Atmospheric Pressure Research Articles

The Issues of Stress and its Reduction Methods in Modern Science

In everyday life, the word "stress" is often used as a synonym for strong excitement, emotions. But this concept is much broader. Stress is the body's reaction to any irritating effects: problems at work, exams, hunger, lack of sleep, even fluctuations in atmospheric pressure. For many people, such stresses interfere with normal psychological, physical and social functioning. Prolonged stress damages the mechanisms of self-regulation of the body and leads to subsequent disturbances of biorhythms. The natural cycle of sleep and wakefulness changes, as a result, performance and self-control decrease, memory and attention deteriorate. Daily fluctuations in hormone levels, breathing rhythms and heartbeat are also disrupted. Chronic stress weakens the immune system, suppresses the protective reactions and barrier functions of the cells of the gastrointestinal tract and skin, which complicates the course and prognosis of any somatic diseases, including infectious. As a result, stress increases the risk of so-called "diseases of civilization" and contributes to their development: hypertension, diabetes mellitus, bronchial asthma, chronic pain, immune disorders and many others

Shaping Outflows and Jets by Ambient Pressure: A Unified Framework

Shaping Outflows and Jets by Ambient Pressure: A Unified Framework

Superconductivity and high hardness in scandium-borides under pressure.

Exploration of new superconducting or superhard transition-metal borides has attracted extensive interest in the past few decades. In this study, we conducted comprehensive theoretical investigations in the scandium-boron binary system by employing a structural search method based upon first-principles density functional theory. Among the six predicted superconducting scandium-borides, ScB14 (Pm3̄) has the highest superconducting transition temperature Tc = 12.3 K and a Vickers hardness of 12.6 GPa at ambient pressure. The superconductor ScB4 (C2/m) has Tc = 3.6 K and a high Vickers hardness of 25.5 GPa at ambient pressure. Further analysis indicates that the previously synthesized ScB15 (P41) is of superhardness. Our discoveries not only enrich the phase diagram of scandium-borides, but also pave the way for future experimental validations and potential applications of superconducting scandium-borides in industry.

Implicating the Role of Au-H Bonds in Photochemical N2 Fixation by Ruthenium Doped Gold Clusters.

Dinitrogen fixation through the Nitrogen Reduction Reaction (NRR) under mild conditions without the use of sacrificial agents has its share of formidable hurdles. It has been shown recently that Ru-doped Au nanoclusters can reduce N2 molecule to NH3 only in the presence of UV-Vis light in aqueous medium. Herein, using theoretical techniques (Density Functional Theory) we shed light on the mechanistic avenues traversed for achieving this prodigious chemical feat. Our findings suggest that the bimetallic Au22Ru6 cluster successfully accomplishes the NRR process under ambient pressure and temperature conditions by the very virtue of its bifunctional nature. Contrary to the existing views, we find that NRR propagates through an alternative associative pathway, where the Ru dopant assists in N2 adsorption while the Au-H bonds formed from Au assisted water splitting is implicated for facilitating NRR.

Hydrogenation of Organic Molecules via Direct Mechanocatalysis.

Mechanochemical hydrogenation of unsaturated C-C and C-O, as well as N-O and C-X bonds is successfully achieved without the use of solvents, ligands, or catalyst powders via ball milling. A variety of catalysts are electroplated onto the walls of the milling vessel, allowing for simple recycling and reuse of the catalytic material. Hydrogen gas is directly introduced into the milling vessel, eliminating the need for hydrogen donor compounds which contribute to waste production and suboptimal atom economy. This approach enables the quantitative hydrogenation of unsaturated carbon-carbon bonds, achieving near-complete conversion within just 20 minutes at ambient temperature and pressures as low as 1.5 bar. Carbonyls, nitro groups, and organohalides were converted within reaction times of up to 12hours. Mechanistic investigations suggest the reaction to be following established mechanisms for hydrogenation. Finally, chemoselective hydrogenation of various reducible functional groups was explored, demonstrating the versatility and efficiency of this solvent-free mechanochemical approach with simple catalyst recycling for hydrogenation reactions.

