bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase behavior and molecular mobility in polyurethane/styrene–acrylonitrile blends
Authors: Vatalis A. S. , Kanapitsas A. , Delides C. G. , Viras K. , Pissis P.
Published: August 2002

Differential scanning calorimetry (DSC), thermally stimulated depolarization currents (TSDC) techniques, dielectric relaxation spectroscopy (DRS), and dynamic mechanical thermal analysis (DMTA), covering together a wide range of temperatures and frequencies, were employed to investigate molecular mobility and microphase separation in blends of crosslinked polyurethane (PUR) and styrene–acrylonitrile (SAN) copolymer, prepared by reactive blending with polymer polyols. The results by each technique indicate that the degree of microphase separation of PUR into hard‐segment (HS) microdomains and soft‐segment (SS) microphase increases on addition of SAN. The various techniques were critically compared to each other, with respect to their characteristic time and length scales, on the basis of activation diagrams (Arrhenius plots). The results show that for the dynamic glass transition of the PUR SS microphase the characteristic time scales at the same temperature are similar for DMTA, DSC, and TSDC and shorter for DRS. In terms of fragility, the PUR/SAN blends are classified as fragile systems. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1071–1084, 2001
New porous perfluoropolyether membranes
Authors: Chaouk Hassan , Wilkie John S. , Meijs Gordon F. , Cheng Han Ying
Published: August 2002

A new family of porous fluorinated membranes was developed from perfluoropolyethers (PFPEs). The PFFE–dimethacrylate (3) was dispersed in isopropanol to form a clear homogeneous solution, which after UV curing in polypropylene molds formed a porous polymer disk. A series of 10 polymers was prepared with ratios of isopropanol to PFPE ranging from 1.3:1 to 0.2:1. The water content of the membranes after hydration varied from 56 to 7% (w/w) and was directly proportional to the percentage of isopropanol used in the polymerization. However, the tensile elastic modulus, which ranged from 0.17 to 15 MPa, was inversely proportional to the water content. The high water content membranes [52 and 46% (w/w)] had a similar permeability to glucose, inulin, and albumin, while the membranes with lower water contents of 37 and 25% displayed progressively lower permeability. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1756–1763, 2001
Modeling the role of stabilizing additives during melt recycling of high‐density polyethylene
Authors: Tsenoglou C. , Kartalis C. N. , Papaspyrides C. D. , Pfaendner R.
Published: August 2002

Post‐use high‐density polyethylene, almost devoid of any stabilizing agents, was restabilized in various degrees and subjected to multiple extrusion cycles at different reprocessing temperatures for assessing its chemical stability. The process‐induced material degradation was attributed primarily to long‐chain branching caused by crosslinking. It was monitored by an increase in viscosity and evaluated on the basis of an approximate expression derived using fundamental principles of macromolecular rheology. It was determined that long‐chain branching increases with temperature and the extent of processing, while decreasing with the amount of restabilizing agent added. A simple model was developed to quantitatively describe the progress of the chemical change by relating it to key material and operational variables. Besides constituting a useful method of monitoring and controlling polymer modification during processing, this model suggests ways of optimizing stabilization according to the particular processing and product requirements. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2207–2217, 2001
Thermogravimetric analysis of poly(3‐hydroxybutyrate) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate)
Authors: Li Si‐Dong , Yu Peter H. , Cheung Man Ken
Published: August 2002

The thermal degradation of poly(3‐hydroxybutyrate) (PHB) and poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB‐HV)] was studied using thermogravimetry (TG). In the thermal degradation of PHB, the temperature at the onset of weight loss (To) was derived by To = 0.97B + 259, where B represents the heating rate (°C/min). The temperature at which the weight loss rate was maximum (Tp) was Tp = 1.07B + 273, and the final temperature (Tf) at which degradation was completed was Tf = 1.10B + 280. The percentage of the weight loss at temperature Tp (Cp) was 69 ± 1% whereas the percentage of the weight loss at temperature Tf (Cf) was 96 ± 1%. In the thermal degradation of P(HB‐HV) (7:3), To = 0.98B + 262, Tp = 1.00B + 278, and Tf = 1.12B + 285. The values of Cp and Cf were 62 ± 7 and 93 ± 1%, respectively. The derivative thermogravimetric (DTG) curves of PHB confirmed only one weight loss step change because the polymer mainly consisted of the HB monomer only. The DTG curves of P(HB‐HV), however, suggested multiple weight loss step changes; this was probably due to the different evaporation rates of the two monomers. The incorporation of 10 and 30 mol % of the HV component into the polyester increased the various thermal temperatures (To, Tp, andTf) by 7–12°C (measured at B = 20°C/min). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2237–2244, 2001
Influence of reaction between second monomer and vinyl group of seed polysiloxane on seeded emulsion polymerization
Authors: He Wei‐Dong , Pan Cai‐Yuan
Published: August 2002

Seeded emulsion polymerization of methyl methacrylate (MMA) or styrene (ST) was carried in the presence of different vinyl‐containing polysiloxane latices (SV‐*) and the core‐shell particles with poly(methyl methacrylate) (PMMA) or polystyrene (PST), as the shells were obtained under different polymerization conditions. Besides the compatibility of the vinyl monomer and its polymer with polysiloxane and the reaction between vinyl monomer with vinyl group of polysiloxane, the content of vinyl group of seed polysiloxane has influence on the morphology and component of the resulted composite particles. The mechanism for the formation of core‐shell structure is discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2752–2758, 2001
Ternary polymer composites: PA6,6/maleated SEBS/glass beads
Authors: Tjong S. C. , Xu S. A.
Published: August 2002

