| 1. |
- Martin, P., et al.
(författare)
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Overview of the RFX-mod fusion science programme
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 0029-5515 .- 1741-4326. ; 53:10, s. 104018-
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Forskningsöversikt (refereegranskat)abstract
- This paper reports the highlights of the RFX-mod fusion science programme since the last 2010 IAEA Fusion Energy Conference. The RFX-mod fusion science programme focused on two main goals: exploring the fusion potential of the reversed field pinch (RFP) magnetic configuration and contributing to the solution of key science and technology problems in the roadmap to ITER. Active control of several plasma parameters has been a key tool in this endeavour. New upgrades on the system for active control of magnetohydrodynamic (MHD) stability are underway and will be presented in this paper. Unique among the existing fusion devices, RFX-mod has been operated both as an RFP and as a tokamak. The latter operation has allowed the exploration of edge safety factor q edge < 2 with active control of MHD stability and studies concerning basic energy and flow transport mechanisms. Strong interaction has continued with the stellarator community in particular on the physics of helical states and on three-dimensional codes.
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| 2. |
- Carbone, V, et al.
(författare)
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To what extent can dynamical models describe statistical features of turbulent flows?
- 2002
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Ingår i: Europhysics letters. - : IOP Publishing. - 0295-5075 .- 1286-4854. ; 58:3, s. 349-355
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Tidskriftsartikel (refereegranskat)abstract
- Statistical features of "bursty" behaviour in charged and neutral fluid turbulence are compared to statistics of intermittent events in a GOY shell model, and avalanches in different models of Self-Organized Criticality (SOC). It is found that inter-burst times show a power law distribution for turbulent samples and for the shell model, a property which is shared only in a particular case of the running sandpile model. The breakdown of self-similarity generated by isolated events observed in the turbulent samples is well reproduced by the shell model, while it is absent in all SOC models considered. On this base, we conclude that SOC models are not adequate to mimic fluid turbulence, while the GOY shell model constitutes a better candidate to describe the gross features of turbulence.
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| 3. |
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| 4. |
- Sorriso-Valvo, Luca, et al.
(författare)
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Intermittency in plasma turbulence
- 2001
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Ingår i: Planetary and Space Science. - 0032-0633 .- 1873-5088. ; 49:12, s. 1193-1200
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Tidskriftsartikel (refereegranskat)
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| 5. |
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| 6. |
- Carbone, V, et al.
(författare)
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Intermittency and turbulence in a magnetically confined fusion plasma
- 2000
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - : American Physical Society (APS). - 1539-3755 .- 1550-2376. ; 62:1, s. R49-R52
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Tidskriftsartikel (refereegranskat)abstract
- The intermittency of the magnetic turbulence in reversed field pinch plasmas was measured. The probability distribution functions of magnetic field differences were not scale invariant because the wings of these functions were more important as the scales become smaller. This phenomena was identified as a classical signature of intermittency. The scaling laws also appeared very close to the external wall of the confinement device.
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| 7. |
- Carbone, V., et al.
(författare)
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Sign-Singularity of the Reduced Magnetic Helicity in the Solar Wind Plasma
- 2010
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 104:18, s. 181101-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the scaling laws of a signed measure derived from the reduced magnetic helicity which has been determined from Cluster data in the solar wind. This quantifies the handedness of the magnetic field; namely, it can be related to the polarization of the magnetic field fluctuations (right or left hand). The measure results to be sign-singular; that is, we do not observe any scale-dependent effect at the ion-and at electron-cyclotron frequencies. Cancellations between right-and left-hand polarizations go on in the dispersive or dissipative range, beyond the electron-cyclotron frequency. This means that the mechanism responsible for the generation of the dispersive or dissipative range is rather insensitive to the polarization of the magnetic field fluctuations.
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| 8. |
- Greco, A., et al.
(författare)
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The Complex Structure Of Magnetic Field Discontinuities In The Turbulent Solar Wind
- 2016
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Ingår i: Astrophysical Journal Letters. - 2041-8205 .- 2041-8213. ; 823:2
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Tidskriftsartikel (refereegranskat)abstract
- Using high-resolution Cluster satellite observations and a multi-dimensional intermittency technique, we show that the magnetic discontinuities in the turbulent solar wind are connected through the spatial scales, going from proton down to electron scales. In some circumstances, their structure resembles the Harris equilibrium profile in plasmas. Observations are consistent with a scenario where many current layers develop in turbulence and where the outflow of these reconnection events are characterized by complex sub-proton networks of secondary islands, in a self-similar way. Although in the past these pictures have been speculated to be separately ubiquitous, through theories and simulations, the present work confirms that "reconnection in turbulence" and "turbulent reconnection" coexist in space plasmas.
