Microwave emission from spinning dust in circumstellar disks

In the high density environments of circumstellar disks dust grains are expected to grow to large sizes by coagulation. Somewhat unexpectedly, recent near-IR observations of PAH features from disks around Herbig Ae/Be stars demonstrate that substantial amount of dust mass in these disks (up to several tens of per cent of the total carbon content) can be locked up in particles with sizes ranging from several to tens of nanometers. We investigate the possibility of detecting the electric dipole emission produced by these nanoparticles as they spin at thermal rates (tens of GHz) in cold gas. We show that such emission peaks in the microwave range and dominates over the thermal disk emission at \nu 5 % of the total carbon abundance is locked up in nanoparticles. We test the sensitivity of this prediction to various stellar and disk parameters and show that if the potential contamination of the spinning dust component by the free-free and/or synchrotron emission can be removed, then the best chances of detecting this emission would be in disks with small opacity, having SEDs with steep sub-mm slopes (which minimizes thermal disk emission at GHz frequencies). Detection of the spinning dust emission would provide important evidence for the existence, properties, and origin of the population of small dust particles in protoplanetary disks, with possible ramifications for planet formation.Comment: 9 pages, 3 figures, submitted to Ap

Gas low pressure low flow rate metering system Patent

Flowmeters for sensing low fluid flow rate and pressure for application to respiration rate studie

High- and low-pressure pneumotachometers measure respiration rates accurately in adverse environments

Respiration-rate transducers in the form of pneumotachometers measure respiration rates of pilots operating high performance research aircraft. In each low pressure or high pressure oxygen system a sensor is placed in series with the pilots oxygen supply line to detect gas flow accompanying respiration