Utilizing historical data from the U.S. nuclear test program and freely available barometric pressure data, we performed an analytical barometric‐pumping efficiency analysis to determine factors ...resulting in late‐time radionuclide gas seeps from underground nuclear explosions. We considered 16 underground nuclear explosions with similar geology and test setup, of which five resulted in the measurement of late‐time radionuclide gas concentrations at the ground surface. The factors we considered include barometric frequency and amplitude, depth of burial, air‐filled porosity, intact‐rock permeability, fracture aperture, and fracture spacing. The analysis indicates that the best discriminators of late‐time radionuclide gas seeps for these explosions are barometric frequency and amplitude and air‐filled porosity. While geologic information on fracture aperture and spacing is not available for these explosions, the sensitivity of barometric‐pumping efficiency to fracture aperture indicates that it would likely also be a good discriminator.
Plain Language Summary
Variations in air pressures (barometric variations) can drive gases created during underground nuclear explosions to the ground surface. The changes in air pressure above the ground push and pull the air in connected spaces between rocks (fractures) allowing these pressure changes to access hundreds of meters into the subsurface. Some barometric variations and geologies are more conducive to driving gases to the ground surface than others. Using a model that combines the effect of the barometric variations and geology, we are able to identify scenarios that are more likely to lead to gases arriving at the ground surface after an underground nuclear explosion. Identifying underground nuclear explosions that will likely result in gases arriving at the ground surface and entering the atmosphere provides information for investigators trying to verify nuclear test ban treaties.
Key Points
Barometric‐pumping efficiency facilitates discrimination of underground nuclear explosions leading to late‐time seeps
Longer high‐efficiency barometric periods and higher high‐efficiency amplitudes indicate a greater chance of late‐time seeps
Low air‐filled porosity indicates a greater chance of late‐time seeps
Gas samples taken from two historic underground nuclear tests done in 1989 at the Nevada National Security Site (NNSS), formerly the Nevada Test Site (NTS), were examined to determine how xenon ...isotopes fractionate because of early-time cavity processes, transport through the rock, or dispersal through tunnels. Xenon isotopes are currently being used to distinguish civilian sources of xenon in the atmosphere from sources associated with underground nuclear explosions (UNEs). The two nuclear tests included (1) BARNWELL, a test conducted in a vertical shaft approximately 600 m below ground surface at Pahute Mesa, and (2) DISKO ELM, a horizontal line-of-sight test done in P-tunnel approximately 261 m below the surface of Aqueduct Mesa. Numerical flow and transport models developed for the two sites had mixed success when attempting to match the observed xenon isotope ratios. At the BARNWELL site, the simulated xenon isotope ratios were consistent with measurements from the chimney and ground surface, and appeared to have been affected primarily by fractionation during subsurface transport. At the DISKO ELM site, samples taken from two elevations in the chimney failed to show the degree of fractionation predicted by the models during transport, and did not show evidence for significant fractionation due to early-time condensation of refractory xenon-precursor radionuclides into the melt glass. Gas samples taken from the adjacent tunnels in the days following the test showed mixed evidence for early-time separation of xenon isotopes from their iodine precursors.
•Following an underground nuclear explosion (UNE), both explosion-induced cavity evolution and transport processes in rock can affect xenon-isotope fractionation.•Comparison of simulated to observed xenon-isotope ratios for two historical UNE sites reveals how complex interpreting cavity or transport processes from observed ratios may be.•For all relevant fractionation processes investigated, no negative impact is found for the discrimination capability between nuclear explosions and nuclear reactors based on the isotopic activity ratios of radioxenon isotopes.
Purpose
Adult spinal deformity (ASD) surgery gives good clinical outcomes but has a high rate of mechanical complications (MC). In 2016, Lafage described the age-adjusted alignment thresholds (AAAT) ...to adapt the correction in relation to patient’s age proposing less aggressive corrections for the elderly population. The aim of this review was to clarify the effectiveness of AAAT to achieve good health-related quality of life (HRQoL) and their relationship with post-operative MC.
Materials and methods
We performed a review of the literature, including articles reporting data on post-operative HRQoL and MC rates in relation to the AAAT. Data were stratified according to whether they matched the AAAT, dividing the population in undercorrected (U), matched (M) and overcorrected (O). The quality of the included studies was assessed using the GRADE and MINORS systems.
Results
S
ix articles reporting data from 1,825 patients were included. The different categories (U, M and O) had homogeneous pre-operative sagittal parameters (
p
> 0.05) that became statistically different after surgeries (
p
< 0.05). Proximal junctional kyphosis (PJK) was more frequent in the O group compared to U (
p
= 0.05). Post-operative HRQoL parameters were similar in the 3 groups (
p
> 0.05). The quality of the included studies was generally low with a high bias risk.
