Search Results

You are looking at 1 - 10 of 26 items for

  • Author or Editor: M. Roberts x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract  

The quantitative determination of Li, Be, B, F is feasible using a sensitive and non-destructive method by the analysis of the prompt -rays induced with charged particles (PIGE). The irradiation source is a Van de Graaff accelerator, and -analysis has to be performed during the irradiation. Measurements were made at the CERI laboratory in Orléans with the PIGE method using a 100×300 m2 focused beam of 3MeV particles. Among the applications, micas along a drill core from the Beauvoir granite were analyzed. Bulk analyses of light elements in the drill core have previously been made. Coarse-grained micas were selected, individually irradiated and directly analyzed in polished thin sections from different elevations in the drill core. The sensitivity depends on the cross-sections of the nuclear reactions, on the particle current and on the duration of the irradiation. With a particle current irradiation of 25 nA during 1000 seconds, a 20 ppm limit of detection is reached for Be, 25 ppm for Li, 900 ppm for B and 450 ppm for F. A large variation of Be contents in the micas was found at equal drill hole elevations, and there was no strong correlation between whole-rock compositions and the mineral chemistry. The latter have been determined both by PIGE and by mineral separation and ICP analyses. On the other hand, a strong Li–F correlation was observed between the fluor-polylithionite and muscovite end-members, supporting previous analyses from equal elevation wells on sorted micas. Be–Li correlation is poorly defined, but the contents of the micas analyzed remained between the contents of bityite (Be–Li bearing mica) and lepidolites (Li-bearing micas) end-members. This suggests a solid-solution between the end-members, the extent of which is very narrow because the Be contents were not higher than 500 ppm. The detection limit is a function of the spatial resolution, because the current of the incident (or p) particles decreases with the impact size. The results show that the analysis of small individual grains of minerals with PIGE can thus be complementary to other analytical methods such as the electronic microprobe.

Restricted access

Abstract

Both the United States and the European Union have set goals for worldwide leadership of science and technology. While the U. S. leads in most input quantitative indicators, output indicators may be more specific for determining present leadership. They show that the EU has taken the lead in important metrics and is challenging the U. S. in others. Qualitative indicators of fields of research and development, based on expert review studies organized by the authors, confirm that many EU labs are equal or better than those in the U. S.

Restricted access

Abstract  

Decommissioning and decontamination work, safeguards related measurements for special nuclear materials, and many other in-situ applications require that the measuring system be taken to the sample and not the other way around. In addition to a portable detector, these types of measurements need a lightweight, rugged, battery operated MCA. Canberra's solution to this need is the versatile InSpector Multi-Channel Analyzer. This single instrument includes the MCA memory management, a high voltage power supply for either a NaI or a Ge detector, a spectroscopy grade amplifier, a digital stabilizer, and an ADC. It has a total weight of 3,2 kg, including batteries.

Restricted access
Restricted access
Periodica Mathematica Hungarica
Authors:
J. Fink
,
M. Jacobson
,
L. Kinch
, and
J. Roberts
Restricted access

Abstract  

Remote-handled transuranic nuclear waste poses a particular challenge for assaying due to the high neutron and -ray background that emanate from the non-fissile, but highly radioactive material, contained within the waste. The utilization of a Radio Frequency Quadrupole (RFQ) linac with a neutron flux of the order of 1010 n/s/4 has shown that, in principle, the differential die-away technique can be used to reliably assay this special class of nuclear waste.

Restricted access
Journal of Evolutionary Psychology
Authors:
Tamsin K. Saxton
,
Robert P. Burriss
,
Alice K. Murray
,
Hannah M. Rowland
, and
S. Craig Roberts

Abstract

Research on human attraction frequently makes use of single-modality stimuli such as neutral-expression facial photographs as proxy indicators of an individual's attractiveness. However, we know little about how judgments of these single-modality stimuli correspond to judgments of stimuli that incorporate multi-modal cues of face, body and speech. In the present study, ratings of attractiveness judged from videos of participants introducing themselves were independently predicted by judgments of the participant's facial attractiveness (a neutral-expression facial photograph masked to conceal the hairstyle), body attractiveness (a photograph of the upper body), and speech attractiveness (the soundtrack to the video). We also found that ratings of the face, body and speech were positively related to each other. Our results support the assumption that the single-modality stimuli used in much attractiveness research are valid proxy indicators of overall attractiveness in ecologically valid contexts, and complement literature showing cross-modality concordance of trait attractiveness, but also recommend that research relying on assessments of individual attractiveness take account of both visual and vocal attractiveness where possible.

Restricted access

Abstract

Paper sheets impregnated with flame retardants made from agricultural residues and other additives were studied with the cone calorimeter. The use of sugar beet ethanol eluent (SBE), CaCl2, and ZnCl2 lowered the peak rate of heat release (PRHR) the most in comparison to water treated material. The average effective heat of combustion (AEHC) was lowered by most of our treatments with the exception of BMIC (butylmethylimidazolium chloride)/starch (BMS). The average mass loss rate was lowered by all the treatments, but the most by the use of ZnCl2 and CaCl2 treatments. Mass losses were the least with SBE, CaCl2/NaOH/starch, and CaCl2/NaOH treatments. The BMS sample exhibited the greatest total heat release while SBE samples gave the smallest value of the parameter. The flame retarding effect of SBE was ascribed to the presence of ferulates which prevented the formation of volatile products by condensing into polycyclic aromatic residue.

Restricted access

Abstract

Starches with varying amylose content, one hydroxypropylated high amylose starch and two thermoplastic starches (pre-gelatinized and with V type crystals) were gelatinized in the presence of added water. Gelatinization was characterized using wide-angle X-ray scattering and modulated temperature differential scanning calorimetry (mT-DSC) with a heat-cool temperature profile. The gelatinization endotherms were recorded in total heat capacity curves that were resolved into storage (reversing) and loss heat capacities, and non-reversing heat capacity curve. The endotherms were mainly of non-reversing nature, with a small contribution from the reversing component. Starch melting is a plasticizer-assisted disruption of crystals and other structures such as starch–lipid complexes and granules. Reversibility was limited since the native amylopectin crystals are rarely recrystallized and starch–lipid complexes do not reform. Recrystallization is predominantly due to subsequent slow formation of V type amylose crystals, with some B type due to recrystallization of amylopectin.

Restricted access

Response to “Nature fix: Addiction to outdoor activities”

R. C. Buckley’s commentary on Heirene, R. M., Shearer, D., Roderique-Davies, G., & Mellalieu, S. D. (2016). Addiction in extreme sports: An exploration of withdrawal states in rock climbers. Journal of Behavioral Addictions, 5, 332–341.

Journal of Behavioral Addictions
Authors:
Robert M. Heirene
,
David Shearer
,
Stephen D. Mellalieu
, and
Gareth Roderique-Davies

Buckley’s commentary on our study of rock climber’s withdrawal experiences raises a number of important questions surrounding the concept of extreme or adventure sports addiction. Drawing on the few available investigations of this topic, we respond to Buckley’s questions here, though emphasize the need for further studies of extreme sports addiction in order to provide more empirically informed answers.

Open access