Initial Pressure Research Articles

Development of a test specimen carrier for the Taylor anvil test using 3D additive printing technology

Dynamic material testing is increasingly crucial for establishing a comprehensive description of material models. One of the primary testing methods is the Taylor Anvil Test (TAT). In this test, strain rates of up to 105 s−1 can be achieved at impact speeds of 250 m/s. Proper evaluation of a specific material specimen in this test relies on delivering the test specimen to the impact point both centrally and perpendicularly, as well as at the moment of reaching the maximum impact speed. This Article addresses the development of a new carrier for round test specimens manufactured using additive 3D printing technology from a polyactide polymer adapted for the TAT device with a calibre of 17 mm. The Article closely examines the influence of geometric parameters of the carrier itself, optimized using the Ansys Fluid Flow software, with a focus on internal ballistics, particularly to achieve perpendicular impact and maximum impact speed without causing the destruction of the carrier. A new type of test carrier was designed and subsequently tested for round test specimens made of the aluminium alloy Al 2024-T3, evaluating both the impact speeds of the carrier under identical initiation pressure parameters in the filling chamber and the impact speed parameters of the specimen, respectively, the strain rate of the test specimen.

Thermal decomposition and shock response mechanism of crystalline and amorphous 2,4-dinitroanisole (DNAN) by ReaxFF/lg reactive molecular dynamics simulations

DNAN (2,4-dinitroanisole) is a popular melt-cast carrier explosive in the field of insensitive ammunition. The decomposition mechanisms of crystalline and amorphous DNAN were explored in this work through ReaxFF-lg molecular dynamic simulations under constant temperature (2000 K, 2500 K and 3000 K), programmed heating (10 K/ps) and the multiscale shock technique (MSST) (8 km/s, 9 km/s and 10 km/s). The evolution of initial decay reactions, number of products and clusters were performed to reveal the differences in the decomposition mechanisms between crystalline and amorphous of DNAN. Initial molecules of crystals were consumed faster in constant temperature simulations, while initial molecules of amorphous were consumed faster at MSST simulations. The O-C bond breakage was the most important thermolysis reaction and dimerization reaction was the most important shock reaction. Dimerization, intermolecular hydrogen transfer, and intermolecular oxygen transfer occur only at constant temperature and MSST simulations, and direct dissociation reactions of OH groups occur only in the amorphous case. Products analysis showed that CH3O was very important product in all simulations. Clusters analysis showed that the number of clusters in the crystals was greater than in the amorphous case for all shock velocities at MSST simulations. The fitted activation energies showed that the crystalline case was more susceptible to thermal decomposition reactions, and the fitted the initiation pressures for crystalline DNAN was 13.58 GPa, which was higher than the experimental value. There was no doubt that the molecular packing style would affect their decomposition behaviors. These results could help to increase the understanding for decomposition mechanisms of crystalline and amorphous energetic materials.

Influence of aerodynamic valve structural parameters on detonation initiation and back pressure characteristics of air-breathing pulse detonation engine

In order to enhance the stability of detonation initiation in air-breathing pulse detonation engines (APDE), while simultaneously mitigating the non-stationary back pressure disturbance due to the huge pressure gain in the APDE, a central blunt body aerodynamic valve (aero-valve) was developed and tested with a single-tube pulse detonation combustor (PDC). The detonation initiation and back pressure characteristics of PDC were then discussed. In order to reveal the influence of the aero-valve's structural parameters on the cold-state filling, detonation initiation, and back pressure characteristics of PDC, numerical simulations were carried out based on the experimental setup. The numerical results indicated that the cold-state flow characteristics within the aero-valve was predominantly influenced by the inner diameter of the aero-valve shell (Das), while the cold-state flow inside the combustor was primarily dominated by the axial distance from the thrust wall to the aero-valve shell (Lx) and the inner diameter of the aero-valve outlet (dout). And dout has a larger impact on the cold-state flow inside the combustor. During the hot state, reducing Lx or dout is beneficial for both the generation of detonation and the suppression of back pressure, with the most significant gain effect coming from decreasing dout. The optimal combination scheme for the aero-valve is identified as Das/R = 4.5, Lx/R = 0.25 and dout/R = 0.7, where R is the detonation combustor radius. The PDC equipped with this optimized aero-valve not only has better detonation initiation characteristics, but also a smaller pressure oscillation ratio.

