Air Trapping Research Articles

Effect of non metallic doping in GeC gas sensors on gas response performance: the first principles study

In this paper, the stability, electronic structure and optical properties of monolayer GeC, B, N and P doped GeC systems are systematically investigated based on the first principles of density functional theory. The results show that the results show that the intrinsic GeC monolayer has a weak adsorption capacity for CH4 and C2H2, which is unfavourable for the sensing and trapping of CH4 and C2H2 gases. Based on calculated adsorption distance, adsorption energy and charge transfer, we find that P-GeC monolayer is the most sensitive to CH4 and C2H2 molecules, and the most of gas molecules act as acceptors to gain electrons from GeC monolayer. The adsorption energy of CH4 is smaller than that of C2H2 gas molecule, which implies that C2H2 is more easily desorbed from P-GeC. Moreover, the work function changes significantly when gas molecules adsorbed on B, N, P-GeC, and Recovery times indicate that B, N and P doped GeC monolayers are more selective and sensitive to C2H2 molecules compared to CH4 molecules. The research work aims to provide a theoretical basis for the application of GeC-based gas sensors, and P-doped GeC monolayers can be used as candidate materials for C2H2 gas sensing and trapping.

Air trap and removal on a pressure driven PDMS-based microfluidic device.

With the development of microfluidic technology, microfluidic chips have played a positive role in applications such as cell culture, microfluidic PCR, and nanopore gene sequencing. However, the presence of bubbles interferes with fluid flow and has a significant impact on experimental results. There are many reasons for the generation of bubbles in microfluidic chips, such as pressure changes inside the chip, air vibration inside the chip, and the open chip guiding air into the chip when driving fluid. This study designed and prepared a microfluidic device based on polydimethylsiloxane. First, air was actively introduced into the microfluidic chip, and bubbles were captured through the microfluidic device to simulate the presence of bubbles inside the chip in biological experiments. To remove bubbles trapped in the microfluidic chip, distilled water, distilled water containing surfactants, and mineral oil were pumped into the microfluidic chip. We compared and discussed the bubble removal efficiency under different driving fluids, driving pressures, and open/closed channel configurations. This study helps to understand the mechanism of bubble formation and removal in microfluidic devices, optimize chip structure design and experimental reagent selection, prevent or eliminate bubbles, and reduce the impact of bubbles on experiments.

Exploring the link between a novel approach for computer aided lung sound analysis and imaging biomarkers: a cross-sectional study

BackgroundComputer Aided Lung Sound Analysis (CALSA) aims to overcome limitations associated with standard lung auscultation by removing the subjective component and allowing quantification of sound characteristics. In this proof-of-concept study, a novel automated approach was evaluated in real patient data by comparing lung sound characteristics to structural and functional imaging biomarkers.MethodsPatients with cystic fibrosis (CF) aged > 5y were recruited in a prospective cross-sectional study. CT scans were analyzed by the CF-CT scoring method and Functional Respiratory Imaging (FRI). A digital stethoscope was used to record lung sounds at six chest locations. Following sound characteristics were determined: expiration-to-inspiration (E/I) signal power ratios within different frequency ranges, number of crackles per respiratory phase and wheeze parameters. Linear mixed-effects models were computed to relate CALSA parameters to imaging biomarkers on a lobar level.Results222 recordings from 25 CF patients were included. Significant associations were found between E/I ratios and structural abnormalities, of which the ratio between 200 and 400 Hz appeared to be most clinically relevant due to its relation with bronchiectasis, mucus plugging, bronchial wall thickening and air trapping on CT. The number of crackles was also associated with multiple structural abnormalities as well as regional airway resistance determined by FRI. Wheeze parameters were not considered in the statistical analysis, since wheezing was detected in only one recording.ConclusionsThe present study is the first to investigate associations between auscultatory findings and imaging biomarkers, which are considered the gold standard to evaluate the respiratory system. Despite the exploratory nature of this study, the results showed various meaningful associations that highlight the potential value of automated CALSA as a novel non-invasive outcome measure in future research and clinical practice.

