The stability and the shape of the heaviest nuclei

In this paper, we report a systematic study of the heaviest nuclei within the relativistic mean field (RMF) model. By comparing our results with those of the Hartree-Fock-Bogoliubov method (HFB) and the finite range droplet model (FRDM), the stability and the shape of the heaviest nuclei are discussed. The theoretical predictions as well as the existing experimental data indicate that the experimentally synthesized superheavy nuclei are in between the fission stability line, the line connecting the nucleus with maximum binding energy per nucleon in each isotopic chain, and the $\beta$-stability line, the line connecting the nucleus with maximum binding energy per nucleon in each isobaric chain. It is shown that both the fission stability line and the $\beta$-stability line tend to be more proton rich in the superheavy region. Meanwhile, all the three theoretical models predict most synthesized superheavy nuclei to be deformed.Comment: 6 pages, 7 figures, to appear in Journal of Physics

Alpha-decay chains of 173288115^{288}_{173}115 and 172287115^{287}_{172}115 in the Relativistic Mean Field theory

In the recent experiments designed to synthesize the element 115 in the $^{243}$Am+$^{48}$Ca reaction at Dubna in Russia, three similar decay chains consisting of five consecutive $\alpha$-decays, and another different decay chain of four consecutive $\alpha$-decays are detected, and the decay properties of these synthesized nuclei are claimed to be consistent with consecutive $\alpha$-decays originating from the parent isotopes of the new element 115, $^{288}115$ and $^{287}115$, respectively\cite{ogan.03}. Here in the present work, the recently developed deformed RMF+BCS method with a density-independent delta-function interaction in the pairing channel is applied to the analysis of these newly synthesized superheavy nuclei $^{288}115$, $^{287}115$, and their $\alpha$-decay daughter nuclei. The calculated $\alpha$-decay energies and half-lives agree well with the experimental values and with those of the macroscopic-microscopic FRDM+FY and YPE+WS models. In the mean field Lagrangian, the TMA parameter set is used. Particular emphasis is paid on the influence to both the ground-state properties and energy surfaces introduced by different treatments of pairing. Two different effective interactions in the particle-particle channel, i.e., the constant pairing and the density-independent delta-function interaction, together with the blocking effect are discussed in detail.Comment: 17 pages, 5 figure

Study of Radiative Leptonic D Meson Decays

We study the radiative leptonic $D$ meson decays of D^+_{(s)}\to \l^+\nu_{\l}\gamma (\l=e,\mu,\tau), $D^0\to \nu\bar{\nu}\gamma$ and D^0\to \l^+\l^-\gamma ($l=e,\mu$) within the light front quark model. In the standard model, we find that the decay branching ratios of $D^+_{(s)}\to e^+\nu_e\gamma$, $D^+_{(s)}\to\mu^+\nu_{\mu}\gamma$ and $D^+_{(s)}\to\tau^+\nu_{\tau}\gamma$ are $6.9\times 10^{-6}$ ($7.7\times 10^{-5}$), $2.5\times 10^{-5}$ ($2.6\times 10^{-4}$), and $6.0\times 10^{-6}$ ($3.2\times 10^{-4}$), and that of D^0\to\l^+\l^-\gamma (\l=e,\mu) and $D^0\to\nu\bar{\nu}\gamma$ are $6.3\times 10^{-11}$ and $2.7\times 10^{-16}$, respectively.Comment: 23 pages, 6 Figures, LaTex file, a reference added, to be published in Mod. Phys. Lett.

Spurious Shell Closures in the Relativistic Mean Field Model

Following a systematic theoretical study of the ground-state properties of over 7000 nuclei from the proton drip line to the neutron drip line in the relativistic mean field model [Prog. Theor. Phys. 113 (2005) 785], which is in fair agreement with existing experimental data, we observe a few spurious shell closures, i.e. proton shell closures at Z=58 and Z=92. These spurious shell closures are found to persist in all the effective forces of the relativistic mean field model, e.g. TMA, NL3, PKDD and DD-ME2.Comment: 3 pages, to appear in Chinese Physics Letter

Identification of the orphan gene Prod 1 in basal and other salamander families.

