A self-sustaining nonlinear dynamo process in Keplerian shear flows

A three-dimensional nonlinear dynamo process is identified in rotating plane Couette flow in the Keplerian regime. It is analogous to the hydrodynamic self-sustaining process in non-rotating shear flows and relies on the magneto-rotational instability of a toroidal magnetic field. Steady nonlinear solutions are computed numerically for a wide range of magnetic Reynolds numbers but are restricted to low Reynolds numbers. This process may be important to explain the sustenance of coherent fields and turbulent motions in Keplerian accretion disks, where all its basic ingredients are present.Comment: 4 pages, 7 figures, accepted for publication in Physical Review Letter

Pseudobatos horkelii, Brazilian Guitarfish

The Brazilian Guitarfish (Pseudobatos horkelii) is a small (to 138 cm total length) shark-like ray that occurs in the Southwest Atlantic from Rio de Janeiro, Brazil, to northern Argentina. It is demersal on soft substrates of the continental shelf inshore to 150 m depth. It is captured in intense and largely unmanaged commercial and artisanal demersal trawl, gillnet, longline, and beach seine fisheries throughout its geographic range. There are three estimates of population reduction. First, in Rio Grande do Sul, total landings increased from 842 t in 1975 to 1,804 t in 1984 and then declined continuously to 157 t in 2001, the equivalent of a >99% reduction over three generations (55.5 years). Second, the average research trawl catch-per-unit-effort of Brazilian Guitarfish in southern Brazil over the years 1993 to 1999 was 17% of that observed during 1975 to 1986, also the equivalent of a >99% reduction over three generations. Fisheries remain intense and unmanaged there. Third, in Uruguay, this guitarfish is captured frequently in gillnets and longlines, is landed, and is sometimes targeted, and it is also captured in artisanal trawl fisheries. Catches from research trawls there in the 1980s and early 1990s were on average around 1,400 kg/hr, and between 2013 and 2017 were only 480 kg/hr, the equivalent of a >92% reduction over three generations. In Argentina, it is suspected that intense and inadequately managed gillnet fishing pressure has led to declines in abundance there as well. Overall, due to intense and inadequately managed fishing pressure throughout its range, and steep population declines, it is inferred that the Brazilian Guitarfish has undergone a population reduction of >80% over the past three generations (55.5 years), and it is assessed as Critically Endangered A2bd.Fil: Pollom, R.. University Fraser Simon; CanadáFil: Barreto, R.. Instituto Chico Mendes de Conservacao Da Biodiversidade; BrasilFil: Charvet, P.. Universidade Federal do Paraná; BrasilFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J. M.. Wildlife Conservation Society; Estados UnidosFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Martins, M. F.. Universidade Federal Do Rio Grande.; BrasilFil: Montealegre Quijano, S.. Universidade Federal de Sao Paulo; BrasilFil: Motta, F.. Universidade Federal de Sao Paulo; BrasilFil: Paesch, L.. Dirección Nacional de Recursos Acuáticos; UruguayFil: Rincon, G.. Universidade Federal Do Maranhao.; Brasi

Atlantoraja castelnaui, Spotback Skate

The Spotback Skate (Atlantoraja castelnaui) is a medium-sized (to 147 cm total length) skate that occurs in the Southwest Atlantic from Rio de Janeiro, Brazil, to Buenos Aires, Argentina. It inhabits the continental shelf and upper slope from inshore to 300 m depth. It is captured in intense and largely unmanaged demersal trawl fisheries throughout its geographic range. Two lines of evidence indicate a population reduction. First, in Santa Catarina State, Brazil, catch-per-unit-effort (CPUE) declined by an estimated 54% between 1974 and 1981. Second, a 75% decline in CPUE was estimated from 1994 to 1999 in Rio Grande do Sul, Brazil. Both declines are consistent with a population reduction of >99% over three generation lengths (48 years). This large skate has a slow life history, and many skates with similar characteristics have undergone severe population reductions and face increased extinction risk. It is highly susceptible to exploitation and does not have any refuge from fishing at depth. Overall, due to declining abundance from intense and largely unmanaged fishing through most of its range combined with its large size and presumed late age-at-maturity (and therefore high sensitivity to fishing pressure), it is suspected that the Spotback Skate has undergone a population reduction of >80% over the past three generation lengths (48 years), and it is assessed as Critically Endangered A2bd.Fil: Pollom, R.. University Fraser Simon; CanadáFil: Barreto, R.. Instituto Chico Mendes de Conservacao Da Biodiversidade; BrasilFil: Charvet, P.. Universidade Federal do Paraná; BrasilFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J. M.. Wildlife Conservation Society; Estados UnidosFil: Faria, V.. Universidade Federal Do Ceara; BrasilFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Motta, F.. Universidade Federal de Sao Paulo; BrasilFil: Paesch, L.. Direccion Nacional de Recursos Acuaticos ; UruguayFil: Rincon, G.. Universidade Federal Do Maranhao.; Brasi

