Search Results (34)

Substantial progress has been made in the development of radiation countermeasures, resulting in the recent approval of several mitigators; however, there has yet to be an approved prophylactic radioprotectant. Research on countermeasure performance in mixed neutron and gamma radiation fields has also been scarce. Fibroblast-stimulating lipopeptide (FSL-1) is a novel synthetic agonist for toll-like receptor 2/6. In previous studies, the administration of FSL-1 before and after gamma radiation significantly improved survival outcomes for mice through the activation of the NF-κB pathway. In the current study, we tested FSL-1’s radioprotective abilities in a mixed radiation field that models one produced by a nuclear detonation in 11–14-week-old C57BL/6 male and female mice. We demonstrate that a single dose of 1.5 mg/kg of FSL-1 administered 12 h prior to 65% neutron 35% gamma mixed-field (MF) irradiation enhances survival, accelerates recovery of hematopoietic cell and stem cell populations, reduces inflammation, and protects innate immune function in mice. FSL-1’s ability to recover blood and protect immune functions is important in countering the high rate of incidence of sepsis caused by MF radiation’s damaging effects. These results demonstrate that FSL-1 is a promising prophylactic countermeasure where exposure to MF radiation is anticipated. Full article

This study evaluates the performance of two-dimensional (2D) detonation simulations against recent experimental measurements for a stoichiometric hydrogen–air mixture at 25 kPa. The validation parameters rely on the average cell size ($\lambda$), the cell size variability ($2\sigma /\lambda$), and the dynamics of both the relative detonation speed (D/D_CJ) and the local induction zone length (${\Delta }_i$) along the cell cycle. We select Mével 2017’s and San Diego’s chemical models for 2D simulations, after evaluating 13 chemical models with Zeldovich–von Neumann–Döring (ZND) simulations. From this model selection, the effects of nitrogen chemistry and diffusion (Navier–Stokes or Euler equations) are evaluated on the validation parameters. The main findings are as follows: the simulations conducted with the Mével 2017 (with N₂ chemistry) model provide the best agreement with ${\lambda }_{\mathrm{mean}}^{\exp }$ (≈17%), while the experimental cell variability ($2\sigma /\lambda$) is reproduced within 20% by most simulation cases. This model (Mével 2017 with N₂ chemistry) also presents good agreement with both the ${\Delta }_i$ and D/D_CJ dynamics, whereas San Diego’s simulations under-predict them along the cell. Interestingly, the speed decay along the cell length exhibits self-similar behavior across all cases, suggesting independence from cell size variability, unlike the ${\Delta }_i$ dynamics. Finally, this study demonstrates the minimal impact of the diffusion on the simulation results. Full article

In the maritime industry, hydrogen fuel cell ships demonstrate significant potential for development due to their environmental friendliness and high efficiency. However, the risks of fire and explosion caused by hydrogen leakage pose severe challenges to their safety. To enhance the safety of hydrogen fuel cell ships and mitigate the explosion hazards caused by leakage, this study employs the XiFoam solver in the OpenFOAM v9 to establish an explosion model for a full-scale hydrogen fuel cell compartment within a hydrogen fuel cell ship. The model simulates the transient explosion process following high-pressure hydrogen leakage under varying initial hydrogen concentrations and premixed fuel conditions. By analyzing the temporary evolution of temperature distribution, flame front propagation, and explosion pressure, the study provides a comprehensive understanding of the safety implications of hydrogen leakage at different locations within the fuel cell. Specifically, increasing the hydrogen concentration from ΦH₂ = 0.10 to ΦH₂ = 0.18 and ΦH₂ = 0.20 significantly elevates the overpressure peak and accelerates the flame speed from 250 m/s to 370 m/s, with local pressure gradients approaching the deflagration to detonation transition threshold. The simulation results contribute valuable insights into optimizing hydrogen fuel cell design, formulating effective fire safety strategies, and improving overall ship safety. Full article

