Costos Ambientales y Eficiencia Productiva en la Producción Agraria del Partido de Pergamino

Mediante un modelo de frontera de producción estocástica se analizó el nivel de eficiencia técnica para la producción de soja, maíz y trigo en empresas agropecuarias del partido de Pergamino, Buenos Aires, Argentina. El costo asociado a tres indicadores ambientales: balances de nutrientes, balance de materia orgánica y erosión hídrica, se consideró como parte de los insumos de producción. En promedio, la soja 1ra es el cultivo con costo ambiental más elevado, con un costo ambiental 53u $s /ha mayor que en la secuencia trigo/soja y 76 u$s /ha mayor que en maíz. Se estimó un nivel de eficiencia promedio del 85%. Si bien este valor implica la posibilidad de aumentar un 15% la producción para un mismo nivel de insumos, es un valor elevado si se lo compara con mediciones realizadas en otros sistemas agrícolas extensivos. Aunque un alto nivel de eficiencia es consistente con un buen uso de los recursos, los resultados sugieren que es posible reducir los costos ambientales de los sistemas de producción mediante cambios en la combinación de cultivos. En la actualidad existe una fuerte predominancia del cultivo de soja en toda la región agrícola de Argentina. Una mayor superficie de cultivos con menores costos ambientales podría conseguirse mediante la implementación de políticas que fomenten estas producciones.A stochastic frontier model is employed to analyze technical efficiency for soybeans, corn and wheat production in commercial farms in Pergamino, Buenos Aires, Argentina. The cost associated with three environmental indicators: nutrients balances, organic carbon balance and water erosion, is modeled as an input for efficiency estimation. On average, growing soybeans has an environmental cost 53 u $s /ha higher than growing the double crop wheat/soybeans and 76 u$s /ha higher than growing maize. Estimated average efficiency for agricultural production is 85%. This value indicates the possibility of increasing production by 15% while keeping the inputs level constant. This efficiency level is high compared to efficiency estimates for extensive agricultural systems reported by other authors. While a high efficiency level is consistent in a good use of available resources, results suggest the possibility of reducing environmental costs through changes in land allocation Currently, land share for soybeans is the highest of all crops in the main agricultural region. A larger share of crops with lower environmental costs could be achieved with policies that provide incentives for increasing the planting area for these crops

Investigation of electrochemically-induced repassivation of Al 7075-T6 and Al 2024-T3 as a function of applied stress and galvanic corrosion

The repassivation behavior of Al alloys 7075-T6 and 2024-T3 was investigated by means of pitting scan (PS) technique (Fig. 1) (Trueba, Trasatti, 2015). The effect of mechanical load and galvanic coupling was estimated by considering principally the electrochemical characteristics of the reverse curve, namely the pit transition potential (Eptp), the associated current density (iptp) and the steepness. The load levels explored were mostly below the elastic limit, using four point bent-beam (4PBB) stress-corrosion test specimens (ASTM G39-99). CRES 304 or Ti6Al4V alloy were physically joined with Al sheet for simulating stress-induced galvanic corrosion. Different experimental variables (e.g. irev, [Cl-], pH, scan rate, etc.) were also considered. The study was complemented with corrosion morphology analysis. Please click Additional Files below to see the full abstract

Chemical Raman Enhancement of Organic Adsorbates on Metal Surfaces

Using a combination of first-principles theory and experiments, we provide a quantitative explanation for chemical contributions to surface-enhanced Raman spectroscopy for a well-studied organic molecule, benzene thiol, chemisorbed on planar Au(111) surfaces. With density functional theory calculations of the static Raman tensor, we demonstrate and quantify a strong mode-dependent modification of benzene thiol Raman spectra by Au substrates. Raman active modes with the largest enhancements result from stronger contributions from Au to their electron-vibron coupling, as quantified through a deformation potential, a well-defined property of each vibrational mode. A straightforward and general analysis is introduced that allows extraction of chemical enhancement from experiments for specific vibrational modes; measured values are in excellent agreement with our calculations.Comment: 5 pages, 4 figures and Supplementary material included as ancillary fil

Investigation of SCC of high strength aluminum alloys by means of slow strain rate test and cyclic anodic polarization in combination

