Progress toward a cosmic dust collection facility on space station

Scientific and programmatic progress toward the development of a cosmic dust collection facility (CDCF) for the proposed space station is documented. Topics addressed include: trajectory sensor concepts; trajectory accuracy and orbital evolution; CDCF pointing direction; development of capture devices; analytical techniques; programmatic progress; flight opportunities; and facility development

High energy particles accelerated during the large solar flare of 1990 May 24: X/γ-ray observations

The PHEBUS experiment aboard GRANAT observed γ-ray line emission and γ-ray continuum above 10 MeV from the 24 May, 1990 solar flare. Observations and interpretation of the high-energy continuum have been discussed previously. Here we re-examine these, combining the PHEBUS observations above 10 MeV with calculations of the pion decay continuum to quantitatively constrain the accelerated ion energy distribution at energies above 300 MeV. The uncertainty in the determination of the level of the primary electron bremsstrahlung as well as the lack of measurements on the γ-ray emission above 100 MeV combine to allow rather a wide range of energy distribution parameters (in terms of the number of protons above 30 MeV, the spectral index of the proton distribution and the high energy cut-off of the energetic protons). Nevertheless we are able to rule out some combinations of these parameters. Using the additional information provided by the γ-ray line observations we discuss whether it is possible to construct a consistent picture of the ions which are accelerated in a wide energy range during this flare. Our findings are discussed with respect to previous works on the spectrum of energetic protons in the 10 MeV to GeV energy range

Comparative Analysis of Non-thermal Emissions and Study of Electron Transport in a Solar Flare

We study the non-thermal emissions in a solar flare occurring on 2003 May 29 by using RHESSI hard X-ray (HXR) and Nobeyama microwave observations. This flare shows several typical behaviors of the HXR and microwave emissions: time delay of microwave peaks relative to HXR peaks, loop-top microwave and footpoint HXR sources, and a harder electron energy distribution inferred from the microwave spectrum than from the HXR spectrum. In addition, we found that the time profile of the spectral index of the higher-energy (\gsim 100 keV) HXRs is similar to that of the microwaves, and is delayed from that of the lower-energy (\lsim 100 keV) HXRs. We interpret these observations in terms of an electron transport model called {\TPP}. We numerically solved the spatially-homogeneous {\FP} equation to determine electron evolution in energy and pitch-angle space. By comparing the behaviors of the HXR and microwave emissions predicted by the model with the observations, we discuss the pitch-angle distribution of the electrons injected into the flare site. We found that the observed spectral variations can qualitatively be explained if the injected electrons have a pitch-angle distribution concentrated perpendicular to the magnetic field lines rather than isotropic distribution.Comment: 32 pages, 12 figures, accepted for publication in The Astronomical Journa

Mobility of antimony, arsenic and lead at a former mine, Glendinning, Scotland

Elevated concentrations of antimony (Sb), arsenic (As) and lead (Pb) in upland organic-rich soils have resulted from past Sb mining activities at Glendinning, southern Scotland. Transfer of these elements into soil porewaters was linked to the production and leaching of dissolved organic matter and to leaching of spoil material. Sb was predominantly present in truly dissolved (< 3 kDa) forms whilst As and Pb were more commonly associated with large Fe-rich/organic colloids. The distinctive porewater behaviour of Sb accounts for its loss from deeper sections of certain cores and its transport over greater distances down steeper sections of the catchment. Although Sb and As concentrations decreased with increasing distance down a steep gully from the main spoil heap, elevated concentrations (~ 6-8 and 13-20 μg L− 1, respectively) were detected in receiving streamwaters. Thus, only partial attenuation occurs in steeply sloping sections of mining-impacted upland organic-rich soils and so spoil-derived contamination of surface waters may continue over time periods of decades to centuries

James Anderson (1812-1867)

