Showing papers by "Roma Tre University published in 2006"

Estrogen signaling multiple pathways to impact gene transcription.

Abstract: Steroid hormones exert profound effects on cell growth, development, differentiation, and homeostasis. Their effects are mediated through specific intracellular steroid receptors that act via multiple mechanisms. Among others, the action mechanism starting upon 17beta-estradiol (E2) binds to its receptors (ER) is considered a paradigmatic example of how steroid hormones function. Ligand-activated ER dimerizes and translocates in the nucleus where it recognizes specific hormone response elements located in or near promoter DNA regions of target genes. Behind the classical genomic mechanism shared with other steroid hormones, E2 also modulates gene expression by a second indirect mechanism that involves the interaction of ER with other transcription factors which, in turn, bind their cognate DNA elements. In this case, ER modulates the activities of transcription factors such as the activator protein (AP)-1, nuclear factor-kappaB (NF-kappaB) and stimulating protein-1 (Sp-1), by stabilizing DNA-protein complexes and/or recruiting co-activators. In addition, E2 binding to ER may also exert rapid actions that start with the activation of a variety of signal transduction pathways (e.g. ERK/MAPK, p38/MAPK, PI3K/AKT, PLC/PKC). The debate about the contribution of different ER-mediated signaling pathways to coordinate the expression of specific sets of genes is still open. This review will focus on the recent knowledge about the mechanism by which ERs regulate the expression of target genes and the emerging field of integration of membrane and nuclear receptor signaling, giving examples of the ways by which the genomic and non-genomic actions of ERs on target genes converge.

Search for neutral MSSM Higgs bosons at LEP

Abstract: The four LEP collaborations, ALEPH, DELPHI, L3 and OPAL, have searched for the neutral Higgs bosons which are predicted by the Minimal Supersymmetric standard model (MSSM). The data of the four collaborations are statistically combined and examined for their consistency with the background hypothesis and with a possible Higgs boson signal. The combined LEP data show no significant excess of events which would indicate the production of Higgs bosons. The search results are used to set upper bounds on the cross-sections of various Higgs-like event topologies. The results are interpreted within the MSSM in a number of “benchmark” models, including CP-conserving and CP-violating scenarios. These interpretations lead in all cases to large exclusions in the MSSM parameter space. Absolute limits are set on the parameter cosβ and, in some scenarios, on the masses of neutral Higgs bosons.

The Emergence of Life: From Chemical Origins to Synthetic Biology

Abstract: Preface 1. The conceptual framework of the research on the origin of life on Earth 2. Approaches to the definitions of life 3. Selection in prebiotic chemistry - why this ... and not that? 4. The bottle neck - macromolecular sequences 5. Self-organization 6. Emergence and emergent properties 7. Self-replication and self-reproduction 8. Autopoiesis - the logic of cellular life 9. Compartments 10. Reactivity and transformation of vesicles 11. Approaches to the minimal cell Outlook Bibliography.

Elastic J/psi production at HERA

Abstract: Cross sections for elastic production of J/Psi mesons in photoproduction and electroproduction are measured in electron proton collisions at HERA using an integrated luminosity of 55 pb^{-1}. Results are presented for photon virtualities Q^2 up to 80 GeV^2. The dependence on the photon-proton centre of mass energy W_{gamma p} is analysed in the range 40 < \Wgp < 305 GeV in photoproduction and 40 < \Wgp < 160 GeV in electroproduction. The \Wgp dependences of the cross sections do not change significantly with Q^2 and can be described by models based on perturbative QCD. Within such models, the data show a high sensitivity to the gluon density of the proton in the domain of low Bjorken x and low Q^2. Differential cross sections d\sigma/dt, where t is the squared four-momentum transfer at the proton vertex, are measured in the range |t|<1.2 GeV^2 as functions of \Wgp and Q^2. Effective Pomeron trajectories are determined for photoproduction and electroproduction. The J/Psi production and decay angular distributions are consistent with s-channel helicity conservation. The ratio of the cross sections for longitudinally and transversely polarised photons is measured as a function of Q^2 and is found to be described by perturbative QCD based models.

