Flow Time Research Articles

Comparative Efficacy of Extracorporeal Versus Conventional Cardiopulmonary Resuscitation in Adult Refractory Out-of-Hospital Cardiac Arrest: A Retrospective Study at a Single Center.

Background: Extracorporeal cardiopulmonary resuscitation (ECPR) has the potential to improve neurological outcomes in patients with refractory out-of-hospital cardiac arrest (OHCA), offering an alternative to conventional cardiopulmonary resuscitation (CCPR). However, its effectiveness in OHCA remains controversial despite advancements in resuscitation techniques. Methods: This retrospective single-center study compared neurological outcomes and 30-day survival between ECPR and CCPR patients from January 2014 to January 2022. Patients aged 18-75 with witnessed OHCA, minimal no flow and low flow times, and cardiac arrests occurring at home or in public places were included. All patients were transported directly to our institution, a tertiary medical center serving the southeastern region of Seoul, where extracorporeal membrane oxygenation implantation was consistently performed in the emergency department. Neurological outcomes were assessed using Cerebral Performance Category scores, with good outcomes defined as scores of 1-2. Statistical analyses included logistic regression models and Kaplan-Meier survival curves, adjusted for confounders using inverse probability of treatment weighting. Results: ECPR was associated with significantly better neurological outcomes than CCPR (p < 0.001). Factors predicting poor outcomes included older age and longer low flow times, while male sex and shockable rhythms were protective. No significant difference was found in 30-day survival between the ECPR and CCPR groups, although a trend toward better survival was noted with ECPR. Conclusions: ECPR may improve neurological outcomes in patients with refractory OHCA compared to CCPR, although it does not significantly affect 30-day survival. Further studies are necessary to validate these findings and explore the long-term impacts of ECPR.

Influence law of air flow and water immersion duration on the risk of secondary oxidation spontaneous combustion of coal

To further elucidate the variations of secondary oxidation spontaneous combustion risk of lignite under different air flows and immersion time. Secondary oxidation experiments of short-term water-immersed coal and long-term water-immersed coal were conducted under four air flows. The results show that, the presence of a temperature inflection point during primary oxidation process, when coal temperature exceeds it, both the oxygen consumption rate and heat release intensity of long-term water-immersed coal are lower, furthermore, decrease in air flow leads to reduction in the temperature inflection point. The oxygen consumption rate and heat release intensity during the primary oxidation process exceed those observed during the subsequent secondary oxidation process. In the secondary oxidation process, long-term water-immersed coal exhibits higher rates of oxygen consumption and heat release intensity compared to short-term water-immersed coal. Additionally, the oxygen-consuming activation energy for oxygen consumption of long-term water-immersed coal is lower. The increase in air flow and water immersion time generally leads to the extreme value of the limit parameters, such as the local maximum of minimal thickness of residual coal and the lower limit oxygen fraction, the local minimum of the maximal air leakage intensity develops in the direction of increasing the risk of spontaneous combustion of coal in goaf.

Granular memristors with tunable stochasticity.

Most realizations of memristive devices exhibit characteristic noise sometimes described as random telegraph noise. These fluctuations in current, ubiquitous in nature, carry significant implications for device performance, reliability, and the broader landscape of memristor technology applications. Here, we study inherent random fluctuations observed in silver based granular memristive devices operating under steady bias conditions. Random telegraph noise observed in our system is characterized in terms of distributions of ON and OFF times of the current flow at a particular bias. We find that these fluctuations adhere to power law statistics with , where τOFF/ON denotes the time during which the output value remains below or above a specified threshold. We follow the fluctuations for up to four decades. Significantly, unlike previous studies, we find the emergence of a new regime of behavior where the power law exponent varies as a function of applied bias. We find that our results are best described by the Marcus-Tang expression for diffusion along intersecting parabolae with bias as the driving force. The predictions of this picture of dynamics also provide a satisfactory explanation for the quiescence of the OFF/ON state of our devices.

Uncertainty analysis in river quality management considering failure probability: controllable and uncontrollable input pollutants.

