bluuebunny/crossref_metadata_2025 huggingface dataset:
Effective Control of Two Elimination Processes from a Hydridobis(silyl)iron(IV) Complex
Authors: Sato Takahiro , Tobita Hiromi , Ogino Hiroshi
Published: March 2003

A novel hydridobis(silyl)iron(IV) complex Cp*(CO)Fe(H){SiMe2O(2-C5H4N)}2 (1) (Cp*=η5-C5Me5) was synthesized in high yield. Two elimination processes from 1 were effectively controlled by the reaction conditions: HSiMe2O(2-C5H4N) is eliminated on heating or UV-irradiation, whereas HO(2-C5H4N) is eliminated in the presence of Et3Al. The latter reaction was applied to a “silylene introduction” toward a silyl complex producing a silyl(silylene) complex.
Pulmonary function abnormality and respiratory tract irritation symptoms in epichlorohydrin‐exposed workers in Taiwan
Authors: Luo Jiin‐Chyuan , Kuo Hsen‐Wen , Cheng Tsun‐Jen , Chang Ming J.W.
Published: March 2003

Background

Epichlorohydrin (ECH) is a strong irritant of the eyes, respiratory tract, and skin. The aims of this study were to examine the dose‐response relationship between observed abnormal pulmonary function tests and respiratory tract irritation symptoms among epichlorohydrin‐exposed workers in Taiwan.

Methods

A total of 167 workers were randomly selected from a resin synthesis factory. Sixty‐six air samples were taken to determine ECH concentration in the workplace. Demographic data, work history, smoking status, and respiratory tract irritation symptoms were gathered by a standard self‐administered questionnaire. Pulmonary function tests were also performed.

Results

There were 13 of 41 (31.7%) abnormal mean mid‐expiratory flow (MMEF) among the high‐ECH‐exposed workers, 11 of 38 (29%) among the low‐ECH‐exposed workers, and 4 of 59 (6.8%) among non‐ECH‐exposed workers. There was a significant linear trend between ECH exposure and the prevalence of small airway abnormalities (P = 0.007) after adjusting for other factors. There was also a significant dose‐response relationship of respiratory tract irritation symptoms (cough, phlegm, chest tightness, and dyspnea) among the ECH‐exposed workers.

Conclusions

This study suggests that obstructive lung abnormalities and small airway lung damage are associated with ECH exposure. The study also suggests that exposure to very low concentrations (<0.2 ppm) causes significant higher prevalence of respiratory tract irritation symptoms. Causal inferences from the findings cannot be made from this cross‐sectional study and further longitudinal studies are needed to better clarify the nature of the observed associations. Am. J. Ind. Med. 43:440–446, 2003. © 2003 Wiley‐Liss, Inc.
Pulmonary effects of welding fumes: Review of worker and experimental animal studies
Authors: Antonini James M. , Lewis Anthony B. , Roberts Jenny R. , Whaley David A.
Published: March 2003

Background

Approximately one million workers worldwide perform welding as part of their work duties. Electric arc welding processes produce metal fumes and gases which may be harmful to exposed workers.

Methods

This review summarizes human and animals studies which have examined the effect of welding fume exposure on respiratory health. An extensive search of the scientific and occupational health literature was performed, acquiring published articles which examined the effects of welding on all aspects of worker and laboratory animal health. The databases accessed included PubMed, Ovid, NIOSHTIC, and TOXNET.

Results

Pulmonary effects observed in full‐time welders have included metal fume fever, airway irritation, lung function changes, susceptibility to pulmonary infection, and a possible increase in the incidence of lung cancer. Although limited in most cases, animal studies have tended to support the findings from epidemiologic studies.

Conclusions

Despite the numerous studies on welding fumes, incomplete information still exists regarding the causality and possible underlying mechanisms associated with welding fume inhalation and pulmonary disease. The use of animal models and the ability to control the welding fume exposure in toxicology studies could be utilized in an attempt to develop a better understanding of how welding fumes affect pulmonary health. Am. J. Ind. Med. 43:350–360, 2003. Published 2003 Wiley‐Liss, Inc.
Respiratory symptoms in kitchen workers
Authors: Svendsen Kristin , Sjaastad Ann Kristin , Sivertsen Ingvill
Published: March 2003

Introduction

A possible association between cooking fumes and respiratory diseases other than cancer has not been studied earlier.

Methods

All employees at 67 selected kitchens were asked to answer a personal questionnaire regarding the presence of dyspnea, serious dyspnea, cough, and respiratory symptoms in connection with work. The study group consisted of 139 women and 100 men.

Results

The prevalence of dyspnea (RR = 4.1 (2.7–6.3)), serious dyspnea (RR = 2.9 (1.5–5.7)), and symptoms in connection with work (RR =  4.3 (2.7–6.7)) were statistically significantly higher for the female kitchen workers compared to the controls. For the men only dyspnea (RR = 1.8 (1.4–2.3)) and symptoms in connection with work (RR = 2.1 (1.6–2.7)) showed an increased prevalence. An analysis of possible predictors for respiratory symptoms in connection with work gave an odds ratio of 3.2 (P = 0.000) for “working in a restaurant kitchen.”

