Novel waveguide configuration for convenient and sensitive fluorescence and Raman measurements of liquids over optical fibers

Fluorescence has been measured from a waveguide formed by a PTFE tube with an internal coating of a low-refractive-index amorphous fluoropolymer. The configuration is suited to taking measurements from liquids having a refractive index down to 1.32, including, in particular, aqueous solutions. The parameters which determine the optical collection efficiency have been mathematically modelled. We have produced waveguides up to 1m long, and with 0.955 mm and 0.445 mm internal radii, and measured a (fluorescence) collection enhancement factor of 3 from a 140 mm long, 0.955 mm internal radius waveguide. Work is continuing to increase the enhancement factor

Metal-Insulator Transition Revisited for Cold Atoms in Non-Abelian Gauge Potentials

We discuss the possibility of realizing metal-insulator transitions with ultracold atoms in two-dimensional optical lattices in the presence of artificial gauge potentials. Such transitions have been extensively studied for magnetic fields corresponding to Abelian gauges; they occur when the magnetic flux penetrating the lattice plaquette is an irrational multiple of the magnetic flux quantum. Here we present the first study of these transitions for non-Abelian U(2) gauge fields, which can be realized with atoms with two pairs of degenerate internal states. In contrast to the Abelian case, the spectrum and localization transition in the non-Abelian case is strongly influenced by atomic momenta. In addition to determining the localization boundary, the momentum fragments the spectrum and the minimum energy viewed as a function of momentum exhibits a step structure. Other key characteristics of the non-Abelian case include the absence of localization for certain states and satellite fringes around the Bragg peaks in the momentum distribution and an interesting possibility that the transition can be tuned by the atomic momenta.Comment: 4 pages, 4 figures, see http://physics.gmu.edu/~isatija/recentpub.htm for high resolution figure

Woman as a factor in industrial evolution

Thesis (M.A.)--Boston Universit

The Perceived Impact of a Short-Term Monolingual Karen Language Learning Experience on the Teaching Practices of Low-Literacy Adult English Language Instructors

A limited amount of research on low-educated low-literate adult English language learners exists. An even smaller body of literature addresses innovation and teacher change of the instructors of this demographic. Adult refugees need basic language competency to participate with dignity in a new culture. This study explores the impact of increasing teacher empathy for the monolingual language learning environment that most first-wave refugees encounter upon arrival in the United States and identifies the instructional innovations and modifications that result. Nine participants, all low-level adult ELL instructors from a number of community-based adult language schools, took part in a Karen language class over several weeks. Questionnaires, journaling, audio-recording, and researcher observation were used to study the perceived impact of this professional development language-learning experience on the participants’ teaching practice. The results fall into two categories: Experience and Impact. Within these categories are additional areas where a sharp increase in empathy results as each teacher-participant reports direct and immediate impact on teaching practices. Findings include: a renewed appreciation for the difficulty of the learners’ task, a recognition of the futility of extraneous teacher-talk, a deeper understanding of a variety of classroom behaviors, and a reinforcement of previously learned educational principles such as allowing silent periods for absorption, theme consistency and teaching a limited amount of content per class session. Findings demonstrate that this non-Roman alphabet monolingually-taught class is an experience that deeply challenges the current thought and perspectives of the teacher-participants. Reflective teaching practice is enhanced via this study as a means to create improvements in teaching and in adult learning

Dark energy perturbations in NN-body simulations

We present $N$-body simulations which are fully compatible with general relativity, with dark energy consistently included at both the background and perturbation level. We test our approach for dark energy parameterised as both a fluid, and using the parameterised post-Friedmann (PPF) formalism. In most cases, dark energy is very smooth relative to dark matter so that its leading effect on structure formation is the change to the background expansion rate. This can be easily incorporated into Newtonian $N$-body simulations by changing the Friedmann equation. However, dark energy perturbations and relativistic corrections can lead to differences relative to Newtonian $N$-body simulations at the tens of percent level for scales k < (10^{-3} \unicode{x2013} 10^{-2})\,\mathrm{Mpc}^{-1}, and given the accuracy of upcoming large scale structure surveys such effects must be included. In this paper we will study both effects in detail and highlight the conditions under which they are important. We also show that our $N$-body simulations exactly reproduce the results of the Boltzmann solver CLASS for all scales which remain linear