In situ-preparation and characterization of silver-HEMA/PEGDA hydrogel matrix nanocomposites: Silver inclusion studies into hydrogel matrix

Poly(ethylene glycol) diacrylate (PEGDA) of different molecular weights (Mn = 575 and 700) was used as crosslinking agent for the photopolymerization of 2-hydroxyethyl methacrylate (HEMA) in order to obtain HEMA/PEGDA-based hydrogels. Composites were synthesized in situ employing a new methodology that implies the addition of different quantities of silver nitrate aqueous solution to the monomer mixture with the finality to obtain hydrogels with different silver nanoparticles’ spatial density and distribution. Samples were characterized by thermal, optical, spectroscopic and structural/morphological methods. Thermal studies showed that the increase of PEGDA molecular weight and the AgNO₃ concentration in the reaction mixture enhance the glass transition temperature and the thermal stability of the composites. This behavior could be related to the silver coordination with the polymer network. Infrared spectroscopy with Fourier transform and Raman analyses were realized in order to corroborate the sample chemical structure by the identification of specific functional groups. Surface hydrogel morphology was visualized with scanning electron microscopy analysis, detecting a homogeneous micro-porous surface for the samples obtained from high molecular weight PEGDA. Presence of silver nanoparticles was established by X-ray fluorescence spectroscopy and UV/Vis methods. In this last case, the characteristic silver nanoparticle plasmon was observed. Using Transmission Electron Microscopy it was possible to visualize a homogeneous spatial distribution of spherical silver nanoparticles with very narrow diameter distribution that rounds about 14–21 ± 5 nm. In general, the silver nanoparticle presence in the compounds enhances considerably their thermal/morphological characteristics.     

The Coulomb Hole of the Ne Atom

We analyze the Coulomb hole of Ne from highly-accurate CISD wave functions obtained from optimized even-tempered basis sets. Using a two-fold extrapolation procedure we obtain highly accurate results that recover 97 % of the correlation energy. We confirm the existence of a shoulder in the short-range region of the Coulomb hole of the Ne atom, which is due to an internal reorganization of the K-shell caused by electron correlation of the core electrons. The feature is very sensitive to the quality of the basis set in the core region and it is not exclusive to Ne, being also present in most of second-row atoms, thus confirming that it is due to K-shell correlation effects.     

Facile and highly diastereo and regioselective synthesis of novel octahydroacridine-isoxazole and octahydroacridine-1,2,3-triazole molecular hybrids from citronella essential oil

A novel and highly efficient synthetic approach for the expedite construction of new octahydroacridine-isoxazole- and octahydroacridine-1,2,3-triazole-based molecular hybrids is first reported. Rapid access to the octahydroacridine core was achieved in a highly diastereoselective fashion via cationic Povarov reaction of N-propargyl anilines and citronella essential oil (Cymbopogon nardus). The subsequent 1,3-dipolar and Cu (I) catalyzed alkyne-azide cycloaddition reaction of the terminal alkyne fragment with the corresponding oxime or azide affords the desired 3,5-isoxazoles and 1,2,3-triazoles, respectively, as interesting molecular hybrid models for pharmacological studies.

     

Feasibility of post-gadolinium three-dimensional gradient-echo sequence to evaluate the pulmonary arterial vasculature

Purpose

To determine the feasibility of post-gadolinium three-dimensional gradient-echo (3D-GE) sequence for the evaluation of the pulmonary arterial vasculature in patients with suspected pulmonary embolism (PE) and in patients with a variety of other disease processes.

Materials and Methods

Twenty-six consecutive patients (18 females, 8 males; mean age±S.D., 46.6±21.1 years) who underwent chest magnetic resonance imaging (MRI) including post-gadolinium 3D-GE sequence for the evaluation of PE (Group A, n=13) and a variety of other disease processes (Group B, n=13) were included in the study. Post-gadolinium 3D-GE MR sequences were retrospectively, independently and blindly evaluated by two reviewers for the image quality of pulmonary arterial vasculature, and findings of PE and other disease processes. Clinical and imaging follow-up data for all patients were obtained. Interobserver agreement was calculated by kappa statistics.

Results

All central and lobar pulmonary arteries, 71.4–89.6% of segmental arteries and 46.7–52.7% of subsegmental arterial units in both groups were visualized with sufficient diagnostic image quality on post-gadolinium 3D-GE sequences. PE involving lobar and segmental arteries was diagnosed in two patients in each group. Other disease processes including pneumonia, lung nodules, superior vena cava stenosis, lung metastases, chronic lymphocytic leukemia and aortic aneurysm were detected in 10 of 26 patients. There was good to excellent interobserver agreement (0.73 to 1.00) for all findings.

Conclusion

Post-gadolinium 3D-GE sequence may be an alternative technique for the visualization of central, lobar and segmental arteries, and may diagnose PE and other pathologies involving the chest in different patient populations.     

A confirmation of agreement of different approaches for?scalar?gauge-invariant metric perturbations during inflation

We revisit an extension of the well-known formalism for gauge-invariant scalar metric fluctuations to study the spectra for both the inflaton and gauge-invariant (scalar) metric fluctuations in the framework of a single-field inflationary model, in which the quasi-exponential expansion is driven by an inflaton which is minimally coupled to gravity. The proposal here examined is valid also for fluctuations with large amplitudes, but for cosmological scales, where vector and tensor perturbations can be neglected and the fluid is irrotacional.     

Coherent Superpositions of Photon Creation Operations and Their Application to Multimode States of Light

We present a concise review of recent experimental results concerning the conditional implementation of coherent superpositions of single-photon additions onto distinct field modes. Such a basic operation is seen to give rise to a wealth of interesting and useful effects, from the generation of a tunable degree of entanglement to the birth of peculiar correlations in the photon numbers and the quadratures of multimode, multiphoton, states of light. The experimental investigation of these properties will have an impact both on fundamental studies concerning, for example, the quantumness and entanglement of macroscopic states, and for possible applications in the realm of quantum-enhanced technologies.     

Spirolactone syntheses through a rhodium-catalyzed intramolecular C-H insertion reaction: model studies towards the synthesis of syringolides

Model studies towards the total synthesis of syringolides using a rhodium-catalyzed intramolecular C-H insertion reaction as the key step are described. A highly stereospecific synthesis of spirolactones is achieved employing this methodology.     

Chromium(III) complexes with terdentate 2,6-bis(azolylmethyl)pyridine ligands: Synthesis, structures and ethylene polymerization behavior

Reactions of 2,6-bis(bromomethyl)pyridine with 3,5-dimethylpyrazole and 1H-indazole yield the terdentate ligands 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine (5) and 2,6-bis(indazol-2-ylmethyl)pyridine (6). The molecular structure of the new compound 6 was determined by single-crystal X-ray diffraction. These ligands react with the CrCl₃(THF)₃ complex in THF to form neutral complexes of general formula [CrCl₃{2,6-bis(azolylmethyl)pyridine-N,N,N}] (7, 8) which are isolated in high yields as stable green solids and characterized by means of elemental analysis, magnetic moments, IR, and mass spectroscopy. Theoretical calculations predict that the thermodynamically preferred structure of the complexes is the fac configuration. After reaction with methylaluminoxane (MAO) the chromium(III) complexes are active in the polymerization of ethylene.