Showing papers by "Virginia Tech published in 2005"
TL;DR: The development, current features, and some directions for future development of the Amber package of computer programs, which contains a group of programs embodying a number of powerful tools of modern computational chemistry, focused on molecular dynamics and free energy calculations of proteins, nucleic acids, and carbohydrates.
Abstract: We describe the development, current features, and some directions for future development of the Amber package of computer programs. This package evolved from a program that was constructed in the late 1970s to do Assisted Model Building with Energy Refinement, and now contains a group of programs embodying a number of powerful tools of modern computational chemistry, focused on molecular dynamics and free energy calculations of proteins, nucleic acids, and carbohydrates.
7,672 citations
TL;DR: In this paper, an integrated approach to understand tourist motivation and attempts to extend the theoretical and empirical evidence on the causal relationships among the push and pull motivations, satisfaction, and destination loyalty is presented.
2,831 citations
TL;DR: As agricultural production intensified over the past few decades, producers became more and more dependent on agrochemicals as a relatively reliable method of crop production.
Abstract: Pathogenic microorganisms affecting plant health are a major and chronic threat to food production and ecosystem stability worldwide As agricultural production intensified over the past few decades, producers became more and more dependent on agrochemicals as a relatively reliable method of crop
2,246 citations
TL;DR: The findings indicate that perceived ease of use, compatibility and trustworthiness are significant predictors of citizens’ intention to use an e‐government service.
Abstract: . Electronic government, or e-government, increases the convenience and accessibility of government services and information to citizens. Despite the benefits of e-government – increased government accountability to citizens, greater public access to information and a more efficient, cost-effective government – the success and acceptance of e-government initiatives, such as online voting and licence renewal, are contingent upon citizens’ willingness to adopt this innovation. In order to develop ‘citizen-centred’ e-government services that provide participants with accessible, relevant information and quality services that are more expedient than traditional ‘brick and mortar’ transactions, government agencies must first understand the factors that influence citizen adoption of this innovation. This study integrates constructs from the Technology Acceptance Model, Diffusions of Innovation theory and web trust models to form a parsimonious yet comprehensive model of factors that influence citizen adoption of e-government initiatives. The study was conducted by surveying a broad diversity of citizens at a community event. The findings indicate that perceived ease of use, compatibility and trustworthiness are significant predictors of citizens’ intention to use an e-government service. Implications of this study for research and practice are presented.
1,989 citations
TL;DR: In this article, the authors show that the loss of foundation tree species changes the local environment on which a variety of other species depend and how this disrupts fundamental ecosystem processes, including rates of decomposition, nutrient fluxes, carbon sequestration, and energy flow.
Abstract: In many forested ecosystems, the architecture and functional ecology of certain tree species define forest structure and their species-specific traits control ecosystem dynamics. Such foundation tree species are declining throughout the world due to introductions and outbreaks of pests and pathogens, selective removal of individual taxa, and over-harvesting. Through a series of case studies, we show that the loss of foundation tree species changes the local environment on which a variety of other species depend; how this disrupts fundamental ecosystem processes, including rates of decomposition, nutrient fluxes, carbon sequestration, and energy flow; and dramatically alters the dynamics of associated aquatic ecosystems. Forests in which dynamics are controlled by one or a few foundation species appear to be dominated by a small number of strong interactions and may be highly susceptible to alternating between stable states following even small perturbations. The ongoing decline of many foundation species provides a set of important, albeit unfortunate, opportunities to develop the research tools, models, and metrics needed to identify foundation species, anticipate the cascade of immediate, short- and long-term changes in ecosystem structure and function that will follow from their loss, and provide options for remedial conservation and management.
1,665 citations
TL;DR: Increased acid-to-pulp ratio reduced the dimensions of the nanocrystals thus produced and the critical concentration was increased and the biphasic range became narrower; a suspension made from a bleached kraft eucalyptus pulp gave very similar properties to the softwood nanocrystal suspension when prepared under similar hydrolysis conditions.
