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Objective To provide a reference for avoiding the harm to critical target organs following considerable inhalation exposure to the transuranium element americium (Am) as well as post-accident decorporation or other radiation protection measures. Methods We established calculation programs based on the generic criteria for internal radiation emergency preparedness and response in the IAEA Safety Guide No.GSG-2 and current new ICRP biokinetic models and parameters, taking an inhalation of 241Am (activity mean aerodynamic diameter of 5 μm, σ = 2.5) by an adult worker as an example; and determined that the critical target organs were the lung AI region, red bone marrow, and the main source organs leading to acute doses to the critical target organs were the lung AI region, blood, and trabecular bone surface. Results The retention fractions in the main source organs over time after 241Am inhalation were calculated. Conclusion After being absorbed into blood, Am moves quickly to other parts, and Am of different absorption types shows similar early changes in retention fractions in blood: the retention fractions of Am of S, M, and F types in blood peak around 0.03 d, and then halve around 1.7 d. Inhaled Am shows different changes over time in retention fractions in the lung AI region and trabecular bone surface in the early stage: the retention fractions of S- and M-type Am in the lung AI region change little with time, while F-type Am transfers quickly from the lung to blood; In trabecular bone surface, S-type Am increases quickly in the first 7 d, M-type Am gradually increases mainly in the first 2 weeks, and F-type Am increases quickly in the first 2 d.
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Objective To evaluate the migration of plutonium aerosol caused by α recoil. Methods In this paper, the recoil deposition and Brownian motion of plutonium-containing nanoaerosols were simulated by Monte Carlo method. The recoil angle and the vertical first landing time of Brownian motion in the process of settling were sampled, and then the lateral displacements of Brownian motion were sampled to determine the final settling position of aerosol. Results For aerosols with particle sizes of 10-50 nm, the maximum migration distance of a single recoil settling was 1.39 μm. Brownian motion increased the migration capacity. Although there was a high likelihood that aerosols settled within 100 μm, there remained a slight probability of long-term suspension in the air. Conclusion The α recoil is one of the mechanisms of plutonium aerosol migration. An important mechanism for long-distance migration of nanoaerosols is that Brownian motion after recoil may cause them to suspend for a long time.
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For ordinary people, when it comes to nuclear, radiation occurs to their mind, for fear of nuclear. In fact, radiation is almost everywhere. More than 80 percent of our exposure is from natural sources and only less than 20 percent is human made-mainly from radiation applications used in medicine. The dose we absorb from natural background radiation is about 2.4 mSv per year.
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Objective Collect and analyze data of radiation level of 210Po/210Pb in cigarettes in China, evaluate the internal radiation dose caused by smoking to Chinese smokers and compare it with other countries. Methods The radiation levels of 210Po/210Pb in cigarettes in domestic and foreign countries were summarized and analyzed, and the fractions of 210Po/210Pb in mainstream smoke were recommended, and the internal radiation doses to smokers in China were estimated. Results In 2015, there were 320 million smokers among aged 15 and above in China with an average smoking amount of 15.2 cigarettes per day. The average activities of 210Po/210Pb weighted by the number of cigarette brands were 28.2 mBq per cigarette and 39.3 mBq per cigarette respectively. The mainstream smoke fraction of 20% of 210Po was used to make the does estimation which was the mean value of the experimental results of simulator and volunteers, and that of 210Pb was 10% measured by simulators. Based on the average smoking amount per day and the number of smokers in China, the annual effective dose of current smokers in China is 126 μSv·a−1, and the collective effective dose is 40746 man·Sv. Conclusion The content of 210Po/210Pb in Chinese cigarettes is about 2～3 times that of other country's cigarettes. However, the fraction of mainstream smoke and dose conversion coefficient of 210Po/210Pb adopted in this paper are different from those in other literatures. Therefore, the estimated dose of 20 cigarettes for Chinese smokers is lower than that for smokers in some countries.
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Objective:To investigate the diagnosis and treatment of abdominal cocoon (AC).Methods:The clinical manifestations, findings during surgery, treatments, and follow-up results of 26 cases of AC were retrospectively studied from Jan 2001 to Jan 2019.Results:All of 26 cases were diagnosed as AC definitely by laparotomy, and were categorized into 2 types: type Ⅰ is of absence of second enterocoelia (18 cases, 69%) while type Ⅱ shows second enterocoelia (8cases, 31%). Twenty cases (12 type Ⅰ, 8 type Ⅱ) underwent membrane excision and careful enterodialysis to release the small intestine entirely or partially, while the other 6 cases (all were type Ⅰ) did not. All the patients recovered smoothly.Conclusions:AC can be categorized into two types, Surgery is recommended for type Ⅱ and part of type Ⅰ with severe complications.
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The Gram negative strain H8005 was isolated from alkali silt on the site of paper mill. Under optimum conditions, the alkali cellulase activitig (CMCase) of shaking flask culture of H8005 was 4.2 IU/mL. The optimal conditions for the enzymatic reaction were about 55℃ and pH 8.0. At pH 7.0～9.0, the enzyme showed high activity and good stability. Mn~(2+ ), Fe~(3+) were the activators and Cu~(2+) , Pb~(2+ )were the inhibitors of the enzyme. The novel cellulase produced by H8005 showed great potential in the textile biofinishing and detergent industry.