Spherical Protrusions Research Articles

Semi-analytical calculation model for friction of polymers on the example of POM ∣ PE-UHMW and steel ∣ PE-UHMW

In this paper, a semi-analytical calculation model for the coefficient of friction (COF) of single spherical protrusions is presented. It allows the prediction of the deformative friction part (μdef) and adhesive friction part (μadh) of the friction pairings steel ∣ polyethylene with ultra-high molecular weight (PE-UHMW) and polyoxymethylene (POM) ∣ PE-UHMW. The experimental studies included unlubricated friction tests, which served to determine the total COF (μtot), as well as tests being lubricated with silicone oil, from which μdef is obtained. Based on the verification tests, it could be shown that both states of lubrication result in the same deformation and that the relationship between the rear angle (ω) and μdef postulated in the calculation model is valid. Therefore, friction tests with segmented spheres were carried out, which allow a specific variation of the ω.It can be concluded that for both pairings the μdef is generally of minor significance (approx. 1/3 μtot) and the influence of the μadh predominates (approx. 2/3 μtot) the friction process. Furthermore the μtot decreases with increasing contact pressure especially in the low pressure range and depends on the form of motion (continuous and discontinuous).

Elevating high-temperature insulation performance of silica aerogels enabled by innovative surface-structured opacifiers

Silica aerogel, recognized as an exceptional material for thermal insulation, has gained considerable attention in thermal protection. However, its inherent infrared transparency compromises its insulating performance at high temperatures. To address this limitation, incorporating micron-sized opacifier particles has emerged as a crucial strategy. This study introduces a novel opacifier particle, distinguished by surface protrusions inspired by the ’structural absorption’ mechanism, and assesses its extinction capabilities. Then, a thorough analysis was conducted to understand how the shape, volume, and numbers of these surface protrusions influence the radiative heat transfer properties of silica aerogels. The findings reveal that the presence of protrusions on the opacifier surface significantly enhances its extinction capacity, consequently reducing the radiative thermal conductivity of silica aerogels. Notably, cylindrical protrusions demonstrate the most effective extinction properties compared to spherical protrusions and rectangular protrusions. Additionally, for opacifier particles with cylindrical protrusions, there exists an optimal number of 12 protrusions that minimize the radiative thermal conductivity of the aerogel. At 1300 K, the radiative thermal conductivity of the silica aerogel doped with opacifiers featuring 12 protrusions is 22.6 % lower than that of the silica aerogel doped with opacifiers lacking protrusions. Moreover, it was observed that maintaining a constant diameter of cylindrical protrusions while increasing their height diminishes the radiative thermal conductivity of silica aerogel. However, the effect on the radiative thermal conductivity becomes less significant beyond a certain protrusion height. The outcomes of this study provide significant insights into the innovation of opacifiers.

Granular protruded irregular Cu2O catalysts for efficient CO2 reduction to C2 products

The electrochemical reduction of carbon dioxide (CO2) to high-energy multi-carbon compounds is a significant challenge. Efforts have been made to design efficient catalysts for high selectivity toward multi-carbon products. In this study, granular protruded irregular Cuprous oxide (Cu2O) nanoparticles were synthesized using a simple water bath wet chemical reduction method. Polyethylene glycol (PEG) was utilized as a directing agent to control the morphology of Cu2O in the process. The optimized irregular Cu2O (ir-Cu2O) catalyst exhibits a remarkable faraday efficiency of 69.3% (±3.3%) for double-carbon compounds (C2), which is significantly higher than that of polyhedral Cu2O (p-Cu2O) (50.4%±1.1%) synthesized without adding PEG. Cu2O nanoparticles with irregular shape featuring randomly distributed spherical protrusions offer more active sites for CO2 adsorption than p-Cu2O catalysts, which is beneficial for the conversion of CO2 to C2. In addition, in situ infrared spectra reveal that ir-Cu2O reduces CO2 to C2 mainly through the coupling of the CO* and CHO*, thereby promoting the formation of C2. These findings provide valuable insights for the design of high-efficiency electrocatalysts for CO2 electroreduction to C2.

