Full Collapse Research Articles

Full scale test on reinforced concrete elements of an existing bridge: on-site investigation and laboratory testing design

The evaluation of mechanical characteristics and degradation level of existing bridges is a highly relevant topic today. This paper presents the initial phases of an integrated experimental-numerical research project focused on a pre-scheduled demolition of an existing reinforced concrete bridge. The controlled demolition of existing bridges represents an invaluable opportunity, allowing to deepen our comprehension on their behavior, especially when degradation analysis is concerned. Both on-site tests and subsequent laboratory experiments design are carried out on full-scale elements extracted from the bridge. These tests are complemented by Finite Element analyses conducted at various levels of detail. Specifically, after the description of the knowledge phases of the bridge performed on-site, the paper illustrates the preliminary numerical analyses carried out to support the customized design of the experimental setup, where mean values of all material parameters are assumed to acquire the essential information on the expected test results. Additionally, Monte Carlo analysis has been performed to evaluate the impact of statistical variability of material parameters on structural response. This aspect is particularly relevant for the design of the experimental test setup, due to the large forces involved and large displacements expected in order to reach the full collapse of the beams.

Investigation into the Suitability of AA 6061 and Ti6Al4V as Substitutes for SS 316L Use in the Paraplegic Swivel Mechanism

SS 316L, a low-carbon 316 Stainless Steel, has been used to manufacture swivel mechanisms for paraplegic patients, but its weight is relatively high compared to a few materials in its range of properties. Aluminum alloy 6061 and Titanium alloy (Ti6Al4V) offer lightweight and incredible strength-to-weight ratio, hence their use for medical, aerospace, and automotive applications. This study, therefore, seeks a replacement for SS 316L. A 3D model of a swivel mechanism was developed to compare the performance of the swivel mechanism made with SS 316L, AA 6061, and Ti6Al4V. The kinematic analysis of the mechanism based on a range of weights: 1kN, 1.1 kN, 1.2 kN, 1.3 kN, 1.4 kN, and 1.5 kN was carried out to generate the inputs for the simulation. The 3D model was made with SolidWorks, and the results of the kinematic analysis were used to define the simulation parameters for the mechanism. Two scenarios generated depicted the full collapse of the mechanism and the full extension. The results showed that AA 6061 and Ti6Al4V outperformed SS 316L with higher yield strength and factor of safety. Therefore, swivel plates made with AA 6061 and Ti6Al4V have higher yield strength than those made with SS 316L, adding to the advantage that they have a higher strength-to-weight ratio. From this analysis and known knowledge of the cost of these materials, the optimal replacement considering cost with yield strength is AA 6061. However, Ti6Al4V is a better alternative for the strength-to-weight ratio for SS 316L.

Novel Thermoreversible Reverse-Phase-Shift Foam With Deployment System for Treatment of Penetrating Globe Trauma in a Newly Described Porcine Model.

The initial management of penetrating ocular injuries is a major sight-threatening problem for both civilian and military medicine. A novel device (Eye-Aid) temporarily tamponades leakage from such injuries while being easy to remove upon arrival to specialized ophthalmologic care. Eye-Aid consists of a protective eye shield with an adhesive backing that connects to a portable canister containing rapidly deployable thermoresponsive foam. The aim of this study was to compare the use of the novel Eye-Aid device to control in a new live swine ocular injury model. Bilateral penetrating ocular injuries were created on 14 male Yorkshire swine in a standardized manner using a 16-gauge needle device to puncture the central cornea and cause a full-thickness wound. Researchers randomized eye intervention side, with the contralateral eye used as paired control. Two minutes after the injury, the eye shield components of the Eye-Aid system, which has a sticky pad for attachment to the skin and a luer-lock for foam deployment, were placed bilaterally. Eight minutes after the injury, foam was deployed for the intervention eye according to the device instructions for use. For the control eye, no additional procedures were performed. Six hours post-injury, end A-scan and intraocular pressure (IOP) were measured. Primary study outcome was change in axial length of the globe. Secondary outcomes were as follows: (1) Presence of full anterior chamber collapse, defined as a lack of measurable anterior lens capsule-reflex (ALC-reflex) on A-scan and (2) change in IOP. Outcomes were analyzed as paired intra-animal data, with intervention and control data for each animal. A paired t-test was used to analyze the difference in axial length change and IOP change between treatment groups, whereas a conditional logistic regression was used to analyze dichotomous ALC-reflex outcome and estimate the odds ratio associated with the Eye-Aid device. A significant difference (P < .0001) in mean change in axial length between intervention (-210 μm) and control (-1,202 μm) groups was found. There was a significant difference in ALC-reflex presence, with 79% of eyes having an ALC-reflex in the intervention group, compared to 14% in the control (P = .008). IOP remained higher in the intervention group, with a mean change of -1.5 mmHg for the intervention group compared to -4.0 mmHg in the control (P = .0001). This study describes the first development of an in vivo large animal ocular injury model that realistically approximates the emergent time course and pathophysiology of patients with full-thickness corneal open globe injuries. It also gives the first description of using thermoreversible hydrogel foam for such injuries. Eye-Aid was found to be significantly better than control for treatment of such injuries, based on measurements of both structure and pressure. Assuming that the absence of an ALC-reflex demonstrates complete anterior chamber collapse, the Eye-Aid group demonstrated a 79% eye "save" rate compared to only 14% in the control group, as described earlier. This results in a Number Needed to Treat of 3 for this finding. Eye-Aid additionally demonstrated several characteristics that would be beneficial in a device targeted for emergent deployment by non-ophthalmologists.

