Low Density Research Articles

Ultra flexible silica aerogel with excellent mechanical properties for durable oil-water separation

Flexible Silica aerogel has a broad application prospect in the field of oil-water separation due to its low density and high porosity. However, its poor mechanical properties limit its application and it is a challenge to improve its mechanical properties while maintaining its excellent oil absorption capacity. In this work, we add silica sol to the silica source system formed by vinyltrimethoxysilane (VTMS) and vinylmethyl dimethoxysilane (VMDMS) to prepare silica sol-reinforced flexible silica aerogels by ambient pressure drying. The introduction of silica sol provides more -OH groups that can be used as condensation sites. The hydrolysis products of VTMS and VMDMS undergo dehydration condensation reaction with these exposed -OH groups and co-polymerize, resulting in a more robust three-dimensional porous structure. Silica sol- reinforced vinyl flexible silica aerogel is prepared with excellent mechanical properties. Its maximum strain can reach 80% in 10 compression-decompression cycles without destroying its structure. Its hydrophobic angle was 145.7 °. Most particularly, compared to conventional flexible aerogel,when the silica sol-reinforced vinyl flexible silica aerogel is used in oil-water separation applications, it does not need to be dried after absorbing oil but only mechanically squeezed to expel the absorbed organic solvent. It can be reused hundreds of times, which greatly improves the efficiency of oil-water separation.

Impacto incremental de la dispersión poblacional sobre los recursos de personal sanitario en Atención Primaria

ObjectiveTo quantify the incremental impact that population dispersion has on the number of health personnel in Primary Care in Alto Aragón, using a reproducible method. MethodDescriptive observational study that compares health the number of health personnel (family medicine, pediatrics and nursing) in EAP and PA emergencies in 2019 in an unpopulated and dispersed territory such as Huesca, with the number that would correspond to it by applying population ratios per professional of hypothetical constructs with different population densities. ResultsHuesca, with respect to the national average, has 39% more PA health personnel. There are 239 additional professionals (112 in family medicine, 2 in pediatrics and 115 in nursing), 130 in emergencies and 109 in EAP.With the average of the five most densely populated provinces, it would reduce this staff by 49%, and with the average of the five least densely populated provinces, it would increase it by 12%. ConclusionsThere is a relationship between low population density and a greater number of family medicine and PC nurses, but not with pediatrics.The powerful incremental effect that dispersion has on health care spending gives it a relevant role in the regional financing system.Comparing PC health personnel in scenarios with different population density is a useful method for quantifying the impact of dispersion.

The effect of wind turbines with low rotor power density on power fluctuations

Increasing penetration of variable renewable energy, particularly wind power, necessitates improved grid integration strategies. One option that has received little attention to date is to adapt the design of the turbines in the direction of lower rotor power density. By simulating various turbine models with different specifications at selected locations, the effects on several performance indicators are investigated. Since no single suitable performance indicator exists, a comparison of widely used indicators is made, whereby the introduction of new parameters proves to be useful. Results show that lowering rotor power density through reduced generator output significantly mitigates power fluctuations in the 10-minute range. Considering an entire wind farm instead of an individual turbine, total annual production is slightly decreased, while the required connected load to the grid is substantially reduced.

Non-Invasive Blood-Brain Barrier Disruption Using Acoustic Holography With a Clinical Focused Ultrasound System.

Holographic methods can be used with phased array transducers to shape an ultrasound field. We tested a simple method to create holograms with a hemispherical 1024-element phased array transducer and explored how it could benefit ultrasound-mediated blood-brain barrier (BBB) disruption. With this method, individual acoustic simulations for each element of the transducer were simultaneously loaded into computer memory. Each element's phase was systematically modulated until the combined field matched a desired pattern. The method was evaluated with a 220 kHz transducer being tested clinically to enhance drug delivery via BBB disruption. The holograms were evaluated in a tissue-mimicking phantom and in vivo in experiments disrupting the BBB in rats and in a macaque. We also explored whether this approach could mitigate secondary reflections from the skull using simulations of transcranial focusing in clinical treatments of transcranial sonication for BBB disruption. This approach can enlarge the focal volume in a patient-specific manner and could reduce the number of sonication targets needed to disrupt large volumes, improve the homogeneity of the disruption, and improve our ability to detect microbubble activity in tissues with low vascular density. Simulations suggest that the method could also mitigate secondary reflections during transcranial sonication.

