Sparse Coding Predicts Optic Flow Specificities of Zebrafish Pretectal Neurons

Zebrafish pretectal neurons exhibit specificities for large-field optic flow patterns associated with rotatory or translatory body motion. We investigate the hypothesis that these specificities reflect the input statistics of natural optic flow. Realistic motion sequences were generated using computer graphics simulating self-motion in an underwater scene. Local retinal motion was estimated with a motion detector and encoded in four populations of directionally tuned retinal ganglion cells, represented as two signed input variables. This activity was then used as input into one of two learning networks: a sparse coding network (competitive learning) and backpropagation network (supervised learning). Both simulations develop specificities for optic flow which are comparable to those found in a neurophysiological study (Kubo et al. 2014), and relative frequencies of the various neuronal responses are best modeled by the sparse coding approach. We conclude that the optic flow neurons in the zebrafish pretectum do reflect the optic flow statistics. The predicted vectorial receptive fields show typical optic flow fields but also "Gabor" and dipole-shaped patterns that likely reflect difference fields needed for reconstruction by linear superposition.Comment: Published Conference Paper from ICANN 2018, Rhode

Enunciation and Plurilingualism in the Francophone and Anglophone African Novel

Abstract: My dissertation proposes to analyze the problematic of language and power in African literature written in French and English. Focusing on novels produced within the controversial contexts of La Francophonie and The Commonwealth, this thesis investigates the tight relationship between language, power and identity. By going beyond normative approaches which focus on the variations of the authorial languages inherited from colonization and nativist readings that continuously seek to establish the primacy of orality, this project analyzes how Francophone and Anglophone African writers—typically authors who chose to write in a language other than their maternal ones—write resistance. It exposes how political, cultural and identity concerns are articulated in linguistic terms. Following a discussion on the genesis of Francophone and Anglophone literature in Africa and a review of the cultural spaces brought along by La Francophonie and The Commonwealth, and drawing on theories of enunciation and plurilingualism, this study undertakes to identify the other languages in the background of the authorial French and English to subsequently analyze the relevance of the various languages’ “mise-en-texte.” Four novels are chosen as practical examples in this analysis; they are Mariama Ba’s Une si longue lettre, Tsitsi Dangarembga’s Nervous Conditions, Chinua Achebe’s Things Fall Apart and Cheikh Hamidou Kane’s L’Aventure ambiguë. Keywords: Francophonie, Commonwealth, Postcolonialism, Francophone literature, Anglophone literature, Commonwealth literature, Enunciation, Plurilingualism, Resistance Literature

Calibration Methods for Eddy Current Measurement Systems

Calibration of eddy current measurement systems is an important factor for attaining the accuracy and precision of measurement that quantitative nondestructive evaluation requires. The quantity of interest in most forms of eddy current inspection is △Z, the change in probe impedance induced by a flaw. Flaw signals produced by surface-breaking cracks are small; typical flaw signals for an air core probe amount to a few tenths of one percent of the probe’s impedance in air. Such small signals are easily obscured by the impedance changes caused by small variations in the height of the probe above the workpiece (lift-off). To discriminate against lift-off, conventional eddy current instruments determine the phase of △Z relative to lift-off and the magnitude of the component of △Z in quadrature with lift-off. But this information is not sufficient to perform flaw signal inversion; rather, the absolute magnitude and phase of △Z are necessary. Thus, quantitative inversion of eddy current signals to obtain flaw sizes requires methods for calibrating eddy current measurement system

Conditional Image-Text Embedding Networks

This paper presents an approach for grounding phrases in images which jointly learns multiple text-conditioned embeddings in a single end-to-end model. In order to differentiate text phrases into semantically distinct subspaces, we propose a concept weight branch that automatically assigns phrases to embeddings, whereas prior works predefine such assignments. Our proposed solution simplifies the representation requirements for individual embeddings and allows the underrepresented concepts to take advantage of the shared representations before feeding them into concept-specific layers. Comprehensive experiments verify the effectiveness of our approach across three phrase grounding datasets, Flickr30K Entities, ReferIt Game, and Visual Genome, where we obtain a (resp.) 4%, 3%, and 4% improvement in grounding performance over a strong region-phrase embedding baseline.Comment: ECCV 2018 accepted pape

Status of non-cocoa tree species in cocoa multistrata systems of southern

Investigations to assess the status of non-cocoa tree species in the cocoa systems of southern Cameroon were carried out in four contrasting locations, distinguished by ecology, population density and land use intensity. One set of inventory was done in each of the 20 selected cocoa farms with an average surface area of 1.4 ha in every location. The inventory was carried out over 25% of each farmland following a gradient directed transect method. Within each cocoa farm, only indigenous tree species and shrubs with the capacity of being transformed into tree species were considered. Our findings showed that there was in total 165 different non-cocoa tree species in the 80 cocoa fields observed. The number of shared species between locations was relatively high (54% to 74%). Frequency distribution of the number of species classified by the number of farms where they were found showed that most species were fairly rare. Tree species richness varied widely between cocoa farms within locations. These findings suggest the need for the various stakeholders of the sector to take appropriate actions to protect endangered species of ecological and economical importance in order to enhance the sustainability of these systems. Keywords: Species diversity, cocoa systems, land use, sustainability. International Journal of Biological and Chemical Sciences Vol. 2 (2) 2008: pp. 207-21

Alexander's disease and the story of Louise.

We describe the rare condition known as Alexander's disease or Alexander's leukodystrophy, which is essentially a childhood dementia. We then present the case of Louise Davies (we are using Louise's real name with the permission and special request of her mother), a woman who was diagnosed with this disease at the age of 5 years and is still alive at the age of 38, making her the longest known survivor of this condition. Although now severely impaired, both physically and mentally, and able to do very little, she has lived far longer than expected. We present some neuropsychological results from her childhood before measuring her decline over the past four years. We conclude by considering whether or not the diagnosis was correct and why she has lived so long

Alexander's disease and the story of Louise.

We describe the rare condition known as Alexander's disease or Alexander's leukodystrophy, which is essentially a childhood dementia. We then present the case of Louise Davies (we are using Louise's real name with the permission and special request of her mother), a woman who was diagnosed with this disease at the age of 5 years and is still alive at the age of 38, making her the longest known survivor of this condition. Although now severely impaired, both physically and mentally, and able to do very little, she has lived far longer than expected. We present some neuropsychological results from her childhood before measuring her decline over the past four years. We conclude by considering whether or not the diagnosis was correct and why she has lived so long

GHZ-type and W-type entangled coherent states: generation and Bell-type inequality tests without photon counting

We study GHZ-type and W-type three-mode entangled coherent states. Both the types of entangled coherent states violate Mermin's version of the Bell inequality with threshold photon detection (i.e., without photon counting). Such an experiment can be performed using linear optics elements and threshold detectors with significant Bell violations for GHZ-type entangled coherent states. However, to demonstrate Bell-type inequality violations for W-type entangled coherent states, additional nonlinear interactions are needed. We also propose an optical scheme to generate W-type entangled coherent states in free-traveling optical fields. The required resources for the generation are a single-photon source, a coherent state source, beam splitters, phase shifters, photodetectors, and Kerr nonlinearities. Our scheme does not necessarily require strong Kerr nonlinear interactions, i.e., weak nonlinearities can be used for the generation of the W-type entangled coherent states. Furthermore, it is also robust against inefficiencies of the single-photon source and the photon detectors.Comment: 8 pages, 5 figures, to be published in Phys. Rev.