Master of Science

thesisAdmittance-type robotic devices are commonly used to complete tasks that require a high degree of precision and accuracy because they appear nonbackdrivable to many disturbances from the environment. Admittance-type robots are controlled using admittance control; a human interacts directly with a force sensor mounted to the robot, and the robot is computer-controlled to move in response to the applied force. The experiment herein was conducted to determine under which operating conditions human velocity control is optimized for admittance devices that are controlled under proportional-velocity control, and to determine the degradation in control under nonoptimal conditions. In this study, the desired velocity of the device was shown on a visual display. The desired velocity was shown with a scaling factor from the actual velocity of the device because the device often moved at velocities too slow to perceive visually. The admittance gain, ka, desired velocity, Vd, and the visualization scale factor, S were tuned to adjust the user's experience when interacting with an admittance device. We found that in velocity-tracking tasks, scaling the visual feedback only has a significant effect on performance for very slow desired velocities (0.1mm/s), for the range of velocities tested here. In this thesis, we give evidence that there exists a range of velocities and forces within which humans optimally interact with admittance-type devices. We found that the optimal range of velocities is between 0.4mm/s and 1.0mm/s, inclusive, and the optimal range of forces is between 0.4 N and 4.0 N, inclusive. To ensure optimal velocity-control performance, the admittance gain should be selected such that the desired velocity and target force remain within their respective optimal ranges simultaneously. We also found that on average subjects moved faster than the desired velocity when the desired velocity was 0.1 mm/s and subjects were slower than the desired velocity when it was higher than 0.4 mm/s. For each admittance gain there is a different threshold velocity at which velocity-control accuracy is optimal in the aggregate. If the device operates at a velocity that is faster or slower than the threshold velocity the operator will tend to lag or lead the desired velocity, respectively

Quantum attacks on Bitcoin, and how to protect against them

The key cryptographic protocols used to secure the internet and financial transactions of today are all susceptible to attack by the development of a sufficiently large quantum computer. One particular area at risk are cryptocurrencies, a market currently worth over 150 billion USD. We investigate the risk of Bitcoin, and other cryptocurrencies, to attacks by quantum computers. We find that the proof-of-work used by Bitcoin is relatively resistant to substantial speedup by quantum computers in the next 10 years, mainly because specialized ASIC miners are extremely fast compared to the estimated clock speed of near-term quantum computers. On the other hand, the elliptic curve signature scheme used by Bitcoin is much more at risk, and could be completely broken by a quantum computer as early as 2027, by the most optimistic estimates. We analyze an alternative proof-of-work called Momentum, based on finding collisions in a hash function, that is even more resistant to speedup by a quantum computer. We also review the available post-quantum signature schemes to see which one would best meet the security and efficiency requirements of blockchain applications.Comment: 21 pages, 6 figures. For a rough update on the progress of Quantum devices and prognostications on time from now to break Digital signatures, see https://www.quantumcryptopocalypse.com/quantum-moores-law

Stability of ESCRT III Snf7 Polymer Influenced by: Bro1 and Vps2/Vps24

The endosomal sorting complexes required for transport (ESCRT) are protein complexes that remodel cellular membranes. The ESCRT III membrane machinery has been implicated in regulating membrane bound receptor proteins through the multi-vesicular body (MVB) pathway, during the end of cytokinesis, and being manipulated by the HIV virus during infection. My thesis project focuses on the in vivo regulation of ESCRT III. Bro1 binding to the Snf7 protein polymer helped stabilize ESCRT III. With this understanding that Bro 1 stabilizes the Snf7 polymer, two questions can be posed: Does it block Vps4 mediated Snf7 disassembly? Or does it block Vps2 and Vps24 from capping the Snf7 polymer? The latter of these two questions is the focus of my thesis. My research has shown the interaction of the capping Vps2:Vps24 dimer to only slightly affect protein sorting in the ESCRT pathway

Levels of Citation of Nonhuman Animal Studies Conducted at a Canadian Research Hospital

The publication of scientific articles that receive few or no citations raises questions of the appropriate use of resources as well as ethics. In the case of animal research, the ethics issue extends beyond human patients to nonhuman animals, as the research subjects them to pain and, typically, to death. This study is a citation analysis of animal research conducted at Toronto\u27s Hospital for Sick Children (HSC). Of the 594 publications (1990 to 1995) on animal research by affiliates of HSC, 29% received Iower than 10 citations in a 10-year period. We compare the research history of 13 best and 13 worst HSC scientists. Worst researchers continue to do infrequently cited research. Recommendations indicate how institutions and researchers can become more effective and accountable

It Isn\u27t Always Sexy When Both are Bright and Shiny: Considering Alternatives to Sexual Selection in Elaborate Monomorphic Species

Since the dawn of abstract thinking, humans have wondered about the seemingly unnecessary elaborate ornamentations of birds. Gaudy colours, cumbersome tails, complex vocalizations and bizarre displays are found in bird species from all corners of the globe. Darwin (1871) provided an elegant explanation for the existence of these non-utilitarian traits: they increase mating success, and although they may impair survival, the costs of producing and bearing elaborate ornaments can be repaid in the currency of additional offspring. Darwin’s model still serves as the foundation for our concept of sexual selection but great strides have been made in our understanding of sexual selection processes since his time (e.g. Zahavi 1975, 1977, Lande 1980, Hamilton & Zuk 1982, Kirkpatrick 1982, Grafen 1990, Andersson 1994). The great majority of work to date has focused on species in which males alone are elaborately ornamented. Far less has been published on the function of ornaments that are expressed in both sexes (Kraaijeveld et al. 2007), a condition sometimes termed ‘elaborate monomorphism.’ As such, the question remains whether the strong generalizations that we make regarding male ornamentation also apply to species in which both sexes are ornamented

The effect of cities and distance on COVID-19 spreading in the United States

The COVID-19 pandemic has evolved over time through multiple spatial and temporal dynamics. The varying extent of interactions among different geographical areas can result to a complex pattern of spreading so that influences between these areas can be hard to discern. Here, we use cross-correlation analysis to detect synchronous evolution and potential inter-influences in the time evolution of new COVID-19 cases at the county level in the USA. Our analysis identified two main time periods with distinguishable features in the behavior of correlations. In the first phase, there were few strong correlations which only emerged between urban areas. In the second phase of the epidemic, strong correlations became widespread and there was a clear directionality of influence from urban to rural areas. In general, the effect of distance between two counties was much weaker than that of the counties population. Such analysis can provide possible clues on the evolution of the disease and may identify parts of the country where intervention may be more efficient in limiting the disease spread.Comment: 18 pages, 7 figure