bluuebunny/crossref_metadata_2025 huggingface dataset:
Welfare effects of maize technologies in marginal and high potential regions of Kenya
Authors: Karanja D.D. , Renkow M. , Crawford E.W.
Published: August 2005

This paper describes the findings of a study that used a multi‐market model to assess the potential impact of improved maize technologies on the welfare of various types of rural and urban households in Kenya. The modelling results indicate that technologies developed for high potential regions are likely to have more profound aggregate impacts on maize production and lead to greater reductions in import demand (if prices are controlled) or maize prices (if maize prices are flexible). Technology adoption in high potential regions is likely to have substantially greater positive impacts on aggregate real incomes, but inferior income distributional outcomes compared to technology adoption in marginal regions.
Is research on marginal lands catching up? The case of unfavourable wheat growing environments⋆
Authors: Lantican M.A. , Pingali P.L. , Rajaram S.
Published: August 2005

It is widely believed that the Green Revolution had very little effect in unfavourable or marginal environments. Many researchers have been concerned about the slow progress of technical change in marginal environments and the level of research resources allocated to these areas. This paper provides empirical evidence that there has been significant growth in wheat yield potential in marginal environments, especially during the post‐Green Revolution. International yield trial data, covering all major wheat growing environments from 1964 to 1999, were used in estimating the growth in wheat yield potential and changes in yield variability. The global database on wheat varietal adoption and yield gains based on estimated wheat yield growth rates were used to determine production increases due to wheat breeding research. Results show greater progress in shifting the wheat yield frontier in marginal areas, particularly in drought and high temperature environments. Furthermore, yield variability in marginal environments has notably declined, while it has increased slightly in favourable environments. While initial gains came from crossover of varieties from favourable environments, targeted breeding efforts have contributed significantly to more recent productivity growth in marginal environments. Increased production from marginal environments accounted for around 25% of the total wheat production increase in 1997. These findings show greater progress in wheat research and the huge potential of improving wheat productivity in unfavourable environments.
Farm productivity and efficiency in the CEE applicant countries: a synthesis of results
Authors: Gorton Matthew , Davidova Sophia
Published: August 2005

This article draws together results from farm efficiency studies in six Central and East European countries that are part of the EU enlargement process. The main questions addressed concern whether there is a clear superiority of one organisational type, namely, family farms, over corporate structures (production co‐operatives and various types of farming companies) and the nature of the relationship between size and farm efficiency. Results from empirical research show that there is no clear cut evidence of corporate farms being inherently less efficient for all farming activities than family farms. Where significant differences have been found in favour of family farms against the average corporate farm, the best corporate farms still tend to perform as well as the best family farms. As far as size in concerned, in countries in transition where small family farms are well established and managed continuously by the present farm household, they appear to be less inefficient compared to larger cohorts as against countries where small family farms are a relatively new phenomenon.
Land degradation, drought and food security in a less‐favoured area in the Ethiopian highlands: a bio‐economic model with market imperfections
Authors: Holden Stein , Shiferaw Bekele
Published: August 2005

This paper presents a bio‐economic model of Andit Tid, a severely degraded crop‐livestock farming system with high population density and good market access in the highlands of Ethiopia. Land degradation, population growth, stagnant technology, and drought threaten food security in the area. Drought or weather risk appears to have increased in recent years. The bio‐economic model is used to analyse the combined effects of land degradation, population growth, market imperfections and increased risk of drought on household production, welfare and food security. We find that the indirect effects of drought on household welfare through the impact on crop and livestock prices are larger than the direct production effects of drought. Provision and adoption of credit for fertiliser, although risky in itself, may lead to increased grain production and improved household welfare and food security. Provision of credit may have a negative effect on conservation incentives but this effect may be mitigated by linking a conservation requirement to the provision of credit for fertiliser.
Distributive leakages of agricultural support: some empirical evidence
Authors: Salhofer Klaus , Schmid Erwin
Published: August 2005

The paper evaluates the transfer efficiency of the Austrian bread grain policy taking into account distributive leakages, i.e. how much of the transfers officially intended to support farm income are finally realised in the upstream and downstream industries. Gardner's [Am. J. Agric. Econ. 65 (1983) 225] well‐known measure of average transfer efficiency (ATE) is augmented for the case of more than two social groups and computer‐intensive simulation procedures are utilised to deal with parameter uncertainty.
Public investment and regional inequality in rural China
Authors: Zhang Xiaobo , Fan Shenggen
Published: August 2005

This paper develops a method for decomposing the contributions of various types of public investment to regional inequality and applies the method to rural China. Public investments are found to have contributed to production growth in both the agricultural and rural non‐agricultural sectors, but their contributions to regional inequality have differed by type of investment and the region in which they are made. All types of investment in the least‐developed western region reduce regional inequality, whereas additional investments in the coastal and central regions worsen regional inequality. Investments in rural education and agricultural R&D in the western region have the largest and most favorable impacts on reducing regional inequality.
Investment and equity effects of land regularisation: the case of Nicaragua⋆
Authors: Deininger Klaus , Chamorro Juan Sebastian
Published: August 2005

