Chronoamperometric flow-cell designed to be unaffected by air bubbles.

In this paper, we present a new design for a chronoamperometric flow cell in which air bubbles do not interfere with the control of potential between the working and reference electrodes. The flow-through dual-detection cell consists of two independent parts: an upper compartment containing a quiescent supporting electrolyte solution and a channel that operates under hydrodynamically controlled conditions. In this system, the working and counter electrodes can be placed directly in contact with both compartments, whereas the reference electrode can be assembled to be either isolated or in contact with the flowing stream channel. The design ensures that the potential applied to the working electrode (controlled in the upper compartment) is similar to the potential applied in the flowing channel. The performance of the proposed flow cell in generating accurate results, even in the presence of air bubbles, was evaluated through successive air-analyte-air injections. In both series where the analyte was introduced, suitable reproducibility was achieved. The robustness of the design was definitively proven by performing a series of measurements in analytical applications for the determination of hydrogen peroxide in antiseptic samples, yielding very satisfactory results.

The strength and hydraulic conductivity characteristics of sewage sludge ash and natural soil mixtures - a sustainable alternate landfill liner material.

This paper examines the feasibility of the natural soil and sewage sludge ash (SSA) mixtures, which satisfy the criteria to be used as landfill liners. The effect of SSA content on hydraulic conductivity and strength characteristics of natural soil and SSA mixtures has been investigated through a series of laboratory tests. The results demonstrate that mixtures exhibit an increase in both hydrodynamic diffusion coefficient and strength with the increasing SSA content. With the content of SSA from 0% to 5%, the values of the hydrodynamic diffusion coefficient (D) ranged from 3.5 × 10-10 to 15 × 10-10 cm2/s. The increase in the hydrodynamic diffusion coefficient is minor for low SSA content and significant for SSA content exceeding 5%. The inclusion of 5% SSA content results in a hydrodynamic diffusion coefficient that is approximately three times higher than that observed in natural soil. The results were obtained from soil triaxial tests, revealing that the mixtures containing SSA exhibited a significant increase in both the initial tangent modulus and the ultimate principal stress difference compared to those of natural soil. The SSA content with the highest value exhibits maximum initial tangent modulus and ultimate principal stress. The comprehensive analysis of the strength and hydraulic diffusion conductivity of the mixtures demonstrates that the incorporation of 3% SSA results in a significant enhancement in strength, while marginally increasing hydrodynamic diffusion coefficients. Therefore, it can be inferred that the utilization of mixtures containing 3% SSA content as a liner material is suitable.

Synergistic enhancement in hydrodynamic cavitation combined with peroxymonosulfate fenton-like process for bpa degradation: New insights into the role of cavitation bubbles in regulation reaction pathway.

The combination of hydrodynamic cavitation (HC) and Fenton-like oxidation technology can dramatically enhance the pollutant removal capacity, however, the synergistic effect of cavitation and catalysts on reactive oxygen species (ROS) generation remained enigmatic. In this study, we established a combined system based on HC and Ce-MnFe2O4 activated peroxymonosulfate (PMS) for BPA removal, and attentions were paid on the role of cavitation bubbles. The results show that the combination of HC in Ce-MnFe2O4 activated PMS could mediate the degradation of BPA from the non-radical pathway dominated by 1O2 to •O2- dominated radical pathway. Both controlled experiments and theoretical calculations revealed that the cavitation bubbles with different sizes play the dominant role in ROS generation. The microjets produced by the collapse of cavitation bubbles could create a large number of oxygen vacancy defects on Ce-MnFe2O4 surface, which modify the activation barrier of PMS and facilitate the generation of •O2- thermodynamically. The stable existing cavitation bubbles with the size of 100∼400 nm could create considerable gas-liquid interface. The molecular dynamics simulations show that the nano bubbles can concentrate the BPA and increase the probability of contacts between BPA and Ce-MnFe2O4, hence effectively solve the issues of short lifetime of •O2- radicals and limited mass transfer distance to strengthen the reaction. In addition, the PMS/Ce-MnFe2O4/HC system not only achieves the satisfied COD (95 %) and TOC (65 %) removal efficiency but also enabled the BPA-contaminated water with a low energy cost of 0.065 kWh·m-3 and oxidant cost, highlighting the application potential of the HC technology for contaminated water.