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| 9. |
- Guigliano, Robert P, et al.
(författare)
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Early versus delayed, provisional eptifibatide in acute coronary syndromes.
- 2009
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Ingår i: New England Journal of Medicine. - : Massachusetts Medical Society. - 0028-4793 .- 1533-4406. ; 360:21, s. 2176-2190
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Tidskriftsartikel (refereegranskat)abstract
- Background Glycoprotein IIb/IIIa inhibitors are indicated in patients with acute coronary syndromes who are undergoing an invasive procedure. The optimal timing of the initiation of such therapy is unknown. Methods We compared a strategy of early, routine administration of eptifibatide with delayed, provisional administration in 9492 patients who had acute coronary syndromes without ST-segment elevation and who were assigned to an invasive strategy. Patients were randomly assigned to receive either early eptifibatide (two boluses, each containing 180 µg per kilogram of body weight, administered 10 minutes apart, and a standard infusion 12 hours before angiography) or a matching placebo infusion with provisional use of eptifibatide after angiography (delayed eptifibatide). The primary efficacy end point was a composite of death, myocardial infarction, recurrent ischemia requiring urgent revascularization, or the occurrence of a thrombotic complication during percutaneous coronary intervention that required bolus therapy opposite to the initial study-group assignment ("thrombotic bailout") at 96 hours. The key secondary end point was a composite of death or myocardial infarction within the first 30 days. Key safety end points were bleeding and the need for transfusion within the first 120 hours after randomization. Results The primary end point occurred in 9.3% of patients in the early-eptifibatide group and in 10.0% in the delayed-eptifibatide group (odds ratio, 0.92; 95% confidence interval [CI], 0.80 to 1.06; P=0.23). At 30 days, the rate of death or myocardial infarction was 11.2% in the early-eptifibatide group, as compared with 12.3% in the delayed-eptifibatide group (odds ratio, 0.89; 95% CI, 0.79 to 1.01; P=0.08). Patients in the early-eptifibatide group had significantly higher rates of bleeding and red-cell transfusion. There was no significant difference between the two groups in rates of severe bleeding or nonhemorrhagic serious adverse events. Conclusions In patients who had acute coronary syndromes without ST-segment elevation, the use of eptifibatide 12 hours or more before angiography was not superior to the provisional use of eptifibatide after angiography. The early use of eptifibatide was associated with an increased risk of non–life-threatening bleeding and need for transfusion.
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| 10. |
- Harrington, Robert A., et al.
(författare)
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The Thrombin Receptor Antagonist for Clinical Event Reduction in Acute Coronary Syndrome (TRA.CER) trial : study design and rationale
- 2009
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Ingår i: American Heart Journal. - : Elsevier BV. - 0002-8703 .- 1097-6744. ; 158:3, s. 327-334
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Tidskriftsartikel (refereegranskat)abstract
- Background The protease-activated receptor 1 (PAR-1), the main platelet receptor for thrombin, represents a novel target for treatment of arterial thrombosis, and SCH 530348 is an orally active, selective, competitive PAR-1 antagonist. We designed TRA.CER to evaluate the efficacy and safety of SCH 530348 compared with placebo in addition to standard of care in patients with non-ST-segment elevation (NSTE) acute coronary syndromes (ACS) and high-risk features. Trial design TRA.CER is a prospective, randomized, double-blind, multicenter, phase III trial with an original estimated sample size of 10,000 subjects. Our primary objective is to demonstrate that SCH 530348 in addition to standard of care will reduce the incidence of the composite of cardiovascular death, myocardial infarction (MI), stroke, recurrent ischemia with rehospitalization, and urgent coronary revascularization compared with standard of care alone. Our key secondary objective is to determine whether SCH 530348 will reduce the composite of cardiovascular death, MI, or stroke compared with standard of care alone. Secondary objectives related to safety are the composite of moderate and severe GUSTO bleeding and clinically significant TIMI bleeding. The trial will continue until a predetermined minimum number of centrally adjudicated primary and key secondary end point events have occurred and all subjects have participated in the study for at least I year. The TRA.CER trial is part of the large phase III SCH 530348 development program that includes a concomitant evaluation in secondary prevention. Conclusion TRA.CER will define efficacy and safety of the novel platelet PAR-1 inhibitor SCH 530348 in the treatment of high-risk patients with NSTE ACS in the setting of current treatment strategies.
