Metal shearing energy absorber

A metal shearing energy absorber is described. The absorber is composed of a flat thin strip of metal which is pulled through a slot in a cutter member of a metal, harder than the metal of the strip. The slot's length, in the direction perpendicular to the pull direction, is less than the strip's width so that as the strip is pulled through the slot, its edges are sheared off, thereby absorbing some of the pulling energy. In one embodiment the cutter member is a flat plate of steel, while in another embodiment the cutter member is U-shaped with the slot at its base

Radical pair intersystem crossing: Quantum dynamics or incoherent kinetics?

Magnetic field effects on radical pair reactions arise due to the interplay of coherent electron spin dynamics and spin relaxation effects, a rigorous treatment of which requires the solution of the Liouville-von Neumann equation. However, it is often found that simple incoherent kinetic models of the radical pair singlet-triplet intersystem crossing provide an acceptable description of experimental measurements. In this paper we outline the theoretical basis for this incoherent kinetic description, elucidating its connection to exact quantum mechanics. We show in particular how the finite lifetime of the radical pair spin states, as well as any additional spin-state dephasing, leads to incoherent intersystem crossing. We arrive at simple expressions for the radical pair spin state interconversion rates to which the functional form proposed recently by Steiner et al. [J. Phys. Chem. C 122, 11701 (2018)] can be regarded as an approximation. We also test the kinetic master equation against exact quantum dynamical simulations for a model radical pair and for a series of $\text{PTZ}^{\bullet+}\text{-Ph}_\text{n}\text{-PDI}^{\bullet-}$ molecular wires

Rose Mary

https://digitalcommons.library.umaine.edu/mmb-vp/6338/thumbnail.jp

Spin-dependent charge recombination along para-phenylene molecular wires

We have used an efficient new quantum mechanical method for radical pair recombination reactions to study the spin-dependent charge recombination along PTZ$^{\bullet+}$--Ph$_n$--PDI$^{\bullet-}$ molecular wires. By comparing our results to the experimental data of E. Weiss {\em et al.} [J. Am. Chem. Soc. {\bf 126}, 5577 (2004)], we are able to extract the spin-dependent (singlet and triplet) charge recombination rate constants for wires with $n=2-5$. These spin-dependent rate constants have not been extracted previously from the experimental data because they require fitting its magnetic field-dependence to the results of quantum spin dynamics simulations. We find that the triplet recombination rate constant decreases exponentially with the length of the wire, consistent with the superexchange mechanism of charge recombination. However, the singlet recombination rate constant is nearly independent of the length of the wire, suggesting that the singlet pathway is dominated by an incoherent hopping mechanism. A simple qualitative explanation for the different behaviours of the two spin-selective charge recombination pathways is provided in terms of Marcus theory. We also find evidence for a magnetic field-independent background contribution to the triplet yield of the charge recombination reaction, and suggest several possible explanations for it. Since none of these explanations is especially compelling given the available experimental evidence, and since the result appears to apply more generally to other molecular wires, we hope that this aspect of our study will stimulate further experimental work.Comment: 12 pages, 10 figure

Spin-selective electron transfer reactions of radical pairs: beyond the Haberkorn master equation

Radical pair recombination reactions are normally described using a quantum mechanical master equation for the electronic and nuclear spin density operator. The electron spin state selective (singlet and triplet) recombination processes are described with a Haberkorn reaction term in this master equation. Here we consider a general spin state selective electron transfer reaction of a radical pair and use Nakajima-Zwanzig theory to derive the master equation for the spin density operator, thereby elucidating the relationship between non-adiabatic reaction rate theory and the Haberkorn reaction term. A second order perturbation theory treatment of the diabatic coupling naturally results in the Haberkorn master equation with an additional reactive scalar electron spin coupling term. This term has been neglected in previous spin chemistry calculations, but we show that it will often be quite significant. We also show that beyond second order in perturbation theory, i.e., beyond the Fermi golden rule limit, an additional reactive singlet-triplet dephasing term appears in the master equation. A closed form expression for the reactive scalar electron spin coupling in terms of the Marcus theory parameters that determine the singlet and triplet recombination rates is presented. By performing simulations of radical pair reactions with the exact Hierarchical Equations of Motion (HEOM) method, we demonstrate that our master equations provide a very accurate description of radical pairs undergoing spin-selective non-adiabatic electron transfer reactions. The existence of a reactive electron spin coupling may well have implications for biologically relevant radical pair reactions such as those which have been suggested to play a role in avian magnetoreception

