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Objective The radioactivity level in historical waste from a plant is high, and decommissioning operators may be exposed to high radiation doses. The objective of the study is to carry out a radiation safety analysis of the retrieval and conditioning of naturally occurring radioactive material (NORM) waste, put forward appropriate radiation protection measures, and minimize the exposure doses of operators. Methods The source terms of NORM waste in the temporary storehouse were analyzed; MicroShield, a point kernel integration program, was used for modeling and calculation; and radiation protection measures under decommissioning conditions were put forward based on on-site monitoring data. Results The maximum gamma dose rate calculated near the waste pile in the temporary storehouse was 313.9 μGy/h, equivalent to the monitoring level; distance decay and appropriate shielding measures significantly reduced gamma dose rates for operators. Conclusion Decommissioning sites of temporary storehouses are of great harm to operators. Measures such as shielding, isolation, remote operations, and personal protection can effectively reduce the exposure doses of operators.
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Objective To establish a sourceless efficiency calibration method by coupling Monte Carlo simulation with analytical calculation. Methods Monte Carlo simulation was used to calculate the point-to-point detection efficiency of specific detectors to establish a detection efficiency grid. The detection efficiency of point source, disc, cylindrical, beaker, spherical, U-tube and Marlin cup samples was analyzed using numerical integration method after detection efficiency grid interpolation. Results The above coupling method was used for sourceless efficiency calibration. Within the energy range of 0.2–3 MeV, the relative deviation of calibration between coupling method and Monte Carlo simulation was mostly less than 10%, the maximum relative deviation was 18.06%, and the computation time was reduced by at least 86%. The above coupling method was used for sourceless efficiency calibration of an HPGe detector manufactured by ORTEC for point source detection, which was in good agreement with the experimental calibration, and the relative deviations were less than 10%. Conclusion This method can be generalized and used in the sourceless efficiency calibration of HPGe, LaBr3, and NaI detectors.
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Endoglucanase (EG) is an important component of cellulases and play an important role in cellulose degradation. However, its application is limited due to the low yield of endoglucanase from natural microorganisms. Efficient heterologous expression of endoglucanase is an effective way to solve this problem. To obtain the engineered Saccharomyces cerevisiae for high-yield endoglucanase, endoglucanase gene was cloned from Clostridium cellulovorans, with a total length of 1 996 bp, encoding 440 amino acids, and the complete expression cassette (PαEGC) was constructed with the PGK promoter sequence from Saccharomyces cerevisiae, α-signal peptide sequence from pPIC9K plasmid and CYC1 terminator sequence from pSH65 plasmid by gene splicing by overlap extension PCR (SOE PCR), and the expression vector of endoglucanase in Saccharomyces cerevisiae was constructed by rDNA integration. The relationship between copy number and protein expression was explored. Random multicopy expression of endoglucanase was performed in Saccharomyces cerevisiae. The copy number of endoglucanase was identified by Droplet Digital PCR and explore the relationship between copy number and protein expression.The engineered Saccharomyces cerevisiae of endoglucanase with copy numbers of 1, 3, 4, 7, 9, 11, 15, 16, 19, 21, 22 and 23 were obtained by rDNA integration, respectively. The results showed that when the copy number was 15, the enzyme activity was the highest, namely 351 U/mL. The engineered strain of Saccharomyces cerevisiae for endoglucanase was successfully constructed, which can provide reference for the heterologous expression of other industrial enzymes.
Subject(s)
Cellulase/genetics , Genetic Engineering , Industrial Microbiology , Plasmids/genetics , Saccharomyces cerevisiae/geneticsABSTRACT
Currently, the dose distribution calculation used by commercial treatment planning systems (TPSs) for high-dose rate (HDR) brachytherapy is derived from point and line source approximation method recommended by AAPM Task Group 43 (TG-43). However, the study of Monte Carlo (MC) simulation is required in order to assess the accuracy of dose calculation around three-dimensional Ir-192 source. In this study, geometry factor was calculated using segmented sources integration method by dividing microSelectron HDR Ir-192 source into smaller parts. The Monte Carlo code (MCNPX 2.5.0) was used to calculate the dose rate D(r,theta) at a point (r,theta) away from a HDR Ir-192 source in spherical water phantom with 30 cm diameter. Finally, anisotropy function and radial dose function were calculated from obtained results. The obtained geometry factor was compared with that calculated from line source approximation. Similarly, obtained anisotropy function and radial dose function were compared with those derived from MCPT results by Williamson. The geometry factor calculated from segmented sources integration method and line source approximation was within 0.2% for r> or =0.5 cm and 1.33% for r=0.1 cm, respectively. The relative-root mean square error (R-RMSE) of anisotropy function obtained by this study and Williamson was 2.33% for r=0.25 cm and within 1% for r>0.5 cm, respectively. The R-RMSE of radial dose function was 0.46% at radial distance from 0.1 to 14.0 cm. The geometry factor acquired from segmented sources integration method and line source approximation was in good agreement for r> or =0.1 cm. However, application of segmented sources integration method seems to be valid, since this method using three-dimensional Ir-192 source provides more realistic geometry factor. The anisotropy function and radial dose function estimated from MCNPX in this study and MCPT by Williamson are in good agreement within uncertainty of Monte Carlo codes except at radial distance of r=0.25 cm. It is expected that Monte Carlo code used in this study could be applied to other sources utilized for brachytherapy.
Subject(s)
Anisotropy , Brachytherapy , Organothiophosphorus Compounds , Uncertainty , WaterABSTRACT
PURPOSE: The diverse experimental environments in microarray technology, such as the different platforms or different RNA sources, can cause biases in the analysis of multiple microarrays. These systematic effects present a substantial obstacle for the analysis of microarray data, and the resulting information may be inconsistent and unreliable. Therefore, we introduced a simple integration method for combining microaray data sets that are derived from different experimental conditions, and we expected that more reliable information can be detected from the combined data set rather than from the separated data sets. MATERIALS AND METHODS: This method is based on the distributions of the gene expression ratios among the different microarray data sets and it transforms, gene by gene, the gene expression ratios into the form of the reference data set. The efficiency of the proposed integration method was evaluated using two microarray data sets, which were derived from different RNA sour-ces, and a newly defined measure, the mixture score. RESULTS: The proposed integration method intermixed the two data sets that were obtained from different RNA sources, which in turn reduced the experimental bias between the two data sets, and the mixture score increased by 24.2%. A data set combined by the proposed method preserved the inter-group relationship of the separated data sets. CONCLUSION: The proposed method worked well in adjusting systematic biases, including the source effect. The ability to use an effectively integrated microarray data set yields more reliable results due to the larger sample size and this also decreases the chance of false negatives.
Subject(s)
Bias , Dataset , Gene Expression , RNA , Sample SizeABSTRACT
PBL and CTM integration method is a kind of heuristic education mode of regarding student as the center of education.In order to explore the application result of this teaching method in the curriculum of nursing ethics laws and regulations,we put this mode into practice and regard nursing students as research objects.Questionnaire investigation and paper test are applied to evaluate the teaching effect.The study result shows that PBL and CTM integration method is certainly a well-established method to enhance teaching quality in the curriculum of nursing ethics laws and regulations.