Highly Chemoselective Thiocarbonyl Oxidation upon Reaction of 4-Methyl-3-phenyl-2-thiazolidinethione with Singlet Oxygen

4-Methyl-3-phenyl-2-thiazolidinethione was reacted with both photochemically and chemically generated singlet oxygen. Despite reaction conditions which were selected to favor oxidation of the sulfide group, both reactions afforded a single product arising solely from thiocarbonyl oxidation.     

Theory of phononic gaps induced by inertial amplification in finite structures

The characteristics of inertial amplification induced gaps are derived and compared with those of local resonance and Bragg gaps in finite lattices. Deep inertial amplification gaps at low frequencies are obtained without using a multitude of unit cells. These gaps remain deep regardless of boundary conditions, excitation direction or mode.     

Neue Thiosubstituierte Butadien- Und Butenin Verbindungen Aus Hexachlorbutenen Und Thiolen

2,3-Di-H-butene compound 1 gave compounds 3a-f , 4a , 4e , and 5a-d in the presence of thiols 2a-f and Et 3 N (or NaOH). Compound 7e was obtained from the reaction of 1,3-Di-H-butene 6 with naphthylthiol in DMF. In the presence of NaOH, compound 6 and 2 mmol of thiol 2g in EtOH gave compounds 8 , 9 , 10 , and 11 .     

Dynamics of knowledge creation in global participatory science communities: open innovation communities from a network perspective

Significant attention has been given to advancing cyber-infrastructures to support virtual engineering and science communities based on the proposition that virtual organizations can more effectively create and leverage knowledge due to diverse information, skills, and resources to enhance capacity to innovate. Yet, relatively little is known about desirable organizing processes in virtual open science communities. To this end, a simulation-based exploratory study is conducted to better understand the conditions that confer increased rates of innovation in such socio-technical systems. Three types of open science communities are identified and simulated using agent simulation as a method of inquiry. Simulation results show that centrality, as a measure of degree of connectedness, correlates with innovation output in exploratory and service communities up to a point. Also, utility-oriented communities have social network structures with low density and high centrality, which suggest high potential for innovation.     

ATRP of methyl methacrylate initiated with a bifunctional initiator bearing bromomethyl functional groups: Synthesis of the block and graft copolymers

This article reports the synthesis of the block and graft copolymers using peroxygen‐containing poly(methyl methacrylate) (poly‐MMA) as a macroinitiator that was prepared from the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in the presence of bis(4,4′‐bromomethyl benzoyl peroxide) (BBP). The effects of reaction temperatures on the ATRP system were studied in detail. Kinetic studies were carried out to investigate controlled ATRP for BBP/CuBr/bpy initiating system with MMA at 40 °C and free radical polymerization of styrene (S) at 80 °C. The plots of ln ([M_o]/[M_t]) versus reaction time are linear, corresponding to first‐order kinetics. Poly‐MMA initiators were used in the bulk polymerization of S to obtain poly (MMA‐b‐S) block copolymers. Poly‐MMA initiators containing undecomposed peroygen groups were used for the graft copolymerization of polybutadiene (PBd) and natural rubber (RSS‐3) to obtain crosslinked poly (MMA‐g‐PBd) and poly(MMA‐g‐RSS‐3) graft copolymers. Swelling ratio values (q_v) of the graft copolymers in CHCl₃ were calculated. The characterizations of the polymers were achieved by Fourier‐transform infrared spectroscopy (FTIR), ¹H‐nuclear magnetic resonance (¹H NMR), gel‐permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and the fractional precipitation (γ) techniques. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1364–1373, 2010     

Minimum entropy generation for laminar flow at constant wall temperature in a circular duct for optimum design

Entropy generation for hydrodynamically and thermally developing laminar flow in a circular duct at constant wall temperature is investigated. Optimum temperature difference between fluid inlet temperature and wall temperature is determined for minimum entropy generation rate. An equation for optimum temperature difference at minimum entropy generation rate is given. It is seen that the optimum dimensionless temperature difference is a finite value for a duct length approaching zero for low temperature differences. It is possible to calculate the optimum pressure loss for given wall and inlet fluid temperature differences and corresponding optimum dimensions of a circular duct can be determined with these results. An example for the dimensioning of an air-conditioning heat exchanger tube for given wall and air inlet temperatures and heat transferred is presented.     

A study of mechanism of nickel interferences in hydride generation atomic absorption spectrometric determination of arsenic and antimony

Studies have been carried out to clarify the mechanism of nickel interferences in the hydride generation atomic absorption spectrometric determination of arsenic and antimony. The most serious nickel interferences are observed when nickel/nickel boride nanoparticles are produced during NaBH₄ reduction. In this study these particles have been observed to have diameters of less than 40 nm and sorb As(III), As(V) and Sb(III) species rather than arsine and stibine generated as so far assumed. Bulk chemical composition and surface structure of these nanoparticles were studied and it was found that if the NaBH₄ reduction is carried out while passing nitrogen through the solution the black nanoparticles were composed of Ni₂B and, if the reduction is carried out under air the black nanoparticles were found to consist of Ni₃B or possibly a mixture of Ni(0) and Ni₂B. Surface analysis studies with scanning electron microscopy, energy dispersive X-ray spectrometry, X-ray photoelectron spectrometry and X-ray diffraction analysis have shown that the particles have amorphous structure consisting of Ni(0), Ni₂B, Ni₃B and Ni(OH)₂. However, sorption studies have shown that Ni(0) and Ni(OH)₂ do not sorb the analyte ions and arsine and stibine significantly.