We use data from Nicaragua to examine the impact of award of registered and non‐registered title on land values and changes in land‐attached investment. Registration, acquisition through purchase, and agrarian reform title all are associated with significant increases in the value of plots. Receipt of registered title is found to increase land values by 30% and at the same time greatly increase the propensity to invest, bringing such investment closer to the optimum. In line with descriptive statistics indicating great demand for land right regularisation especially from the poor, this suggests that titling can have a positive distributional effect. At the same time, the legal validity and official recognition of the titles issued appears to be of great importance.
Short‐term employment transitions of the Canadian labour force: rural‐urban differences in underemployment
Authors: Vera‐Toscano Esperanza , Phimister Euan , Weersink Alfons
Published: August 2005

Using data from the Canadian Survey of Labour and Income Dynamics (SLID) for the period 1993–1996, we examine patterns and determinants of labour‐force transitions of adequately employed and underemployed workers in an attempt to explore whether employment dynamics significantly differ between rural and urban workers so as to disadvantage rural economic performance. The results indicate that rural adequately employed workers are significantly more likely to enter underemployment but once they are underemployed, they also have a higher probability of re‐entering adequate employment. Further, we also found weak evidence that the education level of workers has a lower impact on the probability of moving out of underemployment in rural than in urban areas. In addition, rural women are significantly less likely than their male counterparts and urban workers to enter adequate employment, although the presence of young children does not seem to especially constrain the employment of rural women. The results suggest that labour‐force transition in and out of adequate employment, and particularly underemployment, significantly differ between rural and urban workers and should be taken into account when evaluating employment hardship in rural Canada.
The impact of seed industry concentration on innovation: a study of US biotech market leaders
Authors: Schimmelpfennig David E. , Pray Carl E. , Brennan Margaret F.
Published: August 2005

Agricultural research drives increases in agricultural productivity, and the number of private agricultural input firms has been declining. The empirical relationship between the number of firms doing applied biotechnology crop research and the amount of research output they produce is investigated in a research profit function model. Increases in seed industry concentration have reduced biotech research intensity in the United States in the 1990s. Concentration and research are simultaneously determined and are influenced by the appropriability of research results and the state of technological opportunity.
Agricultural diversification and integrated pest management in Bangladesh
Authors: Mahmoud Chowdhury , Shively Gerald
Published: August 2005

We study factors associated with a shift toward diversified, high‐valued vegetable crops and the incentives associated with the use of IPM methods for vegetable producers in Bangladesh. The primary objective is to measure how IPM technologies affect the crop and technology choices of low‐income rice farmers. A three‐season household optimisation model is used to study crop and technology choice under price and yield uncertainty. The model is parameterised using data from vegetable farms and experimental IPM trials conducted in Bangladesh. Simulation results show that access to IPM technology and IPM availability combined with access to credit increase household welfare and lead to higher rates of vegetable adoption. Off‐farm employment opportunities work against vegetable cultivation and IPM use by risk‐averse farmers. Implications for policy and extension efforts are highlighted.
Consumer preferences for cowpea in Cameroon and Ghana
Authors: Langyintuo A.S. , Ntoukam G. , Murdock L. , Lowenberg‐DeBoer J. , Miller D.J.
Published: August 2005

Consumer preference information is essential to targeting research. This paper reports an effort of a multi‐disciplinary team to measure the market value of cowpea characteristics. Five samples were purchased once per month in seven markets in Ghana and Cameroon starting in September 1996. In the market, price and vendor characteristics were noted. In the laboratory, size of grains, testa color, testa texture, eye color and damage levels were recorded. A hedonic pricing regression model was used. Results indicate that grain size is the most important characteristic. Consumers seem more sensitive to bruchid (Callosobruchus maculates) damage than hypothesized. Cowpeas with white testa command a clear premium only in one of the Ghanaian markets. In Ghana, black eyes sell at a premium, but in Cameroon black eyes are discounted. In general, this study indicates that quality characteristics are very important in West African food markets. Even low income consumers are willing to pay a premium for products that match their preferences, and they are vigilant in identifying products that do not meet their standards. Purchasing samples on a regular basis and hedonic pricing offers a practical way for biological scientists and economists to work together to measure these consumer preferences.
The role of education on the adoption of chemical fertiliser under different socioeconomic environments in Ethiopia
Authors: Asfaw Abay , Admassie Assefa
Published: August 2005

Studies on input adoption consider education as one of the most important factors that affect adoption decisions. However, very little is known about the spill‐over effect of intra‐household education on the adoption process and about the impact of education on adoption decisions under different socioeconomic conditions. We investigate these two issues using a discrete choice model. The results indicate that the decision making process is a decentralised one in which educated adult members of the household actively participate in the decision making process. This casts doubt on the traditional assumption that the household head is the sole decision maker. The results reveal that there is a substantial and statistically significant intra‐household spill‐over effect of education on the adoption decision of households. The results of the study also show that the coefficient of the education and the environment interaction variable is negative and statistically significant. This demonstrates that education and socioeconomic environments could be substitutes in modern environments and complementary in traditional ones. This implies that the expansion of education in traditional areas may be more attractive than in modern areas since education is usually the only means to enhance the ability of farmers to acquire, synthesise and respond to innovations such as chemical fertiliser.
Credit market access and profitability in Tunisian agriculture
Authors: Foltz Jeremy D.
Published: August 2005

