Drop-like Structures Research Articles

Comparing Dermatoscopic Features With Slit Skin Smear and Histopathology in Diagnosis of Cutaneous Leishmaniasis.

To evaluate dermatoscopic features of cutaneous leishmaniasis and to compare its diagnostic accuracy against slit skin smear and skin histopathology. This cross-sectional study was conducted at the Department of Dermatology, Pakistan Navy Station (PNS) Shifa Hospital, Karachi, Pakistan, from August 2021 to August 2022. A total of 200 lesions from 70 patients of cutaneous leishmaniasis diagnosed with slit skin smear for Leishmania-Donovan (LD) bodies and skin biopsy were included via non-probability consecutive sampling technique. Dermatoscopic evaluation was performed via a handheld dermatoscope (DELTA 20T; HEINE,Gilching, Germany) on 10x magnification. All dermatoscopic images were analyzed by two different observers who had command of dermatoscopy. Data analysis was done using Statistical Package for the Social Sciences SPSS version 27 (IBM Corp., Armonk, NY, USA). Common dermatoscopic findings were erythema 200 (100%), hyperkeratosis 140 (70%), crusting 50 (25%), ulceration 42 (21%), milia-like structure 58 (29%), tear drop-like structure 46 (23%), yellow tears 70 (35%), and white starburst pattern 68 (34%). Less common findings were yellow hue 28 (14%), orange areas 26 (13%) and scar seven (3.5%). Vascular structures frequently observed were linear vessels 109 (54.5%), dotted vessels 80 (40%), and hairpin vessels 61 (30.5%); less common findings were comma-shaped vessels 52 (26%), arborizing vessels 20 (10%), crown vessels nine (4.5%). Comparison of dermatoscopic features was done with slit skin smear for LD bodies (p value = 0.003 ) and histopathology (p value = 0.001). Dermatoscopy is a non-invasive technique that is helpful in diagnosing cutaneous leishmaniasis, saving time in making rapid diagnosis and saving the need to undergo extensive invasive investigation. Yield of dermatoscopy was comparable to slit smear for LD bodies and histopathology and was found to be effective in making rapid diagnosis with significant accuracy (p value <0.05).

Diversification of Vascular Occlusions and Crystal Deposits in the Xylem Sap Flow of Five Tunisian Grapevines.

Xylem vessels are essential pivotal organs in bulk hydraulic flow through the whole woody plant. However, environmental constraints generate disagreements in xylem structures, which are characterized by air emboli and occlusions formations, compromising water conductivity in grapevines. The aim of this work was to explore xylem morphology dynamics through the xylem sap flow of five Tunisian grapevine cultivars during the natural bleeding sap periods of 2019, 2021, and 2022. In fact, Sakasly, Khamri, Hencha, Razegui1, and Razegui2 rain-fed grapevine cultivars revealed differential responses towards xylem sap movement. The results demonstrated that the xylem sap flow was significantly more abundant in 2019 than 2021 and 2022 bleeding sap campaigns. A variation was revealed between the cultivars regarding the xylem sap flow. In fact, Sakasly gave the best xylem flow during the three campaigns. Razegui1 and Razegui2 registered approximately similar xylem sap flow, while Hencha and Khamri present the lowest sap fluxes during the three campaigns. Moreover, several vascular occlusions forms were identified from stem cross sections using environmental scanning electron microscopy (ESEM), including tyloses, gels, starch, and gum deposits. The highest occlusion number was observed in Sakasly, Razegui1, and Razegui2 cultivars. Among different biogenic calcium shapes, several were observed for the first time in grapevine, including multi-faceted druse, cubic, crystalline sand, styloids, spherical, or drop-like structures. Considering their lower flow and totally blocked vessels, both Hencha and Khamri confirmed their susceptibility to environmental constraints. However, Sakasly, Razegui1, and Razegui2 cultivars presented higher tolerance according to their sap flow and xylem morphology.

