100,774 research outputs found
Applications of microstructured fibre technology in aerospace and defence
No full textThe EMRS DTC project "Photonic Fibres for Active Sensor Systems" aimed to assess the potential impact of microstructured fibres for security and defence applications. Results achieved have suggested enormous potential for these novel fibre types to influence the next generation of photonic systems for security and defence applications. However, it is important to establish where the fibres can offer the greatest advantages and what research still needs to be done to drive the technology towards real platform solutions
MINERAL DUST ELEMENTAL COMPOSITION OVER THE LAST 220 KYR FROM THE EPICA-DOME C ICE CORE (EAST ANTARCTICA)
No full textMineral windblown aerosol (dust) represents a small fraction of the total mass of atmospheric aerosols. However, it may play an important role in climate and, in turn, it is itself sensitive to climatic changes.The investigation of the temporal variability of dust flux as well as the changes of its mineralogical composition within different climatic periods offers a unique way of assessing the source-related environmental changes, the variation in atmospheric circulation, and the potential influence of dust on biogeochemical cycles, for several key elements (such as Si and Fe). The mineral composition of dust found in ice cores is still poorly known, because few techniques are able to provide information on the chemical composition of the insoluble aerosol fraction, because of the very low mass of dust usually present in polar ice samples. Total volume of mineral content is provided by Coulter Counter measurements, and the dust record shows higher dust input during glacial periods than during interglacials (Delmonte et al., 2004). Sr and Nd isotopic tracers for identification of dust provenance to East Antarctica suggest southern South America as the dominant common source for dust in glacial periods of the late Pleistocene (Delmonte et al., 2004), whereas dust provenance during interglacials periods is still highly uncertain. Elemental composition of mineral dust from the Dome C ice core (75ø 06' S, 123ø 21' E) drilled in the framework of the European Project for Ice Coring in Antarctica (EPICA) is presented, showing measurements obtained by the Proton Induced X-ray Emission (PIXE) technique applied on insoluble atmospheric dust in ice cores. Within this work, substantial improvements to the experimental set-up and data processing have been made, compared to previously presented works on the first 2200 m of the EDC ice core, corresponding to about 220 kyr of climatic history (Marino et al., 2004; Ghermandi et al., 2003). The PIXE technique, based on X-ray spectrometry, allows direct measurements on filters of the insoluble dust fraction without sample pre-treatment, with analytical detection limits less than 1 ppb. The minimum required mass density of sample material on the filter is about 0.1 microg cm-2. Improvements made here allowed us to obtain accurate records of 8 major and minor crustal elements (Si, Al, Fe, Ti, K, Ca, Mg, Na). The data for these 8 elements, as well as their proportions as oxides, are shown for different climatic periods. Because O, Si, Al, Fe, Ti, K, Ca, Mg, Na are the principal constituents (99.90 %
Lexical Representations, Event Structure and Quantification
No full textIn this paper, we discuss the relation intervening between distributivity and the
participants in an event. We argue that there is a strict dependency between aspectual
features and the quantificational properties of each participantsin a given situation; we
also argue for a distinction of events in terms of their polyadicity, or their number of
arguments. In more general terms, we propose a principled way to deal with the
problem of representing the structure of events and their relation with the situation
and the participants in that situation.
At first we introduce a "static" description of predicates as conceptual representations
in a computational lexicon, where event structure is expressed in terms of a
combination of time “t” and event “e” which may assume a variable or a constant value
according to aspectual class and to the number and type of arguments of the predicate.
We hypothesize internal quantification on the event-time only whenever a variable is
associated with “t”, and external quantification on the number of events only when a
variable is associated with “e” in the static description.
Then we deal with “dynamic” quantificational properties of events which derive from
syntactic and semantic properties of the utterance or situation in which they are
contextualized. In this case we propose two main notions Global and Internal that
apply to event structure and establish a point of view by means of which to decide
whether temporal interpretation affects the overall event, or only portions of it; the two
notions are also related to factuality of the event, and to its perfectivity. Finally, we
discusse the introduction of a function that relates participants in the event according
to their quantificational nature and the event structure itself. With respect to the
subdivision of quantification into distributive and collective operators, we establish a
mapping from participants into the event inward, and outward
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
Remote OPO Pumping with Photonic Fibres
No full textIn this paper we seek to assess the advantages offered by index guiding holey fibres and air-core photonic band-gap fibres for high power beam delivery applications with robust single-mode guidance. We explore the practical performance factors associated with each fibre type and consider how these may affect implementation and operation in real aerospace and defence systems. As an example of such a system, we report the use of a photonic crystal fibre as a pump delivery fibre in an optical parametric oscillator (OPO).E.J. O’Driscoll, M.A. Watson, T. Delmonte, M.N. Petrovich, V. Finazzi, J.C. Baggett, T.M. Monro, D.J. Richardso
A text-to-speech system for Italian
No full textA system for the automatic translation of any text of Italian into naturally fluent speech is presented. The system, planned for use in a reading machine for the blind, is build up around a Phonological Processor (hence FP) and synthesizes speech-by joining LPC coded diphones. The FP maps into prosodic structures the phonological rules of Italian. Structural information is provided by such hierarchical prosodic constituents as Syllable (S), Metrical Foot (MF), Phonological Word (PW), Intonationa T Group (IG). Onto these structures, phonological rules are applied such as the "letter-to-sound" rules, automatic word stress rules, internal stress hierarchy rules indicating secondary stress, external sandhi rules, phonological focus assignment rules, logical focus assignment rules
Handwritten biographical information on Paulina T. McClung Merritt
No full textA handwritten biography of Paulina T. McClung Merritt by an unknown author, 1892.
Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection.
No full textIFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells
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