bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduced raft‐association of NF155 in active MS‐lesions is accompanied by the disruption of the paranodal junction
Authors: Maier Olaf , Baron Wia , Hoekstra Dick
Published: April 2007

Neurofascin155 (NF155) is required for the establishment of the paranodal axo‐glial junction, the predominant interaction site between myelin and axon. It has been shown that the distribution of NF155 is altered in demyelinating diseases such as multiple sclerosis (MS). However, little is known about the biochemical mechanisms underlying these changes. We therefore compared NF155 in postmortem tissue of active and chronic inactive MS lesions with white matter from healthy controls. Although NF155 showed a very similar expression in all control white matter samples, a strong individual variation was observed in MS‐lesions with NF155‐levels reduced in most samples. At the same time an NF155‐fragment was increased in MS‐lesions, suggesting that NF155 is subject to protein degradation in lesion sites. Interestingly, the association of NF155 to membrane microdomains (rafts) was reduced in all lesions, irrespective of the amount of NF155, indicating that membrane association of NF155 was generally affected. Therefore, myelin fractionation experiments were performed to analyze the fate of paranodal proteins during demyelination. Although NF155 was enriched in heavy myelin from both control white matter and active MS‐lesions, association of Caspr1/paranodin with heavy myelin was abolished in MS‐lesions, demonstrating that paranodal junctions are disrupted. In conclusion, the data support the hypothesis that efficient raft‐association of NF155 is essential for the assembly of the paranodal junction and demonstrate that reduced association of NF155 to lipid rafts is accompanied by the disassembly of the paranodal junction and thus contributes to the demyelination process in MS. © 2007 Wiley‐Liss, Inc.
Exploring the clinical and social determinants of prescribing anticholinergic medication for Chinese patients with schizophrenia
Authors: Yu‐Tao Xiang , Yong‐Zhen Weng , Chi‐Ming Leung , Wai‐Kwong Tang , Ungavri Gabor Sandor
Published: April 2007

Aims

To‐date few studies have investigated prescription patterns of anticholinergic medication (ACM) in Chinese patients with schizophrenia in general and outpatients in particular. This study examined the frequency and socio‐demographic and clinical correlates of ACM in Hong Kong (HK) and Beijing (BJ), China.

Methods

Five hundred and five clinically stable outpatients with schizophrenia were randomly selected and interviewed in HK and BJ using standardized assessment instruments. Basic socio‐demographic and clinical data and psychotropic drug prescriptions were collected at the time of the diagnostic interview.

Results

ACM was found in 47.7% of (n = 241) the whole sample and in 54.1 and 41.2% of the HK and BJ samples, respectively. ACM was associated with more frequent use of antipsychotic (AP) polypharmacy, typical AP drugs, and a combination of depot and oral AP, less use of clozapine and atypical and oral AP, a lack of health insurance, higher doses of APs, severity of extrapyramidal side effects (EPS), a higher number of APs prescribed, and study sites. In multiple logistic regression analysis, higher doses of APs, less frequent use of an atypical AP, and study sites all remained significantly associated with ACM.

Conclusion

Although the ethnic and clinical characteristics of the two samples were nearly identical, there was a wide variation in the frequency of ACM prescriptions between HK and BJ suggesting that socio‐cultural and economical factors as well as traditions of psychiatric practice all played a role in determining the use of ACM. Prescribing ACM in neither site was in line with current recommendation. Copyright © 2007 John Wiley & Sons, Ltd.
Effects of smoking marijuana on focal attention and brain blood flow
Authors: O'Leary Daniel S. , Block Robert I. , Koeppel Julie A. , Schultz Susan K. , Magnotta Vincent A. , Ponto Laura Boles , Watkins G. Leonard , Hichwa Richard D.
Published: April 2007

Using an attention task to control cognitive state, we previously found that smoking marijuana changes regional cerebral blood flow (rCBF). The present study measured rCBF during tasks requiring attention to left and right ears in different conditions. Twelve occasional marijuana users (mean age 23.5 years) were imaged with PET using [15O]water after smoking marijuana or placebo cigarettes as they performed a reaction time (RT) baseline task, and a dichotic listening task with attend‐right‐ and attend‐left‐ear instructions. Smoking marijuana, but not placebo, resulted in increased normalized rCBF in orbital frontal cortex, anterior cingulate, temporal pole, insula, and cerebellum. RCBF was reduced in visual and auditory cortices. These changes occurred in all three tasks and replicated our earlier studies. They appear to reflect the direct effects of marijuana on the brain. Smoking marijuana lowered rCBF in auditory cortices compared to placebo but did not alter the normal pattern of attention‐related rCBF asymmetry (i.e., greater rCBF in the temporal lobe contralateral to the direction of attention) that was also observed after placebo. These data indicate that marijuana has dramatic direct effects on rCBF, but causes relatively little change in the normal pattern of task‐related rCBF on this auditory focused attention task. Copyright © 2007 John Wiley & Sons, Ltd.
Health‐status of adult survivors of childhood cancer: A large‐scale population‐based study from the British childhood cancer survivor study
Authors: Reulen Raoul C. , Winter David L. , Lancashire Emma R. , Zeegers Maurice P. , Jenney Meriel E. , Walters Stephen J. , Jenkinson Crispin , Hawkins Mike M.
Published: April 2007

