We examined whether significant constraints on matter-antimatter admixture can be derived from gamma-ray observations of colliding clusters of galaxies with Fermi-LAT. We selected ten known systems ...of colliding clusters of galaxies for the analysis and computed the upper bounds on matter-antimatter admixture in these systems, which range from 7 x 10 super(-9) to 2 x 10 super(-6). This allowed us to exclude a symmetric universe on scales of order ~ 20 Mpc at the confidence level of 99.9%. Adopting the number of systems of colliding galaxy clusters from the Marenostrum Universe cosmological simulation, we checked if the Fermi-LAT second source catalog contains a sufficient number of gamma-ray sources to provide us with the required number of sources possibly associated with pp annihilation from cluster-anticluster collisions. We found that a matter-antimatter-symmetric universe is strongly ruled out on scales of order ~ 20 Mpc if a matter-antimatter admixture in these bullet-like systems is of functionof > ~ 10 super(-5), and on scales of order ~ 400 Mpc if functionof > ~ 10 super(-4).
ABSTRACT
Clusters of galaxies are mainly formed by merging of smaller structures, according to the standard cosmological scenario. If the mass of a substructure is ≳10 per cent of that of a galaxy ...cluster, the temperature distribution of the intracluster medium (ICM) in a merging cluster becomes inhomogeneous. Various methods have been used to derive the two‐dimensional projected temperature distribution of the ICM. However, methods for studying temperature distribution along the line of sight through the cluster were absent. In this Letter, we present the first measurement of the temperature standard deviation along the line of sight, using as a reference case the multifrequency Sunyaev–Zel’dovich measurements of the Bullet Cluster. We find that the value of the temperature standard deviation is high and equals to (10.6 ± 3.8) keV in the Bullet Cluster. This result shows that the temperature distribution in the Bullet Cluster is strongly inhomogeneous along the line of sight and provides a new method for studying galaxy clusters in depth.
An experimental study of combustion in diffusion and coaxial mesoscale burner arrays was conducted. To that end, different linear and planar arrangements were tested, and blow-off limits, flame ...geometry, and oscillations parameters were determined. The new results of the experiments showed that the coaxial burner arrays, in general, are characterized by leaner values of the blow-off limit compared to premixed flames. Moreover, the large planar arrangement (square 5 × 5) provides the global blow-off equivalence ratio value of about 0.1 at low thermal power operating modes (less than 2 kW). All arrays of coaxial jets feature flame separation into small coaxial flamelets. However, linear coaxial arrangements provide complete flame separation, whereas jets of a planar array are not fully separated and merged in pairs. At the equivalence ratio value less than 0.45, separated flames start oscillating strongly until the blow-off occurs, that is unacceptable in terms of combustion efficiency, pollutant emission, and related parameters. Therefore, the most favorable operating modes correspond to the equivalence ratio ranging from 0.45 to 0.6.
Abstract
New data about the state of Cr
3+
doping ions in a single crystal of YGa
3
(BO
3
)
4
have been obtained by studying different methods. Using electron paramagnetic resonance, it was found ...that the Cr
3+
ions substitute the trivalent gallium ions. The obtained spin Hamiltonian parameters of the Cr
3+
ions in the YGa
3
(BO
3
)
4
single crystal (g = 1.9743 ± 0.0004; D = −0.465 ± 0.001 cm
−1
; E = −0.013 ± 0.001 cm
−1
) were analyzed and compared with those in TmAl
3
(BO
3
)
4
, EuAl
3
(BO
3
)
4
, and YAl
3
(BO
3
)
4
. The deviation of the Z-axis in the spectrum from the crystallographic axis С
3
is 1,7 degrees in YGa
3
(BO
3
)
4
.
