Stability Indicating RP-HPLC Method For Determination Of Itraconazole In Bulk Drug And In Capsule Dosage Form

Stability Indicating RP HPLC method was developed for estimation of Itraconazole in bulk drug and in capsule dosage form. An isocratic separation was achieved using Phenomenex symmetry C8 (250 ×4.6 mm) 5?m [Part number - 00G-4249-E0] column with a flow rate of 1.0 ml/min and detection wavelength at 254 nm. The mobile phase consisted of 20 mM potassium dihydrogen orthophosphate buffer (pH=5.5): Acetonitrile: Methanol (20:40:40 % v/v). The method was rectilinear from 10-60 ?g/ml and displayed adequate precision (RSD < 2.0%) & accuracy (99.31-101.16%). The proposed method is found to be specific with respect to degradation product formed after Acidic hydrolysis, Oxidation, Thermal and Photolytic degradation. The Itracoazole was found to be stable under alkaline stress condition. Acidic, thermal, photolytic stress conditions showed moderate degradation whereas the oxidative stress condition showed severe degradation. The proposed chromatographic method can be used for estimation of drug during stress testing & formal stability studies.

An Adaptive Regressor-Free Fourier Series-Based Tracking Controller for Robot Manipulators: Theory and Experimental Evaluation

SUMMARY In this article, we propose a nonlinear Proportional+Derivative (PD) tracking controller with adaptive Fourier series compensation. The proposed controller uses a regressor-free adaptive scheme that relies on a trigonometric polynomial with varying coefficients to solve the control problem. Asymptotic convergence of the position and velocity errors is proven via a formal stability analysis based on Lyapunov and LaSalle theory for discontinuous systems. The proposed controller is validated on a 2-degrees of freedom robot manipulator. The experimental results validate the theoretically obtained results and reflect the effect of certain parameters in the transient behavior of the error dynamics. Certain robustness properties are also observed.

Analyzing Failed Institutional Change Attempts

Theoretical advances in the study of institutional change center around a productive paradox. While change agents can take strategic action to change institutions, institutions display a remarkable level of formal stability. From this paradox, we expect that attempts to change institutions are an empirical regularity and that many formal change attempts will fail. This article contributes to historical institutionalism by analyzing the political effects of failed formal institutional change attempts on institutional sequences. Failed institutional change attempts could be mere blips, having little effect on subsequent institutional trajectories, or even inoculate against future attempts. Failed attempts could also lay the ideational groundwork, aid in coalition building, and garner concessions for subsequent institutional change, or convince change agents to alter their strategy. The article suggests analytical strategies to assess the effects of failed institutional change attempts, drawing on examples from comparative politics and two extended case illustrations from Italian party politics and the Affordable Care Act in the United States.

On the Dynamics of a Gravitational Dipole

The main purpose of this paper is to investigate nonlinear oscillations of the gravitational dipole in a neighborhood of its nominal mode. The orbit of the center of mass is assumed to be circular or elliptic with small eccentricity. Consideration is given both to planar and arbitrary spatial deviations of the gravitational dipole from its position corresponding to the nominal mode. The analysis is based on the classical Lyapunov and Poincaré methods and the methods of Kolmogorov – Arnold – Moser (KAM) theory. The necessary calculations are performed using computer algorithms. An analytic representation is given for conditionally periodic oscillations. Special attention is paid to the problem of the existence of periodic motions of the gravitational dipole and their Lyapunov stability, formal stability (stability in an arbitrarily high, but finite, nonlinear approximation) and stability for most (in the sense of Lebesgue measure) initial conditions.

ASSESSMENT OF THE FORMAL STABILITY OF KNITTED FABRICS ON THE CYLINDRICAL BEND OF THE PLATES

The article analyzes the results of theoretical studies of the dimensional stability of knitted fabrics with different fibrous composition. The coefficient of form stability Кф according to the deformability data of knitted fabrics, modeled in the form of bending of a rectangular plate along a cylindrical surface, is proposed.

Spectral clustering of combinatorial fullerene isomers based on their facet graph structure

After Curl, Kroto and Smalley were awarded 1996 the Nobel Prize in chemistry, fullerenes have been subject of much research. One part of that research is the prediction of a fullerene’s stability using topological descriptors. It was mainly done by considering the distribution of the twelve pentagonal facets on its surface, calculations mostly were performed on all isomers of C40, C60 and C80. This paper suggests a novel method for the classification of combinatorial fullerene isomers using spectral graph theory. The classification presupposes an invariant scheme for the facets based on the Schlegel diagram. The main idea is to find clusters of isomers by analyzing their graph structure of hexagonal facets only. We also show that our classification scheme can serve as a formal stability criterion, which became evident from a comparison of our results with recent quantum chemical calculations (Sure et al. in Phys Chem Chem Phys 19:14296–14305, 2017). We apply our method to classify all isomers of C60 and give an example of two different cospectral isomers of C44. Calculations are done with our own Python scripts available at (Bille et al. in Fullerene database and classification software, https://www.uni-ulm.de/mawi/mawi-stochastik/forschung/fullerene-database/, 2020). The only input for our algorithm is the vector of positions of pentagons in the facet spiral. These vectors and Schlegel diagrams are generated with the software package Fullerene (Schwerdtfeger et al. in J Comput Chem 34:1508–1526, 2013).

Path-Tracking of a WMR Fed by Inverter-DC/DC Buck Power Electronic Converter Systems

This paper is concerned with path-tracking control of a wheeled mobile robot. This robot is equipped with two permanent magnet brushed DC-motors which are fed by two inverter-DC/DC Buck power converter systems as power amplifiers. By taking into account the dynamics of all the subsystems we present, for the first time, a formal stability proof for this control problem. Our control scheme is simple, in the sense that it is composed by four internal classical proportional-integral loops and one external classical proportional-derivative loop for path-tracking purposes. This is the third paper of a series of papers devoted to control different nonlinear systems, which proves that the proposed methodology is a rather general approach for controlling electromechanical systems when actuated by power electronic converters.

The dynamics of trait variance in multi-species communities

In this paper, we establish the explicit connection between deterministic trait-based population-level models (in the form of partial differential equations) and species-level models (in the form of ordinary differential equations), in the context of eco-evolutionary systems. In particular, by starting from a population-level model of density distributions in trait space, we derive what amounts to an extension of the typical models at the species level known from adaptive dynamics literature, to account not only for abundance and mean trait values, but also explicitly for trait variances. Thus, we arrive at an explicitly polymorphic model at the species level. The derivations make precise the relationship between the parameters in the two classes of models and allow us to distinguish between notions of fitness on the population and species levels. Through a formal stability analysis, we see that exponential growth of an eigenvalue in the trait covariance matrix corresponds to a breakdown of the underlying assumptions of the species-level model. In biological terms, this may be interpreted as a speciation event: that is, we obtain an explicit notion of the blow-up of the variance of (possibly a linear combination of) traits as a precursor to speciation. Moreover, since evolutionary volatility of the mean trait value is proportional to trait variance, this provides a notion that species at the cusp of speciation are also the most adaptive. We illustrate these concepts and considerations using a numerical simulation.