Thermodynamic Interactions Research Articles

Two-Level Static Floatation Tool Used in Belt Grinding for Root Fillet of Titanium Alloy Blade

The root fillet of key components in aero-engines, such as the blade, blisk, and blade ring, is the most stress-concentrated area during thermodynamic interactions. The root fillet is constructed with a small curvature radius and variable curvature in different sections. Variable curvature is difficult to achieve with the integrated heat in the grinding process, and the surface quality of the root fillet is therefore greatly influenced. A “horseshoe nest”may be created in the high-temperature air environment, which would significantly affect the fatigue life of the key components. Therefore, to solve the problem of precision grinding for a variable-curvature root fillet, a two-level static floatation tool is proposed for belt grinding. First, the system design of the two-level static floatation tool is introduced, and the principle of the two-level static air floating is analyzed based on fluid dynamics. Second, the deformation and stress distribution of the two-level static floatation tool is analyzed when combined with the belt grinding process for a variable-curvature root fillet. Finally, an experiment performed on the root fillet of an aero-engine titanium alloy blade is described. The results show that the surface roughness is less than 0.4 μm, the profile precision errors are less than 5%, the transition is smooth between the plane and the fillet (blade surface to root fillet rabbet), and a longitudinal texture on the blade root fillet is formed.

Quantification of Available Water Capacity Comparing Standard Methods and a Pedostructure Method on a Weakly Structured Soil

Abstract. The purpose of this study was to evaluate the use of the pedostructure concept to determine the soil available water capacity, specifically the field capacity (FC). Pedostructure describes the soil aggregate structure and its thermodynamic interaction with water. Specifically, this work compared the calculation of soil water-holding properties based on the pedostructure concept with other standard methods for determining FC and permanent wilting point (PWP). The standard methods evaluated were the FAO texture estimate (FAO method), the Saxton-Rawls pedotransfer functions (PTFs method), and the water content at predefined soil suction (330 and 15,000 hPa) as measured with a pressure plate apparatus (PP method). Additionally, two pedostructure methods were assessed: the thermodynamic water retention curve (TWRC method) and the thermodynamic pedostructure (TPC method). Undisturbed loamy fine sand soil from a field in Millican, Texas, was analyzed at both the Ap and E horizons. The results showed that the estimated water content at FC and PWP for the three standard methods and for the TWRC method were in relative agreement. However, the TPC method used characteristic transition points in the modeled contents of different water pools in the soil aggregate and was higher for the Ap horizon, but in agreement with the other methods for the E horizon. For example, for the Ap horizon of the soil analyzed in this study, the FC estimated with the standard and TWRC methods ranged from 0.073 to 0.150 m3H2O m-3soil, while the TPC method estimate was 0.221 m3H2O m-3soil. Overall, the different methods showed good agreement in estimating the available water; however, the results also showed some variations in these estimates. It is clear that the TPC method has advantages over the other methods in considering the soil aggregate structure and modeling the soil water content within the aggregate structure. The thermodynamic nature of the TPC method enabled the use of both the soil shrinkage curve and the water retention curve in a weakly structured soil. It is expected that the TPC method would provide more comprehensive advances in understanding the soil water-holding properties of structured soils with higher clay contents. Keywords: Available water, Field capacity, Pedostructure, Pedotransfer functions, Permanent wilting point.

Molecular interaction balanced one- and two-dimensional hybrid nanoarchitectures for high-performance supercapacitors.

Hybridisation of one-dimensional (1D) and two-dimensional (2D) materials to enhance charge storage has received considerable attention, but a fundamental understanding of the inherent ratio-dependent charge transfer mechanisms associated with the modulation of their molecular interactions is still within the community. Herein, we examined 1D surface oxidised carbon nanotubes (Ox-CNTs) and 2D reduced graphene oxide (rGO) to understand their ratio-dependent charge transfer and molecular interaction dynamics. We found that stepwise ultrasonication and the self-assembly process can control the thermodynamic molecular interactions, which result in rGO and Ox-CNT suspensions not only well dispersed in N,N-dimethylformamide but also self-organised into sandwiched nanoarchitectures. We reveal that the enhanced charge storage performance originated from the Ox-CNT-mediated low contact resistance between the active material and the current collector, and the incorporation of rGO leads to a significant ion diffusion coefficient and gives rise to numerous ion diffusion channels for high rate retention. Through a systematic electrochemical characterisation, we found that the GC5 : 5 hybrids (mass ratio of rGO to Ox-CNT) provide the best compromise-balance ratio between rGO and Ox-CNT for realising a champion energy density (9 W h kg-1) and power density (10 kW kg-1) beyond the state-of-the-art performance of the individual materials. Our results herald the advent of molecular level hybridisation of 1D-2D materials for high-performance electrochemical energy storage.

