Vector-like Quarks at the Origin of Light Quark Masses and Mixing

We show how a novel fine-tuning problem present in the Standard Model can be solved through the introduction of a single flavour symmetry G, together with three $Q = - 1/3$ quarks, three $Q = 2/3$ quarks, as well as a complex singlet scalar. The symmetry G is extended to the additional fields and it is an exact symmetry of the Lagrangian, only spontaneously broken by the vacuum. Specific examples are given and a phenomenological analysis of the main features of the model is presented. It is shown that even for vector-like quarks with masses accessible at the LHC, one can have realistic quark masses and mixing, while respecting the strict constraints on process arising from flavour changing neutral currents (FCNC). The vector-like quark decay channels are also described.Comment: 25 pages, no figure

A squeeze-like operator approach to position-dependent mass in quantum mechanics

We provide a squeeze-like transformation that allows one to remove a position dependent mass from the Hamiltonian. Methods to solve the Schr\"{o}dinger equation may then be applied to find the respective eigenvalues and eigenfunctions. As an example, we consider a position-dependent-mass that leads to the integrable Morse potential and therefore to well-known solutions

The FuGas 2.5 updated for the effects of surface turbulence on the transfer velocity of gases at the atmosphere–ocean interface

Accurately estimating air–water gas exchanges requires considering other factors besides wind speed. These are particularly useful for coastal ocean applications, where the sea-state varies at fine spatial and temporal resolutions. We upgrade FuGas 2.5 with improved formulations of the gas transfer velocity parametrized based on friction velocity, kinetic energy dissipation, roughness length, air-flow conditions, drift current and wave field. We then test the algorithm with field survey data collected in the Baltic Sea during spring–summer of 2014 and 2015. Collapsing turbulence was observed when gravity waves were the roughness elements on the sea-surface, travelling at a speed identical to the wind. In such cases, the turbulence driven transfer velocities (from surface renewal and micro-scale wave breaking) could be reduced from 20 cm h1 to 5 cm h1. However, when peak gravity waves were too flat, they were presumably replaced by capillary-gravity waves as roughness elements. Then, a substantial increase in the turbulence and roughness length was observed, despite the low and moderate winds, leading to transfer velocities up to twice as large as those predicted by empirical u10-based formulations.FCT/MCTES (PIDDAC) through project LARSyS: FCT Pluriannual funding 2020-2023 UIDB/EEA/50009/2020; FCT: DL57/2016/CP [1361]/CT[0008].info:eu-repo/semantics/publishedVersio

Electroactive Nanostructured Membranes (ENM): Synthesis and Electrochemical Properties of Redox Mediator-Modified Gold Nanoparticles Using a Dendrimer Layer-by-Layer Approach

The layer-by-layer (LbL) self-assembly process has become an important tool in the fabrication of nanostructured devices for electrochemical applications, especially in those cases where control at the molecular level is required. In this paper we present a system based on electroactive nanostructured membranes (ENM) with ITO-PVS/PAMAM-Au LbL electrodes, in which a redox mediator (Me) is electrodeposited around the Au nanoparticles to form an ITO-PVS/PAMAM-Au@Me system. The redox mediators used were Co, Fe, Ni and Cu hexacyanoferrates. The 3-bilayer ITO-PVS/PAMAM-Au@Me system was characterized electrochemically by cyclic voltammetry and electrochemical impedance spectroscopy. All hexacyanoferrate modified electrodes showed electrocatalytic activity towards hydrogen peroxide, thus demonstrating that this new approach can be used in biosensors and nanodevices, where a redox mediator is required

Recovery of substrates and macro-benthos after fishing trials with a new Portuguese clam dredge

The effect of dredging on bottom structure was assessed, to estimate the damage inflicted on the benthic macrofauna left on the dredge path and to evaluate aggregations of scavengers within the track. Sediment suspended during dredging rapidly resettled both on sand and sandy-mud bottoms. Dredge tracks were deeper on sandy-mud sediments and persisted longer than in sandy sediments. The disappearance of tracks in both sediment types depended both on current strength and wave action. Damage and mortality induced by dredging on the macrobenthic animals left on the dredge path was relatively low. Post-fishing diver observations showed that damaged animals left on the dredge path rapidly attracted scavengers, mainly Ophiura albida. Immediately after the tow ophiuras reached densities 8 times greater in the track region than in the background. However, they dispersed again rapidly because only few damaged fauna were available on the dredge tracks. Undamaged or slightly damaged shellfish started to rebury immediately after escaping from the dredge

Cuerpo y disciplina, orden y poder: Del Instructor Popular a los Tribunales Infantiles

