An Eigenvector-Based Test for Local Stationarity Applied to Array Processing

In sonar array processing, a challenging problem is the estimation of the data covariance matrix in the presence of moving targets in the water column, since the time interval of data local stationarity is limited. This work describes an eigenvector-based method for proper data segmentation into intervals that exhibit local stationarity, providing data-driven higher bounds for the number of snapshots available for computation of time-varying sample covariance matrices. Application of the test is illustrated with simulated data in a horizontal array for the detection of a quiet source in the presence of a loud interferer

W-Algebras of Negative Rank

Recently it has been discovered that the W-algebras (orbifold of) WD_n can be defined even for negative integers n by an analytic continuation of their coupling constants. In this letter we shall argue that also the algebras WA_{-n-1} can be defined and are finitely generated. In addition, we show that a surprising connection exists between already known W-algebras, for example between the CP(k)-models and the U(1)-cosets of the generalized Polyakov-Bershadsky-algebras.Comment: 12 papes, Latex, preprint DFTT-40/9

Intrinsic Absorption in the Spectrum of NGC 7469: Simultaneous Chandra, FUSE, and STIS Observations

We present simultaneous X-ray, far-ultraviolet, and near-ultraviolet spectra of the Seyfert 1 galaxy NGC 7469 obtained with the Chandra X-Ray Observatory, the Far Ultraviolet Spectroscopic Explorer, and the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. Previous non-simultaneous observations of this galaxy found two distinct UV absorption components, at -560 and -1900 km/s, with the former as the likely counterpart of the X-ray absorber. We confirm these two absorption components in our new UV observations, in which we detect prominent O VI, Ly alpha, N V, and C IV absorption. In our Chandra spectrum we detect O VIII emission, but no significant O VIII or O VII absorption. We also detect a prominent Fe K alpha emission line in the Chandra spectrum, as well as absorption due to hydrogen-like and helium-like neon, magnesium, and silicon at velocities consistent with the -560 km/s UV absorber. The FUSE and STIS data reveal that the H I and C IV column densities in this UV- and X-ray- absorbing component have increased over time, as the UV continuum flux decreased. We use measured H I, N V, C IV, and O VI column densities to model the photoionization state of both absorbers self-consistently. We confirm the general physical picture of the outflow in which the low velocity component is a highly ionized, high density absorber with a total column density of 10^20 cm^-2, located near the broad emission line region, although due to measurable columns of N V and C IV, we assign it a somewhat smaller ionization parameter than found previously, U~1. The high velocity UV component is of lower density, log N=18.6, and likely resides farther from the central engine as we find its ionization parameter to be U=0.08.Comment: Minor correction to abstract; STScI eprint #1683; 50 pages, incl. 19 figures, 4 tables; Accepted to Ap

Sympterygia acuta, Bignose Fanskate

The Bignose Fanskate (Sympterygia acuta) is a small (to 62 cm total length) skate that occurs in the Southwest Atlantic from Rio de Janeiro, Brazil to Bahía Blanca, Buenos Aires, Argentina. It inhabits the continental shelf from inshore to 188 m depth. It is captured in intense largely unmanaged demersal trawl fisheries throughout its geographic range. It is one of the most commercially important species and the wings are sold mainly to Asian markets at high prices. In southern Brazil, research trawl catchper-unit-effort revealed a decline in biomass of 74.5% between 1974 and 2005, equivalent to a population reduction of >83% scaled over three generations (40.5 years). This species is a target of the longline fishery in Uruguay, but now it is uncommonly captured in research trawl surveys there. Further, in Argentina, total skate landings have peaked and are declining as a result of overfishing. Overall, due to intense and largely managed trawl fisheries that operate throughout its geographic and depth range, it is suspected that the Bignose Fanskate has undergone a population reduction of >80% over the past three generations (40.5 years), and it is assessed as Critically Endangered A2bd.Fil: Pollom, R.. University Fraser Simon; CanadáFil: Barreto, R.. Centro Nacional Pesquisa E Conservação Da Biodiversidad; 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; Urugua

Psammobatis bergi, Blotched Sandskate

The Blotched Sandskate (Psammobatis bergi) is a small (to 61 cm total length) skate that occurs in the Southwest Atlantic from Rio de Janeiro, Brazil to the northern San Jorge Gulf, Chubut, Argentina. It inhabits the inner continental shelf at depths of 10-80 m. It is caught in demersal trawl fisheries, which are intense in parts of its range. It is typically discarded dead where caught. Its continued common presence in trawls and its small size suggest that it may have a productive enough life history to withstand fishing pressure and the population is suspected to be stable. Therefore, the Blotched Sandskate is assessed as Least Concern.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

