7 research outputs found
The comparative biology of New Zealand oystercatchers
Oystercatchers comprise a distinctive group of mollusc-eating shorebirds. They form an extremely uniform monogeneric family which has not undergone any major adaptive radiations into a diversity of ecological niches, but rather has dispersed from original centres of distribution to occupy identical niches in new geographical localities. The uniformity of structure and habit displayed within the group has been attributed by Larson (1957) to a high ecobiotic specialisation with centripetal selection involved. Throughout their range, oystercatchers exploit identical ecological niches which require specialised habits for successful utilisation. The specialised feeding habits of oystercatchers are well documented (Murphy, 1925; Dewar, 1940; Larson, 1957; Tinbergen and Norton-Griffiths, 1964; Dare, 1966), and a natural consequence of this specialisation is that it is restrictive to adaptive radiation
229 Highly differentiated carcinoma of the endometrium after menopausal estrogen — what happens if you don't treat it directly?
International comparison of current transformer calibration systems up to 10 kA at 50 Hz frequency
Current transformers (CTs) are precision devices
that scale high currents down to values that can be easily handled
by measurement equipment. To support CT applications in
revenue metering, a comparison on AC current transformer calibration
systems was performed among 15 European national
metrology institutes using a precision CT as the travelling device.
The first comparison results for the transformation ratios (4, 5, 6,
8, 10) kA/5 A of the travelling CT at nominal burden of 5 VA and
15 VA indicate good agreement between the participating laboratories.
The main differences are found for phase displacement, at
least partly caused by the instability of the traveling standard