Showing papers by "University of Catania published in 2010"

Observation of long-range, near-side angular correlations in proton-proton collisions at the LHC

Abstract: This is the pre-print version of the Published Article, which can be accessed from the link below - Copyright @ 2010 Springer Verlag

Elliptic Flow of Charged Particles in Pb-Pb Collisions at root s(NN)=2.76 TeV

Abstract: We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at root s(NN) p = 2.76 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region (vertical bar eta vertical bar < 0.8) and transverse momentum range 0.2 < p(t) < 5.0 GeV/c. The elliptic flow signal v(2), measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is 0.087 +/- 0.002(stat) +/- 0.003(syst) in the 40%-50% centrality class. The differential elliptic flow v(2)(p(t)) reaches a maximum of 0.2 near p(t) = 3 GeV/c. Compared to RHIC Au-Au collisions at root s(NN) = 200 GeV, the elliptic flow increases by about 30%. Some hydrodynamic model predictions which include viscous corrections are in agreement with the observed increase.

The age of temporary advantage

Abstract: The creation and management of temporary competitive advantages has emerged as an alternative to sustainable models of competitive advantage in the strategy literature. We review the literature and discuss questions related to the antecedents, consequences and the management temporary advantage in the introduction of this special issue. The overall goal is to ask: What would the field of strategic management look like if sustainable advantages did not exist? We summarize the papers published in this special issue and highlight directions for future research. Copyright © 2010 John Wiley & Sons, Ltd.

Cellular Stress Responses, The Hormesis Paradigm, and Vitagenes: Novel Targets for Therapeutic Intervention in Neurodegenerative Disorders

Abstract: Despite the capacity of chaperones and other homeostatic components to restore folding equilibrium, cells appear poorly adapted for chronic oxidative stress that increases in cancer and in metabolic and neurodegenerative diseases. Modulation of endogenous cellular defense mechanisms represents an innovative approach to therapeutic intervention in diseases causing chronic tissue damage, such as in neurodegeneration. This article introduces the concept of hormesis and its applications to the field of neuroprotection. It is argued that the hormetic dose response provides the central underpinning of neuroprotective responses, providing a framework for explaining the common quantitative features of their dose–response relationships, their mechanistic foundations, and their relationship to the concept of biological plasticity, as well as providing a key insight for improving the accuracy of the therapeutic dose of pharmaceutical agents within the highly heterogeneous human population. This article desc...

Measurement of the Depth of Maximum of Extensive Air Showers above 10(18) eV

Abstract: We describe the measurement of the depth of maximum, Xmax, of the longitudinal development of air showers induced by cosmic rays. Almost four thousand events above 10^18 eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/- 0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed.

Transverse-Momentum and Pseudorapidity Distributions of Charged Hadrons in pp Collisions at root s=7 TeV

Abstract: Charged-hadron transverse-momentum and pseudorapidity distributions in proton-proton collisions at root s = 7 TeV are measured with the inner tracking system of the CMS detector at the LHC. The charged-hadron yield is obtained by counting the number of reconstructed hits, hit pairs, and fully reconstructed charged-particle tracks. The combination of the three methods gives a charged-particle multiplicity per unit of pseudorapidity dN(ch)/d eta vertical bar(vertical bar eta vertical bar<0.5) = 5.78 +/- 0.01(stat) +/- 0.23(stat) for non-single-diffractive events, higher than predicted by commonly used models. The relative increase in charged-particle multiplicity from root s = 0.9 to 7 TeV is [66.1 +/- 1.0(stat) +/- 4.2(syst)]%. The mean transverse momentum is measured to be 0.545 +/- 0.005(stat) +/- 0.015(syst) GeV/c. The results are compared with similar measurements at lower energies.

