Complex Equilibrium Research Articles

Ligand-Directed Approach in Polyoxometalate Synthesis: Formation of a New Divacant Lacunary Polyoxomolybdate [γ-PMo10 O36 ]7.

Polyoxometalates (POMs) have received increasing attention over the last decades for extending their application and properties that originate from novel structures. For the synthesis of a variety of POM structures, multivacant lacunary POMs are key precursors, which are typically synthesized by empirically controlling the complex equilibrium in aqueous solvents. Unfortunately, despite the excellent catalytic and electrochemical properties of "polyoxomolybdates", only one multivacant lacunary species, i.e., [A-α-PMo9 O34 ]9- , has been identified and isolated because multivacant lacunary polyoxomolybdates are typically unstable. Here we report a ligand-directed approach for the selective formation of an unprecedented lacunary polyoxomolybdate in organic solvents. By structure transformation of a pyridine-coordinated [A-α-PMo9 O34 ]9- , a new γ-Keggin-type divacant lacunary polyoxomolybdate [γ-PMo10 O36 ]7- was obtained, which can be further used as a precursor for synthesizing a POM-organic hybrid.

Counting monster potentials

We study the large momentum limit of the monster potentials of Bazhanov-Lukyanov-Zamolodchikov, which — according to the ODE/IM correspondence — should correspond to excited states of the Quantum KdV model.We prove that the poles of these potentials asymptotically condensate about the complex equilibria of the ground state potential, and we express the leading correction to such asymptotics in terms of the roots of Wronskians of Hermite polynomials.This allows us to associate to each partition of N a unique monster potential with N roots, of which we compute the spectrum. As a consequence, we prove — up to a few mathematical technicalities — that, fixed an integer N , the number of monster potentials with N roots coincides with the number of integer partitions of N , which is the dimension of the level N subspace of the quantum KdV model. In striking accordance with the ODE/IM correspondence.

Approximation of the Constant in a Markov-Type Inequality on a Simplex Using Meta-Heuristics

Markov-type inequalities are often used in numerical solutions of differential equations, and their constants improve error bounds. In this paper, the upper approximation of the constant in a Markov-type inequality on a simplex is considered. To determine the constant, the minimal polynomial and pluripotential theories were employed. They include a complex equilibrium measure that solves the extreme problem by minimizing the energy integral. Consequently, examples of polynomials of the second degree are introduced. Then, a challenging bilevel optimization problem that uses the polynomials for the approximation was formulated. Finally, three popular meta-heuristics were applied to the problem, and their results were investigated.

Role of 2‒13C Isotopic Glyphosate Adsorption on Silver Nanoparticles Based on Ninhydrin Reaction: A Study Based on Surface—Enhanced Raman Spectroscopy

Glyphosate is one of the most commonly used and non-selective herbicides in agriculture, which may directly pollute the environment and threaten human health. A simple and effective approach to its detection is thus quite necessary. Surface-enhanced Raman scattering (SERS) spectroscopy was shown to be a very effective method to approach the problem. However, sensitivity in SERS experiments is quite low, caused by different orientation/conformation of the adsorbed molecules on the metal surface, which limit its detection by using SERS. In this paper, 2‒13C‒glyphosate (hereafter: 13–GLP) was designed as a model molecule for theoretical and experimental studies of the molecule structure. Vibrational modes were assigned based on the modeling results obtained at the B3LYP/6-311++G** level by density functional theory (DFT) calculations, which were performed to predict the FT‒IR and Raman spectra. Band downshifts were caused by 13C atom isotopic substitution with mass changed. Moreover, SERS spectra of 13–GLP by combining ninhydrin reaction on Ag NPs were obtained. Isotopic Raman shifts are helpful in identifying the components of each Raman band through vibrations across the molecular system. They are coupled by probe molecules and thus bind to the substrates, indirectly offering the opportunity to promote interactions with Ag NPs and reduce the complex equilibrium between different orientation/conformation of glyphosate molecules on the metal surface.

Improved Description of Charge-Transfer Potential Energy Surfaces via Spin-Component-Scaled CC2 and ADC(2) Methods.

