Stern Theory Research Articles

Electrochemical Hydrophobic Tri‐layer Interface Rendered Mechanically Graded Solid Electrolyte Interface for Stable Zinc Metal Anode

AbstractThe aqueous zinc‐ion battery is promising as grid scale energy storage device, but hindered by the instable electrode/electrolyte interface. Herein, we report the lean‐water ionic liquid electrolyte for aqueous zinc metal batteries. The lean‐water ionic liquid electrolyte creates the hydrophobic tri‐layer interface assembled by first two layers of hydrophobic OTF− and EMIM+ and third layer of loosely attached water, beyond the classical Gouy–Chapman–Stern theory based electrochemical double layer. By taking advantage of the hydrophobic tri‐layer interface, the lean‐water ionic liquid electrolyte enables a wide electrochemical working window (2.93 V) with relatively high zinc ion conductivity (17.3 mS/cm). Furthermore, the anion crowding interface facilitates the OTF− decomposition chemistry to create the mechanically graded solid electrolyte interface layer to simultaneously suppress the dendrite formation and maintain the mechanical stability. In this way, the lean‐water based ionic liquid electrolyte realizes the ultralong cyclability of over 10000 cycles at 20 A/g and at practical condition of N/P ratio of 1.5, the cumulated areal capacity reach 1.8 Ah/cm2, which outperforms the state‐of‐the‐art zinc metal battery performance. Our work highlights the importance of the stable electrode/electrolyte interface stability, which would be practical for building high energy grid scale zinc‐ion battery.

Compressibility Behavior of Bentonites by Stern Theory based on Constant Surface Charge Conditions

AbstractThe compressibility behavior of clays is governed by the electrical double layer formed around the clay particles. The Gouy-Chapman diffuse double layer theory is often utilized to predict the compressibility behavior of clay minerals. The theory does not consider the effect of the size of the cations, however, and thus predicts unrealistically small void ratios for compacted bentonites under large mechanical pressures expected in high-level nuclear waste-repository applications. In this study, the Stern layer was introduced to incorporate the cation size effect in the prediction of the compressibility behavior of bentonites. The overall diffuse double-layer thickness at large pressures was much smaller than the initially assumed Stern layer thickness based on the exchangeable cation size for all the bentonites studied. A compressible Stern layer was, therefore, considered for the first time in the prediction of the compressibility behavior of bentonites. The compression behavior of the Stern layer under the applied loading is influenced by the ratio of the mid-plane to the Stern potential, which is dependent on the type and composition of the exchangeable cations on the clay surface. Stern layer compression was initiated when the potential ratio was in the range 0.65–0.75 for bentonites with various surface cation characteristics. The incorporation of cation size and a compressible Stern layer provided significant improvements over the existing models in predicting the compressibility behavior of bentonites over a wide pressure range. The compressibility data predicted by the proposed model showed very good agreement with the data measured for five bentonites from the literature in the pressure range 0.1–42 MPa.

The evidence interval and the Bayesian evidence value: On a unified theory for Bayesian hypothesis testing and interval estimation.

Interval estimation is one of the most frequently used methods in statistical science, employed to provide a range of credible values a parameter is located in after taking into account the uncertainty in the data. However, while this interpretation only holds for Bayesian interval estimates, these suffer from two problems. First, Bayesian interval estimates can include values which have not been corroborated by observing the data. Second, Bayesian interval estimates and hypothesis tests can yield contradictory conclusions. In this paper a new theory for Bayesian hypothesis testing and interval estimation is presented. A new interval estimate is proposed, the Bayesian evidence interval, which is inspired by the Pereira-Stern theory of the full Bayesian significance test (FBST). It is shown that the evidence interval is a generalization of existing Bayesian interval estimates, that it solves the problems of standard Bayesian interval estimates and that it unifies Bayesian hypothesis testing and parameter estimation. The Bayesian evidence value is introduced, which quantifies the evidence for the (interval) null and alternative hypothesis. Based on the evidence interval and the evidence value, the (full) Bayesian evidence test (FBET) is proposed as a new, model-independent Bayesian hypothesis test. Additionally, a decision rule for hypothesis testing is derived which shows the relationship to a widely used decision rule based on the region of practical equivalence and Bayesian highest posterior density intervals and to the e-value in the FBST. In summary, the proposed method is universally applicable, computationally efficient, and while the evidence interval can be seen as an extension of existing Bayesian interval estimates, the FBET is a generalization of the FBST and contains it as a special case. Together, the theory developed provides a unification of Bayesian hypothesis testing and interval estimation and is made available in the R package fbst.

