Localized Necking Research Articles

The influence of material model on the neck development for aluminium alloy sheet

The neck development for bore expansion problem is analyzed. Static implicit calculations are carried out for the A2219 Aluminium alloy sheet using ABAQUS/Standard. The equations to give the conditions of the onset of the localized necking of sheet metal based on the general bifurcation theory are presented for plane stress. Since accurate calculation of stresses and strains are the basis for the necking prediction, both associated and non-associated flow rule are adopted in the material model in which Hill’s quadratic functions are used. User defined subroutine UMAT is developed using a fully implicit integration scheme. The results of necking prediction show that necking occurrence delays for the Hill solid using both AFR and NAFR based model compared with Mises solid and necking occurrence slightly delays for the Hill solid using AFR based model compared with Hill solid using NAFR based model. Initial necking occurs when equivalent plastic strain is respectively 0.33, 0.39 and 0.348 for the Mises solid and Hill solids using AFR and NAFR based models. Theses indicate that the material model has significant influence on the accuracy of necking prediction.

Ductile failure and damage localization in Al6061‐T6 characterized by in situ X‐ray computed tomography and neural network segmentation

AbstractDamage initiation and localization in uniaxial tension tests of an Al6061‐T6 alloy are evaluated and quantified using in situ X‐ray computed tomography and a neural network segmentation strategy. This segmentation strategy offers significant advantages over traditional thresholding in quantifying microstructural and damage evolution metrics. Void nucleation was observed to occur throughout the deformation process, whereas void volume did not grow significantly until later stages of deformation. Localized analysis determined that void nucleation begins in and around the necked region during the early stages of deformation, whereas limited damage nucleation occurs outside of the neck until late stages of deformation. Lastly, inhomogeneities in void and particle spacing in the initial undeformed state of the material are observed to correlate well with the location of damage localization and necking during deformation. These results provide new insights into the ductile failure of Al alloys and how preexisting defects influence damage and rupture.

Deep Learning-Based Segmentation of Head and Neck Organs-at-Risk with Clinical Partially Labeled Data.

Radiotherapy is one of the main treatments for localized head and neck (HN) cancer. To design a personalized treatment with reduced radio-induced toxicity, accurate delineation of organs at risk (OAR) is a crucial step. Manual delineation is time- and labor-consuming, as well as observer-dependent. Deep learning (DL) based segmentation has proven to overcome some of these limitations, but requires large databases of homogeneously contoured image sets for robust training. However, these are not easily obtained from the standard clinical protocols as the OARs delineated may vary depending on the patient's tumor site and specific treatment plan. This results in incomplete or partially labeled data. This paper presents a solution to train a robust DL-based automated segmentation tool exploiting a clinical partially labeled dataset. We propose a two-step workflow for OAR segmentation: first, we developed longitudinal OAR-specific 3D segmentation models for pseudo-contour generation, completing the missing contours for some patients; with all OAR available, we trained a multi-class 3D convolutional neural network (nnU-Net) for final OAR segmentation. Results obtained in 44 independent datasets showed superior performance of the proposed methodology for the segmentation of fifteen OARs, with an average Dice score coefficient and surface Dice similarity coefficient of 80.59% and 88.74%. We demonstrated that the model can be straightforwardly integrated into the clinical workflow for standard and adaptive radiotherapy.

Effects of Genotype and Diet on Performance, Carcass Traits, and Blood Profiles of Slow-Growing Chicks Obtained by Crosses of Local Breed with Commercial Genotype

