Tripled yield in direct-drive laser fusion through statistical modelling.

Focusing laser light onto a very small target can produce the conditions for laboratory-scale nuclear fusion of hydrogen isotopes. The lack of accurate predictive models, which are essential for the design of high-performance laser-fusion experiments, is a major obstacle to achieving thermonuclear ignition. Here we report a statistical approach that was used to design and quantitatively predict the results of implosions of solid deuterium-tritium targets carried out with the 30-kilojoule OMEGA laser system, leading to tripling of the fusion yield to its highest value so far for direct-drive laser fusion. When scaled to the laser energies of the National Ignition Facility (1.9 megajoules), these targets are predicted to produce a fusion energy output of about 500 kilojoules-several times larger than the fusion yields currently achieved at that facility. This approach could guide the exploration of the vast parameter space of thermonuclear ignition conditions and enhance our understanding of laser-fusion physics.

[Study of the resistome of human microbial communities using a targeted panel of antibiotic resistance genes in COVID-19 patients].

AIM: To study overall drug resistance genes (resistome) in the human gut microbiome and the changes in these genes during COVID-19 in-hospital therapy. MATERIALS AND METHODS: A single-center retrospective cohort study was conducted. Only cases with laboratory-confirmed SARS-CoV-2 RNA using polymerase chain reaction in oro-/nasopharyngeal swab samples were subject to analysis. The patients with a documented history of or current comorbidities of the hepatobiliary system, malignant neoplasms of any localization, systemic and autoimmune diseases, as well as pregnant women were excluded. Feces were collected from all study subjects for subsequent metagenomic sequencing. The final cohort was divided into two groups depending on the disease severity: mild (group 1) and severe (group 2). Within group 2, five subgroups were formed, depending on the use of antibacterial drugs (ABD): group 2A (receiving ABD), group 2AC (receiving ABD before hospitalization), group 2AD (receiving ABD during hospitalization), group 2AE (receiving ABD during and before hospitalization), group 2B (not receiving ABD). RESULTS: The median number of antibiotic resistance (ABR) genes (cumulative at all time points) was significantly higher in the group of patients treated with ABD: 81.0 (95% CI 73.8-84.5) vs. 51.0 (95% CI 31.1-68.4). In the group of patients treated with ABD (2A), the average number of multidrug resistance genes (efflux systems) was significantly higher than in controls (group 2B): 47.0 (95% CI 46.0-51.2) vs. 21.5 (95% CI 7.0-43.9). Patients with severe coronavirus infection tended to have a higher median number of ABR genes but without statistical significance. Patients in the severe COVID-19 group who did not receive ABD before and during hospitalization also had more resistance genes than the patients in the comparison group. CONCLUSION: This study demonstrated that fewer ABR genes were identified in the group with a milder disease than in the group with a more severe disease associated with more ABR genes, with the following five being the most common: SULI, MSRC, ACRE, EFMA, SAT.

Direct Measurements of DT Fuel Preheat from Hot Electrons in Direct-Drive Inertial Confinement Fusion.

Hot electrons generated by laser-plasma instabilities degrade the performance of laser-fusion implosions by preheating the DT fuel and reducing core compression. The hot-electron energy deposition in the DT fuel has been directly measured for the first time by comparing the hard x-ray signals between DT-layered and mass-equivalent ablator-only implosions. The electron energy deposition profile in the fuel is inferred through dedicated experiments using Cu-doped payloads of varying thickness. The measured preheat energy accurately explains the areal-density degradation observed in many OMEGA implosions. This technique can be used to assess the viability of the direct-drive approach to laser fusion with respect to the scaling of hot-electron preheat with laser energy.

Direct-drive laser fusion: status, plans and future.

