Low Pressure Research Articles

Modeling Solubility Induced Elemental Fractionation of Noble Gases in Oils

This study explores the estimation of solubility-induced elemental fractionation of noble gases in hydrocarbon-based oils through existing empirical and theoretical models, complemented by a novel molecular simulation-based approach. Quantifying such fractionation is essential for a deeper understanding of fluid processes and migration in subsurface geological resources, an area currently lacking in experimental data. To address this, the research introduces a predictive model that employs the Peng-Robinson equation of state and a fugacity-coefficient-based method to assess noble gas elemental fractionation in hydrocarbons, including normal alkanes, cycloalkanes, and aromatics. However, this model struggles with precise quantitative predictions, prompting the introduction of adjusted cross-interaction parameters to enhance its performance. Furthermore, molecular simulations, in conjunction with the refined equation of state, are shown to offer a novel method for calculating noble gas fractionation coefficients across different hydrocarbon solvents. A key finding is the identification of a universal master curve, demonstrating that noble gas solubility fractionation at low pressure in simple hydrocarbon solvents can be quantitatively determined by temperature and density alone, without the need for detailed compositional information. Consequently, a new correlation is proposed for deriving elemental fractionation coefficients based solely on oil temperature and density, offering significant improvements over existing empirical methods for a wide range of temperature. Although limitations are noted when applying this approach to oils rich in complex heavy components like resins and asphaltenes, it allows to address inconsistencies observed in traditionally used experimental correlations at high temperatures.

Economic limitation of recent heterogeneous catalysts for ammonia synthesis

The economic performance of newly developed catalysts for ammonia synthesis, Ru/Ca(NH2)2 and Ru/Pr2O3, are evaluated by process simulation using Aspen Plus©. The results show that the high activity of the new catalysts reduces the electricity cost for pressurizing reactant gases; however, the electricity for lowering the temperature in ammonia separation through liquefaction is significant due to the mitigated pressure and almost compensates for the decreased cost. The results show an economic limitation to current research trends that develop a catalyst for ammonia synthesis under low pressure. It is noted that catalyst costs are high due to expensive ruthenium; thus, the lifetime of catalysts significantly influences the total cost. With the assumption of a long lifetime of catalysts, the new catalysts are advantageous when the electricity cost is high, the characteristics of the case in which renewable energy is employed. As the future direction of the catalyst development, recycling or extending the lifetime of the catalysts and replacing Ru with cheap metal will be crucial from the economic viewpoint. Moreover, effective methods for ammonia collection, such as adsorbents, should be focused on reducing the electricity of ammonia liquefaction in cooling separation and giving a vital meaning to the condition mitigated by the newly developed catalysts.

Ammonia pyrolysis oxidation excited by nanosecond pulsed discharge: Global/fluid models hybrid solution

The kinetic characteristics of plasma-assisted oxidative pyrolysis of ammonia are studied by using the global/fluid models hybrid solution method. Firstly, the stable products of plasma-assisted oxidative pyrolysis of ammonia are measured. The results show that the consumption of NH3/O2 and the production of N2/H2 change linearly with the increase of voltage, which indicates the decoupling of non-equilibrium molecular excitation and oxidative pyrolysis of ammonia at low temperatures. Secondly, the detailed reaction kinetics mechanism of ammonia oxidative pyrolysis stimulated by a nanosecond pulse voltage at low pressure and room temperature is established. Based on the reaction path analysis, the simplified mechanism is obtained. The detailed and simplified mechanism simulation results are compared with experimental data to verify the accuracy of the simplified mechanism. Finally, based on the simplified mechanism, the fluid model of ammonia oxidative pyrolysis stimulated by the nanosecond pulse plasma is established to study the pre-sheath/sheath behavior and the resultant consumption and formation of key species. The results show that the generation, development, and propagation of the pre-sheath have a great influence on the formation and consumption of species. The consumption of NH3 by the cathode pre-sheath is greater than that by the anode pre-sheath, but the opposite is true for OH and O(1S). However, within the sheath, almost all reactions do not occur. Further, by changing the parameters of nanosecond pulse power supply voltage, it is found that the electron number density, electron current density, and applied peak voltages are not the direct reasons for the structural changes of the sheath and pre-sheath. Furthermore, the discharge interval has little effect on the sheath structure and gas mixture breakdown. The research results of this paper not only help to understand the kinetic promotion of non-equilibrium excitation in the process of oxidative pyrolysis but also help to explore the influence of transport and chemical reaction kinetics on the oxidative pyrolysis of ammonia.