Improved Energy Harvesting from Wideband Vibrations by Nonlinear Piezoelectric Converters

Abstract: Vibration harvesters typically are linear mass-spring devices working at resonance. A different approach is here proposed based on nonlinear converters that exploit stochastic resonance with white-noise excitation. It consists of a piezoelectric beam converter coupled to permanent magnets to create a bistable system. Under proper conditions, the system bounces between two stable states in response to random excitation, which significantly improves energy harvesting from wide-spectrum vibrations. The background theory is discussed based on a simplified monodimensional model which includes nonlinearity. A cantilever beam with added nonlinearity was simulated by using a MATLAB® Stochastic Differential Equation (SDE) Toolbox demonstrating the expected improvement under white-noise vibrations. Nonlinear converters were then realized by screen printing low-curing-temperature lead zirconate titanate (PZT) films on steel cantilevers equipped with magnets. Experimental tests were performed by measuring both the beam deflection and the output voltage under excitation by random vibrations at varying degree of nonlinearity added to the system. The obtained results show that the performances of the converter in terms of output voltage at parity of mechanical excitation are markedly improved when the system is made bistable. Furthermore, the principle was also preliminarily validated on a MEMS U-shaped cantilever beam that was purposely designed and fabricated in SOI technology. This demonstrates the possibility to downscale the principle here proposed in the perspective of a MEMS harvester based on nonlinear piezoelectric converters.

Idiopathic pulmonary fibrosis: a disease with similarities and links to cancer biology

Abstract: Several clinical trials have recently targeted specific pathways implicated in the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, IPF remains plagued by a median survival of 3 yrs and emphasises the need for further research with new insights and perspectives. The prevailing pathogenic hypotheses assume that either an inflammatory process or an independent epithelial/fibroblastic disorder may propagate the disease process. Based on knowledge developed with considerable scientific evidence, we provide our perspectives with an alternative point of view that IPF be considered as a neoproliferative disorder of the lung. Genetic alterations, response to growth and inhibitory signals, resistance to apoptosis, myofibroblast origin and behaviour, altered cellular communications, and intracellular signalling pathways are all fundamental pathogenic hallmarks of both IPF and cancer. The concept of IPF as a lethal malignant disorder of the lung might extend beyond the pathogenic link between these two diseases and disclose new pathogenic mechanisms leading to novel therapeutic options, adopted from cancer biology. Moreover, this vision might dawn the awareness of the public, political and scientific community of this devastating disease from an angle different from the current perception and provoke new ideas and studies to get a better understanding to control the otherwise relentless progressive disease.

Assessment of metabolic brain damage and recovery following mild traumatic brain injury: a multicentre, proton magnetic resonance spectroscopic study in concussed patients

Abstract: Concussive head injury opens a temporary window of brain vulnerability due to the impairment of cellular energetic metabolism. As experimentally demonstrated, a second mild injury occurring during this period can lead to severe brain damage, a condition clinically described as the second impact syndrome. To corroborate the validity of proton magnetic resonance spectroscopy in monitoring cerebral metabolic changes following mild traumatic brain injury, apart from the magnetic field strength (1.5 or 3.0 T) and mode of acquisition, we undertook a multicentre prospective study in which a cohort of 40 athletes suffering from concussion and a group of 30 control healthy subjects were admitted. Athletes (aged 16-35 years) were recruited and examined at three different institutions between September 2007 and June 2009. They underwent assessment of brain metabolism at 3, 15, 22 and 30 days post-injury through proton magnetic resonance spectroscopy for the determination of N-acetylaspartate, creatine and choline-containing compounds. Values of these representative brain metabolites were compared with those observed in the group of non-injured controls. Comparison of spectroscopic data, obtained in controls using different field strength and/or mode of acquisition, did not show any difference in the brain metabolite ratios. Athletes with concussion exhibited the most significant alteration of metabolite ratios at Day 3 post-injury (N-acetylaspartate/creatine: -17.6%, N-acetylaspartate/choline: -21.4%; P < 0.001 with respect to controls). On average, metabolic disturbance gradually recovered, initially in a slow fashion and, following Day 15, more rapidly. At 30 days post-injury, all athletes showed complete recovery, having metabolite ratios returned to values detected in controls. Athletes self-declared symptom clearance between 3 and 15 days after concussion. Results indicate that N-acetylaspartate determination by proton magnetic resonance spectroscopy represents a non-invasive tool to accurately measure changes in cerebral energy metabolism occurring in mild traumatic brain injury. In particular, this metabolic evaluation may significantly improve, along with other clinical assessments, the management of athletes suffering from concussion. Further studies to verify the effects of a second concussive event occurring at different time points of the recovery curve of brain metabolism are needed.

