Elevated Surface Tension Research Articles

Wpływ napięcia międzyfazowego między ropą a wodą na stabilność emulsji ropnych

"The stability of crude oil emulsions sourced from wells in two distinct fields distinguished by varying physical-chemical properties was analysed. The oil taken from the wells of Muradkhanli and Balakhani fields of State Oil Company of the Azerbaijan Republic (SOCAR) has been used as the research object. Demulsification of both oils, whose composition differs in the amount of high molecular compounds, has been investigated through the static settling method for 2, 4, 6, 8, 10 and 12 hours, and the amount of residual water in the oil has been recorded. In the same time interval, the oils have been tested by adding n-hexane and phenol to them, respectively. During the experiments, it was discovered that after the addition of n-hexane, which is a saturated hydrocarbon, the surface tension force increased in both oil samples and caused the formation of water in the form of a dispersed phase in the oil, which resulted in an increase in stability. In particular, as the concentration of n-hexane in oil increased, oil emulsions became aggregative and kinetically stable. The experiments conducted involving the addition of phenol to oils revealed that an increase in the volume of phenol in the oil led to a decrease in the surface tension force at the oil-water boundary, thereby accelerating the demulsification process. Subsequently, the research extended to investigating the emulsion stability of the oil samples by adding phenol and n-hexane in varying proportions. It was observed that an increase in the phenol ratio expedited the demulsification process, whereas a higher hexane ratio weakened it. Throughout the experimental tests, fluctuations in demulsification rates were noted upon the addition of organic substances to the oil samples. Furthermore, an increase in the concentration of high molecular compounds in the oil composition resulted in elevated surface tension, posing challenges in separating the water phase from the oil. The demulsification ability of organic substances added to crude oil samples, compositions A, B and C (25% n-hexane and 75% phenol (conditional name A), 50% n-hexane and 50% phenol (conditional name B), 75% n-hexane and 25% phenol (conditional name C)) prepared on the basis of these organic substances was examined depending on the surface tension.

Polyhexamethylene guanidine aerosol triggers pulmonary fibrosis concomitant with elevated surface tension via inhibiting pulmonary surfactant

Environmental chemicals inhalation exposure could induce pulmonary fibrosis, which is characterized by the excessive proliferation of fibroblasts and accumulation of extracellular matrix components, in which surface tension usually plays vital roles. Polyhexamethylene guanidine (PHMG) was first recognized as a potential hazard ingredient in humidifier disinfectants, which caused an outbreak of pulmonary fibrosis in South Korea. However, the underlying mechanisms involved in PHMG-induced pulmonary fibrosis have not yet been fully elucidated. Therefore, this study mainly focuses on the effect of PHMG on surface tension to unveil the influence and involved mechanisms in PHMG-induced pulmonary fibrosis. C57BL/6J mice were exposed to sub-acute PHMG aerosol for 8 weeks. The results indicated that PHMG induced pulmonary fibrosis combined with elevated surface tension. Results from in vitro study further confirmed PHMG elevated surface tension by inhibited pulmonary surfactant. Mechanistically, PHMG suppressed the key surfactant protein SP-B and SP-C by inhibiting protein expression and block their active sites. The present study, for the first time, revealed the molecular mechanism of PHMG-induced pulmonary fibrosis based on pulmonary surfactant inhibition mediated surface tension elevated. And pulmonary surfactant may be a potential target for further intervention to prevent PHMG-induced fibrosis or alleviate the symptom of relevant patients.

Surface tension of liquid nickel: Re-evaluated and revised data

Nickel is an important component in many alloys, so reliable surface tension data in the liquid phase are essential for simulation processes in the metal industry. First results for surface tension of liquid nickel from our working group by Aziz et al. [1], which led to the first publication on the topic of our Electromagnetic Levitation (EML) setup, delivered unusual high values compared to the literature, which itself covers a wide range. To find the reason for this behaviour the aim of this work was to investigate the surface tension of nickel samples from different suppliers at similar purity grades by the Oscillating Drop (OD) technique using the EML setup of the Thermophysics and Metalphysics Group at Graz University of Technology. Since no significant deviations between samples from different suppliers have been found, an extensive literature research according to various experimental and evaluation parameters has been performed. In the course of this investigation, the earlier obtained experimental data of Aziz et al. were re-evaluated. Due to gained awareness in evaluating the translational frequency in vertical direction, the mystery of these elevated surface tension results could be solved, so that in the end the originally obtained results of Aziz have been drastically decreased through re-evaluation.

