107,906 research outputs found
Covalent Modification of Carbon Surfaces by Direct and Redox Catalysed Oxidation of Carboxylates in Acetonitrile – Concepts and Mechanisms
No full textElectrografting is a relevant process that allows getting modified electrodes where organic molecules are covalently bonded to the electrode surface. The modification is typically performed using electrochemical reactions, where the transient passage by free radicals allows the formation of covalent bonds with the electrode surface. These intermediaries are generated over a wide potential window, and they are commonly prone to a second electron transfer (oxidation or reduction). Thus, this reaction competes with the surface reactions, slowing down the formation of films on the electrode. In the case of carboxylate oxidation, these competitive processes have been minimized by using a redox-catalysed process which occurs at low oxidation potentials. The rate at which modifications procedures occur is relevant in the sense that they determine the properties of the polymeric films covalently attached to the electrode surfaces. Therefore, this review focuses on the main aspects of the direct and redox-catalysed oxidation of carboxylates as a tool for the covalent modification of the surface of different carbon electrodes
Chan An Ancient Maya Farming Community
No full textThe farming community of Chan thrived for over twenty centuries, surpassing the longevity of many larger Maya urban centers. Between 800 BC and 1200 AD it was a major food production center, and this collection of essays reveals the important role played by Maya farmers in the development of ancient Maya society. Chan offers a synthesis of compelling and groundbreaking discoveries gathered over ten years of research at this one archaeological site in Belize. The contributors develop three central themes, which structure the book. They examine how sustainable farming practices maintained the surrounding forest, allowing the community to exist for two millennia. They trace the origins of elite Maya state religion to the complex religious belief system developed in small communities such as Chan. Finally, they describe how the group-focused political strategies employed by local leaders differed from the highly hierarchical strategies of the Classic Maya kings in their large cities. In breadth, methodology, and findings, this volume scales new heights in the study of Maya society and culture.Cover -- Title -- Copyright -- Contents -- List of Figures -- List of Tables -- Foreword -- Acknowledgments -- 1. Introducing the Chan Site: Farmers in Complex Societies -- Part 1. Time, Space, and Landscapes -- 2. A Changing Cultural Landscape: Settlement Survey and GIS at Chan -- 3. Ceramics and Chronology at Chan -- 4. Agricultural Practices at Chan: Farming and Political Economy in an Ancient Maya Community -- 5. Agroforestry and Agricultural Production of the Ancient Maya at Chan -- Part 2. Life in a Farming Community Center -- 6. Ritual in a Farming Community -- 7. Nonroyal Governance at Chan's Community Center -- 8. "Empty" Spaces and Public Places: A Microscopic View of Chan's Late Classic West Plaza -- Part 3. Diversity across the Chan Community -- 9. Recognizing Difference in Small-Scale Settings: An Examination of Social Identity Formation at the Northeast Group, Chan -- 10. Organization of Chert Tool Economy during the Late and Terminal Classic Periods at Chan: Preliminary Thoughts Based upon Debitage Analyses -- 11. Limestone Quarrying and Household Organization at Chan -- Part 4. Bodies, Material Culture, and Meaning -- 12. The Chan Community: A Bioarchaeological Perspective -- 13. Creating Community with Shell -- 14. Obsidian Acquisition, Trade, and Regional Interaction at Chan -- 15. Contextualizing Ritual Behavior: Caches, Burials, and Problematical Deposits from Chan's Community Center -- Part 5. Conclusion -- 16. Learning from an Ancient Maya Farming Community -- References -- List of Contributors -- Index -- A -- B -- C -- D -- E -- F -- G -- H -- I -- J -- K -- L -- M -- N -- O -- P -- Q -- R -- S -- T -- V -- W -- X -- YThe farming community of Chan thrived for over twenty centuries, surpassing the longevity of many larger Maya urban centers. Between 800 BC and 1200 AD it was a major food production center, and this collection of essays reveals the important role played by Maya farmers in the development of ancient Maya society. Chan offers a synthesis of compelling and groundbreaking discoveries gathered over ten years of research at this one archaeological site in Belize. The contributors develop three central themes, which structure the book. They examine how sustainable farming practices maintained the surrounding forest, allowing the community to exist for two millennia. They trace the origins of elite Maya state religion to the complex religious belief system developed in small communities such as Chan. Finally, they describe how the group-focused political strategies employed by local leaders differed from the highly hierarchical strategies of the Classic Maya kings in their large cities. In breadth, methodology, and findings, this volume scales new heights in the study of Maya society and culture.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
