Relaxation dynamics induced in glasses by the absorption of hard X-ray photons

X-ray photon correlation is used to probe the slow dynamics of the glass-former B2O3 across the glass transition. In the undercooled liquid phase the decay times of the measured correlation functions are consistent with visible light scattering results and independent of the incoming flux; in the glass they are instead temperature independent and show a definite dependence on the X-ray flux. This dependence can be exploited to obtain information on the volume occupied by the atoms that move in the glass following an absorption event. The length scale derived in this way, of the order of the nanometer, is consistent with that reported for the dynamical heterogeneities, suggesting the existence of a new scheme to get access to this fundamental quantity

LDPC coded transmissions over the Gaussian broadcast channel with confidential messages

We design and assess some practical low-density parity-check (LDPC) coded transmission schemes for the Gaussian broadcast channel with confidential messages (BCC). This channel model is different from the classical wiretap channel model as the unauthorized receiver (Eve) must be able to decode some part of the information. Hence, the reliability and security targets are different from those of the wiretap channel. In order to design and assess practical coding schemes, we use the error rate as a metric of the performance achieved by the authorized receiver (Bob) and the unauthorized receiver (Eve). We study the system feasibility, and show that two different levels of protection against noise are required on the public and the secret messages. This can be achieved in two ways: i) by using LDPC codes with unequal error protection (UEP) of the transmitted information bits or ii) by using two classical non-UEP LDPC codes with different rates. We compare these two approaches and show that, for the considered examples, the solution exploiting UEP LDPC codes is more efficient than that using non-UEP LDPC codes.Comment: 5 pages, 5 figures, to be presented at IEEE ICT 201

Practical LDPC coded modulation schemes for the fading broadcast channel with confidential messages

The broadcast channel with confidential messages is a well studied scenario from the theoretical standpoint, but there is still lack of practical schemes able to achieve some fixed level of reliability and security over such a channel. In this paper, we consider a quasi-static fading channel in which both public and private messages must be sent from the transmitter to the receivers, and we aim at designing suitable coding and modulation schemes to achieve such a target. For this purpose, we adopt the error rate as a metric, by considering that reliability (security) is achieved when a sufficiently low (high) error rate is experienced at the receiving side. We show that some conditions exist on the system feasibility, and that some outage probability must be tolerated to cope with the fading nature of the channel. The proposed solution exploits low-density parity-check codes with unequal error protection, which are able to guarantee two different levels of protection against noise for the public and the private information, in conjunction with different modulation schemes for the public and the private message bits.Comment: 6 pages, 4 figures, to be presented at IEEE ICC'14 - Workshop on Wireless Physical Layer Securit

Security gap analysis of some LDPC coded transmission schemes over the flat and fast fading Gaussian wire-tap channels

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The stellar-to-halo mass relation over the past 12 Gyr

Understanding how galaxy properties are linked to the dark matter halos they reside in, and how they co-evolve is a powerful tool to constrain the processes related to galaxy formation. The stellar-to-halo mass relation (SHMR) and its evolution over the history of the Universe provides insights on galaxy formation models and allows to assign galaxy masses to halos in N-body dark matter simulations. We use a statistical approach to link the observed galaxy stellar mass functions on the COSMOS field to dark matter halo mass functions from the DUSTGRAIN simulation and from a theoretical parametrization from z=0 to z=4. We also propose an empirical model to describe the evolution of the stellar-to-halo mass relation as a function of redshift. We calculate the star-formation efficiency (SFE) of galaxies and compare results with previous works and semi-analytical models.Comment: accepted for publication in A&A, matching version in pres

PREPARING OF THE CHAMELEON COATING BY THE ION JET DEPOSITION METHOD

Preparation of chameleon coatings using an Ionized Jet Deposition (IJD) technique is reported in the present paper. IJD is a new flexible method for thin film deposition developed by Noivion, Srl. The chameleon coatings are thin films characterised by a distinct change of their tribological properties according to the external conditions. The deposited films of SiC and TiN materials were examined by the Raman spectroscopy, SEM and XPS. The results of the Raman spectroscopy have proved an amorphous structure of SiC films. The data from XPS on TiN films have shown that the films are heavily oxidized, but also prove that the films are composed of TiN and pure Ti. The SEM provided information about the size of grains and particles constituting the deposited films, which is important for tribological properties of the films. Deposition of the chameleon coating is very complex problem and IJD could be ideal method for preparation of this coating

The MURALES survey. VI. Properties and origin of the extended line emission structures in radio galaxies

This is the sixth paper presenting the results of the MUse RAdio Loud Emission line Snapshot survey (MURALES). We observed 37 radio sources from the 3C sample with z<0.3 and declination <20 degrees with the MUSE optical integral field spectrograph at the VLT. We here focus on the properties of the extended emission line regions (EELRs) that can be studied with unprecedented detail thanks to the depth of these observations. Line emission in the 10 FRIs is, in most cases, confined to within 4 kpc) ionized gas is seen in all but two of the 26 FRIIs. It usually takes the form of elongated or filamentary structures, typically extending between 10 and 30 kpc, but also reaching distances of ~80 kpc. We find that 1) the large-scale ionized gas structures show a tendency to be oriented at large angles from the radio axis, and 2) the gas on a scale of a few kpc from the nucleus often shows ordered rotation with a kinematical axis forming a median angle of 65 degrees with the radio axis. We also discuss the velocity field and ionization properties of the EELRs. The observed emission line structures appear to be associated with gaseous "superdisks" formed after a gas rich merger. The different properties of the EELR can be explained with a combination of the source evolutionary state and the orientation of the "superdisk" with respect to the radio axis. The general alignment between the superdisks and radio axis might be produced by stable and coherent accretion maintained over long timescales.Comment: Pre-proofs version - Accepted for publication in A&