bluuebunny/crossref_metadata_2025 huggingface dataset:
Catalytic combustion of chlorinated ethylenes over H‐zeolites
Authors: López‐Fonseca R , Gutiérrez‐Ortiz J I , Gutiérrez‐Ortiz M A , González‐Velasco J R
Published: January 2003

Several H‐zeolites (H‐Y, H‐ZSM‐5 and H‐MOR) were investigated for the catalytic combustion of chlorinated ethylenes, namely 1,1‐dichloroethylene and trichloroethylene. Conversion was inversely related to the chlorine content of the feed molecule. H‐ZSM‐5 zeolite was the most active catalyst in 1,1‐dichloroethylene combustion whereas H‐MOR was the most effective zeolite for trichloroethylene destruction. Temperature‐programmed desorption of ammonia and diffuse reflectance FT‐IR measurements of adsorbed pyridine revealed that strong Brønsted acidity plays an important role in controlling the activity of H‐zeolites. The main combustion products were CO, CO2, HCl, and Cl2. Additionally, small amounts of highly chlorinated by‐products were also detected, namely trichloroethylene and tetrachloroethylene. H‐zeolites showed a great selectivity to HCl formation.

© 2002 Society of Chemical Industry
Metal sorption by biomass of melanin‐producing fungi grown in clay‐containing medium
Authors: Fomina Marina , Gadd Geoffrey M
Published: January 2003

The sorption of toxic metals by fungal mycelia grown in clay‐containing medium is reported in this work. Biomass of melanin‐producing microfungi of the genus Cladosporium (C cladosporioides, C resinae and C herbarum) and Aureobasidium pullulans, clay minerals and fungal mycelia grown in clay‐containing medium were compared for their equilibrium Cu and Cd uptake from pH‐buffered solutions using experimental sorption isotherms. Bentonite (Cherkassy) in the natural form was shown to be the best Cu sorbent compared with the other clays and clay minerals tested. Cu sorption isotherms fitted the Langmuir sorption model for all cases. Comparison of Cu and Cd uptake for biomass and bentonite showed a lower biomass uptake capacity but a considerably higher affinity of the biosorbent for the solute. The presence of kaolinite and palygorskite in the medium generally reduced both Cu and Cd sorption capacity and the metal‐binding ability of the fungal–clay mixtures. In contrast, addition of bentonite into the medium did not appreciably alter the Cd sorption ability but increased the sorption of Cu by A pullulans and C cladosporioides grown in this medium. A common feature for all fungi grown in the presence of bentonite was an increase in the Cu sorption capacity (Qmax) of the biomineral sorbents and a reduction in their affinity (Langmuir parameter b) compared with control biomass. A difference between predicted and experimental data obtained for biomass grown on bentonite medium was also observed. The connection between the sorption capacity of biomass grown in clay‐containing medium, mycelial morphology and the structure of fungal pellets is discussed and a mechanism for the changed sorption capacity of the combined biomineral sorbents is proposed which involves blocking or modification of binding sites on biotic and abiotic components of the ‘biomineral’ association.

© 2002 Society of Chemical Industry
Removal of aqueous phenolic compounds from a model system by oxidative polymerization with turnip (Brassica napus L var purple top white globe) peroxidase
Authors: Duarte‐Vázquez Miguel A , Ortega‐Tovar Mónica A , García‐Almendarez Blanca E , Regalado Carlos
Published: January 2003

Turnip roots, which are readily available in Mexico, are a good source of peroxidase, and because of their kinetic and biochemical properties have a high potential as an economic alternative to horseradish peroxidase (HRP). The efficiency of using turnip peroxidase (TP) to remove several different phenolic compounds as water‐insoluble polymers from synthetic wastewater was investigated. The phenol derivatives studied included phenol, 2‐chlorophenol, 3‐chlorophenol, o‐cresol, m‐cresol, 2,4‐dichlorophenol and bisphenol‐A. The effect of pH, substrate concentration, amount of enzyme activity, reaction time and added polyethylene glycol (PEG) was investigated in order to optimize reaction conditions. A removal efficiency ≥85% was achieved for 0.5 mmol dm−3 phenol derivatives at pH values between 4 and 8, after a contact time of 3 h at 25 °C with 1.28 U dm−3 of TP and 0.8 mmol dm−3 H2O2. Addition of PEG (100–200 mg dm−3) significantly reduced the reaction time required (to 10 min) to obtain >95% removal efficiency and up to 230% increase in remaining TP activity. A relatively low enzyme activity (0.228 U dm−3) was required to remove >95% of three phenolic solutions in the presence of 100–200 mg dm−3 PEG. TP showed efficient and fast removal of aromatic compounds from synthetic wastewaters in the presence of hydrogen peroxide and PEG. These results demonstrate that TP has good potential for the treatment of phenolic‐contaminated solutions.

© 2002 Society of Chemical Industry
Freeze‐drying of lignin peroxidase: influence of lyoprotectants on enzyme activity and stability
Authors: Capolongo Antonio , Barresi Antonello A , Rovero Giorgio
Published: January 2003

The effect of different lyoprotectants (sucrose, dimethyl‐succinate buffer (DMS), bovine serum albumin (BSA), mannitol and dextran, mw 60 kDa) on the stability of the enzyme lignin peroxidase (LiP, EC number: 1.11.1.‐), both during the freeze‐drying process and storage were investigated. The shelf stability tests were performed at 4 °C and 27 °C. Both DMS buffer and sucrose showed a good protective action: the former was particularly effective during the process, while the latter improved the stability during storage. In contrast, mannitol and dextran had negative effects, reducing the activity also in the lignin peroxidase solution. BSA was discarded because, in the range of compatible concentrations with LiP, it does not confer a consistent structure to the freeze‐dried product.