Direct Electron Transfer Mediated Electrochemical Activation of Persulfates by Reticulated Vitreous Carbon Cathode

The electrochemical activation of peroxymonosulfate (PMS) and peroxydisulfate (PDS) for pollutant degradation has gained increasing attention. In this work, reticulated vitreous carbon (RVC) electrodes were prepared at a low cost and investigated for the cathodic activation of PMS/PDS for Acid Orange 7 degradation. The RVC was characterized by SEM, TGA, XRD, Raman spectroscopy, XPS, EIS, and compression test. The superior activity outperformed previous reports in terms of low current density operation (1–10mA/cm2), high degradation rates (0.13–0.49min−1), low energy consumption (0.03–0.23 kWh/m3/order) without involvement of catalysts. The process was optimized for current density, PMS dosage, pollutant concentration, pH, water matrix, and supporting electrolyte. Under the optimal current density (3mA/cm2), the addition of 0.5mM of PMS boosted the degradation rate by 9.6 times to 0.4470min−1 and reduced the electrical energy consumption by 90.1% to 0.0243 kWh/m3/order in 50mM of Na2SO4. Moreover, up to 117mg/L of H2O2 was produced in 1hour by the reduction of oxygen, with current efficiencies between 78–24%. The process showed little deterioration in 10 cycles, worked for a variety of pollutants, and was not affected by the water matrix. The H-cell experiments confirmed that 90% degradation took place on the cathode. Scavenging experiments and electrochemical tests suggested that the transitional state of PMS⁎ and O2•− mediated the direct electron transfer mechanism for AO7 degradation. Eighteen degradation products were identified by HPLC-MS and categorized into 4 degradation pathways. Finally, their toxicity was assessed by the ECOSAR programme.

Microstructural evolution and corrosion behavior of non-isothermally heat treated hypoeutectic Al-Si-Cu alloy

In the present work the effect of non-isothermal heat treatments on the microstructure and corrosion resistance of a hypoeutectic Al-Si-Cu die-cast alloy was studied. The microstructural aspects were examined by confocal laser scanning microscopy and scanning electron microscopy. The corrosion behavior was studied by potentiodynamic polarization tests. In the as-cast condition, the microstructure consisted of needle-like Si particles and Fe-rich intermetallics, besides the Al matrix. The non-isothermal treatments promoted spheroidization of Si particles, decreasing its volume fraction. The corrosion resistance was affected by concentration of the Si particles. The corrosion mechanism is discussed based on the microstructural evolution of the Al-Si-Cu alloy. The main influencing factor was the volume fraction of Si particles. The non-isothermally treated samples exhibited lower corrosion current density than the as-cast alloy, showing superior corrosion resistance.

Egyptian patients with axial spondyloarthritis: The frequency and predictors of renal impairment

Aim of the workTo determine the frequency of and risk factors for renal impairment in patients with axial spondyloarthritis (axSpA). Patients and methodsFifty axSpA patients participated in this study. In accordance with the Kidney Disease Outcomes Quality Initiative (K/DOQI) criteria, patients were split into two groups: group 1comprised renal impairment and group 2 comprised non-renal impairment. The ankylosing spondylitis (AS) disease activity score (ASDAS), Bath AS disease activity index (BASDAI) and estimated glomerular filtration rate were assessed. ResultsThe mean age of patients was 38.9 ± 11.7 years, males were 54 % and the disease duration was 11.36 ± 6.1 years. The mean ASDAS score was 5.58 ± 1.38 and BASDAI was 5.18 ± 1.55. The eGFR was 76.4 ± 36.2 ml/min/1.73 m2 and 28 % had positive human leucocytic antigen (HLA-B27). 80 % were receiving biologic therapy. Nephropathy by ultrasound and renal impairment were detected in 34 % and 52 % of the cases respectively. The cumulative dose of non-steroidal anti-inflammatory drugs (NSAIDs), C-reactive protein, erythrocyte sedimentation rate, low density cholesterol, blood urea nitrogen, creatinine, proteinuria, ASDAS and BASDAI were significantly higher in those with renal impairment(p = 0.0001, p = 0.0001, p = 0.001, p = 0.035, p = 0.0001, p = 0.0001, p = 0.0001, p = 0.001, p = 0.001 respectively) while the eGFR and high density lipoprotein were significantly lower (p = 0.001and p = 0.02). Only the cumulative dose of NSAIDs was a significantly independent variable influencing the development of renal impairment (OR=1.01, CI; 1.001–1.02, p = 0.024) at cut-off level > 1166.3 g. ConclusionsRenal impairment is frequent in axSpA patients with decreased eGFR and high disease activity. The cumulative dose of NSAIDs is a significant predictor of renal impairment.

