Hybrid image/ray-shooting UHF radio propagation predictor for populated indoor environments

A novel model for indoor wireless communication, based on a dual image and ray-shooting approach, is presented. The model, capable of improved site-specific indoor propagation prediction, considers multiple human bodies moving within the environment. In a modern office at 2.45GHz, the combined effect of pedestrian traffic and a moving receiver causes rapid temporal fading of up to 30dB.

RF performance of a 418-MHz radio telemeter packaged for human vaginal placement

The electrical and communication performance of a 0.8-mu W UHF temperature telemeter designed for human vaginal placement is discussed; a solenoidal loop antenna was used, occupying a volume of 0.1 cm(3). In situ, measured power absorption was between 19-25 dB, resulting in an effective operating range of 10 m. Capacitive loading lowered the antenna's resonant frequency by 1.4% and there was a significant polarization change in the radiated output.

Vaginal temperature sensing using UHF radio telemetry

User induced errors are common when women repetitively employ conventional probe type thermometers to chart their basal body temperatures in an effort to indicate ovulation. An alternative technique employing a two-part telemetric thermometer is proposed, with low-power, SAWR-controlled UHF radio as the transmission medium. Worn overnight in the vagina, the 1 mu W erp telemetry transmitter sends pulse modulated data continuously to a microcontroller in a nearby receiver; a real time clock enables programmable sampling and storage of the subject's temperature to 0.1 degrees C resolution. Initial clinical results indicate an enhanced performance compared to oral and axillary temperature trends taken by a mercury-in-glass thermometer. Polar plots of both the isolated and body-worn telemetry transmitte are presented; body indced attenuations of up to 30 dB were measured.

DENSE GAS IN NEARBY GALAXIES .9. A SURVEY FOR HNC

Ten detections and five tentative detections of hydrogen isocyanide (HNC) J=1-0 emission are reported from a survey including sixteen galaxies. Full maps are presented for the nuclear regions of NGC 253 and IC 342, partial maps for Maffei 2, M 82, and M 83. Toward IC 342, the HNC and HCO+ distributions differ from those observed in 12CO, 13CO, HCN, CS, and NH3. This is likely a consequence of the density structure. Relative HNC abundances are with 10(-10)-10(-9) much smaller than those measured in nearby dark clouds and appear to be slightly smaller than those in regions of massive star formation of the Galactic disk. This is consistent with the presence of dense warm gas or a frequent occurrence of shocks in the nuclear regions of the galaxies observed. As in prominent Galactic star forming regions, 3 mm HNC line emission tends to be weaker than the corresponding emission from HCN and HCO+. Toward Arp 220, however, the 3 mm HNC/HCN line intensity ratio is > 1. HNC/HCO+, HNC/CO, and HNC to 20 cm radio continuum luminosity ratios are also particularly large. A possible interpretation is the presence of cool quiescent gas outside the central region which contains the starburst. In the other ultraluminous galaxy observed, NGC 6240, X(HNC) 10 smaller than in Arp 220, demonstrating that the molecular composition in ultraluminous galaxies is far from being uniform.

Transmission characteristics of a vaginally-worn UHF radio telemeter

A vaginally-worn temperature telemeter may be used by women to chart their basal body temperature for ovulation detection. The telemeter uses a temperature to pulse width converter to key a Colpitts oscillator which is controlled in frequency by a 418 MHz SAW resonator. The circuit’s tank inductor acts as a compact, multi-turn loop antenna with a radiated power in isolation of around 1 uW. The transmission characteristics of the system are affected by the proximity of the human body, which acts as an electrically-large lossy dielectric. The RF link-budget must allow for the reduction in total emitted power, directional body-induced fading, and polarization effects. The polar power patterns of the telemeter were measured for both isolated and in-situ cases, using horizontal and vertical polarization. The power patterns were numerically integrated to determine relative emitted power, and a reference dipole used to determine the emitted power for the isolated device. In isolation the telemeter radiation is vertically polarized and isotropic in nature. With the telemeter in-situ, total body absorption was found to be over 20 dB, with directional fades of up to 40 dB; there was extensive cross-polarization, with up to 60% of radiated power horizontally polarized. With limited radiated power and directional fading, the operating range for the telemeter is limited to single room operation (less than 10m). The majority of RF radiation is absorbed by the body, but the radiation hazard is negligible due to the low power level of the device. The high level of cross-polarization suggests that either horizontal or vertically polarized base-station antennas may be used.

