1,130 research outputs found
Stability of Quantum Motion: Beyond Fermi-golden-rule and Lyapunov decay
We study, analytically and numerically, the stability of quantum motion for a
classically chaotic system. We show the existence of different regimes of
fidelity decay which deviate from Fermi Golden rule and Lyapunov decay.Comment: 5 pages, 5 figure
To Get Back from Chemistry to Physics. Lord Rayleigh, la chimica e la determinazione dei pesi atomici
Profound and far-reaching theoretical implications. La spettrometria di massa di Aston e il suo impatto sulla fisica del nucleo
Iron causes lipid oxidation and inhibits proteasome function in multiple myeloma cells: A proof of concept for novel combination therapies
Adaptation to import iron for proliferation makes cancer cells potentially sensitive to iron toxicity. Iron loading impairs multiple myeloma (MM) cell proliferation and increases the efficacy of the proteasome inhibitor bortezomib. Here, we defined the mechanisms of iron toxicity in MM.1S, U266, H929, and OPM-2 MM cell lines, and validated this strategy in preclinical studies using Vk*MYC mice as MM model. High-dose ferric ammonium citrate triggered cell death in all cell lines tested, increasing malondialdehyde levels, the by-product of lipid peroxidation and index of ferroptosis. In addition, iron exposure caused dose-dependent accumulation of polyubiquitinated proteins in highly iron-sensitive MM.1S and H929 cells, suggesting that proteasome workload contributes to iron sensitivity. Accordingly, high iron concentrations inhibited the proteasomal chymotrypsin-like activity of 26S particles and of MM cellular extracts in vitro. In all MM cells, bortezomib-iron combination induced persistent lipid damage, exacerbated bortezomib-induced polyubiquitinated proteins accumulation, and triggered cell death more efficiently than individual treatments. In Vk*MYC mice, addition of iron dextran or ferric carboxymaltose to the bortezomib-melphalan-prednisone (VMP) regimen increased the therapeutic response and prolonged remission without causing evident toxicity. We conclude that iron loading interferes both with redox and protein homeostasis, a property that can be exploited to design novel combination strategies including iron supplementation, to increase the efficacy of current MM therapies
New AGNs discovered by H.E.S.S
During the last year, six new Active Galactic Nuclei (AGN) have been
discovered and studied by H.E.S.S. at Very High Energies (VHE). Some of these
recent discoveries have been made thanks to new enhanced analysis methods and
are presented at this conference for the first time. The three blazars 1ES
0414+009, SHBL J001355.9-185406 and 1RXS J101015.9-311909 have been targeted
for observation due to their high levels of radio and X-ray fluxes, while the
Fermi/LAT catalogue of bright sources triggered the observation of PKS 0447-439
and AP Librae. Additionally, the BL Lac 1ES 1312-423 was discovered in the
field-of-view (FoV) of Centaurus A thanks to the large exposure dedicated by
H.E.S.S. to this particularly interesting source. The newly-discovered sources
are presented here and in three companion presentations at this conference.Comment: 8 pages, 3 figures, proceeding from the 25th Texas Symposium on
Relativistic Astrophysics (Heidelberg, Germany, 2010
Absolute properties of the binary system BB Pegasi
We present a ground based photometry of the low-temperature contact binary BB
Peg. We collected all times of mid-eclipses available in literature and
combined them with those obtained in this study. Analyses of the data indicate
a period increase of 3.0(1) x 10^{-8} days/yr. This period increase of BB Peg
can be interpreted in terms of the mass transfer 2.4 x 10^{-8} Ms yr^{-1} from
the less massive to the more massive component. The physical parameters have
been determined as Mc = 1.42 Ms, Mh = 0.53 Ms, Rc = 1.29 Rs, Rh = 0.83 Rs, Lc =
1.86 Ls, and Lh = 0.94 Ls through simultaneous solution of light and of the
radial velocity curves. The orbital parameters of the third body, that orbits
the contact system in an eccentric orbit, were obtained from the period
variation analysis. The system is compared to the similar binaries in the
Hertzsprung-Russell and Mass-Radius diagram.Comment: 17 pages, 3 figures, accepted for Astronomical Journa
The gas turbulence in planetary nebulae: quantification and multi-D maps from long-slit, wide-spectral range echellogram
This methodological paper is part of a short series dedicated to the
long-standing astronomical problem of de-projecting the bi-dimensional,
apparent morphology of a three-dimensional distribution of gas. We focus on the
quantification and spatial recovery of turbulent motions in planetary nebulae
(and other classes of expanding nebulae) by means of long-slit echellograms
over a wide spectral range. We introduce some basic theoretical notions,
discuss the observational methodology, and develop an accurate procedure
disentangling all broadening components of the velocity profile in all spatial
positions of each spectral image. This allows us to extract random, non-thermal
motions at unprecedented accuracy, and to map them in 1-, 2- and 3-dimensions.
We present the solution to practical problems in the multi-dimensional
turbulence-analysis of a testing-planetary nebula (NGC 7009), using the
three-step procedure (spatio-kinematics, tomography, and 3-D rendering)
developed at the Astronomical Observatory of Padua. In addition, we introduce
an observational paradigm valid for all spectroscopic parameters in all classes
of expanding nebulae. Unsteady, chaotic motions at a local scale constitute a
fundamental (although elusive) kinematical parameter of each planetary nebula,
providing deep insights on its different shaping agents and mechanisms, and on
their mutual interaction. The detailed study of turbulence, its stratification
within a target and (possible) systematic variation among different sub-classes
of planetary nebulae deserve long-slit, multi-position angle, wide-spectral
range echellograms containing emissions at low-, medium-, and high-ionization,
to be analyzed pixel-to-pixel with a straightforward and versatile methodology,
extracting all the physical information stored in each frame at best.Comment: 11 page, 10 figures, A&A in pres
Charge fluctuations and electron-phonon interaction in the finite- Hubbard model
In this paper we employ a gaussian expansion within the finite-
slave-bosons formalism to investigate the momentum structure of the
electron-phonon vertex function in the Hubbard model as function of and
. The suppression of large momentum scattering and the onset a small- peak structure, parametrized by a cut-off , are shown to be
essentially ruled by the band narrowing factor due to the
electronic correlation. A phase diagram of and in the whole
- space is presented. Our results are in more than qualitative agreement
with a recent numerical analysis and permit to understand some anomalous
features of the Quantum Monte Carlo data.Comment: 4 pages, eps figures include
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