Minimum Surface Area Research Articles

Fiber statistics of nonwoven materials by SEM images - influence of number of images

Abstract Electrospun nonwovens are widely applied in biomedicine and various other fields. For control of the manufacturing process and quality assurance Scanning electron microscopy (SEM) imaging is one standard practice. In this study, statistical datasets of 60 SEM images of three nonwoven samples were evaluated using Gaussian fit to obtain numerical results of their fiber diameter distributions. The question of how much effort is required for acceptable imaging and processing is being discussed. As determined here, for reliable statistics, a minimum surface area of the nonwoven has to be evaluated. The fiber diameter should be in a range of approximately 2 - 3% of the edge length of the square equivalent of the evaluated image area, using sufficiently magnified SEM images, in which the fiber diameter is imaged over at least 30 pixels.

Sections of Convex Bodies in John’s and Minimal Surface Area Position

Abstract We prove several estimates for the volume, the mean width, and the value of the Wills functional of sections of convex bodies in John’s position, as well as for their polar bodies. These estimates extend some well-known results for convex bodies in John’s position to the case of lower-dimensional sections, which had mainly been studied for the cube and the regular simplex. Some estimates for centrally symmetric convex bodies in minimal surface area position are also obtained.

Variationally Improved Bézier Surfaces with Shifted Knots

The Plateau-Bézier problem with shifted knots is to find the surface of minimal area amongst all the Bézier surfaces with shifted knots spanned by the admitted boundary. Instead of variational minimization of usual area functional, the quasi-minimal Bézier surface with shifted knots is obtained as the solution of variational minimization of Dirichlet functional that turns up as the sum of two integrals and the vanishing condition gives us the system of linear algebraic constraints on the control points. The coefficients of these control points bear symmetry for the pair of summation indices as well as for the pair of free indices. These linear constraints are then solved for unknown interior control points in terms of given boundary control points to get quasi-minimal Bézier surface with shifted knots. The functional gradient of the surface gives possible candidate functions as the minimizers of the aforementioned Dirichlet functional; when solved for unknown interior control points, it results in a surface of minimal area called quasi-minimal Bézier surface. In particular, it is implemented on a biquadratic Bézier surface by expressing the unknown control point P 11 as the linear combination of the known control points in this case. This can be implemented to Bézier surfaces with shifted knots of higher degree, as well if desired.

Study of Steel Electro-dissolution Behavior in Presence of Some Surfactants. Electrochemical Investigation and Surface Active Properties Determination

Steel electro-dissolution performance was investigated in orthophosphoric acid in the presence of N-oleyl 1.3 diaminopropane, Benzalkounuim chloride, Soduim lauryl sulphate and Di-Isononyl phthalate as a surfactant using potentiodynamic polarization measurements. The retardation performance of these surfactants was examined. The surfactant surface active parameters were estimated based on surface tension measurements. The parameters calculated comprise the critical micelle concentration (CMC), maximum surface excess (Гmax), minimum surface area (Amin) and effectiveness (πCMC). The micellization thermodynamic parameters (ΔGmic, ΔSmic) for the estimated surfactants were also computed. Results obtained from surface active properties are comparable with those gained from galvanostatic polarization measurements. Temperature influence on the steel dissolution performance was examined at 25 to 40oC range. Steel kinetic study in orthophosphoric acid- free solution and orthophosphoric acid containing surfactant was also examined. The dissolution kinetic and activated parameters were computed. Results based on microscopy measurement indicate that, addition of new four surfactants, resulting in the solution shows potential, a discrete progress in the metal texture was monitored. Improvement produced in electro-polishing bath by the investigated SAS that owing to the adsorption of such surface active agents on the anode surface.

Computing minimal surfaces with differential forms

We describe a new algorithm that solves a classical geometric problem: Find a surface of minimal area bordered by an arbitrarily prescribed boundary curve. Existing numerical methods face challenges due to the non-convexity of the problem. Using a representation of curves and surfaces via differential forms on the ambient space, we reformulate this problem as a convex optimization. This change of variables overcomes many difficulties in previous numerical attempts and allows us to find the global minimum across all possible surface topologies. The new algorithm is based on differential forms on the ambient space and does not require handling meshes. We adopt the Alternating Direction Method of Multiplier (ADMM) to find global minimal surfaces. The resulting algorithm is simple and efficient: it boils down to an alternation between a Fast Fourier Transform (FFT) and a pointwise shrinkage operation. We also show other applications of our solver in geometry processing such as surface reconstruction.

