农产品中微量元素锗的分析方法研究

对农产品中微量元素锗的分析方法进行了综述.其分析方法包括原子荧光光谱法、原子发射光谱法、原子吸收光谱法、原子质谱法、X射线光谱法、分光光度法、分子荧光法、化学发光法、催化极谱法、溶出伏安法和离子色谱法等.     

Galileo ultraviolet spectrometer experiment: initial venus and interplanetary cruise results

The Galileo Extreme Ultraviolet Spectrometer obtained a spectrum of Venus atmospheric emissions in the 55.0- to 125.0-nanometer (nm) wavelength region. Emissions of helium (58.4 nm), ionized atomic oxygen (83.4 nm), and atomic hydrogen (121.6 nm), as well as a blended spectral feature of atomic hydrogen (Lyman-beta) and atomic oxygen (102.5 nm), were observed at 3.5-nm resolution. During the Galileo spacecraft cruise from Venus to Earth, Lyman-alpha emission from solar system atomic hydrogen (121.6 nm) was measured. The dominant source of the Lyman-alpha emission is atomic hydrogen from the interstellar medium. A model of Galileo observations at solar maximum indicates a decrease in the solar Lyman-alpha flux near the solar poles. A strong day-to-day variation also occurs with the 27-day periodicity of the rotation of the sun.     

Comet kohoutek: ultraviolet images and spectrograms

Emissions of atomic oxygen (1304 angstroms), atomic carbon (1657 angstroms), and atomic hydrogen (1216 angstroms) from Comet Kohoutek were observed with ultraviolet cameras carried on a sounding rocket on 8 January 1974. Analysis of the Lyman alpha halo at 1216 angstroms gave an atomic hydrogen production rate of 4.5 x 10(29) atoms per second.     

Three-dimensional atomic-scale imaging of impurity segregation to line defects

Clouds of impurity atoms near line defects are believed to affect the plastic deformation of alloys. Three-dimensional atom probe techniques were used to image these so-called Cottrell atmospheres directly. Ordered iron-aluminum alloys (40 atomic percent aluminum) doped with boron (400 atomic parts per million) were investigated on an atomic scale along the <001> direction. A boron enrichment was observed in the vicinity of an <001> edge dislocation. The enriched region appeared as a three-dimensional pipe 5 nanometers in diameter, tangent to the dislocation line. The dislocation was found to be boron-enriched by a factor of 50 (2 atomic percent) relative to the bulk. The local boron enrichment is accompanied by a strong aluminum depletion of 20 atomic percent.     

直接进样石墨炉原子吸收法与氢化物原子荧光法测定自然水中铅的比较

比较直接进样石墨炉原子吸收法和氢化物原子荧光法测定自然水中铅的优越性。实验表明,直接进样石墨炉原子吸收法的线性范围。0～50μg/L,原子荧光为0～50μg/L,原子吸收和原子荧光相关系数r都优于0.9990。原子吸收法的检出限为2.75μg/L,原子荧光为0.645μg/L。用标准偏差考察方法的精密度,用加标回收考察方法的准确性,加标回收率均84.0%～119.5%,测定值均在标准值范围内。这2种方法都能较好的满足水中铅分析的要求,测定水中铅含量原子荧光光度法是一种比较好的方法。     

原子荧光光度计测定硒的检出限和精密度

[目的]验证原子荧光法测定硒的检出限和精密度的准确性。[方法]运用双道原子荧光光度计AFS-9730测定硒的检出限和精密度,检验其是否满足环境保护部新颁布的《水质汞、砷、硒、铋和锑的测定原子荧光法》(HJ 694—2014)对检出限和精密度的要求。[结果]原子分光光度计测定硒的检出限为0.005 2μg/L,相对标准偏差为0.78%。[结论]原子分光光度计测定硒的检出限和精密度满足环境保护部新颁布的《水质汞、砷、硒、铋和锑的测定原子荧光法》(HJ 694—2014)的要求。     

Quantum state transfer between matter and light

We report on the coherent quantum state transfer from a two-level atomic system to a single photon. Entanglement between a single photon (signal) and a two-component ensemble of cold rubidium atoms is used to project the quantum memory element (the atomic ensemble) onto any desired state by measuring the signal in a suitable basis. The atomic qubit is read out by stimulating directional emission of a single photon (idler) from the (entangled) collective state of the ensemble. Faithful atomic memory preparation and readout are verified by the observed correlations between the signal and the idler photons. These results enable implementation of distributed quantum networking.     

