16 research outputs found
The Halo Occupation Distribution of Black Holes: Dependence on Mass
We investigate the halo occupation distribution (HOD) of black holes within a
hydrodynamic cosmological simulation that directly follows black hole growth.
Similar to the HOD of galaxies/subhalos, we find that the black hole occupation
number can be described by the form N_BH proportional to 1+ (M_Host)^alpha
where alpha evolves mildly with redshift indicating that a given mass halo
(M_Host) at low redshift tends to host fewer BHs than at high redshift (as
expected as a result of galaxy and BH mergers). We further divide the
occupation number into contributions from black holes residing in central and
satellite galaxies within a halo. The distribution of M_BH within halos tends
to consist of a single massive BH (distributed about a peak mass strongly
correlated with M_Host), and a collection of relatively low-mass secondary BHs,
with weaker correlation with M_Host. We also examine the spatial distribution
of BHs within their host halos, and find they typically follow a power-law
radial distribution (i.e. much more centrally concentrated than the subhalo
distribution). Finally, we characterize the host mass for which BH growth is
feedback dominated (e.g. star formation quenched). We show that halos with
M_Host > 3 * 10^12 M_sun have primary BHs that are feedback dominated by z~3
with lower mass halos becoming increasingly more affected at lower redshift.Comment: 10 pages, 7 figures, submitted to MNRA
Multimessenger astronomy with pulsar timing and X-ray observations of massive black hole binaries
We demonstrate that very massive (>10^8\msun), cosmologically nearby (z<1)
black hole binaries (MBHBs), which are primary targets for ongoing and upcoming
pulsar timing arrays (PTAs), are particularly appealing multimessenger
carriers. According to current models for massive black hole formation and
evolution, the planned Square Kilometer Array (SKA) will collect gravitational
wave signals from thousands of such massive systems, being able to individually
resolve and locate in the sky several of them (maybe up to a hundred). By
employing a standard model for the evolution of MBHBs in circumbinary discs,
with the aid of dedicated numerical simulations, we characterize the gas-binary
interplay, identifying possible electromagnetic signatures of the PTA sources.
We concentrate our investigation on two particularly promising scenarios in the
high energy domain, namely, the detection of X-ray periodic variability and of
double broad K\alpha iron lines. Up to several hundreds of periodic X-ray
sources with a flux >10^-13 erg s^-1 cm^-2 will be in the reach of upcoming
X-ray observatories. Double relativistic K\alpha lines may be observable in a
handful of low redshift (z<0.3) sources by proposed deep X-ray probes, such as
Athena. (Abridged)Comment: 19 pages, 11 figures, submitted to MNRAS, minor revision of the
reference lis
A 5âyear update of patients with HPV positive versus negative oropharyngeal cancer after radiochemotherapy in Austria
Simple and More Efficient PRFs with Tight Security from LWE and Matrix-DDH
We construct efficient and tightly secure pseudorandom functions (PRFs) with only logarithmic security loss and short secret keys. This yields very simple and efficient variants of well-known constructions, including those of Naor-Reingold (FOCS 1997) and Lewko-Waters (ACM CCS 2009). Most importantly, in combination with the construction of Banerjee, Peikert and Rosen (EUROCRYPT 2012) we obtain the currently most efficient LWE-based PRF from a weak LWE-assumption with a much smaller modulus than the original construction. In comparison to the only previous construction with this property, which is due to Doettling and Schroeder (CRYPTO 2015), we use a modulus of similar size, but only a single instance of the underlying PRF, instead of parallel instances, where is the security parameter. Like Doettling and Schroeder, our security proof is only almost back-box, due to the fact that the number of queries made by the adversary and its advantage must be known a-priori.
