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Abstract

The paper presents a list of over 100 amphipod taxa hitherto recorded in the Admiralty Bay, South Shetlands (Tab. 1). In Tab. 2 the distributional patterns of Amphipoda in upper and middle sublittoral (depth 5-150 m) of the Admiralty Bay are given. Notes on the taxonomy of some taxa are presented.

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Authors and Affiliations

Krzysztof Jażdżewski
Claude de Broyer
Włodzimierz Teodorczyk
Alicja Konopacka
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Abstract

We propose a numerical surface integral method to study complex acoustic systems, for interior and exterior problems. The method is based on a parametric representation in terms of the arc’s lengths in curvilinear orthogonal coordinates. With this method, any geometry that involves quadric or higher order surfaces, irregular objects or even randomly rough surfaces can be considered. In order to validate the method, the modes in cubic, spherical and cylindrical cavities are calculated and compared to analytical results, which produced very good agreement. In addition, as examples, we calculated the scattering in the far field and the near field by an acoustic sphere and a cylindrical structure with a rough cross-section.

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Authors and Affiliations

Juan Antonio Guel-Tapia
Francisco Villa-Villa
Alberto Mendoza-Suarez
Hector Pérez-Aguilar
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Abstract

The paper presents the method and results of low-frequency noise measurements of modern mid-wavelength infrared photodetectors. A type-II InAs/GaSb superlattice based detector with nBn barrier architecture is compared with a high operating temperature (HOT) heterojunction HgCdTe detector. All experiments were made in the range 1 Hz - 10 kHz at various temperatures by using a transimpedance detection system, which is examined in detail. The power spectral density of the nBn’s dark current noise includes Lorentzians with different time constants while the HgCdTe photodiode has more uniform 1/f - shaped spectra. For small bias, the low-frequency noise power spectra of both devices were found to scale linearly with bias voltage squared and were connected with the fluctuations of the leakage resistance. Leakage resistance noise defines the lower noise limit of a photodetector. Other dark current components give raise to the increase of low-frequency noise above this limit. For the same voltage biasing devices, the absolute noise power densities at 1 Hz in nBn are 1 to 2 orders of magnitude lower than in a MCT HgCdTe detector. In spite of this, low-frequency performance of the HgCdTe detector at ~ 230K is still better than that of InAs/GaSb superlattice nBn detector.

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Authors and Affiliations

Łukasz Ciura
Andrzej Kolek
Waldemar Gawron
Andrzej Kowalewski
Dariusz Stanaszek

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