The Fluorescence Detector of the Pierre Auger Observatory

Abstract: The Pierre Auger Observatory is a hybrid detector for ultra-high energy cosmic rays. It combines a surface array to measure secondary particles at ground level together with a fluorescence detector to measure the development of air showers in the atmosphere above the array. The fluorescence detector comprises 24 large telescopes specialized for measuring the nitrogen fluorescence caused by charged particles of cosmic ray air showers. In this paper we describe the components of the fluorescence detector including its optical system, the design of the camera, the electronics, and the systems for relative and absolute calibration. We also discuss the operation and the monitoring of the detector. Finally, we evaluate the detector performance and precision of shower reconstructions.

Charge Pump Circuits: An Overview on Design Strategies and Topologies

Abstract: Due to the continuous power supply reduction, charge pumps circuits are widely used in integrated circuits (ICs) devoted to several kind of applications such as smart power, nonvolatile memories, switched capacitor circuits, operational amplifiers, voltage regulators, SRAMs, LCD drivers, piezoelectric actuators, RF antenna switch controllers, etc. The main focus of this tutorial manuscript is to provide a deep understanding of the charge pumps behavior, to present useful models and key parameters and to organically and in details discuss the optimized design strategies. Finally, an overview of the main different topologies is also included.

Small-world behavior in time-varying graphs.

Abstract: Connections in complex networks are inherently fluctuating over time and exhibit more dimensionality than analysis based on standard static graph measures can capture. Here, we introduce the concepts of temporal paths and distance in time-varying graphs. We define as temporal small world a time-varying graph in which the links are highly clustered in time, yet the nodes are at small average temporal distances. We explore the small-world behavior in synthetic time-varying networks of mobile agents and in real social and biological time-varying systems.

Increased Sclerostin Serum Levels Associated with Bone Formation and Resorption Markers in Patients with Immobilization-Induced Bone Loss

Abstract: Context: Sclerostin, a Wnt signaling antagonist on the osteoblasts produced by osteocytes, is regulated by mechanical strain and is implicated in the pathogenesis of disuse bone loss. There are no data on sclerostin in humans. Objective: The aim of the study was to evaluate sclerostin in patients immobilized after stroke, compared with control subjects, and to analyze its relationship with markers of bone formation and resorption. Design: This was a cross-sectional study. Setting and patients: We studied 40 postmenopausal women immobilized after a single episode of stroke 6 months or longer after onset, and 40 postmenopausal women from the general community. Bone status was assessed by quantitative ultrasound measurements at the calcaneus. Bone alkaline phosphatase (b-AP), carboxy-terminal telopeptide of type I collagen (CrossLaps), and sclerostin were evaluated by ELISA. We also used ELISA to measure serum levels of Dickkopf-1, another soluble inhibitor of Wnt/β-catenin signaling, highly expressed by ost...

Safety and Efficacy of the Subclavian Approach for Transcatheter Aortic Valve Implantation With the CoreValve Revalving System

Abstract: Background—Transcatheter aortic valve implantation (TAVI) is a new option for patients with severe aortic stenosis at high surgical risk The standard retrograde approach through the femoral artery is contraindicated in case of unfavorable iliofemoral anatomy or extensive disease In these patients, a trans-subclavian approach may be feasible Methods and Results—Between June 2007 and July 2009, TAVI with the CoreValve bioprosthesis (Medtronic, Minneapolis, Minn) was performed in 514 consecutive patients at 13 Italian hospitals, using the subclavian approach in 54 cases The median logistic EuroSCORE was significantly higher in the subclavian (194; interquartile range, 125 to 298) versus femoral group (253; interquartile range, 151 to 366) (P=003), as well as the rate of comorbidities Procedural success was obtained in 100% versus 984% of the subclavian versus femoral groups, respectively (P=062), with intraprocedural mortality of 0% versus 09% (P=100) The most common in-hospital complication

