| 1. |
- Dromey, B, et al.
(författare)
-
Picosecond metrology of laser-driven proton bursts.
- 2016
-
Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Tracking primary radiation-induced processes in matter requires ultrafast sources and high precision timing. While compact laser-driven ion accelerators are seeding the development of novel high instantaneous flux applications, combining the ultrashort ion and laser pulse durations with their inherent synchronicity to trace the real-time evolution of initial damage events has yet to be realized. Here we report on the absolute measurement of proton bursts as short as 3.5±0.7 ps from laser solid target interactions for this purpose. Our results verify that laser-driven ion acceleration can deliver interaction times over a factor of hundred shorter than those of state-of-the-art accelerators optimized for high instantaneous flux. Furthermore, these observations draw ion interaction physics into the field of ultrafast science, opening the opportunity for quantitative comparison with both numerical modelling and the adjacent fields of ultrafast electron and photon interactions in matter.
|
|
| 2. |
- Warwick, J., et al.
(författare)
-
Experimental Observation of a Current-Driven Instability in a Neutral Electron-Positron Beam
- 2017
-
Ingår i: Physical Review Letters. - : AMER PHYSICAL SOC. - 0031-9007 .- 1079-7114. ; 119:18
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the first experimental observation of a current-driven instability developing in a quasineutral matter-antimatter beam. Strong magnetic fields (amp;gt;= 1 T) are measured, via means of a proton radiography technique, after the propagation of a neutral electron-positron beam through a background electron-ion plasma. The experimentally determined equipartition parameter of epsilon(B) approximate to 10(-3) is typical of values inferred from models of astrophysical gamma-ray bursts, in which the relativistic flows are also expected to be pair dominated. The data, supported by particle-in-cell simulations and simple analytical estimates, indicate that these magnetic fields persist in the background plasma for thousands of inverse plasma frequencies. The existence of such long-lived magnetic fields can be related to analog astrophysical systems, such as those prevalent in lepton-dominated jets.
|
|
| 3. |
- Mineo Bianchi, F, et al.
(författare)
-
Posterior muscle-fascial reconstruction and knotless urethro-neo bladder anastomosis during robot-assisted radical cystectomy: Description of the technique and its impact on urinary continence
- 2019
-
Ingår i: Archivio italiano di urologia, andrologia : organo ufficiale [di] Societa italiana di ecografia urologica e nefrologica. - : PAGEPress Publications. - 2282-4197. ; 91:1, s. 5-10
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: The aim of our study is to describe the use of posterior muscle-fascial reconstruction during urethro-ileal anastomosis in bladder cancer (BC) patients submitted to robot-assisted radical cystectomy (RC) with orthotopic neobladder (ON) and its role in facilitating day- and night-time continence recovery during a 12-month follow up. Materials and methods: We prospectively collected data from 42 consecutive patients who underwent RARC with totally intracorporeal ON and extended pelvic lymph node dissection (PLND) at our Institution from June 2014 to October 2017. Prior to the urethro-neobladder anastomosis we reconstructed the Denonvilliers Fascia (DF) as previously described for radical prostatectomy using a bidirectional barbed suture. Day and night-time recovery rates were reported at 3, 6 and 12 months after surgery, with continent patients being those using either no urinary pads or 1 safety pads. Results: Median age at surgery was 63 yrs, 41 (97.6%) patients were male. 28 (66.7%) patients presented a clinical T2 disease. Median operative time and median ON reconstruction time were 450 minutes and 180 minutes respectively. 13 (31%) individuals had non-organ confined disease, with 11 (26.2%) patients with positive lymph nodes (median 3 positive lymph nodes) and 2 (4.8%) with non-urothelial cancer at final pathologic examination. Median hospital stay and median catheterization time were 7 (IQR 7-8) and 21 (IQR 19-22). During first 30 post-operative days we recorded 7 (16.7%) low-grade Clavien and 2 (4.8%) IIIa Clavien complications, whereas between 30 and 90 postoperative days we recorded 4 (9.5%) low-grade, 4 (9.5) IIIa and 1 (2.4%) IIIb complications. Day-time and night-time continence rates were 61.9% vs 52.4%, 73.8% vs 64.3% and 90.5% vs 73.8% at three, six and twelve months follow up. Day-time continence was significantly superior in the younger group (97% vs 57%, p 0.01); night-time continence rates were also superior among < 70 yrs patients, despite not reaching statistical significance (77% vs 57%, p 0.3). Conclusions: Posterior muscle-fascial reconstruction aids continence recovery in BC patients undergoing RARC with ON, with younger and fitter patients most benefitting from ON reconstruction.
|
|
| 4. |
|
|
| 5. |
- Ahmed, Hamad, et al.
