967 resultados para 17th and 18th centuries


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Writers on military matters from the 14th century until the late 18th century either regretted the decadence of their times compared with Antiquity, or they saw no great change in military affairs since Antiquity. Few saw a revolutionary change ushered in by gunpowder, although this number increased since the great "querelle" about the Ancients and the Moderns under Louis XIV. In the early 19th century, the balance tipped, and few would have denied that technology had profoundly changed warfare. All this is a far cry, however, from any contemporary perception of a "Military Revolution" in the 16th and 17th centuries.

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The Sun-Earth connection is studied using long-term measurements from the Sun and from the Earth. The auroral activity is shown to correlate to high accuracy with the smoothed sunspot numbers. Similarly, both geomagnetic activity and global surface temperature anomaly can be linked to cyclic changes in the solar activity. The interlinked variations in the solar magnetic activity and in the solar irradiance cause effects that can be observed both in the Earth's biosphere and in the electromagnetic environment. The long-term data sets suggest that the increase in geomagnetic activity and surface temperatures are related (at least partially) to longer-term solar variations, which probably include an increasing trend superposed with a cyclic behavior with a period of about 90 years.

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A Hale cycle, one complete magnetic cycle of the Sun, spans two complete Schwabe cycles (also referred to as sunspot and, more generally, solar cycles). The approximately 22-year Hale cycle is seen in magnetic polarities of both sunspots and polar fields, as well as in the intensity of galactic cosmic rays reaching Earth, with odd- and even-numbered solar cycles displaying qualitatively different waveforms. Correct numbering of solar cycles also underpins empirical cycle-to-cycle relations which are used as first-order tests of stellar dynamo models. There has been much debate about whether the unusually long solar cycle 4 (SC4), spanning- 1784–1799, was actually two shorter solar cycles combined as a result of poor data coverage in the original Wolf sunspot number record. Indeed, the group sunspot number does show a small increase around 1794–1799 and there is evidence of an increase in the mean latitude of sunspots at this time, suggesting the existence of a cycle ‘‘4b’’. In this study, we use cosmogenic radionuclide data and associated reconstructions of the heliospheric magnetic field (HMF) to show that the Hale cycle has persisted over the last 300 years and that data prior to 1800 are more consistent with cycle 4 being a single long cycle (the ‘‘no SC4b’’ scenario). We also investigate the effect of cycle 4b on the HMF using an open solar flux (OSF) continuity model, in which the OSF source term is related to sunspot number and the OSF loss term is determined by the heliospheric current sheet tilt, assumed to be a simple function of solar cycle phase. The results are surprising; Without SC4b, the HMF shows two distinct peaks in the 1784–1799 interval, while the addition of SC4b removes the secondary peak, as the OSF loss term acts in opposition to the later rise in sunspot number. The timing and magnitude of the main SC4 HMF peak is also significantly changed by the addition of SC4b. These results are compared with the cosmogenic isotope reconstructions of HMF and historical aurora records. These data marginally favour the existence of SC4b (the ‘‘SC4b’’ scenario), though the result is less certain than that based on the persistence of the Hale cycle. Thus while the current uncertainties in the observations preclude any definitive conclusions, the data favour the ‘‘no SC4b’’ scenario. Future improvements to cosmogenic isotope reconstructions of the HMF, through either improved modelling or additional ice cores from well-separated geographic locations, may enable questions of the existence of SC4b and the phase of Hale cycle prior to the Maunder minimum to be settled conclusively.

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The aim of this paper is to point out benefits as well as disadvantages associated with the use of locally available, not necessarily standardized, components in stand-alone electrical power systems at rural locations. Advantages and challenges arising when the direct involvement in design, construction and maintenance of the power system is reserved to people based in the area of implementation are discussed. The presented research is centered around one particular PV-diesel hybrid system in Tanzania; a case study in which technical and social aspects related to the particular power system are studied.

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Sociologisk Forsknings digitala arkiv

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Este trabalho teve o principal objetivo de contribuir para o entendimento do contexto social que circunda empreendedores inovadores brasileiros e espanhóis que emergem em seus próprios países de origem, procurando mapear e entender relações sociais relevantes estabelecidas durante o delicado período de emergência de seus empreendimentos no final do século XX e começo do XXI. Autores alinhados com o pensamento da sociologia econômica foram utilizados como referência para a determinação das perguntas de pesquisa, que provocaram a realização de um estudo comparativo entre empreendedores finalistas de um mesmo prêmio atribuído a empreendedores inovadores brasileiros e espanhóis. No total, 19 empreendedores oriundos de setores emparelhados em ambos os países foram entrevistados e documentos sobre eles e seus empreendimentos foram levantados, possibilitando verificar, entre outras coisas, a influência relativamente homogênea do contexto social de ambos os países no período de emergência de empreendimentos fundados por empreendedores advindos de classes sociais mais elevadas destas sociedades, com especial ênfase nas complicadas características do padrão de financiamento dos empreendimentos, no aumento consistente do apoio social e público ao empreendedorismo, no elevado envolvimento emocional que os empreendedores estabelecem com seus empreendimentos e no peculiar papel das relações de confiança construídos entre os empreendedores, seus sócios e funcionários