© 2002 Society of Chemical Industry
Modelling arsenic(III) adsorption from water by sulfate‐modified iron oxide‐coated sand (SMIOCS)
Authors: Vaishya Rakesh Chandra , Gupta Sudhir Kumar
Published: January 2003

A medium developed by coating BaSO4 and Fe on quartz sand known as sulfate‐modified iron oxide‐coated sand (SMIOCS) was evaluated for the removal of arsenic(III) from simulated water with an ionic strength of 0.01 M NaNO3 during batch studies. The medium was characterised for BET surface area, alkali‐resistance, acid‐resistance and the presence of iron and barium on the coated surface. Two simplified kinetic models, ie active available site (AAS) and chemical reaction rate models, were tested to investigate the adsorption mechanisms. The values of rate constants for both the models were found to decrease with increasing As(III) concentrations in the solute. The inverse relationship of rate constants of the reaction rate model with BET surface area showed that As(III) adsorption on SMIOCS was not due to physisorption but to chemisorption. A study of the effect of solute temperature showed that the adsorption of As(III) on SMIOCS media was due to chemisorption. The results of isothermal studies conducted at different pH values showed that adsorption data satisfied both the Langmuir and the Freundlich isotherm models. The adsorption of As(III) on the medium was pH dependent and maximum removal was observed in the pH range of 7–9.

© 2002 Society of Chemical Industry
Late‐glacial and early Holocene changes in vegetation and lake‐level at Hauterive/Rouges‐Terres, Lake Neuchâtel (Switzerland)
Authors: Magny Michel , Thew Nigel , Hadorn Philippe
Published: January 2003

Palynological and sedimentological analyses of a sedimentary sequence sampled at Hauterive/Rouges‐Terres, Lake Neuchâtel (Switzerland) provide documentation of changes in vegetation and lake‐level during the Bølling, Younger Dryas and Preboreal pollen zones, and have allowed a comparison with sequences covering the same period from other sites located in the western part of the Swiss Plateau. The Juniperus–Hippophaë zone (regional pollen assemblage zone (RPAZ) CHb‐2, first part of the Bølling, ca. 14 650–14 450 cal. yr BP) was characterised by a generally low lake‐level. A weak rise occurred during this zone. The Juniperus–Hippophaë to Betula zone transition coincided with a lake‐level lowering, interrupted by a short‐lived but marked phase of higher lake‐level recorded at the neighbouring site of Hauterive‐Champréveyres, but not present at Hauterive/Rouges‐Terres owing to an erosion surface. Shortly after the beginning of the Betula zone (RPAZ CHb‐3, second part of the Bølling, ca 14 450–14 000 cal. yr BP), a marked rise in lake‐level occurred. It was composed of two successive periods of higher level, coinciding with high values of Betula, separated by a short episode of relatively lower lake‐level associated with raised values in Artemisia and other non‐arboreal pollen. The last part of RPAZ CHb‐3 saw a fall in lake‐level. The lower lake‐levels during RPAZ CHb‐2 to early RPAZ CHb‐3 can be correlated with the abrupt warming at the beginning of the Greenland Interstadial (GI) 1e thermal maximum. The successive episodes of higher lake‐level punctuating the GI 1e might be linked to the so‐called Intra‐Bølling Cold Oscillations identified from several palaeoclimatic records in the North Atlantic area, and also documented in oxygen‐isotope data sets from Swiss Plateau lakes. The Hauterive/Rouges‐Terres lake‐level record provides evidence for marked climatic drying through the second part of the Younger Dryas event (GS1), during the GS1–Preboreal (RPAZ CHb‐4b–4c) transition (except for a rise at ca. 11 450–11 400 cal. yr BP), and at the RPAZ CHb‐4c–5 (Preboreal–Boreal) transition, following the Preboreal Oscillation (after 11 150 cal. yr BP). The Preboreal Oscillation coincided with higher lake‐levels, its end being followed by a rapid expansion of Corylus, Quercus, Ulmus and Tilia. The Hauterive/Rouges‐Terres lake‐level record suggests that radiocarbon plateau at 12 600, 10 000 and 9500 14C yr BP corresponded to periods of generally lower lake‐level. This suggests that an increase in solar activity may have contributed to both climatic dryness and a decrease in atmospheric radiocarbon content. Copyright © 2002 John Wiley & Sons, Ltd.
Late Quaternary vegetation changes around Lake Rutundu, Mount Kenya, East Africa: evidence from grass cuticles, pollen and stable carbon isotopes
Authors: Wooller M. J. , Swain D. L. , Ficken K. J. , Agnew A. D. Q. , Street‐Perrott F. A. , Eglinton G.
Published: January 2003

