bluuebunny/crossref_metadata_2025 huggingface dataset:
Monodisperse polystyrene microspheres by dispersion copolymerization of styrene and other vinyl comonomers: Characterization and protein adsorption properties
Authors: Hou Xiaohui , Liu Bailing , Deng Xiaobo , Zhang Baotan , Yan Jufang
Published: April 2007

Dispersion polymerization is a very attractive method for preparing micron‐size monodisperse polymeric microspheres. The applications of microspheres have been greatly extended by using comonomers. In the present study, five kinds of polystyrene microspheres of 4–6 μm in diameters bearing different surface functional groups were synthesized by copolymerization of styrene and various vinyl comonomers. Their surface physicochemical characteristics were examined, including average particle size and size distribution, concentration of surface functional groups, as well as hydrophobicity. Concentration of FT‐IR spectra of different samples were also discussed. The effects of microspheres' surface physicochemical properties on the isotherms of adsorption and chemisorption of BSA were determined. The results show that microspheres bearing different surface function groups have different capacity of protein adsorption. Besides, since the protein adsorption behaviors were more complex than the ideal adsorption model, the isotherms could not fit Freundlich model very well. Possible reasons were discussed. Knowledge gained from these results may be utilized for rational design of carriers of receptors and antibodies used in solid‐phase immunoassay, especially Scintillation proximity assay in High‐throughput Screening. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 2007
Structural and mechanical evaluations of a topology optimized titanium interbody fusion cage fabricated by selective laser melting process
Authors: Lin Chia‐Ying , Wirtz Tobias , LaMarca Frank , Hollister Scott J.
Published: April 2007

A topology optimized lumbar interbody fusion cage was made of Ti‐Al6‐V4 alloy by the rapid prototyping process of selective laser melting (SLM) to reproduce designed microstructure features. Radiographic characterizations and the mechanical properties were investigated to determine how the structural characteristics of the fabricated cage were reproduced from design characteristics using micro‐computed tomography scanning. The mechanical modulus of the designed cage was also measured to compare with tantalum, a widely used porous metal. The designed microstructures can be clearly seen in the micrographs of the micro‐CT and scanning electron microscopy examinations, showing the SLM process can reproduce intricate microscopic features from the original designs. No imaging artifacts from micro‐CT were found. The average compressive modulus of the tested caged was 2.97 ± 0.90 GPa, which is comparable with the reported porous tantalum modulus of 3 GPa and falls between that of cortical bone (15 GPa) and trabecular bone (0.1–0.5 GPa). The new porous Ti‐6Al‐4V optimal‐structure cage fabricated by SLM process gave consistent mechanical properties without artifactual distortion in the imaging modalities and thus it can be a promising alternative as a porous implant for spine fusion. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res 2007
Host response to sponge implants differs between subcutaneous and intraperitoneal sites in mice
Authors: Mendes Juliana B. , Campos Paula P. , Ferreira Mônica A. N. D. , Bakhle Y. S. , Andrade Silvia P.
Published: April 2007

Synthetic matrices have been used widely to repair and/or to replace biological tissues. However, there is relatively little information on the effect of different anatomical compartments on the host response to foreign implants. We have analyzed such responses to sponge implants in subcutaneous and in intraperitoneal sites in mice at days 3, 5, and 8 postimplantation by measuring inflammation, angiogenesis, and production of proangiogenic/inflammatory cytokines. The angiogenic response, assessed by hemoglobin content and by morphometric analysis of the number of vessels, was higher in intraperitoneal implants. Levels of vascular endothelial growth factor in intraperitoneal implants were 14‐fold higher than in subcutaneous implants at day 3 and remained high for the next 5 days. Neutrophil accumulation as determined by myeloperoxidase activity was the same in both types of implants. Macrophage accumulation (N‐acetylglucosaminidase activity) was also similar on days 3 and 8 in both implants. Levels of the chemokine CXCL2/KC were always higher, but those of CCL2/JE lower, in the intraperitoneal implant. These results demonstrate that the anatomical site of the implant markedly influenced the host response to synthetic matrices. Our results provide a greater understanding of factors affecting the biocompatibility of exogenous materials placed at different anatomical sites. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007
Time dependent mechanical properties of bone cement. An in vitro study over one year
Authors: Nottrott Markus , Mølster Anders Odd , Gjerdet Nils Roar
Published: April 2007

Changes in mechanical properties of bone cements over time are of clinical importance, but not well documented. Specifications for testing do not address the time factor. This study recorded changes in compressive properties and microstructure of one bone cement stored under simulated physiological conditions (water at 37°C) from 20 min up to 1 year and in dry air at 37°C for comparison. Compressive strength increased within the first week (p < 0.001), decreased at 1 month (p < 0.001), and remained at that level at 1 year. Elastic modulus showed a similar development. Maximum strain values, indicating plastic deformability, increased continuously over 1 year. Microscopy revealed microcracks between the pre‐polymer beads and the matrix in specimens tested after 20 min, whereas there were less cracks in 1 year specimens. Increase in strength during the first week is due to polymerization and formation of interpenetrating molecular networks. The subsequent decrease could be due to the plasticizing effect of water uptake, as supported by higher values for dry specimens. It can be speculated that microcracks which could be initiated while reducing an arthroplasty at 15 min, acting as initiators for fatigue fractures in the cement mantle, contribute to cement failure. It is recommended that testing of bone cements should be performed after extended ageing at simulated physiological conditions, for the present cement at least 5 weeks. Results obtained at less than one week could be influenced by ongoing polymerization, as well as microcracks and lower coherence between the prepolymer beads and the matrix. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007
Polyurethane hydrogel colored contact lens with gradient water content
Authors: Chen Yongjun , Narayanswamy Babu , Chew Mike
Published: April 2007