The effects of genotype and diet on growth performance, carcass traits and blood metabolites were investigated. The commercial Ross 308 (R) chickens genotype, a local Black Transylvanian Naked Neck (BTNN) breed, and their crosses were used in an 81-day study. A total of 720 one-d-old chicks were allotted into eight groups in a 4 × 2 factorial design with 4 genotypes: Rmale × Rfemale (R), BTNNmale × Rfemale (BTNN-R), BTNNmale × BTNNfemale (BTNN), Rmale × BTNNfemale (R-BTNN), and 2 diets: control and low-metabolisable energy (LME). Genotype affected performance parameters, namely body weight gain (BWG), feed intake (FI), energy intake (EI), feed conversion ratio (FCR), energy conversion ratio (ECR), and production efficiency factor (PEF), irrespective of growth phase (p < 0.05). Diet had no significant effect on overall BWG, EI, ECR and PEF, except that it increased FI and FCR. Genotype influenced the carcass and organ yields (p < 0.05), except bursa weight, while diet had no significant effect. Blood parameters (total cholesterol, triglycerides, glucose, albumin and phosphorus) were affected only by genotype (p < 0.05). In summary, results show that from the two crossbreedings obtained between R and BTNN genotypes, the BTNN-R growth performance and carcass traits were superior to R-BTNN, even though both have had a similar improved plasma response. Lowering the ME level did not significantly affect the BWG but increased FI and FCR, whereas the production index was similar regardless of the genotype. Based on the present results, we concluded that the BTNN-R crosses are the most suitable for use in alternative rearing systems for slow-growing chickens.

Effectiveness of adding rehabilitation of cervical related sensorimotor control to manual therapy and exercise for neck pain: A randomized controlled trial

BackgroundLocal neck treatments and sensorimotor training can improve cervical proprioception and balance, but it remains unclear what treatments and treatment combination achieve the best outcomes. ObjectivesTo investigate the most effective interventions to improve disturbances in joint position sense (JPS) and balance and their effects on neck pain, dizziness and related features in the short- and long-terms. Design2x2 factorial, randomized controlled trial. MethodsParticipants with neck pain (n = 152) were randomly allocated to one of four intervention groups: i) local neck treatment (NT), ii) NT + JPS/oculomotor exercises (JPS/OC), iii) NT + balance exercises, and iv) all treatments. Participants received 12 treatments over 6 weeks. Primary outcomes were postural sway and joint position error. Secondary outcomes included gait speed, dizziness, pain intensity and disability, cervical range of motion, functional ability, and quality of life. Outcome measures were taken at baseline, posttreatment and 3-, 6- and 12-month follow-ups. ResultsAll four interventions resulted in short- and long-term improvements in primary and secondary outcomes with medium to large effect sizes, but JPS and balance in neck torsion improved most with the addition of a combined program of JPS/OC + balance exercises to NT while balance in neck neutral improved most with the addition of balance exercises. Adding sensorimotor training was also more effective in maintaining levels of improvement in neck pain and disability at 6- and 12-months. Effect sizes of additional treatment benefits were medium to large. ConclusionsAdding specific training of JPS/OC and balance to NT best addresses deficits in cervical proprioception and balance. Clinical trial registration numberxxxxx.

Differences in sentinel lymph node biopsy utilization in eligible melanoma patients treated with Mohs micrographic surgery or wide local excision: A population-based logistic regression model and survival analysis

Primary melanoma management relies on tumor extirpation and staging sentinel lymph node biopsy (SLNB) in eligible patients. This study compares SLNB utilization in patients undergoing wide local excision (WLE) or Mohs micrographic surgery (MMS). American Joint Committee on Cancer seventh edition≥patients with T1b melanoma undergoing WLE or MMS in the Surveillance, Epidemiology, and End Results program were included. Propensity score matching was performed to compare patients who underwent MMS or WLE. Kaplan-Meier analysis and Fine-Gray cumulative incidence functions were used for overall and melanoma-specific survival. Eight hundred twenty-five MMS cases and 38,760 WLE cases were identified. SLNB was performed in 32.61% of MMS patients and 61.77% of WLE patients with positive rates of 12.5% and 14.82%, respectively. Multiple logistic regression of factors associated with SLNB utilization revealed that WLE, male gender, younger age, extremity location, and nodular and rare melanoma subtypes were significantly associated with increased odds of receiving SLNB whereas head and neck location and lentigo maligna melanoma subtype were significantly less likely to receive SLNB. Potential selection bias from a retrospective data set. Patients receiving WLE for≥T1b melanoma are more likely to receive a SLNB than patients undergoing MMS.

