Acoustic propagation in the Brazil current system off the Southeastern coast

The Brazil Current (BC) is perhaps the less studied subtropical boundary current of the world ocean. Within this region, the BC develops vigorous meanders and rings. A combination of numerical simulations and observational studies are important tools to unravel these phenomena. Direct current measurements are rare and usually too short to depict the mean, long term circulation patterns. Similarly, quasi-synoptic hydrographic data in the region is sparse. Acoustic waves are an efficient tool for covering large regions of the water column in a synoptic way. Acoustic tomography can be therefore useful to better predict through inversion for the effective sound speed field and its assimilation to a circulation model the oceanographic fields of interest (temperature, salinity, density). Such information is particularly important for initialization and data assimilation to regional models for which small and meso-scale processes are of fundamental interest. In this paper, a preliminary study of acoustic propagation modeling through two vertical sections off the Brazilian southeastern coast is presented. Actual hydrographic data from DEPROAS 2003 sea trial serve to construct the physical parameters that characterize these sections

Water mass, front and meanders of the Brazil Current seen through acoustics: a preliminary study

The Brazil Current (BC) is perhaps the least studied subtropical boundary current of the world's oceans. Within this region, the BC develops vigorous meanders and rings. A combination of numerical simulations and observational studies are important tools for unravelling these phenomena. Direct current measurements are rare and usually too short to depict the mean, long term circulation patterns. Similarly, quasi-synoptic hydrographic data in the region is sparse. Acoustic waves are an efficient tool for covering large regions of the water column in a synoptic way. Acoustic tomography can, therefore, be useful to better predict, through inversion for the effective sound speed field and its assimilation to a circulation model, the oceanographic fields of interest (temperature, salinity, density). Such information is particularly important for initialization and data assimilation to regional models for which small and meso-scale processes are of fundamental interest. In this paper, a preliminary study of acoustic propagation modelling through one vertical section off the Brazilian southeastern coast is presented. The acoustic rays are trapped in a minimum sound speed channel bounded by Antarctic Intermediate Water and Upper Circumpolar Deep Water. Between this so-created deep channel and the shel break, one interesting region from the acoustic viewpoint is identified. Notable variations in the transmission loss field are found in this region when the Brazil Current front is moving. In addition, the results show the baroclinic currents more sensitive to salinity variations than sound speed structure, as well as acoustic propagation

Range-dependent acoustic tomography based on a feature model for monitoring the Cabo Frio upwelling (Brazil)

info:eu-repo/semantics/publishe

Feature-oriented acoustic tomography: Upwelling at Cabo Frio (Brazil)

info:eu-repo/semantics/publishe

Alelopatia e homeopatia no manejo da tiririca (Cyperus rotundus) Allelopathy and homeopathy in the management of nutsedge (Cyperus rotundus)

A tiririca (Cyperus rotundus) é uma espécie daninha de difícil manejo, causadora da redução do estande e do rendimento em plantios comerciais das mais variadas culturas. Devido à sua agressividade, capacidade de reprodução, alta dispersão e rusticidade, seu controle é difícil e oneroso. Objetivou-se com este trabalho avaliar métodos alternativos de controle da tiririca baseados na alelopatia e na homeopatia. No manejo com alelopatia, testaram-se extratos aquosos de feijão-de-porco (Canavalia ensiformes), mucuna-preta (Stizolobium aterrimum), alecrim-pimenta (Lippia sidoides) e capim-limão (Cymbopogon citratus). Com a homeopatia foi utilizada a escala centesimal hahnemanniana, onde se testaram as dinamizações 3CH, 6CH, 9CH e 12CH. Ambos os experimentos foram conduzidos em caixas gerbox transparentes, contendo areia grossa lavada, grãos de 1 a 3 mm de espessura, e 10 tubérculos sadios de tiririca, distribuídos uniformemente ao longo do recipiente. Após a aplicação dos tratamentos, os recipientes foram dispostos em estufa do tipo BOD a 25 ºC, com fotoperíodo de 12 horas, onde permaneceram por 15 dias até a avaliação final. O extrato que apresentou o melhor manejo da tiririca foi o de alecrim-pimenta, que diminuiu o percentual de emergência e o vigor das plântulas; o extrato dessa espécie ocasionou maior efeito na redução do comprimento das plântulas de tiririca do que 2,5 kg ha-1 i.a. atrazina - herbicida utilizado para comparação. A homeopatia não apresentou diferença entre as dinamizações, não tendo assim efeito satisfatório no controle da tiririca. Os extratos de capim-limão, mucuna-preta e feijão-de-porco não apresentaram efeitos alelopáticos. No entanto, o extrato de alecrim-pimenta é promissor no manejo alternativo de tiririca, sendo necessários novos estudos para elucidação dos princípios químicos envolvidos e da sua real ação no metabolismo da planta.The nutsedge (Cyperus rotundus) is a harmful weed of difficult control, causing reduction of stand and yield of a wide variety of commercial crops. Due to its aggressiveness, reproduction capacity, high dispersion and rusticity, its control is difficult and costly. The aim of this work was to evaluate alternative methods of nutsedge control based on allelopathy and homeopathy. In the management with allelopathy, aqueous extracts of jack bean (Canavalia ensiformes), black velvet bean (Stizolobium aterrimum), rosemary pepper (Lippia sidoides) and lemon grass (Cymbopogon citratus) were tested. With homeopathy, the Hahnemannian centesimal scale was used, testing the 3CH, 6CH, 9CH and 12CH dynamizations. Both experiments were conducted in transparent Gerboxes containing washed coarse sand, 1 to 3 mm thick grains, and 10 healthy nutsedge tubers, distributed evenly within the container. After the application of the treatments, the containers were placed in a BOD germination chamber at 25 oC with a 12 hour photoperiod, where they remained for 15 days until the final evaluation. The extract presenting the best nutsedge management was rosemary pepper, which reduced plantlet emergence percentage and vigor, with the extract of this species causing a length reduction in the nutsedge plant higher than that of 2.5 kg ha-1 a.i. of atrazine, the herbicide used for comparison. The homeopathy treatment did not present a significant difference, not exhibiting the expected effect with its nutsedge control dynamizations. The lemon grass, black velvet bean and jack bean extracts did not present allelopathic effects. However the rosemary pepper extract was found to be promising as a nutsedge alternative management, with further studies being necessary to elucidate the chemical principles involved and its true action in the metabolism of the plant