Passive State Research Articles

Study on the compressive performance of hyperelastic seismic isolation materials under passive confinement of surrounding rock simulated by CFRP tubes

Tunnel engineering has played a significant role in the development of human society. However, due to geological constraints, tunnels are prone to losing stability and safety under strong seismic forces. High-elasticity, super-tough polymer-inorganic composite tunnel isolation materials (PTIM), based on polyurethane elastomers, can meet the requirements for tunnel isolation, but research on their passive confinement mechanical properties remains insufficient. This study designed an experimental method to simulate the passive confinement state of tunnel isolation materials. The method uses CFRP tube confinement and core loading to replicate the actual stress conditions within a confined tunnel space. Based on the experimental data, a constitutive model for PTIM under passive confinement was established. The results show that the initial elastic modulus (Ec0) of PTIM and the CFRP confinement stiffness (K) are significantly correlated with the material's stress-strain curve, axial peak stress and strain, circumferential strain, compressive performance, and elastic modulus. Based on these mechanical properties as characteristic values, a tri-linear constitutive model for PTIM with different mix ratios under various confinement stress conditions was established. The high degree of agreement between the predicted data and the experimental data validates the effectiveness of the model.

Influence of graphene nanoplatelets on the passivation and corrosion resistance of carbon steel bars in ordinary portland cement mortar

This study investigates the influence of adding graphene nanoplatelets (GNPs) to mortar mixtures on the corrosion behavior of embedded carbon steel rebars. Mortar mixtures were prepared with a water-to-cement ratio of 0.42 and GNP replacement levels of 0, 0.05, and 1 percent by weight of cement. After 28 days of curing in an environmental chamber, the passivity and kinetics of chloride induced corrosion initiation for the rebars were studied using a suite of electrochemical tests. The results suggest that incorporating GNPs at low concentrations may enhance the passivity and resistance to chloride-induced corrosion of carbon steel rebars; however, due to the large variability in the data, the findings are inconclusive. Potentiodynamic measurements revealed that the estimated average polarization resistance of steel rebars in 0 G (no GNP), 0.05 G, and 1 G specimens in the passive state was on average −182.3, −276.5, and −304.2 kΩ, respectively. Upon exposure to chloride solution, 0 G specimens, with an average corrosion potential of −600 mV vs. SCE, exhibited the lowest resistance, whereas 0.05 G specimens, with an average of −491 mV vs. SCE, showed the highest corrosion resistance. Results from electrical impedance spectroscopy were consistent with the potentiodynamic findings. Surface characterization also revealed that the inclusion of GNPs does not alter the surface roughness of the interface between steel rebar and paste. However, the interface between rebar ribs and mortar paste had higher surface roughness and porosity in all specimens regardless of GNPs replacement level. Visual inspections confirmed that the area around the rebar ribs at the interface is more conducive to the formation of crevice and pitting corrosion.

Research on the Corrosion Resistance and Cytotoxicity of Medical Forged Co-28Cr-6Mo Alloy

Co-Cr-Mo alloy as a human body implant material has a long history, because of its excellent corrosion resistance and biocompatibility, and is widely used in human hip joint materials. Co-Cr-Mo alloy in the human body is often in a passivation state; the formation of dense oxide film on the alloy surface prevents further corrosion of the alloy. The main component of the passivation film is the oxide of Cr, so a layer of oxide film formed by Cr on the surface of Co-Cr-Mo alloy is the reason for its good corrosion resistance. In biocompatibility, cytotoxicity is the first choice and necessary option for biological evaluation, and cytotoxicity can quickly detect the effect of materials on cells in a relatively short time. Therefore, this research conducted a comparative evaluation on the corrosion resistance and biocompatibility of forged Co-Cr-Mo alloys produced in domestic and foreign alloys in line with medical standards. Three simulated human body fluids and Princeton electrochemical station were selected for corrosion resistance experiments, and it was found that the corrosion resistance of four alloys in sodium citrate solution inside and outside China would be reduced. All the alloys exhibit secondary passivation behavior in Hanks solution, which improves the corrosion resistance of the alloys. According to the self-corrosion potential Ecorr analysis, the corrosion resistance of domestic B alloy is the best, while that of foreign R31537 alloy is poor. In the biocompatibility experiment, the biocompatibility of Co-Cr-Mo alloy was evaluated through the measurement of contact Angle and cytotoxicity reaction. The experimental results show that Co-Cr-Mo alloy is a hydrophilic material, and the contact Angle of foreign R31537 alloy is smaller, indicating that the surface of R31537 alloy is more suitable for cell adhesion and spreading. According to the qualitative and quantitative analysis of the cytotoxicity experiment, the toxic reaction grade of domestic A, B and R31537 alloy is grade 1, the toxic reaction grade of C alloy is grade 2, and C alloy has a slight toxic reaction.