Woody, subalpine shrubs and grasses currently surround Lake Rutundu, Mount Kenya. Multiple proxies, including carbon isotopes, pollen and grass cuticles, from a 755‐cm‐long core were used to reconstruct the vegetation over the past 38 300 calendar years. Stable carbon‐isotope ratios of total organic carbon and terrestrial biomarkers from the lake sediments imply that the proportion of terrestrial plants using the C4 photosynthetic pathway was greater during the Late Pleistocene than in the Holocene. Pollen data show that grasses were a major constituent of the vegetation throughout the Late Pleistocene and Holocene. The proportion of grass pollen relative to the pollen from other plants was greatest at the last glacial maximum (LGM). Grass cuticles confirm evidence that C4 grass taxa were present at the LGM and that the majority followed the cold‐tolerant NADP‐MEC4 subpathway. Copyright © 2003 John Wiley & Sons, Ltd.
Products of compact spaces and the axiom of choice II
Authors: De la Cruz Omar , Hall Eric , Howard Paul , Keremedis Kyriakos , Rubin Jean E.
Published: January 2003

This is a continuation of [2]. We study the Tychonoff Compactness Theorem for various definitions of compactness and for various types of spaces (first and second countable spaces, Hausdorff spaces, and subspaces of ℝK). We also study well ordered Tychonoff products and the effect that the multiple choice axiom has on such products.
The Fraenkel‐Carnap question for Dedekind algebras
Authors: Weaver George , George Benjamin
Published: January 2003

It is shown that the second‐order theory of a Dedekind algebra is categorical if it is finitely axiomatizable. This provides a partial answer to an old and neglected question of Fraenkel and Carnap: whether every finitely axiomatizable semantically complete second‐order theory is categorical. It follows that the second‐order theory of a Dedekind algebra is finitely axiomatizable iff the algebra is finitely characterizable. It is also shown that the second‐order theory of a Dedekind algebra is quasi‐finitely axiomatizable iff the algebra is quasi‐finitely characterizable.
On the axiom of extensionality in the positive set theory
Authors: Esser Olivier
Published: January 2003

This is a study of the relative interpretability of the axiom of extensionality in the positive set theory. This work has to be considered in the line of works of R. O. Gandy, D. Scott and R. Hinnion who have studied the relative interpretability of the axiom of extensionality in set theories of Zermelo and Zermelo‐Fraenkel.
Storage Modulus and Surface Morphology of Poly(vinyl alcohol)/Alumina Hybrid Hydrogels
Authors: Mitsumata Tetsu , Yuge Masashi , Morino Shinichi , Iwakura Kenji , Koyama Kiyohito
Published: January 2003

The storage moduli, shear moduli and surface morphologies of poly(vinyl alcohol) (PVA) and alumina hybrid hydrogels were investigated. The storage moduli of hybrid hydrogels with higher alumina contents were found to be 1.5 times higher than those of PVA gels. This increase in modulus might be attributed to the cohesion of alumina to the PVA network.

SEM photograph of Al7 PVA/alumina hybrid hydrogel. The photograph was taken with a magnification of × 220.

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SEM photograph of Al7 PVA/alumina hybrid hydrogel. The photograph was taken with a magnification of × 220.
Organometallic Polymers of the Transition Metals
Authors: Abd‐El‐Aziz Alaa S.
Published: January 2003

This article provides a comprehensive review of the synthesis, properties and applications of organometallic polymers of the transition metals. The different classes of organometallic polymers are described according to their structural make‐up, as well as by their methods of synthesis. A number of examples of each class are given to emphasize the richness and diversity in these areas of research. In addition to linear polymers, hyperbranched, crosslinked, star and dendritic polymers are also described. The properties that transition metal‐containing organometallic polymers possess, as well as the applications that these materials have found in various domains are highlighted.

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Single‐Chain‐Particles of Poly(N‐isopropylacrylamide)
Authors: Yang Hu , Yan Xiaohu , Cheng Rongshi
Published: January 2003

Spherical single‐chain‐particles of poly(N‐isopropylacrylamide) were prepared in aqueous solution above the lower critical solution temperature upon the addition of sodium dodecyl sulfate. The size of the single‐chain‐particles was investigated by means of transmission electron microscopy and viscosity measurements of the corresponding solutions, indicating the absence of inter‐chain entanglements among the single‐chain‐particles.

Schematic of the preparation of PNIPAM single‐chain‐globules in solution.

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Schematic of the preparation of PNIPAM single‐chain‐globules in solution.
A Novel Class of Betaine‐Type Polyampholytes with Stimuli‐Responsive and Complexing Properties
Authors: Koizhaiganova Raushan B. , Kudaibergenov Sarkyt E. , Geckeler Kurt E.
Published: January 2003

Linear and crosslinked betaine‐type polyampholytes based on ethyl 3‐aminocrotonate and unsaturated carboxylic acids have been synthesized by very fast polymerization in bulk and solution. Bulk polymerization occurred exothermically even at room temperature and without adding an initiator. The polyampholytes showed stimuli‐responsive properties with respect to pH, ionic strength, water/organic solvent mixtures, and metal ion complexation.

Temperature profile of the polymerization reaction for an equimolar mixture of CRO and AA with time in the absence of initiator.

