966 resultados para Maxwell, James Clerk, 1831-1879


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Purpose: James Clerk Maxwell is usually recognized as being the first, in 1854, to consider using inhomogeneous media in optical systems. However, some fifty years earlier Thomas Young, stimulated by his interest in the optics of the eye and accommodation, had already modeled some applications of gradient-index optics. These applications included using an axial gradient to provide spherical aberration-free optics and a spherical gradient to describe the optics of the atmosphere and the eye lens. We evaluated Young’s contributions. Method: We attempted to derive Young’s equations for axial and spherical refractive index gradients. Raytracing was used to confirm accuracy of formula. Results: We did not confirm Young’s equation for the axial gradient to provide aberration-free optics, but derived a slightly different equation. We confirmed the correctness of his equations for deviation of rays in a spherical gradient index and for the focal length of a lens with a nucleus of fixed index surrounded by a cortex of reducing index towards the edge. Young claimed that the equation for focal length applied to a lens with part of the constant index nucleus of the sphere removed, such that the loss of focal length was a quarter of the thickness removed, but this is not strictly correct. Conclusion: Young’s theoretical work in gradient-index optics received no acknowledgement from either his contemporaries or later authors. While his model of the eye lens is not an accurate physiological description of the human lens, with the index reducing least quickly at the edge, it represented a bold attempt to approximate the characteristics of the lens. Thomas Young’s work deserves wider recognition.

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A 330--360 GHz spectral survey of the hot molecular core associated with the 'cometary' ultracompact HII region G 34.3+/-0.15 observed with the James Clerk Maxwell Telescope has detected 338 spectral lines from at least 35 distinct chemical species plus 19 isotopomers. 70 lines remain unidentified. Chemical abundance and rotation temperature have been determined by rotation diagram analysis for 12 species, and lower limits to abundance found for 38 others.

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We report photometric observations for comet C/2012 S1 (ISON) obtained during the time period immediately after discovery (r = 6.28 AU) until it moved into solar conjunction in mid-2013 June using the UH2.2 m, and Gemini North 8 m telescopes on Mauna Kea, the Lowell 1.8 m in Flagstaff, the Calar Alto 1.2 m telescope in Spain, the VYSOS-5 telescopes on Mauna Loa Hawaii and data from the CARA network. Additional pre-discovery data from the Pan STARRS1 survey extends the light curve back to 2011 September 30 (r = 9.4 AU). The images showed a similar tail morphology due to small micron sized particles throughout 2013. Observations at submillimeter wavelengths using the James Clerk Maxwell Telescope on 15 nights between 2013 March 9 (r = 4.52 AU) and June 16 (r = 3.35 AU) were used to search for CO and HCN rotation lines. No gas was detected, with upper limits for CO ranging between 3.5-4.5 × 1027 molecules s-1. Combined with published water production rate estimates we have generated ice sublimation models consistent with the photometric light curve. The inbound light curve is likely controlled by sublimation of CO2. At these distances water is not a strong contributor to the outgassing. We also infer that there was a long slow outburst of activity beginning in late 2011 peaking in mid-2013 January (r ~ 5 AU) at which point the activity decreased again through 2013 June. We suggest that this outburst was driven by CO injecting large water ice grains into the coma. Observations as the comet came out of solar conjunction seem to confirm our models.

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James Monroe (1758-1831) was appointed Secretary of State by President James Madison in 1811. He remained in this position until March, 1817, with the exception of the period from October 1, 1814, to February 28, 1815, when he was ad interim Secretary of State. Monroe encouraged President James Madison and Congress to declare war on Great Britain, feeling it would be the most effective way to change offensive British policies. The United States declared war on June 17, 1812, after which he served as Secretary of War. Monroe later became President of the United States from 1817 until 1824.

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Le relevé DEBRIS est effectué par le télescope spatial Herschel. Il permet d’échantillonner les disques de débris autour d’étoiles de l’environnement solaire. Dans la première partie de ce mémoire, un relevé polarimétrique de 108 étoiles des candidates de DEBRIS est présenté. Utilisant le polarimètre de l’Observatoire du Mont-Mégantic, des observations ont été effectuées afin de détecter la polarisation due à la présence de disques de débris. En raison d’un faible taux de détection d’étoiles polarisées, une analyse statistique a été réalisée dans le but de comparer la polarisation d’étoiles possédant un excès dans l’infrarouge et la polarisation de celles n’en possédant pas. Utilisant la théorie de diffusion de Mie, un modèle a été construit afin de prédire la polarisation due à un disque de débris. Les résultats du modèle sont cohérents avec les observations. La deuxième partie de ce mémoire présente des tests optiques du polarimètre POL-2, construit à l’Université de Montréal. L’imageur du télescope James-Clerk-Maxwell passe de l’instrument SCUBA à l’instrument SCUBA-2, qui sera au moins cent fois plus rapide que son prédécesseur. De même, le polarimètre suit l’amélioration et un nouveau polarimètre, POL-2, a été installé sur SCUBA-2 en juillet 2010. Afin de vérifier les performances optiques de POL-2, des tests ont été exécutés dans les laboratoires sub-millimétriques de l’Université de Western Ontario en juin 2009 et de l’Université de Lethbridge en septembre 2009. Ces tests et leurs implications pour les observations futures sont discutés.

