Effect of nutrient input frequency on the structure and dynamics of the marine pelagic community: A modeling approach

33 páginas, 9 figuras, 2 tablas.An analysis of the induced changes in both total productivity and community structure as a consequence of different pulsed nutrient inputs has been made by using two different ecosystem modeling tools. One was a modified version of the N-based model proposed by Fasham et al. (1990) for pelagic ecosystems and the other the plankton functional type model by Vichi et al. (2007). Both models lead to higher total biomass production with a pulsed nutrient input compared to a continuous supply, affecting both phytoplankton and zooplankton. Detailed responses are, however, different among plankton groups depending on the frequency of pulsed nutrient input and the complexity of the model. The differences in biomass production were higher for an oscillation period of 150-170 days following a sinusoidal supply pattern. A tidal mixing-induced nutrient supply was also simulated by using both models and a larger biomass increment was observed compared to that obtained with the sinusoidal pattern. Finally, a theoretical application of this approach to the pelagic ecosystem of the North Western Alboran Sea shows a preferential selection of diatoms and larger zooplankton under discontinuous nutrient inputs.This work was funded by the Spanish National Research Program, Project; CTM2005–08142-C03–01. D.M. was supported by the Spanish Postdoc Fellowship Program and E.R. by a grant from the Spanish FPU fellowship.Peer reviewe

Acceso al mercado de productos lácteos de Europa: Un análisis de equilibrio parcial para evaluar las potenciales ganancias de los exportadores argentinos

A partial equilibrium model is used to quantify price differentials not explained by tax policy and efficiency cost in the international trade of dairy products between Argentina and some countries of European Union (EU). Prices of imports of EU from Argentina and European producer of the domestic variety welfare fall when liberalization of non-tariff barriers are reduced or eliminated as well as European consumer’s welfare and Argentinean exporter’s earnings are increased. A sensibility analysis is carried out, changing substitution and supply elasticity and exporter’s earnings are shown for four alternative stages. The conclusions are that exporters obtain higher earnings by eliminating or reducing non-tariff barriers when substitution elasticity is higher, mainly for cheese. More inelastic supply products obtain higher earnings for Argentinean exporters (mainly in powdered milk). Finally, an alternative stage is explored where elimination of non-tariff barriers results in higher imports from the rest of the world. Results show a greater increase in Argentinean exporter’s earnings for cheese products and lower earnings for powdered milk

Pruebas para identificar cultivares

El objetivo del presente trabajo es discutir las pruebas más complejas y más utilizadas para emplear los cultivares de las plantas cultivadas. Dichas pruebas se realizaron y sus características se determinaron para escoger la más eficiente. Las características más importantes para ejecutar tales pruebas y encontrar las más eficientes son: identificación varietal para determinar si una variedad es pura y evaluación para determinar si las características de una muestra de semilla corresponden a las descritas en su respectiva etiqueta comercial. También, se presenta una discusión sobre si las características, antes mencionadas, están acordes con la legislación presente sobre el particular, y que deben ser acatadas por todos los países del mundo. Las pruebas más eficientes son: de cámaras de crecimiento y diferentes pruebas de electroforesis.The objective of this research is to discuss the more complex and more utilized test to identify the cultivars of the cultivated plants. The tests were made and their characteristics were determined in order to choose the most efficient tests. the most important characteristics to take into account in order to find the most efficients test are: Identification of the variety to show if it is a pure variety and the evaluation of the characteristics stated on the comerciallabel. I include a discussion on the Characteristis above mentioned and how important is follow the legislation udes worlwide on this topic. The used most efficient test are the growth chamber and the differentelectrophoresis system

Access to European dairy product markets: A Computable Partial Equilibrium analysis to assess Argentine exporters surplus

