Total Number Of Particles Research Articles

In vivo study to assess fat embolism resulting from the Reamer-Irrigator-Aspirator 2 system compared to a novel aspirator-based concept for intramedullary bone graft harvesting

IntroductionFat embolism (FE) following intramedullary (IM) reaming can cause severe pulmonary complications and sudden death. Recently, a new harvesting concept was introduced in which a novel aspirator is used first for bone marrow (BM) aspiration and then for subsequent aspiration of morselized endosteal bone during sequential reaming (A + R + A). In contrast to the established Reamer-Irrigator-Aspirator (RIA) 2 system, the new A + R + A concept allows for the evacuation of fatty BM prior to reaming. In this study, we hypothesized that the risk of FE, associated coagulopathic reactions and pulmonary FE would be comparable between the RIA 2 system and the A + R + A concept.Materials and methodsIntramedullary bone graft was harvested from intact femora of 16 Merino sheep (age: 1–2 years) with either the RIA 2 system (n = 8) or the A + R + A concept (n = 8). Fat intravasation was monitored with the Gurd test, coagulopathic response with D-dimer blood level concentration and pulmonary FE with histological evaluation of the lungs.ResultsThe total number and average size of intravasated fat particles was similar between groups (p = 0.13 and p = 0.98, respectively). D-dimer concentration did not significantly increase within 4 h after completion of surgery (RIA 2: p = 0.82; A + R + A: p = 0.23), with an interaction effect similar between groups (p = 0.65). The average lung area covered with fat globules was similar between groups (p = 0.17).ConclusionsThe use of the RIA 2 system and the novel A + R + A harvesting concept which consists of BM evacuation followed by sequential IM reaming and aspiration of endosteal bone, resulted in only minor fat intravasation, coagulopathic reactions and pulmonary FE, with no significant differences between the groups. Our results, therefore, suggest that both the RIA 2 system and the new A + R + A concept are comparable technologies in terms of FE-related complications.

High-frequency electric knife smoke particles: An experimental study on factors influencing emission characteristics

During surgery, the use of a high-frequency electric knife produces smoke, which can be harmful to the health of indoor medical staff and patients. The quantity and particle size distribution of smoke particles produced by different tissues may vary. Understanding the release characteristics of these smoke particles is necessary to clarify their impact on the surgical environment and to seek effective smoke control methods. A previous comparative analysis of human and pig tissues revealed that they share similar water and fat compositions in certain anatomical regions. In this study, we investigated the emission characteristics of smoke particles from various tissues of pigs (skeletal muscle, liver, kidney, skin, and subcutaneous fat) under different operating powers of an electric knife. We measured the indoor particle number concentration (particle concentration), and estimated the PM2.5 mass concentration (PM2.5 concentration), particle size distribution, and emission rate of the smoke particles. The study obtained the particle emission rates of different tissues under different electric knife operating powers, results of which showed that (1) during the operation of the electric knife, mainly small particles below 1 μm are produced. Among them, particles of 0.3 μm were the most abundant, with a particle concentration level of up to 109 particles/m3, accounting for 85.17–97.64% of the total particle number, and as the particle size increased, the particle concentration and percentage decreased significantly. (2) The water and fat compositions of different tissues influenced the indoor particle concentration and emission rate of the smoke emitted by the electric knife. Among different tissues, subcutaneous fat tissue had the lowest particle concentration and emission rate. (3) The electric knife operating power mainly affected particles below 1 μm, and except for kidney tissue, the indoor concentration and emission rate of these particle sizes were positively correlated with the power. The experimental results can provide data reference for the use of high-frequency electric knives in surgeries involving different human tissues in the operating room.

Enhanced vacuum pair production by combination of two spatially separated electric fields

The effective enhancement of the pair production rate using a subcritical electromagnetic field is an active area of interest in quantum electrodynamics. Enhanced pair production was investigated using the Dirac–Heisenberg–Wigner (DHW) formalism with spatially separated electric fields. Symmetric and asymmetric combinations of two separate electric fields with the same temporal shape were considered. The interplay and dynamical assistance between the fields were examined from a numerical perspective to elucidate the effects of the spatial distance and asymmetry of the field on the pair production efficiency. For the symmetric combination, the total particle number was reduced with an increase in the distance between the two fields up to one Compton length and then remained constant with distance. For the asymmetric combination, the total number of created pairs increased significantly up to a distance of one Compton length. It was also determined that not only was the separation distance crucial for enhancing pair production, but the spatial field asymmetries were also important, both of which had nontrivial effects on the particle momentum distribution. Finally, we have studied the validity of the DHW and analytical approximation in the spatially separated two electric fields. We found that the analytical approximation could almost estimate the DHW results.

