Local Failure Research Articles

Hypofractionated versus standard fractionation radiotherapy for merkel cell carcinoma

Purpose/Objective(s)Merkel cell carcinoma (MCC) radiation treatment has historically consisted of standard 1.8–2 Gy fractions treated daily over 4–6 weeks. Hypofractionated treatment regimens have demonstrated tumor control and toxicity equivalence to standard fractionation regimens for common cutaneous malignancies such as basal cell and squamous cell carcinomas. Herein we report the outcomes of hypofractionated versus standard fractionation radiotherapy for MCC at our institution.Materials/MethodsThe study involved a retrospective review of MCC patients treated with radiotherapy. Treatment characteristics and patient outcomes, including acute toxicities, disease recurrence and survival data were collected. The cumulative incidence of local and distant failures was estimated, with death as a competing risk.ResultsA total of 29 treatment courses for 24 patients were included, of which 13 involved standard fractionation with curative intent, 10 involved hypofractionated radiotherapy with curative intent, and 6 involved single fraction (8 Gy) palliative radiation. Half the patients were treated to a head/neck site. A subset of patients treated adjuvantly with curative intent included 8 standard fractionation and 8 hypofractionated radiotherapy patients. No statistically significant differences in local and/or distant failure or overall survival was observed between the patient groups.ConclusionHypofractionated radiotherapy for MCC was associated with similar treatment outcomes relative to standard fractionation. In our limited patient sample, hypofractionated radiation treatment achieved similar results with similar toxicity and fewer treatments. Further analysis of a larger patient population with longer follow up is needed to confirm treatment tolerability and efficacy.

Progressive failure analysis of laminates with an open hole subjected to compressive loading (OHC) using the enhanced semi-discrete modeling framework

The Open-hole compressive (OHC) strength of a fiber reinforced laminate is one of the most critical allowables for design of aerostructures. In this paper, results for predicting the OHC strength using the semi-discrete damage modeling framework are presented. The predictions are seen to capture experimentally observed failure mechanisms and measured failure loads. The constitutive model includes local axial compressive failure (and subsequent load bearing at a reduced plateau stress) while maintaining numerical robustness. Standard stacking sequences (quasi-isotropic, “hard” and “soft”) have been analyzed and compared to publicly available databases. Additionally, the model is challenged to predict delamination-dominated failure due to ply-scaling. Overall, the model is able to capture relevant failure mechanisms, while the ultimate loads are predicted with good accuracy. Therefore, this framework can be used with confidence in predicting OHC strengths of laminates.

Effectiveness of radiotherapy in delaying treatment changes in primary or secondary immunorefractory oligoprogressive patients: preliminary results from a single-center study.

To investigate whether the addition of radiotherapy could be an appropriate option to delay the time-to-next systemic treatment (TTNsT) in patients with oligoprogressive solid tumors who had acquired or innate resistance to immune checkpoint inhibitors (ICIs). Patients with oligoprogressive disease treated with ICIs and radiotherapy at our Institute from January 2019 to June 2023 were retrospectively identified. Patients were stratified as primary or secondary immunorefractory according to the time of onset of ICI resistance. TTNsT and Time-To-Resistance (TTR) were the primary outcomes. Secondary outcomes included: post-radiotherapy first progression-free survival (pR-PFS), Local Control (LC), Overall Survival (OS), and treatment-related toxicities. In addition, out-of-field effects (such as the abscopal effect) of radiotherapy have been hypothesized. The survival rates were analyzed using the Kaplan-Meier method and long-rank test. 40 out of 105 screened patients with oligoprogressive disease met the inclusion criteria. Of these, 28 had an acquired drug resistance while 12 had an innate drug resistance. Radiotherapy was offered as a local treatment approach in all patients. RT techniques were classified into three regimens: standard palliative hypofractionated radiotherapy (hypo-RT), stereotactic radiotherapy (SRS/SBRT), and lattice radiotherapy (LRT). After a median follow-up of 22.5months, the median TTR was 4months (range 3-4) in patients with innate resistance vs 14months (range 7-36) in patients with acquired resistance. Median TTNsT among patients with acquired and those with innate resistance was not reached (NR) vs 24months (range 7-72). Overall, only six patients suffered from a local failure. Although out-of-field effects of radiotherapy were hypothesized, we were unable to record them as they did not occur during the observation period. Regardless of the radiation dose, there was no observable ≥ Grade 2 acute or late treatment-related toxicity. Our preliminary results seem to confirm that the integration of radiotherapy and ICIs may allow for the continuation of systemic therapy beyond progression, which can have a subsequent benefit in terms of survival outcomes even in patients with innate resistance.