The stress corrosion cracking (SCC) behavior of high strength 7075-T6 and 2024-T3 Al alloys in NaCl solutions is investigated by means of slow strain rate test (SSRT) and cyclic anodic polarization in combination. Smooth, dog-bone shaped flat tension test specimens, having gage section areas of 40 mm2 and 32 mm2, respectively, and 90 mm of gage length, were machined in the longitudinal (rolling) direction from the commercial wrought sheets (Aviometal Spa). The tensile test was performed at a constant strain rate (ἐ = 10-7, 10-6 or 10-5 s-1) from a pre-load of about 5 kN until fracture. The electrochemical system consisted in non-connected two Plexiglas cylindrical cells that were fixed at the middle of the opposite surfaces of the tensile specimen (working electrode, surface area at each side of 2 cm2). The variation of the open circuit potential (OCP) during straining was measured with respect to saturated calomel reference electrode (SCE) by connecting the two electrode system to a Gamry potentiostat. Contemporarily, the opposite surface was electrochemically perturbed by imposing consecutive cyclic anodic polarizations with open circuit potential measurements in between (OCP/polarization sequences), using an Ir-coated Ti auxiliary electrode, another SCE and a second Gamry potentiostat. At least two combined experiments for each test condition were carried out for repeatability check. Experiments with no OCP/polarization sequence during straining, and vice versa, were performed for reference purposes. The stress-strain curves of Al 7075-T6 (Fig. 1a) show that the ultimate strength and failure strain decrease in aggressive environment as the strain rate is lowered, regardless the electrochemical perturbation, being in agreement with reported data [1]. More interestingly, quasi-periodic stress relaxation/recovery events above the elastic region in correspondence with the dissolution/repassivation cycle were detected for ἐ ≤ 10-6 s-1 and 0.1667 mV/s of potential scan rate (n). The resolved negative spikes in the stress time derivative curve and the related polarization curves (as log | I | - t) for ἐ = 10-7 s-1, 0.6 M NaCl and n = 0.1667 mV/s are reported in Figure 1b. The spike pattern along the time axe was dependent on ἐ and NaCl concentration. The results from ongoing combined experiments with Al 2024-T3 for verification of the above findings will be presented altogether with empirical data analysis for a quantitative insight into the environmentally assisted failure mechanisms. Please click Additional Files below to see the full abstract

Physical, Biochemical and Biological Characterization of Two Opposite Areas in the Southern Adriatic Sea (Mediterranean Sea)

The Drini and Manfredonia Gulfs were investigated in May 2008 and April 2009, respectively. The gulfs are located in the South Eastern (Gulf of Drini) and South Western (Gulf of Manfredonia) Adriatic Sea. The areas are partially influ- enced by two main Adriatic surface currents: the Eastern Adriatic Current-EAC that flows north-westward along the eastern side, and the Western Adriatic Current-WAC that flows south-eastward along the western side of the basin. The spatial variations of temperature, salinity, fluorescence, dissolved oxygen concentration, Coloured Dissolved Or- ganic Matter-CDOM, nutrients, chlorophyll a and phytoplankton composition parameters in the two areas were ob- served and compared. CDOM regulates the penetration of UV light into the sea and plays an important role in many hydrological and biogeochemical processes on the sea surface layer including primary productivity. The phytoplankton specific diversity of the Gulf of Manfredonia showed a spring community with dinoflagellates (21 taxa) as the main important fraction, coccolithophorales (6 taxa) and diatoms with 10 identified taxa. The phytoplankton distribution along the eastern coast showed a different biodiversity: a prevalence of dinoflagellates (58 taxa) included harmful mi- croalgae such as Alexandrium, Dinophysis and Lingulodinium genus. Diatoms were less abundant, among them Pseudo-nitzschia was also reported which could include some potentially toxic species. Nanoplankton are ever abun- dant in offshore waters and an exceptional bloom of cyanobacteria was registered in Buna-Boyana estuary due to strong industrial impact. The gulfs showed similar physical and biochemical characteristics despite the WAC carried out along the western Adriatic Sea the water rich in nutrients from the major northern Italian rivers. No correlations were found between CDOM and chlorophyll a in the two areas and this implied that, probably, the primary source of CDOM might come from terrestrial input rather than the biological production from phytoplankton. The Gulf of Drini is impacted by the runoff of the Buna-Bojana River that makes this gulf an eutrophic area despite the mostly eastern side of the Adri- atic being an oligotrophic basin

