Tension Parameters Research Articles

Holographic zero sound from spacetime-filling branes

We use holography to study sound modes of strongly-interacting conformal field theories with non-zero temperature, T , and U(1) chemical potential, μ. Specifically, we consider charged black brane solutions of Einstein gravity in (3+1)-dimensional Anti-de Sitter space coupled to a U(1) gauge field with Dirac-Born-Infeld action, representing a spacetime-filling brane. The brane action has two free parameters: the tension and the non-linearity parameter, which controls higher-order terms in the field strength. For all values of the tension, non-linearity parameter, and T /μ, and at sufficiently small momentum, we find sound modes with speed given by the conformal value and attenuation constant of hydrodynamic form. In particular we find sound at arbitrarily low T /μ, outside the usual hydrodynamic regime, but in the regime where a Fermi liquid exhibits Landau’s “zero” sound. In fact, the sound attenuation constant as a function of T /μ qualitatively resembles that of a Fermi liquid, including a maximum, which in a Fermi liquid signals the collisionless to hydrodynamic crossover. We also explore regimes of the tension and non-linearity parameter where two other proposed definitions of the crossover are viable, via pole collisions in Green’s functions or peak movement in the charge density spectral function.

A novel semi-empirical method for adjusting solubility parameters to surface tension based on the use of Stefan's rule

The correct calculi of surface tension and solubility parameters are of paramount importance for many fields of chemical engineering and materials design, such as encapsulation methods, dispersion of nanopowders, phase compatibility in chemical blends and nanocomposites, among others. The solubility parameters play a key role in these applications along with the surface tension. Until now, the relationship between solubility parameters and surface tension was only indirect, through the Skaarup-Beerbower formula, although well known physicochemical rules, such as Stefan's rule, could be applied to them directly, as shown in this study. A new method for adjusting the Hildebrand solubility parameters for surface tension through the use of the ratio of the coordination numbers, molar volume and surface tension is presented. The proposed rules are precise, simple and have direct practical applications for the development of new materials.

Fluid Property Effects on the Splashing in Teapot Effect

Liquid flowing on a curved solid surface usually leads to a typical teapot effect. As the jet velocity increases, the liquid detaches from a curved solid surface completely in one streamline or partially in multiple streamlines. We called the latter splashing. Former studies attributed the splashing behavior to the breaking of the balance between the centrifugal force and the pressure drop across the liquid flow. This study disclosed that the parameters of surface tension, viscosity, and additive molecules of liquid significantly affected the jet splashing in teapot effect. A liquid with a higher Weber number (lower surface tension) and a lower Reynolds number (higher viscosity) prefers to separate from the solid surface in one streamline. Besides, a liquid with larger molecular weight additives is easier to splash. Molecular dynamics simulations disclosed that a higher water molecule density around the additive molecules with a larger cohesive force could more effectively suppress splashing. There is no ...

Effect of Polysorbates on Solids Wettability and Their Adsorption Properties

The wettability of solids is important from both practical and theoretical viewpoints. In this study, we measured the contact angle of aqueous solutions of polysorbates (Tween 20, Tween 60, and Tween 80) on polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), polyamide (nylon 6), and quartz. Based on the obtained results, the adsorption of Tween 20 (T20), Tween 60 (T60), and Tween 80 (T80) at the solid-water interface was determined based on the structure and size of their molecules. Next, the tendency of polysorbates to adsorb at the solid-water interface was considered based on the Gibbs standard free energy of adsorption (ΔGadso). This energy was evaluated using various methods, including a method we propose based on the critical micelle concentration (CMC) and the contact angle of water and solution at the CMC, as well as their surface tension. The ΔGadso values obtained by this method were comparable to those calculated from the Langmuir equation. Taking into account the Tweens tendency to adsorb at the solid-water interface, the measured contact angle, the components and parameters of surface tension of Tweens solutions and solids, and the surface tension of water and its Lifshitz-van der Waals component that we determined, the wetting process in the solid-solution drop-air system was analyzed. The results based on the mentioned parameters showed that it is possible to predict the wettability of apolar, monopolar, and bipolar solids using the aqueous Tweens solution and their solution adhesion.

