Shock Parameters Research Articles

Statistical inference of Poisson censored δ-shock model

In this article, the sufficient statistics, complete statistics, and a uniformly minimum variance unbiased estimate (UMVUE) of the failure parameters of the Poisson censored δ -shock model are obtained, which are based on the sample data of shock arrival time. The maximum likelihood estimates of the shock parameters are also obtained by using the EM algorithm, which is based on the total number of observed shock samples. Finally, the estimation errors and convergence rate of the EM iteration are simulated numerically using Matlab R2016b.

The Detection Prospect of the Counter Jet Radiation in the Late Afterglow of GRB 170817A

The central engine of a gamma-ray burst (GRB) is widely believed to launch a pair of oppositely moving jets, i.e., the forward jet moving toward us and the counter jet regressing away. The forward jet generates the radiation typically observed in GRBs, while the counter jet has not been detected yet due to its dimness. GRB 170817A, a short burst associated with a binary neutron star merger event, is a nearby event (z = 0.0097) with an off-axis structured energetic forward jet and hence probably the most suitable target for searching the counter jet radiation. Assuming the same properties for the forward and counter jet components as well as the shock parameters, the fit to the multiwavelength afterglow emission of GRB 170817A suggests a peak time ∼quite a few ×103 day of the counter jet radiation, but the detection prospect of this new component is not promising. Anyhow, if the shock parameters (ϵ e and ϵ B) of the counter jet component are (a few times) higher than that of the forward shock, e.g., the posterior results of the magnetic energy fraction of the forward shock and the counter jet are log10ϵB =−4.23−0.69+1.42 and log10ϵB,cj =−3.65−2.11+3.06 , respectively, as still allowed by the current data, the counter jet afterglow emission will be enhanced and hence may be detected. A few hours of exposure by JWST in the F356W band will stringently test such a scenario.

The runaway nature and origin of α Crucis system

Massive stars are always the focus of astronomical research and a significant part of them (10–20%) moves in space at a high (supersonic) velocity. This paper presents the results of a study of the α Crucis system, located at ∼114 pc distance from the Sun, with an observed bow shock around it. We used data and images from the Gaia and WISE space telescopes. The coordinates, distance, and proper motion of the α Crucis system were used to determine its space velocity. We managed to find a stellar cluster to which the α Crucis system belongs, that is, it has not been ejected from its parent cluster, but is moving in space together with other members of the cluster. The α Crucis system has a velocity of ∼1.3 km/s relative to the star cluster. The geometric parameters of the bow shock are compatible with other known bow shocks. The bow shock is unaligned, i.e., most likely interstellar medium (ISM) large-scale motions are responsible for the resulting bow shock, which is further evidence that the α Crucis system is not runaway in nature.

Influence of footshock number and intensity on the behavioral and endocrine response to fear conditioning and cognitive fear generalization in male rats

Foot-shock paradigms have provided valuable insights into the neurobiology of stress and fear conditioning. An extensive body of literature indicates that shock exposure can elicit both conditioned and unconditioned effects, although delineating between the two is a challenging task. This distinction holds crucial implications not only for the theoretical interpretation of fear conditioning, but also for properly evaluating putative preclinical models of post-traumatic stress disorder (PTSD) involving shock exposure. The characteristics of shocks (intensity and number) affect the strength of learning, but how these characteristics interact to influence conditioned and unconditioned consequences of shocks are poorly known. In this study, we aimed to investigate in adult male rats the impact of varying shock number and intensity on the endocrine and behavioral response to contextual fear conditioning and fear generalization to a novel environment markedly distinct from the shock context (i.e., fear generalization). Classical biological markers of stress (i.e., ACTH, corticosterone, and prolactin) were sensitive to manipulations of shock parameters, whereas these parameters had a limited effect on contextual fear conditioning (evaluated by freezing and distance traveled). In contrast, behavior in different novel contexts (fear generalization) was specifically sensitive to shock intensity. Notably, altered behavior in novel contexts markedly improved, but not completely normalized after fear extinction, hypoactivity apparently being the result of both conditioned and unconditioned effects of foot-shock exposure. The present results will contribute to a better understanding of shock exposure as a putative animal model of PTSD.

