bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies on the copolymerization of methyl methacrylate with N‐(o/m/p‐chlorophenyl) itaconimides
Authors: Anand Vishal , Choudhary Veena
Published: August 2002

The article describes the synthesis and characterization of N‐aryl itaconimide monomers such as: N‐(p‐chlorophenyl) itaconimide (PI)/N‐(m‐chlorophenyl) itaconimide (MI)/N‐(o‐chlorophenyl) itaconimide (OI) and its copolymerization behavior with MMA. The homopolymers and copolymers of N‐aryl itaconimides and methyl methacrylate (MMA, M2) were synthesized by varying the mol fraction of N‐aryl itaconimides in the initial feed from 0.1 to 0.5 using azobisisobutyronitrile (AIBN) as an initiator and tetrahydrofuran (THF) as the solvent. Copolymer composition was determined using 1H‐NMR spectroscopy [by taking the ratio of intensities of signals due to OCH3 of MMA (δ = 3.59 ppm) and the aromatic proton (δ = 7.2–7.5 ppm) of N‐aryl itaconimides] and percent nitrogen content. The reactivity ratios were found to be r1 = 1.33 and r2 = 0.36 (PI‐MMA) r1 = 1.15 and r2 = 0.32 (MI‐MMA) and r1 = 0.81 and r2 = 0.35 (OI‐MMA). Molecular weight as determined using high‐performance liquid chromatography decreased with increasing mol fraction of itaconimides in copolymers. All the polymers had a polydisperstivity index in the range of 1.5–2.6.Thermal characterization was done using differential scanning calorimetry and dynamic thermogravimetry in nitrogen atmosphere. Incorporation of these N‐aryl itaconimides in PMMA backbone resulted in an improvement in glass transition temperature (Tg) and thermal stability. Percent char increased with the increase of PI/MI/OI content in the copolymers. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2078–2086, 2001
Effect of metallic oxides on thermal stability of ethylene–propylene terpolymer
Authors: Zaharescu T. , Podina C. , Wurm D.
Published: August 2002

Thermal stability of ethylene–propylene terpolymer (EPDM) loaded with various metallic oxides (PbO, CuO, NiO, Fe2O3, Cr2O3, TiO2, ZrO2) was assessed by the oxygen uptake method. The effects of 5 phr oxide of thermal aging of elastomer were investigated under isothermal (180°C) and isobaric (air at normal pressure) conditions. The influence of this was pointed out. Some mechanistic considerations on the oxidative degradation of EPDM are presented. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2155–2158, 2001
Reaction kinetics of liquid crystalline epoxy cured with aromatic diamine: Its synthesis and mechanical and electrical characteristics
Authors: Lee J. Y. , Shim M. J. , Lee H. K. , Kim S. W.
Published: August 2002

The effect of the molar ratio of diglycidyl ether of 4,4′‐biphenyl (DGEBP) to p‐phenylene diamine (PDA) on the cure reaction rate was studied by the Kissinger and isoconversional equations. The cure mechanism was studied by FTIR analysis and the liquid crystalline phase structure was analyzed by wide angle X‐ray diffraction (WAXD). With an increasing molar ratio of DGEBP/PDA, the preexponential factor was increased by the increasing collision probability between epoxide groups and primary or secondary amine groups in noncataltyic or catalytic modes. The activation energy also increased because of the increasing content of rigid rodlike mesogen and the high crosslink density, which hindered the diffusion of functional groups. The activation energies obtained from the Kissinger equation were in good agreement with average values obtained from the isoconversional equation. The WAXD pattern showed a smectic layer structure with a layer thickness of 15.3 Å and an intermolecular distance of 4.3 Å. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2372–2380, 2001
Miscibility and adhesive properties of EVA‐based hot‐melt adhesives. II. Peel strength
Authors: Takemoto Mototsugu , Kajiyama Mikio , Mizumachi Hiroshi , Takemura Akio , Ono Hirokuni
Published: August 2002

A series of ethylene vinyl acetate copolymers (EVA) were blended with some tackifier resins that were made from wood extracts, and possible relations between their miscibility and properties as hot‐melt adhesives (HMA) were investigated. From our previous report on miscibility of various EVA‐based HMAs, we chose some blends that represent some of the typical miscibility types and investigated their peel strengths. When the blends were miscible at testing temperatures, the temperature at which the maximum value of peel strength was recorded tended to move toward higher temperature as tackifier content of blends increased. This result corresponds to the storage modulus of the blends whose curves tended to move toward higher temperature as tackifier content of blends increased when blend components were miscible as well as their maximum values of tan δ, or glass transition temperatures. It was characteristic for peel strength that there existed second peaks on peel strengths curves at ∼ 100°C, which adhesive tensile strengths for the blends did not have. In terms of relationship between miscibility and HMA performances, we suggest that there are several factors other than miscibility that affect absolute values of peel strength more directly than miscibility; this idea has to be investigated further in the a future study. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 726–735, 2002
Study of the synthesis and characterization of methacrylate photoresists
Authors: Fu S. C. , Lin H. W. , Chou W. Y. , Wang L. A. , Hsieh K. H.
Published: August 2002

