Study of Dissipative Collisions of 20^{20}Ne (∼\sim7-11 MeV/nucleon) + 27^{27}Al

The inclusive energy distributions of complex fragments (3 $\leq$Z $\leq$ 9) emitted in the reactions $^{20}$Ne (145, 158, 200, 218 MeV) + $^{27}$Al have been measured in the angular range 10$^{o}$ - 50$^{o}$. The fusion-fission and the deep-inelastic components of the fragment yield have been extracted using multiple Gaussian functions from the experimental fragment energy spectra. The elemental yields of the fusion-fission component have been found to be fairly well exlained in the framework of standard statistical model. It is found that there is strong competition between the fusion-fission and the deep-inelastic processes at these energies. The time scale of the deep-inelastic process was estimated to be typically in the range of $\sim$ 10$^{-21}$ - 10$^{-22}$ sec., and it was found to decrease with increasing fragment mass. The angular momentum dissipations in fully energy damped deep-inelastic process have been estimated from the average energies of the deep-inelastic components of the fragment energy spectra. It has been found that, the estimated angular momentum dissipations, for lighter fragments in particular, are more than those predicted by the empirical sticking limit.Comment: 16 pages, 9 figure

See-saw fermion masses in an SO(10) GUT

In this work we study an SO(10) GUT model with minimum Higgs representations belonging only to the 210 and 16 dimensional representations of SO(10). We add a singlet fermion S in addition to the usual 16 dimensional representation containing quarks and leptons. There are no Higgs bi-doublets and so charged fermion masses come from one-loop corrections. Consequently all the fermion masses, Dirac and Majorana, are of the see-saw type. We minimize the Higgs potential and show how the left-right symmetry is broken in our model where it is assumed that a D-parity odd Higgs field gets a vacuum expectation value at the grand unification scale. From the renormalization group equations we infer that in our model unification happens at 10^{15} GeV and left-right symmetry can be extended up to some values just above 10^{11} GeV. The Yukawa sector of our model is completely different from most of the standard grand unified theories and we explicitly show how the Yukawa sector will look like in the different phases and briefly comment on the running of the top quark mass. We end with a brief analysis of lepton number asymmetry generated from the interactions in our model.Comment: 30 pages, 10 figure

Evidence of large nuclear deformation of 32^{32}S∗^{*} formed in 20^{20}Ne + 12^{12}C reaction

Deformations of hot composite $^{32}$S$^{*}$ formed in the reaction $^{20}$Ne ($\sim$ 7 -- 10 MeV/nucleon) + $^{12}$C have been estimated from the respective inclusive $\alpha$-particle evaporation spectra. The estimated deformations for $^{32}$S$^{*}$ have been found to be much larger than the `normal' deformations of hot, rotating composites at similar excitations. This further confirms the formation of highly deformed long-lived configuration of $^{20}$Ne + $^{12}$C at high excitations ($\sim$ 70 -- 100 MeV) -- which was recently indicated from the analysis of the complex fragment emission data for the same system. Exclusive $\alpha$-particle evaporation spectra from the decay of hot composite $^{32}$S$^{*}$ also show similar behaviour.Comment: 9 pages, 6 figure

Scanning probe imaging of coexistent ferromagnetism and ferroelectricity at room temperature

Room temperature coexistence of ferromagnetism and ferroelectricity in a thin film of a novel material of nominal composition PbTi0.5Fe0.5O3-d is probed by standard ferroelectric and ferromagnetic hysteresis loop measurements and by scanning probe microscopy of various kinds. Both magnetic domains and ferroelectric domains are observed in the same spatial region of the material, implying phase coexistence in this system. For both order parameters, sample morphology strongly affects roughness of the domain walls.Comment: 15 pages, 5 figure

In-vivo magnetic resonance imaging of hyperpolarized silicon particles

Silicon-based micro and nanoparticles have gained popularity in a wide range of biomedical applications due to their biocompatibility and biodegradability in-vivo, as well as a flexible surface chemistry, which allows drug loading, functionalization and targeting. Here we report direct in-vivo imaging of hyperpolarized 29Si nuclei in silicon microparticles by MRI. Natural physical properties of silicon provide surface electronic states for dynamic nuclear polarization (DNP), extremely long depolarization times, insensitivity to the in-vivo environment or particle tumbling, and surfaces favorable for functionalization. Potential applications to gastrointestinal, intravascular, and tumor perfusion imaging at sub-picomolar concentrations are presented. These results demonstrate a new background-free imaging modality applicable to a range of inexpensive, readily available, and biocompatible Si particles.Comment: Supplemental Material include

Giant Dipole Resonance Width in near-Sn Nuclei at Low Temperature and High Angular Momentum

High energy gamma-rays in coincidence with low energy yrast gamma-rays have been measured from 113Sb, at excitation energies of 109 and 122 MeV, formed by bombarding 20Ne on 93Nb at projectile energies of 145 and 160 MeV respectively to study the role of angular momentum (J) and temperature (T) over Giant Dipole Resonance (GDR) width. The maximum populated angular momenta for fusion were 67hbar and 73hbar respectively for the above-mentioned beam energies. The high energy photons were detected using a Large Area Modular BaF2 Detector Array (LAMBDA) along with a 24-element multiplicity filter. After pre-equilibrium corrections, the excitation energy E* was averaged over the decay steps of the compound nucleus (CN). The average values of temperature, angular momentum, CN mass etc. have been calculated by the statistical model code CASCADE. Using those average values, results show the systematic increase of GDR width with T which is consistent with Kusnezov parametrization and the Thermal Shape Fluctuation Model. The rise of GDR width with temperature also supports the assumptions of adiabatic coupling in the Thermal Shape Fluctuation Model. But the GDR widths and corresponding reduced plots with J are not consistent with the theoretical model at high spins.Comment: 19 pages, 10 figures, Submitted to Physics Review

Hamiltonian chaos in a coupled BEC -- optomechanical cavity system

We study a hybrid optomechanical system consisting of a Bose-Einstein condensate (BEC) trapped inside a single-mode optical cavity with a moving end-mirror. The intracavity light field has a dual role: it excites a momentum side-mode of the condensate, and acts as a nonlinear spring that couples the vibrating mirror to that collective density excitation. We present the dynamics in a regime where the intracavity optical field, the mirror, and the side-mode excitation all display bistable behavior. In this regime we find that the dynamics of the system exhibits Hamiltonian chaos for appropriate initial conditions.Comment: 5 figure