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

Mustelus fasciatus, Striped Smoothhound

The Striped Smoothhound (Mustelus fasciatus) is a medium-sized (to 177 cm total length) shark that occurs in the Southwest Atlantic from Santa Catarina, Brazil, to southern Buenos Aires Province, Argentina. It is demersal on the continental shelf and upper slope, from inshore to 500 m depth. It is captured in intense and largely unmanaged commercial and artisanal demersal trawl, gillnet, and beach seine fisheries throughout its range. There are two population reduction estimates from research trawl surveys: (1) the southern Brazilian shelf; and, (2) the Argentina-Uruguay Common Fishing Zone. First, on the southern Brazilian shelf, catches of adults in research trawl surveys declined by 95% between 1981 and 2005, equivalent to a >99% population reduction over three generation lengths (43.5 years). Second, in the coastal region of the Bonaerensean District of northern Argentina and Uruguay, the biomass of this shark in trawl surveys decreased by 96% between 1994 and 1999, also equivalent to a >99% reduction over three generations. Due to the level of intense and largely unmanaged fishing pressure across its range, combined with its relatively unproductive life history, and noted declines, it is suspected that the Striped Smoothhound has undergone a population reduction of >80% over the past three generations (43.5 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 Do 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

Myliobatis ridens, Shortnose Eagle Ray

The Shortnose Eagle Ray (Myliobatis ridens) is a medium-sized (to 70 cm disc width) ray that occurs in the Southwest Atlantic from Santa Catarina, Brazil, to Buenos Aires Province, Argentina. It inhabits inshore bays and estuaries at depths of 5-47 m. It is captured in intense and largely unmanaged artisanal gillnet and beach seine fisheries throughout much of its geographic range. The meat from this species may be consumed or sold locally or discarded. In Rio Grande do Sul, beach seine and drifting gillnet fisheries are intense and capture this species in relatively high numbers. Eagle rays, in general, declined in that state by 91% in research trawls between 1974 and 2005. Gillnets are used in Argentina to target elasmobranchs, including eagle rays, and it is suspected that declines have occurred there due to overfishing. Overall, due to the level of intense and largely unmanaged fisheries that operate throughout its range, its lack of refuge at depth, its unproductive life history, and noted declines in eagle rays in general, it is suspected that the Shortnose Eagle Ray has undergone a population reduction of >80% over the past three generations (18 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

Psammobatis extenta, Zipper Sandskate

The Zipper Sandskate (Psammobatis extenta) is a small (to 35 cm total length) skate that occurs in the Southwest Atlantic from Rio de Janeiro, Brazil to the San Jorge Gulf, Santa Cruz, Argentina. It inhabits the continental shelf at depths of 13-160 m. It is caught in commercial and artisanal demersal trawl fisheries, which are intense in parts of its range, and is typically discarded dead where caught. This species is still caught commonly in fisheries despite a long history of fishing pressure and it is not suspected to be close to reaching the population reduction thresholds. Therefore, the Zipper Sandskate is assessed as Least Concern.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

Mustelus schmitti, Narrownose Smoothhound

The Narrownose Smoothhound (Mustelus schmitti) is a small (to 109 cm total length) shark that occurs in the Southwest Atlantic from Rio de Janeiro, Brazil to south of Puerto Deseado, Santa Cruz, Argentina. It inhabits the continental shelf and estuaries at depths of 2–195 m. It is captured in intense and largely unregulated commercial and artisanal demersal trawl, gillnet, and beach seine fisheries throughout its geographic range. On the southern Brazilian shelf, catches of adults in research trawl surveys declined by 90% between 1972 and 2002, equivalent to a population reduction of 88% over three generation lengths (28 years). In Uruguay, landings peaked at over 3,200 t in 1999 and have declined steadily since. This fishery was considered over-exploited by 2006. Similar levels of unmanaged exploitation are suspected to be leading to declines in Argentina. This species has a similar geographic and depth distribution to the Critically Endangered Striped Smoothhound (Mustelus fasciatus). Overall, due to the intense and largely unmanaged fishing pressure it is exposed to throughout its range, its lack of refuge at depth, and documented declines, it is suspected that the Narrownose Smoothhound has undergone a population reduction of >80% over the past three generations (28 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