Thermodynamics of adsorption on nanocellulose surfaces

Understanding the thermodynamic interactions of cellulose nanomaterials with their environment is important to understand the forces behind their self-organization and co-organisation with other compounds, and to be able to use self-assembly to form new functional multicomponent materials. This review analyzes published studies that determined the thermodynamic parameters of the surface interactions of and adsorption of various compounds (proteins, polymers, and small molecules/ions) onto cellulose nanomaterials. We compiled the data reported and performed a meta-analysis for better comparison and to find trends in the published data. We first introduce the methods employed and describe the adsorption isotherm models typically used to describe the adsorption thermodynamics on nanocellulose surfaces. We then discuss and analyze the published results for the interaction of the various compounds with nanocellulose surfaces. The systems that have been reported on most were adsorption of natural binding proteins and various pollutants from water, such as heavy metal ions, dyes, and drugs. Interactions between cellulose surfaces and the cellulose binding module were generally both enthalpy- and entropy-driven, where the negative binding enthalpy indicates the formation of specific interactions between peptides and the carbohydrate backbone. On the other hand, interactions with charged molecules were mostly endothermic and purely entropy-driven, indicating that the adsorption on nanocellulose surfaces can be described as an interaction between opposite charges, where the entropy increase that arises from the release of surface-structured water molecules and counterions from the electronic double layer supplies the major contribution to the free energy of adsorption. We performed a meta-analysis on all published data, and found a linear relationship between ∆H and ∆S with the slope equal to the reference temperature, irrespective of whether the interacting compound is a specific cellulose binding protein, a non-specific binding protein, a polymer, or a small molecule/ion. This indicates that the process of adsorption is the same for all compounds and takes place with a constant change in Gibbs free energy of interaction, ∆G, where a change in interaction enthalpy is offset by change in entropy change upon binding and vice versa.

The electric double layer structure modulates poly-dT25 conformation and adsorption kinetics at the cationic lipid bilayer interface.

The conformation and adsorption kinetics of oligonucleotides at lipid membrane interfaces are crucial to their biological functions, but are yet not clearly understood. Poly-dT oligonucleotide molecules have been widely used as primers for reverse translation of RNA molecules, as well as a surface recognition agent for mRNA purification and extraction. In this research, the adsorption processes of poly-dT25 on lipid membranes in different ionic solutions were investigated by sum frequency generation vibrational spectroscopy (SFG-VS) together with a single molecule tracking technique in situ and in real time. These systematic studies provide us with molecular insight into the chemical and physical nature of oligonucleotide-membrane interactions, and show us how the electric double layer (EDL) structure changes the conformation and adsorption kinetics of oligonucleotides. The SFG-VS results indicate that an increase of ionic concentration not only decreases the adsorption density of oligonucleotides but also changes the conformation of oligonucleotides from an elongated conformation to a coiled conformation, causing stronger thermodynamic interactions with membranes, as demonstrated by single molecule tracking techniques. It is also shown that the ionic solution can tune the balance between the surface diffusion rate and solution diffusion rate of oligonucleotides significantly. These results demonstrated that the spectra and kinetics collected by in situ label-free SFG-VS detection and the single molecular tracking technique can provide new molecular insights into the mechanisms of oligonucleotide-membrane interactions. These new understandings may help researchers to control the assembly of oligonucleotide-liposome complexes and to improve the efficiency of transportation and delivery of oligonucleotide molecules.