Combustion through detonation marks an important leap in efficiency over standard deflagration methods. This research introduces a Pulsed Detonation Combustor (PDC) model that uses Hydrogen as fuel and Oxygen as an oxidizer, specifically targeting carbon-free combustion efforts. The PDC aerodynamic features boost operating cycle frequency and facilitate Deflagration-to-Detonation Transition (DDT) within distances less than 200 mm by means of Hartmann–Sprenger resonators and cross-flow fuel/oxidizer injection. The achievement of quality mixing in a short-time filling process represents not only higher cycle operation but also enhanced performances. The scope of this paper is to assess the impact of different fuel injectors with different opening areas on the performances of the PDC. This assessment, expressed as a function of the Equivalence Ratio (ER), is conducted using two primary methods. Instantaneous static pressures are recorded and processed to extract the maximum and average cycle pressure and characterize the pressure augmentation. Thrust measurements obtained using a load cell are averaged over the detonation cycle to calculate the time-averaged thrust. The specific impulse is subsequently determined based on these thrust measurements and the corresponding mass flow data. Full article

System failure in large-scale electrolyzer and fuel cell installations may cause the formation of explosive H₂–air–steam mixtures. Detonation properties (e.g., detonation cell size) and flame dynamics features (e.g., flame acceleration, runup distance, and deflagration-to-detonation transition “DDT”) of these mixtures were investigated experimentally and numerically to gain a more in-depth understanding of the hazards of H₂–air–steam under conditions pertinent to PEM-based electrolyzers and fuel cells (temperatures between 50 °C and 80 °C and pressures between 20 and 40 bar). While our results confirm the findings of previous studies in terms of the cooling effects of steam on detonation, we found that operating pressures between 20 and 40 bar counteract the effect of steam, making the H₂–air–steam mixture more detonable. This is particularly evident from the experimental data on detonation cell size and runup distance at pressures greater than 20 bar. Full article

Detonation combustion represents a significant advancement in efficiency over traditional deflagration methods. This paper presents a Pulsed Detonation Combustor (PDC) model that is designed with an aerodynamic mixing chamber featuring Hartmann–Sprenger resonators and crossflow injection. This design enhances operational cycle frequency and enables sustained detonation over short distances (below 200 mm). The PDC’s performance was evaluated through a comprehensive full-factorial experimental campaign, incorporating four factors with four discrete levels each. Testing was conducted using both hydrogen/air and hydrogen/oxygen mixtures, highlighting the PDC’s potential as a carbon-free combustion chamber suitable for both air-breathing and space-based propulsion systems. One advantage is the versatility of our PDC breadboard, which lies in its applicability to both terrestrial and in-space applications, such as interplanetary travel or trajectory corrections. Thrust measurements were recorded using a load cell and time-averaged thrust levels were determined over the detonation cycle and are reported herein, together with the specific impulse. The results underscore the PDC’s promise as an efficient propulsion technology for future aerospace applications. Full article

In this work, a previously developed three-feature Artificial Neural Network (ANN) model with dimensional inputs is directly applied to predict the cell size of hydrocarbon/ammonia/nitrous oxide mixtures and compare these to experimental data. This model uses as inputs three ZND parameters (M_CJ, Δ_I, and ${\dot{\sigma }}_{\mathit{max}}$), which are mainly calculated using Konnov’s and Mével’s mechanisms. A similar prediction is obtained with the two mechanisms for the biogas–O₂, H₂–O₂, H₂–N₂O, and NH₃–O₂ mixtures, indicating that the model is not only limited to Konnov’s chemical kinetic mechanism which was used for its training. The overall good agreement between the ANN predictions and the actual experimental values for the aforementioned mixtures, which are not used in the original training of the ANN model, is promising and shows its potential for application and extension to other mixtures and initial conditions, provided that the chemical kinetic parameters describing the ideal reaction zone structure could be computed. The model is then used to compare experimental cell size data from two detonation tube facilities, and also different chemical kinetic mechanisms for NH₃-N₂O mixtures. In the end, the original ANN model is expanded with the inclusion of additional cell size data, showing a slightly lower mean error for the predicted cell sizes if the data for the mixtures considered in this study are taken into account for the training of the new ANN model. Full article

