Search Results (152)

We investigate the partial differential equation system which describes the double-diffusion convection phenomena with the reduction formalism. Double-diffusion refers to when two scalar quantities with different diffusivity, such as heat and solute concentration, contribute to density gradients within a fluid under the influence of gravity. The time-dependent self-similar trial function is applied and analytic results are presented for the dynamical variables and analyzed in detail. Additionally, the entropy production was derived as well. In the second part of the study we investigate the role of an additional heat source. Full article

CO₂ displacement is a key technique that was examined through numerical methods in a 3D Hele–Shaw cell, with CO₂ as the displacing phase and shear-thinning fluids as the displaced phase. Without interfacial tension effects, the displacement shows branching patterns forming two vertically symmetric fingers, regardless of whether the displacing fluid is air or CO₂. Under CO₂ displacement, viscous fingering propagates farther and achieves higher displacement efficiency than air. Compared with air displacement, the finger advancing distance increases by 0.0035 m, and the displacement efficiency is 15.2% higher than that of air displacement. Shear-thinning behavior significantly influences the process; stronger shear thinning enhances interfacial stability and suppresses fingering. As the power-law index n increases (reducing shear thinning), the fingering length extends. Variations in interfacial tension reveal it notably affects fingering initiation and velocity in CO₂ displacement of non-Newtonian fluids, but has a weaker impact on fingering formation. Interfacial tension suppresses short-wavelength perturbations, critical to interface stability, jet breakup, and flows, informing applications like foam-assisted oil recovery and microfluidics. Full article

The evolution of a flame front in a channel was considered in a two-dimensional approximation. In the approximation of the potential flow of combustion products and unburned mixture, the formation of a finger-shaped flame was considered after ignition at the closed end of the channel, on the channel axis, and on the side wall of the channel. The prerequisites for the formation of a tulip-shaped flame were considered in a potential approximation. The method of conformal mapping was used. Simple analytical functions were used that allowed equipotential lines and streamlines to be transformed. The shape of the flame front was obtained. The analytical results were compared with the experimentally obtained results of the flame front evolution and with numerical results obtained by other authors. The conditions for the applicability of the conformal mapping to a reacting gas mixture were given. Full article

Raynaud’s Phenomenon (RP), characterized by episodic reductions in peripheral blood flow, leads to significant discomfort and functional impairment. Existing therapeutic strategies focus on pharmacological treatments, external heat supplementation and exercise-based rehabilitation, but fail to address biomechanical contributions to vascular dysfunction. We introduce a computational approach rooted in topological transformations of hand prehension, hypothesizing that specific hand postures can generate transient geometric structures that enhance thermal and hemodynamic properties. We examine whether a flexed hand posture—where fingers are brought together to form a closed-loop toroidal shape—may modify heat transfer patterns and blood microcirculation. Using a combination of heat diffusion equations, fluid dynamics models and topological transformations, we implement a heat transfer and blood flow simulation to examine the differential thermodynamic behavior of the open and closed hand postures. We show that the closed-hand posture may preserve significantly more heat than the open-hand posture, reducing temperature loss by an average of 1.1 ± 0.3 °C compared to 3.2 ± 0.5 °C in the open-hand condition (p < 0.01). Microvascular circulation is also enhanced, with a 53% increase in blood flow in the closed-hand configuration (p < 0.01). Therefore, our findings support the hypothesis that maintaining a closed-hand posture may help mitigate RP symptoms by preserving warmth, reducing cold-induced vasoconstriction and optimizing peripheral flow. Overall, our topologically framed approach provides quantitative evidence that postural modifications may influence peripheral vascular function through biomechanical and thermodynamic mechanisms, elucidating how shape-induced transformations may affect physiological and pathological dynamics. Full article

Background/Objectives: Mechanical compression of the median nerve is believed to be responsible for idiopathic carpal tunnel syndrome (CTS) due to fibrosis of the subsynovial connective tissue (SSCT). Vascular consequences have also been observed in structures of the carpal tunnel, raising speculation regarding the role of factors such as ischemia and edema in CTS pathology. Methods: We performed a mega-analysis from our database of over 10 years of studies. Mixed-effects models were used to address the disconnect between mechanical and vascular influences on CTS; the effects of biomechanical factors and CTS status were evaluated on carpal tunnel tissue mechanics and blood flow. Altered blood flow was also induced during tissue motion to draw inferences regarding the cyclical relationship between tissue mechanics and fluid flow changes on CTS pathology. Results: Greater movement speed and flexed wrist postures were found to contribute to greater shear strain. Flexed wrist postures and greater fingertip force were found to increase median nerve blood flow. Greater CTS severity was associated with lower median nerve blood flow. Finally, brachial blood flow restriction as a surrogate for elevated carpal tunnel pressure was found to alter tissue motion and increase carpal tunnel tissue shear strain. Conclusions: Finger movement speed, force application, wrist posture, and altered fluid flow in the carpal tunnel contribute to changes in outcomes associated with the development of CTS. The mechanistic findings from this paper should be incorporated into future research to update the damage model for CTS pathology. Full article