Direct imaging of reconstructed atoms on TiO2 (110) surfaces

Determining the atomic structures of oxide surfaces is critical for understanding their physical and chemical properties but also challenging because the breaking of atomic bonds in the formation of the surface termination can involve complex reconstructions. We used advanced transmission electron microscopy to directly observe the atomic structure of reduced titania (TiO2) (110) surfaces from directions parallel to the surface. In our direct atomic-resolution images, reconstructed titanium atoms at the top surface layer are clearly imaged and are found to occupy the interstitial sites of the TiO2 structure. Combining observations from two orthogonal directions, the three-dimensional positioning of the Ti interstitials is identified at atomic dimensions and allows a resolution of two previous models that differ in their oxygen stoichiometries.     

Multiphoton ionization of atoms

Studies of multiphoton ionization of atoms have revealed several unexpected characteristics. The confluence of the experimental evidence leads to the hypothesis that the basic character of the atomic response involves highly organized, coherent motions of entire atomic shells. The important regime, for which the radiative field strength is greater than an atomic unit (e/a(2)(0)), can be viewed in approximate correspondence with the physics of fast (approximately 10 MeV per atomic mass unit) atom-atom scattering. This physical picture provides a basis for the expectation that stimulated emission in the x-ray range can be produced by direct, highly nonlinear coupling of ultraviolet radiation to atoms.     

原子吸收光谱法在土壤环境监测中的应用

原子吸收光谱法是土壤环境监测中的一项重要技术.对原子吸收光谱法的检测方法、土壤样品的前处理以及原子吸收光谱法在土壤环境监测中的应用进行了归纳和评述.同时,对原子吸收光谱法未来的发展趋势进行了展望：随着原子吸收光谱技术的提高以及样品前处理技术的不断成熟和进步,原子吸收光谱技术在土壤环境监测中的应用范围越来越广.     

Ultraviolet Emissions Observed near Venus from Mariner V

A Lyman-alpha airglow of atomic hydrogen measured in the outer atmosphere of Venus showed that atomic hydrogen is present. The variation as a function of height indicates that the temperature of the upper atmosphere of Venus is lower than that of Earth. An ultraviolet airglow of atomic oxygen was not found. An ultraviolet nightglow was observed on the dark limb.     

Composition measurements of the topside ionosphere

Data from a magnetic mass spectrometer flown on the Explorer 31 satellite show that the ionosphere above 1000 kilometers usually consists of hydrogen ions as the predominant species. Between this altitude and perigee (500 kilometers) the dominant ion species shifts to atomic oxygen, with a significant amount of atomic nitrogen ions also present. Helium ions are present in small quantities at all altitudes. Other minor ions observed are those of 2, 7, 8, 15, 18, and 20 atomic mass units.     

Atomic Control of the SrTiO3 Crystal Surface

The atomically smooth SrTiO(3) (100) with steps one unit cell in height was obtained by treating the crystal surface with a pH-controlled NH(4)F-HF solution. The homoepitaxy of SrTiO(3) film on the crystal surface proceeds in a perfect layer-by-layer mode as verified by reflection high-energy electron diffraction and atomic force microscopy. Ion scattering spectroscopy revealed that the TiO(2) atomic plane terminated the as-treated clean surface and that the terminating atomic layer could be tuned to the SrO atomic plane by homooepitaxial growth. This technology provides a well-defined substrate surface for atomically regulated epitaxial growth of such perovskite oxide films as YBa(2)Cu(3)O(7-delta).     

