bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of ortho‐ and para‐Ring Activation on the Kinetics of SNAr Reactions of 1‐Chloro‐2‐nitro‐ and 1‐Phenoxy‐2‐nitrobenzenes with Aliphatic Amines in Acetonitrile
Authors: Crampton Michael R. , Emokpae Thomas A. , Isanbor Chukwuemeka , Batsanov Andrei S. , Howard Judith A. K. , Mondal Raju
Published: December 2005

Rate constants are reported for reaction of 4‐substituted 1‐chloro‐2,6‐dinitrobenzenes 1, 6‐substituted 1‐chloro‐2,4‐dinitrobenzenes 2, and some of the corresponding 1‐phenoxy derivatives, 3 and 4, with n‐butylamine, pyrrolidine and piperidine in acetonitrile as solvent. Values of k1, the rate constant for nucleophilic attack at the 1‐position, increase with increasing ring‐activation but may be reduced by steric repulsion at the reaction centre which increases in the order Cl < OPh, and n‐butylamine < pyrrolidine ≈ piperidine. ortho‐Substituents may also have adverse steric effects, and those of the trifluoromethyl group are particularly serious. X‐ray crystal structures of phenyl 2,4‐dinitro‐6‐trifluoromethylphenyl ether and phenyl 2,6‐dinitro‐4‐trifluoromethylphenyl ether are reported. Base catalysis in the 1‐phenoxy derivatives is attributed to rate‐limiting proton transfer from the zwitterionic intermediates 6 to base. Values of rate constants for this process decrease with increasing steric congestion at the reaction centre and in the order n‐butylamine > pyrrolidine > piperidine. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
The Domino Oxa‐Michael Addition–Aldol Reaction: Access to Variably Substituted Tetrahydroxanthenones
Authors: Ohnemüller (née Schmid) Ulrike K. , Nising Carl F. , Nieger Martin , Bräse Stefan
Published: December 2005

Tetrahydroxanthenones represent the core of many natural products, most of which exhibit interesting biological activities. In the course of our synthetic efforts towards the total synthesis of the secalonic acids, which contain two of these tricyclic units, we have investigated the influence of substituents on the one‐step domino oxa‐Michael addition–aldol reaction leading to tetrahydroxanthenones. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
A novel method to identify gene–gene effects in nuclear families: the MDR‐PDT
Authors: Martin E.R. , Ritchie M.D. , Hahn L. , Kang S. , Moore J.H.
Published: December 2005

It is now well recognized that gene–gene and gene–environment interactions are important in complex diseases, and statistical methods to detect interactions are becoming widespread. Traditional parametric approaches are limited in their ability to detect high‐order interactions and handle sparse data, and standard stepwise procedures may miss interactions that occur in the absence of detectable main effects. To address these limitations, the multifactor dimensionality reduction (MDR) method [Ritchie et al., 2001: Am J Hum Genet 69:138–147] was developed. The MDR is wellsuited for examining high‐order interactions and detecting interactions without main effects. The MDR was originally designed to analyze balanced case‐control data. The analysis can use family data, but requires a single matched pair be selected from each family. This may be a discordant sib pair, or may be constructed from triad data when parents are available. To take advantage of additional affected and unaffected siblings requires a test statistic that measures the association of genotype with disease in general nuclear families. We have developed a novel test, the MDR‐PDT, by merging the MDR method with the genotype‐Pedigree Disequilibrium Test (geno‐PDT)[Martin et al., 2003: Genet Epidemiol 25:203–213]. MDR‐PDT allows identification of single‐locus effects or joint effects of multiple loci in families of diverse structure. We present simulations to demonstrate the validity of the test and evaluate its power. To examine its applicability to real data, we applied the MDR‐PDT to data from candidate genes for Alzheimer disease (AD) in a large family dataset. These results show the utility of the MDR‐PDT for understanding the genetics of complex diseases. Genet. Epidemiol. 2006. © 2005 Wiley‐Liss, Inc.
The correlation and sequence architecture of the Ormskirk Sandstone Formation in the Triassic Sherwood Sandstone Group of the East Irish Sea Basin, NW England
Authors: Meadows N. S.
Published: December 2005

The existing stratigraphic nomenclature applied to the Early and Middle Triassic Sherwood Sandstone Group in NW England has resulted from more than 150 years of geological investigation, but is characterized by a lithostratigraphic system that is insufficiently flexible to allow for variations in lithology and sedimentary facies within a continental depositional system. A revised well correlation based on the detrital mineralogical and chemical composition of the Ormskirk Sandstone Formation in four offshore wells, that is then extended to provide near‐basin‐wide well correlations using a regional shale marker, confirms previously suggested but unproven diachroneity at the top of the Sherwood Sandstone Group. It also reveals the presence of incised valleys filled by stacked amalgamated fluvial channel sandstones and cut into previously deposited aeolian and sandflat sequences as well as older fluvial channel sandstones. The combination of well correlations indicates that the valleys were incised by a fluvial system flowing NW from the Cheshire Basin into the East Irish Sea Basin and then west towards the Peel and Kish Bank basins. The stratal geometry of the upper part of the Sherwood Sandstone Group is suggested to conform to models of climatically mediated alternations of fluvial degradation and aggradation in response to changes in the relationship between sediment flux and stream discharge. This model is supported in the Sherwood Sandstone Group by climatically driven variations in the non‐channelized facies which record upward wetting and drying cycles that can be locally tied to fluvial incision surfaces, and suggest a hierarchy of at least three levels of climatic cyclicity recorded within the sedimentary succession. Copyright © 2006 John Wiley & Sons, Ltd.
Neuroprotective actions of endogenous interleukin‐1 receptor antagonist (IL‐1ra) are mediated by glia
Authors: Pinteaux Emmanuel , Rothwell Nancy J. , Boutin Herve
Published: December 2005

