Search Results (159)

This review examines the role of differential forms, Pfaffian systems, and hypersurfaces in general relativity. These mathematical constructions provide the essential tools for general relativity, in which the curvature of spacetime—described by the Einstein field equations—is most elegantly formulated using the Cartan calculus of differential forms. Another important subject in this discussion is the notion of conformal geometry, where the relevant invariants of a metric are characterized by Élie Cartan’s normal conformal connection. The previous analysis is then used to develop the null surface formulation (NSF) of general relativity, a radical framework that postulates the structure of light cones rather than the metric itself as the fundamental gravitational variable. Defined by a central Pfaffian system, this formulation allows the entire spacetime geometry to be reconstructed from a single scalar function, Z, whose level surfaces are null. Full article

We report a comprehensive study on the effect of H₂SeO₄ electrolyte temperature on the composition, defect, morphological, and luminescent properties of porous anodic aluminum oxide (AAO). An increase in the synthesis temperature led to a decrease in the AAO cell diameter from 85–115 nm to 38–58 nm (depending on the electrolyte concentration) and enhanced the etching of the AAO walls, which even resulted in the disintegration of the AAO into individual fibers at 40 °C. The selenium concentration in the samples formed in 0.5–1.5 M H₂SeO₄ in the temperature range of 5–40 °C did not exceed 2 at.% and fell below the detection limit at 40 °C. The formation of a nanocrystalline Al₂O₃ phase was observed in the H₂SeO₄ electrolyte at 40 °C. The samples exhibited weak photoluminescence. We identified three types of paramagnetic centers in AAO formed in H₂SeO₄: F⁺ centers (N_sF = 8.2 × 10¹⁵ g⁻¹), newly discovered centers with an unpaired electron localized on an oxygen atom (N_sO = 10¹⁷ g⁻¹), and centers associated with selenate radicals (N_sS = 6 × 10¹⁸ g⁻¹). By comparing the photoluminescence spectra and defect concentrations, we conclude that the luminescence of AAO formed in selenic acid is exclusively due to F⁺ centers, while other paramagnetic centers do not contribute. Full article

This paper focuses on handling traffic demands dynamically in a multi-layer IP-over-elastic optical network (IP-over-EON). We propose a mechanism that uses two types of optical resources. Some resources are visible for the network layer to serve IP traffic. Another part is hidden and reserved for handling congestions solely in the optical layer when resources in the network layer are insufficient. In such a case, the proposed algorithm tries to establish a new lightpath, allocating hidden optical resources. Extensive discrete-event computer simulations were conducted under various network conditions to evaluate the performance of the proposed solution, using two network topologies, the NSF15 and UBN24 networks. The results obtained confirm that the new solution allows for a significant decrease in the bandwidth blocking probability with better utilization of resources compared to the reference scenario (only IP). Full article

Engineering education has faced significant and deep-rooted challenges, including outdated curricula and pedagogical practices, limited access for underrepresented groups, and persistent diversity gaps, that collectively undermine its ability to equip future generations of engineers for a rapidly evolving world. The changes that are needed to reform engineering education are monumental and highlight not only the need for systemic transformation of educational structures but also a fundamental shift in the mindsets of those leading the change. Faculty, professional staff, and administrators must develop knowledge and skills that go beyond their disciplinary training to drive sustainable reform. This article presents a professional development curriculum that has, for over a decade, equipped academic change agents with the tools to implement lasting change. Drawing on experiences from teams supported by the National Science Foundation’s Revolutionizing Engineering Departments (NSF RED) program, the article highlights proven strategies that academic change agents can master and situates them within the broader literature on change in higher education. Specifically, we focus on how academic change agents can develop capacity for systems thinking, build their ability to communicate effectively with various community members, leverage strategic partnerships to increase impact, and cultivate a supportive community of practice with other change agents. Full article