Mapping mantle flow during retreating subduction: Laboratory models analyzed by feature tracking

Abstract: [1] Three-dimensional dynamically consistent laboratory models are carried out to model the large-scale mantle circulation induced by subduction of a laterally migrating slab. A laboratory analogue of a slab–upper mantle system is set up with two linearly viscous layers of silicone putty and glucose syrup in a tank. The circulation pattern is continuously monitored and quantitatively estimated using a feature tracking image analysis technique. The effects of plate width and mantle viscosity/density on mantle circulation are systematically considered. The experiments show that rollback subduction generates a complex three-dimensional time-dependent mantle circulation pattern characterized by the presence of two distinct components: the poloidal and the toroidal circulation. The poloidal component is the answer to the viscous coupling between the slab motion and the mantle, while the toroidal one is produced by lateral slab migration. Spatial and temporal features of mantle circulation are carefully analyzed. These models show that (1) poloidal and toroidal mantle circulation are both active since the beginning of the subduction process, (2) mantle circulation is intermittent, (3) plate width affects the velocity and the dimension of subduction induced mantle circulation area, and (4) mantle flow in subduction zones cannot be correctly described by models assuming a two-dimensional steady state process. We show that the intermittent toroidal component of mantle circulation, missed in those models, plays a crucial role in modifying the geometry and the efficiency of the poloidal component.

Layout and performance of RPCs used in the Argo-YBJ experiment

Abstract: The layout of the RPCs, used in the Argo-YBJ experiment to image with a high space-time granularity the atmospheric shower, is described in this paper. The detector has been assembled to provide both digital and analog informations in order to cover a wide particle density range with a time accuracy of 1 ns. The experimental results obtained operating the chambers in streamer mode at sea level with a standard gas mixture are presented.

Continuous symmetries of difference equations

Abstract: Lie group theory was originally created more than 100 years ago as a tool for solving ordinary and partial differential equations. In this article we review the results of a much more recent program: the use of Lie groups to study difference equations. We show that the mismatch between continuous symmetries and discrete equations can be resolved in at least two manners. One is to use generalized symmetries acting on solutions of difference equations, but leaving the lattice invariant. The other is to restrict them to point symmetries, but to allow them to also transform the lattice.

Three-dimensional instantaneous mantle flow induced by subduction

Abstract: [1] We conduct three-dimensional subduction experiments by a finite element approach to study flow around slabs, which are prescribed based on a transient stage of upper mantle subduction from a laboratory model. Instantaneous velocity field solutions are examined, focusing on the toroidal vs. poloidal components as a function of boundary conditions, plate width, and viscosity contrast between slab and mantle. We show how the slab-to-mantle viscosity ratio determines the strength of toroidal flow, and find that the toroidal flow component peaks for slab/mantle viscosity ratios ∼100, independent of slab width or geometry.

Probing the Evolution of Infrared Properties of z ∼ 6 Quasars: Spitzer Observations

Abstract: We present Spitzer observations of 13 z ~ 6 quasars using the Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS). All the quasars except SDSS J000552.34-000655.8 (SDSS J0005-0006) were detected with high signal-to-noise ratio in the four IRAC channels and the MIPS 24 μm band, while SDSS J0005-0006 was marginally detected in the IRAC 8.0 μm band and not detected in the MIPS 24 μm band. We find that most of these quasars have prominent emission from hot dust, as evidenced by the observed 24 μm fluxes. Their spectral energy distributions (SEDs) are similar to those of low-redshift quasars at rest frame 0.15-3.5 μm, suggesting that accretion disks and hot-dust structures for these sources have already reached maturity. However, SDSS J0005-0006 has an unusual SED that lies significantly below low-redshift SED templates at rest frame 1 and 3.5 μm and thus shows a strong near-IR (NIR) deficit and no hot-dust emission. Type I quasars with extremely small NIR-to-optical flux ratios such as SDSS J0005-0006 are not found in low-redshift quasar samples, indicating that SDSS J0005-0006 has different dust properties at high redshift. We combine the Spitzer observations with X-ray, UV/optical, millimeter/submillimeter, and radio observations to determine bolometric luminosities for all the quasars. We find that the four quasars with central black hole mass measurements have Eddington ratios of order unity.

