Minimum Surface Area Research Articles

Lifshitz entanglement entropy from holographic cMERA

We study entanglement entropy in free Lifshitz scalar field theories holographically by employing the metrics proposed by Nozaki, Ryu and Takayanagi in [1] obtained from a continuous multi-scale entanglement renormalisation ansatz (cMERA). In these geometries we compute the minimal surface areas governing the entanglement entropy as functions of the dynamical exponent z and we exhibit a transition from an area law to a volume law analytically in the limit of large z. We move on to explore the effects of a massive deformation, obtaining results for any z in arbitrary dimension. We then trigger a renormalisation group flow between a Lifshitz theory and a conformal theory and observe a monotonic decrease in entanglement entropy along this flow. We focus on strip regions but also consider a disc in the undeformed theory.

Aggregation behavior and antimicrobial activity of a micellar system of binary ionic liquids

Ionic liquid (IL) surfactants have attracted great attention as potential alternatives to conventional surfactants because of their unique tailor-made physicochemical properties. However, in most cases, the aggregations formed by single IL surfactants in aqueous media are unstable, even when using a large amount of surfactant. To address this limitation, here we investigated the aggregation behavior of binary IL surfactant micelles composed of the ILs choline oleate ([Cho][Ol]) and choline laurate ([Cho][Lau]) in aqueous media using tensiometry and dynamic light scattering measurements. Micellar and interfacial parameters including critical micelle concentration (cmc), micellar interaction parameters (β), activity coefficients (f1 and f2), surface excess concentration (Гmax), minimum surface area per molecule (Amin), and the size of surfactant aggregates were studied. In addition, various thermodynamic parameters such as the Gibbs free energy of micellization (∆Gomic), standard Gibbs free energy of adsorption (∆Goad), molar free energy (Gmin), and the excess Gibbs free energy of micellization (ΔGex) were also evaluated. A non-ideal synergistic interaction was observed for the mixed IL surfactant system, which formed larger micelles (105–120 nm) compared with those formed with a single IL (86–102 nm). The formed micelles were found to be thermodynamically stable with regards to all the mole ratio of ILs system. The antimicrobial activity of the single as well of the mixed IL system against Gram-positive and -negative bacteria displayed a low toxicity profile that fell in the range of “practically harmless” (100–1000 mg L−1). The results suggested that the micellar system composed of mixed IL surfactants provides unique physical, chemical, and biological properties may offer novel opportunities for various applications such as oil dispersants.

Impact of stagnation and sampling volume on water microbial quality monitoring in large buildings

Microbial drinking water quality can be altered in large buildings, especially after stagnation. In this study, bacterial profiles were generated according to the stagnation time and the volume of water collected at the tap. Successive volumes of cold and hot water were sampled after controlled stagnation periods. Bacterial profiles revealed an important decline (> 2 log) in culturable cells in the first 500 mL sampled from the hot and cold water systems, with a steep decline in the first 15 mL. The strong exponential correlation (R2 ≥ 0.97) between the culturable cell counts in water and the pipe surface-to-volume ratio suggests the biofilm as the main contributor to the rapid increase in suspended culturable cells measured after a short stagnation of one-hour. Results evidence the contribution of the high surface-to-volume ratio at the point of use and the impact of short stagnation times on the increased bacterial load observed. Simple faucets with minimal internal surface area should be preferred to minimize surface area. Sampling protocol, including sampling volume and prior stagnation, was also shown to impact the resulting culturable cell concentration by more than 1000-fold. Sampling a smaller volume on first draw after stagnation will help maximize recovery of bacteria.