Polymethacrylate copolymers used as single‐layer resists (SLR) were investigated in this study. A photoacid generator (PAG) in the chemically amplified resist (CAR) can generate a Brönsted proton after light stimulation, which can catalyze the deprotection reaction of t‐butyl methacrylate during the postexposure baking (PEB) process. Excimer lasers (KrF and ArF) were used as light source to evaluate the lithographic performance of resists. The hydrophobic property of the resist changed to hydrophilic property after the deprotection reaction by light exposure, which made the exposed resist soluble in the base developer. The deprotection reaction was analyzed by using FTIR and the reaction kinetics of the resist is discussed. The effects of the t‐butyl methacrylate and the isobornyl methacrylate in the resists on the light sensitivity, contrast, reactive ion etching (RIE) resistance, and lithographic performance were systematically investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1860–1869, 2002
Poly(dimethylsiloxane)urethane‐co‐poly(methyl methacrylate) with 2,4‐toluene diisocyanate and m‐xylene diisocyanate. I. Compatibility and impact strength of copolymers
Authors: Ma Chen‐Chi M. , Du Yi‐Chang , Wang Feng‐Yih , Wang Hui‐Chung , Yang Jen‐Chang
Published: August 2002

In this study, slightly crosslinked poly(dimethylsiloxane)urethane‐co‐poly(methyl methacrylate) (PDMS urethane‐co‐PMMA) graft copolymers based on two diisocyanates, 2,4‐toluene diisocyanate (2,4‐TDI) and m‐xylene diisocyanate (m‐XDI), were successfully synthesized. Glass‐transition behaviors of the copolymers were investigated. Results confirm that PDMS–urethane and PMMA are miscible in the 2,4‐TDI system, but are only partially miscible in the m‐XDI system. The methylene groups adjoining the isocyanate in the m‐XDI system show increased phase‐separation behavior over the 2,4‐TDI system, in which the benzene ring adjoins the isocyanate. The functional group of PDMS–urethane improves the impact strength of the copolymers. The toughness depends on the compatibility of PDMS–urethane and PMMA segments in the copolymers. In the m‐XDI system, the impact strength of the copolymer containing 3.75 phr macromonomer achieves a maximum value (from 13.02 to 22.21 J/m). The fracture behavior and impact strength of the copolymers in the 2,4‐TDI system are similar to that of PMMA homopolymer, although they are independent of the macromonomer content in the copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1875–1885, 2002
Preparation of cibacron blue F3GA‐attached polyamide hollow fibers for heavy metal removal
Authors: Say Rıdvan , şenel Serap , Denizli Adil
Published: August 2002

Dye‐affinity adsorption has been used increasingly for heavy metal removal. Synthetic hollow fibers have advantages as support matrices in comparison to conventional bead supports because they are not compressible and they eliminate internal diffusion limitations. The goal of this study was to investigate in detail the performance of hollow fibers composed of modified polyamide to which Cibacron Blue F3GA was attached for the removal of heavy metal ions. The Cibacron Blue F3GA loading was 1.2 mmol/g. The internal matrix was characterized by scanning electron microscopy. No significant changes in the hollow fiber cross‐section or outer layer morphology were observed after dye modification. The effect of the initial concentration of heavy metal ions and medium pH on the adsorption efficiency were studied in a batch reactor. The adsorption capacity of the hollow fibers for the selected metal ions [i.e., Cu(II), Zn(II) and Ni(II)] were investigated in aqueous media with different amounts of these ions (10–400 ppm) and at different pH values (3.0–7.0). The maximum adsorptions of metal ions onto the Cibacron Blue F3GA‐attached hollow fibers were 246.2 mg/g for Cu(II), 133.6 mg/g for Zn(II), and 332.7 mg/g for Ni(II). Furthermore, a Langmuir expression was calculated to extend the adsorption equilibrium. Nitric acid (0.1M) was chosen as the desorption solution. High desorption ratios (up to 97%) were observed in all cases. Consecutive adsorption/desorption operations showed the feasibility of repeated use of this novel sorbent system. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3089–3098, 2002; DOI 10.1002/app.2338
Exhibits facilitate histology laboratory instruction: Student evaluation of learning resources
Authors: McMillan Paul J.
Published: August 2002

Some professional schools have replaced microscopes for histology laboratory instruction with printed and electronic media. It is recognized that these media cannot replace experience with the microscope and that there is a cognitive dissonance of completely replacing microscope study. In addition, students believe that their time is not optimally used in the traditional histology laboratory. Therefore, at Loma Linda University, nine weekly microscope exhibits consisting of 10–15 slides each were prepared. For each exhibited slide, a one page “atlas” is provided, consisting of labeled low‐ and high‐power color micrographs taken from that slide and an informative legend. By referring to the atlas, the student can easily identify the exact field and the labeled features with little help from an instructor. A live or taped video demonstration of the microscope exhibit is available on the first day of the exhibit. During the eighth week of the quarter, students were asked to evaluate the various learning resources available to them. No resource was valued significantly more than the microscope exhibits, but the video demonstrations were valued significantly more than the printed black and white atlas or the color atlas on CD. These exhibits have been used for 2 years to instruct a class of 90 dental students. Advantages are (1) students' time is used efficiently, (2) only one slide set and a fourth as many microscopes need be maintained compared with a traditional laboratory, and (3) one‐of‐a‐kind slides derived from research activities provide for high impact learning. Anat Rec (New Anat) 265:222–227, 2001. © 2001 Wiley‐Liss, Inc.
Perturbed turnover of microtubule‐based nutritive tubes in ovarioles of virgin and precocene‐treated Dysdercus fasciatus
Authors: Stebbings Howard
Published: August 2002

