bluuebunny/crossref_metadata_2025 huggingface dataset:
Variation in the effects of take‐all disease on grain yield and quality of winter cereals in field experiments
Authors: Gutteridge Richard J , Bateman Geoffrey L , Todd Alan D
Published: January 2003

Relationships between take‐all intensity and grain yield and quality were determined in field experiments on cereal crops using regression analyses, usually based on single‐point disease assessments made during anthesis or grain‐filling. Different amounts of take‐all were achieved by different methods of applying inoculum artificially (to wheat only) or by using different cropping sequences (in wheat, triticale or barley) or sowing dates (wheat only) in crops with natural inoculum. Regressions of yield or thousand‐grain weight on take‐all intensity during grain filling were similar to those on accumulated disease (area under the disease progress curve) when these were compared in one of the wheat experiments. Regressions of yield on take‐all intensity were more often significant in wheat than in the less susceptible crops, triticale and barley, even when a wide range of disease intensities was present in the latter crops. The regressions usually had most significance when there were plots in the severe disease category. Thousand‐grain weight and hectolitre weight usually responded similarly to total grain yield. Decreased yield was often accompanied by a significant increase in the percentage of small grains. When severe take‐all was present in wheat, regressions showed that nitrogen uptake was usually impaired. This was sometimes accompanied, however, by increased percentage nitrogen in the grain as a consequence of smaller grain size with decreased endosperm. Significant effects of take‐all, both positive and negative, on Hagberg falling number in wheat sometimes occurred. Significant regressions of yield on take‐all assessed earlier than usual, ie during booting rather than grain‐filling in wheat and triticale and during anthesis/grain‐filling rather than ripening in barley, had steeper slopes. This is consistent with observations that severe disease that develops early can be particularly damaging, whilst the crops, especially barley, can later express tolerance by producing additional, healthy roots. The regression parameters, including maximum potential yield (y‐axis intercept) and the extrapolated maximum yield loss, also varied according to the different growing conditions, including experimental treatments and other husbandry operations. These differences must be considered when assessing the economic potential of a control measure such as fungicidal seed treatment.

© 2003 Society of Chemical Industry
Co‐induction of glutathione‐S‐transferases and multidrug resistance associated protein by xenobiotics in wheat
Authors: Theodoulou Frederica L , Clark Ian M , He Xiao‐Li , Pallett Kenneth E , Cole David J , Hallahan David L
Published: January 2003

Herbicide safeners are known to protect monocotyledonous crops from herbicide injury by accelerating the metabolism of herbicides. We have investigated the effects of the safener cloquintocet‐mexyl, which protects small‐grain cereals against the graminicidal herbicide, clodinafop‐propargyl. Subtractive suppression hybridisation was used to identify wheat genes which are up‐regulated by treatment not only with cloquintocet‐mexyl but also with phenobarbital, which is known to stimulate xenobiotic metabolism in animals and plants. DNA sequences of five glutathione transferases (GSTs) belonging to three different classes and a multidrug resistance associated protein (MRP) homologue were identified in the screen. The chemical inducibility of these clones was confirmed by Northern analysis. The MRP protein was shown to be induced by treatments with cloquintocet‐mexyl and phenobarbital and to be localised to the tonoplast. Since clodinafop‐propargyl is not known to be metabolised by glutathionylation, the significance of GST induction is interpreted in terms of a generalised response to chemical stress, particularly the generation of active oxygen species.

This work establishes herbicide safeners as useful tools for the identification of genes encoding herbicide‐metabolising enzymes.

© 2003 Society of Chemical Industry
Development of a new management strategy for the control of root‐knot nematodes (Meloidogyne spp) in organic vegetable production
Authors: Atkins Simon D , Hidalgo‐Diaz Leopoldo , Kalisz Helen , Mauchline Tim H , Hirsch Penny R , Kerry Brian R
Published: January 2003

The nematophagous fungus, Pochonia chlamydosporia (Goddard) Zare & Gams, has been investigated as a potential biological control agent for use in integrated pest management strategies for Meloidogyne incognita (Kof & White) Chitwood in vegetable crops. The release of the fungus as a biological control agent requires a diagnostic method to monitor its spread in the environment and to gain knowledge of its ecology. Only molecular methods are sufficiently discriminating to enable the detection of specific isolates of fungi in soil. A method to extract DNA from soil was developed to increase the efficacy of PCR‐based diagnostic tests that use specific primers. A selected isolate of P chlamydosporia var catenulata was applied at densities similar to those that occur naturally in nematode‐suppressive soils. The fungus significantly reduced nematode infestations in soil following a tomato crop, in a strategy that combined the use of the fungus with crop rotation. The survival of the fungus in soil was also examined in controlled conditions in which it remained in soil in densities significantly greater than its original application rate for at least 5 months. Hence, it seems that populations of this fungus may be built up in soil and have significant effects on the regulation of root‐knot nematode populations.

