Transaction costs and their implications to formation of contractual arrangements: aspects of machinery contracting by family farmers in the centro-serra region of Rio Grande do Sul.

A mecanização da produção agrícola desempenha um importante e crescente papel no curso do desenvolvimento agrícola e rural. A mecanização oferece diversas melhorias potenciais nos sistemas de produção tais como o incremento da produtividade da terra e do trabalho, a redução dos riscos, e aumento da qualidade e segurança alimentar de produtos de origem animal e vegetal. Entretanto, os investimentos necessários para compra de máquinas, especialmente para pequenos produtores, podem não ser a opção de menor custo em comparação com a obtenção de serviços de mecanização por meio de diferentes arranjos contratuais. Para .. escolher a melhor forma de contratar serviços de mecanização é necessário avaliar tanto os . custos convencionais das máquinas quanto os custos de transação, O principal objetivo desta pesquisa foi estimar a importância dos custos de transação na tomada de decisão sobre a seleção de arranjos contratuais alternativos para contratação de serviços de mecanização. Nossa hipótese era de. que os custos de transação podem ser maiores que os custos das máquinas, podendo, com isso, ser de cruclal Importância na seleção do tipo de arranjo contratual para contratar serviços de mecanização. Os dados empíricos de custos de máquinas e de transação foram coletados junto a agricultores familiares da Região Centro-Serra (RS), os quais contrataram serviços de colheita para milho de diferentes fornecedores formais e informais. Os resultados mostraram que os custos de transação podem ser mais elevados que os custos das máquinas e, com isso, influenciam de forma significativa a preferência agricultores familiares por determinado tipo de arranjo contratual para obtenção de serviços de mecanização. ABSTRACT - The mechanization of agricultural production plays an important and in course of time increasing role in the course of agricultural and rural development. Mechanization offers several potential improvements to farming systems such as increased land and labor productivity, reduction of risks, and increase of quality and food safety of animal and plant products. However, investments in own machinery, in particular for small holders, may not be the least-cost option in comparison with outsourcing the required machinery services through different contractual relationships. To choose the optimal contract for obtaining machinery services, it is necessary to evaluate conventional machinery costs as well as transaction costs. The main objective of this research was to assess the role of transaction costs in the choice among alternative contractual arrangements for provision of machinery services. Our hypothesis was that transaction costs can be higher than machinery costs, and therefore, they can play a leading role in the choice of contractual arrangements for provision of machinery services. The empirical data on conventional machinery and transaction costs were collected from farms in Southern Brazil that procure services for maize harvest through various informal and formal contractual forms. We found that transaction costs can be higher than conventional machinery costs, and therefore, influence the choice of contractual arrangement

A First-Principles Study of Zinc Oxide Honeycomb Structures

We present a first-principles study of the atomic, electronic, and magnetic properties of two-dimensional (2D), single and bilayer ZnO in honeycomb structure and its armchair and zigzag nanoribbons. In order to reveal the dimensionality effects, our study includes also bulk ZnO in wurtzite, zincblende, and hexagonal structures. The stability of 2D ZnO, its nanoribbons and flakes are analyzed by phonon frequency, as well as by finite temperature ab initio molecular-dynamics calculations. 2D ZnO in honeycomb structure and its armchair nanoribbons are nonmagnetic semiconductors but acquire net magnetic moment upon the creation of zinc-vacancy defect. Zigzag ZnO nanoribbons are ferromagnetic metals with spins localized at the oxygen atoms at the edges and have high spin polarization at the Fermi level. However, they change to nonmagnetic metal upon termination of their edges with hydrogen atoms. From the phonon calculations, the fourth acoustical mode specified as twisting mode is also revealed for armchair nanoribbon. Under tensile stress the nanoribbons are deformed elastically maintaining honeycomblike structure but yield at high strains. Beyond yielding point honeycomblike structure undergo a structural change and deform plastically by forming large polygons. The variation in the electronic and magnetic properties of these nanoribbons have been examined under strain. It appears that plastically deformed nanoribbons may offer a new class of materials with diverse properties.Comment: http://prb.aps.org/abstract/PRB/v80/i23/e23511

Modified Paschos-Wolfenstein relation and extraction of weak mixing angle sin^2 theta_W

