123 research outputs found
Il trattamento chirurgico dei tumori maligni del labbro. Esperienza personale
I tumori maligni del labbro rappresentano circa l’1-2% delle
neoplasie cervico-facciali. Tali lesioni sono più frequentemente costi -
tuite da carcinomi spinocellulari e basocellulari che nel complesso
rappresentano il 25% di tutti i tumori orali. Mentre il carcinoma
spinocellulare si localizza soprattutto sul labbro inferiore, il carcino -
ma basocellulare si riscontra maggiormente sul labbro superiore .Il
sesso maschile risulta essere sensibilmente il più colpito. L’etiopatoge -
nesi di queste neoplasie è legata all’esposizione solare, al fumo, alla
predisposizione genetica (mutazione del gene soppressore p53), all’e -
voluzione di forme di precancerosi, quali radiodermiti, cheiliti croni -
che, xeroderma pigmentosum. Inoltre, alcuni Autori enfatizzano il
ruolo svolto da diversi agenti virali quali HPV16, HPV24, HSV1 e
HSV2. Il trattamento dei carcinomi del labbro è prevalentemente
chirurgico ed è fondamentalmente rappresentato dall’escissione della
lesione e successiva ricostruzione del labbro. Le tecniche riparative
sono numerose e per la maggior parte basate sull’utilizzo di lembi
cutanei locali di scorrimento e di rotazione. La ricostruzione del lab -
bro comporta un notevole impegno al fine di preservare quanto più
possibile forma e funzioni essendo il labbro fondamentale nell’ali -
mentazione, nella fonazione e nella mimica espressiva.
Gli Autori riportano la loro esperienza riguardo il trattamento chi -
rurgico di 19 pazienti, 17 di sesso maschile, di età compresa tra 58 e
84 anni (età media 72 anni), affetti da carcinoma del labbro (16 spi -
nocellulari, 3 basocellulari) con prevalenza di forme ben differenziate.
Vengono inoltre discusse le principali problematiche ricostruttive ine -
renti la preservazione degli aspetti estetici e funzionali delle labbra
Technical note: Rapid image-based field methods improve the quantification of termite mound structures and greenhouse-gas fluxes
Termite mounds (TMs) mediate biogeochemical processes with global relevance,
such as turnover of the important greenhouse gas methane (CH4).
However, the complex internal and external morphology of TMs impede an
accurate quantitative description. Here we present two novel field methods,
photogrammetry (PG) and cross-sectional image analysis, to
quantify TM external and internal mound structure of 29 TMs of three termite
species. Photogrammetry was used to measure epigeal volume (VE),
surface area (AE) and mound basal area (AB) by
reconstructing 3-D models from digital photographs, and compared against a
water-displacement method and the conventional approach of approximating TMs
by simple geometric shapes. To describe TM internal structure, we introduce
TM macro- and micro-porosity (θM and θμ), the
volume fractions of macroscopic chambers, and microscopic pores in the wall
material, respectively. Macro-porosity was estimated using image analysis of
single TM cross sections, and compared against full X-ray computer tomography
(CT) scans of 17 TMs. For these TMs we present complete pore fractions to
assess species-specific differences in internal structure. The PG method
yielded VE nearly identical to a water-displacement method, while
approximation of TMs by simple geometric shapes led to errors of
4–200 %. Likewise, using PG substantially improved the accuracy of
CH4 emission estimates by 10–50 %. Comprehensive CT scanning
revealed that investigated TMs have species-specific ranges of
θM and θμ, but similar total porosity. Image
analysis of single TM cross sections produced good estimates of
θM for species with thick walls and evenly distributed
chambers. The new image-based methods allow rapid and accurate quantitative
characterisation of TMs to answer ecological, physiological and
biogeochemical questions. The PG method should be applied when measuring
greenhouse-gas emissions from TMs to avoid large errors from inadequate shape
approximations
Single-hit resolution measurement with MEG II drift chamber prototypes
Drift chambers operated with helium-based gas mixtures represent a common
solution for tracking charged particles keeping the material budget in the
sensitive volume to a minimum. The drawback of this solution is the worsening
of the spatial resolution due to primary ionisation fluctuations, which is a
limiting factor for high granularity drift chambers like the MEG II tracker. We
report on the measurements performed on three different prototypes of the MEG
