X射线荧光技术在萨尔布拉克金矿区的综合应用

本文介绍了利用 X射线荧光技术在萨尔布拉克金矿区现场开展地质研究等方面综合应用的一些事例 ,说明将荧光技术和地质、物化探成果有机结合能扩大其在金矿区的应用范围     

Elasticity of CaSnO3 perovskite

The elastic properties of CaSnO₃ perovskite have been measured by both ultrasonic interferometry and single-crystal X-ray diffraction at high pressures. The single-crystal diffraction data collected using a diamond-anvil cell show that CaSnO₃ perovskite does not undergo any phase transitions at pressures below 8.5?GPa at room temperature. Ultrasonic measurements in the multianvil press to a maximum pressure of ～8?GPa at room temperature yielded S- and P-wave velocity data as a function of pressure. For a third-order Birch-Murnaghan EoS the adiabatic elastic moduli and their pressure derivatives determined from these velocity data are K _S0=167.2±3.1?GPa, K ^′ _S0=4.89±0.17, G ₀=89.3±1.0?GPa, G ^′ ₀=0.90±0.02. The quoted uncertainties include contributions from uncertainties in both the room pressure length and density of the specimen, as well as uncertainties in the pressure calibration of the multianvil press. Because the sample is a polycrystalline specimen, this value of K _S0 represents an upper limit to the Reuss bound (conditions of uniform stress) on the elastic modulus of CaSnO₃ perovskite. If the value of αγT is assumed to be 0.01, the value of K _S0 corresponds to K _T0=165.5±3.1?GPa. The 10 P-V data obtained by single-crystal diffraction were fit with a third-order Birch–Murnaghan equation-of-state to obtain the parameters V ₀=246.059±0.013 ų, K _T0=162.6±1.0?GPa, K ^′ _T0=5.6±0.3. Because single-crystal measurements under hydrostatic conditions are made under conditions of uniform stress, they yield bulk moduli equivalent to the Reuss bound on a polycrystalline specimen. The results from the X-ray and ultrasonic experiments are therefore consistent. The bulk modulus of CaSnO₃ perovskite lies above the linear trend of K ₀ with inverse molar volume, previously determined for Ca perovskites. This prevents an estimation of the bulk modulus of CaSiO₃ perovskite by extrapolation. However, our value of G ₀ for CaSnO₃ perovskite combined with values for CaTiO₃ and CaGeO₃ forms a linear trend of G ₀ with octahedral tilt angle. This allows a lower bound of 150?GPa to be placed on the shear modulus of CaSiO₃ by extrapolation.     

Thermal expansion and structural transformations of stuffed derivatives of quartz along the LiAlSiO4–SiO2 join: a variable-temperature powder synchrotron XRD study

 The structural behavior of stuffed derivatives of quartz within the Li_{1− x} Al_{1− x} Si_{1+ x} O₄ system (0 ≤ x ≤ 1) has been studied in the temperature range 20 to 873 K using high-resolution powder synchrotron X-ray diffraction (XRD). Rietveld analysis reveals three distinct regimes whose boundaries are defined by an Al/Si order-disorder transition at x=∼0.3 and a β–α displacive transformation at x=∼0.65. Compounds that are topologically identical to β-quartz (0 ≤ x < ∼0.65) expand within the (0 0 1) plane and contract along c with increasing temperature; however, this thermal anisotropy is significantly higher for structures within the regime 0 ≤ x < ∼0.3 than for those with compositions ∼0.3 ≤ x < ∼0.65. We attribute this disparity to a tetrahedral tilting mechanism that occurs only in the ordered structures (0 ≤ x < ∼0.3). The phases with ∼0.65 ≤ x ≤ 1 adopt the α-quartz structure at room temperature, and they display positive thermal expansion along both a and c from 20 K to their α–β transition temperatures. This behavior arises mainly from a rotation of rigid Si(Al)-tetrahedra about the <100> axes. Landau analysis provides quantitative evidence that the charge-coupled substitution of Li+Al for Si in quartz dampens the α–β transition. With increasing Li+Al content, the low-temperature modifications exhibit a marked decrease in spontaneous strain; this behavior reflects a weakening of the first-order character of the transition. In addition, we observe a linear decrease in the α–β critical temperature from 846 K to near 0 K as the Li+Al content increases from x=0 to x=∼0.5. Received: 26 June 2000 / Accepted: 1 December 2000     

θ—2θ型粉末衍射仪研究溶液水合结构新进展

介绍了近年来研究开发的０－２０型粉末衍射仪研究溶液结构的实验测量方法，衍射强度数据处理技术，以及多原子离子水溶液体系水合结构研究的最新进展。叙述了定性解释液体衍射强度曲线和结构曲线黄金规则的经验公式。     

