First measurement of the polarization observable E and helicity-dependent cross sections in single π0 photoproduction from quasi-free nucleons

The double-polarization observable E and the helicity-dependent cross sections σ1/2 and σ3/2 have been measured for the first time for single π0 photoproduction from protons and neutrons bound in the deuteron at the electron accelerator facility MAMI in Mainz, Germany. The experiment used a circularly polarized photon beam and a longitudinally polarized deuterated butanol target. The reaction products, recoil nucleons and decay photons from the π0 meson were detected with the Crystal Ball and TAPS electromagnetic calorimeters. Effects from nuclear Fermi motion were removed by a kinematic reconstruction of the π0N final state. A comparison to data measured with a free proton target showed that the absolute scale of the cross sections is significantly modified by nuclear final-state interaction (FSI) effects. However, there is no significant effect on the asymmetry E since the σ1/2 and σ3/2 components appear to be influenced in a similar way. Thus, the best approximation of the two helicity-dependent cross sections for the free neutron is obtained by combining the asymmetry E measured with quasi-free neutrons and the unpolarized cross section corrected for FSI effects under the assumption that the FSI effects are similar for neutrons and protons

Beef cattle production system competitiveness in the south of brazil

The internal competitiveness of the beef cattle production systems in the Southern Region of Brazil was studied. Thirty-six beef cattle farmers of the state of Rio Grande do Sul were interviewed during the first quarter of 2010. The main indicators that affect the farm gate sector competitiveness were defined: technology, management, market relations, and institutional environment. Then, those indicators were developed into 10, 10, 4 and 7 factors respectively. They were assigned indivi- dual weights in order to calculate their competi- tiveness indices (CI) with specific equations. The competitiveness indices for the 4 indicators and the 31 factors were also calculated, and they ranged from unfavorable to very favorable. The Item Response Theory was employed to statistically treat the data. Data analysis also employed the Correspondence Analysis Technique (ANACOR) available in the SPSS software in its 18.0 version. The average CI of the production systems 7.27, which is considered a favorable one. The main cri- tical competitiveness factors include the producers' organization, price formation, strategic planning and availability of technological innovations. Researches like the current one are of fundamen- tal importance to develop strategies to be carried out by both the public and the private sectors aiming to enhance competitiveness of the beef production chain.Objetivou-se mensurar a competitividade in- terna dos sistemas de produção que atuam na bovinocultura de corte na Região Sul do Brasil. Foram realizadas entrevistas durante o primeiro trimestre de 2010 com 36 pecuaristas que atuam na bovinocultura de corte no Estado do Rio Grande do Sul. Foram definidos os principais direciona- dores que afetam a competitividade dentro da porteira, sendo estes a tecnologia, a gestão, as relações de mercado e o ambiente institucional. Posteriormente estes foram desdobrados em dez, dez, quatro e sete fatores, respectivamente, sendo atribuídos pesos específicos para cada um deles a fim de determinar o índice de competitividade (IC) por meio de equações específicas. Foi calculado também o grau de competitividade dos quatro direcionadores e dos 31 fatores, variando de muito desfavorável a muito favorável. Os resulta- dos foram analisados estatisticamente pela teoria de resposta ao item e pela análise de correspon- dência através do software SPSS. Os sistemas de produção apresentaram, em média, um IC favo rável (7,27). Entre os principais fatores críticos de competitividade destacaram-se a organização dos produtores, formação de preços, planejamento estratégico e o acesso a inovações tecnológicas. Estes trabalhos são fundamentais para identificar as ações prioritárias a ser realizadas pelos órgãos públicos, privados e de fomento para alcançar maior competitividade a cadeia produtiva da carne bovina