Implicit-explicit Runge-Kutta schemes and applications to hyperbolic systems with relaxation

Abstract: We consider new implicit-explicit (IMEX) Runge-Kutta methods for hyperbolic systems of conservation laws with stiff relaxation terms. The explicit part is treated by a strong-stability-preserving (SSP) scheme, and the implicit part is treated by an L-stable diagonally implicit Runge-Kutta methods (DIRK). The schemes proposed are asymptotic preserving (AP) in the zero relaxation limit. High accuracy in space is obtained by Weighted Essentially Non Oscillatory (WENO) reconstruction. After a description of the mathematical properties of the schemes, several applications will be presented.

Charged-particle multiplicity measurement in proton-proton collisions at $\sqrt{s}=7$ TeV with ALICE at LHC

Abstract: Charged-particle production was studied in proton-proton collisions collected at the LHC with the ALICE detector at centre-of-mass energies 0.9 TeV and 2.36 TeV in the pseudorapidity range vertical bar eta vertical bar < 1.4. In the central region (vertical bar eta vertical bar < 0.5), at 0.9 TeV, we measure charged-particle pseudo-rapidity density dN(ch)/d eta = 3.02 +/- 0.01(stat.)(-0.05)(+0.08)(syst.) for inelastic interactions, and dN(ch)/d eta = 3.58 +/- 0.01 (stat.)(-0.12)(+0.12)(syst.) for non-single-diffractive interactions. At 2.36 TeV, we find dN(ch)/d eta = 3.77 +/- 0.01(stat.)(-0.12)(+0.25)(syst.) for inelastic, and dN(ch)/d eta = 4.43 +/- 0.01(stat.)(-0.12)(+0.17)(syst.) for non-single-diffractive collisions. The relative increase in charged-particle multiplicity from the lower to higher energy is 24.7% +/- 0.5%(stat.)(-2.8)(+5.7)%(syst.) for inelastic and 23.7% +/- 0.5%(stat.)(-1.1)(+4.6)%(syst.) for non-single-diffractive interactions. This increase is consistent with that reported by the CMS collaboration for non-single-diffractive events and larger than that found by a number of commonly used models. The multiplicity distribution was measured in different pseudorapidity intervals and studied in terms of KNO variables at both energies. The results are compared to proton-antiproton data and to model predictions.

Charged-Particle Multiplicity Density at Midrapidity in Central Pb-Pb Collisions at root s(NN)=2.76 TeV

Abstract: The first measurement of the charged-particle multiplicity density at midrapidity in Pb-Pb collisions at a center-of-mass energy per nucleon pair root s(NN) = 2.76 TeV is presented. For an event sample corresponding to the most central 5% of the hadronic cross section, the pseudorapidity density of primary charged particles at midrapidity is 1584 +/- 4(stat) +/- 76(syst), which corresponds to 8.3 +/- 0.4(syst) per participating nucleon pair. This represents an increase of about a factor 1.9 relative to pp collisions at similar collision energies, and about a factor 2.2 to central Au-Au collisions at root s(NN) = 0.2 TeV. This measurement provides the first experimental constraint for models of nucleus-nucleus collisions at LHC energies.

Alignment of the ALICE Inner Tracking System with cosmic-ray tracks

Abstract: ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 mu m in some cases (pixels). The sources of alignment information include survey measurements, and the reconstructed tracks from cosmic rays and from proton-proton collisions. The main track-based alignment method uses the Millepede global approach. An iterative local method was developed and used as well. We present the results obtained for the ITS alignment using about 10(5) charged tracks from cosmic rays that have been collected during summer 2008, with the ALICE solenoidal magnet switched off.