© 2003 Society of Chemical Industry
Herbicide risk assessment for non‐target aquatic plants: sulfosulfuron – a case study
Authors: Davies Joanna , Honegger Joy L , Tencalla Francesca G , Meregalli Giovanna , Brain Philip , Newman Jonathan R , Pitchford Hannah F
Published: January 2003

Herbicides entering the aquatic environment by spray drift, run‐off and leaching to field drains may cause adverse effects on non‐target aquatic vegetation. The potential for such effects has typically been evaluated from tests with floating, monocotyledonous Lemna sp. However, concern has been expressed as to whether this species could be used to indicate potential effects on other vegetation types, particularly rooted, submerged, emergent or dicotyledonous species. In 1997, the Centre for Aquatic Plant Management undertook development of new tests based on the additional species, Glyceria maxima (Hartm) Holmb, Lagarosiphon major (Ridl) Moss and Myriophyllum spicatum L. The resulting methodology was used to assess the effects of the sulfonylurea herbicide, sulfosulfuron on these species. Data presented here demonstrate that exposure to initial sulfosulfuron concentrations of 3.33 µg litre−1 for up to 21 days was tolerated by these species and that adverse effects were observed only when plants were exposed to initial concentrations of 3.33 and 10 µg litre−1 for 70 days. As the occurrence of such high initial concentrations for long periods is unlikely in the aquatic environment, sulfosulfuron is not expected to have adverse effects on the growth of these species. This study has also demonstrated that G maxima, L major and M spicatum grown in small outdoor tanks can be used successfully to assess the effects of crop‐protection products on non‐target aquatic flora.

© 2003 Society of Chemical Industry
Mode of action and pesticidal activity of the natural product dunnione and of some analogues
Authors: Khambay Bhupinder P S , Batty Duncan , Jewess Philip J , Bateman Geoffrey L , Hollomon Derek W
Published: January 2003

This paper reports the investigation of the insecticidal and fungicidal activity of dunnione, a natural product obtained inadvertently as a by‐product of a synthesis programme. Dunnione exhibits no insecticidal activity but has an unusually broad spectrum of antifungal activity. In vitro and in vivo (preventative) activities were comparable to those of several long‐established fungicides (eg carbendazim). However, in whole‐plant assays, its eradicant activity was unexpectedly low, probably due to poor dose‐transfer from leaf surface to fungus. The level of residual activity appears to be influenced by the formulation. Finally, its potential as a lead structure was assessed, and several analogues synthesised which exhibited high activity in the in vitro assays. Mode‐of‐action studies revealed that dunnione exerts its action primarily through initiation of redox cycling. This contrasts to the activity of BTG 505, the biochemical/chemical precursor, which does not initiate redox cycling but instead exhibits both insecticidal and fungicidal activity by inhibiting mitochondrial Complex III.

© 2003 Society of Chemical Industry
Use of the normal coordinates in variational and perturbative ab initio handling of the vibronic and spin–orbit couplings in Π electronic states of linear tetra‐atomic molecules
Authors: Perić Miljenko , Stevanović Ljiljana
Published: February 2003

Avariational and a perturbative approach are developed to handle the combined effect of the vibronic and spin–orbit couplings in Π electronic states of tetra‐atomic molecules with linear equilibrium geometry. Both of them are based on the use of the normal vibrational bending coordinates. The perturbative treatment is carried out via two schemes for partition of the model Hamiltonian: In the first, the spin–orbit coupling term is treated as a perturbation; in the second, it is included in the zeroth‐order Hamiltonian. It is demonstrated that both perturbative approaches lead to the same second‐order formulae when the spin–orbit coupling constant is small compared to the bending frequency, but much larger than the splitting of potential surfaces upon bending. These approaches are used to calculate the vibronic and spin–orbit structure in the X2Π electronic state of HCCS by employing the ab initio‐computed potential energy surfaces. Complete numerical equivalence of the results obtained with the present variational approach and those generated by the algorithms employing internal vibrational coordinates is demonstrated. The restrictions concerning the applicability of the perturbative approaches are discussed in terms of the agreement between the results obtained by means of them with those generated in the corresponding variational computations. The general reliability of the model employed is checked by comparing the theoretical results with the available experimental data. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2003
A two‐dimensional self‐adaptive hydrodynamic scheme for the assessment of the effects of structures on flooding phenomena in river basins
Authors: Cioffi Francesco , Gallerano Francesco
Published: January 2003

In order to assess the effects of river and floodplain engineering projects on flooding, a new self‐adaptive hydrodynamic scheme for the simulation of two‐dimensional river flows is proposed. The depth‐averaged motion equations are solved numerically using a fractional step method, in which the convective terms are calculated using the inverse characteristics method and the remaining terms with an explicit method based on a finite difference method. The integration is performed on a dynamically self‐adaptive calculus grid, which allows representation of the movable boundary between wetting and drying regions of the basins to follow the effective development, in time and space, of the expansion phenomenon of flood. The proposed procedure allows the grid's dynamic refinement to avoid coordinate transformation or the use of unstructured grids. The proposed method is simple and allows the thickening of the grid to accommodate the flooding phenomena on the floodplain and to calculate the velocity in the domain regions in which a higher space resolution is required. Therefore, flows running through structures such as weirs, gates, bridges or culverts can be simulated. In the paper two different case studies, approached with the proposed self‐adaptive calculation scheme, are discussed. The studies concern the analysis of the effects of structures, such as roads or embankments, on flooding phenomena in the Tiber and Tanaro basins respectively. Copyright © 2003 John Wiley & Sons, Ltd.
Effects of flow regulation on disturbance frequencies and in‐channel bryophytes and macroalgae in some upland streams
Authors: Downes Barbara J. , Entwisle Timothy J. , Reich Paul
Published: January 2003

