6,960 research outputs found
Evidence for Stagnation of the Harvard Sublobe (Lake Michigan Lobe) in Northeastern Illinois, U.S.A., from 24Â 000 to 17Â 600Â BP and Subsequent Tundra-Like Ice-Marginal Paleoenvironments from 17Â 600 to 15Â 700Â BP
Glacial deposits of the last glaciation associated with the Harvard sublobe (Lake Michigan lobe) in northeastern Illinois, U.S.A., occur between sediment with dateable organics. The lower organics include fragments of Picea sp. as young as 24 000 ± 270 BP. The supraglacial organics occur sparsely in laminated silt and fine sand in landforms that are positioned relatively high on the landscape, such as deposits from ice-walled lakes. These terrestrial organics yield ages that are 2500 to 1300 14C years older than organics at the base of sediment successions in nearby kettle basins. Basal 14C ages from four upland sites range from 17 610 ± 270 to 16 120 ± 80 BP. Our revised time-distance diagram of the Harvard sublobe now reflects a period of stagnation from 24 000 to about 17 600 BP. The supraglacial lacustrine silt yielded plant macrofossil assemblages of primarily tundra plants, including Salix herbacea and Dryas integrifolia. These plants likely grew in supraglacial and ice-marginal environments. The ostracode fauna include Cytherissa lacustris and Limnocythere friabilis. Geomorphic relations and ostracode ecology indicate that more than 17 m of ice buttressed some of the supraglacial lakes.Les sĂ©diments glaciaires associĂ©s au sous-lobe de Harvard, dans le Nord-Est de lâIllinois, sont intercalĂ©s dans des sĂ©diments dont la matiĂšre organique peut ĂȘtre datĂ©e. Des fragments de Picea sp. sont prĂ©sents dans les couches sous-jacentes et remontent au plus Ă 24 000 ± 270 BP. La matiĂšre organique sus-jacente est dissĂ©minĂ©e dans les limons laminĂ©s et les sables fins de dĂ©pĂŽts de lacs de barrage glaciaire perchĂ©s. Cette matiĂšre organique livre des Ăąges 14C qui sont de 2500 Ă 1300 ans plus vieux que la matiĂšre organique de la base des sĂ©diments des marmites glaciaires (kettles). Les Ăąges 14C de quatre sites perchĂ©s vont de 17 610 ± 270 Ă 16 120 ± 80 BP. Notre rĂ©vision du diagramme distance-temps du sous-lobe de Harvard traduit lâexistence dâune pĂ©riode de stagnation glaciaire entre 24 000 et 17 600 BP. Le limon lacustre sus-jacent contient des assemblages macrofossiles de toundra, avec Salix herbacea et Dryas integrifolia. Ces plantes croissaient dans des milieux proches des glaces. Le contexte gĂ©omorphologique et lâĂ©cologie des ostracodes (Cytherissa lacustris et Limnocythere friabilis) indiquent que certains lacs supraglaciaires Ă©taient Ă©tayĂ©s par plus de 17 m de glace
The Mg/Caâtemperature relationship in brachiopod shells: calibrating a potential palaeoseasonality proxy
Brachiopods are long-lived, long-ranging, extant organisms, of which some groups precipitate a relatively diagenetically stable low magnesium calcite shell. Previous work has suggested that the incorporation of Mg into brachiopod calcite may be controlled by temperature (Brand et al., 2013). Here we build upon this work by using laser ablation sampling to define the intra-shell variations in two modern brachiopod species,Terebratulina retusa (Linnaeus, 1758) and Liothyrella neozelanica (Thomson, 1918). We studied three T. retusa shells collected live from the Firth of Lorne, Scotland, which witnessed annual temperature variations on the order of 7 °C, in addition to four L. neozelanica shells, which were dredged from a water depth transect (168â1488 m) off the north coast of New Zealand. The comparison of intra-shell Mg/Ca profiles with shell ÎŽ<sup>18</sup>O confirms a temperature control on brachiopod Mg/Ca and supports the use of brachiopod Mg/Ca as a palaeoseasonality indicator. Our preliminary temperature calibrations are Mg/Ca = 1.76 ± 0.27 e<sup>(0.16 ± 0.03)T</sup>, R<sup>2</sup> = 0.75, for T. retusa and Mg/Ca = 0.49 ± 1.27 e<sup>(0.2 ± 0.11)T</sup>, R<sup>2</sup> = 0.32, for L. neozelanica (errors are 95% confidence intervals)
Grown organic matter as a fuel raw material resource
An extensive search was made on biomass production from the standpoint of climatic zones, water, nutrients, costs and energy requirements for many species. No exotic species were uncovered that gave hope for a bonanza of biomass production under culture, location, and management markedly different from those of existing agricultural concepts. A simulation analysis of biomass production was carried out for six species using conventional production methods, including their production costs and energy requirements. These estimates were compared with data on food, fiber, and feed production. The alternative possibility of using residues from food, feed, or lumber was evaluated. It was concluded that great doubt must be cast on the feasibility of producing grown organic matter for fuel, in competition with food, feed, or fiber. The feasibility of collecting residues may be nearer, but the competition for the residues for return to the soil or cellulosic production is formidable
Revealing Relationships among Relevant Climate Variables with Information Theory
A primary objective of the NASA Earth-Sun Exploration Technology Office is to
understand the observed Earth climate variability, thus enabling the
determination and prediction of the climate's response to both natural and
human-induced forcing. We are currently developing a suite of computational
tools that will allow researchers to calculate, from data, a variety of
information-theoretic quantities such as mutual information, which can be used
to identify relationships among climate variables, and transfer entropy, which
indicates the possibility of causal interactions. Our tools estimate these
quantities along with their associated error bars, the latter of which is
critical for describing the degree of uncertainty in the estimates. This work
is based upon optimal binning techniques that we have developed for
piecewise-constant, histogram-style models of the underlying density functions.
