Moment Interaction Research Articles

Evidence-Based Practices in a Social Project: Promotion of Executive Functions in Children from Northeastern Brazil

ABSTRACT Evidence points to the possibility of promoting executive functions (EF) through school interventions. Little is known, however, about the effectiveness of this type of intervention in situations of social vulnerability. This study investigated the effectiveness of an EF intervention program applied with a sample of preschool children, in a situation of socioeconomic vulnerability, assisted by a non-governmental organization (NGO) in northeastern Brazil. Participants were 46 children (mean age = 4.67 years; SD = 0.71), divided into experimental (EG = 25) and control (CG = 21) groups. The children were assessed before and after the intervention regarding measures of EF and behavior indices. The intervention was applied over 3 months by two professionals from the NGO. There was no group x moment interaction effect on the performance measure used, however, fewer difficulties were observed posttest in the EG in relation to the CG, according to the informant-based measures. From the parents’ reports, difficulties in inhibitory control (IC) decreased in the EG. From the parents’ and teachers’ reports, difficulties in hyperactivity, conduct problems and behavior problems (BP) total indices also decreased in the EG. A simple mediation model suggested that gains in IC mediated the intervention impact on gains in BP as observed by the parents. Interventions in EF for socioeconomically vulnerable children can minimize the deleterious effects of poverty on neurocognitive development. This study shows the applicability and effects of this type of intervention in an educational context, within the scope of a community assistance social project, bringing neuropsychology and social requirements closer together.

Director orientational instability in a planar flexoelectric nematic cell with easy axis gliding

The orientational instability of a director in a planar flexoelectric nematic liquid crystal cell in a constant electric field oriented perpendicular to the cell substrates is investigated. The easy axis on the surface of one of the polymer substrates can change its orientation, which is due to the impact of the initial surface orientation, liquid crystal, and electric field. The influence of the latter leads to the reorientation of the elastic parts of the polymer molecules of the substrate, which is a consequence of the interaction of intrinsic or induced dipole moments with the electric field. The corresponding contribution of such an interaction to the surface free energy of the nematic is considered to be linear or quadratic in terms of the electric field strength E. It is established that the orientational instability of the director has a threshold in the case of quadratic effect of the electric field and is thresholdless if the effect is linear. The temporal behavior of the director after the application of voltage with the subsequent transition of the system to a stationary state and its return to the initial homogeneous state after switching off the voltage is studied. The characteristic turn-on/off times of the system and the time of reaching the stationary state are calculated and their dependence on the system parameters is investigated. The transmittance of the nematic liquid crystal cell is calculated for a normally incident light.

Derivation of a normalised failure surface for square CECFST columns embedded with circular steel tube: A unified approach

Concrete-Encased Concrete-Filled Steel Tube (CECFST) columns are a new type of composite columns that possess great strength, stiffness, ductility, corrosion and fire resistance. To fully realise their benefits, an accurate design approach of calculating the strength of these members is necessary. In this paper, the plastic stress distribution (PSD) and load contour (LC) methods in the design code of predicting the cross-section strength of CECFST columns is first evaluated through numerical and published experimental data. Considering the shortcomings of conventional design methods, a unified design approach is then developed. Compared to the conventional PSD method, the developed method can yield conservative resistance predictions for uniaxial eccentric loaded (UEL) CECFST columns. In addition, instead of using linear moment interaction curves to predict the strength of biaxial eccentric loaded (BEL) CECFST columns, elliptical moment interaction curves are adopted in the proposed design approach. Most importantly, a normalised 3D axial-load–biaxial-moment (n–my–mz) interaction surface can be generated through the proposed method, which only requires determining 6 critical points on the interaction surface. Unlike the conventional design approach, in which the UEL and BEL composite columns need to be respectively designed through PSD and LC methods, a unified design procedure can be achieved through the proposed approach. Besides, the confinement effect from both the steel tube and the stirrups can also be considered in the proposed approach and much higher accuracy and consistency can be achieved in predicting the cross-section strength of CECFST columns.

Oriented External Electric Fields Regurating the Reaction Mechanism of CH4 Oxidation Catalyzed by Fe(IV)-Oxo-Corrolazine: Insight from Density Functional Calculations.

