Efficient Magnetic Vortex Acceleration by femtosecond laser interaction with long living optically shaped gas targets in the near critical density plasma regime.

We introduce a novel, gaseous target optical shaping laser set-up, capable to generate short scale length, near-critical target profiles via generated colliding blast waves. These profiles are capable to maintain their compressed density for several nanoseconds, being therefore ideal for laser-plasma particle acceleration experiments in the near critical density plasma regime. Our proposed method overcomes the laser-target synchronization limitations and delivers energetic protons, during the temporal evolution of the optically shaped profile, in a time window of approximately 2.5 ns. The optical shaping of the gas-jet profiles is optimised by MagnetoHydroDynamic simulations. 3D Particle-In-Cell models, adopting the spatiotemporal profile, simulate the 45 TW femtosecond laser plasma interaction to demonstrate the feasibility of the proposed proton acceleration set-up. The optical shaping of gas-jets is performed by multiple, nanosecond laser pulse generated blastwaves. This process results in steep gradient, short scale length plasma profiles, in the near critical density regime allowing operation at high repetition rates. Notably, the Magnetic Vortex Acceleration mechanism exhibits high efficiency in coupling the laser energy into the plasma in the optically shaped targets, resulting to collimated proton beams of energies up to 14 MeV.

Non-linear QED approach for betatron radiation in a laser wakefield accelerator.

Laser plasma-based accelerators provide an excellent source of collimated, bright, and adequately coherent betatron-type x-ray pulses with potential applications in science and industry. So far the laser plasma-based betatron radiation has been described within the concept of classical Liénard-Wiechert potentials incorporated in particle-in-cell simulations, a computing power-demanding approach, especially for the case of multi-petawatt lasers. In this work, we describe the laser plasma-based generation of betatron radiation at the most fundamental level of quantum mechanics. In our approach, photon emission from the relativistic electrons in the plasma bubble is described within a nonlinear quantum electrodynamics (QED) framework. The reported QED-based betatron radiation results are in excellent agreement with similar results using Liénard-Wiechert potentials, as well as in very good agreement with betatron radiation measurements, obtained with multi-10-TW lasers interacting with He and multielectron N[Formula: see text] gas targets. Furthermore, our QED approach results in a dramatic reduction of the computational runtime demands, making it a favorable tool for designing betatron radiation experiments, especially in multi-petawatt laser facilities.

Design, manufacturing, evaluation, and performance of a 3D-printed, custom-made nozzle for laser wakefield acceleration experiments.

Laser WakeField Acceleration (LWFA) is extensively used as a high-energy electron source, with electrons achieving energies up to the GeV level. The produced electron beam characteristics depend strongly on the gas density profile. When the gaseous target is a gas jet, the gas density profile is affected by parameters, such as the nozzle geometry, the gas used, and the backing pressure applied to the gas valve. An electron source based on the LWFA mechanism has recently been developed at the Institute of Plasma Physics and Lasers. To improve controllability over the electron source, we developed a set of 3D-printed nozzles suitable for creating different gas density profiles according to the experimental necessities. Here, we present a study of the design, manufacturing, evaluation, and performance of a 3D-printed nozzle intended for LWFA experiments.

Efficient plasma electron accelerator driven by linearly chirped multi-10-TW laser pulses.

The temporal rearrangement of the spectral components of an ultrafast and intense laser pulse, i.e., the chirp of the pulse, offers significant possibilities for controlling its interaction with matter and plasma. In the propagation of ultra-strong laser pulses within the self-induced plasma, laser pulse chirp can play a major role in the dynamics of wakefield and plasma bubble formation, as well as in the electron injection and related electron acceleration. Here, we experimentally demonstrate the control of the generation efficiency of a relativistic electron beam, with respect to maximum electron energy and current, by accurately varying the chirp value of a multi-10-TW laser pulse. We explicitly show that positively chirped laser pulses, i.e., pulses with instantaneous frequency increasing with time, accelerate electrons in the order of 100 MeV much more efficiently in comparison to unchirped or negatively chirped pulses. Corresponding Particle-In-Cell simulations strongly support the experimental results, depicting a smoother plasma bubble density distribution and electron injection conditions that favor the maximum acceleration of the electron beam, when positively chirped laser pulses are used. Our results, aside from extending the validity of similar studies reported for PW laser pulses, provide the ground for understanding the subtle dynamics of an efficient plasma electron accelerator driven by chirped laser pulses.

The importance of the laser pulse-ablator interaction dynamics prior to the ablation plasma phase in inertial confinement fusion studies.

This work presents studies which demonstrate the importance of the very early heating dynamics of the ablator long before the ablation plasma phase begins in laser driven inertial confinement fusion (ICF) studies. For the direct-drive fusion concept using lasers, the development of perturbations during the thermo-elasto-plastic (TEP) and melting phases of the interaction of the laser pulse with the ablator's surface may act as seeding to the subsequent growth of hydro-dynamic instabilities apparent during the acceleration phase of the interaction such as for instance the Rayleigh-Taylor and the Richtmyer-Meshkov, which strongly affect the implosion dynamics of the compression phase. The multiphysics-multiphase finite-element method (FEM) simulation results are experimentally validated by advanced three-dimensional whole-field dynamic imaging of the surface of the ablator allowing for a transverse to the surface spatial resolution of only approximately 1 nm. The study shows that the TEP and melting phases of the interaction are of crucial importance since transverse perturbations of the ablator's surface can reach tens of nanometres in amplitude within the TEP and melting phases. Such perturbations are of Rayleigh type and are transferred from the ablator to the substrate from the very first moments of the interaction. This article is part of a discussion meeting issue 'Prospects for high gain inertial fusion energy (part 1)'.

