744 research outputs found
Imaging backscattering through impurity-induced antidots in quantum Hall constrictions
We exploit the biased tip of a scanning gate microscope (SGM) to induce a
controlled backscattering between counter-propagating edge channels in a wide
constriction in the quantum Hall regime. We compare our detailed conductance
maps with a numerical percolation model and demonstrate that conductance
fluctuations observed in these devices as a function of the gate voltage
originate from backscattering events mediated by localized states pinned by
potential fluctuations. Our imaging technique allows us to identify the
necessary conditions for the activation of these backscattering processes and
also to reconstruct the constriction confinement potential profile and the
underlying disorder
Spatially-resolved analysis of edge-channel equilibration in quantum Hall circuits
We demonstrate an innovative quantum Hall circuit with variable geometry
employing the moveable electrostatic potential induced by a biased atomic force
microscope tip. We exploit this additional degree of freedom to identify the
microscopic mechanisms that allow two co-propagating edge channels to
equilibrate their charge imbalance. Experimental results are compared with
tight-binding simulations based on a realistic model for the disorder
potential. This work provides also an experimental realization of a beam mixer
between co-propagating edge channels, a still elusive building block of a
recently proposed new class of quantum interferometers
Nuevos estudios en el sector Casa del Kuraca del sitio el Shincal de Quimivil (Departamento de Belén, provincia de Catamarca, Argentina)
Fil: Giovannetti, Marco Antonio. DivisiĂłn ArqueologĂa. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Espina, Josefina. DivisiĂłn ArqueologĂa. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Cochero, Gregoria. DivisiĂłn ArqueologĂa. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Corrado, Gustavo. DivisiĂłn ArqueologĂa. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Aljanati, Lucia. DivisiĂłn ArqueologĂa. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Valderrama, Mariana. DivisiĂłn ArqueologĂa. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin
Tc-99m labelled bone scintigraphy in suspected cardiac amyloidosis
AIMS: To perform evaluation of widely embraced bone scintigraphy-based non-biopsy diagnostic criteria (NBDC) for ATTR amyloid cardiomyopathy (ATTR-CM) in clinical practice, and to refine serum free light chain (sFLC) ratio cut-offs that reliably exclude monoclonal gammopathy (MG) in chronic kidney disease. METHODS AND RESULTS: A multi-national retrospective study of 3354 patients with suspected or histologically proven cardiac amyloidosis (CA) referred to specialist centres from 2015 to 2021; evaluations included radionuclide bone scintigraphy, serum and urine immunofixation, sFLC assay, eGFR measurement and echocardiography. Seventy-nine percent (1636/2080) of patients with Perugini grade 2 or 3 radionuclide scans fulfilled NBDC for ATTR-CM through absence of a serum or urine monoclonal protein on immunofixation together with a sFLC ratio falling within revised cut-offs incorporating eGFR; 403 of these patients had amyloid on biopsy, all of which were ATTR type, and their survival was comparable to non-biopsied ATTR-CM patients (p = 0.10). Grade 0 radionuclide scans were present in 1091 patients, of whom 284 (26%) had CA, confirmed as AL type (AL-CA) in 276 (97%) and as ATTR-CM in only one case with an extremely rare TTR variant. Among 183 patients with grade 1 radionuclide scans, 122 had MG of whom 106 (87%) had AL-CA; 60/61 (98%) without MG had ATTR-CM. CONCLUSION: The NBDC for ATTR-CM are highly specific [97% (95% CI 0.91-0.99)] in clinical setting, and diagnostic performance was further refined here using new cut-offs for sFLC ratio in patients with CKD. A grade 0 radionuclide scan all but excludes ATTR-CM but occurs in most patients with AL-CA. Grade 1 scans in patients with CA and no MG are strongly suggestive of early ATTR-type, but require urgent histologic corroboration
How future surgery will benefit from SARS-COV-2-related measures: a SPIGC survey conveying the perspective of Italian surgeons
COVID-19 negatively affected surgical activity, but the potential benefits resulting from adopted measures remain unclear. The aim of this study was to evaluate the change in surgical activity and potential benefit from COVID-19 measures in perspective of Italian surgeons on behalf of SPIGC. A nationwide online survey on surgical practice before, during, and after COVID-19 pandemic was conducted in March-April 2022 (NCT:05323851). Effects of COVID-19 hospital-related measures on surgical patients' management and personal professional development across surgical specialties were explored. Data on demographics, pre-operative/peri-operative/post-operative management, and professional development were collected. Outcomes were matched with the corresponding volume. Four hundred and seventy-three respondents were included in final analysis across 14 surgical