Thermal properties of products based on ABS / PC

Polymer blends are capable of providing materials with extended useful properties beyond the range that can be obtained from single polymers. Acrylonitrile-butadiene-styrene and polycarbonate blends are important industrial materials, especially, in the machine building industry, as ABS improves the processing properties of parts and their toughness, and they also feature positive thermodynamic interaction between PC and styrene-acrylonitrile (SAN) copolymer as a part of ABS. DSC method was used to study the thermal properties of ABS and ABS/PC blends with various ratios. The result from this work shows that abnormal endothermic effect in the ABS glass transition region implies an inadequate manufacturing process for automotive components. The paper studied the influence of ABS/PC blend ratios on the value of glass transition temperature and delta Cp, and it was found that the Tg value for SAN/PC increased with decreasing ABS for ABS/PC blends with mass ratio of 75/25, 60/40, 50/50.

Characterizing Drug-Polymer Bead Interactions Using Isothermal Titration Calorimetry

Isothermal titration calorimetry was used to investigate thermodynamic and kinetic binding interactions between 4 clinically relevant drugs: doxorubicin (Dox), irinotecan (Iri), mitoxantrone (Mitox), and topotecan (Topo) and a range of commercially available embolization microspheres. Five drug-eluting beads were chosen to consider the effect of bead size (ranging from 70-150 μm to 500-700 μm) and bead type (sulfonate-modified polyvinylalcohol hydrogel, known commercially as DC BeadM1™, and a sulfonate-modified polyethylene glycol hydrogel bead, known commercially as LifePearl™). The molar ratio of drug to SO3− was found to be 0.9:1, 0.8:1, 0.4:1, and 0.9:1 for Dox, Iri, Mitox, and Topo, respectively. These findings indicate the steric effects of drug shape, charge, and size on binding ability. Four distinct bead sizes all produced drug:bead binding ratios of >0.9:1 doxorubicin:SO3−, thus indicating that bead size does not affect binding stoichiometry. Interestingly, bead size did affect the rate of binding as bead size was found to be indirectly proportional to binding rate. Finally, it was found for the sulfonate-modified polyethylene glycol hydrogel beads that doxorubicin binding was faster (at certain ratios of drug to bead) than that for the sulfonate-modified polyvinylalcohol hydrogel yet was maximal at a drug to bead ratio of only 0.7:1.

Aggregation behaviour of tetracaine hydrochloride with Gemini surfactants and the formation of silver nanoparticles using drug-Gemini surfactants mixture

This study aimed to encapsulate drug into the silver nanoparticles (AgNPs) by using drug-Gemini surfactant mixed aggregate. The applicability of drug-surfactant based AgNPs is to carry the maximum amount of drug during the drug delivery process. The nano-size mixed aggregate was prepared by a local anaesthetic amphiphilic drug, tetracaine hydrochloride (TC) and Gemini surfactants, pentamethylene-1, 5-bis(tetradecyldimethylammonium bromide) (GS-5, 14-5-14) and hexamethylene-1,6-bis(tetradecyldimethylammonium bromide) (GS-6, 14-6-14). Surface tension and conductance measurements were used to determine the physiological and thermodynamic interaction parameters of TC-GS-5/GS-6. The negative βm values suggested as the synergistic interactions observed between TC and GS-5/GS-6 mixed aggregate. The TC-GSs mixture was used to stabilizing silver nanoparticles (AgNPs) with a different mole fraction αTC 0.0–0.99 in aqueous media. The resulting AgNPs characterized by UV–Vis spectroscopy and transmission electron microscopy (TEM). Dynamic light scattering (DLS) suggested that the different types of aggregate formed in aqueous media depending on the internal packing arrangements of TC-GS-5/GS-6. The mole fraction base formulation of drug-surfactant could control the mixed aggregates which could be used to formed drug-surfactant based nanoparticles to enhance the performance of drug delivery.