Polyamide 6,6 (PA6,6)/maleated styrene–hydrogenated butadiene–styrene (SEBS) blends filled with up to 20% spherical glass beads (GBs) were prepared by extrusion and subsequent injection molding. Tensile and impact tests were used to examine the effect of GB additions on the mechanical behavior of PA6,6/SEBS–g–MA 80/20 blend. Tensile measurements showed that the GB additions improve the stiffness of the PA6,6/SEBS–g–MA 80/20 blend but had little effect on its tensile ductility. The impact test revealed that the impact strength of PA6,6/SEBS–g–MA 80/20 blend tends to decrease with increasing GB content. Therefore, the GB additions were beneficial to maintain a stiffness‐to‐toughness balance of the PA6,6/SEBS–g–MA 80/20 blend. Finally, the correlation between the experimental tensile stiffness and strength with various theoretical models is discussed. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3231–3237, 2001
Thermal analyses of poly(3‐hydroxybutyrate), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate), and poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate)
Authors: He Ji‐Dong , Cheung Man Ken , Yu Peter H. , Chen Guo‐Qiang
Published: August 2002

Thermal analyses of poly(3‐hydroxybutyrate) (PHB), poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) [P(HB–HV)], and poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) [P(HB–HHx)] were made with thermogravimetry and differential scanning calorimetry (DSC). In the thermal degradation of PHB, the onset of weight loss occurred at the temperature (°C) given by To = 0.75B + 311, where B represents the heating rate (°C/min). The temperature at which the weight‐loss rate was at a maximum was Tp = 0.91B + 320, and the temperature at which degradation was completed was Tf = 1.00B + 325. In the thermal degradation of P(HB–HV) (70:30), To = 0.96B + 308, Tp = 0.99B + 320, and Tf = 1.09B + 325. In the thermal degradation of P(HB–HHx) (85:15), To = 1.11B + 305, Tp = 1.10B + 319, and Tf = 1.16B + 325. The derivative thermogravimetry curves of PHB, P(HB–HV), and P(HB–HHx) confirmed only one weight‐loss step change. The incorporation of 30 mol % 3‐hydroxyvalerate (HV) and 15 mol % 3‐hydroxyhexanoate (HHx) components into the polyester increased the various thermal temperatures To, Tp, and Tf relative to those of PHB by 3–12°C (measured at B = 40°C/min). DSC measurements showed that the incorporation of HV and HHx decreased the melting temperature relative to that of PHB by 70°C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 90–98, 2001
Analysis of a crease‐resisting finish on linen fabrics using Fourier transform infrared spectroscopy and visible and near‐infrared spectroscopy
Authors: Mccall R. D. , Kernaghan K. J. , Sharma H. S. S.
Published: August 2002

A wide range of chemical reagents are capable of producing a satisfactory crease‐resisting finish for cellulosic fabrics and are currently available on the market. However, these agents do not work as efficiently on linen relative to cotton or rayon. Untreated linen controls and samples treated with a N‐methylol reagent were investigated for physical and chemical changes, and an attempt was made to quantify the crosslinking bonds formed and assess other changes in the treated fabrics using Fourier transform infrared spectroscopy (FTIR) and visible and near‐infrared spectroscopy (NIR). The results were compared with nitrogen analysis data, crease‐recovery angle measurements, and abrasion‐resistance tests in an attempt to assess the effectiveness of the treatment relative to the responses of the instrumental techniques. This study shows correlations between the visible and NIR and FTIR spectra and the crease‐recovery angle and abrasion resistance. The study also indicates that FTIR may be useful in assessing the crosslinking bonding changes associated with the dimethylol urea treatment of linen to achieve improved crease recovery. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1886–1896, 2001
A novel approach for the determination of the physicomechanical properties of polymers by vibrational spectroscopy: The tensile strength of polybutadiene rubber
Authors: Pandey G. C. , Kumar Ajay , Garg R. K.
Published: August 2002

In an attempt to extend the applications of IR spectroscopy, we report here on a novel method for the determination of the tensile strength (Ts) of polybutadiene rubber (PBR). A simple linear correlation between Ts and the peak absorbance ratio was developed. The method is simple, direct, and fast and involves only the measurement of the absorbance ratio from the IR spectrum of PBR film. The results obtained by this (IR‐based) method and the currently used (ASTM) method, for quality control/quality assurance purposes, were in good agreement. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2135–2139, 2001
Graft copolymerization of methyl acrylate onto nylon1010 initiated by potassium diperiodatonickelate(IV)
Authors: Liu Yinghai , Li Weiping , Deng Kuilin , Zhang Jinsong
Published: August 2002