The pro‐inflammatory cytokine interleukin‐1 (IL‐1), contributes to neuronal inflammation and cell death induced by ischemia, excitotoxicity, or trauma, while administration of IL‐1 receptor antagonist (IL‐1ra) reduces neuronal injury. The aim of the present study was to test the hypothesis that endogenous IL‐1ra is neuroprotective in vivo and in vitro, and to identify its mechanism of actions. Mice lacking IL‐1ra (IL‐1ra knock‐out (KO]) exhibited a dramatic increase in neuronal injury (3.6‐fold increase in infarct size) induced by transient cerebral ischemia compared to wild‐type (WT) animals. Basal cell death of cultured cortical neurons from WT and IL‐1ra KO was identical, and treatment with NMDA or AMPA (20 μM) increased cell death to the same extent in WT and IL‐1ra KO neurons. However, basal and NMDA‐ or AMPA‐induced cells death was significantly higher in glial–neuronal co‐cultures from IL‐1ra KO than from WT mice. We further showed that pure microglial cultures, but not pure astrocytes cultures, released IL‐1ra in response to treatment with conditioned medium from NMDA‐ or AMPA‐treated primary neurons. These results demonstrate that endogenous IL‐1ra produced by microglia is neuroprotective in cerebral ischemia or excitotoxicity. © 2005 Wiley‐Liss, Inc.
Caspase inhibition in apoptotic T cells triggers necrotic cell death depending on the cell type and the proapoptotic stimulus
Authors: Scheller Carsten , Knöferle Johanna , Ullrich Anett , Prottengeier Johannes , Racek Tomas , Sopper Sieghart , Jassoy Christian , Rethwilm Axel , Koutsilieri Eleni
Published: December 2005

CD95 (Fas/Apo‐1) triggers apoptotic cell death via a caspase‐dependent pathway. Inhibition of caspase activation blocks proapoptotic signaling and thus, prevents execution of apoptosis. Besides induction of apoptotic cell death, CD95 has been reported to trigger necrotic cell death in susceptible cells. In this study, we investigated the interplay between apoptotic and necrotic cell death signaling in T cells. Using the agonistic CD95 antibody, 7C11, we found that caspase inhibition mediated by the pancaspase inhibitor, zVAD‐fmk, prevented CD95‐triggered cell death in Jurkat T cells but not in A3.01 T cells, although typical hallmarks of apoptosis, such as DNA fragmentation or caspase activation were blocked. Moreover, the caspase‐independent cell death in A3.01 cells exhibited typical signs of necrosis as detected by a rapid loss of cell membrane integrity and could be prevented by treatment with the radical scavenger butylated hydroxyanisole (BHA). Similar to CD95‐induced cell death, apoptosis triggered by the DNA topoisomerase inhibitors, camptothecin or etoposide was shifted to necrosis when capsase activation was inhibited. In contrast to this, ZVAD was fully protective when apoptosis was triggered by the serpase inhibitor, Nα‐tosyl‐phenyl‐chloromethyl ketone (TPCK). TPCK was not protective when administered to anti‐CD95/ZVAD‐treated A3.01 cells, indicating that TPCK does not possess anti‐necrotic activity but fails to activate the necrotic death pathway. Our findings show (a) that caspase inhibition does not always protect apoptotic T cells from dying but merely activates a caspase‐independent mode of cell death that results in necrosis and (b) that the caspase‐inhibitor‐induced shift from apoptotic to necrotic cell death is dependent on the cell type and the proapoptotic stimulus. J. Cell. Biochem. 97: 1350–1361, 2006. © 2005 Wiley‐Liss, Inc.
Structure, magnetizability, and nuclear magnetic shielding tensors of bis‐heteropentalenes. IV. Dihydrophospholophosphole isomers
Authors: Cuesta Inmaculada García , Sánchez De Merás Alfredo M. J. , Lazzeretti Paolo
Published: December 2005

The geometry of the heteropentalenes formed by two phosphole units has been determined at the DFT level. The magnetic susceptibility and the nuclear magnetic shielding at the nuclei of these systems have also been calculated using gauge‐including atomic orbitals and a large Gaussian basis set to achieve near Hartree–Fock estimates. A comparative study of the various isomers, of their flattened analogs, and of the parent phosphole molecule, shows that the [3,4‐c] isomer is the most aromatic system in the set considered, assuming diatropicity and degree of planarity as indicators, even if it is the less stable in terms of total molecular energy. Plots of magnetic field‐induced current densities confirm diatropicity of P‐containing bis‐heteropentalenenes, showing, however, significant differences from the analogous systems with distinct heteroatoms. The maps give evidence of spiral flow nearby CC bonds, compatible with prevalent distortive behavior of π electrons exalted by pyramidalization at P, and competing against the σ electron compression, which would favor planar structure. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 344–351, 2006
Parallel coupled perturbed CASSCF equations and analytic CASSCF second derivatives
Authors: Dudley Timothy J. , Olson Ryan M. , Schmidt Michael W. , Gordon Mark S.
Published: December 2005

A parallel algorithm for solving the coupled‐perturbed MCSCF (CPMCSCF) equations and analytic nuclear second derivatives of CASSCF wave functions is presented. A parallel scheme for evaluating derivative integrals and their subsequent use in constructing other derivative quantities is described. The task of solving the CPMCSCF equations is approached using a parallelization scheme that partitions the electronic hessian matrix over all processors as opposed to simple partitioning of the 3 N solution vectors among the processors. The scalability of the current algorithm, up to 128 processors, is demonstrated. Using three test cases, results indicate that the parallelization of derivative integral evaluation through a simple scheme is highly effective regardless of the size of the basis set employed in the CASSCF energy calculation. Parallelization of the construction of the MCSCF electronic hessian during solution of the CPMCSCF equations varies quantitatively depending on the nature of the hessian itself, but is highly scalable in all cases. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 352–362, 2006
Glycation of caseinate by fructose and fructo‐oligosaccharides during controlled heat treatment in the ‘dry’ state
Authors: Oliver Christine M , Melton Laurence D , Stanley Roger A
Published: December 2005

