A feasibility study was performed on the use of a recirculation system for the mass culturing of rotifers at industrial level. Rotifer culture systems with a culture volume of 750 1 were operated at three different stocking densities (3000, 5000 and 7000 individuals ml(-1)) in a completely closed recirculation system. At all operating rotifer densities, a reliable production of 2.2 billion rotifers could be obtained on a daily basis during 3 weeks. Excellent water quality was maintained by the use of protein skimmers, the use of ozone and a submerged biofilter. The microbial counts remained stable during the whole culture period (10(6) CFU ml(-1) on marine agar and 10(4) CFU ml(-1) on TCBS after 15 and 23 days, respectively). No difference in HUFA and protein content were obtained between rotifers harvested from the recirculation system or from a conventional batch culture system. Compared to a commercial batch culture system, the use of a recirculation system can contribute to a 43% saving on the capital investment and the annual operation cost. By using this system, capital investment cost is considerably reduced by 46%. Savings are also made on labour cost (65%) and feed cost (21%) during a 1-year production.In general terms, it can be stated that by using a simple recirculation system, a cost-effective technology and a reliable rotifer culture can be obtained. (C) 2003 Elsevier B.V. All rights reserved.

Surveys for bacteriological analysis were carried out in 1990-1991 in two different marine fish hatcheries located in Greece and northern Spain. Samples were taken from 12 different routine productions of Brachionus plicatilis before and during enrichment. Isolates were characterized by whole cell fatty acid methyl ester analysis and by BIOLOG metabolic fingerprinting. Vibrio anguillarum and/or Vibrio alginolyticus were dominant Vibrio species in the rotifer samples taken after enrichment and rinsing, before being delivered to the fish larvae. None of the Vibrio anguillarum strains belonged to the pathogenic serotypes for juvenile and adult fish. (C) 1997 Elsevier Science B.V.

Investigation of a new, high efficiency technique for the preparation of laboratory sources of 68Ga by electrocodeposition of 68GeCu3 from dilute alkaline cyanide baths is reported. Procedures are described which have resulted in stable and aherent plates of millicurie intensity. The specific activity of the material is shown to be a critical factor in producing thin (⩽1 mg/cm2) sources while achieving plating efficiencies in excess of 75%.

In a recent publication1, we presented a new 200 ppm measurement of the vacuum decay rate,λT of orthopositronium (o-Ps) formed in a gas. Our result, λT = 7.0516 ± 0.0013 µs−1, represents a factor of four improvement over previous measurements. Our result is in substantial agreement with experimental results, the most recent of which are2–5: 7.056 ± 0.007 µs−1, 7.045 ± 0.006 µs−1, 7.051 ± 0.005 µs−1, and 7.050 ± 0.013 µs−1. These values are 1–2.5 standard deviations above the present theoretical value6,7 and our new measurement exceeds theory by 10 experimental standard deviations.

We compare the results of precision electron $g$-factor experiments at low energy and at 110 keV. The agreement between these measurements constitutes the most precise laboratory confirmation to date of the predictions of special relativity. Relativistic electromagnetic theory and Thomas precession are verified in this test. We also consider limits on possible effects of acceleration.

We report a new measurement of positron polarization ($\stackrel{\ensuremath{\rightarrow}}{P}$) in $^{68}\mathrm{Ga}$ decay. Using a new polarimeter the asymmetry ($A$) in the decay of positronium in a magnetic field was measured to 5%. When combined with a calculation of the positron depolarization on stopping in MgO powder the overall uncertainty in $P$ is 11%. The most precise prior determination of $P$ was to 12% accuracy. An eventual precision of 1% in $A$ and 0.1% in comparison of asymmetries from different sources is anticipated. In addition to the $^{68}\mathrm{Ga}$ work we point out the possible use of the polarimeter in a number of new measurements including a determination of ${e}^{+}$ polarization in ${\ensuremath{\mu}}^{+}$ and nuclear decay and in a $g\ensuremath{-}2$ experiment.