Apparent Tension Research Articles

Are all yeast biosurfactants really capable of lowering surface tension below 30 mN/m ?

The study discusses pitfalls in attempts to determine reliable surface tension values for the culture media and their extracts for two biosurfactant-producing yeast strains: Rhodotorula graminis and Rhodotorula babjevae. The values obtained from an Axisymmetric Drop Shape Analysis (ADSA) tensiometer showed systematically more and more shallow dynamic surface tension decays, suggesting a deterioration of their surface activity. The rate of this apparent surface activity loss was shown to depend on the sample history, with slower changes observed in vigorously shaken samples. On the other hand, the force-based Wilhelmy plate method provided apparently stable surface tension values of the order of 30 mN/m, in accordance with numerous previous literature reports on similar yeast biosurfactants. Both observations can be justified by the presence of an oil emulsified by biosurfactants produced by the yeast. We show that the odd (apparent) surface tension results are in fact the measurement artifacts resulting from slow demulsification and subsequent oil-spreading assisted by the yeast biosurfactants. The apparent surface tension reduction is thus indeed caused by the presence of biosurfactants, but its value does not represent their real adsorption in a thermodynamic sense. Consequently, the often reported in the literature very low surface tension values for the yeast culture media, of the order of 30±5 mN/m, should be treated with caution, especially if the emulsion stabilized with the biosurfactant had not been fully destabilized prior to the measurement.

Preparation and structural characterization of pullulan and whey protein isolate-based electrospun nanofiber

The impact of blended ratios was analyzed on the development and characterization of electrospun fibers using various combinations of pullulan (PUL) and whey protein isolate (WPI). The physical parameters like apparent viscosity, electrical conductivity and surface tension of blended solutions were improved after the addition of PUL in the blends, resulting in a uniform electrospun nanofiber. Scanning electron microscope (SEM) of nanofibers revealed bead-free, smooth and uniform structural conformation. Whereas, the uniformity of nanofiber was compromised by using higher concentrations of WPI in the blend. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and Thermogravimetry analysis further confirmed the strong molecular interaction between polysaccharide and protein. The incorporation of WPI in PUL based electrospun nanofibers enhanced hydrophobicity, potentially facilitating the delivery of bioactive compounds. The WPI and PUL:WPI-based nanofibers demonstrated robust antioxidant potential, due to the presence of total phenolic contents (TPC). The stability of PUL interaction with WPI (β-lactoglobulin and α-lactalbumin) was confirmed through hydro-carbon (C–H) and hydrogen bond interactions by molecular docking. Finally, we can conclude that polysaccharide and protein-based nanofiber can be used to deliver bioactive compounds in food and pharmaceutical industries.

Membrane stretch as the mechanism of activation of PIEZO1 ion channels in chondrocytes

Osteoarthritis is a chronic disease that can be initiated by altered joint loading or injury of the cartilage. The mechanically sensitive PIEZO ion channels have been shown to transduce injurious levels of biomechanical strain in articular chondrocytes and mediate cell death. However, the mechanisms of channel gating in response to high cellular deformation and the strain thresholds for activating PIEZO channels remain unclear. We coupled studies of single-cell compression using atomic force microscopy (AFM) with finite element modeling (FEM) to identify the biophysical mechanisms of PIEZO-mediated calcium (Ca2+) signaling in chondrocytes. We showed that PIEZO1 and PIEZO2 are needed for initiating Ca2+ signaling at moderately high levels of cellular deformation, but at the highest strains, PIEZO1 functions independently of PIEZO2. Biophysical factors that increase apparent chondrocyte membrane tension, including hypoosmotic prestrain, high compression magnitudes, and low deformation rates, also increased PIEZO1-driven Ca2+ signaling. Combined AFM/FEM studies showed that 50% of chondrocytes exhibit Ca2+ signaling at 80 to 85% nominal cell compression, corresponding to a threshold of apparent membrane finite principal strain of E = 1.31, which represents a membrane stretch ratio (λ) of 1.9. Both intracellular and extracellular Ca2+ are necessary for the PIEZO1-mediated Ca2+ signaling response to compression. Our results suggest that PIEZO1-induced signaling drives chondrocyte mechanical injury due to high membrane tension, and this threshold can be altered by factors that influence membrane prestress, such as cartilage hypoosmolarity, secondary to proteoglycan loss. These findings suggest that modulating PIEZO1 activation or downstream signaling may offer avenues for the prevention or treatment of osteoarthritis.

