<p dir="ltr">Nanoparticles have seen immense development in the past several decades due to their intriguing physicochemical properties. The modern chemist is interested not only in methods of synthesizing nanoparticles with tunable properties but also in the chemistry that nanoparticles can drive. While several methods exist to synthesize nanoparticles, it is often advantageous to put nanoparticles on a variety of conductive substrates for multiple applications (such as energy storage and conversion). Despite enjoying over 200 years of development, the electrodeposition of nanoparticles suffers from a lack of control over nanoparticle size and morphology. Understanding that structure-function studies are imperative to understand the chemistry of nanoparticles, new methods are necessary to electrodeposit a variety of nanoparticles with control over macro-morphology but also microstructure. When a nanodroplet full of a metal salt precursor is incident on the electrode biased sufficiently negative to drive electroplating, nanoparticles form at a shocking rate (on the order of microseconds to milliseconds). We start with the general nuts-and-bolts of the experiment (nanodroplet formation and methods for electrodeposition). The deposition of new nanomaterials often requires one to develop new methods of measurement, and we detail new measurement tools for quantifying nanoparticle porosity and nanopore tortuosity within single nanodroplets. Owing to the small size of the nanodroplets and fast mass transfer, the use of nanodroplets also allows the electrodeposition of high entropy alloy nanoparticles at room temperature. Electrodeposition in aqueous nanodroplets can also be combined with stochastic electrochemistry for a variety of interesting studies. We detail the quantification of the growth kinetics of single nanoparticles in single aqueous nanodroplets. Nanodroplets can also be used as tiny reactors to trap only a few molecules, and the reactivity of those molecules can be electrochemically probed and evaluated with time. Overall, this burgeoning synthetic tool is providing unexpected avenues of tunability of metal nanoparticles on conductive substrates. Moreover, there is little understanding of how ion transfer can affect the fundamental of nanoparticle synthesis with nanodroplet-mediated electrodeposition. This thesis details different experiments performed to study the role of ion transfer during the nucleation and growth of nanoparticles.</p>

Sperm competition is a widely-recognized and powerful selective force. Male accessory glands are organs found across animal taxa that can influence sperm performance, and thus may be selected for in competitive contexts. In fishes, these organs are in fact rare, but display great diversity in form and function across species. Although the accessory gland is known to play a role in mate attraction, parental care, fertilization, or post-copulatory competition in a few select species, the role of this organ remains a mystery in most species. Many fishes with accessory glands also exhibit alternative reproductive tactics (ARTs), which add an extra layer of complexity to how species respond to sperm competition. Because males of different ARTs typically experience different levels of sperm competition risk, it’s possible they may differentially invest in accessory glands to overcome this competition. In this thesis, I used the plainfin midshipman fish (Porichthys notatus), a species with both ARTs and an accessory gland, to experimentally investigate the role of the accessory gland in sperm competition and uncover how this organ may differ between ARTs. Over a two-year period, I studied tactic-specific investment in the accessory gland in fish from the beaches of British Columbia. I also examined the effects of seminal fluid, produced in part by the accessory gland, on sperm performance and morphology. I found that males adopting the ‘guarder’ male tactic invested more in one region (the lobules) of this organ, while males adopting the smaller ‘sneaker’ male tactic invested more the other region of the gland (the nodes). Using data collected over five years, I found that guarder males also invested more in their whole accessory glands. Additionally, I report that sperm swam faster in the presence of seminal fluid, and seminal fluid increased sperm head size in both male tactics and increased midpiece size in guarder males. These results suggest that the plainfin midshipman accessory gland may have dual functions, one of which may be to aid sperm competitive ability through enhancements in swimming speed and potentially more successful sperm morphology. Taken together, the results of my thesis improve our knowledge of the role of non-sperm components like seminal fluid and the accessory gland in sperm competition, and demonstrate how species with ARTs can have varying physiological responses to such competition. Only a handful of studies have considered the effects of seminal fluid on sperm performance. By examining sperm competition in a more biologically relevant way and incorporating the effects of a little-studied organ that impacts sperm competition, we should be able to more generally and accurately appreciate the dynamics of post-copulatory competition and fertilization. / Thesis / Master of Science (MSc)

