On experiments in harmonically excited cantilever plates with 1:2 internal resonance

Nonlinear Dynamics - This work presents some experimental results for resonant nonlinear response of hyperelastic plates for 1:2 internal resonance. Previously developed topology optimization...     

Specific Molecular Interactions of Dihydropyridine Moiety in Polar and Non-Polar Solvents at Various Concentrations and Temperatures 303–318 K on Ultrasonic Data

Russian Journal of Physical Chemistry A - Ultrasonic studies of compounds of dihydropyridine series in polar and non-polar solvents at various concentrations and temperatures 303–318 K....     

Proton/Metal–Ligand Stability Constants of Complexes of Sr(II), Cr(II), and Al(III) with N-Phthaloyl Aminoacid and Benzimidazole Derivatives in Dioxane–Water Mixture

Russian Journal of Physical Chemistry A - Formation of complexes Sr(II), Cr(II), and Al(III) with ligands (1,3-dioxo-1,3-dihydro-2H-isoindol-2-yl)acetic acid (L1),...     

Studies on photodissociation dynamics of butadiene monoxide at 193 nm

Butadiene monoxide (BMO) undergoes the S(0)-->S(1) transition, involving the excitation of both pi and n electrons to pi(*) orbital, at 193 nm. After relaxing to the ground electronic state via internal conversion, BMO molecules undergo intramolecular rearrangement and subsequently dissociate to form unexpected OH radicals, which were detected state selectively by laser-induced fluorescence technique, and the energy state distribution was measured. OH is produced vibrationally cold, OH(nu(")=0,J(")), with the rotational population characterized by a rotational temperature of 456+/-70 K. The major portion (approximately 60%) of the available energy is partitioned into internal degrees of the photofragments, namely, vibration and rotation. A considerable portion (25%-35%) also goes to the relative translation of the products. The Lambda doublet and spin-orbit ratios of OH were measured to be nearly unity, implying statistical distribution of these states and, hence, no preference for any of the Lambda doublet (Lambda+ and Lambda-) and spin-orbit (Pi(3/2) and Pi(1/2)) states. Formation time of the nascent OH radical was measured to be <100 ns. Different products, such as crotonaldehyde and methyl vinyl ketone, were detected by gas chromatography as stable products of photodissociation. A reaction mechanism for the formation of all these photoproducts, transient and stable, is proposed. The multiple pathways by which these products can be formed have been theoretically optimized, and energies have been calculated. Absorption cross section of BMO at 193 nm was measured, and quantum yield of OH generation channel was also determined.     

Biocatalytic Synthesis of Allylic and Allenyl Sulfides through a Myoglobin‐Catalyzed Doyle–Kirmse Reaction

The first example of a biocatalytic [2,3]‐sigmatropic rearrangement reaction involving allylic sulfides and diazo reagents (Doyle–Kirmse reaction) is reported. Engineered variants of sperm whale myoglobin catalyze this synthetically valuable C?C bond‐forming transformation with high efficiency and product conversions across a variety of sulfide substrates (e.g., aryl‐, benzyl‐, and alkyl‐substituted allylic sulfides) and α‐diazo esters. Moreover, the scope of this myoglobin‐mediated transformation could be extended to the conversion of propargylic sulfides to give substituted allenes. Active‐site mutations proved effective in enhancing the catalytic efficiency of the hemoprotein in these reactions as well as modulating the enantioselectivity, resulting in the identification of the myoglobin variant Mb(L29S,H64V,V68F), which is capable of mediating asymmetric Doyle–Kirmse reactions with an enantiomeric excess up to 71 %. This work extends the toolbox of currently available biocatalytic strategies for the asymmetric formation of carbon–carbon bonds.     

3D Anisotropic Diffusion on GPUs by Closed-Form Local Tensor Computations

We present an efficient implementation of volumetric anisotropic image diffusion filters on modern programmable graphics processing units (GPUs), where the mathematics behind volumetric diffusion is effectively reduced to the diffusion in 2D images. We hereby avoid the computational bottleneck of a time consuming eigenvalue decomposition in $\mathbb{R}^3$. Instead, we use a projection of the Hessian matrix along the surface normal onto the tangent plane of the local isodensity surface and solve for the remaining two tangent space eigenvectors. We derive closed formulas to achieve this and prevent the GPU code from branching. We show that our most complex volumetric anisotropic diffusion filters gain a speed up of more than 600 compared to a CPU solution.     

Synthesis of dypnone by solvent free self condensation of acetophenone over nano-crystalline sulfated zirconia catalyst

Nano-crystalline sulfated zirconia catalyst, prepared by two-step sol–gel method, has been studied for the solvent free self condensation of acetophenone to dypnone. The influence of calcination temperature on the structural, textural and catalytic activity of sulfated zirconia has been analyzed. The surface acidity along with the structural and textural features of the catalyst influenced its activity. The conversion of acetophenone was found to be effected by the variation in the reaction and calcination temperature, however, the dypnone selectivity was not affected much. The catalyst calcined at 650 °C, showed maximum dypnone selectivity of 92% with 68.2% acetophenone conversion at 170 °C after 7 h. The catalyst was reused up to five cycles with marginal decrease in acetophenone conversion, however, without losing its selectivity for dypnone.     

Esterification of caprylic acid with alcohol over nano-crystalline sulfated zirconia

The catalytic activity of nano-crystalline sulfated zirconia catalyst, prepared by sol–gel method and characterized by various analytical tools, was evaluated for the esterification of caprylic acid with different short chain alcohols. The lower concentration of catalyst (0.5 wt%) exhibited 96–98% conversion of caprylic acid with methanol and 100% selectivity for methyl caprylate at 60 °C. The conversion was decreased with increasing carbon chain of alcohols namely with ethanol, n-propanol and n-butanol at 60 °C but increased significantly (91–98%) at higher reaction temperature. The selectivity for respective alkyl caprylate was observed to be 100% irrespective of the alcohol used. The activity of the catalyst was slightly decreased with successive five reaction cycles due to the water formed during the reaction.     

Immobilized dimeric chiral Mn(III) salen complex on short channel ordered mesoporous silica as an effective catalyst for the epoxidation of non-functionalized alkenes

Chiral dimeric Mn(III) salen complex with 1R, 2R-(?)-diaminocyclohexane collar was immobilized on short channel large pore sized silica through a long linker of {(CH₂)₃–NH–melamine–piperazine} to investigate its performance in enantioselective epoxidation of chromenes, indene, styrene and cis β-methyl styrene in the presence of pyridine N-oxide (PyNO) as an axial base using aqueous NaOCl as an oxidant at 0 °C. The immobilized catalyst system showed high turnover frequency (TOF) and enantioselectivity for the smaller and bulkier alkenes like styrene, indene, 2,2-dimethylchromene and 6-cyano-2,2-dimethylchromene (ee up to 98%). These results are the best reported for heterogeneous catalyst under biphasic reaction conditions and were comparable to the dimeric Mn(III) salen system under homogeneous condition. The performance of the immobilized catalyst was retained for six reuse experiments. This protocol was extended to the synthesis of an antihypertensive drug (S)-Levchromakalim (ee 98%) at 1 g level.