Sparse coding with memristor networks.

Sparse representation of information provides a powerful means to perform feature extraction on high-dimensional data and is of broad interest for applications in signal processing, computer vision, object recognition and neurobiology. Sparse coding is also believed to be a key mechanism by which biological neural systems can efficiently process a large amount of complex sensory data while consuming very little power. Here, we report the experimental implementation of sparse coding algorithms in a bio-inspired approach using a 32 × 32 crossbar array of analog memristors.

Feature Extraction Using Memristor Networks.

Crossbar arrays of memristive elements are investigated for the implementation of dictionary learning and sparse coding of natural images. A winner-take-all training algorithm, in conjunction with Oja's rule, is used to learn an overcomplete dictionary of feature primitives that resemble Gabor filters. The dictionary is then used in the locally competitive algorithm to form a sparse representation of input images.

A comparison of two factorial designs, a complete 3 x 3 factorial and a central composite rotatable design, for use in binomial response experiments in aquatic toxicology.

Using an amphibian toxicity testing protocol, comparative studies were conducted to assess the predictive precision, degree of similarity of results and efficiency of a central composite rotatable design (CCRD) in relation to a conventional complete 3x3 factorial design. Data were treated with response surface analysis using generalized linear models (glm) and application of profile deviance to generate confidence intervals. Design comparisons were based on studies conducted using the Frog Embryo Teratogenesis Assay-Xenopus (FETAX) protocol to examine the interaction of three toxicants at pH levels ranging from 4.

Comparative effects of pH and Vision herbicide on two life stages of four anuran amphibian species.

Vision, a glyphosate-based herbicide containing a 15% (weight:weight) polyethoxylated tallow amine surfactant blend, and the concurrent factor of pH were tested to determine their interactive effects on early life-stage anurans. Ninety-six-hour laboratory static renewal studies, using the embryonic and larval life stages (Gosner 25) of Rana clamitans, R. pipiens, Bufo americanus, and Xenopus laevis, were performed under a central composite rotatable design.

Effect of pH and Release on two life stages of four anuran amphibians.

Using three native Canadian and one exotic anuran species, the interactive toxicity of pH and the forestry used-herbicide Release (triclopyr [3,5,6-trichloro-2-pyridl-oxyacetic acid]) was assessed. Embryonic and larval (Gosner 25) stages of Rana pipiens, Rana clamitans, Bufo americanus, and Xenopus laevis were exposed to treatments for at least 96 h in a static-renewal system using a central composite rotatable design. Mortality and the prevalence of malformations were modeled using generalized linear models with a profile deviance approach to obtain confidence intervals.