Radical addition of nitrones to acrylates mediated by SmI2: asymmetric synthesis of gamma-amino acids employing carbohydrate-based chiral auxiliaries

Alkyl nitrones possessing N-substituted sugars as chiral auxiliaries were found to effectively undergo an SmI(2)-mediated radical addition to n-butyl acrylate affording gamma-amino acid derivatives with high diastereomeric control.     

Low reheating temperature and the visible sterile neutrino

We present here a scenario, based on a low reheating temperature T(R)<100 MeV at the end of (the last episode of) inflation, in which the coupling of sterile neutrinos to active neutrinos can be as large as experimental bounds permit (thus making this neutrino "visible" in future experiments). In previous models this coupling was forced to be very small to prevent a cosmological overabundance of sterile neutrinos. Here the abundance depends on how low the reheating temperature is. For example, the sterile neutrino required by the Liquid Scintillator Neutrino Detector result may not have any cosmological problem within our scenario.     

Loops, Reflection Structures and Graphs with Parallelism

The correspondence between right loops (P, +) with the property “(*) ?a, b ∈ P : a ? (a ? b) ? b” and reflection structures described in [4] is extended to the class of graphs with parallelism (P, ε, ∥). In this connection K-loops correspond with trapezium graphs, i.e. complete graphs with parallelism satisfying two axioms (T1), (T2) (cf. §3 ). Moreover (P, ε, ∥ +) is a structure loop (i.e. for each a ∈ P the map a ⁺ : P → P; x → a + x is an automorphism of the graph with parallelism (P, ε, ∥)) if and only if (P, +) is a K-loop or equivalently if (P, ε, ∥) is a trapezium graph.     

Observation of self-focusing of light mediated by cubic nonlinearities in potassium titanyl phosphate

We report our observations of the transient self-narrowing of light beams mediated by dominant Kerr nonlinearities and two-photon absorption in a bulk potassium titanyl phosphate crystal near conditions for second-harmonic generation. Drastic differences between upconversion and downconversion processes are highlighted.     

Palladium nanoparticles stabilised by polyfluorinated chains

Palladium nanoparticles can be prepared by reduction of palladium(II) chloride in the presence of different compounds featuring long perfluorinated carbon chains.     

Crossed graphene: Stability and electronic structure

Carbon has always attracted attention due to its rich chemistry and the almost complementary properties of the natural phases graphite and diamond. While graphite is a highly anisotropic semi‐metal, diamond shows high hardness and thermal conductivity and is a wide‐gap insulator. With the discovery of graphene, fullerenes, and carbon nanotubes which resemble properties of the two crystalline phases, research on those and novel carbon materials emerged. Since carbon is forming different covalent bonds, there is a multitude of possibilities to create new structures by just combining sp, sp², and sp³ bonded carbon. Here we report on the discovery of a new sp² and sp³ bonded carbon structure which can be seen as a crossed graphene structure providing hybrid properties of graphene and diamond by means of an evolutionary algorithm.

     

Notes on projective normality of reducible curves

We give some results on quadratic normality of reducible curves canonically embedded and partially extend this study to their projective normality.     

Trifunctionalization of the purine scaffold using Mg and Zn organometallic intermediates

Starting from an appropriate 6-chloro-2-TMS-purine derivative, a regioselective functionalization of the purine scaffold was achieved successively at positions 8, 6, and 2 via zinc and magnesium intermediates which were generated either by a direct zincation with TMPZnCl·LiCl or by an I/Mg exchange with iPrMgCl.