Efeito da deformação à frio da martensita, do tempo e da temperatura de envelhecimento sobre a microestrutura e dureza do aço maraging 300

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2015O efeito da deformação mecânica a frio da martensita e do tempo de envelhecimento na dureza e microestrutura de um aço maraging 300 foi estudado. A análise microestrutural foi realizada por microscopia ótica (MO), microscopia eletrônica de varredura (MEV) e de transmissão (MET). Por magnetômetro de amostra vibrante (VSM) e por Raio-X foram verificadas a porcentagem de austenita reversa e a textura cristalográfica, respectivamente. As deformações foram realizadas em amostras previamente austenitizadas a 820 °C por 30 minutos e resfriadas em água. Foram utilizadas duas reduções de altura das amostras (50 e 85%). Após a redução as amostras foram envelhecidas a 450, 500, 550 ou 600 °C por diversos tempos. Para efeito da comparação um conjunto de amostras sem deformação também foram envelhecidas nas mesmas condições anteriores. Verificou-se a precipitação de intermetálicos Ni3(Ti, Mo), Fe2Mo e que a deformação mecânica ocasionou um aumento máximo de dureza de 114 HV no estado temperado. A deformação mecânica também retardou a formação da austenita reversa e propiciou um refino mais homogêneo da microestrutura. Abstract : The effects of cold mechanical work on martensite and aging on the hardness and microstructure of a maraging 300 steel was analyzed. The microstructural analysis was measured by optical microscopy (MO), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The vibrating sample magnetometer (VSM) and X-Ray were used to verify the amount of reverse austenite and the crystallographic texture, respectively. The samples were previously austenitized at 820 °C for 30 minutes and followed by water quenching. Two height reduction of samples were used (50 e 85%). In sequence, the samples were aged at 450, 500, 550 or 600 °C for different periods of time. For comparison purposes a set of non-deformed samples was submitted to the same aging conditions. The precipitation of intermetallic Ni3(Ti, Mo) and Fe2Mo was detected. Also the mechanical deformation caused the growth of hardness to a maximum 114HV for quenched state. The Mechanical deformation also delayed the formation of reverse austenite and provided a more homogeneous refinement of the microstructure

Monitoring Patient Response to Pembrolizumab With Peripheral Blood Exhaustion Marker Profiles

Exhausted T cells are effector T cells that are silenced due to continuous T cell receptor (TCR) stimulation from persistent antigens. Characteristics of exhaustion include the increased expression of multiple inhibitory receptors such as programme death-1[PD-1], lymphocyte activation gene 3 [LAG-3], T cell Ig and mucin domain [TIM-3], the loss of effector cytokine secretion and altered transcriptional profile. The PD-1/PD-L1 interaction induces functional exhaustion of tumor-reactive cytotoxic T cells and interferes with anti-tumor T cell immunity. T cell exhaustion has been observed in metastatic melanoma patients where the exhaustion of tumor specific T cells suggests that tumor clearance has been impeded and contributed to tumor immune escape. Checkpoint immunotherapies are antibodies designed to block the interaction between the inhibitory receptors expressed on T cells and their respective ligands. Therapies such as anti-PD-1 (Pembrolizumab and Nivolumab) block these inhibitory receptors and are associated with a significant improvement in overall survival and progression free survival. However, only 20–40% of metastatic melanoma patients experience long-term benefit. In a cohort of 16 metastatic melanoma patients receiving pembrolizumab, blood was serially collected before each infusion (mean 8.3; range 1–12 cycles). The presence of inhibitory markers LAG-3, TIM-3, and PD-1 on the surface of T cells was examined and assessed in relation to patient response to identify if inhibitory markers can be used to differentiate responders from non-responders for Pembrolizumab. We confirmed that across a range of cycles (range 1–26) of pembrolizumab, PD-1 expression was significantly higher on CD4+ T cells from non-responders compared to responders and TIM-3 expressed on the surface of CD8+ T cells was significantly higher in non-responders compared to responders. This longitudinal data confirms previous studies that assessed single timepoints. This study provides preliminary evidence that PD-1 and TIM-3 may be predictive of non-responders when assessed over multiple treatment cycles

The prognostic value of tumor mitotic rate in children and adolescents with cutaneous melanoma:A retrospective cohort study

Background: Mitotic rate is a strong predictor of outcome in adult patients with primary cutaneous melanoma, but for children and adolescent patients this is unknown. Objective: We sought to assess the prognostic value of primary tumor mitotic rate in children and adolescents with primary melanoma. Methods: This was a cohort study of 156 patients who were <20 years of age and who had clinically localized cutaneous melanoma. Patients <12 years of age were classified as children and those 12 to 19 years of age as adolescents. Clinicopathologic and outcome data were collected. Recurrence-free and melanoma-specific survival were calculated. Univariable and multivariable analyses were performed using Cox proportional hazard models. Results: Thirteen of 156 patients (8%) were children. The mitotic rate was ≥1/mm2 in 104 patients (67%) and correlated with increasing Breslow thickness. A positive sentinel node was found in 23 of 61 patients (38%) in whom a sentinel lymph node biopsy specimen was obtained. The median follow-up was 61 months. Five-year melanoma-specific and recurrence-free survival rates were 91% and 84%, respectively. Mitotic rate was a stronger predictor of outcome than tumor thickness and was the only factor independently associated with recurrence-free survival. Limitations: This research was conducted at a single institution and the sample size was small. Conclusion: Mitotic rate is an independent predictor of recurrence-free survival in children and adolescents with clinically localized melanoma

