Transient energy exchange between a primary structure and a set of oscillators: return time and apparent damping

In this paper we examine the conditions that influence the return time, the time it takes before energy returns from a set of satellite oscillators attached to a primary structure. Two methods are presented to estimate the return time. One estimate is based on an analysis of the reaction force on a rigid base by a finite number of oscillators as compared with an infinite number of continuously distributed oscillators. The result gives a lower-bound estimate for the return time. A more accurate estimation results from considering the dynamic behavior of a set of oscillators as waves in a waveguide. Such an analogy explains energy flow between a primary structure and the oscillators in terms of pseudowaves and shows that a nonlinear frequency distribution of the oscillators leads to pseudodispersive waves. The resulting approximate expressions show the influence of the natural frequency distribution within the set of oscillators, and of their number, on the return time as compared with the asymptotic case of a continuous set with infinite oscillators. In the paper we also introduce a new method based on a Hilbert envelope to estimate the apparent damping loss factor of the primary structure during the return time considering transient energy flow from the primary structure before any energy reflects back from the attached oscillators. The expressions developed for return time and damping factor show close agreement with direct numerical simulations. The paper concludes with a discussion of the return time and its relation to apparent damping and optimum frequency distribution within a set of oscillators that maximize these quantities.     

Transient thermo-elastic waves in a half-space with thermal relaxation

We use the Cagniard-De Hoop method to develop the displacement and temperature fields in a half-space subjected on its free surface to an instantaneously applied heat source. We include in our analysis the thermal relaxation time of heat conduction, which insures that the termal waves propagate with a finite signal speed. We express our solution in terms of a small thermo-elastic coupling coefficient, and obtain explicit expressions for the wave-speeds and wave-amplitudes. Due to the existence of the thermal damping, we give only the short-time solution. We then present numerical results for the dilatation and the temperature so as to illustrate the salient features of the problem.

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Zusammenfassung Die Autoren benutzen die Methode von Cagniard-De Hoop zur Ermittlung des Verschiebungs-und des Temperaturfeldes in einem elastischen Halbraum unter dem Einfluß einer an der freien Oberfläche plötzlich angebrachten Wärmequelle. Sie berücksichtigen dabei die Relaxationszeit der Wärmeleitung, welche eine endliche Fortpflanzungsgeschwindigkeit der Wärmewellen garantiert. Die Lösung wird in einem kleinen thermoelastischen Koppelungskoeffizienten ausgedrückt, und es werden explizite Ausdrücke für die Fortpflanzungsgeschwindigkeiten und Wellenamplituden gegeben. Mit Rücksicht auf die thermische Dämpfung werden nur kurzfristige Lösungen betrachtet. Schließlich werden numerische Resultate für die Dilatation und die Temperatur angegeben, um die wesentlichen Eigenschaften des Problems zu illustrieren.

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This work was in part (A.H.N.) supported by the National Science Foundation under Grant GK-277 at the University of California, San Diego.     

Über faktorisierbare nichtauflösbare Gruppen

Ohne ZusammenfassungDiese Arbeit entstand, während der Verfasser als Stipendiat der Alexander von Humboldt-Stiftung an der Universität Freiburg weilte.Ich möchte mich an dieser Stelle für das Interesse an dieser Arbeit und die wertvollen Anregungen bei den Herren Dr. Peter Hauck und Prof. Dr. Otto H. Kegel bedanken.     

Formulation and Characterization of Chitosan-Decorated Multiple Nanoemulsion for Topical Delivery In Vitro and Ex Vivo

In the present study, chitosan-decorated multiple nanoemulsion (MNE) was formulated using a two-step emulsification process. The formulated multiple nanoemuslion was evaluated physiochemically for its size and zeta potential, surface morphology, creaming and cracking, viscosity and pH. A Franz diffusion cell apparatus was used to carry out in vitro drug-release and permeation studies. The formulated nanoemulsion showed uniform droplet size and zeta potential. The pH and viscosity of the formulated emulsion were in the range of and suitable for topical delivery. The drug contents of the simple nanoemulsion (SNE), the chitosan-decorated nanoemulsion (CNE) and the MNE were 71 ± 2%, 82 ± 2% and 90 ± 2%, respectively. The formulated MNE showed controlled release of itraconazole as compared with that of the SNE and CNE. This was attributed to the chitosan decoration as well as to formulating multiple emulsions. The significant permeation and skin drug retention profile of the MNE were attributed to using the surfactants tween 80 and span 20 and the co-surfactant PEG 400. ATR-FTIR analysis confirmed that the MNE mainly affects the lipids and proteins of the skin, particularly the stratum corneum, which results in significantly higher permeation and retention of the drug. It was concluded that the proposed MNE formulation delivers drug to the target site of the skin and can be therapeutically used for various cutaneous fungal infections.     

