Development of Plasma Window for gas charge stripper at RIKEN RIBF

A differential pumping system with a Plasma Window (PW) has been developed for an application to a window-less He gas charge stripper. A PW with Southern Methodist University design was newly fabricated and tested off-line for evaluation of differential pumping efficiency. Switching gases for plasma seed from Ar to He was tested. It was found that the PW reduced the pressure at the first differential pumping section to 1/13 for Ar and to 1/17 for He, comparing with differential pumping without PW. At the second pumping section, the pressures were drastically reduced to 1/160 and to 1/4,520 for Ar and He, respectively. These pressure reduction factors indicate that one differentially pumped stage could be removed from a conventional differential pumping system.     

Radioisotope production at the Kazakhstan cyclotron

Cyclotrons play an important role for production of carrier-free radioisotopes for various applications in the nuclear medicine, industry, ecology and science. Kazakhstan variable energy isochronous cyclotron, K = 50 MeV, is a 150 cm compact-pole 3 sector positive ion machine. It generates different beams of light ions: protons 6-30 MeV, deuterons 12.5-25 MeV, ³He-ions 18.5-62 MeV, alpha-particles 25-50 MeV. In the last years the cyclotron is rather intensively used for radioisotopes production to meet the needs of the Republic of Kazakhstan. The main users of radioisotope products are the Institutions of Healthcare Ministry and enterprises of oil-chemistry, metallurgy, mining, scientific institutes etc. In this submission a survey on radionuclides production including ²⁰¹Tl, ⁶⁷Ga, ⁵⁷Co, ¹⁰⁹Cd, ⁸⁸Y, ⁸⁵Sr is presented. Practically at all production stages (target preparation, extraction, purification and concentration of a product) original approaches were realized: (1) at target production by means of electrolysis the modes of reverse plating of the material for irradiation and technological layers were finalized, and at ⁶⁷Ga production new extraction with better characteristics were used; that made the deeper purification from zinc, copper and iron possible. At the development of the technologies of the sealed sources production the following results were obtained: (1) ¹⁰⁹Cd production for X-ray fluorescence analysis, and production of experimental samples for Mössbauer sources ⁵⁷Co at rhodium and palladium backings. The tracers ²³⁷Pu, ⁸⁸Y and ⁸⁵Sr used for development of the set of methods for ²³⁹Pu, ²⁴⁰Pu, ⁹⁰Sr and ²⁴¹Am determination in the samples from Semipalatinsk Test Site were produced via nuclear reactions with alpha-particles on ²³⁵U and protons on ⁸⁸Sr, ⁸⁵Rb targets. Produced radiopharmaceutical preparations ²⁰¹Tl chloride and ⁶⁷Ga citrate are supplied to medical centers of Almaty.     

Efficient route to RIKEN click probes for glycoconjugation

A convenient route to RIKEN click probes for glycoconjugation to the amino groups of lysines was established. N-Glycoclusters prepared with human serum albumin by the new method showed the same cell interaction profiles as those synthesized previously. The new route has thus significantly expanding the applicability to glycoconjugation and drug delivery systems.     

Charged particle activation analysis at RIKEN: Past,present and future

To study the effect of rhizosphere pH condition on the cadmium uptake movement, ¹⁰⁹Cd, was applied as a radioisotope tracer to a soybean plant grown in a water culture at pH 4.5 or pH 6.5. The distribution of ¹⁰⁹Cd in the soybean plant was observed radiographically with an imaging plate (IP). The amount of Cd transported from the root to the upper part of the plant at pH 4.5 was approximately two times higher than that at pH 6.5. However, the movement of Cd in the upper part of the plant was similar under both pH conditions. The distribution of Cd inside the internodes at pH 4.5 also showed similar pattern to that at pH 6.5, suggesting that once Cd reached to the vessel of the root, the movement of Cd was not dependent on rhizosphere pH conditions.     

Radioisotope sources for X-ray fluorescence analysis

Problems involved in developing radioisotope sources and the characteristics of potentially useful radioisotopes for X-ray fluorescence analysis are presented. Some of the isotopes, which are not in use but look very promising, are indicated.     

