Preferred Transition Research Articles

Desulfinylation of Prop-2-enesulfinic Acid: Experimental Results and Mechanistic Theoretical Analysis

The potential energy surfaces of the desulfinylation of prop-2-enesulfinic acid (13) in CH(2)Cl(2) solution at -15 degrees C have been explored by quantum calculations and analyzed with kinetic data obtained for the reaction in absence or presence of additives. Monomeric 13 adopts a preferred conformation with gauche S=O/sigma(C(1)-C(2) bond pairs and the O-H bond pointing toward C(3). It equilibrates with the more stable dimer (13)(2) (at -15 degrees C) formed by two O-H...O=S hydrogen bonds and in which the S=O/sigmaC(1)-C(2) are gauche also, but the SOH moieties are antiperiplanar with respect to sigma(C(1)-C(2)). Dimer (13)(2) undergoes desulfinylation into propene + SO(2) + 13 following a one-step, concerted mechanism. The preferred transition state is a six-membered, chairlike transition structure (C...S elongation and S-O...H...C(3) hydrogen transfer occur in concert) in which the S=O/sigma(C(1)-C(2)) bonds are gauche (S=O adopt pseudoaxial positions). There are at least 48 transition states, each one defining a different pathway, all with similar calculated free energies (DeltaG(double dagger) = 25.3-28.6 kcal/mol), which makes the bimolecular (autocatalyzed) retro-ene elimination of SO(2) competing (entropy factor) with a monomolecular process for which the transition state (calculated DeltaG(double dagger) = 24.3 kcal/mol) implies only one molecule of sulfinic acid. This agrees with the experimental rate law of the reaction which is first order in the concentration of dimer (13)(2). SO(2), CF(3)COOH, and BF(3) x Me(2)O do not catalyze the reaction. In the presence of an excess of BF(3) x Me(2)O the desulfinylation is completely inhibited due to the formation of a stable tetramolecular complex of type (CH(2)=CHCH(2)SO(2)H x BF(3))(2) (18), for which quantum calculations show that the S=O/sigma(C(1)-C(2)) bonds are antiperiplanar whereas the S-OH/sigma(C(1)-C(2)) bonds are gauche. Independently of the additive, the retro-ene eliminations of SO(2) are calculated to be concerted and have transition states adopting six-membered cyclic structures in which S=O and sigma(C(1)-C(2)) are gauche, the S=O interacting with the additive. Preliminary experiments suggested that the thermodynamically unfavored ene reaction of SO(2) with propene can occur at low temperature using 1 equiv of BF(3).

Stress induced preferred orientation and phase transition for ternary WC xN y thin films

We deposit ternary WC x N y thin films on Si (1 0 0) substrates at 500 °C using direct current (DC) reactive magnetron sputtering in a mixture of CH 4/N 2/Ar discharge, and explore the effects of substrate bias ( V b) on the intrinsic stress, preferred orientation and phase transition for the obtained films by virtue of X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and selective area electron diffraction (SAED). We find that with increasing the absolute value of V b up to 200 V the carbon ( x) and nitrogen ( y) atom concentrations of WC x N y films keep almost constant with the values of 0.75 and 0.25, respectively. The XPS and SAED results, combined with the density-functional theory (DFT) calculations on the electronic structure of WC 0.75N 0.25, show our obtained WC x N y films are single-phase of carbonitrides. Furthermore, we find that the compressive stress sharply increases with increasing the absolute value of V b, which leads to a pronounced change in the preferred orientation and phase structure for the film, in which a phase transition from cubic β-WC x N y to hexagonal α-WC x N y occurs as V b is in the range of −40 to −120 V. In order to reveal the relationship between the stress and phase transition as well as preferred orientation, the DFT calculations are used to obtain the elastic constants for β-WC x N y and α-WC x N y . The calculated results show that the preferred orientation is dependent on the competition between strain energy and surface energy, and the phase transition can be attributed to a decrease in the strain energy.

