Search Results (26)

Background: Spontaneous ventilation with intubation (SVI) during video-assisted thoracoscopic surgery (VATS) has been introduced as a hybrid technique that combines the physiological benefits of spontaneous breathing with the safety of a secured airway. However, its application in patients with chronic obstructive pulmonary disease (COPD) remains controversial due to concerns about hypercapnia, hypoxemia, and dynamic hyperinflation. To date, no study has directly compared COPD and non-COPD patients undergoing VATS lobectomy under SVI using identical anesthetic and surgical protocols. Methods: A prospective observational study was conducted between January 2022 and December 2024 at a single tertiary thoracic surgery center. A total of 36 patients undergoing elective VATS lobectomy with SVI were included and divided into two groups: COPD (n = 17) and non-COPD (n = 19), based on GOLD criteria. All patients were intubated with a double-lumen tube and allowed to maintain spontaneous ventilation during one-lung ventilation (OLV) after recovery from neuromuscular blockade. Arterial blood gas (ABG) samples were collected at four predefined time points (T1–T4), and intraoperative respiratory parameters, hemodynamics, spontaneous ventilation time, and spontaneous ventilation fraction (SpVent%) were recorded. Postoperative outcomes, including ICU stay, complications, and conversion to controlled ventilation, were analyzed. Statistical comparisons were performed using t-test, Mann–Whitney U test, chi-square test, and ANCOVA with adjustment for age, sex, BMI, and FEV₁%. Results: All 36 procedures were successfully completed under SVI without conversion to controlled mechanical ventilation or thoracotomy. Baseline demographics were comparable between COPD and non-COPD patients regarding age (68.4 ± 6.9 vs. 67.8 ± 7.1 years; p = 0.78) and BMI (27.1 ± 4.6 vs. 26.3 ± 4.2 kg/m²; p = 0.56), while pulmonary function was significantly lower in COPD patients (FEV₁/FVC 53.8% (IQR 47.5–59.9) vs. 82.4% (78.5–85.2); p < 0.001). The duration of spontaneous ventilation was significantly longer in the COPD group (82 ± 14 min vs. 58 ± 16 min; p < 0.001), and remained significant after ANCOVA adjustment (β = +23.7 min; p = 0.001). The SpontVent% was higher in COPD patients (80% [70–90] vs. 60% [45–80]), showing a trend toward significance (p = 0.11). Intraoperative permissive hypercapnia was well tolerated: peak PaCO₂ levels at T3 were higher in COPD (52 ± 6 mmHg) than in non-COPD patients (47 ± 5 mmHg; p = 0.06), without pH dropping below 7.25 in either group. No significant differences were observed in mean arterial pressure, oxygen saturation, ICU stay (1.1 ± 0.4 vs. 1.0 ± 0.5 days; p = 0.48), or postoperative complication rates (p = 0.67). All patients were extubated in the operating room. Conclusions: Intubated spontaneous ventilation during VATS lobectomy is feasible and safe in both COPD and non-COPD patients when performed by experienced teams. COPD patients, despite impaired baseline lung function, were able to maintain spontaneous breathing for significantly longer periods without developing severe hypercapnia, acidosis, or hemodynamic instability. These findings suggest that SVI may represent a lung-protective alternative to fully controlled one-lung ventilation, particularly in hypercapnia-adapted COPD patients. Further multicenter studies are warranted to validate these results and define standardized thresholds for CO₂ tolerance, patient selection, and intraoperative monitoring during SVI. Full article