River regulation can cause various downstream changes to the physical environment of stream channels. Here, we examined whether disturbance of the stream bed and/or degree of emergence of large substrata affect the diversity and abundances of bryophytes and macroalgae in three regulated and three unregulated upland streams. We marked and mapped randomly selected rocks in situ for each stream and measured the rates at which these substrata disappeared. We recorded percentage covers of bryophytes and macroalgae in each stream on rocks of differing sizes (‘small’ <10 cm, ‘medium’ = 10–20 cm, ‘large’ >20 cm maximum top dimension) and lying either loosely on top of the bed or packed into it; we also recorded when rocks were emergent. We found strong positive associations between plant cover (mostly bryophytes) and substrate size, consistent with the hypothesis that substratum stability primarily drives bryophyte abundance. Nevertheless, highest covers of bryophytes in unregulated streams were found on emergent rocks, which tended to be large, meaning that disturbance and emergence effects were difficult to discriminate. Regulated streams did not have lower disturbance frequencies than unregulated systems. Percentage covers of plants, primarily bryophytes, were lower in regulated systems because of reduced cover on large substrata, but not small or medium ones. Together, these two pieces of evidence suggest that effects of river regulation on bryophytes were not caused by altered disturbance frequencies. A more likely explanation is that regulated streams have little of the daily or weekly rises and falls in discharge that occur in unregulated streams because of small rainfall events. Consequently, large rocks in regulated streams have only narrow zones that are subject to a variety of wetted conditions, which may be more suitable for bryophyte growth and colonization than constant submergence. Distinguishing between disturbance and emergence effects is important for setting environmental flows: alleviating the former requires more flushing flows whilst the latter requires greater temporal variability in non‐flood flows. Copyright © 2003 John Wiley & Sons, Ltd.
Beaver herbivory and its effect on cottonwood trees: influence of flooding along matched regulated and unregulated rivers
Authors: Breck Stewart W. , Wilson Kenneth R. , Andersen Douglas C.
Published: January 2003

We compared beaver (Castor canadensis) foraging patterns on Fremont cottonwood (Populus deltoidessubsp.wislizenii) saplings and the probability of saplings being cut on a 10 km reach of the flow‐regulated Green River and a 8.6 km reach of the free‐flowing Yampa River in northwestern Colorado. We measured the abundance and density of cottonwood on each reach and followed the fates of individually marked saplings in three patches of cottonwood on the Yampa River and two patches on the Green River. Two natural floods on the Yampa River and one controlled flood on the Green River between May 1998 and November 1999 allowed us to assess the effect of flooding on beaver herbivory. Independent of beaver herbivory, flow regulation on the Green River has caused a decrease in number of cottonwood patches per kilometre of river, area of patches per kilometre, and average stem density within cottonwood patches. The number of saplings cut per beaver colony was three times lower on the Green River than on the Yampa River but the probability of a sapling being cut by a beaver was still higher on the Green River because of lower sapling density there. Controlled flooding appeared to increase the rate of foraging on the Green River by inundating patches of cottonwood, which enhanced access by beaver. Our results suggest regulation can magnify the impact of beaver on cottonwood through interrelated effects on plant spatial distribution and cottonwood density, with the result that beaver herbivory will need to be considered in plans to enhance cottonwood populations along regulated rivers. Published in 2002 by John Wiley & Sons, Ltd.
Fish community alterations due to pollution and damming in Tietê and Paranapanema rivers (Brazil)
Authors: Barrella Walter , Petrere Miguel
Published: January 2003

The Tietê River crosses the metropolitan region of São Paulo (Brazil) and receives a large amount of pollution, in contrast to Paranapanema River which runs in a less populated area. In the inferior portions of the basins of these rivers, a series of reservoirs has been built for hydroelectric energy generation which improve the water quality due to the decantation of suspended soils and aeration in the water spills.

Twenty‐nine sampling sites were established along the two rivers and in each sampling site, two groups of eight gillnets were used with standardized sizes in two seasons: winter (dry season: June–September 1994) and summer (rainy season: December–March 1995). The fishes were measured and weighed.

Twenty‐five parameters related to the water were recorded. PCA and cluster analysis helped to identify two groups of sampling sites. The first one corresponds to the rainy season samples, while the second corresponds to the dry season samples, so evidencing strong seasonal environmental variation. However, the dry season group is still divided into polluted and non‐polluted sites, showing that during drought there are larger effects of pollutant concentration due to the decreased flow.