Minimum polyhedron with $n$ vertices

We study a polyhedron with $n$ vertices of fixed volume having the minimum surface area. Completing the proof of Fejes Tóth, we show that all faces of a minimum polyhedron are triangles, and further prove that a minimum polyhedron does not allow deformation of a single vertex. We also present possible minimum shapes for $n ≤ 12$. Some of them are quite unexpected, in particular $n = 8$.

Systematic Studies of Sodium γ-Octyl Aspartate to evaluate its Biodegradation, Surface Parameters, Micellization Aspects and Thermodynamic Properties of its Binary Mixture using Electrolytes

γ-octyl aspartate has been synthesized with 46.2% yield. The optimized conditions for esterification of aspartic acid and n-octanol are 24 hours duration and 1:1 molar ratio of reactants (aspartic acid: n-octanol). FT-IR, 1H NMR and CHNS element analysis techniques are used for structure elucidation of γ -octyl aspartate. Surface/ interfacial studies, micellization aspects, thermodynamic parameters, biodegradability and binary salt behaviour of sodium γ-octyl aspartate have been studied. The CMC of synthesized surfactants was 0.0078 mol/L, whereas minimum surface area per surfactant molecule was calculated as 29.49 Å2m2; calculated aggregation number was 34 and micelle radius (r) found to be 1.40 nm. The degree of counter-ion dissociation (α) was determined to be 0.86. Thermodynamic parameter - standard free energy of adsorption (ΔG0ads) was calculated as -18.70 kJ/mol. The shape of micelle of synthesized surfactant was noticed to be spherical but during binary studies in some cases, it was found to be cylindrical. OECD and Winkler’s method were used to determine biodegradation of sodium γ-octyl aspartate found to be 95.1 %.

Synthesis, surface properties and bioactivity of novel 4-Substituted 1,2,3-Triazole quaternary ammonium surfactants

Series of novel 1,2,3-triazole based quaternary ammonium surfactants with different hydrophobic chain length and head group substituents were synthetized and characterized. Their surface properties and aggregation behavior were discussed on the basis of tensiometry and conductimetry measurements by using several parameters, including critical micelle concentration (CMC), surface tension at the cmc (γcmc), adsorption efficiency (pC20), effectiveness of surface tension reduction (Πcmc), minimum surface area occupied by a molecule (Amin) at the air − water interface and standard Gibbs free energy of micellization ΔGMic0. These heterocyclic surfactants exhibit much lower CMC values as compared with those reported for conventional alkyltriethyl ammoniums and alkylbenzyldiethyl ammonium salts. Their micelles formation and surface adsorption in aqueous media can be tuned out through a suitable choice of the substituent attached to the polar head. Triethyl ammonium (CnTzTEA] and diethylbenzyl ammonium surfactants (CnTzBz) showed improved micellization behavior than tetradecyl diethyl ammonium (CnTzC14) homologous. The in vitro antimicrobial activity of the surfactants againstB. subtilis, P. aerugenosa and A.niger strains was also investigated. CnTzBz series possessing benzyl chain showed better activity against all the tested microorganisms with minimum inhibitory concentration ranging from 6 to 57 μmol/L.

Optimal Sizing of Cylindrical Receivers for Surround Heliostat Fields Using fluxtracer

Abstract This article presents an innovative approach for optimizing the dimensions of cylindrical receivers for solar tower systems. In this approach, a single set of rays, representative of a complete annual ray-tracing simulation of the solar tower system, is used and processed to evaluate numerous receiver designs simultaneously and to select the optimum. The simultaneous evaluation of receiver designs is achieved by exploiting the geometrical properties of the intersection between a ray and a cylinder, which allows estimating the annual energy intercepted by receivers of different heights without the need for processing the annual set of rays more than one time. Once the annual intercepted energy is known for each receiver, the application of a costing function estimating the receiver cost as a function of its surface area allows to estimate their cost and, therefore, to select the receiver dimensions that will yield a minimum surface area for a given annual energy interception factor. The overall workflow to carry out the mentioned receiver optimization approach has been implemented by adapting several open-source tools that The Cyprus Institute (CyI) is developing in collaboration with the Australian National University (ANU) to assist in the modeling, analysis, design, and optimization of concentrated solar thermal (CST) systems. This article also presents a detailed overview of the overall simulation workflow as well as a case study demonstrating the capabilities of the approach.

