Spreading Behavior Research Articles

Differential gliding motility responses of Chryseobacterium sp. strain PMSZPI isolated from uranium ore deposit on hard and soft substrates

The Bacteroidota bacterium, Chryseobacterium sp. strain PMSZPI isolated from sub-surface soil of uranium ore deposit was shown to move on solid surfaces via gliding motility resulting in the formation of thin spreading colonies. In this study, we attempted to understand the influence of the surfaces, soft or hard/rigid, on the motility behaviour of PMSZPI cells. The computational tool T9GPred in combination with LC-MS/MS analysis established the presence of orthologs of vital gliding motility proteins in PMSZPI. We analyzed the single cell or population motility phenotypes of PMSZPI under spreading and non-spreading conditions. A low percentage of agar or soft agar (0.35%) with low nutrient levels induced more active gliding motility in individual cells leading to increased colony spreading. Microscopic analyses indicated the self-assembly of the gliding cells into irregular edged or spherical microcolonies based on the agar concentration. Cells moved at a speed of 0.2 to 0.6 µm s-1 on low-percentage gliding permissive agar (0.35%) surface in contrast to significant inhibition of motility on rigid or hard agar (1.5%) surface. RNA sequencing and real-time quantitative PCR (qPCR) analysis revealed increased expression of gliding motility genes under low agar conditions consistent with increased spreading behaviour. These findings provide the first glimpse into the gliding motility behaviour of a Bacteroidota bacterium from metal enriched environment that apparently could have implications on bacterial adaptation to changing surface environments.

Flame spread characteristics of densified wood with various sample widths and densities

Densified wood (DW) is a novel functional material with great mechanical properties, its structural characteristics make it attractive as an ideal building material for mid-to-high-rise timber constructions. However, its flame spread characteristics is not yet fully understood, which threatens its further developments and applications. This study experimentally and analytically investigates the impact of density and width on the flame spread behaviors and heat transfer characteristics of DW. Flame spread rate, mass loss rate (MLR), and flame height decrease with increasing wood density. Both MLR and flame height increase with the increasing width, while flame spread rate increases first and then decreases. Dimensionless power-law relationships among them were established, which well predict the measurements. The dominant gaseous heat transfer transits from radiation to convection with the increase of density. The critical density for this transition is increased with width. Both width and density impact the preheating length and total heat flux, which are combined to influence the flame spread rate. A dimensionless correlation among them was established with an R2 of 0.915 to the experiments of current and previous publications. This work helps to understand flame spread of DW and benefits the fire safety in timber construction.

Evaporation, spreading, and possible uptake of droplets on sorghum (Sorghum bicolor) and cowpea (Vigna unguiculata) leaves using an imaging-based technology.

Sprayed agrochemical droplets have a dynamic evolution on the leaf surface, undergoing changes in shape and volume due to spreading, evaporation, and adsorption. To better understand these processes, an accessible imaging-based experimental methodology is presented to precisely measure droplet spreading, evaporation, and potential uptake by a leaf within a controlled relative humidity environment. Laboratory experiments were conducted to determine the effect of hydrocarbon surfactants, accelerators (light mineral oil), and humectants (high fructose corn syrup) on droplet spread, evaporation, and potential uptake when applied to sorghum (Sorghum bicolor 'Tricker') and cowpea (Vigna unguiculata) leaves. Experiments on cowpea leaves showed uniform spreading and no change in evaporation compared to the predicted rate. In contrast, on sorghum leaves, results suggest that the volume loss rate exceeds the predicted evaporation rate (up to 23%), indicating a potential uptake by the leaves. Some accelerated dynamics on sorghum can be attributed to the lateral spreading observed on hairy leaves along the veins, increasing the contact area by an average of 65%. However, samples containing light mineral oil, typically considered an accelerant to aid in uptake, demonstrated the highest rate but exhibited minimal spreading. The study demonstrates how droplet composition affects droplet dynamics on waxy and hairy leaves by using an imaging-based methodology to measure evaporation rates, volume loss, contact angle, wetted area, and spreading behavior. The findings highlight some of the complex coupling between the crop protection product composition and droplet life cycle on a leaf. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Investigation of pulsating behavior and oxygen concentration of flame spread over sub-flash n-butanol fuel in a circular tube