A New Equation between Surface Tension and Solubility Parameters of Cellulose Derivatives depending on DS: Application on Cellulose Acetate

Generally, grafting alkylated chains onto cellulose backbone modifies its physicochemical properties strongly, and the variation in the hydrophobicity of the cellulose causes significant modifications of these superficial characteristics. In this sense, this study highlighted the effect of the hydrophobicity-hydrophilic balance brought by the level of grafting chains on the surface tension, and relationship between the surface tension measurements and the solubility parameters of activated surface. The results obtained from FTIR and 13 C NMR analysis confirmed the molecular structure of acetylated compounds with substitution occurring preferably at C-6, C-2 and C-3 hydroxyl positions, respectively. The surface active properties were investigated by the density of elaborated polymers and its relationship with the Parachors based on the Group Contribution Method. This study may help to increase the using natural and biodegradable fibers as surface-activity industrial materials. The calculations of Parachors (P) and densities of cellulose acetates samples (CA) at different substitution degree (DS) make to find a new relationship between the surface tension and the DS. These equations show that the surface tension variation depending on DS can be linearly or polynomial which explains that the surface tension of the cellulose acetate is highly depends on its DS

A new variant of Lane–Riesenfeld algorithm with two tension parameters

We present a generalization of Lane–Riesenfeld algorithm with two tension parameters for curve design. The generalization incorporates existing families as special cases: Hormann–Sabin's family, Romani's family, J-spline family, and Siddiqi's improved binary four-point family. The new family also has common members with dual de Rham-type approximating schemes when n is even. Analysis of the new family indicates that there are parameter choices that provide higher continuity and higher generation degree than available with any of those existing families.

Design of the laser dieless drawing process of tubes from magnesium alloy using FEM model

This paper is dedicated to a computer aided design of the laser dieless drawing process used for production of magnesium alloy tubes. Using laser as a heat source allows quick control of the heating and helps to regulate the temperature during sample deformation. One of important problems related to the development of this technology is a prediction of diameters of final product. The problem is caused by the character of the process in which elongation of tubes not predetermined by the tool but takes place due to pulling and free forming of the material. To design of technology a code based on finite element method (FEM) dedicated to the laser dieless drawing process and related method of design was developed.A numerical experiment was carried out by performing calculations with varied tension and heating parameters. The calculation results (in form of technological diagrams) allow determination of the process parameters needed for reaching specific final dimensions of the tube and for explanation of limitations of this process related to low ductility of the tubes. Examples of a fracture observed in experiments were related to a neck formation during elongation of the tubes. Two reasons for the neck formation were observed in modeling. The first was related to overheating of a tube and high gradient of temperatures along a centerline of the tube. The second corresponds to a high value of deformation and material hardening.To validation of the FEM model, measured values of temperature, load, tube diameter and fracture monitoring were used. Further, the model allowed to identify a window of permissible process parameters. It was shown that using out-of-the-window parameters leads to non-homogeneous distribution of the tube diameter or fracture.Based on the model results a set of selected design parameters from the processing window were used for a practical production of tubes from AZ31 alloy with a preset external diameter. Analyses of microstructure of initial tubes and tubes after the laser dieless drawing show that the process allows to obtain tubes with homogeneous distribution of grains and to improve initial inhomogeneity of the microstructure.

Nucleation kinetics of MgCl2–ethanol adduct for the supported Ziegler–Natta catalysts with a thermodynamic approach

MgCl2–ethanol adducts play a key role in the synthesis of supported Ziegler–Natta catalysts. The morphology of the MgCl2–ethanol adducts, which is controlled by their crystallization process, can determine the structure and thus the property of the polyolefin products. Here we study the nucleation kinetics of MgCl2–ethanol adducts by measuring the metastable zone width (MSZW) and induction time at different temperatures. Supersaturation ratios used in induction time measurements were predicted by the Mixed Solvent Electrolyte (MSE) model embedded in OLI System. Nývlt′s approach was applied to determine MSZW. By the induction time measurement, the effect of temperature, and supersaturation were studied. It was found that induction time decreases as either temperature or supersaturation increases. The measured MSZW and induction time are used to estimate the nucleation kinetics of the system, and thereby distinguishing between the homogeneous and heterogeneous mechanisms. The interfacial tension and other related nucleation parameters were calculated from the induction time data. XRD and TGA indicate that the MgCl2–ethanol adduct has the stoichiometry of MgCl2·6C2H5OH.