Abstract 9492: Transcatheter Amplatzer Occluder Device Closure of Post-Myocardial Infarct Pseudoaneurysm: A Case Report

Introduction: Left Ventricular Pseudoaneurysm (LVP) is defined as cardiac wall rupture leading to a formation of wall with thrombus, pericardial, or scar tissue functioning as a pouch for blood. A loculated pericardial effusion (LPE), and right ventricular pericardial fistula (RVPF) have never been reported in literature. Here, we report the first case of a 70 year old male who developed a LVP, LPE, and RVPF. Case Description: A 70 year old male with a past medical history of hypertension presented with inferior wall STEMI. Cardiac catheterization demonstrated left anterior descending (LAD) with 80% occlusion and right coronary artery (RCA) with 100% occlusion. Percutaneous intervention of RCA with aspiration thrombectomy and two drug eluting stents was performed. Echocardiogram the following day demonstrated a LVP. A transesophageal echocardiogram (TEE) demonstrated LVP near the mid-inferior interventricular septum draining into the pericardial space, and LPE from the apical inferior left ventricle (LV) extending to the apical cap of the right ventricle (RV). Computed tomography angiography (CTA) demonstrated a multiloculated collection at the inferior septal aspect of LV contained by the pericardial space. Patient was a high risk for surgery. LVP was closed via a 24 mm atrial septal defect (ASD) occluder device. Intraoperative TEE demonstrated an ASD occluder device at the mid inferior septum at the location of the LVP neck with minimal residual flow into the LPE and a fistula connecting the LPE space with RV. RVFP was managed conservatively. LAD was managed medically. Patient was discharged home safely on guideline directed medical therapy. Discussion: LVP rate is 0.0026% following myocardial injury. It is reported that untreated LVP have a rupture risk of about 30% and a mortality rate of 50%. Prompt treatment is required to prevent mortality. Surgical management is the standard of care. A multidisciplinary heart team deemed the patient a high risk. Therefore, transcatheter treatment was sought in the patient above. Conclusions: Surgical treatment is standard of care for LVP, but transcatheter wall closure with an ASD device is a promising technique not only for high-risk surgical candidates such as above, but as a gold standard of treatment for LVP.

Effect of in utero exposure to hyperthermia on postnatal hair length, skin morphology, and thermoregulatory responses.

Skin and hair coat play important functions in maintaining homeostasis and thermoregulation for cattle, which can affect all modes of heat loss. Our objective was to investigate the effect of hyperthermia experienced in utero during late gestation on postnatal hair length, skin properties, and thermoregulation. Pregnant dams were heat stressed (n = 41) or actively cooled (n = 41) for the last ∼56 d of gestation and gave birth to heifers that were in utero heat stressed (IUHT) or in utero cooled (IUCL), respectively. Hair samples and skin tissue biopsies were collected from neck and rump locations at birth (d 0), 1 wk after weaning (d 63), and at 12 mo. Hair samples were also obtained at 4 and 8 mo. Skin tissue was stained with hematoxylin and eosin to visualize morphology. Hair length (short and long hairs, undercoat and topcoat, respectively), stratum corneum (SC) area, SC thickness, epidermis thickness, sweat gland (SWT) number, SWT cross-sectional area, SWT average size, sebaceous gland (SEB) number, SEB cross-sectional area, SEB average size, and sweat gland depth were assessed. Respiration rate, skin temperature, sweating rate, and rectal temperature was measured weekly from d 7 to 63. Additionally, thermoregulatory patterns were measured every 4 h over a 36-h interval beginning 4 d after weaning. Data were analyzed using PROC MIXED in SAS with a main effect of in utero treatment with location and time points analyzed separately. No difference in hair parameters were detected at d 0 or 12 mo. At d 63, IUHT heifers had longer average hair length (14.8 vs. 13.8 ± 0.2 mm, standard error), shorter undercoats (9.3 vs. 10.4 ± 0.3 mm), longer topcoats (19.6 vs. 17.1 ± 0.3 mm), and a greater difference between topcoat and undercoat (10.1 vs. 7.0 ± 0.4 mm). At 4 mo, IUHT heifers had longer average hair lengths (26.1 vs. 22.2 ± 1.0 mm) and longer topcoats (36.9 vs. 33.9 ± 1.1 mm), and at 8 mo, IUHT had longer average hair lengths (17.9 vs. 16.2 ± 0.6 mm), relative to IUCL. At d 0, IUHT heifers had more (13 vs. 9 ± 2 glands) but smaller average sized SEB (neck: 1,636 vs. 2,238 ± 243 µm2; rump: 2,100 vs. 3,352 ± 379 µm2) and reduced SC area (79,243 vs. 169,419 ± 13,071 µm2). At d 63, IUHT had fewer SEB (11 vs. 15 ± 2 glands), smaller SWT (0.16 vs. 0.23 ± 0.02 mm2), fewer SWT (16 vs. 23 ± 4 glands), and deeper SWT (0.5 vs. 0.4 ± 0.03 mm). At 12 mo, IUHT had greater distance from the skin surface to the most superficial SWT (0.016 vs. 0.015 ± 0.0004 mm), shorter distance to the deepest SWT (0.031 vs. 0.033 ± 0.001 mm), and smaller SWT (81.1 vs. 108.9 ± 10.8 µm2), relative to IUCL. When measured both weekly and hourly, IUHT heifers had higher rectal temperature and sweating rate. Overall, in utero hyperthermia triggers long-lasting hair and skin adaptations, possibly leading to differences in postnatal thermoregulation.