Investigation of pulsating behavior and oxygen concentration of flame spread over sub-flash n-butanol fuel in a circular tube

The pinning characteristics of droplets and the self-repair mechanism of lubricating film on nanoporous surface: A molecular dynamics perspective

The nanoscale pore gives rich dynamic information to the flow behavior of the droplets exuded on the SLIPS (Smooth Liquid-Infused Porous Surface). The key to realizing fast self-healing of lubricating film is to understand the dynamic law of droplets at nano-orifice. In this paper, a dynamics model of the exudation and spreading behavior is established by the non-equilibrium molecular dynamics simulation. The characteristics and the mechanism of pinning and spreading of nano-droplets were studied. We found that adjusting the wettability and pore diameter can change the liquid exudation and the pinning time of droplets at the orifice. The weaker wettability and larger pore diameter both can increase the exudation velocity and reduce the pinning time of the droplets, which then improves the spreading of exuded droplets and the self-repairing efficiency of the damaged liquid film. As the pore diameter increases, the spreading area of the droplets on the surface of the pore increases. The increase in the wettability also facilitates the spreading behavior, but the outflow rate of the liquid from the pore decreases. Under the combined effect of the two factors, the spreading area of droplets first increases and then decreases with the wettability increases. The results provide potential insights into the spreading mechanism of nanodroplets on porous surfaces.

Highly efficient flame retardancy and fire spread behavior of rigid polyurethane foams with extremely low content of flame retardant

In recent years, flame-retardant rigid polyurethane foam (RPUF) has once again captured the scholars’ attention due to the growing the growing demands in the field of building energy efficiency. However, the inherent flammability of RPUF is high and the complexities of its flame-retardant mechanisms remain inadequately understood. In this study, a modified biomass material, amino starch phosphate ester was successfully synthesized which was then combined with expandable graphite (EG) and incorporated into RPUF. The research delved into the optimal ratio and minimal flame-retardant additive required to achieve the stringent UL-94 V-0 rating, while also thoroughly investigating the flame retardancy and thermal properties of the composite system. The findings revealed that with just 6 wt.% of flame retardants, the RPUF achieved the UL-94 V-0 rating, with a 41.1 % reduction in peak heat release rate (pHRR) and a 23.7 % decrease in total heat release (THR). Additionally, it diminishes the flame's size and width, leading to quicker extinction, while also lowering the internal combustion temperature of the polyurethane, thereby delaying both preheating and combustion times. The synergistic interaction between amino starch phosphate ester and EG during combustion results in the formation of a dense, continuous char layer, effectively inhibiting the pyrolysis and combustion of RPUF. This study provides a theoretical foundation for the development of efficient flame-retardant systems for RPUF.

Analysis of time-dependent hydrophobic recovery on plasma-treated superhydrophobic polypropylene using XPS and wettability measurements

In specific applications like ice-repellent coatings or membrane separation technology, wettability is a key parameter affecting the applicability of commodity polymers. This study presents a technique to fine-control the wetting properties of a hierarchically structured polypropylene surface, enabling the transition between superhydrophobic and superhydrophilic states. To demonstrate the tunability of the wetting properties of polypropylene (PP) substrate, we prepared in a consecutive way superhydrophobic (advancing contact angle (CAadv) of 152°) and superhydrophilic (CAadv of 0°) material by solvent-treatment and mild air plasma treatment. The optimal plasma treatment parameters to achieve superhydrophilic wetting behaviour, which is stable for at least one week of storage in air was also explored. Water contact angle measurement and X-ray photoelectron spectroscopy were used to monitor the time dependency of hydrophobic recovery on a hierarchically structured PP surface. With a simple model considering structural and wetting parameters, we characterized the droplet spreading behaviour of plasma-treated roughened surfaces, which exhibited superhydrophilic wetting behaviour with equilibrium CAadv of nearly 0°. The proposed model, which aligns well with experimental data, can be used to compare the droplet spreading behaviour of plasma-treated roughened surfaces.