Effect of a Floating Elastic Plate/Membrane on the Motion Due to a Ring Source in Water With Porous Bed

The velocity potentials due to the presence of a horizontal circular ring of wave sources of timedependent strength in water of finite constant depth with a floating elastic plate or a floating membrane are determined. The uniform bottom is composed of non-dissipative porous medium. The problems are formulated as the initial value problems and the Laplace transform method is used to solve these. For time-harmonic source strength, the steady-state analysis of the potentials reveals the existence of outgoing progressive waves. Graphs for the surface profiles are presented for different values of the tension parameter for the membrane, flexural rigidity of ice and the porous-effect parameter.

On a stable family of four-point nonlinear subdivision schemes eliminating the Gibbs phenomenon

The Chaikin’s scheme presents the interesting property of not producing Gibbs phenomenon. The problem arises when we need a scheme that provides a higher order of approximation. In this case linear schemes are not a good option, as they produce Gibbs phenomenon close to discontinuities. In this article a new four-point nonlinear family of subdivision schemes that eliminate the Gibbs phenomenon is presented. It is based on the linear family of four-point subdivision schemes depending on a tension parameter introduced in Dyn et al. (2005). A simple algebraic transformation leads to an easy way of introducing nonlinearity in the original family of schemes. The non-interpolatory characteristic of the nonlinear scheme can be modulated just varying the value of the tension parameter. Results about the stability, convergence and the elimination of the Gibbs phenomenon are presented. Some numerical comparisons of the results obtained in the generation of curves are also shown, leading to the conclusion that the high order nonlinear schemes are more suitable for this purpose.

C1 sign, monotonicity and convexity preserving Hermite polynomial splines of variable degree

This paper proposes an algorithm for constructing interpolatory Hermite polynomial splines of variable degree, which preserve the sign, the monotonicity and the convexity of the data. The polynomial segments are represented as Bézier curves. The degree of each segment plays the role of the tension parameter of the spline. We discuss extensively the monotonicity and convexity criteria, detailing a strict and a weak form of monotonicity preservation, as well as their implications on the Hermite interpolation. We also propose a global method for estimating the nodal derivatives of the spline. We evaluate the results of this method in an extensive set of examples, comparing them with a number of local derivative estimation methods from the pertinent literature. The algorithm is numerically stable, simple to implement, and it is of linear complexity, since the related mathematical conditions can be expressed as linear inequalities with respect to the control points of the spline.

Myocardial GLP-1 Receptor Activation in the Presence of Glucose: Strong Partners

Glucagon-like peptide 1 (GLP-1) receptor agonists increase the intracellular calcium levels of atrial cardiomyocytes in a protein kinase A dependent manner. This elicits a positive inotropic effect. Furthermore, the translocation of GLUT1 is promoted. The relevance of the latter process is unclear, therefore we assessed the influence of energy substrates. Muscle strips (trabeculae; n = 86) were isolated from human right atrial appendages obtained from patients undergoing heart surgery (n = 34), mounted on hooks, electrically stimulated (1 Hz) and treated with a single dose of exenatide (15 nM), GLP-1(7–36) amide (180 nM), GLP-1(9–36) amide (200 nM), isoproterenol (100 nM), or increasing concentrations of calcium (4.0 and 7.2 mM). Either 11.2 mM glucose or 22.4 mM pyruvate served as the energy substrate. Developed force, diastolic tension and relaxation parameters were recorded and analyzed. Administration of exenatide and GLP-1(7–36) amide, but not GLP-1(9–36) amide, led to a transient positive inotropic effect in the presence of pyruvate and glucose. This effect tended to be more pronounced in glucose-treated muscle strips at maximal developed force and steady state conditions. Both isoproterenol and calcium exerted a strong positive inotropic effect with no difference regarding the energy substrate. In conclusion, the positive inotropic effect of GLP-1 receptor agonists is more pronounced in glucose enriched Tyrode’s solution, which might be linked to the previously reported translocation of GLUT1.

