Bioaccessibility and human health risk : chromium in Glasgow

The assessment of risk to human health from contaminated land is based on a comparison of predicted human exposure to a contaminant with a Health Criteria Value (HCV) that represents an exposure below which there is thought to be little or no risk to human health. Most assessment tools, such as the Contaminated Land Exposure Assessment Model (CLEA), use estimates of exposure based on intake (consumption rate) rather than on measures of uptake (the amount of contaminant which enters the bloodstream), thus allowing comparison with HCVs, which are also based on intake apposed to uptake. Soil Guideline Values (SGVs) derived using the CLEA model assume that a soil contaminant will be taken up into the body to the same extent as from the medium of exposure used to derive the oral HCV (e.g. soluble salts of Cr(VI)). This is a conservative assumption as contaminants can be tightly bound to other soil components, thus reducing bioavailability (the fraction of a contaminant that can be absorbed by the body)

The non-vanishing effect of detuning errors in dynamical decoupling based quantum sensing experiments

Characteristic dips appear in the coherence traces of a probe qubit when dynamical decoupling (DD) is applied in synchrony with the precession of target nuclear spins, forming the basis for nanoscale nuclear magnetic resonance (NMR). The frequency of the microwave control pulses is chosen to match the qubit transition but this can be detuned from resonance by experimental errors, hyperfine coupling intrinsic to the qubit, or inhomogeneous broadening. The detuning acts as an additional static field which is generally assumed to be completely removed in Hahn echo and DD experiments. Here we demonstrate that this is not the case in the presence of finite pulse-durations, where a detuning can drastically alter the coherence response of the probe qubit, with important implications for sensing applications. Using the electronic spin associated with a nitrogen-vacancy centre in diamond as a test qubit system, we analytically and experimentally study the qubit coherence response under CPMG and XY8 dynamical decoupling control schemes in the presence of finite pulse-durations and static detunings. Most striking is the splitting of the NMR resonance under CPMG, whereas under XY8 the amplitude of the NMR signal is modulated. Our work shows that the detuning error must not be neglected when extracting data from quantum sensor coherence traces

Development Status of a CVD System to Deposit Tungsten onto UO2 Powder via the WCI6 Process

Nuclear Thermal Propulsion (NTP) is under development for deep space exploration. NTP's high specific impulse (> 850 second) enables a large range of destinations, shorter trip durations, and improved reliability. W-60vol%UO2 CERMET fuel development efforts emphasize fabrication, performance testing and process optimization to meet service life requirements. Fuel elements must be able to survive operation in excess of 2850 K, exposure to flowing hydrogen (H2), vibration, acoustic, and radiation conditions. CTE mismatch between W and UO2 result in high thermal stresses and lead to mechanical failure as a result UO2 reduction by hot hydrogen (H2) [1]. Improved powder metallurgy fabrication process control and mitigated fuel loss can be attained by coating UO2 starting powders within a layer of high density tungsten [2]. This paper discusses the advances of a fluidized bed chemical vapor deposition (CVD) system that utilizes the H2-WCl6 reduction process

Spin properties of dense near-surface ensembles of nitrogen-vacancy centres in diamond

We present a study of the spin properties of dense layers of near-surface nitrogen-vacancy (NV) centres in diamond created by nitrogen ion implantation. The optically detected magnetic resonance contrast and linewidth, spin coherence time, and spin relaxation time, are measured as a function of implantation energy, dose, annealing temperature and surface treatment. To track the presence of damage and surface-related spin defects, we perform in situ electron spin resonance spectroscopy through both double electron-electron resonance and cross-relaxation spectroscopy on the NV centres. We find that, for the energy ($4-30$~keV) and dose ($5\times10^{11}-10^{13}$~ions/cm$^2$) ranges considered, the NV spin properties are mainly governed by the dose via residual implantation-induced paramagnetic defects, but that the resulting magnetic sensitivity is essentially independent of both dose and energy. We then show that the magnetic sensitivity is significantly improved by high-temperature annealing at $\geq1100^\circ$C. Moreover, the spin properties are not significantly affected by oxygen annealing, apart from the spin relaxation time, which is dramatically decreased. Finally, the average NV depth is determined by nuclear magnetic resonance measurements, giving $\approx10$-17~nm at 4-6 keV implantation energy. This study sheds light on the optimal conditions to create dense layers of near-surface NV centres for high-sensitivity sensing and imaging applications.Comment: 12 pages, 7 figure

Spatial mapping of band bending in semiconductor devices using in-situ quantum sensors

Band bending is a central concept in solid-state physics that arises from local variations in charge distribution especially near semiconductor interfaces and surfaces. Its precision measurement is vital in a variety of contexts from the optimisation of field effect transistors to the engineering of qubit devices with enhanced stability and coherence. Existing methods are surface sensitive and are unable to probe band bending at depth from surface or bulk charges related to crystal defects. Here we propose an in-situ method for probing band bending in a semiconductor device by imaging an array of atomic-sized quantum sensing defects to report on the local electric field. We implement the concept using the nitrogen-vacancy centre in diamond, and map the electric field at different depths under various surface terminations. We then fabricate a two-terminal device based on the conductive two-dimensional hole gas formed at a hydrogen-terminated diamond surface, and observe an unexpected spatial modulation of the electric field attributed to a complex interplay between charge injection and photo-ionisation effects. Our method opens the way to three-dimensional mapping of band bending in diamond and other semiconductors hosting suitable quantum sensors, combined with simultaneous imaging of charge transport in complex operating devices.Comment: This is a pre-print of an article published in Nature Electronics. The final authenticated version is available online at https://dx.doi.org/10.1038/s41928-018-0130-

Supporting public involvement in interview and other panels: a systematic review.

BACKGROUND: Members of the public are increasingly being invited to become members of a variety of different panels and boards. OBJECTIVE: This study aimed to systematically search the literature to identify studies relating to support or training provided to members of the public who are asked to be members of an interview panel. SEARCH STRATEGY: A systematic search for published and unpublished studies was carried out from June to September 2015. The search methods included electronic database searching, reference list screening, citation searching and scrutinizing online sources. INCLUSION CRITERIA: We included studies of any design including published and unpublished documents which outlined preparation or guidance relating to public participants who were members of interview panels or representatives on other types of panels or committees. DATA SYNTHESIS: Results were synthesised via narrative methods. MAIN RESULTS: Thirty-six documents were included in the review. Scrutiny of this literature highlighted ten areas which require consideration when including members of the public on interview panels: financial resources; clarity of role; role in the interview process; role in evaluation; training; orientation/induction; information needs; terminology; support; and other public representative needs such as timing, accessibility and support with information technology. DISCUSSION AND CONCLUSIONS: The results of the review emphasize a range of elements that need to be fully considered when planning the involvement of public participants on interview panels. It highlights potential issues relating to the degree of involvement of public representatives in evaluating/grading decisions and the need for preparation and on-going support