Potential and Charge Distribution at Semiconductor-electrolyte Interfaces

The present article deals with the basic concepts of charge and potential distribution at semiconductor-electrolyte interfaces. The authors use examples to show how external polarization and the variation of the electrolyte composition can change the potential drop across the space-charge region in the semiconductor and in the Helmholtz double layer at the interface. The article also contains a detailed discussion of the effects exerted by surface properties and by injection of carries on the distribution of charge and potential.     

Charge exchange mass spectrometry at high energy

It is shown that charge exchange mass spectra using various reagent ions can be determined on a commercial double focusing mass spectrometer. The experiment relies upon the presence of a collision region held at a potential above ground with the product ions being selected by their unique kinetic energies. Cyclohexene has been studied in detail and the results are in agreement with previous thermochemical and field ionization kinetics data. Agreement with reported charge exchange spectra of n-propanol, taken at lower energies, is good. The present results, including both the variation of spectra with reagent gas and the small range of kinetic energies present in the charge exchange beam, indicate that a resonant or near resonant process is involved. Thus, the internal energy of the nascent ion is defined within quite narrow limits, just as is the case for charge exchange at lower energy.     

金/铜纳米异质界面的电荷转移等离激元调控

金属纳米结构由于其独特的局域表面等离激元共振现象而倍受关注,对催化、传感、纳米医学以及光学器件等具有重要意义.电荷转移等离激元共振强烈依赖于纳米单元间的导电结点,可产生频率连续可调的共振光吸收和光散射,为获得高度局域化的增强光磁场和光热效应提供了可能.然而,受制于已有构筑手段和有限的结构种类,相关研究仍处于初级阶段.针对此,本工作发展了一种十分简单、有效的Au/Cu纳米异质结点调控策略,利用廉价易得的天然DNA分子在金纳米粒子“种子”表面发生非特异性吸附,有效控制铜在金表面发生异相成核时的相间接触面积,得到导电结点宽度连续可调的电荷转移纳米粒子二聚体.实验光谱和理论模拟显示,结点宽度、铜和金纳米粒子的尺寸是决定电荷转移等离激元性质的重要参数,其分别可由DNA吸附量、Cu²⁺加入量和金纳米粒子尺寸加以控制,进而实现共振波长在可见至近红外区的宽广调节.通过与其它吸附分子对比证明了DNA吸附调控模式的独特性.这种具有可调控导电结点的双金属纳米异质界面为实现电荷转移等离激元共振与催化和传感等功能的集成以及相关应用探索奠定了重要基础.     

Charge dependence of adsorption energy of ions at electrodes

Analysis of the energetic and geometric characteristics of the inner part of the electrical double layer has been carried out in the presence of the specific adsorption of ions accompanied by change in the dimensions and dielectric properties of the inner layer. On the basis of the formulae for the electrochemical potential of the adsorbed ion on the electrode surface and for the components of the inner layer capacity, the equations of the Frumkin isotherm and of its parameters have been derived. It has been shown that, in general, the Frumkin isotherm is non-linear at the given electrode charge and the charge dependence of the adsorption equilibrium constant has a parabolic form. The results of the corresponding theoretical calculations have been compared with the experimental data obtained by the study of the specific adsorption of tetra-alkylammonium cations on a bismuth electrode in ethanolic and aqueous solutions. Good agreement of the experimental results with those calculated theoretically confirm the validity of the equations derived.     

Charge flipping at work: a case of pseudosymmetry

Charge flipping (CF) is an amazingly simple structure solution method that uses single-crystal X-ray diffraction data. It is truly ab initio, no preliminary information on atom types, chemical composition, or space group symmetry is required. The algorithm is iterative and alternates between real and reciprocal spaces. Its simplest version only changes (flips) the sign of the electron density below a threshold, while in reciprocal space, it prescribes the moduli of observed structure factors. In this communication, we apply the algorithm in practice. The selected example presents a whole range of difficulties: it is large, contains only light atoms, is noncentrosymmetric, and shows a particularly awkward pseudosymmetry. To solve it with any of the traditional methods requires many hours of computer time, followed by a day of expert's handwork to find missing and to remove spurious atoms. In contrast, the CF algorithm provides the complete structure in a few seconds and without human intervention. It is also remarkable that the success rate is 100%, that is, any starting point in the high-dimensional phase space leads to the solution. The treatment of translational pseudosymmetry is obviously a favorable case. Similar resistant structures with pseudosymmetries or ambiguous space groups are the practical applications where the CF method could well complement standard software procedures.     

