硝酸介质中单甲基肼与亚硝酸的反应动力学

采用分光光度法研究硝酸介质中单甲基肼(MMH)与亚硝酸(HNO2)的反应。HNO2和MMH反应动力学速率方程为－dc(HNO2)/dt=kc(H+)c1.1(NO－3)c1.1(MMH)c(HNO2)。当t＝2.6℃、c(NO－3)＝0.50mol/L时,反应速率常数k=(115±2)(mol/L)－3.2•s－1,反应活化能Ea=(37.8±0.1)kJ/mol。研究结果表明：在硝酸介质中,甲基肼与亚硝酸能快速反应;提高酸度、MMH浓度或硝酸根浓度均有利于亚硝酸的还原。     

单甲基肼还原Np(Ⅴ)的反应动力学

用分光光度法研究了HNO3介质中单甲基肼(MMH)还原Np(Ⅴ)的动力学行为.通过考察还原剂浓度和酸度等条件对Np(Ⅴ)动力学过程的影响,确定了反应的动力学速率方程为-dc(Np(Ⅴ))/dt=kc(Np(Ⅴ))c0.36(MMH)c(H+),在温度θ=35℃,离子强度为2 mol/L时,反应速率常数k=0.004 79(mol/L)-1.36/min.研究了离子强度、c(U(Ⅵ))和温度对反应的影响.结果表明,离子强度和c(U(Ⅵ))对反应速率无显著影响;反应活化能为60.43 kJ/mol,随着温度的升高,反应速率加快.并在此基础上推测了可能的反应机理.     

Pu催化HNO_2氧化U(Ⅳ)的研究

研究了Pu存在条件下HNO2氧化U(Ⅳ)的反应,并考察了HNO2浓度、反应温度、HNO3浓度、Pu浓度对U(Ⅳ)氧化速率的影响。结果表明:Pu对HNO2氧化U(Ⅳ)的反应具有显著催化作用;获得了Pu催化条件下HNO2氧化U(Ⅳ)的动力学方程:-dc(U(Ⅳ))/dt=kc(U(Ⅳ))c1.3(HNO3)c1.3(NO-2),得到了29℃时的反应速率常数k=(0.69±0.04)L2.6/(mol 2.6·min)。并对反应历程进行了探讨。     

硝酸体系中AHA与HNO_2的反应动力学研究

本工作研究HNO3体系下AHA与HNO2的反应动力学。研究得到该反应的反应动力学速率方程式为-dc(HNO2)/dt=kc(HNO2)c0.25(AHA)c(HNO3)。在t=10℃、I=0.5mol·kg-1条件下,反应速率常数k=(0.4814±0.0375)L1.25·mol-1.25·s-1。实验研究了反应温度对反应速率的影响。结果表明,随着反     

双羟基脲与HNO2的反应动力学及对Pu(Ⅲ)的稳定作用

研究了HClO4和HNO3体系中双羟基脲(DHU)与HNO2的反应动力学.结果表明,HClO4和HNO3体系下DHU与HNO2的反应动力学速率方程式均为-dc(HNO2)/dt=k·c(HNO2 )1·c(DHU )0·c(H+)-0.15,反应对DHU均呈零级.在HClO4体系下,θ=15 ℃, I=0.5 mol/kg时,反应速率常数k1=(2.37±0.04) mol0.15/(L0.15·min);在HNO3体系下,θ=10 ℃, I=0.5 mol/kg时,反应速率常数k2= (1.29±0.06) mol0.15/(L0.15·min)(n=8).同时考察了反应温度对反应速率的影响,结果表明,随着温度的升高, 反应速率均明显加快, HClO4和HNO3体系对应的反应活化能分别为68.2 kJ/mol和76.8 kJ/mol.在HClO4和HNO3体系中,随着离子强度的增加,氧化还原反应的表观速率常数k'均下降.过量的DHU在HNO3溶液中可以很好的稳定Pu(Ⅲ)48 h而不被氧化.     

