bluuebunny/crossref_metadata_2025 huggingface dataset:
An improved method for the analysis of sennosides in Cassia angustifolia by high‐performance liquid chromatography
Authors: Bala Shashi , Uniyal G. C. , Dubey Toshi , Singh S. P.
Published: August 2002

A reversed‐phase column liquid chromatographic method for the analysis of sennosides A and B present in leaf and pod extracts of Cassia angustifolia has been developed using a Symmetry C18 column and a linear binary gradient profile. The method can be utilised for the quantitative determination of other sennosides as a baseline resolution for most of the constituents was achieved. The method is economical in terms of the time taken and the amount of solvent used (25 mL) for each analysis. The validity of the method with respect to analysis was confirmed by comparing the UV spectra of each peak with those of reference compounds using a photodiode array detector. Copyright © 2001 John Wiley & Sons, Ltd.
Age and space distributions of monoterpenes in fresh needles of Picea abies (L) Karst. determined by gas chromatography‐mass spectrometry
Authors: Holubová V. , Hrdlic̆ka P. , Kubán̆ V.
Published: August 2002

Monoterpenes (α‐ and β‐pinene, δ‐3‐carene, camphene, α‐phellandrene and limonene) were determined by Gas Chromatography‐Mass Spectrometry in fresh needles of Picea abies (L) Karst. situated in three ecologically different regions of Moravia. Through the use of cryogenic grinding for critical sample homogenisation, solvent extraction with cold n‐hexane, followed by GC analysis with mass detection, very low quantities of sample (0.1–0.3 g needles) could be processed, thus permitting a comparison of amounts of monoterpenes in needles of different ages and a determination of changes in concentrations of monoterpenes in needles at different locations on the tree. The amount of α‐phellandrene decreased with the age of the needles, and the content of δ‐3‐carene was higher in apical branches compared to lateral ones. Copyright © 2001 John Wiley & Sons, Ltd.
Detection of fetal structural abnormalities at the 11–14 week ultrasound scan
Authors: Carvalho M. H. B. , Brizot M. L. , Lopes L. M. , Chiba C. H. , Miyadahira S. , Zugaib M.
Published: August 2002

The aim of this study was to evaluate the detection of fetal structural abnormalities by the 11–14 week scan. 2853 pregnant women were submitted to a routine ultrasound scan between the 11th and 14th week and the fetal skull, brain, spine, abdominal wall, limbs, stomach and bladder were examined. Following the scans the patientes were examined in the second or third trimester of pregnancy. An isolated increased nuchal translucency was not considered an abnormality. However, these patients had an early echocardiography assessment. Fetal structural abnormalities were classified as major or minor and of early or late onset. A total of 130 (4.6%) defects were identified and 29 (22.3%) of these were diagnosed at the 11–14 week scan, including nine cardiac defects associated with increased nuchal translucency. The antenatal ultrasound detection rate was 71.5%, and 31.2% were detected in the first‐trimester assessment. 78.8% of the major defects were diagnosed by the prenatal scan and 37.8% by the 11–14 week scan. Fetal structural abnormalities at the 11–14 week scan were detected in approximately 22.3% of the cases, therefore, a second‐trimester anomaly scan is important in routine antenatal care to increase the prenatal detection of fetal defects. Copyright © 2002 John Wiley & Sons, Ltd.
Dilemmas encountered by health practitioners offering nuchal translucency screening: a qualitative case study
Authors: Williams Clare , Alderson Priscilla , Farsides Bobbie
Published: August 2002

Objective

To explore dilemmas experienced by practitioners involved in routine prenatal nuchal translucency (NT) screening.

Design

Qualitative study incorporating multidisciplinary practitioner discussion groups led by a health care ethicist.

Setting

Inner‐city teaching hospital with fetal medicine unit.

Participants

Thirty‐two practitioners whose work relates directly or indirectly to perinatal care.

Results

Practitioners identified a number of dilemmas, many of which centred on the tension between pregnancy being seen as a normal or a ‘risky’ time. Practitioners and women were perceived to have contrasting reasons for screening, with women welcoming the opportunity to ‘see’ their baby on the ultrasound scan, whilst practitioners were screening for abnormalities. These differing agendas led to various dilemmas particularly in relation to information giving, performing scans incorporating NT screening and promoting individual client choice.

Conclusions

Plans to introduce routine NT screening need careful prospective consideration of the potential implications for both providers and users of the service. The discussion groups also identified the need for training in the complex communication skills required and an awareness of the related ethical dilemmas, plus the need for increased time and resources to enable practitioners to promote informed choice. Copyright © 2002 John Wiley & Sons, Ltd.
Diabetes mellitus in Sudan: the size of the problem and the possibilities of efficient care
Authors: Mohamed Ahmed Awad , Hassan Ahmed Nada
Published: August 2002

Sudan has, for a long time, suffered economic collapse, drought and civil war. Diabetes mellitus is currently emerging as an important health problem, especially in urban areas. The actual prevalence of diabetes is unknown although one small study showed a prevalence of 3.4%. Diabetes is the commonest cause of hospital admission and morbidity due to a non‐communicable disease (7 and 10% respectively). The problems of diabetes care in Sudan include the lack of efficient diabetes care centres, lack of specially trained personnel, the high cost of anti‐diabetic treatments, poor compliance with therapy or diet, ignorance and wrong beliefs, food and dietary factors and gender‐related problems. The goal of efficient diabetes care can be achieved through implementing a national diabetes programme. This programme should be responsible for personnel training, establishing model care centres, patients' education, availability and affordability of insulin, scientific and clinical research and primary prevention. Copyright © 2001 John Wiley & Sons, Ltd.
Survey of knowledge and practice on oral contraceptive and emergency contraceptive pills of drugstore personnel in Hat Yai, Thailand
Authors: Ratanajamit Chaveewan , Chongsuvivatwong Virasakdi
Published: August 2002