The purpose of this study was to investigate the effect of childhood cancer and its treatment on self‐reported health‐status in 10,189 adult survivors of childhood cancer in Britain. Age‐ and sex‐adjusted scores on the SF‐36 Mental and Physical Component Summary scales (MCS, PCS, respectively) were compared between survivors and UK norms, and between subgroups of survivors, by multiple regression. Survivors had comparable scores to UK‐norms on the MCS scale (difference (D) = −0.1, 99% CI: −0.5, 0.3). The difference in scores between survivors and UK‐norms on the PCS scale varied by age (pheterogeneity < 0.001). Young survivors (16–19 years) scored similarly to UK‐norms (D = 0.5, (−1.1, 2.2), whereas the age groups of 25 and older scored statistically and clinically significantly below UK‐norms (all p‐values < 0.0001), with Ds ranging between −2.3 (−3.5, −1.2) and −3.7 (−5.0, −2.4). Survivors of central nervous system (CNS) and bone tumors scored significantly (p‐value at all ages <0.003) below UK‐norms on the PCS scale. Specifically, these survivors were substantially more limited in specific daily activities such as, for example, walking a mile (40, 63%, respectively) when compared to UK‐norms (16%). In conclusion, childhood cancer survivors rate their mental health broadly similarly to those in the general population. Survivors of CNS and bone tumors report their physical health‐status to be importantly below population norms. Although self‐reported physical health is at least as good as in the general population among young survivors, this study suggests that perceived physical health declines more rapidly over time than in the general population. © 2007 Wiley‐Liss, Inc.
Quantum chemical investigation of hydrogen‐bond strengths and partition into donor and acceptor contributions
Authors: Raub Stephan , Marian Christel M.
Published: April 2007

We present a simple increment model for use in the rapid scoring of hydrogen bond strengths employing 15 chemically diverse donor and 28 acceptor terms. The increments cover a large variety of hydrogen bond donor and acceptor groups and are more specific than SYBYLatom types. The increments have been fitted to quantum chemicalab initiointeraction energies of 81 small hydrogen‐bonded complexes determined at the level of second‐order Møller‐Plesset perturbation theory (MP2). The complexes have been chosen such as to represent the most important types of donor‐acceptor pairs found in biological systems. Sulphur is found to be a strong hydrogen bond acceptor while its donor capacities are weak. By taking CH acidic H donors into account, a linear correlation between MP2 energies and the increment model with a coefficient of correlation ofr2= 0.994 has been accomplished. The transferability of the fitted parameters has been assessed on a second set of complexes including larger molecules of biological relevance. Very good agreement has been achieved for noncyclic hydrogen bonds. Cooperative effects are not accounted for by the current increment model. For this reason, binding energies of strong cyclic hydrogen bonds, as e.g. present in DNA base pairs, are underestimated by about 30–40%. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
Calculating rate constants with updated Hessians using variational transition state theory with multidimensional tunneling
Authors: Chuang Yao‐Yuan
Published: April 2007

Variational transition state theory with multidimensional tunneling (VTST/MT) has been used for calculating the rate constants of reactions. The updated Hessians have been used to reduce the computational costs for both geometry optimization and trajectory following procedures. In this paper, updated Hessians are used to reduce the computational costs while calculating the rate constants applying VTST/MT. Although we found that directly applying the updated Hessians will not generate good vibrational frequencies along the minimum energy path (MEP), however, we can either re‐compute the full Hessian matrices at fixed intervals or calculate the Block Hessians, which is constructed by numerical one‐side difference for the Hessian elements in the “critical” region and Bofill updating scheme for the rest of the Hessian elements. Due to the numerical instability of the Bofill update method near the saddle point region, we have suggested a simple strategy in which we follow the MEP until certain percentage of the classical barrier height from the barrier top with full Hessians computed and then performing rate constant calculation with the extended MEP using Block Hessians. This strategy results a mean unsigned percentage deviation (MUPD) around 10% with full Hessians computed till the point with 80% classical barrier height for four studied reactions. This proposed strategy is attractive not only it can be implemented as an automatic procedure but also speeds up the VTST/MT calculation via embarrassingly parallelization to a personal computer cluster. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007
The effect of Ginkgo biloba on the cerebellum of aging SAMP mouse—A TUNEL, bcl‐2, and fMRI study
Authors: Wai Maria S.M. , Rudd John A. , Chan W.Y. , Antonio Gregory E. , Yew David T.
Published: April 2007

EGb 761, an extract from Ginkgo biloba that possesses neuroprotective properties, was fed to a strain of fast aging mice (SAMP‐8) beginning at 3 weeks of age until they were sacrificed at 3 months and 11 months, respectively, along with an age‐matched control group without herbal feeding. The aim of the study was to determine (1) the status of apoptosis and the status of bcl‐2, a molecule involved in the fate of cells following injury, in the cerebella of these mice and (2) to analyze the functional changes as shown by fMRI images. The data indicated that there were no differences in apoptosis between the mice fed with EGb 761 and the control group at the two time points of 3 and 11 months of age. For bcl‐2 positive cells, there was a decrease in density only in the cerebella of 11‐month‐old mice fed with the herbal extract when compared with controls. Functional studies indicated that while no changes were observed in the 3‐month‐old mice fed with Ginkgo biloba, an expansion of activated sites, possibly related to “synaptic reorganization and pathway alteration,” was observed in the 11‐month‐old mice. Microsc. Res. Tech., 2007. © 2007 Wiley‐Liss, Inc.
Development of strategies for conditional RNA interference
Authors: Allen Danny , Kenna Paul F. , Palfi Arpad , McMahon Helena P. , Millington‐Ward Sophia , O'Reilly Mary , Humphries Pete , Farrar G. Jane
Published: April 2007

