Fluid Characteristics Research Articles

Fabrication and characterization of potato short amylose, zein, and pectin ternary composite particles stabilized pickering emulsions and their application on nuciferine delivery

Nuciferine exhibits properties such as reducing blood sugar and fat, however, it is hindered by its poor water solubility and low bioavailability. Pickering emulsions can efficiently encapsulate, protect and deliver active ingredients. In recent years, the use of biologically derived natural materials as emulsifiers to construct Pickering emulsions has become a research hotspot. This research utilized an enzymatic hydrolysis technique to produce short amylose. Subsequently, a ternary composite of short amylose (DBS), zein, and pectin (PEC) was formulated to stabilize Pickering emulsion, with the incorporation of nuciferine aiming to enhance the performance of lotus leaves in terms of both stability and bioavailability. The study revealed that varying amounts of DBS addition had a significant impact on the micromorphological structure and functional properties of DBS-Zein-PEC ternary composite particles. Specifically, the addition of 0.4 g of DBS led to a notable reduction in particle size to 735.2 nm and Zeta potential to −29.6 mV, creating a three-dimensional network with a closely packed lamellar structure. Optimal process conditions for preparing Pickering emulsion included a 3-minute homogenization time, rotation speed of 15000 rpm, and 5 % ternary composite particle addition. Under these conditions, O/W Pickering emulsion was successfully prepared, achieving a 90.5 % encapsulation rate for nuciferine. The resulting emulsion exhibited a minimum particle size of 4.09 μm, displayed good storage stability, resistance to salt ions and pH variations, viscous fluid characteristics, tolerance to oral and gastric environments, and slow release of nuciferine in the small intestine, thereby enhancing its bioavailability. These findings offer insights into the loading and delivery of nuciferine and serve as a technical guide for developing highly stable emulsion gel systems.

Application of omega 3,6 with Moringa oleifera suplemented vitamin E on rumen fluid characteristics, microbial protein synthesis, and methane gas production in goats on suboptimal lands

Changes in feeding patterns were needed to overcome the problem of methane gas emissions from ruminant livestock and the problem of low productivity at the smallholder livestock level. This solution involves direct action against the gas produced in the stomach of ruminants by providing feed containing active substances to reduce the microbes that produce gas in the stomach. One alternative feed that was often used as a promoter of improving rumen fluid characteristics was the use of omega 3.6 sources together with Moringa leaves enriched with vitamin E. This research aimed to investigate the effect of feeding on methane gas production in goats. The research method used a Randomized Block Design (RAK) with four treatments and five replications in vitro. From the research results, it could be concluded that the use of omega 3.6 together with Moringa leaves enriched with vitamin E was able to reduce methane gas production by 25.62% with a Volatile Fatty Acid (VFA) value of 144.53 mM, pH around 6.99, NH3 11.87 mg/100ml, microbial biomass 20.42 mg/ml, microbial protein 217.58mg/ml, bacterial colony 5.34x109 cells/ml and protozoa population 29x106 cells/ml. This conclusion shows that the use of omega 3.6 with Moringa oleifera supplemented with vitamin E has the potential to consistently improve rumen fluid characteristics and reduce methane gas emissions by using a combination of omega 3.6 sources and Moringa leaves in suboptimal land, as well as vitamin E supplementation.

Analysis of disturbance factors of magnetorheological damper in continuous impact buffer system

Abstract Magnetorheological (MR) impact buffering systems are widely used in vehicle suspensions, bridge damping, and aircraft landing gear due to their excellent buffering performance and rapid response time. However, under the condition of high-speed continuous impact, magnetorheological damper (MRD) operate in complex environments where various internal and external uncertainties can negatively affect control performance. This paper analyzes the impact of disturbance signals on MR buffering systems and explores control strategies to mitigate these effects. First, we established a hysteresis model based on experimental data and identified parameters using a genetic algorithm to determine the influence of hysteresis disturbances. Next, we developed a temperature model based on the thermal characteristics of SG-MRF2035 magnetorheological fluid, fitting the relationship between temperature and dynamic viscosity to identify temperature disturbances. The results showed that when disturbances were considered, the system exhibited higher peak damping forces and a deviation from the desired ‘platform effect’ in the damping force-displacement relationship. Finally, we applied an Active Disturbance Rejection Control(ADRC) strategy, which effectively compensated for the hysteresis and temperature disturbances, enhancing the system’s robustness. Compared to PID control, the ADRC-controlled system demonstrated lower peak damping forces and a damping force-displacement relationship closer to the desired platform effect.