During early oogenesis in Dysdercus fasciatus, anteriorly positioned nurse cells supply each oocyte with mRNA, ribosomes, and proteins via a microtubule‐rich nutritive tube that lengthens as the oocyte is displaced backwards down an ovariole. Nurse cell–dependent development of an oocyte continues until the latter reaches a particular stage of oogenesis after which the nutritive tube supplying it becomes redundant and breaks down. The signal for nutritive tube breakdown is believed to derive from the oocyte, and to be developmental stage‐specific. To explore this, nutritive tube turnover has been investigated following the experimental inhibition of oocyte maturation both by the prevention of mating, and also the topical application of precocene II. In each case, the nutritive tubes with their component microtubules continued to extend and failed to show normal tube redundancy, typified by microtubule rearrangement and then depolymerisation. This provided an in vivo demonstration that the dynamics of a large microtubule aggregate are influenced by the developmental state of the cytoplasm. Arch. Insect Biochem. Physiol. 50:31–40, 2002. © 2002 Wiley‐Liss, Inc.
Isolation and partial characterization of gypsy moth BTR‐270, an anionic brush border membrane glycoconjugate that binds Bacillus thuringiensis Cry1A toxins with high affinity
Authors: Valaitis Algimantas P. , Jenkins Jeremy L. , Lee Mi Kyong , Dean Donald H. , Garner Karen J.
Published: August 2002

BTR‐270, a gypsy moth (Lymantria dispar) brush border membrane molecule that binds Bacillus thuringiensis (Bt) Cry1A toxins with high affinity, was purified by preparative gel electrophoresis. Rabbit antibodies specific for the Bt toxin‐binding molecule were raised. Attempts to label BTR‐270 by protein‐directed techniques were futile, but it was degraded by proteases with broad specificity indicating the presence of a peptide. Carbohydrate was detected by labeling with digoxigenin hydrazide following periodate oxidation. Mild alkaline hydrolysis destroyed toxin and antibody binding, suggesting O‐linked glycans are involved in the activity. GC/MS composition analysis showed that the predominant sugars were galactose, glucose, and N‐acetyl galactosamine with lesser amounts of N‐acetyl glucosamine, glucuronic acid, xylose, and fucose. The carbohydrate moiety accounted for 73% of its total mass. Amino acid analysis showed a high content of aspartic/asparagine, threonine, and serine residues in the protein moiety. The purified glycoconjugate was not visualized using Coomassie or silver staining procedures, but stained “blue” using the cationic dye Stains‐all. BTR‐270 was labeled with biotin and used as a diagnostic probe for screening and identifying toxins that bind to the receptor. Toxin‐binding kinetics obtained using a biosensor demonstrated that the receptor binds Cry1Aa and Cry1Ab toxins with high affinity, and displays a weaker affinity for Cry1Ac, in correlation with the toxicity of these toxins towards gypsy moth. Arch. Insect Biochem. Physiol. 46:186–200, 2001. © 2001 Wiley‐Liss, Inc.
Sex pheromone levels in pheromone glands and identification of the pheromone and hydrocarbons in the hemolymph of the moth Scoliopteryx libatrix L. (Lepidoptera: Noctuidae)
Authors: Subchev M. , Jurenka R.A.
Published: August 2002

The hydrocarbon sex pheromone (13‐methyl‐Z6‐heneicosene) of Scoliopteryx libatrix L. (Lepidoptera: Noctuidae) was found to reach its highest levels on pheromone glands of 3‐day‐old females. Pheromone levels were not different between the time of maximum calling (end of scotophase) and at the middle of photophase. Overwintering females collected in October had sex pheromone present. Decapitation did not lower the amount of pheromone present, indicating that a head factor is not involved in maintaining pheromone titers. Hemolymph also contained the pheromone, indicating that it is made by oenocytes and transported to the sex pheromone gland. Longer chain length hydrocarbons were also identified from the hemolymph and on the cuticular surface. Quantitative differences in hydrocarbon profiles were found with more methyl‐branched hydrocarbons found in the hemolymph than on the cuticular surface. Arch. Insect Biochem. Physiol. 47:35–43, 2001. © 2001 Wiley‐Liss, Inc.
Effect of nutrient deprivation on ribosomal RNA and ribosomal protein mRNA in cultured mosquito cells
Authors: Liu Jun , Fallon Ann M.
Published: August 2002

The effect of nutrient deprivation on RNA and protein synthesis in cultured Aedes albopictus mosquito cells was investigated by replacing the culture medium with phosphate‐buffered saline. After a 2 h starvation treatment, incorporation of radiolabeled precursor into total RNA was inhibited by 50%, and after 4 h, incorporation of amino acids into protein was inhibited by 50%. To investigate directly the effects of starvation on rRNA synthesis, ribosomal subunits were prepared from treated cells by sucrose density gradient centrifugation. After 4 h in saline, incorporation of [3H]uridine into ribosomal subunits had declined to baseline levels. Even after 8 h starvation, however, the effect was reversed by refeeding with complete medium, in which cells resumed rRNA synthesis and ribosomal subunit assembly. During 8 h starvation, total amounts of rRNA detected by northern blot remained stable. Ribosomal protein mRNA abundance was measured on northern blots, using probes corresponding to L8 and L31 ribosomal protein genes. The content of these ribosomal protein mRNAs was unchanged during starvation, or during treatment with actinomycin D. These results suggest that ribosomal protein mRNAs belong to a long‐lived mRNA population, and suggest that post‐transcriptional regulation of ribosomal protein synthesis is an important regulatory mechanism in growing mosquito cells. Arch. Insect Biochem. Physiol. 37:239–247, 1998. © 1998 Wiley‐Liss, Inc.
EquiX—A search and query language for XML
Authors: Cohen Sara , Kanza Yaron , Kogan Yakov , Sagiv Yehoshua , Nutt Werner , Serebrenik Alexander
Published: August 2002

