Spherical Protrusions Research Articles

FORCED CONVECTION BASED HEAT TRANSFER ANALYSIS OF SPHERICAL DIMPLE AND PROTRUSION SURFACE IN TURBULENT FLOW

An experimental and numerical investigation is performed to study the effect of dimple and protrusion geometry on the heat transfer enhancement and the friction factor of surfaces with dimples and protrusions subjected to turbulent flow. The parameters used to compare the spherical dimples and protrusions are Nusselt Number, friction factor, and flow pattern. These parameters are obtained for a Reynolds number of 10500-60900. The spherical dimple results showed the greater heat transfer, which is about 6.97% higher and pressure loss which is 5.07% lower than the spherical protrusion. The realistic heat transfer augmentation capabilities of channels with dimples and protrusions can be studied from the experimental results. The comparison is made with respect to the smooth rectangular channel under the same flow and thermal boundary conditions. The numerical analysis is performed which shows the different vortex flow structures of the spherical dimples and protrusions channel.

Lipid Droplets Can Spontaneously Bud Off from a Symmetric Bilayer

Lipid droplets (LDs) are cytosolic organelles that protrude from the endoplasmic reticulum membrane under energy-rich conditions. How an LD buds off from the endoplasmic reticulum bilayer is still elusive. By using a continuous media description, we computed the morphology of a lipid droplet embedded in between two identical monolayers of a bilayer. We found that beyond a critical volume, the droplet morphology abruptly transits from a symmetrical elongated lens to a spherical protrusion. This budding transition does not require any energy-consuming machinery, or curvature-inducing agent, or intrinsic asymmetry of the bilayer; it is solely driven by the large interfacial energy of the LD, as opposed to the bilayer surface tension. This spontaneous budding mechanism gives key insights on cellular LD formation.

Особливості морфометричної будови імаго Oesophagostomum venulosum (Rudolphi, 1809)

The study of biodiversity, morphological and biological peculiarities of pathogens of invasive animal diseases in natural and anthropogenically transformed ecosystems is an important task of modern population and applied ecological parasitology. The dominant position among helminthiasis of the digestive organs in ruminants occupy strongylatoses of the gastrointestinal tract. One of the components of the strongylates fauna, which parasitizes on sheep, is Oesophagostomum venulosum Rudolphi, 1809.In order to study the morphological features of the structure of imaginal forms of nematodes of the species Oe. venulosum and determination of their differential metric characteristics, the study of sexually mature oesophagostomes isolated from the intestines of sheep was conducted. Collection of helminths was carried out by the method of complete helminthology of the thick intestine of animals. The congenital morphological features of oesophagostomes are the presence of a clearly separated main vesicle, well-developed major papillae, the outer and inner radial corona around the mouth. Species Oe. venulosum in females is characterized by peculiarities in the structure of the caudal end, vulva, oviduct, vagina. It was found that the length of the body and main vesicle in females was 27.73 and 9.3% higher than that of males and averaged 18.75 ± 0.58 mm and 0.43 ± 0.01 mm, respectively. Indices of body width and major vesicles of mature males and females ranged 0,30–0,64 mm, 0,34–0,43 mm and did not differ significantly. New data on morphological and metric parameters of females Oe. venulosum, which increase the effectiveness of differentiation of helminths to the species. The parameters of the esophagus width in different sites, the width of the body in the vulva and the anus, the width and length of the spherical protrusion in the vulva area are determined. It was found that the length of the eggs in the femoral cavity and in the secretion it secretes significantly changes, the eggs are thickened, decreasing by 13.97%. The length and width of the eggs allocated by the female Oe. venulosum, on average, is 82.51 ± 2.37 and 53.51 ± 1.17 μm, respectively, and have a structure characteristic of the strongylidsc type eggs.

Comparison of Two Types of Overoxidized PEDOT Films and Their Application in Sensor Fabrication.