Narcine brasiliensis, Lesser Numbfish

The Lesser Numbfish (Narcine brasiliensis) is a small (to 45 cm total length) ray that occurs in the Southwest Atlantic from southern Brazil to Buenos Aires Province, Argentina. It is benthic on soft substrates of the continental shelf at depths of 6?60 m. It is captured in intense and largely unmanaged commercial and artisanal trawl and beach seine fisheries throughout much of its geographic range. A population reduction is suspected from the peak and subsequent declines in reported ray landings from the Rio del Plata area. This species is discarded when caught and discard survival rates are unknown, but are suspected to be variable based on the injuries of captured individuals. Although this ray is subject to high fishing pressure across its range, it is still observed commonly in fisheries despite this pressure. It is suspected that the Lesser Numbfish has undergone a population reduction of 20-29% over the past three generations (26 years), and it is assessed as Near Threatened (nearly meeting Vulnerable A2d).Fil: Pollom, R.. University Fraser Simon; CanadáFil: Barreto, R.. Instituto Chico Mendes de Conservacao Da Biodiversidade; BrasilFil: Charvet, P.. Universidade Federal do Paraná; BrasilFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J. M.. Wildlife Conservation Society; Estados UnidosFil: Faria, V.. Universidade Federal Do Ceara; BrasilFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Marcante, F.. Universidade Federal Do Rio Grande.; BrasilFil: Montealegre Quijano, S.. Universidade Federal de Sao Paulo; BrasilFil: Motta, F.. Universidade Federal de Sao Paulo; BrasilFil: Paesch, L.. Dirección Nacional de Recursos Acuáticos; UruguayFil: Rincon, G.. Universidade Federal Do Maranhao.; Brasi

Sympterygia bonapartii, Smallnose Fanskate

The Smallnose Fanskate (Sympterygia bonapartii) is a medium-sized (to 88 cm total length) skate that occurs in the Southeast Pacific in the Strait of Magellan, Chile, and in the Southwest Atlantic from Rio de Janeiro, Brazil to Santa Cruz, Argentina. It is demersal on the continental shelf and upper slope and inhabits depths down to 100 m and occasionally to 500 m deep. This skate is captured in intense artisanal and commercial demersal trawl and longline fisheries and recreational fisheries in Argentina. Research trawl surveys conducted on the southern Brazilian shelf indicate a reduction in catch-per-unit-effort (CPUE) of 94% between 1980 and 2005. In Uruguay, research surveys exhibit an increase in catch-per-unit-effort between 1984 and 2008 followed by a stabilization. Overall, the Smallnose Fanskate is subjected to intense largely unregulated fishing pressure across most of its range, but is able to survive when discarded. The larger part of this species' range is in central and southern Argentina where fishing mortality is likely to be lower. Due to the level of fisheries mortality that this species is exposed in the northern part of its range, balanced with lower pressure in the south, and its high survivorship when discarded, it is suspected that the Smallnose Fanskate has undergone a population reduction of 20-29% over the past three generations (49.5 years), and it is assessed as Near Threatened (nearly meeting Vulnerable A2bd).Fil: Pollom, R.. University Fraser Simon; CanadáFil: Barreto, R.. Instituto Chico Mendes de Conservacao Da Biodiversidade; BrasilFil: Charvet, P.. Universidade Federal do Paraná; BrasilFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J. M.. Wildlife Conservation Society; Estados UnidosFil: Faria, V.. Universidade Federal Do Ceara; BrasilFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Marcante, F.. Universidade Federal de Pernambuco; BrasilFil: Montealegre Quijano, S.. Universidade Federal de Sao Paulo; BrasilFil: Motta, F.. Universidade Federal de Sao Paulo; BrasilFil: Paesch, L.. Dirección Nacional de Recursos Acuáticos; UruguayFil: Rincon, G.. Universidade Federal Do Maranhao.; Brasi

Scyliorhinus haeckelii, Freckled Catshark

The Freckled Catshark (Scyliorhinus haeckelii) is a small (to 57 cm total length) shark that occurs in the Southwest Atlantic from Bahia, Brazil to northern Argentina. It inhabits the continental shelf and upper slope at depths of 37-402 m, and is often associated with deep-water reefs. This catshark is captured in artisanal and commercial trawl, gillnet, and longline fisheries, and is increasingly retained and sometimes targeted. Fishing pressure is present across its range and is intense in some places, however there are very few data on its catchability and level of interaction with fisheries. Association with deepsea corals indicates that it may have some refuge from trawls over untrawlable areas. Since it is unknown if fishing is causing a population reduction, there is currently inadequate information available to assess the Freckled Catshark beyond Data Deficient.Fil: Pollom, R.. University Fraser Simon; CanadáFil: Barreto, R.. Instituto Chico Mendes de Conservacao Da Biodiversidade; BrasilFil: Charvet, P.. Universidade Federal do Paraná; BrasilFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J. M.. Wildlife Conservation Society; Estados UnidosFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Montealegre Quijano, S.. Universidade Federal de Sao Paulo; BrasilFil: Motta, F.. Universidade Federal de Sao Paulo; BrasilFil: Paesch, L.. Dirección Nacional de Recursos Acuáticos; UruguayFil: Rincon, G.. Universidade Federal Do Maranhao.; Brasi

