2,745 research outputs found
Detection of GRB signals with Fluorescence Detectors
Gamma Ray Bursts are being searched in many ground based experiments
detecting the high energy component (GeV TeV energy range) of the photon
bursts. In this paper, Fluorescence Detectors are considered as possible
candidate devices for these searches. It is shown that the GRB photons induce
fluorescence emission of UV photons on a wide range of their spectrum. The
induced fluorescence flux is dominated by GRB photons from 0.1 to about 100 MeV
and, once the extinction through the atmosphere is taken into account, it is
distributed over a wide angular region. This flux can be detected through a
monitor of the diffuse photon flux, provided that its maximum value exceeds a
threshold value, that is primarily determined by the sky brightness above the
detector. The feasibility of this search and the expected rates are discussed
on the basis of the current GRB observations and the existing fluorescence
detectors.Comment: 16 pages 9 eps figure
Bonnard´s representation of the perception of substance
Artists are said to be like neuroscientists able to exploit the capacities of the brain to generate aesthetic experience (Zeki, 2001). Pierre Bonnard (1867-1947) has been recognized as one of the greatest and most enigmatic masters of the 20th century painting. For his understanding of the eye movements, attentional shifts mechanism and the representation in his paintings of the complexity of the physiological process of vision perception, something that he famously referred to as "the transcription of the adventures of the optic nerve", he is considered a revolutionary painter. Our recent eye movements study on Bonnard's paintings evidences a "temporal-extended" mechanism in the control of scanpaths that refers to a progression of the scanpath pattern during repetitive viewings and supports the phenomenon of late emotional response which was one of the artist's artistic and perceptual objective
Magnetism and domain formation in SU(3)-symmetric multi-species Fermi mixtures
We study the phase diagram of an SU(3)-symmetric mixture of three-component
ultracold fermions with attractive interactions in an optical lattice,
including the additional effect on the mixture of an effective three-body
constraint induced by three-body losses. We address the properties of the
system in by using dynamical mean-field theory and variational Monte
Carlo techniques. The phase diagram of the model shows a strong interplay
between magnetism and superfluidity. In the absence of the three-body
constraint (no losses), the system undergoes a phase transition from a color
superfluid phase to a trionic phase, which shows additional particle density
modulations at half-filling. Away from the particle-hole symmetric point the
color superfluid phase is always spontaneously magnetized, leading to the
formation of different color superfluid domains in systems where the total
number of particles of each species is conserved. This can be seen as the SU(3)
symmetric realization of a more general tendency to phase-separation in
three-component Fermi mixtures. The three-body constraint strongly disfavors
the trionic phase, stabilizing a (fully magnetized) color superfluid also at
strong coupling. With increasing temperature we observe a transition to a
non-magnetized SU(3) Fermi liquid phase.Comment: 36 pages, 17 figures; Corrected typo
Sniff test: does what we measure at the nose reflect what happens in the chest wall?
Nasal pressure measured during sniff (SNIP) is a technically simple voluntary test. Since the contraction of the diaphragm expands the abdomen, the volume variation during sniff manoeuvre should therefore be predominantly abdominal in order to be considered a specific index of diaphragm strength. We aimed to verify if and how SNIP varied according to thoraco-abdominal volume variations. We measured abdominal volume variations, using opto-electronic plethysmography, during quiet breathing (ABQB) and sniff manoeuvres (ABSN) in supine position on 30 patients (age: 42; FVC:47.5%; FEV1:30%) on the waiting list for lung transplant. SNIP was measured simultaneously with ABSN. 68 sniff were analysed and classified into 4 groups according to ABSN: 16 with thoracic paradox, 24 predominantly abdominal, 16 predominantly thoracic and 12 with abdominal paradox. By definition ABSN was different (p<0.001) among the 4 groups, whereas ABQB (~75%; p=0.373) and SNIP (~53 cmH2O, p= 0.792) were similar (figure 1). SNIP did not change with the different thoraco-abdominal strategies. The diaphragm was not weak and leaded inspiration, therefore ABSN varied because the patients misperformed the manoeuvre. In order to not misunderstand the clinical significance of a sniff test, care should be paid also in thoraco-abdominal movement because SNIP, per se, cannot differentiate between thoracic or diaphragmatic manoeuvre with the risk to lose its specificity
Limitations on the principle of stationary phase when it is applied to tunneling analysis
Using a recently developed procedure - multiple wave packet decomposition -
here we study the phase time formulation for tunneling/reflecting particles
colliding with a potential barrier. To partially overcome the analytical
difficulties which frequently arise when the stationary phase method is
employed for deriving phase (tunneling) time expressions, we present a
theoretical exercise involving a symmetrical collision between two identical
wave packets and an one-dimensional rectangular potential barrier. Summing the
amplitudes of the reflected and transmitted waves - using a method we call
multiple peak decomposition - is shown to allow reconstruction of the scattered
wave packets in a way which allows the stationary phase principle to be
recovered.Comment: 17 pages, 2 figure
COVID-19 outbreak response, a dataset to assess mobility changes in Italy following national lockdown
