Optimization of detector placements in reduction of multiple counts for μSR measurements at China Spallation Neutron Source

An Experimental Muon Source (EMuS) has been proposed to conduct muon spin rotation/relaxation/resonance (μSR) measurements at China Spallation Neutron Source (CSNS). To make better use of muons in each pulse, a highly segmented μSR spectrometer with more than 2000 detector channels is under design. Due to such high granularity of detectors, multiple counting events generated from particle scattering or spiral motion of positrons in a strong longitudinal field should be carefully considered in the design. According to the simulation, long scintillators have a good capability of angular discrimination. Detectors with cuboid geometries are better than those with frustum shapes. The cuboid detector with a length of 50 mm is longer enough to get the optimal range of discrimination angle. In a real μSR spectrometer, detectors can be placed parallelly along the beam direction or pointing to the sample. A figure of merit (FoM) has been proposed to compare such two arrangements by integrating their impacts on multiple counts and total counting loss in zero and longitudinal fields. The outstanding performance of multiple counting rejection due to the angular discrimination capability makes the pointing arrangement achieve much higher FoM. The simulation results can provide good support for the design of the highly segmented μSR spectrometer.

A study on the impact of the users’ characteristics on the performance of wearable fall detection systems

Wearable Fall Detection Systems (FDSs) have gained much research interest during last decade. In this regard, Machine Learning (ML) classifiers have shown great efficiency in discriminating falls and conventional movements or Activities of Daily Living (ADLs) based on the analysis of the signals captured by transportable inertial sensors. Due to the intrinsic difficulties of training and testing this type of detectors in realistic scenarios and with their target audience (older adults), FDSs are normally benchmarked against a predefined set of ADLs and emulated falls executed by volunteers in a controlled environment. In most studies, however, samples from the same experimental subjects are used to both train and evaluate the FDSs. In this work, we investigate the performance of ML-based FDS systems when the test subjects have physical characteristics (weight, height, body mass index, age, gender) different from those of the users considered for the test phase. The results seem to point out that certain divergences (weight, height) of the users of both subsets (training ad test) may hamper the effectiveness of the classifiers (a reduction of up 20% in sensitivity and of up to 5% in specificity is reported). However, it is shown that the typology of the activities included in these subgroups has much greater relevance for the discrimination capability of the classifiers (with specificity losses of up to 95% if the activity types for training and testing strongly diverge).

Characterization of a medium-sized CLLB scintillator: single neutron/gamma detector for radiation monitoring

The use of a single neutron/gamma detector is an interesting solution to detect and identify gamma emitters and also special nuclear materials (SNM), being able to discriminate between the two kinds of particles and also to perform good-resolution gamma spectroscopy. In this framework, we present a comprehensive characterization of a medium sized (2" × 2") CLLB (Cs2LiLaBr6:Ce) scintillation detector, in order to give the necessary information to assess its deployment in applications regarding homeland security and radiation monitoring. In particular, the parameters studied are: energy resolution, full-energy peak gamma efficiency, time resolution, thermal neutron/gamma discrimination capability, decay time of the signals, high counting rate performance and minimum detectable activities (of 137Cs and 252Cf sources). We employed digital nuclear electronics combined with a pulse shape discrimination algorithm to acquire and analyze the data. We compared our results with reported data for smaller CLLB scintillators, finding good agreement. Experiments were combined with Monte Carlo simulations (using GEANT4 v10.6.0 and MCNP5 v1.60) in order to complement the characterization. The obtained results suggest that the 2” × 2” CLLB detector offers better performance with respect to other scintillators of the same size such as NaI(Tl), CsI, CeBr, etc. which are commonly used in a radiation monitoring systems.

