Isoconfigurational Elastic Constants and Liquid Fragility of a Bulk Metallic Glass Forming Alloy

Samples of Zr46.25Ti8.25Cu7.5Ni10Be27.5 were isothermally annealed and quenched near the glass transition temperature and studied by the pulse-echo overlap technique. The shear modulus G of the samples shows a strong reversible dependence on annealing temperatures and, thus, on the specific configurational potential energy of the equilibrium liquid. The low-T dependence of G of the configurationally frozen glasses shows linear temperature dependence as expected by Debye-Grüneisen theory. The T dependence of G in the liquid state is directly related to the viscosity and fragility of the liquid

Connection between fluency and comprehension through the use of readers\u27 theater

Throughout my teaching career I have been curious as to why some students are able to comprehend a reading passage with greater ease than other students. I have taught first, second, and third grade and in all three grades I observed similar issues with the students who have difficulty with comprehending a reading passage. Most of the students I worked with who had difficulty with comprehension also had a hard time reading fluently. This made me wonder if reading fluency had an impact on reading comprehension. A fluent reader is one who can orally read at an appropriate rate and use expression to show the reader understands the meaning of the text (Griffith & Rasinski, 2004). After discussing this thought with many other teachers and reading research articles, I wondered if using Readers’ Theaters in the classroom to improve students’ reading fluency would in turn improve students’ reading comprehension. Due in part to my collaboration and research I explored the following research question, Does student fluency through the use of Reader\u27s Theater increase the student\u27s comprehension

Calcium entry into stereocilia drives adaptation of the mechanoelectrical transducer current of mammalian cochlear hair cells

Mechanotransduction in the auditory and vestibular systems depends on mechanosensitive ion channels in the stereociliary bundles that project from the apical surface of the sensory hair cells. In lower vertebrates, when the mechanoelectrical transducer (MET) channels are opened by movement of the bundle in the excitatory direction, Ca2+ entry through the open MET channels causes adaptation, rapidly reducing their open probability and resetting their operating range. It remains uncertain whether such Ca2+-dependent adaptation is also present in mammalian hair cells. Hair bundles of both outer and inner hair cells from mice were deflected by using sinewave or step mechanical stimuli applied using a piezo-driven fluid jet. We found that when cochlear hair cells were depolarized near the Ca2+ reversal potential or their hair bundles were exposed to the in vivo endolymphatic Ca2+ concentration (40 µM), all manifestations of adaptation, including the rapid decline of the MET current and the reduction of the available resting MET current, were abolished. MET channel adaptation was also reduced or removed when the intracellular Ca2+ buffer 1,2-Bis(2-aminophenoxy)ethane-N,N,N′,N′-tetraacetic acid (BAPTA) was increased from a concentration of 0.1 to 10 mM. The findings show that MET current adaptation in mouse auditory hair cells is modulated similarly by extracellular Ca2+, intracellular Ca2+ buffering, and membrane potential, by their common effect on intracellular free Ca2+. Hearing and balance depend on the transduction of mechanical stimuli into electrical signals. This process depends on the opening of mechanoelectrical transducer (MET) channels located at the tips of the shorter of pairs of adjacent stereocilia (1), which are specialized microvilli-like structures that form the hair bundles that project from the upper surface of hair cells (2,3). Deflection of hair bundles in the excitatory direction (i.e., toward the taller stereocilia) stretches specialized linkages, the tip-links, present between adjacent stereocilia (3⇓–5), opening the MET channels. In hair cells from lower vertebrates, open MET channels reclose during constant stimuli via an initial fast adaptation mechanism followed by a much slower, myosin-based motor process, both of which are driven by Ca2+ entry through the channel itself (6⇓⇓⇓⇓⇓⇓–13). In mammalian auditory hair cells, MET current adaptation seems to be mainly driven by the fast mechanism (14⇓–16), although the exact process by which it occurs is still largely unknown. The submillisecond speed associated with the adaptation kinetics of the MET channels in rat and mouse cochlear hair cells (17, 18) indicates that Ca2+, to cause adaptation, has to interact directly with a binding site on the channel or via an accessory protein (16). However, a recent investigation on rat auditory hair cells has challenged the view that Ca2+ entry is required for fast adaptation, and instead proposed an as-yet-undefined mechanism involving a Ca2+-independent reduction in the viscoelastic force of elements in series with the MET channels (19). In the present study, we further investigated the role of Ca2+ in MET channel adaptation in mouse cochlear hair cells by deflecting their hair bundles using a piezo-driven fluid jet, which is believed to produce a more uniform deflection of the hair bundles (20⇓⇓–23) compared with the piezo-driven glass rod (19, 24)

