10,110 research outputs found
Quantum correlation dynamics in photosynthetic processes assisted by molecular vibrations
During the long course of evolution, nature has learnt how to exploit quantum
effects. In fact, recent experiments reveal the existence of quantum processes
whose coherence extends over unexpectedly long time and space ranges. In
particular, photosynthetic processes in light-harvesting complexes display a
typical oscillatory dynamics ascribed to quantum coherence. Here, we consider
the simple model where a dimer made of two chromophores is strongly coupled
with a quasi-resonant vibrational mode. We observe the occurrence of wide
oscillations of genuine quantum correlations, between electronic excitations
and the environment, represented by vibrational bosonic modes. Such a quantum
dynamics has been unveiled through the calculation of the negativity of
entanglement and the discord, indicators widely used in quantum information for
quantifying the resources needed to realize quantum technologies. We also
discuss the possibility of approximating additional weakly-coupled off-resonant
vibrational modes, simulating the disturbances induced by the rest of the
environment, by a single vibrational mode.
Within this approximation, one can show that the off-resonant bath behaves
like a classical source of noise
The interaction-strength interpolation method for main-group chemistry: benchmarking, limitations, and perspectives
We have tested the original interaction-strength-interpolation (ISI)
exchange-correlation functional for main group chemistry. The ISI functional is
based on an interpolation between the weak and strong coupling limits and
includes exact-exchange as well as the G\"orling-Levy second-order energy. We
have analyzed in detail the basis-set dependence of the ISI functional, its
dependence on the ground-state orbitals, and the influence of the
size-consistency problem. We show and explain some of the expected limitations
of the ISI functional (i.e. for atomization energies), but also unexpected
results, such as the good performance for the interaction energy of
dispersion-bonded complexes when the ISI correlation is used as a correction to
Hartree-Fock.Comment: 20 pages, 20 figure
Plasma flows and magnetic field interplay during the formation of a pore
We studied the formation of a pore in AR NOAA 11462. We analysed data
obtained with the IBIS at the DST on April 17, 2012, consisting of full Stokes
measurements of the Fe I 617.3 nm lines. Furthermore, we analysed SDO/HMI
observations in the continuum and vector magnetograms derived from the Fe I
617.3 nm line data taken from April 15 to 19, 2012. We estimated the magnetic
field strength and vector components and the LOS and horizontal motions in the
photospheric region hosting the pore formation. We discuss our results in light
of other observational studies and recent advances of numerical simulations.
The pore formation occurs in less than 1 hour in the leading region of the AR.
The evolution of the flux patch in the leading part of the AR is faster (< 12
hour) than the evolution (20-30 hour) of the more diffuse and smaller scale
flux patches in the trailing region. During the pore formation, the ratio
between magnetic and dark area decreases from 5 to 2. We observe strong
downflows at the forming pore boundary and diverging proper motions of plasma
in the vicinity of the evolving feature that are directed towards the forming
pore. The average values and trends of the various quantities estimated in the
AR are in agreement with results of former observational studies of steady
pores and with their modelled counterparts, as seen in recent numerical
simulations of a rising-tube process. The agreement with the outcomes of the
numerical studies holds for both the signatures of the flux emergence process
(e.g. appearance of small-scale mixed polarity patterns and elongated granules)
and the evolution of the region. The processes driving the formation of the
pore are identified with the emergence of a magnetic flux concentration and the
subsequent reorganization of the emerged flux, by the combined effect of
velocity and magnetic field, in and around the evolving structure.Comment: Accepted for publication in Astronomy and Astrophysic
Reconstructing the ancient urban landscape in a long-lived city: the Asculum Project, combining research, territorial planning and preventative archaeology