Surface energetics play a key role in the delivery of a dry powder inhaler formulation into the lungs, as there must be a sufficient balance of adhesive and cohesive forces to allow optimal lung delivery. In this study, measuring the surface energies of a set of single drug and carrier (budesonide or theophylline with either mannitol or lactose) with different levels of surfactant using Inverse Gas Chromatography, and comparing them to their lung deposition performance using a Next Generation Impactor established a relationship between the two. A 1:10 mixing ratio of budesonide with either carrier was found to have the highest FPF. Coating the carriers with 0.05% sodium lauryl sulphate resulted in a further increase in the FPF when using either budesonide or theophylline as the API, and the same results were seen when a sonocrystallised version of the API was substituted for the micronised form. The calculated IGC values then showed that the highest performing formulations had the lowest dispersive energy and total free surface energy. Furthermore, a trend was observed in the work of adhesion (Wa) and work of cohesion (Wc) for each set of formulations depending on which API was chosen, where for the less polar drug (budesonide) a higher Wa/Wc ratio was associated with the highest formulation performance, and for the more polar drug (theophylline) a smaller Wa/Wc ratio was associated with the highest formulation performance, enabling the estimation of lung performance for a set of single drug and carrier using their surface energy data. / Kuwait’s government and the Ministry of Health of Kuwait

At present, structural health monitoring efforts focus primarily on the sensors and sensing systems for detecting instances and locations of damage through techniques such as X-ray, micro CT, acoustic emission, infrared thermography, lamb wave etc., which only detect cracks at relatively large length scales and rely heavily on sensors and sensing systems which are external to the material system. As an alternative to conventional commercially available SHM techniques, the current work explores processing-structure-property relationships starting from carbon nanotube (CNT) based nanocomposites to particulate composites with nanocomposite binder/matrix materials, i.e. hybrid particulate composites to investigate deformation and damage sensing capabilities of inherently sensing materials and structures through their piezoresistive (coupled electro-mechanical) response. Initial efforts focused on controlling the dispersion of CNTs and orientation of CNT filaments within nanocomposites under dielectrophoresis to guide design and fabrication process of nanocomposites by tuning CNT concentration, applied AC electric field intensity, frequency and exposure time. It is observed that a combination of exposure time to AC electric field and the AC field frequency are the key drivers of filament width and spacing and that the network for filament formation is much more efficient for pristine CNTs than for acid treated functionalized CNTs. With the knowledge obtained from controlling the morphological features, AC field-induced long range alignment of CNTs within bulk nanocomposites was scaled up to form structural test coupons. The morphology, electrical and mechanical properties of the coupons were investigated. The anisotropic piezoresistive response both for parallel and transverse to CNT alignment direction within bulk composite coupons under various loading conditions was obtained. It is observed that control of the CNT network allows for the establishment of percolation paths and piezoresistive response well below the nominal percolation threshold observed for random, so called well-dispersed CNT network distributions. The potential for use of such bulk nanocomposites in SHM applications to detect strain and microdamage accumulation is further demonstrated, underscoring the importance of microscale CNT distribution/orientation and network formation/disruption in governing the piezoresistive sensitivities. Finally, what may be the first experimental study in the literature is conducted for real-time embedded microscale strain and damage sensing in energetic materials by distributing the CNT sensing network throughout the binder phase of inert and mock energetic composites through piezoresistive response for SHM in energetic materials. The incorporation of CNTs into inert and mock energetic composites revealed promising self-diagnostic functionalities for in situ real-time SHM applications under quasi-static and low velocity impact loading for solid rocket propellants, detonators and munitions to reduce the stochastic nature of safety characterization and help in designing insult tolerant energetic materials. / Ph. D. / At present, structural health monitoring (SHM) efforts focus primarily on the sensors and sensing systems for detecting instances and locations of damage, which only detect cracks at relatively large length scales and rely heavily on sensors and sensing systems which are external to the material system. As an alternative to conventional commercially available SHM techniques, the current work explores the incorporation of carbon nanotubes (CNTs) into nanocomposites and particulate composites to investigate deformation and damage sensing capabilities of inherently sensing materials and structures through their coupled electromechanical response. Initial efforts focused on controlling the dispersion of CNTs and orientation of CNT filaments within nanocomposites to guide design and fabrication process of nanocomposites. With the knowledge obtained from controlling the morphological features, long range alignment of CNTs within bulk nanocomposites was scaled up to form structural test coupons. The potential for use of such bulk nanocomposites in SHM applications to detect strain and microdamage accumulation is further demonstrated. Finally, what may be the first experimental study in the literature is conducted for real-time embedded deformation and damage sensing in inert and mock energetic composites to reduce the stochastic nature of safety characterization and help in designing insult tolerant solid rocket propellants, detonators and munitions.

Global change holds complex consequences for Earth's ecosystems, with global warming simultaneously affecting multiple aspects including individual physiology, population dynamics and ecosystem processes. In a recent study on stream decomposition under global warming, Réveillon, et al. (2022) combined individual-level laboratory assessments of metabolic rates and leaf-litter ingestion with experimentally parameterized consumer-resource models, designed to reveal how stream-detritivore populations respond to combined impacts of warming and declining body size. Their findings of reduced energetic efficiency, weakened detritivore populations and reduced decomposition in warmed streams expand our understanding of how global change mechanistically links changes from the individual to the ecosystem level.

