Respiratory plasticity in response to changes in oxygen supply and demand

Aerobic organisms maintain O2 homeostasis by responding to changes in O2 supply and demand in both short and long time domains. In this review, we introduce several specific examples of respiratory plasticity induced by chronic changes in O2 supply (environmental hypoxia or hyperoxia) and demand (exercise-induced and temperature-induced changes in aerobic metabolism). These studies reveal that plasticity occurs throughout the respiratory system, including modifications to the gas exchanger, respiratory pigments, respiratory muscles, and the neural control systems responsible for ventilating the gas exchanger. While some of these responses appear appropriate (e.g., increases in lung surface area, blood O2 capacity, and pulmonary ventilation in hypoxia), other responses are potentially harmful (e.g., increased muscle fatigability). Thus, it may be difficult to predict whole-animal performance based on the plasticity of a single system. Moreover, plastic responses may differ quantitatively and qualitatively at different developmental stages. Much of the current research in this field is focused on identifying the cellular and molecular mechanisms underlying respiratory plasticity. These studies suggest that a few key molecules, such as hypoxia inducible factor (HIF) and erythropoietin, may be involved in the expression of diverse forms of plasticity within and across species. Studying the various ways in which animals respond to respiratory challenges will enable a better understanding of the integrative response to chronic changes in O2 supply and deman

Unstable Maternal Environment, Separation Anxiety, and Heightened CO2 Sensitivity Induced by Gene-by-Environment Interplay

Background: In man, many different events implying childhood separation from caregivers/unstable parental environment are associated with heightened risk for panic disorder in adulthood. Twin data show that the occurrence of such events in childhood contributes to explaining the covariation between separation anxiety disorder, panic, and the related psychobiological trait of CO2 hypersensitivity. We hypothesized that early interference with infant-mother interaction could moderate the interspecific trait of response to CO2 through genetic control of sensitivity to the environment. Methodology: Having spent the first 24 hours after birth with their biological mother, outbred NMRI mice were crossfostered to adoptive mothers for the following 4 post-natal days. They were successively compared to normally-reared individuals for: number of ultrasonic vocalizations during isolation, respiratory physiology responses to normal air (20%O2), CO2-enriched air (6% CO2), hypoxic air (10%O2), and avoidance of CO2-enriched environments. Results: Cross-fostered pups showed significantly more ultrasonic vocalizations, more pronounced hyperventilatory responses (larger tidal volume and minute volume increments) to CO2-enriched air and heightened aversion towards CO2- enriched environments, than normally-reared individuals. Enhanced tidal volume increment response to 6%CO2 was present at 16–20, and 75–90 postnatal days, implying the trait’s stability. Quantitative genetic analyses of unrelated individuals, sibs and half-sibs, showed that the genetic variance for tidal volume increment during 6%CO2 breathing was significantly higher (Bartlett x = 8.3, p = 0.004) among the cross-fostered than the normally-reared individuals, yielding heritability of 0.37 and 0.21 respectively. These results support a stress-diathesis model whereby the genetic influences underlying the response to 6%CO2 increase their contribution in the presence of an environmental adversity. Maternal grooming/licking behaviour, and corticosterone basal levels were similar among cross-fostered and normally-reared individuals. Conclusions: A mechanism of gene-by-environment interplay connects this form of early perturbation of infant-mother interaction, heightened CO2 sensitivity and anxiety. Some no

Operational Implementation of a Commercial Thinning Trial Using Micro-Forestry Equipment

A technical report detailing the operational implementation and analysis of a commercial thinning trial using micro-forestry equipment in the Burns Lake Community Forest K1A licence area near Burns Lake, British Columbia. Operations were conducted over 11 trial sections between November 21, 2023 and February 3, 2024, during which various parameters were sampled pre- and post-treatment, including leave tree basal area per hectare, stem density, percent defect, mechanical damage, extracted volume and machine productivity. Operational and environmental factors affecting these parameters are discussed, and the implications for the management of a long-term commercial thinning program using this equipment type are explored.Forestry, Faculty ofUnreviewedGraduat

The End of the World as We Know It: Urban Debaters and the Education of Pete Bavis.

The End of the World as We Know It: Urban Debaters and the Education of Pete Bavis

Utilising Atomic Layer Deposition (ALD) to Develop Efficient Hematite-based Photoanodes for Photocatalytic Water-Splitting

It is a scientific consensus that the consumption of fossil fuels result in carbon dioxide (CO2) emissions that negatively impact the climate, in a phenomenon referred to as ‘global warming’ or ‘climate change’.1 To address this problem, novel fuels are required that have a lowered carbon footprint, with hydrogen often hailed as future fuel of combustion vehicles.2 However, a low carbon, renewable means of hydrogen production is required to fully address this problem.3 Water-splitting using solar energy offers a route to renewable, clean hydrogen production. Hematite, α-Fe2O3, is an n-type semiconductor that shows promise as a photoanode in a water-splitting photoelectrochemical cell. Cheap, stable, abundant and with a suitable bandgap, α-Fe2O3 possesses many of the desirable criteria for use in this context.4 However, it is also plagued with electronic issues such as poor charge transport, short carrier lifetimes and low conductivity. 5 This work attempts to address these problems by using plasma enhanced atomic layer deposition (PEALD) to produce nanostructured hematite films with improved properties. Using a ferrocene precursor in a vapour push setup, a process was designed with a pulse purge sequence of 2-5-5-4s (precursor-purge-coreactant-purge) and 0.05nm/cycle growth rate. The performance of the films was then assessed using photoelectrochemical techniques, with film modifications, including Al2O3 underlayers and interlayer doping, explored as a means of improving performance. Specifically, a 0.5nm underlayer was found to improve photocurrent dramatically, exhibiting a peak performance of 1.29 mA cm-2 at 0.7 VAg/AgCl, coupled with a ~250mV cathodic shift in onset potential from the non-modified Fe2O3. Layer or delta doping with Al2O3 offered further improvements in onset potential, with the addition of discrete, 1.2nm thick Al2O3 interlayers generating an impressive VOnset of 0.73 VRHE. This was further lowered to 0.61 VRHE with the addition of a CoPi surface layer. Finally, the effects of heat exposure are addressed, with low energy ion scattering (LEIS) spectroscopy employed to discern compositional changes in the films following heating. Key observations here were the heat-induced migration of aluminium from the underlayers, as well as the suppression of Sn migration from the FTO substrate. In particular, these suppression effects were pronounced for the ALD films compared to other methods of deposition. This provided insight into the mechanisms behind the photoelectrochemical improvements witnessed, while raising questions on the effects of heat exposure on hematite/FTO based photoanodes