River quality management involves complex challenges due to inherent uncertainties in various parameters, especially when dealing with controllable and uncontrollable pollutants. This study integrates a finite volume approach, called SEF (symmetric exponential function), with Monte Carlo simulations in MATLAB to solve the advection-dispersion equation, focusing on evaluating river quality protection tools by considering failure probability (Pf). Critical specifications for maintaining reliable river ecosystem performance are identified. We simulate assimilation capacity for managing river water quality against controllable pollutants to satisfy allowable pollution concentration at the high-reliability index. Using the Genetic Programming (GP) algorithm, a new accurate equation for assimilation capacity calculation is presented considering Pffor the first time. Results indicate that flow velocity significantly affects river assimilation capacity: increasing velocity can shift the river to a hazardous state while decreasing it allows for greater pollutant assimilation. Sustainable protection tools, including dilution flow and detention time, are considered to manage uncontrollable pollutants within a specific time (Tc) and river length constraints (Lc), safeguarding river water quality for both human and animal populations. Dilution flow is practical for specific base velocities but ineffective at high base flow rates. Conversely, detention time consistently protects water quality across all base flow velocities within the Lc constraint. Moreover, this study introduces the ratio of detention time to initial pollution contact duration as a vital water quality index to protect the rivers' environment. Combining numerical methods with reliability analysis and soft computing techniques, this research provides valuable insights into river system dynamics and protecting river water quality.

Blood-brain barrier water permeability across the adult lifespan: A multi-echo ASL study.

An emerging biomarker of blood-brain barrier (BBB) permeability is the time of exchange (Tex) of water from the blood to tissue, as measured by multi-echo arterial spin labeling (ASL) MRI. This new non-invasive sequence, already tested in mice, has recently been adapted to humans and optimized for clinical scanning time. In this study, we studied the normal variability of Tex over age and sex, which needs to be established as a reference for studying changes in neurological disease. We evaluated Tex, cerebral blood flow (CBF) and arterial transit time (ATT) in 209 healthy adults between 26 and 87 years, over age and sex, using general linear models in gray matter, white matter, and regionally in cerebral lobes. After QC, 194 participants were included in the main analysis, and the results demonstrated that both gray matter (GM) and white matter (WM) BBB permeability was higher with higher age (Tex lower by 0.47 ms per year in GM [p < 0.05], and by 0.49 ms in WM, for females; no significant for males), with the largest Tex difference in the frontal lobes (0.64 ms decrease per year, p = 0.011, population average). CBF was lower with higher age in the GM (-0.71 mL/min/100g per year, p < 0.001, for females; -0.31 mL/min/100g per year, p < 0.05, for males). When correcting Tex models for CBF and ATT, effect of age on Tex disappears in the GM, but not in the WM (β=-0.28, p = 0.08). The CBF findings of this study are in line with previous studies, demonstrating the validity of the new sequence. The BBB water permeability variation over age and sex described in this study provides a reference for future BBB research.

Comparison of synthetic unit hydrograph methods for flood assessment in a dryland, poorly gauged basin (Napostá Grande, Argentina)

&lt;p&gt;This paper examined and compared the reliability of two popular unit hydrograph methods for flood assessment in a dryland, poorly gauged basin: the Soil Conservation Service (NRCS-UH) method and the geomorphologic instantaneous unit hydrograph (GIUH) model. In addition, two different estimates of the basin's time of concentration were compared, along with varying values of the runoff curve number, to compute the watershed lag. Simulations were performed for the upper Napostá Grande (SW Buenos Aires, Argentina), using eight historic rainfall-runoff events to validate the resulting hydrograph at the basin outlet. Validation used runoff volume, peak flow, and recession time as an alternative to time to peak, for which only mean daily data were available. Results revealed great discrepancies in unit hydrograph parameters for varying determination methods, time of concentration estimates, and basin lag factors, as well as lower-than-standard peak rate factors for GIUH hydrographs. The comparison of simulated with observed hydrographs suggested a better agreement of GIUH for the highest retardance factor, as it produced the smaller peaks with the longer recession. This study informs on the complex relationships involved in unit hydrograph (UH) determination for the studied basin and warns about the variability of obtained results depending on the applied methodology, the caution needed in the systematic use of standard parameters, and the importance of verifying the accuracy of results. This provides a valuable framework for flood assessment within regional, ungauged basins with similar characteristics, which may exhibit comparable total runoff volumes for the same rainfall event but not necessarily equivalent flood hydrographs.&lt;/p&gt;

