Contrasting Ultra-Low Frequency Raman and Infrared Modes in Emerging Metal Halides for Photovoltaics.

Lattice dynamics are critical to photovoltaic material performance, governing dynamic disorder, hot-carrier cooling, charge-carrier recombination, and transport. Soft metal-halide perovskites exhibit particularly intriguing dynamics, with Raman spectra exhibiting an unusually broad low-frequency response whose origin is still much debated. Here, we utilize ultra-low frequency Raman and infrared terahertz time-domain spectroscopies to provide a systematic examination of the vibrational response for a wide range of metal-halide semiconductors: FAPbI3, MAPbI x Br3-x , CsPbBr3, PbI2, Cs2AgBiBr6, Cu2AgBiI6, and AgI. We rule out extrinsic defects, octahedral tilting, cation lone pairs, and "liquid-like" Boson peaks as causes of the debated central Raman peak. Instead, we propose that the central Raman response results from an interplay of the significant broadening of Raman-active, low-energy phonon modes that are strongly amplified by a population component from Bose-Einstein statistics toward low frequency. These findings elucidate the complexities of light interactions with low-energy lattice vibrations in soft metal-halide semiconductors emerging for photovoltaic applications.

Development and evaluation of an artificial intelligence-based workflow for the prioritization of patient portal messages.

Objectives: Accelerating demand for patient messaging has impacted the practice of many providers. Messages are not recommended for urgent medical issues, but some do require rapid attention. This presents an opportunity for artificial intelligence (AI) methods to prioritize review of messages. Our study aimed to highlight some patient portal messages for prioritized review using a custom AI system integrated into the electronic health record (EHR). Materials and Methods: We developed a Bidirectional Encoder Representations from Transformers (BERT)-based large language model using 40 132 patient-sent messages to identify patterns involving high acuity topics that warrant an immediate callback. The model was then implemented into 2 shared pools of patient messages managed by dozens of registered nurses. A primary outcome, such as the time before messages were read, was evaluated with a difference-in-difference methodology. Results: Model validation on an expert-reviewed dataset (n = 7260) yielded very promising performance (C-statistic = 97%, average-precision = 72%). A binarized output (precision = 67%, sensitivity = 63%) was integrated into the EHR for 2 years. In a pre-post analysis (n = 396 466), an improvement exceeding the trend was observed in the time high-scoring messages sit unread (21 minutes, 63 vs 42 for messages sent outside business hours). Discussion: Our work shows great promise in improving care when AI is aligned with human workflow. Future work involves audience expansion, aiding users with suggested actions, and drafting responses. Conclusion: Many patients utilize patient portal messages, and while most messages are routine, a small fraction describe alarming symptoms. Our AI-based workflow shortens the turnaround time to get a trained clinician to review these messages to provide safer, higher-quality care.

Addressing spatiotemporal signal variations in pair correlation function analysis.

Fluorescence correlation spectroscopy (FCS) is a cornerstone technique in optical microscopy to measure, for example, the concentration and diffusivity of fluorescent emitters and biomolecules in solution. The application of FCS to complex biological systems, however, is fraught with inherent intricacies that impair the interpretation of correlation patterns. Critical among these intricacies are temporal variations beyond diffusion in the quantity, intensity, and spatial distribution of fluorescent emitters. These variations introduce distortions into correlated intensity data, thus compromising the accuracy and reproducibility of the analysis. This issue is accentuated in imaging-based approaches such as pair correlation function (pCF) analysis due to their broader regions of interest compared with point-detector-based approaches. Despite ongoing developments in FCS, attention to systems characterized by a spatiotemporal-dependent probability distribution function (ST-PDF) has been lacking. To address this knowledge gap, we developed a new analytical framework for ST-PDF systems that introduces a dual-timescale model function within the conventional pCF analysis. Our approach selectively differentiates the signals associated with rapid processes, such as particle diffusion, from signals stemming from spatiotemporal variations in the distribution of fluorescent emitters occurring at extended delay timescales. To corroborate our approach, we conducted proof-of-concept experiments on an ST-PDF system, wherein the, initially, uniform distribution of fluorescent microspheres within a microfluidic channel changes into a localized accumulation of microspheres over time. Our framework is offering a comprehensive solution for investigating various phenomena such as biomolecular binding, sedimentation, and particle accumulation.

Technical aspects of rod-insertion forceps (persuader) application in reducing construct failure after lumbar spine fusion surgery: a biomechanical cadaveric study in Germany.