CO2 capture using functionalized MIL-101(Cr) metal–organic frameworks: Functionality nanoarchitectonics of nanospace for CO2 adsorption

In this study, we investigated the effect of functional groups of metal–organic frameworks (MOFs) on CO2 adsorption at low pressure through experimental and computational approaches. We compared the performance of −SO3H, –NO2, aryl –NH2, and alkyl –NH2 groups (in similar molar quantities) in CO2 adsorption under the same conditions. The adsorption efficiency followed in the order: alkyl –NH2 > -SO3H>aryl –NH2 > –NO2 because of the different adsorption mechanisms over the groups. The main mechanism over alkyl –NH2 was the formation of ammonium carbamate via the carbamic acid formation. The adsorption mechanism over −SO3H and aryl –NH2 groups was Lewis acid-base and H-bonding interactions, while that over –NO2 group was solely Lewis acid-base interaction. The alkyl amine exhibited the best performance (in adsorption capacity, selectivity, and adsorption heat) due to its ability to form carbamate readily. On the contrary, aryl amine demonstrated lower performance than −SO3H groups, attributed to their low capability to form carbamate. These findings underscore the importance of amine type in CO2 adsorption, highlighting that aryl amines, different from alkyl amines, perform worse than other functional groups, such as −SO3H.

Petrogenesis of magmatic charnockite-biotite granite suite from parts of the Chotanagpur granite gneissic complex (CGGC), eastern Indian shield: Implication for the break down of the Columbia Supercontinent

A rare porphyritic charnockite that is girdled by and mineralogically grades to biotite granite occurs as a part of the Chotanagpur granite gneiss complex (CGGC) in and around Massanjore, Jharkhand, India. Preservation of certain textural features, including (a) euhedral to subhedral grains of orthopyroxene, (b) low dihedral angle subtended by orthopyroxene and plagioclase grains, and (c) relict intergranular and porphyritic textures, are consistent with the view that orthopyroxene in the studied rocks has a magmatic origin. Preserved magmatic features and other petrological attributes of these rocks do not support any significant mass change beyond a few tens of microns during the overprinting high-grade metamorphism. The geochemical variation of the felsic rock suite (porphyritic charnockite and biotite granite) indicates that they are cogenetic and are derived from a ferroan A-type granitoid magma by crystal fractionation. The observed geochemical trend of the studied felsic rock suites has been simulated by phase equilibria modelling in the open system using the system components Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-O2. The observed mineralogical and geochemical attributes and the results of the modelling study are consistent with a petrogenetic process in which high magma temperature (> 900 °C), low pressure, and low water activity in the parental melt favoured the separation of an orthopyroxene bearing cumulate assemblage (orthopyroxene + plagioclase + quartz + K-feldspar + ilmenite + magnetite) in the initial part of the magmatic differentiation. Removal of this anhydrous cumulitic assemblage raised the bulk H2O content in the residual melt. Orthopyroxene became unstable with respect to biotite in the evolved melt that eventually crystallised minerals that formed the biotite granite. An increase in magma fO2 also restricts the orthopyroxene stability in felsic magma. Taken together all the petrological and geochemical attributes, we demonstrate that fractionation of an orthopyroxene-bearing crystal cumulate from the melt is essential to form the charnockites, and that the biotite granite forms from the evolved melt after the fractionation. The charnockite-biotite granite association of the studied area was formed in an extensional tectonic setting, presumably during the breakdown of the Columbia Supercontinent.

