Variation Of Tension Research Articles

Hypoxia-Mediated Decrease of Ovarian Cancer Cells Reaction to Treatment: Significance for Chemo- and Immunotherapies.

Hypoxia, a common factor ruling the microenvironment composition, leads to tumor progression. In this hypoxic context, cytokines and cells cooperate to favor cancer development and metastasis. Tumor hypoxia is heterogeneously distributed. Oxygen gradients depend on the vicinity, functionality of blood vessels, and oxygen ability to diffuse into surrounding tissues. Thus, the vasculature state modulates the microenvironment of the tumor cells. Cells sense and react to small variations in oxygen tension, which explains the lack of tumor cells’ unicity in their reaction to drugs. Ovarian cancers are highly hypoxia-dependent, ascites worsening the access to oxygen, in their reactions to both chemotherapy and new immunotherapy. Consequently, hypoxia affects the results of immunotherapy, and is thus, crucial for the design of treatments. Controlling key immunosuppressive factors and receptors, as well as immune checkpoint molecule expression on tumor, immune and stromal cells, hypoxia induces immunosuppression. Consequently, new approaches to alleviate hypoxia in the tumor microenvironment bring promises for ovarian cancer immunotherapeutic strategies. This review focuses on the effects of hypoxia in the microenvironment and its consequences on tumor treatments. This opens the way to innovative combined treatments to the advantage of immunotherapy outcome in ovarian cancers.

Effect of Core Liquid Surface Tension on the Liquid Marble Shell

AbstractLiquid marble is a non‐wetting droplet coated with micro‐ or nanometer sized particles and exhibits great versatility as a standalone system. Unique features such as low evaporation rate, low friction, and a porous shell enable it to be a potential tool for gas sensing, cell culture, and drug delivery. With the growing number of interests in these fields, it is important to understand the structure of the liquid marble shell and how it behaves with the variation of the surface tension of the core liquid. This paper investigates the thickness and the mass of liquid marble shell at various surface tension values. Surfactant mediated surface tension reduction allows the encapsulating particles to penetrate more into the core liquid and decreases the shell thickness. The shell thickness decreases significantly with the surface tension, whereas the mass remains almost constant. Interestingly, the trend reverses with further decrease of the surface tension. In this regime, both the thickness and the mass of the shell increase due to interfacial jamming. This work provides a new insight into understanding the contribution of the particle distribution at the shell for the stability and the measurement of the effective surface tension of a liquid marble.

Numerical investigations on load transfer of mooring line considering chain–seabed dynamic interaction

Taut or semi-taut mooring lines are often used in deep-sea area to connect the floating structures to the anchors in the seabed. In previous studies, the quasi-static analysis method was adopted to assess the load transfer of the mooring line. However, the inertia effect of mooring line and chain–seabed dynamic interaction cannot be neglected in practice. In this paper, the soil strain rate effect was incorporated in the chain–seabed dynamic analyses, and the load transfer mechanism of mooring line was investigated based on the proposed model. The numerical model was firstly verified with the quasi-static analysis results and experimental data under dynamic condition, and then the contributions of different forces to the variations of line tension were evaluated. It is found that two factors (inertia force and soil resistance) have a great influence on the mooring line tension variation. The inertial effect is dominated under high-frequency condition, and the maximum line tension at the fairlead is larger than that under static condition. However, the tension at the pad-eye under dynamic condition always has a certain increase. The reason is that partial reverse soil resistance under dynamic condition increases the tension at the pad-eye.

A coupled continuum-statistical model to predict interfacial deformation under an external field

HypothesisCoupling the continuum approach with a statistical one may help in the development of a generic thermodynamic model to theoretically analyse the variations of interfacial tension and subsequent deformation of an interface between a pair of fluids under a field exposure. In this direction, the local variations of interfacial tension due to the redistribution of interfacial molecules have been expressed as the functions of the molecular interaction potentials for a variety of externally applied fields. Numerical ExperimentsTwo continuum-statistical models for interfacial tension have been developed by choosing two different types of molecular interaction potentials. The proposed analytical models have been successfully integrated with the Cahn-Hilliard and Navier-Stokes framework before solving them numerically using computational tools. FindingsEffects of field exposure on the redistribution of the molecules and the molecular interaction potentials can be correlated to the local variations of the interfacial tension and interfacial deformations. The calculations related to thetemperature dependence ofinterfacialthickness andinterfacialtension matches well with the experimental data. The simulated results show a nearly accurate prediction of the pre-existing experimental and theoretical results on interfacial deformation under electric, magnetic and optical fields.