In this article, the graft copolymerization of methyl acrylate (MA) onto nylon1010 by using potassium diperiodatonickelate(IV) [Ni(IV)]–nylon1010 redox system as initiator was studied in alkaline medium. The effect of different factors on grafting parameters was investigated. The structure of the graft copolymer was determined by infrared (IR), X‐ray diffraction, and scanning electron microscope (SEM). It was found that Ni(IV)–nylon1010 system is an efficient redox initiator for this graft copolymerization. A single‐electron transfer mechanism is proposed to explain the formation of radicals and the initiation. The graft copolymer was used as the compatibilizer in blends of poly(methyl methacrylate) (PMMA) and nylon1010. The SEM photographs indicate that the graft copolymer greatly improved the compatibility of the blend. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2636–2640, 2001
Effects of ethyl acetate on the soap‐free emulsion polymerization of 4‐vinylpyridine and styrene. I. Aspects of the mechanism
Authors: Ni Henmei , Ma Guanghui , Nagai Masatoshi , Omi Shinzo
Published: August 2002

A series of experiments were carried out on the soap‐free emulsion polymerization mechanism of 4‐vinyl pyridine (4VP)/styrene (St) and the solvent, ethyl acetate (EA), by using the cationic initiator, 2,2′‐azobis(2‐amidinopropane) 2HCl (V50). To investigate the mechanism of polymerization in detail, a particular quasi‐static polymerization system—the reaction mixture in a sealed bottle allowed to stand without agitation during the whole polymerization period—was employed. The partition of monomers at ambient and solid content of the latex during the quasi‐static polymerization in the presence of 8 wt % EA was measured by 1H‐NMR, and the variation of particle size was observed by scanning electron microscopy (SEM). The solubility of 4VP and St in water decreased as the amount of EA increased. Meanwhile, most of the EA was partitioned in the oil phase, even in the cases where the charged amount of EA was much lower than the solubility of EA (∼ 8 wt %) in water at ambient. The solubility of EA in water was also affected by the composition of 4VP and St (i.e., increased as the fraction of 4VP increased, but decreased as the fraction of St increased). This observation, as well as the quantitative analysis of the quasi‐static emulsion polymerization, indicated that the initial reaction in the soap‐free emulsion polymerization was closely related to the disturbance of the interface of monomer/water phase, which triggered the generation of monomer droplets. Therefore, a new mechanism was proposed for the nucleation of soap‐free emulsion polymerization, namely, the nucleation was performed in the droplets. The droplets absorbed the oligomeric radicals generated in the aqueous phase to continue the polymerization, as well as to promote the colloidal stability of the droplets. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2679–2691, 2001
Effects of ethyl acetate on the soap‐free emulsion polymerization of 4‐vinylpyridine and styrene. II. Aspects of the mechanism
Authors: Ni Henmei , Ma Guanghui , Nagai Masatoshi , Omi Shinzo
Published: August 2002

The kinetics of the soap‐free emulsion polymerization of 4‐vinylpyridine and styrene, as well as the morphology development during the polymerization, were investigated with 1H‐NMR, scanning electron microscopy, transmission electron microscopy, and differential scanning calorimetry. To clarify the process of particle nucleation and particle growth, we focused on the effects of the addition of ethyl acetate (8 wt %) combined with lower rates of agitation (100 and 200 rpm). The results showed that both the nucleation and the growth of particles were related to the monomer droplets stemming from the interface of the monomer and aqueous phases by the disturbance by agitation and/or from the condensation of monomers dissolved in the aqueous phase. Besides the diffusion of monomer molecules through the aqueous phase, the incorporation, among the species previously formed, of monomer droplets was a major cause of monomer transport in the emulsion polymerization system. The particle morphology was controlled by the miscibility of the monomers and (co)polymer, rather than the phase separation due to the different compositions of the copolymers in the particles. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2692–2708, 2001
Dissolution of latex films after γ‐ray treatment
Authors: Aydin K. , Adiyaman N. , Uğur Ş. , Pekcan Ö.
Published: August 2002

Latex films were prepared by annealing pyrene (Py)‐labeled poly(methyl methacrylate) particles at glass‐transition temperature (100°C). These films were then irradiated by γ‐rays from 60Co in a gamma cell at room temperature at the same dose rate (rad/h) for 30 min. Before dissolution films were annealed at elevated temperatures for a 30‐min time interval to complete the film formation process. Steady‐state fluorescence (SSF) technique were used to monitor the dissolution of these irradiated latex films. The dissolution of films in chloroform–heptane (80–20%) mixture was monitored in real time by the Py fluorescence intensity change. Relaxation constants k0 and desorption coefficients Dd of polymer chains were measured. It was observed that both Dd and k0 values first increased and then decreased by increasing the annealing temperature. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 129–137, 2002
Influence of different dopants on the adsorption, morphology, and properties of self‐assembled films of poly(o‐ethoxyaniline)
Authors: Paterno Leonardo G. , Mattoso Luiz H. C.
Published: August 2002

Self‐assembled films of poly(o‐ethoxyaniline)—POEA alternated with sulfonated lignin (SL)—were successfully produced, and their kinetics of formation and growth investigated for different dopants (hydrochloric acid, methanesulfonic acid, p‐toluenesulfonic acid, and camphorsulfonic acid). These films were characterized by ultraviolet‐visible spectroscopy, atomic force microscopy, surface potential, and electrical resistance measurements. It has been observed that the bulkiest dopants led to a greater time for the polymer deposition and greater amount of material adsorbed. This can be explained by the lower mobility and lower solvation of the bulkiest dopant counterions, which led to a higher screening effect of the charges present in the POEA chains and therefore to a more compact molecular conformation. The morphology of the POEA films were also greatly affected by the type of dopant used, being rougher for the bulkiest dopants. The POEA films also exhibited different electrical responses upon ethylene exposure depending on the dopant, indicating a promising use for gas sensor applications. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1309–1316, 2002
Community patterns generated by human harvesting on Chilean shores: a review
Authors: Moreno Carlos A.
Published: August 2002

1. The Chilean rocky coast has been exploited for food by coastal gatherers for at least 8500 years BP and probably was an important factor in how prehistoric people were able to colonize the South Americas Pacific Rim. The main species targeted in the past were the same as those today except that now the gatherers are resident and the fishing activity is more intense and persistent.