Transverse systems along the extensional Tyrrhenian margin of central Italy and their influence on volcanism

Abstract: [1] The Tyrrhenian margin of central Italy has undergone Plio-Quaternary extension, developing NW-SE normal faults and NE-SW faults. The NE-SW faults decrease in frequency toward NE with the stretching factor β, becoming negligible for β 0.21. These data suggest that the NE-SW transtensive structures are transfer faults of the NW-SE normal faults due to relevant differential extension (Δβ > 0.21) within a stretched crust (β > 1.3). The minor dip-slip and strike-slip components of the NE-SW and NW-SE faults, respectively, possibly result from the NW-SE extension due to the southeastward slab retreat beneath the Calabrian arc. The NE-SW and NW-SE extensions in the central southern Tyrrhenian Sea account for the composite kinematics of the NE-SW structures, which, in turn, exert a twofold role in controlling volcanism. Where their dip-slip component forms basins, the associated decompression induces magma accumulation (developing central volcanoes) at the intersection among NW-SE and NE-SW systems. Where transfer faults are mainly strike slip, their inferred subvertical attitude enhances their permeability to magma, accounting for the observed NE-SW fissure eruptions. Regional extension, forming NW-SE faults, enhances the overall generation and rise of magma along the margin, but NE-SW structures focus magma rise and emplacement at shallower levels.

Corporate social responsability and value creation. Determinants and mutual relationships in a sample of European listed firms.

Abstract: The purpose of this paper is twofold: i) to point out the determinants of a firm orientation to stakeholders' interests; ii) to analyze the relationship between shareholder value and stakeholder value as firm goals. Both issues are empirically verified on a sample of European listed companies. Empirical evidence shows that time, nationality, industry, size and level of growth of a firm determine its stakeholder ratings. Although the empirical evidence presented concerning the link between the creation of shareholder value and stakeholder value is neither unequivocal nor statistically significant, it can be inferred that a firm pursues stakeholders satisfaction to achieve a better value performance.

Correlated increase in CO2 fumarolic content and diffuse emission from La Fossa crater (Vulcano, Italy): Evidence of volcanic unrest or increasing gas release from a stationary deep magma body?

Abstract: [1] The peculiarity of the quiescent La Fossa volcano is the occurrence of “crises” characterized by strong increases of fumarole T and output and by chemical changes indicative of an increasing input of magmatic fluids. Several surveys carried out during a new “crisis” began in November 2004 indicate that the total diffuse CO2 emission for the crater area increases by one order of magnitude during crises (up to 1600 ton·d−1 in December 2005). Concern exists on the possibility that these crises be related to an unrest process leading to eruption. The repetition along decades of the same gas compositional variations during crises, their temporal coincidence with increases of the local shallow seismicity, and the lack of any significant ground motion, rather suggest that they correspond to moments of increasing volatile release from a stationary magma system.

An SRR based microwave absorber

Abstract: In this letter, the authors present the design of a resonant microwave absorber made by a proper array of split ring resonators (SRRs). The physical mechanism behind the operation of the proposed component is based on the SRR resonance, arising when the structure is excited by a properly polarized impinging wave. A resistive sheet, located nearby the resonating SRRs, absorbs the electromagnetic energy of the incoming field, without destroying the resonance condition of the SRRs. The two relevant features of the proposed absorber are its electrical thickness, which is very small compared with the operating wavelength, and the lack of a metallic backing, which represent a common part of conventional absorber layouts. The full-wave simulations presented in the paper confirm the effectiveness of the proposed absorber for microwave applications. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 2171–2175, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21891