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| 11. |
- Morrow, DA, et al.
(författare)
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Evaluation of a novel antiplatelet agent for secondary prevention in patients with a history of atherosclerotic disease: design and rationale for the Thrombin-Receptor Antagonist in Secondary Prevention of Atherothrombotic Ischemic Events (TRA 2 degrees P)-TIMI 50 trial
- 2009
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Ingår i: American Heart Journal. - : Elsevier BV. - 0002-8703. ; 158:3, s. 335-341
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Thrombin potently activates platelets via interaction with the protease-activated receptor 1. SCH 530348 is a novel antiplatelet agent that selectively inhibits the cellular actions of thrombin via antagonism of the protease-activated receptor 1. Because SCH 530348 does not interfere with other pathways for hemostasis, it is possible that SCH 530348 reduces thrombosis with less increase in bleeding than do other potent antiplatelet agents. STUDY DESIGN: TRA 2 degrees P-TIMI 50 is a phase III, randomized, double-blind, placebo-controlled, multinational clinical trial designed to evaluate the efficacy and safety of SCH 530348 during long-term treatment of patients with established atherosclerotic disease receiving standard therapy (up to 27,000). Eligible patients with a history of myocardial infarction, ischemic stroke, or peripheral arterial disease are randomized 1:1 to SCH 530348 2.5 mg daily or matched placebo until the end of study. Randomization is stratified by the qualifying disease and planned use of a thienopyridine. The primary end point is the composite of cardiovascular death, myocardial infarction, stroke, or urgent coronary revascularization. The major secondary end point is the composite of cardiovascular death, myocardial infarction, or stroke. The evaluation of long-term safety includes bleeding defined by the GUSTO and TIMI criteria. Recruitment began in September 2007. The trial will continue until 2,279 primary end points and 1,400 secondary end points are recorded with expected completion in 36 to 44 months from first enrollment. CONCLUSIONS: TRA 2 degrees P-TIMI 50 is evaluating whether a new approach to platelet inhibition via interruption of thrombin-mediated platelet activation reduces major cardiovascular events with a favorable safety profile in patients with established atherosclerosis.
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| 12. |
- Perri, S., et al.
(författare)
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Magnetic turbulence in space plasmas : Scale-dependent effects of anisotropy
- 2009
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 114, s. A02102-
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Tidskriftsartikel (refereegranskat)abstract
- The presence of a background magnetic field induces anisotropy in magnetic turbulence. Understanding properties of anisotropy is important to characterize turbulence power spectrum. This paper presents a case study of anisotropy by using a minimum variance analysis, in three different regions of the heliosphere, namely in the solar wind, and in the Earth's foreshock and magnetosheath behind a quasiparallel bow shock. A strong anisotropy is found in all cases, with very interesting cross-scale effects at the ion cyclotron frequency. In particular, (1) the eigenvalues of the variance matrix have a strong intermittent behavior, with very high localized fluctuations below the ion cyclotron scale. As a consequence the probability distribution functions are almost Gaussian5 above the ion cyclotron scale and become power laws at smaller scales; (2) the minimum variance direction is almost parallel to the background magnetic field at scales larger than the ion cyclotron scale in the solar wind and in the foreshock, while their probability density functions become broader at smaller scales. In the magnetosheath the minimum variance direction exhibits a tendency to become nearly perpendicular to the large-scale magnetic field below the ion cyclotron scale.
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| 13. |
- Polimeno, P., et al.