Sublimation of volatiles from H2O:CO2 bulk ices in the context of comet 67P/Churyumov–Gerasimenko. II. Noble gases

The ROSINA instrument on board the Rosetta spacecraft measured, among others, the outgassing of noble gases from comet 67P/Churyumov–Gerasimenko. The interpretation of this dataset and unravelling underlying desorption mechanisms requires detailed laboratory studies. We aim to improve our understanding of the desorption patterns, trapping, and fractionation of noble gases released from the H$_ $O:CO$_ $-dominated ice of comet 67P. In the laboratory, ice films of neon, argon, krypton, or xenon (Ne, Ar, Kr, and Xe) mixed in CO$_ $:H$_ $O were prepared at 15 K. Temperature-programmed desorption mass spectrometry is employed to analyse the desorption behaviour of the noble gases. Mass spectrometric ROSINA data of 67P were analysed to determine the fraction of argon associated with CO$_ $ and H$_ $O, respectively. CO$_ $ has a significant effect on noble gas desorption behaviour, resulting in the co-release of noble gases with CO$_ $, decreasing the amount of noble gas trapped within water, shifting the pure phase noble gas peak desorption temperature to lower temperatures, and prolonging the trapping of neon. These effects are linked to competition for binding sites in the water ice and the formation of crystalline CO$_ $. Desorption energies of the pure phase noble gas release were determined and found to be higher than those previously reported in the literature. Enhancement of the Ar/Kr and Ar/Xe ratios are at best 40<!PCT!> and not significantly influenced by the addition of CO$_ $. Analysis of ROSINA mass spectrometric data shows that the fraction of argon associated with H$_ $O is 0.53 pm 0.30, which cannot be explained by our laboratory results. Multicomponent ice mixtures affect the desorption behaviour of volatiles compared to simple binary mixtures and experiments on realistic cometary ice analogues are vital to understanding comet outgassing.

Pore-to-field scale modeling of residual gas trapping in tight carbonate underground gas reservoirs

The deep saline aquifer and depleted gas reservoirs are suitable candidates for CO2 storage. The estimation of residual gas and corresponding flowing behavior are major parameters for successful CO2 trapping in geological formations. In this article the residual gas trapping phenomenon in pore scale has been studied using Micro-CT images. In macro scale, the results of imbibition experiments on core plug samples have been considered to determine residual gas saturation (RGS) and the corresponding water relative permeability. In the field scale, pressure transient data in water leg has been used to determine the water relative permeability at RGS in a tight carbonate reservoir in Middle East. In the proposed workflow, an artificial intelligence approach is applied to determine absolute permeability profile. Then, a numerical dynamic single well model is built to calculate the water relative permeability. The comparison of core and pressure transient data shows that the absolute permeability and water relative permeability from core imbibition test are significantly overestimated while the results of gas-water simulation in pore scale confirmed the real field transient data. The proposed method can be used by industrial reservoir simulator to define rock/fluid interaction parameters in simulation of CO2 storage in depleted underground gas reservoirs.

Brief communication: Identification of 140 000-year-old blue ice in the Grove Mountains, East Antarctica, by krypton-81 dating

Abstract. The presence of exceptionally old ice and relative ease of access make Antarctic blue-ice areas (BIAs) attractive paleoclimate archives. However, only a handful of BIAs, mostly situated in West Antarctica and along the Transantarctic Mountains, have been investigated for this purpose. Here, we present the age of surface ice from the Grove Mountains BIA in Princess Elizabeth Land, East Antarctica, determined by measuring 81Kr in the trapped air. Two samples yield an average age of 143-29+33 kyr. Together with the reported terrestrial age of a chondrite, we conclude that the Grove Mountains BIA holds considerable potential for paleoclimate studies.

Elevated Prostaglandin E2 Synthesis Is Associated with Clinical and Radiological Disease Severity in Cystic Fibrosis.

