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LOFT (Large Observatory For X-ray Timing) is one of the four candidate missions currently
under assessment study for the M3 mission in ESAs Cosmic Vision program to be launched in
2024. LOFT will carry two instruments with prime sensitivity in the 2–30 keV range: a 10
m2 class large area detector (LAD) with a <1° collimated field of view
and a wide field monitor (WFM) instrument. The WFM is based on the coded mask principle,
and 5 camera units will provide coverage of more than 1/3 of the sky. The prime goal of
the WFM is to detect transient sources to be observed by the LAD. With its wide field of
view and good energy resolution of <500 eV, the WFM will be an excellent instrument
for detecting and studying GRBs and X-ray flashes. The WFM will be able to detect
~150 gamma ray bursts per year, and a burst alert system will enable the
distribution of ~100 GRB positions per year with a ~1 arcmin location
accuracy within 30 s of the burst.
The World Heritage Site of Wanar in Senegal features 21 stone circles, remarkable not least because they were erected in the twelfth and thirteenth century AD, when Islam ruled the Indian Ocean and Europe was in its Middle Ages. The state of preservation has benefited the exemplary investigation currently carried out by a French-Senegalese team, which we are pleased to report here. The site began as a burial ground to which monumental stones were added, perhaps echoing the form of original funerary houses. Found in a neighbouring field were scoops left from the cutting out of the cylindrical monoliths from surface rock. While the origins of Wanar lie in a period of state formation, the monuments are shown to have had a long ritual use. The investigation not only provides a new context for one of the most important sites in West Africa but the precise determination of the sequence and techniques used at Wanar offers key pointers for the understanding of megalithic structures everywhere.
The effect of steric hindrance on reorientational molecular dynamics has been studied both theoretically and experimentally in well-defined geometries. We show that, even for a nonwetting fluid, confinement quenches reorientation. This is unambiguously probed by the nuclear relaxation of 33S and 13C in a set of calibrated porous glasses saturated with CS2.
2H NMR relaxation times of selectively deuterated polar molecules confined to a set of calibrated nanoporous silica glasses are reported. These experiments, combined with the consideration of different time scales in the theory of surface relaxation, show how confinement effects can provide detailed information on the rotational dynamics of temporarily adsorbed liquid layers in presence of biphasic fast exchange.
We report on the performance of the digital baseband feedback circuit developed to readout and process signals from arrays of transition edge sensors for SPICA-SAFARI in frequency domain multiplexing (FDM). The standard procedure to readout the SQUID current amplifiers is to use a feedback loop (flux-locked loop: FLL). However the achievable FFL bandwidth is limited by the cable transport delay td, which makes standard feedback inconvenient. A much better approach is to use baseband feedback. We have developed a model of the electronic readout chain for SPICA-SAFARI instrument by using an Anlog-digital co-simulation based on Simulink-System Generator environment.
Torsional Couette flow between a rotating disk and a stationary wall is studied experimentally. The surface of the disk is either rigid or covered with a compliant coating. The influence of wall compliance on characteristic flow instabilities and on the laminar–turbulent flow transition is investigated. Data obtained from analysing flow visualizations are discussed. It is found that wall compliance favours two of the three characteristic wave patterns associated with the transition process and broadens the parameter regime in which these patterns are observed. The results for the effects of wall compliance on the third pattern are inconclusive. However, the experiments indicate that the third pattern is not a primary constituent of the laminar–turbulent transition process of torsional Couette flow.
In this paper, a claw pole permanent magnet machine is studied using a 3D scalar potential formulation. First, the
discretisation of Maxwell's equations using Whitney's elements is presented.
Especially, the method to take the winding current distribution into account by means of source fields is detailed.
Then, a numerical model of the studied machine is presented. Simulation results (inductance, EMF, torque) are discussed
by comparison with experimental ones.
An experiment has been performed with the LULI
Multi-TeraWatt Laser. The acceleration of electrons injected
in a plasma wave generated by the laser wakefield mechanism
has been observed with a maximum energy gain of 1.5 MeV.
It has been shown that the electrons deflected during the
interaction, could scatter on the walls of the experimental
chamber, and fake a high-energy signal. A special effort
has been given in the electron detection to separate the
accelerated electrons signal from the background noise.The
experimental results agree with theoretical predictions
and numerical simulations when 3D effects on the electron
beam are taken into account.
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