Consulta: subjectFacets:"Aggregation"
Registros recuperados: 57
Data/hora: 11/06/2024 00:05:28

Influencia de diferentes manejos agrícolas sobre el crecimiento radical y su relación con la agregación del suelo.
Provedor de dados: 32
Autores: Torres Guerrero, Carlos Alberto.
Los suelos de México han sido degradados en los últimos años en buena parte por la acción del hombre. Debido a las prácticas agronómicas empleadas en la mayor parte del país (labranza convencional, monocultivos y remoción de residuos vegetales de cosechas anteriores) los suelos con potencial agrícola se han visto disminuidos en su productividad. La Agricultura de Conservación (AC) ofrece un aprovechamiento sustentable del recurso suelo, asegurando su estabilidad y estructura, con el propósito de aumentar los rendimientos de los cultivos. El experimento que se reporta es de larga duración. Se inició en 1991 en el Batán Texcoco, Estado de México, en el Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT) y consta de 32 parcelas con diferentes...
Palavras-chave: Labranza; Agricultura de conservación; Raíces; Agregación; Maestría; Edafología; Tillage; Conservation agriculture; Roots; Aggregation.
Ano: 2012
URL: http://hdl.handle.net/10521/1755

The aggregation of Chauliognathus species (Coleoptera, Cantharidae) and its possible role for coexistence and mimicry
Provedor de dados: 76
Autores: Machado,Vilmar; Araújo,Aldo Mellender de.
The relative population sizes of a species complex of Chauliognathus are reported, as well as their spatial distribution associated with different patches of food plants. Field work was done at Fazenda Santa Isabel, municipality of Guaíba, State of Rio Grande do Sul, Brazil. The results suggest that two mechanisms account for the reduction in food competition among the species involved: one is asynchrony in the appearance of the species in the area, and the other is aggregation in different patches of food plants. Since the species here reported show a similar colour pattern (yellow-black) the possibility of the occurrence of serial mimicry in this complex of species is dicussed.
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Chauliognathus; Aggregation; Competition; Mimicry; Coleoptera.
Ano: 2001
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0073-47212001000200002

Determinação da agregação do solo - metodologia em uso na Embrapa Agropecuária Oeste.
Provedor de dados: 14
Autores: SALTON, J. C.; SILVA, W. M.; TOMAZI, M.; HERNANI, L. C.
bitstream/item/79247/1/COT2012184.pdf
Tipo: Comunicado Técnico (INFOTECA-E)
Palavras-chave: Avaliação; Agregação; Evaluation; Aggregation; Analisys.; Análise; Solo.; Soil.
Ano: 2012
URL: http://www.infoteca.cnptia.embrapa.br/infoteca/handle/doc/952808

Indicator-Based Geostatistical Models For Mapping Fish Survey Data
Provedor de dados: 5
Autores: Petitgas, Pierre; Woillez, Mathieu; Doray, Mathieu; Rivoirard, Jacques.
Marine research survey data on fish stocks often show a small proportion of very high-density values, as for many environmental data. This makes the estimation of second-order statistics, such as the variance and the variogram, non-robust. The high fish density values are generated by fish aggregative behaviour, which may vary greatly at small scale in time and space. The high values are thus imprecisely known, both in their spatial occurrence and order of magnitude. To map such data, three indicator-based geostatistical methods were considered, the top-cut model, min–max autocorrelation factors (MAF) of indicators, and multiple indicator kriging. In the top-cut and MAF approaches, the variable is decomposed into components and the most continuous ones...
Tipo: Text
Palavras-chave: Top-cut; MAF; Indicators; Co-kriging; Skewed distribution; Anchovy; Bay of Biscay; Fisheries survey data; Aggregation.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00429/54021/55339.pdf

Association between bluefin tuna schools and oceanic features in the western Mediterranean
Provedor de dados: 5
Autores: Royer, Francois; Fromentin, Jean-marc; Gaspar, P.
We present an analysis of the distribution of bluefin tuna Thunnus thynnus schools spotted during aerial surveys in the Gulf of Lions, in relation to oceanographic features. Bio-optical and thermal properties of the sea surface derived from high-resolution sensors (AVHRR and SeaWiFS) were studied on a daily basis, and an edge-detection technique was applied to detect frontal zones. Geostatistics and point-process analyses were used to evaluate the role of the environment in structuring the spatial pattern of bluefin tuna (BFT). The distribution of schools spotted was strongly non-stationary both in space and time; this is believed to be an effect of the survey design (transect sampling) and the influence of transient oceanographic structures (surface...
Tipo: Text
Palavras-chave: Thunnus thynnus; Gulf of Lions; Point process analysis; Front detection; Sea surface temperature; Ocean colour; Aggregation.
Ano: 2004
URL: http://archimer.ifremer.fr/doc/00000/10786/7585.pdf

Examples of spatial and temporal variations of some fine-grained suspended particle characteristics in two Danish coastal water bodies
Provedor de dados: 5
Autores: Mikkelsen, Oa.
In June and September of 1999, a LISST-100 in situ laser diffraction particle sizer was used to analyse the temporal and spatial variation of the beam attenuation coefficient, the in situ median particle (aggregate) diameter and the median volume concentration of suspended matter in two Danish coastal water bodies. One of the study sites was generally exposed to wind, while the other was quite sheltered. Measurements of the mass concentration of total suspended matter and chl a were made simultaneously. The in situ median effective density, settling velocity and vertical flux of the suspended matter are computed. Results demonstrate that in September, the in situ median aggregate diameter, settling velocity and vertical flux was smaller (by a factor of up...
Tipo: Text
Palavras-chave: Agrégation; Diffraction laser; Spectre de taille des particules; Dimension fractale; Vitesse de sédimentation; Aggregation; Laser diffraction; Particle size spectra; Fractal dimension; Settling velocity.
Ano: 2002
URL: http://archimer.ifremer.fr/doc/00322/43328/42899.pdf

Surface functionalization determines behavior of nanoplastic solutions in model aquatic environments
Provedor de dados: 5
Autores: Tallec, Kevin; Blard, Océane; González-fernández, Carmen; Brotons, Guillaume; Berchel, Mathieu; Soudant, Philippe; Huvet, Arnaud; Paul-pont, Ika.
Plastic debris are classified as a function of their size and recently a new class was proposed, the nanoplastics. Nano-sized plastics have a much greater surface area to volume ratio than larger particles, which increases their reactivity in aquatic environment, making them potentially more toxic. Only little information is available about their behavior whereas it crucially influences their toxicity. Here, we used dynamic light scattering (DLS) to explore the influence of environmental factors (fresh- and saltwater, dissolved organic matter) on the behavior (surface charge and aggregation state) of three different nano-polystyrene beads (50 nm), with (i) no surface functionalization (plain), (ii) a carboxylic or (iii) an amine functionalization. Overall,...
Tipo: Text
Palavras-chave: Nanoplastic; Dynamic light scattering; Behavior; Aggregation; Salinity; Organic matter.
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00485/59652/62684.pdf

