Distinct Failure Patterns Research Articles

SURG-11. PATTERNS OF RECURRENCES OF OLFACTORY NEUROBLASTOMA AFTER SURGICAL RESECTION

Abstract INTRODUCTION Patterns of failure in patients with olfactory neuroblastoma (ONB) according to two surgical approaches, craniofacial resection (CFR) and endoscopic surgery (ENDO), have yet to be analyzed. METHODS We retrospectively reviewed 30 patients with surgically treated ONB between January 1995 and October 2018. Sixteen (53.3%) patients underwent CFR (9 CFR alone, 7 ENDO-assisted CFR) and 14 (46.7%) underwent ENDO. Twenty-one (70.0%) patients underwent post-operative radiotherapy (RT). RESULTS At a median follow-up of 53.8 months (range 10.4–195.3), the 5-year progression-free survival (PFS) and 10-year overall survival were 37.3% and 57.5%, respectively. Patients with adjuvant RT had a 5-year PFS of 46.7%, whereas those treated with surgery alone had a 5-year PFS of 19.4% (p = 0.01). Locoregional failure (LRF) occurred in ten patients (median 59.6 months after initial diagnosis; range 12.7–59.7). Neck node metastasis occurred in 23.3% (7 of 30). Five patients with ENDO showed LRF and underwent proper subsequent treatments with either surgery or adjuvant RT. Approximately 31.3% patients (five patients) in the CFR group experienced distant metastasis in the intracranial dura region (median 116.4 months after initial diagnosis; range 2.6–142.4). Three of four patients who developed LRF after CFR developed dura-based metastasis. CONCLUSIONS Both dura-based and neck node metastasis in the delayed phase were distinct patterns of failure in ONB. Patterns of recurrence differed based on surgical approach; dura-based metastases were common after CFR. LRF was the distinct failure pattern in ENDO, but could be successfully salvaged. Treatment outcome was improved considerably with RT following surgical resection.

Effects of height/diameter ratio on failure and damage properties of granite under coupled bending and splitting deformation

In underground mining, rock roofs with different thicknesses have distinct failure patterns under the complex stress. To understand the height/diameter ratio (H/D) on failure properties and damage characteristics under the coupled bending and splitting deformation, a series of point-bending tests were conducted on granite disc samples with the same diameter but different heights. The micro-crack evolution during the test was measured and recorded by acoustic emission experiments. Test results indicated that the height/diameter ratio determines the failure mode of granite samples. The sample with the H/D less than 0.4 is primarily fractured in the bending mode. Once the H/D exceeds 0.4, the failure pattern transforms into the splitting pattern. According to analysis of the ringing count rate in the acoustic emission signals, more than 60% of the damage accumulates rapidly in the yield stage, while the damage in other stages increases steadily. In addition, the damage evolution curves calculated from the plastic region are consistent with those calculated by the ringing count rate, so that the damage properties of the granite disc samples are obtained under the complicated stress. The rapid accumulation of the damage indicates the sharp change of the stress inside the rock sample, which is the precursor information of the failure of rock samples.

An experimental investigation on Parallel Bamboo Strand Lumber specimens under quasi static and impact loading

This paper investigates the compression behaviour of 42 Parallel Bamboo Strand Lumber (PBSL) specimens under quasi-static and drop-weight impact loading. 25 mm × 25 mm square specimens with varying heights and fibre orientations were tested to investigate compression and impact resistance of PBSL. Quasi-static results indicated a distinct 5-stage failure pattern for the complete quasi-static loading history with a 45° failure plane in all specimens when the compression load was applied parallel to the fibres. Specimen height did not affect the ultimate load carrying capacities but showed considerable influence on the initial stiffness as well as the post-ultimate loading regime. Experimental results showed that the deformation ratio and the energy absorption ratio for longer specimens were not affected by fibre orientations. Low-velocity drop-weight impacts were conducted under 25.4 J and 101.5 J energy levels. Specimen height did not play any significant factor during impact testing. The initial impact level dominated the maximum deformation and dynamic energy absorption observed in specimens that failed showing a 4-stage deform procedure. Although the deformation patterns between fibre orientations were distinctly different, similar energy absorption capacities were obtained regardless of specimen height. Comparison of experimental evidences obtained from quasi-static and drop-weight impact tests clearly showed that the compression response of PBSL is strain-rate sensitive.

