A Holarctic perspective on mammalian evolution: The evolutionary and biogeographic history of red-backed voles and their close relatives (Rodentia: Arvicolinae)

The influence of Quaternary environmental changes on demography and geographic distribution is paramount to understanding how contemporary genetic diversity is partitioned in high-latitude species. This history of change in northern ecosystems sets the stage for forecasting how species inhabiting tundra and boreal forest will respond to the ongoing shift in climate. Utilizing broad geographic and taxonomic sampling, a multilocus species tree approach, ecological niche models, and population genetic techniques, I investigate the evolutionary and biogeographic history of a Holarctic mammal, the northern red-backed vole (Clethrionomys rutilus) and the systematics of the tribe it belongs to, Clethrionomyini. This tribe of forest and alpine voles is distributed throughout the Holarctic and diversified in the Northern Hemisphere over the last 5 MY. The biogeographic history of C. rutilus is characterized by subdivision and subsequent expansion from multiple refugia, including previously unidentified refugia in central Asia. Several taxonomic issues are resolved by the use of multilocus data, including support of a polyphyletic Clethrionomys, prompting the suggestion of splitting the genus into two. Diversification in the tribe is not characterized by pulses of diversification, as previously suggested. The dynamic geographic, genealogic, and demographic history of C. rutilus and Clethrionomyini provides insight into the Quaternary biogeography of the northern high-latitudes in Asia and North America

MAMMALS ON MOUNTAINSIDES REVISITED: ANALYZING MULTIPLE DIMENSIONS OF DIVERSITY TO GAIN NEW INSIGHT ON COMMUNITY ASSEMBLY AND BIOGEOGRAPHY

Understanding how biodiversity is distributed, maintained, and altered is a fundamental goal of ecology and is especially important for predicting the effects of ongoing rapid environmental change. Traditionally, diversity has been described in taxonomic terms using the number and abundance of species (e.g., species richness). However, biodiversity is multi-faceted and includes functional (ecological traits) and phylogenetic (evolutionary relationships) dimensions that emphasize the similarities and differences among species. Functional diversity is particularly appealing because it quantifies the range and prevalence of traits in an assemblage and helps link patterns of diversity to the ecological processes that generate them. I used a multi-dimensional diversity approach to investigate elevation-diversity patterns, community assembly processes, and patterns and drivers of change in small mammal community structure over the last century in mountain ranges in the Great Basin of western North America. In Chapter 1, I developed a novel trait-based approach for discriminating between environmental filtering and biotic interactions as possible drivers of species co-occurrence across environmentally heterogeneous sites. Expectations of environmental filtering were assessed using species similarity in the traits of habitat affinity and geographic range location whereas expectations of biotic interactions were based on similarity of diet and body size. When applying this hypothesis-testing framework to small mammal species pairs distributed among and within local sites distributed across three broad elevational gradients, most associations were consistent with environmental filtering. However, negative associations among four species pairs were consistent with expectations under biotic interactions, including two pairs for which competitive exclusion has previously been documented (two species of chipmunk of the genus Tamias and two species of pocket mice of the genus Perognathus). Discerning the mechanisms responsible for co-occurrence patterns was made possible by developing and testing explicit hypotheses based on trait similarity. Although the appreciation and measurement of multiple dimensions of biodiversity has grown recently, refinement of trait data for mammals is much needed. Most studies rely on categorical rather than continuous traits. As a result, finer variation present among species is overlooked which may obscure patterns, particularly for studies on smaller species pools. In Chapter 2, I identified three continuous ecomorphological traits that have a demonstrable link to function and reflect traditionally used functional guilds. Specifically, I investigated the relative medullary thickness (RMT) of the kidney as a measure of habitat affinity (mesic-to-xeric spectrum), hair density as a measure of thermoregulatory ability, and an integrated suite of cranial and dental measurements as an indication of diet specialization. Each trait captured traditional functional group differences for 32 species of Great Basin small mammals while also illuminating meaningful within-group variation. Although each trait had a strong phylogenetic signal, phylogeny alone obscures informative ecological differences (similar to the use of categories). The greater resolution of continuous trait data will facilitate more refined assessments of functional diversity and improve efforts to test ecological theories and track responses to environmental change. With an improved functional trait matrix, including the ecomorphological traits from Chapter 2, I revisited the classic elevation-diversity relationship in Chapter 3 by investigating patterns of functional and phylogenetic diversity in addition to species richness along three elevational gradients. Elevation-species richness relationships are one of the most widely studied biogeographic patterns, but there have been few investigations using other dimensions of diversity. In contrast to the well-established mid-elevation peak in species richness, functional and phylogenetic diversity generally increased with elevation. Deviations among dimensions reveal that species richness is a poor surrogate for these other dimensions of diversity for small mammals. Decomposing functional diversity into subsets of traits that reflect specific niche axes can provide insight into the drivers of community assembly over elevation. Specifically, clustering of traits associated with abiotic conditions and habitat affinities provides evidence for environmental filtering where overdispersion among traits corresponding to resource acquisition and use suggests biotic interactions (namely competition) are structuring assembly among community members. I found strong evidence for environmental filtering in both low and high-elevation communities. Evidence for competition as a driver was not consistent with theoretical expectations under the stress dominance hypothesis, guild assembly rules, or competitor limitation of range margins. In Chapter 4, I used resurveys of sites in Great Basin National Park and vicinity to track functional diversity responses to climate and habitat change. Over the 86-year interval between surveys, functional diversity decreased even though species richness and total community abundance were stable at sites. In general, communities become less functionally even; species with more generalized traits became more dominant and climate and habitat specialists constituted smaller components of most communities. Larger species with lower reproductive potential also tended to fare worse over time. Functional evenness decreased more due to climate responses whereas functional divergence and dispersion were reduced more among habitat traits. In sum, this analysis indicates how the individual and interactive effects of change in abiotic conditions, cover types, and resource base are translated to change in community structure through species’ traits. My results emphasize the importance of using abundance-weighted functional diversity metrics to detect subtle or early-stage changes to community structure that may serve as an early warning of more dramatic diversity loss in the future

