180 research outputs found
Superconducting magnesium diboride films on Silicon with Tc0 about 24K grown via vacuum annealing from stoichiometric precursors
Superconducting magnesium diboride films with Tc0 ~ 24 K and sharp transition
\~ 1 K were successfully prepared on silicon substrates by pulsed laser
deposition from a stoichiometric MgB2 target. Contrary to previous reports,
anneals at 630 degree and a background of 2x10^(-4) torr Ar/4%H2 were performed
without the requirement of Mg vapor or an Mg cap layer. This integration of
superconducting MgB2 films on silicon may thus prove enabling in
superconductor-semiconductor device applications. Images of surface morphology
and cross-section profiles by scanning electron microscopy (SEM) show that the
films have a uniform surface morphology and thickness. Energy dispersive
spectroscopy (EDS) reveals these films were contaminated with oxygen,
originating either from the growth environment or from sample exposure to air.
The oxygen contamination may account for the low Tc for those in-situ annealed
films, while the use of Si as the substrate does not result in a decrease in Tc
as compared to other substrates.Comment: 5 pages, 4 figures, 15 references; due to file size limit, images
were blure
High temporal stability of supercurrents in MgB(2) materials
Fine grained polycrystalline samples of MgB(2) superconductor were
synthesized from the elements to contain < 5 % of impurity phases, according to
X-ray powder diffractometry. The superconductive transition was sharp with a
midpoint Tc = 38.5 K. The magnetization in the vortex state was studied as a
function of applied field H, temperature T, and time t. From the equilibrium
magnetization, the London penetration depth was obtained. The supercurrent
density J(T,H,t) in the vortex state (derived from the irreversible
magnetization) decreases approximately linearly with T, in contrast to the
quasi-exponential falloff in high-Tc superconductors. The current is highly
stable in time, with normalized decay rates S = -d ln(J)/d ln(t) well below
those in high-Tc materials. These results are compared with those of other
superconductors.Comment: PDF file containing text and 6 figures, 12 pages tota
A unique measles B3 cluster in the United Kingdom and the Netherlands linked to air travel and transit at a large international airport, February to April 2014
Rita de Sousa (Bolseira EUPHEM) - Investigadora do Departamento de Doenças Infeciosas do Instituto Ricardo JorgeThis report describes a joint measles outbreak investigation between public health officials in the United Kingdom (UK) and the Netherlands following detection of a measles cluster with a unique measles virus strain. From 1 February to 30 April 2014, 33 measles cases with a unique measles virus strain of genotype B3 were detected in the UK and the Netherlands, of which nine secondary cases were epidemiologically linked to an infectious measles case travelling from the Philippines. Through a combination of epidemiological investigation and sequence analysis, we found that measles transmission occurred in flight, airport and household settings. The secondary measles cases included airport workers, passengers in transit at the same airport or travelling on the same flight as the infectious case and also household contacts. This investigation highlighted the particular importance of measles genotyping in identifying transmission networks and the need to improve vaccination, public health follow-up and management of travellers and airport staff exposed to measles.info:eu-repo/semantics/publishedVersio
Conductive Buffer Layers and Overlayers for the Thermal Stability of Coated Conductors
We analyze fundamental issues related to the thermal and electrical stability
of a coated conductor during its operation. We address the role of conductive
buffer layers in the stability of Ni-based coated conductors, and the effect of
a metallic cap layer on the electrical properties of Ni alloy-based
superconducting tapes. For the first case we report on the fabrication of a
fully conductive RABiTS architecture formed of bilayers of conductive oxides
SrRuO3 and LaNiO3 on textured Ni tapes. For the second case we discuss
measurements of current-voltage relations on Ag/YBa2Cu3O7-d and Cu/Ag/
YBa2Cu3O7-d prototype multilayers on insulating substrates. Limitations on the
overall tape structure and properties that are posed by the stability
requirement are presented.Comment: 4 pages, 5 figure
Effective Vortex Pinning in MgB2 thin films
We discuss pinning properties of MgB2 thin films grown by pulsed-laser
