3 VE 5 KROMLU ÇELİKLERDE TANTALYUM VE KROM İLAVESİNİN MİKROYAPIYA VE ÇENTİK DARBE DİRENCİNE ETKİSİ

3 VE 5 KROMLU ÇELİKLERDE TANTALYUM VE KROM İLAVESİNİN MİKROYAPIYA VE ÇENTİK DARBE DİRENCİNE ETKİSİÖzetKrom molibden (tungsten) [Cr-Mo (W)] çelikleri yüksek sıcaklık ve basınçlı buharın geçtiği petrokimya endüstrisindeki, enerji santrallerindeki vb. kullanılan borularda tercih edilmektedir. Bu şartlarda gerekli mukavemetin sağlanması çelikteki alaşım elementlerine bağlıdır. Alaşım elementlerinin kompozisyonlarının değişmesi çeliğin mikroyapısal ve mekanik özelliklerini değiştirmektedir. Bu çalışmada, daha önce üretimi yapılan Cr-Mo (Cr-W) çeliklerine alternatif olabilecek, ağırlıkça % 3, % 5 Cr ve % 3 W ana alaşım elementlerini içeren düşük Cr’lu çelikler döküm yolu ile üretilip sıcak olarak haddelenmiştir. Bu çalışmada farklı oranlarda Cr ve Ta içeren çeliklerin mikroyapıları ve çentik darbe dirençleri incelenmiştir. 3 Cr’lu alaşımlarda mikroyapıda ferrit ve beynit gözlemlenirken, 5 Cr’lu alaşımlarda mikroyapıda beynit ve martenzit gözlemlenmiştir. Ayrıca, Cr ve Ta ilaveleri alaşımların sünekliklerinde azalmaya sebep olmuştur.Anahtar Kelimeler: Cr-W Çelikleri, Çentik Darbe Direnci, Tantalyum, KromTHE EFFECT OF TANTALUM AND CHROMIUM ADDITION ON MICROSTRUCTURE AND NOTCH IMPACT STRENGTH IN 3 AND 5 CHROMIUM STEELSAbstractChromium molybdenum (tungsten) (Cr-Mo (W)) steels are widely used for the high pressure and temperature use in pipes in petrochemical industry and power plants. Providing the required strength under these conditions depends on the composition of the steel. The change in the ratio of alloying elements changes the microstructural and mechanical properties of steel. In this study, low chromium steels containing 3% and 5% Cr and 3% W as major alloying elements, which may be alternative to Cr-Mo (Cr-W) steels currently being produced, were produced by casting and hot rolled. In this study, microstructure and the notch toughness of steels which contain different amounts of Cr and Ta were investigated. The results showed that 3 Cr steels have a microstructure consist of bainite and ferrite, whereas 5 Cr steels have a microstructure consist of bainite and martensite. The addition of Cr and Ta cause a decrease in ductility of the alloys.Keywords: Cr-W Steels, Notch Toughness, Tantalum, Chromiu

Impression Cytology in Different Types of Contact Lens Users

This study compared tear function tests and cytologic changes on the conjunctival surface in asymptomatic patients wearing contact lens of different materials. Included in this study were 40 eyes wearing daily wear 4 week replacement hydrogel (H) lenses, 32 eyes wearing silicone hydrogel (SiH) lenses, 18 eyes wearing rigid gas-permeable (RGP) lenses, and 21 healthy eyes (no lenses) as the control group. Epithelial morphology of the conjunctival surface was evaluated, based on Nelson classification with conjunctival impression cytology (CIC), after the tear break-up time (TBUT) and Schirmer test were performed. The mean values of the Schirmer and TBUT tests were significantly higher in the control group than in the other lens groups (p < 0.001). Grade 0 was the most frequent CIC in the control group (66.7%) and least frequent in the SiH lens group (40.6%); grade I was least frequent in the control and RGP groups (33.3%) and most frequent in the SiH lens group (40.6%). Moreover, grade 2 was most frequent in the SiH lens group (18.8%). There was no statistically significant difference in goblet cell densities between the groups (p = 0.462). In addition to the different Schirmer and TBUT test results between contact lens wearers and healthy non-wearers, some cytologic changes may occur on the ocular surface with direct mechanical effects of contact lenses. This simple and noninvasive technique may be used to evaluate the ocular surface with regard to intolerance to contact lenses