A total of 415 kg of fish were caught, corresponding to 8324 individuals belonging to 64 different species, in 22 families and four orders of Teleostei. The largest catches occurred in the middle Tietê River. The catches in the reservoirs of the Tietê River during the rainy season are superior to those of the dry season. On the other hand, sampling sites located in running water presented an inverse pattern with the largest catches in the dry season. In river Paranapanema, catches are lower than in the Tietê River, except in Rosana Reservoir during the rainy season. Fish diversity was shown to be a good indicator of environmental stress. In Tietê River an expressive fall in species richness was detected in the polluted stretches, with dominance of one or two species. In the intermediary stretches, the presence of rapids increases the amount of dissolved oxygen, allowing the development of the most abundant and diverse fish community of the river. Fish communities in the reservoirs of the inferior stretch of Tietê River are more diverse. On the other hand, the damming of the superior reaches of Paranapanema River provoked a decrease in diversity. O the whole, types of local fish communities detected, showing different compositions and specific abundances, revealed different ecological situations. A discriminant analysis revealed that the parameters of the water influencing the fish community were: dissolved oxygen, conductivity, nitrogen (nitrate, ammoniacal and albuminoid), phosphate, alkalinity, hardness and iron. Copyright © 2003 John Wiley & Sons, Ltd.
The impact of changes in teaching and learning on furniture and the learning environment
Authors: Cornell Paul
Published: January 2003

The knowledge economy is ushering in new attitudes about teaching and learning. As a result, different kinds of furniture are being specified for the classroom. These are more flexible and comfortable and do more to accommodate technology and information. Furniture also now plays a role in making learning environments more fun and dynamic, even more inspirational.
Improving the environment for learning: An expanded agenda
Authors: Van Note Chism Nancy , Bickford Deborah J.
Published: January 2003

The need for change in the design of learning spaces demands radical rethinking of many powerful traditional assumptions, yet this activity is vital to the success of higher education in the future.
Casein kinase II phosphorylates translation initiation factor 5 (eIF5) in Saccharomyces cerevisiae
Authors: Maiti Tapan , Bandyopadhyay Amitabha , Maitra Umadas
Published: January 2003

Eukaryotic translation initiation factor 5 (eIF5) interacts with the 40S initiation complex (40S–eIF3–mRNA–Met‐tRNAf–eIF2–GTP) to promote the hydrolysis of ribosome‐bound GTP. In Saccharomyces cerevisiae, eIF5 is encoded by a single‐copy essential gene, TIF5, that is required for cell growth and viability. In this work, we show that eIF5 immunoprecipitated from cell‐free extracts of 32P‐labelled yeast cells is phosphorylated on multiple serine residues. Phosphopeptide mapping reveals four major sites of phosphorylation that appear to be identical to recombinant yeast eIF5 sites phosphorylated in vitro by casein kinase II. Furthermore, analysis of eIF5 isolated from a yeast strain having a conditional mutant of casein kinase II indicates that phosphorylation of eIF5 is completely abolished at the non‐permissive temperature. Additionally, haploid yeast strains were constructed to contain Ser‐to‐Ala mutations at the five casein kinase II consensus sequences in eIF5; in these cells, eIF5 phosphorylation was absent. Surprisingly, substitution of the TIF5 gene mutated at these sites for the wild‐type gene had no obvious effect on cell growth under normal growth conditions. The implications of these results in eIF5 function are discussed. Copyright © 2002 John Wiley & Sons, Ltd.
Identification of multicopy suppressors of cell cycle arrest at the G1–S transition in Saccharomyces cerevisiae
Authors: Muñoz Ivan , Simón Ernesto , Casals Núria , Clotet Josep , Ariño Joaquín
Published: January 2003

Inactivation of HAL3 in the absence of SIT4 function leads to cell cycle arrest at the G1–S transition. To identify genes potentially involved in the control of this phase of the cell cycle, a screening for multicopy suppressors of a conditional sit4 hal3 mutant (strain JC002) has been developed. The screening yielded several genes known to perform key roles in cell cycle events, such as CLN3, BCK2 or SWI4, thus proving its usefulness as a tool for this type of studies. In addition, this approach allowed the identification of additional genes, most of them not previously related to the regulation of G1–S transition or even without known function (named here as VHS1‐3, for viable in a hal3 sit4 background). Several of these gene products are involved in phospho‐dephosphorylation processes, including members of the protein phosphatase 2A and protein phosphatases 2C families, as well as components of the Hal5 protein kinase family. The ability of different genes to suppress sit4 phenotypes (such as temperature sensitivity and growth on non‐fermentable carbon sources) or to mimic the functions of Hal3 was evaluated. The possible relationship between the known functions of these suppressor genes and the progress through the G1–S transition is discussed. Copyright © 2002 John Wiley & Sons, Ltd.
Isolation and sequencing of the Candida albicans MSI3, a putative novel member of the HSP70 family
Authors: Cho Tamaki , Toyoda Mika , Sudoh Masayuki , Nakashima Yukihiko , Calderone Richard A , Kaminishi Hidenori
Published: January 2003

