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The article discusses the revival of cyclodextrins as active pharmaceutical ingredients, highlighting their unique molecular structure and biocompatible properties. Cyclodextrins have been traditionally used as excipients in pharmaceutical formulations but are now being explored as active ingredients in treating various diseases such as COVID-19, neuromuscular blockade, Stargardt, hemophilia, atherosclerosis, Alzheimer's, Parkinson's, diabetic kidney disease, dry eye disease, focal segmental glomerulosclerosis, Alport syndrome, and Niemann–Pick C. The potential of cyclodextrins as artificial receptors or cholesterol modulators is also explored, showing promise in scavenging toxic compounds and modulating cholesterol levels in the body. The article emphasizes the need for further research to standardize the synthesis process of cyclodextrin derivatives and understand their long-term effects. [Extracted from the article]

This paper is concerned with the spatiotemporal dynamics of a three species competition–competition–predation Lotka–Volterra system with cross-diffusion. Firstly, by applying cross-diffusion coefficients as the bifurcation parameter, we demonstrate that our model undergoes a spatially inhomogeneous Hopf bifurcation around positive constant steady state when the bifurcation parameter is varied through a critical value. In addition, we prove that the obtained spatially inhomogeneous bifurcating periodic solutions are stable when cross-diffusion coefficients lie in suitable ranges. Secondly, we establish the sufficient conditions for the global asymptotical stability of positive constant steady state. Finally, we prove that the system admits only the positive constant steady state when cross-diffusion coefficients is small enough, which implies that the system does not create stationary patterns when cross-diffusions are small enough. A common feature in the most existing research papers is that the bifurcation parameter that induces Hopf bifurcation appears in the reaction terms rather than diffusion terms. We demonstrate that the spatially inhomogeneous Hopf bifurcation can be induced by the effect of cross-diffusion terms. Our results show that cross-diffusion plays a crucial role in the formation of spatially inhomogeneous periodic oscillatory patterns. [ABSTRACT FROM AUTHOR]

In this study, the complexation of gallic acid with various lanthanide and actinide ions (La3+, Sm3+, Th4+, and UO22+) was investigated under aqueous conditions at elevated temperatures by potentiometric titration, with ionic strength of I = 0.10 mol dm−3 KCl. Stability constants for complexation of related metal-ions were determined using HYPERQUAD2013 software. The formation of complexes was considered at temperatures of 25 °C, 37 °C, and 45 °C. By examining the dependence of complex formation on temperature, the thermodynamic parameters of each complex were calculated. It was observed that the stability constant values varied with temperature. Additionally, cytotoxicity studies were conducted on MCF-7 and A-549 cell lines as part of the conclusion. [ABSTRACT FROM AUTHOR]

The measurement of vitamin B1 in pure and pharmaceutical formulations was proposed by using a straightforward and sensitive spectrophotometric approach. Sulfacetamide (SFA) is diazotized, then coupled with vitamin B1 in alkaline media to produce a colored azo dye complex with a stability constant of 5.597 × 105 L/mol. The product is stable, with a maximum absorption wavelength of 489.5 nm, molar absorptivity of 10108 L/mol∙cm, Sandell's sensitivity of 0.0334 μg/cm2, detection limit of 0.0135 μg/mL, and Beer's law being observed over the concentration range of 0.2–20.0 μg/mL. The stability constant and stoichiometry of the produced azo dye were calculated using the continuous variation (Job's) and mole ratio methods. The suggested approach was used successfully in the determination of vitamin B1 in its pharmaceutical formulations. [ABSTRACT FROM AUTHOR]

We study the movement of the living organism in a band form towards the presence of chemical substrates based on a system of partial differential evolution equations. We incorporate Einstein's method of Brownian motion to deduce the chemotactic model exhibiting a traveling band. It is the first time that Einstein's method has been used to motivate equations describing the mutual interaction of the chemotactic system. We have shown that in the presence of limited and unlimited substrate, traveling bands are achievable and it has been explained accordingly. We also study the stability of the constant steady states for the system. The linearized system about a constant steady state is obtained under the mixed Dirichlet and Neumann boundary conditions. We are able to find explicit conditions for linear instability. The linear stability is established with respect to the L2-norm, H1-norm, and L∞-norm under certain conditions. [ABSTRACT FROM AUTHOR]

Cyclodextrin enhances the activity of bioactive compounds through the formation of inclusion complexes (ICs), but its effect on diverse compound structures and processing methods is poorly understood. Here, our goal is to provide a comprehensive and cohesive insight into hydroxypropyl-β-cyclodextrin (HPβCD) complexation with cinnamaldehyde (CINN), citral (CIT), or their combination (MIX), prepared via kneading (KN), or freeze-drying (FD) using analytical techniques and computational simulations. Thermodynamic analysis revealed an exothermic and spontaneous (ΔG < 0) complexation process, with CINN-ICs exhibiting greater stability constants at 25 °C than CIT-ICs. Among the methods, CIT-KN displayed the highest efficiency (90.7%) and drug loading (9%), while CINN-KN showcased higher zeta potential (−23.2 mV), controlled release (35%), and antimicrobial activity (against both gram-positive and gram-negative bacteria). Computer simulations confirmed the absence of ternary complexes (CINN+CIT in HPβCD) and revealed the coexistence of association and ICs. Thermal analyses demonstrated high thermal stability (up to 207 °C) of included compounds, enhancing the suitability of these complexes for high-temperature processes. Additionally, CINN-KN incorporation into methylcellulose creates an active film, which effectively inhibited the proliferation of L. monocytogenes and S. Choleraesuis in cheeses (up to 1.3 cm halo inhibition), even following exposure to temperatures as high as 50 °C. Through combined experiments and computations, we uncovered how processing affects ICs performance with bioactive compounds, confirming their associative interactions with HPβCD. Thus, we underscore that the active function of ICs containing bioactive compounds relies not only on compound structure but also on processing methods, involving a collaborative interplay between both factors. [ABSTRACT FROM AUTHOR]

This review aims to provide the readership with an overview of the applications of the time-resolved spectroscopic techniques (often combined with steady-state measurements) in the elucidation of the mechanism of the photochemical behaviour of diaryl- and triarylamines. Such derivatives undergo cyclization to the carbazoles or ionization to the corresponding amine radical cations depending on both the nature of the starting substrates and the reaction conditions. In this context, time-resolved spectroscopy techniques allowed for the detection and the full characterization of all the excited states and the transients involved in these processes. The main characteristics of such species, including lifetime, time-resolved absorption spectra, quantum yield values and rate constants of formation and decay in both homogeneous and micro-heterogeneous environment (e.g. aqueous surfactant solutions) are thus summarized in the presented paper. This review focuses on the application of laser flash photolysis as a key spectroscopic tool in the elucidation of the mechanism of the photoinduced [6π]-electrocyclization reaction of diaryl- and triarylamines. This time-resolved methodology led to detect and demonstrate that transients triplet state of the amine; the triplet and the ground state of the 4a,4b-dihydrocarbazole are formed in a consecutive adiabatic pathway. [ABSTRACT FROM AUTHOR]

