A simple phenylation of heteroaromatic compounds using diphenyliodonium triflate

In this study a novel method for direct synthesis of 2-phenyl heteroaromatic arenes was successfully developed. The title compounds were synthesized by reaction of heteroaromatic compounds with diphenylene iodonium trifluoromethanesulfonate in the presence of 5?mol% Pd(OAc)₂ under mild reaction conditions (THF, 60?°C, 24?h). The proposed reaction mechanism was studied by HPLC.     

Discovering the Active Sites for C3 Separation in MIL‐100(Fe) by Using Operando IR Spectroscopy

A reducible MIL‐100(Fe) metal–organic framework (MOF) was investigated for the separation of a propane/propene mixture. An operando methodology was applied (for the first time in the case of a MOF) in order to shed light on the separation mechanism. Breakthrough curves were obtained as in traditional separation column experiments, but monitoring the material surface online, thus providing evidences on the adsorption sites. The qualitative and quantitative analyses of Fe^II and, to some extent, Fe^III sites were possible, upon different activation protocols. Moreover, it was possible to identify the nature and the role of the active sites in the separation process by selective poisoning of one family of sites: it was clearly evidenced that the unsaturated Fe^II sites are mainly responsible for the separation effect of the propane/propene mixture, thanks to their affinity for the unsaturated bonds, such as the C?C entities in propene. The activity of the highly concentrated Fe^III sites was also highlighted.     

Quantitative measurements of undiilator spatial coherence at the ALS

Modern synchrotron-based X-ray fluorescence microscopy (XFM) has become a critical tool for many a research program, addressing extremely broad and highly relevant scientific questions. Their ability to map trace elemental content and probe local chemical state has been applied to numerous scientific areas in the life sciences [1 Paunesku, T. 2006. J Cell Biochem, 99(6): 1489–502. [Crossref], [PubMed] , [Google Scholar]–3 Bohic, S. 2012. J Struct Biol, 177(2): 248–58. [Crossref], [PubMed] , [Google Scholar]], the environmental and earth sciences [4 Fittschen, U. E. A. and Falkenberg, G. 2011. Spectrochimica Acta Part B-Atomic Spectroscopy, 66(8): 567–580. [Crossref] , [Google Scholar], 5 Lombi, E. 2011. Analytical and Bioanalytical Chemistry, 400(6): 1637–1644. [Crossref], [PubMed] , [Google Scholar]], the materials sciences, as well as in cultural heritage studies. The newest generation of instruments utilizes high-brightness X-ray sources and incorporate state-of-the-art focusing optics and detector systems. Advances in X-ray sources and nanofocusing optics, for example, have allowed these instruments to achieve spatial resolutions of 20–30 nm using diffractive optics such as Fresnel zone plates and 200 nm using reflective optics such as Kirkpatrick-Baez mirrors. New beamlines, now in the design stage, aim to achieve similar (and better) resolutions within the next five years.     

聚二烯丙基二甲基氯化铵与核酸相互作用的共振光散射光谱及分析应用

实验基于核酸与聚阳离子聚二烯丙基二甲基氯化铵(PDDA)的相互作用导致共振光散射(RLS)增强的现象来测定核酸。考察了pH值、PDDA浓度和离子强度对体系共振光散射强度的影响。在优化条件下,建立了用RLS光谱测定微量核酸的新方法。方法的抗干扰能力较强,可允许大部分的常见金属离子、核苷酸、氨基酸、糖、蛋白质等干扰物质的存在。同时用于合成样品的分析,结果令人满意。     

An experimental study of approximation algorithms for the joint spectral radius

We describe several approximation algorithms for the joint spectral radius and compare their performance on a large number of test cases. The joint spectral radius of a set Σ of $n \times n$ matrices is the maximal asymptotic growth rate that can be obtained by forming products of matrices from Σ. This quantity is NP-hard to compute and appears in many areas, including in system theory, combinatorics and information theory. A dozen algorithms have been proposed this last decade for approximating the joint spectral radius but little is known about their practical efficiency. We overview these approximation algorithms and classify them in three categories: approximation obtained by examining long products, by building a specific matrix norm, and by using optimization-based techniques. All these algorithms are now implemented in a (freely available) MATLAB toolbox that was released in 2011. This toolbox allows us to present a comparison of the approximations obtained on a large number of test cases as well as on sets of matrices taken from the literature. Finally, in our comparison we include a method, available in the toolbox, that combines different existing algorithms and that is the toolbox’s default method. This default method was able to find optimal products for all test cases of dimension less than four.     