Size-Dependent Mechanical Properties and Excavation Responses of Basalt with Hidden Cracks at Baihetan Hydropower Station through DFN–FDEM Modeling

Basalt is an important geotechnical material for engineering construction in Southwest China. However, it has complicated structural features due to its special origin, particularly the widespread occurrence of hidden cracks. Such discontinuities significantly affect the mechanical properties and engineering stability of basalt, and related research is lacking and unsystematic. In this work, taking the underground caverns in the Baihetan Hydropower Station as the engineering background, the size-dependent mechanical behaviors and excavation responses of basalt with hidden cracks were systematically explored based on a synthetic rock mass (SRM) model combining the finite-discrete element method (FDEM) and discrete fracture network (DFN) method. The results showed that: (1) The DFN–FDEM model generated based on the statistical characteristics of the geometric parameters of hidden cracks can consider the real structural characteristics of basalt, whereby the mechanical behaviors found in laboratory tests and at the engineering site could be exactly reproduced. (2) The representative elementary volume (REV) size of basalt blocks containing hidden cracks was 0.5 m, and the mechanical properties obtained at this size were considered equivalent continuum properties. With an increase in the sample dimensions, the mechanical properties reflected in the stress–strain curves changed from elastic–brittle to elastic–plastic or ductile, the strength failure criterion changed from linear to nonlinear, and the failure modes changed from fragmentation failure to local structure-controlled failure and then to splitting failure. (3) The surrounding rock mass near the excavation face of underground caverns typically showed a spalling failure mode, mainly affected by the complex structural characteristics and high in situ stresses, i.e., a tensile fracture mechanism characterized by stress–structure coupling. The research findings not only shed new light on the failure mechanisms and size-dependent mechanical behaviors of hard brittle rocks represented by basalt but also further enrich the basic theory and technical methods for multi-scale analyses in geotechnical engineering, which could provide a reference for the design optimization, construction scheme formulation, and disaster prevention of deep engineering projects.

On the nature of nano twin-induced shear band formation in a dispersion strengthened copper alloy under micro-mechanical loading

A key challenge in metallic alloys with high ductility is understanding how microstructural inhomogeneities influence shear localization, leading to localized plastic deformation and material failure. In this study, we explore the phenomenon of shear localization in coarse-grained copper, a material traditionally regarded as having low susceptibility to such behavior. Contrary to conventional understanding, our findings reveal that microstructural inhomogeneities play a pivotal role in inducing extensive strain localization during low strain rate micro-mechanical loading. The presence of fine precipitate particles leads to strain localization at small strains and low strain rates by activating shear localization driven by void formation mechanisms. Furthermore, nanoscale precipitates act as sites for dislocation pile-up within deformed structures of shear bands, leading to the formation of nano twins within these bands. Consequently, precipitate particles serve a dual role: contributing to strain localization and potential cracking, while also enhancing the alloy’s strength and ductility through nano-twinning mechanisms. This investigation offers a novel perspective on the interplay between material microstructure and deformation behavior, challenging existing paradigms in materials science.

Study on Dynamic Mechanical Properties and Failure Pattern of Thin-Layered Schist

This paper studies the effect of schistosity on the dynamic mechanical properties and failure pattern of thin-layered schist. Wudang Group schist with thin layers is selected as the research object, and the influence of the dynamic mechanical properties and failure pattern of schist under different angles and spacing is studied by combining an SHPB test and numerical simulation. The results indicate that under dynamic loading, the stress–strain curve demonstrates elastic compression, plastic deformation, and strain softening stages. Moreover, it is observed that the dynamic critical failure strength of schist exhibits typical “U”-type strength anisotropy. Specimens with a schistosity angle of 0° or 90° exhibit higher dynamic compressive strength under dynamic loading, with axial splitting and schistosity splitting as predominant failure modes. Conversely, when the schistosity angles are 30°, 45° or 60°, there is a noticeable decrease in compressive strength accompanied predominantly by shear failure along with local compressive shear failure. We additionally noted that as the spacing between schists decreases from 22 mm to 7 mm, there is a gradual reduction in dynamic compressive strength by approximately 20.3%.

