Toy Models for Galaxy Formation versus Simulations

We describe simple useful toy models for key processes of galaxy formation in its most active phase, at z > 1, and test the approximate expressions against the typical behaviour in a suite of high-resolution hydro-cosmological simulations of massive galaxies at z = 4-1. We address in particular the evolution of (a) the total mass inflow rate from the cosmic web into galactic haloes based on the EPS approximation, (b) the penetration of baryonic streams into the inner galaxy, (c) the disc size, (d) the implied steady-state gas content and star-formation rate (SFR) in the galaxy subject to mass conservation and a universal star-formation law, (e) the inflow rate within the disc to a central bulge and black hole as derived using energy conservation and self-regulated Q ~ 1 violent disc instability (VDI), and (f) the implied steady state in the disc and bulge. The toy models provide useful approximations for the behaviour of the simulated galaxies. We find that (a) the inflow rate is proportional to mass and to (1+z)^5/2, (b) the penetration to the inner halo is ~50% at z = 4-2, (c) the disc radius is ~5% of the virial radius, (d) the galaxies reach a steady state with the SFR following the accretion rate into the galaxy, (e) there is an intense gas inflow through the disc, comparable to the SFR, following the predictions of VDI, and (f) the galaxies approach a steady state with the bulge mass comparable to the disc mass, where the draining of gas by SFR, outflows and disc inflows is replenished by fresh accretion. Given the agreement with simulations, these toy models are useful for understanding the complex phenomena in simple terms and for back-of-the-envelope predictions.Comment: Resubmitted to MNRAS after responding to referee's comments; Revised figure

On the reliability of electrical drives for safety-critical applications

The aim of this work is to present some issues related to fault tolerant electric drives,which are able to overcome different types of faults occurring in the sensors, in thepower converter and in the electrical machine, without compromising the overallfunctionality of the system. These features are of utmost importance in safety-criticalapplications. In this paper, the reliability of both commercial and innovative driveconfigurations, which use redundant hardware and suitable control algorithms, will beinvestigated for the most common types of fault: besides standard three phase motordrives, also multiphase topologies, open-end winding solutions, multi-machineconfigurations will be analyzed, applied to various electric motor technologies. Thecomplexity of hardware and control strategies will also be compared in this paper, sincethis has a tremendous impact on the investment costs

Joint constraints on the Galactic dark matter halo and Galactic Centre from hypervelocity stars

Article / Letter to editorSterrewach

Combining weak and strong lensing in cluster potential reconstruction

We propose a method for recovering the two-dimensional gravitational potential of galaxy clusters which combines data from weak and strong gravitational lensing. A first estimate of the potential from weak lensing is improved at the approximate locations of critical curves. The method can be fully linearised and does not rely on the existence and identification of multiple images. We use simulations to show that it recovers the surface-mass density profiles and distributions very accurately, even if critical curves are only partially known and if their location is realistically uncertain. We further describe how arcs at different redshifts can be combined, and how deviations from weak lensing can be included.Comment: 9 pages, 5 figures, A&A in press, changes to match the accepted versio

Comparación del test directo de anticuerpos fluorescentes y el cultivo bacteriológico para detección de Brucella suis

Methods available for detection of Brucella sp from different specimens include bacteriological culture or detection of specific DNA fragments by polymerase chain reaction. The use of fluorescein-labeled anti-Brucella globulin for demonstrating this antigen in animal tissues is a simple, easy, reproducible, cheap and fast technique. The aim of this work was to evaluate the gamma globulin fraction of polyclonal anti-Brucella abortus serum labeled with fluorescein iso-tio-cyanate (FITC-labeled antibody): 1) against different smooth and rough Brucella sp, 2) against bacterium of other genus, and 3) to compare direct fluorescent antibody test results with bacteriological culture for the detection of B. suis in different tissues from infected animals. This conjugate stained all Brucella sp with different intensities but it did not stain any heterologous bacterium tested. Background fluorescence associated with its use on smears from infected sources of different specimens was particularly low. Most of the infected tissues showed the presence of yellowish-green fluorescent organisms with brucella morphology. The tested FITC-labeled antibody allows a quick, effective and inexpensive diagnosis of brucellosis.El diagnóstico de brucelosis se apoya en el cultivo bacteriológico o en la detección de fragmentos de ADN de la bacteria mediante la reacción en cadena de la polimerasa. El empleo de una inmunoglobulina anti-Brucella conjugada a fluoresceína para la detección de este antígeno en tejidos constituye una técnica simple, fácil, reproducible, económica y rápida. El objetivo de este trabajo fue evaluar la fracción gammaglobulínica de un suero policlonal anti-Brucella abortus marcada con isotiocianato de fluoresceína (FITC), 1) contra distintas especies lisas y rugosas de Brucella sp, 2) contra bacterias de otros géneros, y 3) comparar los resultados obtenidos con la inmunofluorescencia directa y el cultivo bacteriológico para la detección de B. suis en distintos tejidos de porcinos infectados. Este conjugado detectó todas las brucelas con distinta intensidad de fluorescencia, pero no hubo fluorescencia inespecífica cuando se ensayaron las bacterias de otros géneros. La fluorescencia de fondo en muestras de los distintos tejidos infectados fue baja. La mayoría de los tejidos infectados mostraron la presencia de microorganismos verde-fluorescentes con la morfología de las brucelas. El anticuerpo conjugado a FITC permitió un diagnóstico de brucelosis rápido, efectivo y económico