1,406 citations
TL;DR: The web server provides access to a tool that automates estimates of pKs as well as other related characteristics of biomolecules such as isoelectric points, titration curves and energies of protonation microstates, and is intended for a broad community of biochemists, molecular modelers, structural biologists and drug designers.
Abstract: The structure and function of macromolecules depend critically on the ionization (protonation) states of their acidic and basic groups. A number of existing practical methods predict protonation equilibrium pK constants of macromolecules based upon their atomic resolution Protein Data Bank (PDB) structures; the calculations are often performed within the framework of the continuum electrostatics model. Unfortunately, these methodologies are complex, involve multiple steps and require considerable investment of effort. Our web server http://biophysics.cs.vt.edu/H++ provides access to a tool that automates this process, allowing both experts and novices to quickly obtain estimates of pKs as well as other related characteristics of biomolecules such as isoelectric points, titration curves and energies of protonation microstates. Protons are added to the input structure according to the calculated ionization states of its titratable groups at the user-specified pH; the output is in the PQR (PDB + charges + radii) format. In addition, corresponding coordinate and topology files are generated in the format supported by the molecular modeling package AMBER. The server is intended for a broad community of biochemists, molecular modelers, structural biologists and drug designers; it can also be used as an educational tool in biochemistry courses.
1,247 citations
TL;DR: Iron-sulfur [Fe-S] clusters are ubiquitous and evolutionary ancient prosthetic groups that are required to sustain fundamental life processes and important mechanistic questions related to the biosynthetic process involve the molecular details of how these clusters are assembled on scaffold proteins, how they are transferred from scaffolds to target proteins, and how the biosynthesis process is regulated.
Abstract: ▪ Abstract Iron-sulfur [Fe-S] clusters are ubiquitous and evolutionary ancient prosthetic groups that are required to sustain fundamental life processes. Owing to their remarkable structural plasticity and versatile chemical/electronic features [Fe-S] clusters participate in electron transfer, substrate binding/activation, iron/sulfur storage, regulation of gene expression, and enzyme activity. Formation of intracellular [Fe-S] clusters does not occur spontaneously but requires a complex biosynthetic machinery. Three different types of [Fe-S] cluster biosynthetic systems have been discovered, and all of them are mechanistically unified by the requirement for a cysteine desulfurase and the participation of an [Fe-S] cluster scaffolding protein. Important mechanistic questions related to [Fe-S] cluster biosynthesis involve the molecular details of how [Fe-S] clusters are assembled on scaffold proteins, how [Fe-S] clusters are transferred from scaffolds to target proteins, how various accessory proteins part...
1,242 citations
TL;DR: This paper presents the 12th update of the human obesity gene map, which incorporates published results up to the end of October 2005, and shows putative loci on all chromosomes except Y.
Abstract: This paper presents the eleventh update of the human obesity gene map, which incorporates published results up to the end of October 2004. Evidence from single-gene mutation obesity cases, Mendelian disorders exhibiting obesity as a clinical feature, transgenic and knockout murine models relevant to obesity, quantitative trait loci (QTLs) from animal cross-breeding experiments, association studies with candidate genes, and linkages from genome scans is reviewed. As of October 2004, 173 human obesity cases due to single-gene mutations in 10 different genes have been reported, and 49 loci related to Mendelian syndromes relevant to human obesity have been mapped to a genomic region, and causal genes or strong candidates have been identified for most of these syndromes. There are 166 genes which, when mutated or expressed as transgenes in the mouse, result in phenotypes that affect body weight and adiposity. The number of QTLs reported from animal models currently reaches 221. The number of human obesity QTLs derived from genome scans continues to grow, and we have now 204 QTLs for obesity-related phenotypes from 50 genome-wide scans. A total of 38 genomic regions harbor QTLs replicated among two to four studies. The number of studies reporting associations between DNA sequence variation in specific genes and obesity phenotypes has also increased considerably with 358 findings of positive associations with 113 candidate genes. Among them, 18 genes are supported by at least five positive studies. The obesity gene map shows putative loci on all chromosomes except Y. Overall, >600 genes, markers, and chromosomal regions have been associated or linked with human obesity phenotypes. The electronic version of the map with links to useful publications and genomic and other relevant sites can be found at http://obesitygene.pbrc.edu.