Low-power radio telemetry: the potential for remote patient monitoring

Radio-based signalling devices will play an important role in future generations of remote patient monitoring equipment, both at home and in hospital. Ultimately, it will be possible to sample vital signs frompatients, whatever their location and without them necessarily being aware that a measurement is being taken. This paper reviews currentmethods for the transmission by radio of physiological parameters over ranges of 0.3, 3 and 30 m, and describes the radiofrequency hardware required and the carrier frequencies commonly used. Future developments, including full duplex systems and the use of more advanced modulation schemes, are described. The paper concludeswith a case studyof a humantemperature telemeter built to indicateovulation. Clinical results clearly show the advantage to be had in adopting radio biotelemetry in this instance.

TEMPORALLY AND SPATIALLY-RESOLVED PLASMA PARAMETERS AND EEDF MEASUREMENTS IN A LOW-FREQUENCY DISCHARGE

A time-resolved Langmuir probe technique is used to measure the dependence of the electron density, electron temperature, plasma potential and electron energy distribution function (EEDF) on the phase of the driving voltage in a RF driven parallel plate discharge. The measurements were made in a low-frequency (100-500 kHz), symmetrically driven, radio frequency discharge operating in H-2, D-2 and Ar at gas pressures of a few hundred millitorr. The EEDFs could not be represented by a single Maxwellian distribution and resembled the time averaged EEDFs reported in 13.56 MHz discharges. The measured parameters showed structure in their spatial and temporal dependence, generally consistent with a simple oscillating sheath model. Electron temperatures of less than 0.1 eV were measured during the phase of the RF cycle when both electrodes are negative with respect to the plasma.

TIME-RESOLVED OPTICAL-EMISSION AND ELECTRON-ENERGY DISTRIBUTION FUNCTION MEASUREMENTS IN RF PLASMAS

Comparisons between experimentally measured time-dependent electron energy distribution functions and optical emission intensities are reported for low-frequency (100 and 400 kHz) radio-frequency driven discharges in argon. The electron energy distribution functions were measured with a time-resolved Langmuir probe system. Time-resolved optical emissions of argon resonance lines at 687.1 and 750.4 nm were determined by photon-counting methods. Known ground-state and metastable-state excitation cross sections were used along with the measured electron energy distribution functions to calculate the time dependence of the optical emission intensity. It was found that a calculation using only the ground-state cross sections gave the best agreement with the time dependence of the measured optical emission. Time-dependent electron density, electron temperature, and plasma potential measurements are also reported.

Detection of Voigt Spectral Line Profiles of Hydrogen Radio Recombination Lines toward Sagittarius B2(N)

We report the detection of Voigt spectral line profiles of radio recombination lines (RRLs) toward Sagittarius B2(N) with the 100 m Green Bank Telescope (GBT). At radio wavelengths, astronomical spectra are highly populated with RRLs, which serve as ideal probes of the physical conditions in molecular cloud complexes. An analysis of the Hn alpha lines presented herein shows that RRLs of higher principal quantum number (n > 90) are generally divergent from their expected Gaussian profiles and, moreover, are well described by their respective Voigt profiles. This is in agreement with the theory that spectral lines experience pressure broadening as a result of electron collisions at lower radio frequencies. Given the inherent technical difficulties regarding the detection and profiling of true RRL wing spans and shapes, it is crucial that the observing instrumentation produce flat baselines as well as high-sensitivity, high-resolution data. The GBT has demonstrated its capabilities regarding all of these aspects, and we believe that future observations of RRL emission via the GBT will be crucial toward advancing our knowledge of the larger-scale extended structures of ionized gas in the interstellar medium (ISM).

Plasma somatostatin and gastrointestinal peptides in Alzheimer's disease and vascular dementia

Few markers distinguish between different dementia types. As dementia affects many body systems outside the central nervous system, we investigated gastrointestinal regulatory peptides as possible disease markers in Alzheimer's Disease (AD) and vascular dementia (VaD). Subjects with mild-to-moderate dementia were diagnosed as probable AD and VaD according to defined criteria. Gastrointestinal peptides were stimulated using a standardized meal test, administered after an overnight fast to 58 dementia patients (40 AD, 18 VaD) and 47 controls matched for age and sex. Blood samples were taken at designated time intervals, and basal and stimulated plasma concentrations of eleven peptides were determined by radio-immunoassay. Results were analysed using the Kruskal-Wallis one-way analysis of variance; the Mann-Whitney U test was used in post hoc analysis where appropriate. There were significant differences in somatostatin levels but in none of the other peptides. Basal somatostatin was significantly increased in VaD compared to controls (p