607 research outputs found
Anisotropy and directional pinning in YBa2Cu3O 7-x with BaZrO3 nanorods
No full textMeasurements of anisotropic transport properties (dc and high-frequency regime) of driven vortex matter in YBa2Cu3O 7-x with elongated strong-pinning sites (c-axis aligned, self-assembled BaZrO3 nanorods) are used to demonstrate that the effective-mass angular scaling takes place only in intrinsic physical quantities (flux-flow resistivity), and not in pinning-related Labusch parameter and critical currents. Comparison of the dynamics at different time scales shows evidence for a transition of the vortex matter toward a Mott phase, driven by the presence of nanorods. The strong pinning in dc arises partially from a dynamic effect. © 2013 Author(s)
Cosmological evolution of thermal relic particles in f (R) gravity
No full textBy considering f(R) gravity models, the cosmic evolution is modified with respect to the standard ΛCDM scenario. In particular, the thermal history of particles results is modified. In this paper, we derive the evolution of relics particles (weakly interacting massive particles) assuming a reliable f(R) cosmological solution and taking into account observational constraints. The connection to the PAMELA experiment is also discussed. Results are consistent with constraints coming from BICEP2 and PLANCK experiments
Directional pinning and anisotropy in YBa2Cu3O 7-x with BaZrO3 nanorods: Intrinsic and nanorods-induced anisotropy
No full textWe present a study of the anisotropic vortex parameters as obtained from measurements of the microwave complex resistivity in the vortex state with a tilted applied magnetic field in YBa2Cu3O7-x thin films with BaZrO3 nanorods. We present the angular dependence of the vortex viscosity η, the pinning constant kp and the upper limit for the creep factor χM. We show that the directional effect of the nanorods is absent in η, which is dictated by the mass anisotropy γ. By contrast, pinning-mediated properties are strongly affected by the nanorods. It is significant that the pinning and creep affected by the nanorods is detectable also at our very high operating frequency, which implies very short-range displacements of the vortices from their equilibrium position. © 2014 Elsevier B.V. All rights reserved
L'insediamento subappenninico di Conelle di Arcevia (Ancona)
No full textSi presentano i risultati dello studio dei materiali ceramici provenienti da Conelle di Arcevia (AN), scavi Puglisi 1958-1969, riferibili al Bronzo recente. I materiali presi in esame sono attribuibili principalmente ad una fase antica del Subappenninico, anche se la presenza di elementi più tardi potrebbe far ipotizzare un’occupazione in un momento avanzato della stessa facies. Sono stati rinvenuti anche alcuni frammenti decorati ad incisioni ed excisioni, i quali, data la loro esigua presenza tra i materiali provenienti dagli scavi Puglisi, potrebbero testimoniare un permanere di tale stile decorativo anche nei periodi successivi all’Appenninico. The authors present the results of the study of ceramic material from the excavation of Conelle di Arcevia, by Puglisi (1958-1969), ascribed to the Late Bronze Age. The material examined can be mainly attributed to an ancient phase of the Subapennine, even if the presence of later elements could suggest a more recent occupation of the site during the same culture. Among the fragments analysed, some are decorated with incisions and excisions, which, even if the quantity found in the Puglisi excavations is limited, could suggest a continuing use of these decorative styles after the Apennine period
Measurements and removal of substrate effects on the microwave surface impedance of YBCO films on SrTiO3