In Thailand, oral contraceptive (OC) and emergency contraceptive pill (ECP) are available as over‐the‐counter (OTC) drugs, and drugstores share 30% of services. While the rate of dispensing contraceptive pills has increased, the knowledge and awareness of ECP use is limited among users and providers. The objective of this study was to assess knowledge and practice of drugstore personnel on providing OC and ECP, in order to improve the quality of services. Drugstores located in Hat Yai District, Songkhla Province, Southern Thailand, were the accessible population. There were 109 drugstores, half of them owned by pharmacists. The population was stratified by owner (pharmacist or non‐pharmacist) and randomly selected to obtain a sample size of 30 drugstores for each class. Two study methods, questionnaire interview and secret shopping, were used to measure knowledge, and practice, respectively. History‐taking, drug‐choosing, and advice‐giving were the domains measured. The results demonstrated that knowledge on OC was fair, but that on ECP was poor. Pharmacists had better knowledge of proper history taking and ECP indication than non‐pharmacists. OC and ECP provision were inappropriately practised in drugstores in the study area. A majority of drugstores were mainly owned by non‐pharmacists. For OC practice, drug‐choosing was good, but history‐taking and advice‐giving were poor in both groups. Although both groups dispensed ECP poorly, pharmacists dispensed significantly better than non‐pharmacists. Among non‐pharmacist staff, the average scores of OC advice‐giving, and ECP dispensing, were statistically significantly better among those working in pharmacist‐owned drugstores. Both knowledge and practice on OC and ECP should be improved in both types of drugstores in the study area. Copyright © 2001 John Wiley & Sons, Ltd.
Association between terbinafine and arthralgia, fever and urticaria: symptoms or syndrome?
Authors: van Puijenbroek Eugène P. , Egberts Antoine C. G. , Meyboom Ronald H. B. , Leufkens Hubert G. M.
Published: August 2002

Purpose

The antifungal agent terbinafine has been approved for marketing in The Netherlands since 1992. Adverse drug reactions (ADRs) may occur in about 10% of the patients, the majority gastrointestinal disorders and skin reactions. Since the introduction of terbinafine, the Netherlands Pharmacovigilance Foundation Lareb received eight reports of arthralgia during the use of this drug. In four reports the additional presence of skin reactions was mentioned, two of these reports concerned urticaria. Two patients who reported arthralgia also had a fever. These reports were described in more detail, and analysed statistically in order to determine whether symptoms are interrelated.

Methods

All reports with known gender and a reporting date between 1 March 1992 and 1 January 1999, concerning patients older than 10 years, were included. The extent to which the symptoms urticaria, fever and arthralgia were interrelated was examined by logistic regression modelling.

Results

Case series as well as the results of the statistical analysis show a clustering of symptoms among reports of patients using terbinafine. Both urticaria and arthralgia were statistically significantly associated with reports on terbinafine compared to all other reports in the database.

Conclusion

The findings might point towards a clustering of these symptoms in patients using terbinafine. Possibly these symptoms have a shared aetiology, presumably an immunological reaction. Copyright © 2001 John Wiley & Sons, Ltd.
Antihypertensive drug treatment in a Swedish community: Skaraborg hypertension and diabetes project
Authors: Bøg‐Hansen Erik , Lindblad Ulf , Ranstam Jonas , Melander Arne , Råstam Lennart
Published: August 2002

Purpose

To describe and compare the pattern of antihypertensive drug prescriptions during different time periods.

Methods

Antihypertensive prescriptions were registered in all patients who underwent an annual follow‐up during 1998 (n = 984), 1992–1993 (n = 924), and 1981 (n = 689), at the hypertension outpatient clinic in primary health care, Skara, Sweden.

Results

From 1981 to 1998 the total prescriptions of thiazides declined from 61 to 10% (p < 0.001), whilst prescriptions of calcium antagonists increased from 4 to 30% (p < 0.001), and ACE inhibitors from zero to 23% (p < 0.001). Prescriptions of calcium antagonists and ACE inhibitors increased during 1990–1995, but during 1996–1998 a significant decrease in primary prescriptions of calcium antagonists was demonstrated (OR: 0.15; 95% CI: 0.06–0.36). During all periods, females were more frequently treated with older types of antihypertensive drugs than males. In the analysis of total prescriptions in 1998 women were prescribed calcium antagonists (OR: 0.59; 95% CI: 0.45–0.78) and ACE inhibitors (OR: 0.43; 95% CI: 0.31–0.58) less frequently than men.

