Minimum Surface Area Research Articles

Birth of baby universes from gravitational collapse in a modified-gravity scenario

We consider equilibrium models of spherical boson stars in Palatini f(ℛ) = ℛ + ξℛ2 gravity and study their collapse when perturbed. The Einstein-Klein-Gordon system is solved using a recently established correspondence in an Einstein frame representation. We find that, in that frame, the endpoint is a nonrotating black hole surrounded by a quasi-stationary cloud of scalar field. However, the dynamics in the f(ℛ) frame is dramatically different. The innermost region of the collapsing object exhibits the formation of a finite-size, exponentially-expanding baby universe connected with the outer (parent) universe via a minimal area surface (a throat or umbilical cord). Our simulations indicate that this surface is at all times hidden inside a horizon, causally disconnecting the baby universe from observers above the horizon. The implications of our findings in other areas of gravitational physics are also discussed.

Interfacial and micellar synergistic interactions between a phosphonium surface active ionic liquid and TX-100 nonionic surfactant: Surface tension and 1H NMR investigations

The adsorption and self-aggregation behaviors of a mixed system made of a cationic surface active ionic liquid (SAIL), dodecyltriphenylphosphnium bromide (C12TPB), and a nonionic surfactant, polyoxyethylene p-tertoctylphenyl ether (TX-100), were investigated in aqueous solution using tensiometry and 1H NMR measurements. From the surface tension data, relevant physico-chemical parameters were determined for different proportions of the components: critical micelle concentration (cmc), surface saturation adsorption, minimum surface area per surfactant molecule and surface tension at the cmc. The obtained data were treated through different theoretical models, namely those of Clint, Rubingh, Maeda and Rosen, which allow the determination of key thermodynamic properties. The results revealed, in both the mixed micelles and surface monolayer, the existence of a non-ideal behavior due to rather strong attractive links, confirmed by the 1H NMR data analysis. They are attributed mainly, besides the hydrophobic interaction, to firstly the ion–dipole interaction and the complex formation between the polyoxyethylene head of TX-100 and the quaternary phosphonium group of C12TPB, and secondly to an intermolecular π-π stacking and a hydrogen-bonds formation between the protons in α position of the phosphonium and the oxygen atoms of polyoxyethylene units of TX-100, giving rise to a strong synergism.

Mixed micellization analysis of tri-substituted SAIL and amphiphilic drug mixture in aqueous/salt media at diverse temperatures

Abstract The present work aimed to study the mixed micellar behaviour of a tri-substituted imidazolium based surface-active ionic liquid (SAIL), 1-tetradecyl-2,3-dimethylimidazolium bromide [C14bmim][Br], with a drug Nortriptyline hydrochloride (NOT) in the water/salt (Na2SO4) medium using surface tension measurements (298.15 K) alongwith conductivity measurements (298.15K–313.15K). Lower experimentally obtained cmc values compared to their ideal values suggest that the investigated amphiphiles interact strongly. The values of micellar mole fraction (X 1) based on the several proposed models (Rubingh, Motomura, and Rodenas) and the ideal micellar mole fraction (X id ) were assessed, and the predicted outcomes indicate that NOT has a significant contribution to the formation of mixed micelles, which increases as the [C14bmim][Br] mole fraction is increased. The negative values of micellization’s Gibbs free energy (ΔGm 0) between the examined amphiphiles were an indication of spontaneous mixed micelle formation. Micellar changes in entropy (ΔSm 0) and enthalpy (ΔHm 0) were also computed and discussed. Using surface tension measurements, surface-active parameters like surface tension at cmc (γ cmc ), minimum surface area per IL molecule (A min), maximum surface excess concentration (τ max), effectiveness of surface tension reduction (π cmc ), and cmc of mixed system have been estimated. The results showed an improved adsorption and micellization properties of these mixtures which will surely contribute to the tremendous rise of these mixed systems in drug delivery applications.

Assessment of removal rate coefficient in vertical flow constructed wetland employing machine learning for low organic loaded systems

Secondary datasets of 42 low organic loading Vertical flow constructed wetlands (LOLVFCWs) were assessed to optimize their area requirements for N and P (nutrients) removal. Significant variations in removal rate coefficients (k20) (0.002–0.464 md−1) indicated scope for optimization. Data classification based on nitrogen loading rate, temperature and depth could reduce the relative standard deviations of the k20 values only in some cases. As an alternative method of deriving k20 values, the effluent concentrations of the targeted pollutants were predicted using two machine learning approaches, MLR and SVR. The latter was found to perform better (R2 = 0.87–0.9; RMSE = 0.08–3.64) as validated using primary data of a lab-scale VFCW. The generated model equations for predicting effluent parameters and computing corresponding k20 values can assist in a customized design for nutrient removal employing minimal surface area for such systems for attaining the desired standards.

