Development and validation of a versatile HPLC-DAD method for simultaneous determination of the antiviral drugs daclatasvir,ledipasvir, sofosbuvir and ribavirin in presence of seven potential impurities. Application to assay of dosage forms and dissolution studies

This study describes a simple, sensitive, specific and generic HPLC-DAD method for simultaneous determination of four drugs prescribed for treatment of Hepatitis C Virus (HCV) infection. Investigated drugs include daclatasvir (DAC), ledipasvir (LED), sofosbuvir (SOF) and ribavirin (RIB). Successful separation was accomplished using Thermohypersil BDS-C8 column (4.6?×?250?mm, 5?µm) with gradient elution of the mobile phase consisted of mixed phosphate buffer pH 7.5 and methanol. Gradient elution started with 25% methanol, ramped up linearly to 80% in 15?min then kept constant till the end of the run. Flow rate was 1.5?mL/min. Peak areas were measured at 235, 260, 315, and 332?nm for RIB, SOF, DAC, and LED, respectively. Peaks of the analytes were perfectly resolved with retention times 2.0, 12.1, 14.7, and 17.2?min for RIB, SOF, DAC, and LED, respectively. The developed method was validated according to ICH guidelines with respect to system suitability, linearity, ranges, accuracy, precision, specificity, robustness, and limits of detection and quantification. The proposed method showed good linearity in the ranges 5–500, 2–300, 0.5–75, and 0.5–75?µg/mL for RIB, SOF, DAC, and LED respectively. Limits of detection were 0.10–0.66?μg/mL for the analyzed drugs. Specificity was established by separation of target drugs from 7 process-related impurities for SOF including its major metabolite (GS-331007). Applicability of the proposed method to real life situations was assessed through the analysis of four different pharmaceutical formulations and satisfactory results were obtained. Additionally, dissolution profiles of the 4 drugs were studied using the developed method.     

Assessing Understanding of Planning and Scheduling Theory and Practice on Construction Projects

Abstract

Despite attention being paid to the development of planning and scheduling theory, it is unclear whether project stakeholders and practitioners have sufficient understanding about how it applies in practice. A study was conducted with the aim of assessing practitioners’ perceptions of planning and scheduling theory and practice on construction projects in Oman. Data were gathered through a questionnaire-based survey and analyzed using the relative importance index. Respondents were asked to consider: (1) the suitability and efficiency of existing planning methods; (2) scheduling development and performance control; and (3) knowledge-based planning and scheduling concepts. The analysis revealed no significant variations among respondents’ perceptions in regard to the above topics. The findings did, however, reveal a number of factors that are of equal importance to the development of project planning and scheduling. The overall findings imply that practicing managers should implement new management strategies that foster knowledge-based planning and scheduling concepts for a more effective construction process. Recommendations are made for improvement that include the need for practicing managers to professionalize project planning and scheduling based on a more proactive and knowledge-based planning approach, which is supported by management.     

Analytical method of two‐dimensional inverse heat conduction problem using Laplace transformation: Effect of number of measurement points

An analytical method has been developed for the inverse problem of two‐dimensional heat conduction using the Laplace transform technique. The inverse problem is solved for only two unknown surface conditions and the other surfaces are insulated in a finite rectangular body. In actual temperature measurement, the number of points in a solid is usually limited so that the number of temperature measurements required to approximate the temperature change in the solid becomes too small to obtain an approximate function using a half polynomial power series of time and the Fourier series of the eigenfunction. In order to compensate for this lack of measurement points, the third‐order Spline method is recommended for interpolating unknown temperatures at locations between measurement points. Eight points are recommended as the minimum number of temperature measurement points. The calculated results for a number of representative cases indicate that the surface temperature and the surface heat flux can be predicted well, as revealed by comparison with the given surface condition. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(7): 618–629, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10116     

Development of high strength Sn-0.7Cu solders with the addition of small amount of Ag and In