955 citations
TL;DR: In this article, the authors summarized data for δ18O in zircons that have been analyzed from 1,200 dated rocks ranging over 96% of the age of Earth.
Abstract: Analysis of δ18O in igneous zircons of known age traces the evolution of intracrustal recycling and crust-mantle interaction through time. This record is especially sensitive because oxygen isotope ratios of igneous rocks are strongly affected by incorporation of supracrustal materials into melts, which commonly have δ18O values higher than in primitive mantle magmas. This study summarizes data for δ18O in zircons that have been analyzed from 1,200 dated rocks ranging over 96% of the age of Earth. Uniformly primitive to mildly evolved magmatic δ18O values are found from the first half of Earth history, but much more varied values are seen for younger magmas. The similarity of values throughout the Archean, and comparison to the composition of the “modern” mantle indicate that δ18O of primitive mantle melts have remained constant (±0.2‰) for the past 4.4 billion years. The range and variability of δ18O in all Archean zircon samples is subdued (δ18O(Zrc)=5–7.5‰) ranging from values in high temperature equilibrium with the mantle (5.3± 0.3‰) to slightly higher, more evolved compositions (6.5–7.5‰) including samples from: the Jack Hills (4.4–3.3 Ga), the Beartooth Mountains (4.0–2.9 Ga), Barberton (3.5–2.7 Ga), the Superior and Slave Provinces (3.0 to 2.7 Ga), and the Lewisian (2.7 Ga). No zircons from the Archean have been analyzed with magmatic δ18O above 7.5‰. The mildly evolved, higher Archean values (6.5–7.5‰) are interpreted to result from exchange of protoliths with surface waters at low temperature followed by melting or contamination to create mildly elevated magmas that host the zircons. During the Proterozoic, the range of δ18O(Zrc) and the highest values gradually increased in a secular change that documents maturation of the crust. After ∼1.5 Ga, high δ18O zircons (8 to >10‰) became common in many Proterozoic and Phanerozoic terranes reflecting δ18O(whole rock) values from 9 to over 12‰. The appearance of high δ18O magmas on Earth reflects nonuniformitarian changes in the composition of sediments, and rate and style of recycling of surface-derived material into magmas within the crust.
940 citations
TL;DR: Switchgrass has potential as a renewable fuel source, but such use will likely require large infrastructural changes; and, even at maximum output, such systems could not provide the energy currently being derived from fossil fuels.
Abstract: Switchgrass (Panicum virgatum L.)—a perennial, warm-season (C4) species—evolved across North America into multiple, divergent populations. The resulting natural variation within the species presents considerable morphological diversity and a wide range of adaptation. The species was adopted as a crop—initially as a forage—only in the last 50 yr. Its potential uses have recently been expanded to include biofuels. Management of switchgrass for biofuels is informed by an understanding of the plant's biology. Successful establishment requires attention to seed dormancy and weed control as well as proper depth and date of planting. The plant's growth rate is closely tied to temperature, but timing of reproductive development is linked to photoperiod. Accordingly, the period of vegetative growth can be extended by planting lower-latitude cultivars at higher latitudes. This strategy may provide a yield advantage, but cold tolerance can become limiting. Switchgrass is thrifty in its use of applied N; it appears a...
TL;DR: Analysis of the PsJN colonization patterns showed that this strain colonizes grapevine root surfaces, as well as cell walls and the whole surface of some rhizodermal cells, and cell wall-degrading endoglucanase and endopolygalacturonase secreted by PsN explained how the bacterium gains entry into root internal tissues.