Temperature dependence of surface microstructure of 316 L stainless steel exposed to low-energy hydrogen ion irradiation

The austenitic 316 L stainless steel (316LSS) is an important metal for nuclear installations due to its high strength, good plastic toughness and excellent corrosion resistance, and is commonly used as the plasma-facing and structural material. In this study, 316LSS samples are irradiated with low-energy hydrogen ions (35 eV) at the temperature of 400–1300 K to investigate the surface microstructure evolution. The experimental results show that the surface of 316LSS samples remains relatively smooth at 400 K and 600 K after irradiation. Significant surface roughening including spherical protrusions is formed on the surface at 800 K and 1100 K, and step-like streaks are observed at 1300 K. However, no drastic change in the surface morphology is observed in the separate annealing experiments at 800–1300 K. It has been shown that hydrogen ion irradiation mainly causes the surface microstructure evolution of 316LSS samples. After hydrogen plasma exposure, a large number of adatoms are first formed on the surface of 316LSS because of bubble growth. The adatoms then preferentially reach the defects by diffusion at certain temperatures, and aggregate into spherical protrusions with low surface energy. The qualitative simulation results show that the irradiation temperature affects the diffusion and aggregation of adatoms on the surface, and the radius of the spherical protrusions gradually increases due to the decrease of the surface binding energy and the increase of the irradiation fluence.

Jewellery of the Martynivka Circle among Materials of Saltiv Culture: Data Analysis

In the paper jewellery from sites and complexes of the Saltiv culture, which do not chronologically fit within the boundaries of its existence, is considered. The studied jewellery is typical for the hoards of Martynivka circle (group II, subgroup 1). It is represented by four burial complexes and one hoard. Dmytriivka cemetery was investigated by S. Pletneva. Two trapezoidal pendants ornamented with punched rows of dots on the edge from catacombs no. 151 and no. 154 (fig. 1A: 1). Items from the Khatskivskyi hoard, the Kovrai locality, and three finds from the Luchistoye burial ground are known with such an ornamentation system. In general, such pendants can be dated by the 5th—7th centuries (fig. 1). Sukha Homilsha cemetery 1 was investigated by V. Mikheev. Burial no. 54 contained a vorvorka (fig. 2). Burial date: late 8th—early 9th centuries. Analogies in size are presented in several hoards, in ornamentation — from the settlement of Kryvets 4. In general, these items are typical for the hoards of Martynivka circle, the second half of the 6th— the middle third quarter of the 7th centuries. Bochkove cemetery has been studied by O. Laptev since 2014. Grave no. 2 (fig. 3; 4) contained two trapezoidal pendants ornamented with four spherical protrusions and two rows of pressed dots along the edge (fig. 5; 6). Similar pendants are associated with the Penkivka monuments and hoards of the Martynivka circle. Myrna Dolyna hoard discovered in 2019. The complex includes: 1) blacksmith tools and several iron items (fig. 7: 1—11); 2) four screams (fig. 7: 12—15); 3) fragments of a bronze cauldron and a pair of phaleras (fig. 8); 4) heraldic belt decorations, including matrices and semi-finished products (fig. 9; 10); 5) Roman coins (fig. 11). Only six heraldic decorations (fig. 9: 1-3; 10: 1—3) are known among Slavic antiquities at the level of broad analogies. All the considered sites of the Saltiv culture with finds of jewellery from the Martynivka circle are concentrated in the Siverskyi Donets basin. Both individual finds and treasures are known here. In the upper reaches of the river, monuments of the Kolochyn culture are known, and below — of the Penkivka culture. The chronology of the complexes of the Dmytriivka cemetery and the Myrna Dolyna hoard can be determined within the general framework of the existence of culture. However, the chronology of burial no. 54 of the Sukha Homilsha-1, burial no. 2 of the Bochkove cemetery and the chronology of the Martynivka circle decorations differ by almost a century (table 1). Consequently, such adornments could be found by the inhabitants of the Khazar Khaganate and reused in everyday life or attire.

Area difference between monolayers facilitates budding of lipid droplets from vesicles.