Methane is the simplest alkane and can be used as an alternative energy source for oil and coal, but the greenhouse effect caused by its leakage into the air is not negligible, and its conversion into liquid methanol not only facilitates transportation, but also contributes to carbon neutrality. In order to find an efficient method for converting methane to methanol, CH4 oxidation catalyzed by Fe(IV)-Oxo-corrolazine (Fe(IV)-Oxo-Cz) and its reaction mechanism regulation by oriented external electric fields (OEEFs) are systematically studied by density functional calculations. The calculations show that Fe(IV)-Oxo-Cz can abstract one H atom from CH4 to form the intermediate with OH group connecting on the corrolazine ring, with the energy barrier of 25.44 kcal mol−1. And then the product methanol is formed through the following rebound reaction. Moreover, the energy barrier can be reduced to 20.72 kcal mol−1 through a two-state reaction pathway. Furthermore, the effect of OEEFs on the reaction is investigated. We found that OEEFs can effectively regulate the reaction by adjusting the stability of the reactant and the transition state through the interaction of electric field-molecular dipole moment. When the electric field is negative, the energy barrier of the reaction decreases with the increase of electric intensity. Moreover, the OEEF aligned along the intrinsic Fe‒O reaction axis can effectively regulate the ability of forming the OH on the corrolazine ring by adjusting the charges of O and H atoms. When the electric field intensity is −0.010 a.u., the OH can be directly rebounded to the CH3· before it is connecting on the corrolazine ring, thus forming the product directly from the transition state without passing through the intermediate with only an energy barrier of 17.34 kcal mol−1, which greatly improves the selectivity of the reaction.

Topology optimization of structural frames based on a nonlinear Timoshenko beam finite element considering full interaction

AbstractThis article presents an approach for the topology optimization of frame structures composed of nonlinear Timoshenko beam finite elements (FEs) under time‐varying excitation. Material nonlinearity is considered with a nonlinear Timoshenko beam FE model that accounts for distributed plasticity and axial–shear–moment interactions through appropriate hysteretic interpolation functions and a yield/capacity function, respectively. Hysteretic variables for curvature, shear, and axial deformations represent the nonlinearities and evolve according to first‐order nonlinear ordinary differential equations (ODEs). Owing to the first‐order representation, the governing dynamic equilibrium equations, and hysteretic evolution equations can thus be concisely presented as a combined system of first‐order nonlinear ODEs that can be solved using a general ODE solver. This avoids divergence due to an ill‐conditioned stiffness matrix that can commonly occur with Newmark–Newton solution schemes that rely upon linearization. The approach is illustrated for a volume minimization design problem, subject to dynamic excitation where an approximation for the maximum displacement at specified nodes is constrained to a given limit, that is, a drift ratio. The maximum displacement is approximated using the p‐norm, thus facilitating the derivation of the analytical sensitivities for gradient‐based optimization. The proposed approach is demonstrated through several numerical examples for the design of structural frames subjected to sinusoidal base excitation.

Distinguishing “Through-Space” from “Through-Bonds” Contribution in Indirect Nuclear Spin–Spin Coupling: General Approaches Applied to Complex JPP and JPSe Scalar Couplings

We present herein two complementary theoretical approaches for analyzing the transmission pathways of indirect nuclear spin-spin couplings in high-resolution nuclear magnetic resonance. This phenomenon is notably conceptually poorly understood in complex experimental situations in which both nonbonded ["through-space" (TS)] and more "classical" bonding ("through-bond") spin-spin coupling pathways are potentially involved. The computational approaches we propose allow the visualization and discussion of individual transmission pathways and estimation of their relative weight from numerical contributions to the spin-spin coupling constant J-value. The first approach is based on the analysis of contributions limited to occupied molecular orbitals [focused on occupied molecular orbitals (FOMO)]. The second approach encompasses the consideration of both occupied and vacant orbitals [global molecular orbital contributions (GMOC)], and, besides the contributions from individual pathways, also considers their cross contributions. Both approaches are applicable to large systems with complex interactions of nuclear magnetic moments. Herein, we have first applied the FOMO and GMOC computational approaches to simple diphosphine models and then extended the analysis to JPP and JPSe experimentally measured in a constrained selenated (diphosphino)naphthalene compound. The new computational tools contributed evidence for the importance of the single lone pair not only from phosphorus but also from selenium in TS spin-spin transmission. It evidenced and modeled for the first time the existence of spin-spin transmission pathways mixing classical covalent bonding parts with a lone pair overlap of proximate heteroatoms (P and Se).

