Kinetic simulations of turbulent magnetic-field growth by streaming cosmic rays

Efficient acceleration of cosmic rays (via the mechanism of diffusive shock acceleration) requires turbulent, amplified magnetic fields in the shock's upstream region. We present results of multidimensional particle-in-cell simulations aimed at observing the magnetic field amplification that is expected to arise from the cosmic-ray current ahead of the shock, and the impact on the properties of the upstream interstellar medium. We find that the initial structure and peak strength of the amplified field is somewhat sensitive to the choice of parameters, but that the field growth saturates in a similar manner in all cases: the back-reaction on the cosmic rays leads to modification of their rest-frame distribution and also a net transfer of momentum to the interstellar medium, substantially weakening their relative drift while also implying the development of a modified shock. The upstream medium becomes turbulent, with significant spatial fluctuations in density and velocity, the latter in particular leading to moderate upstream heating; such fluctuations will also have a strong influence on the shock structure.Comment: 8 pages, 6 figures, accepted by Ap

Efficacy of Radiofrequency Ablation or Spinal Cord Stimulation for Management of Chronic Mechanical Low Back Pain

With over 191 million prescriptions for opioid medications being written annually, 11.5 million Americans abusing opioid prescription medications each year and on average 130 Americans dying from opioid overdoses every day1, finding alternatives to opioids for the management of chronic pain is more important now than ever. Since the early 1999s opioids have been the primary method for managing chronic pain. While the number of opioid prescriptions has decreased since its peak in 2010, the morphine milligram equivalents of the prescriptions written today are generally three times greater than they were in 1999. Non-pharmacological methods for chronic pain management such as radiofrequency ablation, spinal cord stimulation, acupuncture, massage, chiropractic, and meditation are available and are being offered to patients more often now than during peak opioid prescription writing. Many patients may be hesitant to try these different methods for pain management for a number of reasons: radiofrequency ablation and spinal cord stimulation are more invasive than pain medications, research confirming their efficacy compared with opioid medications is limited, and many patients whose pain is controlled on opioids fear that changing therapy might increase their pain. Of the non-medicinal therapies, radiofrequency ablation and spinal cord stimulation will be examined as pain relief tools for patients with chronic mechanical low back pain. If they are found to be effective, then they could be confidently recommended to these patients, either as a replacement or an adjunctive analgesic therapy, thus diminishing the reliance on opioids

Automatic Dependent Surveillance Broadcast (ADS-B) Security Mitigation through Multilateration

Automatic Dependent Surveillance Broadcast (ADS-B) was mandated January 1st, 2020 to all commercial aircraft that fly over 10,000 ft. This radio frequency (RF) based technology is part of an international plan to phase out radar-based surveillance within the airspace. Unfortunately, due to a lack of encryption and other security measures, ADS-B transmission remains open for possible exploitation. This thesis will explore the use of Multilateration (MLAT) to validate location data provided within the ADS-B framework. MLAT uses the Time Difference of Arrival (TDOA) at multiple locations to determine the origin of a received signal. Additionally, as MLAT greatly depends on the topology of receiver location, multiple configurations will be examined and simulated within the confines of a real-world application. Finally, adversary spoofing scenarios were explored by injecting a stationary and moving adversary into the system. The adversary transmitted ADS-B location data from a different origin than the packets would indicate to create a fake aircraft in the airspace. The performance of the MLAT model was analyzed to determine its ability to flag the adversary’s data as suspicious

Particle-in-cell simulation of astrophysical plasmas: probing the origin of cosmic rays

Cosmic rays, the product of natural extraterrestrial particle accelerators far more powerful than the LHC, were first detected a century ago. A standard model of cosmic-ray acceleration in supernova remnants has begun to emerge, but a number of questions still require satisfactory answers. The maximum particle energy attainable via the most favored mechanism, diffusive shock acceleration, is limited by the amplitude of magnetic-field turbulence in the unshocked interstellar or circumstellar medium, but cosmic rays are observed at high enough energies that some magnetic-field amplification is required. By what mechanisms might this amplification occur, and can it operate to a great enough extent to account for those cosmic rays thought to be of Galactic origin? A number of proposed solutions involve instabilities arising from interactions between cosmic rays and the upstream plasma, whose evolution becomes highly nonlinear. A related question explored is whether the presence of accelerated particles in the shock vicinity has any microscopic effect on the instabilities governing the shock itself. Particle-in-cell kinetic simulations allow us to investigate the growth and saturation of these instabilities at the (astrophysically) microscopic scale, providing valuable insights and important considerations for self-consistent macroscopic models of particle acceleration

