title: Control-theoretical stress-testing for cross-platform compliance

authors: McCarthy, Harry George Andrew

subjects: LQR

abstract: Modern systems are required more and more to be able to provide performance reliability qualities for not just one system but cross platform as well. Stress testing applications allow for performance testing of a system, however, when applied across different platforms the performance of the application is not a one to one comparison. This thesis introduces the idea of applying control theory to provide consistent resource percentage utilisation when stress testing cross platform. Proportional Integral Derivative (PID) control, Linear Quadratic Regulator (LQR) control and a PID Assisted LQR control were utilised as three control system in this thesis. While the PID controller provided the best results across multiple platforms, its inability to control all the variables in the system along with multiple different state
objectives (CPU and memory) leads to the need for a system model approach. LQR controllers provide this model based approach but at the cost of being unable to adapt across different platforms and to unpredictability in the system. Finally, a combined approach PID Assisted LQR control. PID Assisted LQR control gave the best of both PID and LQR control approach and had improvements in the case of where the system was most unpredictable but lacked any significant improvements in areas where the model gave an accurate representation of the system.

text: Control-theoretical stress-testing for cross-platform compliance Modern systems are required more and more to be able to provide performance reliability qualities for not just one system but cross platform as well. Stress testing applications allow for performance testing of a system, however, when applied across different platforms the performance of the application is not a one to one comparison. This thesis introduces the idea of applying control theory to provide consistent resource percentage utilisation when stress testing cross platform. Proportional Integral Derivative (PID) control, Linear Quadratic Regulator (LQR) control and a PID Assisted LQR control were utilised as three control system in this thesis. While the PID controller provided the best results across multiple platforms, its inability to control all the variables in the system along with multiple different state
objectives (CPU and memory) leads to the need for a system model approach. LQR controllers provide this model based approach but at the cost of being unable to adapt across different platforms and to unpredictability in the system. Finally, a combined approach PID Assisted LQR control. PID Assisted LQR control gave the best of both PID and LQR control approach and had improvements in the case of where the system was most unpredictable but lacked any significant improvements in areas where the model gave an accurate representation of the system.

year: 2020

title: Dynamics of immobilized and native Escherichia coli dihydrofolate reductase by quasielastic neutron scattering

authors: Tehei, Moeava

abstract: The internal dynamics of native and immobilized Escherichia coli dihydrofolate reductase (DHFR) have been examined using incoherent quasielastic neutron scattering. These results reveal no difference between the high frequency vibration mean-square displacement of the native and the immobilized E. coli DHFR. However, length-scale-dependent, picosecond dynamical changes are found. On longer length scales, the dynamics are comparable for both DHFR samples. On shorter length scales, the dynamics is dominated by local jump motions over potential barriers. The residence time for the protons to stay in a potential well is  = 7.95 ± 1.02 ps for the native DHFR and  = 20.36 ± 1.80 ps for the immobilized DHFR. The average height of the potential barrier to the local motions is increased in the immobilized DHFR, and may increase the activation energy for the activity reaction, decreasing the rate as observed experimentally. These results suggest that the local motions on the picosecond timescale may act as a lubricant for those associated with DHFR activity occurring on a slower millisecond timescale. Experiments indicate a significantly slower catalytic reaction rate for the immobilized E. coli DHFR. However, the immobilization of the DHFR is on the exterior of the enzyme and essentially distal to the active site, thus this phenomenon has broad implications for the action of drugs distal to the active site.

text: Dynamics of immobilized and native Escherichia coli dihydrofolate reductase by quasielastic neutron scattering The internal dynamics of native and immobilized Escherichia coli dihydrofolate reductase (DHFR) have been examined using incoherent quasielastic neutron scattering. These results reveal no difference between the high frequency vibration mean-square displacement of the native and the immobilized E. coli DHFR. However, length-scale-dependent, picosecond dynamical changes are found. On longer length scales, the dynamics are comparable for both DHFR samples. On shorter length scales, the dynamics is dominated by local jump motions over potential barriers. The residence time for the protons to stay in a potential well is  = 7.95 ± 1.02 ps for the native DHFR and  = 20.36 ± 1.80 ps for the immobilized DHFR. The average height of the potential barrier to the local motions is increased in the immobilized DHFR, and may increase the activation energy for the activity reaction, decreasing the rate as observed experimentally. These results suggest that the local motions on the picosecond timescale may act as a lubricant for those associated with DHFR activity occurring on a slower millisecond timescale. Experiments indicate a significantly slower catalytic reaction rate for the immobilized E. coli DHFR. However, the immobilization of the DHFR is on the exterior of the enzyme and essentially distal to the active site, thus this phenomenon has broad implications for the action of drugs distal to the active site.

year: 2006-10

title: Ko wai tēnei e tū ake nei? Activating collectivity and accountability through grounded positioning

authors: Rata, Arama

abstract: Building on conference conversations about positionality—about who we are and how our identities shape our views of the world, about the connections and disconnections experienced between us, and about our proximities to place, power, and privilege—this piece brings together four conference participants to continue to reflect on what positionality means, on why it is important, and on how to practice it in non-performative, well-developed, and mutually nourishing ways. Their dialogue reflects active and critical positioning in process and practice, creating opportunities for acknowledging our relationships and activating both collectivity and accountability in the various spaces where we live, work, create, and hope.

text: Ko wai tēnei e tū ake nei? Activating collectivity and accountability through grounded positioning Building on conference conversations about positionality—about who we are and how our identities shape our views of the world, about the connections and disconnections experienced between us, and about our proximities to place, power, and privilege—this piece brings together four conference participants to continue to reflect on what positionality means, on why it is important, and on how to practice it in non-performative, well-developed, and mutually nourishing ways. Their dialogue reflects active and critical positioning in process and practice, creating opportunities for acknowledging our relationships and activating both collectivity and accountability in the various spaces where we live, work, create, and hope.

year: 2021-12