bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of the molecular architecture of low‐density polyethylene on the texture and mechanical properties of blown films
Authors: Guichon O. , Séguéla R. , David L. , Vigier G.
Published: January 2003

Three types of low‐density polyethylene materials were investigated with respect to the influence of the molecular architecture on the mechanical and use properties of blown films. The materials were a branched polyethylene synthesized by free‐radical polymerization under high‐pressure (HP‐LDPE), a linear ethylene–hexene copolymer (ZN‐LLDPE) produced by low‐pressure Ziegler–Natta catalysis, and an ethylene–hexene copolymer (M‐LLDPE) from metallocene catalysis. The extrusion and blowing conditions were identical for the three materials, with a take‐up ratio of 12 and a blow‐up ratio of 2.5. The blown films displayed a decreasing puncture resistance in the order M‐LLDPE, ZN‐LLDPE, and HP‐LDPE. In parallel, the tear resistance of the films became increasingly unbalanced in the same order of the polymers. The morphological study showed an increased anisotropy of the films in the same polymer order, the crystalline lamellae being increasingly oriented normal to the take‐up direction. This texturing caused a detrimental effect on the mechanical properties of the films, notably increasing the capacity for crack propagation. The phenomenon was ascribed to the kinetics of chain relaxation in the melt that governed the ability of the chains to recover an isotropic state from the flow‐induced stretching before crystallization. The puncture resistance was examined in terms of both texture and strain‐hardening capabilities. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 327–340, 2003
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

The 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

Deformation 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

We 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

The 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

Silicic 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

This 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

Sugar 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

Genome‐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

Accurate 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

As 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

Resistance 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

Channelization 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

Several 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

To 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

The 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

This 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.
A tale of two classrooms
Authors: Van Note Chism Nancy
Published: January 2003

We know too much about how learning occurs to continue to ignore the ways in which learning spaces are planned, constructed, and maintained.
Designing collaborative learning places: Psychological foundations and new frontiers
Authors: Graetz Ken A. , Goliber Michael J.
Published: January 2003

Physical environment plays an important role in shaping human social interaction. This chapter explores this issue from a psychological perspective, drawing on theories and research from environmental and social psychology. It explores characteristics of effective collaborative work environments.
Embracing the hybrid model: Working at the intersections of virtual and physical learning spaces
Authors: Skill Thomas D. , Young Brian A.
Published: January 2003

The creation of new learning environments should embrace both virtual and real spaces. This chapter explores options for integrating these two modes of learning and offers e‐learning and learning environment integration and design implications.
Navigating the white waters of collaborative work in shaping learning environments
Authors: Bickford Deborah J.
Published: January 2003

The effective creation of spaces conductive to learning calls for a new level of campus collaboration that will yield exciting and rejuvenating spaces that no one group could conceive in isolation.
Educator and architect partnerships for success
Authors: Butz James
Published: January 2003

An architect explains the various planning steps necessary to create new spaces on campuses and reflects on characteristics of working relationships that are most effective in creating informed learning spaces.
Developing a classroom vision and implementation plan
Authors: Christensen Hughes Julia
Published: January 2003

This chapter focuses on the process used at one university for developing a long‐term vision and implementation plan for the renovation and refurbishment of existing classroom space.
Put your money where your mouth is: A case study
Authors: DeGuire North Joan
Published: January 2003

Outdated classrooms are common in higher education. This chapter unveils the story of what resulted when a college's new focus on teaching led to tackling its outmoded classroom inventory.
Innovative models of learning environments
Authors: Dittoe William
Published: January 2003

Several exciting spaces at colleges and universities throughout the country show how the built environment can enhance learning.
Molecular cloning and DNA analysis of a gene encoding α mating pheromone from the yeast Saccharomyces naganishii
Authors: Kodama Takuya , Hisatomi Taisuke , Kanemura Tomokazu , Mokubo Ken , Tsuboi Michio
Published: January 2003