GRAS transcription factors regulate cell division planes in moss overriding the default rule

Plant cells are surrounded by a cell wall and do not migrate, which makes the regulation of cell division orientation crucial for development. Regulatory mechanisms controlling cell division orientation may have contributed to the evolution of body organization in land plants. The GRAS family of transcription factors was transferred horizontally from soil bacteria to an algal common ancestor of land plants. SHORTROOT (SHR) and SCARECROW (SCR) genes in this family regulate formative periclinal cell divisions in the roots of flowering plants, but their roles in nonflowering plants and their evolution have not been studied in relation to body organization. Here, we show that SHR cell autonomously inhibits formative periclinal cell divisions indispensable for leaf vein formation in the moss Physcomitrium patens, and SHR expression is positively and negatively regulated by SCR and the GRAS member LATERAL SUPPRESSOR, respectively. While precursor cells of a leaf vein lacking SHR usually follow the geometry rule of dividing along the division plane with the minimum surface area, SHR overrides this rule and forces cells to divide nonpericlinally. Together, these results imply that these bacterially derived GRAS transcription factors were involved in the establishment of the genetic regulatory networks modulating cell division orientation in the common ancestor of land plants and were later adapted to function in flowering plant and moss lineages for their specific body organizations.

4D segmentation of the thoracic aorta from 4D flow MRI using deep learning

Background4D flow MRI allows the analysis of hemodynamic changes in the aorta caused by pathologies such as thoracic aortic aneurysms (TAA). For personalized management of TAA, new biomarkers are required to analyze the effect of fluid structure iteration which can be obtained from 4D flow MRI. However, the generation of these biomarkers requires prior 4D segmentation of the aorta. ObjectiveTo develop an automatic deep learning model to segment the aorta in 4D from 4D flow MRI. MethodsSegmentation is addressed with a U-Net based segmentation model that treats each 4D flow MRI frame as an independent sample. Performance is measured with respect to Dice score (DS) and Hausdorff distance (HD). In addition, the maximum and minimum surface areas at the level of the ascending aorta are measured and compared with those obtained from cine-MRI. ResultsThe segmentation performance was 0.90 ± 0.02 for the DS and the mean HD was 9.58 ± 4.36 mm. A correlation coefficient of r = 0.85 was obtained for the maximum surface and r = 0.86 for the minimum surface between the 4D flow MRI and cine-MRI. ConclusionThe proposed automatic approach of 4D aortic segmentation from 4D flow MRI seems to be accurate enough to contribute to the wider use of this imaging technique in the analysis of pathologies such as TAA.

A many-body dissipative particle dynamics parametrisation scheme to study behaviour at air-water interfaces.

In this article, we present a general parametrisation scheme for many-body dissipative particle dynamics (MDPD). The scheme is based on matching model components to experimental surface tensions and chemical potentials. This allows us to obtain the correct surface and mixing behaviours of complex, multicomponent systems. The methodology is tested by modelling the behaviour of nonionic polyoxyethylene alkyl ether surfactants at an air/water interface. In particular, the influence of the number of ethylene oxide units in the surfactant head group is investigated. We find good agreement with many experimentally obtained parameters, such as minimum surface area per molecule; and a decrease in the surface tension with increasing surfactant surface density. Moreover, we observe an orientational transition, from surfactants lying directly on the water surface at low surface coverage, to surfactants lying parallel or tilted with respect to the surface normal at high surface coverage. The parametrisation scheme is also extended to cover the zwitterionic surfactant lauryldimethylamine oxide (LDAO), where we provide good predictions for the surface tension at maximum surface coverage. Here, if we exceed this coverage, we are able to demonstrate the spontaneous production of micelles from the surface surfactant layer.

To thread or not to thread? Effective potentials and threading interactions between asymmetric ring polymers.