Poly(3,4-ethylenedioxythiophene) (PEDOT) films were prepared by electro-oxidation on Au microelectrodes in an aqueous solution. Electrolyte solutions and polymerization parameters were optimized prior to overoxidation. The effect of overoxidation time has been optimized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which results in the film overoxidized for 45 s at 1.35 V presenting a strong adsorption. The other one-step overoxidation film prepared by direct CV ranging from −0.6 V to 1.35 V was polymerized for comparison. Scanning electron microscope (SEM) analysis and Fourier transform infrared (FTIR) spectroscopy were used for monitoring morphological changes and the evolution of functional groups. Both of them indicate increased abundant oxygen functional groups and roughness, yet the products exhibit dendritic morphology and piles of spherical protrusions, respectively. Moreover, double-step overoxidized film showed better electrochemical performance toward lead ion sensing. These characterizations highlight some novel properties that may be beneficial for specific sensing applications.

A Looping-Based Model for Quenching Repression.

We model the regulatory role of proteins bound to looped DNA using a simulation in which dsDNA is represented as a self-avoiding chain, and proteins as spherical protrusions. We simulate long self-avoiding chains using a sequential importance sampling Monte-Carlo algorithm, and compute the probabilities for chain looping with and without a protrusion. We find that a protrusion near one of the chain’s termini reduces the probability of looping, even for chains much longer than the protrusion–chain-terminus distance. This effect increases with protrusion size, and decreases with protrusion-terminus distance. The reduced probability of looping can be explained via an eclipse-like model, which provides a novel inhibitory mechanism. We test the eclipse model on two possible transcription-factor occupancy states of the D. melanogaster eve 3/7 enhancer, and show that it provides a possible explanation for the experimentally-observed eve stripe 3 and 7 expression patterns.

Heat transfer and hydraulic resistance in channels with spherical protrusions

This article presents an analytical overview of experimental studies of hydraulic resistance and heat transfer in channels with disturbed flow surfaces in the form of systems of spherical protrusions in a wide range of flow and design parameters. A uniform approach to generalization of experimental data by various authors has been developed considering differences in the geometry of heat-transfer surfaces. Uniform universal generalizing dependences have been obtained for the hydraulic resistance and heat transfer coefficients in channels with spherical protrusions.

Mechanism of Spontaneous Blebbing Motion of an Oil-Water Interface: Elastic Stress Generated by a Lamellar-Lamellar Transition.

A quaternary system composed of surfactant, cosurfactant, oil, and water showing spontaneous motion of the oil-water interface under far-from-equilibrium condition is studied in order to understand nanometer-scale structures and their roles in spontaneous motion. The interfacial motion is characterized by the repetitive extension and retraction of spherical protrusions at the interface, i.e, blebbing motion. During the blebbing motion, elastic aggregates are accumulated, which were characterized as surfactant lamellar structures with mean repeat distances d of 25 to 40 nm. Still unclear is the relationship between the structure formation and the dynamics of the interfacial motion. In the present study, we find that a new lamellar structure with d larger than 80 nm is formed at the blebbing oil-water interface, while the resultant elastic aggregates, which are the one reported before, have a lamellar structure with smaller d (25 to 40 nm). Such transition of lamellar structures from the larger d to smaller d is induced by a penetration of surfactants from an aqueous phase into the aggregates. We propose a model in which elastic stress generated by the transition drives the blebbing motion at the interface. The present results explain the link between nanometer-scale transition of lamellar structure and millimeter-scale dynamics at an oil-water interface.

Lidocaine induces ROCK-dependent membrane blebbing and subsequent cell death in rabbit articular chondrocytes.

