National Postdoctoral Association

Epsilon near zero (ENZ) materials have potential in various applications such as all-optical switching and quantum information. Materials that support ENZ modes include metamaterials, semiconductors, and transparent conducting oxides (TCOs) like indium tin oxide (ITO). ITO supports an ENZ mode in the near-infrared (IR), giving rise to large nonlinearities and enabling strong optically induced changes in its refractive index. Recently, a perovskite TCO, La-doped BaSnO3 (LBSO) has demonstrated wide tunability of the ENZ wavelength ranging from the near IR to mid-IR regions. In this work, we use a reflective gold layer to access the Ferrell-Berreman (FB) mode of LBSO, a special class of leaky optical mode that occurs at the material’s ENZ wavelength. The FB mode has strong extinction, making it an ideal candidate for reflection modulation. Here, we interrogate the charge carrier dynamics of multiple Au-coated LBSO samples with varying ENZ wavelengths, paying special attention to the tuning behavior of the FB mode. We find that, upon UV excitation, injected charge carriers are long-lived compared to other transparent conducting oxides and that the photoexcited carriers induce strong modulation of the FB mode. This Au-coated LBSO shows promise for infrared optical switching applications, especially those requiring high thermal stability.

We report 850 °C operation of ultrawide bandgap (UWBG) Al-rich Al<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.68</sub>Ga<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.32</sub>N channel high electron mobility transistors (HEMTs) at atmospheric pressure in nitrogen ambient. Temperature dependent DC electrical characteristics were measured in situ up to 850 °C, after exposure to 850 °C for 60 minutes, and at 25 °C after high temperature testing. At 850 °C (time, t = 0 min), all HEMTs tested maintained an on/off ratio greater than 10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> (maximum of 4.6×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup>). The threshold voltage demonstrated excellent stability with less than ±10% deviation. After returning to 25 °C, the devices showed negligible degradation. In fact, the off-state gate current decreased and on/off ratio slightly increased. The robustness of these UWBG AlGaN transistors at temperatures up to 850 °C demonstrates their viability for extreme environment applications.

This paper presents experimental characterization of shock layer radiative heating relevant to Titan atmospheric entry, with a focus on the CN Red and Violet systems, measured in the Electric Arc Shock Tube (EAST) at NASA Ames Research Center. Tests were conducted in the Low Density Shock Tube (LDST), and included incident shocks from 3.8 to 7.6 km/s and fill pressures of 30 and 90 mTorr in a mixture of 2.2% CH4 in N2 by mole. The measured radiance indicates strong chemical and thermal non-equilibrium, thus requiring accurate chemical kinetics and non-Boltzmann modeling of the state populations. Numerical simulations using DPLR and NEQAIR were employed to reproduce the experimental results. The main kinetic processes are highlighted, and different sets of non Boltzmann rates are evaluated against emission and absorption spectroscopy data. Results reveal limitations in current models, with increasing deviations towards lower velocity and pressure. Selection of faster heavy particle rates improves agreement with the CN Violet emission, while updates to the spectroscopic database show improved agreement over some wavelength range but overpredict CN Red at lower wavelengths. Comparisons with measured spectra, inferred state densities, and complementary TDLAS measurements indicate the need for further model refinement to reconcile these differences.

Review of: Bajatierra Ruiz, Martín (2025). Análisis de la teoría de la representación política. Una propuesta para Castilla-La Mancha. Valencia: Tirant lo Blanch.