Technically, we introduce all-prefix universal hash functions (APUHFs), which are hash functions that are (almost-)universal, even if any prefix of the output is considered. We give simple and very efficient constructions of APUHFs, and show how they can be combined with the augmented cascade of Boneh et al. (ACM CCS 2010) to obtain our results. Along the way, we develop a new and more direct way to prove security of PRFs based on the augmented cascade
The Luminosity Function of Fermi-detected Flat-Spectrum Radio Quasars
Fermi has provided the largest sample of {\gamma}-ray selected blazars to
date. In this work we use a complete sample of FSRQs detected during the first
year of operation to determine the luminosity function (LF) and its evolution
with cosmic time. The number density of FSRQs grows dramatically up to redshift
\sim0.5-2.0 and declines thereafter. The redshift of the peak in the density is
luminosity dependent, with more luminous sources peaking at earlier times; thus
the LF of {\gamma}-ray FSRQs follows a luminosity-dependent density evolution
similarly to that of radio-quiet AGN. Also using data from the Swift Burst
Alert Telescope we derive the average spectral energy distribution of FSRQs in
the 10 keV-100 GeV band and show that there is no correlation of the peak
{\gamma}-ray luminosity with {\gamma}-ray peak frequency. The coupling of the
SED and LF allows us to predict that the contribution of FSRQs to the Fermi
isotropic {\gamma}-ray background is 9.3(+1.6/-1.0) (\pm3% systematic
uncertainty) in the 0.1-100GeV band. Finally we determine the LF of unbeamed
FSRQs, finding that FSRQs have an average Lorentz factor of {\gamma} =
11.7(+3.3/-2.2), that most are seen within 5\circ of the jet axis, and that
they represent only ~0.1 % of the parent population.Comment: Submitted to the Astrophysical Journa
Effects of a pulmonary rehabilitation program on physical capacity, peripheral muscle function and inflammatory markers in asthmatic children and adolescents: study protocol for a randomized controlled trial
Rapid discrimination of archaeal tetraether lipid cores by liquid chromatography-tandem mass spectrometry
The Origins of AGN Obscuration: The 'Torus' as a Dynamical, Unstable Driver of Accretion
Multi-scale simulations have made it possible to follow gas inflows onto
massive black holes (BHs) from galactic scales to the accretion disk. When
sufficient gas is driven towards the BH, gravitational instabilities
generically form lopsided, eccentric disks that propagate inwards. The lopsided
stellar disk exerts a strong torque on the gas disk, driving inflows that fuel
rapid BH growth. Here, we investigate whether the same gas disk is the 'torus'
invoked to explain obscured AGN. The disk is generically thick and has
characteristic ~1-10 pc sizes and masses resembling those required of the
torus. The scale heights and obscured fractions of the predicted torii are
substantial even in the absence of strong stellar feedback providing the
vertical support. Rather, they can be maintained by strong bending modes and
warps excited by the inflow-generating instabilities. Other properties commonly
attributed to feedback processes may be explained by dynamical effects:
misalignment between torus and host galaxy, correlations between local SFR and
turbulent gas velocities, and dependence of obscured fractions on AGN
luminosity or SFR. We compare the predicted torus properties with observations
of gas surface density profiles, kinematics, scale heights, and SFR densities
in AGN nuclei, and find that they are consistent. We argue that it is not
possible to reproduce these observations and the observed column density (N_H)
distribution without a clumpy gas distribution, but allowing for clumping on
small scales the predicted N_H distribution is in good agreement with
observations from 10^20-27 cm^-2. We examine how N_H scales with galaxy and AGN
properties, and find that AGN feedback may be necessary to explain some trends
with luminosity and/or redshift. The torus is not merely a bystander or passive
fuel source for accretion, but is itself the mechanism driving accretion.Comment: 20 pages, 10 figures, accepted to MNRAS (matches accepted version
Benzimidazole and aminoalcohol derivatives show in vitro anthelmintic activity against Trichuris muris and Heligmosomoides polygyrus
8 pĂĄginas, 4 tablas.Background: Infections by gastrointestinal nematodes cause significant economic losses and disease in both humans and animals worldwide. The discovery of novel anthelmintic drugs is crucial for maintaining control of these parasitic infections. Methods: For this purpose, the aim of the present study was to evaluate the potential anthelmintic activity of three series of compounds against the gastrointestinal nematodes Trichuris muris and Heligmosomoides polygyrus in vitro. The compounds tested were derivatives of benzimidazole, lipidic aminoalcohols and diamines. A primary screening was performed to select those compounds with an ability to inhibit T. muris L1 motility by > 90% at a single concentration of 100 ”M; then, their respective IC50 values were calculated. Those compounds with IC50 < 10 ”M were also tested against the adult stage of T. muris and H. polygyrus at a single concentration of 10 ”M. Results: Of the 41 initial compounds screened, only compounds AO14, BZ6 and BZ12 had IC50 values < 10 ”M on T. muris L1 assay, showing IC50 values of 3.30, 8.89 and 4.17 ”M, respectively. However, only two of them displayed activity against the adult stage of the parasites: BZ12 killed 81% of adults of T. muris (IC50 of 8.1 ”M) and 53% of H. polygyrus while BZ6 killed 100% of H. polygyrus adults (IC50 of 5.3 ”M) but only 17% of T. muris. Conclusions: BZ6 and BZ12 could be considered as a starting point for the synthesis of further structurally related compounds. GraphicalFinancial support came from MINECO: RETOS (AGL2016â79813âC2â1R/2R) and Junta de Castilla y LeĂłn coâfinanced by FEDER, UE [LE020P17]. EVG was funded by FPU17/00627; VCGA and MAB are recipients of Junta de Castilla y Leon (JCyL) (LE082â18, LE051â18, respectively) and MMV by the Spanish âRamon y Cajalâ Programme (Ministerio de EconomĂa y competitividad; MMV, RYCâ2015â18368).Peer reviewe