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The aim of the present study was to investigate the effects of hydrocortisone during the prenatal period and its later repercussions on the fertility and sexual behavior of male rats. Pregnant rats were treated (s.c.) with hydrocortisone acetate, at 1.5 mg/day on the 17th, 18th, and 19th days of gestation. Decreased body weight and no alteration in anogenital distance were observed in male offspring. Adulthood, presented reductions of body weight, plasma testosterone levels, and seminal-vesicle wet weight without secretion as well as no alteration in the wet weights of the testes, epididymis, and seminal vesicle with secretion in the treated group. Males exposed to hydrocortisone during the prenatal period were able to mate with normal females, which became pregnant but exhibited an increased number of post-implantation losses. In spite of this, these treated males exhibited decreased male sexual behavior and the appearance of female sexual behavior after these male rats were castrated and pretreated with exogenous estrogen. These results indicate that exposure to hydrocortisone in the later stages of pregnancy may have a long-term effect on the fertility and sexual behavior of mate rats, suggesting an incomplete masculinization and defeminization of the central nervous system. (C) 2003 Elsevier B.V. (USA). All rights reserved.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Essays on the history of Brazilian dipterology. III. Three remarkable notices from the 18th century, mainly related to myiasis-producing flies (Cochliomyia and Dermatobia). This paper registers reports about dipterans made by three Portuguese who lived in Brazil during the 18th century. Luiz Gomes Ferreira, in his book "Erario mineral" ["Mineral revenue"], wrote curious passages related with myiasis-causing flies of the genus Cochliomyia. Jose Rodrigues de Mello registered, in Latin verses, the folklore for curing myiases caused by Cochliomyia hominivorax in cattle. Luiz dos Santos Vilhena, in the last of his twenty letters dealing with several aspects of life in Brazil, made reference to horseflies, human bot flies and mosquitos.

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This paper registers reports about dipterans made by three Portuguese who lived in Brazil during the 18th century. Luiz Gomes Ferreira, in his book "Erário mineral" ["Mineral revenue"], wrote curious passages related with myiasis-causing flies of the genus Cochliomyia. José Rodrigues de Mello registered, in Latin verses, the folklore for curing myiases caused by Cochliomyia hominivorax in cattle. Luiz dos Santos Vilhena, in the last of his twenty letters dealing with several aspects of life in Brazil, made reference to horseflies, human bot flies and mosquitos.

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Our understanding of the climate of northern Sweden during the late Holocene is largely dependent on proxy-data series. These datasets remain spatially and temporally sparse and instrumental series are rare prior to the mid 19th century. Nevertheless, the glaciology and paleo-glaciology of the region has a strong potential significance for the exploration of climate change scenarios, past and future. The aim of this thesis is to investigate the 19th and 20th century climate in the northern Swedish mountain range. This provides a good opportunity to analyse the natural variability of the climate before the onset of the industrial epoch. Developing a temporal understanding of fluctuations in glacier front positions and glacier mass balance that is linked to a better understanding of their interaction and relative significance to climate is fundamental in the assessment of past climate. I have chosen to investigate previously unexplored temperature data from northern Sweden from between 1802 and 1860 and combined it with a temperature series from a synoptic station in Haparanda, which began operation in 1859, in order to create a reliable long temperature series for the period 1802 to 2002. I have also investigated two different glaciers, Pårteglaciären and Salajekna, which are located in different climatic environments. These glaciers have, from a Swedish perspective, long observational records. Furthermore, I have investigated a recurring jökulhlaup at the glacier Sälkaglaciären in order to analyse glacier-climate relationships with respect to the jökulhlaups. A number of datasets are presented, including: glacier frontal changes, in situ and photogrammetric mass balance data, in situ and satellite radar interferometry measurements of surface velocity, radar measurements, ice volume data and a temperature series. All these datasets are analysed in order to investigate the response of the glaciers to climatic stimuli, to attribute specific behaviour to particular climates and to analyse the 19th and 20th century glacier/climate relationships in northern Sweden. The 19th century was characterized by cold conditions in northern Sweden, particularly in winter. Significant changes in the amplitude of the annual temperature cycle are evident. Through the 19th century there is a marked decreasing trend in the amplitude of the data, suggesting a change towards a prevalence of maritime (westerly) air masses, something which has characterised the 20th century. The investigations on Salajekna support the conclusion that the major part of the 19th century was cold and dry. The 19th century advance of Salajekna was probably caused by colder climate in the late 18th and early 19th centuries, coupled with a weakening of the westerly airflow. The investigations on Pårteglaciären show that the glacier has a response time of ~200 years. It also suggests that there was a relatively high frequency of easterly winds providing the glacier with winter precipitation during the 19th century. Glaciers have very different response times and are sensitive to different climatic parameters. Glaciers in rather continental areas of the Subarctic and Arctic can have very long response times because of mass balance considerations and not primarily the glacier dynamics. This is of vital importance for analyzing Arctic and Subarctic glacier behaviour in a global change perspective. It is far from evident that the behaviour of the glacier fronts today reflects the present climate.