bluuebunny/crossref_metadata_2025 huggingface dataset:
Three‐dimensional stochastic finite element method for elasto‐plastic bodies
Authors: Anders Maciej , Hori Muneo
Published: August 2002

A new stochastic finite element method (SFEM) is formulated for three‐dimensional softening elasto‐plastic bodies with random material properties. The method is based on the Karhunen–Loeve and polynomial chaos expansions, and able to efficiently estimate complete probabilistic characteristics of the response, such as moments or PDFs. To reduce the computational complexity in the three‐dimensional setting, two alterations are made with respect to the two‐dimensional SFEM proposed earlier by the authors. First, a variability preserving modification of the Karhunen–Loeve expansion is rigorously derived and applied in the stochastic discretization of random fields representing material properties. Second, an efficient algorithm for parallel processing is developed, with time consumption being the same order as for an ordinary FEM, rendering the proposed SFEM an effective alternative to Monte‐Carlo simulation. The applicability of the proposed method to stochastic analysis of strain localization is examined using Monte‐Carlo simulation. Then, it is applied to a fault formation problem which is a recent concern of earthquake engineering. Ground surface layers are modelled by a softening elasto‐plastic body, and the evolution of probabilistic characteristics of the rupture process is analysed in detail. Some practical observations are made regarding the nature of the fault formation from the stochastic viewpoint. Copyright © 2001 John Wiley & Sons, Ltd.
Random walk method for the two‐ and three‐dimensional Laplace, Poisson and Helmholtz's equations
Authors: Chati Mandar K. , Grigoriu Mircea D. , Kulkarni Salil S. , Mukherjee Subrata
Published: August 2002

The random walk method (RWM) is developed here for solving the Laplace, Poisson, and Helmholtz equations in two and three dimensions. The RWM is a local method, i.e. the solution at an arbitrary point can be determined without having to obtain the complete field solution. The method is based on the properties of diffusion processes, the Itô formula, the Dynkin formula, the Feynman–Kac functional, and Monte Carlo simulation. Simplicity, stability, accuracy, and generality are the main features of the proposed method. The RWK is inherently parallel and this fact has been fully exploited in this paper. Extensive numerical results have been presented in order to understand the various parameters involved in the method. Copyright © 2001 John Wiley & Sons, Ltd.
A monolithic smoothing‐gap algorithm for contact‐impact based on the signed distance function
Authors: Belytschko T. , Daniel W. J. T. , Ventura G.
Published: August 2002

A new algorithm has been developed for smoothing the surfaces in finite element formulations of contact‐impact. A key feature of this method is that the smoothing is done implicitly by constructing smooth signed distance functions for the bodies. These functions are then employed for the computation of the gap and other variables needed for implementation of contact‐impact. The smoothed signed distance functions are constructed by a moving least‐squares approximation with a polynomial basis. Results show that when nodes are placed on a surface, the surface can be reproduced with an error of about one per cent or less with either a quadratic or a linear basis. With a quadratic basis, the method exactly reproduces a circle or a sphere even for coarse meshes. Results are presented for contact problems involving the contact of circular bodies. Copyright © 2002 John Wiley & Sons, Ltd.
How Quality Award‐Winning Governments Handle Customer Service
Authors: Kline James J.
Published: August 2002

Recognizing that customer service is becoming an increasingly important function of government, quality award‐winning governments, at all levels and around the world, are not only seeking customer feedback, but are incorporating customer satisfaction measures into their strategic plans. Thus, they are setting customer standards that are evaluated regularly, benchmarking customer service procedures against the best in business, and including customer service training, benchmarking, and customer satisfaction performance measures in labor contracts. This article, which examined the customer service practices of quality award‐winning governments at the federal, state, and local level in the United Kingdom, United States, and Australia, demonstrates the worldwide nature of the quality improvement and customer satisfaction effort. © 2001 John Wiley & Sons, Inc.
Galectin‐3 is differentially expressed during peripheral nerve development: Dependence on the Schwann cell phenotype
Authors: Pesheva Penka , Nellen Joerg , Biersack Hans‐Juergen , Probstmeier Ranier
Published: August 2002

Whereas the animal lectin galectin‐3 is only barely detectable in the adult sciatic nerve, its expression level is substantially upregulated in the damaged nerve (1). In the present study, we demonstrate that in the mouse, the expression of galectin‐3 increases during normal peripheral nerve development and is further potentiated in the adult sciatic nerve under conditions of in vitro degeneration. In cell cultures derived from neonatal sciatic nerve galectin‐3 is expressed by about 50% of L1‐positive Schwann cells. Comparable results were obtained for cultured late immature Schwann cells derived from hindlimbs of 17.5‐day‐old mouse embryos. In cell cultures derived from hindlimbs of 14‐day‐old embryos, by contrast, only about 5% of the L1‐positive early immature Schwann cells expressed galectin‐3. Our findings demonstrate that the upregulation of galectin‐3 expression by activated adult Schwann cells is not a part of a dedifferentiation program, but rather attributes to a phenotype specific for injury‐activated Schwann cells.
Extension of high‐order compact schemes to time‐dependent problems
Authors: Spotz W. F. , Carey G. F.
Published: August 2002

In this article, we present an extension of our previous approaches for steady‐state higher‐order compact (HOC) difference methods to time‐dependent problems. The formulation also provides a framework for similar treatment of other HOC spatial schemes. A stability analysis is provided for transient convection‐diffusion in 1D and transient diffusion in 2D. Supporting numerical experiments are included to illustrate stability and accuracy as well as oscillatory and dissipative behavior. © 2001 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 17: 657–672, 2001
Solomon Islands: blending traditional power and modern structures in the state
Authors: Turnbull Jane
Published: August 2002