Understanding the changes induced by the incorporation of trees in low densities into livestock systems: relevance of a long-term interdisciplinary experimental platform

Understanding the changes induced by the incorporation of trees in low densities into livestock systems: relevance of a long-term interdisciplinary experimental platform

Exceptional hardness in multiprincipal element alloys via hierarchical oxygen heterogeneities

Refractory multiprincipal element alloys (RMPEAs) are potential successors to incumbent high-temperature structural alloys, although efforts to improve oxidation resistance with large additions of passivating elements have led to embrittlement. RMPEAs containing group IV and V elements have a balance of properties including moderate ductility, low density, and the necessary formability. We find that oxidation of group IV-V RMPEAs induces hierarchical heterogeneities, ranging from nanoscale interstitial complexes to tertiary phases. This microstructural hierarchy considerably enhances hardness without indentation cracking, with values ranging between 12.1 and 22.6 GPa from the oxide-adjacent metal to the surface oxides, a 3.7 to 6.8× increase over the interstitial-free alloy. Our fundamental understanding of the oxygen influence on phase formation informs future alloy design to enhance oxidation resistance and obtain exceptional hardness while preserving plasticity.

Objective Determination of Site-of-Lesion in Auditory Neuropathy.

Auditory neuropathy (AN), a complex hearing disorder, presents challenges in diagnosis and management due to limitations of current diagnostic assessment. This study aims to determine whether diffusion-weighted magnetic resonance imaging (MRI) can be used to identify the site and severity of lesions in individuals with AN. This case-control study included 10 individuals with AN of different etiologies, 7 individuals with neurofibromatosis type 1 (NF1), 5 individuals with cochlear hearing loss, and 37 control participants. Participants were recruited through the University of Melbourne's Neuroaudiology Clinic and the Murdoch Children's Research Institute specialist outpatient clinics. Diffusion-weighted MRI data were collected for all participants and the auditory pathways were evaluated using the fixel-based analysis metric of apparent fiber density. Data on each participant's auditory function were also collected including hearing thresholds, otoacoustic emissions, auditory evoked potentials, and speech-in-noise perceptual ability. Analysis of diffusion-weighted MRI showed abnormal white matter fiber density in distinct locations within the auditory system depending on etiology. Compared with controls, individuals with AN due to perinatal oxygen deprivation showed no white matter abnormalities ( p > 0.05), those with a neurodegenerative conditions known/predicted to cause VIII cranial nerve axonopathy showed significantly lower white matter fiber density in the vestibulocochlear nerve ( p < 0.001), while participants with NF1 showed lower white matter fiber density in the auditory brainstem tracts ( p = 0.003). In addition, auditory behavioral measures of speech perception in noise and gap detection were correlated with fiber density results of the VIII nerve. Diffusion-weighted MRI reveals different patterns of anatomical abnormality within the auditory system depending on etiology. This technique has the potential to guide management recommendations for individuals with peripheral and central auditory pathway abnormality.

Maximizing growth without compromising wood density: Selecting superior Norway spruce clones

The study examined a free-growing (initial stand density 400 trees ha–1), 50-year-old grafted clonal Norway spruce plantation in Eastern Latvia to assess the genetic control and variability of growth traits and wood density. The latter was used as a proxy for structural timber strength. Results showed moderately high heritability in growth traits and moderate variability in wood density among clones, with an estimated genetic coefficient of variation CVg, of 8.6%. Even when grown at a very low density on nutrient-rich soil, 85% of the trees met the density requirements for construction timber (C18 in accordance with EN 338). The negative correlation between growth traits and wood density was weak at both individual tree and clonal levels (–0.08 &lt; rP &lt; –0.06; –0.16 &lt; rG &lt; –0.09), making it feasible to select fast-growing clones with wood density required for structural timber. The observed variation underscores the importance of selective breeding to ensure optimal timber quality, with implications for enhancing sawn wood strength grades and promoting climate-resilient forestry practices. Keywords: tree breeding; structural timber; clonal forestry; wood properties; plantation forestry; climate-smart forestry

Comparative Genomics Analysis of the Populus Epidermal Pattern Factor (EPF) Family Revealed Their Regulatory Effects in Populus euphratica Stomatal Development