A new tension B-spline method for third-order self-adjoint singularly perturbed boundary value problems

The aim of this paper is to present a new kind of tension B-spline, called hyperbolic-trigonometric tension B-spline of order n, which is generated over the space span {sin(τt),cos(τt),sinh(τt),cosh(τt),1,t,…,tn−5}, n≥5, where τ is tension parameter. This kind of B-spline has most properties of usual polynomial B-splines and enjoys some other advantageous properties as well. Also, hyperbolic-trigonometric tension B-spline method is applied for solving self-adjoint singularly perturbed problems. We use some numerical examples to illustrate the accuracy and implementation of the method.

Wetting and adhesion properties of rhamnolipid and surfactin

The measurements of the contact angle of the aqueous solution of rhamnolipid (RL) and surfactin (SF) on polytetrafluoroethylene (PTFE), polyethylene (PE), polymethyl methacrylate (PMMA), nylon 6 and quartz were performed. The obtained values of the contact angle were analyzed by applying the components and parameters of the surface tension of aqueous solution of surfactants, PTFE, PE, PMMA, nylon 6 and quartz. This analysis showed that the contact angle of the solution on the hydrophobic solids can be predicted theoretically knowing the Lifshitz-van der Waals component of the water surface tension, the surface tension of the solids and that of the solution. Based on the contact angle values the critical surface tension of studied solids wetting, the adsorption of surfactants at the solid-water interface, the standard Gibbs free energy of adsorption as well as the work of adhesion of solutions to PTFE, PE, PMMA, nylon 6 and quartz surfaces were determined. It proved that the critical surface tension of wetting of the studied solids is different from their surface tension and that the work of adhesion of the aqueous solutions of RL and SF to PTFE, PE, PMMA, nylon 6 and quartz surfaces can be predicted from the components and parameters as well as the total surface tension of solids and solutions.

Constraining brane tension using rotation curves of galaxies

We present in this work a study of brane theory phenomenology focusing on the brane tension parameter, which is the main observable of the theory. We show the modifications steaming from the presence of branes in the rotation curves of spiral galaxies for three well known dark matter density profiles: Pseudo isothermal, Navarro-Frenk-White and Burkert dark matter density profiles. We estimate the brane tension parameter using a sample of high resolution observed rotation curves of low surface brightness spiral galaxies and a synthetic rotation curve for the three density profiles. Also, the fittings using the brane theory model of the rotation curves are compared with standard Newtonian models. We found that Navarro-Frenk-White model prefers lower values of the brane tension parameter, on the average λ ∼ 0.73 × 10−3eV4, therefore showing clear brane effects. Burkert case does prefer higher values of the tension parameter, on the average λ ∼ 0.93 eV4 − 46 eV4, i.e., negligible brane effects. Whereas pseudo isothermal is an intermediate case. Due to the low densities found in the galactic medium it is almost impossible to find evidence of the presence of extra dimensions. In this context, we found that our results show weaker bounds to the brane tension values in comparison with other bounds found previously, as the lower value found for dwarf stars composed of a polytropic equation of state, λ ≈ 104 MeV4.

Dimensional Accuracy in Dry Micro Wire Electrical Discharge Machining

Dimensional accuracy is important in fabricating miniaturized product in order to reduce the material waste and machining cost as well as to achieve a better quality product. This paper presents the analysis and modelling of dimensional accuracy in dry micro wire electrical discharge machining with control parameters of gap voltage and wire tension. The investigation was performed on stainless steel using integrated multi-process micro machine tools DT 110 with compressed air as the dielectric fluid and tungsten as the wire electrode. The dimensional accuracy was determined through kerf width differences of the machined slots. The kerf width was measured using scanning electron microscope. Full factorial was used to design the experiment while analysis of variance (ANOVA) was used to analyse the results as well as to evaluate the adequacy of the developed model. Based on ANOVA, both parameters; gap voltage and wire tension have high influence on kerf width differences. The optimum machining parameters for minimum kerf width differences were found to be 85 V gap voltage and 10 % wire tension. The developed model is adequate since the percentage error (2.13 %) is relatively small. It is recommended that different type of gases should be used for further investigation in order to determine the accuracy of the dry micro wire EDM.