The miniaturization and increasing functionality of electronic devices lead to significant heat generation, negatively impacting their performance and longevity. Efficient thermal management is crucial to maintain temperature within safe operating limits. Using nanofluids in mini-channel heat sinks and optically tuned nanofluids in agricultural greenhouses has emerged as a viable solution for active cooling. This study investigates the thermal cycling performance of PCM-based heat sinks with and without pin fins to assess their suitability for long-term thermal management applications. Thermal cycling tests are conducted on PCM-based heat sinks containing RT-42 PCM and different pin fin configurations made from aluminum 2024-T851. The tests evaluated stability under a constant 10 W heat flux during both charging and discharging phases for baseline cases without fins. The results indicate that the maximum temperature difference between the 30th and 40th thermal cycles was only 0.97 °C, representing a mere 2.08% variation. This observation highlights the ability of PCM-based heat sinks to maintain a consistent temperature profile even under repeated thermal loading conditions. The PCM-based triangular pin fin heat sink was more effective than the circular and square pin fin heat sinks. It maintained the lowest average temperature at 32.83 °C and had the lowest rate of temperature increase during charging, at 0.463 °C per minute. Furthermore, the combination of PCM and triangular fins demonstrated superior thermal stability compared to other configurations. The maximum temperature difference between the first and 40th thermal cycles for this configuration is observed at only 0.83 °C with 1.38% variation. This exceptionally low-temperature difference underscores the effectiveness of the triangular pin fin design in promoting heat dissipation and maintaining thermal stability. The results highlight the potential of PCMs to enhance the long-term performance of electronic devices by maintaining optimal operating temperatures. [ABSTRACT FROM AUTHOR]

In this paper, we consider a spatially distributed equation with a periodic boundary condition and the zero integral mean condition in the spatial variable. The boundary-value problem under consideration has a family of solutions that are piecewise constant with respect to the spatial variable and have one discontinuity point. Conditions for the stability of such solutions are determined. The existence of piecewise constant solutions with more than one discontinuity point is shown. An algorithm for calculating solutions to the boundary-value problem by numerical methods is presented. A numerical analysis of the dynamics of the boundary-value problem is performed. [ABSTRACT FROM AUTHOR]

Complex formation of vanadium(V) with 4-(2',3',4'-trihydroxyphenyl)-3-nitro-5-sulfoazobenzene (R) in the presence of cationic surfactants (CS), cetylpyridinium chloride (CPCl), cetylpyridinium bromide (CPBr), and cetyltrimethylammonium bromide (CTMABr), is studied. Vanadium(V) and R form a colored complex at a component ratio of 1 : 2 and pH of 5.0–5.5. The absorbance maximum of the complex is at 449 nm, while the reagent under these conditions absorbs light at 395 nm. In the presence of cationic surfactants, mixed-ligand complexes with a component ratio of V(V) : R : CS = 1 : 2 : 2 are formed, which results in a bathochromic shift of the absorbance maximum. Additionally, the pH value for the maximum complex formation shifts to a more acidic medium compared to the homoligand V(V)–R complex. The absorbance of the V(V) : R : CPCl, V(V): R : CPBr, and V(V) : R : CTMABr complexes is maximal at 457, 461, and 466 nm, respectively. The yield of these complexes is the highest at pH of 3.5–4.0 for VV(V) : R : CPCl and V(V): R : CPBr, and at a pH of 2.5–3.0 for V(V) : R : CTMABr. The formation of both homoligand and mixed-ligand vanadium(V) complexes depends on the reaction time, temperature, and concentrations of the reacting components. The determined stability constants indicate the high stability of the resulting mixed-ligand complexes. The specific conductivity of the complexes under the optimal conditions of complex formation was determined using conductometric titration. Calibration curves for the determination of vanadium(V) as homoligand and mixed-ligand complexes are linear. The effect of foreign ions and masking agents on the determination of V(V) as homoligand and mixed-ligand complexes was analyzed; it was shown that the presence of cationic surfactants significantly increases the selectivity of the reaction. An analysis of water samples from Lake Khanbulan, Lankaran District, Azerbaijan Republic using the developed procedure showed the presence of small amounts of vanadium(V). [ABSTRACT FROM AUTHOR]

A model two-dimensional acoustic waveguide with lateral impedance boundary conditions (and outgoing boundary conditions at the waveguide outlet) is considered. The governing operator is proved to be bounded below with a stability constant inversely proportional to the length of the waveguide. The presence of impedance boundary conditions leads to a non self-adjoint operator which considerably complicates the analysis. The goal of this paper is to elucidate these complications and tools that are applicable, as simply as possible. This work is a continuation of prior waveguide studies (where self-adjoint operators arose) by J. M. Melenk et al. (2023), and L. Demkowicz et al. (2024). [ABSTRACT FROM AUTHOR]

The crown-containing bis(chromophoric) chemosensor for mercury(II) cations in an aqueous solution was synthesized using the azide—alkyne 1,3-dipolar cycloaddition click reaction. The synthesized compound contains the 4-methoxy-1,8-naphthalimide fragment acting as the electron excitation energy donor and styrylpyridine being the chromorphore-acceptor. Upon the excitation of the naphthalimide residue with the visible light, the resonance energy transfer (RET) occurs, and its efficiency decreases as a result of complex formation with Hg2+ cations. The changes in the fluorescence spectrum observed upon the addition of Hg2+ allow one to detect the ratiometric fluorescence response due to an increase in the ratio of emission intensities in the donor and acceptor channels. Based on the spectrophotometric and spectrofluorimetric titration data, the logarithms of the stability constants (logK) for the 1 : 1 metal—ligand complex were calculated to be 5.37±0.05 and 5.81±0.06, respectively. The proposed fluoroionophore is characterized by the detection limit of Hg2+ ions in water at pH 4.5 equal to 40 nmol L−1. The ability of the synthesized chemosensor to perform fluorescence imaging of mercury(II) cations in living cells was also analyzed. [ABSTRACT FROM AUTHOR]

