Resonance radiative decays as a tool for its parity determination

Radiative decays of the spin 1/2 baryonic resonances R with the decay mode R -> KN in case of small energy release are considered. Pentaquark is an example of such resonance. It is shown that in case of positive resonance parity corrections to the soft photon radiation formula are large even at low photon energies > 20 MeV and structure terms contributions may be essential, if R size > 1 fm. This effect is absent in case of negative parity. Particularly, measurements of the gamma spectrum in pentaquark radiative decays may allow us to determine its parity.Comment: 5 page

Dephasing and Metal-Insulator Transition

The metal-insulator transition (MIT) observed in two-dimensional (2D) systems is apparently contradictory to the well known scaling theory of localization. By investigating the conductance of disordered one-dimensional systems with a finite phase coherence length, we show that by changing the phase coherence length or the localization length, it is possible to observe the transition from insulator-like behavior to metal-like behavior, and the transition is a crossover between the quantum and classical regimes. The resemblance between our calculated results and the experimental findings of 2D MIT suggests that the observed metallic phase could be the result of a finite dephasing rate.Comment: 10 figures, to be published in Phys. Rev. B63, Jan. 15, (2000

Neutron EDM from Electric and Chromoelectric Dipole Moments of Quarks

Using QCD sum rules, we calculate the electric dipole moment of the neutron d_n induced by all CP violating operators up to dimension five. We find that the chromoelectric dipole moments of quarks \tilde d_i, including that of the strange quark, provide significant contributions comparable in magnitude to those induced by the quark electric dipole moments d_i. When the theta term is removed via the Peccei-Quinn symmetry, the strange quark contribution is also suppressed and d_n =(1\pm 0.5)[1.1e(\tilde d_d + 0.5\tilde d_u)+1.4(d_d-0.25d_u)].Comment: 4 pages, revtex, v2: missing overall factor of two reinstate

Mechanical response of self-ion irradiated, single crystal, FCC micropillars

Increasing energy demands and regulations on cleaner and more efficient energy sources has reinvigorated research into next generation nuclear reactors. The safe and optimal operation of the various proposed reactors requires the cladding and structural metals to perform under a combination of extreme environments including radiation damage levels \u3e100 dpa. This presentation will highlight a rapid screening technique developed at Sandia National Laboratories to determine the relative merit of implementing various advanced structural alloys and composites in high radiation environments. In addition to an overview of the technique and the wealth of alloy systems it has been applied to, this presentation will focus on the detailed mechanisms that can be elucidated from the micropillar compression of ion irradiated single crystal copper and nickel. Single crystal Cu micropillars self-ion irradiated up to 190 dpa at the end of range were compressed along the \u3c110\u3e to 10% strain. To elucidate the interaction of different length scales on the mechanical response, three specimen configurations were explored: large 10 μm tall, intermediate 5 μm tall, and small 4 μm tall pillars. In a similar manner, pristine and self-ion irradiated \u3c111\u3e Ni pillars were subject to in-situ microcompression in a scanning electron microscope (SEM). By performing these experiments during real time SEM observation a direct correlation between the mechanical responses and the pillars’ structural evolution can be obtained. Specifically, the dynamics resulting from the defect free channel formation and subsequent localization can be associated with heterogeneous plastic flow. This presentation will highlight the multiple length scale effects that are active during the micropillar compression of self-ion irradiated, single crystal, FCC micropillars. These results will be discussed in the context of an end of range effect, a damage gradient effect, and size effects, as well as compared to other small scale mechanical testing methods of ion and neutron irradiated materials. Finally, the benefits and limitations of applying these methods to rapidly screen advanced materials for potential future nuclear reactor applications will be discussed. This study is supported by the Division of Materials Science and Engineering, Office of Basic Energy Sciences, U.S. Department of Energy. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000

Chiral Baryon Fields in the QCD Sum Rule

We study the structure of local baryon fields using the method of QCD sum rule. We only consider the single baryon fields and calculate their operator product expansions. We find that the octet baryon fields belonging to the chiral representations [(3,3*)+(3*,3)] and [(8,1)+(1,8)] and the decuplet baryon fields belonging to the chiral representations [(3,6)+(6,3)] lead to the baryon masses which are consistent with the experimental data of ground baryon masses. We also calculate their decay constants, check our normalizations for baryon fields in PRD81:054002(2010) and find that they are well-defined.Comment: 12 pages, 6 figure, 1 table, accepted by EPJ