Production and Characterization of Immune Ascitic Fluids to Vibrio cholerae R-Variant Strains

Production and Characterization of Immune Ascitic Fluids to Vibrio cholerae R-Variant Strains

Miscellaneous prospects of invasive Lantana camara biomass-a standpoint on bioenergy generation and value addition.

Investigation of Lantana camara biomass for potential bioenergy generation integrates invasive species (IS) management with the unabated demand for bio-energy. In the present investigation, L. camara was used to produce bio-oil by thermochemical conversion (pyrolysis). The resultant product evinced energy yield of 62.58% with 64.95% of elemental carbon (C) content and endorsed the suitability of L. camara bio-oil for biofuel applications and value addition. Thermogravimetric (TG-DTG) analysis revealed a short thermal degradation profile, whereas spectroscopic analyses detected a host of organic compounds such as esters, phenols, ketones, aldehydes, aliphatics, and aromatics. The economic analysis of L. camara biomass conversion technology carried out in this study proved to be commercially competitive and viable versus petroleum refining. Antimicrobial and antioxidant assays with bio-oil evinced highest zone of inhibition (ZOI) against Candida albicans (31.02mm), and displayed strong antioxidant property (DPPH IC50 value 233.72 ± 0.2μg/ml). The bio-oil exhibited rheological characteristics of shear thinning and pseudoplastic fluid, particularly at low and intermediate shear rates. The present study highlights the multifaceted advantages of utilizing L. camara biomass, which include environmental remediation via waste management, bioenergy generation, and the feasibility of generating value-added products.

Physical and dynamic characterization of biodegradable oil-based magnetorheological fluid

Physical and dynamic characterization of biodegradable oil-based magnetorheological fluid

CFD analysis of pore morphology, gravity, and fluid characteristics influences on water flooding process

In this research, computational fluid dynamics (CFD) was employed to examine the two-phase flow of water and oil in a porous medium. For this purpose, the Navier-Stockes equations, which describe fluid motion, and the Cahn-Hillard phase field, which defines the interface between two phases, are coupled. The numerical discretization system of equations was solved using the finite element method (FEM) with the COMSOL software. To validate the results and the phase-field model (PFM), the Lucas and Washburn equation was used together with the experimental data. Through this study, the effective parameters were evaluated in two parts. In the first part, seven models with different pore morphologies were designed, and the impact of petrophysical parameters of the reservoir, including the shape of pores, connectivity of pores with or without throat lines, porous media heterogeneity, and relative permeability, on oil recovery was investigated. The second part was devoted to performing sensitivity analysis on the effect of fluid properties, including interfacial tension, wettability, viscosity ratio, injected fluid flow, and gravity, upon enhanced oil recovery (EOR) in different morphologies. Owing to the uniform distribution of capillary pressure in the patterns with the throat lines, the sweep efficiency of the injected fluid was found to be better, and thereby oil production increased. The results of the present work proved the significant influence of gravity on EOR, so that by applying gravity to the solution domain, the breakthrough time and oil recovery factor increased by 20 minutes and 28.6 %, respectively. Moreover, the velocity of the injected fluid as a representative of the flow rate had the greatest effect on EOR, with a 35 % increase in production.

Synovial fluid analysis in healthy green turtles Chelonia mydas in Taiwan.