Laser shock peening for enhanced fatigue resistance in steel structures: Insights from Q960 steel study

Fatigue damage of steel structures is often likened to the “cancer” of structural engineering. Fatigue failure, characterized by the absence of apparent signs before occurrence, usually leads to significant losses. To investigate the potential of laser shock peening (LSP) as an effective method for improving the fatigue performance of steel structures, square plates and compact tension (CT) specimens made of Q960 structural steel were designed. The surface integrity, fatigue crack growth (FCG) performance, microstructural grain size, and fracture morphology of specimens were compared at different laser shock parameters. The results show that LSP implanted a high level of beneficial residual compressive stress in a mild way, and no obvious surface defects were introduced. A noticeable retardation effect was found in the FCG of LSPed specimens, and this effect becomes more pronounced with the increase of laser pulse energy. Compressive residual stress is a more dominant factor in enhancing fatigue performance compared to grain refinement for the small-grained metals studied. LSP can effectively reduce the FCG rate of Q960 high-strength steel, showing promising application prospects in strengthening the fatigue hazard zone of steel structures.

Continuum and line emission from accretion shocks at T tauri stars – I. Correlations with shock parameters

ABSTRACT Fourteen models are calculated with the shock velocity ranging from 200 to 330 km s$^{-1}$ and pre-shock hydrogen nucleon density ranging from $2.5\times 10^{12}$ to $4\times 10^{13}$ cm$^{-3}$. Among them the summed emergent flux of all spectral lines accounts for about 0.1–0.3 of the total veiling flux. The hydrogen Balmer continuum accounts for 0.17–0.1, while a nearly constant fraction close to 0.5 comes from emission produced by the stellar atmosphere. The main results derived from the veiling continuum energy distributions are two strong correlations: (1) the Balmer jump (BJ) increases as FK, the shock kinetic energy flux, decreases; and (2) at a fixed fraction of surface coverage by accretion shocks $r_{\lambda }$, the ratio of veiling to photospheric continuum flux at wavelength λ decreases as FK decreases. Using the BJ–FK and $r_{4500\,\mathring{\rm A}}$–FK relations, the observed excess continua of 10 T Tauri stars are modelled. For BP Tau and 3 Orion stars our accretion luminosities are higher than published values by a factor of a few. For the six Chamaeleon I stars, our observed accretion luminosities are about 27–78 per cent higher than corresponding published values. Comparison of model results on the He i λ5876 Å flux with observed data indicates that, while those stars with dominant λ5876 Å narrow components can be readily accounted for by the calculated models, those with much stronger broad components cannot, and suggests that for the latter objects the bulk of their excess continua at 5876 Å do not originate from accretion shocks.

Assessment of Safe Early Fixation Strategies in a Cohort Polytraumatized Patients – How is the Surgical Treatment Influenced by the Injury Pattern?

Abstract Background While the inital assessment and the intial treatment of potentially life-threatening injuries is well-described, the surgical treatment strategy following initial resuscitation remains controversial. Timepoint of surgery and type of surgery still reamin topic of discussions. Various, different strategies for optimal timing of fracture fixation in polytrauma patients exist. Aims This study tests the hypothesis that a concept of clearing patients for early definitive surgery that relies on anatomical and physiologic parameters is influenced by the injury distribution. Methods Polytrauma patients treated at a Level 1 trauma center (01.01.2016 - 31.12.2018). Inclusion: primary admission, injury severity score (ISS) ≥16points, requirement of surgical fixation of major extremity or a truncal injury. Exclusion: death <72h after admission, severe traumatic brain injury (TBI). Stratification according to surgical fixation concept: Early total care (ETC, all surgeries <24 h), safe definitive surgery (SDS, staged surgeries <72h), and damage control orthopaedics (DCO, definitive care after stabilization). Endpoints: mortality, complication rates. Parameters of interest: Injury severity and distribution (ISS/AIS), pathophysiologic parameters of hemorrhagic shock, coagulopathy, hypothermia, soft tissue trauma. Results 527 patients, mean age 54.8 SD19.9 years, mean ISS 26.9 SD9.0 points, mortality 20.5%. Group ETC (n=21, 3.9%), Group SDS (n = 284, 53.9%), Group DCO (n = 222, 42.1%). Abdominal and spinal injuries associated with ETC (AIS Abdomen; OR 2.1, 95%CI 1.1 to 4.0, p = 0.026: AIS Spine OR 2.0, 95%CI 1.2 to 3.4, p = 0.007). Extremity and pelvic injuries associated with SDS (OR 1.8, 95%CI 1.1 to 2.8, p = 0.012 and OR 1.3, 95%CI 1.0 to 1.7, p = 0.036), head injuries associated with DCO (OR1.5, 95%CI 1.3 to 1.8, p <0.001). Head injuries were most relevant for mortality and were associated with patients undergoing DCO (29.7%) (ETC; 23.8%, SDS; 13.0%). Conclusion The concept of staged early fixation for major extremity and axial injuries (SDS) was successfully applied in the majority of patients. Predominant head and abdominal injuries were associated with ETC or DCO. The injury distribution influences decision making towards surgical management that is associated with a low complication rate.