Zapteryx brevirostris, Shortnose Guitarfish

The Shortnose Guitarfish (Zapteryx brevirostris) is a small (to 66 cm total length) benthic shark-like ray that occurs in the Southwest Atlantic from Espírito Santo state, Brazil to Buenos Aires, Argentina. It inhabits inshore waters over soft substrates at depths of 2–140 m. It is captured in intense and largely unmanaged artisanal and commercial demersal trawl and gillnet fisheries throughout its geographic range. There are two estimates of population reduction. First, in Santa Catarina state, Brazil, catch-perunit-effort (CPUE) decreased 90% from 100 kg/hr in the 1980s to 10 kg/hr in 2005, the equivalent of a population reduction of >85% over three generation lengths (21 years). Second, in Uruguay, the research trawl survey CPUE declined by nearly 40%; in the 1980s and early 1990s, 2,200 kg/hr were caught, and between 2013 and 2017 there were just over 1,400 kg/hr caught, the equivalent of a population reduction of >25% over three generation lengths (21 years). Furthermore, demographic analyses have shown that this species is being overfished given the level of mortality it is exposed to. This guitarfish is subjected to intense and mostly unmanaged fishing pressure across its limited range, it has no refuge at depth, and where recorded in landings it has declined. Overall, it is suspected that the Shortnose Guitarfish has undergone a population reduction of 50–79% over the past three generation lengths (21 years), and it is assessed as Endangered A2bd.Fil: Pollom, R.. University Fraser Simon; CanadáFil: Barreto, R.. Instituto Chico Mendes de Conservacao Da Biodiversidade; BrasilFil: Charvet, P.. Universidade Federal do Paraná; BrasilFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J. M.. Wildlife Conservation Society; Estados UnidosFil: Faria, V.. Universidade Federal Do Ceara; BrasilFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Marcante, F.. Universidade Federal Do Rio Grande.; BrasilFil: Montealegre Quijano, S.. Universidade Federal de Sao Paulo; BrasilFil: Motta, F.. Universidade Federal de Sao Paulo; BrasilFil: Paesch, L.. Dirección Nacional de Recursos Acuáticos; UruguayFil: Rincon, G.. Universidade Federal Do Maranhao.; Brasi

Gear transmission dynamic: Effects of tooth profile deviations and support flexibility

In this work a non-linear dynamic model of spur gear transmissions previously developed by the authors is extended to include both desired (relief) and undesired (manufacture errors) deviations in the tooth profile. The model uses a hybrid method for the calculation of meshing forces, which combines FE analysis and analytical formulation, so that it enables a very straightforward implementation of the tooth profile deviations. The model approach handles well non-linearity due to the variable meshing stiffness and the clearances involved in gear dynamics, also including the same phenomena linked to bearings. In order to assess the ability of the model to simulate the impact of the deviations on the transmission dynamics, an example is presented including profile deviations under different values of transmitted torque. Several results of this example implementation are presented, showing the model's effectiveness.This paper has been developed in the framework of Project DPI2006-14348 funded by the Spanish Ministry of Science and Technology

Tetronace puelcha, argentine torpedo

The Argentine Torpedo (Tetronarce puelcha) is a medium-sized (to 120 cm total length) ray that occurs in the Southwest Atlantic from Espírito Santo, Brazil to San Jorge Gulf, Argentina. It is benthic on the continental shelf and slope at depths of 10–600 m, and also inhabits coastal lagoons. It is captured in intense and largely unmanaged commercial and artisanal demersal trawl and gillnet fisheries, which operate throughout most of its geographic range. Individuals that are caught are typically discarded at sea, but levels of post-release mortality are unknown. On the southern Brazilian shelf, this species declined by 97% in research trawl catch-per-unit-effort (CPUE) from 340 kg/hr in the 1980s to 10 kg/hr in 2005, equivalent to a >99% reduction over three generations. There are few data from Uruguay and Argentina, but this ray is rarely caught and may have undergone a similar decline there. Overall, due to the level of intense and inadequately managed fisheries throughout most of its range, its suspected unproductive life history, and significant estimated declines in CPUE in some areas, it is suspected that the Argentine Torpedo has undergone a population reduction of >80% over the past three generations (37.5 years), and it is assessed as Critically Endangered A2bd.Fil: Pollom, R.. University Fraser Simon; CanadáFil: Barreto, R.. Instituto Chico Mendes de Conservacao Da Biodiversidade; BrasilFil: Charvet, P.. Universidade Federal do Paraná; BrasilFil: Chiaramonte, Gustavo Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia". Estación Hidrobiológica de Puerto Quequén (sede Quequén); ArgentinaFil: Cuevas, J. M.. Wildlife Conservation Society; Estados UnidosFil: Herman, K.. Georgia Aquarium; Estados UnidosFil: Montealegre-Quijano, S.. Universidade Federal de Sao Paulo; BrasilFil: Motta, F.. Universidade Federal de Sao Paulo; BrasilFil: Paesch, L.. Dirección Nacional de Recursos Acuáticos; UruguayFil: Rincon, G.. Universidade Federal Do Maranhao.; Brasi