Effects of low-frequency voltage on nonlinear standing wave excitation, plasma uniformity, and ion dynamics in dual-frequency asymmetric capacitive discharges

It is known that in very-high-frequency (VHF) capacitively coupled plasmas, the higher harmonics generated by nonlinear sheath motion can enhance the standing wave effect (SWE), which can lead to center-peaked plasma density profiles. In this work, an improved nonlinear electromagnetic model incorporating a transmission line model, an electron momentum balance model, a bulk plasma model, a collisionless nonlinear numerical sheath model, and an ion Monte-Carlo collision (MCC) model is developed to study the effects of low-frequency (LF) voltage VL on the nonlinear standing wave excitation, plasma uniformity, and ion energy and angular distribution functions (IEDFs and IADFs) in dual-frequency (DF) asymmetric capacitive argon discharges at relatively low pressure of 3 Pa. The plasma diffusion in the radial direction and ion dynamics within the LF oscillating sheath are self-consistently considered. The LF voltage VL at 2 MHz varies from 0 to 700 V while the HF voltage VH at 60 MHz is fixed at 100 V. Simulation results indicate that without the addition of an LF source (i.e. VL= 0 V), there are a considerable number of high-order harmonics with short wavelengths, leading to significant SWE and central peak in the radial plasma density profile. Nevertheless, the high-order harmonic excitations tend to be weakened and merely occur around the phase of the full LF sheath collapse due to a shorter characteristic damping time of the surface waves as VL increases. This, combined with increased surface wavelengths of both the driving frequency and the higher harmonics at a higher VL , leads to suppressed standing waves and improved plasma uniformity. Meanwhile, the simulations show that both the low and the high energy peaks of IEDF move towards higher energies, and the energy peak separation width ΔE becomes wider with the increase of VL . The IEDF at the radial center of the powered electrode exhibits a broader ΔE than that at the edge. For the IADF, an increased VL results in more ions incident on the electrode with a smaller deflection angle. Because of a thinner sheath and a higher sheath voltage at the electrode center, the peak value of IADF at the electrode center is greater than that at the edge.

Time-varying spillovers in high-order moments among cryptocurrencies

This study uses high-frequency (1-min) price data to examine the connectedness among the leading cryptocurrencies (i.e. Bitcoin, Ethereum, Binance, Cardano, Litecoin, and Ripple) at volatility and high-order (third and fourth orders in this paper) moments based on skewness and kurtosis. The sample period is from February 10, 2020, to August 20, 2022, which captures a pandemic, wartime, cryptocurrency market crashes, and the full collapse of a stablecoin. Using a time-varying parameter vector autoregressive (TVP-VAR) connectedness approach, we find that the total dynamic connectedness throughout all realized estimators grows with the time frequency of the data. Moreover, all estimators are time dependent and affected by significant events. As an exception, the Russia–Ukraine War did not increase the total connectedness among cryptocurrencies. Analysis of third- and fourth-order moments reveals additional dynamics not captured by the second moments, highlighting the importance of analyzing higher moments when studying systematic crash and fat-tail risks in the cryptocurrency market. Additional tests show that rolling-window-based VAR models do not reveal these patterns. Regarding the directional risk transmissions, Binance was a consistent net transmitter in all three connectedness systems and it dominated the volatility connectedness network. In contrast, skewness and kurtosis connectedness networks were dominated by Litecoin and Bitcoin and Ripple were net shock receivers in all three networks. These findings are expected to serve as a guide for portfolio optimization, risk management, and policy-making practices.