Study of mechanical characteristics of additively manufactured Co-Cr-Mo-2/4/6Ti alloys for knee implant material

This paper presents study of microstructure, aspect ratio (i.e. ratio of deposition width to deposition height), tensile and compression testing results along with their fractography, and abrasion resistance of the optimized depositions of new materials for knee implant developed by adding 2, 4, and 6 wt% of Ti to Co-Cr-Mo alloy by μ-plasma based additive manufacturing process. It is complemented with finite element analysis of tibial tray made of the developed alloys. Minimum aspect ratio of 1.11 and continuous deposition was obtained for 264 W μ-plasma power, 2.5 g/min deposition material powder mass flow rate, and 50 mm/min deposition head travel speed. Hence it was used for manufacturing multi-layer multi-track depositions of powder of Co-Cr-Mo-xTi alloys. Co-Cr-Mo-xTi alloys showed high % of Co-rich matrix consisting of α-Co phase formed to minor alloying elements Ni and Fe and ε-Co phase stabilized by molybdenum, ß-Ti phase, inter-metallic phase CoTi 2 , and lamellar chromium carbides Cr 7 C 3 and Cr 23 C 6 on grain boundaries which will impart more wear and corrosion resistance to Co-Cr-xTi alloys. Their samples fractured within their gauge length with slight localized necking indicating strain localization in a very small region before their ductile fracture during their tensile testing. Optimized deposition of Cr-Co-Mo-4Ti alloy has more uniform distribution of porosity and absence of thermal crack which is desirable for knee implant material as it allows better osseointegration with the human bones and tissues. It has higher tensile and compressive yield strength, ultimate tensile and compressive strength, and ductility indicated by higher % elongation and % increase in cross-section area due to more uniform porous structure, finer grain size, absence of thermal cracks, and presence of chromium carbide phases which obstruct movement of dislocations. It also has minimum value of avg. scratch track width and coefficient of friction, and maximum value of scratch hardness number imparting it better abrasion resistance due to presence of fine lamellar carbide phases. Finite element analysis of tibial tray revealed that equivalent Von-Mises stress and total deformation increase with increase in wt% of Ti in Co-Cr-Mo alloy. This study found Co-Cr-Mo-4Ti alloy as a better knee implant material due to its uniform porosity without thermal cracks, finer grain size, higher yield compressive and tensile strength, higher ductility, and abrasion resistance. • Optimized multi-layer multi-track deposition of Co-Cr-Mo-xTi alloys for better knee implant material. • Equivalent Von-Mises stress and total deformation increase with wt% of Ti in Co-Cr-Mo alloy. • Co-Cr-Mo-xTi alloys have α-Co, ε-Co, ß-Ti, CoTi 2 phases, and Cr 7 C 3 and Cr 23 C 6 on grain boundaries. • Uniform porosity without micro-cracks gives higher tensile and compressive strength to Co-Cr-Mo-4Ti. • Its finer grains, higher abrasion resistance, lower friction coefficient make it better knee implant material.