Ru3+和［RuNO］3+的速差动力学分析方法

建立了用速差动力学分光光度法分析同一体系中Ru³⁺和［RuNO］³⁺的方法。在盐酸羟胺存在下，测定了Ru³⁺和［RuNO］³⁺与bipy的反应表观速率常数、浓度级次及反应平衡常数。通过测量反应产物Ru(bipy)²⁺₃的起始反应速率和平衡时的浓度，由建立的相关线性方程组计算出Ru³⁺和［RuNO］³⁺的浓度。Ru³⁺和［RuNO］³⁺的回收率分别为96%~105%和95%~106%。加入EDTA能较好地掩蔽常见金属离子的干扰。     

高氯酸体系中AHA与HNO_2的反应动力学研究

本工作研究HNO3体系下AHA与HNO2的反应动力学。研究得到该反应的反应动力学速率方程式为-dc(HNO2)/dt=kc(HNO2)c0.25(AHA)c(HNO3)。在t=10℃、I=0.5mol·kg-1条件下,反应速率常数k=(0.4814±0.0375)L1.25·mol-1.25·s-1。实验研究了反应温度对反应速率的影响。结果表明,随着反应温度的升高,反应速率明显加快,相应的反应活化能?E=46.92kJ·mol-1。在离子强度I=0.5～3.0mol·kg-1范围内,氧化还原反应的表观速率常数k′随离子强度I的增加而有所增大,但增大幅度不甚明显。对该反应的机理进行了简要讨论。高氯酸体系中AHA与HNO_2…     

Purex流程中二甲基羟胺与甲基肼的分析

研究了在测定1BP中的N,N-甲基羟胺(DMHAN)和甲基肼(MMH)的浓度之前用TODGA将其中的Pu(Ⅲ)萃取出来;并基于所发现的在室温下pH为2.0～5.5时,Fe3+只与DMHAN反应而不与稀的MMH发生反应;以及在室温下pH为0～5.5时,稀的I2溶液只与MMH发生反应而不与稀的DMHAN反应;分别建立了用F...     

高氯酸、硝酸体系中乙异羟肟酸与

分别在HClO4和HNO3体系中用分光光度法研究了乙异羟肟酸(AHA)与HNO2的反应动力学,得到其反应动力学速率方程式为:—dc(HNO2)/dt=k.c(HNO2)1.c(AHA)0.75.c(HClO4)0.5和—dc(HNO2)/dt=k.c(HNO2)1.c(AHA)0.25.c(HNO3)1。在HClO4体系中,当θ=5℃,I=0.5 mol/kg时,反应速率常数k=(2.37±0.21)L1.25/(mol1.25.s);在HNO3体系中,当θ=10℃,I=0.5 mol/kg时,反应速率常数k=(0.482±0.048)L1.25/(mol1.25.s)。同时考察了反应温度对反应速率的影响。结果表明,在HClO4和HNO3体系中,随着温度的升高,反应速率均明显加快,反应活化能分别为99.0 kJ/mol和46.9 kJ/mol;随着离子强度的增加,氧化还原反应的表观速率常数k′均有所增加,但增幅不明显。     

甲醛肟与HNO_2氧化还原反应动力学

用分光光度法研究了高氯酸体系中甲醛肟(FO)与亚硝酸的还原动力学,其动力学方程式为:-dc(HNO2)/dt=kc(HNO2)c1.32(FO)c0.96(Cl O4-),其中在1.0℃时,k=(7.55±0.50)(mol/L)2.28/s,活化能Ea=(65.16±6.52)kJ/mol。增加甲醛肟浓度、高氯酸根浓度和温度,HNO2还原速度增加,H+浓度对还原反应基本无影响。     

Identification of radiation treatment of wheat （Triticum aestivum. L）and rice （Oryza sativa. L） samples using thermoluminescence of contaminating minerals

Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence （TL） is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture （NIFA）, Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities （TL1） than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves （TL2）. The ratio of the area of first glow curve to that of second glow curve （TL1/TL2） was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results （comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves）, all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.     

有效探测面积大于1000 cm2的正比计数器测量系统性能测试

为对自制的活性面积高达1 000 cm²的大面积源进行表面发射率定值,同时作为现有2πα、2πβ表面发射率标准装置能力的扩充,研制了一套内置式大面积2π多丝正比计数器测量系统,并利用活性区直径为8 mm的²⁴¹Am点源及活性区面积为10 cm×15 cm的大面积²⁴¹Am和⁹⁰Sr-⁹⁰Y源对其进行计量学性能测试。结果表明：计数器内计数响应均匀性优于±0.4%,有效探测面积达1 400 cm²;所得²⁴¹Am源高压坪曲线的坪长为1 400 V,坪斜为0.27%/100 V,坪区内计数变化为0.87%;⁹⁰Sr-⁹⁰Y源高压坪曲线的坪长为300 V,坪斜为0.75%/100 V,坪区内计数变化为0.80%;10次测量重复性好于0.4%,8 h内短期稳定性好于0.3%,1 a内长期稳定性好于0.8%。     

Preparation of Zn/TiO2 powder and its photocatalytic performance for oxidation of P-nitrophenol

Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn （11）. When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.     

