Clean quartz matters for cosmogenic nuclide analyses: An exploration of the importance of sample purity using the CRONUS-N reference material

Reference materials are key for assessing inter-laboratory variability and measurement quality, and for placing analytical uncertainty bounds on sample analyses. Here, we investigate four years of data resulting from repeated processing of the CRONUS-N reference material for cosmogenic ¹⁰Be and ²⁶Al analyses. At University of Vermont, we prepared a CRONUS-N aliquot with most of our sample batches from 2013 to 2017; these reference material samples were then distributed to four different accelerator mass spectrometry facilities, yielding 73 ¹⁰Be analyses and 58 ²⁶Al analyses. We determine CRONUS-N ¹⁰Be concentrations of (2.26 ± 0.14) x 10⁵ atoms g⁻¹ (n = 73, mean, 1 SD) and ²⁶Al concentrations of (1.00 ± 0.08) x 10⁶ atoms g⁻¹ (n = 58, mean, 1 SD). We find a reproducibility of 6.3% for ¹⁰Be and 7.7% for ²⁶Al (relative standard deviations). We also document highly variable ²⁷Al and Mg concentrations and a ¹⁰Be dispersion twice as large as the mean AMS analytic uncertainty. Analyses of the CRONUS-N material with and without density separation demonstrate that non-quartz minerals are present in the material and have a large impact on measured concentrations of ²⁷Al, ¹⁰Be, and impurities; these non-quartz minerals represent only a very small portion of the total mass (0.6–0.8%) but have a disproportionally large effect on the resulting data. Our results highlight the importance of completely removing all non-quartz mineral phases from samples prior to Be/Al extraction for the determination of in situ cosmogenic ¹⁰Be and ²⁶Al concentrations.     

大气气溶胶中若干有机物的含量和季节变化

研究、探讨青岛近岸大气气溶胶中多芳烃类化合物的浓度水平、变化特征及影响因素。用高效液相色谱荧光检测法分析了青岛近岸大气气溶胶中的多环芳烃(PAHs)的含量水平,共检出13种多环芳烃化合物。结果表明该类化合物总量(∑PAHs)具有明显的季节特征,呈现春季<秋季<冬季的特征,人类活动可能是其主要来源。     

16排螺旋CT智能跟踪技术在下肢动脉CTA中的应用

目的探讨16排螺旋CT造影剂跟踪技术在下肢动脉CTA造影中的应用价值。方法对53例采用跟踪技术组病例与46例未采用跟踪技术组病例的下肢动脉CTA图像效果进行对照分析。结果采用跟踪技术的下肢动脉CTA的造影成功率及图像质量优于未采用跟踪技术组。结论下肢动脉CTA常规采用智能跟踪技术可提高CT成像的成功率及图像质量,利于下肢动脉病变的诊断。     

GE VCT-高图像质量和低剂量的和谐

在本文中讨论了实现图像质量和X射线剂量的和谐和同一的重要性,介绍了GELightSpeedVCT在硬件,软件和临床应用上降低病人剂量的方法。VCT在实现各向同性高分辨率的同时努力提高X射线的有效利用率,降低病人剂量,真正实现了高图像质量和低剂量的和谐。     

用于颗粒土微观力学行为试验的微型三轴试验仪

颗粒土的微观力学行为（如土颗粒的运动与破碎等）决定着其宏观应力-应变行为,如应变局部化、应力硬化等。为研究颗粒土的微观力学行为,开发了一台微型三轴试验装置。它的轴向加载系统由伺服控制的步进转动马达与涡轮传动的减速器组成,围压由GDS压力控制器提供,压力室采用高透光率,高强度的轻质材料制成。借助于X射线显微CT及图像处理分析技术,该装置能实现对干砂土微尺寸试样（直径为8 mm,高度为16 mm）在三轴剪切条件下微观特性的无损检测。采用该三轴试验装置对粒径为0.60～1.18 mm 的LBS（Leighton Buzzard sand）试样在1.5 MPa的围压下进行了试验。结果显示,试验装置测得应力-应变曲线合理,显微CT 图像特征清晰,能够用于颗粒土体微观土力学行为的试验研究。     

砂土颗粒三维形态的定量表征方法

颗粒形态是影响砂土力学特性的重要因素,特别是影响砂土在低应力状态下的抗剪强度、剪胀效应和临界状态行为,以及高应力状态下的颗粒破碎行为。因此,准确地重构砂粒的三维形态,并量化计算其形态表征参数是研究砂粒形态效应的前提工作。借助于高精度的CT扫描技术和图像处理技术,获得近海石英砂和风化花岗岩残积砂这两类砂土颗粒的三维形态信息。采用球谐函数序列实现两种砂颗粒三维形态的准确重构,并通过球谐函数分析计算砂土颗粒的体积来验证该方法的有效性。基于球谐重构的三维砂粒表面,提出了实用性的方法来计算砂粒的表面积、表面曲率和三维尺寸等,进而计算砂粒的三维球度、圆度和伸长率等形态表征参数。结果表明,当球谐函数阶达到15时,其重构的砂粒基本形状和表面纹理均与真实砂粒非常接近;近海石英砂在水流搬运和磨蚀的作用下颗粒形态较为规则和圆滑,球度和圆度较大,而风化花岗岩残积砂则在物理风化和剥蚀作用下颗粒形态较为复杂和粗糙,球度和圆度较小;而这两种地质作用对砂土颗粒的伸长率则没有明显的影响。     

