Isotope Shift in the Dielectronic Recombination of Three-Electron ANd57+

Isotope shifts in dielectronic recombination spectra were studied for Li-like ^ANd⁵⁷⁺ ions with A=142 and A=150. From the displacement of resonance positions energy shifts dE^142?150(2s-2p_1/2)=40.2(3)(6)??meV [(stat)(sys)] and dE^142?150(2s-2p_3/2)=42.3(12)(20)??meV of 2s-2p_jtransitions were deduced. An evaluation of these values within a full QED treatment yields a change in the mean-square charge radius of ^142?150d?r²?=-1.36(1)(3)??fm². The approach is conceptually new and combines the advantage of a simple atomic structure with high sensitivity to nuclear size.

Uptake of carbon, nitrogen and phosphorus by phytoplankton along the 20 degrees W meridian in the NE Atlantic between 57.5 degrees N and 37 degrees N

Phytoplankton biomass and rate of production were measured along a transect from 57.54 degreesN to 37.01 degreesN in the northeast Atlantic during July 1996 and at a series of stations over a 7-day period at 37 degreesN 20 degreesW. Surface nutrient concentrations ranged from 4 mu mol l(-1) NO3-, and 0.35 mu mol l(-1) PO43- at 57.54 degreesN to <10 nmol l(-1) NO3- and similar to 10 nmol l(-1) PO43- at 37.01 degreesN. The greatest phytoplankton biomass and production were measured in the vicinity of a frontal system at 50 degreesN, and there was a general decline in total phytoplankton biomass and production to the south of the transect. Production was measured in three size fractions. At the station with the highest chlorophyll concentrations (50.34 degreesN), phytoplankton cells larger than 5 mum dominated the assemblage, accounting for 72% of the chlorophyll concentration (22.9 mg m(-2)) and 51% of primary production (54.1 mmol Cm-2 d(-1)), but picophytoplankton production was also high (43%). At 57 degreesN, carbon fixation by the > 5 mum fraction accounted for 75% of the daily production of 60.75 mmol Cm-2 d(-1). At 37 degreesN, picophytoplankton was the dominant group, accounting for similar to 58% (10 mg m(-2)) of chlorophyll and similar to 64% (46 mmol Cm-2 d(-1)), of primary production. Nitrate, ammonium and phosphate uptake rates also were determined. Although high nitrate uptake rates were measured in the surface water at similar to 50 degreesN, the greatest uptake rates of both depth-integrated nitrate and ammonium were at the south of the transect. At 37 degreesN, a deep euphotic zone was present and light penetrated through the nitracline; total nitrate uptake was enhanced because of assimilation at the base of the euphotic zone. As a consequence, high values of depth-integrated f-ratio were measured in the oligotrophic waters at the south of the transect. Phosphate was predominantly incorporated into the picoplankton fraction, which included heterotrophic and autotrophic components, at all stations and a significant proportion of phosphate uptake occurred in the dark. The C:N:P assimilation ratios were variable throughout the region; phosphate uptake was generally greater than would be expected if nutrient assimilation were in proportion to the Redfield ratio. (C) 2001 Elsevier Science Ltd. All rights reserved.

V-band 57-65 GHz receiver

A simple V-band radio IQ receiver architecture based around a six-port monolithic microwave integrated circuit (MMIC) is presented. The receiver assembly is designed to cover the 57-65 GHz broadband wireless communication system frequency allocation. The receiver that has an integral 10 dB microstrip antenna consumes 120 mW of dc power and occupies an area of 23 mm x 16 mm. The receiver can be used in heterodyne or in homodyne mode and has the capacity to demodulate quadrature amplitude modulation (QAM), binary phase shift keying (BPSK)/quadrature phase shift keying (QPSK)/offset quadrature phase shift keying (OQPSK). At 60 GHz the receiver can operate over 10 m range for transmitter effective isotropic radiated power (EIRP) of 20 dBm.