Surface Streaks Research Articles

Investigation of the detergency properties of mixtures of biocides and nonionic surfactants using a new simplified hard surface cleaning method

AbstractThe present study explores the cleaning efficacy of a set of nonionic surfactants (linear ethoxylated alcohol, secondary ethoxylated alcohols with 5, 7, and 9 ethoxy groups, glycoside surfactants, polyglycerol surfactants, and an ethoxylated sorbitan monolaurate) combined with cationic biocides—alkyl quaternary ammonium salts. A simple hard surface cleaning methodology was applied, which was shown to discriminate well between poor and good cleaning formulations. In addition to cleaning efficacy, surface aesthetics such as gloss and haze were evaluated together to assess surface streaking caused by a residual surfactant layer. The haziness determination turned out to be the key feature revealing the complex cleaning performance of multi‐component products.

Scaling and Flow Structure of Langmuir Turbulence in Inertial Frames

Abstract This paper provides a framework that unifies the characteristics of Langmuir turbulence, including the vortex force effect, velocity scalings, vertical flow structure, and crosswind spacing between surface streaks. The widely accepted CL2 mechanism is extended to explain the observed maximum alongwind velocity and downwelling velocity below the surface. Balancing the extended mechanism in the Craik–Leibovich equations, the scalings for the alongwind velocity u, crosswind velocity υ, and vertical velocity w are formulated as Here, Uf is the friction velocity, Us is the Stokes drift on the surface, and La = (Uf/Us)1/2 is the Langmuir number. Simulations using the Stratified Ocean Model with Adaptive Refinement in large-eddy simulation (LES-SOMAR) mode validate the scalings and reveal physical similarity for velocity and crosswind spacing. The horizontally averaged velocity along the wind on the surface grows with time, whereas υ/V and w/W are confined. The root-mean-square (rms) of w peaks at wrms/W ≈ 0.85 at a depth of 1.3Zs, where Zs is the e-folding scale of the Stokes drift. The crosswind spacing Lp grows linearly with time but is finally limited by the depth of the water H, with maximum Lp/H = 3.3. This framework agrees with measurement collected in six different field campaigns.

Coexistence of different mechanisms underlying the dynamics of supersonic turbulent flow over a compression ramp

Supersonic turbulent flow over a compression ramp is studied using wall-resolved large eddy simulation with a freestream Mach number of 2.95 and a Reynolds number [based on δ0: the thickness of incoming turbulent boundary layer (TBL)] of 63 560. The unsteady dynamics of the present shock wave/turbulent boundary layer interaction (STBLI) flow are investigated by using dynamic mode decomposition techniques, linear and nonlinear disambiguation optimization, local stability analysis (LSA), and global stability analysis (GSA). By analyzing the dynamic system for the STBLI flow, three dynamically important modes with characteristic spanwise wavelengths of 2δ0, 3δ0, and 6δ0 are captured. The 2δ0 mode approximates the spanwise scale of the Görtler-like vortices and Görtler mode of LSA, suggesting the presence of Görtler instability, which is believed to be related to the unsteady motion of streaks downstream of reattachment in the flow. The features of the 3δ0 mode are also observed in large-scale motions of the incoming TBL, implying the existence of a convective mechanism that is excited and maintained by such motions. Additionally, the GSA results show the most unstable mode features a spanwise wavelength of around 6δ0, indicating the existence of global instability that is believed to be related to the oscillating motion of separation shock. The coexistence of these three mechanisms is confirmed. Discussions on the above findings provide an interpretation for low-frequency unsteadiness that the unsteadiness of surface streaks results from the combined effects of the Görtler instability near flow reattachment and the convection of large-scale motions in the incoming boundary layer, while the low-frequency shock motion may be related to a global mode driven by upstream disturbances.

