University of Mataram

Engagement has been shown to influence students’ understanding and achievement, yet little is known about how engagement with statements relates to students’ understanding of corresponding proofs. In this paper, we take a step towards addressing this gap by investigating whether engaging with statements is associated with better understanding of proofs by contradiction and contraposition. Eighty-seven Indonesian undergraduate mathematics education students, organized in four groups, participated in the study. Two groups (n = 43) were randomly selected to first engage with the statements—reflecting on their meaning, judging their truth, and attempting to prove or disprove them—before responding to an instrument designed to measure their understanding of given proofs for the same statements; the other two groups (n = 44) proceeded directly to the instrument. There were six statements overall, three proved by contradiction and three by contraposition. We found that students who engaged with the statements achieved significantly higher mean scores on measures of proof understanding than those who did not, with a medium effect size. Regression analyses confirmed engagement as a significant predictor of students’ understanding for both proof methods, and individual semi-structured interviews with 12 participants provided qualitative support for these findings. Overall, our findings identify engagement with statements as a meaningful factor in students’ proof understanding and suggests that selectively incorporating an engagement stage before introducing key proofs may enhance undergraduate mathematics instruction beyond the typical Definition-Theorem-Proof (DTP) approach.

Mesophotic coral ecosystems (MCEs), found at depths of 30–150 m, represent a promising refuge for shallow-reef organisms facing increasing anthropogenic pressures. However, the biodiversity connectivity between shallow reefs and MCEs is poorly understood. This study investigates the patterns of fish biodiversity overlap and divergence between shallow (5–10 m) and the upper MCEs (30–40 m) coral ecosystems in Karimunjawa National Park (KNP), Indonesia, using environmental DNA (eDNA) metabarcoding targeting the mitochondrial 12 S rRNA gene. Water samples were collected from both depth zones and analyzed and sequenced using Oxford Nanopore MinION. We identified 6,145 operational taxonomic units (OTUs) in the shallow reef and 5,034 in the upper MCEs ecosystem, with 3,043 or 37.3

Jabon (Neolamarckia cadamba) and sengon (Falcataria moluccana), widely planted in Indonesia's community forests, are fast-growing species used as raw materials in the timber industry. Their low density limits their use in final products. This study aimed to evaluate their quality using eco-friendly surface-charred modification with butane gas torches. Three treatments were applied: (1) charred surface (Ch), (2) charred surface followed by removal of residual charcoal (Ch + B), and (3) un-charred surface (control). Properties were evaluated by measuring charring quality, mechanical properties, dimensional stability, termite resistance, and chemical component alteration. The charring characteristics assessment showed Ch surfaces had higher char thickness and mass loss than Ch + B surfaces for both wood species. The average anti-swelling efficiency of charred wood increased by 21-36% compared to control, indicating improved dimensional stability. The mechanical properties and termite resistance showed no significant changes in charred wood surfaces (Ch and Ch + B) for both species compared to untreated wood. Fourier-Transform Infrared Spectroscopy results demonstrated changes in chemical groups (holocellulose, lignin, carbohydrate) for both species after charring at wavelengths of 800-1800 cm(-)1. These findings suggest surface-charred modification can improve dimensional stability of both wood species. However, further enhancements in mechanical properties and durability are needed.

. Today, the demand for fuel, globally, has increased along with the development of industrial and transportation technology. Meanwhile, petroleum reserves are increasingly depleting. Biodiesel, a monoalkyl ester of long-chain fatty acids, is the best alternative to replace petroleum-derived diesel. One of them is Calophyllum inophyllum L. (local name nyamplung) seed oil. This oil is non-edible, and not a commercial oil, and more than 50% of the seeds contain oil, so it has the potential to be converted into biodiesel. The purpose of this study was to optimize biodiesel synthesis through observation of various parameters that affect the reaction, such as reaction duration, oil and ethanol ratio, enzyme amount, and reaction temperature. Design Expert v.13 was used to observe the interaction between variables. The recommended reaction model is a quadratic model with an R2 value of 0.78, a P-value of 0.0083, and a lack of fit with a P-value of 0.1640. The recommended optimum reaction conditions are a reaction duration of 4.42 h, an oil and ethanol ratio (g/v) of 1: 5.82 (w/v), an amount of enzyme of 3.79 g, and a reaction temperature of 52.46 degrees C. This optimum condition produces predicted and actual yields of 75.03% and 74.96%, respectively.

Mathematics is considered difficult for some students because it tends to be irrelevant to everyday life practices or culture. This study aims to investigate the mathematical structures inherent in the Wariga system and identify its unique characteristics as a form of cultural mathematics to serve as a recommendation for its utilization in mathematics education. The research employed an ethnographic design within an ethnomathematics framework. The primary data collection instruments consisted of field notes, structured interview guides, and documentation studies. The key participants included three groups: a young Wariga educator and maestro, two Bayan officials and traditional leaders, and a community member. Data were analyzed using qualitative techniques, including data reduction, data display, and conclusion drawing and verification. The findings revealed that the Wariga incorporates several mathematical structures and concepts, such as modular arithmetic (modulo 7), a mapping system (naptun), and nested cycles (windon). It combines mathematical, astronomical, and cosmological principles to determine auspicious days for activities like rice planting, weddings, and traditional ceremonies. The study concludes that mathematics has naturally emerged and developed within the Bayan community as a tradition sustained through the Wariga. These findings recommend the integration of Wariga into contextual mathematics learning to foster computational thinking and suggest the development of digital software to simulate its calculations.