Fluid Exchange Research Articles

Light Codes for Fast Two-Way Human-Centric Visual Communication

Visual codes, such as QR codes, are widely used in several applications for conveying information to users. However, user interactions based on spatial codes (e.g., displaying codes on phone screens for exchanging contact information) are often tedious, time consuming, and prone to errors due to image corruptions such as noise, blur, saturation, and perspective distortions. We propose Light Codes (LICO), a novel method for fast and fluid exchange of information among users. Light codes are based on transmitting and receiving temporal codes (instead of spatial) using compact and low-cost transceiver devices. The resulting approach enables seamless and near instantaneous exchange of short messages among users with minimal physical and cognitive effort. We design novel coding techniques, hardware prototypes, and applications that are optimized for human-centric communication, and facilitate fast and fluid user-to-user interactions in various challenging conditions, including a range of distances, motion, and ambient illumination. We evaluate the performance of the proposed methods both via quantitative analysis and user study based comparisons with several existing approaches including display-camera links, Bluetooth, and near-field communication, which show strong preference toward Light Codes in various real-world application scenarios.

Analysis of the subsurface and fluid temperature monitoring by long-term operation of borehole heat exchangers

Owing to the prevailing escalation in energy costs, escalating energy demands, depletion of conventional resources, and escalating greenhouse gas emissions, there has been an expeditious upsurge in the worldwide proliferation of alternative energy sources. Geothermal systems, in particular, are highly coveted as environmentally friendly and sustainable renewable energy reservoirs, offering efficacious cooling and heating capabilities for various structures (Xu et al., 2020; Ghasemi-Fare & Basu, 2013). The energy exchange efficiency of geothermal systems is significantly contingent upon the ground temperature, enabling the discharge of energy into the ground for cooling purposes in summer and its retrieval for heating requirements during winter. However, long-term operation of geothermal energy systems can engender an imbalance in thermal recovery through the heating and cooling processes, consequently influencing the thermomechanical behavior of the subsurface over time (Baek et al., 2017). Geothermal systems, also known as ground source heat pumps (GSHPs), are designed to operate for around 20 years, while the heat source component can be utilized for an extended duration ranging from 30 to 50 years. Understanding heat transfer characteristics and long-term performance of geothermal energy systems is crucial for optimal utilization and efficiency. However, research often lacks field investigation data, specifically for long-term monitoring and validation of fluid temperatures and subsurface temperature profiles. This research conducted comprehensive long-term measurements to assess fluid and subsurface temperature behavior in a borehole heat exchanger (BHE) system. The study examined the impact of sustained BHE performance on surface and subsurface temperature dynamics. A sophisticated three-dimensional numerical model was developed based on empirical insights from the field study and validated using monitored data. The analysis included inlet/outlet fluid temperature, spatial heterogeneity of ground temperature profiles, thermal recovery processes, and alterations caused by residual thermal energy.
 Furthermore, additional temperature sensors were deployed at various depths to monitor temperature changes at distinct levels within the subground.
 In this study, an advanced three-dimensional (3D) numerical model was developed utilizing the Finite Element Method (FEM) to effectively capture the intricate heat transfer processes occurring around BHEs. The geometry mesh was generated using a specialized triangular mesh generator, enabling spatial variation of element sizes to accurately represent the geometry and temperature distribution patterns. To address the specific requirements of U-tube heat exchanger loops, where the steepest temperature gradient is anticipated, a meticulously chosen element size of 0.7 mm, was employed. As the model extends towards the lateral boundaries, particularly in the radial direction, the element size gradually increases to ensure faithful representation of the system's characteristics. To properly account for diverse vertical temperature gradients, the number of elements and the vertical distance between slices were systematically adjusted within a range of 0.01 to 5 m. This meticulous variation facilitated accurate consideration of the distinct vertical temperature profiles. Notably, the finest discretization was applied near the bottom of the BHE (approximately z = -155 m) and at the top surface, characterized by a significant temperature gradient.
 The depicted Figure 2 showcases the model's performance in analyzing the fluid profile in comparison to the monitored data over a duration of 600 hours. This comparison reveals that the maximum relative difference between the monitored and simulated values for the inlet and outlet fluid temperature does not exceed 2.649 and 2.296 degrees Celsius, respectively. These findings offer compelling evidence of the exceptional accuracy of the proposed numerical modeling approach, thus affirming its suitability for examining the long-term sustainability of BHE systems.

