26 research outputs found
Airflow Dynamics of Human Jets: Sneezing and Breathing - Potential Sources of Infectious Aerosols
10.1371/journal.pone.0059970PLoS ONE84
Radio & Optical Interferometry: Basic Observing Techniques and Data Analysis
Astronomers usually need the highest angular resolution possible, but the
blurring effect of diffraction imposes a fundamental limit on the image quality
from any single telescope. Interferometry allows light collected at
widely-separated telescopes to be combined in order to synthesize an aperture
much larger than an individual telescope thereby improving angular resolution
by orders of magnitude. Radio and millimeter wave astronomers depend on
interferometry to achieve image quality on par with conventional visible and
infrared telescopes. Interferometers at visible and infrared wavelengths extend
angular resolution below the milli-arcsecond level to open up unique research
areas in imaging stellar surfaces and circumstellar environments.
In this chapter the basic principles of interferometry are reviewed with an
emphasis on the common features for radio and optical observing. While many
techniques are common to interferometers of all wavelengths, crucial
differences are identified that will help new practitioners avoid unnecessary
confusion and common pitfalls. Concepts essential for writing observing
proposals and for planning observations are described, depending on the science
wavelength, angular resolution, and field of view required. Atmospheric and
ionospheric turbulence degrades the longest-baseline observations by
significantly reducing the stability of interference fringes. Such
instabilities represent a persistent challenge, and the basic techniques of
phase-referencing and phase closure have been developed to deal with them.
Synthesis imaging with large observing datasets has become a routine and
straightforward process at radio observatories, but remains challenging for
optical facilities. In this context the commonly-used image reconstruction
algorithms CLEAN and MEM are presented. Lastly, a concise overview of current
facilities is included as an appendix.Comment: 45 pages, 14 Figures; an abridged version of a chapter to appear in
Volume 2 of Planets, Stars and Stellar Systems, to be published in 2011 by
Springe
Randomized phase II/III confirmatory treatment selection design with a change of survival end points: Statistical design of Radiation Therapy Oncology Group 1216
An overview of the effect of bioaerosol size in coronavirus disease 2019 transmission
The fast spread of coronavirus disease 2019 (COVID‐19) constitutes a worldwide challenge to the public health, educational and trade systems, affecting the overall well‐being of human societies. The high transmission and mortality rates of this virus, and the unavailability of a vaccine or treatment, resulted in the decision of multiple governments to enact measures of social distancing. Such measures can reduce the exposure to bioaerosols, which can result in pathogen deposition in the respiratory tract of the host causing disease and an immunological response. Thus, it is important to consider the validity of the proposal for keeping a distance of at least 2 m from other persons to avoid the spread of COVID‐19. This work reviews the effect of aerodynamic diameter (size) of particles carrying RNA copies of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). A SARS‐CoV‐2 carrier person talking, sneezing or coughing at distance of 2 m can still provide a pathogenic bioaerosol load with submicron particles that remain viable in air for up to 3 h for exposure of healthy persons near and far from the source in a stagnant environment. The deposited bioaerosol creates contaminated surfaces, which if touched can act as a path to introduce the pathogen by mouth, nose or eyes and cause disease