Abstract Laelia halbingeriana Salazar & Soto Arenas is a wild epiphytic orchid endemic to Oaxaca, Mexico, that is collected with no plans for its management or conservation. The objective of this study was to propagate and evaluate the in vitro development of this species in the culture media with a variety of mineral salts and growth regulators. Groups of three plants, 1.2 to 1.4 cm tall, were established in receptacles with culture medium containing 30 g L−1 sucrose, 1 mg L−1 thiamine, 100 mg L−1 inositol and 0.5 mg L−1 benzyl aminopurine (BAP). Proportions of Murashige and Skoog (1962) or Knudson (1946) mineral salts were varied (100, 66 and 33%). The growth regulators indoleacetic acid (IAA) and kinetin (Kin) were used at various concentrations (0.5 + 0.5 mg L−1, 1 + 1 mg L−1 and 2 + 2 mg L−1). pH was adjusted to 5.8, and 5.5 g L−1 agar was added. After 120 days of incubation, the plants that were cultivated in 66% and 100% Knudson media were 2.1 cm tall and had 4.8 roots, while the plants in 100% Murashige and Skoog media were 1.5 cm tall and had 2.5 roots. For 120 days, the plants had a logarithmic trend in vertical growth (R2≥0.96). Several plant characteristics were evaluated simultaneously using a cluster analysis, which found that the best culture medium for Laelia halbingeriana development contains 100% Knudson mineral salts, 0.5 mg L−1 BAP, 0.5 mg L−1 IAA, and 0.5 mg L−1 KIN.

Resumen Laelia halbingeriana es una orquídea epífita silvestre, endémica de Oaxaca, México, colectada sin planes de manejo, y este trabajo tuvo el objetivo de propagar y evaluar el desarrollo in vitro de esta especie en medios de cultivo que variaron en sales minerales y reguladores de crecimiento. Grupo de 3 plantas de 1.2 a 1.4 cm de altura se establecieron en cada frasco con medios de cultivo que tenian 30 g L−1 de sacarosa, 1 mg L−1 de tiamina, 100 mg L−1 de inositol y 0.5 mg L−1 de bencilaminopurina, BAP, variando las sales minerales de Murashige y Skoog (1962) o Knudson (1946) (100, 66 y 33%) los reguladores de crecimiento: ácido indolacético, AIA, y kinetina, Kin, y su concentración (0.5+0.5 mg L−1, 1+1 mg L−1 y 2+2 mg L−1). El pH se ajustó a 5.8, y agregó 5.5 g L−1 de agar. Transcurridos 120 días de incubación, las plantas que estuvieron en medios Knudson 100 y 66 %, tuvieron 2.1 de altura y 4.8 raíces, mientras las plantas en medios Murashige y Skoog 100 % tuvieron 1.5 de altura y 2.5 raíces. Durante 120 días, las plantas mostraron crecimiento en altura con una tendencia logarítmica (R2≥0.96). Al evaluar simultáneamente varias características de plantas mediante análisis clúster, se determinó que el mejor medio de cultivo para el desarrollo de Laelia halbingeriana tenía las sales minerales Knudson al 100%, 0.5 mg L−1 de BAP, 0.5 mg L−1 de AIA, 0.5 mg L−1 de KIN.

Resumo Este trabalho objetivou avaliar períodos secos e chuvosos nas sub-regiões da Bacia Hidrográfica do Rio São Francisco (BHSF) utilizando o Índice de Precipitação Padronizado (SPI) e cadeias de Markov. Cada sub-região da BHSF possui características físicas e climáticas específicas, dessa forma foram utilizadas quatro estações pluviométricas contendo dados com 46 anos, de 1970 a 2015, obtidas na Agência Nacional de Águas (ANA), representativas de cada sub-região. O SPI foi calculado para as escalas de tempo de seis e doze meses e as matrizes de probabilidades de transição foram obtidas utilizando as cadeias de Markov. As matrizes de transição mostraram que, em ambas as escalas, caso a condição climática estivesse em classe de seca severa ou chuvosa, a mudança para outra classe seria pouco provável a curto prazo. Correlacionando esta informação com as probabilidades da distribuição estacionária, foi possível encontrar as regiões que têm maiores possibilidades de no momento futuro estar sob clima chuvoso ou de seca. Os tempos de recorrência calculados para as estações inseridas no semiárido foram menores quando comparado com o valor do tempo da estação representativa do Alto São Francisco que possui maiores níveis de precipitação, confirmando a predisposição do semiárido em apresentar maiores chances de períodos futuros de seca.