Local anesthetics are administered intraarticularly for pain control in orthopedic clinics and surgeries. Although previous studies have shown that local anesthetics can be toxic to chondrocytes, the underlying cellular mechanisms remain unclear. The present study investigates acute cellular responses associated with lidocaine-induced toxicity to articular chondrocytes. Rabbit articular chondrocytes were exposed to lidocaine and their morphological changes were monitored with live cell microscopy. The viability of chondrocytes was evaluated using a fluorescence based LIVE/DEAD assay. Acute treatment of chondrocytes with lidocaine (3-30 mM) induced spherical protrusions on the cell surface (so called "membrane blebbing") in a time- and concentration-dependent manner. The concentration-response relationship for the lidocaine effect was shifted leftward by elevating extracellular pH, as expected for the non-ionized lidocaine being involved in the bleb formation. ROCK (Rho-kinase) inhibitors Y-27632 and fasudil completely prevented the lidocaine-induced membrane blebbing, suggesting that ROCK activation is required for bleb formation. Caspase-3 levels were unchanged by 10 mM lidocaine (p = 0.325) and a caspase inhibitor z-VAD-fmk did not affect the lidocaine-induced blebbing (p = 0.964). GTP-RhoA levels were significantly increased (p < 0.001), but Rho inhibitor-1 failed to suppress the membrane blebbing (p = 0.875). Lidocaine (30 mM) reduced the cell viability of isolated chondrocytes (p < 0.001) and in situ chondrocytes (p < 0.001). The chondrotoxicity was attenuated by pretreatment of cells with ROCK inhibitors or a myosin-II inhibitor blebbistatin (p < 0.001). These findings suggest that lidocaine induces ROCK-dependent membrane blebbing and thereby produces a cytotoxic effect on chondrocytes. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:754-762, 2016.

Generalization of Experimental Data on Heat Transfer and Hydraulic Resistance of Channels with Spherical Protrusions

Experimental investigations of hydraulic resistance and heat transfer in channels with intensifiers in the form of systems of spherical protrusions have been generalized in a wide range of working and design parameters. A unified approach to the correlation of experimental data of various investigators with account for the differences in the geometry of heat transfer surfaces has been worked out. Unified universal dependences for the coefficients of hydraulic resistance and heat transfer in channels with spherical protrusions are obtained.

Membrane shrinkage and cortex remodelling are predicted to work in harmony to retract blebs.

Numerous cell types undergo an oscillatory form of dynamics known as blebbing, whereby pressure-driven spherical protrusions of membrane (known as blebs) expand and contract over the cell's surface. Depending on the cell line, blebs play important roles in many different phenomena including mitosis and locomotion. The expansion phase of cellular blebbing has been mathematically modelled in detail. However, the active processes occurring during the retraction phase are not so well characterized. It is thought that blebs retract because a cortex reforms inside, and adheres to, the bleb membrane. This cortex is retracted into the cell and the attached bleb membrane follows. Using a computational model of a cell's membrane, cortex and interconnecting adhesions, we demonstrate that cortex retraction alone cannot account for bleb retraction and suggest that the mechanism works in tandem with membrane shrinking. Further, an emergent hysteresis loop is observed in the intracellular pressure, which suggests a potential mechanism through which a secondary bleb can be initiated as a primary bleb contracts.

Global contraction or local growth, bleb shape depends on more than just cell structure

When the plasma membrane of a cell locally delaminates from its actin cortex the membrane is pushed outwards due to the cell׳s internal fluid pressure. The resulting spherical protrusion is known as a bleb. A cell׳s ability to function correctly is highly dependent on the production of such protrusions with the correct size and shape. Here, we investigate the nucleation of large blebs from small, local neck regions. A mathematical model of a cell׳s membrane, cortex and interconnecting adhesions demonstrates that these three components are unable to capture experimentally observed bleb shapes without the addition of further assumptions. We have identified that combinations of global cortex contraction and localised membrane growth are the most promising methods for generating prototypical blebs. Currently, neither proposed mechanism has been fully tested experimentally and, thus, we propose experiments that will distinguish between the two methods of bleb production.