Hydrothermal vents are “oases” of biological productivity and endemicity on the seafloor. Chemosynthetic communities at deep-sea hydrothermal vents are characterized by high abundance and endemism. The distribution of species among these isolated habitats supports regional biodiversity and stability, so understanding the fundamental processes is a key target of conservation. Larval dispersal resulting from deep-ocean circulations is one of the major factors influencing the diversity and distributions of vent animals. By combining a biophysical model with biological larvae traits, we quantify potential larval dispersal of vent species via ocean circulation in the Azores Triple Junction. Here we present results from a biophysical model of larval dispersal run for the hydrothermal vent benthic mussel Bathymodiolus azoricus. Several scenarios were implemented, based on similar data sets, although changing values for one or two parameters, such as swimming behaviour and planktonic larvae duration. Results showed that larvae retention is the most common pattern from the Azores Triple Junction vent fields mussel. The Rainbow vent field is rather isolated, being the sink population of the Menez Gwen and Lucky Strike but with a very low number of larvae exchange. Results are discussed in the framework of spatial management to maintain the populations after an impact by natural or human disturbance. Full article

The underwater lavatories aboard ships are compact and suffer from inadequate ventilation, thereby increasing the likelihood of infection and odor issues. The crew will endure discomfort from the poor air quality within the lavatories, especially following prolonged travel. This study establishes a three-dimensional numerical model of an underwater lavatory unit, employing computational fluid dynamics (CFD) to assess ventilation performance and contaminant distributions. The concentration of odor gas and the fate of particles within the lavatory were evaluated for a duration of 3 min subsequent to flushing, considering two scenarios: occupants using either the toilet or the urinal. Additionally, the exhaust air volume and the layouts of the lavatory vents were optimized. The results indicate that the individual using the toilet has a lower concentration of ammonia inhalation, and both scenarios remain unaffected by odors within 60 s after flushing. In contrast to the scenario of using the toilet, the case of using the urinal poses notably fewer risks of human contact, with 65.7% of the deposited particles residing on the urinal surfaces and a mere 8.9% adhering to the manikin surfaces. Enhancing the exhaust air volume can facilitate odor removal in the urinal scenario while slightly improving odor control in the case of using the toilet. An airflow rate of 250 m³/h resulted in a 40% increase in particle deposition within the urinal and a roughly 70% decrease on the manikin during the toileting scenario. The existing ship lavatory ventilation is insufficient to manage the risk of aerosol exposure and sense of smell in the breathing zone of standing crew. The air quality within a lavatory can be significantly improved by employing upper air-supply and lower air-exhaust ventilation. Full article

Electrical cabinet fire scenarios constitute a significant risk within nuclear facilities, emphasizing the need to mitigate uncertainties in risk evaluations. Owing to the disparate nature of electrical cabinet parameters, only a few factors have been experimentally explored and statistically analyzed to assess their impact on peak HRR. In this study, we conducted both a cabinet parameter study and a combustible configuration study to systematically evaluate their influence on peak HRR and time-to-peak HRR. A series of 51 simulation matrices were created using statistical experiment design (SED) and ANOVA to quantify the influence of cabinet volume, combustible surface area, vent area, ignition characteristics, and burning behavior (e.g., HRRPUA and duration). A computational fluid dynamics (CFD) model, specifically a Fire Dynamics Simulator (FDS), was used to model the ignition source and flame spread inside of the electrical cabinet that influence peak HRR. The most impactful parameters influencing peak HRR and time-to-peak HRR were identified. The findings revealed that the configuration of combustibles and the placement of the ignition source play a pivotal role in determining the peak HRR. A partition screening analysis was conducted to identify the conditions under which the ventilation area becomes a more significant parameter. Additionally, a comparison between experimental results and numerical simulations demonstrated good agreement, further validating the predictive capability of the model. Full article

Acute lower respiratory tract infections are a leading cause of death in individuals under the age of 5 years, mostly in low- and middle-income countries (LMICs). The lack of respiratory support systems contributes to the poor outcomes. Bubble CPAP is widely used for non-invasive respiratory support, but sicker children often require support over what CPAP provides in the form of BiPAP. We developed and tested a simple bubble-based bilevel ventilator (Bubble bi-vent) and compared it with a standard care BiPAP device. The bubble bilevel device consisted of a single tube submerged in a water-sealed column to maintain end-expiratory positive airway pressure. It moves vertically via an electric motor to also provide inspiratory positive airway pressure for augmentation of lung volumes, with the duration and frequency of breaths controlled by a microprocessor. We tested this novel device in passively breathing mechanical lung models for infants and small children. We compared pressure and tidal volume delivery between the novel device and a Trilogy BiPAP ventilator. The results showed that the Bubble bi-vent could deliver set pressures in a mechanical lung and was comparable to a standard Trilogy ventilator. While two different bubble-based bilevel pressure devices have been piloted for neonates and adults, our results demonstrate the feasibility of bubble bilevel ventilation for infants and small children with moderate to severe lung disease for whom this was previously not described. Full article