Drought stress seriously threatens plant growth. The improvement of plant water use efficiency (WUE) and drought tolerance through stomatal regulation is an effective strategy for coping with water shortages. Epidermal patterning factor (EPF)/EPF-like (EPFL) family proteins regulate stomatal formation and development in plants and thus contribute to plant stress adaptation. Here, our analysis revealed the presence of 14 PeEPF members in the Populus euphratica genome, which exhibited a relatively conserved gene structure with 1–3 introns. Subcellular localisation prediction revealed that 9 PeEPF members were distributed in the chloroplasts of P. euphratica, and 5 were located extracellularly. Phylogenetic analysis indicated that PeEPFs can be divided into three clades, with genes within the same clade revealing a relatively conserved structure. Furthermore, we observed the evolutionary conservation of PeEPFs and AtEPF/EPFLs in certain domains, which suggests their conserved function. The analysis of cis-acting elements suggested the possible involvement of PeEPFs in plant response to multiple hormones. Transcriptomic analysis revealed considerable changes in the expression level of PeEPFs during treatment with polyethylene glycol and abscisic acid. The overexpression of PeEPF2 resulted in low stomatal density in transgenetic lines. These findings provide a basis for gaining insights into the function of PeEPFs in response to abiotic stress.

TEM investigation of the interface formation during transfer of 3C-SiC(001) layer onto 6H-SiC(0001) wafer

At present, intensive research is underway in the field of vacuum-sublimation growth of 3C-SiC. Transfer of a thin (001)3C-SiC layer onto a 6H-SiC wafer is a promising way to fabricate a 3C-SiC/6H-SiC substrate for growing device-quality homoepitaxial films of low defect density. The article presents the results of the structural characterization of an interface formed during the transfer of a 3C-SiC layer onto a 6H-SiC(0001) wafer, performed with transmission electron microscopy (TEM). A 3C-SiC film with a thickness of about 10 μm, grown by chemical vapor deposition (CVD) on a Si(001) substrate, was utilized in the study. Silicon acted as a bonding material in the transfer process. The morphology and microstructure of the interface between a 6H-SiC substrate and a 3C-SiC (001)-oriented layer are under consideration. TEM investigation reveals an effect of “self”-orientation of the layer with respect to the wafer during the transfer process: an interaction between the molten silicon layer and silicon carbide throughout crystallization results in the generation of defined orientation relationships with respect to substrate axes. An analysis of selected area electron diffraction patterns taken from interfaces showed the relationships to be 3C-SiC{001}‖ 6H-SiC(0001) and 3C-SiC⟨11¯0⟩∼‖ 6H-SiC⟨112¯0⟩.

A study based on high-density data examines the current status and evolution laws of heavy metal environmental capacity in the Bardawu area of the Qinghai-Tibet Plateau

As the first ladder of China, the Qinghai-Tibet Plateau has always been known as the “roof of the world”. Its environmental carrying capacity can be estimated more accurately than other regions because of its harsh natural environment, low population density, limited industrial and agricultural development, and low human activities. However, the current ecological risks of Co and threshold research are limited, and there is a lack of awareness of W’s environmental risks. Hence, this study assessed the ecological support potential of the Bardawu region within Dulan County, Qinghai Province, using 7373 soil specimens, determined regional soil baseline measures, and applied the substance equilibrium linear technique along with the ecological aggregate indicator technique to examine the heavy metal content of the soil. A comprehensive evaluation of the environmental capacity and health risks was conducted to provide a reference for pastoral planning. The findings indicated that the cumulative static ecological capacity of the six trace heavy elements in the soil was ranked as follows: Cr > Li > Ni > Cu > W > Co, with W and Co positioned as the final pair. The remaining areas with a high environmental capacity were predominantly found in the study zone. The central sector exhibited diminished environmental capacity in the southwest and northeast and presented a contamination hazard. Land use, soil type, and geological type considerably affected the six elements in the study area at the p < 0.05. The Bardawu region’s mean comprehensive index of soil environmental capacity was 0.98, indicating an intermediate level of environmental capacity and a moderate health risk. This study focuses on the geological context and influence of pastoral activities on the soil, augments the distribution of various elements across the Tibetan Plateau, and suggests preliminary soil governance strategies. The findings of this study lay the groundwork for soil environmental conservation and remediation efforts in highland regions.