The molecular level understanding of electronic transport properties depends on the reliable theoretical description of charge-transfer (CT)-type electronic states. In this paper, the performance of spin-component-scaled variants of the popular CC2 and ADC(2) methods is evaluated for CT states, following benchmark strategies of earlier studies that revealed a compromised accuracy of the unmodified models. In addition to statistics on the accuracy of vertical excitation energies at equilibrium and infinite separation of bimolecular complexes, potential energy surfaces of the ammonia-fluorine complex are also reported. The results show the capability of spin-component-scaled approaches to reduce the large errors of their regular counterparts to a significant extent, outperforming even the coupled-cluster single and double method in many cases. The cost-effective scaled-opposite-spin variants are found to provide a remarkably good agreement with the CCSDT-3 reference data, thereby being recommended methods of choice in the study of charge-transfer states.

An insulating doped antiferromagnet with low magnetic symmetry as a room temperature spin conduit

We report room-temperature long-distance spin transport of magnons in antiferromagnetic thin-film hematite doped with Zn. The additional dopants significantly alter the magnetic anisotropies, resulting in a complex equilibrium spin structure that is capable of efficiently transporting spin angular momentum at room temperature without the need for a well-defined, pure easy-axis or easy-plane anisotropy. We find intrinsic magnon spin-diffusion lengths of up to 1.5 μm, and magnetic domain governed decay lengths of 175 nm for the low-frequency magnons, through electrical transport measurements demonstrating that the introduction of nonmagnetic dopants does not strongly reduce the transport length scale, showing that the magnetic damping of hematite is not significantly increased. We observe a complex field dependence of the nonlocal signal independent of the magnetic state visible, in the local magnetoresistance and direct magnetic imaging of the antiferromagnetic domain structure. We explain our results in terms of a varying and applied field-dependent ellipticity of the magnon modes reaching the detector electrode allowing us to tune the spin transport.

Thermodynamic mathematical model of the Kastanozem complex and new principles of sustainable semiarid protective silviculture management

The Kastanozem complex in the dry steppe of southern Russia underlies an artificially-constructed forest strips. Deep ploughing to a depth of 45 cm was used to process the soil prior to planting. Between 20 and 40 cm depth, soil density was high, 1.57 t m−3. Soil hardness was also high, 440 psi. Soil aggregates greater than 5 cm in size were impermeable to tree roots. The content of such aggregates was high, comprising 35%. The number of tree roots with diameters greater than 0.5 cm that cross the soil profile was as low as 0.15 to 0.3 pcs cm−2. The soil matric potential signifying water availability was low in the vegetation period −0.9 MPa to a depth of 1.0 m. According to modelling experiments, the main salt components in the soil solution drive the transfer of soil organic matter (SOM) and heavy metals (HM). The composition of the soil solution determined by the calcium carbonate equilibrium (CCE) and the association and complexation of ions. ION-3 software was used to calculate the ion equilibrium in the soil solution. Macro-ions Cа2+, Mg2+, SO42−, and CO32− partly bonded as ion pairs. Oversaturation of the soil solution with CaCO3 was calculated according to the analytical content of macro-ion, which was high up to 1000 units, and its value decreased in response to ionic strength, activity, association, complexation, and thermodynamic equilibrium of macro-ions in the soil solution. Oversaturation calculated for Salic Solonetz and Gleyic Solonetz soil solutions was small considering the SOM content. Calculations indicate the profile and lateral loss of C from the soil to the vadose zone. The content of Pb in the soil solution was calculated sirca 75%–80%. The calculated coefficient of Pb2+ association was as high as 52.0. The probability of Pb passivation by SOM in the Kastanozem complex was significant. The probability of uncontrolled transfer and accumulation of HM in the soil and vadose zone was high. Biogeosystem Technique (BGT*) transcendental methodology, an innovative methodology created for stable geomorphological system formation to achieve sustainable agriculture and silviculture, was applied. The BGT* elements were: intra-soil milling of the 30–60 cm soil layer for geophysical conditioning; intra-soil continuously-discrete pulse watering for plants and trees to improve the hydrologic regime. The BGT* methodology reduced HM mobility, controlled biodegradation, enriched nutrient biogeochemical cycling, increased C content, increased soil productivity, and reversible carbon sequester in biological form.