Hyaluronan size and concentration: Effect on key biophysical and biochemical features.

The effect of hyaluronan (HA) molecular weight (MW) and concentration (c) on key features of HA-formulations was systematically studied, in vitro, exploring the widest range/number of MW/c to date. Nine pharmaceutical-grade HA-samples (60-2500 kDa) were hydrodynamically characterized using Size-Exclusion-Chromatography-Triple-Detector-Array (SEC-TDA) also providing conformational data. HAs aqueous solutions (thirteen concentrations in the range 0.1-32 g/L) were tested for dynamic viscosity (η). η dependence on MW/c was analyzed providing mathematical correlations not only for the specific-zero-shear-viscosity, but also for the critical-shear-rate and the shear-thinning-extent. Besides confirming the dilute- and semi-dilute- c-regimes for the HAs, a third concentrated regime was evidenced for the 220-2500 kDa samples. Data on how MW affects the dependence of viscosity parameters on c and vice-versa were provided. The 60-90 kDa HAs proved stable to thermal sterilization and enzymatically catalyzed hydrolysis, while the 220-2500 kDa samples depolymerized to an extent depending, beyond concentration, on MW. HA size did not significantly affect fibroblasts behavior: under the conditions here tested, the HAs similarly sustained human-dermal-fibroblasts growth and wound-healing also showing comparable effect on collagen-I, elastin and hyaluronan-synthase-1 expression. Overall, results valuably contribute to the understanding of the HA MW/c impact on the rheological, stability and biochemical features of the final formulations also providing mathematical correlations allowing for their optimization towards specific performance.

Hypoxia extreme events in a changing climate: Machine learning methods and deterministic simulations for future scenarios development in the Venice Lagoon.

Climate change pressures include the dissolved oxygen decline that in lagoon ecosystems can lead to hypoxia, i.e. low dissolved oxygen concentrations, which have consequences to ecosystem functioning including biogeochemical cycling from mild to severe disruption. The study investigates the potential of machine learning (ML) and deterministic models to predict future hypoxia events. Employing ML models, e.g. Random Forest and AdaBoost, past hypoxia events (2008-2019) in the Venice Lagoon were classified with an F1 score of around 0.83, based on water quality, meteorological, and spatio-temporal factors. Future scenarios (2050, 2100) were estimated by integrating hydrodynamic-biogeochemical and climate projections. Results suggest hypoxia events will increase from 3.5 % to 8.8 % by 2100, particularly in landward lagoon areas. Summer prediction foresee a rise from 118 events to 265 by 2100, with a longer hypoxia-prone season. This model is a valuable tool for developing hypoxia scenarios, aiding in identifying restoration hotspots for climate-threatened lagoons.

Influence of Oxygen Exposure on Lignin Preservation during Sediment Lateral Transport in the Ocean: Insights from Molecular Dynamics Simulations.

Understanding the fate of terrestrial organic carbon (terrOC) preservation in the marine environments is critical for deciphering the biogeochemical processes associated with the global carbon cycle and the Earth's climate change. The mechanisms controlling terrOC preservation are not completely understood, while lateral oxygen exposure time (OET) is considered as a critical controlling factor. Here, we first utilized molecular dynamics simulations to investigate the structural properties of lignin under anoxic, suboxic, and oxic conditions for understanding the mechanisms of terrOC preservation during sediment lateral transport in the ocean. Our finding suggested that oxygen exposure was indispensable for terrOC degradation through influencing the structural stability and reactivity of lignin. Our simulated results showed that in suboxic environments, prolonged OET may enhance terrOC preservation. Our organic geochemical results suggested that terrOC preferably preserved in coarse silts (20-63 µm) than fine silts (<20 µm) in suboxic environments, largely due to hydrodynamics-driven prolonged OET in coarse sediments, which may efficiently reduce CO2 emissions. Overall, our study sheds new light on the mechanisms of lateral OETs on terrOC preservation in suboxic conditions and, from a unique molecular structural perspective, provides insights into the impact of prolonged OETs on terrOC oxidative degradation in the marine environment.

