Disciplinary problems among high achiever students: the types and the causes

This qualitative study has been done to 24 teachers and 72 students from various secondary schools in Penang, Malaysia, in order to investigate the effect of between class ability grouping (BCAG) on high achiever secondary school students. Studies reported that BCAG triggered correspondence bias among teachers, which eventually affect them to show different perception and expectations towards high achiever classes (HAC) and low achiever classes (LAC) students. Symbolic interaction theories explained that individuals tend to be affected by others’ expectation, and therefore behave in a way they were expected to. Therefore, according to the previous studies on BCAG, it was assumed that HAC students would achieve better and would not be significantly involved in disciplinary problems. After semi-structured interview had been conducted in order to collect the data, and two-cycled analyses method, namely In-Vivo and Thematic Analyses had been operated in order to analyze the massive amount of qualitative data, the it was discovered that HAC students were involved with disciplinary problems, such as being disrespectful to teachers, paying less attention in the classroom, neglecting assignments and doing external work during classes. Other findings of this study showed that the disciplinary problems among HAC are related to their self-esteem types due to locus of control difference, as well as bigger issues apart from the competition among themselves. School management system, BCAG itself, reciprocal envy between HAC and LAC students, as well as their inclination towards tuition centers contributed to disciplinary problems among HAC students

Wild-Type Phosphoribosylpyrophosphate Synthase (PRS) from Mycobacterium tuberculosis: A Bacterial Class II PRS?

The 5-phospho-α-D-ribose 1-diphosphate (PRPP) metabolite plays essential roles in several biosynthetic pathways, including histidine, tryptophan, nucleotides, and, in mycobacteria, cell wall precursors. PRPP is synthesized from α-D-ribose 5-phosphate (R5P) and ATP by the Mycobacterium tuberculosis prsA gene product, phosphoribosylpyrophosphate synthase (MtPRS). Here, we report amplification, cloning, expression and purification of wild-type MtPRS. Glutaraldehyde cross-linking results suggest that MtPRS predominates as a hexamer, presenting varied oligomeric states due to distinct ligand binding. MtPRS activity measurements were carried out by a novel coupled continuous spectrophotometric assay. MtPRS enzyme activity could be detected in the absence of Pi. ADP, GDP and UMP inhibit MtPRS activity. Steady-state kinetics results indicate that MtPRS has broad substrate specificity, being able to accept ATP, GTP, CTP, and UTP as diphosphoryl group donors. Fluorescence spectroscopy data suggest that the enzyme mechanism for purine diphosphoryl donors follows a random order of substrate addition, and for pyrimidine diphosphoryl donors follows an ordered mechanism of substrate addition in which R5P binds first to free enzyme. An ordered mechanism for product dissociation is followed by MtPRS, in which PRPP is the first product to be released followed by the nucleoside monophosphate products to yield free enzyme for the next round of catalysis. The broad specificity for diphosphoryl group donors and detection of enzyme activity in the absence of Pi would suggest that MtPRS belongs to Class II PRS proteins. On the other hand, the hexameric quaternary structure and allosteric ADP inhibition would place MtPRS in Class I PRSs. Further data are needed to classify MtPRS as belonging to a particular family of PRS proteins. The data here presented should help augment our understanding of MtPRS mode of action. Current efforts are toward experimental structure determination of MtPRS to provide a solid foundation for the rational design of specific inhibitors of this enzyme

Photochemical Ring-Opening and Intramolecular Hydrogen Shift Reactions in Sulfur Analogues of α-Pyrone

A combined matrix isolation FTIR and theoretical DFT(B3LYP)/6-311++G(d,p) study of the photochemistry of sulfur analogues of α-pyrone [2H-thiopyran-2-one (TP) and 2H-pyran-2-thione (PT)] was carried out. The vibrational spectra of monomers of the compounds isolated in low-temperature argon matrixes were studied experimentally and assigned completely on the basis of theoretical calculations. UV irradiation (λ > 337 nm) of the studied compounds isolated in low-temperature matrixes results mainly in the ring-opening reaction by means of the cleavage of the α-bond. Other photoprocesses, not involving the α-bond-cleavage step (such as generation of Dewar valence isomer), correspond to the minor reaction channels in both studied compounds. The ring-opening photoreaction in PT represents the first reported case of an α-bond cleavage in a compound with a CS group attached to a six-membered ring, in which the internal strain practically does not exist, whereas the corresponding reaction in TP (a cleavage of a C−S bond in the α position with respect to a carbonyl group) is now reported for the first time. Following the ring-opening reactions, isomerization processes and intramolecular hydrogen shift reactions were observed, enabling production of TP from PT and vice versa. A detailed study of such processes was undertaken, and kinetical and mechanistical data are presented and discussed

SUPPORT VECTOR MACHINE TO ESTIMATE VOLUME OF EUCALYPT TREES

ABSTRACT This study aimed to test the application of the technique of support vector machines (SVM) to estimate the volume of eucalyptus trees. The data used in this study were from of 2307 trees of clonal hybrids (Eucalyptus grandis x Eucalyptus urophylla) located in southern Bahia. In the definition of stratification traditionally used 53 stratums were defined (defined by the stratification project and clone). He set the model of Schumacher and Hall for each stratum. The SVM were constructed to correlate the volume of trees on the basis of other independent variables which may be numeric as dbh and height and categorical as genetic material and design. The estimates were analyzed using statistical and graphical analysis of residues. The analysis consisted of the graphical inspection statistical dispersion of errors (residuals) in relation to the percentage of the values observed, and the analysis of the histogram of residues. The statistics used were the correlation between the observed and estimated volumes. The model of Schumacher and Hall showed the correlation between observed and predicted values of 0,993, and the SVM set of correlated 0,994. The SVM technology showed good adaptation to the problem, and this can use to predict the volumetric production of planted forests

SUPPORT VECTOR MACHINE TO ESTIMATE VOLUME OF EUCALYPT TREES

ABSTRACT This study aimed to test the application of the technique of support vector machines (SVM) to estimate the volume of eucalyptus trees. The data used in this study were from of 2307 trees of clonal hybrids (Eucalyptus grandis x Eucalyptus urophylla) located in southern Bahia. In the definition of stratification traditionally used 53 stratums were defined (defined by the stratification project and clone). He set the model of Schumacher and Hall for each stratum. The SVM were constructed to correlate the volume of trees on the basis of other independent variables which may be numeric as dbh and height and categorical as genetic material and design. The estimates were analyzed using statistical and graphical analysis of residues. The analysis consisted of the graphical inspection statistical dispersion of errors (residuals) in relation to the percentage of the values observed, and the analysis of the histogram of residues. The statistics used were the correlation between the observed and estimated volumes. The model of Schumacher and Hall showed the correlation between observed and predicted values of 0,993, and the SVM set of correlated 0,994. The SVM technology showed good adaptation to the problem, and this can use to predict the volumetric production of planted forests

Inhibition of <i>Mt</i>PRS enzyme activity by A) ADP; B) GDP; and C) UMP.

<p><i>Mt</i>PRS expressed as its fractional activity; and ADP, GDP and UMP concentrations were plotted on log scale.</p

Comparative of apparent kinetic parameters for <i>Mt</i>PRS substrate pair ATP/R5P.

<p>Comparative of apparent kinetic parameters for <i>Mt</i>PRS substrate pair ATP/R5P.</p

Proposed kinetic mechanisms for <i>Mt</i>PRS using A) purine or B) pyrimidine 5′-trisphosphate nucleotides, as diphosphoryl group donors.

<p>Random order of addition for ATP or GTP and ordered addition of UTP or CTP substrates, with ordered release of products.</p