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.

Micromechanical Analysis on the Failure Criterion of Ductile Material

AbstractBased on finite element simulation, the void growth behavior in a 3D cell model subjected to low stress triaxiality was studied. The distribution rule of stress-strain near the void was investigated, as well as the developing trend of volume of void. The analysis results indicated that it is not appropriate to regard void volume fraction as a damage parameter under the low stress triaxiality condition. Further research was carried out to verify the reliability of the fracture strain as element failure criterion by comparing the uniaxial tension simulation and experiment results. More studies were conducted to analyze the void growth under low stress triaxiality by introducing the critical equivalent plastic strain as the material failure parameter

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

INTERACTION OF WHEY PROTEIN WITH MODIFIED STAINLESS STEEL SURFACES

Modified stainless steel surfaces were fouled with whey protein solutions to study the deposition mechanisms and the effects of surface modification. Stainless steel samples were coated with diamond-like carbon (DLC) and titanium nitride (TiN). These surfaces are expected to present different surface chemistries to stainless steel in terms of their functional groups and hydrophobic or hydrophilic nature. Thus, it is expected that foulant-surface interactions will differ for the various fouled surfaces. The substrates were exposed to a flowing whey protein solution in a fouling rig designed to achieve laminar flow. X-ray Photoelectron Spectroscopy (XPS) was used to study the initial protein-surface interactions of samples fouled for 1 minute at 75°C. Ellipsometry was used to study the fouling and cleaning performance of samples fouled at 75°C and 85°C for up to 30 minutes followed by ultrasonic caustic cleaning of selected samples. XPS showed the presence of similar protein functional groups on all fouled surfaces. The bonding mechanisms during fouling of DLC is different to the stainless steel and TiN surfaces. The peptide link played a more active role at the deposit-surface interface for the non-polar DLC surface, while it was less significant for the two polar surfaces. Ellipsometry revealed that for the three surfaces, fouling increased in the order DL

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

Effects of rare earth nanoparticles (M = Sm2O3, Ho2O3, Nd2O3) addition on the microstructure and superconducting transition of Bi1.6Pb0.4Sr2Ca2Cu3O10+δ ceramics

The effect of rare earth nanoparticles, M=Sm2O3, Nd2O3 and Ho2O3 added to (Bi1.6Pb0.4Sr2Ca2Cu3O10+δ)1-x(M)x, where x = 0.00 - 0.05, superconductor were studied by X-ray diffraction technique (XRD), resistivity (R), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDX). The volume fraction of high-Tc phase, Bi-2223, decreased from 84% for pure sample to 48, 30 and 23% at x = 0.05 for Sm2O3, Ho2O3 and Nd2O3 additions, respectively. The critical temperature Tc(R=0) that is 102 K for the pure sample decreased to 78, 73 and 69 K at x = 0.05 for samples with Sm2O3, Nd2O3 and Ho2O3 nanoparticles additions, respectively. The additions of rare earth nanoparticles decreased the grain size and increased the random orientation of the grains. The results showed that the phases’ formations, variations of lattice parameters and electrical properties are sensitive to the size of nanoparticles and magnetic properties of its ions

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

Stripes in Quantum Hall Double Layer Systems

We present results of a study of double layer quantum Hall systems in which each layer has a high-index Landau level that is half-filled. Hartree-Fock calculations indicate that, above a critical layer separation, the system becomes unstable to the formation of a unidirectional coherent charge density wave (UCCDW), which is related to stripe states in single layer systems. The UCCDW state supports a quantized Hall effect when there is tunneling between layers, and is {\it always} stable against formation of an isotropic Wigner crystal for Landau indices $N \ge 1$. The state does become unstable to the formation of modulations within the stripes at large enough layer separation. The UCCDW state supports low-energy modes associated with interlayer coherence. The coherence allows the formation of charged soliton excitations, which become gapless in the limit of vanishing tunneling. We argue that this may result in a novel {\it ``critical Hall state''}, characterized by a power law $I-V$ in tunneling experiments.Comment: 10 pages, 8 figures include