Flow shop manufacturing layout as low carbon approach for application in bonding wire drawing industry

Modern manufacturing environments are yet to fulfil the evergrowing competitive supply and demand due to the limitation of conventional production approaches. A low-carbon approach incorporating the change from process to product-centric manufacturing systems could conserve energy while fulfilling supply and demand requirements in a competitive market. Current study had conducted a case study in a bonding wire factory that operates on process-oriented system with job shop layout. Preliminary data collection had assessed the existing practices on the factory's shop floor, and simulation model using WITNESS software was developed using this data. A job shop to flow shop conversion framework was developed with the integration of factors such as shop floor layout, order release, and dispatch rule play crucial roles in the conversion process of the production system. Based on the application of the conversion framework encompassing six future production system models, CL-SPT model which uses flow shop as layout, CONLOAD as order release and shortest processing time as the dispatch rule is selected as the best performing and economical production system. This model enhanced the output and average flow time by 2.7% and 27.7%, respectively, in tandem with low-carbon requisites while retaining machine utilization performance equivalent to the conventional system.

Evaluating the Antidiabetic Activity of Aloe niebuhriana Latex in Alloxan-Induced Diabetic Rats and the Development of a Novel Effervescent Granule-Based Delivery System.

Background: Ethnomedicine exhibits potential in developing affordable effective antidiabetic agents. Aim: This work aimed to explore the antidiabetic properties of Aloe niebuhriana latex extract both in vivo, utilizing alloxan-induced diabetic rats, and in vitro, through α-amylase enzyme testing. Additionally, it sought to formulate optimal effervescent granules derived from the extract. Methods: The α-amylase inhibition assay was performed using the α-amylase kit using biochemical analyzers. Experimental diabetes was induced in animals with alloxan. On Day 14 postdiabetes induction, body weight, fasting blood glucose, and lipid profile parameters were determined. Also, six effervescent granule preparations of the extract were formulated using wet granulation. Based on its physical and organoleptic properties, a formulation was selected and optimized. Results: The extract displayed modest α-amylase inhibition, with an IC50 value of 439.2 μg/mL. Both doses of A. niebuhriana extract (200 and 400 mg/kg) significantly reduced blood glucose level compared to their respective Day 1 levels (p < 0.001). Moreover, the extract at a dose of 400 mg/kg significantly normalized lipid profile compared to the diabetic control groups (p < 0.05 - 0.001). Six formulations containing the extract were prepared (F1-F6), and F6 containing 200 mg of the extract was selected for optimization due to its favorable odor, taste, foaming, and effervescent properties, high solubility, and absence of turbidity and adhesion. The formulated F6 granules successfully met the quality parameters assessed including flow time, pH effervescent time, angle of repose, bulk density, tapped density, Carr's index, and Hausner's ratio. Conclusion: This study highlights the antidiabetic potential of A. niebuhriana latex extract, potentially attributed to its hypolipidemic, hypoglycemic, and α-amylase inhibitory effects. The successful formulation and evaluation of the extract as effervescent granules suggest its potential as an antidiabetic drug.

Numerical Analysis of Levee Failure Characteristics for Flood Hydrograph Patterns

Recent climate change has significantly affected the magnitude and frequency of rainfall, which critically affects the safety of levees and leads to severe flooding damage when levees fail. This study aimed to analyze the impact of the shape of flood hydrographs on levee failure characteristics using numerical analysis. Three types of flood hydrographs derived from lognormal, beta, and Weibull probability density functions (PDFs) were utilized, with each showing differences in the timing and magnitude of the peak flows. Levee overtopping and failure phenomena were simulated using a three-dimensional numerical analysis model, namely, FLOW-3D. The simulation results indicate that the failure patterns of levees vary, depending on the PDF used, with the lognormal PDF showing significant levee failure, owing to relatively high initial flows. These results suggest that a rapid increase in the flow at the onset is a direct factor that causes levee failure. These numerical analysis results highlight the importance of understanding the characteristics of each probability density function to accurately predict and effectively respond to levee failure risk. Future research should focus on a more precise analysis of levee failure mechanisms as well as the propagation and impacts of flood waves resulting from such failures.

