Assessing diffusive fluxes and pore water radon activities via a single automated experiment

We present a laboratory system to evaluate radon flux and pore water radon via automated sediment equilibration experiments. The setup includes a measured mass of sediment and water inside a gas-tight reaction flask connected in a closed loop to a radon-in-air analyzer. Diffusive fluxes are determined either from the near-linear slope of the activity versus time over the first several hours or by running the experiment longer to estimate the equilibrium concentration via a curve fitting approach. By combining the equilibrium activity with relevant physical parameters, one can also estimate the pore water concentrations.     

Radical Cyclization/ipso‐1,4‐Aryl Migration Cascade: Asymmetric Synthesis of 3,3‐Difluoro‐2‐propanoylbicyclo[3.3.0]octanes

A novel method for the asymmetric synthesis of 3,3‐difluoro‐2‐propanoylbicyclo‐[3.3.0]octanes involves an unprecedented intramolecular radical cyclization/ipso‐1,4‐aryl migration cascade.     

The Morita?Baylis?Hillman Reaction of Chiral Highly Oxygenated Cyclopent‐2‐enones

The Morita? Baylis? Hillman (MBH) reactions of (4S,5R,7R,8R)‐ and (4R,5R,7R,8R)‐4‐hydroxy‐7,8‐dimethoxy‐7,8‐dimethyl‐6,9‐dioxaspiro[4.5]dec‐2‐en‐1‐ones ( 2 and 3 , resp.) with aldehydes using various catalysts were studied. A combination of Bu₃P/phenol in THF was found being optimum conditions giving the corresponding MBH adducts with high diastereoisomeric ratios. After separation, each stereomerically pure isomer of the MBH adducts was subjected to hydrolysis employing 1% aq. CF₃COOH (TFA) in a water bath of an ultrasonic cleaner to afford the corresponding polyhydroxylated cyclopentenones in good yields.     

Synthesis of gem-difluoromethylenated bicyclo[m.n.0]alkan-1-ols and their ring-expansion to gem-difluoromethylenated macrocyclic lactones

Fluoride-catalyzed stereoselective nucleophilic addition of PhSCF(2)SiMe(3) (1) to α-carboethoxycycloalkanones 2 followed by intramolecular radical cyclization of the resulting cis-3 adduct afforded the corresponding gem-difluoromethylenated bicyclic compounds 4, which underwent ring-expansion followed by the Baeyer-Villiger-type oxidation of the resulting macrocyclic ketone intermediates to give gem-difluoromethylenated macrocyclic lactones 5.     

Synthesis and spectroscopic characterization of red-shifted spironaphthoxazine based optical switch probes

Spironaphthoxazine (NISO) is an efficient optical switch probe that has applications in high contrast detection of Förster resonance energy transfer (FRET) using optical lock-in detection (OLID). NISO exists in two distinct states, spiro (SP) and merocyanine (MC), that can be independently controlled by using alternate irradiation with near ultraviolet and visible light. Unfortunately, the SP-state of NISO has an absorption centered at 350 nm, which may lead to phototoxic effects when manipulating the probe within a living cell. To overcome this problem we introduce new, red-shifted amino-substituted NISO probes compared to NISO that undergo an efficient SP to MC transition in response to irradiation by using 405-nm light, which is less damaging to living cells. This study details the synthesis of amino-substituted NISO and their N-hydroxysuccinimide ester and maleimide derivatives and their use in generating covalent attached protein conjugates. This study also presents a characterization of the spectroscopic and optical switching properties of these red-shifted NISO probe in solution.     

The potential use of nanosilver-decorated titanium dioxide nanofibers for toxin decomposition with antimicrobial and self-cleaning properties

While chemical and biological attacks pose risk to human health, clean air is of scientific, environmental and physiological concerns. In the present contribution, the potential use of nanosilver-decorated titanium dioxide (TiO₂) nanofibers for toxin decomposition with antimicrobial activity and self-cleaning properties was investigated. Titanium dioxide nanofibers were prepared through sol-gel reaction followed by an electrospinning process. Following the Japan Industrial Standard (JIS) protocol, decompositions of nitrogen oxide (NOx) and volatile organic compound (VOC) by the TiO₂ nanofibers suggested that these materials were capable of air treatment. To further enhance their anti-microbial activity, silver nanoparticles were decorated onto the TiO₂ nanofibers’ surfaces via photoreduction of silver ion in the presence of the nanofibers suspension. Furthermore, tests of photocatalytic activity of the samples were performed by photodegrading methylene blue in water. The nanofibrous membranes prepared from these nanofibers showed superhydrophilicity under UV. Finally, the possibility of using these hybrid nanofibers in environmental and hygienic nanofiltration was proposed, where the self-cleaning characteristics was expected to be valuable in maintenance processes.     

Efficient synthesis of alkyl 2,3-unsaturated glucopyranosides from glycals mediated by ytterbium(III) triflate-trialkyl aluminum

Treatment of glycals with trialkylaluminum in the presence of a catalytic amount of Yb(OTf)₃ leads to the corresponding alkyl 2,3-unsaturated glycosides in good to excellent yields. Reactions of protected glycals are achieved under very mild conditions.     

Lanthanide triflate catalyzed generation of N-acyliminium ions from α-amido sulfones: the synthesis of (1-alkyl-1-aryl)methyl phenyl sulfones

The reaction of α-amido sulfones with various aromatic and heteroaromatic compounds in the presence of a catalytic amount of lanthanide triflate provides a facile route for the synthesis of (1-alkyl-1-aryl)methyl phenyl sulfones.     

Measurement of radon and thoron progeny size distributions and dose assessments at the mineral treatment industry in Thailand

A new portable type cascade impactor has been developed to determine the activity size distribution of radon and thoron progeny in a natural environment more efficiently. The modified impactor consists of 4 stages with a back up filter stage for the collection of aerosol samples. The aerosol cut points in the impactor are set for 10, 2.5, 1 and 0.5 μm at a flow rate of 4 L min^?1. Five CR-39 chips were used as alpha detectors for each stage. In order to separate α particles emitted from radon and thoron progeny, CR-39 detectors are covered with aluminum-vaporized Mylar films. The thickness of each film is adjusted to allow α particles emitted from radon and thoron progeny to reach the CR-39 detectors. The technique has been successfully tested in field studies, particularly inside a mineral treatment industry in Thailand to estimate doses in the working environment. The dose calculations by lung dose evaluation program showed that activity median aerodynamic diameters played a significant role in determining the particle size distributions of the attached radon and thoron progeny. The dose conversion factor determined from short term measurements due to exposure from the inhalation of thoron and its progeny was found to be 4 times higher than comparable values for radon and its progeny. The effective dose for workers exposed to radon is about 4–6 times higher than thoron.