Discovery and insights from DSX mission's high-power VLF wave transmission experiments in the radiation belts.

Space weather phenomena can threaten space technologies. A hazard among these is the population of relativistic electrons in the Van Allen radiation belts. To reduce the threat, artificial processes can be introduced by transmitting very-low-frequency (VLF) waves into the belts. The resulting wave-particle interactions may deplete these harmful electrons. However, when transmitting VLF waves in space plasma, the antenna, plasma, and waves interact in a manner that is not well-understood. We conducted a series of VLF transmission experiments in the radiation belts and measured the power and radiation impedance under various frequencies and conditions. The results demonstrate the critical role played by the plasma-antenna-wave interaction around high-voltage space antennae and open the possibility to transmit high power in space. The physical insight obtained in this study can provide guidance to future high-power space-borne VLF transmitter developments, laboratory whistler-mode wave injection experiments, and the interpretation of various astrophysical and optical phenomena.

Deposition fluxes of lead, cadmium, copper and polynuclear aromatic hydrocarbons (PAH) on the verges of a major highway.

Deposition fluxes of Pb, Cd, Cu and a range of 11 PAH compounds have been determined at distances of 3.8-220 m from the M6 motorway in northwest England over a period of 21 months. Considerable temporal variation is seen in the deposition fluxes, but time-averaged data show that fluxes of Cd, Cu and the PAH compounds are highly elevated close to the road, decreasing to background levels within 20-40 m. Whilst lead also shows considerable roadside enhancement, its deposition continues to decline over the full 220-m measurement interval. Background deposition levels for all pollutants measured are of the same order as other reported data. Analysis of deposition samples for organic compounds by gas chromatography-mass spectrometry revealed a wide range of mainly hydrocarbon compounds.

The budget of lead, copper and cadmium for a major highway.

Data on deposition fluxes and concentrations of lead, cadmium and copper in road drainage water at proximate sites on the M6 motorway in northwest England have been analysed. The integration of fluxes over a year indicates that metal removal in road drainage water exceeds that deposited on the roadside verges, most markedly in the case of copper. From estimates of the source strength for lead, it is concluded that approximately 90% of emissions are dispersed by the atmosphere away from the immediate vicinity of the road. These findings are supported by estimation of integrated deposition since the opening of the road, derived from analysis of roadside soils.

Carbon dioxide assimilation in some aerial plant organs and tissues.

CO2 fixation characteristics of a number of mature (but not senescing) tissues and organs (the outer layers of green pod and the seed testa of Vicia faba L.; the outer layers of green pod and seeds of Trigonella foenum-graecum L.; the outer layers of the green fruit of Lycopersicon esculentum Mill.) were studied and compared with their respective C3 leaf characteristics. On a chlorophyll basis phosphoenolpyruvate carboxylase, malic enzyme (NADP) and malate dehydrogenase (NAD and NADP) acitivites were much higher in the non-leaf tissues (except for V. faba seed testa) than the leaf tissues. Generally, on a protein basis the differences were less significant. All tissues possessed ribulose-1.5-diphosphate carboxylase activity though there was great variation in activities both on a protein and chlorophyll basis. Protein: chlorophyll ratios varied greatly from tissue to tissue being lowest in the leaf tissue (11.5-14.0) and highest in V. faba seed testa (805.5). Chlorophyll a:b ratios were all between 2 and 3. (14)CO2 uptake in the dark by L. esculentum fruit slices was about 1/3 that in the light and the major, initially labelled product was malate both in the light and dark. Neither typical C4-photosynthesis or crassulacean acid metabolism were exhibited by the non-leaf tissues and it was considered that the increased levels of certain enzyme activities were present to refix and recycle respired CO2.