This paper presents the results of the two-dimensional modeling of the hydrodynamic instability of a detonation wave, which results in the formation of an oscillating cellular structure on the wave front. This cellular structure of the wave, unstable due to its origin, demonstrates the constant statistically averaged characteristics of the cell size. The suppression of detonation propagation in synthesis gas mixtures with air using a combustible inhibitor is studied numerically. Contrary to the majority of inhibitors being either inert substances, which do not take part in the chemical reaction, or take part in chemical reaction but do not contribute to energy release, the suggested inhibitor is also a fuel, which enters into an exothermic reaction with oxygen. The unsaturated hydrocarbon propylene additive is used as an inhibitor. The dependence of the effect of the inhibitor content on the mitigation of detonation for various conditions of detonation initiation is researched. The results make it possible to determine a critical percentage of inhibitor which prevents the occurrence of detonation and the critical percentage of inhibitor which destroys a developed detonation wave. Full article

Rotating detonation engines (RDEs) are considered to be promising thrusters for aerospace propulsion. Detonation initiation in RDEs can be accompanied by a destructive explosion of an excess volume of the fuel mixture in the combustor. To exclude this phenomenon, a “mild” rather than “strong” initiation of detonation is required. For the mild initiation of detonation in RDEs, it is necessary to ignite a mixture of a certain minimum volume sufficient for deflagration-to-detonation transition (DDT). In this study, the critical conditions for detonation initiation through DDT in a semiconfined slit combustor simulating the RDE combustor with a separate supply of ethylene and oxygen diluted with nitrogen (from 0 to 40%) were obtained experimentally. It turned out that for the mild initiation of detonation, it is necessary to ignite the mixture upon reaching the critical (minimum) height of the combustible mixture layer. Thus, for the mild initiation of detonation in the undiluted C₂H₄ + 3O₂ mixture filling such a slit combustor, the height of the mixture layer must exceed the slit width by approximately a factor of 12. In terms of the transverse size of the detonation cell λ the minimum layer height of such mixtures in experiments is ~150λ. Compared to the experiments with the premixed composition, the critical height of the layer is 20% larger, which is explained by the finite rate of mixing. As the degree of oxygen dilution with nitrogen increases, the critical height of the layer increases, and the role of finite rate mixing decreases: the results no longer depend on the method of combustible mixture formation. Full article

Long-term research into radiation exposure significantly expanded following World War II, driven by the increasing number of individuals falling ill after the detonation of two atomic bombs in Japan. Consequently, researchers intensified their efforts to investigate radiation’s effects using animal models and to study disease models that emerged post-catastrophe. As a result, several parameters have been established as essential in these models, encompassing radiation doses, regimens involving single or multiple irradiations, the injection site for transplantation, and the quantity of cells to be injected. Nonetheless, researchers have observed numerous side effects in irradiated animals, prompting the development of scoring systems to monitor these animals’ well-being. The aim of this review is to delve into the historical context of using animals in radiation research and explore the ethical considerations related to animal welfare, which has become an increasingly relevant topic in recent years. These concerns have prompted research groups to adopt measures aimed at reducing animal suffering. Consequently, for animal welfare, the implementation of a scoring system for clinical and behavioral monitoring is essential. This represents one of the primary challenges and hurdles in radiation studies. It is concluded that implementing standardized criteria across all institutions is aimed at ensuring result reproducibility and fostering collaboration within the scientific community. Full article

Cardiovascular diseases (CVDs) remain a leading cause of death in the European population, primarily attributed to atherosclerosis and subsequent complications. Although statin drugs effectively prevent atherosclerosis, they fail to reduce plaque size and vascular stenosis. Bare metal stents (BMS) have shown promise in acute coronary disease treatment but are associated with restenosis in the stent. Drug-eluting stents (DES) have improved restenosis rates but present long-term complications. To overcome these limitations, nanomaterial-based modifications of the stent surfaces have been explored. This study focuses on the incorporation of detonation nanodiamonds (NDs) into a plasma electrolytic oxidation (PEO) coating on nitinol stents to enhance their performance. The functionalized ND showed a high surface-to-volume ratio and was incorporated into the oxide layer to mimic high-density lipoproteins (HDL) for reverse cholesterol transport (RCT). We provide substantial characterization of DND, including stability in two media (acetone and water), Fourier transmission infrared spectroscopy, and nanoparticle tracking analysis. The characterization of the modified ND revealed successful functionalization and adequate suspension stability. Scanning electron microscopy with EDX demonstrated successful incorporation of DND into the ceramic layer, but the formation of a porous surface is possible only in the high-voltage PEO. The biological assessment demonstrated the biocompatibility of the decorated nitinol surface with enhanced cell adhesion and proliferation. This study presents a novel approach to improving the performance of nitinol stents using ND-based surface modifications, providing a promising avenue for cardiovascular disease. Full article