DbMPIKT: a database of kinetic and thermodynamic mutant protein interactions

BackgroundProtein-protein interactions (PPIs) play important roles in biological functions. Studies of the effects of mutants on protein interactions can provide further understanding of PPIs. Currently, many databases collect experimental mutants to assess protein interactions, but most of these databases are old and have not been updated for several years.ResultsTo address this issue, we manually curated a kinetic and thermodynamic database of mutant protein interactions (dbMPIKT) that is freely accessible at our website. This database contains 5291 mutants in protein interactions collected from previous databases and the literature published within the last three years. Furthermore, some data analysis, such as mutation number, mutation type, protein pair source and network map construction, can be performed online.ConclusionOur work can promote the study on PPIs, and novel information can be mined from the new database. Our database is available in http://DeepLearner.ahu.edu.cn/web/dbMPIKT/ for use by all, including both academics and non-academics.

On the miscibility of PVDF/PMMA polymer blends: Thermodynamics, experimental and numerical investigations

In this paper the miscibility of PVDF/PMMA blends was studied using different approaches: experimental tests, thermodynamics and numerical simulation. The first part of this study is devoted to the experimental work and aims to investigate the miscibility of blends by different experimental techniques. First, blends of PVDF/PMMA at different ratios were compounded and characterized using physico-chemical and rheological methods. The effect of PMMA content on the crystallization behavior of PVDF in the blend was experimentally investigated. At a second stage, the thermodynamic interaction parameter of Flory-Huggins was evaluated as a function of the PMMA proportion in the blends based on the experimental data related to the PVDF melting point and enthalpy. Besides, a numerical method has been developed using Fluent Ansys software to describe the coalescence phenomenon under different scenarios of viscosity ratios and grain sizes of polymers. The confrontation of the code simulation results with the experimental and thermodynamic approaches has shown a good agreement for reproducing the behavior of miscible polymers as well as their aptitude to form a homogeneous blend.

Aspects regarding the efficiency of nanosilica as an interfacial compatibilizer of a polypropylene/ethylene vinyl-acetate immiscible blend

The effects of blending sequence and residence time on the efficiency of nanosilica as an interfacial compatibilizer of an immiscible blend of polypropylene and ethylene vinyl-acetate (PP/EVA) with unstable droplet-matrix morphology, melt-compounded in a twin-screw extruder, was investigated. Morphological analysis revealed that the nanosilica particles are adsorbed at the blend interface, irrespective of the processing conditions adopted, which is in good agreement with predictions based on the thermodynamic interactions, kinetics of mixing and rheological parameters. It was observed that the effectiveness of interfacial nanosilica in the compatibilization of the PP/EVA blend is greatly dependent on the mixing time, and the blending sequence is less important. The size of the EVA droplets is reduced when PP/EVA blends are processed with longer residence times, and increases with shorter mixing times. The results reported herein and in a previous publication [Polym Test 34 (2014) 175–182] suggest that the interfacial nanosilica layer does, in fact, inhibit the coalescence while at the same time hindering the break-up of EVA droplets during the PP/EVA melt blending, with the net effect being dependent on the magnitude of these two time-related mechanisms.

Measuring macromolecular size distributions and interactions at high concentrations by sedimentation velocity

In concentrated macromolecular solutions, weak physical interactions control the solution behavior including particle size distribution, aggregation, liquid-liquid phase separation, or crystallization. This is central to many fields ranging from colloid chemistry to cell biology and pharmaceutical protein engineering. Unfortunately, it is very difficult to determine macromolecular assembly states and polydispersity at high concentrations in solution, since all motion is coupled through long-range hydrodynamic, electrostatic, steric, and other interactions, and scattering techniques report on the solution structure when average interparticle distances are comparable to macromolecular dimensions. Here we present a sedimentation velocity technique that, for the first time, can resolve macromolecular size distributions at high concentrations, by simultaneously accounting for average mutual hydrodynamic and thermodynamic interactions. It offers high resolution and sensitivity of protein solutions up to 50 mg/ml, extending studies of macromolecular solution state closer to the concentration range of therapeutic formulations, serum, or intracellular conditions.