Strain development and damage accumulation under ion irradiation of polycrystalline Ge-Sb-Te alloys
The atomic displacement produced by ion irradiation with 150 keV Ar+ ions has been studied in Ge1Sb2Te4 and Ge2Sb2Te5. Electrical, optical and structural measurements have been employed to characterize the induced electrical and structural modifications. At low temperature the amorphization threshold, evaluated by in situ reflectivity measurements, is independent of the composition and the crystalline structure, and it is equal to 1 x 1013 cm-2. At room temperature, at which dynamic annealing can take place, Ge2Sb2Te5 and Ge1Sb2Te4 in the rocksalt phase exhibit the same amorphization threshold (3 x 1013 cm-2). In the trigonal structure, instead, a higher fluence is required to amorphize the Ge1Sb2Te4, compared to Ge2Sb2Te5. The observed differences between the two compositions can be explained considering the effect of dynamic annealing during ion irradiation of the trigonal phase, which is characterized by the presence of van der Waals gaps. These may act as a preferential sink for the diffusion of the displaced atoms and the filling of these gaps tunes the electronic and structural properties. Filling of about 30% of the gaps produces an electronic transition from metallic to insulating behavior. By further increasing the disorder and filling more than 70% of the gaps the films convert into the rocksalt phase
Optical Relative Calibration and Stability Monitoring for the Auger Fluorescence Detector
The stability of the fluorescence telescopes of the Pierre Auger Observatory
is monitored with the optical relative calibration setup. Optical fibers
distribute light pulses to three different diffuser groups within the optical
system. The total charge per pulse is measured for each pixel and compared with
reference calibration measurements. This allows monitoring the short and long
term stability with respect of the relative timing between pixels and the
relative gain for each pixel. The designs of the LED calibration unit (LCU) and
of the Xenon flash lamp used for relative calibration, are described and their
capabilities to monitor the stability of the telescope performances are
studied. We report the analysis of relative calibration data recorded during
2004. Fluctuations in the relative calibration constants provide a measure of
the stability of the FD.Comment: 4 pp. To appear in the proceedings of 29th International Cosmic Ray
Conference (ICRC 2005), Pune, India, 3-11 Aug 200
Crystallization properties of melt-quenched Ge-rich GeSbTe thin films for phase change memory applications
The crystallization process of melt quenched Ge-rich GeSbTe films, with composition optimized for memory applications, has been studied by optical reflectance measurements. The optical properties have been related to the structure and composition by means of the effective medium approximation. The compositional variations have been investigated by transmission electron microscopy and electron energy loss spectroscopy. Amorphous materials prepared by melt-quenching with different laser energy densities have been studied. For the energy density of 1.5 J cm−2, a uniform amorphous layer, with embedded Ge crystalline grains, is obtained. The film exhibits a crystallization temperature of 275 °C and no relevant phase separation during crystallization. For a lower energy density of 1 J cm−2, only half of the film thickness is quenched to the amorphous phase, with Ge depletion. The crystallization temperature of the Ge depleted film is 245 °C, and a partial phase separation occurs
Perineural invasion in vulvar squamous-cell carcinoma is an independent risk factor for cancer-specific survival, but not for locoregional recurrence: results from a single tertiary referral center
SIMPLE SUMMARY: Vulvar squamous cell carcinoma is a rare tumor but represents a serious health issue, especially due to the increasing incidence over the past decades. Many efforts have been made to identify new prognostic and therapeutic factors and, in this context, growing evidence concerning a pivotal role of perineural invasion. With this study, we investigated the role of perineural invasion in a large cohort of FIGO stage Ib-IIIc vulvar squamous cell carcinomas and found that perineural invasion-positive tumors have more aggressive biological behaviors and showed reduced cancer-specific survival as compared to perineural invasion-negative tumors, while this feature does not appear to be related to a greater risk to develop loco-regional recurrence. Further evaluations are warranted to confirm the prognostic role of perineural invasion and its potential use to tailor adjuvant treatment. ABSTRACT: The aims of this study were to assess the prevalence of perineural invasion (PNI) in vulvar squamous cell carcinoma (VSCC) and its prognostic role in locoregional recurrence (LRR) and cancer-specific survival (CSS). We performed a retrospective analysis of 223 consecutive stage IB–IIIC surgically treated VSCCs at S. Anna Hospital, University of Turin, from 2000 to 2019. We identified 133/223 (59.6%) patients with PNI-positive VSCCs. PNI was associated with aggressive biological features (i.e., advanced FIGO stage, larger tumor diameter, greater depth of invasion, a higher number of metastatic lymph nodes, and lymphovascular invasion) and shorter 5-year CSS (78% vs. 90%, log-rank p = 0.02) compared with PNI-negative VSCCs. Multivariate analysis showed that PNI (HR 2.99 CI 95% 1.17–7.63; p = 0.02) and the presence of tumor cells on pathological surgical margins (HR 3.13 CI 95% 1.37–7.13; p = 0.007) are independent prognostic factors for CSS. PNI does not appear to be related to LRR, but is an independent prognostic factor for worse survival outcomes. Future studies are necessary to explore the possible value of PNI in tailoring the choice of adjuvant treatment
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