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Search Results: 1 - 10 of 325308 matches for " S. Riccò "
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Recovering Metallicity in A4C60: The Case of Monomeric Li4C60
M. Riccò,M. Belli,D. Pontiroli,M. Mazzani,T. Shiroka,D. Arcon,A. Zorko,S. Margadonna,G. Ruani
Physics , 2007, DOI: 10.1103/PhysRevB.75.081401
Abstract: The restoration of metallicity in the high-temperature, cubic phase of Li4C60 represents a remarkable feature for a member of the A4C60 family (A = alkali metal), invariably found to be insulators. Structural and resonance technique investigations on Li4C60 at T > 600 K, show that its fcc structure is associated with a complete (4e) charge transfer to C60 and a sparsely populated Fermi level. These findings not only emphasize the crucial role played by lattice symmetry in fulleride transport properties, but also re-dimension the role of Jahn-Teller effects in band structure determination. Moreover, they suggest the present system as a potential precursor to a new class of superconducting fullerides.
An optically stimulated superconducting-like phase in K3C60 far above equilibrium Tc
M. Mitrano,A. Cantaluppi,D. Nicoletti,S. Kaiser,A. Perucchi,S. Lupi,P. Di Pietro,D. Pontiroli,M. Riccò,A. Subedi,S. R. Clark,D. Jaksch,A. Cavalleri
Physics , 2015,
Abstract: The control of non-equilibrium phenomena in complex solids is an important research frontier, encompassing new effects like light induced superconductivity. Here, we show that coherent optical excitation of molecular vibrations in the organic conductor K3C60 can induce a non-equilibrium state with the optical properties of a superconductor. A transient gap in the real part of the optical conductivity and a low-frequency divergence of the imaginary part are measured for base temperatures far above equilibrium Tc=20 K. These findings underscore the role of coherent light fields in inducing emergent order.
Signal Coding and CMOS Gates for Combinational Functional Blocks of Very Deep Submicron Self-checking Circuits
Cecilia Metra,Michele Favalli,Bruno Riccò
VLSI Design , 2000, DOI: 10.1155/2000/42016
Abstract: In this paper we propose signal coding and CMOS gates that are suitable to self-checking circuits with combinational functional blocks implemented also by next generation, very deep submicron technology. In particular, our functional blocks satisfy the Strongly Fault-Secure property with respect to a wide set of possible, internal faults including not only conventional stuck-ats, but also transistor stuck-ons, transistor stuck-opens, resistive bridgings, delays, crosstalks and transient faults, that are very likely to affect next generation ICs. Compared to alternative, existing solutions, that proposed here does not imply any critical constraint on the circuit electrical parameters. Therefore, it is suitable to be adopted to design very deep submicron self-checking circuits which, compared to todays' circuits, will present significantly increased sensitivity to parameter variations occurring during fabrication.
MOCA: A Low-Power, Low-Cost Motion Capture System Based on Integrated Accelerometers
Elisabetta Farella,Luca Benini,Bruno Riccò,Andrea Acquaviva
Advances in Multimedia , 2007, DOI: 10.1155/2007/82638
Abstract: Human-computer interaction (HCI) and virtual reality applications pose the challenge of enabling real-time interfaces for natural interaction. Gesture recognition based on body-mounted accelerometers has been proposed as a viable solution to translate patterns of movements that are associated with user commands, thus substituting point-and-click methods or other cumbersome input devices. On the other hand, cost and power constraints make the implementation of a natural and efficient interface suitable for consumer applications a critical task. Even though several gesture recognition solutions exist, their use in HCI context has been poorly characterized. For this reason, in this paper, we consider a low-cost/low-power wearable motion tracking system based on integrated accelerometers called motion capture with accelerometers (MOCA) that we evaluated for navigation in virtual spaces. Recognition is based on a geometric algorithm that enables efficient and robust detection of rotational movements. Our objective is to demonstrate that such a low-cost and a low-power implementation is suitable for HCI applications. To this purpose, we characterized the system from both a quantitative point of view and a qualitative point of view. First, we performed static and dynamic assessment of movement recognition accuracy. Second, we evaluated the effectiveness of user experience using a 3D game application as a test bed.