Thermodynamic and physicochemical properties evaluation for formation and characterization of oil-in-water nanoemulsion

Kinetically stable nanoemulsion with droplet size <500 nm has emerged as an advanced material in wide industrial applications because of its unique structural and physicochemical properties. Nanoemulsions are stabilized by surfactants or emulsifiers by lowering the interfacial tension (IFT) between the dispersed and continuous phases to an ultra-low value. In the present study, surfactants are screened based on their ability to lower the IFT values for proper formulation of stable nanoemulsion. The critical micelle concentration (CMC) of surfactants obtained from the interfacial tension-concentration isotherm curve (IFCV) was used to evaluate surface excess concentration (Гmax), minimum surface area per molecule (Amin), adsorption efficiency (pC20), surface tension at CMC (γCMC), effectiveness of adsorption (Πcmc) along with thermodynamic parameters (ΔGmic and ΔGads). The experimental results of thermodynamic parameters reveal that adsorption phenomenon predominates over micellization. A meticulous evaluation of derived parameters suggests the suitability of non-ionic surfactant (Tween 80) over ionic surfactants (CTAB and SDS) for formation of stable oil-in-water (O/W) emulsion. In solubilization study, the ultra-low IFT value (10−3 to 10−5 mN/m) between oil-middle phase emulsion with 0.5 wt% Tween 80 at varying salinity calculated by Chun-Huh equation indicates the increased solubility of oil in emulsion. Nanoemulsions prepared by high energy method using Tween 80 and n-heptane with droplet size in the range 91.05 to 40.16 nm manifest kinetic stability due to continuous Brownian motion of droplets. The dissolving capacity of crude oil in nanoemulsion was determined by miscibility test. The synergetic effect of silica nanoparticles (NPs) in presence of Tween 80 shows enhancement in stability of nanoemulsion with drop in droplets size from 36.15 to 21.37 nm and surface charge of −59.05 mV. The formulated nanoemulsions show Pseudo-plastic behavior with viscosity in the range of 9–12.5 mPa-s, which is further improved in presence of nanoparticles.

Quasinormal modes and greybody factors of [formula omitted] gravity minimally coupled to a cloud of strings in [formula omitted] dimensions

In this paper we have studied the propagation of a massless scalar field minimally coupled to a black hole with the source of cloud of strings in 2+1f(R) gravity theory. In particular we have found analytical results for the decay rate, reflection coefficient, greybody factors, as well as the black hole temperature. On the other hand, our quasinormal modes analyses reveal stability in the propagation of a massless scalar field in the cloud of strings black hole spacetime. However, under a suitable choose of parameters an instability is found. Furthermore based on the Bekenstein conjecture on the quantization of the surface area of the black hole we find the minimal surface area associated to the black hole horizon which is in agreement with Bekenstein’s proposal.

Micellization and aggregation behavior of crocin with bovine serum albumin: A biophysical study

The interaction of bovine serum albumin (BSA) with a naturally occurring surfactant (trans-crocetin di-(β-D-gentiobiosyl) ester, crocin) was studied under biophysical conditions by using various techniques such as surface tensiometry, UV–visible spectrophotometery and fluorescence. Upon the addition of a small amount of BSA, the λmax of a crocin dispersion in water shifted to lower wavelengths, indicating either a ground state complex formation between BSA and crocin or solubilization of BSA into the micelles of crocin. The critical micelle concentration (cmc) of crocin decreases in the presence of increasing BSA concentrations. The complex formation constant (KC), surface pressure πcmc, maximum surface excess (Γmax), the minimum surface area per molecule (Amin), enthalpy (ΔH0), entropy (ΔS0), and Gibbs free energy change (ΔG0) were calculated for the BSA-crocin interactions. BSA fluorescence was quenched in the presence of crocin. The fluorescence data were used for determining the apparent association constant (Kapp), the Stern-Volmer constant (KSV), the bimolecular rate constant of the quenching process (kq) and the thermodynamic parameters.

A Study on the Contact Ellipse and the Contact Pressure During the Wheel Wear through Passing the Tracks including Several Sharp Curves

Wheel wear has been a concern in the railway for several decades. Studying the form change of the wheel/rail contacts in particular railways consisting of sharp curves helps to identify the risk of severe or catastrophic wear to minimize maintenance costs in order to be competitive in the transportation business. In this paper, the wheel/rail contact was studied on the particular railways. The experimental measurement of wheel profiles was used as an input to Hertz Contact Theory (HCT). It was found that: 1) for these railways the wheel flange is highly worn; 2) a 5th order polynomial function is appropriate to model the wear behavior of the critical wheel; 3) the minimum and maximum contact ellipse surface areas occur in Sd=22.29 mm and Sd=32 mm, respectively; 4) the maximum and minimum surface areas of the contact ellipse occur at points in which the contact pressure are minimum and maximum, respectively; and finally 5) the flange thickness region between 25 to 29 mm can be chosen as an appropriate range for the wheel maintenance purposes.