Background

RNA interference (RNAi) represents a powerful tool with which to undertake sequence‐dependent suppression of gene expression. Synthesized double‐stranded RNA (dsRNA) or dsRNA generated endogenously from plasmid or viral vectors can be used for RNAi. For the latter, polymerase III promoters which drive ubiquitous expression in all tissues have typically been adopted. Given that dsRNA molecules must contain few 5′ and 3′ over‐hanging bases to maintain potency, employing polymerase II promoters to drive tissue‐specific expression of RNAi may be problematic due to potential inclusion of nucleotides 5′ and 3′ of siRNA sequences.

Methods

To circumvent this, polymerase II promoters in combination with cis‐acting hammerhead ribozymes and short‐hairpin RNA sequences have been explored as a means to generate potent dsRNA molecules in tissues defined by the promoter in use.

Results

The novel constructs evaluated in this study produced functional siRNA which suppressed the enhanced green fluorescent protein (eGFP) both in vitro and in vivo (in mice). Additionally, the constructs did not appear to elicit a significant type‐1 interferon response compared to traditional H1‐transcribed shRNA.

Conclusions

Given the potential ‘off‐target’ effects of dsRNAs, it would be preferable in many cases to limit expression of dsRNA to the tissue of interest and moreover would significantly augment the resolution of RNAi technologies. Notably, the system under evaluation in this study could readily be adapted to achieve this objective. Copyright © 2007 John Wiley & Sons, Ltd.
Strategy as a configuration of activities: evidence that strategy absence exists
Authors: Rodwell John J. , Shadur Mark A.
Published: April 2007

Qualitative content analysis on company documents is used to inductively operationalize strategy as a configuration of activities in medium and large companies in the Australian information technology industry.

Three specific configurations were found: Global Exporters, Flexible Scanners and Drifters. The Global Exporters and Flexible Scanners have similarities with prior strategy types. In contrast, the Drifters provide evidence for the concept of strategy absence. The configurations found highlight the value of considering strategic change in terms of quantum change.

Copyright © 2007 John Wiley & Sons, Ltd.
Rapid evaluation and discrimination of γ‐irradiated carbohydrates using FT‐Raman spectroscopy and canonical discriminant analysis
Authors: Kizil Ramazan , Irudayaraj Joseph
Published: April 2007

Chemical changes induced by gamma irradiation of selected sugar systems—honey and fructose—were investigated through their molecular fingerprint using Fourier transform Raman spectroscopy (FT‐Raman). Generalized two‐dimensional (2‐D) correlation spectroscopy was applied to FT‐Raman spectra of the control and 17 kGy irradiated fructose to elucidate changes in the chemical structure upon irradiation. The irradiation induced changes in the ring (below 700 cm−1) and conformational structure (800–1500 cm−1) of fructose were identified by means of a 2‐D FT‐Raman correlation spectroscopy. The irradiation damage depicted from the CH stretch region (2800–3000 cm−1) of the FT‐Raman spectra of honey was used to develop a pattern recognition model for classifying honey based on the irradiation dose. A hybrid partial least squares (PLS)–canonical variate analysis (CVA) with the optimum number of factors from PLS was used for rapid discrimination of honeys irradiated at 1, 5, 10 or 17 kGy. The present study demonstrated that FT‐Raman spectroscopy, together with chemometrics, could be a rapid tool for classification of foodstuffs with high sugar content and provides a viable option to explore radiation‐induced modifications to sugar systems subjected to irradiation processing. Copyright © 2007 Society of Chemical Industry
On the mathematical model of a viscoelastic bar
Authors: Takači Arpad , Takači Djurdjica
Published: April 2007

In this paper we consider a mathematical model describing the shock of a rigid body and a linear viscoelastic bar, resting on a rigid base, in the frames of the Mikusiński operator calculus. We determine and analyse the character of the exact solution of the corresponding problem in the field of Mikusiński operators. We construct an approximate solution of this problem, and estimate the error of approximation. The mentioned problem is taken from the papers (J. Mech. NCSR Vietnam Tom 1991; 13(2):1–7; Nonlinear Anal. Theory Meth. Appl. 2001; 43:547–561). Copyright © 2007 John Wiley & Sons, Ltd.
A numerical–analytical combined method for vibration of a beam excited by a moving flexible body
Authors: Ouyang Huajiang , Mottershead John E.
Published: April 2007

The vibration of a beam excited by a moving simple oscillator has been extensively studied. However, the vibration of a beam excited by an elastic body with conformal contact has attracted much less attention. This is the subject of the present paper. The established model is more complicated but has a much wider range of applications than the moving‐oscillator model.