Explicit and asymptotic solutions for frictional incomplete half-plane contacts subject to general oscillatory loading in the steady-state

This contribution presents an asymptotic formulation for the stick-slip behaviour of incomplete contacts under oscillatory variation of normal load, moment, shear load and differential bulk tension. The asymptotic description allows us not only to approximate the size of the slip zones during the steady-state of a cyclic problem without knowledge of the geometry or contact law, but provides a solution when all known analytical solutions for incomplete contacts reach their limitations, that is, in the presence of a varying moment and a differential bulk tension large enough to reverse the direction of slip at one end of the contact. An insightful comparison between the mathematically explicit analytical solution and the asymptotic approach is drawn using the example geometry of a shallow wedge.

A study on surface morphology and tension in laser powder bed fusion of Ti-6Al-4V

When reporting surface quality, the roughest surface is a reference for the measurements. In LPBF due to recoil pressure and scan movement, asymmetric surface is shaped, and surface roughness has different values in different measurement orientations. In this research, the influence of the laser powder bed fusion (LPBF) process parameters on surface tension and roughness of Ti-6AI-4 V parts in three orientations are investigated. To improve the mechanical properties, heat treatment was carried out and added to the designed matrix to generate a comprehensive data set. Taguchi design of experiment was employed to print 25 samples with five process parameters and post-processing. The effect and interaction of the parameters on the formation of surface profile comprising tension, morphology and roughness in various directions have been analysed. The main contribution of this paper is developing a model to approximate the melting pool temperature and surface tension based on the process parameters. Other contributions are an analysis of process parameters to determine the formation and variation of surface tension and roughness and explain the governing mechanisms through rheological phenomena. Results showed that the main driving factors in the variation of surface tension and formation of the surface profile are thermophysical properties of the feedstock, rheology and the temperature of the melting pool. Also, the results showed that while the value of surface tension is the same for each test case, morphology and the value of roughness are different when analysing the surface in perpendicular, parallel and angled directions to laser movement.

Determination of Dynamic Interfacial Tension during the Generation of Tiny Droplets in the Liquid-Liquid Jetting Flow Regime.

Liquid-liquid dispersion coupled with droplet formation and mass transfer of surfactants is one of the most typical phenomena in many chemical processes. As in every aspect of this process, the interfacial tension variation caused by the unsaturated adsorption of surfactants on the droplet surface plays an important role. This article focuses on microdroplet formation and the dynamic interfacial behavior of surfactants in the jetting regime. In a capillary embedded step T-junction device, controllable preparation of monodisperse droplets is achieved, and a correlation for predicting droplet sizes is established. A method for measuring the dynamic interfacial tension is provided. Mass transfer coefficients are then calculated for Tween 20 during the droplet formation process by a semiempirical correlation. The results indicate that dynamic interfacial tensions are lower than those obtained when the surfactant is adsorbed to equilibrium. Based on the tip-streaming phenomenon, mass transfer coefficients for Tween 20 can reach up to ∼10-3 m/s, higher than those obtained in coaxial microfluidic devices. All the preliminary results shed light on the nature of droplet formation and will be of significance for application in industrial apparatuses.

An Experimental Technique t o Determine t he Permissible Warp Tension Variation At t he Required Pick Density

Weaving is considered to be the most versatile means of manufacturing fabric. Due to versatility, process control is mandatory to ensure the quality of the woven fabric becomes a diverse task with a broader scope. With the advent of technology speed of weaving has been drastically increased due to which variation in warp tension becomes an inevitable fact for value-added technical products. Further, variation in warp tension results in different pick density which causes a shade variation due to different amounts of dye penetration along with the fabric. Maintain constant pick density throughout weaving is considered as the most important aspect. The pick density is greatly affected by the warp gaiting tension at which the fabric is woven and experiment results revealed that the warp gaiting tension is considerably changed when the beam is weaved down. Authors attempt to statistically analyze the quantitative relationship between the warp gaiting tension and the pick density. However, due to the high level of variability of warp gaiting tension along the warp with slightly scattered nature of experimental data, setting up a relationship with adequate accuracy is beyond achievable. Hence the warp gaiting tension is first grouped using a statistical technique and established the relationship for each group. The level of accuracy for each model is evaluated at 95% of the confidence interval and thereby determined the permissible tolerance in warp gaiting tension under which the required pick density could be still achieved.

