Direct Repulsion Research Articles

Chemical composition and insecticidal activity of Artemisia absinthium L. essential oil against adults of Tenebrio molitor L.

Many researchers and manufacturers around the world have shown interest in essential oils and their components. Artemisia absinthium L., commonly known as wormwood, is a medicinal and aromatic bitter herb frequently used in traditional medicine since ancient times. The objective of this research was to study the chemical composition and evaluate the insecticidal activities of A. absinthium essential oil (AEO) against Tenebrio molitor L., mealworm battle. We explored its effectiveness through several means, including direct contact, fumigation and repulsion of insects. Phytochemical analysis was performed using GC-MS technique. The main components identified in the essential oil were camphor (32.34%), chamazulene (13.92%), and terpinen-4-ol (10.18%). These results highlight that Algerian A. absinthium plants are valuable resources due to their bioactive compounds. In particular, the results obtained in our investigation suggest that the essential oil obtained from A. absinthium has the potential to be used as a natural bioinsecticide.

Application of laminarin as a novel coagulant aid to improve coagulation-ultrafiltration efficiency

Polyacrylamide (PAM) is the most commonly used coagulant aid in coagulation-ultrafiltration (C-UF) systems; however, its hydrolyzed monomer is harmful to the human nervous system. In this study, laminarin (LA), was extracted from Laminaria japonica and used as a novel coagulant aid to improve coagulation efficiency and reduce membrane fouling during the C-UF process. Optimal LA usage conditions were systematically examined and compared with those of PAM to evaluate their potential for industrial applications. The results revealed that coagulation efficiency could be enhanced by 15–35% with moderate LA addition, which exhibited comparable aid effects to PAM. LA exhibited the highest coagulation aid effect at pH 8–9, and under this condition, turbidity and natural organic matter (NOM) removal achieved 82% and 54%, respectively. Compared with a one-time LA dosing strategy, the pollutant removal capacity of batch dosing was superior. Even in lower water temperatures (5–15 °C), coagulation efficiency was still satisfied, which exhibited a good practical application perspective. The coagulation aid role of LA should be attributed to its long-chain molecular structure, which enhances the bridging role between micro flocs and assists floc growth, thus facilitating the formation of large flocs. In addition, LA adsorption on floc surface was conducive to the direct electrostatic repulsion effect of electronegative membrane, which resulted in a more porous cake layer and higher membrane flux. Therefore, LA exhibits excellent application potential for eliminating NOM while simultaneously reducing membrane fouling through the C-UF process.

Context-effect bias in capuchin monkeys (Sapajus spp.): exploring decoy influences in a value-based food choice task

Decision making is known to be liable to several context effects. In particular, adding a seemingly irrelevant alternative (decoy) to a set of options can modify preferences: typically, by increasing choices towards whatever option clearly dominates the decoy (attraction effect), but occasionally also decreasing its appeal and generating a shift in the opposite direction (repulsion effect). Both types of decoy effects violate rational choice theory axioms and suggest dynamic processes of preference-formation, in which the value of each alternative is not determined a priori, but it is instead constructed by comparing options during the decision process. These effects are well documented, both in humans and in other species: e.g., amoebas, ants, honeybees, frogs, birds, cats, dogs. However, evidence of decoy effects in non-human primates remains surprisingly mixed. This study investigates decoy effects in capuchin monkeys (Sapajus spp.), manipulating time pressure across different conditions, to test whether such effects require time-consuming comparative processes among available alternatives. Whereas the time-dependent nature of decoy effects is a robust finding in the human literature, this is its first investigation in non-human animals. Our results show that capuchins exhibit an attraction effect with decoys targeting their preferred food, and that this effect disappears under time pressure; moreover, we observe preliminary evidence of a repulsion effect when decoys target instead the less-preferred food, possibly due to the larger distance between decoy and target in the attribute space. Taken together, these results provide valuable insight on the evolutionary roots of comparative decision making.

Carbon and vacancy centers in hexagonal boron nitride

Creation of defect with predetermined optical, chemical and other characteristics is a powerful tool to enhance the functionalities of materials. Herewith, we utilize density functional theory to understand the microscopic mechanisms of formation of defects in hexagonal boron nitride based on vacancies and substitutional atoms. Through in-depth analysis of the defect-induced band structure and formation energy in varying growth conditions, we uncovered a dominant role of interdefect electron paring in stabilization of defect complexes. The electron reorganization modifies the exchange component of the electronic interactions which dominates over direct Coulomb repulsion or structural relaxation effects making the combination of acceptor- and donor-type defect centers energetically favorable. Based on an analysis of a large number of defect complexes we develop a simple picture of the inheritance of electronic properties when individual defects are combined together to form more complex centers.