Modelling study on pedestrian evacuation dynamics considering exit selection behaviour under flood disaster

Flood spreading in metro stations is a dangerous hazard that frequently causes casualties and property losses. However, pedestrian evacuation under flood spreading scenarios has not been fully investigated. To fill this gap,we propose an extend Floor-Field model incorporating flood spreading and exit selection behaviour of individuals. In the model, the dynamic flood spreading process on metro platforms is expressed by using a simulation software named Mike21. The optimal exit selected by pedestrians in each step is decided on three factors, that is pedestrian density around the exit, pedestrian distance to the exit, and water depth at the exit. Meanwhile, the movement speed of pedestrain also changes with the water depth at each time step. Based on this, the transition probability to neighbor cell including static field, dynamic field, height field, and water flow field is calculated. This results in a flood evacuation model considering the pedestrian's behaviour when choosing an exit. The effects of flooding, pedestrian density, different exit selection behaviours, water flow field, and inlet flow on evacuation were thoroughly analysed. The analysis demonstrates that the likelihood of flooding significantly impacts the evacuation of pedestrians from the subway station; the more flooding is taken into account, the more influential the impact. In addition, the effect of inlet flow on evacuation is also noteworthy; considering exit selection behaviour can significantly increase the effectiveness of evacuation. The study's findings can be used to develop evacuation plans for flooded metro stations.

Information spread behavior of clubhouse: A value-attitude-behavior model perspective

The prevalence of social media has significantly facilitated the spread and diffusion of online memes. The Clubhouse voice community application, which gained popularity rapidly during the COVID-19 pandemic and became widely used, can be regarded as a form of internet meme. However, the underlying reasons for this phenomenon have been scarcely explored. In this context, the purpose of this study is to understand the dissemination mechanisms of the Clubhouse voice community. Specifically, this research employs the value-attitude-behavior model to investigate the relationships between social value, attitude, immediate response syndrome, and information spread behavior on Clubhouse. To achieve this objective, the snowball sampling technique was used to recruit Clubhouse users to complete a questionnaire. The collected data were assessed for reliability and validity before being analyzed using structural equation modeling for confirmatory factor analysis and model verification. The results indicated that the social value of joining Clubhouse is positively associated with participants’ attitudes toward participation. Additionally, attitudes toward participation were found to be positively associated with both immediate response syndrome and information spread behavior, thus showing a positive association between immediate response syndrome and information spread behavior. This study reveals the pathways of internet meme dissemination, offering insights into the factors driving the formation of internet memes.

Step flow mechanism in dissolutive wetting Cu/Ni systems

The Cu-Ni system is a typical dissolutive system due to its mutual dissolution across a wide range of temperatures and compositions. We characterized the effects of Ni dissolution on the wetting behavior of liquid Cu by combining high-temperature wetting experiments, in-situ observation of spreading and solidification, microstructure analysis of the quenched droplets, and computational fluid dynamic (CFD) simulations. In the very early moment, at 1100 °C, when the Cu droplet is brought in contact with the Ni substrate, it oscillates due to capillarity and is dampened by inertial effects, while the significant Ni dissolution at 1150 °C largely reduced the initial oscillations. Later, a peculiar spreading behavior is observed and we propose to describe it through a 4-step mechanism: pinning of the contact line by a newly formed solid solution layer at the interface acting as a physical barrier, driving of liquid towards the solidified edge due to a Ni-concentration induced Marangoni flow, forming of a precursor film ahead of the solidified edge caused by the strong Cu-Ni interactions and Marangoni flow, and finally depinning due to overflow as a result of liquid accumulation at the solidified edge. The formation of a solid solution layer is confirmed by in-situ observation and quenching. The Ni-concentration induced Marangoni flow is characterized experimentally and further investigated by CFD simulations. The proposed step flow mechanism can be potentially relevant to other dissolutive wetting systems (e.g. Bi/Sn, Ag/Cu and Cu/Fe systems), which are crucial for high-temperature processing techniques.