Use of a disjunctive kriging to model areas of high pelagic fish density in acoustic fisheries surveys
Provedor de dados: 5
Autores: Petitgas, Pierre.
Schooling fish may aggregate in very high densities covering very small areas. Thus the probability of hitting such high-density spots during a large-scale sampling is very low. The sampling fluctuations of the tail of the histogram are thought to be very significant. The stock biomass estimate and its precision rely greatly on how precisely the tail of the histogram can be sampled. In order to acquire elements for improving survey designs and abundance estimators wc study here the relation in space that the high values have with the other values. A disjunctive kriging approach is used. Different quantiles of the histogram are coded by indicators. The spatial structure of each indicator and its spatial covariation with the others are studied by computing...
Tipo: Text
Palavras-chave: Distribution spatiale; Agrégation; Abondance; Estimation; Géostatistique; Échantillonnage; Spatial distribution; Aggregation; Abundance estimation; Geostatistics; Sampling.
Ano: 1993
URL: http://archimer.ifremer.fr/doc/00190/30076/28564.pdf

Phytoplankton morphology controls on marine snow sinking velocity
Provedor de dados: 5
Autores: Laurenceau-cornec, Emmanuel C.; Trull, Thomas W.; Davies, Diana M.; De La Rocha, Christina L.; Blain, Stephane.
During the second KErguelen Ocean and Plateau compared Study (KEOPS2) in October-November 2011, marine snow was formed in roller tanks by physical aggregation of phytoplankton assemblages sampled at 6 stations over and downstream of the Kerguelen Plateau. Sinking velocities, morphology, bulk composition (transparent exopolymer particles, biogenic silica, particulate organic carbon), and phytoplankton contents were measured individually on 66 aggregates to identify controls on sinking velocities. Equivalent spherical diameters (ESD) ranged from 1 to 12 mm, and the particle aspect ratios, Corey shape factors, and fractal dimensions (D-F1 = 1.5, D-F2 = 1.8) were close to those of smaller natural aggregates (0.2 to 1.5 mm) collected in polyacrylamide...
Tipo: Text
Palavras-chave: Sinking velocity Marine snow; Aggregation; Phytoplankton; Porosity.
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00352/46275/46044.pdf

Predation has no competition: factors influencing space and resource use by echinoids in deep-sea coral habitats, as evidenced by continuous video transects
Provedor de dados: 5
Autores: Stevenson, Angela; Mitchell, Fraser J. G.; Davies, Jaime S.
Predation and competition are highly influential factors determining space use in foraging animals, and ultimately contribute to the spatial heterogeneity observed within habitats. Here we investigated the influence of competition and predation on space and resource use via continuous video transect observations – a tool that has not previously been employed for this purpose. This study therefore also evaluates video data as a pragmatic tool to study community interactions in the deep sea. Observations were compiled from 15 video transects spanning five submarine canyons in the Bay of Biscay, France. Substrate choice, positioning on the coral, echinoid aggregate size, and the presence/absence of predators (e.g. fish and decapods) as well as competitors...
Tipo: Text
Palavras-chave: Aggregation; Bay of Biscay; Cidaris cidaris; Community interactions; Deep sea; Echinothuriidae; NE Atlantic; Refuge; Space use.
Ano: 2015
URL: http://archimer.ifremer.fr/doc/00242/35303/33829.pdf

Aerodynamical, immunological and pharmacological properties of the anticancer antibody cetuximab
Provedor de dados: 5
Autores: Maillet, A; Congy Jolivet, N; Le Guellec, S; Vecellio, L; Hamard, S; Courty, Y; Courtois, Anthony; Gauthier, F; Diot, P; Thibault, G; Lemarie, E; Heuze Vourc' H, N.
Purpose. Despite an increasing interest in the use of inhalation for local delivery of molecules for respiratory diseases and systemic disorders, methods to deliver therapy through air-ways has received little attention for lung cancer treatment. However, inhalation of anticancer drugs is an attractive alternative route to systemic administration which results in limited concentration of the medication in the lungs, and triggers whole-body toxicity. In this study, we investigated the feasibility of nebulization for therapeutic antibodies, a new class of fully-approved anticancer drugs in oncology medicine.   Materials and methods. Cetuximab, a chimeric IgG1 targeting the epidermal growth factor receptor (EGER), was nebulized using three types of delivery...
Tipo: Text
Palavras-chave: Nebulizer; Lung cancer; Cetuximab; Anticancer antibody; Aggregation; Aerosol.
Ano: 2008
URL: http://archimer.ifremer.fr/doc/2008/publication-4201.pdf

Effect of relative humidity on emergence and on dispersal and regrouping of first instar Nezara viridula (L.) (Hemiptera: Pentatomidae)
Provedor de dados: 82
Autores: Hirose,Edson; Panizzi,Antônio R.; Cattelan,Alexandre J.
Laboratory studies with 1st instar of southern green stink bug, Nezara viridula (L.) indicated that relative humidity (RH) greatly affected nymph emergence and survivorship up to the 2nd instar, reaching the maximum value (&lt;FONT FACE=Symbol&gt;»&lt;/FONT&gt; 90%) with RH of &gt; 80%. At 60% RH, 60% of the nymphs emerged and survived, while with 0% RH only &lt;FONT FACE=Symbol&gt;»&lt;/FONT&gt; 15% of eggs hatched, and most nymphs died. Emerged nymphs from egg masses placed in plastic boxes with a gradient of humidity remained on egg shells for ca. one day. After this period, they dispersed and regrouped on top of shells 6.8 ± 0.67 times, until they abandoned the shells toward the source of humidity, avoiding the water-saturated areas. Duration taken for...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Heteroptera; Stink bug; Behavior; Aggregation; Microclimate.
Ano: 2006
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1519-566X2006000600006

The chemical volatiles (Semiochemicals) produced by neotropical stink bugs (Hemiptera: Pentatomidae)
Provedor de dados: 82
Autores: Moraes,Maria C.B.; Pareja,Martín; Laumann,Raúl A.; Borges,Miguel.
In recent years the growing concern about environmental changes and how we are using the natural resources have triggered a search for natural products as alternatives to synthetic pesticides. The stink bugs produce a wide variety of chemical compounds (semiochemicals) that show potential to manage these insects. The stink bugs Chinavia impicticornis (Stål), C. ubica (Rolston), Dichelops melacanthus (Dallas), Euschistus heros (F.), Piezodorus guildinii (Westwood), Thyanta perditor (Westwood) and Tibraca limbativentris (Stål) had their blends of defensive compounds evaluated both qualitative and quantitatively. The main compounds identified on the glands of Brazilian stink bugs are: 2-alkenals, mainly the E isomer; saturated aliphatic hydrocarbons; and 4...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Pheromone; Allelochemical; Aggregation; Behaviour; Soybean.
Ano: 2008
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1519-566X2008000500001