A partial equilibrium model is used to quantify price differentials not explained by tax policy and efficiency cost in the international trade of dairy products between Argentina and some countries of European Union (EU). Prices of imports of EU from Argentina and European producer of the domestic variety welfare fall when liberalization of non-tariff barriers are reduced or eliminated as well as European consumer’s welfare and Argentinean exporter’s earnings are increased. A sensibility analysis is carried out, changing substitution and supply elasticity and exporter’s earnings are shown for four alternative stages. The conclusions are that exporters obtain higher earnings by eliminating or reducing non-tariff barriers when substitution elasticity is higher, mainly for cheese. More inelastic supply products obtain higher earnings for Argentinean exporters (mainly in powdered milk). Finally, an alternative stage is explored where elimination of non-tariff barriers results in higher imports from the rest of the world. Results show a greater increase in Argentinean exporter’s earnings for cheese products and lower earnings for powdered milk.Computable partial equilibrium; dairy market; non-tariff barriers

Assessing the efects of eliminating non-tariff barriers over the Argentine Textile Exports

This paper offers a quantification of price differentials not explained by tariff policy and the assessment of efficiency costs burned on different economic agents involved in textile products trade between Argentina (exporter) and Brazil (domestic producer). Simulations are carried out to show the effects of the distortion of price differentials, considered like non tariff barriers or a set of them and others obstacle to trade. From the removal of non tariff barriers results that consumers and exporters obtain grater consumer surplus and profits, respectively, while domestic producers loose part of their producer surplus. Consumers and exporters are better because of changes in terms of trade; in some products consumers obtain graters benefits than exporters and vice versa. Likewise, changes in elasticities (direct elasticity of supply and demand) were simulated to observe distortions in previous results.Textile sector; computable partial equilibrium; commercial policy

Diagnóstico de Osteoartrosis de Articulación Témporomandibular con T%omografía Computada de Haz Cónico

La osteoartrosis es una patología de carácter degenerativo que afecta a la articulación temporomandibular. Si bien el examen clínico representa una herramienta fundamental para su diagnóstico, los estudios imagenológicos son los que permitirán la confirmación de dicho diagnóstico. En la actualidad la tomografía computada de haz cónico resulta el método de elección debido a que nos permite ver con detalle las estructuras óseas de la articulación temporomandibular en diferentes planos utilizando una dosis baja de radiación en comparación con la tomografía computada médic

Eftect of storage conditions on viability of centrosema pubescens Seed

Este trabajo tuvo como objetivo estudiar el efecto de Ia escarificaciôn química y de las condiciones de almacenamiento sobre Ia viabilidad de las semillas de Centrosema pibescens, Benth. Una gran proporción de un lote de semillas no germinó al ser colocado bajo condiciones favorables para Ia germinacion. El porcentaje de germinación aumentó significativamente, cuando las coberturas de las semillas se rompieron antes de iniciar Ia prueba. Las semillas escarificadas con ácido sulfúrico concentrado mostraron más del 80% de gerrninación, mientras que las no tratadas solo germinaron en un 30%. El tiempo máximo de tratamiento con ácido, que no afecta la germinacion, fue de 20 minutos. Se determinó también que semillas tratadas y no tratadas, almacenadas a temperatura y humedad relativa alias (33°C/ 90% HR), se deterioraron rápidamente, presentando fuerte infestación de hongos. Las semillas almacenadas a temperatura y humedad relativas bajas (20°/! 40% HA), mantuvieron Ia viabilidad durante, por to menos, seis meses. El almacenamiento en recipientes sellados jugó papel importante en el mantenimiento de Ia calidad de las semillas de Centroseina pubescens. Debido a que estas semillas son higroscópicas, su cantidad de humedad se equilibra con Ia del ambiente dentro del recipiente durante los dos primeros meses de almacenamiento.Experiments were carried out with seeds of Cenir.ccnu, pithem,cm to study the effect of sulphuric acid scarification on germination and the effect of storage conditions on viability. Al large portion of the seed lot examined, failed to germinate under conditions suitable for germination. Under the same conditions, germination percentage was greatly increased when hard seed coats were broken. Seeds treated with concentrated sulfuric acid, gave more than 80% germination while only 30% of the nontreated seeds germinated. The maximum time of exposure of seeds to sulfuric acid, without impairing germination was of 20 minutes. Both, treated and untreated seeds stored at high temperature and high humidity deteriorated very rapidly showing heavy fungi infestations. Treated or untreated seeds stored at low temperature and low humidity maintained full vaibility for at least six months. Storage in sealed containers mantains the quality of (eti,ivdnia pu/'en seed for long periods; since seeds are hygroscopic, their moisture content equilibrates with the humidity of the internal atmosphere in sealed containers within the first two months of storage