Geomechanical risk assessment of injection test for a carbon storage site appraisal, offshore Northern Territory

A geomechanical study has been conducted to assess the risk of formation fracturing and sanding during a water injection test. Considering the temperature difference between the storage formation and the injection fluid, the cooling effects could lead to a reduction of almost 15% in fracture initiation pressure (FIP). Notably, the FIP for perforations aligned with the maximum horizontal stress direction are lower than the minimum horizontal stress. While injection pressures surpassing FIP might trigger tensile fracturing in specific perforations, fracture propagation from the wellbore remains unlikely if the injection pressure remains below the field’s minimum horizontal stress. The pressure requirements for current envisaged matrix injection rates fall below the estimated FIPs. Consequently, the risk of formation fracturing during the injection test is deemed low. The propensity of sanding during flowback, considering a range of rock weakening and thermal effects of water injection, is also found to be low.

Impact of the water-wedge deterioration effect of pulsating water injection on AE waveforms and crack propagation during fracturing processes

Pulsating hydraulic fracturing (PHF) is a promising technology for enhancing the extraction of coalbed methane. In this study, the effects of pulsating water response of coal fractures were investigated. Prior to quasi-static fracturing, coal samples were subjected to pulsating water injection for 120 min. The fracturing process was monitored using an acoustic emission (AE) system and compared with direct fracturing without pulsating water injection. The Hilbert–Huang transform theory was employed for the analysis. The AE signals were examined in time and frequency domains, across various parameters, including intrinsic mode function (IMF) components, energy, three-dimensional spectrum, location features, and crack development. The results indicated a 37.82 % reduction in initiation pressure, accompanied by decreased AE counts and the promotion of gradual fracture initiation. Initially, the AE waveform amplitudes decreased, followed by an increase in distinctive patterns. Water injection primarily reduced the amplitudes during unstable fracturing, shifting the extreme IMF component forward. Moreover, it decreased the peak energy, shortened the energy release duration, and improved the signal-to-noise ratio during crack propagation. Water injection also narrowed the frequency distribution range, concentrated the energy distribution, expanded the extent of the fracture, increased the number of location points, and induced more macroscopic cracks within the coal body.

The Prevalence of Exclusive Breastfeeding Practice and Its Predictors in the First Six Months of Life Among Working Mothers in Riyadh, Saudi Arabia.

Introduction The United Nations Children's Fund (UNICEF) and the World Health Organization (WHO) recommendations are early initiation of breastfeeding and exclusive breastfeeding (EBF) for the first six months of infants' lives.Despite the WHO and UNICEF recommendationsand expanding evidence of the significance of exclusive breastfeeding, about two-thirds of infants worldwide have not received exclusive breastfeeding for the six recommended months. This study aims to estimate the prevalence of working mothers exclusively breastfeeding in the first six months of infants' lives and investigate their predictors in Riyadh, Saudi Arabia. Methods A cross-sectional community-based study was conducted for four months in 2022. The study included working mothers who have a child in the age range of 6-24 months living in Riyadh. Data was collected through an online questionnaire and analyzed using the Statistical Package for the Social Sciences (SPSS)version 29 (IBM SPSS Statistics, Armonk, NY) program. Results A sample of 118 participants were included in the study. Their prevalence for EBF practice for the recommended period is 28% (n=33). Around 58.5% (n=69) of the participants did not receive breastfeeding counseling during antenatal visits. Almost half the infants were given prelacteal feeding. Male infants are two times more likely to be exclusively breastfed for the recommended period than female infants. Work-related pressures were a key factor in the discontinuation of breastfeeding (53.4%, n=63). Conclusion This study highlights the lack of breastfeeding counseling and breastfeeding work regulation, alongside concerns about colostrum avoidance and prelacteal feeding. While EBF rates show progress, delayed initiation and work-related pressures remain challenges. Gender disparity in exclusive breastfeeding urges targeted interventions for more equitable outcomes.