Returns on IT Investment: Could We Do Better?

Spending on IT continues to show long-term growth throughout the economy, apparently reflecting a belief in the economic benefits of IT. However, we also see organizations struggle in practice to demonstrate such benefits. Conventional thinking suggests that individual organizations can improve their performance in this area through better financial analysis of opportunities. But does this characterization of the solution reflect the real problem? Is there more value that can be achieved through IT at a macro level or are we simply seeing market competition with winners and losers? And will better understanding of the detailed financial consequences of IT systems enable businesses to improve decisions and achieve greater returns? This panel session will challenge conventional thinking on IT value both at a macro and micro economic level. In the process, it will balance the perspectives of research with those from practice and consider the role of alternative theoretical lenses

Creating, Capturing and Measuring Value From IT Investments: Could We Do Better?

Spending on IT continues to show long-term growth throughout the economy, reflecting an apparent belief in the economic benefits of IT. However, we also see organizations struggle in practice to demonstrate such benefits. Conventional thinking suggests that individual organizations can improve their performance in this area through better financial analysis of opportunities. But does this characterization of the solution reflect the real problem? Is there more value that can be achieved through IT at a macro level or are we simply seeing market competition with winners and losers? And will better understanding of the detailed financial consequences of IT systems enable businesses to improve decisions and achieve greater returns? This 2009 ICIS panel session reflected on the literature on IT value over the last thirty years, the future direction of research and the relationship between research and the needs of business in this area

Learning disentangled representations with semi-supervised deep generative models

Variational autoencoders (VAEs) learn representations of data by jointly training a probabilistic encoder and decoder network. Typically these models encode all features of the data into a single variable. Here we are interested in learning disentangled representations that encode distinct aspects of the data into separate variables. We propose to learn such representations using model architectures that generalise from standard VAEs, employing a general graphical model structure in the encoder and decoder. This allows us to train partially-specified models that make relatively strong assumptions about a subset of interpretable variables and rely on the flexibility of neural networks to learn representations for the remaining variables. We further define a general objective for semi-supervised learning in this model class, which can be approximated using an importance sampling procedure. We evaluate our framework's ability to learn disentangled representations, both by qualitative exploration of its generative capacity, and quantitative evaluation of its discriminative ability on a variety of models and datasets

