Changes In Diameter Research Articles

Studying Radiation-Induced Degradation of Reinforced Concrete Structures: Review and Numerical Analysis of Reinforcement Corrosion Processes in Concrete

This study addresses the operational degradation of reinforced concrete structures of buildings and facilities where radioactive materials and waste are handled, if degradation is caused by the joint effect of ionizing radiation from materials (substances) handled and factors affecting the overall aging of concrete, reinforcement bars, and their combination. The research focuses on gamma radiation and its physical, chemical, and mechanical effects, triggering corrosion processes in reinforcement bars during the operation of reinforced concrete structures. Changes in the structural behavior of existing and newly built facilities, where radioactive materials and waste (with a focus on highly and moderately radioactive waste) are handled, must be predictable during the extended period of operation. Prognostication methods and assessment models must be accessible to various specialists, including design engineers. Available software packages and numerical analysis tools are used to devise these methods and models. This research project demonstrates the numerical modeling of electrochemical corrosion triggered by oxygen diffusion in concrete. The COMSOL Multiphysics software package was used to develop a model of a reinforced concrete wall segment. This model was used to analyze and prognosticate electrochemical processes in a structure during its future operation. Results of numerical modeling show that corrosion-triggered changes in the original diameter of reinforcement do not exceed tenths (11.2–12.4%) for the predicted service life of 100 years. Studies should be continued in this direction because such factors as radiolysis, carbonization, radiation heating, and changes in the aggregate can have an adverse effect on structures during their operation.

Indoleamine 2, 3-dioxygenase Regulates the Differentiation of T Lymphocytes to Promote the Growth of Gastric Cancer Cells through the PI3K/Akt/mTOR Pathway.

To investigate the regulatory mechanism of indoleamine 2, 3-dioxygenase (IDO) in T lymphocyte differentiation and its role in promoting the growth of gastric cancer (GC) cells through the PI3K/Akt/mTOR pathway. GC cell lines (MFC and NCI-N87) and PBMC cells were co-cultured and IDO inhibitor 1-methyl-tryptophan (1-MT) was added. The proliferation was detected by CCK-8, the apoptosis was detected by flow cytometry, and the contents of TNF-α, IL-1β, IL-6, IL-8, and INF-γ were detected by ELISA. The expression levels of PI3K, p-PI3K, Akt, p-Akt, mTOR, and p-mTOR were tested using Western blot, and the proportion of CD4+/CD8+, CD4+CD25+Foxp3+Treg cells was detected by flow cytometry. C57BL/6 mice were used to establish the MFC GC mouse model and treated with 1-MT. The changes in body weight and tumor diameter were measured. Ki-67, CD4+, CD8+, and CD25+ expressions were detected by immunohistochemistry. IDO promoted the proliferation of MFC and NCI-N87 cells, inhibited apoptosis, and decreased the levels of TNF-α, IL-1β, IL-6, IL-8, and INF-γ in the supernatant after co-culture with BPMC. The expressions of p-AKT, p-mTOR, and p-PI3K increased after 1-MT treatment. The proportion of CD4+/CD8+ cells was increased and the proportion of Treg cells was decreased in PBMC cells after the addition of 1-MT. Overexpression of IDO suppressed T cells differentiation by inhibiting the PI3K/Akt/mTOR pathway. In vivo, 1-MT treatment reduced the tumor size and weight, increased CD4+ and CD8+ positive area proportion, and decreased Ki-67 and CD25+ positive area proportion. Co-culture of GC cells and immune cells promotes the proliferation of GC cells and inhibits apoptosis, which can be reversed by 1-MT. IDO may suppress the proliferation of T lymphocyte through inhibiting the PI3K/Akt/mTOR signaling pathway. This provides new evidence for the potential of exploiting IDO inhibitors for GC treatment.