Numerical modelling of Energy Quay Walls to assess their thermal be-haviour

The use of the subsurface as a heating and cooling source through shallow geothermal installations has increased in the last decades [10]. So-called Energy Geostructures (EGs) represent a more innovative technology, serving the dual purpose of providing structural support to the ground/building and exchanging heat with the ground [2]. EGs can serve the purposes of several energy applications: they can be coupled with ground source heat pumps to provide space heating and cooling as well as domestic hot water.
 Energy sheet pile walls (ESPs) are a novel type of EG consisting of sheet pile walls equipped with steel pipe heat exchangers. When they are used to support the banks of canals or in port docks, they allow extraction of thermal energy from both soil and water [12]. The latter are called Energy quay walls (EQW) and are currently experimented at selected sites along canals in the Netherlands [7]. The energy efficiency of EQWs is expected to be influenced by the undisturbed ground temperature profile, ground thermal conductivity and thermal capacity, and operational and construction parameters [8] [9]. However, due to the lack of standard methods for the design of EQWs, further studies are needed to fully understand both their thermal and thermo-mechanical behaviour [1]. Based on the data collected from an EQW test field installed in Delft (NL) (Figure 1(a)), a Finite Element (FE) numerical model was developed for the accurate 3D analysis of the heat exchange phenomena taking place in the EQW.
 The EQW test site is characterized by two different heat exchanger types: the first one reaches 3 m depth and is aimed at exchanging heat mostly with the canal water. The second one has a depth of 15 m and exchanges heat with both water and soil. A monitoring system was installed composed by a total of 56 thermistors, 20 thermowells and 5 flowmeters to measure respectively the soil and canal water temperature, the heat exchanger fluid temperature and the flow velocity of both heat exchanger fluid and canal water. Different thermal activation combinations of deep and shallow loops were tested to assess the EQW thermal behaviour and the induced temperature changes into the soil [5].
 To analyse in detail the EQW thermal performance, the FE numerical model was built with the COMSOL Multiphysics software. The considered heat exchange processes are convection within the heat-carrier fluid and between the canal and the soil, and conduction in the soil and other solid domains. Radiation phenomena were considered negligible in the model. The FE model was set up using the built-in “heat transfer in pipes” module allowing quicker computations by representing heat exchanger pipes in a simplified 1D fashion. The domain dimension was chosen in order to keep the lateral and bottom surfaces far enough from the EQW, to avoid boundary effects. For the boundary conditions, a fixed temperature of 12°C [3] was assigned to the bottom domain boundary while the detected air temperature time history was assigned to the top of the domain. Thermal insulation was assigned to the lateral boundary surfaces. The water canal was directly simulated as part of the domain. The heat convective flow of water was taken into account by using inflow and outflow boundary conditions and by assigning to the canal the detected water velocity. A thermal initialization calculation was performed to start the calculation with accurate initial conditions in terms of temperature distribution within the domain [6]. The thermal conductivity, specific heat capacity and density of the different soil layers were determined through empirical correlations based on cone penetration tests results carried out near the EQW [11], corroborated by literature datasets based on the geological characterization of the soil [4]. Heat exchange between the EQW and the surrounding soil was simulated by activating the heat transfer flow within the pipes, assigning the measured inlet temperature and fluid velocity.
 An example comparison between the measured gained thermal power and the simulated results for the first 200 days of thermal activation of the EQW is shown in Figure 1(b). Except for the first 20 days of thermal activation, characterised by unreliable measurements because both the heat pump and the monitoring system were being tested to check the integrity of the system, it can be observed that the numerical simulation effectively reproduces the gained thermal power, as well as the induced temperature changes into the soil (not shown for the sake of brevity).
 After model validation against the data collected from the test field research activities continue. Further numerical parametric analyses are performed to identify the best combination of design and site parameters to maximize the energy efficiency. Additionally thermo-mechanical analyses are used to assess the magnitude of thermally induced displacements and stresses.

Biomaterials used for tissue engineering of barrier-forming cell monolayers in the eye.