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A lo largo de este proyecto, se analizarán los comienzos de la radio en las primeras décadas del siglo XX, teniendo como objetivo describir el desarrollo científico-tecnológico y las rivalidades político-militares de las potencias europeas de Reino Unido y Alemania. En primer lugar se verán los precursores de la radio que existían anteriormente al surgimiento de la radiotelegrafía como la telegrafía óptica, la telegrafía eléctrica o el teléfono. Al igual que los primeros investigadores, como James Clerk Maxwell o Heinrich Rudolf Hertz, gracias a los cuales el origen de la radio fue posible. También se analizará el contexto histórico-político de Reino Unido y Alemania donde se muestran las características de las dos grandes potencias del momento, el Imperio Británico y el Imperio Alemán. Además, la cada vez mayor importancia de la telegrafía sin hilos, hará necesaria una organización internacional, dando lugar a las Conferencias Internacionales de Radiotelegrafía y que enfrentarán a estas dos potencias por defender sus intereses. Guillermo Marconi, por parte de Reino Unido, y Telefunken, por parte de Alemania, serán las principales marcas comerciales de radiotelegrafía, no solo en sus respectivos países, sino también en el resto del mundo. Entre ambas compañías se verán las rivalidades por la incesante lucha de patentes, el desarrollo tecnológico y el control de los mercados. También se tratará el enfrentamiento directo que se produjo en la Primera Guerra Mundial, donde la radio jugaría un papel fundamental. Por último, se analizarán los comienzos de la radiodifusión en la segunda década del siglo XX, donde la radio ya estaba consolidada como uno de los medios de comunicación más importante de la época, capaz de llegar a todos los rincones del planeta y perfectamente integrada en la sociedad del momento. ABSTRACT. Throughout this project, it will be analyzed the beginning of the radio in the first decades of the XX century, having as goal to describe the scientific-technological development and the political-militaries opponents of the European’s countries, United kingdom and Germany. Firstly, it will be shown the radio’s precursors before the origin of the wireless telegraphy, like: optical telegraphy, electric telegraphy or telephone. Moreover, it will show the first researchers like: Clerk Maxwell or Heinrich Hertz, thanks to them, the origin of the radio was possible. In addition, it will analyze the historical-political context of United Kingdom and Germany, where it is shown the main features of the Britain Empire and the German Empire. Moreover, the importance of the telegraphy without wire will make necessary and international organization, resulting the International Conferences of Wireless Telegraphy and it will put together these main countries in order to protect their interests. Guglielmo Marconi, by United Kingdom, and Telefunken, by Germany, they will be the main commercials brand of the wireless telegraphy, not only in their countries, but also in all over the world. Between both companies will be seen the main competitions for their patens, the technology development and the market’s control. Moreover, it will be dealt the direct conflict in the First World of War, where the radio has a fundamental role. Finally, it will be analyze the beginning of the wireless broadcasting in the second decade of the XX century, where the radio was established as one of the most important media of the age, able to arrive at every places of the world and it was perfectly integrated in the society of that moment.

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A fugitive slave case in Maine, 1837-1841 / [by Henry S. Burrage] -- James Russell Lowell's two visits to Portland in 1857 / [by Henry S. Burrage] -- James Phinney Baxter / [by Henry S. Burrage] -- Franklin Simmons, sculptor / [by Henry S. Burrage] -- The Maine Historical Society in Brunswick, 1822-1880 / by Kenneth C.M. Sills -- The Maine Historical Society at Portland / by Augustus F. Moulton.

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Correspondence,a large part of which relates to negotiations for the Louisiana Purchase and the Monroe-Pinkney treaty,the War of 1812,the Florida Purchase, South American independence, and Virginia politics; an account ...

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Published in 1880 under title: The life of Gen. James A. Garfield.

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Mode of access: Internet.