Conclusion

There were significant changes in type of antihypertensive drugs used, both by time and between genders. Changes during the latest years indicate that the prescription pattern can be greatly influenced by new scientific reports and economic debate. Copyright © 2002 John Wiley & Sons, Ltd.
The effect of various anhydride modifications on mechanical properties and water absorption of oil palm empty fruit bunches reinforced polyester composites
Authors: Abdul Khalil H P S , Ismail H , Ahmad M N , Ariffin A , Hassan K
Published: August 2002

The chemical modification of oil palm empty fruit bunches (EFB) using non‐catalysed reaction with acetic, propionic and succinic anhydrides were investigated. Proof of modification was indicated by the increase of weight and was confirmed by Fourier‐transform infrared analysis (FT‐IR). The mechanical and water‐absorption properties of all anhydride‐modified EFB composites were evaluated at different volume fractions (Vf). The properties were improved for these modified fibres, whereas unmodified EFB fibres exhibited poor mechanical properties and higher water absorption. Acetic anhydride modification showed the greatest benefit on composite properties, followed by propionic and succinic anhydride modification.

© 2001 Society of Chemical Industry
Synthesis, characterization and polychelatogenic properties of poly[(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid)‐co‐(methacrylic acid)]
Authors: Rivas Bernabé L , Martínez Esteban , Pereira Eduardo , Geckeler Kurt E
Published: August 2002

Poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid), poly(methacrylic acid), and five copolymers of poly[(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐co‐(methacrylic acid)] were synthesized by radical polymerization and obtained in yields >97%. The polymers were characterized by FT‐IR, [1H]NMR, and [13C]NMR and studied by means of the Liquid‐phase Polymer‐based Retention (LPR) technique. The metal ion retention ability of the copolymers for Cu(II), Cd(II), Co(II), Hg(II), Ni(II), Zn(II), Cr(III) and Ag(I) was investigated at different pH values because of their environmental and analytical interest. The retention profiles of the copolymers were compared with those of the corresponding homopolymers and retention of metal ions was found to increase with increasing pH.

© 2001 Society of Chemical Industry
Effect of a silane coupling agent on the properties of white rice husk ash–polypropylene/natural rubber composites
Authors: Ismail H , Mega L , Khalil H P S Abdul
Published: August 2002

White rice husk ash (WRHA)–polypropylene (PP)/natural rubber (NR) composites were prepared using a Brabender Plasticorder at 180 °C and a rotor speed of 50 rev min−1. The mechanical and water‐absorption properties were studied. The incorporation of WRHA into the PP/NR matrix has resulted in the improvement of the tensile modulus; however, the tensile strength, elongation at break and stress at yield decreased with increasing WRHA loading. Poor filler matrix interactions are believed to be responsible for the decrease in the properties. Incorporation of a silane coupling agent, 3‐aminopropyl triethoxysilane (3‐APE), improved tensile modulus, tensile strength and stress at yield of the composites. Water‐absorption studies indicate that the use of the coupling agent reduced the amount of water absorbed by the composites.

© 2001 Society of Chemical Industry
Degradation of high barrier ethylene–vinyl alcohol copolymer under mild thermal‐oxidative conditions studied by thermal analysis and infrared spectroscopy
Authors: Lagaron José M , Giménez Enrique , Saura Juan J
Published: August 2002

A study of the thermal‐oxidative degradation of a high barrier ethylene–vinyl alcohol copolymer with 32 mol% of ethylene (EVOH) has been carried out by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and Fourier‐transform infrared spectroscopy (FTIR) under mild temperature conditions above melting. It was found that time exposures of up to 11 h at temperatures between 9 and 33 °C above the EVOH melting point resulted in polymer weight losses of up to 3.6% with colour formation. The weight loss was faster at short times and slowed down with increasing exposure time. DSC showed a small decrease in crystallinity and melting point, melting‐peak broadening and a slight increase in the glass transition temperature of the samples subjected to the more severe thermal‐oxidative treatment. The FTIR experiments showed transformation of the vinyl alcohol hydroxyl groups into carbonyl groups and creation of double bonds. Changes in degradation kinetics and perhaps in mechanisms are thought to occur with increasing exposure time. Moreover, FTIR measurements suggest that transformation of the hydroxyl groups leads to a weakening of the overall hydrogen bonding strength in the degraded samples, and therefore a reduction in intermolecular cohesion can be anticipated.

© 2001 Society of Chemical Industry
A study on the preparation of polymer/montmorillonite nano‐composite materials by photo‐polymerization
Authors: Huimin Wang , Minghua Mei , Yongcai Jiang , Qingshan Li , Xiaohong Zhang , Shikang Wu
Published: August 2002

The preparation of polymer/montmorillonite intercalation composite materials was studied by two kinds of photo‐polymerization reaction (photo‐acid generation and photo‐radical generation). Small‐angle X‐ray diffraction was used for the structural characterization of montmorillonite contained in the products. Results indicated that, after chemical modification of montmorillonite, the monomer (methyl methacrylate) and the prepolymer (m‐cresol/HMMM) were able to intercalate into the layers of clay and to polymerize ‘in situ’, thus producing photo‐polymerized composite materials. The advantages and shortcomings of the method of photo‐polymerization for the preparation of these composite materials are discussed.

© 2001 Society of Chemical Industry
Interpolymer complex polyampholytic hydrogel of chitosan and carboxymethyl cellulose (CMC): synthesis and ion effect
Authors: Yan Lifeng , Qian Fang , Zhu Qingshi
Published: August 2002

Interpolymer complexes of chitosan and carboxymethyl cellulose were synthesized by γ‐irradiation in acetic acid/water solution, using methylenebisacrylamide (MBAAM) as a crosslinker. FTIR and atomic force microscopy were used to determine their structures. The hydrogels swell in water, and their swelling behaviour is strongly affected by the ion strength of the solution, which indicates that a polyampholytic hydrogel is formed.