Conclusions

The results of the study indicate a relationship between working in kitchens and respiratory symptoms. Am. J. Ind. Med. 43:436–439, 2003. © 2003 Wiley‐Liss, Inc.
Morphogenetic Control of Calcite Crystal Growth in Sulfonic Acid Based Hydrogels
Authors: Grassmann Olaf , Löbmann Peer
Published: March 2003

In this paper the mineralization of CaCO3in various hydrogel matrices is presented. Sulfonic acid based hydrogels were prepared by introduction of sulfonate‐containing monomers into a polyacrylamide network. The sulfonate content of polyacrylamide‐co‐vinylsulfonate and polyacrylamide‐co‐allylsulfonate decreases during elution of the copolymers in demineralized water, indicating insufficient linking of the sulfonate‐bearing monomers within the hydrogel. In contrast to this, acrylamidomethylpropanesulfonate (AMPS) effectively copolymerizes with acrylamide (AAm) monomers. To study the influence of spatial arrangement of ionic functional groups within hydrogel networks on the mineralization of CaCO3, AMPS copolymers with different degrees of AMPS cross‐linking were synthesized. For the mineralization experiments the copolymers were placed into a double‐diffusion arrangement. Calcite as the thermodynamically stable modification of CaCO3was obtained with a particular morphology. The pseudocubic habitus resembles aggregates obtained by mineralization in pure polyacrylamide. However, closer examination of the aggregates by scanning electron microscopy (SEM) shows that the crystal growth in the AMPS copolymers is different from that observed in polyacrylamide. Whereas the morphology of the calcite aggregates could be fine‐tuned by using copolymers with different sulfonate content, the spatial distribution of the ionic functional groups alters the course of crystallization. Calcium ions are locally accumulated due to the heterogeneous distribution of functional sulfonate groups within the copolymer network. Thereby the nucleation of calcite is triggered, resulting in enhanced mineralization.
Synthesis, X‐ray Powder Structure, and Magnetic Properties of Layered NiII Methylphosphonate, [Ni(CH3PO3)(H2O)], and NiII Octadecylphosphonate, [Ni{CH3‐(CH2)17‐PO3}(H2O)]
Authors: Bellitto Carlo , Bauer Elvira M. , Ibrahim Said A. , Mahmoud Mohamed R. , Righini Guido
Published: March 2003

[Ni(CH3PO3)(H2O)] (1) and [Ni{CH3‐(CH2)17‐PO3}(H2O)] (2) were synthesised by reaction of NiCl2⋅6 H2O and the relevant phosphonic acid in water in presence of urea. The compounds were characterised by elemental and thermogravimetric analyses, UV‐visible and IR spectroscopy, and their magnetic properties were studied by using a SQUID magnetometer. The crystal structure of 1 was determined “ab initio” from X‐ray powder diffraction data and refined by the Rietveld method. The crystals of 1 are orthorhombic, space group Pmn21, with a=5.587(1), b=8.698(1), c=4.731(1) Å. The compound has a hybrid, layered structure made up of alternating inorganic and organic layers along the b direction of the unit‐cell. The inorganic layers consist of NiII ions octahedrally coordinated by five phosphonate oxygen atoms and one oxygen atom from the water molecule. These layers are separated by bilayers of methyl groups and van der Waals contacts are established between them. A preliminary structure characterisation of compound 2 suggests the crystallisation in the orthorhombic system with the following unit‐cell parameters: a=5.478(7), b=42.31(4), c=4.725(3) Å. The oxidation state of the Ni ion in both compounds is +2, and the electronic configuration is d8 (S=1), as determined from static magnetic susceptibility measurements above 50 K. Compound 1 obeys the Curie–Weiss law at temperatures above 50 K; the Curie (C) and Weiss (θ) constants were found to be 1.15 cm3 K mol−1 and −32 K, respectively. The negative value of θ indicates an antiferromagnetic exchange coupling between near‐neighbouring NiII ions. No sign of 3D antiferromagnetic long‐range order is observed down to T=5 K, the lowest measured temperature. Compound 2 is paramagnetic above T=50 K, and the values of C and θ were found to be 1.25 cm3 K mol−1 and −24 K, respectively. Below 50 K the magnetic behavior of 2 is different from that of 1. Zero‐field cooled (zfc) and field‐cooled (fc) magnetisation plots do not overlap below T=21 K. The irreversible magnetisation, ΔMfc−zfc, obtained as a difference from fc and zfc plots starts to increase at T=20 K, on lowering the temperature, and it becomes steady at T=5 K. The presence of spontaneous magnetisation below T=20 K indicates a transition to a weak‐ferromagnetic state for compound 2.
Reversible Immobilization of Peptides: Surface Modification and In Situ Detection by Attenuated Total Reflection FTIR Spectroscopy
Authors: Rigler Per , Ulrich Wolf‐Peter , Hoffmann Patrik , Mayer Michael , Vogel Horst
Published: March 2003

A generic method is described for the reversible immobilization of polyhistidine‐bearing polypeptides and proteins on attenuated total reflecting (ATR) sensor surfaces for the detection of biomolecular interactions by FTIR spectroscopy. Nitrilotriacetic acid (NTA) groups are covalently attached to self‐assembled monolayers of either thioalkanes on gold films or mercaptosilanes on silicon dioxide films deposited on germanium internal reflection elements. Complex formation between Ni2+ ions and NTA groups activates the ATR sensor surface for the selective binding of polyhistidine sequences. This approach not only allows a stable and reversible immobilization of histidine‐tagged peptides (His–peptides) but also simultaneously allows the direct in situ quantification of surface‐adsorbed molecules from their specific FTIR spectral bands. The surface concentrations of both NTA and His–peptide on silanized surfaces were determined to be 1.1 and 0.4 molecules nm−2, respectively, which means that the surface is densely covered. A comparison of experimental FTIR spectra with simulated spectra reveals a surface‐enhancement effect of one order of magnitude for the gold surfaces. With the presented sensor surfaces, new ways are opened up to investigate, in situ and with high sensitivity and reproducibility, protein–ligand, protein–protein, protein–DNA interactions, and DNA hybridization by ATR–FTIR spectroscopy.
Mossy fiber plasticity and enhanced hippocampal excitability, without hippocampal cell loss or altered neurogenesis, in an animal model of prolonged febrile seizures
Authors: Bender Roland A. , Dubé Celine , Gonzalez‐Vega Rebeca , Mina Erene W. , Baram Tallie Z.
Published: March 2003

