54 research outputs found
Successful conversion strategy in patient submitted to EVAR demanding open surgery: comparative analysis 1997-2011 vs 2012-2020
: Late open conversion in our center has been reviewed in the past 8 years, comparing 1997-2011 (first period group A) with 2012-2020 (second period group B). A retrospective analysis of patients treated at our centre by standard EVAR for infrarenal aortic aneurysm requiring late open conversion between January 1997 and February 2020 was performed. All stent grafts were implanted according to their current IFU all patients. The data concerning intra and postoperative complications were collected. Post-operative evaluated data include: ICU (Intensive Care Unit) stay, major peri-operative (<30 days) complications, in hospital mortality, length of hospital stay, 30-days mortality, and mid-term outcomes. Between January 2012 and February 2020 (group B), in our institution 8 patients previously treated by stent graft with endoleak underwent open surgery. The incidence of conversions and the 30-day mortality rate were compared with that of previous years, from January 1997 to December 2011 (group A). 481 patients submitted to EVAR in a second part of the analysis have been considered, 8 patients underwent late open conversion (1.7%) (Group B) due to endoleak. Among January 1997 and December 2011 overall 268 EVAR were performed; during this first study period, surgical conversion had been performed in 14 patients (5.2%) (Group A). The average time from EVAR to open conversion was four years (range 12-88 months) in Group B, and it was 30 months (range 1-82 months) in Group A. In most cases, in both group A and group B the proximal aortic cross-clamping were infrarenal. After the emergent procedure in Group B (12.5%), we have observed a death, whereas three patients died in Group A in urgent situations (21.4%). The more frequent indication for open surgery is the Endoleak type 1 and migration in the two considered periods. Adherence with current IFU and the technical progress in endoprosthesis design maintain lower rate incidence. In most cases, open surgery for prostheses that require explantation can be performed with infrarenal clamping. Partial removal of the endoprosthesis in selected cases makes open conversion easier and appears durable. The results are unfair by numerous comorbidities; in both periods, urgent graft removal seems to elevate both mortality and morbidity, compared to elective surgery
A combined analysis technique for the search for fast magnetic monopoles with the MACRO detector
We describe a search method for fast moving ()
magnetic monopoles using simultaneously the scintillator, streamer tube and
track-etch subdetectors of the MACRO apparatus. The first two subdetectors are
used primarily for the identification of candidates while the track-etch one is
used as the final tool for their rejection or confirmation. Using this
technique, a first sample of more than two years of data has been analyzed
without any evidence of a magnetic monopole. We set a 90% CL upper limit to the
local monopole flux of in the
velocity range and for nucleon decay
catalysis cross section smaller than .Comment: 29 pages (12 figures). Accepted by Astroparticle Physic
Final results of magnetic monopole searches with the MACRO experiment
We present the final results obtained by the MACRO experiment in the search
for GUT magnetic monopoles in the penetrating cosmic radiation, for the range
. Several searches with all the MACRO sub-detectors
(i.e. scintillation counters, limited streamer tubes and nuclear track
detectors) were performed, both in stand alone and combined ways. No candidates
were detected and a 90% Confidence Level (C.L.) upper limit to the local
magnetic monopole flux was set at the level of cm
s sr. This result is the first experimental limit obtained in
direct searches which is well below the Parker bound in the whole range
in which GUT magnetic monopoles are expected.Comment: 12 pages, Latex, 9 figures and 2 Table
Measurement of the residual energy of muons in the Gran Sasso underground Laboratories
The MACRO detector was located in the Hall B of the Gran Sasso underground
Laboratories under an average rock overburden of 3700 hg/cm^2. A transition
radiation detector composed of three identical modules, covering a total
horizontal area of 36 m^2, was installed inside the empty upper part of the
detector in order to measure the residual energy of muons. This paper presents
the measurement of the residual energy of single and double muons crossing the
apparatus. Our data show that double muons are more energetic than single ones.
