P-31 MR Spectroscopic Analysis of Human Colon Cancer

Abstract

Phosphatic metabolic profiles of nineteen malignant and normal human colon specimens were analyzed by techniques of perchloric acid extraction and ³¹P MR spectroscopy at 202.4 MHz. Thirty-one individual phosphorus-containing intermediaries of metabolism were identified and their relative concentrations in mole-percentages of phosphorus were computed. Metabolic indices representing ratios and sums of individual or grouped metabolites were concurrently computed. The individual metabolite concentrations and metabolic indices were statistically compared revealing significant differences between malignant and normal tissues (see table). Malignant tissues demonstrate significant increases in the phosphomonoesters and diesters along with corresponding decreases in the high-energy phosphate compounds. While these changes may be relative, the increases in the PME and PDE bands most likely represent an increase in cell membrane activity ind P-lipid metabolism. P-31 MR is effective in differentiating malignant from normal tissues.     

Role of attractive methane-water interactions in the potential of mean force between methane molecules in water

On the basis of a Gaussian quasichemical model of hydration, a model of non-van der Waals character, we explore the role of attractive methane-water interactions in the hydration of methane and in the potential of mean force between two methane molecules in water. We find that the hydration of methane is dominated by packing and a mean-field energetic contribution. Contributions beyond the mean-field term are unimportant in the hydration phenomena for a hydrophobic solute such as methane. Attractive solute-water interactions make a net repulsive contribution to these pair potentials of mean force. With no conditioning, the observed distributions of binding energies are super-Gaussian and can be effectively modeled by a Gumbel (extreme value) distribution. This further supports the view that the characteristic form of the unconditioned distribution in the high-epsilon tail is due to energetic interactions with a small number of molecules. Generalized extreme value distributions also effectively model the results with minimal conditioning, but in those cases the distributions are sufficiently narrow that the details of their shape are not significant.     

The Mathematics Attitudes and Perceptions Survey: an instrument to assess expert-like views and dispositions among undergraduate mathematics students

One goal of an undergraduate education in mathematics is to help students develop a productive disposition towards mathematics. A way of conceiving of this is as helping mathematical novices transition to more expert-like perceptions of mathematics. This conceptualization creates a need for a way to characterize students' perceptions of mathematics in authentic educational settings. This article presents a survey, the Mathematics Attitudes and Perceptions Survey (MAPS), designed to address this need. We present the development of the MAPS instrument and its validation on a large (N = 3411) set of student data. Results from various MAPS implementations corroborate results from analogous instruments in other STEM disciplines. We present these results and highlight some in particular: MAPS scores correlate with course grades; students tend to move away from expert-like orientations over a semester or year of taking a mathematics course; and interactive-engagement type lectures have less of a negative impact, but no positive impact, on students' overall orientations than traditional lecturing. We include the MAPS instrument in this article and suggest ways in which it may deepen our understanding of undergraduate mathematics education.