This work develops an econometric model that links credit access with agricultural profitability and investment. Using data collected from rural Tunisia, this work provides direct estimates of credit access and its effects. Econometric estimates are run for agricultural investment and profitability as a function of credit access. The investigation of credit access and its effect suggests that the presence of credit market constraints does impinge significantly on farm profitability, but not on investments.
Agriculture, pesticides and the ecosystem
Authors: Pethig Rüdiger
Published: August 2005

Economists have a good understanding of intra‐economic interdependence and a mature methodology of modelling it. Ecologists focus on the complex and sensitive interactions of species in ecosystems. This paper's objective is to suggest a new micro‐foundation of ecosystem analysis based on economic methodology, to integrate the analyses of the ecosystem and the economy and focus on the interface of ecosystem‐economy relations. Agriculture forms a major part of this interface. The basic assumption is that in the short run the individual organisms of all species behave as if they optimise their costly offensive and defensive activities given other organisms' activities (Nash‐behaviour).

We consider an ecosystem with three species in a unidirectional food chain: buzzards feed on mice, mice feed on grain, and grain feeds on solar energy. A fourth species, humans, also feeds on grain. Humans intervene in the ecosystem in various ways. They can grow grain by using seed, farm labour, pesticides and possibly nature conservation measures to maintain buzzard habitat. Short‐run ecosystem equilibrium is characterised, and it is shown, in particular, how this equilibrium depends on farming activities. We then link this ecosystem model to a simple model of an agricultural economy. Both systems are solved for equilibrium simultaneously. From an economic perspective the ecosystem induces positive and negative externalities in agricultural production and in consumer ‘green’ preferences.

The inefficiencies of the competitive economy are identified and some possibilities to restore efficiency through corrective taxes or subsidies are briefly discussed. We also outline how short‐run equilibria are connected through ecosystem stock‐flow relationships. Due to the complexity of the inter‐temporal analysis, the resulting ecosystem dynamics cannot be characterised in general analytical terms. It is a topic for future research to study the dynamics in numerical analysis to understand under which conditions the joint ecological and economic system is driven toward a (sustainable) steady state.
Rural–urban migration and agricultural productivity: the case of Senegal
Authors: Goldsmith Peter D. , Gunjal Kisan , Ndarishikanye Barnabé
Published: August 2005

This paper explores the relationship between agricultural productivity and rural–urban migration by developing an econometric model and applying it to the case of Senegal. Country level data is used covering the years 1961–1996. Policy implications of reducing rural‐urban migration using agricultural output elasticities are developed. The findings support the hypothesis that rural–urban migration is a positive function of the ratio of urban per capita income to rural per capita income. Moreover, the results support a policy aimed at reducing rural–urban migration flows through increases in per capita earnings derived from increased agricultural investment.
Irrigation water pricing: differential impacts on irrigated farms
Authors: Gómez‐Limón Jose A. , Riesgo Laura
Published: August 2005

European water policy, as set out in the Water Framework Directive (WFD), requires all EU Member States to implement volumetric water pricing at rates that roughly cover the total costs of providing water services. The objective of this paper is to develop a methodology that, for the different types of farm in an irrigable area, will enable us to analyse the differential impact that a pricing policy for irrigation water would have. For this purpose, Multi‐Attribute Utility Theory (MAUT) mathematical programming models were used. The methodology is implemented on a representative area in the Duero Valley in Spain. Our results show the usefulness of differential analysis in evaluating the impact of a water pricing policy. This allows significant differences in the evolution of agricultural incomes to be observed, as well as the recovery of costs by the State, demand for agricultural employment and the consumption of agrochemicals resulting from rising prices of irrigation water in various groups of farmers within a given irrigated area.
Calculating the cost of irrigation induced soil salinization in the tungabhadra project
Authors: Janmaat John
Published: August 2005

Irrigation projects in developing countries have a history of poor performance. Inefficiencies result as water applications deviate from plans and induce greater than projected rates of soil degradation through water logging and salt accumulation. Over time, the collective impact of these forces will converge to an equilibrium with a level of output that may be far below the system's potential. The Tungabhadra Project in south west India is experiencing all of these problems. Integrating geographic, hydrologic, biologic and economic features, the lost production value is estimated for a range of equilibria to which this system may converge. For the lower left bank main canal of the Tungabhadra project, the total economic cost of soil degradation are approximately 14.5% of the system's productive potential while sub‐optimal distribution losses may approach 37.1%
A revised Tobit procedure for mitigating bias in the presence of non‐zero censoring with an application to milk‐market participation in the Ethiopian highlands
Authors: Holloway Garth , Nicholson Charles , Delgado Chris , Staal Steve , Ehui Simeon
Published: August 2005

