72 research outputs found
DIE ROLLE DER KRISTALLINEN ALUMINOSILIKATE BEI DER UMSETZUNG VON KOHLENWASSERSTOFFEN : I. BEDEUTUNG, STRUKTUR UND HERSTELLUNG VON ZEOLITHISCHEN MOLEKULARSIEB-KATALYSATOREN
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
Novi analitiÄki pristup sa smanjenom potroĆĄnjom 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-”L 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, Beerâs law was obeyed in the concentration range of 6â100 and 6â60 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 analitiÄkog pristupa koji 50 puta smanjuje potroĆĄnju organskih otapala u spektrofotometrijskoj analizi na bazi prijenosa naboja (CT). PredloĆŸena metoda koristi ploÄe s 96 jaĆŸica za izvoÄenje analize. CT reakcije izmeÄu elektron-donora i elektron-akceptora izvodi se u jaĆŸicama s 200-”L organskog otapala. Promjene boje mjere se pomoÄu posebnog mikroÄitaÄa za ploÄe s jaĆŸicama. OdreÄeni 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 podruÄju 6â100 i 6â60 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 zadovoljavajuÄa, a relativna standardna devijacija bila je manja od 1,1 %. PredloĆŸena metoda uspjeĆĄno je primijenjena za analizu doziranih farmaceutskih pripravaka koji sadrĆŸe ispitivane lijekove, uz dobru toÄnost i preciznost. Rezultati predloĆŸene metode usporedivi su s rezultatima poznatih metoda. Postupak opisan u ovom radu vrlo je praktiÄan: analitiÄari su manje izloĆŸeni toksiÄnim uÄincima organskih otapala, troĆĄkovi analize smanjeni su 50 puta, a takoÄer ju odlikuje visoka propusnost. Iako je postupak validiran za RML i LSL, ista metoda moĆŸe se upotrijebiti za elektron-donirajuÄi analit koji ulazi u CT reakciju
Spectrophotometric and HPLC determination of deflazacort in pharmaceutical dosage forms
Late Triassic platform, slope and basin deposits in the Pilis Mountains, Transdanubian Range, Hungary
High dose MPA treatment â hormonal changes and clinical results in endometrial carcinomas
- âŠ