Turnpike Property in Optimal Microbial Metabolite Production

Journal of Optimization Theory and Applications - We consider the problem of maximization of metabolite production in bacterial cells formulated as a dynamical optimal control problem (DOCP)....     

EBC-232 and 323: A Structural Conundrum Necessitating Unification of Five In Silico Prediction and Elucidation Methods

Structurally unique halimanes EBC-232 and EBC-323, isolated from the Australian rainforest plant Croton insularis, proved considerably difficult to elucidate. The two diastereomers, which consist an unusual oxo-6,7-spiro ring system fused to a dihydrofuran, were solved by unification and consultation of five in silico NMR elucidation and prediction methods [i.e., ACDLabs, olefin strain energy (OSE), DP4, DU8+ and TD DFT CD]. Structure elucidation challenges of this nature are prime test case examples for empowering future AI learning in structure elucidation.     

Approach to Numerical Implementation of the Drift-Diffusion Model of Field Effects Induced by a Moving Source

Russian Physics Journal - An approach to numerical implementation of the diffusion-drift model is described with application to problem of estimating field effects induced in an object by a...     

Unprecedented 1,14‐seco‐Crotofolanes from Croton insularis: Oxidative Cleavage of Crotofolin C by a Putative Homo‐Baeyer–Villiger Rearrangement

EBC‐162 isolated from Croton insularis, obtained from the northern rainforest of Australia, was structurally affirmed as crotofolin C ( 4 ). Novel oxidative degradation products, EBC‐233 and EBC‐300, which are the first crotofolane endoperoxides, were also isolated. Both endoperoxides were found to be stable intermediates, which are proposed to undergo an unprecedented homo‐Baeyer–Villiger biosynthetic rearrangement to give a new class of 1,14‐seco‐crotofolane diterpenes. Prolonged storage of all isolates assisted in authenticating their natural product status. Anticancer activities of reported compounds are presented.     

A penalty method for grid matching in the mixed Herrmann-Miyoshi scheme

A penalty method for mixed finite element methods is formulated and studied. The Herrmann-Miyoshi scheme for the biharmonic equation is considered. The main idea is to build a perturbed problem with two parameters playing the role of penalties. The perturbed problem is constructed by replacing principal conditions in the mixed variational formulation at the interface by natural conditions containing parameters. Discretization of the perturbed problem is effected by a finite element method. Estimates for the norm of the difference between the solutions of a discrete perturbed problem and of an initial value problem are derived depending on the mesh size and penalties. Recommendations are given as to how to choose penalties so as to fit a mesh size.     

Physical and mathematical modeling of the electron-beam-induced charging of ferroelectrics during the process of domain-structure switching

The results of modeling the dynamic charging processes that arise when ferroelectrics are under the action of an electron beam in a scanning electron microscope are presented. Implementation of the model is based on simultaneous solution of the continuity equation and Poisson equation with allowance for the radiation-stimulated intrinsic conductivity of the irradiated sample and with an initial charge distribution determined using the Monte Carlo method. The multidimensional boundary evolutionary problem is solved using grid methods. The model permits one to study the dynamics of the process of the electron-beam-induced charging of ferroelectrics. Estimates for the values of fields generated by charges accumulated during the irradiation process are presented for a set of modeling parameters corresponding to physical data obtained in experimental observations of the polarization switch for a ferroelectric lithium niobate crystal.     

Building graph separators with the recursive rotation algorithm for the nested dissection method

A recursive rotation algorithm is built and investigated. The algorithm is a possible version of the nested dissection algorithm. The Liu algorithm builds a matrix graph separator by means of rotation of an elimination tree, which reduces the height of the latter. In this case, the nodes of the matrix graph are previously reordered by one of the well-known Cuthill-McKee algorithms, the reverse Cuthill-McKee algorithm, and the King algorithm. Then this procedure is recursively repeated. The recursive rotation algorithm is compared with the multilevel and spectral methods of graph separation for 2D finite-element grids.     

Reaction of <Emphasis Type="Italic">o</Emphasis>-Quinones in Cyclohexane Solutions with Alkyl Radicals Generated by Solution γ-Irradiation

The structures of products formed in reactions of tert-butylated o-quinones with alkyl radicals were determined by ¹H and ¹³C NMR and two-dimensional ¹H-¹H NOESY spectroscopy, and also by gas chromatography-mass spectrometry. The major products formed upon γ-irradiation of deaerated solutions of 4-tert-butyl-1,2-benzoquinone and 3,5-di-tert-butyl-1,2-benzoquinone in cyclohexane are monoalkyl ethers and products of addition to the C=C bond. In the case of 4-tert-butyl-1,2-benzoquinone, these are products of mixed O-C and C-C alkylation; the adduct formed by addition of the cyclohexyl radical to the C=C bond in 3,5-di-tert-butyl-1,2-benzoquinone gives an unsymmetrical dimer whose structure was proved by single-crystal X-ray diffraction.     

Interaction of Alkyl Radicals with Dihydric Phenol Derivatives in Hexane Solutions under γ-Radiolysis

The influence of structurally different dihydric phenols on the radical reactions of hexane in deaerated solutions under -irradiation was studied. It was found that 4-tert-butylpyrocatechol (I), 3,5-diisopropylpyrocatechol (II), 2,5-di-tert-butylhydroquinone (III), and 4,6-di-tert-butylresorcinol (IV) effectively inhibited the formation of hexyl radical combination products. Using the chromatography–mass spectrometry technique, it was shown that the adducts of alkyl radicals with I–III have the structure of a monoalkyl ether. Phenol IV gave a mixture of dimers with O- and C-alkylation products.     

New Casbanes and the First trans-Cyclopropane seco-Casbane from the Australian Rainforest Plant Croton insularis

Investigation of the Australian rainforest plant Croton insularis revealed seven new cis-, two new trans-cyclopropane casbanes, and the first trans-cyclopropane seco-casbane. The relative configuration of the cyclopropane moiety for all compounds (EBC-182, 217, 218, 220, 343, 357, 358, 361, 365, 373; EBC=EcoBiotics Compound) was assigned using ¹³C NMR data. Comparison of the experimental electronic circular dichroism (ECD) spectra with the theoretical curves, calculated by TD-DFT at the B3LYP/6-31+G**//B3LYP/6-31+G** level, in conjunction with NOE data afforded the absolute configuration. EBC-180, 181 and 220 displayed potent activity against cervical carcinoma (HeLa cells).