bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexible supply contracts for short life‐cycle goods: The buyer's perspective
Authors: Milner Joseph M. , Rosenblatt Meir J.
Published: August 2002

In this paper we analyze a two‐period supply contract which allows for order adjustment by the buyer. The buyer is required to place orders for two periods. After observing initial demand, the buyer is then allowed to adjust the second order, paying a per unit order adjustment penalty. We describe the optimal behavior of the buyer under such a contract, both in determining the initial order quantities and in subsequently adjusting the order. We compare the solution to a contract where no adjustment is allowed and to the case where adjustment is allowed without penalty. We demonstrate that flexible contracts can reduce the potentially negative effect of correlation of demand between two periods. Further, we investigate how the duration of the first period vis‐à‐vis the second period affects the profitability of the buyer as a function of the degree of correlation. © 2002 John Wiley & Sons, Inc. Naval Research Logistics, 49: 25–45, 2002; DOI 10.1002/nav.10002
Rendezvous search on labeled networks
Authors: Alpern Steve
Published: August 2002

Two players are independently placed on a commonly labelled network X. They cannot see each other but wish to meet in least expected time. We consider continuous and discrete versions, in which they may move at unit speed or between adjacent distinct nodes, respectively. There are two versions of the problem (asymmetric or symmetric), depending on whether or not we allow the players to use different strategies. After obtaining some optimality conditions for general networks, we specialize to the interval and circle networks. In the first setting, we extend the work of J. V. Howard; in the second we prove a conjecture concerning the optimal symmetric strategy. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 256–274, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10011
MR angiographic investigation of transient focal cerebral ischemia in rat
Authors: Besselmann M. , Liu M. , Diedenhofen M. , Franke C. , Hoehn M.
Published: August 2002

Contrast agent free time‐of‐flight magnetic resonance angiography (TOF‐MRA) was applied to the intraluminal thread occlusion model of experimental stroke in rat. It was combined with perfusion‐ and diffusion‐weighted imaging (PWI and DWI) sequences to correlate occlusion and reopening of the middle cerebral artery with alterations in these well‐established magnetic resonance sequences. Since TOF‐MRA can be repeated without limitations, the time course of vascular patency is demonstrated during an experimental period of up to 8 h (2 h control, 1 h ischemia, 3–6 h reperfusion). With an acquisition time of 10 min, TOF‐MRA proved to be suitable to analyze the vascular state of occlusion and reperfusion repetitively in longitudinal studies. Spatial resolution was sufficient to observe neurovascular structural details. In eight out of 10 animals complete vessel occlusion by the intraluminal thread could be validated by an entirely extinguished signal of the ipsilateral middle cerebral artery (MCA) in the angiograms. This was in accordance with a perfusion deficit in the MCA vascular territory detected by PWI (reduction to 30.4 ± 7.4% relative to contralateral side) and a disturbance of water ion homeostasis monitored by DWI in this area. One animal showed a delayed occlusion after 30 min of MCA occlusion, in another animal vessel occlusion failed. In seven out of the eight successful occlusion experiments there was immediate reperfusion after withdrawal of the thread. One animal showed a delayed reperfusion after suture retraction. Remarkable hemispheric differences in vascular branching of the MCA could be recognized in three out of 10 animals. In conclusion, TOF‐MRA is considered a helpful method to survey even in small laboratory animals the correct time course of vascular occlusion and reopening in experimental ischemia, and provides complementary information to the tissue perfusion status monitored by PWI and the ischemic lesion territory detected by DWI. Copyright © 2001 John Wiley & Sons, Ltd.

Abbreviations used:

ACA,

anterior cerebral artery;

AZACA,

azygos anterior cerebral artery;

AZPA,

azygos pericallosal artery;

CarBif,

carotid bifurcation;

CCA,

common carotid artery;

CCAO,

common carotid artery occlusion;

CP,

caudate‐putamen;

DWI,

diffusion‐weighted imaging;

FLASH,

fast‐low‐angle‐shot;

FOV,

field of view;

Gd‐DTPA,

gadolinium‐diethylene‐triamine‐pentaacetic acid;

ICA,

internal carotid artery;

LDF,

laser doppler flow;

MCA,

middle cerebral artery;

MCAO,

middle cerebral artery occlusion;

MIP,

maximum intensity projection;

MOFrA,

medial orbitofrontal artery;

MR,

magnnetic resonance;

MRA,

magnetic resonance angiography;

MRI,

magnetic resonance imaging;

OlfA,

olfactory artery;

PCA,

posterior cerebral artery;

PPA,

pterygopalatinal artery;

PWI,

perfusion‐weighted imaging;

ROI,

region‐of‐interest;

SI,

signal intensity;

TOF‐MRA,

time‐of‐flight magnetic resonance angiography;

TE,

echo time;

TR,

repetition time.
Unique neuronal tracers show migration and differentiation of SVZ progenitors in organotypic slices
Authors: De Marchis S. , Fasolo A. , Shipley M. , Puche A.
Published: August 2002