Extension mechanism of fracturing in liquid nitrogen fractured coal rock dominated by phase change expansion pressure

In this paper, the liquid nitrogen (LN2) fracturing test research using LN2 phase expansion instead of N2 pressurization was carried out in response to the neglected high phase expansion rate characteristic of LN2, an anhydrous fracturing medium. Expansion pressure measurements, infrared temperature measurements, DIC full-field strain measurements and acoustic emission (AE) signal measurements were used as measurement means. The phase change gas expansion pressure, specimen end-face field, internal fracture signal and end-face temperature changes during the fracturing process were explored. The experimental results show that there was a significant difference in the performance of LN2 cold shock damaged specimens and undamaged specimens during fracturing. The change rule of LN2 phase change expansion pressure under no peripheral pressure went through linearly increasing first and then stabilizing, the slope of the linear phase was 0.029 MPa/s, the expansion pressure in the stabilizing phase was 1.2 MPa and lasted for 12s, and then the specimen ruptured. The initiation pressure of the gas fractured specimen was 2.2 MPa. The surface strain of the specimen was significantly increased during the stabilization stage of expansion pressure, and the maximum values of transverse strain and longitudinal strain were 0.059% and 0.071%, respectively, which were increased by 43.9% and 73.2% within 12 s. At the same time, the number of AE localization points increased from 12 to 78, and the location of the localization points gradually expanded from the two sides of the horizontal slot to the top of the horizontal slot and the outer wall of the specimen. There was a low-temperature zone with obvious temperature gradient in the extended area and no such change existed in the gas fractured specimens. Therefore, the fracture initiation pressure of the damaged specimen is lower than that of the undamaged specimen, and the cracks are more likely to expand and become continuous during the fracturing process, thus producing complex cracks. The use of LN2 with high phase change expansion rate can replace the high-pressure pumping of N2, which is of great significance for the reduction of the implementation time and cost of the LN2 fracturing process.

CO2 fracturing of volcanic rocks under geothermal conditions: Characteristics and process

An enhanced geothermal system using carbon dioxide (CO2) for both reservoir creation and thermal energy extraction has attracted attention; however, studies on the CO2 fracturing of volcanic rocks under geothermal conditions are lacking. This study aimed to elucidate CO2 fracturing characteristics and processes in geothermal volcanic rocks via integrated lab-scale fracturing experiments and numerical simulations of basalt and andesite at 250°C and a confining pressure of 30 MPa. Moreover, it proposed and demonstrated an efficient CO2-based fracturing method based on the obtained insights. Fracturing experiments on basalt and andesite with relatively low initial porosity or permeability implied that CO2 fracturing can be initiated at a lower pressure and produce a more complex fracture pattern than water fracturing because of the ease of fluid permeation (e.g., fluid pressure propagation) in rocks owing to the lower viscosity of CO2. The experiments also revealed that the ease of CO2 permeation can produce thinner fractures than those produced by water fracturing, which may severely inhibit the fracturing of andesite rocks with high initial porosity/permeability. Fracturing simulations of rocks with different initial porosity/permeability provided results consistent with the experimental observations. Moreover, the simulations clarified that fluid pressure propagation during CO2 permeation within an unfractured part of the rock and between induced fractures and the surrounding rock matrix could reduce the fracture initiation pressure by effective stress reduction, increase the complexity of the fracture pattern by large stimulated zone development, and inhibit fracture opening and propagation by decreasing the pressure difference between the fractures and matrix. Based on these findings, we proposed a combined CO2-water fracturing system that addresses the drawbacks while maintaining the advantages of CO2 fracturing.

Thermal Fracture Simulation in Depleted Gas Field Carbon Capture and Storage: Implications for Injectivity and Flow Assurance