We have reported previously that the expression of CGR1 increased at an early stage of the yeast–mycelial transition (morphogenesis) in Candida albicans. We now show that Cgr1p interacts in a yeast two‐hybrid system with the C. albicans Msi3p (CaMsi3p), a putative novel member of the heat shock protein 70 (HSP70) family. The DNA sequence of CaMSI3 encodes a predicted protein of 702 amino acids with a molecular mass of 78.6 kDa. The amino acid sequence of CaMsi3p is 63% identical to Msi3p/Sse1p of the HSP70 family of Saccharomyces cerevisiae. Further, CaMSI3 complemented the temperature‐sensitive phenotype of the msi3− mutant of S. cerevisiae. Other heat shock proteins of C. albicans are required for morphogenesis and are highly antigenic. These observations suggest that CaMSI3 may well provide functions for this organism unrelated to a heat shock function. The DDBJ Accession No. for the sequence reported in this paper is AB061274. Copyright © 2002 John Wiley & Sons, Ltd.
Identification of novel protein–protein interactions at the cytosolic surface of the Sec63 complex in the yeast ER membrane
Authors: Willer Martin , Jermy Andrew J. , Young Barry P. , Stirling Colin J.
Published: January 2003

Precursors of secretory proteins are targeted to the membrane of the endoplasmic reticulum by specific protein complexes that recognize their signal sequence. All eukaryotic cells investigated so far have been found to possess the signal recognition particle (SRP) that targets the majority of precursors to the translocation machinery. In Saccharomyces cerevisiae a number of proteins are translocated independently of SRP. These precursors rely on a different signal sequence‐binding complex, which includes Sec62p, Sec63p, Sec71p and Sec72p. Identifying interactions between individual components of this tetrameric protein complex is important in the understanding of its function. We demonstrate a specific interaction between the only two essential proteins in this complex, Sec62p and Sec63p. Second, we show evidence of homodimerization of Sec72p molecules and further identify the YLR301w gene product as a novel in vivo interacting partner of Sec72p. Finally, we determine the authentic N‐terminus of Sec62p and describe interacting subdomains of both Sec62p and Sec63p. Copyright © 2002 John Wiley & Sons, Ltd.
Metabolic flux analysis of RQ‐controlled microaerobic ethanol production by Saccharomyces cerevisiae
Authors: Franzén Carl Johan
Published: January 2003

Microaerobic ethanol production by Saccharomyces cerevisiae CBS 8066 was investigated at different growth rates in respiratory quotient (RQ)‐controlled continuous culture. The RQ was controlled by changing the inlet gas composition by a feedback controller while keeping other parameters constant. The ethanol yield increased slightly from the anaerobic values with decreasing RQ, reaching a broad maximum at RQ 20 to 12. There was little or no glycerol production at RQ values below 17 over a wide range of dilution rates. Metabolic flux analysis revealed that a decrease in the ethanol yield at RQ 6 coincided with the cyclic, oxidative operation of the TCA cycle reactions. The model indicated that respiratory dissimilation of glucose only occurs when the oxygen uptake rate is high enough to completely substitute for glycerol formation. The cytosolic and the mitochondrial NADH balances were important for determining the flux distributions. The smallest deviations between estimated and measured product yields were obtained when the unknown co‐factor requirements of a limited number of biosynthetic reactions were chosen so that the amount of excess NADH formed in biosynthesis was minimized. The biomass yield was positively correlated with the net amount of NADH reoxidized in respiration and glycerol formation, indicating that the turnover of excess NADH from biosynthesis is an important factor influencing the biomass yield under oxygen‐limiting conditions. Copyright © 2002 John Wiley & Sons, Ltd.
Love-Hate for Man-Machine Metaphors in Soviet Physiology: From Pavlov to “Physiological Cybernetics”
Authors: Gerovitch Slava
Published: February 2003

Argument

Every new level achieved by technology attracted the attention of physiologists and turned their thoughts in a new direction; they often unwittingly modeled life processes in the image of contemporary engineering achievements.

–(Nikolay Bernshteyn [1958] 1997, 392)

This article reinterprets the debate between orthodox followers of the Pavlovian reflex theory and Soviet “cybernetic physiologists” in the 1950s and 60s as a clash of opposing man-machine metaphors. While both sides accused each other of “mechanistic,” reductionist methodology, they did not see anything “mechanistic” about their own central metaphors: the telephone switchboard metaphor for nervous activity (the Pavlovians), and the analogies between the human body and a servomechanism and between the human brain and a computer (the cyberneticians). I argue that the scientific utility of machine analogies was closely intertwined with their philosophical and political meanings and that new interpretations of these metaphors emerged as a result of political conflicts and a realignment of forces within the scientific community and in society at large. I suggest that the constant travel of man-machine analogies back and forth between physiology and technology has blurred the traditional categories of the “mechanistic” and the “organic” in Soviet neurophysiology, as perhaps in the history of physiology in general.
On Heyes' IS–LM–EE proposal to establish an environmental macroeconomics
Authors: Lawn Philip A.
Published: January 2003