Hydrogenation of Organic Molecules via Direct Mechanocatalysis

Mechanochemical hydrogenation of unsaturated C‐C and C‐O, as well as N‐O and C‐X bonds is successfully achieved without the use of solvents, ligands, or catalyst powders via ball milling. A variety of catalysts are electroplated onto the walls of the milling vessel, allowing for simple recycling and reuse of the catalytic material. Hydrogen gas is directly introduced into the milling vessel, eliminating the need for hydrogen donor compounds which contribute to waste production and suboptimal atom economy. This approach enables the quantitative hydrogenation of unsaturated carbon‐carbon bonds, achieving near‐complete conversion within just 20 minutes at ambient temperature and pressures as low as 1.5 bar. Carbonyls, nitro groups, and organohalides were converted within reaction times of up to 12 hours. Mechanistic investigations suggest the reaction to be following established mechanisms for hydrogenation. Finally, chemoselective hydrogenation of various reducible functional groups was explored, demonstrating the versatility and efficiency of this solvent‐free mechanochemical approach with simple catalyst recycling for hydrogenation reactions.

Effect of Gas Pressure on the Oxidation Behavior of Cu and Cu Alloys

This study investigated the effect of gas pressure and alloying elements on the oxidation behavior of copper. Copper alloys containing 1 wt.% of zinc, nickel, or manganese were cast using vacuum induction melting, followed by solution treatment at 400°C for 60 minutes. Oxidation were conducted at 700°C for 60 minutes under pressures of 101325, 20, and 10 Pa. The oxide layers formed at atmospheric pressure on both the pure copper and copper alloys naturally delaminated. In contrast, the oxide layers formed under low-pressure conditions remained intact without delamination. This improved bonding strength between the copper matrix and Cu<sub>2</sub>O was attributed to the formation of large grains and dense oxide layer, which increased the contact area with the copper substrate. Additionally, the oxide layers formed under low-pressure exhibited higher dislocation density, which reduced lattice mismatch and interface energy, thereby contributing to the formation of stable interface. In copper alloys, thicker oxide layers were observed compared to pure copper, with voids detected between the oxide layer and the copper substrate. These voids were presumed to be Kirkendall voids, resulting from the difference in diffusion rates between copper and the alloying elements. However, adhesion evaluations indicated that these voids did not significantly impact interfacial adhesion. Through interface control, dense and stable oxide layers were successfully formed on both pure copper and copper alloys.

Recent advances in surface charge dynamics in dielectric barrier discharge: future strategies for control and technological optimisation

Abstract Dielectric barrier discharges (DBDs) using atmospheric pressure plasma are utilised in various industries, including environmental remediation, semiconductor manufacturing, and energy technology. It is crucial to understand and regulate their properties for technological optimisation. Of particular significance is the surface charge generated by DBDs, as it is the primary physical factor that determines the electric field in the plasma, resulting in overcurrent suppression and radical formation. This study explores recent advancements in research concerning the dynamic properties of surface charge and examines future strategies for optimising DBDs and achieving real-time surface charge control.

Different Inactivation Mechanisms of Staphylococcus aureus and Escherichia coli in Water by Reactive Oxygen and Nitrogen Species Generated from an Argon Plasma Jet.

The atmospheric pressure plasma jet (APPJ) is a promising technology for inactivating waterborne pathogens by generating diverse reactive species under ambient conditions. However, uncertainties regarding the bacterial inactivation mechanisms persist due to varying findings in prior research. This study aimed to clarify the inactivation mechanisms of two representative bacteria, Staphylococcus aureus (S. aureus, Gram-positive) and Escherichia coli (E. coli, Gram-negative), using an argon-based APPJ (Ar-APPJ) system in a controlled medium, primarily deionized water. We identified several reactive oxygen and nitrogen species (RONS), including hydrogen peroxide, peroxynitrous acid/peroxynitrite (ONOOH/ONOO-), hydroxyl radical (•OH), and hydroperoxyl radical/superoxide radical, and evaluated their roles in bacterial inactivation. Inactivation experiments and quantification of suspected RONS revealed that ONOOH was the primary lethal agent for S. aureus, while •OH predominantly inactivated E. coli. Assessment of cell membrane integrity and intracellular RONS levels showed that E. coli, with its thinner cell wall, was more vulnerable to surface damage caused by •OH. In contrast, for S. aureus, with its thicker cell wall, intracellular attack by penetrated ONOOH, being significantly more diffusive than •OH, was more effective, as •OH alone could not induce sufficient surface damage. These findings advance our understanding of bacterial inactivation by the Ar-APPJ and provide valuable insights for designing effective water disinfection strategies utilizing this technology.

Description and operation characteristics of SPECS EnviroESCA

This paper provides the characteristics and operating modes of the SPECS EnviroESCA in sufficient detail that they can be referenced by authors using such instruments and to provide readers with a level of instrumental detail often lacking in research papers. The EnviroESCA is a commercial version of a laboratory near ambient pressure x-ray photoelectron spectroscopy instrument designed to allow samples to be analyzed in gaseous and even liquid environments at higher pressures than are possible for typical XPS instruments. An instrument overview including a description of components and geometries and a table of relevant parameters are provided. Details related to charge compensation, instrument control and analysis software, and different modes of operation are included. Data from a silver sample provide examples of instrument performance and the effect of analyst-controlled variables such as pass energy and gas pressure on the type of data that can be collected.

