bluuebunny/crossref_metadata_2025_split huggingface dataset:
Strain‐induced crystallization in uniaxially drawn PETG plates
Authors: Kattan M. , Dargent E. , Ledru J. , Grenet J. 
Published: August 2002

AbstractThe copolyester poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate) (PETG) is used industrially as an uncrystallizable polymer, whereas PET is an inherently crystallizable polymer. Nevertheless, a crystalline phase could appear in the material. To create a strain‐induced crystalline phase in an initially amorphous PETG material, plates were placed in the heating chamber of a tensile machine at 100°C and uniaxially drawn to obtain different samples with various draw ratios. During DSC analysis of highly drawn samples, perturbations of the baseline appear above the glass‐transition temperature, consisting of weak exothermic and endothermic phenomena. Comparison of DSC and X‐ray diffraction analysis of drawn PETG and PET shows that a strain‐induced crystalline phase appears in this copolyester. A spherulitic superstructure could also appear after lengthy annealing. Analysis of this semicrystalline material allowed estimation of the degree of crystallinity, about 3% after a drawing at high draw ratio and about 11% for undrawn annealed material. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3405–3412, 2001
Soluble polypyrrole copolymers
Authors: Ustamehmetoğlu Belkis , Kizilcan Nilgün , Saraç A. Sezai , Akar Ahmet 
Published: August 2002

AbstractA new class of dimethyl formamide (DMF)– and acetone‐soluble conducting pyrrole–ketonic resin copolymers has been developed. This was accomplished by oxidatively polymerizing pyrrole monomer by Ce(IV) salt in the presence of methyl ethyl ketone formaldehyde resin (MEKF–R). The resulting copolymers were readily dissolved in DMF and acetone. These products were characterized by FTIR and UV‐visible spectroscopy, conductivity, four‐probe conductivity, viscosity, and DSC measurements. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1098–1106, 2001
Preparation and characterization of organosoluble polyimides based on 1,1‐bis[4‐(3,4‐aminophenoxy)phenyl]cyclohexane and commercial aromatic dianhydrides
Authors: Yang Chin‐Ping , Chen Ruei‐Shin , Yu Chien‐Wen 
Published: August 2002

AbstractA bis(ether amine) III‐A containing a cyclohexane cardo group, 1,1‐bis[4‐(4‐aminophenoxy)phenyl]cyclohexane, was synthesized and used as a monomer to prepare polyimides VI‐A with six commercial dianhydrides via three different procedures. The intermediate poly(amic acid)s had inherent viscosities of 0.83–1.69 dL g−1 and were thermally or chemically converted into polyimides. Polyimides were also prepared by high‐temperature direct polymerization in m‐cresol and had inherent viscosities higher than the thermally or chemically cyclodehydrated ones. To improve the solubility of polyimides, six copolyimides were also synthesized from bis(ether amine) III‐A with a pair of dianhydrides, which contained 3,3′,4,4′‐diphenylsulfonetetracarboxylic dianhydride or 4,4′‐hexafluoroisopropylidenediphthalic anhydride. Series VI‐A polyimides were characterized by the good physical properties of their film‐forming ability, thermal stability, and tensile properties. A comparative study of the properties, with the corresponding polyimides derived from 2,2‐bis[4‐(4‐aminophenoxy)phenyl]propane, is also presented. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2750–2759, 2001
Effects of the carboxyl concentration on the solid‐state polymerization of poly(ethylene terephthalate)
Authors: Duh Ben 
Published: August 2002

