A series of high-sensitivity radon detection systems and their applications in nitrogen as well as the boil-off liquid nitrogen measurement.

In modern rare-event search experiments such as neutrino experiments and dark matter search experiments, radon is one of the most important radiation backgrounds since it can emanate from nearly all the materials containing radium and migrate freely in the experiment system. To support the China Dark Matter Experiment (CDEX) at China Jinping Underground Laboratory (CJPL), a series of high-sensitivity radon detection systems with different electrostatic collection chambers were designed, and radon in nitrogen as well as boil-off liquid nitrogen was measured after accurate calibration and enrichment. Results showed that the calibration factors were 2.1 ± 0.2 (counts/h)/(Bq/m3), 21.1 ± 0.7 (counts/h)/(Bq/m3), 186.2 ± 2.2 (counts/h)/(Bq/m3), 387 ± 7 (counts/h)/(Bq/m3) and the 90% confidence level detection limits were 27.22 mBq/m3, 1.89 ∼ 3.06 mBq/m3, 0.41 ∼ 0.68 mBq/m3, 0.44 mBq/m3 for CJPL-HR2, CJPL-HR20, CJPL-HR140 and CJPL-HR300 measurement systems, respectively. Combined with an enrichment system consisting of twenty g CarboACT activated charcoals in a cold trap, the lower level detection limit (LLD) of typical No.1 CJPL-HR140 could reach 1.8 µBq/m3 with three days' enrichment time and three days' measurement time at 20 L/min sampling flowrate. For verification and application, the radon activity concentrations in nitrogen were 0.6 ∼ 1.9 mBq/m3 with an average of 1.1 ± 0.1 mBq/m3.While in boil-off liquid nitrogen, the radon activity concentrations ranged from 0.04 to 0.62 mBq/m3, and they were significantly lower in old-decayed liquid nitrogen compared to newly-filled liquid nitrogen, with a nearly five-fold decrease.

Research on UWB Indoor Positioning System Based on TOF Combined Residual Weighting.

The performance of TDOA positioning based on UWB is limited by the hyperbolic characteristics of TDOA, especially for tags away from the hyperbolic asymptote. Aiming at this problem, a new UWB indoor positioning system is proposed. Firstly, TOF ranging is adopted to build the positioning equations; then the weighted centroid algorithm of four base stations is presented to compute the initial rough position of the tag; and the residual weighting is introduced to optimize the initial tag position; then, the corresponding nonlinear positioning equations, which will be algebraically transformed to one distribution function, are solved, and the optimal tag coordinates can be obtained by the Newton iteration method. Simulation experiments have verified the positioning reliability of the proposed algorithm under different noise environments and for different tag positions.

Low energy SUSY confronted with new measurements of W-boson mass and muon g-2.

The new CDF II measurement of W-boson mass shows a 7σ deviation from the standard model (SM) prediction, while the recent FNAL measurement of the muon g-2 shows a 4.2σ deviation (combined with the BNL result) from the SM. Both of them strongly indicate new physics beyond the SM. In this work, we study the implication of both measurements on low energy supersymmetry. With an extensive exploration of the parameter space of the minimal supersymmetric standard model (MSSM), we find that in the parameter space allowed by current experimental constraints from colliders and dark matter detections, the MSSM can simultaneously explain both measurements on the edge of 2σ level, taking theoretical uncertainties into consideration. The favored parameter space, characterized by a compressed spectrum between bino, wino and stau, with the stop being around 1 TeV, may be covered in the near future LHC searches.

5-Hydroxymethylation alterations in cell-free DNA reflect molecular distinctions of diffuse large B cell lymphoma at different primary sites.

BACKGROUND: 5-Hydroxymethylcytosine (5hmC), an important DNA epigenetic modification, plays a vital role in tumorigenesis, progression and prognosis in many cancers. Diffuse large B cell lymphoma (DLBCL) can involve almost any organ, but the prognosis of patients with DLBCL at different primary sites varies greatly. Previous studies have shown that 5hmC displays a tissue-specific atlas, but its role in DLBCLs at different primary sites remains unknown. RESULTS: We found that primary gastric DLBCL (PG-DLBCL) and lymph node-involved DLBCL (LN-DLBCL) patients had a favorable prognosis, while primary central nervous system DLBCL (PCNS-DLBCL) patients faced the worst prognosis, followed by primary testicular DLBCL (PT-DLBCL) and primary intestinal DLBCL (PI-DLBCL) patients. Thus, we used hmC-CATCH, a bisulfite-free and cost-effective 5hmC detection technology, to first generate the 5hmC profiles from plasma cell-free DNA (cfDNA) of DLBCL patients at these five different primary sites. Specifically, we found robust cancer-associated features that could be used to distinguish healthy individuals from DLBCL patients and distinguish among different primary sites. Through functional enrichment analysis of the differentially 5hmC-enriched genes, almost all DLBCL patients were enriched in tumor-related pathways, and DLBCL patients at different primary sites had unique characteristics. Moreover, 5hmC-based biomarkers can also highly reflect clinical features. CONCLUSIONS: Collectively, we revealed the primary site differential 5hmC regions of DLBCL at different primary sites. This new strategy may help develop minimally invasive and effective methods to diagnose and determine the primary sites of DLBCL.

Additional radiation dose due to atmospheric dispersion of tritium evaporated from a hypothetical reservoir.