A Global Survey of Gravitationally Deformed Volcanoes on Venus

AbstractGravitational instabilities can develop at volcanoes of any size and in any geological setting and can lead to various types of volcano deformation, ranging from small‐scale landslides on the flanks of the edifice to large, deep‐seated sector collapses. As volcanoes grow, they impose an increasing load on the underlying basement, which can result in styles of gravitational deformation where the edifice sags or spreads outward under its own weight. In this study, we utilize our previously developed global catalog of volcanoes on Venus to analyze a subset of edifices that appears to have undergone gravitational deformation. We identify 162 volcanoes that display morphological evidence for gravitational deformation and classify them into four main categories based on associated deformational structures: landsliding, sector collapse, spreading, and sagging. Landsliding of volcano flanks or full sector collapse are the most common and geographically widespread deformational styles on Venus, and account for ∼64% of our data set. Edifices exhibiting structures linked to volcano spreading and sagging are relatively rare; nonetheless, we note for the first time on Venus the presence on a shield volcano of flank terraces, structures linked to sagging. We find that deformed volcanoes are distributed globally, are found at a range of elevations, are spatially proximal to a variety of tectonic structures, and are associated with various crustal thickness values, which together suggest that there are numerous drivers of volcano deformation on Venus.

High risk of early recurrent stroke in patients with near-occlusion with full collapse of the internal carotid artery.

We aimed to validate the prognostic ability and assess interrater reliability of a recently suggested measurement-based definition of near-occlusion with full collapse (distal ICA diameter ≤ 2.0mm and/or ICA ratio ≤ 0.42). 118 consecutive patients with symptomatic near-occlusion were prospectively included and assessed on computed tomography angiography by 2 blinded observers, 26 (22%) had full collapse. At 2days after presenting event, the risk of preoperative stroke was 3% for without full collapse and 16% for with full collapse (p = 0.01). At 28days, this risk was 16% for without full collapse and 22% for with full collapse (p = 0.22). Interrater reliability was perfect (kappa 1.0). Thus, near-occlusion with full collapse should be defined as distal ICA ≤ 2.0mm and/or ICA ratio ≤ 0.42 in order to detect cases with very high risk of early stroke recurrence.

Analiza elastično-plastičnog naprezanja skupljajućih debelih FGM cilindara

This paper addresses the stress analysis of shrink-fitted thick-walled cylinders made of functionally graded material (FGM). Analytical solutions are provided for the elastic-plastic behavior of shrink-fitted axisymmetric thick-walled FGM cylinders based on the linear plane elasticity theory and plasticity laws. Due to the material's functional gradation, mechanical characteristics like Young's modulus, yield stress, and plastic parameters are controlled by a power function along the wall thickness. Considering a plane strain case, elastic-perfectly plastic model and Von Mises yield criterion; theoretical solutions are obtained for both elastic and plastic phases. The radial, hoop, axial, and equivalent Von Mises stresses are obtained for up to 25%, 50%, and 75% of cylinder plasticization for the elastic and plastic zones. Stresses are given in terms of interference and geometrical and mechanical parameters of the assembly. In addition, the interferences to start plastic deformation and the full plastic collapse of the cylinder are discussed. Moreover, the effect of the gradient index on the contact pressure and both the start of yield and plastic collapse pressures are conducted. The analytical results found in the current research are compared with the numerical solutions carried out by Ansys Workbench. Both results show a good agreement.

Back analysis of a building collapse under snow and rain loads in a Mediterranean area

Abstract. At the end of February 2018 the Mediterranean area of Montpellier in France was struck by a significant snowfall that turned into an intense rain event caused by an exceptional atmospheric situation. This rain-on-snow event produced pronounced damage to many buildings of different types. In this study, we report a detailed back analysis of the roof collapse of a large building, namely Irstea Cévennes. Attention is paid to the dynamics of the climatic event, on the one hand, and the mechanical response of the metal roof structure to different snow and rain loads, on the other hand. The former aspect relies on multiple sources of information that provide reliable estimates of snow heights in the area before the rain came into play and substantially modified the load on the roof. The latter aspect relies on detailed finite-element simulations of the mechanical behavior of the roof structure in order to assess the pressure due to snow and rain loading, which could theoretically lead to failure. By combining the two approaches, it is possible to reconstruct the most probable scenario for the roof failure before its full collapse. As an example of building behavior and vulnerability to an atypical rain-on-snow event in the Mediterranean area of France, this detailed case study provides useful key points to be considered in the future for a better mitigation of such events in non-mountainous areas.

