Rewritable Optical Patterns in Light-Responsive Ultrahigh Molecular Weight Polyethylene.

Spiropyran is used as a photochromic dye to create colored patterns in highly drawn ultrahigh molecular weight polyethylene (UHMW PE) films. The dye is incorporated in highly crystalline, drawn UHMW PE tapes and fibers and isomerizes to its merocyanine state upon UV light irradiation, resulting in a color change from transparent to purple. The isomerization from merocyanine to spiropyran to erase the color can be simply induced by using heat or a green LED light. The combination of the use of a mask and the reversibility of the isomerization results in colored patterns that can be written, erased, and rewritten using UV light and heat or green LED light

Multinationality and performance literature: a critical review and future research agenda

The literature on the relationship between the degree of multinationality (M) and performance (P) in the context of multinational enterprises (MNEs) has attracted a large volume of research in the past 50 years. Yet, the theoretical foundations and the empirical conclusions concerning the nature of M–P relationship vary greatly, thus call for a critical review and assessment. We examine 135 articles in 39 leading scholarly journals and classic books published during the period 1960–2015. We use an inductive approach and a qualitative content analysis methodology for our comprehensive and critical review of the literature. We incorporate international business, finance, and accounting perspectives in our analysis. We review the conceptualization and measurement of M, P, the findings on M–P relationships, methodologies, and geographic focus. We identify six key inconsistencies in the existing research, which cause ambiguity in the relevant findings. We make eight recommendations for future research to address these inconsistencies. Thus, our study contributes to the central debate in this research field

Immobilisation of homogeneous olefin polymerisation catalysts. Factors influencing activity and stability

The activity and stability of homogeneous olefin polymerisation catalysts, when immobilised on a support, are dependent on both chemical and physical effects. Chemical factors affecting catalyst activity include the ease of formation of the active species, which is strongly dependent on the transition metal. Catalyst productivity is dependent on the balance between activity and stability. Immobilisation can lead to a lower proportion of active species and therefore lower initial polymerisation activity, but nevertheless give higher polymer yields in cases where increased catalyst stability is obtained. Important physical factors are support porosity and the ability of a support to undergo progressive fragmentation during polymerisation, facilitating monomer diffusion through the growing catalyst/polymer particle. This article illustrates the importance of these factors in olefin polymerisation with both early- and late-transition metal catalysts, with particular reference to the use of silica and magnesium chloride supports as well as to effects of immobilisation on polymer structure and properties

Price Theory and Telecommunications Regulation: A Dissenting View

In recent years, analysts have increasingly invoked neoclassical price theory to justify radical changes in the regulation of the American telecommunications market, namely the trend toward competition and away from traditional regulatory and rate-setting practices. Many economists assert that competition and marginal-cost pricing will eliminate cross-subsidization and promote efficient markets for local and long-distance telephone services and telecommunications equipment. Price theory, however, does not necessarily support structural reform of the telecommunications industry. Indeed, pre-divestiture pricing policy can be defended on the same grounds its critics employ to advocate structural changes. This article assesses the applicability of static price theory to market conditions currently confronting local operating companies. It challenges the widely held belief that structural reform in telecommunications is necessary to achieve economic efficiency, particularly in intraLATA markets. It recommends that regulators view with skepticism arguments derived from price theory that purport to justify significant departures from historic pricing practices and that advocate wholesale competitive entry into intraLATA markets

Synthesis and characterization of tin containing polyhedral oligometallasilsesquioxanes (POMSS)

Tin silicate species have shown good catalytic activity in various oxidn. reactions. In an attempt to mimic surface tin species, several tin contg. silsesquioxanes have been synthesized. Incompletely condensed silsesquioxanes (c-C5H9)7Si7O9(OH)3 and (c-C5H9)7Si7O9(OSiMe3)(OH)2 were reacted with common tin-precursors, which afforded several silsesquioxane ligated tin compds. Divalent stannasilsesquioxanes form dimers of the type [(c-C5H9)7Si7O11(OX)Sn]2 (X = H, SiMe3) with three-coordinated tin centers. The three-coordinated tin(ii) are hydrolytically unstable whereas the octahedrally surrounded tetravalent stannasilsesquioxanes [(c-C5H9)7Si7O11(OX)]Sn(acac)2 (X = H, OSiMe3) are hydrolytically robust. An unprecedented anionic trimeric cluster, {[(c-C5H9)7Si7O12Sn]3(m2-OH)3(m3-OH)}-{HNEt3}+, stabilized by bridging hydroxyl groups was formed when the product formed upon reacting (c-C5H9)7Si7O9(OH)3 with SnCl4 was slowly hydrolyzed. The stannasilsesquioxanes showed no catalytic activity in oxidn. reactions. [on SciFinder (R)

Bimodal ultrahigh molecular weight polyethylenes produced from supported catalysts:the challenge of using a combined catalyst system

\u3cp\u3eMolecular precatalysts complexes (nBuCp)\u3csub\u3e2\u3c/sub\u3eZrCl\u3csub\u3e2\u3c/sub\u3e (Zr) and (η1:η5-Me\u3csub\u3e2\u3c/sub\u3eNCH\u3csub\u3e2\u3c/sub\u3eCH\u3csub\u3e2\u3c/sub\u3eC\u3csub\u3e5\u3c/sub\u3eMe\u3csub\u3e4\u3c/sub\u3e)CrCl\u3csub\u3e2\u3c/sub\u3e (Cr) have been successfully supported on silica nanoparticles, via a single support (SS) or a double support (DS) strategy. These catalyst systems have been successfully used to produce bimodal polyethylenes with an ultrahigh molecular weight polyethylene content in a single reactor. The SS and DS catalyst systems have been fully evaluated under an identical polymerization condition to assess the challenges in tailoring the molecular weight distribution. The results show that a detrimental interaction exists between Zr and Cr catalysts, part of the Cr catalyst species is deactivated during polymerization in the both DS and SS systems. The detrimental interaction in the DS system is reduced because the catalysts are supported on separate nanoparticles. But, surprisingly the two catalysts in the DS system are still able to “communicate” to each other via cocatalyst-induced catalyst leaching or other potential reasons. (Figure presented.).\u3c/p\u3