Seizures induced by fever (febrile seizures) are the most frequent seizures affecting infants and children; however, their impact on the developing hippocampal formation is not completely understood. Such understanding is highly important because of the potential relationship of prolonged febrile seizures to temporal lobe epilepsy. Using an immature rat model, we have previously demonstrated that prolonged experimental febrile seizures render the hippocampus hyperexcitable throughout life. Here we examined whether (1) neuronal loss, (2) altered neurogenesis, or (3) mossy fiber sprouting, all implicated in epileptogenesis in both animal models and humans, were involved in the generation of a pro‐epileptic, hyperexcitable hippocampus by these seizures. The results demonstrated that prolonged experimental febrile seizures did not result in appreciable loss of any vulnerable hippocampal cell population, though causing strikingly enhanced sensitivity to hippocampal excitants later in life. In addition, experimental febrile seizures on postnatal day 10 did not enhance proliferation of granule cells, whereas seizures generated by kainic acid during the same developmental age increased neurogenesis in the immature hippocampus. However, prolonged febrile seizures resulted in long‐term axonal reorganization in the immature hippocampal formation: Mossy fiber densities in granule cell‐ and molecular layers were significantly increased by 3 months (but not 10 days) after the seizures. Thus, the data indicate that prolonged febrile seizures influence connectivity of the immature hippocampus long‐term, and this process requires neither significant neuronal loss nor altered neurogenesis. In addition, the temporal course of the augmented mossy fiber invasion of the granule cell and molecular layers suggests that it is a consequence, rather than the cause, of the hyperexcitable hippocampal network resulting from these seizures. Hippocampus 2003;13:399–412. © 2003 Wiley‐Liss, Inc.
Differential expression of S100 proteins in the developing human hippocampus and temporal cortex
Authors: Chan Wood Yee , Xia Chun‐Lin , Dong Da‐Cui , Heizmann Claus W. , Yew David T.
Published: March 2003

S100 calcium binding proteins have long been known to express in the adult nervous system, but their distribution in the developing brain, especially the human fetal brain, is largely unknown. We used an immunohistochemical method to determine the expression of three S100 proteins, namely S100A4, S100A5, and S100A13, in the human fetal hippocampus and temporal cortex from 12 to 33 weeks of gestation. At 12 weeks, S100A5 was strongly expressed in the cells and fibers of the polymorphic, pyramidal, and molecular layers of the hippocampus. Thereafter, its expression decreased with age. In the temporal cortex, S100A5 expression was detected from 12 weeks onwards, peaked at 20 to 24 weeks, and then decreased with age. The horizontal fibers of the marginal zone were immunoreactive at all stages examined. S100A13 immunoreactivity was also detected in both cells and fibers of the hippocampus at 12 weeks, became slightly stronger at 20 weeks, and then decreased with age. In the temporal cortex, S100A13 immunoreactivity was also strong in all cellular layers at 12 to 24 weeks before it declined with age from 28 weeks onwards. Among the three proteins examined, S100A4 showed the weakest expression, which was detected in the cells and fibers of the hippocampus and the temporal cortex at all stages examined. Our results have demonstrated for the first time, in the human fetal hippocampus and temporal cortex, specific spatio‐temporal patterns of expression of these proteins, all of which are likely to have different roles to play during development despite their pronounced sequence homology. Microsc. Res. Tech. 60:600–613, 2003. © 2003 Wiley‐Liss, Inc.
S100B in brain damage and neurodegeneration
Authors: Rothermundt Matthias , Peters Marion , Prehn Jochen H.M. , Arolt Volker
Published: March 2003

S100B is a calcium‐binding peptide produced mainly by astrocytes that exert paracrine and autocrine effects on neurons and glia. Some knowledge has been acquired from in vitro and in vivo animal experiments to understand S100B's roles in cellular energy metabolism, cytoskeleton modification, cell proliferation, and differentiation. Also, insights have been gained regarding the interaction between S100B and the cerebral immune system, and the regulation of S100B activity through serotonergic transmission. Secreted glial S100B exerts trophic or toxic effects depending on its concentration. At nanomolar concentrations, S100B stimulates neurite outgrowth and enhances survival of neurons during development. In contrast, micromolar levels of extracellular S100B in vitro stimulate the expression of proinflammatory cytokines and induce apoptosis. In animal studies, changes in the cerebral concentration of S100B cause behavioral disturbances and cognitive deficits. In humans, increased S100B has been detected with various clinical conditions. Brain trauma and ischemia is associated with increased S100B concentrations, probably due to the destruction of astrocytes. In neurodegenerative, inflammatory and psychiatric diseases, increased S100B levels may be caused by secreted S100B or release from damaged astrocytes. This review summarizes published findings on S100B regarding human brain damage and neurodegeneration. Findings from in vitro and in vivo animal experiments relevant for human neurodegenerative diseases and brain damage are reviewed together with the results of studies on traumatic, ischemic, and inflammatory brain damage as well as neurodegenerative and psychiatric disorders. Methodological problems are discussed and perspectives for future research are outlined. Microsc. Res. Tech. 60:614–632, 2003. © 2003 Wiley‐Liss, Inc.
Electrospray ionization mass spectrometry and tandem mass spectrometry of clodronate and related bisphosphonate and phosphonate compounds
Authors: Huikko Katri , Kotiaho Tapio , Yli‐Kauhaluoma Jari , Kostiainen Risto
Published: March 2003