The roof slab, as a critical component for partitioning the vertical space within RC frame structures, can effectively mitigate the propagation of shock waves and reduce damage levels in adjacent rooms. This study employed finite element (FE) modeling to investigate the vertical propagation of blast waves and roof ejection velocity in RC frames. The model’s reliability was verified by reconstructing internal explosion tests on RC frames and close-in explosion tests on masonry walls. On this basis, two typical single-room RC frame structures that are vertically adjacent were designed, and numerical simulations of the internal explosion were conducted under four explosive equivalents and four venting coefficients. The propagation of shock waves, load characteristics in the vertically adjacent room, and the dynamic response of roof slabs were examined. The results show that shock waves propagated to the vertically adjacent room decreased by approximately two orders of magnitude for peak overpressure and one order of magnitude for impulse due to the obstruction of shock waves by roof slabs, respectively, compared to the source explosion room. For larger venting coefficients, abundant energy was released through the venting openings, making it difficult to form a quasi-static pressure with a long duration inside the source explosion room. In addition to the shock wave, the explosive ejection of roof slabs in the explosion source room will further exacerbate the damage to the vertically adjacent room. Peak overpressure and impulse propagated to the vertically adjacent room were reduced significantly by the increase in the venting coefficient, resulting in an attenuation of structural damage. Finally, empirical models incorporating the venting coefficient were established to characterize the attenuation coefficients of power parameters, demonstrating the predictive capability for peak overpressure, impulse, and roof ejection velocity in both the explosion source room and the vertically adjacent room. Full article

Numerical simulations reveal the combustion dynamics of hydrogen-blended natural gas (H-BNG) in semi-open spaces. In the typical semi-open space scenario, increasing the hydrogen blending ratio from 0% to 60% elevates peak internal pressure by 107% (259.3 kPa → 526.0 kPa) while reducing pressure rise time by 56.5% (95.8 ms → 41.7 ms). A vent size paradox emerges: 0.5 m openings generate 574.6 kPa internal overpressure, whereas 2 m openings produce 36.7 kPa external overpressure. Flame propagation exhibits stabilized velocity decay (836 m/s → 154 m/s, 81.6% reduction) at hydrogen concentrations ≥30% within 2–8 m distances. In street-front restaurant scenarios, 80% H-BNG leaks reach alarm concentration (0.8 m height) within 120 s, with sensor response times ranging from 21.6 s (proximal) to 40.2 s (distal). Forced ventilation reduces hazard duration by 8.6% (151 s → 138 s), while door status shows negligible impact on deflagration consequences (412 kPa closed vs. 409 kPa open), maintaining consistent 20.5 m hazard radius at 20 kPa overpressure threshold. These findings provide crucial theoretical insights and practical guidance for the prevention and management of H-BNG leakage and explosion incidents. Full article