Subduction convergence and the mode of backarc extension in the Mediterranean region

Abstract: 30-35 Ma ago a major change occurred in the Mediterranean region, from a regionally compressional subduction coeval with the formation of Alpine mountain belts, to extensional subduction and backarc rifting. Backarc extension was accompanied by gravitational spreading of the mountain belts formed before this Oligocene revolution. Syn-rift basins formed during this process above detachments and low-angle normal faults. Parameters that control the formation and the kinematics of such flat-lying detachments are still poorly understood. From the Aegean Sea to the Tyrrhenian Sea and the Alboran Sea, we have analysed onshore the deformation and P-T-t evolution of the ductile crust exhumed by extension, and the transition from ductile to brittle conditions as well as the relations between deep deformation and basin formation. We show that the sense of shear along crustal-scale detachments is toward the trench when subduction proceeds with little or no convergence (northern Tyrrhenian and Alboran after 20 Ma) and away from the trench in the case of true convergence (Aegean). We tentatively propose a scheme explaining how interactions between the subducting slab and the mantle control the basal shear below the upper plate and the geometry and distribution of detachments and associated sedimentary basins. We propose that ablative subduction below the Aegean is responsible for the observed kinematics on detachments (i.e. away from the trench). The example of the Betic Cordillera and the Rif orogen, where the directions of stretching were different in the lower and the upper crust and changed through time, is also discussed following this hypothesis.

Tectonics and seismicity of the Tindari Fault System, southern Italy: Crustal deformations at the transition between ongoing contractional and extensional domains located above the edge of a subducting slab

Abstract: [1] The Tindari Fault System (southern Tyrrhenian Sea, Italy) is a regional zone of brittle deformation located at the transition between ongoing contractional and extensional crustal compartments and lying above the western edge of a narrow subducting slab. Onshore structural data, an offshore seismic reflection profile, and earthquake data are analyzed to constrain the present geometry of the Tindari Fault System and its tectonic evolution since Neogene, including the present seismicity. Results show that this zone of deformation consists of a broad NNW trending system of faults including sets of right-lateral, left-lateral, and extensional faults as well as early strike-slip faults reworked under late extension. Earthquakes and other neotectonic data provide evidence that the Tindari Fault System is still active in the central and northern sectors and mostly accommodates extensional or right-lateral transtensional displacements on a diffuse array of faults. From these data, a multiphase tectonic history is inferred, including an early phase as a right-lateral strike-slip fault and a late extensional reworking under the influence of the subduction-related processes, which have led to the formation of the Tyrrhenian back-arc basin. Within the present, regional, geodynamic context, the Tindari Fault System is interpreted as an ongoing accommodation zone between the adjacent contractional and extensional crustal compartments, these tectonic compartments relating to the complex processes of plate convergence occurring in the region. The Tindari Fault System might also be included in an incipient, oblique-extensional, transfer zone linking the ongoing contractional belts in the Calabrian-Ionian and southern Tyrrhenian compartments.

Lorentz beams and symmetry properties in paraxial optics

Abstract: A new kind of tridimensional scalar optical beams is introduced These beams are called Lorentz beams because the form of their transverse pattern in the source plane is the product of two independent Lorentz functions A closed-form expression of free-space propagation under the paraxial limit is derived Moreover, as the slowly varying part of these fields fulfils the scalar paraxial wave equation, it follows that there also exist Lorentz–Gauss beams, ie beams obtained by multiplying the original Lorentz beam by a Gaussian apodization function Although the existence of Lorentz–Gauss beams can be shown by using two different and independent ways obtained recently by Kiselev (2004 Opt Spectrosc 96 497–81) and Gutierrez-Vega and Bandres (2005 J Opt Soc Am 22 289–98), here we have followed a third different approach, which makes use of Lie's group theory, and which possesses the merit to put into evidence the symmetries present in paraxial optics