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Temperature profile of the polymerization reaction for an equimolar mixture of CRO and AA with time in the absence of initiator.
Synaptic drosophila UNC‐13 is regulated by antagonistic G‐protein pathways via a proteasome‐dependent degradation mechanism
Authors: Aravamudan Bharathi , Broadie Kendal
Published: January 2003

UNC‐13 is a highly conserved plasma membrane‐associated synaptic protein implicated in the regulation of neurotransmitter release through the direct modulation of the SNARE exocytosis complex. Previously, we characterized the Drosophila homologue (DUNC‐13) and showed it to be essential for neurotransmitter release immediately upstream of vesicular fusion (“priming”) at the neuromuscular junction (NMJ). Here, we show that the abundance of DUNC‐13 in NMJ synaptic boutons is regulated downstream of GαS and Gαq pathways, which have inhibitory and facilitatory roles, respectively. Both cAMP modulation and PKA function are required for DUNC‐13 synaptic up‐regulation, suggesting that the cAMP pathway enhances synaptic efficacy via DUNC‐13. Similarly, PLC function and DAG modulation also regulate the synaptic levels of DUNC‐13, through a mechanism that appears independent of PKC. Our results suggest that proteasome‐mediated protein degradation is the primary mechanism regulating DUNC‐13 levels at the synapse. Both PLC‐ and PKA‐mediated pathways appear to regulate synaptic levels of DUNC‐13 through controlling the rate of proteasome‐dependent DUNC‐13 degradation. We conclude that the functional abundance of DUNC‐13 at the synapse, a key determinant of synaptic vesicle priming and neurotransmitter release probability, is primarily regulated by the rate of protein degradation, rather than translocation or transport, convergently controlled via both cAMP and DAG signal transduction pathways. © 2003 Wiley Periodicals, Inc. J Neurobiol 54: 417–438, 2003
Calcium and voltage dependent inactivation of sodium and calcium currents limits calcium influx in helisoma neurons
Authors: Torreano Paul J. , Cohan Christopher S.
Published: January 2003

The control of free intracellular calcium concentration ([Ca2+]i) is necessary for cell survival because of the ubiquitous and essential role this second messenger plays in regulating numerous intracellular processes. Calcium regulation in neurons is especially vigorous because of the large calcium influx that occurs through voltage‐gated channels during membrane depolarization. In this study we examined changes in ionic currents that can limit calcium influx into neurons during electrical activity. We found that the [Ca2+]i in electrically stimulated Helisoma B4 neurons initially increased to a peak and then relaxed to lower concentrations in tandem with a decline in the action potential peak voltage. The decline in [Ca2+]i and the peak action potential voltage in this sodium and calcium driven neuron was found to be a dual manifestation of INa and ICa inactivation. INa and ICa both displayed voltage dependent inactivation. Additionally, INa and ICa progressively inactivated at [Ca2+]i above 200 nM, concentrations readily attained in electrically stimulated B4 neurons. Calcium and voltage dependent INa and ICa inactivation were found to reduce calcium influx during continuous electrical stimulation by decreasing both the magnitude of ICa that could be activated and the percent of the available ICa that would be activated due to the diminished peak action potential voltage. Calculations based on data herein suggest that the voltage and calcium dependent INa and ICa inactivation that occurs during continuous electrical stimulation dramatically reduces calcium influx in this sodium and calcium driven neuron and thus limits the increase in [Ca2+]i. © 2003 Wiley Periodicals, Inc. J Neurobiol 54: 439–456, 2003
Regulation of ganglion cell production by notch signaling during retinal development
Authors: Silva Amila O. , Ercole Cesar E. , McLoon Steven C.
Published: January 2003

Although progenitor cells in developing vertebrate retina are capable of producing all retinal cell types, they are competent to produce only certain cell types at a given time, and this competence changes as development progresses. We asked whether a change in progenitor cell competence is primarily responsible for ending production of a specific cell type, the retinal ganglion cell. Reducing Notch expression using an antisense oligonucleotide in vitro or in vivo increased ganglion cell genesis. The antisense treatment could reinitiate ganglion cell genesis after it had terminated in a region of the retina, but only for a brief period. The failure of the Notch antisense treatment to reinitiate ganglion cell production after this period was not due to the lack of receptor or ligand expression, as both Notch‐1 and Delta‐1 were still expressed. The failure of the Notch antisense treatment to reinitiate ganglion cell production is consistent with the suggestion that the intrinsic competence of progenitor cells changes as development progresses. Because reducing Notch signaling can reinitiate ganglion cell production for a brief period after ganglion cell production has normally ceased, it appears that ganglion cell production initially ends in a region of the retina because of cell‐cell interactions and not because progenitor cells lose the competence to make ganglion cells. Notch signaling appears to temporarily prevent production of ganglion cells in a region, while some other signal must initiate a change in progenitor cell competence, thus permanently ending the possibility of further ganglion cell production. © 2003 Wiley Periodicals, Inc. J Neurobiol 54: 511–524, 2003
Organizational effects of testosterone, estradiol, and dihydrotestosterone on vasopressin mRNA expression in the bed nucleus of the stria terminalis
Authors: Han Tina M. , De Vries Geert J.
Published: January 2003

In adulthood, male rats express higher levels of arginine vasopressin (AVP) mRNA in the bed nucleus of the stria terminalis (BST) than do female rats. We tested whether this sex difference is primarily due to differences in neonatal levels of testosterone. Male and female rats were gonadectomized on the day of birth and treated with testosterone propionate (TP) or vehicle on postnatal days 1, 3, and 5 (P1, P3, and P5). Three months later, all rats were implanted with testosterone‐filled capsules. Two weeks later, brains were processed for in situ hybridization to detect AVP mRNA. We found that neonatal TP treatment significantly increased the number of vasopressinergic cells in the BST over control injections. We then sought to determine the effects of testosterone metabolites, estradiol and dihydrotestosterone, given alone or in combination, on AVP expression in the BST. Rat pups were treated as described above, except that instead of testosterone, estradiol benzoate (EB), dihydrotestosterone propionate (DHTP), a combination of EB and DHTP (EB+DHTP), or vehicle was injected neonatally. Neonatal treatment with either EB or EB+DHTP increased the number of vasopressinergic cells in the BST over that of DHTP or oil treatment. However, treatment with DHTP also significantly increased the number of vasopressinergic cells over that of oil treatment. Hence, in addition to bolstering evidence that estradiol is the more potent metabolite of testosterone in causing sexual differentiation of the brain, these data provide the first example of a masculinizing effect of a nonaromatizable androgen on a sexually dimorphic neuropeptide system. © 2003 Wiley Periodicals, Inc. J Neurobiol 54: 502–510, 2003
Rapsyn‐mediated clustering of acetylcholine receptor subunits requires the major cytoplasmic loop of the receptor subunits
Authors: Huebsch Kimberly A. , Maimone Margaret M.
Published: January 2003

