Lucy : Dancing Around The Cabin Door

https://digitalcommons.library.umaine.edu/mmb-vp/5190/thumbnail.jp

Critical current of a Josephson junction containing a conical magnet

We calculate the critical current of a superconductor/ferromagnetic/superconductor (S/FM/S) Josephson junction in which the FM layer has a conical magnetic structure composed of an in-plane rotating antiferromagnetic phase and an out-of-plane ferromagnetic component. In view of the realistic electronic properties and magnetic structures that can be formed when conical magnets such as Ho are grown with a polycrystalline structure in thin-film form by methods such as direct current sputtering and evaporation, we have modeled this situation in the dirty limit with a large magnetic coherence length ($\xi_f$). This means that the electron mean free path is much smaller than the normalized spiral length $\lambda/2\pi$ which in turn is much smaller than $\xi_f$ (with $\lambda$ as the length a complete spiral makes along the growth direction of the FM). In this physically reasonable limit we have employed the linearized Usadel equations: we find that the triplet correlations are short ranged and manifested in the critical current as a rapid oscillation on the scale of $\lambda/2\pi$. These rapid oscillations in the critical current are superimposed on a slower oscillation which is related to the singlet correlations. Both oscillations decay on the scale of $\xi_f$. We derive an analytical solution and also describe a computational method for obtaining the critical current as a function of the conical magnetic layer thickness.Comment: Extended version of the published paper. Additional information about the computational method is included in the appendi

Are factor endowments fate?

In recent theories of comparative development, the role of institutional differences has been crucial. Yet, what explains comparative institutional evolution? We investigate this issue by studying the coffee exporting economies of Latin America. Although homogeneous in many ways, they experienced radically different paths of economic (and political) development, which is conventionally traced to the differential organization of the coffee industry. We show that the different forms that the coffee economy took in the 19th century was critically determined by the legal environment determining access to land, and that different laws resulted from differences in the nature of political competition and the backgrounds of political elites. Our analysis suggests that explanations of institutional differences that stress economic fundamentals can only be part of the story. At least in the economies that we study, while geography, factor endowments and technology are clearly important, their implications for the institutional structure and thus development are conditional on the form that political competition takes in society. For interesting variations in economic outcomes, endowments are not fate.El papel de las diferencias institucionales ha sido crucial en las teorías recientes del desarrollo comparativo. Pero ¿Qué explica las diferencias comparativas en la evolución institucional? En este trabajo investigamos este asunto estudiando las economías exportadoras de café en Latinoamérica. Aunque similares, estas economías experimentaron diferentes modelos de desarrollo económico (y político) convencionalmente explicados en relación con su diferente organización de la industria cafetera. Este artículo muestra que las diferentes formas adoptadas por la economía cafetera en el siglo XIX estuvieron especialmente determinadas por el entorno legal del acceso a la tierra y de las diferentes leyes resultantes de las diferencias en la naturaleza de la competición política y de la formación de las elites políticas. Nuestro análisis sugiere que las explicaciones de diferencia institucional que presionan los fundamentos de la economía pueden ser sólo una parte de la explicación. Al menos en las economías que hemos estudiado, mientras la geografía, la dotación de recursos y la tecnología son claramente importantes en la explicación, sus implicaciones sobre la estructura institucional y, en consecuencia, sobre el desarrollo, dependen de la forma de competición política adoptada por la sociedad. Para las interesantes variaciones de los resultados económicos los recursos no son el destino

Geologic Setting of the Harvard Conglomerate, Harvard, Massachusetts

Guidebook for field trips to the Boston area and vicinity : 68th annual meeting, New England Intercollegiate Geological Conference, October 8-10, 1976: Trip F-

Report of the Citizens\u27 Dickey-Lincoln Project Impact Review Committee to Governor James B. Longley

The construction of the Dickey-Lincoln Hydroelectric Project. To examine, in depth, the proposal and its impact as seen by various segments of our society. The report will identify the factors that must carry the main weight in making a final determination

An Investigation of the Drag of Windshields in the 8-Foot High-Speed Wind Tunnel

The drag of closed-cockpit and transport-type windshields was determined from tests made at speeds from 200 to 440 miles per hour in the NACA 8-foot high-speed wind tunnel. This speed range corresponds to a test Reynolds number range of 2,510,000 to 4,830,000 based on the mean aerodynamic chord of the full-span model (17.29 inches). The shapes of the windshield proper, the hood, and the tail fairing were systematically varied to include common types and a refined design. Transport types varied from a reproduction of a current type to a completely faired windshield. The results show that the drag of windshields of the same frontal area, on airplanes of small to medium size, may account for 15% of the airplane drag or may be reduced to 1%. Optimum values are given for windshield and tail-fairing lengths; the effect, at various radii is shown. The longitudinal profile of a windshield is shown to be most important and the transverse profile, to be much less important. The effects of retaining strips, of steps for telescoping hoods, and of recessed windows are determined. The results show that the drag of transport-type windshields may account for 21% of the fuselage drag or may be reduced to 2%

Approximate variational coupled cluster theory

We show that it is possible to construct an accurate approximation to the variational coupled cluster method, limited to double substitutions, from the minimization of a functional that is rigorously extensive, exact for isolated two-electron subsystems and invariant to transformations of the underlying orbital basis. This approximate variational coupled cluster theory is a modification and enhancement of our earlier linked pair functional theory. It is first motivated by the constraint that the inverse square root of the matrix that transforms the cluster amplitudes must exist. Low-order corrections are then included to enhance the accuracy of the approximation of variational coupled cluster, while ensuring that the computational complexity of the method never exceeds that of the standard traditional coupled cluster method. The effects of single excitations are included by energy minimization with respect to the orbitals defining the reference wavefunction. The resulting quantum chemical method is demonstrated to be a robust approach to the calculation of molecular electronic structure and performs well when static correlation effects are strong

Toward a descriptive model of galactic cosmic rays in the heliosphere

Researchers review the elements that enter into phenomenological models of the composition, energy spectra, and the spatial and temporal variations of galactic cosmic rays, including the so-called anomalous cosmic ray component. Starting from an existing model, designed to describe the behavior of cosmic rays in the near-Earth environment, researchers suggest possible updates and improvements to this model, and then propose a quantitative approach for extending such a model into other regions of the heliosphere