Spatial soliton all-optical logic gates

Abstract: We demonstrate some basic all-optical (electrically unbiased) logic gates in azobenzene liquid crystalline cells, exploiting their large nonlinearity for light localization and the trans-cis photoisomerization for all-optical external control. Spatial solitons were excited at microwatt power levels at 632.8 nm, whereas gating and switching were achieved with milliwatt beams at 409 nm

Implementation and Sensorless Vector-Control Design and Tuning Strategy for SMPM Machines in Fan-Type Applications

Abstract: This paper presents a complete design methodology for the sensorless vector control of permanent magnet synchronous machine (PMSM) motor drives in fan-type applications. The proposed strategy is built over a linear asymptotic state observer used to estimate the PMSM back-EMF, and a novel tracking controller based on a phase-locked loop (PLL) system, which by synchronizing the estimated and actual d-q frames estimates the rotor speed and position. The paper presents the complete derivation of all associated control-loops, namely state observer, tracking controller, d-q axes current regulator, speed controller, an anti-saturation control loop - which provides inherent operation in the flux-weakening region, and all corresponding anti-windup loops. Detailed design rules are provided for each of these loops, respectively verified through time-domain simulations, frequency-response analysis, and experimental results using a 300 Vdc 3.5 kW PMSM PWM motor-drive, validating both the design methodology and the excellent performance attained by the proposed control strategy

Hydrogeological insights at Stromboli volcano (Italy) from geoelectrical, temperature, and CO2 soil degassing investigations.

Abstract: [1] Finding the geometry of aquifers in an active volcano is important for evaluating the hazards associated with phreato-magmatic phenomena and incidentally to address the problem of water supply. A combination of electrical resistivity tomography (ERT), self-potential, CO2, and temperature measurements provides insights about the location and pattern of ground water flow at Stromboli volcano. The measurements were conducted along a NE-SW profile across the island from Scari to Ginostra, crossing the summit (Pizzo) area. ERT data (electrode spacing 20 m, depth of penetration of ∼200 m) shows the shallow architecture through the distribution of the resistivities. The hydrothermal system is characterized by low values of the resistivity ( 2000 Ω m) except on the North-East flank of the volcano where a cold aquifer is detected at a depth of ∼80 m (resistivity in the range 70–300 Ω m). CO2 and temperature measurements corroborate the delineation of the hydrothermal body in the summit part of the volcano while a negative self-potential anomaly underlines the position of the cold aquifer.

A full-wave numerical approach for modal analysis of 1-D periodic microstrip structures

Abstract: In this paper, a full-wave numerical approach for the analysis and design of one-dimensional (1-D) printed periodic structures is presented. Electromagnetic-bandgap structures and leaky-wave antennas are important special cases of structures that can be analyzed. The proposed technique is based on a mixed-potential integral equation in a unit-cell environment solved by the method of moments in the spatial domain through a triangular Delaunay mesh. The 1-D periodic vector and scalar Green's functions are derived in the spectral domain and an efficient sum of spectral integrals is carried out to obtain the spatial-domain quantities. An appropriate choice of the spectral integration path is used in order to consider leakage effects. The method developed here can thus analyze both bound and leaky modes on printed structures that have an arbitrary metallization within the unit cell.

Measurement of $F_2^{c\bar{c}}$ and $F_2^{b\bar{b}}$ at Low $Q^2$ and x using the H1 Vertex Detector at HERA

Abstract: Measurements are presented of inclusive charm and beauty cross sections in e^+p collisions at HERA for values of photon virtuality 12 \le Q^2 \le 60 GeV^2 and of the Bjorken scaling variable 0.0002 \le x \le 0.005. The fractions of events containing charm and beauty quarks are determined using a method based on the impact parameter, in the transverse plane, of tracks to the primary vertex, as measured by the H1 vertex detector. Values for the structure functions F_2^{c\bar{c}} and F_2^{b\bar{b}} are obtained. This is the first measurement of F_2^{b\bar{b}} in this kinematic range. The results are found to be compatible with the predictions of perturbative quantum chromodynamics and withprevious measurements of F_2^{c\bar{c}}.