Exciton trapping in magnetic wire structures

The lateral magnetic confinement of quasi two-dimensional excitons into wire like structures is studied. Spin effects are take into account and two different magnetic field profiles are considered, which experimentally can be created by the deposition of a ferromagnetic stripe on a semiconductor quantum well with magnetization parallel or perpendicular to the grown direction of the well. We find that it is possible to confine excitons into one-dimensional (1D) traps. We show that the dependence of the confinement energy on the exciton wave vector, which is related to its free direction of motion along the wire direction, is very small. Through the application of a background magnetic field it is possible to move the position of the trapping region towards the edge of the ferromagnetic stripe or even underneath the stripe. The exact position of this 1D exciton channel depends on the strength of the background magnetic field and on the magnetic polarisation direction of the ferromagnetic film.Comment: 10 pages, 7 figures, to be published in J. Phys: Condens. Matte

A culture of silence: modes of objectification and the silencing of disabled bodies

Throughout history different practices have attempted to silence the experiences of disabled people. In this paper we explore some of these practices including the medical, familial, and self-subjugating practices English-speaking Canadian polio survivors experienced throughout their lives. We analyze participant’s experiences of silence and silencing through a Foucauldian lens, drawing on the three modes of objectification to explain the institutional and cultural discourses around polio subjects that acted upon and through the polio body to silence it. Participants’ oral history accounts demonstrate how sociocultural and medical practices effectively silenced survivors from speaking about their polio experiences. However, the trope of silence is also uprooted within oral history traditions. We will demonstrate how participants broke their silence and shifted their perspectives on polio and disability, and how this process contributed to their resistance of hegemonic conceptualizations of disability as defective

Constraining the relative inclinations of the planets B and C of the millisecond pulsar PSR B1257+12

We investigate on the relative inclination of the planets B and C orbiting the pulsar PSR B1257+12 in connection with potential violations of the equivalence principle (Abridged).Comment: LaTex2e, 10 pages, 1 table, 3 figures, 17 references. Small stylistic changes. Version to appear in Journal of Astrophysics and Astronomy (JAA

Automatic calibration of the SHETRAN hydrological modelling system using MSCE

Automatic calibration is preferred because it provides an objective and extensive searching in the feasible parameter space. In this study, the Modified Shuffled Complex Evolution (MSCE) optimization algorithm is applied to automatically calibrate the physically-based spatially-distributed hydrological model SHETRAN in the 705-km2 semi-arid Cobres basin in southern Portugal, with a spatial resolution of 2 km and a temporal resolution of 1 h. Twenty-two parameters are calibrated for the main types of land-use and soil. Nash-Sutcliffe Efficiency (NSE) is 0.86 for calibration and 0.74 for validation for basin outlet; NSE is respectively 0.65 and 0.82 for calibration, 0.69 and 0.63 for validation of internal gauging stations Albernoa and Entradas. As for storm events, NSE is 0.87 and 0.64 respectively for Storms No.1 (during the calibration period) and No.4 (during the validation period) at basin outlet; it is 0.69 and 0.65 for Storm No.4 respectively at Albernoa andEntradas. The results are satisfactory not only for basin outlet but also for internal gauging stations

Goals, Strategies and First Discoveries of AO327, the Arecibo All-Sky 327 MHz Drift Pulsar Survey

We report initial results from AO327, a drift survey for pulsars with the Arecibo telescope at 327 MHz. The first phase of AO327 will cover the sky at declinations of -1 to 28 degrees, excluding the region within 5 degrees of the Galactic plane, where high scattering and dispersion make low-frequency surveys sub-optimal. We record data from a 57 MHz bandwidth with 1024 channels and 125 us sampling time. The 60 s transit time through the AO327 beam means that the survey is sensitive to very tight relativistic binaries even with no acceleration searches. To date we have detected 44 known pulsars with periods ranging from 3 ms to 2.21 s and discovered 24 new pulsars. The new discoveries include three millisecond pulsars, three objects with periods of a few tens of milliseconds typical of young as well as mildly recycled pulsars, a nuller, and a rotating radio transient. Five of the new discoveries are in binary systems. The second phase of AO327 will cover the sky at declinations of 28 to 38 degrees. We compare the sensitivity and search volume of AO327 to the Green Bank North Celestial Cap survey and the GBT350 drift survey, both of which operate at 350 MHz.Comment: Accepted for publication in Ap

Can we see pulsars around Sgr A*? - The latest searches with the Effelsberg telescope