A DNA fragment encoding the precursor peptide for α mating pheromone was isolated from the S. naganishii genome based on the amino acid sequence of the mature pheromone. The precursor peptide contains three copies of the pheromone. Hydrophobicity analysis of the precursor peptide revealed an N‐terminal signal sequence for translocation into the lumen of the endoplasmic reticulum and several signals for a series of secretion‐related processes. However, upstream regulatory sequences necessary for expression of the S. cerevisiae α mating pheromone gene were not found, suggesting the divergence of systems that regulate α mating pheromone gene expression in S. naganishii and S. cerevisiae. Hybridization of a probe corresponding to the S. naganishii α mating pheromone nucleotide sequence to S. naganishii chromosomal DNA revealed a single gene located on either chromosome VI or VII. The S. naganishii α mating pheromone sequence has been deposited in the DDBJ/EMBL/GenBank data library under Accession No. AB086431. Copyright © 2002 John Wiley & Sons, Ltd.
Structural characterization of chromosome I size variants from a natural yeast strain
Authors: Carro David , García‐Martinez José , Pérez‐Ortín José E. , Piña Benjamin
Published: January 2003

Many yeast strains isolated from the wild show karyotype instability during vegetative growth, with rearrangement rates of up to 10−2 chromosomal changes per generation. Physical isolation and analysis of several chromosome I size variants of one of these strains revealed that they differed only in their subtelomeric regions, leaving the central 150 Kb unaltered. Fine mapping of these subtelomeric variable regions revealed gross alterations of two very similar loci, FLO1 and FLO9. These loci are located on the right and left arms, respectively, of chromosome I and encompass internal repetitive DNA sequences. Furthermore, some chromosome I variants lacking the FLO1 locus showed evidence of recombination at a DNA region on their right arm that is enriched in repeated sequences, including Ty LTRs. We propose that repetitive sequences in many subtelomeric regions in S. cerevisiae play a key role in karyotype hypervariability. As these regions encode several membrane‐associated proteins, subtelomeric plasticity may allow rapid adaptive changes of the yeast strain to specific substrates. This pattern of semi‐conservative chromosomal rearrangement may have profound implications, both in terms of evolution of wild strains and for biotechnological processes. Copyright © 2002 John Wiley & Sons, Ltd.
Undesirable growth in a model with capital accumulation and environmental assets
Authors: Bartolini Stefano , Bonatti Luigi
Published: January 2003

The expansion of private production erodes the quality of commonly owned assets, thereby forcing individuals to rely increasingly on private goods to satisfy their needs. In the face of this deterioration, households increase their work effort
and accumulate more capital in order to buy more consumer goods both in the
present and in the future. By so doing, each household contributes to an increase in production and thus has a detrimental—though negligible—impact on commonly owned assets. Hence, the economy converges to a long-run equilibrium level of production that is higher than the level associated with the Pareto-efficient path.
On the implications of technological innovation for environmental policy
Authors: Parry Ian W.H.
Published: January 2003

This paper draws on a number of recent studies to shed light on several policy issues raised by the impact of environmental policies on technological innovation. First, to what extent does induced innovation raise the overall net benefits to society from environmental policies? Second, how does induced innovation affect the appropriate choice among alternative environmental policy instruments? Third, how does it affect the optimal stringency of environmental regulations? Fourth, should environmental policies be supplemented with additional policies to promote innovation, such as research contracts or prizes for new technologies?
Excess capacity and sustainable development in Java Sea fisheries
Authors: Squires Dale , Omar Ishak Haji , Jeon Yongil , Kirkley James , Kuperan K. , Susilowati Indah
Published: January 2003

Excess capacity and overfishing are problems in the open-access, common-pool fisheries of the Java Sea. Data development analysis is used to estimate excess fishing capacity and the number of vessels to decommission in three Java Sea fisheries of Indonesia, the purse seine, mini purse seine, and longline. First- and second-best policy measures are discussed to reduce the excess capacity and give sustainable management and development. The importance of incentive design, asymmetric information, and the regulator's principal–agent problem are emphasized in license limitation programs.
The bilingual as an adaptive system
Authors: Green David W.
Published: January 2003

Dijkstra and van Heuven lucidly summarize the important research generated by the BIA model and provide an excellent case for the BIA+ model with its critical separation of the identification system from the task/decision system. A keynote article necessarily offers a selective exposition of the authors' thinking and so my remarks are an invitation to expand. My first question concerns the scope of the BIA+ model. My remaining questions broadly address a key feature of the BIA+ model – its ability to explain performance changes as a function of task demands
Bilingual word recognition beyond orthography: On meaning, linguistic context and individual differences
Authors: van Hell Janet G.
Published: January 2003