A decade has now passed since Daly made a plea for an environmental macroeconomics. Despite an expanding literature on ‘green’ national accounting and the efforts of ecological economists to measure the sustainable net benefits of a growing macroeconomy, it is only recently that Daly's plea has been adequately answered. This has been achieved with the incorporation by Heyes of an ‘environmental equilibrium’ or EE curve into the familiar IS–LM model. However, the IS–LM–EE model proposed by Heyes is incomplete. By extending Heyes' model to include the role of technological progress and the sustainable net benefits of economic activity, this paper shows that conclusions regarding the desirability of expansionary fiscal and monetary policies alter quite radically. Moreover, it sends out a clear message that environmental concerns should be incorporated into macroeconomic models. They should not be solely confined to microeconomics.
Land tenure and the management of land and trees: the case of customary land tenure areas of Ghana
Authors: Otsuka Keijiro , Quisumbing Agnes R. , Payongayong Ellen , Aidoo J.B.
Published: January 2003

This study explores the effects of land tenure institutions on land use and management using household date from cocoa growing areas of Ghana. Various land tenure institutions with different land rights coexist in our sites, such as allocated family land, inherited land, appropriated village land, and land received as gift. While tree planting and the decision to leave land fallow may be affected by land tenure status, there are no significant differences in labor allocation and revenue of both cocoa and food crops among parcels under different land tenure institutions. These results support the hypothesis that management incentives of cocoa fields, but not food crop fields, tend to be equalized due to the incentive-enhancing effects of granting secure land rights after efforts to plant cocoa trees are expended.
The development impact of genetic use restriction technologies: a forecast based on the hybrid crop experience
Authors: Goeschl Timo , Swanson Timothy
Published: January 2003

Advances in biotechnology have made available gene-manipulation techniques that enable the protection of genetic material from unauthorized use and the prevention of self-supply of commercial seeds by farmers—in order to allow enhanced appropriation of the values of innovation in agricultural R&D. These techniques have become known as Genetic Use Restriction Technologies (GURTs).

This paper forecasts the potential impact of wide-spread adoption of GURTs by the providers of HYV seeds on the yield development in developing countries. To do so, it assesses (1) the effects of enhanced appropriation through GURTs on the technological expansion at the yield frontier and (2) the effects of technological protection of value-adding traits through GURTS on the diffusion of yield gains from the frontier to developing countries. These assessments are based on a particular hypothesis, which is that GURTs will replicate across most staple crops the experiences that were made with a previous use restriction technology (hybridization) in only a few crops. The estimation of impacts is carried out as a simulation and is based on expansion and diffusion parameters estimated for hybrid seeds over a 38-year period. It shows that the impact of GURTs on developing countries' yields will vary considerably. Specifically, those countries that currently have the lowest yields would be most adversely affected in their future yield development by the wide-spread use of GURTs.
Monopolization and the regulation of genetically modified crops: an economic model
Authors: Munro Alistair
Published: January 2003

Although genetically modified organisms (GMOs) have recently attracted a great deal of public attention, analysis of their economic impact has been far less common. This paper puts forward variants of a simple model of crop production, each one tailored to a particular aspect of transgenic food technology. The focus is on the possibility of monopolization and its consequential welfare costs. Risk factors identified include moderate cost savings from transgenic varieties, high seed storage costs, and high risks of crop loss. The paper also discusses some of the possible remedies including tighter regulation of anti-competitive practices and liberalization of the regulations governing the introduction of new GMOs.
The architecture of the bilingual word recognition system: From identification to decision
Authors: Dijkstra Ton , van Heuven Walter J.B.
Published: January 2003

The paper opens with an evaluation of the BIA model of bilingual word recognition in the light of recent empirical evidence. After pointing out problems and omissions, a new model, called the BIA+, is proposed. Structurally, this new model extends the old one by adding phonological and semantic lexical representations to the available orthographic ones, and assigns a different role to the so-called language nodes. Furthermore, it makes a distinction between the effects of non-linguistic context (such as instruction and stimulus list composition) and linguistic context (such as the semantic and syntactic effects of sentence context), based on a distinction between the word identification system itself and a task/decision system that regulates control. At the end of the paper, the generalizability of the BIA+ model to different tasks and modalities is discussed.
Phonological activation in bilinguals: Evidence from interlingual homograph naming
Authors: Jared Debra , Szucs Carrie
Published: January 2003

This study investigated whether bilinguals simultaneously activate phonological representations from both of their languages when reading words in just one. The critical stimuli were interlingual homographs (e.g., PAIN) that were low in frequency in the target language of the study (English) and high in frequency in the nontarget language (French). Both English-French and French-English bilinguals were tested. In each experiment, participants named a block of English experimental words, a block of French filler words, and then a second block of English experimental words. In the first block of English trials, the English-French bilinguals had similar naming latencies for homographs and English-only control words, although they made more errors on homographs. In contrast, the French-English bilinguals showed a homograph disadvantage in both the latency and error data. In the second block of English trials, both the English-French bilinguals and the French-English bilinguals showed homograph interference on latency and error measures. We interpret these results as indicating that the activation of phonological representations can appear to be both language-specific and nonspecific, depending on the characteristics of the bilingual and whether they have recently named words in the nontarget language.
The cost of switching language in a semantic categorization task
Authors: von Studnitz Roswitha E. , Green David W.
Published: January 2003

