Cosmic String Loop Microlensing

Cosmic superstring loops within the galaxy microlens background point sources lying close to the observer-string line of sight. For suitable alignments, multiple paths coexist and the (achromatic) flux enhancement is a factor of two. We explore this unique type of lensing by numerically solving for geodesics that extend from source to observer as they pass near an oscillating string. We characterize the duration of the flux doubling and the scale of the image splitting. We probe and confirm the existence of a variety of fundamental effects predicted from previous analyses of the static infinite straight string: the deficit angle, the Kaiser-Stebbins effect, and the scale of the impact parameter required to produce microlensing. Our quantitative results for dynamical loops vary by O(1) factors with respect to estimates based on infinite straight strings for a given impact parameter. A number of new features are identified in the computed microlensing solutions. Our results suggest that optical microlensing can offer a new and potentially powerful methodology for searches for superstring loop relics of the inflationary era.Comment: 20 pages, 19 figure

Investigating Leadership in Charter Schools: An Examination of the Leadership Traits of Executive Directors in Successful Charter Schools

This study was a qualitative exploration of educational leadership within charter schools in an attempt to identify traits demonstrated by executive directors of successful charter schools. Because much research has been conducted to identify trends in educational leadership, but comparable little within the unique context of charter schools, and because the charter school movement is growing, it is imperative that Boards, CMOs, and advocates of charter schooling understand more clearly what constitutes successful leadership within this sphere. Two research questions were created for this study, and qualitative methods were used to collect and analyze data. Data were collected through personal interviews with four charter school executive directors, document review, field observations, and follow-up interviews. The conceptual framework used to interpret the collected data was based on Leithwood and Duke's six dimensions of educational leadership: instructional, transformational, moral, participative, managerial, and contingent leadership. Data were gathered and analyzed against these six leadership dimensions. A thick description of the experiences and perspectives of the four participants was created. The data provided insight into successful charter school leadership. Some of the findings supported extant research about leadership in other educational contexts, while some indicated some unique characteristics of leadership within a charter school. Participants indicated that the largest demands in their jobs were the quantity of needs as well as the necessary practice of affecting change through systems rather than directly with students. Participants further identified a sense of personal accountability, a change management process, as well as working within all six dimensions of leadership as essential to their successes. These findings and conclusions are reported in Chapters 4 and 5. This study was an exploration of traits and behaviors exhibited by executive directors of successful charter schools. The findings indicate a gap between current understandings of educational leadership in general and that within a charter school. It is expected that this research will help to create a clearer understanding of charter school leadership and provide insight for stakeholders to move forward in locating and training future charter school leaders

Waiting Tolerance: Ramp Delay vs. Freeway Congestion

Waiting tolerance at ramp meters and travel time on the freewaywere measured using a computer administered stated preference (CASP) survey and a virtual experience stated preference (VESP) methodemploying a driving simulator.The selections varied in the number of minutes waiting at a ramp meter with vehicle speed once on the freeway. The subjects ranked the selections in order of preference. The results were statistically analyzed using a binary logit model controlling for demographics, socioeconomic characteristics, daily travel time, and personality scores.The results by the CASP method displayed a preference for freeway congestion to ramp delay, but opposite results were obtained by the VESP method. A number of reasons are posited to explain the difference, but the results indicate that method of stated preference data collection can significantly affect conclusions drawn.Ramp meters; Personality; Stated preference; Driving simulator; Travel time

Weighting Waiting: Evaluating the Perception of In-Vehicle Travel Time Under Moving and Stopped Conditions

This paper describes experiments comparing traditional computer administered stated preference with virtual experience stated preference to ascertain how people value stopped delay compared with stop-and- go or freeflow traffic. The virtual experience stated preference experiments were conducted using a wrap around driving simulator. The two methods produced two different results, with the traditional computer assisted stated preference suggesting that ramp delay is 1.6 Ð 1.7 times more onerous than freeway time, while the driving simulator based virtual experience stated preference suggested that freeway delay is more onerous than ramp delay. Several reasons are hypothesized to explain the differences, including recency, simultaneous versus sequential comparison, awareness of public opinion, the intensity of the stop-and-go traffic, and the fact that driving in the real-world is a goal directed activity. However without further research, which, if any, of these will eventually prove to be the reason is unclear. What is clear is that a comparison of the computer administered stated preference with virtual experience stated preference produces different results, even though both procedures strive to find the same answers in nominally identical sets of conditions. Because people experience the world subjectively, and make decisions based on those subjective experiences, future research should be aimed at better understanding the differences between these subjective methodologies.transportation, travel behavior, driving simulator, ramp meters