Liquid-liquid equilibrium of binary ethanol–polyisobutene and ternary ethanol–water–polyisobutene systems under low- and high-pressure conditions: An assessment using the PC-SAFT equation of state

Sugarcane bioethanol in either anhydrous or hydrous forms stands out as an economically viable bioproduct that can be used as a fuel or feedstock in various innovative applications, reducing human-generated greenhouse gas emissions. Low-molar-mass polyisobutene (PiB) is used as a lubricant in sugarcane-processing plants and is a possible contaminant of sugarcane bioethanol. Understanding the liquid–liquid equilibrium (LLE) of ethanol–PiB binary systems and ethanol–water–PiB ternary systems is essential to avoid undesired phase separation at high-pressure engine conditions and other potential innovative applications. However, the experimental investigation of these systems is significantly hampered by very low polymer solubilities in aqueous ethanol. The LLE of ethanol-PiB and ethanol–water-PiB mixtures was qualitatively investigated using the PC-SAFT equation of state through the development and implementation of extrapolation strategies allowing to estimate ethanol-PiB and water-PiB binary parameters using experimental data obtained for other systems containing lighter alkanes. Phase diagrams were calculated considering temperatures ranging from 298.15 K to 350 K and pressures ranging from 1 bar to 200 bar. It was shown that lower pressures, higher temperatures, lower PiB molar masses, and lower water contents increase the polymer solubility in the solvents. Thus, the risk of liquid–liquid separation can be mitigated by correctly managing such operational parameters. The obtained phase diagrams may present significant quantitative deviations from reality because of the model’s sensitivity to the estimated binary parameters. Thus, they should be interpreted as general qualitative guidelines to avoid and manage undesired phase separation in industrial processes and engines rather than phase equilibrium predictions.

Pressure-induced phase changes in natural fluorapophyllite-(K) studied by Raman spectroscopy

The high-pressure Raman spectra in the low-wavenumber region (50–1200 cm−1) and the hydroxyl stretching vibration region (2600–3800 cm−1) of fluorapophyllite-(K) were collected in the interval of 0.0–50.7 GPa. Experimental results show that fluorapophyllite-(K) undergoes a crystalline-crystalline phase transition from a tetragonal structure (P4/mnc) to an orthorhombic structure (Pnnm) and then amorphization under high pressure conditions. Discontinuous changes in Raman peaks in the hydroxyl vibration region (2600–3800 cm−1) and the low-wavenumber region (50–1200 cm−1) occur at different onset pressures, suggesting that the destabilization of sub-lattices in fluorapophyllite-(K) under high pressure is not synchronous; the weak interlayer H2O structural units are more prone to destabilization at lower pressures than the rigid SiO4 tetrahedral layer units. Therefore, H2O groups in fluorapophyllite-(K) serve as sensitive local probes during the pressure-induced phase transition and amorphization.

Occurrence of methane in organic pores with surrounding free water: A molecular simulation study

Free water contained in shale reservoirs can influence the enrichment and transportation of shale gas. To accurately assess shale gas adsorption in shale reservoirs and improve recovery, it is crucial to understand the occurrence of gas and water. In this study, the occurrence of methane occupying the organic pores surrounded by free water is investigated using Grand Canonical Monte Carlo/Molecular Dynamics simulations, considering the effects of pressure, temperature and pore size. The center of the model represents methane adsorbed/free within the organic pores, while the regions on either side depict free water. Although water does not significantly penetrate organic pores, pressure, temperature, and pore size have a notable impact on the wettability of water on organic surfaces, resulting in variations in the concave liquid surface morphology. This results in varying degrees of competitive adsorption of water and methane near the carbonyl group. At lower pressures, although the capillary pressure decreases sharply with increasing pore size, the improved water wettability increases the extent of its intrusion along the pore surface, thereby enhancing the competitive adsorption of methane and water. At higher pressures, capillary pressure acts as a resistance, preventing water from invading the organic pores in significant quantities. Due to the weak affinity of organic pores for water, the same phenomenon was observed even after increasing the pore size and temperature to improve water wettability. In addition, high temperatures can lead to more pronounced water intrusion. Finally, it is hypothesized that competitive adsorption of methane and water is more pronounced at shallower burial depths and slightly larger pore sizes. This result is expected to provide insights for the accurate evaluation of gas adsorption in water-bearing shales.

Transient Effects by Pintle Motion in Cavitating Venturi Tube for Throttled Bipropellant Thruster

An experimental study was conducted to investigate the behavior of an H2O2/kerosene bipropellant thruster during throttling. The thruster used 90 wt.% hydrogen peroxide, and thrust was controlled using a variable area cavitating venturi valve equipped with a linear motor translating a pintle in a venturi geometry. In particular, transient effects were compared for three settings of pintle motion. Transient effects impacting pressure, temperature, thrust, efficiency, and instability data were analyzed. The results show that even at low chamber pressure, ignition occurred due to throttling, and no instabilities were created by changing the throttling speed. On the contrary, transient movements affected the recorded pressure data, impacting the characteristic velocity and thrust. Finally, this study provided new insight into H2O2/kerosene bipropellant throttling for deep throttling missions. Moreover, using the results from this study, the precision of future control algorithms will be improved.