A mechanistic approach for the optimization of loperamide loaded nanocarriers characterization: Diafiltration and mathematical modeling advantages

Oral bioavailability of loperamide is restricted by its limited absorption in the gastrointestinal tract due to its poor aqueous solubility and its P-glycoprotein (Pgp) substrate characteristic. In addition, ammonium methacrylate copolymers have shown to have mucoadhesive properties, whereas poloxamer 188, has been suggested as a Pgp inhibitor. Thus, in this work, we evaluate conditions that affect physicochemical parameters of ammonium methacrylate/poloxamer 188-based nanocarriers loaded with loperamide hydrochloride. Nanocarriers were synthesized by nanoprecipitation, enhancing loperamide encapsulation efficiency by modifying the aqueous phase to basic pH. The isolation of the non-encapsulated drug fraction from the nanocarriers-incorporated fraction was conducted by centrifugation, ultrafiltration, vacuum filtration and diafiltration. The last method was effective in providing a deeper understanding of drug-nanocarrier loading and interactions by means of modeling the data obtained by it. Through diafiltration, it was determined an encapsulation efficiency of about 93%, from which a 38% ±6 was shown to be reversibly (thermodynamic interaction) and a 62% ±6 irreversibly (kinetic interaction) bound. Finally, release profiles were assessed through empirical and semi-empirical modeling, showing a biphasic release behavior (burst effect 11.34% and total release at 6 h = 33% ±1). Thus, encapsulation efficiency and release profile were shown to have a strong mathematical modeling-based correlation, providing the mechanistic approach presented in this article a solid support for future translational investigations.

Krill-Herd-Based Investigation for Energy Saving Opportunities in Offshore Liquefied Natural Gas Processes

For offshore natural gas liquefaction operation, the single mixed refrigerant process is considered as one of the best and most suitable processes. However, multivariable nonlinear thermodynamic interactions among operating conditions and flow rates of mixed refrigerant ingredients lead to energy losses, which ultimately contributes to high energy consumption for liquefied natural gas production. The present work investigates the energy saving opportunities in the single mixed refrigerant liquefaction process through “krill-herd” strategy which is based on the biological flocking (herding) behavior of individual krill. To find the energy saving opportunities, the krill-herd approach effectively reduced the exergy losses of the compression units and cryogenic heat exchanger up to 18.6 and 41.1%, respectively, as compared to the published liquefaction process. The figure of merit was found as 27.0% in the krill-herd-optimized single mixed refrigerant process, whereas it was 22.2% in the base case.

A three-dimensional multibody tire model for research comfort and handling analysis as a structural framework for a multi-physical integrated system

A tire is an extremely integrated and multi-physical system. From only a mechanical point of view, tires are represented by highly composite multi-layered structures, consisting of a multitude of different materials, synthesized in peculiar rubber matrices, to optimize both the performance and the life cycle. During the tire motion, due to the multi-material thermodynamic interaction within the viscoelastic tire rubber matrix, the dynamic characteristics of a tire may alter considerably. In the following paper, the multibody research comfort and handling tire model is presented. The main purpose of the research comfort and handling tire is to constitute a completely physical carcass infrastructure to correctly transmit the generalized forces and torques from the wheel spindle to the contact patch. The physical model structure is represented by a three-dimensional array of interconnected nodes by means of tension and rotational stiffness and damper elements, attached to the rim modeled as a rigid body. Research comfort and handling tire model purpose is to constitute a structural physical infrastructure for the co-implementation of additional physical modules taking into account the modification of the tire structural properties with temperature, tread viscoelastic compound characteristics, and wear degradation. At the stage, the research comfort and handling tire discrete model has been validated through both static and dynamic shaker test procedures. Static test procedure adopts contact sensitive films for the contact patch estimation at different load and internal pressure conditions, meanwhile the specifically developed sel test regards the tire dynamic characterization purpose at the current stage. The validation of the tire normal interaction in both static and dynamic conditions provided constitutes a necessary development step to the integration of the tangential brush interaction model for studying the handling dynamics and to the analysis of the model response on the uneven surfaces.

