Economic Efficiency, Structure and Scale Economies in the U.S. Dairy Sector

This study uses a new dataset based on the 2000 Agricultural Resource Management Survey, the most recent national survey of dairy producers in the United States. A shadow cost function is employed to decompose and analyze economic efficiency and scale economies. The study details the development of the data employed in the analysis and focuses on the estimation of scale relationships across farms in different regions and of different sizes. Preliminary results point to important scale economies and suggest that surviving small farms are on average more economically efficient but can exploit scale economies to a much lesser degree than larger farms. The preferred specification of the cost function does not show a region of decreasing returns to scale.Industrial Organization,

Reversible 2D Phase Transition Driven by an Electric Field : Visualization and Control on the Atomic Scale

We report on a reversible structural phase transition of a two-dimensional system that can be locally induced by an external electric field. Two different structural configurations may coexist within a CO monolayer on Cu(111). The balance between the two phases can be shifted by an external electric field, causing the domain boundaries to move, increasing the area of the favored phase controllable both in location and size. If the field is further enhanced new domains nucleate. The arrangement of the CO molecules on the Cu surface is observed in real time and real space with atomic resolution while the electric field driving the phase transition is easily varied over a broad range. Together with the well-known molecular manipulation of CO adlayers, our findings open exciting prospects for combining spontaneous long-range order with man-made CO structures such as "molecule cascades" or "molecular graphene". Our new manipulation mode permits us to bridge the gap between fundamental concepts and the fabrication of arbitrary atomic patterns in large scale, by providing unprecedented insight into the physics of structural phase transitions on the atomic scale

Copper Complexes as Effective Competitors for Iodine-free Electrolytes in Dye-Sensitized Solar Cells

Dye-sensitized solar cells, DSSCs, are photoelectrochemical devices well contextualized within the global commitment for the progressive increase of the percentage of electric energy produced by renewable resources. In the last decade the development of novel redox mediators alternative to the ubiquitous iodine-based electrolyte (identified as one of the principal causes of the stagnant PCE values in which the research got bogged down) has been one of the hottest topic of research. Efforts of many scientists have been catalyzed by metal complexes as promising single electron mediators characterized by an easy modulation of many electrochemical and optical features requested to ideal electron shuttles. While tris(diimine) cobalt complexes largely monopolize recent literature, our group has focused on homoleptic 1,10-phenanthroline-based copper complexes relying on the fact that their intrinsic limitations, if suitable tailored, could represent the turning point toward a new generation of electron shuttles. Starting from \u201cstructure vs activity maps\u201d correlating ligand substitutions with the electrochemical features of this class of complexes, we have proposed convenient Cu-based redox couples based on bulky 2-substituted phenanthrolines that reached efficiency higher than 6%, more than doubling the PCE of cells filled with the unique benchmark copper-based redox shuttle (12/22, in figure below) and even exceeding performance of a control I\u2013/I3\u2013-based electrolyte

Estudio prospectivo de las primo infecciones por Babesia bovis en terneros Brahman y Brangus de un área enzoótica de Corrientes, Argentina

Se evaluaron primo-infecciones causadas por Babesia bovis en terneros Brahman y Brangus en zona endémica de Corrientes, mediante la detección de: anticuerpos por ELISA-i, hematocrito y parasitemia en 48 vacas gestantes (195 días), de sus crías dentro de las 6 horas de vida (M1) y periódicamente hasta los 10 meses de edad (M2-M9). Para determinar la ingestión de calostro se utilizó la prueba del glutaraldehído (M1). La prevalencia de B. bovis en vacas fue del 97,91%. Los niveles de anticuerpos (M1) en terneros calostrados (n=15) fue 79,4 (14/15) Porcentaje de Positividad (PP), y el de sus madres 57,5% (47/48) PP (p<0,05) y en los no calostrados - anticuerpos generados durante la gestación - (n=33) fue 4,6 (1/33) PP. Hubo 4 perfi les serológicos, hasta 60 días (37%), 90 (23%), 120 (30%) y después de los 120 (10%). A los 9 meses de edad el 100% de los terneros presentó anticuerpos, sin padecer enfermedad.Occurrence of primary B. bovis infections were evaluated in calves Brahman and Brangus from endemic areas of Corrientes, throughout antibody-detection by iELISA, hematocrit determination and parasitaemia in 48 pregnant cattle (195 days of pregnancy) and their calves within 6 hours of born (M1) and periodically until 10 months of age (M2-M9). Colostrums’ ingestion was determinate by glutaraldehid test (M1). Prevalence of B. bovis in cattle was 97,91%. The level of antibodies (M1) in calves that consumed colostrums (n=15) was 79,4 PP and 57,5 PP in their mothers (p<0,05). In calves that did not consume colostrums -gestation-generated antibodies - it was 4,6 PP. There were 4 serologic profi les that suggest the occurrence of early infections, before day 60th (37%), 90th (23%), 120yh (30%) and belated after 120 days (10%). At the 9th month of age 100% of calves were infected, without evidence of illness.EEA RafaelaFil: Martinez, I. Universidad Nacional del Nordeste. Facultad de Ciencias Veterinarias. Cátedra de Enfermedades Infecciosas; ArgentinaFil: Jacobo, Roberto. Universidad Nacional del Nordeste. Facultad de Ciencias Veterinarias. Cátedra de Enfermedades Infecciosa ; ArgentinaFil: Cipolini, M.F. Universidad Nacional del Nordeste. Facultad de Ciencias Veterinarias. Cátedra de Enfermedades Infecciosa ; ArgentinaFil: Martinez, Diana. Universidad Nacional del Nordeste. Facultad de Ciencias Veterinarias. Cátedra de Enfermedades Infecciosas; ArgentinaFil: Storani, C.A. Universidad Nacional del Nordeste. Facultad de Ciencias Veterinarias. Cátedra de Enfermedades Infecciosas; ArgentinaFil: Ragazzi, A. Universidad Nacional del Nordeste. Facultad de Ciencias Veterinarias. Cátedra de Producción Bovina; ArgentinaFil: Echaide, Ignacio Eduardo. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; ArgentinaFil: Torioni, Susana Marta. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Rafaela; Argentin