CT-guided microcoil versus hook-wire localization of pulmonary nodule prior to video-assisted thoracoscopic surgery without fluoroscopic guidance

BackgroundBoth microcoils and hook-wires are commonly utilized for preoperative pulmonary nodule localization due to their convenience, but it remains unclear which one should be prioritized for recommendation.AimsTo compare the safety and efficacy of microcoils and hook-wires for pulmonary nodule localization.MethodsFrom January 2021 to December 2021, 310 consecutive patients (113 males and 197 females) with 341 pulmonary nodules who underwent CT-guided microcoil or hook-wire localization prior to video-assisted thoracoscopic surgery (VATS) at our center were retrospectively included in this study. There were 161 patients in the microcoil group and 149 patients in the hook-wire group. The successful localization rate, complication rate, radiation exposure, and medical costs were compared between the two groups.ResultsA total of 341 pulmonary nodules were localized, with a success rate of 99% (180/184) in the microcoil group and 93% (146/157) in the hook-wire group, respectively. All patients successfully underwent VATS. Multivariate analysis revealed that hook-wire localization, shorter needle depth into the lung tissue and the longer waiting time from localization to VATS were the risk factors for the localization failure. The incidences of pneumothorax in the microcoil group and hook-wire group were 34.8% (56/161) and 34.9% (52/149), respectively (P = 0.983). The incidences of pneumorrhagia were 13% (24/184) and 46.5% (73/157), respectively (P = 0.000). Multivariate analysis revealed that hook-wire localization and greater depth of needle penetration into lung tissue were risk factors for pneumorrhagia.ConclusionMicrocoil localization of pulmonary nodules is superior to hook-wire localization in terms of efficacy and safety. This finding provides insight into priority and broader promotion of microcoil localization.

Regularity and correlation analysis of regional lymph node metastasis in nonoperative patients with non-small cell lung cancer based on positron emission tomography/computed tomography images

BackgroundDefinitive concurrent chemoradiotherapy (CCRT) is the standard treatment for locally advanced, inoperable non-small cell lung cancer (NSCLC). Previous studies have mainly focused on examining local failure and recurrence patterns after surgery and the principles of lymph node metastasis (LNM) in surgical candidates with NSCLC. However, these studies were just only able to guide postoperative radiotherapy (PORT) and the patterns of LNM in patients with resected NSCLC was inadequate to represent that in locally advanced inoperable NSCLC patients for guiding target volume delineation of CCRT. In this study, we aimed to analyze the metastasis regularities and establish the correlations between different lymph node levels in NSCLC patients without any intervention using positron emission tomography/computed tomography (PET/CT) images.MethodsOverall, 358 patients with N1–N3 NSCLC admitted in our hospital between 2018 and 2022 were retrospectively analyzed. The diagnosis of metastatic lymph nodes was reviewed and determined using the European Organization for Research and Treatment of Cancer standard and the standardized value of the PET/CT examination. Univariate and multivariate analysis were performed to investigate the correlations between the different levels were evaluated by using of the chi-square test and logistic regression model.ResultsThe lymph nodes with the highest metastasis rates in patients with left lung cancer were in order as follows: 10L, 4L, 5, 4R, and 7; while in those with right lung cancer they were 10R, 4R, 7, 2R, and 1R. Notably, we found left lung patients were more likely to have contralateral hilar, mediastinal and supraclavicular lymph nodes involved, and the right lung group exhibited a higher propensity for ipsilateral mediastinum and supraclavicular lymph node invasion. Furthermore, correlation analysis revealed there were significant correlative patterns in the LNM across different levels.ConclusionsThis study elucidated the patterns of primary LNM in patients with NSCLC who had not undergone surgery (without any treatment interventions) and the correlations between lymph node levels. These findings were expected to provide useful reference for target volume delineation in definitive concurrent chemoradiotherapy in locally advanced NSCLC patients.

