The nuclear shell effects near the r-process path in the relativistic Hartree-Bogoliubov theory

We have investigated the evolution of the shell structure of nuclei in going from the r-process path to the neutron drip line within the framework of the Relativistic Hartree-Bogoliubov (RHB) theory. By introducing the quartic self-coupling of $\omega$ meson in the RHB theory in addition to the non-linear scalar coupling of $\sigma$ meson, we reproduce the available data on the shell effects about the waiting-point nucleus $^{80}$Zn. With this approach, it is shown that the shell effects at N=82 in the inaccessible region of the r-process path become milder as compared to the Lagrangian with the scalar self-coupling only. However, the shell effects remain stronger as compared to the quenching exhibited by the HFB+SkP approach. It is also shown that in reaching out to the extreme point at the neutron drip line, a terminal situation arises where the shell structure at the magic number is washed out significantly.Comment: 18 pages (revtex), 8 ps figures, to appear in Phys. Rev.

p-Type semiconducting properties in lithium-doped MgO single crystals

The phenomenally large enhancement in conductivity observed when Li-doped MgO crystals are oxidized at elevated temperatures was investigated by dc and ac electrical measurements in the temperature interval 250-673 K. The concentration of ([Li]^{0}) centers (Li^{+} ions each with a trapped hole) resulting from oxidation was monitored by optical absorption measurements. Both dc and ac experiments provide consistent values for the bulk resistance. The electricalconductivity of oxidized MgO:Li crystals increases linearly with the concentration of ([Li]^{0}) centers. The conductivity is thermally activated with an activation energy of (0.70 +/- 0.01) eV, which is independent of the ([Li]^{0}) content. The \textit{standard semiconducting} mechanism satisfactorily explains these results. Free holes are the main contribution to band conduction as they are trapped at or released from the ([Li]^{0})-acceptor centers. In as-grown MgO:Li crystals, electrical current increases dramatically with time due to the formation of ([Li]^{0}) centers. The activation energy values between 1.3 and 0.7 eV are likely a combination of the activation energy for the creation of ([Li]^{0}) centers and the activation energy of ionization of these centers. Destruction of ([Li]^{0}) centers can be induced in oxidized crystals by application of an electric field due to Joule heating up to temperatures at which ([Li]^{0}) centers are not stable.Comment: LaTeX, 20 pages, 9 Encapsulated Postscript Format Figures, use the version 4.0 of REVTEX 4 macro packag

Highly selective detection of Hg2+ and MeHgI by di-pyridin-2-yl-[4-(2-pyridin-4-yl-vinyl)-phenyl]-amine and its zinc coordination polymer

©2016 the Partner Organisations. Solvothermal reaction of Zn(NO3)2·6H2O with di-pyridin-2-yl-[4-(2-pyridin-4-yl-vinyl)-phenyl]-amine (ppvppa) and 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) in H2O and MeCN at 150 °C yielded a two-dimensional (2D) coordination Zn(ii) polymer [Zn(ppvppa)(1,4-NDC)]n (1). Compound 1 was characterized by elemental analysis, IR spectroscopy, powder X-ray diffraction, single-crystal X-ray diffraction and thermogravimetric analysis. Compound 1 consists of dimeric [Zn2(ppvppa)2] units linked by 1,4-NDC bridges to generate a 2D honeycomb network. Either compound 1 or ppvppa alone can detect Hg2+ or MeHgI selectively and with good sensitivity. Upon addition of Hg2+ ions to a MeCN solution of ppvppa, marked changes in the UV-vis and fluorescence spectra are observed, associated with colour changes, which are easily identified by the naked eye. The pyridinyl rings of ppvppa are coordinated to the Hg2+ ion. This motif in the presence of NO3- ions forms a binuclear complex [Hg2(ppvppa)2(NO3)4] (2), which has been characterized as the solvate [Hg2(ppvppa)2(NO3)4]·H2O·4MeCN (2·H2O·4MeCN) by single-crystal X-ray diffraction studies. In aqueous solution, compound 1 emits pale orange light at ambient temperature and the addition of Hg2+ or MeHgI induces an change of fluorescence color from pale orange to blue. Compound 1 is a promising candidate as a sensitive naked-eye indicator for Hg2+ or MeHgI in water under a UV lamp. Introduction to the international collaboration Prof. Lang and Prof. Brammer met with each other in Nanjing, China when Prof. Brammer taught lectures at Nanjing Tech University last November. Prof. Lang's research involves metal sulfide cluster chemistry, design and development of new coordination complex-based catalysts, bioinorganic chemistry related to mimicking metal sites of enzymes and proteins, and so on. Prof. Brammer's research interest covers supramolecular chemistry and crystal engineering, in particular host-guest chemistry and catalysis in metal-organic frameworks, reactions in molecular solids and fundamentals of intermolecular interactions. Both professors recognised their many mutual research interests and decided to initiate an international collaborative project in the area of coordination polymers. Both will visit the partner's lab in China and UK in the near future and expand this project to a higher level