Laser-direct drive (LDD), along with laser indirect (X-ray) drive (LID) and magnetic drive with pulsed power, is one of the three viable inertial confinement fusion approaches to achieving fusion ignition and gain in the laboratory. The LDD programme is primarily being executed at both the Omega Laser Facility at the Laboratory for Laser Energetics and at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory. LDD research at Omega includes cryogenic implosions, fundamental physics including material properties, hydrodynamics and laser-plasma interaction physics. LDD research on the NIF is focused on energy coupling and laser-plasma interactions physics at ignition-scale plasmas. Limited implosions on the NIF in the 'polar-drive' configuration, where the irradiation geometry is configured for LID, are also a feature of LDD research. The ability to conduct research over a large range of energy, power and scale size using both Omega and the NIF is a major positive aspect of LDD research that reduces the risk in scaling from OMEGA to megajoule-class lasers. The paper will summarize the present status of LDD research and plans for the future with the goal of ultimately achieving a burning plasma in the laboratory. This article is part of a discussion meeting issue 'Prospects for high gain inertial fusion energy (part 2)'.

Geometrical-optics computer model of metal-knitted mesh for calculations of solar pressure on space deployable antenna reflectors.

A novel computer 3D model is presented for calculations of optical parameters (transmittance, reflectance, and absorbance) of a metal-knitted mesh textile as a structural element of deployable antenna reflectors for space satellites. The model is based on geometrical-optics ray tracing upon diffuse scattering of a broadband light source (Sun) at a complex knitted mesh structure with different inclinations to the radiative source. The proposed computer model is built for the special type of metal-wire textile (two-bar large void tricot) possessing extremely high transmittance and is verified by comparison with the experimental measurements of light scattering parameters of real antenna mesh samples of data-relaying satellites (Russian series "Loutch"). The model is used for calculations of solar radiation pressure exerted on a knitted mesh antenna reflector and gives the maximal pressure value of about 0.28 µN/m2.

Origins and Scaling of Hot-Electron Preheat in Ignition-Scale Direct-Drive Inertial Confinement Fusion Experiments.

Planar laser-plasma interaction (LPI) experiments at the National Ignition Facility (NIF) have allowed access for the first time to regimes of electron density scale length (∼500 to 700 µm), electron temperature (∼3 to 5 keV), and laser intensity (6 to 16×10^{14} W/cm^{2}) that are relevant to direct-drive inertial confinement fusion ignition. Unlike in shorter-scale-length plasmas on OMEGA, scattered-light data on the NIF show that the near-quarter-critical LPI physics is dominated by stimulated Raman scattering (SRS) rather than by two-plasmon decay (TPD). This difference in regime is explained based on absolute SRS and TPD threshold considerations. SRS sidescatter tangential to density contours and other SRS mechanisms are observed. The fraction of laser energy converted to hot electrons is ∼0.7% to 2.9%, consistent with observed levels of SRS. The intensity threshold for hot-electron production is assessed, and the use of a Si ablator slightly increases this threshold from ∼4×10^{14} to ∼6×10^{14} W/cm^{2}. These results have significant implications for mitigation of LPI hot-electron preheat in direct-drive ignition designs.

Two-Plasmon Decay Mitigation in Direct-Drive Inertial-Confinement-Fusion Experiments Using Multilayer Targets.

Multilayer direct-drive inertial-confinement-fusion targets are shown to significantly reduce two-plasmon decay (TPD) driven hot-electron production while maintaining high hydrodynamic efficiency. Implosion experiments on the OMEGA laser used targets with silicon layered between an inner beryllium and outer silicon-doped plastic ablator. A factor-of-5 reduction in hot-electron generation (>50 keV) was observed in the multilayer targets relative to pure CH targets. Three-dimensional simulations of the TPD-driven hot-electron production using a laser-plasma interaction code (lpse) that includes nonlinear and kinetic effects show good agreement with the measurements. The simulations suggest that the reduction in hot-electron production observed in the multilayer targets is primarily caused by increased electron-ion collisional damping.

[Guidelines for the management of severe traumatic brain injury. Part 3. Surgical management of severe traumatic brain injury (Options)].