CO₂-enhanced tight oil production can increase crude oil recovery while part of the injected CO₂ is geologically sequestered. This process is influenced by factors such as gas injection rate, oil/gas viscosity ratio, and contact angle. Understanding how these factors affect recovery during CO₂ non-mixed-phase substitution is essential for improving CO₂-enhanced tight oil production technology. In this study, three-dimensional pore structure was numerically simulated using physical simulation software. The effects of three key parameters—the gas injection rate, contact angle and viscosity slope—on flow displacement during a CO₂ non-mixed-phase drive were analyzed. In addition, the study compares the fluid transport behavior under mixed-phase and non-mixed-phase conditions at the pore scale. The simulation results show that increasing the replacement velocity significantly expands the diffusion range of CO₂ and reduces the capillary fingering phenomenon. In addition, the saturation of CO₂ increases with the increase in the viscosity ratio, which further improves the diffusion range of CO₂. The wetting angle is not simply linearly related to the drive recovery, and the recovery is closely related to the interfacial tension and capillary force under the influence of wettability. The recoveries under mixed-phase conditions were slightly higher than those under unmixed-phase conditions. During the mixed-phase replacement process, CO₂ is dissolved into the crude oil, resulting in oil volume expansion, which improves the distance and extent of CO₂ permeation. Full article

Spontaneous pattern formation is a universal phenomenon that occurs in purely physical systems, biology, and human societies. Salt fingering due to differential diffusion of heat and salt in seawater is a typical example, although the general principle that governs pattern formation remains unknown. We show through simple experiments injecting a salt solution into a sucrose solution of equal density that a salt finger exhibits characteristic pattern transitions depending on the injection flow rate. When the rate increases, a linear finger starts meandering, branching, and multiple branching, whereas when the rate is decreased, it produces a beading pattern. These morphological instabilities and associated pattern formation are caused by a local accumulation of kinetic energy that minimizes the flow resistance and maximizes the energy dissipation in the final steady state. We suggest that this energy accumulation mechanism governs a wide variety of pattern formation phenomena in non-equilibrium systems, including morphogenesis of abiotic protocells. Full article

MicroRNA122 (miR-122) is a microRNA that is highly expressed in hepatocytes and has been identified as a prospective therapeutic target and biomarker for liver injury. An expanding body of research has demonstrated that miR-122 is a critical regulator in both the initiation and progression of a wide range of liver diseases. Traditional methods for detecting miR-122 mainly include Northern blotting and qRT-PCR, but they are technically complex and cumbersome, requiring expensive instruments and high technical requirements. In this paper, we present a novel rapid testing method utilizing a lateral flow nucleic acid biosensor (LFNAB) for the sensitive and time-efficient detection of miR-122. This approach offers several advantages, including a high specificity for miR-122, the ability to detect low concentrations of the target molecule, and a significantly reduced testing time compared to conventional detection methods. In this study, a thiol-modified single-stranded detection DNA probe (Det-DNA), a biotinylated single-stranded capture DNA probe (Cap-DNA), and a biotinylated single-stranded control DNA probe (Con-DNA) are used to construct the LFNAB. A gold nanoparticle (AuNP) is a colored tag, which is used to label the Det-DNA probe. The principle of detecting miR-122 is based on dual DNA-miRNA hybridization reactions on the LFNAB to form sandwich-type AuNP-Det-DNA-miR-122-Cap-DNA complexes, which are captured on the test area of LFNAB for visualization and quantification. After systematic optimization of conditions of experiment, the response of LFNAB was highly linear within the scope of 0 pM-100 pM miR-122, and the detection limit in 15 min was 3.90 pM. The use of LFNAB to detect miR-122 in serum and fingertip blood has yielded satisfactory results. This successful application indicates the effectiveness of LFNAB in detecting miR-122 in both serum and fingertip blood samples, showcasing its potential utility in clinical and research settings for assessing miR-122 levels in different biological samples. Full article

