^14C—尿素的制备

报道了由Ｂａ＾１４ＣＯ２制备＾１４Ｃ－尿素的方法，Ｂａ＾１４ＣＯ３于８２０－８５０℃，通过干燥氨气加热反应２．５－３．０ｈ，制得ＢａＮ＾１４Ｃｎ；ＢａＮ＾１４Ｃｎ经过Ｈ２Ｓ水解制得＾１４Ｃ－尿素，放射性产率为８４％，产品经高效液相色（ＨＰＬＣ）分析，化学纯度为９９．８％，放射化学纯度〉９９．９％，比活度可按需要加入载体来调节。     

[1—^14C]棕榈酸的合成

报道了由（＾１４Ｃ）碳酸钡产生＾１４ＣＯ２，并通过格氏反应制备（１－＾１４Ｃ）棕榈酸的方法，其放射性收率为４４．８％，经高效液相色谱分析测得放射化学纯度〉９９．５％，经薄层层析检测确证产品为不含任何杂质的（１－＾１４Ｃ）棕榈酸纯品。     

低压离子色谱法测定Mg^2＋和Ca^2＋离子

用低压离子色谱法测定水中的Ｍｇ＾２＋和Ｃａ＾２＋离子，Ｍｇ＾２＋离子在０－１０μｇ／ｍＬ，Ｃａ＾２＋在０－１２．５μｇ／ｍＬ浓度范围内，分别与其色谱峰具有线性关系。Ｍｇ＾２＋和Ｃａ＾２＋离子的检测限分别为０．１７３μｇ／ｍＬ和０．２７５μｇ／ｍＬ，其相对标准仿偏差分１．３２％和３．６４％，回收率分别为９０．８％和１０１．３％。该方法快速、准确，适用于环境水样及放射性水样中的Ｍｇ＾２＋和Ｃａ＾２＋离     

57Fe+、N2+注入Cu衬底的穆斯堡尔谱研究

＾５７Ｆｅ＾＋和Ｎ＾＋２双离子注入Ｃｕ衬底中,在室温时形成ＮａＣｌ结构的ＦｅＮｘ,ｘ约在０．６３～０．６５之间,退火过程中发现,由于氮的存在,氮原子影响了α－Ｆｅ的体扩散温度,分解的α－Ｆｅ可重新聚集在含Ｎ的原子组团中,形成新的α－Ｆｅ颗粒,其分解温度可高于６００℃。     

YBa2Cu3—xSnxOy超导体系的正电子寿命谱研究

研究了Ｓｎ作Ｃｕ位元素替代的ＹＢａ２Ｃｕ３－ｘＳｎｘＯｙ超导体系（ｘ＝０－１．５）的正电子寿命谱，计算了局域电子密度和缺陷浓度的变化，发现了存在于高浓度替代区域（ｘ＝０．８－１．０）的正电子湮没特征，讨论了对超导电性的影响以及相应的物理机制。     

YBa_2Cu_（3－x）Sn_xO_y超导体系的正电子寿命谱研究

研究了Ｓｎ作Ｃｕ位元素替代的ＹＢａ２Ｃｕ３－ｘＳｎｘＯｙ超导体系（ｘ＝０－１．５）的正电子寿命谱，计算了局域电子密度和缺陷浓度的变化；发现了存在于高浓度替代区域（ｘ＝０．８－１．０）的正电子湮没特征；讨论了对超导电性的影响以及相应的物理机制。     

热中子辐照提高掺硼YBaCuO超导体Jc的研究

掺杂天然硼的熔融织构生长（Ｍｅｌｔ－ｔｅｘｔｕｒｅｄＧｒｏｗｔｈ）的ＹＢｘＢａ２Ｃｕ３Ｏｙ（ｘ＝０．０１５,０．０３５）超导体经注量为５＊１０＾１７ｃｍ＾－２的热中子辐照后,磁临界电流密度Ｊｃ增至３．８倍。＾１０Ｂ（ｎ,α）＾Ｌｉ、＾７Ｌｉ＊（Ｑ＝＋２．７９ＭｅＶ）核反应出射的高能粒子能在超导体中产生均分布的,可以作为磁通钉扎中心的辐照伤,以便提高Ｊｃ。掺硼超导体热中子辐照后射性副产物的半衰期较短     

