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A water calorimeter based on thermistor is developed in this paper, and for the correction of chemical thermal defects in the absolute measurement of absorbed dose to water from proton beam, the design of gas saturated ultrapure water system is completed. By filling the ultrapure water inside the calorimeter core with high purity gas to form saturation condition, the effect of radiation chemical reaction is minimized. And the irradiation reaction of O2 in the ultrapure water is fully occurred through pre-irradiation experiment after the encapsulation of the calorimeter core, so that the water environment inside reaches a stable state without heat loss,which successfully developed a stable zero heat loss water calorimeter and the influence of heat loss on the absolute measurement of absorbed dose to water is minimized, which provides an important basis for the subsequent absolute measurement of absorbed dose to water.

Pulsed radiation field is characterized by short duration and high instantaneous dose rate compared with steady state radiation field, and has been widely used in the development of new detectors, radiological examination, X-ray diagnosis, nuclear accident emergency response and scientific research. Traditional nuclear radiation detectors in the pulsed radiation field often have problems such as signal stacking, ion composite, dead time, etc., which makes it difficult to realize the accurate measurement of pulsed radiation dose. Diamond detectors have the advantages of large bandwidth, high carrier mobility, strong anti-irradiation ability, fast time response, etc. In this paper, we utilize millisecond and nanosecond pulsed X-ray reference radiation field, high dose rate γ irradiation device to carry out the pulsed radiation field response test of single crystal diamond detector TW60019 produced by German PTW company, and we conclude that: the single-pulse response of diamond detector decreases with the increase of pulsed dose, and the single-pulse response of the single-pulse detector decreases with the increase of pulsed dose, and the single-pulse response of the single-pulse detector increases with the increase of pulse dose. It is concluded that the single-pulse response of the diamond detector decreases with the increase of the pulse dose, and similar to the ion complex effect in the ionization chamber in the pulsed radiation field, the diamond detector also suffers from the phenomenon of unsaturated collection in the measurement of large-dose and short-time pulsed radiation, and the detector's collection efficiency decreases with the increase of the single-pulse dose. Based on the experimental phenomenon, the influence of impurities and defects in the synthetic diamond film on the collection efficiency of the detector is analyzed, the impact of back-end electronics systems on collection efficiency during diamond detector signal collection is discussed and it is verified that the diamond detector can meet the requirements of fast response and high instantaneous dose rate of pulsed radiation measurements, which provides a basis for the further realization of the real-time monitoring of the pulsed radiation dose and the solution of the widely existed technical needs of the pulsed radiation dose monitoring in the fields of medical diagnosis and industrial flaw detection. The detector has been used in the following fields: medical diagnosis, industrial flaw detection, etc.

Evaluating metagenomic software is key for optimizing metagenome interpretation and focus of the Initiative for the Critical Assessment of Metagenome Interpretation (CAMI). The CAMI II challenge engaged the community to assess methods on realistic and complex datasets with long- and short-read sequences, created computationally from around 1,700 new and known genomes, as well as 600 new plasmids and viruses. Here we analyze 5,002 results by 76 program versions. Substantial improvements were seen in assembly, some due to long-read data. Related strains still were challenging for assembly and genome recovery through binning, as was assembly quality for the latter. Profilers markedly matured, with taxon profilers and binners excelling at higher bacterial ranks, but underperforming for viruses and Archaea. Clinical pathogen detection results revealed a need to improve reproducibility. Runtime and memory usage analyses identified efficient programs, including top performers with other metrics. The results identify challenges and guide researchers in selecting methods for analyses.

BackgroundThe extraction of 99Mo medical isotopes from off-gas of molten salt reactors (MSRs) has attracted significant attention. However, previous studies focused only on the estimation of 99Mo nuclide production in the reactor core, and limited studies have focused on the expansion of the entire reactor system.PurposeThis study aims to estimate 99Mo production in the off-gas of a molten salt reactor.MethodsIn this study, a 99Mo migration model with noble metal deposition and a flow effect in an MSR was established by using scientific computing software “Mathematica”, and a corresponding verification based on the deposition result of a molten salt reactor experiment (MSRE) was implemented. Subsequently, an analysis was conducted on the impact of changes in the yield, specific activity, and operational status of 99Mo crude product in MSRE off-gas on the stability of production.ResultsThe analysis results of Mo transport in the MSRE show that the production of 99Mo in the off-gas can reach 69.30 TBq with a specific activity of 0.39 PBq∙g-1 under normal operating conditions. In addition, an increase in the removal rate is conducive to the effect on the specific activity of 99Mo whilst the working conditions of bubble surface ratio bubble ratio and oxidation-reduction potential changes have little effect on the specific activity of the product.ConclusionsThe 99Mo in off-gas has high yield and specific activity, and the effects of the conventional operating conditions on the specific activity of 99Mo are beneficial, which indicates that this method can be a potential alternative for 99Mo production.

