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Laser and beam driven wakefields promise orders of magnitude increases in electric field gradients for particle accelerators for future applications. Key areas to explore include the emittance properties of the generated beams and overcoming the dephasing limit in the plasma. In this paper, the first in-depth study of the self-injection mechanism into wakefield structures from nonhomogeneous cluster plasmas is provided using high-resolution two dimensional particle-in-cell simulations. The clusters which are typical structures caused by ejection of gases from a high-pressure gas jet have a diameter much smaller than the laser wavelength. Conclusive evidence is provided for the underlying mechanism that leads to particle trapping, comparing uniform and cluster plasma cases. The accelerated electron beam properties are found to be tunable by changing the cluster parameters. The mechanism explains enhanced beam charge paired with large transverse momentum and energy which has implications for the betatron x-ray flux. Finally, the impact of clusters on the high-power laser propagation behavior is discussed.

We report the first comprehensive study of large amplitude Langmuir waves in a plasma of nanometer-scale clusters. Using an oblique angle single-shot frequency domain holography diagnostic, the shape of these wakefields is captured for the first time. The wavefronts are observed to curve backwards, in contrast to the forwards curvature of wakefields in uniform plasma. Due to the expansion of the clusters, the first wakefield period is longer than those trailing it. The features of the data are well described by fully relativistic two-dimensional particle-in-cell simulations and by a quasianalytic solution for a one-dimensional, nonlinear wakefield in a cluster plasma.

A European consortium of 15 laboratories across nine nations have worked together under the EUROFusion Enabling Research grants for the past decade with three principle objectives. These are: (a) investigating obstacles to ignition on megaJoule-class laser facilities; (b) investigating novel alternative approaches to ignition, including basic studies for fast ignition (both electron and ion-driven), auxiliary heating, shock ignition, etc.; and (c) developing technologies that will be required in the future for a fusion reactor. A brief overview of these activities, presented here, along with new calculations relates the concept of auxiliary heating of inertial fusion targets, and provides possible future directions of research and development for the updated European Roadmap that is due at the end of 2020. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 2)’.

Apheresis is an increasingly important procedure in the treatment of a variety of conditions, sometimes performed via peripheral access because of concern over major complications associated with central venous catheter (CVC) placement. This study sought to determine the safety and success for ultrasound and fluoroscopically guided, non-tunneled dual lumen CVCs placed for apheresis. Prospective data collection was made of 200 attempted CVC placements in the radiology department utilizing real time sonographic guidance. The complications relating to placement were noted in all and the number of passes required for venepuncture and whether a single wall puncture was achieved was recorded in 185 cases. Duration of catheterization and reason for line removal were recorded in all. Our study group included 71 donors providing peripheral blood stem cells for allogeneic transplant. CVCs were successfully placed in all patients, 191 lines in the internal jugular and seven in the femoral vein. 86.5% required only a single pass and 80.5% with only anterior wall puncture. Inadvertent but clinically insignificant arterial puncture occurred in six (3%) cases. In no case did this prevent line placement. There were no other procedure-related complications. 173 (87.4%) catheters were removed the same day. No catheters were removed prematurely. There was one case of prolonged venous bleeding. Our study demonstrates the safety of central venous catheters for apheresis provided that duration of catheterization is short and real-time sonographic guidance is used for the puncture, and guide wire and catheter placement are confirmed fluoroscopically.

A European consortium of 15 laboratories across nine nations have worked together under the EUROFusion Enabling Research grants for the past decade with three principle objectives. These are: (a) investigating obstacles to ignition on megaJoule-class laser facilities; (b) investigating novel alternative approaches to ignition, including basic studies for fast ignition (both electron and ion-driven), auxiliary heating, shock ignition, etc.; and (c) developing technologies that will be required in the future for a fusion reactor. A brief overview of these activities, presented here, along with new calculations relates the concept of auxiliary heating of inertial fusion targets, and provides possible future directions of research and development for the updated European Roadmap that is due at the end of 2020. This article is part of a discussion meeting issue ‘Prospects for high gain inertial fusion energy (part 2)’.