Study Design: A prospective experimental study. Purpose: This biomechanical in vitro study aimed to examine the extent to which the use of a rod persuader (RP) leads to additional mechanical stress on the screw-rod system and determine its influence on the bony anchoring of primary pedicle screws. Overview of Literature: Degenerative spine diseases and deformities are the most common indications for the stabilization and fusion of spinal segments. The pedicle screw-rod system is considered the gold standard for dorsal stabilization, and an RP is also increasingly being considered to fit the spondylodesis material. Methods: Ten lumbar spines from body donors were examined. Bisegmental dorsal spinal lumbar interbody fusion of the L3-L5 segments was performed using a pedicle screw-rod system (ROCCIA Multi-LIF Cage; Silony Medical, Germany). In group 1, the titanium rod was inserted without tension, whereas in group 2, the rod was attached to the pedicle screws at the L4 and L5 levels, creating a 5-mm gap. To attach the rod, the RP was used to press the rod into the pedicle screw. The rod was left in place for 30 minutes and then removed. Results: The rod reduction technique significantly increased the mechanical load on the overall construct measured by strain gauges (p<0.05) and resulted in outright implant failure with pedicle screw pullout in 88.9%. Conclusions: In cases where the spondylodesis material is not fully attached within the pedicle screw, an RP can be used with extreme caution, particularly in osteoporotic bones, to avoid pedicle screw avulsion and screw anchor failure.

A comparison of dysphagia rates between long-segment anterior versus posterior cervical fusion.

OBJECTIVE: The goal of this study was to compare rates of dysphagia and patient-reported outcomes (PROs) following long-segment (≥ 3 levels) anterior cervical spinal fusion (ACF) and posterior cervical spinal fusion (PCF) at 3 and 12 months postoperatively. PROs were also compared for patients with dysphagia versus those without dysphagia. METHODS: A prospectively collected quality improvement database was used to identify patients who had a long-segment cervical spinal fusion. Cohorts were divided into ACF and PCF groups. Eating Assessment Tool-10 scores and PROs were obtained for all patients preoperatively and at 3 and 12 months postoperatively to compare. Multivariate analysis was also performed to evaluate risk factors for dysphagia. RESULTS: A total of 132 patients met the inclusion criteria, 77 of whom had undergone ACF and 55 of whom had undergone PCF. Dysphagia rates between ACF and PCF cohorts were similar at baseline (13.0% vs 18.2%, p = 0.4). New-onset dysphagia rates were also comparable at 3-month follow-up (39.7% vs 23.1%, p = 0.08) and 12-month follow-up (32.6% vs 32.4%, p > 0.99). Patients who underwent PCF had worse Neck Disability Index (NDI) scores at 3 months than did patients with ACF (13.67 ± 9.49 vs 10.55 ± 6.24, respectively; p = 0.03). There were significantly higher NDI scores for patients with dysphagia at 3 months in both the ACF and PCF groups and at 12 months for those in the PCF group. Analogously, EuroQol-5 Dimensions scores were worse for patients with dysphagia; however, this was only significant for patients in the ACF group at 3 months. There were no significant risk factors for the development of dysphagia found on multivariate analysis. CONCLUSIONS: Similar rates and severity of dysphagia were seen following ACF and PCF at 3- and 12-month follow-up. This suggests that long-term dysphagia following cervical fusion surgery may be due to structural changes from the fusion rather than the surgical approach. However, the ACF cohort was significantly younger, and this may have partially accounted for the findings. PROs were also compared for patients with and without dysphagia, demonstrating worsened outcomes in some domains for patients who presented with dysphagia at 3- and 12-month follow-up. This suggests that dysphagia may be associated with a decreased quality of life after cervical fusion.

COPD Subtypes Are Differentially Associated with Cardiovascular Events and COPD Exacerbations.

