Analysis of stock prices of mining business

Stock exchanges have a diversity of so-called business groups and much evidence has been presented by covariance matrix analysis (Laloux et al. (1999) [6], Plerou et al. (2002) [7], Plerou et al. (1999) [8], Mantegna (1999) [9], Utsugi et al. (2004) [21] and Lim et al. (2009) [26]). A market-wide effect plays a crucial role in shifting the correlation structure from random to non-random. In this work, we study the structural properties of stocks related to the mining industry, especially rare earth minerals, listed on two exchanges, namely the TSX (Toronto stock exchange) and the TSX-V (Toronto stock exchange-ventures). In general, raw-material businesses are sensitively affected by the global economy while each firm has its own cycle. We prove that the global crisis during 2006–2009 affected the mineral market considerably. These two aspects compete to control price fluctuations. We show that the internal cycle overwhelms the global economic environment in terms of random matrix theory and overlapping matrices. However, during the period of 2006–2009, the effect of the global economic environment emerges. This result is well explained by the recent global financial/economic crisis. For comparison, we analyze the time stability of business clusters of the KOSPI, that is, the electric/electronic business, using an overlapping matrix. A clear difference in behavior is confirmed. Consequently, rare earth minerals in the raw-material business should be classified not by standard business classifications but by the internal cycle of business.     

Detection of small intrahepatic metastases of hepatocellular carcinomas using diffusion-weighted imaging: comparison with conventional dynamic MRI

Purpose

The purpose of our study was to compare diffusion-weighted MR imaging (DWI) with conventional dynamic MRI in terms of the assessment of small intrahepatic metastases from hepatocellular carcinoma (HCC).

Materials and Methods

In 24 patients with multifocal, small (≤2 cm) intrahepatic metastatic foci of advanced HCC, a total of 134 lesions (≤1 cm, n=81; >1 cm, n=53) were subjected to a comparative analysis of hepatic MRI including static and gadopentetate dimeglumine-enhanced dynamic imaging, and DWI using a single-shot spin-echo echo-planar MRI (b values=50, 400 and 800 s/mm²), by two independent reviewers.

Results

A larger number of the lesions were detected and diagnosed as intrahepatic metastases on DWI [Reviewer 1, 121 (90%); Reviewer 2, 117 (87%)] than on dynamic imaging [Reviewer 1, 107 (80%); Reviewer 2, 105 (78%)] (P<.05). For the 81 smaller lesions (≤1 cm), DWI was able to detect more lesions than dynamic imaging [Reviewer 1, 68 (84%) vs. 56 (69%), P=.008; Reviewer 2, 65 (80%) vs. 55 (68%), P=.031], but there was no statistically significant difference between the two image sets for larger (>1 cm) lesions.

Conclusion

Due to its higher detection rate of subcentimeter lesions, DWI could be considered complementary to dynamic MRI in the diagnosis of intrahepatic metastases of HCCs.     

一种新型Ni(Ⅱ)配位聚合物{[Ni(C18H18N4O5)(DMF)]·(DMF)}n的合成、晶体结构和性质研究

溶剂热法合成了1个新配位聚合物{[Ni(C₁₈H₁₈N₄O₅)(DMF)]·(DMF)}_n。通过元素分析、红外光谱、热重以及X-射线单晶洐射对其进行了表征。该晶体为正交晶系,Pna2₁空间群。该化合物中,C₁₈H₁₈N₄O₅配体通过5个配位原子以及相邻的溶剂分子DMF上的1个配位原子与Ni(Ⅱ)原子配位,形成了1个扭曲的八面体配位构型。热重分析表明该化合物在140 ℃开始发生分解。     

Two-dimensional crystallization of carboxylated benzene oligomers

Various carboxylic acid substitution patterns on the 1,3,5-triphenylbenzene nucleus were explored, and their influence on the symmetry of the resulting two-dimensional (2D) crystal structures was assessed. The symmetry of 1,3,5-benzenetribenzoic acid (H(3)BTB) was reduced by modifying the substitution pattern of the arene and/or adding an additional carboxylic acid. Four analogues belonging to various point groups were studied. Comparison of the monolayers of the analogues to that of H(3)BTB shows that plane group symmetry and molecular symmetry are not correlated: H(3)BTB and its analogues exhibit the same plane group p2 at the heptanoic acid/graphite interface. The 2D crystal structure of the H(3)BTB analogues is more strongly controlled by the geometry of hydrogen-bonding interactions rather than molecular symmetry. Other significant observations in this study include porosity, uncommon hydrogen-bonding motifs, and an unusually high number of inquivalent molecules (Z' = 3) present in the 2D crystal of the lowest symmetry analogue. This research demonstrates that reduction of molecular symmetry based on geometric modification of noncovalent interactions allows for control over porosity of the 2D crystals (close-packed structures to nanoporous networks) without changing the core shape of the molecule.     