Septic arthritis is a frustrating disease in sea turtle rehabilitation because of its unclear pathogenesis, delayed onset during rehabilitation, long-term treatment requirements, and potentially poor prognosis. Radiography, blood cultures, and arthrocentesis have been used as diagnostic tools for suspected cases. However, there is currently a lack of data on the characteristics of synovial fluid in healthy sea turtles. To establish reference data for synovial fluid in sea turtles, we enrolled 14 green turtles Chelonia mydas rescued between 2019 and 2022 from 3 facilities using the following inclusion criteria: normal attitude and appetite, normal motor functions of the 4 limbs, no joint swelling, and no ongoing use of antibiotics for at least 1 mo. Bacterial cultures of blood and synovial fluid from the shoulder joints of these turtles were obtained and a qualitative analysis of the synovial fluid was performed. The results revealed bacterial culture-negative blood and synovial fluids at 37°C. Most characteristics of normal synovial fluid in green turtles, such as being transparent, colorless, and able to create a strand of over 2.5 cm by being pulled with a needle in viscosity trials, as well as the cytology of the normal synovial fluids being dominated by histiocytes and synovial lining cells, lymphocytes, and occasionally a few heterophils or erythrocytes were similar to those in mammals. This study provides information on the normal synovial fluid characteristics of green turtles in Taiwan, which may be beneficial for the diagnosis of joint diseases in sea turtles.

Study on the Rheological Behaviors, Thixotropy, and Printing Characteristics of Screen Printing Slurry for Nd-Fe-B.

The rheological behavior and printing characteristics of the screen-printing slurry for Nd-Fe-B grain boundary diffusion are key factors that determine the quality of printing and magnetic performance. However, few studies have focused on the organic medium, a crucial material for slurry. In this paper, the rheology, thixotropy, and thermal decomposition behavior of the organic vehicle in Nd-Fe-B screen printing slurry were studied. The results show that the organic vehicle formed by terpineol and polyvinyl butyral (PVB) exhibits typical non-Newtonian fluid characteristics, with excellent rheology and thixotropy, ensuring that the slurry prepared from it has excellent static stability and printing consistency. Additionally, the carbon residue of the organic vehicle formed by terpineol and PVB is less than 0.1% at 900 °C, avoiding excessive carbon entering the magnet during the diffusion process. Moreover, studying the rheology and thixotropy of the organic vehicle through a rheometer can quickly screen the slurry system. This work provides valuable guidance for designing an organic vehicle for screen-printing slurry for Nd-Fe-B grain boundary diffusion in future research.

Development and Characterization of Novel Green Cutting Fluids with Nano-additives

In this current investigation, novel cutting fluids developed through a unique combination of food grade emulsifiers, plant based additives (EA) and nano particles (NP) as cutting fluid additives in corn oil (CO) based vegetable oil. Five dissimilar corn-based green cutting fluids (CBGC1, CBGC2, CBGC3, CBGC4, CBGC5) were prepared by varying the weight percentages (wt.%) of EAs (5, 10, 15, 20, 25) with CO, and their thermo-physical properties were meticulously analyzed. Among these formulations, CBGC2 demonstrated superior lubrication performance, making it the most promising oil for further investigation. Subsequently, the effect of different NP was investigated by adding alumina (Al2O3), graphene (Gr) and multi walled carbon nanotubes (MWCNT) NPs in the CBGC2 solution in the ratio of 0.4, 0.8 and 1.2 in weight percent (wt.%) and the experimental results reveal substantial enhancements in thermophysical properties. Among various samples, the nanofluid containing 0.8 wt.% concentration of Al2O3 nanoparticles in CBGC2 exhibited the highest viscosity. Additionally, the thermal conductivity of the nanofluid enhanced by 24.82% when 1.2 wt.% of Gr nanoparticles added oil compared to CBGC2. Furthermore, in tribological tests, CBGC2 with 0.4% Al2O3 exhibited the lowest frictional force among the prepared cutting fluids. The contact angle reduced to a maximum extent by 11.14% for cutting fluids containing 1.2% alumina nanoparticles. These findings suggest that these innovative green cutting fluid formulations with nano-additives hold great potential for improving machining processes in various industrial applications towards sustainability.

