The fundamental cycle of concept construction underlying various theoretical frameworks

In this paper, the development of mathematical concepts over time is considered. Particular reference is given to the shifting of attention from step-by-step procedures that are performed in time, to symbolism that can be manipulated as mental entities on paper and in the mind. The development is analysed using different theoretical perspectives, including the SOLO model and various theories of concept construction to reveal a fundamental cycle underlying the building of concepts that features widely in different ways of thinking that occurs throughout mathematical learning.     

Fluorination of diamond — C4F9I and CF3I photochemistry on diamond (100)

The radiation-induced decomposition of C₄F₉I and CF₃I overlayers at 119 K on diamond (100) surfaces has been shown to be an efficient route to fluorination of the diamond surface. X-ray photoelectron spectroscopy has been used for photoactivation as well as for studying the photodecomposition of the fluoroalkyl iodide molecules, the attachment of the photofragments to the diamond surface, and the thermal decomposition of the fluoroalkyl ligands. Measured chemical shifts agree well with ab initio calculations of both C 1s and F 1s binding energies. It is found that chemisorbed CF₃ groups on diamond (100) decompose by 300 K whereas C₄F₉ groups decompose over the range 300 to 700 K and this reactivity difference is rationalized on steric grounds. Both of these thermal decomposition processes produce surface C---F bonds on the diamond. The surface C---F species thermally decompose over a wide temperature range extending up to 1500 K. Hydrogen passivation of the diamond surface is ineffective in preventing free radical attack from the photodissociated products of the fluoroalkyl iodides; I atoms produced photolytically abstract H from surface C---H bonds to yield hydrogen iodide at 119 K allowing diamond fluorination. The attachment of chemisorbed F species to the diamond (100) surface causes band bending as the surface states are occupied as a result of chemisorption. This results in a shift to higher binding energy of the diamond-related C 1s levels present in the surface and subsurface regions which are sampled by XPS on the diamond. The use of photoactivation of fluoroalkyl iodides for the fluorination of diamond surfaces provides a convenient route compared to other methods involving the action of atomic F, molecular F₂, XeF₂ and F-containing plasmas.     

The effect of voice lessons on the clinical and perceptual skills of graduate students in speech-language pathology

Two groups of 10 speech-language pathology graduate students were each given 7 weeks of singing lessons to determine whether voice lessons could have an effect on their clinical and perceptual skills. Pre-, mid-, and posttests to measure various skills were designed and implemented. With use of paired sample statistical testing, statistically significant results were obtained. In addition, the subjective responses of the students show that the lessons were effective in improving pitch perception, breath control, and legato production or easy onset. This study supports efforts to integrate curricula in vocal performance and speech-language pathology.     

Semi-parametric estimation of covariate effects using the positive stable frailty model

Many biological and medical studies have as a response of interest the time to occurrence of some event, such as the occurrence of a particular symptom or disease, remission, relapse, death due to some specific disease, or simply death. In this paper we study the problem of assessing the effect of potential risk factors on the outcome event of interest through a parametric or semi-parametric frailty model where the lifetimes have a reason to be considered dependent. This dependence may arise because of multiple endpoints within the same individual or because, when studying a single endpoint, there are natural groupings between study subjects. The objective of this paper is to extend both parametric and semi-parametric approaches to regression analysis in which the lifetimes of individuals in a group are effected by the same random frailty which follows a positive stable distribution. Some comparisons of the properties of this frailty distribution with other frailty distributions are made and an example which assesses the effect of a treatment in a litter-matched tumorigenesis study is presented.     

Detailed nuclear structure studies far from stability

State-of-the-art spectroscopy of nuclei far from stability has achieved an extraordinary level of sophistication and detail in the last ten years. In principle, if a state can be populated, it can be characterized by its energy, spin, parity, and major decay paths. Sometimes its lifetime can be measured. In practice, one is confronted with enormous complexity. To convert raw spectroscopic data into nuclear structure data involves a complex process of disentangling gamma rays and conversion electrons into decay schemes. Specifically, coincidence techniques, especially coincidence intensities, play a crucial role in this process. Recent examples and methods from work done at UNISOR are presented.