Iskanje po repozitoriju

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Objavljeno v DiRROS: 21.03.2024; Ogledov: 103; Prenosov: 37
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Povzetek: The aim of the study was to determine whether the presence of inguinal sentinel lymph node (SLN) metastases smaller than 2 mm (micrometastases) subdivided according to the number of micrometastases predicts additional, non-sentinel inguinal, iliac or obturator lymph node involvement in completion lymph node dissection (CLND). Positive inguinal SLN was detected in 58 patients (32 female, 26 male, median age 55 years) from 743 consecutive and prospectively enrolled patients with primary cutaneous melanoma stage I and II who were treated with SLN biopsy between 2001 and 2007. Micrometastases in inguinal SLN were detected in 32 patients, 14 were single, 2 were double, and 16 were multiple. Twenty-six patients had macrometastases. No patient with any micrometastases or a single SLN macrometastasis in the inguinal region had any iliac/obturator non-sentinel metastases after CLND in our series. Furthermore, no patient with single SLN micrometastasis in the inguinal region had any non-sentinel metastases at all after CLND in our series. In these cases respective CLND might be omitted.
Objavljeno v DiRROS: 21.03.2024; Ogledov: 214; Prenosov: 221
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Povzetek: We have developed a 2-D numerical meshless adaptive approach for phase-field modelling of dendritic solidification. The quadtree-based approach decomposes the computational domain into quadtree sub-domains of different sizes. The algorithm generates uniformly-distributed computational nodes in each quadtree sub-domain. We apply the meshless radial basis function generated finite difference method and the forward Euler scheme to discretise governing equations in each computational node. The fixed ratio between the characteristic size and the node spacing of a quadtree sub-domain ensures space adaptivity. The adaptive time-stepping accelerates the calculations further. In the framework of previous research studies, we used the approach to solve quantitative phase-field models for single dendrite growth in pure melts and dilute binary alloys. In the present study, we upgrade the solution procedure for the modelling growth of multiple differently oriented dendrites. Along with the space-time adaptive approach, we apply non-linear preconditioning of the phase-field equation to increase computational efficiency. We investigate a novel numerical approach's accuracy and computational efficiency by simulating the equiaxed dendrite growth from a dilute binary alloy.
Ključne besede: dendritic growth, phase-field method, meshless methods, polycrystalline solidification
Objavljeno v DiRROS: 21.03.2024; Ogledov: 108; Prenosov: 62
Celotno besedilo (2,77 MB)
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Povzetek: Background. Malignant pleural mesothelioma is a rare tumour with increasing frequency throughout the world. Due to long latency after exposure to asbestos, restrictions in the production and use of asbestos have not yet alleviated the burden of mesothelioma. During the last decade, several trials confirmed the benefit of systemic treatment with drugs such as doublets with cisplatina and gemcitabine or pemetrexed for carefully selected patients in good performance status. The purpose of this survey was to assess the impact of systemic treatment for the whole national population of patients with mesothelioma. Patients and methods. A retrospective study included all patients in Slovenia with histologically confirmed diagnosis of malignant pleural mesothelioma in the period from 1974 till 2008. Data from the Cancer Registry of Slovenia were supplemented by review of clinical records of the Institute of Oncology in Ljubljana where virtually all non-surgical treatment for mesothelioma was performed. We analysed the incidence, treatment, and survival of patients treated in the era of infrequent chemotherapy (1974-2003,the first period) and after it (2004-2008, the second period). Results. The survey included 444 patients, of whom 325 and 119 were diagnosed in the first and second period, respectively. Joinpoint regression analysis showed that after 1995 the trend in crude incidence rates increased more rapidly; the annual change was 0.03 per 100,000 per year before 1995 and 0.06 per 100,000 per year after. There was clear male predominance (70%) throughout the period covered by the survey. The proportion of patients above 65 years of age increased from 41.8% to 54.6% for the first and second period, respectively (p = 0.02). With a total of 52 (11.7%) operated patients, surgical treatment was rare and used only for selected patients with early disease and without comorbidity, leading to their relatively long median survival of 13.6 months. Chemotherapy was applied to 56 (17.2%) and to 96 (80.7%) patients during the first and second period, respectively. While a variety of older drugs were used in the first period, the most common regimen in the second period (applied to 91 patients) was doublet of low-dose gemcitabine in prolonged infusion and cisplatin. For the whole population of patients regardless the mode of treatment, median survival was 7.4 and 12.6 months (p-value = 0.037) for the first and second period, respectively. Conclusions. Increasing incidence, male predominance and increased proportion of older patients confirm that the burden of mesothelioma persists in spite o fa 15-years old ban in the production of asbestos. Modern chemotherapy, and in particular treatment with low-dose gemcitabine in prolonged infusion and cisplatin significantly prolonged median survival of patients with malignant pleural mesothelioma in Slovenia.
Objavljeno v DiRROS: 21.03.2024; Ogledov: 99; Prenosov: 33
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Povzetek: After the continuous hot-rolling process, steel bars are immediately placed on the cooling bed. At the beginning of the cooling, the material is at high temperatures, and the yield strength is low. Due to thermal load, yield strength can be exceeded, and permanent plastic strains start accumulating, resulting in possible unwanted shape changes and residual stresses. The present paper aims to develop a thermo-mechanical model for studying and eliminating undesirable phenomena before the products leave the cooling bed. The governing equations are solved for the two-dimensional slice in a strong form, and a modified version of the radial basis function generated finite difference (RBF-FD) method [1]. The initial bar geometry is obtained from the existing meshless hot-rolling simulation system [2]. The thermal and mechanical models are one-way coupled, i.e. the temperature solution represents a driving force for the stress and strain solution. The temperature field is obtained with explicit propagation in time. The convective and radiative heat fluxes on the boundary are updated at each time step using the ray tracing procedure to determine the radiative heat flux. The mechanical part is solved by considering the small strain elasto-plasticity, where the isotropic von Mises temperature-dependent hardening is employed. The global system of nonlinear equations of the mechanical part is solved by the Newton-Raphson method. The closest point projection method is used to solve the constitutive relations. A sensitivity study is performed on the influence of cooling intensity on a rectangular steel bar’s temperature, stress and strain field. We defined the most influential factors for defect formation. For the first time, a novel meshless RBF-FD method is successfully used for solving such a complex industrial problem. The model will be perspectively upgraded from the slice to the three-dimensional model to enable also bending.
Ključne besede: cooling bed, steel bars, thermo-mechanics, strong form, meshless method
Objavljeno v DiRROS: 21.03.2024; Ogledov: 90; Prenosov: 52
Celotno besedilo (1,62 MB)
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