Midazolam as mean sedative agent in out-of-hospital cardiac arrest shock: is it associated to increased mortality?

Abstract Funding Acknowledgements None. Background The choice of a sedative agent for patients undergoing invasive ventilation has been widely studied. However, data regarding the optimal sedation strategy after Out-of-Hospital Cardiac Arrest (OHCA) when the patients are suffering from post-OHCA shock is sparse. Aim To explore whether the use of midazolam in patients admitted for OHCA that are additionally haemodynamically unstable increases in-hospital mortality, cardiovascular (CV) mortality, cerebral performance status (CPC) at discharge, and days of intubation or admission, when used selectively during the acute phase of deteriorating post-OHCA shock patients. Methods We report a prospective, observational, single-centre cohort that included all-comers admitted due to OHCA of presumed cardiac cause between May-2019 and July-2023, that remained comatose at admission. Midazolam was only administrated as the mean sedation agent when the patient was in a hemodynamically deteriorating situation (SCAI D-E). Baseline characteristics, OHCA features, blood samples measurements, in-hospital treatments and neurological condition at discharge were registered. Primary outcome was in-hospital death from any cause. Secondary outcomes included CPC at discharge (1-2 VS 3-5), CV mortality, days of admission, days of intubation, need of tracheostomy, myopathy, enolase at 48h and heart transplant during admission. Patients were stratified according to whether they had received midazolam as mean sedation agent at some stage of admission or not. Results 103 patients of the 109 admitted were included (6 refused consent), 45 of them (43%) received midazolam at some stage of admission. No differences in baseline characteristics were found. Mean age was 60.6 years, 79.6% were male, most frequent comorbidities were hypertension (53.4%) and dyslipidaemia (46.6%), and 20,4% had had a previous myocardial infarction. OHCA characteristics, shock parameters and administered treatments did not significantly differ between the two groups (Table 1). In-hospital mortality was numerically higher in the midazolam group but did not reach statistical significance (56% vs. 38%, p=0.075) (Figure 1). There were no differences neither in secondary outcomes (CV mortality 4% vs. 5%, p=0.865; CPC 1-2 70% vs. 83%, p=0.244; days of intubation 6 vs. 4, p=0.203; tracheostomy 18% vs. 10%, p=0.275; days of admission 14 vs. 15, p=0.851; 48h enolase 38 vs. 29, p=0.919; heart transplant during admission 0% vs. 1,7%, p=0.376; myopathy 30% vs. 21% p=0.282). Conclusion In patients admitted due to OHCA, even though the administration of midazolam is given in unstable patients, it is not related to a higher in-hospital mortality nor poorer outcomes.Table 1.OHCA and shock characteristicsFigure 1.Cumulative Survival

Magnetosheath Ion Field‐Aligned Asymmetry and Implications for Ion Leakage to the Foreshock

AbstractThe ion foreshock is highly dynamic, disturbing the bow shock and the magnetosphere‐ionosphere system. To forecast foreshock‐driven space weather effects, it is necessary to model foreshock ions as a function of upstream shock parameters. Case studies in the accompanying paper show that magnetosheath ions sometimes exhibit strong field‐aligned asymmetry toward the upstream direction, which may be responsible for enhancing magnetosheath leakage and therefore foreshock ion density. To understand the conditions leading to such asymmetry and the potential for enhanced leakage, we perform case studies and a statistical study of magnetosheath and foreshock region data surrounding ∼500 Time History of Events and Macroscale Interactions during Substorms mission bow shock crossings. We quantify the asymmetry using the heat flux along the field‐aligned direction. We show that the strong field‐aligned heat flux persists across the entire magnetosheath from the magnetopause to the bow shock. Ion distribution functions reveal that the strong heat flux is caused by a secondary thermal population. We find that stronger asymmetry events exhibit heat flux preferentially toward the upstream direction near the bow shock and occur under larger IMF strength and larger solar wind dynamic pressure and/or energy flux. Additionally, we show that near the bow shock, magnetosheath leakage is a significant contributor to foreshock ions, and through enhancing the leakage the magnetosheath ion asymmetry can modulate the foreshock ion velocity and density. Our results imply that likely due to field line draping and compression against the magnetopause that leads to a directional mirror force, modeling the foreshock ions necessitates a more global accounting of downstream conditions.