EquiX is a search language for XML that combines the power of querying with the simplicity of searching. Requirements for such languages are discussed, and it is shown that EquiX meets the necessary criteria. Both a graph‐based abstract syntax and a formal concrete syntax are presented for EquiX queries. In addition, the semantics is defined and an evaluation algorithm is presented. The evaluation algorithm is polynomial under combined complexity. EquiX combines pattern matching, quantification, and logical expressions to query both the data and meta‐data of XML documents. The result of a query in EquiX is a set of XML documents. A DTD describing the result documents is derived automatically from the query.
A novel navigation paradigm for XML repositories
Authors: Azagury Alain , Factor Michael E. , Maarek Yoelle S. , Mandler Benny
Published: August 2002

The advances in storage and communications enable users to store massive amounts of data, and to share it seamlessly with their peers. With the advent of XML, we expect a significant portion of this data to be in XML format. We describe here the architecture and implementation of an XML repository that promotes a novel navigation paradigm for XML documents based on content and context. Support for these capabilities is achieved by bringing to bear the organizational power of information retrieval to the domain of semistructured documents. File systems remain the preferred storage infrastructure for the home and business desktop environments. We have built a system, XMLFS, based on the ideas stated above. XMLFS presents a storage abstraction that manifests itself to the client as a familiar file system. However, it breaks the tight coupling between the directory hierarchical structure and the file system. XMLFS creates automatically a directory organization of any XML document collection based on content and context. Each user can navigate through the file system according to her/his domain of interest at that point in time. Our result is a first step towards a solution to the discovery and navigation problems presented by the collective repositories of XML documents in peer‐to‐peer environments.
Relevance judging, evaluation, and decision making in virtual libraries: A descriptive study
Authors: Fitzgerald Mary Ann , Galloway Chad
Published: August 2002

This study explored higher‐order thinking processes in undergraduates using a virtual library. Ten undergraduates pursuing topics pertaining to their academic work were interviewed and observed as they used GALILEO (GeorgiA LIbrary LEarning Online, a virtual library containing many scholarly databases). Specifically, the study focused on relevance judging, evaluation (critical thinking), and decision making. We found a high degree of intermingling between relevance judging and evaluation, along with a number of strategies participants used to assist them in both thinking processes. Also, participants made decisions through one of three avenues in each of their appraisals of online resources.
Ask‐an‐expert services analysis
Authors: Janes Joseph , Hill Chrystie , Rolfe Alex
Published: August 2002

This article discusses the history and emergence of nonlibrary commercial and noncommercial information services on the World Wide Web. These services are referred to as “expert services,” while the term “digital reference” is reserved for library‐related on‐line information services. Following suggestions in library and information literature regarding quality standards for digital reference, researchers make clear the importance of developing a practicable methodology for critical examination of expert services, and consideration of their relevance to library and other professional information services. A methodology for research in this area and initial data are described. Two hundred forty questions were asked of 20 expert service sites. Findings include performance measures such as response rate, response time, and verifiable answers. Sites responded to 70% of all questions, and gave verifiable answers to 69% of factual questions. Performance was generally highest for factual type questions. Because expert services are likely to continue to fill a niche for factual questions in the digital reference environment, implications for further research and the development of digital reference services may be appropriately turned to source questions. This is contrary to current practice and the emergence of digital reference services reported in related literature thus far.
On a discrimination problem for a class of stochastic processes with ordered first‐passage times
Authors: Di Crescenzo Antonio , Ricciardi Luigi M.
Published: August 2002

Consider the Bayes problem in which one has to discriminate if the random unknown initial state of a stochastic process is distributed according to either of two preassigned distributions, on the base of the observation of the first‐passage time of the process through 0. For processes whose first‐passage times to state 0 are increasing in the initial state according to the likelihood ratio order, such problem is solved by determining the Bayes decision function and the corresponding Bayes error. The special case of fixed initial values including a family of first‐passage times with proportional reversed hazard functions is then studied. Finally, various applications to birth‐and‐death and to diffusion processes are discussed. Copyright © 2001 John Wiley & Sons, Ltd.
In vitro protein binding studies with BMS‐204352: lack of protein binding displacement interaction in human serum
Authors: Krishna Rajesh , Yao Ming , Kaczor Donna , Vachharajani Nimish , Srinivas Nuggehally R.
Published: August 2002

