bluuebunny/crossref_metadata_2025_split huggingface dataset:
Molecular orientation of rigid‐rod polyimide films characterized by polarized attenuated total reflection/fourier transform infrared spectroscopy
Authors: Matsuda Sho‐Ichi , Ando Shinji 
Published: January 2003

AbstractThe variations in the molecular orientation of uniaxially drawn rigid‐rod polyimide films were systematically characterized in all three dimensions with polarized attenuated total reflection/Fourier transform infrared spectroscopy. The second‐order orientation coefficients were directly deduced from the anisotropy in IR absorptions of particular bands. With the draw ratio increasing, the state of the molecular orientation changed from being nearly planar to completely uniaxial via biaxial orientation, and the degree of orientation was much larger than that of a semirigid polyimide having an ether linkage at the same draw ratio, which originated from the rigid‐rod structure. In addition, the imide planes were rotationally oriented to the out‐of‐plane direction of the film geometry. Furthermore, the relationship between the molecular chain orientation and the in‐plane birefringence in the biaxial orientation state was examined. The intrinsic birefringence was estimated from biaxial orientation films to be 0.33 at a wavelength of 1307 nm. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 418–428, 2003
Molecular composites made of ionic poly(p‐phenylene terephthalamide) and poly(4‐vinylpyridine): Deformation modes
Authors: Chen W. C. , Sauer J. A. , Hara M. 
Published: January 2003

AbstractDeformation modes were examined on strained thin films of a series of molecular composites containing ionically modified rodlike molecules of poly(p‐phenylene terephthalamide) (PPTA) dispersed in a polar polymer matrix. The rigid molecules were a modified form of PPTA in which the H atom of the amide group was replaced, on 30 mol % of the monomer units, by an ionic propane sulfonate group. The polar polymer matrix of these composites was the flexible‐coil polymer, poly(4‐vinylpyridine). Ionic interactions between the two components increased the effective entanglement strand density and produced changes in the deformation modes. The observed changes were dependent on the relative concentration of the two components and on the nature of the counterion. With K+ as the counterion, the induced deformation mode changed from pure crazing, as in the matrix polymer, to combined crazing and shear deformation at 5 wt % of the ionic polymer and to essentially pure shear deformation as the concentration increased to 15 wt %. However, when Ca2+ was the counterion, pure shear deformation developed at a concentration of only 5 wt %. This effect was attributed to a greater ionic interaction and to a higher effective strand density of the composites, when monovalent K+ was replaced by divalent Ca2+. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 429–436, 2003
Depth profiling of latex blends of fluorinated and fluorine‐free acrylates with laser‐induced secondary mass spectrometry
Authors: Walz Stefanie M. , Malner Thomas E. , Mueller Ulrich , Muelhaupt Rolf 
Published: January 2003

AbstractWe explored phase separation and self‐assembly of perfluoroalkyl segments at the surface of polymer films obtained from latices of semifluorinated acrylate copolymers and the corresponding latex blends of nonfluorinated and semifluorinated polyacrylates. With laser‐induced secondary mass spectrometry the fluorine distribution was measured after annealing above the minimum film‐forming temperature of the polymers up to a depth of several micrometers. Depth profiles of a semifluorinated acrylate homopolymer and latex blends thereof with fluorine‐free alkylacrylates with 25, 50, and 75 mol % semifluorinated acrylate as well as a copolymer comprised of alkyl acrylate and semifluorinated acrylate (50/50 mol %) were investigated. In the case of latex blends containing both semifluorinated polyacrylates and fluorine‐free or low‐fluorine polymers, self‐assembly accounted for enrichment of the perfluoroalkyl segments at the surface. Coatings exhibiting low surface energy and having a substantially reduced total fluorine content were obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 360–367, 2003
Static light scattering, ultraviolet–visible, and fluorescence spectroscopy from fluorescent methyl methacrylate/benzazole dye copolymers displaying an intramolecular proton‐transfer mechanism in the electronically excited state
Authors: Rodembusch Fabiano Severo , da Silveira Nádya Pesce , Samios Dimitrios , Campo Leandra Franciscato , Stefani Valter 
Published: January 2003

