CHARACTERIZATION OF AN ACRYLAMIDE MODIFIED ETHYL ACRYLATE LATEX BY CARBON-13 NMR SPECTROSCOPY

The structure of a 70/30 ethyl acrylate-acrylamide latex made in a semi-continuous process with surfactant has been investigated. The molar composition and relative concentration of the polymers in the serum phase, on the surface and in the particle were characterized by coupling a filtration procedure, serum replacement, with carbon-13 NMR spectroscopy. The development of polymer in the different phases could be monitored by taking samples at timed intervals during the polymerization. Post-treatment of the latex with sodium hydroxide selectively hydrolyzed the copolymerized ethyl acrylate in the serum and on the surface. By measurement of spin lattice relaxation times it was possible to estimate surface concentration of oligomeric polymer     

Decay rates for Bresse system with arbitrary nonlinear localized damping

In this paper we consider a vibrating system of Bresse type, in a one-dimensional bounded domain with nonlinear localized damping mechanisms acting in all the three wave equations. We obtain some rates of decay for its solutions with no restrictions around the coefficients as well as the condition of equal-speed wave propagation. A new result concerning an internal observability for the conservative system was also proved in order to reach the asymptotics above.     

Three-dimensional manganese dioxide-functionalized carbon nanotube electrodes for electrochemical supercapacitors

Three-dimensional manganese dioxide (MnO₂)-functionalized multiwalled carbon nanotube (MWCNT) electrodes have been produced by a simple and scalable thermal decomposition process. The electrodes are prepared by treating planar MWCNT sheets with manganese(II) nitrate (Mn(NO₃)₂) solution and annealing at low temperature (200–300 °C) and ambient pressure. The morphology, chemical composition, and structure of the resulting matrices have been investigated with scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, and X-ray diffraction. Supercapacitors assembled with three-dimensional electrodes exhibit a 14-fold increase in specific capacitance (C _sp) in comparison to those containing pristine, two-dimensional MWCNT electrodes. C _sp varies linearly with Mn(NO₃)₂ thermal decomposition temperature (from 100 to 61 F/g at 0.2 A/g), a trend that is discussed in the context of nitrate reaction chemistry and MWCNT structure. This efficient and promising approach allows for simultaneous enhancement of electrode–electrolyte contact area and incorporation of redox-based charge storage within electrochemical capacitors.     

Gibbs Sampling with Diffuse Proper Priors: A Valid Approach to Data-Driven Inference?

Abstract

This article demonstrates by example that the use of the Gibbs sampler with diffuse proper priors can lead to inaccurate posterior estimates. Our results show that such inaccuracies are not merely limited to small sample settings.     

Random Variable Generation Using Concavity Properties of Transformed Densities

Abstract

Algorithms are developed for constructing random variable generators for families of densities. The generators depend on the concavity structure of a transformation of the density. The resulting algorithms are rejection algorithms and the methods of this article are concerned with constructing good rejection algorithms for general densities.     

The Preparation of 1H-Pyrazole-5-propanoic and 1H-Pyrazole-5-butanoic Acids from Dilithiated C(α),N-Carboalkoxyhydrazones and Succinic or Glutaric Acid Anhydrides

C(α),N-Carboalkoxyhydrazones were dilithiated with excess lithium diisopropylamide, condensed with succinic or glutaric acid anhydride, and cyclized to 1H-pyrazole-5-propanoic or 1H-pyrazole-5-butanoic acids.     

A convenient Synthesis of 6-Substituted-2,2-Dimethyl-2H-1-Benzopyrans

Various 2,2-dimethyl-6-functional-2H-1-benzopyrans were prepared via a halogen-metal exchange reaction followed by treatment with electrophiles. These 6-functionalized chromenes are important synthetic intermediates for preparation of benzopyran-based potassium channel openers.     

Dihalocarbenes Rrom Thallium (I) Ethoxide and Haloforms

It has been known for many years that dihalocarbenes may be generated by the reaction of strong bases with haloforms and that the resulting dihalocarbenes react rapidly with alkenes to produce dihalocyclopropane derivatives.¹ The procedures reported to date suffer from two disadvantages in that they require: 1) the use of a date solvent or the necessity of a two-phase system when a hydrocarbon solvent is used, and 2) the use of covalent nature and unique solubility properties of thallium (I) ethoxide suggested that its use might eliminate, or at least minimize, these diffculties in the generation of dichalocarbenes.     

Addendum to “Ring elements as sums of units”

We give a comment to Theorem 1.1 published in our paper “Ring elements as sums of units” [Cent. Eur. J. Math., 2009, 7(3), 395–399].