During synaptogenesis at the neuromuscular junction, nicotinic acetylcholine receptors (AChRs) are organized into high‐density postsynaptic clusters that are critical for efficient synaptic transmission. Rapsyn, an AChR associated cytoplasmic protein, is essential for the aggregation and immobilization of AChRs at the neuromuscular junction. Previous studies have shown that when expressed in nonmuscle cells, both assembled and unassembled AChR subunits are clustered by rapsyn, and the clustering of the α subunit is dependent on its major cytoplasmic loop. In the present study, we investigated the mechanism of rapsyn‐induced clustering of the AChR β, γ, and δ subunits by testing mutant subunits for the ability to cocluster with rapsyn in transfected QT6 cells. For each subunit, deletion of the major cytoplasmic loop, between the third and fourth transmembrane domains, dramatically reduced coclustering with rapsyn. Furthermore, each major cytoplasmic loop was sufficient to mediate clustering of an unrelated transmembrane protein. The AChR subunit mutants lacking the major cytoplasmic loops could assemble into αδ dimers, but these were poorly clustered by rapsyn unless at least one mutant was replaced with its wild‐type counterpart. These results demonstrate that the major cytoplasmic loop of each AChR subunit is both necessary and sufficient for mediating efficient clustering by rapsyn, and that only one such domain is required for rapsyn‐mediated clustering of an assembly intermediate, the αδ dimer. © 2003 Wiley Periodicals, Inc. J Neurobiol 54: 486–501, 2003
Synaptic activity modifies the levels of dorsal and cactus at the neuromuscular junction of drosophila
Authors: Bolatto Carmen , Chifflet Silvia , Megighian Aram , Cantera Rafael
Published: January 2003

The Drosophila Rel transcription factor Dorsal and its inhibitor Cactus participate in a signal transduction pathway involved in several biologic processes, including embryonic pattern formation, immunity, and muscle development. In contrast with embryonic muscle, where Dorsal is reportedly absent, this protein and Cactus accumulates in the neuromuscular junctions in the muscle of both larvae and adults. The phenotype of homozygous dorsal mutant larvae suggested that Dorsal and Cactus maybe necessary for normal function and maintenance of the neuromuscular system. Here we investigate if these proteins can respond to synaptic activity. Using larval body wall preparations and antibodies specific for Dorsal or Cactus we show that the amount of these proteins at the neuromuscular junction is substantially decreased after electrical stimulation of the nerves or incubation in glutamate, the principal transmitter in this type of synapse. The specificity of the response was tested with a glutamate receptor antagonist (argiotoxin 636). Because the effect can be reproduced using a calcium ionophore (ionomycin treatment) as well as blocked by the inhibition of the muscle ryanodine receptor (tetracaine treatment), the involvement of calcium in this process seems likely. We also observed that the inhibition of the calcium dependent protein phosphatase calcineurin prevents the effect of glutamate on the fluorescence for Dorsal and Cactus, suggesting its participation in a signal transduction cascade that may activate Dorsal in the muscle independently of Toll. Our results are consistent with a novel function of the Rel factor Dorsal in a molecular pathway turned on by neural activity and/or contractile activity. © 2003 Wiley Periodicals, Inc. J Neurobiol 54: 525–536, 2003
Teen pregnancy, motherhood, and unprotected sexual activity
Authors: Koniak‐Griffin Deborah , Lesser Janna , Uman Gwen , Nyamathi Adeline
Published: January 2003

The sexual behaviors and attitudes toward condom use of adolescent mothers (N = 572) from ethnic minority groups were examined. Constructs from social cognitive theory (SCT), the theory of reasoned action (TRA), and the theory of planned behavior (TPB; e.g., intentions to use condoms, self‐efficacy, outcome expectancies) were measured with questionnaires. Measures of AIDS and condom‐use knowledge and selected psychosocial, behavioral, and demographic variables were included. Many adolescents reported early onset of sexual activity, multiple lifetime sexual partners, substance use, and childhood sexual or physical abuse. Only 18% stated a condom was used at last intercourse. Using hierarchical regression analysis, 13% of the variance for factors associated with unprotected sex was accounted for by TRA constructs. Other variables contributed an additional 17% of the variance. Unprotected sex was associated with behavioral intentions to use condoms, pregnancy, having a steady partner, more frequent church service attendance, and ever having anal sex. Findings support the urgent need for broad‐based HIV prevention efforts for adolescent mothers that build on theoretical concepts and address the realities of their lives. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:4–19, 2003
Effectiveness of a pilot project of discharge planning in Taiwan
Authors: Dai Yu‐Tzu , Chang Ying , Hsieh Chang‐Yao , Tai Tong‐Yuan
Published: January 2003

