ABSTRACT
Type Ia Supernovae (SNe Ia) are widely used to measure distances in the Universe. Despite the recent progress achieved in SN Ia standardization, the Hubble diagram still shows some remaining ...intrinsic dispersion. The remaining scatter in supernova luminosity could be due to the environmental effects that are accounted for as mass step correction in the current cosmological analyses. In this work, we compare the local and global colour (U − V), the local star formation rate, and the host stellar mass to the host galaxy morphology. The observed trends suggest that the host galaxy morphology is a relevant parameter to characterize the SN Ia environment. Therefore, we study the influence of host galaxy morphology on light-curve parameters of SNe Ia from the pantheon cosmological supernova sample. We determine the Hubble morphological type of host galaxies for a subsample of 330 SNe Ia. We confirm that the salt2 stretch parameter x1 depends on the host morphology with the p-value ∼10−14. The supernovae with lower stretch value are hosted mainly by elliptical and lenticular galaxies. No correlation for the salt2 colour parameter c is found. We also examine Hubble diagram residuals for supernovae hosted by ‘early-type’ and ‘late-type’ morphological groups of galaxies. The analysis reveals that the mean distance modulus residual in early-type galaxies is smaller than the one in late-type galaxies, which means that early-type galaxies contain brighter supernovae after stretch and colour corrections. However, we do not observe any difference in the residual dispersion for these two morphological groups. The obtained results are in the line with other analyses showing environmental dependence of SN Ia light-curve parameters and luminosity. We confirm the importance of including a host galaxy parameter into the standardization procedure of SNe Ia for further cosmological studies.
Among the other types of supernovae, Type Ia Supernovae (SNe Ia) have less luminosity dispersion at maximum light and show higher optical luminosities. These properties allow to use them as ...cosmological distance indicators that led to the discovery of the accelerating expansion of the Universe. However, even after the luminosity correction for stretch and color parameters—“standardization”, there is a remaining dispersion on the Hubble diagram of ~0.11 mag. This dispersion can be due to SN environmental effects—progenitor age, chemical composition, surrounding dust. In this work we study the impact of SN galactocentric distance (376 Pantheon SNe Ia) and host-galaxy morphology (275 Pantheon SNe Ia) on the light curve parameters. We confirm that the stretch-parameter depends on galactocentric distance and host morphology, but there is no significant correlation for the color. In the epoch of large transient surveys such as the Vera Rubin Observatory’s Legacy Survey of Space and Time, a study of environment and other possible sources of systematical uncertainties in the cosmological analysis is of high priority.
In this paper, the current status of cardiac image registration methods is reviewed. The combination of information from multiple cardiac image modalities, such as magnetic resonance imaging, ...computed tomography, positron emission tomography, single-photon emission computed tomography, and ultrasound, is of increasing interest in the medical community for physiologic understanding and diagnostic purposes. Registration of cardiac images is a more complex problem than brain image registration because the heart is a nonrigid moving organ inside a moving body. Moreover, as compared to the registration of brain images, the heart exhibits much fewer accurate anatomical landmarks. In a clinical context, physicians often mentally integrate image information from different modalities. Automatic registration, based on computer programs, might, however, offer better accuracy and repeatability and save time.
Light and heavy ions particle therapy, mainly by means of protons and carbon ions, represents an advantageous treatment modality for deep-seated and/or radioresistant tumours. An in-beam quality ...assurance principle is based on the detection of secondary particles induced by nuclear fragmentations between projectile and target nuclei. Three different strategies are currently under investigation: prompt γ rays imaging, proton interaction vertex imaging and in-beam positron emission tomography. Geant4 simulations have been performed first in order to assess the accuracy of some hadronic models to reproduce experimental data. Two different kinds of data have been considered: β+-emitting isotopes and prompt γ-ray production rates. On the one hand simulations reproduce experimental β+ emitting isotopes production rates to an accuracy of 24%. Moreover simulated β+ emitting nuclei production rate as a function of depth reproduce well the peak-to-plateau ratio of experimental data. On the other hand by tuning the tolerance factor of the photon evaporation model available in Geant4, we reduce significantly prompt γ-ray production rates until a very good agreement is reached with experimental data. Then we have estimated the total amount of induced annihilation photons and prompt γ rays for a simple treatment plan of ∼1 physical Gy in a homogenous equivalent soft tissue tumour (6 cm depth, 4 cm radius and 2 cm wide). The average annihilation photons emitted during a 45 s irradiation in a 4 π solid angle are ∼2 × 106 annihilation photon pairs and 108 single prompt γ whose energy ranges from a few keV to 10 MeV.
The thorax structure movements (breathing, heart motion and patient motion) during the positron emission tomography (PET) scanning cause deformations and blurring to PET scans. These artifacts are ...important reasons, for the misregistration of PET volumes. In this paper, a breathing simulated PET phantom was constructed by deforming simulated (static) PET volume according to breathing model. The constructed volume was used as a ground truth in the assessment of a nonrigid registration method for cardiac MR and PET volumes. Results showed that the assessed nonrigid registration method was more accurate than a rigid registration method which was used as a reference.
The INNOTEP collaboration investigates for a technological adaptation of high energy physics (HEP) detection and acquisition concepts to the PET issues. We present preliminary results of innovative ...electronics architecture for PET. The concept is based on a deadtimeless pipelined processing of the photosensors signals. After shaping and sampling by a free-running ADC, the pulses are digitally filtered to extract time and energy. The data is processed and selected inline before storage. We present the first tests of the low noise front-end electronics - preamplifier, shaper, ADC - and a time of flight-capable digital filtering technique.
Mod.Phys.Lett. A13 (1998) 3091-3098 It has been recently shown that in order to have Dirac eigenvalues as
observables of Euclidean supergravity, certain constraints should be imposed on
the covariant ...phase space as well as on Dirac eigenspinors. We investigate the
relationships among the constraints in the first set and argue that these
relationships are not linear. We also derive a set of equations expressing the
linear dependency of the constraints in order that the second set of
constraints be linearly independent.
It has been recently shown that in order to have Dirac eigenvalues as observables of Euclidean supergravity, certain constraints should be imposed on the covariant phase space as well as on Dirac ...eigenspinors. We investigate the relationships among the constraints in the first set and argue that these relationships are not linear. We also derive a set of equations expressing the linear dependency of the constraints in order that the second set of constraints be linearly independent.
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