Tmc1 point mutation affects Ca2+ sensitivity and block by dihydrostreptomycin of the mechanoelectrical transducer current of mouse outer hair cells

The transduction of sound into electrical signals depends on mechanically sensitive ion channels in the stereociliary bundle. The molecular composition of this mechanoelectrical transducer (MET) channel is not yet known. Transmembrane channel-like protein isoforms 1 (TMC1) and 2 (TMC2) have been proposed to form part of the MET channel, although their exact roles are still unclear. Using Beethoven (Tmc1Bth/Bth) mice, which have an M412K point mutation in TMC1 that adds a positive charge, we found that Ca2+ permeability and conductance of the MET channel of outer hair cells (OHCs) were reduced. Tmc1Bth/Bth OHCs were also less sensitive to block by the permeant MET channel blocker dihydrostreptomycin, whether applied extracellularly or intracellularly. These findings suggest that the amino acid that is mutated in Bth is situated at or near the negatively charged binding site for dihydrostreptomycin within the permeation pore of the channel. We also found that the Ca2+ dependence of the operating range of the MET channel was altered by the M412K mutation. Depolarization did not increase the resting open probability of the MET current of Tmc1Bth/Bth OHCs, whereas raising the intracellular concentration of the Ca2+ chelator BAPTA caused smaller increases in resting open probability in Bth mutant OHCs than in wild-type control cells. We propose that these observations can be explained by the reduced Ca2+ permeability of the mutated MET channel indirectly causing the Ca2+ sensor for adaptation, at or near the intracellular face of the MET channel, to become more sensitive to Ca2+ influx as a compensatory mechanism

Mobile Device Use Among Rural, Low-Income Families and the Feasibility of an App to Encourage Preschoolers' Physical Activity: Qualitative Study.

BackgroundAs mobile devices are becoming ubiquitous, technology-based interventions provide a promising strategy to positively influence health behaviors of families with young children. However, questions remain about the feasibility and acceptability of intervention delivery via mobile apps in low-income, rural settings and among families with preschoolers.ObjectiveThe aims of this study were to understand the content and context of mobile device use for preschoolers; explore parent beliefs on this topic, including the acceptability of intervention delivery via mobile devices; and test a prototype of an app to encourage preschoolers' physical activity with both parents and children.MethodsParents (n=29) were recruited from 5 preschool centers in eastern, rural Colorado to complete a semistructured telephone interview regarding preschoolers' mobile device use. A second sample of parents (n=31) was recruited from the same preschool centers to view the app prototype independently and provide feedback. A third sample of preschool children (n=24) was videotaped using the app in small groups to measure engagement and record their responses to the app.ResultsFive key content areas emerged from the telephone interviews: (1) mobile devices are an important part of families' everyday routines, and parents have parameters governing their use; (2) parents often use mobile devices as a tool for behavior management; (3) parents clearly distinguish between mobile device use for learning versus entertainment; (4) parents have an overarching desire for balance in regard to their child's mobile device use; and (5) parents were generally supportive of the idea of using mobile apps for intervention delivery. From the app prototype testing with parents, participants reacted positively to the app and felt that it would be useful in a variety of situations. Testing with preschoolers showed the children were highly engaged with the app and a majority remained standing and/or actively moving through the entire length of the app.ConclusionsMobile devices are already integrated into most families' daily routines and appear to be an acceptable method of intervention delivery in low-income families in rural Colorado. The physical activity app represents an innovative way to reach these families and, with further improvements based on participant feedback, will provide children with a unique opportunity to practice key movement skills

Introduction: Transgressing Borders/Boundaries: Gendering Space and Place

Introduction: Transgressing Borders/Boundaries: Gendering Space and Plac

Thermal and elastic properties of Cu–Zr–Be bulk metallic glass forming alloys

The compositional dependence of thermal and elastic properties of Cu–Zr–Be ternary bulk metallic glass forming alloys was systematically studied. There exists a linear relationship between the glass transition temperature Tg and the total Zr concentration. G decreases linearly with increasing Zr concentration as well. The results also show that Tg, shear modulus G, and Poisson's ratio nu are very sensitive to changes in compositions. Low Tg, low G, and relatively high nu can be achieved with high Zr and Ti concentration