MAGNETIC FIELD DYNAMICS IN PLASMA OPENING SWITCH

Computer simulations for magnetic field penetration into plasma of plasma opening switch (POS), and current loop formation in it are presented for various initial plasma densities, currents, and POS geometries. It is shown that the current loop dynamics in the POS is determined by the fast magnetic field penetration in plasma due to the Hall effect. The strong dependence of the current loop longitudinal velocity on the transverse coordinate, together with the influence of the boundary conditions at the POS cathode and anode, lead to the formation of the narrow S-shaped current loop even in a homogeneous plasma. It is shown that the control parameters influencing the dynam-ics of the magnetic field and the motion of the current loop in the POS are the initial plasma density, driving current and cathode radius. The POS resistance is calculated for wide range of initial plasma densities, currents, and cath-ode radiuses. It is shown, that POS resistance is proportional to the total current, inversely proportional to plasma density, and is in the range 10-3…1 Ω for plasma densities 1012…1015 cm-3.

Use of intravenous lidocaine for dose reduction of propofol in paediatric colonoscopy patients: a randomised placebo-controlled study

Background Propofol, a widely used sedative in endoscopic procedures, sometimes causes cardiopulmonary complications. Intravenous lidocaine can diminish visceral pain and decrease the dose of propofol. The purpose of this study was to assess the efficacy and safety of intravenous lidocaine in reducing propofol dosage during paediatric colonoscopy. Methods Forty children who underwent colonoscopy were divided into two groups. Lidocaine hydrochloride (1.5 mg/kg induction and 2 mg/kg/h maintenance) was given intravenously to the lidocaine group, and the same amount of saline was given to the control group after they received lidocaine induction. Propofol initial plasma concentration of 5 μg/mL was targeted, and the procedure was performed after the bispectral index value reached 55. The primary outcome was propofol requirement. Results The propofol requirement in the lidocaine group was decreased by 35.5% (128.6 ± 30.4 mg vs. 199.4 ± 57.6 mg; p < 0.001; 95%CI: − 100.60, − 41.02). The incidence of involuntary body movements was significantly lower in the lidocaine group (p = 0.028; OR = 0.17; 95%CI: 0.03, 0.92). The awakening time (p < 0.001; 95%CI: − 7.67, − 5.13) and recovery times (p < 0.001; 95%CI: − 7.45, − 4.35) were significantly lower in the lidocaine group. Pain was significantly less at 30 min and 60 min after the procedure in the lidocaine group (0 [0–4] vs. 3 [0–5], p < 0. 001; 0 [0–2] vs. 1 [0–3], p = 0.001). There was no difference in the incidence of bradycardia, hypotension, or hypoxia between the two groups. Conclusions For colonoscopy procedures in paediatric patients, intravenous lidocaine reduces the amount of propofol needed, provides better sedation and postprocedural pain management, as well as a reduction in recovery time. Trial registration The trial was registered on November 6, 2020 at China Clinical Trials Registration Center (www.chictr.org.cn) ref.: ChiCTR 2,000,039,706.

Prediction of divertor heat flux width for ITER Pre-Fusion Power Operation using BOUT++ transport code

Prediction of divertor heat flux width is performed for the first and the second Pre-Fusion Power Operation (PFPO) phases specified in the new ITER Research Plan using BOUT++ transport code [Li N.M. et al 2018 Comput. Phys. Commun. 228 69–82]. The initial plasma profiles inside the separatrix are taken from CORSICA scenario studies. Transport coefficients in transport code are calculated by inverting the plasma profiles inside the separatrix and are assumed to be constants in the scrape-off-layer (SOL). An anomalous thermal diffusivity scan is performed with E×B and magnetic drifts. The results in two scenarios identify two distinct regimes: a drift dominant regime when diffusivity is smaller than the respective critical diffusivity χc and a turbulence dominant regime when diffusivity is larger than it. The Goldston heuristic drift model and the ITPA multi-machine experimental scaling yield a lower limit of the width λq. From transport simulations, we obtain the critical diffusivity χc = 0.5 m2⁄ s in 5MA/1.77T PFPO-1 scenario and χc = 0.3 m2⁄ s in 7.5MA/2.65T PFPO-2 scenario. Separatrix temperature and collisionality also have a significant impact on the heat flux width in the drift dominant regime. The investigation clearly yields a scaling for critical thermal diffusivity χc ∝ A½ ⁄ ((Z(1+Z)½ Bp 2)) using ITER scenarios with fixed safety factor q95, major radius R, aspect ratio R/a, and the separatrix temperature T, as well as established the connection with CFETR and C-Mod discharges. This scaling implies that for a given tokamak device with q95, R, R/a, and T fixed, a reduction of poloidal magnetic field by a factor of 3 leads to a 9 times higher critical value of thermal diffusivity χc, possibly yielding a transition from turbulence to drift dominant regime.

