一种新型铒镱共掺碲硅酸盐玻璃的光谱性质及荧光俘获效应研究

用高温熔制法制备了系列Er^3＋／Yb^3＋共掺碲硅酸盐玻璃样品，测试和分析了玻璃样品的吸收光谱、荧光光谱、上转换发光光谱及热稳定性。结果表明：这种玻璃具有较宽的荧光半高宽、较大的受激发射截面，较好的热稳定性。970nm泵浦下该系列玻璃在可见光525，546和658nm这3处存在明显的上转换现象，它们分别由Er^3＋离子^2H11/2→^4 I15/2，4S3/2→^4 I15/2和^4 F9/2→^4 I15/2辐射跃迁产生。另外，测试和讨论了在不同样品厚度下玻璃的光谱特性，如荧光光谱、荧光寿命和上转换发光光谱等。结果表明，荧光俘获效应对Er^3＋离子1．5μm波段荧光及上转换发光都有着较大的影响，并随着玻璃厚度的增加而增大，导致测量值与实际值产生较大的偏差。     

Monte Carlo Simulation of Radiation Trapping in Hg–Ar Fluorescent Discharge Lamps

The line spectra of emitted resonance radiation from mercury and the effective decay rates of the Hg 6³P₁ and 6¹P₁ levels in mercury–argon discharges are simulated by a Monte Carlo method. The hyperfine splitting, the natural isotopic composition, collisional transfer of excitation, foreign gas collisions and quenching are considered to describe in detail the 253.7 nm and 184.9 nm lines. The calculations are performed for Hg vapor densities corresponding to coldest spot temperatures of 5–100°C, and discharge parameters typical for fluorescent lamp operation. The densities of the Hg 6³P₁ and 6¹P₁ levels are consistently estimated by means of a set of balance equations for the Hg 6³P₀, 6³P₁, 6³P₂, and 6¹P₁ excited states. The resulting uv radiation output of the discharge is then estimated for a tube radius of 18 mm, argon pressure of 400 Pa, discharge current 0.4 A, and wall temperatures of 20–80°C. The results obtained show a good agreement as compared with published experimental data.     

Studies on Nuclear Resonant Scattering of Synchrotron Radiation by 40K

The studies on nuclear resonant scattering by ⁴⁰K using synchrotron radiation are reviewed. Brilliant and high pure synchrotron radiation permitted us to observe the nuclear resonant forward scattering by ⁴⁰K in a powdered KCl sample, the excitation of which is impossible with ordinary radioactive sources. Furthermore, nuclear resonant inelastic scattering of synchrotron radiation by ⁴⁰K in the KCl sample at room temperature has been measured using a high-resolution monochromator. Adding to these, from the excitation experiments of ⁴⁰K, the energy and lifetime of the first excited state of ⁴⁰K were confirmed. These measurements clearly show that the studies on the electronic states through hyperfine interactions and the dynamical properties of potassium atoms, which are very important in material science and biology, are possible. It should be noted that ⁴⁰K is the natural isotope of potassium and weakly radioactive. Our observation of forward and inelastic scattering of the radioactive nuclide ⁴⁰K will lead to further studies on other radioactive nuclides the resonant forward and inelastic scattering of which are not observed to date.     

共振瑞利散射法测定棉子糖含量的研究及应用

在pH=9.90的B-R缓冲溶液中,棉子糖能显著降低FeCl3的共振瑞利散射光强度,基于此建立了一种测定棉子糖含量的新方法。在优化实验条件下,FeCl3的共振瑞利散射光谱强度的减少值与棉子糖浓度呈良好的线性关系,线性范围为0.75~3.0μg/mL,相关系数(R=0.9975)。该方法可用于保健食品中棉子糖含量的测定。     

Electronic and Magnetic Transitions in Europium Compounds Studied by Nuclear Forward Scattering of Synchrotron Radiation

Since its observation in 1985, nuclear resonance scattering of synchrotron radiation has become an excellent tool to study hyperfine interactions as well as dynamical effects in solids. It has proven to be a complementary method to Mössbauer spectroscopy. Nuclear resonance scattering combines the advantages of both local probe experiments and scattering techniques. It gives valuable information as well on electronic and magnetic structures and on dynamics in solids. Experiments benefit from the high beam quality of third-generation synchrotron radiation sources, as the small beam size and divergence. Besides the standard isotope ⁵⁷Fe, other Mössbauer isotopes have become more important in nuclear resonant scattering of synchrotron radiation. This article concentrates on the ¹⁵¹Eu isotope.     