Conclusion
The results extrapolated from this review are interesting, as for the same HRQoL the U group had a lower MC rate. Unfortunately, the results are inconsistent, mainly because of the low quality of the included studies and the lack of reporting of some important patient- and surgery-related factors.
Using data recorded with the ANTARES telescope from 2007 to 2015, a new search for dark matter annihilation in the Milky Way has been performed. Three halo models and five annihilation channels, ...WIMP+WIMP→bb¯,W+W−,τ+τ−,μ+μ− and νν¯, with WIMP masses ranging from 50 GeVc2 to 100 TeVc2, were considered. No excess over the expected background was found, and limits on the thermally averaged annihilation cross-section were set.
Core Ideas
Gas transport modeling can estimate ground surface breakthrough after an underground nuclear explosion.
Comparison tracer‐injection experimental and model results reveals parameter ...sensitivity.
Barometric pumping may explain gas breakthrough following an underground nuclear explosion.
Amplitude and period of barometric pressure signal are key in controlling breakthrough.
An underground nuclear explosion (UNE) generates and distributes radioactive gases that can be transported to the ground surface though preexisting and explosion‐induced fractures over timescales of hours to months. If detected, the presence of short‐lived radionuclides in gas is evidence of a recent UNE. Numerical modeling can provide estimates of surface arrival times that can help inform gas monitoring strategies at suspected foreign test sites. Efforts are underway at historic US UNE sites to better understand subsurface gas‐transport processes following a UNE by geologic characterization of the near‐field damage structures, field‐scale tracer experiments, and subsurface air pressure monitoring. The development of numerical models using historical and experimental datasets from former UNE sites can improve predictions by testing conceptual models, highlighting key processes, and constraining parameter ranges. The models developed in this study represent the U20az site at the Nevada National Security Site where the Barnwell device was expended in December 1989. A two‐phase (water and air), dual‐permeability flow and transport model of the U20az site was built to investigate gas transport processes under recent experimental conditions and following the Barnwell nuclear event. Results indicate that the model can explain both the lack of arrival of radioactive gas tracers in a 2013 field experiment as well as the observed arrival of radioactive gases following the 1989 Barnwell event using barometric pressure records from the respective periods, even when additional advective processes associated with the Barnwell detonation are ignored. The results demonstrate that the character of the barometric records may be a key factor in explaining the differences in transport behavior.
Neutrino detectors participate in the indirect search for the fundamental constituents of dark matter (DM) in form of weakly interacting massive particles (WIMPs). In WIMP scenarios, candidate DM ...particles can pair-annihilate into Standard Model products, yielding considerable fluxes of high-energy neutrinos. A detector like ANTARES, located in the Northern Hemisphere, is able to perform a complementary search looking towards the Galactic Centre, where a high density of dark matter is thought to accumulate. Both this directional information and the spectral features of annihilating DM pairs are entered into an unbinned likelihood method to scan the data set in search for DM-like signals in ANTARES data. Results obtained upon unblinding 3170 days of data reconstructed with updated methods are presented, which provides a larger, and more accurate, data set than a previously published result using 2101 days. A non-observation of dark matter is converted into limits on the velocity-averaged cross section for WIMP pair annihilation.
Purpose
In 2017, the GAP score was proposed as a tool to reduce mechanical complications (MC) in adult spinal deformity (ASD) surgery: the reported MC rate for the GAP proportioned category was only ...6%, which is clearly lower to the MC rate reported in the literature. The aim of this study is to analyse if the most recent literature confirms the promising results of the original article.
Materials and methods
Using the PRISMA flow chart, we reviewed the literature to analyse GAP score capacity in predicting MC occurrence. We included articles clearly reporting ASD surgery MC stratified by GAP categories and the score’s overall capacity to predict MC using the area under the curve (AUC). The quality of the included studies was evaluated using GRADE and MINORS systems.
Results
Eleven retrospective articles (1,517 patients in total) were included. The MC distribution per GAP category was as follows: GAP-P, 32.8%; GAP-MD, 42.3%; GAP-SD, 55.4%. No statistically significant difference was observed between the different categories using the Kruskal–Wallis test (
p
= 0.08) and the two-by-two Pearson-Chi square test (P Vs MD,
p
= 0.300; P Vs SD,
p
= 0.275; MD Vs SD,
p
= 0.137). The global AUC was 0.68 ± 0.2 (moderate accuracy). The included studies were of poor quality according to the GRADE system and had a high risk of bias based on the MINORS criteria.
