414 research outputs found
Evidence of orbital reconstruction at interfaces in La0.67Sr0.33MnO3 films
Electronic properties of transition metal oxides at interfaces are influenced
by strain, electric polarization and oxygen diffusion. Linear dichroism (LD)
x-ray absorption, diffraction, transport and magnetization on thin
La0.7Sr0.3MnO3 films, allow identification of a peculiar universal interface
effect. We report the LD signature of preferential 3d-eg(3z2-r2) occupation at
the interface, suppressing the double exchange mechanism. This surface orbital
reconstruction is opposite of that favored by residual strain and independent
of dipolar fields, chemical nature of the substrate and capping.Comment: 13 pages, 5 figure
Evolution of magnetic phases and orbital occupation in (SrMnO3)n/(LaMnO3)2n superlattices
The magnetic and electronic modifications induced at the interfaces in
(SrMnO)/(LaMnO) superlattices have been investigated
by linear and circular magnetic dichroism in the Mn L x-ray absorption
spectra. Together with theoretical calculations, our data demonstrate that the
charge redistribution across interfaces favors in-plane ferromagnetic (FM)
order and orbital occupation, in agreement with the
average strain. Far from interfaces, inside LaMnO, electron localization
and local strain favor antiferromagnetism (AFM) and
orbital occupation. For the high density of interfacial planes ultimately
leads to dominant FM order forcing the residual AFM phase to be in-plane too,
while for the FM layers are separated by AFM regions having
out-of-plane spin orientation.Comment: accepted for publication as a Rapid Communication in Physical Review
Activation of NF-kappaB/Rel transcription factors in human primary peripheral blood mononuclear cells by interleukin 7.
Pathways that regulate the activation of NF-kappaB/Rel transcription factors are known to include signaling through a number of cytokine receptors. Interleukin 7 (IL-7), produced by bone marrow and other stromal cells, is a key factor for differentiation and survival in the lymphoid and other compartments. We found that human recombinant IL-7 induced NF-kappaB/Rel activation, analyzed by electrophoretic mobility shift assay (EMSA), in human peripheral blood T lymphocytes from healthy donors. Induced complexes included p65 and p50 NF-kappaB/Rel subunits. These results demonstrate for the first time that IL-7 can participate in signaling leading to NF-kappaB/Rel activation
A powerful (and likely young) radio-loud quasar at z=5.3
We present the discovery of PSO J191.0569686.43172 (hereafter PSO
J19186), a new powerful radio-loud quasar (QSO) in the early Universe (z =
5.32). We discovered it by cross-matching the NRAO VLA Sky Survey (NVSS) radio
catalog at 1.4 GHz with the first data release of the Panoramic Survey
Telescope and Rapid Response System (Pan-STARRS PS1) in the optical. With a
NVSS flux density of 74.2 mJy, PSO J19186 is one of the brightest radio QSO
discovered at z5. The intensity of its radio emission is also confirmed
by the very high value of radio loudness (R>300). The observed radio spectrum
of PSO J19186 shows a possible turnover around 1 GHz (i.e., 6
GHz in the rest frame), making it a Gigahertz-Peaked Spectrum (GPS) source.
However, variability could affect the real shape of the radio spectrum, since
the data in hand have been taken 25 years apart. By assuming a peak of
the observed radio spectrum between 1 and 2 GHz (i.e. 6 and 13 GHz in
the rest-frame) we found a linear size of the source of 10-30 pc and a
corresponding kinetic age of 150-460 yr. This would make PSO J19186 a newly
born radio source. However, the large X-ray luminosity (5.310
erg s), the flat X-ray photon index (=1.32) and the
optical-X-ray spectral index (=1.329) are typical of
blazars. This could indicate that the non-thermal emission of PSO J19186 is
Doppler boosted. Further radio observations (both on arcsec and parsec scales)
are necessary to better investigate the nature of this powerful radio QSO.Comment: 10 pages, 9 figures, 5 tables, Accepted for publication in A&
Analysis of short-term blood pressure variability in pheochromocytoma/paraganglioma patients
Data on short-term blood pressure variability (BPV), which is a well-established cardiovascular prognostic tool, in pheochromocytoma and paraganglioma (PPGL) patients is still lack and conflicting. We retrospectively evaluated 23 PPGL patients referred to our unit from 2010 to 2019 to analyze 24 h ambulatory blood pressure monitoring (24-h ABPM)-derived markers of short-term BPV, before and after surgical treatment. PPGL diagnosis was assessed according to guidelines and confirmed by histologic examination. The 24-h ABPM-derived markers of short-term BPV included: circadian pressure rhythm; standard deviation (SD) and weighted SD (wSD) of 24-h, daytime, and night-time systolic and diastolic blood pressure (BP); average real variability (ARV) of 24-h, daytime, and night-time systolic and diastolic BP. 7 males and 16 females of 53 ± 18 years old were evaluated. After surgical resection of PPGL we found a significant decrease in 24-h systolic BP ARV (8.8 ± 1.6 vs. 7.6 ± 1.3 mmHg, p < 0.001), in 24-h diastolic BP ARV (7.5 ± 1.6 vs. 6.9 ± 1.4 mmHg, p = 0.031), and in wSD of 24-h diastolic BP (9.7 ± 2.0 vs 8.8 ± 2.1 mmHg, p = 0.050) comparing to baseline measurements. Moreover, baseline 24-h urinary metanephrines significantly correlated with wSD of both 24-h systolic and diastolic BP. Our study highlights as PPGL patients, after proper treatment, show a significant decrease in some short-term BPV markers, which might represent a further cardiovascular risk factor
Analysis of time-profiles with in-beam PET monitoring in charged particle therapy
Background: Treatment verification with PET imaging in charged particle
therapy is conventionally done by comparing measurements of spatial
distributions with Monte Carlo (MC) predictions. However, decay curves can
provide additional independent information about the treatment and the
irradiated tissue. Most studies performed so far focus on long time intervals.
