The design of the n2EDM experiment Ayres, N. J.; Ban, G.; Bienstman, L. ...
The European physical journal. C, Particles and fields,
2021/6, Letnik:
81, Številka:
6
Journal Article
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We present the design of a next-generation experiment, n2EDM, currently under construction at the ultracold neutron source at the Paul Scherrer Institute (PSI) with the aim of carrying out a ...high-precision search for an electric dipole moment of the neutron. The project builds on experience gained with the previous apparatus operated at PSI until 2017, and is expected to deliver an order of magnitude better sensitivity with provision for further substantial improvements. An overview is of the experimental method and setup is given, the sensitivity requirements for the apparatus are derived, and its technical design is described.
It has been proposed that there could be a mirror copy of the standard model particles, restoring the parity symmetry in the weak interaction on the global level. Oscillations between a neutral ...standard model particle, such as the neutron, and its mirror counterpart could potentially answer various standing issues in physics today. Astrophysical studies and terrestrial experiments led by ultracold neutron storage measurements have investigated neutron to mirror-neutron oscillations and imposed constraints on the theoretical parameters. Recently, further analysis of these ultracold neutron storage experiments has yielded statistically significant anomalous signals that may be interpreted as neutron to mirror-neutron oscillations, assuming nonzero mirror magnetic fields. The neutron electric dipole moment collaboration performed a dedicated search at the Paul Scherrer Institute and found no evidence of neutron to mirror-neutron oscillations. Thereby, the following new lower limits on the oscillation time were obtained: τnn′>352 s at B′=0 (95% C.L.), τnn′>6s for 0.4μT<B′<25.7μT (95% C.L.), and τnn′/cosβ>9s for 5.0μT<B′<25.4μT (95% C.L.), where β is the fixed angle between the applied magnetic field and the local mirror magnetic field, which is assumed to be bound to the Earth. These new constraints are the best measured so far around B′∼10μT and B′∼20μT.
High-precision searches for an electric dipole moment of the neutron (nEDM) require stable and uniform magnetic field environments. We present the recent achievements of degaussing and equilibrating ...the magnetically shielded room (MSR) for the n2EDM experiment at the Paul Scherrer Institute. We present the final degaussing configuration that will be used for n2EDM after numerous studies. The optimized procedure results in a residual magnetic field that has been reduced by a factor of two. The ultra-low field is achieved with the full magnetic-field-coil system, and a large vacuum vessel installed, both in the MSR. In the inner volume of
∼
1.4
m
3
, the field is now more uniform and below 300 pT. In addition, the procedure is faster and dissipates less heat into the magnetic environment, which in turn, reduces its thermal relaxation time from
12
h
down to
1.5
h
.
Background:
Mosaicplasty and fresh osteochondral allograft transplantation (OCA) are popular cartilage restoration techniques that involve the single-stage implantation of viable, mature hyaline ...cartilage–bone dowels into chondral lesions of the knee. Recently, there has been greater focus on what represents a clinically relevant change in outcomes reporting, and commonly applied metrics for measuring clinical significance include the minimal clinically important difference (MCID) and substantial clinical benefit (SCB).
Purpose:
To define the MCID and SCB after mosaicplasty or OCA for the International Knee Documentation Committee (IKDC) subjective form and Knee Outcome Survey–Activities of Daily Living (KOS-ADL) and to determine patient factors that are predictive of achieving the MCID and SCB after mosaicplasty or OCA.
Study Design:
Cohort study (diagnosis); Level of evidence, 3.
Methods:
An institutional cartilage registry was reviewed to identify patients who underwent mosaicplasty or OCA. The decision to perform either mosaicplasty or OCA was generally based on chondral defect size. The IKDC and KOS-ADL were administered preoperatively and at a minimum of 2 years postoperatively. Patient responses to the outcome measures were aggregated, and the MCID and SCB of these outcome scores were calculated with anchor-based methods. Multivariate analysis adjusted for age and sex was performed to identify patient factors predictive of achieving the MCID and SCB.
Results:
Of the 372 eligible patients, 151 (41%) were lost to follow-up, 46 (12%) had incomplete preoperative outcome scores and 2 were treated with OCA of the tibia and therefore excluded. In total, 173 knees were analyzed (n = 173 patients; mean age, 33.0 years; 37% female). Seventy-five (43%) and 98 (57%) knees were treated with mosaicplasty and OCA, respectively. The mean ± SD MCIDs for the IKDC and KOS-ADL were 17 ± 3.9 and 10 ± 3.7, respectively. The SCBs for the IKDC and KOS-ADL were 30 ± 6.9 and 17 ± 3.9, respectively. Univariate analysis demonstrated no association between procedure (mosaicplasty or OCA) and likelihood of achieving the MCID or SCB. In the multivariate analysis, lower preoperative IKDC and KOS-ADL scores, higher preoperative Marx Activity Rating Scale scores, lower preoperative 36-Item Short Form Health Survey pain scores, and a history of ≤1 prior ipsilateral knee surgical procedure were predictive of achieving the MCID and/or SCB.
Conclusion:
These values can be used to define a clinically meaningful improvement for future outcome studies. For surgeons considering mosaicplasty or OCA for their patients, these results can help guide clinical decision making and manage patient expectations before surgery.