RF35 | PSAT298 Subacute Thyroiditis Following SARS-CoV-2 mRNA Vaccine

Abstract Background In 2011, Shoenfeld and Agmon-Levin described a distinct clinical entity called the autoimmune/inflammatory syndrome induced by adjuvants (ASIA). Adjuvants are primarily used in vaccines for directing the adaptive immune response. However, adjuvants sometimes trigger undesirable autoimmune effects, especially in genetically predisposed individuals such as those with DRB1 allele mutations. The mRNA vaccine may exert "self-adjuvant" properties through activation of tumor necrosis factor, interferon-alpha and other cytokines secreted by immune cells or cross reactivity of mRNA targeting CoV-2 spike protein with thyroid tissue antigens. With the recent widespread use of SARS-CoV-2 mRNA vaccine, cases of vaccine associated thyroid disorders are becoming more apparent. Case Summary A 45-year-old male with well controlled hypertension and type 2 diabetes mellitus was evaluated for abnormal thyroid function tests with a TSH of 0.078 uIU/mL and Free T4 of 2.17 ng/dl. He reported a history of Hashimoto's chronic thyroiditis. He received the second dose of mRNA COVID-19 vaccine one month prior to presentation. He denied any change in the size of his thyroid gland. He also reported no local neck symptoms, dysphagia, odynophagia or change in voice. A nuclear thyroid uptake and scan showed mildly asymmetric thyroid lobes with markedly decreased 24-hour uptake of 0.7%. Based on his clinical presentation, labs and nuclear imaging he was diagnosed with painless thyroiditis. His thyroid function normalized to a TSH of 0.96uIU/ml and Free T4 of 1.29 ng/dl within 2 months without any intervention. There is a strong possibility that the SARS-CoV-2 vaccine accentuated his underlying Hashimoto's chronic thyroiditis enough to cause this transient episode of painless thyroiditis, particularly considering the close interval between the vaccine and onset of his thyroid abnormalities. Conclusion Autoimmune thyroid abnormalities induced by vaccines have been historically associated with protein vaccines for protection from HPV, HBV, seasonal influenza, etc. The spectrum of these disorders can potentially manifest as a transient side effect or even years later with non-specific findings. The SARS-CoV-2 mRNA vaccine may incite similar immunogenicity though yet unestablished, and physicians should be mindful of this phenomenon. Due to limited data, more rigorous studies are needed to fully understand the underlying pathogenesis of thyroiditis following SARS-CoV-2 vaccine in future. As there have been minimal cases of thyroiditis reported, SARS-CoV-2 vaccine should still be strongly recommended. References Bragazzi NL, Hejly A, Watad A, Adawi M, Amital H, Shoenfeld Y. ASIA syndrome and endocrine autoimmune disorders. Best Pract Res Clin Endocrinol Metab. 2020 Jan;34(1): 101412. doi: 10.1016/j.beem.2020.101412. Epub 2020 Mar 11. PMID: 32265102. Watad A, David P, Brown S, Shoenfeld Y. Autoimmune/Inflammatory Syndrome Induced by Adjuvants and Thyroid Autoimmunity. Front Endocrinol (Lausanne). 2017 Jan 24;7: 150. doi: 10.3389/fendo.2016.00150. PMID: 28167927; PMCID: PMC5256113. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Monday, June 13, 2022 1:12 p.m. - 1:17 p.m.

Effects of fracture models on structural damage and acceleration in naval ships due to underwater explosions

This study examined the structural damage quantitively due to a near-field underwater explosion (UNDEX) using a more reasonable fracture model. Technical backgrounds of the Geers-Hunter UNDEX model and combined HC-LN fracture model based on Hosford-Coulomb (HC) and localized necking (LN) were reviewed. A finite element analysis (FEA) model for which the UNDEX experiment was performed was generated. Two fracture models were applied to the FEA model: constant strain and HC-LN fracture models. A user subroutine was developed to implement the HC-LN fracture model. The material constants for the aluminum alloy that was the model ship material were calculated using tensile tests and their FEAs. The HC-LN fracture model predicted a similar extent of damage to that in the experiment. The constant strain fracture model predicted an unrealistic fracture in the bottom shells that reduced the hull girder bending capacity and thus the increased acceleration history. A damage extent can be estimated accurately only by UNDEX FEAs with a more reasonable fracture model.