Ultrafast laser pulse chirp effects on laser-generated nanoacoustic strains in Silicon.

Nanoacoustic strains are generated in Silicon by chirped femtosecond laser pulses using thin Titanium films as transducers. We investigate the effect that the generating laser pulse chirp has on the amplitude of the induced strains, manifested as Brillouin oscillations observed in degenerate femtosecond pump-probe transient reflectivity measurements. The strain amplitude is larger when negatively chirped pulses are used, which is attributed to the more efficient conversion of laser pulse light into acoustic strain in the Titanium transducer. Our present studies clearly show that the dependence of the Brillouin amplitude and the lattice strain is a non-monotonous function of the laser chirp parameter. An optimum negative laser pulse chirp is found for which the strain amplitude is maximized. A detailed thermomechanical model satisfactorily supports the experimental findings. In such a way, it is possible to suppress or enhance the induced nanoacoustic strain amplitude, thus all-optically controlling it by at least a factor of two.

The influence of the solid to plasma phase transition on the generation of plasma instabilities.

The study of plasma instabilities is a research topic with fundamental importance since for the majority of plasma applications they are unwanted and there is always the need for their suppression. The initiating physical processes that seed the generation of plasma instabilities are not well understood in all plasma geometries and initial states of matter. For most plasma instability studies, using linear or even nonlinear magnetohydrodynamics (MHD) theory, the most crucial step is to correctly choose the initial perturbations imposed either by a predefined perturbation, usually sinusoidal, or by randomly seed perturbations as initial conditions. Here, we demonstrate that the efficient study of the seeding mechanisms of plasma instabilities requires the incorporation of the intrinsic real physical characteristics of the solid target in an electro-thermo-mechanical multiphysics study. The present proof-of-principle study offers a perspective to the understanding of the seeding physical mechanisms in the generation of plasma instabilities.

1,3-ß-D-glucan concentrations in blood products predict false positive post-transfusion results.

1,3-ß-D-glucan (BDG) is increasingly used to diagnose invasive fungal infections (IFI), although false positive results are a concern. To evaluate the potential interaction of blood products with the BDG assay, human albumin (HA), fresh frozen plasma (FFP), undiluted platelet transfusion (UPT) and packed red blood cells (PRBC) were tested for their BDG content using two different b-D-glucan tests. UPTs tested negative, FFP, PBRC and HA tested positive for BDG. In serial dilution, BDG concentration correlated with blood product concentration. To investigate the clinical impact of blood product transfusions, we measured BDG levels before and after the transfusion in three patients (2 PRBC, 1 HA). In the patients receiving PRBC transfusions, BDG values increased from 13 and 17 pg ml(-1) to 183 and 361 pg ml(-1), the HA transfusion increased the serum level from 42 to 58 pg ml(-1). BDG concentrations measured in blood products can be used to predict false positive BDG results.

1,3-ß-D-Glucan contamination of common antimicrobials.

BACKGROUND: 1,3-ß-D-Glucan (BDG) is a fungal cell wall constituent used in the diagnosis of invasive fungal infections. BDG testing, although endorsed by the European Organization for Research and Treatment of Cancer, suffers from limited specificity. False-positive results have been linked to haemodialysis membranes, blood products, antineoplastic agents and antimicrobial use. OBJECTIVES: The aim of this study was to determine whether false-positive BDG results in the context of antimicrobial use are caused by BDG present in infusion solutions. METHODS: We obtained 35 antimicrobial drugs (30 antibiotics and 5 antifungals) and analysed their BDG content using two different assays. RESULTS: Twenty-five antimicrobials (20 antibiotics and all the tested antifungals) contained enough BDG to trigger a positive test. Depending on the substance, BDG varied between 9 and 2818 pg/mL. CONCLUSIONS: A majority of the available antimicrobial substances contained BDG, potentially limiting the utility of BDG testing in the context of prior exposure to these drugs. As the cumulative effects of repeated BDG exposure are unknown, efforts to reduce contamination should be considered.

Effect of previous anesthesia experience on patients' knowledge and desire for information about anesthesia and the anesthesiologist: a 500 patients' survey from Greece.