Creation, stabilization, and investigation at ambient pressure of pressure-induced superconductivity in Bi0.5Sb1.5Te3

In light of breakthroughs in superconductivity under high pressure, and considering that record critical temperatures (Tcs) across various systems have been achieved under high pressure, the primary challenge for higher Tc should no longer solely be to increase Tc under extreme conditions but also to reduce, or ideally eliminate, the need for applied pressure in retaining pressure-induced or -enhanced superconductivity. The topological semiconductor Bi0.5Sb1.5Te3 (BST) was chosen to demonstrate our approach to addressing this challenge and exploring its intriguing physics. Under pressures up to ~50 GPa, three superconducting phases (BST-I, -II, and -III) were observed. A superconducting phase in BST-I appears at ~4 GPa, without a structural transition, suggesting the possible topological nature of this phase. Using the pressure-quench protocol (PQP) recently developed by us, we successfully retained this pressure-induced phase at ambient pressure and revealed the bulk nature of the state. Significantly, this demonstrates recovery of a pressure-quenched sample from a diamond anvil cell at room temperature with the pressure-induced phase retained at ambient pressure. Other superconducting phases were retained in BST-II and -III at ambient pressure and subjected to thermal and temporal stability testing. Superconductivity was also found in BST with Tc up to 10.2 K, the record for this compound series. While PQP maintains superconducting phases in BST at ambient pressure, both depressurization and PQP enhance its Tc, possibly due to microstructures formed during these processes, offering an added avenue to raise Tc. These findings are supported by our density-functional theory calculations.

Optimization of Micropillars Electroplating Bonding Processes and Additives

Abstract With the increasing interconnect density of electronic components, copper–copper direct bonding technology has garnered increasing attention from researchers. The electroplating bonding method is an efficient copper pillar interconnection technique that can be implemented at room temperature and atmospheric pressure. comsol simulation results show that under convective conditions, the plating layer primarily deposits on the convection exit side of the copper plate. Under weak convection and low current density, the plating exhibits deposition characteristics that conform to the substrate surface. As convection intensity increases, preferential deposition begins to occur, although the overall deposition rate decreases. At this point, when the current density is increased, the deposition pattern predominantly shows preferential deposition; however, excessively high current density can lead to copper deposition in nonbonding areas. Orthogonal experimental results indicate that, within the accelerator bis(3-sulfopropyl) disulfide (SPS)–inhibitor polyethylene glycol (PEG)–leveling agent Jenner Green B (JGB)–chloride ion (Cl−) system, the influence of the four additives on bonding strength follows this order: JGB > Cl− > SPS > PEG. The optimal formulation derived from the orthogonal experiments is SPS 2 ppm, PEG (8000) 150 ppm, JGB 5 ppm, and Cl− 30 ppm, which results in a shear strength of 123.2 MPa. These findings suggest that high-strength copper pillar interconnections can be achieved by adjusting physical parameters such as the electric field, flow field, and additive concentrations.

Wide range dielectric behavior characterization of ternary composite (Re-BT-CaO)

This article's primary objective is to investigate a ternary composite's dielectric behavior using time domain spectroscopy (TDS). A heterogeneous mixture of barium titanate (BT) and calcium oxide (CaO) in an epoxy resin matrix (RE) with a predetermined volume fraction level (70%) makes up this type of material. The remaining components (BT and CaO) are variable in increments of 07.50% and complete one another in order to achieve the final percentage, which is 30%. The different composite samples are created using the aforementioned stoichiometric ratios at room temperature and below atmospheric pressure. These mixes are put through a dielectric behavior analysis over a broad frequency range, from DC to 10 GHz. This study intends to highlight the impact of calcium oxide and barium titanate on the composite's dielectric behavior and on the form factor provided by the modified Lichtenecker equation (MLL). It follows a numerical method for optimizing of the predictive model of this law based on a better smoothing of this shape factor in order to allow a better concordance among the predicted values and practical ones. A comparison between the experimental data and the MLL values is performed in order to highlight the proposed model performance on the ternary composite dielectric permittivity estimation quality. This research's focus is on how these materials are used in micro- and nanoelectronics as well as telecommunication components fabrication.