In vivo and in vitro observations of polyhydroxybutyrate granules formed by Dinoroseobacter sp. JL 1447

Polyhydroxybutyrate (PHB) granules formed by a marine aerobic anoxygenic phototrophic bacterial strain Dinoroseobacter sp. JL 1447 were detected using transmission electron microscopy and atomic force microscopy. When Dinoroseobacter sp. JL 1447 was inoculated into a medium with glucose as the sole carbon source, the formation of PHB granules occurred and accumulated with incubation time, reaching their maximum in the stationary phase cultures. PHB granules, formed in the cytoplasm at the cell poles or future cell poles, were remobilized and used by the cells in late stationary complex cultures. When PHB granules formed, cell length elongated from 0.5 to 1.5μm and spherical protrusions appeared on the cell surface. The French press method was used to break the cells and isolate the PHB granules. The freshly prepared and intact PHB granules were spherical with a soft, smooth outer envelope without visible substructures. Upon treating PHB granules with sodium dodecyl sulfate, the envelope was destroyed and nearly parted from the granules, and uniform, spherical structures with a central pore appeared on the granule surface.

Self-recovery of worn surface of TiNi shape memory alloy

Abstract In this study, the thermally induced deformation recovery of TiNi alloy worn surface under dry sliding condition was examined. Surface deformations were simulated under various normal loads and sliding frequencies by a ball-on-disk tribometer system at room temperature. Surface profiles of wear scars were obtained before and after heating in air at 80 °C for 10 min, and the experimental results showed that partial recovery of the worn surface was observed. The partial deformation recovery is relative to recovery of the martensitic transformation-induced slip-dislocations and thermally-induced martensite reorientation variants to austenite. The recovery ratio, which is defined as the deformation recovery in the depth direction, was influenced by normal loads and reciprocating frequencies. As the normal load increased from 2 N to 6 N, the deformation recovery ratio of TiNi alloy decreased from 21.4% to 6.4%. With further increasing to 8 N, the recovery ratio was declined to 4.8%. These observations were explained and discussed with respect to the corresponding wear mechanisms and contact stress distribution during sliding wear tests. For different frequencies, the deformation recovery ratio tended to decrease as the reciprocating frequency increased. In addition, the deformation recovery of worn surface was also simulated by indentation in conjunction with a mechanical polishing process. The results showed that spherical protrusion morphology was observed, and its height (18 μm) was around 50% of the depth of initial indent. It confirmed that the deformation recovery existed under wear conditions, and opened up potential engineering applications of textures.

Исследование теплогидравлической эффективности каналов с кольцевой накаткой и со сферическими выступами при ламинарном, переходном и турбулентном режимах течения

Исследование теплогидравлической эффективности каналов с кольцевой накаткой и со сферическими выступами при ламинарном, переходном и турбулентном режимах течения

Thermal and hydraulic characteristics of discretely rough tubes at transient flow regimes

Results are presented from an experimental study of heat transfer and hydraulic friction in tubes with discrete roughness in the form of annular protrusions and systems of spherical protrusions in forced convection of water. The thermohydraulic efficiency of these tubes is estimated.

An electric dipole and a spherical protrusion on a half-space

The 3D problem on the field of an electric dipole situated near a spherical surface partly projecting from a conducting half-space is considered. An analytical solution is obtained in the quasi-static approximation for rational angular points. The near field of the source is studied for various heights of the spherical protrusion.

Forces on a Wall-Bound Leukocyte in a Small Vessel Due to Red Cells in the Blood Stream

As part of the inflammation response, white blood cells (leukocytes) are well known to bind nearly statically to the vessel walls, where they must resist the force exerted by the flowing blood. This force is particularly difficult to estimate due to the particulate character of blood, especially in small vessels where the red blood cells must substantially deform to pass an adhered leukocyte. An efficient simulation tool with realistically flexible red blood cells is used to estimate these forces. At these length scales, it is found that the red cells significantly augment the streamwise forces that must be resisted by the binding. However, interactions with the red cells are also found to cause an average wall-directed force, which can be anticipated to enhance binding. These forces increase significantly as hematocrit values approach 25% and decrease significantly as the leukocyte is made flatter on the wall. For a tube hematocrit of 25% and a spherical protrusion with a diameter three-quarters that of the vessel, the average forces are increased by ∼40% and the local forces are more than double those estimated with an effective-viscosity-homogenized blood. Both the enhanced streamwise and wall-ward forces and their unsteady character are potentially important in regard to binding mechanisms.