Abstract: Patterns of colonization of Vitis vinifera L. cv. Chardonnay plantlets by a plant growth-promoting bacterium, Burkholderia sp. strain PsJN, were studied under gnotobiotic conditions. Wild-type strain PsJN and genetically engineered derivatives of this strain tagged with gfp (PsJN::gfp2x) or gusA (PsJN::gusA11) genes were used to enumerate and visualize tissue colonization. The rhizospheres of 4- to 5-week-old plantlets with five developed leaves were inoculated with bacterial suspensions. Epiphytic and endophytic colonization patterns were then monitored by dilution plating assays and microscopic observation of organ sections. Bacteria were chronologically detected first on root surfaces, then in root internal tissues, and finally in the fifth internode and the tissues of the fifth leaf. Analysis of the PsJN colonization patterns showed that this strain colonizes grapevine root surfaces, as well as cell walls and the whole surface of some rhizodermal cells. Cells were also abundant at lateral root emergence sites and root tips. Furthermore, cell wall-degrading endoglucanase and endopolygalacturonase secreted by PsJN explained how the bacterium gains entry into root internal tissues. Host defense reactions were observed in the exodermis and in several cortical cell layers. Bacteria were not observed on stem and leaf surfaces but were found in xylem vessels of the fifth internode and the fifth leaf of plantlets. Moreover, bacteria were more abundant in the fifth leaf than in the fifth internode and were found in substomatal chambers. Thus, it seems that Burkholderia sp. strain PsJN induces a local host defense reaction and systemically spreads to aerial parts through the transpiration stream.
TL;DR: In this article, a series of seven linear homopolymers of poly(methylmethacrylate) ranging from 12,470 to 365,700 g/mol M w, were utilized to further explore scaling relationships between viscosity and concentration in a good solvent at 25°C and investigate the impact of these relationships on fiber formation during electrospinning.
15 Aug 2005
TL;DR: In this paper, clusters generated from the training data provide the basis for data smoothing and neighborhood selection and show that the new proposed approach consistently outperforms other state-of-art collaborative filtering algorithms.
Abstract: Memory-based approaches for collaborative filtering identify the similarity between two users by comparing their ratings on a set of items. In the past, the memory-based approach has been shown to suffer from two fundamental problems: data sparsity and difficulty in scalability. Alternatively, the model-based approach has been proposed to alleviate these problems, but this approach tends to limit the range of users. In this paper, we present a novel approach that combines the advantages of these two approaches by introducing a smoothing-based method. In our approach, clusters generated from the training data provide the basis for data smoothing and neighborhood selection. As a result, we provide higher accuracy as well as increased efficiency in recommendations. Empirical studies on two datasets (EachMovie and MovieLens) show that our new proposed approach consistently outperforms other state-of-art collaborative filtering algorithms.
TL;DR: This paper briefly summarizes software reuse research, discusses major research contributions and unsolved problems, provides pointers to key publications, and introduces four papers selected from The Eighth International Conference on Software Reuse (ICSR8).
Abstract: This paper briefly summarizes software reuse research, discusses major research contributions and unsolved problems, provides pointers to key publications, and introduces four papers selected from The Eighth International Conference on Software Reuse (ICSR8).
TL;DR: In this article, three types of piezoelectric devices are investigated and experimentally tested to deter deterministic power harvesting from the vibration of a discharged nickel metal hydride battery.
Abstract: Piezoelectric materials can be used as a means of transforming ambient vibrations into electrical energy that can then be stored and used to power other devices. With the recent surge of microscale devices, piezoelectric power generation can provide a convenient alternative to traditional power sources used to operate certain types of sensors/actuators, telemetry, and MEMS devices. However, the energy produced by these materials is in many cases far too small to directly power an electrical device. Therefore, much of the research into power harvesting has focused on methods of accumulating the energy until a sufficient amount is present, allowing the intended electronics to be powered. In a recent study by Sodano et al. (2004a) the ability to take the energy generated through the vibration of a piezoelectric material was shown to be capable of recharging a discharged nickel metal hydride battery. In the present study, three types of piezoelectric devices are investigated and experimentally tested to deter...
TL;DR: Orthogonal nature of the present catalyst immobilization approach should allow the design of other superparamagnetic nanoparticle-supported asymmetric catalysts for a wide range of organic transformations.
