295 research outputs found
Network Analysis and Greco-Roman Prosopography
Social network analysis as a distinct field of study had its genesis in the anthropological
revolt against structural-functionalism in the late 1960s and early 1970s. It was born through
an awareness among a new generation of scholars that structural- functional models failed
to make adequate space for human agency. Attention to personal networks – who knew
whom, and how closely they were connected – seemed better suited to understanding
individual decision-making than the previous generation's focus on groups and roles. It quickly
became evident that any serious attempt to map social networks of meaningful size – the
population of an entire village, for instance – would all but require a rigorous quantitative
approach..
The Gravitational Polarization in General Relativity: Solution to Szekeres' Model of Quadrupole Polarization
A model for the static weak-field macroscopic medium is analyzed and the
equation for the macroscopic gravitational potential is derived. This is a
biharmonic equation which is a non-trivial generalization of the Poisson
equation of Newtonian gravity. In case of the strong gravitational quadrupole
polarization it essentially holds inside a macroscopic matter source. Outside
the source the gravitational potential fades away exponentially. The equation
is equivalent to a system of the Poisson equation and the nonhomogeneous
modified Helmholtz equations. The general solution to this system is obtained
by using Green's function method and it does not have a limit to Newtonian
gravity. In case of the insignificant gravitational quadrupole polarization the
equation for macroscopic gravitational potential becomes the Poisson equation
with the matter density renormalized by the factor including the value of the
quadrupole gravitational polarization of the source. The general solution to
this equation obtained by using Green's function method has a limit to
Newtonian gravity.Comment: 22 pages, no figures, to appear on Class. Quantum Gra
Viscoresistive MHD Configurations of Plasma in Accretion Disks
We present a discussion of two-dimensional magneto-hydrodynamics (MHD)
configurations, concerning the equilibria of accretion disks of a strongly
magnetized astrophysical object. We set up a viscoresistive scenario which
generalizes previous two-dimensional analyses by reconciling the ideal MHD
coupling of the vertical and the radial equilibria within the disk with the
standard mechanism of the angular momentum transport, relying on dissipative
properties of the plasma configuration. The linear features of the considered
model are analytically developed and the non-linear configuration problem is
addressed, by fixing the entire disk profile at the same order of
approximation. Indeed, the azimuthal and electron force balance equations are
no longer automatically satisfied when poloidal currents and matter fluxes are
included in the problem. These additional components of the equilibrium
configuration induce a different morphology of the magnetic flux surface, with
respect to the ideal and simply rotating disk.Comment: 19 pages, 4 figures. To appear on the Proceedings of the Second
Italian-Pakistani Workshop on Relativistic Astrophysic
Progetto cˇaplja. Un parco fluviale nella nuova isola sul Danubio a Belgrado
Project cˇaplja – a river park in the new island on the Danube in Belgrade
Within multi-annual cooperation between the urban planning institutions from Firenze and Town Planning Institute of Belgrade, the Project Caplja has been developed in the framework of Master Plan 2021, dealing with preservation of the natural and development of recreational functions in the new river island on the left Danube river bank. The project will represent a significant possibility and a leading suggestion for future organization of this wide natural area in the heart of Belgrade
GRB 110709B in the Induced Gravitational Collapse paradigm
Context: GRB110709B is the first source for which Swift BAT triggered twice,
with a time separation of ~10 min. The first emission (Ep. 1) goes from 40s
before the 1{\deg} trigger up to 60s after it. The second (Ep. 2) goes from 35s
before the 2{\deg} trigger to 100s after it.[...] Within the Induced
Gravitational Collapse (IGC) model, we assume the progenitor to be a close
binary system composed of a core of an evolved star and a Neutron Star (NS).
The evolved star explodes as a Supernova (SN) and ejects material that is
partially accreted by the NS. We identify this process with Ep. 1. The
accretion process brings the NS over its critical mass, thus gravitationally
collapsing to a BH. This process leads to the GRB emission, Ep. 2.[...] Aims:
We analyze the spectra and time variability of Ep. 1 and 2 and compute the
relevant parameters of the binary progenitor[...] in the IGC paradigm. Methods:
We perform a time-resolved spectral analysis of Ep. 1 with a blackbody (BB)
plus a power-law (PL) spectral model. We analyze Ep. 2 within the Fireshell
model, identifying the Proper-GRB (P-GRB) and simulating the light curve and
spectrum. We establish the redshift to be z=0.75 [...]. Results: We find for
Ep. 1 a BB temperature following a broken PL with time, with the PL slopes at
early and late times \alpha=0 and \beta=-4+/-2, respectively, and a break at
t=41.21s. The total energy of Ep. 1 and 2 are E_{iso}^1=1.42x10^{53}erg and
E_{iso}^2=2.43x10^{52}erg, respectively. We find at transparency a Lorentz
factor \Gamma~173, laboratory radius of 6.04x10^{13}cm, P-GRB observed
temperature kT_{P-GRB}=12.36keV, baryon load B=0.0057 and P-GRB energy
E_{P-GRB}=3.44x10^{50}erg. [...] Conclusions: We interpret GRB110709B as a
member of the IGC sources, together with GRB970828, GRB090618 and GRB101023.
The XRT data during Ep. 2 offers an unprecedented tool for improving the
diagnostic of GRBs emission.Comment: 12 pages, 17 figures, to appear on A&
Do changes in Lactuca sativa metabolic performance, induced by mycorrhizal symbionts and leaf UV-B irradiation, play a role towards tolerance to a polyphagous insect pest?
: The increased ultraviolet radiation (UV) due to the altered stratospheric ozone leads to multiple plant physiological and biochemical adaptations, likely affecting their interaction with other organisms, such as pests and pathogens. Arbuscular mycorrhizal fungi (AMF) and UV-B treatment can be used as eco-friendly techniques to protect crops from pests by activating plant mechanisms of resistance. In this study, we investigated plant (Lactuca sativa) response to UV-B exposure and Funneliformis mosseae (IMA1) inoculation as well as the role of a major insect pest, Spodoptera littoralis. Lettuce plants exposed to UV-B were heavier and taller than non-irradiated ones. A considerable enrichment in phenolic, flavonoid, anthocyanin, and carotenoid contents and antioxidant capacity, along with redder and more homogenous leaf color, were also observed in UV-B-treated but not in AMF-inoculated plants. Biometric and biochemical data did not differ between AMF and non-AMF plants. AMF-inoculated plants showed hyphae, arbuscules, vesicles, and spores in their roots. AMF colonization levels were not affected by UV-B irradiation. No changes in S. littoralis-feeding behavior towards treated and untreated plants were observed, suggesting the ability of this generalist herbivore to overcome the plant chemical defenses boosted by UV-B exposure. The results of this multi-factorial study shed light on how polyphagous insect pests can cope with multiple plant physiological and biochemical adaptations following biotic and abiotic preconditioning
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