Substitution Mechanism Research Articles

A theoretical study of structure properties and stability in different ligands coordinated Cu-MOFs

A comprehensively theoretical study of structural properties and thermostability is performed to investigate the role of ligands in Metal Organic Frameworks (MOFs). By fitting the experimental EPR spectra, the high order perturbation formulae of a 3 d9 ion in four Cu-MOFs with ligands btm, bte, btp and btb are adopted for orthorhombically and tetragonally elongated octahedral [CuO2N4]12− groups so as to reveal the local environment around central Cu2+, including the detail structure information and local electromagnetic properties. Since the application of MOFs are normally limited by the unsatisfied thermostability, the molecule dynamic (MD) calculation based on density functional theory (DFT) is performed to clarify the influence on the stability of MOFs from the different ligands. Based on the above investigations, the mechanism of ligands substitution in MOFs can be comprehensively understood, which would be useful for designing and synthesizing novel MOFs.

Mechanical Properties and Microstructure Analysis of Cement Mortar Mixed with Iron Ore Tailings

In order to study the feasibility and sand substitution mechanism of cement mortar mixed with iron ore tailings (IOT), iron ore tailings cement mortars (referred to as IOTC) with IOT content of 0%, 25%, and 50% were made and tested. First, the basic properties of IOT used were measured to verify the theoretical feasibility. Second, the uniaxial compressive and tensile strengths, as well as the crack resistance performance of IOTC under different curing ages and different sand substitution rates were tested. Third, the techniques of inductively coupled plasma atomic emission spectrometry (ICP-OES), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), scanning electron microscopy and energy-dispersive spectroscopy (SEM-EDS) were used to study the influence of curing age and different sand substitution rates on the chemical, mineralogical, and microstructural characteristics of IOTC. The sand substitution mechanism of IOT was then discussed. The research results proved the feasibility of using IOT to substitute standard sand in cement mortar. Within substitution rate of 0–50%, the mechanical properties increased with the increase of substitution rate. Though limited chemical effects were found by adding IOT, in comparison with standard sand mortar, more hydration products were found and the pore size distribution was changed for IOTC, which corresponds to its mechanical improvement.

Structure, sequon recognition and mechanism of tryptophan C-mannosyltransferase

C-linked glycosylation is essential for the trafficking, folding and function of secretory and transmembrane proteins involved in cellular communication processes. The tryptophan C-mannosyltransferase (CMT) enzymes that install the modification attach a mannose to the first tryptophan of WxxW/C sequons in nascent polypeptide chains by an unknown mechanism. Here, we report cryogenic-electron microscopy structures of Caenorhabditiselegans CMT in four key states: apo, acceptor peptide-bound, donor-substrate analog-bound and as a trapped ternary complex with both peptide and a donor-substrate mimic bound. The structures indicate how the C-mannosylation sequon is recognized by this CMT and its paralogs, and how sequon binding triggers conformational activation of the donor substrate: a process relevant to all glycosyltransferase C superfamily enzymes. Our structural data further indicate that the CMTs adopt an unprecedented electrophilic aromatic substitution mechanism to enable the C-glycosylation of proteins. These results afford opportunities for understanding human disease and therapeutic targeting of specific CMT paralogs.

Mechanisms of Docking of Superoxide Ions in the Catalytic Cycle of Manganese and Iron Superoxide Dismutases

n this paper, we propose an approach to resolving some questions about the catalytic action of manganese and iron superoxide dismutases. At the level of a pure quantum-chemical calculation using an ORCA 5.0.3 program, a PBE functional and a def2-SVP and def2-TZVP basis sets, the possible mechanisms of superoxide ions binding to the active sites of enzymes, the electron transfer distances and their characteristics were established. It is shown that the initial form of the fifth ligand in both active sites is the hydroxide ion OH–. Before the primary electron transfer, active sites are protonated, the hydroxide ion is converted into a water molecule H2O. Primary electron transfers from the superoxide ion to Mn3+-SOD and Fe3+-SOD occur by the associative mechanism, with the formation of an octahedral complex, at a transfer distance of 1.95 Å and 2.56 Å, respectively. At the second stage, the superoxide ion accepts the electron by the substitution mechanism from Mn2+- SOD at the transfer distance of 2 Å to form bonds with the water molecule and a tyrosine. The superoxide ion accepts the electron from Fe2+-SOD through the outer-sphere mechanism, where it binds to a histidine and the water molecule at the transfer distance of 4.24 Å.