No full textWe reconsider the problem of the measurements of the microwave complex surface impedance in thin superconducting films deposited on SrTiO3 substrates. We perform measurements of the complex surface impedance Z(s)(') = R-s(') + i Delta X-s(') of thin YBa2Cu3O7-delta films deposited by laser ablation on SrTiO3 substrates. The typical oscillations due to the strong temperature variation of the SrTiO3 permittivity are confirmed in R-s(') and observed in Delta X-s('). The effects of the SrTiO3 substrate are evident even well below the superconducting transition temperature of YBa2Cu3O7-delta. Similarly to previous works, we describe the overall response in terms of impedance transformations. We extend the known results by (i) considering the measurements of the imaginary part, (ii) comparing the measurements to the absolute dc resistivity measured on the same sample, and (iii) suggesting a method for measuring the intrinsic thin film surface impedance by adjusting the substrate impedance. To demonstrate the feasibility of microwave measurements of intrinsic properties of films grown onto SrTiO3 substrates, we check the proposed method by measuring the field dependent surface impedance before and after removal of the substrate resonance
Change of strength of vortex pinning in YBCO due to BaZrO3 inclusions
No full textWe probe the short-range pinning properties with the application of microwave currents at very high driving frequencies (47.7 GHz) on YBa2Cu3O7-delta films with and without sub-micrometer BaZrO3 inclusions. We explore the temperature and field ranges 60 K, < T < T-c and 0 <mu H-0 < 0.8 T, with the field applied along the c-axis. The magnetic field induces a much smaller increase of the microwave resistivity, Delta rho(1)(H)+i Delta rho(2)(H), in YBa2Cu3O7-delta/BaZrO3 with respect to pure YBa2Cu3O7-delta.Delta rho(1)(H) is slightly superlinear in pure YBa2Cu3O7-delta (suggesting a possible contribution of thermal activation), but linear or sublinear in YBa2Cu3O7-delta/BaZrO3 (suggesting a possible suppression of thermal activation as a consequence of BaZrO3 inclusions). These features persist up to close to T-c. We discuss our data in terms of the ratio r = Delta rho(2)(H)/Delta rho(1)(H) in the framework of the models for the microwave surface impedance in the mixed state. Large r are found in YBa2Cu3O7-delta/BaZrO3, with little field dependence. By contrast, smaller values and stronger field dependences are found in pure YBa2Cu3O7-delta. We discuss the different field dependence of the pinning constant. (C) 2008 Elsevier B.V. All rights reserved
Corrigendum to: Geology of the Victoria quadrangle (H02), Mercury (Journal of Maps, (2016), 10.1080/17445647.2016.1193777)
No full textWhen the above article was first published online, the third author was incorrectly listed as F. Ferranti. This has now been corrected
Genomic DNA in human blastocoele fluid.
No full textReprod Biomed Online. 2013 Jun;26(6):603-10. doi: 10.1016/j.rbmo.2013.02.012. Epub 2013 Mar 13.
Genomic DNA in human blastocoele fluid.
Palini S1, Galluzzi L, De Stefani S, Bianchi M, Wells D, Magnani M, Bulletti C.
Author information
Abstract
IVF often requires embryo cryopreservation through vitrification. During the vitrification process, the embryos can be collapsed by withdrawing the blastocoele fluid. The metabolomic profile of blastocoele fluid has been recently investigated by high-performance liquid chromatography-electrospray ionization-mass spectrometry to provide metabolite information that can help estimations of implantation efficiency. However, the presence of embryo DNA in blastocoele fluid has not been reported to date. This study shows using real-time PCR that genomic DNA was present in about 90% of blastocoele fluid samples harvested during the vitrification procedure. Moreover, the potential for determining embryo sex directly from blastocoele fluid is demonstrated by amplifying the multicopy genes TSPY1 (on the Y chromosome) and TBC1D3 (on chromosome 17). This opens up the possibility of screening embryos from couples carrying an X-linked disorder to identify male embryos at high risk of disease. The application of whole-genome amplification technologies to fluid samples is also shown to be feasible, potentially allowing more comprehensive genetic tests. As proof of principle, microarray comparative genomic hybridization was attempted to confirm the sex of embryos as well as detect several aneuploidies. However, further studies are needed to validate this approach and confirm that the accuracy is sufficient for diagnostic purposes
Microwave and dc pinning studies of BZO enhanced YBCO thin films.