贵州民族药秋海棠药材中多糖的含量测定

采用硫酸-苯酚法,以无水葡萄糖为对照品,于485nm处测定吸光度,测定秋海棠药材中多糖的含量。在3.01—10.54μg.mL-1范围内吸光度与葡萄糖溶液浓度的线性关系良好（r=0.9997）,平均回收率为98.06%,RSD为0.50%。该方法简便快速、准确可行,为秋海棠药材的质量控制提供了实验依据。     

[Co (C5O2H8)2]·H3COH的 水热合成和晶体结构

合成了[Co (C5O2H8)2]·H3COH金属配合物,通过X射线衍射仪测得配合物[Co(C5O2HD2]·H3COH的晶体结构.晶体属于单斜晶系,空间群为P2 (1)/c,其晶胞参数为a=0.93325(16)nm,b=1.15015(16)nm,c=1.30029(16)nm,α=90.00°,γ=90.00°,...     

Dynamic frictionless contact of a nonlinear beam with two stops

In this work, we consider mathematical and numerical approaches to a dynamic contact problem with a highly nonlinear beam, the so-called Gao beam. Its left end is rigidly attached to a supporting device, whereas the other end is constrained to move between two perfectly rigid stops. Thus, the Signorini contact conditions are imposed to its right end and are interpreted as a pair of complementarity conditions. We formulate a time discretization based on a truncated variational formulation. We prove the convergence of numerical trajectories and also derive a new form of energy balance. A fully discrete numerical scheme is implemented to present numerical results.     

Grain-boundary sliding in elongated microstructures during diffusion creep

In diffusion creep, the contribution of grain-boundary sliding to the overall strain os can be evaluated in arbitrary polycrystals, if the angular distribution of grain boundaries is known. A os value of 0.5 is obtained for two-dimensional (2D) equiaxed microstructures consisting of regular hexagonal grains, equiaxed grains grown from a Voronoi structure or grains having a circular distribution of grain-boundary angles. The os value is also evaluated for uniaxially deformed 2D microstructures, both diffusionally and uniformly deformed. For the former, the deformed microstructure is obtained by the simulation of microstructural evolution in polycrystals with straight grain boundaries. The os value increases gradually with increasing or decreasing strain and is larger in the diffusionally deformed microstructures than in the uniformly deformed microstructures for a given grain aspect ratio. The os value for three-dimensional (3D) polycrystalline microstructures is also obtained from an ellipsoidal distribution of grain-boundary angles. The resultant os value is 0.60 for 3D equiaxed polycrystals and increases gradually with increasing strain.     

Experimental and theoretical investigation of phosphorus in-situ doping of germanium epitaxial layers

We investigate phosphorus in-situ doping characteristics in germanium (Ge) during epitaxial growth by spreading resistance profiling analysis. In addition, we present an accurate model for the kinetics of the diffusion in the in-situ process, modeling combined growth and diffusion events. The activation energy and pre-exponential factor for phosphorus (P) diffusion are determined to be 1.91 eV and 3.75 × 10^?5 cm²/s. These results show that P in-situ doping diffusivity is low enough to form shallow junctions for high performance Ge devices.     

Two-step annealed CdS/CdSe co-sensitizers for quantum dot-sensitized solar cells

CdS/CdSe co-sensitizers on TiO₂ films were annealed using a two-step procedure; high temperature (300 °C) annealing of TiO₂/CdS quantum dots (QDs), followed by low temperature (150 °C) annealing after the deposition of CdSe QDs on the TiO₂/CdS. For comparison, two types of films were prepared; CdS/CdSe-assembled TiO₂ films conventionally annealed at a single temperature (150 or 300 °C) and non-annealed films. The 300 °C-annealed TiO₂/CdS/CdSe showed severe coalescence of CdSe QDs, leading to the blocked pores and hindered ion transport. The QD-sensitized solar cell (QD-SSC) with the 150 °C-annealed TiO₂/CdS/CdSe exhibited better overall energy conversion efficiency than that with the non-annealed TiO₂/CdS/CdSe because the CdSe QDs annealed at a suitable temperature (150 °C) provided better light absorption over long wavelengths without the hindered ion transport. The QD-SSC using the two-step annealed TiO₂/CdS/CdSe increased the cell efficiency further, compared to the QD-SSC with the 150 °C-annealed TiO₂/CdS/CdSe. This is because the 300 °C-annealed, highly crystalline CdS in the two-step annealed TiO₂/CdS/CdSe improved electron transport through CdS, leading to a significantly hindered recombination rate.