The influence of single-point mutation D614G on the binding process between human angiotensin-converting enzyme 2 and the SARS-CoV-2 spike protein-an atomistic simulation study.

SARS-CoV-2 has continuously evolved as changes in the genetic code occur during replication of the genome, with some of the mutations leading to higher transmission among human beings. The spike aspartic acid-614 to glycine (D614G) substitution in the spike represents a "more transmissible form of SARS-CoV-2" and occurs in all SARS-CoV-2 mutants. However, the underlying mechanism of the D614G substitution in virus infectivity has remained unclear. In this paper, we adopt molecular simulations to study the contact processes of the D614G mutant and wild-type (WT) spikes with hACE2. The interaction areas with hACE2 for the two spikes are completely different by visualizing the whole binding processes. The D614G mutant spike moves towards the hACE2 faster than the WT spike. We have also found that the receptor-binding domain (RBD) and N-terminal domain (NTD) of the D614G mutant extend more outwards than those of the WT spike. By analyzing the distances between the spikes and hACE2, the changes of number of hydrogen bonds and interaction energy, we suggest that the increased infectivity of the D614G mutant is not possibly related to the binding strength, but to the binding velocity and conformational change of the mutant spike. This work reveals the impact of D614G substitution on the infectivity of the SARS-CoV-2, and hopefully could provide a rational explanation of interaction mechanisms for all the SARS-CoV-2 mutants.

Нарушения саморегуляции у молодых людей с аффективными расстройствами в условиях пандемии COVID-19

The purpose of the empirical study is assessment or the correlation among disorders of operational level of self-regulation with psychological security parameters, psychological defense mechanisms, and personality traits of young people with affective disorders during the COVID-19 pandemic. The study involved 60 people aged 20-25, 30 of which had affective disorders. In the test group regulative dysfunctions of processes of modelling, programming, results and independence evaluation are due to non-adaptive defense mechanisms of projection, regression, and substitution, security basis views bias as well as self-criticism. People with affective disorders satisfy their security need looking for supportive external environment rather than their intellectual and volitional activity.

СПОСОБЫ ЭЛИМИНАЦИИ ДИССОНАНСА В ВОСПРИЯТИИ ФЕЙКОВЫХ НОВОСТЕЙ: КОГНИТИВНЫЙ ПОДХОД

The purpose of research is to consider the cognitive basis for the formation of fake information and describe the ways of giving this information the characteristics of truth. To achieve this goal, were applied the method of cognitive modeling and cognitive-discourse analysis. In information processing in order to impart truth characteristics to fake information, both cognitive and metacognitive levels are activated. Static declarative knowledge, which is obtained empirically and is stored in the human memory, is not sufficient for the authors of fake news. Such knowledge is objective and does not create the necessary associations. Due to the metacognitive level and its aspect - procedural knowledge, the authors of fake news manage to process the information in such a way that despite its unreliability, newly designed knowledge is perceived as true. This process involves the cognitive mechanisms of generalization, specification, cognitive metonymy, metaphtonymy, conceptual comparison, visualization, frame recurrence, concept substitution, and attention nesting. These mechanisms act as components of the procedural knowledge model which is the basis for the adaptability of fake news to truth indicators. All cognitive mechanisms are characterized by purposefulness, controllability, dynamism and interactivity. We see the prospect of further research in the need to compare the cognitive principles and mechanisms that are in demand in the elimination of cognitive dissonance in the perception of fake news by different authors and on the material of other languages.

Tuning the conductance of carbon rings with impurities and electric fields.

We explore two mechanisms to tune the electronic conductance of carbon atom rings, namely, substitutional impurities and in-plane external electric fields. First-principles calculations and a tight-binding approach are used to model the systems. Two bond configurations are studied, cumulenic and polyynic, which can be relevant depending on the number of carbon atoms in the ring. We find that both impurity substitution and electric field mechanisms allow for modifying the electronic spectrum and transport characteristics. Interestingly, cumulenic and polyynic carbon rings present a different response to these perturbations, which can also be a way to elucidate the bond nature of these structures.