(författare)
-
Experimental Observation of Thin-shell Instability in a Collisionless Plasma
- 2017
-
Ingår i: Astrophysical Journal Letters. - : Institute of Physics Publishing (IOPP). - 2041-8205 .- 2041-8213. ; 834:2
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the experimental observation of the instability of a plasma shell, which formed during the expansion of a laser-ablated plasma into a rarefied ambient medium. By means of a proton radiography technique, the evolution of the instability is temporally and spatially resolved on a timescale much shorter than the hydrodynamic one. The density of the thin shell exceeds that of the surrounding plasma, which lets electrons diffuse outward. An ambipolar electric field grows on both sides of the thin shell that is antiparallel to the density gradient. Ripples in the thin shell result in a spatially varying balance between the thermal pressure force mediated by this field and the ram pressure force that is exerted on it by the inflowing plasma. This mismatch amplifies the ripples by the same mechanism that drives the hydrodynamic nonlinear thin-shell instability (NTSI). Our results thus constitute the first experimental verification that the NTSI can develop in colliding flows.
|
|
| 6. |
- Dieckmann, Mark E, et al.
(författare)
-
Electrostatic shock waves in the laboratory and astrophysics: similarities and differences
- 2018
-
Ingår i: Plasma Physics and Controlled Fusion. - : IOP PUBLISHING LTD. - 0741-3335 .- 1361-6587. ; 60:1
-
Tidskriftsartikel (refereegranskat)abstract
- Contemporary lasers allow us to create shocks in the laboratory that propagate at a speed that matches that of energetic astrophysical shocks like those that ensheath supernova blast shells. The rapid growth time of the shocks and the spatio-temporal resolution, with which they can be sampled, allow us to identify the processes that are involved in their formation and evolution. Some laser-generated unmagnetized shocks are mediated by collective electrostatic forces and effects caused by binary collisions between particles can be neglected. Hydrodynamic models, which are valid for many large-scale astrophysical shocks, assume that collisions enforce a local thermodynamic equilibrium in the medium; laser-generated shocks are thus not always representative for astrophysical shocks. Laboratory studies of shocks can improve the understanding of their astrophysical counterparts if we can identify processes that affect electrostatic shocks and hydrodynamic shocks alike. An example is the nonlinear thin-shell instability (NTSI). We show that the NTSI destabilises collisionless and collisional shocks by the same physical mechanism.
|
|
| 7. |
- Dieckmann, Mark E, et al.
(författare)
-
Particle-in-cell simulation study of a lower-hybrid shock
- 2016
-
Ingår i: Physics of Plasmas. - : AMER INST PHYSICS. - 1070-664X .- 1089-7674. ; 23:6, s. 062111-
-
Tidskriftsartikel (refereegranskat)abstract
- The expansion of a magnetized high-pressure plasma into a low-pressure ambient medium is examined with particle-in-cell simulations. The magnetic field points perpendicular to the plasmas expansion direction and binary collisions between particles are absent. The expanding plasma steepens into a quasi-electrostatic shock that is sustained by the lower-hybrid (LH) wave. The ambipolar electric field points in the expansion direction and it induces together with the background magnetic field a fast E cross B drift of electrons. The drifting electrons modify the background magnetic field, resulting in its pile-up by the LH shock. The magnetic pressure gradient force accelerates the ambient ions ahead of the LH shock, reducing the relative velocity between the ambient plasma and the LH shock to about the phase speed of the shocked LH wave, transforming the LH shock into a nonlinear LH wave. The oscillations of the electrostatic potential have a larger amplitude and wavelength in the magnetized plasma than in an unmagnetized one with otherwise identical conditions. The energy loss to the drifting electrons leads to a noticeable slowdown of the LH shock compared to that in an unmagnetized plasma. Published by AIP Publishing.
|
|
| 8. |
- Dieckmann, Mark E, et al.
(författare)
-
Thin-shell instability in collisionless plasma
- 2015
-
Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - : American Physical Society. - 1539-3755 .- 1550-2376. ; 92:3, s. 031101-
-
Tidskriftsartikel (refereegranskat)abstract
- Thin-shell instability is one process which can generate entangled structures in astrophysical plasma on collisional (fluid) scales. It is driven by a spatially varying imbalance between the ram pressure of the inflowing upstream plasma and the downstreams thermal pressure at a nonplanar shock. Here we show by means of a particle-in-cell simulation that an analog process can destabilize a thin shell formed by two interpenetrating, unmagnetized, and collisionless plasma clouds. The amplitude of the shells spatial modulation grows and saturates after about ten inverse proton plasma frequencies, when the shell consists of connected piecewise linear patches.
|
|