Performance improvement of a U-tube heat exchanger based hydrogen storage reactor by phase change materials

Solid-state hydrogen storage technology using metal hydrides as carriers has great application prospects. This study aims to optimize the heat transfer resistance and absorption kinetics issues encountered in practical applications of LaNi5-H2 storage materials in storage reactors. A mathematical model for the hydrogen absorption process in the reactors based on U-tube and straight-tube heat exchangers was built, and the advantages of U-tube structure and the flow characteristics of the heat transfer fluid on its heat transfer and absorption performance were analyzed. To further enhance the U-tube based reactor's performance, phase change materials (PCM) were subsequently introduced as an auxiliary heat transfer medium, while the amount of PCM and the thermal conductivity of the reaction bed were optimized. The results showed that the appropriate PCM dosage could overcome the inherent defects of the U-tube heat exchanger and significantly improve heat dissipation and reaction rates of the reactor, and the H2 absorption completion time was shortened by 1.4 times. In addition, the increased thermal conductivity of reaction beds is equally important for the enhancement of heat transfer and absorption rate. Nevertheless, further increase of PCM's thermal conductivity has a limited effect on the improvement of the performance.

Effect of perioperative management on early graft function in living donor paediatric kidney transplantation

Abstract Background Paediatric kidney transplantation has an increased risk of surgical and vascular complications, with intensive care monitoring required postoperatively. This study aimed to determine if perioperative management affects early graft function in living donor paediatric kidney transplantation. Methods Clinical data was extracted from the electronic medical record for living donor kidney transplants at two paediatric centres covering the state of New South Wales (NSW), Australia from 2009 to 2021. Estimated glomerular filtration rate (eGFR) of 7 days and 1-month post-transplant were calculated as measures of early graft function. Results Thirty-nine eligible patients (female n (%) 13 (33%)) with a median (IQR) age of 6 (3–9) years and pre-transplant eGFR of 7 (6–10) mL/min/1.73 m2 were analysed. Mean (SD) central venous pressure (CVP) after revascularisation was 11 (4) mmHg. Intraoperatively, mean volume of fluid administered was 84 (39) mL/kg, and 34 (87%) patients received vasoactive agents. Average systolic blood pressure (BP) in the first 24-h post-transplant was 117 (12) mmHg. Postoperatively, median volume of fluid administered in the first 24 h was 224 (159–313) mL/kg, and 17 (44%) patients received vasoactive agents. Median eGFR 7 days and 1-month post-transplant were 115 (79–148) and 103 (83–115) mL/min/1.73 m2, respectively. Linear regression analyses demonstrated that after adjusting for age, the average CVP after revascularisation and average systolic BP in the first 24-h post-transplant were not associated with eGFR in the first month post-transplant. Conclusions Targeted intraoperative and postoperative fluid and haemodynamic characteristics were achieved but did not correlate with early graft function. Graphical Abstract

PSXI-11 In vitro rumen fermentation characteristics of rumen fluid obtained from grain-fed and grass-fed farmed American Bison

Abstract The objective of this pilot study was to examine the impact of diet type on in vitro rumen fermentation characteristics using rumen fluid collected from grain-fed and grass-fed American Bison (Bison bison). Rumen fluid was collected from 6 farmed American Bison at a commercial slaughter facility. At the time of slaughter, 3 grain-fed heifers (< 3 yr) were randomly selected for rumen fluid collection. On a separate day, 3 grass-fed cows (>3 yr) were randomly selected for rumen fluid collection. Rumen fluid was collected from each animal by obtaining rumen contents and filtering the rumen fluid from the digesta. For a given collection day, rumen fluid from the 3 animals was combined with McDougall’s buffering solution to generate rumen fluid buffer solution (RFB). The RFB was added to each pre-weighed digestion vessels (DV) containing no substrate (blanks) or 0.5 g of ground substrate (grain-based diet or forage-based diet). After filling, the DV were capped with one-way valves and incubated for 0, 12, 24, 48, and 72 h. At the end of each incubation period, DV were centrifuged, and supernatant was removed and analyzed for VFA concentrations. The remaining pellet was dried at 60°C for 24 h to determine dry matter digestibility (DMD). Descriptive statistics were used to describe DMD characteristics for rumen fluid collected from bison from each production system. Linear, quadratic, and cubic responses were analyzed for DMD. Linear, quadratic, and cubic contrasts were used to examine DMD over time. In vitro DMD increased quadratically (P < 0.05) for grain-fed bison and linearly (P < 0.05) for grass-fed bison over time. Final 72 h DMD was 84.5% ± 0.05 and 70.0% ± 0.11 for grain-fed and grass-fed bison, respectively. Final molar proportions of acetate, propionate, isobutyrate, and butyrate were 55.3% ± 0.01, 25.8% ± 0.002, 1.9% ± 0.01, and 17.0% ± 0.001 for grain-fed bison and 31.0% ± 0.02, 41.2 ± 0.02, 3.9% ± 0.01, and 23.2% ± 0.01 for grass-fed bison. Molar proportions of all VFA exhibited a cubic response (P < 0.05) over time for rumen fluid collected from both grain-fed and grass-fed bison. These data provide a preliminary insight into in vitro rumen fermentation characteristics of bison from different production systems.

