Inverse Reaction Research Articles

Role of Orbital Interactions and Activation Strain (Distortion Energies) on Reactivities in the Normal and Inverse Electron-Demand Cycloadditions of Strained and Unstrained Cycloalkenes

The Diels-Alder reactivities of a series of cycloalkenes, from the highly strained cyclopropene to the unstrained cyclohexene, have been studied with density functional theory using the M06-2X functional. The normal electron-demand Diels-Alder reactions with cyclopentadiene and the inverse electron-demand Diels-Alder reactions with 3,6-bis(trifluoromethyl)tetrazine were analyzed using the distortion/interaction-activation strain model. Previous studies showed that activation strain computed from the distorted reactants in the transition structures are larger for unstrained than strained cycloalkenes, and that most of the activation energy differences are accounted for by this difference. We have now analyzed the strain and interaction energy curves for the series of cycloalkenes along the reaction coordinate. Our analyses reveal that the strain curves associated with the distortion of the reactants in the Diels-Alder reactions are nearly identical and that the reactivity differences originate from differences in interaction energies. Analysis of the diene-dienophile interactions reveal that the reactivity trends result from differences in the strength of the primary and secondary orbital interactions.

NEW VARIANTS OF VERTICILLIUM DAHLIAE CAUSING SUNFLOWER LEAF MOTTLE AND WILT IN ARGENTINA

The sunflower leaf mottle and wilt caused by Verticillium dahlie Kleb. is a major disease of the crop. The populations of V. dahliae are variable and physiological races of the pathogen have been reported in lettuce, pepper, spinach, sunflower and tomato. The classification of V. dahliae isolates based on their pathogenicity in differential sunflower genotypes to determine races of the pathogen gives useful information for growers and breeding programmes. Two new Verticillium dahliae races causing sunflower leaf mottle and wilt in sunflower hybrids previously known as resistant were recognized. The sunflower inbred lines ADV29 and ADV53 allowed to differentiate specific pathogenicity patterns. One isolate that affected both genotypes was postulated as race VArg3, and another group that did not cause disease on either genotypes was described as race VArg4. Sunflower genotypes showing inverse differential reactions to races VArg3 and VArg4 were not found. However, the observed pathogenicity patterns could be considered a phenotypic marker useful to identify the V. dahliae races VArg3 and VArg4 in monitoring studies. The current presence of four races of V. dahliae affecting sunflower in Argentina is discussed.

Electro-plastic effect on tensile deformation behaviour and microstructural mechanism of AZ31B alloy

The influences of electropulse on mechanical properties of AZ31B alloy were investigated by the electro-plastic (EP) tensile tests. The results show that the flow stress decreases with the increase of the root mean square (RMS) current density, while the elongation to fracture almost remains unchanged after it reaches a certain value. The higher peak current density can lead to a more potent EP effect when the RMS current density remains approximate. The results of microstructure analysis indicate that, the electropulse can reduce the dynamic recrystallisation temperature and promote the grain boundary sliding. The inverse eutectic reaction (α + β = L) will take place at the necking zone under high electropulse, which can optimise the deformation mechanism before the liquid phase is too much.

Microstructure and electric properties of low-pressure plasma sprayed β-FeSi2 based coatings

Thermoelectric material β-FeSi2 based coating was fabricated by the technique low-pressure plasma spray (LPPS) on the Al2O3 substrate from different alloy powders. During the process LPPS, the phase transformation had occurred through the peritectoid, eutectoid reaction and their inverse reaction. The grain size of the as-sprayed β-FeSi2 doped Co coatings was reduced comparing with the original feedstock powders, which implied the thermal conductivity could effectively decreased by the LPPS process. The room temperature electrical conductivity showed metal and semiconductor properties on the as-sprayed and annealed coatings. This method and the results could solve the problems of practical application especially on special-shaped surfaces such as the automobile exhaust pipe or other complex surface shape of the device.