БЕСКОНФЛИКТНАЯ КОММУНИКАЦИЯ: КОГНИТИВНАЯ ОСНОВА ЕЕ РЕАЛИЗАЦИИ

The article discusses the cognitive basis of conflict-free communication, including the principles of “cognitive filter”, relying on a prototype, changing the focus of attention, information accessibility and associative implications, which serve the basis for information processing and distribution in order to neutralize conflict in communication. It has been established that each cognitive principle correlates with the mechanism underlying the construction of a conflict-free meaning. The principle of “cognitive filter” is activated due to the mechanism of generalization, the principle of relying on the prototype is accompanied by the activation of the mechanism for eliminating opposition, the principle of changing the focus of attention is correlated with the mechanism of substitution of concepts, the mechanism of “cognitive fluency” is involved in the activation of the principle of information accessibility, the principle of associative implications is implemented through mechanisms of conceptual metaphor, metonymy and conceptual comparison. We have tried to prove that these cognitive principles and mechanisms are based on the “shared knowledge” factor, which involves both comprehending the constructed and transmitted information, and predicting the intentions and expectations of communication participants, their emotional state and prospects for completing communication in a conflict-free way. Together, they form a model of the cognitive basis of conflict-free communication. It has also been determined that the speech-cognition activity of a person in the context of conflict-free communication is complexly organized, and its explanation requires knowledge at the intersection of a number of sciences. The prospect of this study is the possibility of applying the developed approach to the analysis of other complex phenomena of the language.

The correlation of sulfonation reaction kinetics with the degree of sulfonation (DS) and its effects on microstructure and morphology of electrospun fibers for the membrane of fuel cells.

Sulfonation is among the frequently used surface modification methods to endow new surface properties on polymer fibers. Direct sulfonation is the simplest chemical modification via incorporation of sulfonate functional groups onto fibers' surfaces at ordinary conditions. However, the process of functionalization compromises other properties of the electrospun membrane due to the extent of sulfonation reaction that occurred. This study was carried out to determine the effects on microstructure and morphology of crosslinked electrospun polybenzoxazine (PBz) fibers by correlating the reaction kinetics using a specific reaction parameter with the degree of sulfonation (DS). The kinetics of sulfonation reaction for PBz fibers is an electrophilic-based, first-type substitution mechanism where only one sulfonic acid (-SO3H) group is attached to each of the repeating units in the aromatic structure of PBz under ordinary conditions. From a previous study, the rate of change of ion exchange capacity (IEC) was derived as a logarithmic correlation that increased rapidly for some time and became constant. This study employed the derived empirical relationship based on reaction kinetics to correlate the degree of sulfonation (DS) with IEC at varying reaction time. DS was calculated as 55%, 66% and 77%, for 3, 6 and 24 h, respectively. The maximum IEC of 2.71 with the corresponding DS of 100% was obtained theoretically but since sulfonation reaction kinetics at ordinary conditions proceeds at slower phase, it can only attain 86% DS with maximum IEC of 2.44 at a calculated time of 48 h. Sulfonation was confirmed by the functional groups present in the structural composition of PBz fibers using ATR-FTIR which were quantified based on the absorbance in the IR spectra showing an increased peak height with increased reaction time for the first 6 h. Morphological analyses using SEM images revealed an increase in fiber diameter with increased sulfonation time. In addition, the higher reaction time showed the effects of longer acid exposure which compromised the fibers' structural integrity with the presence of broken fibers and defects on fibers' surfaces after 24 h. The electrospun PBz fibers sulfonated for 6 h achieved the highest IEC value with DS of 66% which was enough to attain the balance of degree of sulfonation with electrochemical and morphological properties.

Alkylborane initiated RAFT polymerization: impact of carboxylic acid deblockers

Oxygen-tolerant, alkylborane initiated RAFT has a partial order rate dependence of 1 for the acid concentration, supporting a homolytic substitution mechanism, and can be conducted with diminished deblocker concentrations when using stronger acids.

