Pharmacokinetic and pharmacodynamic evaluation of floating microspheres of metformin hydrochloride

Metformin hydrochloride (MH), a biguanide antidiabetic, is the drug of choice in obese patients. It is well absorbed from the upper part of gastrointestinal tract and has oral bioavailability of 50% to 60%. The objective of this study was to formulate MH into floating microspheres in order to increase its residence time at the site of absorption and thus improve its bioavailability; and to extend the duration of action along with possibilities of dose reduction. Microspheres were prepared by emulsion solvent evaporation method and evaluated for particle size, entrapment efficiency, buoyancy, and in vitro release; and further characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and differential scanning calorimetry. The pharmacokinetic and pharmacodynamic evaluation of selected formulation was carried out in male Wistar diabetic rats. The data was statistically analyzed by unpaired t-test. A 3.5-fold increase in relative bioavailability was observed. The prolongation of half-life (t_1/2) from 4.5 ± 2.41 h to 14.12 ± 4.81 h indicated extended duration of action. Oral glucose tolerance test (OGTT) was analyzed by one-way analysis of variance followed by Dunnet multiple comparison test, a significant decrease (p < 0.05) in the blood glucose levels was observed when formulations were compared with control rats. Hence, MH floating microspheres were tested at 50 mg/kg and 100 mg/kg body weight, OGTT data showed nonsignificant difference (p >0.05). In conclusion, an effective oral antidiabetics treatment can be achieved by formulating MH into floating microspheres which results in increase in bioavailability along with extended duration of action resulting in possible reduction in dose.     

Laser alexandrite crystals grown by horizontal oriented crystallization technique

Comparative studies were performed for alexandrite crystals, Al₂BeO₄:Cr³⁺, employed in solid state lasers and grown by the horizontal oriented crystallization (HOC) technique and alexandrite crystals grown by the Czochralski (Cz) method. It was shown that the structural quality and possibilities of generation of stimulated emission HOC-crystals are similar to Cz-crystals, whereas their damage threshold is about three times higher. The obtained results and considerably lower cost price of HOC-alexandrite crystals prove their advantageous application in powerful laser systems, which require large laser rods with a higher resistance to laser beam. It is emphasized that application of HOC technique is promising for growth of laser crystals of other high-temperature oxide compounds.     

Synchronized and controlled release of metformin hydrochloride/glipizide from elementary osmotic delivery

Abstract

The combination of metformin hydrochloride (MTF) and glipizide (GLZ) is second-line medication for diabetes mellitus type 2 (DMT2). In the present study, elementary osmotic pump ( EOP) tablet is designed to deliver the combination of MTF and GLZ in a sustained and synchronized manner. By analyzing different variables of the formulation, sodium hydrogen carbonate is introduced as pH modifier to improve the release of GLZ, while ethyl cellulose acts as release retardant to reduce the burst release phase of MTF. A two-factor, three-level face-centered central composite design (FCCD) is applied to investigate the impact of different factors on drug release profile. Compared with conventional tablets, the EOP tablet demonstrates a controlled release behavior with relative bioavailability of 99.2% for MTF and 99.3% for GLZ. Data also shows EOP tablet is able to release MTF and GLZ in a synchronized and sustained manner both in vitro and in vivo.     

膜结晶技术研究进展及应用前景

对一种新的分离技术——膜结晶进行了综述．介绍了膜结晶技术的产生、原理和优点，以及膜结晶的过程及膜结晶器的类型．概述了膜结晶在国内外的发展和应用状况，重点介绍了膜结晶在盐溶液结晶和生物高分子溶液结晶两个方面的研究与应用，并对膜结晶技术的前景作了展望．     

Improved compaction and packing properties of naproxen agglomerated crystals obtained by spherical crystallization technique

Naproxen was crystallized from acetone-water in the presence of different concentrations of hydroxypropylcellulose (HPC). Naproxen particles recrystallized in the presence of HPC exhibited an obvious improvement in their packing, flow, and mechanical properties compared to naproxen recrystallized in the absence of the polymer (control particles). The results showed that the particle size distributions of the treated samples were broader than those obtained when HPC was absent. The agglomerates produced in the presence of 0.25% HPC displayed superior flow characteristics (displaying both a low angle of repose and Carr index) in comparison to samples produced in the presence of other concentrations of HPC. This was attributed to the spherical shape and smooth surface, since the area of contact in the powder bed for spherical agglomerates was smaller than that for other crystal shapes. However it was found that the tensile strength of tablets with the particles isolated in the presence of 1% HPC was increased to a greater extent than tablets produced using the spherical particles. Generally, the tensile strengths of the tablets increased with increasing concentrations of HPC present in the crystallization medium. Differential scanning calorimetry (DSC) and X-ray powder diffraction studies showed that naproxen particles, crystallized in the presence of HPC did not undergo structural modifications.     