Despite the central importance of porous electrodes to any advanced electrochemical system, there is no clear answer to “<i>How to make the best electrode</i>?”. The source of ambiguity lies in the incomplete understanding of convoluted material interactions at smaller – difficult to observe length and timescales. Such mesoscopic interactions, however, abide by the fundamental physical principles such as mass conservation. The porous electrodes are investigated in such a physics-based setting to comprehend the interplay among structural arrangement and off-equilibrium processes. As a result, a synergistic approach exploiting the complementary characteristics of controlled experiments and theoretical analysis emerges to allow mechanistic insights into the associated mesoscopic phenomena. The potential of this philosophy is presented by investigating three distinct electrochemical systems with their unique peculiarities.

No description available.

Large-scale atmospheric disturbances play important roles in determining the general circulation of the atmosphere during the North Pacific boreal winter. A number of scientific questions have been raised due to these disturbances’ spatial and temporal complexity as well as the hydrological implication associated with them. In this dissertation, the principal goal is to further improve our understanding of the atmospheric high frequency (HF) and intermediate frequency (IF) disturbances active over the North Pacific. The study focuses on their energetics, intraseasonal and interannual variability, and the resulting hydrological impact over the eastern North Pacific and Western U.S. including extreme events. To delineate the characteristics of HF and IF disturbances in the troposphere, we first derive a new set of equations governing the local eddy kinetic energy (EKE), and assess the critical processes maintaining local budgets of the HF and IF EKE. The diagnosis assesses the 3-D patterns of energy flux convergence (EFC), barotropic conversion (BT), baroclinic conversion (BC), and cross-frequency eddy-eddy interaction (CFEI). The local EKE budget analysis is followed by an investigation of the modulation of HF and IF eddy activity by different modes of low frequency climate variability. On interannual timescales, the response of various local energetic processes to El Niño-Southern Oscillation (ENSO) determines the HF and IF EKE anomalies and the role of CFEI process is important in producing these anomalies. Also on interannual timescales, winter precipitation deficits associated with suppressed cyclonic activity, i.e., negative HF EKE anomalies, are linked to severe droughts over the U.S. Southern Great Plain (SGP) region. The suppressed cyclonic activity is, in turn, tied to phase changes in the West Pacific (WP) teleconnection pattern. On intraseasonal timescales, variations in HF disturbances (a.k.a. storm tracks) over the North Pacific are closely coupled with tropical convection anomalies induced by the Madden-Julian Oscillation (MJO), and partly drive larger scale intraseasonal flow anomalies in this region through eddy-eddy interactions. Anomalous HF eddy activity induces subseasonal transitions between “wet” and “dry” regimes over the west coast of North America. Also on intraseasonal timescales, the East Asian cold surge (EACS) is found to provide a remote forcing of the winter precipitation anomalies in the western U.S. This modulation is achieved through “atmospheric rivers” (ARs), which are narrow channels of concentrated moisture transport in the atmosphere and are responsible for over 70% of the extreme precipitation events in the western U.S.. EACS effectively modulates the IF disturbance activity over the North Pacific, and the anomalous IF disturbances lead to the formation of an AR over the eastern North Pacific that ultimately induces precipitation anomalies in the western U.S. Analyses of the simulations from the NCAR Community Climate System Model version 4 (CCSM4) demonstrate that the connections among the EACS, AR and western U.S. precipitation are better captured by a model with higher spatial resolutions. The improved simulation of these connections is achieved mainly through a better representation of the IF disturbances, and the associated scale-interaction processes in the higher resolution model.