2. With many pertinent studies from around the world having been published on this topic, mostly conducted in Marine Reserves, this review tries to identify the main patterns that can help us recognize, in the Chilean intertidal, the degree of exploitation on wave exposed and wave protected rocky shore habitats.

3. Three clear patterns were identified depending on the trophic level adopted by the human gatherers in the food chain of the intertidal zone. First, when the humans act as herbivores, collecting the large laminarian Durvillaea antarctica, adult plants disappear from the accessible sites, especially the midlittoral, semi‐exposed and exposed habitats.

4. Second, when humans harvest the ecologically important herbivorous archeogastropoda Fissurella spp., this results in the red alga Mazzaella laminarioides covering almost 100% of the midlittoral rocks. Third, when humans become top predators by collecting the muricid carnivore Concholepas concholepas, then bivalves, mainly Perumytilus purpuratus, cover the rocks in multiple layers.

5. These patterns contribute to the evaluation of the state of conservation of the Chilean rocky intertidal shores, especially because the north and the south are beginning to be connected by a new coastal road. Thus it is necessary to evaluate urgently, on a large spatial scale, the state of conservation of these communities, in order to help select the appropriate places for establishing Marine Reserves.

Copyright © 2001 John Wiley & Sons, Ltd.
Endocast of Sambungmacan 3 (Sm 3): A new Homo erectus from Indonesia
Authors: Broadfield Douglas C. , Holloway Ralph L. , Mowbray Kenneth , Silvers Adam , Yuan Michael S. , Márquez Samuel
Published: August 2002

A new fossil calvaria, Sambungmacan 3 (Sm 3), described in New Fossil Hominid Calvaria From Indonesia—Sambungmacan 3 by Márquez et al., this volume, yields one of the most advanced and complete endocasts yet recovered from Java. This communication provides a thorough interpretation of the external anatomical landmarks observable on Sm 3. Using computer tomography (CT) and traditional morphological measurements, our comparative paleoneurological analyses show that while Sm 3 has a mosaic of features that are similar to both Indonesian and Chinese H. erectus, it also possesses significant characters reminiscent of later hominins. These include a greater degree of asymmetry characterized by a possible left‐occipital, right‐frontal petalial pattern, left‐right volumetric cerebral asymmetry, and marked asymmetry in Broca's cap. Moreover, the frontal lobe offers a more rounded, shortened appearance in contrast to the flat, elongated appearance of other Indonesian fossils (e.g., Sangiran 17). Another unique trait is exhibited in the transverse plane where the widest breadth of Sm 3 occurs more superiorly than in other Indonesian H. erectus. Thus, the endocast of Sm 3 presents a unique morphology not seen previously in the hominin fossil record. While the strong modern human characteristics in this endocast may not represent a particular ancestry, they do allow us to recognize a new dimension of the remarkable variation in Indonesian Homo erectus. Anat Rec 262:369–379, 2001. © 2001 Wiley‐Liss, Inc.
Virtual anthropology (VA): A call for Glasnost in paleoanthropology
Authors: Weber Gerhard W.
Published: August 2002

The adventurous scientist, with a hat protecting him from the fierce sun as he travels from one remote place to another, hunting for fossils of our ancestors, has been a part of the romantic imagination associated with anthropological research in the 20th Century. This picture of the paleoanthropologist still retains a grain of truth. Indeed, many new sites were discovered under troublesome conditions in the recent past and have added substantial information about our origins. But on another front, probably less sensational but no less important, are contributions stemming from the analysis of the already discovered fossils. With the latter, a rapid evolution in anthropologic research took place concurrently with advances in computer technology. After ambitious activities by a handful of researchers in some specialized laboratories, a methodologic inventory evolved to extract critical information about fossilized specimens, most of it preserved in the largely inaccessible interior as unrevealed anatomic structures. Many methodologies have become established but, for various reasons, access to both the actual and the digitized fossils is still limited. It is time for more transparency, for a glasnost in paleoanthropology. Herein are presented some answers to the question of how a high‐tech approach to anthropology can be integrated into a predominantly conservative field of research, and what are the main challenges for development in the future. Anat Rec (New Anat) 265:193–201, 2001. © 2001 Wiley‐Liss, Inc.
XQL and proximal nodes
Authors: Baeza‐Yates Ricardo , Navarro Gonzalo
Published: August 2002

Despite the fact that several models to structure text documents and to query on this structure have been proposed in the past, a standard has emerged only relatively recently with the introduction of XML and its proposed query language XQL, on which we focus in this article. Although there exist some implementations of XQL, efficiency of the query engine is still a problem. We show in this article that an already existing model, Proximal Nodes, which was defined with the goal of efficiency in mind, can be used as an efficient query engine behind an XQL front‐end.
A design analysis model for developing world wide web sites
Authors: Ma Yan
Published: August 2002