Use of Intravenous Lidocaine for Dose Reduction of Propofol in Paediatric Colonoscopy Patients: a Randomised Placebo-controlled Study

Background: Propofol, a widely used sedative in endoscopic procedures, often causes cardiopulmonary complications. Intravenous lidocaine can diminish visceral pain and decrease the dose of propofol. The purpose of this study was to assess the efficacy and safety of intravenous lidocaine in reducing propofol dosage during paediatric colonoscopy.Methods: Forty children who underwent colonoscopy were divided into two groups. Lidocaine hydrochloride (1.5 mg/kg induction and 2 mg/kg/h maintenance) was given intravenously to the lidocaine group, and the same amount of saline was given to the control group after they received lidocaine induction. Propofol initial plasma concentration of 5 μg/mL was targeted, and the procedure was performed after the bispectral index value reached 55. The primary outcome was propofol requirement. Results: The propofol requirement in the lidocaine group was decreased by 35.5% (128.6 ± 30.4 mg vs. 199.4 ± 57.6 mg; p < 0.001; 95%CI: -100.60, -41.02). The incidence of involuntary body movements was significantly lower in the lidocaine group (p = 0.028; OR = 0.17; 95%CI: 0.03, 0.92). The awakening time (p < 0.001; 95%CI: -7.67, -5.13) and recovery times (p < 0.001; 95%CI: -7.45, -4.35) were significantly lower in the lidocaine group. Pain was significantly less at 30 min and 60 min after the procedure in the lidocaine group (0 [0 – 4] vs. 3 [0 – 5], p < 0. 001; 0 [0 – 2] vs. 1 [0 – 3], p < 0.001). The mean lowest blood pressure during the procedure in the control group was significantly lower (p = 0.027; 95%CI: 0.44, 6.86). There was no difference in the incidence of bradycardia, hypotension, or hypoxia between the two groups.Conclusions: For colonoscopy procedures in paediatric patients, intravenous lidocaine reduces the amount of propofol needed, provides better sedation and postprocedural pain management, as well as a reduction in recovery time.Trial registration: The trial was registered on November 6, 2020 at China Clinical Trials Registration Center (www.chictr.org.cn) ref: ChiCTR 2000039706.

Plasma-Induced Catalyst Support Defects for the Photothermal Methanation of Carbon Dioxide

The presence of defects in a catalyst support is known to benefit catalytic activity. In this work, a He-plasma treatment-based strategy for introducing and stabilising defects on a Ni/TiO2 catalyst for photothermal CO2 hydrogenation was established. The impact of pretreatment step sequence—which comprised He-plasma treatment and reduction/passivation—on defect generation and stabilisation within the support was evaluated. Characterisation of the Ni/TiO2 catalysts indicated that defects created in the TiO2 support during the initial plasma treatment stage were then stabilised by the reduction/passivation process, (P-R)Ni/TiO2. Conversely, performing reduction/passivation first, (R-P)Ni/TiO2, invoked a resistance to subsequent defect formation upon plasma treatment and consequently, poorer photothermal catalytic activity. The plasma treatment altered the metal-support interaction and ease of catalyst reduction. Under photothermal conditions, (P-R)Ni/TiO2 reached the highest methane production in 75 min, while (R-P)Ni/TiO2 required 165 min. Decoupling the impacts of light and heat indicated thermal dominance of the reaction with CO2 conversion observed from 200 °C onwards. Methane was the primary product with carbon monoxide detected at 350 °C (~2%) and 400 °C (~5%). Overall, the findings demonstrate the importance of pretreatment step sequence when utilising plasma treatment to generate active defect sites in a catalyst support.

An Ion Source’s View of Its Plasma

Modeling of ion beam extraction from an ECRIS requires special procedures in order to achieve results similar to what is found experimentally. The initial plasma conditions must be included for consistency between experiment and simulation. Space charge forces and their compensation of the extracted ion beam become important with increasing beam intensity. Here we consider the various beam-plasma conditions that occur along any beam line.