Purpose: The meniscal vascularization remains poorly documented, particularly its origin. The aim of this cadaveric study was to describe the origin of the arterial vascularization of the menisci. Methods: This is an anatomical study on human specimens. Twenty knees were used. The average age of the subjects was 82.7 years old (56–97). Ten knees were injected with latex-neoprene and ten knees were injected with colored gelatin mixed with India ink. The same protocol for dissection was used in all cases. Results: The meniscal vascularization is provided by the genicular arteries of the knee originating from the popliteal artery. The superior medial, superior lateral, inferior medial, inferior lateral, and middle genicular arteries had constant pathways. A second middle genicular artery was found in 55% of cases. The inferior lateral genicular artery ran alongside the meniscal's periphery. The inferior medial genicular artery followed the proximal tibial metaphysis. In all dissections, a previously undocumented small artery originated from under the middle genicular arteries. This artery remained extracapsular and followed the medial meniscal periphery. This artery has been named the "medial capsulo-meniscal artery". The genicular arteries formed an extensive peri-articular anastomotic vascularization for the menisci and thus referred to the "peri-meniscal arterial archs". The lateral peri-meniscal arch was predominantly supplied by the inferior lateral genicular artery, while the medial peri-meniscal arch was mainly supplied by the medial capsulo-meniscal artery. Conclusion: The peri-meniscal arterial archs are a vascular complex formed by the genicular arteries of the knee and an artery not previously described: the "capsulo-meniscal artery". These archs have a constant presence but their formation and distribution is different between the medial and lateral menisci. [ABSTRACT FROM AUTHOR]

The formation of mononuclear complexes and a heterovalent compound in the FeII—FeIII—l-Ala—H2O system was observed when using the Clark—Nikolsky oxidation potential at a temperature of 298.15 K and an ionic strength of the (Na(H)ClO4) solution equal to 0.75 mol L−1. The method of successive approximations (iteration) of the Yusupov oxidation function was used to calculate the stability and the model parameters of the mononuclear coordination compounds [FeHL(H2O)5]3+, [Fe(HL)2(H2O)4]3+, [Fe2(HL)2(OH)4(H2O)6]2+, [FeIIIFeII(HL)2(OH)4(H2O)6]+, [FeHL(H2O)5]2+, [Fe(HL)(OH)(H2O)4]+, and [Fe(HL)(OH)2(H2O)3]0 (L is an alanine ligand), the formation constants of these complexes, to determine the regions where they are dominant and their maximum degrees of accumulation, as well as to plot the diagrams of their distribution as a function of pH. It was determined that the heterovalent complex is the most stable and dominates up to pH 9.5. [ABSTRACT FROM AUTHOR]

In this paper, we study Chaplain–Lolas model in three dimensional bounded domain, which describes the invasion and diffusion process of solid tumors during the vascular growth stage. Although the model has received extensive attention since it was proposed, the existence of solutions in three-dimensional space is still missing, and only a global small solution is established by Pang and Wang (Math Models Methods Appl Sci 28(11):2211–2235, 2018) with sufficiently small proliferation coefficient. As for long time behavior, there are only corresponding stability result of constant steady-state for the case without ECM remodelling (Hillen et al. in Math Models Methods Appl Sci 25(1):165–198, 2013; Tao and Winkler in SIAM J Math Anal 47:4229–4250, 2016). If the remodeling effect of ECM is considered, the relevant research is still blank. In this paper, we first pay our attention to the study of existence of global strong solution and long time behavior. We prove that when the ratio of cell proliferation coefficient to chemotactic intensity μ χ 2 is large, there exists a unique global strong solution around the equilibrium state (1, 1, 0), and the global strong solution converges exponentially to the constant equilibrium point. In fact, such a largeness restriction on μ χ 2 is actually necessary to some extent, since that the constant equilibrium point (1, 1, 0) is actually linearly unstable when such a condition is not satisfied. Subsequently, we turn our attention to the study of dynamic behavior of solutions. We introduce a time periodic external force to this system, and prove that the solution will gradually show the same periodic behavior under the action of periodic external force, and become a time periodic solution. At last, we analysis the stability and instability of equilibrium points, and discuss the influence of spatial diffusion, chemotaxis and haptotaxis effect on the stability of solutions. In particular, we find that only chemotaxis can change the stability of the solution and make the originally stable equilibrium (1, 1, 0) unstable, while the haptotactic term has no effect on the stability. [ABSTRACT FROM AUTHOR]

The formation of mononuclear complexes and a heterovalent compound in the FeII—FeIII—l-Ala—H2O system was observed when using the Clark—Nikolsky oxidation potential at a temperature of 298.15 K and an ionic strength of the (Na(H)ClO4) solution equal to 0.75 mol L−1. The method of successive approximations (iteration) of the Yusupov oxidation function was used to calculate the stability and the model parameters of the mononuclear coordination compounds [FeHL(H2O)5]3+, [Fe(HL)2(H2O)4]3+, [Fe2(HL)2(OH)4(H2O)6]2+, [FeIIIFeII(HL)2(OH)4(H2O)6]+, [FeHL(H2O)5]2+, [Fe(HL)(OH)(H2O)4]+, and [Fe(HL)(OH)2(H2O)3]0 (L is an alanine ligand), the formation constants of these complexes, to determine the regions where they are dominant and their maximum degrees of accumulation, as well as to plot the diagrams of their distribution as a function of pH. It was determined that the heterovalent complex is the most stable and dominates up to pH 9.5. [ABSTRACT FROM AUTHOR]

This study is concerned with the mechanism and kinetics of isothermal oxidation of a newly developed oxide dispersion strengthened Fe3Al with Cr and Ti additions (Fe–12.7Al–5.8Cr–0.25Ti–0.35Y2O3) at 900 and 1050 °C for a duration of 2000 h under ambient atmosphere. The oxidation rate is similar at both the temperatures up to 1200 h, beyond which, the rate is higher for the samples oxidized at 1050 °C. The spallation of oxidation products is higher at 900 °C. The rate constants for the reaction and instantaneous rate constants confirm the formation of various types of oxides and other associated processes as a function of time and temperature. The alloy under study has been proven to exhibit superior resistance to oxidation at high temperatures, when compared to other commercially available ODS–Fe3Al alloys and superalloys developed for similar applications. The superior oxidation of this material is due to the formation of stable α-Al2O3 layer along with layers of Fe2O3, Cr2O3 and assimilation of metastable TiO. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) in landfill leachate impacts the toxicity, bioavailability, and migration of heavy metals. The present study investigated the complexation of heavy metals (Cu2+ and Pb2+) with DOM from two landfill leachate samples, representing an old landfill site containing incineration residues and incombustible waste. The logarithms of the stability constant (log KM) and percentage of complexed fluorophores were calculated using both the Ryan–Weber non-linear model and the modified Stern–Volmer model, yielding good agreement. The log KM values (at pH = 6.0 ± 0.1) calculated using both methods for the two sampling points were 5.02–5.13 and 4.85–5.11 for Cu2+–DOM complexation, and 5.01–5.13 and 4.46–4.87 for Pb2+–DOM complexation, respectively. Log KM was slightly higher for binding of DOM with Cu2+ than Pb2+, and the quenching degree was stronger for complexation with Cu2+ (28.5–30.6% and 38.0–45.9%) than Pb2+ (6.5–7.1% and 10.0–15.4%) in both leachate samples. While log KM values were similar, differences in the contributions of functional groups and molecular composition led to varying degrees of quenching. This study reveals the potential for heavy metal binding by DOM in landfill leachate with a unique solid waste composition and emphasizes variations in fluorescence quenching between Cu2+ and Pb2+ despite similar log KM levels. These findings may be useful for assessing heavy metal behavior in landfill leachate and its impacts on the surrounding environment. [ABSTRACT FROM AUTHOR]