VICTORIA: VIrtual neck Curve and True Ostium Reconstruction of Intracranial Aneurysms

PurposeFor the status evaluation of intracranial aneurysms (IAs), morphological and hemodynamic parameters can provide valuable information. For their extraction, a separation of the aneurysm sac from its parent vessel is required that yields the neck curve and the ostium. However, manual and subjective neck curve and ostium definitions might lead to inaccurate IA assessments.MethodsThe research project VICTORIA was initiated, allowing users to interactively define the neck curve of five segmented IA models using a web application. The submitted results were qualitatively and quantitatively compared to identify the minimum, median and maximum aneurysm surface area. Finally, image-based blood flow simulations were carried out to assess the effect of variable neck curve definitions on relevant flow- and shear-related parameters.ResultsIn total, 55 participants (20 physicians) from 18 countries participated in VICTORIA. For relatively simple aneurysms, a good agreement with respect to the neck curve definition was found. However, differences among the participants increased with increasing complexity of the aneurysm. Furthermore, it was observed that the majority of participants excluded any small arteries occurring in the vicinity of an aneurysm. This can lead to non-negligible deviations among the flow- and shear-related parameters, which need to be carefully evaluated, if quantitative analysis is desired. Finally, no differences between participants with medical and non-medical background could be observed.ConclusionsVICTORIAs findings reveal the complexity of aneurysm neck curve definition, especially for bifurcation aneurysms. Standardization appears to be mandatory for future sac-vessel-separations. For hemodynamic simulations a careful neck curve definition is crucial to avoid inaccuracies during the quantitative flow analysis.

Micellization and antimicrobial properties of N-alkyl-(2-hydroxypropyl)morpholinium bromides

New ionic-liquid cationic surfactants have been synthesized on the basis of alkyl (C9, C10, C12, C14) bromides and 1-(4-morpholinyl)-2-propanol. Surface activity and specific electroconductivity of aqueous solutions of the obtained surfactants have been studied by tensiometric and conductometric methods. Depending on the length of the alkyl chain, the values of critical micellization concentration (CMC), maximum adsorption (Гmax), area of minimal cross-sectional surface of polar group of the surfactant (Amin), adsorption efficiency (pC20), surface pressure (πCMC), binding degree of the counter-ion (β), changes of Gibbs free energies of micellization and adsorption processes (ΔGmic and ΔGad) have been determined. Antimicrobial properties of the synthesized ionic-liquid surfactants have been studied on the example of different bacteria and fungus.

Formation of mixed micelles in an aqueous mixture of a biamphiphilic surface active ionic liquid and an anionic surfactant: Experimental and theoretical study

The micellization behaviour of biamphiphilic surface active ionic liquid (BAIL), 3-methyl-1-pentylimidazolium dodecylsulfate [C5mim][C12SO4] with anionic surfactant, sodium dioctylsulfosuccinate (AOT) was investigated using different techniques in an aqueous solution. The values of critical micelle concentration (cmc) and thermodynamic parameters have been ascertained by employing conductometric measurement at (298.15, 308.15 and 318.15) K. The interfacial parameters viz. surface pressure, maximum surface excess concentration, and minimum surface area per surfactant molecule evaluated by using the surface tension measurement at 298.15 K shows the less effectiveness of mixtures to reduce the surface tension. The size and turbidity of the mixed aggregates were investigated using dynamic light scattering (DLS) and turbidimetry. The turbidity results show the existence of micelles as well as mixed aggregates. Different proposed theoretical models like Clint, Rubingh and Motomura was employed for the evaluation of mixed micellar parameters (ideal values of cmc, activity coefficients of the components in the mixed micelle, and interaction parameters etc.) at different compositions. The existence of both the interactions (synergistic and antagonistic) has been inferred in the studied system. The mixed micelle formation was found dependent on micellar composition.

Relationship between Water Surface Area of Qingtu Lake and Ecological Water Delivery: A Case Study in Northwest China

Qingtu Lake is located between Tengger Desert and Badain Jilin Desert, Gansu Province, Northwest China. It is the terminal lake of Shiyang River. In recent years, Qingtu lake has maintained a certain area of water surface and vegetation by artificial water conveyance. It is of great significance in preventing the convergence of the two deserts and restraining the trend of ecological deterioration of Shiyang River Basin. The relationship between the water surface area and the ecological water conveyance have not been thoroughly investigated. This study analyzed the spatial and temporal distribution of water surface area of Qingtu Lake and surrounding reeds by interpreting remote sensing data; the change of water surface area under the influence of meteorological factors and water conveyance by linear regression; the water conveyance to maintain current water surface area by water balance method, as well as the reasonable ecological water delivery in high flow year, normal flow year and low flow year by the means of analyzing the upstream inflow and water consumption in Minqin Basin. The results showed that there is a significant correlation between the water surface area of Qingtu Lake, evaporation and ecological water conveyance, and the minimum and maximum water surface areas generally appear before and after water delivery, indicating that the ecological water delivery and evaporation are the two main factors affecting the water surface area change of Qingtu Lake. The result calculated by linear regression indicated that the ecological water delivery volume to maintain current water surface area of Qingtu Lake is 3.146 × 107 m3/yr, while the value was 3.136 × 107 m3/yr calculated by water balance method. These two results are similar and can be verified with each other. Reasonable ecological water conveyance of Qingtu Lake in high flow year, normal flow year and low flow years were 4 × 107 m3/yr, 3.2 × 107 m3/yr and 2.3 × 107 m3/yr, respectively.