Because the moving body is flexible, the moving loads at the contact interface are not known a priori and must be determined together with the dynamics of the whole system. In this paper, the equation of motion of the beam and the moving body are established separately using a numerical–analytical combined approach. It is found from the numerical results of the simulated example that the vibrations of the moving body and the beam excited by the moving body are significantly influenced by the travelling speed. At very low or very high speeds the dynamic effect is small and the beam deforms to take the shape of its static deflection. Vibrations tend to be greater in the intermediate speed range and the total moving force at the interface of the beam and the moving body can be compressive and tensile. Copyright © 2007 John Wiley & Sons, Ltd.
Evidence of two distinct mechanisms for CC or CO bond formation in the oxidative coupling of phenols
Authors: Roubaty J. L. , Revillon A.
Published: March 2007

The oxidation of 2, 6‐xylenol by oxygen, catalysed by a copper complex, leads to poly‐phenylene ether or quinones according to the amount of added pyridine. The first oxidation step is common in the two processes giving aryloxy radicals. The pH of the medium plays a fundamental role so that at low values a second electron is removed and the diradical rearranges into a cation in acidic medium. This cation may add to the monomer or to H2O thus explaining the production of several quinones. It has been shown that in methanol solvent, a nucleophilic reagent, addition to the cation takes place giving a new product which was characterised by thin layer chromatography (tlc).
Glass transition temperatures of poly N — (N — alkyl)—maleimides
Authors: Barrales‐Rienda J. M. , Gonz Ramos J. Ález , Chaves M. Sánchez
Published: March 2007

The glass transition temperatures (Tgs) of a series of poly N‐(n‐alkyl) maleimides covering only the even members with side chains ranging in length from ethyl to n‐octadecyl have been studied from room temperature to above Tg. Tgs and thermal quantities have been determined from the specific volume‐temperature relations only for the higher (n=8, 10, 12, 14, 16 and 18, where n = no of CH2) members of the series. However for the lower ones (n = 2, 4, 6, 8 and 10) Tgs have been detected from heat capacity‐temperature traces of differential scanning calorimetry diagrams by extrapolation to zero rate of heating. Accurate consistency was found in the values (n = 8 and 10) determined by both experimental methods.

TgS of these polymers continuously decrease as the number of methylene groups in the side chain is increased, and they have been correlated with the size of the n‐alkyl group in the side chain. The results are in accord with a previously studied series concerning the effect of a long side chain on the Tg of a comb‐like polymer in the amorphous state.

Tgs of poly N‐(n‐alkyl) maleimides encompassing a wide range of methylene group content (n = 2, 4, 6, 8, 10 and 12) have been examined according to the Gordon‐Taylor‐Wood extrapolation with the objective of ascertaining the Tg of polyethylene (PE). Our approach of ignoring higher members of the homologous series in this extrapolation appears to be old and well known and it has been variously ascribed to different authors. Extrapolation of Tg values to 100% amorphous PE gives a Tg of 200/pm 10 °K in complete agreement with recent predictions made by Boyer from different sources of data.

The Simha‐Boyer free volume quantity Δa. Tg decreases slowly with the methylene group content in the longer terms (n = 8, 10, 12, 14, 16 and 18) of the series presumably because of a reduction in the polarity or an in‐chain crankshaft loss mechanism which generates free volume in the glassy state, as stated by Boyer.

Tgs do not correlate very well with the contributions of the atomic groups to the cohesive energy density (c.e.d.) so it can be concluded that c.e.d. is not the only factor determining Tg. However, a somewhat improved relationship might be obtained by taking into account the steric hindrance effect according to an approach made by Hayes.
The reactivity of 2‐furaldehyde and its derivatives in polymerisation reactions involving the carbonyl bond
Authors: Gandini Alessandro , Rieumont Jacques
Published: March 2007

The homopolymerisation of 2‐furaldehyde, 5‐methyl‐2‐furaldehyde and 2‐furyl methyl ketone and their cationic copolymerisation (BF3. Et2) with olefins were investigated. All attempts to obtain homopolymers failed because of thermodynamic restrictions. 2‐Furaldehyde and α‐methylstyrene gave an alternating copolymer of low degree of polymerisation, 2‐methyl‐2‐furaldehyde and α‐methylstyrene gave copolymers rich in 5‐methyl‐2‐furaldehyde, indicating a penultimate effect in the growth mechanism. The use of less basic comonomers (cyclopentadiene, styrene, isoprene, etc.) resulted in inhibition or strong retardation of the polymerisation. The use of more basic comonomers (acenaphthy‐lene, N‐vinylcarbazole) resulted in their homopolymerisation. Furyl methyl ketone inhibited the polymerisation of all comonomers tried. A complex between BF3. Et2O and 2‐furaldehyde was isolated and characterised. A general mechanism is offered to explain the behaviour of these systems.
Effect of thermal stresses on the dynamic moduli of abs‐resins
Authors: Booij H. C.
Published: March 2007

The magnitude of the thermal stresses generated among the polymeric constituents in highly grafted ABS‐samples during cooling down from the melt can be calculated by means of the ‘double emulsion model’. The effect of these stresses on the location of the rubber maximum in the loss modulus vs temperature plot can be derived from literature data regarding the pressure dependence of mechanical relaxation times.

The results are in good agreement with those of torsion pendulum tests on a series of ABS‐samples prepared by blending a grafted rubber with various amounts of SAN‐resin. A continuous shift of the rubber loss peak to lower temperatures with decreasing rubber content is observed.

Samples of low rubber content show a split damping peak at low temperatures. The area under the extra peak can be reversibly enlarged or reduced by varying the rate of cooling of the sample in the high temperature region, which indicates that real fracturing of graft molecules cannot be held responsible for this splitting of the peak.