A numerical study on Langmuir circulations and coherent vortical structures beneath surface waves

Langmuir circulations (LCs) arise through the interaction between the Lagrangian drift of the surface waves and the wind-driven shear layer. Quasi-streamwise vortices (QSVs) also form in the turbulent shear layer next to a flat surface. Both vortical structures manifest themselves by inducing wind-aligned streaks on the surface. In this study, numerical simulations of a stress-driven turbulent shear layer bounded by monochromatic surface waves are conducted to reveal the vortical structures of LCs and QSVs, and their interactions. The LC structure is educed from conditional averaging guided by the signatures of predominant streaks obtained from empirical mode decomposition; the width of the averaged LC pair is found to be comparable to the most unstable wavelength of the Craik–Leibovich equation. Coherent vortical structures (CVSs) are identified using a detection criterion based on local analysis of the velocity-gradient tensor and their topological geometry; QSVs accumulated beneath the windward surface are found to dominate the distribution. Employing the variable-interval spatial average to the identified QSVs further reveals that QSVs tend to form in the edge vicinity of the surface streaks induced by the LCs. The transport budgets of streamwise enstrophy are examined to reveal the interaction. It is found that QSVs perturb the streaks resulting in a localized streamwise gradient of the spanwise velocity, that is, vertical vorticity. The vertical shear tilts the vertical vorticity, therefore enhancing streamwise enstrophy production and the formation of QSVs. The results highlight the differences in the CVSs between the Langmuir turbulence and the wall turbulence.

Analysis of streak defects on the surface of high-quality automobile steel SP121 after stamping

Aiming at the streak defects on the surface of high-quality automobile steel SP121 after stamping, the surface profile of the streak defects was analyzed by a confocal laser scanning microscope (CLSM). The micro-morphology and element content of the streak defects area were analyzed by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The results show that compared with the normal area of the strip steel surface, the surface roughness features of the streak defects area of SP121 after stamping are not apparent. There are many linear defects and dot defects perpendicular to the streak defects. The energy spectrum detection shows no element abnormality in the streak defects area. The surface streak defects of SP121 after stamping are caused by the poor contact between the strip steel and the stamping die, which leads to the poor fluidity of the materials during stamping, and finally, the streak defects are formed.

On the scaling of three-dimensional shock-induced separated flow due to protuberances

Supersonic flow over three-dimensional bodies protruding out of the turbulent boundary layer was investigated by means of experiments and numerical computations. A parametric study was performed by varying the shape and dimensions of the protuberance, as well as the freestream Mach numbers (1.5, 2, 2.5, 2.89, and 3.5). Surface streak line visualization, surface pressure measurements, and time-resolved Schlieren visualization were employed along with Reynolds-averaged Navier–Stokes computations to elicit the complex flow features such as the separation line, shock pattern, and the horseshoe vortex, which greatly influence the flow dynamics in the separated region. The rise in surface pressure at mid-span due to separation (plateau pressure) was dependent only on the incoming flow parameters and independent of protuberance geometry. The two-dimensional free interaction theory, applied for normal shock-induced separation, closely predicts the mid-span plateau pressure. Although protuberances are of varying shapes and dimensions, the inviscid bow shock (obtained from Euler computations) provided generalized scales, whose effects on shock boundary layer interactions are analyzed. The radius of curvature of the inviscid shock on the wall plane at the nose, which is theoretically related to the local second derivative (along the shock) of pressure jump, was found to be a determining parameter of mid-span separation length (Lsep). Since the spanwise distance of the sonic point on the inviscid shock was found to be strongly correlated with its nose radius of curvature, it follows that the “strong” portion of the inviscid bow shock fixes the mid-span separation location. These observations concerning mid-span plateau pressure, and the role of strong shock portion in fixing mid-span separation, suggest that the Lsep shall be predicted from a modification of the scaling laws for the length of plateau pressure region in two-dimensional shock boundary layer interaction, with the inclusion of a spanwise relieving effect. A correlation is obtained relating the Lsep with various incoming flow parameters and inviscid shock nose radius. The mid-span vortex core position was found to be linearly related to the Lsep. The radius of curvature of the separation shock is, however, found to be influenced by the entire inviscid shock, including the “weak” portion.