This paper investigates the controlled heating of caseinate with reducing sugars to produce glycoproteins with improved functionality for use in food. Caseinate was combined with inulin, fructose and a mixture of both inulin and fructose and the lyophilisates heated at a controlled water activity for up to 48 h. Caseinate–glucose and caseinate–lactose glycoconjugates were prepared for comparison. Conjugation between caseinate and fructose occurred readily at 60 °C and 67% relative humidity, modifying up to 75% of the lysine groups of caseinate within 48 h. Moreover, when reconstituted, the caseinate–fructose glycoconjugates showed a dramatic increase in viscosity relative to caseinate ‘dry’‐heated alone. At 80% relative humidity the reaction proceeded so rapidly that gels containing darkly coloured particulate matter were formed. Incorporation of inulin prevented formation of caseinate–fructose gels, and minimised browning development while still producing moderately viscous solutions. Based on 13C‐NMR, SDS‐PAGE and electron microscopy techniques, mechanisms by which inulin modified the reaction have been proposed. Copyright © 2005 Society of Chemical Industry
Digestion kinetics of leaf, stem and inflorescence from five species of mature grasses
Authors: Chaves Alexandre V , Burke Jennifer L , Waghorn Garry C , Brookes Ian M
Published: December 2005

The objective of this study was to measure the digestion kinetics for mature (green and non‐senescent) components of five grass species using in sacco and in vitro incubations to define rates of degradation and nutrient release. Mature perennial ryegrass, tall fescue, Yorkshire fog, phalaris and paspalum were hand separated into leaf blade, stem and inflorescence (flower head) for incubations. Concentrations of neutral detergent fibre (NDF) in fractions were in the ranges 492–677 (leaf), 626–718 (stem) and 501–677 (inflorescence) g kg−1 dry matter (DM). Crude protein concentrations in the DM of the respective fractions were 70–236 (leaf blade), 35–77 (stem) and 75–120 (inflorescence) g kg−1 DM. Soluble DM (% of the total) determined after mincing accounted for 31–54% of leaf, 26–56% of stem and 20–49% of inflorescence and fractional degradation of the insoluble DM was very slow, in the ranges 0.04–0.11 (leaf), 0.03–0.05 (stem) and 0.03–0.08 (inflorescence) h−1. After 24 h of in vitro incubation, plant nitrogen content became limiting for fermentation in most instances, especially with tall fescue and paspalum. Volatile fatty acid (VFA) production appeared to be similar for leaf, stem and flower fractions, but the proportion of plant DM released as VFA after 48 h was only 7–12%, with a higher value (19%) for tall fescue. Nitrogen concentration in forage DM was not directly related to VFA yield in vitro. In conclusion, the in sacco kinetics suggested slow colonisation of all components, but especially stem, which will limit the rate of nutrient production. Effective degradability was highest for leaf but rates in vivo will depend on the speed and extent of particle size reduction by chewing during eating and ruminating. Copyright © 2005 Society of Chemical Industry
Stokes polarimetry imaging of rat‐tail tissue in a turbid medium using incident circularly polarized light
Authors: Wu Paul J. , Walsh, Joseph T.
Published: December 2005

Background and Objectives

We describe a Stokes polarimetry imaging technique that quantifies the polarization properties of remitted light backscattered from a sample.

Study Design/Materials and Methods

Right‐ and left‐circularly polarized near‐infrared light was used to illuminate rat‐tail tissue embedded in turbid gelatin.

Results

The degree of linear polarization (DoLP) and degree of circular polarization (DoCP) image‐maps indicate that increasing the depth of the rat tail within the turbid medium and varying the rat‐tail geometry and orientation relative to the light source affected the contrast between structures and adjacent tissue layers.

Conclusion

Stokes polarimetry imaging shows that the intervertebral discs and soft tissue regions of rat tails strongly depolarize incident circularly polarized light. Tendon regions remit light with a more linear form due to birefringence. Both DoLP and DoCP image‐maps provide contrast between tissue structures. When differentiating between unpolarized light and light with low DoCP or DoLP, the polarization of backscattered light from the turbid medium must to be taken into consideration. Lasers Surg. Med. 37:396–406, 2005. © 2005 Wiley‐Liss, Inc.
Clinical efficacy of semiconductor laser application as an adjunct to conventional scaling and root planing
Authors: Kreisler Matthias , Al Haj Haitham , d'Hoedt Bernd
Published: December 2005

Background and Objectives

The aim of the in vitro study was to examine the clinical efficacy of semiconductor laser periodontal pocket irradiation as an adjunct to conventional scaling and root planing.

Materials and Methods

Twenty‐two healthy patients with a need of periodontal treatment (15 women, 7 men, mean age 45.0 ± 10.8 years) with at least four teeth in all quadrants, were included. All of them underwent a conventional periodontal treatment including scaling and root planing. Using a split mouth design, two randomly chosen quadrants (one upper and the corresponding lower one) were subsequently treated with an 809 nm GaAlAs laser operated at a power output of 1.0 Watt using a 0.6 mm optical fiber. The teeth in the control quadrants were rinsed with saline. The clinical outcome was evaluated by means of plaque index (PI), gingival index (GI), bleeding on probing (BOP), sulcus fluid flow rate (SFFR), Periotest® (PT), probing pocket depth (PPD), and clinical attachment loss (CAL) at baseline and at 3 months after treatment. A total of 492 teeth in both groups were evaluated and differences between the laser and the control teeth were analyzed using the Wilcoxon test (P < 0.05).

