209 research outputs found
Constraining DM through 21 cm observations
Beyond reionization epoch cosmic hydrogen is neutral and can be directly
observed through its 21 cm line signal. If dark matter (DM) decays or
annihilates the corresponding energy input affects the hydrogen kinetic
temperature and ionized fraction, and contributes to the Ly_alpha background.
The changes induced by these processes on the 21 cm signal can then be used to
constrain the proposed DM candidates, among which we select the three most
popular ones: (i) 25-keV decaying sterile neutrinos, (ii) 10-MeV decaying light
dark matter (LDM) and (iii) 10-MeV annihilating LDM. Although we find that the
DM effects are considerably smaller than found by previous studies (due to a
more physical description of the energy transfer from DM to the gas), we
conclude that combined observations of the 21 cm background and of its gradient
should be able to put constrains at least on LDM candidates. In fact, LDM
decays (annihilations) induce differential brightness temperature variations
with respect to the non decaying/annihilating DM case up to Delta_delta T_b=8
(22) mK at about 50 (15) MHz. In principle this signal could be detected both
by current single dish radio telescopes and future facilities as LOFAR;
however, this assumes that ionospheric, interference and foreground issues can
be properly taken care of.Comment: 9 pages, submitted to MNRA
Particle energy cascade in the intergalactic medium
We study the development of high-energy (Ein <= 1 TeV) cascades produced by a primary electron of energy Ein injected into the intergalactic medium (IGM). To this aim we have developed the new code MEDEA (Monte Carlo Energy Deposition Analysis) which includes Bremsstrahlung and inverse Compton (IC) processes, along with H/He collisional ionizations and excitations, and electron-electron collisions. The cascade energy partition into heating, excitations and ionizations depends primarily not only on the IGM ionized fraction, xe, but also on redshift, z, due to IC on cosmic microwave background (CMB) photons. While Bremsstrahlung is unimportant under most conditions, IC becomes largely dominant at energies Ein >= 1 MeV. The main effect of IC at injection energies Ein <= 100 MeV is a significant boost of the fraction of energy converted into low-energy photons (h\u3bd < 10.2 eV) which do not further interact with the IGM. For energies Ein >= 1 GeV CMB photons are preferentially upscattered within the X-ray spectrum (h\u3bd > 104 eV) and can free stream to the observer. Complete tables of the fractional energy depositions as a function of redshift, Ein and ionized fraction are given. Our results can be used in many astrophysical contexts, with an obvious application related to the study of decaying/annihilating dark matter (DM) candidates in the high-z Universe
Radio views of cosmic reionization
We use numerical simulations of cosmic reionization and radiative processes
related to the HI 21 cm emission line to produce synthetic radio maps as seen
by next generation radio telescopes that will operate at low radio frequencies
(e.g. LOFAR). Two different scenarios, in which the end of reionization occurs
early (z approx 13) or late (z approx 8) depending on the Initial Mass Function
(IMF) of the first stars and ionizing photon escape fraction, have been
explored. For each of these models we produce synthetic HI 21 cm emission maps
by convolving the simulation outputs with the provisional LOFAR sampling
function in the frequency range 76-140 MHz. If reionization occurs late, LOFAR
will be able to detect individual HI structures on arcmin scales, emitting at a
brightness temperature of approx 35 mK as a 3-sigma signal in about 1000 hours
of observing time. In the case of early reionization, the detection would be
unlikely, due to decreased sensitivity and increased sky temperatures. These
results assume that ionospheric, interference and foreground issues are fully
under control.Comment: 6 pages, 3 figures, Minor changes following referee repor
Moving objects beyond raw and semantic trajectories
Mobile applications, for example for road tra\ufb03c monitoring, mobile health and animal data ecology, call for methods enabling rich and expressive representation of moving objects. This demand motivates the increasing concern for the paradigm of semantic trajectories. In this paper, I overview
related research, focusing in particular on the novel data model of symbolic trajectories proposed for the e\ufb03cient and \ufb02exible handling of semantics-aware trajectories through a Moving Object DBMS
IRAS F02044+0957: radio source in interacting system of galaxies
The steep spectrum of IRAS F02044+0957 was obtained with the RATAN-600 radio
telescope at four frequencies. Optical spectroscopy of the system components,
was carried out with the 2.1m telescope of the Guillermo Haro Observatory.