Assessment of Facial Pain After Internal Carotid Artery Stenting: The Role of External Carotid Artery Overstenting

Background: The external carotid artery (ECA) supplies blood to various facial and neck regions and may contribute to collateral cerebral perfusion. With the rise in carotid artery stenting (CAS) as a treatment for carotid stenosis, ECA overstenting has become a common procedure feature. This study aimed to assess the incidence, characteristics, and duration of facial pain following CAS, hypothesizing that ECA overstenting may contribute to facial pain. Materials and Methods: This prospective study included 55 patients treated with CAS for internal carotid artery (ICA) stenosis at a single center. Patients’ facial pain was evaluated using a numeric rating scale (NRS) before, immediately after, and 24 h post-CAS. Patient data, including demographics, comorbidities, and procedural details, were analyzed to assess the relationship between ICA stenosis degree, ECA diameter changes, and facial pain incidence. Results: CAS was associated with intraoperative facial pain in 27.27% of patients, with 7.28% reporting residual pain 24 h post-procedure. Pain occurrence was significantly higher in patients with lower ICA stenosis (p = 0.04). The median ECA diameter decreased from 4.11 mm to 3.16 mm (p < 0.001) after CAS, with ECA overstenting observed in 96.4% of cases. No significant relationship was found between pain severity and stent width or length. Conclusions: This study highlights that CAS significantly decreases the diameter of ECA. Additionally, ECA overstenting might be associated with perioperative and postoperative facial pain, emphasizing the need for careful monitoring of ECA patency following CAS.

Visualization Study of Methane Deflagration Characteristics in Variable Diameter Pipelines Based on Schlieren Technique

ABSTRACT The phenomenon of pipe diameter change often exists in urban natural gas pipelines. To study the impact of pipe diameter variation on the propagation characteristics of combustible gas deflagration and provide theoretical basis for the prevention and emergency treatment of gas pipeline explosion accidents, this work uses a self-developed circular explosion pipe test bench with a length of 12 m and an inner diameter of 90 mm to study the methane deflagration characteristics in variable diameter pipelines. Under four experimental conditions of variable cross-sectional area ratio (VR) of 1.0, 0.6, 0.4, and 0.2, the schlieren images of the deflagration process of methane/air premixed gas with a methane concentration of 9.5% were captured by a high-speed camera. Combined with the traditional pressure and flame signal point source information, the research results show that the existence of variable diameter pipelines can change the flame structure and shape, causing the flame front to transform into a tulip flame in advance. The flame propagation speed under different experimental conditions is: VR = 0.4 > VR = 0.2 > VR = 0.6. The influence of the variable diameter pipeline on flame velocity depends on the suppression effect of the reflected wave generated by the cross-section area of the variable diameter pipe and the coupling effect of the reduced aperture area of the variable diameter section on the flame acceleration effect. When the reflected wave acts on the flame front, the flame propagation speed decreases, and in severe cases, it will cause flame stagnation and backfire.

Capabilities of positron emission tomography/computed tomography in a comparative assessment of the effect of various targeted therapy options in patients with <i>EGFR</i>-mutated non-small-cell lung cancer

