A study of symmetrical LLL X-Ray polylithic interferometers on the basis of the Takagi equations

The Takagi approach to the dynamical theory of x-ray diffraction has been used to study LLL x-ray polylithic interferometers. A computational tool has been implemented to solve the Takagi equations with boundary conditions of the Cauchy type. The mean intensity, visibility and initial phase of the x-ray fringes generated by displacing the analyzer have been calculated for any wavefront, absorption of the incident radiation and for the most common geometric arrangements. Geometric aberrations of different kinds, introduced during interferometer preparation, are considered. The curve relevant to the calculated difference between the reflected and transmitted x-ray fringes as a function of analyzer rotation is in agreement with the experimental curve.     

Strukturen aus AIB2− und BaAl4−analogen Einheiten. I Die Verbindungen Sr4Pd5P5 und Sr2Pd3P3

Structures with AIB₂? and BaAl₄?type Units. I The Compounds Sr₄Pd₅P₅ and Sr₂Pd₃P₃ Sr₄Pd₅P₅ (Cmcm, a = 4.177(1) Å, b = 31.377(5) Å, c = 8.581(2) Å, Z = 4) und Sr₂ Pd₃P₃(Pmmm, a = 4.199(1) Å, b = 4.212(1) Å, c = 34.227(4) Å, Z = 4) have been prepared by heating the elements. Both structures contain exclusively units characteristic for the AIB_2? and BaAl₄?type. The ratio between isolated P-atoms and P₂?pairs is interpreted with an ionic splitting of the formulas.     

Potentiometrische Titration von Sulfat, Barium und Strontium mit Hilfe einer bleisensitiven Elektrode

Zusammenfassung Die bleisensitive Elektrode der Fa. Orion spricht neben Bleiionen auch auf Sulfationen an. Dies ermöglicht die potentiometrische Titration von Sulfat mit Bariumperchlorat sowie die Titration von Barium und Strontium mit Natriumsulfat. Der günstigste pH-Bereich liegt zwischen 5 und 7. Titriermedium sind Dioxan-Wasser-Gemische. Die Verfahren sind sehr empfindlich und erlauben in allen Fällen die Titration bis herab zu 5·10^–4 mMol.Anwendungsbeispiele für die Bestimmung von Schwefel in organischen Verbindungen nach Schöniger- oder Wickbold-Verbrennung sind angegeben.

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Potentiometric titration of sulphate, barium and strontium by means of a lead-sensitive electrode

The Orion lead electrode was found to be responsive not only to lead ions but to sulphate ions, too. This offers possibilities to titrate sulphate with barium perchlorate and reversely barium and strontium with sodium sulphate. The useful pH range is 5–7. Dioxan-water mixtures serve as solvents. The described methods are highly sensitive and allow determinations down to 5×10^–4 millimoles.Examples are given for the determination of sulphur in organic samples after combustion according to Schöniger or Wickbold.

     

Photoluminescence of green nanophosphors Sr2MgSi2O7 doped with Tb3+ under 374-nm excitation

A series of Sr₂MgSi₂O₇:Tb³⁺ nanophosphors is prepared using a high-temperature solid-state reaction. The x-ray diffraction patterns show that the crystal structure of the sample is not significantly affected by Tb³⁺ ions. However, the images of the scanning electron microscope illustrate that the average size of nanoparticles becomes larger with the increase of Tb³⁺ concentration. Unlike earlier investigations on down-conversion emission of Tb³⁺ ion excited by deep ultraviolet light, in this work, the photoluminescence characteristics of Sr₂MgSi₂O₇ nanophosphors doped with different Tb³⁺ concentrations are analyzed under 374-nm excitations. The intense green emission at 545 nm is observed at an optimal doping concentration of 1.6 mol%. The main reason for the concentration quenching is due to the electric dipole-electric dipole interaction among Tb³⁺ ions.     

