ABSTRACT
Dust grains in the interstellar medium and the outer Solar System commonly have a coating of water ice, which affects their optical properties and surface chemistry. The thickness of these icy mantles may be determined in part by the extent of photodesorption (photosputtering) by background ultraviolet radiation. But this process is poorly understood, with theoretical estimates of the photodesorption rate spanning several orders of magnitude. Here we report measurements of the absolute ultraviolet photodesorption yield of low-temperature water ice. Our results indicate that the rate of photodesorption is appreciable. In particular, it can account for the absence of icy mantles on grains in diffuse interstellar clouds, it exceeds solar-wind ion erosion and sublimation in the outer Solar System, and it is important in determining the lifetimes of icy mantles in dense molecular clouds.
Subject(s)
Extraterrestrial Environment , Ice , Solar System , Spectrophotometry, Ultraviolet , TemperatureSubject(s)
Asian People , Black or African American , Hispanic or Latino , Indians, North American , Minority Groups , Population Surveillance , Respiratory Tract Diseases/ethnology , Adolescent , Adult , Aged , Asia/ethnology , Black People , Cause of Death , Child , Child, Preschool , Female , Health Priorities , Humans , Incidence , Infant , Infant, Newborn , Male , Middle Aged , Pacific Islands/ethnology , Predictive Value of Tests , Primary Prevention , Research , Respiratory Function Tests , Respiratory Tract Diseases/diagnosis , Respiratory Tract Diseases/mortality , Respiratory Tract Diseases/therapy , Risk Factors , Smoking/adverse effects , Smoking/ethnology , Socioeconomic Factors , Survival Rate , United States/epidemiologyABSTRACT
The pulmonary histopathologic features in a sporadic case of Legionnaires' disease are shown. The changes include acute bronchitis with focal ulceration and diffuse acute interstitial pneumonitis. These changes are not those seen with typical bacterial pneumonia but are similar to changes seen when viruses, rickettsiae, chlamydiae, or Mycoplasma pneumoniae organisms are the infecting agents.