A colored contact lens was fabricated by chemically bonding a layer of polyurethane (PU) hydrogel color ink to the bulk soft clear lens. The water content of the PU hydrogel was lower than that of the soft contact lens bulk materials, which provided the appropriate gradient water content of the colored lens. The gradient water content of the colored lens reduced the dehydration of the colored lens and minimized the interface stress between bulk lens surface and color ink layer. The colored lens showed much better comfort and dryness ratings than those of the other commercial color lens and even the clear soft lens used in this study. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2007
The sperm nuclear matrix is required for paternal DNA replication
Authors: Shaman Jeffrey A. , Yamauchi Yasuhiro , Steven Ward W.
Published: April 2007

The mammalian sperm nucleus provides an excellent model for studying the relationship between the formation of nuclear structure and the initiation of DNA replication. We previously demonstrated that mammalian sperm nuclei contain a nuclear matrix that organizes the DNA into loop domains in a manner similar to that of somatic cells. In this study, we tested the minimal components of the sperm nucleus that are necessary for the formation of the male pronucleus and for the initiation of DNA synthesis. We extracted mouse sperm nuclei with high salt and dithiothreitol to remove the protamines in order to form nuclear halos. These were then treated with either restriction endonucleases to release the DNA not directly associated with the nuclear matrix or with DNAse I to digest all the DNA. The treated sperm nuclei were injected into oocytes, and the paternal pronuclear formation and DNA synthesis was monitored. We found that restriction digested sperm nuclear halos were capable of forming paternal pronuclei and initiating DNA synthesis. However, when isolated mouse sperm DNA or sperm DNA reconstituted with the nuclear matrices were injected into oocytes, no paternal pronuclear formation or DNA synthesis was observed. These data suggest that the in situ nuclear matrix attachment organization of sperm DNA is required for mouse paternal pronuclear DNA synthesis. J. Cell. Biochem. 102: 680–688, 2007. © 2007 Wiley‐Liss, Inc.
Inhibition of farnesyl protein transferase sensitizes human MCF‐7 breast cancer cells to roscovitine‐mediated cell cycle arrest
Authors: Węsierska‐Gądek Józefa , Maurer Margarita , Schmid Gerald
Published: April 2007

We reported recently that roscovitine (ROSC), a selective cyclin‐dependent kinase (CDK) inhibitor, arrests human MCF‐7 breast cancer cells in G2phase of the cell cycle, and concomitantly induces apoptosis. Human MCF‐7 breast cancer cells are known to express elevated levels of c‐Ha‐Ras protein. To achieve full biological activity, de novo synthesized c‐Ha‐Ras protein has to be farnesylated and after further processing it needs to be attached to the plasma membrane. Therefore, we decided to prove whether prevention of protein farnesylation would sensitize MCF‐7 cells to the action of ROSC. MCF‐7 cells were treated with 1–40 µM ROSC alone, or in combination with L‐744,832, an inhibitor of farnesyl protein transferase (FTPase). To measure the impact on the proliferation of the cells, we used the CellTiterGlo™ viability assay and FACS analysis was employed to quantify the DNA‐content of the single cells. The amount and phosphorylation status of relevant proteins after lysis of MCF‐7 cells was assessed on Western blots using (phospho)‐specific antibodies. The combined treatment with L‐744,832 and ROSC for 24 h, markedly reduced the number of viable MCF‐7 cells, primarily, by re‐enforcing the cell cycle arrest. Interestingly, the potentiation of the ROSC‐mediated inhibition of cell proliferation became evident during the 48 h post‐incubation period in presence of the FPTase inhibitor. Inhibition of FPTase in ROSC‐treated cells reduced the number of viable cells by approximately 30%. Evidently, the combined treatment sensitizes MCF‐7 cells to the action of ROSC, thereby allowing to reduce the dose of the drug and to minimize side effects. J. Cell. Biochem. 102: 736–747, 2007. © 2007 Wiley‐Liss, Inc.
Bioethanol: fuel or feedstock?
Authors: Rass‐Hansen Jeppe , Falsig Hanne , Jørgensen Betina , Christensen Claus H
Published: April 2007

Increasing amounts of bioethanol are being produced from fermentation of biomass, mainly to counteract the continuing depletion of fossil resources and the consequential escalation of oil prices. Today, bioethanol is mainly utilized as a fuel or fuel additive in motor vehicles, but it could also be used as a versatile feedstock in the chemical industry. Currently the production of carbon‐containing commodity chemicals is dependent on fossil resources, and more than 95% of these chemicals are produced from non‐renewable carbon resources. The question is: what will be the optimal use of bioethanol in a longer perspective? Copyright © 2007 Society of Chemical Industry
Preparation and characterization of organosilicon thin films for selective adhesion of Yarrowia lipolytica yeast cells
Authors: Lehocký Marián , Amaral Priscilla Filomena Fonseca , St'ahel Pavel , Coelho Maria Alice Zarur , Barros‐Timmons Ana Margarida , Coutinho João Araújo Pereira
Published: April 2007