Two useful side benefits have already been discovered. The first allows a
researcher to determine whether there exist sufficient data to estimate the
underlying probability density. The second permits one to determine an
acceptable degree of round-off when compressing data for efficient transfer and
storage. We also demonstrate how mutual information and transfer entropy can be
applied so as to allow researchers not only to identify relations among climate
variables, but also to characterize and quantify their possible causal
interactions.Comment: 14 pages, 5 figures, Proceedings of the Earth-Sun System Technology
Conference (ESTC 2005), Adelphi, M
Categories of First-Order Quantifiers
One well known problem regarding quantifiers, in particular the 1storder
quantifiers, is connected with their syntactic categories and denotations.
The unsatisfactory efforts to establish the syntactic and ontological categories
of quantifiers in formalized first-order languages can be solved by means of the
so called principle of categorial compatibility formulated by Roman Suszko,
referring to some innovative ideas of Gottlob Frege and visible in syntactic
and semantic compatibility of language expressions. In the paper the principle
is introduced for categorial languages generated by the Ajdukiewiczâs classical
categorial grammar. The 1st-order quantifiers are typically ambiguous. Every
1st-order quantifier of the type k \u3e 0 is treated as a two-argument functorfunction
defined on the variable standing at this quantifier and its scope (the
sentential function with exactly k free variables, including the variable bound
by this quantifier); a binary function defined on denotations of its two arguments
is its denotation. Denotations of sentential functions, and hence also
quantifiers, are defined separately in Fregean and in situational semantics.
They belong to the ontological categories that correspond to the syntactic
categories of these sentential functions and the considered quantifiers. The
main result of the paper is a solution of the problem of categories of the
1st-order quantifiers based on the principle of categorial compatibility
Deformation and rupture of armour grade steel under localised blast loading
A series of 30 blast experiments were conducted on monolithic steel panels of two armour grade steels. The two steels evaluated were a high hardness armour (HHA) and a rolled homogenous armour (RHA). Tests were conducted at two standoff distances using a fixed charge diameter. The charge weight was varied to produce specific magnitudes of blast loading and to isolate the rupture threshold of each material. The results indicated that the HHA steel, generally reserved for ballistic protection, outperformed a more ductile RHA steel in terms of both its deformation resistance and rupture threshold. Optical and scanning electron microscopy was utilised for fractographic analysis of the ruptured plates. The failure of the steels in this investigation was found to be initiated by slant shear fracture with little to no localised thinning. This is in contrast to the tensile instability and ductile tearing predicted by established theories of plate rupture for mild steels under blast loading. The deformation and rupture of the candidate steels was analysed for all experimental conditions and compared to current empirical models based on a non-dimensional impulse parameter. While deformation behaviour is well predicted, the blast rupture threshold of the armour grade steels is poorly captured by current empirical modelling approaches. The identified shear fracture mode leads to lower energy absorption capabilities of the material compared to more ductile tensile failure
SOYMOD OARDC: a dynamic simulator of soybean growth, development, and seed yield. I. Theory, structure, and validation
Geographical information retrieval with ontologies of place
Geographical context is required of many information retrieval tasks in which the target of the search may be documents, images or records which are referenced to geographical space only by means of place names. Often there may be an imprecise match between the query name and the names associated with candidate sources of information. There is a need therefore for geographical information retrieval facilities that can rank the relevance of candidate information with respect to geographical closeness of place as well as semantic closeness with respect to the information of interest. Here we present an ontology of place that combines limited coordinate data with semantic and qualitative spatial relationships between places. This parsimonious model of geographical place supports maintenance of knowledge of place names that relate to extensive regions of the Earth at multiple levels of granularity. The ontology has been implemented with a semantic modelling system linking non-spatial conceptual hierarchies with the place ontology. An hierarchical spatial distance measure is combined with Euclidean distance between place centroids to create a hybrid spatial distance measure. This is integrated with thematic distance, based on classification semantics, to create an integrated semantic closeness measure that can be used for a relevance ranking of retrieved objects
Sexual harassment and abuse in sport: The research context
This special issue of the Journal of Sexual Aggression draws on the contributions to a Symposium on âSexual Harassment in Sport â Challenges for Sport Psychology in the New Millenniumâ, held at the Xth Congress of the International Society for Sport Psychology, Skiathos, Greece from May 28th to June 2nd 2001. The symposium, which was organised by the authors of this editorial, was intended to move forward the international research agenda on sexual harassment and abuse in sport and to examine professional practice issues for sport psychologists. It was clear from the attendance of over 60 delegates at that symposium that international interest in this subject is growing. Further evidence of this came from the attendance of 26 members states â from Azerbaijan to Sweden - at a Council of Europe seminar on The Protection of Children, Young People and Women in Sport, held in Helsinki in September 2001
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