A CRISE COMO OPORTUNIDADE PARA O EMPREENDEDOR BRASILEIRO

O empreendedorismo é um marco na estrada para o progresso econômico, e faz uma contribuição enorme à qualidade e às esperanças futuras de um setor, de uma economia ou mesmo de um país. O objetivo deste artigo é comprovar que nos momentos de instabilidade econômica aumenta-se o numero de empreendedores através de dados de pesquisas de instituições reconhecidas utilizando fontes de evidencias quantitativas. Este estudo trata-se de uma pesquisa exploratória, baseada em dados secundários, com análise quantitativa de dados e amparada na literatura científica. Enquanto os indicadores econômicos apresentaram índices negativos devido a uma crise econômica, os indicadores de empreendedorismo mostraram uma reação inversa com índices positivos, caracterizando um aumento nos empreendimentos.

Ethylene Dissociation on Ni3Al(111)

Combining density functional theory, nudged elastic band, and high-energy resolution X-ray photoelectron spectroscopy experiments, we study the early stages and reaction pathways whereby ethylene molecules decompose on Ni3Al(111) prior to graphene nucleation and growth. After characterizing stable configurations of ethylene on the surface, and all intermediate products leading to carbon species, we calculate energy barriers for all relevant processes, including dehydrogenation, isomerization, C–C cleavage, and their respective inverse reactions. This quantitative analysis helps in identifying the most probable reaction pathways. The combination of temperature dependent C 1s core-level photoelectron spectroscopy measurements and of core-level shift calculations for all the different species investigated, allow us to understand the temperature evolution of the surface species and to identify the whole reaction mechanism. A combined analysis of this kind is useful for understanding which species are present on the surface at various temperatures during chemical vapor deposition graphene growth experiments.

Investors’ Fear and Herding Behavior: Evidence from the Taiwan Stock Market

ABSTRACTThis article analyzes the influence of investors’ fear on their investment behavior in the Taiwan stock market. This study used the volatility index (VIX) as a barometer of investors’ fear. Our results show that herding behavior increases with the VIX; that is, herding behavior is encouraged by an increase in investors’ fear. Moreover, our results demonstrate that investors react more quickly to bad news than to good news when their fear increases, supporting the hypothesis of the presence of an asymmetric reaction to news. However, investors react more quickly to good news when their fear decreases, indicating an inverse asymmetric reaction. In addition, our empirical results reveal that herding behavior tends to exist on days with a large trading volume.

CO2 absorption into aqueous solutions of monoethanolamine, piperazine and their blends: Quantum mechanics and molecular dynamics studies

The reaction mechanism and physico-chemical properties of CO2 absorption into aqueous solution of piperazine (PZ), monoethanolamine (MEA) and their blend have been determined by applying (SMD/IEF-PCM) as a solvation model in density functional theory (DFT) calculations and molecular dynamic simulations. Possible absorption pathways were investigated by transition state optimization and intrinsic reaction coordinate (IRC) calculations in the aqueous solution. In the absorption process the low activation energy evaluated for the zwitterion formation specifies this step as a rate determining and indicates the rate activator property of the PZ where PZ-monocarbamate anion is formed easily by zwitterion deprotonation with PZ and MEA as the bases, and decomposes in two path ways: (1) by an inverse reaction of zwitterion deprotonation (2) by a two-step zwitterion mechanism which includes PZ-monocarbamate anion zwitterion intermediate formation and then following by base catalyzed deprotonation of zwitterion. The final products of CO2 absorption process are the anions bicarbonate and PZ-monocarbamate which, according to the obtained results, can be considered respectively favorable from thermodynamics and kinetics aspects.The molecular dynamics results shows that the presence of low concentration of PZ in MEA aqueous solution enhances the CO2 diffusivity and solubility in a 30wt% aqueous amine solution. Consequently, PZ activated MEA aqueous solution can be used as an efficient amine solvent for CO2 absorption.

