloride (2), and 1‐(3‐pent‐4‐enylindenylidene) (oct‐7‐enyl)methylsilyl'butylamidotitaniumdichloride (3) produces polyethylenes that contain ethyl branches. The ethyl branching in the polymers made with complexes 1 and 2 is barely above the 13C NMR detection limit, but the level observed in the polymer made with complex 3 is 17 times greater. Copolymerization of ethylene and 1‐hexene using prepolymerized 3 yields copolymers containing both ethyl and butyl branches. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 734–739, 2006
Transforming growth factor‐β and bone morphogenetic proteins: Cooperative players in chick and murine programmed retinal cell death
Authors: Franke Andreas G. , Gubbe Christian , Beier Marion , Duenker Nicole
Published: January 2006

Transforming growth factor‐β (TGF‐β) and bone morphogenetic protein (BMP) are extracellular molecules known to mediate programmed cell death (PCD) in the developing retina. In the present study, we investigated the expression profiles and activity levels of ligands and receptors of the TGF‐β and BMP4 family during the physiological PCD periods of the developing chick and mouse retina and possible interactions of both proapoptotic molecules in mediating apoptosis in chick and murine retinal whole‐mount cultures. Immunocytochemical double‐labeling studies with the established ganglion cell marker Islet revealed overlapping expression patterns for TGF‐β and BMP4 ligands and receptors on the surface of retinal ganglion cells. The biphasic peak of activity and expression levels of TGF‐β and BMP4 ligands and receptors, revealed by Western blots and mink lung epithelial cell (MLEC) assays, coincided with the two main periods of retinal chick and murine PCD. In organotypic retinal cultures, we were able to increase apoptosis over basal levels by application of recombinant TGF‐β or BMP4. Double‐factor treatment induced an additional increase of apoptosis, suggesting a cooperation of both proapoptotic pathways. A significant increase in the number of apoptotic cells in the ganglion cell layer was observed in a TUNEL staining of retinal whole mounts treated with recombinant TGF‐β or BMP4, suggesting a concerted action of both factors in triggering ganglion cell death. Blockage experiments revealed that both pathways do not interact at the ligand, receptor, or Smad protein level but converge at the transcriptional level of the TGF‐β immediate‐early response gene TIEG and the transcriptional coactivator Gcn5. J. Comp. Neurol. 495:263–278, 2006. © 2006 Wiley‐Liss, Inc.
Structural basis for developmentally regulated changes in cadherin function at synapses
Authors: Elste Alice M. , Benson Deanna L.
Published: January 2006

Members of the cadherin family of calcium‐dependent cell adhesion molecules can bind homophilically across central nervous system (CNS) synapses, but experimental evidence indicates the nature of their contribution to synapse structure and function changes over time. We asked whether changes in function correspond to differences in intrasynaptic distribution. Using quantitative immuno‐electronmicroscopy, we determined where cadherins are localized within synapses at key developmental stages in cultured hippocampal neurons and in hippocampus in vivo. At 5–6 days in culture, when most synapses are newly formed, cadherins are regularly and evenly distributed at synaptic clefts throughout the active zone. In contrast, at 14 days, when the majority of synapses are comparatively mature, cadherin labeling concentrates in discrete clusters. Such clusters can occur at any place within or immediately surrounding synaptic clefts. To assess whether this change in distribution is unique to neurons grown in culture, we compared the distribution of cadherins in the CA1 region of hippocampus at postnatal days 2, 3 (P2–3) and in adult. Consistent with our observations in cultured neurons, synapses in P2–3 hippocampus most often exhibit cadherins distributed regularly throughout the cleft, while adult synapses show predominantly discrete concentrations at single sites. The early developmental pattern of cadherin distribution can also be detected at occasional synapses in adult tissue. Such synapses also have morphological features consistent with immature synapses, suggesting that intrasynaptic cadherin distribution is a feature that may distinguish synapse age. J. Comp. Neurol. 495:324–335, 2006. © 2006 Wiley‐Liss, Inc.
Distributions of two gonadotropin‐releasing hormone receptor types in a cichlid fish suggest functional specialization
Authors: Chen Chun‐Chun , Fernald Russell D.
Published: January 2006

