A data-based stability-preserving model order reduction method for hyperbolic partial differential equations

Nonlinear Dynamics - This paper proposes a data-based approach for model order reduction that preserves incremental stability properties. Existing data-based approaches do typically not preserve...     

Structural and spectroscopic properties of trans-difluoro(1,4,8,12-tetraazacyclopentadecane)chromium(III) perchlorate hydrate

The structure of [CrF(2)([15]aneN(4))]ClO(4).H(2)O ([15]aneN(4)=1,4,8,12-tetraazacyclopentadecane) has been determined by a single-crystal X-ray diffraction study at 173 K. The complex crystallizes in the space group P1- of the triclinic system with two mononuclear formula units in a cell of dimensions a=9.6117(7) A, b=10.2882(7) A, c=11.0001(7) A and alpha=99.7570(10) degrees, beta=105.6080(10) degrees and gamma=113.7130(10) degrees. The complex cation unit has its central Cr atom in an octahedral coordination with four nitrogen atoms and two fluorine atoms in a trans position. Three six-membered and one five-membered chelate rings of the [15]aneN(4) ligand are in a chair-twist(skew)-chair-gauche conformation sequence. The gauche five-membered ring is disordered with the twist six-membered ring opposite. The four H atoms in the chiral N atoms have the trans-II (CTCg) type configuration. The mean Cr-N and Cr-F bonds are 2.095(2) and 1.8752(13) A, respectively. The IR and visible spectral properties are consistent with the result of X-ray crystallography. The resolved band maxima of the electronic d-d spectrum are fitted with secular determinant for quartet state energy of d(3) configuration in tetragonal field including configurational but neglecting spin-orbit coupling. It is confirmed that the fluoride has strong sigma- and pi-donor properties toward the chromium(III) ion and the nitrogen atoms of the [15]aneN(4) ligand also have a strong sigma-donor character.     

Application of metabolic engineering to the production of scopolamine

Scopolamine is an alkaloid widely used in medicine for its anticholinergic activity. The aim of this review is to show that metabolic engineering techniques constitute a suitable tool to improve the production of tropane alkaloids, focusing in particular on scopolamine. We present an overview of results obtained by various research groups, including our own, who have studied the overexpression of genes involved in the biosynthesis of scopolamine in different plant species that produce tropane alkaloids. Experiments carried out to improve production in hairy root cultures will also be described, as well as those attempting to biotransform hyoscyamine into scopolamine in roots and transgenic tobacco cells.     

Controlling the optical bistability and transmission coefficient in a four-level atomic medium

A novel four level atomic configuration is proposed for controlling the optical bistability and transmission coefficient with application on all-optical switching. Two circularly polarized components from a weak linearly-polarized probe beam are interacted separately by two transitions of this medium. A coherent coupling field has derived another atomic transition. It is demonstrated that the transmission coefficient of two orthogonally polarized beams at different frequencies can be achieved by adjusting the magnitude of the external magnetic field. It is found that the threshold of the optical bistability can be controlled by magnitude of the external magnetic field. Also, it is shown that optical bistability can be converted to optical multistability by switching the two orthogonally polarized beams.     

A New Model for Prediction of One Electron Reduction Potential of Nitroaryl Compounds

This paper introduces a simple model for prediction of one electron reduction potential [E(RNO₂/R ^? NO₂^–)] of various nitroaryl compounds. The new method uses energy difference between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) in gas phase at the B3LYP/6‐311++G** level (ΔE_HOMO‐LUMO) and some structural parameters. It was used for 35 nitroaryl compounds including nitrobenzenes, nitrofurans, 2‐nitroimidazoles, 4‐nitroimidazoles, 5‐ninuintidazoles, nitroazaindoles, nitroacridines, and miscellaneous nitroaryl compounds. The root mean square (rms) percent deviation and the average absolute error of predictions of E(RNO₂/R ^? NO₂^–) relative to experiment were decreased from 12.4 % and 0.42 V to 3.5 % and 0.11 V, respectively, upon consideration of several structural parameters. Increment of the value of ΔE_HOMO‐LUMO and inclusion of specific polar groups can increase thermodynamic stability of these compounds.     

