Role of N,N-Dimethylformamide in the Oxidation of Tetraline Using 2,2' - Azobisisobutyronitrile as Initiator

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Kajian Fungsi Ruang Luar pada Pusat Dakwah Islam di Kota Bandung

This area initially serves as a settlement , and began to be utilized as a public space in 1980. But in this time, this area has been changed into the area of Islamic activities in Bandung. This thing finally provides an opportunity for people to socialize, discuss, recreation, learning, and doing other things. Although Site planning of PUSDAI has planned, but in the end some space in PUSDAI experiencing transition function space, from space with a single function into a space with flexible functions, such as parking spaces and parks. So that these changes have an impact on the accessibility of the area , and circulation patterns in this area. And architecture has an important role in the process of formation of PUSDAI or islamic center in function and visual. How to connecting function with each other to form a linkage, where in the linkage / relationship between these functions greatly affect the users become comfortable

Coulomb Gaps in One-Dimensional Spin-Polarized Electron Systems

We investigate the density of states (DOS) near the Fermi energy of one-dimensional spin-polarized electron systems in the quantum regime where the localization length is comparable to or larger than the inter-particle distance. The Wigner lattice gap of such a system, in the presence of weak disorder, can occur precisely at the Fermi energy, coinciding with the Coulomb gap in position. The interplay between the two is investigated by treating the long-range Coulomb interaction and the random disorder potential in a self-consistent Hartree-Fock approximation. The DOS near the Fermi energy is found to be well described by a power law whose exponent decreases with increasing disorder strength.Comment: 4 pages, revtex, 4 figures, to be published in Phys. Rev. B as a Rapid Communicatio

The X-Ray Forest: A New Prediction of Hierarchical Structure Formation Models

We use numerical simulations of structure formation in a Cold Dark Matter model to predict the absorption lines in the soft X-rays produced by heavy elements in the shock-heated intergalactic medium at low redshift. The simulation incorporates a model for metal production in galaxies and the subsequent dispersion of the metals to the intergalactic medium. We analyze in particular absorption lines produced by oxygen, and calculate the ionization stage taking into account the observed X-ray background at the present time. We find that oxygen is fully ionized by the X-ray background in low-density voids, and is mostly in the form of OVII and OVIII in the sheets and filamentary regions. Strong absorption lines of OVII and OVIII with equivalent widths W ~ 100 km/s are produced in filamentary regions of overdensities ~ 100 and temperatures ~ 10^6 K, located in the outskirts of groups and clusters of galaxies. The OVII line at E = 574 eV is generally the strongest one in these systems. Our model predicts that any X-ray source (such as a quasar) should typically show about one OVII absorption line with W > 100 km/s in the interval from z=0 to z=0.3. These lines could be detected with the upcoming generation of X-ray telescopes, and their origin in intervening systems could be confirmed by the association with groups of galaxies and X-ray emitting halos near the line-of-sight at the same redshift. The hot intergalactic medium may be one of the main reservoirs of baryons in the present universe, and the heavy element X-ray absorption lines offer a promising possibility of detecting this new component in the near future.Comment: Accepted by ApJ. The full resolution color GIF version of Fig.2 is include

Quantum and frustration effects on fluctuations of the inverse compressibility in two-dimensional Coulomb glasses

We consider interacting electrons in a two-dimensional quantum Coulomb glass and investigate by means of the Hartree-Fock approximation the combined effects of the electron-electron interaction and the transverse magnetic field on fluctuations of the inverse compressibility. Preceding systematic study of the system in the absence of the magnetic field identifies the source of the fluctuations, interplay of disorder and interaction, and effects of hopping. Revealed in sufficiently clean samples with strong interactions is an unusual right-biased distribution of the inverse compressibility, which is neither of the Gaussian nor of the Wigner-Dyson type. While in most cases weak magnetic fields tend to suppress fluctuations, in relatively clean samples with weak interactions fluctuations are found to grow with the magnetic field. This is attributed to the localization properties of the electron states, which may be measured by the participation ratio and the inverse participation number. It is also observed that at the frustration where the Fermi level is degenerate, localization or modulation of electrons is enhanced, raising fluctuations. Strong frustration in general suppresses effects of the interaction on the inverse compressibility and on the configuration of electrons.Comment: 15 pages, 18 figures, To appear in Phys. Rev.