The Suppression Mechanisms of Passive Memory in Visual Working Memory: The Evidence from Electrophysiology.

Recent studies of visual working memory (VWM) underscore a structured hierarchy of storage states. Memories that are not immediately relevant to the task at hand but are essential for later use are transferred to a passive state, which operates independently of actively maintaining and manipulating current memories. Note that stimulating passive memory forcefully can reactivate it into an active state, resulting in a competition with active memory. Thus, to remain stable representations for both states within VWM, passive memory might involve sustained suppression during activity-silent maintenance to prevent reactivation from disrupting the current active storage. To investigate this, we analyzed lateralized electrophysiology signals while human participants (both women and men) were engaged in a sequential presentation memory task across two experiments. The results revealed positive contralateral delayed activity components and lateralized alpha enhancement for passive memory, neural indicative of suppression on passive storage. In addition, the suppression effect was independent of the memory load in both the active and the passive states. These findings support the notion of sustained suppression during activity-silent maintenance of passive memory, facilitating the stable maintenance of distinct storage states and advancing our understanding of the dynamic coding framework in VWM.

Stability of long uniform slopes in cohesionless soils with seepage parallel to slope surface

A method is employed in this paper for the computation of earth pressures mobilized by landslides in cohesionless soil slopes against retention systems. For calculation purposes, the water table is taken to be parallel to the slope and at a depth zw. Steady seepage is assumed to be taking place in a direction parallel to the slope. End effects are taken into account. In the upper part of the slope, the soil is considered to be in a Rankine active state of equilibrium and a Rankine passive state of equilibrium is assumed to reign in the lower part of the slope. The infinite slope concept is applied to the central part of the slope. The theory shows that the slip surfaces below the water table are curved, not straight lines.The theoretical procedure developed in the present paper was applied to the analysis of an initially unstable long slope that failed in spite of the presence of a shear pile wall made up of a row of closely spaced 1m-diameter bored piles. The retaining system was designed based on the Rankine active state of equilibrium, using a factor of safety of about 1.7. It is shown that, as the shear pile wall was located in the lower part of the slope, it was subjected to a much greater force, compatible with a Rankine passive state of equilibrium, corresponding to a factor of safety of about 0.9. As a result, the shear pile wall was doomed to fail.

Analytical solution of overlying pressure for shallowly buried underwater box tunnel: A case study of box jacking in Suzhou, China

Accurately predicting the overlying pressure is crucial for determining an appropriate cover depth of underwater box tunnels to avoid the uplifting failure. Based on the project of box jacking crossing the Beijing-Hangzhou Grand Canal in Suzhou, the characteristics of overlying pressure variation during tunneling are investigated. The monitoring results reveal that the fluctuation of overlying pressure is weakened during the rapid tunneling process. A modified analytical model for vertical earth pressure is conceived, in which the active and passive limit states for multi-layered soils are both considered. The probable range of overlying pressure obtained by the proposed model is suitable to cover the actual values. The anti-floating behavior of underwater box tunnels for two different working conditions is discussed by calculating the minimum cover depth. Using the calibrated analytical models, a parametric study is conducted to explore the influence of injection pressure, hardened slurry unit weight, soil internal friction angle, soil cohesion, and tunnel geometry. It is found that the injection pressure during the construction process is crucial for determining the necessary cover depth, and the change of box tunnel height makes it easier to trigger the variation of minimum cover depth.