Numerical parametric study on the uniaxial and biaxial compressive behavior of H-shaped steel reinforced concrete composite beam-columns

As a follow-up work of previous experimental efforts, this paper aims to further explore the compressive behavior of Steel Reinforced Concrete (SRC) composite beam-columns with assistance of nonlinear Finite Element Analysis. The FE model was developed in ABAQUS software and it delivered desirable accuracy after calibrating against the dataset collected from published literatures. The validated FE model was then employed to evaluate the fundamental performance of SRC beam-columns under uniaxial eccentric compression and biaxial eccentric compression. On top of that, the fiber section analysis was adopted to build the three-dimensional axial force-bending moment (N-M) interaction diagrams, followed by a parametric study to investigate the effect of material grade, steel ratio, cross-section geometry, load eccentricity and load inclination on the load-carrying capacity of SRC beam-columns, and disclose the complex biaxial interaction mechanism that is not well-considered in current design codes. Based on the numerical data generated from parametric study, the Support Vector Machine method is utilized to intelligently estimate the biaxial moment contours under varying load levels, which exhibits improved accuracy and consistency than the code-specified method and conventional empirical formulae.

Reaction of N-Acetylcysteine with Cu2+: Appearance of Intermediates with High Free Radical Scavenging Activity: Implications for Anti-/Pro-Oxidant Properties of Thiols.

We studied the kinetics of the reaction of N-acetyl-l-cysteine (NAC or RSH) with cupric ions at an equimolar ratio of the reactants in aqueous acid solution (pH 1.4–2) using UV/Vis absorption and circular dichroism (CD) spectroscopies. Cu2+ showed a strong catalytic effect on the 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) radical (ABTSr) consumption and autoxidation of NAC. Difference spectra revealed the formation of intermediates with absorption maxima at 233 and 302 nm (ε302/Cu > 8 × 103 M−1 cm−1) and two positive Cotton effects centered at 284 and 302 nm. These intermediates accumulate during the first, O2-independent, phase of the NAC autoxidation. The autocatalytic production of another chiral intermediate, characterized by two positive Cotton effects at 280 and 333 nm and an intense negative one at 305 nm, was observed in the second reaction phase. The intermediates are rapidly oxidized by added ABTSr; otherwise, they are stable for hours in the reaction solution, undergoing a slow pH- and O2-dependent photosensitive decay. The kinetic and spectral data are consistent with proposed structures of the intermediates as disulfide-bridged dicopper(I) complexes of types cis-/trans-CuI2(RS)2(RSSR) and CuI2(RSSR)2. The electronic transitions observed in the UV/Vis and CD spectra are tentatively attributed to Cu(I) → disulfide charge transfer with an interaction of the transition dipole moments (exciton coupling). The catalytic activity of the intermediates as potential O2 activators via Cu(II) peroxo-complexes is discussed. A mechanism for autocatalytic oxidation of Cu(I)–thiolates promoted by a growing electronically coupled –[CuI2(RSSR)]n– polymer is suggested. The obtained results are in line with other reported observations regarding copper-catalyzed autoxidation of thiols and provide new insight into these complicated, not yet fully understood systems. The proposed hypotheses point to the importance of the Cu(I)–disulfide interaction, which may have a profound impact on biological systems.

Defective MWCNT Enabled Dual Interface Coupling for Carbon‐Based Perovskite Solar Cells with Efficiency Exceeding 22%

AbstractSuffering from sluggish charge transfer kinetics, carbon‐based perovskite solar cells (C‐PSCs) lag far behind the Ag/Au‐based normal PSCs in power conversion efficiency (PCE). Herein, the use of defective multi‐walled CNT (D‐MWCNT) is demonstrated to tune the charge transfer kinetics regarding hole transport layer (HTL) and the interface between HTL and carbon electrode. Benefiting from the electrostatic dipole moment interaction between the terminal oxygen‐containing groups of D‐MWCNT and 2,2′,7,7′‐tetrakis(N,N‐di‐p‐methoxyphenylamine)‐9,9′‐spirobifluorene, an interface coupling at molecular level is established and in turn, allows rapid charge transfer by edge effect induced electron redistribution and 1D hyper‐channels. Meanwhile, a seamless connection between HTL and carbon electrode is achieved in a novel modular C‐PSCs due to D‐MWCNT induced interface coupling with graphene at nanometer scale. Based on this strategy, high PCEs up to 22.07% (with a certified record PCE of 21.9% to date for C‐PSCs) and excellent operational stability have been achieved.

