Novel positive‐working and aqueous‐base‐developable photosensitive poly(imide benzoxazole) precursor

A novel positive‐working and aqueous‐base‐developable photosensitive poly(imide benzoxazole) precursor based on a poly(amic acid hydroxyamide) bearing phenolic hydroxyl groups and carboxylic acid groups, a diazonaphthoquinone (DNQ) photosensitive compound, and a solvent was developed. Poly(amic acid hydroxyamide) was prepared through the polymerization of 2,2‐bis(3‐amino‐4‐hydroxyphenyl)hexafluoropropane, trimellitic anhydride chloride, and 4,4′‐oxydibenzoyl chloride. Subsequently, the thermal cyclization of the poly(amic acid hydroxyamide) precursor at 350 °C produced the corresponding poly(imide benzoxazole). The inherent viscosity of the precursor polymer was 0.17 dL/g. The cyclized poly(imide benzoxazole) showed a high glass‐transition temperature of 372 °C and 5% weight loss temperatures of 535 °C in nitrogen and 509 °C in air. The structures of the precursor polymer and the fully cyclized polymer were characterized with Fourier transform infrared and ¹H NMR. The photosensitive polyimide precursor containing 25 wt % DNQ photoactive compound showed a sensitivity of 256 mJ/cm² and a contrast of 1.14 in a 3‐μm film with a 0.6 wt % tetramethylammonium hydroxide developer. A pattern with a resolution of 5 μm was obtained from this composition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5990–5998, 2004     

Synthesis and properties of novel electrophosphorescent polymers from quinoline‐ and pyridine‐end‐capped polyfluorenes with rhenium(I) chromophores

Novel electrophosphorescent polymers were prepared from quinoline‐ and pyridine‐end‐capped polyfluorenes reacted with 4,4′‐dimethyl‐2,2′‐bipyridyl (tricarbonyl)rhenium(I) chloride. Fourier transform infrared and photoluminescence spectroscopy confirmed that the rhenium complex was successfully incorporated into the polymer backbones. The energy transfer could be reached by an efficient intramolecular process. The emission contributions of the polyfluorene and organic complex were found from the electroluminescence spectra. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1492–1498, 2007     

Antimicrobial activity of rhodomyrtone isolated from Rhodomyrtus tomentosa (Aiton) Hassk

Abstract

Rhodomyrtone was isolated from the leaves of Rhodomyrtus tomentosa (Aiton) Hassk grown in Vietnam using chromatographic methods. Its chemical structure was confirmed by means of spectroscopic data analysis. The pH drop measurement, enzyme activity assays and fluorescence stain were used to examine rhodomyrtone anticaries activity. It was found that rhodomyrtone suppressed acid production by Streptococcus mutans, a major cariogenic agent in human by inhibiting enzyme activities responsible for acid production and tolerance, including membrane bound enzymes F-ATPase and phosphotransferase system (PTS), as well as glycolysis enzymes glyceraldehyphosphate dehydrogenase (GAPDH) and pyruvate kinase (PK) in cytoplasm with the IC₅₀ values of 24?μM, 19?μM, 23?μM and 28?μM, respectively. Moreover, 50?μM rhodomyrtone reduced biofilm biomass formed by S. mutans up to 59% (p?<?0.05). Fluorescent images indicated that cells on the biofilms were significantly killed. Thus, rhodomyrtone is a new and potential anticaries agent against S. mutans.     

On-line investigation of short-lived Os and Re isotopes as a test for chemical studies of 108 (Hs) and 107 (Bh) elements in HCl solutions by continuous chromatography

On-line chemistry studies of short-lived isotopes of Os and Re, as homologs of 108 (Hs) and 107 (Bh), respectively, produced in the nuclear reactions at the (LNR, Dubna) cyclotron have been carried out. It was shown, that Os and Re are not sorbed on cation exchangers, but very strongly sorbed on anion exchangers from diluted HCl solutions. Re is also retained by a TOPO containing sorbent and may be separated from Os. The possibilities of chemical species and oxidation states investigation of short-lived transactinide elements by continuous chromatography have been shown. This revised version was published online in July 2006 with corrections to the Cover Date.     