用液体闪烁计数法绝对测量^3H和^14C比活度

简述了液体闪烁数的单管及双管符合外推方法绝对测量＾３Ｈ、＾１４Ｃ活度的基本原理，零几率校正采用相对探测阈外推法，并提出了近代零几率外推方法，不同方法的测量结果与参考值相比，偏差在０．４－２．０％以内。     

^14C标记农药杀螟松和马拉硫磷的制备

以Ｂａ＾１４ＣＯ３为起始原料制得＾１４ＣＨ３ＯＨ，然后和＾１４ＣＨ３ＯＨ与ＰＳＣｌ３在碱性条件下反应，再加入甲基砂基苯酚，在甲基异丁酮溶剂体系下制得＾１４Ｃ－刹螟松，放化纯度〉９５％，放射性比活度为１８８．７ＢＭｑ／ｍｏｌ，＾１４ＣＨ２ＯＨ与Ｐ２Ｓ５合成的中间体，加顺丁烯酸二乙酯在甲苯溶剂体系中反应制成＾１４Ｃ－马拉硫磷，放化纯度〉９５％，放射性比活度为１５６．４ＭＢｑ／ｍｏｌ。     

14C-绿黄隆结合残留物的微生物释放

研究利用微生物释放土壤中＾１４Ｃ－绿黄隆结合残留物。结果表明，在培育５ｄ后，有３４．４０％－４０．５５％的＾１４Ｃ－结合残留物被释放出来，以可提高态存在于土壤溶液中，其数量在以后的试验过程中变化不大。微生物释放＾１４Ｃ－结合残留物时，主要对存在于富里酸中的结合残留物产生作用，与对照相比，利用的微生物Ｂａｃｉｌｌｕｓ ｍｅｇａｔｅｒｉｕｍ和Ａｒｔｈｒｏｂａｃｔｅｒ ｓｐ。未表现出较细的释放能力。     

13C-UBT诊断Hp的临床价值

通过对100例胃肠道功能紊乱的患者进行胃镜检查、活组织检查、胃窦活检快速Hp检查、^13C-尿素呼气试验(^13C-UBT)和ASSURE^TM Hp快速试验(HpRT)，并以胃镜活检和组织病理检查结果为金标准。结果显示：胃窦活检快速Hp检查法的灵敏度为79％，特异性为76％；^13C—UBT检查的灵敏度为96％，特异性为95％；HpRT检查的灵敏度为86％，特异性为88％。^13C-UBT检查Hp的灵敏度和特异性较好，可作为临床上诊断Hp的首选方法。     

14C-尿素呼气试验诊断幽门螺杆菌感染的临床价值

对来本院消化科就诊的244例有明显症状的患者依规程进行了^14C—尿素呼气试验(^14C—UBT)，并与胃镜、组织学检查结果相比较。结果表明，在244例中124例HP阳性，其中89例得到证实；另35例因患者拒绝胃镜检查而接受了HP根治性治疗，症状消失或减轻明显，证实其准确率达100％。124例患者经4周治疗后，重复^14C—UBT，结果全部转阴。^14C—UBT阴性者120例，其中胃镜证实阴性者9例，胃镜取活检示HP阳性者3例，即此3例为^14C—UBT假阴性。未发现假阳性病例。由此可知，作为非侵人性方法，^14C—UBT简便易行，具有较高的敏感性和特异性，可作为HP诊断的首要方法。     