A Comparative Discussion of the Catalytic Activity and CO2-Selectivity of Cu-Zr and Pd-Zr (Intermetallic) Compounds in Methanol Steam Reforming

The activation and catalytic performance of two representative Zr-containing intermetallic systems, namely Cu-Zr and Pd-Zr, have been comparatively studied operando using methanol steam reforming (MSR) as test reaction. Using an inverse surface science and bulk model catalyst approach, we monitored the transition of the initial metal/intermetallic compound structures into the eventual active and CO2-selective states upon contact to the methanol steam reforming mixture. For Cu-Zr, selected nominal stoichiometries ranging from Cu:Zr = 9:2 over 2:1 to 1:2 have been prepared by mixing the respective amounts of metallic Cu and Zr to yield different Cu-Zr bulk phases as initial catalyst structures. In addition, the methanol steam reforming performance of two Pd-Zr systems, that is, a bulk system with a nominal Pd:Zr = 2:1 stoichiometry and an inverse model system consisting of CVD-grown ZrOxHy layers on a polycrystalline Pd foil, has been comparatively assessed. While the CO2-selectivity and the overall catalytic performance of the Cu-Zr system is promising due to operando formation of a catalytically beneficial Cu-ZrO2 interface, the case for Pd-Zr is different. For both Pd-Zr systems, the low-temperature coking tendency, the high water-activation temperature and the CO2-selectivity spoiling inverse WGS reaction limit the use of the Pd-Zr systems for selective MSR applications, although alloying of Pd with Zr opens water activation channels to increase the CO2 selectivity.

Separation of contributions of isovector E2 and E1 giant resonances in direct and inverse reactions with real and virtual photons

A brief overview of the methods for separating the contributions of isovector electric quadrupole (E2) and dominant dipole (E1) giant resonances in atomic nuclei, which are excited in direct and inverse reactions with photons (real and virtual), is given. The basic parameters of isovector giant resonance E2, which were declared to date by applying some of these methods to the results with 208Pb, are also presented.

Ther-process nucleosynthesis and related challenges

The rapid neutron-capture process, or r -process, is known to be of fundamental importance for explaining the origin of approximately half of the A > 60 stable nuclei observed in nature. Recently, special attention has been paid to neutron star (NS) mergers following the confirmation by hydrodynamic simulations that a non-negligible amount of matter can be ejected and by nucleosynthesis calculations combined with the predicted astrophysical event rate that such a site can account for the majority of r -material in our Galaxy. We show here that the combined contribution of both the dynamical (prompt) ejecta expelled during binary NS or NS-black hole (BH) mergers and the neutrino and viscously driven outflows generated during the post-merger remnant evolution of relic BH-torus systems can lead to the production of r -process elements from mass number A ≳ 90 up to actinides. The corresponding abundance distribution is found to reproduce the solar distribution extremely well. It can also account for the elemental distributions observed in low-metallicity stars. However, major uncertainties still affect our understanding of the composition of the ejected matter. These concern (i) the β -interactions of electron (anti)neutrinos with free neutrons and protons, as well as their inverse reactions, which may affect the neutron-richness of the matter at the early phase of the ejection, and (ii) the nuclear physics of exotic neutron-rich nuclei, including nuclear structure as well as nuclear interaction properties, which impact the calculated abundance distribution. Both aspects are discussed in the light of recent hydrodynamical simulations of NS mergers and microscopic calculations of nuclear decay and reaction probabilities.