Molecular transformation of heavy oil during slurry phase hydrocracking process: influences of operational conditions

The influences of reaction temperature, duration, pressure, and catalyst concentration on the molecular transformation of residual slurry phase hydrocracking process were investigated. The molecular composition of the heteroatom compounds in the residue feedstock and its upgrading products were characterized using high-resolution Orbitrap mass spectrometry coupled with multiple ionization methods. The simultaneous promotion of cracking and hydrogenation reactions was observed with increasing of the reaction temperature and time. Specifically, there was a significant increase in the cracking degree of alkyl side chain, while the removal of low-condensation sulfur compounds such as sulfides and benzothiophenes was enhanced. In particular, the cracking reactions were more significantly facilitated by high temperatures, while an appropriately extended reaction time can result in the complete elimination of the aforementioned sulfur compounds with a lower degree of condensation. Under conditions of low hydrogen pressure and catalyst concentration, the products still exhibit a high relative abundance of easily convertible compounds such as sulfoxides, indicating a significant deficiency in the effectiveness of hydrogenation. The hydrogen pressure exhibits an optimal value, beyond which further increments have no effect on the composition and performance of the liquid product but can increase the yield of the liquid product. At significantly high catalyst concentration, the effect of desulfurization and deoxidation slightly diminishes, while the aromatic saturation of highly condensed compounds was notably enhanced. This hydrogenation saturation effect cannot be attained through manipulation of other operational parameters, thereby potentially benefiting subsequent product processing and utilization. This present study demonstrates a profound comprehension of the molecular-level residue slurry phase hydrocracking process, offering not only specific guide for process design and optimization but also valuable fundamental data for constructing reaction models at the molecular level.

Natural deep eutectic solvents as green and homogeneous catalysts for the glycerolysis of stearic acid: Catalytic activity and kinetic studies

Emulsifier as the mixture of monoglycerides (MG) and diglycerides (DG) is widely used in the food industry such as bakery products, margarines, dairy products, and confectionary. This emulsifier can be produced by glycerolysis of fatty acids using acid catalyst. In this work, natural deep eutectic solvent (NADES) was chosen as a catalyst in the glycerolysis of stearic acid due to greener and sustainable catalyst with advantages such as low vapor pressure, non-toxic, biodegradable, and easy to reuse. The catalytic activity of the NADES, kinetic constants and activation energies for the reaction were investigated. The reaction was carried out at agitation speed (300 rpm), catalyst concentration (5 wt.%), reaction temperatures (120⁰C, 150⁰C and 180⁰C) and reactant mole ratios (1:2, 1:4 and 1:6). Choline chloride-sorbitol NADES has highest catalytic activity on the glycerolysis of stearic acid. The kinetic calculation results using choline chloride-sorbitol NADES as a catalyst validated that the reaction was pseudo second order with an activation energy of 64.04 kJ∙mol-1, and a collision factor of 196,696 L∙mol-1∙min-1. This kinetics data will be useful for reactor design in industrial applications.

Development of a decision aid with cost information for heart failure medication in Singapore

ObjectiveThis study presents the development process of a heart failure (HF) medication decision aid (DA) specific to Singapore context, with the objective of promoting cost conversations. MethodsPhase 1 was to create a DA prototype, where two HF clinicians were consulted on their input and needs. Phase 2 was pilot testing where the prototype was tested on HF patients and revised based on their feedback. ResultsThe DA is a one-page poster that compares only two classes of HF medications. It encompasses seven attributes for comparison, including route of administration, treatment duration, frequency of use, hospitalization rate, survival rate, low blood pressure probability with personalized subsidized cost being the key attribute. A total of 48 patients participated in the pilot testing with only 2 patients (4.2 %) finding the DA difficult to understand. Almost all patients agreed that the DA provided greater clarity in the medication options. ConclusionBy integrating the needs of both clinicians and patients and conducting user testing, we developed a novel HF medication DA. Patients found the tool easy to understand and acceptable. InnovationThis innovative DA aims to improve cost conversations by providing tailored, concise, and locally relevant information for efficient use.

