Damping mechanism for the strongly renormalized cc-axis charge transport in high-TcT_c cuprate superconductors

We analyze the $c$-axis infrared reflectivity of La$_{1.85}$Sr$_{0.15}$CuO$_4$ single crystals. The plasma edge near 6 meV, observed below $T_c$, is due to Cooper-pair tunneling. This low value of the plasma edge is consistent with the $c$-axis plasma frequency ($\nu_p$) obtained from LDA calculations ($>0.1$ eV) if we take into account that the single-particle charge transport along the $c$ axis is strongly incoherent both above and below $T_c$. We find no evidence for a reduction of the $c$-axis scattering rate ($\gamma$) below $T_c$. Our investigation suggests $h\gamma>h\nu_{p}\gg 3.5k_BT_c$, which is exactly opposite to the clean limit. VSGD.94.6.1Comment: 4 pages, figures on request. Revtex, version 2, Materials Science Center Internal Report Number VSGD.94.6.

Tachyon Tunnelling in D-brane-anti-D-brane

Using the tachyon DBI action proposal for the effective theory of non-coincident D$_p$-brane-anti-D$_p$-brane system, we study the decay of this system in the tachyon channel. We assume that the branes separation is held fixed, i.e. no throat formation, and then find the bounce solution which describe the decay of the system from false to the true vacuum of the tachyon potential. We shall show that due to the non-standard form of the kinetic term in the effective action, the thin wall approximation for calculating the bubble nucleation rate gives a result which is independent of the branes separation. This unusual result might indicate that the true decay of this metastable system should be via a solution that represents a throat formation as well as the tachyon tunneling.Comment: 15 pages, 4 figures, Latex file, minor changes, reference adde

Global and Local D-vortices

Codimension-two objects on a system of brane-antibrane are studied in the context of Born-Infeld type effective field theory with a complex tachyon and U(1)$\times$U(1) gauge fields. When the radial electric field is turned on in D2${\bar {\rm D}}$2, we find static regular global and local D-vortex solutions which could be candidates of straight cosmic D-strings in a superstring theory. A natural extension to DF-strings is briefly discussed.Comment: 24 pages, 10 eps figure

Current-Density Functional Theory of the Response of Solids

The response of an extended periodic system to a homogeneous field (of wave-vector $q=0$) cannot be obtained from a $q=0$ time-dependent density functional theory (TDDFT) calculation, because the Runge-Gross theorem does not apply. Time-dependent {\em current}-density functional theory is needed and demonstrates that one key ingredient missing from TDDFT is the macroscopic current. In the low-frequency limit, in certain cases, density polarization functional theory is recovered and a formally exact expression for the polarization functional is given.Comment: 5 pages, accepted in PR

D-brane anti-D-brane effective action and brane interaction in open string channel

We construct the effective action of a $D_p$-brane-anti-$D_p$-brane system by making use of the non-abelian extension of tachyonic DBI action. We succeed the construction by restricting the Chan-Paton factors of two non-BPS $D_p$-branes in the action to the Chan-Paton factors of a $D_p\bar{D}_p$ system. For the special case that both branes are coincident, the action reduces to the one proposed by A. Sen. \\The effective $D_p\bar{D}_p$ potential indicates that when branes separation is larger than the string length scale, there are two minima in the tachyon direction. As branes move toward each other under the gravitational force, the tachyon tunneling from false to true vacuum may make a bubble formation followed by a classical evolution of the bubble. On the other hand, when branes separation is smaller than the string length scale, the potential shows one maximum and one minimum. In this case, a homogeneous tachyon rolling in real time makes an attractive potential for the branes distance. This classical force is speculated to be the effective force between the two branes.Comment: Latex, 14 pages, 1 figure, the version appears in JHE

Mg-modified Zn-Co-Fe-La nano ferrites: a study of structural, morphological, vibrational, electro-optical, dielectric and magnetic evolution

The series of Zn0.4Co0.6−xMgxFe1.9La0.1O4 (x = 0.0, 0.15, 0.30, 0.45, 0.6) nanoferrites prepared via co-precipitation technique. Scherrer and Williamson-Hall (W-H) methods were used to find the crystallite size (29.6–39.2 nm and 31.6–36.3 nm, respectively) and lattice constant was calculated (8.406–8.395 Å). Moreover, Fourier transform infrared (FTIR) spectroscopy revealed the existence of absorption bands along with functional groups. The vibrations of O2- ions at the tetrahedral and octahedral sites were shown by the Raman five active modes. DC resistivity reduced in the range of 5.2961 × 108 Ω cm to 9.6453 × 107 Ω cm for x = 0.0 to x = 0.6, respectively. The maximum DC resistivity and activation energy (0.1035 eV) were obtained at the parent sample (Zn0.4Co0.6Fe1.9La0.1O4). The optical bandgaps reduced from 2.61 to 1.47 eV, as the Mg2+ contents increased. With increasing frequency the dielectric loss and the dielectric constant decrease. The magnetic parameters such as saturation magnetization (Ms = 60.82–25.94 emu/g), remnant magnetization (Mr = 47.82–18.64 emu/g), and coercivity (Hc = 1334–511 Oe) demonstrated reducing trends with the increase of Mg2+ doping. The best magnetic behavior of the as-prepared samples suitable in microwave devices was observed for Zn0.4Co0.6Fe1.9La0.1O4 sample