Cognitive reserve as one of the determinants of the progression of Alzheimer disease.

To assess the validity of Yaakov Stern's theory, which postulates that the first cognitive deficits of Alzheimer disease are delayed in patients with high cognitive reserve, compared to those with low cognitive reserve, but this is subsequently associated with faster cognitive decline when cerebral lesions have reached a certain degree of severity. A retrospective study of 318 patients with Alzheimer disease without associated cerebral disorders, was performed at the Memory Clinic of the University Hospital of Strasbourg. The patients were divided into five groups according to their degree of cognitive reserve, as assessed by their level of education (primary, middle school, intermediate, high school and higher education). Cognitive status was assessed by scores on the Mini Mental Status Examination (MMSE) at the first examination and during follow-up lasting four years or longer. Slopes of cognitive decline were computed and compared between groups using ß linear regression. Patients in the higher education group had higher MMSE scores than those in the other groups at the first consultation, but a statistically significant steeper slope during the follow-up. Our results are consistent with Stern's theoretical model, which assumes that high cognitive reserve is accompanied by compensation mechanisms which hinder the onset of clinical cognitive decline in patients with Alzheimer disease, but that is then associated with a faster decline at a later stage when the reserve is exhausted.

Charging behaviour at the carbonate rock‐water interface in low‐salinity waterflooding: Estimation of zeta potential in high‐salinity brines

AbstractThe study of zeta potential using electro‐kinetic analyzers that measure streaming potential has limitations of measurements to relatively low ionic strength solutions (<0.1 mol/L) due to the threshold limit of streaming potential signal above a certain limit of ionic strength. The objective of this study is to indirectly estimate the zeta potential for higher salinity brine using the zeta potential measurements for low salinity brine, develop an understanding of electrostatic shielding as predicted by the electric double layer (EDL) model, and overcome the limitation of the apparatus. Zeta potential become less negative as ionic strength increases, as per the Gouy–Chapman–Stern theory. It explains the suppression of electro‐kinetic phenomena due to the gradual compression of the diffuse layer. Our calculations show that the zeta potential and the Debye length become nearly constant at higher ionic strength. The ability to estimate zeta potential by the Gouy‐Chapman‐Stern theory at increasing ionic strength is limited. This theory predicts that the concentration of counter‐ions in the Stern layer increases with increasing ionic strength of the brine until the surface charge becomes neutralized and the diffuse layer collapses. However, it ignores the spatial extension of ions. It considers them as a point charge and may not accurately predict the zeta potential at higher ionic strength. The extent of diffuse layer compression is thus limited to the size of the hydrated counter‐ion. It is very unlikely that the measured zeta potential will become zero at higher ionic strength of brines and our calculations show the same.

Cognitive reserve, one of the determinants of the progression of Alzheimer's disease

To appraise the validity of the Yaakov Stern's theory, which postulates that the first cognitive deficits of Alzheimer's disease are delayed in patients with high cognitive reserve, compared to those with low cognitive reserve, but is subsequently associated with faster cognitive decline when cerebral lesions have reached some degree of severity. A retrospective study of 318patients with Alzheimer's disease without associated cerebral disorders, was performed in the Memory Clinic of the University Hospital of Strasbourg. The patients were divided into 5groups according to the degree of cognitive reserve assessed by the level of education (primary, middle school, intermediary, high school and higher education). Cognitive status was assessed by the scores on the Mini Mental Status at the first examination and during a 4-year or more follow-up. Slopes of cognitive decline were computed and compared between groups by ß linear regression. Patients in the higher education group had higher MMSE scores than those in the other groups at the first consultation, but a statistically significant steeper slope during the follow-up. Our results are congruent with the Stern's theoretical model, assuming that high cognitive reserve brings into play compensation mechanisms which hinder the onset of clinical cognitive decline in patients with Alzheimer's disease, but then is associated with a faster decline at a later stage when the reserve is exhausted.

