81 research outputs found

    The Relationship Between Primary 5 and 6 Students’ Perceptions of Parental Encouragement and Their Academic Achievement in Mandarin Learning at An International School, Bangkok

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    This research investigated the relationship between students’ perceptions of parental encouragement and their academic achievement in Mandarin learning at an International School, Bangkok during term 2, and 2014-2015. The study focused on three objectives. The first was to identify the level of student perception of parental encouragement to learn Mandarin in primary 5 and 6. The second was to identify the level of student academic achievement in primary 5 and 6 Mandarin learning. The third was to determine if there was a significant relationship between primary 5 and 6 students’ perceptions of parental encouragement and their Mandarin academic achievement. In order to collect data, the researcher employed a parental encouragement questionnaire adapted from Gardner’s Attitude/Motivation Test Battery (AMTB). For the students’ academic achievement in learning Mandarin, the researcher used the students’ Mandarin academic achievement scores at the end of term 2 in school year 2014- 2015. The findings indicated that there was a significant relationship between primary 5 and 6 students’ perceptions of parental encouragement and their academic achievement. The article concludes with recommendations for practice and for future research

    Single olfactory receptors set odor detection thresholds

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    In many species, survival depends on olfaction, yet the mechanisms that underlie olfactory sensitivity are not well understood. Here we examine how a conserved subset of olfactory receptors, the trace amine-associated receptors (TAARs), determine odor detection thresholds of mice to amines. We find that deleting all TAARs, or even single TAARs, results in significant odor detection deficits. This finding is not limited to TAARs, as the deletion of a canonical odorant receptor reduced behavioral sensitivity to its preferred ligand. Remarkably, behavioral threshold is set solely by the most sensitive receptor, with no contribution from other highly sensitive receptors. In addition, increasing the number of sensory neurons (and glomeruli) expressing a threshold-determining TAAR does not improve detection, indicating that sensitivity is not limited by the typical complement of sensory neurons. Our findings demonstrate that olfactory thresholds are set by the single highest affinity receptor and suggest that TAARs are evolutionarily conserved because they determine the sensitivity to a class of biologically relevant chemicals

    Classification and biological identity of complex nano shapes

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    Everywhere in our surroundings we increasingly come in contact with nanostructures that have distinctive complex shape features on a scale comparable to the particle itself. Such shape ensembles can be made by modern nano-synthetic methods and many industrial processes. With the ever growing universe of nanoscale shapes, names such as “nanoflowers” and “nanostars” no longer precisely describe or characterise the distinct nature of the particles. Here we capture and digitise particle shape information on the relevant size scale and create a condensed representation in which the essential shape features can be captured, recognized and correlated. We find the natural emergence of intrinsic shape groups as well-defined ensemble distributions and show how these may be analyzed and interpreted to reveal novel aspects of our nanoscale shape environment. We show how these ideas may be applied to the interaction between the nanoscale-shape and the living universe and provide a conceptual framework for the study of nanoscale shape biological recognition and identity

    Electro- and photon-induced cooling in BNT-BT-SBET relaxors with in situ optical temperature sensing

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    A novel lead-free luminescent ferroelectric (FE) ceramic, Bi0.5Na0.5TiO3-0.06BaTiO3-0.055Sr0.7Bi0.18Er0.02□0.1TiO3, is developed with an adiabatic temperature change (ΔT) of 0.7 K under an electric-field (E) of 60 kV/cm at room temperature (RT), an anti-stokes fluorescence (FL) cooling and a maximum optical T sensitivity of 0.0055 K-1 at 522 K. Interestingly, the electrocaloric (EC) response reaches a saturation at permittivity-shoulder T of 100 oC, meanwhile the maximized emission intensity of 2H11/2→4I15/2 occurs. T- and E-tunable enhancement of 2H11/2→4I15/2 emission intensity is due to the population inversion from the 4S3/2 to 2H11/2 states caused by an incoherent regime consisting of FE phase and polar nanoregions (PNRs) in a relaxor (R) matrix

    Chemical Components from the Light Petroleum Soluble Fraction of Uvaria cordata (Dunal) Alston

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    Chromatographic separation of the light petroleum extract from the stem bark of Uvaria cordata (Dunal) Alston led to the isolation of the triterpenoids glutinol and taraxerol in addition to the cyclohexene derivatives, pipoxide and its chlorohydrin. A small amount of benzyl benzoate was also isolated