Rate Limiting Steps of Charge Transfer at Conducting Polymers

The rate limiting steps of the charge transfer between the solution and a conducting polymer during the switching between oxidation states are investigated by means of ac electrogravimetry. It is shown that the polymer requires anion entry and cation and solvent expulsion to compensate for the positive charges formed during the polymer oxidation. The insertion/expulsion laws, the diffusion coefficients of the species, and the atomic weights of the inserted/expelled species are determined.     

Charge and potential at the oxide/solution interface

A model of the oxide water interface postulating the existence of a finite layer of hydrolyzed material at the surface is considered. A modified Poisson-Boltzmann equation is obtained for the distribution of ions and potential in this region. Values of the titratable charge and zeta potential are calculated and found to be in good agreement with experimental values reported for these systems.     

A Radioisotope Flow-Circulation Tracer Method for Determination of Sulfur Uptake and Exchange

A combined radioactive flow-circulation tracer method has been developed and applied to a CoMo/Al₂O₃ catalyst for measurement of sulfur uptakes and of catalyst - gas phase sulfur exchange in the H₂S partial pressure range of 2–47 kPa and the temperature range of 373–673 K. Equilibrium between gas-phase and catalyst sulfur species was rapidly achieved. A substantial part of the sulfur uptake was retained as adsorbed (reversible) sulfur species. The exchange of sulfur increased with increase in temperature up to 573 K and in H₂S partial pressure up to 4 kPa.     

Pt／YSZ固体电解质界面氧的电荷传递过程研究

用极化法研究了不同温度和氧分压下Ｐｔ／ＹＳＺ界面氧的电荷传递过程．研究发现氧电荷传递过程的阴、阳极电荷传递系数为１，不随温度和氧分压而变．从实验和反应机理推导得到，Ｐｔ／ＹＳＺ界面的交换电流密度和氧分压之间存在，ｉ０＝２ＦＫｒ（ＫＯ２ＰＯ２）１／４（１＋ＫＯ２ＰＯ２）１／２的关系．通过数学分析还获电化学反应速度常数，氧在Ｐｔ表面上吸附平衡常数等重要参数     

Charge transfer at biotic/abiotic interfaces in biological electrocatalysis

In this opinion paper, we discuss the charge transfer at biotic/abiotic interfaces in man-made and biological electrochemical systems. Specifically, we will first introduce the heterogeneous charge transfer at the bioelectrode interface, followed by the intramolecular change transfer in peptide and protein structures, and finally discuss the extracellular charge transfer in electrogenic microorganisms. In addition to discussion of charge transfer mechanisms and synthetic structures/scaffolds required for it, a particular focus will be given to novel experimental designs that are able to bring new concepts and boost mechanism understanding and applications development. There are also discussions on the combination of modern computational techniques and experimental characterizations.     

铝厂污泥在不同煅烧温度的晶相结构研究

铝厂污泥主要成分是-AlOOH,其中部分是晶体,部分是无定形体。将此污泥分别于450,600,800,1000,1050,1200和1300 ℃进行了煅烧,探讨污泥在不同温度下的晶相变化,为污泥的综合利用提供可靠的数据。采用XRD法和SEM法表征了污泥在不同温度下的晶相结构和显微结构。实验结果表明:随着煅烧温度的提高,污泥发生如下变化过程: 这与常规转化规律不同。在450,600,800,1000和1100 ℃的试样中均形成了-Al2O3和无定形体结构的微晶,随着温度的升高,-Al2O3含量增加而无定形体结构的微晶含量降低。当煅烧温度上升至1200和1300 ℃时, - Al2O3和无定形体结构的微晶全部转变为 - Al2O3。 -Al2O3是介稳态,高活性,-Al2O3是稳定态,低能态。