specialties. Since SARS-CoV-2 pandemic, application of telematic consultations (4.1% vs. 21.6%; pâ<â0.0001) and diagnostic evaluations (16.4% vs. 42.2%; pâ<â0.0001) increased. Elective surgical activities significantly reduced and surgeons opted more frequently for conservative management with a possible indication for elective (26.3% vs. 35.7%; pâ<â0.0001) or urgent (20.4% vs. 38.5%; pâ<â0.0001) surgery. All new COVID-related measures are perceived to be maintained in the future. Surgeons' personal education online increased from 12.6% (pre-COVID) to 86.6% (post-COVID; pâ<â0.0001). Online educational activities are considered a beneficial effect from COVID pandemic (56.4%). COVID-19 had a great impact on surgical specialties, with significant reduction of operation volume. However, some forced changes turned out to be benefits. Isolation measures pushed the use of telemedicine and telemetric devices for outpatient practice and favored communication for educational purposes and surgeon-patient/family communication. From the Italian surgeons' perspective, COVID-related measures will continue to influence future surgical clinical practice
Multidifferential study of identified charged hadron distributions in -tagged jets in proton-proton collisions at 13 TeV
Jet fragmentation functions are measured for the first time in proton-proton
collisions for charged pions, kaons, and protons within jets recoiling against
a boson. The charged-hadron distributions are studied longitudinally and
transversely to the jet direction for jets with transverse momentum 20 GeV and in the pseudorapidity range . The
data sample was collected with the LHCb experiment at a center-of-mass energy
of 13 TeV, corresponding to an integrated luminosity of 1.64 fb. Triple
differential distributions as a function of the hadron longitudinal momentum
fraction, hadron transverse momentum, and jet transverse momentum are also
measured for the first time. This helps constrain transverse-momentum-dependent
fragmentation functions. Differences in the shapes and magnitudes of the
measured distributions for the different hadron species provide insights into
the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb
public pages
Study of the decay
The decay is studied
in proton-proton collisions at a center-of-mass energy of TeV
using data corresponding to an integrated luminosity of 5
collected by the LHCb experiment. In the system, the
state observed at the BaBar and Belle experiments is
resolved into two narrower states, and ,
whose masses and widths are measured to be where the first uncertainties are statistical and the second
systematic. The results are consistent with a previous LHCb measurement using a
prompt sample. Evidence of a new
state is found with a local significance of , whose mass and width
are measured to be and , respectively. In addition, evidence of a new decay mode
is found with a significance of
. The relative branching fraction of with respect to the
decay is measured to be , where the first
uncertainty is statistical, the second systematic and the third originates from
the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb
public pages
Observation of the doubly charmed baryon decay Îcc++âÎcâČ+Ï+
The Îcc++âÎcâČ+Ï+ decay is observed using proton-proton collisions collected by the LHCb experiment at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5.4 fbâ1. The Îcc++âÎcâČ+Ï+ decay is reconstructed partially, where the photon from the ÎcâČ+âÎc+Îł decay is not reconstructed and the pKâÏ+ final state of the Îc+ baryon is employed. The Îcc++âÎcâČ+Ï+branching fraction relative to that of the Îcc++âÎc+Ï+ decay is measured to be 1.41 ± 0.17 ± 0.10, where the first uncertainty is statistical and the second systematic. [Figure not available: see fulltext.
Test of lepton universality in decays
The first simultaneous test of muon-electron universality using
and decays is performed, in two ranges of the dilepton
invariant-mass squared, . The analysis uses beauty mesons produced in
proton-proton collisions collected with the LHCb detector between 2011 and
2018, corresponding to an integrated luminosity of 9 . Each
of the four lepton universality measurements reported is either the first in
the given interval or supersedes previous LHCb measurements. The
results are compatible with the predictions of the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-046.html (LHCb
public pages
Study of charmonium and charmonium-like contributions in B+ â J/ÏηK+ decays
A study of B+â J/ÏηK+ decays, followed by J/Ï â ÎŒ+ÎŒâ and η â γγ, is performed using a dataset collected with the LHCb detector in proton-proton collisions at centre-of-mass energies of 7, 8 and 13 TeV, corresponding to an integrated luminosity of 9 fbâ1. The J/Ïη mass spectrum is investigated for contributions from charmonia and charmonium-like states. Evidence is found for the B+â (Ï2(3823) â J/Ïη)K+ and B+â (Ï(4040) â J/Ïη)K+ decays with significance of 3.4 and 4.7 standard deviations, respectively. This constitutes the first evidence for the Ï2(3823) â J/Ïη decay
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