Power Loss Modelling of GaN HEMT based 3L ANPC Three Phase Inverter for different PWM Techniques

The paper presents a straightforward modelling approach to compute the power loss distribution in GaN HEMT based three phase and three level (3L) active neutral point clamped (ANPC) inverters, for different pulse width modulated techniques. Conduction and switching losses averaged over each PWM switching period are analytically computed by starting from the operating conditions of the AC load and data of GaN power devices. The accuracy of the proposed analytical approach is evaluated through a circuit based power electronics simulation tool, applied to different carrier-based PWM strategies.Comment: 10 pages, 13 figures, 24th European Conference on Power Electronics and Applications ( IEEE EPE 2022 ECCE Europe). This work has been carried out in the framework of the ECSEL-JU Project GaN4AP (Gallium Nitride for Advanced Power Applications) - Grant Agreement No.10100731

Probing the dynamical state of galaxy clusters

We show how hydrostatic equilibrium in galaxy clusters can be quantitatively probed combining X-ray, SZ, and gravitational-lensing data. Our previously published method for recovering three-dimensional cluster gas distributions avoids the assumption of hydrostatic equilibrium. Independent reconstructions of cumulative total-mass profiles can then be obtained from the gas distribution, assuming hydrostatic equilibrium, and from gravitational lensing, neglecting it. Hydrostatic equilibrium can then be quantified comparing the two. We describe this procedure in detail and show that it performs well on progressively realistic synthetic data. An application to a cluster merger demonstrates how hydrostatic equilibrium is violated and restored as the merger proceeds.Comment: 10 pages, 6 figures, submitted to A&

Joint constraints on the Galactic dark matter halo and Galactic Centre from hypervelocity stars

GalaxiesStars and planetary system

Joint constraints on the Galactic dark matter halo and GC from hypervelocity stars

The mass assembly history of the Milky Way can inform both theory of galaxy formation and the underlying cosmological model. Thus, observational constraints on the properties of both its baryonic and dark matter contents are sought. Here, we show that hypervelocity stars (HVSs) can in principle provide such constraints. We model the observed velocity distribution of HVSs, produced by tidal break-up of stellar binaries caused by Sgr A*. Considering a Galactic Centre (GC) binary population consistent with that inferred in more observationally accessible regions, a fit to current HVS data with significance level >5 per cent can only be obtained if the escape velocity from the GC to 50 kpc is VG ≲ 850 km s^(−1), regardless of the enclosed mass distribution. When a Navarro, Frenk and White matter density profile for the dark matter halo is assumed, haloes with VG ≲ 850 km s^(−1) are in agreement with predictions in the Λ cold dark matter model and a subset of models around M200 ∼ 0.5–1.5 × 10^(12) M_⊙ and rs ≲ 35 kpc can also reproduce Galactic circular velocity data. HVS data alone cannot currently exclude potentials with VG > 850 km s^(−1). Finally, specific constraints on the halo mass from HVS data are highly dependent on the assumed baryonic mass potentials. This first attempt to simultaneously constrain GC and dark halo properties is primarily hampered by the paucity and quality of data. It nevertheless demonstrates the potential of our method, that may be fully realized with the ESA Gaia mission