Effect of Silica Fume on the Performances of Self-compacting Repair Mortar

Background Concrete is a widely utilized material in construction worldwide. However, concrete performance could be damaged under aggressive environments, therefore, many concrete structures may require repair and frequent maintenance. Objective The aim of this study is to develop reinforced Self-Consolidating Repair Mortars (SCRMs) incorporating silica fume and polypropylene fibers. Methods This research aimed to study the effect of silica fume as an alternative supplementary cementitious material (SCM) on the performance of fiber reinforced self-consolidating repair mortars (SCRMs). For this purpose, five SCRMs mixes incorporating 0%, 5%, 10%, 15%, and 20% of silica fume as partial cement replacement were prepared. Testing included slump flow, flow time, and unit weight, air-dry unit weight, compressive and flexural strengths, dynamic modulus of elasticity and water absorption. Results The results indicated that the substitution of cement by 15% of silica fume improves the flexural strength and slightly reduce the compressive strength of the fiber-reinforced repair mortar. The lowest values of total shrinkage, water capillary absorption, and sorptivity were observed for repair mortars containing 10% silica fume. In addition, bonding results between repair mortars containing silica fume and old concrete substrate investigated by the bond flexural strength test showed good interlocking, justifying the effectiveness of these produced mortars. Conclusion The results reveal that structural repair mortars containing 10 and 15% silica fume conform with the performance requirements of class R4 materials (European Standard EN 1504-3) and could be used in repair applications.

Measurement of viscosity during vibroextrusion of fiber concrete

Currently, the rheological properties of cement mortars containing dispersed reinforcement have not been studied enough, so it is important to develop a method for measuring the viscosity of fiber concrete mixtures that would simulate the technological process. To consider the flow process and calculate the rheological characteristics of fiber concrete mixtures during vibroextrusion, hydrodynamic theories were applied due to the fact that these mixtures behave like liquids in a vibration field. When solving flow problems, it is taken into account that vibrating fiber concrete mixtures are Newtonian systems. To obtain objective rheological characteristics of fiber concrete mixtures, it is proposed to measure viscosity directly during vibro-extrusion molding of flat products. The peculiarities of the flow of Newtonian fluids between flat fixed walls, which converge in a flat symmetrical rectangular narrowing channel, are considered. It is proposed to determine the reduction of the flow rate of the mixture in the rectangular channel compared to the flow between the plates by the braking coefficient. A graph of the dependence of the braking coefficient on the ratio of the sides of the cross section of the rectangular channel is plotted. 2 formulas are proposed for calculating the braking coefficient. The comparative analysis of the proposed formulas gives a good convergence of the calculation results, the average approximation error is equal to 0.0126%, which indicates a high level of coincidence of the regression equation with a more complex analytical formula. Taking into account the inhibition of the liquid flow in the end zones of the rectangular channel, a formula was proposed for calculating the viscosity of the fiber concrete mixture during the formation of flat products in the narrowing vibroextruder channel. The calculation formula contains the geometric dimensions of the channel, the density and the flow time of the fiber concrete mixture, and to determine the viscosity of the mixture, it is necessary to measure only the time of its complete flow during vibroextrusion. The proposed formula and methodology for calculating viscosity can be used to determine the rheological characteristics of any Newtonian fluids using a flat symmetrical rectangular narrowing channel. In the future, it is planned to continue researching the properties of fiber concrete mixtures under the influence of vibration.

A Wearable Device with Triboelectric Nanogenerator Sensing for Respiration and Spirometry Monitoring.