Traumatic brain injury (TBI) is one of the main causes of mortality and severe disability in young and middle age patients. Patients with severe TBI, who are in coma, are of particular concern. Adequate diagnosis of primary brain injuries and timely prevention and treatment of secondary injury mechanisms markedly affect the possibility of reducing mortality and severe disability. The present guidelines are based on the authors' experience in developing international and national recommendations for the diagnosis and treatment of mild TBI, penetrating gunshot wounds of the skull and brain, severe TBI, and severe consequences of brain injury, including a vegetative state. In addition, we used the materials of international and national guidelines for the diagnosis, intensive care, and surgical treatment of severe TBI, which were published in recent years. The proposed recommendations for surgical treatment of severe TBI in adults are addressed primarily to neurosurgeons, neurologists, neuroradiologists, anesthesiologists, and intensivists who are routinely involved in treating these patients.

[Guidelines for the diagnosis and treatment of severe traumatic brain injury. Part 2. Intensive care and neuromonitoring].

Traumatic brain injury (TBI) is one of the major causes of death and disability in young and middle-aged people. The most problematic group is comprised of patients with severe TBI who are in a coma. The adequate diagnosis of primary brain injuries and timely prevention and treatment of the secondary injury mechanisms largely define the possibility of reducing mortality and severe disabling consequences. When developing these guidelines, we used our experience in the development of international and national recommendations for the diagnosis and treatment of mild traumatic brain injury, penetrating gunshot wounds to the skull and brain, severe traumatic brain injury, and severe consequences of brain injuries, including a vegetative state. In addition, we used international and national guidelines for the diagnosis, intensive care, and surgical treatment of severe traumatic brain injury, which had been published in recent years. The proposed guidelines concern intensive care of severe TBI in adults and are particularly intended for neurosurgeons, neurologists, neuroradiologists, anesthesiologists, and intensivists who are routinely involved in the treatment of these patients.

[POSITIVE END-EXPIRATORY PRESSURE (PEEP) INFLUENCES ON INTRACRANIAL PRESSURE, SYSTEMIC HEMODYNAMICS AND PULMONARY GAS EXCHANGE IN PATIENTS WITH INTRACRANIAl HEMORRHAGE IN CRITICAL STATE].

Positive end-expiratory pressure is one of the main parameters of respiratory support influencing the gas exchange. However, despite the number ofpositive effects, PEEP can compromise venous outflow from the cranial cavity, increased intracranial pressure, decreased venous return and cardiac output and, consequently, reduced blood pressure and cerebral perfusion. The article presents the results of a survey of 39 patients with intracranial hemorrhage in critical state, undergoing respiratory support with different levels of positive end-expiratory pressure. Increasing of PEEP to 15 cm H2O had no adverse effect on mean arterial pressure, heart rate and cerebral perfusion pressure and led only to an clinical insignificant increase (maximum on 2.4 +/- 5.1 mmHg) in intracranial pressure. The greatest hemodynamic changes were observed with increasing PEEP up to 20 cm H2O in patients with preserved compliance ofthe respiratory system. The instability of cerebral perfusion and intracranial pressure associated with a decrease in cardiac output and preload and the exhaustion of compensatory mechanism of peripheral vascular resistance. High levels of PEEP despite the trend towards Cstat reduction will not lead to an increase in the content of extravascular lung water Thus a gradual increase of PEEP to 15 cm H2O can be safe and effective method of improving pulmonary gas exchange in patients with intracranial hemorrhage in critical state.

Gigabar spherical shock generation on the OMEGA laser.

This Letter presents the first experimental demonstration of the capability to launch shocks of several-hundred Mbar in spherical targets--a milestone for shock ignition [R. Betti et al., Phys. Rev. Lett. 98, 155001 (2007)]. Using the temporal delay between the launching of the strong shock at the outer surface of the spherical target and the time when the shock converges at the center, the shock-launching pressure can be inferred using radiation-hydrodynamic simulations. Peak ablation pressures exceeding 300 Mbar are inferred at absorbed laser intensities of ∼3×10(15) W/cm2. The shock strength is shown to be significantly enhanced by the coupling of suprathermal electrons with a total converted energy of up to 8% of the incident laser energy. At the end of the laser pulse, the shock pressure is estimated to exceed ∼1 Gbar because of convergence effects.

