Abstract: Tracer experiments with ¹³C-labelled diatoms Thalassiosira rotula (Bacillariophycea, 98% ¹³C-labelled) were conducted at the Porcupine Abyssal Plain (PAP) in the NE Atlantic (BENGAL Station; 48<b0>50'N, 16<b0>30'W, 4850 m depth) during May/June 2000. In situ enrichment experiments were carried out using deep-sea benthic chamber landers: within the chambers a spring bloom was simulated and the fate of this food-pulse within the abyssal macrobenthic community was followed. In focus was the role of different macrofauna taxa and their vertical distribution within the sediment column in consuming and reworking the freshly deposited material. T. rotula is one of the most abundant pelagic diatoms in the NE Atlantic and therefore 0.2 g of freeze dried T. rotula, equivalent to 1 g algal C m^-2 yr^-1, was injected into each incubation chamber. Three different incubation times of 2.5, 8 and 23 d were chosen in order to follow the uptake of ¹³C-labelled phytodetritus by macrofauna. After only 2.5 d, 77% of all macrofauna organisms showed tracer uptake. After 23 d the highest degree of enrichment was measured and 95% of the individuals had taken up ¹³C from the introduced algal material. In addition to that a downward transport of organic matter was observed, even though the mixing was not very intense. The initial processing of carbon was dominated by polychaetes that made up a percentage of 52% of total macrofauna. In general macrofauna organisms that lived close to the sediment surface had higher access to the simulated food-pulse, confirming the hypothesis that individuals close to the sediment surface have the strongest impact on the decomposition of phytodetritus. In our study we observed only modest vertical entrainment of ¹³C tracers into the sediment. With regard to contradictory results from former ¹³C-enrichment experiments in bathyal regions, compared to results from our study site in the abyssal plain, we thus propose pronounced differences in feeding strategies between macrofauna communities from continental margins and abyssal plains.

Abstract: In F. Stellari and P. Song (2004) the authors have shown a comparison among different detectors used for diagnosing integrated circuits (ICs) by means of the PICA method. In their experiments they used two versions of the SSPD detector (p-SSPD is a prototype version, while c-SSPD is the first commercially available generation of the detector as presented in W. K. Lo et al. (2002), as well as the imaging detector (S-25 photo-multiplier tube (PMT) as discussed in W. G. McMullan (1987)) used in the conventional PICA technique. A microprocessor chip fabricated in a 0.13 μm 1.2 V technology is used to show that c-SSPD provides a significant reduction in acquisition time for the collection of optical waveforms from chips running at very low. In this paper, the authors summarize the main results.

Abstract: Heterodyne experiments have been performed in the middle infrared region of the electromagnetic spectrum using the CO2laser as a radiation source. Theoretically optimum operation has been achieved at kHz heterodyne frequencies using photoconductive Ge:Cu detectors operated at 4°K, and at kHz and MHz frequencies using Pb1-xSnxSe photovoltaic detectors at 77°K. In accordance with the theory, the minimum detectable power observed is a factor of 2/η greater than the theoretically perfect quantum counter, hvΔf. The coefficient 2/η varies from 5 to 25 for the detectors investigated in this study. A comparison is made between photoconductive and photodiode detectors for heterodyne use in the infrared, and it is concluded that both are useful. Heterodyne detection at 10.6 µm is expected to be useful for communications applications, infrared radar, and heterodyne spectroscopy. It has particular significance because of the high radiation power available from the CO2laser, and because of the 8 to 14 µm atmospheric window.