All the entropies on the light-cone

We determine the explicit universal form of the entanglement and Renyi entropies, for regions with arbitrary boundary on a null plane or the light-cone. All the entropies are shown to saturate the strong subadditive inequality. This Renyi Markov property implies that the vacuum behaves like a product state. For the null plane, our analysis applies to general quantum field theories, and we show that the entropies do not depend on the region. For the light-cone, our approach is restricted to conformal field theories. In this case, the construction of the entropies is related to dilaton effective actions in two less dimensions. In particular, the universal logarithmic term in the entanglement entropy arises from a Wess-Zumino anomaly action. We also consider these properties in theories with holographic duals, for which we construct the minimal area surfaces for arbitrary shapes on the light-cone. We recover the Markov property and the universal form of the entropy, and argue that these properties continue to hold upon including stringy and quantum corrections. We end with some remarks on the recently proved entropic a-theorem in four spacetime dimensions.

Penrose-type inequalities with a Euclidean background

The Riemannian Penrose inequality (RPI) bounds from below the ADM mass of asymptotically flat manifolds of nonnegative scalar curvature in terms of the total area of all outermost compact minimal surfaces. The general form of the RPI is currently known for manifolds of dimension up to seven. In the present work, we prove a Penrose-like inequality that is valid in all dimensions, for conformally flat manifolds. Our inequality treats the area contributions of the minimal surfaces in a more favorable way than the RPI, at the expense of using the smaller Euclidean area (rather than the intrinsic area). We give an example in which our estimate is sharper than the RPI when many minimal surfaces are present. We do not require the minimal surfaces to be outermost. We also generalize the technique to allow for metrics conformal to a scalar-flat (not necessarily Euclidean) background and prove a Penrose-type inequality without an assumption on the sign of scalar curvature. Finally, we derive a new lower bound for the ADM mass of a conformally flat, asymptotically flat manifold containing any number of zero area singularities.

3D Printing of Self‐Organizing Structural Elements for Advanced Functional Structures

AbstractA shape evolution approach based on the thermally activated self‐organization of 3D printed parts into minimal surface area structures is presented. With this strategy, the present communication opposes currently established additive manufacturing strategies aiming to stipulate each individual volumetric element (voxel) of a part. Instead, a 3D structure is roughly defined in a 3D printing process, with all its advantages, and an externally triggered self‐organization allows the formation of structural elements with a definition greatly exceeding the volumetric resolution of the printing process. For enabling the self‐organization of printed objects by viscous flow of material, functionally graded structures are printed as rigid frame and melting filler. This approach uniquely combines the freedom in design, provided by 3D printing, with the mathematical formulation of minimal surface structures and the knowledge of the physical potentials governing self‐organization, to overcome the paradigm which strictly correlates the geometrical definition of 3D printed parts to the volumetric resolution of the printing process. Moreover, a transient liquid phase allows local programming of functionalities, such as the alignment of functional particles, by means of electric or magnetic fields.

Impact of Dynamically Exposed Polarity on Permeability and Solubility of Chameleonic Drugs Beyond the Rule of 5.

Conformational flexibility has been proposed to significantly affect drug properties outside rule-of-5 (Ro5) chemical space. Here, we investigated the influence of dynamically exposed polarity on cell permeability and aqueous solubility for a structurally diverse set of drugs and clinical candidates far beyond the Ro5, all of which populated multiple distinct conformations as revealed by X-ray crystallography. Efflux-inhibited (passive) Caco-2 cell permeability correlated strongly with the compounds' minimum solvent-accessible 3D polar surface areas (PSA), whereas aqueous solubility depended less on the specific 3D conformation. Inspection of the crystal structures highlighted flexibly linked aromatic side chains and dynamically forming intramolecular hydrogen bonds as particularly effective in providing "chameleonic" properties that allow compounds to display both high cell permeability and aqueous solubility. These structural features, in combination with permeability predictions based on the correlation to solvent-accessible 3D PSA, should inspire drug design in the challenging chemical space far beyond the Ro5.