Patterns of failures after surgical resection in olfactory neuroblastoma.

Patterns of failure in patients with olfactory neuroblastoma (ONB) according to two surgical approaches, craniofacial resection (CFR) and endoscopic surgery (ENDO), have yet to be analyzed. We retrospectively reviewed 28 patients with surgically treated ONB between January 1995 and October 2017. Fourteen (50.0%) patients underwent CFR (9 CFR alone, 5 ENDO-assisted CFR) and 14 (50.0%) underwent ENDO. Nineteen (67.9%) patients underwent post-operative radiotherapy (RT). At a median follow-up of 53.8months (range 10.4-195.3), the 5-year progression-free survival (PFS) and 10-year overall survival were 37.3% and 57.5%, respectively. Patients with adjuvant RT had a 5-year PFS of 46.7%, whereas those treated with surgery alone had a 5-year PFS of 19.4% (p = 0.01). Locoregional failure (LRF) occurred in ten patients (median 59.6months after initial diagnosis; range 12.7-59.7). Neck node metastasis occurred in 25.0% (7 of 28). Five patients with ENDO showed LRF and underwent proper subsequent treatments with either surgery or adjuvant RT. Approximately 35.7% patients (five patients) in the CFR group experienced distant metastasis in the intracranial dura region (median 116.4months after initial diagnosis; range 2.6-142.4). Three of four patients who developed LRF after CFR developed dura-based metastasis. Both dura-based and neck node metastasis in the delayed phase were distinct patterns of failure in ONB. Patterns of recurrence differed based on surgical approach; dura-based metastases were common after CFR. LRF was the distinct failure pattern in ENDO, but could be successfully salvaged. Treatment outcome was improved considerably with RT following surgical resection.

The Role of Elasto-Plasticity in Cavity Shape and Sand Production in Oil and Gas Wells

Summary Previous experimental observations have shown the formation of distinct failure patterns and cavity shapes under different stress and flow conditions. With isotropic stress, spiral failure patterns with localized shear bands are likely to form. On the other hand, under anisotropic stress, V-shaped cavities, dog-ear cavities, or slit-mode cavities are usually observed. However, the mechanisms for the development of these sanding cavities have not been fully articulated. In addition, to accurately predict the onset of sanding and to predict the sand-production rate, it is crucial to capture the physics of the formation of these cavities during sand production. This paper presents a fully coupled poro-elasto-plastic, 3D sand-production model for sand-production prediction around openhole and perforated wellbores in a weakly consolidated formation. Sanding criteria are based on a combination of shear failure, tensile failure, and compressive failure from the Mohr-Coulomb theory and strain-hardening/softening. After the failure criteria are met, an algorithm for the entrainment of the sand based on the calculation of hydrodynamic forces is implemented to predict sand erosion and transport. Dynamic mesh refinement has been implemented to effectively capture the strain-localization regions. The model has been validated with multiple analytical solutions. In addition, it is applied to compare with previous sand-production experiments that have explored the different cavity shapes formed under different conditions. The model is capable of not only explaining the mechanisms responsible for each type of cavity shape but also predicting the cavity shape that will be formed under a specific set of conditions. Parametric studies for these cases provide an additional insight into the important role that the post-yield, poro-elasto-plastic properties of the sand play in controlling the sanding mechanisms and cavity development. This allows us to predict, much more accurately, the onset of sanding and the sanding rate.