Plasma kinetic simulation in Eulerian approach fully respecting f≥0 requirement and total particle number conservation

Abstract Plasma kinetic simulation in Eulerian approach (PKSiEA) can yield a dynamic description on plasmas and hence is a popular method in theoretical plasmas physics. Its mathematical model consists of 8 members: 5 partial differential equations (PDEs), a phase space boundary condition and an initial condition of the distribution function (PDF) f, and a mandatory non-negativity requirement on f. Because Vlasov equation (VE) is a PDE with variable coefficients and the non-negativity requirement is mandatory, when 5 PDEs (4 Maxwell equations and the VE) are treated as an initial-value problem, the temporal evolution of f is difficult to be attacked by existing popular computational mathematics techniques, such as Fourier analysis technique and finite-difference technique, and hence these techniques do not yield efficient and reliable schemes of the PKSiEA. In a universal scheme of the PKSiEA presented here, because the phase space boundary condition f∣ r=∞,∣υ∣=c = 0 causes the VE to yield a conservation of total particle number ∫fd 3 rd 3 υ, we propose an efficient and strict expression of the f-profile in terms of two classes of functions of phase space coordinates r , υ , and the VE displays a universal relation between two classes. By this new expression, we express the initial-value problem of 5 PDEs in terms of allowed deformation modes from an initial f-profile, and ensure the PKSiEA fully respecting the non-negativity requirement on f.

Breakdown of Langmuir Adsorption Isotherm in Small Closed Systems.

For more than a century, monolayer adsorptions in which adsorbate molecules and adsorbing sites behave ideally have been successfully described by Langmuir's adsorption isotherm. For example, the amount of adsorbed material, as a function of concentration of the material which is not adsorbed, obeys Langmuir's equation. In this paper, we argue that this relation is valid only for macroscopic systems. However, when particle numbers of adsorbate molecules and/or adsorbing sites are small, Langmuir's model fails to describe the chemical equilibrium of the system. This is because the kinetics of forming, or the probability of observing, occupied sites arises from two-body interactions, and as such, ought to include cross-correlations between particle numbers of the adsorbate and adsorbing sites. The effect of these correlations, as reflected by deviations in predicting composition when correlations are ignored, increases with decreasing particle numbers and becomes substantial when only few adsorbate molecules, or adsorbing sites, are present in the system. In addition, any change that augments the fraction of occupied sites at equilibrium (e.g., smaller volume, lower temperature, or stronger adsorption energy) further increases the discrepancy between observed properties of small systems and those predicted by Langmuir's theory. In contrast, for large systems, these cross-correlations become negligible, and therefore when expressing properties involving two-body processes, it is possible to consider independently the concentration of each component. By applying statistical mechanics concepts, we derive a general expression of the equilibrium constant for adsorption. It is also demonstrated that in ensembles in which total numbers of particles are fixed, the magnitudes of fluctuations in particle numbers alone can predict the average chemical composition of the system. Moreover, an alternative adsorption equation, predicting the average fraction of occupied sites from the value of the equilibrium constant, is proposed. All derived relations were tested against results obtained by Monte Carlo simulations.

Effects of Diesel Emissions on Black Carbon and Particle Number Concentrations in the Eastern U.S.

The effects of emissions of diesel engines on black carbon and particle number concentrations, as well as climate-relevant aerosol properties, are explored for a summertime period in the Eastern U.S. using the chemical transport model PMCAMx-UF. A 50% reduction in diesel particulate emissions results in lower (23%) black carbon mass concentrations, as expected, and similar changes both in magnitude (27–30%) and spatial pattern for the absorption coefficient. However, an average 2% increase in the total particle number concentrations is predicted due to a decrease in the coagulation and condensation sinks and, at the same time, a 2% decrease in N100 (particles larger than 100 nm) concentrations. The diesel reduction results suggest that mitigation of large diesel particles and/or particle mass emissions can reduce climate-relevant properties related to the absorption of black carbon and provide health benefits; however, the changes could also have the unintended effect of increased ultrafine particle number concentrations. Changes in cloud condensation nuclei are predicted to be significantly less than expected, assuming a proportional reduction during this photochemically active period. Doubling the diesel emissions results in a domain-averaged 3% decrease in total particle number concentrations and a 3% increase in N100 concentrations. PM2.5 BC concentrations increase on average by 46%, and similar changes (52–60%) are predicted for the absorption coefficient. Extinction coefficients for both perturbation simulations changed by only a few percent due to the dominance of scattering aerosols in the Eastern U.S. during this period characterized by high photochemical activity.