Results

Teeth treated with the laser revealed a significantly higher reduction in tooth mobility, pocket depth, and clinical attachment loss. Twelve percent of the teeth in the laser group showed an attachment gain of 3 mm or more, compared to 7% in the control group. An attachment gain of 2–3 mm was found in 24% of the teeth in the laser group and 18% in the control group. No significant group differences, however, could be detected for the plaque index, gingival index, bleeding on probing, and the sulcus fluid flow rate.

Conclusions

The higher reduction in tooth mobility and probing depths is probably not predominantly related to bacterial reduction in the periodontal pockets but to the de‐epithelization of the periodontal pockets leading to an enhanced connective tissue attachment. The application of the diode laser in the treatment of inflammatory periodontitis at the irradiation parameters described above is a safe clinical procedure and can be recommended as an adjunct to conventional scaling and root planing. Lasers Surg. Med. 37:350–355, 2005. © 2005 Wiley‐Liss, Inc.
Treatment of hypertrophic scars and keloids with a radiofrequency device: A study of collagen effects
Authors: Meshkinpour Azin , Ghasri Peyman , Pope Karl , Lyubovitsky Julia G. , Risteli Juha , Krasieva Tatiana B. , Kelly Kristen M.
Published: December 2005

Background and Objective

To determine the efficacy and safety of the ThermaCool® TC radiofrequency system for treatment of hypertrophic and keloid scars and evaluate treatment associated collagen changes.

Materials and Methods

Six subjects with hypertrophic and four with keloid scars were treated with the ThermaCool® device: one‐third of the scar received no treatment (control), one‐third received one treatment and one‐third received two treatments (4‐week interval). Scars were graded before and then 12 and 24 weeks after treatment on symptoms, pigmentation, vascularity, pliability, and height. Biopsies were taken from four subjects with hypertrophic scars and evaluated with hematoxylin and eosin (H & E) staining, multiphoton microscopy, and pro‐collagen I and III immunohistochemistry.

Results

No adverse treatment effects occurred. Clinical and H & E evaluation revealed no significant differences between control and treatment sites. Differences in collagen morphology were detected in some subjects. Increased collagen production (type III > type I) was observed, appeared to peak between 6 and 10 weeks post‐treatment and had not returned to baseline even after 12 weeks.

Conclusion

Use of the thermage radiofrequency device on hypertrophic scars resulted in collagen fibril morphology and production changes. ThermaCool® alone did not achieve clinical hypertrophic scar or keloid improvement. The collagen effects of this device should be evaluated further in order to optimize its therapeutic potential for all indications. Lasers Surg. Med. 37:343–349, 2005. © 2005 Wiley‐Liss, Inc.
Promotion of Cell Affinity of Porous PLLA Scaffolds by Immobilization of RGD Peptides via Plasma Treatment
Authors: Ho Ming‐Hua , Hou Lein‐Tuan , Tu Chen‐Yuan , Hsieh Hsyue‐Jen , Lai Juin‐Yih , Chen Wei‐Jung , Wang Da‐Ming
Published: December 2005

Summary: In the present work, RGDS (Arg‐Gly‐Asp‐Ser) was immobilized on PLLA scaffolds with plasma treatment. The amount of immobilization, determined by HPLC, was confirmed to be in the effective order. Results from the culture of rat osteosarcoma (ROS), osteoblastic‐like cells, demonstrate that the immobilization of RGDS could effectively enhance the attachment of ROS cells on PLLA and increase the cell density in PLLA scaffolds. In addition, experiments of in vitro mineralization indicate that there were more cells and mineralization focci in the RGDS‐immobilized scaffolds, suggesting a tendency to form bone‐like tissues, compared with the unmodified PLLA scaffold. On the other hand, the PLLA scaffolds immobilized with RGES (Arg‐Gly‐Glu‐Ser) were much less effective in promotion of ROS attachment, suggesting that the enhancement on cell attachment was mainly due to the recognition of RGDS by the adhesion receptors on the cell membrane. The results presented in this work demonstrate that RGDS could be successfully immobilized on PLLA scaffolds with plasma treatment and such modification can make PLLA scaffolds more suitable for culture of osteoblast‐like cells and for generation of bone‐like tissues.

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Patterning of a Random Copolymer of Poly[lactide‐co‐glycotide‐co‐(ε‐caprolactone)] by UV Embossing for Tissue Engineering
Authors: Zhu Aiping , Chen Rongqing , Chan‐Park Mary B.
Published: December 2005

Summary: The random copolymer, poly[lactide‐co‐glycotide‐co‐(ε‐caprolactone)] (PLGACL) diacrylate was prepared by ring‐opening polymerization of L‐lactide, glycolide, and ε‐caprolactone initiated with tetra(ethylene glycol). The diacrylated polymers were extensively characterized. With a UV embossing method, these copolymers were successfully fabricated into microchannels separated by microwalls with a high aspect (height/width) ratio. The PLGACL network films showed good cytocompatibility. Varieties of microstructures were fabricated, such as 10 × 40 × 60, 10 × 80 × 60, 25 × 40 × 60, or 25 × 80 × 60 µm3 structures (microwall width × microchannel width × microwall height). The results demonstrated that smooth muscle cells (SMCs) can grow not only on the microchannel surfaces but also on the surfaces of the microwall and sidewall. The SMCs aligned along the 25 µm wide microwall with an elongated morphology and proliferated very slowly in comparison to those on the smooth surface with a longer cell‐culture term. Few cells could attach and spread on the surface of the 40 µm wide microchannel, while the cells flourished on the 80 µm, or more than 80 µm, wide microchannel with a spindle morphology. The biophysical mechanism mediated by the micropattern geometry is discussed. Overall, the present micropattern, consisting of biodegradable and cytocompatible PLGACL, provides a promising scaffold for tissue engineering.