The adhesion of Yarrowia lipolytica and Saccharomyces cerevisiae on organosilicon thin films deposited on polycarbonate substrates was investigated through a series of adhesion tests in order to obtain a selective substrate for Y. lipolytica cell adhesion. Organosilicon thin films were prepared using atmospheric pressure surface barrier discharge. The surface was characterized by its total surface energy with its components calculated using the acid‐base theory. Assessment of adhesion via cell surface coverage was obtained by standard tests and also through image analysis of yeast cells on the organosilicon layers. The results show that it is possible to create organosilicon thin films for a selective adhesion of Y. lipolytica face to S. cerevisiae behaviour, for potential use in fixed bed biofilm reactors for industrial purposes involving enzyme‐based biotransformations. Copyright © 2007 Society of Chemical Industry
Solvent extraction of lanthanides and yttrium from nitrate medium with CYANEX 925 in heptane
Authors: Li Wei , Wang Xianglan , Zhang Hui , Meng Shulan , Li Deqian
Published: April 2007

The extraction behavior of lanthanides and yttrium usinsg CYANEX 925 (mixture of branched chain alkylated phosphine oxides) in n‐heptane from nitrate medium has been studied. The effects of aqueous phase ionic strength, CYANEX 925 concentration in the organic phase, and temperature on Sm3+, Nd3+and Y3+extraction have been investigated. The extractability of the lanthanides and yttrium increases with increasing nitrate concentration, as well as with increasing CYANEX 925 concentration. An extraction mechanism is proposed based on slope analysis. Furthermore, the infra‐red spectra of CYANEX 925 saturated with lanthanides are employed to provide evidence of the composition of the complex. The relationship between the logarithm of the distribution ratio and lanthanide atomic number is also discussed which indicates that yttrium can be separated from light lanthanides. In addition separation of the light and heavy lanthanide groups is also possible using CYANEX 925. From the temperature dependence data, the thermodynamic parameters values (ΔH, ΔSand ΔG) are calculated. Copyright © 2007 Society of Chemical Industry
The use of toxic solid waste for the adsorption of dyes from waste streams
Authors: Saravanabhavan Subramani , Sreeram Kalarical Janardhanan , Raghava Rao Jonnalagadda , Unni Nair Balachandran
Published: April 2007

The use of chromium‐containing toxic solid wastes from the leather industry for the removal of dyes from waste‐waters has been studied. A batch adsorption model has been employed and the role of various experimental parameters on the efficiency of the process evaluated. The extent of dye removal was studied by varying parameters such as pH, contact time, initial concentration of the dye and amount of adsorbent. The experimental equilibrium data for this system has been analyzed using the linearized forms of Langmuir and Freundlich isotherms. The Langmuir isotherm was found to provide the best theoretical correlation of the experimental data and the adsorption was found to follow pseudo‐second‐order kinetics. The dye adsorbed solid wastes were used for the preparation of pigments. In essence, this study provides a greener solution for chromium‐containing solid wastes, dye containing waste‐waters and dye‐adsorbed chromium solid wastes. Copyright © 2007 Society of Chemical Industry
Combined treatment with Ad‐hTRAIL and DTIC or SAHA is associated with increased mitochondrial‐mediated apoptosis in human melanoma cell lines
Authors: Lillehammer Trine , Engesaeter Birgit O. , Prasmickaite Lina , Maelandsmo Gunhild M. , Fodstad Oystein , Engebraaten Olav
Published: April 2007

Background

Currently, dacarbazine (DTIC) is the only approved systemic treatment for metastatic malignant melanoma. However, the modest treatment effect encourages studies on novel therapeutic molecules, delivery systems and combination therapies. Full‐length TRAIL, delivered from an adenoviral vector (Ad‐hTRAIL), was studied in combination with DTIC or the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA) in human melanoma cell lines.

Methods

The cytotoxic potential of the combination treatments was assessed by cell viability measurements and CalcuSyn analysis. Involvement of apoptosis was analyzed by TUNEL staining, mitochondrial membrane potential measurements, and activation and expression levels of caspases and other mediators of apoptosis.

Results

Ad‐hTRAIL in combination with DTIC or SAHA resulted in additive or synergistic growth inhibition compared to each treatment used as single agent. Both combinations augmented apoptosis, which was mediated through the death receptor (DR) pathway by enhanced activation of caspase‐8, and through increased loss of mitochondrial integrity. Provoked cleavage of Bid, which bridges the extrinsic and intrinsic apoptosis pathways, and downregulation of the anti‐apoptotic mediators Bcl‐XL, Mcl‐1 and XIAP (but not Bcl‐2) were critical contributing factors. Increased levels of DR4 and DR5 were not a common underlying mechanism as DTIC did not affect the levels of either of the receptors. However, SAHA‐induced expression of DR4 may have reduced the TRAIL resistance in the SKMEL‐28 cell line.