Constructing entanglement wedges for Lifshitz spacetimes with Lifshitz gravity

Holographic relationships between entanglement entropy on the boundary of a spacetime and the area of minimal surfaces in the bulk provide an important entry in the bulk/boundary dictionary. While constructing the necessary causal and entanglement wedges is well understood in asymptotically AdS spacetimes, less is known about the equivalent constructions in spacetimes with different asymptotics. In particular, recent attempts to construct entanglement and causal wedges for asymptotically Lifshitz solutions in relativistic gravitational theories have proven problematic. We note a simple observation, that a Lifshitz bulk theory, specifically a covariant formulation of Ho\v{r}ava-Lifshitz gravity coupled to matter, has causal propagation defined by Lifshitz modes. We use these modes to construct causal and entanglement wedges and compute the geometric entanglement entropy, which in such a construction matches the field theory prescription.

Synthesis and Evaluation of a New Trianionic Surfactant for the Removal of Pb(II) by Flotation Method

AbstractSodium (Z)-15-carboxylato-8-(2-(((Z)-3-carboxylatoacryloyl)oxy) ethyl)-4,13-dioxo-5,11,12-trioxa-8,16-diazahentriacont-2-enoate has been synthesized. The chemical structure was confirmed by FT-IR and 1HNMR spectroscopy. The surface properties of the synthesized trianionic surfactant, including the critical micelle concentration (CMC), effectiveness (πcmc), maximum surface excess (Γmax), and minimum surface area (Amin) were determined from surface tension measurements. The efficiency of the trianionic surfactant to remove Pb(II) was determined using a flotation cell at different surfactant concentrations (below, at and beyond the CMC). Flame atomic absorption spectroscopy was used to determine the initial and final concentrations of Pb(II) ions. At pH 6 and a foaming time of 2 hr, the removal efficiency of Pb(II) increases with increasing the trianionic surfactant concentration.

Cooperation between holey graphene and NiMo alloy for hydrogen evolution in an acidic electrolyte

The development of noble-metal-free hydrogen evolution reaction (HER) materials for electrochemical water splitting is the key to achieving low-cost and efficient electrocatalysis that drives electrochemical hydrogen evolution. However, the electrocatalytic activities of most non-noble metals decrease in acidic electrolytes. Here, we have fabricated non-noble-metal electrodes using a bicontinuous and open porous NiMo alloy covered by nitrogen-doped (N-doped) graphene with nanometer-sized holes. This noble-metal-free HER catalyst exhibits performance almost identical with that of a Pt/C electrode, while its original catalytic activity is preserved even in acidic electrolytes. Density functional theory calculations indicate that the interfacial fringes between the nanoholes and NiMo surface induce charge transfer and promote hydrogen adsorption and desorption. The nanometer-sized holes simultaneously provide minimal surface area for chemical reactions, while delaying NiMo dissolution in excessive amounts of...

Drag and heat transfer closures for realistic numerically generated random open-cell solid foams using an immersed boundary method

In this paper, we apply a novel immersed boundary method to simulate pore-scale level fluid flow and convective heat transfer in realistic numerically generated open-cell solid foams in a Cartesian computational domain. Five different periodic foam samples of varying porosities (ε=[0.877,0.948]) are generated by numerically mimicking the actual foam formation process (minimizing surface area). The step-by-step procedure for generating the periodic foam geometries is presented. The specific surface areas of the generated foams of different porosities are compared with real foam geometries showing a reasonable agreement. The Reynolds number (Re) is varied from Re≈0 (creeping flow) to Re≈500, and finally drag and Nusselt correlations have been proposed. A detailed analysis is presented on the local velocity and temperature field for the fluid-solid interaction in a complex cellular porous medium.