Import substitution mechanism for the construction industry in Russia

This study is important for most states, but especially for Russia in the current political situation. Dependence on foreign goods and services can turn out to be not the best result, as, for example, happened in Russia. One of the most important industries in the country is the construction industry. And it currently requires global import substitution. However, to change the situation, it is necessary to understand that the import substitution process cannot happen instantly. Governments of many countries should work on it comprehensively in order not to come to the situation in which the Russian Federation finds itself. Long-standing principles of exporting goods to foreign markets have shown their failure. The massive sale of raw materials and the purchase of a wide range of goods for various spheres from abroad has greatly weakened the country’s economy. This has led to the need to find new solutions on the part of the state. The author’s import substitution mechanism proposed in the article is universal for the construction industry, as it is a system of managerial decisions that allow to develop the country’s own production systematically and to gradually abandon foreign goods. This mechanism will allow for a timely assessment of the production, economic and technological potential of the industry, taking into account the interaction of state and commercial organizations.

Lithium, Phosphorus, and rare earth elements in magmatic garnets from granitic Pegmatites: Coupled substitution and petrogenetic implications

The general chemical formula of garnet can be expressed as X3Y2(ZO4)3 where X, Y, and Z represent dodecahedral, octahedral, and tetrahedral sites, respectively. Lithium, phosphorus, and rare earth elements (including yttrium) in garnets from the Luanzhuang-Guanpo and Ziyugou (ZYG) pegmatite fields in the East Qinling orogen and the Kalu’an (KLA) Li pegmatites in the Chinese Altay orogen have been investigated both at a mineral scale and in the context of pegmatite types to identify the substitution mechanisms for these elements. Our results show that Y + REE or P can enter the garnet lattice through coupled substitution with Li (+Na) that can compensate the charge differences due to Y + REE in the X-site or P in the Z-site of the garnet. Two substitutions, namely [X(Li,Na)+1X(Y,REE)3+1(R2+)–2] and [X(Li,Na)1ZP1XR2+-1ZSi-1], are likely the most important and can account for incorporation of the majority of Y + REE, P, and Li + Na in pegmatite garnets. Whichever substitution becomes predominant in garnets is strongly dependent on the bulk chemistry of pegmatite-forming melts. Consequently, the first substitution dominates in garnets from NYF (niobium-yttrium-fluorine) pegmatites and mixed-type pegmatites with NYF affinity whereas the other one dominates in garnets from relatively P-rich LCT (lithium-cesium-tantalum) and barren pegmatites. Incorporation of Sc and Ti in garnet may also need Li + Na, although Sc and Ti are not as much as Y and REE in pegmatite garnet. The zonings of Y, REE, and Sc in garnet are mainly controlled by the composition of pegmatite-forming melt and consumption of these elements due to the growth of garnet itself and other minerals enriched in Y + REE (e.g., xenotime, fergusonite, monazite, etc.) or Sc (e.g., biotite). Additionally, our results, combined with the data in the literature, show that garnets from NYF pegmatites and mixed-type pegmatites with NYF affinity commonly contain elevated Y (up to ∼ 20000 ppm), REE (up to ∼ 20000 ppm), and Sc (up to ∼ 2400 ppm) but low P (<100 ppm) compared to those from LCT and barren pegmatites. Nevertheless, individual garnets with low concentrations of Y, REE, Sc, and P can occur in any types of pegmatites. Therefore, the coupled substitution between Li + Na and Y + REE or P along with zonings and concentrations of Y, REE, and Sc in garnet should be investigated on a regular basis to interpret pegmatite petrogenesis.

Hybrid Marketplaces with Free Entry of Sellers

We study a hybrid marketplace such as Amazon that sells its own products and sets commissions on third-party sellers that engage in monopolistic competition with free entry. For a large class of microfoundations based on a representative agent, the introduction of its own products by the marketplace is neutral for consumer welfare for a given commission; but this product introduction exerts an ambiguous impact through changes of the commission. A “demand substitution mechanism” pushes for a higher commission; but an “extensive margin mechanism” pushes for a lower commission that is aimed at attracting new sellers and more purchases on the marketplace. For instance, with constant demand elasticities, a hybrid marketplace sets a lower (higher) commission rate and increases (decreases) consumer welfare compared to a pure marketplace if its products face a less (more) elastic demand.