Gonadotropin‐releasing hormone 1 (GnRH1) from the brain controls reproduction in vertebrates via a GnRH‐specific receptor in the pituitary; however, other forms of GnRH are found in all species, suggesting additional roles for this family of peptides. GnRH action depends critically on the location of its cognate receptors in the brain. To understand the potential roles of additional GnRH forms, we localized two known GnRH receptor types in a cichlid fish, Astatotilapia burtoni, in which GnRH1 is socially regulated. Using in situ hybridization, we describe the mRNA expression pattern of these GnRH receptor (GnRH‐R) subtypes in the brain, specifically with respect to GnRH‐producing neurons. Our data suggest that following a gene duplication, the two GnRH receptors have evolved to serve different functions. The type 1 receptor (GnRH‐R1) is expressed less widely than the type 2 receptor (GnRH‐R2). Specifically, GnRH‐R1 is expressed in groups of neurons in the telencephalon, preoptic area, ventral hypothalamus, thalamus, and pituitary. In contrast, GnRH‐R2 is expressed in many more brain areas, including the olfactory bulb, telencephalon, preoptic area, hypothalamus, thalamus, midbrain, optic tectum, cerebellum, hindbrain, and pituitary. The specific distribution of GnRH‐R2 suggests that the GnRH ligands may act via this receptor to influence behavior in A. burtoni. Moreover, only GnRH‐R2 mRNA is colocalized in the three known groups of GnRH‐containing neurons, suggesting that any direct feedback regulation of GnRH by itself must act through this receptor type. Taken together, these data suggest that the two GnRH receptor types serve different functional roles in A. burtoni. J. Comp. Neurol. 495:314–323, 2006. © 2006 Wiley‐Liss, Inc.
Targeting dopamine D2 and cannabinoid‐1 (CB1) receptors in rat nucleus accumbens
Authors: Pickel Virgina M. , Chan Jane , Kearn Christopher S. , Mackie Kenneth
Published: January 2006

The nucleus accumbens (Acb) shell and core are essential components of neural circuitry mediating the reward and motor effects produced by activation of dopamine D2 or cannabinoid‐1 (CB1) receptors. D2 receptors can form heterodimeric complexes with cannabinoid‐1 (CB1) receptors and are also involved in control of the availability of both dopamine and endocannabinoids. Thus, the subcellular locations of D2 and CB1 receptors with respect to each other are implicit to their physiological actions in the Acb. We used electron microscopic immunocytochemistry to determine these locations in the Acb shell and core of rat brain. In each region, many neuronal profiles showed endomembrane and plasmalemmal distributions of one or both receptors. Approximately one‐third of the labeled profiles were somata and dendrites, some of which showed overlapping subcellular distributions of D2 and CB1 immunoreactivities. The remaining labeled profiles were small axons and axon terminals containing CB1 and/or D2 receptors. Of the labeled terminals forming recognizable synapses, ∼20% of those containing CB1 receptors contacted D2‐labeled dendrites, while conversely, almost 15% of those containing D2 receptors contacted CB1‐labeled dendrites. These results provide the first ultrastructural evidence that D2 and CB1 receptors in the Acb shell and core have subcellular distributions supporting both intracellular associations and local involvement of D2 receptors in making available endocannabinoids that are active on CB1 receptors in synaptic neurons. These distributions have direct relevance to the rewarding and euphoric as well as motor effects produced by marijuana and by addictive drugs enhancing dopamine levels in the Acb. J. Comp. Neurol. 495:299–313, 2006. © 2006 Wiley‐Liss, Inc.
Immunogold localization of phocein in dendritic spines
Authors: Haeberlé Anne‐Marie , Castets Francis , Bombarde Guy , Baillat Gilbert , Bailly Yannick
Published: January 2006