Especially at low rubber contents it has been found that the relative increase in rigidity with decreasing temperature is smaller in ABS‐resins than in the pure SAN‐copolymer. This decrease in relative modulus can also be correlated with the absolute value of the thermally induced hydrostatic tension.
Some peculiarities of gel chromatography of non‐modified cellulose on inorganic gels in cadoxen
Authors: Berek Duš , Katuščáková Gabriela , Novák Ivan
Published: March 2007

The possibilities and limitations of gel chromatography of non‐modified cellulose on inorganic supports in the complex solvent cadoxen are shown. The GPC fractionation in this system is possible but the evaluation of the analytical data would be rather complicated. The general problems of application of mixed eluents in gel chromatography are discussed.
The reconstruction problem in graph theory
Authors: Tutte W. T.
Published: March 2007

It is found that the chromatic and characteristic polynomials of a graph are reconstructible. This result is obtained by a process of reconstruction applied to partial results already in the literature.
Liquid multi‐phase separation in solvent‐polymer systems
Authors: Chermin H. A. G.
Published: March 2007

In Simple Flory‐Huggins solvent‐polymer systems liquid three‐phase separation occurs via a homogeneous double plait point. The conditions for three‐phase separation in a system consisting of a solvent and two polydisperse polymer homologues are given.

It is shown that in a simple Flory‐Huggins solvent‐polymer system four and more phase separation cannot occur.

General conditions for a multicritical point are given.
The Influence of Anionic Surfactant on the Stability of Styrene — Acrylonitrile Copolymer Latices
Authors: Ono Hiroshi , Jidai Eiki , Shibayama Kyoichi
Published: April 2007

Styrene — acrylonitrile copolymer latices were prepared by emulsion polymerisation using sodium lauryl sulphate as emulsifier and potassium persulphate as initiator. The effect of sodium lauryl sulphate on the stability of these copolymer latices has been investigated using magnesium chloride as flocculating agent by measuring the rates of flocculation in the presence of various concentrations of surfactant. The values of the critical coagulation concentration (ccc) were found to increase with increasing sufactant concentration for all latices.

The rates of increase in ccc with increasing surfactant concentrations were found to be almost independent of the content of acrylonitrile in the latex particles. The electrophoretic behaviour of these latices in the presence of the ionic surfactant has also been studied. The values of mobilities at ccc were found to decrease slightly with increase in the concentration of the ionic surfactant.
Crystallisation Studies of Trimethylhexamethylene/Hexamethylene Terephthalate Copolymers and Polystyrene Blends
Authors: Sheldon Ronald P. , Wrightson Ian
Published: April 2007

A study has been made of the influence of the non‐crystallising component, trimethyl‐hexamethylene terephthalate, on the crystallisation behaviour of crystallising component, hexamethylene terephthalate in a series of their copolymers. It was found, using Differential Scanning Calorimetry, that as the melting point decreased with composition, the level of crystallinity fell more rapidly than expected on a proportionality basis, the degree of supercooling increased, and there was the emergence of a double crystallisation process. A second study in which the polymers were blended with polystyrene revealed similar influences but with less supercooling.
Problems with Polymers in Dentistry
Authors: Grant Alan
Published: April 2007

Despite the important contributions made by polymers in dental treatment procedures, many shortcomings of these materials are apparent. Rigid type denture base polymers (commonly P.M.M.A.) have low impact and abrasion resistance and lack radiopacity. Resilient polymers used as denture liners may bond poorly to the denture base and suffer changes in physical properties in use. Early problems of colour stability, high polymerisation and thermal contraction, low surface hardness and poor abrasion resistance of the first polymeric filling materials have been only partly overcome by the introduction of polymer/ceramic composites.

In dental cement applications, present bonding systems include unfilled dimethacrylates, which do not attach to dentine. A system based on polyacrylic acid, or copolymers thereof, is believed to bond chemically to the calcium in tooth structure, but the bond to dentine is poorer than that to enamel and also the hydrolytic stability is suspect.
Polymeric Inserts and Implants for the Controlled Release of Drugs
Authors: Graham Neil B.
Published: April 2007

Because of the ability of polymers to exist in glassy, rubbery or solvent‐swollen forms which have very different diffusion coefficients they are able to be used very effectively to control the release of incorporated drugs. As the polymers can vary from inert in vivo to biodegradable an even greater scope for versatile formulation is provided. The various parameters governing the design of controlled release implants are discussed.
Clotting Phenomena at the Blood‐Polymer Interface and Development of Blood Compatible Polymeric Surfaces
Authors: Bantjes Adriaan
Published: April 2007

In the past two decades many attempts have been made to relate surface and interfacial parameters with the blood compatibility of polymeric surfaces. It is however doubtful if by a single parameter the behaviour of blood on a surface can be predicted. Two major aspects of blood compatibility—the prevention of platelet adhesion and the deactivation of the intrinsic coagulation system are determined by the measure and nature of competitive blood protein adsorption on the foreign surface. The adhesion of blood platelets is promoted by adsorbed fibrinogen and gamma globulin, while adsorbed albumin inhibits platelet adhesion. Heparinised surfaces do not adsorb fibrin and consequently no adhesion of platelets takes place. Other surfaces with low platelet adhesion are the hydrogels, certain block copolyetherurethanes, polyelectrolyte complexes and biolised proteins. Heparinised surfaces of the cationically bonded type inhibit the intrinsic coagulation as well, however this may be due to unstable coatings and heparin leakage.