The Learning Strategies in English Subject of Islamic Study Program at IAIN CURUP

The research objective was to find out the PAI students‟ strategies in learning English. The design of the research was presented in quantitative descriptive. The subject of this research was 2nd semester of PAI department students. To know what strategies used, the researcher used Stern theory about Language learning strategies which are divided into five categories namely management and planning, cognitive, communication, interpretational and affective. In collecting the data, the researcher used close-ended questionnaire. The result show that PAI students who got A score used 4 strategies in learning English they are management and planning strategies, cognitive strategies communicative strategies and affective strategies. But affective strategy is more dominant 83.7% as a strategy in learning English. PAI students who got B scores used 3 strategies in learning English they are management and planning strategies, cognitive strategies and affective strategies. Management and planning strategy is more dominant 74.4% as a strategy in learning English. PAI student who got C score 3 strategies in learning English they are cognitive strategies communicative strategies and affective strategies. But cognitive is more dominant 76% as a strategy in learning English. PAI student who got E score used 2 strategies in learning English they are interpretational strategies and affective strategies. But affective strategy is more dominant 90% as a strategy in learning English. Although, the strategies used by student who got A score and E score are alike, however students who got E score do not attend the class, the UTS and UAS properly.

Development of a Capacitance versus Voltage Model for Lithium-Ion Capacitors

The capacitance of Lithium-ion Capacitors (LiCs) highly depends on their terminal voltage. Previous research found that it varies in a nonlinear manner with respect to the voltage. However, none of them modeled the capacitance evolution while considering the physicochemical phenomena that happen in a LiC cell. This paper focuses on developing a new capacitance model that is based on the Stern model of the electrochemical double layer capacitance. The model accounts for the asymmetric V-shape of the C(V) curve, which reflects the variation of the capacitance with respect to the voltage. The novelty of this study concerns the development of a model for LiCs that relies on the fundamental theory of Stern for the differential capacitance. The basic model of Stern is modified in order to account for the hybrid physicochemical structure of LiCs. Moreover, the model was applied to three aged cells to which accelerated calendar aging tests were applied at three voltage values: 2.2, 3 and 3.8 V. A drift of the voltage corresponding to the minimum capacitance was detected for the aged cells. This voltage is related to the neutral state of the positive electrode. The main cause of this phenomenon concerns the loss of lithium ions from the negative electrode of a LiC. In addition, capacitance values decreased after aging, showing an eventual blocking of the pores of the positive electrode. Therefore, the analysis of the C(V) curve was found to be an interesting tool for the interpretation of aging mechanisms.

Electrical Double Layer at Various Electrode Potentials: A Modification by Vibration

This paper proposes a vibration model of ions as an improvement over the conventional Gouy–Chapman–Stern theory, which is used to model the electrical double layer capacitance and to study the ionic dynamics at electrode/electrolyte interfaces. Although the Gouy–Chapman–Stern model is successful for small applied potentials, it fails to explain the observed behavior at larger potentials, which are becoming increasingly important as materials with high charge injection capacities are developed. A time-dependent study on ionic transport indicates that ions vibrate near the electrode surface in response to the applied electric field. This vibration allows us to correctly predict the experimentally observed decreasing differential capacitance at high electrode potential. This new model elucidates the mechanism behind the ionic dynamics at solid–electrolyte interfaces, providing useful insight that may be applied to many electrochemical systems in energy storage, photoelectrochemical cells, and biosensing.

The influence of excluded volume and excess ion polarisability on the capacitance of the electric double layer

ABSTRACTWe apply a modified Poisson–Boltzmann theory which permits ions of different sizes and excess polarisabilities to the study of these properties’ effects on the differential capacitance of the electric double layer. For a planar electrode, we find an analytical expression for the differential capacitance, which is examined in the limits of low- and high-applied potential. In the low potential limit, a reduction of the solution relative permittivity caused by the ion polarisability causes the differential capacitance to decrease above a certain concentration, relative to the Gouy–Chapman–Stern theory. A similar effect is observed for the excluded volume, but only if the ions are of different sizes. In the high potential limit, the differential capacitance decreases inversely with the square root of the applied voltage. In a mixed electrolyte, asymmetries in both ion size and excess polarisability alter the surface adsorption of species: at high potentials, smaller ions displace larger ions and less polarisable ions displace more polarisable ions. The extent of the displacement agrees favourably with experimental data. A further consequence of this displacement is the appearance of a second peak in the differential capacitance, which is enhanced by excess ion polarisability.

Carbon nanotube yarns as strong flexible conductive capacitive electrodes

Carbon nanotube (CNT) yarn, consisting of 23μm diameter CNT filaments, can be used as capacitive electrodes that are long, flexible, conductive and strong, for applications in energy and electrochemical water treatment. We measure the charge storage capacity as function of salt concentration, and use Gouy–Chapman–Stern theory to describe the data. CNT yarn can also be used as conductive scaffold for the application of a porous activated carbon (AC) layer. We show the potential of CNT yarn for the generation of electrical energy from environmental entropy differences, by coating yarn (both with and without AC coating) with ion-exchange membranes (IEMs) and generating power from the salt concentration difference between river water and seawater. The use of flexible and conductive CNT yarns as capacitive electrodes and electrode scaffolds breaks with the paradigm of planar static electrodes, and opens up a range of alternative designs for electrochemical cells with enhanced performance.