The role of microorganisms in phosphorus cycling at river-lake confluences: Insights from a study on microbial community dynamics.

River-lake confluences are key zones in the river-lake network, essential for managing contaminant transport and transformation. However, the role of biogeochemical transformations, particularly in phosphorus (P) dynamics, has been underexplored. As a result, this study looks into the dynamics of microbial communities and how important microbes are to the cycling of P. It was revealed that microorganisms contribute differently to phosphorus cycling in different hydraulic regions. Regions with higher-velocity and finer sediment showed increased microbial diversity and enhanced capabilities for organic phosphorus (OP) mineralization and inorganic phosphorus (IP) solubilization due to lower bio-available P (bio-P) concentrations. In areas characterized by flow deflection (FD), flow stagnation (FST), and flow separation (FSE), distinct P fraction distributions were observed: Total phosphorus (TP) and bio-P were found to be more abundant in the FST and FD regions, but residual phosphorus (Res-P) and calcium phosphorus (Ca-P) were more prevalent in the FSE region. Sediment characteristics, including P species like aluminum-phosphorus (Al-P), OP, iron-associate phosphorus (BD-P), and sediment mid-diameter (D50), significantly influence microbial community composition. These results improve our comprehension of the distribution of microbial community distribution and its role in the phosphorus cycle at river-lake confluence, providing useful provide valuable information for managing river-lake confluences and protecting aquatic ecosystems.

Influence of hollow droplet impact and spreading characteristics on the cylindrical lateral surface.

In this study, 3D model of a hollow glycerin droplet impacting on a cylindrical cross-section was numerically analyzed to coat the lateral surface of the cylinder. The hollow droplets had exterior diameters of 5.5 mm, 5.25 mm, and 5 mm, and the impact velocity was 1 m/s. To model, the influence of droplets on OpenFoam software, the Volume Of Fluid technique was utilized (VOF). The Newtonian, incompressible, and laminar fluid phase of a glycerin droplet was investigated using air with a diameter of 4 mm as the gas phase. The hydrodynamic behavior of droplet collisions as well as fluid properties were investigated. As a result, when can be observed in the simple cylinder, as the outer diameter increased, the spread diameter shrank. The least amount distributed diameter in Case 3 was 1.404, whereas the highest amount in Case 4 was 1.625. The situations with a simple lateral surface, uniform spread occurred, while in cases with a spiral lateral surface, non-uniform spread occurred. Observed the maximum length in Case 3 was 4.12 mm and the minimum was 1.83 mm in Case 4.

Hydrodynamic Simulation and Experiment of a Self-Adaptive Amphibious Robot Driven by Tracks and Bionic Fins.

Amphibious robots have broad prospects in the fields of industry, defense, and transportation. To improve the propulsion performance and reduce operation complexity, a novel bionic amphibious robot, namely AmphiFinbot-II, is presented in this paper. The swimming and walking components adopt a compound drive mechanism, enabling simultaneous control for the rotation of the track and the wave-like motion of the undulating fin. The robot employs different propulsion methods but utilizes the same operation strategy, eliminating the need for mode switching. The structure and the locomotion principle are introduced. The performance of the robot in different motion patterns was analyzed via computational fluid dynamics simulation. The simulation results verified the feasibility of the wave-like swimming mechanism. Physical experiments were conducted for both land and underwater motion, and the results were consistent with the simulation regulation. Both the underwater linear and angular velocity were proportional to the undulating frequency. The robot's maximum linear speed and steering speed on land were 2.26 m/s (2.79 BL/s) and 442°/s, respectively, while the maximum speeds underwater were 0.54 m/s (0.67 BL/s) and 84°/s, respectively. The research findings indicate that the robot possesses outstanding amphibious motion capabilities and a simplistic yet unified control approach, thereby validating the feasibility of the robot's design scheme, and offering a novel concept for the development of high-performance and self-contained amphibious robots.

Hydrodynamic Cavitation as a Method of Removing Surfactants from Real Carwash Wastewater.

