Investigation of wear behavior of aged and non-aged SiC-reinforced AlSi7Mg2 metal matrix composites in dry sliding conditions

Metal matrix composites (MMCs) with their splendid mechanical properties have been specifically designed for use in fields such as aerospace and aviation. The presence of hard ceramic particles in MMC increases the hardness of the matrix product and decreases its coefficient of friction. Therefore, the wear resistance is improved. Moreover, the mechanical properties of these composite materials can be improved by applying heat treatments. In this study, AlSi7Mg2 MMCs with 15 wt% SiC reinforcement were produced by squeeze casting technique. Some of the composites were aged by heat treatment. Hardness values of aged and non- aged composites were compared. In addition, abrasive wear behaviors of these composites were investigated on pin-on-disk device, depending on the load (7, 12 and 17 N), the sliding speed (0.2, 0.3 and 0.4 m/s) and the sliding distance (700, 1000 and 1300 m). Worn surfaces were also analyzed by scanning electron microscopy (SEM). As a result of the analyses, it was determined that both the hardness values and the wear resistance were higher in the composites subjected to aging treatment. Furthermore, it was observed that the increase in the applied load led up to the weight loss. The increase in the sliding distance increased both friction coefficient and weight loss. The increase in sliding speed also made way for the friction coefficient but ensured less weight loss. When SEM images were examined, it was ascertained that deformation and tribo-surface formation had a significant effect on weight losses

First-line treatment of patients with HER2-positive metastatic gastric and gastroesophageal junction cancer

Fluoropyrimidine+cisplatin/oxaliplatin+trastuzumab therapy is recommended for the first-line treatment of HER2-positive metastatic gastric adenocarcinoma. However, there is no comprehensive study on which platinum-based treatment should be preferred. This study aimed to compare the treatment response and survival characteristics of patients with HER2-positive metastatic gastric or gastroesophageal junction (GEJ) cancer who received fluorouracil, oxaliplatin, and leucovorin (mFOLFOX)+trastuzumab or cisplatin and fluorouracil (CF)+trastuzumab as first-line therapy. It was a multicenter, retrospective study of the Turkish Oncology Group, which included 243 patients from 21 oncology centers. There were 113 patients in the mFOLFOX+trastuzumab arm and 130 patients in the CF+trastuzumab arm. The median age was 62 years in the mFOLFOX+trastuzumab arm and 61 years in the CF+trastuzumab arm (P = 0.495). 81.4% of patients in the mFOLFOX+trastuzumab arm and 83.1% in the CF+trastuzumab arm had gastric tumor localization (P = 0.735). The median progression-free survival (PFS) was significantly higher in the mFOLFOX+trastuzumab arm (9.4 months vs. 7.3 months, P = 0.024). The median overall survival (OS) was similar in both groups (18.4 months vs. 15.1 months, P = 0.640). Maintenance trastuzumab was continued after chemotherapy in 101 patients. In this subgroup, the median OS was 23.3 months and the median PFS was 13.3 months. In conclusion, mFOLFOX+trastuzumab is similar to CF+trastuzumab in terms of the median OS, but it is more effective in terms of the median PFS in the first-line treatment of HER2-positive metastatic gastric and GEJ cancer. The choice of treatment should be made by considering the prominent toxicity findings of the chemotherapy regimens

INVESTIGATION OF REINFORCEMENT RATE AFFECTING MECHANICAL PROPERTIES AND MACHINABILITY IN Al-SiCp MMCs

In this study, the effects of various rate of reinforcement materials (SiCp) addition to Al Si7 Mg2 metal matrix composite on mechanical properties and machinability were investigated. It was noticed that the mechanical properties increased with increasing added reinforcement materials rate in 5, 10 and 15 % SiCp reinforced metal matrix composite. The investigation of tool wear and surface roughness was carried out by using different cutting speeds (50, 100 and 150 m/min) and feed rate (0.1, 0.2 and 0.3 mm/rev) at constant depth of cut (1.5 mm) and reinforcement rates. It was observed that, tool wear and surface roughness increased when reinforcement material rate raised at using the same cutting speed and feed values. The tool life was a maximum when 15 % SiCp reinforced metal matrix composite was machined at 150 m/min of cutting speed. The highest surface roughness was also noticed at 15 % SiCp reinforced metal matrix composite machined at 50 m/min of cutting speed and 0.3 mm/rev of feed

Challenges Encountered in the Machining of Ti-6Al-4V from Titanium Alloys: Review

Titanium and its alloys are used as high engineering alloys in various industries such as aerospace, automotive, chemical-petrochemical and biomedical because they have excellent heat resistance, corrosion resistance, toughness, strength, high working temperature and low weight ratio. However, these alloys have low machinability. In the machining of titanium and its alloys, problems such as surface integrity and cutting tool wear are encountered. In this study, subjects such as cutting tools, wear mechanisms, cutting forces, surface roughness are examined in drilling, milling and turning of titanium and its alloys. In addition, the difficulties encountered in the machining of these alloys have been evaluated and the literature studies have been discussed as detail

Profile of patients with acute myocardial infarction in Turkey: Results from TURK MI registry