Conclusion
The actual literature does not corroborate the excellent results reported by the original GAP score article. Further prospective studies, possibly stratified by type of MC and type of surgery, are necessary to validate this score.
Revision after spinal stenosis surgery Le Huec, J. C.; Seresti, S.; Bourret, S. ...
European spine journal,
02/2020, Letnik:
29, Številka:
Suppl 1
Journal Article
Recenzirano
Purpose
To make a literature review on spinal stenosis recurrence after a first surgery and edit rules to avoid this complication.
Methods
We conducted two separate PUBMED searches to evaluate the ...revision post-stenosis and degenerative scoliosis surgery using the terms: lumbar vertebrae/surgery, spinal stenosis, spine, scoliosis and reoperation. The resulting papers were categorized into three groups: (1) those that evaluated reoperation post-simple decompression; (2) those that evaluated spinal decompression and fusion for short (3 levels or less) or long (more than 3 levels) segment spinal fusion; and (3) those diagnosing the stenosis during the surgery.
Results
(1) We found 11 relevant papers that only looked at revision spine surgery post-laminectomy for spinal stenosis. (2) We found 20 papers looked at reoperation post-laminectomy and fusion amongst which there were two papers specifically comparing long-segment (> 3 level) and short-segment (3 or less levels) fusions. (3) In the unspecified group, we found only one article. Fifteen articles were excluded as they were not specifically looking at our objective criteria for revision surgery. In regard to revision post-adult deformity surgery, we found 18 relevant articles.
Conclusions
After this literature review and analysis of post-operative stenosis, it seems important to provide some advice to avoid revision surgeries more or less induced by the surgery. It looks interesting when performing simple decompression without fusion in the lumbar spine to analyse the risk of instability induced by the decompression and facet resection but also by a global balance analysis. Regarding pre-operative stenosis in a previously operated area, different causes may be evocated, like screw or cage malpositionning but also insufficient decompression which is a common cause. Intraoperatively, the use of neuromonitoring and intraoperative CT scan with navigation are useful tool in complex cases to avoid persisting stenosis. Pre-op analysis and planning are key parameters to decrease post-op problems.
Graphic abstract
These slides can be retrieved under Electronic Supplementary Material.
A
bstract
The ANTARES neutrino telescope has an energy threshold of a few tens of GeV. This allows to study the phenomenon of atmospheric muon neutrino disappearance due to neutrino oscillations. In ...a similar way, constraints on the 3+1 neutrino model, which foresees the existence of one sterile neutrino, can be inferred. Using data collected by the ANTARES neutrino telescope from 2007 to 2016, a new measurement of Δ
m
32
2
and
θ
23
has been performed — which is consistent with world best-fit values — and constraints on the 3+1 neutrino model have been derived.
An underground nuclear explosion (UNE) generates radioactive gases that can be transported through fractures to the ground surface over timescales of hours to months. If detected, the presence of ...particular short-lived radionuclides in the gas can provide strong evidence that a recent UNE has occurred. By drawing comparisons between sixteen similar historical U.S. UNEs where radioactive gas was or was not detected, we identified factors that control the occurrence and timing of breakthrough at the ground surface. The factors that we evaluated include the post-test atmospheric conditions, local geology, and surface geology at the UNE sites. The UNEs, all located on Pahute Mesa on the Nevada National Security Site (NNSS), had the same announced yield range (20–150 kt), similar burial depths in the unsaturated zone, and were designed and performed by the same organization during the mid-to-late 1980s. Results of the analysis indicate that breakthrough at the ground surface is largely controlled by a combination of the post-UNE barometric pressure changes in the months following the UNE, and the volume of air-filled pore space above the UNE. Conceptually simplified numerical models of each of the 16 historical UNEs that include these factors successfully predict the occurrence (5 of the UNEs) or lack of occurrence (remaining 11 UNEs) of post-UNE gas seepage to the ground surface. However, the data analysis and modeling indicates that estimates of the meteorological conditions and of the post-UNE, site-specific subsurface environment including air-filled porosity, in combination, may be necessary to successfully predict late-time detectable gas breakthrough for a suspected UNE site.
•Air-filled porosity provides gas storage and influences pneumatic diffusivity that control late-time seepage.•Hydrogeologic setting and characteristic amplitudes of barometric pressure may control late-time seepage following an UNE.•Models reproduce if late-time seepage or containment was observed for each UNE, but timing is not consistently reproduced.
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