(1) Background: To develop a novel capillary refill time measurement system and evaluate its reliability and reproducibility. (2) Methods: Firstly, the utilization of electromagnetic pressure technology facilitates the automatic compression and instantaneous release of the finger. Secondly, the employment of pressure sensing technology and photoelectric volumetric pulse wave analysis technology enables the dynamic monitoring of blood flow in distal tissues. Thirdly, the subjects were recruited to compare the average measurement time and the number of measurements required for successful measurements. The satisfaction of doctors and patients with the instrument was investigated through the administration of questionnaires. Finally, 71 subjects were recruited and divided into two groups, A and B. Three doctors repeated the measurement of the right index fingers of the subjects. In Group A, the same measuring instrument was used, and the consistency of the measurements was evaluated using the intragroup correlation coefficient. In Group B, one doctor repeated the measurement of each subject three times using the same measuring instrument, and the reproducibility of the CRT was evaluated using the analysis of variance of the repeated measurement data. (3) Results: The development of the capillary refill time meter was successful, with an average measurement time of 18 s and a single measurement. This study found that doctor–patient satisfaction levels were 98.3% and 100%, respectively. The intraclass correlation coefficient was 0.995 in Group A, and the p-value was greater than 0.05 in Group B. (4) Conclusions: The non-invasive monitoring of microcirculation has been rendered both rapid and effective, thus paving the way for the further mechanization and standardization of this process. The CRT, when measured using the capillary refill time meter test machine, demonstrated consistent and reproducible results, both when assessed by different researchers and when evaluated across varying measurement sets. Full article

The characteristics of CO₂ seepage in reservoirs have important research significance in the field of CCS technology application. However, the characteristics of macro-scale seepage are affected by the geometrical characteristics of micro-scale media, such as pore size and particle shape. Therefore, in this work, a series of numerical simulations were carried out using the phase field method to study the effect of pore structure simplification on micro-scale displacement process. The influences of capillary number, wettability, viscosity ratio, interfacial tension, and fracture development are discussed. The results show that the overall displacement patterns of the real pore model and the simplified particle model are almost similar, but the oil trapping mechanisms were totally different. There are differences in flow pattern, number of dominant flow channels, sensitivity to influencing factors and final recovery efficiency. The real pore model shows higher displacement efficiency. The decrease in oil wet strength of rock will change the CO₂ displacement mode from pointing to piston displacement. At the same time, the frequency of breakage will be reduced, thus improving the continuity of CO₂. When both pores and fractures are developed in the porous media, CO₂ preferentially diffuses along the fractures and has an obvious front and finger phenomenon. When CO₂ diffuses, it converges from the pore medium to the fracture and diverges from the fracture to the pore medium. The shape of fracture development in the dual medium will largely determine the CO₂ diffusion pattern. Full article

Background: Low-energy far-infrared rays (FIRs) are widely used in the treatment of wounds, lymphedema, and various vascular diseases, and various types of products that emit infrared rays are being used at home for patients with blood flow-related diseases without experimental evidence. Methods: Blood flow and epidermal temperature were measured while applying conductive heat and FIRs via an electric mat (non-intervention) or a loess bio-ball mat (intervention). Results: In the control group (n = 30), there was a minimal change in blood flow and epidermal temperature in the right and left middle fingers (LMF, RMF) as the mat temperature gradually increased. In the experimental group (n = 30), when the mat temperature increased from 25 °C to 50 °C, the blood flow increased by 39.80% in the LMF and by 41.83% in the RMF. In addition, the epidermal temperature increased by 8.78% in the LMF and by 8.44% in the RMF. Conclusions: The FIRs emitted from loess bio-balls can be applied to alleviate symptoms not only in patients with blood flow problems in medical settings but also in people who complain of discomfort due to blood flow disorders or cold hands and feet during their daily life and sleep. Full article

Optically pumped magnetometer magnetoencephalography (OPM-MEG) represents a novel method for recording neural signals in the brain, offering the potential to measure critical neuroimaging characteristics such as effective brain networks. Effective brain networks describe the causal relationships and information flow between brain regions. In constructing effective brain networks using Granger causality, the noise in the multivariate autoregressive model (MVAR) is typically assumed to follow a Gaussian distribution. However, in experimental measurements, the statistical characteristics of noise are difficult to ascertain. In this paper, a Granger causality method based on a cost-reference particle filter (CRPF) is proposed for constructing effective brain networks under unknown noise conditions. Simulation results show that the average estimation errors of the MVAR model coefficients using the CRPF method are reduced by 53.4% and 82.4% compared to the Kalman filter (KF) and maximum correntropy filter (MCF) under Gaussian noise, respectively. The CRPF method reduces the average estimation errors by 88.1% and 85.8% compared to the MCF under alpha-stable distribution noise and the KF method under pink noise conditions, respectively. In an experiment, the CRPF method recoversthe latent characteristics of effective connectivity of benchmark somatosensory stimulation data in rats, human finger movement, and auditory oddball paradigms measured using OPM-MEG, which is in excellent agreement with known physiology. The simulation and experimental results demonstrate the effectiveness of the proposed algorithm and OPM-MEG for measuring effective brain networks. Full article

