Design and numerical analysis of a photonic crystal fiber (PCF)-based flattened dispersion THz waveguide

Optical Review - We present the modeling of a porous core dispersion flatten photonic crystal fiber (PCF) for the fruitful transmission of THz signals. The model comprises only rectangular holes in...     

IFSS, TG, FT-IR spectra of impregnated sugar palm (Arenga pinnata) fibres and mechanical properties of their composites

This study aimed to investigate the effect of resin impregnation on the interfacial shear strength (IFSS), thermogravimetric (TG) and fourier transform infrared (FT-IR) of sugar palm (Arenga pinnata) fibres. In addition, the effect of resin impregnation on the mechanical properties of sugar palm fibre reinforced unsaturated polyester (UP) composites was also studied. The fibres were impregnated with UP via vacuum resin impregnation process at a pressure of 600 mmHg for 5 min. Composites of 10, 20, 30, 40 and 50 % fibre loadings were fabricated and tested for tensile and flexural properties. It was observed that the impregnation process caused the fibres to be enclosed by UP resin and this gave a strong influence to the increase of its interfacial bonding by the increase of its IFSS from single fibre pull-out test. It was also observed with TG and FT-IR spectra that the impregnated fibre had lower moisture uptake than the control and there was no significant increase in thermal stability of the impregnated fibre. The sequence of fibre decomposition started from the evaporation of moisture, hemicelluloses, cellulose, lignin and finally ash content and the presence of these components were proven by FT-IR spectra. For the composite specimens, due to the high interfacial bonding of the impregnated fibre and the matrix, the impregnated composites showed consistently higher tensile strength, tensile modulus, elongation at break, flexural strength, flexural modulus and toughness than the control samples. It was also observed that 30 % fibre loading gave optimum properties.     

Thymoquinone Loaded Topical Nanoemulgel for Wound Healing: Formulation Design and In-Vivo Evaluation

Thymoquinone is a natural bioactive with significant therapeutic activity against multiple ailments including wound healing. The poor aqueous solubility and low skin permeability limit its therapeutic efficacy. The present investigation aimed to improve the biopharmaceutical attributes of thymoquinone to enhance its topical efficacy in wound healing. A nanoemulsion-based hydrogel system was designed and characterized as a nanotechnology-mediated drug delivery approach to improve the therapeutic efficacy of thymoquinone, utilizing a high-energy emulsification technique. The black seed oil, as a natural home of thymoquinone, was utilized to improve the drug loading capacity of the developed nanoemulsion system and reduced the oil droplet size to <100 nm through ultrasonication. The influence of formulation composition, and the ultrasonication process conditions, were investigated on the mean globule size and polydispersity index of the generated nanoemulsion. Irrespective of surfactant/co-surfactant ratio and % concentration of surfactant/co-surfactant mixture, the ultrasonication time had a significant (p < 0.05) influence on the mean droplet size and polydispersity index of the generated nanoemulsion. The developed nanoemulgel system of thymoquinone demonstrated the pseudoplastic behavior with thixotropic properties, and this behavior is desirable for topical application. The nanoemulgel system of thymoquinone exhibited significant enhancement (p < 0.05) in skin penetrability and deposition characteristics after topical administration compared to the conventional hydrogel system. The developed nanoemulgel system of thymoquinone exhibited quicker and early healing in wounded Wistar rats compared to the conventional hydrogel of thymoquinone, while showing comparable healing efficacy with respect to marketed silver sulfadiazine (1%) cream. Furthermore, histopathology analysis of animals treated with a developed formulation system demonstrated the formation of the thick epidermal layer, papillary dermis along with the presence of extensive and organized collagen fibers in newly healed tissues. The outcome of this investigation signifies that topical delivery of thymoquinone through nanoemulgel system is a promising candidate which accelerates the process of wound healing in preclinical study.     