BACKGROUND: The coronary artery calcium score (CACS) and ratio of the pulmonary artery to aorta diameters (PA:A ratio) measured from chest CT scans have been established as predictors of cardiovascular events and chronic obstructive pulmonary disease (COPD) exacerbations, respectively. However, little is known about the reciprocal relationship between these predictors and outcomes. Furthermore, the prognostic implications of COPD subtypes on clinical outcomes remain insufficiently characterized. RESEARCH QUESTION: How can these two chest CT-derived parameters predict subsequent cardiovascular events and COPD exacerbations in different COPD subtypes? STUDY DESIGN AND METHODS: Using COPDGene study data, we assessed prospective cardiovascular disease (CVD) and COPD exacerbation risk in COPD subjects (Global Initiative for Chronic Obstructive Lung Disease spirometric grades 2-4), focusing on CACS and PA:A ratio at study enrollment, with logistic regression models. These outcomes were analyzed in three COPD subtypes: 1,042 Non-emphysema-predominant COPD (NEPD; low attenuation area at -950 Hounsfield units [LAA-950]<5%), 1,324 Emphysema-predominant COPD (EPD; LAA-950≥10%), and 465 Intermediate Emphysema COPD (IE; 5≤LAA-950<10%). RESULTS: Our study indicated significantly higher overall risk for cardiovascular events in subjects with higher CACS (≥median; Odds Ratio (OR): 1.61, 95% Confidence Interval (CI)=1.30-2.00) and increased COPD exacerbations in those with higher PA:A ratios (≥1; OR: 1.80, 95% CI=1.46-2.23). Notably, NEPD subjects showed a stronger association between these indicators and clinical events compared to EPD (with CACS/CVD, NEPD vs. EPD, OR 2.02 vs. 1.41; with PA:A ratio/COPD exacerbation, NEPD vs. EPD, OR 2.50 vs. 1.65); the difference in odds ratios between COPD subtypes was statistically significant for CACS/CVD. INTERPRETATION: Two chest CT parameters, CACS and PA:A ratio, hold distinct predictive values for cardiovascular events and COPD exacerbations that are influenced by specific COPD subtypes. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00608764.

Follow-up Outcomes of Children, Adolescents and Young People on Darunavir-Based Third-line Antiretroviral Therapy - Observational Cohort from Nine African Countries.

BACKGROUND: We assessed clinical outcomes among children, adolescents and young people (< 25 years) on darunavir-based antiretroviral therapy (ART) in nine sub-Saharan African countries. SETTING: Third-line ART centers in Cameroon, Eswatini, Kenya, Lesotho, Nigeria, Rwanda, Uganda, Zambia and Zimbabwe. METHODS: From January 2019 to December 2022, we collected data from a cohort of children, adolescents and young people receiving third-line ART from 9 sub-Saharan African countries. Data on treatment continuity, viral suppression, death and clinic transfers were extracted from medical records and summarized. Cox proportional hazards models were used to identify factors independently associated with retention in care. RESULTS: Of 871 participants enrolled, median age 14.8 (range: 0.2 - 24.7) years, 488 (56.0%) male; 809 (92.9%) [median duration of follow-up of 28.3 months (IQR:17.5 - 45.2)] had final outcomes after initiating third-line ART. Of these, 711 (87.9%) were alive and in care at the end of study follow-up, 29 (3.6%) died, 30 (3.7%) transferred to other facilities, and 39 (4.8%) were lost to follow-up. Retention in care was less likely among males compared to females (aHR: 0.85, 95%CI 0.72-1.0), and in 10-14-year-olds compared to younger children. Adolescents (15-19 years) had higher mortality compared to children <10 years of age (aSHR: 4.20, 95% CI 1.37-12.87). Viral suppression was seen in 345/433 (79.7%), 249/320 (77.8%), and 546/674 (81.0%) patients with results at 6, 12 months and study end, respectively. CONCLUSION: A high proportion of children and young people receiving third-line ART in Sub-Saharan Africa, remain in care, and attain viral suppression during follow-up.

Perioperative complications associated with fluoroscopy C1 lateral mass screw fixation (Goel technique) versus computed tomography-guided navigation technique: A review of 202 cases from the German Spine Registry (DWG-Register).