Surface Penetration without Enrichment: Simulations Show Ion Surface Propensities Consistent with Both Elevated Surface Tension and Surface Sensitive Spectroscopy.

Molecular dynamics was used to investigate ion surface propensities in NaCl, KBr, and CsI solutions with an MP2-based force field. Although NaCl is found to be strongly repelled from the liquid-vapor interface, softer ions, such as I-, penetrate closely to the interface. Despite the surface penetration, the concentration of CsI near the interface is still lower than that in the bulk, thus leading to no surface enrichment. The salt concentration is found to affect relative surface propensities of the ions. More significant surface penetration is observed at higher salt concentrations. Softer ions at higher concentrations form a complex multilayer arrangement that can not be characterized as a simple surface bilayer. The simulated ion distributions explain the spectroscopic evidence of surface perturbation by soft ions with a negative surface excess consistent with an increased surface tension of salt solutions.

Effect of nano-filler graphene on nano-composite system of polystyrene-graphene

By using N-methyl-2-pyrolidone (NMP) and tetrahydrofuran (THF) solvents, the yield of two-dimensional material graphene as carried out via a technique called liquid exfoliation, phases including dispersal of preponderant material (graphite), sonicating the elevated surface tension solvents and decontamination for the eradication of impurities and remnant were implied in this yield. Now, these progressions were implemented by the use of bath Sonicator, ultracentrifuge, and probe Sonicator. Few-layer graphene (FLG) was originated which fused into intricate architecture (polymer matrix) in order to yield nano-composites of polystyrene and graphene via the technique of solution forming at contrasting filler loadings. The study of the upshot of graphene nano-filler, at divergent wt% ages of graphene’s exfoliation at scanty percolation, i.e., (EG) (i = 0, 0.1, 0.3, 0.5, 0.7, 0.9) on mechanical, microstructural, thermal, and electrical properties of polystyrene matrix, was carried out. This was done with the help of atomic force microscopy (AFM), four-probe method, X-ray diffraction (XRD), scanning electron microscopy (SEM), and universal testing machine (UTM). The 1-μm occurrence of two-dimensional sheets of graphene was marked by the SEM outcomes, whereas the composite system that contains polystyrene crests and graphene planes was ascertained via XRD testing. The 0.757-nm thickness which clearly specified the two-dimensional sheets was reckoned by AFM. The maximum increase, in mechanical properties including ultimate tensile strength (UTS), modulus of elasticity (E), and percentage elongation at break point, was 74.75, 150, and 68.65% respectively as related to the pure sample of polystyrene that was accounted in this research at scanty percolation (EG = 0.9 wt%). These properties are the function of filler loading. Electrical conductivity and electrical resistivity were evaluated; an intensification of 121.26% at 0.9% in electrical conductivity of filler loading as related to pure polystyrene was accounted whereas the electrical resistivity was diminished up to 121.19% at the identical filler loading. The ultimate increase in the thermal conductivity was 123.71% at concentration 0.9 wt% of the filler as confirmed by thermal conductivity outcomes. The better dispersion of the filler in the matrix and higher interfacial contact between the filler and polymer create these increasing trends.

Accelerated deflation promotes homogeneous airspace liquid distribution in the edematous lung.

Edematous lungs contain regions with heterogeneous alveolar flooding. Liquid is trapped in flooded alveoli by a pressure barrier-higher liquid pressure at the border than in the center of flooded alveoli-that is proportional to surface tension, T Stress is concentrated between aerated and flooded alveoli, to a degree proportional to T Mechanical ventilation, by cyclically increasing T, injuriously exacerbates stress concentrations. Overcoming the pressure barrier to redistribute liquid more homogeneously between alveoli should reduce stress concentration prevalence and ventilation injury. In isolated rat lungs, we test whether accelerated deflation can overcome the pressure barrier and catapult liquid out of flooded alveoli. We generate a local edema model with normal T by microinfusing liquid into surface alveoli. We generate a global edema model with high T by establishing hydrostatic edema, which does not alter T, and then gently ventilating the edematous lungs, which increases T at 15 cmH2O transpulmonary pressure by 52%. Thus ventilation of globally edematous lungs increases T, which should increase stress concentrations and, with positive feedback, cause escalating ventilation injury. In the local model, when the pressure barrier is moderate, accelerated deflation causes liquid to escape from flooded alveoli and redistribute more equitably. Flooding heterogeneity tends to decrease. In the global model, accelerated deflation causes liquid escape, but-because of elevated T-the liquid jumps to nearby, aerated alveoli. Flooding heterogeneity is unaltered. In pulmonary edema with normal T, early ventilation with accelerated deflation might reduce the positive feedback mechanism through which ventilation injury increases over time.NEW & NOTEWORTHY We introduce, in the isolated rat lung, a new model of pulmonary edema with elevated surface tension. We first generate hydrostatic edema and then ventilate gently to increase surface tension. We investigate the mechanical mechanisms through which 1) ventilation injures edematous lungs and 2) ventilation with accelerated deflation might lessen ventilation injury.

