Search

In order to meet the needs of accurate traceability of dose monitoring instruments in domestic medical, security inspection and other pulse radiation places, a 50-120 kV millisecond pulse X-ray reference radiation field that meets the requirements of norms and standards was established, based on the gate control technology, and its pulse width can be adjustable in the range of 1-6 300 ms. The pulse X-ray reference waveform was established by studying and testing the tube voltage stability, dose linearity, repeatability, pulse waveform and other key parameters of the radiation field, and the pulse dose rate was measured using a cylindrical ionization chamber with a sensitive volume of 30 cm3, and obtained the following research results: when the tube voltage was preset to 60 kV, the relative deviation of the intervened and non-intervened measuring tube voltage did not exceed ±1.5%; the minimum pulse width of the reference waveform pulse output was 20 ms, and a 95% uniform radiation field with a diameter of about 5.5 cm could be generated at 1 m. Moreover, the dose rate range of N series and RQR series radiation quality was extended to 0.002-10 mGy/s and 0.03-250 mGy/s, respectively, which can be used for the metrological traceability of protective instruments.

The development of life beyond planet Earth is a long-standing quest of the human race, but whether normal mammalian embryonic development can occur in space is still unclear. Here, we show unequivocally that preimplantation mouse embryos can develop in space, but the rate of blastocyst formation and blastocyst quality are compromised. Additionally, the cells in the embryo contain severe DNA damage, while the genome of the blastocysts developed in space is globally hypomethylated with a unique set of differentially methylated regions. The developmental defects, DNA damage and epigenetic abnormalities can be largely mimicked by the treatment with ground-based low-dose radiation. However, the exposure to simulated microgravity alone does not cause major disruptions of embryonic development, indicating that radiation is the main cause for the developmental defects. This work advances the understanding of embryonic development in space and reveals long-term extreme low-dose radiation as a hazardous factor for mammalian reproduction.

In order to accurately measure the environmental level dose rate, based on the G(E) function method and conversion of complete spectra without deconvolution method, the energy spectrum and dose rate of X/γ ray was measured for calculating spectrum-dose conversion coefficient. And finally the conversion of energy spectrum to dose rate is realized. The residual difference between the calculated dose rate by the energy spectrum-dose method and the measured dose rate value is approximately 0, which proves that the method is self-consistent. Experiments have been conducted in 137Cs and 60Co radiation fields, and the maximum relative error of dose rate is ±10%, which proves that the G(E) function method and Conversion of complete spectra without deconvolution method are feasible for energy spectrum-dose conversion.

Human eye lens is an organ vulnerable to radiation damage. Through self-developed human skull model, a spherical ionization chamber was embedded in the ball to directly measure the eye lens individual dose equivalent Hp(3). Aiming at the accuracy evaluation of Hp(3) in radiation environment, the following research was carried out in this paper: Firstly, the instrument was calibrated under the S-Cs γ-ray radiation quality condition specified in the GB/T 12162.1 standard, and a calibration factor was obtained, NH=1.19 μSv/pC. Then, the correction factors k(E,α) were determined under different energy and incident angle conditions. At the same time, the background current and polarization effect were experimentally measured. Without the correction of energy and incident angle, the relative error of the energy response was -0.9%-12.6% in the energy range of 33 keV-1.25 MeV, and the relative error of the angle response was -7.9%-0% in the range of -60°-60°. At the same time, the factors affecting the accuracy of the measured value of the chamber were discussed. The relative expanded uncertainty of the calibration factor was 5.6% (k=2); when the energy and incident angle were known and unknown, the relative expanded uncertainty of the measured value of Hp(3) were 9.4% (k=2) and 18% (k=2) respectively. For radiation fields with unknown energy and incident angle, the Hp(3) value in the radiation field can be obtained directly by using the ionization chamber within the uncertainty range. This study can provide a reference for the accurate measurement of individual dose equivalent of eye lens.

