Dust grains are a crucial component of disks around young stellar systems where current observations and theory show that planets form. Dust grains must grow 10 orders of magnitude in size to become planets. However, one of the early steps in this growth phase faces stringent theoretical constraints. The metre barrier relates to two well-studied physical mechanisms which inhibit grain growth beyond centimetre sizes. We report on numerical studies which probe these early stages of planet formation including instabilities that promote dust concentration such as the streaming instability (SI). We explore several different SPH models for dusty gas evolution. We find the linear SI is difficult for SPH to capture because it begins with perturbations below the 1% level. We also employ the Athena 3rd order Eulerian code which has been used to study the SI in the linear phase and the non-linear or saturated phase. We present numerical confirmations of recent analytical predictions of enhancements to the SI growth rates caused by the dust settling to the disk midplane in the earliest stages of the protoplanetary disk evolution. Symmetric analytical predictions for SI growth are not directly relevant to the non-axisymetric, planar geometry of the saturated, non-linear phase. We lay the ground work to explore this in future work. / Thesis / Master of Science (MSc)

A mathematical approach to the concepts of copolymerization of microtubules in the presence of anti-mitotic drugs is presented in this work. A general feature of the mathematical equations is presented. The possibility of having analytical steady state solutions of dynamic equations is investigated. The structure of equations is narrowed down for the specific brand of anti-mitotic drug, colchicine. The behavior of total T-tubulin concentration in the steady state in a regeneration system is investigated and analyzed through the numerical calculations. / Ph. D.

No / Examining two centuries of Balkan politics, from the emergence of nationalism to the retreat of Communist power in 1989, this is the first book to systematically argue that many of the region's problems are external in origin. A decade of instability in the Balkan states of southeast Europe has given the region one of the worst images in world politics. The Balkans has become synonymous with chaos and extremism. Balkanization, meaning conflict arising from the fragmentation of political power, is a condition feared across the globe. This new text assesses the key issues of Balkan politics, showing how the development of exclusive nationalism has prevented the region¿s human and material resources from being harnessed in a constructive way. It argues that the proximity of the Balkans to the great powers is the main reason for instability and decline. Britain, Russia, Austria-Hungary, France and finally the USA had conflicting ambitions and interests in the region. Russia had imperial designs before and after the 1917 Revolution. The Western powers sometimes tolerated these or encouraged undemocratic local forces to exercise control in order to block further Soviet expansion. Leading authority Tom Gallagher examines the origins of these Western prejudices towards the Balkans, tracing the damaging effects of policies based on Western lethargy and cynicism, and reassesses the negative image of the region, its citizens, their leadership skills and their potential to overcome crucial problems.

The gain or loss of whole chromosomes, known as aneuploidy, is a distinguishing feature of cancer cells. The rapid gain or loss of hundreds of genes dramatically alters a cell's genomic landscape and is typically detrimental to cell survival under normal conditions. However, cancer cells display enhanced proliferation and overcome multiple conditions of stress, suggesting aneuploidy may increase cellular fitness. Furthermore, distinct patterns of aneuploidy are found in cancers from different anatomical sites. Despite these observations, scant research has sought to examine the role of aneuploidy in cancer, or determine whether aneuploidy is a driver or passenger mutation, or why certain aneuploidies appear to be selected for and others against. To investigate the role of aneuploidy in cancer cell fitness, we utilized the diploid colorectal cancer (CRC) cell line DLD1 and two trisomic variants carrying an extra copy of either chromosome 7 or chromosome 13, two trisomies frequently seen in colorectal cancer. To assess fitness, we compared proliferation, anchorage-independence, and invasiveness in aneuploid CRC cells versus their diploid counterpart when grown under various culture conditions, including regular media, serum-free media, cytotoxic drug-containing media, and hypoxia. We found that aneuploid cells proliferated better than diploid cells under all but standard culture conditions. Moreover, regardless of growth condition, we found that aneuploid CRC cells formed larger and more numerous colonies in soft agar (anchorage-independent growth), and displayed greater invasiveness (assessed by matrigel invasion assay). Taken together, these results indicate that aneuploidy enhances the fitness of CRC cells under stressful conditions that are likely to occur in the tumor microenvironment. / Master of Science