By mid‐2001, the Solomon Islands government was on the edge of bankruptcy after two years of unrest on Guadalcanal. Solomon Islanders' hopes that the national government can improve their living standards have been dashed, only 23 years after British colonial rule ended on these South‐West Pacific islands. The reasons for the state's limited capacity to facilitate development extend much further than the financial crisis, as a comparison between power relations typically institutionalized in Western liberal democratic states and those institutionalized in the Solomons state shows. The Solomons state is a syncretism of traditional political practices and modern structures. Many of these traditional practices are impeding development. Recent neo‐liberal reforms championed by the previous government, the Asian Development Bank and other aid agencies did little to address these practices and were terminated in the unrest in 2000. If the state is to improve the living standards of ordinary Solomon Islanders, changes in structure, such as the state governments being established following the Townsville Peace Agreement, are not the sole answer. There also need to be changes in the political practices of both officials and politicians at national and local level. Copyright © 2002 John Wiley & Sons, Ltd.
What determines the value of life? a meta‐analysis
Authors: Mrozek Janusz R. , Taylor Laura O.
Published: August 2002

A large literature has developed in which labor market contracts are used to estimate the value of a
statistical life (VSL). Reported estimates of the VSL vary substantially, from less than $100,000
to more than $25 million. This research uses meta‐analysis to quantitatively assess the VSL
literature. Results from existing studies are pooled to identify the systematic relationships between VSL
estimates and each study's particular features, such as the sample composition and research methods. This
meta‐analysis suggests that a VSL range of approximately $1.5 million to $2.5 million
(in 1998 dollars) is what can be reasonably inferred from past labor‐market studies when
“best practice” assumptions are invoked. This range is considerably below many previous qualitative
reviews of this literature. © 2002 by the Association for Public Policy Analysis and Management.
Chemical and electrochemical synthesis of homopolymer and copolymers of 3‐methoxyethoxythiophene with aniline, thiophene and pyrrole for studies of their gas and vapour sensing
Authors: Hosseini S. Hossein , Entezami Ali A.
Published: August 2002

Herein we report chemical and electrochemical formation of poly(3‐methoxyethoxythiophene) and its copolymers with aniline, thiophene and pyrrole which give highly conducting polymeric materials. These are soluble in common organic solvents in the conducting state. The response mechanism of these compounds, to a selection of gases and vapours, was investigated using two techniques: measurement of conductance and mass changes using a four probe method and X‐ray fluorescence (XRF) device, respectively. Prepared films were exposed to hydrogen halides, hydrogen cyanide, halogens, monochloroacetic acid (MCAA), 1‐3‐5 trichloromethylbenzene (TCMB), methylbenzyl bromide (MBB), bromoacetone (BA) and cyanogen bromide (CB). These gas sensors may have advantages compared to other sensors in their ability to operate at room temperature, low concentration, stability in air, sufficient diffusion and their selectivity. Copyright © 2001 John Wiley & Sons, Ltd.
Polymerization of anilinium–DBSA in the presence of clay particles: kinetics and formation of core‐shell structures
Authors: Jia W. , Segal E. , Narkis M. , Siegmann A.
Published: August 2002

This paper is an extension of previous work on polymerization of anilinium–DBSA (dodecylbenzenesulfonic acid) in an aqueous dispersion in the presence of mica or talc silicate particles. The presence of mica or talc particles greatly accelerates the polymerization process of anilinium‐DBSA and an encapsulated structure is formed as well. The catalytic effect of various metallic cations which exist in the chemical compositions of mica or talc on the polymerization kinetics of anilinium‐DBSA was investigated. The conductivity results along with microscopy observations prove a well formed encapsulated structure for the polyaniline/mica composites, but less for the polyaniline/talc composites. The anilinium‐DBSA complex and mica aqueous dispersions pretreated at different temperatures prior to polymerization have shown a significant effect on the polymerization rate of anilinium‐DBSA. The higher the dispersion temperature, the higher is the polymerization rate found. Copyright © 2001 John Wiley & Sons, Ltd.
Protecting polymers in suspension of metal nanoparticles
Authors: Hirai Hidefumi , Yakura Noboru
Published: August 2002

Poly(N‐vinyl‐2‐pyrrolidone) (PVP) was chosen as a protecting polymer for its large protective value among homopolymers. Suspensions of palladium (Pd) nanoparticles were prepared by refluxing solutions of palladium(II) chloride and PVP in methanol. The mean diameter of Pd nanoparticles without adsorbed layer of PVP was controlled in the range 1.1–2.5 nm. The concentration of free PVP in the methanol suspension was determined by using aminoethylated poly(acrylamide) gel beads which adsorbed selectively the PVP‐protected Pd nanoparticles. The amount of PVP adsorbed on Pd nanoparticles increased linearly with the 0.45 power of weight‐averaged molecular weight (Mw) of PVP. The thickness of adsorbed layer of PVP was estimated from the sedimentation coefficient of the PVP‐protected Pd nanoparticles. The adsorbed layer thickness increased linearly with the 0.55 power of Mw of PVP. The radius gyration of free PVP in methanol increased linearly also with the 0.55 power of Mw of PVP. The catalytic activity of the suspension of Pd nanoparticles was determined in the hydrogenation of 1,3‐cyclooctadiene. The activity depended more effectively on the specific surface area of Pd nanoparticles than the adsorbed layer thickness. On the basis of these results, the conformation of protecting PVP molecule on the surface of Pd nanoparticles was proposed. Copyright © 2001 John Wiley & Sons, Ltd.
NG2/HMPG modulation of human articular chondrocyte adhesion to type VI collagen is lost in osteoarthritis
Authors: Midwood Kim S. , Salter Donald M.
Published: August 2002