A large amount of energy is used to heat and cool buildings in the construction industry. Moreover, wood frame buildings' relatively low thermal mass limits energy efficiency and thermal comfort. Thermal energy storage via latent heat can effectively increase the thermal inertia of the building envelope, minimising the indoor temperature fluctuations and improving the occupant thermal comfort. This paper evaluated the energy efficiency and thermal comfort of an air-conditioned wood frame building by using biobased phase change materials (PCM) as the middle layer of a building envelope. Numerical simulations were conducted to investigate the effect of different factors (PCM melting point, surface area, thickness, and position) by adding a PCM layer into building walls to reduce annual heating and cooling energy consumption. The results of the numerical simulations showed that a phase change material layer can effectively decrease the energy demand of buildings, especially in cold areas. Based on the conditions investigated, the optimum solution can reduce the cooling, heating and annual energy consumption by 47%, 34% and 38%, respectively, compared to a reference building without a PCM layer. Moreover, an economic and environmental study of buildings containing biobased PCM is presented. [ABSTRACT FROM AUTHOR]

Purpose: Identifying high-risk populations and diagnosing gastric cancer (GC) early remains challenging. This study aimed to establish and verify a nomogram model for the early diagnosis of GC based on conventional laboratory indicators. Methods: We performed a retrospective analysis of the clinical data of 2,770 individuals with first diagnosis of GC and 1,513 patients with benign gastric disease from January 2018 to December 2022. The cases were divided into the training set and validation set randomly, with a ratio of 7:3. Variable screening was performed by least absolute shrinkage and selection operator (LASSO) and logistic regression analysis. A nomogram was constructed in the training set to assist in the early diagnosis of GC. Results: There were 4283 patients included in the study, with 2998 patients assigned in the training set and 1285 patients in the validation set. Through LASSO regression and logistic regression analysis, independent variables associated with GC were identified, including CEA, CA199, LYM, HGB, MCH, MCHC, PLT, ALB, TG, HDL, and AFR. The nomogram model was constructed using the above 11 independent indicators. The AUC was 0.803 for the training set and 0.797 for the validation set, indicating that the model showed high clinical diagnostic efficacy. The calibration curves and decision curve analysis (DCA) of the nomogram presented good calibration and clinical application ability. Conclusion: Based on the analysis of large sample size, we constructed a nomogram model with 11 routine laboratory indicators, which showed good discrimination ability and calibration. [ABSTRACT FROM AUTHOR]

The inflow of heavy polluted tributaries is one of the main factors that destroy the water quality at the river confluence area and downstream, especially in the wide-shallow river confluence area. In this study, a generalized model of a two-dimensional confluence was established and validated, and dissolved oxygen concentration was used as the water quality indicator. The influence laws and mechanisms of different spur dike layout patterns on the water quality distribution characteristics and the transport and mixing processes at the confluence were explored through numerical simulation. The results show that there is a large area of water pollution at the confluence with the polluted tributary, which is distributed near the outlet of the tributary, and the water quality in this area recovers slowly. The flow ratio is the main factor affecting the distribution of water quality transport at the confluence. Arranging dikes on the opposite bank of the tributary can significantly reduce the area of pollution by adjusting the flow field. Arranging dikes on the tributary side of the confluence can effectively promote water quality mixing through vortex suction between dikes and improve water quality near the tributary side of the river bank. The dissolved oxygen concentration between dikes at the river bank on the tributary side showed an increasing trend along the river direction, and vortex flow velocity showed a decreasing trend, and the increment of dissolved oxygen concentration had a good linear correlation with the interval between dikes and the change in vortex flow velocity between dikes. [ABSTRACT FROM AUTHOR]

The confluence area serves as the pivotal control unit in natural rivers, and the implementation of spur dikes at the confluence enables regulation of flow patterns, influences pollutant mixing, and safeguards against river scouring. This study establishes a three-dimensional hydrodynamic model for the 90° confluence with dikes, aiming to explore the impact of the number, angle, and spacing of the dikes on hydrodynamic characteristics at 90° confluence. The results show that (i) the closer the spacing between the dikes, the wider the range of low water level area upstream becomes. An increased number of dikes makes it easier for the downstream water level to recover. (ii) The area of the high turbulent kinetic energy region increases with the increase in the number of dikes. Among the three angle deployments, the dike deployment angle of 60° corresponds to the largest area of high turbulent kinetic energy. When the spacing between dikes is 0.225 m, it results in the largest area of high turbulent kinetic energy. (iii) The number or spacing of dikes exhibits a negative correlation with the shape parameters of the separation and backflow behind the dikes, whereas there is a positive correlation between the angle of dikes and these shape parameters. (iv) Influenced by the deployment of dikes, novel helical flows will be generated around the dikes at the confluence. The helicity of the clockwise helical flow is comparatively smaller than that of its counterclockwise counterpart. Subsequently, newly generated helical flows undergo fusion and division as it progresses downstream. [ABSTRACT FROM AUTHOR]