Inter-laboratory testing of thermal properties at ambient pressure on reference samples and core samples from the COSC-1 scientific drill hole, central Sweden

Summary We conducted comparative measurements of thermal properties of samples from nine cores of the ICDP COSC-1 borehole and four widely used rock references, using a steady-state and a transient divided-bar device, a transient plane source device, a modified Ångström device, as well as two optical thermal conductivity scanners. In addition, a caloric method provided benchmark values for specific heat capacity. A complementary thin-section analysis of the COSC-1 samples allowed us to calculate specific heat capacity according to Kopp’s law and thermal conductivity according to commonly used mixing models. Our results demonstrate agreement between the various test methods within ±10% for about one half of the investigated samples. Furthermore, almost all results for specific heat capacity agree with the predictions of Kopp’s law, though the significance of this correspondence is limited owing to large uncertainties in the experimental and theoretical values. The results for thermal conductivity fall within the most extreme theoretical bounds that account for anisotropy but for an amphibolite. Thermal anisotropy seems to contribute significantly to the deviations between results of the different transient methods that, however, cannot be reconciled by the available theoretical relations for apparent thermal conductivity of transversely isotropic materials. The combination of characteristic investigation volume of the individual methods and sample heterogeneity has to be considered responsible for variability of results, too, an issue whose clarification is calling for dedicated numerical modelling in the future, with the prospect to characterise thermal heterogeneity from observed differences.

Low-power electrodeless 2.45 GHz microwave plasma generation in ambient air with dielectric resonators

Abstract Microwave (MW) plasma, as an electrodeless non-thermal plasma technique, holds significant potential for gas processing applications under near-ambient conditions. However, current MW plasma methods suffer from low energy efficiency due to the high power required for molecular breakdown via vibrational excitation. A promising approach to mitigate this challenge involves using a pair of high relative permittivity dielectric resonators (DRs) in close proximity to enhance the electric field within the small gap between them, thus reducing power consumption. In this study, we combined simulations and experiments to investigate the electric field enhancement effect of DRs with varying shapes, geometrical parameters (e.g., radius and height), gap distances, and orientations relative to the electric field polarization and MW propagation directions. Simulations performed using Ansys HFSS demonstrate that edge-to-edge configurations of hexagonal, square, and triangular prism DRs can achieve significant electric field enhancement over a broad range of geometric parameters. DRs fabricated from calcium titanate were tested experimentally using a simple setup with a kitchen microwave (2.45 GHz) at ambient pressure. With input power below 100 W, stable and highly confined plasma was generated using hexagonal and triangular prism DRs. These results suggest a simple, cost-effective, and low-power method for generating MW plasma under ambient conditions, offering particular advantages for chemical processing in rural areas utilizing renewable energy resources.

First-principles investigation of structural, electronic, and optical properties of RVO4 (R = Er, Eu, Tb, Yb) orthovanadates under pressure

Abstract First-principles calculations were performed to systematically study RVO4 orthovanadates with tetragonal zircon- and scheelite-type structures. The study focused on structural parameters, pressure-induced structural phase transformation, electronic band structure, and optical properties under ambient conditions and hydrostatic pressures up to 10 GPa. Energy-volume and enthalpy-pressure curves were used to determine the phase transition pressures of RVO4 compounds. Among the four compounds examined in both phases, YbVO4 was determined to be less compressible than the other compounds. The computed band structures indicated that RVO4 compounds in both phases are semiconductors with a direct bandgap at the Γ→ Γ point. Optical spectra such as dielectric constants, refractive index, reflectivity, absorption coefficient, birefringence, optical conductivity, and energy loss function were computed as functions of incident radiation energy in the energy range of 0–45 eV. The optical anisotropy of RVO4 compounds was observed in both phases. The computed birefringence values for zircon (scheelite) RVO4 indicate that they are uniaxial positive (negative) crystals and have a large birefringence value. Hydrostatic pressure was found to play an important role in the structural, optical, and electronic properties of both phases of RVO4 compounds.

Enhanced Wire-Shaped Micro-Supercapacitor Treated with a Continuous Surface Atmospheric Pressure Plasma Jet Approach.