Cell monolayers that form a barrier between two structures play an important role for the maintenance of tissue functionality. In the anterior portion of the eye, the corneal endothelium forms a barrier that controls fluid exchange between the aqueous humor of the anterior chamber and the corneal stroma. This monolayer is central in the pathogenesis of Fuchs endothelial corneal dystrophy (FECD). FECD is a common corneal disease, in which corneal endothelial cells deposit extracellular matrix that increases the thickness of its basal membrane (Descemet's membrane), and forms excrescences (guttae). With time, there is a decrease in endothelial cell density that generates vision loss. Transplantation of a monolayer of healthy corneal endothelial cells on a Descemet membrane substitute could become an interesting alternative for the treatment of this pathology. In the back of the eye, the retinal pigment epithelium (RPE) forms the blood-retinal barrier, controlling fluid exchange between the choriocapillaris and the photoreceptors of the outer retina. In the retinal disease dry age-related macular degeneration (dry AMD), deposits (drusen) form between the RPE and its basal membrane (Bruch's membrane). These deposits hinder fluid exchange, resulting in progressive RPE cell death, which in turn generates photoreceptor cell death, and vision loss. Transplantation of a RPE monolayer on a Bruch's membrane/choroidal stromal substitute to replace the RPE before photoreceptor cell death could become a treatment alternative for this eye disease. This review will present the different biomaterials that are proposed for the engineering of a monolayer of corneal endothelium for the treatment of FECD, and a RPE monolayer for the treatment of dry AMD.

Image-guided subject-specific modeling of glymphatic transport and amyloid deposition

The glymphatic system is a brain-wide system of perivascular networks that facilitate exchange of cerebrospinal fluid (CSF) and interstitial fluid (ISF) to remove waste products from the brain. A greater understanding of the mechanisms for glymphatic transport may provide insight into how amyloid beta (Aβ) and tau agglomerates, key biomarkers for Alzheimer’s disease and other neurodegenerative diseases, accumulate and drive disease progression. In this study, we develop an image-guided computational model to describe glymphatic transport and Aβ deposition throughout the brain. Aβ transport and deposition are modeled using an advection–diffusion equation coupled with an irreversible amyloid accumulation (damage) model. We use immersed isogeometric analysis, stabilized using the streamline upwind Petrov–Galerkin (SUPG) method, where the transport model is constructed using parameters inferred from brain imaging data resulting in a subject-specific model that accounts for anatomical geometry and heterogeneous material properties. Both short-term (30-min) and long-term (12-month) 3D simulations of soluble amyloid transport within a mouse brain model were constructed from diffusion weighted magnetic resonance imaging (DW-MRI) data. In addition to matching short-term patterns of tracer deposition, we found that transport parameters such as CSF flow velocity play a large role in amyloid plaque deposition. The computational tools developed in this work will facilitate investigation of various hypotheses related to glymphatic transport and fundamentally advance our understanding of its role in neurodegeneration, which is crucial for the development of preventive and therapeutic interventions.

Bulat-Klarica-Oreskovic Hypothesis: A Comprehensive Review.

Classical theories of cerebrospinal fluid (CSF) production and flow are taught throughout medical education. The idea that CSF is produced and/or filtered by the choroid plexus and flows in one direction throughout the ventricular system has been a largely accepted thesis. However, modern studies have called into question the validity of this hypothesis, suggesting thatCSF does not move unidirectionallybut rather is driven by microvessel contractions in a to-and-fro manner throughout the cerebrospinal system. Moreover, new insights suggest that in addition to CSF production, the exchange of fluids and proteins between the cortical vasculature and the interstitium may function as the brain's version of a lymphatic system. This comprehensive review provides evidence for a different framework of CSF flow. One that includes perivascular pulsations that push CSF back and forth, allowing exchange between the CSF and interstitium, and with CSF production occurring throughout the cerebrospinal system. These findings could be revolutionary in understanding the pathophysiology of CSF flowand in the treatment of pathologies such as intracranial hypertension, hydrocephalus, Alzheimer's disease, and many others.

Assessment of factors influencing glymphatic activity and implications for clinical medicine.

The glymphatic system is a highly specialized fluid transport system in the central nervous system. It enables the exchange of the intercellular fluid of the brain, regulation of the movement of this fluid, clearance of unnecessary metabolic products, and, potentially, brain immunity. In this review, based on the latest scientific reports, we present the mechanism of action and function of the glymphatic system and look at the role of factors influencing its activity. Sleep habits, eating patterns, coexisting stress or hypertension, and physical activity can significantly affect glymphatic activity. Modifying them can help to change lives for the better. In the next section of the review, we discuss the connection between the glymphatic system and neurological disorders. Its association with many disease entities suggests that it plays a major role in the physiology of the whole brain, linking many pathophysiological pathways of individual diseases.