Seismic behaviour and design of a tall mixed reinforced concrete–steel structure supporting an oil refinery reactor

AbstractThis study investigates the seismic behaviour of a special mixed reinforced concrete-steel structure that supports an oil refinery reactor. The structure is 64.90 m tall and consists of three parts: (a) a reinforced concrete frame basement; (b) a steel braced frame that supports the oil reactor and (c) the steel reactor itself. A three-dimensional model of the structure is created to perform static non-linear (pushover) analyses in order to obtain the capacity curves and understand the overall inelastic behavior of the structure. The results of the pushover analyses reveal that the structure exhibits similar inelastic behavior in both horizontal directions and satisfies the capacity design principles. The structure exhibits limited ductility considering the fact that has been designed with a behavior factor of q = 1.5 and primary damages are expected mainly in concrete members. Subsequently, dynamic non-linear time-history (NLTH) analyses are performed utilizing the three translational components of three seismic motions recorded during past earthquakes. These results involve: (i) the maximum values for displacements, accelerations and base shears; (ii) the maximum stresses at critical points of the oil refining reactor and (iii) the formation of plastic hinges at columns, beams and braces of the structure. Contrary to pushover analyses, NLTH analyses revealed the development of plastic hinges, hence seismic damage, that do not follow the desirable formation pattern. Moreover, the accelerations and displacements observed are expected to cause failure of the piping and mechanical equipment, while local failure of the high-stress areas of the shell of the reactor may be possible. Localized strengthening might be necessary to avoid repair works and downtime after such seismic event.

DEM study of structuralized cemented slopes under excavation conditions

Structuralized cementation has emerged as a promising method for reinforcing excavated slopes. The Discrete Element analysis is conducted on the structuralized cemented slopes under excavation with its validity verified through centrifuge model tests. The results indicate that structuralized cemented slopes exhibit progressive failure from the bottom to the top under excavation conditions. As the slope elevation decreases, the failure mode transitions from tension failure to shear failure, due to the presence of tensile stress only in the upper part of the slope. Microscopically, structuralized cementation prevents contact breakage, reducing fabric anisotropy and the variation of contact orientation from the vertical direction. Macroscopically, it increases the safety limit of slopes. The significant coupling between fabric evolution localization and local failure explains the failure mechanism of structuralized cemented slopes under excavation conditions. Increasing the size of the solidification zone reduces the localization extent of fabric evolution, thereby reinforcing the slope.

Re-irradiation of anaplastic meningioma: higher dose and concomitant Bevacizumab may improve progression-free survival

IntroductionAnaplastic meningiomas, categorized as WHO grade 3 tumors, are rare and highly aggressive, accounting for 1-2% of all meningioma cases. Despite aggressive treatment, including surgery and Radiation, they exhibit a high recurrence rate and poor survival outcomes. The aggressive histopathological features emphasize the urgent need for effective management strategies.MethodsA retrospective multi-institutional analysis was conducted on patients with recurrent anaplastic meningioma who underwent re-irradiation between 2017 and 2023. Clinical, dosimetric, and outcome data were collected and analyzed, focusing on local control, progression free survival and treatment-related adverse events.ResultsThirty-four cases were analyzed, with a median follow-up 11 months after re-irradiation. Progression-free survival at 12 months was 61.9%, with higher doses correlating with better outcomes. Concomitant Bevacizumab improves progression-free survival and reduces the risk of radiation necrosis. CDKN2A homozygote deletion correlated with a higher risk of local failure. Symptomatic radiation necrosis occurred in 20.5% of cases, but its incidence was lower with concomitant Bevacizumab treatment.ConclusionRe-irradiation presents a viable option for recurrent anaplastic meningioma despite the associated risk of radiation necrosis. Higher doses with concomitant Bevacizumab improve clinical outcomes and reduce toxicity. Individualized treatment approaches are necessary, emphasizing the importance of further research to refine management strategies for this challenging disease.

Salvage interstitial brachytherapy for treatment of recurrent endometrial cancers in the vagina: Seven-year single institution experience and review of second recurrence patterns

