Over Eenige Nieuwe Soorten Van Megalops, Dussumieria, Notopterus En Astronesthes

v. ; 27 cm.Publication suspended Mar. 1942-May 1946

Bijdrage Tot De Kennis Der Ichthyologische Fauna Van Borneo. Met Beschrijving Van 16 Nieuwe Soorten Van Zoetwatervisschen.

v. ; 27 cm.Publication suspended Mar. 1942-May 1946

Over Twee Nieuwe Soorten Van Callionymus Van Den Indischen Archipel.

v. ; 27 cm.Publication suspended Mar. 1942-May 1946

Over eenige Nieuwe Soorten Van Blennioiden En Gobioiden Van Den Indischen Archipel.

v. ; 27 cm.Publication suspended Mar. 1942-May 1946

Over Eenige Nieuwe Soorten Van Belone En Hemiramphus Van Java.

v. ; 27 cm.Publication suspended Mar. 1942-May 1946

Oxybelus Brandesii Blkr. Eene Nieuwe Soort Van Ophidini Van Banda Neira

v. ; 27 cm.Publication suspended Mar. 1942-May 1946

Proper Motions of H-alpha filaments in the Supernova Remnant RCW 86

We present a proper motion study of the eastern shock-region of the supernova remnant RCW 86 (MSH 14-63, G315.4-2.3), based on optical observations carried out with VLT/FORS2 in 2007 and 2010. For both the northeastern and southeastern regions, we measure an average proper motion of H-alpha filaments of 0.10 +/- 0.02 arcsec/yr, corresponding to 1200 +/- 200 km/s at 2.5kpc. There is substantial variation in the derived proper motions, indicating shock velocities ranging from just below 700 km/s to above 2200 km/s. The optical proper motion is lower than the previously measured X-ray proper motion of northeastern region. The new measurements are consistent with the previously measured proton temperature of 2.3 +/- 0.3 keV, assuming no cosmic-ray acceleration. However, within the uncertainties, moderately efficient (< 27 per cent) shock acceleration is still possible. The combination of optical proper motion and proton temperature rule out the possibility that RCW 86 has a distance less than 1.5kpc. The similarity of the proper motions in the northeast and southeast is peculiar, given the different densities and X-ray emission properties of the regions. The northeastern region has lower densities and the X-ray emission is synchrotron dominated, suggesting that the shock velocities should be higher than in the southeastern, thermal X-ray dominated, region. A possible solution is that the H-alpha emitting filaments are biased toward denser regions, with lower shock velocities. Alternatively, in the northeast the shock velocity may have decreased rapidly during the past 200yr, and the X-ray synchrotron emission is an afterglow from a period when the shock velocity was higher.Comment: Accepted for publication in MNRA

High- and low energy nonthermal X-ray emission from the cluster of galaxies A 2199

We report the detection of both soft and hard excess X-ray emission in the cluster of galaxies A 2199, based upon spatially resolved spectroscopy with data from the BeppoSAX, EUVE and ROSAT missions. The excess emission is visible at radii larger than 300 kpc and increases in strength relative to the isothermal component. The total 0.1-100 keV luminosity of this component is 15 % of the cluster luminosity, but it dominates the cluster luminosity at high and low energies. We argue that the most plausible interpretation of the excess emission is an inverse Compton interaction between the cosmic microwave background and relativistic electrons in the cluster. The observed spatial distribution of the non-thermal component implies that there is a large halo of cosmic ray electrons between 0.5-1.5 Mpc surrounding the cluster core. The prominent existence of this component has cosmological implications, as it is significantly changing our picture of a clusters's particle acceleration history, dynamics between the thermal and relativistic media, and total mass budgets.Comment: Accepted for publication in Astrophysical Journal, Letter

Prospects for Photo Electron Spectroscopy in a Scanning Transmission Electron Microscope

High spatial resolution microanalysis in scanning transmission electron microscopes is most easily performed when the specimen is inside a magnetic immersion objective lens. Recently a technique has been developed to perform spectroscopy of electrons that originate in this magnetic field. A very special form of photo electron spectroscopy is then possible for thin specimens in the microscope. An energy loss ΔE of a primary electron has the same physical effect as the absorption of a photon of energy ΔE. A coincidence measurement between energy loss electrons and the emitted electrons is expected to give a so called coincidence electron spectrum, or (e,2e) spectrum, of a very small area, which gives the same physical information as photo electron spectroscopy. Normal photo electron spectroscopy of limited spatial resolution, but with high collection efficiency, should also be possible in a scanning transmission electron microscope if the specimen is illuminated with a photon beam. Experiments to test the expectations are in progress