Central questions in psycholinguistic studies on bilingualism are how bilinguals access words in their two languages, and how they control their language systems and solve the problem of cross-language competition. In their excellent paper “The architecture of the bilingual word recognition system: From identification to decision”, Dijkstra and Van Heuven expound their BIA+ model on bilingual word recognition. BIA+ builds on its predecessor BIA, one of the first connectionist models on bilingual word recognition. BIA+ preserves one of BIA's crucial assumptions, namely that the bilingual lexicon is integrated across languages and is accessed in a language non-selective way, an assumption that is supported in many empirical studies and that is now widely accepted in the bilingual literature. Compared to the original BIA model, the BIA+ architecture is further developed (in fact, much more so than the subtle ‘plus’ denotes). BIA+ now includes orthographic, as well as phonological and semantic representations in the word identification system, and a distinction is made between a word identification system and a task/decision system. This latter extension resembles the language task schemas in Green's (1998) Inhibitory Control model. Dijkstra and Van Heuven also distinguish between effects of linguistic and non-linguistic context on performance: linguistic context effects, that arise from lexical, syntactic and semantic sources, are assumed to affect the activity in the word identification system, whereas non-linguistic effects, that can arise from instruction, task demands or participant expectancies, are assumed to affect the task/decision system.
Bilingualism is in dire need of formal models
Authors: Li Ping
Published: January 2003

Each year the Cognitive Science Society honors David Rumelhart by awarding the Rumelhart Prize to an outstanding cognitive scientist whose research makes a significant contribution to the formal analysis of human cognition. Formal models of language, including those of Rumelhart and his associates, are well known to psycholinguists in the monolingual context. The formalism of language in the bilingual context, however, is lamentable: to this date, there are only a handful of models (connectionist or otherwise) that are designed specifically to account for bilingual language processing and acquisition (cf. Li and Farkas, 2002). BIA is one of them. BIA+ is now another.
Detecting and predicting spatial and interannual patterns of temperate forest springtime phenology in the eastern U.S.
Authors: Jenkins J. P. , Braswell B. H. , Frolking S. E. , Aber J. D.
Published: January 2003

We performed a diagnostic analysis of AVHRR‐NDVI and gridded, temperature data for the deciduous forests of the eastern U.S., calibrating temperature accumulation model with satellite data for 1982–1993. The model predicts interannual variability in onset date based upon year‐to‐year changes in springtime temperature. RMS error over the period ranges from 6.9 days in the northern portion of the domain to 10.7 days in the south. The analysis revealed a relationship between temperature accumulation and satellite derived onset date (rank correlation = 0.31–0.62). The required temperature accumulation threshold can be expressed as a function of mean temperature (R2 of 0.90) to facilitate predictive analysis of phenological onset, or when remote sensing data are unavailable.
Detailed analysis of a substorm event on 6 and 7 June 1989 1. Growth phase evolution of nightside auroral activities and ionospheric convection toward expansion phase onset
Authors: Kadokura Akira , Yukimatu Akira‐Sessai , Ejiri Masaki , Oguti Takasi , Pinnock Michael , Hairston Marc R.
Published: January 2003

We have analyzed in detail the evolution of nightside auroral activities and ionospheric convection during the growth phase of an isolated substorm. The following three characteristic auroral activities were identified by meridian scanning photometers (MSP) at ground stations: (1) proton main oval, (2) fast equatorward moving (FEM) arc, and (3) near plasma sheet boundary layer (NPSBL) aurora. The proton main oval corresponds to the main part of the proton auroral region and was located at the equatorward‐most region of the electron auroral emissions and gradually moved equatorward during the growth phase. The FEM arc was a discrete auroral arc having a clear longitudinally elongated form. It appeared about 20 min before the onset on the high‐latitude side of the auroral region and moved equatorward toward the proton main oval. Its equatorward motion gradually slowed as it approached the proton main oval. As the FEM arc moved equatorward, the location of the peak velocity in the nightside return flow of the two‐cell convection also moved equatorward. The auroral breakup occurred in a localized area around the demarcation region between the two return flows, close to the latitude of the FEM arc. This was observed by the UV imager aboard the Akebono satellite. The NPSBL aurora appeared a few minutes before the onset around the poleward‐most region of the aurora and continued even after the onset. Our detailed analysis of these phenomena can give us important clues as to how the growth phase proceeds toward the expansion phase onset.
On the interaction of the solar wind with the interstellar medium: Field aligned MHD flow
Authors: Ratkiewicz Romana , Webb Gary M.
Published: January 2003