The zinc boron complex formation was studied as a function of temperature (25, 50 and 70 °C) in boric acid solutions of various concentration (0.25, 0.50 and 0.68 mol·kg−1). pH was monitored during zinc ion addition by galvanostatic dissolution of a zinc metal electrode, in a solution of boric acid. The determination of the complex formation showed the importance of an accurate model of the polyborate speciation, recalculated for this work based on the previous literature data mainly potentiometric measurements completed by Raman spectroscopy and Ab Initio calculations. Modelling of our experimental results, considering various scenarios of boric acid speciation, was performed using R and PhreeqC, suggesting the formation of an aqueous triborate-zinc (II) complex, ZnB 3 O 3 (OH) 4 (aq) + , according to the reaction: Zn 2 + + 3 B (OH) 3 ⇌ ZnB 3 O 3 (OH) 4 (aq) + + 2 H 2 O + H + . The nature and structure of this aqueous complex disagrees with the results reported previously in the literature. Three formation constants of the triborate-zinc (II) complex were determined at 25, 50 and 70 °C as log 10 K ZnB = − 4.73 ± 0.10, − 4.21 ± 0.16 and − 4.94 ± 0.12, respectively. The evolution of zinc boron complex formation as a function of temperature (between 25 and 70 °C) provides information on the effect of the polyborate predominance in the solution on the complexation of zinc. [ABSTRACT FROM AUTHOR]

The hydrolysis behavior of U(IV) was preliminarily explored by experimental methods, and the hydrolysis characteristics of U(IV) were determined. The results show that the absorption characteristic peak of U(IV) hydrolyzed products is between 380 and 420 nm, the hydrolytic process is not linear and reversible, and the hydrolysis reaction of U(IV) includes multiple processes. There are 4 integer hydrolysis stability constants of U(IV) were experimentally analyzed. With the increasing of OH− concentration, the mean coordination number of OH− increases. [ABSTRACT FROM AUTHOR]

A computational study on the host–guest complexes of neutral bis(4-nitrophenyl)squaramide (SQ) and halide anions is reported. In the gas-phase, the calculated interaction and stabilization energies indicates a diminishing intrinsic affinity of SQ for anions from fluoride to iodide. The nature of interactions is investigated using Natural Bond Orbital (NBO), Quantum Theory of Atoms in Molecules (QTAIM) along with Energy Decomposition Analysis-Natural Orbitals for Chemical Valence (EDA-NOCV). While electrostatic interactions account for roughly 60% of the total, EDA-NOCV analysis demonstrated increasing contributions of orbital interactions from SQ ⋯ I - to SQ ⋯ F - complexes. In solution, thermodynamic cycle analyses and Gibbs free energy calculations reveal a propensity towards the formation of SQ ⋯ F - , taking into account the influence of solvation energies on the overall stability. The consistent trend observed in selectivity both in the gas phase and in solution suggests that changes in solvation energy do not significantly impact the stability of complexes. The findings were additionally supported by a significant correlation observed between the computed and experimental formation constants. [ABSTRACT FROM AUTHOR]

The release and escape of radioactive materials has posed tremendous threats to the global environment. Among various radioactive elements, 90Sr has attracted growing attention due to its long half-life and its tendency to accumulate in bone tissue. Nonetheless, the concentration of 90Sr in radioactive waste is exceedingly low, far below the detection limits of currently available strontium-targeting chemical sensors. Herein, we propose an optical nanosensor (Sr2+-nanosensor) that exhibits an ultra-low detection limit of 0.5 nM, surpassing the 90Sr in the treated radioactive water from the Fukushima. The sensor offers wide sensing range of eight orders of magnitude, rapid response of less than 10 s, and high selectivity against 31 common ions. These excellent performances are attributed to a specific ligand (Sr2+-ligand) for Sr2+ recognition. The Sr2+ is found to be bound by six oxygen atoms from the Sr2+-ligand with a stability constant at least two orders higher than that of other traditional ligands. This study offers invaluable insights for the design of Sr2+-sensing methodologies as well as a technique for detecting trace amounts of environmental radioactive pollution. The release and escape of radioactive 90Sr has attracted growing attention due to its long half-life and its tendency to accumulate in bone tissue. Herein, the authors report an optical nanosensor (Sr2+-nanosensor) that exhibits an ultra-low detection limit of 0.5 nM, a rapid response of less than 10 s, and high selectivity against 31 common ions. [ABSTRACT FROM AUTHOR]

The results of studying the effect of the central metal ion on the stability of gadolinium and holmium complexes with 1,10'-phenanthroline-2,9-dicarboxylic acid diamide are presented. The obtained values of the stability constants of the complexes turned out to be an order of magnitude lower than the previously known values for the complexes of these elements with 4,7-dichloro-1,10'-phenanthroline-2,9-dicarboxylic acid diamide. [ABSTRACT FROM AUTHOR]