Continual neurogenesis in the subventricular zone (SVZ) of postnatal and adult mammalian forebrain has been well documented, but the mechanisms underlying cell migration and differentiation in this region are poorly understood. We have developed novel in vivo and in vitro methods to investigate these processes. Using stereotaxic injections of a variety of tracers/tracker [Cholera Toxin β subunit (CTb‐), Fluorogold (FG), and Cell Tracker Green (CTG)], we could efficiently label SVZ cells. Over several days, labeled cells migrate along the rostral migratory stream (RMS) to their final differentiation site in the olfactory bulb (OB). The compatibility of these tracers/trackers with immunohistochemistry allows for cell labeling with multiple dyes (e.g., CTb and CTG) and/or specific cell antigens. To investigate the dynamics of migration we labeled SVZ progenitor cells with small injections of CTG and monitored the movements of individual cells in fresh parasagittal brain slices over several hours using time‐lapse confocal microscopy. Our observations suggest that tangential cell migration along the RMS occurs more rapidly than radial cell migration into the OB granule cell layer. To investigate migration over longer time periods, we developed an in vitro organotypic slice in which labeled SVZ progenitors migrate along the RMS and differentiate within the OB. The phenotypic characteristics of these cells in vitro were equivalent to those observed in vivo. Taken together, these methods provide useful tools investigating cell migration and differentiation in a preparation that maintains the anatomical organization of the RMS. © 2001 John Wiley & Sons, Inc. J Neurobiol 49: 326–338, 2001
Calcium oscillations in neocortical astrocytes under epileptiform conditions
Authors: Tashiro Ayumu , Goldberg Jesse , Yuste Rafael
Published: August 2002

Morphological and functional alterations in astrocytic glia are often found in epileptic syndromes, although the exact role of astrocytes in epilepsy is poorly understood. During calcium imaging of epileptiform events in juvenile neocortical slices we previously discovered cells with spontaneous oscillations in their intracellular free calcium concentration ([Ca2+]i). We have now characterized these oscillations using two in vitro models of epilepsy and find that they are produced by astrocytes. Astrocytic oscillations are widespread throughout the imaged territories, are remarkably regular and have long periods, averaging 100 s, which become shorter during development. Astrocytic oscillations are uncorrelated among themselves and with epileptiform events, are blocked by internal release antagonists and are stimulated by caffeine. Astrocytic calcium oscillations could mediate reactive astrogliosis, contribute to the pathogenesis of chronic epileptic syndromes, and be used as a diagnostic test for epileptic tissue. © 2002 Wiley Periodicals, Inc. J Neurobiol 50: 45–55, 2002
Binding characteristics of chondroitin sulfate proteoglycans and laminin‐1, and correlative neurite outgrowth behaviors in a standard tissue culture choice assay
Authors: Snow Diane M. , Smith Jeffrey D. , Gurwell Julie A.
Published: August 2002

Neuronal growth cones are capable of sophisticated discrimination of environmental cues, on cell surfaces and in the extracellular matrix, to accomplish navigation during development (generation) and following nervous system injury (regeneration). Choices made by growth cones are commonly examined using tissue culture paradigms in which molecules of interest are purified and substratum‐bound. From observations of growth cone behaviors using these paradigms, assertions are made about choices neuronal growth cones may make in vivo. However, in many cases, the binding, interactions, and conformations of these molecules have not been determined. In the present study, we investigated the binding characteristics of two commonly studied outgrowth regulatory molecules: chondroitin sulfate proteoglycans (CSPGs), which are typically inhibitory to neurite outgrowth during development and following nervous system injury, and laminin, which is typically outgrowth promoting for many neuronal types. Using a novel combination of radiolabeling and quantitative fluorescence, we determined the precise concentrations of CSPGs and laminin‐1 that were bound separately and together in a variety of choice assays. For identically prepared cultures, we correlated neurite outgrowth behaviors with binding characteristics. The data support our working hypothesis that neuronal growth cones are guided by the ratio of outgrowth‐promoting to outgrowth‐inhibiting influences in their environment, i.e., they summate local molecular cues. The response of growth cones to these molecular combinations is most likely mediated by integrins and subsequent activation of signal transduction cascades in growth cones. © 2002 Wiley Periodicals, Inc. J Neurobiol 51: 285–301, 2002
Regulation of the cycling of timeless (tim) RNA
Authors: Wang Garrick K. , Ousley Andrea , Darlington Thomas K. , Chen Dechun , Chen Yifeng , Fu Weili , Hickman Lesley J. , Kay Steve A. , Sehgal Amita
Published: August 2002

Circadian rhythms in Drosophila depend upon expression of the timeless (tim) and period (per) genes, which encode interacting components of the endogenous clock. These two clock genes show a robust circadian oscillation in transcription rate as well as RNA and protein levels. Transcriptional activation of both genes requires the basic helix‐loop‐helix (bHLH) PAS transcription factors dCLOCK (dCLK) and CYCLE (CYC), which bind E‐box elements. We investigated the role of E‐box elements in regulating behavioral rhythmicity and tim gene expression. We show that mutation of the upstream E‐box in the tim gene prevents the rescue by tim cDNA sequences of the arrhythmic tim01 phenotype. RNA encoded by this mutated tim transgene fails to cycle and is expressed at low levels. While a tim transgene carrying a wild‐type E‐box restores behavioral rhythms, tim RNA levels are intermediate to those of the mutant E‐box transgenic lines and wild type, and do not display high amplitude cycling. On the other hand, high‐amplitude RNA cycling was consistently obtained with a tim transgene that contains genomic, rather than cDNA, sequences. To identify additional sequences that may be required for tim cycling, we investigated the role of an E‐box in the first intron of the tim gene through cell culture experiments. In these experiments, the presence of this intron did not have any effect on the activation of tim transcription by dCLK/CYC. As the upstream E‐box was implicated in activation by dCLK/CYC in cell culture, we assayed sequences containing this E‐box for association with proteins in fly head extracts. These studies provide the first biochemical evidence for an in vivo complex containing dCLK and CYC that binds the tim upstream sequence and is detected at all times of day. Together, these data highlight molecular mechanisms that are critical for behavioral rhythms. © 2001 John Wiley & Sons, Inc. J Neurobiol 47: 161–175, 2001
Sodium channel distribution on uninnervated and innervated embryonic skeletal myotubes
Authors: Anson Blake D. , Roberts William M.
Published: August 2002