A model for the electromagnetic spectrum of the inner jets of Cen A

Centaurus A, the closest active galaxy, has been detected from radio to high-energy gamma-rays. The synchrotron radiation by extremely high energy protons may be a suitable mechanism to explain the MeV to GeV emission detected by the instruments of the Compton Gamma-Ray Observatory, as coming from the inner jets. This scenario requires a relatively large magnetic field of about 10^4 G that could be present only close to the central black hole. We investigate the spectral energy distribution (SED) resulting from a one-zone compact acceleration region, where both leptonic and hadronic relativistic populations arise. We present here results of such a model, where we have considered synchrotron radiation by primary electrons and protons, inverse Compton interactions, and gamma-ray emission originated by the inelastic hadronic interactions between relativistic protons and cold nuclei within the jets themselves. Photo-meson production by relativistic hadrons were also taken into account, as well as the effects of secondary particles injected by all interactions. The internal and external absorption of gamma rays is shown to be of great relevance to shape the observable SED, which was also recently constrained by the results of HESS.Comment: 13 pages (ref. style), submitted to MNRAS on December 04, 2008. Waiting for revie

Identification and mapping of a locus conferring plum pox virus resistance in two apricot-improved linkage maps

Sharka disease, caused by the plum pox virus (PPV), is one of the major limiting factors for stone fruit crops in Europe and America. In particular, apricot is severely affected suffering significant fruit losses. Thus, PPV resistance is a trait of great interest for the apricot breeding programs currently in progress. In this work, two apricot maps, earlier constructed with the F1 ‘Goldrich × Currot’ (G×C) and the F2 ‘Lito × Lito’-98 (L×L-98) populations, have been improved including 43 and 37 new simple sequence repeat (SSR) loci, respectively, to facilitate PPV resistance trait mapping. Screening of PPV resistance on the segregating populations classified seedling phenotypes into resistant or susceptible. A non-parametric mapping method, based on the Kruskal–Wallis (KW) rank sum test, was initially used to score marker–trait association, and results were confirmed by interval mapping. Contrary to the putative digenic model inferred from the phenotypic segregations, all significant markers for the KW statistic (P < 0.005) mapped in a unique region of ~21.0 and ~20.3 cM located on the upper part of the G1 linkage group in ‘G×C’ and ‘L×L-98’ maps, respectively. According to the data, PPV resistance is suggested to be controlled by at least one major dominant locus. The association between three SSRs distributed within this region and the PPV resistance was tested in two additional populations (‘Goldrich × Canino’ and ‘Lito × Lito’-00) and breeding program parents. The marker ssrPaCITA5 showed the highest KW value (P < 0.005) in all cases, pointing out its usefulness in marker-assisted selection.This research was supported by a grant from the Ministerio de Ciencia y Tecnología (AGL2004-04126-C02-02/AGR).Peer reviewe

The fictitious diurnal cycle of aerosol optical depth: A new approach for “in situ” calibration and correction of AOD data series

Aerosol optical depth (AOD) very often shows a distinct diurnal cycle pattern, which seems to be an artifact. This phenomenon is the result of a deficient calibration (or an equivalent effect, as filter degradation). The fictitious sinusoidal shape of the AOD diurnal cycle is a function of the cosine of the solar zenith angle (SZA) and its effect is more accentuated during mid-day. The observation of this effect is not easy at current field stations and only those stations with excellent weather conditions permit an easier detection and correction. By taking advantage of this diurnal cycle behavior because of its dependence on the cosine of the SZA, we propose an improved “in situ” calibration correction procedure. The method is named KCICLO because the determination of a constant K and the behavior of AOD as a cycle (ciclo, in Spanish). It can be seen as a modification of the classical Langley technique (CLT) with the same level of accuracy when CLT is applied at high-altitude stations, and results in an accuracy of 0.2–0.5% for the calibration ratio constant K (or 0.002–0.005 in AOD). The application of this correction method to current and old data series at sunny stations is a significant improvement over “in situ” methods, because no other information beyond the AOD data is necessary