EXITE2 Observation of the SIGMA Source GRS 1227+025

We report the EXITE2 hard X-ray imaging of the sky around 3C273. A 2h observation on May 8, 1997, shows a $\sim$260 mCrab source detected at $\sim4\sigma$ in each of two bands (50-70 and 70-93 keV) and located $\sim$30' from 3C273 and consistent in position with the SIGMA source GRS1227+025. The EXITE2 spectrum is consistent with a power law with photon index 3 and large low energy absorption, as indicated by the GRANAT/SIGMA results. No source was detected in more sensitive followup EXITE2 observations in 2000 and 2001 with 3$\sigma$ upper limits of 190 and 65 mCrab, respectively. Comparison with the flux detected by SIGMA shows the source to be highly variable, suggesting it may be non-thermal and beamed and thus the first example of a ``type 2'' (absorbed) Blazar. Alternatively it might be (an unprecedented) very highly absorbed binary system undergoing accretion disk instability outbursts, possibly either a magnetic CV, or a black hole X-ray nova.Comment: 12 pages, 4 figures, accepted for publication in Ap

Influence of TiHX Addition on SHS Porous Shape Memory Alloy

Abstract Porous NiTi alloys are receiving considerable attention as they can be used as scaffold for bone replacement. Most production routes presented in the literature use metal powders as raw material (pure Ni and Ti or prealloyed NiTi powders): among these processes, Self propagating High temperature Synthesis (SHS) is investigated as a possible energy saving, quick and easy method of production. To obtain porous NiTi, compacted Ti and Ni powders are preheated and then ignited, avoiding high reaction temperatures at which the compound melts and consequently pores collapse. A drawback of low reaction temperatures is the formation of secondary phases. In this paper the addition of hydrided titanium (TiHX, x=1.5-1.9) powder is considered. During the reaction, hydrided titanium endothermically decomposes and can act as process controlling media. Reference Ni-Ti and Ni-TiHx mixed powders were reacted and the temperature evolution monitored. Differential Scanning Calorimetry was used to verify the presence of transforming phases (austenite, martensite). Microstructure characterization was performed with X-ray diffraction analysis and scanning electron microscope, equipped with EDX and EBSD detectors. The results confirmed that decomposition of hydrided titanium is the controlling process of the reaction, limiting the availability of Ti and absorbing reaction heat. The presence of TiHx can suppress SHS reaction, leaving un-reacted Ni and Ti powders and high amount of other intermetallic phases. If partial or complete decomposition of TiHx is allowed during preheating of reactants, NiTi production can occur: secondary phases content decreases for increased decomposition of TiHx before SHS reaction

An XMM-Newton look at the strongly variable radio-weak BL Lac Fermi J1544-0639

Fermi J1544-0639/ASASSN-17gs/AT2017egv was identified as a gamma-ray/optical transient on May 15, 2017. Subsequent multiwavelength observations suggest that this source may belong to the new class of radio-weak BL Lacs. We studied the X-ray spectral properties and short-term variability of Fermi J1544-0639 to constrain the X-ray continuum emission mechanism of this peculiar source. We present the analysis of an XMM-Newton observation, 56 ks in length, performed on February 21, 2018. The source exhibits strong X-ray variability, both in flux and spectral shape, on timescales of ~10 ks, with a harder-when-brighter behaviour typical of BL Lacs. The X-ray spectrum is nicely described by a variable broken power law, with a break energy of around 2.7 keV consistent with radiative cooling due to Comptonization of broad-line region photons. We find evidence for a `soft excess', nicely described by a blackbody with a temperature of ~0.2 keV, consistent with being produced by bulk Comptonization along the jet.Comment: 11 pages, 12 figures. Accepted for publication in Astronomy & Astrophysic

As políticas quantificadoras da Educação e as "novas" formas de exclusão: os "inclassificáveis".