Acetylcholine receptor (AChR) and sodium (Na+) channel distributions within the membrane of mature vertebrate skeletal muscle fibers maximize the probability of successful neuromuscular transmission and subsequent action potential propagation. AChRs have been studied intensively as a model for understanding the development and regulation of ion channel distribution within the postsynaptic membrane. Na+ channel distributions have received less attention, although there is evidence that the temporal accumulation of Na+ channels at developing neuromuscular junctions (NMJs) may differ between species. Even less is known about the development of extrajunctional Na+ channel distributions. To further our understanding of Na+ channel distributions within junctional and extrajunctional membranes, we used a novel voltage‐clamp method and fluorescent probes to map Na+ channels on embryonic chick muscle fibers as they developed in vitro and in vivo. Na+ current densities on uninnervated myotubes were approximately one‐tenth the density found within extrajunctional regions of mature fibers, and showed several‐fold variations that could not be explained by a random scattering of single channels. Regions of high current density were not correlated with cellular landmarks such as AChR clusters or myonuclei. Under coculture conditions, AChRs rapidly concentrated at developing synapses, while Na+ channels did not show a significant increase over the 7 day coculture period. In vivo investigations supported a significant temporal separation between Na+ channel and AChR aggregation at the developing NMJ. These data suggest that extrajunctional Na+ channels cluster together in a neuronally independent manner and concentrate at the developing avian NMJ much later than AChRs. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 42–57, 2001
Comparison of several numerical methods for mechanical systems with impacts
Authors: Janin O. , Lamarque C. H.
Published: August 2002

The modellization of mechanical systems with non‐linearities of impact type leads to discontinuities in the velocity. In this paper, we study some numerical methods adapted to the occurrence of such discontinuities from a single‐degree‐of‐freedom vibro‐impact system. Theoretical results of consistency are given for numerical methods valid for smooth ordinary differential equations, with several kinds of procedures for approximating impact times. The algorithms are applied to classical Newmark and Runge–Kutta schemes, and the numerical behaviour is investigated for two categories of periodic response, either with finite or infinite number of impacts per cycle. These numerical methods are compared to a scheme without explicit computation of impact times. We show that high orders of convergence can be obtained with appropriate schemes, and we discuss the time of computation needed in each case. Copyright © 2001 John Wiley & Sons, Ltd.
Stability of time‐splitting schemes for the Stokes problem with stabilized finite elements
Authors: Picasso Marco , Rappaz Jacques
Published: August 2002

The time‐dependent Stokes problem is solved using continuous, piecewise linear finite elements and a classical stabilization procedure. Four order‐one methods are proposed for the time discretization. The first one is nothing but the Euler backward scheme and requires a large linear system involving the velocity and pressure unknowns to be solved. The other three schemes allow velocity and pressure computations to be decoupled, namely the pressure‐matrix method, a method based on an inexact LU factorization, and an operator splitting method. Stability and condition number estimates are derived. Numerical experiments in two space dimensions confirm the theoretical predictions. © 2001 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 17:632–656, 2001
Relationship of psychosocial tasks of pregnancy and attentional functioning in the third trimester
Authors: Stark Mary Ann
Published: August 2002

Because childbearing women function in multiple roles, the capacity to focus or concentrate is an important resource while preparing for birth and parenting. In addition to daily tasks that require mental effort, gravidas have psychosocial demands related to pregnancy. The purpose of this study was to examine the relationship between the psychosocial tasks of pregnancy and the capacity to focus or direct attention. A convenience sample of 57 pregnant women in their third trimester was recruited from prenatal education classes to participate in this descriptive correlational study. After other variables thought to influence attentional functioning were considered, women experiencing the greatest conflict in psychosocial tasks had the most difficulty using directed attention and more negatively evaluated their attentional functioning. In order to empower gravidas to participate in their health care, it is important for researchers and practitioners to understand and support directed attentional functioning, an important area for nursing care and research. © 2001 John Wiley & Sons, Inc. Res Nurs Health 24: 194–202, 2001
Effects of two frequencies of walking on cardiovascular risk factor reduction in Mexican American women§
Authors: Keller Colleen , Treviño Robert P.
Published: August 2002