铝诱导对磁控溅射制备CdZnTe薄膜结晶的影响

选用Cd0.9Zn0.1Te晶体和纯度为99.999%的铝为靶材,结合Al诱导晶化技术,采用磁控溅射法在普通玻璃衬底上制备了CdZnTe薄膜。研究了铝诱导CdZnTe薄膜的结构和形核机理。研究表明,铝诱导的CZT薄膜为闪锌矿结构,且为(111)晶面的取向生长;在薄膜生长过程中,覆盖在CdZnTe表面的铝首先与ZnTe结合,形成了ZnAl2Te4相,并以此为核心,诱导CdZnTe异质形核结晶,重新形成了小晶粒团簇的较致密颗粒状薄膜,提高了薄膜(111)面的优势取向结晶,提高了CdZnTe薄膜的结晶质量。讨论了薄膜的光学性能。     

Holographic-recording improvement in a bismuth silicon oxide crystal by the moving-grating technique

We investigate the enhancement of the diffraction efficiency of dynamic gratings recorded in a bismuth silicon oxide crystal at large modulation by the moving-grating technique. The optimum fringe velocity for maximum diffraction efficiency and the degree of enhancement of the diffraction efficiency at optimum fringe velocity are experimentally found to be dependent on the fringe modulation. We apply this technique to real-time incoherent correlation using bismuth silicon oxide. There are two main advantages in using moving gratings: First, the signal-to-noise ratio can be improved considerably because of the improved diffraction efficiency. Second, the resonant effect reduces the effect of environmental disturbances on the peak-correlation intensity, which is significant when the threshold detection level of the correlator is set.     

Evaluation of Critical Binder Properties Affecting the Compactibility of Binary Mixtures

The aim of this study was to identify essential physical and mechanical properties of various binders and to investigate their influence on the tensile strength and porosity of tablets made from binary mixtures with sodium bicarbonate. The binders were characterized according to axial and radial tensile strength after compression into tablets, yield pressure and minimum porosity during compression, and elastic recovery after compression. The addition of a binder generally resulted in an increase in the tensile strength and a decrease in the porosity of the sodium bicarbonate tablets. The location of the binder in the voids between the sodium bicarbonate particles thus decreasing the porosity of the tablet seemed to be an important consideration. Consequently, the addition of binders with a low yield pressure value and a relatively small elastic recovery value (e.g., polyethylene glycol 3000 and polyvinylpyrrolidone) resulted in tablets of low porosity and high tensile strength, especially in the axial direction. The tensile strength of the pure binder also seemed to be important, especially for binders with a lower degree of deformability (e.g., microcrystalline cellulose and pregelatinised starch). The results also indicated the value of using both axial and radial tensile strength measurements in assessing the effect of a dry binder and showed that the importance of different binder properties varied according to the direction of the tablet strength measurements. The results demonstrated that the applied characteristics of the binders used in this study may serve as a useful tool in evaluating the effectiveness of binders.     

Photoelasticity—-An improvement in the sandwich technique

The development of the sandwich technique in photoelasticity necessitates a suitable cement. The results of experiments using cyanoacrylate IS 12 in cementing Perspex and Araldite are compared with the results of experiments using resorcinol formaldehyde. These show that cyanoacry/ate is much superior in strength and that it has other properties suitable for the purpose.     

Accuracy improvement of XFEM using Wilson's incompatible element technique

Based on the extended finite element method (XFEM) and Wilson incompatible element technique, an incompatible extended finite element method (IXFEM) is presented to deal with the cracked bending problems in this study. The additional displacement modes of Wilson's incompatible element are introduced into the approximation of the XFEM. The internal degrees of freedom induced by additional models are condensed to improve efficiency. Derivation of the equilibrium equations of the IXFEM is performed. Several examples are employed to validate the capabilities of the proposed method. The influence of bending degree on the performance of proposed method is studied by changing the crack length. The numerical results indicate that the stress and displacement solutions of the IXFEM show a slight oscillation. The IXFEM achieves better convergence rate and computational accuracy compared with the traditional XFEM for the bending problems.     

BSTS极性微晶玻璃析晶机理及其制备工艺

BaO-SrO-TiO2-SiO2(BSTS)玻璃系统通过热处理产生晶粒定向的Ba2TiSi2O8极性取向的微晶体.样品在热处理过程的升温阶段和保温阶段通过冷却获得,采用SEM对样品结晶形貌和取向进行分析,研究晶粒生长与温度和时间的关系,从而为工艺的确定提供依据.     

MDA improvement technique for lung counter measurements of uranium workers

A practical and simple method was employed to improve the minimum detectable activity (MDA) for lung counting measurements by summing several accumulated spectra. The method was checked for natural uranium, which produces peaks due to photon energies of 63.3, 92.6 and 185.7 keV. By combining nine measurements, an overall improvement of the MDA by a factor of about 3 was achieved. Uranium contamination levels lower than the MDA of a single spectrum could be detected with acceptable accuracy when analyzing the sum spectra. Specific results are given for four workers occupationally exposed to natural uranium.     

IPMC人工肌肉的制备工艺研究与改进

研究了Nafion117质子交换膜的成膜过程与IPMC人工肌肉的制备过程.制备不同厚度的Nafion膜,在此基础上使用化学沉积法制备IPMC.制备主要分为前期预处理、主化学镀反应和次化学镀反应.由于在制备过程中膜表面产生气泡,需要高速搅拌,既要考虑到气泡快速溢出,又要使Nafion膜不与搅拌棒接触产生划痕,因此采用立式...     