Aeromechanical Analysis of a Next-Generation Mars Hexacopter Rotor

A three-dimensional (3D) aeromechanical analysis is carried out on the rotor blades of a 20 kg conceptual Mars Hexacopter. The objectives are to understand the aeroelastic behavior of its unique ultrathin low-Reynolds-number and high-Mach-number blades and study the interactions of structures, aerodynamics, and control moments in the Martian atmosphere. Beginning with structural analysis in vacuum, comprehensive analysis is carried out in hover and forward flight using 3D Finite Element Method (FEM), three-dimensional (2D) airfoil tables, and free wake. Natural frequencies of the rotor, elastic response of the blade, control moments at the root, airloads of blade sections, and 3D stresses are studied. Two types of designs are considered: a baseline design with pitch axis at the quarter chord and an unconventional design with the pitch axis moved to the midchord. Unusual nose-up elastic twist is observed on the rotor blades that appears to stem from the trapeze effect that counteracts the flattening effect of the propeller moment. By moving the pitch axis to midchord, the control moment is reduced by 30–40% without any noticeable adverse effect on stability due to the low Lock number. Both designs have maximum stresses well below the material limits, but the midchord design has a more uniform distribution of stress in general and lower levels of shear stress in particular. These and many other unconventional phenomena make Martian aeromechanics unique and ripe with possibilities of innovations tailored to its atmosphere.

Insignificance of the anomalous magnetic moment of the quarks in presence of chiral imbalance

We incorporate the anomalous magnetic moment (AMM) of quarks in the framework of PNJL model to study hot and dense magnetised matter with chiral imbalance. For this purpose, the eigen energy solution of the Dirac equation is obtained in presence of constant background magnetic field and chiral chemical potential (CCP) along with the minimal anomalous magnetic moment interaction of the fermion. Although there is a marginal enhancement in the IMC behaviour of the quark condensate due to the combined effects of AMM and CCP, we find that the overall behaviour of the Polyakov loop and the chiral charge density is dominated by the chiral chemical potential. It is further shown that the AMM effects in presence of CCP remains insignificant even after consideration of thermo-magnetically modified moments.

Analysis of the Objective Internal Load in Portuguese Skydivers in the First Jump of the Day.

The general objective of this study was to identify the variation in heart rate (HR) of Portuguese skydivers during 6 moments in their first jump of the day, bearing in mind the variable level of experience. Thirty-one Portuguese skydivers, 28 men and 3 women, aged between 19 and 62, participated in the study, 12 had A and B licenses (less experienced) and 19 had C and D licences (more experienced). The instrument used to record the heart rate of the skydivers at the different moments of their first jump of the day was the WIMU PRO. A repeated measures analysis of variance was used to analyse HR at different moments in the jump and its relation with the variables level of experience. Bonferroni multiple comparisons were performed to study the importance of the differences observed in HR at the different moments. The effect size was evaluated with partial eta squared. The results showed that average HR in this group of skydivers was 130 bpm, in the different moments of the jump. HR increases from the value recorded at rest until the moment of jumping from the plane and opening the parachute, reaching the highest average at that moment, then decreasing until contact with the ground. Comparing the variable, we found that the less experienced had higher HR than the more experienced at all moments during the jump. Statistically significant differences were found at the different moments of the jump, regarding HR (Max: p < 0.001, ƞ2p = 0.820; Min: p < 0.001, ƞ2p = 0.821; AVG: p < 0.001, ƞ2p = 0.834) Level of experience with jumping moment interaction, we only verified differences related to HR Min (p = 0.007, ƞ2p = 0.056),. With regard to experience, the identified differences were not statistically significant. Skydiving triggers an acute adaptive cardiovascular response which is reflected in the increase in the HR, between the moment of boarding the plane and the moment at which the parachute opens, thereafter decreasing until contact with the ground. The most experienced parachutists recorded the highest HR at the moment of landing and the least experienced at the moment of free fall.

