Este trabalho enquadra-se na linha de pesquisa que tem como objetivo a busca de modelos mais precisos para cálculo de parâmetros de linhas aéreas de transmissão na faixa de frequência 0 a 2 MHz. Esta faixa de frequência cobre a maioria das perturbações eletromagnéticas nos sistemas elétricos (manobras, ocorrências de faltas, rejeições de carga, descargas atmosféricas, perturbações harmônicas). Entre 1 Hz e 2 MHz o solo pode ter a condutividade elétrica da mesma ordem de grandeza que o produto entre a constante dielétrica e a frequência angular do sinal incidente no solo, em função da dependência desses parâmetros com a frequência. Consequentemente, as suposições de baixa frequência tradicionalmente adotadas - condutividade do solo constante e permissividade desprezível - podem levar a modelos que não representam de forma adequada a resposta da linha no caso de transitórios rápidos (com espectro de frequência acima de 1 kHz). É apresentado um estudo dos parâmetros de uma linha formada por um único condutor acima de solo condutor imperfeito, - onde a impedância e a admitância de retorno pelo solo são avaliadas através de métodos tradicionais de cálculo e através de integração numérica das formulações de Carson modificadas para inclusão do modelo de solo com parâmetros dependentes da frequência.

In this paper the influence of earth's conductivity and permittivity frequency dependence are evaluated when calculating transversal and longitudinal transmission lines' parameters. The aim is to compare results calculated from the complex plane method and Carson's modified expressions on longitudinal parameters and also between Carson's modified potential-coefficient correction factors and results from approximations methods for transversal admittance parameters. The importance of properly considering the frequency-dependent soil model is presented for oneconductor case, in order to compare the longitudinal and transversal parameters considering the earth's conductivity and permittivity frequency dependence soil model in relation to the common soil representation with a constant conductivity and a permittivity that can be neglected assuming a low frequency approximation.

Objetive: Self-expandable plastic stents (SEPS) are increasingly being used for treatment of postoperative esophageal leak. This complication occurs in 4-27% of patients after radical gastrectomy, and has a high mortality rate up to 60%. The aim of this study is to evaluate the efficacy of SEPS (Polyflex®) for treatment of post-operative eshopago-jejuno anastomosis leak after radical gastrectomy for gastric cancer. Material and methods: During one year period patients who underwent a radical gastrectomy in our hospital for gastric cancer and developed a postoperative anastomotic leak were prospectively included in the study after signing a consent form, and treated with SEPS placement under endoscopic and fluoroscopic control for leak occlusion. Results: Four patients were included (3 men/1 woman). The mean interval between operation and SEPS placement was 16 days (range: 4-34). SEPS deployment was easily performed in all patients with complete occlusion of esophageal lumen in three patients. In the fourth patient we needed to deploy a second coaxial stent to achieve a complete occlusion of the fistula. SEPS migration did not happen in our series. One patient had already developed a mediastinitis by the time we placed the SEPS and he died 3 days later. Extraction of the SEPS was easily performed 4-8 weeks after deployment. Conclusion: We achieved a complete healing of the anastomotic fistula after radical gastrectomy in 3 out of 4 patients, without major complications related to SEPS. Placement of SEPS is an appealing minimally invasive alternative to surgical repair for patients with postoperative anastomotic leak.

Foram conduzidos quatro experimentos de campo, sendo dois no município de Santo Antônio de Goiás-GO e dois no município de Santa Helena de Goiás-GO, nos anos agrícolas de 1998/1999 e 1999/2000, com o objetivo de avaliar a seletividade de herbicidas para a cultura do arroz de terras altas em diferentes estádios da planta, dos cultivares Maravilha, Primavera e Canastra. Os tratamentos foram: metsulfuron-methyl (2,4 g i.a. ha-1) aos 10 e 20 dias após a emergência (DAE); 2,4-D amina (335, 502 e 670 g i.a ha-1) aos 10, 20 e 30 DAE; fenoxaprop-p-ethyl (41,4 g i.a. ha-1) aos 10, 20 e 30 DAE; e clefoxydin (120 g i.a. ha¹) aos 10, 20 e 30 DAE. A seletividade dos herbicidas dependeu do cultivar e do estádio de desenvolvimento da planta do arroz. Assim, os resultados permitem concluir que é recomendada para o cultivar Primavera a aplicação de metsulfuron-methyl aos 20 DAE e de fenoxaprop-p-ethyl e clefoxydin aos 30 DAE; o herbicida 2,4-D amina não é recomendado para este cultivar. Para o cultivar Maravilha, o metsulfuron-methyl e o fenoxaprop-p-ethyl podem ser aplicados em qualquer estádio do crescimento. Os herbicidas 2,4-D amina e clefoxydin são recomendados para aplicação aos 30 DAE. O cultivar Canastra apresentou alta resistência à aplicação dos herbicidas em todos os estádios de crescimento analisados.

Four field experiments were conducted (two in Santo Antônio de Goiás and two in Santa Helena de Goiás - Brazil) in 1998/1999 and 1999/2000, to evaluate the selectivity of upland rice to herbicides at different growth stages. The cultivars tested were Primavera, Maravilha and Canastra and the herbicide treatments were metsulfuron-methyl (2,4 g a.i. ha-1) at 10 and 20 days after emergency (DAE); 2,4-D amine (335, 502 and 670 g a.i. ha-1), at 10, 20 and 30 DAE, fenoxaprop-p-ethyl (41,4 g a.i. ha-1) at 10, 20 and 30 DAE and clefoxydin (120 g a.i. ha-1) at 10, 20 and 30 DAE. The results showed that the selectivity of the herbicides depends on the cultivar and rice growth stage at application time. According to the results, for the cultivar Primavera, the applications of metsulfuron-methyl at 20 DAE and fenoxaprop-p-ehtyl and clefoxydin at 30 DAE are recommended. The herbicide 2,4-D amine is not recommended for this cultivar. For the cultivar Maravilha, metsulfuron-methyl and fenoxaprop-p-ethyl can be applied at any growth stage. The herbicide 2,4-D amine and clefoxydin are recommended for application at 30 DAE. The cultivar Canastra showed high tolerance to all herbicides at any growth stage.