In the authors laboratory a synthetic heparinoid was prepared with the structure ‐ [CH2 ‐ C(CH3 NHSO3 Na ‐ C(H) COONa ‐ CH2 ‐] x̄ with M̄w = (7.5 /pm 1.0) × 105 and an in vivo anticoagulant activity of 50% of heparin. Its coatings on PVC, using tridodecylmethyl‐ammonium chloride as a coupling agent, are stable in plasma and salt solutions and provide surfaces which show negligible platelet adhesion and a strong inhibition of the intrinsic coagulation on contact with blood. Similar results were found with polydimethylsiloxane surfaces coated with this heparinoid.
Crystallinity in EPDM terpolymers
Authors: Gilbert Marianne , Briggs James E. , Omana Wilberto
Published: April 2007

The crystallinity of a series of ‘medium‐high’ green strength EPDM terpolymers has been examined by X‐ray diffraction and thermal analysis. It has been found that the crystallinity of such materials can vary from 0.20% as measured by thermal analysis, and depends on the E:P ratio in the polymer. It is also suggested that it depends on the distribution of E and P units. An explanation for the differing results obtained by thermal analysis and X‐ray diffraction has been proposed. The time taken to achieve maximum crystallinity varied for the series of polymers examined, and the improvement of crystallites continued over extensive periods of time. The final level of crystallinity in the polymers and the rate of changes occurring was temperature dependent. For one sampel (‘Nordel’ 1560) it was shown that crystallinity affected mechanical properties.
Synthesis of some new polyers and copolymers from 2,2‐bis (4‐chlorophenyl) 1, 1, 1‐trichloro ethane (DDT)
Authors: Adam Georgius A. , Husein N. A.
Published: April 2007

DDT (I) was polycondensed with 2,2‐bis(4‐hydroxy phenyl)‐ propane (bisphenol‐A) to form polyether. The following monomers were synthesised from DDT: 2,2‐bis(4‐chloro‐phenyl)1, 1‐dichloroethylene(II), 2,2‐bis(3‐nitro‐4‐chlorophenyl)ethane (III) and 2,2‐bis (3‐nitro‐4‐chloro‐phenylethylene (IV) and polycondensed with bisphenol‐A. They were also copolymerised with bis(4‐chlorophenyl)sulphone and bisphenol‐A in several molar ratios. The polymers and copolymers were characterised by various techniques. The results obtained show that the DDT has a low reactivity, but nitration and dehydrochlorin‐ation increases its reactivity to a significant extent.
Design of polymers for migration imaging application II: Synthesis and polymerisation of p‐isobutyl styrene
Authors: Buckley David A. , Augostini Peter P. , Belli Frank G.
Published: April 2007

A copolymer series was synthesized for migration imaging applications from isobutyl methacrylate and isobutyl styrene such that each homopolymer and all copolymers had glass transition temperature (Tg) near 55°C. The Tg of poly (p‐isobutylstyrene) was predicted from literature values of similar polymers to be near 55°C. Poly (p‐isobutylstyrene) was synthesised by acetylation of isobutyl benzene, reduction of p‐isobutylacetoph‐enone to the carbinol, dehydration to p‐isobutylstyrene and free radical polymerisation to the polymer. The Tg of the homopolymer was 55°C, in excellent agreement with the predicted value. Copolymers of isobutyl methacrylate and p‐isobutyl styrene were synthesised and their Tg's measured across the series by DSC (57°C ± 5°C). refractive index temperature coefficient (42°C ± 5°C). The copolymer series was also characterised by melt viscosity measurements.
Mineral sources of polyorganosiloxane materials
Authors: Atwal Rajinder S. , Bicknell Stanley , Cook Colin B. , Currell Brian R. , Midgley Henry G. , Mooney Anthony J. , Parsonage John R.
Published: April 2007

The trimethylsilylation of biotite and phlogopite gives good yields of polyorganosiloxanes. Al3+ ions have an important influence on the fragmentation of the mineral structure into silicate anions prior to trimethylsilylation.

The authors have shown by using wet analytical techniques as well as X‐ray diffraction and electron probe microanalysis that biotite and phlogopite retain aluminium in preference to magnesium during the course of extensive trimethylsilylation reactions. The labile nature of the >Al‐O‐Si<‐ bonds, and the size of the AI3+ ion which allows exchange between the octahedral and tetrahedral mineral sites, contribute to the good yields of polyorganosiloxanes which can be produced by this method. The mechanism for the reaction is presented. Yields may be increased by decreasing the particle size of the mineral and also by removing polyorganosiloxanes from the mineral surface.
The mechanical properties of some filled polymer cements
Authors: Carrillo Jorge , Hodd K A
Published: April 2007

The tensile and compressive strengths and the elastic moduli of sand and asbestos filled polymer cements, based on the aluminosilicate/poly(acrylic acid) (ASPA) system, have been measured. A progressive decline in property with increasing volume fraction of filler (in the range 5 to 12%) was observed. The decline is interpreted in terms of dilution, lack of matrix‐filler interaction and void content.
Synthesis, structure and properties of liquid crystalline polymers
Authors: Ringsdorf Helmut , Schneller Arnold
Published: April 2007

The following is an extended abstract of a paper presented at the conference on Liquid Crystalline Polymers in Leeds, 1980, summarising the principles of the synthesis of thermotropic liquid crystalline polymers, their structure dependant phase behaviour and their orientation in electric and magnetic fields.
The hydration of a glass‐ionomer (ASPA) cement
Authors: Wilson Alan D. , Crisp Stephen , Paddon John M.
Published: April 2007