Background: Overview of the literature - Fractures of the C1 constitute 3%-13% of all cervical spine injuries in adults. Most isolated C1 fractures are stable and can be treated nonoperatively with external immobilization. Traditional surgical options for C1 fracture treatment are occiput-to-C2 fusion or C1 with lateral mass screws (LMSs). Purpose - The aim is to assess the management and perioperative complications of C1 fractures undergoing LMS fusion between fluoroscopy and computed tomography (CT)-guided navigation. Methods: This was a retrospective multicenter study of data from the DWG-Register of patients who underwent operative treatment for C1 traumatic fracture with LMSs from January 2017 to September 2022. Inclusion criteria - traumatic injury and age > 18 years old. Results: In total, 202 patients with traumatic C1 fracture requiring spinal surgery were identified in the registry; n = 175 (Group 1) were treated conventionally without CT-guided navigation and n = 27 were treated with CT-guided navigation (Group 2). C1-LMS was principally performed by spine surgeons n = 90 (53.4%) and n = 72 (18.5%) by neurosurgeons in both the groups. Intraoperative adverse events were as follows: dural tear in group 1 n = 0 and in group 2 n = 1, vascular injury, with one case in group 1 and no cases in group 2. General complications were: cardiovasculars in group 1 n = 6 (3.4%) and Group 2 n = 4 (14.8%) (P = 0.03), pulmonary complications in group1 n = 2 (1.1%) and n = 9 in group 2 (33.3%) (P < 0.001), stroke n = 1 (0.57%) in group1 and n = 4 in group 2 (14.8%) (P < 0.001), gastrointestinal bleeding n = 1 (0.57%) in group1 and no cases in group 2, renal insufficiency n = 2 (1.1%) in group 1 and n = 3 (11.1%) in group 2 (P = 0.01). One death was recorded in group 2 (3.7%). Conclusion: This series of 404 screws placed in 202 patients over 5 years who underwent two types of C1 fracture fixation had a considerably lower incidence of screw malposition and vertebral artery injury than has previously been reported in the literature. C1 screws can be safely placed with a low risk of vertebral artery and neurologic injury with and without CT-guided navigation support.

A New Case Series Suggests That SCA48 (ATX/STUB1) Is Primarily a Monogenic Disorder.

BACKGROUND: Monoallelic, pathogenic STUB1 variants cause autosomal dominant cerebellar ataxia (ATX-STUB1/SCA48). Recently, a genetic interaction between STUB1 variants and intermediate or high-normal CAG/CAA repeats in TBP was suggested, indicating digenic inheritance or a disease-modifying role for TBP expansions. OBJECTIVE: To determine the presence and impact of intermediate or high-normal TBP expansions in ataxic patients with heterozygous STUB1 variants. METHODS: We describe 21 patients with ataxia carrying a heterozygous STUB1 variant and determined TBP repeat length. RESULTS: A total of 15 of 21 patients (71%) carried a normal TBP<40 allele, 4 (19%) carried an intermediate TBP41-42 allele, and two carried a high-normal TBP40 allele (9.5%). Five of six carriers (83%) of both STUB1 variants and TBP40-42 alleles showed marked cognitive impairment. CONCLUSIONS: SCA48 is predominantly a monogenic disorder, because most patients carried an isolated, heterozygous STUB1 variant and presented with the typical combined phenotype of ataxia and cognitive dysfunction. Still, co-occurrence of TBP41-42 or high-normal TBP40 alleles was relatively frequent and associated with marked cognitive defects (28.5%), suggesting a modifying effect on clinical expression in some cases. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Large Language Model-Based Responses to Patients' In-Basket Messages.

Importance: Virtual patient-physician communications have increased since 2020 and negatively impacted primary care physician (PCP) well-being. Generative artificial intelligence (GenAI) drafts of patient messages could potentially reduce health care professional (HCP) workload and improve communication quality, but only if the drafts are considered useful. Objectives: To assess PCPs' perceptions of GenAI drafts and to examine linguistic characteristics associated with equity and perceived empathy. Design, Setting, and Participants: This cross-sectional quality improvement study tested the hypothesis that PCPs' ratings of GenAI drafts (created using the electronic health record [EHR] standard prompts) would be equivalent to HCP-generated responses on 3 dimensions. The study was conducted at NYU Langone Health using private patient-HCP communications at 3 internal medicine practices piloting GenAI. Exposures: Randomly assigned patient messages coupled with either an HCP message or the draft GenAI response. Main Outcomes and Measures: PCPs rated responses' information content quality (eg, relevance), using a Likert scale, communication quality (eg, verbosity), using a Likert scale, and whether they would use the draft or start anew (usable vs unusable). Branching logic further probed for empathy, personalization, and professionalism of responses. Computational linguistics methods assessed content differences in HCP vs GenAI responses, focusing on equity and empathy. Results: A total of 16 PCPs (8 [50.0%] female) reviewed 344 messages (175 GenAI drafted; 169 HCP drafted). Both GenAI and HCP responses were rated favorably. GenAI responses were rated higher for communication style than HCP responses (mean [SD], 3.70 [1.15] vs 3.38 [1.20]; P = .01, U = 12 568.5) but were similar to HCPs on information content (mean [SD], 3.53 [1.26] vs 3.41 [1.27]; P = .37; U = 13 981.0) and usable draft proportion (mean [SD], 0.69 [0.48] vs 0.65 [0.47], P = .49, t = -0.6842). Usable GenAI responses were considered more empathetic than usable HCP responses (32 of 86 [37.2%] vs 13 of 79 [16.5%]; difference, 125.5%), possibly attributable to more subjective (mean [SD], 0.54 [0.16] vs 0.31 [0.23]; P < .001; difference, 74.2%) and positive (mean [SD] polarity, 0.21 [0.14] vs 0.13 [0.25]; P = .02; difference, 61.5%) language; they were also numerically longer (mean [SD] word count, 90.5 [32.0] vs 65.4 [62.6]; difference, 38.4%), but the difference was not statistically significant (P = .07) and more linguistically complex (mean [SD] score, 125.2 [47.8] vs 95.4 [58.8]; P = .002; difference, 31.2%). Conclusions: In this cross-sectional study of PCP perceptions of an EHR-integrated GenAI chatbot, GenAI was found to communicate information better and with more empathy than HCPs, highlighting its potential to enhance patient-HCP communication. However, GenAI drafts were less readable than HCPs', a significant concern for patients with low health or English literacy.