Phocein, a widely expressed intracellular protein involved in clathrin‐ and dynamin‐dependent membrane dynamics, has been shown to interact with members of the striatin family of proteins, striatin, SG2NA, and zinedin. Immunogold labeling was performed to assess subcellular localization of phocein in neurons of the rodent cerebellar cortex and hippocampal Ammon's horn. Most of the phocein‐bound gold particles were located within dendritic thorns and spines of the cerebellar Purkinje cells and hippocampal pyramidal neurons, as observed previously for striatin in striatal neurons. The postsynaptic profiles containing phocein were engaged in asymmetric synapses with the main types of afferents in the cerebellum and in the hippocampus. In the cerebellum, phocein‐bound immunogold particle numbers ranged from 1–20 in ∼50% of the Purkinje cell spines. In these spines most of the immunogold particles were found in the neuroplasm (∼70%) and on nonsynaptic plasma membrane domains and related structures such as endocytic‐like profiles (∼18%). As soon as the first postnatal week, phocein was detected in the Purkinje cell somatic and dendritic thorns making asymmetric synapses with climbing fibers. During the following weeks the protein was located in the dendritic spines, as observed in the adult molecular layer. Finally, double immunogold labeling revealed a distribution of phocein and SG2NA suggesting that the two proteins could interact in the Purkinje cell spines. The early postnatal expression of phocein, a protein involved in membrane dynamics, suggests that it may have functional relevance in dendritic remodeling during development and potentially in spine plasticity during adulthood. J. Comp. Neurol. 495:336–350, 2006. © 2006 Wiley‐Liss, Inc.
The Metal‐Catalyzed Cyclotrimerization of Ferrocenylethyne – Preparation and Characterization of 1,2,4‐Triferrocenylbenzene
Authors: Fiorentini Simone , Floris Barbara , Galloni Pierluca , Grepioni Fabrizia , Polito Mauro , Tagliatesta Pietro
Published: January 2006

1,2,4‐Triferrocenylbenzene was isolated and fully characterized for the first time. It was obtained, together with 1,3,5‐triferrocenylbenzene, by cyclotrimerization reaction, catalyzed either by metalloporphyrins or cobaltocene. The latter catalyst gave better results. The isomerically different triferrocenylbenzenes exhibit different properties. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Novel Plastic Chromium(III)‐Ion Selective Electrodes Based on Different Ionophoric Species and Plasticizing Solvent Mediators
Authors: Akl Magda A. , Ghoneim Ahmed K. , Abd El‐Aziz Mohammed H.
Published: January 2006

Different ionophoric species, viz.: 18‐crown‐6 (18C6), dibenzo‐18‐crown‐6 (DB18C6) and calix[6]arene (CAX), as electroactive materials, with 2‐nitrophenyloctylether (2‐NPOE), bis(ethylhexyl)sebacate (DOS), dioctyl phthalate (DOP), and didecyl phthalate (DDP) as plasticizing solvent mediators were used to construct Cr3+ selective electrodes in a PVC matrix in the ratio (w/w) PVC: ionophore: plasticizer (60 : 2 : 120). Seven electrodes out of the fabricated 12 electrodes, gave best results in terms of working concentration range (1.0×10−5−1.0×10−1 M) with a close to Nernstian slope of 18.5 and a Nernstian slope of 20.0 mV/decade of activity. The usable pH range of the sensors is 4.0–7.0. The detection limit of the selected electrodes is ≤1.0×10−7 M. The response time of the sensors is 8–35 s, depending on the concentration of Cr3+ used. The selectivity coefficient values indicate that the electrodes are highly selective for Cr3+ over a number of other cations except Pb2+ and Na+ (for some electrodes). The electrodes have successfully been used to determine Cr3+ in certified and real alloys and in effluents of electroplating shops with a precision as relative standard deviation (RSD)<3%, for each of the proposed Cr3+‐ion selective electrodes. The results obtained by the proposed ISEs are in good agreement with the results obtained by direct flame AAS method.
Plugs in nuclear pores: Transcripts in early oocyte development identified with nanotechniques
Authors: Schlune Andrea , Shahin Victor , Enss Karoline , Schillers Herman , Oberleithner Hans
Published: January 2006

