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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.

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.

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.

As a high-effective and broad-spectrum herbicide with high potency and low residue, glyphosate is widely used in agricultural industry throughout the world. It enters the aquatic environment through various pathways such as surface runoff and soil infiltration. Glyphosate at high concentrations can disrupt the physiological systems of numerous aquatic species with severe toxicity including mortality. In this study, the toxicity data of glyphosate was screened from open literature, including 29 acute values covering 5 families and 16 phyla and 13 chronic values covering 3 families and 8 phyla. The species sensitivity distribution (SSD), toxicity percentage ranking (TPR) and risk quotient (RQ) methods were adopted to derive water quality criteria (WQC) and assess the ecological risk. The results showed that the criteria maximum concentration (CMC), criteria continuous concentration (CCC), short-term water quality criterion (SWQC) and long-term water quality criterion (LWQC) of glyphosate were 0.12, 0.035, 0.14 and 0.007 mg·L-1, respectively. The highest concentration of glyphosate was recorded in surface water of Taihu Lake in Nanjing, Jiangsu Province at 52 mg·L-1 . The risk assessment showed that 7.69% of the water bodies in the world are at acute high level and 15.38% are at chronic high level. The results of this study provide a scientific basis for water quality standard formulation and water pollution control for glyphosate. [ABSTRACT FROM AUTHOR]

Objectives: To observe the effects of moxibustion on colonic mast cell degranulation and inflammatory factor expression in rats with diarrhea-predominant irritable bowel syndrome (IBS-D), and explore the potential mechanism of moxibustion in treating IBS-D., Methods: Forty-five rat pups born from 5 healthy SPF-grade pregnant SD rats, with 8 rats were randomly selected as the normal group. The remaining 37 rats were intervened with maternal separation, acetic acid enema, and chronic restraint stress to establish the IBS-D model. The successfully modeled 32 rats were then randomly assigned to a model group, a ketotifen group, a moxibustion group, and a moxibustion-medication group, with 8 rats in each group. The rats in the ketotifen group were intervened with intragastric administration of ketotifen solution (10 mL/kg); the rats in the moxibustion group were intervened with suspended moxibustion on bilateral "Tianshu" (ST 25) and "Shangjuxu" (ST 37); the rats in the moxibustion-medication group were intervened with suspended moxibustion combined with intragastric administration of ketotifen solution. All interventions were administered once daily for 7 consecutive days. The diarrhea rate and minimum volume threshold of abdominal withdrawal reflex (AWR) were calculated before and after modeling, as well as after intervention. After intervention, colonic tissue morphology was observed using HE staining; colonic mucosal ultrastructure was examined by scanning electron microscopy; colonic mast cell ultrastructure was observed using transmission electron microscopy; mast cell degranulation was assessed by toluidine blue staining; serum and colonic levels of histamine, interleukin (IL)-1β, IL-6, IL-1α, trypsin-like enzyme, and protease-activated receptor 2 (PAR-2) were measured by ELISA; the Western blot and real-time quantitative PCR were employed to evaluate the protein and mRNA expression of colonic IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2; the immunofluorescence was used to detect the positive expression of histamine, IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 in the colonic tissue., Results: Compared to the normal group, the rats in the model group exhibited extensive infiltration of inflammatory cells in colonic tissue, severe damage to the colonic mucosa, disordered arrangement of villi, reduced electron density, and a significant decrease in granule quantity within mast cells. The diarrhea rate and mast cell degranulation rate were increased ( P <0.01), AWR minimum volume threshold was decreased ( P <0.01); the serum and colonic levels of histamine, IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 were elevated ( P <0.01); the positive expression of histamine, as well as protein, mRNA and positive expression of IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 in the colon were all elevated ( P <0.01). Compared to the model group, the rats in the ketotifen group, the moxibustion group, and the moxibustion-medication group exhibited significantly reduced infiltration of inflammatory cells in colonic tissue, relatively intact colonic mucosa, orderly arranged villi, increased electron density, and an augmented number of mast cell granules; the diarrhea rate and mast cell degranulation rate were decreased ( P <0.01), and AWR minimum volume threshold was increased ( P <0.01); the serum and colonic levels of histamine, IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 were reduced ( P <0.01); the positive expression of histamine, as well as protein, mRNA and positive expression of IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 in the colon were all decreased ( P <0.01). Compared to the ketotifen group, the moxibustion group showed decreased serum levels of histamine, IL-6, and trypsin-like enzyme ( P <0.01, P <0.05), as well as reduced colonic levels of IL-1β and IL-6 ( P <0.01, P <0.05); the protein expression of colonic IL-1β, IL-1α, and PAR-2 was reduced ( P <0.05), and the positive expression of colonic IL-1β and trypsin-like enzyme was reduced ( P <0.01, P <0.05). Compared to both the ketotifen group and the moxibustion group, the moxibustion-medication group exhibited decreased diarrhea rate and mast cell degranulation rate ( P <0.01), an increased AWR minimum volume threshold ( P <0.01), reduced serum and colonic levels of histamine, IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 ( P <0.01), decreased protein expression of colonic IL-1β, trypsin-like enzyme, and PAR-2 ( P <0.01, P <0.05), reduced mRNA and positive expression of colonic IL-1β, IL-6, IL-1α, trypsin-like enzyme, and PAR-2 ( P <0.01, P <0.05), and decreased positive expression of colonic histamine ( P <0.01)., Conclusions: Moxibustion on "Tianshu" (ST 25) and "Shangjuxu" (ST 37) might inhibit low-grade inflammatory reactions in the colon of IBS-D model rats. The mechanism may be related to the inhibition of histamine and trypsin-like enzyme secreted by mast cell, thereby reducing the expression of related inflammatory factors.