Evaluation of Choroidal Thickness in Patients with Pseudoexfoliation Syndrome and Pseudoexfoliation Glaucoma

Purpose. To compare the macular and peripapillary choroidal thickness in eyes with pseudoexfoliation (PEX) syndrome and PEX glaucoma with the normal eyes of healthy controls. Materials and Methods. In this prospective study, 30 eyes of 30 patients with PEX syndrome, 28 eyes of 28 patients with PEX glaucoma, and 30 eyes of 30 age-matched healthy subjects were enrolled. Choroidal thicknesses in the macular and peripapillary areas were measured by using spectral domain optical coherence tomography. Results. Gender, age, and axial length did not significantly differ between the groups (all, p>0.05). The mean values of choroidal thickness in the macular and peripapillary areas (except the superior quadrant) in the patients with PEX syndrome and PEX glaucoma were lower compared with controls (all p<0.05). The mean values of the macular and peripapillary choroidal thickness in the PEX glaucoma group were lower compared with PEX syndrome group; however this difference was not significant. Conclusions. The findings of this study revealed that macular and peripapillary choroidal thicknesses were decreased in PEX syndrome and PEX glaucoma cases. The role of choroid in the development of glaucomatous damage in patients with PEX syndrome remains unclear

Survival of patients treated with extended-hours haemodialysis in Europe : an analysis of the ERA-EDTA Registry

Background. Previous US studies have indicated that haemodialysis with >= 6-h sessions [extended-hours haemodialysis (EHD)] may improve patient survival. However, patient characteristics and treatment practices vary between the USA and Europe. We therefore investigated the effect of EHD three times weekly on survival compared with conventional haemodialysis (CHD) among European patients. Methods. We included patients who were treated with haemodialysis between 2010 and 2017 from eight countries providing data to the European Renal Association-European Dialysis and Transplant Association Registry. Haemodialysis session duration and frequency were recorded once every year or at every change of haemodialysis prescription and were categorized into three groups: CHD (three times weekly, 3.5-4h/treatment), EHD (three times weekly, >= 6h/treatment) or other. In the primary analyses we attributed death to the treatment at the time of death and in secondary analyses to EHD if ever initiated. We compared mortality risk for EHD to CHD with causal inference from marginal structural models, using Cox proportional hazards models weighted for the inverse probability of treatment and censoring and adjusted for potential confounders. Results. From a total of 142 460 patients, 1338 patients were ever treated with EHD (three times, 7.10.8h/week) and 89 819 patients were treated exclusively with CHD (three times, 3.9 +/- 0.2h/week). Crude mortality rates were 6.0 and 13.5/100 person-years. In the primary analyses, patients treated with EHD had an adjusted hazard ratio (HR) of 0.73 [95% confidence interval (CI) 0.62-0.85] compared with patients treated with CHD. When we attributed all deaths to EHD after initiation, the HR for EHD was comparable to the primary analyses [HR 0.80 (95% CI 0.71-0.90)]. Conclusions. EHD is associated with better survival in European patients treated with haemodialysis three times weekly.Peer reviewe

The association of living donor source with patient and graft survival among kidney transplant recipients in the ERA-EDTA Registry - a retrospective study