Hybrid Numerical Analysis of a high-speed non-volatile Suspended Gate Silicon Nanodot Memory
No full textWe present a hybrid numerical analysis of a high-speed and non-volatile suspended gate silicon nanodot memory (SGSNM) which co-integrates a nano-electromechanical (NEM) control gate with a MOSFET as a readout element and silicon nanodots as a floating gate. A hybrid NEM-MOS circuit simulation is developed by taking account of the pull-in/pull-out operation of the suspended gate and electron tunnelling processes through the tunnel oxide layer as behavioural models. The signals for programming, erasing and reading are successfully achieved at circuit level simulation. The programming and erasing times are found as short as 2.5 nsec for a SGSNM with a 1-?m-long suspended gate, which is a summation of the mechanical pull-in/pull-out times and the tunnel charging/discharging times
Parámetros de avaliação para projetos com melhor aproveitamento de uso
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em ArquiteturaNa atualidade a totalidade de projetos habitacionais parte do principio absurdo do mínimo espaço para reduzir os custos da obra em lugar do utilizar um conceito do espaço necessário. Quase nenhum destes projetos leva em consideração o tamanho do mobiliário disponível no mercado. Isto cria uma incompatibilidade entre a necessidade espacial do usuário e a área disponível nas habitações de interesse social. Os resultados de uma construção com estas falhas entre outros são: O aumento dos custos para o morador que deve ampliar sua casa para poder utilizar o espaço com algo de conforto. A perda de flexibilidade de uso já que o espaço não permite variações no arranjo espacial. As habitações que não têm o equipamento necessário para sua utilização devido à falta de espaço para colocar o mobiliário. O congestionamento visual devido à aglomeração de móveis dentro de um cômodo criando desorganização e desconforto. A perda da privacidade pela carência de um espaço próprio. Os dormitórios sem utilidade durante o dia, que ficam lotados a noite. Como uma possível solução se propôs o conceito de um painel mobiliário o qual deveria contribuir com a facilidade de construção, montagem e pré-fabricação de um imóvel como alternativas para diminuir custos. Ao mesmo tempo este painel conteria o mobiliário necessário para a utilização dos diferentes cômodos e assim aproveitar ao máximo o incipiente espaço em projetos de habitação de interesse social. A fundamentação teórica deste painel foi realizada por meio de pesquisas sobre propostas de habitação social e projetos arquitetônicos que atendessem a princípios de produtos industrializados, assim como o levantamento dos problemas mencionados anteriormente. A realização prática se desenvolveu por meio de uma tabela que funciona como checklist e avaliam o conforto e habitabilidade destes projetos por meio da aplicação dos conceitos de flexibilidade, adaptabilidade e privacidade. Foi realizado também um levantamento de produtos existentes no mercado internacional que apresentam soluções inovadoras para espaços reduzidos tanto pela variedade de funções que o mesmo permite quanto pelas propostas de aproveitamento de espaço no transcurso do dia. Para testar tanto a tabela quanto a aplicabilidade do mobiliário pesquisado se utilizou como estudo de caso o protótipo desenvolvido pela ARQ-UFSC em colaboração com a empresa Battistella
Jerarquía maya entre los dioses lacandones.. Anales del Instituto Nacional de Antropología e Historia. Num. 47 Tomo XVIII (1965) Sexta Época (1939-1966)
No full textAnónimo a) El Libro de los Libros de Chilam Balam, Trad. por Alfredo Barrera Vásquez y Silvia Rendón. México, 1948.Anónimo b) Popol Vuh, The Sacred Book of the Ancient Quiché Maya, English version by Delia Goetz and Sylvanus G. Morley from the translation of Adrián Recinos. University of Oklahoma Press. Norman, 1950.Bruce S., R. D. a) The Book of Chan Kin. (Inédito).Bruce S., R. D. b) Gramática del Lacandón, Tesis profesional, Escuela Nacional de Antropología e Historia. México, 1965. (lnédito).Landa, Fr. D. de. Relación de las Cosas de Yucatán. México, 1959.Marimon y Tudo, S. Fray Antonio Margil über die Lacandonen, 1695. Zeitschrift für Ethnologie, XIV, pp. 130-32. Stuttgart, 1882.Morley, S. G. La Civilización Maya, versión española de Adrián Recinos. México, 1947.Villa Rojas, A. Los Lacandones. (Inédito)
Coulter, Chan L., July 23, 1996 [Interview]