Advisory Service Marketing Profiles for Soybeans over 2002-2004

This report presents marketing profiles and loan deficiency payment/marketing loan gain profiles for the advisory services followed by the AgMAS Project for the 2002, 2003 and 2004 soybean crops. Marketing profiles are constructed by plotting the cumulative net amount priced under each program’s set of recommendations throughout the crop year. Loan deficiency payment/marketing loan gain (LDP/MLG) profiles are constructed by plotting the cumulative percentage of the crop on which the LDP/MLG was claimed during the crop year. Marketing profiles provide information to evaluate the style of advisory services in several ways. The percentage of crop priced is a measure of within-crop year price risk. The higher the proportion of a crop priced, the lower the sensitivity of the farmer’s position value to crop price changes. For example, when 100% of the crop is priced there is no price sensitivity, which means that changes in price do not affect the value of the farmer’s position. On the other hand, when the amount priced is 0%, the value of the farmer’s position will vary in the same proportion as the change in price. Marketing profiles, therefore, allow investigating the evolution of price sensitivity under each service’s set of recommendations along the marketing window. Marketing profiles also provide other useful information. The number of steps in the profile lines and the location of these steps in the marketing window provide information about timing, frequency and size of recommended transactions. It is also possible to determine from the marketing profile figures how intensely a program uses options markets, since when options positions are open the profile line is irregular. In the same way, LDP/MLG profiles provide information about the size and timing of LDP/MLG claims.Agricultural Finance,

Selective Chemical Raman Enhancement for Organic Adsorbates at Metal Surfaces

It has long been observed that in surface enhanced Raman spectroscopy (SERS) relative mode intensities differ from gas- and solution-phase data, which obscures understanding of SERS in general. Using first-principles methods, we examine how chemisorption affects Raman scattering of molecules on metal surfaces relative to gas-phase, and provide a quantitative description of this effect. Calculated Raman spectra for benzene thiol bound at different sites on Au(111) show that chemical enhancement arises from the mode dependent electron-phonon coupling of the metal-molecule interface. Site-dependent enhancements are explained correlated to interfacial electronic structure. Comparison to experiments suggests affinity of benzene thiol for bridge sites on Au(111) surfaces

Advisory Service Marketing Profiles for Corn over 2002-2004

This report presents marketing profiles and loan deficiency payment/marketing loan gain profiles for the advisory services followed by the AgMAS Project for the 2002, 2003 and 2004 corn crops. Marketing profiles are constructed by plotting the cumulative net amount priced under each program’s set of recommendations throughout the crop year. Loan deficiency payment/marketing loan gain (LDP/MLG) profiles are constructed by plotting the cumulative percentage of the crop on which the LDP/MLG was claimed during the crop year. Marketing profiles provide information to evaluate the style of advisory services in several ways. The percentage of crop priced is a measure of within-crop year price risk. The higher the proportion of a crop priced, the lower the sensitivity of the farmer’s position value to crop price changes. For example, when 100% of the crop is priced there is no price sensitivity, which means that changes in price do not affect the value of the farmer’s position. On the other hand, when the amount priced is 0%, the value of the farmer’s position will vary in the same proportion as the change in price. Marketing profiles, therefore, allow investigating the evolution of price sensitivity under each service’s set of recommendations along the marketing window. Marketing profiles also provide other useful information. The number of steps in the profile lines and the location of these steps in the marketing window provide information about timing, frequency and size of recommended transactions. It is also possible to determine from the marketing profile figures how intensely a program uses options markets, since when options positions are open the profile line is irregular. In the same way, LDP/MLG profiles provide information about the size and timing of LDP/MLG claims.Agricultural Finance,

Evaluation of corrosion resistance of biocompatible coatings on magnesium

The work deals with the study of innovative biocompatible coatings for magnesium resorbable osteosynthesisdevices. Conversion layers based on magnesium fl uoride and “diamond like carbon” coatings (DLC) obtainedby chemical vapor deposition were considered in order to reduce the corrosion rate of magnesium to levelscompatible with the time needed for fracture healing. DLC coating was applied on both pure magnesiumand on magnesium after conversion treatment in hydrofl uoric acid. Weight loss tests and potentiodynamicpolarization tests in aerated Hank’s solution at room temperature were performed. The corrosion rate wasabout 100 mg/cm2day for the commercially pure magnesium (99.9 %) in the fi rst 24 hours of exposure. Boththe coatings reduced the short-term corrosion rate but the protective layers did not grant long-term stabilityand corrosion rate rapidly increases approaching the values of uncoated magnesium