The Asculum Project started in 2012 by the Bologna University in agreement with the former Soprintendenza per iBeni Archeologici delle Marche and the Municipality of Ascoli Piceno, mainly as a project of urban archaeology and preventative archaeology in a city which has been inhabited for a very long period of time. A proper integrated methodology and the combination of a wide range of data, including that gathered from geophysical surveys, archaeological digs, historic cartography, bibliographic and archival data, allowed us to reconstruct the cityscape during the Roman Age and its development over the centuries. The understanding of the ancient urban landscape also included a detailed morphological study aimed at the reconstruction of the Roman paleosurface, carried out using data derived from coring samples and stratigraphic digs. In parallel, particular attention was directed to the modern 3D documentation of the historical buildings of the city, by means of laser scanner and the analysis of the stratigraphy of the surviving walls. The new surveys covered, in particular, the still extant Roman buildings, such as the temples incorporated by the churches of San Venanzio and San Gregorio Magno, as well as the Sostruzioni dell’Annunziata. These last acquisitions made it possible to reconstruct the overall layout and urban plan of the town during the Roman Age, as well as to shed new light on the conformation of the ancient landscape at the time of the oldest Piceni settlement. One of the most interesting aspects of the operating practices applied in the project was to reconcile the needs for preservation and research with the aim of a sustainable urban development
Radiative emission of solar features in Ca II K
We investigated the radiative emission of different types of solar features
in the spectral range of the Ca II K line.
We analyzed full-disk 2k x 2k observations from the PSPT Precision Solar
Photometric Telescope. The data were obtained by using three narrow-band
interference filters that sample the Ca II K line with different pass bands.
Two filters are centered in the line core, the other in the red wing of the
line. We measured the intensity and contrast of various solar features,
specifically quiet Sun (inter-network), network, enhanced network, plage, and
bright plage (facula) regions. Moreover, we compared the results obtained with
those derived from the numerical synthesis performed for the three PSPT filters
with a widely used radiative code on a set of reference semi-empirical
atmosphere models.Comment: In Proceedings of the 25th NSO Workshop: Chromospheric Structure and
Dynamic
Strictly correlated uniform electron droplets
We study the energetic properties of finite but internally homogeneous
D-dimensional electron droplets in the strict-correlation limit. The indirect
Coulomb interaction is found to increase as a function of the electron number,
approaching the tighter forms of the Lieb-Oxford bound recently proposed by
Rasanen et al. [Phys. Rev. Lett. 102, 206406 (2009)]. The bound is satisfied in
three-, two-, and one-dimensional droplets, and in the latter case it is
reached exactly - regardless of the type of interaction considered. Our results
provide useful reference data for delocalized strongly correlated systems, and
they can be used in the development and testing of exchange-correlation density
functionals in the framework of density-functional theory
Kf evaluation in GFRP composites by thermography
Since the presence of a notch in a mechanical component causes a reduction in the fatigue strength, it is important to know the kf value for a given notch geometry and material. This parameter is fundamental in the fatigue design of aeronautical components that are mainly made of composites. kf is available in the literature for numerous types of notch but only for traditional materials such as metals. This paper presents a new practice, based on thermographic data, for the determination of the fatigue notch coefficient kf in composite notched specimens. The innovative aspect of this study is therefore to propose the application on composite materials of a new thermographic procedure to determine kf for several notch geometries: circular, U and V soft and severe notches. It was calculated, for each type of notch, as the ratio between the fatigue limits obtained on the cold and hot zone corresponding to the smooth and notched specimen, respectively. Consequently, this research activity provides, for the first time, a little database of kf for two particular typologies of composite materials showing a fast way to collect further values for different laminates and notch geometries
Singularities of Nonlinear Elliptic Systems
Through Morrey's spaces (plus Zorko's spaces) and their potentials/capacities
as well as Hausdorff contents/dimensions, this paper estimates the singular
sets of nonlinear elliptic systems of the even-ordered Meyers-Elcrat type and a
class of quadratic functionals inducing harmonic maps.Comment: 18 pages Communications in Partial Differential Equation
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