Ancient tin production: Slags from the Iron Age Carvalhelhos hillfort (NW Iberian Peninsula)

Provenance and production of tin in the Ancient World has since long been a major topic of discussion among archaeologists. In Western Europe, where significant tin ore (cassiterite) deposits are known, only a few remains of ancient tin production, such as tin slags, have been detected. In the present work, elemental and microstructural analyses by WDXRF, SEM-EDS and XRD were performed on recently recognised tin slags from the Iron Age Carvalhelhos hillfort located in NW Iberia, a territory that represents the largest extension with tin mineralisation in Western Europe. Elemental and microstructural characterisation of cassiterite collected in a pilot field survey in the region of the hillfort are presented and discussed, as well as two ceramic fragments that could be part of a smelting structure and an iron slag from the settlement. Results show that the tin slags have variable but high contents in Sn, similarly to Pre-Medieval tin slags found in other Western European areas, but also high contents of Ta and Nb, which specifically distinguish them from other tin slags, such as those found in SW Britain. Tin ores from the hillfort region frequently have Ta and Nb in cassiterite solid solution or as inclusions of columbite group minerals, relating well with the Carvalhelhos tin slags. Up to present, the Carvalhelhos slags are amongst the very few ancient tin slags known in Western Europe, and their study can contribute to a better knowledge on ancient tin sources and trade routes

Thermodynamics of Chaplygin gas

We clarify thermodynamics of the Chaplygin gas by introducing the integrability condition. All thermal quantities are derived as functions of either volume or temperature. Importantly, we find a new general equation of state, describing the Chaplygin gas completely. We confirm that the Chaplygin gas could show a unified picture of dark matter and energy which cools down through the universe expansion without any critical point (phase transition).Comment: 5 pages, 4 figures, version "Accepted for publication in Astrophysics & Space Science

Newtonian Approach to the Matter Power Spectrum of the Generalized Chaplygin Gas

We model the cosmic medium as the mixture of a generalized Chaplygin gas and a pressureless matter component. Within a neo-Newtonian approach we compute the matter power spectrum. The 2dFGRS data are used to discriminate between unified models of the dark sector and different models, for which there is separate dark matter, in addition to that accounted for by the generalized Chaplygin gas. Leaving the corresponding density parameters free, we find that the unified models are strongly disfavored. On the other hand, using unified model priors, the observational data are also well described, in particular for small and large values of the generalized Chaplygin gas parameter $\alpha$.Comment: Latex file, 5 pages, 11 figures in eps format. For the proceedings of the conference Dark Energy and Dark Matter, 7-11 july 2008, Lyon, Franc

Structural and optical studies of FeSb2 under high pressure

Nanostructured orthorhombic FeSb2 and an amorphous phase were formed by mechanical alloying starting from a mixture of high purity elemental Fe and Sb powders. The effects of high pressures on structural and optical properties were studied using X-ray diffraction (XRD) and Raman spectroscopy (RS). XRD patterns showed the presence of the orthorhombic FeSb2 phase up to the maximum pressure applied (28.2 GPa). The XRD patterns showed also an increase in the amount of the amorphous phase with increasing pressure up to 23.3 GPa. At 14.3 GPa, together with the former phases, a new phase was observed and indexed to a tetragonal FeSb2 phase, but its volume fraction is small at least up to 23.3 GPa. For the orthorhombic FeSb2 phase, the pressure dependence of the volume fitted to a Birch-Murnaghan equation of state gave a bulk modulus = 74.2 +- 3.0 GPa and its pressure derivative = 7.5 +- 0.6. RS measurements were performed from atmospheric pressure up to 45.2 GPa. For the orthorhombic FeSb2 phase, the Raman active mode was observed up to the maximum pressure applied, while the mode disappeared at 16.6 GPa. For pressures higher than 21 GPa, the Raman active mode of a tetragonal FeSb2 phase was observed, confirming ab initio calculations reported in the literature.Comment: 31 pages, 11 figures and 2 tables. Already submitted for publicatio

Idade Precoce De Início Da Atividade Sexual Está Associada A Elevada Prevalência De Lesão Intraepitelial Escamosa De Alto Grau

To evaluate the association of age at first sexual intercourse with the results of the cervicovaginal cytology. Study Design Observational analytical study about the prevalence of altered cervicovaginal cytology results in women aged between 18 and 34 years from a densely populated area in Brazil, during 10 years. The patients were stratified into 2 categories according to their age at first sexual intercourse (13–16 years and 17–24 years). Results From the total of 2,505,154 exams, 898,921 tests were in accordance with the inclusion criteria. Considering women with 4 years or less from the first sexual intercourse as a reference, those with 5 to 9 years and 10 years or more showed a higher prevalence of high-grade squamous intraepithelial lesions (HSILs). Women with an earlier onset of sexual intercourse (13–16 years) showed higher prevalence ratios for atypical squamous cells (ASC), low-grade squamous intraepithelial lesion (LSIL) and HSIL. The prevalence ratio for HSIL adjusted by age at diagnosis and by age at first sexual intercourse was higher only for women with an earlier onset of sexual intercourse. Conclusions The age of first sexual intercourse could be a variable that might qualify the selection among young women who are really at a higher risk for HSIL. © 2017 by Thieme-Revinter Publicações Ltda, Rio de Janeiro, Brazil.3928085UNICAMP, Universidade Estadual de Campina