Cavitation Characteristics in Ultrasonic Soldering and the Erosion Effect

In this work, the cavitation characteristics of the solder sonocapillary action during ultrasonic soldering were studied by a high-speed camera. The effects of ultrasonic power and time on the acoustic pressure, cavitation characteristics, and erosion effects were also investigated. Results showed that cavitation occurred throughout the entire sonocapillary action. Two kinds of bubble structures were observed. The steady bubbles had large sizes and long life periods. The transient bubbles had small sizes and short life periods. The steady bubbles preferentially appeared at the primary filling stage, while the transient bubbles dominated the entire cavitation field. The sonocapillary action was divided into the primary filling stage, the intermediate filling stage, and the completion filling stage. The primary filling stage had low acoustic pressure but high bubble density because the air content in the solder was high and some additional air entered the solder through the triple interface caused by ultrasonic vibration. Higher ultrasonic power resulted in stronger cavitation and, thus, better erosion effect on the substrate.

Design and conductivity optimization of La0.3Sr0.7TiO3/La0.8Sr0.2MnO3 bi-layer structures as tubular segmented-in-series solid oxide fuel cell interconnect☆

This study focused on meeting the stringent stability requirements of tubular segmented-in-series solid oxide fuel cells (SOFCs) in reducing and oxidizing atmospheres. To address this challenge, a bi-layer perovskite ceramic interconnect was designed by controlling the oxygen partial pressure, because of the strong correlation between the conductivity of strontium-doped lanthanum titanate (LST) and the oxygen partial pressure. The LST powder was prepared using solid-phase and sol-gel methods, and their influence on particle size and sintering behavior was compared. LST/lanthanum strontium manganite (LSM) bi-layer ceramic interconnects with varying thicknesses were fabricated through screen printing and co-sintering. The results demonstrate favorable interfacial bonding and excellent chemical compatibility between the ceramic layers. The conductivity of the bi-layer interconnect exhibits a temperature-dependent behavior, peaking at 550 °C. Simulation calculations and research findings validate that the conductivity of the bi-layer interconnect is determined by the thickness of the LSM layer and the oxygen partial pressure at the interconnect interface. Optimal conductivity is achieved with a bi-layer interconnect consisting of approximately 15 μm of LST and 4 μm of LSM. This can be attributed to the efficient regulation of oxygen partial pressure at the interface, effectively mitigating LSM decomposition caused by low oxygen partial pressure and the subsequent reduction in conductivity. These results provide valuable fundamental data and methodology for the development of high-performance interconnects for tubular segmented-in-series SOFCs.

363. REFLUX MICRO-ASPIRATION: WHAT HAVE WE LEARNED

Abstract Background The accurate diagnosis of gastro-oesophageal reflux pulmonary microaspiration has only become possible recently with the introduction of a novel technique of reflux micro-aspiration scintigraphy study combined with single photon emission computed tomography (SPECT) combined with x-ray tomography (CT) in a hybrid instrument. This has allowed the accurate diagnosis of pulmonary and airway contamination with refluxate. Previously only patients with large volume symptomatic reflux aspiration were diagnosed clinically (Mendelson syndrome) or by 2-dimentional barium meal or an older plantar (2 dimensional) technique of scintigraphic aspiration studies. The concept of reflux micro-aspiration has been implicated in multiple pulmonary diseases but without absolute proof from an adequate diagnostic test. Little was known about the natural history, physiology, and response to treatment amongst patients with silent reflux micro-aspiration. The aim of this presentation is to summarise a series of research projects studying the natural history of the disease, common presenting symptoms, pathophysiology and response to treatment. Methods A prospectively populated database of patients referred to a tertiary specialist reflux diagnostic service with atypical and/or treatment resistant reflux was evaluated. The database contained records of consecutive patients including demographic information, presenting symptoms, investigations including imaging, upper gastro-intestinal physiology studies and novel reflux micro-aspiration scintigraphy studies. Treatment details including medical and surgical treatment and post treatment clinical information and investigations. Multiple studies were conducted using the information from the database and findings are summarised in this presentation. Results The novel reflux micro-aspiration scintigraphy with SPECT/CT was compared with other studies (multichannel intraluminal impedance and 24-hour pH monitoring) and was found to be sensitive to reflux occurring outside the oesophagus. Patients with reflux micro-aspiration can present a wide variety of symptoms, commonly a combination of typical symptoms of gastro-oesophageal reflux disease (heartburn and regurgitation) and respiratory symptoms. Reflux micro-aspiration was associated with reduced lower oesophageal sphincter pressure, severe ineffective oesophageal motility (IOM), and pharyngeal contamination with refluxate on reflux scintigraphy. Delayed liquid gastric emptying was not associated with reflux micro-aspiration, however gastroparesis with solids is associated with micro-aspiration. Micro-aspiration was common in patients with giant hiatus hernias and mostly resolved with surgery. Anti-reflux surgery resulted in resolution of aspiration in the majority of patients, however severe IOM was associated with lesser rates of microaspiration resolution. Conclusion Reflux micro-aspiration appears to be a more common manifestation of GORD than previously thought. The work summarised in this presentation discusses the presentation, physiological associations, and treatment of patients with reflux micro-aspiration.

