Aim: Lead aprons are used to protect against scattered radiation from the patient during interventional procedures and certain special conventional radiological examinations. Given the importance of the role lead apro...Aim: Lead aprons are used to protect against scattered radiation from the patient during interventional procedures and certain special conventional radiological examinations. Given the importance of the role lead aprons are supposed to play in radiation protection, we propose to assess their conformity in medical imaging departments in public and religious hospitals in Togo. Materials and method: A multi-centre survey conducted from 26 November to 06 December 2021 in the radiology departments of public and religious health facilities in Togo. All aprons in use were included. The evaluation criteria were physical (visual), quantitative (radiographic) and qualitative (dosimetric). Results: We had registred 43 aprons among wich 27 (62.79%) leaded aprons were labelled non-compliant and 16 (37.21%) were labelled compliant. Of the aprons judged to be non-compliant, 70.37% were more than 10 years old and 96.30% showed defects on the radiographic images. The most common defects were vampire marks (18.64%), multiple folds (16.96%), cracks (16.96%), multiple cracks (15.25%), tears (8.47%), absence of lead (5.08%), holes (3.39%) and lead corrosion (1.69%). Defective aprons (62.96%) had at least two defects. The defects were of thoraco-abdomino-pelvic (74.07%), thoracic (14.82%) and abdomino-pelvic (11.11%) topography. For indirect exposure at 50 and 70 kilovolts, all the aprons had an attenuation factor greater than 90%. After dosimetric measurement, 13.95% of aprons had attenuation factors below 90% for indirect exposure at 100 kilovolts. Conclusion: The compliance of the leaded decks is trifactorial (physical, radiographic and dosimetric). However, there is no significant difference in X-ray attenuation capacity between defective and normal decks.展开更多
Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ ...Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ features. The eutectic Sn-9Zn alloy is among them. This paper investigated the mechanical and electrical properties of Sn-9Zn-x (Ag, Cu, Sb);{x = 0.2, 0.4, and 0.6} lead-free solder alloys. The mechanical properties such as elastic modulus, ultimate tensile strength (UTS), yield strength (YS), and ductility were examined at the strain rates in a range from 4.17 10−3 s−1 to 208.5 10−3 s−1 at room temperature. It is found that increasing the content of the alloying elements and strain rate increases the elastic modulus, ultimate tensile strength, and yield strength while the ductility decreases. The electrical conductivity of the alloys is found to be a little smaller than that of the Sn-9Zn eutectic alloy.展开更多
With the coming of the information era and the flaming of the international communication, the English language has already made itself a very important and universally used language. However, because of the lack of c...With the coming of the information era and the flaming of the international communication, the English language has already made itself a very important and universally used language. However, because of the lack of cultural knowledge of the target language, many cross-cultural contacts turn out to be frustrating or even a failure. Therefore, to guarantee an effective intercultural communication, a lot of knowledge about target culture is needed; besides, people should have a good command of different cultures and should fully understand the cultural differences in intercultural communication. So it is important and of great necessity to take culture into consideration in FLT. But how to acquire cultural knowledge effectively always exists as a problem. In this thesis, the author attempts to solve the problem by using schema theory. Schema is a sort of background knowledge stored in a person's mind in order to perceive and understand the world. Usually if a person possesses more foreign cultural schemata, he or she will behave appropriately in cross-cultural communication. Therefore, the task left is how to help students build up their cultural schemata about a foreign language.展开更多
语义韵是一种特殊的搭配现象,展示的是词语搭配的特殊行为,一般分为积极语义韵、消极语义韵和中性语义韵。EFL(English as a foreign language)学习者的词语搭配行为历来是外语教学研究中的重点。本研究通过对cause和lead to的语义韵研...语义韵是一种特殊的搭配现象,展示的是词语搭配的特殊行为,一般分为积极语义韵、消极语义韵和中性语义韵。EFL(English as a foreign language)学习者的词语搭配行为历来是外语教学研究中的重点。本研究通过对cause和lead to的语义韵研究和学生所做试题的成绩对比,分析研究EFL学习者的英语语义韵意识是否会随英语水平的提高而提高。展开更多
The article mainly discusses the necessity of leading-in in English class and gives some effective methods of Leadingin on how to improve students’learning enthusiasm.