Capillary model of electroosmotic transport of the free solvent through ion-exchange membranes

An equation for calculating the transport number of a free solvent transferred through an ion-exchange membrane using the physicochemical and structural characteristics of the latter and the properties of an equilibrium solution was derived on the basis of the Stern theory of the electric double layer and the concept that represents the ion-exchange membrane as a capillary system. The model calculations showed that modification of the ion-exchange membrane, which decreased the effective pore radius to 2.0–3.5 nm, almost completely suppressed the electroosmotic transport of free water in the membrane system. The experimentally determined tendencies of variation of water electrotransport due to changes in the structural type of membrane and solution concentration agree well with the suggested model description.

Effect of Stern-layer on the compressibility behaviour of bentonites

The Stern theory as applicable to interacting parallel clay platelet systems was used to study the compressibility behaviour of bentonites. For a constant surface electrical potential, the distribution of the total electrical charge among the Stern-layer and the Gouy-layer was found to have significant influence on the electrical potential at the midplane between clay platelets. Consideration of the Stern-layer was found to reduce the repulsive pressure or the swelling pressure between clay platelets at large platelet spacing, whereas the repulsive pressure increased significantly when the interacting Gouy-layers were pushed aside. A far greater repulsive pressure was noted for Ca-bentonite than that occurred for Na-bentonite at a platelet distance close to 1.0 nm. Similarly, strong interaction between clay platelets was noted due to suppressed Gouy-layers when the bulk fluid concentration was increased. The repulsive pressure generated due to the overlapping of the Stern-layers was found to be sensitive to changes in the specific adsorption potential, the dielectric constant of the pore fluid in the Stern-layer, and the surface electrical potential. Comparisons of the calculated pressure–void ratio relationships from the Stern theory and the Gouy-Chapman diffuse double layer theory with the experimental consolidation test results of Na- and divalent-rich bentonites showed that, in general, the Stern theory improved the predictions of pressure–void ratio relationships, particularly for pressures greater than 100 kPa; however, strong agreements were lacking in all the cases studied.

Analogy and metaphor in music therapy. Theory and practice

Two theoretical models of music therapy have been developed and discussed in the past decade. The theory of metaphor as proposed by Aigen is based on the schema theory of Lakoff and Johnson. It explains the connection between musical experience and felt experience by means of its interconnection with metaphors that are based on movement experience in space. The theory of analogy as proposed by Smeijsters is based on Stern's theory of vitality forms and Damasio's theory of the core self. Analogy explains the musical experience by means of the isomorphism between the forms of vitality affects in the core self and the forms of musical phrases. This discussion is highly relevant for music therapists because it is important to explain why music therapy works. Theoretical explanation of music therapy is also important because it is basic to the development of therapy methods and techniques. This article discusses both theories on the basis of theoretical concepts and case studies, arguing that metaphor and analogy both are music-centered concepts. Metaphor is described as a space-oriented perspective, analogy is described as a time-oriented perspective. Both perspectives can explain different music therapy experiences or describe the same music therapy experiences from a different perspective.

Commercial Exploitation or Protected Use? Stern v. Delphi Internet Services Corporation and the Erosion of the Right of Publicity

This article addresses the repercussions of Stern v. Delphi Internet Services Corporation and argues that the decision in Stern opens the door to a broader interpretation of “newsworthiness” and “public interest” that will enable advertisers broader First Amendment protections when using “unauthorized” likenesses. This article posits that artful advertisers could very well use the theory of Stern as a basis for virtually ensuring that every “unauthorized likeness” will enjoy First Amendment protection and not be considered as violative of the right of publicity.

Simple Description of the Capacitance of the Double Layer of a High Concentration Electrolyte

Recently, the electrochemical properties of an ionic liquid have received increasing attention. The simplest model of an ionic liquid is a fluid of charged hard spheres, all of which have the same diameter (the restricted primitive model or RPM), and the simplest theory of the double layer formed by an electrolyte is the Gouy−Chapman−Stern (GCS) theory. This theory is moderately useful for a low concentration electrolyte but is incorrect for a high concentration electrolyte, such as an ionic liquid. Among other things, the GCS theory predicts that the capacitance has a minimum at small electrode charge. In contrast, the capacitance of the double layer of an ionic liquid often has a maximum at small electrode charge. This is predicted by simulations and the modified Poisson−Boltzmann (MPB) theory. The mean spherical approximation (MSA) seems to agree with the simulations and MPB but is applicable only for small electrode charge. In this note we graft the MSA onto the GCS result and obtain qualitatively reasonable results for the capacitance that may be of use. This result is identical to the GCS theory at small concentrations and to the MSA at small electrode charge. A maximum is found for small electrode charge and high concentration.