The urodele amphibians (salamanders) are the only adult tetrapods able to regenerate the limb. It is unclear if this is an ancestral property that is retained in salamanders but lost in other tetrapods or if it evolved in salamanders. The three-finger protein Prod 1 is implicated in the mechanism of newt limb regeneration, and no orthologs have been found in other vertebrates, thus providing evidence for the second viewpoint. It has also been suggested that this protein could play a role in salamander-specific aspects of limb development. There are ten families of extant salamanders, and Prod 1 has only been identified in two of them to date. It is important to determine if it is present in other families and, particularly, the basal group of two families which diverged approximately 200 MYA

Long-term vascular access ports as a means of sedative administration in a rodent fMRI survival model

The purpose of this study is to develop a rodent functional magnetic resonance imaging (fMRI) survival model with the use of heparin-coated vascular access devices. Such a model would ease the administration of sedative agents, reduce the number of animals required in survival experiments and eliminate animal-to-animal variability seen in previous designs. Seven male Sprague-Dawley rats underwent surgical placement of an MRI-compatible vascular access port, followed by implantable electrode placement on the right median nerve. Functional MRI during nerve stimulation and resting-state functional connectivity MRI (fcMRI) were performed at times 0, 2, 4, 8 and 12 weeks postoperatively using a 9.4 T scanner. Anesthesia was maintained using intravenous dexmedetomidine and reversed using atipamezole. There were no fatalities or infectious complications during this study. All vascular access ports remained patent. Blood oxygen level dependent (BOLD) activation by electrical stimulation of the median nerve using implanted electrodes was seen within the forelimb sensory region (S1FL) for all animals at all time points. The number of activated voxels decreased at time points 4 and 8 weeks, returning to a normal level at 12 weeks, which is attributed to scar tissue formation and resolution around the embedded electrode. The applications of this experiment extend far beyond the scope of peripheral nerve experimentation. These vascular access ports can be applied to any survival MRI study requiring repeated medication administration, intravenous contrast, or blood sampling

Partial Derivation of Transformation Properties of Quarks and Leptons

Under the assumptions that $SU(3)_c\times U(1)_Y \times G^{\prime}$ with $G^{\prime}$ simple is a local symmetry group at high energies, that color is parity-conserving, and the Y-charges are irreducible, we show that anomaly constraints imply the minimal set of fermions is fifteen in number. Given this minimal set, we further show that $G^{\prime}$ must be $SU(2)$ and the unbroken gauge symmetry is {\it either} color {\it or} the product of color with electric charge.Comment: 9 pages, UMDHEP 94-72 and IFP-487-UN

CPT conserving cosmological birefringence

We demonstrate that the cosmological birefringence can arise from CPT conserving effect, originated from the CPT-even dimension-six Chern-Simons-like term. We show that a sizable rotation polarization angle in the data of the cosmic microwave background radiation polarization can be induced.Comment: 4 pages, Talk given at 4th International Conference on Flavor Physics (ICFP 2007), Beijing, China, 24-28 Sep 200

Electromagnetically induced transparency and four-wave mixing in a cold atomic ensemble with large optical depth

We report on the delay of optical pulses using electromagnetically induced transparency in an ensemble of cold atoms with an optical depth exceeding 500. To identify the regimes in which four-wave mixing impacts on EIT behaviour, we conduct the experiment in both rubidium 85 and rubidium 87. Comparison with theory shows excellent agreement in both isotopes. In rubidium 87, negligible four-wave mixing was observed and we obtained one pulse-width of delay with 50% efficiency. In rubidium 85, four-wave-mixing contributes to the output. In this regime we achieve a delay-bandwidth product of 3.7 at 50% efficiency, allowing temporally multimode delay, which we demonstrate by compressing two pulses into the memory medium.Comment: 8 pages, 6 figure