The purpose of this study was to examine the effects of a nurse‐designed discharge‐planning project in a teaching hospital in Taiwan. A before‐and‐after quasi‐experimental design was used. Craniotomy (n = 112) and stroke (n = 171) patients were recruited and divided into control and intervention groups. Outcome indicators included length of hospital stay, change in activities of daily living (ADL), rate of nursing home placement, rate of unplanned readmission, and level of satisfaction. In the stroke sample length of hospital stay was shorter in the intervention group than in the control group. In the craniotomy sample unplanned readmission was less frequent in the intervention group than in the control group. No differences were found between the control and intervention groups in other outcome indicators. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:53–63, 2003
Testing the relationship between self‐agency and enactment of health behaviors
Authors: DeSocio Janiece , Kitzman Harriet , Cole Robert
Published: January 2003

A theoretical review provides a rationale for examining self‐agency as a developmental foundation underlying processes of self‐regulated change and a potential moderator of intervention effectiveness among participants in a nurse home‐visitation program. Self‐agency is defined as the conceptual understanding of self as an agent capable of shaping motives, behavior, and future possibilities (Damon & Hart, 1991). Availability of a sample of 186 mothers who received nurse home visitation provided an opportunity to test the relationship between participant self‐agency and enactment of targeted health behaviors. Self‐agency items from the Pearlin Mastery Scale (1978) were used to differentiate mothers who endorsed self‐agency from those who did not. Consistent with the theoretical premise, mothers who endorsed self‐agency at an established threshold were significantly more likely to enact health behaviors promoted during nurse visitation. Results provide support for the relationship between the development of self‐agency and enactment of health behaviors targeted by a nurse home‐visitation program. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:20–29, 2003
Molecular weight control of polyacrylamide with sodium formate as a chain‐transfer agent: Characterization via size exclusion chromatography/multi‐angle laser light scattering and determination of chain‐transfer constant
Authors: Fevola Michael J. , Hester Roger D. , McCormick Charles L.
Published: January 2003

We discuss the synthesis and characterization of polyacrylamide (PAM) homopolymers with carefully controlled molecular weights (MWs). PAM was synthesized via free‐radical solution polymerization under conditions that yield highly linear polymer with minimal levels of hydrolysis. The MW of the PAM homopolymers was controlled by the addition of sodium formate (NaOOCH) to the polymerization medium as a conventional chain‐transfer agent. MWs and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi‐angle laser light scattering analysis; for polymerizations carried out to high conversion, PAM MWs ranged from 0.23 to 6.19 × 106 g/mol, with most samples having PDI ≈2.0. Zero‐shear intrinsic viscosities of the polymers were determined via low‐shear viscometry in 0.514 M NaCl at 25 °C. Data derived from the polymer characterization were used to determine the chain‐transfer constant to NaOOCH under the given polymerization conditions and to calculate Mark–Houwink–Sakurada K and a values for PAM in 0.514 M NaCl at 25 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 560–568, 2003
Anionic copolymerization of hexanelactam with functionalized polyisoprene
Authors: Mateva R. , Filyanova R. , Velichkova R. , Gancheva V.
Published: January 2003

Block copolymers of the A‐B‐C‐B‐A type were synthesized for the first time via the activated anionic polymerization of hexanelactam (HL) with Na‐HL as an initiator and macroactivators [or polymeric activators (PACs)] as elastificators for nylon‐6. The PACs were prepared by the functionalization of telechelic hydroxyl‐terminated poly(ethylene oxide)–polyisoprene–poly(ethylene oxide) copolymers with different diisocyanates. Hexamethylene diisocyanate (1,6‐diisocyanatohexane) and isophorone diisocyanate (5‐isocyanate1‐isocyanatomethyl‐1,3,3‐trimetylcyclohexane) were used as functionalizing agents. This article reports on the effects that the various central elastomeric PAC blocks (type, content, and molecular weight) had on the polymerization kinetics and on the structure and molecular weights of the multiblock copolymers obtained. The copolymers were characterized spectroscopically. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 487–496, 2003
Ultraviolet–ultraviolet dual‐cure process based on acrylate oxetane monomers
Authors: El‐ghayoury Abdelkrim , Boukaftane Chouaib , de Ruiter Barteld , van der Linde Rob
Published: January 2003

A dual‐cure process consisting of two subsequent ultraviolet‐initiated radical and cationic polymerizations was investigated. The process was studied with two acrylate oxetane monomers, one of them having a spacer between the two polymerizable moieties. It was shown by Fourier transform infrared (FTIR) that the first (radical) step was performed successfully for both systems. As for the second (cationic) step, only the monomer with the spacer was able to polymerize, allowing the crosslinking of the polyacrylic chains generated by the first step. The efficiency of the process was confirmed by differential scanning calorimetry because the glass‐transition temperatures of the cured films were −16 and + 34 °C after the first and second steps, respectively. The dual cure of this system was further analyzed by real‐time FTIR, which showed that 86% of the acrylate and 80% of the oxetane moieties were converted after 20 and 50 s of light exposure, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 469–475, 2003
Synthesis and characterization of sulfonated poly(phthalazinone ether ketone) for proton exchange membrane materials
Authors: Gao Yan , Robertson Gilles P. , Guiver Michael D. , Jian Xigao
Published: January 2003