NG2/human melanoma proteoglycan (HMPG) is a chondroitin sulphate proteoglycan (CSPG), expressed by chondrocytes in fetal and in normal and osteoarthritic (OA) adult articular cartilage. NG2/HMPG is a receptor for extracellular matrix proteins, including type VI collagen, and regulates β1 integrin binding to fibronectin. This study was undertaken to identify whether NG2/HMPG had similar activities in human articular chondrocytes (HACs). Normal and OA adult HAC adhesion to fibronectin, type II or type VI collagen was assessed using a methylene blue assay. The requirement for integrins, NG2/HMPG, and integrin‐associated signalling molecules was investigated using anti‐β1 integrin and anti‐HMPG antibodies and pharmacological inhibitors of signalling molecules. The adhesion of normal and OA HACs to fibronectin, type II and type VI collagen was β1 integrin‐dependent. Normal HAC adhesion to type VI collagen was stimulated by anti‐HMPG antibodies. This effect was inhibited by pertussis toxin. Anti‐HMPG antibodies had no effect on OA chondrocyte adhesion to type VI collagen, or on normal and OA cell adhesion to fibronectin and type II collagen. The results show that NG2/HMPG modulates integrin‐mediated interactions of normal HACs with type VI collagen. Loss of this activity may be of importance in the progression of osteoarthritis. Copyright © 2001 John Wiley & Sons, Ltd.
Barley polyamine oxidase: characterisation and analysis of the cofactor and the N‐terminal amino acid sequence
Authors: Radová Anna , Šebela Marek , Galuszka Petr , Frébort Ivo , Jacobsen Susanne , Faulhammer Heinz G. , Peč Pavel
Published: August 2002

This paper reports the first purification method developed for the isolation of an homogeneous polyamine oxidase (PAO) from etiolated barley seedlings. The crude enzyme preparation was obtained after initial precipitation of the extract with protamine sulphate and ammonium sulphate. The enzyme was further purified to a final homogeneity (by the criteria of isoelectric focusing and SDS–PAGE) using techniques of low pressure chromatography followed by two FPLC steps. The purified yellow enzyme showed visible absorption maxima of a flavoprotein at 380 and 450 nm: the presence of FAD as the cofactor was further confirmed by measuring the fluorescence spectra. Barley PAO is an acidic protein (pI 5.4) containing 3% of neutral sugars: its molecular mass determined by SDS–PAGE was 56 kDa, whilst gel permeation chromatography revealed the higher value of 76 kDa. The N‐terminal amino acid sequence of barley PAO shows a high degree of similarity to that of maize PAO and to several other flavoprotein oxidases. The polyamines spermine and spermidine were the only two substrates of the enzyme with Km values 4 × 10−5 and 3 × 10−5 M and pH optima of 5.0 and 6.0, respectively. Barley polyamine oxidase is markedly inhibited by acridine dyes and hydrazines. Weak inhibition was observed with substrate analogues, aminoaldehydes, metal chelating agents and several other compounds. Copyright © 2001 John Wiley & Sons, Ltd.
Studies towards the detection and identification of sesquiterpene pyridine alkaloids in Peritassa campestris by mass spectrometry
Authors: Rodrigues‐Fo Edson , Barros Fábio A. P. , Fernandes João B. , Silva M. Fátima das G. F. da
Published: August 2002

Sesquiterpene pyridine alkaloids were analysed in Peritassa campestris by mass spectrometric techniques such as ESI‐MSMS and GCMS. Ten alkaloids previously isolated from this plant and fully identified by other physical methods, including NMR spectroscopy and X‐ray diffraction, were carefully studied by MS. It was observed that the low mass ions detected at m/z 178 and 206 in both MS techniques tested were characteristic of evoninic and wilfordic acids, which are part of the macrolactone in these sesquiterpene alkaloids. The intensity of a fragment ion detected at m/z 93 in CAD, and especially in EI, spectra was found to be diagnostic in distinguishing between evoninoates and wilfordates. Running parent/daughter or GCMS experiments enabled these substances to be detected in crude fractions of P. campestris. Parent ion scans of m/z 206 were very as a first analysis of an alkaloid mixture. Copyright © 2001 John Wiley & Sons, Ltd.
Mitochondrial DNA depletion presenting prenatally with skin edema and multisystem disease immediately after birth
Authors: Arnon Shmuel , Aviram Rami , Dolfin Tzipora , Regev Rivka , Litmanovits Ita , Tepper Ronnie , Elpeleg Orly N.
Published: August 2002

We describe two newborn sisters who presented in the third trimester with diminished fetal movements and skin edema, but with no other signs of hydrops fetalis. Within hours of birth, both developed profound lactic acidemia, followed by multi‐organ failure. In muscle mitochondria, the activity of all enzymatic complexes that contain mitochondrial DNA (mtDNA)‐encoded subunits was markedly decreased. Southern blot analysis revealed a profound reduction in the mtDNA/nuclear DNA ratio, implying mtDNA depletion. The prenatal identification of skin edema in two patients with mtDNA depletion, and its absence in a healthy sibling, suggest that skin edema should be regarded as a novel manifestation of mtDNA depletion. This finding shows that mtDNA depletion can present prenatally and, consequently, may aid the clinician in making a diagnosis, prenatally, of this genetic defect. Copyright © 2002 John Wiley & Sons, Ltd.
Greenberg dysplasia: first reported case with additional non‐skeletal malformations and without consanguinity
Authors: Horn L.‐C. , Faber R. , Meiner Annchristin , Piskazeck U. , Spranger J.
Published: August 2002

The original article to which this Erratum refers was published in Prenatal Diagnosis 20(12) 2000, 1008–1011.
Clinical characteristics of patients with diabetic foot problems: changing patterns of foot ulcer presentation
Authors: Oyibo S. O. , Jude E. B. , Voyatzoglou D. , Boulton A. J. M.
Published: August 2002

Aims

Patients with diabetic foot complications vary demographically and invariably have other co‐morbidities that affect quality of life. The aim of this study was to identify some clinical characteristics of such patients and to reveal any changes over the recent decades.

