13C NMR substituent effects in tetracyclic diterpenoids

The ¹³C NMR chemical shifts of ent-beyer-15-ene, and one hydroxy and four acetoxy derivatives are reported. The substituent effects of the acetoxy groups upon the saturated and olefinic carbon atoms are discussed. Conformational aspects of the molecules are considered in the light of these effects.     

Nickel supported carbon nanofibers as an active and selective catalyst for the gas-phase hydrogenation of 2-tert-butylphenol

Nickel supported fishbone carbon nanofibers (CNFs) have been prepared by vacuum impregnation (VI) and homogeneous deposition-precipitation (HDP) methods with different nickel loadings (ca. 5%, 9% and 12%) with the aim to study the influence of the metal incorporation method and the nickel loading in the catalytic activity of gas-phase hydrogenation of 2-tert-butylphenol (2-TBP). Moreover, the influence of the nature of the support was also studied by preparing nickel catalysts supported on other carbon (active carbon (AC) and graphite (G)) and non-carbonaceous materials (alumina (AL) and yttria-stabilized zirconia (YSZ)). Different techniques were employed to characterize both the supports and the final Ni catalysts: atomic absorption spectrometry, N(2) adsorption-desorption analysis, temperature-programed reduction (TPR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Catalytic results revealed that the nickel particle size and support properties affected directly to both the catalytic activity of hydrogenation of 2-TBP, and the rate of secondary reactions such as cis to trans isomerization and 2-tert-butylcyclohexanone (2-TBCN) hydrogenation.     

Trace asymptotics for fractional Schrödinger operators

This paper proves an analogue of a result of Bañuelos and Sá Barreto [5] on the asymptotic expansion for the trace of Schrödinger operators on R^d${\mathbb{R}}^d$ when the Laplacian −Δ, which is the generator of the Brownian motion, is replaced by the non-local integral operator (−Δ)^α/2${(-\mathrm{\Delta })}^{\alpha /2}$, 0<α<2$0<\alpha <2$, which is the generator of the symmetric stable process of order α. These results also extend recent results of Bañuelos and Yildirim [6] where the first two coefficients for (−Δ)^α/2${(-\mathrm{\Delta })}^{\alpha /2}$ are computed. Some extensions to Schrödinger operators arising from relativistic stable and mixed-stable processes are obtained.     

Click à la carte: robust semi-orthogonal alkyne protecting groups for multiple successive azide/alkyne cycloadditions

We herein describe an in-depth screening and systematic comparison of five classical silyl alkyne protective groups, to evaluate their potential in the context of multiple successive copper (I)-catalyzed alkyne-azide cycloadditions (CuAAC). We confirm the relative sensitivity of TMS, especially under CuAAC conditions. The relative robustness of its higher analogues, and the discovery of mild silver-catalyzed deprotection conditions selective for TES compared to DPS or TIPS allowed us to design a strategy allowing three successive CuAAC on a single scaffold, as we have illustrated by the synthesis of a tris-triazolo model compound.     

Untersuchung der Aufl?sungsgeschwindigkeit von tern?ren Oxiden in S?uren

Ohne Zusammenfassung     

Quantum communication via controlled holes in the statistical distribution of excitations in a nanoresonator coupled to a Cooper pair box

We propose a scheme to transmit information via the statistical distribution of excitations of a nanomechanical resonator.It employs a controllable coupling between this system and a Cooper pair box.The success probability and the fidelity are calculated and compared with those obtained in an atom-field system in different regimes.Addtionaly,the scheme can also be applied to prepare low excited Fock states.     

Oscillatory behavior of Rh/YSZ under electropromoted conditions

Electrochemical induced oscillations were studied during ethylene oxidation over Rh films deposited on YSZ. Oscillations period and amplitude were for the first time analyzed depending on the applied potential or current, related with cyclic oxidation and reduction reactions and discussed on the basis of the phenomenon of the electrochemical promotion of catalysis.     

Improving the analysis of Y‐SNP haplogroups by a single highly informative 16 SNP multiplex PCR‐minisequencing assay

The SNP haplogroups of the Y‐chromosome are nonrandomly distributed among human populations. They are used for tracing the phylogeographical history of paternal lineages of male individuals and can be a useful tool for approaching the patrilineal bio‐geographic ancestry of unknown forensic evidences. With the aim of facilitating the inference of the principal informative worldwide Y‐SNP haplogroups, we have selected the minimum possible number of key Y‐SNPs to be amplified in a sensitive single multiplex PCR and detected by minisequencing. This assay, that includes 16 Y‐SNPs, was tested for male human specificity, sensitivity, and reproducibility. Its effectiveness was assessed in a set of degraded DNA samples and in a panel of male individuals from different worldwide populations. All these tests demonstrated the convenience of this assay for assigning the major Y haplogroups to forensic evidences by one single PCR‐minisequencing reaction.     

Single Peptide Backbone Surrogate Mutations to Regulate Angiotensin GPCR Subtype Selectivity

Mutating the side-chains of amino acids in a peptide ligand, with unnatural amino acids, aiming to mitigate its short half-life is an established approach. However, it is hypothesized that mutating specific backbone peptide bonds with bioisosters can be exploited not only to enhance the proteolytic stability of parent peptides, but also to tune its receptor subtype selectivity. Towards this end, four [Y]⁶-Angiotensin II analogues are synthesized where amide bonds have been replaced by 1,4-disubstituted 1,2,3-triazole isosteres in four different backbone locations. All the analogues possessed enhanced stability in human plasma in comparison with the parent peptide, whereas only two of them achieved enhanced AT₂R/AT₁R subtype selectivity. This diversification has been studied through 2D NMR spectroscopy and unveiled a putative more structured microenvironment for the two selective ligands accompanied with increased number of NOE cross-peaks. The most potent analogue, compound 2 , has been explored regarding its neurotrophic potential and resulted in an enhanced neurite growth with respect to the established agent C21.