Secondary instability in thin film flows under an inclined plane: growth of lenses on spatially developing rivulets

The response of a thin film flowing under an inclined plane, modelled using the lubrication equation, is studied. The flow at the inlet is perturbed by the superimposition of a spanwise-periodic steady modulation and a decoupled temporally periodic but spatially homogeneous perturbation. As the consequence of the spanwise inlet forcing, the so-called rivulets grow downstream and eventually reach a streamwise-invariant state, modulated along the direction perpendicular to the flow. The linearized dynamics in the presence of a time-harmonic inlet forcing shows the emergence of a time-periodic flow characterized by drop-like structures (so-called lenses) that travel on the rivulet. The spatial evolution is rationalized by a weakly non-parallel stability analysis. The occurrence of the lenses, their spacing and thickness profile, is controlled by the inclination angle, flow rate, and the frequency and amplitude of the time-harmonic inlet forcing. The faithfulness of the linear analyses is verified by nonlinear simulations. The results of the linear simulations with inlet forcing are combined with the computations of nonlinear travelling lenses solutions in a double-periodic domain to obtain an estimate of the dripping length, for a large range of conditions.

Generation of soliton bubbles in a sine-Gordon system with localised inhomogeneities

Nonlinear wave propagation plays a crucial role in the functioning of many physical and biophysical systems. In the propagation regime, disturbances due to the presence of local external perturbations, such as localised defects or boundary interphase walls have gained great attention. In this article, the complex phenomena that occur when sine-Gordon line solitons collide with localised inhomogeneities are investigated. By a one-dimensional theory, it is shown that internal modes of two-dimensional sine-Gordon solitons can be activated depending on the topological properties of the inhomogeneities. Shape mode instabilities cause the formation of bubble-like and drop-like structures for both stationary and travelling line solitons. It is shown that such structures are formed and stabilised by arrays of localised inhomogeneities distributed in space. Implications of the observed phenomena in physical and biological systems are discussed.

Study of the thixotropic behaviors of ferrofluids.

The thixotropic behaviors of ferrofluid samples of different particle concentration were studied using different measurement methods, including the three interval thixotropic test and the hysteresis loop test. The experimental results demonstrated that ferrofluids exhibit significant thixotropic behaviors and the microstructural evolution in ferrofluids behind the macroscopic rheological mechanics is discussed. The influence of magnetic field strength, particle concentration and temperature on the thixotropy of ferrofluids was also analyzed. Microscopic ferrofluid theory was adopted to study the thixotropic behaviors of ferrofluids under different shearing conditions, indicating that different thixotropic behaviors of ferrofluids can be induced by the presence and evolution of different kinds of microstructures, such as linear chain-like and dense drop-like structures. Furthermore, a phenomenal thixotropic model was employed to analyze the experimental results, indicating that a more specific model for ferrofluids is needed. These findings contribute to a better understanding of the microscopic mechanism of the complex rheological behaviors of ferrofluids.

Bubblelike structures generated by activation of internal shape modes in two-dimensional sine-Gordon line solitons.

Nonlinear waves that collide with localized defects exhibit complex behavior. Apart from reflection, transmission, and annihilation of an incident wave, a local inhomogeneity can activate internal modes of solitons, producing many impressive phenomena. In this work we investigate a two-dimensional sine-Gordon model perturbed by a family of localized forces. We observed the formation of bubblelike and droplike structures due to local internal shape mode instabilities. We describe the formation of such structures on the basis of a one-dimensional theory of activation of internal modes of sine-Gordon solitons. An interpretation of the observed phenomena, in the context of phase transition theory, is given. Implications in Josephson junctions with a current dipole device are discussed.

Chemical vapor deposition growth and characterization of drop-like MoS2/MoO2granular films

Monolayer MoS2 is an emerging two-dimensional semiconductor with wide-ranging potential applications in novel optoelectronic devices and catalysis. Here, we report the growth of drop-like monolayer MoS2/MoO2 granular films on SiO2/Si substrate by chemical vapor deposition method. The as-synthesized films were systematically characterized by various means of optical microscopy, X-ray/ultraviolet photoemission spectroscopy, scanning electron microscopy, atomic/kelvin force microscopy, X-ray diffraction, Raman and photoluminescence techniques. The combined results of atomic force microscopy and scanning electron microscopy clearly present novel drop-like granulars and domain boundaries, ascribed to lower growth temperature. X-ray photoemission spectroscopy results complemented by Raman and X-ray diffraction results confirm the formation of MoS2/MoO2 granular films. The ultraviolet photoemission spectroscopy, along with kelvin force microscopy, reveals a different nature of surface potential of drop-like MoS2 granular films compared with crystalline MoS2, owing to electron transfer from MoS2 to MoO2 and drop-like structure. Our study broadens the scope of two-dimensional transition metal dichalcogenides research and reveals the distinct physical properties of drop-like monolayer MoS2 granular films.