Methods

Case notes of patients referred to the Manchester Diabetic Foot Clinic during a 7 year period were examined. Patient demographics, referral source and reason for referral, previous amputations, and diabetes complications at presentation were recorded.

Results

298 patients (185 males) newly attended the foot clinic during the 7 year period (1990–1996). Mean ± SD age and duration of diabetes was 62.5 ± 13.1 and 14.9 ± 11.6 years, respectively. Most patients (73.3%) had type 2 diabetes and 86.7% attended because of foot ulceration. Ulcers were mainly neuroischaemic (52.3%) and located on the forefoot (76.7%). Eighty per cent of patients had clinical evidence of peripheral neuropathy, 60% had peripheral arterial disease (only a third of whom were symptomatic) and 70% had multiple diabetic complications. Hypertension (48.1% versus 32.1%, p = 0.007) and previous amputation (15.2% versus 5.4%, p = 0.01) were commoner in males. Females had a greater prevalence of multiple foot ulcers (21.5% versus 12.7%, p = 0.03), compared with males.

Conclusion

Patients with diabetic foot ulcers have multiple diabetic complications and tend to have predominantly neuroischaemic ulcers. These clinical characteristics are bound to have significant impact on treatment costs and mortality in such patients. Copyright © 2002 John Wiley & Sons, Ltd.
Non‐steroidal anti‐inflammatory drug prescribing patterns in general practice: comparison of a general practitioner‐based survey and a pharmacy‐based survey in France
Authors: Clinard François , Sgro Catherine , Bardou Marc , Dumas Monique , Hillon Patrick , Bonithon‐Kopp Claire
Published: August 2002

Purpose

In order to assess biases occurring in primary care prescription studies, we compared non‐steroidal anti‐inflammatory drug (NSAID) prescribing patterns reported by general practitioners directly (GP‐based survey) and from a pharmacy‐based survey of general practitioner prescribing (pharmacy‐based survey).

Methods

Volunteer GPs of the administrative area of Côte d'Or (France) returned a mailed questionnaire on NSAID prescribing patterns for consecutive patients seen during a 2‐month period. In order to obtain a reference basis, pharmacies of the same administrative area provided all prescriptions that included NSAIDs during a 1‐week period originating in general practice.

Results

The rate of participation was 25% for the GPs and 40% for the pharmacies. Participant GPs were representative of GPs of the area with regard to sex, year of graduation and practice area but pharmacies from rural areas were over‐represented. The GP‐based survey and the pharmacy‐based survey provided respectively 770 and 1050 prescriptions. There were no differences between either survey in the type of NSAIDs prescribed and in the most frequently associated drugs. GPs who volunteered in the GP survey prescribed NSAIDs more frequently orally and at higher doses than GPs involved in the pharmacy‐based survey. They also prescribed more gastroprotective drugs, especially in the elderly. None of these results could be explained by differences in patient characteristics and GP practice areas.

Conclusion

GPs who actively participate in prescription surveys exhibit prescribing patterns that fit better with official recommendations than the average. Although selection biases cannot be ruled out, it is suggested that some changes in GP prescription habits may have been induced by the survey itself. Copyright © 2001 John Wiley & Sons, Ltd.
Results of a postal survey of the reasons for non‐response by doctors in a Prescription Event Monitoring study of drug safety
Authors: Key Cheryl , Layton Deborah , Shakir Saad A. W.
Published: August 2002

Purpose

A Prescription Event Monitoring (PEM) study was carried out by the Drug Safety Research Unit (DSRU) to monitor the safety of irbesartan, an angiotensin II antagonist, immediately after launch in the United Kingdom in September 1997. The DSRU ‘green form’ questionnaire response rate was lower than expected. The manufacturer was conducting a concurrent postmarketing surveillance study. The aim of this cross‐sectional study, was to identify reasons for non‐response by general practitioners in England.

Methods

In PEM, questionnaires are posted to the prescribing general practitioner approximately 6 months after the date of the first prescription for each patient, requesting details of clinical events recorded in the patients' notes since starting treatment. Those that failed to respond were sent a second questionnaire, including tick box questions to elucidate reasons for non‐response.

Results

A total of 21.3% (3088/14502) second send forms were returned. There were 1747 tick box responses. The most common reason specified for non‐response was ‘I was too busy’ (31.2%) followed by ‘no payment included’ (13.4%). Participation in another study accounted for only 3.4%.

Conclusions

The concurrent postmarketing surveillance study was not a significant factor. The general practitioner's workload appeared to have a far larger impact. While research remains a non‐core activity and receives no payment, participation is likely to fall. Researchers need to find means of benefiting the general practitioner if participation is to continue. Copyright © 2002 John Wiley & Sons, Ltd.
Utilization pattern of metamizole in northern Sweden and risk estimates of agranulocytosis
Authors: Bäckström M. , Hägg S. , Mjörndal T. , Dahlqvist R.
Published: August 2002

Objective

This study was carried out in order to investigate the utilization pattern of metamizole to better estimate the quantitative risk of agranulocytosis since a cluster of such cases have been observed in Sweden.