Summary CO2 injection into depleted gas fields causes long-term cooling of the reservoir. Therefore, even if injection pressure stays below the fracture initiation pressure, the cooled volume still creates an extensive stress disturbance that can induce the propagation of large fractures over time. The enhanced injectivity after the onset of this thermal fracturing might jeopardize injection operations due to the risk of hydrate plugging in the injection well caused by the combination of low pressure and low temperature, and large fractures may also increase the risk of loss of containment. Modeling the fracture evolution provides an estimate of the magnitude and timing of these effects. In this study, commercial compositional reservoir simulation software capable of modeling the physical phenomena associated with CO2 injection into depleted natural gas reservoirs has been used. These encompass CO2 mixing with natural gas, water vaporization, thermal effects, and geomechanics. The finite-element geomechanics module used “two-way” coupling, which computes pressure and temperature in the flow simulation module, transmits this information to the geomechanics module to update stress and strain parameters, and uses these parameters to adjust porosity and permeability, thereby enhancing the accuracy and reliability of the overall simulation results. The thermal fracture opening is simulated as increased permeability in the fracture domain by using a fracturing criterion based on the effective stress. The fracture simulations were developed in close relation with flow assurance modeling to determine the operational windows that avoid hydrate formation while maintaining the required injection target. Unlike matrix injection, thermal fracturing shows a substantial reduction in injection bottomhole pressure (BHP), reaching 26 000 kPa (260 bar) in a specific scenario. These findings underscore the crucial consideration of cooling effects and thermal fracturing in carbon capture and storage (CCS) operations, particularly in flow assurance studies where well injectivity significantly influences overall outcomes. Due to the intense cooling-induced stress reduction, thermal fractures may propagate uncontrollably, potentially reaching faults within the reservoir. Temperature distributions along boundary faults may differ markedly from matrix flow conditions, highlighting the need to incorporate these effects into geomechanical studies to mitigate risks associated with fault stability during cooling processes.

Numerical Investigation of Tree-Type Hydraulic Fracturing for Balanced Permeability Enhancement of Heterogenous Coal Seams Based on the Finite-Discrete Element Method Model.

Tree-type hydraulic fracturing (TTHF) is a new technology that can enhance the permeability of coal seams in a balanced manner and increase the coalbed methane production rate. However, the heterogeneity of coal seams is a major challenge in achieving balanced permeability enhancement by TTHF. Traditional methods based on digital image processing are difficult to apply in practice. To address these challenges, we proposed a 2D numerical model of coal seams based on the combined finite-discrete element method (FDEM). The elastic modulus of the coal seams obeys a Weibull distribution, and the coal heterogeneity was quantified by an index m. The effects on the fracture initiation pressure, the fracturing influence range, and displacements of TTHF were analyzed from four aspects, including the homogeneity index of coal, the arrangement angle of branch boreholes, the horizontal stress difference, and the injection rate of the fracturing fluid. The results show that TTHF has a significant effect on the balanced permeability enhancement in coal reservoirs, particularly with strong heterogeneity, and the best permeability enhancement for TTHF is achieved when the branch boreholes are arranged at 45°. The branch boreholes are prefabricated in advance to create a pressure relief area around the injection point, and the hydraulic fracture propagation is affected by the horizontal stress difference only when the fracturing influence range exceeds this area. When the horizontal stress difference increases from 0 to 4 MPa, its fracture initiation pressure increases from 8.93 to 10.86 MPa, with an increase of 21.61%. In addition, the initial stage of fluid injection was found to be crucial for achieving balanced permeability enhancement in TTHF, and a higher injection rate can expand the fracturing influence range. The numerical model has profound implications for the field application of TTHF technology.

Extreme massive hydraulic fracturing in deep coalbed methane horizontal wells: A case study of the Linxing Block, eastern Ordos Basin, NW China

Deep coal seams show low permeability, low elastic modulus, high Poisson’s ratio, strong plasticity, high fracture initiation pressure, difficulty in fracture extension, and difficulty in proppants addition. We proposed the concept of large-scale stimulation by fracture network, balanced propagation and effective support of fracture network in fracturing design and developed the extreme massive hydraulic fracturing technique for deep coalbed methane (CBM) horizontal wells. This technique involves massive injection with high pumping rate + high-intensity proppant injection + perforation with equal apertures and limited flow + temporary plugging and diverting fractures + slick water with integrated variable viscosity + graded proppants with multiple sizes. The technique was applied in the pioneering test of a multi-stage fracturing horizontal well in deep CBM of Linxing Block, eastern margin of the Ordos Basin. The injection flow rate is 18 m3/min, proppant intensity is 2.1 m3/m, and fracturing fluid intensity is 16.5 m3/m. After fracturing, a complex fracture network was formed, with an average fracture length of 205 m. The stimulated reservoir volume was 1 987×104 m3, and the peak gas production rate reached 6.0×104 m3/d, which achieved efficient development of deep CBM.