Context and Aggregation: An Experimental Study of Bias and Discrimination in Organizational Decisions

This paper addresses a notable gap at the intersection of organizational economics and organization science: how does organizational context influence aggregation of individual behavior in organizational decisions? Using basic centralized versus decentralized organizational structures as building blocks for our experimental design, we examine whether assignment of organizational positions, incentive schemes, and structural configuration induce endogenous adaptation in the form of change in reservation levels (bias) or modified discrimination capability in subjects’ behavior. We found that evaluators adapted their reservation and discrimination levels in centralized structures, whereas they did not generally adapt their reservation and discrimination levels when placed in decentralized structures. We identify mechanisms that explain these findings; explain how they influence aggregate, organizational behavior; and discuss implications for research and practice.

Diffusion–Based Virtual MR Elastography of the Liver: Can It Be Extended beyond Liver Fibrosis?

Background: Strong correlation has been reported between tissue water diffusivity and tissue elasticity in the liver. The purpose of this study is to explore the capability of diffusion–based virtual MR elastography (VMRE) in the characterization of liver tumors by extending beyond liver fibrosis assessments. Methods: Fifty-four patients (56 liver tumors: hepatocellular carcinoma (HCC), 31; metastases, 25) who underwent MRE, diffusion-weighted imaging (DWI) (b: 0, 800 s/mm2), and VMRE (b: 200, 1500 s/mm2) were enrolled. The MRE shear modulus (µMRE), apparent diffusion coefficient (ADC), and shifted ADC (sADC) were obtained. Virtual stiffness (µdiff) was estimated from the relationship between µMRE and sADC. A linear discriminant analysis combining VMRE and MRE to classify HCC and metastases was performed in a training cohort (thirty-two patients) to estimate a classifier (C), and evaluate its accuracy in a testing cohort (twenty-two patients). Pearson’s correlations between µMRE, sADC, and ADC were evaluated. In addition to the discriminant analysis, a receiver operating characteristic (ROC) curve was used to assess the discrimination capability between HCC and metastases. Results: The correlations between µMRE and sADC were significant for liver, HCC, and metastases (r = 0.91, 0.68, 0.71; all p < 0.05). Those between µMRE and ADC were weaker and significant only for metastases (r = 0.17, 0.20, 0.55). µdiff values were not significantly different between HCC and metastases (p = 0.56). Areas under the curves (AUC) to differentiate HCC from metastases were as follows: VMRE, 0.46; MRE alone, 0.89; MRE + VMRE, 0.96. The classifier C also provided better performance than MRE alone, in terms of sensitivity (100 vs. 93.5%, respectively) and specificity (92 vs. 76%, respectively, p = 0.046). Conclusions: The correlation between sADC and µMRE was strong both in the liver and in tumors. However, VMRE alone could not classify HCC and metastases. The combination of MRE and VMRE, however, allowed discriminant performance between HCC and metastases.

Development and Validation of a Forensic Multiplex System With 38 X-InDel Loci

In the present study, a novel multiplex system, AGCU X-InDel 38 kit, was designed to amplify 38 X-InDel markers and amelogenin in a single Polymerase Chain Reaction (PCR). To demonstrate the suitability and efficiency for forensic applications, a series of validation experiments were conducted, including sensitivity, species specificity, reproducibility, stability, case samples, balance of peak height, size precision, as well as allele frequency and forensic parameter analysis. The results showed that AGCU X-InDel 38 kit was capable to get full profiles even with 62.5 pg of template DNA, and full profiles can be obtained when hematin concentration ≤25 μmol/L, or hemoglobin concentration ≤50 μmol/L, showing good tolerance to six common inhibitors. Moreover, the analyzed case samples indicated that AGCU X-InDel 38 kit had better performance for degraded and trace DNA samples. The 200 unrelated males from Guangdong Han population showed that the combined PDMale and PDFemale were both more than 0.999999999, and the combined MECKrüger, MECKishida, and MECDesmarais Duo were 0.999369481, 0.999999917, and 0.999941556, respectively. Robust discrimination capability of this novel multiplex system could be demonstrated through the high values of forensic parameters. In conclusion, AGCU X-InDel 38 kit is sensitive, precise, reproducible, and highly informative and could be used as a complementary tool for complex and challenging kinship cases.