An estimation of mechanical stress on alveolar walls during repetitive alveolar reopening and closure

Alveolar overdistension and mechanical stresses generated by repetitive opening and closing of small airways and alveoli have been widely recognized as two primary mechanistic factors that may contribute to the development of ventilator-induced lung injury. A long-duration exposure of alveolar epithelial cells to even small, shear stresses could lead to the changes in cytoskeleton and the production of inflammatory mediators. In this paper, we have made an attempt to estimate in situ the magnitudes of mechanical stresses exerted on the alveolar walls during repetitive alveolar reopening by using a tape-peeling model of McEwan and Taylor (35). To this end, we first speculate the possible ranges of capillary number (Ca) ≡ μU/γ (a dimensionless combination of surface tension γ, fluid viscosity μ, and alveolar opening velocity U) during in vivo alveolar opening. Subsequent calculations show that increasing respiratory rate or inflation rate serves to increase the values of mechanical stresses. For a normal lung, the predicted maximum shear stresses are <15 dyn/cm(2) at all respiratory rates, whereas for a lung with elevated surface tension or viscosity, the maximum shear stress will notably increase, even at a slow respiratory rate. Similarly, the increased pressure gradients in the case of elevated surface or viscosity may lead to a pressure drop >300 dyn/cm(2) across a cell, possibly inducing epithelial hydraulic cracks. In addition, we have conceived of a geometrical model of alveolar opening to make a prediction of the positive end-expiratory pressure (PEEP) required to splint open a collapsed alveolus, which as shown by our results, covers a wide range of pressures, from several centimeters to dozens of centimeters of water, strongly depending on the underlying pulmonary conditions. The establishment of adequate regional ventilation-to-perfusion ratios may prevent recruited alveoli from reabsorption atelectasis and accordingly, reduce the required levels of PEEP. The present study and several recent animal experiments likewise suggest that a lung-protective ventilation strategy should not only include small tidal volume and plateau pressure limitations but also consider such cofactors as ventilation frequency and inflation rate.

Increased phosphatidylcholine concentration in saliva reduces surface tension and improves airway patency in obstructive sleep apnoea

Surface tension may have important role for maintaining upper airway patency in patients with obstructive sleep apnoea. It has been demonstrated that elevated surface tension increases the pharyngeal pressures required to reopen the upper airway following collapse. The aim of the study was to evaluate the associations between the concentrations of endogenous surfactants in saliva with indices of upper airway patency in obstructive sleep apnoea. We studied 20 male patients with obstructive sleep apnoea (age: 60·3 ± 10·3 years; BMI: 25·9 ± 4·6 kg m(-2); AHI: 41·5 ± 18·6 events h(-1)). We obtained 100-μL samples of saliva prior to overnight polysomnographic sleep study. The surface tension was determined using the pull-off force technique. The concentration of phosphatidylcholine (PC) was evaluated by liquid chromatography-mass spectrometry (LC-MS/MS). Regression analysis between apnoea, hypopnoea and apnoea/hypopnoea indices and the ratio of hypopnoea time/total disordered breathing time (HT/DBT) with surface tension and PC were performed. P < 0·05 was considered significant. The mean saliva surface tension was 48·8 ± 8·0 mN m(-1) and PC concentration was 15·7 ± 11·1 nM. The surface tension was negatively correlated with the PC concentration (r = -0·48, P = 0·03). There was a significant positive correlation between surface tension with hypopnoea index (r = 0·50, P = 0·03) and HT/DBT (r = 0·6, P = 0·006), but not apnoea or apnoea/hypopnoea index (P > 0·11). Similarly, PC concentration negatively correlated with hypopnoea index (r = -0·45, P = 0·04) and HT/DBT (r = -0·6, P = 0·004), but not with apnoea index or AHI (P > 0·08). An increase in salivary PC concentration may increase upper airway patency in obstructive sleep apnoea through a reduction in surface tension.