This study applies reader‐response criticism to examine the relationship between and among designers, text, and users of the Galter Health Sciences Library Web site. It asks such questions as “How do Web site designers construct their subject?” or, “Whom do the web designers think their users are?” The study ascertains the intentions of the designers of the GHSL Web site; examines the meanings made by the users through interviews; compares the similarities and differences of designers' intentions with their organization of knowledge represented in the GHSL Web site; and compares the similarities and differences between the designers' intentions and views of the users.
The non‐Gaussian nature of bibliometric and scientometric distributions: A new approach to interpretation
Authors: Ivancheva Ludmila E.
Published: August 2002

An attempt has been made to give an answer to the question: Why do most bibliometric and scientometric laws reveal characters of Non‐Gaussian distributions, i.e., have unduly long “tails”? We tried to apply the approach of the so‐called “Universal Law,” discovered by G. Stankov (1997, 1998). The basic principle we have used here is that of the reciprocity of energy and space. A new “wave concept” of scientific information has been propounded, in which terms the well‐known bibliometric and scientometric distributions find a rather satisfactory explanation. One of the made corollaries is that α = 1 is the most reasonable value for the family of Zipf laws, applied to information or social phenomena.
Effect of naproxen co‐administration on valproate disposition
Authors: Addison R.S. , Parker‐Scott S.L. , Hooper W.D. , Eadie M.J. , Dickinson R.G.
Published: August 2002

The effects of co‐administration of the antiepileptic agent valproic acid (VPA) and the non‐steroidal anti‐inflammatory drug naproxen (NAP) on their relative dispositions (particularly with respect to glucuronidation) were investigated in human volunteers. Seven healthy males received each drug alone and then in combination (orally twice daily for seven days, 500 mg sodium VPA, 500 mg NAP). On day 7 of each dosing phase, serial plasma and 24 h urine samples were collected for analysis. Co‐administration of NAP resulted in significant increases (about 20%, p<0.05) in the apparent plasma clearance of total VPA and in the unbound fraction of VPA in plasma, with the apparent plasma clearance of unbound VPA being unchanged. There were associated increases in the formation clearances to urinary VPA‐glucuronide and 3‐oxo‐VPA, though these were relatively greater for the glucuronidation pathway (and remained significant when formation clearances were calculated using the unbound fraction of drug in plasma). The data thus point to a shift towards glucuronidation as a result of the NAP‐induced increase in the unbound fraction of VPA in plasma. By contrast, VPA co‐administration caused a decrease (of about 10%, p<0.05) in the apparent plasma clearance of total NAP. Taken in hand with in vitro results showing a VPA‐induced displacement (of about 40%) of NAP from plasma protein binding sites, the data strongly support a role for diminished glucuronidation of NAP and its desmethyl metabolite in the presence of co‐administered VPA. Copyright © 2000 John Wiley & Sons, Ltd.
Pharmacokinetics of lovastatin extended‐release dosage form (Lovastatin XL) in healthy volunteers
Authors: Lamson Michael , Phillips Gale , Shen Jason , Lukacsko Peter , Friedhoff Lawrence , Niecestro Robert M.
Published: August 2002

The purpose of this study was to evaluate pharmacokinetics and dose proportionality of lovastatin extended‐release dosage form (ER‐lovastatin) in the dosage levels of 10, 20 and 40 mg in 9 healthy male subjects. Each subject was randomized to receive a single oral dose of ER‐lovastatin either 10, 20 or 40 mg in a three‐way crossover design with a washout period of 7 days between the treatments. Subjects were served dinner at approximately 5:30 PM followed by dosing at approximately 10:00 PM in each study period. Serial plasma samples were collected up to 48 h after dosing and assayed for lovastatin and its active metabolite lovastatin acid using an LC/MS/MS method. The plasma concentration–time profiles of lovastatin and its active metabolite lovastatin acid exhibited delayed‐ and extended‐release characteristics at each dose. Mean (±) values for the Cmax of lovastatin were 1.04±0.43, 2.03±0.65 and 4.03±3.02 ng/ml for the 10, 20 and 40 mg dosage, respectively. The corresponding values for the AUC0–48 h of lovastatin were 14.6±7.8, 34.1 ±13.7, and 53.9±35.6 ng h/ml. The same tendency was also found for Cmax and AUC0−48 h values of lovastatin acid. Results from this study demonstrated as the dose of ER‐lovastatin increased from 10 to 40 mg, the Cmax and AUC0−48 h values of lovastatin as well as lovastatin acid appeared to increase linearly. Copyright © 2002 John Wiley & Sons, Ltd.
Effects of high ELF magnetic fields on enzyme‐catalyzed DNA and RNA synthesis in vitro and on a cell‐free DNA mismatch repair
Authors: Harada Shin‐ichi , Yamada Sotoshi , Kuramata Osamu , Gunji Yoshirou , Kawasaki Masatoshi , Miyakawa Tomokazu , Yonekura Hideto , Sakurai Shigeru , Bessho Kazuo , Hosono Ryuji , Yamamoto Hiroshi
Published: August 2002

Environmental electromagnetic fields have been implicated in human cancers. We examined whether high extremely low frequency (ELF) AC magnetic fields could affect DNA synthesis, transcription or repair, using in vitro model systems with defined sequences. The rate and fidelity of DNA polymerase catalyzed DNA synthesis, as well as of RNA polymerase catalyzed RNA synthesis, were not statistically significantly affected by 60 Hz 0.25–0.5 Tesla magnetic fields. The efficiency of mutS dependent mismatch repair with human cell extracts was also not affected by the magnetic field exposure. The results suggest that the core processes related to the transmission of genetic information are stable under high ELF magnetic fields. Bioelectromagnetics 22:260–266, 2001. © 2001 Wiley‐Liss, Inc.
Control of growth and organ size in Drosophila
Authors: Johnston Laura A. , Gallant Peter
Published: August 2002