AbstractThere are two types of polycondensation reactions in the solid‐state polymerization (SSP) of poly(ethylene terephthalate) (PET), namely, transesterification and esterification. Transesterification is the reaction between two hydroxyl ends with ethylene glycol as the byproduct, and esterification is the reaction between a carboxyl end and a hydroxyl end with water as the byproduct. The SSP of powdered PET in a fluid bed is practically a reaction‐controlled process because of negligible or very small diffusion resistance. It can be proved mathematically that an optimal carboxyl concentration for reaction‐controlled SSP exists only if k2/k1 > 2, where k2 and k1 are the forward reaction rate constants of esterification and transesterification, respectively. Several interesting observations were made in fluid‐bed SSP experiments of powdered PET: (1) the SSP rate increases monotonously with decreasing carboxyl concentration, (2) k2 < k1 in the presence of sufficient catalyst, (3) k1 decreases with increasing carboxyl concentration if the catalyst concentration is insufficient, and (4) the minimum catalyst concentration required to achieve the highest SSP rate decreases with decreasing carboxyl concentration. In the SSP of pelletized PET, both reaction and diffusion are important, and there exists an optimal carboxyl concentration for the fastest SSP rate because esterification, which generates the faster diffusing byproduct, is retarded less than transesterification in the presence of substantial diffusion resistance. The optimal prepolymer carboxyl concentration, which ranges from 25 to 40% of the total end‐group concentration in most commercial SSP processes, increases with increasing pellet size and product molecular weight. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1288–1304, 2002
Constructed shallow zones along navigation canals: vegetation establishment and change in relation to environmental characteristics
Authors: Boedeltje Ger , Smolders Alfons J.P. , Roelofs Jan G.M. , Van Groenendael Jan M. 
Published: August 2002

AbstractAn Erratum has been published for this article in Aquatic Conservation: Marine and Freshwater Ecosystems 12(2), 2002, 251
In recent decades shallow zones have been constructed along navigation canals in the Netherlands which form a potential new habitat for aquatic macrophytes and helophytes absent from traditional canals.
The aim of this study was to examine the relationships between the aquatic plant vegetation that becomes established and the physical and chemical characteristics of water and sediment, in order to find the determinants of species composition and the changes therein. Data were collected in 1998 and 1999 from 80 plots in bank zones at varying stages of development since construction along two navigation canals.
Plots 3–5 years old were partly dominated by rooting submerged macrophytes such as Potamogeton pectinatus, Elodea nuttallii and Potamogeton pusillus; locally non‐rooting species occurred such as Ceratophyllum demersum, Lemna minor and Spirodela polyrhiza. Older plots contained Phragmites australis, locally mixed with free‐floating species. Hydrological isolation from the eutrophic canals was indicated by the presence of Chara vulgaris.
Characteristics of both water layer and sediment could explain the variation in vegetation composition. Rooting submerged macrophytes predominantly occurred in sites with a thin (<2 cm) layer of sediment with relatively low concentrations of organic matter; moreover, ammonium concentrations in the water layer and sediment pore water were relatively low. Stands of non‐rooting macrophytes and of Phragmites australis were characterized by a relatively thick sediment layer and high ammonium levels in the pore water. Light limitation in turbid water, associated with navigation and eutrophication, may also play a role.
Although submerged aquatic macrophytes persist for a relatively short time, shallow zones nevertheless function as a habitat for helophyte communities and contribute to a higher aquatic biodiversity than is associated with traditional banks along navigation canals.
Copyright © 2001 John Wiley & Sons, Ltd.
The Ferret's vomeronasal organ and accessory olfactory bulb: Effect of hormone manipulation in adult males and females
Authors: Kelliher Kevin R. , Baum Michael J. , Meredith Michael 
Published: August 2002

AbstractThe male ferret, a carnivore, was recently shown to possess a vomeronasal organ (VNO). We compared the morphology of the VNO and its associated accessory olfactory bulb (AOB) in male and female ferrets that were killed in adulthood. The volume and surface area of the VNO neuroepithelium were similar in adult gonadectomized male and female ferrets regardless of whether they were treated with testosterone propionate (TP) or oil vehicle. An AOB was localized bilaterally in the medial caudal part of the olfactory bulbs of adult ferrets using soybean agglutin binding and immunostaining for luteinizing hormone‐releasing hormone and tyrosine hydroxylase as well as Nissl staining of coronal, horizontal, and sagittal brain sections. There was no effect of sex or TP treatment on AOB cell layer volume in adult gonadectomized animals. We found the ferret's AOB to be more medially located and much smaller than previously reported in this species, thus highlighting the importance of using several histochemical markers to characterize this structure in any previously unexamined species. Adult male and female ferrets both have a VNO and an associated AOB. More research is needed to determine what role, if any, this accessory olfactory system plays in mediating behavioral and neuroendocrine responses to pheromones in ferrets of either sex. Anat Rec 263:280–288, 2001. © 2001 Wiley‐Liss, Inc.
Improved RP‐HPLC determination of quinine in plasma and whole blood stored on filter paper
Authors: Kolawole J.A. , Mustapha A. 
Published: August 2002

