Needs in scintimammography applications,especially for small animal cardiac imaging,lead to develop a small field of view,high spatial resolution gamma camera with a pinhole collimator.However the ideal pinhole collim...Needs in scintimammography applications,especially for small animal cardiac imaging,lead to develop a small field of view,high spatial resolution gamma camera with a pinhole collimator.However the ideal pinhole collimator must keep a compromise between spatial resolution and sensitivity.In order to design a pinhole collimator with an optimized sensitivity and spatial resolution,the spatial resolution and the geometric sensitivity response as a function of the source to collimator distance has been obtained by means of Monte-Carlo simulation for a small field of view gamma camera with a pinhole collimator of various-hole diameters.The results show that the camera with pinhole of 1 mm,1.5 mm and 2 mm diameter has respectively spatial resolution of 1.5 mm,2.25 mm and 3 mm and geometric sensitivity of 0.016%,0.022%and 0.036%,while the source to collimator distance is 3 cm.We chose the pinhole collimator with hole diameter size of 1.2 mm for our the gamma camera designed based on the trade-off between sensitivity and resolution.展开更多
The effects of ZnO-B2O3 （ZB2） on the sintering behavior and microwave dielectric properties of （Ca0.254Li0.19Sm0.14）TiO3 ceramics were investigated. The densities of the specimens reached the maximum value by addi...The effects of ZnO-B2O3 （ZB2） on the sintering behavior and microwave dielectric properties of （Ca0.254Li0.19Sm0.14）TiO3 ceramics were investigated. The densities of the specimens reached the maximum value by adding 3 wt.% ZB2 and then decreased. The sintering temperature of the specimens was lowered from 1300 to 1100℃ without degradation of the microwave dielectric properties. The （Ca0.254Li0.19Sm0.14）TiO3＋ 3 wt.% ZB2 sintered at 1100℃ for 3 h showed good microwave dielectric properties, εr= 108.2, Qf= 6545 GHz, and rf= 6.5 ppm/℃, respectively, indicating that ZB2 was an effective sintering aid to improve the densification and microwave dielectric properties of （Ca0.254Li0.19Sm0.14）TiO3 ceramics.展开更多
Li/Sb-doped (Na,K)NbO3 with a nominal composition of [Li0.05(Na0.535K0.48)0.95](Nb0.94Sb0.06)O3 ceramic was synthesized by normal sintering. The phase structure, microstructure, and electrical properties were investig...Li/Sb-doped (Na,K)NbO3 with a nominal composition of [Li0.05(Na0.535K0.48)0.95](Nb0.94Sb0.06)O3 ceramic was synthesized by normal sintering. The phase structure, microstructure, and electrical properties were investigated with a special emphasis on the influence of the sintering temperature. A polymorphic phase transition (PPT) from orthorhombic to tetragonal symmetry was observed when the sintering temperature was raised from 1040 to 1050 ℃, whereby the piezoelectric coefficient d33 and the electromechanical coupling coefficient kp reached the peak values of 245 pC·N-1 and 41.2%, respectively. The PPT induced by varying the sintering temperature is due to the different volatilization extents of alkali metals and appears to a lower sintering temperature with increasing Li content. The trace modifying of alkali metal content is more effective than doping B site element to enhance the d33 value.展开更多