A pipeline to analyse time-course gene expression data

The phenotypic diversity of cells is governed by a complex equilibrium between their genetic identity and their environmental interactions: Understanding the dynamics of gene expression is a fundamental question of biology. However, analysing time-course transcriptomic data raises unique challenging statistical and computational questions, requiring the development of novel methods and software. This workflow provides a step-by-step tutorial of the methodology used to analyse time-course data: (1) quality control and normalization of the dataset; (2) differential expression analysis using functional data analysis; (3) clustering of time-course data; (4) interpreting clusters with GO term and KEGG pathway enrichment analysis. As a case study, we apply this workflow to time-course transcriptomic data from mice exposed to four strains of influenza to showcase every step of the pipeline.

Effects of pH on the ultrafast transient absorption of iron (III) meso-tetrakis(4-N-methyl-pyridiniumyl) porphyrin (Fe3+TMPyP) molecular complexes

The meso-tetrakis (methylpyridiniumyl) porphyrin complexed with Fe3+ (Fe3+TMPyP) is an irregular porphyrin, possessing unfilled d external shells with d6 electronic configuration. In aqueous solution, Fe3+TMPyP exists in a complex equilibrium of different forms. Changing the solution pH, these complexes can bind to other species (as OH- and H2O) or form physical aggregates (μ-oxo-dimers), that alter their excited states properties and affect their potential applications. In the present work, we report excited state absorption dynamics of Fe3+TMPyP molecular complexes in different pH employing femtosecond Z-Scan and ultrafast transient absorption techniques. Complementary data were obtained by UV–vis absorption and fluorescence emission spectroscopies. For 532 nm excitation, the Z-Scan technique shows a decrease in the absorption coefficient for Fe3+TMPyP at pH 4.0 and an increase at pHs 7.0 and 9.0. Ultrafast transient absorption reveals the same behavior in the 525−570 nm region for samples at pHs 7.0 and 9.0. Fast relaxations, with lifetimes around 2.0 picoseconds, were obtained for all samples studied, and were attributed to internal conversion relaxation processes. Although the molecular aggregation accelerates the relaxation process of regular porphyrins, μ-oxo-dimers slightly affect the relaxation of Fe3+TMPyP. The prompt conversion of absorbed light energy in heat observed to Fe3+TMPyP porphyrins can be useful for biomedical photothermal applications, such as Photoacoustic Imaging (PAI) and Photothermal Therapy (PTT).

Rationale, Relevance, and Limits of Stress-Induced Psychopathology in Rodents as Models for Psychiatry Research: An Introductory Overview.

Emotional and cognitive information processing represent higher-order brain functions. They require coordinated interaction of specialized brain areas via a complex spatial and temporal equilibrium among neuronal cell-autonomous, circuitry, and network mechanisms. The delicate balance can be corrupted by stressful experiences, increasing the risk of developing psychopathologies in vulnerable individuals. Neuropsychiatric disorders affect twenty percent of the western world population, but therapies are still not effective for some patients. Elusive knowledge of molecular pathomechanisms and scarcity of objective biomarkers in humans present complex challenges, while the adoption of rodent models helps to improve our understanding of disease correlate and aids the search for novel pharmacological targets. Stress administration represents a strategy to induce, trace, and modify molecular and behavioral endophenotypes of mood disorders in animals. However, a mouse or rat model will only display one or a few endophenotypes of a specific human psychopathology, which cannot be in any case recapitulated as a whole. To override this issue, shared criteria have been adopted to deconstruct neuropsychiatric disorders, i.e., depression, into specific behavioral aspects, and inherent neurobiological substrates, also recognizable in lower mammals. In this work, we provide a rationale for rodent models of stress administration. In particular, comparing each rodent model with a real-life human traumatic experience, we intend to suggest an introductive guide to better comprehend and interpret these paradigms.