Flame Emission Spectrometry Using Atomic Absorption Apparatus (I) Determination of Sr In Sea Water

Flame emission determination of Sr in sea water is studied using an ordinary atomic absorption apparatus. The analytical line 4607 A is used with background correction at 4616 A. The ionization is found to be negligible in air acetylene flame with sea water, and the interference of H₂SO₄ is elimentated using the higher part of the flame.     

Aufbau und Erprobung von Flächenstrahlungsquellen als Sekimdärnormale zur Prüfung von Kontaminationsmeßgeraten für Betastrahler und zur Beglauhigung von Flächenstrahlungsquellen als Normale

Zur Prüfung von Kontaminationsmeβgeräten und zur Beglaubigung von Flächenstrahlungsquellen als Normale wurden im Deutscheti Amt für Meβwesen und Warenprüfung zwei Sälze von Flächenstrahlungsquellen mil den Betastrahlen ⁹⁰Sr/⁹⁰Y, ²⁰¹Tl und ⁶⁰Co angefertigt. Durch das dabei verwendete Herstellungsverfahren, bei dem je ein Tropfen rudioakliver Lösung in ein Feld eines vorgegebenen Rasters gebracht wurde, konnte eine sehr gleichmäβige Verteilung der akliven Substanz über die Quellenfläche erreicht und eine unmiltelbare Bestimmung der Flächenaktivitätswerte ermöglicht werden. Der besondere Aufbau der Flächenstrahlungsquellen geslatlet es, auf einfache Weise Meβfehler bei Kontaminationsme βgeräten, die durch das Material der Unterlage, auf dem sich die aktive Substanz befindet, und durch die Dicke der akliven Schicht hervorgerufen tcerden, zu erfassen oder zu eliminieren.     

Isotope Zusammensetzung Der Mineralwässer Der Mongolei

Abstract

The isotopic composition (D, ¹⁸O, ⁸⁷Sr, ³He) of thermal and mineral waters of Mongolia is discussed. The Sr-isotope ratio depends on the rock's contact. Near the Chubsugul-lake ³He-/⁴He-values are high. A certain similarity between the waters of Mongolia and those of East Siberia can be derived from the obtained data.     

微波场对(Ba,Sr)3MgSi2O8：Eu2+,Mn2+荧光粉中Mn2+ 660 nm红光能量传递的影响

研究了2.45 GHz微波灼烧(Ba,Sr)₃MgSi₂O₈：Eu²⁺,Mn²⁺荧光粉的非热效应对Mn²⁺离子660 nm红光发射强度的影响。在相同的加热温度条件下,增加微波场的输出功率,微波非热效应导致Eu²⁺离子蓝光的跃迁概率增加,Eu²⁺通过(Ba,Sr)₃MgSi₂O₈基质晶格把能量传递给Mn²⁺,进而使Mn²⁺的跃迁概率增加,导致红光发射增强。提出了一种微波场非热效应对能量传递影响的新观点,认为在微波加热过程中强微波磁场可能会对像Mn²⁺这样具有顺磁性的激活剂离子的能级结构和能量传递性质产生干扰作用。     

Theoretical STM images of alkaline-earth metal adsorbed Si(1 1 1)3 × 2 surfaces

We have performed total-energy calculations to study theoretical scanning tunneling microscopy (STM) images of the Si(1 1 1)3 × 2 surfaces induced by the adsorption of alkaline-earth metals (AEMs). Previously, in a series of works on Ba/Si(1 1 1) system, we have found that the observed Si(1 1 1)3 × 1-Ba LEED phase indeed has a 3 × 2 periodicity with a Ba coverage of 1/6 ML and the HCC substrate structure. Based on results of the Ba case, we proposed that the HCC structure is also adopted for other AEM atoms, which was confirmed by our recent work. In this paper, we mainly report the STM simulations for different AEM systems to compare with existing experimental data. We discuss the difference in the detailed STM images for different AEM adsorbates. Especially, the difference in filled-state images between Mg and other AEM atoms is attributed to the strong Mg-Si interaction.