Large deflection resistance and fracture of panels subjected to the lateral penetration

This paper is concerned with the plastic behaviors of a rigid indenter into a typical ship side panel with analytical and numerical studies. The focus is on a more comprehensive framework where panel dimensions, indenter shapes, and material failure properties are allowed to change when predicting panel failure initiation and the deformation resistance force. Therefore, concise analytical solutions are derived by the plastic membrane and fracture based on a global stability criterion for large deflection. The power curve fitting to the analytical solutions brings out the brief-expression where the influence of geometric and material parameters is present clearly. In addition, the shape factor CS is introduced to illustrate the indenter's sharpness and enable the semi-analytical solutions to deal with the indenter with various geometries:Experimental results of specimens with a range of dimensions punched by indenters presented in the previous work are used to validate the proposed analytical solutions. Numerical simulations are supplemented and demonstrate that the penetration to fracture initiation and the large deflection resistance are sensitive to specimen dimensions and shape and can be predicted accurately by the proposed solutions. Moreover, the applied fracture criterion in analysis considered the change of the geometric and material properties shows consistency with the numerical observations that panel fails by localized necking. By the extension based on the deformation assumption, the corrected procedure enables the prediction of stiffened panels.

Elasto-capillary necking, bulging and Maxwell states in soft compressible cylinders

Localized pattern formations and “two-phase” deformations are studied theoretically in soft compressible cylinders subject to surface tension and axial loading through several force-controlled loading scenarios. By drawing upon known results for separate yet mathematically similar elastic localization problems, a concise family of analytical bifurcation conditions for localized bulging or necking are derived in terms of a general compressible strain energy function. The effect of material compressibility and strain-stiffening behaviour on the bifurcation point is analysed, and comparisons between our theoretical bifurcation conditions and the corresponding numerical simulation results of Dortdivanlioglu and Javili (Extreme Mech. Lett. 55, 2022) are made. It is then explained how the fully developed “two-phase” (Maxwell) state which evolves from the initial localized bifurcation solution can be comprehensively understood using the simple analytical expressions for the force parameters corresponding to the primary axial tension deformation. The power of this simple analytical approach in validating numerical simulation results for elastic localization and phase-separation-like problems of this nature is highlighted.

Acanthosis Nigricans: Pointer of Endocrine Entities.

Acanthosis nigricans (AN) has been reported in relation to insulin resistance (IR). We aim to review AN through an endocrine and metabolic perspective focusing on IR in association with metabolic complications such as obesity, diabetes mellitus (DM), and metabolic syndrome (MS) with/without polycystic ovary syndrome (PCOS). We revised English papers on PubMed covering publications from the last 5 years. The current prevalence of AN varies from 4.5 to 74% (or even 100%, depending on the studied population), with equal distribution among females and males. Despite higher incidence with an age-dependent pattern, an alarming escalation of cases has been noted for obesity and MS in younger populations. Most frequent IR-associated sites are the neck, axilla, and knuckles, but unusual locations such as the face have also been reported. Quantitative scales such as Burke have been used to describe the severity of the dermatosis, particularly in correlation with IR elements. Dermoscopic examination are required, for instance, in cases with sulcus cutis, hyperpigmented spots, crista cutis, and papillary projections. A skin biopsy may be necessary, but it is not the rule. Both IR that clinically manifests with or without obesity/MS correlates with AN; most studies are cross-sectional, with only a few longitudinal. The approach varied from screening during school periodic checkups/protocols/programs to subgroups of individuals who were already known to be at high cardio-metabolic risk. AN was associated with type2DM, as well as type 1DM. Females with PCOS may already display metabolic complications in 60–80% of cases, with AN belonging to the associated skin spectrum. AN management depends on underlying conditions, and specific dermatological therapy is not generally required, unless the patient achieves metabolic control, has severe skin lesions, or desires cosmetic improvement. In IR cases, lifestyle interventions can help, including weight control up to bariatric surgery. In addition, metformin is a key player in the field of oral medication against DM type 2, a drug whose indication is extended to PCOS and even to AN itself, outside the specific panel of glucose anomalies. In terms of cosmetic intervention, limited data have been published on melatonin, urea cream, topical retinoids, vitamin D analogs, or alexandrite laser. In conclusion, awareness of IR and its associated clinical features is essential to provide prompt recognition of underlying conditions. AN represents a useful non-invasive surrogate marker of this spectrum in both children and adults. The pivotal role of this dermatosis could massively improve endocrine and metabolic assessments.