Gas-rigid-flexible compound blade coupling enhanced experimental study on chaotic mixing of multiphase flow

Efficient fluid mixing is essential for process intensification. This study proposes a new method in which gas-rigid-flexible composite blades are coupled to enhance chaotic mixing in multiphase flow systems. The rigidity and flexibility of the blades were adjusted by intermittent gas injection, which increased the effectiveness of mixing of the liquid-liquid two-phase fluid. This study investigates the influence of different process parameters on the mixing efficiency and quantifies the chaotic characteristics of fluid mixing through pressure-time series analysis of multiscale entropy and the 0–1 test. A high-speed camera recorded the bubble movement in the flow field, while particle image velocimetry (PIV) revealed the enhancement of the properties of the flow field in the system due to the suspended motion of the particles. Using suitable process parameters, gas-rigid-flexible composite blade coupling significantly enhanced the mixing effect, where the mixing time of the G-RFCP system was reduced by 1.42 times compared to that of the CP system. Bubble motion, deformation, and rupture enhanced the mechanical agitation, increasing the intensity of the turbulence and chaotic behaviour. Flow-field analysis indicated a three-fold increase in the vorticity and a 1.04-fold increase in the velocity difference for the G-RFCP system compared with those of the CP system. This study provides theoretical and experimental foundations for understanding chaotic mixing in liquid-liquid two-phase fluids.

Elastic contribution of polymeric fluids augments salinity-gradient-induced electric potential across a microfluidic channel

HypothesisHarnessing electrical energy from salinity gradients, particularly for powering micro and nanoscale devices, has become a focal point of recent research attention, due to its renewable and biocompatible nature. Much of the reported research in that direction revolves around optimizing the membrane architecture and the charge distribution to maximize the induced electric potential, with no particular emphasis on the fluid rheology. However, many of the modern miniature systems, typically the bio-inspired ones, concern fluids with complex rheological characteristics, where the results for Newtonian solvents may not trivially apply. Here, we hypothesize that the interplay between interfacial electro-mechanics and the fluid rheology can influence the effectiveness of salinity-gradient-modulated electrokinetics significantly – an aspect that has largely remained overlooked. Theory and experimentsHere we report the first experiments supplemented by a theoretical model that unveil how that the addition of polymers in a solvent modulates the salinity gradient – induced electric potential in a microfluidic channel. Our theoretical framework considers the simplified Phan-Thien Tanner (sPTT) constitutive model, which represents the viscoelastic characteristics of fluids. Experiments were conducted with combined pressure driven and salinity gradient driven flow through microchannel involving dilute solutions of polyethylene oxide (PEO) of different molecular weights and concentrations to successfully validate the theoretical approach. FindingsOur findings indicate that the induced electrical potential increased non-linearly with the saline concentration ratio across the microchannel, as compared traditional linear response. Our results demonstrate how the elasticity of fluid may enable realizing an optimal benefit to this effect, by arresting the viscous resistance and uplifting the elastic response via utilizing polymeric inclusions of high relaxation times. These results provide specific insights on preferential windows of augmenting the induced streaming potential by harnessing the viscoelastic nature of the solution and the imposed salt concentration, bearing critical implications in miniature energy harvesting and desalination technology.