Crystallization of Methylammonium Lead Halide Perovskites by Optical Trapping

Single crystals of organolead halide perovskites attract much attention to electrooptical and photovoltaic applications. They are usually prepared in precursor solutions incubated at controlled temperatures or under optimized vapor atmosphere conditions, and thus, multiple perovskite crystals are nucleated all over the solution. Multiple nucleation of crystals prevents efficient use of precursors in the preferential growth of large single crystals. An innovative approach is presented for spatiotemporally controlled, selective nucleation and growth of single crystals of lead halide perovskites by optical trapping with a focused laser beam. Upon such trapping in unsaturated precursor solutions, nucleation of MAPbX₃ (MA=CH₃NH₃⁺; X=Cl^?, Br^?, or I^?) is induced at the focal spot through increase in the concentration of perovskite precursors in the focal volume. The rate at which the nucleated crystal grows depends upon whether the perovskite absorbs the trapping laser or not. These findings suggest that optical trapping would be useful to prepare various perovskite single crystals and modify their optical and electronic properties; thereby, offering new methods for engineering of perovskite crystals.     

Continuous-Flow Nanoparticle Trapping Driven by Hybrid Electrokinetics in Microfluidics

We introduce herein an efficient microfluidic approach for continuous transport and localized collection of nanoparticles via hybrid electrokinetics, which delicately combines linear and nonlinear electrokinetics driven by a composite DC-biased AC voltage signal. The proposed technique utilizes a simple geometrical structure, in which one or a series of metal strips serving as floating electrode (FE) are attached to the substrate surface and arranged in parallel between a pair of coplanar driving electrodes (DE) in a straight microchannel. On application of a DC-biased AC electric field across the channel, nanoparticles can be transported continuously by DC bulk electroosmotic flow, and then trapped selectively onto the metal strips due to AC-field induced-charge electrokinetic (ICEK) phenomenon, which behaves as counter-rotating micro-vortices around the ideally polarizable surfaces of FE. Finite-element simulation is carried out by coupling the dual-frequency electric field, flow field and sample mass transfer in sequence, for guiding a practical design of the microfluidic nanoparticle concentrator. With the optimal device geometry, the actual performance of the technique is investigated with respect to DC bias, AC voltage amplitude, and field frequency by using both latex nanospheres (∼500 nm) and BSA molecules (∼10 nm). Our experimental observation indicates nanoparticles are always enriched into a narrow bright band on the surface of each FE, and a horizontal concentration gradient even emerges in the presence of multiple metal strips, which therefore permits localized analyte enrichment. The proposed trapping method is supposed to guide an elaborate design of flexible electrokinetic frameworks embedding FE for continuous-flow analyte manipulation in modern microfluidic systems.     

共振光散射光谱法测定痕量氯离子

定量测定氯离子的传统重量法、滴定法、硫氰酸汞比色法、比浊法的灵敏度和精密度均不够理想。共振光散射光谱法(Resonance Light Scattering RlS)是一种新的分子光谱技术,灵敏度高,可用普通的荧光分光光度计测量。本文用它测定痕量氯离子,结果令人满意。     

共振瑞利散射法测定百草枯的研究

在pH=7.0的NaAc-HAc缓冲溶液中,单独的碘化钾汞试剂或者百草枯溶液的共振瑞利散射(RRS)十分微弱。碘化钾汞试剂和百草枯反应形成疏水性较强纳米微粒,导致RRS急剧增强,从而建立了一个灵敏的测定百草枯的RRS新方法,且对RRS增强的机理进行了初步探讨。实验表明:在λ=497nm处,RRS强度与百草枯浓度有良好的线性关系,线性范围在0.01～13.0mg/L,检出限为8.0μg/L。本法用于大米中百草枯含量的测定,结果满意。     