Aquivion^®-type perfluorosulfonic acid membranes with a polytetrafluoroethylene backbone and short side chains with sulfonic acid groups at the ends have great prospects for operating in hydrogen fuel cells. To improve the conducting properties of membranes, various types of nanofillers can be used. We prepared compositional Aquivion^®-type membranes with embedded detonation nanodiamond particles. Nanodiamonds were chemically modified with sulfonic acid groups to increase the entire amount of ionogenic groups involved in the proton conductivity mechanism in compositional membranes. We demonstrated the rise of proton conductivity at 0.5–2 wt.% of sulfonated nanodiamonds in membranes, which was accompanied by good mechanical properties. The basic structural elements, conducting channels in membranes, were not destroyed in the presence of nanodiamonds, as follows from small-angle neutron scattering data. The prepared compositional membranes can be used in hydrogen fuel cells to achieve improved performance. Full article

Carbon nanoparticles with antimicrobial properties, such as fullerenes, can be distinguished among the promising means of combating pathogens characterized by resistance to commercial antibiotics. However, they have a number of limitations for their use in medicine. In particular, the insolubility of carbon nanoparticles in water leads to a low biocompatibility and especially strong aggregation when transferred to liquid media. To overcome the negative factors and enhance the action of fullerenes in an extended range of applications, for example, in antimicrobial photodynamic therapy, we created new water-soluble complexes containing, in addition to C60 fullerene, purified detonation nanodiamonds (AC960) and/or polyvinylpyrrolidone (PVP). The in vitro antibacterial activity and toxicity to human cells of the three-component complex C60+AC960+PVP were analyzed in comparison with binary C60+PVP and C60+AC960. All complexes showed a low toxicity to cultured human skin fibroblasts and ECV lines, as well as significant antimicrobial activity, which depend on the type of microorganisms exposed, the chemical composition of the complex, its dosage and exposure time. Complex C60+PVP+AC960 at a concentration of 175 µg/mL showed the most stable and pronounced inhibitory microbicidal/microbiostatic effect. Full article

Bifurcation of the characteristic cells into multiple smaller cells and decay of those cells into single large characteristic cell is observed frequently. In the present study the bifurcation phenomenon of the detonation front is investigated for marginally unstable detonations using decomposition technique. Numerical analysis is carried out with detailed chemical kinetics for detonation propagation in H₂/O₂ mixtures at 10 kPa. The dynamic characteristics of the instability at the detonation front, such as the local oscillation frequency and the coherent spatial structure of the oscillation are also studied with dynamic mode decomposition (DMD) technique. The coherent structures of the primary and secondary detonation cells are analyzed during the cell bifurcation process and the mechanism in which the secondary cells are formed is investigated. It is demonstrated that the modal analysis categorizes the instability phenomena clearly and can be effectively utilized to identify the origin and source of the instability. Full article

Widely used in biomedical and bioanalytical applications, the detonation nanodiamonds (NDs) are generally considered to be biocompatible and non-toxic to a wide range of eukaryotic cells. Due to their high susceptibility to chemical modifications, surface functionalisation is often used to tune the biocompatibility and antioxidant activity of the NDs. The response of photosynthetic microorganisms to redox-active NDs is still poorly understood and is the focus of the present study. The green microalga Chlamydomonas reinhardtii was used to assess the potential phytotoxicity and antioxidant activity of NDs hosting hydroxyl functional groups at concentrations of 5–80 μg NDs/mL. The photosynthetic capacity of microalgae was assessed by measuring the maximum quantum yield of PSII photochemistry and the light-saturated oxygen evolution rate, while oxidative stress was assessed by lipid peroxidation and ferric-reducing antioxidant capacity. We demonstrated that hydroxylated NDs might reduce cellular levels of oxidative stress, protect PSII photochemistry and facilitate the PSII repair under methyl viologen and high light associated stress conditions. Factors involved in this protection may include the low phytotoxicity of hydroxylated NDs in microalgae and their ability to accumulate in cells and scavenge reactive oxygen species. Our findings could pave the way for using hydroxylated NDs as antioxidants to improve cellular stability in algae-based biotechnological applications or semi-artificial photosynthetic systems. Full article