This thesis deals with the instabilities of the incompressible boundary-layer flow thatis induced by a disk rotating in otherwise still fluid. The results presented include bothwork in the linear and nonlinear regime and are derived from direct numerical sim-ulations (DNS). Comparisons are made both to theoretical and experimental resultsproviding new insights into the transition route to turbulence. The simulation codeNek5000 has been chosen for the DNS using a spectral-element method (SEM) witha high-order discretization, and the results were obtained through large-scale paral-lel simulations. The known similarity solution of the Navier–Stokes equations for therotating-disk flow, also called the von K ́arm ́an rotating-disk flow, is reproduced by theDNS. With the addition of modelled small simulated roughnesses on the disk surface,convective instabilities appear and data from the linear region in the DNS are anal-ysed and compared with experimental and theoretical data, all corresponding verywell. A theoretical analysis is also presented using a local linear-stability approach,where two stability solvers have been developed based on earlier work. Furthermore,the impulse response of the rotating-disk boundary layer is investigated using DNS.The local response is known to be absolutely unstable and the global response, onthe contrary, is stable if the edge of the disk is assumed to be at radius infinity. Herecomparisons with a finite domain using various boundary conditions give a globalbehaviour that can be both linearly stable and unstable, however always nonlinearlyunstable. The global frequency of the flow is found to be determined by the Rey-nolds number at the confinement of the domain, either by the edge (linear case) or bythe turbulence appearance (nonlinear case). Moreover, secondary instabilities on topof the convective instabilities induced by roughness elements were investigated andfound to be globally unstable. This behaviour agrees well with the experimental flowand acts at a smaller radial distance than the primary global instability. The sharpline corresponding to transition to turbulence seen in experiments of the rotating diskcan thus be explained by the secondary global instability. Finally, turbulence datawere compared with experiments and investigated thoroughly. / <p>QC 20170203</p>

In this thesis I describe the conceptual model of three kinds of instability in terms of precipitation. I describe ways of evaluating their presence in the atmosphere. They are: conditional instability, potential instability and symmetric instability. I have selected three events with strong precipitation in the Czech Republic so that the formation of each of them is with high probability involved in just one of the three kinds of instability. Events are first described using distance and station measurements. Through the NWP model COSMO are created prognostic fields of precipitation and several derived thermodynamic quantities for each event. On the horizontal (for the whole country) and vertical (for selected areas of the Czech Republic) distribution of these variables are demonstrated favourable conditions for the occurrence of the types of instability in the atmosphere. In the event of conditional instability the rainfall occurs in areas with high CAPE and negative or very small positive vertical lapse rate of potential temperature. The event with the potential instability is characterized by the occurrence of negative vertical lapse rate of equivalent potential temperature in the broad layers. The occurrence of symmetric instability suggests a number of indicators. The necessary occurence...