Methods

Cases of agranulocytosis submitted to the Swedish Adverse Drug Reactions Advisory Committee (SADRAC) between 1996 and 1999 were identified. Based on the utilization pattern of metamizole in inpatients at three hospitals and in outpatients in two counties in northern Sweden risk estimates of agranulocytosis during metamizole treatment were estimated. The utilization of metamizole was investigated by scanning 3567 case records at 10 hospital departments as well as stored prescriptions at six pharmacies during a 3‐month study period.

Results

Ten cases of agranulocytosis during treatment with metamizole have been reported to SADRAC over the period 1996 to 1999. During the 3‐month study period metamizole was prescribed to 666 (19%) inpatients. Of these, approximately 96% received the drug for less than 1 week, 7.2% had used the drug previously. At the participating pharmacies 112 metamizole prescriptions for outpatients were found. The drug was prescribed in 34% for less than 1 week, in 28% for 7–15 days, and in 38% for more than 15 days. The mean prescribed daily dose was 2.7 g. Given certain assumptions including the actual amounts prescribed the calculated risks of agranulocytosis would be approximately one out of every 31 000 metamizole‐treated inpatients and one of every 1400 metamizole‐treated outpatients.

Conclusion

This study indicates that in most inpatients the use of metamizole in northern Sweden was within the approved indications for the drug. However, a considerable number of outpatients received the drug for a longer time than recommended and this may carry an increased risk for developing agranulocytosis. Copyright © 2002 John Wiley & Sons, Ltd.
Synthesis of polar vinyl monomer–olefin copolymers by α‐diimine nickel catalyst
Authors: Marques Maria M , Fernandes Susete , Correia Sandra G , Caroço Susana , Gomes Pedro T , Dias Alberto R , Mano João , Rausch Marvin D , Chien James C W
Published: August 2002

Vinyl acetate, methyl methacrylate, acrylonitrile and methyl vinyl ketone were investigated for co‐ and terpolymerization with ethylene and ethylene–propylene. Precursor [bis(N,N ′‐dimesitylimino)acenaphthene]dibromonickel, activated by methylaluminoxane was used as a catalyst system and trialkylaluminium was employed to block the polar groups for these polymerizations. Polymerization activities of the order of magnitude of 106 in the case of vinyl acetate and methyl methacrylate, and 105 in the case of acrylonitrile were achieved. Microanalysis and GPC of acrylonitrile copolymers found about 17 units of acrylonitrile per polymer chain. Copolymers with very different properties from the parent homopolymers were obtained in all cases except that of methyl vinyl ketone.

© 2001 Society of Chemical Industry
Preparation of polystyrene–graphite conducting nanocomposites via intercalation polymerization
Authors: Chen Guo‐Hua , Wu Da‐Jun , Weng Wen‐Gui , He Bin , Yan Wen‐li
Published: August 2002

In situ polymerization of styrene was conducted in the presence of expanded graphite obtained by rapid heating of a graphite intercalation compound (GIC), to form a polystyrene–expanded graphite conducting composite. The composite showed excellent electrically conducting properties even though the graphite content was much lower than in normal composites. The transition of the composite from an electrical insulator to an electrical semiconductor occurred when the graphite content was 1.8 wt%, which is much lower than that of conventional conducting polymer composites. TEM, SEM and other studies suggest that the graphite was dispersed in the form of nanosheets in a polymer matrix with a thickness of 10–30 nm, without modification of the space between carbon layers and the structure of the graphite crystallites. The composite exhibited high electrical conductivity of 10−2 S cm−1 when the graphite content was 2.8–3.0 wt%. This great improvement of conductivity could be attributed to the high aspect ratio (width‐to‐thickness) of the graphite nanosheets. The rolling process strongly affected the conductivity and the mechanical properties of the composite.

© 2001 Society of Chemical Industry
Cationic photopolymerization of polyfunctional 1‐propenyl ether systems
Authors: Sangermano Marco , Malucelli Giulio , Bongiovanni Roberta , Priola Aldo , Annby Ulf , Rehnberg Nicola
Published: August 2002

The cationic photopolymerization of trimethylolpropane tripropenyl ether (TPE), initiated by a diaryl iodonium salt, has been investigated. The influence of the presence of different alcoholic additives on the rates of photopolymerization and on the properties of the networks obtained has been studied. New 1‐propenyl ethers (trimethylolpropane dipropenyl ether (DPE) and its acetyl ester) were synthesized and employed as modifying agents in TPE photopolymerization. The thermal and dynamic‐mechanical properties of the films obtained have been investigated and are correlated with the structure of the networks and to the mechanism of the curing reaction; a microheterogeneous structure of the network was shown by dynamic‐mechanical thermal analysis.

© 2001 Society of Chemical Industry
Shape memory effect of poly(methylene‐1,3‐cyclopentane) and its copolymer with polyethylene
Authors: Jeong Han Mo , Song Ji Hun , Chi Ki Whan , Kim Il , Kim Ki Tae
Published: August 2002

Poly(methylene‐1,3‐cyclopentane) (PMCP) cyclopolymerized from 1,5‐hexadiene by metallocene catalyst, rac‐(ethylenebis(1‐indenyl))Zr(N(CH3)2)2 is partially crystalline and has a value of elongation at break of more than 400% in the temperature range 25–85 °C. The shape memory effect of PMCP with moderate molecular weight is enhanced by sequentially polymerized polyethylene segments, the crystalline phase of which seems to strengthen the fixed structure which memorizes the original shape. The glass transition temperature or melting temperature of PMCP can be selectively used as shape recovery temperature when an appropriate deformation temperature is chosen.

