ABSTRACT
The Phoenix mission investigated patterned ground and weather in the northern arctic region of Mars for 5 months starting 25 May 2008 (solar longitude between 76.5 degrees and 148 degrees ). A shallow ice table was uncovered by the robotic arm in the center and edge of a nearby polygon at depths of 5 to 18 centimeters. In late summer, snowfall and frost blanketed the surface at night; H(2)O ice and vapor constantly interacted with the soil. The soil was alkaline (pH = 7.7) and contained CaCO(3), aqueous minerals, and salts up to several weight percent in the indurated surface soil. Their formation likely required the presence of water.
Subject(s)
Ice , Mars , Water , Calcium Carbonate , Extraterrestrial Environment , Hydrogen-Ion Concentration , Robotics , Spacecraft , TemperatureABSTRACT
The light detection and ranging instrument on the Phoenix mission observed water-ice clouds in the atmosphere of Mars that were similar to cirrus clouds on Earth. Fall streaks in the cloud structure traced the precipitation of ice crystals toward the ground. Measurements of atmospheric dust indicated that the planetary boundary layer (PBL) on Mars was well mixed, up to heights of around 4 kilometers, by the summer daytime turbulence and convection. The water-ice clouds were detected at the top of the PBL and near the ground each night in late summer after the air temperature started decreasing. The interpretation is that water vapor mixed upward by daytime turbulence and convection forms ice crystal clouds at night that precipitate back toward the surface.
Subject(s)
Ice , Mars , Steam , Atmosphere , Extraterrestrial Environment , Spacecraft , Temperature , Time FactorsABSTRACT
A useful analytic model describing the response of a photon-counting (PC) system has been developed. The model describes the nonlinear count loss and apparent count gain arising from the overlap of photomultiplier tube (PMT) pulses, taking into account the distribution in amplitude of the PMT output pulses and the effect of the pulse-height discrimination threshold. Comparisons between the model and Monte Carlo simulations show excellent agreement. The model has been applied to a PC lidar system with favorable results. Application of the model has permitted us to extend the linear operating range of the PC system and to quantify accurately the response of the system in its nonlinear operating regime, thus increasing the useful dynamic range of the system by 1 order of magnitude.
ABSTRACT
One hundred and fifty-three patients with renal stones referred to one teaching hospital have received extracorporeal shock wave lithotripsy (ESWL) treatment as a result of a monthly sessional arrangement organised with a neighbouring lithotripter unit. The results of treatment, assessed 3 months after lithotripsy, showed results comparable with those from any lithotripter centre. Sessional access for lithotripsy may provide a satisfactory way of increasing the number of patients who are treated with lithotripsy by reducing the demand for beds at the hospitals where a lithotripter is sited.