Operator-derived particles and falling bacteria in biosafety cabinets

IntroductionTo ensure the sterility of cell products that cannot undergo conventional sterilization processes, it is imperative to establish and maintain a clean room environment, regulated through environmental monitoring, including particle counts. Nevertheless, the impact of particles generated by operators as potential contaminants remains uncertain. Thus, in this study, we conducted an accelerated test to assess the correlation between particles generated by operators and airborne bacteria, utilizing biosafety cabinets within a typical laboratory setting. These biosafety cabinets create a controlled environment with air conditioning and high-efficiency particulate air (HEPA) filters, offering fundamental data relevant to cell production. Materials and methodsWe conducted a simulation followed by real-time experiments involving human operations to explore the quantity of particles, particle sizes, and the percentage of bacteria within these particles. This investigation focused on conditions with heightened particle generation from operators within a biosafety cabinet. The experiment was conducted on operators wearing textile and non-woven dustless clothing within biosafety cabinets. It entailed tapping the upper arms for a duration of 2 min. ResultsObservations under biosafety cabinet-off conditions revealed the presence of various particles and falling bacteria in textile clothing. In contrast, no particles or falling bacteria were detected in operators wearing dustless clothing within biosafety cabinets. Notably, a correlation between 5 μm particles and colony-forming units in textile clothing was identified through this analysis. The ratio of falling bacteria to the total number of particles within the biosafety cabinet was 0.8 ± 0.5 % for textile clothing, while it was significantly lower at 0.04 ± 0.2 % for dustless clothing. ConclusionThis study demonstrated that the number of particles and falling bacteria varied depending on the type of clothing and that quantitative data could be used to identify risks and provide basic data for operator education and evidence-based control methods in aseptic manufacturing areas. Although, this study aims to serve as an accelerated test operating under worst-case conditions, the results need to make sure the study range in general research.

Respiratory particles: from analytical estimates to disease transmission

Respiratory particles containing infectious pathogens are responsible for a large number of diseases. To define health politics and save lives, it is important to study their transmission mechanisms, namely the path of particles once expelled. This path depends on several driving factors as intrinsic properties of particles, environmental aspects and morphology of the scenario. Following physical arguments and taking into account the results of experimental works, we consider a mathematical drift model for the mixture composed by two phases: air and particles. The relative motion between the two phases is described by a kinematic constitutive relation. We prove the stability of the model for fixed times and establish an a priori estimate for the total number of infectious particles. The upper bound of this estimate exhibits sound physical dependencies on the driving factors, in agreement with the experimental literature and mounting epidemiological evidences. Namely, we establish that the amount of particles expelled and their emission rate can explain why some people are superspreaders. Several numerical simulations illustrate the theoretical results.

Experimental study of CeO2 after hydrothermal aging on emission characteristics of carbon black oxidation process

The CeO2 catalyst is commonly utilized in diesel particulate filter (DPF) to promote soot regeneration. It is necessary to give a particular attention to the performance of hydrothermal aging and the effect on DPF regeneration characteristics. Based on the fixed-bed test bench, the gas and particle emission characteristics of carbon black (PU) oxidation following hydrothermal aging and sieving treatment of CeO2 are investigated under a 3% water concentration condition. CeO2 is subjected to characterization and analysis combined with X-ray Photoelectron Spectroscopy (XPS), Electron Spin Resonance Spectroscopy (ESR), X-ray Powder Diffraction (XRD), and Scanning Electron Microscopy (SEM). The results indicate that the addition of fresh CeO2 proves beneficial in improving the oxidation efficiency (η) of PU, reducing CO emission and the total average particle number (PN). Meanwhile, CO2 emission rapidly increases. After hydrothermal aging, the average catalyst size and agglomeration degree of CeO2 increase, resulting in an increase in lattice defects and bulk oxygen vacancies (VO-b). The reduction of surface oxygen vacancies (VO-s) plays a dominant role in the catalytic oxidation process of PU, leading to a decrease in η and CO2 emission, while CO increase; And the contact mode between CeO2 and PU, as well as alterations in the microstructure of CeO2, consequently contributing to hindering particle movement and reducing total PN. Furthermore, the sieving treatment of catalyst increases particle emission, but significantly promotes the η and reduces harmful gas CO. This research establishes a theoretical and experimental foundation for enhancing the hydrothermal stability of catalysts and controlling particle emission at the DPF outlet.

