112,895 research outputs found
A sequence of flux transfer events potentially generated by different generation mechanisms
No full textFlux transfer events (FTEs) are magnetic structures generated by time-varying reconnection at the dayside magnetopause. Understanding their generation mechanism is important, because it is necessary in order to understand the global contribution of FTEs to the convection process. We present observations of several FTEs sequentially observed by Cluster at the subsolar magnetopause. Cluster detected also several reconnection jets, which seem to be systematically associated with the trailing edge of the FTEs. This association is expected only in the FTEs formed by single X line reconnection but could be compatible also with the multiple X line model, when reconnection at one X line is dominant. Instead, it does not seem compatible with original mechanism proposed by Russell and Elphic (1978). For a large FTE, not associated with any reconnection jet, the Grad-Shafranov reconstruction obtained from Cluster 1 data recovers a flux rope, indicative of multiple X line reconnection. This same FTE was detected also by Cluster 3, which observed an asymmetric signature in the magnetic field component normal to the magnetopause. We show that this asymmetric signature was caused by an outward motion of the magnetopause. The orientation of the other FTEs, obtained from a Grad-Shafranov optimization, shows considerable spread, despite the relatively steady conditions. Our interpretation is that a combination of single and multiple X line reconnection generated these FTEs. The FTEs in the first part of the crossing, associated with reconnection jets, are generated by the single X line model and may therefore not satisfy the Grad-Shafranov assumptions so well. Instead, the last FTE, slower, bigger, and well separated from the previous ones, may be formed by multiple X line reconnection
Virus demyelination
No full textA number of viruses can initiate central nervous system (CNS) diseases that include demyelination as a major feature of neuropathology. In humans, the most prominent demyelinating diseases are progressive multifocal leukoencephalopathy, caused by JC papovirus destruction of oligodendrocytes, and subacute sclerosing panencephalitis, an invariably fatal childhood disease caused by persistent measles virus. The most common neurological disease of young adults in the developed world, multiple sclerosis, is also characterized by lesions of inflammatory demyelination; however, the etiology of this disease remains an enigma. A viral etiology is possible, because most demyelinating diseases of known etiology in both man and animals are viral. Understanding of the pathogenesis of virus-induced demyelination derives for the most part from the study of animal models. Studies with neurotropic strains of mouse hepatitis virus, Theiler's virus, and Semliki Forest virus have been at the forefront of this research. These models demonstrate how viruses enter the brain, spread, persist, and interact with immune responses. Common features are an ability to infect and persist in glial cells, generation of predominantly CD8(+) responses, which control and clear the early phase of virus replication but which fail to eradicate the infection, and lesions of inflammatory demyelination. In most cases demyelination is to a limited extent the result of direct virus destruction of oligodendrocytes, but for the most part is the consequence of immune and inflammatory responses. These models illustrate the roles of age and genetic susceptibility and establish the concept that persistent CNS infection can lead to the generation of CNS autoimmune responses
Characterisation of the response of Aedes mosquito cells to Semliki Forest virus infection
No full textArboviruses are transmitted to vertebrates by arthropod vectors such as mosquitoes
or ticks. The replication of Semliki Forest virus (SFV) (Togaviridae; Alphavirus) in
vertebrate cells is well established and triggers cell death. SFV infection of Aedes
albopictus mosquito cells was characterised. Virus growth curves were compared in
three cell lines. Infection of U4.4 cells was persistent and did not affect growth of the
culture. In contrast, infection of C6/36 and C7-10 cells resulted in a static culture
with no cell division and no cell death. The response of U4.4 cells was characterised
in greater detail using viruses containing fluorescent or luciferase markers within the
replicase or structural open reading frame of the virus genome. Activation of the
STAT/IMD pathway prior to SFV infection significantly reduced virus driven
luciferase expression and virus production. Activation of the Toll pathway prior to
SFV infection had no effect. However, activation of Toll in addition to STAT/IMD
had a cumulative effect on luciferase expression and virus production. viRNAs were
characterised by Illumina Solexa sequencing. Two percent of the small RNA species
found in virus infected cells were derived from virus RNA. These were
predominantly 21 nt long and mapped along the entire SFV genome and genome
complementary RNAs. Generation of these viRNAs was not random. Some areas
produced high frequencies and others no or very few; hot and cold spots respectively.
There were no correlations between viRNA frequency and base pairing or secondary
structures predictions. Cold spot-derived viRNAs were more effective than hot-spot
viRNAs in inhibiting virus replication. Similar results were observed in Aedes
aegypti-derived cells. Attempts were made to investigate the source of these viRNAs
using a virus containing an IRES element which had been reported to prevent virus
replication in insect cells but which did not efficiently do so in this study. A virus
containing the RNAi inhibitor p19 was characterised and shown to increase virus
production.
