Ac losses in type 2 superconductors

Electrical, and calorimetric measurements on alternating current loss in niobium zirconium, niobium titanium, and niobium stannide superconductor

METODO INNOVATIVO PER CREARE UN LAYER NANOSTRUTTURATO HONEYCOMB DI TITANIA, AUTOGENERATO SULLE SUPERFICI DI MATERIALI A BASE TITANIO, DESTINATI AL DOMINIO MEDICALE E CHIRURGICO DEGLI IMPIANTI DENTALI, DELLE PROTESI ORTOPEDICHE E DELLE OSTEOSINTESI.

NANOTECNOLOGIA, TITANIO, PROTESI ORTOPEDICHE, OSTEOSINTESI, NANOSTRUTTUR

Blood Lead Levels In Nevada Children

The purpose of this study was to assess the prevalence of plumbism in children one to six years of age in Nevada. During a four-year period from 1992 – 1996, 10,700 children were screened for evidence of blood lead intoxication. The capillary specimens were analyzed by atomic absorption spectrometry. All children with a lead level =\u3e 10 ug/L were retested using venous blood. Ninety three percent of the children had blood lead levels \u3c 10 µg/d

Updating the orbital ephemeris of the dipping source XB 1254-690 and the distance to the source

XB 1254-690 is a dipping low mass X-ray binary system hosting a neutron star and showing type I X-ray bursts. We aim at obtaining more accurate orbital ephemeris and at constraining the orbital period derivative of the system for the first time. In addition, we want to better constrain the distance to the source in order to locate the system in a well defined evolutive scenario. We apply for the first time an orbital timing technique to XB 1254-690, using the arrival times of the dips present in the light curves that have been collected during 26 years of X-ray pointed observations performed from different space missions. We estimate the dip arrival times using a statistical method that weights the count-rate inside the dip with respect to the level of the persistent emission outside the dip. We fit the obtained delays as a function of the orbital cycles both with a linear and a quadratic function. We infer the orbital ephemeris of XB 1254-690 improving the accuracy of the orbital period with respect to previous estimates. We infer a mass of M$_{2}=0.42\pm 0.04$ M$_{\odot}$ for the donor star, in agreement with the estimations already present in literature, assuming that the star is in thermal equilibrium while it transfers part of its mass via the inner Lagrangian point, and assuming a neutron star mass of 1.4 M$_{\odot}$. Using these assumptions, we also constrain the distance to the source, finding a value of 7.6$\pm 0.8$ kpc. Finally, we discuss the evolution of the system suggesting that it is compatible with a conservative mass transfer driven by magnetic braking.Comment: 13 pages, 5 figures, accepted for publication in Research in Astronomy and Astrophysics (RAA

A re-analysis of the NuSTAR and XMM-Newton broad-band spectrum of Ser~X-1

Context: Ser X-1 is a well studied LMXB which clearly shows a broad iron line. Recently, Miller et al. (2103) have presented broad-band, high quality NuSTAR data of SerX-1.Using relativistically smeared self-consistent reflection models, they find a value of R_in close to 1.0 R_ISCO (corresponding to 6 R_g), and a low inclination angle, less than 10 deg. Aims: The aim of this paper is to probe to what extent the choice of reflection and continuum models (and uncertainties therein) can affect the conclusions about the disk parameters inferred from the reflection component. To this aim we re-analyze all the available public NuSTAR and XMM-Newton. Ser X-1 is a well studied source, its spectrum has been observed by several instruments, and is therefore one of the best sources for this study. Methods: We use slightly different continuum and reflection models with respect to those adopted in literature for this source. In particular we fit the iron line and other reflection features with self-consistent reflection models as reflionx (with a power-law illuminating continuum modified with a high energy cutoff to mimic the shape of the incident Comptonization spectrum) and rfxconv. With these models we fit NuSTAR and XMM-Newton spectra yielding consistent spectral results. Results: Our results are in line with those already found by Miller et al. (2013) but less extreme. In particular, we find the inner disk radius at about 13 R_g and an inclination angle with respect to the line of sight of about 27 deg. We conclude that, while the choice of the reflection model has little impact on the disk parameters, as soon as a self-consistent model is used, the choice of the continuum model can be important in the precise determination of the disk parameters from the reflection component. Hence broad-band X-ray spectra are highly preferable to constrain the continuum and disk parameters.Comment: 13 pages including 8 figures. Accepted for publication in A&

Advanced superconducting magnets investigation

Mathematical models for steady state behavior of composite superconductors and experimental verification using magnet coi

Optical pulsations from a transitional millisecond pulsar

Weakly magnetic, millisecond spinning neutron stars attain their very fast rotation through a 1E8-1E9 yr long phase during which they undergo disk-accretion of matter from a low mass companion star. They can be detected as accretion-powered millisecond X-ray pulsars if towards the end of this phase their magnetic field is still strong enough to channel the accreting matter towards the magnetic poles. When mass transfer is much reduced or ceases altogether, pulsed emission generated by particle acceleration in the magnetosphere and powered by the rotation of the neutron star is observed, preferentially in the radio and gamma-ray bands. A few transitional millisecond pulsars that swing between an accretion-powered X-ray pulsar regime and a rotationally-powered radio pulsar regime in response to variations of the mass in-flow rate have been recently identified. Here we report the detection of optical pulsations from a transitional pulsar, the first ever from a millisecond spinning neutron star. The pulsations were observed when the pulsar was surrounded by an accretion disk and originated inside the magnetosphere or within a few hundreds of kilometres from it. Energy arguments rule out reprocessing of accretion-powered X-ray emission and argue against a process related to accretion onto the pulsar polar caps; synchrotron emission of electrons in a rotation-powered pulsar magnetosphere seems more likely.Comment: 32 pages, 7 figures. The first two authors contributed equally to this wor

A possible solution of the puzzling variation of the orbital period of MXB 1659-298

MXB 1659-298 is a transient neutron star Low-Mass X-ray binary system that shows eclipses with a periodicity of 7.1 hr. The source went to outburst in August 2015 after 14 years of quiescence. We investigate the orbital properties of this source with a baseline of 40 years obtained combining the eight eclipse arrival times present in literature with 51 eclipse arrival times collected during the last two outbursts. A quadratic ephemeris does not fit the delays associated with the eclipse arrival times and the addition of a sinusoidal term with a period of $2.31 \pm 0.02$ yr is required. We infer a binary orbital period of $P=7.1161099(3)$ hr and an orbital period derivative of $\dot{P}=-8.5(1.2) \times 10^{-12}$ s s$^{-1}$. We show that the large orbital period derivative can be explained with a highly non conservative mass transfer scenario in which more than 98\% of the mass provided by the companion star leaves the binary system. We predict an orbital period derivative value of $\dot{P}=-6(3) \times 10^{-12}$ s s$^{-1}$ and constrain the companion star mass between $\sim$0.3 and $0.9 \pm 0.3$ M$_{\odot}$. Assuming that the companion star is in thermal equilibrium the periodic modulation can be due to either a gravitational quadrupole coupling due to variations of the oblateness of the companion star or with the presence of a third body of mass M$_3 >21$ Jovian masses.Comment: 10 pages, 6 figures. Accepted by MNRA