379 research outputs found
First evidence of a strong Magneto-capacitance coupling at room temperature in integrated piezoelectric resonators
In the vicinity of their resonance frequency, piezoelectric resonators are
highly sensitive to small perturbations. The present report is focussed on the
magnetic field as a perturbation source. First, magneto-dielectric modulation
of more than 10% is achieved at room temperature on both ferroelectric single
crystals and quartz discs. Since such piezoelectric resonators are now
available as membranes directly integrated on Silicon wafer, we have checked
the magneto-dielectric modulation in such resonators. We show here for the
first time that a moderate magnetic field of 2.104 Oersteds is able to
efficiently tune the impedance of these resonators in their resonance window.Comment: 11 Pages, 4 figure
Resistive hystersis effects in perovskite oxide-based heterostructure junctions
In this paper, we report the electrical and structural properties of the
oxide-based metal/ferroelectric/metal (MFM) junctions. The heterostructures are
composed of ultrathin layers of La0.7Ca0.3MnO3 (LCMO) as a metallic layer and,
BaTiO3 (BTO) as a ferroelectric layer. Junction based devices, having the
dimensions of 400 x 200 micom2, have been fabricated upon LCMO/BTO/LCMO
heterostructures by photolithography and Ar-ion milling technique. The DC
current-voltage (I-V) characteristics of the MFM junctions were carried out. At
300 K, the devices showed the linear (I-V) characteristics, whereas at 77 K,
(I-V) curves exhibited some reproducible switching behaviours with well-defined
remnant currents. The resulting resistance modulation is very different from
what was already reported in ultrathin ferroelectric layers displaying
resistive switching. A model is presented to explain the datasComment: To be publised in Applied Physics Letter
Taking care of systemic sclerosis patients during COVID-19 pandemic : rethink the clinical activity
COVID-19 outbreak has quickly spread worldwide, causing a high pressure on the health-care system. In Italy, from March 8, 2020, all the deferrable clinical activities have been suspended to increase the health care offer for COVID-19 patients. The hospital organization has been modified also in order to assure non-COVID-19 patients assistance. The Scleroderma Unit of ASST Pini-CTO Hospital, in Milan, in the region mostly hit by SARS-CoV-2 in Italy, follows more than 600 patients affected by systemic sclerosis (SSc). Patients with SSc need a close follow-up with a regular screening of organ involvement and frequent intravenous treatments. All SSc patients have been educated about ministerial directives to limit COVID-19 spread. The organization of our Scleroderma Unit has been quickly rethought to assure SSc patients assistance in safety for them and for health-care workers during urgent visits or infusion therapies. Using electronic way of communication with frequent virtual contact and guarantying home deliveries of some therapies, we allowed a continuity of care also outside the Hospital
STM tunneling spectroscopic studies of YNdxBa2−xCu3O7−δ thin films
We performed tunneling spectroscopy on high quality superconducting YNdxBa2-xCu3O7-delta thin films using a low-temperature scanning tunneling microscope. Superconducting regions show very well-defined gap structures. Disorder introduced by Nd substitution at the Ba site dramatically affects locally the quasiparticle density of states. The measurements show that the impurities induce surface resonant states at energies very close to the Fermi energy, typical of a d-wave superconductor
Theoretical description of deformed proton emitters: nonadiabatic coupled-channel method
The newly developed nonadiabatic method based on the coupled-channel
Schroedinger equation with Gamow states is used to study the phenomenon of
proton radioactivity. The new method, adopting the weak coupling regime of the
particle-plus-rotor model, allows for the inclusion of excitations in the
daughter nucleus. This can lead to rather different predictions for lifetimes
and branching ratios as compared to the standard adiabatic approximation
corresponding to the strong coupling scheme. Calculations are performed for
several experimentally seen, non-spherical nuclei beyond the proton dripline.
By comparing theory and experiment, we are able to characterize the angular
momentum content of the observed narrow resonance.Comment: 12 pages including 10 figure
Numerical simulation of the internal plasma dynamics of post-flare loops
We integrate the MHD ideal equations of a slender flux tube to simulate the
internal plasma dynamics of coronal post-flare loops. We study the onset and
evolution of the internal plasma instability to compare with observations and
to gain insight into physical processes and characteristic parameters
associated with flaring events. The numerical approach uses a finite-volume
Harten-Yee TVD scheme to integrate the 1D1/2 MHD equations specially designed
to capture supersonic flow discontinuities. We could reproduce the
observational sliding down and upwardly propagating of brightening features
along magnetic threads of an event occurred on October 1st, 2001. We show that
high--speed downflow perturbations, usually interpreted as slow magnetoacoustic
waves, could be better interpreted as slow magnetoacoustic shock waves. This
result was obtained considering adiabaticity in the energy balance equation.
