[en] The isoxazole amino acid 2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl) propionic acid (AMPA) (1), which is a highly selective agonist at the AMPA subtype of excitatory amino acid (EAA) receptors, has been used as a lead for the development of two novel EAA receptor antagonists. One of the compounds, 2-amino-3-[3-(carboxymethoxy)-5-methylisoxazol-4-yl]propionic acid (AMOA, 7), was synthesized via O-alkylation by ethyl chloroacetate of the amino acid protected AMPA derivative 4. The other compound, 2-amino-3-[2-(3-hydroxy-5-methylisoxazol-4-yl)-methyl-5-methyl-3-+ ++oxoisoxazolin -4-yl]propionic acid (AMNH, 14) was synthesized with use of 4-(chloromethyl)-3-methoxy-5-methylisoxazole (8) as the starting material. The intermediate 4-(chloromethyl)-2-(3-methoxy-5-methylisoxazol-4-yl)methyl-5-me thylisoxazolin- 3-one (11) was converted into the acetamidomalonate (12), which was stepwise deprotected to give 14. Compounds 7 and 14 were stable in aqueous solution at pH values close to physiological pH. Neither 7 nor 14 showed detectable affinities for the receptor, ion channel, or modulatory sites of the N-methyl-D-aspartic acid (NMDA) receptor complex. Quantitative receptor autoradiographic and conventional binding techniques were used to study the affinities of 7 and 14 for non-NMDA receptor sites. Both compounds were inhibitors of the binding of [3H]AMPA (IC50 = 90 and 29 microM, respectively). Compounds 14 and 7 were both very weak inhibitors of the high-affinity binding of radioactive kainic acid [(3H]KAIN). Compound 14, but not 7, was, however, shown to be an inhibitor of low-affinity [3H]KAIN binding as determined in the presence of 100 mM calcium chloride. In the rat cortical slice preparation, 7 was shown to antagonize excitation induced by 1 with some selectivity, whereas 14 proved to be a rather selective antagonist of KAIN-induced excitation

[en] The possibility to synthesize honeycomb silicene has recently been demonstrated upon providing compelling evidence through the combination of complementary experimental results and density functional theory calculations (Vogt et al 2012 Phys. Rev. Lett. 108 155501). In this case silicene is grown on Ag(111) substrates and shows a nearest neighbour distance of two Si atoms of ∼0.23 nm in agreement with theoretical results for free-standing silicene. In another publication from another group of authors a different silicene arrangement has been claimed previously, where the silicene sheet is strongly compressed with a Si-Si distance amounting to only 0.19 nm (Lalmi et al 2010 Appl. Phys. Lett. 97 223109). This has led to the fundamental question whether silicene could support such a large compressive strain. We will show that the apparent contradictions in the literature can be explained based on a thorough analysis, which reveals that the pure Ag(111) surface can mimic a honeycomb structure, which could easily be misinterpreted as a strained silicene layer. Our discussion will show that there is no evidence for the existence of such strong compressively strained silicene layers.

[en] The nuclear structure of ¹²²Xe has been investigated with measurements of the β⁺/EC decay of ¹²²Cs with the 8π γ-ray spectrometer at the TRIUMF-ISAC facility. The data collected have enabled the determination of relative B(E2) values of some low-energy transitions, and the in-band transitions of the excited 0⁺ bands have been observed. As a result, the 2⁺ rotational band members for the 0₂⁺ and 0₃⁺ states have been firmly identified. (authors)

[en] In this study we report on the modification of the InP(001)(2 x 4) surface upon C₅H₈ exposure, observed by reflectance anisotropy spectroscopy (RAS), synchrotron based PES (SXPS) and LEED. The samples were prepared in ultra high vacuum and the reconstruction formation was controlled by LEED and RAS. The characteristic features at 1.8 eV in the RAS spectra related to the InP(2 x 4) surface is reduced during the deposition of the molecules and shifted towards higher photon energies. SXPS measurements of the C 1s, In 4d and P 2p core level confirm a covalent bonding of the C₅H₈ molecules to the top In-P mixed dimer. The molecules can be desorbed at 400 C and the (2 x 4) reconstruction can be restored. The comparison to DFT total energy calculations supports an interaction between C5H8 and the top-layer dangling bonds. From these results a structural model for the absorption of C₅H₈ on the InP(2 x 4) surface is proposed

[en] The epitaxial growth and the electrical resistance of multilayer silicene on the Ag(111) surface has been investigated. We show that the atomic structure of the first silicene layer differs from the next layers and that the adsorption of Si induces the formation of extended silicene terraces surrounded by step bunching. Thanks to the controlled contact formation between the tips of a multiple probe scanning tunneling microscope and these extended terraces, a low sheet resistance, albeit much higher than the electrical resistance of the underlying silver substrate, has been measured, advocating for the electrical viability of multilayer silicene

[en] The low energy excited $0_{2,3}^{+}$ states in ⁹⁶Sr are amongst the most prominent examples of shape coexistence across the nuclear landscape. In this work, the neutron ${[2s_{1/2}]}^2$ content of the $0_{1,2,3}^{+}$ states in ⁹⁶Sr was determined by means of the d(⁹⁵Sr, p) transfer reaction at the TRIUMF-ISAC2 facility using the SHARC and TIGRESS arrays. Spectroscopic factors of 0.19(3) and 0.22(3) were extracted for the ⁹⁶Sr ground and 1229 keV $0^{+}$ states, respectively, by fitting the experimental angular distributions to DWBA reaction model calculations. A detailed analysis of the γ-decay of the isomeric $0_3^{+}$ state was used to determine a spectroscopic factor of 0.33(13). The experimental results are compared to shell model calculations, which predict negligible spectroscopic strength for the excited $0^{+}$ states in ⁹⁶Sr. The strengths of the excited $0_{2,3}^{+}$ states were also analyzed within a two-level mixing model and are consistent with a mixing strength of $a^2=0.40(14)$ and a difference in intrinsic deformations of $|\mathrm{\Delta }\beta |=0.31(3)$. These results suggest coexistence of three different configurations in ⁹⁶Sr and strong shape mixing of the two excited $0^{+}$ states.