No full textArtificial pinning centers obtained as nanoinclusions of dielectric materials in YBa2Cu3O7-x (YBCO) films are of great
interest in view of their great potential in applications such as coated conductors [1]. In particular, it has been
observed [2] that BaZrO3 (BZO) inclusions in films grown by Pulsed Laser Deposition (PLD) assemble in the form of
nanorods, 30-150 nm long, of typical cross section comparable to the vortex core size. Thus, they are optimal
candidates for effective vortex core pinning. Previous studies [2] have already shown that the BZO nanorods,
oriented approximately along the c-axis, determine a significant increase of the pinning strength both at dc, in terms
of the critical current density Jc and of the maximum pinning force Fp=JcB, and at microwaves, in terms of the
pinning constant kp and of overall consequent reduction of dissipation levels. Despite the promising experimental
results, the physics underlying the enhanced artificial pinning in anisotropic superconductors is still unsettled. In
particular, the interplay between the effective-mass anisotropy of YBCO and the preferential direction given by the
BZO-induced nanocolumns is still an open question. In this framework, we performed a combined study of the
pinning properties of YBCO thin films with BZO nanorods through the two complementary probes, dc measurements
of Jc and microwave measurements of the vortex parameters, including the flux flow resistivity ρff and the pinning
constant kp. The very different dynamic regimes explored through the mentioned techniques allow to fruitfully
investigate the interplay among the various sources of pinning and their different anisotropic properties. Indeed, the
overall anisotropy of pinning is expected to arise from the competition between the mass anisotropy of YBCO, the
preferential direction introduced by the extended BZO structures and the intrinsic pinning occurring in the YBCO
layers. The samples under study are grown by pulsed laser deposition (PLD) from targets with BZO powders at 5%
mol. as extensively reported elsewhere [3]. They are 120 nm thick and c-axis oriented, with Tc ~ 90 K and a zero-field
Jc as high as 3.7 MA cm-2 at 77 K. Dc measurements in tilted fields H (maximum Lorentz force configuration) yielded
Jc(H) as a function of the tilting angle θ between the field direction and the c-axis at several field intensities μ0H≤12
T. The samples were patterned as strips, 30 μm wide and 1 mm long, in the standard four-contact configuration. The
criterion of 1 μV cm-1 was used. The field-induced variation of the microwave complex resistivity was measured at
fields μ0H≤0.8 T on unpatterned samples through a cylindrical sapphire loaded resonator operating at 48 GHz. Both
field sweeps at selected angles and field rotations at selected fields were performed. Because of the small signal
available at θ=90°, the temperature T≈80 K was chosen, being both sufficiently far from Tc to avoid thermal
pair-breaking and compatible with a high enough signal-to-noise ratio. A careful analysis [4] of the microwave
measurements shows that the flux flow resistivity ρff, which is dissipation-related, satisfies the well-known scaling
law [5] for the mass anisotropy, i. e. it can be scaled as ρff(H, θ)= ρff(H/Hc2(θ)), provided that the scaling function is
properly corrected to incorporate the geometrical contribution of the experimental setup [6]. By contrast, no scaling
property can be observed on the pinning constant kp(H, θ), coherently with the presence of extrinsic anisotropy
sources. Quantitative comparison of the angular pinning strength as measured in dc (large vortex displacement) and
at microwaves (very short, ~1 Å, vortex oscillations around equilibrium positions), shows identical behavior in
almosty the full angular range, apart when the field is aligned with the BZO defects (0°) or the a-b planes (90°): in
such cases dc-measured pinning is stronger than microwave-measured pinning. The difference indicates the presence
of a dynamic effect: the strongest, peaked pinning appears only when large vortex displacements, such as those
determined at dc, are involved. The implication of these findings in terms of the operating pinning mechanisms are
discussed in terms of a Mott-like phase for vortices.
References:
[1] J. L. Macmanus-Driscoll et al., Nat. Mater. 3, 439 (2004); J. Gutiérrez et al., Nat. Mater. 6, 367 (2007); B. Maiorov
et al., Nat. Mater. 8 398 (2009)
[2] N. Pompeo et al., Appl. Phys. Lett. 91, 182507 (2007); A. Augieri et al., J. Appl. Phys. 108, 063906 (2010)
[3] V. Galluzzi et al., IEEE Trans. Appl. Supercond. 17, 3628 (2007)
[4] N. Pompeo et al., Physica C 479, 160 (2012)
[5] G. Blatter, V. B. Geshkenbein and A. I. Larkin, Phys. Rev. Lett. 68, 876(1992); Z. Hao and J. R. Clem, Phys. Rev. B 46
- …