Objective To investigate the changes of the upper airway shape and respiratory function in patients with mild and moderate obstructive sleep apnea⁃hypopnea syndrome (OSAHS) before and after wearing mandibular ad⁃ vancement snore stopping devices (MASSD), providing a reference and basis for the treatment mechanisms and clinical efficacy of MASSD for patients with mild and moderate OSAHS. Methods Sixty patients who were diagnosed with mild and moderate OSAHS by polysomnography were selected. Snoring frequency, the apnea hypopnea index and lowest oxygen saturation in 60 patients before and after treatment were compared. The patients’upper airways were scanned by CBCT before and after wearing MASSD. In Vivo Dental software was used to reconstruct the three⁃dimensional shape of upper airway. The upper airway sagittal diameter, the coronal diameter, the minimum cross⁃sectional area and the vol⁃ ume of each segment were measured. The snoring frequency, the apnea hypopnea index and the lowest oxygen satura⁃tion were compared before and after treatment. Results Before wearing MASSD, the snoring frequency, the apnea hy⁃ popnea index, and the minimum oxygen saturation of 60 patients were [946 (542,1 010)], (20.61 ± 5.19), and (78 ± 8)%, respectively. After wearing MASSD, the snore frequency [19(11,30)] and the respiratory disorder index (10.86 ± 4.31) decreased significantly and the minimum oxygen saturation increased (92 ± 3)% . Compared with before wearing MASSD, no statistically significance differences were detected (P > 0.05) except for the sagittal diameter and coronal di⁃ ameter of the surface of the palatum durum. The sagittal diameter and the coronal diameter of each plane of the airway increased, and the minimum cross⁃sectional area of each section of the airway and the volume of each section of the air⁃ way displayed varying degrees of significant increases (P < 0.001) after wearing MASSD. Conclusion Wearing MASSD can open the airways of patients with mild and moderate OSAHS and increase the airway volume of the upper airway to improve the respiratory function.

Solid–liquid organic phase-change micro/nanocapsules are potential candidates for energy storage. Recently, significant progress has been made regarding phase-change micro/nanocapsules in terms of their synthesis, properties, and applications. Extensive research has been conducted to enhance their thermal properties, such as thermal storage capacity, thermal conductivity, and thermal reliability. However, factors that influence the thermal properties of micro/nanocapsules have received little attention. This study presents a comprehensive review of phase-change micro/nanocapsules focusing on their thermal properties and their influencing factors. In addition, the thermal properties of the major solid–liquid organic pure phase-change materials are summarized. Furthermore, common micro/nanoencapsulation methods and their influence on the thermal properties were analyzed. Finally, the potential applications of these phase-change micro/nanocapsules were also investigated. This study was devoted to enhancing the thermal properties of micro/nanocapsules, which play a crucial role in their practical applications. [ABSTRACT FROM AUTHOR]

The quality of broadband power line carrier communication mainly depends on the carrier communication frequency. However, there is a lack of fast and effective optimal carrier frequency selection method. One frequency selection method based on frequency point optimization neural network is proposed by this paper. This method combines transmission line theory and voltage partial reflection theory to build a power line carrier channel mathematical model of the distribution network. The input frequency point sample set is used as the training set of the frequency point optimization neural network to obtain a neural network model that can predict the local optimal frequency point set. Then the actual distribution network is taken as an example for simulation analysis. When inputting any frequency range, the model outputs the corresponding optimal frequency point set. Simulation results show that the algorithm saves a lot of input impedance or channel strength testing time, while the error rate is limited to about 3%.