The median effective concentration of propofol with different doses of esketamine during gastrointestinal endoscopy in elderly patients：a randomized controlled trial

Background: Propofol may result in hypotension, bradycardia, and loss of protective reflexes, especially in elderly patients, while esketamine, a N-methyl-D-aspartate receptor antagonists, has analgesic, anaesthetic and sympathomimetic properties and is known to cause less cardiorespiratory depression. We hypothesized that esketamine may reduce the median effective concentration (EC50) of propofol and cause more stable haemodynamic responses during gastrointestinal endoscopy in elderly patients. Methods: Ninety elderly patients, aged 65-89 years, undergoing gastrointestinal endoscopy were randomly assigned into three groups: SK0.25 group (0.25 mg/kg esketamine), SK0.5 group (0.5 mg/kg esketamine) and saline control group. Anaesthesia was achieved by target-controlled infusion of propofol with an initial plasma concentration of 2.5 μg/ml with different bolus doses of esketamine during gastrointestinal endoscopy. The EC50 of propofol for gastrointestinal endoscopy was determined by using an up-and-down method of Dixon with an adjacent concentration gradient at 0.5μg/mL to prohibit purposeful movements. Cardiovascular parameters were also measured and recorded. Results: Propofol EC50 and its 95% confidence interval for gastrointestinal endoscopy in elderly patients were 1.71 (1.15-2.27) μg/mL in SK0.5 group, 2.45 (1.85-3.05) μg/mL in SK0.25 group and 3.69 (2.59-4.78) μg/mL in control group respectively (P < 0.05). The average percent change to baseline mean arterial pressure (MBP) was -19.7 (7.55), -15.2 (7.14) and -10.1 (6.73) with P＜0.001, in the control group, the SK0.25 group and the SK0.5 group, respectively. Conclusions: Combination medication of propofol with esketamine reduced the propofol EC50 during gastrointestinal endoscopy in elderly patients and caused more stable haemodynamic responses compared with single administration of propofol.

A magnetic reconnection model for hot explosions in the cool atmosphere of the Sun

&lt;p&gt;UV bursts and Ellerman bombs are transient brightenings observed in the low solar atmospheres of emerging flux regions. Observations have discovered the cospatial and cotemporal EBs and UV bursts, and their formation mechanisms are still not clear. The multi-thermal components with a large temperature span in these events challenge our understanding of magnetic reconnection and heating mechanisms in the low solar atmosphere. We have studied magnetic reconnection between the emerging and background magnetic fields. The initial plasma parameters are based on the C7 atmosphere model. After the current sheet with dense photosphere plasma is emerged to &lt;span tabindex=&quot;0&quot; role=&quot;presentation&quot; data-mathml='&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;&gt;&lt;mn&gt;0.5&lt;/mn&gt;&lt;/math&gt;'&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;0.5&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt; Mm above the solar surface, plasmoid instability appears. The plasmoids collide and coalesce with each other, which makes the plasmas with different densities and temperatures mixed up in the turbulent reconnection region. Therefore, the hot plasmas corresponding to the UV emissions and colder plasmas corresponding to the emissions from other wavelenghts can move together and occur at about the same height. In the meantime, the hot turbulent structures basically concentrate above &lt;span tabindex=&quot;0&quot; role=&quot;presentation&quot; data-mathml='&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;&gt;&lt;mn&gt;0.4&lt;/mn&gt;&lt;/math&gt;'&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;0.4&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt; Mm, whereas the cool plasmas extend to much lower heights to the bottom of the current sheet. These phenomena are consistent with the observations of Chen et al. 2019, ApJL. The synthesized Si IV line profiles are similar to the observed one in UV bursts, the enhanced wing of the line profiles can extend to about &lt;span tabindex=&quot;0&quot; role=&quot;presentation&quot; data-mathml='&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;&gt;&lt;mn&gt;100&lt;/mn&gt;&lt;/math&gt;'&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;100&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt; km s&lt;span tabindex=&quot;0&quot; role=&quot;presentation&quot; data-mathml='&lt;math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;&gt;&lt;msup&gt;&lt;mi&gt;&lt;/mi&gt;&lt;mrow class=&quot;MJX-TeXAtom-ORD&quot;&gt;&lt;mo&gt;&amp;#x2212;&lt;/mo&gt;&lt;mn&gt;1&lt;/mn&gt;&lt;/mrow&gt;&lt;/msup&gt;&lt;/math&gt;'&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;&lt;/span&gt;&lt;span&gt;&lt;span&gt;&lt;span&gt;&amp;#8722;&lt;/span&gt;&lt;span&gt;1&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;. The differences are significant among the numerical results with different resolutions, which indicate that the realistic magnetic diffusivity is crucial to reveal the fine structures and realistic plasmas heating in these reconnection events. Our results also show that the reconnection heating contributed by ambipolar diffusion in the low chromosphere around the temperature minimum region is not efficient.&lt;/p&gt;