Micromagnetic study of magnetization reversal in ferromagnetic nanorings

We present results of micromagnetic simulations of thin ferromagnetic rings undergoing magnetization reversal. This geometry is one of few examples in micromagnetics in which the transition states have been found analytically in a one-dimensional (1D) model. According to this model, at low fields and large ring sizes, the energetically preferred transition state is a localized magnetization fluctuation (instanton saddle). At high fields and small ring size, the preferred saddle state is a uniformly rotated magnetization (constant saddle). In the first part of this paper, we use numerical micromagnetic simulations to test these predictions of the 1D analytical model for more realistic situations including a variety of ring radii, annular widths and magnetic fields. The predicted activation energies for magnetization reversal are found to be in close agreement with numerical results even for rings with a large annular width where the 1D approximation would be expected to break down. We find that this approximation breaks down only when the ring's annular width exceeds its radius. In the second part, we present new metastable states found in the large radius limit and discuss how they provide a more complete understanding of the energy landscape of magnetic nanorings.

Testing transitivity in choice under risk

Recently proposed models of risky choice imply systematic violations of transitivity of preference. This study explored whether people show the predicted intransitivity of the two models proposed to account for the certainty effect in Allais paradoxes. In order to distinguish “true” violations from those produced by “error,” a model was fit in which each choice can have a different error rate and each person can have a different pattern of preferences that need not be transitive. Error rate for a choice is estimated from preference reversals between repeated presentations of the same choice. Results showed that few people repeated intransitive patterns. We can retain the hypothesis that all participants were transitive.

Influence of Shock Waves and Muscle Activity at Initial Contact on Walk–Run Transition Evaluated by Two Models

The walk-run transition (WRT) is a well-described phenomenon without any known cause; however, mechanical variables related to human gait have been associated with the WRT. This study tested the hypothesis that shock waves in the tibia and 3rd lumbar vertebra in addition to activity of tibialis anterior, vastus lateralis, and erector spinae muscles could be responsible for the WRT. Thirty subjects walked and ran on a treadmill at 80%, 90%, 100%, 110%, and 120% of preferred transition speed. Shock waves were measured with skin-mounted accelerometers and muscle activity by surface electromyography. The influence on the WRT was analyzed with two models. The shock waves and muscle activity tended to a significant increase (p < .05) for both walking and running with increased speed. The only factor that appeared to be involved in the WRT mechanism was the activity of the tibialis anterior; however, this was only confirmed by one of the two models. The use of different models to analyze the same data for the WRT triggers may give different results; thus, a standard model is required to investigate the influence of given factors on biological phenomena.

Physiological Characteristics of the Preferred Transition Speed in Racewalkers

The preferred transition speed (PTS) at which humans change their gait from walking to running was found to be lower than their energetically optimal transition speed (EOTS). This phenomenon has not been examined in racewalkers. The purpose of this study was to evaluate the PTS and the EOTS in racewalkers compared with controls. Eleven racewalkers and 13 control subjects participated in this study. Subjects arrived at the laboratory on three occasions. Visit I: determination of PTS. Subjects walked at a slow speed that was increased by 0.2 km x h every 30 s until they felt it was easier to run. Then, subjects ran at a high speed and the treadmill speed was reduced by 0.2 km x h every 30 s until they felt it was easier to walk. Visits II and III: subjects walked and ran at PTS - 1 km x h, PTS - 0.5 km x h, PTS, PTS + 0.5 km x h, and PTS + 1 km x h. At each stage, physiological measurements were recorded. PTS was 7.33 +/- 0.33 km x h in controls and 8.20 +/- 0.54 km.h in racewalkers (P < 0.001), and EOTS was 8.00 +/- 0.48 km x h in controls and 8.46 +/- 0.55 km x h in racewalkers (P = 0.039). There was a trend for a smaller difference between PTS and EOTS in racewalkers. V O2 was higher during running at the PTS in both groups (F1, 22 = 5.972, P = 0.023), and there was a trend for a group interaction (F1, 22 = 3.442, P = 0.077). HR and V E were higher at the PTS in racewalkers compared with controls. Racewalkers have a higher PTS and EOTS compared with controls. There is a trend for the difference between the PTS and the EOTS to be smaller in racewalkers compared with controls.