Large gauge effects and the structure of amplitudes

We show that large gauge transformations modify the structure of momentum conservation leading to non-vanishing three-point amplitudes in a simple toy model of a gravitational wave event. This phenomenon resolves an apparent tension between perturbative scattering amplitude computations and exact methods in field theory. The tension is resolved to all orders of perturbation theory once large gauge effects are included via a modified LSZ prescription; if they are omitted, perturbative methods only recover a subset of terms in the full non-perturbative expression. Although our results are derived in the context of specific examples, several aspects of our work have analogues in dynamical gravitational scattering processes.

The architectonic of Foucault's critique

AbstractThis paper presents a new interpretation of Michel Foucault's critical project. It is well known that Foucault's genealogical critique does not focus on issues of justification, but instead tackles “aspectival captivity,” that is, apparently inevitable limits of thought that constrain the subject's freedom but that, in fact, can be transformed. However, it has not been recognized that, according to Foucault, critique can proceed along two distinct paths. In a key passage of “What Is Critique?,” Foucault states that critique is tasked with questioning truth about its effects of power and with questioning power about its discourses of truth. We show that this “double movement” organizes Foucault's critical project as a whole, giving it a significantly wider scope and a more complex structure than has been previously acknowledged. At the heart of the above‐mentioned bifurcation lies an apparent tension between two contrastive roles Foucault assigns to truth‐telling in the context of critique: on the one hand, truth‐telling (as avowal) is a target of critique; on the other, truth‐telling (as parrhesia) is one of critique's methods. We argue that combining these two dimensions in a unified account is crucial for understanding and re‐evaluating Foucault's critical project as a whole. By showing that truth‐telling remains an essential element of Foucauldian critique, this paper also rectifies some influential misinterpretations according to which Foucault's critical project seeks to eliminate truth from the picture.

Organo-Bentonite-Coated Interfaces: Interfacial Properties and Cyclic Response

The accumulation of amphiphilic molecules, nanoparticles, or microorganisms at interfaces has important implications for multiphase flow in porous media. We optimize the composition of stable organo-bentonite suspensions to enhance particle adsorption onto the oil–water interface. Then, we use the pendant drop method to explore time-dependent effects on surface tension and the consequences of contraction–expansion cycles. Brownian motion brings organo-bentonite particles to the oil–water interface where they adsorb and accumulate to reduce the apparent interfacial tension in time. The adsorption energy of platy organo-bentonite particles is significantly higher than the adsorption energy of spherical nanoparticles of the same volume. Then, a shell-like interface develops after particle jamming during droplet contraction, and further contraction leads to shell buckling and wrinkle formation (rather than desorption). The shell-like interface experiences an anisotropic stress field and cannot be described by the Young–Laplace equation. The evolution of interfacial tension during contraction and expansion shows strong hysteresis; furthermore, the results suggest that the number of adsorbed particles at the interface increases with the number of cycles. Natural clay nanoparticles can facilitate the development of cost-effective and environmentally friendly alternatives for field-scale applications.

Disagreeing with Experts

ABSTRACT This paper addresses the question of who should be trusted as an expert and when, particularly in the context of public deliberation. Trust in experts is crucial in making decisions about public policies that involve complex information beyond the expertise of most people. However, fruitful deliberation also requires being able to resist misinformation campaigns, no matter how widespread these might be; being able, in general, to evaluate the evidence at our disposal and form our own opinions. The purpose of this paper is to reflect on this apparent tension between epistemic deference and epistemic independence. The paper has two goals. First, it aims at providing a more nuanced understanding of the question of who should be trusted as an expert by examining cases in which seemingly factual claims are made in public settings by experts. Second, it emphasizes the need to pay attention to the conditions under which we actually trust each other. We suggest that fostering trust in science may be better approached by modifying the conditions under which scientific dialogue takes place, rather than trying to convince the public to trust experts, or blaming them for not doing so.

Time-Resolved Measurements of Interfacial Tension and Flow Speed of the Inclined Water Surface around a Self-propelled Camphor Boat by the Quasi-elastic Laser Scattering Method.

An inclined liquid surface, such as a meniscus, plays an important role in advection and transport phenomena at a liquid's surface. However, there is no time-resolved measurement method for the interfacial tension of an inclined liquid-air interface. Here, a noninvasive method for simultaneous measurements of the interfacial tension and surface flow speed for an inclined water surface is described. This is an upgrade of the quasi-elastic laser scattering method with a closed-loop control system that introduces the dynamically tracked scattered and referential light into the detector. For the evaluation of the tilt compensation by dynamic tracking, the relationship between the apparent interfacial tension and surface inclination was examined for a water meniscus at 0-5° inclinations. It was also demonstrated that simultaneous measurements of the interfacial tension and surface flow speed around a self-propelled camphor boat on a pure water surface inclined by >3° at the back end of the boat are difficult to conduct accurately without dynamic tracking. Both the interfacial tension difference and the backward flow speed increased as the boat speed increased to 0.1 m/s; that had not been evaluated to date because of the high velocity of the boat and the surface inclination of the water around it. The direct experimental evaluation of the interfacial tension and the flow speed supported the model that the driving force of the camphor boat is the interfacial tension difference and the resistance force proportional to the boat velocity reduces its acceleration.