We present a novel Active Magnetic Shield (AMS), designed and implemented for the n2EDM experiment at the Paul Scherrer Institute. The experiment will perform a high-sensitivity search for the ...electric dipole moment of the neutron. Magnetic-field stability and control is of key importance for n2EDM. A large, cubic, 5 m side length, magnetically shielded room (MSR) provides a passive, quasi-static shielding-factor of about 105 for its inner sensitive volume. The AMS consists of a system of eight complex, feedback-controlled compensation coils constructed on an irregular grid spanned on a volume of less than 1000 m3 around the MSR. The AMS is designed to provide a stable and uniform magnetic-field environment around the MSR, while being reasonably compact. The system can compensate static and variable magnetic fields up to ±50μT (homogeneous components) and ±5μT/m (first-order gradients), suppressing them to a few μT in the sub-Hertz frequency range. The presented design concept and implementation of the AMS fulfills the requirements of the n2EDM experiment and can be useful for other applications, where magnetically silent environments are important and spatial constraints inhibit simpler geometrical solutions.
Background:
Treatment of large chondral defects of the knee among patients aged ≥40 years remains a difficult clinical challenge owing to preexisting joint degeneration and the lack of treatment ...options short of arthroplasty.
Purpose:
To characterize the survivorship, predictors of failure, and clinical outcomes of osteochondral allograft transplantation (OCA) of the knee among patients aged ≥40 years.
Study Design:
Case series; Level of evidence, 4.
Methods:
Prospectively collected data were reviewed for 54 consecutive patients aged ≥40 years who were treated with OCA. Preoperative levels of osteoarthritis (according to Kellgren-Lawrence classification) and meniscal volume and quality were graded from review of radiographs and magnetic resonance imaging. Complications, reoperations, and patient responses to validated outcome measures were reviewed. A minimum follow-up of 2 years was required for analysis. Failure was defined by any removal or revision of the allograft or conversion to arthroplasty.
Results:
Among 51 patients (mean age, 48 years; range, 40-63 years; 65% male), a total of 52 knees had symptomatic focal cartilage lesions (up to 2 affected areas) that were classified as Outerbridge grade 4 at the time of OCA and did not involve substantial bone loss requiring shell allografts or additional bone grafting. Mean duration of follow-up was 3.6 years (range, 2-11 years). After OCA, 21 knees (40%) underwent reoperation, including 14 failures (27%) consisting of revision OCA (n = 1), unicompartmental knee arthroplasty (n = 5), and total knee arthroplasty (n = 8). Mean time to failure was 33 months, and 2- and 4-year survivorship rates were 88% and 73%, respectively. Male sex (hazard ratio = 4.18, 95% CI = 1.12-27.13) and a higher number of previous ipsilateral knee operations (hazard ratio = 1.70 per increase in 1 surgical procedure, 95% CI = 1.03-2.83) were predictors of failure. A higher Kellgren-Lawrence osteoarthritis grade on preoperative radiographs was associated with higher failure rates in the Kaplan-Meier analysis but not the multivariate model. At final follow-up, clinically significant improvements were noted in the pain (mean score, 47.8 to 67.6) and physical functioning (56.8 to 79.1) subscales of the Short Form-36, as well as the International Knee Documentation Committee subjective form (45.0 to 63.6), Knee Outcome Survey–Activities of Daily Living (64.5 to 80.1), and overall condition statement (4.5 to 6.8) (P < .001). No significant changes were noted for the Marx Activity Rating Scale (5.1 to 3.9, P = .789).
Conclusion:
A higher failure rate was found in this series of patients aged ≥40 years who were treated with OCA as compared with other studies of younger populations. However, for select older patients, OCA can be a good midterm treatment option for cartilage defects of the knee.
Abstract
Satellite remote sensing is becoming a widely used monitoring technique in coastal sciences. Yet, no benchmarking studies exist that compare the performance of popular satellite-derived ...shoreline mapping algorithms against standardized sets of inputs and validation data. Here we present a new benchmarking framework to evaluate the accuracy of shoreline change observations extracted from publicly available satellite imagery (Landsat and Sentinel-2). Accuracy and precision of five established shoreline mapping algorithms are evaluated at four sandy beaches with varying geologic and oceanographic conditions. Comparisons against long-term in situ beach surveys reveal that all algorithms provide horizontal accuracy on the order of 10 m at microtidal sites. However, accuracy deteriorates as the tidal range increases, to more than 20 m for a high-energy macrotidal beach (Truc Vert, France) with complex foreshore morphology. The goal of this open-source, collaborative benchmarking framework is to identify areas of improvement for present algorithms, while providing a stepping stone for testing future developments, and ensuring reproducibility of methods across various research groups and applications.
We present a novel Active Magnetic Shield (AMS), designed and implemented for the n2EDM experiment at the Paul Scherrer Institute. The experiment will perform a high-sensitivity search for the ...electric dipole moment of the neutron. Magnetic-field stability and control is of key importance for n2EDM. A large, cubic, 5 m side length, magnetically shielded room (MSR) provides a passive, quasi-static shielding-factor of about
10
5
for its inner sensitive volume. The AMS consists of a system of eight complex, feedback-controlled compensation coils constructed on an irregular grid spanned on a volume of less than 1000 m
3
around the MSR. The AMS is designed to provide a stable and uniform magnetic-field environment around the MSR, while being reasonably compact. The system can compensate static and variable magnetic fields up to
±
50
μ
T
(homogeneous components) and
±
5
μ
T/m
(first-order gradients), suppressing them to a few
μ
T
in the sub-Hertz frequency range. The presented design concept and implementation of the AMS fulfills the requirements of the n2EDM experiment and can be useful for other applications, where magnetically silent environments are important and spatial constraints inhibit simpler geometrical solutions.
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