German-English bilinguals decided whether a visually presented word, either German or English, referred to an animate or to an inanimate entity. Bilinguals were slower to respond on a language switch trial than on language non-switch trials but only if they had to make the same response as on the prior trial (e.g., two successive “animate” responses). If they had to change their response from the prior trial, a switch of language speeded responses. This interaction between language switching and response type was abolished for the translations of words previously presented. We consider the implications for theories of language control.
On the temporal delay assumption and the impact of non-linguistic context effects
Authors: Brysbaert Marc , van Wijnendaele Ilse , Duyck Wouter
Published: January 2003

It is not easy to comment on Dijkstra and Van Heuven's model because there are many more aspects we agree with than aspects we feel uncomfortable about. Indeed, the BIA model has played an enormous role in showing us how bilingual visual word recognition can be achieved without recurrence to the intuitively appealing – but wrong – ideas of separate, language-specific lexicons and language-selective access. As in many other research areas, a working computational model has been much more influential in convincing critical readers (and researchers) than any series of empirical findings. The BIA+ model inherits this strength and, hopefully, in the coming years will be implemented in enough detail to exceed its predecessor. In the rest of this comment, we would like to put a cautionary note behind the temporal delay assumption introduced in the target article and provide some additional corroborating evidence for the lack of non-linguistic effects on early processes in the identification system.
The BIA++: Extending the BIA+ to a dynamical distributed connectionist framework
Authors: Jacquet Maud , French Robert M.
Published: January 2003

Dijkstra and van Heuven have made an admirable attempt to develop a new model of bilingual memory, the BIA+. Their article presents a clear and well-reasoned theoretical justification of their model, followed by a description of their model. The BIA+ is, as the name implies, an extension of the Bilingual Interactive Activation (BIA) model (Dijkstra and van Heuven, 1998; Van Heuven, Dijkstra and Grainger, 1998; etc), which was itself an adaptation to bilingual memory of McClelland and Rumelhart's (1981) Interactive Activation model of monolingual memory.
How do bilinguals control their use of languages?
Authors: Roelofs Ardi
Published: January 2003

Dijkstra and Van Heuven sketch the BIA+ model for visual word processing in bilinguals. BIA+ differs in a number of respects from its predecessor, BIA, the leading implemented model of bilingual visual word recognition. Notably, BIA+ contains a new processing component that deals with task demands. BIA+ has not been computationally implemented yet and design decisions still need to be taken. In this commentary, I outline a proposal for modeling the control of tasks in BIA+.
Theories that develop
Authors: Thomas Michael S. C.
Published: January 2003

The target article represents a significant advance in the level of sophistication applied to models of bilingual word recognition, and Dijkstra and van Heuven are to be congratulated on this endeavour. Bearing in mind the success of the (computational) BIA model in capturing detailed patterns of experimental data, I look forward to future simulation results from the BIA+ when the proposals of this new framework are implemented. It is an essential step to draw a distinction between recognition systems and the decision mechanisms that drive responses, and the authors have provided a novel way of apportioning empirical evidence of context effects in bilingual word recognition across this divide. Given the explanatory weight now being placed on decision mechanisms rather than the word recognition system itself, perhaps indeed it is now time to make some simplifying assumptions about the recognition system and start building detailed computational models of the decision component of the system. Implementation will provide the clarity of theorisation and evaluation of theory viability that have been the hallmark of the BIA model thus far.
Stability‐induced modification of sea surface winds over Gulf Stream rings
Authors: Park Kyung‐Ae , Cornillon Peter C.
Published: January 2003

Satellite‐borne scatterometer and infrared data collected over Gulf Stream warm and cold core rings are used to study the effect of the sea‐air temperature difference on the wind speed over rings. The observed acceleration of the wind over warm core rings and deceleration over cold core rings is found to be consistent with that predicted by the planetary boundary layer model of Brown and Foster [1994]. In addition it is shown that the distance over which the winds respond to an ocean surface temperature step is short (≤25km) while the distance over which the marine boundary layer responds to a surface temperature step is long (≥175km).
Detailed analysis of a substorm event on 6 and 7 June 1989: 2. Stepwise auroral bulge evolution during expansion phase
Authors: Kadokura Akira , Yukimatu Akira‐Sessai , Ejiri Masaki , Oguti Takasi , Pinnock Michael , Sutcliffe Peter R.
Published: January 2003