Optimizing time-varying performance and mission aborting policy in resource constrained missions

Intensive efforts have been devoted to mission aborting systems. However, the existing models mostly assumed static performance or failed to consider limited resources (e.g., energy, budget). Motivated by practical applications like unmanned aerial vehicles (UAV), this paper relaxes those assumptions by modeling a resource-constrained system that must complete a required amount of work for a successful mission and accomplish further a return/rescue phase (RP) to survive the system. The operation phase (OP) of the mission may be aborted depending on the number of external shocks (e.g., electromagnetic interferences, radiations) the system has survived and the operation time elapsed, followed by a RP to save the asset. Probabilistic methods are proposed to evaluate the mission success probability (MSP) and system survival probability (SSP). An optimization problem is formulated and solved, which determines the joint optimal time-varying performance policy and OP aborting policy, maximizing the MSP while providing a required level of SSP. A case study of UAV executing a reconnaissance mission is carried out to demonstrate the suggested model and examine influence of the SSP level as well as shock parameters on the mission performance and optimal policies. The advantage of time-varying performance in enhancing the MSP is also demonstrated.

Jet Structure and Burst Environment of GRB 221009A

We conducted a comprehensive investigation of the brightest-of-all-time GRB 221009A, using new insights from very high-energy (VHE) observations from LHAASO and a complete multiwavelength afterglow data set. Through data fitting, we imposed constraints on the jet structure, radiation mechanisms, and burst environment of GRB 221009A. Our findings reveal a structured jet morphology characterized by a core+wing configuration. A smooth transition of energy within the jet takes place between the core and wing, but with a discontinuity in the bulk Lorentz factor. The jet structure differs from both the case of the short GRB 170817A and the results of numerical simulations for long-duration bursts. The VHE emission can be explained by the forward shock synchrotron self-Compton radiation of the core component, but requiring a distinctive transition of the burst environment from uniform to wind-like, suggesting the presence of complex pre-burst mass ejection processes. The low-energy multiwavelength afterglow is mainly governed by the synchrotron radiation from the forward and reverse shocks of the wing component. Our analysis indicates a magnetization factor of 5 for the wing component. Additionally, by comparing the forward shock parameters of the core and wing components, we find a potential correlation between the electron acceleration efficiency and both the Lorentz factor of the shock and the magnetic field equipartition factor. We discuss the significance of our findings, potential interpretations, and remaining issues.

Combustion instability analysis in an ethylene-fueled scramjet combustor under various fuel penetration height conditions using an image-based nonlinear dimensionality reduction method

The present study investigates the effects of fuel penetration height on combustion instabilities in an ethylene-fueled scramjet model combustor with a cavity flameholder. Experiments were performed at the stagnation temperature of 1900 K, the stagnation pressure of 0.37 MPa, and the Mach number of 2. Three fuel injection orifice diameters:2.3, 2.4, and 2.5 mm, were tested to elucidate the effects of ethylene penetration height on combustion instabilities. Furthermore, high-speed measurements of CH* chemiluminescence and shadowgraphs were performed with high-speed video cameras. To examine the dynamics of the combustion instabilities, time-resolved CH* chemiluminescence images and shock parameters, extracted from snapshots of shadowgraphs, were analyzed using a non-linear dimensionality reduction algorithm: Gaussian Process Dynamical Model (GPDM). Thereafter, further analyses on the acquired latent variables were conducted with Recurrence Plot (RP). The experimental results showed that the fuel equivalence ratio (ϕ) range for cavity shear-layer combustion mode expanded as d decreased. Furthermore, for ϕ = 0.18, the instability behavior remarkably changed at around d = 2.4 mm. Therefore, the instability dynamics for ϕ = 0.18 were investigated using GPDM and RP including results from our previous study (d = 2, 3, and 4 mm), revealing differences in the instability behaviors. For d = 3 and 4 mm, jet-wake combustion and ram combustion modes were established alternately with a frequency of about 1600 Hz. In contrast, at d = 2.4 and 2.5 mm, although a similar instability in the d = 4 mm case was present at almost the same oscillation frequency, a different instability behavior was also confirmed. This additional instability exhibited an intermediate state between jet-wake combustion and ram combustion modes. These two instabilities emerged aperiodically. For an unstable combustion in shear layer observed for d = 2 and 2.3 mm, corresponding RPs exhibited black patches, indicating that the oscillation amplitude diminished substantially.