The influences of distraction osteogenesis therapy on airway morphology in patients with craniofacial microsomia

The aim of this study was to explore how mandibular distraction osteogenesis influences morphological changes in the oropharynx and laryngopharynx.This was a retrospective study of airway parameter measurements in CFM patients undergoing mandibular distraction osteogenesis treatment. The indication for surgical treatment was the obvious facial asymmetry. Mimics 17.0 (Materialise Inc., Belgium) was used to build 3D models of the oro- and laryngopharynx. The minimum cross-sectional area (CSA), mean CSA, volume, length, and surface area were measured in the 3D models. All data were entered into SPSS v. 23.0 (SPSS Inc. USA), with statistical differences assessed pre- and postoperatively using the Wilcoxon test.Thirty-two patients diagnosed with CFM were included in this study. Five were classified as type IIa, 21 as type IIb, and six as type III, using the Pruzansky–Kaban classification. The average age of the patients was 8.34 years; 14 were females and 18 were males. The average traction time was 35.59 days and the average length of traction was 35.81 mm.The total volume of the airway was significantly increased after MDO (p = 0.001). In the oropharynx and laryngopharynx segments, the mean CSA, minimum CSA, and surface area were statistically significantly different. According to the results, expansion of oropharynx and laryngopharynx were evident after MDO.Mandibular distraction osteogenensis (MDO) can expand the volume of the oropharynx and laryngopharynx. Therefore, MDO can be considered a clinically useful treatment for changing the structure of the oropharynx and laryngopharynx.

Increased Alveolar Heparan Sulphate and Reduced Pulmonary Surfactant Amount and Function in the Mucopolysaccharidosis IIIA Mouse.

Mucopolysaccharidosis IIIA (MPS IIIA) is a lysosomal storage disease with significant neurological and skeletal pathologies. Respiratory dysfunction is a secondary pathology contributing to mortality in MPS IIIA patients. Pulmonary surfactant is crucial to optimal lung function and has not been investigated in MPS IIIA. We measured heparan sulphate (HS), lipids and surfactant proteins (SP) in pulmonary tissue and bronchoalveolar lavage fluid (BALF), and surfactant activity in healthy and diseased mice (20 weeks of age). Heparan sulphate, ganglioside GM3 and bis(monoacylglycero)phosphate (BMP) were increased in MPS IIIA lung tissue. There was an increase in HS and a decrease in BMP and cholesteryl esters (CE) in MPS IIIA BALF. Phospholipid composition remained unchanged, but BALF total phospholipids were reduced (49.70%) in MPS IIIA. There was a reduction in SP-A, -C and -D mRNA, SP-D protein in tissue and SP-A, -C and -D protein in BALF of MPS IIIA mice. Captive bubble surfactometry showed an increase in minimum and maximum surface tension and percent surface area compression, as well as a higher compressibility and hysteresis in MPS IIIA surfactant upon dynamic cycling. Collectively these biochemical and biophysical changes in alveolar surfactant are likely to be detrimental to lung function in MPS IIIA.

Synthesis and evaluation of new cationic polymeric surfactant based on N-phthalimidomethyl methacrylate

In our previous work N-phthalimidomethyl methacrylate (NPMMA) monomer was prepared through the reaction of N-hydroxymethyl phthalimide with methacrylic acid in the presence of N, N-dicyclohexylcarbodiimide (DCCI) as a condensing agent. Then a new series of copolymers containing imidazole have been synthesized through the reaction of NPMMA monomer with 1-vinylimidazole (VIM) in the presence of benzoyl peroxide as initiator. The copolymer composition was determined by 1H NMR spectroscopy and the values of monomer reactivity ratio (r1= 0.756, r2= 1.033, and r1r2= 0.781) were calculated through Fineman Ross and Kelen-Tudos methods. Conversion of copolymers to surfactants was achieved through quaternization of the imidazole nitrogen with dimethyl sulphate. The chemical structure of the produced monomer, copolymers, co-polymeric surfactants was confirmed by spectroscopic tools. The surface properties included surface tension, foaming power, emulsion stability, critical micelle concentration (CMC) have been measured in aqueous medium by traditional procedures. Also the different air/ water interface parameters including effectiveness (πcmc), efficiency (Pc20), maximum surface excess (Γmax) and minimum surface area (Amin) were also recorded. Moreover, the biodegradability for these cationic surfactants has been investigated and their D % was ranged from 67 to 100 %.