Coastal migratory connections of humpback whales, Megaptera Novaeangliae Borowski, 1871, southern Chile
Provedor de dados: 20
Autores: Galleti, Bárbara; Capella, Juan; Gibbons, Jorge; Cabrera, Elsa.
There is not published information on a comparative analysis about interchange of individual humpback whales between coastal areas of aggregation of the species along southern Chilean coast. Here we present a comparison of individually photo-identified humpback whales obtained off northwestern Chiloé Island, in Patagonian and Fuegian fjords and in the Strait of Magellan near Carlos III Island , to discover movements and interchange of individuals. Comparison of photographs resulted in conclusive matches of four individuals within the four study locations: two whales from Canal Wide (49°55’S, 74°30’W), one whale from Canal Cockburn (54°18’S, 72°15’W) and a mother-calf pair off northwestern Chiloé Island matched whales found near Carlos III. The minimum...
Tipo: Journal Contribution
Palavras-chave: Marine mammals; Migratory species; Aggregation; Cetacea; Megaptera novaeangliae; Http://aims.fao.org/aos/agrovoc/c_1482; Http://aims.fao.org/aos/agrovoc/c_49019.
Ano: 2008
URL: http://hdl.handle.net/1834/4165

Full Rank Rational Demand Systems
Provedor de dados: 31
Autores: LaFrance,   Jeffrey T.; Pope,   Rulon D.
We extend the set of full rank nominal and deflated income demand systems to rational demand systems of any rank and present a unifying expression for the indirect preferences of all full rank demand models.
Tipo: Working or Discussion Paper
Palavras-chave: Aggregation; Functional form; Integrability; Rank; Rational demand systems; Demand and Price Analysis; D12; E21.
Ano: 2006
URL: http://purl.umn.edu/7152

Aggregation Theory for Incomplete Systems
Provedor de dados: 31
Autores: LaFrance,   Jeffrey T.; Beatty,   Timothy K.M.; Pope,   Rulon D.
Gorman's theory of demand is extended comprehensively to incomplete systems. The incomplete systems approach dramatically increases this class of models. The separate roles of symmetry and adding up are identified in the rank and the functional form of this class of models. We show that symmetry determines rank and the maximum rank is three. We show that adding up and 0o homogeneity determines the functional form and there is no functional form restriction for an incomplete system. We prove that every full rank system and reduced rank systems with a minimal level of degeneracy can be written as a polynomial in a single function of income. A complete set of closed form solutions for the indirect objective functions of this class of models is derived. A...
Tipo: Working or Discussion Paper
Palavras-chave: Aggregation; Rank; Functional form; Integrability; Incomplete systems; Weak integrability; Demand and Price Analysis; D12; E21.
Ano: 2005
URL: http://purl.umn.edu/25033

Adjustment is Much Slower than You Think
Provedor de dados: 31
Autores: Caballero,   Ricardo J.; Engel,   Eduardo M.R.A.
In most instances, the dynamic response of monetary and other policies to shocks is infrequent and lumpy. The same holds for the microeconomic response of some of the most important economic variables, such as investment, labor demand, and prices. We show that the standard practice of estimating the speed of adjustment of such variables with partial-adjustment ARMA procedures substantially overestimates this speed. For example, for the target federal funds rate, we find that the actual response to shocks is less than half as fast as the estimated response. For investment, labor demand and prices, the speed of adjustment inferred from aggregates of a small number of agents is likely to be close to instantaneous. While aggregating across microeconomic units...
Tipo: Working or Discussion Paper
Palavras-chave: Speed of adjustment; Discrete adjustment; Lumpy adjustment; Aggregation; Calvo model; ARMA process; Partial adjustment; Expected response time; Monetary policy; Investment; Labor demand; Sticky prices; Idiosyncratic shocks; Impulse response function; Wold representation; Time-to-build; Financial Economics; C22; C43; D2; E2; E5.
Ano: 2003
URL: http://purl.umn.edu/28419

Aggregation of Tariff-Rate Quotas
Provedor de dados: 31
Autores: Lips,   Markus; Rieder,   Peter.
For an analysis of Tariff-Rate Quotas the question arises how to aggregate them. In this paper, two alternative aggregation methods are compared, based on the magnitude of aggregated tariffs or the aggregated quota rent.
Tipo: Journal Article
Palavras-chave: Tariff-Rate Quota; Aggregation; General Equilibrium Modeling; Agricultural and Food Policy; International Relations/Trade.
Ano: 2005
URL: http://purl.umn.edu/97325

Ambiguous Aggregation of Expert Opinions: The Case of Optimal R&amp;D Investment
Provedor de dados: 31
Autores: Athanassoglou,   Stergios; Bosetti,   Valentina; Maere d'Aertrycke,   Gauthier de.
How should a decision-maker allocate R&amp;D funds when a group of experts provides divergent estimates on a technology's potential effectiveness? To address this question, we propose a simple decision-theoretic framework that takes into account ambiguity over the aggregation of expert opinion and a decision-maker's attitude towards it. In line with the paper's focus on R&amp;D investment, decision variables in our model may affect experts' subjective probability distributions of the future potential of a technology. Using results from convex optimization, we are able to establish a number of analytical results including a closed-form expression of our model's value function, as well as a thorough investigation of its differentiability properties. We apply...
Tipo: Working Paper
Palavras-chave: Ambiguity; Expert Opinions; R&amp;D; Convex/Conic Optimization; Aggregation; Research and Development/Tech Change/Emerging Technologies; C61; D81; Q42.
Ano: 2012
URL: http://purl.umn.edu/121719

Welfare Impacts of Agricultural and Non-Agricultural Trade Reforms
Provedor de dados: 31
Autores: Laborde,   David; Martin,   William J.; van der Mensbrugghe,   Dominique.
The variability of protection rates within sectors is frequently particularly high in agriculture relative to non-agriculture. Standard aggregation procedures ignore the variability within sectors, and underweight the importance of highly protected sectors. It therefore seems likely that they underestimate the potential benefits of agricultural trade reform relative to non-agricultural reform. This study examines this question using a new procedure for aggregating trade distortions. It finds that the key impact of using better aggregators is to increase the benefits of both agricultural and non-agricultural reform. It finds that using optimal aggregation procedures increases the measured importance of agricultural trade reform relative to non-agricultural...
Tipo: Conference Paper or Presentation
Palavras-chave: Agricultural trade; Nonagricultural trade; Trade distortions; Tariffs; Aggregation; World Trade Organization; WTO; Trade reform; Food Security and Poverty; International Relations/Trade; F13; F14; Q13; Q17; Q18.
Ano: 2011
URL: http://purl.umn.edu/103958

Process Aggregation and Efficiency.
Provedor de dados: 31
Autores: Bogetoft,   Peter.
We analyse how the aggregation of production processes affects efficiency evaluations. A production unit can be inefficient even though all its production processes are efficient. We show how to test if observed "inefficiencies" may be caused by an aggregation and how to correct efficiency measures for such aggregation generated inefficiencies. The tests and the adjusted efficiency measurement programs involve hypothetical dis-aggregations designed to put the evaluated unit in its best possible light.
Tipo: Working or Discussion Paper
Palavras-chave: Production Processes; Data Envelopment Analysis (DEA); Aggregation; Efficiency; Production Economics.
Ano: 1999
URL: http://purl.umn.edu/24190

