In this work, the effects of seawater exposure and specimen geometry on the mechanical performance of 3D-printed Acrylonitrile Butadiene Styrene (ABS) and carbon fiber-reinforced ABS (ABS/CF) were investigated. Enclosed 3D printers were used to avoid shrinkage and warping of ABS and ABS/CF. The standard specimen types in this research work were ASTM D638 type IV, ISO 527-2 type 1BA, and ASTM D3039 full-section specimens. The tensile tests were strain-controlled tests with a strain rate of 0.1 min− 1. Firstly, the effects of the different specimen types on the tensile strength and Young’s modulus of unaged (as-printed) ABS and ABS/CF were analyzed. Secondly, the three types of specimens were immersed in seawater for 1, 2, and 3 weeks to evaluate moisture absorption and the degradation of the mechanical properties. The results indicated that the test specimen type had a statistically significant effect on the mechanical properties of ABS and ABS/CF, with the ISO 527 specimen exhibiting the lowest tensile strength and Young’s modulus. Moreover, all ABS and ABS/CF specimens showed moisture uptake of less than 1
This study examines, through a feminist empowerment lens, the trajectories that lead Peruvian adolescent mothers into institutional care following pregnancies resulting from sexual violence, and their lived experiences within these settings. Using a qualitative case study design, the research was conducted in a state-accredited protection institution in Lima. Nine adolescent mothers aged 13 to 17 participated in structured observations and group interviews conducted together with in-depth interviews with one adolescent and two institutional authorities. The findings identified three key moments across a continuum of violence and care: sexual violence within the family, disclosure and engagement with legal and health systems, and life inside the institution. Across these phases, participants encountered multiple forms of revictimization, including within institutions meant to provide care. At the same time, the study documents expressions of resistance and agency, including disclosure, peer solidarity, and collective care. These practices illustrate forms of "power from within" and "power with" that emerge under conditions of profound constraint. Rather than positioning institutionalization as protective by default, the analysis shows how care is often delivered through paternalistic and controlling logics that limit autonomy. The study contributes to feminist psychology by conceptualizing empowerment as relational, situated, and negotiated within institutional contexts.
We extend the Standard Model (SM) by introducing a U(1)' gauge boson and a real pseudo-scalar field, both odd under a & Zopf;2 symmetry. The resulting low-energy spectrum consists of a stable vector as the dark matter candidate, and a pseudo-scalar mediator, which interacts with the SM via a Higgs portal coupling and a dimension-five portal connecting it to both the dark and visible photons. We explore the freeze-in of both particles at low reheating temperature, finding a rich yield evolution dynamics in the early Universe. This setup brings a consistent dark matter scenario in which the dark photon relic abundance is generated through freeze-in at low reheating temperatures. In addition to its cosmological viability, the model can be tested at the LHC: Higgs bosons can decay into dark photons and displaced visible photons via the long-lived mediator. These signatures allow us to constrain the Higgs portal coupling using recent searches for non-pointing photons and limits on invisible or undetected Higgs decays. We derive meaningful constraints on the dark matter parameter space, in particular excluding a thermalized mediator in the region compatible with the observed relic abundance.
A guided, stepwise thermodynamic analysis of the ammonia synthesis reaction is presented in the form of a multipart student problem with an accompanying guided computational solution. The activity is designed to strengthen student understanding of chemical potentials (µ), Gibbs (G), and Helmholtz (A) free energies, and their quantitative connection to chemical equilibrium under different thermodynamic constraints. The problem is organized into pedagogically sequenced tasks involving the calculation and interpretation of µ, G, and A as functions of the reaction extent, together with the determination of the equilibrium position (reaction extent) and the equilibrium constant, under conditions of constant temperature–pressure and constant temperature–volume. The influence of pressure and temperature on free energy profiles and equilibrium position is examined quantitatively. A computer-assisted approach is employed to allow students to focus on conceptual understanding rather than extensive numerical calculations or algebraic manipulation. A Wolfram Mathematica notebook is provided to facilitate calculations and visualization of results, supporting the integration of thermodynamic concepts within a unified problem-solving framework applied to a reaction of industrial relevance.
This paper introduces PlatROB, an open-source, modular, and low-cost educational robotics platform designed to facilitate hands-on learning in robotics and AI through system integration. PlatROB comprises four 3D-printable, classroom-ready modules: an Ackermann Drive Module (ADM), an Omnidirectional/Differential Drive Module (ODM/DDM), a Control and Processing Module (CPM) with NVIDIA Jetson Nano, and a 4-DoF Articulated Manipulation Module (AMM). Inter-module communication uses standardized I2C over DB9 connectors, integrating Arduino microcontrollers, motor drivers, encoders, IMUs, and ultrasonic sensors. Module costs range from $129 to $341. Performance validation shows the ADM supports 10 kg payload, achieves 25 cm turning radius and has 120 min autonomy (3 kg load), while the CPM sustains 40-100 min operation depending on neural-network workloads. The AMM provides 450 g payload capacity for introductory manipulation tasks. Successfully deployed in workshops and university courses with over 160 learners, demonstrating significant learning gains (p < 0.05) across academic levels and enabling teleoperation and autonomous navigation projects. All mechanical and electronic design files, build manuals, and validation code are open-source to support replication in resource-constrained settings. By providing a scalable, documented hardware-software stack compatible with ROS/ROS2, PlatROB lowers barriers to experiential learning in SLAM, perception, and advanced autonomy.
