What follows is a short report on the Business Meeting of the Astronomy and World Heritage Working Group held on Thursday August 6, 2009. This was the first formal Business Meeting of the Working Group since its formation following the signing of the Memorandum of Understanding between the IAU and UNESCO on Astronomy and World Heritage in October 2008.

The δ Scuti stars are pulsating variables located in the lower part of the Cepheid instability strip with spectral types from A2 to F0 on the main sequence, and from A3 to F5 at luminosity class III. These variables show short periods (< 0.3day) and luminosity amplitudes ranging from a few thousandths of a magnitude to several tenths. Over the last few years, significant progress has been made in the detection of pulsating modes in the framework of the multisite campaigns, e.g. STACC (Frandsen et al. 1996), DSN (Breger et al. 1998), STEPHI (Michel et al. 2000). For the 1998 STEPHI IX photometry campaign, the δ Scuti star V534 Tau of the Pleiades cluster (see Table 1) was monitored during a three week, three continent run. Preliminary results are reported here.

We study the limitation possibilities of bulk Bi high Tc materials. For this we test these materials with a.c. or d.c. currents above their critical currents. We study particularly the evolution of the voltage with time or with current. The material, the value of the current and the time duration play important parts. For sintered Bi samples the voltage depends only on the current even for values much larger than the critical current. With textured samples the V(I) curves shows an hysteretic behaviour due to a warming up. The textured materials are more interesting than sintered ones in terms of required volume for the current limitation. In both cases the superconductors are in a dissipative state but not in the normal state. This state is nevertheless reached if the dissipated energy inside the sample is sufficient. We have tried to apply a magnetic field on the samples in order to trigger a more effective limitation. The voltage increases but with a limited effect for currents much higher (3–4 times) than the critical zero field current. We think that the dissipative state is due mainly to the grain boundaries which become resistive above the critical current.

Un limiteur de courant supraconducteur pourrait être utilisé en haute tension. La plupart des matériaux à haute température critique existants actuels ont été testés en situation de limitation du courant. Les matériaux massifs sont classés par densité de courant critique croissante qui correspondent à des comportements différents. Le champ critique lors des transitions semble être de l'ordre de 1 kV/m.

Afin de déterminer la capacité à limiter le courant du composé ${\rm Y}_1{\rm Ba}_2{\rm Cu}_3{\rm O}_{7-\delta}$ texturé, des études en courants de transport élevés, en régime pulsé et en régime permanent alternatif, ont été menées. Il en résulte que YBaCuO possède une forte capacité de transport du courant en régime pulsé (9000 A soit 23 000 $\ {\rm A} / {\rm cm}^2$ dans un barreau de 4 cm de long) et en régime permanent alternatif (3000 A soit 7800 $\ {\rm A} / {\rm cm}^2$) et que le retour à l'état normal par dépassement du courant critique est très abrupt.

Des forts courants pulsés d'une durée comprise entre 1,25 et 20 ms ont été appliqués à T = 77 K à des conducteurs Bi:2223 texturés par forgeage à chaud ou frittés. Pour des pulses de courant ${I>I_{\rm c}}$, deux comportements sont observés : quand la température moyenne de l'échantillon est inférieur à ${T_{\rm c}}$, le matériau retourne dans l'état supraconducteur avant la fin du pulse de courant. Au dessus de ${T_{\rm c}}$, l'échantillon transite dans l'état normal après le pulse de courant à cause de l'élévation de température. Ceci induit une puissance instantanée importante appliquée au conducteur de 182 GW/m3. À I = 15Ic, des champs électriques de 400 à 1000 V/m sont obtenus sur des éléments frittés et texturés.

The ZZ Ceti stars form a class of variable white dwarfs: the hydrogen dominated atmosphere ones, which do pulsate in an instability strip in the effective temperature range 13000K-11500K. We know 22 such ZZ Ceti white dwarfs. Their variations are caused by nonradial g-mode pulsations with periods are in the range 100-1000 seconds.

A subsample of the ZZ Ceti stars shows amplitude variations on time scales of the order of one month. These variations could be driven by nonlinear phenomena.