AbstractAnalysis of quinine in plasma and whole blood samples dried on filter paper is described. Sample preparation involves liquid extraction of plasma and whole blood from the filter paper and subsequent solid‐phase extraction using C8 Bond Elut cartridges. A reverse‐phase liquid chromatography system with UV detection and fluorescence detection was used. The analytical characteristics of the method are reported, with a quantification limit of 0.1 µg mL−1 and within an assay coefficient of variation of 5.6–8.4% in plasma and 6.5–12% in whole blood. Representative chromatograms are shown as a function of time for samples from human subjects after ingestion of a single 400‐mg dose of quinine sulphate. Quinidine, dihydroquinine and metabolites are well separated from quinine with a resolution of above 1 (Rs>1). Copyright © 2000 John Wiley & Sons, Ltd.
The mental accounting of sunk time costs: why time is not like money
Authors: Soman Dilip 
Published: August 2002

AbstractThe sunk‐cost effect, an irrational attention to non‐recoverable past costs while making current decisions, has been documented widely in the domain of monetary costs. In this paper, I study the effect of past time investments on current decisions. In three experiments using choice situations, I demonstrate that the sunk‐cost effect is not observed for past investments of time, but the effect reappears when the investments are expressed as monetary quantities. I further propose that this ‘pseudo‐rationality’ is due to the fact that individuals lack the ability to account for time in the same way as they account for money. In two additional experiments, I facilitate the accounting of time and show that the irrational sunk‐cost effect reappears. In a final experiment, I test my propositions in a setting where subjects make real investments of time and subsequently make real choices. Copyright © 2001 John Wiley & Sons, Ltd.
Diversity in the mechanisms of gene regulation by estrogen receptors
Authors: Sanchez Rocio , Nguyen Denis , Rocha Walter , White John H. , Mader Sylvie 
Published: August 2002

AbstractThe sequencing of the human genome has opened the way for using bioinformatics to identify sets of genes controlled by specific regulatory signals. Here, we review the unexpected diversity of DNA response elements mediating transcriptional regulation by estrogen receptors (ERs), which control the broad physiological effects of estrogens. Consensus palindromic estrogen response elements are found in only a few known estrogen target genes, whereas most responsive genes contain only low‐affinity half palindromes, which may also control regulation by other nuclear receptors. ERs can also regulate gene expression in the absence of direct interaction with DNA, via protein–protein interactions with other transcription factors or by modulating the activity of upstream signaling components, thereby significantly expanding the repertoire of estrogen‐responsive genes. These diverse mechanisms of action must be taken into account in screening for potential estrogen‐responsive sequences in the genome or in regulatory regions of target genes identified by expression profiling. BioEssays 24:244–254, 2002. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/bies.10066
Polyps, peptides and patterning
Authors: Bosch Thomas C.G. , Fujisawa Toshitaka 
Published: August 2002

AbstractPeptides serve as important signalling molecules in development and differentiation in the simple metazoan Hydra. A systematic approach (The Hydra Peptide Project) has revealed that Hydra contains several hundreds of peptide signalling molecules, some of which are neuropeptides and others emanate from epithelial cells. These peptides control biological processes as diverse as muscle contraction, neuron differentiation, and the positional value gradient. Signal peptides cause changes in cell behaviour by controlling target genes such as matrix metalloproteases. The abundance of peptides in Hydra raises the question of whether, in early metazoan evolution, cell–cell communication was based mainly on these small molecules rather than on the growth‐factor‐like cytokines that control differentiation and development in higher animals. BioEssays 23:420–427, 2001. © 2001 John Wiley & Sons, Inc.
Plectin repeats and modules: strategic cysteines and their presumed impact on cytolinker functions
Authors: Janda Lubomír , Damborský Jiří , Rezniczek Günther A. , Wiche Gerhard 
Published: August 2002