From micro scale to boundary value problem: using a micromechanically based model

A 3D multi-scale approach is presented to investigate the mechanical behavior of a macroscopic specimen consisting of a granular assembly, as a boundary value problem. The core of this approach is a multi-scale coupling, wherein the finite element method is used to solve a boundary value problem and a micromechanically based model is employed as constitutive relationship used at a representative volume element scale. This approach provides a convenient way to link the macroscopic observations with intrinsic microscopic mechanisms. The plane strain triaxial loading condition is selected to simulate the occurrence of strain localization. A series of tests are performed, wherein distinct failure patterns are observed and analyzed. A system of shear band naturally appears in a homogeneous setting specimen. By defining the shear band area, microstructural mechanisms are separately investigated inside and outside the shear band. The normalized second-order work introduced as an indicator of instability occurrence is analyzed not only on the macroscale but also on the micro scale.

Oversized solutions to big problems: The political economy of partnerships and environmental cleanup in India

Managing polluted industrial waste from small firms in poor communities is a challenge in many developing countries. In recent years, partnerships among national governments, private sector actors, investors, and foreign aid donors have become popular solutions to address the problem. We argue, however, some partnerships may exhibit a boom and bust pattern that potentially leaves communities worse off in the long run. We test this argument by analyzing variations in the effectiveness of Common Effluent Treatment Plants (CETPs) built in India. We first examine the boom-bust cycle in a public-private partnership CETP in the city of Kanpur. We then extend the analysis to all 88 CETPs in India between 1986 and 2004. We use difference-in-difference techniques to evaluate the effectiveness of CETPs that are fully public, fully private, and those that augmented capacity via partnerships among governments, private sector actors and foreign donors. Our findings suggest that these public-private partnerships tend to follow distinct patterns of success and failure over time.

True-triaxial compressive behaviour of concrete under passive confinement

With the new triaxial testing system developed to generate passive confinement, 117 normal-weight concrete cubes were tested under 13 loading schemes, including biaxial compression and triaxial compression with both uniform and non-uniform passive confinement. The distinct failure patterns were observed under different monotonic loading schemes. The characteristics of peak strength and corresponding axial strain were investigated and compared with data for concrete under traditional triaxial testing. The peak strength and corresponding axial strain have been observed to be related to the confinement stiffness, non-uniform stiffness ratio and the maximum lateral strain. On comparison, it revealed that the models calibrated from the traditional triaxial testing could predict the peak strength with an error within ±10% but cannot well predict the corresponding axial strain.

Blinde vlekken in zorg voor het vrouwenhart

Abstract Cardiology has long been considered as a man’s disease and the discipline has been developed with the male patient as the common standard. In the past 25 years, technical developments have revealed that distinct female patterns of ischemic heart disease and heart failure exist that require a different diagnostic and therapeutic approach compared to the male patient. Although our knowledge has enormously increased and cardiovascular disease in women is now number the number one cause of death worldwide, clinical implementation into a more gender sensitive approach of patients is hampered by resistance within the male-dominated cardiology community. This currently results in less optimal treatment of female cardiac patients. This paper will describe the historical perspective and look forward to the steps that that are needed to improve every day cardiology care for female patients.

Effect of modifying the screw access channels of zirconia implant abutment on the cement flow pattern and retention of zirconia restorations

The effect of managing the screw access channels of zirconia implant abutments in the esthetic zone has not been extensively evaluated. The purpose of this study was to determine the effect of an insert placed within the screw access channel of an anterior zirconia implant abutment on the amount of cement retained within the restoration-abutment system and on the dislodging force. Thirty-six paired zirconia abutments and restorations were fabricated by computer-aided design and computer-aided manufacturing and were divided into 3 groups: open abutment, with the screw access channel unfilled; closed abutment, with the screw access channel sealed; and insert abutment, with a thin, tubular metal insert projection continuous with the screw head and placed into the abutment screw access channel. The restorations were cemented to the abutments with preweighed eugenol-free zinc oxide cement (TempBond NE). Excess cement was removed, and the weight of the cement that remained in the restoration-abutment system was measured. Vertical tensile dislodging forces were recorded at a crosshead speed of 5 mm/min after incubation in a 37°C water bath for 24 hours. The specimens were examined for the cement flow pattern into the screw access channel after dislodgement. Data were analyzed with ANOVA, followed by multiple comparisons by using the Tukey honestly significant difference test (α = .05). The mean (standard deviation) of retentive force values ranged from 108.1 ± 29.9 N to 148.3 ± 21.0 N. The retentive force values differed significantly between the insert abutment and both the open abutment (P < .05) and closed abutment groups (P < .01). Distinct patterns of cement failure were noted. The weight of the cement that remained in the system differed significantly, with both open abutment and insert abutment being greater than closed abutment (P < .05). Modifying the internal configuration of the screw access channel of an esthetic zirconia implant abutment with a metal insert significantly affected both the cement retained within the abutment itself and the retention capabilities of the zirconia restoration cemented with TempBond NE cement.