Radio pulsars in relativistic binary systems are unique tools to study the curved space-time around massive compact objects. The discovery of a pulsar closely orbiting the super-massive black hole at the centre of our Galaxy, Sgr A*, would provide a superb test-bed for gravitational physics. To date, the absence of any radio pulsar discoveries within a few arc minutes of Sgr A* has been explained by one principal factor: extreme scattering of radio waves caused by inhomogeneities in the ionized component of the interstellar medium in the central 100 pc around Sgr A*. Scattering, which causes temporal broadening of pulses, can only be mitigated by observing at higher frequencies. Here we describe recent searches of the Galactic centre region performed at a frequency of 18.95 GHz with the Effelsberg radio telescope.Comment: 3 pages, 2 figures, Proceedings of IAUS 291 "Neutron Stars and Pulsars: Challenges and Opportunities after 80 years", 201

Pulsar J1411+2551: A Low Mass New Double Neutron Star System

In this work, we report the discovery and characterization of PSR J1411+2551, a new binary pulsar discovered in the Arecibo 327 MHz Drift Pulsar Survey. Our timing observations of the radio pulsar in the system span a period of about 2.5 years. This timing campaign allowed a precise measurement of its spin period (62.4 ms) and its derivative (9.6 $\pm$ 0.7) $\times 10^{-20}\, \rm s\, s^{-1}$; from these, we derive a characteristic age of $\sim 10\,$Gyr and a surface magnetic field strength of 2.5 $\times 10^{9}$ G. These numbers indicate that this pulsar was mildly recycled by accretion of matter from the progenitor of the companion star. The system has an eccentric ($e\, = \, 0.17$) 2.61 day orbit. This eccentricity allows a highly significant measurement of the rate of advance of periastron, $\dot{\omega} = 0.07686 \pm 0.00046 ^{\circ}~{\rm yr}^{-1}$. Assuming general relativity accurately models the orbital motion, this implies a total system mass M = $2.538 \pm 0.022 M_{\odot}$. The minimum companion mass is $0.92\, M_{\odot}$ and the maximum pulsar mass is $1.62\, M_{\odot}$. The large companion mass and the orbital eccentricity suggest that PSR J1411+2551 is a double neutron star system; the lightest known to date including the DNS merger GW 170817. Furthermore, the relatively low orbital eccentricity and small proper motion limits suggest that the second supernova had a relatively small associated kick; this and the low system mass suggest that it was an ultra-stripped supernova.Comment: Accepted for publication in APJ letter

Pulsar J0453+1559: A Double Neutron Star System with a Large Mass Asymmetry

To understand the nature of supernovae and neutron star (NS) formation, as well as binary stellar evolution and their interactions, it is important to probe the distribution of NS masses. Until now, all double NS (DNS) systems have been measured to have a mass ratio close to unity (q $\geq$ 0.91). Here we report the measurement of the individual masses of the 4.07-day binary pulsar J0453+1559 from measurements of the rate of advance of periastron and Shapiro delay: The mass of the pulsar is 1.559(5) $M_{\odot}$ and that of its companion is 1.174(4) $M_{\odot}$; q = 0.75. If this companion is also a neutron star (NS), as indicated by the orbital eccentricity of the system (e=0.11), then its mass is the smallest precisely measured for any such object. The pulsar has a spin period of 45.7 ms and a spin derivative of 1.8616(7) x$10^-19$; from these we derive a characteristic age of ~ 4.1 x $10^9$ years and a magnetic field of ~ 2.9 x $10^9$ G,i.e, this pulsar was mildly recycled by accretion of matter from the progenitor of the companion star. This suggests that it was formed with (very approximately) its current mass. Thus NSs form with a wide range of masses, which is important for understanding their formation in supernovae. It is also important for the search for gravitational waves released during a NS-NS merger: it is now evident that we should not assume all DNS systems are symmetric

Pedagogia crítica e direitos humanos: fundamentos para uma proposta pedagógico-crítica em direitos humanos

Este artigo reflete sobre a necessidade de encontrar uma teoria pedagógica que ofereça sustentação à ação educativa em Direitos Humanos, apresentando uma proposta pedagógico-crítica alicerçada nos pressupostos da teoria e da pedagogia críticas, privilegiando a pedagogia freireana, numa perspectiva atualizada para os Direitos Humanos. Nesse sentido, o trabalho tem o propósito de discutir um fundamento teórico-crítico para a Educação em Direitos Humanos, buscando novas formas de investigação e de análise para sua compreensão, apropriando-se de conceitos críticos como conscientização, autonomia, diálogo e emancipação. Finalmente, considera que uma prática pedagógica crítica em Direitos Humanos contribui para a leitura do mundo do excluído, para sua inclusão na sociedade e para a compreensão de que é possível desconstruir relações e práticas sociais injustas.(undefined