Using Locusta Migratoria as a Nitrogen Source for the Growth and Development of Microorganisms

Characteristics and the use as culture media of protein hydrolysate from Locusta migratoria were determined in comparison with different peptones. After powdering, it was hydrolyzed chemically (acid hydrolysis) and obtained product Locust Peptone (LP). The contents of protein, fat, nitrogen, ash, minerals, total sugars and amino acids of LP were determined and it was seen that it has both organic and inorganic materials enough to use as a component of the medium. The effects of different concentrations added 20g/l glucose of LP on the growth of four test bacteria (Escherichia coli, Bacillus subtilis, Pseudomonas putida and Staphylococcus aureus) and test yeasts (Rhodotorula glutinis, Candida albicans, Saccharomyces cerevisiae) were investigated and it was found that the optimal concentration for bacteria and yeast are %0,6 and LP was compared with bacteriological peptone (BP), fish peptone (FP) and meat peptone (MP) .The obtained results with surface streaking and shaking culture procedures showed that LP yielded a little higher or equal FP and BP in both normal bacteria, but these values were lower than values obtained from MP. The results show that LP performed similar to or even better than commercial peptones as nitrogen sources for microorganisms growth. A new peptone has been developed from locust for microbiological media in the present study.

Characteristics of Streaky Thermal Footprints on Wind Waves

AbstractCoherent vortices in the aqueous surface layer beneath wind waves manifest themselves by inducing elongated high‐speed streaks on the interface. Analyses of thermal images taken in the wind‐wave flume reveal that the mean streak spacing scaled by the viscous length, , depends strongly on the wind‐wave condition. This contradicts the wall‐bounded turbulent flow in which the scaled mean streak spacing approaches a canonical value, . Comparative numerical simulations of shear flow bounded by flat and wavy surfaces are conducted to explain the variation. In the low‐wind range with insignificant surface waves, ; the reduction of is attributed to the insufficient shear rate to form the elongated streaks. For the moderate‐wind range in which surface waves become pronounced but remain to be unbroken, is still less than 100. Analysis of the vorticity transport in the simulated wavy flows reveals that the presence of non‐breaking waves enhances the formation of quasi‐streamwise vortices and the surface streaks. For the high‐wind range, surface waves break and the breakers wipe out the streaks. The streaks quickly reestablish in the wake of the breaker with mean spacing but are destructed again by the following breaker.

Coherent surface structure induces unique epitaxial overgrowth of metastable octacalcium phosphate on stable hydroxyapatite at critical fluoride concentration

The phase transformation from soluble calcium phosphates to less-soluble hydroxyapatite (HAP) is a thermodynamically natural route. This process is irreversible, and effective use of poorly reactive HAP to repair teeth that have no cellular metabolism remains challenging. However, this thermodynamically controlled transformation may apparently be reversed through the fast nucleation and growth of metastable phases, leading to a reactive HAP surface. Here, the assembled HAP-nanorod phase is demonstrated to change into the metastable octacalcium phosphate (OCP) phase in a calcium phosphate solution containing 0.8 ppm fluoride. Grown OCPs display parallel surface streaks and their 11¯0 and 00l (l: odd) electron-diffraction spots are often not visible. The streaked, elongated OCP gradually grows into large plates with flat surfaces that exhibit an intense11¯0 spot. Crystal-structure models reveal that the unique epitaxial overgrowth of OCP on HAP occurs since both materials share coherent {100} faces, resulting in the distinctive disappearance of 11¯0 and 00l OCP spots. A polysynthetic twin model that reliably explains this disappearance is proposed for the growth of OCP. This apparent reverse phase transformation produces hybrid calcium phosphates consisting of HAP cores and highly reactive outer OCP layers that are promising for the repair of dentin caries. Statement of significanceThis paper demonstrates important and interesting finding regarding formation of calcium phosphates in relation to their crystal structures.We first show that hydroxyapatite (HAP), the major constituent of human teeth and bone, can reversely change to its precursor, octacalcium phosphate (OCP), contrary to thermodynamic-stability rule. This apparent reverse phase transformation occurs through sharing the coherent {100} faces of both materials under controlled fluoride concentration. Nanoscale similarity of two crystal surfaces enables structurally shared epitaxial overgrowth of OCP on HAP aided by faster growth rate of OCP than that of HAP.This reaction produces hybrid crystal consisting of outer OCP and core HAP, that has not been known before and is able to be applied to dentin caries repair.

Clinical and Dermoscopic Features of Fungal Melanonychia: Differentiating from Subungual Melanoma.