Cathodic Protection of Carbon Steel in Soil: A Study of Induced Passivation

Two-month experiments were carried out with carbon steel electrodes buried in an artificial sand wetted at 50–55% of saturation with a 0.07 mol L−1 Na2SO4·10H2O solution. Various protection potentials (corrected from the ohmic drop) were applied from −0.60 to −1.13 V/Cu-CuSO4. In each case, the behavior of the electrode protected by cathodic polarization was compared with that of an unprotected electrode. The electrochemical study was performed using voltammetry, linear polarization resistance measurements, and EIS. Surface characterization of the coupons was carried out using optical microscopy and X-ray diffraction. First, cathodic protection was observed to induce a spreading of the electrolyte on the metal surface because of electrocapillary effects. The active area, or more precisely the wet area, of the electrode increased, leading to a decrease in soil electrolyte resistance Rs measured using EIS. This phenomenon was experimentally confirmed via visual observations of the surface of the coupons at the end of the experiments. Secondly, cathodic protection induced a passivation of the steel surface. The passive state persisted for 35 to 85 h after cathodic protection was stopped and could be studied during various periods of interruption of the protection. In each case, the OCP of the previously polarized coupons reached high values, actually 200–250 mV higher than those measured for the unprotected coupons, and was associated with high polarization resistance Rp values (~40 kΩ cm2). Depassivation of the metal finally occurred, a phenomenon revealed by simultaneous important drops of both OCP and Rp.

Effect of static magnetic field on corrosion of X70 pipeline steel in dilute sodium bicarbonate solutions

This paper focuses on the effect of a 0.1 T static horizontal magnetic field on the corrosion of X70 pipeline steel in 0–0.05 mol/L sodium bicarbonate solutions. The weight loss data indicate that the magnetic field reduces the average corrosion rate during immersion within 48 h in all the test solutions. The magnetic field tends to increase the average corrosion rates for the immersion time of 72 h and 96 h. The magnetic field increases the proportion of magnetite in corrosion products formed on the specimen of immersion in 0.05 mol/L sodium bicarbonate solution for 168 h. The open-circuit potentials (OCP) are in the active zone of the E-pH diagram within 48 h immersion with 0 T and 0.1 T magnetic field. A 0.1 T magnetic field delays the process for the electrode to enter the passive zone of the E-pH diagram. The linear polarisation resistance (LPR) data shows that the resistance of the active zone with 0.1 T magnetic field is larger than that with 0 T. The electrochemical impedance results also indicate that the electrode is in an active state when the potential is below −700 mVSCE and in a passive state when the potential is above −200 mVSCE.

Effect of ZnAl-NO2 LDH on chloride entrapment and protection of iron reinforcement in mortar samples

Layered double hydroxides (LDHs) have gained attention in the concrete research field, appearing as prospective additives for controlling chloride attack, and as micro or nano deliverers of corrosion inhibitors. This work reports the effect of ZnAl-NO2 LDH on the evolution of chloride concentration in the pore solution and on the corrosion resistance of iron in mortar samples exposed to 3.5 % NaCl solution. To this end, Ag/AgCl sensors were used to monitor the ingress of chloride ions into mortar, while the electrochemical state of the iron was evaluated by electrochemical impedance spectroscopy. Furthermore, the mortars were analyzed by XRD and TGA, and the total amount of chloride was measured with a commercial sensor. Mortars with LDH showed a slower increase of chloride ions in the pore solution and the preservation of the passive state of the Fe. The presence of LDHs did not cause a significant structural change in the mortars, which was evidenced by the similar distribution of the high frequency resistance as a function of depth in the samples with and without the additive. Finally, the amount of bound chloride in the cementitious material was higher in the LDH-containing mortars. In conclusion, ZnAl-NO2 LDH exhibited a positive effect on the protection of reinforcement embedded in mortar samples when subjected to chloride ingress.

Evaluation of Passive Films on 17-7PH and 410 Stainless Steel Exposed to NaCl Solution.

This work covers the formation of a passive state for two different alloys used in the aeronautical industry. The aim of this study is to investigate the effectiveness of passivation treatments on 17-7PH and 410 SS (stainless steel) samples, specifically when performed with citric and nitric acid solutions at 49 °C using an immersion time of 90 min and subsequent exposure in 3.5 wt.% NaCl solution. Employing the cyclic potentiodynamic polarization (CPP) technique, the corrosion properties of the passivated material were evaluated according to the ASTM G65-11 standard. A microstructural analysis was performed using scanning electron microscopy (SEM). The passivated layer was characterized via X-ray photoelectron spectroscopy. In the results, the CPP curves showed positive hysteresis, indicating pitting localized corrosion, and 17-7PH steel passivated at 49 °C for 90 min in citric acid exhibited lower corrosion rate values equivalent to ×10-3 mm/year.