This study explores how patients and stakeholders envision integrated digital health systems. Background/Objectives: Integrating artificial intelligence (AI), wearable data, electronic health records (EHRs), and patient-reported outcomes could enable proactive and personalized healthcare. However, current solutions remain fragmented and poorly aligned with user expectations. This study aimed to explore patient and stakeholder needs for AI-driven integration and propose a conceptual framework to inform future system design. Methods: As part of the NSF Innovation Corps (I-Corps) program, we conducted semi-structured interviews with 44 participants representing Health Enthusiasts, Chronic Condition Managers, and Low-Engagement Users. Interviews followed the I-Corps customer discovery framework and were thematically analyzed using a hybrid deductive–inductive approach. Results: Participants highlighted four priorities: (i) interoperability and unification of data from wearables, EHRs, and self-reports; (ii) actionable personalization with predictive insights; (iii) trust and transparency in AI recommendations, often requiring clinician oversight; and (iv) usability through low-friction, intuitive interfaces. Age- and persona-specific differences emerged: younger participants favoring predictive features and older participants emphasizing safety, reassurance, and clinical integration. Conclusions: This exploratory qualitative study identified stakeholder needs that informed a conceptual framework for integrated digital health platforms. While preliminary, the framework provides a blueprint for future technical development and validation of patient- and provider-centered systems. Full article

This study investigates how a rural Hispanic-Serving Institution (HSI) in New Mexico created and maintained a humanizing STEM educational environment amidst repeated and overlapping natural disasters between 2020 and 2024. Specifically, we explore the impacts of the COVID-19 pandemic, severe wildfires, water contamination, and a chemical leak on a STEM initiative known as SomosSTEM (“We are STEM”), a five-year, NSF-funded program at New Mexico Highlands University (NMHU). SomosSTEM integrates culturally responsive, research-intensive educational experiences throughout the critical first two years of undergraduate life science programs. Through qualitative analysis of institutional practices and student experiences, we found that SomosSTEM exemplifies a humanizing educational approach defined by authentic care, commitment, and intentional relationship-building by faculty, staff, and administrators. Importantly, our findings underscore that humanizing education must be inherently place-based and attend to the inherent interconnectedness of educational environments with their physical and ecological contexts. This understanding promotes a more expansive and placed-based understanding of humanizing education and highlights the disproportionate effects of environmental crises on rural, resource-limited institutions serving marginalized communities. We emphasize the critical need for integrating environmental justice, STEM equity, and sustainability in higher education. Full article

Densely integrated microarchitectures spanning three-dimensional integrated circuits (3D-ICs), chiplet-based designs, and system-in-package (SiP) assemblies make heat a first-order security concern rather than a mere reliability issue. This review consolidates the landscape of thermal side-channel attacks (TSCAs) on densely integrated microarchitectures: we systematize observation vectors and threat models, clarify core concepts and assumptions, compare the most credible evidence from the past decade, and distill the main classes of defenses across the hardware–software stack. We also explain why hardening against thermal leakage is integral to cyber–physical system (CPS) security and outline the most promising research directions for the field. The strategic relevance of this agenda is reflected in current policy and funding momentum, including initiatives by the United States Department of Homeland Security and the Cybersecurity and Infrastructure Security Agency (DHS/CISA) on operational technology (OT) security, programs by the National Science Foundation (NSF) on CPS, and Canada’s Regional Artificial Intelligence Initiative and Cyber-Physical Resilience Program (RAII, >CAD 35 million), to bridge advanced microelectronics with next-generation cybersecurity. This survey offers a clear, high-level map of the problem space and a focused baseline for future work. Full article

In the face of climate challenges and growing social inequalities, ESG (Environmental, Social, Governance) has become a key framework for sustainable development. Within the EU, forestry—covering about one third of Europe—is increasingly addressed through ESG principles in the 2030 New EU Forest Strategy (NSF 2030). This study aims to systematize the diversity and similarities of EU Member States’ forest policies using ESG indicators aligned with NFS 2030 objectives. We do not assess policy outcomes but rather identify clusters of countries with similar forest-economy profiles to fill a research gap and support more coherent strategies. Using hierarchical clustering on selected ESG indicators, we find very high variability in EU forest policies. The results confirm that NFS 2030 can serve as an analytical tool to identify clusters of countries with similar ESG profiles and tailor policies to their contexts. The identification of eight clusters per ESG segment underscores the need for a differentiated, flexible approach to achieving common EU forest objectives. Despite similarities within clusters, diverse economic, environmental, and social conditions often require differentiated policies tailored to each country’s unique context. Full article