BACKGROUND: This study aimed at assessing the effect of previous anesthesia experience on patients' knowledge of anesthesia and the role of anesthesiologists, on what they would want to know about anesthesia and the way they would like to be informed. METHODS: Questionnaires with fixed questions were distributed to consenting, consecutive surgical patients before the pre-anesthetic visit. Patients were divided into two groups: patients with previous anesthesia experience (Group A) and patients without previous anesthesia experience (Group B). The questionnaires included patients' demographics, questions related to their knowledge about the anesthesiologists' role and about their desire for information. RESULTS: 500 questionnaires were analyzed. The majority of patients (94.2%) know that the anesthesiologist is a specialized doctor and 89.2% believe that the anesthesiologist watches over the patient throughout surgery. These results were similar in both groups. The majority of patients (98.2%) also want to meet the anesthesiologist before surgery and 78% want even more information. Only 65.6% want to be aware of all possible complications, in both groups, while 17.6% do not want to know anything about complications. In general, answers to specific questions regarding what the patients want to know about anesthesia did not differ between groups. The vast majority of patients wish to talk with the anesthesiologist before surgery. CONCLUSION: Previous anesthesia experience did not seem to influence patients' desire for meeting the anesthesiologist and seeking information. A strong desire to personally meet the anesthesiologist is expressed and patients' desire for even more information is noted.

Anesthesia for laparoscopic surgery in a patient with myotonic dystrophy (Steinert's disease): beneficial use of sugammadex, but incorrect use of pethidine: a case report.

Patients with Myotonic Dystrophy show an unpredictable response to several anesthetic drugs including opioids, neuromuscular blocking agents and especially reversal agents like neostigmine. We describe the case of a 40 year old patient with myotonic dystrophy who underwent laparoscopic cholecystectomy and ovarian cyst removal under general anesthesia. The authors suggest the use of the new reversal agent suggamadex, for reversing neuromuscular blockade caused by rocuronium, in patients suffering from neuromuscular disease and especially from Myotonic Dystrophy, because it rapidly and completely reverses any residual neuromuscular blockade, but also underline the increased susceptibility of these patients to opioids.

Quantifying the spoilage and shelf-life of yoghurt with fruits.

The aim of the present study was to develop a predictive model to quantify the spoilage of yoghurt with fruits. Product samples were stored at various temperatures (5-20 °C). Samples were subjected to microbiological (total viable counts, lactic acid bacteria-LAB, yeasts and moulds) and physico-chemical analysis (pH, titratable acidity and sugars). LAB was the dominant micro-flora. Yeasts population increased at all temperatures but a delay was observed during the first days of storage. Titratable acidity and pH remained almost constant at low temperatures (5 and 10 °C). However, at higher temperatures (>10 °C), an increase in titratable acidity and reduction in pH was observed. Sugar concentration (fructose, lactose and glucose) decreased during storage. A mathematical model was developed for shelf-life determination of the product. It was successfully validated at a temperature (17 °C) not used during model development. The results showed that shelf-life of this product could not be established based only on microbiological data and use of other parameters such as sensory or/and physico-chemical analysis is required. Shelf-life determination by spoilage tests is time-consuming and the need for new rapid techniques has been raised. The developed model could help dairy industries to establish shelf-life predictions on yoghurt with fruits stored under constant temperature conditions.

Awake tracheal intubation using the Airtraq laryngoscope: a case series.

The Airtraq laryngoscope (AL) is a new single use indirect laryngoscope designed to facilitate tracheal intubation in anaesthetised patients either with normal or difficult airway anatomy. It is designed to provide a view of the glottis without alignment of the oral, pharyngeal and tracheal axes. We report four cases of successful awake tracheal intubation using the AL. The first case is a patient with severe ankylosing spondylitis and the other three cases with anticipated difficult airway. An awake intubation under sedation and topical airway anaesthesia was chosen. We consider that the AL can be used effectively to accomplish an awake intubation in patients with a suspected or known difficult airway and may be a useful alternative where other methods for awake intubation have failed or are not available.

Airway management in Greece: a nationwide postal survey.

BACKGROUND: The aim of this study was to identify Greek anesthesiologists' difficult airway management practices, as well as the availability of equipment and familiarity with different airway management techniques. METHODS: A questionnaire containing 21 questions was posted to the vast majority of specialist anesthesiologists practicing in Greece (N.=849). Filled copies of the questionnaire were returned anonymously. RESULTS: Response rate was 42% (360/849). Preoperative evaluation was performed by 95% of the respondents, with senior anesthesiologists relying mostly on subjective estimation of the airway. Ninety percent of the respondents had direct access to a difficult airway cart. Laryngeal masks were available in most anesthesia Departments (86%), but expertise was still unsatisfactory, especially in hospitals with a lower workload. Spreading and familiarity with newer airway adjuncts was insufficient, especially in smaller anesthesia Departments. Only 39% of the respondents had a flexible fibrescope readily available. Sixty percent could be considered skilled with laryngeal masks and 11% with fibrescopes. When the occasion for fibrescope use did occur, less senior anesthesiologists opted for laryngeal masks and were clearly less inclined towards surgical intervention. However, for the more senior anesthesiologists surveyed, the application of a face mask with a ''two hands'' technique and more traditional supraglottic airway devices were found to be more common. CONCLUSION: There are shortfalls in various areas of airway management in Greece, in particular with the availability of modern airway devices and training in fibrescopic intubation.

The influence of premedication and smoking.

The history of smoking and premedication did not influence the proportion of patients who had a cough response to fentanyl when administrated as first agent during induction in anesthesia.