AbstractThe solution behavior of new copolymers of methyl methacrylate and benzazole dyes emitting fluorescence because of an intramolecular proton‐transfer mechanism in the electronically excited state has been investigated by static light scattering, fluorescence spectroscopy, ultraviolet–visible, and gel permeation chromatography. In the dilute regime, with tetrahydrofuran (THF) and chloroform as solvents, the copolymers behave as typical polydisperse linear chains in good solvents. The analysis of the osmotic modulus for concentrated solutions in THF (c ≥ 60 g L−1) indicates the existence of an interchain association mechanism. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 341–350, 2003
In situ polymerization of silicic acid in polyethylene–octene elastomer: Properties and characterization of the hybrid nanocomposites
Authors: Wu Chin‐San , Liao Hsin‐Tzu 
Published: January 2003

AbstractSilicic acid produced from sodium metasilicate hydrate and metallocene polyethylene–octene elastomer (POE) were chosen as the ceramic precursor and the continuous phase, respectively, for preparation of new hybrids by an in situ sol–gel process. To obtain a better hybrid, the acrylic acid‐grafted polyethylene–octene elastomer (POE‐g‐AA) prepared in our laboratory and used as the continuous phase was also investigated. Characterizations of POE/SiO2 and POE‐g‐AA/SiO2 composites were performed by Fourier transform infrared spectroscopy, 29Si solid‐state nuclear magnetic resonance (NMR) spectrometry, X‐ray diffractometry, differential scanning calorimetry, thermogravimetry analysis, and an Instron mechanical tester. The POE‐g‐AA/SiO2 hybrid could give the positive effect on the properties of POE/SiO2 hybrid because the carboxylic acid groups of acrylic acid should act as coordination sites for the silica phase to form chemical bonds. The result of 29Si solid‐state NMR spectra showed that Si atom coordination around SiO4 units is predominantly Q3 and Q4. Also, the POE‐g‐AA/SiO2 hybrid with 15 wt % SiO2 gave the maximum values of tensile strength and glass‐transition temperature because excess particles might cause the separation between the organic and inorganic phases when the silica content was beyond this point. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 351–359, 2003
Manipulation of parasitoids for aphid pest management: progress and prospects
Authors: Powell Wilf , Pickett John A 
Published: January 2003

AbstractThis paper describes research at IACR‐Rothamsted on aphid parasitoid responses to semiochemical foraging stimuli, aimed at developing novel ways of manipulating these behaviours to overcome ecological constraints to biological and integrated pest control. Female parasitoids respond both to aphid sex pheromones acting as kairomones, and to aphid‐induced plant volatiles, acting as synomones. A range of economically important parasitoid species respond to aphid sex pheromones, and their potential for enhancing parasitization of aphid populations has been demonstrated in the field. Commercial production of the pheromone from the plant Nepeta cataria L has been developed and strategies for its use in arable crops are being investigated. Aphid‐induced plant volatiles are released systemically throughout the plant and are aphid species specific, probably induced by elicitors in aphid saliva. Aphid‐infested plants can induce uninfested neighbours to release damage‐related volatiles, plant‐to‐plant communication occurring via the rhizosphere. The plant compound cis‐jasmone has been identified as a plant signal with potential for aphid control, inducing plant defence mechanisms that both deter colonising aphids and attract parasitoids and predators. Such compounds may represent a new generation of crop protectants and their further investigation and development will be aided by the tools generated by genomic and post‐genomic biology.© 2003 Society of Chemical Industry
Identification and exploitation of novel disease resistance genes in sugar beet
Authors: Francis Sally A , Luterbacher Mark C 
Published: January 2003

AbstractSugar beet is a valuable arable crop providing a large proportion of world sugar supplies. It is susceptible to a range of fungal and viral diseases, to most of which there is inadequate genetic resistance. Control instead relies largely on the use of pesticides. To increase the sustainability of sugar‐beet cultivation, strong and durable genetic resistance is urgently needed. This review describes an IACR‐Broom's Barn programme devoted to evaluating Beta germplasm for novel resistance to major viral and fungal diseases, and its progress in elucidating the numbers and locations of the genes responsible.© 2003 Society of Chemical Industry
A genomics approach to crop pest and disease research
Authors: Keon John , Curtis Rosane , Cabrera Hector , Hargreaves John 
Published: January 2003