Growth of Co-Silicides from single crystal and evaporated Si

We have investigated the reaction of a thin Co film with a (100) Si (Si ^c ) or an evaporated Si (Si ^e , which is amorphous) substrate during thermal annealing. On either substrate, Co₂Si and CoSi form simultaneously and the growth of each phase has a square root of time dependence. Both silicides grow faster on Si ^c than on Si ^e . A model is proposed to calculate the effective diffusion constant in each silicide from the growth data of the silicides. The activation energies of the effective diffusion constants in Co₂Si and CoSi grown on Si ^c are 1.7±0.1 eV and 1.8±0.1 eV, respectively; while those on Si ^e are 1.85±0.1 eV and 1.9 ±0.1 eV, respectively. The differences observed for the two substrates are tentatively attributed to the presence of impurities in Si^e and to the microstructural differences of the silicides formed on either substrate.     

Total weight choosability of graphs

A graph G = (V, E) is called (k, k′)‐total weight choosable if the following holds: For any total list assignment L which assigns to each vertex x a set L(x) of k real numbers, and assigns to each edge e a set L(e) of k′ real numbers, there is a mapping f: V∪E→? such that f(y)∈L(y) for any y∈V∪Eand for any two adjacent vertices x, x′, . We conjecture that every graph is (2, 2)‐total weight choosable and every graph without isolated edges is (1, 3)‐total weight choosable. It follows from results in [7] that complete graphs, complete bipartite graphs, trees other than K₂ are (1, 3)‐total weight choosable. Also a graph G obtained from an arbitrary graph H by subdividing each edge with at least three vertices is (1, 3)‐total weight choosable. This article proves that complete graphs, trees, generalized theta graphs are (2, 2)‐total weight choosable. We also prove that for any graph H, a graph G obtained from H by subdividing each edge with at least two vertices is (2, 2)‐total weight choosable as well as (1, 3)‐total weight choosable. © 2010 Wiley Periodicals, Inc. J Graph Theory 66:198‐212, 2011     

Tracking error decision rules and accumulated wealth

There is compelling evidence that typical decision‐makers, including individual investors and even professional money managers, care about the difference between their portfolio returns and a reference point, or benchmark return. In the context of financial markets, likely benchmarks against which investors compare their own returns include easy‐to‐focus‐on numbers such as one's own past payoffs, historical average payoffs, and the payoffs of competitors. Referring to the gap between one's current portfolio return and the benchmark return as ‘tracking error’, this paper develops a simple model to study the consequences and possible origins of investors who use expected tracking error to guide their portfolio decisions, referred to as ‘tracking error types’. In particular, this paper analyses the level of risk‐taking and accumulated wealth of tracking error types using standard mean‐variance investors as a comparison group. The behaviour of these two types are studied first in isolation, and then in an equilibrium model. Simple analytic results together with statistics summarizing simulated wealth accumulations point to the conclusion that tracking error—whether it is interpreted as reflecting inertia, habituation, or a propensity to make social comparisons in evaluating one's own performance—leads to greater risk‐taking and greater shares of accumulated wealth. This result holds even though the two types are calibrated to be identically risk‐averse when expected tracking error equals zero. In the equilibrium model, increased aggregate levels of risk‐taking reduce the returns on risk. Therefore, the net social effect of tracking‐error‐induced risk‐taking is potentially ambiguous. This paper shows, however, that tracking error promotes a pattern of specialization that helps the economy move towards the path of maximum accumulated wealth.     

Determinants of allocative and technical inefficiency in stochastic frontier models: An analysis of Norwegian electricity distribution firms

Recent econometric advances have made it possible to distinguish between persistent and transient technical inefficiency along with allocative inefficiency in stochastic frontier models for panel data. Kumbhakar et al. (2020) and Lai and Kumbhakar (2019) introduce a methodology that allows for the estimation of these inefficiency components and costs therefrom, while including determinants of both components of technical inefficiency. We extend these models to include technical change and determinants of allocative inefficiency (input misallocation). Including a set of variables that influence input misallocation, we are able to determine the effects of these variables on the cost of allocative inefficiency. We provide empirical evidence on the costs of all three types of inefficiency using data on 149 Norwegian electricity distribution firms between 2000 and 2016. We find that the cost of input misallocation is only slightly lower than that of technical inefficiency. Our results reject a commonly imposed modeling assumption that firms are fully allocatively efficient.