Isolation and characterization of degradation products of moxidectin using LC, LTQ FT-MS, H/D exchange and NMR

This study aimed to evaluate the degradation profile and pathways, and identify unknown impurities of moxidectin under stress conditions. During the experiments, moxidectin samples were stressed using acid, alkali, heat and oxidation, and chromatographic profiles were compared with known impurities given in European Pharmacopeia (EP) monograph. Moxidectin has shown good stability under heat, while reaction with alkali produced 2-epi and ?2,3 isomers (impurities D and E in EP) by characteristic reactions of the oxahydrindene (hexahydrobenzofuran) portion of the macrocyclic lactone. Two new, previously unreported, unknown degradation products, i.e. impurity 1 and impurity 2, detected after acid hydrolysis of moxidectin (impurity 2 was also observed to a lesser extent after oxidation), were isolated from sample matrices and identified using liquid chromatography, NMR, high-resolution FT-ICR MS, and hydrogen/deuterium exchange studies. FTMS analysis showed accurate mass of molecular ion peaks for moxidectin at m/z 640.38412, impurity 1 at m/z 656.37952 and impurity 2 at m/z 611.35684, giving rise to daughter ions traceable up to the seventh levels of MSⁿ experiments and supporting the proposed structures. Both unknown impurities along with moxidectin were fully characterized by ¹H, ¹³C, 1D HMBC and 2D (NOESY, COSY and HSQC) NMR experiments. The interpretation of experimental data positively identified impurity 1 as 3,4-epoxy-moxidectin and impurity 2 as 23-keto-nemadectin. The identification of new impurities and correlation of their chromatographic profiles with the EP method is very useful to establish the stability profile of moxidectin and its preparations, as well as add value to the forthcoming moxidectin finished product European Pharmacopeia monographs.

Almost-Perfect Rings and Modules

Following [1 Amini , A. , Ershad , M. , Sharif , H. ( 2008 ). Rings over which flat covers of finitely generated modules are projective . Comm. Algebra 36 : 2862 – 2871 .[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]], a ring R is called right almost-perfect if every flat right R-module is projective relative to R. In this article, we continue the study of these rings and will find some new characterizations of them in terms of decompositions of flat modules. Also we show that a ring R is right almost-perfect if and only if every right ideal of R is a cotorsion module. Furthermore, we prove that over a right almost-perfect ring, every flat module with superfluous radical is projective. Moreover, we define almost-perfect modules and investigate some properties of them.     

Regioselective multi-component synthesis of 1H-pyrazolo[3,4-d]pyrimidine-6(7H)-thiones

A variety of pyrazolo[3,4-d]pyrimidine-6(7H)-thione derivatives were easily synthesized with a novel, simple, efficient, and regioselective method via three-component condensation reaction of 5-methyl-1H-pyrazol-3-amine, arylisothiocyanates, and aldehydes in the presence of catalytic amount of p-toluenesulfonic acid (p-TSA) in 1-butyl-3-methylimidazolium bromide ionic liquid with excellent yields and short reaction times.     

Relativistic Symmetries in the Hulthén-like Potential and Tensor Interaction

In the presence of spin and pseudospin (p-spin) symmetries, the approximate analytical bound states of the Dirac equation for Hulthén-like potential including a Coulomb-like tensor interaction are obtained with any arbitrary spin–orbit coupling number κ using the Pekeris approximation. The generalized parametric Nikiforov–Uvarov (NU) method is used to obtain the energy eigenvalues and the corresponding wave functions in their closed forms. We show that tensor interaction removes degeneracies between spin and p-spin doublets. Some numerical results are also given.     