Pyridine‐Boryl Radical Mediated Decarboxylative Homolytic Substitution of N‐hydroxyphthalimide Ester with Ar2X2 (X=S, Se)

AbstractHerein, we report a metal‐free approach to construct C−X (X=S, Se) bonds with the broadly available N‐hydroxyphthalimide esters and disulfides/diselenides (Ar2X2, X=S or Se) using bis(pinacolato)diboron as the reductant. Density functional theory calculations and control experiments reveal that such a C−X bond formation process is reductive decarboxylation mediated from pyridine‐boryl radical to yield alkyl or aryl radical. The resulting carbon radical then reacts with disulfides or diselenides via a bimolecular homolytic substitution (SH2) mechanism to afford the corresponding sulfides or selenides. This method displays a high functional group tolerance and broad substrate applicability.

Hybrid chameleon swarm algorithm with multi-strategy: A case study of degree reduction for disk Wang–Ball curves

In this paper, an enhanced hybrid chameleon swarm algorithm (CSA) is proposed and applied to the degree reduction problem of disk Wang–Ball (DWB) curve. CSA is a novel population-based algorithm inspired by the hunting behavior of chameleons, its simplicity and easy implementation make it applied to different fields. However, it suffers from premature convergence and easy to fall into local optimum, especially in the face of complex optimization problems. Therefore, this paper proposes an enhanced hybrid CSA (CCECSA, for short). Compared with the classic CSA, the proposed CCECSA mainly introduces three improvements: (1) The crisscross optimization algorithm is mixed to avoid premature convergence, in which the horizontal and vertical crossover can generate moderation solutions to increase the diversity of the population. (2) Elite guidance mechanism is introduced to speed up the convergence. (3) Competitive substitution mechanism is added to replace the worst individual, and an interference strategy is set to prevent the algorithm from falling into a local optimum. The efficiency and robustness of the proposed CCECSA are demonstrated by the comparison results with some advanced meta-heuristic algorithms on CEC2014, CEC2017, and 4 engineering design examples. In addition, for the degree reduction problem of DWB curves, the multi-degree reduction optimization models of its center curve and radius function are established respectively. At the same time, the optimal center curve and radius function of the approximating DWB curves of lower degree are obtained by the proposed CCECSA. The experimental results show that the proposed CCECSA achieves the optimal solution with better convergence and robustness. The source code of CCECSA is publicly available in the supplementary material related to this article.

Enhanced charge carrier density of a p-n BiOCl/BiVO4 heterostructure by Ni doping for photoelectrochemical applications

Pure and doped p-n BiOCl/BiVO4 heterostructures with various Ni contents were studied for photoanode applications in photoelectrochemical cells. All materials were synthesized by the coprecipitation method. The properties of the pure and doped materials were characterized by various techniques, such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, UVvisible spectroscopy, and electrochemical impedance spectroscopy. Furthermore, density function theory calculations were employed to investigate the underlying physical mechanism of the Ni substitution. The materials were applied as the photoanode at an applied bias voltage of +1.9 V (vs. RHE) and irradiated over 4200 s under the solar light simulator. The pure p-n BiOCl/BiVO4 heterostructure showed the highest photocurrent of 1 mA/cm2. After 1% Ni doping, the photocurrent density was enhanced, and the highest photocurrent density was approximately 1.7 mA/cm2. From the theoretical calculation aspect, the role of Ni substitution into the parent p-n BiVO4 and BiOCl materials resulted in a surface state under the conduction band of both parent materials. The result was in agreement with the Mott-Schottky analysis, which showed that the charge carrier density increased as Ni atoms were added to the p-n BiOCl/BiVO4 heterostructure. Therefore, the additional state and the increase in the charge carrier density led to the improved photocatalytic activity of the Ni-doped p-n BiOCl/BiVO4 heterostructure.