Aquatic humic substances (AHS) are defined as an important components of organic matter, being composed as small molecules in a supramolecular structure and can interact with metallic ions, thereby altering the bioavailability of these species. To better understand this behavior, AHS were extracted and characterized from Negro River, located near Manaus city and Carú River, that is situated in Itacoatiara city, an area experiencing increasing anthropogenic actions; both were characterized as blackwater rivers. The AHS were characterized by 13C nuclear magnetic ressonance and thermochemolysis GC–MS to obtain structural characteristics. Interaction studies with Cu (II), Al (III), and Fe (III) were investigated using fluorescence spectroscopy applied to parallel factor analysis (PARAFAC) and two-dimensional correlation spectroscopy with Fourier transform infrared spectroscopy (2D-COS FTIR). The AHS from dry season had more aromatic fractions not derived from lignin and had higher content of alkyls moities from microbial sources and vegetal tissues of autochthonous origin, while AHS isolated in the rainy season showed more metals in its molecular architecture, lignin units, and polysacharide structures. The study showed that AHS composition from rainy season were able to interact with Al (III), Fe (III), and Cu (II). Two fluorescent components were identified as responsible for interaction: C1 (blue-shifted) and C2 (red-shifted). C1 showed higher complexation capacities but with lower complexation stability constants (KML ranged from 0.3 to 7.9 × 105) than C2 (KML ranged from 3.1 to 10.0 × 105). 2D-COS FTIR showed that the COO− and C-O in phenolic were the most important functional groups for interaction with studied metallic ions. [ABSTRACT FROM AUTHOR]

An analysis of the impedance data for the Hg-electrode/salt solutions interface of molecular containers of cucurbiturils containing their supramolecular cationic complexes was carried out. The need to study the properties of such systems is determined by their practical use in the field of supramolecular chemistry, medicine, biochemistry, and nanotechnology. The formation of two types of adsorption layers and a significant change in the adsorption behavior with a change in the initial concentrations of the system components and the electrode potential were established. It was shown that the observed changes are due to a change in the concentration of free molecules of cucurbiturils not involved in complex formation. The high sensitivity of the impedance measurement data to this parameter found this way made it possible to establish the corresponding quantitative dependences for systems with known values of the strength constants for complexes of inorganic cations with cucurbiturils. It was shown that for systems close in nature, this opens up the possibility of finding previously unknown strength constants of cationic cucurbiturils complexes when analyzing impedance measurement data. The work showed the applicability of the proposed method for determining the strength constants of supramolecular cationic cucurbiturils complexes, which can be an alternative to more complex and time-consuming methods. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study of the conversion of vacuum residue in the presence of finely dispersed regenerated spent aluminum-cobalt-molybdenum hydrotreating catalysts in oxide and sulfide forms, as well as manganese acetylacetonate and cobalt acetylacetonate. The value of the yield of light fractions was chosen as the factor determining the efficiency of the process. The proposed catalyst samples are capable of exhibiting catalytic activity in the direction of intermolecular hydrogen transfer reactions, which presumably can lead to an increase in the yield of light fractions by suppressing the formation of compaction products. The experiments were carried out in an autoclave at an atmospheric pressure of 0.1 MPa, with a contact time of 30 min and temperatures of 440 and 460°C. The yield and composition of hydrocarbon gas were analyzed, the yield of narrow fractions of the process was analyzed, and the physicochemical properties of the resulting narrow fractions were determined, such as density, sulfur content, iodine number, kinematic viscosity of diesel fractions, and cetane index of diesel fractions. Material balances of the processes carried out are presented. A comparative analysis of the influence of the proposed catalyst samples on the results of the vacuum residue cracking process in the presence of a suspended catalyst was performed. The increase in the yield of light fractions relative to thermal processes at corresponding temperatures was calculated for each catalyst sample. The rate constants for the formation of light fractions, normalized to the number of moles of the active component of the catalyst samples, are given. The obtained values were compared, and the operating efficiency of each catalyst sample was analyzed. Conclusions are drawn about the prospects for using the proposed catalyst samples in thermodestructive processes of processing heavy oil residues at oil refineries. [ABSTRACT FROM AUTHOR]

The theory of mixed finite element methods for solving different types of elliptic partial differential equations in saddle point formulation is well established since many decades. This topic was mostly studied for variational formulations defined upon the same product spaces of both shape- and test-pairs of primal variable-multiplier. Whenever either these spaces or the two bilinear forms involving the multiplier are distinct, the saddle point problem is asymmetric. The three inf-sup conditions to be satisfied by the product spaces stipulated in work on the subject, to guarantee well-posedness, are known [(see, e.g., Exercise 2.14 of Ern and Guermond (Theory and practice of finite elements, Applied mathematical, sciences, Springer, 2004)]. However, the material encountered in the literature addressing the approximation of this class of problems left room for improvement and clarifications. After making a brief review of the existing contributions to the topic that justifies such an assertion, in this paper we set up finer global error bounds for the pair primal variable-multiplier solving an asymmetric saddle point problem. Besides well-posedness, the three constants in the aforementioned inf-sup conditions are identified as all that is needed for determining the stability constant appearing therein, whose expression is exhibited. As a complement, refined error bounds depending only on these three constants are given for both unknowns separately. [ABSTRACT FROM AUTHOR]

Herein, an accurate and simple spectrophotometric method for investigating cefixime in different formulations is reported. The proposed method elaborates on the complexation of cefixime with vanadyl sulfate in acidic media. The yellow color complexation product manifested its maximum absorbance peak at around 321 nm, and obeyed Beer's law in 2 × 10−6–1 × 10−4 M cefixime concentration. Obtained spectroscopic data were used to calculate standard deviation (S), limit of detection (LOD), limit of quantification (LOQ), and relative standard deviation (RSD) as 6.5 × 10−5, 1.96 × 10−4, 6.5 × 10−4 M, and 0.057%, respectively. In addition, the formation constant associated with the complex obtained, calculated as 5.7 × 1016, indicates that the final complex was remarkably stable. [ABSTRACT FROM AUTHOR]

5-Hydroxy-6-methyluracil (5-OH-6-MU) was shown to form a 1:1 complex with N-acetylcysteine (N-AC), i.e., the compounds interacted in an equimolar ratio. The temperature dependence of the stability constant was studied in the range 291-316 K. The thermodynamic parameters of the complexation process were determined. Aprocedure for the synthesis of the 5-OH-6-MU...N-AC complex was developed based on the results. The toxicity and antihypoxic activity of the complex were subsequently studied. The synthesized compound at a dose of 500 mg/kg in mice had low toxicity and antihypoxic activity significantly superior to those of the reference drugs (5-OH-6-MU and N-AC). [ABSTRACT FROM AUTHOR]

The understanding of the thermodynamic stability and speciation of metal complexes in solution requires access to their enthalpy and entropy of formation. In this work, we specifically focus our investigation on the complexation process of silver(I) ion in acetonitrile (AN) with substituted mono pyridines and cyclic monoamines. The aim of this study is to provide reliable thermodynamic data to obtain insights on metal complex formation, focusing on ligands donor properties and solvation effects. Carefully designed potentiometric and calorimetric experiments allowed to define the species present at different ligand/metal ratios and to obtain the complex formation constants and enthalpies. In general, the enthalpy terms associated with the complex formation are highly exothermic, while the entropy values are always unfavorable. The formation constants of AgLj species for the ligands investigated in AN are compared with those previously obtained in dimethyl sulfoxide (DMSO) and water. The trends in stability constants and enthalpy values are discussed in relation to the pKa data available in the different solvents. Higher pKa values correspond to greater ligand basicity and result in more stable and more enthalpy stabilized complexes. [ABSTRACT FROM AUTHOR]