Design optimization of cable–membrane structures for form-finding and stiffness maximization

Membrane structures are light weight and have a unique characteristic that their surfaces can be curved optionally. On the other hand, the stiffness of membrane structures can be significantly improved by cables. However, cable–membrane structures have mechanical characteristics of that they can maintain their shape only with in-plane tensile stress, so it is important to design their optimal shapes. In the present work, we propose a free-form optimization method for designing cable–membrane structures for form-finding and stiffness maximization. The proposed free-form optimization method is a kind of non-parametric optimization method based on the H1 gradient method. In the form-finding problem, to find the minimum surface areas of membrane structures with specified arbitrary boundaries, the area minimization problem is formulated as a distributed-parameter shape optimization problem considering total length of cables as a constraint condition. Then, we perform shape optimization of cable–membrane structures in the stiffness maximization problem under the constraint conditions of total length of cables, membrane area, and membrane perimeter. The numerical results show the effectiveness of the proposed optimization method, and confirm that the optimal shape of the cable–membrane structures can be designed better than membrane structures without cables and has higher stiffness.

Influence of specific surface area on coal dust explosibility using the 20-L chamber

The relationship between the explosion inerting effectiveness of rock dusts on coal dusts, as a function of the specific surface area (cm2/g) of each component is examined through the use of 20-L explosion chamber testing. More specifically, a linear relationship is demonstrated for the rock dust to coal dust (or incombustible to combustible) content of such inerted mixtures with the specific surface area of the coal and the inverse of that area of the rock dust. Hence, the inerting effectiveness, defined as above, is more generally linearly dependent on the ratio of the two surface areas. The focus on specific surface areas, particularly of the rock dust, provide supporting data for minimum surface area requirements in addition to the 70% less than 200 mesh requirement specified in 30 CFR 75.2.

Non-local observables at finite temperature in AdS/CFT

Within gauge/gravity duality, we consider the AdS-Schwarzschild metric in arbitrary dimensions. We obtain analytical closed-form results for the two-point function, Wilson loop and entanglement entropy for strip geometries in the finite-temperature field-theory dual. According to the duality, these are given by the area of minimal surfaces of different dimension in the gravity background. Our analytical results involve generalised hypergeometric functions. We show that they reproduce known numerical results to great accuracy. Our results allow to identify new physical behaviour: for instance, we consider the entanglement density, i.e. the difference of entanglement entropies at finite and vanishing temperature divided by the volume of the entangling region. For field theories of dimension seven or higher, we find that the entanglement density displays non-monotonic behaviour as function of ℓ · T , with ℓ the strip width and T the temperature. This implies that the area theorem, proven for RG flows in general dimensions, does not apply here. This may signal the emergence of new degrees of freedom for AdS Schwarzschild black holes in eight or more dimensions.

Cusp anomalous dimension and rotating open strings in AdS/CFT

In the context of AdS/CFT we provide analytical support for the proposed duality between a Wilson loop with a cusp, the cusp anomalous dimension, and the meson model constructed from a rotating open string with high angular momentum. This duality was previously studied using numerical tools in [1]. Our result implies that the minimum of the profile function of the minimal area surface dual to the Wilson loop, is related to the inverse of the bulk penetration of the dual string that hangs from the quark-anti-quark pair (meson) in the gauge theory.

Amide type nonionic surfactants: Synthesis and corrosion inhibition evaluation against carbon steel corrosion in acidic medium

Three nonionic cleavable surfactants were prepared from the reaction of sebacic acid and antipyrine and polyethylene glycols with different molecular weights. The chemical structures of the prepared surfactants were determined using FTIR and 1H NMR spectroscopy. The surface activities of the prepared surfactants were measured based on the surface tension measurements at different temperatures. The surface parameters including: surface tension, critical micelle concentration (CMC), maximum surface excess (max) and minimum surface area. The prepared surfactants were evaluated as corrosion inhibitors to prevent the dissolution of carbon steel in 1M HCl using gravimetric method. The results showed that the inhibition efficiency of these compounds is increased by increasing their concentration, immersion time and polyethylene glycol chain length. Where the inhibitive efficiencies of the prepared surfactants at higher immersion time (120h), increased considerably to the maximum values in the range of 93.8%–98.5% at 800ppm by weight and in the range of 77.8–87.6% at 25ppm by weight. The study showed the strong relation between the surface activities of the nonionic surfactants and their inhibition efficiency in the carbon steel protection in 1M HCl.