Wearable devices have been developed for the continuous and long-term monitoring of respiration. Although current wearable devices are able to measure the respiration rate, extracting breathing volume has been challenging. In this paper, we propose a wearable respiration monitoring sensor based on triboelectric nanogenerator (TENG) technology. The proposed device successfully measures both respiration rate and volume in real-time. The device is tested with seven participants for respiration and spirometry studies. The results show that the proposed TENG sensor is able to capture the respiration waveform with high accuracy. All breathing patterns mentioned in this study give a mean absolute error (MAE) within 0.2 breaths per minute and a mean percentage absolute (MPAE) error within 2%. The results of the spirometry study show that the TENG sensor can measure the airflow and volume during exhalation. The flow time graph gives an average correlation of 0.88 compared with that of the reference spirometer. The reconstructed volume time plot from the TENG sensor results in an MAE of 2.43% for the ratio of the forced expiratory volume in 1 s to the forced vital capacity (FEV1/FVC). The proposed device provides a low-cost solution for real-time and wearable monitoring for respiration parameter measurement.

Groundwater well fields in ice-margin valley aquifers - is it easy to protect them, or not? An overview of hydrogeological and legal aspects of determining wellhead protection zones

This paper discusses principles for delineating wellhead protection zones (WHPZ) of groundwater well fields in ice-margin valleys. A distinctive feature of such well fields is that, apart from the often geogenically contaminated water of ice-margin valleys, they are largely supplied with high-quality water from intertill aquifers of neighbouring uplands. However, much of this inflow can be intercepted by wells for agriculture that are increasingly being constructed in the capture zones of existing municipal well fields, thus posing a threat to the quality of water for the public. This problem has been investigated using the example of a municipal well in Wroniawy (Poland) by analysing changes in the recharge components of this well field with a groundwater flow model. The results indicate that the commissioning of agricultural abstractions in the capture zone of this well field reduces inflow from intertill aquifers (8.5 per cent) and precipitation recharge (3.3 per cent), following a change in the extent of the capture zone. The loss of these qualitative recharge components is substituted by an increase in poor-quality water, i.e., surface water (7.3 per cent) and geogenically contaminated water from the ice-margin valley centre (3.8 per cent). Protecting well fields in such locations from adverse water quality changes requires the implementation of quantitative shielding of best-quality water, calling for WHPZ to cover the entire capture zone regardless of water flow timing, which is not provided for in Polish legislation. Costs and constraints of implementing such a WHPZ can be reduced by dividing it into sectors that differ in the scope of limitations, with the only quantitative protection applied to the outermost, medium- and low-vulnerable parts of the capture zone.

РАСЧЕТ ВРЕМЕНИ ИСТЕЧЕНИЯ ВОДОРОДА ИЗ БАЛЛОНА ДЛЯ ОПРЕДЕЛЕНИЯ ХАРАКТЕРИСТИК АВАРИЙНОЙ ВЕНТИЛЯЦИИ

Выполнены расчеты по определению времени истечения водорода и смеси водорода с углекислотой из баллонов емкостью 0,04 м3 при различном начальном давлении газа через отверстия различного размера. Выявлены закономерности влияния различных параметров на время истечения газов. Показано, что при некоторых условиях можно избежать давления взрыва газовой смеси свыше 5 кПа в случае разгерметизации баллона с газом. When determining the room category by explosion and fire hazard, it is assumed that all the contents of the device, cylinder or other equipment completely go into the room, mixed with air, then the mixture explodes. Such a scenario is found the most dangerous. If the room is equipped with emergency ventilation activated by a signal from a fast-acting gas analyser, it is allowed to reduce the mass of flammable gas or vapour when calculating the explosion pressure. When gas in high pressure equipment enters the room, the time of entry depends on the gas quantity, pressure and other properties of the gas. The regulatory documentation for fire safety does not provide recommendations on calculating the gas discharge time from the equipment of the final volume, accompanied by pressure decrease. The purpose of this work is to estimate the gas discharge time from industrial cylinders with a capacity of 0.04 m3 depending on various factors. The task of the work is to calculate the K coefficient in the formula for determining the required air exchange rate of emergency ventilation. To solve this problem, there is considered the discharge of several combustible gases from cylinders with a volume of 0.04 m3 through holes of different diameters at different values of initial gas pressure. It is shown that when hydrogen flows out of a cylinder with an initial pressure of 20 MPa through a hole with a diameter of 4 mm, which corresponds to the full opening of the valve, the discharge time is 26 seconds, and when discharging under the same conditions through a hole with a diameter of 1 mm, the discharge time increases up to 346 seconds. In order to determine the possibility of protecting a room with hydrogen cylinders from an explosion of a hydrogen-air mixture, there were made calculations of explosion pressures values depending on the volume of the room. There are established conditions for the use of emergency ventilation to ensure explosion safety in an accident with a gas cylinder. In order to reduce the explosion pressure for this room to 5 kPa, it is necessary to increase the discharge time up to 300 s (5 minutes). Two ways to increase the flow time are considered: reducing the size of the hole (by inserting a washer into the cylinder valve) and preliminary dilution of combustible gas with incombustible gas when filling the cylinder. It is possible to use both methods at the same time to increase the gas discharge time from the cylinder.