A fines del siglo XIX, en la República Argentina, el periódico mendocino El Instructor Popular publica el intercambio epistolar entre dos graduados de la Escuela Normal de Paraná: Carlos Norberto Vergara y Ernesto A.Bavio. Reprender, reformar y corregir el error, las faltas y la ignorancia, fueron las justificaciones para hacer uso de punteros y palmetas e incorporar la pena, el dolor y la culpa como correctivos, en las instituciones educativas de "la letra con la sangre entra" en manos de "maestros normales que quieren gobernar con el lático". El espistolario visibiliza y reprueba ciertas prácticas que tuvieron al cuerpo infantil como territorio de anclaje para la institucionalización educativa. Puntear esa conjetura nos permite trazar continuidades y discontinuidades entre los "principios de la disciplina" y "los castigos corporales" como antecedentes para los "tribunales infantiles", implementados en la Escuela Quintana de la Provincia de Mendoza, por Florencia Fossatti, en las primeras décadas del siglo XX.Fil: Alvarado, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Ciencias Humanas, Sociales y Ambientales; Argentin

Neutrino helicity asymmetries in leptogenesis

It is pointed out that the heavy singlet neutrinos characteristic of leptogenesis develop asymmetries in the abundances of the two helicity states as a result of the same mechanism that generates asymmetries in the standard lepton sector. Neutrinos and standard leptons interchange asymmetries in collisions with each other. It is shown that an appropriate quantum number, B-L', combining baryon, lepton and neutrino asymmetries, is not violated as fast as the standard B-L. This suppresses the washout effects relevant for the derivation of the final baryon asymmetry. One presents detailed calculations for the period of neutrino thermal production in the framework of the singlet seesaw mechanism.Comment: 11 pages, 1 figure, revtex, matches PRD versio

Can accretion disk properties distinguish gravastars from black holes?

Gravastars, hypothetic astrophysical objects, consisting of a dark energy condensate surrounded by a strongly correlated thin shell of anisotropic matter, have been proposed as an alternative to the standard black hole picture of general relativity. Observationally distinguishing between astrophysical black holes and gravastars is a major challenge for this latter theoretical model. In the context of stationary and axially symmetrical geometries, a possibility of distinguishing gravastars from black holes is through the comparative study of thin accretion disks around rotating gravastars and Kerr-type black holes, respectively. In the present paper, we consider accretion disks around slowly rotating gravastars, with all the metric tensor components estimated up to the second order in the angular velocity. Due to the differences in the exterior geometry, the thermodynamic and electromagnetic properties of the disks (energy flux, temperature distribution and equilibrium radiation spectrum) are different for these two classes of compact objects, consequently giving clear observational signatures. In addition to this, it is also shown that the conversion efficiency of the accreting mass into radiation is always smaller than the conversion efficiency for black holes, i.e., gravastars provide a less efficient mechanism for converting mass to radiation than black holes. Thus, these observational signatures provide the possibility of clearly distinguishing rotating gravastars from Kerr-type black holes.Comment: 12 pages, 12 figures. V2: 14 pages, significant discussion and references added, to appear in Class.Quant.Gra

The X-ray luminous galaxies optically classified as star forming are mostly narrow line Seyfert 1 s

[Context]: The optical and ultraviolet emission lines of galaxies are widely used to distinguish star-forming (SF) galaxies from active galactic nuclei (AGNs). However, this type of diagnostic has some associated uncertainties, because AGNs can be of low luminosity and/or heavily obscured, and the optical emission lines may be dominated by a stellar component. On the other hand, and despite its limitations, X-ray emission can be used as a reliable tracer of luminous AGNs. Several well-studied examples exist where the optical diagnostics are indicative of SF galaxy, but the X-ray properties reveal the presence of an AGN. [Aims]: We aim to characterize the nature of galaxies whose optical emission line diagnostics are consistent with star formation, but whose X-ray properties strongly point towards the presence of an AGN. Understanding these sources is of particular importance in assessing the completeness of AGN samples derived from large galaxy surveys, selected solely on the basis of their optical spectral properties. [Methods]: We construct a large sample of 211 narrow emission line galaxies (NELGs, which have full widths at half maximum (FWHMs) H β emission line star-forming>, we find a bimodal distribution in which 28 have X-ray luminosities in excess of 10 42 erg/s, large thickness parameters (T = F 2-10 keV/F [OIII] > 1) and large X-ray to optical flux ratios (X/O > 0.1), while the rest are consistent with being simply starforming galaxies. Those 28 galaxies exhibit the broadest H β line widths (FWHMs from ~300 to 1200 km s -1), and their X-ray spectrum is steeper than average and often displays a soft excess. [Conclusions]: We therefore conclude that the population of X-ray luminous NELGs with optical lines consistent with those of a starforming galaxy (which represent 19% of our whole sample) is largely dominated by narrow line Seyfert 1s (NLS1s). The occurrence of such sources in the overall optically selected sample is small (<2%), hence the contamination of optically selected galaxies by NLS1s is very small. © ESO, 2012.N. Castelló-Mor gratefully acknowledges the Spanish Ministerio de Ciencia e Innovación for a pre-doctoral fellowship. N.C.-M., X.B., L.B., and F.J.C. acknowledge partial financial support from the Spanish Ministerio de Ciencia e Innovación, through project AYA2010-21490-C02-01.Peer Reviewe