Vários documentos oficiais dos governos federal, estadual e municipal da atualidade insistem em apresentar dados sobre a educação brasileira que demonstram avanços na qualidade da educação ofertada pelas escolas públicas de ensino fundamental. Entretanto, inúmeros estudos demonstram que apesar de mais de 90% das crianças brasileiras em idade escolar estarem incluídas no ensino fundamental, a precariedade dessas escolas não lhes permite nem mesmo a aprendizagem da leitura e da escrita. Buscando conhecer o cotidiano dessas escolas, esse estudo teve como objetivo compreender como se configura hoje o fracasso escolar em uma escola pública de ensino fundamental do município de Vitória-ES, submetida à política quantificadora de avaliação das escolas e suas consequências sobre um aluno e sua família. Escolhi como local da pesquisa uma escola de ensino fundamental de Vitória que obteve em 2009/2010 um dos resultados mais baixos no IDEB do município e por meio de um estudo de caso etnográfico de inspiração fenomenológica acompanhei durante todo o ano letivo de 2011 o cotidiano de uma sala de aula de 8ª série/9º ano e de um aluno com baixo índice de rendimento escolar. Com esse estudo busquei respostas para as seguintes questões: como se configura hoje o fracasso escolar nas escolas públicas brasileiras? Quais são as políticas atuais destinadas aos alunos com baixo índice de rendimento escolar nessas escolas? Quais são as estratégias utilizadas pela escola para que seus índices de rendimento aumentem? Como esses alunos participam de um processo de escolarização que lhes impõe a impossibilidade de aprendizagem? Qual a relação estabelecida entre a escola e a família desses alunos? Os resultados obtidos foram apresentados por meio de uma descrição densa do estudo de caso e a análise final foi desenvolvida a partir de quatro categorias temáticas: 1) A individualização e o descompromisso na escola PAC: os inclassificáveis; 2) O desvalor do professor; 3) O não aprender como decorrência do não ensinar; 4) A família de Wellington e a escola PAC: das representações da escola ao cotidiano vivido sobre páginas em branco

Optical properties of graphite

Optical constants of graphite for ordinary and extraordinary waves are modeled with a modified Lorentz-Drude model with frequency-dependent damping. The model enables the shape of the spectral line to vary over a range of broadening functions with similar kernels and different wings, the broadening type being its adjustable parameter. The model parameters are determined by the acceptance-probability-controlled simulated annealing algorithm. Good agreement with the experimental data is obtained in the entire investigated spectral range (0.12-40 eV for ordinary wave and 2.1-40 eV for extraordinary wave). The significant discrepancies between the experimental data obtained by the reflectance measurements and the electron-energy-loss spectroscopy data are analyzed in details. Inconsistency in terms of unsatisfied Kramers-Kronig relations is discovered in the index of refraction data derived from reflectance measurements, and a method for correcting the data is proposed. © 1999 American Institute of Physics.published_or_final_versio

Hybridized quadrupole-dipole exciton effects in Cu2OCu_2O - Organic Heterostructure

In the present work we discuss resonant hybridization of the $1S$ quadrupole Wannier-Mott exciton (WE) in a $Cu_2O$ quantum well with the Frenkel (FE) dipole exciton in an adjacent layer of organic DCM2:CA:PA. The coupling between excitons is due to interaction between the gradient of electric field induced by DCM2 Frenkel exciton and the quadrupole moment of the $1S$ transition in the cuprous oxide. The specific choice of the organic allows us to use the mechanism of 'solid state solvation' to dynamically tune the WE and FE into resonance during time $\approx 3.3 \: ns$ (comparable with the big life time of the WE) of the 'slow' phase of the solvation. The quadrupole-dipole hybrid utilizes the big oscillator strength of the FE along with the big lifetime of the quadrupole exciton, unlike dipole-dipole hybrid exciton which utilizes big oscillator strength of the FE and big radius of the dipole allowed WE. Due to strong spatial dispersion and big mass of the quadrupole WE the hybridization is not masked by the kinetic energy or the radiative broadening. The lower branch of the hybrid dispersion exhibits a pronounced minimum and may be used in applications. Also we investigate and report noticeable change in the coupling due to a induced 'Stark effect' from the strong local electric field of the FE. We investigated the fine energy structure of the quantum well confined ortho and para excitons in cuprous oxide

Fading of the Transient Anomalous X-ray Pulsar XTE J1810-197

Three observations of the 5.54 s Transient Anomalous X-ray Pulsar XTE J1810-197 obtained over 6 months with the Newton X-Ray Multi-Mirror Mission (XMM-Newton) are used to study its spectrum and pulsed light curve as the source fades from outburst. The decay is consistent with an exponential of time constant 300 days, but not a power law as predicted in some models of sudden deep crustal heating events. All spectra are well fitted by a blackbody plus a steep power law, a problematic model that is commonly fitted to anomalous X-ray pulsars (AXPs). A two-temperature blackbody fit is also acceptable, and better motivated physically in view of the faint optical/IR fluxes, the X-ray pulse shapes that weakly depend on energy in XTE J1810-197, and the inferred emitting areas that are less than or equal to the surface area of a neutron star. The fitted temperatures remained the same while the flux declined by 46%, which can be interpreted as a decrease in area of the emitting regions. The pulsar continues to spin down, albeit at a reduced rate of (5.1+/-1.6)x10^{-12} s s^{-1}. The inferred characteristic age Tau_c = P/2Pdot ~17,000 yr, magnetic field strength B_s ~1.7x10^{14} G, and outburst properties are consistent with both the outburst and quiescent X-ray luminosities being powered by magnetic field decay, i.e., XTE J1810-197 is a magnetar.Comment: 10 pages, 5 figures, accepted by Ap.