This measurement is performed over a standard rock depth range from 3000 to
6500 hg/cm^2.Comment: 28 pages, 9 figure
Search for Nucleon Decays induced by GUT Magnetic Monopoles with the MACRO Experiment
The interaction of a Grand Unification Magnetic Monopole with a nucleon can
lead to a barion-number violating process in which the nucleon decays into a
lepton and one or more mesons (catalysis of nucleon decay). In this paper we
report an experimental study of the effects of a catalysis process in the MACRO
detector. Using a dedicated analysis we obtain new magnetic monopole (MM) flux
upper limits at the level of for
, based on the search for
catalysis events in the MACRO data. We also analyze the dependence of the MM
flux limit on the catalysis cross section.Comment: 12 pages, Latex, 10 figures and 2 Table
Muon Energy Estimate Through Multiple Scattering with the Macro Detector
Muon energy measurement represents an important issue for any experiment
addressing neutrino induced upgoing muon studies. Since the neutrino
oscillation probability depends on the neutrino energy, a measurement of the
muon energy adds an important piece of information concerning the neutrino
system. We show in this paper how the MACRO limited streamer tube system can be
operated in drift mode by using the TDC's included in the QTPs, an electronics
designed for magnetic monopole search. An improvement of the space resolution
is obtained, through an analysis of the multiple scattering of muon tracks as
they pass through our detector. This information can be used further to obtain
an estimate of the energy of muons crossing the detector. Here we present the
results of two dedicated tests, performed at CERN PS-T9 and SPS-X7 beam lines,
to provide a full check of the electronics and to exploit the feasibility of
such a multiple scattering analysis. We show that by using a neural network
approach, we are able to reconstruct the muon energy for 40 GeV. The
test beam data provide an absolute energy calibration, which allows us to apply
this method to MACRO data.Comment: 25 pages, 11 figures, Submitted to Nucl. Instr. & Meth.
Search for diffuse neutrino flux from astrophysical sources with MACRO
Many galactic and extragalactic astrophysical sources are currently
considered promising candidates as high energy neutrino emitters. Astrophysical
neutrinos can be detected as upward-going muons produced in charged-current
interactions with the medium surrounding the detector. The expected neutrino
fluxes from various models start to dominate on the atmospheric neutrino
background at neutrino energies above some tens of TeV. We present the results
of a search for an excess of high energy upward-going muons among the sample of
data collected by MACRO during ~5.8 years of effective running time. No
significant evidence for this signal was found. As a consequence, an upper
limit on the flux of upward-going muons from high-energy neutrinos was set at
the level of 1.7 10^(-14) cm^(-2) s^(-1) sr^(-1).
The corresponding upper limit for the diffuse neutrino flux was evaluated
assuming a neutrino power law spectrum. Our result was compared with
theoretical predictions and upper limits from other experiments.Comment: 19 pages, 8 figures, 2 table
The primary cosmic ray composition between 10**15 and 10**16 eV from Extensive Air Showers electromagnetic and TeV muon data
The cosmic ray primary composition in the energy range between 10**15 and
10**16 eV, i.e., around the "knee" of the primary spectrum, has been studied
through the combined measurements of the EAS-TOP air shower array (2005 m
a.s.l., 10**5 m**2 collecting area) and the MACRO underground detector (963 m
a.s.l., 3100 m w.e. of minimum rock overburden, 920 m**2 effective area) at the
National Gran Sasso Laboratories. The used observables are the air shower size
(Ne) measured by EAS-TOP and the muon number (Nmu) recorded by MACRO. The two
detectors are separated on average by 1200 m of rock, and located at a
respective zenith angle of about 30 degrees. The energy threshold at the
surface for muons reaching the MACRO depth is approximately 1.3 TeV. Such muons
are produced in the early stages of the shower development and in a kinematic
region quite different from the one relevant for the usual Nmu-Ne studies. The
measurement leads to a primary composition becoming heavier at the knee of the
primary spectrum, the knee itself resulting from the steepening of the spectrum
of a primary light component (p, He). The result confirms the ones reported
from the observation of the low energy muons at the surface (typically in the
GeV energy range), showing that the conclusions do not depend on the production
region kinematics. Thus, the hadronic interaction model used (CORSIKA/QGSJET)
provides consistent composition results from data related to secondaries
produced in a rapidity region exceeding the central one. Such an evolution of
the composition in the knee region supports the "standard" galactic
acceleration/propagation models that imply rigidity dependent breaks of the
different components, and therefore breaks occurring at lower energies in the
spectra of the light nuclei.Comment: Submitted to Astroparticle Physic
Wavelength-shifting fibers for calorimetric measurements in a long base line neutrino oscillation experiment
Abstract The NOE Collaboration has proposed a calorimeter to measure the energy of the final states of ν interaction events. The properties of long scintillator bars with wavelength-shifting fiber readout have been studied to develop a calorimeter design option. Various prototypes have been exposed to a cosmic rays stand. The total measured light yield in the middle of a 6 m -long fiber is about 15 photoelectrons. With this photon collection performance, it has been simulated that the calorimeter can achieve 17%/ E and 50%/ E resolutions for electrons and pions, respectively
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