Current status of radiation therapy for prostate cancer

Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.     

The control system for SSRF injection and extraction

This paper introduces the injection and extraction control system design for SSRF,which is a distributed control system aimed at stability and reliability of the pulse power supplies,PPS(Personnel Protection System)and MPS(Machine Protection System).The hardware environment is mainly based on PLC(Programmable Logic Con- troller),and ARM(Advanced RISC Machine)is also applied for studying stability of the power supplies.WinCC and EPICS(Experimental Physics and Industrial Control System)have been selected as the platforms of SCADA(Super- visory Control and Data Acquisition).For unifying the interfacing to the control computer,all front-end equipments are connected via Industrial Ethemet.     

Interaction between uranium and humic acid (Ⅰ): Adsorption behaviors of U(Ⅵ) in soil humic acids

The adsorption behaviors of uranium on three soil humic acids (HAs), which were extracted from soils of different depths at the same site, were investigated under various experimental conditions. The adsorption results showed that U(Ⅵ) in solutions can be adsorbed by the three soil HAs, with the order of FHA (HA from 5 m depth of soil) ＞SHA (HA from the surface) ＞THA (HA from 10 m depth of soil) for adsorption efficiency in each desirable condition, and the adsorption reached equilibrium in about 240 min. Although the maximum adsorption efficiency was adsorption could be described with Langmiur isotherm or Freundlich isotherm equation. The L/S (liquid/solid, mL/g)ratio and pH were important factors influencing the adsorption in our adsorption system besides uranium concentration. The adsorption efficiency decreased with the increase of the L/S ratio and pH at the pH range of 2.0-3.0 for SHA and THA or 2.5 - 6.0 for FHA. However, no significant difference in adsorption of U(Ⅵ) was observed at the experimental temperature. All the results implied that humic substances have different characteristics in samples even collected at the same site.     

水平管内含空气蒸汽强制对流冷凝换热模型研究

为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现：从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。     

The preclinical pharmacological study of dopamine transporter imaging agent 18F-FP-β-CIT

The paper is to study pharmacologic characteristics of 18F-FP-β-CIT (18F-N-(3-fluoropropyl)-2β- carbomethoxy-3β- (4-iodophenyl)nortropane) as an imaging agent for dopamine transporter. The radiochemical purity of 18F-FP-β-CIT in aqueous solution was over 95% after standing at room temperature for 4h. Biodistribution displayed rapid uptake in rat brain (1.375 %ID/organ at 5min and 0.100 %ID/organ at 180 min) and the striatal uptake was 1.444,0.731, 0.397, 0.230 and 0.146 %ID/g at 5, 30, 60, 120 and 180 min, respectively. The values of striatum/cerebellum,striatum/frontal cortex and striatum / hippocampus in rat's brain at 30 min were 3.38, 2.17 and 2.40 respectively. The uptake in striatum can be blocked by β-CFT, suggesting that 18F-FP-β-CIT binds to DAT peculiarly. The compound was rapidly cleared from monkey's blood. The striatal uptake was bilaterally decreased in the left-sided lesioned PD rats, compared with normal control. Brain PET imaging studies in normal monkey showed that 18F-FP-β-CIT was concentrated in striatum. The test of undue toxicity showed that the dose received by mice was 1250 times as by human, which indicates that 18F-FP-β-CIT is very safe. So 18F-FP-β-CIT is a promising PET imaging agent for DAT with safety and validity.     

Information for authors

<正>1.NUCLEAR SCIENCE AND TECHNIQUES(NST),a bimonthly journal,is devoted to all aspects of nuclear science and technology,theoretical or experimental.Its special interest lies in the subjects of synchrotron radiation science and technology;low energy accelerators,radiation technology and applications;radiochemistry,radiopharmaceuticals and nuclear medicine;nuclear electronics and instrumen-     

PLASMA SCIENCE AND TECHNOLOGY AUTHOR INDEX TO VOLUME 16(2014)

正~~