... In 1831, James left Britain as an apprentice with the Hudson's Bay Company. For 20 years he served with energy, judgement, and business acumen in the James Bay, Lake Superior, and Athabasca areas. Then-Governor George Simpson entrusted him with the remote and valuable Mackenzie District. He improved profits by better book-keeping and retrenchment on the upper Yukon basin. His preference was to open trade directly with the Inuit via the Anderson River north of Fort Good Hope. Suddenly, in 1855, he was ordered to take part in the search for John Franklin's expedition. The Admiralty had wearied of the expensive probing of the arctic islands, but Dr. Rae of the Hudson's Bay Company had reported finding relics while surveying Boothia Peninsula. Inuit had told him of white men perishing on an island west of a great river. This was obviously the river down which Captain Back and Dr. King had taken a York Boat in 1834. Now the British government asked the Company to use the same route to check out Rae's report. Simpson had confidence that Anderson would see the matter through without creating new disasters. ... Because he could not carry enough supplies to overwinter, Anderson had to accomplish his mission in the short interval between breakup and the onset of the next winter. On Indian advice to bypass frozen lakes, he chose a new, more direct mountain portage route from Great Slave Lake. Solid ice on Lake Aylmer put him 12 days behind the schedule of Captain Back, whose carefully mapped route he joined at that point. ... On July 31, only two days later than Back, Anderson entered Chantrey Inlet. It was choked with wind-driven floes, and the fragile canoes could not operate as icebreakers. When the men managed to reach Montreal Island, they began finding wood and metal fragments along the shore and in Inuit caches. One chip bore the name "Mr. Stanley" of the Erebus. Using an inflatable rubber raft, three men pushed on to Maconochie Island. ... Anderson, with a true instinct, wanted to search Cape Richardson but was prevented by a "millstream" of jagged ice. Had he done so, he would have encountered, a scant eight kilometres to the west in a cul-de-sac later known as Starvation Cove, the last encampment of the Franklin expedition. Instead, he packed up the raft in the canoes, which had been repaired and regummed, and gave the order to return. Not until 1962 was the whole Back River canoed and kayaked again. ... Anderson's official report was brief and restrained. He had found no papers or bodies and could merely confirm Rae's statement that the disaster had occurred somewhere northwest of the Back. ... Anderson's health had been undermined by the trip. After three more years as chief factor in the Mackenzie District, he asked to be transferred. At Mingan on the St. Lawrence, he straightened out the account books and entertained the governor-general with salmon fishing. He finally retired, as a country squire, to Ontario, where his children were entering the professions. James Anderson's service to the Company was exemplary, and he narrowly missed fame at Starvation Cove. Altogether, he was a fine frontiersman - Canadian style

Strategies for producing biochars with minimum PAH contamination

With the aim to develop initial recommendations for production of biochars with minimal contamination with polycyclic aromatic hydrocarbons (PAHs), we analysed a systematic set of 46 biochars produced under highly controlled pyrolysis conditions. The effects of the highest treatment temperature (HTT), residence time, carrier gas flow and typical feedstocks (wheat / oilseed rape straw pellets (WSP), softwood pellets (SWP)) on 16 US EPA PAH concentration in biochar were investigated. Overall, the PAH concentrations ranged between 1.2 and 100 mg kg-1. On average, straw-derived biochar contained 5.8 times higher PAH concentrations than softwood-derived biochar. In a batch pyrolysis reactor, increasing carrier gas flow significantly decreased PAH concentrations in biochar; in case of straw, the concentrations dropped from 43.1 mg kg-1 in the absence of carrier gas to 3.5 mg kg-1 with a carrier gas flow of 0.67 L min-1; for woody biomass PAHs concentrations declined from 7.4 mg kg-1 to 1.5 mg kg-1 with the same change of carrier gas flow. In the temperature range of 350-650°C the HTT did not have any significant effect on PAH content in biochars, irrespective of feedstock type, however, in biochars produced at 750°C the PAH concentrations were significantly higher. After detailed investigation it was deduced that this intensification in PAH contamination at high temperatures was most likely down to the specifics of the unit design of the continuous pyrolysis reactor used. Overall, it was concluded that besides PAH formation, vaporisation is determining the PAH concentration in biochar. The fact that both of these mechanisms intensify with pyrolysis temperature (one increasing and the other one decreasing the PAH concentration in biochar) could explain why no consistent trend in PAH content in biochar with temperature has been found in the literature

Objective auditory brainstem response classification using machine learning

The objective of this study was to use machine learning in the form of a deep neural network to objectively classify paired auditory brainstem response waveforms into either: ‘clear response’, ‘inconclusive’ or ‘response absent’. A deep convolutional neural network was constructed and fine-tuned using stratified 10-fold cross-validation on 190 paired ABR waveforms. The final model was evaluated on a test set of 42 paired waveforms. The full dataset comprised 232 paired ABR waveforms recorded from eight normal-hearing individuals. The dataset was obtained from the PhysioBank database. The paired waveforms were independently labelled by two audiological scientists in order to train the network and evaluate its performance. The trained neural network was able to classify paired ABR waveforms with 92.9% accuracy. The sensitivity and the specificity were 92.9% and 96.4%, respectively. This neural network may have clinical utility in assisting clinicians with waveform classification for the purpose of hearing threshold estimation. Further evaluation using a large clinically obtained dataset would provide further validation with regard to the clinical potential of the neural network in diagnostic adult testing, newborn testing and in automated newborn hearing screening