Modelling and Analysis of Low and Medium-Temperature Pyrolysis of Plastics in a Fluidized Bed Reactor for Energy Recovery

With the growing demand for plastic production and the importance of plastic recycling, new approaches to plastic waste management are required. Most of the plastic waste is not biodegradable and requires remodeling treatment methods. Chemical recycling has great potential as a method of waste treatment. Plastic pyrolysis allows for the cracking of plastic polymers into monomers with heat in the absence of oxygen, allowing energy recovery from the waste. Fluidized bed reactors are commonly used in plastic pyrolysis; they have excellent heat and mass transfer. This study investigates the influence of low and medium process temperatures of pyrolysis on fluidized bed reactor parameters such as static pressure, fluidizing gas velocity, solid movement, and bubble formation. This set of parameters was analyzed using experimental methods and statistical analysis methods such as experimental correlations of changes in fluidized bed reactor velocities (minimal, terminal) due to temperature increases for different particle sizes; CFD software simulation of temperature impact was not found. In this study, computational fluid dynamics (CFD) analysis with Ansys Fluent was conducted for the fluidization regime with heat impact analysis in a fluidized bed reactor (FBR). FBR has excellent heat and mass transfer and can be used with a catalyst with low operating costs. A two-phase Eulerian–Eulerian model with transient analysis was conducted for a no-energy equation and at 100 °C, 500 °C, and 700 °C operating conditions. Fluidizing gas velocity increases the magnitude with an increase of the operating temperature. The point of fluidization could be determined at 1.1–1.2 s flow time at the maximum pressure drop point. With the increase of gas velocity (to 0.5 m/s from 0.25 m/s), fluidizing bed height expands but when the solid diameter is increased from 1.5 mm to 3 mm, the length of the fluidized region decreases. No pressure drop change was observed as the fluidized bed regime was maintained during all analyses. The fluidization regime depends on gas velocity and all the applied fluidization gas velocities were of a value in between the minimal fluidization velocity and the terminal velocity.

Paleoproterozoic Mississippi Valley-type mineralization at Black Angel, Greenland: evidence from sulfide δ66Zn and rhenium-osmium geochronology