Lead-free piezoelectric NaxK1-xNbO3(x=0.3-0.8)(NKN)ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special emphasi...Lead-free piezoelectric NaxK1-xNbO3(x=0.3-0.8)(NKN)ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na content.The grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic,which indicates the presence of a transitional composition between two different orthorhombic phases,which is similar to the behavior of morphotropic phase boundary(MPB)in NaxK1-xNbO3 ceramics.Such MPB-like behavior contributes to the enhanced piezoelectric coefficient d33 of 122 pC/N,planar-mode electromechanical coupling coefficient kP of 28.6%,and dielectric constantεr of 703,respectively for the Na0.7K0.3NbO3 ceramic.Cubic temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 420°C and 200°C,respectively.展开更多
目的探讨人纤维蛋白原(FIB)在急诊创伤性凝血病中的应用及危险因素分析。方法选取2018年1月至2019年12月联保部队第九O八医院收治的100例严重外伤所致创伤性凝血病患者作为观察组,按照随机数字表法分为A组与B组,每组50例;另选取50例急...目的探讨人纤维蛋白原(FIB)在急诊创伤性凝血病中的应用及危险因素分析。方法选取2018年1月至2019年12月联保部队第九O八医院收治的100例严重外伤所致创伤性凝血病患者作为观察组,按照随机数字表法分为A组与B组,每组50例;另选取50例急诊创伤性非凝血病患者作为对照组。A组给予急诊创伤性常规治疗,B组在A组基础上给予人FIB治疗,对照组治疗方法同A组。比较A组和B组治疗前后凝血功能指标[活化部分凝血活酶时间(APTT)、凝血酶原时间(PT)、FIB、D-二聚体(D-D)],24 h新鲜冰冻血浆(FFP)输注量、24 h浓缩红细胞(CRBC)输注量、ICU住院时间及病死率。采用多因素Logistic回归分析影响创伤性凝血病的危险因素。结果治疗后,两组APTT、PT均短于治疗前,FIB水平均高于治疗前,D-D水平均低于治疗前,且B组APTT、PT均短于A组,FIB水平高于A组,D-D水平低于A组,差异有统计学意义(P<0.001)。B组24 h FFP输注量、24 h CRBC输注量均少于A组,病死率低于A组,ICU住院时间短于A组,差异有统计学意义(P<0.05)。观察组APTT、PT均长于对照组,国际标准化比值(INR)、损伤严重程度评分(ISS)、急性生理学和慢性健康状况评价(APACHE)Ⅱ评分、格拉斯哥昏迷(GCS)评分及碱缺失(BD)≥6 mol/L、合并重型颅脑损伤(STBI)、体温<35℃比例均高于对照组,24 h FFP、24 h CRBC输注量均多于对照组,血红蛋白(Hb)水平、血小板计数(PLT)均低于对照组,差异有统计学意义(P<0.05)。多因素Logistic回归分析显示,PLT低、GCS评分<6分、BD≥6 mol/L、合并STBI是创伤性凝血病发生的独立危险因素(P<0.05)。结论人FIB可改善急性创伤性凝血病凝血功能,减少血液输注量,缩短ICU住院时间及降低病死率,临床疗效显著,PLT低水平、GCS评分<6分、BD≥6 mol/L、合并STBI是创伤性凝血病发生的独立危险因素。展开更多
基金Supported by National Foundation of Nature Science of China(No.10275063)
文摘Needs in scintimammography applications,especially for small animal cardiac imaging,lead to develop a small field of view,high spatial resolution gamma camera with a pinhole collimator.However the ideal pinhole collimator must keep a compromise between spatial resolution and sensitivity.In order to design a pinhole collimator with an optimized sensitivity and spatial resolution,the spatial resolution and the geometric sensitivity response as a function of the source to collimator distance has been obtained by means of Monte-Carlo simulation for a small field of view gamma camera with a pinhole collimator of various-hole diameters.The results show that the camera with pinhole of 1 mm,1.5 mm and 2 mm diameter has respectively spatial resolution of 1.5 mm,2.25 mm and 3 mm and geometric sensitivity of 0.016%,0.022%and 0.036%,while the source to collimator distance is 3 cm.We chose the pinhole collimator with hole diameter size of 1.2 mm for our the gamma camera designed based on the trade-off between sensitivity and resolution.
基金supported by the National Natural Science Foundation of China (No. 50572008)
文摘The effects of ZnO-B2O3 （ZB2） on the sintering behavior and microwave dielectric properties of （Ca0.254Li0.19Sm0.14）TiO3 ceramics were investigated. The densities of the specimens reached the maximum value by adding 3 wt.% ZB2 and then decreased. The sintering temperature of the specimens was lowered from 1300 to 1100℃ without degradation of the microwave dielectric properties. The （Ca0.254Li0.19Sm0.14）TiO3＋ 3 wt.% ZB2 sintered at 1100℃ for 3 h showed good microwave dielectric properties, εr= 108.2, Qf= 6545 GHz, and rf= 6.5 ppm/℃, respectively, indicating that ZB2 was an effective sintering aid to improve the densification and microwave dielectric properties of （Ca0.254Li0.19Sm0.14）TiO3 ceramics.
