Nondestructive Measurement of Orbital Angular Momentum for an Electron Beam

Free electrons with a helical phase front, referred to as "twisted" electrons, possess an orbital angular momentum (OAM) and, hence, a quantized magnetic dipole moment along their propagation direction. This intrinsic magnetic moment can be used to probe material properties. Twisted electrons thus have numerous potential applications in materials science. Measuring this quantity often relies on a series of projective measurements that subsequently change the OAM carried by the electrons. In this Letter, we propose a nondestructive way of measuring an electron beam's OAM through the interaction of this associated magnetic dipole with a conductive loop. Such an interaction results in the generation of induced currents within the loop, which are found to be directly proportional to the electron's OAM value. Moreover, the electron experiences no OAM variations and only minimal energy losses upon the measurement, and, hence, the nondestructive nature of the proposed technique.Comment: 5 pages, 3 figures, and supplemental material that is comprised of text and 4 figure

Spin constrained orbital angular momentum control in high-harmonic generation

The interplay between spin and orbital angular momentum in the up-conversion process allows us to control the macroscopic wave front of high harmonics by manipulating the microscopic polarizations of the driving field. We demonstrate control of orbital angular momentum in high harmonic generation from both solid and gas phase targets using the selection rules of spin angular momentum. The gas phase harmonics extend the control of angular momentum to extreme-ultraviolet wavelength. We also propose a bi-color scheme to produce spectrally separated extreme-ultraviolet radiation carrying orbital angular momentum

Measuring the orbital angular momentum spectrum of an electron beam

Electron waves that carry orbital angular momentum (OAM) are characterized by a quantized and unbounded magnetic dipole moment parallel to their propagation direction. When interacting with magnetic materials, the wavefunctions of such electrons are inherently modified. Such variations therefore motivate the need to analyse electron wavefunctions, especially their wavefronts, to obtain information regarding the material’s structure. Here, we propose, design and demonstrate the performance of a device based on nanoscale holograms for measuring an electron’s OAM components by spatially separating them. We sort pure and superposed OAM states of electrons with OAM values of between −10 and 10. We employ the device to analyse the OAM spectrum of electrons that have been affected by a micron-scale magnetic dipole, thus establishing that our sorter can be an instrument for nanoscale magnetic spectroscopy

SHOALS Object Detection

For the past decade, SHOALS (Scanning Hydrographic Operational Airborne Lidar Survey) has proven to be an efficient and cost-effective means for large-area coastal mapping projects. However, its capabilities in the rapid reconnaissance of small underwater obstructions have been less appreciated, despite a demonstrated history of successful detection and spatial identification. This paper discusses SHOALS‘ object detection capabilities in light of the recent developments in object detection algorithms, with multiple situation studies to illustrate its overall performance and latest enhancements. Various aspects of object detection using airborne bathymetric lidar are discussed to highlight the challenges and advantages of using SHOALS for rapid reconnaissance of small underwater obstructions.Durante la última década, SHOALS (Scanning Hydrographic Operational Airborne Lidar Survey) ha demostrado ser un medio eficaz y económico en lo que se refiere a proyectos de cartografía costera a gran escala. Sin embargo, sus capacidades en materia de reconocimiento rápido de pequeñas obstrucciones submarinas han sido menos apreciadas, a pesar de los antecedentes manifiestos de una lograda detección y de una identificación espacial. Este artículo trata sobre las capacidades de detección de objetos del SHOALS a la luz de los recientes desarrollos acaecidos en los algoritmos de detección de objetos, con múltiples estudios de situaciones para ilustrar su funcionamiento general y sus últimas mejoras. Se han abordado varios aspectos de la detección de objetos que utilizan el lidar batimétrico aerotransportado para destacar los retos y las ventajas del uso del SHOALS para un reconocimiento rápido de pequeñas obstrucciones submarinas.Au cours de la dernière décennie, SHOALS (Scanning Hydrographic Operational Airborne Lidar Survey) s‘est révélé être un instrument efficace et rentable en ce qui concerne les projets de carto-graphie côtière à grande échelle. Toutefois, ses capacités en matière de reconnaissance rapide des petites obstructions sous-marines ont été moins appréciées malgré des antécédents avérés de détection réussie et d‘identification spatiale. Cet article traite des capacités de détection d‘objet du SHOALS à la lumière des récents développements intervenus dans les algorithmes de détection d‘objets, avec de nombreuses études de situations qui illustrent l‘ensemble de ses performances et les dernières améliorations. Divers aspects de la détection d‘objets à l‘aide du lidar bathymétrique aéroporté ont été abordés dans le but de souligner les défis et les avantages de l‘utilisation du SHOALS pour la reconnaissance rapide des petites obstructions sous-marines