Background: Previous studies found high but very variable levels of tetranor-PGEM and PGDM (urine metabolites of prostaglandin (PG) E2 and PGD2, respectively) in persons with cystic fibrosis (pwCF). This study aims to assess the role of cyclooxygenase COX-1 and COX-2 genetic polymorphisms in PG production and of PG metabolites as potential markers of symptoms' severity and imaging findings. Methods: A total of 30 healthy subjects and 103 pwCF were included in this study. Clinical and radiological CF severity was evaluated using clinical scoring methods and chest computed tomography (CT), respectively. Urine metabolites were measured using liquid chromatography/tandem mass spectrometry. Variants in the COX-1 gene (PTGS1 639 C>A, PTGS1 762+14delA and COX-2 gene: PTGS2-899G>C (-765G>C) and PTGS2 (8473T>C) were also analyzed. Results: PGE-M and PGD-M urine concentrations were significantly higher in pwCF than in controls. There were also statistically significant differences between clinically mild and moderate disease and severe disease. Patients with bronchiectasis and/or air trapping had higher PGE-M levels than patients without these complications. The four polymorphisms did not associate with clinical severity, air trapping, bronchiectasis, or urinary PG levels. Conclusions: These results suggest that urinary PG level testing can be used as a biomarker of CF severity. COX genetic polymorphisms are not involved in the variability of PG production.

Usefulness of Computed Tomography for Evaluating the Effects of Bronchial Thermoplasty in Japanese Patients with Severe Asthma.

Bronchial thermoplasty (BT) improves clinical outcomes and quality of life for patients with severe asthma and has shown sustained reductions in airway narrowing and air trapping in previous CT studies. However, there is a lack of a comprehensive analysis, including CT evaluation, of clinical outcomes in Japanese patients who have undergone BT for severe asthma. This study aimed to evaluate the impact of BT in Japanese asthma patients, with a focus on the CT metric "WA at Pi10" to assess airway disease. Twelve patients with severe persistent asthma who underwent BT were assessed using ACQ6, AQLQ, pulmonary function tests, FeNO measurement, blood sampling, and chest CT before BT and one year after the third procedure for the upper lobes. The median age of the patient was 62.0 years, 7/12 (58.3%) were male, 4/12 (33.3%) used regular oral corticosteroids, and 8/12 (66.7%) received biologics. Median FEV1% was 73.6%, and median peripheral eosinophil count was 163.8/μL. After one year of BT, ACQ6 scores improved from 2.4 to 0.8 points (p = 0.007), and AQLQ scores improved from 4.3 to 5.8 points (p < 0.001). Significant improvements were also observed in asthma exacerbations, unscheduled visits due to exacerbations, FeNO, and √WA at Pi10 (p < 0.05). The baseline mucus score on the CT findings was negatively correlated with FEV1 (r = -0.688, p = 0.013) and with the maximum mid-expiratory flow rate (r = -0.631, p = 0.028), and positively correlated with the peripheral blood eosinophil count (r = -0.719, p = 0.008). Changes in √WA at Pi10 after one year were positively correlated with changes in the mucus score (r = 0.742, p = 0.007). This study has limitations, including its single-arm observational design and the small sample size. However, BT led to a symptomatic improvement in patients with severe asthma. The validated "√WA at Pi10" metric on CT effectively evaluated the therapeutic response in Japanese asthma patients after BT.

Geological conditions, genetic mechanisms and accumulation patterns of helium resources