Large-diameter rock-socketed monopiles supporting offshore wind turbines in soft clay strata face significant geotechnical risks from negative skin friction (NFS) induced by construction surcharges. While the effects of NFS on axial drag loads are documented, the critical interaction between horizontal pile loading and NFS development remains poorly understood. This research bridges this gap using a rigorously validated 3D finite element model that simulates the complex coupling of vertical substructure loads (5 MN), horizontal loading, and surcharge-induced consolidation. The model’s accuracy was confirmed through comprehensive verification against field data for both NFS evolution under surcharge and horizontal load–displacement behavior. The initial analysis under representative conditions (10 MN horizontal load, 100 kPa surcharge, 3600 days consolidation) revealed that horizontal loading fundamentally distorts NFS distribution in the upper pile segment (0 to −24 m), transforming smooth profiles into distinct dual-peak morphologies while increasing the maximum NFS magnitude by 57% (from −45.4 kPa to −71.5 kPa) and relocating its position 21 m upward. This redistribution was mechanistically linked to horizontal soil displacement patterns. Crucially, the NFS neutral plane remained invariant at the clay–rock interface (−39 m), demonstrating complete independence from horizontal loading effects. A systematic parametric study evaluated key operational factors: (1) consolidation time progressively increased NFS magnitude throughout the clay layer, evolving from near-linear to dual-peaked distributions in the upper clay (0 to −18 m); NFS stabilized in the upper clay after 720 days while continuing to increase in the lower clay (−18 to −39 m) due to downward surcharge transfer, accompanied by neutral plane deepening (from −36.5 m to −39.5 m) and 84% maximum axial force escalation (12.5 MN to 23 MN); (2) horizontal load magnitude amplified upper clay NFS peaks at −3.2 m and −9.3 m, with the shallow peak magnitude increasing linearly with load intensity, though it neither altered lower clay NFS nor neutral plane position; (3) surcharge magnitude increased overall NFS, but upper clay NFS (0 to −18 m) stabilized beyond 100 kPa, while lower clay NFS continued rising with higher surcharges, and the neutral plane descended progressively (from −38 m to −39.5 m). These findings demonstrate that horizontal loading critically exacerbates peak NFS values and redistributes friction in upper pile segments without influencing the neutral plane, whereas surcharge magnitude and consolidation time govern neutral plane depth, total NFS magnitude, and maximum drag load. This research delivers essential theoretical insights and practical guidelines for predicting NFS-induced drag loads and ensuring the long-term safety of offshore wind foundations in soft clays under complex multi-directional loading scenarios. Full article

