McMaster University

About: McMaster University is a education organization based out in Hamilton, Ontario, Canada. It is known for research contribution in the topics: Population & Health care. The organization has 41361 authors who have published 101269 publications receiving 4251422 citations.

Spatially resolved absolute diffuse reflectance measurements for noninvasive determination of the optical scattering and absorption coefficients of biological tissue.

Abstract: The absorption and transport scattering coefficients of biological tissues determine the radial dependence of the diffuse reflectance that is due to a point source. A system is described for making remote measurements of spatially resolved absolute diffuse reflectance and hence noninvasive, noncontact estimates of the tissue optical properties. The system incorporated a laser source and a CCD camera. Deflection of the incident beam into the camera allowed characterization of the source for absolute reflectance measurements. It is shown that an often used solution of the diffusion equation cannot be applied for these measurements. Instead, a neural network, trained on the results of Monte Carlo simulations, was used to estimate the absorption and scattering coefficients from the reflectance data. Tests on tissue-simulating phantoms with transport scattering coefficients between 0.5 and 2.0 mm21 and absorption coefficients between 0.002 and 0.1 mm21 showed the rms errors of this technique to be 2.6% for the transport scattering coefficient and 14% for the absorption coefficients. The optical properties of bovine muscle, adipose, and liver tissue, as well as chicken muscle 1breast2, were also measured ex vivo at 633 and 751 nm. For muscle tissue it was found that the Monte Carlo simulation did not agree with experimental measurements of reflectance at distances less than 2 mm from the incident beam.

The concept of accessibility: A search for an operational form

Abstract: Ingram D. R. (1971) The concept of accessibility: A search for an operational form, Reg. Studies 5, 101–107. The importance of the concept of accessibility in the literature of urban studies requires that a method be found of describing quantitatively the accessibility at a point. The paper is concerned with, firstly, a set of definitions related to the concept of accessibility. A distinction is made between the relative accessibility between two points and the integral, or total, accessibility at a point. Secondly, various operational forms of these definitions are illustrated with reference to the Hamilton, Ontario, urban area. The derivation of the various measures that are developed is discussed. A measure based on the normal, or Gaussian curve is recommended as the most suitable form for determining the integral accessibility at a given point.

Technical note: improved DNA extraction from ancient bones using silica-based spin columns

Abstract: We describe a simple method for extracting polymerase chain reaction-amplifiable DNA from ancient bones without the use of organic solvents. Bone powders are digested with proteinase K, and the DNA is purified directly using silica-based spin columns (QIAquick3, QIAGEN). The efficiency of this protocol is demonstrated using human bone samples ranging in age from 15 to 5,000 years old.