Behavior of eccentrically loaded UHPC filled circular steel tubular short columns

This paper presents experimental results of twelve eccentrically loaded short composite columns made by filling circular steel tubes with ultra-high performance concrete (UHPC) cured under room temperature. Using these test data as benchmarks, finite element models are developed and used to perform parametric studies to determine how the capacities of these columns are affected by load eccentricity and tube diameter-to-thickness ratio. In addition, a relationship between the balanced eccentricity ratio and the confinement coefficient is established. The results of the present study have shown that: (1) failure of these columns is characterized by yielding of the steel tubes, followed immediately by failure of the core concrete; (2) a decrease in diameter-to-thickness ratio increases the peak load and improves the column's post-peak behavior; (3) an increase in the load eccentricity ratio results in a reduction of the load capacity, ductility and stiffness of the column; (4) the compressive strain in the steel tube develops more rapidly due to second-order effect, and the assumption that plane sections remain plane no longer applies when the applied load reaches 80% of the peak load. By comparing the axial force – Bending moment (Nu-Mu) interaction diagrams generated in the present study with existing codes, it is found that the code equations are mostly conservative. A set of trilinear Nu-Mu interaction equations that can produce more accurate results is therefore proposed

Strength capacity of prismatic specimens for masonry constructions made of concrete voussoirs

AbstractThis research shows the results of an experimental campaign of masonry specimens tested until failure. The masonry is made of special voussoirs for the construction of arches and vaults. The voussoirs were made of plain concrete. The experimental campaign focused on obtaining the flexural and the compressive strength of this type of masonry specimens. Specimens were subjected to compressive loads with different eccentricities to obtain the axial load–bending moment interaction diagrams, which indicate the strength of these pieces against eccentric compression. The ultimate purpose of this research is to foresee the behavior of structural elements, such as arches and lowered vaults with a circular directrix, built using this type of voussoirs. These structural elements aim to reintroduce anti‐funicular structural elements in bridges, culvert, tunnel, floor, and roof of buildings. Constructions that solve the basic needs of the population in any country. This innovative idea on a new block geometry, designed specifically for construction of arches, allows covering distances up to 6–7 m. The use of steel is not necessary; therefore, the risk of corrosion is eliminated. Finally, a study on the use of this new masonry type on the statics of arches is assessed.

Experimental Investigation of Large-Scale Eccentrically Loaded GFRP-Reinforced High-Strength Concrete Columns

Ten large-scale high-strength concrete (HSC) circular columns were constructed and tested to failure. Nine columns were internally reinforced with glass fiber-reinforced polymer (GFRP) bars and spirals, whereas one was reinforced with steel bars and spirals to serve as a reference. All columns had a diameter of 350 mm. The variables tested were reinforcement type, spiral pitch, slenderness ratio, eccentricity-to-diameter ratio (e/D), and type of loading (axial or four-point bending). Experimental results showed that both reinforcement types (steel or GFRP) and the spiral pitch did not have a significant effect on the behavior of GFRP-reinforced HSC columns up to the peak load. In addition, a decrease in the axial capacity of the columns as the e/D ratio increased was observed. This was consistent for specimens of both slenderness ratios of 14 and 20. Columns with a higher slenderness ratio showed a lower axial capacity for all specimens tested under the same e/D ratio. Furthermore, slender columns with higher e/D ratio underwent much larger deformations; both axially and laterally. For columns of both slenderness ratios, axial load–bending moment interaction diagrams were produced using the experimental results and were compared to the predictions of available codes and guidelines.

