204 research outputs found
Evolution of the wall shear stresses during the progressive enlargement of symmetric abdominal aortic aneurysms.
No full textThe changes in the evolution of the spatial and temporal distribution of the wall shear stresses (WSS) and gradients of wall shear stresses (GWSS) at different stages of the enlargement of an abdominal aortic aneurysm (AAA) are important in understanding the aetiology and progression of this vascular disease since they affect the wall structural integrity, primarily via the changes induced on the shape, functions and metabolism of the endothelial cells. Particle image velocimetry (PIV) measurements were performed in in vitro aneurysm models, while changing their geometric parameters systematically. It has been shown that, even at the very early stages of the disease, i.e. increase in the diameter ≤ 50%, the flow separates from the wall and a large vortex ring, usually followed by internal shear layers, is created. These lead to the generation of WSS that drastically differ in mean and fluctuating components from the healthy vessel. Inside the AAA, the mean WSS becomes negative along most of the aneurysmal wall and the magnitude of the WSS can be as low as 26% of the value in a healthy abdominal aorta. Two regions with distinct patterns of WSS were identified inside the AAA: the proximal region of flow detachment, characterized by oscillatory WSS of very low mean, and the region of flow reattachment, located distally, where large, negative WSS and sustained GWSS are produced as a result of the impact of the vortex ring on the wall. Comparison of the measured values of WSS and GWSS to an analytical solution, calculated for slowly expanding aneurysms shows a very good agreement, thus providing a validation of the PIV measurements
Lifetime measurements on fission fragments in the A similar to 100 region
No full text5th International Workshop on Nuclear Fission and Fission Product Spectroscopy (FISSION) -- MAY 28-31, 2013 -- Caen, FRANCELifetimes of first 4(+) and 6(+) states have been measured in neutron-rich isotopes of Zr, Mo, Ru and Pd using the recoil distance Doppler shift method at GANIL. The nuclei were produced through a fusion-fission reaction in inverse kinematics. The fission fragments were fully identified in the large-acceptance VAMOS spectrometer and gamma -rays were detected in coincidence with the EXOGAM germanium array. Lifetimes of excited states in the range of 1-100 ps were measured with the Cologne plunger. Preliminary lifetime results are presented as well as a discussion on the evolution of the collectivity in this region.ILL, CEA DSM & DAM, CNRS IN2P3, ENSICAEN, GANILScientific and Technological Council of Turkey [210T043]S. Erturk acknowledges the Scientific and Technological Council of Turkey for their support with project number 210T043
MOLECULAR RESONANCES AND THE JACOBI SHAPE TRANSITION: THE CASE OF Mg+Mg AND Cr
No full textInternational audiencefast rotating 48Cr is predicted to be highly prolate and deformed after a Jacobi shape transition and just before fission. In this article, it is proposed that a narrow and high spin 24Mg+24Mg resonance corresponds to the formation of this exotic 48Cr. Moreover the 24Mg+24Mg reaction has been studied at the Legnaro Tandem at a CM bombarding energy of 45.7 MeV, where a narrow and high spin resonance has been reported previously. To establish the connection between the resonance and a molecular state of 48Cr, the decay of the resonance into the inelastic and fusion-evaporation channels has been investigated. The ON and OFF resonance decay yields have been measured using, for the inelastic channels, the fragment spectrometer PRISMA and the γ array CLARA, and, for the fusion-evaporation channels, the Si array EUCLIDES and the γ array GASP. Strong resonant effects have been observed in the inelastic channels involving the 2+ and 4+ states of the 24Mg ground state (g.s.) band. Weaker effects are also seen in certain fusion-evaporation channels. Both results will be discussed here