Structural study of Cu2−x_{2-x}Se alloys produced by mechanical alloying

The crystalline structures of superionic high temperature copper selenides Cu$_{2-x}$Se ($0 \le x \le 0.25$) produced by Mechanical Alloying were investigated using X-ray diffraction (XRD) technique. The measured XRD patterns showed the presence of the peaks corresponding to the crystalline superionic high temperature $\alpha$-Cu$_2$Se phase in the as-milled sample, and its structural data were determined by means of a Rietveld refinement procedure. After a heat treatment in argon at 200$^\circ$C for 90 h, this phase transforms to the superionic high temperature $\alpha$-Cu$_{1.8}$Se phase, whose structural data where also determined through the Rietveld refinement. In this phase, a very low occupation of the trigonal 32(f) sites ($\sim 3$%) by Cu ions is found. In order to explain the evolution of the phases in the samples, two possible mechanisms are suggested: the high mobility of Cu ions in superionic phases and the intense diffusive processes in the interfacial component of samples produced by Mechanical Alloying.Comment: 2 figures, submitted to Acta Crystallographic

Modelagem tridimensional do edifício Acaiaca: avaliação bioclimática de uma obra modernista brasileira

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMO: Delfim Amorim, arquiteto modernista do edifício Acaica, utilizou arranjos bioclimáticos construtivos (peitoril ventilado, generosas aberturas, brises verticais fixos e cobogós), a fim de otimizar o aproveitamento dos recursos naturais (ventilação natural e iluminação natural) dentro do edifício e promover o conforto ambiental aos usuários. O objetivo do artigo é através da modelagem tridimensional do edifício Acaiaca (utilizando o software Blender), avaliar os arranjos construtivos, que possam promover a qualidade bioclimática do edifício. Para o desenvolvimento da pesquisa foi realizado o percurso metodológico: Coleta documental e pesquisa bibliográfica do Acaiaca; Visita ao edifício; Aprofundamento teórico sobre qualidade ambiental e arquitetura bioclimática; Análise da qualidade ambiental do Acaiaca. Constatou-se que o edifício possui uma série de dispositivos bioclimários, o que contribuiria no controle do desperdício de energia e na qualidade ambiental do edifício, no entanto alguns moradores interviram nesses arranjos obstruindo as aberturas (peitoril ventilado e brises verticais), modificando o desempenho do edifício.ABSTRACT: Delfim Amorim, modernist architect of the Acaica building, used constructive bioclimatic arrangements (ventilated sill, generous openings, fixed vertical windshields and cobogós), in order to optimize the use of natural resources (natural ventilation and natural lighting) within the building and promote comfort to users. The objective of the article is through the three-dimensional modeling of the Acaiaca building (using the Blender software), to evaluate the construction arrangements, which can promote the building's bioclimatic quality. For the development of the research, the methodological path was carried out: Documentary collection and bibliographic research of Acaiaca; Visit to the building; Theoretical deepening on environmental quality and bioclimatic architecture; Analysis of the environmental quality of Acaiaca. It was found that the building has a series of bioclimatic devices, which would contribute to the control of energy waste and the environmental quality of the building, however some residents intervened in these arrangements by blocking the openings (ventilated sill and vertical breezes), modifying the performance of the building.info:eu-repo/semantics/publishedVersio

Aging of a nanostructured Zn50Se50 alloy produced by mechanical alloying

The aging of a nanocrystalline equiatomic ZnSe alloy produced by mechanical alloying was investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. The measured XRD patterns showed that Se atoms located at interfacial component migrated with aging giving raise to a crystalline selenium (c-Se) phase. DSC spectra of heat-treated samples at temperatures above 221oC followed by quenching showed that the c-Se particles changed to the amorphous state. It was also observed that the as-milled and aged samples are highly hydrophilic. The lattice parameters and the average crystallite sizes were calculated as a function of time of aging and temperature of heat treatment.Comment: Submitted to Solid State Communications, 4 figure

Exploratory Behavior, Trap Models and Glass Transitions

A random walk is performed on a disordered landscape composed of $N$ sites randomly and uniformly distributed inside a $d$-dimensional hypercube. The walker hops from one site to another with probability proportional to $\exp [- \beta E(D)]$, where $\beta = 1/T$ is the inverse of a formal temperature and $E(D)$ is an arbitrary cost function which depends on the hop distance $D$. Analytic results indicate that, if $E(D) = D^{d}$ and $N \to \infty$, there exists a glass transition at $\beta_d = \pi^{d/2}/\Gamma(d/2 + 1)$. Below $T_d$, the average trapping time diverges and the system falls into an out-of-equilibrium regime with aging phenomena. A L\'evy flight scenario and applications to exploratory behavior are considered.Comment: 4 pages, 1 figure, new versio

Nonsingular FRW cosmology and nonlinear electrodynamics

The possibility to avoid the cosmic initial singularity as a consequence of nonlinear effects on the Maxwell eletromagnetic theory is discussed. For a flat FRW geometry we derive the general nonsingular solution supported by a magnetic field plus a cosmic fluid and a nonvanishing vacuum energy density. The nonsingular behavior of solutions with a time-dependent $\Lambda(t)$-term are also examined. As a general result, it is found that the functional dependence of $\Lambda(t)$ can uniquely be determined only if the magnetic field remains constant. All these models are examples of bouncing universes which may exhibit an inflationary dynamics driven by the nonlinear corrections of the magnetic field.Comment: 20 pages, 7 figure