The hydration of chemical species formed in the cement‐forming reaction has been studied by measuring the evaporable, and non‐evaporable water contents of a glassionomer cement at various stages in its history. Hydration is accompanied by increase in strength and, as loose water is removed from the matrix, a decrease in plasticity. Hydration is attributed to ionisation of the polymeric carboxylic acid and transfer of metal ions from the glass to the polyelectrolyte.
Applications of Xanthan gum
Authors: Sanderson George R.
Published: April 2007

Xanthan gum, the extracellular polysaccharide from Xanthomonas comperstris, provides aqueous solutions with properties that are extremely useful in a large number of industrial applications, both food and non‐food. These properties, a consequence of xanthan gum's particular molecular shape, are: high at‐rest or low‐shear viscosity even at low gum concentrations, yield value, high pseudoplasticity, increased viscosity in the presence of added salt depending on gum concentration, stable viscosity over a wide range of temperature and pH in the presence of added salt, synergistic increase in viscosity in the presence of guar gum and locust bean gum, thermoreversible gelation with locust bean gum at appropriate gum concentratins, and gelation with di‐and trivalent metal ions and borates under specific conditions. Xanthan gum is thus an excellent stabiliser for a wide variety of suspensions, emulsions, and foams and is highly effective over a range of temperature, pH and ionic strength. In addition, its pseudoplasticity allows the formulation of products which require not only high at‐rest viscosity but also low viscosity under highshear application conditions.
A microfiltration technique for cleaning polymer latices
Authors: Wilkinson M. C. , Hearn J. , Cope P. , Chainey M.
Published: April 2007

A microfiltration technique for cleaning polymer latices is evaluated. The modified millipore microfiltration cell employed is described and optimum operating conditions given: the cell consists of a 47 mm diameter millipore filter supported on a stainless steel mesh and contained within a PTFE body. Double distilled water is pumped through the cell, removing impurities from the latex. The latex particles are retained by the filter: pore blockage is prevented by PTFE coated magnetic stirrer bar. The nature and location (water or polymer phases) of the major impurities encountered with polystyrene latices are identified. The efficiency with which microfiltration removes these impurities is compared with dialysis and ion exchange. Monomer, low molecular weight oligomer, benzaldehyde, and surface active agent are completely removed. However, electrolytic material associated with the polymer phase is not completely removed by this technique. Microfiltration may also be used to concentrate a latex and separate latex particles of different sizes.
Radiation induced ionic polymerisation and grafting of vinyl monomers
Authors: Stannett Vivian T.
Published: April 2007

Some special aspects of the radiation induced ionic polymerisation and grafting of vinyl monomers will be described. In particular the effects of solvents on the cationic polymerisation of the vinyl ethers will be discussed in detail. The unequivocal free ion nature of the polymerisation makes such information of considerable general interest. Estimates of the propagation rate constants with free cation polymerisation in solvents of different dietectric constants and solvation powers will be presented. Finally, some observations on the radiation induced graft polymerisation of ethyl vinyl ether to poly (vinyl chloride) and to polypropylene will be presented.
Use of functionalised silica in catalysis and organic synthesis
Authors: Akelah Ahmed
Published: April 2007

Uses of silica in the immobilisation of enzymes and functionalized reagents for resolution of racemic mixtures and synthesis of peptides, oligonucleotide and other compounds are discussed. Silica is superior over organic polymers in its high chemical stability, and being virtually nonswellable. This inhibits the influence of the solvent on physical and chemical behaviour of attached moeties and permits automisation of batch processes.
Preparation of polyphosphonates
Authors: Currell Brian R. , Grzeskowiak Roman , Lynn Michael E.
Published: April 2007

Polyphenylphosphonates have been prepared by (i) the elimination of hydrogen chloride from mixtures of PhPOCl2 and PhPO(OH)2, (ii) the elimination of methyl chloride from PhPOCl2 and PhPO(OMe)2, and (iii) the elimation of methanol from PhPO(OMe)2 and PhPO(OH)2. Products have been characterised by elemental analyses, gel permeation chromatography, molecular weight measurement and infrared spectroscopy. In each case mixtures of rings and chains were obtained. Polyphosphonates were also obtained by the elimination of hydrogen chloride from mixtures of MePOCl2 and MePO(OH)2 and from mixtures of PhOCl2 and MePO(OH)2.
Preparations and properties of phenanthrene ‐ formaldehyde resins
Authors: Herbert Lesley D. , Robinson J. Gordon , Marr George
Published: April 2007

Phenanthrene was treated with formaldehyde in the presence of sulphuric acid and the yields of resin obtained were dependent on the acid concentration and on the molar ration of formaldehyde to phenanthrene. All of the resins were composed of dimers, trimers, tetramers and higher oligomers. The bridges joining the phenanthryl units were mainly methylene when formaldehyde was in molar deficit relative to phenathrene, but dimethylene ether and acetal bridges were present when the formaldehyde was in molar excess.
[5‐(p‐alkoxy)phenyl‐10, 15, 20‐tri‐phenyl] porphyrin and their rare earth complex liquid crystalline
Authors: Yu Miao , Zhang Wen‐yang , Fan Yong , Jian Wen‐ping , Liu Guo‐fa
Published: April 2007