Fixed transactions costs that prohibit exchange engender bias in supply analysis due to censoring of the sample observations. The associated bias in conventional regression procedures applied to censored data and the construction of robust methods for mitigating bias have been preoccupations of applied economists since Tobin [Econometrica 26 (1958) 24]. This literature assumes that the true point of censoring in the data is zero and, when this is not the case, imparts a bias to parameter estimates of the censored regression model. We conjecture that this bias can be significant; affirm this from experiments; and suggest techniques for mitigating this bias using Bayesian procedures. The bias‐mitigating procedures are based on modifications of the key step that facilitates Bayesian estimation of the censored regression model; are easy to implement; work well in both small and large samples; and lead to significantly improved inference in the censored regression model. These findings are important in light of the widespread use of the zero‐censored Tobit regression and we investigate their consequences using data on milk‐market participation in the Ethiopian highlands.
Avoidant personality disorder and social phobia: distinct enough to be separate disorders?
Authors: Ralevski E. , Sanislow C. A. , Grilo C. M. , Skodol A. E. , Gunderson J. G. , Tracie Shea M. , Yen S. , Bender D. S. , Zanarini M. C. , McGlashan T. H.
Published: August 2005

Objective:  Existing evidence from anxiety disorder research indicates that social phobics (SP) with avoidant personality disorder (AVPD) experience more anxiety and show more impairment than patients with SP alone. The purpose of this study was to examine whether in patients diagnosed with AVPD, the co‐occurrence of SP adds to its severity. We hypothesized that the addition of SP will not add to the severity of AVPD alone.

Method:  Two groups of patients (AVPD = 224; AVPD/SP = 101) were compared at baseline and 2 years later on multiple demographic and clinical variables.

Results:  Patients with AVPD and an additional diagnosis of SP differed little from patients with AVPD alone.

Conclusion:  These findings suggest that AVPD and SP may be alternative conceptualizations of the same disorder.
The Hypothalamus and Primary Headache Disorders
Authors: Gourineni Ramadevi , Zee Phyllis C.
Published: August 2005

A prominent feature of primary headache disorders is the diurnal variation in their timing, and their relationship to sleep. In particular, the temporal and seasonal distribution of cluster headaches and accompanying hormonal changes in migraine, indicate that the circadian system and other sleep and wake generating areas in the hypothalamus may play an important role in their pathophysiology. This article provides a review of the basic neurobiology of circadian rhythms and sleep and its potential implications for understanding the central triggers of some primary headache disorders. The strongest and most direct evidence for a role of the hypothalamus in cluster headache derives from functional brain imaging studies. Furthermore, alteration in the timing and amplitude of hormonal circadian rhythms point to a possible role of the suprachiasmatic nucleus (SCN) in cluster headaches. Improved understanding of the relationship between circadian rhythms, sleep and primary headache disorders is an exciting area of investigation which could lead to innovative circadian and sleep based treatment strategies.
IDENTIFICATION OF IMPORTANT PRODUCTION VARIABLES AFFECTING HARD PRETZEL QUALITY
Authors: YAO N. , FLOROS J.D. , SEETHARAMAN K.
Published: August 2005

The objective of this study was to determine the importance of raw material and processing variables that influence pretzel quality by utilizing a screening experiment design. Eleven variables were selected based on preliminary experiments, and a two‐level‐11‐factor (2

11

) fractional factorial experimental design was used to screen the variables. Several responses were measured for dough before and after extrusion, for half‐baked and fully baked pretzels. These responses are important indicators of consistency and quality during pretzel processing. Results indicated that flour protein content, the amount of water added to make dough and dough mixing time were important variables influencing dough behavior. Caustic concentration affected brightness of half‐baked pretzels but did not influence the color of the final product. Baking time was the most important factor for both half‐baked product and final product qualities. The hardness of fully baked pretzels was influenced by baking time, temperature in baking oven zone 1, drying time and drying temperature. The color of final products was significantly influenced by baking time, while both baking time and drying temperature affected the moisture content of the final product. A key observation was that none of the raw material or dough processing parameters, within the range tested, influenced final pretzel quality as defined by pretzel moisture content, hardness or color.
Mating Type Loci of
Sporisorium reilianum
: Novel Pattern with Three
a
and Multiple
b
Specificities
Authors: Schirawski Jan , Heinze Bernadette , Wagenknecht Martin , Kahmann Regine
Published: August 2005