Based on the methodology for petroleum systems and through the anatomy and geochemical study of typical helium-rich gas fields, the geological conditions, genesis mechanisms, and accumulation patterns of helium resources in natural gas are investigated. Helium differs greatly from other natural gas resources in generation, migration, and accumulation. Helium is generated due to the slow alpha decay of basement U/Th-rich elements or released from the deep crust and mantle, and then migrates along the composite transport system to natural gas reservoirs, where it accumulates with a suitable carrier gas. Helium migration and transport are controlled by the transport system consisting of lithospheric faults, basement faults, sedimentary layer faults, and effective transport layers. Based on the analysis of the helium-gas-water phase equilibrium in underground fluids and the phase-potential coupling, three occurrence states, i.e. water-soluble phase, gas-soluble phase and free phase, in the process of helium migration and accumulation, and three migration modes of helium, i.e. mass flow, seepage, and diffusion, are proposed. The formation and enrichment of helium-rich gas reservoirs are controlled by three major factors, i.e. high-quality helium source, high-efficiency transport and suitable carrier, and conform to three accumulation mechanisms, i.e. exsolution and convergence, buoyancy-driven, and differential pressure displacement. The helium-rich gas reservoirs discovered follow the distribution rule and accumulation pattern of “near helium source, adjacent to fault, low potential area, and high position”. To explore and evaluate helium-rich areas, it is necessary to conduct concurrent/parallel exploration of natural gas. The comprehensive evaluation and selection of profitable helium-rich areas with the characteristics of “source-trap connected, low fluid potential and high position, and proper natural gas volume matched with helium’s” should focus on the coupling and matching of the helium “source, migration, and accumulation elements” with the natural gas “source, reservoir and caprock conditions”, and favorable carrier gas trap areas in local low fluid potential and high positions.

Clinical characterization and outcomes of impulse oscillometry-defined bronchodilator response: an ECOPD cohort-based study

BackgroundThe clinical significance of the impulse oscillometry-defined small airway bronchodilator response (IOS-BDR) is not well-known. Accordingly, this study investigated the clinical characteristics of IOS-BDR and explored the association between lung function decline, acute respiratory exacerbations, and IOS-BDR.MethodsParticipants were recruited from an Early Chronic Obstructive Pulmonary Disease (ECOPD) cohort subset and were followed up for two years with visits at baseline, 12 months, and 24 months. Chronic obstructive pulmonary disease (COPD) was defined as a post-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio < 0.70. IOS-BDR was defined as meeting any one of the following criteria: an absolute change in respiratory system resistance at 5 Hz ≤ − 0.137 kPa/L/s, an absolute change in respiratory system reactance at 5 Hz ≥ 0.055 kPa/L/s, or an absolute change in reactance area ≤ − 0.390 kPa/L. The association between IOS-BDR and a decline in lung function was explored with linear mixed-effects model. The association between IOS-BDR and the risk of acute respiratory exacerbations at the two-year follow-up was analyzed with the logistic regression model.ResultsThis study involved 466 participants (92 participants with IOS-BDR and 374 participants without IOS-BDR). Participants with IOS-BDR had higher COPD assessment test and modified Medical Research Council dyspnea scale scores, more severe emphysema, air trapping, and rapid decline in FVC than those without IOS-BDR over 2-year follow-up. IOS-BDR was not associated with the risk of acute respiratory exacerbations at the 2-year follow-up.ConclusionsThe participants with IOS-BDR had more respiratory symptoms, radiographic structural changes, and had an increase in decline in lung function than those without IOS-BDR.Trial registrationChinese Clinical Trial Registry, ChiCTR1900024643. Registered on 19 July, 2019.

Reduction of non-fill defect in nanoimprint lithography

Abstract Field-by-field type UV nanoimprint lithography equipped with on-demand inkjet dispense system, "Jet and Flash Imprint Lithography (JFIL)", has been developed. In JFIL, the inkjet drops of the resist are still remained independent to each other when imprinting a mold, so that the ambient gas is trapped among the resist drops to generate bubbles. It takes time for the trapped bubbles to disappear, and the bubbles sometimes remain in the cured resist film to cause open defect. Waiting time for gas disappearance results in low throughput and the remained bubbles causes defect problem in JFIL. Fast disappearance of trapped bubbles was demonstrated in case that carbon dioxide gas was used as an ambient gas. On the basis of fluid mechanics, combined drop JFIL (CD-JFIL) and its resist material was developed, in which the resist drops were combined to each other prior to imprinting to minimize trapped gas volume.

