Testing Non-termination in Multi-threaded programs

We study the problem of detecting non - termination in multi - threaded programs due to unwanted race conditions. We claim that the cause of non-termination can be attributed to the presence of at least two loops in two different threads, where the valuations of the loop controlling parameters are inter-dependent, i.e., value of one parameter in one thread depends on the execution sequence in the other thread and vice versa. In this thesis, we propose a testing based technique to analyze finite execution sequences and infer the likelihood of non-termination scenarios. Our technique is a light weight, flexible testing based approach that can be paired with any testing technique. We claim that testing based methods are likely to be scalable to large programs as opposed to static analysis methods. We present an outline of our implementation and prove the feasibility of our approach by presenting case studies on tailored sample programs. We discuss the applicability of our approach to real world larger programs through experimental results. We conclude by discussing the limitations of our approach and future avenues of research along this line of work

The Cavity-Embedded Cooper Pair Transistor as a Charge Detector Operating in the Nonlinear Regime

The cavity-embedded Cooper pair transistor (cCPT) has been shown to be a nearly quantum limited charge detector operating with only a single intracavity photon. Here, we use the inherent Kerr nonlinearity to demonstrate a dispersive charge sensing technique inspired by the Josephson bifurcation amplifier. Operating in the bistable regime close to a bifurcation edge, the cCPT is sensitive to charge shifts of 0.09e in a single-shot readout scheme with a detection time of 3 μs and a detection fidelity of 94%. The readout is implemented with only ∼ 25 intracavity photons in the high oscillation amplitude state, still several orders of magnitude lower than drives used in state-of-the-art radio frequency single electron transistors (rf-SETs). We find that a major limitation to the charge sensitivity of the device is fluctuation-induced switching between the metastable oscillation states in the bistable region. We study the lifetimes of these states across the gate and flux range of the cCPT and find that the switching properties depend on the strength of the Kerr nonlinearity at the cCPT bias point. We also explore a second nonlinear detection scheme where we parametrically pump the cCPT using a time-varying flux close to twice its resonance frequency to induce parametric oscillations. Flux pumping at a detuning on the edge of the parametric oscillation threshold makes the amplitude of oscillations sensitive to the charge environment. With no input drive, we are able to distinguish charge states ∼ 0.1e apart in a measurement time of 1 μs with a fidelity of 83%. The cCPT is a rich nonlinear system in which we observe sub-harmonic oscillations and phase coherent degenerate parametric amplification which could potentially be used to enhance the dispersive charge sensing of the device operating with a single intracavity photon level drive

ADRENERGIC STIMULATION IN ACUTE HYPERGLYCEMIA: EFFECTS ON CELLULAR AND TISSUE LEVEL MURINE CARDIAC ELECTROPHYSIOLOGY

Cardiovascular complications associated with elevated levels of glucose in the blood (Hyperglycemia, HG) is a growing health concern. HG is known to be associated with a variety of cardiovascular morbidities including higher incidence of electrical disturbances. Although effects of chronic HG have been widely investigated, electrophysiological effects of acute hyperglycemia are relatively less known. Further, hyperglycemic effects on adrenergic response is not widely investigated. We used excised ventricular tissues from mice to record trans-membrane potentials during a variety of pacing protocols to investigate cellular/tissue level electrophysiological effects of acute hyperglycemia and adrenergic stimulation (1µM Isoproterenol, a β-adrenergic agonist). A custom program was used to compute action potential durations (APD), maximal rates of depolarization (dv/dtmax), and action potential amplitudes (APA) from the recorded trans-membrane potentials. From these computed measures, electrical restitution and alternans threshold were quantified. Restitution was quantified using the Standard Protocol (SP; basic cycle length BCL= 200ms), Dynamic Protocol (DP; 200-40ms or until blockade) and a novel diastolic interval (DI) control protocol with Sinusoidal Changes in DI. Results from 6 mice show that acute hyperglycemia causes prolongation of the APD. Effects of adrenergic stimulation during acute hyperglycemia were partially blunted compared with non-hyperglycemic state, i.e. hyperglycemia minimized the decrease in APD that was produced by adrenergic stimulation. Similar, but less consistent (across animals) effects were seen in other electrophysiological parameters such as alternans threshold. These results show that acute hyperglycemia may itself alter cellular level electrophysiology of myocytes and importantly, modify adrenergic response. These results suggest that in addition to long term re-modeling that occurs in diabetes, acute changes in glucose levels also affect electrical function and further may contribute to systemically observed changes in diabetes by blunting adrenergic response. Therefore, further investigation into the electrophysiological effects of acute changes in glucose levels are warranted

EVALUATION OF ANGULAR DISTRIBUTION OF INCIDENT FIELD AT THE TRANSMISSION LOSS WINDOW IN MICHIGAN TECH’S REVERBERANT CHAMBER

Transmission Loss prediction accuracy is highly dependent on a good understanding of the angular distribution of incident field on the panel. Traditionally, the incident field has been assumed to be either completely random (equal probability of incidence at all angles from 0° - 90°) or field incidence (where the field is assumed to be completely diffuse between 0° - 78°). Studies1-3 have shown that these models are not completely representative of the incident field. This incident field is studied in the Michigan Tech Transmission Loss suite using two different methods in this study; beamforming and acoustic intensity. The beamforming method uses a linear array and the acoustic intensity method uses an intensity probe mounted on a rotating platform that measures the incoming sound energy at different angles as it is swept over a range of angles. The results from these two methods show that the incident field approximately follows a 0.8 cos ( ) distribution