Sporisorium reilianum
and
Ustilago maydis
are two closely related smut fungi, which both infect maize but differ fundamentally in their mode of plant invasion and site of symptom development. As a prelude to studying the molecular basis of these differences, we have characterized the mating type loci of
S. reilianum. S. reilianum
has two unlinked mating type loci,
a
and
b
. Genes in both loci and adjacent regions show a high degree of synteny to the corresponding genes of
U. maydis
. The
b
locus occurs in at least five alleles and encodes two subunits of a heterodimeric homeodomain transcription factor, while the
a
locus encodes a pheromone/receptor system. However, in contrast to that of
U. maydis
, the
a
locus of
S. reilianum
exists in three alleles containing two active pheromone genes each. The alleles of the
a
locus appear to have arisen through recent recombination events within the locus itself. This has created a situation where each pheromone is specific for recognition by only one mating partner.
Genomewide Identification of Sko1 Target Promoters Reveals a Regulatory Network That Operates in Response to Osmotic Stress in
Saccharomyces cerevisiae
Authors: Proft Markus , Gibbons Francis D. , Copeland Matthew , Roth Frederick P. , Struhl Kevin
Published: August 2005

In
Saccharomyces cerevisiae
, the ATF/CREB transcription factor Sko1 (Acr1) regulates the expression of genes induced by osmotic stress under the control of the high osmolarity glycerol (HOG) mitogen-activated protein kinase pathway. By combining chromatin immunoprecipitation and microarrays containing essentially all intergenic regions, we estimate that yeast cells contain approximately 40 Sko1 target promoters in vivo; 20 Sko1 target promoters were validated by direct analysis of individual loci. The ATF/CREB consensus sequence is not statistically overrepresented in confirmed Sko1 target promoters, although some sites are evolutionarily conserved among related yeast species, suggesting that they are functionally important in vivo. These observations suggest that Sko1 association in vivo is affected by factors beyond the protein-DNA interaction defined in vitro. Sko1 binds a number of promoters for genes directly involved in defense functions that relieve osmotic stress. In addition, Sko1 binds to the promoters of genes encoding transcription factors, including Msn2, Mot3, Rox1, Mga1, and Gat2. Stress-induced expression of
MSN2
,
MOT3
, and
MGA1
is diminished in
sko1
mutant cells, while transcriptional regulation of
ROX1
seems to be unaffected. Lastly, Sko1 targets
PTP3
, which encodes a phosphatase that negatively regulates Hog1 kinase activity, and Sko1 is required for osmotic induction of
PTP3
expression. Taken together our results suggest that Sko1 operates a transcriptional network upon osmotic stress, which involves other specific transcription factors and a phosphatase that regulates the key component of the signal transduction pathway.
Phenotypic Switching inCandida glabrataAccompanied by Changes in Expression of Genes with Deduced Functions in Copper Detoxification and Stress
Authors: Srikantha Thyagarajan , Zhao Rui , Daniels Karla , Radke Josh , Soll David R.
Published: August 2005

Most strains ofCandida glabrataswitch spontaneously between a number of phenotypes distinguishable by graded brown coloration on agar containing 1 mM CuSO4, a phenomenon referred to as “core switching.”C. glabrataalso switches spontaneously and reversibly from core phenotypes to an irregular wrinkle (IWr) phenotype, a phenomenon referred to as “irregular wrinkle switching.” To identify genes differentially expressed in the core phenotypes white (Wh) and dark brown (DB), a cDNA subtraction strategy was employed. Twenty-three genes were identified as up-regulated in DB, four in Wh, and six in IWr. Up-regulation was verified in two unrelated strains, oneaand one α strain. The functions of these genes were deduced from the functions of theirSaccharomyces cerevisiaeorthologs. The majority of genes up-regulated in DB (78%) played deduced roles in copper assimilation, sulfur assimilation, and stress responses. These genes were differentially up-regulated in DB even though the conditions of growth for Wh and DB, including CuSO4concentration, were identical. Hence, the regulation of these genes, normally regulated by environmental cues, has been usurped by switching, presumably as an adaptation to the challenging host environment. These results are consistent with the suggestion that switching provides colonizing populations with a minority of cells expressing a phenotype that allows them to enrich in response to an environmental challenge, a form of rapid adaptation. However, DB is the most commonly expressed phenotype at sites of host colonization, in the apparent absence of elevated copper levels. Hence, up-regulation of these genes by switching suggests that in some cases they may play roles in colonization and virulence not immediately obvious from the roles played by their orthologs inS. cerevisiae.
Ubiquinone Synthesis in Mitochondrial and Microsomal Subcellular Fractions of
Pneumocystis
spp.: Differential Sensitivities to Atovaquone
Authors: Basselin Mireille , Hunt Shannon M. , Abdala-Valencia Hiam , Kaneshiro Edna S.
Published: August 2005