Volumetric differences in the temporomandibular joint in patients with condylar hyperplasia in active and passive state, SPECT/CT study.

Condylar hyperplasia (CH) is a progressive and deforming disease that modifies anatomy of the temporomandibular joint (TMJ) structures. This study aims to correlate the metabolic bone activity of the condyle measured by SPECT with the volumetry anatomic information from the condyle, fossa and joint space provided by CT images, in patients with CH in active and inactive forms. A cross-sectional comparative study was performed with a set of 116 images from healthy and diagnosed CH patients to compare volumetric measures of the TMJ. Images were acquired through a bone tissue mask using a three-dimensional DICOM reconstruction for SPECT/CT and CBCT images and the Threshold option for segmentation with standardized values for each tissue on the HU scale. there are differences (p<0.01), with greater condylar volume on the affected side in patients with active CH compared to passive CH. The volume of the glenoid cavity shows no differences in either form of CH (p>0.05), however, there were differences for the volume of the joint space on the affected right side of hemimandibular elongation (HE) in the active form. The volume of the mandibular condyle on the affected side in CH cases were larger in HE cases in active and inactive form (p<0.01) compared to healthy patients. Similar results were presented for the glenoid cavity and joint space. Volumetric anatomical evaluation of TMJ structures, as well as information on condylar metabolic activity, can be obtained from SPECT/CT. The study shows a greater condylar volume on the affected side of the CH compared to the contralateral side, but there are more significant differences in the active than in the inactive form.

Electrochemical Oxidation Mechanism of Pyrite in a Copper(II)-Citrate-Sodium Thiosulfate Composite System

Pyrite is an important gold carrier during gold leaching, but it is readily oxidized, which causes environmental problems such as acidic mine drainage. Thus, it is necessary to study the oxidation mechanism of pyrite in a gold-leaching electrolyte. The surface oxidation reaction of pyrite is a multi-electron transfer electrochemical oxidation process. Based on this, electrochemical technology was used to explore the electrochemical oxidation mechanism of pyrite in a Cu2+-Cit3−-S2O3 2− system. The surface oxidation products of the pyrite were characterized by Raman spectroscopy and X-ray photoelectron spectroscopy. The experiments showed that the thiosulfate concentration did not change the oxidation mechanism of pyrite at 0.30 V under the conditions of this experiment. Increasing the concentration and potential of thiosulfate accelerated the oxidation rate of pyrite. The electrochemical oxidation of pyrite in the Cu2+-Cit3−-S2O3 2− system occurred in two stages. At low potentials in a passivated state, the process was diffusion-controlled, and the surface oxidation rate was slow. When the potential exceeded 0.50 V, the passivation film on the surface was penetrated, allowing the oxidation reaction on the surface of pyrite to continue. The results of this experiment are useful for deepening the understanding of the oxidation mechanism of pyrite in electrolytes.

An Unpredictable Brain Is a Conscious, Responsive Brain.

Severe traumatic brain injuries typically result in loss of consciousness or coma. In deeply comatose patients with traumatic brain injury, cortical dynamics become simple, repetitive, and predictable. We review evidence that this low-complexity, high-predictability state results from a passive cortical state, represented by a stable repetitive attractor, that hinders the flexible formation of neuronal ensembles necessary for conscious experience. Our data and those from other groups support the hypothesis that this cortical passive state is because of the loss of thalamocortical input. We identify the unpredictability and complexity of cortical dynamics captured by local field potential as a sign of recovery from this passive coma attractor. In this Perspective article, we discuss how these electrophysiological biomarkers of the recovery of consciousness could inform the design of closed-loop stimulation paradigms to treat disorders of consciousness.

