Common and Fundamental Factors in Stock Returns of Canadian Oil and Gas Companies

In this paper, we assess the determinants of Canadian oil and gas stocks returns. We find that the stock return of Canadian energy stock is positively associated with returns on the Canadian stock market, appreciations of crude oil and natural gas prices, growth in internal cash flows and proven reserves, and negatively with interest rates. Surprisingly, however, production volume and a weakening of the Canadian dollar against the U.S. dollar have a negative impact. This latter impact is more pronounced for oil producers than for integrated energy companies. Finally, we find that the influence of the exchange rate, the market return and prices of natural gas on Canadian oil and gas stocks changes significantly over the years 1995-1998 and 2000-2002. Le but de cet article est de mesurer ce qui influence le rendement des actions d'entreprises pétrolières et gazières canadiennes. Nous trouvons que le rendement des actions de ces entreprises énergétiques est influencé positivement par le rendement du marché canadien dans son ensemble, par une appréciation du prix du pétrole et du gaz naturel, par une croissance dans les flux monétaires discrétionnaires de l'entreprise, par la quantité de réserves prouvées de l'entreprise. Nous trouvons également que le volume de production et une dépréciation du dollar canadien par rapport à la devise américaine réduit sensiblement le rendement des titres énergétiques, ce qui va à l'encontre de notre hypothèse initiale. L'impact du taux de change est encore plus marqué pour les producteurs indépendants que pour les entreprises intégrées. En dernier lieu, nous montrons que le marché a subi une cassure significative entre les années 1995-1998 et 2000-2002, spécialement pour ce qui est de l'impact du taux de change, du rendement de marché et du pris du gaz naturel.stock return valuation, panel data analysis, oil and gas industry, rendement des actions, analyse de données transversales, industrie pétrolière et gazière

Biomimetic Synthetic Tissue Scaffolds for Bone Regeneration: A Dissertation

Injury to bone is one of the most prevalent and costly medical conditions. Clinical treatment of volumetric bone loss or hard-to-heal bony lesions often requires the use of proper bone grafting materials, with or without adjuvant anabolic therapeutics. Despite significant problems associated with autografting (donor site morbidity, limited supplies) and allografting (disease transmissions, high graft failure rates) procedures, synthetic bone grafts remain the least utilized clinically. Existing synthetic orthopaedic biomaterials rarely possess a combination of bone-like structural and biochemical properties required for robust osteointegration, scalable and user-friendly characteristics indispensable for successful clinical translations. This thesis tests the hypothesis that by recapitulating key structural elements and biochemical components of bone in 3- and 2-dimensional biomaterials, scalable synthetic bone grafts can be designed to enable expedited healing of hard-to-heal volumetric bone loss. Specifically, FlexBone, a 3-dimensional hydrogel scaffold encapsulating 50 wt% of structurally well integrated nanocrylstalline hydroxyapatite, the main inorganic component of bone, was developed. The large surface area of nanocrystalline hydroxyapatite combined with its intrinsic affinity to proteins and its excellent structural integration with the hydrogel matrix enabled FlexBone to both sequester endogenous protein signals upon press-fitting into an area of skeletal defect and to deliver exogenous protein therapeutics in a localized and sustained manner. We demonstrated that FlexBone enabled the functional healing of critical-size long bone defects in rats in 8 – 12 weeks with the addition of a very low dose of osteogenic growth factor BMP-2/7. This promising synthetic bone graft is now being explored for the delivery of multiple growth factors to expedite the healing of diabetic bony lesions. In addition, a 2-dimensional electrospun cellulose fibrous mesh was chemically modified with sulfate residues to mimic sulfated polysaccharide ECM components of skeletal tissues to enabled progenitor cell attachment and differentiation as well as controlled retention and localized/sustained delivery of protein therapeutics. This sulfated fibrous mesh is currently explored as synthetic periosteum to augment the osteointegration of devitalized structural allografts. Finally, a rat subcutaneous implantation model developed to examine the biocompatibility of newly developed biodegradable shape memory polymer bone substitutes is also presented

Scalable Functional Bone Substitutes: Strategic Integration of Key Structural Elements of Bone in Synthetic Biomaterials

Summary: Introduces recent advances in the evolvement of non-metallic orthopedic biomaterials in the design of organic-inorganic composite bone substitutes

Non-Equilibrium Surface Tension of the Vapour-Liquid Interface of Active Lennard-Jones Particles

We study a three-dimensional system of self-propelled Brownian particles interacting via the Lennard-Jones potential. Using Brownian Dynamics simulations in an elongated simulation box, we investigate the steady states of vapour-liquid phase coexistence of active Lennard-Jones particles with planar interfaces. We measure the normal and tangential components of the pressure tensor along the direction perpendicular to the interface and verify mechanical equilibrium of the two coexisting phases. In addition, we determine the non-equilibrium interfacial tension by integrating the difference of the normal and tangential component of the pressure tensor, and show that the surface tension as a function of strength of particle attractions is well-fitted by simple power laws. Finally, we measure the interfacial stiffness using capillary wave theory and the equipartition theorem, and find a simple linear relation between surface tension and interfacial stiffness with a proportionality constant characterized by an effective temperature.Comment: 12 pages, 5 figures (Corrected typos and References

