title: Efficient data stream classification via probabilistic adaptive windows

authors: Bifet, Albert

subjects: computer science

abstract: In the context of a data stream, a classifier must be able to learn from a theoretically-infinite stream of examples using limited time and memory, while being able to predict at any point. Many methods deal with this problem by basing their model on a window of examples. We introduce a probabilistic adaptive window (PAW) for data-stream learning, which improves this windowing technique with a mechanism to include older examples as well as the most recent ones, thus maintaining information on past concept drifts while being able to adapt quickly to new ones. We exemplify PAW with lazy learning methods in two variations: one to handle concept drift explicitly, and the other to add classifier diversity using an ensemble. Along with the standard measures of accuracy and time and memory use, we compare classifiers against state-of-the-art classifiers from the data-stream literature.

text: Efficient data stream classification via probabilistic adaptive windows In the context of a data stream, a classifier must be able to learn from a theoretically-infinite stream of examples using limited time and memory, while being able to predict at any point. Many methods deal with this problem by basing their model on a window of examples. We introduce a probabilistic adaptive window (PAW) for data-stream learning, which improves this windowing technique with a mechanism to include older examples as well as the most recent ones, thus maintaining information on past concept drifts while being able to adapt quickly to new ones. We exemplify PAW with lazy learning methods in two variations: one to handle concept drift explicitly, and the other to add classifier diversity using an ensemble. Along with the standard measures of accuracy and time and memory use, we compare classifiers against state-of-the-art classifiers from the data-stream literature.

year: 2013

title: Denitrification and availability of carbon and nitrogen in a well-drained pasture soil amended with particulate organic carbon

authors: Stevenson, Bryan A.

subjects: particulate organic carbon

abstract: A well-drained soil in N-fertilized dairy pasture was amended with particulate organic carbon (POC), either sawdust or coarse woody mulch, and sampled every 4 wk for a year to test the hypothesis that the addition of POC would increase denitrification activity by increasing the number of microsites where denitrification occurred. Overall mean denitrifying enzyme activity (DEA), on a gravimetric basis, was 100% greater for the woody mulch treatment and 50% greater for the sawdust treatment compared with controls, indicating the denitrifying potential of the soil was enhanced. Despite differences in DEA, no difference in denitrification rate, as measured by the acetylene block technique, was detected among treatments, with an average annual N loss of ∼22 kg N ha⁻¹ yr⁻¹ Soil water content overall was driving denitrification in this well-drained soil as regression of the natural log of volumetric soil water content (VWC) against denitrification rate was highly significant (r ² = 0.74, P < 0.001). Addition of the amendments, however, had significant effects on the availability of both C and N. An additional 20 to 40 kg N ha⁻¹ was stored in POC-amended treatments as a result of increases in the microbial biomass. Basal respiration, as a measure of available C, was 400% greater than controls in the sawdust treatment and 250% greater than controls in the mulch. Net N mineralization, however, was significantly lower in the sawdust treatment, resulting in significantly lower nitrate N levels than in the control. We attribute the lack of measured response in denitrification rate to the high temporal variability in denitrification and suggest that diffusion of nitrate may ultimately have limited denitrification in the amended treatments. Our data indicate that manipulation of denitrification by addition of POC may be possible, particularly when nitrate levels are high, but quantifying differences in the rate of denitrification is difficult because of the temporal nature of the process (particularly the complex interaction of N availability and soil water content).

text: Denitrification and availability of carbon and nitrogen in a well-drained pasture soil amended with particulate organic carbon A well-drained soil in N-fertilized dairy pasture was amended with particulate organic carbon (POC), either sawdust or coarse woody mulch, and sampled every 4 wk for a year to test the hypothesis that the addition of POC would increase denitrification activity by increasing the number of microsites where denitrification occurred. Overall mean denitrifying enzyme activity (DEA), on a gravimetric basis, was 100% greater for the woody mulch treatment and 50% greater for the sawdust treatment compared with controls, indicating the denitrifying potential of the soil was enhanced. Despite differences in DEA, no difference in denitrification rate, as measured by the acetylene block technique, was detected among treatments, with an average annual N loss of ∼22 kg N ha⁻¹ yr⁻¹ Soil water content overall was driving denitrification in this well-drained soil as regression of the natural log of volumetric soil water content (VWC) against denitrification rate was highly significant (r ² = 0.74, P < 0.001). Addition of the amendments, however, had significant effects on the availability of both C and N. An additional 20 to 40 kg N ha⁻¹ was stored in POC-amended treatments as a result of increases in the microbial biomass. Basal respiration, as a measure of available C, was 400% greater than controls in the sawdust treatment and 250% greater than controls in the mulch. Net N mineralization, however, was significantly lower in the sawdust treatment, resulting in significantly lower nitrate N levels than in the control. We attribute the lack of measured response in denitrification rate to the high temporal variability in denitrification and suggest that diffusion of nitrate may ultimately have limited denitrification in the amended treatments. Our data indicate that manipulation of denitrification by addition of POC may be possible, particularly when nitrate levels are high, but quantifying differences in the rate of denitrification is difficult because of the temporal nature of the process (particularly the complex interaction of N availability and soil water content).