II drift chamber aimed at determining the achievable single-hit resolution. The
prototypes were operated with helium/isobutane gas mixtures and exposed to
cosmic rays, electron beams and radioactive sources. Direct measurements of the
single hit resolution performed with an external tracker returned a value of
110 m, consistent with the values obtained with indirect measurements
performed with the other prototypes.Comment: 18 pages, 18 figure
Measurement of the radiative decay of polarized muons in the MEG experiment
We studied the radiative muon decay by
using for the first time an almost fully polarized muon source. We identified a
large sample (~13000) of these decays in a total sample of 1.8x10^14 positive
muon decays collected in the MEG experiment in the years 2009--2010 and
measured the branching ratio B() =
(6.03+-0.14(stat.)+-0.53(sys.))x10^-8 for E_e > 45 MeV and E_{\gamma} > 40 MeV,
consistent with the Standard Model prediction. The precise measurement of this
decay mode provides a basic tool for the timing calibration, a normalization
channel, and a strong quality check of the complete MEG experiment in the
search for process.Comment: 8 pages, 7 figures. Added an introduction to NLO calculation which
was recently calculated. Published versio
Gas Distribution and Monitoring for the Drift Chamber of the MEG-II Experiment
The reconstruction of the positron trajectory in the MEG-II experiment
searching for the decay uses a cylindrical drift chamber
operated with a helium-isobutane gas mixture. A stable performance of the
detector in terms of its electron drift properties, avalanche multiplication,
and with a gas mixture of controlled composition and purity has to be provided
and continuously monitored. In this paper we describe the strategies adopted to
meet the requirements imposed by the target sensitivity of MEG-II, including
the construction and commissioning of a small chamber for an online monitoring
of the gas quality.Comment: 12 pages, 6 figures, submitted to Journal of Instrumentatio
The measuring systems of the wire tension for the MEG II Drift Chamber by means of the resonant frequency technique
The ultra-low mass Cylindrical Drift Chamber designed for the MEG experiment
upgrade is a challenging apparatus made of 1728 phi = 20 micron gold plated
tungsten sense wires, 7680 phi = 40 micron and 2496 phi = 50 micron silver
plated aluminum field wires. Because of electrostatic stability requirements
all the wires have to be stretched at mechanical tensions of about 25, 19 and
29 g respectively which must be controlled at a level better than 0.5 g. This
chamber is presently in acquisition, but during its construction about 100
field wires broke, because of chemical corrosion induced by the atmospheric
humidity. On the basis of the experience gained with this chamber we decided to
build a new one, equipped with a different type of wires less sensitive to
corrosion. The choice of the new wire required a deep inspection of its
characteristics and one of the main tools for doing this is a system for
measuring the wire tension by means of the resonant frequency technique, which
is described in this paper. The system forces the wires to oscillate by
applying a sinusoidal signal at a known frequency, and then measures the
variation of the capacitance between a wire and a common ground plane as a
function of the external signal frequency. We present the details of the
measuring system and the results obtained by scanning the mechanical tensions
of two samples of MEG II CDCH wires and discuss the possible improvements of
the experimental apparatus and of the measuring technique.Comment: Ten pages, twelve figures, to be submitted to Nuclear Instruments and
Methods
Muon polarization in the MEG experiment: Predictions and measurements
The MEG experiment makes use of one of the world’s most intense low energy muon beams, in order to search for the lepton flavour violating process μ+ → e+ γ. We determined the residual beam polarization at the thin stopping target, by measuring the asymmetry of the angular distribution of Michel decay positrons as a function of energy. The initial muon beam polarization at the production is predicted to be Pμ = −1 by the StandardModel (SM) with massless neutrinos. We estimated our residual muon polarization to be (formula presented) at the stopping target, which is consistent with the SM predictions when the depolarizing effects occurring during the muon production, propagation and moderation in the target are taken into account. The knowledge of beam polarization is of fundamental importance in order to model the background of our μ+ → e+ γ search induced by themuon radiative decay: (formula presented)