AbstractGenome‐wide analyses of gene function and gene expression are beginning to yield valuable information in many areas of biological research, and these genomic tools are now being applied to crop pest and disease research. DNA sequencing of cDNA libraries to generate sets of expressed sequence tags (ESTs) are allowing gene compendiums for crop diseases to be compiled. Annotation of such data collections is also providing a wealth of functional information about gene products through similarities to proteins with known function. The next phase of the functional genomics era will be to employ large‐scale techniques to knock out or silence genes in order to synthesize gene‐specific mutants for phenotypic analysis and to use micro‐array methodology to analyze global gene expression, protein turnover and protein processing during the processes of parasitism and colonization. Application of these technologies promises to accelerate the pace that biological information relevant to crop protection accrues. The ability of researchers to assimilate this information into complex models and workable hypotheses is, thus, set to revolutionize the way we study pests and diseases of crop plants.© 2003 Society of Chemical Industry
Molecular diagnostics for fungal plant pathogens
Authors: McCartney H Alastair , Foster Simon J , Fraaije Bart A , Ward Elaine 
Published: January 2003

AbstractAccurate identification of fungal phytopathogens is essential for virtually all aspects of plant pathology, from fundamental research on the biology of pathogens to the control of the diseases they cause. Although molecular methods, such as polymerase chain reaction (PCR), are routinely used in the diagnosis of human diseases, they are not yet widely used to detect and identify plant pathogens. Here we review some of the diagnostic tools currently used for fungal plant pathogens and describe some novel applications. Technological advances in PCR‐based methods, such as real‐time PCR, allow fast, accurate detection and quantification of plant pathogens and are now being applied to practical problems. Molecular methods have been used to detect several pathogens simultaneously in wheat, and to study the development of fungicide resistance in wheat pathogens. Information resulting from such work could be used to improve disease control by allowing more rational decisions to be made about the choice and use of fungicides and resistant cultivars. Molecular methods have also been applied to the study of variation in plant pathogen populations, for example detection of different mating types or virulence types. PCR‐based methods can provide new tools to monitor the exposure of a crop to pathogen inoculum that are more reliable and faster than conventional methods. This information can be used to improve disease control decision making. The development and application of molecular diagnostic methods in the future is discussed and we expect that new developments will increase the adoption of these new technologies for the diagnosis and study of plant disease.© 2003 Society of Chemical Industry
Laboratory evaluation of temperature effects on the germination and growth of entomopathogenic fungi and on their pathogenicity to two aphid species
Authors: Yeo Helen , Pell Judith K , Alderson Peter G , Clark Suzanne J , Pye Barry J 
Published: January 2003

AbstractAs part of an approach to select potential mycoinsecticides for aphid biocontrol, we investigated the effects of temperature on the growth, germination and pathogenicity of some hyphomycete fungi. Commercially available mycoinsecticides (based on Beauveria bassiana (Balsamo) Vuillemin and Verticillium lecanii (Zimmermann) Viegas) and other isolates of B bassiana, V lecanii, Metarhizium anisopliae (Metschnikoff) Sorokin and Paecilomyces fumosoroseus (Wize) Brown & Smith were evaluated. The rate of in vitro conidial germination of all isolates was slower at 10 and 15 °C than at 20 and 25 °C. Similarly, in vitro growth of most isolates was adversely affected at 10 and 15 °C. The greatest reduction at 10 °C in rates of conidial germination and colony growth, compared with other temperatures, was for M anisopliae isolates. Germination of V lecanii (isolate HRI 1.72) was fastest at 10 °C compared with the other fungi. It was also the most pathogenic of three isolates tested against Aphis fabae Scopoli and Myzus persicae Sulzer at 10, 18 and 23 °C. Generally, A fabae was more susceptible than M persicae to infection by the fungal isolates tested. A significant interaction between aphid species and temperature indicated that the pathogenic nature of an isolate was dependent not only on the target aphid species but also the temperature conditions of the bioassay. The series of studies, detailed above, allowed a temperature profile to be formed for the different isolates. Verticillium lecanii isolate HRI 1.72 (commercialised as Vertalec®) was the most promising isolate selected from results of the series of experiments. Temperature profiles in conjunction with infectivity assays can be useful in selecting appropriate isolates for a particular thermal environment.© 2003 Society of Chemical Industry
Characterisation of target‐site resistance to ACCase‐inhibiting herbicides in the weed Alopecurus myosuroides (black‐grass)
Authors: Moss Stephen R , Cocker Kay M , Brown Amanda C , Hall Linda , Field Linda M 
Published: January 2003