Investigations Into the Influence of Weld Zone on Formability of Fiber Laser-Welded Advanced High Strength Steel

In this study, two different dual phase steel grades DP980 and DP600, and IFHS steel sheets were laser welded by a 2-kW fiber laser. The weld quality of these three different LWBs was assessed with the help of microstructure, micro-hardness and transverse tensile tests. Tensile testing of longitudinal and miniature samples was performed to evaluate the mechanical properties of the weld zone. Formability of parent materials and LWBs were assessed in bi-axial stretch forming condition by Erichsen cupping test. To validate the weld zone properties, 3-D finite element models of Erichsen cupping test of LWBs was developed, and the failures in the deformed cups were predicted using two theoretical forming limit diagrams. It was observed that hardness of the fusion zone and HAZ in laser welded DP600 and IFHS steels was more compared to the respective parent metal. However, 29% reduction in hardness was observed at the outer HAZ of DP980 steel weldments due to tempering of martensite. Reduction of formability was observed for all the LWBs with two distinct failure patterns, and the maximum reduction in formability was observed in the case of DP980 LWBs. The presence of the soft zone is detrimental in forming of welded DP steels.

Genotypic Analysis of the V3 Region of HIV from Virologic Nonresponders to Maraviroc-Containing Regimens Reveals Distinct Patterns of Failure

Changes in HIV tropism from R5 to non-R5 or development of drug resistance is often associated with virologic failure in patients treated with maraviroc, a CCR5 antagonist. We sought to examine changes in HIV envelope sequences and inferred tropism in patients who did not respond to maraviroc-based regimens. We selected 181 patients who experienced early virologic failure on maraviroc-containing therapy in the MOTIVATE trials. All patients had R5 HIV by the original Trofile assay before entry. We used population-based sequencing methods and the geno2pheno algorithm to examine changes in tropism and V3 sequences at the time of failure. Using deep sequencing, we assessed whether V3 sequences observed at failure emerged from preexisting subpopulations. From population genotyping data at failure, 90 patients had R5 results, and 91 had non-R5 results. Of the latter group, the geno2pheno false-positive rate (FPR) value fell from a median of 20 at screening to 1.1 at failure. By deep sequencing, the median percentage of non-R5 variants in these patients rose from 1.4% to 99.5% after a median of 4 weeks on maraviroc. In 70% of cases, deep sequencing could detect a pretreatment CXCR4-using subpopulation, which emerged at failure. Overall, there were two distinct patterns of failure of maraviroc. Patients failing with R5 generally had few V3 substitutions and low non-R5 prevalence by deep sequencing. Patients with non-R5 HIV who were failing developed very-high-prevalence non-R5 HIV (median, 99%) and had very low geno2pheno values.

Embedding of human vertebral bodies leads to higher ultimate load and altered damage localisation under axial compression

Computer tomography (CT)-based finite element (FE) models of vertebral bodies assess fracture load in vitro better than dual energy X-ray absorptiometry, but boundary conditions affect stress distribution under the endplates that may influence ultimate load and damage localisation under post-yield strains. Therefore, HRpQCT-based homogenised FE models of 12 vertebral bodies were subjected to axial compression with two distinct boundary conditions: embedding in polymethylmethalcrylate (PMMA) and bonding to a healthy intervertebral disc (IVD) with distinct hyperelastic properties for nucleus and annulus. Bone volume fraction and fabric assessed from HRpQCT data were used to determine the elastic, plastic and damage behaviour of bone. Ultimate forces obtained with PMMA were 22% higher than with IVD but correlated highly (R2 = 0.99). At ultimate force, distinct fractions of damage were computed in the endplates (PMMA: 6%, IVD: 70%), cortex and trabecular sub-regions, which confirms previous observations that in contrast to PMMA embedding, failure initiated underneath the nuclei in healthy IVDs. In conclusion, axial loading of vertebral bodies via PMMA embedding versus healthy IVD overestimates ultimate load and leads to distinct damage localisation and failure pattern.