A Review of Taro Leaves on Its Phytochemical Screening and Approach on Anti-diabetic Activities on Specific Receptor

Taro, scientifically known as Colocasia esculenta, is a plant that holds considerable nutritional and medicinal importance. Its leaves are structured with multiple layers of palisade and air-filled spongy mesophyll. The vascular traces are surrounded by a ring of vacuolate cells that could extend to both the upper and lower epidermis. The leaves have stomata on both sides, with a higher number on the abaxial side. The stalk of the taro leaf is rich in various compounds such as saponins, flavonoids, tannins, alkaloids, steroids, and terpenoids, which have potential medicinal uses, including wound healing and antioxidant properties. An interesting feature of the taro leaf is the presence of water bubbles on its surface, which trap air in the cavity, forming a silvery layer. Although the bundle sheath is present in the taro leaf, there is no definitive proof to suggest that taro can perform carbon fixation via a C4 pathway. This research offers insights into the morphological characteristics of taro, its culinary uses, cultivation regions, and seasons. It also highlights the genetic variations among different genotypes, which could be useful for breeding programs.

The impact of increasing saline flush volume to reduce the amount of residual air in the delivery system of aortic prostheses-a randomized controlled trial.

Air embolism is a known risk during thoracic endovascular aortic repair (TEVAR) and is associated with an incomplete deairing of the delivery system despite the saline lavage recommended by the instructions for use (IFU). As the delivery systems are identical and residual air remains frequently in the abdominal aortic aneurysm sac, endovascular aortic repair (EVAR) can be used to examine the effectiveness of deairing maneuvers. We aimed to evaluate whether increasing the flush volume can result in a more complete deairing. Patients undergoing EVAR were randomly assigned according to flushing volume (Group A, 1× IFU; Group B, 4× IFU). The Terumo Aortic Anaconda and Treo and Cook Zenith Alpha Abdominal stent grafts were randomly implanted in equal distribution (10-10-10). The quantity of air trapped in the aneurysm sac was measured using a pre-discharge computed tomography angiography (CTA). Thirty patients were enrolled and equally distributed between the two groups, with no differences observed in any demographic or anatomical factors. The presence of air was less frequent in Group A compared to that in Group B [7 (47%) vs. 13 (87%), p = .02], and the air volume was less in Group A compared to that in Group B (103.5 ± 210.4 vs. 175.5 ± 175.0 mm3, p = .04). Additionally, the volume of trapped air was higher with the Anaconda graft type (p = .025). These findings suggest that increased flushing volume is associated with a higher amount of trapped air; thus, following the IFU might be associated with a reduced risk of air embolization. Furthermore, significant differences were identified between devices in terms of the amount of trapped air. [NCT04909190], [ClinicalTrials.gov].

Fast droplets impacting liquid layer under a small angle: a numerical analysis of experimental observations

In presence of a strong wind above a liquid surface, liquid droplets get accelerated and eventually hit the interface with a high speed under a small angle. Experimental studies demonstrate that such droplets may escape the initial crater and either get broken into secondary droplets in the air, or protrude along the interface, leaving behind agitated surface with entrapped bubbles. Here we aim at reproducing the observed phenomena in a numerical model based on Volume of Fluid technique using Basilisk package. On a flat interface, the impacting droplets partially escape the crater and get broken in front of it within the range of impact angles from 15° to 45°, in agreement to the experiments and simple theoretical considerations. In presence of waves, the escaping droplets fly into the air but, being adhered to the crater, get stretched and broken into secondary droplets. For smaller angles, the droplets escape the crater and glide along the interface. The gliding droplet creates a chain of small craters in its wake. The rims between the craters may grow and get scattered into secondary droplets. Large liquid viscosity and small thickness of the liquid layer suppress the growth of the craters and secondary entrainment. Bubble entrapment during such impacts most likely occurs due to crater collapse with trapping air inside. However, such air pockets are not formed systematically in the present model. This discrepancy requires further investigation.

The Effect of Chronic Altitude Exposure on COPD Outcomes in the SPIROMICS Cohort.