© 2001 Society of Chemical Industry
A methodology for the design of photovoltaic water supply systems
Authors: Vilela O. C. , Fraidenraich N.
Published: August 2002

Photovoltaic pumping systems are used nowadays as a valuable alternative to supply water to communities living in remote rural areas. Owing to the seasonal variation and the stochastic behavior of solar radiation, at certain times the supply of water may not be able to meet demand. A study has been made of the relationship between water pumping capacity, reservoir size and water demand, for a given water deficit. As a result, curves of equal water deficit (iso‐deficit lines) can be obtained for various combinations of PV pumping capacity and reservoir size. A methodology to generate those curves is described, using as its main tool the characteristic curve of the system, that is, the relationship between water flow and collected solar radiation. The characteristic curve represents the combined behavior of the water pumping system and the well. The influence of the minimum collected solar radiation level, necessary to start the system's operation (the critical radiation level IC), is also analyzed. Results show that PV pumping systems with different characteristic curves, but with the same critical levels, yield the same set of iso‐deficit lines. This drastically reduces the number of necessary solutions to those corresponding to a few values of IC. Iso‐deficit lines, calculated for the locality of Recife (PE), Brazil, are used to illustrate the sizing procedure PV water supply systems. Copyright © 2001 John Wiley & Sons, Ltd.
Characteristics and educational support needs of underrepresented gifted adolescents
Authors: Stormont Melissa , Stebbins Molly S. , Holliday Gregory
Published: August 2002

The purpose of this article is to present the characteristics and needs of adolescent students who are underrepresented in gifted programs. The specific populations of underrepresented gifted youth who will be addressed in this article include young women, students with learning disabilities, and students living in poverty. The academic and social‐emotional needs of students from underrepresented populations will be presented, followed by strategies professionals can use to support these students. The importance of developing more sensitive identification and outreach programs for these youth is clearly illuminated by their social‐emotional characteristics and academic underachievement. It is important to create support strategies for students at the secondary level, as this may be their last point of entry in the educational system. © 2001 John Wiley & Sons, Inc.
Direct functionalization of polyisobutylene by living initiation with α‐methylstyrene epoxide
Authors: Song J. , Bódis J. , Puskas J. E.
Published: August 2002

This article describes the synthesis and characterization of polyisobutylene (PIB) carrying one primary hydroxyl head group and a tertiary chloride end group, [PhC(CH3)(CH2OH)–PIB–CH2C(CH3)2Cl] prepared with direct functionalization via initiation. The polymerization of isobutylene was initiated with the α‐methylstyrene epoxide/titanium tetrachloride system. Living conditions were obtained from −75 to −50 °C (198–223 K). Low molecular weight samples (number‐average molecular weight ∼ 4000 g/mol) were prepared under suitable conditions and characterized by Fourier transform infrared and 1H NMR spectroscopy. The presence of primary hydroxyl head groups in PIB was verified by both methods. Quantitative Fourier transform infrared with 2‐phenyl‐1‐propanol calibration and 1H NMR performed on both the hydroxyl‐functionalized PIB and its reaction product with trimethylchlorosilane showed that each polymer chain carried one primary hydroxyl head group. The synthetic methodology presented here is an effective and simple route for the direct functionalization of PIB. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1005–1015, 2002
Production of crosslinked, hollow nanoparticles by surface‐initiated living free‐radical polymerization
Authors: Blomberg Susanne , Ostberg Sofia , Harth Eva , Bosman Anton W. , Van Horn Brooke , Hawker Craig J.
Published: August 2002

Surface‐initiated living free‐radical polymerization is employed in a multistep procedure to prepare hollow polymeric nanocapsules. Initially, trichlorosilyl‐substituted alkoxyamine initiating groups are attached to the surface silanol groups of silica nanoparticles. This surface layer of initiating groups is then used to grow functionalized linear chains leading to a core–shell morphology. The choice of functional groups is governed by their ability to undergo facile crosslinking reactions, with both active ester and benzocyclobutene groups being examined. Under either chemical or thermal conditions, the reaction of these functionalities gives a crosslinked polymeric shell that is covalently attached to, and surrounds, the central silica core. Removal of the silica core with HF then gives the hollow polymeric nanocapsules, which are stable under solvent dissolution and thermal treatment because of their crosslinked structure. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1309–1320, 2002
Synthesis and characterization of well‐defined ABC‐type triblock copolymers via atom transfer radical polymerization and stable free‐radical polymerization
Authors: Tunca U. , Erdogan T. , Hizal G.
Published: August 2002

An asymmetric difunctional initiator 2‐phenyl‐2‐[(2,2,6,6 tetramethylpiperidino)oxy] ethyl 2‐bromo propanoate (1) was used for the synthesis of ABC‐type methyl methacrylate (MMA)‐tert‐butylacrylate (tBA)‐styrene (St) triblock copolymers via a combination of atom transfer radical polymerization (ATRP) and stable free‐radical polymerization (SFRP). The ATRP‐ATRP‐SFRP or SFRP‐ATRP‐ATRP route led to ABC‐type triblock copolymers with controlled molecular weight and moderate polydispersity (Mw/Mn < 1.35). The block copolymers were characterized by gel permeation chromatography and 1H NMR. The retaining chain‐end functionality and the applying halide exchange afforded high blocking efficiency as well as maintained control over entire routes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2025–2032, 2002
Polymerizable anthracene derivatives for labeling emulsion copolymers
Authors: Liu Ronghua , Winnik Mitchell A. , Di Stefano Frank , Vanketessan Jai
Published: August 2002