The bisphosphonate family with a P—C—P structure is a broad class of drugs, widely investigated as potential inhibitors in bone diseases and calcium metabolic disorders. In this study, the mass spectrometric (MS) behavior and fragmentation of clodronate and related bisphosphonate and phosphonate compounds was studied by using negative ion electrospray ionization (ESI) with triple quadrupole and ion trap instruments. The effect of pH on the degree of deprotonation of the polyprotic bisphosphonic and phosphonic acids in negative ion ESI‐MS was investigated, and the degree of deprotonation in the ESI mass spectra and the dissociation in the liquid phase were compared. The results provide evidence that the measured ESI mass spectra do not correlate with the chemistry in the liquid phase owing to the decrease in the pH of the solvent droplets during the ion evaporation process and the charge state neutralization in the gas phase. Ion trap MSn provided useful information on the fragmentation study of clodronate and related bisphosphonate and phosphonate compounds, in which interesting fragmentation pathways including the direct elimination of carbon monoxide from deprotonated bisphosphonates and formation of a P—P bond were observed. Reactions between the product ions with a —PO2 group and residual water in the ion trap or in the high‐pressure region of the triple quadrupole instrument formed other unexpected fragmentation paths for all the bisphosphonates studied. Copyright © 2002 John Wiley & Sons, Ltd.
Ceramide in rafts (detergent‐insoluble fraction) mediates cell death in neurotumor cell lines
Authors: Kilkus John , Goswami Rajendra , Testai Fernando D. , Dawson Glyn
Published: March 2003

Detergent‐resistant lipid microdomains (Rafts) were isolated from human oligodendroglioma (HOG), human neuroblastoma (LA‐N‐5), and immortalized dorsal root ganglion (F‐11) cell lines by sucrose‐density gradient ultracentrifugation and shown to be enriched in cholesterol, sphingomyelin, and ceramide. [3H]palmitate labeling allowed the Raft fraction to be easily identified as a sharp peak of 3H radioactivity in the 5–30% sucrose interphase. Treatment of [3H]palmitate‐labeled cells with staurosporine (to activate caspase 8 and induce apoptosis) or exogenous sphingomyelinase specifically increased the [3H]ceramide content of the Raft fraction. Depletion of cholesterol with β‐methylcyclodextran decreased Raft formation and partially blocked staurosporine‐induced apoptosis. Similarly, treatment of cells with Fumonisin B1 to inhibit de novo sphingolipid synthesis by 50% reduced the labeling of the Raft fraction and partially blocked staurosporine‐induced apoptosis. Staurosporine treatment activated neutral sphingomyelinase but had no effect on acid sphingomyelinase activity or on other lysosomal hydrolases, such as α‐L‐fucosidase. Most of the neutral sphingomyelinase activity is in the Raft fraction, suggesting that the conversion of sphingomyelin to ceramide in Rafts is an important event in neural cell apoptosis. © 2003 Wiley‐Liss, Inc.
Electrical Response to Organic Vapor of Conductive Composites from Amorphous Polymer/Carbon Black Prepared by Polymerization Filling
Authors: Li Jun Rong , Xu Jia Rui , Zhang Ming Qiu , Rong Min Zhi
Published: March 2003

In recent years, conductive polymer composites have found applications as gas sensors because of their sudden change in electric resistance of several orders of magnitude when the materials are exposed to certain solvent vapors. However, the composites having this function reported so far are mostly based on crystalline polymeric matrices, which factually sets a limit to materials selection. The present work prepares polystyrene/carbon black composites through polymerization filling and proves that the amorphous polymer composites can also serve as gas sensing materials. The composites' percolation threshold is much lower than that of the composites produced by dispersive mixing. In addition, high responsivity to some organic vapors coupled with sufficient reproducibility is acquired. The experimental data show that molecular weight and molecular weight distribution of the matrix polymer and conducting filler content exert great influence on the electrical response behavior of the composites. As a result, composites performance can be purposely tailored accordingly. Compared with the approaches of melt‐blending and solution‐blending, the current technique is characterized by many advantages, such as simplicity, low cost, and easy to be controlled.

Effect of different organic solvent vapors on the electric resistance of PS/CB composites (CB content = 10.35 vol.‐%).

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Effect of different organic solvent vapors on the electric resistance of PS/CB composites (CB content = 10.35 vol.‐%).
Spinning and Characterization of Conducting Microfibers
Authors: Okuzaki Hidenori , Ishihara Masayoshi
Published: March 2003

Conducting microfibers of poly(3,4‐ethylenedioxythiophene) doped with poly(4‐styrene sulfonate), having a diameter ranging between 4.6 and 16 μm, were fabricated by a wet‐spinning technique. The as‐spun microfiber had no notable orientation of polymer chains with poor crystallinity, and electrical conductivity was in the order of 10−1 S · cm−1 regardless of the diameter. Young's modulus, tensile strength, and elongation at break for the resulting microfiber were 1.1 ± 0.3 GPa, 17.2 ± 5.1 MPa, and 4.3 ± 2.3%, respectively.

SEM image of a PEDOT/PSS microfiber reported here.

