Carbon offers advantages as implant material in human body

Because of such characteristics as high strength and long-term biocompatability, aerospace carbonaceous materials may be used as surgical implants to correct pathological conditions in the body resulting from disease or injury. Examples of possible medical uses include bone replacement, implantation splints and circulatory bypass implants

A New Challenge: Testing the Video Course

This paper offers some preliminary thoughts on the testing ofvideo courses, including a review of the literature and an examinationof the research on the subject. The unique characteristics ofvideo courses suggest that different language learning outcomes maybe expected, which means that creating appropriate tests is thereforea new challenge for language teachers. The paper lists subtesttypes, and gives an example of a test used by the authors. Based onthis experience, a number of guidelines are offered regarding thecreation of appropriate tests, and a direction for future research inthe area is suggested

Effects of dynamical evolution on the distribution of substructures

We develop a semi-analytical model that determines the evolution of the mass, position and internal structure of dark matter substructures orbiting in dark matter haloes. We apply this model to the case of the Milky Way. We focus in particular on the effects of mass loss, dynamical friction and substructure--substructure interactions, the last of which has previously been ignored in analytic models of substructure evolution. Our semi-analytical treatment reproduces both the spatial distribution of substructures and their mass function as obtained from the most recent N-body cosmological calculations of Gao et al. (2004). We find that, if mass loss is taken into account, the present distribution of substructures is practically insensitive to dynamical friction and scatterings from other substructures. Implementing these phenomena leads to a slight increase (~5%) in the number of substructures at r<0.35 r_vir, whereas their effects on the mass function are negligible. We find that mass loss processes lead to the disruption of substructures before dynamical friction and gravitational scattering can significantly alter their orbits. Our results suggest that the present substructure distribution at r>0.35 r_vir reflects the orbital properties at infall and is, therefore, purely determined by the dark matter environment around the host halo and has not been altered by dynamical evolution.Comment: Submitted to MNRAS. 13 pages, 9 figure

Galacticus: A Semi-Analytic Model of Galaxy Formation

We describe a new, free and open source semi-analytic model of galaxy formation, Galacticus. The Galacticus model was designed to be highly modular to facilitate expansion and the exploration of alternative descriptions of key physical ingredients. We detail the Galacticus engine for evolving galaxies through a merging hierarchy of dark matter halos and give details of the specific implementations of physics currently available in Galacticus. Finally, we show results from an example model that is in reasonably good agreement with several observational datasets. We use this model to explore numerical convergence and to demonstrate the types of information which can be extracted from Galacticus.Comment: 35 pages, submitted to New Astronom

Self-Consistent Theory of Halo Mergers - II: CDM Power Spectra

We place additional constraints on the three parameters of the dark matter halo merger rate function recently proposed by Parkinson, Cole & Helly by utilizing Smoluchowski's coagulation equation, which must be obeyed by any binary merging process which conserves mass. We find that the constraints from Smoluchowski's equation are degenerate, limiting to a thin plane in the three dimensional parameter space. This constraint is consistent with those obtained from fitting to N-body measures of progenitor mass functions, and provides a better match to the evolution of the overall dark matter halo mass function, particularly for the most massive halos. We demonstrate that the proposed merger rate function does not permit an exact solution of Smoluchowski's equation and, therefore, the choice of parameters must reflect a compromise between fitting various parts of the mass function. The techniques described herein are applicable to more general merger rate functions, which may permit a more accurate solution of Smoluchowski's equation. The current merger rate solutions are most probably sufficiently accurate for the vast majority of applications.Comment: 11 pages, submitted to MNRA

Education School Challenges: The Increasing Demands on K-8 Teachers

The educational needs of future K-8 teachers in the areas of mathematics and science are greater as a result of the increased (and, I would add, appropriate) student expectations in the area of mathematics and science as enunciated in the SOL and the specific content areas as described in the new licensure requirements. The sophistication and understanding of science and mathematics that is needed at both the elementary school and middle school levels is indeed substantial. However, proficiency in science and mathematics is only one portion of the total needs of new teachers. How are we all, from the Colleges of Arts and Sciences and the Colleges of Education, going to best provide the educational needs within the very restrictive total time that we have available

On the regularity conjecture for the cohomology of finite groups

Non peer reviewedPublisher PD