Three series of porphyrin liquid crystalline compounds, [5‐(p‐alkoxy)phenyl‐10, 15, 20‐tri‐phenyl] porphyrin and their rare earth complexes (Tb (III), Dy (III), Er (III), Yb (III)), with a hexagonal columnar discotic columnar(Colh) phase have been synthesized. These compounds were characterized by elemental analysis, molar conductances, UV‐visible spectra, infrared spectra, luminescence spectra, and cyclic voltammetry. These compounds exhibit more than one mesophases, which transition points of temperature change from −33.6 to 16.0 °C, and transition points of temperature for isotropic liquid also increase from 4.9 to 38.2 °C, with increasing chain length. Their surface photovoltage (SPV) response have also been investigated by the means of surface photovoltage spectroscopy (SPS) and field‐induced surface photovoltage spectroscopy (EFISPS). It was found that their SPV bands are analogous with the UV‐visible absorption spectra and derived from the same transition. Copyright © 2007 John Wiley & Sons, Ltd.
Structural and electrical properties of crystals of substituted polyaniline
Authors: Seshadri Devender T. , Bhat Narendra V.
Published: April 2007

The simultaneous polymerization and crystallization of aniline has been reported earlier. In this article, the X‐ray crystal structure analysis, SEM morphological analysis and electrical properties of such crystals of oligo‐polyanilines are being reported. The structural analysis shows a pseudo‐orthorhombic lattice. The SEM images reveal flaky and triangular growth habit with granular overgrowths on the surface. The bulk conductivities achieved vary from 10−5 S/cm to 10−7 S/cm as the oxidant concentration is reduced from 5 to 0.1%. The temperature dependence showed a transition point upto which there is a decrease in current and above which the current increases. The ESR studies reveal polarons involved in charge conduction and their concentration is proportional to the oxidant concentration. The X‐ray patterns, conductivities, and ESR results have been correlated with the degree of polymerization results obtained from GPC studies. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1127–1137, 2007
Preparation and properties of ZnO and devices
Authors: Izyumskaya N. , Avrutin V. , Özgür Ü. , Alivov Y. I. , Morkoç H.
Published: April 2007

ZnO has gained interest in part because of its large exciton binding energy (60 meV), good for lasing with low threshold. The renewed interest in ZnO is fuelled by availability of high quality substrates, reports of p‐type conductivity, and ferromagnetic behavior when doped with transitions metals. The field is also fuelled by theoretical predictions and perhaps experimental confirmation of ferromagnetism at room temperature for potential spintronics applications. Despite great strides there are still many challenges, the chief among them is the attainment of reproducibly low resistivity p‐type ZnO. While ZnO already has many industrial applications owing to its piezoelectric properties and bandgap in the near UV, its applications to optoelectronic devices utilizing electrical injection has not yet been put to practice mainly due to the lack of p‐type epitaxial layers. This review provides a discussion of some of the growth issues of ZnO‐based epitaxial and heteroepitaxial layers and their use in a variety of devices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cathodoluminescence of single ZnO nanorod heterostructures
Authors: Piechal Bernard , Yoo Jinkyoung , Elshaer Abdelhamid , Mofor Augustine Che , Yi Gyu‐Chul , Bakin Andrey , Waag Andreas , Donatini Fabrice , Dang Le Si
Published: April 2007

Optical properties of ZnO‐based single nanorods are probed by cathodoluminescence (CL) measurements at T = 5 K. We observe a variation of the ZnO near band edge CL by three orders of magnitude along the nanorod axis, accompanied by a spectral blueshift of 10–30 meV. This indicates a rather poor structural quality of the nanorod bottom part, close to the substrate. ZnO/ZnMgO quantum wells grown on top of ZnO nanorods are found to exhibit much stronger confinement effects as compared to their two‐dimensional counterparts, suggesting a reduced spontaneous and piezoelectric polarization effects. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Gas family of proteins of Saccharomyces cerevisiae: characterization and evolutionary analysis
Authors: Ragni Enrico , Fontaine Thierry , Gissi Carmela , Latgè Jean Paul , Popolo Laura
Published: April 2007

The GAS multigene family of Saccharomyces cerevisiae is constituted by five genes (GAS1–GAS5), but GAS1 was the only one to have been characterized to date. Gas1 is a glycosylphosphatidylinositol‐anchored protein predominantly localized in the plasma membrane and is also a representative of family GH72 of glycosidase/transglycosidases, a wide group of yeast and fungal enzymes involved in cell wall assembly. Gas1–Gas5 proteins share a common N‐terminal domain but exhibit different C‐terminal extensions, in which a domain named Cys‐Box is located. This domain is similar to the carbohydrate binding module 43 and is present only in Gas1p and Gas2p. Here we report the expression in P. pastoris of soluble forms of Gas proteins. Gas1, 2, 4 and 5 proteins were secreted with a yield of about 30‐40 mg/l of medium, whereas the yield for Gas3p was about three times lower. Gas proteins proved to be N‐glycosylated. Purified Gas proteins were tested for enzymatic activity. Gas2, Gas4 and Gas5p showed a β‐(1,3)‐glucanosyltransferase activity similar to Gas1p. A phylogenetic tree of the N‐terminal regions of family GH72 members was constructed. Two subfamilies of N‐terminal regions were distinguished: one subfamily, GH72+, contains proteins that possess a Cys‐box in the C‐terminal region, whereas family GH72− comprises proteins that lack a Cys‐box. On the basis of this net distinction, we speculate that the type of C‐tail region imposed constraints to the evolution of the N‐terminal portion. Copyright © 2007 John Wiley & Sons, Ltd.