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Chemo‐Enzymatic Synthesis of Raffinose‐Branched Polyelectrolytes and Self‐Assembly Application in Microcapsules
Authors: Wu Qi , Chen Zhi‐Chun , Lu De‐Shui , Lin Xian‐Fu
Published: December 2005

Summary: A novel biocompatible polyelectrolyte poly(vinyl raffinose‐co‐acrylic acid) (PRCA) containing a raffinose branch was prepared via redox polymerization using Fe2+/K2S2O8/H2O2 starting from enzymatically‐synthesized monomer: 1‐O‐vinyldecanedioyl raffinose. Copolymers with different monomer feed ratios were prepared and characterized with IR, NMR, and GPC. PRCA can be alternated with polycation to form microcapsules on a crystals template by electrostatic layer‐by‐layer technique. The multilayers of PRCA/poly(methacryloyloxyethyl dimethylbenzyl ammonium chloride) (PMBA) on quartz slides and PRCA/poly(dimethyldiallyl ammonium chloride) (PDDA) on acyclovir crystals template were fabricated and characterized with UV‐Vis spectra, the microelectrophoretic measurement, and TEM. Hollow capsules can be formed after the removal of acyclovir crystals template in a buffer solution. The nano‐capsule‐carrying galactose residue is a potential targeting drug‐controlled delivery systems.

Synthesis of PRCA and TEM image of a hollow (PRCA/PDDA)10 capsule.

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Synthesis of PRCA and TEM image of a hollow (PRCA/PDDA)10 capsule.
Structure‐Property Relationships of Linear and Long‐Chain Branched Metallocene High‐Density Polyethylenes Characterized by Shear Rheology and SEC‐MALLS
Authors: Piel Christian , Stadler Florian J. , Kaschta Joachim , Rulhoff Sascha , Münstedt Helmut , Kaminsky Walter
Published: December 2005

Summary: Linear and long‐chain branched high‐density polyethylenes with a molar mass $\overline M _{\rm w}$ between 1 700 and 1 150 000 g · mol−1 were synthesized using metallocene catalyst systems. Depending on the polymerization parameters the molar mass distribution reached values ranging from 2 to 12. The resins were characterized with various analytical methods. The branch detection took place via two independent methods, melt rheology and SEC‐MALLS. New relationships between catalyst structure, polymerization conditions, and the branching content of polyethylenes were established. Besides the branched materials strictly linear polymers are presented; for those no long‐chain branches were detected either by light scattering or by rheology. The viscosity function was observed to be strongly influenced by the molar mass distribution and the degree of long‐chain branching. The molar mass distribution was affected by the catalyst type and the polymerization conditions. A dependence of the melting point and the melting enthalpy on the molar mass was observed.

η0‐$\overline M _{\rm w}$ correlation of the linear and long‐chain branched samples.

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η0‐$\overline M _{\rm w}$ correlation of the linear and long‐chain branched samples.
A Facile Method for Grafting Polymerisation of Acrylonitrile onto LDPE Film with High Grafting Efficiency
Authors: Zhu Jianwu , Deng Jianping , Cheng Shoumei , Yang Wantai
Published: December 2005

Summary: A facile and effective surface grafting polymerisation method was designed and investigated to graft acrylonitrile (AN) onto low‐density polyethylene (LDPE) film using benzoyl peroxide (BPO) as an initiator. This method consisted of two steps. In the first step, BPO was adsorbed on the surface of LDPE film by immersing LDPE film in BPO solution; in the second step, grafting polymerisation of AN onto LDPE film was carried out under heat. Because the grafting polymerisation was carried out with AN in vapour phase and the concentration of AN was very low, the homopolymerisation of AN could be effectively suppressed and therefore the grafting efficiency was very high (approaching 100%). Grafting percent (Gp) could be controlled from 0 to 118% by adjusting reaction conditions in the first step and/or in the second step respectively. A possible model was proposed to interpret the experimental results.

Schematic procedure and chemistry for grafting polymerisation of AN on LDPE film.

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Schematic procedure and chemistry for grafting polymerisation of AN on LDPE film.
The Effect of NaCl on the Conformational Behavior of Acenaphthylene Labeled Poly(N,N‐diethylacrylamide) in Dilute Aqueous Solution
Authors: Chen Yong , Liu Ming‐zhu , Bian Feng‐ling , Wang Bing , Chen Shi‐lan , Jin Shu‐ping
Published: December 2005

Summary: The effect of salts on the conformational behavior of acenaphthylene labeled poly(N,N‐diethylacrylamide) (PDEA/ACE) has been investigated in dilute aqueous solution using UV‐vis and fluorescence spectroscopy. It is demonstrated here that the effectiveness of various salts in changing the lower critical solution temperature (TLCS) of the PDEA/ACE solution followed the Hoffmeister series. The addition of NaCl linearly lowered the TLCS. In dilute aqueous solution, the PDEA/ACE adopted a loose coil conformation below its TLCS. The PDEA/ACE adopted a compact globule conformation above the temperature at which the coil to globule transition (CGT) was completed. A fluorescence anisotropy investigation suggested that a molten globule conformation existed during the CGT of the PDEA/ACE solution. In all of the above three conformations, the PDEA/ACE was more compact in the presence of NaCl than in the absence of any salt.

Temperature and NaCl concentration dependence of fluorescence anisotropy of a PDEA/ACE solution. Inset: thermodynamically stable states of PDEA/ACE.

