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Michel W Barsoum – One of the best experts on this subject based on the ideXlab platform.

  • new solid solution max phases ti0 5 v0 5 3alc2 nb0 5 v0 5 2alc nb0 5 v0 5 4alc3 and nb0 8 zr0 2 2alc
    Materials research letters, 2014
    Co-Authors: Michael Naguib, Grady W Bentzel, J Shah, Joseph Halim, El'ad N. Caspi, Jun Lu, Lars Hultman, Michel W Barsoum

    Abstract:

    We synthesized the following previously unreported aluminum-containing solid solution Mn+1AXn phases: (Ti0.5, V0.5)3AlC2, (Nb0.5, V0.5)2AlC, (Nb0.5, V0.5)4AlC3 and (Nb0.8, Zr0.2)2AlC. Rietveld analysis of powder X-ray diffraction patterns was used to calculate the lattice parameters and phase fractions. Heating Ti, V, Al and C elemental powders—in the molar ratio of 1.5:1.5:1.3:2—to 1, 450°C for 2 h in flowing argon, resulted in a predominantly phase pure sample of (Ti0.5, V0.5)3AlC2. The other compositions were not as phase pure and further work on optimizing the processing parameters needs to be carried out if phase purity is desired.

  • synthesis and oxidation of ti2inc zr2inc ti0 5 zr0 5 2inc and ti0 5 hf0 5 2inc in air
    Journal of Alloys and Compounds, 2006
    Co-Authors: S. Gupta, Elizabeth N. Hoffman, Michel W Barsoum

    Abstract:

    Abstract In this paper, we report on the synthesis and oxidation behavior of Ti 2 InC, Zr 2 InC, (Ti 0.5 ,Hf 0.5 ) 2 InC and (Ti 0.5 ,Zr 0.5 ) 2 InC. The oxidation kinetics were studied thermogravimetrically in air in the 400–700 °C temperature range. With the exception of Ti 2 InC, the oxide layers formed failed to offer any oxidation resistance at 400 °C or higher temperatures. The reaction products are In 2 O 3 , in which some transition metal ions are probably dissolved, and the transition metal oxides. The latter are either amorphous or nanocrystalline. In the case of Ti 2 InC, a protective oxide was formed at 500 °C. However, at higher temperatures, after an incubation period, catastrophic oxidation ensued. In all cases, the oxidation occurred by the inward diffusion of oxygen.

Daniel Hoyer – One of the best experts on this subject based on the ideXlab platform.

  • Localization of 5-HT1B, 5-HT1Dα, 5-HT1E and 5-HT1F receptor messenger RNA in rodent and primate brain
    Neuropharmacology, 1994
    Co-Authors: Anne T. Bruinvels, Daniel Hoyer, B. Landwehrmeyer, Eric L. Gustafson, Margaret M. Durkin, Guadalupe Mengod, Theresa Branchek, José M. Palacios

    Abstract:

    In situ hybridization histochemistry (ISHH) was used to study the distribution of various 5-HT1 receptor messenger RNAs (mRNA) in the mammalian nervous system. Since the cDNAs encoding the different 5-HT1 receptors, have not been cloned in one single species, brains of the species appropriate for the 5-HT1 receptor messenger RNA (mRNA) have been used. Thus, 5-HT1B and 5-HT1Dα, mRNA were determined in rat and mouse brain, while 5-HT1E and 5-HT1F mRNA were studied in human (and monkey) and guinea-pig brain, respectively.

    5-HT1B and 5-HT1Dα hybridization signals were predominantly present in caudate-putamen and cortical areas; in addition, 5-HT1B mRNA was also detected in hippocampus, cerebellum and cerebral arteries. In general, the distribution of 5-HT1B mRNA was characterized by high densities, whereas 5-HT1Dα mRNA was expressed at very low levels. Comparison of the localization of the mRNAs to the regional distributions of the 5-HT1B and 5-HT1D binding sites in rat brain (described in a previous study), revealed that both receptor subtypes could be putative presynaptic heteroreceptors, modulating the release of various neurotransmitters in the central nervous system.

    The mRNA encoding the recently cloned 5-HT1E receptor, which has low affinity for the 5-HT1 receptor ligand 5-carboxamidotryptamine (5-CT), was localized in human brain. It was found to be present in cortical areas, caudate, putamen and amygdala, areas known to contain 5-CT insensitive 5-HT1 binding sites.