AbstractWe provide timestamps for the major zinc-lead (Zn-Pb) Mississippi Valley-type Black Angel deposit (Greenland) based on new pyrite rhenium-osmium (Re-Os) isotope geochemistry data: (1) a Re-Os isochron age 1,884 ± 35 million years ago (Ma – 2σ, 1.8%) for subhedral pyrite cemented by sphalerite ± galena in dolomitized clean limestone, and, (2) a Re-Os model age 1,828 ± 16 Ma (2σ, 0.9%) for epigenetic massive pyrite in siltstone/mudstone cap rock. Zinc-lead mineralization in evaporite-bearing carbonates in the Karrat Basin took place ca. 1,884 Ma at the time of far-field fluid flow associated with back-arc spreading ca. 1,900–1,850 Ma. Mineralization predates the development of the Rinkian foreland basin (ca. 1,850 – &lt; 1,800 Ma) and a collisional stage (ca. 1,830 – &lt; 1,800 Ma) in the context of the telescoping Rinkian and the Nagssugtoqidian Orogens. Replacement of clean carbonate and sustained acid neutralization led to significant sphalerite precipitation ca. 1,884 Ma. Conversely, precipitation of epigenetic massive pyrite in the cap rock ca. 1,828 Ma may signal (1) the lack of chemical reactivity of the cap rock for the pH-buffered conditions needed for Zn-Pb mineralization, and (2) the unfavorable impact of incipient regional Rinkian metamorphism (ca. 1,830–1,800 Ma) and tectonic compression on aquifer permeability and continued brine migration. The initial 187Os/188Os ratio (Osi-pyrite = 1.07 ± 0.32) from isochron regression identifies a crustal origin for Os and, by corollary, other metals in the ca. 1,884 Ma Zn-Pb mineralization. Although the Rae Craton basement rocks comprise the dominant source for metals (based on our Osi-pyrite and δ66Znpyrite/sphalerite data), we identify a complementary contribution in Zn (maximum 12–24%) from Paleoproterozoic sedimentary carbonate. This source of Zn in sedimentary calcite is deemed possible in the context of Paleoproterozoic seawater at high Na/Cl ratio and in the absence of Zn-based eukaryotic metabolism in shallow marine environment.

The Influence of the Assembly Unit of CO2-Cured Secondary Aluminum Ash and CO2-Cured Iron Tailings on High Performance Concrete’s Properties

This paper aims to study the influence of the assembly units of CO2-cured iron tailings (IOT) and CO2-cured secondary aluminum ash (SAA) on the fresh high-performance concrete’s (HPC’s) slump flow and setting time. The mechanical properties including the flexural strength, compressive strength, the bonding strength and the dry shrinkage rate of the hardened HPC are measured. The amount of leached Cr and Zn after immersing in deionized water for 1 month~6 months is measured. The influence of the basalt fibers’ volume ratio and the aspect ratio of the high-performance concrete’s performance is considered. The scanning electron microscopy energy spectrums (SEM-EDS) are obtained. The results show that the slump flow and the setting time of fresh HPC are increased by the added CO2-cured SAA and IOT. The fresh HPC with 10% CO2-cured IOT and 20% CO2-cured SAA had the highest slump flow. The slump flow decreases in the form of cubic function with the placing time. The mechanical strengths and the dry shrinkage rate of HPC during the early curing ages (cured for 0.5 day~7 days) are decreased by the CO2-cured SAA and CO2-cured IOT, while the mechanical strengths at later curing ages (14 days~90 days) are increased by the added CO2-cured SAA and CO2-cured IOT. HPC with 10% CO2-cured SAA and 20% CO2-cured IOT shows the highest mechanical strengths. The amount of leached Cr and Zn is decreased by the CO2 cured SAA and IOT. The relationship between the mechanical strengths and the curing time coincides with the cubic equation. The basalt fibers with a volume ratio of 2% and aspect ratio of 1000 show the highest mechanical strengths, the lowest dry shrinkage rate and the least amount of leached Cr and Zn. CO2-cured SAA and IOT can improve the compactness of HPC’s hydration products. HPC with 10% CO2-cured SAA and 20% CO2-cured IOT shows the highest compact hydration products.

Rheological, Fresh State, and Strength Characteristics of Alkali-Activated Mortars Incorporating MgO and Carbon Nanoparticles.