小肠原发恶性肿瘤18F-FDGPET/CT显像及诊断方法

44例小肠原发疾病患者(恶性25例,良性19例)18F-FDG PET/CT显像资料经组织学、诊断性治疗和/或临床随访证实;采用目测法、定量方法(测病变肠壁的厚度)及半定量方法[测平均标准摄取值(SUVmean)]分析PET/CT影像特点,以最大约登指数(YImax)时的SUVmean及肠壁厚度作为判断良恶性的阈值;以最后诊断结果为标准进行诊断学试验评价。结果显示:(1)小肠恶性肿瘤PET/CT表现为小肠局部肿块形成、局部肠壁增厚、肠管狭窄、肠梗阻及肠系膜淋巴结肿大等征象,而良性病变仅显示小肠肿块形成(χ2=10.40,p<0.01)、局部肠壁增厚(χ2=3.90,p<0.05),二征象有显著性差异。(2)小肠良、恶性病变肠壁厚度分别为(7.53±3.24)mm、(14.24±2.02)mm(t=2.66,p<0.01);YImax=0.589时,肠壁厚度为9.5 mm,诊断灵敏度、特异性和准确度分别为80.00%、78.95%和79.55%。(3)小肠良、恶性病变的SUVmean分别为3.55±1.84、6.98±3.62(t=3.77,p<0.01);YImax=0.379时,SUVmean=3.65,诊断灵敏度、特异性和准确度分别为80.00%、58.85%和70.45%。(4)以小肠肿块形成作为恶性的判断标准,诊断的灵敏度、特异性和准确度分别为84.00%、78.95%和81.82%,YImax=0.630。(5)以小肠局部肿块形成及病灶SUVmean≥3.65、局部肠壁增厚及厚度≥9.50 mm为主要依据,诊断灵敏度、特异性和准确度分别为96.00%、89.47%和93.18%,YImax=0.855。表明18F-FDG PET/CT显像提示小肠局部肿块形成及病灶SUVmean≥3.65、局部肠壁增厚及厚度≥9.50 mm的定性定量征象对准确诊断小肠原发恶性肿瘤具有重要的临床价值。     

Exploratory studies of tokamaks as fusion test reactors

Studies have been performed to explore various plasma burn scenarios for a tokamak test reactor which could follow the next generation of large tokamak experiments. Tradeoffs between an ignited burning plasma and a sub-ignited driven plasma are examined in terms of device size and performance as a fusion engineering test facility. It is found that plasma performance levels, measured by ignition margin, amplification factorQ, and fusion power output, increase with device size, more optimistic transport scaling laws, lower magnetic field ripple, and higher. The performance of a generally low stress (B ₀=4 T) reference device, with major radiusR=4.5 m and minor radiusa=1.3 m in a D-shaped (=1.6) plasma has been evaluated over a wide range of operating parameters. In particular, a moderate fusion power output of 300 MW is obtained, the driven plasma havingQ 10, an edge ripple of 1%, and a density ranging between 1.0 and 1.5×10¹⁴ cm^–3. The same device operated at a higher general level of stress (B ₀=5.3 T) is predicted to achieve ignition, but is not required for the mission of an engineering test facility and would entail greater technical risk.     

拉曼光谱内标法定量分析Purex有机体系中的U(Ⅵ)

本工作研究了Purex后处理流程模拟有机料液中U(Ⅵ)的定量分析方法。首先扣除硝酸铀酰有机溶液拉曼光谱的荧光背景,并以30%TBP/煤油位于1 065cm-1处的特征峰为内标峰,将U(Ⅵ)位于860cm-1处对称伸缩振动峰(ν1)强度与内标峰强度的比值,对铀浓度绘制标准曲线,在U(Ⅵ)质量浓度为5.0~107.0g/L范围内,标准曲线为y=0.063 6x+0.357,r2=0.999。经过内标法处理后的标准曲线具有更好的稳定性,75d后相对强度标准曲线为y=0.062 4x+0.489,r2=0.999。F检验与t检验证明,在显著性水平α=0.05时,两条标准曲线在分析精度与斜率上无显著性差异。使用内标法后,可透过容器壁直接分析铀浓度,容器对检测结果的影响较小,5种容器对U(Ⅵ)检测影响相对误差均不高于3.7%,故检测过程无需进行样品的转移及分装,简化了实验步骤。经内标法修正后,改变拉曼光谱仪的积分时间和激光功率基本不影响U(Ⅵ)的定量检测,从而可选择合适的参数以适应不同浓度U(Ⅵ)溶液分析的需要。     

Comparison of diagnostic accuracy between ^18F-FDG PET and PET/CT for pulmonary neoplasm