Clinical results of active surveillance for extra-abdominal desmoid-type fibromatosis.

The treatment of choice for desmoid-type fibromatosis (DF) has been changed to active surveillance (AS). However, few studies have reported clinical outcomes of AS modality in Asian countries. This study aimed to clarify the significance of AS as a DF treatment modality. A total of 168 lesions from 162 patients with extra-abdominal DF were included. The mean age at diagnosis was 39 years (1-88 years), and the median maximum tumor diameter at the first visit was 64.1 mm (13.2-255.8 mm). The clinical outcomes of AS and the risk factors requiring active treatment (AT) (defined as an event) from AS modality were investigated. Of the 168 lesions, 94 (56%) were able to continue AS, with a 5-year event-free survival of 54.8%. Of the 68 lesions with PD, 21 (30.9%) lesions were able to continue AS. Neck location (p= 0.043) and CTNNB1 S45F mutation (p= 0.003) were significantly associated with the transition to AT, and S45F mutation was a significant factor associated with the transition to AT by multivariate analysis (hazard ratio: 1.96, p= 0.048). AT outcomes after AS were evaluable in 65 lesions, and 49 (75%) lesions did not require a transition to a second AT. AS was revealed as an effective treatment modality. The transition to AT needs to be considered for neck location and CTNNB1 S45F mutation DF. Good results can be obtained by selecting a treatment method that considers the tumor location even in cases that require intervention.

Abnormal three-stage plastic deformation in a 17-4 PH stainless steel fabricated by laser powder bed fusion

A 17-4 PH stainless steel has been additively manufactured (AM) using laser powder bed fusion (LPBF). Different from traditional counterpart, the AM 17-4 PH steel exhibits a peculiar dual-phase microstructure containing large amount of retained austenite (66 vol%) and the rest martensite. This metastable structure is highly susceptible to surface polishing, thus widely scattered data of phase constitution are reported in many previous papers. It is found that the thermal martensite transformation is suppressed by the ultra-fine microstructure produced by LPBF, thus giving rise to a large amount of austenite retained. And as a consequence, plastic deformation of the AM 17-4 steel displays an obvious three-stage behavior: (I) yield plateau, (II) severe work hardening, and (III) final necking. Underlying mechanisms are revealed, respectively. At the beginning of plastic deformation, because there is lacking of further strengthening mechanism upon yielding in the fine-grained structure, a plastic instability caused by local softening occurs and leads to the formation of complex Lüders band. When the accumulated mechanical energy plus the intrinsic chemical energy exceeds activation energy of martensite transformation, further plastic deformation results in severe strain-induced martensite transformation (SIMT). The SIMT endows the AM 17-4 steel with extremely high work hardening ability in stage II, consequently, flow stress rises sharply from 490 MPa to the maximum level of 1090 MPa, and most of the retained austenite is exhausted in this stage. Afterward, the work hardening rate drops below the true stress, an increase in strain produces no additional load increase, local necking occurs and leads to final rupture of the AM 17-4 steel.