Solvent Extraction of Citric Acid with Different Organic Phases

The present work aimed at the study of citric acid solvent extraction in order to establish the composition of the organic phase and to obtain thermodynamic and kinetic data for the chosen system. Discontinuous extraction experiments in a single stage were performed from a synthetic solution of citric acid, with the typical concentration (10% w/v) observed in industrial fermented musts. Exploratory experiments were carried out using different organic phases in order to select the most suitable solvent phase to further continuous extraction tests in a mechanically agitated column. The selected organic phase composition was: Alamine® 336, ExxalTM 13 tridecyl alcohol, and the aliphatic diluent EscaidTM 110. Next, the effects of the contact time and of the concentrations of extractant and modifier on the citric acid extraction were studied. Among the investigated conditions, the best one was 10 minutes of contact time, 30% w/v of Alamine® 336, and 10% w/v of ExxalTM 13 tridecyl alcohol. For this condition, the equilibrium isotherm (28°C ± 2°C) was determined, and the equilibrium constant was calculated (36.8 (mol·L-1)-1.5). It was considered that trioctylamine and citric acid complexation reaction occurs mainly with non-dissociated citric acid form, because the aqueous feed solutions’ pH is lower than the citric acid pKa1. It was found that 1.5 molecules of the extractant, on average, are required to react with one citric acid molecule, which can indicate that reactions with different extractant/citric acid ratios occur simultaneously. Next, the rate constants for the direct and inverse reactions, 2.10 (mol·L-1)-1.5·s-1 and 5.69 × 10-2 s-1, respectively, were calculated. Coefficients of determination (R2) values higher than 0.93 were found in these calculations, suggesting that the results obtained using a computer modeling would be very close to those results obtained experimentally. Therefore, the present work provides data required to future modelling, design, and simulation of citric acid solvent extraction processes.

Study of the population of neutron-rich heavy nuclei in the A~200 mass region via multinucleon transfer reactions

Multineutron and multiproton transfer channels, populated in the inverse kinematics reaction 197 Au+130 Te at Elab =1.07 GeV, were measured at Laboratori Nazionali di Legnaro using the presently heaviest ion beam delivered by the PIAVE-ALPI accelerator complex and detecting both projectile-like and targetlike ions. To this end the large solid angle magnetic spectrometer PRISMA was coupled to a second arm for the detection of the heavy fragments in kinematic coincidence with the light ones selected and identified with the spectrometer. The data analysis is still in progress and will allow to compare the yields of both light and heavy partner with theoretical predictions performed with the GRAZING code to get quantitative information on transfer channels and the effect of evaporation and fission on the production rate of primary fragments. The mass integrated Z distribution, extracted from the experimental data, evidenced the population of proton pickup channels that, in conjunction with the neutron stripping ones from the 130 Te, open the path for the production of neutron-rich heavy nuclei. In the following, we will present some preliminary results as well as details on the experimental configuration and perspectives for future investigations in the neutron-rich heavy region.

INSTITUTIONAL FRAMEWORK OF STATE FINANCIAL CONTROL

Introduction. Institualization of state financial control system in the terms of market transformation requires punctual and effective reforms that can increase the efficiency of its functioning and improve public administration. Efficiency of public financial control depends on the level of development of formal and social restraints. To determine the impact of these regulations within the institutional foundations of the state financial control the consideration and control mechanism that ensures the functioning of the institution should be considered. Methods. The dialectical method, instruments of system analysis of financial and economic processes, methods of comparative analysis, abstraction, algebra and geometric methods, evaluation and generalization were used in the study. Results. Institutional line of modern economic science has the ability to overcome the problems of economic theory that are determined by the misbalance in the economy. The institutional system of the state financial control is based on the certain standards that are considered to be after-effects of previous traditions in society or adopted from other countries. The principles of state financial control are examined through the prism of law-makers, holders of rights and obligations and the mechanism of control. Is has been found that there is interdependence between formal and social restraints and a mechanism of control. The author of the article suggests that the institutional foundations of the system of state financial control in Ukraine have been created. The formulated rules of domestic law, social transformation and resource provision of control mechanism prove this statement. Discussion. In order to effectively reform the system of state financial control in Ukraine it necessary to simultaneously modernize the institutional foundations and to ensure the following the financial discipline. In this case, an important condition for the further development of state financial control in the context of its institualization and the establishment of public and private relationships is an inverse business reaction (a signal of necessary changes in formal with the help of informal norms and ensure the strengthening of the national economy).

Synthesis and interconversions of reduced, alkali-metal supported iron-sulfur-carbonyl complexes.

