330 research outputs found

    What's in a pattern? Examining the Type of Signal Multivariate Analysis Uncovers At the Group Level

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    Multivoxel pattern analysis (MVPA) has gained enormous popularity in the neuroimaging community over the past few years. At the group level, most MVPA studies adopt an "information based" approach in which the sign of the effect of individual subjects is discarded and a non-directional summary statistic is carried over to the second level. This is in contrast to a directional "activation based" approach typical in univariate group level analysis, in which both signal magnitude and sign are taken into account. The transition from examining effects in one voxel at a time vs. several voxels (univariate vs. multivariate) has thus tacitly entailed a transition from directional to non-directional signal definition at the group level. While a directional group-level MVPA approach implies that individuals have similar multivariate spatial patterns of activity, in a non-directional approach each individual may have a distinct spatial pattern. Using an experimental dataset, we show that directional and non-directional group-level MVPA approaches uncover distinct brain regions with only partial overlap. We propose a method to quantify the degree of spatial similarity in activation patterns over subjects. Applied to an auditory task, we find higher values in auditory regions compared to control regions.Comment: Revised versio

    Herpes Simplex Virus Hepatitis in an Immunocompetent Host Resembling Hepatic Pyogenic Abscesses

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    Herpes simplex virus (HSV) hepatitis represents a rare complication of HSV infection, which can progress to acute liver failure and, in some cases, death. We describe an immunocompetent 67-year-old male who presented with one week of fever and abdominal pain. Computed tomography (CT) scan and magnetic resonance imaging (MRI) of the abdomen showed multiple bilobar hepatic lesions, some with rim enhancement, compatible with liver abscesses. Subsequent liver biopsy, however, revealed hepatocellular necrosis, HSV-type intranuclear inclusions, and immunostaining positive for herpes virus type 2 (HSV-2). Though initially treated with broad-spectrum antibiotics, following histologic diagnosis of HSV hepatitis, the patient was transitioned to intravenous acyclovir for four weeks and he achieved full clinical recovery. Given its high mortality and nonspecific presentation, one should consider HSV hepatitis in all patients with acute hepatitis with multifocal hepatic lesions of unknown etiology. Of special note, this is only the second reported case of HSV liver lesions mimicking pyogenic abscesses on CT and MRI

    Factors affecting individual foraging specialization and temporal diet stability across the range of a large “generalist” apex predator

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    Individual niche specialization (INS) is increasingly recognized as an important component of ecological and evolutionary dynamics. However, most studies that have investigated INS have focused on the effects of niche width and inter- and intraspecific competition on INS in small-bodied species for short time periods, with less attention paid to INS in large-bodied reptilian predators and the effects of available prey types on INS. We investigated the prevalence, causes, and consequences of INS in foraging behaviors across different populations of American alligators (Alligator mississippiensis), the dominant aquatic apex predator across the southeast US, using stomach contents and stable isotopes. Gut contents revealed that, over the short term, although alligator populations occupied wide ranges of the INS spectrum, general patterns were apparent. Alligator populations inhabiting lakes exhibited lower INS than coastal populations, likely driven by variation in habitat type and available prey types. Stable isotopes revealed that over longer time spans alligators exhibited remarkably consistent use of variable mixtures of carbon pools (e.g., marine and freshwater food webs). We conclude that INS in large-bodied reptilian predator populations is likely affected by variation in available prey types and habitat heterogeneity, and that INS should be incorporated into management strategies to efficiently meet intended goals. Also, ecological models, which typically do not consider behavioral variability, should include INS to increase model realism and applicability

    The face of the party? Leadership personalisation in British campaigns

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    The personal characteristics of political elites play an important role in British elections. While the personalisation of the media’s election coverage has been the subject of much debate, we know less about the conditions under which voters receive personalised messages directly from elites during the campaign. In this paper, we use a new dataset that includes more than 3,300 local communications from the 2015 general election to explore variation in the personalisation of campaign messaging. We find that there is systemic variation in terms of where photographs of party leaders are included in election communications, which provides further evidence that campaign messages are deployed strategically to portray the candidate – and their party – in the best possible light

    Shear wave velocity prediction using seismic attributes and well log data

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    Formation’s properties can be estimated indirectly using joint analysis of compressional and shear wave velocities. Shear wave data isnot usually acquired during well logging, which is most likely for costsaving purposes. Even if shear data is available, the logging programs provide only sparsely sampled one-dimensional measurements: this informationis inadequate to estimate reservoir rock properties. Thus, if the shear wave data can be obtained using seismic methods, the results can be used across the field to estimate reservoir properties. The aim of this paper is to use seismic attributes for prediction of shear wave velocity in a field located in southern part of Iran. Independent component analysis(ICA) was used to select the most relevant attributes to shear velocity data. Considering the nonlinear relationship between seismic attributes and shear wave velocity, multi-layer feed forward neural network was used for prediction of shear wave velocity and promising results were presented
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