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SEM image of a PEDOT/PSS microfiber reported here.
Multiphase‐Separated Polyurethanes Studied by Micro‐Raman Spectroscopy
Authors: Janik Helena , Pałys Barbara , Petrovic Zoran S.
Published: March 2003

Micro‐Raman spectroscopy has been used to investigate the chemical micro‐heterogeneity of multiphase‐separated poly(ether urethanes) (PETU). Analysis of PETU cross‐sections by means of micro‐Raman spectroscopy revealed the nearly complete absence of soft segments in AI aggregates (called globules). These aggregates are in the order of a few micrometers in size. The composition of the matrix and the AII aggregates (spherulites) was comparable.

Example of an AFM image (sample 706, scan size 25 μm, converted to monochromatic image).

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Example of an AFM image (sample 706, scan size 25 μm, converted to monochromatic image).
Influence of the annealing conditions on the polarization and electromechanical response of high‐energy‐electron‐irradiated poly(vinylidene fluoride trifluoroethylene) copolymer
Authors: Xia Feng , Wang Y. K. , Li Hengfeng , Huang Cheng , Ma Y. , Zhang Q. M. , Cheng Z.‐Y. , Bateman Fred B.
Published: March 2003

In this study, we investigated the influence of annealing conditions before irradiation on the ferroelectric and electromechanical properties of uniaxially stretched high‐energy‐electron‐irradiated poly(vinylidene fluoride trifluoroethylene) (HEEIP) copolymer (68/32 mol %) films. For films annealed at one fixed temperature before the irradiation (one‐step annealing), the highest crystallinity, which was highly desirable for enhancing the electromechanical response, was obtained only for films annealed between 132 and 136 °C. In addition, annealing over 10 h in this temperature window resulted in a large increase in the crystal lamellar thickness, which was required for reducing the polarization hysteresis to a minimum in the HEEIP samples. For improvements in the mechanical qualities of the uniaxially stretched films, a two‐step annealing procedure was investigated; that is, before the irradiation, the films were first annealed at a lower temperature to release the mechanical stress in the films due to the stretching and then were annealed in the high‐temperature window to raise the crystallinity and crystalline size. The experimental results indicated that this approach could produce uniaxially stretched HEEIP films with much improved mechanical qualities. Furthermore, the uniaxially stretched HEEIP films with this two‐step annealing exhibited the same electromechanical response as or an even higher one than that from the one‐step‐annealed HEEIP films. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 797–806, 2003
Alkylating reactivity and herbicidal activity of chloroacetamides
Authors: Jablonkai Istvan
Published: March 2003

The relationship between S‐ and N‐alkylating reactivity and herbicidal activity within a series of chloroacetamides, including several commercial herbicides and newly synthesised analogues was studied. The S‐alkylating reactivity of selected chloroacetamides, as well as those of atrazine and chlorfenprop‐methyl, was determined by in vitro GSH conjugation at a ratio of GSH to alkylating agent of 25 : 1. A spectrophotometric reaction using 4‐(4‐nitrobenzyl)pyridine was used to characterise the N‐alkylating reactivity of the chemicals. Our results indicate that a reduced level of N‐alkylating reactivity correlates with an improved herbicidal efficacy at a practical rate. However, the phytoxicity of the molecules is not simply dependent on chemical reactivities, but strictly related to the molecular structure, indicating that lipophilicity, uptake, mobility and induction of detoxifying enzymes may also be decisive factors in the mode of action.

© 2002 Society of Chemical Industry
A review of physiological and biochemical aspects of resistance to atrazine and paraquat in Hungarian weeds
Authors: Szigeti Zoltán , Lehoczki Endre
Published: March 2003

The most important results in the field of atrazine and paraquat resistance research by Hungarian researchers are reviewed. Pleiotropic effects accompanying atrazine resistance were investigated in atrazine‐resistant (AR) and susceptible (S) biotypes of horseweed (Conyza canadensis (L) Cronq). No significant difference in carbon dioxide assimilation rate was found between the AR and S plants. The rates of the Hill reaction of the AR and S chloroplasts exhibited different temperature dependence. The thylakoid membrane lipids contained a lower amount of polar lipid and the fatty acid content exhibited a higher degree of unsaturation in the AR biotype. Photosynthetic apparatus of the AR biotype had better adaptive ability at low temperature and showed enhanced susceptibility to high‐temperature stress. AR horseweed plants had reduced activity of xanthophyll cycle, limited capacity of light‐induced non‐photochemical and photochemical quenching, higher photosensitivity and susceptibility to photo‐inhibition. In the case of paraquat resistance, horseweed found in Hungary exhibited a resistance factor of 450; the resistance is not based on an elevated level and activity of the antioxidant enzyme system. The suggested role of polyamines in the resistance mechanisms can be excluded. The higher putrescine and total polyamine content of paraquat‐treated R leaves can be regarded as a general stress response rather than as a symptom of paraquat resistance. A paraquat‐inducible, nuclear‐coded protein, which presumably functions by carrying paraquat to the vacuole, is supposed to play a role in resistance.

