Kinetic Mode Research Articles

MHD and Ion Kinetic Waves in Field-aligned Flows Observed by Parker Solar Probe

Abstract Parker Solar Probe (PSP) observed predominately Alfvénic fluctuations in the solar wind near the Sun where the magnetic field tends to be radially aligned. In this paper, two magnetic-field-aligned solar wind flow intervals during PSP’s first two orbits are analyzed. Observations of these intervals indicate strong signatures of parallel/antiparallel-propagating waves. We utilize multiple analysis techniques to extract the properties of the observed waves in both magnetohydrodynamic (MHD) and kinetic scales. At the MHD scale, outward-propagating Alfvén waves dominate both intervals, and outward-propagating fast magnetosonic waves present the second-largest contribution in the spectral energy density. At kinetic scales, we identify the circularly polarized plasma waves propagating near the proton gyrofrequency in both intervals. However, the sense of magnetic polarization in the spacecraft frame is observed to be opposite in the two intervals, although they both possess a sunward background magnetic field. The ion-scale plasma wave observed in the first interval can be either an inward-propagating ion cyclotron wave (ICW) or an outward-propagating fast-mode/whistler wave in the plasma frame, while in the second interval it can be explained as an outward ICW or inward fast-mode/whistler wave. The identification of the exact kinetic wave mode is more difficult to confirm owing to the limited plasma data resolution. The presence of ion-scale waves near the Sun suggests that ion cyclotron resonance may be one of the ubiquitous kinetic physical processes associated with small-scale magnetic fluctuations and kinetic instabilities in the inner heliosphere.

Separation of durene and prehnitene by metal-organic framework UiO-66

The adsorption performances of durene (DR) and prehnitene (PR) (molar ratio of 1:1) by MIL-53(Cr), UiO-66, ZIF-8 and Cu-BTC at 298.15 K were evaluated by adsorption experiments and simulation with Grand-canonical Monte Carlo method. UiO-66 exhibited the highest selectivity for DR and PR. Thus UiO-66 was selected and taken as the adsorbent subsequently. The adsorption kinetics and thermodynamics of DR and PR were studied in detail. Studies on kinetics showed that the data could be correlated well by the pseudo-second-order kinetic mode. The adsorption isotherms conformed to the Langmuir isotherm. The adsorption processes were spontaneous and exothermic. The adsorption capacity of DR was lower than that of PR according to the single component adsorption, while it showed the opposite trend in the competitive adsorption. The selectivity of DR and PR could reach 2.60 at 298.15 K. In conclusion, UiO-66 can be a feasible adsorbent to separate DR and PR for industrial application.

Abstract 9976: New Risk Factors for Improved Identification of Coronary Artery Disease Risk in Type 2 Diabetes by Substituting Paraoxonase 1 Activity for HDL Cholesterol in Atherogenic Ratios

Introduction: HDL cholesterol (HDL-C) may not always represent the HDL function. This study was conducted to help predict the risk of coronary artery disease (CAD) in patients with type 2 diabetes (T2D) based on substituting paraoxonase 1 (PON1) as an important enzyme in HDL function for that of HDL-C in the atherogenic ratios LDL-C/HDL-C and log (TG/HDL-C). Methods: A total of 274 subjects undergoing diagnostic coronary angiography in this study; 92 without significant CAD and 182 with severe CAD. The hydrolysis rate of phenylacetate as a PON1 substrate was spectrophotometrically measured in kinetic mode. The area under the ROC curve (AUC) was calculated to quantify the overall discriminative capacity of the variables. Results: ROC analyses showed that LDL-C/PON1 (AUC=0.66, p=0.02) and log (TG/PON1) (AUC=0.65, p=0.019) had higher predictive powers compared with LDL-C/HDL-C (AUC=0.55, p=0.221) and log (TG/HDL-C) (AUC=0.57, p=0.121) for CAD characterization in T2D patients. Also, AUCs of LDL-C/PON1 (AUC=0.74, p=0.014) and log (TG/PON1) (AUC=0.67, p=0.057) were higher than those of LDL-C/HDL-C (AUC=0.51, p=0.469) and log (TG/HDL-C) (AUC=0.53, p=0.364) for predicting CAD in T2D patients with HbA1c ≥7%. The multiple regression analysis with adjustments for gender, age, BMI, duration of T2D, metformin and statin therapy indicated that LDL-C/PON1 [adjusted OR=1.1 (0.99,1.23), p=0.085] and log (TG/PON1) [adjusted OR=3.76 (0.94,14.89), p=0.058] were independently predictors of CAD in T2D patients. Conclusions: New cardiometabolic biomarkers using PON1 provide an incremental predictive value compared with those using HDL-C in identifying subjects at increased risk for CAD among patients with T2D and poor glycemic control. This study sought to exploit the lipoprotein-related biomarkers of CAD from a more effective perspective in T2D. Our findings may help develop clinically cost-effective and functional laboratory measurements to evaluate HDL function.

