Application of Doehlert experimental design for the removal of radium from aqueous solution by cross-linked phenoxycalix[4]pyrrole-polymer using Ba(II) as a model.

Ra-226 is a naturally occurring radionuclide that is derived from uranium-238 series, and it is present at low concentrations in rocks, soil, and groundwater. Many efforts have been exerted for the decontamination of radium from aqueous media in order to meet the increasing water demand of the population. To this aim, a new polymer based on cross-linked phenoxycalix[4]pyrrole was designed and employed in solid/liquid extractions in order to remove radium from aqueous solutions. Preliminary experiments have highlighted the capability of this polymer to extract 22% of Ra-226 from aqueous acidic solution. The optimization of the extraction experimental factors in the direction to attend the maximum removal of Ra-226 from water was carried out employing Ba2+ due to its similar chemical behavior as radium, in order to minimize the consumption of Ra-226 solutions and the risk of radioactive contamination. Doehlert experimental plan was then applied to determine the optimal conditions (pH, time, temperature) for the removal of Ba2+ from aqueous solutions.

A click mediated route to a novel fluorescent pyridino-extended calix[4]pyrrole sensor: synthesis and binding studies.

A novel fluorescent aryl-extended phenoxycalix[4]pyrrole ditopic sensor with enhanced cation recognition properties was efficiently synthesized via click chemistry and characterized through both molecular fluorescence and nuclear magnetic resonance spectroscopy. Results demonstrate the selectivity of this fluorescent sensor for fluoride when taking into account its interaction with anions, while its cation binding properties showed selectivity for iron, and its sensing properties for several cations in dimethylsulfoxide. This work introduces a new ditopic receptor able to complex major environmentally relevant species and depicts the importance of click chemistry in the introduction of new tetra-chromophoric calix[4]pyrrole binding platforms with specific photophysical properties.

Swine Atrioventricular Node Ablation Using Stereotactic Radiosurgery: Methods and In Vivo Feasibility Investigation for Catheter-Free Ablation of Cardiac Arrhythmias.

BACKGROUND: Linear accelerator-based stereotactic radiosurgery delivered to cardiac arrhythmogenic foci could be a promising catheter-free ablation modality. We tested the feasibility of in vivo atrioventricular (AV) node ablation in swine using stereotactic radiosurgery. METHODS AND RESULTS: Five Large White breed swine (weight 40-75 kg; 4 females) were studied. Single-chamber St Jude pacemakers were implanted in each pig. The pigs were placed under general anesthesia, and coronary/cardiac computed tomography simulation scans were performed to localize the AV node. Cone beam computed tomography was used for target positioning. Stereotactic radiosurgery doses ranging from 35 to 40 Gy were delivered by a linear accelerator to the AV node, and the pigs were followed up with weekly pacemaker interrogations to observe for potential electrocardiographic changes. Once changes were observed, the pigs were euthanized, and pathology specimens of various tissues, including the AV node and tissues surrounding the AV node, were taken to study the effects of radiation. All 5 pigs had disturbances of AV conduction with progressive transition into complete heart block. Macroscopic inspection did not reveal damage to the myocardium, and pigs had preserved systolic function on echocardiography. Immunostaining revealed fibrosis in the target region of the AV node, whereas no fibrosis was detected in the nontargeted regions. CONCLUSIONS: Catheter-free radioablation using linear accelerator-based stereotactic radiosurgery is feasible in an intact swine model.

Point defect engineered Si sub-bandgap light-emitting diode.

We present a novel approach to enhance light emission in Si and demonstrate a sub-bandgap light emitting diode based on the introduction of point defects that enhance the radiative recombination rate. Ion implantation, pulsed laser melting and rapid thermal annealing were used to create a diode containing a self-interstitial-rich optically active region from which the zero-phonon emission line at 1218 nm originates.