Surface instabilities in granular matter and ion-sputtered surfaces

We apply a theoretical approach, originally introduced to describe aeolian ripples formation in sandy deserts, to the study of surface instability in ion sputtered surfaces. The two phenomena are distinct by several orders of magnitudes and by several physical mechanisms, but they obey to similar geometrical constraints and therefore they can be described by means of the same approach. This opens a novel conceptual framework for the study of the dynamical surface roughening and ripple formation on crystal and amorphous surfaces during ion sputtering.Comment: 14 pages, 3 figure

How ripples turn into dots: modeling ion-beam erosion under oblique incidence

Pattern formation on semiconductor surfaces induced by low energetic ion-beam erosion under normal and oblique incidence is theoretically investigated using a continuum model in form of a stochastic, nonlocal, anisotropic Kuramoto-Sivashinsky equation. Depending on the size of the parameters this model exhibits hexagonally ordered dot, ripple, less regular and even rather smooth patterns. We investigate the transitional behavior between such states and suggest how transitions can be experimentally detected.Comment: 11 pages, 4 figures, submitted for publication, revised versio

Ripples and ripples: from sandy deserts to ion-sputtered surfaces

We study the morphological evolution of surfaces during ion sputtering and we compare their dynamical corrugation with aeolian ripple formation in sandy deserts. We show that, although the two phenomena are physically different, they must obey similar geometrical constraints and therefore they can be described within the same theoretical framework. The present theory distinguishes between atoms that stay bounded in the bulk and others that are mobile on the surface. We describe the excavation mechanisms, the adsorption and the surface mobility by means of a continuous equation derived from the study of dune formation on sand. We explore the spontaneous development of ordered nanostructures and explain the different dynamical behaviours experimentally observed in metals or in semiconductors or in amorphous systems. We also show that this novel approach can describe the occurrence of rotation in the ripple direction and the formation of other kinds of self-organized patterns induced by changes in the sputtering incidence angle

Yellow Fever immunization: an integrative review on vacinal security / Imunização contra Febre Amarela: uma revisão integrativa sobre segurança vacinal

Introduction: Yellow fever (YF) is an acute, febrile, non-contagious infectious disease caused by arboviruses. Clinically, YF ranges from asymptomatic to malignant forms. The disease is transmitted by the bite of the female hematophagous arthropods of the Culicidae family. The main form of prevention of YF is vaccination. In this bias, some conditions determine the highest incidence of adverse effects of vaccination, such as: primary vaccination in people over 60 years of age, vaccination of patients with immunosuppressive diseases or hematological diseases. Adverse effects are also related to the techniques used, material used and patient guidance. Materials and methods: The databases used were Lilacs and Scielo to review the national and indexed literature about safety of yellow fever vaccine. The descriptors were: “immunization” and “yellow fever”. Original articles in Portuguese or English published from January 2010 to April 2020 were included. Articles that do not address vaccine safety and those that did not contain a Brazilian author were excluded. Editorials and reviews were excluded. Discussion: 71 articles were found. Of these, 66 were excluded because they did not meet the inclusion criteria. Thus, five studies were included. They claim, based on epidemiology, that most adverse reactions are due to the immunogenicity of the pertussis component – especially in children under 12 months of age – and methodological administration errors – such as primary vaccination in those over 60 years of age. The most common effects are fever, rash and hypersensitivity. Adverse reactions are rare, and serious ones, such as viceroscopic disease, are a minority. This scenario is caused by high efficiency in the quality verification of the National Immunization Program in Brazil. However, the efficiency of vaccination could increase through legislative mechanisms that regulate the forms of presentation on the packaging, avoiding waste and expiration. Conclusion: Little is national production on the theme. References indicate high safety and quality in the surveillance and legislation of immunization - despite, greater training of professionals involved in prescription and administration could increase the cost benefit of vaccination. Thus, the discussion and clarification about vaccine safety is one of the foundations for opposing the growing of against-vaccination trend. Financial Support: This scientific work does not have financial support from institutions or people