Coevolutionary dynamics of a variant of the cyclic Lotka–Volterra model with three-agent interactions

We study a variant of the cyclic Lotka-Volterra model with three-agent interactions. Inspired by a multiplayer variation of the Rock-Paper-Scissors game, the model describes an ideal ecosystem in which cyclic competition among three species develops through cooperative predation. Its rate equations in a well-mixed environment display a degenerate Hopf bifurcation, occurring as reactions involving two predators plus one prey have the same rate as reactions involving two preys plus one predator. We estimate the magnitude of the stochastic noise at the bifurcation point, where finite size effects turn neutrally stable orbits into erratically diverging trajectories. In particular, we compare analytic predictions for the extinction probability, derived in the Fokker-Planck approximation, with numerical simulations based on the Gillespie stochastic algorithm. We then extend the analysis of the phase portrait to heterogeneous rates. In a well-mixed environment, we observe a continuum of degenerate Hopf bifurcations, generalizing the above one. Neutral stability ensues from a complex equilibrium between different reactions. Remarkably, on a two-dimensional lattice, all bifurcations disappear as a consequence of the spatial locality of the interactions. In the second part of the paper, we investigate the effects of mobility in a lattice metapopulation model with patches hosting several agents. We find that strategies propagate along the arms of rotating spirals, as they usually do in models of cyclic dominance. We observe propagation instabilities in the regime of large wavelengths. We also examine three-agent interactions inducing nonlinear diffusion.

Evaluation and Application of Port Industrial Upgrading Based on Global Value Chain of Complex Network

Wang, Z.P., 2020. Evaluation and application of port industrial upgrading based on global value chain of complex network. In: Al-Tarawneh, O. and Megahed, A. (eds.), Recent Developments of Port, Marine, and Ocean Engineering. Journal of Coastal Research, Special Issue No. 110, pp. 231–234. Coconut Creek (Florida), ISSN 0749-0208.This paper transforms cluster escalation into complex networks where social networks, explicit and implicit knowledge networks interact with each other based on the level of knowledge and social relationship, then the relationship between variational inequality theory and optimum works out an equilibrium status of network and complex network, so as to explore how the network traffic and complex network equilibrium are subjected to change with the cluster scale. In the end, the cluster has realized its scalability.

Ultrafast high-resolution analysis of human milk oligosaccharides by multicapillary gel electrophoresis

There is recently growing interest towards synthesized human milk oligosaccharides (HMOs) as baby formula additives, and interestingly also as dietary supplements for adults. Currently quite a few manufacturers synthesize HMOs, however, their analysis is challenging, both in resolution and speed. In this paper an ultrafast high-resolution method is introduced for the separation of HMOs by multicapillary gel electrophoresis. Two gel compositions were evaluated with complementary resolving power. One was a conventionally used industrial standard carbohydrate separation matrix, resolving oligosaccharides according to their charge to hydrodynamic volume ratios. The other one was a borate-buffered dextran gel, which utilized the secondary equilibrium of the borate-vicinal diol complexation to enhance resolution. Considering the rapid analysis time and multiplexing (12-channel system), a 96 well sample plate can be analyzed in less than 80 min with the conventional type carbohydrate separation matrix and in less than one hour with the borate-buffered dextran gel. Exploiting the one fluorophore per molecule labeling stoichiometry, the limit of detection (S/N > 3) and limit of quantitation (S/N > 10) were determined as 0.025 and 0.100 mg/mL, respectively, with good linearity. Based on the calibration plot, the quantities of several low concentration HMOs were determined from a human milk sample.

Predictive values of colon microbiota in the treatment response to colorectal cancer.

The crosstalk between the colon mucosa and the microbiota represents a complex and delicate equilibrium. Gastrointestinal diseases such as inflammatory bowel disease and colorectal cancer (CRC) are associated with a state of altered microbiota composition known as dysbiosis, which seems to play a causative role in some of these illnesses. Recent reports have shown that the colorectal microbiome is responsible for the response and safety to treatments against CRC, especially immunotherapy, hence opening the possibility to use bacteria as a predictive marker and also as a therapeutic agent. The review objective is to summarize updated reports about the the implication of the colorectal microbiome in the development of CRC, in treatment response and its potential as a therapeutic approach.

