Authors:Nobuyuki Shirakawa, Takao Furukawa, Minoru Nomura and Kumi Okuwada
proportion of articles published by authors in North America, Europe and East Asia has increasingly balanced, leading to the formation of a tri-polar structure of IEEE technological activities. Quantitativeanalysis of IEEE publications reveals structural
Authors:Lukasz Cieśla, Anna Petruczynik, Michał Hajnos, Anna Bogucka-Kocka and Monika Waksmundzka-Hajnos
Coumarins are interesting group of natural compounds, because of their biological and pharmacological activity, and are widely investigated. They are normally found in complex mixtures, e.g. plant extracts, and are difficult to separate in one chromatographic run. Mixtures of coumarins have been separated by two-dimensional thin-layer chromatography on CN-silica plates by use of aqueous and nonaqueous mobile phases. Complete separation was also achieved by use of graft thin-layer chromatography on connected layers — silica with RP-18W or CN-silica with silica. The systems characterized by the best efficiency and selectivity were used for separation of coumarin fractions from extracts of selected
plants. These orthogonal systems were used for quantitative analysis of selected coumarins. The results obtained show two dimensional thin-layer chromatography is useful tool for quantification of some furanocoumarins in plant extracts. The best results were obtained on connected silica and octadecyl silica layers.
A simple, rapid, and stability-indicating RPTLC method has been established and validated for quantitative analysis of two oral antidiabetic agents, the sulfonylureas gliclazide and glipizide, in tablets. Analysis was performed on RP-18 plates with 60% (
) acetonitrile in pH 2.3 phosphate buffer as mobile phase. Compact spots were obtained for gliclazide (
0.38 ± 0.02, mean ± SD) and glipizide (
0.51 ± 0.03). Detection and quantification were performed by classical densitometry at 215 nm, the wavelength of maximum absorption of gliclazide and glipizide. Calibration plots were constructed in the range 0.8–1.8 μg per 10 μL (per spot) for both drugs and were linear with good correlation coefficients (
= 0.998 ± 0.001, mean ± SD, for gliclazide and
= 0.993 ± 0.002 for glipizide). The limits of detection and quantification were 50 and 200 ng per spot, respectively, for gliclazide and 60 and 300 ng for glipizide. The method was validated for robustness, precision, accuracy, stability, and specificity. The drugs were subjected to acidic and alkaline hydrolysis, oxidation, photo-degradation, and heating and were found to be susceptible to some stress conditions. However, the degradation products were well resolved from the pure drugs with significantly different
Inula cappa (family Compositae) is used in the Ayurvedic medicinal system for the treatment of bronchitis, diabetes, fever, hypertension, and rheumatism. The proposed high-performance thin-layer chromatography (HPTLC) study offers coherent evaluation of isoalantolactone, germacranolide, β-sitosterol, and lupeol from I. cappa root. Methanolic solutions of isoalantolactone, germacranolide, β-sitosterol, and lupeol were applied on an HPTLC plate and they were scanned at 525 nm. The mobile phase toluene—methanol (9.4:0.6, v/v) was used for all the phytochemicals. After development, all the plates were air-dried at room temperature, derivatized with anisaldehyde–sulfuric acid reagent and heated at 105°C. This study aids the identification of these compounds and provides an easy and simple method for the simultaneous estimation of these markers in the I. cappa roots. The method would serve as an expedient tool in routine analyses to corroborate the drug through good constancy.
This study analyses the research output of Nepal in S&T during 2001–10 on several parameters including its growth and country publications share in the world's research output, country publications share in various subjects in the national and global context, pattern of research communication in core domestic and international journals, geographical distribution of publications, share of international collaborative publications at the national level as well as across subjects and characteristics of high productivity institutions, authors and cited papers. The Scopus Citation Database has been used to retrieve the publication data for 10 years.
Authors:Hayun Hayun, Rina Rahmawati, Yahdiana Harahap and Santi Purna Sari
–MS/MS method for quantitativeanalysis of curcumin in human plasma, which will be able to provide a variety of options for researchers.
Chemical and reagents
Curcumin (USP Reference standard) was
Method validation of quantitativeanalysis
Methanol stock solutions containing the three analytes were prepared, and the chemical structures of three active components were showed in Fig. 2 . Different concentrations of the three analytes
Authors:Takao Furukawa, Nobuyuki Shirakawa and Kumi Okuwada
This study proposes a quantitative analysis of researcher mobility (i.e. transfer from one institution to another) and collaborative networks on the basis of author background data extracted from biographical notes in scientific articles to identify connections that are not revealed via simple co-authorship analysis. Using a top-ranked journal in the field of computer vision, we create a layered network that describes various aspects of author backgrounds, demonstrating a geographical distribution of institutions. We classify networks according to various dimensions including authors, institutions and countries. The results of the quantitative analysis indicate that mobility networks extend beyond the typical collaborative networks describing institutional and international relationships. We also discuss sectoral collaboration considering the mobility networks. Our findings indicate a limitation of collaborative analysis based on bibliometric data and the importance of tracing researcher mobility within potential networks to identify the true nature of scientific collaboration.