Understanding Frothing of Liquid Mixtures: A Surfactantlike Effect at the Origin of Enhanced Liquid Film Lifetimes.

The formation of froth in mixtures of liquids is well documented, particularly in oil mixtures. However, in nonvolatile liquids and in the absence of surface-active molecules, the origin of increased liquid film lifetimes had not been identified. We suggest a stabilizing mechanism resulting from the nonlinear variations of the surface tension of a liquid mixture with its composition. We report on experimental lifetimes of froths in binary mixtures and show that their variations are well predicted by the suggested mechanism. We demonstrate that it prescribes the thickness reached by films before their slow drainage, a thickness which correlates well with froth lifetimes for both polar and nonpolar liquids.

Seabed trenching near the mooring anchor: History cases and numerical studies

The floating platform with taut or semi-taut mooring systems is the main option for oil and gas exploitations in deep sea. However, it has been reported that the reciprocating motion of the mooring line tends to induce the seabed trench near the anchor, which consequently reduces the anchor capacity. In this paper, two parts of work have been carried out to enhance the understanding of the seabed trench. Firstly, the dimensions of reported trenches in the field as well as their formation conditions are summarized, and four feature points are proposed to describe the trench profile. Secondly, a numerical method considering mooring line dynamics to predict the final trench profiles is proposed, which contains two simulation modules, i.e. mooring line dynamics and seabed trenching. The method is verified using the data from the field and centrifuge tests. The influences of the mooring line tension and soil strength on trench profiles are comprehensively investigated further. The results show that obvious trenches are likely to form when the amplitude of mooring line tension variation is large and the soil shear strength is low. The main impact of the formed trenches is that the loading direction at the pad-eye tends to be horizontal.

Experimental methodology for bubble content measurement of thin films

The inclusion of micro bubbles often exists in polyimide films (PI) during the liquid molding process, which can largely affect the mechanical performance. However, there lacks an effective method to quantify the bubble content. Herein, an obvious tension variation of a pre-stressed polyimide film is observed firstly in a vacuum test. This phenomenon is assumed that, when the vacuum level of the testing environment increases, the inner bubbles would expand mainly out of plane, resulting in an in-plane contraction, and the tension varies accordingly. This tension variation ability is found quite stable despite of the stochastic micro-bubble distribution, which could be utilized to quantify the bubble content. Moreover, a film with meso-size bubbles is tested to have the similar tension variation ability. According to the experimental results, the tension variation ability can be basically stable when the bubbles in the length and width directions reach a certain number (e.g. 10).

Effects on cerebral blood flow of position changes, hyperoxia, CO2 partial pressure variations and the Valsalva manoeuvre: A study in healthy volunteers.