The building up of observed stellar scaling relations of massive galaxies and the connection to black hole growth in the TNG50 simulation

Abstract We study how mock-observed stellar morphological and structural properties of massive galaxies are built up between z = 0.5 and z = 3 in the TNG50 cosmological simulation. We generate mock images with the properties of the CANDELS survey and derive Sersic parameters and optical rest-frame morphologies as usually done in the observations. Overall, the simulation reproduces the observed evolution of the abundances of different galaxy morphological types of star-forming and quiescent galaxies. The log M* − log Re and log M* − log Σ1 relations of the simulated star-forming and quenched galaxies also match the observed slopes and zeropoints to within 1-σ. In the simulation, galaxies increase their observed central stellar mass density (Σ1) and transform in morphology from irregular/clumpy systems to normal Hubble-type systems in the Star Formation Main Sequence at a characteristic stellar mass of ∼1010.5 M⊙ which is reflected in an increase of the central stellar mass density (Σ1). This morphological transformation is connected to the activity of the central Super Massive Black Holes (SMBHs). At low stellar masses (109 < M*/M⊙ < 1010) SMBHs grow rapidly, while at higher mass SMBHs switch into the kinetic feedback mode and grow more slowly. During this low-accretion phase, SMBH feedback leads to the quenching of star-formation, along with a simultaneous growth in Σ1, partly due to the fading of stellar populations. More compact massive galaxies grow their SMBHs faster than extended ones of the same mass and end up quenching earlier. In the TNG50 simulation, SMBHs predominantly grow via gas accretion before galaxies quench, and Σ1 increases substantially after SMBH growth slows down. The simulation predicts therefore that quiescent galaxies have higher Σ1 values than star-forming galaxies for the same SMBH mass, which disagrees with alternative models, and may potentially be in tension with some observations.

Autoclave dissolution of platinum metals in hydrochloric acid oxidizing media

The paper provides the results obtained in the study of the features of metallic platinum, rhodium and iridium dissolution in hydrochloric acid solutions under hydrothermal autoclave conditions. Hydrogen peroxide was used as an oxidizing agent. Solid and liquid phases were brought into contact after reaching a predetermined temperature, which is critically important in the study of rhodium black and platinum plate dissolution kinetics due to the high rates of these processes. The concentrations of metals in solutions were determined by atomic absorption spectroscopy and inductively coupled plasma mass spectrometry. The forms of rhodium, iridium, and platinum chlorocomplexes in solutions were determined using the spectrophotometric method. As a result of the experiments, the conditions of platinum plate and rhodium quantitative dissolution (in the form of affined powder and a plate) were determined and it was shown that at 210 °C in 6M hydrochloric acid as a medium with the addition of 5 vol.% hydrogen peroxide, iridium taken in the form of affined powder went into the solution by 50 % within more than 50 h, while the platinum plate dissolved completely at 130 °C in about 120 min. Kinetic data analysis using the shrinking core model showed that rhodium black and affined rhodium and iridium powders dissolve under autoclave conditions in a kinetic mode. The results obtained can be used both in analytical chemistry for the quantitative determination of inert platinum metals and in refining production to improve the technology for processing raw materials containing platinum group metals (PGMs) and to optimize approaches to the synthesis of pure chlorocomplex compounds of PGMs.

