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"Force and energy."
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Push and pull
\"Describes the forces of push and pull using everyday objects such as strollers and wagons. Includes experiments\"-- Provided by publisher.
Book
Computational Design of Nisub.6@Ptsub.1Msub.31 Clusters for Multifunctional Electrocatalysts
High-efficiency and low-cost multifunctional electrocatalysts for hydrogen evolution reaction (HERs), oxygen evolution reaction (OERs) and oxygen reduction reaction (ORRs) are important for the practical applications of regenerative fuel cells. The activity trends of core–shell Ni[sub.6]@M[sub.32] and Ni[sub.6]@Pt1M31 (M = Pt, Pd, Cu, Ag, Au) were investigated using the density functional theory (DFT). Rate constant calculations indicated that Ni[sub.6]@Pt[sub.1]Ag[sub.31] was an efficient HER catalyst. The Volmer–Tafel process was the kinetically favorable reaction pathway for Ni[sub.6]@Pt[sub.1]M[sub.31]. The Volmer–Heyrovsky reaction mechanism was preferred for Ni[sub.6]@M[sub.32]. The Pt active site reduced the energy barrier and changed the reaction mechanism. The ORR and OER overpotentials of Ni[sub.6]@Pt[sub.1]Ag[sub.31] were calculated to be 0.12 and 0.33 V, indicating that Ni[sub.6]@Pt[sub.1]Ag[sub.31] could be a promising multifunctional electrocatalyst. Ni[sub.6]@Pt[sub.1]M[sub.31] core–shell clusters present abundant active sites with a moderate adsorption strength for *H, *O, *OH and *OOH. The present study shows that embedding a single Pt atom onto a Ni@M core–shell cluster is a rational strategy for designing an effective multifunctional electrocatalyst.
Journal Article
The science of forces
A look at the science behind force, friction, and the laws of motion and energy.
Book
states in a unitarized coupled-channel approach
Starting from an effective Lagrangian with heavy quark spin symmetry embedded, the coupled-channel dynamics of the doubly charmed systems [Formula omitted] is investigated. The potential underlying our investigation includes t-channel pseudoscalar and vector meson exchanges. A series of S-wave bound states with isospin [Formula omitted] is found by applying the first iterated solution of the N/D method: one state with binding energy 23 MeV in the [Formula omitted] [Formula omitted] channel, three states with binding energy 26, 30 and 7 MeV (relative to the thresholds from low to high, respectively) in the [Formula omitted] [Formula omitted]- [Formula omitted]- [Formula omitted] system and three states with binding energy 32, 8 and 16 MeV in the [Formula omitted] [Formula omitted]- [Formula omitted]- [Formula omitted] system. Those [Formula omitted] states serve as the open-charm partners of the hidden charm pentaquarks [Formula omitted] observed by the LHCb Collaboration.
Journal Article
Energy
\"In this book, readers will learn how energy affects the movement of objects through the air, the warmth we feel on our skin when the sun shines, and many concepts in between\"--Provided by publisher.
Book
Effects of Methyl Substitution and Leaving Group on E2/Ssub.N2 Competition for Reactions of Fsup.− with RY
The competition between base-induced elimination (E2) and bimolecular nucleophilic substitution (S[sub.N]2) is of significant importance in organic chemistry and is influenced by many factors. The electronic structure calculations for the gas-phase reactions of F[sup.−] + RY (R = CH[sub.3], C[sub.2]H[sub.5], [sup.i]C[sub.3]H[sub.7], [sup.t]C[sub.4]H[sub.9], and Y = Cl, I) are executed at the MP2 level with aug-cc-pVDZ or ECP/d basis set to investigate the α-methyl substitution effect. The variation in barrier height, reaction enthalpy, and competition of S[sub.N]2/E2 as a function of methyl-substitution and leaving group ability has been emphasized. And the nature of these rules has been explored. As the degree of methyl substitution on α-carbon increases, the E2 channel becomes more competitive and dominant with R varying from C[sub.2]H[sub.5], [sup.i]C[sub.3]H[sub.7], to [sup.t]C[sub.4]H[sub.9]. Energy decomposition analysis offers new insights into the competition between E2 and S[sub.N]2 processes, which suggests that the drop in interaction energy with an increasing degree of substitution cannot compensate for the rapid growth of preparation energy, leading to a rapid increase in the S[sub.N]2 energy barrier. By altering the leaving group from Cl to I, the barriers of both S[sub.N]2 and E2 monotonically decrease, and, with the increased number of substituents, they reduce more dramatically, which is attributed to the looser transition state structures with the stronger leaving group ability. Interestingly, ∆E[sub.0] [sup.‡] exhibits a positive linear correlation with reaction enthalpy (∆H) and halogen electronegativity. With the added number of substituents, the differences in ∆E[sub.0] [sup.‡] and ∆H between Y = Cl and I likewise exhibit good linearity.
