To investigate if magnetic fields are present in Wolf-Rayet stars, we selected a few stars in the Galaxy and one in the Large Magellanic Cloud (LMC). We acquired low-resolution spectropolarimetric observations with the ESO FORS 2 instrument during two different observing runs. During the first run in visitor mode, we observed the LMC Wolf-Rayet star BAT99 7 and the stars WR 6, WR 7, WR 18, and WR 23 in our Galaxy. The second run in service mode was focused on monitoring the star WR 6. Linear polarization was recorded immediately after the observations of circular polarization. During our visitor observing run, the magnetic field for the cyclically variable star WR 6 was measured at a significance level of 3.3σ ( B z = 258 ± 78 G). Among the other targets, the highest value for the longitudinal magnetic field, B z = 327 ± 141 G, was measured in the LMC star BAT99 7. Spectropolarimetric monitoring of the star WR 6 revealed a sinusoidal nature of the B z variations with the known rotation period of 3.77 d, significantly adding to the confidence in the detection. The presence of the rotation-modulated magnetic variability is also indicated in our frequency periodogram. The reported field magnitude suffers from significant systematic uncertainties at the factor 2 level, in addition to the quoted statistical uncertainties, owing to the theoretical approach used to characterize it. Linear polarization measurements showed no line effect in the stars, apart from WR 6. BAT99 7, WR 7, and WR 23 do not show variability of the linear polarization over two nights.
SPO1 DNA contains only 5 cleavage sites for restriction enzymes which recognize and cleave the sequence 5'-G-G-C-C (HaeIII or BsuR). Fragments of SPO1 DNA cloned in E. coli to substitute 5'-hydroxymethyluracil (HMU) by thymine (T) remain resistant to HaeIII indicating that this unexpectedly small number of cleavages by HaeIII is not correlated with the presence of HMU in the normal phage DNA. It was previously shown that SPO1 is neither subject to B. subtilis R restriction (Trautner et al., 1974) nor modification in vivo (Günthert et al., 1975). We now show that SPO1 DNA can however be restricted and modified in vitro.
An infinite staged Ettingshausen cooler of exponential shape has been constructed, using an oriented single crystal of Bi9+lb3. The magnetic field of B =0.75 T was provided by a permanent magnet system. A maximal temperature difference AT=42 K was achieved maintaining the heat sink at T=160 K. Referring to the temperature range and magnetic field strength used, this result represents a large cooling effect for an Ettingshausen cooling device. A simulation program that takes into account the temperature dependence of the transport coefficients was developed. Not only the predicted maximal temperature difference but also the ele.ctrical current necessary to obtain this maximum are in reasonable agreement with experimental results
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