The lung pathogen
Pneumocystis
spp. is the causative agent of a type of pneumonia that can be fatal in people with defective immune systems, such as AIDS patients. Atovaquone, an analog of ubiquinone (coenzyme Q [CoQ]), inhibits mitochondrial electron transport and is effective in clearing mild to moderate cases of the infection. Purified rat-derived intact
Pneumocystis carinii
cells synthesize de novo four CoQ homologs, CoQ
7
, CoQ
8
, CoQ
9
, and CoQ
10
, as demonstrated by the incorporation of radiolabeled precursors of both the benzoquinone ring and the polyprenyl chain. A central step in CoQ biosynthesis is the condensation of
p
-hydroxybenzoic acid (PHBA) with a long-chain polyprenyl diphosphate molecule. In the present study, CoQ biosynthesis was evaluated by the incorporation of PHBA into completed CoQ molecules using
P. carinii
cell-free preparations. CoQ synthesis in whole-cell homogenates was not affected by the respiratory inhibitors antimycin A and dicyclohexylcarbodiimide but was diminished by atovaquone. Thus, atovaquone has inhibitory activity on both electron transport and CoQ synthesis in this pathogen. Furthermore, both the mitochondrial and microsomal fractions were shown to synthesize de novo all four
P. carinii
CoQ homologs. Interestingly, atovaquone inhibited microsomal CoQ synthesis, whereas it had no effect on mitochondrial CoQ synthesis. This is the first pathogenic eukaryotic microorganism in which biosynthesis of CoQ molecules from the initial PHBA:polyprenyl transferase reaction has been unambiguously shown to occur in two distinct compartments of the same cell.
Candida albicans
Biofilm-Defective Mutants
Authors: Richard Mathias L. , Nobile Clarissa J. , Bruno Vincent M. , Mitchell Aaron P.
Published: August 2005

Biofilm formation plays a key role in the life cycles and subsistence of many microorganisms. For the human fungal pathogen
Candida albicans
, biofilm development is arguably a virulence trait, because medical implants that serve as biofilm substrates are significant risk factors for infection. The development of
C. albicans
biofilms in vitro proceeds through an early phase, in which yeast cells populate a substrate, an intermediate phase, in which pseudohyphal and hyphal cell types are produced, and a maturation phase, in which continued cell growth is accompanied by accumulation of an extracellular matrix. Here we report the results of a screen for
C. albicans
biofilm-defective mutants, in which homozygous insertions in
NUP85
,
MDS3
,
KEM1
, and
SUV3
were found to block biofilm development. Confocal microscopic examination suggests that
nup85
,
suv3
, and
mds3
mutations cause early-phase arrest, whereas the
kem1
mutation causes intermediate-phase arrest. All of the mutants are defective in hypha production in several media. Analysis of mixed-biofilm development indicates that all of the mutants are defective in the production of hyphae in the context of a biofilm. Because all of the mutants are defective in the retention of cells in the biofilm, we infer that hyphae provide an adherent scaffold that stabilizes the biofilm structure.
Development of a condition assessment model for transmission line in-service wood crossarms
Authors: Pandey M D , Ho V , Bedi S , Woodward S B
Published: August 2005

Wood transmission structures, such as H frames, have been extensively used to support electrical transmission lines throughout Canada. The transmission infrastructure is in general aging, and fungal decay of wood crossarms poses a significant risk of failure under adverse weather conditions. A crossarm failure in the transmission system can result in forced outages and customer disruptions that lead to significant economic losses. This paper presents a condition assessment model to prioritize the replacement of transmission crossarms that are near the end of their service life. The proposed standard involves a visual condition rating system, which is validated by results of full-scale testing of a sample of in-service crossarms. Aerial inspection of transmission lines using the proposed visual rating system is a simple, economical, fast, and effective method of assessment. The proposed approach would ensure a more consistent compliance with the condition-based replacement standard specified in the Canadian (Canadian Standards Association Standard CSA 22.3 No. 1-01) and North American (US National Electric Safety Code 2002 edition) standards.Key words: transmission structure, wood crossarms, decay, condition assessment, full-scale testing, visual rating system, statistical data analysis, bending strength.
A reasoning process in support of integrated project control
Authors: Li J , Moselhi O , Alkass S
Published: August 2005

This paper presents a reasoning process that assists members of project teams in performing integrated time and cost control. The process utilizes an object-based model to represent the data structure of a project. A set of resource performance indicators and a factor indicator serves as a group of sensors designed to detect problem-source factors behind unacceptable performance. Problem-source factors and possible corrective actions were identified, making use of the literature and an Internet-based questionnaire. Casual links between earned-value-based variances, performance indicators, problem-source factors, and corrective actions are established. The degree of linkage strength is expressed using fuzzy set theory. Reasons behind unacceptable performance are determined using fuzzy binary relation operations. Possible corrective actions are suggested based on the identified reasons. Three levels of reasoning reports can be generated at individual resource, control-object, and project levels. The reasoning process has been implemented in a prototype system, developed in the World Wide Web. The prototype has an open architecture that allows users to add reasons and actions to those referred to previously. An example project is analyzed to demonstrate the use of the proposed process and illustrate its capabilities. Key words: project control, fuzzy reasoning, progress reporting, diagnose system.
Bond strength of glass fibre reinforced polymer reinforcing bars in normal and self-consolidating concrete
Authors: Esfahani M Reza , Kianoush M Reza , Lachemi M
Published: August 2005