Functional Characterization of a Novel Aquaporin from Dictyostelium discoideum Amoebae Implies a Unique Gating Mechanism

The social amoeba Dictyostelium discoideum is a widely used model organism for studying basic functions of protozoan and metazoan cells, such as osmoregulation and cell motility. There is evidence from other species that cellular water channels, aquaporins (AQP), are central to both processes. Yet, data on D. discoideum AQPs is almost absent. Despite cloning of two putative D. discoideum AQPs, WacA, and AqpA, water permeability has not been shown. Further, WacA and AqpA are expressed at the late multicellular stage and in spores but not in amoebae. We cloned a novel AQP, AqpB, from amoeboidal D. discoideum cells. Wild-type AqpB was impermeable to water, glycerol, and urea when expressed in Xenopus laevis oocytes. Neither stepwise truncation of the N terminus nor selected point mutations activated the water channel. However, mutational truncation by 12 amino acids of an extraordinary long intracellular loop induced water permeability of AqpB, hinting at a novel gating mechanism. This AqpB mutant was inhibited by mercuric chloride, confirming the presence of a cysteine residue in the selectivity filter as predicted by our structure model. We detected AqpB by Western blot analysis in a glycosylated and a non-glycosylated form throughout all developmental stages. When expressed in D. discoideum amoebae, AqpB-GFP fusion constructs localized to vacuolar structures, to the plasma membrane, and to lamellipodia-like membrane protrusions. We conclude that the localization pattern in conjunction with channel gating may be indicative of AqpB functions in osmoregulation as well as cell motility of D. discoideum.

Structure of the floral parts of Crocus vernus (L.) Hill.

In the climatic conditions of Lublin, &lt;i&gt;Crocus vernus&lt;/i&gt; blooms from the third decade of March until the third decade of April. The flowers live for 3-4 days. Micromorphological investigations of the tepals and perianth tube as well as of the stamens and pistil were carried out using scanning electron microscopy. The anatomical features of the perianth segments and flower stem were examined with the use of light and fluorescence microscopy. Pollen grains were observed under a light microscope. It was found that the adaxial and abaxial epidermal cells formed papillae in the middle and lower part of the tepals. Much smaller papillae are formed in the upper region of the perianth tube. Elongated non-glandular and glandular trichomes, with spherical protrusions at the tip, are found at the base of the filaments. The filaments are distinguished by epidermal cells with a longitudinally striated cuticle and by the presence of papillae of varying number and size. The cylindrical papillae on the stigma of the pistil are covered by a wrinkled cuticle. The style is surrounded by the perianth tube along a significant length. A narrow space is formed between these organs, and it is filled by the nectar. Stylar channels are found in the style. We observed calcium oxalate crystals and numerous plastids in the parenchymal cells surrounding these channels. Inaperturate, spherical pollen grains are covered by numerous tryphine (or pollenkitt) droplets. This paper also discusses the functions of the papillae found in the epidermis of the perianth and filaments.

Facile fabrication of superhydrophobic coatings with polyimide particles using a reactive electrospraying process

A facile method for polyimide (PI) coating with enhanced hydrophobicity through the deposition of morphology controlled PI particles is presented. An electrospraying process combined with in situ imidization was employed in the fabrication of the PI particles for controllable morphologies as well as hydrophobic multilayered films. We confirmed that in situ imidization accompanying evaporation of the solvent affected the surface morphology of the PI particles during the reactive electrospraying process. The competition of in situ imidization and solvent evaporation in the heating process induces not only the formation of a dimple structure but also the formation of a hollow structure, which was affected by the droplet size. The multilayered film produced by deposition of the PI particles had a microstructured surface with spherical protrusion, micro-dimples, and micro-channels. The multilayered film of PI particles exhibited a hydrophobic surface with water contact angle of 151° due to the microstructured surface of PI coating which was simply but effectively generated by reactive electrospray technique.