Multiple impact effects of helium-driven shocks on thin fiber-metal laminates

Fiber Metal Laminates (FMLs) have garnered considerable attention and are increasingly being utilized in the development of protective armors for explosion and ballistic scenarios. While most research has focused on assessing the response of FMLs to single impacts, real battlefield situations often require shielding structures to endure multiple impacts. Thus, this study revolves around the creation of hybrid FMLs designed for shock shielding purposes. The primary focus is on how these laminates withstand repetitive impacts from high-intensity shock waves, aiming to pinpoint the optimal sequence that offers the highest resistance against multiple shock impacts. To establish effective shielding, a multi-layered FML configuration is employed. This configuration incorporates AA6061-T6 facing plates, ballistic-grade synthetic materials like aramid/epoxy ply, and ultra-high molecular weight polyethylene (UHMWPE)/epoxy ply. Additionally, a paperboard/epoxy lamina is introduced to induce functional grading based on layerwise shock impedance mismatches. Shock impact experiments are conducted using a shock tube equipped with helium as the driver gas. Critical shock parameters, including Mach Number, positive impulse, and peak overpressure, are meticulously evaluated. For validation purposes, a numerical model is employed to project the damage profile as a function of radial distance across different laminate sequences. The study unveils that ply deformations are strongly influenced by the arrangement of core layers, particularly the positions of the paperboard and UHMWPE layers within the core structure. To contextualize the findings, the shock impact results obtained from this study are compared with those from prior experiments that employed nitrogen-driven shocks.

Prediction of Surface Residual Stresses after Laser Shock Processing on TC4 Titanium Alloy Using Different Neural Network Agent Models

Nowadays, it has become a trend to use finite element simulation instead of experimental processes, and this is widely used in the fields of structural mechanics, fluid mechanics, fracture mechanics, and so on. By replacing the experimental process with finite element simulation, we can reduce time and costs; however, when using finite element simulation, we need to define a series of settings, such as modeling, material assignment, environment settings, and many other operations. For laser shock processing intensification, the simulation experiment process is cumbersome and time-consuming. It involves performing neural network agent modeling, replacing finite element simulation with the learning and prediction capabilities of neural networks, learning by using some of the simulation results as a training sets for the neural network, and then learning by using the remaining simulation results as testing sets to test the predictive ability of the neural network agent model. TC4 titanium alloy was selected as the experimental material. Three kinds of neural network agent models, a genetic algorithm-optimized BP network, a strong classifier design based on BP_Adaboost, and an extreme learning machine, instead of finite element simulation experiments, were used to predict the residual stresses generated on the surfaces of the material under different laser shock parameters. Comparing the prediction performances of different neural network agent models, the genetic algorithm-optimized BP network shows the best prediction performance, and its prediction value matches well with the experimental value. The R2, RMSE, and MAE of the testing sets of the BP network optimized using the genetic algorithm were 0.9985, 44.4518, and 30.6285, respectively. The BP network agent model optimized using the genetic algorithm for laser shock parameters other than the 208 sets of data also had good prediction performance, and the predicted values were similar to the actual experimental results. The prediction results show that the BP network optimized using the genetic algorithm can predict the residual stresses on the surface of TC4 titanium alloy material under strengthening via laser shock processing; the genetic algorithm-optimized BP neural network agent model is more convenient and quicker compared to the finite element simulation, and the predicted value is also similar to the actual value. It can thus be used to replace finite element simulation by establishing a more convenient and quicker neural network agent model.