© 2002 Society of Chemical Industry
Effects of shear rate, viscosity ratio and liquid crystalline polymer content on morphological and mechanical properties of polycarbonate and LCP blends
Authors: Tan L P , Yue C Y , Tam K C , Lam Y C , Hu X
Published: August 2002

Studies were conducted on the effects of shear rate, viscosity ratio and liquid crystalline polymer (LCP) content on the morphological and mechanical properties of polycarbonate (PC) and LCP blends. The LCP (LC5000) used was a thermotropic liquid crystalline polymer consisting of 80/20 of parahydroxybenzoic acid and poly(ethylene terephthalate) (PHB/PET). The viscosity ratio (viscosity of LCP: viscosity of matrix) was varied by using two processing temperatures. Due to the different sensitivity of materials to temperature, variation in the processing temperature will lead to varying viscosity of the components in the blends. Based on this principle, the processing temperature could be manipulated to provide a favourable viscosity ratio of below unity for fibre formation. To study the effect of shear rate, the flow rate of the blend and the mould thickness were varied. The shear rate has a significant effect on the fibrillation of the LCP phase. The effect was more prominent when the viscosity ratio was low and the matrix viscosity was high. At 5 wt% LCP, fibrillation did not occur even at low viscosity ratios and high shear rates. It was also observed that the LCP content must be sufficiently high to allow coalescence of the dispersed phase for subsequent fibrillation to occur.

© 2002 Society of Chemical Industry
A metallic intermediate band high efficiency solar cell
Authors: Luque Antonio , Martí Antonio
Published: August 2002

The theory of a novel type of solar cell is presented that contains a base made of a semiconductor with a metal‐like intermediate band (IB). The behavior of the IB and of the entire cell is studied taking into account photon recycling, that is, the emission of luminescent photons that may be subsequently absorbed. The results show that, in ideal conditions, this device is more efficient than the best two‐junction series‐connected tandem cells. This advantage might be maintained for less ideal cases. Although the material needed to achieve this device is yet unknown, some hints are given in the paper concerning its synthesis. Copyright © 2001 John Wiley & Sons, Ltd.
Multiple band and impurity photovoltaic solar cells: General theory and comparison to tandem cells
Authors: Green Martin A.
Published: August 2002

One way to improve photovoltaic solar energy performance is to absorb photons by processes involving multiple energy thresholds, such as in tandem cells, that employ multiple solar cells of different semiconductor bandgaps. Recently, another multiple threshold approach has been analysed based on a single bandgap cell with an intermediate impurity band. In the present work, the approach is extended to the N‐band cell, shown to be capable of higher performance than an N‐cell tandem. A generic approach to obtaining the selective photon absorption required for high efficiency is also described and the resulting insights applied to a new analysis of the impurity photovoltaic effect. Copyright © 2001 John Wiley & Sons, Ltd.
Ammonia recycling and cadmium confinement in chemical bath deposition of CdS thin layers
Authors: Malinowska B. , Rakib M. , Durand G.
Published: August 2002

Cadmium sulfide thin layers in polycrystalline solar cells are produced by chemical bath deposition (CBD). This process produces wastes containing ammonia and cadmium. These two chemicals must be recovered, and if possible recycled, from an environmental and economic point of view. A process has been implemented in order to recover ammonia and to confine cadmium. A new closed reactor has been designed and fabricated in order to trap ammonia vaporized during the deposition step. Ammonia is absorbed from the exhaust gas from the CBD reactor. The wastes are treated in an ex situ process which enables recovery of the major part of the large amounts of ammonia used in the process. Concentrated solutions of pure ammonia are obtained (more than 10 mol/l). In connection with this operation, all of the cadmium, except a very small amount, is precipitated, mainly as cadmium sulfide, owing to decomposition of the thiourea introduced in excess. Microfiltration with a glass‐fiber filter of about 0.7 μm cut‐off produces a filtrate of very low cadmium concentration (< 10 μg/l). Optimization of both pH and residual ammonia concentration should make it possible to lower this residual cadmium concentration. This effluent is the only waste product of the process. The filtration cake containing cadmium compounds may be stored in specialized landfills after standard treatment or, better, treated to recover and recycle the metal without generation of any other harmful effluent. Copyright © 2001 John Wiley & Sons, Ltd.
Long‐term stability of dye‐sensitised solar cells
Authors: Hinsch A. , Kroon J. M. , Kern R. , Uhlendorf I. , Holzbock J. , Meyer A. , Ferber J.
Published: August 2002

Accelerated ageing tests on large numbers of nanocrystalline dye‐sensitised solar cells (nc‐DSC) show that, to first order, separation between the effects of the stresses of visible light soaking, UV illumination and thermal treatment on long‐term stability is possible. The corresponding mechanisms are electrochemical, photochemical and purely chemical in nature. It was found that visible light soaking alone is not a dominant stress factor. A dramatic improvement in UV stability has been achieved by using MgI2 as additive to the electrolyte. Thermal stress appears to be one of the most critical factors determining the long‐term stability of nc‐DSC and is strongly related to the chemical composition of electrolyte solvents and additives. Encouraging stability results have been obtained for cells based on pure nitrile‐based solvents: (1) A minor decrease in performance of initially 5.5% solar efficient cells has been found after 2000 h at 60°C without light soaking; (2) After 900 h ageing at 85°C, a decrease of 30% in maximum power has been observed; (3) After 3400 h of combined thermal stress and continuous light soaking (45°C, 1 sun equivalent) good stability with 15% decrease in maximum power can be demonstrated. It should be noted that such good thermal stability has not been reported previously for dye‐sensitised solar cells so far. Copyright © 2001 John Wiley & Sons, Ltd.
Experimental evidence of parasitic shunting in silicon nitride rear surface passivated solar cells
Authors: Dauwe Stefan , Mittelstädt Lutz , Metz Axel , Hezel Rudolf
Published: August 2002