Lipid droplets (LDs) are intracellular organelles that play a central role in cellular lipid balance and energy homeostasis. Though extensive experimental studies have been carried out on LD biogenesis, relatively little is known about the mechanical interaction between LDs and vesicles, and in particular effects of area difference between vesicle leaflets on LD evolution are not theoretically rationalized. Here we theoretically explore how the monolayer area difference regulates the budding and morphological evolution of an LD embedded in the vesicle membrane. It is shown that both the monolayer area difference and interfacial energy strength, attributed to the LD-membrane contact, facilitate the LD budding with the confined LD evolving from a bulge to a spherical protrusion. The budding direction is towards the monolayer with more phospholipids. Outward and inward budding phase diagrams are established with respect to the interfacial energy strength and area ratio between the outer and inner monolayers. Moreover, the osmotic pressure of the vesicle promotes the LD budding at a small monolayer area difference and inhibits the budding at a relatively large monolayer area difference.

Regulation of the fabric wet adhesion property through structural design of desirable scale: A theoretical suggestion

It is a universal phenomenon existing in both manufacture and everyday life that fabrics tend to adhere under wet condition. The phenomenon is closely related to the interaction of the fabric surface structure and the liquid. Among the complex structures and numerous varieties of fabrics, the features of typical fabric structures are employed to establish a geometrical model (including structural configuration of spherical protrusion, cylinder, loop, and pore) in order to investigate wet adhesion property under the existence of massive liquid media. Through mechanical analysis on material-liquid bridge system (consisting of fabric material, liquid bridge adhering to the material, and the solid-liquid interface), a quantitative computational theoretical model is built with parameters including critical distance [Formula: see text], radius of the structure R*, apparent receding contact angle [Formula: see text], wetted sphere angle [Formula: see text], and so on, finding the rules and proposing a series of preferred ranges of regulating structural parameters to effectively achieve desirable fabric wet adhesion property in different circumstances. The research findings could be applied to the scientific prediction and on demand regulation of fabric wet adhesion property. They are of great significance with regard to improving the convenience of fabric wet processing, application properties under wet environments, apparel health and comfort for human body, and so on.

Sustainability and Cost Effectiveness Analysis of Staggered Jet Impingement on Solar Thermal Collector

The sustainability index, waste energy ratio and improvement potential of a staggered air jet impingement on the staggered spherical protrusions of a roughened absorber plate were derived for the present study to evaluate exergy losses and irreversibility in the system. The experimental analysis was carried out for selected parameters: relative streamwise pitch, relative spanwise pitch and relative jet diameter to hydraulic diameter ratio. The flow Reynolds number ranged from 4000–18,000. The augmentation in Nusselt number and friction factor compared to a smooth surface was 4.9 and 12.4 times, respectively. The statistical correlation developed determined the maximum thermohydraulic performance parameter and exergetic efficiency be 3.02 and 3.87%, respectively. The magnitude of the sustainability index, waste energy ratio and improvement potential was found to be 1.0347, 0.962 and 10.84, respectively, for the entire range of tested parameters. A cost analysis was also performed to evaluate the cost-effectiveness of the solar thermal system with and without turbulent promoters.

Blebs-Formation, Regulation, Positioning, and Role in Amoeboid Cell Migration.

In the context of development, tissue homeostasis, immune surveillance, and pathological conditions such as cancer metastasis and inflammation, migrating amoeboid cells commonly form protrusions called blebs. For these spherical protrusions to inflate, the force for pushing the membrane forward depends on actomyosin contraction rather than active actin assembly. Accordingly, blebs exhibit distinct dynamics and regulation. In this review, we first examine the mechanisms that control the inflation of blebs and bias their formation in the direction of the cell’s leading edge and present current views concerning the role blebs play in promoting cell locomotion. While certain motile amoeboid cells exclusively form blebs, others form blebs as well as other protrusion types. We describe factors in the environment and cell-intrinsic activities that determine the proportion of the different forms of protrusions cells produce.

