Search results for "Zen"
showing 10 items of 3479 documents
Chiral Polyisocyanates from an Azomonomer with a Very High Chiral Induction
2001
The synthesis of new chiral polyisocyanates is described. For this purpose a new chiral azobenzene containing monomer with the chiral center in α-position to the isocyanate group was synthesized. The anionic copolymerization was carried out in THF as solvent with potassium cyanide that was complexed by 18-crown-6 as initiator. This allowed a better control of the reaction and thereby the synthesis of polyisocyanates with a fairly low polydispersity. The copolymers show an extremely high transfer of chirality from the chiral side groups to the helical backbone in dilute solution. Copolymers with only 1.6 mol % of chiral side groups show nearly the full optical rotation and exist predominantl…
Chiral donor–π-acceptor azobenzene dyes
2009
Abstract Four chiral donor–π-acceptor azobenzene dye conjugates were synthesized and characterized. Chiral moieties, namely (S)-(+)-2-(6-methoxy-2-naphthyl)propionic acid (naproxen) and (S)-2-aminopropionic acid ( l -alanine), were attached to either the donor end or the acceptor site of the azo compound using ester or amide bonds, respectively. The structures of the molecules were verified using 1H NMR, 13C NMR and ESI TOF mass spectrometry; spectral properties were evaluated with UV–vis and CD spectrometry whilst thermal stability was determined by TGA. The compounds displayed a broad absorption maximum in the visible region between 433 and 483 nm. All compounds showed relatively high the…
Novel azobenzene precursors for NLO active polyuretanes: Synthesis, quantum chemical and experimental characterization
2009
Abstract For the development of electro optical active polyurethanes six new derivatives of 2-{(2-hydroxyethyl)-[4-(4-nitrophenylazo)phenyl]amino}ethanol and two of 2-{(2-hydroxyethyl)-[4-(5-nitropyridin-2-ylazo)phenyl]amino}ethanol were synthesized by azocoupling reaction. Molecular geometry, hyperpolarizability βFF and ground state dipole moment μg were acquired by RHF ab initio (6–31G∗∗) calculations using HyperChem software package. To characterize NLO performance of synthesized azo compounds second order non linear coefficients d31 and d33 were measured as function of chromophore load in guest–host films (PMMA). Eight synthesized compounds can be grouped in four similar gross formula p…
1986
The terpolymerization of the three monomers (3-vinyl phenylazo)methylmalodinitrile (1), (3-vinyl phenylazo)phenylsulfid (2) or 1-(3-vinylphenylazo)-1,1′-diphenyl methylacetate (3) with methyl methacrylate and butanediol-1,4-dimethyacrylate leads to networks in which the thermolabile azo groups remain intact. Both, the azo monomer and the crosslinking agent are essentially quantitatively incorporated into the network before the conversion of the third monomer is complete. The networks have been characterized in terms of their swelling in benzene, chlorobenzene, and methacrylonitrile. Die Terpolymerisation der drei Monomeren (3-Vinylphenylazo)-methylmalodinitril (1), (3-Vinylphenylazo)phenyls…
Surface relief grating recording in azobenzene epoxy films
2018
This work has been supported by National research program IMIS2. I would like to thank Larisa Grigorjeva and Aleksejs Zolotarjovs from Institute of Solid state physics, University of Latvia for FTIR measurements.
4-hydroxy-ONN-azoxybenzene
2000
The oxidation of 4-hydroxyazobenzene provided a mixture of two azoxy compounds, which were separated by column chromatography. The isomer with the higher melting point appeared to belong to the α (ONN) series, as determined by X-ray diffraction. The molecule, C12H10N2O2, is almost planar. The benzene rings are twisted by 11.7 (2) (substituted) and 4.1 (1)° (unsubstituted) with respect to the ONN plane. The molecules are connected to one another by strong O—H⋯O hydrogen bonds forming chains extended along [001], which are bound by much weaker C—H⋯O hydrogen bonds forming layers in the bc plane.
Disorder in the crystals of trans-4-fluoroazoxybenzene. Synthesis, spectral properties, crystal structures and DFT calculations
2005
Abstract Two crystals of trans-4-fluoroazoxybenzene were obtained using two different methods. Oxidation of 4-fluoroazobenzene provided crystals of trans-4-fluoroazoxybenzene (I) consisting of two isomers; 51% α (ONN) and 49% β (NNO) isomer. From trans-amino-azoxybenzenes in Schiemann reaction it were obtained crystals of trans-4-fluoro-NNO-azoxybenzenes (II, β isomer) containing 4.7% of the α-isomer according to the HPLC analysis. The crystal structures of I and II were determined by the X-ray diffraction method. In the crystal I two nitrogen atoms of azoxy bridge and fluorine atom are disordered. In the crystal II, there are two independent molecules of trans-4-fluoroazoxybenzene; the mol…
Ādas mezenhimālo cilmes šūnu fenotipa raksturojums pēc neirotrofo faktoru inducētas neirodiferenciācijas
2015
Ādas mezenhimālās cilmes šūnas (Ā-MCš), pakļautas specifiskiem faktoriem, spēj diferencēties par neironiem un glijas šūnām. Maģistra darba mērķis bija analizēt Ā-MCš fenotipu pēc neirotrofo faktoru inducētas neirodiferenciācijas. Neiroektodermas gēnu ekspresiju Ā-MCš analizēja ar qPCR, cilmes šūnu pluripotences un mezenhimālo marķieru ekspresiju ar plūsmas citometriju, Sigma-1 receptora ekspresiju (SigmaR1) ar qPCR un IF, kā arī BDNF sekrēciju ar ELISA. Ā-MCš fenotipu salīdzināja ar ReNcell CX šūnām. Retīnskābes indukcijas barotnē novēroja nervu kores gēnu ekspresijas pieaugumu. Cilmes šūnu marķieru ekspresija pēc diferenciācijas kritās. Mezenhimālo marķieru ekspresija samazinājās vienā no …
Extact der Sämbelichen Landtäglichen Schlüssen de Anno MDCXVIII bis MDCCXLIV
1751
Die deutschen Ostseeprovinzen Rußlands: geschichtlich, kulturell und wirtschaftlich dargestellt von Kennern [Deutschen Ostseeprovinzen Russlands...]
1918
Inhalt: Geleitwort zu der aus Anlaß der Livland-Estland-Ausstellung erscheinenden Neuauflage / Theodor Schiemann. Geleitwort / Dr. Theodor Schiemann, Dr. Otto v. Beh. 1). Ueberblick über die Geschichte der deutsche Kolonie an der Ostsee / von Theodor Schiemann. 2). Die Bevölkerung / von H.v.R. 3). Politische Verfassung und Selbstverwaltung des Landes / von Georg Freiherrn v. Satz. 4). Die Städte / von Arend Buchholtz. 5). Agrarverfassung und Landwirtschaft / von Wilhelm Bührig. 6). Handel und Industrie / von Hermann Hassel. 7). Evangelisch-lutherische Kirche und Gewissensfreiheit / von Christian v. Bornhaupt. 8). Das Unterrichtswesen / von Leopold Krüger. 9). Recht und Gericht / von Otto v.…