Assessment of radiological dose and emergency planning zones of TRIGA Mark-II research reactor of Bangladesh due to a postulated severe accidental condition

Radiological dose and emergency planning zones assessment has been conducted for dry and rainy seasons in Bangladesh for the TRIGA Mark-II research reactor. A postulated severe accident of a plane crash was considered in this analysis. Due to the full collapse of the reactor building and core damage, core inventory radionuclides were released at their highest release fraction. In this instance, doses due to the release of radionuclides such as Xe, Kr, I, and Cs were estimated using two different atmospheric dispersion models utilizing meteorological data collected from the Bangladesh Meteorological Department. The source term analysis has been performed using the ORIGEN 2.1 code. The HotSpot 3.1.2 and RASCAL 4.3 codes were used for the assessment of radiological doses. Based on the results of both the RASCAL 4.3 and HotSpot 3.1.2 codes, the TEDE and thyroid CDE were found to be substantially higher than the allowable limit in a large area. The dose values were compared to the dose standards of the IAEA General Safety Requirements (GSR) Part 7 and the United States Environmental Protection Agency (U.S. EPA) to identify the evacuation, sheltering and iodine prophylactic administration distances for both dry and rainy seasons. The evacuation and sheltering distances were obtained at approximately 2.25–5 km, 4.5–15 km, and 3–6.6 km, 3.7–8.5 km according to U.S. EPA dose criteria in the dry and rainy seasons, respectively. On the other hand, according to IAEA GSR part 7 dose criteria, the evacuation and sheltering distances are obtained at 1.5–3.5 km and 2.5–5.25 km in the dry and rainy seasons, respectively. Thus required emergency protective actions must be undertaken by the local authority to lessen the health impact on the general public.

Bronchoscopic Lung Volume Reduction: Highlighting the Patient Selection Process

Patients with advanced emphysema frequently experience severe dyspnea that is inadequately treated with medical therapy alone. Over the past 4 years, we have seen increased usage of bronchoscopic lung volume reduction (BLVR) with endobronchial valves. Success of the procedure is dependent on patient selection because it is not necessarily appropriate for all patients with severe emphysema. (Table 1) The purpose of this review is to highlight the selection process at a single institution. We also discuss the influence of this process on outcomes. Between March 1, 2019, and October 12, 2021, 2402 patients were referred to a dedicated chronic obstructive pulmonary disease clinic at Mayo Clinic – Rochester, whereas 161 patients were subsequently referred for multidisciplinary BLVR review. Of those patients, 53 (32.9%) were selected to receive valves and 35 (21.7%) ultimately underwent the procedure. The main reasons for exclusion included an incompatible quantitative computed tomography analysis (n=37, 34.3%), presence of pulmonary nodule or active malignancy (n=14, 13.0%), or need for completion of pulmonary rehabilitation (n=9, 8.3%). Full or partial (>70%) target lobe collapse was observed in 58.6% of patients who received valves. Those with collapse experienced statistically significant improvements in spirometric measures. Twelve patients experienced a pneumothorax (34.3%), with 10 patients requiring thoracostomy tube placement and prolonged hospitalization (median, 11 days; range, 4-39 days). Nineteen patients required a secondary procedure within the first year. The study highlights how a multidisciplinary approach to the BLVR selection process enables individualization of a complex procedure and enhances the exclusion of inappropriate candidates.

Warning of a forthcoming collapse of the Atlantic meridional overturning circulation

The Atlantic meridional overturning circulation (AMOC) is a major tipping element in the climate system and a future collapse would have severe impacts on the climate in the North Atlantic region. In recent years weakening in circulation has been reported, but assessments by the Intergovernmental Panel on Climate Change (IPCC), based on the Climate Model Intercomparison Project (CMIP) model simulations suggest that a full collapse is unlikely within the 21st century. Tipping to an undesired state in the climate is, however, a growing concern with increasing greenhouse gas concentrations. Predictions based on observations rely on detecting early-warning signals, primarily an increase in variance (loss of resilience) and increased autocorrelation (critical slowing down), which have recently been reported for the AMOC. Here we provide statistical significance and data-driven estimators for the time of tipping. We estimate a collapse of the AMOC to occur around mid-century under the current scenario of future emissions.

