Yazar "Demirel, N" seçeneğine göre listele

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    All-solid-state PVC membrane Ag+-selective electrodes based on diaza-18-crown-6 compounds
    (Springer Wien, 2004) Isildak, I; Yolcu, M; Isildak, O; Demirel, N; Topal, G; Hosgoren, H
    Two diaza-crown ether compounds were synthesized and evaluated as Ag+-selective carriers in polyvinylchloride (PVC) membrane electrodes of solid-state type. The all-solid-state PVC membrane electrode based on N,N-Dibenzyl-dibenzo-diaza-18-crown-6 exhibited a super-Nernstian response (75+/-10 mV per decade) over the concentration range of 1x10(-1) to 7x10(-6) M of Ag+ ion and a detection limit of 3x10(-6) M, at a wide range of pH (pH 4-7). The response time of the electrode was fast (less than similar to10s), and it can be used for three months without any significant deviation in potential. The proposed all-solid-state PVC membrane electrodes revealed high selectivity toward Ag+ ion with respect to alkali, alkaline earth, heavy and transition metal ions. A flow-through cell of all-solid-state PVC membrane Ag+-selective electrode based on N,N-Dibenzyl-dibenzo-diaza-18-crown-6 has also been prepared and applied for flow-injection analysis of Ag+ ion in solution.
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    Chiral separation of amino acids by chiral octamide derivatives of calixarenes derived from resorcinol by impregnation on a polymeric support
    (Pergamon-Elsevier Science Ltd, 2005) Seyhan, S; Özbayrak, Ö; Demirel, N; Merdivan, M; Pirinccioglu, N
    Chiral amide derivatives of octaester calixresorcarene were synthesized and employed as chiral stationary phases for chiral discrimination of amino acid derivatives. Enantiomers of phenylglycine and tryptophan were easily discriminated as their sodium and potassium salts. In addition, phenylalanine-trytophan, phenylglycine-trytophan mixtures were separated by column chromatography. (c) 2005 Elsevier Ltd. All rights reserved.
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    Crystal structure of an inclusion complex between chiral monoaza-15-crown-5 and S(-)-1-phenyl-ethyl ammonium percholorate
    (R Oldenbourg Verlag, 2003) Özbey, S; Kaynak, FB; Togrul, M; Demirel, N; Hosgören, H
    A new type of inclusion complex, S(-)-1 phenyl ethyl ammonium percholorate complex of R-(-)-2-ethyl-N-benzyl-4,7,10,13-tetraoxa-1-azacyclopentadecane, has been prepared and studied by NMR, IR and single crystal X-ray diffraction techniques. The compound crystallizes in space group P2(1) with cell dimensions a = 10.0000(8), b - 12.281(2), c = 12.331(1)Angstrom, beta = 102.052(7), Z = 2. The host-guest complex is held together by a strong system of hydrogen bonds between the two protons of the ammonium ion as well as the nitrogen and four oxygen atoms of the crown ether The C-O and C-C distances of the 15-membered ring average 1.418 and 1.501 Angstrom while the O-C-C and C-O-C angles average 110.2 and 113.3degrees. The average N-C distance is 1.476 Angstrom.
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    The effect of benzo substitution on complexation of diaza 18-crown-6 ethers derivatives with NaClO4
    (Springer, 2005) Köylü, MZ; Demirel, N; Polat, FD; Yilmaz, A; Hosgören, H; Balci, M
    The complexation of the crown ethers with Na+ ion was studied. H-1-NMR chemical shifts are discussed in terms of structural modi. cation as well as also binding studies with UV-vis spectra were included.
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    Enantioselective transport of amino acids as their potassium and sodium salts by optically active diaza-18-crown-6 ethers having arene sidearms
    (Pergamon-Elsevier Science Ltd, 2004) Demirel, N; Bulut, Y; Hosgören, H
    The enantioselective transport of amino acids as their sodium and potassium salts has been investigated by optically active diaza crown ethers. The reversed enantioselectivity of chiral crown ether 1 was observed. (C) 2004 Elsevier Ltd. All rights reserved.
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    Serum zinc and copper levels in southeastern Turkish children with giardiasis or amebiasis
    (Humana Press Inc, 2001) Karakas, Z; Demirel, N; Tarakcioglu, M; Mete, N
    Alterations of serum zinc (Zn) and copper (Cu) concentrations are commonly found in patients suffering from gastrointestinal infections and with hepatic, renal, cardiovascular, and malignant diseases. In this study, the serum Zn and Cu levels in 20 children with giardiasis and in 40 children with amebiasis were evaluated. The serum Zn levels showed a significant decrease when compared to controls (p<0.001). After metronidazole therapy, a significant increase in Zn levels was observed (p<0.001). There was no significant difference in serum Cu levels between patients and controls before therapy. Before therapy, the serum Cu/Zn ratio in children with either giardiasis or amebiasis was significantly higher than that of the control group. After therapy, the Cu/Zn ratio was found to be back to normal. There were no significant differences in serum Zn levels and Cu/Zn ratios between children with and without diarrhea and there was no significant difference in children with or without failure to thrive. We concluded that Zn deficiency and elevated Cu/Zn ratio could be acute-phase responses to parasitic infections in children with giardiasis or amebiasis and that a successful treatment of the primary disorder will lead to complete recovery. Further studies are in progress to confirm the benefit of Zn supplementation during the acute phase of the disease, particularly in zinc-deficient regions of the world, such as in the case of Turkey.