Proton exchange membrane fuel cells (PEMFCs) are one of the most promising technologies for addressing the energy crisis. However, the nonuniform distribution of reactant gases and generated water limits actual performance. In this study, a novel composite flow field was designed by combining serpentine and wavy flow fields. Experimental and simulation work were carried out to study the multiphysical field transport mechanism. Over a wide relative humidity range from 20% to 100%, the maximum power density of the cell clamped by the composite flow field reaches 1.01 W cm–2, representing an improvement ratio of 20.9% compared to the traditional flow field. Under both dry and high-humidity conditions, the charge transfer resistance and mass transfer resistance of the composite flow field decreased by more than 40%. This enhancement is attributed to the distribution uniformity of reactant gases and current density, avoiding a local gas deficiency. Additionally, it promotes the uniform dispersion of generated water through a rapid flow under the flow field ribs. This allows limited water to wet the membrane under dry conditions while preventing local water accumulation or flooding under high-current or high-humidity conditions. Therefore, this study provides valuable insights for developing PEMFCs with superior mass transfer efficiency and high-humidity adaptability.

Abstract Legal and human rights scholarship generally interprets the UN Guiding Principles on Business and Human Rights (UNGPs) as requiring business enterprises to provide remedy for human rights abuses through their grievance mechanisms. Empirical evidence that company grievance mechanisms (CGMs) provide remedy for human rights abuses in practice is lacking, and there is limited research on how practitioners understand the UNGPs in relation to company grievance mechanisms. Practitioners have significant agency in interpreting the UNGPs in the practice of company grievance mechanisms, and understanding their perspectives is necessary to understand how human rights norm uptake occurs in corporations. Through a reflexive thematic analysis of data from semi-structured interviews with 29 practitioners, this article produces an empirically grounded account of how the UNGPs are translated into the practice of company grievance mechanisms. Practitioners often view company grievance mechanisms in terms of established operational logics. The concepts of ‘access to remedy’ and ‘human rights’ in the UNGPs are not necessarily interpreted by practitioners as requiring adherence to legal or other substantive prescriptions. The research findings suggest that the schisms in interpretation over whether the UNGPs should be interpreted as substantive and/or procedural prescriptions or serve as a process-centric series of steps which structure an ongoing conversation around the design, implementation, and monitoring of CGMs. In practice, the UNGPs are unlikely to serve as prescriptions that constrain of direct managerial discretion over CGMs. Instead, it may be more beneficial to consider how more participatory approaches can include and empower rightsholders.

San Martín Texmelucan, Puebla, enfrenta una grave crisis de inseguridad y violencia, con serias repercusiones sociales y económicas. En 2020, fue la 24ª ciudad más violenta de México, según el Consejo Ciudadano para la Seguridad Pública, lo que resalta la urgencia de analizar cómo este entorno afecta a los adolescentes, quienes pueden sufrir bajo rendimiento académico, abandono escolar, ansiedad, depresión y agresión. Este artículo examina los efectos psicosociales de la violencia en los estudiantes del CETis No. 17 de San Martín Texmelucan. Aunque la mayoría no reporta un impacto directo en su rendimiento académico, muchos experimentan efectos emocionales, como ansiedad y miedo al desplazarse entre su hogar y la escuela. También enfrentan conflictos interpersonales, baja autoestima y comportamientos de riesgo. Estos hallazgos subrayan la necesidad de programas de apoyo psicológico y mejoras en la seguridad escolar para mitigar los efectos de la violencia en los jóvenes.

As Automated Driving Systems (ADS) advance toward higher levels of automation (SAE Levels 3-5), the role of human drivers is shifting from active control to supervision and intervention. However, traditional human-automation interaction frameworks do not fully account for the dynamic team-based coordination required for effective ADS integration. Poor adaptability and coordination between drivers and ADS can result in critical safety failures, as seen in real-world incidents. This research focuses on human-autonomy teaming (HATs) in ADS, emphasizing collaborative adaptation, shared decision-making, and real-time interaction metrics to enhance safety and user experience. By incorporating team cognition theory and layered dynamical models, this research aims to develop human-machine teaming metrics that facilitate adaptive and context-aware cooperation. Key research questions include: (1) How do human drivers and ADS dynamically interact? (2) What team cognition metrics effectively measure human-ADS adaptability? (3) How can real-time analytics improve driver-ADS collaboration and safety?