© 2003 Society of Chemical Industry
Developmental D‐methamphetamine treatment selectively induces spatial navigation impairments in reference memory in the Morris water maze while sparing working memory
Authors: Williams Michael T. , Morford Laronda L. , Wood Sandra L. , Wallace Tanya L. , Fukumura Masao , Broening Harry W. , Vorhees Charles V.
Published: March 2003

In previous studies, we have shown that P11‐20 treatment with D‐methamphetamine (MA) (10 mg/kg × 4/day at 2‐h intervals) induces impairments in spatial learning and memory in the Morris water maze after the offspring reach adulthood. Using a split‐litter, multiple dose, design (0, 5, 10, and 15 mg/kg MA administered s.c. 4/day at 2‐h intervals), the spatial learning effect was further explored with a multiple shifted platform (reversal), reference memory‐based procedure and a working memory procedure. Prior to spatial learning, animals were first tested for swimming ability (in a straight swimming channel), sequential learning (in the Cincinnati multiple‐T water maze), and proximal cue learning (in the Morris water maze). Rats were then assessed in the hidden platform, reference memory‐based spatial version of the Morris maze for acquisition and on five subsequent phases in which the platform was moved to new locations. After the reference memory‐based, fixed platform position learning phases, animals were tested in the trial‐dependent, matching‐to‐sample, working memory version of the Morris maze. No group differences were found in straight channel, sequential maze, or cued Morris maze performance. By contrast, all MA groups were impaired in spatial learning during acquisition, multiple shift, and shifted with a reduced platform phases of reference memory‐based learning. In addition, MA animals were impaired on memory (probe) trials during the acquisition and shifted with a reduced platform phases of learning. No effects on trial‐dependent, matching‐to‐sample, working memory were found. The findings demonstrate that neonatal treatment with MA induces a selective impairment of reference memory‐based spatial learning while sparing sequential, cued, and working memory‐based learning. Synapse 48:138–148, 2003. © 2003 Wiley‐Liss, Inc.
A cadherin‐like protein functions as a receptor for Bacillus thuringiensis Cry1Aa and Cry1Ac toxins on midgut epithelial cells of Bombyx mori larvae
Authors: Hara Hirotaka , Atsumi Shogo , Yaoi Katsuro , Nakanishi Kazuko , Higurashi Satoshi , Miura Nami , Tabunoki Hiroko , Sato Ryoichi
Published: March 2003

Aminopeptidase N (APN) and cadherin‐like protein (BtR175) from Bombyx mori larvae were examined for their roles in Cry1Aa‐ and Cry1Ac‐induced lysis of B. mori midgut epithelial cells (MECs). APNs and BtR175 were present in all areas of the midgut, were particularly abundant in the posterior region, and were found only on columnar cell microvilli and not on the lateral membrane that makes cell–cell contacts. This distribution was in accordance with the distribution of Cry1A‐susceptible MECs in the midgut. The lytic activity of Cry1Aa and Cry1Ac on collagenase‐dissociated MECs was linearly dependent on toxin concentration. Although pre‐treatment of MECs with anti‐BtR175 antibody was observed to partially inhibit the lytic activity exerted by 0.1–1 nM Cry1Aa toxin or 5 nM Cry1Ac toxin, no significant inhibition was observed when MECs were pre‐treated with anti‐APN antibody. These results suggest that BtR175 functions as a major receptor for Cry1A toxins in the midgut of B. mori larvae.
The human interleukin‐6 (IL‐6) receptor exists as a preformed dimer in the plasma membrane
Authors: Schuster Björn , Meinert Werner , Rose-John Stefan , Kallen Karl-Josef
Published: March 2003

The recently solved X‐ray structure of the extracellular portion of the interleukin‐6 (IL‐6) receptor (IL‐6R) revealed an IL‐6R dimer in the crystal lattice which probably represents a physiological dimer. Performing coprecipitation experiments with two differently tagged IL‐6R variants expressed in COS‐7 cells, we show that an IL‐6R dimer exists in the plasma membrane in the absence of IL‐6. Ligand binding does not seem to affect the dimerization status. When lysates of COS‐7 cells expressing only one of the IL‐6R variants are mixed, spontaneous dimerization occurs. Thus, the IL‐6R dimer observed in the crystal structure represents a physiologically occurring phenomenon.
Ets, Ap‐1 and GATA factor families regulate the utrophin B promoter: potential regulatory mechanisms for endothelial‐specific expression
Authors: Perkins Kelly J. , Davies Kay E.
Published: March 2003

Duchenne muscular dystrophy is caused by dystrophin deficiency, which can be prevented in the mdx mouse model by over‐expression of an autosomal homologue, utrophin. Utrophin has two characterised full‐length promoters, A and B. No data are available on the transcriptional regulation of B utrophin, which has been recently localised to the endothelium. Similar to characterised endothelial promoters, Ets and Ap‐1 individually trans‐activate the human B core promoter. Synergistic activation by GATA‐2 and c‐jun to the order of 20‐fold was observed.
Propagation of transients in a random medium
Authors: Wenzel Alan R.
Published: March 2003

The propagation of transient scalar waves in a three−dimensional random medium is considered. The analysis is based on the smoothing method. An integro−differential equation for the coherent (or average) wave is derived and solved for the case of a statistically homogeneous and isotropic medium and a delta−function source. This yields the coherent Green’s function of the medium. It is found that the waveform of the coherent wave depends generally on the distance from the source measured in terms of a certain dimensionless parameter. Based on the magnitude of this parameter, three propagation zones, called the near zone, the far zone, and the intermediate zone, are defined. In the near zone the evolution of the waveform is determined primarily by attenuation of the high−frequency components of the wave, whereas in the far zone it is determined mainly by dispersion of the low−frequency components. The intermediate zone is a region of transition between the near and far zones. The results show that, in general, the randomness of the medium causes a gradual smoothing and broadening of the waveform, as well as a decrease in amplitude of the wave, with propagation distance. In addition, the propagation speed of the wave is reduced. It is also found that an oscillating tail appears on the waveform as the propagation distance increases.
Discrete state perturbation theory via Green’s functions
Authors: Rubinson William
Published: March 2003