Titanium–aluminum–vanadium (Ti6Al4V) is a material chosen for spine, orthopedic, and dental implants due to its combination of desirable mechanical and biological properties. Lasers have been used to modify metal surfaces, enabling the generation of a surface on Ti6Al4V with distinct micro- and nano-scale structures. Studies indicate that topography with micro/nano features of osteoclast resorption pits causes bone marrow stromal cells (MSCs) and osteoprogenitor cells to favor differentiation into an osteoblastic phenotype. This study examined whether the biological response of human MSCs to Ti6Al4V surfaces is sensitive to laser treatment-controlled micro/nano-topography. First, 15 mm diameter Ti6Al4V discs (Spine Wave Inc., Shelton, CT, USA) were either machined (M) or additively manufactured (AM). Surface treatments included no laser treatment (NT), nanosecond laser (Ns), femtosecond laser (Fs), or nanosecond followed by femtosecond laser (Ns+Fs). Surface wettability, roughness, and surface chemistry were determined using sessile drop contact angle, laser confocal microscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Human MSCs were cultured in growth media on tissue culture polystyrene (TCPS) or test surfaces. On day 7, the levels of osteocalcin (OCN), osteopontin (OPN), osteoprotegerin (OPG), and vascular endothelial growth factor 165 (VEGF) in the conditioned media were measured. M NT, Fs, and Ns+Fs surfaces were hydrophilic; Ns was hydrophobic. AM NT and Fs surfaces were hydrophilic; AM Ns and Ns+Fs were hydrophobic. Roughness (Sa and Sz) increased after Ns and Ns+Fs treatment for both M and AM disks. All surfaces primarily consisted of oxygen, titanium, and carbon; Fs had increased levels of aluminum for both M and AM. SEM images showed that M NT discs had a smooth surface, whereas AM surfaces appeared rough at a higher magnification. Fs surfaces had a similar morphology to their respective NT disc at low magnification, but higher magnification revealed nano-scale bumps not seen on NT surfaces. AM Fs surfaces also had regular interval ridges that were not seen on non-femto laser-ablated surfaces. Surface roughness was increased on M and AM Ns and Ns+Fs disks compared to NT and Fs disks. OCN was enhanced, and DNA was reduced on Ns and Ns+Fs, with no difference between them. OPN, OPG, and VEGF levels for laser-treated M surfaces were unchanged compared to NT, apart from an increase in OPG on Fs. MSCs grown on AM Ns and Ns+Fs surfaces had increased levels of OCN per DNA. These results indicate that MSCs cultured on AM Ns and AM Ns+Fs surfaces, which exhibited unique roughness at the microscale and nanoscale, had enhanced differentiation to an osteoblastic phenotype. The laser treatments of the surface mediated this enhancement of MSC differentiation and warrant further clinical investigation. Full article

Background: Early caries management is essential to enable reversal of white spot lesions without the further need for operative interventions, especially in primary dentition. Silver-based compounds can be quite effective in arresting caries lesions; however, a major drawback is teeth staining. This study aimed to evaluate the remineralization potential and aesthetic effects of novel, green-synthesized nano-silver fluoride (NSF) on artificial white spot lesions in primary teeth in comparison to 38% silver diamine fluoride (SDF) and silver diamine fluoride/potassium iodide (SDF/KI). Materials and Methods: NSF was synthesized using green tea extract. Sixty primary teeth specimens with artificial enamel lesions were randomly divided into five groups depending on the applied material: 38% SDF, 38% SDF/KI, single and double application of NSF, and control group. Treatments were followed by pH cycling. Surface microhardness and photographic analysis were conducted to assess remineralization and staining. Statistical analysis was conducted using non-parametric tests including Kruskal–Wallis and Mann–Whitney U tests with Bonferroni correction. Results: The greatest increase in microhardness was observed in the group receiving double NSF application. Its remineralizing potential was comparable to that of 38% SDF/KI, with no statistically significant difference (p = 1.000). Importantly, NSF-treated samples exhibited no teeth discoloration, unlike the black staining observed in SDF and SDF/KI groups. Conclusions: Green-synthesized NSF is a promising alternative to conventional SDF and SDF/KI, offering remineralization benefits without compromising aesthetics. The eco-friendly formulation and non-staining properties support its potential for clinical use in pediatric dentistry. Full article

This study investigates the influence of die design parameters on forging forces and thermomechanical responses during near-solidus forging (NSF) of complex steel components. Finite element simulations using Forge NxT analyzed six die configurations varying geometry orientation, gating system design (conical, cylindrical, curvilinear), and draft angles (20° and 30°), with 42CrMo4E steel modeled at 1360 °C. Key responses including punch and lateral forces, temperature distribution, strain localization, and die stress were evaluated to assess design effects. Results showed that the gating system geometry critically controls material flow and load requirements. The conical gating design with a 30° draft angle yielded the lowest punch (141.54 t) and lateral (149.44 t) forces, alongside uniform temperature and strain distributions, which improve product quality by minimizing defects and incomplete filling. Lower lateral forces also reduce die opening risk, enhancing die life. In contrast, the base case with a 20° draft angle exhibited higher forces and uneven strain, increasing die stress and compromising part quality. These findings highlight the importance of selecting appropriate gating systems and draft angles to reduce forming loads, increase die life, and improve uniform material flow, contributing to better understanding of die design in NSF of complex steel components. Full article