Imbibition of saline solutions into dry and prewetted porous media

Infiltration of saline solutions and pure water into homogeneous packs of prewetted and air-dry silica sands was investigated using a light transmission system. Four sand grades and five solutions were considered. Narrow fingers with a sharp, almost saturated, wetting front were observed in the air-dry sands. The water content left behind the fingertip of saline solutions was higher than for pure water, resulting in a greater lateral expansion of the saline fingers over time. The rate of lateral expansion scaled with the square root of time, likely due to classic liquid sorption with the possible addition of water vapor diffusion. At early time, the salty fingers moved faster, but were ultimately overtaken by the pure water fingers. In prewetted sand, the wetting fronts were diffuse and never exceeded 26% saturation, less than third that seen in the initially air-dry media. The plumes in the prewetted sand were also much wider and their shape varied. In the prewetted sand the elevated surface tension of the saline solutions was the major cause for the observed differences in finger width and velocity, yet appeared to be insignificant in air-dry sand. Here, in addition to the density effect, absorption of the saline solution to the silica sand influenced the depth of wetting, finger velocity, and subsequent lateral expansion.

The Role of Pulmonary Collectin N-terminal Domains in Surfactant Structure, Function, and Homeostasis in Vivo

The N-terminal domains of the lung collectins, surfactant proteins A (SP-A) and D (SP-D), are critical for surfactant phospholipid interactions and surfactant homeostasis, respectively. To further assess the importance of lung collectin N-terminal domains in surfactant structure and function, a chimeric SP-D/SP-A (D/A) gene was constructed by substituting nucleotides encoding amino acids Asn(1)-Ala(7) of rat SP-A with the corresponding N-terminal sequences from rat SP-D, Ala(1)-Asn(25). Recombinant D/A migrated as a 35-kDa band on reducing SDS-PAGE and as a ladder of disulfide-linked multimers under nonreducing conditions. The recombinant D/A bound and aggregated phosphatidylcholine containing vesicles as effectively as rat SP-A. Mice in which endogenous pulmonary collectins were replaced with D/A were developed by human SP-C promoter-driven overexpression of the D/A gene in SP-A(-/-) and SP-D(-/-) animals. Analysis of lavage fluid from SP-A(-/-,D/A) mice revealed that glycosylated, oligomeric D/A was secreted into the air spaces at levels that were comparable with the authentic collectins and that the N-terminal interchange converted SP-A from a "bouquet" to a cruciform configuration. Transmission electron microscopy of surfactant from the SP-A(-/-,D/A) mice revealed atypical tubular myelin containing central "target-like" electron density. Surfactant isolated from SP-A(-/-,D/A) mice exhibited elevated surface tension both in the presence and absence of plasma inhibitors, but whole lung compliance of the SP-A(-/-,D/A) animals was not different from the SP-A(-/-) littermates. Lung-specific overexpression of D/A in the SPD(-/-) mouse resulted in hetero-oligomer formation with mouse SP-A and did not correct the air space dilation or phospholipidosis that occurs in the absence of SP-D. These studies indicate that the N terminus of SP-D 1) can functionally replace the N terminus of SP-A for lipid aggregation and tubular myelin formation, but not for surface tension lowering properties of SP-A, and 2) is not sufficient to reverse the structural and metabolic pulmonary defects in the SP-D(-/-) mouse.

Mechanics of edematous lungs.

Using the parenchymal marker technique, we measured pressure (P)-volume (P-V) curves of regions with volumes of approximately 1 cm3 in the dependent caudal lobes of oleic acid-injured dog lungs, during a very slow inflation from P = 0 to P = 30 cmH2O. The regional P-V curves are strongly sigmoidal. Regional volume, as a fraction of volume at total lung capacity, remains constant at 0.4-0.5 for airway P values from 0 to approximately 20 cmH2O and then increases rapidly, but continuously, to 1 at P = approximately 25 cmH2O. A model of parenchymal mechanics was modified to include the effects of elevated surface tension and fluid in the alveolar spaces. P-V curves calculated from the model are similar to the measured P-V curves. At lower lung volumes, P increases rapidly with lung volume as the air-fluid interface penetrates the mouth of the alveolus. At a value of P = approximately 20 cmH2O, the air-fluid interface is inside the alveolus and the lung is compliant, like an air-filled lung with constant surface tension. We conclude that the properties of the P-V curve of edematous lungs, particularly the knee in the P-V curve, are the result of the mechanics of parenchyma with constant surface tension and partially fluid-filled alveoli, not the result of abrupt opening of airways or atelectatic parenchyma.

