X-ray determination of the mean amplitudes of vibration and debye temperatures of some rare earth monochalcogenides

The x-ray diffraction intensities of Bragg reflections have been measured at room temperature for thulium selenide, samarium sulphide, samarium selenide and samarium telluride. On the basis of a common amplitude approximation, the Debye-Waller factor, the mean amplitude of vibration and the Debye temperature have been evaluated. The values of the Debye temperatures and mean amplitudes of vibration are 176±16°K, 0·185 ± 0·017 Å (TmSe), 155 ± 7°K, 0·244 ± 0·012 Å (SmS), 153 ± 14°K, 0·221 ± 0·020 Å (SmSe) and 151 ± 20°K, 0·204 ± 0·027 Å (SmTe).     

Kinetics of the formation of silver dimers: early stages in the formation of silver nanoparticles

Silver clusters too small to support a plasmon band possess interesting fluorescence properties as well as being a convenient route to studying the early stages of nanoparticle formation. Fluorescent silver clusters are synthesized in toluene solution, and the formation is monitored herein by laser flash photolysis (LFP). Kinetic analysis of the formation of the Ag clusters is consistent with the formation of the smallest possible clusters, silver dimers (Ag(2)), whereby a mechanism for the formation of these clusters is provided as well as the first reported extinction coefficient and association constant for Ag(0) to form Ag(2). The formation of Ag(2) clusters is contrasted with the formation of Ag nanoparticles in aqueous media, and the particular stability and selectivity toward Ag(2) in this system is also studied using LFP.     

帕隆藏布流域堆积体边坡的工程地质特征及稳定性评价

位于藏东南的帕隆藏布流域,处在东喜马拉雅构造结的北缘,是新构造强烈隆升区,断层、褶皱等地质构造发育。在青藏高原隆升及气候变化等内外动力作用下,研究区内堆积体分布广泛,具有独特的工程地质特征并成为该区内地质灾害的主要物源。由于河流的下切及川藏公路的修建,形成了许多高陡的堆积体边坡,以冰碛边坡最为典型。由于其特殊的物源特征及形成过程,冰碛物具有粒度分布范围广、粗粒含量多等与其他沉积物不同的粒度特征。冰碛物粒度分布范围广的特征,导致随着研究尺度的不同,其结构特征也不相同,具有明显的尺度效应。冰碛土的力学强度一般强于其他堆积体,但受不同粒径颗粒的含量及分布、形成时代的影响,其力学特征也有所差异。作者对川藏公路沿线部分典型的剖面进行了量测,所量测的剖面虽然只是整个斜坡的一部分,与经验数据相比,仍表现出高陡的特征,而且很多边坡在既高且陡的形态下仍能保持稳定。本文以极限平衡理论为基础,采用多种方法对这类边坡的稳定性进行计算分析,求出边坡的安全系数。考虑各种地震烈度下边坡的稳定性,得出这些边坡的安全系数与地震加速度具有严格的指数相关关系。     

Dose–Response Relationship of Photobiomodulation Therapy on Matrix Metalloproteinase in Healing Dynamics of Diabetic Neuropathic Ulcers—An in vivo Study

Individuals with diabetic foot ulcers have overlapped the inflammatory, proliferative and remodeling phase, making the tissue vulnerable to delayed healing responses. We aimed to establish the dose–response relationship of photobiomodulation therapy of different doses and matrix metalloproteinases in the healing dynamics of diabetic neuropathic ulcers. Diabetes was induced in 126 Albino Wistar rats, and neuropathy was induced to the hind paw by a sciatic nerve injury method. An excisional wound was created on the neuropathy-induced leg. Photobiomodulation therapy of dosages 4, 6, 8, 10, 12 and 15 J cm⁻² and wavelength 655 nm and 808 nm was irradiated. Photobiomodulation therapy of dosages 4, 6 and 8 J cm⁻² showed better wound healing properties with optimized levels of matrix metalloproteinases-1 and 8. We observed a strong dose response in the experimental group treated with 6 and 8 J cm⁻². The findings from the present study conclude that photobiomodulation therapy of dosages 4, 6 and 8 J cm⁻² is suggestive of usefulness in diabetic neuropathic ulcer healing. Markers like matrix metalloproteinases may give a clear direction on response to the therapy. Based on the findings from the present study, we recommend to validate the findings for safety and efficacy in future through human prospective randomized controlled clinical trials.     

Silver as an example of the applications of photochemistry to the synthesis and uses of nanomaterials

Photochemistry is a powerful tool for controlled synthesis of metal nanoparticles, their modification and in many of the applications that these materials have. Plasmon transitions offer a unique way of delivering energy with exquisite spatial and temporal control and can be used to advantage where visible wavelength control is required. This account of research at the University of Ottawa summarizes details of the synthesis, modification and applications of silver nanostructures.     

Photochemical Norrish type I reaction as a tool for metal nanoparticle synthesis: importance of proton coupled electron transfer

The Norrish type I photocleavage is an excellent source of strongly reducing free radicals that can be used to convert soluble metal ions into their atomic state that proceed to form nanoparticles. Proton coupled electron transfer (PCeT) is a useful tool to interpret the mechanism for metal ion reduction, a process that in these systems involves multisite PCeT, with proton and electron having separate receiving substrates.     

Plasmon-mediated photopolymerization maps plasmon fields for silver nanoparticles

Visible light exposure of films containing silver nanoparticles (AgNPs) shows that the enhanced field around AgNPs in a thin film containing an azo free radical initiator (AIBN) and a triacrylate selectively cross-links the triacrylate within the plasmonic region around the particles. The cross-linked polymer is less soluble than its precursor and behaves as a solubility switch. After the film is developed with ethanol, polymer-encapsulated nanoparticles are preserved on the surface. The 8-10 nm polymer structure that encapsulates the particles effectively maps and preserves the morphology of the plasmon field in AgNP-controlled nanostructures.     

W1{infty}-convergence of the discrete free boundary for obstacle problems

We examine the discrete free boundaries arising from a finiteelement discretization of a variational inequality. We giveL error bounds for the Hausdorff distance of the discrete andtrue free boundary, as well as for the normals. The theoreticalresults are confirmed by numerical experiments in two and threedimensions.     

Dual-stage lithography from a light-driven, plasmon-assisted process: a hierarchical approach to subwavelength features

A hierarchy of lithographic-type imaging generating 3 μm lines incorporating subdiffraction limit features was obtained through a novel two-step reaction process. Photochemically generated ketyl radicals were used to make defined lines of silver nanoparticles. The excitation of nanoparticle surface plasmons was then used to generate highly localized heat that causes polymerization selectively on the surfaces of excited particles. The nylon-6 polymer that is generated serves as a solubility switch used to retain the features on the substrate selectively; various imaging techniques were used to establish the nature of the nylon shells. This work shows that the heat generated by plasmon excitation can be exploited to generate negative-type lithographic features with dimensions well below the diffraction limit.