Real photons produced from photoproduction in pppp collisions

We calculate the production of real photons originating from the photoproduction in relativistic $pp$ collisions. The Weizs$\ddot{\mathrm{a}}$cker-Williams approximation in the photoproduction is considered. Numerical results agree with the experimental data from Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC). We find that the modification of the photoproduction is more prominent in large transverse momentum region.Comment: 2 figure

Experimental and Numerical Investigation on Progressive Collapse Resistance of Post-tensioned Precast Concrete Beam-Column Sub-assemblages

In this paper, four 1/2 scaled precast concrete (PC) beam-column sub-assemblages with high performance connection were tested under push-down loading procedure to study the load resisting mechanism of PC frames subjected to different column removal scenarios. The parameters investigated include the location of column removal and effective prestress in tendons. The test results indicated that the failure modes of unbonded post-tensioned precast concrete (PTPC) frames were different from that of reinforced concrete (RC) frames: no cracks formed in the beams and wide opening formed near the beam to column interfaces. For specimens without overhanging beams, the failure of side column was eccentric compression failure. Moreover, the load resisting mechanisms in PC frames were significantly different from that of RC frames: the compressive arch action (CAA) developed in concrete during column removal was mainly due to actively applied pre-compressive stress in the concrete; CAA will not vanish when severe crush in concrete occurred. Thus, it may provide negative contribution for load resistance when the displacement exceeds one-beam depth; the tensile force developed in the tendons could provide catenary action from the beginning of the test. Moreover, to deeper understand the behavior of tested specimens, numerical analyses were carried out. The effects of concrete strength, axial compression ratio at side columns, and loading approaches on the behavior of the sub-assemblages were also investigated based on validated numerical analysis

Singularity in the boundary resistance between superfluid 4^4He and a solid surface

We report new measurements in four cells of the thermal boundary resistance $R$ between copper and $^4$He below but near the superfluid-transition temperature $T_\lambda$. For $10^{-7} \leq t \equiv 1 - T/T_\lambda \leq 10^{-4}$ fits of $R = R_0 t^{x_b} + B_0$ to the data yielded $x_b \simeq 0.18$, whereas a fit to theoretical values based on the renormalization-group theory yielded $x_b = 0.23$. Alternatively, a good fit of the theory to the data could be obtained if the {\it amplitude} of the prediction was reduced by a factor close to two. The results raise the question whether the boundary conditions used in the theory should be modified.Comment: 4 pages, 4 figures, revte

X-ray Properties of Radio-Selected Dual Active Galactic Nuclei

Merger simulations predict that tidally induced gas inflows can trigger kpc-scale dual active galactic nuclei (dAGN) in heavily obscured environments. Previously with the Very Large Array, we have confirmed four dAGN with redshifts between $0.04 < z < 0.22$ and projected separations between 4.3 and 9.2 kpc in the SDSS Stripe 82 field. Here, we present $Chandra$ X-ray observations that spatially resolve these dAGN and compare their multi-wavelength properties to those of single AGN from the literature. We detect X-ray emission from six of the individual merger components and obtain upper limits for the remaining two. Combined with previous radio and optical observations, we find that our dAGN have properties similar to nearby low-luminosity AGN, and they agree well with the black hole fundamental plane relation. There are three AGN-dominated X-ray sources, whose X-ray hardness-ratio derived column densities show that two are unobscured and one is obscured. The low obscured fraction suggests these dAGN are no more obscured than single AGN, in contrast to the predictions from simulations. These three sources show an apparent X-ray deficit compared to their mid-infrared continuum and optical [OIII] line luminosities, suggesting higher levels of obscuration, in tension with the hardness-ratio derived column densities. Enhanced mid-infrared and [OIII] luminosities from star formation may explain this deficit. There is ambiguity in the level of obscuration for the remaining five components since their hardness ratios may be affected by non-nuclear X-ray emissions, or are undetected altogether. They require further observations to be fully characterized.Comment: 11 pages, 5 figures, Accepted for publication in the Astrophysical Journa

Effects of lattice distortion and Jahn–Teller coupling on the magnetoresistance of La0.7Ca0.3MnO3 and La0.5Ca0.5CoO3 epitaxial films

