Partial characterization,UV-induction and photoprotective function of sunscreen pigment,scytonemin from Rivularia sp. HKAR-4

Scytonemin, located in the extracellular polysaccharide sheath of some cyanobacterial species is considered an efficient natural photoprotectant against lethal doses of ultraviolet (UV) radiations. In the present study, scytonemin from the cyanobacterium Rivularia sp. HKAR-4 was partially characterized and investigated for its induction by UV radiation as well as its role in photoprotection. High-performance liquid chromatography (HPLC) with photodiode-array detection studies revealed the presence of an UV-absorbing compound with absorption maximum at 386 nm. Based on its absorption spectrum and ion trap liquid chromatography/mass spectrometry (LC/MS) analysis, the compound was confirmed as scytonemin. In comparison to photosynthetically active radiation, a significant induction in the synthesis of scytonemin was found under UV-stress. Scytonemin also exhibited efficient photoprotective ability by detoxifying the in vivo reactive oxygen species (ROS) generated by UV radiation and by reducing the formation of thymine dimers. To the best of our knowledge this is the first report on the UV-screening effects of scytonemin on in vivo ROS generation and thymine dimer formation in any cyanobacterial strain. Based on these findings, we conclude that scytonemin may play a vital role in the survival and sustainability of cyanobacterial life in adverse environmental conditions such as under high solar irradiances.     

Mapping of cosmic radiation dose in Croatia

The Earth is continually bombarded by high-energy particles coming from the outer space and the sun. These particles, termed cosmic radiation, interact with nuclei of atmospheric constituents and decrease in intensity with depth in the atmosphere. Measurements of photon and gamma radiation, performed with a Radiameter at 1 m above the ground, indicated dose rates of 50-100 nSv/h.The neutron dose rate was measured with the CR-39 track etch detector calibrated by the CERN-EU high-energy Reference Field (CERF) facility. Correlation between neutron dose rates and altitudes at 36 sites was examined in order to obtain a significant positive correlation coefficient; the resulting linear regression enabled estimation of a neutron dose at particular altitude. The measured neutron dose rate in Osijek (altitude of 89 m, latitude of 45.31° N) was 110 nSv/h.     

Activity concentrations and dose rates from decorative granite countertops

The gamma radiation emitted from a variety of commercial decorative granites available for use in U.S. homes has been measured with portable survey meters as well as an NaI(Th) gamma spectrometer. The ⁴⁰K, U-nat, and ²³²Th activity concentrations were determined using a full-spectrum analysis. The dose rates that would result from two different arrangements of decorative granite slabs as countertops were explored in simulations involving an adult anthropomorphic phantom.     

Radionuclides in marine mammals off the Portuguese coast

Radionuclide analyses were performed in tissue samples including muscle, gonad, liver, mammary gland, and bone of marine mammals stranded on the Portuguese west coast during January-July 2006. Tissues were collected from seven dolphins (Delphinus delphis and Stenella coeruleoalba) and one pilot whale (Globicephala sp.). Samples were analyzed for ²¹⁰Po and ²¹⁰Pb by alpha spectrometry and for ¹³⁷Cs and ⁴⁰K by gamma spectrometry. Po-210 concentrations in common dolphin’s muscle (D. delphis) averaged 56 ± 32 Bq kg⁻¹ wet weight (w.w.), while ²¹⁰Pb averaged 0.17 ± 0.07 Bq kg⁻¹ w.w., ¹³⁷Cs averaged 0.29 ± 0.28 Bq kg⁻¹ w.w., and ⁴⁰K 129 ± 48 Bq kg⁻¹ w.w. Absorbed radiation doses due to these radionuclides for the internal organs of common dolphins were computed and attained a 1.50 μGy h⁻¹ on a whole body basis. ²¹⁰Po was the main contributor to the weighted absorbed dose, accounting for 97% of the dose from internally accumulated radionuclides. These computed radiation doses in dolphins are compared to radiation doses from ²¹⁰Po and other radionuclides reported for human tissues. Due to the high ²¹⁰Po activity concentration in dolphins, the internal radiation dose in these marine mammals is about three orders of magnitude higher than in man.     

放射源在线监控系统设计与应用

为了防止在用放射源发生脱落、丢失、超标使用、私自转移等情况,最大限度避免辐射安全事故。有必要设计建立放射源在线监控系统,对放射源放射性指标(辐射剂量率)及所处位置(经纬度)实行连续的自动监测。并通过各级监管平台设置放射源超标、异动等报警程序,全面提升放射源科学监管水平。     

220千伏高压输电线路对电磁环境的影响分析及防治对策

通过对220kV输电线路电磁辐射的实际测量和理论计算,研究和讨论了220kV单回路和双回路输电线产生的电磁辐射对环境的影响,并提出降低电磁辐射水平的对策与建议。     

论辐射事故发生原因和预防、解决措施

随着科学技术和社会经济的高速发展,核技术在工业、农业、医疗等领域得到了越来越广泛的应用,但其在带给人类巨大经济效益的同时,也给社会安全带来了潜在的威协,辐射事故时有发生,不仅污染环境,甚至危及人们的身体健康和生命。文中对辐射事故发生的类型、级别以及发生的原因进行了分析,提出了预防和解决的措施。     

徐州市电磁辐射环境的污染现状调查及评价

调查了徐州市电磁辐射污染源的状况,分析了其电磁辐射环境质量的现状,并对全市电磁辐射环境质量进行了评价,指出了分析工作中存在的问题,提出了防治对策。     

High background radiation investigated by gamma spectrometry of the soil in the southwestern region of Cameroon

The aim of this work is to determine the radioactivity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K in sub-surface (0-5 cm) soil samples collected from Awanda, Bikoué, Ngombas in the southwestern region of Cameroon, to assess their contribution to the external dose exposure relative to the United Nation Scientific Committee on Effects of Atomic Radiation (UNSCEAR) data. An HPGe p-type detector coupled to a multichannel analyzer was used to perform measurements and data processing. The activity concentrations of ²²⁶Ra varied from 0.06 ± 0.01 to 0.27 ± 0.02 kBq kg⁻¹ with a mean value of 0.13 ± 0.01 kBq kg⁻¹ wet weight. The activity concentrations of ²³²Th varied from 0.10 ± 0.01 to 0.70 ± 0.05 kBq kg⁻¹ with a mean value of 0.39 ± 0.03 kBq kg⁻¹ wet weight, and ⁴⁰K concentrations varied from 0.37 ± 0.02 to 1.53 ± 0.11 kBq kg⁻¹ with a mean value of 0.85 ± 0.07 kBq kg⁻¹ wet weight, respectively. The mean value of outdoor annual effective doses were estimated to be 0.48 mSv y⁻¹, 0.39 mSv y⁻¹ and 0.38 mSv y⁻¹ from Ngombas, Awanda and Bikoué, respectively. The studied areas can be said to have a high background radiation level.     

套管喷旋流技术在热交换器中的应用

套管式空气预热器的传热元件是由两根不同直径的管子套在一起组成,外管由高温烟气获取热量,充分利用排烟余热,内管中通入冷空气,内外管通过对流和辐射的传热方式实现热量传递,是一种结构简单、换热效率高的新型空气换热器。