Here we investigate the reliability of MC predictions of space and time (decay
rate) profiles shortly after irradiation, and we show how the decay rates can
give an indication about the elements of which the phantom is made up.
Methods and Materials: Various phantoms were irradiated in clinical and
near-clinical conditions at the Cyclotron Centre of the Bronowice proton
therapy centre. PET data were acquired with a planar 16x16 cm PET system.
MC simulations of particle interactions and photon propagation in the phantoms
were performed using the FLUKA code. The analysis included a comparison between
experimental data and MC simulations of space and time profiles, as well as a
fitting procedure to obtain the various isotope contributions in the phantoms.
Results and conclusions: There was a good agreement between data and MC
predictions in 1-dimensional space and decay rate distributions. The fractions
of C, O and C that were obtained by fitting the decay
rates with multiple simple exponentials generally agreed well with the MC
expectations. We found a small excess of C in data compared to what was
predicted in MC, which was clear especially in the PE phantom.Comment: 9 pages, 5 figures, 1 table. Proceedings of the 20th International
Workshop on Radiation Imaging Detectors (iWorid2018), 24-28 June 2018,
Sundsvall, Swede
Comment on newly found Charge Density Waves in infinite layer Nickelates
Recent works[1-3] reported evidence for charge density waves (CDWs) in
infinite layer nickelates (112 structure) based on resonant diffraction at the
Ni edge measured at fixed scattering angle. We have found that a
measurement with fixed momentum transfer, rather than scattering angle, does
not show a resonance effect. We have also observed that a nearby structural
Bragg peak from the substrate appears due to third harmonic content of the
incident beam, and spreads intensity down to the region of the attributed CDW
order. This was further confirmed by testing a bare substrate. We suggest
procedures to confirm an effective resonant enhancement of a diffraction peak
Detectors for the next-generation PET scanners
Next-generation PET scanners are expected to fulfill very high requirements in terms of spatial, energy and timing resolution. Modern scanner performances are inherently limited by the use of standard photomultiplier tubes. The use of Silicon Photomultiplier (SiPM) matrices is proposed for the construction of a small animal PET system with depth of interaction capabilities. Measurements showing that SiPM matrices are highly ideal for PET applications, have been reported
Analysis methods for in-beam PET images in proton therapy treatment verification: a comparison based on Monte Carlo simulations
Background and purpose: In-beam Positron Emission Tomography (PET) is one of
the modalities that can be used for in-vivo non-invasive treatment monitoring
in proton therapy. PET distributions obtained during various treatment sessions
can be compared in order to identify regions that have anatomical changes. The
purpose of this work is to test and compare different analysis methods in the
context of inter-fractional PET image comparison for proton treatment
verification.
Methods: For our study we used the FLUKA Monte Carlo code and artificially
generated CT scans to simulate in-beam PET distributions at different stages
during proton therapy treatment. We compared the Beam-Eye-View method, the
Most-Likely-Shift method, the Voxel-Based-Morphology method and the gamma
evaluation method to compare PET images at the start of treatment, and after a
few weeks of treatment. The results were compared to the CT scan.
Results and conclusions: Three-dimensional methods like VBM and gamma are
preferred above two-dimensional methods like MLS and BEV if much statistics is
available, since the these methods allow to identify the regions with anomalous
activity. The VBM approach has as disadvantage that a larger number of MC
simulations is needed. The gamma analysis has the disadvantage that no clinical
indication exist on tolerance criteria. In terms of calculation time, the BEV
and MLS method are preferred. We recommend to use the four methods together, in
order to best identify the location and cause of the activity changes.Comment: 9 pages, 5 figure
- …