The rotating-disk boundary layer is not only a simpler model for the study of cross-flow instability than swept-wing boundary layers but also a useful simplification of many industrial-flow applications where rotating configurations are present. For the rotating disk, it has been suggested that a local absolute instability, leading to a global instability, is responsible for the small variation in the observed laminar-turbulent transition Reynolds number however the exact nature of the transition is still not fully understood. This thesis aims to clarify certain aspects of the transition process. Furthermore, the thesis considers the turbulent rotating-disk boundary layer, as an example of a class of three-dimensional turbulent boundary-layer flows. The rotating-disk boundary layer has been investigated in an experimental apparatus designed for low vibration levels and with a polished glass disk that gave a smooth surface. The apparatus provided a low-disturbance environment and velocity measurements of the azimuthal component were made with a single hot-wire probe. A new way to present data in the form of a probability density function (PDF) map of the azimuthal fluctuation velocity, which gives clear insights into the laminar-turbulent transition region, has been proposed. Measurements performed with various disk-edge conditions and edge Reynolds numbers showed that neither of these conditions a↵ect the transition process significantly, and the Reynolds number for the onset of transition was observed to be highly reproducible. Laminar-turbulent transition for a ‘clean’ disk was compared with that for a disk with roughness elements located upstream of the critical Reynolds number for absolute instability. This showed that, even with minute surface roughness elements, strong convectively unstable stationary disturbances were excited. In this case, breakdown of the flow occurred before reaching the absolutely unstable region, i.e. through a convectively unstable route. For the rough disk, the breakdown location was shown to depend on the amplitude of individual stationary vortices. In contrast, for the smooth (clean-disk) condition, the amplitude of the stationary vortices did not fix the breakdown location, which instead was fixed by a well-defined Reynolds number. Furthermore, for the clean-disk case, travelling disturbances have been observed at the onset of nonlinearity, and the associated disturbance profile is in good agreement with the eigenfunction of the critical absolute instability. Finally, the turbulent boundary layer on the rotating disk has been investigated. The azimuthal friction velocity was directly measured from the azimuthal velocity profile in the viscous sublayer and the velocity statistics, normalized by the inner scale, are presented. The characteristics of this three-dimensional turbulent boundary-layer flow have been compared with those for the two-dimensional flow over a flat plate and close to the wall they are found to be quite similar but with rather large differences in the outer region. / <p>QC 20150119</p>

Lateral ankle sprains are the most common musculoskeletal injury among the general population and U.S. military personnel. Despite the common perception of being a minor injury, at least 1 out of 3 individuals with a previous ankle sprain will develop chronic ankle instability (CAI). This clinical phenomenon creates a significant barrier for patients to return to their prior level of physical function. Specifically, CAI is associated with reductions in physical activity level, leading to decreases in lower health-related quality of life and increase risk of developing of post-traumatic ankle osteoarthritis. Current evidence has largely focused on characterizing the mechanical and sensorimotor insufficiencies associated with CAI in adolescent and young-adult populations, with little attention on middle- and older-aged adults. This restricts our understanding of how these insufficiencies associated with CAI that develop in early adulthood progress over time and contribute to other chronic diseases such as post-traumatic osteoarthritis. Therefore, the overall objective of this study was to compare self-reported and physical function between three age groups: 1) young, 2) middle-aged, and 3) older-aged adults with and without CAI. We hypothesized participants with CAI would have age-related changes in self-reported and physical function compared to non-injured individuals across the lifespan. The objective of this dissertation was to compare regional and global health- related quality of life (HRQoL), static and dynamic balance, spinal reflex excitability of the soleus muscle, open- and closed-kinetic chain dorsiflexion range of motion and spatiotemporal gait parameters between those with and without CAI across the lifespan. Her callIt was hypothesized that all self-reported and physical characteristics would be decrease with age, but significantly more in those with CAI compare to non-injured individuals. Results from the first study demonstrated participants with CAI had worse regional HRQoL compared to healthy-controls as evidenced by the lower Foot and Ankle Disability Index scores. Likewise, participants with CAI reported having worse overall physical function and pain interference during activity compared to healthy-controls. There was no significant interaction for Injury (CAI and healthy-control) and Age group (young, middle, and old) for any dependent variable. In the second, it was determined that static and dynamic balance, spinal reflex excitability, ankle (dorsiflexion and plantarflexion) and hip extension torque were all lower in the older-aged participants compared to the younger-aged adults. In addition, it was determined that participants with CAI had decreased dorsiflexion range of motion, ankle (dorsiflexion and plantar flexion) and hip extension peak isometric torque compared to the healthy-control group. However, no significant interaction was found for Injury (CAI & healthy-control) and Age (young, middle, old) for any dependent variable. In the third study, there were no differences in spatiotemporal gait parameters between groups (CAI vs. healthy-controls) or age categories. It can be concluded from this dissertation that regardless of the age, individuals with CAI have worse region-specific HRQoL, lower overall physical function, greater pain interference, limited dorsiflexion range of motion, and decreased ankle and hip peak isometric torque compared to healthy-controls. Several age-related observations were found including decreased static and dynamic balance, ankle and hip strength, and spinal reflex excitability. Though no relationship was found between CAI and age, several interactions were found to be trending towards significance. Therefore, future work is needed to better understand the consequences of CAI on middle- and older-aged adults.