Transplantation experiments have shown that developing metazoan organs carry intrinsic information about their size and shape. Organ and body size are also sensitive to extrinsic cues provided by the environment, such as the availability of nutrients. The genetic and molecular pathways that contribute to animal size and shape are numerous, yet how they cooperate to control growth is mysterious. The recent identification and characterization of several mutations affecting growth in Drosophila melanogaster promises to provide insights. Many of these mutations affect the extrinsic control of animal size; others affect the organ‐intrinsic control of pattern and size. In this review, we summarize the characteristics of some of these mutations and their roles in growth and size control. In addition, we speculate about possible connections between the extrinsic and intrinsic pathways controlling growth and pattern. BioEssays 24:54–64, 2002. © 2002 John Wiley & Sons, Inc.
Securing genome stability by orchestrating DNA repair: removal of radiation‐induced clustered lesions in DNA
Authors: Dianov Grigory L. , O'Neill Peter , Goodhead Dudley T.
Published: August 2002

In addition to double‐ and single‐strand DNA breaks and isolated base modifications, ionizing radiation induces clustered DNA damage, which contains two or more lesions closely spaced within about two helical turns on opposite DNA strands. Post‐irradiation repair of single‐base lesions is routinely performed by base excision repair and a DNA strand break is involved as an intermediate. Simultaneous processing of lesions on opposite DNA strands may generate double‐strand DNA breaks and enhance nonhomologous end joining, which frequently results in the formation of deletions. Recent studies support the possibility that the mechanism of base excision repair contributes to genome stability by diminishing the formation of double‐strand DNA breaks during processing of clustered lesions. BioEssays 23:745–749, 2001. © 2001 John Wiley & Sons, Inc.
Antioxidant activity of 4‐flavonil‐1,4‐dihydropyridine derivatives
Authors: Kruk Irena , Kladna Aleksandra , Lichszteld Krzysztof , Michalska Teresa , Aboul‐Enein Hassan Y. , Tunçbilek Meral , Ertan Rahmiye
Published: August 2002

The effect of 4‐flavonil‐1,4‐dihydropyridine derivatives on a chemical system involving a superoxide radical anion was tested using the chemiluminescence and spectrophotometry methods. All tested compounds enhanced the light emission from the system. The obtained results indicated that the tested derivatives may catalyze the conversion of superoxide radicals, thus showing superoxide dismutase activity. © 2001 John Wiley & Sons, Inc. Biopolymers (Biospectroscopy) 62: 163–167, 2001
Micro‐Raman characterization of high‐ and low‐spin heme moieties within single living erythrocytes
Authors: Wood Bayden R. , McNaughton Don
Published: August 2002

Raman microspectroscopy was applied to monitor porphyrin perturbation associated with the tense‐relaxed (T → R) state transition of hemoglobin (Hb) within a single red blood cell. The spectra exhibited dramatic changes in the spin state region (1650–1500 cm−1) and the methine CH deformation region (1250–1200 cm−1) between the 27‐ and 54‐min interval following reoxygenation. Principal components analysis revealed a sigmoidal curve when the PC1 scores versus time were plotted. The inflection point on the curve corresponded to the T → R transition point spectrum, indicating the cell is composed of Hb in a mixture of spin states. The results of this work illustrate the dynamics of porphyrin perturbation during erythrocyte respiration and may have applications in the diagnosis and treatment of red blood cell disorders including thalassemia and sickle cell anemia. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 259–262, 2002
Ordering in aqueous polysaccharide solutions. II. Optical rotation and heat capacity of aqueous solutions of a triple‐helical polysaccharide schizophyllan*
Authors: Yoshiba Kazuto , Ishino Tetsurou , Teramoto Akio , Nakamura Naotake , Miyazaki Yuji , Sorai Michio , Wang Qi , Hayashi Yoshihito , Shinyashiki Naoki , Yagihara Shin
Published: August 2002

Deuterium oxide solutions of schizophyllan, a triple‐helical polysaccharide, undergoing an order–disorder transition centered at 17°C, were studied by optical rotation (OR) and heat capacity (Cp) to elucidate the molecular mechanism of the transition and water structure in the solution and frozen states. The ordered structure at low temperature consisted of the side chains and water in the vicinity forming an ordered hydrogen‐bonded network surrounding the helix core and was disordered at higher temperature. In the solution state appeared clearly defined transition curves in both the OR and Cp data. The results for three samples of different molecular weights were analyzed theoretically, treating this transition as a typical linear cooperative transition from the ordered to disordered states and explained quantitatively if the molecular weight polydispersity of the sample was considered. The excess heat capacity C defined as the Cp minus the contributions from schizophyllan and D2O was estimated. In the frozen state it increased with raising temperature above 150 K until the mixture melted. This was compared with the dielectric increment observed in this temperature range and ascribed to unfreezable water. From the heat capacity and dielectric data, unfreezable water is mobile but more ordered than free water. In the solution state, the excess heat capacity originates from the interactions of D2O molecules as bound water and structured water, and so forth. Thus the schizophyllan triple helix molds water into various structures of differing orders in solution and in the solid state. © 2002 Wiley Periodicals, Inc. Biopolymers 63: 370–381, 2002
The effect of ethanol on the kinetics of lipase‐mediated enantioselective esterification of 4‐methyloctanoic acid and the hydrolysis of its ethyl ester
Authors: Heinsman Nicole W. J. T. , Valente Ana M. , Smienk Henry G. F. , van der Padt Albert , Franssen Maurice C. R. , de Groot Aede , van ‘t Riet Klaas
Published: August 2002