Background/Objectives: Attaining adequate oxygenation in critically ill patients undergoing invasive ventilation necessitates intense monitoring through pulse oximetry (SpO₂) and frequent manual adjustments of ventilator settings like the fraction of inspired oxygen (FiO₂) and the level of positive end-expiratory pressure (PEEP). Our aim was to compare the quality of oxygenation with the use of automated ventilation provided by INTELLiVENT–Adaptive Support Ventilation (ASV) vs. ventilation that is not automated, i.e., conventional pressure-controlled or pressure support ventilation. Methods: A substudy within a randomized crossover clinical trial in critically ill patients under invasive ventilation. The primary endpoint was the percentage of breaths in an optimal oxygenation zone, defined by predetermined levels of SpO₂, FiO₂, and PEEP. Secondary endpoints were the percentage of breaths in acceptable or critical oxygenation zones, the percentage of time spent in optimal, acceptable, and critical oxygenation zones, the number of manual interventions at the ventilator, and the number and duration of ventilator alarms related to oxygenation. Results: Of the 96 patients included in the parent study, 53 were eligible for this current subanalysis. Among them, 31 patients were randomized to start with automated ventilation, while 22 patients began with conventional ventilation. No significant differences were found in the percentage of breaths within the optimal zone between the two ventilation modes (median percentage of breaths during automated ventilation 19.4 [0.1–99.9]% vs. 25.3 [0.0–100.0]%; p = 0.963). Similarly, there were no differences in the percentage of breaths within the acceptable and critical zones, nor in the time spent in the three predefined oxygenation zones. Although the number of manual interventions was lower with automated ventilation, the number and duration of ventilator alarms were fewer with conventional ventilation. Conclusions: The quality of oxygenation with automated ventilation is not different from that with conventional ventilation. However, while automated ventilation comes with fewer manual interventions at the ventilator, it also comes with more ventilator alarms. Full article

Layered ternary materials with high nickel content are regarded as the most promising cathode materials for high-energy-density lithium-ion batteries, owing to their advantages of high capacity, low cost, and relatively good safety. However, as the nickel content increases in ternary layered materials, their thermal stability noticeably decreases. It is of paramount importance to explore the characteristics of thermal runaway for lithium-ion batteries. In this study, two high-nickel LiNi_0.9Co_0.05Mn_0.05O₂ batteries were laterally heated to thermal runaway in a sealed chamber filled with nitrogen to investigate the thermal characteristics and gas compositions. The temperature of the battery tabs was measured, revealing that both batteries were in a critical state of thermal runaway near 120 degrees Celsius. A quantitative analysis method was employed during the eruption process, dividing it into three stages: ultra-fast, fast, and slow; the corresponding durations for the two batteries were 3, 2, 27 s and 3, 3, 26 s. By comparing the changes in chamber pressure, it was observed that both batteries exhibited a similar continuous venting duration of 32 s. However, the pressure fluctuation ranges of the two samples were 99.5 and 68.2 kPa·m·s⁻¹. Compared to the other sample, the 211 Ah sample exhibited larger chamber pressure fluctuations and reached higher peak pressures, indicating a higher risk of explosion. In the experimental phenomenon captured by a high-speed camera, it took only 1 s for the sample to transition from the opening of the safety valve to filling the experimental chamber with smoke. The battery with higher energy density exhibited more intense eruption during thermal runaway, resulting in more severe mass loss. The mass loss of the two samples is 73% and 64.87%. The electrolyte also reacted more completely, resulting in a reduced number of measured exhaust components. The main components of gaseous ejections are CO, CO₂, H₂, C₂H₄, and CH₄. For the 211 Ah battery, the vented gases were mainly composed of CO (41.3%), CO₂ (24.8%), H₂ (21%), C₂H₄ (7.4%) and CH₄ (3.9%), while those for the other 256 Ah battery were mainly CO (30.6%), CO₂ (28.5%), H₂ (21.7%), C₂H₄ (12.4%) and CH₄ (5.8%). Comparatively, the higher-capacity battery produced more gases. The gas volumes, converted to standard conditions (0 °C, 101 kPa) and normalized, resulted in 1.985 L/Ah and 2.182 L/Ah, respectively. The results provide valuable guidance for the protection of large-capacity, high-energy-density battery systems. The quantitative analysis of the eruption process has provided assistance to fire alarm systems and firefighting strategies. Full article