Improvements on modelling wettability alteration by Engineered water injection: Surface complexation at the oil/brine/rock contact

Several laboratory experiments demonstrated that different water compositions cause rocks to change from oil- to water-wet state. Although it is a consensus that wettability alteration is the main recovery process, modeling the underlying mechanism is still a major challenge. Our main goal is to improve and validate a physically based model to predict contact angles from zeta-potential measurements. We hypothesize that, if rock and oil surface are sufficiently close as consequence of thin water layer, then the charge development of one surface will be affected by the other. We propose a new mass-action formulation for surface complexation modelling that includes the energy interface of two interacting double layers. Currently, surface complexation models consider rock and oil as completely isolated surfaces. Additionally, we develop a method of determining surface complexation equilibrium constants to honor several zeta-potential measurements for different ion concentrations (Na+, Ca2+, Mg2+, SO42− and H+). Finally, we estimate contact angles using disjoining pressure calculations and compare them with experimental ones reported in the literature.For the proposed parallel surface model, the system of equations’ solution is very distinct to isolated surface approach when the interaction between surfaces are close (spacing approximately bellow 2 nm) at high salinity. Regarding zeta-potential prediction for calcite-brine system, we argue that Na+ might not be an indifferent ion as suggested previously. Our simulation results indicate that, besides the renowned potential-determining ions, sodium adsorption on calcite can play an important role in electrostatic interactions, switching surface charge polarity. Thus, we only honor zeta-potential measurements when Na+ is considered in the surface complexation reactions. Finally, contact angle estimation using proposed surface complexation modelling and disjoining pressure theory provide good predictions of seven different cases reported in the literature. We validate our method on a total of 66 and 163 contact angle and zeta-potential measurements, respectively. The present work is a novel approach to represent how electrostatic interactions among rock, brine and oil modify the rock surface charge and the rock wetting state.

Experimental perspective for reactive separation of malonic acid using TBP in natural non-toxic solvents

Recent technological advancement allows the synthesis of malonic acid from the bio-fermentation route by using cost-effective raw material like biomass, which enhances its overall production. The dilute aqueous stream of malonic acid produced from the biological route needs to be recovered. Process intensification with precise operating conditions and low toxicity such as reactive separation is applied for extraction of malonic acid from the dilute aqueous stream by using non-toxic natural solvents like canola oil, sunflower oil, and soybean oil with the tributyl phosphate (TBP) extractant. An in-depth experimental analysis is performed in the present study to evaluate extraction complexation equilibrium constant (KE(MA)), extraction efficiency (E(MA)%), distribution coefficient (KD(MA)), and loading ratio (Z(MA)). The overall loading ratio is less than 0.5 for all solvents, which signifies the formation of 1:1 complexation. KD(MA) and E(MA)% with soybean oil are in range of 0.265–0.832, and 20.683–43.850, for sunflower oil is 0.208–0.763 and 17.227–42.340, for canola oil is 0.301–0.875 and 22.878–45.106. The behavior of TBP-malonic acid complexation equilibrium in the reactive separation process is predicted by comparing relative basicity model values with experimental outputs. The separation process requires a continuous column operation, and the number of transfer stages is evaluated to be 2. Furthermore, the diffusion coefficients (D(MA)) of malonic acid to the natural, non-toxic solvents with variable TBP concentrations are evaluated by employing various empirical correlations. The present study paves the way for future research in continuous in-situ product recovery of malonic acid produced via biological route.

Munc18-1 induces conformational changes of syntaxin-1 in multiple intermediates for SNARE assembly

In neuronal exocytosis, SNARE assembly into a stable four-helix bundle drives membrane fusion. Previous studies have revealed that the SM protein Munc18-1 plays a critical role for precise SNARE assembly with the help of Munc13-1, but the underlying mechanism remains unclear. Here, we used single-molecule FRET assays with a nanodisc membrane reconstitution system to investigate the conformational dynamics of SNARE/Munc18-1 complexes in multiple intermediate steps towards the SNARE complex. We found that single Munc18-1 proteins induce the closed conformation of syntaxin-1 not only in the free syntaxin-1 but also in the t-SNARE (syntaxin-1/SNAP-25) complex. These results implicate that Munc18-1 may act as a gatekeeper for both binary and ternary SNARE complex formation by locking the syntaxin-1 in a cleft of Munc18-1. Furthermore, the kinetic analysis of the opening/closing transition reveals that the closed syntaxin-1 in the syntaxin-1/SNAP-25/Munc18-1 complex is less stable than that in the closed syntaxin-1/Munc18-1 complex, which is manifested by the infrequent closing transition, indicating that the conformational equilibrium of the ternary complex is biased toward the open conformation of syntaxin-1 compared with the binary complex.