year: 2011

title: Te ahi tawhito, te ahi tipua, te ahi nā Mahuika: Re-igniting native women’s ceremony

authors: Murphy, Ngahuia Aroha Grace

subjects: Native women's ceremony

abstract: This research examines the multiple ways in which Māori, and Hawai’ian and Native American women, are re-activating feminine ceremonial forms and recovering sacred relationships with customary feminine deities. Attention is focused on the creation of personal ritual practices that respond to contemporary decolonising and ecological contexts.
A mana wahine theoretical and methodological framework motivated by emancipatory agendas that seek to facilitate transformation is used. Key to mana wahine projects is the creation of space for Native women to define themselves and their own stories and knowledges. This is important because Native women’s voices, knowledge and ritual histories continue to be marginalised. Furthermore, debased colonial renditions of femininity, which have been reproduced, perpetuate patriarchal and colonial politics that engender discord in Native communities today.  
The study used a suite of complimentary methods to engage 45 Native women and men. Interviews and kōrero (discussion), ceremony, mana wahine wānanga (women’s sacred learning space), Native sacred site visits, solicited journals, collaboration in ritual theatre productions, and analysis of mana wahine artworks as discursive texts were employed to gather stories of spiritual continuation that are unique and largely unchartered in academia. 
The empirical material is organised around four themes in four different chapters. The first of these empirical chapters re-interprets colonial ethnographic material alongside karakia (incantations), mōteatea (songs), cosmological and tribal stories, to reveal bold examples of Māori female ritual leadership. The second empirical chapter comprises an analysis of key colonial processes that have attempted to erase Native women’s ritual ontologies and the strident expressions of Native women’s resistance to colonial imperatives. The third empirical chapter investigates the multiple channels through which Native women are restoring their ceremonial lives. The fourth chapter investigates rerenga atua (menstruation) rituals that celebrate the Native feminine body as a cosmological site of communion with feminine deities. 
The rich weave of Native women’s stories of ceremony, old and new, threads into decolonising Indigenous scholarship around the world that also seeks to recover the sacred feminine as a key site of Native sovereignty. These discussions reveal a self-renewing Native belief system based on vibrant and evolving rituals that respond directly to current socio-political, spiritual and ecological realities.

text: Te ahi tawhito, te ahi tipua, te ahi nā Mahuika: Re-igniting native women’s ceremony This research examines the multiple ways in which Māori, and Hawai’ian and Native American women, are re-activating feminine ceremonial forms and recovering sacred relationships with customary feminine deities. Attention is focused on the creation of personal ritual practices that respond to contemporary decolonising and ecological contexts.
A mana wahine theoretical and methodological framework motivated by emancipatory agendas that seek to facilitate transformation is used. Key to mana wahine projects is the creation of space for Native women to define themselves and their own stories and knowledges. This is important because Native women’s voices, knowledge and ritual histories continue to be marginalised. Furthermore, debased colonial renditions of femininity, which have been reproduced, perpetuate patriarchal and colonial politics that engender discord in Native communities today.  
The study used a suite of complimentary methods to engage 45 Native women and men. Interviews and kōrero (discussion), ceremony, mana wahine wānanga (women’s sacred learning space), Native sacred site visits, solicited journals, collaboration in ritual theatre productions, and analysis of mana wahine artworks as discursive texts were employed to gather stories of spiritual continuation that are unique and largely unchartered in academia. 
The empirical material is organised around four themes in four different chapters. The first of these empirical chapters re-interprets colonial ethnographic material alongside karakia (incantations), mōteatea (songs), cosmological and tribal stories, to reveal bold examples of Māori female ritual leadership. The second empirical chapter comprises an analysis of key colonial processes that have attempted to erase Native women’s ritual ontologies and the strident expressions of Native women’s resistance to colonial imperatives. The third empirical chapter investigates the multiple channels through which Native women are restoring their ceremonial lives. The fourth chapter investigates rerenga atua (menstruation) rituals that celebrate the Native feminine body as a cosmological site of communion with feminine deities. 
The rich weave of Native women’s stories of ceremony, old and new, threads into decolonising Indigenous scholarship around the world that also seeks to recover the sacred feminine as a key site of Native sovereignty. These discussions reveal a self-renewing Native belief system based on vibrant and evolving rituals that respond directly to current socio-political, spiritual and ecological realities.

year: 2019