The beneficial effects of moderate‐intensity exercise on cardiorespiratory fitness and body composition are well documented, with the greatest health benefits reported in sedentary individuals who engage in moderate levels of exercise. The published literature contains no quantification of the threshold of lower limits of beneficial exercise or estimates of benefits derived from lower exercise levels. The specific aim of this study was to compare the effects of two walking frequencies, holding intensity and duration constant, on blood lipids, body composition, and exercise maintenance regimens of Mexican American women. A quasi‐experimental design, with two treatment groups and one comparison group, was used to explore the dose‐response effects of low‐intensity exercise on cardiovascular outcomes. Significant interactions were found between walking and total serum cholesterol and skin‐fold sums. This study demonstrated the clinical efficacy of a low‐intensity exercise regimen on cardiovascular risk factors and exercise adherence. © 2001 John Wiley & Sons, Inc. Res Nurs Health 24:390–401, 2001
Testing a preoperative pain management intervention for elders¶
Authors: McDonald Deborah Dillon , Freeland Marjorie , Thomas Glenda , Moore Joan
Published: August 2002

The investigators examined whether elders who have been taught pain management communication skills and pain management information obtain greater postoperative pain relief than elders not taught this information. Thirty‐one elders were randomly assigned preoperatively to a control or communication group in this posttest‐only experiment with repeated measures. Communication group participants were taught pain management, pain communication skills, and the use of two pain‐intensity scales. Control group participants were taught to use the two pain‐intensity scales. Pain was measured with the McGill Pain Questionnaire Short Form. The communication group elders reported less postoperative pain over the course of their hospital stay. Pain management knowledge alone may have enabled the elders to obtain greater pain relief. Nurses may want to incorporate similar pain management information and pain communication skills when teaching elders how to obtain greater postoperative pain relief. © 2001 John Wiley & Sons, Inc. Res Nurs Health 24:402–409, 2001
A 19th century post‐mortem specimen from Deal, Kent
Authors: Anderson T.
Published: August 2002

A disarticulated cranium from a builder's trench displayed clear evidence for surgical removal of the cranial vault. Documentary evidence indicates that the post‐mortem was undertaken between 1812–1869 and the patient was probably a British serviceman. Copyright © 2002 John Wiley & Sons, Ltd.
Proanthocyanidins of mountain birch leaves: quantification and properties
Authors: Ossipova Svetlana , Ossipov Vladimir , Haukioja Erkki , Loponen Jyrki , Pihlaja Kalevi
Published: August 2002

Proanthocyanidins (PAs; condensed tannins) are present in mountain birch leaves in soluble and cell wall‐bound forms. Crude preparations of soluble PAs were isolated from birch leaves and purified by chromatography on a Sephadex LH‐20 column with a yield of about 7% of leaf dry mass. Some chemical characteristics were elucidated with 13C‐NMR and HPLC‐ECI‐MS. Birch leaf PAs were mainly delphinidin type oligo‐ and polymers with average molecular mass of about 3000. In order to quantify PAs, the method involving heating PA‐containing materials in 1‐butanol:hydrochloric acid (95:5, v/v), and spectrophotometric determination of the anthocyanidin monomers so formed was modified and optimised. Mature leaves were characterised by a relatively high content of PAs: mean values for soluble and bound PAs were 103 and 40 mg/g dry mass, respectively. In mature leaves the soluble PAs determined the total protein precipitation capacity (PPC) of extracts. In young leaves, the contribution of PAs to the total content of phenolics and the total PPC of tannins was about 20–25% only. Copyright © 2001 John Wiley & Sons, Ltd.
Determination of marker constituents from Cissus quadrangularis Linn. and their quantitation by HPTLC and HPLC
Authors: Mehta Manisha , Kaur Navneet , Bhutani K. K.
Published: August 2002

Four marker constituents, namely, onocer‐7‐ene‐3α,21β‐diol, δ‐amyrin, δ‐amyrone and 3,3′,4,4′‐tetrahydroxybiphenyl of an Ayurvedic crude drug Cissus quadrangularis Linn. are defined for standardisation purposes. 3,3′,4,4′‐Tetrahydroxybiphenyl has been isolated for the first time from this drug. The contents of the marker constituents were quantitatively determined by HPTLC and HPLC methods in samples collected from five different geographic zones of India. Copyright © 2001 John Wiley & Sons, Ltd.
Detection of Y chromosome‐specific DNA in the plasma and urine of pregnant women using nested polymerase chain reaction
Authors: Al‐Yatama Majda K. , Mustafa Abu S. , Ali Sadiq , Abraham Sobha , Khan Zohra , Khaja Nawal
Published: August 2002

The present study was undertaken to evaluate a nested polymerase chain reaction (PCR) for detection of Y chromosome‐specific fetal DNA in maternal plasma and urine of pregnant women during different gestational stages. DNA isolated from plasma and urine samples of 80 pregnant women (between 7 and 40 weeks' gestation) underwent amplification for Y chromosome‐specific 198 bp DNA by nested PCR. The postpartum analysis of fetal gender showed that 55 women carried male and 25 female fetuses. Among the 55 women bearing male fetuses, Y chromosome‐specific signals were detected in 53 (96%) plasma and 21 (38%) urine samples. Moreover, out of 25 women bearing female fetuses, 3 (12%) and 1 (4%) women had Y chromosome‐specific signal in plasma and urine, respectively. Analysis of results with respect to gestational age revealed that there was no significant difference in the detection of Y chromosome‐specific DNA between different trimesters in maternal plasma of women bearing male fetuses. These results showed that fetus‐specific DNA was detected with high sensitivity (96%) and specificity (88%) in the maternal plasma by nested PCR, and therefore the method could be useful as a non‐invasive procedure for fetal sex determination and prenatal diagnosis. Copyright © 2001 John Wiley & Sons, Ltd.
Diabetic holiday foot syndrome – the dimension of the problem and patients' characteristics
Authors: Morbach Stephan , Möllenberg Jörg , Quante Christoph , Ochs Hermann‐Rudolf
Published: August 2002

Frequency, course and outcome of diabetic foot ulcers originating during foreign holidays, known as the recently described ‘diabetic holiday foot syndrome’, was investigated during an ongoing prospective study.