Deciphering prognostic indicators in non-HIV cryptococcal meningitis: Constructing and validating a predictive Nomogram model.

Cryptococcal meningitis (CM) is a well-recognized fungal infection, with substantial mortality in individuals infected with the human immunodeficiency virus (HIV). However, the incidence, risk factors, and outcomes in non-HIV adults remain poorly understood. This study aims to investigate the characteristics and prognostic indicators of CM in non-HIV adult patients, integrating a novel predictive model to guide clinical decision-making. A retrospective cohort of 64 non-HIV adult CM patients, including 51 patients from previous studies and 13 from the First Hospital of Shanxi Medical University, was analyzed. We assessed demographic features, underlying diseases, intracranial pressure, cerebrospinal fluid characteristics, and brain imaging. Using the least absolute shrinkage and selection operator (LASSO) method, and multivariate logistic regression, we identified significant variables and constructed a Nomogram prediction model. The model's calibration, discrimination, and clinical value were evaluated using the Bootstrap method, calibration curve, C index, goodness-of-fit test, receiver operating characteristic (ROC) analysis, and decision curve analysis. Age, brain imaging showing parenchymal involvement, meningeal and ventricular involvement, and previous use of immunosuppressive agents were identified as significant variables. The Nomogram prediction model displayed satisfactory performance with an akaike information criterion (AIC) value of 72.326, C index of 0.723 (0.592-0.854), and area under the curve (AUC) of 0.723, goodness-of-fit test P = 0.995. This study summarizes the clinical and imaging features of adult non-HIV CM and introduces a tailored Nomogram prediction model to aid in patient management. The identification of predictive factors and the development of the nomogram enhance our understanding and capacity to treat this patient population. The insights derived have potential clinical implications, contributing to personalized care and improved patient outcomes.

Viscoelasticity of maxell fluid in a permeable porous channel

This study examines the flow dynamics and heat transfer characteristics of Maxwell fluid in a channel influenced by magnetohydrodynamics (MHD), Joule heating, thermal radiation, and boundary layer suction/blowing effects. The governing partial differential equations (PDEs) for momentum, energy, and concentration are transformed into ordinary differential equations (ODEs) using similarity transformations. The boundary value problem (BVP) is solved numerically using the bvp4c solver in MATLAB, yielding accurate solutions for velocity, temperature, and concentration profiles under various parameters. Key findings reveal that the porous parameter decreases the velocity profile but increases the temperature profile for both suction and blowing effects. Additionally, the MHD, Deborah, and Eckert numbers significantly influence the velocity and temperature profiles differently under these conditions. This study highlights the crucial role of integrating MHD, thermal, and boundary control effects to optimize performance and efficiency in engineering systems involving Maxwell fluids, with applications in polymer processing, biomedical engineering, electronics cooling, oil recovery, and chemical processing.

Entropy generated nonlinear mixed convective beyond constant characteristics nanomaterial wedge flow

Background and objectiveNanomaterial flows at present have received much attention of the researchers. Such motivation stems for their utilization in pharmaceutical, industrial, petroleum, manufacturing and engineering applications including regenerative medicine, treatment of cancer, electronic device cooling, solar collector, mineral oil, antimicrobial agents, thermal storage system, transformer cooling and X-imaging etc. Higher thermal energy requirement in several electrical and mechanical systems is desired in recent time due to high advancement of science and technology. For important application here the stagnation point flow due to wedge with nonlinear convection is explored. For porous media, the Darcy-Forchheimer relation is considered. Characteristics of nanofluid is added by utilizing Buongiorno's model. Variable fluid characteristics are under consideration. Applied magnetic field is accounted. Energy expression comprises thermal radiation, Brownian motion, Ohmic heating, thermophoresis and heat generation. First order reaction and entropy rate are considered. MethodologyNonlinear differential expressions are changed into dimensionless ordinary systems through adequate transformations. The resultant nonlinear ordinary systems are solved through optimal homotopy analysis technique (OHAM). ResultsOutcomes for influential variables about temperature, velocity, concentration and entropy rate have been arranged. Here results show that for magnetic field the liquid flow and entropy rate have opposite scenarios. Thermal distribution and concentration have reverse effects for random motion variable while similar effect holds for thermophoresis parameter. Magnetic field and diffusion parameters contribute to augment entropy generation. Higher values of temperature dependent electrical conductivity variable lead to increase entropy rate. Thermal distribution for radiation and Eckert number is similar.