Diversification inside a lamprophyric dyke and cone sheet complex converging onto a hidden carbonatite centre (Frederikshåbs Isblink, SW Greenland)

Abstract Both radiating dykes and proximal cone sheets converge onto a positive aeromagnetic anomaly of an inferred carbonatitic centre, hidden beneath a retreating edge of the Frederikshåbs Isblink glacier. This convergence, together with sub-parallel incompatible element patterns by all intrusions, suggests a cogenetic relationship that warrants investigation into potential diversification processes. More primitive high- and low-Mg damtjernites, which for three dykes conform to more porphyritic dyke cores and aphyric margins, respectively, can be explained by high-Mg trends being controlled by the fractionation/accumulation of mainly augite and olivine (or other mafic phases), while discordant low-Mg trends require additional decoupled magnetite fractionation. It is proposed that each dyke intrusion tapped the differentiated top of a central magma chamber, occasionally followed by an unconsolidated mafic cumulate mush, excluding denser magnetites, with in situ flow segregation playing a subordinate additional role. Beyond the most differentiated damtjernite, more evolved phonolitic nephelinites to carbonaceous alnöites split into bulk rock geochemical T-trends that can only relate to late-stage segregations into magmas with varying proportions of interstitial igneous (not secondary) analcime and carbonate – collectively increasing in volume with differentiation. While the analcime component also appears to segregate more readily into veins and ocelli than carbonatite, it is speculated if such low viscosity, density and liquidus rest melts, inside igneous centres, more efficiently aggregated into voluminous, buoyant analcime caps above slightly denser carbonatites. Similar converging plumbing systems and diversification processes are proposed for other complexes, where kimberlitic parents were simply extracted from deeper mantle sources.

Superelastic and strong microfibrous sponges prepared by solution blow spinning for high-efficiency warmth retention

We report a facile strategy for preparing ultralight, mechanically robust, and washable heat-retaining materials via solution blow spinning technology and thermal crosslinking. Fluffy microfibrous assemblies with nonwoven structure were fabricated by blending fibers of stiff and soft polymers and creating a bonding architecture among them. The premise of this design is that polystyrene, which is stiff, can endow materials with rigidity, while thermoplastic polyurethane, which is soft, can absorb energy during mechanical deformation. Moreover, the stability of the sponge was improved by using tris (2-methyl-1-aziridine propionate; TTMA) as a crosslinking agent. The optimized microfibrous sponges present excellent mechanical properties with a large breaking elongation of 42.1% and outstanding resilience in resisting 100 cyclic compressions at 40% strain. Furthermore, the microfibrous sponges exhibit a low volume density of 33.32 mg/cm3, effective heat-preservation ability (low thermal conductivity: 23.1 mW/m·K) and excellent washability. The preparation of microfibrous sponges via solution blow spinning can be a novel route for developing ultralight and superelastic heat retention materials.

A public grid of radiative transfer simulations for Lyman-alpha and metal lines in idealised galactic outflows

The vast majority of star-forming galaxies are surrounded by large reservoirs of gas ejected from the interstellar medium. Ultraviolet absorption and emission lines represent powerful diagnostics to constrain the cool phase of these outflows, through resonant transitions of hydrogen and metal ions. The interpretation of these observations is often remarkably difficult as it requires detailed modelling of the propagation of the continuum and emission lines in the gas. To this aim, we present a large public grid of $ 20,000$ simulated spectra that includes and five metal transitions associated with and which is accessible online. The spectra have been computed with the Monte Carlo radiative transfer code for $5,760$ idealised spherically symmetric configurations surrounding a central point source emission, and characterised by their column density, Doppler parameter, dust opacity, wind velocity, as well as various density and velocity gradients. Designed to predict and interpret and metal line profiles, our grid exhibits a wide diversity of resonant absorption and emission features, as well as fluorescent lines. We illustrate how it can help better constrain the wind properties by performing a joint modelling of observed and spectra. Using simulations and virial scaling relations, we also show that is expected to be a faithful tracer of the gas at $T 10^4-10^5$ K, even if the medium is highly ionised. While is found to probe the same range of temperatures as other metal lines merely trace cooler phases ($T 10^4$ K). As their gas opacity strongly depends on gas temperature, incident radiation field, metallicity and dust depletion, we caution that optically thin metal lines do not necessarily originate from low column densities and may not accurately probe Lyman continuum leakage.