Synthesis and characterization of two new fluorescent macrocycles: A novel fluorescent chemosensor for zinc ion

Two new macrocyclic systems (L¹, L²) containing two emissive naphthalene were synthesized and characterized. The macrocycles were studied by ¹H NMR, ¹³C NMR, COSY, HMQC, DEPT, microanalysis and mass spectroscopy. The influence of metal cations Na⁺, Cr³⁺, Mn²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Hg²⁺ on the spectroscopic properties of the macrocyclic systems in acetonitrile/DMF 9:1 (v/v) mixtures were investigated by means of absorption and emission spectrophotometry. The macrocycle L¹ was found to be as an effective fluorescence sensor for Zn²⁺ ions. Zn²⁺ and Cd²⁺ ions show the most effects on the fluorescence intensity of L².     

Nonisothermal crystallization behavior of isotactic polypropylene/ thermoplastic rubber blends

The morphology and crystallization behavior of blends of polypropylene (PP) and an ethylene-based thermoplastic elastomer (TPO) were investigated by scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The SEM images showed a two-phase morphology for these blends. As TPO was partially crystalline, two distinct peaks were observed in both heating and cooling scans of DSC. The crystallization temperature of TPO in blends was higher than pure TPO. In contrast, the crystallization temperature of PP in blends was lower than pure PP. The crystallization behavior of blends was modeled by Avrami equation. It was observed that the presence of TPO accelerated the growth rate of crystals of PP in PP/TPO blends.     

On string topology of three manifolds

Let M be a closed, oriented and smooth manifold of dimension d. Let LM be the space of smooth loops in M. In [String topology, preprint math.GT/9911159] Chas and Sullivan introduced the loop product, a product of degree -d on the homology of LM. We aim at identifying the three manifolds with “nontrivial” loop product. This is an application of some existing powerful tools in three-dimensional topology such as the prime decomposition, torus decomposition, Seifert fiber space theorem, torus theorem.     

Preparation and investigation of magnetic properties of wüstite nanoparticles

In this work wüstite nanoparticles have been prepared via high-energy ball milling, using high-purity hematite (Fe₂O₃) and iron (Fe) powders as the starting materials. In order to get a single-phase wüstite different mole ratios of (Fe/Fe₂O₃) were milled, using a planetary mill. X-ray diffraction studies of the as-milled powders show that a single-phase wüstite was formed for a mole ratio of 0.6. Lattice parameter of the wüstite was obtained from XRD data, by which a value of 0.072 was obtained for x in Fe_1−xO. A mean crystallite size of 13±1 nm was calculated for the single-phase wüstite, using Scherrer's formula. The morphology of the powders was also checked by TEM. Variations of pressure and temperature in the vial were recorded with respect to the milling time, using a GTM unit. Hysteresis loops of the as-milled powders at 5 K and room temperature have been obtained by SQUID and by VSM systems, respectively. The loops show non-zero coercivity, in contrast to the bulk wüstite. The observed magnetizations can be explained by a model based on the spinel-type defect clusters in non-stoichiometry wüstite.     

A Nanocage for Nanomedicine: Polyhedral Oligomeric Silsesquioxane (POSS)

Ground‐breaking advances in nanomedicine (defined as the application of nanotechnology in medicine) have proposed novel therapeutics and diagnostics, which can potentially revolutionize current medical practice. Polyhedral oligomeric silsesquioxane (POSS) with a distinctive nanocage structure consisting of an inner inorganic framework of silicon and oxygen atoms, and an outer shell of organic functional groups is one of the most promising nanomaterials for medical applications. Enhanced biocompatibility and physicochemical (material bulk and surface) properties have resulted in the development of a wide range of nanocomposite POSS copolymers for biomedical applications, such as the development of biomedical devices, tissue engineering scaffolds, drug delivery systems, dental applications, and biological sensors. The application of POSS nanocomposites in combination with other nanostructures has also been investigated including silver nanoparticles and quantum dot nanocrystals. Chemical functionalization confers antimicrobial efficacy to POSS, and the use of polymer nanocomposites provides a biocompatible surface coating for quantum dot nanocrystals to enhance the efficacy of the materials for different biomedical and biotechnological applications. Interestingly, a family of POSS‐containing nanocomposite materials can be engineered either as completely non‐biodegradable materials or as biodegradable materials with tuneable degradation rates required for tissue engineering applications. These highly versatile POSS derivatives have created new horizons for the field of biomaterials research and beyond. Currently, the application of POSS‐containing polymers in various fields of nanomedicine is under intensive investigation with expectedly encouraging outcomes.