The photochemical reactions of 5H-benzo[a]phenoxazin-5-one with alkylthiols and thiophenol

6-Alkylthio- and 6-phenylthio-5H-benzo[a]phenoxazin-5-ones have been synthesized by the photochemical reaction of 5H-benzo[a]phenoxazin-5-one with alkylthiols and thiophenol.     

Global attractor for the regularized Bénard problem

In this paper, we study the asymptotic behaviour of weak solutions for the regularized Bénard problem. We establish the global existence and uniqueness of weak solutions of this problem and give a proof for the existence of global attractor in the three-dimensional case for this system.     

Pd(OAc)2-catalyzed carbonylation of amines

A phosphine-free catalytic system [Pd(OAc)2-Cu(OAc)2-air] induced a substrate-specific carbonylation of amines in boiling toluene under CO gas (1 atm). Symmetrical N,N'-dialkylureas were obtained by the carbonylation of primary amines. N,N,N'-Trialkylureas were selectively formed by addition of a secondary amine to the above reaction vessel. Secondary amines did not give tetraalkylureas. However, dialkylamines with a phenyl group on their alkyl chains, such as N-monoalkylated benzylic amine or phenethylamine derivatives, underwent a direct aromatic carbonylation to afford five- or six-membered benzolactams. In the carbonylation, the chelation effect or steric repulsion between Pd(II) and the meta-substituent in the ortho-palladation and the ring sizes of cyclopalladation products that were formed prior to carbonylation were found to generate good site selectivity and increase the reaction rate. In contrast, carbonylation of omega-arylalkylamines with a hydroxyl group gave neither ureas nor benzolactams but instead produced 1,3-oxazolidinones smoothly. Hydrochlorides of amines also underwent carbonylation to afford the corresponding amides under the conditions used. This procedure made it possible to prepare ureas of amino acid esters and N-alkylcarbamates in practical yields.     

Solvent effects in the preparation of molecularly imprinted polymers for melatonin using N-propionyl-5-methoxytryptamine as the pseudo template

To clarify the role of diluents in the preparation of molecularly imprinted polymers utilizing only hydrogen bonding, we investigated the effects of diluents by using different solvents. Melatonin (N-acetyl-5-methoxytryptamine), an amide bond and indole ring-containing hormone was chosen as the target molecule. N-Propionyl-5-methoxytryptamine was used as the pseudo template, methacrylic acid as the functional monomer, and solvents were used as diluents. Interactions between the template, the functional monomer, melatonin, and the solvents, were observed by ¹H NMR spectroscopy. The polymers were evaluated by high-performance liquid chromatography. The results suggest the hydrogen bonding-acceptor capacity of the solvent is the most important factor in the preparation of molecularly imprinted polymers for hydrogen bonding-donating molecules. Hydrogen bonding between the template, the functional monomer, and solvent can be estimated from the chemical shifts in ¹H NMR spectra of those molecules in the solvent.     

Global calculations of ground-state axial shape asymmetry of nuclei

Important insight into the symmetry properties of the nuclear ground-state (gs) shape is obtained from the characteristics of low-lying collective energy-level spectra. In the 1950s, experimental and theoretical studies showed that in the gs many nuclei are spheroidal in shape rather than spherical. Later, a hexadecapole component of the gs shape was identified. In the 1970-1995 time frame, a consensus that reflection symmetry of the gs shape was broken for some nuclei emerged. Here we present the first calculation across the nuclear chart of axial symmetry breaking in the nuclear gs. We show that we fulfill a necessary condition: Where we calculate axial symmetry breaking, characteristic gamma bands are observed experimentally. Moreover, we find that, for those nuclei where axial asymmetry is found, a systematic deviation between calculated and measured masses is removed.     

The heating–cooling rate effect on thermal properties of high nickel-rich NiTi shape memory alloy

Journal of Thermal Analysis and Calorimetry - In this study, the effects of heating and cooling rate on the thermal properties of high nickel-rich Ni55Ti45 shape memory alloy were investigated....     

A novel biosurfactant, 2-acyloxyethylphosphonate, isolated from waterblooms of Aphanizomenon flos-aquae

A novel biosurfactant, 2-acyloxyethylphosphonate, was isolated from waterblooms of Aphanizomenon flos-aquae. Its structure was elucidated by chemical degradation and HRFABMS, GC/EI-MS and 1D- and 2D-NMR spectral analyses. The surfactant contained one mole of 2-hydroxyethylphosphonate and one mole of fatty acid, with hexadecanoic acid accounting for 84.1% of the total fatty acid content. The structure was confirmed by synthesis of 2-oleoyloxyethylphosphonate from ethylene oxide, phosphorus acid and oleic acid chloride. Considering the isolated surfactant molecule as hexadecanoyloxyethylphosphonic acid (mw. 364), the critical micelle concentration (CMC) was about 22 mM.     

“Beyond an acronym,STEM is…”: Perceptions of STEM

Although STEM is at the forefront of many educational initiatives, little is known about various professionals’ perceptions of STEM. This mixed‐methods study surveyed 164 preservice teachers, inservice teachers, administrators, informal educators, and STEM professionals. Quantitative and qualitative questions on the survey elicited participants’ perceptions of STEM, STEM support, and STEM careers. Quantitative analysis revealed that profession influenced understandings of STEM, importance of STEM, support for STEM, and perceptions of STEM career opportunities. Qualitative analysis provided rich explanations for the differences in perceptions among professions. This study suggests that science teacher educators need to ensure preservice teachers have understandings of STEM and STEM careers, K‐16 educators need to emphasize the current importance of STEM, and administrators and policymakers need to align visions of STEM with curriculum and pacing guides so teachers feel supported in their STEM endeavors.