Turnover: A Case Study of Middle Managers in the Landscape Industry

The landscape industry in the United States suffers higher turnover among middle management positions. Upper management does not know why this is occurring and currently has no strategy to deal with it. The purpose of this study was to investigate the reasons for high turnover among middle managers and explore the ways to reduce turnover. Reducing turnover may help with the stability of the landscape industry and increase employee retention. Conceptual framework for this study included Maslow\u27s hierarchy of needs, Herzberg\u27s two factor theory, situational theory, and contingency theory. This qualitative exploratory case study addressed the reasons for high turnover of middle managers and the strategies that might prevent high turnover in landscape industry. Three cases were selected, and each case included a sample of 5 middle managers in addition to publicly available company archival information. Middle managers were interviewed using semi-structured interviews. Archival data were used to achieve data saturation. Thematic analysis reviled the following results. The findings indicate that middle managers typically perceive that stress to sell and loss of contracts cause turnover. By creating strategies to reduce stress and manage contract loss, upper management may reduce turnover. The implications for social change include increased viability of landscape companies, which could result in decreased unemployment and increased quality of life for middle managers within the industry

Could Cosmic Rays Affect Instabilities in the Transition Layer of Nonrelativistic Collisionless Shocks?

There is an observational correlation between astrophysical shocks and non-thermal particle distributions extending to high energies. As a first step toward investigating the possible feedback of these particles on the shock at the microscopic level, we perform particle-in-cell (PIC) simulations of a simplified environment consisting of uniform, interpenetrating plasmas, both with and without an additional population of cosmic rays. We vary the relative density of the counterstreaming plasmas, the strength of a homogeneous parallel magnetic field, and the energy density in cosmic rays. We compare the early development of the unstable spectrum for selected configurations without cosmic rays to the growth rates predicted from linear theory, for assurance that the system is well represented by the PIC technique. Within the parameter space explored, we do not detect an unambiguous signature of any cosmic-ray-induced effects on the microscopic instabilities that govern the formation of a shock. We demonstrate that an overly coarse distribution of energetic particles can artificially alter the statistical noise that produces the perturbative seeds of instabilities, and that such effects can be mitigated by increasing the density of computational particles.Comment: 22 pages, 5 figures, published in Ap

Auditing & measuring the need for flexibility in a manufacturing facility

Flexible manufacturing was created out of the need for facilities to be able to efficiently respond to changes in their environment so as to build a competitive advantage. Flexible manufacturing (FM) is currently viewed as a way for facilities to be able to introduce and produce multiple products quickly and more efficiently. In this research we will present some new tools to help managers address the changes that are affecting the facility. An audit was developed to help system designers identify the changes that are impacting the facilities. The audit provides the opportunity to understand the changes that are occurring and provides an avenue for participants to be able to rank and prioritize the changes that are impacting the facility. The second part of the audit will categorize the changes into one of five areas of flexibility, such as machine, process, product, routing and volume. The audit helps designers identify solutions to address the changes and pre-determine acceptable performance measures for the solutions. This is accomplish by asking a series of questions that allows the designers to evaluate their current system and to determine their ideal system. The later part of the thesis will be used to generate general necessity measures for the machine, process, product, routing and volume flexibility

Radio polarimetry studies of magnetic turbulence in supernova remnants

Polarized radio emission from synchrotron radiation can give us unique information about the structure and amplitude of the magnetic fields in supernova remnants. This has implications for theories of particle acceleration at the forward shock of the SNR, in particular those that involve a strong amplification of the magnetic field through cosmic ray-induced instabilities. This turbulent magnetic field is modeled and I calculate the expected characteristics of polarized synchrotron emission and the effects of Faraday rotation as the radiation propagates through the source. The effects of an underlying homogeneous magnetic field or a compressed shock are also studied. Finally, constraints for realistic parameters describing the magnetic turbulence in the region downstream of the shock are discussed