An extensive photometric study of the Blazhko RR Lyrae star RZ Lyr

The analysis of recent, extended multicolour CCD and archive photoelectric, photographic and visual observations has revealed several important properties of RZ Lyr, an RRab-type variable exhibiting large-amplitude Blazhko modulation. On the time-base of \sim110 yr, a strict anticorrelation between the pulsation and modulation period changes is established. The light curve of RZ Lyr shows a remarkable bump on the descending branch in the small-amplitude phase of the modulation, similarly to the light curves of bump Cepheids. We speculate that the stellar structure temporally suits a 4:1 resonance between the periods of the fundamental and one of the higher-order radial modes in this modulation phase. The light-curve variation of RZ Lyr can be correctly fitted with a two-modulation-component solution; the 121 d period of the main modulation is nearly but not exactly four times longer than the period of the secondary modulation component. Using the inverse photometric method, the variations in the pulsation-averaged values of the physical parameters in different phases of both modulation components are determined.Comment: 15 pages, 14 figures, 8 tables. Published in MNRAS, 2012. [v3]: Only change: title correcte

Novel spectrophotometric method for determination of cinacalcet hydrochloride in its tablets via derivatization with 1,2-naphthoquinone-4-sulphonate

This study represents the first report on the development of a novel spectrophotometric method for determination of cinacalcet hydrochloride (CIN) in its tablet dosage forms. Studies were carried out to investigate the reaction between CIN and 1,2-naphthoquinone-4-sulphonate (NQS) reagent. In alkaline medium (pH 8.5), an orange red-colored product exhibiting maximum absorption peak (λmax) at 490 nm was produced. The stoichiometry and kinetic of the reaction were investigated and the reaction mechanism was postulated. This color-developing reaction was employed in the development of a simple and rapid visible-spectrophotometric method for determination of CIN in its tablets. Under the optimized reaction conditions, Beer's law correlating the absorbance with CIN concentration was obeyed in the range of 3 - 100 μg/ml with good correlation coefficient (0.9993). The molar absorptivity (ε) was 4.2 × 105 l/mol/cm. The limits of detection and quantification were 1.9 and 5.7 μg/ml, respectively. The precision of the method was satisfactory; the values of relative standard deviations (RSD) did not exceed 2%. No interference was observed from the excipients that are present in the tablets. The proposed method was applied successfully for the determination of CIN in its pharmaceutical tablets with good accuracy and precisions; the label claim percentage was 100.80 - 102.23 ± 1.27 - 1.62%. The results were compared favorably with those of a reference pre-validated method. The method is practical and valuable in terms of its routine application in quality control laboratories

Novi analitički pristup sa smanjenom potrošnjom organskih otapala u spektrofotometrijskoj analizi temeljenoj na prijenosu naboja: Primjena u analizi nekih antihipertenziva

The present study describes the development of a novel analytical approach that can reduce by 50-fold the consumption of organic solvents in the charge transfer (CT)-based spectrophotometric analysis. The proposed approach employed 96-microwell assay plates for carrying out the reaction. The CT reaction between the electron-donating analyte and electron-accepting reagent was performed in microwells (200-µL of organic solvent) and the color signals were measured with a microwell-plate reader. Optimum conditions for the proposed approach were established for two antihypertensive drugs, namely ramipril (RML) and lisinopril (LSL) as model compounds for the electron-donating analytes, and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) as a -electron acceptor. Under the optimum conditions, Beer’s law was obeyed in the concentration range of 6–100 and 6–60 g mL1 for RML and LSL, respectively. The limits of detection were 0.97 and 1.10 g mL1 for RML and LSL, respectively. The precision of the methods was satisfactory; the values of relative standard deviations did not exceed 1.1 %. The proposed approach was successfully applied to the analysis of pharmaceutical dosage forms with good accuracy and precision. The results were comparable with those of the reported methods. The approach described herein is of great practical value in pharmaceutical analysis because it reduces the exposure of analysts to the toxic effects of organic solvents, lowers the analysis cost by 50-fold, and it has a high throughput property. Although the approach was validated for RML and LSL, the same methodology could be used for any electron-donating analyte for which a CT-reaction can be performed.U radu je opisan razvoj novog analitičkog pristupa koji 50 puta smanjuje potrošnju organskih otapala u spektrofotometrijskoj analizi na bazi prijenosa naboja (CT). Predložena metoda koristi ploče s 96 jažica za izvođenje analize. CT reakcije između elektron-donora i elektron-akceptora izvodi se u jažicama s 200-µL organskog otapala. Promjene boje mjere se pomoću posebnog mikročitača za ploče s jažicama. Određeni su optimalni uvjeti za dva antihipertenzivna lijeka, ramipril (RML) i lizinopril (LSL) koji su upotrebljeni kao modelni spojevi za elektron-donorske analite, i 2,3-diklor-5,6-dicijano-1,4-benzokinon (DDQ) kao -elektronski akceptor. U optimalnim uvjetima Beerov zakon je vrijedio u koncentracijskom području 6–100 i 6–60 g mL1 za RML, odnosno LSL. Granice detekcije bile su 0,97 i 1,1 g mL1 za RML, odnosno LSL. Preciznost metode bila je zadovoljavajuća, a relativna standardna devijacija bila je manja od 1,1 %. Predložena metoda uspješno je primijenjena za analizu doziranih farmaceutskih pripravaka koji sadrže ispitivane lijekove, uz dobru točnost i preciznost. Rezultati predložene metode usporedivi su s rezultatima poznatih metoda. Postupak opisan u ovom radu vrlo je praktičan: analitičari su manje izloženi toksičnim učincima organskih otapala, troškovi analize smanjeni su 50 puta, a također ju odlikuje visoka propusnost. Iako je postupak validiran za RML i LSL, ista metoda može se upotrijebiti za elektron-donirajući analit koji ulazi u CT reakciju

Upper Triassic‒Middle Jurassic resedimented toe-of-slope and hemipelagic basin deposits in the Dinaridic Ophiolite Belt, Zlatar Mountain, SW Serbia

In the Dinaridic Ophiolite Belt, small (m-scale) to large (km-scale) blocks of Middle to Upper Triassic, and Middle to Upper Jurassic, more or less silicified bedded limestone are widely present, both as parts of para-autochthonous successions and as redeposited blocks in ophiolitic mélanges. The studied, approximately 230-m-thick succession in the wider area of Zlatar Mountain, is one of the most important para-autochthonous sections in the Serbian part of the Dinaridic Ophiolite Belt. The succession is made up of an alternation of redeposited carbonate toe-of-slope deposits, sand to clay-sized siliciclastic rocks, hemipelagic mudstones and radiolarite–spongiolite basin facies. In the lower part of the sequence, the components of the siliciclastic beds were derived mostly from low- and medium-grade metamorphic rocks. Similar components, together with sand-sized fragments of ophiolitic rocks, were encountered in small amounts in some redeposited carbonate beds. The chronostratigraphic assignment of the succession is based mostly on foraminifers, but age-diagnostic radiolarians and other microfossil groups were also considered. In the lower part of the probably continuous succession, a Norian–Rhaetian assemblage was recognized; a Sinemurian–Pliensbachian assemblage was encountered up-section, whereas the upper part of the succession could be assigned to the Bajocian–Bathonian. Considering the paleogeographic reconstructions and the analogies of age-equivalent sections, the succession records the depositional history of the Bosnian Basin during the Late Triassic to Middle Jurassic period and may contribute to the understanding of the evolution of the Adriatic margin of the Neotethys Ocean in the transition interval from passive to active margin stages