The quantification of the airborne plastic particles of 0.43–11 μm: Procedure development and application to atmospheric environment

The environmental degradation of microplastics results in ultrafine particles that may incur severe biological concerns. Despite this, the atmospheric existence of plastics of less than a few microns has barely been investigated due to the particle size limit of conventional analytical methods. This study develops a procedure to quantify and characterize plastic particles (including nanoplastics; less than 1 μm) in the air through fractional sampling, a simple pretreatment method, and pyrolysis-gas chromatography-mass spectrometry (pyr-GC/MS). We targeted 11 major polymers, namely, polyethylene, polypropylene, polystyrene, acrylonitrile-butadiene-styrene resin, styrene-butadiene rubber, polymethylmethacrylate, polycarbonate, polyvinyl chloride, polyethylene terephthalate (PET), polyamide 6, and polyamide 66 (PA66). The average spike and recovery rate of each polymer in the aerosol collected on the roof of a four-story building near a major road in Kyoto, Japan, amounted to 78–130%, with a coefficient of variation of less than 15%. By coupling pyr-GC/MS analysis with fractional sampling of particles within the size range of >11 μm, 11–7.0 μm, 7.0–4.7 μm, 4.7–3.3 μm, 3.3–2.1 μm, 2.1–1.1 μm, 1.1–0.65 μm, 0.65–0.43 μm, it was possible to quantify airborne nano- and microplastics by particle size. Polyethylene, polystyrene, PET, and PA66 were detected in the air, and the total mass concentration of tiny plastic particles (0.43–11 μm) amounted to 1.20 μg/m3. This translates into total particle numbers of 3.05 × 106 particles/m3 (assuming spheres), revealing a substantial number of particles under 1 μm. These results will contribute to future studies to understand the atmospheric behaviors of ultrafine plastic particles and their flow-on effects on the respiratory system.

Coulomb and symmetry-energy effects on proton and neutron density-distributions in central heavy-ion collisions, across beam energies and system masses

In this contribution, we review our current and previous investigations of total, proton, and neutron particle number densities and the asymmetry of proton and neutron density distributions achievable in central heavy-ion collisions at beam energy below 800 MeV/nucleon. Furthermore, the effects of the Coulomb interaction and the dependence on a system size in three representative symmetric and asymmetric Ca, Sn and Pb systems are studied. The Boltzmann-Uhlenbeck-Uehling (pBUU) transport and Time-Dependent Hartree-Fock (TDHF) models, employing the SVbas, SkT3 and SVsym Skyrme interactions, are used in these simulations. We find that (i) the highest total densities predicted at Ebeam = 800 MeV/nucleon are on the order of ∼ 2.5ρ0 (ρ0 = 0.16 fm−3), (ii) the proton-neutron asymmetry for maximal densities, δ = (ρnmax−ρpmax)/(ρnmax+ρpmax) do not generally exceed the asymmetry in the initial state of the collision at all beam energies and tend to decrease during the reaction, and (iii) a significant portion of this asymmetry has its microscopic origin in Coulomb forces, masking the pure nuclear contribution. In addition, the evolution of normalized maximal proton, neutron, and total nucleon number density with increasing beam energy, the impact of correlations in the reaction, and the time evolution of the proton and neutron density distributions in the plane transverse to the beam direction are illustrated and discussed.