The Novozym 435® catalyzed esterification and hydrolysis reactions of 4‐methyloctanoic acid (ethyl ester) were investigated. In both the hydrolysis and esterification reactions, the increase of ethanol concentration led to an increase in enantiomeric ratio (E). For hydrolysis of the ethyl ester, the E‐value increased from 5.5 [0% (v/v) EtOH] up to 12 [20% (v/v) EtOH]. In case of esterification, the E‐value was already 16 [14% (v/v) EtOH] and rose to 57 [73% (v/v) EtOH]. When combining these results of esterification and hydrolysis, an enantiomeric ratio of 350 can be estimated for the sequential kinetic resolution of 4‐methyloctanoic acid. In this way, enantiopure 4‐methyloctanoic acid could be obtained after two consecutive reaction steps. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 193–199, 2001.
On‐line stoichiometry and identification of metabolic state under dynamic process conditions
Authors: Herwig Christoph , Marison Ian , von Stockar Urs
Published: August 2002

A method for the on‐line calculation of conversion rates and yield coefficients under dynamic process conditions was developed. The method is based on cumulated mass balances using a moving average method. Elemental balances were used to test the measured cumulated quantities for gross errors and inappropriate stoichiometry definition followed by data reconciliation and estimation of non‐measured conversion rates, using a bioprocess set‐up including multiple on‐line analysis techniques. The quantitative potential of the proposed method is demonstrated by executing transient experiments in aerobic cultures of Saccharomyces cerevisiae on glucose. Rates and yield coefficients could be consistently quantified in shift‐up, shift‐down, and accelerostat experiments. The method shows the capability to describe quantitatively transient changes in metabolism including uncoupling of catabolism and anabolism, also for the case when multiple components of metabolism are not measured. The validity of the experiment can be evaluated on‐line. Additionally, the method detects with high sensitivity inappropriate stoichiometry definition, such as a change in state of metabolism. It was shown that concentration values can be misleading for the identification of the metabolic state. In contrast, the proposed method provides a clear picture of the metabolic state and new physiological regulations could be revealed. Hence, the novelty of the proposed method is the on‐line availability of consistent stoichiometric coefficients allowing a significant speed up in strain characterization and bioprocess development using minimal knowledge of the metabolism. Additionally, it opens up the use of transient experiments for physiological studies. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 345–354, 2001.
Further studies on the contribution of electrostatic and hydrophobic interactions to protein adsorption on dye–ligand adsorbents
Authors: Zhang Songping , Sun Yan
Published: August 2002

The adsorption equilibria of bovine serum albumin (BSA), γ‐globulin, and lysozyme to three kinds of Cibacron blue 3GA (CB)‐modified agarose gels, 6% agarose gel‐coated steel heads (6AS), Sepharose CL‐6B, and a home‐made 4% agarose gel (4AB), were studied. We show that ionic strength has irregular effects on BSA adsorption to the CB‐modified affinity gels by affecting the interactions between the negatively charged protein and CB as well as CB and the support matrix. At low salt concentrations, the increase in ionic strength decreases the electrostatic repulsion between negatively charged BSA and the negatively charged gel surfaces, thus resulting in the increase of BSA adsorption. This tendency depends on the pore size of the solid matrix, CB coupling density, and the net negative charges of proteins (or aqueous ‐ phase pH value). Sepharose gel has larger average pore size, so the electrostatic repulsion‐effected protein exclusion from the small gel pores is observed only for the affinity adsorbent with high CB coupling density (15.4 μmol/mL) at very low ionic strength (NaCl concentration below 0.05 M in 10 mM Tris‐HCl buffer, pH 7.5). However, because CB–6AS and CB–4AB have a smaller pore size, the electrostatic exclusion effect can be found at NaCl concentrations of up to 0.2 M. The electrostatic exclusion effect is even found for CB–6AS with a CB density as low as 2.38 μmol/mL. Moreover, the electrostatic exclusion effect decreases with decreasing aqueous‐phase pH due to the decrease of the net negative charges of the protein. For γ‐globulin and lysozyme with higher isoelectric points than BSA, the electrostatic exclusion effect is not observed. At higher ionic strength, protein adsorption to the CB‐modified adsorbents decreases with increasing ionic strength. It is concluded that the hydrophobic interaction between CB molecules and the support matrix increases with increasing ionic strength, leading to the decrease of ligand density accessible to proteins, and then the decrease of protein adsorption. Thus, due to the hybrid effect of electrostatic and hydrophobic interactions, in most cases studied there exists a salt concentration to maximize BSA adsorption. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 710–717, 2001.
Reactivity and stability of mycelium‐bound carboxylesterase from Aspergillus oryzae
Authors: Converti Attilio , Borghi Adriana Del , Gandolfi Raffaella , Lodi Alessandra , Molinari Francesco , Palazzi Emilio
Published: August 2002