Maintaining adequate blood pressure to ensure proper cerebral blood flow (CBF) during surgery is challenging. Induced mild hypotension, sitting position or unavoidable intra-operative circumstances such as haemorrhage, added to variations in carbon dioxide and oxygen tensions, may influence perfusion. Several of these circumstances may coincide and it is unclear how these may affect CBF. To describe the variation in transcranial Doppler and regional cerebral oxygen saturation (rSO2), as a surrogate of CBF, after cardiac preload and gravitational positional changes. Observational study. Operating room at Hospital Clínic de Barcelona. Ten healthy volunteers, white, both sexes. Measurements were performed in the supine, sitting and standing positions during hyperoxia, hypocapnia and hypercapnia protocols and after a Valsalva manoeuvre. Cardiac index (CI), haemodynamic and respiratory variables, maximal and mean velocities (Vmax, Vmean) (transcranial Doppler) and rSO2 were acquired. Results were analysed using a generalised estimating equation technique. CI increases more than 16% after a preload challenge were not accompanied by differences in rSO2 or Vmax - Vmean. With positional changes, Vmean decreased more than 7% (P = 0.042) from the supine to the seated position. Hyperoxia induced a cerebral rSO2 increase more than 6% (P = 0.0001) with decreases in Vmax, Vmean and CI values more than 3% (P = 0.001, 0.022 and 0.001) in the supine and standing position. During hypocapnia, CI rose more than 20% from supine to seated and standing (P = 0.0001) with a 4.5% decrease in cerebral rSO2 (P = 0.001) and a decrease of Vmax - Vmean more than 24% in all positions (P = 0.001). Hypercapnia increased cerebral rSO2 more than 17% (P = 0.001), Vmax - Vmean more than 30% (P = 0.001) with no changes in CI. After a Valsalva manoeuvre, rSO2 decreased more than 3% in the right hemisphere in the upright position (P = 0.001). Vmax - Vmean decreased more than 10% (P = 0.001) with no changes in CI. CBF changes in response to cerebral vasoconstriction and vasodilatation were detected with rSO2 and transcranial Doppler in healthy volunteers during cardiac preload and in different body positions. Acute hypercapnia had a greater effect on recorded brain parameters than hypocapnia.

Dynamic Analysis of Semi-submersible Under the Postulated Failure of Restraining System with Buoy

Coupled dynamic analyses of a deep-water Semi-submersible platform, in the South China Sea region, is carried out under postulated damage of the restraining system for both 10 and 100-years return period events. Under the combined action of wind, wave, and current loads, motion responses of Semi-submersible at 1500 and 2000 m water depths are analyzed in time-domain. Dynamic tension variations in the mooring lines are investigated for a fatigue failure using the S–N curve approach. Inclusion of a submerged buoy in the mooring system resulted in a marginal increase of the response due to a reduction in the restoration force of the mooring lines; submerged buoy also resulted in additional damping. The results of numerical studies showed an increase in tension in the mooring lines, which are adjacent to the damaged ones, causing reduced fatigue life. With the inclusion of submerged buoy in the mooring system, there is a considerable decrease in tension variation in mooring lines, increasing fatigue life. Failure of a mooring line causes an increase in tension of the adjacent mooring line, but not valid under all circumstances. It is seen from the studies that despite the postulated failure induced in a mooring, the adjoining line remains unaffected due to a steady coupling motion of the platform.

Variations in Wettability and Interfacial Tension during Alkali-Polymer Application for High and Low TAN Oils.

The injection of chemicals into sandstones can lead to alterations in wettability, where oil characteristics such as the TAN (total acid number) may determine the wetting state of the reservoir. By combining the spontaneous imbibition principle and the evaluation of interfacial tension index, we propose a workflow and comprehensive assessment to evaluate the wettability alteration and interfacial tension (IFT) when injecting chemical-enhanced oil-recovery (EOR) agents. This study examines the effects on wettability alteration due to the application of alkaline and polymer solutions (separately) and the combined alkali–polymer solution. The evaluation focused on comparing the effects of chemical agent injections on wettability and IFT due to core aging (non-aged, water-wet and aged, and neutral to oil-wet), brine composition (mono vs. divalent ions); core mineralogy (~2.5% and ~10% clay), and crude oil type (low and high TAN). Amott experiments were performed on cleaned water-wet core plugs as well as on samples with a restored oil-wet state. IFT experiments were compared for a duration of 300 min. Data were gathered from 48 Amott imbibition experiments with duplicates. The IFT and baselines were defined in each case for brine, polymer, and alkali for each set of experiments. When focusing on the TAN and aging effects, it was observed that in all cases, the early time production was slower and the final oil recovery was longer when compared to the values for non-aged core plugs. These data confirm the change in rock surface wettability towards a more oil-wet state after aging and reverse the wettability alteration due to chemical injections. Furthermore, the application of alkali with high TAN oil resulted in a low equilibrium IFT. By contrast, alkali alone failed to mobilize trapped low TAN oil but caused wettability alteration and a neutral–wet state of the aged core plugs. For the brine composition, the presence of divalent ions promoted water-wetness of the non-aged core plugs and oil-wetness of the aged core plugs. Divalent ions act as bridges between the mineral surface and polar compound of the in situ created surfactant, thereby accelerating wettability alteration. Finally, for mineralogy effects, the high clay content core plugs were shown to be more oil-wet even without aging. Following aging, a strongly oil-wet behavior was exhibited. The alkali–polymer is demonstrated to be efficient in the wettability alteration of oil-wet core plugs towards a water-wet state.