Due to the complexity of ligand-charge distribution models and the controversies regarding the additivity of heavy metal adsorption on iron (hydr)oxides–organic composites, a convenient criterion for determining additivity was proposed in this study, based on the modeling results of the component additivity method and the Cd adsorption mechanisms on the composites. The content of humic acid (HA) (3–41%) and iron (hydr)oxides properties (e.g., specific surface area) are the main factors affecting the simulation results. The reason is that the electrostatic interaction between the components in composites changes the affinity between them and Cd. By optimizing the stability constants for Cd adsorption on ferrihydrite (Fh)/goethite (Gt) and HA, the simulation deviation of Cd adsorption on Fh–HA composites can be reduced from around 10% to less than 5%, while that on Gt–HA composites can be reduced from 10 to 60% to less than 10%. The carboxyl group of HA (HA–COOH) and the single-coordinated hydroxyl group of iron minerals (≡FeOH0.5−) are the main functional groups that bind to Cd. The ratio of covered HA–COOH (i.e., deactivated HA–COOH) to ≡FeOH0.5− can be used as a criterion for determining additivity. When the ratio exceeds 0.2, the simulation deviation caused by electrostatic interaction cannot be ignored and it is necessary to optimize the stability constant for Cd adsorption on each component. This method is convenient to predict adsorption of cationic heavy metals on iron (hydr)oxides–organic composites in the environment. [ABSTRACT FROM AUTHOR]

Proteases, such as trypsin, are essential for extracting collagen in various industrial applications. The potential applications of rare earth nanomaterials, specifically yttrium nanoparticles, have attracted significant interest across various fields due to their distinctive characteristics, including high dielectric constant and thermal stability. Biomineralization has emerged as a promising approach to synthesize protein-inorganic nanomaterials with hierarchical structures and desired functions. In the present investigation, a novel protease-templated biomineralization strategy was developed for synthesizing protease-(NH4)2Y3F11•H2O hybrid nanomaterials using a one-pot method under very mild conditions. For modifying the morphologies of (NH4)2Y3F11•H2O throughout biomineralization, protease has been demonstrated to be a highly promising biotemplate. Protease was utilized as a template for morphological control in the biomineralization procedure, which resulted in a gradual transformation of the initially formed (NH4)2Y3F11•H2O octahedral structures into uniform nanospheres. The applicability of this approach was supported by successfully utilizing various proteases to synthesize protease-(NH4)2Y3F11•H2O hybrid nanospheres. In addition to a strong and desirable luminescent signal, these hybrid nanospheres demonstrated extensive recycling because of their high enzymatic activity, stability and durability. The protease-mediated biomineralization approach offers an easy and robust approach to develop innovative protease-inorganic composites. Its moderate reaction conditions and simple operation render it a viable tool for developing stable and reusable enzyme reactors in various industrial applications. [ABSTRACT FROM AUTHOR]

New macrocyclic Schiff bases, lower rim disubstituted imine derivatives of thia- and calix[4]arenes 7 and 8 adopted in a cone stereoisomeric conformation, bearing two tert-butyl substituents grafted to iminophenol coordinating sites, and containing a spacer composed of two methylene bridges were synthesized. The prepared compounds were characterized by a complex of physicochemical methods in solution (1H/13C NMR spectroscopy, MALDI TOF mass spectrometry) and in the crystalline phase (IR spectroscopy, single-crystal X-ray diffraction (XRD)). In crystals calix[4]arene 7 forms a solvate in which acetonitrile or methanol molecules are included into the macrocycle cavity, whereas the crystals of thiacalix[4]arene 8 contain no solvent molecules. The difference in the conformational behavior of the macrocyclic platform was evidenced when comparing the crystal structures of calix[4]arene 7 and thiacalix[4]arene 8. The stoichiometry and the logarithm and stability constant values of the corresponding complexes of the synthesized macrocyclic Schiff bases with 3d-metal cations (CoII, NiII) in solution were determined using spectrophotometry titration. When interacting with CoII cations, compound 7 forms complexes with stoichiometry Lig: M = 1: 1 and 1: 2 (Lig is ligand, and M is metal). In the case of compound 8, complexes with the stoichiometry Lig: M = 1: 4, as well as 1: 2, are observed, which presumably indicates the involvement of "soft" sulfur atoms in the interaction with the metal cations. The replacement of CoII cations by NiII resulted in the formation in the solution of complexes with the stoichiometry Lig: M = 2: 1, 1: 1 and Lig: M = 1: 1, 1: 2 for compounds 7 and 8, respectively. [ABSTRACT FROM AUTHOR]

The stability constants of the complexes of europium(III) and terbium(III) ions with terephthalic acid anions were determined by potentiometric titration over a wide pH range. The luminescent properties of these complexes were studied. It was shown that the complexes are most stable in slightly acidic solutions. Analysis of the photoluminescence emission spectra confirmed the adequacy of the proposed model of complexation. [ABSTRACT FROM AUTHOR]

The solubility of crystalline MoO3 in HCl solutions with variable concentration was investigated at 100, 155, 200, 250, 300, 350°C and saturated vapor pressure. The results showed that the MoO3 solubility increases with increasing HCl concentration. Using the OptimA program, the Gibbs energies of MoO2Cl2 complex have been determined. The stability constants of MoO2Cl2 are calculated according to the reaction: The pK values are 1.07 ± 0.29; 1.06 ± 0.49; 1.74 ± 0.71; 1.83 ± 0.47; 1.50 ± 0.28; 0.95 ± 0.57, respectively, at 100, 155, 200, 250, 300, 350°C (saturated vapor pressure). [ABSTRACT FROM AUTHOR]

We establish the Hyers–Ulam stability of a second-order linear Hill-type h-difference equation with a periodic coefficient. Using results from first-order h-difference equations with periodic coefficient of arbitrary order, both homogeneous and non-homogeneous, we also establish a Hyers–Ulam stability constant. Several interesting examples are provided. As a powerful application, we use the main result to prove the Hyers–Ulam stability of a certain third-order h-difference equation with periodic coefficients of one form. [ABSTRACT FROM AUTHOR]

