Single layer YBaCuO-Gradiometer galvanically coupled to DC-SQUIDS were prepared on bicrystal substrates. The devices were operated at 77 K without any shielding. The best performance obtained was a field gradient resolution of 0,s pTlemdHz for a device with a baseline of 7 mm and a pickup-area of 2 cm2.

For many SQUID applications such as biomagnetism or non-destructive evaluation it is convenient or even necessary to work without the restrictions of a magnetically shielded room. This contribution deals with two sensors appropriate for this purpose.In the first concept we present a flip chip arrangement of a single-layer flux transformer and a single-layer SQUID, taking advantage of a simple technology. The SQUID was prepared on a 15 × 15 mm 2 SrTiO 3 24 • bicrystal and located in the common line of two-parallel-loop arrangements. The flipped antenna was designed as a two-parallel-loop gradiometer with 26 mm baseline on a 10 × 40 mm 2 LaAlO 3 single-crystal substrate. A field gradient sensitivity of 1 nT cm −1 0 was obtained. We could demonstrate a field gradient resolution of 20 fT cm −1 Hz 1/2 at 1 kHz in an unshielded environment.In the second concept we integrated both the flux antenna and the SQUID on a SrTiO 3 bicrystal. The tighter coupling scheme results in smaller devices for similar field gradient sensitivities. The integrated SQUID is designed as a 3 × 8 mm 2 device on a 10 × 10 mm 2 bicrystal substrate. The remaining space is used for test structures and SQUIDs without antennae, in order to control the technology as well as the SQUID design. Parallel processed dummy substrates were used to monitor the quality of film growth by x-ray analysis. The quality of our SQUID design will be discussed on the basis of the measured field gradient sensitivity and noise. The reliability of the devices is demonstrated by an NDE type measurement.

The gill structure of Arctic char from a low ionic (1-2 µmol Cl -) high mountain lake (2344 m above sea level) showed distinct seasonal changes. From spring to early winter chloride cells (responsible for ion uptake) were numerous, and during summer gill epithelia were highly hypertrophic resulting in a thick blood-to-water barrier. This gill morphology is typical for fish from soft water habitats and reflects osmoregulatory responses. In mid-winter, however, both chloride cell numbers and epithelia thickness were reduced and comparable to the situation in freshwater with high ionic contents. This pattern correlated with seasonal fluctuations of water chemistry. The most significant correlation was found with CO 2 which accumulated under the ice cover, reaching a tenfold oversatturation. The concentration of Ca, Na, and Cl varied only by a factor of two or less and the correlation with the epithelial thickness was much weaker.

No abstract