Woody plant encroachment (WPE) is transforming grasslands globally, yet accurately mapping this process remains challenging. State-funded, publicly available high-resolution aerial imagery offers a potential solution, including the USDA’s National Agriculture Imagery Program (NAIP) and NSF’s National Ecological Observatory Network (NEON) Aerial Observation Platform (AOP). We evaluated the accuracy of land cover classification using NAIP, NEON, and both sources combined. We compared two machine learning models—support vector machines and random forests—implemented in R using large training and evaluation data sets. Our study site, Konza Prairie Biological Station, is a long-term experiment in which variable fire and grazing have created mosaics of herbaceous plants, shrubs, deciduous trees, and evergreen trees (Juniperus virginiana). All models achieved high overall accuracy (>90%), with NEON slightly outperforming NAIP. NAIP underperformed in detecting evergreen trees (52–78% vs. 83–86% accuracy with NEON). NEON models relied on LiDAR-based canopy height data, whereas NAIP relied on multispectral bands. Combining data from both platforms yielded the best results, with 97.7% overall accuracy. Vegetation indices contributed little to model accuracy, including NDVI (normalized digital vegetation index) and EVI (enhanced vegetation index). Both machine learning methods achieved similar accuracy. Our results demonstrate that free, high-resolution imagery and open-source tools can enable accurate, high-resolution, landscape-scale WPE monitoring. Broader adoption of such approaches could substantially improve the monitoring and management of grassland biodiversity, ecosystem function, ecosystem services, and environmental resilience. Full article

In response to systemic inequities in mathematics education, we developed and evaluated a five-year, multi-phase curriculum model to cultivate effective secondary mathematics teacher leaders. Supported by NSF Noyce Master Teacher Fellowships, the APLUS in MATH (APLUS in Math: Alabama Practitioner Leaders for Underserved Schools in Mathematics) program engaged 22 inservice teachers through graduate coursework, National Board Certification preparation, and leadership project development. Using a mixed-methods design, we analyzed data from classroom observations (MCOP²), National Board Certification assessments, course performance ratings, and teacher leadership project proposals. Results indicate significant improvements in instructional practices, content knowledge, and leadership readiness. Findings underscore the importance for sustained, structured professional development to prepare teachers as instructional experts and change agents in high-need educational contexts. Full article

With rising urgency around carbon emissions and climate change, electrification has emerged as a central focus in traditionally combustion-reliant industries. With increasing regulatory restrictions on automotive and smaller off-highway markets (<25 hp), the heavy equipment industry faces growing pressures to adopt hybrid and fully electric solutions. Current literature primarily addresses technical electrification challenges, leaving a gap in understanding industry perspectives. This study explores trends, challenges, and expectations of electrification from industry representatives’ viewpoints, using data from 84 surveys conducted at the CONEXPO/CONAGG trade show and sentiment analysis of 100 interview notes gathered through an NSF Innovation Corps workshop. Results indicate substantial uncertainty toward electrification, with key limitations including power-to-weight ratios, high costs, maintenance, leakage concerns, and reliability of electronic components. The majority (77%) preferred traditional hydraulic systems due to familiarity and reliability, though concerns over maintenance and environmental impact remain prevalent. Participants anticipate a gradual industry transition, projecting widespread adoption of hybrid solutions in 10–15 years and longer timelines for fully electric systems. Effective adoption of greener technologies is likely through industry-wide standards and financial incentives. This study emphasizes the industry’s cautious yet gradually increasing openness to electrification amidst persistent technological and economic challenges. Full article