Metabolic imaging across scales reveals distinct prostate cancer phenotypes.

Hyperpolarised magnetic resonance imaging (HP-13C-MRI) has shown promise as a clinical tool for detecting and characterising prostate cancer. Here we use a range of spatially resolved histological techniques to identify the biological mechanisms underpinning differential [1-13C]lactate labelling between benign and malignant prostate, as well as in tumours containing cribriform and non-cribriform Gleason pattern 4 disease. Here we show that elevated hyperpolarised [1-13C]lactate signal in prostate cancer compared to the benign prostate is primarily driven by increased tumour epithelial cell density and vascularity, rather than differences in epithelial lactate concentration between tumour and normal. We also demonstrate that some tumours of the cribriform subtype may lack [1-13C]lactate labelling, which is explained by lower epithelial lactate dehydrogenase expression, higher mitochondrial pyruvate carrier density, and increased lipid abundance compared to lactate-rich non-cribriform lesions. These findings highlight the potential of combining spatial metabolic imaging tools across scales to identify clinically significant metabolic phenotypes in prostate cancer.

Using the ADDIE Model of Instructional Design to Create Programming for Comprehensive ABA Treatment.

ABA research abounds with articles on increasing or decreasing a small set of behaviors. These articles fit nicely within the framework of Focused ABA Treatment in which the goal of treatment centers on only a few behaviors. However, many behavioral practitioners spend most of their time developing Comprehensive ABA Treatment in which a large number of behaviors are systematically changed across multiple developmental domains. Few resources are available to help in designing and implementing such programming. This article presents a model from the field of instructional design for the development of comprehensive programming. Applying the ADDIE model-Analyze, Design, Develop, Implement, Evaluate-the article identifies a consistent process to follow, critical actions to take, and helpful resources to use when developing comprehensive programming for individuals with autism.

Evaluating the Efficacy of Chronic Galantamine on Sustained Attention and Cholinergic Neurotransmission in A Pre-Clinical Model of Traumatic Brain Injury.