Individuals with COPD have airflow obstruction and maldistribution of ventilation. For those living at high altitude, any gas exchange abnormality is compounded by reduced partial pressures of inspired oxygen. Does residence at higher-altitude exposure affect COPD outcomes, including lung function, imaging characteristics, symptoms, health status, functional exercise capacity, exacerbations, or mortality? From the SPIROMICS cohort, we identified individuals with COPD living below 1,000 ft (305 m) elevation (n= 1,367) versus above 4,000 ft (1,219 m) elevation (n= 288). Multivariable regression models were used to evaluate associations of exposure to high altitude with COPD-related outcomes. Living at higher altitude was associated with reduced functional exercise capacity as defined by 6MWD (-32.3 m, (-55.7 to -28.6)). There were no differences in patient-reported outcomes as defined by symptoms (CAT, mMRC), or health status (SGRQ). Higher altitude was not associated with a different rate of FEV1 decline. Higher altitude was associated with lower odds of severe exacerbations (IRR 0.65, (0.46 to 0.90)). There were no differences in small airway disease, air trapping, or emphysema. In longitudinal analyses, higher altitude was associated with increased mortality (HR 1.25, (1.0 to 1.55)); however, this association was no longer significant when accounting for air pollution. Chronic altitude exposure is associated with reduced functional exercise capacity in individuals with COPD, but this did not translate into differences in symptoms or health status. Additionally, chronic high-altitude exposure did not affect progression of disease as defined by longitudinal changes in spirometry.

A computationally efficient approach to model reactive transport during CO2 storage in naturally fractured saline aquifers

Energy storage is critical to any decarbonization, energy sustainability, and energy security strategy. Natural gas, CO2, and hydrogen will compete for sizeable geological storage sites in the future, and society needs to consider all possible storage sites. Saline aquifers and depleted hydrocarbon reservoirs have emerged as key sites for storage. While carbonate rocks possess significant storage potential, as evidenced by successful CO2-enhanced oil recovery (CO2-EOR) projects, most operational and planned Carbon Capture and Storage (CCS) initiatives primarily focus on sandstones. Consequently, extensive fundamental and applied research is necessary to advance technologies for carbonate rock utilization and capitalize on the storage capacities of vast saline aquifers and infrastructure available in near-abandoned depleted carbonate reservoirs. However, the challenges posed by the fracture systems and the substantial heterogeneity inherent to such reservoirs necessitate a comprehensive understanding of rock integrity and the role of fracture networks in the overall storage process. Moreover, modeling CCS in carbonates introduces additional complexities due to reactive minerals, such as calcite and dolomite, which can undergo reactions with injected CO2. Consequently, a numerical formulation capable of producing accurate results within a reasonable computational time is required, considering computationally intensive processes like fracture flow and geochemical reactions. In this work, three approaches to modeling naturally fractured media were assessed, such as the explicit representation of fractures through local grid refinement (LGR), the traditional dual permeability/dual porosity model (DPDK), and the embedded discrete fracture model (EDFM). The combination of EDFM with dynamic gridding in the matrix gridblocks demonstrated superior computational efficiency compared to LGR and DPDK simulations. This novel approach was 75 times faster than LGR and 37 times faster than DPDK while yielding comparable results in terms of different CO2 retention forms (free supercritical fluid, dissolved in water, and residual trapped gas) in one of the geological models investigated. Therefore, it was proposed a novel combination of EDFM and dynamic gridding as a suitable and accurate numerical approach to simulate reactive CO2 transport in fractured saline aquifers. This approach offers a practical means of efficiently evaluating carbonate reservoir targets for CCS projects, enabling effective decision-making in energy storage endeavors.

Three-Dimensional Amplitude versus Offset Analysis for Gas Hydrate Identification at Woolsey Mound: Gulf of Mexico

The Gulf of Mexico Hydrates Research Consortium selected the Mississippi Canyon Lease Block 118 (MC118) as a multi-sensor, multi-discipline seafloor observatory for gas hydrate research with geochemical, geophysical, and biological methods. Woolsey Mound is a one-kilometer diameter hydrate complex where gas hydrates outcrop at the sea floor. The hydrate mound is connected to an underlying salt diapir through a network of shallow crestal faults. This research aims to identify the base of the hydrate stability zone without regionally extensive bottom simulating reflectors (BSRs). This study analyzes two collocated 3D seismic datasets collected four years apart. To identify the base of the hydrate stability zone in the absence of BSRs, shallow discontinuous bright spots were targeted. These bright spots may mark the base of the hydrate stability field in the study area. These bright spots are hypothesized to produce an amplitude versus offset (AVO) response due to the trapping of free gas beneath the gas hydrate. AVO analyses were conducted on pre-stacked 3D volume and decreasing amplitude values with an increasing offset, i.e., Class 4 AVO anomalies were observed. A comparison of a time-lapse analysis and the AVO analysis was conducted to investigate the changes in the strength of the AVO curve over time. The changes in the strength are correlated with the decrease in hydrate concentrations over time.

