176 research outputs found
Constraining massive gravity with recent cosmological data
A covariant formulation of a theory with a massive graviton and no negative
energy state has been recently proposed as an alternative to the usual General
Relativity framework. For a spatially flat homogenous and isotropic universe,
the theory introduces modified Friedmann equations where the standard matter
term is supplemented by four effective fluids mimicking dust, cosmological
constant, quintessence and stiff matter, respectively. We test the viability of
this massive gravity formulation by contrasting its theoretical prediction to
the Hubble diagram as traced by Type Ia Supernovae (SNeIa) and Gamma Ray Bursts
(GRBs), the measurements from passively evolving galaxies, Baryon
Acoustic Oscillations (BAOs) from galaxy surveys and the distance priors from
the Cosmic Microwave Background Radiation (CMBR) anisotropy spectrum. It turns
out that the model is indeed able to very well fit this large dataset thus
offering a viable alternative to the usual dark energy framework. We finally
set stringent constraints on its parameters also narrowing down the allowed
range for the graviton mass.Comment: 10 pages, 1 figure, 2 tables, accepted for publication on Physical
Review
Accelerating cosmology in Rastall's theory
In an attempt to look for a viable mechanism leading to a present-day
accelerated expansion, we investigate the possibility that the observed cosmic
speed up may be recovered in the framework of the Rastall's theory, relying on
the non-conservativity of the stress-energy tensor, i.e. . We derive the modified Friedmann equations and show that they
correspond to Cardassian-like equations. We also show that, under suitable
assumptions on the equation of state of the matter term sourcing the
gravitational field, it is indeed possible to get an accelerated expansion, in
agreement with the Hubble diagram of both Type Ia Supernovae (SNeIa) and Gamma
Ray Bursts (GRBs). Unfortunately, to achieve such a result one has to postulate
a matter density parameter much larger than the typical
value inferred from cluster gas mass fraction data.Comment: 8 pages, 1 eps figure; revised to match the version accepted for
publication in Il Nuovo Cimento
Some Experimental Investigations on Gas Turbine Cooling Performed with Infrared Thermography at Federico II
This paper reviews some experimental measurements of convective heat transfer coefficient distributions which are connected with the cooling of gas turbines, performed by the authors' research group at the University of Naples Federico II with infrared thermography. Measurements concern impinging jets, cooling of rotating disks, and gas turbine blades, which are either stationary or rotating. The heated thin foil sensor, associated with the detection of surface temperature by means of infrared thermography, is exploited to accurately measure detailed convective heat transfer coefficient maps. The paper also intends to show how to correctly apply the infrared technique in a variety of gas turbines cooling problems
MSF: An Efficient Mobile Phone Sensing Framework
Recent evolutions in smartphones, today provided with several sensors, have the strong processing capabilities needed to extract from raw sensed data sensor meaningful high-level views of the physical context around the user. A new promising research area called mobile sensing promotes completely decentralized sensing based on smartphone capabilities only. However, current mobile sensing solutions are not very mature; yet, because they are based on ad hoc software solutions tailored to one specific technical problem (e.g., power management, resource locking, etc.), they are difficult to reuse and integrate in different projects, and they do not focus on the performance efficiency of the monitoring support. To overcome those limitations, this paper proposes Mobile Sensing Framework (MSF), a flexible platform to ease the development of mobile sensing applications through the definition of a common set of facilities that mask all low-level technical details in reading and processing raw sensor data. MSF has been optimized also to enhance performances for Android-based systems, and we report an extensive set of experimental results that assess our architecture and quantitatively compare it with a selection of other mobile sensing systems by showing that MSF outperforms them by presenting lower CPU usage and memory footprints
Effects of the stroke length and nozzle-to-plate distance on synthetic jet impingement heat transfer
This study focuses on the combined e ect of the nozzle-to-plate distance andof the stroke length on the cooling performances of impinging synthetic jets.Infrared thermography is used as temperature transducer in conjunction withthe heated thin foil heat transfer sensor to measure time- and phase-averagedconvective heat transfer...The authors wish to thank Mr. G. Sicardi for contributing the realization
of the experimental setup. Carlo Salvatore Greco, Andrea Ianiro and Gennaro
Cardone have been partially supported by Grant DPI2016-79401-R funded by
the Spanish State Research Agency (SRA) and European Regional Development
Fund (ERDF).Publicad
Radial-orbit instability in modified Newtonian dynamics
The stability of radially anisotropic spherical stellar systems in modified
Newtonian dynamics (MOND) is explored by means of numerical simulations
performed with the N-body code N-MODY. We find that Osipkov-Merritt MOND models
require for stability larger minimum anisotropy radius than equivalent
Newtonian systems (ENSs) with dark matter, and also than purely baryonic
Newtonian models with the same density profile. The maximum value for stability
of the Fridman-Polyachenko-Shukhman parameter in MOND models is lower than in
ENSs, but higher than in Newtonian models with no dark matter. We conclude that
MOND systems are substantially more prone to radial-orbit instability than ENSs
with dark matter, while they are able to support a larger amount of kinetic
energy stored in radial orbits than purely baryonic Newtonian systems. An
explanation of these results is attempted, and their relevance to the MOND
interpretation of the observed kinematics of globular clusters, dwarf
spheroidal and elliptical galaxies is briefly discussed.Comment: 9 pages, 4 figures, accepted for publication in MNRA
Dual inhibition of TGFβ and AXL as a novel therapy for human colorectal adenocarcinoma with mesenchymal phenotype
A subset of colorectal cancer (CRC) with a mesenchymal phenotype (CMS4) displays an aggressive disease, with an increased risk of recurrence after surgery, reduced survival, and resistance to standard treatments. It has been shown that the AXL and TGFβ signaling pathways are involved in epithelial-to-mesenchymal transition, migration, metastatic spread, and unresponsiveness to targeted therapies. However, the prognostic role of the combination of these biomarkers and the anti-tumor effect of AXL and TGFβ inhibition in CRC still has to be assessed. To evaluate the role of AXL and TGFβ as negative biomarker in CRC, we conducted an in-depth in silico analysis of CRC samples derived from the Gene Expression Omnibus. We found that AXL and TGFβ receptors are upregulated in CMS4 tumors and are correlated with an increased risk of recurrence after surgery in stage II/III CRC and a reduced overall survival. Moreover, we showed that AXL receptor is differently expressed in human CRC cell lines. Dual treatment with the TGFβ galunisertib and the AXL inhibitor, bemcentinib, significantly reduced colony formation and migration capabilities of tumor cells and displayed a strong anti-tumor activity in 3D spheroid cultures derived from patients with advanced CRC. Our work shows that AXL and TGFβ receptors identify a subgroup of CRC with a mesenchymal phenotype and correlate with poor prognosis. Dual inhibition of AXL and TGFβ could represent a novel therapeutic strategy for patients with this aggressive disease
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