Study of the electrostatic repulsion of the carboxylic surface in the diffusion layer by scanning electrochemical microscopy

AbstractThe behavior of electrostatic repulsion in the diffusion layer on the electrode is significant for understanding electrochemical processes with a diffusion control step. In this work, the electrostatic repulsion at the carboxylic acid‐containing surface of a 3‐mercaptopropionic acid self‐assembled monolayer (MPA SAM) in the diffusion layer on the tip electrode was revealed by scanning electrochemical microscopy (SECM). A direct surface repulsion system was designed between [Fe(CN)6]4− and the carboxylate groups in the diffusion layer. The pH‐modulated electrostatic repulsion of the carboxylic surface led to the repulsion of [Fe(CN)6]4− during diffusion, interrupting the regeneration of [Fe(CN)6]4− to [Fe(CN)6]3− on MPA SAM. Therefore, the approaching curve underwent a characteristic inversion from positive feedback to negative feedback dramatically. Electrostatic repulsion of the carboxylic surface was confirmed by linear sweep voltammetry and substrate generation/tip collection. Furthermore, the electrostatic repulsion of the carboxylic surface was visualized by SECM imaging technology. This work has contributed to broadening the recognition of electrostatic repulsion in the diffusion layer.

Neural coding for the illusion of direction repulsion of transparently moving stimuli

Neural coding for the illusion of direction repulsion of transparently moving stimuli

Electron cascade for distant spin readout

The spin of a single electron in a semiconductor quantum dot provides a well-controlled and long-lived qubit implementation. The electron charge in turn allows control of the position of individual electrons in a quantum dot array, and enables charge sensors to probe the charge configuration. Here we show that the Coulomb repulsion allows an initial charge transition to induce subsequent charge transitions, inducing a cascade of electron hops, like toppling dominoes. A cascade can transmit information along a quantum dot array over a distance that extends by far the effect of the direct Coulomb repulsion. We demonstrate that a cascade of electrons can be combined with Pauli spin blockade to read out distant spins and show results with potential for high fidelity using a remote charge sensor in a quadruple quantum dot device. We implement and analyse several operating modes for cascades and analyse their scaling behaviour. We also discuss the application of cascade-based spin readout to densely-packed two-dimensional quantum dot arrays with charge sensors placed at the periphery. The high connectivity of such arrays greatly improves the capabilities of quantum dot systems for quantum computation and simulation.

Expectations about motion direction affect perception and anticipatory smooth pursuit differently.

Smooth pursuit eye movements and visual motion perception rely on the integration of current sensory signals with past experience. Experience shapes our expectation of current visual events and can drive eye movement responses made in anticipation of a target, such as anticipatory pursuit. Previous research revealed consistent effects of expectation on anticipatory pursuit-eye movements follow the expected target direction or speed-and contrasting effects on motion perception, but most studies considered either eye movement or perceptual responses. The current study directly compared effects of direction expectation on perception and anticipatory pursuit within the same direction discrimination task to investigate whether both types of responses are affected similarly or differently. Observers (n = 10) viewed high-coherence random-dot kinematograms (RDKs) moving rightward and leftward with a probability of 50%, 70%, or 90% in a given block of trials to build up an expectation of motion direction. They were asked to judge motion direction of interleaved low-coherence RDKs (0%-15%). Perceptual judgements were compared with changes in anticipatory pursuit eye movements as a function of probability. Results show that anticipatory pursuit velocity scaled with probability and followed direction expectation (attraction bias), whereas perceptual judgments were biased opposite to direction expectation (repulsion bias). Control experiments suggest that the repulsion bias in perception was not caused by retinal slip induced by anticipatory pursuit, or by motion adaptation. We conclude that direction expectation can be processed differently for perception and anticipatory pursuit.NEW & NOTEWORTHY We show that expectations about motion direction that are based on long-term trial history affect perception and anticipatory pursuit differently. Whereas anticipatory pursuit direction was coherent with the expected motion direction (attraction bias), perception was biased opposite to the expected direction (repulsion bias). These opposite biases potentially reveal different ways in which perception and action utilize prior information and support the idea of different information processing for perception and pursuit.