However, a time--dependent forcing from the basis is needed to reproduce the
reiteration of the event which resembles observational patterns -commonly known
as quasi--periodic pulsations (QPPs)- which are related with large scale
characteristic longitudes of coherence. This result reinforces the
interpretation that the QPPs are a response to the pulsational flaring
activity.Comment: Accepted MNRAS, 10 pages, 14 figures, 1 tabl
Narrow-band search of continuous gravitational-wave signals from Crab and Vela pulsars in Virgo VSR4 data
Paper producido por "The LIGO Scientific Collaboration and the Virgo Collaboration". (En el registro se mencionan solo algunos autores de las decenas de personas que participan).In this paper we present the results of a coherent narrow-band search for continuous gravitational-wave signals from the Crab and Vela pulsars conducted on Virgo VSR4 data. In order to take into account a possible small mismatch between the gravitational wave frequency and two times the star rotation frequency, inferred from measurement of the electromagnetic pulse rate, a range of 0.02 Hz around two times the star rotational frequency has been searched for both the pulsars. No evidence for a signal has been found and 95% confidence level upper limits have been computed both assuming polarization parameters are completely unknown and that they are known with some uncertainty, as derived from X-ray observations of the pulsar wind torii. For Vela the upper limits are comparable to the spin-down limit, computed assuming that all the observed spin-down is due to the emission of gravitational waves. For Crab the upper limits are about a factor of two below the spin-down limit, and represent a significant improvement with respect to past analysis. This is the first time the spin-down limit is significantly overcome in a narrow-band search.publishedVersionFil: Maglione, C. Argentinian Gravitational Wave Group; Argentina.Fil: Quiroga, G. Argentinian Gravitational Wave Group; Argentina.Fil: Reula, O. Argentinian Gravitational Wave Group; Argentina.Fil: Dominguez, E. Argentinian Gravitational Wave Group; Argentina.Fil: Ortega, W. Argentinian Gravitational Wave Group; Argentina.Fil: Aasi, J. LIGO. California Institute of Technology; Estados Unidos de América.Física de Partículas y Campo
Inference for variograms
The empirical variogram is a standard tool in the investigation and modelling of spatial
covariance. However, its properties can be difficult to identify and exploit in the
context of exploring the characteristics of individual datasets. This is particularly true
when seeking to move beyond description towards inferential statements about the
structure of the spatial covariance which may be present. A robust form of empirical
variogram based on a fourth-root transformation is used. This takes advantage of the
normal approximation which gives an excellent description of the variation exhibited
on this scale. Calculations of mean, variance and covariance of the binned empirical
variogram then allow useful computations such as confidence intervals to be added to
the underlying estimator. The comparison of variograms for different datasets provides
an illustration of this. The suitability of simplifying assumptions such as isotropy and
stationarity can then also be investigated through the construction of appropriate test
statistics and the distributional calculations required in the associated p-values can be
performed through quadratic form methods. Examples of the use of these methods in
assessing the form of spatial covariance present in datasets are shown, both through
hypothesis tests and in graphical form. A simulation study explores the properties of
the tests while pollution data on mosses in Galicia (North-West Spain) are used to
provide a real data illustration
Relativistic Hartree-Bogoliubov description of the deformed ground-state proton emitters
Ground-state properties of deformed proton-rich odd-Z nuclei in the region
are described in the framework of Relativistic Hartree
Bogoliubov (RHB) theory. One-proton separation energies and ground-state
quadrupole deformations that result from fully self-consistent microscopic
calculations are compared with available experimental data. The model predicts
the location of the proton drip-line, the properties of proton emitters beyond
the drip-line, and provides information about the deformed single-particle
orbitals occupied by the odd valence proton.Comment: 9 pages, RevTeX, 3 PS figures, submitted Phys. Rev. Letter
B Cells Regulate Neutrophilia during Mycobacterium tuberculosis Infection and BCG Vaccination by Modulating the Interleukin-17 Response
We have previously demonstrated that B cells can shape the immune response to Mycobacterium tuberculosis, including the level of neutrophil infiltration and granulomatous inflammation at the site of infection. The present study examined the mechanisms by which B cells regulate the host neutrophilic response upon exposure to mycobacteria and how neutrophilia may influence vaccine efficacy. To address these questions, a murine aerosol infection tuberculosis (TB) model and an intradermal (ID) ear BCG immunization mouse model, involving both the μMT strain and B cell-depleted C57BL/6 mice, were used. IL (interleukin)-17 neutralization and neutrophil depletion experiments using these systems provide evidence that B cells can regulate neutrophilia by modulating the IL-17 response during M. tuberculosis infection and BCG immunization. Exuberant neutrophilia at the site of immunization in B cell-deficient mice adversely affects dendritic cell (DC) migration to the draining lymph nodes and attenuates the development of the vaccine-induced Th1 response. The results suggest that B cells are required for the development of optimal protective anti-TB immunity upon BCG vaccination by regulating the IL-17/neutrophilic response. Administration of sera derived from M. tuberculosis-infected C57BL/6 wild-type mice reverses the lung neutrophilia phenotype in tuberculous μMT mice. Together, these observations provide insight into the mechanisms by which B cells and humoral immunity modulate vaccine-induced Th1 response and regulate neutrophila during M. tuberculosis infection and BCG immunization. © 2013 Kozakiewicz et al
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