Among 435 study patients, 17 (3.9%) experienced their foot lesions during a foreign holiday. Unaccustomed exercise and barefoot walking on the beach were the predominant causative events leading to the observed lesions. Patients suffering from the described condition were of younger age and had shorter known diabetes duration than patients with foot lesions of other origin. There was also a higher proportion of male patients, a lower prevalence of ischemic lesions, and a shorter delay of presentation to the foot clinic among the ‘holiday foot’ group. Severity of the lesions at presentation (Wagner classification) and frequency of unavoidable amputation were comparable for patients in both groups.

Our results demonstrate the need for including preventative considerations during holiday travels and unaccustomed exercise in intensified education for diabetic patients at high risk for foot lesions. Copyright © 2001 John Wiley & Sons, Ltd.
Accessing third‐party data for research: trust me? trust me not?
Authors: Dreyer Nancy A.
Published: August 2002

Epidemiologists are often asked to evaluate product safety or provide information about the history of disease and use of health services. Most of this research is conducted through sponsorship from a governmental or other non‐profit agency, or with direct support from a for‐profit company with an economic interest in the outcome. Vast amounts of information that are routinely collected for administrative and billing purposes may also be used for research. These data can reveal information about the etiology of disease, utilization patterns of prescription drugs, and trends in disease occurrence. Using third‐party data requires a trusting partnership between researchers and data custodians. Although such data offer public health benefits, their use can also lead to embarrassment and legal action. Five guiding principles will help outside contractors facilitate access to third‐party data and avoid pitfalls. (1) Understand the sponsor's objectives by understanding the purpose of the research. (2) Identify and approach data resources that have appropriate information. (3) Consider special issues relating to accessing confidential information. (4) Establish terms of the research engagement with the sponsor. (5) Establish ground rules with the data provider. Copyright © 2001 John Wiley & Sons, Ltd.
Oxidative polymerization of N‐vinylcarbazole in polymer matrix
Authors: Ustamehmetoğlu Belkis , Sezer Esma , Saraç A Sezai
Published: August 2002

A new class of soluble conductive poly(N‐vinylcarbazole) (PVCz) compounds has been developed by oxidative matrix polymerization of N‐vinylcarbazole (NVCz) by Ce(IV) in the presence of poly(ethylene glycol) (PEG). PEG was found to be a more suitable matrix with which to obtain a stable homogenous ternary complex solution when compared with poly(acrylic acid) (PAA) and poly(vinylpyrrolidone) (PVP). The role of PEG, NVCz and Ce(IV) concentration, order of component addition, the structure of the polymer matrix, molecular weight of polymer and the effect of solvent have been investigated. Obtaining soluble PEG–Ce(III)–PVCz ternary complexes was shown by cyclic voltammetric measurements, and the initial rate of formation NVCz cation radicals as calculated using UV–visible spectrophotometry. Advantageously with these soluble complexes, conductivities could be measured both in solution and in the solid state.

© 2001 Society of Chemical Industry
Peroxide macro‐initiators for improving biodegradability of polymers
Authors: Voronov Stanislav , Donchak Vladimir , Harhai Hhristina , Tokarev Viktor , Fernandez Claudio
Published: August 2002

Modification of dextrin by tert‐butylperoxy methanol or its acylation with cyclic anhydride containing a peroxide group resulted in macro‐initiators with randomly located peroxide fragments in the polysaccharide.

When dextran was oxidized with iodic acid, dialdehydedextran was obtained. Its aldehyde groups reacted with tert‐butyl hydroperoxide to give functional peroxide groups. The content of peroxide fragments depended directly on the ratio of reagents.

The resulting macro‐initiators may be used for synthesizing graft copolymers with polystyrene on poly(butyl acrylate) containing polysaccharide.

© 2001 Society of Chemical Industry
Electrical conductivity properties of poly[(maleic acid)‐co‐(vinyl pyrrolidone)] salts in aqueous solutions
Authors: Ríos Hernán E
Published: August 2002

The interaction of alkaline ions with an anionic dicarboxylic polyelectrolyte is studied by means of electrical conductivity measurements. The results show that lithium, sodium and potassium counter‐ions interact in a very different way with this polyelectrolyte. The Kohlrausch plots bend downwards in the high‐dilution zone. The limiting equivalent conductivities of these polymers were then determined according to Vink's method by a polynomial adjustment of specific conductivity data. Whereas the dissociation order follows the sequence Li+ > Na+ > K+, the trend in equivalent conductivity follows the reverse order, and apparently is mainly determined by the equivalent conductivity of the counter‐ions. The interaction parameter f was determined using the Manning theory for the limiting equivalent conductivity of the polyion species. From the values of the latter parameters, the average distance between charges agrees well with that calculated from simple geometrical calculations for a mesomeric configuration. An alternative method was used to obtain the relative interaction parameter f* as a function of polymer concentration. The results can be explained in terms of the hydration parameters and the limiting equivalent conductivities of the counter‐ions.