Numerical modeling of fracture propagation of supercritical CO2 compound fracturing

The exploitation of shale gas is promising due to depletion of the conventional energy and intensification of the greenhouse effect. In this paper, we proposed a heat-fluid-solid coupling damage model of supercritical CO2 (SC-CO2) compound fracturing which is expected to be an efficient and environmentally friendly way to develop shale gas. The coupling model is solved by the finite element method, and the results are in good agreement with the analytical solutions and fracturing experiments. Based on this model, the fracture propagation characteristics at the two stages of compound fracturing are studied and the influence of pressurization rate, in situ stress, bedding angle, and other factors are considered. The results show that at the SC-CO2 fracturing stage, a lower pressurization rate is conducive to formation of the branches around main fractures, while a higher pressurization rate inhibits formation of the branches around main fractures and promotes formation of the main fractures. Both bedding and in situ stress play a dominant role in the fracture propagation. When the in situ stress ratio (σx/σy) is 1, the presence of bedding can reduce the initiation pressure and failure pressure. Nevertheless, it will cause the fracture to propagate along the bedding direction, reducing the fracture complexity. In rocks without bedding, hydraulic fracturing has the lengthening and widening effects for SC-CO2 induced fracture. In shale, fractures induced at the hydraulic fracturing stage are more likely to be dominated by in situ stresses and have a shorter reorientation radius. Therefore, fracture branches propagating along the maximum principal stress direction may be generated around the main fractures induced by SC-CO2 at the hydraulic fracturing stage. When the branches converge with the main fractures, fracture zones are easily formed, and thus the fracture complexity and damage area can be significantly increased. The results are instructive for the design and application of SC-CO2 compound fracturing.

Relative Yield of Thermal and Nonthermal Emission during Weak Flares Observed by STIX during 2021 September 20–25

The disparate nature of the thermal–nonthermal energy partition during flares, particularly during weak flares, is still an open issue. Following the Neupert effect, quantifying the relative yield of X-ray emission in different energy bands can enable the inferring of the underlying energy release mechanism. During 2021 September 20–25, the Solar Orbiter mission—being closer to the Sun (∼0.6 au) and having a moderate separation angle (<40°) from the Sun–Earth line—offered a unique opportunity to analyze multiwavelength emission from ∼200 (mostly weak) flares, commonly observed by the Spectrometer Telescope for Imaging X-rays (STIX), STEREO-A, GOES, and the Solar Dynamics Observatory. Associating the quotient (q f ) of hard X-ray fluence (12–20 keV) and soft X-ray flux (4–10 keV) with the peak soft X-ray flux enabled us to identify strongly nonthermal flares. A multiwavelength investigation of spectral and imaging-mode observations of the 20 strongly nonthermal weak flares reveals an inverse relationship of q f with the emission measure (and density), and a positive relationship with the flare plasma temperature. This indicates that the plasma in tenuous loops attains higher temperatures compared to that in the denser loops, in response to nonthermal energy deposition. This is in agreement with the plasma parameters of the coronal loops, as derived by applying the one-dimensional Palermo–Harvard hydrodynamical code to coronal loop plasma with different initial coronal loop base pressures when subjected to similar heating inputs. Our investigation, therefore, indicates that the plasma parameters of the flaring loop in the initial phase have a decisive role in the thermal–nonthermal energy partitioning.

Numerical investigation into the thermo-hydro-mechanical behavior in unsaturated soils considering hypergravity effect

Unsaturated soils are commonly found in coastal regions and marine sediments, where understanding the thermo-hydro-mechanical (THM) behavior, especially regarding phase transition, is crucial for related practical engineering applications. Centrifugal model offers an effective means to reflect the prototype with smaller scale and shorter duration under hypergravity conditions. Present studies on similarity based on governing equation analysis of the THM coupled responses are mainly focused on saturated rather than unsaturated soils, nor involved with different boundary conditions. This paper theoretically derives the similarity of THM behavior of unsaturated soils between the centrifugal model and prototype, and numerically assesses the similarity considering Dirichlet / Neumann condition based on the open-source FEM code OpenGeoSys. In addition, numerical results shows that phase transition between liquid water and water vapor will occur under temperature variation, and pore pressure difference rather than initial pore pressure causes the difference of THM coupled responses. Significant pore pressure variation will be amplified with increase of gas diffusion coefficient, and large air entry pressure corresponds to high liquid saturation and obvious phase transition.