Merging Metadata – Building on Existing Standards to Create a Field Book Registry
Carolyn Sheffield,Sonoe Nakasone,Ricc Ferrante,Tammy Peters
Libreas : Library Ideas , 2011,
Abstract: The Field Book Project is a cross-disciplinary project to develop an online registry for field books and other primary source materials related to biodiversity research. Led by Rusty Russell and Anne Van Camp, this project is a joint initiative of the Smithsonian Institution Archives and the National Museum of Natural History. This paper presents the metadata structure established for building the Field Book Registry. The project team is committed to involving members of the library, archives, museum, and biodiversity communities in the development of the Field Book Registry. We invite your comments and discussion regarding the work presented here.
断裂力学
J.R.Ricc,张秀琴
力学进展 , 1987, DOI: 10.6052/1000-0992-1987-2-J1987-029
Abstract: 断裂力学是当前正在向着许多方面推进的一个活跃的研究领域.对研究趋向和良机的本评述,指出了非线性断裂力学在近些年来很有发展前途.列举了若干复杂的研究课题,例如延性-脆性转变,在很大塑性或蠕变条件下的破坏,在疲劳载荷下的裂纹顶端过程,以及对复合材料进行断裂分析所需要的新的有效方法等.继续把着重点放在细观尺度断裂过程上,借助于固体力学与材料科学交缘处的研究,有希望了解各种材料的脆性与延性响应的原子层次的理论,了解细观空洞成核和扩展的机制.非常需要表征裂纹顶端过程和分离机制的严格的实验.在岩土工程学和地震断层动力学方面的断裂现象,同样提出了重要的研究难题.
Tailoring the nature and strength of electron-phonon interactions in the SrTiO$_3$(001) two-dimensional electron liquid
Z. Wang,S. McKeown Walker,A. Tamai,Z. Ristic,F. Y. Bruno,A. de la Torre,S. Riccò,N. C. Plumb,M. Shi,P. Hlawenka,J. Sánchez-Barriga,A. Varykhalov,T. K. Kim,M. Hoesch,P. D. C. King,W. Meevasana,U. Diebold,J. Mesot,M. Radovic,F. Baumberger
Physics , 2015,
Abstract: Surfaces and interfaces offer new possibilities for tailoring the many-body interactions that dominate the electrical and thermal properties of transition metal oxides. Here, we use the prototypical two-dimensional electron liquid (2DEL) at the SrTiO$_3$(001) surface to reveal a remarkably complex evolution of electron-phonon coupling with the tunable carrier density of this system. At low density, where superconductivity is found in the analogous 2DEL at the LaAlO$_3$/SrTiO$_3$ interface, our angle-resolved photoemission data show replica bands separated by 100\,meV from the main bands. This is a hallmark of a coherent polaronic liquid and implies strong long-range coupling to a single longitudinal optical phonon mode. In the overdoped regime the preferential coupling to this mode decreases and the 2DEL undergoes a crossover to a more conventional metallic state with weaker short-range electron-phonon interaction. These results place constraints on the theoretical description of superconductivity and allow for a unified understanding of the transport properties in SrTiO$_3$-based 2DELs.