Self-consistent core-pedestal ITER scenario modeling

The purpose of these integrated ITER simulations is to identify dependencies that can impact the performance of ITER. The dependence of fusion power production, temperature and density pedestals, and core profiles on varying magnetic-q, edge density fueling strength, neoclassical transport, magnetic field strength, and alpha heating, are examined. It is noted that ion modes usually dominate the interior, while electron modes dominate the barrier. The electron mode without flow shear is substantially stronger. The q increase tends to cause more kinetic ballooning modes at the edge and the q decrease means that the peeling is getting worse, but the ballooning is getting better. The large edge q tends to provide hollow density while small edge q gives normal density profile. This is consistent with the observation that the density of particles is inversely proportional to the density of the plasma current. The rise in the source of the edge particle increases the density of the edge and the reaction rate close to the edge increases temperature fluxes, resulting in weak pedestal barriers. When neoclassical transport is turned off or the strength of B-field is increased, the pronounced edge barriers are identified. In addition, a distinct effect on the magnetohydrodynamic (MHD) modes is observed due to the increased B-field. The interesting aspect is that the barrier collapses about q = 2 as the stability of MHD has decreased to replace the barrier with a continuous slope but with roughly the same fusion power. This would actually be good for a reactor. The slope of the H-mode pedestal is found to be reduced due to the alpha heating. It is expected that the problem of edge-localized modes causing damage to the first wall will be eased. The effects of circular, elongated, and general geometry on plasma profiles are also compared and contrasted. The circular geometry has a hollow density profile and no edge or internal thermal transport barrier (ETB or ITB). However, both ETBs and ITBs can be found in the elongated geometry. In general geometry, there is a weaker ETB, comparable ITBs, but a higher edge particle transport barrier than in elongated geometry. Higher density near the edge, on the other hand, causes more wall erosion, so elongated geometry might be the best option.

Changing Cross-Reactivity for Different Immunoassays Using the Same Antibodies: Theoretical Description and Experimental Confirmation

Many applications of immunoassays involve the possible presence of structurally similar compounds that bind with antibodies, but with different affinities. In this regard, an important characteristic of an immunoassay is its cross-reactivity: the possibility of detecting various compounds in comparison with a certain standard. Based on cross-reactivity, analytical systems are assessed as either high-selective (responding strictly to a specific compound) or low-selective (responding to a number of similar compounds). The present study demonstrates that cross-reactivity is not an intrinsic characteristic of antibodies but can vary for different formats of competitive immunoassays using the same antibodies. Assays with sensitive detection of markers and, accordingly, implementation at low concentrations of antibodies and modified (competing) antigens are characterized by lower cross-reactivities and are, thus, more specific than assays requiring high concentrations of markers and interacting reagents. This effect was confirmed by both mathematical modeling and experimental comparison of an enzyme immunoassay and a fluorescence polarization immunoassay of sulfonamides and fluoroquinolones. Thus, shifting to lower concentrations of reagents decreases cross-reactivities by up to five-fold. Moreover, the cross-reactivities are changed even in the same assay format by varying the ratio of immunoreactants’ concentrations and shifting from the kinetic or equilibrium mode of the antigen-antibody reaction. The described patterns demonstrate the possibility of modulating immunodetection selectivity without searching for new binding reactants.

An energetic hot wind from the low-luminosity active galactic nucleus M81*

For most of their lifetime, super-massive black holes (SMBHs) commonly found in galactic nuclei obtain mass from the ambient medium at a rate well below the Eddington limit1, which is mediated by a radiatively inefficient, hot accretion flow2. Both theory and numerical simulations predict that a strong wind must exist in such hot accretion flows3–6. The wind is of special interest not only because it is an indispensable ingredient of accretion but also, perhaps more importantly, because it is believed to play a crucial role in the evolution of the host galaxy via the so-called kinetic mode active galactic nucleus feedback7,8. Observational evidence for this wind, however, remains scarce and indirect9–12. Here we report the detection of a hot outflow from the low-luminosity active galactic nucleus in M81, based on Chandra high-resolution X-ray spectroscopy. The outflow is evidenced by a pair of Fe xxvi Lyα lines redshifted and blueshifted at a bulk line-of-sight velocity of ±2.8 × 103 km s−1 and a high line ratio of Fe xxvi Lyα to Fe xxv Kα implying a plasma temperature of 1.3 × 108 K. This high-velocity, hot plasma cannot be produced by stellar activity or the accretion inflow onto the SMBH. Our magnetohydrodynamical simulations show that, instead, it is naturally explained by a wind from the hot accretion flow, propagating out to ≳106 times the gravitational radius of the SMBH. The kinetic energy and momentum of this wind can significantly affect the evolution of the circumnuclear environment and beyond. Chandra X-ray spectroscopy reveals a 108 K plasma outflow in the low-luminosity active galactic nucleus M81. Magnetohydrodynamical simulations show this energetic wind to originate from a hot accretion flow and impact its host galaxy.