The Changing Face of Allotments:Findings from a Comprehensive Birmingham Study

Interest in allotments is growing across the country, yet relatively little is known about them. Who are the current plot‐holders; what do they grow and the volumes of crops harvested; what are the wider health and social benefits gained from being a plot‐holder; how are allotments responding to an era of local government austerity? To explore these issues, we undertook a survey of allotment tenants and site secretaries across Birmingham's 113 sites in the most substantial study of plot‐holders undertaken in recent years. This article highlights the key findings and the potential implications for policy makers, local councillors and national politicians. It also indicates the need for similar studies elsewhere in the country to confirm or modify the picture suggested from this initial study

Trade studies for nuclear space power systems

As human visions of space applications expand and as we probe further out into the universe, our needs for power will also expand, and missions will evolve which are enabled by nuclear power. A broad spectrum of missions which are enhanced or enabled by nuclear power sources have been defined. These include Earth orbital platforms, deep space platforms, planetary exploration, and terrestrial resource exploration. The recently proposed Space Exploration Initiative (SEI) to the Moon and Mars has more clearly defined these missions and their power requirements. Presented here are results of recent studies of radioisotope and nuclear reactor energy sources, combined with various energy conversion devices for Earth orbital applications, SEI lunar/Mars rovers, surface power, and planetary exploration

Hourly historical and near-future weather and climate variables for energy system modelling

Energy systems are becoming increasingly exposed to the impacts of weather and climate due to the uptake of renewable generation and the electrification of the heat and transport sectors. The need for high-quality meteorological data to manage present and near-future risks is urgent. This paper provides a comprehensive set of multi-decadal, time series of hourly meteorological variables and weather-dependent power system components for use in the energy systems modelling community. Despite the growing interest in the impacts of climate variability and climate change on energy systems over the last decade, it remains rare for multi-decadal simulations of meteorological data to be used within detailed simulations. This is partly due to computational constraints, but also due to technical barriers limiting the use of meteorological data by non-specialists. This paper presents a new European-level dataset which can be used to investigate the impacts of climate variability and climate change on multiple aspects of near-future energy systems. The datasets correspond to a suite of well-documented, easy-to-use, self-consistent, hourly- and nationally aggregated, and sub-national time series for 2 m temperature, 10 m wind speed, 100 m wind speed, surface solar irradiance, wind power capacity factor, solar power factor, and degree days spanning over 30 European countries. This dataset is available for the historical period 1950–2020 and is accessible from https://doi.org/10.17864/1947.000321 (Bloomfield and Brayshaw, 2021a). As well as this a companion dataset is created where the ERA5 reanalysis is adjusted to represent the impacts of near-term climate change (centred on the year 2035) based on five high-resolution climate model simulations. These data are available for a 70-year period for central and northern Europe. The data are accessible from https://doi.org/10.17864/1947.000331 (Bloomfield and Brayshaw, 2021b). To the authors’ knowledge, this is the first time a comprehensive set of high-quality hourly time series relating to future climate projections has been published, which is specifically designed to support the energy sector. The purpose of this paper is to detail the methods required for processing the climate model data and illustrate the importance of accounting for climate variability and climate change within energy system modelling from the sub-national to European scale. While this study is therefore not intended to be an exhaustive analysis of climate impacts, it is hoped that publishing these data will promote greater use of climate data within energy system modelling.</p

Gas adsorption studies and microcalorimetry on some iron oxides

A volumetric gas adsorption apparatus uas built and calibrated with two surface area standards. The nitrogen adsorption and desorption isotherms were determined for five iron oxides and the specific surface area was calculated. Four of the oxides were found to be mesoporous. [alpha]s-plots were constructed using the non-porous sample (haematite) as the reference. An attempt was made to measure the effectiveness of an organic pretreatment on two of the porous samples by comparing their surface areas and pore size distributions before and after treatment. A commercial flow microcalorimeter was used to investigate the adsorption and desorption of 1-butanol and 1,2-epoxybutane on one of the porous samples and haematite. For haematite the adsorption of both 1-butanol and 1,2-epoxybutane were reversible. The surface area of both samples estimated from microcalorimetry were smaller than their measured specific surface areas, probably because of water precoverage. The heat of 1-butanol adsorption on sample 'A' was a function of concentration, the number of previous adsorption-desorption cycles and the volume of solvent passed over the surface prior to the adsorption. The adsorption of 1,2-epoxybutane on sample 'A' was substantially irreversible. Dilution effects became important for both samples for concentrations above ca. 1.0 wt.%. A speculative water vapour adsorption experiment was performed using the microcalorimeter. Comparisons were made of the water adsorption-desorption properties of all the samples. The observed effects could not be simply explained. The heats and rates of water adsorption and desorption increased with increasing sample temperature.<p