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Temperature and NaCl concentration dependence of fluorescence anisotropy of a PDEA/ACE solution. Inset: thermodynamically stable states of PDEA/ACE.
A Solvent Free Graft Copolymerization of Maleic Anhydride onto Cellulose Acetate Butyrate Bioplastic by Reactive Extrusion
Authors: Wibowo Arief C. , Desai Shrojal M. , Mohanty Amar K. , Drzal Lawrence T. , Misra Manjusri
Published: December 2005

Summary: Interfacial adhesion between fibers and matrix is a crucial factor for effective stress transfer from matrix to fiber; especially in short fiber reinforced composite systems. The use of a chemical compatibilizer is an efficient means to achieve such adhesion. Maleic anhydride‐grafted‐cellulose acetate butyrate (CAB‐g‐MA) is one such compatibilizer which can be used in biocomposite fabrication, and this has been synthesized in our laboratory by utilizing a twin‐screw reactive extrusion process in the presence of a free radical initiator (2,5‐dimethyl‐2,5‐di(tert‐butylperoxy)hexane). The unique feature of this process is its solvent‐free approach for grafting of maleic anhydride onto CAB, without hydroxyl group protection. CAB‐g‐MA was characterized using FTIR as well as by a non‐aqueous titration method. The effects of initiator and monomer concentrations and various processing conditions on the graft content were also investigated. The preliminary results show that by adding approximately 10 wt.‐% of CAB‐g‐MA into a plasticized cellulose acetate butyrate (TEB)‐industrial hemp fiber biocomposites system, an improvement in tensile strength (20%) and in tensile modulus (45%) were obtained. These results are promising in that they pave the way for future studies involving the use of CAB‐g‐MA as a suitable compatibilizer for cellulose ester‐natural fiber biocomposites.

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Polymerization of Cyclic Monomers, 12
Authors: Moszner Norbert , Zeuner Frank , Fischer Urs Karl , Rheinberger Volker , de Meijere Armin , Bagutski Viktor
Published: December 2005

Summary: The radical polymerization of different substituted methyl 2‐(bicyclo[3.1.0]hex‐1‐yl) acrylates, 1a–f, was initiated by 2,2′‐azoisobutyronitrile (AIBN) at 65 °C in chlorobenzene. The radical homopolymerization of 1a–f occurred through the opening of the cyclopropane ring, and lead to polymers with number‐average molecular weights of 13 000 to 434 400 g · mol−1 and glass transition temperatures between 77 and 121 °C. The monomers 1a–f showed a similar reactivity to MMA (in the copolymerization with MMA). Selected monomers were determined to be diluent monomers for dental filling composites and enable the preparation of composites that show a significantly reduced polymerization shrinkage, compared to composites based on dimethacrylate diluents.

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Effects of Heat and Pressure on Microstructures of Isobutylene‐Isoprene Rubber (IIR)/Clay Nanocomposites
Authors: Lu Yong‐Lai , Liang Yu‐Rong , Wu You‐Ping , Zhang Li‐Qun
Published: December 2005

Summary: In this work, the effects of heat and pressure on microstructures of isobutylene‐isoprene rubber/clay nanocomposites prepared by solution intercalation (S‐IIRCNs) are investigated. Not only are the local intercalated structures monitored by wide‐angle X‐ray diffraction, but the spatial distributions of the silicate particles are also observed by transmission electron microscopy. The changing behavior of microstructures of S‐IIRCNs is strongly dependent on the temperature of the thermal treatment. The observed phenomena are completely different from those in IIRCNs prepared by melt blending (M‐IIRCNs), which were reported in a previous paper. Various experiments suggest that the presence of residual solvent molecules in S‐IIRCN plays a key role on the microstructural change of S‐IIRCNs caused by heat and pressure. The possible microstructural models for untreated and treated S‐IIRCNs are presented, which could well interpret all observed phenomena. Finally, guidelines are proposed for adjusting the curing conditions of the system to achieve the desired intercalated/exfoliated morphology, and a new method for preparing rubber/clay nanocomposites with good dispersion states by melt blending is put forward.

TEM images of IIR/clay nanocomposites prepared by solution‐intercalation before (left) and after thermal treatment at 160 °C and atmospheric pressure (right).

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TEM images of IIR/clay nanocomposites prepared by solution‐intercalation before (left) and after thermal treatment at 160 °C and atmospheric pressure (right).
Synthesis and Surface Morphology of Tetraaniline‐block‐Poly(L‐lactate) Diblock Oligomers
Authors: Wang Hanfu , Guo Peng , Han Yanchun
Published: December 2005

Summary: Tetraaniline‐block‐poly(L‐lactide) diblock oligomers are synthesized via ring‐opening polymerization. The diblock oligomers cast from an L‐lactide selective solvent (chloroform) show spherical aggregates for the leucoemeraldine state, and ring‐like structures that are composed of much smaller spherical aggregates for the emeraldine state. The formation mechanisms of the two different surface morphologies are discussed in detail.

Surface morphology changes induced by oxidation of the aniline segment of tetraaniline‐block‐poly(L‐lactate) and drying effects.

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Surface morphology changes induced by oxidation of the aniline segment of tetraaniline‐block‐poly(L‐lactate) and drying effects.
Cobalt‐Mediated Radical Polymerization of Vinyl Acetate in Miniemulsion: Very Fast Formation of Stable Poly(vinyl acetate) Latexes at Low Temperature
Authors: Detrembleur Christophe , Debuigne Antoine , Bryaskova Rayna , Charleux Bernadette , Jérôme Robert
Published: December 2005

Summary: Poly(vinyl acetate) macroinitiators end‐capped by a Co(acac)2 complex (PVAc–Co(acac)2), prepared in bulk by cobalt‐mediated radical polymerization (CMRP), are used for the controlled radical polymerization of vinyl acetate in miniemulsion to give high‐molecular‐weight polymers and high monomer conversion. Stable poly(vinyl acetate) latexes with solid contents ranging from 25 to 30 wt.‐% are prepared within unusually short reaction times (∼1 h) at low temperatures (0–30 °C).