Children\u2019s ethical thinking: the \u201cMelArete\u201d project

\u201cMelArete\u201d is an educative and research project promoted by the Center of Educational and Didactic Research of the University of Verona in Italy. The word \u201cMelArete\u201d originates from the union of the Greek terms \u201cmel\ue9te\u201d (which means \u201ccare\u201d) and \u201caret\ue9\u201d (which means \u201cvirtue\u201d). The project is aimed at educating children to virtue ethics and exploring their ethical thinking (Mortari and Mazzoni, 2014). The theoretical background is grounded in the Aristotelian and Socratic ethical visions. Important references are also found in the philosophy of care (Held, 2006; Mortari, 2015; Noddings, 1984, 1992) and in the concept of Ricoeur (1990) about the distinction between ethics and morality. The epistemological background of the research refers to \u201cnaturalistic inquiry\u201d (Lincoln and Guba, 1985), according to which the phenomenon under study should be investigated in the context where it appears. The project involves children attending kindergarten (5-6 y.o.) and primary school (9-10 y.o.). The experience is aimed at encouraging children to reflect about the concepts of \u201cgood\u201d and \u201ccare\u201d, about the general idea of \u201cvirtue\u201d and about some specific virtues, such as courage, generosity, respect and justice. The activities designed to reach these educative aims and collect data for the research are the following: class conversations, narratives, vignettes, games. Another important activity is the \u201cdiary of virtue\u201d, a journal where children reflect on their everyday ethical experience. The qualitative data analysis, that follows an inductive and phenomenological approach (Mortari, 2007), is still in progress. However, we can already present some specific examples that show the richness of children\u2019s ethical thinking

Initial Penetration of an Elastic Axially Symmetric Indenter into a Rigid-Perfectly-Plastic Half-Space

This paper is concerned with the axially symmetric plastic flow of a rigid perfectly-plastic nonhardening halfspace. The initial penetration of the elastic indenter is studied based on Haar and von Karman hypothesis. The analytical distribution of contact stress and the approximate penetration depth of the indenter are obtained

Adiabatic or Non-Adiabatic? Unraveling the Nature of Initial Conditions in the Cosmological Gravitational Wave Background

The non-thermal nature of the stochastic gravitational-wave background of cosmological origin (CGWB) poses a challenge in defining the initial conditions for the graviton overdensity. Specifically, the adiabatic initial condition, which holds for Cosmic Microwave Background (CMB) photons, is not guaranteed a priori for the primordial GWs. In this letter, we compute the initial conditions for the cosmological background generated by quantum fluctuations of the metric during inflation. Our analysis reveals that adiabatic initial conditions are no longer valid. The violation of adiabaticity arises from the presence of independent tensor perturbations during inflation, which behave as two extra fields that affect the standard single-clock argument. Since the energy density of the CGWB is subdominant compared to ordinary matter, gravitational radiation plays a negligible role in Einstein's equations. Therefore, the only way to compute the initial conditions is to perturb the energy-momentum tensor defined in terms of the gravitational strain. A direct consequence of our finding is that the initial conditions from inflation enhance the total CGWB angular power-spectrum by an order of magnitude compared to the standard adiabatic case.Comment: 7 pages, 1 figur

Circular Polarization of the Astrophysical Gravitational Wave Background

The circular polarization of gravitational waves is a powerful observable to test parity violation in gravity and to distinguish between the primordial or the astrophysical origin of the stochastic background. This property comes from the expected unpolarized nature of the homogeneous and isotropic astrophysical background, contrary to some specific cosmological sources that can produce a polarized background. However, in this work we show that there is a non-negligible amount of circular polarization also in the astrophysical background, generated by Poisson fluctuations in the number of unresolved sources, which can be detected by the third-generation interferometers with signal-to-noise ratio larger than one. We also explain in which cases the gravitational wave maps can be cleaned from this extra source of noise, exploiting the frequency and the angular dependence, in order to search for signals from the early Universe. Future studies about the detection of polarized cosmological backgrounds with ground- and space-based interferometers should account for the presence of such a foreground contribution.Comment: 10 pages, 1 figure. V2 matches the version accepted by PRL for publicatio

Growth and magnetism of self-organized arrays of Fe(110) wires formed by deposition on kinetically grooved W(110)

Homoepitaxy of W(110) and Mo(110) is performed in a kinetically-limited regime to yield a nanotemplate in the form of a uniaxial array of hills and grooves aligned along the [001] direction. The topography and organization of the grooves were studied with RHEED and STM. The nanofacets, of type {210}, are tilted 18° away from (110). The lateral period could be varied from 4 to 12nm by tuning the deposition temperature. Magnetic nanowires were formed in the grooves by deposition of Fe at 150°C on such templates. Fe/W wires display an easy axis along [001] and a mean blocking temperature Tb=100KComment: Proceedings of ECOSS 2006 (Paris