Investigation of Solid Dispersion of Atorvastatin Calcium in Polyethylene Glycol 6000 and Polyvinylpyrrolidone

Purpose: To improve the solubility and bioavailability of atorvastatin calcium (ATC), a poorly watersoluble 3-hydroxy 3-methyl glutaryl CoA (HMG-CoA) reductase inhibitor, by a solid dispersion technique using polyethylene glycol 6000 (PEG 6000) or polyvinylpyrrolidone k30 (PVP K30).Methods: The solid dispersions were characterised by differential scanning calorimetry (DSC), powder x-ray diffraction (PXRD) and Fourier transformed infrared (FT-IR) spectroscopy. The dissolution characteristics of the formulations were determined in vitro, while the bioavailability of the solid dispersion and suspension was evaluated in rats.Results: DSC, PXRD and FT-IR data confirmed the formation of solid dispersion. The dissolution results showed that almost 95 % of ATC in ATC- PVP K30 solid dispersion dissolved in 5 min. The amount of ATC in ATC-PVP K30 SD, ATC-PEG 6000 SD and pure ATC that dissolved in 60 min was 103, 85 and 93 %, respectively. In addition, in vivo bioavailability studies in rats showed that area under concentration-time curve (AUC) and peak concentration (Cmax) of ATC-PVP K30 solid dispersion was 3.5-fold and 4.9-fold higher than that of the drug in suspension. Time to attain peak concentration (Tmax) of ATC-PVP K30 solid dispersion was 0.25 ± 0.00 h, which is shorter than 0.83 ± 0.26 h for suspension.Conclusion: The results obtained indicates that solid dispersions of ATC made with polyethylene glycol 6000 and polyvinylpyrrolidone K30 are an effective new approach to designing formulations of poorly soluble ATC for greatly enhanced solubility and bioavailability.Keywords: Solid dispersion, Atorvastatin, Polyethylene glycol, Polyvinypyrrolidone K30, Bioavailability, Dissolutio

Delay-dependent stabilization of stochastic interval delay systems with nonlinear disturbances

This is the post print version of the article. The official published version can be obtained from the link below - Copyright 2007 Elsevier Ltd.In this paper, a delay-dependent approach is developed to deal with the robust stabilization problem for a class of stochastic time-delay interval systems with nonlinear disturbances. The system matrices are assumed to be uncertain within given intervals, the time delays appear in both the system states and the nonlinear disturbances, and the stochastic perturbation is in the form of a Brownian motion. The purpose of the addressed stochastic stabilization problem is to design a memoryless state feedback controller such that, for all admissible interval uncertainties and nonlinear disturbances, the closed-loop system is asymptotically stable in the mean square, where the stability criteria are dependent on the length of the time delay and therefore less conservative. By using Itô's differential formula and the Lyapunov stability theory, sufficient conditions are first derived for ensuring the stability of the stochastic interval delay systems. Then, the controller gain is characterized in terms of the solution to a delay-dependent linear matrix inequality (LMI), which can be easily solved by using available software packages. A numerical example is exploited to demonstrate the effectiveness of the proposed design procedure.This work was supported in part by the Engineering and Physical Sciences Research Council (EPSRC) of the UK under Grant GR/S27658/01, the Nuffield Foundation of the UK under Grant NAL/00630/G, and the Alexander von Humboldt Foundation of Germany

Experimental method for biaxial tensile strength of fabrics and preliminary investigations

This paper presents a novel experimental approach to determine the biaxial strength of fabrics. A double-layer cruciform specimen was proposed based on the improvement of previous test specimen. The design and manufacture process of the novel specimen was described in detail. Uniaxial and biaxial tests of a specific material were performed subsequently. Based on numerical simulation, the biaxial strength of the fabrics was preliminary investigated. And the correlation between uniaxial and biaxial strength of the material was discussed. The proposed experiments could characterize the biaxial strength of fabrics, and the biaxial strength of the fabrics at 1:1 tension is higher than the weft strength and little lower than the warp strength

Research on Some Phenomenon of E-Government Service Capacity Distribution in Mainland China Based on Multi-channel Perspective

In the context of the government\u27s increasing emphasis on e-government services, this is an urgent need for empirical research of large sample and multi-channels. Therefore, based on the government website, WeChat, Micro-blog, app, by using the existing mature evaluation index system, this paper analyzes e-government service capacity of the city above prefecture- level and provincial. Then, this paper selects the administrative level, economic level, regional balance as the differentiation attribute. It is found that both administrative level and economic level are positively correlated with government service capacity in all the channels. The channel capacity distribution varies related to attribute of administrative and economic, government type of city and province, but it is not restricted by level and region. It provides direction and intensity management to balance and promote channel service capacity for China government

An Improved Chloroplast DNA Extraction Procedure for Whole Plastid Genome Sequencing

Background: Chloroplast genomes supply valuable genetic information for evolutionary and functional studies in plants. The past five years have witnessed a dramatic increase in the number of completely sequenced chloroplast genomes with the application of second-generation sequencing technology in plastid genome sequencing projects. However, costeffective high-throughput chloroplast DNA (cpDNA) extraction becomes a major bottleneck restricting the application, as conventional methods are difficult to make a balance between the quality and yield of cpDNAs. Methodology/Principal Findings: We first tested two traditional methods to isolate cpDNA from the three species, Oryza brachyantha, Leersia japonica and Prinsepia utihis. Both of them failed to obtain properly defined cpDNA bands. However, we developed a simple but efficient method based on sucrose gradients and found that the modified protocol worked efficiently to isolate the cpDNA from the same three plant species. We sequenced the isolated DNA samples with Illumina (Solexa) sequencing technology to test cpDNA purity according to aligning sequence reads to the reference chloroplast genomes, showing that the reference genome was properly covered. We show that 40–50 % cpDNA purity is achieved with our method. Conclusion: Here we provide an improved method used to isolate cpDNA from angiosperms. The Illumina sequencing results suggest that the isolated cpDNA has reached enough yield and sufficient purity to perform subsequent genom

An Efficient Process for Pretreatment of Lignocelluloses in Functional Ionic Liquids

Background and Aims. The complex structure of the lignocelluloses is the main obstacle in the conversion of lignocellulosic biomass into valuable products. Ionic liquids provide the opportunities for their efficient pretreatment for biomass. Therefore, in this work, pretreatment of corn stalk was carried out in ultrasonic-assisted ionic liquid including 1-butyl-3-methylimidazolium chloride [BMIM]Cl, 1-H-3-methylimidazolium chloride [HMIM]Cl, and 1-(1-propylsulfonic)-3-imidazolium chloride [HSO3-pMIM]Cl at 70°C for 2 h. We compared the pretreatments by ionic liquid with and without the addition of deionized water. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were employed to analyze the chemical characteristics of regenerated cellulose-rich materials. Results. [HMIM]Cl and [HSO3-pMIM]Cl were effective in lignin extraction to obtain cellulose-rich materials. FTIR analysis and SEM analysis indicated the effective lignin removal and the reduced crystallinity of cellulose-rich materials. Enzymatic hydrolysis of cellulose-rich materials was performed efficiently. High yields of reducing sugar and glucose were obtained when the corn stalk was pretreated by [HMIM]Cl and [HSO3-pMIM]Cl. Conclusions. Ionic liquids provided the ideal environment for lignin extraction and enzymatic hydrolysis of corn stalk and [HMIM]Cl and [HSO3-pMIM]Cl proved the most efficient ionic liquids. This simple and environmentally acceptable method has a great potential for the preparation of bioethanol for industrial production