Surgical treatment of idiopathic macular holes with a fovea-sparing technique and 20% SF6 gas tamponade

Purpose: To assess the macular hole (MH) closure rate and final visual acuity after idiopathic MH treatment with a modified fovea-sparing technique and 20% SF6 gas tamponade. Material and Methods: Fifteen patients (16 eyes; 12 women and 3 men; mean age (standard deviation or SD), 65.5 (5.90 years)) with Gass stage 2 to stage 4 MHs were involved in the study. Before surgery, mean best-corrected visual acuity (BCVA) (SD) was 0.15 (0.09), and mean MH diameter (SD), 437.2 (164.7) µm. Patients underwent surgical treatment with the modified fovea-sparing technique and 20% SF6 gas tamponade of two-week duration and were instructed to maintain a face-down position for a week after surgery. Results: At 1 month after the first surgery, MHs were closed in 11/16 eyes (68.75%). In addition, mean BCVA (SD) in eyes with closed MHs improved significantly from 0.15 (0.09) to 0.48 (0.16) (р = 0.000000). Of the five eyes in which the MH had failed to close after primary fovea-sparing surgery, two received a gas fluid exchange gas tamponade with 15% С3F8, and these patients were advised to maintain a face down position for 3 more weeks. In addition, in another two eyes, the vitreous cavity was revised, and the internal limiting membrane (ILM) was removed by a conventional technique with 15% С3F8 gas tamponade. Moreover, one patient rejected repeat intervention. In the four eyes in which the MH had failed to close after primary fovea-sparing surgery, after a repeat intervention, the MH was closed, and mean BCVA (SD) improved to 0.35 (0.04). There was no significant difference between the eyes in which the MH failed to close and the eyes in which the MH did close after primary surgery in terms of mean MH size (SD) (455 (203) µm versus 415 (155) µm, р = 0.66) or MH duration. Conclusion: A long gas tamponade (longer than 1 week) is required to improve the closure rate with the fovea-sparing ILM peeling technique for idiopathic MHs.

Using physical simulations to motivate the use of differential equations in models of disease spread

The SIR model is a differential equations based model of the spread of an infectious disease that compartmentalises individuals in a population into one of three states: those who are susceptible to a disease (S), those who are infected and can transmit the disease to others (I), and those who have recovered from the disease and are now immune (R). This Classroom Note describes how to initiate teaching the SIR model with two concrete physical simulations to provide students with first-hand experience with some of the nuanced behaviour of how an infectious disease spreads through a closed population. One simulation physically models disease spread by the exchange of fluids, using pH to simulate infection. A second simulation incorporates randomness through the use of a probability game to keep track of the state of each individual at each time step. Both simulations invite students to ask questions about what factors influence disease spread. The concrete experience from the physical simulations enables students to make connections to the abstract mathematical representation of the SIR model and discuss the sources of stochasticity present in the spread of an infectious disease.

Resuscitating the Endothelial Glycocalyx in Trauma and Hemorrhagic Shock.

The endothelium is lined by a protective mesh of proteins and carbohydrates called the endothelial glycocalyx (EG). This layer creates a negatively charged gel-like barrier between the vascular environment and the surface of the endothelial cell. When intact the EG serves multiple functions, including mechanotransduction, cell signaling, regulation of permeability and fluid exchange across the microvasculature, and management of cell-cell interactions. In trauma and/or hemorrhagic shock, the glycocalyx is broken down, resulting in the shedding of its individual components. The shedding of the EG is associated with increased systemic inflammation, microvascular permeability, and flow-induced vasodilation, leading to further physiologic derangements. Animal and human studies have shown that the greater the severity of the injury, the greater the degree of shedding, which is associated with poor patient outcomes. Additional studies have shown that prioritizing certain resuscitation fluids, such as plasma, cryoprecipitate, and whole blood over crystalloid shows improved outcomes in hemorrhaging patients, potentially through a decrease in EG shedding impacting downstream signaling. The purpose of the following paragraphs is to briefly describe the EG, review the impact of EG shedding and hemorrhagic shock, and begin entertaining the notion of directed resuscitation. Directed resuscitation emphasizes transitioning from macroscopic 1:1 resuscitation to efforts that focus on minimizing EG shedding and maximizing its reconstitution.