Numerical Investigation of Effect of Temperature Profile Imposed on the Crucible Surface on Oxygen Incorporated at the Crystal Melt Interface for 450 mm Diameter Silicon Single Crystal Growth in Presence of CUSP Magnetic Field Using Czochralski Technique

Numerical investigation has been carried out to study the effect of thermal boundary condition on turbulent melt flow and oxygen transfer inside a crucible used to grow 450 mm diameter silicon single crystal using Czochralski method. Two types of thermal boundary conditions, namely, isothermal crucible surface and experimentally measured temperatures on the crucible surface have been imposed on the crucible wall and crucible bottom. Melt motion owing to buoyancy, surface tension variation at the free melt surface as well as crystal and crucible rotation has been considered. Effect of CUSP magnetic field has also been investigated. Melt having aspect ratio of 1 and 0.5, representing high and moderate level of melt inside the crucible have been considered. K-epsilon turbulent model with low Reynolds number formulation has been used for turbulence modelling. Melt motion governed by natural convection, Marangoni convection and crystal as well as crucible rotation shows higher oxygen concentration at melt crystal interface for aspect ratio of 1, when experimental temperature profile is imposed at the crucible wall. For melt aspect ratio of 0.5, natural convection and Marangoni convection dependent melt show higher oxygen concentration for isothermal crucible wall boundary condition. Marangoni convection in absence of rotation of crystal and crucible leads to low oxygen concentration zone near the crystal outer surface, the size of which is larger for melt aspect ratio of 0.5. Maximum turbulent viscosity values for aspect ratio of 1, in case of experimental temperature at the crucible are higher compared to isothermal case, which is just the opposite of the trend for aspect ratio of 0.5. Imposing a CUSP magnetic field leads to similar distribution of turbulent viscosity for both types of thermal boundary conditions, irrespective of the type of thermal boundary condition. Oxygen concentration at the melt crystal interface is found to be higher in presence of CUSP magnetic field. Value of maximum turbulent viscosity for the two boundary condition are similar for melt aspect ratio of 1.0. Crucible surface temperature profile for aspect ratio of 1, on actual melt aspect ratio of 0.5 predicts lower oxygen concentration at melt crystal interface. Values and distribution of turbulent viscosity is however the same for both temperature profiles.

The potential of wire feed pulsation to influence factors that govern weld penetration in GMA welding

Derivative welding processes are in many cases capable of altering phenomena that determine fundamental aspects of weld bead formation. Some of these evolutions act over the wire feed dynamics. However, in this scenario, the effects of the wire feed pulsation on the weld bead formation governing factors have not been fully explored yet. Therefore, this work aimed at examining how a wire feed pulsation approach affects the droplet transfer in gas metal arc welding and how its interaction with the molten pool defines the weld bead penetration. Bead-on-plate weldments were produced by varying the wire feed pulsation frequency, yet keeping the same levels of arc energy and wire feed speed, with the power source operating in constant voltage and current modes. To assess the droplet transfer behavior, high-speed imaging was used. The geometry of the weld beads was compared in terms of fusion penetration. The results showed that an increase in the wire feed pulsation frequency intensifies the detachment frequency of the droplets, being possible to accomplish a stable metal transfer with them straightly projected toward the weld pool, which contributed to a centralized-increased penetration profile. Based on a descriptive model, it was demonstrated that the increase in droplet momentum or kinetic energy, due to the wire feed pulsation, was not enough to justify the penetration enhancement. It was concluded that the wire feed dynamics can also stimulate surface tension variations in the weld pool and therefore disrupt the behavior of its mass and heat convection, supporting fusion penetration.