Optimization of the Design of an Amphiphilic Biodegradable Polymer for Tissue-engineering Application

Biodegradable polymers have been widely utilized as drug delivery vehicles and tissue engineering scaffolds. We previously designed amphiphilic triblock copolymer poly(lactic acid)-b-poly(ethylene glycol)-b-poly(lactic acid) (PELA) and its hydroxyapatite (HA) composites for bone tissue engineering applications. The hydrophilic electrospun PELA-HA composite exhibited aqueous stability and elastic handling characteristics, and was able to template the proliferation and osteogenesis of bone marrow stromal cells (BMSCs) in vitro and in vivo when spiral-wrapped into cylinders and press-fit into critical size femoral segmental defects in rats. However, the slow degradation of PELA has prevented timely disappearance of the scaffold and impeded more effective restoration of biomechanical integrity of the defect. To accelerate degradation, in this work we designed poly(lactic/glycolic acid)-b-poly(ethylene glycol)-b-poly(lactic/glycolic acid) (PELGA) with varying ratios of glycolide and lactide and confirmed their more accelerated degradations as compared to PELA. Processing conditions (e.g. solvent-casting vs. electrospinning, with or without hydration) significantly impacted the structural characteristics of PELGA and their HA composites. The PEG crystallization in PELGA was not as strong as in PEG homopolymers, giving rise to a lower Tm. HA could be well dispersed in PELGA and electrospun to give a uniform composite where the crystallization of PEG was promoted by water resulting in enhanced mechanical strength upon hydration. These HA-contained electrospun meshes exhibited excellent cytocompatibility and efficacy in templating osteogenesis of rat BMSCs in vitro

Improving the prediction of glassy dynamics by pinpointing the local cage

The relationship between structure and dynamics in glassy fluids remains an intriguing open question. Recent work has shown impressive advances in our ability to predict local dynamics using structural features, most notably due to the use of advanced machine learning techniques. Here we explore whether a simple linear regression algorithm combined with intelligently chosen structural order parameters can reach the accuracy of the current, most advanced machine learning approaches for predicting dynamic propensity. To do this we introduce a method to pinpoint the cage state of the initial configuration -- i.e. the configuration consisting of the average particle positions when particle rearrangement is forbidden. We find that, in comparison to both the initial state and the inherent state, the structure of the cage state is highly predictive of the long-time dynamics of the system. Moreover, by combining the cage state information with the initial state, we are able to predict dynamic propensities with unprecedentedly high accuracy over a broad regime of time scales, including the caging regime

Crystallization in suspensions of hard spheres: A Monte Carlo and Molecular Dynamics simulation study

The crystallization of a metastable melt is one of the most important non equilibrium phenomena in condensed matter physics, and hard sphere colloidal model systems have been used for several decades to investigate this process by experimental observation and computer simulation. Nevertheless, there is still an unexplained discrepancy between simulation data and experimental nucleation rate densities. In this paper we examine the nucleation process in hard spheres using molecular dynamics and Monte Carlo simulation. We show that the crystallization process is mediated by precursors of low orientational bond-order and that our simulation data fairly match the experimental data sets

Can Monkeys (Macaca mulatta) Represent Invisible Displacement?

Four experiments were conducted to assess whether or not rhesus macaques (Macaca mulatta) could represent the unperceived movements of a stimulus. Subjects were tested on 2 computerized tasks, HOLE (monkeys) and LASER (humans and monkeys), in which subjects needed to chase or shoot at, respectively, a moving target that either remained visible or became invisible for a portion of its path of movement. Response patterns were analyzed and compared between target-visible and target-invisible conditions. Results of Experiments 1, 2, and 3 demonstrated that the monkeys are capable of extrapolating movement. That this extrapolation involved internal representation of the target's invisible movement was suggested but not confirmed. Experiment 4, however, demonstrated that the monkeys are capable of representing the invisible displacements of a stimulus

Point Defects in Crystals of Charged Colloids

Charged colloidal particles - both on the nano and micron scales - have been instrumental in enhancing our understanding of both atomic and colloidal crystals. These systems can be straightforwardly realized in the lab, and tuned to self-assemble into body-centered cubic (BCC) and face-centered cubic (FCC) crystals. While these crystals will always exhibit a finite number of point defects, including vacancies and interstitials - which can dramatically impact their material properties - their existence is usually ignored in scientific studies. Here, we use computer simulations and free-energy calculations to characterize vacancies and interstitials in both FCC and BCC crystals of point-Yukawa particles. We show that, in the BCC phase, defects are surprisingly more common than in the FCC phase, and the interstitials manifest as so-called crowdions: an exotic one-dimensional defect proposed to exist in atomic BCC crystals. Our results open the door to directly observing these elusive defects in the lab.Comment: 8 pages, 4 figure