Synthesis and biological activity of 3,5-diacetyl-2,6-dimethylpyridine derivatives

Chemistry of Heterocyclic Compounds - Aldol-crotonic condensation reactions of 3,5-diacetyl-2,6-dimethylpyridine with various aldehydes were used to synthesize bisazachalcone derivatives, which...     

Cinnamal Sensing and Luminescence Color Tuning in a Series of Rare-Earth Metal−Organic Frameworks with Trans-1,4-cyclohexanedicarboxylate

Three isostructural metal–organic frameworks ([Ln₂(phen)₂(NO₃)₂(chdc)₂]·2DMF (Ln³⁺ = Y³⁺ for 1, Eu³⁺ for 2 or Tb³⁺ for 3; phen = 1,10-phenanthroline; H₂chdc = trans-1,4-cyclohexanedicarboxylic acid) were synthesized and characterized. The compounds are based on a binuclear block {M₂(phen)₂(NO₃)₂(OOCR)₄} assembled into a two-dime nsional square-grid network containing tetragonal channels with 26% total solvent-accessible volume. Yttrium (1)-, europium (2)- and terbium (3)-based structures emit in the blue, red and green regions, respectively, representing the basic colors of the standard RGB matrix. A doping of Eu³⁺ and/or Tb³⁺ centers into the Y³⁺-based phase led to mixed-metal compositions with tunable emission color and high quantum yields (QY) up to 84%. The bright luminescence of a suspension of microcrystalline 3 in DMF (QY = 78%) is effectively quenched by diluted cinnamaldehyde (cinnamal) solutions at millimolar concentrations, suggesting a convenient and analytically viable sensing method for this important chemical.     

Deployment of the encapsulation-dehydration protocol to cryopreserve diverse microalgae held at the Institute of Soil Biology, Academy of Sciences of the Czech Republic

Twenty-seven strains of soil algae isolated from highly diverse provenances and habitats were assessed for their capacity to withstand cryopreservation using encapsulation/dehydration. Survival was assessed following the release of algae from alginate beads treated with sodium hexametaphosphate and regrowth was assessed using NAJA Image Analysis. Regrowth occurred in 19 strains, with > 50% survival being observed in 15. Algal tolerance to osmotic dehydration and evaporative desiccation was critical to the success of the method. Recovery in five out of the remaining eight recalcitrant strains was enhanced by substituting sorbitol for the osmotic pretreatment or by combining encapsulation with two-step controlled rate cooling.     

Simultaneous microdetermination of sulphur,carbon and nitrogen by reaction gas chromatography

Summary A simultaneous microdetermination of C, N and S, based on reaction GC, with a commercial analyser for the microdetermination of C, H, N and O, is described. The sample, covered with a mixture of WO₃ and SnO₂, is combusted in a stream of helium with added oxygen, and the mixture of pyrolysis products is oxidized completely by passage through a layer of granulate SnO₂. Conversion of SO₃ into SO₂, reduction of nitrogen oxides and absorption of unreacted oxygen proceed in a layer of Cu, and halogens are trapped by metallic antimony. Particular attention is paid to determination of sulphur in liquid samples without weighing.

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Simultane Mikrobestimmung von Schwefel, Kohlenstoff und Stickstoff mittels Reaktions-Gaschromatographie

Zusammenfassung Die simultane Mikrobestimmung von C, N und S mittels Reaktions-Gaschromatographie unter Benutzung eines kommerziellen Analysators für die Mikrobestimmung von C, H, N und S wurde beschrieben. Eine Probe wird nach Überschichtung mit einer Mischung aus WO₃ und SnO₂ im Heliumstrom unter einmaligem Sauerstoffzusatz verbrannt. Das Gemisch der Pyrolyseprodukte wird mit Hilfe einer Schicht aus granuliertem SnO₂ zu Ende oxydiert. Die Konversion von SO₃ in SO₂, die Reduktion von Stickstoffoxiden und die Absorption nicht verbrauchten Sauerstoffs verlaufen in der Cu-Schicht, Halogene werden in der Endphase von metallischem Antimon eingefangen. Besondere Aufmerksamkeit wird auch der Bestimmung von Schwefel in flüssigen Proben ohne Wägung gewidmet.

     

Electrochemical extraction of ytterbium from LiCl–KCl-YbCl3-ZnCl2 melt by forming Zn–Yb alloys

Journal of Solid State Electrochemistry - The electrochemical behavior of Yb(III) was studied at a W electrode in LiCl–KCl–ZnCl2 molten salt system. Cyclic voltammetry, square wave...     

Determination of Evans blue as a blood–brain barrier integrity tracer in plasma and brain tissue by UHPLC/UV method

Blood–brain barrier changes are an integral part of many neurodegenerative diseases. Evans blue is an intravital dye that binds to albumin and can therefore be used to monitor extravasation of this plasma protein across blood–brain barrier in animal models of neurodegeneration. To monitor extravasation of albumin across blood–brain barrier, we developed and validated an ultrahigh-performance liquid chromatography method for the analysis of Evans blue in rat plasma and brain samples. Analyte was separated on ACQUITY UPLC BEH C18 column (2.1?mm?×?50?mm) using a 5-min gradient run and detected by a UV detector. The limits of quantification (LOQ) were 10?µg/mL in plasma and 0.5?µg/g in brain samples. The limits of detection (LOD) were 1?µg/mL in plasma and 0.015?µg/g in brain samples. The method showed excellent linearity with regression coefficients higher than 0.99. The accuracy was within the range of 91–105%. The inter-day precision was in the range of 1.3–8%. The benefits of using UPLC are selectivity, short analysis period, and thus, a very good sample throughput. Using this method, we analyzed albumin extravasation across blood–brain barrier in transgenic rat model for tauopathy SHR-72 and age-matched control animals.     

Reliable Condensation Curing Silicone Elastomers with Tailorable Properties

The long-term stability of condensation curing silicone elastomers can be affected by many factors such as curing environment, cross-linker type and concentration, and catalyst concentration. Mechanically unstable silicone elastomers may lead to undesirable application failure or reduced lifetime. This study investigates the stability of different condensation curing silicone elastomer compositions. Elastomers are prepared via the reaction of telechelic silanol-terminated polydimethylsiloxane (HO-PDMS-OH) with trimethoxysilane-terminated polysiloxane ((MeO)₃Si-PDMS-Si(OMe)₃) and ethoxy-terminated octakis(dimethylsiloxy)-T8-silsesquioxane ((QM^OEt)₈), respectively. Two post-curing reactions are found to significantly affect both the stability of mechanical properties over time and final properties of the resulting elastomers: Namely, the condensation of dangling and/or unreacted polymer chains, and the reaction between cross-linker molecules. Findings from the stability study are then used to prepare reliable silicone elastomer coatings. Coating properties are tailored by varying the cross-linker molecular weight, type, and concentration. Finally, it is shown that, by proper choice of all three parameters, a coating with excellent scratch resistance and electrical breakdown strength can be produced even without an addition of fillers.