ABSTRACT
The Philae lander provides a unique opportunity to investigate the internal structure of a comet nucleus, providing information about its formation and evolution in the early solar system. We present Comet Nucleus Sounding Experiment by Radiowave Transmission (CONSERT) measurements of the interior of Comet 67P/Churyumov-Gerasimenko. From the propagation time and form of the signals, the upper part of the "head" of 67P is fairly homogeneous on a spatial scale of tens of meters. CONSERT also reduced the size of the uncertainty of Philae's final landing site down to approximately 21 by 34 square meters. The average permittivity is about 1.27, suggesting that this region has a volumetric dust/ice ratio of 0.4 to 2.6 and a porosity of 75 to 85%. The dust component may be comparable to that of carbonaceous chondrites.
ABSTRACT
BACKGROUND: Plasma viscosity (PV) is used in the investigation of hyperviscosity syndrome. We have evaluated the performance of a new bench-top free oscillation rheometer, ReoRox from Medirox, and established a new reference range. METHODS: Performance of the free oscillation rheometry (FOR) method was evaluated examining within-run and between-run imprecision, duration of measurement and operator simplicity. Furthermore, influence of storage on the PV measurements was assessed and a reference range based on plasma from 585 healthy men and women was established. RESULTS: Imprecision of the free oscillation rheometer was comparable to other viscometers and performance of the instrument was satisfying. The non-parametrical reference range established was 1.22-1.44 mPa s at 37â (2.5th and 97.5th percentiles). CONCLUSIONS: We have established a FOR PV reference range to support clinical decision-making. Furthermore, we found high pre-analytical stability of the samples and an analytical imprecision comparable to other PV methods.
Subject(s)
Blood Viscosity , Leukemia/blood , Multiple Myeloma/blood , Rheology , Waldenstrom Macroglobulinemia/blood , Adolescent , Adult , Aged , Female , Humans , Male , Middle Aged , Rheology/instrumentation , Rheology/methods , SyndromeABSTRACT
The design and operation of a new generation of digital imaging riometer systems developed by Lancaster University are presented. In the heart of the digital imaging riometer is a field-programmable gate array (FPGA), which is used for the digital signal processing and digital beam forming, completely replacing the analog Butler matrices which have been used in previous designs. The reconfigurable nature of the FPGA has been exploited to produce tools for remote system testing and diagnosis which have proven extremely useful for operation in remote locations such as the Arctic and Antarctic. Different FPGA programs enable different instrument configurations, including a 4 × 4 antenna filled array (producing 4 × 4 beams), an 8 × 8 antenna filled array (producing 7 × 7 beams), and a Mills cross system utilizing 63 antennas producing 556 usable beams. The concept of using a Mills cross antenna array for riometry has been successfully demonstrated for the first time. The digital beam forming has been validated by comparing the received signal power from cosmic radio sources with results predicted from the theoretical beam radiation pattern. The performances of four digital imaging riometer systems are compared against each other and a traditional imaging riometer utilizing analog Butler matrices. The comparison shows that digital imaging riometer systems, with independent receivers for each antenna, can obtain much better measurement precision for filled arrays or much higher spatial resolution for the Mills cross configuration when compared to existing imaging riometer systems.
ABSTRACT
The ice-rich south polar layered deposits of Mars were probed with the Mars Advanced Radar for Subsurface and Ionospheric Sounding on the Mars Express orbiter. The radar signals penetrate deep into the deposits (more than 3.7 kilometers). For most of the area, a reflection is detected at a time delay that is consistent with an interface between the deposits and the substrate. The reflected power from this interface indicates minimal attenuation of the signal, suggesting a composition of nearly pure water ice. Maps were generated of the topography of the basal interface and the thickness of the layered deposits. A set of buried depressions is seen within 300 kilometers of the pole. The thickness map shows an asymmetric distribution of the deposits and regions of anomalous thickness. The total volume is estimated to be 1.6 x 10(6) cubic kilometers, which is equivalent to a global water layer approximately 11 meters thick.
Subject(s)
Ice , Mars , Water , Extraterrestrial Environment , Radar , SpacecraftABSTRACT
The martian subsurface has been probed to kilometer depths by the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument aboard the Mars Express orbiter. Signals penetrate the polar layered deposits, probably imaging the base of the deposits. Data from the northern lowlands of Chryse Planitia have revealed a shallowly buried quasi-circular structure about 250 kilometers in diameter that is interpreted to be an impact basin. In addition, a planar reflector associated with the basin structure may indicate the presence of a low-loss deposit that is more than 1 kilometer thick.
