Under the policies proposed by recent International Atomic Energy Agency (IAEA) circulars and policy papers, implementation of safeguards exists when any purified aqueous uranium solution or uranium ...oxides suitable for isotopic enrichment or fuel fabrication exists. Under IAEA Policy Paper 18, the starting point for nuclear material under safeguards was reinterpreted, suggesting that purified uranium compounds should be subject to safeguards procedures no later than the first point in the conversion process. In response to this technical need, a combination of simulation models and experimental measurements were employed in previous work to develop and validate gamma-ray nondestructive assay monitoring systems in a natural uranium conversion plant (NUCP). In particular, uranyl nitrate (UO2(NO3)2) solution exiting solvent extraction was identified as a key measurement point (KMP). Passive nondestructive assay techniques using high resolution gamma-ray spectroscopy were evaluated to determine their viability as a technical means for drawing safeguards conclusions at NUCPs, and if the IAEA detection requirements of 1 significant quantity (SQ) can be met in a timely manner. Building upon the aforementioned previous validation work on detector sensitivity to varying concentrations of uranyl nitrate via a series of dilution measurements, this work investigates detector response parameter sensitivities to gamma-ray signatures of uranyl nitrate. The full energy peak efficiency of a detection system is dependent upon the sample, geometry, absorption, and intrinsic efficiency parameters. Perturbation of these parameters translates into corresponding variations of the 185.7keV peak area of the 235U in uranyl nitrate. Such perturbations in the assayed signature impact the quality or versatility of the safeguards conclusions drawn. Given the potentially high throughput of uranyl nitrate in NUCPs, the ability to assay 1 SQ of material requires uncertainty «1%. Accounting for material self-shielding properties, pipe thickness, and source-detector orientation is instrumental in determining the robustness of gamma-ray detection in the process monitoring of uranyl nitrate in NUCPs. Monte Carlo models and ray-tracing models were employed to determine the sensitivity of the detected 185.7keV photon to self-shielding properties, pipe thickness, and source-detector geometry. Considering the implementation of the detection of 1 SQ, diversion of 1 SQ becomes essentially undetectable given the systematic uncertainty, in addition to considerations such as propagating uncertainties due to pipe offset/position, as well as minor variations in pipe thickness. Consequently, pipe thickness was the most sensitive variable in affecting full energy efficiency of the 185.7keV signature peak with up to 8% variation in efficiency for ±0.5mm changes in Schedule 40 304L stainless steel piping. Furthermore, computation of the attenuation correction factor of the uranyl nitrate solution CF(AT) (i.e. εsample) using Parker's method using with the approximation for the geometrical factor κ≈π/4 was validated through experimental, Monte Carlo and ray-tracing calculations for a uranyl nitrate filled transfer pipe segment. Quantifying sensitivity in detector position, as well as voiding effects due to bubbly flow or laminar flow with an air gap in the uranyl nitrate becomes increasingly important as considerations from (static) design-scale measurements translate into (dynamic) field operations tests.
Polymedicated neonates and young infants may be at risk of harmful cumulative exposure to toxic excipients like ethanol, propylene glycol and benzyl alcohol during routine clinical care. The aim of ...this study was to calculate the cumulative daily alcohol exposure (mg/kg/day) in polymedicated neonates and infants and compare these levels to the tolerance limits found in guidelines published by European Medicines Agency (EMA). As part of the SEEN study, all medicinal products administered to neonates and infants were recorded. All included neonates received ≥2 medicinal products/day and infants ≥3 medicinal products/day. Daily excipient levels were calculated based on quantities obtained from manufacturers or databases. Excipient levels were compared to tolerance limits proposed by the EMA. Altogether, 470 neonates and 160 infants were included, recording 4207 prescriptions and 316 products. In total, 45% (n = 288) of patients were exposed to an alcohol of interest; 2% (n = 14) were exposed to benzyl alcohol (BA), 38% (n = 237) to ethanol and 23% (n = 146) to propylene glycol (PG). Of the total number of prescriptions involving ethanol‐containing medicinal products (n = 334), 51% would alone exceed tolerance limit of 6 mg/kg/day. Of the total number of prescriptions involving PG‐containing medicinal products (n = 174), 70% would alone exceed a maximum tolerance limit of 50 mg/kg/day. Maximal daily exposure to ethanol (1563 mg/kg/day) or PG (954 mg/kg/day) exceeded the tolerance limits recommended by EMA 260.5 and 19.1 times, respectively. Tolerance limits for ethanol and PG as proposed by the EMA are frequently exceeded in polymedicated neonates and infants due to the cumulative effect of these alcohols. Alternative formulations may minimize excipient exposure.