Epoxy-Printed Circuit Board Interfacial Fracture Reliability Under Three-Point and Four-Point Bend Loading After Sustained Elevated Temperature Exposure

Abstract The survivability and reliability of commercial electronic components under very high thermo-mechanical loads are improved using underfilling and potting methods. Potting protects from operating conditions such as moisture, water, or corrosive agents. Furthermore, potting offers damping against shock and vibrations, heat dissipation, and structural support. Being one of the most cost-efficient methods, potting greatly increases reliability and therefore reduces costs for replacements and repairs. It also addresses trapped hot air issues better than other restraint technologies. In potted electronic assemblies, interfacial delamination at the epoxy and printed circuit board (PCB) interface has been one of the major failure modes. Interfacial delamination happens at the epoxy/PCB interface under dynamic shock loads, which leads to failures at the solder interconnects of the electronic components. Sustained operation and storage at elevated temperatures change the interfacial characteristics at the epoxy/PCB interface. This research is focused on interfacial failure mechanics at epoxy/PCB interfaces with high-temperature isothermal aging. In the selection of the epoxy potting material and the reliability assessments of the supplemental restraint systems, fracture parameters such as steady-state strain energy release rate stress and fracture toughness are critical. Rectangular beam specimens of the epoxy/PCB interface are fabricated for different potting compounds, and the fracture behavior is studied under quasi-static monotonic three-point and four-point bend loads. One of the main differences between three-point and four-point bend loading is that the maximum bending stress occurs at the midpoint under the point of loading of the specimen in three-point bending, whereas the peak stress is distributed over the section of the specimen between the loading points in four-point bending. Four different potting compounds with diverse properties have been studied. The recommended curing schedule from the manufacturer has been chosen and followed for all the potting compounds. The epoxy/PCB interfacial samples are aged at a high temperature of 100 °C for 30–180 days. Damage has been assumed to happen at the epoxy/PCB interface under dynamic loads. The critical load of crack initiation for the epoxy/PCB interface has been determined from the experimental findings, and it is used in the computation of fracture toughness values. The fracture toughness values are compared for the various epoxy/PCB systems based on the number of days of thermal aging and the method of flexure testing. A cohesive zone model has been constructed for predominantly mode-I delamination with four-point bend stress to predict the interfacial delamination behavior at the epoxy/PCB interfaces. It has been assumed that the bulk material is linear elastic during the bending load. The cohesive zone has been modeled at the interface, where the interfacial fracture has been assumed to occur. The fracture behavior in the simulation is predicted based on the fracture parameters determined through the experiment. The computed cohesive zone parameters are unique to the interfaces, and they can be used across various applications with the same epoxy/PCB interface to predict interfacial delamination and to select a more suitable potting material.

Differences in chamber structure contribute to the incidence of venous air trap chamber coagulation during AN69ST-CHF: clinical and in vitro evaluation