We use computer simulations to study a system of two unlinked ring polymers, whose length and bending stiffness are systematically varied. We derive the effective potentials between the rings, calculate the areas of minimal surfaces of the same, and characterize the threading between them. When the two rings are of the same kind, threading of a one ring through the surface of the other is immanent for small ring-ring separations. Flexible rings pierce the surface of the other ring several times but only shallowly, as compared to the stiff rings which pierce less frequently but deeply. Typically, the ring that is being threaded swells and flattens up into an oblate-like conformation, while the ring that is threading the other takes a shape of an elongated prolate. The roles of the threader and the threaded ring are being dynamically exchanged. If, on the other hand, the rings are of different kinds, the symmetry is broken and the rings tend to take up roles of the threader and the threaded ring with unequal probabilities. We propose a method how to predict these probabilities based on the parameters of the individual rings. Ultimately, our work captures the interactions between ring polymers in a coarse-grained fashion, opening the way to large-scale modelling of materials such as kinetoplasts, catenanes or topological brushes.

Energetically optimal dimensions of parallelepiped-shaped industrial structures

Technical structures with a parallelepiped form are frequently used in various areas of industry. For example, as fluid containers, ice and minerals piles, underground and surface storages and cooling chambers. A task of determining the optimum dimensions of the structure to minimize the energy expenses to support a normative temperature in the structure arises. The minimum surface area of the structure at a given volume is accepted as a criterion of optimality. A problem of unconstrained optimization for a structure with a parallelepiped form was formulated and solved. Equations to determine the optimum dimensions of width, height and length of the structure were obtained. It was determined that a cube is the most optimal form.

Tensiometric and Fluorescence Study of Cationic Gemini Surfactant with Some Special Alcohols

Special alcohols have been used as additives to study interfacial properties of cationic Gemini surfactant pentanediyl- 1, 5-bis (dimethyldodecylammonium bromide) (12-5-12). As these branched chain alcohols (in comparison with linear chain alcohols) are playing a measure roll in creating a microemulsion with Gemini surfactants. The surface tension values were measured by using ring detachment method. During the experiments, the ring was cleaned well by heating it in alcohol flame. The critical micelle concentration (cmc) values were obtained from surface tension (γ) versus logCt plots. The γ values decreased continuously and then become constant along a wide concentration range. The point of break, when the constancy of surface tension begins, was taken as the cmc of the system. Calculated Parameters are cmc, Гmax (maximum surface excess concentration), Amin (minimum surface area per molecule), C20 (the concentration of surfactant where the surface tension of the solvent is being reduced by 20 mN.m-1), (free energy of the given air/water interface), and the standard Gibbs energy of adsorption, ΔG­­0ads. An important property of micelle formation is the mean aggregation number which provides direct information about the general size and shape of the aggregates formed by amphiphiles in solution, and how these properties are related to the molecular structure of the amphiphiles. Mixed micellization behavior has been shown by these parameters. The mean aggregation number (Nagg­) of mixed micelles has been obtained by using the steady state fluorescence quenching method. Some other concerned parameters including dielectric constant (D), binding constant (KSV) were calculated in this study by using the ratio of intensity of peaks.

Mathematical Modeling for Corner Strap Combined Footings Resting on the Ground: Part 2

This research shows a mathematical model for the design of corner strap combined footings supported on the ground that supports a concentrated load and two orthogonal moments in each column. It is considered that the pressure on the ground varies linearly. The first part of this investigation shows a model to obtain the minimum surface or optimal area in plan. The methodology is based on the concept that the integral of the bending shear is the moment. The traditional model considers a uniform pressure (maximum pressure) of the soil on the corner footing and the two edge footings, because the reaction of the soil on each footing is applied in the center of each footing. Four numerical examples are shown for the design of corner strap combined footings. This model is more general because it can be applied to corner combined footings, simply considering the sides in the X direction of the footings 1 and 3 equal, and the sides in the Y direction of the footings 1 and 2 equal.

Area and Spectrum Estimates for Stable Minimal Surfaces

This paper mainly concerns the area growth and bottom spectrum of complete stable minimal surfaces in a three-dimensional manifold with scalar curvature bounded from below. When the ambient manifold is the Euclidean space, by an elementary argument, it is shown directly from the stability inequality that the area of such minimal surfaces grows exactly as the Euclidean plane. Consequently, such minimal surfaces must be flat, a well-known result due to Fisher-Colbrie and Schoen as well as do Carmo and Peng. In the case of general ambient manifold, explicit area growth estimate is also derived. For the bottom spectrum, a self-contained argument involving positive Green’s function is provided for its upper bound estimates. The argument extends to stable minimal hypersurfaces in a complete manifold of dimension up to six with sectional curvature bounded from below.