We report the synthesis, interconversions and X-ray structures of a set of [mFe-nS]-type carbonyl clusters (where S = S2-, S22- or RS-; m = 2-3; n = 1-2). All of the clusters have been identified and characterized by single crystal X-ray diffraction, IR and 13C NMR. Reduction of the parent neutral dimer [μ2-(SPh)2Fe2(CO)6] (1) with KC8 affords an easily separable ∼1 : 1 mixture of the anionic, dimeric thiolate dimer K[Fe2(SPh)(CO)6(μ-CO)] (2) and the dianionic, sulfido trimer [K(benzo-15-crown-5)2]2[Fe3(μ3-S)(CO)9] (3). Oxidation of 2 with diphenyl-disulfide (Ph2S2) cleanly returns the starting material 1. The Ph-S bond in 1 can be cleaved to form sulfide trimer 3. Oxidation of sulfido trimer 3 with [Fc](PF6) in the presence of S8 cleanly affords the all-inorganic persulfide dimer [μ2-(S)2Fe2(CO)6] (4), a thermodynamically stable product. The inverse reactions to form 3 (dianion) from 4 (neutral) were not successful, and other products were obtained. For example, reduction of 4 with KC8 afforded the mixed valence Fe(i)/Fe(ii) species [((FeS2)(CO)6)2FeII]2- (5), in which the two {Fe2S2(CO)6}2- units serve as bidendate ligands to a Fe(ii) center. Another isolated product (THF insoluble portion) was recrystallized in MeCN to afford [K(benzo-15-crown-5)2]2[((Fe2S)(CO)6)2(μ-S)2] (6), in which a persulfide dianion bridges two {2Fe-S} moieties (dimer of dimers). Finally, to close the interconversion loop, we converted the persulfide dimer 4 into the thiolate dimer 1 by reduction with KC8 followed by reaction with the diphenyl iodonium salt [Ph2I](PF6), in modest yield. These reactions underscore the thermodynamic stability of the dimers 1 and 4, as well as the synthetic and crystallization versatility of using the crown/K+ counterion system for obtaining structural information on highly reduced iron-sulfur-carbonyl clusters.

Determining the 14O(α,p)17F astrophysical rate from Measurements at TwinSol

The 14O(α,p)17F reaction is an important trigger reaction to the α-p process in X-ray bursts. The most stringent experimental constraints on its astrophysical rate come from measurements of the time-inverse reaction, 17F(p,α)14O. Previous studies of this inverse reaction have sufficiently characterized the high-energy dependence of the cross section but there are still significant uncertainties at lower energies. A new measurement of the 17F(p,α)14O cross section is underway at the Twin Solenoid (TwinSol) facility at the University of Notre Dame using an in-flight secondary 17F beam. The initial results are promising but improvements are needed to complete the measurement. The initial data and plans for an improved measurement are presented in this manuscript.

Water relations and photosynthetic water use efficiency as indicators of slow climate change effects on trees in a tropical mountain forest in South Ecuador

The effects of an increasing moisture on trees of the tropical species-rich mountain rain forest in the South Ecuadorian Andes was investigated, using the daily total water consumption (TWC) and the instantaneous water use efficiency (WUE, ratio of photosynthetic CO2 uptake per water loss by transpiration) as ecophysiological indicators. Two canopy and one sub-canopy tree species, (Vismia tomentosa, Clusiaceae, an as of yet unknown Lauracee, and Spirotheca rosea, Bombacaceae) were the experimental objects. Seasonal changes as well as a long-term (18 months) trend of increasing precipitation caused an inverse reaction of the TWC of the trees. Because of a rather unlimited water supply to the trees from a permanently high water content of the soil, transpiration followed mainly the atmospheric demand of water vapor, and increasing moisture hence reduced water loss by transpiration. It was hypothesized that in spite of the reduction in transpiratory water loss photosynthetic carbon acquisition would be not or less affected due to an increase in water use efficiency. Concomitant measurements of photosynthetic net CO2 uptake showed the expected increase of WUE in V. tomentosa and S. rosea, but no clear reaction of the Lauracee. Accompanying measurements of stem extension growth confirmed an undiminished growth of V. tomentosa and S. rosea but showed also suspended growth of the Lauracee during the wettest months. While TWC can be continuously monitored with the heat dissipation technique, WUE is determined by leaf porometry in campaigns for which access to the canopy is required. Simultaneous recordings of the gas exchange of leaves at 4 different positions in the crown of one of the experimental trees (V. tomentosa) showed the usability of the trait WUE in combination with the total daily water consumption as indicator set for assessing the response of trees to a subtly changing climate. However, not all tree species appear as likewise useful indicator trees.