The present work aimed to evaluate whether the use of an innovative method such as hydrodynamic cavitation (HC) is suitable for the simultaneous removal of surfactants of different chemical natures (non-ionic, anionic and cationic) from actual car wash wastewater at different numbers of passes through the cavitation zone and different inlet pressures. An additional novelty was the use of multi-criteria decision support, which enabled the selection of optimal HC conditions that maximized the removal of each group of surfactants and chemical oxygen demand (COD) with minimal energy input. For the optimal HC variants, Fourier transform infrared spectroscopy (FT-IR/ATR) as well as investigations of surface tension, zeta potential, specific conductivity, system viscosity and particle size were carried out. The highest reduction of non-ionic surfactants was found at 5 bar inlet pressure and reached 35.5% after 120 min. The most favourable inlet pressure for the removal of anionic surfactants was 3 bar and the removal efficiency was 77.2% after 120 min, whereas the most favourable inlet pressure for cationic surfactant removal was 3 bar, with the highest removal of 20% after 120 min. The obtained results clearly demonstrate that HC may constitute an effective, fast and cost-efficient method for removing surfactants from real industrial wastewater.

Escape motility of multicellular magnetotactic prokaryotes.

Microorganisms often actively respond to multiple external stimuli to navigate toward their preferred niches. For example, unicellular magnetotactic bacteria integrate both oxygen sensory information and the Earth's geomagnetic field to help them locate anoxic conditions in a process known as magneto-aerotaxis. However, for multicellular magnetotactic prokaryotes (MMPs), the colonial structure of 4-16 cells places fundamental constraints on collective sensing, colony motility and directed swimming. To investigate how colonies navigate environments with multiple stimuli, we performed microfluidic experiments of MMPs with opposing magnetic fields and oxygen gradients. These experiments reveal unusual back-and-forth excursions called 'escape motility', in which colonies shuttle along magnetic field lines, punctuated by abrupt-yet highly coordinated-changes in collective ciliary beating. Through cell tracking and numerical simulations, we demonstrate that escape motility can arise through a simple magneto-aerotaxis mechanism, which includes the effect of magnetic torques and chemical sensing. At sufficiently high densities of MMPs, we observe the formation of dynamic crystal structures, whose stability is governed by the magnetic field strength and near-field hydrodynamic interactions. The results shed light on how some of the earliest multicellular organisms navigate complex physico-chemical landscapes.

Structure Prediction of Large RNAs with AlphaFold3 Highlights its Capabilities and Limitations.

DeepMind's AlphaFold3 webserver offers exciting new opportunities to make structural predictions of heterogeneous macromolecular systems. Here we attempt to apply AlphaFold3 to large RNA molecules whose 3D atomic structures are unknown but whose physical dimensions have been studied experimentally. One difficulty that we encounter is that models returned by AlphaFold3 often contain severe steric clashes and, less frequently, clear breaks in the phosphodiester backbone, with the probability of both events increasing with the length of the RNA. Restricting attention to those RNAs for which non-clashing models can be obtained, we find that hydrodynamic radii computed from the AlphaFold3 models are much larger than those reported experimentally under low salt conditions but are in better agreement with those reported in the presence of polyvalent cations. For two RNAs whose shapes have been imaged experimentally, the computed anisotropies of the AlphaFold3-predicted structures are too low, indicating that they are excessively spherical; extending this analysis to larger RNAs shows that they become progressively more spherical with increasing length. Overall, the results suggest that AlphaFold3 is capable of producing plausible models for RNAs up to ∼2000 nucleotides in length, but that thousands of predictions may be required to obtain models free of geometric problems.

Hydrodynamics- and remote sensing-based model for estimating the effects of cohesive sediment transport on lagoon siltation in Southwestern Taiwan.