The features of the magnetoresistance of carbon nanotubes modified with Fe

Two specimens of modified multi-wall carbon nanotubes (MWCNT) with a mass fraction of iron of 0.20 and 0.29 have been obtained by the method of metal reduction from aqueous salt solution. According to structural and phase investigations, modified MWCNT contain Fe3C, α-Fe (ferromagnetic phase), and iron oxides FeO and Fe2O3 (antiferromagnetic phases with a Néel temperature of 188 K and 260 K, respectively) particles up to 8 nm in size. It is experimentally found that for MWCNT modified simultaneously by several ferromagnetic phases with different coercive forces, a giant magnetoresistive effect is observed at room temperature. For MWCNT modified with only one ferromagnetic phase, the giant magnetoresistance has not been experimentally detected. With temperature decrease, the magnetoresistance dependence on magnetic field for such modified nanotubes acquires a specific butterfly-like form, which is characteristic of the magnetic ordering of ferromagnetic and antiferromagnetic phases due to exchange anisotropy. For MWCNT modified with only one ferromagnetic phase there has been an effect of asymmetric magnetoresistance, which is related to the presence in the specimen of inhomogeneous transverse Hall voltages due to the pronounced spin-orbit interaction of conduction electrons and magnetic moments of the magnetic phase, and an anisotropic magnetoresistive effect.

Behavior of stiffened and multi-cell L-shaped CFST columns under eccentric compression

The mechanical behavior of the traditional special-shaped concrete-filled steel tubular (CFST) columns can be improved by employing longitudinal stiffeners or using multi-cell cross-section. In practical application, the stiffened and multi-cell L-shaped CFSTs are often subjected to bi-directional loading. However, there are only few research studies on their performance as loaded eccentrically with different orientations of the loading and there is no relevant design guideline. This paper reports tests on 16 L-shaped CFST columns (nine stiffened, six multi-cell specimens and one reference specimen) loaded in eccentric compression. The main variables were the angle indicating the orientation of the load action line (0°, 45°, 135°, 180° and 225°), load eccentricity ratio (0, 0.25 and 0.5) and slenderness ratio (31.5 and 41.9). Finite element models for the eccentrically loaded stiffened and multi-cell L-shaped CFST columns were developed. Based on the parametric analysis, practical design methods were proposed for predicting the bearing capacity based on the stability loss and the axial force vs. bending moment interaction diagrams for the members considering the influence of the load orientation at the end face of the column.

Antiferromagnetism mediated by heavy electrons: High-order RKKY

Can the antiferromagnetic (AF) order be induced via the local moments' hybridization with the heavy electrons instead of conduction electrons? We address this intriguingly fundamental question via a prototypical model to describe the interplay between local moments and heavy electrons. We discover that the AF order can be mediated via the heavy electrons through the mechanism of the high-order Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction. Moreover, our analysis employing a slave-spin representation uncovers that the heavy electron band can enhance the RKKY interaction of local moments (despiteits high-order nature) via enlarging its effective mass. The potential relevance to the heavy fermion compound ${\mathrm{Ce}}_{3}(\mathrm{Pt}/\mathrm{Pd}){\mathrm{In}}_{11}$ is also discussed.

Multiscale investigation of magnetic field distortion on surface of ferromagnetic materials caused by stress concentration for metal magnetic memory method

In this paper, we use multiscale modeling to explore the coupling of the atomic orbital and magnetic moment and their evolutions under the excitations of external stress and magnetic fields. Our results of density functional theory (DFT) calculations show that strain-induced spin reorientation and redistribution of orbital coupling are the fundamental reasons for altering the atomic magnetic moment, magnetic anisotropy, and exchange interactions. Also, magnetic anisotropy and exchange interactions are found to play a more crucial role in the magnetization reversal process than the atomic magnetic moment. By using micromagnetics approach and the finite element method (FEM), the macroscopic magnetic properties such as coercivity, magnetic permeability, and remanence alter as a consequence of modified electronic structure, which eventually leads to the distortion of the macroscopic magnetic field of the stress concentration area. Through DFT, micromagnetics and FEM approaches, the cross-scale simulations herein highlight the remarkable short-range orbital ordering and coupling in ferromagnetic materials which provide the fresh insight in the stress-magnetic coupling for MMM applications.

Missing He–McKellar–Wilkens geometric quantum phase

We discuss the appearance of a missing geometric quantum phase from the interaction of the permanent electric dipole moment of a neutral particle with the magnetic field produced by a uniform distribution of the magnetic charges inside an infinitely long non-conductor cylinder with an inner radius r a . This geometric quantum phase is associated with the missing magnetic charge per unit length in a region with a cylindrical shape of radius r a and gives rise to an analogue of the He–McKellar–Wilkens geometric quantum phase. By searching for bound state solutions, we show that an Aharonov–Bohm-type effect arises from the influence of the missing geometric quantum phase on the eigenvalues of energy.