Actin-myosin dynamics during bleb stabilization

Blebs are pressure driven spherical protrusions of the plasma membrane which form when a patch of cell membrane is detached from the cortex and expands under the influence of flowing cytosol. The stabilization of the membrane protrusion is characterized by a complete degradation of the old cortex (actin scar) and the formation of a new cortex beneath the protruded membrane, a process that takes about 20 seconds in Dictyostelium Discoideum cells. The mechanism by which the cortex is degraded at the actin scar and simultaneously reformed at the developing bleb boundary is not fully understood.

Porous superhydrophobic‐superoleophilic polytetrafluoroethylene fibrous membranes with tertiary structures for efficient oil/water separation

AbstractThe separation of stable oil/water emulsions is an urgent global issue. In this work, a porous and superhydrophobic polytetrafluoroethylene (PTFE) fibrous membrane was obtained by first centrifugal spinning PTFE/potato starch fibers and then heat treating the fibers to remove the starch. Results showed that spherical protrusions and irregular striped protrusions appeared on the surface of the prepared PTFE fibers, which significantly increased the roughness and hydrophobicity of the fibrous membrane. In addition, number density and shapes of these protrusions could be tuned by changing the extent of the heat treatment and the potato amylose content during the fiber preparation. The water contact angle on the structured PTFE membranes was as high as 160°, and the water sliding angle was as low as 3.4°. The results of oil/water separation experiments showed that the oil removal rate reached 99.5% based a permeability of 3670 L/m2/h, which suggested that the obtained PTFE fibrous membrane has great potential for use in oil/water emulsions separation.

Antifungal Activity and Biocontrol Mechanism of Fusicolla violacea J-1 against Soft Rot in Kiwifruit Caused by Alternaria alternata

Alternaria alternata is the main pathogenic species of various crops, including kiwifruit (Actinidia cinensis). In this study, an antagonistic fungus, J-1, with high antifungal activity against A. alternata was isolated from A. cinensis “Hongyang.” The strain J-1 was identified as Fusicolla violacea via morphological identification and DNA sequencing. This study aimed to evaluate the antifungal activity and potential mechanism of the strain J-1 against A. alternata. The strain J-1 exhibited antifungal activity against A. alternata, with an inhibition rate of 66.1% in vitro. Aseptic filtrate (AF) produced by the strain J-1 could suppress the mycelial growth and conidia germination of A. alternata at the inhibition rates of 66.8% and 80%, respectively, as well as suppress the spread of Alternaria rot in fresh kiwifruit. We observed that many clusters of spherical protrusions appeared at the mycelial tips of A. alternata after treatment with 200 mL L−1 AF of J-1. Scanning electron microscopy analysis results showed that the mycelial structures were bent and/or malformed and the surfaces were rough and protuberant. Variations in temperature, pH, and storage time had little effect on the antifungal activity of the AF. Moreover, the AF could damage the integrity of cell membranes and cause intracellular content leakage. Meanwhile, the chitinase and β-1,3-glucanase enzyme activities increased significantly, indicating that the function of A. alternata cell wall was seriously injured. Eleven antimicrobial metabolites were identified by gas chromatography–mass spectrometry (GC–MS). The strain J-I and its AF exhibited well broad-spectrum antifungal activity against Diaporthe eres, Epicoccum sorghinum, Fusarium graminearum, Phomopsis sp., and Botryosphaeria dothidea, with inhibition rates ranging from 34.4% to 75.1% and 42.7% to 75.2%, respectively. Fusicolla violacea J-1 is a potential biocontrol agent against A. alternata and other fungal phytopathogens.

Bulging-to-Budding Transition of Lipid Droplets Confined within Vesicle Membranes.