Early cancer detection by cell-free DNA faces multiple challenges: low fraction of tumor cell-free DNA, molecular heterogeneity of cancer, and sample sizes that are not sufficient to reflect diverse patient populations. Here, we develop a cancer detection approach to address these challenges. It consists of an assay, cfMethyl-Seq, for cost-effective sequencing of the cell-free DNA methylome (with > 12-fold enrichment over whole genome bisulfite sequencing in CpG islands), and a computational method to extract methylation information and diagnose patients. Applying our approach to 408 colon, liver, lung, and stomach cancer patients and controls, at 97.9% specificity we achieve 80.7% and 74.5% sensitivity in detecting all-stage and early-stage cancer, and 89.1% and 85.0% accuracy for locating tissue-of-origin of all-stage and early-stage cancer, respectively. Our approach cost-effectively retains methylome profiles of cancer abnormalities, allowing us to learn new features and expand to other cancer types as training cohorts grow.

Proton beam therapy (PBT) can achieve the effect of precision radiotherapy due to its unique Bragg peak. In the process of proton therapy, the peak can be accurately located to the tumor area, which can give the tumor a larger dose of irradiation, reduce the damage to normal tissues and organs, and reduce the occurrence of side effects. Therefore, it is very important to locate the Bragg peak of proton beam in real time in proton therapy. In this paper, a cyclotron is used to generate proton beam, and a diamond detector is used to test the radiation characteristics of proton beam, and the Bragg peak and the beam spot center are measured (0, 35 mm). Thus, accurate Bragg peak value of proton beam was obtained, which guaranteed the accuracy of proton therapy.

Research on radiation protection dosimetry mainly focuses on continuous radiation in the world, but pulsed ionizing radiation has been widely used in the fields of industrial detection, X-ray diagnosis, security inspection and scientific research. The active electronic dosimeter has been widely used in the fields of environmental monitoring, regional monitoring, personal dose monitoring and emergency monitoring. The active electronic dosimeters are calibrated in continuous radiation field, and they cannot measure short pulse and high dose rate pulsed ionizing radiation accurately. The active radiation dosimeter can be divided into G-M counter type, scintillator detector type, semiconductor detector type and ionization chamber type according to different radiation detection principles. The measurement of pulsed X-ray dose is very difficult due to its short duration and high instantaneous dose rate. Taking nanosecond radiation pulse as an example, its single pulse dose usually reaches more than 1 μSv, and the instantaneous dose rate can reach more than 105 Sv/h. For G-M counter and semiconductor detector, there are problems of measurement stacking and detection dead time, so it is difficult to achieve such a high dose-rate response, and there is an over-response problem in the instrument, which will inevitably affect the accuracy of monitoring results. The measurement of pulsed radiation dose (rate) is difficult. However, pulsed ionizing radiation has been widely used in many fields, such as the development of new detector, industrial flaw detection, X-ray diagnosis, nuclear emergency response and scientific research, etc. In this paper, the reference ionizing radiation field of pulsed X-ray was established based on steady-state X-ray machine, pulsed X-ray machine and portable X-ray machine. In order to measure the dose of pulsed reference field, the theoretical calculation, Monte Carlo simulation and experiment method were used to develop a secondary standard ionization chamber for millisecond pulsed X-rays. From the experimental data, it can be seen that the mainstream active dosimeters currently sold have low pulse dose response and even give false readings, which are not suitable for short pulse and high dose rate measurement and early warning, will cause safety trouble to personal. The dosimetric characteristics, such as pulse time, pulse dose and instantaneous dose rate were studied based on pulsed X-ray secondary standard ionization chamber and pulsed time measurement system. The lower limit and upper limit of instantaneous dose rate of the established pulsed X-ray reference radiation field are 2.5×10-3 Sv/h and 6.7×105 Sv/h respectively. Pulse time is adjustable between 50 ns and 10 s. The dose rate range of pulsed X-ray reference radiation field established in this study covers environmental level, radiation protection level, diagnosis level, treatment level, emergency level and nuclear critical accident level, which can be used to calibrate the pulsed radiation dose monitoring instrument. It is helpful to further study the pulsed radiation response characteristics of active radiation dosimeter and personal radiation dosimeter.