BMS‐204352, a maxi‐K channel opener, is currently under development for the treatment of stroke. Protein binding of BMS‐204352 was determined in sera from several species, namely, rat, monkey, dog, and human. Data indicated that the compound was shown to be highly protein bound in serum from all species (ca. 99.6%). In order to test for the potential for drug–drug interactions and competitive displacement of BMS‐204352 by diazepam, phenytoin, propranolol, and warfarin, in vitro experiments were performed using spiked human serum and ex vivo human plasma samples. Protein binding was determined using equilibrium dialysis for 4 h at maximal therapeutic concentrations for each drug alone or in appropriate combination in spiked serum samples. Ex vivo samples from a clinical BMS‐204352 study (0, 1, and 24 h) were dialyzed separately after addition of diazepam, phenytoin, propranolol, or warfarin. Drug content in biological matrices was measured for radioactivity using liquid scintillation counting. Results indicated that (1) addition of diazepam, phenytoin, propranolol, or warfarin did not alter the free fraction of BMS‐204352; (2) BMS‐204352 did not displace diazepam, phenytoin, propranolol, or warfarin from their protein binding sites, and (3) comparison of ex vivo plasma samples after BMS‐204352 dosing indicated no impact of BMS‐204352 and/or its metabolites on the free fraction of diazepam, phenytoin, propranolol, or warfarin. In conclusion, the potential for a drug–drug interaction due to alterations in protein binding with BMS‐204352 is unlikely. Copyright © 2001 John Wiley & Sons, Ltd.
A critical evaluation of the brain efflux index method as applied to the nitric oxide synthase inhibitor, aminoguanidine
Authors: Raybon Joseph J. , Boje Kathleen M.K.
Published: August 2002

The Brain Efflux Index (BEI) method is an in vivo procedure designed to quantitate saturable efflux mechanisms resident at the blood–brain barrier (BBB). The present work utilized the BEI method to assess the BBB efflux mechanisms of [14C]aminoguanidine, a nitric oxide synthase inhibitor. The BEI for [14C]aminoguanidine was >100% (relative to [3H]inulin diffusion) over a range of 41–184 pmol after 40 min. The unusually high retention (>100%) of [14C]aminoguanidine suggested brain parenchymal sequestration, either by neuronal uptake or tissue protein binding. The uptake of [14C]aminoguanidine in dendritic neuronal endings (synaptosomes) showed a saturable concentration dependency, consistent with a carrier‐mediated process. Nonlinear least‐squares regression yielded the following Michaelis–Menten and diffusional (kns) parameters for synaptosomal [14C]aminoguanidine uptake: Vmax=118.50± 28.77 pmol x mg protein−1/3 min; Km=58.34±8.33 μM; kns=0.15±0.029 pmol x mg protein−1/3 min/μM; mean±SEM; n=3 concentration profiles). Protein binding studies using brain tissue showed negligible binding. In summary, this work identified three principle findings: (1) An apparent lack of quantifiable aminoguanidine BBB efflux; (2) a previously undescribed synaptosomal accumulation process for aminoguanidine; and (3) an interesting limitation of the BEI technique where unusual brain parenchymal sequestration yields values >100%. Copyright © 2001 John Wiley & Sons, Ltd.
Elliptically polarized magnetic fields do not alter immediate early response genes expression levels in human glioblastoma cells
Authors: Yomori Hiroyuki , Yasunaga Katsuaki , Takahashi Chie , Tanaka Ayako , Takashima Shinji , Sekijima Masaru
Published: August 2002

Expression of immediate early response genes such as c‐fos, c‐jun, and c‐myc in response to 1‐500 μT resultant (r) 60 Hz elliptically polarized (EP) magnetic fields (MFs), typical of environmental MFs polarization under overhead power lines, was analyzed in both at transcriptional and translational levels using human glioblastoma (T98G) cells. Pseudo synchronized T98G cells at G1 phase were exposed to EP‐MFs (1, 20, 100, and 500 μTr) for up to 3 h, but produced no statistical difference (P>0.05) in the levels of expression ratio at both the transcriptional and translational levels at 30 min for c‐fos and c‐jun and at 180 min for c‐myc after serum stimulation. In addition, exposure of T98G cells to linearly (vertical and horizontal) and/or circularly polarized MFs (500 μTr) produced no significant change (P>0.05) in the expression ratio at both transcriptional and post‐transcriptional levels. Thus, there was no evidence that linearly or rotating polarized MFs enhanced early response gene expression in these studies. These results suggest that environmental MFs at 1–500 μT flux density are unlikely to induce carcinogenesis through a mechanism involving altered expression of the immediate early response genes. Bioelectromagnetics 23:89–96, 2002. © 2002 Wiley‐Liss, Inc.
Effects of 5 s exposures to a 50 μT, 20 Hz magnetic field on skin conductance and ratings of affect and arousal
Authors: Stevens Paul
Published: August 2002

This study investigated the effect of a weak magnetic field (50 μT, 20 Hz sinusoidal, 5 s duration) on concurrent perceptions of visual stimuli. Subjects were seated between Helmholtz coils and gave post‐exposure ratings for the affective content and arousing nature of presented images. They were blind as to the presence or absence of a simultaneously presented field. Skin conductance and arousal ratings did not show significant differences between experimental and control conditions, but the affective content rating did (P = 0.041), with the images viewed under field exposure being rated as having a more positive affect. Such measures might thus be useful as additional indicators of magnetic field detection. A post‐hoc analysis of skin conductance profiles showed that 48% of subjects exhibited a lowering of skin conductance during field exposure, 34% exhibited no apparent reaction, and 17% exhibited an increase. Overall ratings given by each of the groups appeared to relate to these physiological profiles. Bioelectromagnetics 22:219–223, 2001. © 2001 Wiley‐Liss, Inc.
Growth and differentiation of PC6 cells: the effects of pulsed electromagnetic fields (PEMF)
Authors: Shah J.P. , Midkiff P. , Brandt P.C. , Sisken B.F.
Published: August 2002