The reactivity and thermostability of a novel mycelium‐bound carboxylesterase from lyophilized cells of Aspergillus oryzae are explored in organic solvent. Ethanol acetylation was selected as reference esterification reaction. High carboxylesterase activity cells were used as biocatalyst in batch esterification tests at 12.5 < So < 125 mmol L−1, 5.0 < Xo < 30 g L−1, 0.49 < log P < 4.5 and 30 < T < 80°C, as well as in residual activity tests after incubation at 40 < T < 90°C. The starting rates of product formation were used to estimate with the Arrhenius model the apparent activation enthalpies of the enzymatic reaction (29–33 kJ mol−1), the reversible unfolding (56–63 kJ mol−1), and the irreversible denaturation (22 kJ mol−1) of the biocatalyst. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 232–237, 2002.
Production of different morphologies of biocompatible polymeric materials by supercritical CO2 antisolvent techniques
Authors: Elvassore Nicola , Baggio Marco , Pallado Paolo , Bertucco Alberto
Published: August 2002

High‐value biocompatible‐polymers have been processed with supercritical antisolvent techniques to produce solid structures of different shape and size. In particular, a class of hyaluronic acid‐derived polymers (Hyaff11‐p100, Hyaff11‐p80, Hyaff11‐p75, Hyaff 302) have been used to obtain various morphologies such as microspheres, threads, fibers, networks, and sponges. The effect of thermodynamic variables on precipitation were highlighted in some preliminary batch experiments. Then, different products were obtained by tuning the values of operating parameters. Threads and fibers were the result of a continuous supercritical antisolvent (SAS) process where a concentrated polymer solution was pumped through a micrometric nozzle: The threads showed a reticular internal structure with an adjustable type of cavity. For production of networks and sponges, the concentration of polymer plays the key role. Below a critical value it was not possible to obtain a continuous network, while above it, a structure similar to that of the natural bone with three types of internal microporosity were obtained. Again, by tuning pressure and polymer concentration, the internal porosity could be controlled. Microparticles were also produced by the SAS process, and a control of their morphology was achieved by varying the concentration of the polymer in the starting solution and the density of organic solvent‐CO2 mixtures. All the products obtained by SAS have negligible content of residual solvent. A qualitative interpretation of experimental results is presented. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 73: 449–457, 2001.
DegP‐coexpression minimizes inclusion‐body formation upon overproduction of recombinant penicillin acylase in Escherichia coli
Authors: Lin Wen‐Jer , Huang Shin‐Wei , Chou C. Perry
Published: August 2002

We demonstrated the enhancement of recombinant penicillin acylase (PAC) production in Escherichia coli by increasing the intracellular concentration of the periplasmic protease DegP. Using appropriate host/vector systems (e.g., HB101 harboring pTrcKnPAC2902 or MDΔP7 harboring pTrcKnPAC2902) in which the expression of the pac gene was regulated by the strong trc promoter, the overproduction of PAC was often limited by periplasmic processing and inclusion bodies composed of protein aggregates of PAC precursors were formed in the periplasm. The amount of these periplasmic inclusion bodies was significantly reduced and PAC activity was significantly increased upon coexpression of DegP. The specific PAC activity reached an extremely high level of 674 U/L/OD600 for MDΔP7 harboring pTrcKnPAC2902 and pKS12 under optimum culture conditions. However, such improvement in the production of PAC was not observed for the expression systems (e.g., MDΔP7 harboring pCLL2902) in which the periplasmic processing was not the step limiting the production of PAC. The results suggest that DegP could in vivo assist the periplasmic processing though the enzyme is shown to be not absolutely required for the formation of active PAC in E. coli. In addition, the steps limiting the production of PAC are identified and the reasons for the formation of PAC inclusion bodies are discussed here. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 73: 484–492, 2001.
Bromoperoxidase activity in microplantlet suspension cultures of the macrophytic red alga Ochtodes secundiramea
Authors: Rorrer Gregory L. , Tucker Mary P. , Cheney Donald P. , Maliakal Sanjiv
Published: August 2002

Bromoperoxidase is an enzyme found in marine macroalgae that catalyzes the bromination of organic substrates. Photosynthetic microplantlet suspension cultures derived from the macrophytic red alga Ochtodes secundiramea were shown to possess bromoperoxidase. The optimum pH for O. secundiramea bromoperoxidase activity in cell‐free extracts was 6.0, and the half‐saturation constant for bromination of the exogeneous substrate monochlorodimedone (MCD) was 18 μM. O. secundiramea microplantlets were cultivated in a bubble‐column photobioreactor at an incident light intensity of 38 μE m−2 s−1 (71% of light‐saturated photosynthesis, 10:14 light:dark photoperiod), and the kinetics of cell growth and bromoperoxidase production were followed. At these conditions, the specific growth rate was 0.052 day−1. The lowest specific bromoperoxidase activity of 0.3 μmol MCD g−1 cell min−1 occurred during the midexponential phase of growth, and then increased steeply to 1.9 μmol MCD g−1 cell min−1 during the late stationary phase, suggesting that bromoperoxidase production was part of secondary metabolism. The estimated bromoperoxidase content in the cell mass at late stationary phase was 67 μg g−1 dry cell mass, demonstrating that bioreactor production of marine bromoperoxidase is feasible. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 74: 389–395, 2001.