A Continuous-Time Urn Model for a System of Activated Particles

We study a system of M particles with jump dynamics on a network of N sites. The particles can exist in two states, active or inactive. Only the former can jump. The state of each particle depends on its position. A given particle is inactive when it is at a given site, and active when it moves to a change site. Indeed, each sleeping particle activates at a rate λ>0, leaves its initial site, and moves for an exponential random time of parameter μ>0 before uniformly landing at a site and immediately returning to sleep. The behavior of each particle is independent of that of the others. These dynamics conserve the total number of particles; there is no limit on the number of particles at a given site. This system can be represented by a continuous-time Pólya urn with M balls where the colors are the sites, with an additional color to account for particles on the move at a given time t. First, using this Pólya interpretation for fixed M and N, we obtain the average number of particles at each site over time and, therefore, those on the move due to mass conservation. Secondly, we consider a large system in which the number of particles M and the number of sites N grow at the same rate, so that the M/N ratio tends to a scaling constant α>0. Using the moment-generating function technique added to some probabilistic arguments, we obtain the long-term distribution of the number of particles at each site.

Investigating the contribution of grown new particles to cloud condensation nuclei with largely varying preexisting particles – Part 1: Observational data analysis

Abstract. This study employed multiple techniques to investigate the contribution of grown new particles to the number concentration of cloud condensation nuclei (CCN) at various supersaturation (SS) levels at a rural mountain site in the North China Plain from 29 June to 14 July 2019. On 8 new particle formation (NPF) days, the total particle number concentrations (Ncn) were 8.4 ± 6.1×103 cm−3, which was substantially higher compared to 4.7 ± 2.6×103 cm−3 on non-NPF days. However, the CCN concentration (Nccn) at 0.2 % SS and 0.4 % SS on the NPF days was significantly lower than those observed on non-NPF days (p<0.05). This was due to the lower cloud activation efficiency of preexisting particles resulting from organic vapor condensation and smaller number concentrations of preexisting particles on NPF days. A case-by-case examination showed that the grown new particles only yielded a detectable contribution to Nccn at 0.4 % SS and 1.0 % SS during the NPF event on 1 July 2019, accounting for 12 % ± 11 % and 23 % ± 12 % of Nccn, respectively. The increased Nccn during two other NPF events and at 0.2 % SS on 1 July 2019 were detectable but determined mainly by varying preexisting particles rather than grown new particles. In addition, the hygroscopicity parameter values, concentrations of inorganic and organic particulate components, and surface chemical composition of different sized particles were analyzed in terms of chemical drivers to grow new particles. The results showed that the grown new particles via organic vapor condensation generally had no detectable contribution to Nccn but incidentally did. However, this conclusion was drawn from a small size of observational data, leaving more observations, particularly long-term observations and the growth of preexisting particles to the CCN required size, needed for further investigation.

Silicone Particles in Capsules Around Breast Implants: An Investigation Into Currently Available Implants in North America.

Breast implants have always been composed of a silicone elastomer envelope filled with either silicone gel or saline. Breast implant illness (BII) is a set of symptoms that has previously been linked to the leakage of silicone particles from the implants into the body. Our research aimed to quantify the number of silicone particles present in the capsules of breast implants available in North America. Thirty-five periprosthetic capsules were sampled and analyzed, and silicone particles were counted and measured. The capsule surface area was then measured and utilized to calculate particle density and total number of silicone particles. Eighty-five percent of capsules analyzed from silicone gel implants contained silicone, with an average of 62 particles per mm3 of capsular tissue. These implants had approximately 1 million silicone particles per capsule. In contrast, none of the saline implant capsules contained silicone. Capsules from macrotextured tissue expanders contained fewer and larger silicone particles. Silicone gel implants presented silicone particle bleeding into the periprosthetic capsule, totaling on average 1 million silicone particles per capsule. On the other hand, no silicone particle bleeding was observed from saline breast implants. These data suggest that particle bleeding comes from the inner silicone gel, and not from the smooth outer silicone shell. Previous studies have reported the presence of breast implant illness in patients with both silicone- and saline-filled implants. Therefore, our data suggest that silicone migration is not the sole cause of BII.

Exclusion processes on a roundabout traffic model with constrained resources.