Epidemiology of tuberculosis in a low-incidence Italian region with high immigration rates: differences between not Italy-born and Italy-born TB cases
Anna Odone, Matteo Riccò, Matteo Morandi, Bianca M Borrini, Cesira Pasquarella, Carlo Signorelli
BMC Public Health , 2011, DOI: 10.1186/1471-2458-11-376
Abstract: Data was obtained from the Regional TB surveillance system, from where personal data, clinical features and risk factors of all notified TB cases were extracted.5377 TB cases were reported. The proportion of immigrants with TB, over the total number of TB cases had progressively increased over the years, from 19.1% to 53.3%. In the not Italy-born population, TB incidence was higher than in Italians (in 2006: 100.7 cases per 100 000 registered not Italy-born subjects and 83.9/100 000 adding 20% of estimated irregular presences to the denominators. TB incidence among Italians was 6.5/100 000 Italians). A progressive rise in the not Italy-born incident cases was observed but associated with a decline in TB incidence. Not Italy-born cases were younger compared to the Italy-born cases, and more frequently classified as "new cases" (OR 2.0 95%CI 1.61-2.49 for age group 20-39); 60.7% had pulmonary TB, 31.6% extra pulmonary and 7.6% disseminated TB. Risk factors for TB in this population group were connected to lower income status (homeless: OR 149.9 95%CI 20.7-1083.3 for age group 40-59).In low-incidence regions, prevention and control of TB among sub-groups at risk such as the foreign-born population is a matter of public health concern. In addition, increasing immigration rates may affect TB epidemiology. TB among immigrants is characterized by particular clinical features and risk factors, which should be analyzed in order to plan effective action.With 9.4 million new cases estimated in 2009 by the World Health Organization (WHO), tuberculosis (TB) is a worldwide epidemic [1]. The regions most affected by TB are in low-income and middle-income countries within Asia and sub-Saharan Africa. In industrialised countries, even tough a decline in TB incidence rates has been shown over the last century [2], an increase in immigration [3] of people from high TB incidence areas has recently contributed to reverse this downward trend [4-6] and to the re-emergence of TB as a matte
NMR study of the Mott transitions to superconductivity in the two Cs_3C_60 phases
Yoshihiko Ihara,Henri Alloul,Pawel Wzietek,Daniel Pointiroli,Marcello Mazzani,Mauro Riccó
Physics , 2010, DOI: 10.1103/PhysRevLett.104.256402
Abstract: We report an NMR and magnetometry study on the expanded intercalated fulleride Cs_3C_60 in both its A15 and face centered cubic structures. NMR allowed us to evidence that both exhibit a first-order Mott transition to a superconducting (SC) state, occuring at distinct critical pressures p_c and temperatures T_c. Though the ground state magnetism of the Mott phases differs, their high $T$ paramagnetic and SC properties are found similar, and the phase diagrams versus unit volume per C_60 are superimposed. Thus, as expected for a strongly correlated system, the inter-ball distance is the relvevant parameter driving the electronic behavior and quantum transitions of these systems.
NMR study of the Superconducting gap variation near the Mott transition in Cs$_{3}$C$_{60}$
P. Wzietek,T. Mito,H. Alloul,D. Pontiroli,M. Aramini,M. Riccò
Physics , 2013, DOI: 10.1103/PhysRevLett.112.066401
Abstract: Former extensive studies of superconductivity in the \textit{A}$_{3}$C$_{60}$ compounds, where \textit{A} is an alkali, have led to consider that Bardeen Cooper Schrieffer (BCS) electron-phonon pairing prevails in those compounds, though the incidence of electronic Coulomb repulsion has been highly debated. The discovery of two isomeric fulleride compounds Cs$_{3}$C$_{60}$ which exhibit a transition with pressure from a Mott insulator (MI) to a superconducting (SC) state clearly re-opens that question. Using pressure ($p$) as a single control parameter of the C$_{60}$ balls lattice spacing, one can now study the progressive evolution of the SC properties when the electronic correlations are increased towards the critical pressure $p_{c}$ of the Mott transition. We have used $^{13}$C and $^{133}$Cs NMR measurements on the cubic phase A15-Cs$_{3}$C$_{60}$ just above $p_{c}=5.0(3)$ kbar, where the SC transition temperature $T_{c}$ displays a dome shape with decreasing cell volume. From the $T$ dependence below $T_{c}$ of the nuclear spin lattice relaxation rate $(T_{1})^{-1}$ we determine the electronic excitations in the SC state, that is $2\Delta$, the SC gap value. We find that $2\Delta $ increases with decreasing $p$ towards $p_{c}$, where $T_{c}$ decreases on the SC dome, so that $2\Delta /k_{B}T_{c}$ increases regularly upon approaching the Mott transition. These results bring clear evidence that the increasing correlations near the Mott transition are not significantly detrimental to SC. They rather suggest that repulsive electron interactions might even reinforce elecron-phonon SC, being then partly responsible for the large $T_{c}$ values, as proposed by theoretical models taking the electronic correlations as a key ingredient.
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