Aimed at comparing diagnostic accuracy of 18F-FDG PET with PET/CT for pulmonary neoplasm,a study based on multi-center clinical trial of the diagnoses,in randomized and semi-blind ways,was executed from January 2006 to June 2007.It included 55 patients,i.e.16 with histopathologically proved lung tumors,16 with tuberculosis and 23 with benign lesions (inflammation,pseudotumor,granuloma,fibrosis and others).The histopathologic and clinic results were served as reference standard.Statistical significances in pulmonary nodule diagnosis between 18F-FDG PET and PET/CT were determined with 95% confidence interval obtained by ROC analysis.The 18F-FDG PET detected lung neoplasm with a sensitivity of 87.5% (14/16),a specificity of 59.0% (23/39),an accuracy of 67.3% (37/55) and a positive-likelihood ratio of 2.13.The 18F-FDG PET/CT detected lung neoplasm with a sensitivity of 93.8% (15/16),a specificity of 61.5% (24/39),an accuracy of 70.9% (39/55) and a positive-likelihood ratio of 2.43.The area under curves (AUC) of 18F-FDG PET and PET/CT were 0.803±0.068 and 0.799±0.063,respectively.It can be concluded that the diagnostic accuracy for malignant pulmonary nodules between 18F-FDG PET and PET/CT was not statistically different.     

A comparative method for testing graphite used in nuclear reactors

The purity of the graphite used in graphite-moderated thermal reactors is a factor of prime importance. This article describes a method for testing the reactor feasibility of graphite. The gist of the method involves comparison of flux attenuation of thermal neutrons in the test graphite and in a standard graphite specimen. The method serves in determining the diffusion length L or the effective absorption cross section of graphite, where L₀ and ₀ for the standard graphite are known. The error incurred in determining does not exceed 2.5%. The simplicity of the method recommends its use for large-scale testing of graphite under factory conditions.     

Formation of porosity in uranium under the action of thermal cycling

In accelerated thermal cycling with a cycle of 50 sec period, considerable changes appear in uranium after 50–1000 cycles, depending upon the temperature range of the cycle. Cycling in the temperature range of the -phase (with heating up to between 550 and 600 °C) produces in texturcd uranium (containing about 0.1% carbon) a directional deformation and porosity, accompanied by a drop in density. After 5000 cycles, the drop in density amounts to 8% Thermal cycling with = ß = -transformations produces a pronounced distortion of the original shape of uranium speclmens and intense porosity formation, with a considerable drop in density, which attains 30% after 1000 cycles.     

三氯化铁分光光度法测定药物中亚甲基二膦酸

通过三氯化铁与亚甲基二膦酸形成络合物，采用分光光度法，建立了注射用亚锡亚甲基二膦酸盐冻干药盒中亚甲基二膦酸含量的测定方法。结果表明，亚甲基二膦酸质量浓度在0.02~0.08 g/L范围内与吸光度A呈良好线性关系，线性回归方程y=14.61x+0.029 7，线性相关系数r=0.999 1。加标回收率为98.8%~102.0%，相对标准偏差为0.97%(n=6)。该方法可用于快速准确地测定注射用亚锡亚甲基二膦酸盐冻干药盒中亚甲基二膦酸的含量。     

Latest Results from the Damavand Tokamak Experiments

Damavand is a small tokamak (a = 7 cm, R = 36 cm) with an elongated plasma cross section (k 2) and a poloidal divertor. Its passive coils within the vacuum chamber provide the plasma formation at the torus center and act as a passive stabilizer for the plasma current. The experimental measurements presented here are the latest results related to the Damavand discharge main behavior with graphite limiters (before the device modification) during the ohmic heating phase. In this respect, we have evaluated some of the characteristic parameters such as edge safety factor (q_a 3.1), energy confinement (_E = 0.4 ms), electron temperature (T_e = 161 eV), and so on, during normal operation of the plasma current. The assessment of disruption phase of the plasma current has been considered by estimating the characteristic parameters of thermal and current quenches to be about 6 eV and 6 MA/s, respectively. Here, also we have monitored the evolution of the line emission of impurity (C, O) ions in the central deuterium plasma. The relative density of carbon and oxygen impurity levels has been estimated to be 2.6 and 1.4%, respectively. It is concluded that the impurity radiation loss is much higher during disruption phase of plasma current.