Learning Disentangled Representations with Semi-Supervised Deep Generative Models

Variational autoencoders (VAEs) learn representations of data by jointly training a probabilistic encoder and decoder network. Typically these models encode all features of the data into a single variable. Here we are interested in learning disentangled representations that encode distinct aspects of the data into separate variables. We propose to learn such representations using model architectures that generalise from standard VAEs, employing a general graphical model structure in the encoder and decoder. This allows us to train partially-specified models that make relatively strong assumptions about a subset of interpretable variables and rely on the flexibility of neural networks to learn representations for the remaining variables. We further define a general objective for semi-supervised learning in this model class, which can be approximated using an importance sampling procedure. We evaluate our framework's ability to learn disentangled representations, both by qualitative exploration of its generative capacity, and quantitative evaluation of its discriminative ability on a variety of models and datasets.Comment: Accepted for publication at NIPS 201

Ferroelectric thin films for microsystems

Deposition, integration and application issues of ferroelectric thin films are briefly reviewed. Applications in ultrasonic micromotors and infra-red sensors are treated in more detail. Current results on stress measurements across the ferroelectric phase transition and on pyroelectric devices are presented

Exploring factors affecting the timely transition of ventilator assisted individuals in Ontario from acute to long-term care: Perspectives of healthcare professionals

# Rationale Ventilator Assisted Individuals (VAIs) frequently remain in intensive care units (ICUs) for a prolonged period once clinically stable due to a lack of transition options. These VAIs occupy ICU beds and resources that patients with more acute needs could better utilize. Moreover, VAIs experience improved outcomes and quality of life in long-term and community-based environments. # Objective To better understand the perspectives of healthcare providers (HCPs) working in an Ontario ICU regarding barriers and facilitators to referral and transition of VAIs from the ICU to a long-term setting. # Methods We conducted semi-structured interviews with ten healthcare providers involved in VAI transitions. # Main Results Perceived barriers included long wait times for long-term care settings, insufficient bed availability at discharge locations, medical complexity of patients, long waitlists, and a lack of transparency of waitlists. Facilitators included strong partnerships and trusting relationships between referring and discharge locations, a centralized referral system, and utilization of community partnerships across care sectors. # Conclusions Insufficient resourcing of long-term care is a key barrier to transitioning VAIs from ICU to long-term settings; strong partnerships across care sectors are a facilitator. System-level approaches, such as a single-streamlined referral system, are needed to address key barriers to timely transition

Fabrication and Characterization of Pzt Thin-Film Vibrators for Micromotors

For the first time we have characterized a micromotor driven by a piezoelectric PZT (PbZrxTi1-xO3) thin film. Sputter and sol-gel techniques have been applied for the deposition of the PZT films onto a silicon stator membrane, which is 20-30 mu m thick and has a diameter of 4 mm. The amplitudes of the membrane deflections are measured by means of laser interferometry. They are as large as 800 nm V-1 at the first resonance (26 kHz) and 60 nm V-1 at 1 kHz. This is one order of magnitude larger than previously reported for a ZnO-activated device of similar geometry. The motor operates at 1-3 V-r.m.s., with speeds of up to 200 rpm at 1.1 V-r.m.s. and torques of 35 nN m at 2.5 V-r.m.s. and 1 mN force between rotor and stator. Compared with the conceptually identical ZnO version published by Racine et al., this is an improvement by a factor of three in speed per volt. Taking into account the linear increase of the torque with the stator vibration frequency, the torque per volt is a factor of two higher. A long-term test of 100 h showed no degradation of the motor performance

Properties of Piezoelectric Pzt Thin Films for Microactuator Applications

The piezoelectric properties of lead zirconate titanate (PZT) thin films deposited on thick silicon substrates and thin silicon membranes were investigated using optical interferometry. The effect of the geometrical constraints and clamping effects on the piezoelectric response is discussed. The study of the dielectric permittivity and the loss as a function of the amplitude of the alternating electric field reveals that extrinsic contributions to the dielectric permittivity become active at large fields. The DC electric field has the effect of freezing out the extrinsic contributions. The influence of the dielectric loss on the piezoelectric properties is discussed