A variety of sites for CVC insertion are available: right internal jugular vein (IJV), left IJV, subclavian veins and femoral veins (Fig. 3). Venous access can also be gained by means of recanalization of occluded veins, translumbar and transhepatic hepatic venous approaches, but these are uncommon.(9) IJVs are preferable to subclavians (SCVs) for central access sites because stenosis rates are as high as 50% in the latter.(3)(5)(6)(8)(10) The right IJV is preferred because the path to the superior vena cava - right atrium (SVC-RA) is short and straight and is commonly larger calibre than the left;(8) this reduces the difficulty when inserting left CVCs around several curvatures(2)(7)(8) (Fig. 4). If the calibre of the right IJV is suboptimal or occluded, the left IJV should be used. In HD patients, the order of decreasing preference of potential central venous access is: SCV, the femoral (right then left) and, lastly, the IVC by means of a translumbar approach.(4) There are lower rates of thrombosis, stenosis and occlusion with indwelling tunnelled IJV CVCs than with SCV CVCs.(11) The CVC is then advanced through the tunnel using the tapered CVC trocar (Fig. 21). Commonly, the most resistance through the tunnel is at the clavipectoral fascia or where the platysma inserts onto the clavicle. Steady and firm pressure is required to control any forceful manoeuvres and prevent inadvertent trocar advancements. Then, the trocar tip is manipulated out of the skin puncture site. The hub of the tunnelled CVC should be buried up to the skin entry site, further into the tunnel than required, allowing for subsequent partial withdrawal should a CVC kink occur.(6) This allows the CVC tip position to be altered. It is important to confirm the correct orientation of the tip of the HD CVC -- the venous (blue) port is the laterally positioned port on the anterior thoracic surface. Some interventionalists request that the patient voluntarily inhale, hold their breath, and then Valsalva while the introducer-CVC exchange is made. However, others do not rely on patient compliance, and instruct their surgical nurse to remove the guide wire and sheath introducer en bloc. This allows the radiologist the opportunity to readily pinch and occlude the hub of the sheath in one hand while the dilator is removed and to insert the tip of the CVC with the other (which lies millimetres away from the sheath orifice) (Fig. 25). Unreliable and uncooperative patients may require the use of the latter process, but longer sheaths that extend into the IVC, a supra-atmospheric environment, a Trendelenburg position or having someone lift the patient's legs will help raise central venous pressures. The safest method would be to use of a peel-away sheath with a 1-way hemostatic valve. Eventually, the CVC is inserted and the peel-away sheath is separated and removed, pulling the opposing sides away from one another with a digit on the apex of the CVC.

In this paper, a modified MMSE receiver for multicarrier DS-CDMA operating in fading, multipath radio channels is presented. This structure is computationally efficient when the channel is rapidly time-varying. Subspace concepts are applied in a proposed blind implementation. The simulations show that the new receiver can produce enhanced performance.

Inferior vena cavae (IVC) can be of unusual geometry, often having odd shapes and being oriented (in long axes) away from the horizontal plane. However, after insertion of a filter, most IVC adopt a circular cross-section. The objective of this study was to determine if the IVC diameter estimated by frontal measurement (cavogram equivalent) reflects the true circular diameter of the infrarenal vena cava. Diameter estimation is clinically important in the correct selection of a filter, because mega cavae (diameter 28 mm or greater) require a particular filter. The infrarenal IVC was measured on computed tomographic (CT) scans in 136 patients. The frontal diameter was recorded as that which would be obtained by a cavogram. Corrected circular diameter was obtained by mapping the circumference of each cross-section on CT to a straight line and calculating diameter from circumference. The average frontal caval diameter was 20.5 (standard deviation 3.7) mm, whereas the average corrected circular diameter was 23.0 (standard deviation 3.4) mm. By frontal measurements, 6 IVC diameters were 28.0 mm or greater. Similarly, by corrected circular diameter, 6 IVC diameters were 28.0 mm or greater. However, of the 6 mega cavae extrapolated to cavograms, only 3 corresponded to mega cavae when corrected for true circular diameter. Yet, of the 6 mega cavae identified by corrected circular diameter measurement, 3 were not identified by frontal diameter assessment. Of the 6 patients with true mega cavae, 2 were being evaluated for right lower quadrant pain, 2 for lymphoma, 1 for a pelvic mass, and 1 for staging of a head and neck cancer. Cavograms can over- or underestimate the true diameter of an IVC, and may thus lead to incorrect filter choice. It is recommended that a sonogram or CT scan be obtained to visualize the IVC in cases of suspected mega cava, and that true circular diameters be used for selection and placement of IVC filters.