AGGREGATION WITHOUT SEPARABILITY: TESTS OF U.S. AND MEXICAN AGRICULTURAL PRODUCTION DATA
Provedor de dados: 31
Autores: Lin,   Ni; Davis,   George C.; Shumway,   C. Richard.
The generalized composite commodity theorem (Lewbel 1996) is used to test for consistent aggregation of U.S. and Mexican agricultural production data in each of the categories for which earlier tests rejected homothetic separability. All U.S. agricultural outputs can be justifiably aggregated into as few as four categories. All Mexican agricultural outputs can be aggregated into as few as five categories. The aggregation of all outputs into a single output cannot be supported in either country by sufficient conditions provided by the generalized composite commodity theorem and/or a homothetically separable technology.
Tipo: Conference Paper or Presentation
Palavras-chave: Aggregation; Separability; Generalized composite commodity theorem; Demand and Price Analysis.
Ano: 1998
URL: http://purl.umn.edu/20927

Investigating Distance Effects on Environmental Values: A Choice Modelling Approach
Provedor de dados: 31
Autores: Concu,   Giovanni B.
This paper describes a Choice Modelling experiment set up to investigate the relationship between distance and willingness to pay for environmental quality changes. The issue is important for the estimation and transfer of benefits. The Choice Modelling experiment allows testing distance effects on parameters of environmental attributes that imply different trade-offs between use and non-use values. The sampling procedure is designed to provide a "geographically balanced" sample. Several specifications of the distance covariate are compared and distance effects are shown to take complex shapes. Welfare analysis shows that disregarding distance produces under-estimation of individual and aggregated benefits and losses, seriously hindering the reliability of...
Tipo: Conference Paper or Presentation
Palavras-chave: Aggregation; Choice Modelling; Distance; Geographical Sampling; Specification Tests; Environmental Economics and Policy; Q51; H4; D6.
Ano: 2006
URL: http://purl.umn.edu/25566

U.S. Demand for Food and Nutrition in the 20th Century
Provedor de dados: 31
Autores: Beatty,   Timothy K.M.; LaFrance,   Jeffrey T.
A great deal of research on farm and food policy and consumer choice focuses on the link between food consumption and nutrition. This paper presents and applies a new method to analyze the demand for food and nutrients, and consumer welfare. The foundation for this method is the recent extension of the Gorman class of exactly aggregable demand models to incomplete demand systems. The purposes of this approach are to derive and implement coherent, flexible empirical models of food and nutrient demand, to estimate the model parameters consistently with aggregate data, and to make inferences on the impacts of farm and food policy changes on food and nutrient demand and consumer welfare of those policies. We apply this framework to annual per capita U.S....
Tipo: Working or Discussion Paper
Palavras-chave: Aggregation; Agricultural policy; Food demand; Gorman Systems of Demands; Nutrition; Demand and Price Analysis; Food Consumption/Nutrition/Food Safety.
Ano: 2005
URL: http://purl.umn.edu/25105

AN ECONOMETRIC MODEL OF THE DEMAND FOR FOOD AND NUTRITION
Provedor de dados: 31
Autores: LaFrance,   Jeffrey T.
A flexible, full rank two model of food consumption that is globally consistent with economic theory, aggregates across income, demographic variables, and variations in micro demand parameters, and accommodates tradeoffs between tastes and nutrition is derived.  The econometric demand model is estimated with per capita U.S. consumption of 21 foods on the time period 1919-1994, excluding the World War II years 1942-1946.  An approach for inferring the percentage of nutrients available from individual commodities in the U.S. food supply is derived and implemented empirically on the time period 1949-1995 for the nutrients energy, protein, total fat, carbohydrates, and cholesterol.  The two sets of model results are combined to generate time paths for income...
Tipo: Working or Discussion Paper
Palavras-chave: Aggregation; Demand; Food; Nutrition; Hicksian Compensated Price Elasticities; Demand and Price Analysis; Food Consumption/Nutrition/Food Safety.
Ano: 1999
URL: http://purl.umn.edu/25004

The Measurement of the Energy Intensity of Manufacturing Industries: A Principal Components Analysis
Provedor de dados: 31
Autores: Bernard,   Jean-Thomas; Cote,   Bruno.
Energy intensity is the ratio of energy use to output. Most industries deal with several energy sources and outputs. This leads to the usual difficulties of aggregating heterogeneous inputs and outputs. We apply principal components analysis to assess the information derived from six energy intensity indicators. We use two measures of total energy use (thermal and economic) and three measures of industry output (value added, value of production, and value of shipments). The data comes from manufacturing industries in Quebec, Ontario, Alberta, and British Columbia from 1976 to 1996. We find that the variation of the six energy intensity indicators that is accounted for by the first principal component is quite large. However, depending on how variables are...
Tipo: Working or Discussion Paper
Palavras-chave: Energy intensity; Aggregation; Principal components analysis; Resource /Energy Economics and Policy; Q40; C43; L60.
Ano: 2002
URL: http://purl.umn.edu/10544

Welfare Measurement and Representative Consumer Theory
Provedor de dados: 31
Autores: Smith,   V. Kerry; von Haefen,   Roger H.
This paper generalizes results from Anderson, De Palma, and Thisse [1992] linking individual random utility and aggregate representative individual demand models, to consider a comparable relation for the willingness to pay functions for quality attributes of marketed goods. It also suggests how the logic can be used to describe links between choice occasion and aggregate models (across occasions) for an individual.
Tipo: Working or Discussion Paper
Palavras-chave: Willingness to pay; RUM; Aggregation; Consumer/Household Economics; DG1; Q2.
Ano: 1997
URL: http://purl.umn.edu/10646

Building Gorman's Nest
Provedor de dados: 31
Autores: LaFrance,   Jeffrey T.; Beatty,   Timothy K.M.; Pope,   Rulon D.
Gorman Engel curves are extended to incomplete systems. The roles of Slutsky symmetry and homogeneity/adding up are isolated in the rank and functional form restrictions for Gorman systems. Symmetry determines the rank condition. The maximum rank is three for incomplete and complete systems. Homogeneity/adding up determines the functional form restrictions in complete systems. There is no restriction on functional form in an incomplete system. Every full rank and minimal deficit reduced rank Gorman system has a representation as a polynomial in a single function of income. This generates a complete taxonomy of indirect preferences for Gorman systems. Using this taxonomy, we develop models of incomplete Gorman systems that nest rank and functional form and...
Tipo: Working or Discussion Paper
Palavras-chave: Aggregation; Functional form; Gorman Engel curves; Incomplete demand systems; Rank; Weak integrability; Demand and Price Analysis; D12; E21.
Ano: 2004
URL: http://purl.umn.edu/25027