BackgroundFungal melanonychia (FM) is a rare nail disorder that presents as dark pigmentation in the nail plate because of fungal nail infection. The diagnosis of FM is occasionally confusing because its appearance is similar to melanonychia due to other causes including malignant melanoma. Dermoscopy could help increase the accuracy of diagnosing the cause of pigmented nail lesions. However, dermoscopic features of FM are not well elucidated.ObjectiveThis study aimed to investigate clinical and dermoscopic characteristics of FM.MethodsThe clinical features and dermoscopic findings of 20 patients diagnosed with FM and 14 patients diagnosed with subungual melanoma the Department of Dermatology of Pusan National University Hospitals (Busan and Yangsan) were retrospectively reviewed.ResultsFM mainly occurred as a solitary form in the toenail. Patients in the FM group were older than those in the subungual melanoma group. The most distinguishable general dermoscopic features in FM were a distal diffuse pattern, distal linear pattern, and light brown to yellowish color. FM-associated specific dermoscopic patterns such as the reverse triangular pattern, subungual hyperkeratosis, scale on the nail surface, and white or yellowish streaks were dominantly observed in the FM group compared to the subungual melanoma group.ConclusionFM-associated dermoscopic patterns and distal diffuse and linear patterns could be helpful diagnostic clues for differential diagnosis of FM from subungual melanoma.

Investigation of valence band reconstruction methods for attosecond streaking data from surfaces.

We analyze simulated streaked valence band photoemission with atomic streaking theory-based reconstruction methods to investigate the differences between atomic gas-phase streaking and valence band surface streaking. The careful distinction between atomic and surface streaking is a prerequisite to justify the application of atomic streaking theory-based reconstruction methods to surface streaking measurements. We show that neglecting the band structure underestimates the width of reconstructed photoelectron wavepackets, consistent with the Fourier transform limit of the band spectrum. We find that a fit of Gaussian wavepackets within the description of atomic streaking is adequate to a limited extent. Systematic errors that depend on the near-infrared skin depth, an inherently surface-specific property, are present in temporal widths of wavepackets reconstructed with atomic streaking theory-based methods.

Clinical profile and gram negative bacterial profile of urinary tract infection in children attending a tertiary care hospital of Tamilnadu, India

Background: Urinary tract infection (UTI) is one of the most common infections caused by bacterial pathogens seen mostly in developing countries. This study was done to assess the clinical and gram negative bacterial profile of pathogens causing urinary tract infection, which helps the clinician to diagnose early and give presumptive antibiotic to prevent complications.Methods: Specimen was collected in sterile, leak proof container by clean catch mid-stream technique. Isolation of uropathogens was performed by a surface streak procedure on both blood agar and Mac Conkey Agar (Himedia, India) using semi quantitative method by using standard loop technique and Identified as per standard CLSI guidelines. Antibiogram of the isolates was performed and read as per standard manufacturer’s instructions.Results: UTI was more common in female children than male, and half were in the age group 1-5 years. Fever is the most common presentation (58.6%) followed by dysuria (46.4%) abdominal pain (45%) and decreased appetite (23.6%). Escherichia coli was the most common (73.6%) isolate followed in order by Klebsiella sps (15.7%), Citrobacter sps (2.1%) Proteus sps (5%) and Pseudomonas sps (3.5%). Nitrofurantoin (86%) was the most sensitive antibiotic followed by cefexime (84.7%), gentamicin (82%) and ciprofloxacin (81%) for E. coli. Klebsiella was sensitive to gentamycin, ciprofloxacin. Greater degree of resistance was noted to ampicillin, cotrimoxazole and nalidixic acid.Conclusions: The common clinical feature assosciated with UTI was fever and commonest causative organism for UTI was E. coli. The appropriate antibiotic in-vitro were cefexime and gentamicin in this study. Higher degree of resistance was found in antibiotics such as amipicllin, cotrimioxazole, cephalexin, nalidixicacid.

Change of the Surface Structure by F Doping in BiS2-Based Superconductor CeO1-xFxBiS2

The observation of the surface structure on single crystalline CeO1-xFxBiS2 (x = 0.5, and 0.7) was performed successfully using a scanning tunneling microscopy. In the sample with x = 0.5, the square lattice composed of Bi atoms was observed. In addition, defects of the surface atoms and streaks were detected on the surface as in the case of NdO0.7F0.3BiS2 single crystal. With further F doping, the surface structure of sample with x = 0.7 showed a novel structure, termed by the “bone” structure. This result suggests that the F concentration affects the surface structure.