Vocal Acoustic and Auditory-Perceptual Characteristics During Fluctuations in Estradiol Levels During the Menstrual Cycle: A Longitudinal Study

Estradiol production varies cyclically, changes in levels are hypothesized to affect the voice. The main objective of this study was to investigate vocal acoustic and auditory-perceptual characteristics during fluctuations in the levels of the hormone estradiol during the menstrual cycle. A total of 44 volunteers aged between 18 and 45 were selected. Of these, 27 women with regular menstrual cycles comprised the test group (TG) and 17 combined oral contraceptive users comprised the control group (CG). The study was performed in two phases. In phase 1, anamnesis was performed. Subsequently, the TG underwent blood sample collection for measurement of estradiol levels and voice recording for later acoustic and auditory-perceptual analysis. The CG underwent only voice recording. Phase 2 involved the same measurements as phase 1 for each group. Variables were evaluated using descriptive and inferential analysis to compare groups and phases and to determine relationships between variables. Voice changes were found during the menstrual cycle, and such changes were determined to be related to variations in estradiol levels. Impaired voice quality was observed to be associated with decreased levels of estradiol. The CG did not demonstrate significant vocal changes during phases 1 and 2. The TG showed significant increases in vocal parameters of roughness, tension, and instability during phase 2 (the period of low estradiol levels) when compared with the CG. Low estradiol levels were also found to be negatively correlated with the parameters of tension, instability, and jitter and positively correlated with fundamental voice frequency.

Sv-map between type I and heterotic sigma models

The scattering amplitudes of gauge bosons in heterotic and open superstring theories are related by the single-valued projection which yields heterotic amplitudes by selecting a subset of multiple zeta value coefficients in the α′ (string tension parameter) expansion of open string amplitudes. In the present work, we argue that this relation holds also at the level of low-energy expansions (or individual Feynman diagrams) of the respective effective actions, by investigating the beta functions of two-dimensional sigma models describing world-sheets of open and heterotic strings. We analyze the sigma model Feynman diagrams generating identical effective action terms in both theories and show that the heterotic coefficients are given by the single-valued projection of the open ones. The single-valued projection appears as a result of summing over all radial orderings of heterotic vertices on the complex plane representing string world-sheet.

Formulation and performance test of palm-based foaming agent concentrate for fire extinguisher application

The utilization of foaming agent for fire extinguisher application improves the efficiency of water as a fire extinguishing agent, lowers surface tension, and acts as a foaming agent. The formed foam cools the fire down and covers the burned material to avoid it from further contact with oxygen which may reignite the fire. This study aimed to produce and assess the performance of foaming agent concentrate from palm oil as a fire extinguisher agent. In the performance test, measurements were taken on foam stability, foaming ability, surface tension, interfacial tension, viscosity, contact angle, density, and specific gravity. The formulation was conducted by using the best produced potassium palmitate, potassium methyl ester, and sodium lauric combined with diluents, chelating agent, and other additives at various composition comparisons. The produced foaming agent concentrate was found to be in a rather paste and liquid form with viscosity of 2.34 – 253 cP. It was also found that the resulted foaming agent concentrate dissolved in water at the concentration rate of 1% had a foam stability level of 30-91%, foaming ability of 288 – 503%, surface tension of 19.68 – 25.05 dyne/cm, interfacial tension of 0.54 – 4,20 dyne/cm, viscosity of 1.00 – 1.05 cP, contact angles of 53.75 – 63.79° at 0 minute and 11.84 – 22.42 ° at minute 10, density of 0.99586 – 0.99612 g/cm3, and a specific gravity of 1.00021 – 1.00046. Based on foam stability, foaming ability, and surface tension parameters, it was concluded that NF5 and NF17 were the best formulas.Compared to the other formulas, NF5 formula had the best droplet diameter (minimum 0.14 mm) and droplet density (maximum 3056 droplets/cm2).

Constrained shape preserving rational cubic fractal interpolation functions

In this paper, we discuss the construction of $\mathcal {C}^1$-rational cubic fractal interpolation function (RCFIF) and its application in preserving the constrained nature of a given data set. The $\mathcal {C}^1$-RCFIF is the fractal design of the traditional rational cubic interpolant of the form ${p_i(\theta )}/{q_i(\theta )}$, where $p_i(\theta )$ and $q_i(\theta )$ are cubic and quadratic polynomials with three tension parameters. We present the error estimate of the approximation of RCFIF with the original function in $\mathcal {C}^k[x_1,x_n]$, $k=1,3$. When the data set is constrained between two piecewise straight lines, we derive the sufficient conditions on the IFS parameters of the RCFIF so that it lies between those two lines. Numerical examples are given to support the theoretical results.