Previous studies in our laboratory showed that neurite outgrowth in vitro and nerve regeneration in vivo were stimulated by 2 Hz, 0.3 mT (3 G) pulsed electromagnetic fields (PEMF). To learn more about the effects of PEMF on nerve cells, we exposed PC6 cells, a standard neuronal‐like cell model, to the same pulsed electromagnetic fields for 2 h/day for 2 days and asked whether two different cell processes, proliferation and differentiation, were affected. The cells were also treated with a differentiating agent, nerve growth factor (NGF), to further define any interactive effects. We found that proliferation was unaffected by either PEMF or NGF alone or in combination. Differentiation, expressed as neurite outgrowth, was strongly upregulated with NGF, but this NGF response was significantly depressed in cells treated with PEMF. Bioelectromagnetics 22:267–271, 2001. © 2001 Wiley‐Liss, Inc.
Millimeter wave power density in aqueous biological samples
Authors: Alekseev S.I. , Ziskin M.C.
Published: August 2002

Power density distribution inside a water sample placed between two parallel lossy dielectric plates (Polystyrene) was calculated using Fresnel equations for the frequency range of 42.25–53.57 GHz. Due to the multiple internal reflections from the sample boundaries, the distribution of the power density within the thin sample is more uniform than that within a semi‐infinite medium. The power density in a sample depends on the thicknesses of the sample and the adjacent dielectric plates. For the given frequency range the sample thickness optimal for power density uniformity varies between 0.28 and 0.33 mm. The front plate has a significant effect on the magnitude of the power density within the sample but little effect on the power density distribution. The thicker the rear plate, the greater is the non uniformity of the power density distribution within the sample. Based on the calculated data, we determined the dimension of an exposure chamber providing the optimal power density distribution uniformity for mm‐wave irradiation. Bioelectromagnetics 22:288–291, 2001. © 2001 Wiley‐Liss, Inc.
Analysis of genetic control elements in eukaryotes: Transcriptional activity or nuclear hitchhiking?
Authors: Zohar Muriel , Mesika Adi , Reich Ziv
Published: August 2002

A common way to analyse basal and stimulated activity of eukaryotic genetic control elements, such as promoters and enhancers, is to introduce them into cells via DNA vectors containing an easily assayable reporter gene. Activity is then studied by measurement of transiently produced mRNA or reporter protein. In such assays, it is assumed that the variable measured is proportional to the transcriptional activity of the control element under investigation. Here we question the validity of this generally accepted assumption. Specifically, recent observations indicate that control elements, in addition to modulating transgene transcription, can facilitate the nuclear uptake of their carrier plasmids. This process is mediated by transcription factors or other nuclear proteins harbouring nuclear localisation signals, which bind to the control elements in the cytoplasm and transport the DNA into the nucleus through the protein nuclear import machinery. As the number of mRNA transcripts produced for an epi‐chromosomally expressed transgene is directly related to its copy number inside the nucleus, such transport activity may lead to substantial overestimation of the transcriptional potency of the control element(s) studied. BioEssays 23:1176–1179, 2001. © 2001 John Wiley & Sons, Inc.
Integrin control of cell cycle: a new role for ubiquitin ligase
Authors: Pu Qing Qiu , Streuli Charles H.
Published: August 2002

Receptor tyrosine kinases and integrins are activated by growth factors and extracellular matrix, respectively. Their activation leads to signal transduction cascades that control many aspects of cell phenotype, including progression through the G1 phase of the cell cycle. However, the signalling cassettes driven by growth factors and matrix do not work independently of each other. Integrin triggering is essential to facilitate kinase‐ and GTPase‐mediated signals and thereby drive efficient transfer of information through the growth factor–cyclin axis. A recent study indicates that an additional type of player has a key role in adhesion‐regulated control of cell cycle, namely ubiquitin ligase.(1) BioEssays 24:17–21, 2002. © 2002 John Wiley & Sons, Inc.
The ups and downs of daily life: Profiling circadian gene expression in Drosophila
Authors: Etter Paul D. , Ramaswami Mani
Published: August 2002

Circadian rhythms are responsible for 24‐hour oscillations in diverse biological processes. While the central genes governing circadian pacemaker rhythmicity have largely been identified, clock‐controlled output molecules responsible for regulating rhythmic behaviors remain largely unknown. Two recent reports from McDonald and Rosbash1 and Claridge‐Chang et al.2 address this issue. By identifying a large number of genes whose mRNA levels show circadian oscillations, the reports provide important new information on the biology of circadian rhythm. In addition, the reports illustrate both the power and limitations of microarray‐based methods for profiling mRNA expression on a genomic scale. BioEssays 24:494–498, 2002. © 2002 Wiley Periodicals, Inc.
Antiviral potential of chemokines
Authors: Mahalingam Surendran , Clark Kristopher , Matthaei Klaus I. , Foster Paul S.
Published: August 2002

