The Effects of Housing Environments on the Performance of Activity-Recognition Systems Using Wi-Fi Channel State Information: An Exploratory Study.

Recently, device-free human activity⁻monitoring systems using commercial Wi-Fi devices have demonstrated a great potential to support smart home environments. These systems exploit Channel State Information (CSI), which represents how human activities⁻based environmental changes affect the Wi-Fi signals propagating through physical space. However, given that Wi-Fi signals either penetrate through an obstacle or are reflected by the obstacle, there is a high chance that the housing environment would have a great impact on the performance of a CSI-based activity-recognition system. In this context, this paper examines whether and to what extent housing environment affects the performance of the CSI-based activity recognition systems. Activities in daily living (ADL)⁻recognition systems were implemented in two typical housing environments representative of the United States and South Korea: a wood-frame apartment (Unit A) and a reinforced concrete-frame apartment (Unit B), respectively. The experimental results show that housing environments, combined with various environmental factors (i.e., structural building materials, surrounding Wi-Fi interference, housing layout, and population density), generate a significant difference in the accuracy of the applied CSI-based ADL-recognition systems. This outcome provides insights into how such ADL systems should be configured for various home environments.

Phylogenetic analysis of gamma-proteobacteria inferred from nucleotide sequence comparisons of the house-keeping genes adk, aroE and gdh: comparisons with phylogeny inferred from 16S rRNA gene sequences.

Nucleotide sequence comparisons of three house-keeping genes, adenylate kinase (adk), shikimate dehydrogenase (aroE), and glucose-6-phosphate dehydrogenase (gdh), were used to infer the phylogeny of 33 gamma-proteobacteria. Phylogenetic trees inferred from each gene, and from the concatenated sequences of all three genes, are, in general, similar to a 16S rRNA gene-inferred tree. Similar grouping of bacteria are revealed at the family, genus, species and strain levels in all five trees. The house-keeping genes, however, show a higher rate of nucleotide sequence substitutions. Consequently, they can possibly probe deeper branches of a phylogenetic tree than the 16S rRNA gene. However, because their nucleotide sequences are not as highly conserved among gamma-proteobacteria, family- or genus-specific primers would need to be designed for the amplification of any of these three house-keeping genes. Since these genes are used in multilocus sequence typing, it is expected that the number of sequences publicly available for many taxa will increase over time proving them very useful either at complementing 16S rRNA-inferred phylogenies or for specific, targeted, phylogenetic analysis.

Modulation of lipid biosynthesis contributes to stress resistance and longevity of C. elegans mutants.

Many lifespan-modulating genes are involved in either generation of oxidative substrates and end-products, or their detoxification and removal. Among such metabolites, only lipoperoxides have the ability to produce free-radical chain reactions. For this study, fatty-acid profiles were compared across a panel of C. elegans mutants that span a tenfold range of longevities in a uniform genetic background. Two lipid structural properties correlated extremely well with lifespan in these worms: fatty-acid chain length and susceptibility to oxidation both decreased sharply in the longest-lived mutants (affecting the insulinlike-signaling pathway). This suggested a functional model in which longevity benefits from a reduction in lipid peroxidation substrates, offset by a coordinate decline in fatty-acid chain length to maintain membrane fluidity. This model was tested by disrupting the underlying steps in lipid biosynthesis, using RNAi knockdown to deplete transcripts of genes involved in fatty-acid metabolism. These interventions produced effects on longevity that were fully consistent with the functions and abundances of their products. Most knockdowns also produced concordant effects on survival of hydrogen peroxide stress, which can trigger lipoperoxide chain reactions.