BACKGROUND: No publications in the Russian medical literature have examined the potential of positron emission tomography combined with computed tomography through a comparative evaluation of the effect of various targeted therapies involving tyrosine kinase inhibitors in patients with non-small cell lung cancer and mutations in the EGFR gene. AIM: To explore the capabilities of positron emission tomography combined with computed tomography based on the RECIST 1.1 criteria and changes in SUVmax and SUVmean metabolic parameters for the comparative assessment of the tumor response to targeted monotherapy and combination therapy with tyrosine kinase inhibitors in patients with EGFR-mutant non-small cell lung cancer. MATERIALS AND METHODS: The 2019–2022 examination records of positron emission tomography combined with computed tomography with 18F-fluorodeoxyglucose (18F-FDG) in 105 patients with non-small cell lung cancer were analyzed, including 75 patients with EGFR-activating mutation. The radiation exposure was adjusted individually and ranged from 45 to 90 mSv. The volume activity of the 18F-FDG radiopharmaceutical was 260–500 MBq. The change in the total largest diameters of the target lesions and SUVmax and SUVmean metabolic parameters were assessed before treatment initiation and 1.5–2.0 months after it. The follow-up duration for the changes in positron emission tomography combined with computed tomography findings in 17 patients with non-small cell lung cancer was at least 12 months. RESULTS: According to positron emission tomography combined with computed tomography images and SUVmax and SUVmean changes, disease progression was significantly less common (p = 0.043 and p =0.029) in patients with EGFR-mutant non-small cell lung cancer from Groups 2 and 3 who received combination therapy with tyrosine kinase inhibitors and bevacizumab or chemotherapy than in Group 1 and control group (4.2% vs. 20.0%–21.8%). An insignificant trend (p =0.092) to a higher partial response to therapy (58.3% vs. 40.0%) was noted. Similar changes in the total largest diameters of the target lesions at the early stage of therapy appeared to be not significant (p =0.187). Within the long-term follow-up of some patients with non-small cell lung cancer, in at least 50% of cases, changes in the total largest lesion diameters are consistent with the relevant SUVmax and SUVmean alterations found in the first control study. CONCLUSIONS: Based on the positron emission tomography combined with computed tomography data and alterations in SUVmax and SUVmean metabolic parameters, the early tumor response to combined therapy with tyrosine kinase inhibitors and bevacizumab or chemotherapy compared with targeted monotherapy with tyrosine kinase inhibitors or chemotherapy of the control group was characterized by a significantly lower rate of metabolic disease progression, although a similar tendency of the change in the total largest diameters of target lesions according to RECIST 1.1. was not significant. Changes in SUVmax and SUVmean metabolic parameters at the early stage of therapy are at least 50% faster than similar changes in the total largest diameters of the target lesions, which can be used for the timely identification of patients with a high risk of further progression as determined by RECIST 1.1.

Aerodynamic analysis of flattened pappus structures with linearly radial changes in filament diameter

Significant advances have been made in understanding the interaction between airflow and dandelion seed pappus models consisting of a central disk and tens of filaments. Previous theoretical analyses and numerical simulations assumed a radially constant filament diameter. However, experimental measurements revealed that the filament diameter could vary radially. The effect of radial variations in filament diameter on the interaction between airflow and dandelion seeds has not yet been explored. This piece of work, therefore, numerically investigated the flow patterns around five flattened pappus models with linearly radial changes in filament diameter and the aerodynamic forces acting on these models, across particle Reynolds numbers from 38 to 603. The vortex size, pressure coefficient and streamwise speed in the wake zones in the xoz plane (The z-axis coincides with the symmetry axis of the pappus structure.), the pressure coefficient, radial speed and streamwise speed in the xoy plane, the drag coefficient of the entire pappus model, and the aerodynamic force acting on a single filament were quantitatively analyzed and compared across the five models. It reveals that the radial change in filament diameter indeed results in the variations in these physical quantities among the five models. The variations can be significantly influenced by the particle Reynolds number, although these physical quantities exhibit different degrees of sensitivity. Our findings here will enhance the modeling of dandelion seed dispersal by wind and aid in optimizing the design of micro aircraft inspired by the architecture of real dandelion seed pappus structures.

Late intervention for type II endoleak is not determined by early sac diameter or volume changes after EVAR.

To compare the diagnostic accuracy and predictive value of aneurysm sac volume measurement versus maximum diameter measurement of abdominal aortic aneurysm sac after endovascular aneurysm repair (EVAR) in patients with type II endoleak. Retrospective study on a cohort of 103 patients who presented with a type II endoleak after EVAR for infrarenal abdominal aortic aneurysm. Maximum diameter and volumetric measurements were calculated on computed tomography follow-up scans at 3 months and 1 year after index surgery. Pearson correlation coefficient was used to determine linear association between diameter and volume; Mann-Whitney U test was used to compare patients with and without later intervention for type II endoleak with regard to diameter and volume change. The correlation between diameter and volume measurement was high (Rho: 0.890-0.980 with P < 0.0001). In 38 out of 103 patients (37%) with type II endoleak, a later intervention for endoleak management was performed; early diameter (P = 0.097), or volume (P = 0.387) change could not predict risk for later intervention. Both diameter and volume measurements can be used in the imaging follow-up of patients with endoleak type II after EVAR; however early changes in diameter or volume of the aneurysm sac cannot predict late intervention for type II endoleak.

