Ernst Florens Friedrich Chladni (1756–1827) and the origins of modern meteorite research     

Ursula B. Marvin 《Meteoritics & planetary science》1996,31(5):545-588

Abstract— In 1794, Ernst F. F. Chladni published a 63-page book Über den Ursprung der von Pallas gefundenen und anderer ihr änlicher Eisenmassen und über einige damit in Verbindung stehende Naturerscheinungen in which he proposed that meteor-stones and iron masses enter the atmosphere from cosmic space and form fireballs as they plunge to Earth. These ideas violated two strongly held contemporary beliefs: (1) fragments of rock and metal do not fall from the sky, and (2) no small bodies exist in space beyond the Moon. From the beginning, Chladni was severely criticised for basing his hypotheses on historical eyewitness reports of falls which others regarded as folk tales and for taking gross liberties with the laws of physics. Eight years later, the study of fallen stones and irons was established as a valid field of investigation. Today, some scholars credit Chladni with founding meteoritics as a science; others regard his contributions as scarcely worthy of mention. Writings by his contemporaries suggest that Chladni's book alone would not have led to changes of prevailing theories; thus, he narrowly escaped the fate of those scientists who propose valid hypotheses prematurely. However between 1794 and 1798, four falls of stones were witnessed and widely publicized. There followed a series of epoch-making analyses of fallen stones and “native irons” by the chemist Edward C. Howard and the mineralogist Jacques-Louis de Bournon. They showed that all the stones were much alike in texture and composition but significantly different from the Earth's known crustal rocks. Of primary importance was Howard's discovery of nickel in the irons and the metal grains of the stones. This linked the two as belonging to the same natural phenomenon. The chemical results, published in 1802 February, persuaded leading scientists in England, France, and Germany that bodies fall from the sky. Within a few months, chemists in France reported similar results and a new field of study was inaugurated internationally—although opposition lingered on until 1803 April, when nearly 3,000 stones fell at L'Aigle in Normandy and transformed the last skeptics into believers. Chladni immediately received full credit for his hypothesis of falls, but decades passed before his linking of falling bodies with fireballs received general acceptance. His hypothesis of their origin met with strong resistance from those who argued that stones formed within the Earth's atmosphere or were ejected by lunar volcanoes. After 1860, when both of these hypotheses were abandoned, there followed a century of debate between proponents of an interstellar vs. a planetary origin. Not until the 1950s did conclusive evidence of their elliptical orbits establish meteorite parent bodies as members of the solar system. Thus, nearly 200 years passed before the questions of origin that Chladni raised finally were resolved.  相似文献   

THE METEORITICAL SOCIETY: 1933 to 1993     

Ursula B. Marvin 《Meteoritics & planetary science》1993,28(3):261-314

Abstract— In August, 1933, at the Field Museum of Natural History in Chicago, The Society for Research on Meteorites was founded with an enrollment of 57 charter members and Frederick C. Leonard and Harvey H. Nininger as the first President and Secretary-Treasurer, respectively. Within five years, the Society had doubled in size, with members from the U.S.A. and ten other nations. Annual meetings were suspended during World War II (1942 through 1945) and when it reconvened in 1946 the members adopted the name “The Meteoritical Society”. By that time personal and professional antagonisms had arisen that threatened to fragment the Society and led, in 1949, to the resignation of Nininger and his wife. Throughout the 1950s the Society was widely regarded as a small, disorganized and essentially moribund organization. Revitalization of the Society began in the early 1960s after the advent of the Space Age when the Society steadily gained members with expertise in mineralogy, petrology, isotope geochemistry, electron microprobe and neutron activation analysis, and impact dynamics. When Nininger was persuaded rejoin in 1963, he found a renewed Society. In the election year of 1966 a group of youthful insurgents nominated an alternate slate to that proposed by the Council and won every contested seat on the Council except that of the Editor. The Society's first publication Contributions of the Society for Research on Meteorites was published as a section of Popular Astronomy and from 1935 to 1946 reprints of the items (articles, reviews, and notices) were bound and distributed separately each year. When the Society changed its name in 1946, its journal became Contributions of the Meteoritical Society, which continued publication until Popular Astronomy ceased publication in 1952. A new journal, Meteoritics, was instituted in 1953. After 1956, its publication lapsed for six years but began again in 1963 and has continued under the leadership of four successive editors becoming one of the most frequently cited geoscience journals. In 1970, the Society also became a co-sponsor with The Geochemical Society of Geochimica et Cosmochimica Acta, but the future of this arrangement remains in doubt. In 1938, the Society had gained considerable prestige by its acceptance as a full Affiliate of the American Association for the Advancement of Science, but in view of its increasingly international membership and activities the Society terminated its affiliation with the AAAS in 1976. Again in response to its international status, in 1992 The Meteoritical Society affiliated with the International Union of Geological Sciences. The Society held its first annual meeting outside North America at the Universität Tübingen in West Germany in 1971. Subsequently, it met in Europe every second year until 1990, when it met at Perth in Western Australia. During the 1980s, the membership of the Society grew to more than 900 and the annual meetings attracted between 300 and 450 participants. As meteoritical research continues to probe the borderlands with astrophysics, planetary science, and terrestrial geology, and as younger members assume leadership roles, a productive future seems assured for both meteoritical science and The Meteoritical Society.  相似文献   