远离星下点的lead(浮冰间的开阔水域)对回波波形有重要影响,使计算得到的瞬时海面高存在较大偏差。精确地区分出回波波形中的lead波形,能有效提高瞬时海面高(SSH)的测量精度。目前常用Laxon13算法(PP和SSD)来识别回波中的lead波形,进而...远离星下点的lead(浮冰间的开阔水域)对回波波形有重要影响,使计算得到的瞬时海面高存在较大偏差。精确地区分出回波波形中的lead波形,能有效提高瞬时海面高(SSH)的测量精度。目前常用Laxon13算法(PP和SSD)来识别回波中的lead波形,进而计算海冰的出水高度。本文针对Cryosat-2高度计的SARIn模式数据,在Laxon13算法的基础上进行改进,新增了8参数,采用了一种更为精确的lead识别算法,即计算回波能量值在各参数下的统计量,设定分界值(阈值)以识别出lead。该方法采用MAX、PP、PPL、PPR、SSD、LEW、TEW、SLEW、KURT、SKEW共10种参数对lead进行识别,绘制了实验区域基于各个参数的分类图示并识别出lead波形,与Arctic and Antarctic Research Institute(AARI)提供的实际冰况图进行对比分析,确定lead有效识别的5参数。展开更多
Objective To investigate the blood lead level in children aged 0-6 years in urban areas of China. Methods Fourteen cities were selected as sites under surveillance. A total of 44 045 peripheral blood specimens were co...Objective To investigate the blood lead level in children aged 0-6 years in urban areas of China. Methods Fourteen cities were selected as sites under surveillance. A total of 44 045 peripheral blood specimens were collected from 2004 to 2006, during which 15 727, 14 737, and 13 584 specimens were tested in 2004, 2005, and 2006, respectively. Tungsten atomizer absorption spectrophotometer was employed to determine blood lead level. Results The geometric mean blood lead level in the tested children was 47.10 μg/L with 10.10% ≥100 μg/L, 46.17 μg/L with 7.78% ≥100 μg/L, and 47.03 μg/L with 7.30% ≥ 100μg/L in 2004, 2005, and 2006, respectively. The blood lead levels seemed to tend to rise in parallel with the increase of age of the children and were higher in boys （48.84 μg/L, 47.56μg/L, and 47.78 μg/L in the 3 respective years） than in girls （45.00 μg/L, 44.53μg/L, and 46.13 μg/L）. Conclusion The blood lead levels in children in cities of China are lower than those in previous national studies, but higher than those in developed countries. Childhood lead poisoning remains a public health problem in China.展开更多
Soil contaminated with heavy metals cadmium （Cd） and lead （Pb） is hard to be remediated. Phytoremediation may be a feasible method to remove toxic metals from soil, but there are few suitable plants which can hype...Soil contaminated with heavy metals cadmium （Cd） and lead （Pb） is hard to be remediated. Phytoremediation may be a feasible method to remove toxic metals from soil, but there are few suitable plants which can hyperaccumulate metals. In this study, Cd and Pb accumulation by four plants including sunflower （Helianthus annuus L.）, mustard （Brassicajuncea L.）, alfalfa （Medicago sativa L.）, ricinus （Ricinus communis L.） in hydroponic cultures was compared. Results showed that these plants could phytoextract heavy metals, the ability of accumulation differed with species, concentrations and categories of heavy metals. Values of BCF （bioconcentration factor） and TF （translocation factor） indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals. Changes on the biomass of plants, pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures. Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals, such as pH and Eh regulations, and so forth.展开更多
A field trial was conducted to evaluate the reduction of bioavailability of heavy metals including lead (Pb), zinc (Zn) and cadmium (Cd) in a soil contaminated by mining tailings in Shaoxing, Zhejiang, China. Three co...A field trial was conducted to evaluate the reduction of bioavailability of heavy metals including lead (Pb), zinc (Zn) and cadmium (Cd) in a soil contaminated by mining tailings in Shaoxing, Zhejiang, China. Three commercial phosphate (P) fertilizers including phosphate rock (PR), calcium magnesium phosphate (CMP), and single superphosphate (SSP) were applied to the plot at three P application rates, 50, 300, and 500 g/m2 with 9 treatments and control (CK). Plants, water soluble and exchangeable (WE) extra...展开更多
The removal of heavy-metal ions from aqueous solutions by using dried activated sludge has been investigated in batch systems. Effect of solution pH, initial metal ion concentration, and temperature were determined. T...The removal of heavy-metal ions from aqueous solutions by using dried activated sludge has been investigated in batch systems. Effect of solution pH, initial metal ion concentration, and temperature were determined. The results of the kinetic studies showed that the uptake processes of the two metal ions（Cd（Ⅱ） and Pb（Ⅱ）） followed the pseudo-second-order rate expression. The equilibrium data fitted very well to both the Langmuir and Freundlich adsorption models. The FT-IR analysis showed that the main mechanism of Cd（Ⅱ） and Pb（Ⅱ） biosorption onto dried activated sludge was their binding with amide I group.展开更多