We have analyzed in detail the auroral bulge evolution during the expansion phase of an isolated substorm, which was observed by the UV imager aboard the Akebono satellite. It was found that there were three distinct stages in the evolution. Stage 1 was characterized by rapid poleward and azimuthal (predominantly westward) expansions in a short time (about 2 min). Stage 2 was characterized by a very slow poleward and slower and continuous azimuthal expansions. There was a certain period for transition between stage 1 and stage 2, and it was characterized by a very slow poleward and rapid eastward expansions. Stage 3 started about 11 min after the onset and was characterized by a sudden reactivation of the rapid poleward and azimuthal expansions. The reactivation started around the initial onset meridian and then spread both eastward and westward. At the azimuthal front, the expansion first occurred at the lowest latitudes, spread poleward to around the highest latitudes of stage 1, and then spread further poleward after a brief interval. Hence, the local expansion also had three distinct stages similar to the global one. The ground‐based observations showed that the highest latitude of the local first stage was very close to the latitude of auroral activity that appeared near the ionospheric plasma sheet boundary layer (PSBL) region a few minutes before the onset. The further poleward expansion during the local third stage started with a significant intensification of the poleward‐most auroral activity. During the local third stage, the bright electron auroral region was bifurcated into a poleward expanding part and an equatorward moving part. The proton auroral emission coexisted in the bulge during the local first and second stages and almost disappeared soon after the bifurcation during the local third stage. Based on these observations, we discuss the evolution in the magnetosphere during the expansion phase.
Nonradiating sources, the Aharonov‐Bohm effect, and the question of measurability of electromagnetic potentials
Authors: Marengo Edwin A. , Ziolkowski Richard W.
Published: January 2003

A new characterization of nonradiating (NR) sources is derived that is based on electromagnetic potentials. In the new description a hierarchy of NR sources is systematically created that includes certain nonlocalized NR sources having the property that their curl is localized. The important class of spatially localized NR sources, whose fields vanish everywhere in the exterior of the source, corresponds to a special case of the general theory. The new NR source developments are discussed in connection with the question of measurability of electromagnetic potentials as enabled by the Aharonov‐Bohm (A‐B) effect, whereby quantum mechanical effects of the potentials can be observed in regions of vanishing electromagnetic fields but nonvanishing electromagnetic potentials. A necessary condition is derived for an electrodynamic A‐B effect in the exterior of a spatially localized NR source. By exploring this condition, it is concluded that for time‐varying, information‐carrying fields (as required, e.g., in communications and remote sensing applications) the required A‐B conditions of vanishing fields and nonvanishing potentials are not possible in the exterior of a NR source; i.e., electrodynamically, if the fields vanish everywhere outside the source, then the potentials also vanish there. This does not necessarily hold under static conditions in which nontrivial potentials with physically observable quantum effects can exist in the exterior of a source having zero external fields.
Analysis of temperature profiles for investigating stream losses beneath ephemeral channels
Authors: Constantz Jim , Stewart Amy E. , Niswonger Richard , Sarma Lisa
Published: January 2003

Continuous estimates of streamflow are challenging in ephemeral channels. The extremely transient nature of ephemeral streamflows results in shifting channel geometry and degradation in the calibration of streamflow stations. Earlier work suggests that analysis of streambed temperature profiles is a promising technique for estimating streamflow patterns in ephemeral channels. The present work provides a detailed examination of the basis for using heat as a tracer of stream/groundwater exchanges, followed by a description of an appropriate heat and water transport simulation code for ephemeral channels, as well as discussion of several types of temperature analysis techniques to determine streambed percolation rates. Temperature‐based percolation rates for three ephemeral stream sites are compared with available surface water estimates of channel loss for these sites. These results are combined with published results to develop conclusions regarding the accuracy of using vertical temperature profiles in estimating channel losses. Comparisons of temperature‐based streambed percolation rates with surface water‐based channel losses indicate that percolation rates represented 30% to 50% of the total channel loss. The difference is reasonable since channel losses include both vertical and nonvertical component of channel loss as well as potential evapotranspiration losses. The most significant advantage of the use of sediment‐temperature profiles is their robust and continuous nature, leading to a long‐term record of the timing and duration of channel losses and continuous estimates of streambed percolation. The primary disadvantage is that temperature profiles represent the continuous percolation rate at a single point in an ephemeral channel rather than an average seepage loss from the entire channel.
Plankton distribution spectra: inter‐size class variability and the relative slopes for phytoplankton and zooplankton
Authors: Martin A. P. , Srokosz M. A.
Published: January 2003

Transects of a region of the North Atlantic, conducted in spring 1997, provide simultaneous measurements of a number of biophysical variables. These data are used to quantify the degree of spatial heterogeneity in the horizontal distributions of zooplankton, phytoplankton and potential temperature. More specifically, the spectral slope is calculated for the distribution of chlorophyll a, potential temperature and individual size‐classes of zooplankton. A comparison of the estimated slopes provides the first evidence, from continuous measurements, that the gradient of zooplankton spectra may vary according to the size of the organism and, furthermore, that it may be steeper than that for phytoplankton both as an individual size class (500–1000 μm) and as an ensemble (250–2000 μm). The latter result is the exact opposite of conventional wisdom founded on previous observations. Our results highlight significant deficiencies in current models for plankton patchiness.