In the past few years, a large number of new chemokines (chemotactic cytokines) and chemokine receptors have been discovered. The growth in knowledge about these molecules has been achieved largely through advances in bioinformatics and the expansion of expression sequence tag (EST) databases. It is now clear that chemokines are crucial in controlling both the development and functioning of leukocytes and that their role is not restricted to cell attraction, as originally assumed. In particular, recent findings provide strong support for the idea that chemokines and their receptors are especially important in the control of viral infection and replication. Thus, specific chemokines are now known to enhance the cytotoxic activity of infected cells, thus inhibiting further virus replication. In addition, some chemokines orchestrate the recruitment of activated leukocytes to foci of infection to aid viral clearance. Viruses, in turn, have evolved various defences against chemokines. These range from the production of proteins that inhibit biological activity of the host chemokine to the hijacking of the chemokine system, whereby certain viruses utilize chemokine receptors for their entry. The latter viral defence can itself be blocked by chemokines. Altogether, these findings illustrate the central role of chemokines in many different phases of the immune response, particularly those aspects involving antiviral defence, a variety and versatility that was not fully appreciated even a few years ago. BioEssays 23:428–435, 2001. © 2001 John Wiley & Sons, Inc.
Hot news: temperature‐sensitive humans explain hereditary disease
Authors: Friedberg Errol C.
Published: August 2002

The skin‐cancer‐prone hereditary disease xeroderma pigmentosum is typically characterized by defective nucleotide excision repair (NER) of DNA. However, since all subunits of the core basal transcription factor TFIIH are required for both RNA polymerase II basal transcription and NER, some mutations affecting genes that encode TFIIH subunits can result in clinical phenotypes associated with defective basal transcription. Among these is a syndrome called trichothiodystrophy (TTD) in which the prominent features are brittle hair and nails, and dry scaly skin. A recent study provides dramatic support for the so‐called transcription hypothesis of TTD.(1) Specifically, several patients have been shown to carry a mutation in the XPD gene, which encodes a thermolabile form of XPD protein, resulting in loss of hair during febrile episodes. BioEssays 23:671–673, 2001. © 2001 John Wiley & Sons, Inc.
Making a vertebrate limb: New players enter from the wings
Authors: Martin Gail
Published: August 2002

What initiates vertebrate limb development and induces limbs to form where they do? For several years the answer to this intriguing question has been framed in terms of a working model that limb induction depends on a dialogue between two members of the Fibroblast Growth Factor (FGF) family of intercellular signaling molecules, FGF8 and FGF10. Now, a recent paper has written roles for signals encoded by WNT genes, the vertebrate relatives of the Drosophila wingless gene, into the script.(1) BioEssays 23:865–868, 2001. © 2001 John Wiley & Sons, Inc.
Inhibition of light emission from the bioluminescent bacterium Vibrio fischeri after exposure to triclosan and related hygiene care products
Authors: Martin Esther B. , Mansfield Lucielle P. , Smith Alan , Forsythe Stephen James
Published: August 2002

The affect of the anti‐microbial agent triclosan (alternative names Microban® and Irgasan DP300) on the light emission by the bioluminescent bacterium Vibrio fischeri was determined. Triclosan at concentrations greater than 0.2% (w/v) caused cell lysis and immediate (<5 s) loss of light emission. Exposure to triclosan at lower concentrations caused a decrease in light output over time. The rate of the decrease in light output followed a cuboid relationship, of which the initial rate (first 60 s) of light loss was proportional to the concentration of triclosan. The effect on light output by two commercially available hygiene products containing triclosan also caused a similar response in light loss. Copyright © 2001 John Wiley & Sons, Ltd.
Enterobacter cloacae leukotoxin: modulation of reactive oxidant species generated by neutrophils
Authors: Barnes Ana Isabel , Paraje María Gabriela , Orsilles Miguel , Albesa Inés
Published: August 2002

A leukotoxin purified from Enterobacter cloacae culture by saline precipitation, gel chromatography and HPLC was studied as a modulator of reactive oxidant species (ROS) produced by human neutrophils. Chemiluminescence showed that stimulation of ROS was achieved at a low leukotoxin concentration, but ROS production decreased when the toxin was applied at concentrations above 30 µg/mL. Also, the addition of 100 µg toxin/mL significantly reduced the activating effect of phorbol myristate acetate (PMA) and low doses of toxin did not produce an opposite effect toward the stimulation produced by PMA. Normal neutrophils showed a linear correlation between the inverse of ROS production and time, but the kinetic reaction changed when toxins were added to the cells and the ROS formation increased directly with time. Copyright © 2001 John Wiley & Sons, Ltd.
Effect of conformation on the chemiluminescence efficiency of light‐producing 2‐methyl‐6‐(4‐methoxyphenyl)imidazo[1,2‐α]pyrazin‐3(7H)‐ones
Authors: Teranishi Katsunori
Published: August 2002