This work derives a nonlinear optical spatio-temporal instability. It is a perturbative analysis that begins from Maxwell’s equations and its constituent relations to derive a vectorial nonlinear wave equation. In fact, it is a new theoretical method that has been developed that builds on previous aspects of nonlinear optics in a more general way. The perturbation in the wave equation derived is coupled with its complex conjugate which has been taken for granted so far. Once decoupled it gives rise to a second-order equation and thus a true instability regime because the wavevector can become complex. The solution obtained for the perturbation that co-propagates with the driving laser is a generalization to modulation and filamentation instability, extending beyond the nonlinear Schrodinger and nonlinear transverse diffusion equations[1][2]. As a result of this new mechanism, new phenomena can be explored. For example, the Kerr Nonlinear Instability can lead to exponential growth, and hence amplification. This can occur even at wavelengths that are typically hard to operate at, such as into far infrared wave- lengths. This provides a mechanism for obtaining amplification in the far infrared from a small seed pulse without the need for population inversion. The analysis provides the basic framework that can be extended to many different avenues. This will be the subject of future work, as outlined in the conclusion of this thesis.

The overarching goal of this work is to advance the current knowledge of hydrodynamic instabilities (namely, Richtmyer-Meshkov and Kelvin-Helmholtz instabilities) and associated turbulent mixing phenomena which is important for several emerging technologies and verification/validation of numerical models being developed to study these phenomena. Three experimental campaigns were designed to focus on understanding the evolution of the instability under different impulsive acceleration histories and highlight the impact of initial conditions on the developing turbulent flow environment. The first campaign highlights the importance of initial baroclinic torque distribution along the developing shocked interface in a twice-shocked variable-density flow environment. The second campaign is a parametric study which aims at providing a large dataset for validating models in literature as well as simulations. In the last study, a new type of initial condition was designed to study the effect of initial conditions on late time turbulent flows. A description of the optical diagnostic techniques developed in our laboratory in order to complete these studies will be given. Now each campaign will be introduced. In the first campaign, an inclined interface perturbation is used as the initial condition. The Mach number (1.55), angle of inclination (60 degrees), and gas pair (N2/CO2) were held constant. The parameter which changed was the distance that the initial condition was placed relative to the end of the shock tube (i.e., the end of the test section). Three distances were used. The vorticity distribution was found to be very different for the most developed case after reshock. Furthermore, the most developed case started to develop an inertial range before reshock. The second campaign is parametric and seeks to test a proposed inclined interface scaling technique. The data is also useful for comparing to Ares simulation results. The parameter space covered Mach number (1.55 and 2.01), inclination angle (60 degrees and 80 degrees), and Atwood number (0.23 and 0.67). PLIF was developed and used to collect data for four cases before and after reshock. Linear and nonlinear cases developed very differently before reshock, but their mixing widths converged after reshock. The last campaign involves a new perturbation technique which generates what will be referred to as a complex interface. Counter-flowing jets were placed near the interface exit ports to create shear. The perturbation was made more complex by also injecting light (heavy) gas into the heavy (light) one. Density and velocity statistics were collected simultaneously. The complex case retained a signature of the inclined interface perturbation at late time before reshock and developed a larger inertial range than its inclined interface counterpart. Important parameters for a variable-density turbulence model are also presented.