Slow lactate gluconate exchange in calcium complexes during precipitation from supersaturated aqueous solutions

Saturated solutions of calcium l-lactate in water or in deuterium oxide continuously dissolve calcium l-lactate by addition of solid sodium d-gluconate and become strongly supersaturated in calcium d-gluconate due to no or slow precipitation. The quantification of total dissolved calcium allied with the calcium complexes equilibrium constants allowed an ion speciation, which shows an initial non-thermal and spontaneous supersaturation of more than a factor of 50 at 25 °C only slowly decreasing after initiation of precipitation of calcium d-gluconate after a lag phase of several hours. A mathematical model is proposed, based on numerical solution of coupled differential equations of dynamics of l-lactate and d-gluconate exchange during the lag phase for precipitation and during precipitation. A slow exchange of l-lactate coordinated to calcium with d-gluconate is indicated with a time constant of 0.20 h−1 in water and of 0.15 h−1 in deuterium oxide and a kinetic deuterium/hydrogen isotope effect of 1.25. Such spontaneous non-thermal supersaturation and slow ligand exchange with a pseudo first order equilibration process with a half-life of 3.5 h in water for calcium hydroxycarboxylates can help to understand the higher calcium bioavailability from calcium hydroxycarboxylates compared to simple salts.

Harmonic-cavity stabilization of longitudinal coupled-bunch instabilities with a nonuniform fill

In synchrotrons, nonuniform fill patterns, which give rise to beam phase transients and a spread in synchrotron tune between bunches, have been observed to damp longitudinal coupled-bunch instabilities driven by higher-order modes in rf cavities. The transients are especially large in the presence of Landau cavities, which are used commonly in storage-ring light sources and particularly in the new generation of diffraction-limited storage rings. A method has recently been devised to predict the beam transient including complex form factors for the different bunches. This has now been extended to accurately predict the growth-rates and oscillation frequencies of coupled-bunch modes for arbitrary fill patterns, taking the individual complex form factors and equilibrium phases of the different bunches into account. In this paper, the extended method is presented and the theory is outlined. For a case with significant transient beam loading, predictions of the resulting beam transient and bunch profiles are compared to measurements. Predictions of coupled-bunch mode behavior are then benchmarked against results from the macroparticle tracking code mbtrack with good agreement. Finally, the method is used to predict the behavior of coupled-bunch modes as a function of the fields in passive Landau cavities.

SHY2 as a node in the regulation of root meristem development by auxin, brassinosteroids, and cytokinin.

In multicellular organisms, the balance between cell division and differentiation determines organ size, and represents a central unknown in developmental biology. In Arabidopsis roots, this balance is mediated between cytokinin and auxin through a regulatory circuit converging on the IAA3/SHORT HYPOCOTYL 2 (SHY2) gene. Here, we show that crosstalk between brassinosteroids (BRs) and auxin occurs in the vascular transition zone to promote root meristem development. We found that BR increases root meristem size by up-regulating expression of the PINFORMED 7 (PIN7) gene and down-regulating expression of the SHY2 gene. In addition, BES1 could directly bind to the promoter regions of both PIN7 and SHY2, indicating that PIN7 and SHY2 mediate the BR-induced growth of the root meristem by serving as direct targets of BES1. Moreover, the PIN7 overexpression and loss-of-function SHY2 mutant were sensitive to the effects of BR and could partially suppress the short-root phenotypes associated with deficient BR signaling. Interestingly, BRs could inhibit the accumulation of SHY2 protein in response to cytokinin. Taken together, these findings suggest that a complex equilibrium model exists in which regulatory interactions among BRs, auxin, and cytokinin regulate optimal root growth.