Throughout oogenesis, huge amounts of RNA are produced that are needed for early development. Early stages of oocyte development are characterized by high transcriptional activity whereas translation of maternal RNA dominates late stages. Nuclear pore complexes (NPCs), located in the nuclear envelope (NE), mediate bidirectional macromolecule exchange between the nuclear and cytosolic compartments including RNA export. Here, we report on structural correlates of this transport pathway at single NPC level. Using atomic force microscopy (AFM), we imaged the nucleoplasmic (“inner”) surface of the NE of Xenopus laevis oocytes in different stages of development. We found that NPC frequency per nucleus increases with maturation. However, individual NPCs are more active in immature stages. In early stages, known for high transcriptional activity, we found nearly 10% of NPC central channels plugged with a 400–800 kDa mass. In contrast, the incidence of plugged NPCs was below 1% in late oocyte stages. On‐site RNA digestion led to a change in plug shape from prominent to flat while plug mass decreased by almost 20%. Quantitative AFM analysis revealed that RNase exposure reduced total nucleoplasmic NPC mass by about 58 and 25% in early and late stage oocytes, respectively. We conclude: (i) NPCs of immature oocytes are more active in RNA transport, (ii) Plugs identified at the nucleoplasmic entrance of NPC central channels represent ribonucleoproteins exiting the nucleus, (iii) RNA is a structural component of the NPC nanomachine. J. Cell. Biochem. 98: 567–576, 2006. © 2006 Wiley‐Liss, Inc.
Effects of cadmium on structure and enzymatic activity of Cu,Zn‐SOD and oxidative status in neural cells
Authors: Huang Yen‐Hua , Shih Chwen‐Ming , Huang Chang‐Jen , Lin Chun‐Mao , Chou Chih‐Ming , Tsai Meng‐Ling , Liu Tsang Pai , Chiu Jen‐Fu , Chen Chien‐Tsu
Published: January 2006

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disorder disease. Ten percent of the ALS patients are congenital (familial ALS), and the other 90% are sporadic ALS (SALS). It has been shown that mutations found in the Cu,Zn‐SOD cause 20% of the familial ALS due to its low enzyme activity. We hypothesized that heavy metals may interfere the structure of Cu,Zn‐SOD protein to suppress its activity in some of the SALS. In this study, we expressed and characterized the recombinant human Cu,Zn‐SOD under various concentrations of Cu2+, Zn2+, and Cd2+. By atomic absorption spectrophotometry, we demonstrated that adding of cadmium significantly increased the content of cadmium ion, but reduced its Zn2+ content and enzyme activity of the Cu,Zn‐SOD protein. The data of circular dichroism spectra demonstrated that the secondary structure of Cu,Zn‐SOD/Cd is different from Cu,Zn‐SOD, but close to apo‐SOD. In addition to the effect of cadmium on Cu,Zn‐SOD, cadmium was also shown to induce neural cell apoptosis. To further investigate the mechanism of neural cell apoptosis induced by cadmium, we used proteomics to analyze the altered protein expressions in neural cells treated with cadmium. The altered proteins include cellular structural proteins, stress‐related and chaperone proteins, proteins involved in reactive oxygen species (ROS), enzyme proteins, and proteins that mediated cell death and survival signaling. Taken together, in this paper, we demonstrate that cadmium decreases the content of Zn2+, changes the conformation of Cu,Zn‐SOD protein to decrease its enzyme activity, and causes oxidative stress‐induced neural cell apoptosis. J. Cell. Biochem. 98: 577–589, 2006. © 2006 Wiley‐Liss, Inc.
Quantitative analysis of localization and nuclear aggregate formation induced by GFP‐lamin A mutant proteins in living HeLa cells
Authors: Hübner S. , Eam J.E. , Wagstaff K.M. , Jans D.A.
Published: January 2006