Parametric Sensitivity Analysis of Mooring Chains of a Floating Offshore Wind Turbine in Shallow Water

Floating offshore wind turbines (FOWTs) are severely restricted in numerous sea areas due to challenges from the strong nonlinear characteristics of mooring chains in shallow water (less than 50 m). Therefore, this paper introduces a design method of mooring chains of a FOWT at a water depth of 44 m and carries out a parametric sensitivity analysis on length, nominal diameter, and clump weights of mooring chains. The results of the study found that compared with the mooring chains in deep water, the mooring chains in shallow water show obvious nonlinear characteristics in mooring tension, the lying section of the mooring chain on the seabed, and the mooring chain spatial angle, which brings great risk to the safe operation of FOWTs. The change in the nominal diameter of the mooring chain has a certain impact on the dynamic characteristics of a FOWT, but it is not as significant as that from the change in the length of the mooring chain. In addition, a mooring chain in shallow water is prone to the slack–taut phenomenon; thus, this paper puts forward an optimization investigation using clump weights at the suspension section of the mooring chain, which improved the performance of the mooring chain significantly.

A Relative Permeability Model of Coal Based on Fractal Capillary Bundle Assumption

Summary As the pore and fracture structure of coal significantly influence gas-water relative permeability (GWRP), it is crucial to study the GWRP in coal reservoirs for optimizing gas production. This paper provided parameters such as pore size range and capillary bundle porosity by referring to existing mercury intrusion porosimetry (MIP) experiments. The effective porosity coefficient and gas-water phase critical pore size were introduced to improve the GWRP model for coal based on the assumption of fractal capillary bundle. The GWRP model depends on changes in phase saturation, maximum and minimum capillary tube pore diameters, porosity, capillary size distribution dimension Df, and fractal dimension of tortuosity Dt. It demonstrated that models for various coal samples from the southern Qinshui Basin exhibit good agreement with the GWRP experimental data. In addition, the improved GWRP model was used to simulate coalbed methane (CBM) production and water production. The findings suggested that as water and gas are continuously extracted, effective stress rises as reservoir pressure and water saturation decline, leading to a more even distribution of capillary diameter and an increase in capillary degree. Furthermore, the effect of structural parameters on CBM production was also discussed.

The Influence of Non-Pressure Pipes Filled to Different Degrees on the Hydraulic Characteristics of Channel–Pipe Combined Irrigation Systems

Modern irrigation areas often use a combination of channels and pipes for irrigation. Due to changes in terrain, inflow, and pipe diameter, pipelines are often prone to experiencing a state of no pressure. This lack of pressure affects not only the velocity distribution and water surface profile of the main channel but also the velocity distribution and flow distribution of the pipeline. Therefore, in this study, we employed a combination of physical model experiments and theoretical analysis to study the influence of non-pressure pipelines on the hydraulic characteristics of channel–pipe combined irrigation systems filled to different degrees. Through this, the variation laws of the flow velocity distribution, turbulence intensity, water surface, diversion width, and diversion ratio under different filling degrees were obtained. The non-pressure pipeline flow velocity expression was obtained through dimensional analysis, and the calculation formula for the non-pressure pipeline flow velocity coefficient was fitted using linear regression analysis. The relative error between the calculated value and the measured value did not exceed 8.81%. The research results presented in this article can provide technical support for the design and maintenance of channel–pipe combined irrigation systems.

