Development of a theory of the spectral reflectance of minerals, part 4

A theory of the spectral reflectance or emittance of particulate minerals was developed. The theory is expected to prove invaluable in the interpretation of the remote infrared spectra of planetary surfaces

“That’s Much Easier Said than Done”: The Realities of Social Justice Pedagogy in Schools

Teaching for critical social justice is an attempt by classroom teachers to promote equity within their classrooms. Researchers have analyzed the impact of preservice teachers’ readiness to address social justice issues in their classrooms upon exiting their teacher education programs. However, despite reports of already practicing K-12 teachers’ attempts to teach for social justice in their classrooms, there is little connection to teacher education programs. This postcritical qualitative study addresses the research gap by highlighting the understandings and experiences of four intern teachers simultaneously enrolled in a teacher education program while participating in a critical social justice focus group. Findings from the critical social justice focus group revealed intern teachers’ understandings of critical social justice included: (1) embracing a critical awareness, (2) advocacy: “it’s about the students”, and (3) praxis defeat

A Variational Principle for the Asymptotic Speed of Fronts of the Density Dependent Diffusion--Reaction Equation

We show that the minimal speed for the existence of monotonic fronts of the equation $u_t = (u^m)_{xx} + f(u)$ with $f(0) = f(1) = 0$, $m >1$ and $f>0$ in $(0,1)$ derives from a variational principle. The variational principle allows to calculate, in principle, the exact speed for arbitrary $f$. The case $m=1$ when $f'(0)=0$ is included as an extension of the results.Comment: Latex, postcript figure availabl

Techniques for carrying out radiative transfer calculations for the Martian atmospheric dust

A description is given of the modification of a theory on the reflectance of particulate media so as to apply it to analysis of the infrared spectra obtained by the IRIS instrument on Mariner 9. With the aid of this theory and the optical constants of muscovite mica, quartz, andesite, anorthosite, diopside pyroxenite, and dunite, modeling calculations were made to refine previous estimates of the mineralogical composition of the Martian dust particles. These calculations suggest that a feldspar rich mixture is a very likely composition for the dust particles. The optical constants used for anorthosite and diopside pyroxenite were derived during this program from reflectance measurements. Those for the mica were derived from literature reflectance data. Finally, a computer program was written to invert the measured radiance data so as to obtain the absorption coefficient spectrum which should then be independent of the temperature profile and gaseous component effects

The effect of a cutoff on pushed and bistable fronts of the reaction diffusion equation

We give an explicit formula for the change of speed of pushed and bistable fronts of the reaction diffusion equation when a small cutoff is applied at the unstable or metastable equilibrium point. The results are valid for arbitrary reaction terms and include the case of density dependent diffusion.Comment: 7 page

Traveling Wave Solutions of Advection-Diffusion Equations with Nonlinear Diffusion

We study the existence of particular traveling wave solutions of a nonlinear parabolic degenerate diffusion equation with a shear flow. Under some assumptions we prove that such solutions exist at least for propagation speeds c {\in}]c*, +{\infty}, where c* > 0 is explicitly computed but may not be optimal. We also prove that a free boundary hy- persurface separates a region where u = 0 and a region where u > 0, and that this free boundary can be globally parametrized as a Lipschitz continuous graph under some additional non-degeneracy hypothesis; we investigate solutions which are, in the region u > 0, planar and linear at infinity in the propagation direction, with slope equal to the propagation speed.Comment: 40 pages, 1 figur

Field tuned critical fluctuations in YFe2Al10: Evidence from magnetization, 27Al (NMR, NQR) investigations

We report magnetization, specific heat, and NMR investigations on YFe2Al10 over a wide range in temperature and magnetic field and zero field (NQR) measurements. Magnetic susceptibility, specific heat and spin-lattice relaxation rate divided by T (1/T1T) follow a weak power law (T^-0.4) temperature dependence, which is a signature of critical fluctuations of Fe moments. The value of the Sommerfeld-Wilson ratio and linear relation between 1/T1T and chi(T) suggest the existence of ferromagnetic correlations in this system. No magnetic ordering down to 50 mK in Cp(T) and the unusual temperature and field scaling of the bulk and NMR data are associated with a magnetic instability which drives the system to quantum criticality. The magnetic properties of the system are tuned by field wherein ferromagnetic fluctuations are suppressed and a crossover from quantum critical to FL behavior is observed with increasing magnetic field