Domain wall description of superconductivity

In the present work we shall address the issue of electrical conductivity in superconductors in the perspective of superconducting domain wall solutions in the realm of field theory. We take our set up made out of a dynamical complex scalar field coupled to gauge field to be responsible for superconductivity and an extra scalar real field that plays the role of superconducting domain walls. The temperature of the system is interpreted through the fact that the soliton following accelerating orbits is a Rindler observer experiencing a thermal bath.Comment: 9 pages, 5 figures, Latex. Version to appear in PL

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

Optical Identification of He White Dwarfs Orbiting Four Millisecond Pulsars in the Globular Cluster 47 Tucanae

We used ultra-deep UV observations obtained with the Hubble Space Telescope to search for optical companions to binary millisecond pulsars (MSPs) in the globular cluster 47 Tucanae. We identified four new counterparts (to MSPs 47TucQ, 47TucS, 47TucT and 47TucY) and confirmed those already known (to MSPs 47TucU and 47TucW). In the color magnitude diagram, the detected companions are located in a region between the main sequence and the CO white dwarf cooling sequences, consistent with the cooling tracks of He white dwarfs of mass between 0.15 Msun and 0.20 Msun. For each identified companion, mass, cooling age, temperature and pulsar mass (as a function of the inclination angle) have been derived and discussed. For 47TucU we also found that the past accretion history likely proceeded in a sub-Eddington rate. The companion to the redback 47TucW is confirmed to be a non degenerate star, with properties particularly similar to those observed for black widow systems. Two stars have been identified within the 2-sigma astrometric uncertainty from the radio positions of 47TucH and 47TucI, but the available data prevent us from firmly assessing whether they are the true companions of these two MSPs.Comment: 27 pages, 7 figures, Accepted for publication by Ap

Podridões em estacas de roseira, minirrosa e mussaendra no Estado do Ceará.

bitstream/CNPAT/10226/1/cot_129.pd

Queima de folhas jovens de plantas de dendê causada por espécie de Phytophthora.

Publicado também em: CONGRESSO BRASILEIRO DE FITOPATOLOGIA, 16., 1983, Belém, PA. Programa, resumos e colóquios. [S.l.]: Sociedade Brasileira de Fitopatologia, 1983. p. 120-121

Fungos que deterioram amêndoas de cajueiro no Brasil.

bitstream/item/33813/1/Ct-064.pd

Discovery of three new millisecond pulsars in Terzan 5

We report on the discovery of three new millisecond pulsars (namely J1748-2446aj, J1748-2446ak and J1748-2446al) in the inner regions of the dense stellar system Terzan 5. These pulsars have been discovered thanks to a method, alternative to the classical search routines, that exploited the large set of archival observations of Terzan 5 acquired with the Green Bank Telescope over 5 years (from 2010 to 2015). This technique allowed the analysis of stacked power spectra obtained by combining ~206 hours of observation. J1748-2446aj has a spin period of ~2.96 ms, J1748-2446ak of ~1.89 ms (thus it is the fourth fastest pulsar in the cluster) and J1748-2446al of ~5.95 ms. All the three millisecond pulsars are isolated and currently we have timing solutions only for J1748-2446aj and J1748-2446ak. For these two systems, we evaluated the contribution to the measured spin-down rate of the acceleration due to the cluster potential field, thus estimating the intrinsic spin-down rates, which are in agreement with those typically measured for millisecond pulsars in globular clusters. Our results increase to 37 the number of pulsars known in Terzan 5, which now hosts 25% of the entire pulsar population identified, so far, in globular clusters.Comment: 10 pages, 6 figures. ApJ (accepted

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

Radio timing and optical photometry of the black widow system PSR J1518+0204C in the globular cluster M5

We report on the determination of astrometric, spin and orbital parameters for PSR J1518+0204C, a "black widow" binary millisecond pulsar in the globular cluster M5. The accurate position and orbital parameters obtained from radio timing allowed us to search for the optical companion. By using WFC3/HST images we identified a very faint variable star (m_F390W > 24.8, m_F606W > 24.3, m_F814W > 23.1) located at only 0.25" from the pulsar's timing position. Due to its strong variability, this star is visible only in a sub-sample of images. However, the light curve obtained folding the available data with the orbital parameters of the pulsar shows a maximum at the pulsar inferior conjunction and a possible minimum at the pulsar superior conjunction. Furthermore, the shape of the optical modulation indicates a heating process possibly due to the pulsar wind. This is the first identification of an optical companion to a black widow pulsar in the dense stellar environment of a globular cluster.Comment: Accepted for publication by ApJ; 24 Pages, 5 Figures, 1 Tabl