610 research outputs found
Cosmology of the Randall-Sundrum model after dilaton stabilization
We provide the first complete analysis of cosmological evolution in the Randall-Sundrum model with stabilized dilaton. We give the exact expansion law for matter densities on the two branes with arbitrary equations of state. The effective four-dimensional theory leads to standard cosmology at low energy. The limit of validity of the low energy theory and possible deviations from the ordinary expansion law in the high energy regime are finally discussed
Extracorporeal membrane oxygenation as "bridge" to lung transplantation: what remains in order to make it standard of care?
Since its introduction into clinical practice, lung transplantation
(LTx) is gradually becoming a worldwide standard treatment for
patients with a broad spectrum of end-stage respiratory diseases
(1\u20133). From 1995 to 2010, more than 30,000 LTx have been
performed, and it is worth noting that in recent years the number
of LTx has been progressively increasing to more than
3,000/year in 2010, with a post-transplant graft half-life that
went from 4.7 in the 1990s to 5.9 in the new millennium (4).
However, the crude mortality rate of patients awaiting LTx is
higher than mortality for other solid organs. Mortality rate in
2009 for patients on the waiting list for LTx was about 14.1% in
North America (www.srtr.org) and 14.7% in Italy (www.airt.it).
What are the reasons for these unacceptable mortality rates?
First, patients have to wait for the graft longer than patients
waiting for other organs because of the small number of lungs
suitable for transplantation (5). Second is the lack of supportive
therapies that are able to replace respiratory function when
the primary pulmonary diseases evolve from \u201crespiratory insufficiency\u201d
to \u201crespiratory failure,\u201d characterized by refractory
hypoxemia and hypercapnia
Radiative Inflation and Dark Energy
We propose a model based on radiative symmetry breaking that combines
inflation with Dark Energy and is consistent with the WMAP 7-year regions. The
radiative inflationary potential leads to the prediction of a spectral index
0.955 \lesssim n_S \lesssim 0.967 and a tensor to scalar ratio 0.142 \lesssim r
\lesssim 0.186, both consistent with current data but testable by the Planck
experiment. The radiative symmetry breaking close to the Planck scale gives
rise to a pseudo Nambu-Goldstone boson with a gravitationally suppressed mass
which can naturally play the role of a quintessence field responsible for Dark
Energy. Finally, we present a possible extra dimensional scenario in which our
model could be realised.Comment: 15 pages, 4 figures; v2: references added, appendix added, Section 5
slightly modified; content matches published versio
Biological Responses to Cadmium Stress in Liverwort Conocephalum conicum (Marchantiales)
Oxidative damage (production and localization of reactive oxygen species) and related response mechanisms (activity of antioxidant enzymes), and induction of Heat Shock Protein 70 expression, have been studied in the toxi-tolerant liverwort Conocephalum conicum (Marchantiales) in response to cadmium stress using two concentrations (36 and 360 µM CdCl2). Cadmium dose-dependent production of reactive oxygen species (ROS) and related activity of antioxidant enzymes was observed. The expression level of heat shock protein (Hsp)70, instead, was higher at 36 µM CdCl2 in comparison with the value obtained after exposure to 360 µM CdCl2, suggesting a possible inhibition of the expression of this stress gene at higher cadmium exposure doses. Biological responses were related to cadmium bioaccumulation. Since C. conicum was able to respond to cadmium stress by modifying biological parameters, we discuss the data considering the possibility of using these biological changes as biomarkers of cadmium pollution
Parity violation in the Cosmic Microwave Background from a pseudoscalar inflaton
If the inflaton is a pseudoscalar, then it naturally interacts with gauge
fields via an axion-like coupling to . Through
this coupling, the rolling inflaton produces quanta of the gauge field, that in
their turn source the tensor components of the metric perturbations. Due to the
parity-violating nature of the system, the right- and the left-handed tensor
modes have different amplitudes. Such an asymmetry manifests itself in the form
of non-vanishing TB and EB correlation functions in the Cosmic Microwave
Background (CMB). We compute the amplitude of the parity-violating tensor modes
and we discuss two scenarios, consistent with the current data, where
parity-violating CMB correlation functions will be detectable in future
experiments.Comment: 9 pages, 1 figure; v2: a minor numerical mistake corrected,
references added; v3: minor changes, matches published versio
Goldberger-Wise variations: stabilizing brane models with a bulk scalar
Braneworld scenarios with compact extra-dimensions need the volume of the
extra space to be stabilized. Goldberger and Wise have introduced a simple
mechanism, based on the presence of a bulk scalar field, able to stabilize the
radius of the Randall-Sundrum model. Here, we transpose the same mechanism to
generic single-brane and two-brane models, with one extra dimension and
arbitrary scalar potentials in the bulk and on the branes. The single-brane
construction turns out to be always unstable, independently of the bulk and
brane potentials. In the case of two branes, we derive some generic criteria
ensuring the stabilization or destabilization of the system.Comment: 8 pages, 2 figures. 1 figure and one subsection added. version
published on PR
Review : Best Practices In Educating Sustainability and Heritage
This result has been produced as a part of O1 INTELECTUAL OUTPUT "01: Review of the Best Practices on Educating Sustainability and Heritage"
within HERSUS project, Erasmus + Strategic Partnerships for higher education
Maximal Temperature in Flux Compactifications
Thermal corrections have an important effect on moduli stabilization leading
to the existence of a maximal temperature, beyond which the compact dimensions
decompactify. In this note, we discuss generality of our earlier analysis and
apply it to the case of flux compactifications. The maximal temperature is
again found to be controlled by the supersymmetry breaking scale, T_{crit} \sim
\sqrt{m_{3/2} M_P}.Comment: 10 pages, 10 figures. v2:comment and references adde
Surface Superconductivity in Niobium for Superconducting RF Cavities
A systematic study is presented on the superconductivity (sc) parameters of
the ultrapure niobium used for the fabrication of the nine-cell 1.3 GHz
cavities for the linear collider project TESLA. Cylindrical Nb samples have
been subjected to the same surface treatments that are applied to the TESLA
cavities: buffered chemical polishing (BCP), electrolytic polishing (EP),
low-temperature bakeout (LTB). The magnetization curves and the complex
magnetic susceptibility have been measured over a wide range of temperatures
and dc magnetic fields, and also for di erent frequencies of the applied ac
magnetic field. The bulk superconductivity parameters such as the critical
temperature Tc = 9.26 K and the upper critical field Bc2(0) = 410 mT are found
to be in good agreement with previous data. Evidence for surface
superconductivity at fields above Bc2 is found in all samples. The critical
surface field exceeds the Ginzburg-Landau field Bc3 = 1.695Bc2 by about 10% in
BCP-treated samples and increases even further if EP or LTB are applied. From
the field dependence of the susceptibility and a power-law analysis of the
complex ac conductivity and resistivity the existence of two different phases
of surface superconductivity can be established which resemble the Meissner and
Abrikosov phases in the bulk: (1) coherent surface superconductivity, allowing
sc shielding currents flowing around the entire cylindrical sample, for
external fields B in the range between Bc2 and Bcohc3, and (2) incoherent
surface superconductivity with disconnected sc domains between Bcohc3 and Bc3.
The coherent critical surface field separating the two phases is found to be
Bcoh c3 = 0.81Bc3 for all samples. The exponents in the power law analysis are
different for BCP and EP samples, pointing to different surface topologies.Comment: 15 pages, 21 figures, DESY-Report 2004-02
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