3 research outputs found
Robust Control Charts for Monitoring Process Mean of Phase-I Multivariate Individual Observations
No full textHoteling’s T2 control charts are widely used in industries to monitor multivariate processes. The classical estimators, sample mean, and the sample covariance used in T2 control charts are highly sensitive to the outliers in the data. In Phase-I monitoring, control limits are arrived at using historical data after identifying and removing the multivariate outliers. We propose Hoteling’s T2 control charts with high-breakdown robust estimators based on the reweighted minimum covariance determinant (RMCD) and the reweighted minimum volume ellipsoid (RMVE) to monitor multivariate observations in Phase-I data. We assessed the
performance of these robust control charts based on a large number of Monte Carlo simulations by considering different data scenarios and found that the proposed control charts have better performance compared to existing methods.Memorial University Open Access Author's Fun
Computational Reconstructions of Extracellular Action Potentials and Local Field Potentials of a Rat Cerebellum Using Point Neurons
No full textA polyphasic approach to the study of chitinolytic bacteria in soil
No full textChitin is the most abundant nitrogen-containing polymer in nature, with >1x10^10 tonnes
produced annually in terrestrial and marine habitats. Chitinolytic bacteria are able to
degrade this recalcitrant substrate through a multiplicity of chitinases. A polyphasic
approach was taken to studying these organisms within three diverse soil communities.
Fluorometric assays employing 4-methylumbelliferyl-labelled chitinooligosaccharides were
used to estimate basal soil chitinase activity as well as its chitinolytic potential in response
to a- and b-chitin amendment. A molecular approach was adopted to profile the bacterial
community and functional chi gene diversity within the soils. Finally, a method of exploring
the metaexoproteome, enabling investigation of the dominant chitin degraders at
a functional level, was developed and implemented. The metaexoproteome and metaproteome,
extracted with an existing method, were compared and used to infer the functional
dominance of chitinolytic phyla.
The basal chitinase activity in all soils was found to be low, yet chitin amendment rapidly
induced chitinases in all soils although intersite differences were seen. b-chitin amendment
induced more chitinolytic activity in Cayo Blanco (CB) compared to Sourhope (SH). The
Test Soil (TS), a site biannually amended with carapaces, retained higher chitinolytic
potential many months after chitin had been consumed.
Next-generation pyrosequencing enabled >50% of the potential OTUs present in the soil
to be recovered. The 16S rRNA gene analysis of SH revealed dominant phyla to be Proteobacteria,
Actinobacteria, and Acidobacteria with little change between amendments. The
TS was dominated by the same phyla but saw a proliferation of Actinobacteria with chitin
amendment. CB experienced the inverse response to the Test Soil, initially dominated by
Actinobacteria only for Proteobacteria to dominate with amendment. Firmicutes were also
prevalent with b-chitin amendment.
Functional chi gene analysis found Streptomyces-like GH19 chi genes to dominate in both
SH and CB. A rare Actinomycete Planobispora dominated chitin-amended TS. This organism
is usually found in extremely arid soil. It was not found in the 16S rRNA gene analysis or the metaproteome; further analysis is required to confirm its presence. Streptomyces-
like GH18 chi genes only dominated CB with amendment and were absent in SH.
A large number of OTUs were identified as uncultured organisms suggesting a large pool
of uncharacterized GH18 chi genes.
Metaproteomics is the functional analysis of complex communities at a given point in time.
The heterogeneity of soil, associated microbial communities, and presence of interfering
compounds make the extraction of protein from soil a technical challenge. Chitinases
are extracellular and so the metaexoproteome was targeted after development of a novel
method that biased extraction towards exoproteins. The protocol successfully extracted the
largest soil metaproteome to date. Actinobacterial chitinases were found to be functionally
dominant in the Test Soil, especially in response to b-chitin amendment