Reconciling Moral Responsibility with Multiplicity in Conway’s Principles

ABSTRACT Anne Conway’s commitment to the moral responsibility of creatures, or created beings, is seemingly in tension with her unique metaphysics. Conway is committed to individual moral responsibility. Conway insists that an innocent person ought not be punished for someone else’s sin. Interesting recent work highlights a unique aspect of Conway’s position that creatures are multiplicities: not only are creatures integrated into the larger whole of creation, but also their parts are mutually integrated into one another. The latter, which I will call ‘ontological overlap,’ renders the boundaries between creatures unclear. However, creatures must be distinct enough from each other to provide a proper subject for individual moral responsibility. This contribution suggests that Conway’s account of vital power can resolve an apparent tension between ontological overlap and individual moral responsibility and, more broadly, that Conway has a relational metaphysics of moral subjecthood.

Horses as players in equine sports

ABSTRACT Though animal ethics in sport obviously applies most urgently to cases of animals at mortal risk (e.g., hunting and bullfighting) or vulnerable to various types of abuse (e.g., doping and harmful training practices), less obvious domains bear scrutiny as well. Here I examine whether we can strictly take not just riders but horses to be players in equine sports. There is an apparent tension in the concept of equestrian prowess, a peculiar blend of skills and attitudes, between regarding horses as subjects of persuasion or collaboration and treating them as objects of control. As our understanding of animal cognition and behaviour continues to improve, it becomes increasingly clear that animal intelligence and agential capacities are far greater than we formerly presumed. In this light, using Suits’s theory of games, I argue that horses are game players that sometimes consent (or assent) and sometimes refuse to play equine sports. Drawing on recent accounts of horse-rider partnership and on my own equestrian background, I conclude by sketching a utopian vision of what equine sports could be.

Girls of Riyadh Revisited: Investigating the Quality of the English Collaborative Translation of Rajaa Alsanea’s Arabian Novel

The paper aims to assess the quality of the English collaborative translation of Rajaa Alsanea’s Arabian novel Girls of Riyadh, focusing on linguistic and cultural features of the Target Text, a few of which are sometimes nonexistent in the Source Text. The mixed literal/functional approach to collaborative translation seems to be inconsistent, the paper observes, and it is possibly due to both the apparent tension between the self-translator and her co-translator Marilyn Booth and the prominence of the target culture sometimes recurrent in the Source Text. The paper addresses two questions: To what extent has collaborative translation affected the quality of rendering linguistic, social, and cultural references of the Source Text, such as idiomatic expressions, lexical terms, songs, names of celebrities, religious, and literary references, and traditional festivities? How effective have the literal and functional approach been in this collaborative translation? The findings of this study show that the translation procedures employed, such as omission, addition, and alteration, are sometimes unacceptable. Significantly, the study raises awareness about how the potential tension between the self-translator and the co-translator in the inclusion and exclusion of certain parts of texts can affect the quality of the end product. This paper recommends a fresh ‘critical translation’ of the ST that fills specific points which has been overlooked in the current ‘simple translation’: i.e., by paying attention to the message and intention of the author and suggesting to the use of different procedures by the two translators. The paper recommends that instead of implementing erratically two opposite approaches, the functional and literal approaches, as has been done, collaborative translators should follow one of them only. The current study suggests potential solutions to improve the quality of the English translation of this novel.