Microscale, wire-shaped flexible supercapacitors are gaining significant attention due to the growing demand for wearable electronics and microrobotic technologies. Among various materials, copper sulfide stands out as an ideal candidate because of its superior electrochemical properties, which can be attributed to its nanostructured composition. This structure enhances the surface area, reduces ion transport distances, and improves charge-discharge kinetics. However, conventional electrode synthesis methods-such as annealing and hydrothermal processes-are limited by long production times and scalability issues, making them unsuitable for wire-shaped supercapacitor development. In this study, an innovative fabrication technique using an atmospheric pressure plasma jet (APPJ) for both surface treatment and material synthesis is proposed. By integrating the APPJ with a winding mechanism, roll-to-roll processing for continuous production is enabled, significantly enhancing the scalability of the manufacturing process. The fabricated wire-shaped microscale electrodes demonstrate high specific capacitance (153.39 mF cm-2), specific energy density (15.48 µWh cm-2), and excellent capacitance retention (91.32%) after 30000 charge-discharge cycles. Furthermore, a wire-shaped solid-state flexible asymmetric supercapacitor is assembled using the fabricated electrodes in a coaxial configuration. The supercapacitor exhibits exceptional flexibility and energy storage performance, underscoring the practical applicability of the proposed method for advanced electronics.

Assessment of Airfoil Lightning Strikes Characterization on Aircraft in Dynamic Conditions

Lightning is a long-gap high-current discharge event in nature, and its enormous discharge energy can cause structural damage to struck objects. Relevant studies have shown that aircraft in the air are exposed to a higher risk of lightning strikes than ground objects. However, most studies on aircraft lightning strikes have used static models, and there are still shortages of research objects under high-speed movements. Therefore, it is necessary to conduct an investigation of the lightning strike characteristics of aircraft under dynamic conditions to ensure flight safety fully. In this study, the lightning strike characteristics of airfoil under dynamic conditions have been simulated by studying two variables, airspeed and angle of attack, while employing the Leader Progression Model (LPM). The results show that adjustments in the angle of attack cause changes in the atmospheric pressure field, and a maximum pressure difference of up to 5.44 × 104 Pa is observed at the angle of attack of 15°, which results in a change in the average electric field strength Estr, leading to a 33.63% difference in the upward leader trigger height. At an airspeed equal to 120 m/s, the trigger height in the low-pressure region is only 54.7% of that in the high-pressure region (435 m and 795 m, respectively). A higher lightning strike risk is found in areas of higher air pressure and is positively correlated with angle of attack and airspeed.

Ion Irradiation-Induced Coordinatively Unsaturated Zn Sites for Enhanced CO Hydrogenation.

Defect engineering critically influences metal oxide catalysis, yet controlling coordinatively unsaturated metal sites remains challenging due to their inherent instability under reaction conditions. Here, we demonstrate that high-flux argon ion (Ar+) irradiation above recrystallization temperatures generated well-defined coordinatively unsaturated Zn (CUZ) sites on ZnO(101̅0) surfaces that exhibited enhanced stability and activity for CO hydrogenation. Combining low-temperature scanning probe microscopy, ambient pressure X-ray photoelectron spectroscopy, and surface-ligand infrared spectroscopy with density functional theory calculations, we identified <12̅10> step edges exposing CUZ sites as the dominant active sites. These sites facilitate hydrogen-assisted CO dissociation through a mechanism distinct from formate-mediated pathways on stoichiometric ZnO. The ion-irradiation approach effectively addressed instability of Zn species, a major problem in ZnO catalysis, enabling stable performance in syngas conversion when combined with zeolites. Our atomic scale investigation provided spectroscopic fingerprints for active sites on the ZnO catalyst and insights into the structure-activity relationships of ZnO for CO hydrogenation. Our approach for engineering thermally stable defect sites in oxide catalysts provided opportunities for rational catalyst design beyond traditional preparation methods.

Visualization and Parameters Determination of Supersonic Flows in Convergent-Divergent Micro-Nozzles Using Schlieren Z-Type Technique and Fluid Mechanics

Small-scale and supersonic convergent-divergent type micro-nozzles with characteristic sizes of around a few centimeters and exit and throat radii of tenths of millimeters were the subjects of this study. Using the schlieren Z-type optical technique, the supersonic airflows established at the exit of seven nozzles were visualized. The dependence of the shock cell characteristics on the nozzle pressure ratio (NPR), defined as the ratio of stagnation pressure to atmospheric pressure, was analyzed. The dependence of the nozzle thrust and the specific impulse on the NPR ratio and the mass flow rate was also studied using a simple device based on concepts of fluid mechanics. The results obtained are in agreement with similar results obtained in recently published research on double-bell nozzles. The thrust of all nozzles depends linearly on the shock-cell spacing, which is one of the most relevant findings of this research. In other words, the output airflow structure determines the performance of the nozzles, such as the thrust or the specific impulse they produce. These small nozzles offer significant advantages over conventional nozzles in low energy consumption and lower manufacturing cost, making them suitable for scientific research in space micro-propulsion and cooling microelectronic systems, among other applications.