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????????????????????????????????λ???????????EA-IRMS?????????????????????????о??????????????????????106????????????????λ??????δ¹³C?????????????????????δ¹³C????????-21.50‰?????????????????????????δ¹³C???Δδ¹³Cp-r??С??-0.95‰??????????ж??????131????????????м???????????65???????????????????????-4?????????????齨????EA-IRMS??????????????????δ¹³C?????????Ч?????????????????????????????????????-4??????     

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????????????????????????????????????????????ī?N-?????????????????????????????????????????????????????????????а???????Edman????????????????????????????????????LC-HRMS????????????MS/MS???????з????????????HRMS/MS???????????λ????????????????????????N-????????????[M+H]⁺????????????????????????????????2-?????????????????HETE?????????????C-N???????HETE?????????????????????????????????????m/z 105.036 3?????????C₄H₉OS??N-???????????????????????HFBI??????????????????-?????GC/MS???????????     

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MC-ICP-MS测量铀中低丰度铀同位素比值

高精密度地测量铀材料中的铀同位素组成信息,特别是低丰度铀同位素²³⁴U和²³⁶U,是核取证研究的重要内容。本研究采用多接收电感耦合等离子体质谱（MC-ICP-MS）测量铀同位素比值,将两种黄饼样品的酸消解液制备成²³⁸U浓度约21 000 ng/g和180 ng/g的待测样品,采用外标标准化法和标准样品交叉法校正质量分馏效应,MC-ICP-MS对²³⁸U浓度约180 ng/g的样品中²³⁵U/²³⁸U测量的相对实验标准偏差可低于0.014%。为降低超档离子流信号对低丰度铀同位素分析的影响,建立了法拉第杯接地方法,使轰击到法拉第杯上的²³⁸U⁺产生的电流在到达前置放大器之前被引入大地,该方法对²³⁸U浓度约21 000 ng/g的样品中²³⁴U/²³⁵U测量的相对实验标准偏差可低于0.020%,对浓缩铀GBW04234和GBW04238中²³⁶U/²³⁵U测量的相对实验标准偏差小于0.11%,测量结果与参考值在不确定度范围内一致。该方法的精密度较高、结果准确,可识别铀同位素组成存在一定差异的核材料,为核取证和核保障监督提供技术支持。     

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???ù???????-???????-???????ü????о????????????????????????????????????????????????????????????????????????????????????????60????????35min??PDMS/DVB?????????Ч??????????????????????????????????????????(25.88%)??3-???(14.08%)???????????????(12.06%)???????????(9.32%)??????(4.50%)???????(4.34%)?????????????????????????????     

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????????????-????Ч????????????????????????????????谷???????????????BondElut Plexa ^TM PCX????????????????????????????????1%?????????????????BondElut Plexa ^TM PCX??????????????????0.1%?????5mmol•L^-1?????????????ó???Ч?????????????????????????????谷???????0.5??g•kg^-1????????0.5~5.0??g•kg^-1???????????????????70%???????????С??12%????????????谷???????1.0ng•L^-1????????1.0~10.0ng•L^-1???????????????????75%???????????С??10%??     

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?????????Ч??????-????????(UPLC-MS/MS)??????????13?????????????????????????Na₂EDTA-Mcllvaine??????????????λ?????????????HLB???????????????????????????￡????????(MRM)????????????ж???????????????5~200 μg/kg????Χ???????????????????????0.990;??????13???????5.0??50.0??100.0 μg/kg 3???????????????????64.55%~117.62%?????????????С??14.28%???????????С??12.81%?????????1.0 μg/kg??????????5.0 μg/kg???????????????????????????????????????????????????????????????????     

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??????Ч??????????????÷????????????????????????Kromasil-C₁₈ ???????50mm??4.6mm??5??m??????V(????):V(0.1%????)=75??25??1mmol•L^-1??????????????????????????з???????ó???????????????????3200QTrap?????????????????????????????MRM????跽????м????????ε??????Χ?3.0~3000.0??g•L^-1???????????3.0??g•L^-1?????????????????????????????????С??15%????????-1.40%~2.07%??????????????????98.2??7.6??%????????á??÷????????????????????????????????????????????????????????????????????о???     

改良全蒸发技术测量铀同位素比

全蒸发热表面电离质谱(TE-TIMS)是测定铀主同位素比(²³⁵U/²³⁸U)最经典的方法,但受限于强峰拖尾等因素影响,次同位素比(²³⁴U/²³⁸U、²³⁶U/²³⁸U)的测量精密度不高,存在偏差。本工作研究目标动态加热程序、动态和静态相结合的接收程序、强峰拖尾校正、不同接收器效率校正、质量歧视校正等,建立了改良全蒸发-热表面电离质谱技术(MTE-TIMS)高精度测定铀同位素比的方法,通过测试标准物质验证方法的准确性和可靠性。结果表明：采用MTE-TIMS法测量²³⁵U丰度为2%的铀样品,其²³⁵U/²³⁸U、²³⁴U/²³⁸U和²³⁶U/²³⁸U的方法精密度分别为0.024%、0.06%和0.19%,测量值与参考值的偏差分别为0.025%、0.19%和0.38%。     

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????????????-?????????LC-MS/MS???????????д??????м???????????????????ü???嶡??????????????????C18????????????????????????0.02%???-??????????XBridge RP-18????????????LC-MS/MS????????????ж??????????????????м???????????????????????????????裻???????????????裬???????????????????0.5~2 μg/kg??S/N≥3????27???????2 μg/kg??10 μg/kg??????￡????????????5.3%~15%??2.3%~8.2%??????????????73.0%~120%??79.0%~108%???÷???????????????????????????????27?????????????????????     