This study investigates localized siltation in the Cigu Lagoon, Southwestern Taiwan, using an integrated approach of hydrodynamic modeling and remote sensing. In regions where in situ data is scarce, remote sensing provides critical complementary data inputs for our sediment model. We employed a multilayered mud sediment model, incorporating initial suspended sediment concentration (SSC) data derived from Landsat imagery, to identify the morphological changes taking place in the lagoon. Over the past few decades, sandbar migration and sedimentation have led to a significant shrinkage of the Cigu Lagoon, which is now at risk of disappearing if a full understanding of the underlying factors is not reached. The loss of the lagoon would have severe implications for the local ecosystem and habitat, as well as for the fishermen who rely on the lagoon for their livelihoods. Our results showed that sedimentation in the Cigu Lagoon is a compounded consequence of the action of the tidal cycle and of waves. Throughout the simulation period, the SSC in the Cigu Lagoon ranged from 1 g m -3 to 50 g m -3. The annual siltation rate of the lagoon due to cohesive sediment transport was 0.82 cm. The simulation results showed that the siltation mainly occurred during the winter, with the dominant factor being the frequent strong waves at this time of year. This study suggests that a management plan for the Cigu Lagoon must be devised and implemented, and that remote sensing and hydrodynamic modeling are valuable tools in communicating about the complex processes involved in a sedimentary system and informing relevant decision-making at the stage of management.

Response surface optimization of a single-step castor oil-based biodiesel production process using a stator-rotor hydrodynamic cavitation reactor.

In order to combat environmental pollution and the depletion of non-renewable fuels, feasible, eco-friendly, and sustainable biodiesel production from non-edible oil crops must be augmented. This study is the first to intensify biodiesel production from castor oil using a self-manufactured cylindrical stator-rotor hydrodynamic cavitation reactor. In order to model and optimize the biodiesel yield, a response surface methodology based on a 1/2 fraction-three-level face center composite design of three levels and five experimental factors was used. The predicted ideal operating parameters were found to be 52.51°C, 1164.8 rpm rotor speed, 27.43 min, 8.4:1 methanol-to-oil molar ratio, and 0.89% KOH concentration. That yielded 95.51% biodiesel with a 99% fatty acid methyl ester content. It recorded a relatively low energy consumption and high cavitation yield of 6.09 × 105 J and 12 × 10-3 g/J, respectively. The generated biodiesel and bio-/petro-diesel blends had good fuel qualities that were on par with global norms and commercially available Egyptian petro-diesel. The preliminary cost analysis assured the feasibility of the applied process.

Strong Subseasonal Variability of Oxic Methane Production Challenges Methane Budgeting in Freshwater Lakes.

Methane (CH4) accumulation in the well-oxygenated lake epilimnion enhances the diffusive atmospheric CH4 emission. Both lateral transport and in situ oxic methane production (OMP) have been suggested as potential sources. While the latter has been recently supported by increasing evidence, quantifying the exact contribution of OMP to atmospheric emissions remains challenging. Based on a large high-resolution field data set collected during 2019-2020 in the deep stratified Lake Stechlin and on three-dimensional hydrodynamic modeling, we improved existing CH4 budgets by resolving each component of the mass balance model at a seasonal scale and therefore better constrained the residual OMP. All terms in our model showed a large temporal variability at scales from intraday to seasonal, and the modeled OMP was most sensitive to the surface CH4 flux estimates. Future efforts are needed to reduce the uncertainties in estimating OMP rates using the mass balance approach by increasing the frequency of atmospheric CH4 flux measurements.

In-situ algal control by two-stage nanobubble technology in Taihu Lake: Efficacy and ecological impact.

Hydrodynamic cavitation and ozone nanobubble-coupled hydrodynamic cavitation have demonstrated effective algae control in laboratories, but their in-situ potential, especially impact on nutrient salt degradation and microbial communities remain unclear. This study applied two-stage nanobubble technology, combining hydrodynamic cavitation and ozone nanobubbles, in a 3300 m2 semi-enclosed area of Taihu Lake to address these gaps. Results show that the technology efficiently controls algae, reduces odors, improves anaerobic conditions, and lowers ammonia nitrogen. Over 20 days, chlorophyll-a concentration reduced by 77.46% and cyanobacterial phycocyanin by 89.47%. Additionally, the concentrations of 2-MIB, GSM, and DMTS fell below threshold values. Notably, the relative abundance of Cyanobacteria in sediment dropped from 8.53% in the control area to only 1.59%-3.65% in the experimental area. The technology also achieved a significant reduction in ammonia nitrogen, with removal efficiencies of 78.53% in the water column and 39.17% in sediments, though the removal of total phosphorus was limited. Furthermore, the two-stage nanobubble system enhanced the abundance of nitrogen-cycling microorganisms and genes in the water, while promoting nitrogen- and phosphorus-related microbial communities in sediments and inhibiting the cyanobacteria-associated genus Cyanobium PCC-6307. Thus, Two-stage nanobubble technology can be employed for in-situ algal control in aquatic ecosystems.