Low n electromagnetic modes in spherical tokamaks

The performance of spherical tokamak reactors depends on plasma β, and an upper limit is set by long-wavelength kinetic ballooning modes (KBMs). We examine how these modes become unstable in spherical-tokamak reactor relevant plasmas, which may contain significant fast-ion pressure. In a series of numerically generated equilibria of increasing β, the KBM becomes unstable at sufficiently high plasma β, and for such cases, it is also significantly unstable even in the long-wavelength limit. The β threshold for the KBMs is similar to the ideal Magnetohydrodynamics (MHD) threshold, and in cases without fast ions, their frequencies are as predicted by diamagnetic-drift stabilised MHD. To isolate and explore the KBMs, simulations are performed where the pressure gradient is entirely due to the density profile, or entirely due to the temperature profile; the resulting KBMs have similar properties in the long-wavelength regime. The introduction of energetic ions restricts the KBMs to longer wavelengths, and reduces the β threshold somewhat; for parameter regimes of current-day devices, this is such long wavelength that a global analysis would become necessary. Mode frequencies in plasmas with a significant fast particle population are seen to be controlled by fast particle precession frequencies.

MASS CONDUCTIVITY FOR DRYING NUCLEI AND SEED SUNFLOWER SHELLS

The mass-conduction (diffusion) properties of sunflower seeds of the "MAS 95 OL" variety were experimentally investigated. From the experimental drying curves obtained in the intradiffusion kinetic mode at two temperatures of the drying agent (air), the coefficients of mass conductivity (moisture diffusion) were calculated by the zonal method, which are presented as dependences on the moisture content of the core and shell, respectively. It is shown that the coefficients of mass conductivity of nuclei and shells depend on the moisture content of the material and differ significantly both in magnitude and in the nature of the concentration dependences. The coefficient of mass conductivity of nuclei in different areas of moisture content is 15-25 times higher than that of shells, this is explained by differences in the structure of these materials. In the area of moisture content less than 0.5 kg / (kg of dry materiall), both dependences have the same character of concave functions increasing with moisture content, this is a consequence of the same mechanism of mass transfer dominating in this area of moisture content, which is osmotic mass transfer. In seed kernels, the area of moisture content of more than 0.5 kg / (kg of dry material) is absent, but in seed shells it is present and vapor diffusion dominates in it. The data on the coefficient of mass conductivity for seed shells were compared with the coefficient of mass conductivity of another capillary-porous colloidal material with a similar structure - wood. The nature of the concentration dependences for both materials is the same, which is explained by the similarity of the morphological structure of wood and seed shells, which have a tree-like structure. The coefficient of mass conductivity of the seed kernel was compared with the coefficients of mass conductivity of other capillary-porous colloidal materials of plant and animal origin. Comparison showed that they have the same order of mass conductivity coefficient: 10-9 m2/s. This is explained by the identical structure of these materials, which have a cellular structure, and, probably, by the same mechanisms of mass transfer at the corresponding moisture content. The obtained data on the coefficients of mass conductivity of the kernel and shell of sunflower seed can be used for the kinetic calculation of the process of convective drying of this material based on the solution of the differential equations of internal heat and mass transfer A.V. Lykov with the representation of the seed as a two-layer body.

Kinetic instability in inductively oscillatory plasma equilibrium.

A uniform in space, oscillatory in time plasma equilibrium sustained by a time-dependent current density is analytically and numerically studied resorting to particle-in-cell simulations. The dispersion relation is derived from the Vlasov equation for oscillating equilibrium distribution functions, and used to demonstrate that the plasma has an infinite number of unstable kinetic modes. This instability represents a kinetic mechanism for the decay of the initial mode of infinite wavelength (or equivalently null wave number), for which no classical wave breaking or Landau damping exists. The relativistic generalization of the instability is discussed. In this regime, the growth rate of the fastest growing unstable modes scales with γ_{T}^{-1/2}, where γ_{T} is the largest Lorentz factor of the plasma distribution. This result hints that this instability is not as severely suppressed for large Lorentz factor flows as purely streaming instabilities. The relevance of this instability in inductive electric field oscillations driven in pulsar magnetospheres is discussed.

Impact of shaping on microstability in high-performance tokamak plasmas

We have used the local-δf gyrokinetic code GS2 to perform studies of the effect of flux-surface shaping on two highly-shaped, low- and high-β JT-60SA-relevant equilibria, including a successful benchmark with the GKV code. We find that for a high-performance plasma, i.e. one with high plasma beta and steep pressure gradients, the turbulent outwards radial fluxes may be reduced by minimizing the elongation. We explain the results as a competition between the local magnetic shear and finite-Larmor-radius (FLR) stabilization. Electromagnetic studies indicate that kinetic ballooning modes are stabilized by increased shaping due to an increased sensitivity to FLR effects, relative to the ion-temperature-gradient instability. Nevertheless, at high enough β, increased elongation degrades the local magnetic shear stabilization that enables access to the region of ballooning second-stability.