Effects of fuel distribution on thermal environment and fire hazard

AbstractFire accidents in buildings are occurring and claiming thousands of lives each year. Due to various architectural designs, fire hazards would be unique to each building layout. This paper discusses how fire hazard varies with the arrangement of the fuel inside buildings. To comprehensively present the effect of fuel distribution on fire behaviour, results from large‐scale experiments, bench‐scale experiments, empirical correlations, and numerical studies are provided. In large‐scale fire tests, two different cases of wood cribs were tested to demonstrate the effects of porosity on heat generation and fire spread behaviour. Due to the limitations of experimental conditions, the variation in heat release rate attributable to differences in fuel porosity and surface area has been also qualitatively investigated using a cone calorimeter test. To bring the gap between experimental observations and real‐word scenarios, a numerical study is also performed. This study further explores the effects of fuel distribution (considering porosity and surface area of fuel throughout the compartment) and ventilation on fire spread beyond the fire compartment. The computational fluid dynamics (CFD) simulations show how the distribution of fuel in different ways can lead fire to spread beyond its origin, as observed in many fire accidents. The paper suggests that designers should consider such critical fire scenarios in performance‐based design.

Research on the dynamics of flame propagation and overpressure evolution in full-scale residential gas deflagration

To determine the effect of ignition height on indoor flame spread behavior and overpressure development, a comprehensive full-scale deflagration testing facility was established. Extensive experimental research was conducted within this facility. The findings indicate that indoor flame reignition and the occurrence of secondary explosions are most pronounced with intermediate ignition. Furthermore, the explosion overpressure generated during the reverse turn of shock wave propagation is greater than that produced by the forward turn. In comparison to the peak overpressure Pext in the master bedroom for top, middle, and bottom ignition, the peak overpressure Pext in the second bedroom increased by approximately 14.48 %, 15.04 %, and 19.20 %, respectively. When comparing middle ignition to top ignition, the propagation speed of shock waves in the kitchen balcony, restroom, second bedroom, and master bedroom was enhanced by 34.21 %, 40.85 %, 40.70 %, and 34.65 %, respectively. Furthermore, when comparing middle ignition to bottom ignition, the propagation speed of shock waves in these areas experienced a significant increase of 126.32 %, 124.39 %, 123.26 %, and 113.86 %, respectively. These research findings provide a theoretical foundation and empirical data to support the investigation and analysis of the causes of indoor gas explosion incidents.

Mathematical modeling for the production performance of cyclic multi-thermal fluid stimulation process in layered heavy oil reservoirs

Multi-thermal fluid (MTF), with a unique thermophysical characteristics, has been widely applied in the enhanced heavy oil recovery processes. Especially for the layered heavy oil reservoirs, MTF shows more attractive than the conventional saturated steam. In this study, we propose an improved mathematical model for the production performance of cyclic MTF stimulation process in layered heavy oil reservoirs. In this model, based on a three-zone assumption, we first derive a productivity model for the thermal-fluids huff-n-puff process in layered heavy oil reservoirs. Thereafter, considering the typical EOR mechanisms of non-condensable gases in MTF, the viscosity reduction effect caused by CO2 dissolution and the effect of formation energy supplement caused by N2 are mathematically described. Simultaneously, because of the nonlinear temperature spreading behavior in the formation, an MTFs flooding experiment is also performed to characterize the effect. Meanwhile, a heating radius model with the consideration of steam overlap effect is also involved in our model. Then, the calculation results are compared against the results of a commercial simulator to confirm the accuracy, while a sensitivity analysis on the reservoir and operation parameters is performed. This paper provides a quick estimation approach for the productivity of cyclic MTF stimulation process in layered heavy oil reservoirs.