Whole-genome landscapes of major melanoma subtypes

Melanoma of the skin is a common cancer only in Europeans, whereas it arises in internal body surfaces (mucosal sites) and on the hands and feet (acral sites) in people throughout the world. Here we report analysis of whole-genome sequences from cutaneous, acral and mucosal subtypes of melanoma. The heavily mutated landscape of coding and non-coding mutations in cutaneous melanoma resolved novel signatures of mutagenesis attributable to ultraviolet radiation. However, acral and mucosal melanomas were dominated by structural changes and mutation signatures of unknown aetiology, not previously identified in melanoma. The number of genes affected by recurrent mutations disrupting non-coding sequences was similar to that affected by recurrent mutations to coding sequences. Significantly mutated genes included BRAF, CDKN2A, NRAS and TP53 in cutaneous melanoma, BRAF, NRAS and NF1 in acral melanoma and SF3B1 in mucosal melanoma. Mutations affecting the TERT promoter were the most frequent of all; however, neither they nor ATRX mutations, which correlate with alternative telomere lengthening, were associated with greater telomere length. Most melanomas had potentially actionable mutations, most in components of the mitogen-activated protein kinase and phosphoinositol kinase pathways. The whole-genome mutation landscape of melanoma reveals diverse carcinogenic processes across its subtypes, some unrelated to sun exposure, and extends potential involvement of the non-coding genome in its pathogenesis

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Activating kinase mutations in melanoma

Research Doctorate - Doctor of Philosophy (PhD)The treatment of patients with metastatic melanoma has been revolutionized by the discovery of crucial activating kinase mutations, making melanoma susceptible to targeted kinase inhibition. The result is that melanoma, once a notoriously treatment resistant malignancy, has become the poster child for the promise of personalized cancer therapy. We have sought to identify what the incidence of various kinase mutations are in a group of 192 melanoma patients, sampled from a population that harbors one of the highest rates of melanoma in the world, and what this may mean for their prognosis and treatment. In our cohort of patients with advanced melanoma, mutations in BRAF, NRAS, KIT and KRAS occurred with frequencies of 24.5%, 20.8%, 4.7% and 2.6%, respectively. We show that BRAF-mutant melanomas have a specific clinical profile. Furthermore, we reveal that BRAF and NRAS mutant melanomas show significant differences in their respective rates of metastatic spread and overall survival. Our mutation screen also revealed two relatively common juxtamembranous MET single nucleotide polymorphisms to be significantly over-represented in our melanoma patient cohort. As the identification of some of these clinically relevant mutations will become routine in the workup of patients with advanced melanoma, we turned our attention to the search of a phenotype/genotype association that may be employed by anatomical pathologists to triage cases for molecular analysis. Using m-RNA extracted from formalin-fixed paraffin embedded melanoma tissue, we identified a number of genes differentially expressed in BRAF, NRAS and KIT-mutant melanomas. The levels of these differentially expressed genes were then assessed using immunohistochemical staining and quantitative scoring on a matching melanoma tissue microarray. We show a strong correlation in the expression data and immunohistochemical staining for some of the genes identified. Some of these differences in protein staining were also shown to be capable of having a good predictive capacity for identifying cases likely to harbor KIT mutations. Quantitative cytomorphological analysis identified a BRAF-mutant melanoma specific morphological phenotype, characterized by larger cellular volumes, more rounded shapes and lower degrees of cellular pleomorphism. In conclusion, we show that incorporating discriminatory clinical; cytomorphological and immunohistochemical data can generate a decision tree algorithm with fair to good predictive power for the detection of KIT and BRAF-mutant melanomas

Efeito de ciclos de deformação nas propriedades mecânicas e cinética de transformação em aços maraging C300 com alto teor de Ti