SEC chromatograms for the PVAc–Co(acac)2 macroinitiator and PVAc latex obtained under ultrasonication for 6 min at 0 °C (79% monomer conversion).

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SEC chromatograms for the PVAc–Co(acac)2 macroinitiator and PVAc latex obtained under ultrasonication for 6 min at 0 °C (79% monomer conversion).
Influence of Copolymerization on Fragmentation Behavior Using Ziegler‐Natta Catalysts
Authors: Zheng Xuejing , Pimplapure Makarand S. , Weickert Günter , Loos Joachim
Published: December 2005

Summary: A morphological investigation was carried out on different Ziegler‐Natta catalysts during the early stages of propylene homo‐ and propylene‐ethylene copolymerization. For similar polymerization conditions, but dependent on the nature of the catalysts, fragmentation occurs layer‐by‐layer or instantaneously into a large amount of small pieces. However, the incorporation of comonomer ethylene slows down the fragmentation progress. This is believed to be the result of the higher mobility of the just formed propylene‐ethylene copolymer molecules at the active sites.

SEM images of the cross‐sectional morphology of polymer particles from catalyst‐I.

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SEM images of the cross‐sectional morphology of polymer particles from catalyst‐I.
A syndrome of irreversible leukoencephalopathy following pediatric allogeneic bone marrow transplantation
Authors: Minn A. Yuriko , Fisher Paul G. , Barnes Patrick D. , Dahl Gary V.
Published: December 2005

Background

Despite decreases in overall mortality following bone marrow transplantation (BMT), a number of complications such as neurotoxicity have been described and often associated with immunosuppressive agents. The syndrome of reversible posterior leukoencephalopathy has been described in patients receiving cyclosporin and FK‐506. We report here a subset of children who developed a syndrome of previously undescribed irreversible leukoencephalopathy following allogeneic BMT.

Patients and Methods

Between 1996 and 2002, 138 pediatric patients received an allogeneic BMT at Lucile Salter Packard Children's Hospital at Stanford. Six cases of irreversible leukoencephalopathy were observed. Cases were defined as children who exhibited progressive and continued, severe neurologic deterioration lasting greater than 2 weeks and consistent with non‐localizing, central nervous system abnormalities. Medical records and magnetic resonance images (MRIs) were reviewed.

Results

Median age of the affected patients at BMT was 7.8 years. All six received cyclosporin, but none had elevated drug levels. Encephalopathy occurred at a median of 53 days (range 14–77) following BMT. Symptoms at onset of leukoenceophalopathy included confusion and altered mental status, sluggish pupillary responses, abnormal movements, and seizures. Two patients died during their neurologic decline. Four patients remain alive with persistent encephalopathy. MRI showed abnormalities in all patients including periventricular or subcortical white matter involvement in all, and basal ganglia lesions in three.

Conclusions

We report a syndrome of irreversible neurologic deficits and cerebral white matter abnormalities following allogeneic BMT, yet not associated with elevated cyclosporin levels. A precise mechanism for this syndrome is lacking and warrants further consideration. Pediatr Blood Cancer 2007;48:213–217. © 2006 Wiley‐Liss, Inc.
Ceric(IV) ion‐induced graft copolymerization of acrylamide and ethyl acrylate onto cellulose
Authors: Gupta Kailash C , Khandekar Keerti
Published: December 2005

Graft copolymerization of acrylamide (AAm) and ethyl acrylate (EA) onto cellulose has been carried out from their binary mixtures using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 25 ± 1 °C. The extent of acrylamide grafting increased in the presence of the EA comonomer. The composition of the grafted chains (FAAm = 0.52) was found to be constant during the feed molarity variation from 7.5 × 10−2 to 60.0 × 10−2 mol L−1, whereas the composition of the grafted chains (FAAm) was found to be dependent on feed composition (fAAm) and reaction temperature. The effects of ceric(IV) ion concentration, reaction time and temperature on the grafting parameters have been studied. The grafting parameters showed an increasing trend up to 6.0 × 10−3 mol L−1 concentration of CAN at a feed molarity of 30.0 × 10−2 mol L−1 and showed a decreasing trend on further increasing the concentration of CAN (>6.0 × 10−3 mol L−1) at a constant concentration of nitric acid (5.0 × 10−2 mol L−1). The composition of the grafted chains (FAAm) was determined by IR spectroscopy and nitrogen content and the data obtained then used to determine the reactivity ratios of the acrylamide (r1) and ethyl acrylate (r2) comonomers by using a Mayo and Lewis plot. The reactivity ratios of acrylamide and ethyl acrylate were found to be r1 = 0.54 and r2 = 1.10, respectively, and hence the sequence lengths of acrylamide (m̄M1) and ethyl acrylate (m̄M2) in the grafted chains are arranged in an alternating form, as the product of the reactivity ratios of acrylamide and ethyl acrylate (r1 × r2) is less than unity. The rate of graft copolymerization of the comonomers onto cellulose was found to be dependant on the ‘squares’ of the concentrations of the comonomers and on the ‘square root’ of the concentration of ceric ammonium nitrate. The energy of activation (ΔEa) of graft copolymerzation was found to be 5.57 kJ mol−1 within the temperature range from 15 to 50 °C. On the basis of the results, suitable reaction steps have been proposed for the graft copolymerzation of acrylamide and ethyl acrylate comonomers from their mixtures. Copyright © 2005 Society of Chemical Industry
Molecular design, synthesis, and electro‐optic properties of novel Y‐type polyesters with high thermal stability of second harmonic generation
Authors: Lee Ju‐Yeon , Jung Won‐Taek , Lee Won‐Jung
Published: December 2005