This paper presents the results of an experimental study on bond strength of reinforcing bars made of glass fibre reinforced polymers (GFRP) embedded in normal and self-consolidating concrete. The study included pull-out tests of 36 GFRP reinforcing bars embedded in concrete specimens. Different parameters such as type of concrete, bar location, and cover thickness were considered as variables in different specimens. The results showed that the type of bond failure was by splitting of concrete for all specimens. The bond strength of bottom GFRP reinforcing bars was almost the same for both normal concrete and self-consolidating concrete. For the top bars, however, the bond strength of self-consolidating concrete was less than that of normal concrete.Key words: bond strength, glass FRP, reinforcing bars, top-bar effect, self-consolidating concrete.
Seismic performance of high-strength concrete square columns confined with carbon fiber reinforced polymers (CFRPs)
Authors: Hosseini A , Khaloo Ali R , Fadaee S
Published: August 2005

This paper presents the results of an experimental and analytical study on high-strength, reinforced-concrete (RC) columns with different levels of initial ductility enhanced with carbon fiber reinforced polymer (CFRP) wraps. Six square columns 260 mm wide and 1650 mm long were tested under constant axial load and reversed cyclic lateral load. The test specimens were divided into three groups. Groups I and II were designed and detailed according to the requirements of American Concrete Institute ACI318-02 for intermediate-moment frames. Group I was wrapped with CFRP, group II was control specimens, and group III was designed and detailed according to the requirements of ACI318-02 for special-moment frames. Each group consisted of two columns with ρsl = 1.5% and 3.0% longitudinal steel rebars, where ρsl is the ratio of area of longitudinal reinforcement to gross area of concrete. The moment–curvature is numerically calculated for sections with fiber reinforced polymer (FRP) confinement. The theoretical prediction provides conservative results compared with the test data. Based on the test results, CFRP enhanced ultimate displacement and curvature ductility by 53% and 79%, respectively, in column WI4 with four longitudinal bars and 27% and 28%, respectively, in column WI8 with eight longitudinal bars. Moreover, the performance of wrapped columns was enhanced to a level higher than that of unwrapped columns designed according to special-moment frames.Key words: strengthening, ductility, FRP wrap, moment–curvature, high-strength concrete.
Application of the equivalent static force procedure for the seismic design of multistorey buildings with vertical mass irregularity
Authors: Tremblay Robert , Merzouq Sina , Izvernari Carmen , Alexieva Krasimira
Published: August 2005

The seismic forces and deformations obtained from the equivalent static force procedure and the dynamic analysis method proposed for the 2005 National Building Code of Canada are compared for 4-, 8-, 12-, and 16-storey buildings with structural mass irregularity. Setbacks resulting in 200% and 300% mass discontinuities located at 25%, 50%, or 75% of the building height were considered. The buildings are located in Vancouver and Montréal, and lateral loads are resisted by concentrically braced steel frames. The storey shear forces, overturning moments, and storey drifts obtained from static analysis were found to exceed the values determined from dynamic analysis for all irregular structures except at the base of "podium-type" buildings located at the Vancouver site.Key words: mass, static, dynamic, seismic, shear, overturning moment, deflections, braced steel frames.
Epigenome programming by Polycomb and Trithorax proteins
Authors: Cernilogar Filippo M , Orlando Valerio
Published: August 2005

Polycomb group (PcG) and Trithorax group (TrxG) proteins work, respectively, to maintain repressed or active transcription states of developmentally regulated genes through cell division. Data accumulated in the recent years have increased our understanding of the mechanisms by which PcG and TrxG proteins regulate gene expression. The discovery that histone methylation can serve as a specific mark for PcG and TrxG complexes has provided new insight into the mechanistic function of this cell-memory system.Key words: Polycomb, Trithorax, RNAi, cell memory, noncoding RNA, epigenome.
Role of histone acetylation in the control of gene expression
Authors: Verdone Loredana , Caserta Micaela , Mauro Ernesto Di
Published: August 2005

Histone proteins play structural and functional roles in all nuclear processes. They undergo different types of covalent modifications, defined in their ensemble as epigenetic because changes in DNA sequences are not involved. Histone acetylation emerges as a central switch that allows interconversion between permissive and repressive chromatin domains in terms of transcriptional competence. The mechanisms underlying the histone acetylation-dependent control of gene expression include a direct effect on the stability of nucleosomal arrays and the creation of docking sites for the binding of regulatory proteins. Histone acetyltransferases and deacetylases are, respectively, the enzymes devoted to the addition and removal of acetyl groups from lysine residues on the histone N-terminal tails. The enzymes exert fundamental roles in developmental processes and their deregulation has been linked to the progression of diverse human disorders, including cancer.Key words: gene expression, transcription, HATs, HDACs, nucleosome.
Reduction of hydraulic conductivity changes in an in-ground bioreactor
Authors: Anello Gioseph , Lamarche Philippe , Héroux Jean A
Published: August 2005