Synthesis and Properties of Alkyl Bis-Guanidinium Acetates Surfactants

Abstract Novel surfactants with double hydrophilic groups (cocopropane and tallowpropane bis-guanidinium acetates), were synthesized and tested to evaluate both the basic surfactant properties and the unique application performance. Surface tension, conductivity and contact angle measurements were used to study the self-aggregation behavior in aqueous solution. Aggregation parameters were calculated such as adsorption efficiency and effectiveness (pC20 and CAC/C20), the maximum surface excess concentration (Гmax) and minimum surface area permolecule (Amin). The thermodynamic parameters of aggregation based conductivity measurements revealed that the aggregation process was spontaneous and entropy-driven. Compared to DTAC and CTAC, the alkyl bis-guanidinium acetates showed a higher emulsification capacity with both liquid kerosene and soybean oil. The evaluation of antimicrobial activity showed that the alkyl bisguanidinium acetates exhibited strong antibacterial activity against the tested strains at a concentration of 50 ppm.

Design and heat transfer optimization of a 1 kW free-piston stirling engine for space reactor power system

The Free-Piston Stirling engine (FPSE) is of interest for many research in aerospace due to its advantages of long operating life, higher efficiency, and zero maintenance. In this study, a 1-kW FPSE was proposed by analyzing the requirements of Space Reactor Power Systems (SRPS), of which performance was evaluated by developing a code through the Simple Analysis Method. The results of SAM showed that the critical parameters of FPSE could satisfy the designed requirements. The heater of the FPSE was designed with the copper rectangular fins to enhance heat transfer, and the parametric study of the heater was performed with Computational Fluid Dynamics (CFD) software STAR-CCM+. The Performance Evaluation Criteria (PEC) was used to evaluate the heat transfer enhancement of the fins in the heater. The numerical results of the CFD program showed that pressure drop and Nusselt number ratio had a linear growth with the height of fins, and PEC number decreased as the height of fins increased, and the optimum height of the fin was set as 4 mm according to the minimum heat exchange surface area. This paper can provide theoretical supports for the design and numerical analysis of an FPSE for SRPSs.

New holographic generalization of entanglement entropy

We introduce a quantity, called pseudo entropy, as a generalization of entanglement entropy via post-selection. In the AdS/CFT correspondence, this quantity is dual to areas of minimal area surfaces in time-dependent Euclidean spaces which are asymptotically AdS. We study its basic properties and classifications in qubit systems. In specific examples, we provide a quantum information theoretic meaning of this new quantity as an averaged number of Bell pairs when the post-selection is performed. We also present properties of the pseudo entropy for random states. We then calculate the pseudo entropy in the presence of local operator excitations for both the two dimensional free massless scalar CFT and two dimensional holographic CFTs. We find a general property in CFTs that the pseudo entropy is highly reduced when the local operators get closer to the boundary of the subsystem. We also compute the holographic pseudo entropy for a Janus solution, dual to an exactly marginal perturbation of a two dimensional CFT and find its agreement with a perturbative calculation in the dual CFT. We show the linearity property holds for holographic states, where the holographic pseudo entropy coincides with a weak value of the area operator. Finally, we propose a mixed state generalization of pseudo entropy and give its gravity dual.

Symmetric convex sets with minimal Gaussian surface area

Let $\Omega\subset\Bbb{R}^{n+1}$ have minimal Gaussian surface area among all sets satisfying $\Omega=-\Omega$ with fixed Gaussian volume. Let $A=A_x$ be the second fundamental form of $\partial\Omega$ at $x$, i.e., $A$ is the matrix of first order partial derivatives of the unit normal vector at $x\in\partial\Omega$. For any $x=(x_1,\ldots,x_{n+1})\in\Bbb{R}^{n+1}$, let $\gamma_n(x)=(2\pi)^{-n/2}e^{-(x_1^2+\cdots+x_{n+1}^2)/2}$. Let $\|A\|^{2}$ be the sum of the squares of the entries of $A$, and let $\|A\|_{2\to 2}$ denote the $\ell_{2}$ operator norm of $A$.