A Case Study of the Possible Meteorological Causes of Unexpected Fire Behavior in the Pantanal Wetland, Brazil

This study provides insights into large fires in the Pantanal by analyzing the atmospheric conditions that influenced the rapid fire evolution between 13 and 14 November 2023, when fire fronts spread rapidly, leading to critical situations for firefighters. The observation-based analysis helped us to identify some characteristics of the fire’s evolution and the meteorological conditions in the region. Furthermore, two simulations were run with the Meso-NH model, which was configured with horizontal resolutions of 2.5 km and 5 km. The fire behavior, characterized by satellite observations, revealed periods with a sudden increase in active fire numbers. High temperatures and low relative humidity in the region characterized the fire weather conditions. The simulations confirmed the critical fire condition, showing the benefits of increasing the resolution of numerical models for the Pantanal region. The convection-resolving simulation at 2.5 km showed the repeated development of gust fronts in the late afternoon and early evening. This study highlights this dynamic that, coupled with intense surface wind gusts, was crucial for the intensification of the fire spread and unexpected behavior. This study is a first step toward better understanding fire dynamics in the Pantanal through atmospheric modeling, and it can support strategies for firefighting in the region.

Laser Direct Writing of Setaria Virids-Inspired Hierarchical Surface with TiO2 Coating for Anti-Sticking of Soft Tissue.

In minimally invasive surgery, the tendency for human tissue to adhere to the electrosurgical scalpel can complicate procedures and elevate the risk of medical accidents. Consequently, the development of an electrosurgical scalpel with an anti-sticking coating is critically important. Drawing inspiration from nature, we identified that the leaves of Setaria Virids exhibit exceptional non-stick properties. Utilizing this natural surface texture as a model, we designed and fabricated a specialized anti-sticking surface for electrosurgical scalpels. Employing nanosecond laser direct writing ablation technology, we created a micro-nano textured surface on the high-frequency electrosurgical scalpel that mimics the structure found on Setaria Virids leaves. Subsequently, a TiO2 coating was deposited onto the ablated scalpel surface via magnetron sputtering, followed by plasma-induced hydrophobic modification and treatment with octadecyltrichlorosilane (OTS) to enhance the surface's affinity for silicone oil, thereby constructing a self-lubricating and anti-sticking surface. The spreading behavior of deionized water, absolute ethanol, and dimethyl silicone oil on this textured surface is investigated to confirm the effectiveness of the self-lubrication mechanism. Furthermore, the sticking force and quality are compared between the anti-sticking electrosurgical scalpel and a standard high-frequency electrosurgical scalpel to demonstrate the efficacy of the nanosecond laser-ablated micro-nano texture in preventing sticking. The findings indicate that the self-lubricating anti-sticking surface fabricated using this texture exhibits superior anti-sticking properties.

Wetting behavior of Ti-Ni-xNb filler alloy on (HfTaZrNbTi)C high-entropy carbide ceramic

Exploring the wetting behavior of active filler alloys on high-entropy ceramic is critical to clarifying the solid/liquid interface reaction mechanism and guiding the preparation of high-performance composites. The wetting and spreading behaviors of the molten Ti-Ni-xNb filler alloys, both without and with different Nb concentrations, on (HfTaZrNbTi)C high-entropy carbide (HEC) ceramic were investigated at 1330 °C under a vacuum atmosphere using a sessile drop method. The wetting process of the Ti-Ni-xNb filler alloys was characterized by four distinct stages: (i) adhesion stage, (ii) rapid decreasing stage, (iii) sluggish spreading stage, and (iv) final equilibrium stage. The Ti-Ni-xNb filler alloys all exhibited good wettability on the HEC ceramic, with the final contact angle remaining around 47-48°. The interfacial structure was identified as a sequence of HEC/Ti-based HEC’ diffusion layer/TiCx reaction layer/Ti2Ni layer/alloy droplet in all wetting systems. Notably, the introduced Nb element participated in the interfacial reactions between HEC and the filler alloy, modifying the morphology of the solidified droplet and accelerating the rapidly decreasing stage of the alloys on the ceramic. Nb atoms replaced some of the Ti atoms in the TiCx reaction layer, which restrained the atomic diffusion, leading to the formation of thinner reaction layers. The spreading kinetics were initially governed by interfacial reactions and later by the diffusion of Ti and Ni into the ceramic substrate, exhibiting a transition from reaction-controlled to diffusion-controlled spreading.