We describe the synthesis of three anthracene–methacrylate monomers [9‐methacryloxymethyl‐10‐methyl anthracene (4), 9‐methacryloxyethyloxymethyl‐10‐methyl anthracene (5), and 9‐methacryloxy‐10‐methyl anthracene (6)] as well as their emulsion copolymers containing butylacrylate. When films prepared from latex dispersions containing 4 or 5 were heated, the anthracene (An) group was cleaved from the polymer at temperatures above 120 °C. Lower temperatures induced this reaction when strong acids were present. In 4 and 5, the polymerizable group is connected to the An ring via a 9‐CH2O linkage. The cleavage reaction requires more stringent conditions when the connection involves a benzylic ether (5) instead of a benzylic ester. Polymers prepared from 6, with an AnO bond, were stable for 1 h at 150 °C in the presence of 0.5 wt % p‐toluene sulfonic acid. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1495–1504, 2001
Novel refreshable N‐halamine polymeric biocides containing imidazolidin‐4‐one derivatives
Authors: Sun Yuyu , Chen Tay‐Yuan , Worley S. D. , Sun Gang
Published: August 2002

A novel cyclic‐amine monomer, 1‐acryloyl‐2,2,5,5‐tetramethylimidazolidin‐4‐one (ACTMIO), was synthesized in a good yield through the reaction of acryloyl chloride with 2,2,5,5‐tetramethylimidazolidin‐4‐one and was fully characterized with Fourier transform infrared and 1H NMR studies. ACTMIO was copolymerized with several widely used acrylic and vinyl monomers under ordinary conditions. In the presence of triallyl‐1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trione, ACTMIO was easily grafted onto most textile fabrics. After regular chlorine bleach treatment, N‐halamine derivatives of the corresponding polymeric materials exhibited antibacterial properties against Escherichia coli, and these properties were durable and refreshable with chlorine bleaching. The relationship between the structures and antibacterial properties of the samples is further discussed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3073–3084, 2001
Elastic behavior of bimodal poly(dimethylsiloxane) networks
Authors: Zhang Lin‐Xi , Jiang Zhou‐Ting , Zhao De‐Lu
Published: August 2002

The rubberlike elastic behavior of bimodal poly(dimethylsiloxane) (PDMS) networks was investigated by the Monte Carlo simulation method and enumeration calculation method on the basis of the rotational‐isomeric‐state (RIS) model. These bimodal PDMS networks consist of short chains (chain length from 10 to 20) as well as long chains (chain length equal to 150). For long PDMS chains, through generating many PDMS conformations in the equilibrium state using the Monte Carlo simulation method we can obtain the average Helmholtz free energy and the average energy. For short PDMS chains with chain lengths from 10 to 20, as the total number of conformations is only from 6.56 × 103 to 3.87 × 108, we adopt the enumeration calculation method. The deformation is partitioned nonaffinely between the long and short chains, and this partitioning can be determined by requiring the free energy of the deformed network to be minimized. Chain dimensions and thermodynamic statistical properties of bimodal PDMS networks at various elongation ratios are discussed. We find that elastic force f increases with elongation ratio λ; the energy contribution fu to elastic force is significant, and the ratio of ranges from 0.15 to 0.36 at T = 343 K. In the meantime, elastic force f increases with the average energy 〈U〉. The energy change in the process of tensile elongation is taken over, which has been ignored in previous theories. Our calculations may provide some insights into the phenomena of rubberlike elasticity of bimodal networks. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 105–114, 2002
Constant loss in Brillouin spectra of polymers
Authors: Kisliuk A. , Novikov V. N. , Sokolov A. P.
Published: August 2002

The polarized (VV) and depolarized (VH) light scattering spectra of polyisobutylene, poly(methyl methacrylate), and glycerol were measured in the gigahertz frequency range at temperatures below and above the glass transition. Both VV and VH spectra exhibit a significant constant loss contribution that appears as a frequency‐independent imaginary part of the susceptibility spectrum. Existence of the frequency‐independent susceptibility in VV spectra below the Brillouin lines suggests that the constant loss also appears in mechanical relaxation in the gigahertz frequency range. Intensity of the constant loss increases strongly with temperature. Analysis of the spectra and literature data suggests that the constant loss can be general for many glass‐forming systems, but it is hidden in many cases by other relaxation contributions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 201–209, 2002
Volume‐exclusion effects in polyethylene blends filled with carbon black, graphite, or carbon fiber
Authors: Thongruang Wiriya , Balik C. Maurice , Spontak Richard J.
Published: August 2002

Conductive polymer composites possessing a low percolation‐threshold concentration as a result of double percolation of a conductive filler and its host phase in an immiscible polymer blend afford a desirable alternative to conventional composites. In this work, blends of high‐density polyethylene (HDPE) and ultrahigh molecular weight polyethylene (UHMWPE) were used to produce ternary composites containing either carbon black (CB), graphite (G), or carbon fiber (CF). Blend composition had a synergistic effect on electrical conductivity, with pronounced conductivity maxima observed at about 70–80 wt % UHMWPE in the CB and G composites. A much broader maximum occurred at about 25 wt % UHMWPE in composites prepared with CF. Optical and electron microscopies were used to ascertain the extent to which the polymers, and hence filler particles, are segregated. Differential scanning calorimetry of the composites confirmed that the constituent polymers are indistinguishable in terms of their thermal signatures and virtually unaffected by the presence of any of the fillers examined here. Dynamic mechanical analysis revealed that CF imparts the greatest stiffness and thermal stability to the composites. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1013–1023, 2002
Survivorship and discourses of identity
Authors: Little Miles , Paul Kim , Jordens Christopher F.C. , Sayers Emma‐Jane
Published: August 2002