[Guidelines for the management of severe head injury. Part 1. Neurotrauma system and neuroimaging].

Traumatic brain injury is one of the main causes of mortality and disability in young and middle-aged individuals. The patients with severe traumatic brain injury who are in coma are the most difficult to deal with. Appropriate diagnosis of the primary brain injuries and early prevention and treatment of secondary damage mechanisms largely determine the possibility of reducing mortality and severe disabling consequences. The authors compiled these guidelines based on their experience in development of international and Russian recommendations on the diagnosis and treatment of mild traumatic brain injury, penetrating gunshot injury of the skull and brain, severe traumatic brain injury, and severe consequences of brain injuries, including a vegetative state. In addition, we used the materials of international and Russian recommendations on the diagnosis, intensive care, and surgical treatment of severe traumatic brain injury published in recent years. The proposed recommendations are related to organization of medical care and diagnosis of severe traumatic brain injury in adults and are primarily addressed to neurosurgeons, neurologists, neuroradiologists, anesthesiologists, and emergency room doctors, who are routinely involved in management of these patients.

[Influence of cerebral perfusion pressure and cardiac output on brain oxygenation and metabolism].

The article contains results of examination of correlation between systemic hemodynamic and brain oxygenation and metabolism in patients with intracranial hemorrhage. Cardiac index (CI) and cerebral perfusion pressure (CPP) levels were compared to brain oxygenation and metabolism in 8 patients with intracranial hemorrhage (137 measurements). CI alterations didn't influence on PbrO2, glucose level or lactate/pyruvate ratio in the brain interstitial fluid in patients with traumatic brain injury. CPP elevation led to cerebral metabolism improvement. Optimal metabolic state was mentioned in CPP > 80 mm Hg. CPP elevation led to PbrO2 increasing in patients with subarachnoid hemorrhage due to aneurism rupture. This phenomenon can be explained by damage mechanisms of cerebral blood flow autoregulation. In these cases CI elevation was accompanied by worsening of aerobic metabolism in theoretically intact regions and improving it in injured brain regions.

[Effect of normobaric hyperoxia on cerebral oxygenation, metabolism and oxidative stress in patients with subarachnoid hemorrhage caused by intracranial aneurysm rupture].

The development of cerebral vasospasm in subarachnoid hemorrhage (SAH) due to cerebral aneurysms rupture results in cerebral circulation disturbances. Application of normobaric hyperoxia can be an effective way for improving of oxygen delivery to injured brain tissues. The purpose of this study was to assess of normobaric hyperoxia influence on intracranial pressure (ICP), cerebral oxygenation and metabolism, oxidative stress and endogenous factors of vascular regulation in II critically ill patients with nontraumatic SAH due to cerebral aneurysms rupture. Increase of FiO2 from 0.3 to 0.5 and 1.0 was accompanied with brain oxygen tension (PbrO2) increase and cerebral extraction ratio for oxygen (O2ER) decrease. Application of normobaric hyperoxia had no effect on ICP, cerebral perfusion pressure, arterial blood pressure and cerebral metabolism. The results obtained from patients with nontraumatic SAH showed an evident increase of oxidative stress which had a significant effect on vascular endothelial function, causing an imbalance in the endogenous regulation of vascular tone. Application of normobaric hyperoxia was not accompanied by an increase of free-radical processes in critically ill patients with nontraumatic SAH due to cerebral aneurysms rupture.

Experimental validation of the two-plasmon-decay common-wave process.

The energy in hot electrons produced by the two plasmon decay instability, in planar targets, is measured to be the same when driven by one or two laser beams and significantly reduced with four for a constant overlapped intensity on the OMEGA EP. This is caused by multiple beams sharing the same common electron-plasma wave. A model, consistent with the experimental results, predicts that multiple laser beams can only drive a resonant common two plasmon decay electron-plasma wave in the region of wave numbers bisecting the beams. In this region, the gain is proportional to the overlapped laser beam intensity.

Time-resolved measurements of hot-electron equilibration dynamics in high-intensity laser interactions with thin-foil solid targets.