Insights into the Mechanisms of K+ Permeation in K+ Channels from Computer Simulations

Ion permeation, selectivity, and the behavior of the K+ channel selectivity filter have been studied intensively in the previous two decades. The agreement among multiple approaches used to study ion flux in K+ channels suggests a consensus mechanism of ion permeation across the selectivity that has been put to the test in recent years with the proposal of an alternative way by which ions can cross the selectivity filter of K+ channels via direct Coulomb repulsion between contacting cations. Past experimental work by Zhou and MacKinnon (J. Mol. Biol. 2004, 338, 839) showed that mutation of the site S4 reduces the total occupancy of the selectivity filter to less than two ions on average by lowering the occupancy of the S2-S4 configuration without changing the S1-S3 configuration much, and this reduction of occupancy means that ion configurations different from the ones involved in the canonical mechanism are likely to be involved. At that time, calculations using complicated kinetic networks to relate occupancy to conduction did not provide deeper insight into the conduction mechanism. Here, to help solve this enigma, umbrella sampling simulations have been performed to evaluate the potential of mean force of two KcsA mutant channels where the S4 site is substituted. Our new results provide insights into the significance of threonine in this position, revealing the effect of substitution on the alternate mechanisms of conduction proposed, involving either water or vacant sites.

The contribution of local and global motion adaptation in the repulsive direction aftereffect.

After adapting to a certain motion direction, our perception of a similar direction will be repelled away from the adapting direction, a phenomenon known as the direction aftereffect (DAE). As the motion system consists of local and global processing stages, it remains unclear how the adaptation of the two stages contributes in producing the DAE. The present study addresses this question by independently inducing adaptation at local and global motion-processing levels. Local adaptation was manipulated by presenting test stimuli at either adapted or nonadapted locations. Global adaptation was manipulated by embedding one or five global motion directions in the adapting motion. Repulsive DAE, when measured using a multiple-element test pattern, was stronger when it was produced by global adaptation than when produced by local adaptation. Specifically, the DAE resulting from local adaptation (a) decreased when test orientations differed from adapting orientation, (b) decreased when local directions were disambiguated using plaid stimuli, (c) remained the same even when attention was focused at specific test locations during adaptation, and (d) increased when tested with a single element. Overall, these findings suggest that the strength of repulsive DAE depends on both the motion-processing level at which adaptation occurs and the level at which the DAE was tested. Furthermore, the repulsive DAE arising from local adaptation alone can be explained by the propagation of local speed repulsion instead of local direction repulsion. Findings are discussed in the context of how motion aftereffects arise from the adaptation of a hierarchical motion system.

Direct capture and electrostatic repulsion in the self-assembly of rare-earth atom superlattices on graphene

We show that the moir\'e pattern of graphene on Ir(111) acts as efficient template for the self-assembly of well-ordered superlattices of single rare-earth adatoms. Using Sm and Dy as representative of early and late lanthanides, we observe that the array quality is determined by the deposition temperature and by a large direct capture area, leading to partial dimer formation. These superlattices result from the combination of the inhomogeneous substrate potential for adatom diffusion generated by the moir\'e and the interatomic electrostatic repulsion originating from electron transfer to graphene. Deposition temperature- and coverage-dependent experiments quantify the energy barriers for adatom diffusion between adjacent graphene lattice sites and between moir\'e unit cells, as well as the amount of charge transferred to the substrate by each adatom.

Combining local and global cues to motion

A spinning, moving object, such as a football with a surface texture, combines motion signals from rotation and translation. The interaction between these two kinds of signal was studied psychophysically with moving, circular clouds of dots, which also could move within the cloud. If the cloud moved near-vertically downwards but the dots within it moved obliquely, the apparent path of the cloud was attracted to that of the dots, as previously demonstrated with moving Gabor patches (Tse & Hseih Vision Research, 46, 3881-3885, 2006; Lisi & Cavanagh Current Biology, 25, 2535-40, 2015). This attractive effect was enhanced in parafoveal viewing and by not presenting a frame around the dots. A larger effect in the opposite direction (repulsion) was found for the perceived direction of the dots when they moved near-vertically and the cloud containing them moved obliquely. These results are discussed in relation to Gestalt principles of perceived relative motion and, more recently, Bayes-inspired accounts of the interaction between local and global motion.