    Accuracy of mRNA Translation in Bacterial Protein Synthesis

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    Reading of messenger RNA (mRNA) by aminoacyl-tRNAs (aa-tRNAs) on the ribosomes in the bacterial cell occurs with high accuracy. It follows from the physical chemistry of enzymatic reactions that there must be a trade-off between rate and accuracy of initial tRNA selection in protein synthesis: when the current accuracy, the A-value, approaches its maximal possible value, the d-value, the kinetic efficiency of the reaction approaches zero. We have used an in vitro system for mRNA translation with purified E. coli components to estimate the d- and A-values by which aa-tRNAs discriminate between their cognate and near cognate codons displayed in the ribosomal A site. In the case of tRNALys, we verified the prediction of a linear trade-off between kinetic efficiency of cognate codon reading and the accuracy of codon selection. These experiments have been extended to a larger set of tRNAs, including tRNAPhe, tRNAGlu, tRNAHis, tRNACys, tRNAAsp and tRNATyr, and linear efficiency-accuracy trade-off was observed in all cases. Similar to tRNALys, tRNAPhe discriminated with higher accuracy against a particular mismatch in the second than in the first codon position. Remarkably high d-values were observed for tRNAGlu discrimination against a C-C mismatch in the first codon position (70 000) and for tRNAPhe discrimination against an A-G mismatch in the second codon position (79 000). At the same time, we have found a remarkably small d-value (200) for tRNAGlu misreading G in the middle position of the codon (U-G mismatch). Aminoglycoside antibiotics induce large codon reading errors by tRNAs. We have studied the mechanism of aminoglycoside action and found that the drug stabilized aminoacyl-tRNA in a codon selective in relation to a codon non-selective state. This greatly enhanced the probability of near cognate aminoacyl-tRNAs to successfully transcend the initial selection step of the translating ribosome. We showed that Mg2+ ions, in contrast, favour codon non-selective states and thus induce errors in a principally different way than aminoglycosides.  We also designed experiments to estimate the overall accuracy of peptide bond formation with, including initial selection accuracy and proofreading of tRNAs after GTP hydrolysis on EF-Tu. Our experiments have now made it possible to calibrate the accuracy of tRNA selection in the test tube to that in the living cells. We will now also be able to investigate the degree to which the accuracy of tRNA selection has been optimized for maximal fitness.

    Accuracy of genetic code translation and its orthogonal corruption by aminoglycosides and Mg2+ ions

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    We studied the effects of aminoglycosides and changing Mg2+ ion concentration on the accuracy of initial codon selection by aminoacyl-tRNA in ternary complex with elongation factor Tu and GTP (T-3) on mRNA programmed ribosomes. Aminoglycosides decrease the accuracy by changing the equilibrium constants of 'monitoring bases' A1492, A1493 and G530 in 16S rRNA in favor of their 'activated' state by large, aminoglycoside-specific factors, which are the same for cognate and near-cognate codons. Increasing Mg2+ concentration decreases the accuracy by slowing dissociation of T-3 from its initial codon-and aminoglycoside-independent binding state on the ribosome. The distinct accuracy-corrupting mechanisms for aminoglycosides and Mg2+ ions prompted us to re-interpret previous biochemical experiments and functional implications of existing high resolution ribosome structures. We estimate the upper thermodynamic limit to the accuracy, the 'intrinsic selectivity' of the ribosome. We conclude that aminoglycosides do not alter the intrinsic selectivity but reduce the fraction of it that is expressed as the accuracy of initial selection. We suggest that induced fit increases the accuracy and speed of codon reading at unaltered intrinsic selectivity of the ribosome

    Proofreading neutralizes potential error hotspots in genetic code translation by transfer RNAs

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    The ribosome uses initial and proofreading selection of aminoacyl-tRNAs for accurate protein synthesis. Anomalously high initial misreading in vitro of near-cognate codons by tRNAHis and tRNAGlu suggested potential error hotspots in protein synthesis, but in vivo data suggested their partial neutralization. To clarify the role of proofreading in this error reduction, we varied the Mg2+ ion concentration to calibrate the total accuracy of our cell-free system to that in the living Escherichia coli cell. We found the total accuracy of tRNA selection in our system to vary by five orders of magnitude depending on tRNA identity, type of mismatch, and mismatched codon position. Proofreading and initial selection were positively correlated at high, but uncorrelated at low initial selection, suggesting hyperactivated proofreading as a means to neutralize potentially disastrous initial selection errors

    Accuracy of initial codon selection by aminoacyl-tRNAs on the mRNA-programmed bacterial ribosome

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    We used a cell-free system with pure Escherichia coli components to study initial codon selection of aminoacyl-tRNAs in ternary complex with elongation factor Tu and GTP on messenger RNA-programmed ribosomes. We took advantage of the universal rate-accuracy trade-off for all enzymatic selections to determine how the efficiency of initial codon readings decreased linearly toward zero as the accuracy of discrimination against near-cognate and wobble codon readings increased toward the maximal asymptote, the d value. We report data on the rate-accuracy variation for 7 cognate, 7 wobble, and 56 near-cognate codon readings comprising about 15% of the genetic code. Their d values varied about 400-fold in the 200-80,000 range depending on type of mismatch, mismatch position in the codon, and tRNA isoacceptor type. We identified error hot spots (d = 200) for U:G misreading in second and U:U or G:A misreading in third codon position by His-tRNA(His) and, as also seen in vivo, Glu-tRNA(Glu). We suggest that the proofreading mechanism has evolved to attenuate error hot spots in initial selection such as those found here
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