Conclusion

Administration of Ad‐hTRAIL in combination with DTIC or SAHA enhances apoptosis in human melanoma cell lines, and suggests that the therapeutic potential of such treatment strategies should be further evaluated for possible clinical use. Copyright © 2007 John Wiley & Sons, Ltd.
Lentivirus vector‐mediated gene transfer to the developing bronchiolar airway epithelium in the fetal lamb
Authors: Yu Ze‐Yan , McKay Karen , van Asperen Peter , Zheng Maolin , Fleming Jane , Ginn Samantha L. , Kizana Eddy , Latham Margot , Feneley Michael P. , Kirkland Peter D. , Rowe Peter B. , Lumbers Eugenie R. , Alexander Ian E.
Published: April 2007

Background

Development of effective and durable gene therapy for treatment of the respiratory manifestations of cystic fibrosis remains a formidable challenge. Obstacles include difficulty in achieving efficient gene transfer to mature airway epithelium and the need to stably transduce self‐renewing epithelial progenitor cells in order to avoid loss of transgene expression through epithelial turnover. Targeting the developing airway epithelium during fetal life offers the prospect of circumventing these challenges.

Methods

In the current study we investigated vesicular stomatitis virus glycoprotein (VSVg)‐pseudotyped HIV‐1‐derived lentivirus vector‐mediated gene transfer to the airway epithelium of mid‐gestation fetal lambs, both in vitro and in vivo. In the in vitro studies epithelial sheet explants and lung organ culture were used to examine transduction of the proximal and more distal airway epithelium, respectively. For the in vivo studies, vector was delivered directly into the proximal airway.

Results

We found that even during the early pseudoglandular and canalicular phases of lung development, occurring through mid‐gestation, the proximal bronchial airway epithelium was relatively mature and highly resistant to lentivirus‐mediated transduction. In contrast, the more distal bronchiolar airway epithelium was relatively permissive for transduction although the absolute levels achieved remained low.

Conclusion

This result is promising as the bronchiolar airway epithelium is a major site of pathology in the cystic fibrosis airway, and much higher levels of transduction are likely to be achieved by developing strategies that increase the amount of vector reaching the more distal airway after intratracheal delivery. Copyright © 2007 John Wiley & Sons, Ltd.
Glutamine as an energy substrate in cultured neurons during glucose deprivation
Authors: Peng Liang , Gu Li , Zhang Hongliang , Huang Xueshi , Hertz Elna , Hertz Leif
Published: April 2007

During glucose deprivation an increase in aspartate formation from glutamine has been observed in different brain preparations, including synaptosomes and cultured astrocytes. To what extent this reaction, which provides a substantial amount of energy, occurs in different types of neurons is unknown. The present study shows that 14CO2 formation from [U‐14C]glutamine in cerebellar granule neurons, a glutamatergic preparation, increased by 60% during glucose deprivation, indicating enhanced aspartate formation or increased complete oxidative degradation of glutamine. In primary cultures of cerebrocortical interneurons, a GABAergic preparation, the rate of 14CO2 production from [U‐14 C] glutamine was four times lower and not stimulated by glucose deprivation. During incubation with glutamine (0.8 mM) as the only metabolic substrate, cerebellar granule cells maintained an oxygen consumption rate of 12 nmol/min/mg protein, corresponding to an aspartate formation of 8 nmol/min/mg protein (three oxidations occur between glutamine and aspartate) or to a total oxidative degradation of 3 nmol/min/mg protein. During glucose deprivation, the rate of aspartate formation increased, and during a 20‐min incubation in phosphate‐buffered saline it amounted to 3.3 nmol/min/mg protein at 0.2 mM glutamine, which might have been more if measured at 0.8 mM glutamine. These values are consistent with the rate of glutamine utilization calculated based on oxygen consumption and leaves open the possibility that some glutamine is completely degraded oxidatively, as has been shown by other authors based on pyruvate recycling and labeling of lactate from aspartate in cerebellar granule neurons. © 2007 Wiley‐Liss, Inc.
Building global leadership at Avery Dennison
Authors: Schuler Terry
Published: April 2007

As Avery Dennison grew from a collection of autonomous international businesses to a more integrated global corporation, the demands on leaders called for new capabilities. Several years of effort and a new leadership model led to an integrated, competency‐driven leadership development system, supported by powerful tools and processes—and hard‐earned wisdom about how to grow global leaders. The company draws talent from around the world, manages the talent pool as a global asset, and gives managers global experiences and responsibilities to help them develop the skills needed to become global leaders. It also holds managers deeply accountable for developing leaders, and measuring and rewarding their results. © 2007 Wiley Periodicals, Inc.
Action learning helps PepsiCo's sales leaders develop business acumen and innovation skills
Authors: Cone Jay , Woodard Michael
Published: April 2007

To help sales leaders understand their customers' business and innovate ways to create value for customers, PepsiCo's Strategic Customer Leadership Forum combines executive involvement, multiple learning modalities, and action learning projects that focus on real work and produce real gains for PepsiCo and its customers. A fast‐paced curriculum enhanced with technology—including computer‐based simulations and online assessments—emphasizes experiential learning in the context of addressing actual customer issues and goals. Executive sponsorship of action learning teams and selection of projects “keeps it real” and builds high‐level commitment to the learning process. © 2007 Wiley Periodicals, Inc.
The story‐driven organization
Authors: Drake David B. , Lanahan Brian
Published: April 2007

The old metaphors for business—war, science, the machine—are distancing and constrain an organization's ability to envision possibilities for action. Understanding motivation and behavior in terms of story—character, objective, and conflict—enables leaders to better engage both the minds and hearts of employees and manage change. The authors explain the elements of story and present six guidelines for tapping its power. Applications include connecting employees to the organization's mission; understanding and managing the cultural implications of system and process change; and marshalling the tension inherent in conflicting objectives, such as product performance and environmental stewardship, as a source of energy and innovation. © 2007 Wiley Periodicals, Inc.
Longitudinal excursion and strain in the median nerve during novel nerve gliding exercises for carpal tunnel syndrome
Authors: Coppieters Michel W. , Alshami Ali M.
Published: April 2007

