矿化剂对铝酸钙粉的结构与光谱性能的影响

研究了矿化剂对制备铝酸钙粉的结构与性能的影响.研究中以铝矾土和石灰石为原料,加入一定量的矿化剂,混合均匀,经高温煅烧制得铝酸钙粉.借助于红外光谱、X射线粉末衍射、差热-热重分析等手段对不同原料的铝酸钙粉的结构、组成及性能进行了表征和研究,并对矿化剂在合成铝酸钙中的矿化机理进行探讨.研究表明:加入矿化剂后,可在更低温度条件下煅烧制备出铝酸钙粉,有利于节能减排.红外光谱分析、XRD分析、DTA-TG分析显示:未加矿化剂煅烧时,生成的产物主要是Ca3Al10O18,CaAl2Si2O8.加入矿化剂后煅烧生成的产物主要是易浸出Al2O3的CaAl3BO7和Ca3Al10O18,而不易浸出Al2O3的CaAl2Si2O8的含量大大降低.同时显示,加入矿化剂后,原料中的方解石(CaCO3)分解更容易;CaCO3与铝矾土反应更充分;更有利于促使铝矾土中的Al-Si键断裂,将铝矾土中的Al释放出来;并可降低铝酸钙的煅烧温度.研究还显示:加入矿化剂后,可以改变原产物的晶体结构与成分,有利于降低煅烧反应温度.     

庆大霉素与水溶性CdTe量子点的荧光共振能量转移作用

以巯基丙酸(mercaptopropionic acid,MPA)为稳定剂合成水溶性CdTe最子点(quantum dots,QDs),以CdTe QDs作为能量供体.庆大霉素(Gentamycin,GT)作为能垦受体,建立了荧光共振能量转移(fluorescence resonance energy transfer,FRET)体系.在690 nm处可见发射峰,半峰宽约10 nm,在一定范围内荧光强度与GT的含量旱线性关系,线性范围为2～20 mg·L-1,相关系数r=0.986 7.优化了不同的激发波长、pH、离子强度、时间和温度等凼素对反应的影响,并应用傅里叶变换红外光谱(Fourier transform infrared spectroscopy,FTIR)和高效液相色谱(high-performance liquid chromatography,HPLC)分别表征了化学结构和相对专一性.结果表明巯基丙酸的巯基中S原子和羧基中氧原子与纳米微粒表面的富Cd离子发生了配位作用,CdTe QDs与GT的耦合主要是通过量子点周围巯基丙酸羧基(-COOH)中的氧原子与GT的胺基(-NH2)形成分子问氧键实现的;GT与CdTe QDs的结合率为0.35:1.研究表明GT可以作为检测CdTe QDs标记牛血清白蛋白(bovine serum albumin,BSA)的荧光增敏剂,荧光强度值增强6倍,应用前景广阔.     

ICP等离子体鞘层附近区域发光光谱特性分析

为了独立控制鞘层附近区域离子密度和离子能最分布,采用光发射谱(OES)测量技术,对不同射频功率、放电气压和基底偏压下感应耦合等离子体鞘层附近区域辉光特性进行了研究.原子谱线和离子谱线特性分析表明,在鞘层附近区域感应耦合等离子体具有较高的离子密度和较低的电子温度.改变放电气压和射频功率,对得到的光谱特性分析表明,鞘层附近区域离子密度随射频功率的增大而线性增大,在低压下随气压的升高而增大.低激发电位原子谱线强度增加迅速,高激发电位原子谱线强度增加缓慢,而离子谱线强度增加很不明显.改变基底直流偏压,对得到的发射光谱强度变化分析表明,谱线强度随基底正偏压的增加而增大.随着基底负偏压的加入,谱线强度先减小而后增大;直流偏压为-30 V时,光谱强度最弱.快速离子和电子是引起Ar激发和电离过程的主要能量来源.     