Relaxation and Coarsening Dynamics in Superconducting Arrays

We investigate the nonequilibrium coarsening dynamics in two-dimensional overdamped superconducting arrays under zero external current, where ohmic dissipation occurs on junctions between superconducting islands through uniform resistance. The nonequilibrium relaxation of the unfrustrated array and also of the fully frustrated array, quenched to low temperature ordered states or quasi-ordered ones, is dominated by characteristic features of coarsening processes via decay of point and line defects, respectively. In the case of unfrustrated arrays, it is argued that due to finiteness of the friction constant for a vortex (in the limit of large spatial extent of the vortex), the typical length scale grows as $\ell_s \sim t^{1/2}$ accompanied by the number of point vortices decaying as $N_v \sim 1/t$. This is in contrast with the case that dominant dissipation occurs between each island and the substrate, where the friction constant diverges logarithmically and the length scale exhibits diffusive growth with a logarithmic correction term. We perform extensive numerical simulations, to obtain results in reasonable agreement. In the case of fully frustrated arrays, the domain growth of Ising-like chiral order exhibits the low-temperature behavior $\ell_q \sim t^{1/z_q}$, with the growth exponent $1/z_q$ apparently showing a strong temperature dependence in the low-temperature limit.Comment: 9 pages, 5 figures, to be published in Phys. Rev.

Characterisation of dust emissions from machined engineered stones to understand the hazard for accelerated silicosis

Engineered stones are novel construction materials associated with a recent upsurge in silicosis cases among workers in the stonemason industry. In order to understand the hazard for the short latency of lung disease among stonemasons, we simulated real-time dust exposure scenario by dry-machining engineered stones in controlled conditions, capturing and analysing the respirable dust generated for physical and chemical characteristics. Natural granite and marble were included for comparison. Cutting engineered stones generated high concentrations of very fine particles ( 80% respirable crystalline silica content, in the form of quartz and cristobalite. Engineered stones also contained 8–20% resin and 1–8% by weight metal elements. In comparison, natural stones had far lower respirable crystalline silica (4- 30%) and much higher metal content, 29–37%. Natural stone dust emissions also had a smaller surface area than engineered stone, as well as lower surface charge. This study highlighted the physical and chemical variability within engineered stone types as well as between engineered and natural stones. This information will ultimately help understand the unique hazard posed by engineered stone fabrication work and help guide the development of specific engineering control measures targeting lower exposure to respirable crystalline silica.Chandnee Ramkissoon, Sharyn Gaskin, Leigh Thredgold, Tony Hall, Shelley Rowett, Richard Gu

Quantum phase transitions in superconducting arrays under external magnetic fields

We study the zero-temperature phase transitions of two-dimensional superconducting arrays with both the self- and the junction capacitances in the presence of external magnetic fields. We consider two kinds of excitations from the Mott insulating phase: charge-dipole excitations and single-charge excitations, and apply the second-order perturbation theory to find their energies. The resulting phase boundaries are found to depend strongly on the magnetic frustration, which measures the commensurate-incommensurate effects. Comparison of the obtained values with those in recent experiment suggests the possibility that the superconductor-insulator transition observed in experiment may not be of the Berezinskii-Kosterlitz-Thouless type. The system is also transformed to a classical three-dimensional XY model with the magnetic field in the time-direction; this allows the analogy to bulk superconductors, revealing the nature of the phase transitions.Comment: 9 pages including 7 figures, to appear in Phys. Rev.

Spatiotemporal Stochastic Resonance in Fully Frustrated Josephson Ladders

We consider a Josephson-junction ladder in an external magnetic field with half flux quantum per plaquette. When driven by external currents, periodic in time and staggered in space, such a fully frustrated system is found to display spatiotemporal stochastic resonance under the influence of thermal noise. Such resonance behavior is investigated both numerically and analytically, which reveals significant effects of anisotropy and yields rich physics.Comment: 8 pages in two columns, 8 figures, to appear in Phys. Rev.

Mapping nanoscale electrostatic field fluctuations around graphene dislocation cores using four-dimensional scanning transmission electron microscopy (4D-STEM)

Defects in crystalline lattices cause modulation of the atomic density, and this leads to variations in the associated electrostatics at the nanoscale. Mapping these spatially varying charge fluctuations using transmission electron microscopy has typically been challenging due to complicated contrast transfer inherent to conventional phase contrast imaging. To overcome this, we used four-dimensional scanning transmission electron microscopy (4D-STEM) to measure electrostatic fields near point dislocations in a monolayer. The asymmetry of the atomic density in a (1,0) edge dislocation core in graphene yields a local enhancement of the electric field in part of the dislocation core. Through experiment and simulation, the increased electric field magnitude is shown to arise from "long-range" interactions from beyond the nearest atomic neighbor. These results provide insights into the use of 4D-STEM to quantify electrostatics in thin materials and map out the lateral potential variations that are important for molecular and atomic bonding through Coulombic interactions