This study presents a comprehensive assessment of the fresh state, rheological, and mechanical properties of alkali-activated mortars (AAMs) developed by incorporating magnesium oxide (MgO) and nanomaterials. A total of 24 AAM mixes with varying content of MgO, multi-walled carbon nanotube (MWCNT), and reduced graphene oxide (rGO) were developed following the one-part dry mix technique using powder-based activators/reagents. The effects of the types/combinations of source materials (binary or ternary)/reagents, MgO (0 to 5%), MWCNT (0 to 0.6%), and rGO (0 to 0.6%) were evaluated in terms of the mini-slump flow, setting times, viscosity, yield stress, compressive strength, ultrasonic pulse velocity (UPV), and microstructural properties. The results showed that the addition of finer MgO/nano-fillers produced a higher viscosity and yield stress accompanied by a lower slump flow and setting times. The addition of 5% MgO resulted in the lowest slump flow of 80 mm, 2-2.5 times higher viscosity, and the reduction in the initial and final setting times of about 21% and 16%, respectively. Mixes with MWCNT showed about 5-10% higher viscosity whereas for mixes with rGO, the values were noted to be 8% higher, on average, than the mixes with no MWCNT or rGO. All the developed AAMs exhibited shear-thinning behavior. The 28-day compressive strength of the AAMs ranged from 37 MPa to 49 MPa with 5% MgO and up to a 0.3% MWCNT/rGO addition increased the compressive strength. Correlations among the fresh state, rheological, and mechanical properties such as the viscosity, slump flow, setting time, compressive strength, and UPV are also described.

Prospective Evaluation of Autonomic Function and Intestinal Blood Flow in Health and Irritable Bowel Syndrome Shows Differences Limited to Patients With Constipation Predominance.

Autonomic dysfunction may contribute to symptom generation in irritable bowel syndrome (IBS), possibly driven by psychological morbidity and activation of the hypothalamic-pituitary-adrenal axis. Previous data are conflicting, perhaps due to lack of accounting for differential bowel patterns in IBS (constipation vs. diarrhea) or by diverse methodologies used to measure autonomic function. Our aim was to determine if autonomic response differed between IBS subtypes and healthy controls. Forty female volunteers (20 IBS and 20 healthy) underwent comprehensive autonomic testing, fasting and postprandially, and in response to cold pressor and deep breathing challenges. Pulse transit time (PTT) and ultrasound measurements of intestinal blood flow were used as measures of systemic and local autonomic function, respectively. Outcomes were adjusted for baseline psychological comorbidities and gastric emptying (measured concurrently with scintigraphy). Findings, confined to IBS patients with predominant constipation (IBS-C), included (1) lower fasting and a trend to larger postprandial increase in superior mesenteric artery end-diastolic velocity; (2) lower fasting PTT, suggesting higher sympathetic tone, but no difference in postprandial PTT change; and (3) attenuated increase in postprandial aortic peak systolic velocity. Response to systemic autonomic challenges did not differ between IBS and health. Some psychological factors mediated differences between groups in the fasting, but not postprandial, state. IBS-C patients display systemic and local autonomic imbalance providing some support for recent therapies aimed at modulating autonomic state specifically in this patient group (e.g., acustimulation).

Comprehensive analysis of environmental dispersion of buoyant particles in three-dimensional open-channel flows

Understanding the environmental dispersion dynamics of buoyant particles in three-dimensional open-channel flows is vital for comprehending various ecological and hydraulic processes associated with open channels. This study employs Aris' concentration moment method to construct a model to assess the overall environmental dispersion characteristics of buoyant particle transport in the flow through a rectangular channel. Analytical solutions for concentration moments of buoyant particles are strictly derived using the separation of variables method. The overall characteristics of buoyant particle transport are analyzed using multiple-order concentration moments. Results show that the overall drift velocity Veff¯, the overall longitudinal dispersion Deff¯, and the overall skewness γ1¯ will eventually reach a stable state with different necessary times, jointly affected by R and Pez, where R is the aspect ratio and Pez reflects the relative strength of the vertical migration and the effective diffusion of buoyant particles. Veff¯ gradually increases with time for the three-dimensional laminar open-channel flow with R≈1 during the preliminary stage, in contrast to the gradual decrease in the corresponding two-dimensional flow. The skewness of the buoyant particles exhibits a mutual transformation between the positive and negative status. R primarily affects the concentration distribution of buoyant particles during the initial stage. Pez significantly influences the concentration distribution pattern throughout both the initial and long-term evolution of the buoyant particle cloud. The maximum cross-sectional average concentration of buoyant particles gradually decreases over time, with a substantial reduction rate in the open channel of small R.