Inference in Linear Regression Models with Many Covariates and Heteroskedasticity

The linear regression model is widely used in empirical work in Economics, Statistics, and many other disciplines. Researchers often include many covariates in their linear model specification in an attempt to control for confounders. We give inference methods that allow for many covariates and heteroskedasticity. Our results are obtained using high-dimensional approximations, where the number of included covariates are allowed to grow as fast as the sample size. We find that all of the usual versions of Eicker-White heteroskedasticity consistent standard error estimators for linear models are inconsistent under this asymptotics. We then propose a new heteroskedasticity consistent standard error formula that is fully automatic and robust to both (conditional)\ heteroskedasticity of unknown form and the inclusion of possibly many covariates. We apply our findings to three settings: parametric linear models with many covariates, linear panel models with many fixed effects, and semiparametric semi-linear models with many technical regressors. Simulation evidence consistent with our theoretical results is also provided. The proposed methods are also illustrated with an empirical application

Dying without Dignity: Homeless Deaths in Los Angeles County: 2000 - 2007

This report is an investigation into 2,815 homeless deaths in Los Angeles County between January, 2000 and May, 2007, based on statistics provided by the Los Angeles County Coroner's office. When a homeless person dies they do not often get the same sense of dying with dignity as a housed person. December 21st has been commemorated as the National Homeless Persons' Memorial Day by the National Coalition for the Homeless in partnership with the National Health Care for the Homeless Council for communities around the nation to commemorate the lives of homeless people that passed away.Local advocates and service providers celebrate the lives of thousands of homeless people in hundreds of cities around the nation with candlelight vigils, a reading of names, and other acts to remember the lives of those lost while living on the streets of our nation.This report is an investigation into homeless deaths in Los Angeles County between January, 2000 and May, 2007, based on statistics from the Los Angeles County Coroner's office. It is our hope that the homeless people who make up the statistics in this report did not die in vain and that policy makers move to implement the recommendations of this report in an effort to provide the dignity they did not find while living on the streets of our community. Equally important, to implement these strategies to help prevent the untimely deaths of homeless people in the future

Environmentally Friendly Industries: An Examination of Ecotourism as the Solution to the Environmental Degradation Caused by the International Tourism Industry

The increasing visibility of ecological alterations due to global climate change have required high-impact industries to reexamine their environmental impact. Transnational organizations such as the United Nations have identified the current management practices of the international tourism industry as a significant contributing factor to global warming. The high volume implications of the large-scale establishments necessary to lodging facilities in the tourism trade are responsible for damages such as resource depletion and pollution. Existing levels of environmental impact show irreparable and imminent damage to the world environment if current methods of the industry are allowed to continue. New trends in consumer purchasing habits have allowed a segment of the tourism industry to emerge called ecotourism: a sector believed to be significantly less harmful and predominantly helpful in reversing adverse impacts. This paper will examine the specific benefits of ecotourism, including decreased carbon footprints, locally sustainable business models, widespread public education regarding fragile ecosystems, and increased levels of strategic financial stability. Each of these topics illustrate how ecotourism properties exhibit a drive for obtainable levels of environmental protection that is severely lacking within their traditional counterparts. These benefits are subsequently weighed against the corresponding negative impacts ecotourism locations can create. Aspects such as true environment impact, unsustainable sites, species and environment alteration, and financial impracticability will be examined. The ability of ecotourism to overcome such downfalls and rise above traditional tourism practices is particularly emphasized throughout the argument. Due to advancements in modern management practices and increased emphasis on social responsibility, this paper seeks to show that ecotourism is a positive and viable solution to the environmental degradation caused by the international tourism industry

Data Supporting the Figures in Freshwater composition and connectivity of the Connecticut River plume during ambient flood tides

Supporting data for figures in Freshwater composition and connectivity of the Connecticut River plume during ambient flood tides by Michael M. Whitney, Yan Jia, Kelly L. Cole, Daniel G. MacDonald, Kimberly D. Huguenard. The scientific journal article is published in Frontiers in Marine Science (2021). The main objectives of this study on the Connecticut River plume formed during ambient flood tidal conditions are: 1) determining the contributions of river source waters from different parts of the tidal cycle and 2) quantifying the degree and spatial distribution of connectivity of these source waters with the bounding plume fronts. A high-resolution numerical modeling approach is taken. Data are from the Regional Ocean Modeling System (ROMS) results for the study area. Files are in MATLAB data format and are named FigureXX_data.mat. Variable names and units correspond to graphed data of each figure in the journal article

Radiation detectors and sources enhanced with micro/nanotechnology

The ongoing threat of nuclear terrorism presents major challenges to maintaining national security. Currently, only a small percentage of the cargo containers that enter America are searched for fissionable bomb making materials. This work reports on a multi-channel radiation detection platform enabled with nanoparticles that is capable of detecting and discriminating all types of radiation emitted from fissionable bomb making materials. Typical Geiger counters are limited to detecting only beta and gamma radiation. The micro-Geiger counter reported here detects all species of radiation including beta particles, gamma/X-rays, alpha particles, and neutrons. The multi-species detecting micro-Geiger counter contains a hermetically sealed and electrically biased fill gas. Impinging radiation interacts with tailored nanoparticles to release secondary charged particles that ionize the fill gas. The ionized particles collect on respectively biased electrodes resulting in a characteristic electrical pulse. Pulse height spectroscopy and radiation energy binning techniques can then be used to analyze the pulses to determine the specific radiation isotope. The ideal voltage range of operation for energy discrimination was found to be in the proportional region at 1000VDC. In this region, specific pulse heights for different radiation species resulted. The amplification region strength which determines the device sensitivity to radiation energy can be tuned with the electrode separation distance. Considerable improvements in count rates were achieved by using the charge conversion nanoparticles with the highest cross sections for particular radiation species. The addition of tungsten nanoparticles to the microGeiger counter enabled the device to be four times more efficient at detecting low level beta particles with a dose rate of 3.2uR/hr (micro-Roentgen per hour) and just under three times more efficient than an off the shelf Geiger counter. The addition of lead nanoparticles enabled the gamma/X-ray microGeiger counter channel to be 28 times more efficient at detecting low level gamma rays with a dose rate of 10uR/hr when compared to a device without nanoparticles. The addition of 10B nanoparticles enabled the neutron microGeiger counter channel to be 17 times more efficient at detecting neutrons. The device achieved a neutron count rate of 9,866 counts per minute when compared to a BF3 tube which resulted in a count rate of 9,000 counts per minute. By using a novel micro-injection ceramic molding and low temperature (950°C) silver paste metallizing process, the batch fabrication of essentially disposable micro-devices can be achieved. This novel fabrication technique was then applied to a MEMS neutron gun and water spectroscopy device that also utilizes the high voltage/temperature insulating packaging

Supporting Data for Freshwater composition and connectivity of the Connecticut River plume during ambient flood tides

Supporting data for figures in Freshwater composition and connectivity of the Connecticut River plume during ambient flood tides by Michael M. Whitney, Yan Jia, Kelly L. Cole, Daniel G. MacDonald, Kimberly D. Huguenard. The scientific journal article is published in Frontiers in Marine Science (2021). The main objectives of this study on the Connecticut River plume formed during ambient flood tidal conditions are: 1) determining the contributions of river source waters from different parts of the tidal cycle and 2) quantifying the degree and spatial distribution of connectivity of these source waters with the bounding plume fronts. A high-resolution numerical modeling approach is taken. Data are from the Regional Ocean Modeling System (ROMS) results for the study area. Files are in MATLAB data format and are named FigureXX_data.mat. Variable names and units correspond to graphed data of each figure in the journal article