As a novel class of proton exchange membrane materials for use in fuel cells, sulfonated poly(phthalazinone ether ketone)s (SPPEKs) were prepared by the modification of poly(phthalazinone ether ketone). Sulfonation reactions were conducted at room temperature with mixtures of 95–98% concentrated sulfuric acid and 27–33% fuming sulfuric acid with different acid ratios, and SPPEK was obtained with a degree of sulfonation (DS) in the desired range of 0.6–1.2. The presence of sulfonic acid groups in SPPEK was confirmed by Fourier transform infrared analysis, and the DS and structures were characterized by NMR. The introduction of sulfonic groups into the polymer chains increased the glass‐transition temperature above the decomposition temperature and also led to an overall decrease in the decomposition temperature. Membrane films were cast from SPPEK solutions in N,N‐dimethylacetamide. Water uptakes and swelling ratios of SPPEK membrane films increased with DS, and SPPEKs with DS > 1.23 were water‐soluble at 80 °C. Proton conductivity increased with DS and temperature up to 95 °C, reaching 10−2S/cm. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 497–507, 2003
Monitoring photopolymerization reactions with optical pyrometry
Authors: Falk Benjamin , Vallinas Santiago M. , Crivello James V.
Published: January 2003

This article describes the development of optical pyrometry (OP) as a new analytical technique for the continuous monitoring of the progress of both free‐radical and cationic photopolymerizations. The method is rapid, reproducible, and very easy to implement. A temperature profile of a photopolymerization can be obtained. Preliminary studies have shown that the temperatures of some polymerizing monomers can easily reach temperatures in excess of 250 °C. The effects of the mass and reactivity of the monomer, light intensity, structures, and concentrations of the photoinitiators and monomers as well as the presence or absence of oxygen on various free‐radical and cationic photopolymerizations were examined with this method. Coupling of real‐time infrared spectroscopy with OP provides a convenient method for simultaneously monitoring both the chemical conversion and the temperature of a photopolymerization. This combined technique affords new insights into the effects of temperature‐induced autoacceleration on the course of photopolymerizations. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 579–596, 2003
Local chain‐configuration dependence of the mechanisms of the chemical reaction of poly(vinyl chloride). IX. Novel results on stereoselectivity of chlorination reaction
Authors: Martínez G. , Millán J. , Contreras J.
Published: January 2003

A poly(vinyl chloride) (PVC) sample was chlorinated in solution in the presence of 2,2′‐azobisisobutyronitrile and by the fluid‐bed method. The aim was to evaluate the scope of the stereoselectivity of the chlorination reaction. The quantitative microstructural analysis of the residual PVC with a degree of chlorination was followed by 13C NMR spectroscopy. From the evolution of the content of isotactic (mm), heterotactic (mr), and syndiotactic (rr) triads and of mmmm, mmmr, and rmmr isotactic pentads in the unchlorinated parts of the polymer, it was unambiguously inferred that the chlorination reaction proceeds by a stereoselective mechanism in that the mr heterotactic triads are the most reactive structures followed by the isotactic triad at mmmr and rmmr pentads. This conclusion was confirmed on the basis of the Fourier transform infrared results. The results provide valuable information regarding the effect of tacticity and related local conformations in the chemical reactions of PVC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 508–519, 2003
Polystyrene latices containing dodecanamide‐modified poly(propyleneimine) dendrimers
Authors: Xu Zushun , Ford Warren T.
Published: January 2003

Polymerization of styrene in aqueous dispersions of the dodecanamide derivative of poly(propyleneimine) dendrimer DAB‐dendr‐(NH2)64 and sodium dodecyl sulfate (SDS) produced stable latices. With initial SDS concentrations of 10 mM or less, molar ratios of SDS to dendrimer end groups ranging from 2.3:1 to 9.5:1, and less than 10 wt % of SDS relative to styrene, the polystyrene latices had diameters of 30–60 nm and coefficients of variation of diameters of less than 10% when measured by transmission electron microscopy. Higher concentrations of SDS gave more polydisperse latices. The polystyrene latices formed with SDS and the dodecanamide‐modified dendrimer were almost the same size and polydispersity as those formed with SDS and the parent primary amine dendrimer DAB‐dendr‐(NH2)64. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 597–605, 2003
Preparation of supported yttrium alkoxides as catalysts for the polymerization of lactones and oxirane
Authors: Martin E. , Dubois Ph. , Jerome R.
Published: January 2003

Two methods have been reported that allow yttrium alkoxides to be supported on porous silica and to be used afterward as heterogeneous catalysts in the ring‐opening polymerization of oxirane and ϵ‐caprolactone. In the two methods, [tris(hexamethyldisilyl)‐amide]yttrium {Y[N(SiMe3)2]3} is the metal alkoxide precursor. It is directly reacted with the silanol groups of the support, in the first method, and this is followed by alcoholysis of the unreacted amide groups. The flexibility of this method seems to be limited because the grafting density and the structure of the grafted Y alkoxide (less than one alkoxide by metal) are independent of the experimental conditions. In the second method, Y[N(SiMe3)2]3 is first reacted with 1 or 2 equiv of alcohol with the formation of the mixed Y alkoxide/amide. The amide functions are used to attach Y to the support. This method is free from side reactions, quite reproducible, and well suited to support one type of active species (monoalkoxide or dialkoxide). Preliminary experiments with ϵ‐caprolactone polymerization have confirmed the activity of the supported Y alkoxide, whatever preparation method is used. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 569–578, 2003
Theoretical study of the thermolysis reaction of β‐hydroxynitriles in the gas phase
Authors: Chamorro Eduardo , Quijano Jairo , Notario Rafael , Sánchez Claudia , León Luis A. , Chuchani Gabriel
Published: January 2003