Response to the comments on “Cellular aggregation dictates universal spreading behaviour of a whole-blood drop on a paper strip”

In 2023, we published a research article in the Journal of Colloidal and Interface Science, based on our experimental findings and substantiating scaling arguments leading to a simple theoretical insight on the effect of red blood cell (RBC) aggregation on the wicking behaviour of a finite volume of blood as it navigates through the porous passages of a paper matrix (Laha et al., 2023). Of late, we received comments from Li (2024), which offered certain suggestions regarding the possible improvement of the capillary bundle model as considered in our article for analyzing the transport of blood through the paper pores. Herein, we provide a detailed discussion on each of the points raised by Li (2024) and rationalize our views in further details in addition to the contents already provided in our concerned article.

Comment on “Cellular aggregation dictates universal spreading behaviour of a whole-blood drop on a paper strip”

Laha et al. studied the diffusive behavior of a whole-blood drop on filter paper using the generalized capillary bundle model. However, some model parameters should be further refined to accurately reflect the physics involved in this diffusion process. Moreover, citations are missing for some key equations. Addressing these aspects will improve the model applicability to this application and benefit readers in accessing more accurate and detailed information.

Focal adhesion kinase regulates tendon cell mechanoresponse and physiological tendon development.

Tendons enable locomotion by transmitting high tensile mechanical forces between muscle and bone via their dense extracellular matrix (ECM). The application of extrinsic mechanical stimuli via muscle contraction is necessary to regulate healthy tendon function. Specifically, applied physiological levels of mechanical loading elicit an anabolic tendon cell response, while decreased mechanical loading evokes a degradative tendon state. Although the tendon response to mechanical stimuli has implications in disease pathogenesis and clinical treatment strategies, the cell signaling mechanisms by which tendon cells sense and respond to mechanical stimuli within the native tendon ECM remain largely unknown. Therefore, we explored the role of cell-ECM adhesions in regulating tendon cell mechanotransduction by perturbing the genetic expression and signaling activity of focal adhesion kinase (FAK) through both invitro and invivo approaches. We determined that FAK regulates tendon cell spreading behavior and focal adhesion morphology, nuclear deformation in response to applied mechanical strain, and mechanosensitive gene expression. In addition, our data reveal that FAK signaling plays an essential role in invivo tendon development and postnatal growth, as FAK-knockout mouse tendons demonstrated reduced tendon size, altered mechanical properties, differences in cellular composition, and reduced maturity of the deposited ECM. These data provide a foundational understanding of the role of FAK signaling as a critical regulator of insitu tendon cell mechanotransduction. Importantly, an increased understanding of tendon cell mechanotransductive mechanisms may inform clinical practice as well as lead to the discovery of diagnostic and/or therapeutic molecular targets.

Molten CMAS resistance strategy for PS-PVD TBCs based on laser textured and Al-modified bionic structure

Plasma spray-physical vapor deposition (PS-PVD) is a promising third-generation thermal barrier coatings (TBCs) technique. Feather-like columnar TBCs with excellent strain tolerance and low thermal conductivity can be achieved using PS-PVD. However, molten CMAS (CaO–MgO–Al2O3–SiO2) can penetrate coatings and accelerate PS-PVD TBCs failure due to the feather-like columnar structure. Hence, a strategy is proposed to alleviate molten CMAS corrosion. The super-hydrophobicity structure is fabricated via laser texturing on the surface of PS-PVD TBCs to repel molten CMAS wetting and spreading. Then, a thin layer of the Al-film is deposited on the laser-textured surface. Next, the Al-modified layer is in situ synthesized after vacuum heat treatment, preventing the infiltration of molten CMAS into the TBCs and reducing the coating damage. The results show that the contact angle of laser textured and Al-modified PS-PVD TBCs (LT-Al) at room temperature increased from 12.3° to 168.8°. The wetting and spreading behavior of molten CMAS of as-sprayed (AS), laser textured (LT), and LT-Al coatings is observed in situ at 1230 °C for 1800 s. The LT-Al coatings exhibited excellent CMAS corrosion resistance, attributed to the laser-textured micro-nano structures and Al-modified layer protection. The findings may be an effective approach for solving the disadvantage of PS-PVD feather-like columnar structure TBCs.