Is Storage at a Loss Merely an Illusion of Spatial Aggregation?
Provedor de dados: 31
Autores: Franken,   Jason R.V.; Garcia,   Philip; Irwin,   Scott H.
The storage-at-a-loss paradox—stocks despite inadequate price growth to cover storage costs—is an unresolved issue of long-standing interest to economists. Alternative explanations include risk premiums for futures market speculators, convenience yields from holding stocks, and mismeasurement/aggregation of data. Statistical analyses of regional and elevator corn and soybean price growth in Illinois suggest limited aggregation effects and reveal a pattern of regional- and elevator-level backwardations in the presence of Illinois corn stocks that is inconsistent with aggregation explanations for storage at a loss. Interviews with elevator managers support the existence of convenience yields.
Tipo: Journal Article
Palavras-chave: Aggregation; Convenience yield; Corn; Intertemporal arbitrage; Regional and elevator data; Soybeans; Storage at a loss; Agribusiness; Marketing.
Ano: 2009
URL: http://purl.umn.edu/90658

Constant market shares analysis: uses, limitations and prospects
Provedor de dados: 31
Autores: Ahmadi-Esfahani,   Fredoun Z.
In this paper, we generalise the constant market shares (CMS) framework, with particular attention to the underlying theoretical conditions required for diagnostic interpretation. The approach is applied to the analysis of the export performance of the Australian processed food sector in South-East Asia over the period 1980–2003. We conclude that the usefulness of CMS analysis for evaluating a country’s international trade performance depends upon the empirical validity of the aggregation assumptions implicit in the diagnostic interpretation.
Tipo: Journal Article
Palavras-chave: Aggregation; Armington model; Competitiveness; Constant market shares; Marketing.
Ano: 2006
URL: http://purl.umn.edu/116983

On the Solutions to Full Rank Three Gorman Systems
Provedor de dados: 31
Autores: LaFrance,   Jeffrey T.
This letter closes a gap in the set of solutions for the full rank three systems of Gorman Engel curves and presents a unified expression for the indirect preferences in this case.
Tipo: Working or Discussion Paper
Palavras-chave: Aggregation; Rank; Functional form; Integrability; Research Methods/ Statistical Methods; D12; E21.
Ano: 2005
URL: http://purl.umn.edu/25048

Using Weak Separability and Generalized Composite Commodity Theorem in Modeling Ground Beef Demand
Provedor de dados: 31
Autores: Schulz,   Lee L.; Schroeder,   Ted C.; Xia,   Tian.
Replaced with revised version of paper 06/15/11.
Tipo: Conference Paper or Presentation
Palavras-chave: Aggregation; Generalized Composite Commodity Theorem; Beef demand; Weak separability; Demand and Price Analysis; Q13; Q18; R32.
Ano: 2011
URL: http://purl.umn.edu/103904

TESTING AGGREGATION WITHOUT SEPARABILITY IN MEAT DEMAND: AN INVESTIGATION OF THE GENERALIZED COMPOSITE COMMODITY THEOREM
Provedor de dados: 31
Autores: Davis,   George C.
In the estimation of aggregate meat demand systems, weak separability is often a maintained assumption.  However, only a few studies have tested and failed to reject this assumption.  Recently, Lewbel (1996) developed a generalized composite commodity theorem (GCCT) that is less restrictive than weak separability.  In this study, a data set in which the weak separability conditions for aggregation have been rejected is reconsidered to determine if aggregation can be based on the GCCT.  Some subtleties of Lewbel's testing procedure that are not discussed by Lewbel are considered, and the fundamental problem of formulating aggregates prior to conducting tests for aggregation is addressed.
Tipo: Conference Paper or Presentation
Palavras-chave: Aggregation; Demand; Weak separability; Generalized composite commodity theorem.; Demand and Price Analysis; Livestock Production/Industries.
Ano: 1998
URL: http://purl.umn.edu/20895

Data Aggregation and Vertical Price Transmission: An Experiment with German Food Prices
Provedor de dados: 31
Autores: von Cramon-Taubadel,   Stephan; Loy,   Jens-Peter; Meyer,   Jochen.
The impact of cross sectional aggregation over individual retail stores on the estimation and testing of vertical price transmission between the wholesale and retail levels is investigated using a unique data set of individual retail prices in Germany. Systematic differences between the results of estimations using aggregated data on the one hand, and disaggregated data on the other, are discussed theoretically and confirmed empirically. The results suggest that estimation with aggregated data generates misleading conclusions about price transmission behavior at the level of the individual units (i.e. retail stores) that underlie these aggregates.
Tipo: Conference Paper or Presentation
Palavras-chave: Aggregation; Vertical Price Transmission; Food Prices; Germany; Demand and Price Analysis; Marketing; L11; D40.
Ano: 2006
URL: http://purl.umn.edu/25291

Yield trend estimation in the presence of non-constant technological change and weather effects
Provedor de dados: 31
Autores: Conradt,   Sarah; Bokusheva,   Raushan; Finger,   Robert; Kussaiynov,   Talgat.
The application of yield time series in risk analysis prerequisites the estimation of technological trend which might be present in the data. In this paper, we show that in presence of highly volatile yield time series and non-constant technology, the consideration of the weather effect in the trend equation can seriously improve trend estimation results. We used ordinary least squares (OLS) and MM, a robust estimator. Our empirical analysis is based on weather data as well as farm-level and county-level yield data for a sample of grain-producing farms in Kazakhstan.
Tipo: Presentation
Palavras-chave: Yield detrending; Weather information; Robust trend estimation; Aggregation; Risk and Uncertainty; Q19.
Ano: 2012
URL: http://purl.umn.edu/122541

Unstable Individual Bids and Stable Market Demand
Provedor de dados: 31
Autores: Alfnes,   Frode; Rickertsen,   Kyrre; Shogren,   Jason F.
We explore preference stability at the individual and market level. We examine individual bidding behavior among 116 French consumers who participated in experimental auctions conducted seven months apart for five types of fish. We reject preference stability at the individual level, but not at the aggregate market level.
Tipo: Conference Paper or Presentation
Palavras-chave: Aggregation; Consumer preferences; Demand; Experimental auctions; Food choice; Marketing; C91; D12; Q13.
Ano: 2011
URL: http://purl.umn.edu/114219

Aggregation and Calibration of Agricultural Sector Models Through Crop Mix Restrictions and Marginal Profit Adjustments
Provedor de dados: 31
Autores: Wiborg,   Torben; McCarl,   Bruce A.; Rasmussen,   Svend; Schneider,   Uwe A.
All agricultural sector models must deal with aggregation and calibration somehow. The aggregation problem involves treating a group of producers as if they all responded in the same way as a single representative unit. The calibration problem concerns making a model reproduce as closely as possible an empirically observed set of decision maker actions. This paper shows how both calibration and aggregation are addressed through crop mix restrictions combined with marginal profit adjust-ments.
Tipo: Conference Paper or Presentation
Palavras-chave: Mathematical programming; Aggregation; Calibration; Crop mix; Marginal cost; Agricultural sector model; Agribusiness; C6; C61; Q1; Q11; Q17; Q18; R12; R13; R14.
Ano: 2005
URL: http://purl.umn.edu/24567