Plain s-Wave Superconductivity near Magnetic Criticality: Enhancement of Attractive Electron–Boson Coupling Vertex Corrections

Recent experiments revealed that the plain $s$-wave state without any sign-reversal emerges in various metals near the magnetic criticality. To understand this counter-intuitive phenomenon, we study the gap equation for the multiorbital Hubbard-Holstein model, by analyzing the vertex correction (VC) due to the higher-order electron-correlation effects. We find that the phonon-mediated orbital fluctuations are magnified by the VC for the susceptibility ($\chi$-VC). In addition, the charge-channel attractive interaction is enlarged by the VC for the coupling-constant ($U$-VC), which is significant when the interaction has prominent $q$-dependences so the Migdal theorem fails. Due to both $\chi$-VC and $U$-VC, the plain $s$-wave state is caused by the small electron-phonon interaction near the magnetic criticality against the repulsive Coulomb interaction. We find that the direct Coulomb repulsion for the plain $s$-wave Cooper pair is strongly reduced by the "multiorbital screening effect".

Altered motion repulsion in Alzheimer\u2019s disease

Recent research in Alzheimer’s disease (AD) indicates that perceptual impairments may occur before the onset of cognitive declines, and can thus serve as an early noninvasive indicator for AD. In this study, we focused on visual motion processing and explored whether AD induces changes in the properties of direction repulsion between two competing motions. We used random dot kinematograms (RDKs) and measured the magnitudes of direction repulsion between two overlapping RDKs moving different directions in three groups of participants: an AD group, an age-matched old control group, and a young control group. We showed that motion direction repulsion was significantly weaker in AD patients as comparing to both healthy controls. More importantly, we found that the magnitude of motion repulsion was predictive of the assessment of clinical severity in the AD group. Our results implicate that AD pathology is associated with altered neural functions in visual cortical areas and that motion repulsion deficit is a behavioral biomarker for the tracking of AD development.

Individual differences in context-dependent effects reveal common mechanisms underlying the direction aftereffect and direction repulsion

Both spatial and temporal context influence our perception of visual stimuli. For instance, both nearby moving stimuli and recently viewed motion can lead to biases in the perceived direction of a moving stimulus. Due to similarities in the spatial tuning properties of these spatial and temporal context-dependent effects, it is often assumed that they share a functional goal in motion processing and arise from common neural mechanisms. However, the psychophysical evidence concerning this assumption is inconsistent. Here we used an individual differences approach to examine the relationship between different effects of contextual modulation on perception. We reasoned that if measures of contextual modulation share a common underlying mechanism, they should exhibit a strong positive correlation across participants. To test this hypothesis, estimates of the direction aftereffect, direction repulsion, the tilt aftereffect and contrast adaptation were obtained from 54 healthy participants. Our results show pronounced interindividual differences in the effect sizes of all four tasks. Furthermore, there was a strong positive correlation between the estimates of the direction aftereffect and direction repulsion. This correlation was also evident in the threshold elevations that accompanied these repulsive biases in perceived direction. While the effects of contrast adaptation did not correlate with any of the other tasks, there was a weak, but non-significant, correlation between the direction and tilt aftereffects. These results provide evidence for common mechanisms underlying the direction aftereffect and direction repulsion.

Superconductivity in the two-dimensional electron gas induced by high-energy optical phonon mode and large polarization of theSrTiO3substrate

Theory of superconductivity generated in one atomic layer thick two dimensional electron gas by a single flat band of high energy longitudinal optical phonons is considered. The polar dielectric $SrTiO_{3}$ (STO) exhibits such an energetic phonon mode and the 2DEG is created both when one unit cell $FeSe$ layer is grown on its $\left( 100\right) $ surface and on the interface with another dielectric like $LaAlO_{3}$ (LAO). We obtain a quantitative description of both systems solving the gap equation for $T_{c}$ without making use of approximations like the Kirzhnits Ansatz for arbitrary chemical potential $\mu $, electron-phonon coupling $\lambda $ and the phonon frequency $\Omega $, and direct (RPA) electron-electron repulsion strength $\alpha $. The high temperature superconductivity in 1UC$FeSe$/STO is possible due to a combination of three factors: high LO phonon frequency, large electron-phonon coupling $\lambda \sim 0.5$ and huge dielectric constant of the substrate suppression the Coulomb repulsion. It is shown that very low density electron gas in the interfaces is still capable of generating superconductivity of the order of $0.1$ K in LAO/STO. Superconductivity persists even on the band edge $\mu =0$.