Personal identity is self‐evidently important to us all. Identity is a philosophically complex subject, but there is some agreement that memory, embodiment and continuity are essential components. The sense of memory includes ‘future memory’, the kind of memory we would like to construct for ourselves as our lives proceed. While the sense of personal identity is internal to the individual, a sense of that person's identity exists in the minds of others. Extreme experiences threaten the element of continuity, because they may bring bodily changes as well as cognitive changes that challenge central values. Restoring or preserving continuity is a major task for survivors. The ways in which people experience discontinuity because of cancer illness, and the ways in which they manage this experience emerges from the narratives of the survivors of cancer and in the narratives of health care workers who look after them. People manage discontinuity by reference to stable ‘anchor points’ in their beliefs and values; by re‐constructing versions of their pre‐experience identities, drawing on past memory and finding ways to preserve a continuity between past memory, present experience and constructions of the future; by using the experience to develop established facets of identity; and by imbuing the experience with meaning and recognising the enlarged identity made possible by survival. Those who cannot achieve a sense of continuity may feel alienated from themselves, their friends and family. All these methods of management may be used by one person to negotiate the post‐experience identity in its different social interactions.

The experience of the survivor can be further understood by recognising the challenge posed by extreme experience to the sense of continuity of both embodied self and memory. A satisfactory discourse of survival has yet to enter the public domain. This lack adds to the burdens of survivors, including those who have survived cancer. Copyright © 2002 John Wiley & Sons, Ltd.
Psychological adjustment of ‘surgery‐only’ pediatric neuro‐oncology patients: a retrospective analysis
Authors: Meyer Eugene A. , Kieran Mark W.
Published: August 2002

A recent increase in diagnoses of pediatric neuro‐oncology tumors combined with recent advancements in medical treatment of such tumors has resulted in a growing cohort of pediatric brain tumor survivors. These survivors are at risk for short and long‐term psychological adjustment problems. Most studies regarding these survivors have focused on children who have received combinations of surgery, radiation, and chemotherapy as medical treatment. The sub‐group of pediatric neuro‐oncology patients who receive surgery as the only form of medical treatment has not been closely followed for adjustment problems. In this study, data were retrospectively collected from semi‐structured clinical interviews with 34 ‘surgery‐only’ pediatric neuro‐oncology patients who were 2 weeks to 5 years off medical treatment for their tumor. These data suggest that these survivors may be experiencing significant short and long‐term mood, behavioral, and academic adjustment problems in comparison to national averages for children regarding these issues. Additional research examining the psychological adjustment process for surgery‐only pediatric neuro‐oncology patients is needed to validate these preliminary findings and facilitate the development of targeted interventions to address the identified adjustment problems. Copyright © 2002 John Wiley & Sons, Ltd.
Quality of life in childhood cancer survivors
Authors: Zebrack Brad J. , Chesler Mark A.
Published: August 2002

The successful treatment for children with cancer has greatly increased the survival rates for these young people compared to children diagnosed with cancer 30 years ago. These new medical realities direct attention to the psychosocial consequences of successful treatment and subsequent survival. In this paper, quality of life in 176 childhood cancer survivors (age 16–28) is assessed using a survey instrument designed for cancer survivors. In addition, the instrument is evaluated for its utility with this population.

Survivors indicate that symptoms often associated with treatment are at a minimum but that other long‐term effects like fatigue, aches, and pain negatively impact quality of life. They rate themselves high on happiness, feeling useful, life satisfaction and their ability to cope as a result of having had cancer but their hopefulness is tempered by uncertainty. Whereas the salience of spiritual and religious activities appears to be low, having a sense of purpose in life and perceiving positive changes as a result of cancer are associated with positive quality of life. A lower valence of physical concerns reflects the vitality and positive life outlook of a young population. Copyright © 2002 John Wiley & Sons, Ltd.
Permafrost–glacial evolution during the Holocene in the Italian Central Alps
Authors: Guglielmin M. , Cannone N. , Dramis F.
Published: August 2002

This paper discusses the Holocene evolution of two sites in the Central Italian Alps, the Foscagno Valley and the Stelvio–Livrio area, in terms of the interaction between permafrost distribution and glacial history. The applicability of phytosociological vegetation survey to investigate recent glacial evolution where geomorphological evidence is poor or totally absent is also illustrated. Bottom temperature of snow measurements and detailed geomorphologic survey and air‐photo interpretation were carried out in the Stelvio–Livrio area. Boreholes were drilled in each site, one (24 m deep) in the Foscagno rock glacier (2510 m ASL), the second (100.3 m deep) in dolostone‐limestone bedrock at the Stelvio Pass (3000 m ASL). The latter borehole is a component of the PACE European Permafrost Monitoring Network. In Foscagno Valley, the formation of permafrost during a cold and dry phase of the Holocene allowed the preservation of an ice body which otherwise would have disappeared. More recently, a Little Ice Age glacier advance, whose exact location and extension were defined by means of the analysis of vegetal associations, induced some degradation in the permafrost. In the Stelvio–Livrio area, a cold‐based glacier apparently had much less influence on the local permafrost evolution and thermal regime. Copyright © 2001 John Wiley & Sons, Ltd.

