EFFICACY OF ONE-ON-ONE PEER TUTORING IN IMPROVING THE PROBLEM-SOLVING PERFORMANCE AMONG THE GRADE 10 LEARNERS

This study aimed to determine the effectiveness of peer tutoring on the mathematical problem-solving performance of Grade 10 students in a public school in Cebu City during S.Y. 2021-2022. Utilizing a single-group pre-test and post-test research design, the study assessed the impact of peer tutoring on selected students' problem-solving performance in mathematics. Participants were chosen based on their math performance, and peer tutoring was conducted in a one-on-one tutor-tutee format. Two research tools were used: a Learner’s Questionnaire to gather students’ profiles and perceptions of the peer tutoring sessions and a Learners’ Achievement Test to measure their mathematical problem-solving performance. Both descriptive and inferential statistics were employed to analyze the data. Descriptive statistics, including weighted means and Likert scales, were used to summarize the students’ perceptions, while a z-test and paired t-test were used to compare pre-test and post-test scores. The results showed a significant improvement in the students' mathematical problem-solving abilities after the peer tutoring intervention, with a significant increase in their post-test scores. Furthermore, students perceived peer tutoring as highly beneficial in enhancing their understanding and ability to solve math problems. Based on these findings, it is recommended that educators utilize peer tutoring as an instructional strategy to improve students' mathematical problem-solving skills. This approach can also foster greater student participation and interest in learning mathematics.  Article visualizations

Macrocyclic colibactin induces DNA double-strand breaks via copper-mediated oxidative cleavage.

Colibactin is an assumed human gut bacterial genotoxin, whose biosynthesis is linked to the clb genomic island that has a widespread distribution in pathogenic and commensal human enterobacteria. Colibactin-producing gut microbes promote colon tumour formation and enhance the progression of colorectal cancer via cellular senescence and death induced by DNA double-strand breaks (DSBs); however, the chemical basis that contributes to the pathogenesis at the molecular level has not been fully characterized. Here, we report the discovery of colibactin-645, a macrocyclic colibactin metabolite that recapitulates the previously assumed genotoxicity and cytotoxicity. Colibactin-645 shows strong DNA DSB activity in vitro and in human cell cultures via a unique copper-mediated oxidative mechanism. We also delineate a complete biosynthetic model for colibactin-645, which highlights a unique fate of the aminomalonate-building monomer in forming the C-terminal 5-hydroxy-4-oxazolecarboxylic acid moiety through the activities of both the polyketide synthase ClbO and the amidase ClbL. This work thus provides a molecular basis for colibactin's DNA DSB activity and facilitates further mechanistic study of colibactin-related colorectal cancer incidence and prevention

Multiple Charge-Transfer Emissions from Different Metal−Ligand Pairs in Ruthenium Diimines

Ruthenium diimines are unique in their emissivity. Optical excitation with light of less than 500 nm leads to a strong emission in the 600−700 nm range. All emissive ruthenium complexes appear to undergo intersystem crossing from the absorptive singlet metal-to-ligand charge-transfer (MLCT) state to an emissive triplet MLCT state localized on the lowest-energy metal−ligand pair. In contrast to this currently accepted model, in which a single emissive state is populated and then equilibrates among other states based on a particular set of conditions, the excitation-wavelength dependence of the [(bpy)2RudppH]3+ emission suggests two emissive pathways. One populates an emissive MLCT state localized on a bpy−Ru pair, and the other populates a lower-energy MLCT state localized on the dpp−Ru pair

Optical Memory and Multistep Luminescence Thermochromism in Single Crystals of K₂Na[Ag(CN)₂]₃

Single crystals of the layered compound K2Na[Ag(CN)2]3 exhibit a dual emission with high-energy (HE) and low-energy (LE) phosphorescence bands at 313 and 402 nm, respectively. Remarkably, the crystals exhibit “optical memory”, in which a new emission band with intermediate energy (IE) at 380 nm is generated upon laser irradiation (λex = 266 nm) at cryogenic temperatures. The irradiated crystals reinstate their original luminescence spectrum upon heating to room temperature and then recooling. In addition to these unusual “write/read/erase” changes, the crystals also exhibit multistep luminescence thermochromism such that the LE/HE intensity ratio increases between 17 and 80 K but then decreases upon further heating. The unprecedented occurrence of both novel phenomena in one compound has been related to reversible photophysical changes instead of irreversible photochemical changes