Backstreaming ions at a high Mach number interplanetary shock

Context.Solar Orbiter, a mission developed by the European Space Agency, explores in situ plasma across the inner heliosphere while providing remote-sensing observations of the Sun. The mission aims to study the solar wind, but also transient structures such as interplanetary coronal mass ejections and stream interaction regions. These structures often contain a leading shock wave that can differ from other plasma shock waves, such as those around planets. Importantly, the Mach number of these interplanetary shocks is typically low (1–3) compared to planetary bow shocks and most astrophysical shocks. However, our shock survey revealed that on 30 October 2021, Solar Orbiter measured a shock with an Alfvén Mach number above 6, which can be considered high in this context.Aims.Our study examines particle observations for the 30 October 2021 shock. The particles provide clear evidence of ion reflection up to several minutes upstream of the shock. Additionally, the magnetic and electric field observations contain complex electromagnetic structures near the shock, and we aim to investigate how they are connected to ion dynamics. The main goal of this study is to advance our understanding of the complex coupling between particles and the shock structure in high Mach number regimes of interplanetary shocks.Methods.We used observations of magnetic and electric fields, probe-spacecraft potential, and thermal and energetic particles to characterize the structure of the shock front and particle dynamics. Furthermore, ion velocity distribution functions were used to study reflected ions and their coupling to the shock. To determine shock parameters and study waves, we used several methods, including cold plasma theory, singular-value decomposition, minimum variance analysis, and shock Rankine-Hugoniot relations. To support the analysis and interpretation of the experimental data, test-particle analysis, and hybrid particle in-cell simulations were used.Results.The ion velocity distribution functions show clear evidence of particle reflection in the form of backstreaming ions several minutes upstream. The shock structure has complex features at the ramp and whistler precursors. The backstreaming ions may be modulated by the complex shock structure, and the whistler waves are likely driven by gyrating ions in the foot. Supra-thermal ions up to 20 keV were observed, but shock-accelerated particles with energies above this were not.

Research and Application of Anti-electric Shock Communication Terminal Based on Internet of Things Technology

Leakage protection cannot effectively identify the voltage and current reception signals of electric shock grounding points that may pose a danger to personal safety through analysis of electric shock parameters, which is inherently inadequate. When a communication electric shock safety accident occurs, the accident site can be visually displayed in the safety prevention and control center, and an alarm is sent out. Meanwhile, relevant control instructions are issued to cut off the accident communication phase line to prevent secondary injury. In this paper, artificial intelligence and Internet of Things technology are applied to the communication system. The tag sensor is used in the monitoring system and is also used as the perception layer. The electric shock receiving signal obtained under the control circuit structure of the Internet of Things is determined by means of S transformation. The physical characteristics of wave frequency sensitivity are analyzed. Then, the external characteristics of biological shock are extracted with the help of the working frequency of each band of wavelet multi-resolution analysis, so that the electric shock model can deal with the hazards that cannot be identified by the traditional perception layer. The deep neural network is optimized to improve the recognition probability. Experiments verify that the recognition rate of the biological electric shock is as high as 99%, which further improves the stability of the leakage protection device and provides a guarantee for the normal operation of the communication system.

Extracorporeal Blood Purification with CytoSorb in 359 Critically Ill Patients

Introduction: Critically ill patients with inflammatory dysregulation and organ disfunction may benefit from blood purification, although the use of this technique has not been described in large case series. We evaluated clinical outcomes and survival in high-risk intensive care unit (ICU) patients who underwent extracorporeal blood purification. Methods: 359 consecutive ICU patients treated with CytoSorb were included. Results: Main admission diagnoses were 120 (34%) refractory cardiac arrest under mechanical chest compression; 101 (28%) profound cardiogenic shock; 81 (23%) post-cardiotomy cardiogenic shock; and 37 (10%) respiratory failure. Fifteen patients (4%) were positive for SARS-CoV-2 infection. We observed 49% 30-day mortality, 57% ICU mortality, and 62% hospital mortality, all lower than the 71% mortality predicted by SAPS II and 68% predicted by SOFA score. Parameters of shock and organ failure, above all vasoactive inotropic score, reduced during CytoSorb treatment. Multivariable analysis identified SAPS II, lactate dehydrogenase, ICU stay duration, vasoactive inotropic score, lactates, intra-aortic counterpulsation on top of VA-ECMO, and total bilirubin as predictors of mortality. No CytoSorb-related complications occurred. Conclusion: CytoSorb treatment was effective in reducing laboratory parameters of shock and vasoactive inotropic score with possible survival implications in a large population of critically ill patients.