AbstractPlectin, a member of the cytolinkers protein family, plays a crucial role in cells as a stabilizing element of cells against mechanical stress. Its absence results in muscular dystrophy, skin blistering, and signs of neuropathy. The C‐terminal domain of plectin contains several highly homologous repeat domains that also occur in other cytolinkers. Secondary structure analysis revealed that the building block of these domains, the PLEC repeat, is similar to the ankyrin repeat. We present a model that attempts to explain how the C‐terminal domain, which comprises ∼1900 amino acid, could be stabilized to maintain its structural integrity even under extensive mechanical stress. In this model, larger solenoid modules formed from PLEC repeats can be disulfide‐bridged via conserved cysteines. Our hypothesis suggests that this process could be mediated by cytoplasmic NOS‐generated products, such as the radical peroxynitrite. Reinforcement of molecular structure would provide a rationale why during exercising or physical stress radicals areformed without necessarily being deleterious. This article contains supplementary material that may be viewed at the BioEssays website at http://www.interscience.wiley.com/jpages/0265‐9247/suppmat/23/v23_11.1064.html. BioEssays 23:1064–1069, 2001. © 2001 John Wiley & Sons, Inc.
Effect of genetic background and culture conditions on the production of herpesvirus‐based gene therapy vectors
Authors: Ozuer Ali , Wechuck James B. , Goins William F. , Wolfe Darren , Glorioso Joseph C. , Ataai Mohammad M. 
Published: August 2002

AbstractHerpes simplex virus type‐1 (HSV‐1) represents a unique vehicle for the introduction of foreign DNA to cells of a variety of tissues. The nature of the vector, the cell line used for propagation of the vector, and the culture conditions will significantly impact vector yield. An ideal vector should be deficient in genes essential for replication as well as those that contribute to its cytotoxicity. Advances in the engineering of replication‐defective HSV‐1 vectors to reduce vector‐associated cytotoxicity and attain sustained expression of target genes make HSV‐1 an attractive gene‐delivery vehicle. However, the yield of the less‐cytotoxic vectors produced in standard tissue‐culture systems is at least three order of magnitudes lower than that achieved with wild‐type virus. The low overall yield and the complexity involved in the preparation of HSV vectors at high concentrations represent major obstacles in use of replication‐defective HSV‐derived vectors in gene therapy applications. In this work, the dependence of the vector yield on the genetic background of the virus is examined. In addition, we investigated the production of the least toxic, lowest‐yield vector in a CellCube bioreactor system. After initial optimization of the operational parameters of the cellcube system, we were able to attain virus yields similar to or better than those values attained using the tissue culture flask system for vector production with significant savings with respect to time, labor, and cost. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 685–692, 2002; DOI 10.1002/bit.10162
Kinetic constants determination for an alkaline protease from Bacillus mojavensis using response surface methodology
Authors: Beg Qasim Khalil , Saxena R. K. , Gupta Rani 
Published: August 2002

AbstractThe kinetic constants for an alkaline protease from Bacillus mojavensis were determined using a central composite circumscribed design (CCCD) where concentration of substrate (casein) and the assay temperature were varied around their center point. The Km,Vmax, Kcat, activation energy (Ea) and temperature coefficient (q10) were determined and the values of these kinetic constants obtained were found comparable to that obtained with conventional methods. The Michaelis‐Menten constant (Km) for casein decreased with corresponding increase in Vmax, as reaction temperature was raised from 45–60°C. The protease exhibited Km of 0.0357 mg/ml, 0.0270 mg/ml, 0.0259 mg/ml, and 0.0250 mg/ml at 45, 50, 55, and 60°C, respectively, whereas Vmax values at these temperatures were 74.07, 99.01, 116.28, and 120.48 μg/ml/min, respectively, as determined by response surface methodology. The Arrhenius plot suggested that the enzyme undergoes thermal activation above 45°C until 60–65°C followed by thermal inactivation. Likewise, the energy of activation (Ea) was more between 45–55°C (9747 cal/mol) compared to Ea between 50–60°C (4162 cal/mol). © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 289–295, 2002.
Metabolic engineering of Pseudomonas putida for the utilization of parathion as a carbon and energy source
Authors: Walker Andy W , Keasling Jay D 
Published: August 2002