Trace element levels in pleural effusions.

Trace element levels in pleural effusions.

Heterostructural Mixed Oxides Prepared via ZnAlLa LDH or ex-ZnAl LDH Precursors-Effect of La Content and Its Incorporation Route.

The effect of La content and its incorporation route on physicochemical properties of ZnO/Zn(Al,La)2O4 or La2O3–ZnO/ZnAl2O4 mixed oxides with a spinel structure obtained from ZnAlLa Layered double hydroxides (LDHs) or ex-ZnAl LDH materials was investigated. The heterostructural nanocomposites with the similar Zn/Al molar ratio and varied La content were prepared by two techniques: via co-precipitation and thermal treatment of ZnAlLa LDHs at 500 °C or via incipient wetness impregnation of ex-ZnAl LDHs with aqueous solutions of lanthanum nitrate and subsequent thermal treatment. The obtained series of materials were characterized by the following techniques: X-ray fluorescence (XRF), N2 adsorption (BET), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis with evolved gas analysis (TG/DTG/EGA), scanning transmission electron microscopy (STEM) energy-dispersive X-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM) and Fourier-transform infrared spectroscopy (FFT). The evaluation of activity toward the high-temperature water gas shift (HT-WGS) within the temperature range of 350–420 °C was carried out on the basis of rate constant measurements in the kinetic mode using a differential reactor. The co-precipitation technique allowed for a better distribution of La in bulk and on the spinel surface than in case of lanthanum incorporation via impregnation. ZnO/Zn(Al,La)2O4 or La2O3–ZnO/ZnAl2O4 mixed oxides were characterized by moderate activity in the HT-WGS reaction. The results reveal that introduction of lanthanum oxide over 2.4–2.8 wt% induces the phase separation of the ZnAl2O4 spinel, forming ZnO on the ZnAl2O4 spinel surface.

Pedestal stability analysis on MAST in preparation for MAST-U

In preparation for the upcoming MAST-U campaign, pedestal stability of spherical tokamaks is revisited by investigating standard H-mode discharges on MAST. As a step beyond previous studies, both ion and electron profiles are used for obtaining equilibria and a diverse set of pedestals is evaluated. Stability analysis with the ELITE and CGYRO codes shows that MAST pedestals are constrained by kinetic ballooning modes and medium toroidal mode number peeling-ballooning modes, with most unstable modes ranging from n = 25 to n = 45. In discharges with a steep q profile at the edge a larger number of poloidal harmonics is excited for each toroidal mode. A comparison with discharges on DIII-D with matched shape and similar non-dimensional parameters indicates that the increased shear at lower aspect ratio stabilizes low n peeling modes.

A novel CNTs-Fe3O4 synthetized via a ball-milling strategy as efficient fenton-like catalyst for degradation of sulfonamides

A novel composite (CNTs-Fe3O4) was synthesized by a ball-milling strategy and characterized by BET, SEM, FTIR, XRD and VSM. The as-fabricated CNTs-Fe3O4 was used to remove six sulfonamides by a Fenton degradation process, including sulfanilamide (SAM), sulfamerazine (SMR), sulfadimethoxine (SMX), sulfadiazine (SDZ), sulfamethazine (SMT) and sulfametoxydiazine (SMD). The degradation behaviors of six sulfonamides in CNTs-Fe3O4/H2O2 system and the relationship between molecular structure of sulfonamides and their degradation behaviors were investigated systematically. Batch experimental results showed that the as-fabricated CNTs-Fe3O4 had excellent Fenton catalytic activity for the degradation of sulfonamides due to its unique porous structure and the good combination mode of CNTs with Fe3O4 particles. The first-order kinetic mode could better describe the degradation behaviors of six sulfonamides in CNTs-Fe3O4/H2O2 system, and the degradation rate constant could be ordered as: SAM < SMT < SDZ < SMR < SMD < SMX. The quantitative relationship between the Mulliken charge of sulfonamides (x) and their degradation rate constant (y) in CNTs-Fe3O4/H2O2 system could be described as: y = - 28.719x + 15.67 (R2 = 0.957). Finally, the possible synthesis mechanisms of CNTs-Fe3O4 and the degradation mechanisms of sulfonamides in CNTs-Fe3O4/H2O2 system was proposed.