A DFT study on the removal of adsorbed sulfur from a nickel(111) surface: Reducing anode poisoning

This report presents the results of our studies on the second step of the post-treatment of the solid-oxide fuel cells (SOFCs) that have been poisoned by sulfur from traces of H 2S in the fuel. The removal of strongly adsorbed atomic sulfur from a planar Ni(111) surface at 0.25 ML coverage is investigated in order to explore possible ways to regain the activity of SOFCs poisoned by sulfur deposition on the anode. The predominant reaction pathway studied consists of the adsorption and dissociation of molecular oxygen, followed by the formation and desorption of sulfur dioxide. Using periodic DFT calculations, preferred adsorption sites, energies, transition states and kinetic barriers are calculated for the resulting intermediate and product species, SO x ∗ ( x = 0 – 2 ) and ∗O. Generally, concurring with the limited experimental data available at temperature >750 K, our research illustrates the considerable exergonic nature that describes the formation and desorption of SO 2, and shows that the removal of the remaining 25% of sulfur after the first step of post-treatment of the fuel cell can be accomplished by means of high-temperature oxidation.

Relatively low temperature synthesis of hexagonal tungsten carbide films by N doping and its effect on the preferred orientation, phase transition, and mechanical properties

The authors deposited N-doped tungsten carbide thin films on Si(100) substrates at 500°C using direct-current reactive magnetron sputtering in a mixture of CH4∕N2∕Ar discharge and explored the effects of N doping on the preferred orientation, phase transition, and mechanical properties of the films by using x-ray diffraction, x-ray photoelectron spectroscopy, and nanoindentation measurements. They found that N doping significantly influenced the compressive stress, which led to a pronounced change in the preferred orientation, phase structure, and hardness for the tungsten carbide film. A phase transition from β-WC to α-WC occurred when N doping was in the range of 2.9 and 4.7at.%, meaning that α-WC can be obtained at relatively low temperature (500°C). To reveal the relationship between the stress and phase transition, as well as preferred orientation, the density-functional theory based on first principles was used to calculate the elastic constants and shear modulus for tungsten carbide with a structure of β-WC or α-WC. The calculated results showed that the preferred orientation depended on the competition between strain energy and surface energy, as well as the grains competitive growth, and the phase transition can be attributed to a decrease in the strain energy. The hardness of α-WC was harder than β-WC because the shear modulus for α-WC was larger than that of β-WC, whereas the bulk modulus for α-WC was almost equal to that of β-WC.

Cardinal Consistency of Reciprocal Preference Relations: A Characterization of Multiplicative Transitivity

Consistency of preferences is related to rationality, which is associated with the transitivity property. Many properties suggested to model transitivity of preferences are inappropriate for reciprocal preference relations. In this paper, a functional equation is put forward to model the ldquocardinal consistency in the strength of preferencesrdquo of reciprocal preference relations. We show that under the assumptions of continuity and monotonicity properties, the set of representable uninorm operators is characterized as the solution to this functional equation. Cardinal consistency with the conjunctive representable cross ratio uninorm is equivalent to Tanino's multiplicative transitivity property. Because any two representable uninorms are order isomorphic, we conclude that multiplicative transitivity is the most appropriate property for modeling cardinal consistency of reciprocal preference relations. Results toward the characterization of this uninorm consistency property based on a restricted set of (n-1) preference values, which can be used in practical cases to construct perfect consistent preference relations, are also presented.

Interdisciplinary Approach to Intransitivity of Preferences in Decision Making

Abstract The known problem of intransitivity of preferences arising in decision making is revised in view of risks of invalid decisions based on formal methods. The cognitive approach to analysis is applied considering transitivity of preferences as heuristics with a limited domain of validity. A conception of rational intransitivity of expert's preferences is advanced. With this in view, the adaptive approach to develop mathematical means of problem solving traditionally using the axiom of transitivity is proposed. The original implementation of the adaptive approach is presented for the general problem of the best element selection with diversity of similar problems within the general one.

How to create appealing temporal color transitions?

Many applications, such as AmbiLight TV and atmosphere creation with dynamic light, generate colored light that changes gradually from one color to another. However, there is not much scientific knowledge on how to create suitable color transitions. This study investigates what is perceptually the most optimal way to create a temporal color transition between two colors. The first experiment measured the ability to distinguish between two temporal color transitions. The reference transition was a linear interpolation between two colors in CIELab, the test transitions were arcs defined in different planes going through the linear transition. Discrimination thresholds ranged between 2.5 and 12.5 ΔEab, depending on the color pair, direction, and duration of the transition. In the second experiment, several perceptually different color transitions were compared. The most preferred transitions were a linear transition in CIELab and a linear transition in RGB. The results suggest that it is possible to design a general algorithm for temporal color transitions that is appreciated by human observers, independent of color pair and application.

