Influence of pigment properties on UV‐curing efficiency

The curable formulations containing monomer‐diacrylate, photoinitiator‐p‐methoxybenzoyldiphenylphosphine oxide/benzyldimethylketal, additive reactive‐triethylamine, and inorganic thermoresistant pigments‐white, red, green, and blue were cured by UV exposure films. A series of experiments was carried out to investigate the relationship between the particle size distribution of the inorganic pigment and the colorimetric and mechanical properties of the UV acrylic curable coatings. Pendulum hardness and appearance of the films depend on the content and particle size distribution of the pigment. Optimal particle size distribution and pigment content were established to obtain the best films concerning their pendulum hardness and chromatic parameters. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 247–252, 2007     

Efficient photochromic transformation of a new fluorenyl diarylethene: one- and two-photon absorption spectroscopy

Efficient reversible phototransformation of a new diarylethene-fluorene derivative, 1,2-bis(5-(9,9-didecyl-7-nitro-9H-fluoren-2-yl)-2-methylthiophen-3-yl)cyclopent-1-ene (1), was demonstrated in organic media under low-intensity laser excitation. Linear photophysical characterization of 1 was performed at room temperature in solvents of different polarity and viscosity. Significantly, close to unity quantum yield for the cyclization reaction of 1 was shown in nonpolar solutions. The lifetimes of the excited states of the open (OF) and closed (CF) forms of 1 were measured by a femtosecond transient absorption technique, and corresponding values of ～0.7 and ～0.9 ps were shown in dichloromethane (DCM), respectively. Degenerate two-photon absorption (2PA) spectra of the OF and CF of 1 were obtained over a broad spectral range by the open aperture Z-scan method under 1 kHz femtosecond excitation. The values of 2PA cross sections of the OF in DCM (～50-70 GM) were found to increase up to 1 order of magnitude (～600 GM) after cyclization to the CF. The nature of cyclization and cylcoreversion processes were investigated by quantum chemistry with employment of DFT-based methods implemented in the Gaussian'09 program. The potential of 1 for application in optical data storage was shown using poly(methyl methacrylate)-doped films and two-photon fluorescence microscopy readout.     

Gold-silver alloy nanoshells: a new candidate for nanotherapeutics and diagnostics

We have developed novel gold-silver alloy nanoshells as magnetic resonance imaging (MRI) dual T₁ (positive) and T₂ (negative) contrast agents as an alternative to typical gadolinium (Gd)-based contrast agents. Specifically, we have doped iron oxide nanoparticles with Gd ions and sequestered the ions within the core by coating the nanoparticles with an alloy of gold and silver. Thus, these nanoparticles are very innovative and have the potential to overcome toxicities related to renal clearance of contrast agents such as nephrogenic systemic fibrosis. The morphology of the attained nanoparticles was characterized by XRD which demonstrated the successful incorporation of Gd(III) ions into the structure of the magnetite, with no major alterations of the spinel structure, as well as the growth of the gold-silver alloy shells. This was supported by TEM, ICP-AES, and SEM/EDS data. The nanoshells showed a saturation magnetization of 38 emu/g because of the presence of Gd ions within the crystalline structure with r₁ and r₂ values of 0.0119 and 0.9229 mL mg^-1 s^-1, respectively (Au:Ag alloy = 1:1). T₁- and T₂-weighted images of the nanoshells showed that these agents can both increase the surrounding water proton signals in the T₁-weighted image and reduce the signal in T₂-weighted images. The as-synthesized nanoparticles exhibited strong absorption in the range of 600-800 nm, their optical properties being strongly dependent upon the thickness of the gold-silver alloy shell. Thus, these nanoshells have the potential to be utilized for tumor cell ablation because of their absorption as well as an imaging agent.     

Phase Transfer Catalysis in Phosphorus Chemistry

Phase-transfer catalysis (PTC) has been widely used for the synthesis of organic compounds for more than three decades. The scope and mechanistic features of PTC have been the aim of numerous studies. This review focuses on the application of phase transfer catalysis in synthesis of phosphorus compounds.     

Unsteady heat transfer from an elliptic cylinder

Numerical methods are used to investigate the transient heat transfer from an elliptic cylinder to a steady stream of viscous, incompressible fluid. The temperature of the cylinder is considered spatially uniform but not constant in time. The momentum and heat balance equations were solved numerically in elliptic coordinate system. The solutions span the parameter ranges 5 ? Re ? 40, 1 ? Pr ? 100 and axis ratio ε, 0.1 ? ε ? 0.75. The computations were focused on the influence of the axis ratio and volume heat capacity ratio on the heat transfer rate.     

Free convection between two horizontal concentric cylinders filled with a porous medium — a perturbed solution

Summary A theoretical analysis of the steady free convection in a saturated porous medium confined between two horizontal concentric cylinders is made in this paper. It is assumed that the flow is driven by a constant vertical temperature gradient. Analytical solutions in terms of Bessel functions for the first-order perturbed flow and temperature field from the heat conduction steady state are determined. Four types of thermal convection with cellular structure are found, and the dependence of the critical Darcy-Rayleigh number on the thickness of the annular region is obtained for these flow types. Typical streamlines and isotherms corresponding to these critical modes are presented. It is worth mentioning that these results have a bearing on the design of thermal insulators.     

An empirical evaluation of P system testing techniques

This paper presents the existing techniques for P system testing and performs an empirical evaluation of their fault-detection efficiency. The comparison is performed using mutation testing and, based on the results obtained, some improved testing methodologies are proposed.     

Acoustic resonant response of smooth or rough 3D small objects

This paper presents a new method in order to appreciate the roughness of elliptical or spherical small bodies by using ultrasound. This thing is possible by knowing about 2-4 acoustic resonance frequencies. The maximum diameter and medium roughness of the bodies are evaluated. Small bodies such as tumors can be detected, when other medical devices like ultrasound or tomography computerized cannot evaluate the surface shape because of limited spatial resolution. The method is intended to be used in oncological medicine for early non-invasive diagnostic for cancer, because tumor tissue has outer surface more or less rough, depending on whether or not it is malignant.     

SEM‐EDX and microftir studies on evaluation of protection capacity of some thin phosphate layers

This article presents the SEM‐EDX and microFTIR study and the corrosion behavior of new five types of phosphated coatings obtained by coprecipitation in acid aqueous medium of some metal cations, pursuing the influence of the addition of other cations and a moderator of precipitation, on the uniformity and compactness of the layers and on the morphology of dendritic structure of Zn(II) and Fe(II) phosphates. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc.     

Expedient Immobilization of TEMPO by Copper‐Catalyzed Azide‐Alkyne [3+2]‐Cycloaddition onto Polystyrene Resin

TEMPO was readily grafted by copper(I)‐catalyzed azide‐alkyne cycloaddition onto polystyrene. Starting with commercially available Merrifield resin (4.3 mmol/ g) almost quantitative loading of TEMPO onto the polymer was achieved (≥ 4 mmol/ g). The so obtained PS‐CLICK‐TEMPO allowed the oxidation of alcohols to aldehydes with bleach or molecular oxygen as the terminal oxidant with high yields and selectivity in multiple cycles without loss of activity.