Safety and efficacy of percutaneous mechanical thrombectomy in the treatment of acute medium- or high-risk pulmonary embolism: a single-center retrospective cross-sectional study.

Patients with acute and high-risk pulmonary embolism have a high mortality rate, and the optimal treatment for these patients has still not been fully established. Although anticoagulation therapy is currently the preferred treatment for pulmonary embolism, for some patients with intermediate- or high-risk pulmonary embolism, anticoagulation therapy alone has a higher probability of long-term pulmonary hypertension and also seriously worsens the quality of life of patients. This paper mainly reports the efficacy and safety of percutaneous mechanical thrombectomy (PMT) in patients with acute medium- or high-risk pulmonary embolism in Taizhou Hospital of Zhejiang Province so as to provide some clinical basis for the treatment of such patients in the future. This study mainly collected the clinical data of 43 patients who were admitted to Taizhou Hospital of Zhejiang Province from May 2018 to May 2023 due to acute medium-to-high-risk pulmonary embolism and received PMT treatment. Preoperative and postoperative blood tests, vital signs, and echocardiographic parameters were compared. The incidence of intraoperative and postoperative complications in follow-up at 1, 6, and 12 months was also recorded. Mechanical treatment included thrombus fragmentation complemented with aspiration. Among the 43 patients, 22 patients were treated with thrombus fragmentation coupled with a pigtail catheter and aspiration using a 6-F multipurpose angiographic (MPA) catheter, 11 were treated by AngioJet, and 10 were treated with an AcoStream catheter. Local thrombolysis treatment with small dose of urokinase was administered in some patients according to the patient's risk of bleeding. Among the patients, 41 patients received a successful operation, representing a surgical success rate of 95.3%. There was one patient with pulmonary infection who died after discharge. There were significant differences in vital signs between the 48-hour preoperative timepoint and the 48-hour postoperative timepoint including cardiac index, pulse, mean arterial pressure, and oxygen saturation (P<0.001). The blood test indicators of carbon dioxide partial pressure and creatinine level did not show obvious abnormalities, but differences in hemoglobin, oxygen partial pressure, and lactate level were statistically significant. In terms of cardiac ultrasound, pulmonary artery pressure and right atrial diameter change were significantly different (P<0.001). There were seven cases of local hematoma at the puncture site, three cases of infection at the puncture site, and nine cases of transient cardiac arrest during the operation. All 41 patients were followed up: one patient died after being discharged due to aggravation of pulmonary infection during hospitalization, one patient died of intracerebral hemorrhage 9 months after the operation, one patient developed recurrent pulmonary embolism, and five patients had no obvious improvement in chest tightness. PMT can be used as a safe and effective treatment option for acute medium-to-high-risk pulmonary embolism.

A comparative study on the efficacy of laparoscopic ureteroureterostomy versus single ureteral bladder reimplantation in treating pediatric complete renal duplication.

To explore the therapeutic value of laparoscopic ureteroureterostomy compared to single ureteral bladder reimplantation in the treatment of pediatric complete renal duplication. This retrospective study included 80 pediatric patients with complete renal duplication who underwent surgical treatment at the First Affiliated Hospital of Zhengzhou University from January 2015 to December 2022. Patients were divided into two groups based on the surgical approach: the laparoscopic ureteroureterostomy group (LUU group, n = 45) and the single ureteral bladder reimplantation group (UR group, n = 35). The two groups were compared in terms of operative time, intraoperative blood loss, number of stent placements, postoperative length of hospital stay, changes in ante-posterior diameter (APD) of the affected upper kidney pelvis before and after surgery, changes in upper ureteral diameter (UD), changes in upper renal cortex thickness (RCT) and variations in renal function. The LUU group demonstrated significantly shorter operative time (t = 3.480, P = 0.004), less intraoperative blood loss (t = -2.465, P = 0.0196), and reduced postoperative length of stay (t = 2.308, P = 0.027) compared to the UR group. There was no significant difference between the two groups regarding the number of stent placements (x2 = 0.762, P = 0.383). The UR group had four cases of long-term complications (two cases of anastomotic stricture, one case of vesicoureteral reflux, and one case of recurrent urinary tract infection), while the LUU group experienced one case of long-term complication (one case of anastomotic stricture), with no significant difference between groups (x2 = 1.493, P = 0.222). Both groups showed significant improvement in preoperative and postoperative APD, UD, RCT and affected side differential renal function (DRF). However, the differences in improvement values for upper kidney pelvis APD (ΔAPD; t = -0.032, P = 0.962), upper RCT (ΔRCT; t = -0.042, P = 0.957), ureteral diameter (ΔUD; t = 1.832, P = 0.079), and differential renal function (ΔDRF; Z = 1.895, P = 0.073) were not statistically significant. Both LUU and UR procedures are safe and effective in treating pediatric complete renal duplication. Compared to UR, LUU results in shorter operative time, less intraoperative blood loss, and reduced postoperative length of stay, while also causing less damage to the bladder.