Transformation of SOX9(+) cells by Pten deletion synergizes with steatotic liver injury to drive development of hepatocellular and cholangiocarcinoma

SOX9 (Sex-determining region Y Box 9) is a well-characterized transcription factor that is a marker for progenitor cells in various tissues. In the liver, cells delineated by SOX9 are responsible for regenerating liver parenchyma when cell proliferation is impaired following chronic injury. However, whether these SOX9(+) cells play a role in liver carcinogenesis has not been fully understood, although high SOX9 expression has been linked to poor survival outcome in liver cancer patients. To address this question, we developed a liver cancer mouse model (Pten(loxP/loxP); Sox9-Cre(ERT+); R26R(YFP)) where tumor suppressor Pten (phosphatase and tensin homolog deleted on chromosome ten) is deleted in SOX9(+) cells following tamoxifen injection. In this paper, we employ lineage-tracing to demonstrate the tumorigenicity potential of the Pten(-), SOX9(+) cells. We show that these cells are capable of giving rise to mixed-lineage tumors that manifest features of both hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (CCA). Our results suggest that PTEN loss induces the transformation of SOX9(+) cells. We further show that to activate these transformed SOX9(+) cells, the presence of liver injury is crucial. Liver injury, induced by hepatotoxin 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) or high-fat diet (HFD), substantially increases tumor incidence and accelerates liver carcinogenesis from SOX9(+) cells in Pten null mice but not in control mice. We further examine the mechanisms underlying tumor formation in this model to show that concurrent with the induction of niche signal (i.e., Wnt signaling), liver injury significantly stimulates the expansion of tumor-initiating cells (TICs). Together, these data show that (1) SOX9(+) cells have the potential to become TICs following the primary transformation (i.e. Pten deletion) and that (2) liver injury is necessary for promoting the activation and proliferation of transformed SOX9(+) cells, resulting in the genesis of mixed-lineage liver tumors

The relative importance of electron-electron interactions compared to disorder in the two-dimensional "metallic" state

The effect of substrate bias and surface gate voltage on the low temperature resistivity of a Si-MOSFET is studied for electron concentrations where the resistivity increases with increasing temperature. This technique offers two degrees of freedom for controlling the electron concentration and the device mobility, thereby providing a means to evaluate the relative importance of electron-electron interactions and disorder in this so-called ``metallic'' regime. For temperatures well below the Fermi temperature, the data obey a scaling law where the disorder parameter ($k_{\rm{F}}l$), and not the concentration, appears explicitly. This suggests that interactions, although present, do not alter the Fermi-liquid properties of the system fundamentally. Furthermore, this experimental observation is reproduced in results of calculations based on temperature-dependent screening, in the context of Drude-Boltzmann theory.Comment: 5 pages, 6 figure

Two-species percolation and Scaling theory of the metal-insulator transition in two dimensions

Recently, a simple non-interacting-electron model, combining local quantum tunneling via quantum point contacts and global classical percolation, has been introduced in order to describe the observed ``metal-insulator transition'' in two dimensions [1]. Here, based upon that model, a two-species-percolation scaling theory is introduced and compared to the experimental data. The two species in this model are, on one hand, the ``metallic'' point contacts, whose critical energy lies below the Fermi energy, and on the other hand, the insulating quantum point contacts. It is shown that many features of the experiments, such as the exponential dependence of the resistance on temperature on the metallic side, the linear dependence of the exponent on density, the $e^2/h$ scale of the critical resistance, the quenching of the metallic phase by a parallel magnetic field and the non-monotonic dependence of the critical density on a perpendicular magnetic field, can be naturally explained by the model. Moreover, details such as the nonmonotonic dependence of the resistance on temperature or the inflection point of the resistance vs. parallel magnetic are also a natural consequence of the theory. The calculated parallel field dependence of the critical density agrees excellently with experiments, and is used to deduce an experimental value of the confining energy in the vertical direction. It is also shown that the resistance on the ``metallic'' side can decrease with decreasing temperature by an arbitrary factor in the degenerate regime ($T\lesssim E_F$).Comment: 8 pages, 8 figure