The chemical speciation of binary and ternary VO2+-picolinic acid (HPic) complexes with the amino acids: Leucine (Leu, HL), Isoleucine (Ile, HL), Valine (Val, HL), Tryptophan (Thr, HL), Glutamine (Gln, HL), Lysine (Lys, HL), Arginine (Arg, HL) and Tyrosine (Tyr, H2L) were obtained. This study was performed by potentiometric titrations at 25 °C using 1.0 mol·dm−3 NaCl as the ionic medium. The experimental data were analyzed with the least squares program LETAGROP, and the respective distribution diagrams were obtained with the HYSS program. The relative stability parameters Δlog10K, log10X and %R.S were determined. [ABSTRACT FROM AUTHOR]

Phenyl-bis-(4,5-dihydroxy-2,7-disulfonato-3-naphthyl)methane, tetrasodium salt, self-assembles into a dimer in water. This dimer host forms complexes with a 1:1 host to guest stoichiometry with cyclodextrins (α, β and γ) in aqueous solution. The inclusion geometry of the cyclodextrins in the cavity of the dimer host is found to vary due to different sizes of the cyclodextrins. The complexation studies indicated that there is no distinction between host and guest for the cyclodextrin (α, β and γ) and the dimer. The stability constants of the dimer host with α-, β- and γ-cyclodextrins were 622, 2450 and 963 M−1, respectively. [ABSTRACT FROM AUTHOR]

Cobalt distribution and speciation were quantified in space and time in the water column of a small, stratified, eutrophic lake, Linsley Pond, North Branford, CT. While scrupulously employing clean techniques, we used ligand exchange with dimethylglyoxime and cathodic stripping voltammetry to evaluate free and complexed forms of Co. Free aquo Co ion concentrations [Co2+] were found in the range from 0.014 to 0.28 nM from June to October 2018. Despite the orthograde distribution for total dissolved Co (0.42–3.34 nM), free Co2+ was higher in the epilimnion, decreasing with depth. Natural organic ligand concentrations [L] were in the span from 0.7 to 8.1 nM, with conditional stability constants (as logK) in the range from 9.43 to 11.13. Nearly all of the Co was complexed with highly selective ligands, and patterns suggest three controlling processes: (1) Co release from dissolving Mn (and perhaps Fe) oxides, (2) possible limitation by solubility of CoS(s), and (3) stabilization in solution via complexation by strong ligands. No correlation was observed between dissolved organic carbon and [L] in this study, suggesting that the ligands are not a simple subset of total dissolved organic matter, but may be specific compounds, perhaps S based. The hypothesis that the biological activity of plankton in Linsley Pond might be limited by micronutrient Co is only weakly supported. Cobalamin (VB12) measured via enzyme-linked immunosorbent assays ranged from 0.033 to 0.048 nM in this lake and does not follow a simple pattern with either total dissolved Co or Co2+, or with biological activity as indicated by chlorophyll levels. [ABSTRACT FROM AUTHOR]

The speciation in aqueous solution at 25 °C using 1.0 mol·dm−3 KNO3 as the ionic medium, was studied on the ternary copper(II) complexes formed with 1,10'-Phenanthroline (Phen) and the amino acids: Glycine (HGly, HL), α-Alanine (HαAla, HL), β-Alanine (HβAla, HL), Proline (HPro, HL), Serine (HSer, HL), Threonine (HThr, HL), Methionine (HMet HL) and Phenylalanine (HPhe, HL). The potentiometric data were analyzed with the program LETAGROP. The stability of the ternary complexes compared to the binary ones were evaluated in terms of ∆log K and % R.S. To analyze the potential structures present in the solution, we examined the absorption and circular dichroism (CD) spectra. Our analysis indicated the existence of ternary complexes, most of which exhibited square pyramid geometry for most of the amino acids. Nevertheless, the circular dichroism investigations suggested that these ternary complexes were unstable, potentially due to the presence of inversion bands. [ABSTRACT FROM AUTHOR]

The paper deals with CrAlYN/CrAlYO multilayer coatings obtained by the plasma-assisted vacuum-arc deposition onto a WC–8Co alloy substrate. It is investigated how the layer number and thickness of 16- and 32-layer coatings with the thickness of ~240 and ~120 nm, respectively, affect the phase composition, crystal structure parameters, roughness, surface morphology, and physical and mechanical properties. The X-ray diffraction analysis shows that the obtained multilayer coatings have a multiphase structure consisting of nitride CrN and AlN and oxide Cr2O3 and AlYO3 phases. It is found that the roughness of the 32-layer CrAlYN/CrAlYO coating is almost 2 times lower than that of the 16-layer coating. It is shown that the larger number of layers and their lower thickness have a positive effect on physical and mechanical properties of the coatings. The hardness of the 32-layer coating increases by 52%. The synchrotron X-ray diffraction analysis of the 32-layer CrAlYN/CrAlYO coating shows its thermal stability up to ~1020°C during heating in air, while during heating in vacuum, its thermal stability keeps constant up to at least 1500°C. [ABSTRACT FROM AUTHOR]

The dissociation constants of Schiff bases, (E)-1-[(2,4-dichlorophenylimino)methyl]naphthalen-2-ol, (E)-1-[(2-chloro-4-nitrophenylimino)methyl]naphthalen-2-ol, (E)-1-[(2,4-dimethoxyphenylimino)methyl]naphthalen-2-ol, and their stability constants with the copper(II) metal ion were determined potentiometrically. The experimental conditions were arranged to achieve coordination in aqueous-ethanol solutions [ethyl alcohol (30%) and water (70%) at 25.0±0.1°C and a constant ionic strength of 0.1 mol/dm3 NaCl]. It was detected that each ligand has two dissociation constants, which are associated to the protonated imine nitrogen and the hydroxyl group. The dissociation constants of these ligands and their stability constants of Cu(II) complexes were computed and discussed in relation to their structural configuration, substituents and basicity. The difference in basicity or acidity of these Schiff base ligands were explained in terms of the inductive effect, resonance and steric effect. Keto-enol tautomerism was discussed in the context of hydrogen bonding, basicity of the imine group and hydrogen acidity of the hydroxyl group; a zwitterionic tautomer might develop as well. The chemical species existing in the solution at experimental conditions used were presented with speciation diagrams. The SUPERQUAD program was used to compute dissociation and stability constants as well as the speciation diagrams. The aims of this study was to determine potentiometrically the dissociation constants of the Schiff base ligands used and the stability constants of their complexes with Cu(II). [ABSTRACT FROM AUTHOR]