The current understanding of lactate metabolism in fish is based almost entirely on interpretation of concentration measurements that cannot be used to infer changes in flux. Moreover, the transporters regulating these fluxes have never been characterized in rainbow trout. My goals were: (1) to quantify lactate fluxes in rainbow trout under normoxic resting conditions, during acute hypoxia, and exercise by continuous infusion of [U-14C] lactate; (2) to determine lactate uptake capacity of trout tissues by infusing exogenous lactate in fish rest and during graded exercise, and (3) to clone monocarboxylate transporters (MCTs) and determine the effects of exhausting exercise on their expression. Such information could prove important to understand the mechanisms underlying the classic “lactate retention” seen in trout white muscle after intense exercise. In normoxic resting fish, the rates of appearance (Ra) and disappearance (Rd) of lactate were always matched (~18 to 13 µmol kg-1 min-1), thereby maintaining a low baseline blood lactate concentration (~0.8 mM). In hypoxic fish, Ra lactate increased from baseline to 36.5 µmol kg-1 min-1, and was accompanied by an unexpected 52% increase in Rd reaching 30.3 µmol kg-1 min-1, accounting for a rise in blood lactate to 8.9 mM. In exercising fish, lactate flux was stimulated > 2.4 body lengths per second (BL s-1). As the fish reached critical swimming speed (Ucrit), Ra lactate was more stimulated (+67% to 40.4 μmol kg-1 min-1) than Rd (+41% to 34.7 μmol kg-1 min-1), causing an increase in blood lactate to 5.1mM. Fish infused with exogenous lactate stimulated Rd lactate by 300% (14 to 56 μmol kg-1 min-1) during graded exercise, whereas the Rd in resting fish increased by only 90% (21 to 40 µmol kg-1 min-1). Four MCT isoforms were partially cloned and characterized in rainbow trout: MCT1b was the most abundant in heart, and red muscle, but poorly expressed in gill and brain where MCT1a and MCT2 were prevalent. MCT4 was more expressed in the heart. Transcript levels of MCT2 (+260%; brain), MCT1a (+90%; heart) and MCT1b (+50%; heart) were stimulated by exhausting exercise. This study shows that: (i) the increase in Rd lactate plays a strategic role in reducing the lactate load imposed on the circulation. Without this response, blood lactate accumulation would double; (ii) a high capacity for lactate disposal in rainbow trout tissues is elicited by the increased blood-to-tissue lactate gradient when extra lactate is administered; and (iii) rainbow trout may be unable to release large lactate loads rapidly from white muscle after exhausting exercise (lactate retention) because they poorly express MCT4 in white muscle and fail to upregulate its expression during exercise.

Au cours de la croissance et de la maturation, le muscle squelettique subit de nombreux changements. Principalement on constate une augmentation considérable de la masse musculaire concomitante à l’augmentation de la capacité de force et plusieurs résultats suggèrent que la maturation affecte la fonction musculaire à la fois au niveau de la commande motrice et du métabolisme énergétique. Pour des raisons éthiques évidentes, la fonction musculaire n’a été que peu étudiée chez l’enfant. Malgré leur caractère strictement non-invasif les techniques de résonance magnétique n’ont été que peu utilisées pour caractériser cette fonction chez l’enfant et les résultats controversés ne permettent pas de dégager un consensus. Dans ce travail la fonction musculaire de l’enfant sain a été étudiée in vivo par Imagerie et Spectroscopie de Résonance Magnétique. Par IRM, nous nous avons mis en évidence que la capacité de force volontaire maximale d’un muscle reste proportionnelle à sa taille de l’enfance à l’âge adulte. Par ailleurs nos résultats obtenus par SRM du P31 ont clairement montré que la capacité oxydative et la production d’ATP mitochondriale était augmentée avant la puberté, illustrant que les enfants sollicitaient plus leur métabolisme aérobie que les adultes pour répondre à la demande énergétique pour une intensité donnée. De plus, nos résultats ont montré que la filière énergétique de la glycolyse anaérobie était pleinement mature dès l’enfance. Enfin, face à la difficulté pour mettre en place des études longitudinales chez l’homme nous avons développé un protocole expérimental permettant le suivi longitudinal de la fonction musculaire au cours du développement chez le rat. / Growth and maturation are accompanied by important changes in skeletal muscle function (e.g. muscle mass and strength dramatically increase). Moreover, some evidences strongly suggest that maturation significantly affects skeletal muscle function both at the neural drive and energetics levels. For ethical reasons, few studies have been performed in children. Despite their non traumatic aspect the MR techniques, it has been barely used in this context. In this work, the skeletal muscle function of healthy children has been characterized in vivo using MRI and 31P-MRS. Our results refuted the hypothesis of a motor drive immaturity in children. We did not report any change in the relationship between muscle volume measured by MRI and maximum isometric strength or in specific strength from childhood to adulthood. The ability of a given muscle volume to produce force seems not to change during growth. Then, we investigated whether development affects muscle energetics using 31P-MRS comparing prepubescent boys and men. Our results showed that, for a similar total energy cost, the aerobic contribution to ATP production was significantly higher in boys and compensated for by a reduced PCr breakdown while glycolysis was similar whatever the age. In addition, the recovery rate of PCr after the standardized exercise was faster in boys illustrating a higher maximal oxidative capacity before puberty. Finally, our understanding of skeletal muscle function in children is still limited by the difficulty to perform longitudinal studies. In that respect, we have initiated an original protocol allowing the longitudinal investigation of the gastrocnemius muscle throughout development in rat.