Search results for "COMPOUND"
showing 10 items of 35174 documents
Water in stereoselective organocatalytic reactions
2009
In this review, recent advances in asymmetric organocatalytic reactions carried out with variable amounts of water, from substoichiometric to a large excess (reaction medium), are discussed. We also summarize several proposed mechanisms for the different possibilities of the action of water both in the increased activity of the catalyst and in the asymmetric induction. Finally, the application of this catalytic methodology to the enantioselective synthesis of valuable compounds through enamine or iminium catalysis is presented.
Ortho -Functionalized Aryltetrazines by Direct Palladium-Catalyzed C−H Halogenation: Application to Fast Electrophilic Fluorination Reactions
2016
International audience; A general catalyzed direct C-H functionalization of s-tetrazines is reported. Under mild reaction conditions, N-directed ortho-C-H activation of tetrazines allows the introduction of various functional groups, thus forming carbon-heteroatom bonds: C-X (X=I, Br, Cl) and C-O. Based on this methodology, we developed electrophilic mono- and poly-ortho-fluorination of tetrazines. Microwave irradiation was optimized to afford fluorinated s-aryltetrazines, with satisfactory selectivity, within only ten minutes. This work provides an efficient and practical entry for further accessing highly substituted tetrazine derivatives (iodo, bromo, chloro, fluoro, and acetate precurso…
The Effect of Electrolytic Solution Composition on the Structure, Corrosion, and Wear Resistance of PEO Coatings on AZ31 Magnesium Alloy
2020
Plasma electrolytic oxidation coatings were prepared in aluminate, phosphate, and silicate-based electrolytic solutions using a soft-sparking regime in a multi-frequency stepped process to compare the structure, corrosion, and wear characteristics of the obtained coatings on AZ31 magnesium alloy. The XRD results indicated that all coatings consist of MgO and MgF2, while specific products such as Mg2SiO4, MgSiO3, Mg2P2O7, and MgAl2O4 were also present in specimens based on the selected solution. Surface morphology of the obtained coatings was strongly affected by the electrolyte composition. Aluminate-containing coating showed volcano-like, nodular particles and craters distributed over the …
Synergistic effect of W incorporation and pulsed current mode on wear and tribocorrosion resistance of coatings grown by plasma electrolytic oxidatio…
2019
Ceramic coatings were grown by plasma electrolytic oxidation on 7075 Al alloy using unipolar and bipolar pulsed current waveforms with 20 and 40% cathodic duty cycles, from a silicate-based bath without and with the addition of Na2WO4. Pancake-like morphology was dominant on the coatings grown by unipolar waveform, while the bipolar waveforms promoted volcano-like morphology, increased the roughness of the coating surface and the formation of more compact layers. The coatings produced using the bipolar waveforms provided higher resistances toward both tribocorrosion and dry sliding conditions, while further improvement was achieved by the presence of tungsten. The coatings produced in tungs…
Vinificazione in bianco in presenza di chips di quercia di origine e livello di tostatura diversi
2011
Some musts from Grillo grapes, a cultivar autochthonous of western Sicily, fermented with medium toasted American oak chips or with non toasted French oak chips (Classic Line – HTS enology) have been vinified. the wines were significantly different as regards the contents in volatile and non volatile compounds extracted from American and French oak chips. a slight increase in alcoholic fermentation rate and in some cases a higher content of ethyl esters and medium chain fatty acids, were observed in musts charged with chips, independently of their origin. In wines obtained from musts charged with french medium toasted oak chips, the content in furans was higher (5-methylfurfural, trans-meth…