Surface modification effects on ammonium perchlorate wettability

Solid propellants are commonly used for propulsion systems due to their high volumetric thrust and reliability. Powder bed, binder jetting manufactured propellants will enable unique geometries to be made that are necessary for designers to achieve high thrust levels. However, changes to the particulate wettability from the solvent-based manufacturing technique must be understood such that propellants with adequate mechanical properties are achieved. In this work, the wettability of ammonium perchlorate (AP) crystal surfaces is quantified with solvent and air plasma treatments. Removal of adventitious carbon from AP surface decreases the polybutadiene contact angle from 34 ± 1° to 15 ± 4°. The presence of hydrocarbons from non-polar solvents used in this study with lower vapor pressure was observed to have a similar effect as the adventitious carbon whereas higher vapor pressure solvents have minimal influence on the final wettability of AP surfaces. Polar solvents were determined to alter the surface topology by creating a more hydrophobic surface when compared to the plasma treated samples. An increase in concentration of amine surface groups overcomes the decrease in wettability from carbonaceous residue and surface morphology. The extension and implications of these findings to powder bed, binder jetting manufacturing for propellants is discussed.

Plantar pressure in relation to hindfoot varus in people with unilateral upper motor neuron syndrome.

Hindfoot varus deformity is common in people with unilateral upper motor neuron syndrome (UMNS) and can be dynamic or persistent. The aims of this study were (1) to gain insight into plantar pressure characteristics of people with chronic UMNS in relation to hindfoot varus and (2) to propose a quantitative outcome measure, based on plantar pressure, for the scientific evaluation of surgical interventions. In this retrospective study, a cohort comprising plantar pressure data of 49 people with UMNS (22 "no hindfoot varus", 18 "dynamic hindfoot varus", and 9 "persistent hindfoot varus"), and 586 healthy controls was analyzed. As an indication of plantigrade foot contact, the ratio between the plantar contact area of the affected and the non-affected foot was calculated. To investigate spatial and temporal aspects of plantar pressure, normalized plantar pressure patterns and center of pressure trajectories were computed. People with UMNS had lower plantar pressure area ratios compared to healthy controls. Additionally, increased plantar pressure underneath the lateral foot was found in people with a persistent hindfoot varus. Center of pressure trajectories were more lateral during the first 26% of the stance phase in people with a dynamic hindfoot varus and during the first 82% of the stance phase in people with a persistent hindfoot varus compared to healthy controls. Spatial and temporal differences in plantar pressure were found in people with dynamic or persistent hindfoot varus deformity. We propose to primarily use the medio-lateral center of pressure trajectory as outcome measure for the scientific evaluation of surgical interventions targeting hindfoot varus.