© 2001 Society of Chemical Industry
Part 3. General kinetic model of the sulfonation of PEEK fluoroarylketone chain‐end repeat unit
Authors: Daoust D , Devaux J , Godard P
Published: August 2002

The sulfonation kinetics of the fluoroarylketone chain‐end repeat unit of PEEK was studied. To achieve this objective, the sulfonation reactions of a trimer, a tetramer and a polymer, each fluoroarylketone ended, were followed by 19F NMR.

A general kinetic model was developed to determine the kinetic constants from 19F NMR data. The reliability of the kinetic model and of its mathematical expression was ensured. The kinetic constants are then calculated and discussed. In particular, they were compared with the dimer rate constants previously determined.

Lastly and as a conclusion of this work, a general kinetic model describing the sulfonation of main chain repeat units of PEEK is proposed.

© 2001 Society of Chemical Industry
Effect of the type of nylon chain‐end on the compatibilization of PP/PP‐GMA/nylon 6 blends
Authors: Tedesco Adriana , Krey Patrícia F , Barbosa Ronilson V , Mauler Raquel S
Published: August 2002

Polyamide and polypropylene (PP) are two important classes of commercial polymers; however, their direct mixing leads to incompatible blends with poor properties. Polypropylene functionalized with glycidyl methacrylate (PP‐GMA) was used as a compatibilizer in blends of PP and nylon 6, because of the possible reaction of NH2 and COOH groups with the epoxide group of GMA. Two types of nylon 6 with different ratios between NH2 and COOH groups were used. The one with higher concentration of COOH groups was less compatible with PP in a binary blend. When PP‐GMA was used as a compatibilizer, a better dispersion of nylon in the PP matrix was obtained together with better mechanical properties for both nylons used in this work.

© 2001 Society of Chemical Industry
Use of radiation grafted PVC–acrylamide membranes in radioactive waste treatment
Authors: Maziad Nabila A , Sayed Magda S , Hegazy El‐Sayed A
Published: August 2002

Acrylamide monomer (AAm) was grafted onto poly(vinyl chloride) (PVC) films using γ‐radiation to produce high performance functional membranes which can be employed as ion‐exchangers. The preparation and characterization of the synthetic membranes are investigated. To elucidate their possible applications, some selected properties have been studied. In addition, thermal properties have been studied using thermogravimetric analysis and differential scanning calorimetry; X‐ray diffraction has been used to determine changes in polymer morphology. The selectivity of such membranes towards different radionuclides has also been investigated. On the basis of these investigations, the applicability of the prepared membranes is determined and discussed. The prepared PVC‐g‐PAAm has a great tendency to remove 60Co from a radioactive liquid waste containing both 60Co and 137Cs.

© 2002 Society of Chemical Industry
Effect of composition and polyesterification catalysts on the optical properties of cured polyesters
Authors: Simitzis J , Zoumpoulakis L , Soulis S
Published: August 2002

Unsaturated polyesters based on ethylene glycol have been synthesized using a variety of anhydride, saturated and unsaturated dicarboxylic acids and various catalysts. The structure of the polyesters and the effect of the different compositions on the colour of cured polyesters are studied by FTIR, DSC and colorimetry. The structure of cured polyesters greatly depends on the isomerization of maleic acid to fumaric acid during polyesterification. The colour of unsaturated polyesters cured with the most common curing system (MEKP as initiator and CoNp as accelerator) is firstly influenced by the curing accelerator CoNp via the d–d transitions of the transition metal cobalt. Secondly, the composition of the dicarboxylic acids and anhydride used in the polyesterification influences the colour of the polyesters which depends especially on the isomerization of maleic acid. The cured maleate polyesters have more unreacted double bonds and more polar structure because of the presence of carbonyl groups, compared to the corresponding fumarate polyesters, and this structure affects the colour. The residual catalysts from the polyesterification have minor influence on the colour of cured polyesters.

Copyright © 2002 Society of Chemical Industry
Polymerization of ethylene using a SiO2–MgCl2 supported bis(cyclopentadienyl)zirconium(IV) or titanium(IV) dichloride catalyst
Authors: Sensarma Soumen , Sivaram Swaminathan
Published: August 2002

Silica supported MgCl2–Cp2MCl2 (M = Ti or Zr) catalysts (Si–Mg–M) were prepared by deposition of a homogeneous solution of a metallocene and anhydrous magnesium chloride in tetrahydrofuran (THF) onto a high surface area silica (SiO2). Catalyst thus prepared show higher polymerization activity when compared to metallocenes supported on either silica or magnesium chloride alone. The molecular weight and polydispersity of the poly(ethylene)s obtained from metallocenes supported on SiO2–MgCl2 were found to be higher and narrower, respectively, relative to silica or MgCl2 supported metallocene catalysts.

© 2002 Society of Chemical Industry
Structure and imidization of polyamic acid salt Langmuir–Blodgett films
Authors: Jin Bangkun , He Pingsheng , Zhou Yue , Chen Yin
Published: August 2002

Polyimide Langmuir‐Blodgett (LB) films were prepared with a Pyromellitic dianhydride‐4, 4′ oxydianiline precursor, and the properties of the polyamic acid salt monolayer characterized by different methods. The π‐A relationship revealed that the precursor monolayer exhibits anisotropy on the water surface, the Wilhelmy plate being more sensitive to pressure when it is perpendicular to the compression direction. FTIR results showed that polyamic acid salt LB films have lower imidization energy than the corresponding painting films and can be imidized at lower temperature. The molecular arrangement in the LB films was studied by X‐ray diffraction and polarized FTIR, showing that the polyamic acid salt LB film is of Y‐type, in which the molecules are highly oriented, with the main chain lying parallel to the substrate and the long fatty acid chains stretching out at a certain angle.