Abstract This work evaluated dry and rainy conditions in the subregions of the São Francisco River Basin (BHSF) using the Standardized Precipitation Index (SPI) and Markov chains. Each subregion of the BHSF has specific physical and climatic characteristics. The data was obtained from the National Water Agency (ANA), collected by four pluviometric stations (representative of each subregion), covering 46 years of data, from 1970 to 2015. The SPI was calculated for the time scales of six and twelve months and transition probabilities were obtained using the Markov chain. Transition matrices showed that, at both scales, if the climate conditions were severe drought or rainy, switching to another class would be unlikely in the short term. Correlating this information with the probabilities of the stationary distribution, it was possible to find the regions that are most likely to be under rainy or dry weather in the future. The recurrence times calculated for the stations that belong to the semi-arid region were smaller when compared to the value of the return period of the representative station of Upper São Francisco that has higher levels of precipitation, confirming the predisposition of the semi-arid region to present greater chances of future periods of drought.

OBJETIVO: Avaliar a dose absorvida em folículos tireoidianos devido aos elétrons de baixa energia, como os elétrons Auger e os de conversão interna, além das partículas beta, para os radioisótopos de iodo (131I, 132I, 133I, 134I e 135I) usando o método Monte Carlo. MATERIAIS E MÉTODOS: O cálculo da dose foi feito ao nível folicular, simulando elétrons Auger, conversão interna e partículas beta, com o código MCNP4C. Os folículos (colóide e células foliculares) foram modelados como esferas, com diâmetros do colóide variando de 30 a 500 mm. A densidade considerada para os folículos foi a da água (1,0 g.cm-³). RESULTADOS: Considerando partículas de baixa energia, o percentual de contribuição do 131I na dose total absorvida pelo colóide é de aproximadamente 25%, enquanto os isótopos de meia-vida física curta apresentaram contribuição de 75%. Para as células foliculares, esse percentual é ainda maior, chegando a 87% para os iodos de meia-vida curta e 13% para o 131I. CONCLUSÃO: Com base nos resultados obtidos, pode-se mostrar a importância de se considerar partículas de baixa energia na contribuição para a dose total absorvida ao nível folicular (colóide e células foliculares) devido aos radioisótopos de iodo (131I, 132I, 133I, 134I e 135I).

OBJECTIVE: To evaluate the absorbed dose in thyroid follicles due to low-energy electrons such as Auger and internal conversion electrons, besides beta particles, for iodine radioisotopes (131I, 132I, 133I, 134I and 135I) utilizing the Monte Carlo method. MATERIALS AND METHODS: The dose calculation was performed at follicular level, simulating Auger, internal conversion electrons and beta particles, with the MCNP4C code. The follicles (colloid and follicular cells) were modeled as spheres with colloid diameter ranging from 30 to 500 mm, and with the same density of water (1.0 g.cm-³). RESULTS: Considering low-energy particles, the contribution of 131I for total absorbed dose to the colloid is about 25%, while the contribution due to short-lived isotopes is 75%. For follicular cells, this contribution is still higher achieving 87% due to short-lived iodine and 13% due to 131I. CONCLUSION: The results of the present study demonstrate the importance of considering low-energy particles in the contribution for the total absorbed dose at follicular level (colloid and follicular cells) due to iodine radioisotopes (131I, 132I, 133I, 134 I and 135I).