Modelization of surfactant flooding: Methodology for determining the interfacial tension function of surfactant concentration and salinity

To predict accurately the amount of oil that can be recovered by a process of surfactant flood injection, a fine modelization of variation of interfacial tension between oil phase and aqueous phase with the reservoir conditions is required. Unfortunately, data of interfacial tension variation with all the parameters, i.e. temperature, salinity and surfactant concentration, are not always available when numerical simulation of the reservoir production is performed. In that case, interpolation is often used, but then cannot be fully representative of the variations. The work presented here details a new numerical model used to describe interfacial tension with all the parameters listed below. This model fit well experimental data obtained for this study. The asymmetry of the model allows to take into account the specificity of industrial formulations, when the interfacial tension at large salinities is different from interfacial tension at zero salinity. The protocol to determine experimental data of optimal salinity and interfacial tensions for such industrial formulations is detailed. The correlation described in this paper is also used to perform numerical experiments of injection of a formulation containing surfactant in porous media to recover oil. The 1D experiments are constructed using realistic parameters from literature. Sensitivity to optimal salinity is described using the interfacial tension model developed here, as well as its impact on oil production.

Effect of thermal convection on thermocapillary migration of a surfactant-laden droplet in a microchannel

Despite its significance in droplet-based microfluidic technologies with the use of thermal stimuli and surfactants, coupling effects of thermal- and surfactant-induced Marangoni stresses on the transport of droplets in microchannels are not fully uncovered yet. To facilitate studies in this area, we present a three-dimensional numerical study on the thermocapillary migration of an insoluble-surfactant-laden droplet under Poiseuille flow in a microchannel. This work is realized via our own front-tracking finite-difference method with further integration of the energy conservation equation and the surface surfactant transport equation. Our numerical results agree well with the previously reported analytical results for ambient conditions with negligible thermal convection. In this study, we mainly focus on the effects of the thermal convection at high thermal Peclet numbers and find that it induces a significant change in the thermal Marangoni stress. As a consequence, the migration of surfactant-laden droplets in the microchannel is significantly retarded by the thermal convection, which is observed for two different ambient conditions, i.e., the imposed temperature increasing or decreasing along the main flow direction. To understand the mechanism underlying the effects of the thermal convection, we analyze the distributions of the temperature, surfactant concentration, and the thermal- and surfactant-induced surface tension variations over the droplet surface. Notably, the surfactant-induced Marangoni stress always opposes the thermal-induced Marangoni stress for the entire range of thermal Peclet numbers considered in this study, but the competition between them is significantly alternated by the thermal convection in a quantitative manner.

Surface tension of strange stars mediated by a color-flavor-locked equation of state

We investigate the surface tension of strange quark stars by making use of a color-flavor-locked (CFL) equation of state. Compact objects with anisotropic pressures provide richer systems for studying surface tension variations, and establishing physically viable ranges of parameters in maintaining hydrostatic equilibrium of quark matter at densities exceeding that of nuclear material. The strange quark mass, the QCD gap energy, and the MIT bag constant are key parameters in the CFL equation of state used, and thus feature in calculations of the surface tension.

Synthesis and surface activity of photoresponsive hybrid surfactants containing both fluorocarbon and hydrocarbon chains

HypothesisHybrid surfactants containing both alkyl and fluoroalkyl chains within the same molecule where modification of the azobenzene group will enable us to switch the superhydrophobic nature with an external light source, and the optical behavior will vary depending on the structure of the hydrophobic chains. ExperimentsSurface activity and its optically-induced variation of the azobenzene-modified hybrid surfactants were characterized using the surface tensiometry, UV–vis and NMR spectroscopy and theoretical calculation. FindingsThe hybrid surfactants are superhydrophobic in nature reducing the surface tension of water to near 20 mN/m. Photo-isomerization of the azobenzene group induces a drastic surface tension variation (Δγ), and particularly the compositions containing the octyl-fluorocarbon chain exhibit remarkable Δγ as much as 30 mN/m which is even higher than that of the conventional surfactants (Δγ ≈ 14–20 mN/m). Theoretical calculation suggests significantly higher hydrophilicity of the cis isomer, causing the drastic switch in the surface activity. These results indicate the promise of the hybrid surfactants as efficient surface/interface manipulators.