deposition (PLD) and by electron-beam (EB) evaporation. Two mechanisms are
identified that contribute most effectively to the pinning of vortices in
randomly oriented films. The EB process produces low defected crystallites with
small grain size providing enhanced pinning at grain boundaries without
degradation of Tc. The PLD process produces films with structural disorder on a
scale less that the coherence length that further improves pinning, but also
depresses Tc
Differentiating Schizophrenia from Bipolar Illness on 18 F FDG PET CT Based on white Matter Metabolism; an under-Utilised Parameter
18F-FDG PET/CT positron emission tomography studies (FDG-PET) have shown similar cortico-limbic metabolic dysregulation in bipolar disorder and schizophrenia, with hypoactive prefrontal cortex coupled with hyperactive anterior limbic areas. However, it is not clear whether white matter metabolism connecting these regions is differently affected in the two disorders. Forty eight patients with schizophrenia mean age ± S.D] 31.6 ± 7.8 and 56 patients with bipolar disorder [mean age±S.D] 46.2 ± 8.9 underwent an 18F-FDG PET/CT scan. Normalized datasets the two groups of patients were compared on a voxel-by-voxel basis using a two-sample t statistic test as implemented in SPM8, and adding age as covariate. Group differences were assessed applying a threshold of p<0.0005. White matter metabolic rates significantly differed between schizophrenia and bipolar disorder, whereas no differences were shown for cortical activity. This is the first 18F-FDG PET/CT to our best knowledge, directly comparing subjects with schizophrenia to those with bipolar disorder. It reports decreased activity in the center of large fronto-temporal and cerebellar white matter tracts in patients with schizophrenia in respect to those with bipolar disorder. This feature may characterize and differentiate the regional brain metabolism of the two illnesses
A serious game architecture for green mobility
Good driving behavior is a significant factor for road safety and green mobility. A countermeasure to overcome the coarse driving behavior and a methodology to captivate optimal driving traits are discussed in this work. For which, the serious games concept was exploited to improvise the driver performance by deploying diversified game logics (scores, incentives and live game for performance evolution) on a smartphone-based user interface. The application was tested in ASTA ZERO (Active Safety Test Area) in Sweden. The tests comprised of variations (good and bad driving behavior) in driving pattern for analyzing the impact of the application on the driver performance
Growth mechanism of superconducting MgB2 films prepared by various methods
The growth mechanisms of MgB2 films obtained by different methods on various
substrates are compared via a detailed cross-sectional scanning electron
microscopy (SEM) study. The analyzed films include (a) samples obtained by an
ex-situ post-anneal at 900 degree of e-beam evaporated boron in the presence of
an Mg vapor (exhibiting bulk-like Tc0 about 38.8 K), (b) samples obtained by
the same ex-situ 900 degree anneal of pulsed laser deposition (PLD)-grown Mg+B
precursors (exhibiting Tc0 ~ 25 K), and (c) films obtained by a low-temperature
(600 - 630 degree) in-situ anneal of PLD-grown Mg+B precursors (with Tc0 about
24 K). A significant oxygen contamination was also present in films obtained
from a PLD-grown precursors. On the other hand, it is clearly observed that the
films obtained by the high-temperature reaction of e-beam evaporated B with Mg
vapor are formed by the nucleation of independent MgB2 grains at the film
surface, indicating that this approach may not be suitable to obtain smooth and
(possibly) epitaxial films.Comment: 1 table, 4 figures, 17 references, 16 pages PDF fil
Temperature and Field Dependence of the Energy Gap of MgB2/Pb planar junction
We have constructed MgB2/Pb planar junctions for both temperature and field
dependence studies. Our results show that the small gap is a true bulk property
of MgB2 superconductor, not due to surface effects. The temperature dependence
of the energy gap manifests a nearly BCS-like behavior. Analysis of the effect
of magnetic field on junctions suggests that the energy gap of MgB2 depends
non-linearly on the magnetic field. Moreover, MgB2 has an upper critical field
of 15 T, in agreement with some reported Hc2 from transport measurements.Comment: 5 pages, 5 figures. Submitted to Phys. Rev.
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