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The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (~2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.
Since the classical work of Sir Thomas Holland at the beginning of this century on the charnockite series in Peninsular India there have appeared numerous papers describing rocks from all over the world which have been claimed to belong to this series. The rocks from the type area around Madras have now been re-examined, with particular reference to their chemistry and chemical mineralogy, to provide further evidence for their mode of origin.
Following petrographic descriptions, fifteen new analyses of these rocks are presented together with trace element determinations, and these are shown to produce smooth curves on a variation diagram. For several rocks all the constituent minerals have been analysed, and it has thus been possible to discuss the mineralogical location of the various major and trace elements in these rocks. Trace element determinations are presented for the 43 minerals analysed together with those for a further 35 minerals not chemically analysed, and their variation within the mineral species is discussed.
The possible modes of origin of these rocks are considered, and from the evidence obtained they are held to represent a plutonic igneous rock series which has undergone recrystallization in the solid state on being subjected to plutonic metamorphism.
This article describes cracking during microcompression of Si, InAs, MgO, and MgAl2O4 crystals and compares this with previous observations on Si and GaAs micropillars. The most common mode of cracking was through-thickness axial splitting, the crack growing downward from intersecting slip bands in pillars above a critical size. The splitting behavior observed in all of these materials was quantitatively consistent with a previous analysis, despite the differences in properties and slip geometry between the different materials. Cracking above the slip bands also occurred either in the side or in the top surface of some pillars. The driving forces for these modes of cracking are described and compared with observations. However, only through-thickness axial splitting was observed to give complete failure of the pillar; it is, therefore, considered to be the most important in determining the brittle-to-ductile transitions that have been observed.
Recent progress with in-situ observations by electron microscopy is briefly surveyed by referring to developments in instrumentation for reflection and low energy electron imaging as well as for high resolution transmission imaging and spectroscopy. New opportunities have been opened up by environmental microscopy. With increased levels of illumination intensity, the ever present question of beam-induced effects is of mounting concern particularly in studies of non-metallic materials.
Recent applications of scanned probe microscopy are defined often going hand in hand with improved spectroscopy. These methods can provide information about dynamic response extending down towards the femotsecond time scale for resettable, repeatable phenomena and may thus help to fill the gap in the microscopist's coverage of material behavior. Although the use of photon pulses is best developed, ultra-short electron pulses are now available. Various options are therefore to hand in either transmission electron microscopy or scanning transmission electron microscopy operation for combining the spatial resolution of electrons with the spectral selectivity and precision of photons. With purely photon pump-probe operation, good spatial resolution can perhaps be obtained using the tip field-enhancement effect in scanning probe microscopy (SPM) and has also recently been impressively demonstrated in two-photon photo-electron microscopy (PEEM) operation.