Study of quantitative and qualitative variations in essential oils of Sicilian oregano biotypes
2015
Essential oil (EO) was extracted using hydrodistillation from samples of Origanum vulgare subspecies hirtum (Link) Ietswaart, gathered from the wild in various parts of Sicily, Italy; GC-FID and GC-MS analyses were subsequently performed. The aim of the study was to analyze the relationship between essential oil yields and the geographical distribution of oregano wild populations based on variations in environmental factors as collection sites. Moreover, the purpose was to group Origanum vulgare subspecies hirtum biotypes according to the chemical composition of the EO. The seven principal components in the EO was thymol (24.0–54.4%), γ-terpinene (9.8–30.5%), ρ-cymene (5.2–18.7%), α-terpine…
Regulation of motility of cells from marine sponges by calcium ions
1996
Sponges are known not to contain muscle and nerve cells. Since sponge cells are characterized by high motility we determined the effect of intracellular calcium ion concentration ([Ca2+]i) on their motility. Addition of the Ca2+ ionophore ionomycin to dissociated cells from the marine sponge Suberites domuncula caused in Ca(2+)-containing artificial seawater (ASW) an increase in motility from 0.2 micron/min (absence of the ionophore) to 3.7 microns/min (presence of ionomycin). When the experiments were performed in Ca(2+)-free medium, no effect of ionomycin could be observed. In parallel experiments the changes of [Ca2+]i using the dye Fura-2 were measured. The experiments revealed that ion…
XPS structural data and correlation with Mossbauer spectra for Tin-organic compounds: adducts of RnSnCl4-n with 1,2-bis(diphenylphosphino)ethane
1982
Abstract Core level X-ray photoelectron spectra of 1:1 adducts of SnCl4 and RSnCl3 with DPE {[RnSnCl4−n} · DPE (n = 1, R = Me, Bun, Octn, Phn; n = 2, R = Ph; DPE = 1,2-bis(diphenylphosphino)ethane], have been measured in solid phase. The Sn3d 5 2 binding energies, corrected for the Madelung potential at the metal atom, are well correlated with both partial atomic charge on tin, accounting for relaxation upon ionization, and 119Sn Mossbauer isomer shifts. The results are discussed in terms of these molecular parameters.
Cadmium Metal–Organic Frameworks Based on Ditopic Triazamacrocyclic Linkers: Unusual Structural Features and Selective CO 2 Capture
2017
International audience; Two three-dimensional cadmium metal organic frameworks with general formula [Cd-2(L-1)(H2O)(3)](NO3)(0.7)(HCOO)(0.2)Br-0.1 (Cd2L1, L-1 = 1,4,7-tris(4-carboxybenzy1)-1,4,7-triazacyclononane) and Cd(HL2)(H2O)(2) (CdL2, L-2 = 1,4,7-tris(3-(4-benzoate)prop-2-yn-1-yl)-1,4,7-triazacydononane) based on 1,4,7-triazacyclononane N-functionalized by different arylcarboxylic acids were prepared under solvothermal conditions and characterized by single crystal X-ray analysis and porosity measurements. The crystal structure of Cd2L1 reveals a cationic net with a bcs topology,. and nodes are constituted by dinuclear cadmium complexes, in which each cadmium atom adopts a hexacoordin…
Ekstemporālā receptūra Dzirciema aptiekā
2018
Mūsdienās Latvijā samazinājies aptieku skaits, kur var pagatavot zāles ekstemporāli (ex tempore no latīņu valodas nozīmē „pēc nepieciešamības”). Taču tas pakalpojums joprojām ir vajadzīgs un aktuāls, jo rūpnieciski ražoti medikamenti nevar pilnībā apmierināt klientu pieprasījumu pēc individualizētas pieejas zāļu izgatavošanā. Darba mērķis bija apkopot teorētisko informāciju par ekstemporālo receptūru un praktiski izanalizēt Dzirciema aptiekas ex tempore receptes. Izvirzītie uzdevumi bija apkopot teorētisko informāciju par aptieku un farmācijas vēsturi Latvijā, ekstemporāli pagatavojamām zāļu formām, normatīviem dokumentiem, kuri reglamentē zāļu izgatavošanu Latvijas aptiekās, kā arī veikt p…