Many solar cells incorporating SiNxfilms as a rear surface passivation scheme have not reached the same high level of cell performance as solar cells incorporating high‐temperature‐grown silicon dioxide films as a rear surface passivation. In this paper, it is shown by direct comparison of solar cells incorporating the two rear surface passivation schemes, that the performance loss is mainly due to a lower short‐circuit current while the open‐circuit voltage is equally high. With a solar cell test structure that features a separation of the rear metal contacts from the passivating SiNxfilms, the loss in short‐circuit current can be reduced drastically. Besides a lower short‐ circuit current, dark I–V curves of SiNxrear surface passivated solar cells exhibit distinct shoulders. The results are explained by parasitic shunting of the induced floating junction (FJ) underneath the SiNxfilms with the rear metal contacts. The floating junction is caused by the high density of fixed positive charges in the SiNxfilms. Other two‐dimensional effects arising from the injection level dependent SRV of the Si/SiNxinterfaces are discussed as well, but, are found to be of minor importance. Pinholes in the SiNxfilms and optical effects due to a different internal rear surface reflectance can be excluded as a major cause for the performance loss of the SiNxrear surface passivated cells. Copyright © 2002 John Wiley & Sons, Ltd.
Linear solvation energy (LSE) correlations of the solvatochromic response and x‐ray structure analysis of hydrophilically N‐substituted Michler's ketone derivatives
Authors: El‐Sayed Mohamed , Müller Hardy , Rheinwald Gerd , Lang Heinrich , Spange Stefan
Published: August 2002

Bathochromic UV–Vis spectral shifts of two hydrophilically N‐substituted Michler's ketone derivatives, 4,4′‐bis[di(2‐hydroxyethyl)amino]benzophenone [MK(OH)4] (1) and 4‐(dimethylamino)‐4′‐[di(2‐hydroxyethyl)‐amino]benzophenone [MK(OH)2] (3), were measured in 28 solvents of different polarity. For MK(OH)4 and MK(OH)2 in non‐polar, dipolar aprotic and hydrogen‐bonding solvents, the solvatochromic responses of the two solutes conform exactly to the requirements of the Kamlet‐Taft linear solvation free energy model of solvent–solute interactions. The contribution of the hydrogen‐bond accepting property of the solvent on the bathochromic band shift of MK(OH)4 and MK(OH)2 increases with increasing number of their OH groups at the N‐substituent. The x‐ray crystallographic analysis for MK(OH)2 reveals the presence of strong intermolecular hydrogen bonds between the carbonyl oxygen atom and the 2‐hydroxyethyl group, which plays a significant role in the colour of the crystals. Copyright © 2001 John Wiley & Sons, Ltd.
Complexation of dicarboxylates and phosphates by a semisynthetic alkaloid‐based cyclophane in water
Authors: Lara Karen Ochoa , Godoy‐Alcántar Carolina , Rivera Ismael León , Eliseev Alexey V. , Yatsimirsky Anatoly K.
Published: August 2002

Dicationic N,N′‐dibenzylated cyclophane‐type derivative 1 of a bisisoquinoline macrocyclic alkaloid, S,S‐(+)‐tetrandrine, was prepared and characterized. In aqueous solution 1 undergoes dimerization, which was studied by the concentration dependence of its 1H NMR signals. The salt effect on the dimerization constant was analyzed by using different versions of Debye–Hückel‐type equations. 1H NMR titration of 1 by 10 dicarboxylate anions of different structures revealed strong peak binding selectivity for succinate in the series of α,ω‐dicarboxylates. Aromatic carboxylates have larger binding constants and for o‐phthalate the formation of both 1:1 and 1:2 host–guest complexes is observed. Binding of nucleotides (AMP, ADP and ATP) to 1 is surprisingly insensitive to the guest charge, indicating a major contribution of stacking interactions of the nucleobase with 1. Copyright © 2001 John Wiley & Sons, Ltd.
CO2 fixation and activation by metal complexes of small polyazacyclophanes
Authors: Andrés Sergio , Escuder Beatriu , Doménech Antonio , García‐España Enrique , Luis Santiago V. , Marcelino Victor , Llinares José M. , Ramírez José A. , Soriano Conxa
Published: August 2002

The interaction of the cyclophanes 2,6,9,13‐tetraaza[14]paracyclophane (L1) and 2,6,9,13‐tetraaza[14]metacyclophane (L2) and of their Zn2+ and Cu2+ complexes with CO32− and its protonated forms is described. The actuation of the Cu2+–L2 system as an electrocatalyst for the reduction of CO2 to CO in water is advanced. Copyright © 2001 John Wiley & Sons, Ltd.
Kinetic models for solution imidization of polyamic acid containing naphthalene‐pendant group
Authors: Leu Tsu‐Shang , Wang Chun‐Shan
Published: August 2002