Regional socioeconomic characteristics and density of general practitioners in Germany: A nationwide cross-sectional and longitudinal spatial analysis

ObjectivesLimited healthcare availability impacts population health. Regional disparities in GP density across Germany raise questions about their association with regional socioeconomic characteristics. Study designThis longitudinal nationwide ecological German study used regional data at the county level (n = 401) from 2015 to 2019 provided by the Federal Institute for Research on Building, Urban Affairs and Spatial Development (BBSR). The outcome was general practitioners (GPs) density, defined as the number of GPs per 10,000 inhabitants. MethodsUnivariate Moran's I, cluster analysis (LISA), and spatial lag of X (SLX) models were employed to analyse the spatial distribution of GP density and its correlation with various regional socioeconomic characteristics from a cross-sectional and longitudinal perspective. ResultsIn contrast to the univariate analysis, rural counties showed the highest GP density the multivariate model. Several counties were identified as embedded in low- or high-GP-density clusters. In 2015 and 2019, larger household size (2015: std. β = −2.31, p = 0.021; 2019: std. β = −4.14, p < 0.001) and higher unemployment rate (2015: std. β = −2.84, p = 0.005; 2019: std. β = −5.47, p < 0.001) were associated with lower GP density. In the longitudinal model, a greater increase in the unemployment rate was related to a greater decrease in GP density (std. β = −2.17, p = 0.030). ConclusionA higher regional unemployment rate is linked to lower GP availability in Germany, and a greater increase in the unemployment rate was related to a greater decrease in GP availability over time. This necessitates policy intervention to avoid socioeconomic disparities in GP care.

Impact of planting density and shoot thinning on alstroemeria flowering, soil attributes and cost economics

A field experiment was conducted to assess the impact of various planting densities and levels of shoot thinning on cut flower yield, quality, soil chemical properties and cost economics in the commercially cultivated alstroemeria cultivar 'Capri'. The experiment involved three planting densities (4, 6 and 8 plants/m2) along with three shoot thinning levels (10 %, 20 % and 30 %). It was observed that higher planting density (4 plants/m2) promoted the length of cut stem, early bud formation, and flowering, optimal quality parameters, including maximum stem thickness, cut stem weight, floret quantity/stem, floret size, number of flowering stems/plant (yield) and vase life. Exclusive use of higher vegetative mass removal (30 % shoot thinning) was found to improve quality parameters such as the length of cut stem, number of flowering stems, stem thickness, weight of cut stem, floret quantity/stem, floret size, vase life, and early flowering. Soil samples were collected from each treatment and the consequent lab analysis revealed that the lower planting density and shoot thinning level resulted in maximum soil organic carbon, nitrogen, phosphorous and potassium content. In conclusion, planting density of 4 plants/m2 and 30 % shoot thinning emerged as the optimal combination for enhancing quantitative parameters in commercial alstroemeria cultivation. The study underscores the importance of strategic planting practices and vegetative mass management for maximizing yield and quality in alstroemeria production, along with ensuring higher economic returns.

Role of the Built Environment, Roadway Characteristics, and Socioeconomic Factors in Keeping Teen Drivers Safe: An Investigation of the Factors Most Related to Teen Driver Fatalities

The role of engineering, through infrastructure design, is known to influence safe driving behavior generally, yet the areas of possible intervention that could improve safe outcomes for teens are less understood. It is critical to identify interventions specific to teens, as they have different driving risk factors than more seasoned drivers, and motor vehicle crashes are the second leading cause of death among teens in the United States. We examined 5,210 fatal crashes from 2015 to 2019 in Ohio using Fatality Analysis Reporting System data. We employed multinomial logistic regression to associate the likelihood of fatal crashes involving younger teens (16 to 17 years old) or older teens (18 to 19 years old) relative to adults (20 years and older) with built environment, socioeconomic, and roadway characteristics at crash locations. Separating crashes into the two groups of teens allowed us to distinguish the possible impact of training, as younger teens are mandated to undergo driving education and behind-the-wheel training under Ohio’s graduated driver licensing laws. We found that compared with neighborhood socioeconomics, built environment factors were more significant predictors of the likelihood of fatal crashes involving younger teens compared with adults. Specifically, fatal crashes at locations with lower road density and more diverse land use were more likely to involve younger teens. Although these results could be related to a mix of younger teen driver behavior and exposure factors, the finding highlights that improving the safety of local roads in urban and rural settings could help stem teen driving fatalities.