Roma Tre University

About: Roma Tre University is a education organization based out in Rome, Lazio, Italy. It is known for research contribution in the topics: Large Hadron Collider & Galaxy. The organization has 4434 authors who have published 15352 publications receiving 374888 citations. The organization is also known as: Universita degli Studi Roma Tre & RomaTre.

On the transmission‐dominated to reprocessing‐dominated spectral state transitions in Seyfert 2 galaxies

Abstract: We present Chandra and XMM-Newton observations of a small sample (11 objects) of optically selected Seyfert 2 galaxies, for which ASCA and BeppoSAX had suggested Compton-thick obscuration of the active galactic nucleus (AGN). The main goal of this study is to estimate the rate of transitions between 'transmission-dominated' and 'reprocessing-dominated' states. We discover one new transition in NGC 4939, with a possible additional candidate in NGC 5643. This indicates a typical occurrence rate of at least ∼0.02 yr -1 . These transitions could be due to large changes of the obscuring gas column density, or to a transient dimming of the AGN activity, the latter scenario being supported by detailed analysis of the best-studied events. Independently of the ultimate mechanism, comparison of the observed spectral dynamics with Monte Carlo simulations demonstrates that the obscuring gas is largely inhomogeneous, with multiple absorbing components possibly spread through the whole range of distances from the nucleus between a fraction of parsecs up to several hundred parsecs. As a by-product of this study, we report the first measurement ever of the column density covering the AGN in NGC 3393 (N H ≃ 4.4 x 10 24 cm -2 ), and the discovery of soft X-ray extended emission, apparently aligned along the host galaxy main axis in NGC 5005. The latter object most likely hosts an historically misclassified low-luminosity Compton-thin AGN.

The Nutritional Flavanone Naringenin Triggers Antiestrogenic Effects by Regulating Estrogen Receptor α-Palmitoylation

Abstract: Naringenin (Nar) is a component of fruits and vegetables associated with healthful benefits, such as in osteoporosis, cancer, and cardiovascular diseases. These protective effects have been linked with Nar antiestrogenic as well as estrogenic activities. Previous studies indicate that Nar impaired estrogen receptor (ER) alpha signaling by interfering with ERalpha-mediated activation of ERK and phosphoinositide 3-kinase signaling pathways in the absence of effects at the transcriptional level. The present studies evaluated the hypothesis that these Nar antagonistic effects occur at the level of the plasma membrane. Our results indicate that Nar induces ERalpha depalmitoylation faster than 17beta-estradiol, which results in receptor rapid dissociation from caveolin-1. Furthermore, Nar impedes ERalpha to bind adaptor (modulator of nongenomic actions of the ER) and signaling (c-Src) proteins involved in the activation of the mitogenic signaling cascades (i.e. ERK and phosphoinositide 3-kinase). On the other hand, Nar induces the ER-dependent, but palmitoylation-independent, activation of p38 kinase, which in turn is responsible for Nar-mediated antiproliferative effects in cancer cells. Altogether, these data highlight new ER-dependent mechanisms on the root of antiproliferative and antiestrogenic effects of Nar. Moreover, the different modulation of ERalpha palmitoylation exerted by different ligands represents a pivotal mechanism that drives cancer cell to proliferation or apoptosis.

Leptonic decay constants $f_{K},f_{D},$ and $f_{{D}_{s}}$ with $N_{f} = 2+1+1$ twisted-mass lattice QCD

Abstract: We present a lattice QCD calculation of the pseudoscalar decay constants ${f}_{K}$, ${f}_{D}$ and ${f}_{{D}_{s}}$ performed using the gauge configurations produced by the European Twisted Mass Collaboration with ${N}_{f}=2+1+1$ dynamical quarks, which include in the sea, besides two light mass degenerate quarks, also the strange and charm quarks with masses close to their values in the real world. The simulations are based on a unitary setup for the two light mass-degenerate quarks and on a mixed action approach for the strange and charm quarks. We use data simulated at three different values of the lattice spacing in the range $0.06--0.09\text{ }\text{ }\mathrm{fm}$ and at pion masses in the range $210--450\text{ }\text{ }\mathrm{MeV}$. Our main results are ${f}_{{K}^{+}}/{f}_{{\ensuremath{\pi}}^{+}}=1.184(16)$, ${f}_{{K}^{+}}=154.4(2.0)\text{ }\text{ }\mathrm{MeV}$, which incorporate the leading strong isospin breaking correction due to the up and down quark mass difference, and ${f}_{K}=155.0(1.9)\text{ }\text{ }\mathrm{MeV}$, ${f}_{D}=207.4(3.8)\text{ }\text{ }\mathrm{MeV}$, ${f}_{{D}_{s}}=\phantom{\rule{0ex}{0ex}}247.2(4.1)\text{ }\text{ }\mathrm{MeV}$, ${f}_{{D}_{s}}/{f}_{D}=1.192(22)$ and $({f}_{{D}_{s}}/{f}_{D})/({f}_{K}/{f}_{\ensuremath{\pi}})=1.003(14)$ obtained in the isospin symmetric limit of QCD. Combined with the experimental measurements of the leptonic decay rates of kaon, pion, $D$ and ${D}_{s}$ mesons our results lead to the following determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements: $|{V}_{us}|=0.2269(29)$, $|{V}_{cd}|=0.2221(67)$ and $|{V}_{cs}|=1.014(24)$. Using the latest value of $|{V}_{ud}|$ from superallowed nuclear $\ensuremath{\beta}$ decays the unitarity of the first row of the CKM matrix is fulfilled at the per mill level.

GeSn/SiGeSn Heterostructure and Multi Quantum Well Lasers

Abstract: GeSn and SiGeSn are promising materials for the fabrication of a group IV laser source offering a number of design options from bulk to heterostructures and quantum wells. Here, we investigate GeSn/SiGeSn multi quantum wells using the optically pumped laser effect. Three complex heterostructures were grown on top of 200 nm thick strain-relaxed Ge0.9Sn0.1 buffers. The lasing is investigated in terms of threshold and maximal lasing operation temperature by comparing multiple quantum well to double heterostructure samples. Pumping under two different wavelengths of 1064 and 1550 nm yields comparable lasing thresholds. The design with multi quantum wells reduces the lasing threshold to 40 ± 5 kW/cm2 at 20 K, almost 10 times lower than for bulk structures. Moreover, 20 K higher maximal lasing temperatures were found for lower energy pumping of 1550 nm.

Search for resonances decaying into top-quark pairs using fully hadronic decays in pp collisions with ATLAS at √s=7 TeV

Abstract: A search for resonances produced in 7 TeV proton-proton collisions and decaying into top-quark pairs is described. In this Letter events where the top-quark decay produces two massive jets with large transverse momenta recorded with the ATLAS detector at the Large Hadron Collider are considered. Two techniques that rely on jet substructure are used to separate top-quark jets from those arising from light quarks and gluons. In addition, each massive jet is required to have evidence of an associated bottom-quark decay. The data are consistent with the Standard Model, and limits can be set on the production cross section times branching fraction of a Z′ boson and a Kaluza-Klein gluon resonance. These limits exclude, at the 95% credibility level, Z′ bosons with masses 0.70-1.00 TeV as well as 1.28-1.32 TeV and Kaluza-Klein gluons with masses 0.70-1.62 TeV.