The kinetics and mechanisms of the solution imidization of polyamic acid resulting from a diamine, bis(4‐aminophenoxy‐3,5‐dimethylphenyl)naphthylmethane, and a dianhydride, 3,3′4,4′‐diphenylsulfonetetracarboxylic dianhydride, were studied at three various temperatures (145, 165, and 180 °C). The results were confirmed by means of 1H NMR and gel permeation chromatography (GPC). Kinetic parameters were obtained by an isothermal study, and the results were quite close to second‐order kinetics for the homogeneous solution imidization. In addition, Carother's equation, Mark–Houwink theory, and GPC were used to explain the molecular weight of the imidization processes. The apparent activation energy (Ea) was 104 KJ/mol, and the pre‐exponential factor (k0) was 3.48 × 1014. The proposed kinetic mechanism is in good agreement with the kinetic models. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4139–4151, 2001
Synthesis and self‐assembly of fluorinated block copolymers
Authors: Hillmyer Marc A. , Lodge Timothy P.
Published: August 2002

Fluorinated block copolymers combine the unique properties of fluoropolymers and the intriguing self‐assembly of hybrid macromolecules. The preparation of the title molecules by selective fluorination procedures and the effect of fluorine incorporation on the material thermodynamics are presented. We highlight two fluorination schemes developed in our laboratory, difluorocarbene and perfluoroalkyliodide additions to polydienes, that allow for the selective and tunable incorporation of different fluorinated groups into model block copolymers. The fluorination changes the physical properties of the parent materials and leads to interesting changes in the component incompatibilities. The role of fluorination in determining block copolymer thermodynamics in both the solid state and in solution and in ultimately exploiting fluorination to produce novel, higher order structures is central to our research efforts. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 1–8, 2002
Polymerization of acrylamide photoinitiated by tris(2,2′‐bipyridine)ruthenium(II)–amine in aqueous solution: Effect of the amine structure
Authors: Rivarola Claudia R. , Bertolotti Sonia G. , Previtali Carlos M.
Published: August 2002

The photopolymerization of acrylamide (AA) initiated by the metallic complex tris(2,2′‐bipyridine)ruthenium(II) [Ru(bpy)3+2] in the presence of aliphatic and aromatic amines as co‐initiators was investigated in aqueous solution. Aromatic amines, which are good quenchers of the emission of the metal‐to‐ligand‐charge‐transfer excited state of the complex, are more effective co‐initiators than those that do not quench the luminescence of Ru(bpy)3+2, such as aliphatic amines and aniline. Laser‐flash photolysis experiments show the presence of the reduced form of the complex, Ru(bpy)3+1, for all the amines investigated. For aliphatic amines, the yield of Ru(bpy)3+1 increases with temperature, and on the basis of these experiments, a metal‐centered excited state is proposed as the reactive intermediate in the reaction with these amines. The decay of the transient Ru(bpy)3+1 is faster in the presence of AA. This may be understood by an electron‐transfer process from Ru(bpy)3+1 to AA, regenerating Ru(bpy)3+2 and producing the radical anion of AA. It is proposed that this radical anion protonates in a fast process to give the neutral AA radical, initiating in this way the polymerization chain. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4265–4273, 2001
Preparation of functionalized block copolymers based on a polysiloxane backbone by anionic ring‐opening polymerization
Authors: Bauer Josef , Hüsing Nicola , Kickelbick Guido
Published: August 2002

Polysiloxane diblock copolymers containing a pure polysiloxane backbone were prepared by the functionalization of poly(dimethylsiloxane)‐b‐poly(methylvinylsiloxane) copolymers. The copolymers were obtained by the sequential anionic copolymerization of either 1,3,5,7‐tetramethyl‐1,3,5,7‐tetravinylcyclotetrasiloxane or 1,3,5‐trimethyl‐1,3,5‐trivinylcyclotrisiloxane with hexamethylcyclotrisiloxane. The two vinyl monomers showed large differences in the propagation rates, but both could be used for the formation of polysiloxane block copolymers. Differences in the polymerization sequences were investigated and revealed that better control was obtained if the slower propagating monomer was polymerized first. The method permitted the synthesis of block copolymers with molecular weight distributions around 1.4 and lower and high block purities. The vinyl groups of the block copolymers were quantitatively and selectively functionalized by hydrosilation or epoxidation reactions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1539–1551, 2002
Synthesis and burst strength of water‐swollen immunoisolatory tubules
Authors: Isayeva Irada S. , Gent Alan N. , Kennedy Joseph P.
Published: August 2002

A series of amphiphilic hydrogel tubules have been prepared by copolymerizing/crosslinking hydrophilic poly(dimethylacrylamide) segments with hydrophobic di‐, tri‐, and octamethacrylate‐telechelic polyisobutylene crosslinkers, and their elastic modulus and burst strength in the water‐swollen state were investigated. Because the burst characteristics of hydrogels have not yet been quantitatively investigated, equipment was designed and built to generate fundamental insight into the burst properties of thin‐walled (200–250 μm) narrow lumen (2–3 mm i.d.) water‐swollen tubules. The theory developed to describe quantitatively the inflation behavior of thin‐walled rubber tubules was adapted to treat our experimental observations. Changes in the burst strength, elastic modulus, and expansion during the inflation of hydrogel tubules were interpreted in terms of the molecular weight of the hydrophilic segments between crosslinking sites (Mc,hydrophilic), which in turn was calculated according to the rubber elasticity theory. According to these investigations, the burst strength of our water‐swollen amphiphilic tubules is in the 0.2–0.5 MPa range, which is sufficient for implantation and immunoisolatory applications. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2075–2084, 2002