Pulmonary Administration of Vasoactive Substances by Perfluorochemical Ventilation

Therapeutic management of respiratory distress syndrome, pneumonia, and pulmonary hypertension includes delivery of biologically active agents to the neonatal lung. However, mechanical abnormalities of the lung, intrapulmonary shunting, ventilation-perfusion mismatching, and elevated surface tension impede effective systemic or intratracheal delivery of agents to the lung during conventional gas ventilation. The objective of this study was to test the hypothesis that perfluorochemical (PFC) liquid ventilation can be used for pulmonary administration of vasoactive drugs (PAD) and to compare these responses to those elicited with intravascular (IV) administration during tidal liquid ventilation. Cardiovascular responses of 16 preterm and neonatal lambs to randomized doses of acetylcholine, epinephrine, and priscoline were studied. Physiologic gas exchanged and acid-base balance were maintained using previously described tidal liquid ventilation techniques. In subgroups of animals, the distribution pattern of carbon 1- and choline 14-labeled dipalmitoylphosphatidylcholine (14C-DPPC) in saline and the responses to priscoline after hypoxia-induced pulmonary hypertension and hypoxemia administered during liquid ventilation were studied. Dose-response curves for PAD and IV administration demonstrated progressive, dose-dependent, cholinergic responses to acetylcholine (decreased mean systemic arterial pressure [MAP] and heart rate), sympathomimetic responses to epinephrine (increased MAP and heart rate), and alpha-adrenergic blockade responses to priscoline (decreased MAP and mean pulmonary arterial pressure). Compared with IV administration, PAD of priscoline resulted in a significantly greater decrease in pulmonary relative to systemic arterial pressure; this response was potentiated by hypoxia, reduced pulmonary pressures to near normal values, and improved oxygenation. The 14C-DPPC in saline was distributed relatively homogeneously throughout the lung by PAD, with 80% of the lung pieces receiving amounts of 14C-DPPC with +/-20% of the mean value. This study demonstrates that vasoactive agents can be delivered to the lung directly by PAD during PFC liquid ventilation. The inherent advantages of this method relate to the physical properties of PFC liquid ventilation as a vehicle (respiratory gas solubility, low surface tension-enhancing distribution, and inertness precluding interaction) and physiological properties of the lung as an exchanger.

Reassessment of interaction between gut detergents and tannins in lepidoptera and significance for gypsy moth larvae

Surface-active lysophospholipids are thought to interfere with tannin-protein interactions and may comprise an adaptation in Lepidoptera to tannin-rich diets. We found several lysophospholipids and phospholipids at about eight times the critical micelle concentration (CMC) in the midguts of gypsy moth larvae, which exhibited appropriately reduced surface tensions. We confirmed the interfering activity of lysophosphatidylcholine (lysolecithin) in a model astringency assay using tannic acid and hemoglobin (hemanalysis), but discovered that tannic acid and red oak tannin extracts precipitate the lipid from simulated midgut solutions quantitatively, even at pH 10. Leaf tannin extracts from trees on which gypsy moths grew and reproduced poorly precipitated lysolecithin more effectively than did extracts from trees on which gypsy moths performed well. Adding tannic acid to midgut fluid elevated surface tension, and about 25% of larvae feeding on oak leaves exhibited elevated midgut surface tension, suggesting a loss of surfactants. Larvae appear able to replace lost surfactants to a limited degree. An important effect of leaf tannins, and perhaps other phenolics, may be to reduce concentrations of surface-active phospholipids in the midgut and produce lipid or other dietary deficiencies in insects.

Use of the drop volume of amniotic fluid in estimating the risk for respiratory distress syndrome in the newborn infant

The present study describes the testing and function of the drop-volume method in the analysis of fetal lung maturity with use of amniotic fluid. Elevated surface tension resulting from a lack of surface-active phospholipids (surfactant) is the primary etiologic defect in the development of respiratory distress syndrome. The drop-volume method quantifies the surface tension of amniotic fluid with use of the fact that the volume of a falling drop of liquid is proportional to the quantity of surfactant in the solution. The drop-volume method requires only 2 minutes and 2 ml of amniotic fluid and predicts fetal lung maturity with an accuracy equal to or greater than that of other tests currently in use.