Online fabrication and characterization of capsule populations with a flow-focusing microfluidic system
No full textThis paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.We have designed a microfluidic system that combines a double flow-focusing setup for calibrated capsule fabrication with a microchannel for the characterization of their mechanical properties. The double flow-focusing system consists of a first Y junction to create the microdroplets and of a second Y junction to introduce the cross-linking agent allowing the membrane formation. The human serum albumin (HSA) aqueous solution for the dispersed solution, hydrophobic phase for the continuous solution and cross-linking agent solution are introduced by means of syringe pumps. A wavy channel after the second junction allows to control the reticulation time. A cylindrical microchannel then enables to deform and characterize the capsules formed. The mechanical properties of the capsule membrane are obtained by inverse analysis (Chu et al. 2011). The results show that the drop size increases with the flow rate ratio between the central and lateral channels and does not change much regardless of the flow rate of the reticulation phase. The mean shear modulus of the capsules fabricated after 23 s of reticulation is of the order of the surface tension of HSA solution with Dragoxat indicating that the reticulation time is too short to form an elastic membrane around the droplet. When the reticulation time is increased to 60 s, the membrane shear modulus is multiplied by a factor of 3 confirming that a solid membrane has formed around the drop
High-Precision Spectroscopy of O Benchmarking Ab Initio Calculations in Light Nuclei
No full textInternational audienceHigh-precision spectroscopy of 20O benchmarking ab-initio calculations in light nucleiI. Zanon,1, 2 E. Cl´ement,3 A. Goasduff,1 J. Men´endez,4 T. Miyagi,5, 6, 7 M. Assi´e,8 M. Ciemala,9F. Flavigny,10 A. Lemasson,3 A. Matta,10 D. Ramos,3 M. Rejmund,3 L. Achouri,10 D. Ackermann,3D. Barrientos,11 D. Beaumel,8 G. Benzoni,12 A.J. Boston,13 H.C. Boston,13 S. Bottoni,14, 12 A. Bracco,12, 14D. Brugnara,1, 15 G. de France,3 N. de Sereville,8 F. Delaunay,10 P. Desesquelles,8 F. Didierjean,16C. Domingo-Prato,17 J. Dudouet,18 J. Eberth,19 D. Fern´andez,20 C. Foug`eres,3 A. Gadea,17 F. Galtarossa,8V. Girard-Alcindor,3 V. Gonzales,21 A. Gottardo,1 F. Hammache,8 L.J. Harkness-Brennan,13 H. Hess,19D.S Judson,13 A. Jungclaus,22 A. Ka¸ska¸s,23 Y.H. Kim,24 A. Ku¸so˘glu,25 M. Labiche,26 S. Leblond,3C. Lenain,10 S.M. Lenzi,27 S. Leoni,12 H. Li,3 J. Ljungvall,8 J. Lois-Fuentes,20 A. Lopez-Martens,8A. Maj,28 R. Menegazzo,27 D. Mengoni,15, 27 C. Michelagnoli,3, 24 B. Million,12 D.R. Napoli,1 J. Nyberg,29G. Pasqualato,15, 27 Zs. Podolyak,30 A. Pullia,12 B. Quintana,31 F.Recchia,15, 27 D. Regueira-Castro,20 P. Reiter,19K. Rezynkina,32 J.S. Rojo,33 M.D. Salsac,34 E. Sanchis,21 M. S¸enyi˘git,23 M. Siciliano,34, 35 D. Sohler,36O. Stezowski,18 Ch. Theisen,34 A. Utepov,3, 10 J.J. Valiente-Dob´on,1 D. Verney,8 and M. Zielinska341INFN Laboratori Nazionali di Legnaro, Legnaro, Italy.2Dipartimento di Fisica e Scienze della Terra, Universit`a di Ferrara, Ferrara, Italy.3Grand Acc´el´erateur National d’Ions Lourds (GANIL), CEA/DRF-CNRS/IN2P3, Caen, France4Department of Quantum Physics and Astrophysics and Institute of Cosmos Sciences, University of Barcelona, Spain5Technische Universit¨at Darmstadt, Department of Physics, Darmstadt, Germany6ExtreMe Matter Institute, GSI Helmholtzzentrum f¨ur Schwerionenforschung GmbH, Darmstadt, Germany7Max-Planck-Institut f¨ur Kernphysik, Heidelberg, Germany8Universit´e Paris-Saclay, CNRS/IN2P3, IJCLab, 91405 Orsay, France9IFJ PAN, Krakow, Poland.10Universit´e de Caen Normandie, ENSICAEN, CNRS/IN2P3, LPC Caen UMR6534, F-14000 Caen, France.11CERN, CH-1211 Geneva 23, Switzerland12INFN Sezione di Milano, I-20133 Milano, Italy13Oliver Lodge Laboratory, The University of Liverpool, Liverpool, UK.14Dipartimento di Fisica, Universit`a di Milano, Milano, Italy15Dipartimento di