Synthesis of superparamagnetic and thermoresponsive hybrid nanoparticles via surface‐mediated RAFT polymerization of di(ethylene glycol) ethyl ether acrylate and (oligoethylene glycol) methyl ether acrylate

A reversible addition‐fragmentation chain transfer (RAFT) agent was directly anchored onto superparamagnetic Fe₃O₄ nanoparticles (SPNPs) in a simple procedure using a ligand exchange reaction of 2‐[(dodecylsulfanylcarbonylthiolsulfanyl) propionic acid] (DCPA) with oleic acid initially present on the surface of Fe₃O₄ nanoparticles. The DCPA‐modified SPNPs were then used for the surface‐mediated RAFT polymerization of di(ethylene glycol) ethyl ether acrylate and (oligoethylene glycol) methyl ether acrylate to fabricate structurally well‐defined hybrid SPNPs with temperature‐responsive poly[di(ethylene glycol) ethyl ether acrylate‐co‐(oligoethylene glycol) methyl ether acrylate] shell and magnetic Fe₃O₄ core. Evidence of a well‐controlled surface‐mediated RAFT polymerization was gained from a linear increase of number‐average molecular weight with overall monomer conversions and relatively narrow polydispersity indices of the copolymers grown from the SPNPs. The resultant hybrid nanoparticles exhibited superparamagnetic property with a saturation magnetization of 55.1–19.4 emu/g and showed a temperature‐responsive phenomenon as the temperature changed between 25 and 40 ^°C. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3420–3428     

Time-resolved and high-resolution MRA in a rabbit model of pulmonary embolism at 7 T: preliminary results

Purpose

Evaluate feasibility of using time-resolved and high-resolution, contrast-enhanced magnetic resonance angiography (MRA) at 7 T for characterization of an animal model of pulmonary embolism.

Methods

MRAs were performed in five rabbits using a 7-T MR scanner. Preceding the MR studies, each rabbit underwent a pulmonary artery catheterization with balloon placement. Two doses of gadodiamide were injected: first during a time-resolved MRA, immediately followed by a high-resolution acquisition. Balloon was then deflated, permitting reperfusion for 5 min. A second dose was then injected and another high-resolution MRA acquired. Measurements of signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR) and vessel cross-sections down to fourth-order branches were made, among other parameters.

Results

Occlusion was detected in all rabbits. Despite a TE of 0.58 ms for the time-resolved MRA, regions of nonuniform enhancement attributed to susceptibility effects at the 7-T field were observed in perfused lung. Mean SNR=7.5±3.3 and 134.2±46.5 for the lung and aorta, respectively, and mean CNR=126.7±46.4 for aorta versus lung were obtained. Diameters of vessels in lung that was never occluded were not statistically different from those in reperfused lung.

Conclusion

Results show that time-resolved and high-resolution MRA of the lung are feasible at 7 T and provide high SNR, CNR and resolution, but TEs smaller than 0.58 ms are required to avoid susceptibility artifacts in time-resolved MRAs.     

Preparation of (99m)Tc labeled vitamin C (ascorbic acid) and biodistribution in rats

The aim of this study was to label ascorbic acid with (99m)Tc and to investigate its radiopharmaceutical potential in rats. Ascorbic acid was labeled with (99m)Tc using the stannous chloride method. The radiochemical purity of [(99m)Tc]ascorbic acid ((99m)Tc-AA) was determined by RTLC, paper electrophoresis, and RHPLC methods. The labeling yield was found to be 93+/-5.0%. The maximum labeling yield of (99m)Tc-AA was determined at pH 5 and 25 degrees C. The biodistribution studies related to (99m)Tc-AA were done in male albino Wistar rats. (99m)Tc-AA, which has a specific activity of 13.02 GBq/mmol, was administered into the tail vein of the rats. The rats were sacrificed at 15, 30, 60, and 120 min after the injection by heart puncture under ether anaesthesia. The organs were weighed after removal. Their activities were counted using a Cd(Te) detector equipped with a RAD 501 count system. The %ID/g (% of injected dose per gram of tissue weight) in each organ and in blood was calculated. Maximum uptake of (99m)Tc-AA was observed in prostate and kidneys at the 60th min. (99m)Tc-AA may be a promising radiopharmaceutical for the imaging of prostate and kidneys.     

Photoelectrochemical oxidation of methanol on oxide nanosheets

Photoelectrochemical oxidation of alcohol on various nanosheet electrodes such as Nb6O17, Ca2Nb3O10, Ti(0.91)O2, Ti4O9, and MnO2 system host layers were measured to evaluate the photocatalysis of water photolysis with alcohol as a sacrificial agent. The nanosheet electrodes were prepared by the layer-by-layer (LBL) method, using electrostatic principles. The highest photooxidation current density was observed in methanol solution for Nb6O17 and Ca2Nb3O10 nanosheets, while the density was lower for Ti(0.91)O2, Ti4O9, and MnO2 nanosheets in decreasing order. The rank in the photocurrent density was in agreement with that in the photocatalytic activity, which means that the degree of photooxidation of the alcohol determines the activity of the alcohol in the water photolysis process. The photocurrent was independent of the number of nanosheet layers on the electrode, indicating that only the mono-nanosheet layer attached directly on a substrate acts as a photoelectrocatalyst and that the interlayer space is not important. Consequently, higher photooxidation current on the Nb6O17 mono-nanosheet layer means that the charge separation of electron and hole under illumination is very large and that the hole-capturing process by CH3OH is very quick compared with the surface recombination on the Nb6O17 nanosheet. The adsorption of a transition metal cation on the nanosheet acted as the surface recombination center, because the photocurrent decreased after the adsorption. The photocatalytic mechanism has been discussed in detail in terms of various photoelectrochemical behaviors.     

