bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractTurnip 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

AbstractThe 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

AbstractA 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

AbstractPalynological 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

AbstractWoody, 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

AbstractThis 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

AbstractIt 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

AbstractThis 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

AbstractThe 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.magnified imageSEM 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

AbstractThis 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

AbstractSpherical 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.magnified imageSchematic 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

AbstractLinear 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.magnified imageTemperature 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

AbstractUNC‐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

AbstractThe 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

AbstractAlthough 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

AbstractIn 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

AbstractDuring 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