论外部性脑积水的临床和CT诊断

随医学影像学的发展，本病已非少见疾病，笔者就所收集的８０例，对本病的某些问题作进一步讨论本病的ＣＴ诊断，国内外尚无统一标准。额顶区蛛网膜下腔扩大作为本病主要诊断依据，暂定为６ｍｍ，作为诊断参考，正确认识本病的重要意义在于鉴别于脑萎缩，以及硬膜下积液，与文献材料一致，本病以原发性者居多（６７／８０），而继发性者，本组病例中以化脓性脑膜炎为多见。强调对本病的诊断，不能以有无头围增大作为主要诊断依据，本     

Diffraction by plane sectors and polygons

Time-domain theory of edge and edge-and-vertex diffraction is briefly reviewed and its applications to diffraction by polygons, pyramids and curved reflectors are discussed. The time-domain theory is based on canonical functions defined in terms of inverse trigonometric and algebraic functions, which ensures its numerical efficiency.     

Pressure-induced phase transition in synthetic trioctahedral Rb-mica

 The crystal structure of a synthetic Rb analog of tetra-ferri-annite (Rb–TFA) 1M with the composition Rb_0.99Fe²⁺ _3.03(Fe³⁺ _1.04 Si_2.96)O_10.0(OH)_2.0 was determined by the single-crystal X-ray diffraction method. The structure is homooctahedral (space group C2/m) with M1 and M2 occupied by divalent iron. Its unit cell is larger than that of the common potassium trioctahedral mica, and similar lateral dimensions of the tetrahedral and octahedral sheets allow a small tetrahedral rotation angle α=2.23(6)°. Structure refinements at 0.0001, 1.76, 2.81, 4.75, and 7.2 GPa indicate that in some respects the Rb–TFA behaves like all other micas when pressure increases: the octahedra are more compressible than the tetrahedra and the interlayer is four times more compressible than the 2:1 layer. However, there is a peculiar behavior of the tetrahedral rotation angle α: at lower pressures (0.0001, 1.76, 2.81 GPa), it has positive values that increase with pressure [from 2.23(6)° to 6.3(4)°] as in other micas, but negative values −7.5(5)° and −8.5(9)° appear at higher pressures, 4.75 and 7.2 GPa, respectively. This structural evidence, together with electrostatic energy calculations, shows that Rb–TFA has a Franzini A-type 2:1 layer up to at least 2.81 GPa that at higher pressure yields to a Franzini B-type layer, as shown by the refinements at 4.75 and 7.2 GPa. The inversion of the α angle is interpreted as a consequence of an isosymmetric displacive phase transition from A-type to B-type structure between 2.81 and 4.75 GPa. The compressibility of the Rb–TFA was also investigated by single-crystal X-ray diffraction up to a maximum pressure of 10 GPa. The lattice parameters reveal a sharp discontinuity between 3.36 and 3.84 GPa, which was associated with the phase transition from Franzini-A to Franzini-B structure. Received: 21 October 2002 / Accepted: 25 February 2003     

肺癌的胸片体层片与CT、BAG的X线表现分析和诊断价值比较

目的：探讨胸片，体层片和CT，支气管动脉造影（BAG）对肺癌的诊断价值并对其进行比较。方法：对照病理检查结果对101例患者的胸片、体层片和CT、BAG的X线表现和诊断价值进行了回顾性分析。结果：61例肺癌：胸片、体层片诊断正确43例（70.5%）；定性困难16例（26.2%）;误诊8例(13.1%)。CT诊断正确57例（93.4%）；误诊4例（6.6%）。40例肺癌：BAG中有肿瘤血管改变者35例（87.5%）。特征性造影表现有肿瘤血管（27例、67.5%）；肿瘤染色（20例、50%）；肿瘤包绕（835例、87.5%）。结论：胸片、体层片和CT对肺癌具有很高的诊断价值，以CT为优。胸片、体层片显示段以上支气管情况和肿块整体形态较好，CT显示肿瘤的内部结构，轮廓、瘤周、纵隔胸膜转移和纵隔旁及脊柱旁区病灶具有明显优势。BAG对肺癌有一定的诊断价值。     

川西高原西康群极低级变质岩特征

川西高原广泛分布的西康群，原视为区域低温动力变质作用低绿片岩相变质岩，近期通过1：5万区调，根据粘土矿物X粉晶测试及岩石显微结构鉴定等成果，将其归属于极低级变质岩，并认为区域极低级变质作用主要源于印支造山前的成岩（埋藏）变质作用。     

参加第49届丹佛X射线年会有感

报道了第49届丹佛X射线年会的概况。会议期间,痒于微束装置及其分析技术、全反射技术与应用、探测器研制、薄层分析、样品制备、半导体材料分析等，受到广泛关注。