Magnetic model for Ba_2Cu_3O_4Cl_2

Ba_2Cu_3O_4Cl_2 consists of two types of copper atoms, Cu(A) and Cu(B). We study the corresponding Heisenberg model with three antiferromagnetic couplings, J_AA, J_BB and J_AB. We find interesting frustration effects due to the coupling J_AB.Comment: 6 pages, LaTeX, 3 eps figures, to appear in JMM

The Capacity-Building Support Activities of the Integrated Support Center for Nuclear Nonproliferation and Nuclear Security of the Japan Atomic Energy Agency

International cooperation is essential to support states in building the human resources necessary for maintaining and strengthening nuclear security. As the nation’s only comprehensive nuclear research and development institute, the Japan Atomic Energy Agency (JAEA) has long-standing experience developing and operating nuclear technology in all steps of the fuel cycle. The Integrated Support Center for Nuclear Nonproliferation and Nuclear Security (ISCN) was established within the JAEA in December 2010 as Japan’s Center of Excellence for nuclear security. The ISCN provides assistance with capacity building to states throughout Asia and some other regions. The objective of this article is to describe the contribution of the ISCN to human resources development in the field of nuclear security, using its contributions to regional physical protection training and computer security training as illustrative examples. This article also considers the lessons learned from the ISCN’s experience that may benefit other nuclear security training and support centers

Recent Surface Studies Using Biassed Secondary Electron Imaging

The growth and surface diffusion of Cs on Si(100) and Ag on Fe(110) have been studied using biassed secondary electron imaging (b-SEI) and Auger electron spectroscopy (AES). The b-SEI technique was found capable of detecting Cs on the Si surface with a 0.5% ML sensitivity. Unusual diffusion profiles containing linear sections were obtained for coverages (θ) \u3c 1/2 ML. The general form of these profiles were reproduced using a 2-phase model, where Cs chains act as sources of mobile adatoms, in conjunction with a diffusion coefficient of the form D ~ θ (1- Cθ). This form of D, obtained from Boltzmann-Matano analysis, is consistent with diffusion theory including strongly repulsive Cs-Cs interactions. An adatom diffusion energy, Ed, = 0.47 ± 0.05 eV was found to be consistent with measurements of the diffusion coefficient made in the temperature range 333 ≤ T ≤ 363K. The growth mode for Ag on Fe(110) was determined by AES and b-SEI to be Stranski-Krastanov, with islands growing on top of two intermediate layers. Diffusion experiments conducted on finite Ag patches show that following annealing, adatoms dissociate from the islands and second monolayer and contribute to the observed expansion of the first monolayer. The diffusion results also indicate that while islands are still present, there is a competition between adatoms entering and leaving the second monolayer

Study of nuclear correlation effects via 12C(p,n)12N(g.s.,1+) at 296 MeV

We report measurements of the cross section and a complete set of polarization observables for the Gamow--Teller ${}^{12}{\rm C}(\vec{p},\vec{n}){}^{12}{\rm N}({\rm g.s.},1^+)$ reaction at a bombarding energy of 296 MeV. The data are compared with distorted wave impulse approximation calculations employing transition form factors normalized to reproduce the observed beta-decay $ft$ value. The cross section is significantly under-predicted by the calculations at momentum transfers $q \gtrsim$ 0.5 ${\rm fm^{-1}}$. The discrepancy is partly resolved by considering the non-locality of the nuclear mean field. However, the calculations still under-predict the cross section at large momentum transfers of $q$ $\simeq$ 1.6 ${\rm fm^{-1}}$. We also performed calculations employing random phase approximation response functions and found that the observed enhancement can be attributed in part to pionic correlations in nuclei.Comment: 5 figures, submitted to Phys. Lett.