In vivo high‐resolution synchrotron radiation imaging of collagen‐induced arthritis in a rodent model

In vivo microstructures of the affected feet of collagen‐induced arthritic (CIA) mice were examined using a high‐resolution synchrotron radiation (SR) X‐ray refraction technique with a polychromatic beam issued from a bending magnet. The CIA models were obtained from six‐week‐old DBA/1J mice that were immunized with bovine type II collagen and grouped as grades 0–3 according to a clinical scoring for the severity of arthritis. An X‐ray shadow of a specimen was converted into a visual image on the surface of a CdWO₄ scintillator that was magnified using a microscopic objective lens before being captured with a digital charge‐coupled‐device camera. Various changes in the joint microstructure, including cartilage destruction, periosteal born formation, articular bone thinning and erosion, marrow invasion by pannus progression, and widening joint space, were clearly identified at each level of arthritis severity with an equivalent pixel size of 2.7 µm. These high‐resolution features of destruction in the CIA models have not previously been available from any other conventional imaging modalities except histological light microscopy. However, thickening of the synovial membrane was not resolved in composite images by the SR refraction imaging method. In conclusion, in vivo SR X‐ray microscopic imaging may have potential as a diagnostic tool in small animals that does not require a histochemical preparation stage in examining microstructural changes in joints affected with arthritis. The findings from the SR images are comparable with standard histopathology findings.     

More on super-replication formulae (II)

We find three more new super-replicable functions by using certain congruence subgroups between Γ ₁(N) and Γ ₀(N), and generalize the recursion formulas for replicable functions to those of super-replicable functions.     

Optical characteristics of m-plane InGaN/GaN multiple quantum well grown on LiAlO2 (1 0 0) by MOVPE

We investigate the optical properties of m-plane InGaN/GaN multiple quantum well grown on LiAlO₂ substrate by metal organic vapor phase epitaxy. Polarization-dependent photoluminescence and polarization-dependent photoluminescence excitation measurements have been performed at low temperature to study the optical absorption and emission characteristics. The main emission band possesses large polarization anisotropy which may be attributed to the anisotropic biaxial strain. We found the optical emission is not influenced by the polarization-induced electric field from the excitation-dependent photoluminescence measurements. From our results, we attribute the low-temperature emission band around 3.2 eV to interband transition in the quantum well. Besides, the mechanism of the main emission band is associated with interband transition and subsequent carrier localization. The realization of good-quality non-polar GaN-based devices can then be expected in near future.     

Reducing dislocation density in GaN films using a cone-shaped patterned sapphire substrate

The threading dislocation (TD) density in GaN films grown directly on flat sapphire substrates is typically >10¹⁰/cm², which can deteriorate the properties of GaN-based LEDs significantly. This paper reports an approach to reducing the TD density in a GaN layer using a variety of patterned sapphire substrates (PSS). A cone-shaped PSS produced by metal organic chemical vapor deposition (MOVCD) was used for GaN deposition. Three types of GaN specimens were prepared at the initial nucleation stage, middle growth stage and final growth stage. The TDs generated on the cone-shaped PSS were analyzed by transmission electron microscopy (TEM) and a strain mapping simulation using HRTEM images, which evaluated the residual strain distribution. A large number of TDs were generated and the residual strain by the lattice distortions remained above the top of the cone-shaped regions. However, no TDs and residual strain were observed at the slope of the cone-shaped regions. This might be due to the formation of a GaN layer by lateral overgrowth at the slope of the cone-shaped regions, resulting in less lattice mismatch and incoherency between the GaN and sapphire. In conclusion, the TD density in the GaN layer could be reduced significantly, approximately 10⁷/cm², using the cone-shaped PSS.     

Synthesis and bioactive properties of macroporous nanoscale SiO2–CaO–P2O5 bioactive glass

A macroporous nanoscale bulk bioactive glass (SiO₂–CaO–P₂O₅ system) was prepared by sol–gel co-template method. Porosimeter analysis showed that the as-synthesized bioactive glasses (BGs) had a porosity of 85% and exhibited a multimodal pore size distribution, nanopores (10–40 nm) and macropores (100 nm–10 μm). Morphological and structural characterizations showed the pores were interconnected with pore walls of about 250 nm in width and 1 μm in length. In vitro bioactivity test indicated that the as-synthesized bulk BGs exhibited faster apatite layer formation capability than the conventional sol–gel BGs. Additionally, the deposited layer was identified as hydroxycarbonate apatite, which is similar to the inorganic part of human bone.