Techniques for infecting mosquitoes via a blood meal feed were established. No
infection was observed with virus replicon particles carrying a fluorescent marker
gene. Infection was established using virus containing p19
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
The vanishing author in computer-generated works: a critical analysis of recent Australian case law
No full textAbstract
The use of software is ubiquitous in the creation of many copyright works, yet the requirement in copyright law that every work have a human author who engages in independent intellectual effort means that its use may prevent copyright subsistence. Several recent Australian cases have refocused attention on authorship as an essential criterion of copyright subsistence, and these cases suggest that much computer-produced output may be authorless and thus lack copyright protection. This article, the first in a two-part series, analyses how each case deals with the question of authorship of computer-produced works and why the use of software diminishes copyright protection for a significant number of computer-generated works. The article critiques the application of conventional notions of human authorship developed in the pre-computer age to modern productions and suggests alternative approaches to authorship that satisfy both the major objectives of copyright policy and the need to adapt to the computer age. The article argues that, without a broader judicial approach to authorship of computer-generated works, Parliament must remedy the lacuna in protection for these ‘authorless’ works. Possible solutions for reform are suggested. In a forthcoming article, the author comprehensively examines those reform proposals
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Stably stratified shear-produced turbulence and large-scalewaves in a lid driven cavity
No full textWe study experimentally stably stratified sheared turbulence and large-scale flows and waves in a lid driven cavity with a non-zero vertical mean temperature gradient. Geometrical properties of the large-scale vortex (e.g., its size and form) and the level of small-scale turbulence inside the vortex are controlled by the buoyancy (i.e., by the temperature stratification). The observed velocity fluctuations are produced by the shear of the large-scale vortex. At larger stratification obtained in our experiments, the strong turbulence region is located at the upper part of the cavity where the large scale vortex exists. In this region the Brunt-Väisälä frequency is small and increases in the direction outside the large-scale vortex. This is the reason of that the large-scale internal gravity waves are observed in the regions outside the large-scale vortex. We found these waves by analyzing the non instantaneous correlation functions of the temperature and velocity fields. The observed large-scale waves are nonlinear because the frequency of the waves determined from the temperature field measurements is two times smaller than that obtained from the velocity field measurements. The measured intensity of the waves is of the order of the level of the temperature turbulent fluctuations
Thin electron-scale layers at the magnetopause
No full textWe use data from the four Cluster satellites to examine the microphysics of a thin electron-scale layer discovered on the magnetospheric side of the magnetopause. Here the ion and electron motions are decoupled in a layer about 20 km (a few electron scales) wide, including currents and strong electric fields. In this layer the electrons are E x B drifting with the ions as a background, and the region can be described by Hall MHD physics. A unique identification of the source of the thin layer is not possible, but our observations are consistent with recent simulations showing thin layers associated with the separatrix extending far away from a reconnection diffusion region
Ratio of n-6/n-3 in the diets of beef cattle
No full textEffects of feeding heat-treated canola (C), soybean (S) and flax (F) or mixtures on growth and slaughter characteristics, taste and fatty acid (FA) composition of beef tissue were investigated using 128 crossbred steers to determine the potential of improving the nutritional quality of beef for humans. For Trial 1 (48 steers), dietary treatments were: roasted C, extruded C, roasted S, extruded S, roasted F and extruded F. For Trial 2 (80 steers), the dietary treatments were: S:F (1:1), S:C (1:1), C:F (1:1) and S:F:C (1:1:1), and the oilseeds were processed either by roasting or extruding before mixing. Soybean meal and soybean oil were used to give equivalent lipid and protein contents to each experimental diet. The basal diet consisted of grass silage, barley grain, vitamins and minerals. Steers were fed for a minimum of 100d then slaughtered at a uniform degree of finish. Growth and slaughter characteristics of the steers were only slightly affected by dietary treatment in that the soybean-fed steers consumed more feed and had a higher average daily gain than the canola or flax-fed animals in Trial 1. There was no difference in taste panel parameters for any of the treatments. Inclusion of flax in the diet increased the total n-3 content of meat. Similar results were found for canola and C18:1n-9 although this was not the case for soybean and the n-6 FA. For the n-6 FA in the PL and neutral lipid fractions of the meat samples, levels were correlated with high dietary levels of n-6 or n-9 with low levels of n-3 while for the n-3 FA, levels were correlated with high dietary n-3 levels and low n-6 levels. Oilseed processing method did not have an effect on any fatty acid levels. It is possible to modify the FA composition of beef meat toward a healthier profile by including heat-treated oilseeds in the diet to influence the degree of lipid metabolism in the rumen.ID: S0377840111004007; M3: Article; Accession Number: S0377840111004007; Author: M.A. McNiven (a, ⁎); Author: J.L. Duynisveld (b); Author: T. Turner (a); Author: A.W. Mitchell (a); Affiliation: Department of Health Management, Atlantic Veterinary College, University of PEI, Charlottetown, PEI, Canada C1A 4P3; Affiliation: Agriculture and Agri-Food Canada, Nappan, NS, Canada B0L 1C0; Keyword: Oilseeds; Keyword: Roasted; Keyword: Extruded; Keyword: Fatty acids; Keyword: Healthy fat; Number of Pages: 11; Language: English
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Identifying idiolect in forensic authorship attribution: an n-gram textbite approach
No full textForensic authorship attribution is concerned with identifying authors of disputed or anonymous documents, which are potentially evidential in legal cases, through the analysis of linguistic clues left behind by writers. The forensic linguist “approaches this problem of questioned authorship from the theoretical position that every native speaker has their own distinct and individual version of the language [. . . ], their own idiolect” (Coulthard, 2004: 31). However, given the diXculty in empirically substantiating a theory of idiolect, there is growing concern in the Veld that it remains too abstract to be of practical use (Kredens, 2002; Grant, 2010; Turell, 2010). Stylistic, corpus, and computational approaches to text, however, are able to identify repeated collocational patterns, or n-grams, two to six word chunks of language, similar to the popular notion of soundbites: small segments of no more than a few seconds of speech that journalists are able to recognise as having news value and which characterise the important moments of talk. The soundbite oUers an intriguing parallel for authorship attribution studies, with the following question arising: looking at any set of texts by any author, is it possible to identify ‘n-gram textbites’, small textual segments that characterise that author’s writing, providing DNA-like chunks of identifying material
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