Aggregation Issues in the Estimation of Linear Programming Productivity Measures
Provedor de dados: 31
Autores: Shaik,   Saleem; Mishra,   Ashok K.; Atwood,   Joseph A.
This paper demonstrates the sensitivity of the linear programming approach in the estimation of productivity measures in the primal framework using Malmquist productivity index and Malmquist total factor productivity index models. Specifically, the sensitivity of productivity measure to the number of constraints (level of dis-aggregation) and imposition of returns to scale constraints of linear programing is evaluated.  Further, the shadow or dual values are recovered from the linear program and compared to the market prices used in the ideal Fisher index approach to illustrate sensitivity.  Empirical application to U.S. state-level time series data from 1960-2004 reveal productivity change decreases with increases in the number of constraints.  Further,...
Tipo: Report
Palavras-chave: Aggregation; Share-weights; Single and multiple output and input; Malmquist productivity index; Malmquist total factor productivity index; Agribusiness; Production Economics.
Ano: 2011
URL: http://purl.umn.edu/101783

TESTING AGGREGATION CONSISTENCY ACROSS GEOGRAPHY AND COMMODITIES
Provedor de dados: 31
Autores: Liu,   Qinghua; Shumway,   C. Richard.
Consistent aggregation of production data across commodities and states was tested using Lewbel's generalized composite commodity theorem (GCCT).  This was the first empirical GCCT test for consistent geographic aggregation and was applied to two groups of states.  Consistent commodity aggregation was tested in all states for two output groups and three input groups and in one state for a larger number of groups.  Using a more powerful test procedure than previously applied to production data, most tests for commodity aggregation gave ambiguous results.  Consistent geographic aggregation was generally supported across Pacific Northwest states but was ambiguous across all Western states.   Key words: Aggregation, commodity, geographic, composite commodity...
Tipo: Conference Paper or Presentation
Palavras-chave: Aggregation; Commodity; Geographic; Composite commodity theorem; Multiple-comparison tests.; Research Methods/ Statistical Methods.
Ano: 2003
URL: http://purl.umn.edu/22201

Unstable Individual Preferences and Stable Aggregate Demand: French Consumers’ Willingness to Pay for Farmed and Wild Cod
Provedor de dados: 31
Autores: Alfnes,   Frode; Rickertsen,   Kyrre.
We use panel data from two experiments conducted five months a part to investigate the stability of individual preferences and aggregate demand for five types of fish. Even though the bids in the two experiments are positively correlated, they clearly suggest that the individual preferences are unstable. This may be explained by internal desire for variety or by external effects such as new relevant information, seasonality in preferences, changes in the quality of the fish, and changes in the market price of fish. However, the aggregate demand curves of the participants are stable when we control for changes in the perceived quality of the fish and price expectations of the participants. In other words, the stability is generated by aggregation rather...
Tipo: Conference Paper or Presentation
Palavras-chave: Aggregation; Consumer preferences; Demand; Experimental markets; Food choices; Consumer/Household Economics; Demand and Price Analysis; C91; D12; Q13.
Ano: 2009
URL: http://purl.umn.edu/49968

On-farm broiler welfare assessment and associated training
Provedor de dados: 89
Autores: Butterworth,A.
Around the world, people who care for animals as stock keepers, stockmen, farmers, producers are placed in a position where they can greatly influence the quality of life of the animals they manage. This is particularly true in broiler chickens, where large numbers of animals can be cared for by comparatively small numbers of people. There is an international progression to start to assess poultry welfare on farm by looking at the animals themselves using (Animal Based Measures ABMs) rather than by looking exclusively at the resources provided (space, light heat, litter material - Resource Based Measures RBM's). In general, the areas being assessed are: Are the animals properly fed and supplied with water? Are the animals properly housed? Are the animals...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Poultry assessment; Farm assessment; Welfare Quality protocol; Animal based measures; Outcome based measures; Resource based measures; Welfare score; Aggregation; Management support; Principles; Criteria.
Ano: 2013
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1516-635X2013000200001

Physical quality of an Oxisol after different periods of management systems
Provedor de dados: 90
Autores: Rossetti,Karina de Vares; Centurion,José Frederico; Sousa Neto,Eurico Lucas de.
Management systems may lead to a loss of soil physical quality as a result of removal of the plant cover and excessive agricultural mechanization. The hypothesis of this study was that the soil aggregate stability, bulk density, macro- and microporosity, and the S index and saturated hydraulic conductivity may be used as indicators of the soil physical quality. The aim was to study the effects of different periods and managements on the physical attributes of a medium-textured Red Oxisol under soybean and corn for two growing seasons, and determine which layers are most susceptible to variations. A completely randomized experimental design was used with split plots (five treatments and four layers), with four replications. The treatments in 2008/09...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Aggregation; S index; Saturated hydraulic conductivity.
Ano: 2013
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832013000600009

Aggregate stability as affected by short and long-term tillage systems and nutrient sources of a hapludox in southern Brazil
Provedor de dados: 90
Autores: Veiga,Milton da; Reinert,Dalvan José; Reichert,José Miguel.
The ability of a soil to keep its structure under the erosive action of water is usually high in natural conditions and decreases under frequent and intensive cultivation. The effect of five tillage systems (NT = no-till; CP = chisel plowing and one secondary disking; CT = primary and two secondary distings; CTb = CT with crop residue burning; and CTr = CT with removal of crop residues from the field), combined with five nutrient sources (C = control, no nutrient application; MF = mineral fertilizers according to technical recommendations for each crop; PL = 5 Mg ha-1 y-1 fresh matter of poultry litter; CM = 60 m³ ha-1 y-1 slurry cattle manure; and SM = 40 m³ ha-1 y-1 slurry swine manure) on wet-aggregate stability was determined after nine years (four...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Soil tillage; Manure; Sampling time; Soil structure; Aggregation.
Ano: 2009
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832009000400003

Aggregate stability by the "high energy moisture characteristic" method in an oxisol under differentiated management
Provedor de dados: 90
Autores: Silva,Érika Andressa da; Oliveira,Geraldo César de; Silva,Bruno Montoani; Carducci,Carla Eloize; Avanzi,Junior Cesar; Serafim,Milson Evaldo.
Studies testing the High Energy Moisture Characteristic (HEMC) technique in tropical soils are still incipient. By this method, the effects of different management systems can be evaluated. This study investigated the aggregation state of an Oxisol under coffee with Brachiaria between crop rows and surface-applied gypsum rates using HEMC. Soil in an experimental area in the Upper São Francisco region, Minas Gerais, was studied at depths of 0.05 and 0.20 m in coffee rows. The treatments consisted of 0, 7, and 28 Mg ha-1 of agricultural gypsum rates distributed on the soil surface of the coffee rows, between which Brachiaria was grown and periodically cut, and compared with a treatment without Brachiaria between coffee rows and no gypsum application. To...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Aggregation; Coffee production; Management systems; Method.
Ano: 2014
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832014000500028