Cholinergic disruptions underlie attentional deficits following traumatic brain injury (TBI). Yet, drugs specifically targeting acetylcholinesterase (AChE) inhibition have yielded mixed outcomes. Therefore, we hypothesized that galantamine (GAL), a dual-action competitive AChE inhibitor and α7 nicotinic acetylcholine receptor (nAChR) positive allosteric modulator, provided chronically after injury, will attenuate TBI-induced deficits of sustained attention and enhance ACh efflux in the medial prefrontal cortex (mPFC), as assessed by in vivo microdialysis. In Experiment 1, adult male rats (n = 10-15/group) trained in the 3-choice serial reaction time (3-CSRT) test were randomly assigned to controlled cortical impact (CCI) or sham surgery and administered GAL (0.5, 2.0, or 5.0 mg/kg; i.p.) or saline vehicle (VEH; 1 mL/kg; i.p) beginning 24-h post-surgery and once daily thereafter for 27 days. Measures of sustained attention and distractibility were assessed on post-operative days 21-25 in the 3-CSRT, following which cortical lesion volume and basal forebrain cholinergic cells were quantified on day 27. In Experiment 2, adult male rats (n = 3-4/group) received a CCI and 24 h later administered (i.p.) one of the three doses of GAL or VEH for 21 days to quantify the dose-dependent effect of GAL on in vivo ACh efflux in the mPFC. Two weeks after the CCI, a guide cannula was implanted in the right mPFC. On post-surgery day 21, baseline and post-injection dialysate samples were collected in a temporally matched manner with the cohort undergoing behavior. ACh levels were analyzed using reverse phase high-performance liquid chromatography (HPLC) coupled to an electrochemical detector. Cortical lesion volume was quantified on day 22. The data were subjected to ANOVA, with repeated measures where appropriate, followed by Newman-Keuls post hoc analyses. All TBI groups displayed impaired sustained attention versus the pooled SHAM controls (p's < 0.05). Moreover, the highest dose of GAL (5.0 mg/kg) exacerbated attentional deficits relative to VEH and the two lower doses of GAL (p's < 0.05). TBI significantly reduced cholinergic cells in the right basal forebrain, regardless of treatment condition, versus SHAM (p < 0.05). In vivo microdialysis revealed no differences in basal ACh in the mPFC; however, GAL (5.0 mg/kg) significantly increased ACh efflux 30 min following injection compared to the VEH and the other GAL (0.5 and 2.0 mg/kg) treated groups (p's < 0.05). In both experiments, there were no differences in cortical lesion volume across treatment groups (p's > 0.05). In summary, albeit the higher dose of GAL increased ACh release, it did not improve measures of sustained attention or histopathological markers, thereby partially supporting the hypothesis and providing the impetus for further investigations into alternative cholinergic pharmacotherapies such as nAChR positive allosteric modulators.

Feasibility of pharmacy-based research opportunity to enhance community testing and surveillance.

BACKGROUND: Approximately 89% of the US population lives within five miles of a community pharmacy, which provides a network of geographically distributed recruitment nodes for testing and surveillance of infection and disease. OBJECTIVES: Establish feasibility of Pharmacy-based Research Opportunities To Enhance Community Testing and Surveillance in the context of SARS-CoV-2 infection in a community pharmacy setting with University of Kentucky serving as the coordinating center and research hub for sample analysis. METHODS: Two community pharmacies in Kentucky served as community-based recruitment sites to assess SARS-CoV-2 exposure through longitudinal (5 visits over 56 days) collection of nasal swabs and blood samples from subjects. RESULTS: Fifty subjects were recruited between May 2022 and December 2023 for longitudinal sample collection. Three phases of recruitment were investigated by first establishing standard operating procedures in an urban pharmacy, then expanding recruitment at a second pharmacy in a rural setting, and finally increasing recruitment at the urban pharmacy. During the first phase of recruitment, 12 participants were recruited. Of these participants, two never scheduled a visit after the initial screening. The median time for study completion from first to last visit within this phase was 59 days (interquartile range: 56-68 days). During the second phase of recruitment, eight of nine participants completed all five visits. The median time to complete all visits was 105 days (interquartile range: 98-112 days). During the ongoing third phase, 29 subjects were recruited, and 19 participants completed all required visits and the remainder continue to schedule follow-up appointments. CONCLUSION: Community pharmacies have a significant role in promoting public health. The geographic distribution of community pharmacies makes them appealing locations for recruitment of outpatient cohorts for local surveillance of infections and chronic inflammatory conditions with opportunities for broad implementation of this project for clinical trials in underserved communities.

The bearing capacity of asteroid (65803) Didymos estimated from boulder tracks.

The bearing capacity - the ability of a surface to support applied loads - is an important parameter for understanding and predicting the response of a surface. Previous work has inferred the bearing capacity and trafficability of specific regions of the Moon using orbital imagery and measurements of the boulder tracks visible on its surface. Here, we estimate the bearing capacity of the surface of an asteroid for the first time using DART/DRACO images of suspected boulder tracks on the surface of asteroid (65803) Didymos. Given the extremely low surface gravity environment, special attention is paid to the underlying assumptions of the geotechnical approach. The detailed analysis of the boulder tracks indicates that the boulders move from high to low gravitational potential, and provides constraints on whether the boulders may have ended their surface motion by entering a ballistic phase. From the 9 tracks identified with sufficient resolution to estimate their dimensions, we find an average boulder track width and length of 8.9 ± 1.5 m and 51.6 ± 13.3 m, respectively. From the track widths, the mean bearing capacity of Didymos is estimated to be 70 N/m2, implying that every 1 m2 of Didymos' surface at the track location can support only ~70 N of force before experiencing general shear failure. This value is at least 3 orders of magnitude less than the bearing capacity of dry sand on Earth, or lunar regolith.