Interface Strengthening and Toughening Mechanism of Hot Rolled Multilayer TWIP/40Si2CrMo Steels

Layered metal composites play an increasingly important role in aerospace, automotive, and nuclear energy. Compared with a single metal or alloy, the layered metal composite exhibits an excellent strong-plastic matching effect. In this paper, multilayer TWIP/40Si2CrMo steels with different hot rolling reductions were successfully fabricated by the vacuum hot rolling. The results show that the multilayer steels can improve the lower yield strength of TWIP steel and lower the fracture elongation of 40Si2CrMo steel. In addition, with the increase of the hot rolling reduction, the mechanical properties and interfacial bonding strength of multilayer steels were improved, while the size and number of interfacial oxides decrease, and the fracture mode was also changed. This shows that a higher hot rolling reduction will promote the breakage of the interface oxides and make them appear dispersed, thereby improving the bonding strength of the interface, effectively suppressing the delamination and local necking of the multilayer steel, and making the multilayer steel show a higher ability of uniform plastic deformation. At the same time, under the dual action of layer thickness scale and interface strengthening effect, the brittle layer of multilayer steel presents a multiple tunnel crack mode. It was beneficial to alleviate the stress concentration and further improve the strengthening and toughening effect of multilayer steel.

Temperature Dependence of Fracture Behavior and Mechanical Properties of AISI 316 Austenitic Stainless Steel

A combination of fractographic and metallographic analysis during tensile tests over the temperature ranging from 20 °C to 750 °C were carried out to investigate the fracture behaviors and deformation modes so as to clarify the temperature dependence of mechanical properties of AISI 316 austenitic stainless steel. Planar slip mode of deformation was observed during tensile tests at 20 °C due to a relatively low SFE (stacking fault energies). Pronounced planar slip characteristics were observed in the range of 350–550 °C, and the resultant localized deformation led to the formation of shear bands. The dislocation cross-slip was much easier above 550 °C, leading to the formation of cell/subgrain structures. The preferential microvoid initiation and subsequent anisotropic growth behavior in the shear bands led to large-size and shallow dimples on the fracture surfaces in the range of 350–550 °C. However, the microvoid tended to elongate along the tensile direction in the localized necking region above 550 °C, resulting in small-size and deep dimples. The shear localization reduced the uniform deformation ability and accelerated the fracture process along shear bands, leading to a plateau in uniform elongation and total elongation in the range of 350–550 °C. The higher capability to tolerate the localized deformation through sustained necking resulted in a significant increase in the total elongation above 550 °C.

Enhancing fatigue resistance of nanocrystalline Ni/Ni-W laminated composites

The fatigue strength of nanocrystalline Ni/Ni-W laminated composites was investigated. The results reveal that the fatigue resistance of the Ni/Ni-W laminated composites is improved compared with that of monotonic Ni. Shear banding and voiding are two modes dominating fatigue damage of the composites. A deformation map is proposed to elucidate the critical condition of the formation of shear bands and voids, as well as the transition of two damage modes. The ultrathin Ni-W layers introduced into the laminated composites hindered the crack crossing the heterogeneous interface through their local thinning and necking, and thus improved the fatigue strength.

Back pain prevention program: An evaluation after a 10-year implementation amongst dental students.

Many studies show a higher prevalence of back pain for dentists and dental students than in the general population. This leads to a need to integrate an effective back pain prevention program (BPPP) into the student's curriculum. We have implemented such a program for 10 years, and the objective was to evaluate its effectiveness. Data from 102 dentists and students who benefited from the BPPP were collected. Back pain prevalence and its intensity (0-10 scale) regarding neck, upper back and lower back location were studied, as well as sex, age, implementation or not of elements of the BPPP into daily practice, and if so at what moment of the professional life. For identical items, answers were compared with those from a national survey conducted amongst French students and practitioners in 2018. Amongst the BPPP beneficiaries, 60% were suffering from chronic back pain versus 77% in the previous national survey (p< .001). Mean pain intensity was lower in each location for the BPPP beneficiaries on the 0-10 scale: neck 1.91 vs. 2.40 (p= .05); upper back 1.94 vs. 2.72 (p< .001); lower back 2.26 vs. 2.67 (p= .15). Respondents who implemented elements of the BPPP from the start of their clinical practice showed a prevalence of chronic back pain of 48.4%, against 77% for respondents who did so only from the first year or after (p< .05). Our BPPP seems to show a positive preventive effect on dentists and students after a 10-year implementation. It is a solid basis that can however be further improved.