Modeling and simulation of laser-ignited Al-PTFE reactive material in vacuum

Despite extensive investigations elucidating the initial response behavior of Al-PTFE (aluminized polytetrafluoroethylene) under atmospheric pressure, research on their response in lean-oxygen environments pertinent to propulsion and explosion scenarios is still lacking. This paper theoretically analyzes the multi-physical processes of laser-ignited Al-PTFE, identifying the initial response, main chemical reaction paths, and gas-phase product flow mechanisms. A dynamic reaction model of Al-PTFE considering material moving front, chemical reactions, gas-phase product dynamics, and variations in thermophysical properties, was developed. The robust coupling scheme in the model addresses nonlinear equations and fluid-solid coupling boundary conditions. Validation was achieved by comparing the ablation depth and plume number density field calculated by the model with the experimental results in the literature. The model reveals a positive correlation between laser fluence and both temperature growth rate and ablation depth of Al-PTFE, with the effects mainly observed in the FWHM of the pulsed laser due to the thermal decomposition of the PTFE matrix. Simulations of the equilibrium constants and molar fractions of 19 components in the Al-PTFE ablation plume within the temperature range of 2000 K to 30,000 K at 0.001 Pa indicate that the equilibrium constants for dissociative reactions exceed those for ionization reactions, primarily in the early plume formation stages. Analysis of kinetic parameters and ambient pressure effects shows that during laser ablation, the maximum temperature of the plume initially appears near the ablation surface, shifting to the front, where the maximum velocity is always located. An elliptical shock wave forms due to adiabatic expansion of the plume, creating a cavity inside the plume. Lower ambient pressure increases plume expansion velocity, temperature, and size.

Potential impacts of climate change on cephalopods in a highly productive region (Northwest Pacific): Habitat suitability and management

Cephalopods occupy a mid-trophic level in marine ecosystems and are vital both ecologically and as fishery resources. However, under the pressure of climate change and fishing, the sustainability of cephalopod resources requires reasonable management. This study aims to study climate change and fishing impacts on the common economic cephalopod species habitats using species distribution models. We take the northwest Pacific Ocean region as an example, which stands out as a significant region for cephalopod production around the world. Results found that the habitats of cephalopods are moving to higher latitudes or deeper waters (Bohai Sea, mid-bottom Yellow Sea, or the Okinawa Trough waters) under climate change. Additionally, these regions are currently under lower fishing pressure, which suggests that species migration might mitigate the effects of warming and fishing. This study provides the large-scale assessment of the distribution range of cephalopods affected by climate change coping with fishing pressure in the northwest Pacific Ocean. By identifying climate refuges and key fishing grounds, we underscore the importance of this information for managing cephalopod resources in the context of climate adaptation and sustainable fishing practices.

381. MULTICENTER PAN-CANADIAN EXPERIENCE OF PER ORAL ENDOSCOPIC MYOTOMY (POEM) FOR THE TREATMENT OF ACHALASIA: A RETROSPECTIVE STUDY

Abstract Background Per oral endoscopic myotomy (POEM) has emerged as a modality for the surgical treatment of achalasia using a minimally invasive approach with similar clinical efficacy to laparoscopic Heller myotomy. Japanese, European, American and International clinical practice guidelines now cite POEM as a first line treatment for achalasia. In Canada, single-centre experiences with POEM have shown promising results. This study aims to capture the pan-Canadian national experience with POEM for the treatment of achalasia across multiple institutions. Methods This was a retrospective study of patients who underwent POEM for achalasia across four Canadian institutions (St. Joseph's Healthcare Hamilton, Kingston Health Sciences Centre, Surrey Memorial Hospital and Montreal Sacred Heart Hospital) between 2012 to 2022. Pre-operative, procedural and post-operative data was collected. Our primary outcome was the proportion of patients with normal Eckhardt score (≤ 3) at 4 weeks. Secondary outcomes included procedure related adverse events, length of stay in hospital, post-procedure lower esophageal sphincter pressures, post-procedure gastroesophageal reflux disease (GERD) and response rate at further timepoints. Outcomes are reported as either proportions (%) or medians (IQR). Results POEM was attempted in 369 patients with a success rate of 99%. The median duration of surgery was 64 (47 – 89) minutes and length of stay was ≤1 day in 88% of patients. Peri-operative complications occurred in 11% of patients, all of which were Clavien-Dindo Grade ≤III. The post-operative response rate (Eckhardt score ≤3) was 100%, 98% and 95% at 1, 6 and 12 months, respectively. Additional interventions for achalasia following POEM were required in 6% of patients. High DeMeester scores, endoscopic esophagitis and symptomatic GERD were reported in 36%, 43% and 44%, respectively. 93% of GERD was treated with PPI therapy. Conclusions POEM is safe and feasible in Canadian institutions with efficacy in keeping with current international literature.