The exposition of stationary state perturbation theory via the Green’s function method in Goldberger and Watson’s Collision Theory is reworked in a way that makes explicit its mathematical basis. It is stressed that the theory consists of the construction of, and manipulations on, a mathematical identity. The perturbation series fall out of the identity almost immediately. The logical status of the method is commented on.
Motion of a body in general relativity
Authors: Geroch Robert , Jang Pong Soo
Published: March 2003

A simple theorem, whose physical interpretation is that an isolated, gravitating body in general relativity moves approximately along a geodesic, is obtained.
Casimir operators of complementary unitary groups
Authors: Aguilera−Navarro M. C. K. , Aguilera−Navarro V. C.
Published: March 2003

A relationship between all the generalized Casimir operators of complementary unitary groups is derived, both in the fermion and boson realizations of the corresponding Lie algebras. It is shown that the number of independent Casimir operators of unitary groups reduces essentially to half the number for self−conjugate irreducible representations.
On the determination of the relativistic wave equations associated with a given representation of S
L (2,C)
Authors: Hurley William J. , Sudarshan E. C. G.
Published: March 2003

Straightforward algebraic techniques are presented and used to determine the structure of wave equations whose relativistic covariance is governed by two representations of SL (2,C), S0(Λ) = (1,1/2) ⊕ (1/2,1) ⊕ (1/2,0) ⊕ (0,1/2) and S1(Λ) = S0(Λ) ⊕ (1/2,0) ⊕ (0,1/2), subject to the requirements that the equations should be parity preserving, admit an invariant Hermitian bilinear form realized by a numerical matrix η, and that they should describe a particle with a unique mass and spin. It is shown that S0(Λ) leads to a unique algebraic structure, that of the Rarita–Schwinger equation, whereas S1(Λ) leads either to a trivial extension of the former case or to a family of equations whose matrices have a minimal algebra with degree one higher than that of the former case. One such example reproduces the equation presented by Glass. When, contrary to custom, a singular η matrix is considered, it is shown that S1(Λ) allows for equations whose coefficient matrices are reducible but indecomposable. These equations are completely equivalent to the Rarita–Schwinger equation in the free case, but the added components may enter the dynamics in the presence of certain interactions. The present examples serve to illustrate techniques which may be applied in the study of any relativistic wave equation.
The renormalized projection operator technique for nonlinear stochastic equations. III
Authors: LoDato Vincent A.
Published: March 2003

The solution of the nonlinear stochastic equation L (x,t,ω) ψ (x,t,ω) =g (x,t)+f [ψ (x,t,ω)] is found via the renormalized projection operator technique and is approximated to be 〈ψ (x,t) 〉=ℱℱdx′dt′ 〈Gp(x,t ‖x′,t′) 〉 {ψint(x′,0)+g (x′,t′) } −ℱℱdx′dt′〈P (x′,t′) 〉 = o e ing−brace)=ℱℱdx″dt″〈Gp(x,t ‖x′,t ′) G0(x′,t′‖x″,t″〉 [ψint(x″,0)+g (x″,t″)]}+ ℱℱdx′dt′〈Gp(x,t ‖x′,t′〉 〈f [ψH(x′,t′)]〉. The terms 〈Gp(x,t ‖x′,t′) 〉 and 〈Gp(x,t ‖x′,t′) G0(x′,t′‖x″,t″) 〉 are the stochastic one- and two-point Green’s functions. Also three conditions are shown that the projection operator must have in order to insure convergence.
Master equations in quantum stochastic processes
Authors: Chen Etang
Published: March 2003

Pauli master equation is derived rigorously in the framework of quantum stochastic processes.
A non-Lie algebraic framework and its possible merits for symmetry descriptions
Authors: Ktorides C. N.
Published: March 2003

A nonassociative algebraic construction is introduced which bears a relation to a Lie algebra ℒ paralleling the relation between an associative enveloping algebra and ℒ. The key ingredient of this algebraic construction is the presence of two parameters which relate it to the enveloping algebra of ℒ. The analog of the Poincaré–Birkhoff–Witt theorem is proved for the new algebra. Possibilities of physical relevance are also considered. It is noted that, if fully developed, the mathematical framework suggested by this new algebra should be non-Lie. Subsequently, a certain scheme resulting from specific considerations connected with this (non-Lie) algebraic structure is found to bear striking resemblance to a recent phenomenological theory proposed for explaining CP violation by the K0 system. Some relevant speculations are also made in view of certain recent trends of thought in elementary particle physics. Finally, in an appendix, a Gell-Mann–Okubo-like mass formula for the new algebra is derived for an SU (3) octet.
Differential geometry and internal symmetry
Authors: Mirman R.
Published: March 2003

It is shown using a generalized Lyra space that the concept of internal symmetry can be expressed in the language of differential geometry. By this method invariant and noninvariant interactions are generated by a gauge formalism.
Neutron transport problems in a spherical shell
Authors: Sahni D. C.
Published: March 2003

The density transform method has been extended to cover spherically symmetric transport problems in a spherical shell. The density transform is expanded in plane geometry normal modes and explicit singular integral equations are derived for the expansion coefficients. It is shown that the Green’s function method, introduced by Case et al., gives the same representation of total flux. The singular integral equations for the expansion coefficients are rederived using the analytic properties of some sectionally holomorphic functions introduced by the above authors.
The Weyl correspondence and path integrals
Authors: Mizrahi Maurice M.
Published: March 2003