In vivo imaging and computational modeling of nonlinear shear waves in living skeletal muscles

How the state of living muscles modulates the features of nonlinear elastic waves generated by external dynamic loads remains unclear because of the challenge of directly observing and modeling nonlinear elastic waves in skeletal muscles in vivo, considering their active deformation behavior. Here, this important issue is addressed by combining experiments performed with an ultrafast ultrasound imaging system to track nonlinear shear waves (shear shock waves) in muscles in vivo and finite element analysis relying on a physically motivated constitutive model to study the effect of muscle activation level. Skeletal muscle was loaded with a deep muscle stimulator to generate shear shock waves (SSWs). The particle velocities, second and third harmonics, and group velocities of the SSWs in living muscles under both passive and active states were measured in vivo. Our experimental results reveal, for the first time, that muscle states have a pronounced effect on wave features; a low level of activation may facilitate the occurrence of both the second and third harmonics, whereas a high level of activation may inhibit the third harmonic. Finite element analysis was further carried out to quantitatively explore the effect of active muscle deformation behavior on the generation and propagation of SSWs. The simulation results at different muscle activation levels confirmed the experimental findings. The ability to reveal the effects of muscle state on the features of SSWs may be helpful in elucidating the unique dynamic deformation mechanism of living skeletal muscles, quantitatively characterizing diverse shock wave-based therapy instruments, and guiding the design of muscle-mimicking soft materials.

Determination and Prediction of Corrosion Integrity on RV Discovery Via Non-Destructive Test (NDT) And Artificial Neural Network (ANN)

Marine environment is a harsh and severe environment for a metal structure like vessel, oil rigs and port infrastructure. A regular survey or monitoring is needed to reduce a structure failure due to the corrosion. To be seaworthy, a vessel should undergo a regular survey under specified timeframe. This survey is time consuming and costly. An alternative approach is required to predict the structural integrity of a vessel. Artificial Neural Network is one of the current methods that can be used to predict the deterioration rate of a structure. Corrosion integrity of RV-Discovery was determined via plate thickness measurement, coating thickness measurement and potential measurement. The data obtained from these measurements were used in artificial neural network to predict the deterioration rate. The results indicate that the plate and coating thickness reduction percentage is within minimal range while the average potential changes show that the structure is in passivation state. It implies that the structural integrity is in a good state with no or minimal maintenance required. The prediction of deterioration rate also shows that Scaled Conjugate Gradient (SCG) training algorithm was able to predict with over 95% of confidence and low mean square error.

Feeling anxious and being engaged in a warming world: climate anxiety and adolescents' pro-environmental behavior.

Climate anxiety is increasingly prevalent among adolescents worldwide. Are climate-anxious adolescents prone to engage in pro-environmental behavior? Or might the association between climate anxiety and pro-environmental be curvilinear, such that high levels of climate anxiety become 'paralyzing'? And do these associations depend on whether adolescents believe that, with effort, the worst impacts of climate change can still be prevented? We addressed these questions in three studies (two preregistered; combined N = 2,211), conducted across two countries. We used cross-sectional and longitudinal methods, and various measures of climate anxiety and pro-environmental behavior. We performed Bayesian regression analyses comparing two models that tested competing hypotheses. The first model included a linear effect of climate anxiety on pro-environmental behavior, and the second model included both a linear and a curvilinear (i.e. inverted U-shaped) effect of climate anxiety on pro-environmental behavior. Next, we added environmental efficacy to the best fitting model and explored its moderating effects. Adolescents reported low-to-moderate levels of climate anxiety. Across the board, we found evidence for a small, positive, and mostly linear (rather than curvilinear) association between climate anxiety and pro-environmental behavior. While Study 1 supported a curvilinear association (Bayes Factor (BF) = 18.87), Studies 2 and 3 mostly supported a linear model (BFs range 6.86-12.71), except for weak support (BF = 1.62) for a curvilinear association between climate anxiety symptoms and public sphere pro-environmental behavior. Adolescents' environmental efficacy moderated this link for public sphere (e.g. activism), but not private sphere (e.g. recycling), pro-environmental behavior. Climate-anxious adolescents are prone to engage in pro-environmental behavior. We found limited evidence for 'eco-paralysis' (i.e. a passive state of pro-environmental behavioral stasis) at high levels of climate anxiety. Our results are consistent with the possibility that supporting adolescents' environmental efficacy will help climate-anxious adolescents engage in public sphere pro-environmental behavior.

