Search results for "stil"
showing 10 items of 1452 documents
A microscale Kjeldahl nitrogen determination for environmental waters.
2008
A microscale Kjeldahl system has been designed which has been homemade reduced. The digestor unit of a macroKjeldahl system and a modified glassware microdistillation unit have been used. The optimal conditions for digestion and distillation have been established for ammonium and methylamine as model compound of organic amino nitrogen. The optimised procedure has been applied to the determination of Kjeldahl nitrogen in water samples. Recoveries near 100% and good precision have been achieved. This procedure combines nitrogen miniaturized system and the use of a selective ion electrode for ammonia detection. The analysis time was reduced 4.8 times and the analysis cost 6.6 times compared wi…
Quantification of some volatile aromatic compounds of apricot by adding standards
1988
The quantification of twelve volatile aromatic compounds of apricot was realized by adding known amounts of pure compounds directly in the slurry before analysis by vacuum distillation and gas chromatography. This method was compared with the classical technique using an internal standard and was applied to two different apricot cultivars. Large differences were observed between the amounts of volatiles calculated by the two methods. They are due to the differences between the extraction coefficients of the quantified compounds and to the retentions of volatiles on nonvolatile compounds, which may vary according to the polarity.
Staining mitochondria in Saccharomyces cerevisiae.
1969
After testing various procedures (amidoblack 10B, acid fuchsin-methyl blue, Luxol fast blue MBS-phloxine, toluidine blue O, Jams green B and pinacyanol), three stains can be recommended for staining both types of mitochondria (globose and threadlike) in the cells of Saccharomyces cerevisiae: (1) 0.1% solution of amidoblack 10B in citrate buffer (pH 3.0) for 10 min; (2) 0.01% solution of toluidine blue O in phosphate buffer (pH 6.0) for 30 min; (3) 0.01% solution of Janus green B in distilled water (pH 5.6) for 30 min. The latter stain is most specific because its staining reaction depends upon the action of the mitochondrial enzyme cytochrome c oxidase. Yet, low concentrations and short inc…
Traditional and new analytical methodology
2010
International audience
Quality control of commercial mustard by thin-layer chromatography
2005
Horseradish samples ( Cochlearis armoracia L. ) and mustard samples ( Sinapis alba L. ) were extracted with 70:30 ( v/v ) methanol-water in accordance with ISO method 91671. Samples of commercial mustard with and without horseradish were submitted to the same extraction procedure. Separation of the active compounds from these samples were performed on silica gel 60 plates with preconcentration zone and on silica gel F 254 high-performance thin-layer chromatography plates, with iso -propanol-25% ammonia, 90 + 10 ( v/v ), containing different volumes of distilled water (1, 2, 3, or 5 parts), as mobile phases. After development the compounds were visualized in UV light at λ = 254 nm or by expo…
Study on the histamine-like activity of guanfacine
1990
Abstract The effects of guanfacine have been studied on guinea-pig isolated atria and diethylstilboestrol-treated rat isolated uterus to determine whether it possesses histamine-like activity. Guanfacine produced a concentration-dependent negative chronotropic effect which was not modified by ranitidine (0.1 μM). In rat isolated uterus contracted by KCl, clonidine (5–5000 μM) produced concentration-dependent relaxation which was blocked by ranitidine (0.1 μM), but guanfacine only produced relaxation at high concentrations (100–1000 μM), and this was not affected by ranitidine (0.1 μM). It is concluded that guanfacine, unlike clonidine, does not produce effects due to activation of H2-recept…
Valodas nozīme personības raksturiezīmju atklāsmē Cicerona vēstulēs
2019
Šī maģistra darba mērķis ir izpētīt noteiktu adresātu vēstules dažādos Cicerona dzīves posmos, mēģinot noskaidrot, kā vēstulēs caur valodu, kādiem mākslinieciskās izteiksmes līdzekļiem, atklājas Cicerona personības spilgtākās šķautnes, un to, vai tās atšķiras privāta rakstura vēstulēs un publiskā sarakstē. Mēģināts noskaidrot, vai ir pamanāmas atšķirības izteiksmē tuvākiem cilvēkiem vai, teiksim, politiskiem oponentiem. Tāpēc, lai varētu aplūkot pēc iespējas atšķirīgākus adresātus, tika izvēlēti tuvākie ģimenes locekļi un draugi, kā arī vēsturiski zināmas Romas autoritātes, ar kurām Cicerons bija uzturējis saraksti. Darba gaitā tiek aplūkots Cicerona atstātais epistolārais mantojums, apskat…
Il cinema del nuovo millennio. Geografie, forme, autori
2020
Il volume è la risposta a un’esigenza di comprensione e chiarificazione circa le sorti di un oggetto non ancora storicizzabile, perché tuttora presente e in costante cambiamento: un oggetto eterogeneo che abbiamo voluto ricondurre sotto la generica definizione di “cinema contemporaneo”, la cui nascita abbiamo fatto risalire – altrettanto genericamente – all’inizio degli anni Duemila. Tale scelta dipende dalla necessità, largamente argomentata in ciascuno dei saggi che compongono il testo, di connettere l’origine e lo sviluppo di quello che qui chiamiamo “cinema contemporaneo” agli eventi e alle trasformazioni sociali e politiche che hanno attraversato fin qua il xxi secolo. Che cos’è e come…
Azacoccones F-H, new flavipin-derived alkaloids from an endophytic fungus Epicoccum nigrum MK214079.
2020
Abstract Three new flavipin-derived alkaloids, azacoccones F-H (1–3), along with six known compounds (4–9) were isolated from the endophytic fungus Epicoccum nigrum MK214079 associated with leaves of Salix sp. The structures of the new compounds were established by analysis of their 1D/2D nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectroscopy (HRESIMS) data. The absolute configuration of azacoccones F-H (1–3) was determined by comparison of experimental electronic circular dichroism (ECD) data with reported ones and biogenetic considerations. Epicocconigrone A (4), epipyrone A (5), and epicoccolide B (6) exhibited moderate antibacterial activity again…
Current and Potential Use of Citrus Essential Oils
2013
Since the Middle Ages, citrus essential oils (EOs) have been widely used for their bactericidal, virucidal, fungicidal, antipara- sitical, insecticidal, medicinal and cosmetic proprieties. Also nowadays, they find important applications in pharmaceutical, sanitary, cosmetic, agricultural and food industries. The best method to extract EOs from citrus plant tissue is steam distillation because of a vari- ety of extracted volatile molecules such as terpenes and terpenoids, phenol-derived aromatic components and aliphatic components. In vitro physicochemical assays classify most of them as antioxidants.