Development of neurosurgery in Southern California and the Los Angeles County/University of Southern California Medical Center

Journal ArticleThe Los Angeles County General Hospital has played an integral role in the development of medicine and neurosurgery in Southern California. From its fledgling beginnings, the University of Southern California School of Medicine has been closely affiliated with the hospital, providing the predominant source of clinicians to care for and to utilize as a teaching resource the immense and varied patient population it serves

Efficient Simulation Of Multicarrier Digital Communication Systems In Nonlinear Channel Environments

The effectiveness of computer simulation as a tool for the design and analysis of communication systems is often limited by the long execution times required for many simulations. When simulating multicarrier digital communication systems operating over nonlinear channels, the required high sampling rate contributes significantly to long execution times. A new method that reduces the sampling rate of simulations of such systems is developed. This Partial Sum of Products (ParSOP) method reduces the sampling rate by generating only the intermodulation products that lie in a frequency band of interest. The ParSOP method requires that the bandpass nonlinearity be represented by memoryless operations on the complex envelope of the signal and that the subcarriers constituting the frequency-division multiplexed signal are sufficiently separated to prevent significant adjacent channel interference. Simulation results for such systems show that an order of magnitude reduction in the sampling rate is possible while producing only minimal error in the bit error rate estimate. © 1993 IEE

The Establishment of Institutional Review Boards in the U.S. Background History

View the recording of a related lecture delivered on February 23, 2022: [LINK]https://purl.dlib.indiana.edu/iudl/media/197x61mb8x[/LINK]Prior to the twentieth century, research ethics were primarily governed by individual conscience and professional codes of conduct. Whether and how humans might be investigated, however, has always been subject to the laws and customs of the society and government at the time. For many reasons, in the second half of the twentieth century, an elaborate set of rules and regulations about research were established by the American government to protect individual and public interests. What follows is a discussion of why federal rules and regulations were established, including the Institutional Review Boards. Originally written April 29, 2005; updated August 31, 2021

Origins of the HIVs and the AIDS Outbreaks

The AIDS pandemic was caused by human immunodeficiency virus type 1 group M (HIV-1M). It is not widely appreciated that there are three other HIV outbreaks that emerged independently in different regions of Africa during the last century. To date, 13 HIVs have been discovered, but only four of which became major outbreaks to varying degrees. HIV-1M is responsible for 90% of over 35 million deaths, and the other three epidemic HIVs are estimated to have infected from 25,000 to 750,000 people each. A handful of key determinants explain how and why this happened, including human interaction with the simian sources from which the HIVs emerged, but much more important were new ways that people spread the viruses to one another. The latter included population movement and urbanization, changes in sexual relations, war, and above all new medical procedures (unsterile injections and inadequately tested blood transfusions). The emergence of the viruses and their epidemic spread were not the result of a random mutation, but rather depended upon the combination of specific circumstances at different places and times. The AIDS pandemic was not a chance, natural occurrence; it is much more accurately described as a (hu)man-made disaster

Properties of High-Redshift Lyman Alpha Clouds I. Statistical Analysis of the SSG Quasars

Techniques for the statistical analysis of the \Lya\ forest in high redshift quasars are developed, and applied to the low resolution (25 \AA) spectra of 29 of the 33 quasars in the Schneider-Schmidt-Gunn (SSG) sample.We find that the mean absorption increases with $z$ approximately as a power law $(1+z)^{\gamma+1}$ with $\gamma = 2.46\pm 0.37$. The mean ratio of \Lya\ to Lyman $\beta$ absorption in the clouds is $0.476\pm 0.054$. We also detect, and obtain ratios, for Lyman $\beta$, $\gamma$, and possibly $\epsilon$. We are also able to quantify the fluctuations of the absorption around its mean, and find that these are comparable to, or perhaps slightly larger than, that expected from an uncorrelated distribution of clouds. The techniques in this paper, which include the use of bootstrap resampling of the quasar sample to obtain estimated errors and error covariances, and a mathematical treatment of absorption from a (possibly non-uniform) stochastic distribution of lines, should be applicable to future, more extensive, data sets.Comment: 29 pages, LaTeX using aastex30 macros, forthcoming as CfA preprin