Background and Aim:&nbsp;There is no up-to-date study representing Turkish population that gives information about patient profile, treatment choice and prognosis in patients with acute myocardial infarction (AMI). In this study, we present characteristics of AMI patients from a recently conducted TURKMI registry&nbsp;Methods:&nbsp;TURKMI registry included consecutive patients with acute coronary syndromes who were hos- pitalized between 1-15 November 2018 in 50 hospitals representing the country’s population based on 12 Euronuts regions. Demographic characteristics, risk factors, history of cardiovascular diseases and comor- bidities were recorded in each patients.Results:&nbsp;TURKMI Registry included 1930 patients [504 female (26.1%), 1426 male (73.9%), median (IQR) age 62 (53-71)]. Of those, 1191 (61.7%) had NSTEMI, and 739 (38.3%) had STEMI. NSTEMI patients were older (median age 63 (54-72) vs. 60 (51-69); p&lt;0.001). Most of the patients were male (71.3% for NSTEMI and 78.1% for STEMI). Diabetes, hypertension and hyperlipidemia were higher in NSTEMI patients; however, smoking was higher in STEMI patients (Table 1). History of MI, coronary bypass, percutaneous coronary intervention, and heart fail- ure were significantly higher in NSTEMI patients (Table 2). Among the associated disease, chronic obstructive pulmonary disease and chronic kidney disease were significantly higher in NSTEMI patients (Table 3).&nbsp;Conclusions:&nbsp;Most common risk factors in AMI were hypertension and smoking, each of them were avail- able nearly half of the patients. The third and fourth most common risk factor was diabetes and hyperlip- idemia, respectively. Distribution of risk factors differ in STEMI and NSTEMI patients. History of MI and coronary interventions were more common in NSTEMI patients.</div

The relationship between pan-immune-inflammation value and survival outcomes in patients with metastatic renal cell carcinoma treated with nivolumab in the second line and beyond: a Turkish oncology group kidney cancer consortium (TKCC) study

Background Pan-immune-inflammation value (PIV) is an easily accessible immune marker based on peripheral blood to estimate prognosis in patients with cancer. This study evaluates the prognostic value of PIV in patients with metastatic renal cell carcinoma (mRCC) treated with nivolumab

Baseline clinical characteristics and patient profile of the TURKMI registry: Results of a nation-wide acute myocardial infarctionregistry in Turkey

Objective: The TURKMI registry is designed to provide insight into the characteristics, management from symptom onset to hospital discharge, and outcome of patients with acute myocardial infarction (MI) in Turkey. We report the baseline and clinical characteristics of the TURKMI population. Methods: The TURKMI study is a nation-wide registry that was conducted in 50 centers capable of percutaneous coronary intervention selected from each EuroStat NUTS region in Turkey according to population sampling weight, prioritized by the number of hospitals in each region. All consecutive patients with acute MI admitted to coronary care units within 48 hours of symptom onset were prospectively enrolled during a predefined 2-week period between November 1, 2018 and November 16, 2018. Results: A total of 1930 consecutive patients (mean age, 62.0 +/- 13.2 years; 26.1\% female) with a diagnosis of acute MI were prospectively enrolled. More than half of the patients were diagnosed with non-ST elevation MI (61.9\%), and 38.1\% were diagnosed with ST elevation MI. Coronary angiography was performed in 93.7\% and, percutaneous coronary intervention was performed in 73.2\% of the study population. Fibrinolytic therapy was administered to 13 patients (0.018\%). Aspirin was prescribed in 99.3\% of the patients, and 94\% were on dual antiplatelet therapy at the time of discharge. Beta blockers were prescribed in 85.0\%, anti-lipid drugs in 96.3\%, angiotensin converting enzyme inhibitors in 58.4\%, and angiotensin receptor blockers in 7.9\%. Comparison with European countries revealed that TURKMI patients experienced MI at younger ages compared with patients in France, Switzerland, and the United Kingdom. The most prevalent risk factors in the TURKMI population were hypercholesterolemia (60.2\%), hypertension (49.5\%), smoking (48.8\%), and diabetes (37.9\%). Conclusion: The nation-wide TURKMI registry revealed that hypercholesterolemia, hypertension, and smoking were the most prevalent risk factors. TURKMI patients were younger compared with patients in European Countries. The TURKMI registry also confirmed that current treatment guidelines are largely adopted into clinical cardiology practice in Turkey in terms of antiplatelet, anti-ischemic, and anti-lipid therapy

The prevalence of microalbuminuria and relevant cardiovascular risk factors in Turkish hypertensive patients.

Objectives: A growing body of data illustrates the importance of microalbuminuria (MAU) as a strong predictor of cardiovascular risk in the hypertensive population. The present study was designed to define the prevalence of MAU and associated cardiovascular risk factors among Turkish hypertensive outpatients. Study design: Representing the Turkish arm of the multinational i-SEARCH study involving 1,750 sites in 26 countries around the world, a total of 1,926 hypertensive patients from different centers were included in this observational and cross-sectional survey study. Patients with reasons for a false-positive MAU test were excluded. The prevalence of MAU was assessed using a dipstick test, and patients were inquired about comorbidities, comedication, and known cardiovascular risk factors. Results: The overall prevalence of MAU was 64.7% and there was no difference between genders. Most of the patients (82.5%) had uncontrolled hypertension, 35.6% had dyslipidemia, and 35.5% had diabetes, predominantly type 2. Almost one-third of the patients (26.4%) had at least one cardiovascular-related comorbidity, with 20.3% having documented coronary artery disease (CAD). Almost all patients (96.8%) had one or more risk factors for cardiovascular disease in addition to hypertension, including family history of myocardial infarction or CAD, diabetes, dyslipidemia, lack of physical exercise, and smoking. A trend towards higher MAU values in the presence of CAD was determined. Conclusion: Microalbuminuria tests should be routinely used as a screening and monitoring tool for the assessment of subsequent cardiovascular morbidity and mortality among hypertensive patients. © 2011 Turkish Society of Cardiology