Investigation of an anaesthetic drug (tetracaine hydrochloride) in the presence of ionic fluid and surfactant: Mixed micellization & spectroscopic studies

The effect of ionic liquid and cationic surfactant on the physicochemical characteristic of an anaesthetic drug (tetracaine hydrochloride, TCH) has been studied in the current task. The ionic fluid (1-hexadecyl-3-methyl imidazolium chloride, SAIL) and cationic surfactant (cetylpyridinium chloride, CPC) used in this study are of the same hydrophobic chain length. Tensiometric and absorption spectroscopic methods have been castoff to study the interaction of TCH with SAIL/CPC. The critical micelle concentration (cmc) values of single and mixed amphiphiles were computed by the surface tension method. In addition to cmc, maximum surface excess concentrations (Γmax), minimum surface areas per surfactant molecule (Amin), surface tension at the cmc (γcmc), surface tension reduction efficiency (πcmc), and several thermodynamic parameters of mixed micellization were measured. The calculated average value for the interaction parameter (βRub) suggests TCH show higher synergistic interaction with SAIL compared to CPC. The better attractive interaction (synergism) between SAIL and TCH is also confirmed by UV–visible spectroscopy. The absorption spectra of the drug show increase in the absorption with increasing the concentration of surfactants without any shift confirming the formation of a new complex. The binding constant value is more for the TCH + SAIL mixture.

Syntheses, Properties, and Aggregation Behavior of Novel Carboxylate-Based Silicone Surfactants.

Two new anionic silicone surfactants were synthesized for the first time from dichloromethylvinylsilane or trichlorovinylsilane through hydrolysis-condensation and then thiol-ene reactions. Their structures were characterized by FT-IR, 1 H NMR and ESI-MS. The surface tension (γ), critical aggregate concentration (CAC), surface pressure at CAC ( ) and minimum surface area per surfactant molecule ( ) were studied by surface tension and electrical conductivity, demonstrating their high surface activity at the gas/liquid interface. Transmission electron microscopy measurements showed that uniform spherical aggregates former in aqueous solution for both surfactants. Moreover, the size of the aggregates was determined to be in the range from 50 to 300 nm by dynamic light scattering.

The first space-filling polyhedrons of polymer cubic cells originated from Weaire-Phelan structure created by polymerization induced phase separation

The Weaire–Phelan structure is a three-dimensional structure composed of two different polyhedra having the same volume, i.e., pyritohedron and truncated hexagonal trapezohedron. It was proposed by Weaire and Phelan in 1993 as a solution of the Kelvin problem of filling space with no gaps with cells of minimum surface area and equal volume. It was found in physical systems including liquid foam and a metal alloy while it has never been constructed as organic materials. We report herewith the first polymeric Weaire–Phelan structure constructed through phase-separation of a single polymer species that is synthesized by simple polyaddition between tetrakis(3-mercaptopropionate) and 1,6-diisocyanatohexane. The structure has the order of micrometers and is amorphous unlike reported crystal structures similar to the Weaire–Phelan structure.

Novel synthesized anionic gemini and monomeric surfactants bearing sulphonate group as petro-dispersing/collecting agents: Design, characterization and surface-active properties

Conventional and gemini anionic sulphonate surfactants of variable alkyl chain length (8, 10, and 12 carbon atoms), were synthesized by three steps reactions using ethylenediamine, alkyl halides and sodium 3-chloro-2-hydroxypropane-1-sulfonate. Various spectroscopic tools (i.e., 1H and 13C NMR and IR spectra) were used to clarify the structures of synthesized surfactants. The solution surface properties of synthesized surfactants were studied by critical micelle concentration (CMC). Both maximum surface excess and minimum surface area per surfactant molecule were measured. Besides, the adsorption and micellization performance of the synthesized surfactants, which were estimated by the parameter of free adsorption energy (ΔGads0) and micellization (ΔGmic0) were measured. Moreover, the behavior of the synthesized surfactants as petroleum-collecting or dispersing agents has been studied in solid and diluted forms in water with different salinity. The results indicate that the synthesized surfactants possess superior petroleum-dispersing properties in water solutions of different salinity. Whereas the dispersing effect was improved by rising the hydrophobicity of these compounds. Furthermore, all the synthesized conventional and gemini anionic surfactants have a high ability to adsorb at the surface than micellized in the solution.

Energy solvency. A new concept to prevent energy poverty in Spain.

