Synthesis of spiro-pyridopyridine analogues by Grubbs' catalyst mediated alkene and enyne metathesis reaction

A practical synthesis of spiro-naphthyridinone derivatives is described by the combination of the Claisen rearrangement and ring-closing metathesis/ring-closing enyne metathesis process. The RCM or RCEM proceeded smoothly in the presence of Grubbs' first generation catalyst at room temperature under a nitrogen atmosphere.     

Wormholes supported by polytropic phantom energy

It is generally agreed that the acceleration of the Universe can best be explained by the presence of dark or phantom energy. The equation of state of the latter shows that the null energy condition is violated. Such a violation is the primary ingredient for sustaining traversable wormholes. This paper discusses wormholes supported by a more general form called polytropic phantom energy. Its equation of state results in significant generalizations of the phantom-energy and, in some cases, the generalized Chaplygin-gas wormhole models, both of which continue to receive considerable attention from researchers. Several specific solutions are explored, namely, a constant redshift function, a particular choice of the shape function, and an isotropic-pressure model with various shape functions. Some of the wormhole spacetimes are asymptotically flat, but most are not.     

Thin-shell wormholes from charged black holes in generalized dilaton-axion gravity

This paper discusses a new type of thin-shell wormhole constructed by applying the cut-and-paste technique to two copies of a charged black hole in generalized dilaton-axion gravity, which was inspired by low-energy string theory. After analyzing various aspects of this thin-shell wormhole, we discuss its stability to linearized spherically symmetric perturbations.     

Mass measurements in the endpoint region of the rp-process at SHIPTRAP

The Penning-trap mass spectrometer SHIPTRAP was designed for precision mass measurements of radionuclides produced in fusion–evaporation reactions. The latest measurement campaign covered heavy nuclei (A>90) related to the astrophysical rapid proton capture process. The masses of 34 neutron-deficient radionuclides have been measured since February 2006 with relative uncertainties between 5×10⁻⁸ and 1×10⁻⁷. Furthermore, the use of an octupolar RF excitation for the time-of-flight ion-cyclotron-resonance technique was investigated and an increase of the resolving power by a factor of ten was observed in agreement with simulations. This will allow to resolve isomeric states with excitation energies of a few 10 keV only.      

Experimental studies at JYFLTRAP

JYFLTRAP is a Penning trap system at the accelerator laboratory in Jyväskylä, Finland that enables high-precision experiments with stored, exotic species that are produced at the IGISOL facility. On one hand, these can be performed within the trap itself, like e.g. mass spectrometry. On the other hand, the trap can be used to provide the highly purified species for further experiments, e.g. for trap-assisted nuclear decay spectroscopy. This contribution focuses on these two possible applications with the presentation of some recent results on superallowed beta decays.     

Higher dimensional homogeneous cosmology in Lyra geometry

Assuming a homogeneous perfect fluid withρ =ρ(t) andp =p(t), we have obtained exact solutions for cosmological models in higher-dimension based on Lyra geometry. Depending on the form of metric chosen, the model is similar to FRW type. The explicit solutions of the scale factor are found via the assumption of an equation of statep =mρ, where m is a constant. Some astrophysical parameters are also calculated.     

The Finslerian compact star model

We construct a toy model for compact stars based on the Finslerian structure of spacetime. By assuming a particular mass function, we find an exact solution of the Finsler–Einstein field equations with an anisotropic matter distribution. The solutions are revealed to be physically interesting and pertinent for the explanation of compact stars.     

On thermal instabilities in a viscoelastic fluid

The Bénard-Marangoni thermal instability problem for a viscoelastic Jeffreys’ fluid layer bounded above by a realistic free deformable surface and by a plane surface below is investigated using a linear stability analysis. It has been shown that both the relaxation time and surface deflection have a destabilizing effect unlike the retardation time. A point of codimension 2 has been identified which means that instability here takes the form of a competition between stationary and oscillatory convections. When the lower boundary is free but plane, an analytic treatment has identified an oscillatory disturbance with zero critical wavenumber which is not found in the absence of surface deformation.