Increase in the Charge State of the Uranium Ion Beam Generated by the MEVVA Ion Source

The Metal Vapor Vacuum Arc (MEVVA) ion source and its modifications are investigated at the Institute of Theoretical and Experimental Physics (ITEP). In a series of the experiments, the possibility of increasing the charge state of the generated uranium ion beam was revealed. The charge state increases as a result of developing a high-current vapor vacuum arc discharge from the source cathode to an auxiliary anode located in an increasing axial magnetic field. The uranium ion beam with a total current of 150 mA was obtained, U⁷⁺ uranium ions being 10% of the current.     

A field-emission source of charges based on nanotubes for low-temperature experiments

Methods for the production of field-emission sources of charges on the basis of carbon nanotubes are described. These sources can be used to study the properties of injected charges in cryogenic liquids and crystals (the area of the source surface is about several square millimeters, the dissipated power is <10^?6 W). The first and second batches of sources were produced by means of the deposition of nanotubes from an arc discharge on a flat copper substrate and via mechanical rubbing of nanotubes into a porous metal, respectively. Tests of sources from the first batch in a diode with a gap of 0.5 mm showed that in superfluid He-II, the current of negative charges at a level of 10^?12 A arises when the voltage at the cathode is U = ?140 V and increases to 10^?9 A, when U rises to 170 V. When the voltage polarity changes, the current of positive charges arises in the diode for the voltage U ≥ 240 V. A source from the first batch was used to observe the movement of negative and positive charges in solid-helium samples at T < 75 mK. For second-batch sources, the current of negative charges at a level of 10^?12 A in superfluid He-II arises at U = ?260 V.     

A laser desorption ion-mobility increment spectrometer for detection of ultralow concentrations of nitro compounds

A compact instrument that implements for the first time a method for analyzing substances, in which laser desorption of analyzed molecules and laser ionization of an air sample are combined with the ionmobility increment spectroscopy, is described. Pulse radiation of the fourth harmonic of a portable (2.6 kg) GSGG: Cr³⁺: Nd³⁺ laser (λ = 266 nm) is used. The detection limit of the developed laser desorption spectrometer of the ion-mobility increment is 40 pg for trinitrotoluene (TNT), and the linear dynamic range for TNT is 0.1–20.0 ng. The results from detection of nitro compounds are presented: trinitrotoluene, cyclotrimethylene trinitramine (RDX), and octogen (HMX). It is shown that laser desorption of nitro compounds from a metal is accompanied by their decomposition on the surface and emission of fragments. An ion signal is obtained for nitro compounds that were ionized outside the spectrometer.     

Signal standardization of the secondary ion mass spectrometry (SIMS) microscope for quantification of halogens and calcium in biological applications

The secondary ion mass spectrometry (SIMS) microscope is able to map chemical elements in tissue sections. Although absolute quantification of an element remains difficult, a relative quantitative approach is possible for soft tissue by using carbon (¹²C) as an internal reference present at large homogeneous and constant concentration in specimen and embedding resin. In this study, this approach is used to standardize the signal of an SIMS microscope for the quantification of halogens (¹⁹F^—, ³⁵Cl^— and ⁷⁹Br^—) and calcium (⁴⁰Ca⁺). Standard preparation was determined based on homogeneity and stability criteria by molecular incorporation (halogens) or mixing (calcium) in methacrylate resin. Standard measurements were performed by depth analysis on areas of 8 μm (halogens) and 150 μm (calcium) in diameter for 10–30 min, under Cs⁺ (halogens) or O₂⁺ (calcium) bombardment. Results obtained from 100–120 measurements for each standard dilution show that the relationship between the signal intensity measured and the elemental concentration (μg/mg of wet tissue or mm ) is linear in the range of biological concentrations. This quantitative approach was applied firstly to bromine of the 5-bromo-2′-deoxyuridine (BrdU) used as nuclear marker of rat hepatocytes in proliferation. The second model concerns depletion of calcium concentration in cortical compartment in Paramecium tetraurelia during exocytosis. Then signal standardization in SIMS microscopy allows us to correlate quantitative results with those obtained from other methods.     