© 2002 Society of Chemical Industry
Belt furnace gettering and passivation of n‐web silicon for high‐efficiency screen‐printed front‐surface‐field solar cells
Authors: Ebong A. , Hilali M. , Rohatgi A. , Meier D. , Ruby D. S.
Published: August 2002

Six different resistivities (0.32, 0.57, 1.2, 2.2, 9.1 and 20 Ω cm) were investigated to understand the dopant–defect interaction in n‐type, antimony‐doped, dendritic web silicon ribbon, and to study its response to gettering and passivation during belt furnace processing (BFP). The as‐grown lifetime was found to be a strong function of resistivity with higher resistivity displaying higher lifetime. Phosphorus gettering at 925° C/6 min raised the as‐grown lifetime of ∼1 μs in 20 Ω cm n‐web to 5.4 μs. A combination of phosphorus gettering followed by simultaneous Al gettering and SiN hydrogenation raised the 20 Ω cm n‐web lifetime to 78 μs. Unlike the as‐grown web, the processed lifetime was greater than 75 μs for all resistivities, with no clear doping dependence. This is attributed to the very effective gettering and passivation during the belt furnace processing. Front surface field (FSF) n+–n–p+ cells were fabricated by spin‐on phosphorus diffusion on the front and screen‐printed Al on the back. A lifetime value of over 100 μs was obtained in a 14.2% screen‐printed FSF n‐web solar cell fabricated on 100‐μm‐thick 20 Ω cm substrate. The screen‐printed FSF cell fabricated on (111) FZ gave an efficiency of 14.9% with a fill factor of 77.6%. These results are supported by model calculations, which revealed a maximum efficiency of ∼15% for 100‐μm‐thick planar screen‐printed FSF cells and their insensitivity to bulk lifetime above 60 μs. Copyright © 2001 John Wiley & Sons, Ltd.
Preparation of polythioamides from dialdehydes and diamines with sulfur by the Willgerodt–Kindler type reaction
Authors: Kanbara Takaki , Kawai Yoritatsu , Hasegawa Kiyoshi , Morita Hiroyuki , Yamamoto Takakazu
Published: August 2002

Willgerodt–Kindler type reactions of dialdehydes and diamines in the presence of sulfur were investigated for preparation of polythioamides. The one‐pot, three‐component polycondensation afforded various polythioamides in moderate to good yields. The appropriate reaction conditions were examined for the separate monomers. The results led us to the proposed mechanism for the polycondensation including formation of the intermediate Schiff base polymers followed by the successive nucleophilic attack of polysulfide anions to the azomethine units to give the thioamide groups. Structure, solubility, and thermal properties of the polythioamides were also compared with those of analogous polyamides. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3739–3750, 2001
Synthesis of photoreactive calixarene derivatives containing pendant cyclic ether groups
Authors: Nishikubo Tadatomi , Kameyama Atsushi , Tsutsui Kousuke
Published: August 2002

New photoreactive calixarene derivatives containing cationically polymerizable pendant oxetane groups (calixarenes 1a,b, 2a,b, and 3a,b) were synthesized in good yields by the substitution reaction of C‐methylcalix[4]resorcinarene (CRA), p‐methylcalix[6]arene (MCA), and p‐tert‐butylcalix[8]arene (BCA) with (3‐methyloxetan‐3‐yl)methyl 4‐toluenesulfonate and (3‐ethyloxetan‐3‐yl)methyl 4‐toluenesulfonate with potassium hydroxide as a base and tetrabutylammonium bromide as a phase‐transfer catalyst in N‐methyl‐2‐pyrrolidone, respectively. Calixarene derivatives containing cationically polymerizable pendant oxirane groups (calixarenes 4, 5, and 6) were also prepared in good yields by the substitution reaction of CRA, MCA, and BCA with epibromohydrin, respectively, with cesium carbonate as a base in N‐methyl‐2‐pyrrolidone. The thermal stability of the obtained calixarene derivatives containing pendant oxetane groups or oxirane groups was examined with thermogravimetric analysis, and it was found that these calixarene derivatives had thermal stability beyond 340 °C. The photochemical reaction of calixarenes 1, 2, and 3 containing pendant oxetane groups was examined with certain photoacid generators in the film state. In this reaction system, calixarene 1a, composed of a CRA structure and pendant (3‐methyloxetan‐3‐yl)methyl groups, showed the highest photochemical reactivity when bis‐[4‐(diphenylsulfonio)phenyl]sulfide bis(hexafluorophosphate) was used as the catalyst. The photochemical reaction of calixarenes 4, 5, and 6 containing pendant oxirane groups was also examined, and it was found that the photoinitiated cationic polymerization of calixarenes 4, 5, and 6 proceeded smoothly under the same conditions; however, the reaction rates were lower than those of the corresponding calixarenes 1, 2, and 3 containing pendant oxetane groups. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1169–1179, 2001
Spontaneous alternating copolymerization of isobutoxyallene with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione
Authors: Yamamoto Shin‐Ichi , Sanda Fumio , Endo Takeshi
Published: August 2002