Abstract: Novel heterogenized asymmetric catalysts were synthesized by immobilizing preformed Ru catalysts on magnetite nanoparticles via the phosphonate functionality and were characterized by a variety of techniques, including TEM, magnetization, and XRD. These nanoparticle-supported chiral catalysts were used for enantioselective heterogeneous asymmetric hydrogenation of aromatic ketones with very high enantiomeric excess values of up to 98.0%. The immobilized catalysts were easily recycled by magnetic decantation and reused for up to 14 times without loss of activity and enantioselectivity. Orthogonal nature of the present catalyst immobilization approach should allow the design of other superparamagnetic nanoparticle-supported asymmetric catalysts for a wide range of organic transformations.
TL;DR: A review of recent developments on particle formation from polymers using supercritical fluids has been reviewed with an emphasis on articles published during 2000-2003 as discussed by the authors, focusing on the production of polymer particles that contain active ingredients.
Abstract: Recent developments on particle formation from polymers using supercritical fluids have been reviewed with an emphasis on articles published during 2000–2003. First, a brief description of the basic operating principles of the various particle formation processes is presented. These include the rapid expansion of supercritical solutions (RESS), the gas antisolvent process (GAS), supercritical antisolvent process (SAS) and its various modifications, and the particles from gas-saturated solution (PGSS) processes. An account of the general review articles that have been published in previous years is then provided. The publications that have appeared over the past 4 years have been reviewed under two groupings, one involving the production of particles from pure polymers, and the other involving the production of polymer particles that contain active ingredients, especially those that pertain to pharmaceuticals. The majority of the efforts in the current supercritical particle formation technology is indeed on the production of polymer particles that are of pharmaceutical significance. In each grouping, the publications were further categorized according to the primary role played by the supercritical fluid in the process, namely whether it was used as a solvent, or as an antisolvent, or as a solute. This review is the first comprehensive review specifically focused on the formation of particles from polymers.
[...]
TL;DR: A definition and framework for a novel type of adaptive data network: the cognitive network, in which the collection of elements that make up the network observes network conditions and then, using prior knowledge gained from previous interactions with the network, plans, decides and acts on this information.
Abstract: This paper presents a definition and framework for a novel type of adaptive data network: the cognitive network. In a cognitive network, the collection of elements that make up the network observes network conditions and then, using prior knowledge gained from previous interactions with the network, plans, decides and acts on this information. Cognitive networks are different from other "intelligent" communication technologies because these actions are taken with respect to the end-to-end goals of a data flow. In addition to the cognitive aspects of the network, a specification language is needed to translate the user's end-to-end goals into a form understandable by the cognitive process. The cognitive network also depends on a software adaptable network that has both an external interface accessible to the cognitive network and network status sensors. These devices are used to provide control and feedback. The paper concludes by presenting a simple case study to illustrate a cognitive network and its framework
TL;DR: In this article, it is shown that microorganisms play an important part on the formation of many fine-grained soils, can alter the behavior of coarse grained soils (including hydraulic conductivity, diffusion and strength), accelerate geochemical reactions by orders of magnitude, promote both weathering and aging, and alter the chemical and mechanical properties of specimens after sampling.
Abstract: The understanding of soil behavior during the last 300 years has centered on mechanical principles, geological processes, and later on, mineralogy and the relevance of colloidal chemistry. More recently, research in biology and earth science has enabled important advances in understanding the crucial involvement of microorganisms in the evolution of the earth, their ubiquitous presence in near surface soils and rocks, and their participation in mediating and facilitating most geochemical reactions. Yet, the effect of biological activity on soil mechanical behavior remains largely underexplored in the geotechnical field. The purposes of this paper are to introduce microbiological concepts, identify and illustrate their potential roles in soils and rocks, and stimulate interest in seeking improved understanding of their importance and potential for advancing the states of knowledge and practice in geotechnical engineering. It is shown that microorganisms play an important part on the formation of many fine grained soils, can alter the behavior of coarse grained soils (including hydraulic conductivity, diffusion and strength), accelerate geochemical reactions by orders of magnitude, promote both weathering and aging, and alter the chemical and mechanical properties of specimens after sampling. While extensive research is needed to delineate the full impact of biomass and biomediated reactions on soil behavior, it is anticipated that a proper understanding of biological principles will lead to improved soil characterization, enhanced understanding of soil behavior, and even alternative geotechnical engineering solutions.