催化共振光散射法测定痕量亚硝酸根

根据磷酸中亚硝酸根对溶解O2氧化I^-生成I3^-的反应具有明显催化作用,I3^-与结晶紫结合使共振光散射（RLS）增强,建立了测定痕量NO2^-的催化共振光散射法。考察了体系RLS强度的影响因素,优化了反应条件。最大RLS峰位于690．6nm波长处,NO2^-的浓度在2．20～340μg／L范围内与RLS强度增强值呈良好的线性关系,方法检出限为0．68μg／L。用于环境水样中NO2^-测定,与文献方法对照结果满意。     

Radiation doses at high altitudes and during space flights

There are three main sources of radiation exposure during space flights and at high altitudes—galactic cosmic radiation, solar cosmic radiation and radiation of the earth's radiation belt. Their basic characteristics are presented in the first part of this paper.Man's exposure during space flights is discussed in the second part of the paper. Particular attention is devoted to the quantitative and qualitative characteristics of the radiation exposure on near-earth orbits: both theoretical estimation as well as experimental data are presented. Some remarks on radiation protection rules on-board space vehicles are also given.The problems connected with the radiation protection of air crew and passengers of subsonic and supersonic air transport are discussed in the last part of the paper. General characteristics of on-board radiation fields and their variations with flight altitude, geomagnetic parameters of a flight and the solar activity are presented, both based on theoretical estimates and experimental studies. The questions concerning air crew and passenger radiation protection arising after the publication of ICRP 60 recommendation are also discussed. Activities of different institutions relevant to the topic are mentioned; strategies to manage and check this type of radiation exposure are presented and discussed. Examples of results based on the author's personal experience are given, analyzed and discussed.     

Interference by Desferrioxamine of Spin Trapping Oxy-Radicals For ESR Analysis

Abstract

The iron chelator desferrioxamine (DEF), commonly used to assess the involvement of iron in oxy-radical production, was examined with respect to its effect on spin trapping oxy-radicals generated independently of iron. OH. was generated by photolysis of H₂O₂- was generated by photolysis of Cds dispersions and by the hypoxanthine-xanthine oxidase system.In the presence of DEF, the amount of the radicals detected by spin trapping techniques of ESR with 5,5-dimethyl-1-pyrroline-1-oxide was greatly diminished. These results confirmed that DEF is an oxy-radical scavenger and, in addition, indicated that it should not be used to assess the involvement of iron in oxy-radical generation during spin trapping with nitrones for ESR analysis.

An additional finding was that a new radical, as yet uncharacterized, was generated by UV irraditional of DEF.     

离子交换-原子捕集-火焰原子吸收光谱法测定水中的超痕量镍

在文中所述条件下,镍的原子捕集灵敏度较常规法高320倍,即在离子交换法浓缩仅40倍的情况下,可使镍的测定灵敏度提高12800倍,从而成功实现了ppt级超痕量镍的测定。     

Effect of Ultraviolet Radiation Scattering by Deionized Water

Russian Journal of Physical Chemistry A - The effect of an increase in the intensity of light scattering from a deionized water sample in air over time in the UV region is revealed. The dependence...     

结晶紫共振光散射法测定脱氧核糖核酸

研究了三苯甲烷类碱性染料结晶此与DNA作用的共振光散射光谱,在pH9.2-10.5的范围内,加入DNA导致结晶紫共振光散射增强,在512nm处,存在一共振光散射增强峰,其强度与DNA的浓度呈线性关系,据此建立了一种测定DNA的菜振光散射法,方法的线性范围为0－900ng/mL,检出限为5.02mg/mL.已用于混合样品中的DNA的测定.     

测定新药雷洛昔芬的曲利本红共振瑞利散射法

在 pH1.4的醋酸钠 -盐酸缓冲溶液中,曲利本红和雷洛昔芬自身的共振瑞利散射(RRS)均很微弱,只在470nm处有很弱的散射信号,但当它们结合形成离子缔合物后,RRS大大增强,而且产生了新的散射峰,在310～530nm范围内呈现高的散射强度,且以396nm处的散射信号最强 ;RRS强度在0～6.3mg·L-1的范围内与雷洛昔芬的质量浓度成正比 ;方法灵敏度高,对雷洛昔芬的检出限(σ=3)为10.9μg·L-1,而且选择性、稳定性俱佳,由此建立了一种用RRS法测定痕量雷洛昔芬的方法 ;方法用于Evista片中雷洛昔芬含量的测定,结果令人满意