Analogues of the light‐producing substrate 2‐methyl‐6‐(4‐methoxyphenyl)imidazo[1,2‐α]pyrazin‐3(7H)‐one, with restrictions on the dihedral angles between the pyrazine and the 4‐methoxyphenyl rings, were synthesized. These compounds were used to investigate the effects of the conformation between the pyrazine and 4‐methoxyphenyl rings on their chemiluminescence efficiencies in aqueous solutions. The effects of the conformation on the chemiluminescence efficiencies were clearly observed; the decrease of the dihedral angle caused a light‐enhancing effect and, conversely, the increase of the angle dramatically decreased the chemiluminescence efficiency. These effects on the chemiluminescence efficiencies are attributed to the influence of the conformation on the fluorescence efficiency of the emitter. Copyright © 2001 John Wiley & Sons, Ltd.
Vibrational study of polymorphism of tetralin derivative for treatment of cardiovascular diseases
Authors: Taddei Paola , Torreggiani Armida , Fini Giancarlo
Published: August 2002

Vibrational spectroscopy coupled with thermogravimetry (TG) and differential scanning calorimetry (DSC) was used to characterize racemic propanoic acid, 2‐methyl‐5,6,7,8‐tetrahydro‐6‐(methylamino)‐1,2‐naphthalenediyl ester hydrochloride (CHF‐1035), which is a new DA2 dopaminergic receptor/α2 agonist and β blocker under clinical investigation for the treatment of congestive heart failure. Raman spectroscopy disclosed at least two different CHF‐1035 polymorphs; the marker bands characteristic of each form were identified. The modifications undergone by the CHF‐1035 drug as a consequence of grinding and heating were investigated. Mechanical and gentle thermal treatments caused a polymorphic transformation of the drug crystal form. Raman spectroscopy proved suitable for investigating the possible presence of different polymorphic forms, their relative stability, and interconversion tendency in relation to industrial manufacturing processes undergone by the drug (i.e., grinding, compression, and heating). © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 289–293, 2002
Towards the development of a minimal cell model by generalization of a model of Escherichia coli: Use of dimensionless rate parameters
Authors: Browning Samuel T. , Shuler Michael L.
Published: August 2002

A model of a minimal cell would be a valuable tool in identifying the organizing principles that relate the static sequence information of the genome to the dynamic functioning of the living cell. Our approach for developing a minimal cell model is to first generalize an existing model of Escherichia coli by expressing reaction rates as ratios to a set of reference parameters. This generalized model is a prototype minimal cell model that will be developed by adding detail to explicitly include each chemical species. We tested the concept of a generalized model by testing the effect of scaling all enzyme‐catalyzed reactions in the E. coli model. The scaling has little effect on cellular function for a wide range of kinetic ratios, where the kinetic ratio is defined as the rate of all enzyme‐catalyzed reactions in a given model relative to those in the E. coli model. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 76: 187–192, 2001.
Haloalkane hydrolysis with an immobilized haloalkane dehalogenase
Authors: Dravis B. C. , Swanson P. E. , Russell A. J.
Published: August 2002

Haloalkane dehalogenase from Rhodococcus rhodochrous was covalently immobilized onto a polyethyleneimine impregnated γ‐alumina support. The dehalogenating enzyme was found to retain greater than 40% of its original activity after immobilization, displaying an optimal loading (max. activity/supported protein) of 70 to 75 mg/g with an apparent maximum (max. protein/support) of 156 mg/g. The substrate, 1,2,3‐trichloropropane, was found to favorably partition (adsorb) onto the inorganic alumina carrier (10 to 20 mg/g), thereby increasing the local reactant concentration with respect to the catalyst's environment, whereas the product, 2,3‐dichloropropan‐1‐ol, demonstrated no affinity. Additionally, the inorganic alumina support exhibited no adverse effects because of solvent/component incompatibilities or deterioration due to pH variance (pH 7.0 to 10.5). As a result of the large surface area to volume ratio of the support matrix and the accessibility of the bound protein, the immobilized biocatalyst was not subject to internal mass transfer limitations. External diffusional restrictions could be eliminated with simple agitation (mixing speed: 50 rpm; flux: 4.22 cm/min). The pH‐dependence of the immobilized dehalogenase was essentially the same as that for the native enzyme. Finally, both the thermostability and resistance toward inactivation by organic solvent were improved by more than an order of magnitude after immobilization. © 2001 John Wiley & Sons, Inc. Biotechnol Bioeng 75: 416–423, 2001.
Hybrid model building methodology using unsupervised fuzzy clustering and supervised neural networks
Authors: Ronen M. , Shabtai Y. , Guterman H.
Published: August 2002

This paper suggests a model building methodology for dealing with new processes. The methodology, called Hybrid Fuzzy Neural Networks (HFNN), combines unsupervised fuzzy clustering and supervised neural networks in order to create simple and flexible models. Fuzzy clustering was used to define relevant domains on the input space. Then, sets of multilayer perceptrons (MLP) were trained (one for each domain) to map input–output relations, creating, in the process, a set of specified sub‐models. The estimated output of the model was obtained by fusing the different sub‐model outputs weighted by their predicted possibilities. On‐line reinforcement learning enabled improvement of the model. The determination of the optimal number of clusters is fundamental to the success of the HFNN approach. The effectiveness of several validity measures was compared to the generalization capability of the model and information criteria. The validity measures were tested with fermentation simulations and real fermentations of a yeast‐like fungus, Aureobasidium pullulans. The results outline the criteria limitations. The learning capability of the HFNN was tested with the fermentation data. The results underline the advantages of HFNN over a single neural network. © 2002 John Wiley & Sons, Inc. Biotechnol Bioeng 77: 420–429, 2002; DOI 10.1002/bit.10132