Charge sparsity: An index to quantify cation effects on clay dispersion in soils
Provedor de dados: 63
Autores: Melo,Thadeu Rodrigues de; Machado,Wesley; Tavares Filho,João.
ABSTRACT: Few approaches have been developed to measure the isolated effect of exchangeable cations on clay dispersion in soils. In this study, the charge sparsity (CS) index was proposed using the ratio between the cations hydrated ionic radius and valence. The index capacity to measure cation effects on clay dispersion in soils was also evaluated. Three Ferralsols, sampled at different sites in Paraná State, Brazil, were homoionized with Ca2+, Mg2+, K+, or Na+ prior to evaluation of the clay dispersion degree. Published independent data for two soils and clays were also used. We tested the capacity of CS and II, the latter proposed by Marchuck and Rengasamy (2011), to predict clay dispersion in soils. The CS predicted the dispersion degree more...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Colloids; Electrical double layer; Aggregation; Flocculation; Zeta potential.
Ano: 2020
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-90162020000101400

An assemblage of terrestrial isopods (Crustacea) in southern Brazil and its contribution to leaf litter processing
Provedor de dados: 104
Autores: Quadros,Aline F.; Araujo,Paula B.
We present an assemblage of terrestrial isopods in Parque Estadual de Itapuã, southern Brazil, and estimate the contribution of two species to the leaf litter processing. After one year of sampling, we obtained 3748 individuals of six species and four eco-morphologic groups (in order of abundance): Balloniscus glaber Araujo &amp;amp; Zardo, 1995, Atlantoscia floridana (van Name, 1940), Pseudodiploexochus tabularis (Giambiagi de Calabrese, 1939), Trichorhina sp., Alboscia itapuensis Araujo &amp;amp; Quadros, 2005 and Novamundoniscus gracilis Lopes &amp;amp; Araujo, 2003. Total monthly density corresponded to 368 individuals per square meter. The species A. itapuensis and N. gracilis represented less than 1% of total individuals. All the others showed...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Aggregation; Eco-morphological groups; Feeding rates; Isopoda; Species association.
Ano: 2008
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0101-81752008000100009

Diversity of metazoan parasites in Colossoma macropomum (Serrasalmidae) from the lower Jari River, a tributary of the Amazonas River in Brazil
Provedor de dados: 36
Autores: GONÇALVES,Bianca Barata; OLIVEIRA,Marcos Sidney Brito; BORGES,William Felix; SANTOS,Gracienhe Gomes; TAVARES-DIAS,Marcos.
ABSTRACT This study investigated the diversity of metazoan parasites in Colossoma macropomum from the Jari River, in the eastern Amazon, northern Brazil. We collected a total of 4966 parasites from 34 fishes, including monogeneans (Anacanthorus spathulatus, Mymarothecium boegeri, Notozothecium janauachensis and Linguadactyloides brinkmanni), nematodes (Spectatus spectatus larvae, Contracaecum sp. larvae andProcamallanus (Spirocamallanus) inopinatus), digeneans (Cladorchiidae metacercariae), acanthocephalans (Neoechinorhynchus buttnerae), crustaceans (Ergasilus turucuyus, Argulus multicolor, Perulernaea gamitanae and Braga patagonica), mites and leeches. The dominance was of monogenean species, found in the gills of the hosts. The parasites exhibited high...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Aggregation; Diversity; Endoparasites; Freshwater fish.
Ano: 2018
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0044-59672018000300211

Parasitic diversity of a wild Satanoperca jurupari population, an ornamental cichlid in the Brazilian Amazon
Provedor de dados: 36
Autores: TAVARES-DIAS,Marcos; OLIVEIRA,Marcos Sidney Brito; GONÇALVES,Raissa Alves; NEVES,Lígia Rigor.
ABSTRACT Assessment of biodiversity is fundamental for the understanding of ecological interactions, but fish parasites were neglected in biodiversity estimates for a long time. The aim of this paper was to investigate the diversity of parasites in Satanoperca jurupari in the Amazon River system in Brazil. Of the fish examined, 90.0% were parasitized by one or more species of protozoans and metazoans, and a total of 3,110,094 parasites were collected. Ichthyophthirius multifiliis, Piscinoodinium pillulare, Sciadicleithum juruparii, Clinostomum marginatum, Posthodiplostomum sp., Genarchella genarchella, Argulus multicolor and Ergasilus coatiarus were found. However, I. multifiliis and P. pillulare were the most prevalent, abundant and dominant parasites,...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Aggregation; Cichlidae; Freshwater fish; Parasites.
Ano: 2017
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0044-59672017000200155

ECOLOGICAL ASPECTS OF THE PARASITES IN Cichlasoma bimaculatum (CICHLIDAE), ORNAMENTAL FISH FROM THE BRAZILIAN AMAZON
Provedor de dados: 37
Autores: TAVARES-DIAS,Marcos; ALVES GONÇALVES,Raissa; BRITO OLIVEIRA,Marcos Sidney; RIGÔR NEVES,Ligia.
ABSTRACT This study investigated the parasitic fauna of Cichlasoma bimaculatum of a tributary from the Amazon River system, northern Brazil. The prevalence of infection was 94.6 % and, in total, 428 267 parasites, such as Ichthyophthirius multifiliis, Piscinoodinium pillulare (Protozoa), Gussevia arilla (Monogenoidea), Posthodiplostomum sp. (Digenea) and Procamallanus (Spirocamallanus) inopinatus (Nematoda) were collected. However, the dominance was mainly of I. multifiliis, while P. (S.) inopinatus was the parasite species with the lower levels of prevalence and abundance of infection. These parasite species showed an aggregated dispersion pattern. The parasitic fauna was characterized by the presence of few species of parasites with high prevalence and...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Aggregation; Endoparasites; Freshwater fish; Infection.
Ano: 2017
URL: http://www.scielo.org.co/scielo.php?script=sci_arttext&pid=S0120-548X2017000200006

Spatial distribution, association patterns and richness of tree species in a seasonal forest from the Serra Geral formation, southern Brazil
Provedor de dados: 39
Autores: Sühs,Rafael Barbizan; Budke,Jean Carlos.
This study aimed to determine the spatial distribution of the most abundant tree species, to look for relationships that may be responsible for their distribution and to compare the expected richness along the Serra Geral formation in the state of Rio Grande do Sul , Brazil. An one-hectare plot was divided in 100 contiguous 10 x 10 m sampling units and all individuals with at least 4.8 cm diameter at breast high were measured and identified. Each sampling unit received a description of the spatial position through metric coordinates (x,y) in order to quantify the spatial pattern. Later, an association index among species was applied. The observed richness was rarefied and compared to other surveys located on the slopes of Serra Geral in Rio Grande do Sul....
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Rarefaction; Diversity metrics; Spatial association; Aggregation.
Ano: 2011
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0102-33062011000300014