Nerve and tendon gliding exercises are advocated in the conservative and postoperative management of carpal tunnel syndrome (CTS). However, traditionally advocated exercises elongate the nerve bedding substantially, which may induce a potentially deleterious strain in the median nerve with the risk of symptom exacerbation in some patients and reduced benefits from nerve gliding. This study aimed to evaluate various nerve gliding exercises, including novel techniques that aim to slide the nerve through the carpal tunnel while minimizing strain (“sliding techniques”). With these sliding techniques, it is assumed that an increase in nerve strain due to nerve bed elongation at one joint (e.g., wrist extension) is simultaneously counterbalanced by a decrease in nerve bed length at an adjacent joint (e.g., elbow flexion). Excursion and strain in the median nerve at the wrist were measured with a digital calliper and miniature strain gauge in six human cadavers during six mobilization techniques. The sliding technique resulted in an excursion of 12.4 mm, which was 30% larger than any other technique (p ≤ 0.0002). Strain also differed between techniques (p ≤ 0.00001), with minimal peak values for the sliding technique. Nerve gliding associated with wrist movements can be considerably increased and nerve strain substantially reduced by simultaneously moving neighboring joints. These novel nerve sliding techniques are biologically plausible exercises for CTS that deserve further clinical evaluation. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:972–980, 2007
Survival of bone marrow‐derived mesenchymal stem cells in a xenotransplantation model
Authors: Wang Yan , Chen Xi , Armstrong Marilyn Ann , Li Gang
Published: April 2007

Mesenchymal stem cells (MSCs) are immunoprivileged and the allogeneic MSCs implantation has been used to facilitate tissue repairs such as bone and cartilage defect. The present study aimed to investigate the feasibility of xenogeneic MSCs implantation. Green fluorescent protein (GFP) transgenic rat bone marrow‐derived MSCs were loaded into HA/TCP Skelite™ blocks and implanted intramuscularly into the quadriceps of the MF1 and SCID mice. After 11 weeks, the implants were harvested and processed for further examinations. The peripheral blood mononuclear cells of each animal were also collected to measure the in vitro immune responses using mixed lymphocyte culture and cytotoxic assay. In the MF1 mice, some surviving MSCs were found in the explants after 11 weeks of implantation, but there was no sign of new bone formation as neither osteocalcin mRNA nor osteoid tissues were detected in the explants; the lymphocyte proliferation and cytotoxicity against donor MSCs were significantly increased in the animals with the xenogeneic MSCs implantation compared with the control littermates without transplantation. In the control SCID mice, osteoid tissues derived from the implanted MSCs were found in the explants; no difference of lymphocyte proliferation and cytotoxicity against the donor MSCs was detected between the SCID mice with or without MSCs implantation. The data suggested that rat MSCs survived the 11 weeks of xenotransplantation in the MF1 mice, but the increased host immune sensitization led to the impaired in vivo osteogenesis potential of MSCs. © 2007 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:926–932, 2007
Multicyclic Poly(ether sulfone)s Derived from Tris(4‐hydroxyphenyl)ethane
Authors: Garaleh Mazen , Polefka Claudia , Schwarz Gert , Kricheldorf Hans R.
Published: April 2007

Polycondensations of 4,4′‐difluorodiphenylsulfone with tris(4‐hydroxy phenyl)ethane were performed in DMSO with variation of feed ratio and concentration. For feed ratios of 1.0:1.3–1.0:1.5, soluble multicyclic poly(ether sulfone)s were obtained when the monomer concentration was below 0.05 M. The conversions were never complete under standard conditions, and doubling the reaction time yielded perfect multicyclic products free of endgroups; however, a small fraction of the product was crosslinked under these conditions. Quite similar results were obtained with 4,4′‐dichlorodiphenylsulfone at higher temperatures. When K2CO3 was replaced by tertiary amines, conversions and molecular weights were lower. The multicyclic poly(ether sulfone)s were characterized by MALDI‐TOF mass spectrometry, SEC, and DSC measurements. Broad molecular weight distributions with polydispersities in the range of 2.4–3.9 were found, and, surprisingly, two glass transitions were detectable in the DSC heating curves.

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Synthesis and Characterization of UV‐Curable Resins from the Glycolysis of PET: Vinyl Ether/Maleate UV‐Curing System
Authors: Auvergne Rémi , Colomines Gaël , Robin Jean‐Jacques , Boutevin Bernard
Published: April 2007

The synthesis and characterization of photopolymerizable unsaturatedα,ω‐bismaleate poly(ethylene terephthalate) oligomer resins based on glycolysis of PET waste using diethylene glycol and the study of their photopolymerization with divinyl ethers have been described in a previous article. The use of PET glycolysis by DEG can be problematic because this oligoester is partially crystalline. The objective of this paper is to develop the UV‐curing technology for a new kind of glycolysate that are completely amorphous. Glycolysates with different molecular weights have been synthesized and functionalized by a methyl hemiester of maleic acid. The photopolymerization of these new functionalized oligoesters with divinyl ether is studied and the materials obtained are characterized. The influence of the glycolysate structures on the properties of the crosslinked materials is highlighted.