Formation of emerging disinfection byproducts from agricultural biomass-derived DOM: Overlooked health risk source

Carbon-derived dissolved organic matter (CDOM) are inevitably released to surface water during returning agricultural biomass carbon to farmland, which are potential precursors of disinfection byproducts (DBPs). In this study, CDOM was extracted from aerobic incineration (“OX”) and anoxic pyrolysis (“PY”) of three kinds of straw (wheat, corn, and rice), and the emerging DBPs from them were deciphered. The CDOM with molecular weight < 1 kDa in the OX and PY groups accounted for 53–87%, and it was higher in the PY group. A total 1343–2107 of CHO and 641–1761 of CHNO formulas were detected in the CDOM derived from the OX group, among which 74%-83% contained aromatic structures rich in oxygen containing groups. 1919–3289 of CHO and 785–1954 of CHNO formulas were observed in the PY group, and 77%-86% of them were lignins/CRAM-like compounds. Surprisingly, 765–2158 and 895–1648 of emerging DBPs were identified in the OX and PY groups, and the proportions of N-DBPs were 20.3–54.8% and 2.8–4.8%, respectively. Based on HOCl addition and Cl substitution mechanisms, the H/C ratios of the DBP precursors in the OX and PY groups were in the range of 0.2–1.5 and 0.6–2.0, respectively. The DBPs derived from the OX group exhibited higher cytotoxicity and genotoxicity due to the higher aromaticity and more N-DBPs. Thus, returning agricultural biomass carbon, particularly that produced by direct combustion, to farmland brought potential threat to drinking water safety.

The Role of Defence Mechanisms in Coping with Stress in PTSD Patients

In the context of the war in Ukraine, the risk of post-traumatic stress disorders increases, which in critical cases cause the development of chronic mental illnesses and a decline in physiological functions. In connection with the emergence of a feeling of helplessness due to the inability to act effectively in a dangerous situation, various psychological defence mechanisms are formed to overcome intrapsychic conflicts. The purpose of this stud was to investigate the dominant mechanisms in individuals with post-traumatic stress disorder who had been in regions with different scenarios for the development of hostilities since the beginning of the war, using the PlutchikKellerman-Conte methodology. The information was collected from people of different age categories, types of employment, educational qualification levels, and gender who were in Kyiv, Kharkiv, and Lviv during the first two months of the full-scale war and periodically moved through the territory of Central and Western Ukraine. Cases of short-term residence abroad were also considered during the study. The results of the tension of psychological defence indicate that in individuals with post-traumatic stress disorder that stayed in different regions of Central and Western Ukraine since the beginning of the war, the projection mechanism dominated (75%), and the substitution mechanisms (12.5%) and denial mechanisms (12.5%) were equally distributed. The dominance of the projection may indicate the transfer of intrapsychic conflict to the outside. In this case, the external world is perceived by the individual as the main carrier of the threat from which they need to protect themselves. Instead, denial may indicate ignoring certain aspects of reality. Respondents who are prone to substitution use the approach of transferring repressed emotions, which can be expressed in the form of anger, fear, and hostility towards more accessible objects that are no less dangerous than those that led to frustrating experiences. It was determined that the total sample tension does not exceed 50%. This may indicate the ability of patients with post-traumatic stress disorder to resolve intrapsychic conflicts that have developed at the moment. The results of the study may be of practical interest to specialists investigating the identification and generation of methods for the prevention and treatment of post-traumatic stress disorder

Bio-Inspired Deaminative Hydroxylation of Aminoheterocycles and Electron-Deficient Anilines.

Among the tools available to chemists for drug design of bioactive compounds, the bioisosteric replacement of atoms or groups of atoms is the cornerstone of modern strategies. Despite the undeniable interest in amino-to-hydroxyl interchange, enzymatic deaminative hydroxylation remains unmatched. Herein, we report a user friendly and safe procedure to selectively convert aminoheterocycles to their hydroxylated analogues by means of a simple pyrylium tetrafluoroborate salt. The hydroxylation step relies on a Lossen-type rearrangement under mild conditions thus avoiding the use of strong hydroxide bases. In addition to biorelevant heterocycles, the deaminative hydroxylation of electron-deficient anilines was also demonstrated. Finally, mechanistic experiments allowed the identification of the key intermediates, thus unveiling a rather unusual mechanism for this formal aromatic substitution.