Reliability centered prediction technique for diagnostic modeling and improvement

A diagnosability prediction metric is developed for system modeling of component failure rates and unjustified removals. The metric emphasizes ambiguity of system component indications as well as system structure. The metric is evaluated using historical data from the bleed air control system (BACS) on the Boeing737-300. Four design changes are suggested based on improving system diagnosability by changing component functions, modifying indications, and adding or changing sensors. The resulting designs are compared via Boeing's life cycle cost mechanism, DEPCOST model, based on cost improvements. It is shown that system improvements based on this prediction technique will increase the quality of a product since increased diagnosability decreases life cycle costs.     

Strain‐induced crystallization in rubber: A new measurement technique

The crystallinity of stretched crystallizable rubbers is classically investigated using X‐ray diffraction. In this study, we propose a new method based on temperature measurement and quantitative calorimetry to determine rubber crystallinity during mechanical tests. For that purpose, heat power density are first determined from temperature variation measurements and the heat diffusion equation. The increase in temperature due to strain‐induced crystallization is then deduced from the heat power density by subtracting the part due to elastic couplings. The heat capacity, the density, and the enthalpy of fusion are finally used to calculate the crystallinity from the temperature variations due to strain‐induced crystallization. The characterization of the stress–strain relationship and the non‐entropic contributions to rubber elasticity is not required. This alternative crystallinity measurement method is therefore a user‐friendly measurement technique, which is well adapted in most of the mechanical tests carried out with conventional testing machines. It opens numerous perspectives in terms of high speed and full crystallinity field measurements.     

Computer-aided study and multivariate optimization of nanomolar metformin hydrochloride analysis using molecularly imprinted polymer electrochemical sensor based on silver nanoparticles

Journal of Materials Science: Materials in Electronics - In this research project, a selective and sensitive sensor was electrochemically designed to measure metformin hydrochloride (MET) based on...     

A crystallization conditions study of the Ti‐doped barium hexaferrite powders synthesized with the glass crystallization technique for microwave applications

For microwave applications Titanium doped M‐type hexagonal ferrites have been synthesized by means of glass crystallization technique varying the crystallization parameters and the melt doping concentrations. The chosen melt dopings were x = 5.4 and 7.2 mole‐% TiO₂ with the following basic composition (mole‐%): 40 BaO + 33 B₂O₃ + (27‐x) Fe₂O₃ + x TiO₂. We have studied the dependencies between the magnetic properties, the valence of the iron ions in the glasses and the powders, the formation of new dielectric phases and the microwave absorption. After the Ti⁴⁺ ions substitutions, the magnetocrystalline anisotropy changed, this effect was observed in the static magnetic properties (_JH_C and M_S) measured using a vibration sample magnetometer. Furthermore the Ti⁴⁺ ions preferably occupy mainly the 2a as well as slightly the 2b sites in the lattice of the barium hexaferrite, which are studied using Mössbauer spectroscopy. Besides, the X‐ray diffraction studies proved that the formation of the ferrimagnetic (BaFe_12‐xTi_xO₁₂) and dielectric (BaTi₆O₁₃) phases are dependent on the crystallization parameters. The controlled influencing of lattice sites occupation and of the Fe²⁺ content in the ferrimagnetic phase as well as the controlled formation of the dielectric phase rate during the annealing are possibilities to optimize the microwave absorption of Ti‐doped barium hexaferrite powders synthesized by glass crystallization technique.     

Millisecond crystallization of amorphous silicon films by Joule-heating induced crystallization using a conductive layer

This study revolved around the introduction of a crystallization technology for amorphous silicon film using Joule-heating. As part of this study, an electric field was applied to a conductive layer to induce Joule-heating in order to generate the intense heat needed to carry out the crystallization of amorphous silicon. Polycrystalline silicon was produced via Joule-heating through a solid state transformation under typical processing conditions. Uniformly distributed fine grains were obtained due to enormously high heating rate of this process. Crystallization was accomplished throughout the sample within the range of milliseconds of the heating, thus demonstrating the possibility of a crystallization route for amorphous silicon films at room temperature.     

Room temperature crystallization by RF plasma

The crystallization of amorphous thin films was achieved by radiofrequency (RF) plasma treatment. Although various amorphous films are crystallized after 2 min or so, the sample temperature is lower than 150 °C without compulsory cooling even when the films are treated for 1 h. This treatment works on amorphous films of various materials, independently of the film preparation method and substrate materials. Sol-gel-derived TiO₂ films were densified and simultaneously crystallized to anatase structure by the plasma treatment and the obtained films indicate almost the same photocatalytic activities as that of thermally crystallized TiO₂ films. Plasma-crystallized sputtered indium tin oxide (ITO) films have a bixbite structure and the resistivity reached to 1.6 × 10^− 4 Ω cm while the crystallization condition was not optimized. Amorphous silicon films with a small mount of crystallites were deposited by sputtering method and were crystallized by the plasma treatment.