Diversity of parasites in wild Astronotus ocellatus (Perciformes, Cichlidae), an ornamental and food fish in Brazil
Provedor de dados: 42
Autores: TAVARES-DIAS,MARCOS; NEVES,LIGIA R.
ABSTRACT The community composition of parasites was characterized in Astronotus ocellatus from a tributary of the Amazon River, northern Brazil. The prevalence was 87.9%, and a total of 526,052 parasites were collected, with a mean of 15,941 parasites per host. Nine taxa of ecto- and endo-parasites were identified, but Ichthyophthirius multifiliis was the dominant species, while Piscinoodinium pillulare, Clinostomum marginatum and Argulus multicolor were the least prevalent parasites. The parasite community was characterized by a low species richness, low diversity and low evenness. Host body size was not found to influence the composition of the parasite community, and there was no significant correlation between abundance of any parasite species and host...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Aggregation; Amazon; Ectoparasites; Endoparasites; Freshwater fish.
Ano: 2017
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652017000502305

Physiopathological modulators of amyloid aggregation and novel pharmacological approaches in Alzheimer's disease
Provedor de dados: 42
Autores: DEFELICE,FERNANDA G.; FERREIRA,SÉRGIO T.
The biological mechanisms underlying the neuropathology of Alzheimer's disease (AD) are complex, as several factors likely contribute to the development of the disease. Therefore, it is not surprising that a number of different possible therapeutic approaches addressing distinct aspects of this disease are currently being investigated. Among these are ways to prevent amyloid aggregation and/or deposition, to prevent neuronal degeneration, and to increase brain neurotransmitter levels. Here, we discuss possible roles of endogenous modulators of Abeta aggregation in the physiopathology of AD and some of the strategies currently under consideration to interfere with brain levels of beta-amyloid, its aggregation and neurotoxicity.
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Alzheimer's disease; Abeta peptide; Aggregation; Neurotoxicity; Physiopathological modulators.
Ano: 2002
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0001-37652002000200006

Dispersal of Cotesia flavipes in sugarcane field and implications for parasitoid releases
Provedor de dados: 53
Autores: Dinardo-Miranda,Leila Luci; Fracasso,Juliano Vilela; Costa,Viviane Pereira da; Lopes,Diego Olympio Teixeira.
Diatraea saccharalis Fabr. (Lepidoptera: Crambidae) is a major sugarcane pest in Brazil. The management of infested areas is based on the release of Cotesia flavipes (Cameron) (Hymenoptera: Braconidae), a parasitoid of D. saccharalis larvae, but there are doubts about the effectiveness of C. flavipes, primarily regarding its rate of dispersal in sugarcane fields. Thus, the objective of this study was to evaluate the dispersal of C. flavipes in a sugarcane field and suggest a release method that provides higher parasitoid efficiency. The study was carried out in four areas of approximately 1 ha, in which stalk pieces containing 20 D. saccharalis larvae were distributed in a rectangular grid, and 12,000 C. flavipes adults were released at four points, that...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Sugarcane borer; Diatraea saccharalis; Biological control; Aggregation; Pest management.
Ano: 2014
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0006-87052014000200011

Stabilization of partially folded states in protein folding/misfolding transitions by hydrostatic pressure
Provedor de dados: 56
Autores: Ferreira,S.T.; Chapeaurouge,A.; De Felice,F.G.
In the last few years, hydrostatic pressure has been extensively used in the study of both protein folding and misfolding/aggregation. Compared to other chemical or physical denaturing agents, a unique feature of pressure is its ability to induce subtle changes in protein conformation, which allow the stabilization of partially folded intermediate states that are usually not significantly populated under more drastic conditions (e.g., in the presence of chemical denaturants or at high temperatures). Much of the recent research in the field of protein folding has focused on the characterization of folding intermediates since these species appear to be involved in a variety of disease-causing protein misfolding and aggregation events. The exact mechanisms of...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: High pressure; Protein folding; Misfolding; Amyloid; Aggregation.
Ano: 2005
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2005000800009

Volume and energy folding landscape of prion protein revealed by pressure
Provedor de dados: 56
Autores: Cordeiro,Y.; Kraineva,J.; Winter,R.; Silva,J.L.
The main hypothesis for prion diseases proposes that the cellular protein (PrP C) can be altered into a misfolded, ß-sheet-rich isoform, the PrP Sc (from scrapie). The formation of this abnormal isoform then triggers the transmissible spongiform encephalopathies. Here, we discuss the use of high pressure as a tool to investigate this structural transition and to populate possible intermediates in the folding/unfolding pathway of the prion protein. The latest findings on the application of high pressure to the cellular prion protein and to the scrapie PrP forms will be summarized in this review, which focuses on the energetic and volumetric properties of prion folding and conversion.
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Prion; High pressure; Structural conversion; Aggregation.
Ano: 2005
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2005000800006

Genomics and X-ray microanalysis indicate that Ca2+ and thiols mediate the aggregation and adhesion of Xylella fastidiosa
Provedor de dados: 56
Autores: Leite,B.; Ishida,M.L.; Alves,E.; Carrer,H.; Pascholati,S.F.; Kitajima,E.W.
The availability of the genome sequence of the bacterial plant pathogen Xylella fastidiosa, the causal agent of citrus variegated chlorosis, is accelerating important investigations concerning its pathogenicity. Plant vessel occlusion is critical for symptom development. The objective of the present study was to search for information that would help to explain the adhesion of X. fastidiosa cells to the xylem. Scanning electron microscopy revealed that adhesion may occur without the fastidium gum, an exopolysaccharide produced by X. fastidiosa, and X-ray microanalysis demonstrated the presence of elemental sulfur both in cells grown in vitro and in cells found inside plant vessels, indicating that the sulfur signal is generated by the pathogen surface....
Tipo: Info:eu-repo/semantics/other
Palavras-chave: Xylella fastidiosa; Aggregation; Adhesion; Methionine sulfoxide reductase; Biofilm.
Ano: 2002
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-879X2002000600003

Relationship between raindrops and ultrasonic energy on the disruption of a Haplic Cambisol
Provedor de dados: 64
Autores: Ribeiro,Bruno Teixeira; Lima,José Maria de; Mello,Carlos Rogério de; Sá,Marcos Aurélio Carolino de; Oliveira,Geraldo César de.
The aim of this work was to compare aggregate disruption of undisturbed soil samples by ultrasonic energy to aggregate disruption caused by the energy of simulated raindrops, to provide equations that can describe this relationship, and to evaluate whether aggregate stability, expressed by sonication method, may be used to estimate the effect that raindrops have on undisturbed soil samples. Undisturbed soil samples from A, Bi and C horizons of a Cambisol were submitted to different levels of ultrasonic energy and simulated raindrops. Sieved samples (aggregates) were also submitted to different levels of ultrasonic energy so that both disturbed and undisturbed conditions of samples could be compared. The results showed that the method using ultrasonic...
Tipo: Info:eu-repo/semantics/article
Palavras-chave: Aggregation; Soil structure; Ultrasound.
Ano: 2009
URL: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1413-70542009000300021