AbstractResistance to aryloxyphenoxypropionate (AOPP), cyclohexanedione (CHD) and phenylurea herbicides was determined in UK populations of Alopecurus myosuroides Huds. Two populations (Oxford AA1, Notts. A1) were highly resistant (Resistance indices 13–>1000) to the AOPP and CHD herbicides fenoxaprop, diclofop, fluazifop‐P and sethoxydim, but only marginally resistant to the phenylurea, chlorotoluron. Analyses of acetyl coenzyme A carboxylase (ACCase) activity showed that an insensitive ACCase conferred resistance to all the AOPP/CHD herbicides investigated. Another population, Oxford S1, showed no resistance to sethoxydim at the population level, but contained a small proportion of plants (<10%) with an insensitive ACCase. Genetic studies on the Notts A1 and Oxford S1 populations demonstrated that target site resistance conferred by an insensitive ACCase is monogenic, nuclearly inherited with the resistant allele showing complete dominance. Investigations of the molecular basis of resistance in the Notts A1 population showed that sethoxydim resistance in A myosuroides was associated with the substitution of an isoleucine in susceptible with a leucine in resistant plants, which has also been found in three other resistant grass‐weed species (Setaria viridis (L) Beauv, Avena fatua L, Lolium rigidum Gaud).© 2003 Society of Chemical Industry
Depositional response of a headwater stream to channelization, East Central Illinois, USA
Authors: Landwehr Kyle , Rhoads Bruce L. 
Published: January 2003

AbstractChannelization typically modifies the energy regime and sediment transport capacity of rivers, triggering morphologic adjustments. Most past studies of channelization have focused on erosional responses involving channel incision and widening. Depositional adjustments to channelization, although noted in previous work, have not been documented in detail. This study investigates the depositional response of the Spoon River, a headwater agricultural stream in Illinois, USA, to channelization. Historical aerial and ground‐based photography show that channelization of the Spoon River in the early 20th century produced a wide, deep trapezoidal drainage channel. Following this channelization, unvegetated alternate and mid‐channel bars developed on the bottom of the ditch. Sedimentological analysis of bar stratigraphy indicates that the bars grew through vertical accretion of horizontal sheets of sand‐and‐gravel bedload and organic‐rich drapes of fine‐grained suspended load. The horizontal sheets of sand and gravel are consistent with the braided conditions shown on historical photographs. Late‐stage bar growth appears to have been dominated by progressive overbank deposition of suspended load as indicated by the presence of a thick, fine‐grained organic‐rich A horizon immediately below the surface of each bar. The development of a soil layer also suggests that the bars are stable—an inference supported by the thick grass cover on the bar surfaces. The net result of the depositional response is the formation of a meandering channel flanked by a discontinuous floodplain on the bottom of the ditch.The construction of a wide ditch relative to original stream size is a key factor promoting a depositional response to channelization. Allowing or actively promoting floodplain elements to form in overwidened ditches may be a viable management option for improving the environmental quality of channelized agricultural streams. The Spoon River has a diverse fish community compared to channelized streams in East Central Illinois that lack a meandering low‐flow channel. This morphological configuration apparently enhances geomorphological and ecological variability while sustaining the drainage function of the ditch. Copyright © 2003 John Wiley & Sons, Ltd.
Carrier phase synchronization for GMSK signals
Authors: Vassallo Enrico , Visintin Monica 
Published: January 2003