Although A‐type lamins are ubiquitously expressed, their role in the tissue‐specificity of human laminopathies remains enigmatic. In this study, we generate a series of transfection constructs encoding missense lamin A mutant proteins fused to green fluorescent protein and investigate their subnuclear localization using quantitative live cell imaging. The mutant constructs used included the laminopathy‐inducing lamin A rod domain mutants N195K, E358K, M371K, R386K, the tail domain mutants G465D, R482L, and R527P, and the Hutchinson–Gilford progeria syndrome‐causing deletion mutant, progerin (LaAΔ50). All mutant derivatives induced nuclear aggregates, except for progerin, which caused a more lobulated phenotype of the nucleus. Quantitative analysis revealed that the frequency of nuclear aggregate formation was significantly higher (two to four times) for the mutants compared to the wild type, although the level of lamin fusion proteins within nuclear aggregates was not. The distribution of endogenous A‐type lamins was altered by overexpression of the lamin A mutants, coexpression experiments revealing that aberrant localization of the N195K and R386K mutants had no effect on the subnuclear distribution of histones H2A or H2B, or on nuclear accumulation of H2A overexpressed as a DsRed2 fusion protein. The GFP‐lamin fusion protein‐expressing constructs will have important applications in the future, enabling live cell imaging of nuclear processes involving lamins and how this may relate to the pathogenesis of laminopathies. J. Cell. Biochem. 98: 810–826, 2006. © 2006 Wiley‐Liss, Inc.
Gingival fibroblasts are better at inhibiting osteoclast formation than periodontal ligament fibroblasts
Authors: de Vries Teun J. , Schoenmaker Ton , Wattanaroonwong Nutthamon , van den Hoonaard Marije , Nieuwenhuijse Arlies , Beertsen Wouter , Everts Vincent
Published: January 2006

Various studies indicate that periodontal ligament fibroblasts (PLF) have some similarities to osteoblasts, for example they have the capacity to induce the formation of osteoclast‐like cells. Here, we investigated whether a second population of tooth‐associated fibroblasts, gingival fibroblasts (GF), has similar osteoclastogenesis properties. PLF and GF were co‐cultured with peripheral blood mononuclear cells (PBMC) in the presence and absence of dexamethasone and 1α,25dihydroxycholecalciferol (dex + vit D3) on plastic and on cortical bone slices. Tartrate resistant acid phosphatase (TRACP) positive multinucleated cells (MNCs) were more abundant in co‐cultures with PLF than in GF‐PBMC co‐cultures, more abundant on plastic compared to bone and more abundant in the presence of dex + vit D3. In line with these findings was an inhibition of MNC formation and not inhibition of existing osteoclasts by medium conditioned by GF. We next investigated whether expression of molecules important for osteoclastogenesis differed between the two types of fibroblasts and whether these molecules were regulated by dex + vit D3. OPG was detected at high levels in both fibroblast cultures, whereas RANKL could not be detected. Resorption of bone did not occur by the MNCs formed in the presence of either fibroblast subpopulation, suggesting that the fibroblasts secrete inhibitors of bone resorption or that the osteoclast‐like cells were not functional. The incapacity of the MNCs to resorb was abolished by culturing the fibroblast‐PBMC cultures with M‐CSF and RANKL. Our results suggest that tooth‐associated fibroblasts may trigger the formation of osteoclast‐like cells, but more importantly, they play a role in preventing bone resorption, since additional stimuli are required for the formation of active osteoclasts. J. Cell. Biochem. 98: 370–382, 2006. © 2006 Wiley‐Liss, Inc.