TL;DR: To better appreciate the strength and direction of experienced emotions, it is recommended that state "dominance" be evaluated in the context of asymmetrical activation of left-frontal (dominance) versus right- frontal (submission) brain regions.
Abstract: This article provides a review of research on the hemispheric specialization in emotional processing during the past 40 years and the theoretical models derived from the conceptual analysis of these results. The publications reviewed here were collected to better appreciate the cortical lateralization of emotional perception (visual and auditory), expression (facial and prosodic), and experience. Four major models of emotional processing are discussed--the Right Hemisphere, Valence, Approach-Withdrawal, and Behavioral Inhibition System-Behavioral Activation System models. Observing the relative merits and limitations of these models, a new direction for exploration is offered. Specifically, to better appreciate the strength and direction (i.e., approach versus withdrawal) of experienced emotions, it is recommended that state "dominance" be evaluated in the context of asymmetrical activation of left-frontal (dominance) versus right-frontal (submission) brain regions.
TL;DR: An overview of where the field currently stands when it comes to having evidence-based methods and instruments available for use in assessing anxiety and its disorders in children and adolescents is provided.
Abstract: We provide an overview of where the field currently stands when it comes to having evidence-based methods and instruments available for use in assessing anxiety and its disorders in children and adolescents. Methods covered include diagnostic interview schedules, rating scales, observations, and self-monitoring forms. We also discuss the main purposes or goals of assessment and indicate which methods and instruments have the most evidence for accomplishing these goals. We also focus on several specific issues that need continued research attention for the field to move forward toward an evidence-based assessment approach. Finally, tentative recommendations are made for conducting an evidence-based assessment for anxiety and its disorders in children and adolescents. Directions for future research also are discussed.
TL;DR: In this paper, the authors examine two forms of myopia in accountability in organizations and challenge the normative assumption that more accountability is necessarily better, by examining two common misperceptions about accountability.
Abstract: This article challenges a normative assumption about accountability in organizations: that more accountability is necessarily better. More specifically, it examines two forms of “myopia” that chara...
05 Dec 2005
TL;DR: A renewed look at signal classification using spectral coherence and neural networks is taken, the performance of which is characterized by Monte Carlo simulations.
Abstract: Channel sensing and spectrum allocation has long been of interest as a prospective addition to cognitive radios for wireless communications systems occupying license-free bands. Conventional approaches to cyclic spectral analysis have been proposed as a method for classifying signals for applications where the carrier frequency and bandwidths are unknown, but is, however, computationally complex and requires a significant amount of observation time for adequate performance. Neural networks have been used for signal classification, but only for situations where the baseband signal is present. By combining these techniques a more efficient and reliable classifier can be developed where a significant amount of processing is performed offline, thus reducing online computation. In this paper we take a renewed look at signal classification using spectral coherence and neural networks, the performance of which is characterized by Monte Carlo simulations
TL;DR: In this paper, the latest progress in the field of polypseudorotaxanes and polyrotaxanes is reviewed in four parts: (1) main chain systems, (2) side chain systems and (3) other systems with related structures and properties, potential applications and future directions.
TL;DR: In this article, a path-analysis model revealed significant paths between hedonic value and resulting emotional pleasure and arousal variables, and a pattern of significant paths was also found between these three variables and global attitude, willingness to purchase, and willingness to patronize the on-line store.
Abstract: With the use of an on-line retailer's Web site and an experimental method with 103 university students, statistical support through path analysis was found for positive influences of optimum stimulation level (preferred level of environmental stimulation) and recreational shopping on hedonic value (trying an image-interactivity feature of an apparel Web site as a stimulating experience). The Web site's mixandmatch image interactivity feature allowed creation of visual images of product combinations. The path-analysis model revealed significant paths between hedonic value and resulting emotional pleasure and arousal variables. A pattern of significant paths was also found between these three variables and global attitude, willingness to purchase, and willingness to patronize the on-line store. Theoretical and managerial conclusions are provided. © 2005 Wiley Periodicals, Inc.