Medical Interns' Knowledge, Attitude, and Practice Toward People Living with HIV: Multicenter Experience from Saudi Arabia.

Discrimination by some healthcare providers toward people living with HIV/AIDS has been documented. Differences in cultural backgrounds make it harder for future doctors, who need a lot of knowledge and a positive attitude to treat patients. In conservative countries like Saudi Arabia, not enough is known about how much medical interns know about HIV and how they feel about people living with HIV/AIDS. From April to September 2021, this cross-sectional study use non-probability random sampling and utilized a self-administered questionnaire to collected the data from 346 medical interns who had graduated from five different medical schools. Most of the subjects correctly identified the main transmission routes, such as unprotected sex (94.57%), blood and body fluid exchange (94.19%), and sharing needles or syringes (91.47%). But they did not know what the most common co-infections were for HIV patients or how to protect themselves after exposure. This paper showed that medical interns have some stigmatizing behaviors toward patients living with HIV, as 31.1% and 22.9% agreed, respectively, that they would feel more sympathetic toward people who get AIDS from blood transfusions compared to IV drug users (IDU). Medical interns also showed some positive attitudes, as more than half of the sample (56.2%) would not isolate beds for people living with HIV/AIDS. The study's conclusion is that HIV education and training programs should be added for medical interns, which might have a significant positive impact on their attitude.

3D printed chamber for live cell imaging on an upright epifluorescence microscope

ABSTRACT Live cell imaging is a standard technique in experimental biology that enables the observation of isolated cells and tissue slices in real time and the testing of cellular responses to changes in buffer composition. However, most live cell imaging devices require the use of dedicated microscopes and/or specialised stage adaptors, and come at a reasonably high cost. We employed 3D printing technology to create a low-cost imaging chamber with side ports to exchange fluids, to be used on upright microscopes. The chamber increased the functionality of a standard upright epifluorescent microscope to allow dynamic, real-time calcium imaging of cultured hypothalamic astrocytes from mice, and to test the effects of ATP stimulation upon calcium signalling. It was also used on slices obtained from the mouse brain using a brain matrix slicer. The advantages of this chamber include a very simple design that can be used with upright epifluorescence microscopes, does not require any special stage adaptor, and includes ports to permit fluid exchange during imaging. This chamber is ideal for educational settings with undergraduate laboratories that do not have access to dedicated inverted fluorescent microscopes for tissue culture experiments.

Neuroinflammatory disorders of the brain and inner ear: a systematic review of auditory function in patients with migraine, multiple sclerosis, and neurodegeneration to support the idea of an innovative 'window of discovery'.

Hearing can be impaired in many neurological conditions and can even represent a forme fruste of specific disorders. Auditory function can be measured by either subjective or objective tests. Objective tests are more useful in identifying which auditory pathway (superior or inferior) is most affected by disease. The inner ear's perilymphatic fluid communicates with the cerebrospinal fluid (CSF) via the cochlear aqueduct representing a window from which pathological changes in the contents of the CSF due to brain inflammation could, therefore, spread to and cause inflammation in the inner ear, damaging inner hair cells and leading to hearing impairment identifiable on tests of auditory function. A systematic review of the literature was performed, searching for papers with case-control studies that analyzed the hearing and migraine function in patients with neuro-inflammatory, neurodegenerative disorders. With data extracted from these papers, the risk of patients with neurological distortion product otoacoustic emission (DPOAE) was then calculated. Patients with neurological disorders (headache, Parkinson's disease, and multiple sclerosis) had a higher risk of having peripheral auditory deficits when compared to healthy individuals. Existing data lend credence to the hypothesis that inflammatory mediators transmitted via fluid exchange across this communication window, thereby represents a key pathobiological mechanism capable of culminating in hearing disturbances associated with neuroimmunological and neuroinflammatory disorders of the nervous system.