Are metal-induced hypersensitivities in harbor seals associated with liver function?     

Kakuschke A  Valentine-Thon E  Griesel S  Fonfara S  Siebert U  Prange A 《Marine pollution bulletin》2011,62(8):1891-1894

Environmental exposure to metals is believed to affect marine mammal health adversely including immunosuppression or acute as well as chronic inflammatory processes leading to hypersensitivities or autoimmune diseases. Metal-specific hypersensitivities were found in several pinnipeds of the North Sea. However, hypersensitivity is a complex phenomenon whose characteristics are still not completely understood; in particular, effects on health are not well established. In the present study, we compared basic hematological and biochemical parameters of seals with and without metal-specific hypersensitivities. We found altered hematological parameters and liver enzyme patterns in seals with a metal-induced hypersensitivity, including a reduction in macrophages, an increase in lymphocytes, and elevated levels of lactate dehydrogenase. These findings support the suggestion of a chronic influence of metal pollutants on the health of marine mammals of the North Sea.  相似文献   

Geoacoustic character,sedimentology and chronology of a cross-shelf Holocene sediment deposit off Cabo Frio,Brazil (southwest Atlantic Ocean)     

Ursula Mendoza  Arthur Ayres Neto  Rodrigo C. Abuchacra  Cátia Fernandes Barbosa  Alberto G. Figueiredo Jr.  Manoela C. Gomes  Andre L. Belem  Ramsés Capilla  Ana Luiza S. Albuquerque 《Geo-Marine Letters》2014,34(4):297-314

The Cabo Frio region in the state of Rio de Janeiro, southeast coast of Brazil, is characterized by a local coastal upwelling system and converging littoral sediment transport systems that are deflected offshore at Cabo Frio, as a consequence of which a thick cross-shelf sediment deposit has developed over time. To investigate the evolution of this muddy deposit, geophysical, sedimentological and geochemical data from four sediment cores (3.8–4.1 m in length) recovered in water depths between 88 and 141 m were analyzed. The high-resolution seismic data show variable sediment thicknesses ranging from 1 to 20 m, comprising two sedimentary units separated by a high-impedance layer at a depth of about 10 m below the seafloor at the coring sites. According to the available age datings, the upper sedimentary unit is late Pleistocene to Holocene in age, whereas the lower unit (not dated) must, by implication, be entirely Pleistocene in age. The boomer-seismic reflection signal can be divided into three echo-types, namely transparent (inner shelf), stratified (middle shelf) and reflective (outer shelf), each type seemingly related to the local sediment composition. The upper 4 m of the upper sedimentary unit is dominated by silty sediment on the middle shelf, and by upward-fining sediments (silty sand to sandy silt) on the inner and outer shelf. The downcore trends of P-wave velocity, gamma-ray density and acoustic impedance are largely similar, but generally reversed to those of water and organic carbon contents. Total organic carbon contents increase with decreasing mean grain size, periodic fluctuations suggesting temporal changes in the regional hydrodynamics and primary productivity fuelled by the local upwelling system. The reconstruction of sedimentation rates in the course of the Holocene is based on 35 AMS age datings of organic material recovered from variable downcore depths. These range from a maximum of 13.3 cm/decade near the base of the inner shelf core (7.73–7.70 ka BP) to generally very low values (<0.11 cm/century) over the last thousand years in all cores. Over the last 6 ka there appear to have been three distinct sedimentation peaks, one between 6 and 5 ka BP, another between 4 and 3 ka PB, and one around 1 ka BP. Due to different time intervals between dates, not every peak is equally well resolved in all four cores. Based on the similar sedimentology of the inner and outer shelf cores, an essentially identical sedimentation model is proposed to have been active in both cases, albeit at different times. Thus, already during the last glacial maximum, alongshore sediment transport was deflected offshore by a change in shoreline orientation caused by the Cabo Frio structural high. The source of terrigenous material was probably a barrier-island complex that was subsequently displaced landward in the course of sea-level rise until it stabilized some 6.5 ka BP along the modern coast.  相似文献   