AbstractPseudomonas putida KT2442 was engineered to use the organophosphate pesticide parathion, a compound similar to other organophosphate pesticides and chemical warfare agents, as a source of carbon and energy. The initial step in the engineered degradation pathway was parathion hydrolysis by organophosphate hydrolase (OPH) to p‐nitrophenol (PNP) and diethyl thiophosphate, compounds that cannot be metabolized by P. putida KT2442. The gene encoding the native OPH (opd), with and without the secretory leader sequence, was cloned into broad‐host‐range plasmids under the control of tac and taclac promoters. Expression of opd from the tac promoter resulted in high OPH activity, whereas expression from the taclac promoter resulted in low activity. A plasmid‐harboring operons encoding enzymes for p‐nitrophenol transformation to β‐ketoadipate was transformed into P. putida allowing the organism to use 0.5 mM PNP as a carbon and energy source. Transformation of P. putida with the plasmids harboring opd and the PNP operons allowed the organism to utilize 0.8 mM parathion as a source of carbon and energy. Degradation studies showed that parathion formed a separate dense, non‐aqueous phase liquid phase but was still bioavailable. © 2002 Wiley Periodicals, Inc. Biotechnol Bioeng 78: 715–721, 2002.
Activity of different Candida antarctica lipase B formulations in organic solvents
Authors: Secundo Francesco , Carrea Giacomo , Soregaroli Carla , Varinelli Donatella , Morrone Raffaele 
Published: August 2002

AbstractThe activity of different formulations of Candida antarctica lipase B (CALB), such as crude CALB, purified CALB, purified CALB lyophilized with PEG (CALB + PEG) or oleic acid (CALB + OA), and the commercial formulation Novozym 435, was determined in toluene, carbon tetrachloride, and 1,4‐dioxane at various water activities (aw). The reaction between vinylacetate and 1‐octanol was used as the model reaction and both transesterification (formation of 1‐octylacetate) and hydrolytic (formation of acetic acid from vinylacetate) activities were determined. For equal amounts of lipase protein, CALB + PEG (and to a lesser extent CALB + OA) displayed higher activity than that of the other formulations; for instance, in toluene (aw < 0.1), it was 260‐, 13‐, and 1.8‐fold more active than crude CALB, purified CALB, and Novozym 435, respectively. Moreover, the transesterification activity of CALB + PEG was of the same order of magnitude (51%) of the activity shown by the enzyme in the hydrolysis of vinylacetate in aqueous buffer. These results suggest that PEG and oleic acid could act as lyoprotectants, preventing the formation of intermolecular interactions during the lyophilization process that might be responsible for protein denaturation. No diffusional limitation was observed for CALB + PEG‐catalyzed reactions. Purified CALB, in contrast to the other formulations, showed a marked activity increase (2.1 to 7.8‐fold) as a function of aw and, in 1,4‐dioxane, it was 3.5‐fold more active when it was added to the solvent after previous dissolution of the lyophilized powder in water. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 73: 157–163, 2001.
Highly efficient synthesis of ampicillin in an “aqueous solution‐precipitate” system: Repetitive addition of substrates in a semicontinuous process
Authors: Youshko Maxim I. , van Langen Luuk M. , de Vroom Erik , van Rantwijk Fred , Sheldon Roger A. , Švedas Vytas K. 
Published: August 2002

AbstractThe synthesis of ampicillin catalyzed by Escherichia coli penicillin acylase was optimized in an aqueous system with partially dissolved antibiotic nucleus 6‐aminopenicillanic acid (6‐APA). The yields of both 6‐APA and acyl donor could be improved by repetitively adding substrates to the reaction, allowing the concentration of 6‐APA to remain saturated throughout. In this reaction concept, with four subsequent additions of substrates, 97% conversion of 6‐APA and 72% of D‐(−)‐phenylglycine methyl ester (D‐PGM) to ampicillin was achieved. The synthetic potential of this concept was estimated using a mathematical model which showed that by increasing the amount of added substrates a nearly quantitative conversion of 6‐APA and 85% conversion of acyl donor into ampicillin could be achieved . © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 73: 426–430, 2001.