The venting event of thermal runaway has attracted public attention due to safety issues aroused by frequent fire accidents of new energy vehicles. However, the quantitative description of venting behavior is incomplete for tests in a sealed chamber due to the initial violent injection. In this study, nine types of batteries covering 28 cases in total were employed to investigate the influence of energy density, ambient temperature, pressure, and SOC on the venting behavior, characterized by normalized gas amount; maximum gas releasing rate; and venting durations t₅₀, t₉₀, t₉₅, and t₉₉. Then, a ‘two-point’ fitting method was proposed to modify outcomes concerning real-time gas amounts. The results show that at 100% SOC, the normalized gas amount ranges within 0.075–0.105 mol/Ah for NCM batteries and 0.025–0.035 mol/L for LFP batteries, while the maximum gas releasing rate presents a strongly positive correlation with the capacity of NCM batteries (0.04–0.31 mol/s) and a slight increase for LFP batteries (0.02–0.06 mol/s). Eventually, the three venting patterns were summarized and advanced according to the energy density and SOC of the targeted battery. This research can provide a reference for risk evaluations of the venting process and safety design for structure and pressure relief in battery systems. Full article

The ventilation system is the only channel for gas exchange inside and outside the gas tunnel, which determines whether the high-risk gas in the tunnel can be exhausted in time after a gas leakage accident; thus, it is essential to study the dynamic ventilation characteristics. A fire-retarding division of the gas tunnel in Songjiang District of Shanghai is taken as the study object, and, based on the similarity theory, a similarity experiment platform is built. The simulation experiments of exhaust are carried out under different exhaust velocities, ventilation equivalent diameters and initial gas concentrations by using the control variable method. The changes in ventilation duration and gas concentration are analyzed in detail. The conclusions are as follows: (1) Time–concentration curves at all positions in the gas tunnel exhibit an “asymptote” distribution. (2) Average gas concentration has a linear relationship with time at the beginning and becomes an exponential relationship after a certain time. (3) When the exhaust velocity is 5 m/s, the initial gas concentration is 15%VOL; when the equivalent diameter of the vent in the model is 0.2 m, the ventilation duration is 100.2 s. A calculation model of ventilation duration for the standard gas tunnel is established, and the application limits of the model are 1 ≤ v ≤ 5, 0.5 ≤ d ≤ 1.5, and 5 ≤ ${\phi }_o$ ≤ 25. (4) In practical engineering, an exhaust velocity of 5 m/s and an equivalent ventilation diameter of 1 m are relatively optimal ventilation parameters. Full article

Chinese Fan Palm, Livistona chinensis, was introduced as an ornamental plant towards the end of the nineteenth century in Pakistan, and since then, it has been used as a popular plant in urban landscaping. It dominates the green belt of parks, recreational gardens and road verges in Lahore, Pakistan. Recent trends in the plantation of fast-growing palm species and other exotics have replaced L. chinensis in urban landscaping. In this study, observations made on the daily routine of foraging of L. chinensis berries by two common urban birds, the red vented bulbul (Pycnonotus cafer) and the house crow (Corvus brachyrhynchos), showed that their consumption of berries peaked in December and January, but the duration of foraging was shown to be longer in house crows as compared to red vented bulbuls. This period of consumption corresponds to the time when the pulp of the berries has become soft, and during this period, no other fruits are available in the urban landscape. Nutrient analysis showed that the pulp of the ripened berries is a rich source of nutrients, and these berries are providing an ideal winter food to counter the increased energetic demands experienced by urban birds during the coldest part of the year, thus helping birds avoid the risk of starvation. This dietary intake of berries by birds also provides a rationale to popularize L. chinensis as an essential component of the planting palette of the urban landscape. This research can be considered as starting point for broad public support to improving landscape planning for managing nature in cities. Full article