Precursor of disintegration of Greenland's largest floating ice tongue

Abstract. The largest floating tongue of Greenland’s ice sheet, Nioghalvfjerdsbræ, has been relatively stable with respect to areal retreat until 2022. Draining more than 6 % of the ice sheet, a disintegration of Nioghalvfjerdsbræ's floating tongue and subsequent acceleration due to loss in buttressing are likely to lead to sea level rise. Therefore, the stability of the floating tongue is a focus of this study. We employed a suite of observational methods to detect recent changes at the calving front. We found that the calving style has changed since 2016 at the southern part of the eastern calving front, from tongue-type calving to a crack evolution initiated at frontal ice rises reaching 5–7 km and progressing further upstream compared to 2010. The calving front area is further weakened by an area upstream of the main calving front that consists of open water and an ice mélange that has substantially expanded, leading to the formation of a narrow ice bridge. These geometric and mechanical changes may be a precursor of instability of the floating tongue. We complement our study by numerical ice flow simulations to estimate the impact of future ice-front retreat and complete ice shelf disintegration on the discharge of grounded ice. These idealized scenarios reveal that a loss of the south-eastern area of the ice shelf would lead to a 0.2 % increase in ice discharge at the grounding line, while a sudden collapse of the frontal area (46 % of the floating tongue area) will enhance the ice discharge by 5.1 % due to loss in buttressing. Eventually, a full collapse of the floating tongue increases the grounding line flux by 166 %.

Ca2+ and cAMP open differentially dilating synaptic fusion pores.

Neuronal dense-core vesicles (DCVs) contain neuropeptides and much larger proteins that affect synaptic growth and plasticity. Rather than using full collapse exocytosis that commonly mediates peptide hormone release by endocrine cells, DCVs at the Drosophila neuromuscular junction release their contents via fusion pores formed by kiss-and-run exocytosis. Here, we used fluorogen-activating protein (FAP) imaging to reveal the permeability range of synaptic DCV fusion pores and then show that this constraint is circumvented by cAMP-induced extra fusions with dilating pores that result in DCV emptying. These Ca2+-independent full fusions require PKA-R2, a PKA phosphorylation site on Complexin and the acute presynaptic function of Rugose, the homolog of mammalian neurobeachin, a PKA-R2 anchor implicated in learning and autism. Therefore, localized Ca2+-independent cAMP signaling opens dilating fusion pores to release large cargoes that cannot pass through the narrower fusion pores that mediate spontaneous and activity-dependent neuropeptide release. These results imply that the fusion pore is a variable filter that differentially sets the composition of proteins released at the synapse by independent exocytosis triggers responsible for routine peptidergic transmission (Ca2+) and synaptic development (cAMP).

On Tehching Hsieh’s Disappearance: Interrupting the Prevailing Narratives of the Artworld

Abstract In the Clinton Hill neighbourhood of Brooklyn, New York, sits a nondescript eatery called The Market. The restaurant, like many small New York City restaurants, is unremarkable. Little evidence exists to capitalize on the reputation of its owner, famed performance artist Tehching Hsieh. This article examines Tehching Hsieh’s The Market as a continuation of the artist’s renowned oeuvre to consider how the restaurant might represent Hsieh’s lifelong negotiation of the boundary between art and life. By examining the restaurant as a continuation of Hsieh’s work, I consider how understandings of Hsieh’s life and work are constructed upon binaries of immigrant idealism and art world genius, which exemplify the tension between artistry and livelihoods. In arguing that The Market represents a full collapse of art and life, I consider how the restaurant both refuses such binaries and continues the interrogations of labour, withdrawal, and repetition that are present in Hsieh’s lifeworks.

A comprehensive approach for quantifying the reliability of ship hulls under propagating fatigue cracks

Traditional approaches for reliability assessment of ship hulls under propagating cracks mostly rely on comparing the value of a certain fracture mechanics parameter calculated at the crack tip to the fracture toughness of the material. This assumption may not accurately represent the failure event since the fracture resistance is not only affected by the material properties but also by the component geometry. Furthermore, this approach may not properly account for the possibility of elastic-plastic fracture in the ship hull. This paper presents a novel probabilistic approach for quantifying the reliability of ship hulls under propagating fatigue cracks. The approach utilizes the failure assessment diagram (FAD) to define the performance function of the hull and can account for the occurrence of various possible failure mechanisms ranging from brittle fracture to full plastic collapse. The Weibull stress criterion is utilized to quantify the critical crack tip opening displacement which is adopted herein to represent the fracture resistance of the cracked hull. Monte Carlo simulation is used to quantify the failure probability and the reliability index of the ship hull under encountered wave loads and propagating cracks. The approach is illustrated on a tanker operating in the Atlantic Ocean.