3,4‐Di‐(2′‐hydroxyethoxy)‐4′‐nitrostilbene was prepared and condensed with terephthaloyl chloride, adipoyl chloride, and sebacoyl chloride to yield novel Y‐type polyesters containing NLO‐chromophore dioxynitrostilbenyl groups, which constituted parts of the polymer backbone. Polymers were found soluble in common organic solvents such as acetone and N,N‐dimethylformamide. They showed thermal stability up to 300 °C in thermogravimetric analysis with glass‐transition temperatures obtained from differential scanning calorimetry in the range 110–152 °C. The second harmonic generation (SHG) coefficients (d33) of poled polymer films at a 1064 cm−1 fundamental wavelength were around 3.51 × 10−8 esu. The dipole alignment exhibited high thermal stability even at 10 °C higher than the glass‐transition temperature, and there was no SHG decay below 120 °C for one of these polymers due to the partial main‐chain character of polymer structure, which was acceptable for NLO device applications. Copyright © 2005 Society of Chemical Industry
Study on the nonisothermal crystallization behavior of poly(vinyl alcohol)/attapulgite nanocomposites by DSC analysis
Authors: Peng Zhiqin , Chen Dajun
Published: December 2005

Attapulgite (AT)‐reinforced poly(vinyl alcohol) (PVA) nanocomposite films were prepared by solution‐casting technique. The nonisothermal crystallization behaviors of PVA bulk and PVA/AT nanocomposites have been investigated by differential scanning calorimetry (DSC). It has been found that the uniformly dispersed AT nanorods in the matrix have great influence on the glass transition temperature and crystallization behavior of PVA matrix. The Jeziorny method has been employed to analyze the DSC data. The results show that Jeziorny method could describe this system very well. Comparing with the PVA bulk, PVA/AT nanocomposites have higher crystallinity Xt, shorter semicrystallization time t1/2, and higher crystallization rate constant Zc. It can be concluded that AT can be used as an effective nucleating agent and has effects on the growth of crystallites in the crystallization process of PVA matrix. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 534–540, 2006
Formation of oriented polypeptides on Au(111) surface depends on the secondary structure controlled by peptide length
Authors: Sakurai Toshihiko , Oka Sayaka , Kubo Atsushi , Nishiyama Katsuhiko , Taniguchi Isao
Published: December 2005

We synthesized three different lengths of poly(L‐lysine) containing an ‐SH group at the terminal (PLLn‐SH, n (polymerization degree) = 4, 10, 30) and adsorbed them on an Au(111) surface. To analyze the formation process and the structure of self‐assembled monolayers (SAMs), we used atomic force microscopy (AFM) and Fourier transform infrared reflection absorption spectra (FT‐IR RAS). At the initial stage of SAM growth, formation of nanosize domains was confirmed by AFM imaging. The α‐helical PLL30‐SH exhibited a well‐defined SAM structure after adsorption reached equilibrium. The α‐helical PLL30‐SH was almost perpendicular to the gold surface and exhibited interesting molecular packing due to the secondary structure of PLL30‐SH and the underlying Au(111) array. The tilt angle of the helix axis from the substrate normal was estimated to be about 50° (AFM) and 44° (FT‐IR RAS) respectively. On the other hand, PLL4‐SH and PLL10‐SH formed β‐sheet‐type SAMs on the Au(111) surface based on the structure determined by FT‐IR RAS spectrum. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd.
Characterization of N‐glycans of recombinant human thyrotropin using mass spectrometry
Authors: Morelle Willy , Donadio Sandrine , Ronin Catherine , Michalski Jean‐Claude
Published: December 2005

Thyroid‐stimulating hormone is a vital component of the regulatory mechanism that maintains the structure and function of the thyroid gland and governs thyroid hormone release. In this paper we report the first detailed structural characterization of the N‐linked oligosaccharides of recombinant human thyroid‐stimulating hormone (rhTSH). Using a strategy combining mass spectrometric analysis and sequential exoglycosidase digestion, we have defined the structures of the N‐glycans released from recombinant human thyrotropin by peptide N‐glycosidase F. All glycans are complex‐type glycans and are mainly of the bi‐ and triantennary type with variable degrees of fucosylation and sialylation. The major non‐reducing epitope in the complex‐type glycans is: NeuAcα2‐3Galβ1‐4GlcNAc (sialylated LacNAc). The carbohydrate microheterogeneity at the three glycosylation sites was studied using reversed‐phase high‐performance liquid chromatography (RP‐HPLC), concanavalin A affinity chromatography and mass spectrometric techniques, including both matrix‐assisted laser desorption/ionization (MALDI) and electrospray. rhTSH was reduced, carboxymethylated and then digested with trypsin. The mixture of peptides and glycopeptides was subjected to RP‐HPLC and the structures of the glycopeptides were determined by MALDI in conjunction with on‐target exoglycosidase digestions. After PNGase F digestion, the peptide moiety of the glycopeptide was determined by the presence of the b‐ and y‐series ions derived from its amino acid sequence in the quadrupole time‐of‐flight tandem mass (QTOF‐MS/MS) spectrum. Glycosylation sites Asn‐α52 and Asn‐α78 contain mainly bi‐ and triantennary complex‐type glycans. Only glycosylation site Asn‐α52 bears fucosylated N‐glycans. Minor tetraantennary complex structures were also observed on both glycosylation sites. Profiling of the carbohydrate moieties of Asn‐β23 indicates a large heterogeneity. Bi‐, tri‐, and tetraantennary N‐glycans were present at this site. These data demonstrate site‐specificity of glycosylation in the α subunit but not in the β subunit of rhTSH with Asn‐α52 bearing essentially di‐ and triantennary glycans with or without core fucosylation and bi‐ and triantennary glycans with no core fucosylation being attached to Asn‐α78. Copyright © 2005 John Wiley & Sons, Ltd.