Observational data allow us to conclude that this object is a pair of
interacting galaxies, a LINER and a HII galaxy, at .Comment: 2 pages, 2 EPS-figures, uses newpasp.sty. To appear in Proc. IAU
Colloq. 184, AGN Surveys, ed. R. F. Green, E. Ye. Khachikian, & D. B. Sanders
(San Francisco: ASP
Expansion of different subpopulations of CD26 ?/low T cells in allergic and non-allergic asthmatics
CD26 displays variable levels between effector (TH17 >> TH1 > TH2 > Treg) and naive/memory (memory > naive) CD4(+) T lymphocytes. Besides, IL-6/IL(-)6R is associated with TH17-differentiation and asthma severity. Allergic/atopic asthma (AA) is dominated by TH2 responses, while TH17 immunity might either modulate the TH2-dependent inflammation in AA or be an important mechanism boosting non-allergic asthma (NAA). Therefore, in this work we have compared the expression of CD26 and CD126 (IL-6Ralpha) in lymphocytes from different groups of donors: allergic (AA) and non-allergic (NAA) asthma, rhinitis, and healthy subjects. For this purpose, flow cytometry, haematological/biochemical, and in vitro proliferation assays were performed. Our results show a strong CD26-CD126 correlation and an over-representation of CD26(-) subsets with a highly-differentiated effector phenotype in AA (CD4(+)CD26(-/low) T cells) and NAA (CD4(-)CD26(-) gammadelta-T cells). In addition, we found that circulating levels of CD26 (sCD26) were reduced in both AA and NAA, while loss of CD126 expression on different leukocytes correlated with higher disease severity. Finally, selective inhibition of CD26-mRNA translation led to enhanced T cell proliferation in vitro. These findings support that CD26 down-modulation could play a role in facilitating the expansion of highly-differentiated effector T cell subsets in asthma
Polymorphisms in the BER and NER pathways and their influence on survival and toxicity in never-smokers with lung cancer
Polymorphisms in DNA repair pathways may play a relevant role in lung cancer survival in never-smokers. Furthermore, they could be implicated in the response to chemotherapy and toxicity of platinum agents. The aim of this study was to evaluate the influence of various genetic polymorphisms in the BER and NER DNA repair pathways on survival and toxicity in never-smoker LC patients. The study included never-smokers LC cases diagnosed from 2011 through 2019, belonging to the Lung Cancer Research In Never Smokers study. A total of 356 never-smokers cases participated (79% women; 83% adenocarcinoma and 65% stage IV). Survival at 3 and 5 years from diagnosis was not associated with genetic polymorphisms, except in the subgroup of patients who received radiotherapy or chemo-radiotherapy, and presented with ERCC1 rs3212986 polymorphism. There was greater toxicity in those presenting OGG1 rs1052133 (CG) and ERCC1 rs11615 polymorphisms among patients treated with radiotherapy or chemo-radiotherapy, respectively. In general, polymorphisms in the BER and NER pathways do not seem to play a relevant role in survival and response to treatment among never-smoker LC patients
Statistics of the gravitational force in various dimensions of space: from Gaussian to Levy laws
We discuss the distribution of the gravitational force created by a
Poissonian distribution of field sources (stars, galaxies,...) in different
dimensions of space d. In d=3, it is given by a Levy law called the Holtsmark
distribution. It presents an algebraic tail for large fluctuations due to the
contribution of the nearest neighbor. In d=2, it is given by a marginal
Gaussian distribution intermediate between Gaussian and Levy laws. In d=1, it
is exactly given by the Bernouilli distribution (for any particle number N)
which becomes Gaussian for N>>1. Therefore, the dimension d=2 is critical
regarding the statistics of the gravitational force. We generalize these
results for inhomogeneous systems with arbitrary power-law density profile and
arbitrary power-law force in a d-dimensional universe
- …