Boston College

About: Boston College is a education organization based out in Boston, Massachusetts, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 9749 authors who have published 25406 publications receiving 1105145 citations. The organization is also known as: BC.

Chemical and microphysical characterization of ambient aerosols with the aerodyne aerosol mass spectrometer

Abstract: The application of mass spectrometric techniques to the realtime measurement and characterization of aerosols represents a significant advance in the field of atmospheric science. This review focuses on the aerosol mass spectrometer (AMS), an instrument designed and developed at Aerodyne Research, Inc. (ARI) that is the most widely used thermal vaporization AMS. The AMS uses aerodynamic lens inlet technology together with thermal vaporization and electron-impact mass spectrometry to measure the real-time non-refractory (NR) chemical speciation and mass loading as a function of particle size of fine aerosol particles with aerodynamic diameters between similar to 50 and 1,000 nm. The original AMS utilizes a quadrupole mass spectrometer (Q) with electron impact (EI) ionization and produces ensemble average data of particle properties. Later versions employ time-of-flight (ToF) mass spectrometers and can produce full mass spectral data for single particles. This manuscript presents a detailed discussion of the strengths and limitations of the AMS measurement approach and reviews how the measurements are used to characterize particle properties. Results from selected laboratory experiments and field measurement campaigns are also presented to highlight the different applications of this instrument. Recent instrumental developments, such as the incorporation of softer ionization techniques (vacuum ultraviolet (VUV) photo-ionization, Li(+) ion, and electron attachment) and high-resolution ToF mass spectrometers, that yield more detailed information about the organic aerosol component are also described. (c) 2007 Wiley Periodicals, Inc.

Re-examining perceived ease of use and usefulness

Abstract: Recently, Adams, et al. (1992) presented the results of two studies designed to replicate previous work by Fred Davis (1989) regarding perceived usefulness, ease of use, and their influence on the usage of information technology. Specifically, these authors sought to: (1) evaluate the psychometric properties of the ease of use and usefulness scales, and (2) empirically examine the relationship between the constructs (or traits) of usefulness, ease of use, and reported levels of usage.

On the Number and Size of Nations

Abstract: This paper studies the equilibrium determination of the number of countries in different political regimes, and in different economic environments, with more or less economic integration. We focus on the trade-off between the benefits of large jurisdictions and the costs of heterogeneity of large and diverse populations. Our model implies that (i) democratization leads to secessions; (ii) in equilibrium one generally observes an inefficiently large number of countries; (iii) the equilibrium number of countries is increasing in the amount of economic integration.