Cultivating the sustainable city: urban agriculture policies and gardening projects in Minneapolis,Minnesota     

Ursula Lang 《Urban geography》2013,34(4):477-485

In the past 20 years, municipal governments across the United States have increasingly tried to incorporate environmental efforts into city business and policies. Urban sustainability has become the key concept around which such activities are organized. Official sustainability plans are most often implemented through indicators and metrics. In Minneapolis, Minnesota, urban gardening, in a variety of forms, has been the focus of ongoing citizen- and NGO-led environmental efforts, as well as municipal measures of sustainability. Here, debates around the recent adoption of a city urban agriculture policy, as well as a program to encourage the installation of raingardens in neighborhoods across the city, reveal some of the rich variations in gardening practices and spaces. These far exceed the relatively narrow official focus on sustainability indicators. Better understanding how urban sustainability initiatives might work with, but also move beyond, indicators may provide directions toward wider visions of sustainable urban life.  相似文献   

Simulation of oceanic volume transports through Fram Strait 1995–2005     

Kerstin Fieg  Rüdiger Gerdes  Eberhard Fahrbach  Agnieszka Beszczynska-Möller  Ursula Schauer 《Ocean Dynamics》2010,60(3):491-502

We discuss the model representation of volume transports through one of the most climate-relevant ocean passages, the Fram Strait. We compare results from a coupled ocean–sea ice model with different resolutions (∼1/12° and ∼1/4°) and measurements from a mooring array along 79° N. The 1/4° model delivers a realistic mean climate state and realistic net volume transports. However, this model fails to reproduce the observed intense barotropic recirculation that reaches far north in Fram Strait. This recirculation is captured in the higher resolution version of the model. Other differences exist in the circulation over the East Greenland Shelf and in the temperature of Atlantic waters in the Fram Strait region as well as in surface heat fluxes. We find that a combination of high-resolution model results and long-term measurements can improve the interpretation of measured and simulated processes and reduce the uncertainties in exchange rates between Arctic and the North Atlantic.  相似文献   

Predation and competition effects on the size diversity of aquatic communities     

Xavier D. Quintana  Matías Arim  Anna Badosa  José María Blanco  Dani Boix  Sandra Brucet  Jordi Compte  Juan J. Egozcue  Elvira de Eyto  Ursula Gaedke  Stéphanie Gascón  Luis Gil de Solá  Kenneth Irvine  Erik Jeppesen  Torben L. Lauridsen  Rocío López-Flores  Thomas Mehner  Susana Romo  Martin Søndergaard 《Aquatic Sciences - Research Across Boundaries》2015,77(1):45-57

  相似文献   

A diatom-inferred record of reduced effective precipitation during the Last Glacial Coldest Phase (28.8–18.0?cal kyr BP) and increasing Holocene seasonality at Lake Pupuke, Auckland, New Zealand     

Thomas Stephens  Daniel Atkin  Ursula Cochran  Paul Augustinus  Michael Reid  Andrew Lorrey  Philip Shane  Alayne Street-Perrott 《Journal of Paleolimnology》2012,48(4):801-817