Time-resolved K(α) spectroscopy has been used to infer the hot-electron equilibration dynamics in high-intensity laser interactions with picosecond pulses and thin-foil solid targets. The measured K(α)-emission pulse width increases from ~3 to 6 ps for laser intensities from ~10(18) to 10(19) W/cm(2). Collisional energy-transfer model calculations suggest that hot electrons with mean energies from ~0.8 to 2 MeV are contained inside the target. The inferred mean hot-electron energies are broadly consistent with ponderomotive scaling over the relevant intensity range.

[Russian multicenter observational clinical study «Register of respiratory therapy for patients with stroke (RETAS)¼: a comparative analysis of the outcomes of stroke]. / Rossiiskoe mnogotsentrovoe observatsionnoe klinicheskoe issledovanie «Registr respiratornoi terapii u patsientov s ONMK (RETAS)¼: sravnitel'naya kharakteristika iskhodov insul'ta.

OBJECTIVE: To analyze the treatment of patients with severe stroke requiring respiratory support, and identify predictors of death. MATERIAL AND METHODS: A multicenter observational clinical study «REspiratory Therapy for Acute Stroke¼ (RETAS) was conducted under the aegis of the «Federation of Anaesthesiologists and Reanimatologists¼ (FAR). The study involved 14 clinical centers and included 1289 stroke patients with respiratory support. RESULTS: We found that initial hypoxemia in the 28-day period was associated with higher mortality than in absence of hypoxemia (in patients with 20 or more NIHSS scores) (76.22% versus 63.45%, p=0.004). Risk factors for lethal outcome: hyperventilation used to relieve intracranial hypertension compared with group of patients who were not treated with hyperventilation (in patients with 20 or more NIHSS scores) (79.55% versus 72.75%, p=0.0336); volume-controlled ventilation (VC) versus pressure-controlled ventilation (PC) (in patients with 20 or more NIHSS scores) (p<0.001); use of clinical methods for monitoring ICP in comparison with instrumental ones (87.64% versus 62.33%, p<0.001). It has been proved that the absence of nutritional insufficiency in patients with stroke is associated with a higher probability of a positive outcome (GOS 4 and 5) in comparison with patients with signs of nutritional insufficiency, for the group with NIHSS less than 14 points (p<0.001). CONCLUSIONS: A group of factors associated with a deterioration in the prognosis of outcomes in patients with stroke who are undergoing ventilation has been identified: hypoxemia at the start of respiratory support, lack of instrumental monitoring of ICP, the use of hyperventilation to correct ICP, ventilation with volume control (VC), as well as the presence of nutritional insufficiency.

Hot-electron preheat and mitigation in polar-direct-drive experiments at the National Ignition Facility.

Target preheat by superthermal electrons from laser-plasma instabilities is a major obstacle to achieving thermonuclear ignition via direct-drive inertial confinement fusion at the National Ignition Facility (NIF). Polar-direct-drive surrogate plastic implosion experiments were performed on the NIF to quantify preheat levels at an ignition-relevant scale and develop mitigation strategies. The experiments were used to infer the hot-electron temperature, energy fraction, and divergence, and to directly measure the spatial hot-electron energy deposition profile inside the imploding shell. Silicon layers buried in the ablator are shown to mitigate the growth of laser-plasma instabilities and reduce preheat, providing a promising path forward for ignition designs at an on-target intensity of about 10^{15}W/cm^{2}.

[Sepsis in patients with intracranial hemorrhage: incidence and influence on outcome].

The aim of the study is to analyze sepsis and septic shock incidence and their influence on the outcome in critically ill patients with intracranial hemorrhage. Sepsis incidence (33,7%) and septic shock incidence (18,6%) in the patients studied did not depend on intracranial hemorrhage etiology. Septic complications led to higher mortality which was 22,8% in patients with sepsis and 74,4% in patients with septic shock. Sepsis and septic shock risk factors are defined. The problem of sepsis and septic shock diagnosis in critically ill patients with intracranial hemorrhage are highlighted.