Magnonics addresses the physical properties of spin waves and utilizes them for data processing. Scalability down to atomic dimensions, operation in the GHz-to-THz frequency range, utilization of ...nonlinear and nonreciprocal phenomena, and compatibility with CMOS are just a few of many advantages offered by magnons. Although magnonics is still primarily positioned in the academic domain, the scientific and technological challenges of the field are being extensively investigated, and many proof-of-concept prototypes have already been realized in laboratories. This roadmap is a product of the collective work of many authors, which covers versatile spin-wave computing approaches, conceptual building blocks, and underlying physical phenomena. In particular, the roadmap discusses the computation operations with the Boolean digital data, unconventional approaches, such as neuromorphic computing, and the progress toward magnon-based quantum computing. This article is organized as a collection of sub-sections grouped into seven large thematic sections. Each sub-section is prepared by one or a group of authors and concludes with a brief description of current challenges and the outlook of further development for each research direction.
A portable monoenergetic 24 keV neutron source based on the 124Sb-9Be photoneutron reaction and an iron filter has been constructed and characterized. The coincidence of the neutron energy from SbBe ...and the low interaction cross-section with iron (mean free path up to 29 cm) makes pure iron specially suited to shield against gamma rays from 124Sb decays while letting through the neutrons. To increase the 124Sb activity and thus the neutron flux, a >1 GBq 124Sb source was produced by irradiating a natural Sb metal pellet with a high flux of thermal neutrons in a nuclear reactor. The design of the source shielding structure makes for easy transportation and deployment. A hydrogen gas proportional counter is used to characterize the neutrons emitted by the source and a NaI detector is used for gamma background characterization. At the exit opening of the neutron beam, the characterization determined the neutron flux in the energy range 20–25 keV to be 6.00±0.30 neutrons per cm2 per second and the total gamma flux to be 245±8 gammas per cm2 per second (numbers scaled to 1 GBq activity of the 124Sb source). A liquid scintillator detector is demonstrated to be sensitive to neutrons with incident kinetic energies from 8 to 17 keV, so it can be paired with the source as a backing detector for neutron scattering calibration experiments. This photoneutron source provides a good tool for in-situ low energy nuclear recoil calibration for dark matter experiments and coherent elastic neutrino-nucleus scattering experiments.
In order to provide secure clamping with a low thermal conductance, some low temperature detectors are held with point contact sapphire ball clamps. While this method is increasingly common, the ...thermal conductance across this interface has not been well studied. We present a direct measurement of the thermal conductance of such clamps between 200 and 600 mK, with a clamping force of approximately
2.7
±
0.3
N
/
clamp
. The thermal conductance of a single sapphire-on-copper clamp was found to be
660
-
210
+
360
(
T
/
K
)
3.1
nW/K. For a sapphire-on-silicon clamp the conductance was found to be
380
-
120
+
190
(
T
/
K
)
2.8
nW/K. The conductance measured is consistent with thermal boundary resistance.
Prospective, randomized controlled trial.
To examine the effects of a 4-week rehabilitation program for chronic ankle instability (CAI) on postural control and lower extremity function.
CAI is ...associated with residual symptoms, performance deficits, and reinjury. Managing CAI is challenging and more evidence is needed to guide effective treatment.
Subjects with unilateral CAI were randomly assigned to the rehabilitation (CAI-rehab, n=16) or control (CAI-control, n=13) group. Subjects without CAI were assigned to a healthy group (n=19). Baseline testing included the (1) center of pressure velocity (COPV), (2) star excursion balance test (SEBT), and (3) Foot and Ankle Disability index (FADI) and FADI-Sports Subscale (FADI-Sport). The CAI-rehab group completed 4 weeks of rehabilitation that addressed range of motion, strength, neuromuscular control, and functional tasks. After 4 weeks, all subjects were retested. Nonparametric analyses for group differences and between-group comparisons were performed.
Subjects with CAI demonstrated deficits in postural control and SEBT reach tasks of the involved limb compared to the uninvolved limb and reported functional deficits of the involved limb compared to healthy subjects. Following rehabilitation, the CAI-rehab group had greater SEBT reach improvements on the involved limb than the other groups and greater improvements in FADi and FADI-Sport scores.
These results demonstrate postural control and functional limitations exist in individuals with CAl. In addition, rehabilitation appears to improve these functional limitations. Finally, there is evidence to suggest the SEBT may be a good functional measure to monitor change after rehabilitation for CAI.
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