Electromagnetic cascades in pulsars

The development of pair photon cascades initiated by high energy electrons above a pulsar polar cap is simulated numerically. The calculation uses the energy of the primary electron, the magnetic field strength, and the period of rotation as parameters and follows the curvature radiation emitted by the primary, the conversion of this radiation e(+) - e(-) pairs in the intense fields, and the quantized synchrotron radiation by the secondary pairs. A recursive technique allows the tracing of an indefinite number of generations using a Monte Carlo method. Gamma ray and pair spectra are calculated for cascades in different parts of the polar cap and with different acceleration models. It is found that synchrotron radiation from secondary pairs makes an important contribution to the gamma ray spectrum above 25 MeV, and that the final gamma ray and pair spectra are insensitive to the height of the accelerating region, as long as the acceleration of the primary electrons is not limited by radiation reaction

Pair production in superstrong magnetic fields

The production of electron-positron pairs by single photons in magnetic fields 10 to the twelth power G was investigated in detail for photon energies near threshold as well as for the asymptotic limit of high photon energy. The exact attenuation coefficient, which is derived and then evaluated numerically, is strongly influenced by the discrete energy states of the electron and positron. Near threshold, it exhibits a sawtooth pattern as a function of photon energy, and its value is significantly below that predicted by the asymptotic expression for the attenuation coefficient. The energy distributions of the created pair are computed numerically near threshold and analytic expressions are derived in the asymptotic limit. These results indicate that as field strength and photon energy increase, it becomes increasingly probable for the pair to divide the photon energy unequally. This effect, as well as the threshold behavior of the attenuation coefficient, could have important consequences for pulsar models

Cascade model of gamma-ray bursts: Power-law and annihilation-line components

If, in a neutron star magnetosphere, an electron is accelerated to an energy of 10 to the 11th or 12th power eV by an electric field parallel to the magnetic field, motion of the electron along the curved field line leads to a cascade of gamma rays and electron-positron pairs. This process is believed to occur in radio pulsars and gamma ray burst sources. Results are presented from numerical simulations of the radiation and photon annihilation pair production processes, using a computer code previously developed for the study of radio pulsars. A range of values of initial energy of a primary electron was considered along with initial injection position, and magnetic dipole moment of the neutron star. The resulting spectra was found to exhibit complex forms that are typically power law over a substantial range of photon energy, and typically include a dip in the spectrum near the electron gyro-frequency at the injection point. The results of a number of models are compared with data for the 5 Mar., 1979 gamma ray burst. A good fit was found to the gamma ray part of the spectrum, including the equivalent width of the annihilation line

A Study of the Learning-Focused School Improvement Model and its Effects on Third Grade Reading Scores in a Suburban, Metropolitan School System

ABSTRACT A STUDY OF THE LEARNING-FOCUSED SCHOOL IMPROVEMENT MODEL AND ITS EFFECT ON THIRD GRADE READING SCORES IN A SUBURBAN, METROPOLITAN SCHOOL SYSTEM by Douglas A. Daugherty In 2001, Congress passed the No Child Left Behind Education Act (NCLB). This act calls for a measurable annual increase in student achievement such that students reach, at a minimum, proficiency on challenging state academic assessments. A historical review of political involvement with education will add to that statement one more objective of the bill: to render more U.S. students globally competitive. Federal funding to state education is tied to the achievement of state standards. To achieve these heightened standards many schools and school systems are adopting whole-school reform models. According to Herman & Stringfield, 1997; Lappan & Houghton, 2003, whole-school reform should address organizational change, staffing, administrative support, curriculum and instruction, supplies and materials, scheduling, and monitoring of student progress and performance; all referred to as central components of the educational process. The purpose of this dissertation was to investigate the effectiveness of one specific whole-school reform model, Learning Focused Schools Program (LFSP), in a suburban school system for its ability to effect student achievement. The Learning Focused Schools Program was studied through its implementation and use in three suburban elementary schools and compared to three similar elementary schools not using the program. Data from students’ test scores were collected and analyzed for student growth. There were several notable findings in this study. For all the students who participated in the LFSP continuously for a period of 3 years, more children met or exceeded standards than those not exposed to LFS. The results were different when the total population was broken into subgroups. Hispanic students and Multiracial students did not show any statistically significant improvement in any assessed category using the LFSP. More ELL students in the LFS treatment group exceeded standards than their peers who were not exposed to LFS. White students and Students with Disabilities did show statistically significant improvement resulting from the LFSP environment. Black students fared best overall when exposed to the LFS Program and mirrored the results of the “ALL Students” subgroup

Missouri Non-Partisan Court Plan: A Dinosaur on the Edge of Extinction or a Survivor in a Changing Socio-Legal Environment, The

Surveys have shown that as America\u27s distrust of the political system increases, so does its unfavorable perception of the judiciary. This article focuses on the challenges to the merit selection of judges. It will provide a historical overview of the Missouri Non-Partisan Court Plan ( the Plan ) and its expansion across the country. The article will explore the positive and negative aspects of the Plan and examine traditional criticisms levied against it. Declining voter confidence in merit system states will be discussed, and the article will analyze and report on declining retention percentages in Missouri and their implications on the Plan. Furthermore, recent attacks in Missouri on the merit selection system by minority groups and the state legislature will be studied. After examining the challenges to the Plan and exploring their possibility of success, the article will provide suggestions and observations to both challengers and defenders of the Plan