Impact of Metal Ions in Porphyrin‐Based Applied Materials for Visible‐Light Photocatalysis: Key Information from Ultrafast Electronic Spectroscopy

Protoporphyrin IX‐zinc oxide (PP‐ZnO) nanohybrids have been synthesized for applications in photocatalytic devices. High‐resolution transmission electron microscopy (HRTEM), X‐ray diffraction (XRD), and steady‐state infrared, absorption, and emission spectroscopies have been used to analyze the structural details and optical properties of these nanohybrids. Time‐resolved fluorescence and transient absorption techniques have been applied to study the ultrafast dynamic events that are key to photocatalytic activities. The photocatalytic efficiency under visible‐light irradiation in the presence of naturally abundant iron(III) and copper(II) ions has been found to be significantly retarded in the former case, but enhanced in the latter case. More importantly, femtosecond (fs) transient absorption data have clearly demonstrated that the residence of photoexcited electrons from the sensitizer PP in the centrally located iron moiety hinders ground‐state bleach recovery of the sensitizer, affecting the overall photocatalytic rate of the nanohybrid. The presence of copper(II) ions, on the other hand, offers additional stability against photobleaching and eventually enhances the efficiency of photocatalysis. In addition, we have also explored the role of UV light in the efficiency of photocatalysis and have rationalized our observations from femtosecond‐ to picosecond‐resolved studies.     

Derivations and generating degrees in the ring of arithmetical functions

In this paper we study a family of derivations in the ring of arithmetical functions of several variables over an integral domain, and compute the generating degrees of the ring of arithmetical functions over the kernel of these derivations.     

Velocity Distributions of Copper and Lithium Atoms Sputtered from a Cu/Li Alloy Measured with Laser Induced Fluorescence

To test its applicability as wall material for nuclear fusion experiments, a copper based binary alloy containing 17 at.% of lithium has been bombarded with a monoenergetic mass-analyzed 6 keV argon ion beam at target temperatures close to room temperature. The velocity distributions of both constituents have been measured by means of laser induced fluorescence. Mean surface binding energies of 2.2 eV for the Li component and 2.4 eV for the Cu component have been derived from the experimental data, while 3.5 eV are obtained for a pure copper target. A comparison of the energies indicates only a moderate lithium enrichment in the first few atomic surface layers of the alloy under irradiation. Furthermore, mean transport velocities of the sputtered particles have been calculated.     

Synthesis and characterization of 5-(arylazo)thiobarbituric acids and their complexes

Summary S-(Arylazo)thiobarbituric acids and their complexes, derived from cobalt(II), nicke(II) and copper(II) were characterized by elemental analyses and spectral measurements. The¹H n.m.r. and i.r. spectra show the ligands to be in the keto-thione form. The strength of the intramolecular hydrogen-bonding is influenced by the electronic requirements of the aryl ring substituents.     

Saturation of the photon-drag voltage at high CO2 laser intensities

p-Type Ge is investigated as a photon-drag detector for high-power pulsed CO₂ laser, using 3-samples of different dimensions and resistivities. Nonlinear behaviour of the photon-drag effect is observed. This phenomena could be accounted for by taking into consideration the decrease of absorption and the increase of resistivity instantaneously at the moment of interaction, rather than the effect of multireflection. The observed saturation at intensities higher than 30 MW/cm₂ could be due to multireflection since its role increases at high intensities. Using the quantum mechanical model with the above considerations it was possible to obtain good agreement to the measured results.     

Kinetics of ion-exchange on montmorillonite clays

The kinetics for the exchange of Li⁺, K⁺, Rb⁺, and Cs⁺ for Na⁺ as the exchangeable cation on bentonite and montmorillonite K10 and KSF have been studied using conductimetric stoppedflow. Dilute aqueous suspensions of the clays, of particle sizes of a few micrometers, were used, so that diffusion was fast and the rate-determining step was the substitution of one cation by another on the lattice surface. The kinetics were treated in terms of relaxation from equilibrium. Relaxation times ranged from 100 to 250 ms, and forward rate constants from 30 to 500 M^?1 s^?1. The reactions had very low activation enthalpies (7–25 kJ mol^?1) and were only slow enough to be studied by the stopped-flow technique because of the large negative entropies of activation (?120 to ?170 J K^?1 mol^?1). © 1993 John Wiley & Sons, Inc.