In this paper, we are concerned with the initial boundary value problem on the partially damped "two fluid" Euler–Maxwell equations in three dimensional periodic domain. Compared with the previous "two fluid" Euler–Maxwell results, our model describes two fluids obey different dynamical evolutions, one is compressible Euler and the other is compressible Euler with damping. The global existence of small smooth solutions near constant steady states is established and the time decay rates of perturbed solutions are obtained. The main challenge is to investigate the asymmetric system and find out the transmission mechanism of dissipation. Although there are various variables obeying different dynamical evolutions, we can still derive the unified time-weighted energy frame to achieve our goal. Our theorem in this paper shows that partially damped "two fluid" Euler–Maxwell system (namely μ + > 0 , μ - = 0 ) also yields the global stability of a constant background. [ABSTRACT FROM AUTHOR]

The synthesis of lower-rim p-tert-butylcalix[4]arene baskets and their complexations is described. The structures of synthesized compounds were confirmed using 1H NMR, 13C NMR, DEPT, NMR, and mass spectrometry. The complexation of these compounds with [60]fullerene (C60) was followed using uv-vis and 1H-NMR, but the stability constants were not determined due to irregular change in absorptions and small chemical shifts change. The complexation of obtained componuds with platinum salts was confirmed also using IR spectroscopy, mass spectrometry and elemental analysis. [ABSTRACT FROM AUTHOR]

This paper investigates customized AA5083 and Al-Mg binary powders produced by gas atomization and assesses cold spray (CS) deposition of these materials with the evaluation of interface quality, deposition efficiency, porosity, and microhardness. While there has been extensive research progress on CS deposition of AA2024, AA6061, and AA7075, less attention has been given to CS 5xxx-series (Al-Mg) aluminum alloys. For the development and investigation of CS Al-Mg series alloys, AA5083 and customized Al-Mg binary powders were fabricated using a close-coupled inert gas atomizer, and those powders were sprayed using a high-pressure cold spray system to produce CS Al-Mg deposits. The microstructural characteristics of the powders, such as lattice constant and the formation of intermetallic networks, were affected by the Mg content of as-atomized powders. Selected CS parameters were able to produce highly dense CS deposits over a range of 1.7-5 wt.% Mg. The Mg content of as-atomized powders also influenced the hardness of the deposits and the DE while having no effect on porosity. The influence of Mg content on powder properties, CS process, and CS Al-Mg deposits has been discussed. [ABSTRACT FROM AUTHOR]

Fluorescence quenching of 3,3,11,11-tetramethyl-8,16-diphenyl-3,4,8,10,11,12,13,16-octahydroacridino[4,3-c]acridine-1,9(2H,5H)dione in liquid mixtures of methanol and acetonitrile have been studied using fluorescence spectroscopy methods. The results obtained are interpreted in terms of nonradiative deactivation of the excited state of the fluorophore due to interaction with a protic solvent. A theoretical analysis of experimental data was carried out, its results were compared with data obtained previously in similar studies in mixtures of methanol and dimethylformamide. The values of a number of model parameters were determined, in particular, the rate constant for the formation of "fluorophore–methanol cluster" complexes and the equilibrium constant of this reaction. The mechanisms of the influence of the aprotic cosolvent on the cluster structure of the mixture and the quantum yield of fluorescence have been analyzed. [ABSTRACT FROM AUTHOR]

The stability constants of triply charged lanthanide ion complexes with citric acid of 1 : 2 stoichiometry were measured by potentiometric titration in a wide pH range, and the relationship between the constants and the lanthanide type was analyzed. A mathematical model for the equilibrium in studied solutions was proposed. [ABSTRACT FROM AUTHOR]

A promising spiro[pyridobenzopyran–indoline] molecular platform for the development of ionochromic systems with a high potential for metal cation chemosensor applications is developed. Evidence for this conclusion is provided the established characteristics and properties of 6-bromo-substituted spiro[pyridobenzopyran–indoline], including ionochromism accompanied by a chromogenic effect in the form of a red shift that reaches 200 nm. The obtained Zn(II), Ni(II), Cu(II), Co(II), and Cd(II) complexes are characterized by a high stability with constants of 105.6–108.6 and 105.0–106.9 for the first and second steps, respectively. The possibilities to obtain selective sensors are associated with the fluorescence detected in the Zn(II) and Cd(II) complexes only. The photostability of the studied complexes, on the one hand, and the high spectral contrast of complex formation of the dynamic 6-bromo-substituted spiro[pyridobenzopyran–indoline] systems on the other, open up the possibility of using chemosensors based on these molecular platforms in the naked-eye colorimetric mode. [ABSTRACT FROM AUTHOR]

In this article, we propose a proper orthogonal decomposition-compact difference scheme (POD-CDS) for the displacement-stress form of a simply supported plate vibration model. We prove that the POD-CDS can preserve the same spatial and temporal convergence rates and unconditional stability with the control constant independent of the time levels for the displacement and the stress in discrete H 1 -norm as the compact difference solution does, as well as improve the computing efficiency significantly, which confirms the reliability of the POD-CDS for long time simulation of the vibration models. Furthermore, we conduct the stability and convergence analysis for the corresponding compact difference scheme in discrete H k -norm as k = 0 , 1 , 2 , respectively, which compensates those missing estimates of the references Q. Li and Q. Yang (Adv. Differ. Equ. 328: 1–19, 2019) and Q. Li, Q. Yang, and H. Chen (Numer. Methods Partial Differ. Equ. 36: 1938–1961, 2020). Numerical experiments are provided to verify these theoretical findings and show that the POD-CDS possesses nearly 10–30 times computing efficiency faster than the compact difference scheme does. [ABSTRACT FROM AUTHOR]

The complexation between Al3+ ([Al(H2O)6]3+) and glycolic acid (GA, C2H4O3) which has a carboxyl group and a hydroxyl group in a molecule was investigated under acidic condition using 27Al NMR, 13C NMR and ESI–MS techniques. The five peaks including a peak due to Al3+ were observed in 27Al NMR spectra for the mixed solution of Al3+ and GA, suggesting the existence of at least four Al-GA complexes. The results of NMR and ESI–MS measurements revealed that GA and Al3+ can form one monodentate complex (AlGA2+) and three bidentate complexes (AlGA+, AlGA2−, and AlGA33−) complexes. From the deconvolution of 27Al NMR spectra and pKa value of GA, the conditional formation constants (log10K) of each complex (GA/Al molar ratio of 25 in mixed solution) can be determined to be 0.94 (AlGA2+), − 0.96 (AlGA+), − 0.77 (AlGA2−) and − 2.21 (AlGA33−), respectively. In addition, the overall formation constant of three bidentate complex at pH 3 was also calculated to be − 1.65. [ABSTRACT FROM AUTHOR]