Efectos del establecimiento de las áreas marinas protegidas en la pesquería argentina de la merluza negra (Dissostichus eleginoides)

At the beginning of the 1990s, the Argentine toothfish fishery gained prominence as a consequence of the rapid expansion of trawler and longliner fleets targeting this species. This fishing area covers the slope and shelf from 60° S to 37° S in the Argentine Exclusive Economic Zone. The main fishing ground is located in the southern area, bordering Namuncurá-Burdwood Bank II (NBBII) and Yaganes (Y) marine protected areas (MPA) established in 2018. In order to determine the impact generated by MPAs on effort distribution, 308 fishing trips carried out between 2010 and 2020, which reported 82% of the total fishing effort of Argentine toothfish declared in that period, were spatially analyzed. The Y-MPA sector categorized as National Marine Reserve and located to the south of Tierra del Fuego reported more than half (58%) of the toothfish catch recorded throughout that period, while the NBBII-MPA located to the east of Tierra del Fuego and south of De los Estados Island represented 17%. The NBBII-MPA sector established as a Strict National Marine Reserve and located to the south of the Burdwood Bank represented 25%. With the establishment of the MPAs, 7.11% of the international requirement has been met. At the moment, effects resulting from the creation of MPAs can only be speculated upon qualitatively, but should be quantified in the near future.A principios de la década de 1990, la pesquería de merluza negra argentina ganó protagonismo gracias a la rápida expansión de las flotas de arrastre y palangre que se dirigían a esta especie. Esta zona de pesca cubre el talud y plataforma desde los 60° S hasta los 37° S en la Zona Económica Exclusiva argentina. El principal caladero se encuentra en la zona sur, colindando con las áreas marinas protegidas (AMP) Banco Namuncurá-Burdwood II (NBBII) y Yaganes (Y), establecidas en 2018. Para determinar el impacto que generan las AMP en la distribución del esfuerzo, se analizaron espacialmente 308 viajes de pesca realizados entre 2010 y 2020, que reportaron 82% del total del esfuerzo pesquero declarado de merluza negra argentina en ese período. El sector Y-AMP categorizado como Reserva Nacional Marina y ubicado al sur de Tierra del Fuego, reportó más de la mitad (58%) de la captura de merluza negra registrada durante ese período, mientras que el NBBII-AMP ubicado al este de Tierra del Fuego y sur de la Isla de los Estados representaron 17%. El sector NBBII-AMP establecido como Reserva Nacional Marina Estricta y ubicado al sur del Banco Burdwood representó el 25%. Con el establecimiento de las AMP se ha cumplido 7,11% del requerimiento internacional. En la actualidad, los efectos resultantes de la creación de AMP solo pueden especularse cualitativamente, pero deberían cuantificarse en un futuro próximo.

Huddle test measurement of a near Johnson noise limited geophone

In this paper, the sensor noise of two geophone configurations (L-22D and L-4C geophones from Sercel with custom built amplifiers) was measured by performing two huddle tests. It is shown that the accuracy of the results can be significantly improved by performing the huddle test in a seismically quiet environment and by using a large number of reference sensors to remove the seismic foreground signal from the data. Using these two techniques, the measured sensor noise of the two geophone configurations matched the calculated predictions remarkably well in the bandwidth of interest (0.01 Hz–100 Hz). Low noise operational amplifiers OPA188 were utilized to amplify the L-4C geophone to give a sensor that was characterized to be near Johnson noise limited in the bandwidth of interest with a noise value of 10−11 m/Hz⎯⎯⎯⎯⎯√10−11 m/Hz at 1 Hz

Passive-performance, analysis, and upgrades of a 1-ton seismic attenuation system

The 10m Prototype facility at the Albert-Einstein-Institute (AEI) in Hanover, Germany, employs three large seismic attenuation systems to reduce mechanical motion. The AEI Seismic-Attenuation-System (AEI-SAS) uses mechanical anti-springs in order to achieve resonance frequencies below 0.5Hz. This system provides passive isolation from ground motion by a factor of about 400 in the horizontal direction at 4Hz and in the vertical direction at 9Hz. The presented isolation performance is measured under vacuum conditions using a combination of commercial and custom-made inertial sensors. Detailed analysis of this performance led to the design and implementation of tuned dampers to mitigate the effect of the unavoidable higher order modes of the system. These dampers reduce RMS motion substantially in the frequency range between 10 and 100Hz in 6 degrees of freedom. The results presented here demonstrate that the AEI-SAS provides substantial passive isolation at all the fundamental mirror-suspension resonances

Band structure and optical properties of germanium sheet polymers

The band structure of H-terminated Ge sheet polymers is calculated using density-functional theory in the local density approximation and compared to the optical properties of epitaxial polygermyne layers as determined from reflection, photoluminescence, and photoluminescence excitation measurements. A direct band gap of 1.7 eV is predicted and a near resonant excitation of the photoluminescence is observed experimentally close to this energy

Local active isolation of the AEI-SAS for the AEI 10 m prototype facility

Abstract: High precision measurements in various applications rely on active seismic isolation to decouple the experiment from seismic motion; therefore, closed feed-back control techniques such as sensor blending and sensor correction are commonly implemented. This paper reviews the active isolation techniques of the Albert Einstein Institute seismic attenuation system (AEI-SAS). Two approaches to improve the well known techniques are presented. First, the influence of the sensor basis for the signal-to-noise ratio in the chosen coordinate system is calculated and second, a procedural optimization of blending filters to minimize the optical table velocity is performed. Active isolation techniques are adapted to the mechanical properties and the available sensors and actuators of the AEI-SAS. The performance of the final isolation is presented and limitations to the isolation are analyzed in comparison to a noise model. The optical table motion reaches approximately 8 × 1 0 − 10 m / H z at 1 Hz, reducing the ground motion by a factor of approximately 100

Thickness uniformity measurements and damage threshold tests of large-area GaAs/AlGaAs crystalline coatings for precision interferometry

Precision interferometry is the leading method for extremely sensitive measurements in gravitational wave astronomy. Thermal noise of dielectric coatings poses a limitation to the sensitivity of these interferometers. To decrease coating thermal noise, new crystalline GaAs/AlGaAs multilayer mirrors have been developed. To date, the surface figure and thickness uniformity of these alternative low-loss coatings has not been investigated. Surface figure errors, for example, cause small angle scattering and thereby limit the sensitivity of an interferometer. Here we measure the surface figure of highly reflective, substrate-transferred, crystalline GaAs/AlGaAs coatings with a custom scanning reflectance system. We exploit the fact that the reflectivity varies with the thickness of the coating. To increase penetration into the coating, we used a 1550 nm laser on a highly reflective coating designed for a center wavelength of 1064 nm. The RMS thickness variation of a two inch optic was measured to be 0.41 ± 0.05 nm. This result is within 10% of the thickness uniformity, of 0.37 nm RMS, achieved with ion-beam sputtered coatings for the aLIGO detector. We additionally measured a lower limit of the laser induced damage threshold of 64 MW/cm2 for GaAs/AlGaAs coatings at a wavelength of 1064 nm. © 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen