Four-stage Mechanism Research Articles

Involving unused land in the economic turnover of the agricultural sector of a region: institutional regulation and economic feasibility

The article shows the necessity of institutional regulation of the process of involving unused agricultural land into the economic turnover of the agrarian sphere of a region. It presents quantitative and qualitative characteristics of previously withdrawn agricultural lands, their territorial distribution by soil and climatic microzones and administrative districts of a region, unused period duration, residual fertility level (in terms of humus content), and land plots degradation degree. A calculation-analytical complex such as an algorithm representing a four-stage mechanism of analysis, preparation and decision-making on the choice of the land plots restoration method and their further use option has been developed and proposed for use. It is recommended to use three options for land plots restoration: direct return to economic turnover in case of a short period of non-use; carrying out cultural and technical measures with subsequent implementation into the turnover; transfer to another category of use in case of a high degree of degradation and low fertility level. The developed algorithm of unused agricultural land involvement is aimed at preserving the land potential of a region, strengthening the rational land use system. The presented stages provide not only theoretical and methodological, but also practical significance. Application scope is scientific organizations, agroindustrial complex management bodies at the municipal and regional levels, and agricultural producers.

Modeling the Cellular Uptake of Functionalized Carbon Nanohorns Loaded with Cisplatin through a Breast Cancer Cell Membrane.

The cisplatin encapsulation into carbon nanohorns (CNH) is a promising nanoformulation to circumvent the drug dissipation and to specifically accumulate it in tumor sites. Herein, biased molecular dynamics simulations were used to analyze the transmembrane transport of the CNH loaded with cisplatin through a breast cancer cell membrane prototype. The simulations revealed a four-stage mechanism: approach, insertion, permeation, and internalization. Despite the lowest structural disturbance of the membrane provided by the nanocarrier, the average free energy barrier for the translocation was 55.2 kcal mol-1, suggesting that the passive process is kinetically unfavorable. In contrast, the free energy profiles revealed potential wells of -6.8 kcal mol-1 along the insertion stage in the polar heads region of the membrane, which might enhance the retention of the drug in tumor sites; therefore, the most likely cisplatin delivery mechanism should involve the adsorption and retention of CNH on the surface of cancer cells, allowing the loaded cisplatin be slowly released and passively transported through the cell membrane.

The Influence of Fluorine-Containing Surfactants and Polymers on Regularities of Lead Dioxide Electrodeposition

Electrochemical synthesis allows one to influence the composition and properties of materials by changing the conditions of electrolysis and electrolyte composition. Lead dioxide due to the simplicity of its electrochemical synthesis, high corrosion resistance and relatively low cost is widely used in electrocatalysis, electroplating, lead-acid batteries, etc. The inclusion of fluorine-containing compounds in the metal oxide matrix provides antistatic, anti-adhesive, anti-corrosion properties, and at the same time the materials retain the properties of metal oxide: high electrical conductivity, resistance to mechanical wear and good adhesion to the substrate.In this work, the regularities of lead dioxide electrosynthesis in the presence of fluorine-containing surfactants with different fluor-carbon chain lengths and polyelectrolytes in the electrolyte were investigated.Electrodeposition was studied in 0.11 M CH3SO3H + 0.01 M Pb (CH3SO3)2. The surfactant was added to the deposition electrolyte in the form of aqueous solutions with a concentration of 3×10-4 M. Determination of current efficiency and partial oxidation current (IPb(II)) was performed by the method described in detail previously [1].The kinetic regularities of PbO2 electrodeposition are satisfactorily described in a four-stage mechanism applied to a wide range of electrolytes (both nitrate and methanesulfonate), including those containing ionic additives, colloidal TiO2 and polyelectrolytes [2,3]. As a rule, at low anodic polarizations (E <1.6 V) the reactions will take place with kinetic control, while at high polarizations the delivery of Pb2+ ions to the electrode surface will be the rate-determining stage. It was found that the addition of surfactants and polyelectrolytes in different ways affect the kinetics of electrodeposition of lead dioxide, without changing the mechanism of the process.The basis of the surface effects is the adsorption of additives on the electrode surface. The adsorption on the electrode of methanesulfonate and fluoride ions significantly affects the rate of the discharge-ionization stage. This effect is due to a number of factors that lead to changes in the concentration of reacting particles in the surface layer and the activation energy of the electrode process. Since the value of surface charge is positive, a decrease in the value of the potential in the plane of localization of the activated complex will increase the rate of the charge transfer stage, which is observed in practice in solutions containing short-chain perfluoroalkyl surfactants and low concentrations of Nafion® polymer. During the adsorption of a polyelectrolyte or anionic surfactant on the surface of the electrode, the value of such potential can not only decrease significantly, but even become negative due to recharging of the electric double layer. This possibility is indicated by the change in the electrokinetic potential of PbO2 from positive to negative by adding anionic surfactants and polymers to the electrolyte.The inhibition parameter reflects both the electrostatic and chemical interaction of the activated complex with the adsorption layer, which leads to an increase in the activation energy of the charge transfer stage. Increasing the volume concentration of the additive in the electrolyte leads to an increase in the degree of filling of the electrode surface, which will cause a decrease in the rate of the charge transfer stage due to blocking of active centers on the electrode surface.Since the process of formation of lead dioxide takes place together with the reaction of oxygen evolution, the dependences of PbO2 current efficiencies (CE) on the electrodeposition potential were investigated to assess the influence of surfactants on the lead dioxide electrodeposition.In the low polarizations area, the PbO2 CE remains virtually unchanged, close to 100%. In this area, the deposition process is controlled by kinetic stages. If the additive does not inhibit the deposition of lead oxide, CE is close to 100% and is almost independent of the current density. In the next part of the curve the process of electrodeposition of oxide occurs under mixed control. On the descending part of the dependence CE decreases due to the increase in the reaction rate of oxygen evolution when the limiting current of electrodeposition of oxide is observed (diffusion control). References A. Velichenko, T. Luk’yanenko, O. Shmychkova, L. Dmitrikova, Electrosynthesis and catalytic activity of PbO2-fluorinated surfactant composites, J. Chem. Technol. Biotechnol., 95, 3085, (2020). A. Velichenko, T. Luk’yanenko, N. Nikolenko, O. Shmychkova, P. Demchenko, R. Gladyshevskii, Composite electrodes PbO2-Nafion®, J. Electrochem. Soc., 167, 063501 (2020).O. Shmychkova, T. Luk’yanenko, A. Velichenko, Lead dioxide electrocrystallization from nitrate and methanesulfonate electrolytes: The influence of various dopants on initial stages, ECS Transactions, 77, 1617 (2017).

Conversion of glycerol to hydroxyacetone over SrTiO3 -type perovskite: A DFT study

Glycerol is currently a co-product of biodiesel production, and it is well-known to be a platform molecule, which is widely used in etherification, dehydration, dehydrogenation, oxidation, and reforming reactions, to produce chemicals of high value for the chemical industry. In this study, we theoretically address the dehydration of glycerol over the SrTiO3-type perovskite. The study includes the characterization of the transition states and intermediates occurring along the reaction pathway, and a possible mechanism is proposed, as well. The results show that the dehydration of glycerol occurs via a four-stage mechanism corresponding to the adsorption of glycerol on the perovskite, the surface reaction to produce the adsorbed dihydroxyacetone, the elimination of water produce 2,3-enol, and finally the desorption of this enol, which in turn undergoes keto-enol tautomeric equilibrium to form hydroxyacetone (HA). The rate-limiting stage corresponds to the formation of 2,3-enol showing an activation barrier of 106.3 kcal/mol.

CFD-guided development of a pre-chamber ignition system for internal combustion engines

In the present paper, the development of a non-fuelled pre-chamber ignition system is introduced. 3D combustion CFD has been employed to guide the design change. Based on the combustion performance of different pre-chamber designs, one design (B4) is identified as the best one among several designs. Design B4 is selected for detailed evaluations. The results of Design B4 are compared with the baseline SI engine. The fuel economy has been improved by using the pre-chamber ignition system. However, NOx emission is higher than the baseline engine, due to higher in-cylinder pressure and temperature. The combustion process in the pre-chamber is separated into three steps characterised with its heat release, temperature and pressure. Based on the pressure difference between the main chamber and pre-chamber, a four-stage mechanism is proposed to describe the gas exchange between them.

CFD-guided development of a pre-chamber ignition system for internal combustion engines

In the present paper, the development of a non-fuelled pre-chamber ignition system is introduced. 3D combustion CFD has been employed to guide the design change. Based on the combustion performance of different pre-chamber designs, one design (B4) is identified as the best one among several designs. Design B4 is selected for detailed evaluations. The results of Design B4 are compared with the baseline SI engine. The fuel economy has been improved by using the pre-chamber ignition system. However, NOx emission is higher than the baseline engine, due to higher in-cylinder pressure and temperature. The combustion process in the pre-chamber is separated into three steps characterised with its heat release, temperature and pressure. Based on the pressure difference between the main chamber and pre-chamber, a four-stage mechanism is proposed to describe the gas exchange between them.

Electron microscopy observation of electric field-assisted sintering of stainless steel nanoparticles

The intrinsic role of electrical current on the electric field-assisted sintering (EFAS) process of stainless steel 316L nanoparticles has been revealed by both ex situ and in situ experiments. A novel device on the Si chip has been designed and fabricated to fit into the sample holder of a transmission electron microscope for these experiments. The evolution of nanoparticle morphology and microstructures during the EFAS process has been studied using scanning electron microscopy and transmission electron microscopy, which has been combined with the simultaneous measurement of the electric voltage and current changes. A preliminary four-stage mechanism for the EFAS process of stainless steel 316L nanoparticles has been proposed based on these experimental investigations.

Thermodynamic feasibility of the four-stage chloride-induced depassivation mechanism of iron

The atomistic mechanism of chloride-induced depassivation of iron is still debated. A recent study suggests a four-stage depassivation mechanism, in general agreement with the point defect model. The proposed four-stage mechanism is based on reactive force field molecular dynamics simulations and is rather complex but here we use density functional theory to confirm the thermodynamic feasibility of the proposed mechanism. We find that the four surface species, formed in the four stages, have decreasing surface stability, which is consistent with the order of species formed in the depassivation process proposed in the reactive force field molecular dynamics study. The Fe vacancy formation energy, that is the energy needed to form a surface Fe vacancy by removing different surface species, indicates that surface species with more chlorides dissolve more easily from the surface, suggesting that chloride acts as catalyst in the iron dissolution process. The results are consistent with the suggested four-stage reaction mechanism and the point defect model.

The Technology of Media Culture usage in the Educational Environment: Development of Creative Self-Actualization

The article looks at the experience of building a media environment at school as a system of self-education and self-development for modern teenagers. The authors present a model of development of teenagers’ creative self-actualization in the media educational environment, the technology of media culture use in the educational environment and an original diagnostic methodology for determination of the degree of development of school students’ creative self-actualization based on assessment of independent work carried out by teenagers (media projects creation) taking into account emotional and semantic visualization of information and the symbolism of associative-semantic connections to evaluate the quality of the conducted work. As a result of the performed experiment, the authors identified personal characteristics shown by school students in the course of their work on media projects and developed a typology of dominant activities that includes four types of individual characteristics observed in school students: analytical, informational, proactive and synthetic types. Based on this typology the authors have determined the relevance and necessity for differentiation of work with teenagers of different ages in various forms of media educational environment and development of their individual educational paths. Correspondingly, a four-stage mechanism of introduction of a teenager into a media educational environment has been suggested providing for the integration of art into the educational environment. The article presents the results of a pilot project that was carried out in state budgetary educational institutions located in Moscow: School no. 1253, School no. 171, School no. 89 and in the children's creative center Trubetskoy Estate in Khamovniki. The article is intended for scientists, teachers, pedagogues and methodological experts who deal with the issues of media education.

Construction of Antibacterial N-Halamine Polymer Nanomaterials Capable of Bacterial Membrane Disruption for Efficient Anti-Infective Wound Therapy.

The increasing occurrence of bacterial infection at the wound sites is a serious global problem, demanding the rapid development of new antibacterial materials for wound dressing to avoid the abuse of antibiotics and thereby antibiotic resistance. In this work, the authors first report on antibacterial N-halamine polymer nanomaterials based on a strategic copolymerization of 3-allyl-5,5-dimethylhydantoin (ADMH) and methyl methacrylate (MMA), which exhibits in vitro and in vivo antimicrobial efficacy against pathogenic bacteria including Staphylococcus aureus and Escherichia coli. Particularly, when a biological evaluation is run for wound therapy, the N-halamine polymer nanomaterials exhibit a powerful antibacterial efficiency and wound healing ability after a series of histological examination of mouse wound. After the evaluation of biological and chemical surroundings, the proposed four-stage mechanism suggests that, with unique antibacterial NCl bonds, the N-halamine polymer nanomaterials can disrupt the bacterial membrane, as a result causing intracellular content leaked out and thereby cell death. Based on the synergistic action of antibacterial and wound therapy, the N-halamine polymer nanomaterials are expected to be promising as wound dressing materials in medical healing and biomaterials.

A Quantum-Chemical DFT Approach to Elucidation of the Chirality Transfer Mechanism of the Enantioselective Suzuki–Miyaura Cross-Coupling Reaction

The DFT calculations of the simplified model of the asymmetric Suzuki–Miyaura coupling reaction were performed at the M062x/LANL2DZ theory level at first. It was found that enantioselective reactions mediated by the palladium complexes of chiralC,P-ligands follow a four-stage mechanism similar to that proposed previously as one of the most credible mechanisms. It should be underlined that the presence of substituents in the substrates and the chiral ligand atorthopositions determines the energies of possible diastereoisomeric transition states and intermediates in initial reaction steps. This suggests that, in practice, a sharp selection of theoretically possible paths of chirality transfer from the catalyst to the product should have a place and, therefore, the absolute configuration of the formed atropisomeric product is defined and can be predicted.

Effect of zwitterionic surfactants on wetting of quartz surfaces

Advancing contact angle (θ), for aqueous solutions of the zwitterionic surfactants, hexadecanol glycidyl ether glycine Betaine (C16PB), guerbet alcohol hexadecyl glycidyl ether glycine Betaine (C16GPB), hexadecanol polyoxyethylene(3) glycidyl ether glycine Betaine (C16(EO)3PB) and guerbet alcohol hexadecyl polyoxyethylene(3) glycidyl ether glycine Betaine (C16G(EO)3PB), were measured on the quartz surface by the sessile drop analysis. The atomic force microscope (AFM) has been used to detect the nature of adsorption film at quartz surface. The obtained results indicate there are only slightly changes of contact angle as a function of bulk concentration for four surfactants during the experimental concentration range caused by the random arrangement of surfactant molecules at quartz surface through Lifshitz–van der Waals interactions. For C16PB and C16GPB, a similar adsorption density at water–air and quartz–water interface is observed. In the case of C16(EO)3PB and C16G(EO)3PB solutions, a smaller surfactants adsorption at quartz–water interface than at water–air interface probably results from steric effect due to parallel orientation of surfactants in the monolayer at quartz–water interface resulted from the interaction between EO group and quartz. The adsorption characteristics of zwitterionic surfactants remain less variation with the insertion of EO group and the presences of branched-chain in the hydrophobic group are quite opposite. For C16PB and C16(EO)3PB, a three-stage adsorption mechanism has been provided, while a four-stage mechanism must be taken into account for C16 G PB and C16G(EO)3PB. The characteristics of force curves measured by AFM between alkyl-modification tips and surfactant-modification quartz plates can strongly confirm the nature of modified film on quartz surface and ensure the adsorption mechanism provided above.

Nascent tar formation during polyvinylchloride (PVC) pyrolysis

Pyrolysis experiments of polyvinylchloride (PVC) were performed to investigate the effects of peak temperature, holding time, and heating rate on the formation of nascent tar. The nascent tar samples were collected using a wire-mesh reactor where the secondary reactions of the evolved volatiles were minimized. The small compounds, such as benzenes and alkanes, were not detected in nascent tar in wire-mesh reactor, whose components are quite different from those of other tars in tube type reactor and vacuum reactor. At a heating rate of 1000K/s, the quasi-3 rings and 3 rings group aromatics were the major components in nascent tar; while the content of 2 rings group aromatics increased from 7.02% to 31.75% with increasing peak temperature from 500 to 800°C. At a longer holding time of 300s, an increase of 2 rings group aromatics from 7.02% to 50.33% was also observed for the nascent tar at 500°C, indicating that the tar composition significantly changed at different stages of PVC pyrolysis. It seems that 3–4 rings compounds form in the early stage and then 2 rings compounds release in the later stage of PVC pyrolysis. Based on the experimental results in this work, a new four-stage mechanism, including (1) dechlorination accompanied with inner cyclization, (2) aromatic chain scission, (3) release of quasi-3 rings or 3 rings group, and (4) release of 2 rings group, of the PVC tar formation was proposed.

Ab Initio Study of Chemical Activation and Hydrogenation of White Phosphorus in Reaction with Rhodium Trihydride Complex

The four-stage mechanism of reaction of the rhodium trihydride complex [(triphos)RhH3] (triphos=1,1,1-tris(diphenylphosphanylmethyl)ethane) with the white phosphorus molecule resulting in the phosphane and the cyclo-P3 complex [(triphos)M(η3-P3] is analyzed on the basis of ab initio calculations of reactants, products, and intermediate complexes of reaction. It is shown that generation of the transient complex [(triphos)RhH(η1:η1-P4)] followed by intramolecular hydrogen atom migration from the metal to one of the phosphorus atoms is the energetically favourable process. Calculations also show that P4 molecule is activated by coordination to the above complex: the metal-bonded P-P edge is broken, and the tetrahedron P4 is opened to form the butterfly geometry. This activation is realized mainly due to the one-orbital back donation of 4d-electron density from the atom of Rh to the unoccupied antibonding triple degenerate t1*-MO of P4.

Near-Net-Shape Molybdenum Parts Produced by Plasma Spray Forming

Complex and thin-walled refractory metallic parts including molybdenum (Mo) rocket nozzle and crucible were fabricated using plasma spray forming (PSF) followed by hot isostatic pressing (HIPing). Optical microscope (OM), scanning electron microscope (SEM), Archimedes method, Vickers hardness and tensile tests have been employed to study microstructure, density, micro-hardness and mechanical properties of the parts. A lamellar structure consisting of vertical columnar grains, micron-sized pores, partially melted particles and rough interlamellar contacts with gaps of sub-micron sizes between lamellae were found in PSF Mo deposits. Relative density, micro-hardness and ultimate tensile strength (UTS) of the deposits were about 89%, 150 HV0.025 and 44 MPa, respectively. After low-pressure and two-step HIPing, those changed up to about 92%, 250∼400 HV0.025 (interior ∼ exterior layers), 93 MPa, and 97%, 325 HV0.025 and 170 MPa, respectively. Moreover, a four-stage mechanism of HIPing for PSF parts including heating up, recrystallization, lamellae movement, plastic yielding and creep has been proposed and discussed in detail.

How to get firms to invest: A simple solution to the hold-up problem in regulation

Abstract. Many governmental programs are effective only if firms make costly investments. The inability of authorities to precommit to a regulatory scheme creates incentives for firms not to invest and to hold-up the regulator. This paper describes a simple subsidy/tax scheme embedded in a four-stage mechanism that solves the hold-up problem. We design a self-financing subsidy/tax scheme which benefits a complying firm at the expense of a non-complying firm. In order to be credible, the subsidy and tax rates must maximize social welfare for any combination of investment decisions. We show that there exists a unique subgame perfect equilibrium in which all firms invest and no actual implementation with subsidies and taxes is required. We discuss in which cases the mechanism can work under incomplete information.

How to Get Firms to Invest: A Simple Solution to the Hold-Up Problem in Regulation

Many governmental programs are effective only if firms make costly investments. The inability of authorities to precommit to a regulatory scheme creates incentives for firms not to invest and to hold up the regulator. This paper describes a simple subsidy/tax scheme embedded in a four-stage mechanism that solves the hold-up problem. We design a self-financing subsidy/tax scheme which benefits a complying firm at the expense of a non-complying firm. In order to be credible, the subsidy and tax rates must maximize social welfare for any combination of investment decisions. We show that there exists a unique subgame perfect equilibrium in which all firms invest and no actual implementation with subsidies and taxes is required. We discuss in which cases the mechanism can work under incomplete information.

Experimental investigation of the aerodynamic breakup of liquid drops

An experimental investigation was made of the deformation and the mechanism of stripping-type breakup of liquid drops. Experiments were conducted in a 60 X 150 mm cross-sectional shock tube equipped with pulsed laser holographic interferometry. Water drops having diameters of 1030 and 4300 fim were examined for shock wave Mach numbers from 1.3 to 1.5 in atmospheric air. The Weber and Reynolds numbers under these conditions were in the range of 600 to 7600 and 1.38 to 10.4 x 10, respectively. In previous works, the experimental data of the stripping-type breakup were obtained by spark shadowgraphs and streak schlieren methods and high-speed movies. However, in previous works, due to the effect of light scattering through the micromist, the structure of disintegrating drops could not be visualized. The purpose of the present work is, by using holographic interferometry, to re-examine the classical problem of the stripping-type breakup of liquid drops. As a result, a four-stage mechanism of the stripping-type breakup of liquid drops was established.

The electrochemical fluorination of organic compounds: Further data in support of the EC bEC n mechanism

Data in support of the four-stage mechanism EC bEC N result from the electrochemical fluorination of some acyl halides (benzoyl, n-butyryl and iso-butyryl, benzenesulphonyl and p-toluenesulphonyl chlorides) and amines (tripropylamine and N-methylmorpholine).

Structure of the initial stages of oxidation of A1{111} surfaces from low-energy-electron diffraction and Auger electron spectroscopy

The structure of the initial stages of oxidation of A1{111} surfaces has been determined by low-energy-electron diffraction (LEED) and Auger-electron-spectroscopy (AES) measurements. The oxidation process can be described by a four-stage mechanism depending on the oxygen exposure: 0-30 L; 30-100 L; 100-200 L; and 200 onwards. At the end of the first stage, the transition density of states (TDOS) obtained by self-deconvolution of the A1{111} \char22{}25-L RT ${\mathrm{O}}_{2}$-exposure ${L}_{2,3}\mathrm{VV}$ AES spectra and comparison with theoretical calculations of the DOS for this coverage show that the oxygen atoms occupy the fcc threefold hollows in an underlayer configuration, with an interplanar distance ${d}_{12}=0.0\ensuremath{-}0.5$ \AA{}. At 100-L RT ${\mathrm{O}}_{2}$ exposure, AES and LEED indicate the formation of a complete A1{111} 1 \ifmmode\times\else\texttimes\fi{} 1-O overlayer structure with the oxygen atoms occupying the fcc threefold hollows at ${d}_{12}=0.73\ifmmode\pm\else\textpm\fi{}0.05$ \AA{}. At 150 L, ${d}_{12}=0.80\ifmmode\pm\else\textpm\fi{}0.03$ \AA{} for the same A1{111} 1 \ifmmode\times\else\texttimes\fi{} 1-O structure. These LEED values solve the discrepancy with the surface-extended x-ray-absorption fine-structure measurements, and suggest the need for a revision of interplanar distances previously determined by LEED for oxygen-metal structures.