Laminar flame speed measurement and combustion mechanism optimization of methanol–air mixtures

AbstractLaminar flame speeds of methanol/air mixtures at 338–398 K are measured by the heat flux method, extending the range of equivalence ratio up to 2.1. And a new optimized methanol mechanism with 94 reactions is proposed by using the particle swarm algorithm, adjusting 20 Arrhenius pre‐exponential factors in their uncertainty domains. The optimized model is compared with eight methanol combustion mechanisms and experimental data published in recent years, covering a wide range of initial temperatures (298–1537 K), pressures (0.04–50 atm) and equivalence ratios (0.5–2.1). The results show that the optimized mechanism not only improves the accuracy of ignition delay time with rapid compression machine at low temperature but also moderately improve the description of laminar flame speed in lean and stoichiometric conditions. Meanwhile, the optimized model significantly enhances the prediction accuracy of CH3 and CH2O radical, and perfectly captures the evolution trend of HCO radical in laminar flat flame. Overall, the optimized mechanism provides the best overall description of the currently available measurements, leading to more accurate and comprehensive prediction of ignition delay time, laminar flame speed and species concentration.

Modeling and Optimization of Interior Ballistics within Pneumatic Underwater Launchers

A new area of underwater equipment research focus is the use of underwater unmanned vehicles (UUVs) with launch mechanisms to deploy lightweight and small-sized robots for functions including communication, exploration, and detection. The internal ballistic mathematical model of the underwater launch system for small robots is established in this paper. The internal ballistic parameters and the robot displacement and velocity change rule over time are obtained. The optimization calculation of the crucial parameters to be determined by the particle swarm algorithm is completed. Following optimization, the gas cylinder’s initial pressure is 2 MPa, its capacity is 30 L, its opening area is 9.683 × 10−5 m2, and its opening time is 0.02 s. A numerical simulation is performed for the small robot’s underwater launch process, based on the mathematical and physical model supplied by Fluent 2020 software. The results yield the robot’s motion law and the properties of the flow field during the launch process. The purpose of the underwater launcher experiment is to determine the robot’s motion characteristics. The accuracy of the theoretical model is confirmed by comparing and analyzing the numerical simulation results with the actual data.

Numerical simulations of a hydrogen-air pre-detonator for detonation engines

In recent years, heat release associated with the detonation phenomenon is considered a very efficient process. Pressure gain combustors are being developed with detonation waves as the driving force. In this scenario, study of detonation waves has become very important. Deflagration-to-Detonation transition (DDT) is one of the ways used to initiate detonation in the combustors. An attempt has been made in this paper to study the DDT in a tube with obstacles using OPENFOAM. A 2-dimensional rectangular section of a tube containing obstacles filled with stoichiometric hydrogen-air mixtures at different initial conditions have been studied. The effect of changes in the length of the tube, number of obstacles, blockage ratios and initial pressure of the reactants on the detonation wave properties have been studied using numerical simulation based on ddtfoam software. The motivation for this study is to design a pre-detonator for a rotating detonation engine (RDE). In order to make it compatible with the RDE and the test facility, it has been proposed to carry out simulations using shorter lengths of the DDT tube. The number of obstacles has been selected appropriately to obtain detonation at shorter lengths of the tube of the order of 1.5 m, 1.0 m &amp; 0.5 m. As the objective has been to obtain design data for the prototype, the finer details of DDT are not being discussed in this paper.

Novel method for recovering valuable metals from Sn ash: Vacuum carbothermal reduction-directional condensation

Sn ash recycling is an industry with positive development prospects, as it provides better-protected resources, promotes sustainable development, and lays a solid foundation for future development. In this study, an innovative vacuum carbothermal reduction-directional condensation process was developed. The thermodynamic analysis results indicated that the initial reaction pressure and temperature for the carbothermal reduction of the system was 1–10 Pa and 998–1063 K, respectively. The saturation vapor pressure, separation coefficient, and condensation temperature of Sn, Pb, and Zn in the reduced products differed significantly, and their separation could be achieved by controlling the volatilization and condensation temperatures. A single-factor experiment investigated the effects of carbon ratio, temperature, and time on the reduction efficiency, direct yield, and recovery rate. The optimal experimental conditions were the ratio of MeO to C of 4:1, temperature of 1373 K, and time of 120 min. Sn, Pb, and Zn products were obtained at different positions. This process shortens the traditional process, reduces the reduction cost of Sn, and enables the implementation of the process, making it environmentally friendly.