Derivation of diagnostic models based on formalized process knowledge

© IFAC.Industrial systems are vulnerable to faults. Early and accurate detection and diagnosis in production systems can minimize down-time, increase the safety of the plant operation, and reduce manufacturing costs. Knowledge- and model-based approaches to automated fault detection and diagnosis have been demonstrated to be suitable for fault cause analysis within a broad range of industrial processes and research case studies. However, the implementation of these methods demands a complex and error-prone development phase, especially due to the extensive efforts required during the derivation of models and their respective validation. In an effort to reduce such modeling complexity, this paper presents a structured causal modeling approach to supporting the derivation of diagnostic models based on formalized process knowledge. The method described herein exploits the Formalized Process Description Guideline VDI/VDE 3682 to establish causal relations among key-process variables, develops an extension of the Signed Digraph model combined with the use of fuzzy set theory to allow more accurate causality descriptions, and proposes a representation of the resulting diagnostic model in CAEX/AutomationML targeting dynamic data access, portability, and seamless information exchange

Letter from Charles E. Fay to John Muir, 1910 Mar 28.

early appointment of a nominating committee. For some reasons a geographical distribution of its membership is desirable and the use of the mail renders it a feasible if not ideal method. Perhaps it might be well if the appointment were made before the summer holidays.How much we desired your presence at our last annual meeting!- the largest we have had, and a body of men that I know it would have delighted you to meet, as they also would have been glad to do you honor. Possibly the pleasure is only deferred. Surely we hope for an opportunity to grasps your hand and joy together in our common ideals.Yours faithfullyCharles E. Fay.[illegible]Tufts College, Mass.Mar. 28. 1910.Mr John Muir,President of the American Alpine ClubMartinez, California.Dear Mr. President:The name of Sir Ernest [Shackleton?] has been put in nomination for honorary membership in the Alpine Club. To validate an election the vote of the Executive Committee must be unanimous.Will you kindly signify (by return of mail if possible) whether you ass[illegible]t to his election?May I take this occasion to call attention to the fact that the next annual meeting is the triennial election of officers, and to suggest the0473

DESIGN, DEVELOPMENT, AND APPLICATION OF A TRANSDUCER TO QUANTIFY TENSION IN THE MEDIAL COLLATERAL LIGAMENT OF THE ELBOW

Techniques have evolved for quantifying human tendon and ligament forces in the lower extremity; however, custom developed systems for the upper extremity, particularly the elbow, are not well described. Consequently, ligament forces of the human elbow joint have not been reported. Knowledge of the magnitudes of tension of the primary valgus stabilizer, the anterior bundle of the medial collateral ligament (AMCL), would allow for an improved understanding of the load environment of this tissue. Mechanisms of AMCL injury include chronic high intensity overuse, radial head fracture, and elbow dislocations. This work focused on the design and development of a custom designed E- form frame buckle transducer to quantify AMCL tension in vitro. To understand the basic biomechanical characteristics of the AMCL, a series of in vitro studies employing this device were conducted. The specific objectives of this work were: (1) to quantify the magnitude of AMCL tension through the arc of elbow flexion; (2) to determine the effect of wrist flexor muscle loading on the magnitude of AMCL tension through the arc of elbow flexion; and (3) to evaluate the effect of radial head excision and arthroplasty on the magnitude of AMCL tension through the arc of elbow flexion. The chief findings were: (1) AMCL tension increased with increasing angles of elbow flexion (i.e. AMCL tension was greater at full flexion than at full extension); (2) increased wrist flexor muscle loading caused AMCL tension levels to decrease; and (3) radial head excision increased AMCL tension levels, whereas metallic radial head arthroplasty restored near­ normal AMCL tension levels. Furthermore, for all investigations, AMCL tension levels were greater with the arm oriented in the valgus position than in the dependent (i.e. vertical) position. Improved knowledge of AMCL tissue biomechanics will allow for the design and evaluation of improved methods of AMCL repair/reconstruction and rehabilitation, and assist in the development of an artificial AMCL and in vitro biomechanical models of the elbow. Furthermore, this transducer will permit numerous additional projects to be explored that will investigate the ligament and soft tissue loading at the elbow, shoulder, and wrist

Rewriting History: The Impact of the Cuban Missile Crisis on American Journalism

The Cuban Missile Crisis represented a unique moment in the history of American foreign policy because it was the first time that the world faced a nuclear standoff. The threat of a third World War allowed US government officials to deceive the press under the guise of protecting national security. Since the fall of the Berlin Wall and the release of thousands of documents from ex-Soviet and American archives, historians are rethinking the narrative of the Cuban Missile Crisis that has been presented in the press during and after the crisis. This paper will explore the relationship that President Kennedy cultivated with the press to promote his political agenda and the impact that this relationship had on the reporting of future foreign policy crises