The new concept of energy solvency is defined as the ability of a person buying or renting a dwelling to meet the energy costs necessary to keep the dwelling comfortable, without falling into energy poverty. The energy efficiency certificate information is used to calculate the economic expenditure that is theoretically necessary to maintain the property comfortable. This is a more robust value for calculating the energy poverty indicator 2M than the available data on real expenditure. Dwellings' maximum surface may be determined in order to guarantee the energy solvency, depending on the climate zone, the energy class, the energy sources used, and the household's net income. The results indicate that in 15% of situations, it is not possible to have a dwelling that exceeds the minimum surface area stipulated by law without incurring an energy risk situation. It is also observed that in 86% of the cases, energy solvency is achieved for dwellings with energy classes A, B, C, and D, up to 120 m2. It is concluded that, by knowing the energy solvency before renting or buying a home, it is possible to prevent energy poverty by avoiding those operations in which it is known that this will happen.

Levelized cost of water assessment for small-scale desalination plant based on forward osmosis process

Availability and supply of fresh water is one of the most relevant challenges to be faced in the upcoming years. Efforts are being made worldwide to develop cost-effective and environmentally friendly technologies for the desalination of water. This work assesses the techno-economic performance of a forward osmosis desalination plant based on thermo-responsible polymers as a draw solute. Analysis of the plant performance for drinkable water production is carried out using a mathematical model for a small-scale application in Lipari (Sicily, Italy). Economic analysis was performed assuming that the thermal energy is provided by either a waste heat source or solar thermal collector, while electrical energy is supplied by either photovoltaic modules or from the grid. It was found that the lowest levelized cost of water of 2.68 €/m3 was reached with a photovoltaic + waste heat configuration and with the highest transmembrane pressure (hence the minimum membrane surface area). This cost is higher than that achieved with a reverse osmosis desalination plant of similar capacity with electricity supplied by photovoltaic modules, equal to 1.65 €/m3. As such forward osmosis technology must undergo significant improvements to become economically competitive.

Development of Li Metal Batteries with Improved Safety

Development of Li metal batteries (LMBs) has attracted worldwide attention in recent years due to their much higher theoretical energy densities than those of conventional Li ion batteries. LMBs with high energy density and long cycle life have been demonstrated by several institutions and companies recently.1,2 LMBs may be safe in their early stage of cycling due to the small geometric surface area of Li metal anode. However, after long term cycling, mossy/dendritic/“dead Li” will form eventually. They will not only lead to the increase of cell thickness, but also lead to powdered Li which pose a safety concern when exposed to air in the extreme case of mechanical damage, especially for their large scale applications.3 Thus, a paradigm change in the electrolyte design is required to minimize the formation of “dead Li” and improve the thermal stability of the batteries. In this work, several approaches have been used to improve the thermal stability of LMBs. (1) Use of electrolyte with high coulombic efficiency to minimize the formation of “dead Li” or mossy Li; (2) use of non-flammable solvent in electrolyte; (3) use of solvent with high boiling point and high flash point. (4) use of electrolyte enabling formation of large size of Li deposition with minimal surface area. This will enable the formation of a lithiophobic SEI layer which can accommodate stress/strain during large volume changes. (5) Screening additives to improve Li CE and safety. The electrolytes with improved safety/stability at extreme conditions will also be reported in this work.1 Niu, C. et al. Balancing interfacial reactions to achieve long cycle life in high-energy lithium metal batteries. Nature Energy, (2021).2 Hu, Q. Li-metal batteries, https://s29.q4cdn.com/695431818/files/doc_presentation/2022/03/March-2022-Investor-Presentation.pdf (2022).3 Louli, A. J. et al. Diagnosing and correcting anode-free cell failure via electrolyte and morphological analysis. Nature Energy 5, 693-702, (2020).

Noncommutative Corrections to the Minimal Surface Areas of the Pure AdS Spacetime and Schwarzschild-AdS Black Hole

Based on the perturbation expansion, we compute the noncommutative corrections to the minimal surface areas of the pure AdS spacetime and Schwarzschild-AdS black hole, where the noncommutative background is suitably constructed in terms of the Poincaré coordinate system. In particular, we find a reasonable tetrad with subtlety, which not only matches the metrics of the pure AdS spacetime and Schwarzschild-AdS black hole in the commutative case, but also makes the corrections real rather than complex in the noncommutative case. For the pure AdS spacetime, the nocommutative effect is only a logarithmic term, while for the Schwarzschild-AdS black hole, it contains a logarithmic contribution plus both a mass term and a noncommutative parameter related term. Furthermore, we show that the holographic entanglement entropy with noncommutativity obeys a relation which is similar to the first law of thermodynamics in the pure AdS spacetime.