(författare)
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Gain-Assisted Optomechanical Position Locking of Metal/Dielectric Nanoshells in Optical Potentials
- 2020
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Ingår i: Acs Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 7:5, s. 1262-1270
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Tidskriftsartikel (refereegranskat)abstract
- We investigate gain-assisted optical forces on dye-enriched silver nanoshell in the quasi-static limit by means of a theoretical/numerical approach. We demonstrate the onset of nonlinear optical trapping of these resonant nanostructures in a counter-propagating Gaussian beam configuration. We study the optical forces and trapping behavior as a function of wavelength, particle gain level, and laser power. We support the theoretical analysis with Brownian dynamics simulations that show how particle position locking is achieved at high gains in extended optical trapping potentials. Finally, for wavelengths blue-detuned with respect to the plasmon-enhanced resonance, we observe particle channeling by the standing wave antinodes due to gradient force reversal. This work opens perspectives for gain-assisted optomechanics where nonlinear optical forces are finely tuned to efficiently trap, manipulate, channel, and deliver an externally controlled nanophotonic system.
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| 14. |
- Polimeno, P., et al.
(författare)
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Position locking of a resonant gain-assisted metallic/dielectric nano-shell in Optical Tweezers
- 2021
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Ingår i: Nuovo Cimento C-Colloquia and Communications in Physics. - 2037-4909. ; 44:4-5
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Tidskriftsartikel (refereegranskat)abstract
- We calculate optical forces on dye-enriched resonant nano-shells in dual-beam Optical Tweezers. We investigate the non-linear gain-assisted enhancement of their optomechanics and study their behaviour through Brownian dynamics simulations. When the wavelength is red detuned with respect to the plasmon resonance, we observe that the particles are efficiently trapped at the laser beam intensity maxima of the dual beam standing wave. Conversely, for blue-detuned wavelengths the nano-shells are channelled through the standing wave antinodes due to the sign reversal of the optical force. This open perspectives for gain-assisted optomechanics where non-linear optical forces are finely tuned to manipulate controlled nano-photonic systems.
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| 15. |
- Servidio, Sergio, et al.
(författare)
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Compressible turbulence in Hall Magnetohydrodynamics
- 2007
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Ingår i: Planetary and Space Science. - : Elsevier BV. - 0032-0633 .- 1873-5088. ; 55:15, s. 2239-2243
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Tidskriftsartikel (refereegranskat)abstract
- By direct numerical simulations we investigate the nonlinear dynamics of a compressible Hall Magnetohydrodynamic (MHD) plasma. At small scales, where the Hall effect dominates, we found an increase of the compressibility of the system and the breakdown of the strong link between velocity and magnetic fields, typical of usual MHD. Moreover, we find that small-scale fluctuations are characterized by an anti-correlation between density and magnetic field intensity. These features characterize the excitation. of a quasi-perpendicular magnetosonic turbulence that can be interpreted as the small-scale signature of the break-down of the MHD nonlinear energy cascade due to Hall effect. Fluctuations with the same properties, based on measurements by Cluster spacecraft in space plasma turbulence during different magnetopause crossings, have been recently observed.
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| 16. |
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| 17. |
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| 19. |
- Valentini, F., et al.
(författare)
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Differential kinetic dynamics and heating of ions in the turbulent solar wind
- 2016
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Ingår i: New Journal of Physics. - : IOP Publishing. - 1367-2630. ; 18
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Tidskriftsartikel (refereegranskat)abstract
- The solar wind plasma is a fully ionized and turbulent gas ejected by the outer layers of the solar corona at very high speed, mainly composed by protons and electrons, with a small percentage of helium nuclei and a significantly lower abundance of heavier ions. Since particle collisions are practically negligible, the solar wind is typically not in a state of thermodynamic equilibrium. Such a complex system must be described through self-consistent and fully nonlinear models, taking into account its multi-species composition and turbulence. Weuse a kinetic hybrid Vlasov-Maxwell numerical code to reproduce the turbulent energy cascade down to ion kinetic scales, in typical conditions of the uncontaminated solar wind plasma, with the aim of exploring the differential kinetic dynamics of the dominant ion species, namely protons and alpha particles. Weshow that the response of different species to the fluctuating electromagnetic fields is different. In particular, a significant differential heating of alphas with respect to protons is observed. Interestingly, the preferential heating process occurs in spatial regions nearby the peaks of ion vorticity and where strong deviations from thermodynamic equilibrium are recovered. Moreover, by feeding a simulator of a top-hat ion spectrometer with the output of the kinetic simulations, we show that measurements by such spectrometer planned on board the Turbulence Heating ObserveR (THORmission), a candidate for the nextM4space mission of the European Space Agency, can provide detailed three-dimensional ion velocity distributions, highlighting important non-Maxwellian features. These results support the idea that future space missions will allow a deeper understanding of the physics of the interplanetary medium.
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