We discuss the role of the local interstellar magnetic field on the interaction of the solar wind with the local interstellar medium (LISM). In particular, we consider the case in which the LISM flow is aligned with the magnetic field. The solar wind inside the termination shock is spherically symmetric, and the LISM magnetic field varies between 0.0 and 3.5 μG. Our simulations show that for the case of field‐aligned flow, increasing the interstellar magnetic field intensity Bis moves the bow shock (when it exists) and heliopause further outward from the Sun. This effect is explained in terms of the force on the plasma. We compare our results with comparable simulations carried out by Aleksashov et al. [2000]. The comparison leads to the conclusion that the mutual dependence between the neutral hydrogen number density and the strength of the magnetic field characterizes the solution for the interaction between the solar wind and interstellar medium. For a given interstellar neutral hydrogen number density (assumed to be available with present observations, or more exactly obtained from future observations), and for a given LISM magnetic field direction and intensity, the model gives distances to the heliopause and the termination shock, and the flow structure ahead of the heliopause. Thus the model can be used to estimate the LISM magnetic field intensity consistent with the observations.
Excitation of field line resonances by MHD waves originating in the solar wind
Authors: Walker A. D. M.
Published: January 2003

Recent observations suggest that in some circumstances a field line resonance may be driven by discrete oscillations in the solar wind. A theoretical model of excitation of magnetohydrodynamic (MHD) field line resonances by waves originating in the solar wind is presented. Such waves occur in the solar wind although their source is not understood. The propagation of an MHD wave in the solar wind is followed through the bow shock and magnetosheath. It is shown how the properties of the magnetospheric cavity are functions of longitude. The incident wave is captured at a longitude where its azimuthal wave number has a value allowing matching to the cavity oscillation. There is significant amplification at the bow shock and at the magnetopause. It is found that the signal penetrates the cavity and excites a field line resonance on the flanks of the magnetosphere in the morning and afternoon sectors. Rather than behaving as a waveguide, the cavity behaves more like an optical filter.
Satellite analysis and PUFF simulation of the eruptive cloud generated by the Mount Etna paroxysm of 22 July 1998
Authors: Aloisi Marco , D'Agostino Marcello , Dean Kenneson Gene , Mostaccio Antonino , Neri Giancarlo
Published: January 2003

We applied the PUFF algorithm [Searcy et al., 1998] to simulate the space‐time evolution of the eruptive cloud generated by one of the main paroxysms to have occurred this past century at Etna volcano, namely the 22 July 1998 explosive event at the Voragine summit crater. The comparison of PUFF simulations to satellite images of the ash cloud at different times allowed us to estimate several parameters of the eruptive event, such as onset time, duration, ash cloud height and shape, and pyroclast size. Based on this analysis, we concluded that the paroxysm started around 1645 GMT, lasted between 20 and 40 min, and generated a Poissonian‐shaped ash column nearly 13 km high and composed of particles with a mean diameter (MD) of 10−3 m and size logarithmic standard deviation (LSD) equal to 1.5. The PUFF simulations using horizontal and vertical diffusivity values of 5000 and 10 m2 s−1, respectively, provided the best agreement to the eruption clouds observed on satellite images. The results were compared to the information available in the literature concerning the eruption, e.g., volcanological, video camera, and volcanic tremor data. The analysis showed that the method of simulating the eruptive clouds and comparing simulations to satellite images can give a contribution to the study of paroxysmal events generated by the Etna volcano. Also, the degree of accuracy of the cloud simulation leads us to be optimistic about the potential of using this method as a tool for hazard mitigation in the Etna region, with particular applications to air traffic.
Steady subsidence of Medicine Lake volcano, northern California, revealed by repeated leveling surveys
Authors: Dzurisin Daniel , Poland Michael P. , Bürgmann Roland
Published: January 2003