TL;DR: It is concluded that, despite potential or observed bene.ts to human society, tilapia aquaculture and open-water introductions cannot continue unchecked without further exacerbating damage to native .sh species and biodiversity.
Abstract: The common name 'tilapia' refers to a group of tropical freshwater .sh in the family Cichlidae (Oreochromis, Tilapia, and Sarotherodon spp.) that are indigenous to Africa and the southwestern Middle East. Since the 1930s, tilapias have been intentionally dispersed worldwide for the biological control of aquatic weeds and insects, as bait.sh for certain capture .sheries, for aquaria, and as a food .sh. They have most recently been promoted as an important source of protein that could provide food security for developing countries without the environmental problems associated with terrestrial agriculture. In addition, market demand for tilapia in developed countries such as the United States is growing rapidly. 2. Tilapias are well-suited to aquaculture because they are highly proli.c and tolerant to a range of environmental conditions. They have come to be known as the 'aquatic chicken' because of their potential as an a.ordable, high-yield source of protein that can be easily raised in a range of environments } from subsistence or 'backyard' units to intensive .sh hatcheries. In some countries, particularly in Asia, nearly all of the introduced tilapias produced are consumed domestically; tilapias have contributed to basic food security for such societies. 3. This review indicates that tilapia species are highly invasive and exist under feral conditions in every nation in which they have been cultured or introduced. Thus, the authors have concluded that, despite potential or observed bene.ts to human society, tilapia aquaculture and open-water introductions cannot continue unchecked without further exacerbating damage to native .sh species and biodiversity. Recommendations include restricting tilapia culture to carefully managed, contained ponds, although exclusion is preferred when it is feasible. Research into culture of indigenous species is also recommended.
TL;DR: In this article, the authors empirically examined whether image interactivity technology (IIT), which enables the creation and manipulation of product images on a retailer's Web site, affects experiential value and instrumental value.
TL;DR: The cloning of ATR1NdWsB has highlighted the presence of a highly conserved novel amino acid motif in avirulence proteins from three different oomycetes and its similarity to a host-targeting signal from malaria parasites suggest a conserved role in pathogenicity.
Abstract: The perception of downy mildew avirulence (Arabidopsis thaliana Recognized [ATR]) gene products by matching Arabidopsis thaliana resistance (Recognition of Peronospora parasitica [RPP]) gene products triggers localized cell death (a hypersensitive response) in the host plant, and this inhibits pathogen development. The oomycete pathogen, therefore, is under selection pressure to alter the form of these gene products to prevent detection. That the pathogen maintains these genes indicates that they play a positive role in pathogen survival. Despite significant progress in cloning plant RPP genes and characterizing essential plant components of resistance signaling pathways, little progress has been made in identifying the oomycete molecules that trigger them. Concluding a map-based cloning effort, we have identified an avirulence gene, ATR1NdWsB, that is detected by RPP1 from the Arabidopsis accession Niederzenz in the cytoplasm of host plant cells. We report the cloning of six highly divergent alleles of ATR1NdWsB from eight downy mildew isolates and demonstrate that the ATR1NdWsB alleles are differentially recognized by RPP1 genes from two Arabidopsis accessions (Niederzenz and Wassilewskija). RPP1-Nd recognizes a single allele of ATR1NdWsB; RPP1-WsB also detects this allele plus three additional alleles with divergent sequences. The Emco5 isolate expresses an allele of ATR1NdWsB that is recognized by RPP1-WsB, but the isolate evades detection in planta. Although the Cala2 isolate is recognized by RPP1-WsA, the ATR1NdWsB allele from Cala2 is not, demonstrating that RPP1-WsA detects a novel ATR gene product. Cloning of ATR1NdWsB has highlighted the presence of a highly conserved novel amino acid motif in avirulence proteins from three different oomycetes. The presence of the motif in additional secreted proteins from plant pathogenic oomycetes and its similarity to a host-targeting signal from malaria parasites suggest a conserved role in pathogenicity.