494 research outputs found
Multilevel latent class analysis for large-scale educational assessment data: Exploring the relation between the curriculum and students' mathematical strategies
A ïŹrst application of multilevel latent class analysis (MLCA) to educational large-scale assessment data is demonstrated. This statistical technique addresses several of the challenges that assessment data offers. Importantly, MLCA allows modeling of the often ignored teacher effects and of the joint inïŹuence of teacher and student variables. Using data from the 2011 assessment of Dutch primary schoolsâ mathematics, this study explores the relation between the curriculum as reported by 107 teachers and the strategy choices of their 1,619 students, while controlling for student characteristics. Considerable teacher effects are demonstrated, as well as signiïŹcant relations between the intended as well as enacted curriculum and studentsâ strategy use. Implications of these results for both more theoretical and practical educational research are discussed, as are several issues in applying MLCA and possibilities for applying MLCA to different types of educational data.Development Psychopathology in context: schoo
Selective Îș Opioid Antagonists nor-BNI, GNTI and JDTic Have Low Affinities for Non-Opioid Receptors and Transporters
Background: Nor-BNI, GNTI and JDTic induce selective Îș opioid antagonism that is delayed and extremely prolonged, but some other effects are of rapid onset and brief duration. The transient effects of these compounds differ, suggesting that some of them may be mediated by other targets. Results: In binding assays, the three antagonists showed no detectable affinity (Kiâ„10 ”M) for most non-opioid receptors and transporters (26 of 43 tested). There was no non-opioid target for which all three compounds shared detectable affinity, or for which any two shared sub-micromolar affinity. All three compounds showed low nanomolar affinity for Îș opioid receptors, with moderate selectivity over ÎŒ and ÎŽ (3 to 44-fold). Nor-BNI bound weakly to the α2C-adrenoceptor (Ki = 630 nM). GNTI enhanced calcium mobilization by noradrenaline at the α1A-adrenoceptor (EC50 = 41 nM), but did not activate the receptor, displace radioligands, or enhance PI hydrolysis. This suggests that it is a functionally-selective allosteric enhancer. GNTI was also a weak M1 receptor antagonist (KB = 3.7 ”M). JDTic bound to the noradrenaline transporter (Ki = 54 nM), but only weakly inhibited transport (IC50 = 1.1 ”M). JDTic also bound to the opioid-like receptor NOP (Ki = 12 nM), but gave little antagonism even at 30 ”M. All three compounds exhibited rapid permeation and active efflux across Caco-2 cell monolayers. Conclusions: Across 43 non-opioid CNS targets, only GNTI exhibited a potent functional effect (allosteric enhancement of α1A-adrenoceptors). This may contribute to GNTI's severe transient effects. Plasma concentrations of nor-BNI and GNTI may be high enough to affect some peripheral non-opioid targets. Nonetheless, Îș opioid antagonism persists for weeks or months after these transient effects dissipate. With an adequate pre-administration interval, our results therefore strengthen the evidence that nor-BNI, GNTI and JDTic are highly selective Îș opioid antagonists
Length-dependent translocation of polymers through nanochannels
We consider the flow-driven translocation of single polymer chains through
nanochannels. Using analytical calculations based on the de Gennes blob model
and mesoscopic numerical simulations, we estimate the threshold flux for the
translocation of chains of different number of monomers. The translocation of
the chains is controlled by the competition between entropic and hydrodynamic
effects, which set a critical penetration length for the chain before it can
translocate through the channel. We demonstrate that the polymers show two
different translocation regimes depending on how their length under confinement
compares to the critical penetration length. For polymer chains longer than the
threshold, the translocation process is insensitive to the number of monomers
in the chain as predicted in Sakaue {\it et al.}, {\it Euro. Phys. Lett.}, {\bf
72} 83 (2005). However, for chains shorter than the critical length we show
that the translocation process is strongly dependent on the length of the
chain. We discuss the possible relevance of our results to biological
transport.Comment: To appear in Soft Matter. 10 pages 9 Figure
Both the C-Terminal Polylysine Region and the Farnesylation of K-RasB Are Important for Its Specific Interaction with Calmodulin
Background: Ras protein, as one of intracellular signal switches, plays various roles in several cell activities such as differentiation and proliferation. There is considerable evidence showing that calmodulin (CaM) binds to K-RasB and dissociates K-RasB from membrane and that the inactivation of CaM is able to induce K-RasB activation. However, the mechanism for the interaction of CaM with K-RasB is not well understood. Methodology/Principal Findings: Here, by applying fluorescence spectroscopy and isothermal titration calorimetry, we have obtained thermodynamic parameters for the interaction between these two proteins and identified the important elements of K-RasB for its interaction with Ca 2+ /CaM. One K-RasB molecule interacts with one CaM molecule in a GTP dependent manner with moderate, micromolar affinity at physiological pH and physiologic ionic strength. Mutation in the polybasic domain of K-Ras decreases the binding affinity. By using a chimera in which the C-terminal polylysine region of K-RasB has been replaced with that of H-Ras and vice versa, we find that at physiological pH, H-Ras-(KKKKKK) and Ca 2+ /CaM formed a 1:1 complex with an equilibrium association constant around 10 5 M 21, whereas no binding reaction of K-RasB-(DESGPC) with Ca 2+ /CaM is detected. Furthermore, the interaction of K-RasB with Ca 2+ /CaM is found to be enhanced by the farnesylation of K-RasB. Conclusions/Significance: We demonstrate that the polylysine region of K-RasB not only contributes importantly to th
Diode-pumped, ion-exchanged Er/Yb waveguide laser at 1.5”m in phosphorus-free silicate glass
We demonstrate the first diode-pumped, planar ErNb waveguide laser. The device was fabricated by thallium-exchange in a phosphorus-free silicate glass. Lasing was achieved with a low threshold of 15 mW, indicating the absence of the severe backtransfer effects previously reported in Er/Yb bulk laser silicate glasses
Easier sieving through narrower pores: fluctuations and barrier crossing in flow-driven polymer translocation
We show that the injection of polymer chains into nanochannels becomes easier
as the channel becomes narrower. This counter intuitive result arises because
of a decrease in the diffusive time scale of the chains with increasing
confinement. The results are obtained by extending the de Gennes blob model of
confined polymers, and confirmed by hybrid molecular dynamics -
lattice-Boltzmann simulations.Comment: 5 pages, 3 figure
Diode-pumped, planar lossless splitter at 1.5 microns for optical networks
We demonstrate the first planar lossless splitter at 1.5”m. The ion-exchanged waveguide circuit in Er/Yb codoped silicate glass achieved 1x2 lossless splitting at 1537nm with a 980 nm laser diode pump
Enzymatic removal of cellulose from cotton/polyester fabric blends
The production of light-weight polyester fabrics from a polyester/cotton blended fabric, by means of the enzymatic removal of the cellulosic part of the material, was investigated. The removal of cotton from the
blended fabric yielded more than 80% of insoluble microfibrillar material by the combined action of high beating effects and cellulase hydrolysis.Other major features of this enzymatic process for converting cotton fibers into microfibrillar material are bath ratio, enzyme dosage and treatment time
Lossless integrated active splitters for optical networks
We discuss the latest results in the European Union RACE II project LIASON to specify and develop "lossless" splitters in integrated optics, combining an erbium-doped planar amplifier and a passive 1xN cascaded y-junction splitter
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