Utilization of metal–polymer interactions for self-aligned directed self-assembly of device relevant features

Self-aligned strategies are required because today’s feature sizes are beyond the resolution limit of the exposure tools. One self-aligned strategy is directed self-assembly (DSA), where block copolymers (BCP) are thermodynamically driven to self-align with a lithographically defined template with chemical contrast and/or topography. It would be particularly advantageous to also encode existing structures into thermodynamic information, then thermodynamics would cause BCP to self-align to these existing structures rectifying placement error. These existing features could be cut masks, which are required to fabricate devices from line and space arrays, or they could be interconnects. Here, we show a technique, by which metal–polymer interactions can be used in place of polymer–polymer interactions. These metal–polymer interactions, which cannot be adequately described by conventional surface energy comparisons, allow for a true self-aligned process. We begin by classifying process relevant metals including gold, aluminum, copper, tungsten, and cobalt, based upon their thermodynamic interactions with poly(styrene-block-methyl methacrylate). We then created guide patterns using metal and dielectric line space arrays. These patterns, when combined with DSA, allow for lines and space patterns to be self-aligned to any exposed metal features and reduce process constraints on exposure tools. Our process can also be used to align line and space patterns to metal layers during the back end of the line processing. A similar process could also be used to guide contact hole shrink to correct for placement error in the initial lithographic template.

Extreme Sea Level Rise off the Northwest Coast of the South China Sea in 2012

Tide gauge data are used to investigate sea level variability off the northwest coast of the South China Sea (SCS) in 2012, and a significant sea level elevation with a magnitude approaching 79 mm is observed. Analysis suggests that an abnormal sea surface heat flux and freshwater flux may have contributed to this abnormal rise in sea level, together with the remote influence of an ENSO event. Further investigation shows that the event was dominated by the positive freshwater flux, where large volumes of water entered the ocean, and a maximum is centered to the south of Guangdong province, China. Simultaneously, a positive anomalous heat flux occurred in the northwestern part of the SCS, which is considered to have made a positive contribution to the high local sea level elevation. In addition to the heat flux, the ENSO event also had a significant effect on the event, where the La Nina-induced northwest Pacific cyclone contributed to sea level rise over the northwestern SCS through dynamic and thermodynamic interactions.

Thermodynamic Interactions Study of Some Ethylene Glycols in Aqueous Aniline Solutions at Different Temperatures: An Acoustical and Volumetric Approach

With densities and ultrasonic speeds, interactions of aniline with ethylene glycol, diethylene glycol, and triethylene glycol are measured at T = (293.15–308.15) K. From the densities, the (apparen...

Derivation and numerical profile analysis of a hierarchically formulated microscopic model of hemoglobin oxygen binding

To address complex thermodynamic systems with multiple interacting events, we have developed the concept of hierarchical thermodynamic interactions. In this study, this concept is extended to protein-ligand systems with similar but not identical protein subunits, and applied to the analysis of previously published NMR and UV–vis monitored hemoglobin oxygen binding data. Non–linear regression provided estimated errors for statistically significant parameters, but not for null (zero) valued parameters. A numerical/graphical profiling approach was therefore used to assess confidence intervals and correlations for both the statistically significant and nulled valued parameters in this model. Individual parameters were set to fixed values around their best–fit value, and the subset of statistically significant parameters re–minimized against hemoglobin oxygen binding data. Plots provide a graphical representation of parameter confidence intervals and correlations, and demonstrate how the two different data types – UV–vis and NMR – constrain the range of values for each parameter. This analysis further illustrates the value of hierarchically formulated models for the analysis of complex state systems, and illuminates the complexity of parameter space around the derived minimum microscopic model of hemoglobin oxygen binding.

Microphase structure of polyurethane-polyurea copolymers as revealed by solid-state NMR: Effect of molecular architecture

1H spin-diffusion solid-state NMR, in combination with other techniques, was utilized to investigate the effect of molecular architecture, solubility parameter of hard and soft segments, and their length on the domain size, interphase thickness and degree of phase separation in polyurethane-ureas based on oligomeric 4,4′-diisicyanate diphenylmethane, methylene-bis-(2-chloroaniline) and polyols based on polyethylene oxide, polypropylene oxide and polybutadiene with different length. Polyurethane-ureas based on polyethylene oxide soft blocks did not form rigid domains as a result of absence of microphase separation. The domain sizes of the hard segments in polyurethane-ureas under study practically did not show any dependence on their composition, but interphase thicknesses are higher for systems based on polybutadiene soft blocks. This indicates that the degree of phase separation depends strongly not only on the binary thermodynamic interaction between hard and soft segments in polyurethane-ureas, but is also influenced by their molecular architectures in the experimental temperature range.