文摘Aim: Lead aprons are used to protect against scattered radiation from the patient during interventional procedures and certain special conventional radiological examinations. Given the importance of the role lead aprons are supposed to play in radiation protection, we propose to assess their conformity in medical imaging departments in public and religious hospitals in Togo. Materials and method: A multi-centre survey conducted from 26 November to 06 December 2021 in the radiology departments of public and religious health facilities in Togo. All aprons in use were included. The evaluation criteria were physical (visual), quantitative (radiographic) and qualitative (dosimetric). Results: We had registred 43 aprons among wich 27 (62.79%) leaded aprons were labelled non-compliant and 16 (37.21%) were labelled compliant. Of the aprons judged to be non-compliant, 70.37% were more than 10 years old and 96.30% showed defects on the radiographic images. The most common defects were vampire marks (18.64%), multiple folds (16.96%), cracks (16.96%), multiple cracks (15.25%), tears (8.47%), absence of lead (5.08%), holes (3.39%) and lead corrosion (1.69%). Defective aprons (62.96%) had at least two defects. The defects were of thoraco-abdomino-pelvic (74.07%), thoracic (14.82%) and abdomino-pelvic (11.11%) topography. For indirect exposure at 50 and 70 kilovolts, all the aprons had an attenuation factor greater than 90%. After dosimetric measurement, 13.95% of aprons had attenuation factors below 90% for indirect exposure at 100 kilovolts. Conclusion: The compliance of the leaded decks is trifactorial (physical, radiographic and dosimetric). However, there is no significant difference in X-ray attenuation capacity between defective and normal decks.
文摘Although there are many lead-free soldering alloys on the market, none of them have ideal qualities. The researchers are combining binary alloys with a variety of additional materials to create the soldering alloys’ features. The eutectic Sn-9Zn alloy is among them. This paper investigated the mechanical and electrical properties of Sn-9Zn-x (Ag, Cu, Sb);{x = 0.2, 0.4, and 0.6} lead-free solder alloys. The mechanical properties such as elastic modulus, ultimate tensile strength (UTS), yield strength (YS), and ductility were examined at the strain rates in a range from 4.17 10−3 s−1 to 208.5 10−3 s−1 at room temperature. It is found that increasing the content of the alloying elements and strain rate increases the elastic modulus, ultimate tensile strength, and yield strength while the ductility decreases. The electrical conductivity of the alloys is found to be a little smaller than that of the Sn-9Zn eutectic alloy.
文摘With the coming of the information era and the flaming of the international communication, the English language has already made itself a very important and universally used language. However, because of the lack of cultural knowledge of the target language, many cross-cultural contacts turn out to be frustrating or even a failure. Therefore, to guarantee an effective intercultural communication, a lot of knowledge about target culture is needed; besides, people should have a good command of different cultures and should fully understand the cultural differences in intercultural communication. So it is important and of great necessity to take culture into consideration in FLT. But how to acquire cultural knowledge effectively always exists as a problem. In this thesis, the author attempts to solve the problem by using schema theory. Schema is a sort of background knowledge stored in a person's mind in order to perceive and understand the world. Usually if a person possesses more foreign cultural schemata, he or she will behave appropriately in cross-cultural communication. Therefore, the task left is how to help students build up their cultural schemata about a foreign language.
文摘语义韵是一种特殊的搭配现象,展示的是词语搭配的特殊行为,一般分为积极语义韵、消极语义韵和中性语义韵。EFL(English as a foreign language)学习者的词语搭配行为历来是外语教学研究中的重点。本研究通过对cause和lead to的语义韵研究和学生所做试题的成绩对比,分析研究EFL学习者的英语语义韵意识是否会随英语水平的提高而提高。
文摘The article mainly discusses the necessity of leading-in in English class and gives some effective methods of Leadingin on how to improve students’learning enthusiasm.
