717 research outputs found
Critical rainfall thresholds for triggering shallow landslides in the Serchio River Valley (Tuscany, Italy)
Abstract. The Serchio River Valley, in north-western Tuscany, is a well-known tourism area between the Apuan Alps and the Apennines. This area is frequently hit by heavy rainfall, which often triggers shallow landslides, debris flows and debris torrents, sometimes causing damage and death. The assessment of the rainfall thresholds for the initiation of shallow landslides is very important in order to improve forecasting and to arrange efficient alarm systems. With the aim of defining the critical rainfall thresholds for the Middle Serchio River Valley, a detailed analysis of the main rainstorm events was carried out. The hourly rainfall recorded by three rain gauges in the 1935–2010 interval was analysed and compared with the occurrence of shallow landslides. The rainfall thresholds were defined in terms of mean intensity I, rainfall duration D, and normalized using the mean annual precipitation. Some attempts were also carried out to analyze the role of rainfall prior to the damaging events. Finally, the rainfall threshold curves obtained for the study area were compared with the local, regional and global curves proposed by various authors. The results of this analysis suggest that in the study area landslide activity initiation requires a higher amount of rainfall and greater intensity than elsewhere
Distinct Contributions of Median Raphe Nucleus to Contextual Fear Conditioning and Fear-Potentiated Startle
Ascending 5-HT projections from the
median raphe nucleus (MRN), probably to the
hippocampus, are implicated in the acquisition
of contextual fear (background stimuli), as
assessed by freezing behavior. Foreground cues
like light, used as a conditioned stimulus (CS) in
classical fear conditioning, also cause freezing
through thalamic transmission to the amygdala.
As the MRN projects to the hippocampus and
amygdala, the role of this raphe nucleus in fear
conditioning to explicit cues remains to be
explained. Here we analyzed the behavior of
rats with MRN electrolytic lesions in a
contextual conditioning situation and in a fear-potentiated
startle procedure. The animals
received MRN electrolytic lesions either before
or on the day after two consecutive training
sessions in which they were submitted to 10
conditioning trials, each in an experimental
chamber (same context) where they. received
foot-shocks (0.6 mA, 1 sec) paired to a 4-sec
light CS. Seven to ten days later, the animals
were submitted to testing sessions for assessing
conditioned fear when they were placed for five
shocks, and the duration of contextual freezing
was recorded. The animals were then submitted
to a fear-potentiated startle in response to a 4-sec
light-CS, followed by white noise (100 dB, 50 ms). Control rats (sham) tested in the same
context showed more freezing than did rats
with pre- or post-training MRN lesions. Startle
was clearly potentiated in the presence of light CS in the sham-lesioned animals. Whereas pretraining
lesions reduced both freezing and fear-potentiated
startle, the post-training lesions
reduced only freezing to context, without
changing the fear-potentiated startle. In a
second experiment, neurotoxic lesions of the
MRN with local injections of N-methyl-D-aspartate
or the activation of 5-HT1A somatodendritic
auto-receptors of the MRN by
microinjections of the 5-HT1A receptor agonist
8-hydroxy- 2-(di-n-propylamino)tetralin (8-OH-DPAT)
before the training sessions also reduced
the amount of freezing and the fear-potentiated
startle. Freezing is a prominent response of
contextual fear conditioning, but does not seem
to be crucial for the enhancement of the startle
reflex by explicit aversive cues. As fear-potentiated
startle may be produced in posttraining
lesioned rats that are unable to freeze
to fear contextual stimuli, dissociable systems
seem to be recruited in each condition. Thus,
contextual fear and fear-potentiated startle are
conveyed by distinct 5-HT-mediated circuits of
the MRN
Avaliação do padrão tecnológico e tendências da Agricultura de Precisão - Safra 2011/12.
Resumo: Embora os conceitos e tecnologias da Agricultura de Precisão (AP) são bastante difundidos no Brasil, a AP ainda é pouco utilizada em algumas regiões produtoras de grãos. O presente trabalho teve como objetivo fazer um levantamento sobre a utilização da AP, por meio da aplicação de um questionário via web e impresso. Foram encaminhados 250 e-mails convidando produtores e técnicos a responderem o questionário, além da realização de uma reunião técnica sobre AP em Guaraí/TO. Após análise das respostas obtidas, 67% dos produtores que responderam ao questionário informaram que iniciaram as atividades de AP entre dois e cinco anos. O tamanho do grid mais utilizado é de 5 hectares, sendo o serviço predominantemente realizado por empresas prestadoras de serviço, contudo os equipamentos e a interpretação dos resultados é realizada pela equipe técnica da propriedade. Embora não consigam observar a redução no custo de produção com a utilização da AP, os produtores discordam que os custos da AP sejam maiores que os benefícios observados. Além disso, os equipamentos e softwares hoje empregados na AP são um obstáculo ao crescimento e ao investimento na tecnologia. Como o questionário foi respondido por produtores e técnicos de diversas regiões do Brasil, constatou-se que o trabalho com AP ainda é bastante recente. Mesmo com conhecimento sobre a técnica e os benefícios que a tecnologia proporciona a utilização ainda é bastante restrita e necessita de mais acesso à informação e capacitação técnica, a fim de ter um uso mais eficaz e eficiente
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