CE3玉兔号月球车APXS特征X射线能谱信息分析

通过对CE3玉兔号月球车粒子激发X射线谱仪（APXS）获取的数据进行处理,获得测点的累积特征X荧光计数率谱线,经小波滤波,消除放射性涨落对X荧光谱线的影响。由能量刻度获得了月球车着陆点月壤元素X射线特征能量峰,由此分析了着陆点月壤元素的成分,得知测量点月壤元素成分包括Si、Ca、Al、Mg、K、P、S、Fe、Ti、Ni、Cr、Mo、Sr、Y、Zr、Nb。研究结果为月陆地质演化提供了有利的参数制约。     

高压密闭消解-电感耦合等离子体光谱和质谱联合测定海洋地质样品中52种元素

An improved analytical method to determine the content of 52 major, minor and trace elements in marine geological samples, using a HF-HCl-HNO_3 acid system with a high-pressure closed digestion method(HPCD), is studied by an inductively coupled plasma optical emission spectrometry(ICP-OES) and an inductively coupled plasma mass spectrometry(ICP-MS). The operating parameters of the instruments are optimized, and the optimal analytical parameters are determined. The influences of optical spectrum and mass spectrum interferences, digestion methods and acid systems on the analytical results are investigated. The optimal spectral lines and isotopes are chosen, and internal standard element of rhodium is selected to compensate for matrix effects and analytical signals drifting. Compared with the methods of an electric heating plate digestion and a microwave digestion, a high-pressure closed digestion method is optimized with less acid, complete digestion,less damage for digestion process. The marine geological samples are dissolved completely by a HF-HCl-HNO_3 system, the relative error(RE) for the analytical results are all less than 6.0%. The method detection limits are 2–40μg/g by the ICP-OES, and 6–80 ng/g by ICP-MS. The methods are used to determine the marine sediment reference materials(GBW07309, GBW07311, GBW07313), rock reference materials(GBW07103, GBW07104,GBW07105), and cobalt-rich crust reference materials(GBW07337, GBW07338, GBW07339), the obtained analytical results are in agreement with the certified values, and both of the relative standard deviation(RSD) and the relative error(RE) are less than 6.0%. The analytical method meets the requirements for determining 52 elements contents of bulk marine geological samples.     

High‐temporal resolution fluvial sediment source fingerprinting with uncertainty: a Bayesian approach

This contribution addresses two developing areas of sediment fingerprinting research. Specifically, how to improve the temporal resolution of source apportionment estimates whilst minimizing analytical costs and, secondly, how to consistently quantify all perceived uncertainties associated with the sediment mixing model procedure. This first matter is tackled by using direct X‐ray fluorescence spectroscopy (XRFS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses of suspended particulate matter (SPM) covered filter papers in conjunction with automatic water samplers. This method enables SPM geochemistry to be quickly, accurately, inexpensively and non‐destructively monitored at high‐temporal resolution throughout the progression of numerous precipitation events. We then employed a Bayesian mixing model procedure to provide full characterization of spatial geochemical variability, instrument precision and residual error to yield a realistic and coherent assessment of the uncertainties associated with source apportionment estimates. Applying these methods to SPM data from the River Wensum catchment, UK, we have been able to apportion, with uncertainty, sediment contributions from eroding arable topsoils, damaged road verges and combined subsurface channel bank and agricultural field drain sources at 60‐ and 120‐minute resolution for the duration of five precipitation events. The results presented here demonstrate how combining Bayesian mixing models with the direct spectroscopic analysis of SPM‐covered filter papers can produce high‐temporal resolution source apportionment estimates that can assist with the appropriate targeting of sediment pollution mitigation measures at a catchment level. © 2015 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.     

外源硒对罗布麻幼苗生长及光合作用的影响

硒是植物生长发育的必需元素,能促进植物生长。采用盆栽试验的方法,研究了施用不同浓度的外源硒对一年生罗布麻幼苗生长及叶绿素荧光参数的影响。研究结果表明：根施（R）和叶面喷施（L）两种施硒方式下,硒浓度与罗布麻一年生幼苗生长及叶绿素荧光参数有极显著相关性,表现为,一定浓度范围内（0～1.5 mg·kg^-1）,随着硒浓度的增加,罗布麻茎干重、叶干重、株高、茎粗、主叶对数和侧枝数均有有不同程度的上升;Fv/Fm、Fv/Fo、Ψo、φEo、PIABS、均随着施硒浓度的增加而增加;V_K、V_J、V_I均随着施硒浓度的增加而逐渐下降,S_m逐渐上升;说明施硒促进了罗布麻叶PSII的活性,提高了PSII反应中心的开放程度,增大其光能利用率。但随着供应浓度的进一步提高,各项生长及荧光指标有所降低,因此过量的硒供应对于罗布麻生长不利,而且有益与有害之间的范围很小,具体罗布麻栽培中要严格控制硒用量在1～3 mg·kg^-1范围内。搜索 #SrsZzqBAngjSTips { Z-INDEX: 999999999; POSITION: absolute; WIDTH: 56px; HEIGHT: 24px; LEFT: 1342177.27em } #SrsZzqBAngjSTips A { POSITION: relative; LINE-HEIGHT: 24px; MARGIN: -32px 0px 0px; PADDING-LEFT: 23px; WIDTH: auto; DISPLAY: block; BACKGROUND: url(http://mat1.gtimg.com/www/sogou/sogou_tips_v1.png) no-repeat 0px 0px; HEIGHT: 24px; COLOR: #000; FONT-SIZE: 12px; TEXT-DECORATION: none } #SrsZzqBAngjSTips A:hover { BACKGROUND-POSITION: 0px -34px; COLOR: #45a1ea }