The gas‐phase thermal decomposition of 3‐hydroxypropionitrile, 3‐hydroxybutyronitrile, and 3‐hydroxy‐3‐methylbutyronitrile has been studied at the MP2/6‐31G(d) level of theory at 683.15 K and 0.06 atm. Results based both in energy and structure data seem to indicate a favorable route of decomposition via a six‐membered cyclic transition state (similar to those suggested for thermal decomposition of other related compounds, such as β‐hydroxyketones, β‐hydroxyalkenes, and β‐hydroxyalkynes) rather than a four‐membered cyclic transition state or even a quasiheterolytic pathway. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Computation of quantum system by second‐order matrix symplectic scheme
Authors: Hanwei Yi , Zhongyuan Zhou , Peizhu Ding , Yu L. H.
Published: January 2003

In this article the work of Vazquez and Zhang Meiqing et al. has been developed in such a way that it can be used to calculate time evolution of quantum system. In Heisenberg picture, operator symplectic schemes have been changed into matrix symplectic schemes by use of the expansion method, the matrix schemes satisfy equal time commutation relation (ETCR) in the matrix form. The second‐order matrix scheme is used to calculate one‐dimensional nonlinear harmonic oscillator. The calculated result is compared with results obtained by Runge–Kutta scheme. Calculated results show that results computed by ETCR‐preserving and symplectic scheme is consistent with physics theory. It also shows that it is rational and effective as well as reliable to use ETCR‐preserving symplectic scheme to calculate time evolution of quantum system in Heisenberg picture. It is proved that second‐order symplectic scheme has more computing accuracy than does first‐order symplectic scheme. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
Modeling the dynamics of human energy regulation and its implications for obesity treatment
Authors: Abdel‐Hamid Tarek K.
Published: January 2003

Obesity has reached epidemic proportions in the United States and is threatening to become a global epidemic. Even more concerning, the incidence of overweight continues to increase. The health consequences and economic costs to individuals and to society are considerable. Obesity is associated with many serious health complications, including coronary heart disease, type 2 diabetes mellitus, hypertension, selected cancers, and musculoskeletal disorders. In the U.S., direct and indirect medical costs attributable to obesity are estimated to approach $100 billion yearly. Obesity develops when a chronic imbalance exists between energy intake, in the form of food and drink, and energy expenditure. To date, the emphasis of treatment has been on the energy intake side of the energy balance equation. This, in part, is because it has been difficult to demonstrate the efficacy of exercise as a treatment strategy. This paper attempts to demonstrate the utility of system dynamics modeling to study and gain insight into the physiology related to weight gain and loss. A simulation model is presented that integrates nutrition, metabolism, hormonal regulation, body composition, and physical activity. These processes are typically fragmented between many different disciplines and conceptual frameworks. This work seeks to bring these ideas together highlighting the interdependence of the various aspects of the complex human weight regulation system. The model was used as an experimentation vehicle to investigate the impacts of physical activity on body weight and composition. The results replicate the “mix” of results reported in the literature, as well as providing causal explanation for their variability. In one experiment, weight loss from a moderate level of daily exercise was comparable to the loss from dieting (when both produced equivalent energy deficits). Perhaps of greater significance, the exercise intervention protected against the loss of fat‐free mass, which occurs when weight loss is achieved through dieting alone, and thus promoted favorable changes in body composition. In a second experiment, exercise regimens of moderate to high level of intensity proved counter‐productive as weight‐reducing strategies for an obese sedentary subject. This was due to the limited energy reserves (specifically, muscle glycogen) available to such individuals. However, when the diet was changed from a balanced composition to one that was highly loaded with carbohydrates, it became possible to sustain the intense exercise regimen over the experimental period, and achieve a significant drop in body weight. The results underscore the significant interaction effects between diet composition and physical activity, and emphasize the critical role that diet composition can have in exercise‐based treatment interventions. Copyright © 2002 John Wiley & Sons, Ltd.
Critical systems thinking as a way to manage knowledge
Authors: Gao Fei , Li Meng , Nakamori Yoshiteru
Published: January 2003

This paper is the first to introduce critical systems thinking into the present study of knowledge and its management. Our preliminary study showed two things about critical systems thinking. First, it provides comprehensive and creative insight into tackling the increasing complexity of human knowledge and knowledge management processes through the organic connection and division of knowledge systems. Second, it encourages the critical use of available methodologies in a coherent way to cope with corresponding subsystems or processes, which breaks down the complexity into convenient units. Based on critical systems thinking, we divided knowledge into two aspects: static substance knowledge and dynamic process knowledge. This division not only provides a concise theoretical framework but also allows knowledge managers and workers to clearly understand the gravity of their work and to selectively utilize well‐established methodologies in the practice of knowledge‐related activities. This paper serves as an introduction to an application of critical system thinking and total systems intervention in diversified human knowledge topics. Copyright © 2002 John Wiley & Sons, Ltd.
A proposed taxonomy of management systems
Authors: Felix Reto
Published: January 2003

Management systems are part of virtually every organization. However, so far no systematic effort has been made to distinguish different stages in the adaptive process of management systems according to sophistication criteria. By building on existing theories in the areas of systems control, cybernetics, and general systems theory, this paper develops and presents a taxonomy of management systems. It is shown that flowing‐equilibrium (F‐E) management systems can explain systems behavior that cannot be explained by management theory based on cybernetics or double‐loop learning. Copyright © 2002 John Wiley & Sons, Ltd.