In this study we aimed to compare patient and graft survival of kidney transplant recipients who received a kidney from a living-related donor (LRD) or living-unrelated donor (LUD). Adult patients in the ERA-EDTA Registry who received their first kidney transplant in 1998-2017 were included. Ten-year patient and graft survival were compared between LRD and LUD transplants using Cox regression analysis. In total, 14 370 patients received a kidney from a living donor. Of those, 9212 (64.1%) grafts were from a LRD, 5063 (35.2%) from a LUD and for 95 (0.7%), the donor type was unknown. Unadjusted five-year risks of death and graft failure (including death as event) were lower for LRD transplants than for LUD grafts: 4.2% (95% confidence interval [CI]: 3.7-4.6) and 10.8% (95% CI: 10.1-11.5) versus 6.5% (95% CI: 5.7-7.4) and 12.2% (95% CI: 11.2-13.3), respectively. However, after adjusting for potential confounders, associations disappeared with hazard ratios of 0.99 (95% CI: 0.87-1.13) for patient survival and 1.03 (95% CI: 0.94-1.14) for graft survival. Unadjusted risk of death-censored graft failure was similar, but after adjustment, it was higher for LUD transplants (1.19; 95% CI: 1.04-1.35). In conclusion, patient and graft survival of LRD and LUD kidney transplant recipients was similar, whereas death-censored graft failure was higher in LUD. These findings confirm the importance of both living kidney donor types.Peer reviewe

Recovery of kidney function in patients treated with maintenance dialysis-a report from the ERA-EDTA Registry

Background. Literature on recovery of kidney function (RKF) in patients with end-stage kidney disease treated with maintenance dialysis (i.e. >90days) is limited. We assessed the incidence of RKF and its associated characteristics in a European cohort of dialysis patients. Methods. We included adult patients from the European Renal Association-European Dialysis and Transplant Association Registry who started maintenance dialysis in 1997-2016. Sustained RKF was defined as permanent discontinuation of dialysis. Temporary discontinuation of >= 30days (non-sustained RKF) was also evaluated. Factors associated with RKF adjusted for potential confounders were studied using Cox regression analyses. Results. RKF occurred in 7657 (1.8%) of 440996 patients, of whom 71% experienced sustained RKF. Approximately 90% of all recoveries occurred within the first 2years after Day 91 of dialysis. Of patients with non-sustained RKF, 39% restarted kidney replacement therapy within 1year. Sustained RKF was strongly associated with the following underlying kidney diseases (as registered by the treating physician): tubular necrosis (irreversible) or cortical necrosis {adjusted hazard ratio [aHR] 20.4 [95% confidence interval (CI) 17.9-23.1]}, systemic sclerosis [aHR 18.5 (95% CI 13.8-24.7)] and haemolytic uremic syndrome [aHR 17.3 (95% CI 13.9-21.6)]. Weaker associations were found for haemodialysis as a first dialysis modality [aHR 1.5 (95% CI 1.4-1.6)] and dialysis initiation at an older age [aHR 1.8 (95% CI 1.6-2.0)] or in a more recent time period [aHR 2.4 (95% CI 2.1-2.7)]. Conclusions. Definitive discontinuation of maintenance dialysis is a rare and not necessarily an early event. Certain clinical characteristics, but mostly the type of underlying kidney disease, are associated with a higher likelihood of RKF.Peer reviewe

Trends in Mortality Due to Myocardial Infarction, Stroke, and Pulmonary Embolism in Patients Receiving Dialysis

IMPORTANCE During the past decades, improvements in the prevention and management of myocardial infarction, stroke, and pulmonary embolism have led to a decline in cardiovascular mortality in the general population. However, it is unknown whether patients receiving dialysis have also benefited from these improvements. OBJECTIVE To assess the mortality rates for myocardial infarction, stroke, and pulmonary embolism in a large cohort of European patients receiving dialysis compared with the general population. DESIGN, SETTING, AND PARTICIPANTS In this cohort study, adult patients who started dialysis between 1998 and 2015 from 11 European countries providing data to the European Renal Association Registry were and followed up for 3 years. Data were analyzed from September 2020 to February 2022. EXPOSURES Start of dialysis. MAIN OUTCOMES AND MEASURES The age- and sex-standardized mortality rate ratios (SMRs) with 95% CIs were calculated by dividing the mortality rates in patients receiving dialysis by the mortality rates in the general population for 3 equal periods (1998-2003, 2004-2009, and 2010-2015). RESULTS In total, 220 467 patients receiving dialysis were included in the study. Their median (IQR) age was 68.2 (56.5-76.4) years, and 82 068 patients (37.2%) were female. During follow-up, 83 912 patients died, of whom 7662 (9.1%) died because of myocardial infarction, 5030 (6.0%) died because of stroke, and 435 (0.5%) died because of pulmonary embolism. Between the periods 1998 to 2003 and 2010 to 2015, the SMR of myocardial infarction decreased from 8.1 (95% CI, 7.8-8.3) to 6.8 (95% CI, 6.5-7.1), the SMR of stroke decreased from 7.3 (95% CI, 7.0-7.6) to 5.8 (95% CI, 5.5-6.2), and the SMR of pulmonary embolism decreased from 8.7 (95% CI, 7.6-10.1) to 5.5 (95% CI, 4.5-6.6). CONCLUSIONS AND RELEVANCE In this cohort study of patients receiving dialysis, mortality rates for myocardial infarction, stroke, and pulmonary embolism decreased more over time than in the general population.Peer reviewe

