Developing a New Partnership

Many factors contribute to the success and impact of a Mathematics Resource Teacher on K-5 mathematics instruction. Developing a strong partnership with stakeholders and sharing a common vision for quality mathematics instruction are key factors in the successful implementation of the Mathematics Resource Teacher program. In this article, we share the experience of elementary school principal, Timothy Martino, as he prepared to open a new elementary school in August 2012. Frederick Douglass Elementary opened with a full-time, school-embedded Mathematics Resource Teacher, Mrs. Cindy Brady. Timothy Martino and Mrs. Brady developed a partnership with division-level central office staff and with the teachers of Frederick Douglass Elementary. Thus, they began the journey toward improving mathematics instruction for students through a team approach

Statistical analysis of the 70 meter antenna surface distortions

Statistical analysis of surface distortions of the 70 meter NASA/JPL antenna, located at Goldstone, was performed. The purpose of this analysis is to verify whether deviations due to gravity loading can be treated as quasi-random variables with normal distribution. Histograms of the RF pathlength error distribution for several antenna elevation positions were generated. The results indicate that the deviations from the ideal antenna surface are not normally distributed. The observed density distribution for all antenna elevation angles is taller and narrower than the normal density, which results in large positive values of kurtosis and a significant amount of skewness. The skewness of the distribution changes from positive to negative as the antenna elevation changes from zenith to horizon

Understanding Variations in Circularly Polarized Photoluminescence in Monolayer Transition Metal Dichalcogenides

Monolayer transition metal dichalcogenides are promising materials for valleytronic operations. They exhibit two inequivalent valleys in the Brillouin zone, and the valley populations can be directly controlled and determined using circularly polarized optical excitation and emission. The photoluminescence polarization reflects the ratio of the two valley populations. A wide range of values for the degree of circularly polarized emission, Pcirc, has been reported for monolayer WS2, although the reasons for the disparity are unclear. Here we optically populate one valley, and measure Pcirc to explore the valley population dynamics at room temperature in a large number of monolayer WS2 samples synthesized via chemical vapor deposition. Under resonant excitation, Pcirc ranges from 2% to 32%, and we observe a pronounced inverse relationship between photoluminescence (PL) intensity and Pcirc. High quality samples exhibiting strong PL and long exciton relaxation time exhibit a low degree of valley polarization, and vice versa. This behavior is also demonstrated in monolayer WSe2 samples and transferred WS2, indicating that this correlation may be more generally observed and account for the wide variations reported for Pcirc. Time resolved PL provides insight into the role of radiative and non-radiative contributions to the observed polarization. Short non-radiative lifetimes result in a higher measured polarization by limiting opportunity for depolarizing scattering events

Participation And performance In 8.02x Electricity And Magnetism: The First Physics MOOC From MITx

Massive Open Online Courses are an exciting new avenue for instruction and research, yet they are full of unknowns. In the Spring of 2013, MITx released its first introductory physics MOOC through the edX platform, generating a total enrollment of 43,000 students from around the world. We describe the population of participants in terms of their age, gender, level of education, and country of origin, highlighting both the diversity of 8.02x enrollees as well as gender gap and retention. Using three midterm exams and the final as waypoints, we highlight performance by different demographic subpopulations and their retention rates. Our work is generally aimed at making a bridge between available MOOC data and topics associated with the Physics Education Research community.Comment: 4 pages, 5 figures, Accepted for publication in the Physics Education Research Conference Proceedings, Portland OR 201

Where are the Hedgehogs in Nematics?

In experiments which take a liquid crystal rapidly from the isotropic to the nematic phase, a dense tangle of defects is formed. In nematics, there are in principle both line and point defects (``hedgehogs''), but no point defects are observed until the defect network has coarsened appreciably. In this letter the expected density of point defects is shown to be extremely low, approximately $10^{-8}$ per initially correlated domain, as result of the topology (specifically, the homology) of the order parameter space.Comment: 6 pages, latex, 1 figure (self-unpacking PostScript)

Fermi Surface Nesting and Nanoscale Fluctuating Charge/Orbital Ordering in Colossal Magnetoresistive Oxides

We used high resolution angle-resolved photoemission spectroscopy to reveal the Fermi surface and key transport parameters of the metallic state of the layered Colossal Magnetoresistive (CMR) oxide La1.2Sr1.8Mn2O7. With these parameters the calculated in-plane conductivity is nearly one order of magnitude larger than the measured DC conductivity. This discrepancy can be accounted for by including the pseudogap which removes at least 90% of the spectral weight at the Fermi energy. Key to the pseudogap and many other properties are the parallel straight Fermi surface sections which are highly susceptible to nesting instabilities. These nesting instabilities produce nanoscale fluctuating charge/orbital modulations which cooperate with Jahn-Teller distortions and compete with the electron itinerancy favored by double exchange

A descriptive study of the tones in the Chengtu dialect (Szechuan, China) and the intonation of certain types of sentences

First, tones pronounced in isolation behave differently from those pronounced in connected speech. In connected speech they go through perturbation. This is usually governed by the position they occupy in the phrase or by the tonal environment. It may also be governed by grammatical structure, though this does not form part of my present inquiry.Second, besides the four naming tones in the Chengtu dialect, I found six other tones which, together with those naming tones, could be grouped into four tonemes. It is the interchange of these tones which formed the study of the tonal behaviour in the first part of this thesis.Third, intonation does exist in the Chengtu dialect. It is superimposed on the whole sentence. And it is this superimposed intonation that modifies the individual tones and not the individual tones that decide the intonation of the sentence.My purpose in undertaking this study has been twofold. On one hand, it is my hope that the work may serve as a teaching manual for intonation in the Chengtu dialect. In the process of acquiring the right intonation, the advanced student may find the numerous examples useful. Though they are taken only from the speech of two people (the informant and myself), they more or less represent the main speech characteristics of the Chengtu dialect.Oh the other hand, the material I assembled and particularly the conclusions I reached may be of some value to students of other dialects. Tone sandhi has already been studied in many Chinese dialects , though without the help of the more modern instruments. It would be desirable for similar work to be done on A eresting question is whether in other dialects intonation is also indicated by the perturbation of one particular syllable, which in the case of the Chengtu dialect is the final syllable. It would also be interesting to know if the resulting tunes could be divided neatly into two or more patterns. If a number of other dialects could be studied along lines similar to the present inquiry, we could then perhaps come to a more general explanation of tonal behaviour and intonation in the Chinese dialects