Leveling surveys of a 193‐km circuit across Medicine Lake volcano (MLV) in 1954 and 1989 show that the summit area subsided by as much as 302 ± 30 mm (−8.6 ± 0.9 mm/yr) with respect to a datum point near Bartle, California, 40 km to the southwest. This result corrects an error in the earlier analysis of the same data by Dzurisin et al. [1991], who reported the subsidence rate as −11.1 ± 1.2 mm/yr. The subsidence pattern extends across the entire volcano, with a surface area of nearly 2000 km2. Two areas of localized subsidence by as much as 20 cm can be attributed to shallow normal faulting near the volcano's periphery. Surveys of an east–west traverse across Lava Beds National Monument on the north flank of the volcano in 1990 and of a 23‐km traverse across the summit area in 1999 show that subsidence continued at essentially the same rate during 1989–1999 as 1954–1989. Volcano‐wide subsidence can be explained by either a point source of volume loss (Mogi) or a contracting horizontal rectangular dislocation (sill) at a depth of 10–11 km. Volume loss rate estimates range from 0.0013 to 0.0032 km3/yr, depending mostly on the source depth estimate and source type. Based on first‐order quantitative considerations, we can rule out that the observed subsidence is due to volume loss from magma withdrawal, thermal contraction, or crystallizing magma at depth. Instead, we attribute the subsidence and faulting to: (1) gravitational loading of thermally weakened crust by the mass of the volcano and associated intrusive rocks, and (2) thinning of locally weakened crust by Basin and Range deformation. The measured subsidence rate exceeds long‐term estimates from drill hole data, suggesting that over long timescales, steady subsidence and episodic uplift caused by magmatic intrusions counteract each other to produce the lower net subsidence rate.
On the cause of Scotian Shelf Water crossovers
Authors: Cho Yang‐Ki , Beardsley Robert C. , Sheremet Vitalii A.
Published: January 2003

Satellite images and hydrographic data show episodic flows of Scotian Shelf Water (SSW) across the Northeast Channel to Georges Bank. These flows carry nutrients, plankton, and larval fish and may play an important role in the ecology of Georges Bank. Despite their importance, there is yet no clear explanation of the crossover mechanism. We show here using numerical model results and hydrographic data that the jet flowing along the front between the relatively dense Slope Water and the light Shelf Water is a primary factor in driving SSW crossovers. The crossover of SSW depends on the density difference between these two water masses.
Basal temperature evolution of North American ice sheets and implications for the 100‐kyr cycle
Authors: Marshall Shawn J. , Clark Peter U.
Published: January 2003

We simulate three‐dimensional ice temperature fields to examine spatial‐temporal history of the subglacial thermal environment during the last glacial cycle. Model results suggest that 60–80% of the Laurentide Ice Sheet was cold‐based (frozen to the bed) at the LGM, and therefore unable to undergo large‐scale basal flow. The fraction of warm‐based ice increases significantly through the ensuing deglaciation, with only 10–20% of the Laurentide Ice Sheet frozen to the bed by 8 kyr BP. This basal thermal evolution, a function of both climatic and ice sheet history, could enable a dynamical switch to widespread basal flow through the deglacial period. Because basal flow has the capacity to evacuate large amounts of ice from the interior of continental ice sheets, creating thin and climatically‐vulnerable ice masses, this switch in flow regime may have played a significant role in glacial terminations and the 100‐kyr glacial cycle.
A COAMPS™ reanalysis for the Eastern Pacific: Properties of the diurnal sea breeze along the central California coast
Authors: Kindle John C. , Hodur Richard M. , deRada Sergio , Paduan Jeffrey D. , Rosenfeld Leslie K. , Chavez Francisco Q.
Published: January 2003

This paper introduces and evaluates a new atmospheric model reanalysis product for the U.S. west coast from the Navy's operational Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS™) implemented on a triply nested 81/27/9 km grid. Wind measurements from Monterey Bay Aquarium Research Institute (MBARI) moorings are used to evaluate a two year time series of the model output from October 1998 to October 2000. The model accurately reproduced both the landward decrease in the large‐scale wind field and the shoreward intensification of the diurnal cycle during the summer season. This new reanalysis product will be required for accurate high resolution (km) coastal (0–10 km) simulations of the U.S. west coast by ocean models.