Analytical Mechanics of Chemical Reactions. V. Application to the Linear Reactive H +H_2 Systems

Natural collision coordinates and a zeroth‐order vibrational–adiabatic approximation are used to treat linear reactive collisions. Nonadiabatic effects on barrier transmission and on vibrational state of products are calculated. The present results are classical and are compared with exact classical numerical results for the H+H_2 reaction in the range 7–20 kcal/mol of initial relative translational energy. The agreement is encouraging and the results support the concepts introduced earlier of statistical adiabaticity and of nonadiabatic leak. At low energies the reaction is adiabatic on the average (initial vibrational phase average), thus justifying activated complex theory for this system. The relative importance of reaction path curvature and of vibrational frequency variation along the reaction path in inducing nonadiabatic effects is described. Implications for a quantum treatment, activated complex theory, and highly nonadiabatic systems are noted

Analytical Mechanics of Chemical Reactions. VI. Rotational and Vibrational Distributions of the H + H_2 Reaction in a Plane

Rotational and vibrational distributions for the exchange reaction H+H_(2)→H_(2)+H are obtained numerically for reaction in a plane and compared with the vibrationally adiabatic solutions. Evidence is obtained regarding the two adiabatic solutions for the final rotational state predicted earlier and for the disappearance of one of these at higher initial relative velocity. Good agreement between calculations based on natural collision coordinates and these based on Cartesian coordinates was found, where tested. The vibrational motion for reaction in a plane is fairly adiabatic on the average at energies of thermal interest. Connections with other properties are noted. The results support the idea of statistical adiabaticity suggested earlier in this series and thus support a derivation of activated complex theory based on this concept

Computing shortest paths in 2D and 3D memristive networks

Global optimisation problems in networks often require shortest path length computations to determine the most efficient route. The simplest and most common problem with a shortest path solution is perhaps that of a traditional labyrinth or maze with a single entrance and exit. Many techniques and algorithms have been derived to solve mazes, which often tend to be computationally demanding, especially as the size of maze and number of paths increase. In addition, they are not suitable for performing multiple shortest path computations in mazes with multiple entrance and exit points. Mazes have been proposed to be solved using memristive networks and in this paper we extend the idea to show how networks of memristive elements can be utilised to solve multiple shortest paths in a single network. We also show simulations using memristive circuit elements that demonstrate shortest path computations in both 2D and 3D networks, which could have potential applications in various fields

Ostensive signals support learning from novel attention cues during infancy

Social attention cues (e.g., head turning, gaze direction) highlight which events young infants should attend to in a busy environment and, recently, have been shown to shape infants' likelihood of learning about objects and events. Although studies have documented which social cues guide attention and learning during early infancy, few have investigated how infants learn to learn from attention cues. Ostensive signals, such as a face addressing the infant, often precede social attention cues. Therefore, it is possible that infants can use ostensive signals to learn from other novel attention cues. In this training study, 8-month-olds were cued to the location of an event by a novel non-social attention cue (i.e., flashing square) that was preceded by an ostensive signal (i.e., a face addressing the infant). At test, infants predicted the appearance of specific multimodal events cued by the flashing squares, which were previously shown to guide attention to but not inform specific predictions about the multimodal events (Wu and Kirkham, 2010). Importantly, during the generalization phase, the attention cue continued to guide learning of these events in the absence of the ostensive signal. Subsequent experiments showed that learning was less successful when the ostensive signal was absent even if an interesting but non-ostensive social stimulus preceded the same cued events

Global Existence for the Generalized Two-Component Hunter-Saxton System

We study the global existence of solutions to a two-component generalized Hunter-Saxton system in the periodic setting. We first prove a persistence result for the solutions. Then for some particular choices of the parameters (α, κ), we show the precise blow-up scenarios and the existence of global solutions to the generalized Hunter-Saxton system under proper assumptions on the initial data. This significantly improves recent result

Conditions for separability in generalized Laplacian matrices and nonnegative matrices as density matrices

Recently, Laplacian matrices of graphs are studied as density matrices in quantum mechanics. We continue this study and give conditions for separability of generalized Laplacian matrices of weighted graphs with unit trace. In particular, we show that the Peres-Horodecki positive partial transpose separability condition is necessary and sufficient for separability in ${\mathbb C}^2\otimes {\mathbb C}^q$. In addition, we present a sufficient condition for separability of generalized Laplacian matrices and diagonally dominant nonnegative matrices.Comment: 10 pages, 1 figur

Designing a supply network for a startup company

Thesis (M. Eng. in Logistics)--Massachusetts Institute of Technology, Engineering Systems Division, 2010.Cataloged from student submitted PDF version of thesis.Includes bibliographical references (p. 86-88).Our thesis introduces a supply chain framework catered for startup companies. Startup companies face unique circumstances such as constraints on financial and human resources, and greater uncertainty in demand. From our work with XL Hybrids, a startup company that hybridizes aftermarket vehicles, as well as interviews and literature review, we have attempted to distill supply chain strategies that can be applied to startup companies. To plan XL Hybrids' supply chain, we developed models for the following aspects of their supply chain: production scheduling, capacity planning, inventory policy, and component distribution. By running different demand and pricing scenarios, we gained an understanding of the impact of these variables on the four aspects of XL Hybrid's supply chain. Based on the scenario analysis and supply chain framework that we developed, we recommend that XL Hybrids be conservative with capacity expansion while strategically sourcing key components after considering volume discounts and different distribution methods.by Marcus S. Causton and Jianmin Wu.M.Eng.in Logistic

2-mercaptobenzothiazole corrosion inhibitor deposited at ultra-low pressure on model copper surfaces

International audienceAdsorption of 2-mercaptobenzothiazole (2-MBT) at ultra-low pressure and room temperature on metallic and pre-oxidized Cu(111) surfaces and its thermal stability were investigated using X-ray photoelectron spectroscopy in order to better understand the interfacial corrosion inhibiting properties. 2-MBT is lying flat in the monolayer with two sulphur atoms bonded to Cu and decomposes partially yielding atomic sulphur when interacting with metallic copper prior to forming molecular multilayers. Decomposition is prevented by surface pre-oxidation with 2D oxide dissociation accelerating the 2-MBT initial adsorption kinetics. 2-MBT further decomposes and partially desorbs above 100 • C. A pre-adsorbed 2-MBT monolayer on metallic copper inhibits surface corrosion

Molecular scale insights into interaction mechanisms between organic inhibitor film and copper

A model experimental approach, providing molecular scale insight into the build up mechanisms of a corrosion inhibiting interface, is reported. 2-mercaptobenzimidazole (2-MBI), a widely used organic inhibitor, was deposited from the vapor phase at ultra-low pressure on copper surfaces in chemically-controlled state, and X-ray photoelectron spectroscopy was used in situ to characterize the adsorption mechanisms upon formation of the inhibiting film. On copper surfaces prepared clean in the metallic state, the intact molecules lie flat at low exposure, with sulfur and both nitrogen atoms bonded to copper. A fraction of the molecules decomposes upon adsorption, leaving atomic sulfur on copper. At higher exposure, the molecules adsorb in a tilted position with sulfur and only one nitrogen bonded to copper, leading to a densification of 2-MBI in the monolayer. A bilayer is formed at saturation with the outer layer not bonded directly to copper. In the presence of a pre-adsorbed 2D oxide, oxygen is substituted and the molecules adsorb intactly without decomposition. A 3D oxide prevents the bonding of sulfur to copper. The molecular film formed on metallic and 2D oxide pre-covered surfaces partially desorbs and decomposes at temperature above 400 °C, leading to the adsorption of atomic sulfur on copper