Time Evolution via S-branes

Using S(pacelike)-branes defined through rolling tachyon solutions, we show how the dynamical formation of D(irichlet)-branes and strings in tachyon condensation can be understood. Specifically we present solutions of S-brane actions illustrating the classical confinement of electric and magnetic flux into fundamental strings and D-branes. The role of S-branes in string theory is further clarified and their RR charges are discussed. In addition, by examining ``boosted'' S-branes, we find what appears to be a surprising dual S-brane description of strings and D-branes, which also indicates that the critical electric field can be considered as a self-dual point in string theory. We also introduce new tachyonic S-branes as Euclidean counterparts to non-BPS branes.Comment: 62 pages, 10 figures. v2 references adde

Coaching and Communication Training for HPV Vaccination: A Cluster Randomized Trial

BACKGROUND AND OBJECTIVES: US health departments routinely conduct in-person quality improvement (QI) coaching to strengthen primary care clinics' vaccine delivery systems, but this intervention achieves only small, inconsistent improvements in human papillomavirus (HPV) vaccination. Thus, we sought to evaluate the effectiveness of combining QI coaching with remote provider communication training to improve impact. METHODS: With health departments in 3 states, we conducted a pragmatic 4-arm cluster randomized clinical trial with 267 primary care clinics (76% pediatrics). Clinics received in-person QI coaching, remote provider communication training, both interventions combined, or control. Using data from states' immunization information systems, we assessed HPV vaccination among 176 189 patients, ages 11 to 17, who were unvaccinated at baseline. Our primary outcome was the proportion of those, ages 11 to 12, who had initiated HPV vaccination at 12-month follow-up. RESULTS: HPV vaccine initiation was 1.5% points higher in the QI coaching arm and 3.8% points higher in the combined intervention arm than in the control arm, among patients ages 11 to 12, at 12-month follow-up (both P < .001). Improvements persisted at 18-month follow-up. The combined intervention also achieved improvements for other age groups (ages 13-17) and vaccination outcomes (series completion). Remote communication training alone did not outperform the control on any outcome. CONCLUSIONS: Combining QI coaching with remote provider communication training yielded more consistent improvements in HPV vaccination uptake than QI coaching alone. Health departments and other organizations that seek to support HPV vaccine delivery may benefit from a higher intensity, multilevel intervention approach

A Novel Methodology Using Simplified Approaches for Identification of Cracks in Beams

Abstract In this paper, natural frequency based forward and inverse methods are proposed for identifying multiple cracks in beams. Forward methods include simplified definition of the natural frequency drops caused by the cracks. The ratios between natural frequencies obtained from multi-cracked and un-cracked beams are determined by an approach that uses the local flexibility model of cracks. This approach does not consider nonlinear crack effects that can be easily neglected when the number of cracks is not excessive. In addition, an expression, which removes the necessity of repeating natural frequency analyses, is given for identifying the connection between the crack depths and natural frequency drops. These simplified approaches play crucial role in solving inverse problem using constituted crack detection methodology. Solution needs a number of measured modal frequency knowledge two times more than the number of cracks to be detected. Efficiencies of the methods are verified using the natural frequency ratios obtained by the finite element package. The crack detection methodology is also validated using some experimental natural frequency ratios given in current literature. Results show that the locations and depths ratios of cracks are successfully predicted by using the methods presented

Quantification and characterisation of porosity in selectively laser melted Al–Si10–Mg using x-ray computed tomography

We used X-ray computed tomography (CT), microscopy and hardness measurements to study Al–Si10–Mg produced by selective laser melting (SLM). Specimens were subject to a series of heat treatments including annealing and precipitation hardening. The specimen interiors were imaged with X-ray CT, allowing the non-destructive quantification and characterisation of pores, including their spatial distribution. The specimens had porosities less than 0.1%, but included some pores with effective cross-sectional diameters up to 260 μm. The largest pores were highly anisotropic, being flat and lying in the plane normal to the build direction. Annealing cycles caused significant coarsening of the microstructure and a reduction of the hardness from (114 ± 3) HV, in the as-built state, to (45 ± 1) HV, while precipitation hardening increased this to a final hardness of (59 ± 1) HV. The pore size and shape distributions were unaffected by the heat treatments. We demonstrate the applicability of CT measurements and quantitative defect analysis for the purposes of SLM process monitoring and refinement