DNA imaging. Getting a feel for genetic variations

A team of researchers has come up with a novel atomic imaging microscope that may dramatically speed the task of linking genetic variants to diseases. The microscope is a modification of the popular atomic force microscope (AFM), which uses an ultrasharp tip to map surfaces of everything from computer chips to DNA at the atomic level. By using this molecule-sized tip, the researchers were able get their AFM to march down a strand of DNA and identify uniquely shaped reporter molecules engineered to tag the genetic variations.     

原子吸收光谱法测定梅干菜中微量元素的含量

[目的]用原子吸收光谱法测定梅干菜中微量元素的含量,为梅干菜的食用及进一步开发利用提供参考。[方法]以浙江省丽水市自制的梅干菜为样品,采用湿法消解对样品进行处理,用原子吸收光谱法测定了梅干菜中Ca、Mg、Fe、Mn、Zn、Cu、Pb、Cd8种微量元素的含量。I结果]原子吸收光谱法测定的标准曲线相关系数为0．9974～0．9995,相对标准偏差为0．36％～2．80％。加标回收率为96．25％～105．68％。测定表明,梅干菜样品中的Cu、Zn、Fe、Ca、Mg、Mn、Pb、Cd含量分别为0．653、10．687、42．152、707．519、17．786、14．330、0、0.425μg／kg,微量元素含量高低顺序为Ca〉Fe〉Mg〉Mn〉Zn〉Cu〉Cd〉Pb。[结论]梅干菜中含有大量的Ca,且Fe的含量较高,Cd的含量未超过国家标准限量,且未检出Pb,证明梅干菜中微量元素的含量完全符合国家安全标准,可放心食用。     

Standards of time and frequency at the outset of the 21st century

After 50 years of development, microwave atomic clocks based on cesium have achieved fractional uncertainties below 1 part in 10(15), a level unequaled in all of metrology. The past 5 years have seen the accelerated development of optical atomic clocks, which may enable even greater improvements in timekeeping. Time and frequency standards with various levels of performance are ubiquitous in our society, with applications in many technological fields as well as in the continued exploration of the frontiers of basic science. We review state-of-the-art atomic time and frequency standards and discuss some of their uses in science and technology.     

Mariner 6: ultraviolet spectrum of Mars upper atmosphere

Emission features from ionized carbon dioxide and carbon monoxide were measured in the 1900- to 4300-angstrom spectral region. The Lyman alpha 1216-angstrom line of atomic hydrogen and the 1304-, 1356-, and 2972-angstrom lines of atomic oxygen were observed.     

大蒜中部分微量元素的含量分析

[目的]进一步研究开发大蒜中的微量元素组分。[方法]用火焰-原子吸收法、石墨炉-原子吸收法、原子荧光法测定大蒜中Mn、Zn、Cu、Cd、Sr、Fe、Pb、Hg、Se等元素的含量,并进行分析。[结果]试验表明,大蒜中有害元素Hg、Pb、Cd含量较低,Mn、Cu、Fe等有益元素含量较高。[结论]大蒜中含有丰富的微量元素,具有很高的开发利用价值。     

石墨炉原子吸收分光光度法测定水中铜铅镉镍铬的方法研究

建立了石墨炉原子吸收分光光度法测定水中铜、铅、镉、镍、铬的分析方法。优化了仪器条件,通过检出限、精密度和准确度的测试,验证了该方法在金属元素分析中的准确性和有效性,能够满足环境水样中铜、铅、镉、镍、铬的分析要求。     

Direct sub-angstrom imaging of a crystal lattice

Despite the use of electrons with wavelengths of just a few picometers, spatial resolution in a transmission electron microscope (TEM) has been limited by spherical aberration to typically around 0.15 nanometer. Individual atomic columns in a crystalline lattice can therefore only be imaged for a few low-order orientations, limiting the range of defects that can be imaged at atomic resolution. The recent development of spherical aberration correctors for transmission electron microscopy allows this limit to be overcome. We present direct images from an aberration-corrected scanning TEM that resolve a lattice in which the atomic columns are separated by less than 0.1 nanometer.