IntroductionInterstitial brachytherapy (ISBT) is a known treatment for vaginal recurrence of endometrial cancer. This study reviews a large tertiary institution's ISBT experience and outcomes for vaginal recurrences. Material and MethodsPatients who underwent salvage ISBT for vaginal recurrence of endometrial cancer from January 1, 2014 - August 31, 2021, were identified. Initial and salvage disease factors and treatments were recorded. Outcomes were calculated including overall survival, local, and distant failure. ResultsThirty-nine patients were included; thirty received external beam radiotherapy and interstitial brachytherapy (EBRT + ISBT) while nine received ISBT alone. At initial diagnosis, the ISBT alone group had an older median age, with stage IA-IV disease, frequently receiving adjuvant treatment, compared to the EBRT with ISBT group with mainly stage IA disease who did not. Median follow up was 22 months and median time to recurrence 14 months (16.5 months in EBRT + ISBT group and 14 in the ISBT alone group). Two-year overall survival was 85% for all patients, 85.6% and 83.3%in the EBRT + ISBT and ISBT alone groups, respectively. Local failure was 22.7% for all patients,16.7% in the EBRT + ISBT group and 11.1% in the ISBT alone group. Median HRCTV D90 (EQD2) was 76.8 Gy in the EBRT + ISBT group, and 57.9 Gy in the ISBT alone group. Late grade 3 or higher toxicity occurred in only three patients. ConclusionsEBRT + ISBT is an effective treatment for endometrial cancer vaginal recurrence, with acceptable toxicity. ISBT alone is an option for patients with contraindications to or with previous treatment of pelvic radiation.

Usefulness of using the superficial temporal pedicle as the recipient site for microvascular anastomosis in facial reconstruction: A retrospective study of 94 cases

In cranio-cervico-facial reconstructive surgery, it is accepted that the use of free flaps is the treatment of choice. The multiple antecedents can place the surgeon in situations of vascular deserts. The aim of our study is to report and analyse our experience of the use of temporal vessels in primary and secondary reconstructive surgery. A retrospective study was conducted between 01/01/2010 and 31/03/2023. Patients who underwent cranio-cervico-facial reconstruction using free flaps, with use of the superficial temporal pedicle as the recipient site for the vascular anastomosis were included. Early and late complication and failure rates were analysed according to type of reconstruction, location and risk factors for free flap failure. A total of 94 patients underwent craniocervical-facial reconstruction using a free flap anastomosed to the superficial temporal pedicle (in primary or secondary situations). Ten patients underwent reconstruction of the upper third, 58 the middle third and 26 the lower third. With an overall complication rate of 28.7% (21.3% minor complications and 7.4% major complications). Our study proves the reliability of the superficial temporal pedicle, both in the primary situation (with a success rate of 93.9%) and in the secondary situation (with a success rate of 89.3%), as well as its versatility whatever the cranio-cervico-facial level to be reconstructed. This study demonstrates the value of preserving the superficial temporal pedicle in craniofacial reconstruction surgery. This is because it is a preferred recipient site for reconstructions of the upper and middle thirds in the primary situation or in the event of recourse.

Analysis of fuel storage tanks under internal deflagrations with different venting technologies: an experimental and numerical study

This study investigates small-scale fuel storage tanks subjected to internal methane-air explosions, focusing on three depressurization technologies using roof ventilation to mitigate overpressure and damage. Tests with low methane-air concentrations were conducted to generate a pseudo-static internal pressure. This approach minimized scale effects and aligned internal pressure frequency with real-scale tank behavior during deflagrations. The first prototype features a tank with a frangible roof activated by localized brittle failure of stitch welds around the roof-to-shell junction. This confirms that stitched weld patterns ensure controlled brittle failure with activation pressure estimated by a simplified equation. The second technology employs a sequential ventilation strategy, starting with a small hinged panel followed by stitch weld failure, managing low to medium-intensity explosions with the small vent alone, and allowing rapid operational recovery. In severe explosions, the hinged door facilitates earlier activation of the frangible roof, reducing the initial pressure rise rate and controlling the roof opening direction. Lastly, the study explores tanks with commercial explosion vent panels as an alternative to traditional frangible roofs, offering a practical solution for retrofitting existing tanks. Each technology enhances safety in fuel storage facilities by effectively managing internal pressures during explosive events.

Supraclavicular lymph node metastasis should not be defined as regional lymph node metastasis in cervical and upper thoracic esophageal squamous cell carcinoma.