Mesh in prolapse surgery: an imaging perspective

Mesh in prolapse surgery: an imaging perspective

Effect of polypropylene fibers on the uplift behavior of model footings embedded in sand

ABSTRACT: The kinematics of failure and the uplift response of plates embedded in sand and in fiber-reinforced sand layers at distinct embedment depths, when subjected to vertical pullout tests, are the main topics discussed in the present technical note. The uplift capacity of plates in sand backfill layers is increased by the insertion of 0.5% fibers in the backfilled material. The enhancement of the uplift capacity increases from about 70% for embedment depth/plate diameter ratio (H/D) equal to 1.0 to about 30% for H/D equal to 2.0, when compared with sand backfill at the same embedment. Distinct failure patterns were observed for plates embedded in sand and in fiber-reinforced sand backfills: intense radial cracking was observed for sand backfill, but only a few concentric fissures were seen for fiber-reinforced backfill, the former starting at tiny displacements and the latter appearing at large displacements. The fiber-reinforced sand layers demonstrated the ability to continue to increase strength with ongoing deformation, suggesting a very ductile material.

Sex differences in the morphological failure patterns following hip resurfacing arthroplasty

BackgroundMetal-on-metal hybrid hip resurfacing arthroplasty (with a cementless acetabular component and a cemented femoral component) is offered as an alternative to traditional total hip arthroplasty for the young and active adult with advanced osteoarthritis. Although it has been suggested that women are less appropriate candidates for metal-on-metal arthroplasty, the mechanisms of prosthesis failure has not been fully explained. While specific failure patterns, particularly osteonecrosis and delayed type hypersensitivity reactions have been suggested to be specifically linked to the sex of the patient, we wished to examine the potential influence of sex, clinical diagnosis, age of the patient and the size of the femoral component on morphological failure patterns in a large cohort of retrieved specimens following aseptic failure of hip resurfacing arthroplasty.MethodsFemoral remnants retrieved from 173 hips with known patient's sex were morphologically analyzed for the cause of failure. The results were compared with the control group of the remaining 31 failures from patients of unknown sex. The odds ratios (OR) and 95% confidence intervals (CI) of the following morphologically defined variables were calculated using logistic regression analysis: periprosthetic fractures (n = 133), osteonecrosis (n = 151), the presence of excessive intraosseous lymphocyte infiltration (n = 11), and interface hyperosteoidosis (n = 30). Logistic regression analysis was performed both unadjusted and after adjustment for sex, age, the size of the femoral component, and preoperative clinical diagnosis.ResultsFemoral remnants from female patients had a smaller OR for fracture (adjusted OR: 0.29, 95% CI 0.11, 0.80, P for difference = 0.02) and for the presence of osteonecrosis (adjusted OR: 0.16, 95% CI 0.04, 0.63, P for difference = 0.01). However, women had a higher OR for both the presence of excessive intraosseous lymphocyte infiltration (adjusted OR: 10.22, 95% CI 0.79, 132.57, P for difference = 0.08) and interface hyperosteoidosis (adjusted OR: 4.19, 95% CI 1.14, 15.38, P for difference = 0.03).ConclusionsWithin the limitations of this study, we demonstrated substantial sex differences in distinct failure patterns of metal-on-metal hip resurfacing. Recognition of pathogenically distinct failure modes will enable further stratification of risk factors for certain failure mechanisms and thus affect future therapeutic options for selected patient groups.