Performance time and leak pressure of hand-sewn and skin staple intestinal anastomoses and enterotomies in cadaveric cats.

To compare time to construct completion and leak testing between hand-sewn and skin staple anastomoses and enterotomies in cats. Ex vivo, randomized study. Fresh feline cadavers (n = 20). Jejunal segments (8 cm) were harvested and tested on the same day as euthanasia. From each cadaver, one segment was randomly assigned to control (C), hand-sewn enterotomy (HSE), and skin staple enterotomy (SSE) groups, and two segments were randomly assigned to hand-sewn anastomosis (HSA) and skin staple anastomosis (SSA) groups. Construct completion time, initial leak pressure (ILP), and maximum intraluminal pressure were compared. Leakage location was reported. Mean time (s) ± SD was longer (p < .001) for HSA (317.0 ± 50.9) than SSA (160.8 ± 13.1) and for HSE (172.0 ± 36.5) than SSE (20.3 ± 5.0). ILP (mean ± SD) for C (600.0 mmHg ±0.0) was higher (p < .001) than all constructs. ILP (mean ± SD) for SSA (124.2 mmHg ±83.7) was not different (p = .49) than HSA (86.1 ± 51.9), but HSE (200.3 ± 114.7) was higher (p < .001) than SSE (32.2 ± 39.7). Immediate leakage from the center of enterotomy closure was observed in 7/20 SSE. HSA construct completion took twice as long as SSA with no difference in intraluminal pressures. Although HSE construct completion took 8x as long as SSE, HSE had higher intraluminal pressures. In cats, SSA may be an alternative to HSA for intestinal anastomosis, but SSE is not recommended as an alternative to HSE for intestinal enterotomy closure.

Abstract A058: Mesenchymal stem cells act as a selective pressure for High Grade Serous Ovarian Cancer initiation

Abstract High grade serous ovarian cancer (HGSOC) is the most common and lethal subtype of ovarian cancer accounting for 80-90% of diagnoses. Despite its high incidence and mortality, the mechanisms of cancer initiation are unclear. The majority of HGSOC originates in the fallopian tube epithelium (FTE) with support of underlying mesenchymal stromal/stem cells (MSCs). MSCs are stromal progenitor cells that play important roles in wound healing and, in the context of cancer, tumor progression. We showed that MSCs within the tumor microenvironment, termed cancer associated MSCs (CA-MSCs) harbor a unique, age-associated epigenetic signature that is essential for tumor growth and metastasis. Surprisingly, we identified rare subsets of MSCs from benign tubes that exhibit similar epigenetic changes to cancer educated CA-MSCs suggesting that the pro-oncogenic MSC phenotype exists prior to cancer initiation. These “high risk” MSCs (hrMSCs) increase with age, are enriched in BRCA mutation carrier patients, promote cancer cell proliferation, and most notably, elicit tumor formation in primary, non-cancerous FTE. To elucidate the mechanism of hrMSC-induced malignant transformation of FTE, we characterized the effect that hrMSCs have on primary FTE. HrMSCs promoted increased growth of FTE relative to normal/low risk MSCs (lrMSCs) derived from the same patient. These MSCs lack the epigenetic signature/transcriptome of hrMSCs/CA-MSCs. Intriguingly, we co-cultured FTE with hrMSCs at a 1:1 ratio and discovered robust DNA damage in the form of DNA double strand breaks (53BP1 foci) in FTE at 24 hours. Furthermore, conditioned media from hrMSCs supported the recovery of FTE following damage with other DNA damaging agents. We hypothesize that the DNA damage function of hrMSCs serves as a selective pressure for mutation in FTE (1st hit). Additionally, we hypothesize that hrMSCs simultaneously provide growth signals to FTE allowing for evasion of DNA damage-induced cell death (2nd hit). Lastly, we hypothesize that both hrMSC functions are required for genesis of HGSOC. Citation Format: Geyon L. Garcia, Huda I. Atiya, Lan G. Coffman. Mesenchymal stem cells act as a selective pressure for High Grade Serous Ovarian Cancer initiation [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr A058.