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Characterization of Polyelectrolyte Complexes Based on Maleic Anhydride Alternating Copolymers by Static and Dynamic Light Scattering
Authors: Boyko Volodymyr , Richter Sven , Mende Mandy , Schwarz Simona , Zschoche Stefan , Arndt Karl‐Friedrich
Published: April 2007

The influence of the hydrophobicity of oppositely charged polyelectrolytes based on maleic anhydride alternating copolymers on the complex formation has been investigated by means of DLS and SLS. The change of hydrophobicity of the stock polyions was provided by variation of the comonomer (ethylene, isobutylene and styrene) in the polymer backbone. The particle size and the polydispersity at certain mixing ratios increase with increasing hydrophobicity of the used polyelectrolytes. Below the isoelectric point (1:1 interaction stoichiometry) an increase in the mixing ration−/n+leads to an increasing molar mass and density of the PECs within separate series while the polydispersity is decreasing. The radius of gyration and the hydrodynamic radius are less affected by the mixing ratio in this range. Above the isoelectric point, size and molar mass of the PECs increase strongly and depend on the amount and stabilizing efficiency of the added stabilizing polyelectrolyte. All studied PECs are found to be of spherical shape with different internal structure depending on the used polymers and the mixing ratio.

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Kinetic Analysis of Isothermal and Nonisothermal Epoxy‐Amine Cures by Model‐Free Isoconversional Methods
Authors: Perrin François‐Xavier , Nguyen Thi Minh Hanh , Vernet Jean‐Louis
Published: April 2007

Model‐free and model‐fitting kinetic approaches were applied to isothermal and nonisothermal DSC data on epoxy cure. The dependence of the effective activation energy on the extent of cure was determined using integral and differential isoconversional methods. A different shape of the dependence in the kinetically controlled regime (α < 0.4) was found when compared to the dependence typically reported for epoxy‐amine systems. This result was shown to arise from the presence of low amounts of bisphenol A in the present epoxy that are efficient catalysts for epoxy amine reaction. A model‐free method prediction of isothermal cure from isothermal data has also been considered.

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Macromol. Chem. Phys. 7/2007
Authors: Garaleh Mazen , Polefka Claudia , Schwarz Gert , Kricheldorf Hans R.
Published: April 2007

Back Cover: Multicyclic aromatic poly(ether sulfone)s were prepared from tris(4‐hydroxy phenyl)ethane and 4,4′‐difluoro‐ or 4,4′‐dichlorophenylsulfone as relatively inexpensive examples of a new nanoarchitecture. Depending on the feed ratio, these multicyclic polyethers may contain OH or F(Cl) functional groups allowing for further modification or fixation on functional surfaces. Further details can be found in the Full Paper by M. Garaleh, C. Polefka, G. Schwarz, and H. R. Kricheldorf* on page 747.
Modulation of the oncogenic potential of β‐catenin by the subcellular distribution of plakoglobin
Authors: Li Laiji , Chapman Kimberly , Hu Xiuying , Wong Annissa , Pasdar Manijeh
Published: April 2007

Plakoglobin (Pg) and β‐catenin are homologous proteins that function in cell–cell adhesion and signaling. The cadherin‐associated form of these proteins mediates adhesion, whereas the cytosolic/nuclear form has a signaling role. Despite their interactions with common cellular partners, β‐catenin has a well‐documented oncogenic potential while Pg has a less characterized tumor suppressor activity. We showed previously that Pg overexpression in Pg‐deficient SCC9 cells (SCC9‐Pg‐WT) induced Bcl‐2 expression and inhibited apoptosis. To assess the exact role of Pg in Bcl‐2 expression, we generated and characterized SCC9 transfectants expressing Pg with a restricted cytoplasmic (Pg‐NES) or nuclear (Pg‐NLS) distribution. We show that Bcl‐2 was expressed regardless of Pg localization, although its level was substantially lower in SCC9‐Pg‐NLS cells. Bcl‐2 expression coincided with increased nuclear β‐catenin levels (Pg‐NES) or a decrease in the level of total and nuclear β‐catenin associated with N‐cadherin and α‐catenin (Pg‐WT and ‐NLS) cells. Bcl‐2 expression also was induced in SCC9 cells overexpressing β‐catenin. In contrast, SCC9 cells expressing mutant Pg proteins, unable to interact with N‐cadherin and α‐catenin, had noticeably lower Bcl‐2 levels. Our data suggest that Bcl‐2 expression is induced by β‐catenin and modulated by Pg. We show that the inhibition of β‐catenin‐dependent TCF transactivation had no effect on Bcl‐2 levels, suggesting that induction of Bcl‐2 expression by β‐catenin and its modulation by Pg may involve factors other than, or in addition, to, TCF. These results provide a possible mechanism for the tumor suppressor activity of Pg via its role as a regulator of the oncogenic potential β‐catenin. © 2007 Wiley‐Liss, Inc.
Persisting hyperekplexia after idiopathic, self‐limiting brainstem encephalopathy
Authors: van de Warrenburg Bart P.C. , Cordivari Carla , Brown Peter , Bhatia Kailash P.
Published: April 2007