Maneuvering thermal conductivity of magnetic nanofluids by tunable magnetic fields

We report an experimental investigation of magnetic field dependent thermal conductivity of a transformer oil base magnetic fluid as a function of volume fractions. In the absence of magnetic field, thermal conductivity increases linearly with an increase in volume fraction, and magnitude of thermal conductivity thus obtained is lower than that predicted by Maxwell's theory. This reveals the presence of clusters/oligomers in the system. On application of magnetic field, it exhibits a non-monotonous increase in thermal conductivity. The results are interpreted using the concept of a two-step homogenization method (which is based on differential effective medium theory). The results show a transformation of particle cluster configuration from long chain like prolate shape to the aggregated drop-like structure with increasing concentration as well as a magnetic field. The aggregated drop-like structure for concentrated system is supported by optical microscopic images. This shape change of clusters reduces thermal conductivity enhancement. Moreover, this structure formation is observed as a dynamic phenomenon, and at 226 mT field, the length of the structure extends with time, becomes maximum, and then reduces. This change results in the increase or decrease of thermal conductivity.

An investigation of a viscosity-magnetic field hysteretic effect in nano-ferrofluid

Both poly-α-olefin synthetic oil and water based Fe3O4 ferrofluids have been prepared by chemical co-precipitation method. X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer methods have been used to characterize the structure, morphology and magnetic property of Fe3O4 nanoparticles, respectively. The magnetoviscous properties of both dilute and concentrated ferrofluids are studied by torsional oscillation cup viscometer. A parameter Δη*=(ηde−ηin/ηin), is named as viscosity-magnetic field hysteretic effect and studied. The results show that in horizontal ring-magnetic field, the relative reduced viscosity Δη* is positive at high magnetic fields and negative at low fields. It has been found that the viscosity-magnetic field hysteretic effect is affected by the magnetic force Fm and the hydrodynamical force Fh among the particles. The formation and destruction of chain-like or drop-like structures with polydispersity lead to the formation of negative viscosity-magnetic field hysteretic effect in concentrated ferrofluids. The model developed here illustrates the experimental results.

The Effect of Ectoins on the Structural Organization of the Tear Fluid Monolayer

We investigate the influence of Ectoin on the structural organization of the natural and artificial tear fluid lipid layers (ATFLL) using surface activity analysis and topographical studies. The natural meibomian lipids exhibit a continuous pressure-area isotherm without any phase transitions. In the presence of ectoin, the isotherm is expanded towards higher area per molecule implying decreased interaction between the lipid molecules. The AFM scans show presence of fiber like structures in the natural meibomian lipid film. In the presence of ectoine, droplet-like structures are observed which are hypothesized to be triacyl glycerols excluded from the lipid film. ATFLL illustrate the fluidizing effect of ectoine on the lipid films where the pressure-area isotherms are expanded in the presence of ectoin. With the addition of a triacyl glycerol to the mixture of DPPC and Chol-Palmitate, we observed the formation of similar drop-like structures in the presence of ectoine as in the case of natural meibomian lipid films. Consequently, the hypothesis explaining the exclusion of tri/di acyl glycerol from the meibomian lipid film in the presence of ectoine in the subphase is confirmed which lead us to a model describing the fluidizing effect of ectoine on meibomian lipid films.

Magnetoviscous properties of Fe3O4 silicon oil based ferrofluid

A Fe3O4 silicon oil-based ferrofluid (FF) was prepared and the viscosity properties of the FFs were investigated by a rotating viscometer and a torsional oscillation cup viscometer, respectively. Experimental results show that the viscosity of the FFs decreases with increasing temperature, and increases with increasing magnetic field intensity due to the existence of the magnetic particles. The hysteresis curve of the viscosity–magnetic field shows that the formation and destruction of chain-like or drop-like structures has obvious effect on the viscosity of the FFs. When the field is relatively strong, the viscosity at the decreasing stage is higher than that at the increasing stage. In contrast, when the field is relatively weak, the viscosity at the decreasing stage is slightly lower than that at the increasing stage. In addition, the relation between viscosity of the FFs and time under the magnetic field shows that time is an effective factor in the evolution of the magnetically induced structures.