A classical density functional theory for interfacial layering of ionic liquids

Ionic liquids have attracted much recent theoretical interest for broad applications as environmentally-friendly solvents in separation and electrochemical processes. Because of the intrinsic complexity of organic ions and strong electrostatic correlations, the electrochemical properties of ionic liquids often defy the descriptions of conventional mean-field methods including the venerable, and over-used, Gouy–Chapman–Stern (GCS) theory. Classical density functional theory (DFT) has proven to be useful in previous studies of the electrostatic properties of aqueous electrolytes but until recently it has not been applied to ionic liquids. Here we report predictions from the DFT on the interfacial properties of ionic liquids near neutral or charged surfaces. By considering the molecular size, topology, and electrostatic correlations, we have examined major factors responsible for the unique features of electric-double layers of ionic-liquid including formation of long-range and alternating structures of cations and anions at charged surfaces.

Generalized stern models of the electric double layer considering the spatial variation of permittvity and finite size of ions in saturation regime.

The interaction between a charged metal implant surface and a surrounding body fluid (electrolyte solution) leads to ion redistribution and thus to formation of an electrical double layer (EDL). The physical properties of the EDL contribute essentially to the formation of the complex implant-biosystem interface. Study of the EDL began in 1879 by Hermann von Helmholtz and still today remains a scientific challenge. The present mini review is focused on introducing the generalized Stern theory of an EDL, which takes into account the orientational ordering of water molecules. To ascertain the plausibility of the generalized Stern models described, we follow the classical model of Stern and introduce two Langevin models for spatial variation of the relative permittivity for point-like and finite sized ions. We attempt to uncover the subtle interplay between water ordering and finite sized ions and their impact on the electric potential near the charged implant surface. Two complementary effects appear to account for the spatial dependency of the relative permittivity near the charged implant surface — the dipole moment vectors of water molecules are predominantly oriented towards the surface and water molecules are depleted due to the accumulation of counterions. At the end the expressions for relative permittivity in both Langevin models were generalized by also taking into account the cavity and reaction field.

Combining electrochemistry and direct force measurements: from the control of surface properties towards applications

Direct force measurements contributed in the last years much to our understanding of the diffuse double layer of charged interfaces in electrolyte solutions. Such measurements have been performed with the atomic force microscope or the surface force apparatus. This review gives an overview over the recent studies based on force measurements with electrode surfaces. Not only bare metal electrodes but also electrodes modified by different organic layers, including electroactive films, have been studied by these techniques. Direct force measurements indicate that further effects besides classical Gouy–Chapman–Stern theory have to be taken into consideration in order to describe the force profiles. In addition to the long-range forces also the adhesion between surfaces can be tuned by potentiostatic control. New single-molecule techniques based on the atomic force microscope allow to probe the extension of polymer strands or their desorption from solid interfaces. In combination with electrochemistry, it became now possible to tune the desorption behavior of polymer strands or to measure the electromechanical coupling of motors from single strands of electroactive polymers.

A mean spherical approximation study of the capacitance of an electric double layer formed by a high density electrolyte

In a recent grand canonical Monte Carlo simulation and modified Poisson–Boltzmann (MPB) theoretical study of the differential capacitance of a restricted primitive model double layer at high electrolyte densities, Lamperski, Outhwaite and Bhuiyan (J. Phys. Chem. B 2009, 113, 8925) have reported a maximum in the differential capacitance as a function of electrode charge, in contrast to that seen in double layers at lower ionic densities. The venerable Gouy–Chapman–Stern (GCS) theory always yields a minimum and gives values for the capacitance that tend to be too small at these higher densities. In contrast, the mean spherical approximation (MSA) leads to better agreement with the simulation results than does the GCS approximation at higher densities but the agreement is not quite as good as for the MPB approximation. Since the MSA is a linear response theory, it gives predictions only for small electrode charge. Nonetheless, the MSA is of value since it leads to analytic results. A simple extension of the MSA to higher electrode charges would be valuable.