Global torques and stochasticity as the drivers of massive black hole pairing in the young Universe

The forthcoming Laser Interferometer Space Antenna (LISA) will probe the population of coalescing massive black hole (MBH) binaries up to the onset of structure formation. Here we simulate the galactic-scale pairing of $\sim10^6 M_\odot$ MBHs in a typical, non-clumpy main-sequence galaxy embedded in a cosmological environment at $z = 7-6$. In order to increase our statistical sample, we adopt a strategy that allows us to follow the evolution of six secondary MBHs concomitantly. We find that the magnitude of the dynamical-friction induced torques is significantly smaller than that of the large-scale, stochastic gravitational torques arising from the perturbed and morphologically evolving galactic disc, suggesting that the standard dynamical friction treatment is inadequate for realistic galaxies at high redshift. The dynamical evolution of MBHs is very stochastic, and a variation in the initial orbital phase can lead to a drastically different time-scale for the inspiral. Most remarkably, the development of a galactic bar in the host system either significantly accelerates the inspiral by dragging a secondary MBH into the centre, or ultimately hinders the orbital decay by scattering the MBH in the galaxy outskirts. The latter occurs more rarely, suggesting that galactic bars overall promote MBH inspiral and binary coalescence. The orbital decay time can be an order of magnitude shorter than what would be predicted relying on dynamical friction alone. The stochasticity, and the important role of global torques, have crucial implications for the rates of MBH coalescences in the early Universe: both have to be accounted for when making predictions for the upcoming LISA observatory.Comment: Accepted for publication in MNRAS; 15 pages, 10 Figures, 2 Table

Performance of a Y-Ba-Cu-O superconducting filter/GaAs low noise amplifier hybrid circuit

A superconducting 7.3 GHz two-pole microstrip bandpass filter and a GaAs low noise amplifier (LNA) were combined into an active circuit and characterized at liquid nitrogen temperatures. This superconducting/semiconducting circuit's performance was compared to a gold filter/GaAs LNA hybrid circuit. The superconducting filter/GaAs LNA hybrid circuit showed higher gain and lower noise figure than its gold counterpart

Relativistic models for quasi-elastic neutrino scattering

We present quasi-elastic neutrino-nucleus cross sections in the energy range from 150 MeV up to 5 GeV for the target nuclei 12C and 56Fe. A relativistic description of the nuclear dynamics and the neutrino-nucleus coupling is adopted. For the treatment of final-state interactions (FSI) we rely on two frameworks succesfully applied to exclusive electron-nucleus scattering: a relativistic optical potential and a relativistic multiple-scattering Glauber approximation. At lower energies, the optical-potential approach is considered to be the optimum choice, whereas at high energies a Glauber approach is more natural. Comparing the results of both calculations, it is found that the Glauber approach yields valid results down to the remarkably small nucleon kinetic energies of 200 MeV. We argue that the nuclear transparencies extracted from A(e,e'p) measurements can be used to obtain realistic estimates of the effect of FSI mechanisms on quasi-elastic neutrino-nucleus cross sections. We present two independent relativistic plane-wave impulse approximation (RPWIA) calculations of quasi-elastic neutrino-nucleus cross sections. They agree at the percent level, showing the reliability of the numerical techniques adopted and providing benchmark RPWIA results.Comment: revised version,28 pages, 7 figures, accepted in Phys.Rev.

Versatile multipass cell for laser spectroscopic trace gas analysis

The design, construction and characterization of a novel circular multipass cell for sensitive trace gas analysis are presented. This cell allows for easy modification of the optical path length without any changes of its physical parameters. Furthermore, it is suited for three different detection techniques: direct absorption, wavelength modulation and photoacoustics. To demonstrate its performance, mixing ratios of 13CO2 and N2O were measured from ambient air, using a quantum cascade laser. With the direct absorption method, noise equivalent 1-s precisions of 2.7ppb and 0.2ppb are achieved for 13CO2 and N2O, respectively. The wavelength modulation technique resulted in 4.3ppb precision with 1-s averaging for the 13CO2 measurements. AQ-factor of 190 and a normalized noise equivalent minimum absorption of 1.3×10−8cm−1 W Hz−1/2 are achieved using the photoacoustic techniqu

Reduced Brace Section (RXS) Proof of Concept: Phase 1B

This report presents the results from the second phase of a proof-of-concept series of tests of the reduced braced section (RXS) system. This system is intended to provide a cost-effective alternative for the design of Concentrically Braced Frames (CBFs) under earthquake loads. The second test investigated the behavior of the RXS system under cyclic loading. The hysteretic behavior of the specimen indicated that the behavior of the RXS system was sensitive to the eccentricity of the load imposed on the brace. Eccentric loading caused premature local bucking of the reduced section, which reduced the ability of the system to dissipate energy under repeated load reversals into the nonlinear range of response. The behavior observed during the test shows that local buckling is a mode of failure that must be prevented in this type of system because of its adverse effect on the ability of the system to dissipate energy. Also, the design of the system must take into account a minimum eccentricity of the load transmitted to the brace at the brace-frame connection. An alternative to improve the behavior of the system under repeated load reversals is to reinforce the reduced section in order to increase the local bucking load. This report includes the applicable information specified in TEST REPORTING REQUIREMENTS [AISC, 2002, S9].This research was sponsored in part by Butler Heavy Structures

Distribuição dos Foraminíferos e Tecamebas Ocorrentes no Manguezal do Rio Baguaçu, Cananéia, São Paulo - Relações com Parâmetros Ambientais

Neste estudo foram analisadas amostras coletadas ao longo de um perfil no interior de um manguezal no Rio Baguaçu (Cananéia, Brasil). Observou-se que as associações de foraminíferos refletiram um gradiente de confinamento acentuado à medida que as estações amostradas afastaram-se do canal principal de circulação, ocorrendo, neste sentido, diminuição da abundância e da diversidade da fauna por volume de amostra. Foram constatadas, ainda, evidências de correlação destes microrganismos com os valores de salinidade e temperatura observados no sedimento, assim como com a estrutura física da vegetação de mangue

The generalised relativistic Lindhard functions

We present here analytic expressions for the generalised Lindhard function, also referred to as Fermi Gas polarisation propagator, in a relativistic kinematic framework and in the presence of various resonances and vertices. Particular attention is payed to its real part, since it gives rise to substantial difficulties in the definition of the currents entering the dynamics.Comment: 48 pages, 2 figures, to be published in EPJ