Variational multiscale methods for premixed combustion based on a progress-variable approach

In this study, novel computational techniques for the numerical simulation of premixed combustion based on a progress-variable formulation are proposed. Two new variational multiscale methods within a finite element framework are developed for the system of mass, momentum and progress-variable equations: a purely residual-based variational multiscale method and an algebraic variational multiscale-multigrid method. The proposed methods are tested for the numerical example case of a flame–vortex interaction using Arrhenius chemical kinetics. This actually laminar reactive flow problem may serve as a model problem for interactions of turbulent flows and (premixed) flames. The results obtained from this test case show that both methods are capable of accurately predicting the features expected during the progression of the flame–vortex interaction. The evolution of both a pocket of unburned gas and a secluded, drop-like structure, which detaches itself and moves upwards, are accurately predicted already for a relatively coarse discretization.

Rheological properties of ferrofluids with microstructures

This paper presents results of a theoretical study of the effects of linear chain-like as well asbulk drop-like heterogeneous aggregates on the rheological properties and behaviour offerrofluids. The results demonstrate that the appearance of both these internal structuresleads to a strong (one–two orders of magnitude) increase of the ferrofluid effectiveviscosity under the action of the magnetic field applied parallel to the gradient ofthe ferrofluid flow. When the ferrofluid fills a thin channel (gap) placed into anormal magnetic field, the drop-like structures can overlap with the channel. In thecase of a rigid connection between the drop-like domains and the channel walls,the appearance of elastic and yield stress effects on the ferrofluid is expected.

Tip structure determination by scanning tunneling microscopy

A real-space image of the geometry of a tungsten tip by scanning tunneling microscopy is presented. The micrographs show the existence of distinctly faceted mini tips, which are approximately 1000 Å wide and have a radius of the order of 10 Å and top angle ⩽ 50° with respect to the axis of the tungsten wire. SEM and STEM pictures show a very rough tip structure on a micron scale and confirm the existence and dimensions of the mini tips, which are situated on top of a drop-like structure probably formed after in-situ melting of the top of the tip.

Tip structure determination by scanning tunneling microscopy

A real-space image of the geometry of a tungsten tip by scanning tunneling microscopy is presented. The micrographs show the existence of distinctly faceted mini tips, which are approximately 1000 Å wide and have a radius of the order of 10 Å and top angles ≤50° with respect to the axis of the tungsten wire. SEM and STEM pictures show a very rough tip structure on a micron scale and confirm the existence and dimensions of the mini tips, which are situated on top of a drop-like structure probably formed after in-situ melting of the top of the tip.

VITAL STAINING OF AMŒBOCYTE TISSUE OF LIMULUS

1. Neutral red, as a representative of the basic dyes, stains the granules of the amœbocytes. The stained granules lose their stain gradually in neutral and almost immediately in acid solutions. Alkaline solutions intensify the staining.2. In addition to the granules, droplike structures in the amœbocytes are stained with neutral red. The latter are very much more resistant to decoloration than the granules. They do not give off spontaneously the stain as readily as do the granules, nor are they as readily decolorized under the influence of acid as are the latter.3. The effect of acid and alkali on the neutral red stain in amœbocytes can be demonstrated not only in single cells microscopically, but also in the test tube if we use amœbocyte tissue previously stained with basic or acid stains. Acids cause the giving off of basic dyes, and alkali causes the loss of acid dyes which had previously combined with the tissue. This relation prevails notwithstanding the fact that acid and basic dyes stain different parts of the tissue. Neither heating nor a preliminary treatment of the tissue with acid and alkali alters this result.4. We conclude from these experiments that vital stains may be taken up by cells in two forms, (1) through the electrostatic forces of primary or secondary valencies they may be attached to the granules or to the cell protoplasm, or, (2) they may be present in a solution in circumscribed areas of the cell. In the latter form they behave towards environmental factors in a way similar to solutions of the stain. It is possible that also the acid vital dyes exist in the latter form, whenever they are taken into a cell.