The method of Weyl transforms is used to rigorously derive path integral forms for position and momentum transition amplitudes from the time-dependent Schrödinger equation for arbitrary Hermitian Hamiltonians. It is found that all paths in phase space contribute equally in magnitude, but that each path has a different phase, equal to 1/h/ times an ’’effective action’’ taken along it. The latter is the time integral of p⋅q̇−h (p,q), h (p,q) being the Weyl transform of the Hamiltonian operator H, which differs from the classical Hamiltonian function by terms of order h/2, vanishing in the classical limit. These terms, which can be explicitly computed, are zero for relatively simple Hamiltonians, such as (1/2M)[P−eA (Q)]2+V (Q), but appear when the coupling of the position and momentum operators is stronger, such as for a relativistic spinless particle in an electromagnetic field, or when configuration space is curved. They are always zero if one opts for Weyl’s rule for forming the quantum operator corresponding to a given classical Hamiltonian. The transition amplitude between two position states is found to be expressible as a path integral in configuration space alone only in very special cases, such as when the Hamiltonian is quadratic in the momenta.
Invariant imbedding and the Fredholm integral equation
Authors: Wang Alan P.
Published: March 2003

The standard method of solving the Fredholm integral equation is either to use Neumann series or to convert to an equivalent algebraic equation via the eigenvalues. This paper uses an idea similar to that given by Ueno and others. The integral equation is transformed into a Cauchy problem which can be approximated effectively by modern high speed digital computer.
Ergodic properties of a particle moving elastically inside a polygon
Authors: Hobson Arthur
Published: March 2003

The flow of a classical particle bouncing elastically inside an arbitrary polygon is investigated. If every interior angle is a rational multiple of π, there exists precisely one isolating integral in addition to the energy; this integral is described in detail; any possible third integral is nonisolating. If one or more interior angles is an irrational multiple of π, the second integral becomes everywhere nonisolating and non-Lebesgue-measurable, i.e., the second integral disappears. The flow of two hard points bouncing elastically in a finite one-dimensional box is equivalent to the flow of a point particle moving elastically inside a right triangle having interior angle tan−1 (m2/m1)1/2, so the preceding remarks apply to this model. Nonrigorous arguments are given in support of the notion that the polygon model is ergodic and mixing, but is not a C-system.
Space averaging techniques of determinantal measures
Authors: Kelson I. , Shadmon G.
Published: March 2003

Techniques for evaluating approximate space-averages of determinantal measures are discussed. The concept of combinatorial structure diagrams is introduced and investigated.
Unequal mass spinor-spinor Bethe–Salpeter equation
Authors: Brennan B. J.
Published: March 2003

Coupled radial equations are derived for the ladder approximation Bethe–Salpeter equation describing a system of two spin- (1/2) particles of unequal masses interacting to form a bound state of total mass zero. The numerical behavior of the coupling parameter λ as a function of the mass ratio is examined for known analytical equal-mass solutions. In addition a perturbation method is employed to investigate the behavior of λ for small values of the exchange mass.
Local and covariant quantizations of linearized Einstein’s equations. II
Authors: Bracci L. , Strocchi F.
Published: March 2003

The local and covariant quantizations of the linearized Einstein’s equations, in which the space–time translations may not commute with the metric operator, are analyzed. A translations may not commute with the metric operator, are analyzed. A general characterization of the subspace ℋ’ of physical vectors is given in terms of the two point function, independently of the Fock space representation of the gravitational potential hμν. Under very general conditions all the ℋ′ are found to coincide with that of the Gupta formulation, thus showing that the physical content is the same as in the Gupta case. The analog of the Landau gauge in quantum gravity is defined and explicitly constructed through a Fock space representation of hμν. Spinless gravitons can occur only in a quantization which exhibits unconventional features.
Lorentz covariant treatment of the Kerr–Schild geometry
Authors: Gürses Metin , Gürsey Feza
Published: March 2003

It is shown that a Lorentz covariant coordinate system can be chosen in the case of the Kerr–Schild geometry which leads to the vanishing of the pseudo energy–momentum tensor and hence to the linearity of the Einstein equations. The retarded time and the retarded distance are introduced and the Liénard–Wiechert potentials are generalized to gravitation in the case of world-line singularities to derive solutions of the type of Bonnor and Vaidya. An accelerated version of the de Sitter metric is also obtained. Because of the linearity, complex translations can be performed on these solutions, resulting in a special relativistic version of the Trautman–Newman technique and Lorentz covariant solutions for spinning systems can be derived, including a new anisotropic interior metric that matches to the Kerr metric on an oblate spheroid.
The electromagnetic field on a simplicial net
Authors: Sorkin Rafael
Published: March 2003

The ’’Regge calculus’’ approach is extended to the electromagnetic case. To this end an ’’affine’’ tensor formalism and associated exterior calculus are developed. The simplicial approach to linear field equations is illustrated by the two-dimensional scalar wave equation, on which also a discussion of the treacherous character of the continuum limit is based.
Cylindrically symmetric solutions of a scalar–tensor theory of gravitation
Authors: Singh T.
Published: March 2003

The cylindrically symmetric solutions for the Einstein–Rosen metric of a scalar–tensor theory proposed by Dunn have been obtained. A method has been given by which one can obtain, under certain conditions, solutions of this scalar–tensor theory from known solutions of the empty space field equations of Einstein’s theory of gravitation. It is also found that one of the solutions of the scalar–tensor theory is nonsingular in the sense of Bonnor. Further some special solutions are obtained which reduce to the well-known solution of Levi-Civita and a time dependent solution obtained by Misra and Radhakrishna.
A Bäcklund transformation in two dimensions
Authors: Chen Hsing-Hen
Published: March 2003

Bäcklund transformation method is applied to find solutions of a nonlinear evolution equation. This equation describes weakly dispersive nonlinear shallow water wave in two space dimensions.