    The regional distribution of the 5-HT1Fip mRNA was determined in guinea-pig brain: high densities were observed in various cortical areas, the hippocampal formation and claustrum, which are regions known to contain 5-CT insensitive 5-HT1 or non 5-HT1A/1B/1C/1D[3H]5-HT binding sites.

    Altogether, this ISHH study describes the distribution of mRNAs of recently cloned 5-HT1 receptors in rodent and primate brain and compares these results to the distribution of the heterogeneous population of 5-HT1 binding sites.

  • interaction of the α adrenoceptor agonist oxymetazoline with serotonin 5 ht1a 5 ht1b 5 ht1c and 5 ht1d receptors
    European Journal of Pharmacology, 1991
    Co-Authors: Philippe Schoeffter, Daniel Hoyer

    Abstract:

    Oxymetazoline was recognized with nanomolar affinity by 5-HT1A, 5-HT1B and 5-HT1D binding sites and mimicked the effects of 5-hydroxytryptamine with about the same potency and intrinsic activity as the endogenous amine in the corresponding functional tests. At 5-HT1C receptors, oxymetazoline behaved as a mixed agonist-antagonist. Clonidine had minimal activity. Methiothepin antagonized the effects of oxymetazoline (7.4 5-HT1A, 5-HT1B and 5-HT1D receptors and a partial agonist at 5-HT1C receptors.

  • Interaction of the α-adrenoceptor agonist oxymetazoline with serotonin 5-HT1A, 5-HT1B, 5-HT1C and 5-HT1D receptors
    European Journal of Pharmacology, 1991
    Co-Authors: Philippe Schoeffter, Daniel Hoyer

    Abstract:

    Oxymetazoline was recognized with nanomolar affinity by 5-HT1A, 5-HT1B and 5-HT1D binding sites and mimicked the effects of 5-hydroxytryptamine with about the same potency and intrinsic activity as the endogenous amine in the corresponding functional tests. At 5-HT1C receptors, oxymetazoline behaved as a mixed agonist-antagonist. Clonidine had minimal activity. Methiothepin antagonized the effects of oxymetazoline (7.4

David Shugar – One of the best experts on this subject based on the ideXlab platform.

  • interaction of thymidylate synthase with the 5 thiophosphates 5 dithiophosphates 5 h phosphonates and 5 s thiosulfates of 2 deoxyuridine thymidine and 5 fluoro 2 deoxyuridine
    Biological Chemistry, 2001
    Co-Authors: Barbara Golos, Jolanta M Dzik, Z Kazimierczuk, Joanna Ciesla, Zbigniew Zielinski, Jadwiga Jankowska, Adam Kraszewski, Jacek Stawinski, W Rode, David Shugar

    Abstract:

    : New analogs of dUMP, dTMP and 5-fluoro-dUMP, including the corresponding 5‘-thiophosphates (dUMPS, dTMPS and FdUMPS), 5‘-dithiophosphates (dUMPS2, dTMPS2 and FdUMPS2), 5‘-H-phosphonates (dUMP-H, dTMP-H and FdUMP-H) and 5‘-S-thiosulfates (dUSSO3, dTSSO3 and FdUSSO3), have been synthesized and their interactions studied with highly purified mammalian thymidylate synthase. dUMPS and dUMPS2 proved to be good substrates, and dTMPS and dTMPS2 classic competitive inhibitors, only slightly weaker than dTMP. Their 5-fluoro congeners behaved as potent, slow-binding inhibitors. By contrast, the corresponding 5‘-H-phosphonates and 5‘-S-thiosulfates displayed weak activities, only FdUMP-H and FdUSSO3 exhibiting significant interactions with the enzyme, as weak competitive slow-binding inhibitors versus dUMR The pH-dependence of enzyme time-independent inhibition by FdUMP and FdUMPS was found to correlate with the difference in pKa values of the phosphate and thiophosphate groups, the profile of FdUMPS being shifted (approximately 1 pH unit) toward lower pH values, so that binding of dUMP and its analogs is limited by the phosphate secondary hydroxyl ionization. Hence, together with the effects of 5‘-H-phosphonate and 5‘-S-thiosulfate substituents, the much weaker interactions of the nucleotide analogs (3-5 orders of magnitude lower than for the parent 5‘-phosphates) with the enzyme is further evidence that the enzyme’s active center prefers the dianionic phosphate group for optimum binding.