253 research outputs found
Epitaxial thin films oxides on Fe: what happens when a low dimensional oxide grows on a highly reactive metal substrate?
No full textThe investigation of oxide films with a thickness of a few nanometers or below grown on another substrate is a scientific topic that has recently attracted a huge amount of experimental and theoretical research work [1].
In this contribution we shall focus on some of the recent advances in understanding the formation of transition metal oxide/Fe interfaces [2,3]. Fe can be considered on the one hand as a prototypical example of ferromagnetic material, and on the other hand as an example of a highly reactive metal. The former characteristic makes it particularly appealing for spintronic applications and magnetic storage media, while the latter makes the preparation of well-defined oxide/metal interfaces a difficult task. For this reason, despite the large body of literature focusing on the preparation and characterization of ultra-thin oxide films on inert materials such as noble and quasi noble metals, comparatively little is known about the atomic scale mechanisms driving the formation of the transition metal oxide/Fe interfaces.
In the first part of the talk we shall discuss the stabilization of single-layer-thick oxide films on Fe, by using selected examples involving the deposition of transition metals on the well-ordered and defect-free Fe(001)-p(1 × 1)O surface. This is characterized by one oxygen atom per surface unit cell which can be used as a reservoir for the stabilization and investigation of Fe-supported twodimensional transition metal oxides [4,5], avoiding at the same time the Fe oxidation occurring when more traditional preparation procedures (such as for instance metal deposition in a reactive oxygen atmosphere) are employed.
In the second part we shall discuss the growth of oxide films out of the interfacial layer, with particular emphasis on the growth mode leading at the same time to sharp interfaces, useful to correctly modeling the interfacial physical phenomena, and atomically flat surfaces, crucial to allow scanning probe microscopy studies down to the atomic scale.
References: [1] See e.g. S.Valeri and G. Pacchioni, eds., Oxide Ultrathin Films (Wiley-VCH Verlag, Weinheim,2011).
[2] M. Finazzi, L. Duò, and F. Ciccacci, Surf. Sci. Rep. 64, 139 (2009).
[3] M. Finazzi, L. Duò, and F. Ciccacci, eds., Magnetic Properties of Antiferromagnetic Oxide Materials: Surfaces, Interfaces and Thin Films (Wiley-VCH Verlag, Weinheim, 2010).
[4] A. Picone, G. Bussetti, M. Riva, A. Calloni, A. Brambilla, L. Duò, F. Ciccacci, and M. Finazzi, Phys. Rev. B 86, 075465 (2012).
[5] A. Picone, G. Fratesi, M. Riva, G. Bussetti, A. Calloni, A. Brambilla, M.I. Trioni, L. Duò, F. Ciccacci, M. Finazzi, Phys. Rev. B 87 (2013) 085403
A lei fora (e contra) da lei: a Amazônia como limiar
No full textRepresentada pela literatura, a Amazônia confi gura-se enquanto espaço fronteiriço, à margem da história, como se verifi ca em Inferno verde, de Alberto Rangel. Dessa obra, examina-se “Hospitalidade”, comparado, a seguir, com “Meu tio o Iauaretê”, de Guimarães Rosa. Embora, relativamente ao estilo e à estrutura, os dois contos sejam diferentes, expõem, ambos, um lugar noturno e selvático, com um homem extraviado no mato e com um assassino que lhe dá abrigo. Deste modo, Rangel e Rosa interrogam a hospitalidade num espaço banido e selvagem e propõem uma questão radical sobre o limite entre aquilo que é dentro ou fora da Lei. Questionam o limiar primordial separando e conjungindo, ao mesmo tempo, o humano e o animalLiterary representations of the Amazon tend to confi gure the region as a border space, outside of history, as in Alberto Rangel’s Inferno verde. This article opens with an examination of Rangel’s “Hospitality”, followed by Guimarães Rosa’s “Meu tio o Iauretê”. Despite stylistic and structural differences, the two short stories share nocturnal, wild settings, and depict a man who is lost in the wilderness and an assassin who houses him. In this manner Rangel and Rosa probe the meaning of hospitality in a remote and untamed space, and raise radical questions about the boundaries between what lies within and outside the parameters of the Law, while interrogating the primordial threshold that both separates and connects humans and animals
O comum e o disperso: história (e geografia) literária na Itália contemporânea
No full textA partir das reflexões teóricas elaboradas na passagem entre o século XX e o século XXI, o presente texto tenta dar conta tanto da relação entre historiografia e produção literária, quanto da relação entre lógica temporal e distribuição espacial, que vêm sendo repensadas pela crítica italiana dos últimos anos. Nessa nova constelação problemática, o que se pode entrever é uma forte preocupação com o horizonte histórico e com a deriva da forma no atual contexto nacional. As obras consideradas são, em particular, as de Alberto Asor Rosa e de Franco Moretti
Chromium oxide single layer on Fe(100)
No full textLow-dimensional oxide nanostructures, supported on well-defined metal surfaces, have been the subject of intensive study because of their relevance both in fundamental physics and in technological applications [1,2]. The ultimate limit of an ultrathin oxide film is a two-dimensional (2-D) oxide monolayer on a metal substrate, consisting of only one unit cell in thickness. However, if the growth of oxide ultra-thin layers is performed on an iron substrates in a background pressure of oxygen (the so-called reactive deposition) the iron oxidation prevents the formation of a sharp interface [3].
In this oral, we show that a sharp interface between a single layer of chromium oxide and the Fe(001) surface can be obtained by growing the Cr on the pre-oxidized Fe(001)-p(1x1)O. Two chromium oxide phases have been detected at different Cr coverages, by using scanning tunnelling microscopy (STM) and low-energy electron diffraction (LEED) techniques. The experimental data are discussed in the light of ab-initio simulations of the electronic, energetic, and geometric properties of the growing film. Our findings demonstrate a potential to fabricate a sharp interface between the iron and transition metal oxides.
References
[1] F. P., Netzer, F. Allegretti, S. Surnev, J. Vac. Sci.Technol. B 28, 3268503 (2010).
[2] G. Pacchioni and S. Valeri, Oxide Ultrathin Films (WILEY-VCH, Germany, 2012).
[3] M. Finazzi, A. Brambilla, L. Duò, G. Ghiringhelli, M. Portalupi, F. Ciccacci, Phys. Rev. B 70, 235420 (2004)
A dynamic Bayesian network model for predicting organ failure associations without predefining outcomes
No full textCritical care medicine has been a field for Bayesian networks (BNs) application for investigating relationships among failing organs. Criticisms have been raised on using mortality as the only outcome to determine the treatment efficacy. We aimed to develop a dynamic BN model for detecting interrelationships among failing organs and their progression, not predefining outcomes and omitting hierarchization of organ interactions. We collected data from 850 critically ill patients from the national database used in many intensive care units. We considered as nodes the organ failure assessed by a score as recorded daily. We tested several possible DBNs and used the best bootstrapping results for calculating the strength of arcs and directions. The network structure was learned using a hill climbing method. The parameters of the local distributions were fitted with a maximum of the likelihood algorithm. The network that best satisfied the accuracy requirements included 15 nodes, corresponding to 5 variables measured at three times: ICU admission, second and seventh day of ICU stay. From our findings some organ associations had probabilities higher than 50% to arise at ICU admittance or in the following days persisting over time. Our study provided a network model predicting organ failure associations and their evolution over time. This approach has the potential advantage of detecting and comparing the effects of treatments on organ function
- …
