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Abstract: This research was focused on the effect of Ti and S content on the formation of non-metallic inclusions and their influence on the mechanical properties and machinability of low-carbon ferritic– pearlitic steels. An analysis and classification of the non-metallic inclusions were carried out. The tensile strength and impact toughness were determined from samples taken in the rolling direction. Machinability investigations were carried out on a CNC turning machine and by analyzing the surface roughness. TiO-TiN inclusions are present in steels with an increased Ti content. In these steels, the hardness, tensile strength, and cutting forces increase with a higher proportion of Ti. In the second group of steels with increased contents of S, Al, and Ca, MnS and CaO-Al2O3-MnS non-metallic inclusions are formed. As the S content increases, the tensile strength and cutting forces decrease, while the impact toughness increases. In steels with added Ti, the This research was focused on the effect of Ti and S content on the formation of non-metallic inclusions and their influence on the mechanical properties and machinability of low-carbon ferritic– pearlitic steels. An analysis and classification of the non-metallic inclusions were carried out. The tensile strength and impact toughness were determined from samples taken in the rolling direction. Machinability investigations were carried out on a CNC turning machine and by analyzing the surface roughness. TiO-TiN inclusions are present in steels with an increased Ti content. In these steels, the hardness, tensile strength, and cutting forces increase with a higher proportion of Ti. In the second group of steels with increased contents of S, Al, and Ca, MnS and CaO-Al2O3-MnS non-metallic inclusions are formed. As the S content increases, the tensile strength and cutting forces decrease, while the impact toughness increases. In steels with added Ti, the machining is more difficult, but a finer surface is achieved after turning, while a higher S content results in an increased fraction of softer sulfide inclusions, which reduce the cutting forces but also result in a reduced surface quality. turning, while a higher S content results in an increased fraction of softer sulfide inclusions, which reduce the cutting forces but also result in a reduced surface quality.
Keywords: non-metallic inclusions, mechanical properties, machinability, surface roughness
Published in DiRROS: 03.09.2024; Views: 124; Downloads: 366
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Abstract: This paper brings several contributions to the classical Forster-Bell-Narasimhan conjecture and the Yang problem concerning the existence of proper and almost proper (hence complete) injective holomorphic immersions of open Riemann surfaces in the affine plane ${\mathbb C}^2$ satisfying interpolation and hitting conditions. We also show that in every compact Riemann surface there is a Cantor set whose complement admits a proper holomorphic embedding in ${\mathbb C}^2$. The focal point is a lemma saying the following. Given a compact bordered Riemann surface, $M$, a closed discrete subset $E$ of its interior ${\mathring M}=M\setminus bM$, a compact subset $K\subset {\mathring M}\setminus E$ without holes in $\mathring M$, and a ${\cal C}^1$ embedding $f: M\hookrightarrow \mathbb C^2$ which is holomorphic in $\mathring M$, we can approximate $f$ uniformly on $K$ by a holomorphic embedding $F: bM\hookrightarrow {\mathbb C}^2$ which maps $E\cup bM$ out of a given ball and satisfies some interpolation conditions.
Keywords: Riemann surfaces, complex curves, complete holomorphic embedding
Published in DiRROS: 15.07.2024; Views: 220; Downloads: 126
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Keywords: radiochemotherapy, definitive radiochemotherapy, esophageal cancer
Published in DiRROS: 05.07.2024; Views: 268; Downloads: 61
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Abstract: The purpose of the study was to improve treatment efficacy for locally advanced rectal cancer (LARC) by shifting half of adjuvant chemotherapy preoperatively to one induction and two consolidation cycles. Patients and methods Between October 2011 and April 2013, 66 patients with LARC were treated with one induction chemotherapy cycle followed by chemoradiotherapy (CRT), two consolidation cycles, surgery and three adjuvant capecitabine cycles. Radiation doses were 50.4 Gy for T2-3 and 54 Gy for T4 tumours in 1.8 Gy daily fraction. The doses of concomitant and neo/adjuvant capecitabine were 825 mg/m2/12h and 1250mg/m2/12h, respectively. The primary endpoint was pathologic complete response (pCR). Results Forty-three (65.1%) patients were treated according to protocol. The compliance rates for induction, consolidation, and adjuvant chemotherapy were 98.5%, 93.8% and 87.3%, respectively. CRT was completed by 65/66 patients, with G % 3 non-hematologic toxicity at 13.6%. The rate of pCR (17.5%) was not increased, but N and the total-down staging rates were 77.7% and 79.3%, respectively. In a median follow-up of 55 months, we recorded one local relapse (LR) (1.6%). The 5-year disease-free survival (DFS) and overall survival (OS) rates were 64.0% (95% CI 63.89%64.11) and 69.5% (95% CI 69.39%69.61), respectively. Conclusions In LARC preoperative treatment intensification with capecitabine before and after radiotherapy is well tolerated, with a high compliance rate and acceptable toxicity. Though it does not improve the local effect, it achieves a high LR rate, DFS, and OS.
Keywords: rectal cancer, neoadjuvant chemotherapy, preoperative chemoradiotherapy
Published in DiRROS: 11.06.2024; Views: 244; Downloads: 123
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Abstract: Radiochemotherapy is the main treatment for patients with squamous cell carcinoma of the anal canal. Anaemia is reported to have adverse effect on survival in cancer patients. The aim of the study was to evaluate the influence of anaemia on radiochemotherapy treatment outcome in patients with squamous cell carcinoma of the anal canal. Patients and methods. One hundred consecutive patients with histologically confirmed squamous cell carcinoma of the anal canal were treated radically with 3-dimensional conformal or intensity-modulated radiation therapy followed by brachytherapy or external beam radiotherapy boost and with concurrent mitomycin C and 5-fluorouracil. The influence on survival of pre-treatment, mean on-treatment and end-of-treatment haemoglobin (Hb) concentrations was studied. Results. The 5-year locoregional control, disease free survival, disease specific survival and overall survival rates for all patients were 72%, 71%, 77% and 62%, respectively. In univariate analysis, patients with pre-treatment and end-oftreatment Hb > 120 g/L survived statistically significantly better compared to patients with Hb % 120 g/L. Patients with mean on-treatment Hb > 120 g/L only had statistically significant better locoregional control and overall survival than patients with Hb % 120 g/L. In multivariate analysis, independent prognostic factors were pre-treatment Hb (> 120 g/L vs. % 120 g/L) for overall survival (hazard ratio [HR] = 0.419, 95% confidence interval [CI] = 0.190%0.927, p = 0.032) and stage (I & II vs. III) for disease specific (HR = 3.523, 95% CI = 1.375%9.026, p = 0.009) and overall survival (HR = 2.230, 95% CI = 1.167%4.264, p = 0.015). Conclusions. The pre-treatment, mean on-treatment and end-of-treatment Hb concentration > 120 g/L carried better prognosis for patients for with squamous cell carcinoma of the anal canal treated with radiochemotherapy. The pre-treatment Hb > 120 g/L was an independent prognostic factor for overall survival of patients with anal canal cancer.
Keywords: anaemia, anal canal squamous cell carcinoma, radiochemotherapy
Published in DiRROS: 30.04.2024; Views: 384; Downloads: 214
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