Numerical Evidence of Turbulence Generated by Nonbreaking Surface Waves

AbstractNumerical simulation of monochromatic surface waves propagating over a turbulent field is conducted to reveal the mechanism of turbulence production by nonbreaking waves. The numerical model solves the primitive equations subject to the fully nonlinear boundary conditions on the exact water surface. The result predicts growth rates of turbulent kinetic energy consistent with previous measurements and modeling. It also validates the observed horizontal anisotropy of the near-surface turbulence that the spanwise turbulent intensity exceeds the streamwise component. Such a flow structure is found to be attributed to the formation of streamwise vortices near the water surface, which also induces elongated surface streaks. The averaged spacing between the streaks and the depth of the vortical cells approximates that of Langmuir turbulence. The strength of the vortices arising from the wave–turbulence interaction, however, is one order of magnitude less than that of Langmuir cells, which arises from the interaction between the surface waves and the turbulent shear flow. In contrast to Langmuir turbulence, production from the Stokes shear does not dominate the energetics budget in wave-induced turbulence. The dominant production is the advection of turbulence by the velocity straining of waves.

Torsion and Bending Properties of OneShape and WaveOne Instruments

IntroductionThe purpose of this study was to compare the torsion and bending properties of OneShape (OS; Micro Mega, Besançon, France) and WaveOne (WO; Dentsply Maillefer, Ballaigues, Switzerland) single-file systems. MethodsThe torsional strength of OS size #25, 0.06 taper and WO primary size #25, 0.08 taper was measured by using a torsiometer after fixing the apical 5 mm of the instrument rigidly. A scanning electron microscope was used to characterize the topographic features of the fracture surfaces of broken files. The files were tested for bending resistance by using the cantilever bending test. Data were statistically analyzed using the independent t test. Statistical significance level was set at P < .05. ResultsWO had a significantly higher torsional resistance than OS (P < .001). The average bending resistance as measured by the maximum force (gf) to bend instruments revealed that the WO had a significantly lower resistance to bend than OS (P < .001). Scanning electron microscopic analysis of the fractured cross-sectional surfaces revealed typical features of torsional failure including skewed dimples near the center of the fracture surface and circular abrasion streaks. ConclusionsThe WO single-file system showed higher torsional resistance and flexibility than the OS single-file system. Different cross-sectional geometry and the alloy from which the instrument is manufactured could have significant influence on the torsional resistance and flexibility of the instruments.

Study on Piezoelectric Effect and Magnetic Properties of Tourmalines

The piezoelectric effect was determined and the magnetization testing of diverse tourmalines was carried out in this paper. The results show that static voltage on both ends of tourmaline crystal enhances gradually with pressure enhancing, but there is no linear function between each other. At the very time when crystal breaks, the static voltage can reach a maximum value. The direction of the static voltage is reverse when giving and losing pressure. The performances of piezoelectric strength are as follows: Elbaite&gt;Schorl&gt;Dravite. The piezoelectricity on both ends of tourmaline crystal is stronger than that on cylinder surface, which is 3 ~ 4 times of the cylindrical surface. The piezoelectric strength of tourmaline crystal has nothing to do with its crystal volume but has something to do with the crystal surface streak. The performance is that the more limpid of the crystal surface streak is, the more obvious of the piezoelectric effect is. The overall tourmaline magnetization is weak. Magnetic susceptibility is a linear function of the refractive index and Fe-contents. Magnetic susceptibility of Schorl is greater than that of Elbaite. Saturation magnetization and remanence magnetic of Schorl are greater perpendicular to than parallel to C axis.

Scaling of heat transfer augmentation due to mechanical distortions in hypervelocity boundary layers

We examine the response of hypervelocity boundary layers to global mechanical distortions due to concave surface curvature. Surface heat transfer and visual boundary layer thickness data are obtained for a suite of models with different concave surface geometries. Results are compared to predictions using existing approximate methods. Near the leading edge, good agreement is observed, but at larger pressure gradients, predictions diverge significantly from the experimental data. Up to a factor of five underprediction is reported in regions with greatest distortion. Curve fits to the experimental data are compared with surface equations. We demonstrate that reasonable estimates of the laminar heat flux augmentation may be obtained as a function of the local turning angle for all model geometries, even at the conditions of greatest distortion. This scaling may be explained by the application of Lees similarity. As a means of introducing additional local distortions, vortex generators are used to impose streamwise structures into the boundary layer. The response of the large scale vortices to an adverse pressure gradient is investigated. Surface streak evolution is visualized over the different surface geometries using fast response pressure sensitive paint. For a flat plate baseline case, heat transfer augmentation at similar levels to turbulent flow is measured. For the concave geometries, increases in heat transfer by factors up to 2.6 are measured over the laminar values. The scaling of heat transfer with turning angle that is identified for the laminar boundary layer response is found to be robust even in the presence of the imposed vortex structures.