Inhibition of metal corrosion in neutral aqueous solutions by succinic acid salts

The adsorption, protective and passivating effect of sodium succinate and a blend of sodium alkenylsuccinates SKAP-25 on the oxidized surface of copper, copper-nickel alloy MNZh5-1 and low-carbon steel St3 in a neutral chloride solution were studied. The free adsorption energy (–ΔG0a,max) values for all studied metals suggest chemisorption interaction of these organic anion with oxidized metals surfaces: (–ΔG0a,max) for St3 60.2 kJ/mol, for copper 77.4 kJ/mol and for copper alloy 89.3 kJ/mol. Sodium succinate is able to stabilize the passive state of the MNZh5-1 alloy in a neutral chloride buffer solution. On copper, copper alloy and St3, protection against local depassivation is observed up to a certain concentration, above which the protective properties of sodium succinate decrease. Polarization measurements on the air-oxidized surface of low-carbon steel St3 showed that sodium succinate and SKAP-25, as well as their compositions with 2-mercaptobenzothiazole (2-MBT), are able to reduce anodic dissolution currents and increase the local depassivation potential. Corrosion tests of St3 in a 0.01 M NaCl solution proved the advantage of using the composition of SKAP-25 with 2-MBT (7.1:1) in comparison with the individual compound: the degree of protection of St3 at Cinh=7 mmol/L is 99%, and sodium succinate+SKAP-25 (1:1) at Cinh=7 mmol/L is Z=93%.

Monomer-Dimer Equilibrium of Human Cystatin C During Internalization Into Cancer Cells.

Human cystatin C (hCC) is a physiologically important protein that serves as intra- and extracellular cysteine proteinase inhibitor in homeostasis. However, in pathological states it dimerizes and further oligomerizes accumulating into a toxic amyloid. HCC forms an active monomer in the extracellular space and becomes an inactive dimer when internalized in cellular organelles. However, hCC cell penetration and its oligomeric state during this process are not well understood. To determine if and how the oligomeric state influences hCC transmembrane migration, we investigated the internalization of the hCC wild type protein as well as three different mutants, which exclusively exist in the monomeric or multimeric state into HeLa cells via confocal fluorescence microscopy. Our results showed that the preferred pathway was endocytosis and that the oligomeric state did not significantly influence the internalization because both monomeric and dimeric hCC migrated into HeLa cells. Considering the differences of the active monomeric and the passive dimeric states of hCC, our findings contribute to a better understanding of the intra and extra cellular functions of hCC and their interaction with cysteine proteases.

Ignoring and collective passivity in relation to information systems: How actors avoided engagement with data about wait times in Swedish healthcare

Although digital technology (DT) is often introduced with the aim of enhancing organizational knowledge transfer and learning, these aims often fail to materialize. The information systems (IS) literature attributes such unexpected outcomes to inappropriate technology design and implementation, as well as to overuse, misuse, and non-use of technology. However, we know little about how actors misuse or fail to use technology and data, thereby failing to acquire and act upon the knowledge necessary to achieve organizational learning. Leveraging the literature on strategic ignorance, we explore how actors expected to use technology for learning purposes justify their non-engagement with it. Studying an implementation of a DT with the purpose of facilitating organizational learning on basis of provided data in health care, we identify seven ignoring justifications through which the target users of the DT avoided key knowledge acquisition and knowledge-based action activities. These sensemaking behaviors accumulated to a state of collective passivity in relation to the DT. Our conceptualization contributes to and connects theories of organizational learning in the IS literature and strategic ignoring.

Influence of Water Radiolysis on the Passive Properties of 316L-Stainless Steel.

This work aims to study the effect of radiolytic species induced by water radiolysis on the passive behavior of 316L stainless steel. For this purpose, the stainless steel/neutral and aerated 0.02 M Na2SO4, electrolyte solution interface was irradiated with proton beams. A wide range of energies between 2 and 16 MeV was selected, varying the maximum of the energy deposition between 0.5 and 122 μm in water from the interface. The irradiation experiments were performed at the CEMHTI cyclotron in Orléans and the 4 MV Van de Graaff accelerator at IP2I in Lyon (France). A dedicated irradiation device implemented with a 3-electrode cell dedicated to perform electrochemical measurements allows to measure the surface reactivity of the stainless steel as a function of the irradiation conditions. Results show that whatever the beam energy, the corrosion potential remains unchanged. It indicates that the very short-lived, highly reactive radiolytic species drive the corrosion potential and not only the recombination products such H2O2 or H2. The stainless steel remains in the passive state whatever the irradiation conditions. However, it is shown that, during irradiation, the passive film is less protective. This evolution is attributed to radiolysis of bound water molecules in the passive film.