We examine slow magnetoacoustic disturbances in a local, isothermal, gravitationally stratified two-fluid model. The charged and neutral components have separate kinematic viscosities and are coupled by ion–neutral friction. Using a consistent thin-flux-tube equilibrium, we derive the linear velocity equations and retain the complete transformed viscous operator. The ion-like branch has the usual stratification cutoff. For the self-consistent reference state, the cutoff is 2.24 mHz. To first order in the locally constant ion viscosity, the imaginary frequency correction changes sign at k=1/(4Hi), where k is the longitudinal wavenumber and Hi is the charged fluid density scale height. This behavior is a property of the transformed local amplitude and is not interpreted as viscous energy production. The homogeneous neutral equation admits a finite underdamped interval only if a quadratic discriminant condition is satisfied. In the fixed-temperature hydrogen collision model, this condition reduces approximately to νnνni/cSn2<1. Here νn is the neutral kinematic viscosity (in m2s−1), νni is the neutral-ion collision frequency (in s−1), and cSn is the neutral sound speed, so the ratio is dimensionless. The corresponding spatial scale interval does not satisfy the thin-tube and neutral continuum orderings for resolved chromospheric structures. It is therefore reported as a formal property of the reduced model rather than as a solar prediction. The calculation isolates the dissipation channels but does not model non-local thermodynamic equilibrium (non-LTE) radiative transfer or propagation through a height-dependent chromosphere.
Galaxy rotation curves alone do not provide a decisive test between dark matter and phenomenological alternatives. We examine four isolated SPARC galaxies for which resolved rotation curves and weak-lensing constraints provide a useful test of the κ-model. In this phenomenological construction, a galaxy is described in a mechanical base governed by standard Newtonian gravity in the present weak-field calculation, while reconstructed large-scale spatial quantities are related to the base by a density-dependent mapping to an observer bundle. The same density–κ relation is applied to all four galaxies. It reproduces the measured rotation curves with residuals comparable to those obtained with the MOND formulation used here and predicts a semi-Keplerian decline beyond the measured baryonic disc. A separate application of the same mapping to projected densities yields an outer weak-lensing trend. As an extended-baseline consistency test, the model is also applied to M31 without fitting an additional outer-halo parameter to the outer kinematic points. Because the main sample contains only four objects and the outer-halo and lensing constructions involve explicit phenomenological assumptions, the results constitute a proof of concept rather than evidence for a complete alternative to dark matter or modified gravity. The predicted outer decline and projected-density relation are falsifiable with larger samples combining resolved outer kinematics and galaxy–galaxy weak lensing.
Students' cognitive achievement and learning motivation are essential factors influencing success in science education. However, conventional teacher-centered instruction often provides limited opportunities for active participation, resulting in low cognitive learning outcomes and learning motivation. The Teams Games Tournament (TGT) cooperative learning model is designed to promote active engagement, collaboration, and healthy competition among students. This study aimed to examine the effect of the TGT cooperative learning model on eighth-grade students' cognitive learning outcomes and science learning motivation. A quasi experimental research design employing a posttest-only control group design was used. Participants were selected through purposive sampling, with one class assigned as the experimental group receiving instruction through the TGT cooperative learning model and another class serving as the control group receiving conventional instruction. Data were collected using a cognitive achievement test and a science learning motivation questionnaire. The data were analyzed using an independent-samples t-test for cognitive learning outcomes and descriptive statistics for learning motivation. The results showed that the experimental group obtained a higher mean cognitive score (60.0) than the control group (51.2). Furthermore, the independent-samples t-test indicated a statistically significant difference between the two groups (p < 0.05). The results also demonstrated an increase in students' science learning motivation following the implementation of the TGT cooperative learning model. These findings indicate that the TGT cooperative learning model has a significant positive effect on students' cognitive learning outcomes and science learning motivation.
Scientific literacy is recognized as one of the essential competencies required for students to address the challenges of the twenty-first century, including rapid scientific and technological development and increasingly complex global issues. However, the 2018 Programme for International Student Assessment (PISA) reported that Indonesian students' scientific literacy remains below the international average. This study aimed to describe the scientific literacy levels of eighth-grade junior high school students. A quantitative descriptive research design was employed involving 222 eighth-grade students from a public junior high school during the 2022/2023 academic year. Data were collected using a scientific literacy test consisting of multiple-choice, complex multiple-choice, matching, and true–false items. The test assessed three scientific literacy competencies: explaining scientific phenomena, evaluating and designing scientific investigations, and interpreting scientific data and evidence, within the topic of Substances Pressure and Its Applications in Everyday Life. The data were analyzed using descriptive statistics. The results indicated that students achieved an average score of 41.48% for explaining scientific phenomena (moderate category), 66.32% for evaluating and designing scientific investigations (good category), and 50.00% for interpreting scientific data and evidence (moderate category). Overall, the findings suggest that the scientific literacy of eighth-grade students remains at a moderate level, indicating the need for instructional strategies that further promote scientific reasoning and inquiry-based learning.
Student-centered learning has become a fundamental approach in twenty-first-century education to equip learners with the competencies required to address the rapid advancement of science and technology. Among the various student-centered instructional approaches, Problem-Based Learning (PBL) has been widely recognized for promoting active engagement and meaningful learning. This study aimed to describe the implementation of the Problem-Based Learning model in eighth-grade science classrooms and to examine students' responsses to its implementation. A descriptive research design was employed involving 28 eighth-grade students and three classroom observers. Data were collected using validated observation sheets to assess the implementation of the PBL model by teachers and students, as well as a student responsse questionnaire. All research instruments were validated by three experts prior to data collection. The data were analyzed descriptively using percentage analysis. The findings revealed that the implementation of the Problem-Based Learning model reached 98%, indicating that the learning process was carried out with a very high level of implementation fidelity. In addition, students expressed positive responses toward the PBL model, suggesting that it effectively supported active participation and meaningful learning during science instruction. These findings demonstrate that Problem-Based Learning is a feasible and well-accepted instructional approach for promoting student-centered science learning at the junior high school level.