Measurement of the radiative decay of polarized muons in the MEG experiment
We studied the radiative muon decay (Formula presented.) by using for the first time an almost fully polarized muon source. We identified a large sample ((Formula presented.) 13,000) of these decays in a total sample of (Formula presented.) positive muon decays collected in the MEG experiment in the years 2009–2010 and measured the branching ratio (Formula presented.) for (Formula presented.) and (Formula presented.) , consistent with the Standard Model prediction. The precise measurement of this decay mode provides a basic tool for the timing calibration, a normalization channel, and a strong quality check of the complete MEG experiment in the search for (Formula presented.) process
Search for the lepton flavour violating decay μ+→ e +γ with the full dataset of the MEG experiment: MEG Collaboration
The final results of the search for the lepton flavour violating decay μ+→ e +γ based on the full dataset collected by the MEG experiment at the Paul Scherrer Institut in the period 2009–2013 and totalling 7.5 × 10 14 stopped muons on target are presented. No significant excess of events is observed in the dataset with respect to the expected background and a new upper limit on the branching ratio of this decay of B(μ+→ e +γ) < 4.2 × 10 - 13 (90 % confidence level) is established, which represents the most stringent limit on the existence of this decay to date
Search for the lepton flavour violating decay μ+→ e +γ with the full dataset of the MEG experiment: MEG Collaboration
none84siThe final results of the search for the lepton flavour violating decay mu(+) -> e(+)gamma based on the full dataset collected by the MEG experiment at the Paul Scherrer Institut in the period 2009-2013 and totalling 7.5x10(14) stopped muons on target are presented. Nosignificant excess of events is observed in the dataset with respect to the expected background and a new upper limit on the branching ratio of this decay of B(mu(+) -> e(+) gamma) < 4.2 x 10(-13) (90 % confidence level) is established, which represents the most stringent limit on the existence of this decay to date.Baldini, A.M.; Bao, Y.; Baracchini, E.; Bemporad, C.; Berg, F.; Biasotti, M.; Boca, G.; Cascella, M.; Cattaneo, P.W.; Cavoto, G.; Cei, F.; Cerri, C.; Chiarello, G.; Chiri, C.; Corvaglia, A.; de Bari, A.; De Gerone, M.; Doke, T.; D’Onofrio, A.; Dussoni, S.; Egger, J.; Fujii, Y.; Galli, L.; Gatti, F.; Grancagnolo, F.; Grassi, M.; Graziosi, A.; Grigoriev, D.N.; Haruyama, T.; Hildebrandt, M.; Hodge, Z.; Ieki, K.; Ignatov, F.; Iwamoto, T.; Kaneko, D.; Kang, T.I.; Kettle, P.-R.; Khazin, B.I.; Khomutov, N.; Korenchenko, A.; Kravchuk, N.; Lim, G.M.A.; Maki, A.; Mihara, S.; Molzon, W.; Mori, Toshinori; Morsani, F.; Mtchedilishvili, A.; Mzavia, D.; Nakaura, S.; Nardò, R.; Nicolò, D.; Nishiguchi, H.; Nishimura, M.; Ogawa, S.; Ootani, W.; Orito, S.; Panareo, M.; Papa, A.; Pazzi, R.; Pepino, A.; Piredda, G.; Pizzigoni, G.; Popov, A.; Raffaelli, F.; Renga, F.; Ripiccini, E.; Ritt, S.; Rossella, M.; Rutar, G.; Sawada, R.; Sergiampietri, F.; Signorelli, G.; Simonetta, M.; Tassielli, G.F.; Tenchini, F.; Uchiyama, Y.; Venturini, M.; Voena, C.; Yamamoto, A.; Yoshida, K.; You, Z.; Yudin, Yu. V.; Zanello, D.Baldini, A. M.; Bao, Y.; Baracchini, E.; Bemporad, C.; Berg, F.; Biasotti, M.; Boca, Gianluigi; Cascella, M.; Cattaneo, P. W.; Cavoto, G.; Cei, F.; Cerri, C.; Chiarello, G.; Chiri, C.; Corvaglia, A.; DE BARI, Antonio; De Gerone, M.; Doke, T.; D’Onofrio, A.; Dussoni, S.; Egger, J.; Fujii, Y.; Galli, L.; Gatti, F.; Grancagnolo, F.; Grassi, M.; Graziosi, A.; Grigoriev, D. N.; Haruyama, T.; Hildebrandt, M.; Hodge, Z.; Ieki, K.; Ignatov, F.; Iwamoto, T.; Kaneko, D.; Kang, T. I.; Kettle, P. R.; Khazin, B. I.; Khomutov, N.; Korenchenko, A.; Kravchuk, N.; Lim, G. M. A.; Maki, A.; Mihara, S.; Molzon, W.; Mori, Toshinori; Morsani, F.; Mtchedilishvili, A.; Mzavia, D.; Nakaura, S.; Nardo', Roberto; Nicolò, D.; Nishiguchi, H.; Nishimura, M.; Ogawa, S.; Ootani, W.; Orito, S.; Panareo, M.; Papa, A.; Pazzi, R.; Pepino, A.; Piredda, G.; Pizzigoni, G.; Popov, A.; Raffaelli, F.; Renga, F.; Ripiccini, E.; Ritt, S.; Rossella, M.; Rutar, G.; Sawada, R.; Sergiampietri, F.; Signorelli, G.; Simonetta, M.; Tassielli, G. F.; Tenchini, F.; Uchiyama, Y.; Venturini, M.; Voena, C.; Yamamoto, A.; Yoshida, K.; You, Z.; Yudin, Y. u. V.; Zanello, D
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