Lipid droplets (LDs) are intracellular organelles that act as reservoirs for energy homeostasis and phospholipid balance between supply and consumption. In comparison with extensive studies on LD biogenesis from a biological viewpoint, little is known about the mechanical interaction between LDs and vesicles. Here we perform a systematic theoretical study on the budding and morphological evolution of an artificial LD embedded within the lipid membrane of a pressurized vesicle. It is found that LD bulging and budding depend on the bending rigidity and spontaneous curvature of the vesicle membrane, LD-vesicle interfacial interaction energy strength and size ratio, and osmotic pressure of the vesicle. Beyond critical interfacial interaction strength, the embedded LD undergoes a discontinuous shape transition from a lens-shaped bulge to a spherical protrusion connecting to the nearly spherical vesicle lumen via an infinitesimally small monolayer neck. Moreover, a positive monolayer spontaneous curvature promotes budding transition. As the vesicle becomes smaller, higher cost of the monolayer stretching energy is required for an LD to achieve budding transition. Budding phase diagrams distinguishing the embedded and budding states of the LD-vesicle complex accounting for osmotic pressure and interfacial interaction strength are established with the budding transition boundary displaying a nonmonotonic feature. Our results reveal how embedded LDs overcome soft membrane confinement and protrude, and provide fundamental insights into the clustering of nanoparticles between vesicle monolayers.

New ablation evolution behaviors in micro-hole drilling of 2.5D Cf/SiC composites with millisecond laser

2.5D Cf/SiC composite has been a key heat-resistant ceramic matrix composite (CMC) in aerospace field due to the special structure characteristics. Against the existing research almost focus on 'ablation behavior' in laser processing of CMC, this paper put forward the 'ablation evolution behavior' for the first time, and reveals the 'ablation evolution behavior' in micro-hole machining of 2.5D Cf/SiC composites with millisecond laser. The results show that 0° fiber experiences the ablation evolution from filiform connection, flat ellipse, needle-like to convex structure. And the 90° fiber suffers the ablation evolution from cylindrical structure, lotus lead shape, bud-shape to closed shape. The core of the 90° fibers undergoes the topography structures from cylindrical protrusion, spherical protrusion to needle-like. Except for the honeycomb structure studied in existing research, four new recast layer structures, named transverse strip, longitudinal strip, shell structure, and multi-layer structure are found and analyzed. Further, the mechanism analysis reveals that the recast layer contains both oxidized characteristics and highly carbonized characteristics. In addition, the microstructural analysis shows that three types of particle topography adhere to the recast layer, that are spherical micro-protrusion (20–48 μm), bubble particles (5–15 μm), and sub-micron particles (<1 μm).

Measurement of pressure redistribution and shear stiffness of a mattress with a gel-like layer by a three-axis force sensing device with a spherical protrusion and a surrounding disc

Measurement of pressure redistribution and shear stiffness of a mattress with a gel-like layer by a three-axis force sensing device with a spherical protrusion and a surrounding disc

Description, measurement, and automatic classification of the Plasmodium berghei oocyst morphology during early differentiation in vitro

After colonization of the mosquito midgut by the malaria parasite, Plasmodium differentiates from an invasive, motile ookinete to a multiplicative, sessile oocyst. Despite their importance in establishing the infection and increasing its population, relatively little is known about the early morphological transformation associated with these changes in function. Oocyst differentiation begins with the formation of a spherical protrusion near the center of the crescent-shaped ookinete. As this protuberance grows, it engulfs the content of the two distal ends, thus rounding the cell. In this work, scrutinized observations of the overall changes in shape, coupled with the migration of the malaria pigment granules and the nucleus into the protuberance, revealed that the movement of the cell content happens in an anteroposterior manner. The resulting data, formalized as morphometric measurements, led to the identification of 5 transitional stages and to the development of a computer training algorithm that automatically classifies them. Since cell differentiation has been associated with redox fluctuations, the classification algorithm was tested with parasites stained with a glutathione-specific fluorescent probe. This revealed changes in the glutathione content during differentiation that are suggestive of a redox modulation during transformation. • Plasmodium ookinetes differentiate into reproductive oocysts after mosquito invasion. • Visual scrutiny of the transformation led to the recognition of 5 transitional stages. • Transformation and organelle migration happens in an anteroposterior manner. • A machine learning algorithm was developed to automatically classify these stages. • The discretization into stages allowed the determination of GSH oscillations.

