Fragmentation of Single-Particle Strength around the Doubly Magic Nucleus

Spectroscopic factors of neutron-hole and proton-hole states in ^{131}Sn and ^{131}In, respectively, were measured using one-nucleon removal reactions from doubly magic ^{132}Sn at relativistic energies. For ^{131}In, a 2910(50)-keV γ ray was observed for the first time and tentatively assigned to a decay from a 5/2^{-} state at 3275(50) keV to the known 1/2^{-} level at 365 keV. The spectroscopic factors determined for this new excited state and three other single-hole states provide first evidence for a strong fragmentation of single-hole strength in ^{131}Sn and ^{131}In. The experimental results are compared to theoretical calculations based on the relativistic particle-vibration coupling model and to experimental information for single-hole states in the stable doubly magic nucleus ^{208}Pb.

Gamma Decay of Unbound Neutron-Hole States in

Excited states in the nucleus ^{133}Sn, with one neutron outside the double magic ^{132}Sn core, were populated following one-neutron knockout from a ^{134}Sn beam on a carbon target at relativistic energies at the Radioactive Isotope Beam Factory at RIKEN. Besides the γ rays emitted in the decay of the known neutron single-particle states in ^{133}Sn additional γ strength in the energy range 3.5-5.5 MeV was observed for the first time. Since the neutron-separation energy of ^{133}Sn is low, S_{n}=2.402(4) MeV, this observation provides direct evidence for the radiative decay of neutron-unbound states in this nucleus. The ability of electromagnetic decay to compete successfully with neutron emission at energies as high as 3 MeV above threshold is attributed to a mismatch between the wave functions of the initial and final states in the latter case. These findings suggest that in the region southeast of ^{132}Sn nuclear structure effects may play a significant role in the neutron versus γ competition in the decay of unbound states. As a consequence, the common neglect of such effects in the evaluation of the neutron-emission probabilities in calculations of global ß-decay properties for astrophysical simulations may have to be reconsidered.

Design and characterization of biofunctional magnetic porous silicon flakes.

Magnetic porous silicon flakes (MPSF) were obtained from mesoporous silicon layers formed by multi-step anodization and subsequent composite formation with Fe oxide nanoparticles by thermal annealing. The magnetic nanoparticles adhered to the surface and penetrated inside the pores. Their structure evolved as a result of the annealing treatments derived from X-ray diffraction and X-ray absorption analyses. Moreover, by tailoring the magnetic load, the dynamic and hydrodynamic properties of the particles were controlled, as observed by the pressure displayed against a sensor probe. Preliminary functionality experiments were performed using an eye model, seeking potential use of MPSF as reinforcement for restored detached retina. It was observed that optimal flake immobilization is obtained when the MPSF reach values of magnetic saturation >10(-4)Am(2)g(-1). Furthermore, the MPSF were demonstrated to be preliminarily biocompatible in vitro. Moreover, New Zealand rabbit in vivo models demonstrated their short-term histocompatibility and their magnetic functionality as retina pressure actuators.

Characterization and cytocompatibility of hybrid aminosilane-agarose hydrogel scaffolds.

Agarose hydrogels containing aminopropyl triethoxy silane (APTS) have been prepared and evaluated as scaffolds for adhesion and proliferation of human mesenchymal stem cells (hMSCs). The preparation of the hydrogels involved the conventional melting of agarose in water followed by addition of APTS as functional group carrier. The resulting hydrogel supports have been studied by Fourier transformed infrared spectroscopy in order to get an insight into the hybrid molecular structure. X-ray photoelectron spectroscopy has been used for the analysis of the surface chemical composition of the hydrogels. It is deduced from these data that the resulting hybrid structure presents two phases with a clear tendency toward APTS surface segregation. Moreover, the observation of the desiccated hydrogel surfaces by atomic force microscopy shows that the films acquire a filament-mesh structure for increasing APTS content, while the pure agarose supports exhibit a granular structure. As a result of such a structure, the hydrogel surfaces show a hydrophobic behavior, as determined by water contact angle measurements. The biocompatibility of such platforms is supported by adhesion-proliferation assays performed with hMSCs. It is concluded that although adhesion is lower on APTS rich scaffolds, the proliferation rate on these surfaces is higher so that total number of proliferating cells does not significantly depend on APTS content in the hydrogels.