Spatial variation of the kappa index in the Earth’s plasma sheet: RCMI results

&lt;p&gt;Astrophysical plasmas are collisionless and correlated systems in which particles are out of thermal equilibrium and can be characterized by non-Maxwellian distribution functions. Amongst those nonthermal distribution functions, the kappa distribution has been widely used and satisfactorily modeled numerous space plasma environments such as ring current and plasma sheet. The particles spectra observed by detector measurements onboard the satellites (e.g., Time History of Events and Macroscale Interactions during Substorms (THEMIS)) indicate that the energy fluxes of plasma sheet particles can be fitted well by the kappa distribution (or combinations thereof). Besides, many empirical models have also used such distributions to estimate fluxes at different energies. Statistically, in the RCM simulations, at all times, even geomagnetically quiet conditions, the initial plasma distribution is assumed to be a kappa function with &amp;#954;&amp;#8776;6. However, based on the flux spectra constructed by THEMIS data, the kappa index has a significant dawn-dusk asymmetry and a clear dependency on the geocentric distance (R) and the magnetic local time (MLT). Using the averaged RCMI calculated energy fluxes in the equatorial plane we intend to analyze the spatial distribution of the spectral index both for ions (&amp;#954;&lt;sub&gt;i&lt;/sub&gt;) and electrons (&amp;#954;&lt;sub&gt;e&lt;/sub&gt;) in this region and compare the simulation results with observations.&lt;/p&gt;

#28: Serum Posaconazole Concentrations Among Children, Adolescents, and Young Adults Receiving Delayed-Release Tablet And Intravenous Posaconazole

Background Posaconazole is a broad-spectrum antifungal used for prophylaxis and treatment of invasive fungal infections. There are limited data on the optimal dosing, safety, and effectiveness of the delayed-released tablets (DRT) and intravenous (IV) formulations in immunocompromised pediatric and adolescent patients. Methods A retrospective chart review was performed to study all immunocompromised patients who received DRT or IV formulations of posaconazole at our institution from January 1, 2014, to July 31, 2019, and had at least one plasma trough concentration. Plasma concentrations ≥0.7 µg /mL were considered therapeutic for prophylaxis, and ≥1.0 µg/mL for treatment. We describe our experience including dosing, plasma trough concentrations, safety, and tolerability. Results We identified 54 patients (28 males/26 females) who received DRT or IV formulations of posaconazole. The median age was 14 years (range 2–21 years). Thirty-one (57%) patients received posaconazole for treatment and 23 (43%) for prophylaxis. The most common underlying condition was hematological malignancies (66%) and 19 patients (35%) had received an allogeneic HSCT and were receiving immunosuppressive therapy. Overall, 36 (67%) patients achieved targeted initial plasma trough concentrations (median 1.3 µg/mL, IQR 0.758–1.760 µg/mL) (Figure). The median daily dose among patients &lt;13 years of age who achieved the targeted initial plasma trough concentrations was 7.3 mg/kg/day (IQR 6.8–11.0) for the DRT formulation and 9.8 mg/kg/day (IQR 7.4–11.7) for the IV formulation. The median daily dose among patients ≥ 13 years of age who achieved the targeted initial plasma trough concentrations was 4.9 mg/kg/day (IQR 4.1–6.5) for the DRT formulation and 5.6 mg/kg/day (IQR 3.9–5.8) for the IV formulation. Concomitant use of H2-receptor blockers (H2RA) and/or proton pump inhibitors (PPI) medications were not associated with failure to achieve target trough levels (P = 0.96). Thirty-six patients (67%) developed transaminitis, mostly grade 1. Conclusions Our results show that DRT and IV formulations are safe and effective in immunocompromised children, adolescents, and young adults. Higher dosing per body weight of DRT and IV posaconazole may be required in patients &lt;13 years of age compared with patients 13 years of age and older to achieve therapeutic plasma concentrations. It appears that neither a PPI nor an H2RA has an effect on the plasma exposure of the DRT.