Enhanced casing molten salt thermal energy storage through cobblestone-fin composite: Multi-objective optimization with RSM and NSGA-II

In this paper, the thermal storage performance of molten salt phase change materials in a triplex-tube latent heat thermal energy system designed by mixing fins and pebbles is studied. Commercial Computational fluid dynamics software is utilized for simulating and analyzing the latent heat system. The influence of stone arrangement, rotating speed and heat transfer fluid temperature on the melting performance of latent heat thermal energy system is emphatically discussed. The results show that the change of pebble diameter has a significant influence on the melting characteristics of latent heat thermal energy system. When the pebble diameter is 1 mm and arranged in 3 rows and 3 columns, latent heat thermal energy system has the best heat storage effect. At the same time, the effects of rotating machinery and heat transfer fluid temperature on the thermal performance of latent heat thermal energy system are discussed. Finally, the response surface method and the non-dominated sorting genetic algorithm II are employed to optimize the design, after optimization, the system's heat storage capacity increases by 19.04 kJ, and the melting time decreases by 16.12 s. Therefore, it is suggested that the optimized latent heat thermal energy system can significantly enhance heat transfer efficiency.

Mesoscopic Simulation on Centrifugal Melt Electrospinning of Polyetherimide and Polyarylethernitrile

Polyetherimide (PEI) and polyarylethernitrile (PEN) are high–performance materials for various applications. By optimizing their fiber morphology, their performance can be further enhanced, leading to an expanded range of applications in carbon fiber composites. However, developing processes for stable and efficient fiber production remains challenging. This research aims to simulate the preparation of high–performance ultrafine PEI or PEN fibers using electrospinning. A mesoscopic simulation model for centrifugal melt electrospinning was constructed to compare and analyze the changes in molecular chain orientation, unfolding, fiber diameter, and fiber yield under high-voltage electrostatic fields. The simulation results showed that temperature and electric field force had a particular impact on the diameter and yield of PEI and PEN fibers. Changes in rotational speed had negligible effects on both PEI and PEN fibers. Additionally, due to their different molecular structures, PEI and PEN, which have different chain lengths, exhibit varied spinning trends. This study established a mesoscopic dynamic foundation for producing high-performance ultrafine fibers and provided theoretical guidance for future electrospinning experiments.