The biodegradation of dissolved naphthalene was studied in the laboratory, in preparation for a field-scale investigation of enhanced bioremediation in a permeable barrier. The laboratory experiments were performed, under water saturated conditions, in acrylic columns packed with silica sand. The sand contained 1% by volume of granular activated carbon (GAC). Naphthalene, nutrient, and nitrate solutions were pumped through, and concentrations and liquid pressures were monitored. One objective of the laboratory study was to determine if the decrease in hydraulic conductivity caused by microbial growth could be reduced. It was believed that biomass would attach preferentially to the small proportion of GAC added to the sand. Scanning electron microscope micrographs showing evidence of preferential attachment of biomass on the GAC are presented in this paper. A calculation indicates that the decrease in hydraulic conductivity could be less than 6%. Data gathered to design the field scale bioreactor and the design and assessment of the performance of the permeable barrier are presented elsewhere. Key words: hydraulic conductivity, biomass growth, in-situ bioreactor, granular activated carbon, naphthalene.
Correlation of δ15N and δ18O in NO3- during denitrification in groundwater
Authors: Chen David J.Z , MacQuarrie Kerry T.B
Published: August 2005

Stable isotopes of nitrogen and oxygen are important tools for investigating the occurrence of denitrification in groundwater. Previous investigators have noted a linear relationship between δ15N and δ18O field data collected from shallow groundwater systems, but the reason for such a linear correlation is not clear. In this study, we represent denitrification reactions using parallel, first-order kinetics, and reaction rate constants that depend on the nitrogen or oxygen isotope present in nitrate. The derived mathematical relationship between δ15N and δ18O indicates that nitrogen and oxygen isotopes should fractionate at a constant ratio. Using the laboratory reaction rate constants obtained by Olleros (1983), our equations give a theoretical fractionation ratio value of b = 0.51. A review of published field studies in which denitrification in groundwater has been confirmed, and δ15N and δ18O data has been collected, shows that the mean fractionation ratio value is 0.55 (standard deviation = 0.08, n = 6). The field values therefore agree well with the predicted fractionation ratio value of b = 0.51. It is concluded that a linear relationship between δ15N and δ18O values, with a slope (b) close to 0.51, provides additional, unambiguous evidence that denitrification is responsible for nitrate concentration decline and enrichment in nitrogen isotope values in shallow groundwater. Key words: nitrate, groundwater, denitrification, isotopes, enrichment factor, fractionation ratio.
Effectiveness of 3 antagonistic bacterial isolates to control Rhizoctonia solani Kühn on lettuce and potato
Authors: Grosch Rita , Faltin Franziska , Lottmann Jana , Kofoet A , Berg Gabriele
Published: August 2005

Rhizoctonia solani causes yield losses in numerous economically important European crops. To develop a biocontrol strategy, 3 potato-associated ecto- and endophytically living bacterial strains Pseudomonas fluorescens B1, Pseudomonas fluorescens B2, and Serratia plymuthica B4 were evaluated against R. solani in potato and in lettuce. The disease-suppression effect of the 3 biocontrol agents (BCAs) was tested in a growth chamber and in the field. In growth chamber experiments, all 3 BCAs completely or significantly limited the dry mass (DM) losses on lettuce and the disease severity (DS) caused by R. solani on potato sprouts. Strain B1 showed the highest suppression effect (52% on average) on potato. Under field conditions, the DS on both crops, which were bacterized, decreased significantly, and the biomass losses on lettuce decreased significantly as well. The greatest disease-suppression effect on potato was achieved by strain B1 (37%), followed by B2 (33%) and then B4 (31%), whereas the marketable tuber yield increased up to 12% (B1), 6% (B2), and 17% (B4) compared with the pathogen control at higher disease pressure. Furthermore, in all experiments, B1 proved to be the most effective BCA against R. solani. Therefore, this BCA could be a candidate for developing a commercial product against Rhizoctonia diseases. To our knowledge, this is the first report on the high potential of endophytes to be used as a biological control agent against R. solani under field conditions.Key words: biocontrol, Rhizoctonia solani, field grown lettuce and potato, antagonistic bacteria, endophytes.
Underrepresentation of short palindromes in Selenomonas ruminantium DNA: evidence for horizontal gene transfer of restriction and modification systems?
Authors: Pristas Peter , Piknova Maria
Published: August 2005

Molecular analysis of isolates of the rumen bacterium Selenomonas ruminantium revealed a high variety and frequency of site-specific (restriction) endonucleases. While all known S. ruminantium restriction and modification systems recognize hexanucleotide sequences only, consistently low counts of both 6-bp and 4-bp palindromes were found in DNA sequences of S. ruminantium. Statistical analysis indicated that there is some correlation between the degree of underrepresentation of tetranucleotide words and the number of known restriction endonucleases for a given sequence. Control analysis showed the same correlation in lambda DNA but not in human adenovirus DNA. Based on the data presented, it could be proposed that there is a much higher historical occurrence of restriction and modification systems in S. ruminantium and (or) frequent horizontal gene transfer of restriction and modification gene complexes.Key words: Selenomonas, palindromes, restriction-modification.