Increasing numbers and improved overall survival of patients on kidney replacement therapy over the last decade in Europe : an ERA Registry study

Background The aim of this study was to describe the trends in the incidence, prevalence and survival of patients on kidney replacement therapy (KRT) for end-stage kidney disease (ESKD) across Europe from 2008 to 2017. Methods Data from renal registries in 9 countries and 16 regions that provided individual patient data to the ERA Registry from 2008 to 2017 were included. These registries cover 34% of the general population in Europe. Crude and standardized incidence and prevalence per million population (pmp) were determined. Trends over time were studied using Joinpoint regression. Survival probabilities were estimated using Kaplan-Meier analysis and hazard ratios (HRs) using Cox regression analysis. Results The standardized incidence of KRT was stable [annual percentage change (APC): -1.48 (-3.15; 0.21)] from 2008 (146.0 pmp) to 2011 (141.6 pmp), followed by a slight increase [APC: 1.01 (0.43; 1.60)] to 148.0 pmp in 2017, although trends in incidence varied across countries. This increase was primarily due to a rise in the incidence of KRT in men older than 65 years. Moreover, as a cause of kidney failure, diabetes mellitus is increasing. The standardized prevalence increased from 2008 (990.0 pmp) to 2017 (1166.8 pmp) [APC: 1.82 (1.75; 1.89)]. Patient survival on KRT improved in the time period 2011-13 compared with 2008-[adjusted HR: 0.94 (0.93; 0.95)]. Conclusion This study showed an overall increase in the incidence and prevalence of KRT for ESKD as well as an increase in the KRT patient survival over the last decade in Europe.Peer reviewe

Data from the ERA-EDTA Registry were examined for trends in excess mortality in European adults on kidney replacement therapy

The objective of this study was to investigate whether the improvement in survival seen in patients on kidney replacement therapy reflects the enhanced survival of the general population. Patient and general population statistics were obtained from the European Renal Association-European Dialysis and Transplant Association (ERA-EDTA) Registry and the World Health Organization databases, respectively. Relative survival models were composed to examine trends over time in all-cause and cause-specific excess mortality, stratified by age and modality of kidney replacement therapy, and adjusted for sex, primary kidney disease and country. In total, 280,075 adult patients started kidney replacement therapy between 2002 and 2015. The excess mortality risk in these patients decreased by 16% per five years (relative excess mortality risk (RER) 0.84; 95% confidence interval 0.83-0.84). This reflected a 14% risk reduction in dialysis patients (RER 0.86; 0.85-0.86), and a 16% increase in kidney transplant recipients (RER 1.16; 1.07-1.26). Patients on dialysis showed a decrease in excess mortality risk of 28% per five years for atheromatous cardiovascular disease as the cause of death (RER 0.72; 0.70-0.74), 10% for non-atheromatous cardiovascular disease (RER 0.90; 0.88-0.92) and 10% for infections (RER 0.90; 0.87-0.92). Kidney transplant recipients showed stable excess mortality risks for most causes of death, although it did worsen in some subgroups. Thus, the increase in survival in patients on kidney replacement therapy is not only due to enhanced survival in the general population, but also due to improved survival in the patient population, primarily in dialysis patients.Peer reviewe