Chromatographic analysis of branched and debranched starch structure: Variability of their results.

Starch structure determination is crucial for understanding its properties and applications. However, method-dependent variations in size determination can lead to ambiguous interpretations. This study investigates the ambiguities in starch structure determination by evaluating the variation in size of four commercial branched starches as determined by average molar mass, gyration radius, hydrodynamic radius, and chain-length distribution. The starches were analyzed using high-performance size-exclusion chromatography (HPSEC) coupled with multi-angle laser light scattering (MALLS) and refractive index detector (RI), and after debranching by HPSEC-RI and high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detector (PAD). MALLS-derived MW values for amylose and amylopectin were higher than those obtained using the hydrodynamic volume method. The molecular weight of amylopectin chains, determined by the degree of polymerization (DP), ranged between 2.1 and 2.9 × 103 g/mol for short chains, and between 4.1 × 103 and 1.1 × 104 g/mol for long chains. Differences in amylopectin chain content were observed between HPSEC-RI and HPAEC-PAD, highlighting the complementary nature of these techniques. The study underscores the need for standardizing chromatography-based methodologies in starch research, particularly with the advent of new technologies.

Hydrodynamic driven microplastics in Dongting Lake, China: Quantification of the flux and transportation.

Hydrodynamic conditions have a significant effect on the fate of microplastics (MPs). Moreover, research on the relation between hydrodynamic conditions and MPs in freshwater environments is critical and unquantified. In this regard, herein, a methodological framework integrating system monitoring with numerical simulation has been developed and successfully implemented for Dongting Lake, a large freshwater lake fed by multiple rivers. According to time-series monitoring and hydrological data, 199.29/128.50 trillion MP items entered or exited Dongting Lake in 2021. In addition, a coupled numerical model identified four key areas of MP accumulation, which overlap with nature reserves and agricultural zones, posing considerable risks to the ecological gene pool and food security. The quantitative results obtained using the developed framework enable calculation of MP inflow and outflow fluxes and facilitate analysis of MP transportation. Overall, this study provides a scientific basis for preventing and controlling MP pollution in Dongting Lake and offers valuable insights for future research on related issues in freshwater ecosystems.

Hydrodynamic frictional performance of fouled panels: a comparative study of different coating types.

This research study delves into the hydrodynamic frictional characteristics of fouled panels coated with different types of coatings, investigating how fouling coverage and surface roughness influence drag. The investigation incorporates data on the overall percentage coverage of fouling, as well as roughness measurements obtained through a 3D profilometer. Drag data collected from a flowcell simulation of real-world flow conditions complements these measurements. Notably, the determination of the level of fouling leverages the capabilities of CIE L*a*b as an image analysis method, focusing on the overall coverage rather than individual fouling species. The objective is to illustrate how fouled panels perform under varying flow and coating conditions compared to their clean counterparts. Furthermore, the paper proposes a roughness scaling approach that considers both the percentage coverage and measured areal roughness for each coating type, encompassing both fouled and unfouled areas. This approach provides valuable insights into the combined effects of fouling and surface roughness on hydrodynamic performance, enhancing our understanding of the intricate interplay between these factors.

Exact hydrodynamic manifolds for the linear Boltzmann BGK equation I: spectral theory.

We perform a complete spectral analysis of the linear three-dimensional Boltzmann BGK operator resulting in an explicit transcendental equation for the eigenvalues. Using the theory of finite-rank perturbations, we confirm the existence of a critical wave number k crit which limits the number of hydrodynamic modes in the frequency space. This implies that there are only finitely many isolated eigenvalues above the essential spectrum at each wave number, thus showing the existence of a finite-dimensional, well-separated linear hydrodynamic manifold as a combination of invariant eigenspaces. The obtained results can serve as a benchmark for validating approximate theories of hydrodynamic closures and moment methods and provides the basis for the spectral closure operator.