Journal Article
Experiments with forces
Read and Experiment is an engaging series that uses fun experiments to introduce children to analytical thinking, scientific concepts and experimental procedures. Through fun, carefully designed experiments, it encourages children to get hands-on with science, asking questions and seeking their own answers by following the illustrated step-by-step instructions. The title gets them familiar with the science of forces.
Book
First-principles study of the interaction between H/He impurities and vacancy in tetragonal Be$$_{12}$$Ti
First-principles calculations have been executed to investigate the interaction between H/He impurities and vacancy in tetragonal Be [Formula omitted]Ti. The solution energies of four types of most stable H [Formula omitted]V complexes are lower than that of He [Formula omitted]V complexes. The binding energies of H atom to four types of vacancies are all lower than that of He atom to vacancies, indicating that He-vacancy complexes can serve as a trap to capture other impurity atoms. Besides, the formation energies of vacancy decrease when a single H or He atom is implanted into vacancy space, and the influence of He atom is greater than that of H atom. The exist of He atom in the H [Formula omitted]HeV complexes leads to the increase of solution energies comparing with H [Formula omitted]V complexes. In all the H [Formula omitted]HeV complexes, the distances between any two H atoms are larger than that in a H [Formula omitted] molecule, indicating that H [Formula omitted] molecules can not be formed in these complexes. The trapping behaviours of He-vacancy complexes for H atoms are as follows: a HeV [Formula omitted] and a HeV [Formula omitted] complex can both trap up to three H atoms, a HeV [Formula omitted] complex can capture up to two H atoms, and a HeV [Formula omitted] complex can capture up to ten H atoms. The number of H atoms trapped by three types of HeV [Formula omitted] complexes reduces compared with that of mono-vacancy for H atoms, indicating that the retention of H atoms within the vacancy space in Be [Formula omitted]Ti is suppressed by doping of He atom. The present results provide a foundational image of He-vacancy trapping mechanism for H atoms, which contributes significantly to the study on the synergistic effect of hydrogen and helium in tetragonal Be [Formula omitted]Ti.
Journal Article
Experiments with forces
Genuine scientists test their theories through experiments, using the results to uncover truly amazing discoveries. In this beneficial STEM-based book, readers are the scientists diving into experiments about forces such as gravity, friction, and magnetism. Theyll use easy-to-find materials such as balloons, erasers, and rulers to perform step-by-step experiments, learning more about forces at work in the world all around them. A summary of each carefully illustrated experiment reviews what the result conveys about the concept, while extra activities encourage more experimentation, an attribute of every great scientist.
Book
Synthesis of MOF-Derived Hybrids for Efficient Electrocatalytic Reduction of CO.sub.2 to Syngas
Electrocatalytic CO.sub.2 reduction into controllable clean syngas (H.sub.2 and CO) by using clean electric energy is an environment-friendly strategy for the cycle of carbon resources. However, there are still some challenges in this process, such as low current density and high onset potential. In this work, ZIF-8 is used as the precursor to adjust the ratio of metal Ni and Cu to control the composition of syngas (H.sub.2/CO 0.6:1-8:1). When metal Ni and Cu are both present, the onset potential can be effectively reduced, and the limiting current density would increase at the same time. Through subsequent experimental characterization and analysis, the catalyst of Ni Cu-1 effectively reduces the onset potential and increases the limiting current density. What's more, the superior CO.sub.2 electroreduction performance is attributed to the high binding energy of pyridine N in Ni NC, and the introduction of Cu in Ni Cu-1 is beneficial to the generation of syngas with adjustable composition. The research provides a feasible method for electrocatalytic CO.sub.2RR to reasonably utilize H.sub.2 competition reaction and regulate the proportion of syngas.
Journal Article