Spin-glass phase transition and behavior of nonlinear susceptibility in the Sherrington-Kirkpatrick model with random fields

The behavior of the nonlinear susceptibility $\chi_3$ and its relation to the spin-glass transition temperature $T_f$, in the presence of random fields, are investigated. To accomplish this task, the Sherrington-Kirkpatrick model is studied through the replica formalism, within a one-step replica-symmetry-breaking procedure. In addition, the dependence of the Almeida-Thouless eigenvalue $\lambda_{\rm AT}$ (replicon) on the random fields is analyzed. Particularly, in absence of random fields, the temperature $T_f$ can be traced by a divergence in the spin-glass susceptibility $\chi_{\rm SG}$, which presents a term inversely proportional to the replicon $\lambda_{\rm AT}$. As a result of a relation between $\chi_{\rm SG}$ and $\chi_3$, the latter also presents a divergence at $T_f$, which comes as a direct consequence of $\lambda_{\rm AT}=0$ at $T_f$. However, our results show that, in the presence of random fields, $\chi_3$ presents a rounded maximum at a temperature $T^{*}$, which does not coincide with the spin-glass transition temperature $T_f$ (i.e., $T^* > T_f$ for a given applied random field). Thus, the maximum value of $\chi_3$ at $T^*$ reflects the effects of the random fields in the paramagnetic phase, instead of the non-trivial ergodicity breaking associated with the spin-glass phase transition. It is also shown that $\chi_3$ still maintains a dependence on the replicon $\lambda_{\rm AT}$, although in a more complicated way, as compared with the case without random fields. These results are discussed in view of recent observations in the LiHo$_x$Y$_{1-x}$F$_4$ compound.Comment: accepted for publication in PR

Aspectos econômicos da criação de abelhas indígenas sem ferrão (Apidae: Meliponini) no Nordeste paraense.

Realidade do Nordeste Paraense; Realidade de Tracuateua; Custos de investimento e manutenção de um meliponário; Custo de investimento; Descrição dos itens que compõem o custo de instalação; Custo operacional; Custo variável; Custo fixo; Aspectos econômicos; Possibilidade de Financiamento; Programa Nacional da Agricultura Familiar (Pronaf); Dificuldades e recomendações.Versão eletrônica. 1ª impressão: 2010

Diagnóstico pouco usual de obstrução da traqueia

AbstractMale, 54 years old, with smoking habits. The patient complaints were cough, with bleeding secretions in the previous two months. Because of the persistence of the symptoms, a broncoscopy was proposed. This exam showed multiple lesions in the traquea, nearly 2cm above the vocal cords that compromised the airway and did not allow the progression of the bronchoscope. For this reason, it was decided to introduce a tracheal prosthesis. Because of instability, and the suspicion of malignancy we started thoracic irradiation. The histological specimen was compatible with anaplastic Lymphoma, CD 30+.Because of respiratory distress, with stridor, the prothesis was removed. The traquea was permeable after this.The patient was discharged and oriented to Clinical Haematology. He is clinically stable and under monitoring, having now completed a chemotherapy treatment with CHOP (Ciclophosphamide, Adriamycin or Hydroxydorubicin, Vincristine or Oncovin and Prednisone).The primary mediastinal Large Cells Lymphoma represents 11.5% of the Large Cells Lymphomas (2% of the non-Hodgkin’s Lymphomas). This neoplasm is in many studies considered incurable, but there are some positive results with the combination of radiotheraphy and chemotherapy. If there is any airway compromise, the tracheal prosthesis may be one option for the resolution of the respiratory insufficiency.Rev Port Pneumol 2006; XII (3): 303-30

Control of state and state entanglement with a single auxiliary subsystem

We present a strategy to control the evolution of a quantum system. The novel aspect of this protocol is the use of a \emph{single auxiliary subsystem}. Two applications are given, one which allows for state preservation and another which controls the degree of entanglement of a given initial state

Using the economic surplus method to assess economic impacts of new technologies: case studies of Embrapa.

Abstract - Assessment of economic impacts of new technologies delivers helpful information to justify investment efforts in research and development to generate new technologies. In Brazilian agricultural research and development, it?s a convention to assess economic impacts of technologies generated and adapted by EMBRAPA. As soon as new technologies are adopted, expost assessment is conducted to evaluate net benefits of its adoption. In agricultural research, the economic surplus method represents one of the suitable frameworks to measure the aggregated social benefits of a research project. With this method it is possible to estimate the return of investments by calculating a variation of consumer and producer surplus through a technological change originated by research results. Therefore, in a first step the gain of adoption i.e., increases in productivity, quality improvements, cost reduction etc. is estimated. In a second step, costs involved in generation and adaptation of the technology are enumerated. The difference between the gains and the costs of generation and transfer represents the net benefit of the technology, explained by the net present value, the internal rate of return and the benefit-costratio. The so far obtained results serve as additional information for each technology to improve its adoption by beneficiaries and to enable access to the new financing sources. Some examples of such technologies are (a) the finishing of lambs in confinement in the Brazilian semi-arid Northeast during the dry season, when feeding resources are scarce and the lamb meat prices are high; (b) strategic vermifugation of goats herds and sheep flocks in the Brazilian semi-arid areas; (c) standardized cuts for goat and sheep carcass and (d) enrichment of the native pastures in Brazilian Northeast with Cynodon dactylon for sheep production. The assessment of the economic impacts of these technologies estimated positive net present values for all four considered technologies, internal rates of return of 26.2% (a), 13.8% (b), 52.8% (c) and 31.0% (d) and the benefit-cost-ratios of 2.92 (a), 1.19 (b), 11.64 (c) and 3.37 (d)

Impactos econômicos de novas tecnologias: um estudo de caso da Embrapa Caprinos.

A avaliaçao de impactos de tecnologias permite o levantamento de informações extremamente relevantes para justificar os esforços direcionados à pesquisa e desenvolvimento no intuito de gerar novas tecnologias. Na pesquisa agropecuaria brasileira, a avaliaçao de impactos das tecnologias geradas pela Embrapa está se tornando algo rotineiro. Assim que novas tecnologias passam a ser adotadas, avaliaçôes ex-post sao conduzidas para estimar os beneficios liquidos de sua adoçao. Para tanto, num primeiro passa, os beneficios obtidos com a adoçao, como aumento de produtividade, melhoria da qualidade, reduçao de custos etc. sao estimados. Em seguida, sao levantados os custos da geraçao, adaptaçao e transferência da tecnologia para os usuarios. A diferença entre os beneficios da adoçao e os custos de geraçao, adaptaçao e transferência representa o beneficio liquido, expresso pela valor presente liquido e pela taxa interna de retorno. Os resultados obtidos, até entao, representam uma informaçao adicional para cada tecnologia, favorecendo sua adoçao pelos beneficiários e permitindo o acesso a novas fontes de fomento à pesquisa e desenvolvimento. Um exemplo de tecnologia gerada com participaçao da Embrapa e adotada por produtores rurais no Semi-Arido é a terminaçao de cordeiros em confinamento, durante a estaçao seca, quando a base alimentar é reduzida e os preços da carne sao elevados. A avaliaçao dos impactos econômicos dessa tecnologia determinou uma taxa interna de retorno de 32,0% para os investimentos feitos em pesquisa e desenvolvimento na Embrapa, o que é bem superior às alternativas disponiveis para aplicaçao do recurso