L'évolution holocène de deux sites des Alpes centrales italiennes, la vallée de Foscagno et la région de Stelvio‐Livrio, est discutée pour contribuer à la compréhension des relations entre la distribution du pergélisol et l'histoire glaciaire. Un autre but de l'étude était de vérifier la possibilité d'utiliser des relevés phytosociologiques pour comprendre l 'évolution récente glaciaire de zones où des évidences géomorphologiques sont maigres ou totalement absentes et de mieux comprendre ainsi la distribution du pergélisol. Des mesures BTS, des levés géomorphologiques détaillés et des interprétations de photos aériennes de la zone Stelvio‐Livrio ont été réalisés. Enfin, deux sondages ont été implantés : l'un (24 m de profondeur) dans le glacier rocheux de Foscagno (2510 m) et l'autre dans le substratum rocheux (100.3 m de profondeur) du Col du Stelvio (3000 m). Ce dernier sondage fait partie du réseau européen PACE de surveillance du pergélisol. Des levés phytosociologiques ont été réalisés dans les deux zones. Dans la vallée de Foscagno, la formation du pergélisol pendant une phase froide et aride de l'Holocène a permis la conservation d'un corps de glace qui, autrement, aurait disparu. Plus récemment, une avancée glaciaire pendant le Petit Age Glaciaire (dont la localisation et l'exacte extension ont été reconnues par les études phytosociologiques) a provoqué la dégradation du pergélisol. Dans la zone de Stelvio‐Livrio, un glacier à base froide a apparemment beaucoup moins influencé la distribution du pergélisol et son régime thermique. Copyright © 2001 John Wiley & Sons, Ltd.
Luminescence age and palaeoenvironmental implications of a late Pleistocene ground wedge on the Northeastern Tibetan Plateau
Authors: Porter Stephen C. , Singhvi Ashok , Zhisheng An , Zhongping Lai
Published: August 2002

A periglacial ground wedge in bajada gravel near the northern base of the Qinghai Nan Shan underlies loess of late‐ and postglacial age. The composition and structure of the wedge fill are consistent with an ice‐wedge origin, implying former permafrost and relatively moist conditions at this locality. A luminescence date of 15,100±1600 years from the wedge fill marks the end of ice‐wedge activity, which is inferred to have been during the last glaciation. The present mean annual air temperature (MAAT) (−0.7 °C) is too high to produce frost cracking and ice‐wedge formation, but snowline depression of ca. 700–800 m in the adjacent mountains is consistent with a reduction in MAAT of at least 3.8 °C during the last glacial maximum. Such a temperature depression would reduce MAAT to values equivalent to Arctic regions now experiencing active ice‐wedge growth. The absence of loess of full‐glacial age and the presence of a weakly developed palaeosol atop the bajada gravel imply a stable, cold land surface. Qinghai Lake, although reduced in size at that time, likely raised local humidity to levels that favoured ice‐wedge growth in this low‐altitude sector (ca. 3000–3400 m) of the Tibetan Plateau. Copyright © 2001 John Wiley & Sons, Ltd.

Près de la base septentrionale de Qinghai Nan Shan, un coin périglaciaire a été observé dans le gravier d'une bahada recouverte de loess tardi‐ et postglaciaire. La composition et la structure du remplissage du coin peuvent s'expliquer par le développement d'un coin de glace, ce qui implique l'existence autrefois d'un pergélisol et de conditions relativement humides. Une date de 15.100 +/− 1600 ans a été obtenue par luminescence pour le remplissage ; cette date marquerait la fin de l'activité du coin de glace qui serait, de ce fait, apparu pendant la dernière glaciation. De nos jours, la température moyenne annuelle de l'air (MAAT) est de −0.7 °C, température trop élevée pour produire la fissuration par le gel et la formation d'un coin de glace ; toutefois, l'abaissement de la limite des neiges éternelles d'environ 700 à 800 m dans les montagnes voisines indique une réduction de la température moyenne annuelle d'au moins 3.8 °C pendant le maximum de la dernière glaciation. Une telle diminution de température aurait réduit la température à une valeur semblable à celle des régions arctiques où se développent de nos jours des coins de glace. L'absence de loess d'âge glaciaire et la présence d'un paléosol faiblement développé au sommet du gravier de la bahada implique que la surface est restée stable et froide. A cette époque, le lac Qinghai, quoique réduit en taille, a probablement augmenté l'humidité locale et favorisé la croissance de coins de glace dans ce secteur de faible altitude (vers 3000–3400 m) du Plateau tibétain. Copyright © 2001 John Wiley & Sons, Ltd.
Measurement and theory of ploughing boulder movement
Authors: Ballantyne Colin K.
Published: August 2002