Motivated by the vehicular traffic phenomenon at roundabouts, we examine how the limited availability of resources affects the movement of two distinct types of particles on bidirectional lanes connected by two bridges, with each bridge specifically designated for the transportation of one species. To provide a theoretical ground for our findings, we employ a mean-field framework and successfully validate them through dynamic Monte Carlo simulations. Based on the theoretical analysis, we analytically derive various stationary properties, such as the particle densities, phase boundaries, and particle currents, for all the possible symmetric as well as asymmetric phases. The qualitative as well as quantitative behavior of the system is significantly affected by the constraint on the number of resources. The complexity of the phase diagram shows a nonmonotonic behavior with an increasing number of particles in the system. Analytical arguments enable the identification of several critical values for the total number of particles, leading to a qualitative change in the phase diagrams. The interplay of the finite resources and the bidirectional transport yields unanticipated and unusual features such as back-and-forth transition, the presence of two congested phases where particle movement is halted, as well as shock phases induced by boundaries and the bulk of the system. Also, it is found that spontaneous symmetry-breaking phenomena are induced even for very few particles in the system. Moreover, we thoroughly examine the location of shocks by varying the parameters controlling the system's boundaries, providing insights into possible phase transitions.

Stable COPD Picture through Exhaled Breath Condensate, Questionnaires and Tests. A Proof of Concept Study

Background: Changes in lung structures persist in stable Chronic Obstructive Pulmonary Disease (COPD), but their correlation with the clinical picture remains unclear. The purpose of this study was to assess the stable COPD picture via the relationship between exhaled breath condensate (EBC) particle concentration and the Saint George Respiratory Questionnaire (SGRQ), COPD Assessment Test (CAT), and six-minute walking test (6 MWT). Methods: 12 stable COPD and 12 healthy subjects participated in the study. The EBC was collected with Rtube and analyzed using the Accusizer FxNano. Particle concentration was measured and correlated with the findings of the tools used to assess the health status and functional profile of COPD. The results’ analysis was performed with the Spearman’s test and the Mann-Whitney U - test. Results: The COPD group presented a worse picture of health status and functional profile compared to the healthy group. Correlations were observed between components of the SGRQ and CAT. The two groups presented similar levels of EBC particle concentrations, but the number of small particles was higher in COPD subjects. A correlation of the EBC particle concentration with the activity and total score of the SGRQ was only observed in the healthy group. Conclusion: The total particle number was similar in the COPD and healthy groups. A few correlations between the EBC particles and tools used were also observed. The use of EBC particle concentration to monitor COPD status cannot be claimed with confidence because of the small sample size. Further research is necessary, particularly in large-scale groups.

Conserved Restricted Solid-on-Solid Model

We introduce and study a model for the movement of surfaces, namely the conserved, restricted solid-on-solid model. The surface configurations are restricted such that the difference between the heights at adjacent sites is no more than one. In addition, the total number of particles is preserved by the dynamics of the model. Mean-field approximations are used to approximate the one-site probability function of the model in both time-independent and time-dependent regimes. In the time-dependent regime, we found that for the height at one site, the average evolves like t 1/6 and squared fluctuations like t 1/3.

Development and demonstration of the protective efficacy of a convertible respiratory barrier enclosure: a simulation study.

The efficacy of previously developed respiratory barrier enclosures to limit healthcare workers' exposure to aerosols from COVID-19 patients remains unclear; in addition, the design of these devices is unsuitable for transportation or other emergency procedures. Therefore, we developed a novel negative pressure respiratory isolator to improve protection from patient-generated aerosols and evaluated its protective effect in conversion to systemic isolator. This in vitro study simulated droplets by nebulizing 1% glycerol + 99% ethanol solution. We performed cardiopulmonary resuscitation (CPR) and converted a respiratory barrier enclosure into a systemic isolator with a respiratory barrier as well as a respiratory barrier with negative pressure generator (NPG), which were compared with control and room air. During the procedure, particles were counted for 30 seconds and the count was repeated 10 times. During CPR, the total number of particles in the respiratory barrier with NPG (280,529; interquartile range [IQR], 205,263-359,195; P=0.970) was similar to that in the control (308,789; IQR, 175,056-473,276). Using NPG with a respiratory barrier reduced the number of particles to 27,524 (IQR, 26,703- 28,905; P=0.001). Particle number during conversion of the respiratory barrier into a systemic isolator was also lower than in the control (25,845; IQR, 19,391- 29,772; P=0.001). The novel isolator was converted to a systemic isolator without air leakage. The aerosol-blocking effect of the isolator was quantified using a particle counter during CPR. Further studies comparing the barrier effect of isolators within various pressure differentials are warranted.