The importance of supraclavicular lymph node (SCLN) metastasis in cervical and upper thoracic esophageal squamous cell carcinoma (ESCC) has not been determined. The aim of the present study was to provide a detailed definition of the range of SCLN regions and to explore whether SCLNs should be considered as a regional lymph nodes for patients with cervical and upper thoracic ESCC. A retrospective analysis was performed on 230 patients with locally advanced cervical or upper thoracic ESCC who underwent radical radiotherapy and chemotherapy. The range of SCLN regions was defined in detail on contrast enhanced computed tomography images of the neck. According to whether the patient had lymph node metastasis in the supraclavicular region, the included patients were divided into two groups, and the survival differences and reasons for treatment failure between the two groups were analyzed. Of the 230 patients with ESCC, 71 (30.87%) exhibited lymph node metastases in the supraclavicular region. The median overall survival time of ESCC patients with and without SCLN metastasis was 17 and 30 months, respectively (P<0.001). After propensity score matching (PSM), the median overall survival time of ESCC patients with and without SCLN metastasis was 17 and 28 months, respectively (P<0.001). During the follow-up period, there were a total of 101 cases of failure of treatment in the irradiation field, 6 cases had esophageal metastasis in the non-irradiated field and 27 cases had regional lymph node metastasis in the non-irradiated field. In addition, there were 33 cases of metastasis to the distant lymph nodes or organs. There was no significant difference in the local treatment failure rate between the groups with or without SCLN metastasis in both the irradiation field and the non-irradiation field, but the probability of distant metastasis in the SCLN metastasis group was significantly higher than that in the group without SCLN metastasis (P=0.025). In conclusion, patients with cervical and upper thoracic ESCC with SCLN metastasis have a poor prognosis and the median overall survival time is closer to that of metastatic ESCC than ESCC with regional lymph node metastasis; therefore, SCLNs should not be defined as regional lymph nodes in patients with cervical and upper thoracic ESCC.

Acoustic emission monitoring of a large-scale 50-year-old prestressed concrete bridge girder during an eccentric three-point bending test

Deterioration of reinforced and prestressed concrete structures is one of the main challenges in structural engineering. As the majority of our infrastructure is built around 1960-1980, most structures have reached or will soon reach their design lifetime, giving rise to more structural problems and costs in the coming decades. It is therefore important to develop efficient assessment schemes allowing to assure the safety and reliability of these existing structures and to estimate their residual lifetime. Within the framework of the Bridge|50 research project, a 50-year-old prestressed concrete bridge showing signs of corrosion damage was decommissioned. The bridge girders were recovered and have been subjected to large-scale load tests with varying loading patterns. This paper presents the results acquired during acoustic emission (AE) monitoring of one of the I-shaped girders during a monotonic three-point bending test with an eccentric point load. The results show that the failure mode and location could be detected based on AE activity and zonal AE localization. The onset of concrete cracking was observed by a decrease in peak frequency of the AE signals. Average frequency (AF) and rise angle (RA) value analysis was used to characterize the crack mode, which shifted from tensile to shear mode during bending.

Assessment of aluminium alloys’ formability by elevated temperature testing

Abstract This work presents an investigation of the warm formability of AA7075-T6 aluminium alloy sheets using both experimental and numerical methods. Forming limit diagrams (FLDs) can be created by plotting the failure criteria on a graph with two axes representing major and minor strains. Sheets with a grid can be used to quantify both large and minor strains. General techniques available for the grid involve regular patterns of circles in this experiment. Experiments were conducted at various temperature levels, including room temperature, 100, 120, 140, 160, and 180 °C, as well as different strain rates. The investigation has revealed a significant impact of temperature on formability, while the effect of forming speed is quite insignificant across the whole range studied. At an ageing temperature of 140 °C, the distribution of precipitates is evenly balanced, resulting in improved mechanical strength. To offer accurate numerical models for warm-forming processes, a proposed constitutive model is introduced for aluminium alloy sheets. The present model incorporates plastic anisotropy and the effects of temperature and strain rate dependence. An investigation was conducted on the stress-strain behaviour of thin sheets composed of AA7075-T6 aluminium alloy under elevated temperatures and different strain rates. The objective was to ascertain the appropriate fitting parameters. It was associated with ABAQUS finite element modelling. The recommended material model was utilized to build finite element models, which were subsequently compared to the experimental data. The findings obtained from simulated isothermal uniaxial tensile tests were compared to the empirical measurements. The models used in the tensile test accurately predicted the material’s mechanical response. The predicted failure location, punch forces, and strain distributions for all three forming processes were found to be in close agreement with the experimental results. During deep draw operation, the warm forming limit curves were utilized to precisely predict both the pierce depth at which failure occurs and the precise location where the failure initiates.

Spinal laser interstitial thermal therapy and radiotherapy for thoracic metastatic epidural spinal cord compression.