Effects of Storage Time and Temperature on the Fermentation Characteristics of Rumen Fluid from a High-Forage Diet

The objective of this experiment was to investigate the effects of storage temperature and preservation time on the fermentation characteristics of rumen fluid collected from six Hu sheep fed a high-forage diet. The storage temperatures were set at −80 °C and −20 °C, and the preservation times were labelled as follows: 0 d (fresh rumen fluid, D0), 7 d (D7), 14 d (D14), 30 d (D30), 60 d (D60), 120 d (D120), and 240 d (D240). A repeated-measures design was applied to analyze the fermentation characteristics of rumen fluid across each preservation time point and storage temperature. The results showed that storage temperature had no significant effects on pH value, ammonia nitrogen (NH3-N), microbial protein (MCP), and volatile fatty acid (VFA) concentration and proportion (p > 0.05). Specifically, the pH value increased on D7, D14, and D60 (p < 0.05), while the MCP concentration decreased on D7, D14, D30, D120, and D240 but increased on D60 (p < 0.05), and the concentration of NH3-N decreased on D14 (p < 0.05). The acetate concentration increased on D30, while the concentrations of propionate, butyrate, valerate, and total VFA increased on D60 (p < 0.05). The concentration of isovalerate decreased on D60, and isobutyrate and branched-chain VFA concentrations decreased on D120 (p < 0.05). The proportion of acetate increased on D30, while the butyrate and valerate proportions increased on D60, and the proportions of isovalerate, isobutyrate, and branched-chain VFA decreased on D60 (p < 0.05). For rumen fluid from a high-forage diet, the storage temperature (−80 °C and −20 °C) did not affect its fermentation characteristics, suggesting that rumen fluid could be preserved at −80 °C or −20 °C without altering its fermentation characteristics. The fermentation parameters of rumen fluid changed significantly after 7 days of preservation; hence, it is recommended to finish determining the fermentation parameters of rumen fluid within 7 days of collection. The concentrations and proportions of most VFA changed after 30 days of preservation; therefore, it is recommended that VFA determination should be completed within 30 days of rumen fluid collection.

Experimental study on the mass transfer and microscopic distribution characteristics of remaining oil and CO2 during water-miscible CO2 flooding

Accurate understanding and quantitative characterization of the microscopic distribution and mobilization mechanisms of remaining oil are crucial for further enhancing oil recovery during CO2 flooding. In this study, miscible CO2 flooding experiments after water flooding were performed to investigate the mass transfer and microscopic distribution characteristics of remaining oil and CO2 using micro-computed tomography technique. Additionally, the distribution characteristics of multiphase fluids (oil, water and CO2) in the pores were comprehensively investigated. Furthermore, the mass transfer effects during the miscible CO2 flooding process, as well as the CO2 sequestration ratio (SR) and sequestration factor (SF) were systematically examined. The experimental results show that the ultimate oil recovery factor after miscible CO2 flooding were 80.9 %, 70.7 %, and 64.7 %, respectively. During the water flooding stage, the produced oil mainly consisted of light hydrocarbons (C5–C16), followed by medium hydrocarbons (C17–C27). The remaining oil was mainly in cluster and network pattern, followed by multiple and oil film pattern. After miscible CO2 flooding, the produced gas mainly consisted of CO2 and CH4, with a significant increase in the mass fraction of light hydrocarbons (C5–C16) in the produced oil. The remaining oil was mainly in multiple and singlet pattern, followed by network and film pattern, with a small portion in cluster pattern. The higher the displacement rate, the smaller the SR, but most of the injected CO2 (SR > 70 %) was retained in the porous media, demonstrating the feasibility of CO2 geological sequestration during the miscible flooding process.