On twisted Fourier analysis and convergence of Fourier series on discrete groups

We study norm convergence and summability of Fourier series in the setting of reduced twisted group $C^*$-algebras of discrete groups. For amenable groups, F{\o}lner nets give the key to Fej\'er summation. We show that Abel-Poisson summation holds for a large class of groups, including e.g. all Coxeter groups and all Gromov hyperbolic groups. As a tool in our presentation, we introduce notions of polynomial and subexponential H-growth for countable groups w.r.t. proper scale functions, usually chosen as length functions. These coincide with the classical notions of growth in the case of amenable groups.Comment: 35 pages; abridged, revised and update

Bis(1,10-phenanthroline) copper complexes with tailored molecular architecture: from electrochemical features to application as redox mediators in dye-sensitized solar cells

In the last few years, copper coordination compounds turned out to be effective competitors of cobalt complexes as redox mediators in the formulation of iodine-free electrolytes for dye-sensitized solar cells (DSSCs). However, the lack of a clear correlation between electrochemical signatures of copper complexes (i.e. half-wave potential and heterogeneous electron transfer rate) and photoelectrochemical performance of solar devices makes difficult the optimization of their coordination sphere. Therefore, to partially fill this gap and to elucidate the intrinsic correlation between the molecular architecture of these complexes and their electrochemical features, we prepared four Cu+/2+redox couples in which the copper center is coordinated by two 1,10-phenanthrolines bearing various substituents in position 2. These complexes were well characterized, from both electrochemical and spectroscopic point of view, and tested as electron shuttles in lab-scale photoelectrochemical cells sensitized with two efficient \ucf\u80-extended benzothiadiazole dyes. It appeared that 2-aryl-1,10-phenanthrolines effectively combine suitable optical and electrochemical properties. While a fast electron transfer kinetics generally positively affects the dye regeneration process, an optimal balance between dye regeneration efficiency, mass transport and heterogeneous electron transfer at both the counter electrode and at the TiO2interface, must be achieved in order to optimize DSSC performance. Within our series, the top performer was [Cu(2-tolyl-1,10-phenanthroline)2]+/2+which achieved a relative 20% and 15% improvement in power conversion efficiency (under 100 mW s\ue2\u88\u921simulated AM 1.5G illumination) with respect to control cells filled with [Co(bpy)3]2+/3+(bpy = 2,2\ue2\u80\ub2-bipyridine) and I\ue2\u88\u92/I3\ue2\u88\u92electrolytes, respectively

Efeito de espécies vegetais em bordadura em cebola sobre a densidade populacional de tripes e sirfídeos predadores.

Analisou-se a relação entre o efeito do plantio de diferentes espécies vegetais, em bordadura, na cultura da cebola, Allium cepa L, na incidência de Thrips tabaci Lind. e sirfídeos predadores, Toxomerus spp. O experimento foi conduzido na Epagri, EE de Ituporanga, de agosto a dezembro de 1998. Os tratamentos foram cebola em monocultivo; cebola + trigo mourisco (Fagopyrum esculentum Moench); cebola + nabo forrageiro (Raphanus sativus L. var. oleiferus Metzg.); cebola + cenoura (Daucus carota L., cv. Nantes e cv. Brasília); cebola + milho (Zea mays L.); cebola + rúcula (Eruca sativa L.) + vegetação espontânea. O plantio de diferentes espécies vegetais em bordadura não provocou diferenças significativas na incidência de tripes e sirfídeos predadores. A produtividade comercial de bulbos de cebola foi similar em sistema de monocultivo e diversificado, sugerindo ser possível adotar tais sistemas sem perdas em rendimento