Removability of the logarithmic singularity for the elliptic PDEs with measurable coefficients and its consequences

This paper introduces the notion of log-regularity (or log-irregularity) of the boundary point \(\zeta \) (possibly \(\zeta =\infty \)) of the arbitrary open subset \(\Omega \) of the Greenian deleted neigborhood of \(\zeta \) in \({\mathbb {R}}^2\) concerning second order uniformly elliptic equations with bounded and measurable coefficients, according as whether the log-harmonic measure of \(\zeta \) is null (or positive). A necessary and sufficient condition for the removability of the logarithmic singularity, that is to say for the existence of a unique solution to the Dirichlet problem in \(\Omega \) in a class \(O(\log |\cdot - \zeta |)\) is established in terms of the Wiener test for the log-regularity of \(\zeta \). From a topological point of view, the Wiener test at \(\zeta \) presents the minimal thinness criteria of sets near \(\zeta \) in minimal fine topology. Precisely, the open set \(\Omega \) is a deleted neigborhood of \(\zeta \) in minimal fine topology if and only if \(\zeta \) is log-irregular. From the probabilistic point of view, the Wiener test presents asymptotic law for the log-Brownian motion near \(\zeta \) conditioned on the logarithmic kernel with pole at \(\zeta \).     

Generalized entropic structures and non-generality of Jaynes’ Formalism

The extremization of an appropriate entropic functional may yield to the probability distribution functions maximizing the respective entropic structure. This procedure is known in Statistical Mechanics and Information Theory as Jaynes’ Formalism and has been up to now a standard methodology for deriving the aforementioned distributions. However, the results of this formalism do not always coincide with the ones obtained following different approaches. In this study we analyse these inconsistencies in detail and demonstrate that Jaynes’ formalism leads to correct results only for specific entropy definitions.     

On minimal and Chen immersions in space forms

By using the push-out map we obtain some results on minimal immersions and Chen immersions with non-flat normal bundle in space forms under some conditions. We then build up many examples of minimal and Chen immersions.     

Lichens and mosses for correlation between trace elements and 210Po in the areas near coal-fired power plant at Yatağan, Turkey

The lichensRhizoplaca melanophthalma, Cladonia convoluta, Cladonia pyxidata and the mossesGrimmia pulvinata, Hypnum cupressiforme were analyzed for Pb, Cr, Cd, Co, Ni, Mn, Cu, Zn and Fe using atomic absorption spectrophotometry over a wide area around a coal-fired power plant located in Yataan. The results were compared with the ²¹⁰Po concentrations previously measured in the same samples. Correlations between ²¹⁰Po and trace elements for different moss and lichen species of the same localization and for different localizations for the same species were also studied. In general trace element concentrations do not show significant differences from site to site for all species except Mn in Hypnum cupressiforme and ²¹⁰Po in Grimmia pulvinata. To discuss the ²¹⁰Pb level and sources in indicator plants analyzed, also radium contents of surface soil at each sampling station was measured and compared with the average values for similar soil types in the literature.     

Swelling of interpenetrating networklike particles in a soft polymer matrix

Fast transient fluorescence technique was used to monitor swelling of hard latex particles in a soft polymer matrix. Various film samples were prepared from pyrene (P) and/or naphthalene (N)-labeled poly(methyl methacrylate) (PMMA) particles in a low-molecular-weight poly(isobutylene) (PIB) matrix. These PMMA particles contain interpenetrating PIB channels. Film samples were annealed at elevated temperatures to promote particle swelling. Fluorescence lifetimes, tau, were measured for each film sample. It was observed that tau values decrease as the PIB content in the matrix is increased. The decrease in tau was explained by the increase in quenching of excited P and N molecules by low-molecular-weight PIB penetrating into the PIB channels in the PMMA particles. A drastic decrease in tau above a certain temperature was attributed to the effect of particle size on the swelling of the latex particles in the PIB matrix. It was observed that small particles (P-labeled) swell at much lower annealing temperatures than large (N-labeled) particles.     

Visible light photoelectrochemical activity of K4Nb6O17 intercalated with photoactive complexes by electrostatic self-assembly deposition

Electrostatic self-assembly deposition (ESD) results in the intercalation of Ru(bpy)₃²⁺ or methylene blue (MB) into the niobate layered oxide right after the cations come into contact with [Nb₆O₁₇]⁴⁻ nanosheets. Monolayers can be obtained by the exfoliation of proton exchanged K₄Nb₆O₁₇ (KNbO) in an aqueous tetrabutylammonium (TBA) solution as revealed by the atomic force microscopy micrographs. UV-vis spectra show that intercalated films are able to absorb in the visible light range. Heat-treatment of Ru(bpy)₃²⁺ resulted in the red-shift in the absorption spectra, which was assigned to the enhancement in the interaction between the complex molecules and [Nb₆O₁₇]⁴⁻ host layer. Intercalated niobate layered oxides are able to produce photocurrent as a result of the electron transfer from the excited guest molecule to the host layer under visible light illumination. Ru(bpy)₃²⁺ intercalated niobate layered oxide shows photocatalytic activity under visible light illumination to produce H₂ from water-methanol solution.