Test of Universality in Anisotropic 3D Ising Model

Chen and Dohm predicted theoretically in 2004 that the widely believed universality principle is violated in the Ising model on the simple cubic lattice with more than only six nearest neighbours. Schulte and Drope by Monte Carlo simulations found such violation, but not in the predicted direction. Selke and Shchur tested the square lattice. Here we check only this universality for the susceptibility ratio near the critical point. For this purpose we study first the standard Ising model on a simple cubic lattice with six nearest neighbours, then with six nearest and twelve next-nearest neighbours, and compare the results with the Chen-Dohm lattice of six nearest neighbours and only half of the twelve next-nearest neighbours. We do not confirm the violation of universality found by Schulte and Drope in the susceptibility ratio.Comment: 6 pages including 4 figures, Physica A, in pres

Modeliranje, upravljanje i eksperimentalno istraživanje novoga raspodijeljenog statičkog kompenzatora jalove snage zasnovanog na višestupanjskom pretvaraču s ulančenim H-mostovima

A novel static synchronous compensator for reactive power compensation of distribution system (DSTATCOM) is proposed, based on the cascaded H-bridge multilevel inverter configuration. The mathematical formulation of the multilevel DSTATCOM is presented using state-space representations. A new software phase-locked loop (SPLL) is presented for grid synchronization and the obtained phase angle of the fundamental component of the grid voltage is utilized for deriving the active and reactive power balancing equations of the multilevel DSTATCOM. The proportional-resonant (PR) controller scheme is adopted for the current tracking control of the inverter, and the average dc-link voltage is controlled using a proportional-integral (PI) controller to regulate the active power flow of the DSTATCOM. Besides, the voltage balancing (VB) control among individual H-bridges is achieved by using separate PI regulators to control the difference voltage between the individual dc-link voltage and the average dc-link voltage. The validity of the proposed multilevel DSTATCOM and its control strategies is substantially confirmed by the extensive simulation results and the experimental results from the prototype system.Predložen je novi statički sinkroni kompenzator za kompenzaciju jalove snage distribucijskog sustava (DSTATCOM) zasnovan na konfiguraciji višestupanjskog pretvarača s ulančenim H-mostovima. Matematički model višerazinskog DSTATCOM-a prikazan je u prostoru stanja. Predstavljena je nova programski izvedena petlja sa zaključanom fazom namijenjena sinkronizaciji s mrežom, a dobiveni fazni kut osnovne komponente mrežnog napona koristi se za izvod jednadžbi ravnoteže aktivne i jalove snage višerazinskog DSTATCOM-a. Usvojen je koncept proporcionalno-rezonantnog regulatora za slijeđenje trajektorije struje pretvarača, a srednji napon istosmjernog međukruga upravlja se korištenjem proporcionalno-integracijskog (PI) regulatora u svrhu regulacije toka radne snage DSTATCOM-a. Osim toga, upravljanje uravnoteženjem napona među pojedinim H-mostovima ostvareno je korištenjem odvojenih PI regulatora za upravljanje razlikom napona među pojedinim istosmjernim međukrugovima te srednjim naponom istosmjernih međukrugova. Valjanost predloženog višestupanjskog DSTATCOM-a i primijenjenih upravljačkih strategija potvrđena je brojnim simulacijskim i eksperimentalnim rezultatima na prototipskoj izvedbi ovog sustava

Fermionic superfluidity: From high Tc superconductors to ultracold Fermi gases

We present a pairing fluctuation theory which self-consistently incorporates finite momentum pair excitations in the context of BCS--Bose-Einstein condensation (BEC) crossover, and we apply this theory to high $T_c$ superconductors and ultracold Fermi gases. There are strong similarities between Fermi gases in the unitary regime and high Tc superconductors. Here we address key issues of common interest, especially the pseudogap. In the Fermi gases we summarize recent experiments including various phase diagrams (with and without population imbalance), as well as evidence for a pseudogap in thermodynamic and other experiments.Comment: Expanded version, invited talk at the 5th International Conference on Complex Matter -- Stripes 2006, 6 pages, 6 figure

A Monte-Carlo study of the AdS/CFT correspondence: an exploration of quantum gravity effects

In this paper we study the AdS/CFT correspondence for N=4 SYM with gauge group U(N), compactified on S^3 in four dimensions using Monte-Carlo techniques. The simulation is based on a particular reduction of degrees of freedom to commuting matrices of constant fields, and in particular, we can write the wave functions of these degrees of freedom exactly. The square of the wave function is equivalent to a probability density for a Boltzman gas of interacting particles in six dimensions. From the simulation we can extract the density particle distribution for each wave function, and this distribution can be interpreted as a special geometric locus in the gravitational dual. Studying the wave functions associated to half-BPS giant gravitons, we are able to show that the matrix model can measure the Planck scale directly. We also show that the output of our simulation seems to match various theoretical expectations in the large N limit and that it captures 1/N effects as statistical fluctuations of the Boltzman gas with the expected scaling. Our results suggest that this is a very promising approach to explore quantum corrections and effects in gravitational physics on AdS spaces.Comment: 40 pages, 7 figures, uses JHEP. v2: references adde

Two-band second moment model and an interatomic potential for caesium

A semi-empirical formalism is presented for deriving interatomic potentials for materials such as caesium or cerium which exhibit volume collapse phase transitions. It is based on the Finnis-Sinclair second moment tight binding approach, but incorporates two independent bands on each atom. The potential is cast in a form suitable for large-scale molecular dynamics, the computational cost being the evaluation of short ranged pair potentials. Parameters for a model potential for caesium are derived and tested