Preparation and characterization of polyelectrolyte complex of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-trimethyl chitosan/gellan gum: evaluation for controlled release of ketoprofen

N,N,N-Trimethyl chitosan, a highly water soluble derivative of chitosan, has been made by reductive methylation of chitosan by a three-step process reported in literature. A novel polyelectrolyte complex of this derivative with gellan gum has been made by mixing the aqueous solutions of the two polymers. The complex was characterized by FTIR, TGA, DSC and SEM techniques. Maximum yield of the complex was obtained at pH 2.0 with a gellan gum:trimethylchitosan ratio of 3:1. The swelling study indicated pH responsiveness of the polyelectrolyte complex sample, with higher swelling under neutral or slightly basic conditions. In vitro studies on the release of the drug ketoprofen from the polyelectrolyte complex matrix were conducted in simulated gastric and intestinal fluids. The results indicated release of 85–90 % of the entrapped drug in the media of pH 6.8 and 7.4 and less than 7 % release in the medium of pH 1.2. The kinetic analysis indicated the drug release to be a first-order process. The mechanism of water transport and drug diffusion is shown to be of Fickian type. The results prove the suitability of the polyelectrolyte complex as a matrix material for delivery of drugs with short half life such as ketoprofen in the slow release mode.     

Anisotropy of the electric transport properties of decagonal Al–Cu–Co(Fe) quasicrystals

The method of growth from a melt solution was used to obtain iron-alloyed (0.08 at %) Al–Cu–Co single crystals with a decagonal symmetry. The temperature dependences of the electrical resistivity in magnetic fields of 0–18 T were measured using samples oriented in the periodic direction (ρ_p(T)) and in the quasi-periodic plane (ρ_q(T)). A strong anisotropy of the resistivity was observed; the ρ_p(T) curve is linear, whereas the ρ_q(T) curve is approximated well by a second-order polynomial. A strong anisotropy of the magnetoresistance was also observed; a positive magnetoresistance Δρ/ρ ~ 10^–3 for the current flowing in the quasiperiodic plane; and a weak (close to zero) negative magnetoresistance for the current flowing along the periodic direction.     

A comparative study of thermal and hydraulic autofrettage

Thermal autofrettage is a potential process to generate beneficial compressive residual stresses at and around the inner wall of a thickwalled cylinder for increasing its pressure carrying capacity. Due to its simplicity and inexpensive arrangement, it can compete with the conventional hydraulic autofrettage process. In this work, a comparative study of the thermal autofrettage and the hydraulic autofrettage is carried out. As the thermal autofrettage does not require hydraulic power pack, the process is more economical than the hydraulic autofrettage. The thermal autofrettage process is also studied for the thick-walled cylindrical vessels subjected to high thermal gradient with or without pressure and is compared with the hydraulic autofrettage. Comparison shows that for cylinders subjected to high thermal gradient without pressure, the thermal autofrettage is superior to the hydraulic autofrettage.     

Specific Energy Prediction for Circular Diamond Saw in Cutting Different Types of Rocks Using Multivariable Linear Regression Analysis

Circular diamond saw performance is affected by a variety of factors. The principal factors requiring consideration when predicting cutting rates are the type and operating features of a diamond saw and the rock characteristics. The laboratory experimental tests are carried out on three groups of rocks (16 types) cut with the help of three types of diamond disk saws with different feed rates and cutting depths at constant peripheral velocity. The quantitative determinations of a wide range of textural, mechanical, and intact properties of rocks are also made. The relationship between the specific cutting energy SE _cut of the sawblade operating parameters and rock properties is established. Applying multivariable linear regression analysis, the predictive model of SE _cut is developed based on the rock property data. Models verified by statistical tests prove their practical validity. __________ Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 3, pp. 56–80, May–June, 2005.     

PVA/Gd2O3@Zno Nanocomposite Films as New Uv-Blockers: Structure and Optical Revelations

Journal of Inorganic and Organometallic Polymers and Materials - Herein we have synthesised Gadolinium oxide doped Zinc oxide (Gd2O3@ZnO) by solution combustion method and incorporated it as a...     

Microstructure and Mechanical Property Correlation of Mg-Si Alloys

Silicon - The present work aims at understanding the microstructure and mechanical property correlation of hypo (Mg-0.5, 0.7, 1.15 wt% Si) and hyper (Mg-2, 4, 6, 8 and 10 wt% Si) eutectic binary...     

Applicability of Field Plate in Double Channel GaN HEMT for Radio-Frequency and Power-Electronic Applications

Silicon - In the present communication, for the first time, applicability of Field Plate (FP) for Double Channel (DC) AlGaN/GaNHEMT is demonstrated. Impact of design space parameters such as field...     

Investigation on DC/RF Performance of LG = 19 nm Heterogeneous Integrated Ga0.15In0.85As/InAs/Ga0.15In0.85As Composite Channel InP HEMT on Silicon Substrate for Future Beyond 5G and Quantum Computing Applications

Silicon - The RF/DC performances of LG = 19&nbsp;nm heterogeneous integrated Ga0.15In0.85As/InAs/Ga0.15In0.85As composite channel based InP HEMT (high electron mobility transistor)...