Effect of Crude Oil on the Geotechnical Properties of Various Soils and the Developed Remediation Methods

Crude oil still affects many countries because it is one of the essential fuel sources. It makes life more manageable in modern communities and cannot be overstated because it is easy to use and find. However, the pollution caused by its use in industries such as mining, transportation, and the oil and gas business, especially soil pollution, cannot be ignored. Soil pollution is an issue in most communities because it influences people and ecology. Accidental infusions and spills of ore oils are prevalent occurrences leading to the entire or fractional exchange of the soil pore fluid by oil-contaminated soils that have affected the geotechnical engineering properties. The liquid limitations for polluted soil grades silty loam and sandy loam decreased by 38% and 16%. Oil contamination leads to decreased permeability; the permeability values for sandy loam soil decreased from (3.6 × 10−6 to 0.25 × 10−6 cm/s) when the oil content increased from 0 to 16%; however, the permeability values for silty loam decreased from (2.6 × 10−6 to 0.25 × 10−6) cm. The current study results exhibit that the geotechnical properties of contaminated soil with oil slag can be modified upon adding cement at different weight percentages (3, 5, and 7%) to the soil. The Atterberg limits and specific gravity of the soil were noticeably reduced when it was stabilised with cement, as well as because oil spills on soil significantly influence the environment. So, there is an immediate and critical need for efficiently removing petroleum hydrocarbon pollutants from contaminated soil. Bioremediation is a new technology gaining interest worldwide to clean up sites that have polluted petroleum hydrocarbons.

A novel EDM method using longitudinal-torsional ultrasonic vibration (LTV) electrodes to improve machining performance for micro-holes

This study proposes a new EDM method using longitudinal-torsional ultrasonic vibration (LTV) electrodes for micro-hole machining to address the problems of debris removal and difficult working fluid exchange in micro-hole processing, which can enhance the micro-hole machining performance. A 38.9 kHz ultrasonic vibration transducer is developed for LTV electrodes, and the fluid distribution in the micro-holes gap is simulated when LTV electrodes were used to process micro-hole. The effect of ultrasonic amplitude on flow rate and debris removal efficiency is discussed. A study is conducted to analyze the morphogenesis of the electrode extremity and the micro-hole inlet/outlet at different amplitudes. This study finds that applying appropriate ultrasonic amplitude (2–4μm longitudinal amplitude, 0.2–0.35μm torsional amplitude) to the electrode effectively reduces the electrode tip and corner wear and the flanging burr of the micro-hole inlet/outlet. Compared EDM micro-hole machining with the rotating electrode only, the material removal rate (MRR) is increased by nearly two times with the simultaneous application of 4 μm longitudinal ultrasonic amplitude and 0.35μm torsional ultrasonic amplitude to the electrode, and reduction of electrode wear and micro-hole taper by approximately 60% and 80% respectively.

Multi-scale multi-physics model of brain interstitial water flux by transcranial Direct Current Stimulation

Objective. Transcranial direct current stimulation (tDCS) generates sustained electric fields in the brain, that may be amplified when crossing capillary walls (across blood-brain barrier, BBB). Electric fields across the BBB may generate fluid flow by electroosmosis. We consider that tDCS may thus enhance interstitial fluid flow. Approach. We developed a modeling pipeline novel in both (1) spanning the mm (head), μm (capillary network), and then nm (down to BBB tight junction (TJ)) scales; and (2) coupling electric current flow to fluid current flow across these scales. Electroosmotic coupling was parametrized based on prior measures of fluid flow across isolated BBB layers. Electric field amplification across the BBB in a realistic capillary network was converted to volumetric fluid exchange. Main results. The ultrastructure of the BBB results in peak electric fields (per mA of applied current) of 32–63 across capillary wall and >1150 in TJs (contrasted with 0.3 in parenchyma). Based on an electroosmotic coupling of 1.0 × 10−9 – 5.6 × 10−10 per , peak water fluxes across the BBB are 2.44 × 10−10 – 6.94 × 10−10 , with a peak 1.5 × 10−4 – 5.6 × 10−4 interstitial water exchange (per mA). Significance. Using this pipeline, the fluid exchange rate per each brain voxel can be predicted for any tDCS dose (electrode montage, current) or anatomy. Under experimentally constrained tissue properties, we predicted tDCS produces a fluid exchange rate comparable to endogenous flow, so doubling fluid exchange with further local flow rate hot spots (‘jets’). The validation and implication of such tDCS brain ‘flushing’ is important to establish.