Automatic travel of a mine hole robot adaptive to changes in hole diameters

Abstract In response to the complex and challenging task of long-distance inspection of small-diameter and variable-diameter mine holes, this paper presents a design for an adaptive small-sized mine hole robot. First, focusing on the environment of small-diameter mine holes, the paper analyzes the robot’s functions and overall structural framework. A two-wheeled wall-pressing robot with good mobility, arranged in a straight line, is designed. Furthermore, an adaptive variable-diameter method is devised, which involves constructing an adaptive variable-diameter model and proposing a control method based on position and force estimators, enabling the robot to perceive external forces. Lastly, to verify the feasibility of the structural design and adaptive variable-diameter method, performance tests and analyses are conducted on the robot’s mobility and adaptive variable-diameter capabilities. Experimental results demonstrate that the robot can move within small-diameter mine holes at any inclination angle, with a maximum horizontal crawling speed of 3.96 m/min. By employing the adaptive variable-diameter method, the robot can smoothly navigate convex platform obstacles and slope obstacles in mine holes with diameters ranging from 70 mm to 100 mm, achieving the function of adaptive variable-diameter within 2 s. Thus, it can meet the requirements of moving inside mine holes under complex conditions such as steep slopes and small and variable diameters.

Quantitative Investigation of Layer-by-Layer Deposition and Dissolution Kinetics by New Label-Free Analytics Based on Low-Q-Whispering Gallery Modes

A new instrument for label-free measurements based on optical Low-Q Whispering Gallery Modes (WGMs) for various applications is used for a detailed study of the deposition and release of Layer-by-Layer polymer coatings. The two selected coating pairs interact either via hydrogen bonding or electrostatic interactions. Their assembly was followed by common Quartz Crystal Microbalance (QCM) technology and the Low-Q WGMs. In contrast to planar QCM sensor chips of 1 cm, the WGM sensors are fluorescent spherical beads with diameters of 10.2 µm, enabling the detection of analyte quantities in the femtogram range in tiny volumes. The beads, with a very smooth surface and high refractive index, act as resonators for circular light waves that can revolve up to 10,000 times within the bead. The WGM frequencies are highly sensitive to changes in particle diameter and the refractive index of the surrounding medium. Hence, the adsorption of molecules shifts the resonance frequency, which is detected by a robust instrument with a high-resolution spectrometer. The results demonstrate the high potential of the new photonic measurement and its advantages over QCM technology, such as cheap sensors (billions in one Eppendorf tube), simple pre-functionalization, much higher statistic safety by hundreds of sensors for one measurement, 5–10 times faster analysis, and that approx. 25, 000 fewer analyte molecules are needed for one sensor. In addition, the deposited molecule amount is not superposed by hydrated water as for QCM. A connection between sensors and instruments does not exist, enabling application in any transparent environment, like microfluidics, drop-on slides, Petri dishes, well plates, cell culture vasculature, etc.

Characterising the Time Course of the Dilatory Response of Healthy Retinal Arteries during Flicker-Light Provocation

Introduction: The dilatory response of healthy retinal arterioles to flicker-light (FL) provocation appears to be biphasic. The vessel diameter rapidly increases (acute phase) over 5–10 s, then barely increases thereafter (maintenance phase) until FL cessation. This reaction is usually characterised at a single point by two parameters: maximum dilation (MD) relative to baseline diameter (MD, %) and time to MD (RT, s). This paper describes the biphasic reaction of retinal arteries during FL provocation using a bi-linear function. Methods: Retinal arterioles from 45 adults were examined during flicker provocation. Each individual time course of arterial diameter change during FL provocation was characterised by a bi-linear equation and compared with MD and RT. Results: Slopes of the acute phase were 0.506%/s, and the maintenance phase was nearly flat (0.012%/s). The mean time at which the reaction changed from acute to maintenance phase was 7.4 s which is significantly different from RT (16.0 s). Mean dilation at this point (2.987%) was significantly different from MD (3.734%), but it was still 80% of MD in less than half of RT. Conclusion: Bi-linear fitting parameters better characterises the arterial dilatory response than MD and RT. Further stratification of clinical groups using bi-linear fitting may provide insight of the underlying physiology of vessel dilation for different pathologies.