Sequences Analysis of a Gene Encoding Extracellular Xylanase in Streptomyces costaricanus 45I-3

Streptomyces costaricanus 45I-3 is a bacterial strain belongs to actinomycetes group isolated from peat soil. Thebacterium is known to produce extracellular xylanase. The aims of this study were to analyze DNA sequence andsub-clone gene involved in the synthesis of extracellular xylanase. Complete DNA sequence predicted to encodexylanase genes was isolated from bacterial genome using Inverse Polymerase Chain Reaction (I-PCR). Total DNAsequence of 1664 bp in size obtained from I-PCR consisted of two open reading frames (ORF) in opposite direction.ORF1 was 1029 bp and ORF2 (partial sequence) was 309 bp. Analysis sequence using BlastX indicated that ORF1was homologous with xylanase bacterium enrichment culture clone Xyl8B8 (GenBank accession No. AFH35005.1),i.e. 95% in identity and 99% in similarity. In addition, ORF2 was homologous with glyoxalase bacterium enrichmentculture clone Xyl8B8 (GenBank accession No. AFH35007.1), i.e. 95% in identity and 98% in similarity. Analysis ofamino acid sequence revealed that ORF1 consisted of 2 domains, i.e. glyco-hydrolase 11 (GH11) and CarbohydrateBinding Type 2 (CBM2). Active site was found at 130th amino acid on GH11 domain. Visualization of 3-dimensionstructure showed that 1029 bp fragment is of 19 areas.

A DFT study on the functionalization of C60 fullerene with 1,2-benzoquinone

We investigated the capability of 1,2-benzoquinone as an abundant molecule in natural and biological systems to functionalize C60 fullerene. DFT calculations indicate that C60 acts as a dienophile in inverse electron-demand Diels-Alder cycloaddition reaction with 1,2-benzoquinone. Moreover, different functional groups were employed to manipulate the geometric and electronic properties of the complex. The adsorption energies increase by rising the electron withdrawing ability of functional groups as followed: -NO2>-CN>-COOH>-CHO>-H>-F>-CH3>-OH>-NH2. While all groups change the HOMO-LUMO energy gap of C60 slightly, –NH2 decreases it about 23%.

The origin of high sulfate concentrations and hydrochemistry of the Upper Miocene–Pliocene–Quaternary aquifer complex of Jifarah Plain, NW Libya

The high uncontrolled groundwater extraction in Jifarah Plain, NW Libya, causes a modification of natural flow systems, inducing seawater intrusion and causing groundwater quality deterioration. The principal aim of this study is to identify the hydrogeochemical processes in this coastal aquifer in order to verify the main sources of sulfate concentration increase that occurs in the system. In order to achieve this aim, water samples were collected from 134 sampling wells in the study area and analyzed for the major cations and anions; physical and chemical parameters were measured, such as water level, electrical conductivity, pH and temperature. The analytical results obtained in the hydrochemical study were interpreted using Piper diagram, ion correlations with Na+/Cl−, SO4 2−, Cl− and TDS, in conjunction with calculation of the ionic deviations of the conservative freshwater/seawater mixture and saturation indices using the PHREEQC 2.16 software. The large SO4 2− anomaly observed in groundwater near the coast was explained by the presence of seawater intrusion and upconing of deep saline water in these areas. This conclusion is based on high chloride concentrations, the inverse cation exchange reactions and the lower piezometric level compared to sea level. Inland, in Sabratah, the high SO4 2− values are related to gypsum dissolution from the Upper Miocene Formation in the lower part of the upper aquifer. These locally high SO4 2− concentrations in the south of the study area show overall increase in the upstream direction, which also suggests the dissolution of evaporites from the mountain aquifers in the south. High SO4 2− concentration is also related to the effect of the scattered sebkha deposits in some areas along the coast.