Poloxamer 407 based-nanoparticles for controlled release of methotrexate

Poloxamer 407 (P407)-based nanoparticles were produced by the high pressure homogenization method for the encapsulation and delivery of methotrexate (MTX), aiming intravenous therapeutic applications. The surface of these nanoparticles was functionalized by conjugation of P407 with folic acid (FA) or with MTX, which served as targeting ligand agents. MTX-P407 conjugate was also developed to increase the final drug cargo. Two hydrophobic derivatives of MTX, MTX di-ethylated ester (MTX-OEt) and the ionic complex MTX-dimethyldioctadecylammonium bromide (MTX-DODAB) were produced and entrapped onto P407-based nanoparticles. All formulations developed revealed a monodisperse character comprising small and narrow nanoparticles (<100 nm). P407 nanoparticles (functionalized with FA) and MTX-P407 nanoparticles, both loaded with MTX-OEt, demonstrated a slow drug release profile. The effect of lipase from Aspergillus oryzae on the hydrolysis of the linkage between the P407 and MTX, and consequent MTX release profile, was also evaluated. We observed a controlled and slow release of MTX (<50% of release after 11 days) in the presence of enzyme. These MTX-P407 nanoparticles loaded with MTX-OEt induced a great effect against Caco-2 cancer cells (40% of cell death after 72 h of incubation), demonstrating higher efficiency than the free MTX at the same concentration.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2019 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. The authors also thanks to FCT for funding their scholarship: Jennifer Noro (SFRH/BD/121673/2016) and Carla Silva (SFRH/IF/00186/2015). This work has also received funding from the European Union Horizon 2020 research and innovation program under grant agreement NMP-06-2015-683356 FOLSMART.info:eu-repo/semantics/publishedVersio

Complete set of polarization transfer coefficients for the 3He(p,n){}^{3}{\rm He}(p,n) reaction at 346 MeV and 0 degrees

We report measurements of the cross-section and a complete set of polarization transfer coefficients for the ${}^{3}{\rm He}(p,n)$ reaction at a bombarding energy $T_p$ = 346 MeV and a reaction angle $\theta_{\rm lab}$ = $0^{\circ}$. The data are compared with the corresponding free nucleon-nucleon values on the basis of the predominance of quasi-elastic scattering processes. Significant discrepancies have been observed in the polarization transfer $D_{LL}(0^{\circ})$, which are presumably the result of the three-proton $T$ = 3/2 resonance. The spin--parity of the resonance is estimated to be $1/2^-$, and the distribution is consistent with previous results obtained for the same reaction at $T_p$ = 48.8 MeV.Comment: 4 figures, Accepted for publication in Physical Review

Thin Ice Target for 16^{16}O(p,p') experiment

A windowless and self-supporting ice target is described. An ice sheet with a thickness of 29.7 mg/cm$^2$ cooled by liquid nitrogen was placed at the target position of a magnetic spectrometer and worked stably in the $^{16}$O$(p,p')$ experiment at $E_{p}=392$ MeV. Background-free spectra were obtained.Comment: 14 pages, 4 figures, Nucl. Instr. & Meth. A (in press

Tight-binding parameters and exchange integrals of Ba_2Cu_3O_4Cl_2

Band structure calculations for Ba_2Cu_3O_4Cl_2 within the local density approximation (LDA) are presented. The investigated compound is similar to the antiferromagnetic parent compounds of cuprate superconductors but contains additional Cu_B atoms in the planes. Within the LDA, metallic behavior is found with two bands crossing the Fermi surface (FS). These bands are built mainly from Cu 3d_{x^2-y^2} and O 2p_{x,y} orbitals, and a corresponding tight-binding (TB) model has been parameterized. All orbitals can be subdivided in two sets corresponding to the A- and B-subsystems, respectively, the coupling between which is found to be small. To describe the experimentally observed antiferromagnetic insulating state, we propose an extended Hubbard model with the derived TB parameters and local correlation terms characteristic for cuprates. Using the derived parameter set we calculate the exchange integrals for the Cu_3O_4 plane. The results are in quite reasonable agreement with the experimental values for the isostructural compound Sr_2Cu_3O_4Cl_2.Comment: 5 pages (2 tables included), 4 ps-figure

Transport Properties, Thermodynamic Properties, and Electronic Structure of SrRuO3

SrRuO$_3$ is a metallic ferromagnet. Its electrical resistivity is reported for temperatures up to 1000K; its Hall coefficient for temperatures up to 300K; its specific heat for temperatures up to 230K. The energy bands have been calculated by self-consistent spin-density functional theory, which finds a ferromagnetic ordered moment of 1.45$\mu_{{\rm B}}$ per Ru atom. The measured linear specific heat coefficient $\gamma$ is 30mJ/mole, which exceeds the theoretical value by a factor of 3.7. A transport mean free path at room temperature of $\approx 10 \AA$ is found. The resistivity increases nearly linearly with temperature to 1000K in spite of such a short mean free path that resistivity saturation would be expected. The Hall coefficient is small and positive above the Curie temperature, and exhibits both a low-field and a high-field anomalous behavior below the Curie temperature.Comment: 6 pages (latex) and 6 figures (postscript, uuencoded.) This paper will appear in Phys. Rev. B, Feb. 15, 199