Research and assessment of the molybdenum oxide (VI) nanoparticles toxiсity under inhalation in WISTAR line rats in comparison with the micro-sized chemical analog

Introduction. Molybdenum (VI) oxide nanoparticles (MoO3 NPs) are being actively introduced into practical use as part of catalysts, optics, plastics, textiles, coatings, and lubricants, gas sensors, and crude oil refining processes. MoO3 NPs are known to exhibit toxic properties when interacting with living systems. Atmospheric air pollution with potentially dangerous MoO3 NPs can contribute to the inhalation exposure in the population and, as a result, the development of health disorders caused by the toxic effect of the nanomaterial. In this regard, the study of the adverse effects caused by MoO3 NPs entering the body during aerogenic exposure is particularly relevant.
 
 The aim of the study. Investigation and evaluation of subacute toxicity of MoO3 NPs by the inhalation route of entry into the body in comparison with a microsized chemical analogue.
 
 Materials and methods. The physical properties of MoO3 NPs were studied in comparison with microparticles (MPs). In an experiment on Wistar rats, a comparative analysis was performed and a characteristic of the pathogenetic features of the toxic effect of particles during subacute inhalation exposure at a concentration of 1.84 mg/m3 was given.
 
 Results. According to the totality of physical properties, the MoO3 sample under study is a nanomaterial with an average particle size of 58.8 nm, constituting 84.2% of the total number of particles. MoO3 NPs accumulate in the heart, lungs, kidneys, and brain. The concentration of molybdenum is by 2.50–15.85 times higher than the control levels. The highest content of the studied element was found in the lungs. Bioaccumulation of MP MoO3 was noted only in the lungs, while the concentration of molybdenum is by 3.00 times less in comparison with the exposure to NPs. When exposed to MoO3 NPs, more pronounced changes in biochemical (an increase in the activity of alkaline phosphatase, LDH, the concentration of total bilirubin and creatinine by 1.29–2.11 times) and hematological parameters (a decrease in the number of platelets and thrombocrit by 1.2 times) of blood were noted relative to the impact of a microscale analogue. Under the influence of NPs and MPs of MoO3, pathomorphological changes develop in the lungs, brain, and liver tissues. When exposed to NPs, compensatory lung emphysema, focal microvesicular steatosis in hepatocytes, and acute plethora in the liver were found, which were not detected during exposure to NPs.
 
 Limitations. The study was performed only with subacute inhalation exposure to NPs and MPs of MoO3 in Wistar rats.
 
 Conclusion. MoO3 NPs have a higher degree of bioaccumulation and toxicity relative to MPs. The results of the study make it possible to expand theoretical concepts and gain new knowledge in the field of nanotoxicology about the features of the toxic effect of nano-sized MoO3 with multiple inhalation routes of entry into the body at a concentration of 1.84 mg/m3.
 
 Compliance with ethical standards. The study was carried out in accordance with the European Convention for the Protection of Vertebrate Animals used for Experimental or other Scientific Purposes (ETS No. 123) and the requirements of the Ethics Committee of the Federal Scientific Center for Medical and Preventive Technologies for Public Health Risk Management (protocol No. 6 of 20.01 .2021).

Efficient vacuum pair production in frequency chirped electric fields with spatiotemporal inhomogeneity

Vacuum pair production under intense electromagnetic fields is an intriguing prediction in quantum electrodynamics (QED), and has become a topic of considerable interest with the rapid advancements in laser technologies. The pair production efficiency can be enhanced using chirped electric fields. In this study, the effects of electric field chirping on electron–positron pair production in different oscillating electric fields were investigated using the Dirac–Heisenberg–Wigner (DHW) formalism. We primarily considered quadratic and sinusoidal chirped electric fields. The results revealed that chirping significantly influences the momentum spectra of the generated particles in an electric field dominated by low-frequency tunneling effects, resulting in pronounced oscillations of the momentum spectrum, particularly in a sinusoidal chirped field. However, multiphoton processes gradually emerge as the chirp parameter increases. Consequently, in a high-frequency electric field dominated by multiphoton processes, the number density of the generated particles increases with the chirping parameter in a quadratic chirped field, whereas the momentum distribution remains relatively symmetric. However, in a sinusoidal chirped electric field, introducing a chirp parameter immediately alters the momentum distribution and enhances pair production rate. Moreover, there exists an optimal chirp parameter and the total particle number is enhanced approximately more than an order of magnitude with optimal chirping in a sinusoidal chirped electric field. These findings provide valuable insights into the intricate dynamics of pair production under the influence of chirping in different oscillating electric fields, and offer potential directions for future research in this domain.