基金financially supported by the Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20090006110010)Beijing Natural Science Foundation(No.2112028)
文摘Li/Sb-doped (Na,K)NbO3 with a nominal composition of [Li0.05(Na0.535K0.48)0.95](Nb0.94Sb0.06)O3 ceramic was synthesized by normal sintering. The phase structure, microstructure, and electrical properties were investigated with a special emphasis on the influence of the sintering temperature. A polymorphic phase transition (PPT) from orthorhombic to tetragonal symmetry was observed when the sintering temperature was raised from 1040 to 1050 ℃, whereby the piezoelectric coefficient d33 and the electromechanical coupling coefficient kp reached the peak values of 245 pC·N-1 and 41.2%, respectively. The PPT induced by varying the sintering temperature is due to the different volatilization extents of alkali metals and appears to a lower sintering temperature with increasing Li content. The trace modifying of alkali metal content is more effective than doping B site element to enhance the d33 value.
基金supported by the National Natural Science Foundation of China(No.50842028)the National Basic Research Priorities Program of China(No.2007CB613301)
文摘Lead-free piezoelectric NaxK1-xNbO3(x=0.3-0.8)(NKN)ceramics were fabricated by normal sintering at 1060°C for 2 h.Microstructures and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na content.The grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3NbO3 ceramic,which indicates the presence of a transitional composition between two different orthorhombic phases,which is similar to the behavior of morphotropic phase boundary(MPB)in NaxK1-xNbO3 ceramics.Such MPB-like behavior contributes to the enhanced piezoelectric coefficient d33 of 122 pC/N,planar-mode electromechanical coupling coefficient kP of 28.6%,and dielectric constantεr of 703,respectively for the Na0.7K0.3NbO3 ceramic.Cubic temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 420°C and 200°C,respectively.
文摘目的探讨人纤维蛋白原(FIB)在急诊创伤性凝血病中的应用及危险因素分析。方法选取2018年1月至2019年12月联保部队第九O八医院收治的100例严重外伤所致创伤性凝血病患者作为观察组,按照随机数字表法分为A组与B组,每组50例;另选取50例急诊创伤性非凝血病患者作为对照组。A组给予急诊创伤性常规治疗,B组在A组基础上给予人FIB治疗,对照组治疗方法同A组。比较A组和B组治疗前后凝血功能指标[活化部分凝血活酶时间(APTT)、凝血酶原时间(PT)、FIB、D-二聚体(D-D)],24 h新鲜冰冻血浆(FFP)输注量、24 h浓缩红细胞(CRBC)输注量、ICU住院时间及病死率。采用多因素Logistic回归分析影响创伤性凝血病的危险因素。结果治疗后,两组APTT、PT均短于治疗前,FIB水平均高于治疗前,D-D水平均低于治疗前,且B组APTT、PT均短于A组,FIB水平高于A组,D-D水平低于A组,差异有统计学意义(P<0.001)。B组24 h FFP输注量、24 h CRBC输注量均少于A组,病死率低于A组,ICU住院时间短于A组,差异有统计学意义(P<0.05)。观察组APTT、PT均长于对照组,国际标准化比值(INR)、损伤严重程度评分(ISS)、急性生理学和慢性健康状况评价(APACHE)Ⅱ评分、格拉斯哥昏迷(GCS)评分及碱缺失(BD)≥6 mol/L、合并重型颅脑损伤(STBI)、体温<35℃比例均高于对照组,24 h FFP、24 h CRBC输注量均多于对照组,血红蛋白(Hb)水平、血小板计数(PLT)均低于对照组,差异有统计学意义(P<0.05)。多因素Logistic回归分析显示,PLT低、GCS评分<6分、BD≥6 mol/L、合并STBI是创伤性凝血病发生的独立危险因素(P<0.05)。结论人FIB可改善急性创伤性凝血病凝血功能,减少血液输注量,缩短ICU住院时间及降低病死率,临床疗效显著,PLT低水平、GCS评分<6分、BD≥6 mol/L、合并STBI是创伤性凝血病发生的独立危险因素。