A 2D continuous-discrete mixed seepage model considering the fluid exchange and the pore pressure discontinuity across the fracture for simulating fluid-driven fracturing

A 2D continuous-discrete mixed seepage model considering the fluid exchange and the pore pressure discontinuity across the fracture for simulating fluid-driven fracturing

Quantifying the influence of fracture parameters on flow behavior and pressure propagation in complex networks of discrete fractures within low-permeability reservoirs

Fractures in low and ultra-low permeability reservoirs create a complex network, affecting fluid flow patterns and pressure propagation. However, limited research exists on fluid flow patterns and the impact of fracture properties on pressure within these networks. To address this, we introduce fracture shadow area and fracture penetration ratio concepts derived from studying single fracture reservoirs. Using a sophisticated model of a complex fracture network, we analyze how various fracture properties influence fluid flow patterns and reservoir pressure. Fractures are classified into five categories based on the development level. Through orthogonal experiments and multiple regression methods, we derive a formula that quantifies the pressure influence. We find that longer and denser cracks enhance fluid exchange and pressure propagation capacity. Moreover, increasing crack opening expands the area of pressure drop. Notably, fractures aligned with pressure propagation significantly decrease reservoir pressure. The hierarchical sequence of crack traits with the greatest influence is identified as crack length, crack opening, crack density, and crack angle. Our findings shed light on the intricate relationship between fracture properties and pressure dynamics.

Investigation on Water Invasion Mode and Remaining Oil Utilization Rules of Fractured-Vuggy Reservoirs: A Case Study of the Intersection Region of S99 Unit in Tahe Oilfield

Fractured-vuggy reservoirs are a new target in carbonate oil and gas exploration and development. Because of well-developed reservoir bodies, including fractures and caverns, bottom water invasion can be observed in oilfield development, with low utilization efficiency of crude oil in the reservoir. Accordingly, this study focused on the intersection region of the S99 unit of the Tahe fractured-vuggy reservoirs. Based on seismic data, the reservoir bodies can be divided into three types—caverns, fractures, and broken solution pores. Using the same location condition assignment algorithm, four single-type models are fused into a multi-scale discrete three-dimensional geological model of fractured and cavernous reservoirs, and the corresponding fractured-vuggy reservoir model was established for numerical simulation. The single-well historical fitting precision exceeded 85%. Furthermore, the development can be divided into four stages—initial stage of production, peak production stage, liquid control and oil stabilization stage, and scale gas injection stable. Streamlining sweep analysis determined the utilization and distribution characteristics of the remaining oil in the reservoir. It can be concluded that structure, caverns, and fractures were the main controlling factors affecting the remaining oil distribution in the fractured-vuggy reservoir. The fluid exchange among single-well reserve zones was calculated using streamline-based quantitative sweep analysis and interwell flow quantitative analysis method. Through source-sink quantitative analysis, interwell flow relations were derived, and three water breakthrough modes were further concluded: violent flooding, slow ascending of water cut, and low cut or intermittent water production.

A randomized controlled comparative study of different fluid exchange modes in urgent-start peritoneal dialysis in patients with end-stage renal disease: automated peritoneal dialysis combined with manual fluid exchange vs. manual fluid exchange alone

During urgent-start peritoneal dialysis (USPD) in end-stage renal disease (ESRD) patients, both adequate dialysis and skill training for fluid exchange are essential. However, automated peritoneal dialysis (APD) alone or manual fluid exchange peritoneal dialysis (MPD) alone could meet the above demands. Therefore, our study combined APD with MPD (A-MPD), and compared A-MPD with MPD, aiming to find the most appropriate treatment mode. This was a single-center, prospective, randomized controlled study. All eligible patients were randomized into the MPD and A-MPD groups. All patients underwent a five-day USPD treatment 48 h after catheter implantation, and they were followed up for six months after discharge. Overall, 74 patients were enrolled in this study. Among these, 14 and 60 patients quit due to complications during USPD and completed the study (A-MPD = 31, MPD = 29), respectively. Compared with MPD, the A-MPD treatment mode had a better effect on removing serum creatinine, blood urea nitrogen, and potassium and improving serum carbon dioxide combining power levels; it had less time expenditure on the fluid exchange by nurses (p < 0.05). In addition, patients in the A-MPD group had higher scores on the skill tests than those in the MPD group (p = 0.002). However, no significant differences in short-term peritoneal dialysis (PD) complications, PD technical survival rate, or mortality were found between the two groups. Therefore, the A-MPD mode could be recommended as an adoptable and suitable PD modality for USPD in the future.