Analysis of the characteristics, distribution and rate of movement of ploughing boulders reveals several attributes that throw light on the mechanism of boulder movement. Ploughing boulders occur only in areas of active solifluction, on frost‐susceptible soils with low plastic and liquid limits. During movement they rotate to adopt an alignment of least resistance. Excavations revealed thick ice lenses under the base of a boulder in winter, and emergent shear planes in frontal ridges. Rates of boulder movement average from zero to a few centimetres per year and are exponentially related to gradient. The differential thermal conductivity (diffusivity) of the boulder and surrounding soil implies that the seasonal freezing plane descends more rapidly through the boulder, causing ice‐lens growth at the boulder base; conversely, the thaw plane reaches the base of the boulder whilst the surrrounding soil is still frozen. A limit‐equilibrium model of boulder movement by gelifluction suggests that movement results from trapping of excess water under boulders during thaw, elevation of sub‐boulder porewater pressures to above‐hydrostatic levels and consequent reduction in shearing resistance at the base of the boulder. Movement is initiated by thaw of soil immediately downslope, but allows trapped water to escape, reducing porewater pressures and allowing stability to be regained. This model appears consistent with the observed characteristics, distribution and behaviour of ploughing boulders. Copyright © 2001 John Wiley & Sons, Ltd.
Identification of protein fold and catalytic residues of γ‐hexachlorocyclohexane dehydrochlorinase LinA
Authors: Nagata Yuji , Mori Katsuki , Takagi Masamichi , Murzin Alexey G. , Damborský Jiří
Published: August 2002

γ‐Hexachlorocyclohexane dehydrochlorinase (LinA) is a unique dehydrochlorinase that has no homologous sequence at the amino acid‐sequence level and for which the evolutionary origin is unknown. We here propose that LinA is a member of a novel structural superfamily of proteins containing scytalone dehydratase, 3‐oxo‐Δ5‐steroid isomerase, nuclear transport factor 2, and the β‐subunit of naphthalene dioxygenase—all known structures with different functions. The catalytic and the active site residues of LinA are predicted on the basis of its homology model. Nine mutants that carry substitutions of the proposed catalytic residues were constructed by site‐directed mutagenesis. In addition to these, eight mutants that have a potential to make contact with the substrate were prepared by site‐directed mutagenesis. These mutants were expressed in Escherichia coli, and their activities in crude extract were evaluated. Most of the features of the LinA mutants could be explained on the basis of the present LinA model, indicating its validity. We conclude that LinA catalyzes the proton abstraction via the catalytic dyad H73‐D25 by a similar mechanism as described for scytalone dehydratase. The results suggest that LinA and scytalone dehydratase evolved from a common ancestor. LinA may have evolved from an enzyme showing a dehydratase activity. Proteins 2001;45:471–477. © 2001 Wiley‐Liss, Inc.
The leghemoglobin proximal heme pocket directs oxygen dissociation and stabilizes bound heme
Authors: Kundu Suman , Snyder Barry , Das Kaustuv , Chowdhury Pramit , Park Jaehun , Petrich Jacob W. , Hargrove Mark S.
Published: August 2002

Sperm whale myoglobin (Mb) and soybean leghemoglobin (Lba) are two small, monomeric hemoglobins that share a common globin fold but differ widely in many other aspects. Lba has a much higher affinity for most ligands, and the two proteins use different distal and proximal heme pocket regulatory mechanisms to control ligand binding. Removal of the constraint provided by covalent attachment of the proximal histidine to the F‐helices of these proteins decreases oxygen affinity in Lba and increases oxygen affinity in Mb, mainly because of changes in oxygen dissociation rate constants. Hence, Mb and Lba use covalent constraints in opposite ways to regulate ligand binding. Swapping the F‐helices of the two proteins brings about similar effects, highlighting the importance of this helix in proximal heme pocket regulation of ligand binding. The F7 residue in Mb is capable of weaving a hydrogen‐bonding network that holds the proximal histidine in a fixed orientation. On the contrary, the F7 residue in Lba lacks this property and allows the proximal histidine to assume a conformation favorable for higher ligand binding affinity. Geminate recombination studies indicate that heme iron reactivity on picosecond timescales is not the dominant cause for the effects observed in each mutation. Results also indicate that in Lba the proximal and distal pocket mutations probably influence ligand binding independently. These results are discussed in the context of current hypotheses for proximal heme pocket structure and function. Proteins 2002;46:268–277. © 2002 Wiley‐Liss, Inc.
Cooperative helix stabilization by complex Arg–Glu salt bridges
Authors: Olson C. Anders , Spek Erik J. , Shi Zhengshuang , Vologodskii Alexander , Kallenbach Neville R.
Published: August 2002

Among the interactions that stabilize the native state of proteins, the role of electrostatic interactions has been difficult to quantify precisely. Surface salt bridges or ion pairs between acidic and basic side chains have only a modest stabilizing effect on the stability of helical peptides or proteins: estimates are roughly 0.5 kcal/mol or less. On the other hand, theoretical arguments and the occurrence of salt bridge networks in thermophilic proteins suggest that multiple salt bridges may exert a stronger stabilizing effect. We show here that triads of charged side chains, Arg+–Glu−–Arg+ spaced at i,i+4 or i,i+3 intervals in a helical peptide stabilize alpha helix by more than the additive contribution of two single salt bridges. The free energy of the triad is more than 1 kcal/mol in excess of the sum of the individual pairs, measured in low salt concentration (10 mM). The effect of spacing the three groups is severe; placing the charges at i,i+4 or i,i+3 sites has a strong effect on stability relative to single bridges; other combinations are weaker. A conservative calculation suggests that interactions of this kind between salt bridges can account for much of the stabilization of certain thermophilic proteins. Proteins 2001;44:123–132. © 2001 Wiley‐Liss, Inc.