Low-level mediation of directionally specific motion aftereffects: Motion perception is not necessary

Previous psychophysical experiments with normal human observers have shown that adaptation to a moving dot stream causes directionally specific repulsion in the perceived angle of a subsequently viewed moving probe. In this study, we used a two-alternative forced choice task with roving pedestals to determine the conditions that are necessary and sufficient for producing directionally specific repulsion with compound adaptors, each of which contains two oppositely moving, differently colored component streams. Experiment 1 provided a demonstration of repulsion between single-component adaptors and probes moving at approximately 90° or 270°. In Experiment 2, oppositely moving dots in the adaptor were paired to preclude the appearance of motion. Nonetheless, repulsion remained strong when the angle between each probe stream and one component was approximately 30°. In Experiment 3, adapting dot pairs were kept stationary during their limited lifetimes. Their orientation content alone proved insufficient for producing repulsion. In Experiments 4–6, the angle between the probe and both adapting components was approximately 90° or 270°. Directional repulsion was found when observers were asked to visually track one of the adapting components (Exp. 6), but not when they were asked to attentionally track it (Exp. 5), nor while they passively viewed the adaptor (Exp. 4). Our results are consistent with a low-level mechanism for motion adaptation. This mechanism is not selective for stimulus color and is not susceptible to attentional modulation. The most likely cortical locus of adaptation is area V1.Electronic supplementary materialThe online version of this article (doi:10.3758/s13414-016-1160-1) contains supplementary material, which is available to authorized users.

Controlling O coverage and stability by alloying Au and Ag.

One of the most critical factors in oxidation catalysis is controlling the state of oxygen on the surface. Au and Ag are both effective selective oxidation catalysts for various reactions, and their interactions with oxygen are critical for determining their catalytic performance. Here, we show that the state of oxygen on a catalytic surface can be controlled by alloying Au and Ag. Using temperature programmed desorption, density functional theory (DFT), and Monte Carlo simulations, we examine how alloying Au into an Ag(110) surface affects O2 dissociation, O coverage, and O stability. DFT calculations indicate that Au resides in the second layer, in agreement with previous experimental findings. The minimum ensemble size for O2 dissociation is 2 Ag atoms in adjacent rows of the second layer. Surprisingly, adsorbed O2 and the dissociation transition state interact directly with metal atoms in the adjacent trough, such that Au in this position inhibits O2 dissociation by direct repulsion with oxygen electronic states. Using Monte Carlo simulations based on DFT energetics, we create models of the surface that agree closely with our experimental results. Both show that the O2 uptake decreases nearly linearly as the Au concentration increases, and no O2 uptake occurs for Au concentrations above 50%. For Au concentrations greater than 18%, increasing the Au concentration also decreases the stability of the adsorbed O. Based on these results, the O coverage and O stability can be tuned, in some cases independently. We also study how the reactivity of the surface is affected by these factors using CO2 oxidation as a simple test reaction.

The Compressibility of pH‐Sensitive Microgels at the Oil–Water Interface: Higher Charge Leads to Less Repulsion

AbstractpH‐responsive microgels are unique stabilizers for stimuli‐sensitive emulsions that can be broken on demand by changing the pH value. However, recent experiments have indicated that electrostatic interactions play a different role to that in conventional Pickering emulsions. The influence of charges on the interactions between microgels at the oil–water interface is now described. Compression isotherms of microgels with different charge density and architecture were determined in a Langmuir trough, and counter‐intuitive results were obtained: Charged microgels can be compressed more easily than uncharged microgels. The compressibility of microgels is thus not determined by direct Coulomb repulsion. Instead, the different swelling of the microgels in the charged and the uncharged states is proposed to be the key parameter.

The Compressibility of pH‐Sensitive Microgels at the Oil–Water Interface: Higher Charge Leads to Less Repulsion

pH-responsive microgels are unique stabilizers for stimuli-sensitive emulsions that can be broken on demand by changing the pH value. However, recent experiments have indicated that electrostatic interactions play a different role to that in conventional Pickering emulsions. The influence of charges on the interactions between microgels at the oil-water interface is now described. Compression isotherms of microgels with different charge density and architecture were determined in a Langmuir trough, and counter-intuitive results were obtained: Charged microgels can be compressed more easily than uncharged microgels. The compressibility of microgels is thus not determined by direct Coulomb repulsion. Instead, the different swelling of the microgels in the charged and the uncharged states is proposed to be the key parameter.