痕量铱同位素的负离子质谱分析方法研究

铱（Ir）同位素组成可作为理想的核燃料燃耗指示信息。提高Ir待测离子的电离效率,以获得足够强度且稳定的离子流是精确测量痕量Ir同位素组成的关键。因Ir电离电位较高,极难形成稳定的正离子,因此需采用负离子模式。本研究通过对比不同的灯丝材料、灯丝结构、涂样条件、电离温度等因素,建立并优化了Ir的负离子转化条件。通过采用Pt单带、Ba(OH)₂为发射剂涂样,并缓慢提高灯丝电流,50 ng的Ir电离效率可达9.8×10^-4。经氧同位素校正后,Ir涂样量10 ng以上的n(¹⁹¹Ir)/n(¹⁹³Ir)同位素比值与标准溶液的参考值在误差范围内一致,且相对标准偏差优于0.2%,能够满足痕量Ir同位素组成的测量精度要求。     

ID-TIMS法测定环境样品中微量铀

ID-TIMS technique was used to measure the uranium content and uranium isotope ratios for environmental samples, in which 233U was used as spike. Compared with traditional methods in which 235U is used as spike, this method simplifies the analysis steps. Furthermore, the results of uranium isotope ratios calculated by ID-TIMS technique were well consistent with those measured directly by TIMS. For ng level uranium the precision of 235U/238U was less than 0.7%, that of 234U/238U less than 10%.     

Quasicrystalline Materials

SIMS matrix effects (mass interferences, sputter yield variations and practical ion yield variations) were evaluated in freeze-fractured, freeze-dried cultured cells at the ～0.5 μm spatial resolution of the Cameca IMS-3f ion microscope. Cell lines studied include normal rat kidney (NRK), 3T3 mouse fibroblast, L6 rat myoblast, chinese hamster ovary (CHO) and rat kangaroo kidney (PtK2) cells. High mass resolution studies indicated that the secondary ion signals of H^—, C^—, O^—, Na⁺, Mg⁺, CN^—, P^—, S^—, Cl^—, K⁺ and Ca⁺ were free from major mass interferences. However, a large mass interference was observed for nitrogen at mass 14. No significant sputtering yield difference between the nuclear and cytoplasmic compartments of the cells studied was observed. The subcellular distributions of the major (H, C, N and O) and minor (P, S, K, Cl, Na, Mg and Ca) matrix elements were found to be largely homogeneous with the exception of Ca, which was observed mainly in the cell cytoplasm. Practical ion yield variations were compared by three different approaches: (i) by the use of cells doped with known electrolyte concentrations, (ii) by quantitative ion implantation, and (iii) by analysis of the same cell with both electron probe and ion microscope. Each approach indicated an absence of significant practical ion yield differences between the nuclear and cytoplasmic regions of these specimens. These observations indicate that secondary ion signals in this type of sample are not significantly affected by local matrix effect variations. Hence, qualitative imaging of such specimens provides a true representation of subcellular elemental distribtions. These observations should allow the development of quantitative ion imaging methodologies and enhance the applicability of ion microscopy to biomedical problems.     

RPQ-IC检测系统测量低丰度铀同位素

介绍了采用 Finnigan MAT 2 62热电离质谱计检测 NBS U 0 1 0、浓缩 2 3 3 U硝酸溶液 ( IRMM-0 40 a)。采用阻滞电位四极杆 ( RPQ) -IC装置测量低丰度铀 2 3 4 U、2 3 5U、2 3 6U的同位素丰度比 ,并与 Faraday(法拉第杯 )检测的数据进行比较。采用偏转法对 RPQ产额进行了校正。实验表明 :所得结果在误差范围内 ,RPQ-IC测量结果比 RPQ-FAR测量结果偏高 0 .1 4% ;RPQ-IC测量低丰度铀同位素的内精度比法拉第杯测量结果高 ,外精度比 FAR杯测量结果也高 ;RPQ产额变化比较大 ,但只要注意产额校正 ,可以得到满意的结果     

Enhancing image contrast of carbon nanotubes on cellular background using helium ion microscope by varying helium ion fluence

Carbon nanotubes (CNTs) have become an important nano entity for biomedical applications. Conventional methods of their imaging, often cannot be applied in biological samples due to an inadequate spatial resolution or poor contrast between the CNTs and the biological sample. Here we report a unique and effective detection method, which uses differences in conductivities of carbon nanotubes and HeLa cells. The technique involves the use of a helium ion microscope to image the sample with the surface charging artefacts created by the He⁺ and neutralised by electron flood gun. This enables us to obtain a few nanometre resolution images of CNTs in HeLa Cells with high contrast, which was achieved by tailoring the He⁺ fluence. Charging artefacts can be efficiently removed for conductive CNTs by a low amount of electrons, the fluence of which is not adequate to discharge the cell surface, resulting in high image contrast. Thus, this technique enables rapid detection of any conducting nano structures on insulating cellular background even in large fields of view and fine spatial resolution. The technique demonstrated has wider applications for researchers seeking enhanced contrast and high‐resolution imaging of any conducting entity in a biological matrix – a commonly encountered issue of importance in drug delivery, tissue engineering and toxicological studies.