A semi-automated hybrid algorithm for accurate detection and counting of chemically etched tracks

In this paper, we present an accurate and comprehensive semi-automated algorithm for detection and counting the chemically etched tracks on polycarbonate nuclear Track detectors. The proposed algorithm consists of two main phases: a preprocessing phase for image preparation and quality improvement. It uses a format conversion into gray-scale image and contrast enhancement procedure. The contrast enhancement procedure employs the first-order fuzzy moment of the image and the Sugeno class of fuzzy complements to maximize the parametric indices of fuzziness of the image. In one feature extraction phase, two intrinsic characteristics of tracks are defined and formulated as topological feature (TF) and chromatic feature (CF). TF refers to tracks shape and geometry which are characterized and quantized by calculating the local Gray Level Spatial Correlation histogram of the tracks and CF refers to the color intensity difference of the tracks borders and tracks centric areas. The CF characterizes this difference specified to the tracks. After the feature extraction phase, the algorithm enters the detection and counting phase in which the fuzzy sets of background, noise (including small objects, notches, etc.) and track are constructed. Detected objects are then characterized according to their membership values to the fuzzy sets. The algorithm is designed in order to be applicable for different forms of tracks and track counting systems. Accuracy, linearity, sensitivity to the input parameters and comprehensibility of the method are validated in the simulation section.     

Supervised nuclear track detection of CR-39 detectors by cellular automata

In this paper, cellular automata are used to detect the nuclear tracks in the track images captured from the surface of CR-39 detectors. Parameters of the automaton as the states, neighborhood, rules and quality parameters are defined optimally for the track image data set under analysis. The presented method is a supervised computational algorithm which comprises a rule definition phase as the learning procedure. Parameter optimization is also performed to adapt the algorithm to the data set used.     

Deformation of inherent structures to detect long-range correlations in supercooled liquids

We propose deformations of inherent structures as a suitable tool for detecting structural changes underlying the onset of cooperativity in supercooled liquids. The non-affine displacement (NAD) field resulting from the applied deformation shows characteristic differences between the high temperature liquid and supercooled state, which are typically observed in dynamic quantities. The average magnitude of the NAD is very sensitive to temperature changes in the supercooled regime and is found to be strongly correlated with the inherent structure energy. In addition, the NAD field is characterized by a correlation length that increases upon lowering the temperature towards the supercooled regime.     

Synthesis and characterization of a new porphyrin-polyoxometalate hybrid material and investigation of its catalytic activity

In the present work, the preparation of a new organic-inorganic hybrid material in which tetrakis(p-aminophenylporphyrin) is covalently linked to a Lindqvist structure of polyoxometalate, is reported. This new porphyrin-polyoxometalate hybrid material was characterized by (1)H NMR, FT-IR and UV-Vis spectroscopic methods and cyclic voltammetry. These spectro- and electrochemical studies provided spectral data of the synthesis of this compound. Cyclic voltammetry showed the influence of the porphyrin on the redox process of the polyoxometalate. The catalytic activity of this hybrid material was investigated in the alkene epoxidation with NaIO(4).     

Electrostatic spray deposition of graphene nanoplatelets for high-power thin-film supercapacitor electrodes

Thin-film electrodes of graphene nanoplatelets (GNPs) were fabricated through the electrostatic spray deposition (ESD) technique. The combination of a binder-free deposition technique and an open pore structure of graphene films results in an excellent power handling ability of the electrodes. Cyclic voltammetry measurements of 1-μm-thick electrodes yield near rectangular curves even at a very high scan rate of 20 V s^?1. Thin-film electrodes (1 μm thickness) show specific power and energy of about 75.46 kW kg^?1 and 2.93 W h kg^?1, respectively, at a 5 V s^?1 scan rate. For the thin-film electrode, about 53 % of the initial specific capacitance of electrodes at low scan rates was retained at a high scan rate of 20 V s^?1. Although the thickness of the thin-film electrodes has influence on their rate capability, an electrode with an increased thickness of 6 μm retained about 30 % if its initial capacitance at a very high scan rate of 20 V s^?1. The results show that the ESD-fabricated GNP electrodes are promising candidates for thin-film energy storage for applications that require moderate energy density and very high power and rate handling ability.     

Radiation Effects on Geodesics in de Sitter Space: A Classical Approach

In this work we first obtain a trajectory of a freely falling charged particle in de Sitter space and then in the classical approach, the effect of electromagnetic self-force on particle’s trajectory has been considered. Finally, some limits for the problem have been presented.