文摘远离星下点的lead(浮冰间的开阔水域)对回波波形有重要影响,使计算得到的瞬时海面高存在较大偏差。精确地区分出回波波形中的lead波形,能有效提高瞬时海面高(SSH)的测量精度。目前常用Laxon13算法(PP和SSD)来识别回波中的lead波形,进而计算海冰的出水高度。本文针对Cryosat-2高度计的SARIn模式数据,在Laxon13算法的基础上进行改进,新增了8参数,采用了一种更为精确的lead识别算法,即计算回波能量值在各参数下的统计量,设定分界值(阈值)以识别出lead。该方法采用MAX、PP、PPL、PPR、SSD、LEW、TEW、SLEW、KURT、SKEW共10种参数对lead进行识别,绘制了实验区域基于各个参数的分类图示并识别出lead波形,与Arctic and Antarctic Research Institute(AARI)提供的实际冰况图进行对比分析,确定lead有效识别的5参数。
文摘Objective To investigate the blood lead level in children aged 0-6 years in urban areas of China. Methods Fourteen cities were selected as sites under surveillance. A total of 44 045 peripheral blood specimens were collected from 2004 to 2006, during which 15 727, 14 737, and 13 584 specimens were tested in 2004, 2005, and 2006, respectively. Tungsten atomizer absorption spectrophotometer was employed to determine blood lead level. Results The geometric mean blood lead level in the tested children was 47.10 μg/L with 10.10% ≥100 μg/L, 46.17 μg/L with 7.78% ≥100 μg/L, and 47.03 μg/L with 7.30% ≥ 100μg/L in 2004, 2005, and 2006, respectively. The blood lead levels seemed to tend to rise in parallel with the increase of age of the children and were higher in boys （48.84 μg/L, 47.56μg/L, and 47.78 μg/L in the 3 respective years） than in girls （45.00 μg/L, 44.53μg/L, and 46.13 μg/L）. Conclusion The blood lead levels in children in cities of China are lower than those in previous national studies, but higher than those in developed countries. Childhood lead poisoning remains a public health problem in China.
基金Project supported by the National Natural Science Foundation of China(No.20477029,20337010)the National Basic Research Program(973)of China(No.2004CB18506).
文摘Soil contaminated with heavy metals cadmium （Cd） and lead （Pb） is hard to be remediated. Phytoremediation may be a feasible method to remove toxic metals from soil, but there are few suitable plants which can hyperaccumulate metals. In this study, Cd and Pb accumulation by four plants including sunflower （Helianthus annuus L.）, mustard （Brassicajuncea L.）, alfalfa （Medicago sativa L.）, ricinus （Ricinus communis L.） in hydroponic cultures was compared. Results showed that these plants could phytoextract heavy metals, the ability of accumulation differed with species, concentrations and categories of heavy metals. Values of BCF （bioconcentration factor） and TF （translocation factor） indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals. Changes on the biomass of plants, pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures. Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals, such as pH and Eh regulations, and so forth.
基金the National Natural Sci-ence Foundation of China (No. 40771100, 40432004)
文摘A field trial was conducted to evaluate the reduction of bioavailability of heavy metals including lead (Pb), zinc (Zn) and cadmium (Cd) in a soil contaminated by mining tailings in Shaoxing, Zhejiang, China. Three commercial phosphate (P) fertilizers including phosphate rock (PR), calcium magnesium phosphate (CMP), and single superphosphate (SSP) were applied to the plot at three P application rates, 50, 300, and 500 g/m2 with 9 treatments and control (CK). Plants, water soluble and exchangeable (WE) extra...
基金The National New Century Scholarship (No. NCET-05-0387) the France-China P2R Programs and the Specialized Research Fundfor the Doctoral Program of Higher Education (No. 20050247016)
文摘The removal of heavy-metal ions from aqueous solutions by using dried activated sludge has been investigated in batch systems. Effect of solution pH, initial metal ion concentration, and temperature were determined. The results of the kinetic studies showed that the uptake processes of the two metal ions（Cd（Ⅱ） and Pb（Ⅱ）） followed the pseudo-second-order rate expression. The equilibrium data fitted very well to both the Langmuir and Freundlich adsorption models. The FT-IR analysis showed that the main mechanism of Cd（Ⅱ） and Pb（Ⅱ） biosorption onto dried activated sludge was their binding with amide I group.