In situ
X-ray diffraction was used to study the structural and elastic properties of huntite-type borates in the temperature range of RT-1073 K. In the radioluminescence (RL) spectra, the Cr
3+
-related emission bands were observed in the red wavelength range, and the presence of other defect-related bands was also registered in some cases. Thermally stimulated luminescence (TSL) glow curves were acquired over a wide temperature range, and the trap depths of the most prominent bands were calculated. The
11
B NMR spectra show that two nonequivalent spectral components exist for BO
3
structural elements.
Water is characterized by large molecular electric dipole moments and strong interactions between molecules; however, hydrogen bonds screen the dipole-dipole coupling and suppress the ferroelectric ...order. The situation changes drastically when water is confined: in this case ordering of the molecular dipoles has been predicted, but never unambiguously detected experimentally. In the present study we place separate H
O molecules in the structural channels of a beryl single crystal so that they are located far enough to prevent hydrogen bonding, but close enough to keep the dipole-dipole interaction, resulting in incipient ferroelectricity in the water molecular subsystem. We observe a ferroelectric soft mode that causes Curie-Weiss behaviour of the static permittivity, which saturates below 10 K due to quantum fluctuations. The ferroelectricity of water molecules may play a key role in the functioning of biological systems and find applications in fuel and memory cells, light emitters and other nanoscale electronic devices.
We propose a morphological analysis for searches of extended γ-ray emission associated with dark matter annihilation. Our approach is based on the likelihood analysis including the spatial templates ...produced by taking into account the residual count maps in the energy band where the dark matter annihilation spectrum has a prominent spectral feature. The approach is tested on the example of the possible dark matter annihilation signal from the Virgo cluster of galaxies.
Context. X-ray cavities and extended radio sources (“cocoons”) surrounding active galactic nuclei (AGN) have been detected by the Chandra X-ray mission and radio interferometers. A joint analysis of ...X-ray and radio maps suggests that pressure values of non-thermal radio-emitting particles derived from the radio maps are not sufficient to inflate the X-ray cavities. We propose using the Sunyaev-Zel'dovich (SZ) effect, whose intensity strongly depends on the pressure, to find the hitherto undetected, dynamically-dominant component in the radio cocoons. Aims. Numerical simulations show that plasma with a high temperature (109–1010 K) is a good candidate for inflating the AGN cocoons. To constrain the population of high energy electrons inside AGN cocoons that is predicted by numerical simulations, we study different methods for maximizing the contribution of such energetic electrons to the SZ effect. Methods. Our calculations of intensity maps of the SZ effect include relativistic corrections and utilize both analytic models and numerical 2D simulations. Results. We demonstrate that the spectral function at a frequency of 217 GHz has an absolute maximum at a temperature higher than 109 K, therefore the measurement of the SZ effect at this frequency is a powerful tool for potentially revealing the dynamically-dominant component inside AGN jet-driven radio cocoons. A new method is proposed for excluding the contribution from the low energy, non-relativistic electrons to the SZ effect by means of observations at two frequencies. We show how one may correct for a possible contribution from the kinematic SZ effect. The intensity maps of the SZ effect are calculated for the self-similar Sedov solution, and application of a predicted ring-like structure on the SZ map at a frequency of 217 GHz is proposed to determine the energy released during the active jet stage. The SZ intensity map for an AGN cocoon in a distant elliptical is calculated using a 2D numerical simulation and including relativistic corrections to the SZ effect. We show the intensity spectrum of the SZ effect is flat at high frequencies if gas temperature is as high as kbTe = 500 keV.
A study was made of a thermal interface based on a two-dimensional allotropic modification of carbon (graphene), presented in the form of a powder, for cooling integrated circuits. Such physical ...properties of the thermal interface as thermal conductivity, heat capacity, thermal diffusivity, and density are determined by the empirical method. The process of heat transfer in the most efficient thermal interface sample during the operation of integrated circuits in the ANSYS engineering analysis system is presented. The prospects of using pressed graphene powder as a thermal interface in order to eliminate the use of a binder are described. The paper also makes a comparison with the most effective type of thermal interfaces currently in use.
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