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    Synthesis of chiral crown ethers and complexation with chiral protonated amine compounds
    (Springer, 2004) Togrul, M; Demirel, N; Kaynak, FB; Özbey, S; Hosgören, H
    The X-ray crystal structure of IX, perchlorate salt of R-(-)-2-ethyl-N-benzyl-4,7,19,13-tetraoxa-8,9-benzo-1-azacyclopentadec-8-ene has been determined. In the molecule, the protonated nitrogen atom participates in two N-(HO)-O-... hydrogen bonds. The unusually high proton affinity of aza crown ether leads to the formation of diastreomer instead of complex formation with chiral R-(+)-1-phenyl ethyl ammonium perchlorate and S-(-)-1-phenyl ethyl ammonium perchlorate. The complex ability of host ethers was evaluated in terms of structural modification.
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    Synthesis of chiral diaza 18-crown-6 ethers from chiral amines and molecular recognition of potassium and sodium salts of amino acids
    (Pergamon-Elsevier Science Ltd, 2003) Demirel, N; Bulut, Y
    A practical synthesis of chiral amine precursors 3 and 4 and chiral diaza 18-crown-6 ethers 5. 6 and 7 starting from chiral amines are reported. The molecular recognition of these chiral crown ethers for amino acids potassium and sodium salts has been characterized by UV-vis. The selectivity order is Phe>Thr>Ala. In the case of 6 the cavity of the macrocycle plays ail important role in recognition. (C) 2003 Elsevier Ltd. All rights reserved.
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    Synthesis of new chiral diaza 18-crown-6 ethers from chiral amines
    (Science Reviews 2000 Ltd, 2003) Demirel, N; Turgut, Y; Hosgören, H
    Practical syntheses of versatile building blocks of crown ethers 1 and 2, chiral amine precursors 3-6 and chiral diaza 18-crown-6 ethers 7-12 are reported starting from chiral amines.
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    Synthesis of novel chiral C2-symmetric diaza-18-crown-6 ether derivatives and their enantioselective recognition of amino acid derivatives
    (Springer, 2006) Turgut, Y; Demirel, N; Hosgören, H
    New chiral diaza-18-crown-6 ether derivatives, 5 and 6 were synthesized from (R)-(-)-2-amino-1-butanol. These chiral artificial receptors exhibit pronounced chiral recognition toward the enantiomers of L- and D- amino acid derivatives. The highest enantioselectivity was observed in the case of Trp-OMe center dot HCl (K-D/ K-L= 12.5).
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    Synthesis of R-(-)-2-ethyl-N-benzyl (benzo-monoaza-15-crown-5) and the crystal structure of its sodium perchlorate complex
    (Springer, 2003) Özbey, S; Kaynak, FB; Togrul, M; Demirel, N; Hosgören, H
    A new complex of a chiral monoaza-crown ether, [R-(-)-2-ethyl-N-benzyl-4,7,10,13-tetraoxa-8,9-benzo-1-azacyclopentadec-8-ene.NaClO4], has been prepared and studied by x-ray diffraction. The compound crystallizes in space group P2(1) with cell dimensions a = 8.721(1), b = 16.318(2), c = 8.905( 1) Angstrom, beta = 100.80(1)degrees. The sodium cation is heptacoordinated and located significantly out of the best plane of the macrocycle ring. The donor atoms of the macrocycle are in the half-chair arrangement.
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    Thorium(IV) and uranium(VI) sorption studies on octacarboxymethyl-C-methylcalix[4]resorcinarene impregnated on a polymeric support
    (Elsevier, 2003) Demirel, N; Merdivan, M; Pirinccioglu, N; Hamamci, C
    The impregnation of octacarboxymethyl-C-methylcalix[4]resorcinarene into a polymeric matrix, Amberlite XAD-4, is reported and was characterized by infrared spectroscopy. The sorption capacity of the impregnated resin is 0.34 x 10(-3) mol g(-1). The resin was used for the sorption of thorium(IV) and uranium(VI) from aqueous solution. The properties of capacity, pH effect, and breakthrough curves of the impregnated resin were investigated. The capacity of the resin for Th(IV) and U(VI) was found to be 0.29 and 0.27 x 10(-3) mol g(-1), respectively. The metal ions were eluted with 0.4-2 M HCl or HNO3. Chromatographic separation of Th(W) and U(VI) was accomplished by adjustment of pH to 3.0 and 6.0, respectively. The impregnated resin exhibits a high chemical stability, reusability and fast equilibration. Separation of Th(W) and U(VI) from other metal cations in synthetic solution was achieved. (C) 2003 Elsevier Science B.V. All rights reserved.