Changes in intratumor heterogeneity in blood perfusion in intradermal human melanoma xenografts during tumor growth assessed by DCE-MRI

The purpose of this study was to use dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) to search for systematic intratumor heterogeneity in blood perfusion in human melanoma xenografts growing intradermally in BALB/c-nu/nu mice. Six xenografted tumors of an amelanotic human melanoma line (A-07) were included in the study. DCE-MRI was performed daily for 5 days by using spoiled-gradient recalled sequences. Tumor images of E.F (E is initial extraction fraction and F is perfusion) were produced by subjecting DCE-MRI data to Kety analysis. E.F was used as a measure of tumor blood perfusion, since comparative studies have shown that E.F is closely related to blood perfusion in A-07 tumors. The E.F images indicated that the intratumor heterogeneity in blood perfusion was similar in all investigated tumors. The blood perfusion was low in the center of the tumors and increased toward the tumor periphery in the dorsal and ventral direction by a factor of 3-4, but not in the lateral and medial direction. The magnitude of the heterogeneity increased by a factor of approximately 2 during tumor growth. In conclusion, intradermal human melanoma xenografts show significant systematic intratumor heterogeneity in blood perfusion.     

A cell-centered Lagrangian hydrodynamics scheme on general unstructured meshes in arbitrary dimension

We describe a cell-centered Godunov scheme for Lagrangian gas dynamics on general unstructured meshes in arbitrary dimension. The construction of the scheme is based upon the definition of some geometric vectors which are defined on a moving mesh. The finite volume solver is node based and compatible with the mesh displacement. We also discuss boundary conditions. Numerical results on basic 3D tests problems show the efficiency of this approach. We also consider a quasi-incompressible test problem for which our nodal solver gives very good results if compared with other Godunov solvers. We briefly discuss the compatibility with ALE and/or AMR techniques at the end of this work. We detail the coefficients of the isoparametric element in the appendix.     

Temperature dependence of the Ho L2‐edge XMCD spectra of Ho6Fe23

An X‐ray magnetic circular dichroism (XMCD) study performed at the Ho L_2,3‐edges in Ho₆Fe₂₃ as a function of temperature is presented. It is demonstrated that the anomalous temperature dependence of the Ho L₂‐edge XMCD signal is due to the magnetic contribution of Fe atoms. By contrast, the Ho L₃‐edge XMCD directly reflects the temperature dependence of the Ho magnetic moment. By combining the XMCD at both Ho L₂‐ and L₃‐edges, the possibility of determining the temperature dependence of the Fe magnetic moment is demonstrated. Then, both μ_Ho(T) and μ_Fe(T) have been determined by tuning only the absorption L‐edges of Ho. This result opens new possibilities of applying XMCD at these absorption edges to obtain quantitative element‐specific magnetic information that is not directly obtained by other experimental tools.     

The use of vibrational spectroscopy to study the pathogenesis multiple sclerosis and other neurological conditions

Spectroscopy techniques are valuable tools in biomedical research and have been used extensively in the study of disease. However, neurological conditions such as multiple sclerosis (MS) have received little attention and the available spectroscopy studies are limited, both in overall numbers of patients studied and the disease samples considered. MS is a complex immune-mediated disease, with variable clinical courses and limited therapeutic options. This review aims to summarize current literature in the area, demonstrating how spectroscopy techniques can provide valuable information to inform and advance research into the most common neurological condition affecting young adults.     

A line-broadening analysis model for the microstructural characterization of nanocrystalline materials from asymmetric x-ray diffraction peaks

Nanograin sizes and crystal lattice microstrains in nanocrystalline materials are typically evaluated from the broadening of their x-ray diffraction (XRD) peaks under the assumption of symmetrical diffraction profiles. Since this assumption is not entirely satisfactory, we formulate a line-broadening analysis model of a single peak that considers explicitly the XRD peak asymmetry. The model is a generalization of the variance method in which the shape of the XRD peaks is idealized through asymmetrical split pseudo-Voigt functions. The model is validated on two nanocrystalline powders.     

Completeness in Supergravity Constructions

We prove that the supergravity r- and c-maps preserve completeness. As a consequence, any component \({\mathcal{H}}\) of a hypersurface {h = 1} defined by a homogeneous cubic polynomial h such that \({-\partial^2h}\) is a complete Riemannian metric on \({\mathcal{H}}\) defines a complete projective special Kähler manifold and any complete projective special Kähler manifold defines a complete quaternionic Kähler manifold of negative scalar curvature. We classify all complete quaternionic Kähler manifolds of dimension less or equal to 12 which are obtained in this way and describe some complete examples in 16 dimensions.