The role of the social network structure on the spread of intensive agriculture: an example from Navarre, Spain

Social networks influence decision-making in agricultural landscapes by affecting how farmers access knowledge and resources. However, researchers ignore the disparate structures built to access different kinds of knowledge and resources and the social mechanisms that take place on such farmers advice networks. We explored the role of social networks in decision-making among farmers in Navarre (Spain) to understand how and why some practices spread among farming communities. Social network analysis allows us to understand how farmers in this region share both knowledge and resources, and the potential implications of this sharing for the landscape. We find that large-scale farmers undertaking intensive land management are at the core of the network in this region, controlling the flow of knowledge and resources related to farm management, policy, technology, and finance. The central position of these farmers in the social network, and their reputation, is key to the spread of intensive farming practices in the region, which ultimately may lead to homogenization of local agricultural landscapes. Understanding farmer network structures in a context of agricultural intensification can help tease out the social mechanisms, such as farmers joining each other in cooperatives, behind the spread of agricultural practices. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Many thanks to all the participants, especially to the lead author?s host Patxi Sueskun, and the people from the local cooperative: Rogelio Rodriguez, Andrea Ayestaran, and Leire Elorz. Without their help, this work would have not been possible. The lead author would also like to mention Julen Ugalde for his support in Canada during the data analysis and Jesse Rieb, Jesse Sayles, Jacopo Baggio, Karina Benessaiah, Carrie Dai, and Yevgen Nazarenko for their help at different stages of this research. Likewise, we are grateful for the insightful comments of the four reviewers that have made this paper stronger and sharper

Prefatory Note: Happiness and the Teaching of English

Happiness is the full use of one\u27s powers along the lines of excellence in a life that offers scope. Could the above Greek definition of happiness serve as an all-encompassing goal for teachers of English in the secondary school? If so, how could we encourage the full, excellent use of all of our students\u27 talents in ways calculated to improve their public and private lives? In helping students use all their talents, would we not also counteract the perception that the quality of English instruction has declined

There\u27s Nothing New under the Sun

The attempt to unite theory and practice in the education of English teachers has taken many forms: courses in which theoreticians attempt to illuminate the practice of professional teachers or student teachers; situations in which teacher-education faculty cooperate with teachers; student teachers; and the community; in order to make programs more responsive to community needs; and instruction in which school-based apprenticeship is stressed. Until research can provide a firm base for the structure and content of methods courses; professionals must rely on their own judgment as to the placement of emphasis. An adaptation of Lee J. Cronbach\u27s research paradigm; used at the University of Northern Iowa; Cedar Falls; maximizes the transfer of educational theory into teaching practice. English education majors; exposed to the practical experience of student teaching; are also provided with the opportunity to discuss the teaching encounter on a theoretical level; within a classroom setting. Plans for a future course; which will combine the disciplines of English education and educational psychology; are also outlined. (KS

ARPA-Lincoln C-Band Observable Radar (ALCOR) receiver modernization

This project presents an overview and analysis of a project to modernize the ALCOR receiver. An overview of the existing system with specific detail given to the receiver system is presented. This is followed by a general presentation of the system design changes to be made. Specific analysis is given to the receiver design changes being made. This analysis shows that the new receiver is at least as capable as the existing receiver in all respects. In fact, the new receiver outperforms the existing receiver in some aspects. These design changes are presented within the scope of the overall project which is to reduce system operation and maintenance costs by modernizing the system with commercial off-the-shelf equipment and extensive diagnostic and fault isolation capabilities.Includes bibliographical references (leaf 46)California State University, Northridge. Department of Engineering

Prefatory Note

Culture is an instrument wielded by professors to manufacture professors, who then when their turn comes, will manufacture professors. - Simone Weil The high culture to which Simone Weil is referring in the above quotation is the kind of culture Professors E. D. Hirsch, Jr., and Allan Bloom refer to in their books Cultural Literacy and The Closing of the American Mind. It is not the culture which the authors of this volume are addressing. These freshmen Presidential Scholars are interested in the popular culture of their peers and associates