Effect of material properties on ballistic energy absorption of woven fabrics subjected to different levels of inter-yarn friction

Inter-yarn friction plays a significant role in ballistic energy absorption of woven fabrics. In the past decade, a few studies have been reported on the effect of inter-yarn friction on ballistic energy absorption. It has been reported that ballistic energy absorption of a woven fabric increases until an optimum value of the coefficient of friction11COF = Co-efficient of friction (COF) and decreases beyond that. However, a fundamental understanding of how yarn material properties affect this optimum friction value is still elusive. The effect of yarn material properties on different modes of ballistic energy absorption, when subjected to different inter-yarn friction level, is also not understood. In order to address this lacuna, this work presents a detailed numerical analysis of woven fabrics with different material properties but constant toughness subjected to different inter-yarn friction using the finite element framework. The results show that for materials with a low value of longitudinal modulus and higher value of failure strain, the threshold friction level is of lesser magnitude than in materials with a high value of longitudinal modulus and lower failure strain value. An explanation of this phenomenon has also been attempted based on a study of longitudinal stress wave velocity in woven fabrics with different levels of inter-yarn friction. It has also been found that an increase in the inter-yarn friction level increases the ballistic energy absorption in fabric strain energy mode while it decreases the energy absorption in fabric kinetic energy mode up to the threshold friction value. The results are expected to be a guide to choose woven fabrics while attempting to improve their ballistic performance by impregnating them with shear thickening fluids22STF = Shear thickening fluid (STF).

Kinetic ballooning mode unstable in the 2nd stability regime as a possible source of the low-k broadband fluctuation observed in the wide-pedestal QH-mode

The kinetic ballooning mode destabilized by the ion magnetic curvature drift resonance in the 2nd ballooning stability regime is shown to be a plausible candidate for the low-k broadband fluctuation recently observed in the wide-pedestal quiescent-H (QH) mode of DIII-D. With its intrinsic real frequency approaching very closely to the ion pressure diamagnetic frequency in the pedestal-like condition with a steep gradient, this mode can be nearly free from the first-order ExB flow shear effect driven by the ion pressure gradient. As a result, it can be sensitive to the next-order one by toroidal rotation, with the possible strong excitation in the low toroidal rotation limit. The frequency in the lab frame and the peak wavenumber spectrum of the mode appear to be in the range similar to those of the observed low-k fluctuation.

Impact of shape on pedestal characteristics in the wide pedestal quiescent H-mode in the DIII-D tokamak

Experiments on the DIII-D tokamak have advanced the operational limits of wide pedestal quiescent H-mode plasmas towards increased ITER relevance by simultaneously demonstrating well-matched plasma shape and net zero injected torque. Wide pedestal QH-modes are a compelling candidate regime for a future power producing device because they maintain a stationary pedestal without ELMs via additional edge transport. The pedestal is wider than what would be predicted from kinetic ballooning mode physics due to enhanced edge transport generated by broadband turbulence, a limit cycle oscillation, or some combination thereof. Compared to the double null shape, the lower single null shape is observed to have a lower density, narrower pedestal width, larger density fluctuations over a broad range of wavenumber, and operates closer to the peeling-ballooning instability boundary calculated from the simple pedestal scaling, , which is still observed to be wider than the EPED prediction.

Kinetics of the Formation and Dissolution of Anodic Aluminum Oxide in Electrolytes Based on Sulfuric and Selenic Acids

Measurements were made to study the kinetics of the formation and dissolution of porous anodic aluminum oxide in electrolytes based on sulfuric and selenic acids at temperatures from 0 to 30°C. It was shown that there is a significant difference in the kinetics of the dissolution of anodic aluminum oxide at the bottom of the pores during its formation and throughout the walls of the porous structure after the termination of the anodizing. In the anodizing of aluminum in 2.0 M H2SO4 in kinetic mode, the apparent activation energy of the dissolution of anodic aluminum oxide at the bottom of the pores is 53.2 ± 1.8 kJ/mol, whereas in the chemical dissolution of the walls of the porous structure, this quantity is 83.3 ± 2.1 kJ/mol. The observed difference in the dissolution kinetics predicts the increase in maximum accessible thickness of the porous anodic aluminum oxide film with decreasing electrolyte temperature.