How to create appealing temporal color transitions?

Abstract— Many applications, such as AmbiLight TV and atmosphere creation with dynamic light, generate colored light that changes gradually from one color to another. However, there is not much scientific knowledge on how to create suitable color transitions. This study investigates what is perceptually the most optimal way to create a temporal color transition between two colors. The first experiment measured the ability to distinguish between two temporal color transitions. The reference transition was a linear interpolation between two colors in CIELab, the test transitions were arcs defined in different planes going through the linear transition. Discrimination thresholds ranged between 2.5 and 12.5 ΔEab, depending on the color pair, direction, and duration of the transition. In the second experiment, several perceptually different color transitions were compared. The most preferred transitions were a linear transition in CIELab and a linear transition in RGB. The results suggest that it is possible to design a general algorithm for temporal color transitions that is appreciated by human observers, independent of color pair and application.

A method to implement effective My-page service system using three-dimensional vectors

This paper proposes a method to construct My-page, which is an effective one-to-one-marketing method for internet service providers. In conventional methods, customer preference and market information are managed with two-dimensional vectors of customer and preference category axes. In this proposed method, we add time axis to make it three-dimensional vectors in order to manage the preference transitions and the market trends. One of the problems of three-dimensional vectors is its huge volume of information. In order to solve this problem, the three-dimensional vector was compressed using the MPEG algorithm. As a result, the amount of data could be compressed to less than 5%, and the problem was solved. Furthermore, we have found a few trend leaders in the groups, which confirm that there is a possibility to make appropriate recommendations to the other group member based on the transitions of the trend leaders.

What is the mechanism of amine conjugate additions to pyrazole crotonate catalyzed by thiourea catalysts?

Aminoindanol-derived thioureas catalyze proton transfer and do not stabilise anions in an asymmetric conjugate addition to pyrazole crotonate. Calculations show that the urea H-bonds play different roles in the preferred transition state and in the one leading to the minor enantiomer in the mechanism of hydroxy-thiourea catalyzed conjugate additions to pyrazole crotonates.

Effects of nitrogen flow rate on the preferred orientation and phase transition for niobium nitride films grown by direct current reactive magnetron sputtering

We deposit niobium nitride (NbN) thin films on Si(1 0 0) substrates using direct current (dc) reactive magnetron sputtering in discharging a mixture of N2 and Ar gas, and explore the effects of nitrogen flow rate () on the preferred orientation (PO), phase transition and mechanical properties for the obtained films by virtue of x-ray diffraction and nanoindentation measurements. We find that with increasing the biaxial compressive stress increases, which leads to a pronounced change in the PO and phase structure for the film. A phase transition from δ (face-centred cubic) to δ′ (hexagonal) occurs in the film as the biaxial stress increases to a critical value of about 3.9 GPa, which can be attributed to a decrease in the strain energy. With a further increase in the biaxial stress, the fraction of the δ′ phase in the film increases, and finally the film only has a single phase, δ′-NbN, resulting in a consistent increase in hardness.

Comparative Genomic Study Reveals a Transition from TA Richness in Invertebrates to GC Richness in Vertebrates at CpG Flanking Sites: An Indication for Context-Dependent Mutagenicity of Methylated CpG Sites

Vertebrate genomes are characterized with CpG deficiency, particularly for GC-poor regions. The GC content-related CpG deficiency is probably caused by context-dependent deamination of methylated CpG sites. This hypothesis was examined in this study by comparing nucleotide frequencies at CpG flanking positions among invertebrate and vertebrate genomes. The finding is a transition of nucleotide preference of 5′ T to 5′ A at the invertebrate-vertebrate boundary, indicating that a large number of CpG sites with 5′ Ts were depleted because of global DNA methylation developed in vertebrates. At genome level, we investigated CpG observed/expected (obs/exp) values in 500 bp fragments, and found that higher CpG obs/exp value is shown in GC-poor regions of invertebrate genomes (except sea urchin) but in GC-rich sequences of vertebrate genomes. We next compared GC content at CpG flanking positions with genomic average, showing that the GC content is lower than the average in invertebrate genomes, but higher than that in vertebrate genomes. These results indicate that although 5′ T and 5′ A are different in inducing deamination of methylated CpG sites, GC content is even more important in affecting the deamination rate. In all the tests, the results of sea urchin are similar to vertebrates perhaps due to its fractional DNA methylation. CpG deficiency is therefore suggested to be mainly a result of high mutation rates of methylated CpG sites in GC-poor regions.