Seismic displacements of landfills and deformation of geosynthetics due to base sliding

Seismic design of waste landfills has been a subject of intense research over the past two decades, primarily due to the severe environmental impact of a potential failure. The majority of the related studies have been focused on the stability assessment of landfills utilizing permanent deformation methods. However, previous investigations have not fully addressed the impact of the composite liner system on the seismic performance of the geostructure, mainly expressed as potential sliding development, which is greatly affected by the geometry and the resulting initial static stress state of the landfill. Therefore, the aforementioned issues are investigated via a detailed parametric study, where the dynamic behaviour of the composite liner system is examined both analytically and numerically. The conducted coupled analyses indicated that the most significant parameters of the complex dynamic response of waste landfills can be reduced in two ratios that comprise functions of the main characteristics of the geostructure and of the excitation. Moreover, two distinct failure patterns have been identified with respect to the characteristics of the distribution of the permanent displacements along the interface and the axial deformation along the geosynthetic. The occurrence conditions of these failure patterns can be determined in terms of the two abovementioned ratios as verified by the analytical results of the critical acceleration of a simple SDOF system.

Contact Damage of Curved Multi-Layered Ceramics: Prepared by Slip Casting Technique

Contact damage of curved multi-layered systems, consisting of a brittle zirconia (3Y-TZP)/Alumina (Al2O3) coating – prepared by slip casting – on a compliant polymeric substrate from indentation by a hard tungsten carbide sphere is investigated. The essence of this study is to compare the structural performance of layered ceramics, and monolithic ceramic in the brittle coating and compliant substrate of dental crown-like systems. The specimens are loaded at the axis of symmetry. The failure evolution to initiate cracking and final failure patterns in curved multi-layered specimens are compared to those of the single layer specimens of the same thickness and the same study are conducted again with the flat specimens. The onset of fracture is observed in situ using a video camera. It is demonstrated that in all specimens, cone cracking occurs prior to radial cracking, with the latter being defined as the primary mode of catastrophic failure. The multi-layered ZTA (Zirconia Toughened Alumina) specimens prepared by slip casting possessed a distinct final failure pattern in comparison with a single layer specimen. The results of this study provide useful guidelines for building brittle multi-layered coating systems with the functionally graded feature, and complex shapes with geometrical uniformity.

Simulation of Damage-features in a Lug Joint using Guided Waves

A lug joint is one of the several `hotspots' in an aerospace structure which experiences fatigue damage. Several fatigue tests on lug joint samples prepared from 0.25 in plate of Aluminum (Al) 2024 T351 indicated a distinct failure pattern. All samples failed at the shoulders. Therefore, in the current study, different notch sizes are introduced at the shoulders and both experimental and modeled active health monitoring with piezoelectric transducers is performed. Simulations of the real time experiments are carried out using FE analysis. The crack geometry and piezoelectric transducer orientation in lug joint samples are kept same both in experiments and in simulation. Results presented illustrate the feasibility of guided waves in interrogating damage in lug joints. A comparison of sensor signals between experimental and simulated signals, in the time-frequency domain, show fairly good correlation. The frequency transform on the sensor signal data yield useful information for characterizing damage. Sensor sensitivity studies using a distance-based outlier technique are conducted to classify sensor data for different damage states. This information can be used in a number of applications including damage localization by reducing redundant sensors, and optimal sensor placement for SHM.

Failure patterns caused by localized rise in pore‐fluid overpressure and effective strength of rocks

In order to better understand the interaction between pore‐fluid overpressure and failure patterns in rocks we consider a porous elasto‐plastic medium in which a laterally localized overpressure line source is imposed at depth below the free surface. We solve numerically the fluid filtration equation coupled to the gravitational force balance and poro‐elasto‐plastic rheology equations. Systematic numerical simulations, varying initial stress, intrinsic material properties and geometry, show the existence of five distinct failure patterns caused by either shear banding or tensile fracturing. The value of the critical pore‐fluid overpressure pc at the onset of failure is derived from an analytical solution that is in excellent agreement with numerical simulations. Finally, we construct a phase‐diagram that predicts the domains of the different failure patterns and pc at the onset of failure.