Detailed abundances of a large sample of giant stars in M 54 and in the Sagittarius nucleus

Abstract: Homogeneous abundances of light elements, α-elements, and Fe-group elements from high-resolution FLAMES spectra are presented for 76 red giant stars in NGC 6715 (M 54), a massive globular cluster (GC) lying in the nucleus of the Sagittarius dwarf galaxy. We also derived detailed abundances for 27 red giants belonging to the Sgr nucleus. Our abundances measure the intrinsic metallicity dispersion (∼0.19 dex, rms scatter) of M 54, with the bulk of stars peaking at [Fe/H] ∼− 1.6 and a long tail extending to higher metallicities, similar to ω Cen. The spread in these probable nuclear star clusters exceeds those of most GCs: these massive clusters are located in a region intermediate between normal GCs and dwarf galaxies. The GC M 54 exibits a Na-O anticorrelation, a typical signature of GCs, which is instead absent for the Sgr nucleus. The light elements (Mg, Al, Si) participating in the high temperature Mg-Al cycle show that the entire pattern of (anti)correlations produced by proton-capture reactions in H-burning is clearly different between the most metal-rich and most metal-poor components in the two most massive GCs in the Galaxy, confirming early results based on the Na-O anticorrelation. As in ω Cen, stars affected by most extreme processing, i.e. showing the signature of more massive polluters, are those of the metal-rich component. These observations can be understood if the burst of star formation giving birth to the metal-rich component was delayed by as much as 10−30 Myr with respect to the metal-poor one. The evolution of these massive GCs can be easily reconciled in the general scenario for the formation of GCs sketched previously by ourselves, taking into account that ω Cen may have already incorporated the surrounding nucleus of its progenitor and lost the remainder of the hosting galaxy while the two are still observable as distinct components in M 54 and the surrounding field.

Detection of pulmonary congestion by chest ultrasound in dialysis patients.

Abstract: Objectives This study sought to investigate clinical and echocardiographic correlates of the lung comets score. Background Early detection of pulmonary congestion is a fundamental goal for the prevention of congestive heart failure in high-risk patients. Methods We undertook an inclusive survey by a validated ultrasound (US) technique in a hemodialysis center to estimate the prevalence of pulmonary congestion and its reversibility after dialysis in a population of 75 hemodialysis patients. Results Chest US examinations were successfully completed in all patients (N = 75). Before dialysis, 47 patients (63%) exhibited moderate to severe lung congestion. This alteration was commonly observed in patients with heart failure but also in the majority of asymptomatic (32 of 56, 57%) and normohydrated (19 of 38, 50%) patients. Lung water excess was unrelated with hydration status but it was strongly associated with New York Heart Association functional class (p < 0.0001), left ventricular ejection fraction (r = –0.55, p < 0.001), early filling to early diastolic mitral annular velocity (r = 0.48, p < 0.001), left atrial volume (r = 0.39, p = 0.001), and pulmonary pressure (r = 0.36, p = 0.002). Lung water reduced after dialysis, but 23 patients (31%) still had pulmonary congestion of moderate to severe degree. Lung water after dialysis maintained a strong association with left ventricular ejection fraction (r = –0.59, p < 0.001), left atrial volume (r = 0.30, p = 0.01), and pulmonary pressure (r = 0.32, p = 0.006) denoting the critical role of cardiac performance in the control of this water compartment in end-stage renal disease. In a multiple regression model including traditional and nontraditional risk factors only left ventricular ejection fraction maintained an independent link with lung water excess (beta = –0.61, p < 0.001). Repeatability studies of the chest US technique (Bland-Altman plots) showed good interobserver and inter-US probes reproducibility. Conclusions Pulmonary congestion is highly prevalent in symptomatic (New York Heart Association functional class III to IV) and asymptomatic dialysis patients. Chest ultrasound is a reliable technique that detects pulmonary congestion at a pre-clinical stage in end-stage renal disease.