Direct Aspiration versus Combined Technique for Distal Medium-Vessel Occlusions: Comparison on a Human Placenta Model.

Mechanical thrombectomy appears to be a promising option for distal medium-vessel occlusions, for which intravenous thrombolysis is effective but may be insufficient when used alone. This study aimed to determine the optimal technique for these distal mechanical thrombectomies using the human placenta model. Twenty-four procedures were performed, allowing comparison of direct aspiration (n = 12) versus the combined technique (n = 12). Two positions of the aspiration catheter were tested for each of these techniques: in direct contact with the clot and at a distance from it (5-10 mm). Two types of clots were tested: red blood cell-rich clots and fibrin-rich clots. First-pass recanalization and induced arterial collapse and traction were assessed. The first-pass recanalization was less frequent for direct aspiration than for the combined technique, without reaching statistical significance (41.7% versus 75.0%, P = .098). Full collapse (P < .001) and extended arterial traction (P = .001) were significantly less frequent for direct aspiration. For direct aspiration with the aspiration catheter not in direct contact with the clot, there was not a single first-pass recanalization and there was systematic arterial collapse, resulting in a no-flow in the aspiration syringe. The combined technique appears to be more harmful, and although direct aspiration has a lower rate of first-pass recanalization, it seems appropriate to try direct aspiration as a first-line procedure. However, if the aspiration catheter cannot reach the clot, it is not useful or even risky to try aspiration alone. These results need to be confirmed by clinical studies.

Carotid Endarterectomy in Patients with Near Occlusion with Full or Partial Collapse

Carotid Endarterectomy in Patients with Near Occlusion with Full or Partial Collapse

Analysis of progressive collapse process of RC structures based on hybrid framework of FEM-physics engine

High-fidelity collapse process and reasonable debris accumulation and distribution after collapse are very critical to carry out post-disaster investigations and show why collapse happens. Moreover, previous researches on progressive collapse is more concerned with structural behavior in resisting collapse and pays little attention to the dynamic response after collapse criterion is reached. Therefore, a hybrid numerical framework is developed through combining the advantages of the finite element method (FEM) and the physics engine (PE), which provides new ideas for studying the full collapse process of structures. In this paper, based on previous work, such hybrid framework is further developed with efforts on element merging technique in the model mapping process from a FE model to a PE model and determination of connection constraints in the PE model. Then, a new Python-based interface program is developed to integrate the FE model using LS-DYNA and the PE model using Blender 3D. The accuracy of FEM-PE framework is verified by a collapse test of a flat plate structure, and an RC frame structure is designed for studying full process of progressive collapse. Results show that FEM-PE simulation can achieve accurate nonlinear structure behavior at small deformation and high-fidelity collapse at large deformation. To obtain reasonable debris accumulation, a single beam, column and slab should be meshed with the element number no more than 3, 2 and 3 × 3 in PE models, respectively. For a seismically designed RC frame structure, a single column removal scenario cannot initiate the collapse, but the simultaneous removal of a corner and a neighouring penultimate column generates the propagated collapse mode.

Symptomatic and asymptomatic carotid near-occlusions have very similar angiographic appearance on CT-angiography

The aim of this study was to compare the angiographic appearance of symptomatic and asymptomatic carotid near-occlusion. We have found no such previous study. The study hypothesis was that among symptomatic patients with ≥ 50% carotid stenosis, near-occlusion is more common and near-occlusions are more severe than among asymptomatic persons with ≥ 50% carotid stenosis. We reassessed consecutive CTAs from 4042 persons, 645 had ≥ 50% carotid stenosis, and 385 (60%) symptomatic. Near-occlusion was similarly common in symptomatic (105, 27%) and asymptomatic (56, 24%) cases. Among near-occlusions, the angiographic appearance was very similar between symptomatic and asymptomatic cases: mean stenosis lumen diameter (0.7 mm), distal ICA diameter (2.1 mm), and ECA ratio (0.79) were the same in both groups. Mean ICA ratio (0.46 and 0.48) and share of full collapse was very similar (45% and 42%). These findings add to the pathophysiological understanding of carotid near-occlusion.