A continuous, 1,420-cm sediment record from Lake Pupuke, Auckland, New Zealand (37°S) was analysed for diatom taxonomy, concentration and flux. A New Zealand freshwater diatom transfer function was applied to infer past pH, electrical conductivity, dissolved reactive phosphorus and chlorophyll a. A precise, mixed-effect regression model of age versus depth was constructed from 11 tephra and 13 radiocarbon dates, with a basal age of 48.2?cal kyr BP. Diatom-inferred changes in paleolimnology and climate corroborate earlier inferences from geochemical analyses (Stephens et al. 2012), with respect to the timing of marked climate changes in the Last Glacial Coldest Phase (LGCP; 28.8?C18.0?cal kyr BP), the Last Glacial Interglacial Transition (LGIT; 18.0 to ca. 12?C10?cal kyr BP) and the Holocene, the onset of which is difficult to discern from LGIT amelioration, but which includes an early climatic optimum (10.2?C8.0?cal kyr BP). The LGCP is readily defined by a reduction in lake level and effective precipitation, whereas the LGIT represents a period of rising lake level, with greater biomass during the Holocene. There was limited change in diatom assemblage structure, influx or inferred water quality during a Late Glacial Reversal (LGR; 14.5?C13.8?cal kyr BP), associated with heightened erosional influx. In contrast, an LGIT peak in paleoproductivity is recorded by increased diatom influx from 13.8 to 12.8?cal kyr BP. Changes in sediment influx and biomass record complex millennial-scale events attuned to the Antarctic Cold Reversal (ACR; 14.5?C12.8?cal kyr BP). Additional millennial-scale environmental change is apparent in the Holocene, with marked changes in lake circulation beginning at 7.6?cal kyr BP, including the onset of seasonal thermal stratification and rapid species turnover at 5.7?cal kyr BP. The most rapid diatom community turnover accompanied widely varying nutrient availability and greater seasonality during the last 3.3?cal kyr. Rising seasonality appears to have been linked to strengthened Southern Westerlies at their northern margins during the middle and late Holocene.  相似文献   

Soil conditions in damaged North Queensland mangroves     

Ursula L. Kaly  Gonneke Eugelink  Alistar I. Robertson 《Estuaries and Coasts》1997,20(2):291-300

Selected physical, chemical, and biological characteristics of soils in mechanically damaged North Queensland mangrove forests were examined and compared with undisturbed controls. Soils in nine forests were tested in a factorial sampling programme designed to examine effects of (i) severity of mechanical damage to forests (severely damaged: trees removed and soils disrupted by bulldozing; versus damaged: trees felled no bulldozing; versus controls: trees and soils undisturbed), (ii) soil depth, (iii) forests (10s–100s km apart), and (iv) sites within forests (10s–100s m apart). Characteristics examined were soil compaction, grain size, pH, percent by weight of total C, N, P, K, S, and Fe and the density of crab burrows. Three of the 10 variables examined: total N, total P, and density of crab holes, decreased with mechanical damage to forests. The loss of potentially-limiting nutrients and of an important bioturbator at severely damaged sites suggests the need for further experimental investigation of soil characteristics with respect to natural regeneration and efforts of mangrove restoration.  相似文献   

MELIMEX,an experimental heavy metal pollution study: Chemical speciation and biological availability of copper in lake water     

Dr. Peter Baccini  Ursula Suter 《Aquatic Sciences - Research Across Boundaries》1979,41(2):291-314

The chemical speciation of dissolved copper was investigated in waters from the limno-corrals of the MELIMEX project and compared with speciation data from other Swiss lakes. Copper is complexed primarily by organic ligands having molecular sizes between 10⁴ and 10³ daltons. The mean concentration of the ligands is approximately 5×10⁻⁷ mole/mg DOC. The conditional stability constants (pH=8.8) are about 10¹¹. An increased metal load did not induce an increase of binding ligands. A comparison of calculated Cu²⁺ concentration with corresponding copper contents in the biomass leads to the conclusion that organic ligands and pH are the most important factors in deciding the biological availability of copper. However the sorption capacity of the biomass depends as well on the variety of plankton species.  相似文献