Achilles Tendon Mechanical But Not Morphological Properties Change with Rehabilitation in Patients with Chronic Midportion Achilles Tendinopathy

ABSTRACT Purpose Achilles tendinopathy (AT) is associated with altered tendon’s morphological and mechanical properties, yet it is unclear whether these properties are reversed upon mechanical loading to promote tendon healing. This study aims to determine the extent to which pathological tendon’s morphological and mechanical properties adapt throughout a 12-week eccentric rehabilitation protocol. Methods Forty participants with midportion AT were recruited and participated in a 12-week eccentric rehabilitation program. Function and symptoms were recorded through the Victorian Institute of Sports Assessment-Achilles (VISA-A) and hopping. The tendon’s morphological (i.e. volume, midportion cross-sectional area (CSA) and anteroposterior (AP) diameter) and mechanical (i.e. stiffness, Young’s modulus, and tendon non-uniform displacement) properties were measured at baseline and at 6 and 12 weeks of the intervention. Results Significant functional improvements were observed, with VISA-A scores and hopping results showing marked improvements (p &lt; 0.001). Morphologically, no significant changes in volume, midportion CSA, or AP diameter were found, although a trend toward decreased CSA between 30-70% of tendon length was noted. Mechanically, significant increases in Achilles tendon stiffness (p = 0.001) and Young’s modulus (p &lt; 0.001) were observed over the course of the rehabilitation program. No differences in tendon non-uniform displacement were found following a 12-week rehabilitation program. Conclusions These findings suggest that tendon adaptation in response to mechanical loading primarily involves changes in mechanical properties rather than morphology, highlighting the complexity and variability in tendon adaptation. Clinically, these mechanical properties could be considered in the load progression throughout rehabilitation as potentially higher strains will be induced when clinical improvements precede mechanical adaptations.

Retinal blood vessel diameter changes with 60-day head-down bedrest are unaffected by antioxidant nutritional cocktail

Long-term human spaceflight can lead to cardiovascular deconditioning, but little is known about how weightlessness affects microcirculation. In this study, we examined how the retinal microvessels and cerebrovascular regulation of 19 healthy male participants responded to long-term head-down bedrest (HDBR), an earth-based analog for weightlessness. In addition, we examined whether an anti-inflammatory/antioxidant cocktail could prevent the vascular changes caused by HDBR. In all study participants, we found a decrease in retinal arteriolar diameter by HDBR day 8 and an increase in retinal venular diameter by HDBR day 16. Concurrently, blood pressure at the level of the middle cerebral artery and the cerebrovascular resistance index were higher during HDBR, while cerebral blood flow velocity was lower. None of these changes were reversed in participants receiving the anti-inflammatory/antioxidant cocktail, indicating that this cocktail was insufficient to restore the microvascular and cerebral blood flow changes induced by HDBR.

Insights Into Pool Boiling Heat Transfer on Minichannel Surfaces Through Point and Field Measurements

Abstract In this study, saturated pool boiling experiments were conducted on copper minichannel and flat surfaces at atmospheric pressure using water as the working fluid. The heat transfer performance was assessed through point measurements with a heater block, cartridge heaters, and thermocouples, as well as field measurements using a thin-foil heater and infrared thermography. Two copper minichannel surfaces with square cross sections of 1 mm (minichannel-1) and 2 mm (minichannel-2) side lengths were tested and compared to a flat surface. Minichannel-1 and minichannel-2 enhanced the critical heat flux (CHF) by 17% and 45%, respectively, and improved the heat transfer coefficient by 24–40% and 51–75%, respectively, compared to the flat surface. Minichannel-2 exhibited the lowest and most uniform boiling surface temperature, making it the best performer among the three. There was no significant change in departure frequency among the surfaces, and no significant change in departure diameter for the flat surface and minichannel-1. However, minichannel-2 had lower departure diameters due to its deeper channels, which prevented bubble coalescence and maintained low departure diameters. Additionally, minichannel-2 delayed vapor film formation by breaking it with its deeper fins, thereby improving CHF and slightly enhancing bubble dynamics. The enhancement in boiling heat transfer is primarily attributed to the increased surface area provided by the minichannels, with a minor contribution from improved bubble dynamics. However, the dominant factor in enhancing pool boiling heat transfer on minichannel surfaces is the increase in surface area.