AbstractSeveral carrier phase recovery schemes for Gaussian minimum shift keying (GMSK) modulated signals are derived and analysed in terms of squaring loss and acquisition time.Two bandwidths are considered for the GMSK signal:BTb=0.5 and 0.25, following the recommendations of the Consultative Committee for Space Data Systems. Pre‐encoding is assumed to remove the inherent differential encoding of the GMSK modulations.The carrier phase recovery schemes are derived from the approximate expression of the GMSK signal as an OQPSK signal or as the superposition of two OQPSK signals maximuma posteriori/maximum likelihood phase estimation is considered, with perfect clock reference; both non‐data‐aided and decision–directed schemes are analysed. Moreover, in the case of GMSK withBTb=0.25, an equalizer is also included in the synchronizer loop to remove inter‐symbol interference. High and low signal to noise ratio (SNR) approximations are considered to simplify the structure of the synchronizers.It is shown that, for the consideredBTbvalues, the complex synchronizers initially derived do not provide any improvements over their simplified versions; the introduction of the equalizer for GMSK withBTb=0.25 leads to a better performance. Moreover, it is shown that GMSK withBTb=0.5 has a better performance than unfiltered OQPSK, which is better than GMSK withBTb=0.25. The SNR values above which the high SNR approximation turns out to be convenient with respect to the low SNR approximation are also given. Copyright © 2002 John Wiley & Sons, Ltd.
Intersegment handover performance in integrated terrestrial satellite systems
Authors: Leo M. , Luglio M. 
Published: January 2003

AbstractTo achieve a global cellular network, integration among segments offering different coverage (indoor, outdoor and global) must be pursued. Of course, the possibility to hold the call switching among different segments must be guaranteed. Hence, efficient algorithms to perform intersegment handover (ISHO) must be implemented.The paper aims at analysing some ISHO procedures developed in the frame of some European projects and other proposed in the literature, in a scenario with satellite and terrestrial segments interworking to achieve a worldwide cellular coverage.Performance evaluation will be carried out for different system configurations utilizing a dynamic satellite constellation simulator in the time domain. The impact of the distance user‐gateway on performance will be addressed. For each procedure, the execution delay and its complementary cumulative distribution have been evaluated for different constellation geometries at different distances from the gateway. Copyright © 2002 John Wiley & Sons, Ltd.
Analyzing GPS signals to investigate path diversity effects of non‐geostationary orbit satellite communication systems
Authors: Lin Hsin‐Piao , Tseng Ming Jian 
Published: January 2003

AbstractThe concept behind path diversity is that a user who can access several satellites simultaneously will be able to communicate more effectively than a user who could only access one. The success of this method depends on the environment, the satellite constellation, and diversity combining technology. This paper explores the path diversity effects of non‐geostationary orbit (NGO) satellite personal communication services, for different degrees of user mobility, under various scenarios, using the constellation of the global positioning system (GPS). Measurements are taken near downtown Taipei. Three types of mobilities (fixed‐point, pedestrian, and vehicular) are examined, and the switch diversity and maximum ratio combining method are applied to determine the path diversity gain and calculate bit error probability. The error probability performance of applying diversity schemes in coherent binary phase shift keying (BPSK) and non‐coherent differential phase shift keying (DPSK) modulations over Rician fading channels are also analysed and evaluated by using the characteristic function method. The results show that fading can be significantly reduced and diversity greatly increased. A significant diversity gain and improvement in bit error rate (BER) can be expected in all cases by simply applying switch diversity scheme. Besides, for the maximum ratio combining method, the results imply that summing two satellite signals suffices to increase diversity and improve the bit error rate performance. Copyright © 2002 John Wiley & Sons, Ltd.
Static and adaptive routing in ISL networks from a constellation perspective
Authors: Franck Laurent , Maral Gérard 
Published: January 2003

AbstractThis paper presents and evaluates different routing schemes in a constellation of non‐geostationary satellites. Routing decisions may or may not take into account the state of the network. While taking into account the network state is likely to bring an improvement in both the network utilization and the quality of service, it also makes the routing architecture more complex. This paper proposes to evaluate the advantages and disadvantages of these different design approaches for routing. Copyright © 2002 John Wiley & Sons, Ltd.