Fabrication and Evaluation of Voriconazole Loaded Transethosomal Gel for Enhanced Antifungal and Antileishmanial Activity

Voriconazole (VRC) is a broad-spectrum antifungal agent belonging to BCS class II (biopharmaceutical classification system). Despite many efforts to enhance its solubility, this primary issue still remains challenging for formulation scientists. Transethosomes (TELs) are one of the potential innovative nano-carriers for improving the solubility and permeation of poorly soluble and permeable drugs. We herein report voriconazole-loaded transethosomes (VRCT) fabricated by the cold method and followed by their incorporation into carbopol 940 as a gel. The prepared VRCT were evaluated for % yield, % entrapment efficiency (EE), surface morphology, possible chemical interaction, particle size, zeta potential, and polydispersity index (PDI). The optimized formulation had a particle size of 228.2 nm, a zeta potential of −26.5 mV, and a PDI of 0.45 with enhanced % EE. Rheology, spreadability, extrudability, in vitro release, skin permeation, molecular docking, antifungal, and antileishmanial activity were also assessed for VRCT and VRC loaded transethosomal gel (VTEG). Ex-vivo permeation using rat skin depicted a transdermal flux of 22.8 µg/cm²/h with enhanced efficiency up to 4-fold. A two-fold reduction in inhibitory as well as fungicidal concentration was observed against various fungal strains by VRCT and VTEG besides similar results against L-donovani. The development of transethosomal formulation can serve as an efficient drug delivery system through a topical route with enhanced efficacy and better patient compliance.     

X-ray diffraction study on amorphous gallium

Amorphous films of some μm in thickness, prepared by low temperature condensation in an ultra-high vacuum onto liquid helium cooled substrates, have been studied in situ by using an X-ray diffractometer operating in a symmetrical reflection mode. The structure factor of gallium has been obtained over the wavevector range 1.3 to 16.1 Å⁻ by means of two wavelengths, Cr_K and Mo_K, monochromatized by balanced filters. The average number of nearest neighbours deduced from the well-resolved first maximum in the radial distribution function is equal to 9.3 atoms. The results are compared to those previously found by electron diffraction measurements on thin films and also to the structure of supercooled liquid.     

Detection and characterization of olmutinib reactive metabolites by LC–MS/MS: Elucidation of bioactivation pathways

Olmutinib (Olita?) is an orally bioavailable third generation epidermal growth factor receptor tyrosine kinase inhibitor. Olmutinib was approved in South Korea in May 2016 for the treatment of patients suffering from locally advanced or metastatic epidermal growth factor receptor T790M mutation‐positive non‐small cell lung cancer. Reactive olmutinib intermediates may be responsible for the severe side effects associated with the treatment. However, literature review revealed no previous reports on the structural identification of reactive olmutinib metabolites. In this work, the formation of reactive olmutinib metabolites in rat liver microsomes was investigated. Methoxylamine, glutathione, and potassium cyanide were used as capturing agents for aldehyde, iminoquinones, and iminium intermediates, respectively. The stable complexes formed were identified using liquid chromatography–tandem mass spectrometry. The major phase I metabolic pathway observed in vitro was hydroxylation of the piperazine ring. Seven potential reactive intermediates were characterized, including three iminium ions, three iminoquinones, and one aldehyde. Based on the findings, various bioactivation pathways were postulated. Hence, identifying the reactive intermediates of olmutinib that may be the cause of severe side effects can provide new insights, leading to improved treatments for patients.     

Assessment of adsorption properties of inorganic–organic hybrid cyclomatrix type polyphosphazene microspheres for the removal of Pb(II) ions from aqueous solutions

Abstract

Inorganic–organic hybrid cyclomatrix type polyphosphazene microspheres (poly[cyclotriphosphazene-co-(4,4′-diaminodiphenylmethane)]) (HDMS) and poly[cyclotetraphosphazene-co-4,4′-diaminodiphenylmethane)] (ODMS) were prepared to investigate their possible use as alternative adsorbents for the comparative study on Pb(II) ions removal from aqueous solutions. The structures of the microspheres were elucidated by Fourier Transform Infrared (FTIR) spectroscopy and Dynamic Light Scattering (DLS) measurements, and the surface morphologies were also observed by Scanning Electron Microscopy (SEM). The adsorption of Pb(II) ions onto HDMS and ODMS from aqueous solutions was examined by means of pH, temperature, contact time and concentration. Furthermore, adsorption kinetics and isotherm models were applied and the experimental data fitted well with Langmuir isotherm and pseudo-second-order kinetic models. The maximum adsorption capacities of HDMS and ODMS for Pb(II) ions were obtained as 157.8 and 308.0?mg g^?1 at 20?°C and pH 5.5, respectively.