BackgroundDuring continuous kidney replacement therapy (CKRT) in patients with sepsis and critical conditions, circuit coagulation can occur, often for unclear reasons. In this study, we investigate how the structure of the venous air trap chamber may contribute to venous air trap chamber coagulation. Clinical data were evaluated and experiments were performed.MethodsThe clinical evaluation involved patients who underwent continuous hemofiltration (CHF) using an acrylonitrile-co-methallyl sulfonate surface-treated (AN69ST) hemofilter (AN69ST-CHF) and either an ACH-Σ or Prismaflex CKRT machine in our ICU from April to July 2019. The patient data were divided into two groups based on CKRT machine and the percentage of CHF procedures that could continuously be performed for 22 h (CHF target achievement rate), and coagulation sites were evaluated. Statistical analysis was performed by the Mann–Whitney U test and Pearson’s chi-square test. For in vitro experiments, a system was constructed to circulate a 33% glycerol solution at a flow rate of 150 ml/min. In a venous air trap chamber, fluid dye disappearance times and fluid movements were visually evaluated.ResultsThe clinical evaluation included 22 procedures (8 patients) in the ACH-Σ group and 22 procedures (11 patients) in the Prismaflex group, without significant differences in patient backgrounds between the groups. The CHF target achievement rate was 72.7% (16/22) in the ACH-Σ group and 77.3% (17/22) in the Prismaflex group, revealing no significant difference (p = 0.73). However, significantly fewer venous air trap chamber coagulations were observed in the Prismaflex group (1/5) than in the ACH-Σ group (5/6) (p < 0.01). In vitro evaluation found that the dye disappearance time was significantly shorter when using the Prismaflex device (17.5 s ± 0.7 s) than the ACH-Σ device (51.2 s ± 0.7 s; p < 0.05). Visual evaluation revealed that in the ACH-Σ venous air trap chamber the upper layer of the accumulated fluid was quite stagnant, whereas fluid flowed with uniform agitation through the Prismaflex venous air trap chamber. Hence, differences were observed in fluid flow and retention in the vein air trap chambers, depending on the chamber structure.ConclusionChamber structure may contribute to the occurrence of venous air trap chamber coagulation during CKRT.

Fabric and Fluid Inclusions Characterization of a Stalagmite from Eastern Spain: A Precondition for Noble Gas Analysis by Step-Crushing Methodology

Fluid inclusions in stalagmites are becoming increasingly important for paleoclimate research. Within this framework, noble gas thermometry, based on noble gases dissolved in water from fluid inclusions, provides quantitative estimations of cave air paleotemperature. Two major issues of Noble Gas Temperature (NGT) determination on speleothems are (1) the potential lack of enough water for the analysis and (2) the presence of trapped gas not dissolved in water that can be released during the analysis from biphasic or all-gas fluid inclusions, as its contribution to the bulk noble gas signal can hinder NGT results. Although the step-crushing method helps to reduce the second issue, it also decreases the amount of water available for the calculations. In order to obtain reliable NGT results with low uncertainties, a major challenge is still to reach a balance between sufficient water for analysis and a small amount of “atmospheric” gas. The difficulty is that the extraction process cannot be standardized since it strongly depends on the type of sample. The objective of this work is to investigate how the characteristics of the speleothem can determine the adequacy of the extraction process. For this purpose, we consider a stalagmite from a Mediterranean cave that consists of columnar elongated calcite and contains a significant quantity of fluid inclusions, which suggests good potential for NGT analysis. Results, however, were poorly satisfactory. Trying to understand the source of the problems, an integrated study of petrography and petrophysical features was performed. The samples were found to be different depending on the stage of coalescence of crystals and thus separated into “open” and “closed” fabrics. Classic petrographic analysis and non-destructive (nuclear magnetic resonance) techniques were used to characterize the type and amount of fluid inclusions present in both types of fabrics. The study indicates that the closed fabric (total coalescence of calcite crystals) has most water trapped in water-filled, small intracrystalline fluid inclusions that usually contain very little gas. This fabric is very suitable for NGT determination, but since the amount of water is quite small, the sample should be crushed in only one step with a large number of beats to break all the inclusions. In contrast, samples with open fabric (partial coalescence of calcite crystals) contain a higher amount of water and, also, gas-filled large intercrystalline fluid inclusions. For this fabric, step-crushing of the sample is necessary. However, the low amount of water left for the second and third crushings could lead to flawed NGT results. Thus, we suggest modifying the method to get rid of part of the gas in the first crushing while leaving enough water for the following steps. This work shows the importance of characterizing speleothems and fluid inclusions, including their petrography and petrophysical characteristics, before starting NGT analysis, allowing the selection of the most favorable samples and the customization of the step-crushing procedure.