Magnetohydrodynamic Shocks Revisited: Magnetically Constraining the Upstream Solar Wind Condition

Magnetohydrodynamic (MHD) shocks are commonly found in various space and astrophysical systems. One often encounters the problem that only the magnetic field data are available when studying interplanetary shocks and planetary bow shocks in the solar system, and not the plasma data due to instrumental and/or telemetry limitations. We aim to reveal the mathematical structure of the MHD Rankine–Hugoniot relation under the condition that magnetic field changes across the shock are known, which can be devised into a diagnosis tool to constrain the shock parameters. The perturbative solution is already known for the Rankine–Hugoniot equation. The solution is combined with the condition of the de Hoffmann–Teller frame for the vanishing convective electric field, and we obtain a two-dimensional matrix equation for the density jump and the Alfvén Mach number. The lesson is that the shock parameters (density jump and Alfvén Mach number) are analytically obtained by inverting the MHD Rankine–Hugoniot equation under the condition that the plasma beta is either a priori set or known. Further numerical studies indicate that the presented shock jump estimation works particularly well for quasi-perpendicular shocks. Moreover, a test case with the Earth bow shock crossing data supports our theoretical development. The presented method opens the door to determining or constraining the shock parameters even if the data are limited to the magnetic field only.

Electron Heating in Shocks: Statistics and Comparison

AbstractSupernova remnant (SNR) shocks are the highest Mach number non‐relativistic shocks in electron‐ion plasmas. These shocks are the most efficient particle accelerators in space. SNR shock parameters are inferred from measurements of electromagnetic radiation from heated and accelerated particles. Temperature of the shock heated electrons is one of the most important parameters in supernova remnant shocks. Knowledge of the downstream electron‐to‐ion temperature ratio or of the ratio of the downstream electron temperature to the incident ion energy is crucial for understanding physics of the very high‐Mach number SNR shocks. Heliospheric shocks have substantially lower Mach numbers than SNR shocks but can be extensively studied in in situ observations with further extrapolation of the findings to higher Mach numbers. Magnetospheric Multiscale mission observations of the Earth bow shock are used to analyze dependence of the electron heating on the shock Mach number. It is found that the ratio of the downstream electron temperature to the incident ion energy decreases with the increase of the Mach number. At high Mach numbers this ratio and stabilizes at about 2.5%. The electron‐to‐ion temperature ratio stabilizes at about 10%. The peak electron temperature occurs at the overshoot maximum, further downstream electrons cool down. The mean ratio of the 4.5 s averages of the downstream and maximum electron temperatures is 0.85. Electron heating does not follow the thermodynamic adiabatic law. The heating and cooling behavior implies that the energy is provided by the overall cross‐shock potential while small‐scale electric fields rapidly isotropize the electron distribution.

The ultra-long GRB 220627A at z = 3.08

Context. GRB 220627A is a rare burst with two distinct γ-ray emission episodes separated by almost 1000 s that triggered the Fermi Gamma-ray Burst Monitor twice. High-energy GeV emission was detected by the Fermi Large Area Telescope coincident with the first emission episode but not the second. The discovery of the optical afterglow with MeerLICHT led to MUSE observations which secured the burst redshift to z = 3.08, making this the most distant ultra-long gamma-ray burst (GRB) detected to date. Aims. The progenitors of some ultra-long GRBs have been suggested in the literature to be different to those of normal long GRBs. Our aim is to determine whether the afterglow and host properties of GRB 220627A agree with this interpretation. Methods. We performed empirical and theoretical modelling of the afterglow data within the external forward shock framework, and determined the metallicity of the GRB environment through modelling the absorption lines in the MUSE spectrum. Results. Our optical data show evidence for a jet break in the light curve at ∼1.2 days, while our theoretical modelling shows a preference for a homogeneous circumburst medium. Our forward shock parameters are typical for the wider GRB population, and we find that the environment of the burst is characterised by a sub-solar metallicity. Conclusions. Our observations and modelling of GRB 220627A do not suggest that a different progenitor compared to the progenitor of normal long GRBs is required. We find that more observations of ultra-long GRBs are needed to determine if they form a separate population with distinct prompt and afterglow features, and possibly distinct progenitors.