The spontaneous copolymerization of isobutoxyallene (1) with 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione (2) was carried out to afford a copolymer with a number‐average molecular weight of 5900–10,300. The copolymer consisted of a 2,3‐polymerization unit of 1 and a NN polymerization unit of 2, maintaining an alternating character regardless of the monomer feed ratio. The corresponding copolymerization of 1 with 2 in the presence of methanol afforded the adduct of the compounds without the polymer, indicating the generation of a zwitterion of 1 and 2. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1564–1571, 2001
Copolymerization with depropagation: A study of α‐methyl styrene/methyl methacrylate in solution at elevated temperatures
Authors: Palmer D. E. , McManus N. T. , Penlidis A.
Published: August 2002

In free‐radical polymerization, solvents are routinely used to reduce the solution viscosity and molecular weight. In the case of the α‐methyl styrene/methyl methacrylate copolymer system, reducing the monomer concentration also has significant effects on the copolymer composition and maximum conversion obtained. Reactivity‐ratio studies as well as full‐conversion‐range data were provided, and the results were compared to similar data in the bulk phase from our earlier work. A 30 wt % toluene solution was used for all experimental conditions. Copolymer composition modeling results were also presented. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1753–1763, 2001
Water‐soluble acrylamide copolymers. IX. Preparation and characterization of the cationic derivatives of poly(acrylamide‐co‐n,n‐dimethylacrylamide), poly(acrylamide‐co‐methacrylamide), and poly(acrylamide‐co‐n‐t‐butylacrylamide)
Authors: Klimchuk Keith A. , Hocking Martin B. , Lowen Stephen
Published: August 2002

This article extends the preparative details of a series of nonionic copolymers of acrylamide with N,N‐dimethylacrylamide, methacrylamide, and N‐t‐butylacrylamide to the synthesis of cationic derivatives of these new copolymers. The described procedures gave products with cationicities of 14–26 mol %. We measured the mean squared radii of gyration and intrinsic viscosities of aqueous solutions of these products at several different pHs and NaCl concentrations to compare these values with those determined for the nonionic precursors and related commercial cationic polymers. Because the molecular weights of the examples measured varied widely, it was difficult to establish definite trends. However, the large values obtained for the mean squared radii of gyration and intrinsic viscosities, relative to the nonionic precursors of these polymers, demonstrated that the charged groups had a qualitatively greater effect on polymer extension than the nonpolar bulky groups. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2525–2535, 2001
Emulsion copolymerization of butyl acrylate with cationic monomer using interfacial redox initiator system
Authors: Luo Yingwu , Schork F. Joseph
Published: August 2002

The polymerization kinetics of butyl acrylate/[2‐(methacryloyoxy)ethyl]trimethyl ammonium chloride (BA/MAETAC) macroemulsion and miniemulsion copolymerizations was investigated with cumene hydroperoxide/tetraethylenepentamine as a redox initiator system. The postulate of an interfacial copolymerization with the two‐component redox initiator system (one hydrophobic and the other hydrophilic) was confirmed. Adding MAETAC had a complex effect on the polymerization kinetics of BA. The influence was ascribed to variations in the nucleation mechanism, which were dependent on the level of MAETAC, and the polymerization method (macroemulsion vs miniemulsion). It was proposed that at the beginning of a macroemulsion copolymerization with high MAETAC composition the micellar copolymerization occurred, which controlled the nucleation process. The hydration properties of the latex were used to characterize the copolymer composition. The composition of the copolymer from the interfacial polymerization was very heterogeneous. The copolymer composition was lower in BA when there was an increase in BA conversion or the particle size. Adding salt increased the MAETAC content and decreased the BA content in the copolymer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2696–2709, 2001
Surfactant characteristics of polystyrene/poly(ethylene oxide) macromonomers in aqueous solution and on polystyrene latex particles: Two‐step emulsion polymerizations
Authors: Gibanel Sebastien , Heroguez Valerie , Forcada Jacqueline
Published: August 2002

Macromonomers were synthesized by anionic “living” polymerization. They comprised a poly(ethylene oxide) hydrophilic block and a hydrophobic block or sequence terminated with an unsaturation. The surface activity properties of these materials (critical micelle concentration and parking area) were determined, and the values were compared and discussed in terms of the molecular structure of these new surfactants. Some of the macromonomers were employed as emulsifiers in two‐step emulsion polymerizations. The data obtained were discussed while taking into account the different chemical structures of the macromonomers and the efficiency of these species as emulsifiers in the polymerization recipes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2767–2776, 2001
Analysis of solvent diffusion in high‐density polyethylene using NMR imaging techniques
Authors: Malveau C. , Beaume F. , Germain Y. , Canet D.
Published: August 2002

Two different samples of high‐density polyethylene (HDPE) were studied. One (isotropic) was extracted from the material core, whereas the other (anisotropic) involved two sides that were in contact with the injection mold. Using radiofrequency field gradients, it was observed by NMR microscopy that these two sides favor toluene penetration into the material. Solvent diffusion in both samples could be successfully modeled, as demonstrated by the comparison between experimental NMR images and simulated images. Weight measurements appear to be consistent with the quantitative conclusions derived from NMR microscopy data. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2781–2792, 2001