Clubbing finger is a significant clinical indicator, and its early detection is essential for the diagnosis and treatment of associated diseases. However, traditional diagnostic methods rely heavily on the clinician’s subjective assessment, which can be prone to biases and may lack standardized tools. Unlike other diagnostic challenges, the characteristic changes of clubbing finger are subtle and localized, necessitating high-precision feature extraction. Existing models often fail to capture these delicate changes accurately, potentially missing crucial diagnostic features or generating false positives. Furthermore, these models are often not suited for accurate clinical diagnosis in resource-constrained settings. To address these challenges, we propose MSG-YOLO, a lightweight clubbing finger detection model based on YOLOv8n, designed to enhance both detection accuracy and efficiency. The model first employs a multi-scale dilated residual module, which expands the receptive field using dilated convolutions and residual connections, thereby improving the model’s ability to capture features across various scales. Additionally, we introduce a Selective Feature Fusion Pyramid Network (SFFPN) that dynamically selects and enhances critical features, optimizing the flow of information while minimizing redundancy. To further refine the architecture, we reconstruct the YOLOv8 detection head with group normalization and shared-parameter convolutions, significantly reducing the model’s parameter count and increasing computational efficiency. Experimental results indicate that the model maintains high detection accuracy with reduced parameter and computational requirements. Compared to YOLOv8n, MSG-YOLO achieves a 48.74% reduction in parameter count and a 24.17% reduction in computational load, while improving the mAP0.5 score by 2.86%, reaching 93.64%. This algorithm strikes a balance between accuracy and lightweight design, offering efficient and reliable clubbing finger detection even in resource-constrained environments. Full article

To effectively address the issue of premature failure caused by the unbalanced distribution of pressure drops between the stages of a traditional two-stage finger seal, this study proposes a method to improve the pressure drop balance by increasing the protection height of the second stage back plate. We established a new numerical calculation model for a two-stage finger seal, based on the porous media model. After verifying the precision of the model, we conducted a numerical analysis to examine the impact of the protection height of the second stage back plate on the flow and heat transfer characteristics of the two-stage finger seal. We then conducted a differentiated structural design for each stage of the two-stage finger seal. The research results are as follows: the pressure drop at the second stage of the traditional two-stage finger seal exceeds that of the first stage; when the protection height of the second stage back plate of the traditional two-stage finger seal is increased from 1.5 mm to 1.57 mm, forming a two-stage pressure equalizing finger seal structure, the pressure drop between the two stages is balanced, but the leakage is greater than that of the traditional two-stage finger seal; a grate seal structure was arranged between the first and second stages of the two-stage pressure equalizing finger seal to form a two-stage pressure equalizing finger seal with grate teeth, which exhibits significantly lower leakage compared to the two-stage pressure equalizing finger seal. However, the proportion of pressure drop at the first and second stages of the two-stage pressure equalizing finger seal is 36.8% and 42.1%, respectively, while the grate tooth stage accounts for 21.1%, resulting in an imbalanced pressure drop once again. Increasing the protection height of the second stage back plate in the two-stage pressure equalizing finger seal with grate teeth to 1.6 mm results in a 37.5% pressure drop at the first and second stages, and a 25% pressure drop at the grate tooth stage. The two-stage finger seal balances the pressure drop and matches the leakage of the traditional two-stage finger seal. The maximum temperatures of the first and second stages of the finger seal are 0.7% lower and 2.6% higher compared to the traditional two-stage finger seal. This suggests that a differential multi-stage finger seal is the optimal structure. Full article

We present the case of a 23-year-old woman who reported weakness in the left upper limb, decreased warmth, numbness in the fingers, pain in the clavicular region, and a severe cold sensation in the limb. A thermal imaging camera examination was performed for diagnostic purposes, which guided further diagnostic and therapeutic management towards arterial thoracic outlet syndrome (aTOS). Following surgery and rehabilitation procedures, significant remission of symptoms was achieved and the patient’s condition improved. This is the first report on the diagnosis of aTOS using thermal imaging, paving the way for further clinical research into this effective, rapid, and radiation-free method of diagnostic imaging. Conclusion: Thermal imaging is one of the most effective, readily available, and patient-safe methods for diagnosing vascular disease associated with flow disruption. Full article