Tese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Ciência e Engenharia de Materiais, Florianópolis, 2020.Aços maraging são ligas quaternárias de Ni, Ti, Mo e Co de ultra alta resistência utilizado em componentes que exigem alta confiabilidade. Este trabalho tem como objetivo estudar a influência de ciclos de deformação da martensita e da austenita na microestrutura, propriedades mecânicas e cinética de formação da austenita reversa e dos precipitados Ni3(Ti, Mo) durante o envelhecimento de um aço maraging C300 com alto teor de Ti. Foi estudado o efeito de 3 condições distintas de deformação: forjada com 50% de redução de altura a quente; forjada com 50% de redução de altura a quente seguida por 50% de redução de altura a frio; e laminada com 50% de redução de altura a quente e 50% de redução a frio. Para controle, uma condição sem deformação também foi analisada. Estas quatro condições foram então envelhecidas à 723, 773 e 873 K (450, 500 e 600 °C) por diversos tempos e analisadas por microscopia óptica, eletrônica de varredura e de transmissão, microdureza Vickers, difração de Raios-X e dilatometria. Como resultado, a matriz martensítica foi verificada como sendo tetragonal, independente do estado de deformação. A deformação acelerou a cinética de precipitação do Ni3(Ti, Mo) que chegou a uma fração volumétrica máxima de 19% após 50 h de envelhecimento a 773 K (500 °C), além de reduzir significativamente o tempo necessário para se atingir o pico de dureza em todas as temperaturas de envelhecimento estudada. Embora a formação do Ni3(Ti, Mo) tenha sido mais rápida na condição laminada, sua dissolução ocorreu de forma mais rápida na condição forjada a quente, onde foi acompanhada de uma aceleração da formação da austenita reversa. O cálculo da variação da resistência mecânica realizado a partir da medição dos raios médios e da fração volumétrica para o precipitado Ni3(Ti, Mo) mostraram que este é o principal endurecedor dos aços maraging, contudo, a relevância deste precipitado sobre a resistência mecânica total varia entre a amostra com e sem deformação. A deformação também gerou uma dilatação em direções preferenciais quando ocorre a formação de austenita reversa, podendo gerar distorções em peças envelhecidas por elevados tempos e temperaturas.Abstract: Maraging steels are ultra high strength Ni, Ti, Mo and Co quaternary alloys used in components that require high reliability. This work aims to study the influence of deformation cycles of martensite and austenite on the microstructure, mechanical properties and formation kinetics of reverse austenite and Ni3(Ti, Mo) and Fe-Mo precipitates of a high content C300 maraging steel. For this purpose, 3 different deformation conditions were studied: hot forged with height reduction of 50%; cold forged follow by hot forged, both with height reduction of 50%; and hot rolled followed by hot rolled, both with height reduction of 50%. For control, a condition without deformation, called 0%, was also analyzed. These four conditions were then aged at 723, 773 and 873 K (450, 500 and 600 ° C) for several times and analyzed by optical end scanning and transmission electronics microscopy, Vickers microhardness, X-ray diffraction and dilatometry. As a result, the martensitic matrix was found to be tetragonal, regardless of the deformation state. The deformation accelerated the precipitation kinetics of Ni3(Ti, Mo) which reached a maximum volumetric fraction of 19% after 50 h of aging at 773 K (500 °C), in addition to significantly reducing the time required to reach the peak of hardness in all studied aging temperatures. Although the faster formation of this phase in the rolled condition, its dissolution occurred more quickly in the hot forged condition, accompanied by an acceleration of the reverse austenite formation. The calculation of the increase on mechanical resistance, carried out from the measurement of the average radius and volumetric fraction for the Ni3(Ti, Mo) precipitate, showed that this precipitate is the main hardener in maraging steels, however, the relevance of this precipitate on the total mechanical resistance varies between the sample with and without deformation. The deformation also generated an expansion in preferential directions when the formation of reverse austenite occurs, which can form distortions in parts aged by high times and temperatures

Detailed Pathological Examination of Completion Node Dissection Specimens and Outcome in Melanoma Patients with Minimal (&lt;0.1 mm) Sentinel Lymph Node Metastases

Nonsentinel lymph nodes (NSLNs) are rarely involved in patients with minimal volume melanoma metastases in sentinel lymph nodes (SLNs). Therefore, it has been suggested that completion lymph node dissection (CLND) is not required. However, the lack of routine immunohistochemical staining and multiple sectioning may have led to failure to identify additional positive nodes. The present study sought to more reliably determine the tumor status of NSLNs in patients with minimally involved SLNs and their clinical outcome. A total of 21 tumor-negative CLND specimens from 20 patients with SLN metastases of <0.1 mm in diameter treated between 1991 and 2013 were examined with a more detailed pathologic protocol (five new sections stained with/for H&E, S-100, HMB45, Melan-A, and H&E). Clinical follow-up data were also obtained. Of the 343 examined NSLNs, 1 was found to harbor a 0.18-mm subcapsular sinus metastasis. No metastases were identified in the other NSLNs. Median follow-up was 48 months (range 17-130 months). Six patients (30 %) developed a recurrence. At the end of follow-up, 15 patients (75 %) were alive without sign of melanoma recurrence and 5 patients (25 %) had died of melanoma. Estimated 5-year melanoma-specific survival was 64 %. The patient with the additional positive NSLN remains without recurrence after 130 months follow-up. Although the risk of additional nodal involvement is low, detailed pathologic examination may identify NSLN metastases not identified using routine protocols. Therefore, nodal clearance appears to be the safest option for these patients, pending the results of prospective trials