Nowadays, a major concern of Sn-Cu based solder alloys is focused on continuously improving the comprehensive properties of solder joints formed between the solders and substrates. In this study, the influence of Ag and/or In doping on the microstructures and tensile properties of eutectic Sn-0.7Cu lead free solder alloy have been investigated. Also, the effects of temperature and strain rate on the mechanical performance of Sn-0.7Cu, Sn-0.7Cu-2Ag, Sn-0.7Cu-2In and Sn-0.7Cu-2Ag-2In solders were investigated. The tensile tests showed that while the ultimate tensile strength (UTS) and yield stress (YS) increased with increasing strain rate, they decreased with increasing temperature, showing strong strain rate and temperature dependence. The results also revealed that with the addition of Ag and In into Sn-0.7Cu, significant improvement in YS (∼255%) and UTS (∼215%) is realized when compared with the other commercially available Sn-0.7 wt. % Cu solder alloys. Furthermore, the Sn-0.7Cu-2Ag-2In solder material developed here also exhibits higher ductility and well-behaved mechanical performance than that of eutectic Sn-0.7Cu commercial solder. Microstructural analysis revealed that the origin of change in mechanical properties is attributed to smaller β-Sn dendrite grain dimensions and formation of new inter-metallic compounds (IMCs) in the ternary and quaternary alloys.     

Duplex treatment of 304 AISI stainless steel using rf plasma nitriding and carbonitriding

Surface of 304 AISI austenitic stainless steel has been modified using duplex treatment technique of nitriding and carbonitriding. A thick modified nitrided layer, of approximately 20 µm, has been achieved when rf inductively coupled plasma was adjusted at 450 W for processing time of only 10 min. After performing the nitrided layer, the nitrided samples were carbonitrided using the same technique at different acetylene partial pressure ratios ranges from 10% to 70%, the balance was pure nitrogen. Different amount of nitrogen and carbon species are diffused underneath the surface through the nitrided layer during carbonitriding process and are found to be gas composition dependent. The treated samples were characterized by glow discharge optical spectroscopy, X-ray diffractometry, scanning electron microscopy and Vickers microhardness tester. The microstructure of the duplex treated layer indicates the formation of γ?-Fe₄N, Fe₃C, CrN and nitrogen-expanded austenite (γ_N). The thickness of the duplex treated layer increases with increasing the acetylene partial pressure ratio. The surface microhardness of duplex treated samples has been found to be gas composition dependent and increased by 1.29 fold in comparison to the nitrided sample.     

Electrical Properties of Li-doped P-type ZnO Ceramics

Li-doped p-type ZnO ceramics were prepared by conventional methods according to the chemical formula Zn1-xLixO2 where x=0.5, 1.0, 1.5 and 2.0 mole fraction, respectively.The crystal structures of the prepared samples were studied by X-ray diffraction analysis.The dielectric properties (including dielectric constant ε'and dielectric loss ε") and dc-electrical conductivity [σ(Ω-1.cm-1)] were investigated.The dielectric constant ε' was sharply decreased at the low frequency range and independent on frequency at high frequency range.Otherwise, the dielectric loss ε" varied with frequency and showed absorption peak located from 200 Hz to 4 kHz and moved to higher frequency as the concentration of Li+ doped increased.It was found that dcelectrical conductivity logσ varied from -9 to -5 and the energy gap width were calculated by using Arrhenius equation.The p-type conductivity of Li-doped ZnO may be attributed to the formation of a Lizn-Lii donor complex, which is limited by reducing the amount of Lii.     

The use of Jacobi polynomials in the numerical solution of coupled system of fractional differential equations

In this paper, we study shifted Jacobi polynomials and develop a simple but highly accurate scheme for the numerical solution of coupled system of fractional differential equations. We derive some operational matrices of integration and differentiation of fractional order. By the application of these matrices we provide a theoretical treatment to approximate the solutions of the corresponding system. We use Matlab to perform necessary operations. The applicability of the technique is shown with some examples and the results are displayed graphically.     

Location monitoring approach: multiple mix-zones with location privacy protection based on traffic flow over road networks

Multimedia Tools and Applications - Nowadays communication by using mobile vehicle getting popularity and user experience map services like Google maps to reach at the destination. It is also clear...     

Oxidation Resistance of the Aluminide Coating Formed on Carbon Steels

Low and medium carbon steels were aluminized by the pack aluminizing technique using halideactivated pure-Al and Fe-Al packs. The effect of mixture composition, aluminizing temperatureand time and C content of the steel substrate on the structure and thickness of the aluminidelayer, and on the oxidation resistance was investigated. The optimum oxidation resistance canbe achieved with a low carbon steel substrate when the intermetallic phases Fe3Al and FeAlform the surface of the aluminide layer. In this case, the Al concentration at the surface of thealuminide coating is at least ≥15 wt pct. Formation of high Al concentration phases (FeAl3 andFe2Al5) during aluminizing should be avoided as they tend to embrittle the aluminide layer andreduce its oxidation resistance.