With regard to an inland nuclear power plant bordered by a reservoir, a major concern was that fresh water might be polluted and the human body might be radiation exposed due to the discharge of liquid radioactive effluents. In contrast to other radionuclides in the effluents, tritium has specific dispersion behavior in the aquatic environment such as emission into the air along with water evaporation. Further, the evaporated tritium in the air could go toward the territorial system where the wind blows. As a result, the person staying in the vicinity of the plant discharge point would be exposed with an additional radiation dose. In light of this characteristic, this study first introduced this new exposure pathway and investigated the additional radiation dose on the basis of a hypothetical reservoir. The results indicated that annual tritium evaporation fraction is approximately 2.5%, which is a comparable level with the radioactive decay factor. This would produce an additional radiation dose of 0.63 µSv/a to a person staying 50 m away from the plant discharge point for the case of 1 g/a tritium discharge. Tritium evaporation effects could be decreased through controlling the discharge depth. Thus, a preliminary suggestion to adopt a deep discharge instead of surface discharge was proposed from the ALARA (as low as reasonably achievable) criterion of radiation protection.

Modeling of radon exhalation from soil influenced by environmental parameters.

Atmospheric radioactive noble gas radon (Rn-222) originates from soil gas exhaled in the atmospheric surface layer. Radon exhalation rates from soil as well as corresponding meteorological and soil parameters were recorded for two subsequent years. Based on long-term field data, a statistical regression model for the radon exhalation and the most important influencing parameters soil water content, temperature of soil and air, air pressure and autocorrelation of the exhalation rate was established. The fitting result showed that the multivariate model can explain up to 61% of the variation of the exhalation rate. First, the exhalation rate increases up to 80 Bq m-2 h-1 with increasing soil water content. Later, at water content >10%, increasing soil wetness suppressed the exhalation rate: at values higher than 24% to approximately one third. The air temperature had a distinct positive effect while the soil temperature had a strong negative effect on the exhalation rate, indicating their different influencing-mechanisms on the exhalation. The air pressure was negligible. The lagged values of radon exhalation had to be included in the model, as the variable shows strong autocorrelation.

RADON EXHALATION FROM SOIL AND ITS DEPENDENCE FROM ENVIRONMENTAL PARAMETERS.

An automatic measuring apparatus called exhalometer for measurement of the radon exhalation rate from soil is introduced. It consists of a pneumatic driven accumulation chamber with an open bottom, a PC-based control system, six Lucas cells for radon measurement and sensors for environmental parameters. It allows moving the accumulation chamber and hereby opening or closing it. The exhalation rate is determined through the increase of radon in the accumulation chamber. For studying exhalation and the affecting factors, the exhalometer was placed at an undisturbed meadow for the entire year of 2015. The daily radon exhalation rate ranges from 2.5 to 50.7 Bq m-2 h-1 with an average of 25.3 Bq m-2 h-1. The exhalation rate shows daily and seasonal variations with its maximum in the afternoon and in spring. The dependence on several environmental parameters is discussed. The stable performance indicates the system's fitness for long-term measurements.

STUDY ON A STEP-ADVANCED FILTER MONITOR FOR CONTINUOUS RADON PROGENY MEASUREMENT.

Traditional fixed-filter radon progeny monitors are usually clogged with the loading of dust and cannot be used for radon progeny continuous measurement for long period. To solve this problem, a step-advanced filter (SAF) monitor for radon progeny measurement was developed. This monitor automatically roll and stop the filter at each interview. Radon progeny is collected on a 'fresh' filter at a flowrate of 3 L/min. At the same time, alpha and beta particles emitted from filter are recorded by a PIPS detector. A newly developed alpha-beta spectrum method was used for radon progeny concentration calculation. The 218Po, 214Pb and 214Bi concentrations as well as equilibrium equivalent concentration (EEC) could be worked out at the same time. The lower level limit detection of this monitor is 0.48 Bq m-3 (EEC) for 1h interval. Comparison experiments were carried out in the radon chamber at the National Institute of Metrology of China. The measurement results of this SAF monitor are consistent with EQF3220 (SARAD GmbH, Germany), and the uncertainty is smaller. Due to its high sensitivity, the periodical variation of radon progeny concentration can be easily observed by this monitor. The SAF moniter is suitable for continuous measurement in both indoor and outdoor environments.

Study on peak shape fitting method in radon progeny measurement.

Alpha spectrum measurement is one of the most important methods to measure radon progeny concentration in environment. However, the accuracy of this method is affected by the peak tailing due to the energy losses of alpha particles. This article presents a peak shape fitting method that can overcome the peak tailing problem in most situations. On a typical measured alpha spectrum curve, consecutive peaks overlap even their energies are not close to each other, and it is difficult to calculate the exact count of each peak. The peak shape fitting method uses combination of Gaussian and exponential functions, which can depict features of those peaks, to fit the measured curve. It can provide net counts of each peak explicitly, which was used in the Kerr method of calculation procedure for radon progeny concentration measurement. The results show that the fitting curve fits well with the measured curve, and the influence of the peak tailing is reduced. The method was further validated by the agreement between radon equilibrium equivalent concentration based on this method and the measured values of some commercial radon monitors, such as EQF3220 and WLx. In addition, this method improves the accuracy of individual radon progeny concentration measurement. Especially for the (218)Po peak, after eliminating the peak tailing influence, the calculated result of (218)Po concentration has been reduced by 21 %.