Studies of La0.7Ca0.3MnO3 epitaxial films on substrates with a range of lattice constants reveal two dominant contributions to the occurrence of colossal negative magnetoresistance (CMR) in these manganites: at high temperatures (T → TC, TC being the Curie temperature), the magnetotransport properties are predominantly determined by the conduction of lattice polarons, while at low temperatures (T ≪ TC/, the residual negative magnetoresistance is correlated with the substrate-induced lattice distortion which incurs excess magnetic domain wall scattering. The importance of lattice polaron conduction associated with the presence of Jahn–Teller coupling in the manganites is further verified by comparing the manganites with epitaxial films of another ferromagnetic perovskite, La0.5Ca0.5CoO3. Regardless of the differences in the substrate-induced lattice distortion, the cobaltite films exhibit much smaller negative magnetoresistance, which may be attributed to the absence of Jahn–Teller coupling and the high electron mobility that prevents the formation of lattice polarons. We therefore suggest that lattice polaron conduction associated with the Jahn–Teller coupling is essential for the occurrence of CMR, and that lattice distortion further enhances the CMR effects in the manganites

Cost-effective River Water Quality Management using Integrated Real-Time Control Technology

This is the author accepted manuscript. The final version is available from American Chemical Society via the DOI in this record.Integrated real-time control (RTC) of urban wastewater systems is increasingly presented as a promising and emerging strategy to deliver improved surface water quality by responsive operation according to real-time data collected from the sewer system, treatment plant and the receiving water. However, the detailed benefits and costs associated with integrated RTC have yet to be comprehensively evaluated. Built on state-of-the-art modelling and analytical tools, a three-step framework is proposed to develop integrated RTC strategies which cost-effectively maximize environmental outcomes. Results from a case study show integrated RTC can improve river quality by over 20% to meet the “good status” requirements of the EU Water Framework Directive with a 15% reduced cost, due to responsive aeration with changing environmental assimilation capacity. The cost-effectiveness of integrated RTC strategies is further demonstrated against tightening environmental standards (to the strictest levels) and against two commonly used compliance strategies. Compared to current practices (seasonal/monthly based operation), integrated RTC strategies can reduce costs whilst improving resilience of the system to disturbances and reducing environmental risk.The authors would like to thank the financial support from the SANITAS project (EU FP7 Marie Curie Initial Training Network – ITN – 289193), data provision for the case study from North Wyke Farm, and support from the Building Resilience into Risk Management project (EP/N010329/1) and the third author’s Safe & SuRe research fellowship (EP/K006924/1) both funded by the UK EPSRC

Understanding degenerate ground states of a protected quantum circuit in the presence of disorder

A recent theoretical proposal suggests that a simple circuit utilizing two superinductors may produce a qubit with ground state degeneracy [P. Brooks et al., Phys. Rev. A 87, 052306 (2013)]. We perform a full circuit analysis along with exact diagonalization of the circuit Hamiltonian to elucidate the nature of the spectrum and low-lying wave functions of this $0-\pi$ device. We show that the ground state degeneracy is robust to disorder in charge, flux and critical current as well as insensitive to modest variations in the circuit parameters. Our treatment is non-perturbative, provides access to excited states and matrix elements, and is immediately applicable also to intermediate parameter regimes of experimental interest.Comment: 9 pages, 8 figure

Synchrotron Mössbauer spectroscopic study of ferropericlase at high pressures and temperatures

The electronic spin state of Fe^(2+) in ferropericlase, (Mg_(0.75)Fe_(0.25))O, transitions from a high-spin (spin unpaired) to low-spin (spin paired) state within the Earth’s mid-lower mantle region. To better understand the local electronic environment of high-spin Fe^(2+) ions in ferropericlase near the transition, we obtained synchrotron Mössbauer spectra (SMS) of (Mg_(0.75),Fe_(0.25))O in externally heated and laser-heated diamond anvil cells at relevant high pressures and temperatures. Results show that the quadrupole splitting (QS) of the dominant high-spin Fe^(2+) site decreases with increasing temperature at static high pressure. The QS values at constant pressure are fitted to a temperature-dependent Boltzmann distribution model, which permits estimation of the crystal-field splitting energy (Δ_3) between the d_(xy_ and d_(xz) or d_(zy) orbitals of the t_(2g) states in a distorted octahedral Fe^(2+) site. The derived Δ_3 increases from approximately 36 meV at 1 GPa to 95 meV at 40 GPa, revealing that both high pressure and high temperature have significant effects on the 3d electronic shells of Fe^(2+) in ferropericlase. The SMS spectra collected from the laser-heated diamond cells within the time window of 146 ns also indicate that QS significantly decreases at very high temperatures. A larger splitting of the energy levels at high temperatures and pressures should broaden the spin crossover in ferropericlase because the degeneracy of energy levels is partially lifted. Our results provide information on the hyperfine parameters and crystal-field splitting energy of high-spin Fe^(2+) in ferropericlase at high pressures and temperatures, relevant to the electronic structure of iron in oxides in the deep lower mantle