Stability and the time-dependent structure of gait variability in walking and running

Participants were asked to walk and run continuously (5 min trials) at speeds associated with preferred gait transition speeds. During slow running the local dynamic stability of the head was decreased compared with fast walking, with the reverse being true for the local dynamic stability of the ankle. The standard deviation of relative phase of the knee and ankle also was greater during slow running than fast walking. These findings for stability were mirrored in the detrended fluctuation analysis of the peak to peak interval of the head and ankle. Taken collectively these results support the proposition that larger long range correlations in the stride interval are associated with decreases in measures of stability.

Intra‐seasonal atmospheric variability and extreme precipitation events in the European‐Mediterranean region

The low frequency atmospheric variability over the European‐Mediterranean region is described by the weather regimes, obtained by using a clustering algorithm applied on the September‐December geopotential height at 500 hPa. Links between the European‐Mediterranean weather regimes and extremes of precipitation over Europe are examined. We focus on the autumn season, when heavy precipitation episodes are likely to occur over the Mediterranean coasts. In the second part of this paper, we study whether the European‐Mediterranean weather regimes can be related to the phases of some intra‐seasonal atmospheric oscillation. By using the Multi‐Channel Singular Spectrum Analysis (MSSA), we identify a 50‐day oscillation over the European‐Mediterranean region. The phases of this oscillation are found to be consistent with the preferred weather regimes transitions. This could influence intra‐seasonal predictability and suggests that links between the episodic (weather regimes) and oscillatory (intra‐seasonal oscillations) approaches may also apply to the regional scale.

Stable Running with Segmented Legs

Spring-like leg behavior is found in both humans and animals when running. In a spring-mass model, running proves to be self-stable in terms of external perturbations or variations in leg properties (for example, landing angle). However, biological limbs are not made of springs, rather, they consist of segments where spring-like behavior can be localized at the joint level. Here, we use a two-segment leg model to investigate the effects of leg compliance originating from the joint level on running stability. Owing to leg geometry a non-linear relationship between leg force and leg compression is found. In contrast to the linear leg spring, the segmented leg is capable of reducing the minimum speed for self-stable running from 3.5 m s-1 in the spring-mass model to 1.5 m s-1 for almost straight joint configurations, which is below the preferred transition speed from human walking to running (≈2 m s-1). At moderate speeds the tolerated range of landing angle is largely increased (17° at 5 m s-1) compare with the linear leg spring model (2°). However, for fast running an increase in joint stiffness is required to compensate for the mechanical disadvantage of larger leg compression. This could be achieved through the use of non-linear springs to enhance joint stiffness in fast running.

Effects of substrate bias on the preferred orientation, phase transition and mechanical properties for NbN films grown by direct current reactive magnetron sputtering

NbN films are deposited using direct current reactive magnetron sputtering in discharge of a mixture of N2 and Ar gas, and the effects of substrate bias (Vb) on the preferred orientation, phase transition, and mechanical properties for NbN films are explored by x-ray diffraction, selective area electron diffraction, and nanoindentation measurements. It is found that Vb has a significant influence on the stress in NbN films, leading to a pronounced change in the preferred orientation, phase structure, and hardness. As the substrate is at voltage floating, the stress is tensile. In contrast, as negative Vb is applied, the stress becomes compressive, and increases with increasing the absolute value of negative Vb. It is observed that a phase transition from δ (face-centered cubic) to δ′ (hexagonal) for NbN films occurs as Vb is in the range of −80to−120V, which can be attributed to a decrease in the strain energy for NbN films. In order to explore the relationship between the stress and phase transition as well as preferred orientation, density-functional theory based on first principles is used to calculate the elastic constants and shear modulus for NbN with a structure of δ or δ′. The calculated results show that the shear modulus for δ′-NbN is larger than that for δ-NbN, whereas the bulk modulus for δ′-NbN is almost equal to that for δ-NbN, resulting in a difference in hardness for δ- or δ′-NbN single crystal.