The NuTeV collaboration reported anomalously large weak mixing angle sin^2 theta_W in comparison with the standard model prediction. Neutrino and antineutrino charged- and neutral-current events are analyzed for extracting sin^2 theta_W. Although the Paschos-Wolfenstein relation is not directly used in the analysis, it plays an important role in the determination. Noting that the target nucleus, iron, is not an isoscalar nucleus, we derive a leading-order expression for a modified Paschos-Wolfenstein relation for nuclei, which may have neutron excess. Then, using charge and baryon-number conservations for nuclei, we discuss a nuclear correction in the sin^2 theta_W determination. It is noteworthy that nuclear modifications are different between valence up- and down-quark distributions. We show this difference effect on the NuTeV sin^2 theta_W deviation.Comment: 5 pages, REVTeX4.0, revtex4.cls, url.sty, natbib.sty, revsymb.sty, 10pt.rtx, aps.rtx, amssymb.sty, amsfonts.sty, 3 eps figures. Phys. Rev. D in press. Email: [email protected] See also http://hs.phys.saga-u.ac.j

Pion Production in Neutrino-Nucleon Reactions

We construct a model for the weak pion production off the nucleon, which in addition to the weak excitation of the $\Delta(1232)$ resonance and its subsequent decay into $N\pi$, it includes also some background terms required by chiral symmetry. We re-fit the $C_5^A(q^2)$ form factor to the flux averaged $\nu_\mu p \to \mu^-p\pi^+$ ANL $q^2-$differential cross section data, finding a substantially smaller contribution of the $\Delta$ pole mechanism than traditionally assumed in the literature. We also show that the interference between the Delta pole and the background terms produces parity-violating contributions to the pion angular differential cross section.Comment: To appear in the proceedings of Fifth International Workshop on. Neutrino-Nucleus Interactions in the Few-GeV Region. May 30, 2007 - June 3, 2007. Fermilab, Batavia, Illinois US

Building the case for biofortification: measuring and maximizing impact in the HarvestPlus program

This paper describes the research and related activities that HarvestPlus undertook at each stage of the research process—discovery, proof of concept, delivery at scale—to establish and continuously strengthen the evidence base for program impact. Structured around the program’s theory of change, the evidence base includes estimates of the magnitude of potential impacts on key development outcomes as well as support for key assumptions that underlie outcomes along the impact pathway from release of biofortified varieties through adoption by farmers, consumption by consumers, and ultimately, to improved nutritional status. The HarvestPlus experience has important lessons for research for development (R4D) programs, many of which struggle to demonstrate progress towards outcomes and impacts throughout the research process.Keywords: Research for Development (R4D), Impact Assessment, Theory of Change, Micronutrient Deficiencies, Crop Varietal Improvemen

Changing the Magnetic Configurations of Nanoclusters Atom-by-Atom

The Korringa-Kohn-Rostoker Green (KKR) function method for non-collinear magnetic structures was applied on Mn and Cr ad-clusters deposited on the Ni(111) surface. By considering various dimers, trimers and tetramers, a large amount of collinear and non-collinear magnetic structures is obtained. Typically all compact clusters have very small total moments, while the more open structures exhibit sizeable total moments, which is a result of the complex frustration mechanism in these systems. Thus, as the motion of a single adatom changes the cluster structure from compact to open and vice versa, this can be considered as a magnetic switch, which via the local exchange field of the adatom allows to switch the cluster moment on and off, and which might be useful for future nanosize information storage.Comment: 7 page

The influence of direct DD-meson production to the determination on the nucleon strangeness asymmetry via dimuon events in neutrino experiments

Experimentally, the production of oppositely charged dimuon events by neutrino and anti-neutrino deep inelastic scattering (DIS) is used to determine the strangeness asymmetry inside a nucleon. Here we point out that the direct production of $D$-meson in DIS may make substantial influence to the measurement of nucleon strange distributions. The direct $D$-meson production is via the heavy quark recombination (HQR) and via the light quark fragmentation from perturbative QCD (LQF-P). To see the influence precisely, we compute the direct $D$-meson productions via HQR and LQF-P quantitatively and estimate their corrections to the analysis of the strangeness asymmetry. The results show that HQR has stronger effect than LQF-P does, and the former may influence the experimental determination of the nucleon strangeness asymmetry.Comment: 9 latex pages, 7 figure

Observation of the onset of strong scattering on high frequency acoustic phonons in densified silica glass

The linewidth of longitudinal acoustic waves in densified silica glass is obtained by inelastic x-ray scattering. It increases with a high power alpha of the frequency up to a crossover where the waves experience strong scattering. We find that \alpha is at least 4, and probably larger. Resonance and hybridization of acoustic waves with the boson-peak modes seems to be a more likely explanation for these findings than Rayleigh scattering from disorder.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Letter