We examine a dome within the boundary between Fracastorius crater and Mare Nectaris. The dome has a noticeable vent structure and appears to be perpendicular to wrinkle ridges in the southern Mare Nectaris basin. The spectral signature of this dome, derived from Clementine UVVIS and Chandrayaan-1 M³ reflectance data, revealed that Fracastorius has low TiO₂ content and primarily basaltic material. Using altimeter data, we measured the dome diameter to be 28.6 km, with a dome height of 241.5 m, and a flank slope of 1°. Based on rheological modeling of the dome and a viscoelastic model of the presumed feeder dike, we obtained a magma viscosity of 3.1 × 10⁵ Pa s, an effusion rate of 5.9 m³ s⁻¹, a duration of multiple effusion processes of 4.15 years, and a magma rise speed of 2.1 × 10⁻⁴ m s⁻¹. From these measurements, we estimate the feeder dike geometry to have a horizontal dike length of 234 km and a width of 11.8 m. A comparison of the Fracastorius dome with other noted lunar domes with similar morphometric properties reveal similar magma viscosities to domes found near craters Mee, Milichius and Petavius. Full article

The unsaturated zone of the subsurface plays a critical role in the environmental fate and transport of a wide range of environmental contaminants, and is also important for plant growth and agriculture. Quantitative prediction of processes in the unsaturated zone requires knowledge of how water content varies with elevation above the water table, a relationship known as the capillary pressure (P_c)–saturation (S) relationship. While the P_c–S relationship is conventionally thought of as being primarily a property of the porous medium and fluids, previous work found evidence suggesting that it actually results from a dynamic equilibrium between capillary forces and phenomena driven by evaporation. The focus of this work was on gaining a further understanding of the role of evaporation on the P_c–S relationship. The work made use of a tall instrumented laboratory column connected to an external reservoir for maintaining water table height. Following an initial imbibition experiment, the column was saturated and allowed to drain, and then water content was monitored in the column as a function of height over 1207 days (3.31 years). While initial imbibition and drainage were rapid, on the order of hours, redistribution and evaporation effects became apparent over longer time scales (hundreds of hours). A drying front moving downward in the column was apparent from changes in the slopes of saturation vs. time curves as it passed individual sensors; unlike previous experiments with a more fully-vented column, the evaporation front appeared to stall, balanced by the capillary-driven upward flow of water. Over the full multi-year duration of the experiment, seasonal trends in water saturation were apparent, with significant, reversible variations observed that closely followed atmospheric conditions. Specifically, saturation above the water table appeared to increase during the spring and summer months and decrease during the fall and winter months, despite the constant water table location, consistent with a changing driving force for evaporation. This result may suggest the likelihood of seasonal effects in the long-term transport and fate of contaminants in the unsaturated zone. Full article

Throughfall makes up the major portion of understory rainfall, and thereby plays a vital role in regulating the hydrological and biogeochemical processes in forest ecosystems. The aim of this study was to explore the alterations in throughfall and the associated chemical composition (Ca²⁺, Na²⁺, K⁺, Mg²⁺, H⁺, SO₄²⁻, NO₃⁻, Cl⁻, and F⁻) under Quercus acutissima Carruth. and Broussonetia papyrifera (L.) L’Her. ex Vent. trees, in relation to trunk distance and rainfall characteristics. Event-based measurements were carried out from April to December 2018 in a subtropical forest of eastern China. The throughfall amount (T_F) and throughfall ratio (T_F%) of Q. acutissima (35.7 mm, 83.0%) were higher than those of B. papyrifera (32.1 mm, 74.7%). Although no significant species differences in the ion concentrations of throughfall were detected, almost all ions (Ca²⁺, Na²⁺, K⁺, Mg²⁺, H⁺, SO₄²⁻, NO₃⁻, and Cl⁻) were enriched after passing through the canopies of the two tree species. T_F and T_F% increased with increasing distance from the trunk, while the concentrations of most ions in throughfall increased, since the trunk was approximated. Regression analysis and redundancy analysis revealed that rainfall amount, duration and intensity exerted significant impacts on throughfall generation and ion concentrations, and the antecedent dry period had a notable influence only on ion concentrations. Our findings indicated that forest canopy and rainfall characteristics play an important role in the alterations in throughfall and the associated chemical compositions. Full article