Hypergolic ignition induced by head-on collision of bi-propellant droplets: Monoethanolamine-based fuel and hydrogen peroxide

Hypergolic ignition by the binary collision of H2O2 and Monoethanolamine (MEA)-NaBH4 droplets has been experimentally studied with an emphasis on droplet inter-mixing, heat transfer, droplet swelling, and flame propagation. The entire ignition is phenomenally categorized into five stages. The H2O2 droplet penetrates the MEA- NaBH4 droplet after the collision and coalesces with it. The H2O2 fluid rapidly restores its sphericity inside the coalesced droplet, which is theoretically proved to be driven by interfacial tension. The average measured restoration time is 14.0 ms. Large-scaled bubbles are generated at the interfacial structure, leading to swelling of the coalesced droplet. The existence of apparent interface tension tends to limit the rate of droplet inflation at the beginning. As more bubbles are produced, the interface tension wanes, and the droplet swells rapidly. The droplet surface expansion rate is identified via the gray-level information in recorded images. A theoretical model quantifying the swelling rate was established based on the underlying mechanism for the swelling of the reacting droplet, which can be attributed to the flash boiling of the superheated H2O2 fluid. As bubbles accumulate inside the coalesced droplet, a dual-bell-shaped droplet configuration is formed. A flame ring structure is observed when the ignition occurs. Luminant flame sustains more than 10 ms until the fuel vapor is depleted.

Body Forces Drive the Apparent Line Tension of Sessile Droplets.

The line tension of a three-phase contact line is implicated in a wide variety of interfacial phenomena, but there is ongoing controversy, with existing measurements spanning six orders of magnitude in both signs. Here, we show that computationally obtained magnitudes, sign changes, and nontrivial variations of apparent line tension can be faithfully reproduced in a parsimonious model that incorporates only liquid-substrate interactions. Our results suggest that the origin for the remarkable variation lies in the failure of a widely used estimation method to eliminate body forces, leading measured line tensions to behave like an extensive quantity.

Program for a Transgender Existentialism

Abstract Trans theory is characterized in part by the apparent tension between discursive analyses of cisgender society and phenomenological descriptions of trans experiences. While traditional inquiry into the history of philosophy proposes an interminable opposition between phenomenology and discourse analysis, Henry Rubin's alternative suggestion is that within the domain of trans studies these methods are complementary. Discourse analysis and phenomenology converge in trans studies because they are submitted to the same ethical and political imperative: the systematic development of the trans archive. Both discourse analysis and phenomenology as methods in trans studies are directed toward the development of a genuinely trans history, perspective, and theory, with special methodological consideration of the way that this perspective is misunderstood or obscured by dominant frameworks within cisgender society. In what follows, the author provides a brief reconstruction of two major interventions in trans phenomenology, demonstrating that each is carefully concerned with distinctly archival considerations. The author further argues that each project remains unfinished because of an incomplete bracketing of medicalized cisgender concepts. The article then proposes a brief alternative program aimed at the full suspension of cisgender categories that the author calls transgender existentialism.

Hydroxypropyl methylcellulose orally disintegration films produced by tape casting with the incorporation of green propolis ethanolic extract using the printing technique

Green propolis ethanol extract (GPEE) is one of the most used compounds in folk medicine. Alternative dosage forms, such as orally disintegrating films (ODFs) and forms of incorporation of active principles, such as the printing technique, are arousing interest due to the possibility of producing personalized dosages and possible reduction of the degradation of compounds. The aim of this study was to evaluate the effect of green propolis ethanol extract (GPEE) incorporation on hydroxypropyl methylcellulose (HPMC) using the printing technique (1–4 print layers). GPEE was characterized by apparent viscosity, density, and surface tension. The ODFs with different numbers of printed layers were characterized in relation to color, moisture content, mechanical properties, structure, disintegration time, surface pH, stability, cytotoxicity, and anti-inflammatory activity tests. GPEE showed properties similar to those observed for commercial inks. The number of printed layers affected film properties. ODFs with GPEE showed anti-inflammatory activity, where a reduction of about 40% NO 2 − concentration against macrophage cells was found after adding one GPEE layer. As such, printing on hydroxypropyl methylcellulose oral films as a vehicle for green propolis ethanolic extract represents an interesting alternative to produce materials with controlled anti-inflammatory activity. • Viscosity, density and surface tension values of GPEE are similar to commercial inks. • Oral films of HPMC-based printed are a promising way to deliver active compounds. • HPMS-based printed films maintain the stability of phenolic compounds. • Films printed with green propolis ethanol extract have anti-inflammatory activity.

Quantification of Apparent Membrane Tension and Membrane-to-Cortex Attachment in Animal Cells Using Atomic Force Microscopy-Based Force Spectroscopy.

Reliable quantification of a cell's biophysical properties is key for understanding the role of mechanics in cell biology. Plasma membrane tension, the energetic cost of increasing the surface area of the plasma membrane, has been shown to regulate a plethora of cellular processes, ranging from leading edge formation to phagocytosis and membrane trafficking. Here, we describe the measurement of this key mechanical property of the cell surface using atomic force microscopy (AFM)-based force spectroscopy. Depending on the nature of the force curve acquisition, AFM measurements can quantify various membrane tension components, such as apparent membrane tension and membrane-to-cortex attachment (MCA). We discuss the biophysical background (1), required materials (2), sample preparation (3.1), AFM-probe calibration and functionalization (3.2), force curve acquisition (3.3) and data analysis and representation (3.4).

