Dynamics of Oscillators Coupled by a Medium with Adaptive Impact

In this article we study the dynamics of coupled oscillators. We use mechanical metronomes that are placed over a rigid base. The base moves by a motor in a one-dimensional direction and the movements of the base follow some functions of the phases of the metronomes (in other words, it is controlled to move according to a provided function). Because of the motor and the feedback, the phases of the metronomes affect the movements of the base while on the other hand, when the base moves, it affects the phases of the metronomes in return. For a simple function for the base movement (such as $y = \gamma_{x} [r \theta_1 + (1 - r) \theta_2]$ in which $y$ is the velocity of the base, $\gamma_{x}$ is a multiplier, $r$ is a proportion and $\theta_1$ and $\theta_2$ are phases of the metronomes), we show the effects on the dynamics of the oscillators. Then we study how this function changes in time when its parameters adapt by a feedback. By numerical simulations and experimental tests, we show that the dynamic of the set of oscillators and the base tends to evolve towards a certain region. This region is close to a transition in dynamics of the oscillators; where more frequencies start to appear in the frequency spectra of the phases of the metronomes

Surface analysis of space telescope material specimens

Qualitative and quantitative data on Space Telescope materials which were exposed to low Earth orbital atomic oxygen in a controlled experiment during the 41-G (STS-17) mission were obtained utilizing the experimental techniques of Rutherford backscattering (RBS), particle induced X-ray emission (PIXE), and ellipsometry (ELL). The techniques employed were chosen with a view towards appropriateness for the sample in question, after consultation with NASA scientific personnel who provided the material specimens. A group of eight samples and their controls selected by NASA scientists were measured before and after flight. Information reported herein include specimen surface characterization by ellipsometry techniques, a determination of the thickness of the evaporated metal specimens by RBS, and a determination of trace impurity species present on and within the surface by PIXE

Perceived Difficulty Accessing Medical Care And 30-Day Prescription Drug Adherence Post-Myocardial Infarction

Introduction: Prescription drugs can reduce the risk of adverse events post-myocardial infarction (MI), but despite the known benefits, use of these drugs remains low. Prior research has found that younger patients, women, minorities, and those with limited access to care are less likely to be adherent. Currently, little is known on how perceptions of access to care affect adherence rates. Objective: To determine the association between patients\u27 perceived difficulty accessing care and adherence to prescription drugs 30 days after an MI event in young patients. Methods: VIRGO (Variation in Recovery: Role of Gender on Outcomes of Young Acute Myocardial Infarction Patients) is a prospective cohort study of young MI patients, 18-55 years of age. Patients\u27 baseline perceived difficulty accessing care and adherence to prescription drugs at 30 days were measured by self-report. Bivariate comparisons of patient characteristics were evaluated using student t-tests and the chi-square test, with statistical significance of p\u3c0.05. The relationship between perceived difficulty accessing care and adherence was tested using multivariate logistic regression that sequentially adjusted for sociodemographic characteristics, medical history, and health insurance status. Results: Almost half of all patients (45.1%) experienced some difficulty accessing the care that they need. Approximately, 17.4% reported extreme or moderate perceived difficulty and 27.7% reported their perceived difficulty as somewhat or not at all. The three primary reasons patients perceived difficulty were cost, lack of health insurance, and difficulty getting an appointment. In adjusted analyses, patients with extreme or moderate perceived difficulty were 25% less likely to be adherent (OR= 0.75, 95% CI: 0.51-1.13) than those reporting no difficulty, and patients reporting somewhat or little difficulty were 14% less likely to be adherent (OR= 0.86, 95% CI: 0.62-1.19) than those with no perceived difficulty. Conclusions: Patients\u27 perceptions of difficulty accessing care do not predict 30-day prescription drug adherence after accounting for health insurance status. Healthcare providers should consider the health insurance status of young patients with MI as well as their perceived difficulty accessing care as potential factors that may contribute to one-month medication adherence rates

Interaction and Mixing Effects in Two and One Dimensional Hole Systems

This thesis describes electrical measurements performed on low dimensional p- type devices, fabricated from GaAs/AlGaAs heterostructures. The Coulomb interaction between holes is similar to that between electrons. However, the kinetic energy is suppressed, which makes interaction effects particularly important. Holes may also be used to study band structure effects which arise from spin-orbit coupling in the valence band. The effects of Coulomb interactions in low dimensional electron systems are currently being studied extensively. Experiments presented in this thesis indicate the possible importance of Coulomb exchange interactions in both one and two dimensional hole systems (1DHSs,2DHSs). Tilted magnetic field studies of 2DHSs in the quantum Hall regime indicate that Landau levels at even filling factors will not cross. For high filling factor, this is attributed to a spin-orbit mixing effect which arises from the low symmetry of the system. At lower filling factor, activation-energy measurements verify that the energy gaps decrease and then increase as the field is tilted. However, the energy gap versus field dependences do not exhibit the curvature that might be expected from a perturbative anticrossing. It is speculated that the origin of this effect is a phase transition driven by the exchange interaction. Balanced arguments contrasting the relative strengths of the mixing and interactions theories are provided. The second part of this thesis describes a new method for the fabrication of ballistic 1DHSs, which exhibit clear conductance quantization. The quantization changes from even to odd multiples of e2/h as a function of the magnetic field in the plane of the heterostructure, as "spin splitting" causes the 1D subbands to cross. Measurements of the 1D subband energy spacings are used together with the magnetic fields at which the crossings occur to calculate the in-plane g factors of the 1D subbands. These are found to increase as the number of occupied 1D subbands decreases. This enhancement of the g factor is attributed to exchange interactions; possible mixing explanations are also discussed. At higher magnetic fields, the pattern of quantization features shows that the subbands have crossed many times, and that the 1DHS can be strongly magnetized.EPSR