Spinal laser interstitial thermal therapy (sLITT) is a less invasive alternative to surgery for metastatic epidural spinal cord compression. Here, we analyze outcomes of patients treated with sLITT either in conjunction with radiotherapy or as a standalone salvage therapy. We included patients with thoracic vertebral metastatic cord compression treated with sLITT. Outcomes included freedom from local failure (FFLF) and overall survival (OS). Factors associated with FFLF were identified with univariable and multivariable analyses via a Cox proportional hazards model. Between 2013-2022, 129 patients received sLITT to 144 vertebral segments; 69% were radiotherapy naïve, 81% were radioresistant histologies, and 74% were centered in the vertebral body. Median age was 61 years. Pre-sLITT Bilsky score was 3 in 28%, 2 in 33%, and 1c in 37%. Radiotherapy was delivered in conjunction with sLITT for 80% of cases, including 68% that received stereotactic radiotherapy, at a median of 5 days after sLITT. Median follow-up was 9.1 months. One-year FFLF and OS was 80% and 78%, respectively. On multivariable analysis, variables independently associated with adverse FFLF included paraspinal/foraminal disease location (p = 0.001), and post-sLITT imaging Bilsky score of 2 (p = 0.073) or 3 (p = 0.011). Prior radiotherapy, technique of radiotherapy, and time between radiotherapy and sLITT were not associated with FFLF. sLITT with radiotherapy is an effective minimally invasive treatment approach for thoracic metastatic epidural spinal cord compression. Early treatment response may serve as a prognostic imaging biomarker.

Experimental investigation on the fracture process and infrared radiation characteristics of structure rockburst under gradient loading

To investigate the macroscopic failure characteristics and infrared thermal imaging evolution of structure rockburst under gradient stress, gradient stress loading simulation tests were conducted using a true triaxial rockburst testing apparatus with combined gradient and hydraulic-pneumatic loading. Tests included three stress gradient coefficients and four structural surface angles. Macroscopic failure observations and infrared thermal imaging of the unloading surfaces were analyzed to understand the characteristics of structure rockburst and the influence of structural surfaces. Two infrared thermal imaging evolution parameters, the relative temperature mean (HRT) and the coefficient of variation (COV), were introduced to explore precursor indicators of structure rockburst. The results indicated that: (1) The dip angle of the structural surface (θ) and the stress gradient coefficient (k) both affect the peak stress during rockburst. (2) The structural surface angle significantly influences rockburst characteristics: θ = 30° or 60° results in shear slip-type rockbursts along or exposed on the structural surface, while θ = 0° or 90° manifests as buckling and tensile cracking-type rockbursts. (3) Infrared thermal imaging reveals that from initial loading to rockburst, temperature distribution transitions from uniform to normal, and then to non-normal. Accumulation of high-temperature points near rockburst indicates failure locations, with increased k intensifying non-normal distribution. (4) Peak values of HRT and COV positively correlate with k. (5) Fluctuations or sharp increases in HRT and COV values serve as precursors for predicting debris spalling and rockburst events.

Effect of loading rate on local deformation of rock-like models with locked segment

To investigate the influence of loading rate on the local deformation and failure characteristics of rock-like models with a locked segment, this study fabricated them using quartz sand and barite powder as aggregates, and gypsum as cementing material. Uniaxial compression tests, combined with strain cube monitoring and the digital image correlation technique, were employed to analyze the mechanical properties, internal and external deformation characteristics, crack propagation, and failure modes at different loading rates. The results showed that as the loading rate increased, the strength of these models initially increased significantly and then slightly decreased, primarily due to the complex interaction between the longitudinal and transverse deformations of the models and the stress concentration intensity at the crack tips. The fluctuation in the principal strain axis's deflection angle revealed the complex process of stress wave propagation and particle adjustment within the models, with more pronounced fluctuations observed at higher loading rates. The stress intensity factors, KIand KII, at the crack tips first increased and then decreased with increasing loading rate, with KI consistently higher than KII. The strain concentration phenomenon in the rock-like models occurred earlier with increasing loading rates, and the corresponding crack closure stress exhibited a decreasing trend. Higher loading rates caused earlier crack initiation and faster propagation. As the loading rate increased, the crack paths shortened, and both damage density and severity increased significantly, indicating brittle failure. This study provides important experimental evidence and theoretical support for understanding the effects of loading rate in rock mass engineering.