Apparent line tension induced by surface-active impurities.

Line tension in wetting processes is of high scientific and technological relevance, but its understanding remains vague, mainly because it is difficult to determine. A widely used method to extract line tension relies on the variation of a droplet's contact angle with the droplet's size. Such an approach yields the apparent line tension, which is an effective parameter that factors in numerous contributions to the finite-size dependence, thus masking the actual line tension in terms of the excess free energy of the three-phase contact line. Based on our recent computer simulation study, we investigate how small amounts of nonionic surfactants, such as surface-active impurities, contribute to the apparent line tension in aqueous droplets. When depositing polydisperse droplets, their different surface area-to-volume ratios can result in different final bulk concentrations of surfactants, different excess adsorptions to the interfaces, and, consequently, different contact angles. We show that already trace amounts of longer-chained surfactants in a pre-contaminated liquid are enough to affect measurements of the apparent line tension. Our analysis quantifies to what extent "background" impurities, inevitably present in all kinds of experimental settings, limit the resolution of line tension measurements, which is crucial for avoiding data misinterpretation.

Deformation and necking of liquid droplets in a magnetic field

Pendant droplets of water and paramagnetic solutions are studied in the presence of uniform and nonuniform magnetic fields produced by small permanent magnet arrays, both in static conditions and during dynamic pinch-off. Static measurements of the droplet shape are analyzed in terms of an apparent surface tension γapp or an effective density ρeff. The change of surface tension of deionized water in a uniform field of 450 mT is insignificant, 0.19 ± 0.21 mNm−1. Measurements on droplets of compensated zero-susceptibility solutions of Cu2+, Mn2+, and Dy3+, where the shape is unaffected by any magnetic body force, show changes of surface tension of about −1% in 500 mT. Magnetic field gradients of up to 100 T2 m−1 deform the droplets and lead to changes of ρeff that are negative for diamagnetic solutions (buoyancy effect) and positive for paramagnetic solutions. The droplet profile of strongly paramagnetic 0.1 molar DyCl3 solution is analyzed, treating the nonuniform vertical field gradient as a spatial variation of gravity. The influence of Maxwell stress on the droplet shape is discussed. In dynamic measurements, the droplet shape at pinch-off is recorded by high-speed photography and analyzed in terms of a relative change of dynamic surface tension in the presence of a magnetic field. The surface-tension-dependent prefactor of the scaling law that governs the pinch-off dynamics shows no difference for pure water or 0.11 M DyCl3 solutions in the field. The nonuniform field has no influence in the pinch-off region because the filament diameter is much less than the capillary length.

Language management, discursive power, and English as lingua franca in island countries and territories

Both geographical factors and colonial histories have contributed to the marginalization of many islands. In the context of globalization, European colonial languages often dominate, and the Standard English ideology has been gradually internalized alongside the spread of English worldwide. Islands face an apparent tension between promoting local languages for the purpose of strengthening social and cultural cohesion and maintaining the favored status of European colonial languages in order to facilitate integration into global markets. Languages are, however, ideologically constructed, and the dominant status of English and other European languages on islands has created a cultural system of ideas, norms, and values originating from the West. This turns islands into norm followers, creating difficulties for the construction of island identities and making it impossible to act from a position of discursive power on the international plane. This paper argues that island governments should carry out language management in such a way as to promote the idea of English as a lingua franca for use in global intercultural communications and thereby enhance the island’s discursive power while strengthening social and cultural cohesion.

Democratic Deliberation and the Resource Curse

AbstractOil and gas discoveries in developing countries are often associated with shortsighted economic policies and, in response, with calls to insulate resource management from populist impulses. The authors report on a randomized experiment that tested methods to overcome this apparent tension between sound resource governance and democratic politics. Soon after Tanzania's discovery of major natural gas reserves, the authors invited a nationally representative sample of voters to take part in an intensive public deliberation of policy options, at an event featuring nationally recognized experts and small-group discussions. Democratic deliberation reinforced the public's strong preference for rapid spending of gas revenues, but also increased support for various prudential and economically orthodox measures, such as the independent oversight of gas revenues, limits on government borrowing, and selling gas abroad rather than subsidizing fuel at home. These effects were driven by deliberation per se, rather than a pure information treatment, and show no evidence of contamination by facilitator effects or peer effects in group deliberations.