Commensurate Fluctuations in the Pseudogap and Incommensurate spin-Peierls Phases of TiOCl

X-ray scattering measurements on single crystals of TiOCl reveal the presence of commensurate dimerization peaks within both the incommensurate spin-Peierls phase and the so-called pseudogap phase above T_c2. This scattering is relatively narrow in Q-space indicating long correlation lengths exceeding ~ 100 A below T* ~ 130 K. It is also slightly shifted in Q relative to that of the commensurate long range ordered state at the lowest temperatures, and it coexists with the incommensurate Bragg peaks below T_c2. The integrated scattering over both commensurate and incommensurate positions evolves continuously with decreasing temperature for all temperatures below T* ~ 130 K.Comment: To appear in Physical Review B: Rapid Communications. 5 page

The New Handshake: Where We Are Now

The internet has empowered consumers in new and exciting ways. It has opened more efficient avenues for consumers to buy just about anything. Want proof? Just pull out your smartphone, swipe your finger across the screen a few times, and presto – your collector’s edition Notorious RBG bobblehead is on its way from China. Unfortunately, however, the internet has not yet delivered on its promise to improve consumer protection

Algebra Rules Object Boxes as an Authentic Assessment Task of Preservice Elementary Teacher Learning in a Mathematics Methods Course

The purpose of this study was to describe elementary preservice teachers’ difficulties with understanding algebraic generalizations that were set in an authentic context. Fifty-eight preservice teachers enrolled in an elementary mathematics methods course participated in the study. These students explored and practiced with authentic, hands-on materials called “object boxes,” then created sets of their own object box materials. Each algebra rules object box contained materials to illustrate and describe four different algebraic generalizations, or “rules.” The variables “n” and “z” were used in each of the generalizations. For each generalization, there was a set of objects attached to a piece of mat board that showed three cases of the generalization for different values of “n.” Two sets of cards accompanied these objects, giving word problems, defining variables, stating equations, and explaining the algebraic generalizations. Students matched word problems to the object sets, defined variables and checked their work, then wrote algebraic generalizations for the object sets and used the reverse sides of the equation cards to check their work. Projects were graded with a rubric. Students were then surveyed about their difficulties. Results of the analysis showed that students were able to make an assortment of authentic materials in a variety of contexts and enjoyed the creative aspects of the project, but found the algebraic content challenging. The most common mathematical difficulties were being able to define the variable, and identify the pattern. Examples of effective student materials are provided

Intertidal reef communities of the Marmion & Shoalwater Islands marine parks

Intertidal platform reefs are a distinctive feature of the Perth coastline. Occurring adjacent to shoreline beaches and also as isolated offshore reefs, these limestone platforms have been formed by wave action over many centuries. Rising and falling tides exert a major influence on the structure of intertidal reef communities, and this influence typically results in a distinctive distribution of organisms based on their tolerance to being exposed to the air when the tide is low. Those inhabiting the highest part of the rocky shore, and therefore exposed more often and for longer periods, are typically hardy, desiccation-resistant species. Those living further seaward are more frequently submerged, although even these organisms may be exposed to the drying sun during particularly low tides, or can be periodically buried by the deposition of shifting beach sand. During winter storms, large waves may crash onto these reefs, stripping away algae and dislodging animals. Yet despite such harsh conditions, intertidal reefs can support a diverse assemblage of algae and invertebrates. Intertidal reefs are recognised as key ecological values of the Marmion and Shoalwater Islands marine parks that are located adjacent to the Perth metropolitan area. Between 2009 and 2012, marine scientists from DEC’s Marine Science Program and the WA Herbarium worked with local marine park staff to survey some of the numerous intertidal reefs in these marine parks to improve our understanding of the communities they support

The Gates Of Gladness : On The Road To Sunshine Land

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Suppression of the commensurate spin-Peierls state in Sc-doped TiOCl

We have performed x-ray scattering measurements on single crystals of the doped spin-Peierls compound Ti(1-x)Sc(x)OCl (x = 0, 0.01, 0.03). These measurements reveal that the presence of non-magnetic dopants has a profound effect on the unconventional spin-Peierls behavior of this system, even at concentrations as low as 1%. Sc-doping suppresses commensurate fluctuations in the pseudogap and incommensurate spin-Peierls phases of TiOCl, and prevents the formation of a long-range ordered spin-Peierls state. Broad incommensurate scattering develops in the doped compounds near Tc2 ~ 93 K, and persists down to base temperature (~ 7 K) with no evidence of a lock-in transition. The width of the incommensurate dimerization peaks indicates short correlation lengths on the order of ~ 12 angstroms below Tc2. The intensity of the incommensurate scattering is significantly reduced at higher Sc concentrations, indicating that the size of the associated lattice displacement decreases rapidly as a function of doping.Comment: 7 pages, 5 figure