Lubricating Performances of Nano Organic-Molybdenum as Additives in Water-Based Liquid during Cold Rolling

The non-parathion nano organic molybdenum (Nano-Mo) was adopted to substitute for the conventional extreme-pressure and anti-wear additives, uniformly dispersed in water-based cold rolling liquid for steel strips. The tribological properties of the water-based cold rolling liquid were tested by the four-ball machine, and the lubricity of the cold-rolling liquid for steel strip was evaluated on the 4-high cold rolling experiments. Besides, the worn surfaces of the steel balls were observed by an optical microscope. Results indicated that Nano-Mo as additive in water-based cold rolling liquid, compared with the conventional emulsions, PB values was increased by 4%, and friction coefficient and wear scar diameter were decreased by 10.8% and 13.1%, the lubricity of rolling liquid was verified by cold rolling test which showed that this liquid had the excellent lubricant performance to reduce the rolling force, save energy consumption and get thinner strip. Optical microscope was used to observe the strips surface which showed that strip surface streaks were clear, scratches were less and shallow. By roughness test and EDS analysis, defects were filled with nanoparticles, friction and wear were reduced effectively. In addition, tensile properties had been studied after rolling lubrication, but the results showed no significant effect.

Field Observation on the Horizontal Velocity Profile of Wind-driven Currents with Secondary Circulations

Field observation on the horizontal velocity profile of wind-driven currents with secondary circulations was conducted in the lake of Shinji by using the web camera and the horizontal ADCP, H-ADCP, in order to propose the convenient method of Langmuir observation and to investigate the horizontal profile of wind-driven currents and the occurrence frequency of secondary circulations. Observation results by using the web camera shows the formation of surface streaks when the west wind is strong. H-ADCP was set across the surface streaks. Observation results by using H-ADCP shows the horizontally periodic profiles of wind-driven currents when the west wind is strong. The FFT analysis shows that fourier coefficients and the predominant frequency increase immediately with the increase of wind velocity. It shows the rapid response of periodic profile to the wind velocity.

A numerical study on the evolution and structure of a stress-driven free-surface turbulent shear flow

Turbulent shear flow beneath a flat free surface driven by a surface stress is simulated numerically to gain a better understanding of the hydrodynamic processes governing the scalar transfer across the air-water interface. The simulation is posed to mimic the subsequent development of a wind-driven shear layer as in a previous experiment except that the initiation of the surface waves is inhibited, thus focusing on the boundary effect of the stress-imposed surface on the underlying turbulent flow and vice versa. Despite the idealizations inherent in conducting the simulation, the computed flow exhibits the major surface features, qualitatively similar to those that appear in the laboratory and field experiments. Two distinct surface signatures, namely elongated high-speed streaks and localized low-speed spots, are observed in the simulated flow. Including temperature as a passive tracer and describing an upward heat flux at the surface, we obtain high-speed streaks that are colder and low-speed spots that are warmer than the surrounding regions. The high-speed streaks, arranged with somewhat equal cross-spacing of centimetres scale, are formed by an array of streamwise jets within the viscous sublayer immediately next to the surface. Beneath the streaks, counter-rotating streamwise vortex pairs are observed among other prevailing elongated vortices. However, they are significantly shorter in length and more irregular than their corresponding high-speed streaks at the surface. Accompanying the more organized high-speed streaks, localized regions of low streamwise velocity emerge randomly on the surface. These low-speed spots are attributed to strong upwelling flows which disrupt the viscous sublayer and also bring up the submerged fluids of low streamwise velocity. The occasional interruptions of the streamwise high-speed jets by the upwelling flows account for bifurcation or dislocation of the surface streaks. Statistics of the turbulence are presented and their implications for the formation of the flow structures are discussed.