No full textProfessor of Philosophy Chan L. Coulter was interviewed on June 17, 1996, by Michael Birkner and David Hedrick about his career at Gettysburg College, including memorable colleagues, classes, and controversies.Dunn, Seymour B.; Glatfelter, Charles H.; Hanson, C. Arnold; Crapster, Basil L.; Barnes, Robert D.; Baskerville, Edward J.; Mara, Richard T.; Qually, Ingolf; Bugbee, Bruce W.; Richardson, Norman E.; Bolich, Harry F.; Arms, Richard A.; Mason, Francis C.; Taylor, Kathrine Kressmann; Schmidt, Emile O.; Glassick, Charles E.; Potts, David B.Willard S. Paul Years; Carl Arnold Hanson Years; Charles E. Glassick Years; Gordon A. Haaland Year
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Helical structure of the waves propagating in a spinning Timoshenko beam
No full textThe aim of the paper is to study the cause of a frequency-splitting phenomenon that occurs in a spinning Timoshenko beam. The associated changes in the structure of the progressive waves are investigated to shed light on the relationship between the wave motion in a spinning beam and the whirling of a shaft. The main result is that travelling bending waves in a beam spinning about its central axis have the topological structure of a revolving helix traced by the centroidal axis with right-handed or left-handed chirality. Each beam element behaves like a gyroscopic disc in precession being rotated at the wave frequency with anticlockwise or clockwise helicity. The gyroscopic effect is identified as the cause of the frequency splitting and is shown to induce a coupling between two interacting travelling waves lying in mutually orthogonal planes. Two revolving waves travelling in the same direction in space appear, one at a higher and one at a lower frequency compared with the pre-split frequency value. With reference to a given spinning speed, taken as clockwise, the higher one revolves clockwise and the lower one has anticlockwise helicity, each wave being represented by a characteristic four-component vector wavefunction.Two factors are identified as important, the shear-deformation factor q and the gyroscopic-coupling phase factor ?. The q-factor is related to the wavenumber and the geometric shape of the helical wave. The ?-factor is related to the wave helicity and has two values, +?/2 and ??/2 corresponding to the anticlockwise and clockwise helicity, respectively. The frequency-splitting phenomenon is addressed by analogy with other physical phenomena such as the Jeffcott whirling shaft and the property of the local energy equality of a travelling wave. The relationship between Euler's formula and the present result relating to the helical properties of the waves is also explored
Differences in Radiative Forcing, Not Sensitivity, Explain Differences in Summertime Land Temperature Variance Change Between CMIP5 and CMIP6
No full text© The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Chan, D., Rigden, A., Proctor, J., Chan, P. W., & Huybers, P. Differences in radiative forcing, not sensitivity, explain differences in summertime land temperature variance change between CMIP5 and CMIP6. Earth’s Future, 10(2), (2022): e2021EF002402, https://doi.org/10.1029/2021EF002402.How summertime temperature variability will change with warming has important implications for climate adaptation and mitigation. CMIP5 simulations indicate a compound risk of extreme hot temperatures in western Europe from both warming and increasing temperature variance. CMIP6 simulations, however, indicate only a moderate increase in temperature variance that does not covary with warming. To explore this intergenerational discrepancy in CMIP results, we decompose changes in monthly temperature variance into those arising from changes in sensitivity to forcing and changes in forcing variance. Across models, sensitivity increases with local warming in both CMIP5 and CMIP6 at an average rate of 5.7 ([3.7, 7.9]; 95% c.i.) × 10−3°C per W m−2 per °C warming. We use a simple model of moist surface energetics to explain increased sensitivity as a consequence of greater atmospheric demand (∼70%) and drier soil (∼40%) that is partially offset by the Planck feedback (∼−10%). Conversely, forcing variance is stable in CMIP5 but decreases with warming in CMIP6 at an average rate of −21 ([−28, −15]; 95% c.i.) W2 m−4 per °C warming. We examine scaling relationships with mean cloud fraction and find that mean forcing variance decreases with decreasing cloud fraction at twice the rate in CMIP6 than CMIP5. The stability of CMIP6 temperature variance is, thus, a consequence of offsetting changes in sensitivity and forcing variance. Further work to determine which models and generations of CMIP simulations better represent changes in cloud radiative forcing is important for assessing risks associated with increased temperature variance.This study was supported by the Harvard Global Institute and NSF (Award 1903657). D. Chan was also supported by the Woods Hole Oceanographic Institute Weston Howland Jr. Postdoctoral Fellowship
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