Fisica, Universit`a di Padova, Padova, Italy.16Universit´e de Strasbourg, IPHC, Strasbourg, France.17Instituto de Fisica Corpuscolar, CSIC-Universidad de Valencia, E-46071 Valencia, Spain.18Universit´e de Lyon, Universit´e Lyon-1, CNRS/IN2P3,UMR5822, IP2I, F-69622 Villeurbanne Cedex, France19Institut f¨ur Kernphysik, Universit¨at zu K¨oln, Z¨ulpicher Str. 77, D-50937 K¨oln, Germany20IGFAE and Dpt. de F´ısica de Part´ıculas, Univ. of Santiago de Compostela, Santiago de Compostela, Spain21Departamento de Ingenier´ıa Electr´onica, Universitat de Valencia, Burjassot, Valencia, Spain22Instituto de Estructura de la Materia, CSIC, Madrid, E-28006 Madrid, Spain23Department of Physics, Faculty of Science, Ankara University, 06100 Besevler - Ankara, Turkey24Institue Laue-Langevin, Grenoble, France.25Department of Physics, Faculty of Science, Istanbul University, Vezneciler/Fatih, Istanbul, Turkey.26STFC Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, UK27INFN, Sezione di Padova, I-35131 Padova, Italy.28The Henryk Niewodnicza´nski Institute of Nuclear Physics,Polish Academy of Sciences, 31-342 Krak´ow, Poland29Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala, Sweden30Department of Physics, University of Surrey, Guildford, GU2 7XH, UK31Laboratorio de Radiaciones Ionizantes, Departamento de F´ısica Fundamental,Universidad de Salamanca, E-37008 Salamanca, Spain32Universit´e de Strasbourg, CNRS, IPHC UMR 7178, F-67000 Strasbourg, France33Department of Physics, University of York, York, UK.34Irfu, CEA, Universit´e Paris-Saclay, F-91191 Gif-sur-Yvette, France35Physics Division, Argonne National Laboratory, Lemont (IL) 60439, United States.36Institute for Nuclear Research, Atomki, 4001 Debrecen, HungaryThe excited states of unstable 20O were investigated via γ-ray spectroscopy following the19O(d, p)20O reaction at 8 AMeV. By exploiting the Doppler Shift Attenuation Method, the lifetimeof the 2+2 and 3+1 states were firmly established. From the γ-ray branching and E2/M1 mixing ratiosfor transitions deexciting the 2+2 and 3+1 states, the B(E2) and B(M1) were determined. Variouschiral effective field theory Hamiltonians, describing the nuclear properties beyond ground states,along with a standard USDB interaction, were compared with the experimentally obtained data.Such a comparison for a large set of γ-ray transition probabilities with the valence space in medium 2similarity renormalization group ab-initio calculations was performed for the first time in a nucleusfar from stability. It was shown that the ab-initio approaches using chiral EFT forces are challengedby detailed high-precision spectroscopic properties of nuclei. The reduced transition probabilitieswere found to be a very constraining test of the performance of the ab-initio model
Relevance of single-particle and collective excitations in zirconium isotopes populated by neutron transfer reactions in the 90Zr+208Pb system
No full textMultinucleon transfer reactions studied with magnetic spectrometers
No full textMultinucleon transfer reactions with Ca-40 beams on closed shell nuclei Zr-96 and Pb-208 at energies close to the Coulomb barrier were studied using magnetic spectrometers. The comparison between data and calculations, based on semiclassical models, allowed to identify the different degrees of freedom that influence the evolution of the reaction, like deformation, single, and pair transfer modes
Nature and decay of a Jp=36+ resonance in the 24Mg+24Mg reaction
No full textIt has been proposed to associate the narrow (Γ=170 keV) and high spin (Jπ=36+) resonance in the 24Mg + 24Mg reaction at Ec.m= 45.7 MeV with a hyperdeformed molecular state in 48Cr. Such a description has important consequences for the resonance decay into the favoured inelastic channels. Through fragment‐γ coincidence measurements performed ON and OFF resonance using the PRISMA‐CLARA array, we have established that the 24Mg states selectively populated are the 2+ and 4+ members of the ground state band
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