Symptomatic hyperekplexia is a relatively rare entity, but has been documented in various, mostly brainstem diseases. We report the clinical and neurophysiologic vignette of a patient with a self‐limiting, possibly inflammatory brainstem encephalopathy. Trismus was the presenting feature, but she later developed hyperekplexia. Although most brainstem features resolved spontaneously, the hyperekplexia has persisted. © 2007 Movement Disorder Society
Crystallinity of Linear Low Density Polyethylene and of Blends with High Density Polyethylene
Authors: Edward Graham H.
Published: April 2007

Blends of linear low density and high density polyethylene are examined by x‐ray diffraction and differential scanning calorimetry in order to characterise the crystalline morphology and to investigate the compatibility of the polymers. The polymers are found to form a co‐crystalline phase under a variety of conditions, and can thus be regarded as compatible. The lamellar distributions obtained from the differential scanning calorimetry melting thermograms are found to be dominated by the presence of the high density polyethylene, and this is attributed to the higher mobility of the high density molecules. The lattice parameters of the crystalline phases are found to increase with increasing side branch content.
Ultrasonic Study of Molecular Association of Polyethylenoxide Aqueous Solutions (A Method to Determine Molecular Weight)
Authors: Hassun Subhi Kemal , Al‐Madfai Suham H. F. , Al‐Jarrah Mustafa M. F.
Published: April 2007

Ultrasonic velocity and isoentropic compressibility measurements are reported on aqueous solutions of polyethylenoxide of different molecular weights and different concentrations using pulsed ultrasonic apparatus operating at 2 MHz and 310 K. The data obtained as a function of concentration indicate the magnitude of the contribution due to relaxation of the backbone of the ethylene group. The results show a linear increase of density, velocity and viscosity values with increasing molecular weight and concentration of PEO. In contrast, the isoentropic compressibility decreases with increasing of molecular weight and concentration of PEO. A mathematical equation correlating isoentropic compressibility and molecular weight of the polymer is suggested. This was applied to the calculation of the molecular weight of unknown samples of PEO from their measured isoentropic compressibility; the results obtained agreed well with those obtained from osmometry.
Thermal Degradation of Polystyrene
Authors: Guaita Marino
Published: April 2007

The thermal degradation of polystyrene in the absence of oxygen is examined, at temperatures above or below 300°C. The decrease in degree of polymerisation occurring either with negligible volatilisation at lower temperatures, or with evolution of low molecular weight products at higher temperatures, is simulated by Monte‐Carlo procedures. The results suggest that below 300°C, scission of the polymer chains is random, and involves also a minor fraction of some abnormal, as yet unidentified, structures. Above 300°C, an extensive intermolecular transfer process seems to be the main cause of the decrease in degree of polymerisation, whereas an overall depolymerisation of 100 structural units at each chain scission is the source of volatilisation.
Some Effects of Structure, Composition and Cure on the Water Absorption and Glass Transition Temperature of Amine‐cured Epoxies
Authors: Johncock Peter , Tudgey Graham F.
Published: April 2007

The effect of structure, composition, and cure on the water absorption and Tg of amine‐cured epoxies was investigated. Water absorption is considered to depend on the polar group concentration and type, and on the amount of free volume in the polymer network. The contribution of polar groups in terms of their hydrogen bonding capabilities is reflected by the effect of meta (with respect to the diglycidylamino group) chloro, bromo, and methyl substituents on the water absorption of bis[N,N‐bis(2,3‐epoxypropyl)‐4‐aminophenyl]methane cured with 4,4′‐diaminodiphenylsulphone. The observed water absorptions are in line with the expected electronic effects of the substituents on the basicity of the amine group. Substituents in the ortho position adversely affect the hydrogen bonding capability of the amine group and limit the extent of reaction by steric interference. Examination of four O‐glycidyl systems (Epon 825, Epon 1153/114, Epon 1031, and Dow XD‐7342) cured with 4,4′‐diaminodiphenylsulphone has revealed quite a good linear relationship between the equilibrium water absorption and Tg for a particular hardener concentration irrespective of the epoxy compound employed. Networks ranged from those of low Tg (110°C) and water absorption (1.3%) to those of high values (300°C and 6.1%) for these parameters. Differences in slope for low (50‐65%) and high (100%) stoichiometric amounts of hardener are attributed to differences in the relative importance of OH/epoxy and NH2 or NH/epoxy reactions. The theoretical polar group concentrations and polar group type are much the same for these different systems and thus, free volume is considered to be a function of Tg and to play an important part in determining the level of water absorption.
Network Polymers Based on Epoxy Oligomers and Dicyandiamide
Authors: Markevitch Mikhail A. , Irzhak Vadim I.
Published: April 2007

The formation of network polymers by curing epoxy oligomers with dicyandiamide was investigated. The oligomers had the structure

It was shown that the reaction between hydroxyl and epoxy groups is important in this process. The strength‐deformation properties of the network polymers obtained were studied. Calculations of elastic active network chains were carried out by the method of branching processes. Good agreement was obtained between calculated and experimental data.
13C Nuclear Magnetic Resonance Studies of Phenol‐Formaldehyde Resins and Related Model Compounds 2 ‐ Analysis of Sequence Structure in Resins
Authors: Pethrick Richard A. , Thomson Barry
Published: April 2007

The paper reports 13C nuclear magnetic resonance spectra of novolac resins and the variation of the composition of the reaction mixture during the in situ preparation of resin. It is observed that in the initial stages of the reaction ortho substitution occurs; however the hemiacetal rather than the methylol derivative is observed. These methylol substituted intermediates are highly unstable and a better appreciation of the relative rates of structure formation can be obtained from an analysis of the methylene bridge region, para‐para Bridges are the first to appear, the next are the ortho‐para and finally the ortho‐ortho linkages are observed. Analysis of the relative intensities of ortho and para bridge carbon atoms allows identification of the isomeric composition of the final resin. The proportion of each isomer depends on the catalyst used in synthesis of the resin.
Application of thermal methods in the characterisation of poly(urethane‐urea)s formed by reaction injection moulding
Authors: Ryan Anthony J. , Stanford John L. , Still Richard H.
Published: April 2007

Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) have been used in conjunction with tensile testing and transmission electron microscopy (TEM) to characterise novel segmented poly(urethane‐urea) (PUU) network materials formed by reaction injection moulding (RIM).