Experimental Study of the Heat Transfer Enhancement in Concentric Tubes With Spherical and Pyramidal Protrusions

In the current research project, the thermal performance of a series of newly designed mixers has been investigated. Each mixer has two concentric cylinders comprising two annular slot flow channels around a solid cylindrical rod at the center. In each mixer, the first cylinder around the central solid rod has either spherical or pyramidal protrusions throughout the outer surface. It has been observed that with varying mass flow rate of cold and hot water (1 kg/m3-sec to 5 kg/m3-sec), 17% increase in rate of heat transfer for cold water & 73% for hot water has been observed with a variation in mass flow rate of 1-3 kg/m3-sec with all combination of angles of holes in spherical protrusions. In the case of pyramidal protrusions, the rate of heat transfer has been raised from 16% for cold water & 88% for hot water at varying a mass flow rate of 1-3 kg/m3-sec in all combinations of angles of the top vortex in each protrusion. The effect of imparting the centrifugal force has raised the rates of heat transfer in the range of 24-36% at varying rpm from 60-180 rpm of the central cylinder, with the highest with 120 rpm. A comparison of the heat transfer rates reveals that with increasing the mass flow rates, rpm, angle of the holes in spherical protrusions and angle of the traversed angle at the top corner of each pyramidal protrusion didn’t contribute linearly in terms of rising in the rate of heat transfer.

Aerothermodynamic design and performance analysis of modified nose cones for space reentry vehicles

ABSTRACT Reentry vehicles are blunt-nosed bodies designed primarily to protect them from high heating loads experienced while returning from space. The main intention of this present work is to alleviate the aerodynamic heating of the reentry vehicles by suggesting new geometrical considerations. This proposal implements the surface augmentation of the various conventional nose cones by creating some spherical protrusions over the nose region. This project presents the role of spherical protrusions over the nose part in order to reduce the aerodynamic heating of space reentry vehicles. A comparative numerical study has been made on the existing and proposed reentry bodies to find the degree of reduction in aerodynamic heating. From the numerical simulations, it has been observed that there is a significant alleviation of aerodynamic heating in the proposed nose cone model than in the conventional blunt body. From this simulation analysis, a reduction in aerodynamic heating of about 11% and 35% was observed in the chosen modified spherical and parabolic winged reentry models during hypersonic conditions. This numerical investigation perspicuously explains the importance of placing spherical protrusions over the conventional blunt-nosed reentry vehicles in order to alleviate the maximum degree of aerodynamic heating.

Accessory mammillary bodies formed by the enlarged lateral mammillary nuclei: cytoarchitecture.

Post mortem examination of the hypothalamus of a 79-year-old woman, deceased in cardiac arrest without recorded neurological symptoms, revealed well-defined spherical protrusions located rostro-laterally to the mammillary bodies that appear to be regular size when compared to normal. Cytoarchitectonically, these accessory mammillary bodies are formed by the enlarged lateral mammillary nucleus that is normally a thin shell over the medial. The mammillary nuclei appear to function synergistically in memory formation in rats; however, the functional consequences of the present variation are difficult to interpret due to lack of human data. Most importantly, in addition to the possible functional consequences, lateral mammillary bodies can be falsely identified as various neuropathological processes of the basal diencephalon including gliomas; therefore, it is extremely important to disseminate this unique morphological variant among clinicians.

Fantastic voyage: the journey of intestinal microbiota-derived microvesicles through the body.

As part of their life cycle, Gram-negative bacteria produce and release microvesicles (outer membrane vesicles, OMVs) consisting of spherical protrusions of the outer membrane that encapsulate periplasmic contents. OMVs produced by commensal bacteria in the gastrointestinal (GI) tract of animals are dispersed within the gut lumen with their cargo and enzymes being distributed across and throughout the GI tract. Their ultimate destination and fate is unclear although they can interact with and cross the intestinal epithelium using different entry pathways and access underlying immune cells in the lamina propria. OMVs have also been found in the bloodstream from which they can access various tissues and possibly the brain. The nanosize and non-replicative status of OMVs together with their resistance to enzyme degradation and low pH, alongside their ability to interact with the host, make them ideal candidates for delivering biologics to mucosal sites, such as the GI and the respiratory tract. In this mini-review, we discuss the fate of OMVs produced in the GI tract of animals with a focus on vesicles released by Bacteroides species and the use of OMVs as vaccine delivery vehicles and other potential applications.