Materials were based on a modified liquid 4,4′‐diphenylmethane diisocyanate and a polyether triol in admixture with one of three hindered aromatic diamines: 3,5‐diethyltoluene diamine (DETDA); methylene‐bis‐2,6‐diisopropylaniline (MMIPA); methylene‐bis‐(2‐methyl‐6‐isopropylaniline) (MMIPA).

The materials ranged from tough translucent elastomers to opaque brittle plastics depending on the chemical nature and weight fraction of the hard segments (HS). DSC and DMTA studies showed the PUU materials to be phase‐separated; this was confirmed by TEM and tensile testing. The soft‐segment glass transition temperatures (DSC and DMTA) were independent of composition but varied with diamine structure. Hard‐segment glass transition temperatures could only be evaluated by DMTA and no evidence of crystallinity was found by thermal methods or by wide angle x‐ray diffraction. Heat capacity measurements and DMTA suggested that some degree of phase mixing had occurred, to a greater extent in the DETDA and MDIPA systems.

Phase inversion was observed by DMTA and confirmed at ∼55% hard‐segment content for DETDA systems by tensile testing.
Generational consciousness and retirement communities
Authors: McHugh Kevin E.
Published: April 2007

Time and collective historical experience loom large in the formation of generations. I argue that spatial proximity cements generational consciousness among seniors in Arizona retirement communities who identify themselves as members of the Second World War generation. The argument twins Karl Mannheim's social‐historical conception of generations and Hannah Arendt's political philosophy which underscores the space of appearance in the public realm in identity formation. It is through congregating, interacting and conversing on a daily basis that seniors in retirement enclaves affirm and reaffirm who they are, both to themselves and outsiders. I draw upon a suite of Arizona case studies, 1988–2000, in revealing ‘voices’ for a slice of the Second World War generation. Discussions revolving around family, community and national life reveal beliefs and values coalescing around four themes: (1) splendid isolation; (2) dissolution of values; (3) absence of children; and (4) fraying the social compact. The space of appearance within retirement enclaves engenders a strong sense of collective identity and belonging in ageing and, simultaneously, leads to questions about implications and consequences of intergenerational separation. I conclude with a poignant multigenerational experience as suggestive of the potency of intergenerational contact and exchange. Copyright © 2007 John Wiley & Sons, Ltd.
Low temperature growth of ZnO thin film by metalorganic chemical vapor deposition
Authors: Kim Dong Chan , Kong Bo Hyun , Cho Hyung Koun , Lee Jeong Yong , Park Dong Jun
Published: April 2007

Polycrystalline ZnO thin films with a preferred orientation were successfully grown by metal organic chemical vapor deposition at temperatures ≤300 °C. By injecting additional Ar gas through a by‐pass line, good quality ZnO films were grown at low temperature. The ZnO films grown at substrate temperatures <200 °C showed a porous microstructure whereas a dense undoped ZnO film showing a high conductivity and no Zn phases was grown at 210 °C. The ZnO film grown at low temperatures by MOCVD showed improved emission properties compared with the films grown by sputtering. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical characterization of Zn0.97Mn0.03Se/ZnSe0.92Te0.08 type II multiple‐quantum‐well structures
Authors: Lin D. Y. , Shiu J. J. , Wu J. D. , Yang C. S. , Chou W. C.
Published: April 2007

The optical characterization of type II Zn0.97Mn0.03Se/ZnSe0.92Te0.08 multiple‐quantum‐well structures have been studied using photoluminescence (PL), temperature‐dependent PL, polarized PL, power‐dependent PL, and photoreflectance (PR) in this study. The PL data reveal that the band alignment of the ZnMnSe/ZnSeTe system is type II. Comparing with the theoretical calculation based on the Schrodinger equation, the valence band offset is estimated to be 0.6 eV. From the power‐dependent PL spectra, it is observed that the peak position of PL spectra shows a blueshift under different excitation power. The blueshift can be interpreted in terms of the band‐bending effect due to spatially photoexcited carriers in a type II alignment. The thermal activation energy (EA) for quenching the PL intensity was determined from tem‐ perature‐dependent PL spectra. The thermal activation energy was found to decrease as the thickness of ZnMnSe and ZnSeTe layers decreased. The polarized PL spectra exhibit a large in‐plane polarization with the polarization degree up to 50%. The polarization does not depend on the excitation intensity as well as temperature. The large polarization is an inherent orientation of the interface chemical bonds. The higher transition features observed in PR spectra show a blueshift with the similar trend observed in the PL spectra as decreasing the thickness of ZnSeTe layer. This result provides a consistent evidence for the assumption that square‐like well shapes were built in the ZnSeTe layers. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)