Östenitik paslanmaz çeliklerin gazaltı kaynak yöntemi ile kaynağında koruyucu gazın mekanik özelliklere etkisi

06.03.2018 tarihli ve 30352 sayılı Resmi Gazetede yayımlanan “Yükseköğretim Kanunu İle Bazı Kanun Ve Kanun Hükmünde Kararnamelerde Değişiklik Yapılması Hakkında Kanun” ile 18.06.2018 tarihli “Lisansüstü Tezlerin Elektronik Ortamda Toplanması, Düzenlenmesi ve Erişime Açılmasına İlişkin Yönerge” gereğince tam metin erişime açılmıştır.Bu çalışmada, paslanmaz çeliklerin tungsten inert gas (TIG) kaynak yöntemi ilebirleştirilmesi esnasında kullanılan koruyucu gaz kompozisyonlarının mekanik vemikroyapı özelliklerine etkisinin araştırılmıştır. Çalışmada, AISI 304, AISI 316 ve AISI316Ti tip östenitik paslanmaz çelik malzemeler TIG kaynak yöntemi ile küt alın kaynakdizaynında ve yatay pozisyonda her bir çeliğe uygun ilave metaller kullanılarakbirleştirilmiştir. Birleştirme esnasında koruyucu gaz olarak saf argon, argon+%25 helyum,argon+%5H2 ve Argon+%5N2 kullanılmıştır. Birleştirilen parçaların çekme, eğme, sertlikve bir kısmına çentik darbe gibi mekanik deneyler uygulanmıştır. Bu çalışmalara paraleloptik mikroskopta aydınlık alan ve karanlık alan, tarama elektron mikroskobu (SEM) dahem mikroyapı ve kırılma yüzey morfolojileri hem de noktasal ve çizgisel enerji dağılımıspektrometre (EDS) element analizleri yürütülmüştür. Yapılan deneysel çalışmalardan eldeedilen sonuçlara göre, birleştirme esnasında kullanılan koruyucu gaz kompozisyonununbirleştirilen östenitik paslanmaz çeliklerin hem mikroyapı hem de çekme dayanımı, çentikdarbe tokluğu gibi mekanik özellikleri etkilediğini göstermiştir.The aim of this study was that the effect on shielding gas compositions on the mechanicaland microstructural properties of austenitic stainless steel weldments were investigated. Inthis study, AISI 304, AISI 316 and AISI 316Ti types of austenitic stainless steels will bewelded by gas tungsten arc welding (GTAW) on but joined and flat position using suitablefiller materials for each stainless steel. Pure argon, argon+%25He, argon+%5H2 andargon+%5N2 were used as shielding gases. Various characterization techniques such as,tensile testing, bending testing and hardness measurements have been carried out andcharpy v impact test for some of them at various temperatures were determined. Parallelmicrostructural studies were carried out on welded work pieces. Basic microstructuralinvestigations were performed using optical microscopy with the techniques of light areaand dark areas. Both detailed microstructural studies and fracture surface morphologieswere also carried out using scanning electron microscope (SEM) with the techniques ofpoint and linear elemental energy dispersive spectroscopy (EDS) analysis. The resultsobtained in the experimental work show that shielding gas compositions have an effect onboth microstructures and mechanical properties such as tensile strength, charpy impacttoughness values of the weldments.

A histological and biochemical study of cumulus cells and the oocyte microenviroment in in vitro fertilization patients

*Akaras, Nurhan ( Aksaray, Yazar )Objectives: The aim of this study was to investigate the effect of chemical changes in the follicular fluid and histological changes in the cumulus cells of the oocyte microenvironment on the number of oocytes in infertile patients. Methods: A total of 50 female patients aged 18-35 who presented at the Atatürk University Research Hospital Infertility Clinic and for infertility treatment were included. The patients were divided into 3 groups: Patients with fewer than 5 oocytes were classified as Group 1, patients with 5-20 oocytes comprised Group 2, and Group 3 was made up of patients with >20 oocytes. During the oocyte collection process, follicular fluid was aspirated from the follicles and the cumulus cells were collected. The follicular fluid was stored at -80°C for use in biochemical analysis of malondialdehyde (MDA), total antioxidant status (TAS), total oxidant status (TOS), superoxide dismutase (SOD), glutathione (GSH). Immunohistochemical staining was performed to examine caspase-3 and mechanistic target of rapamycin (mTOR) immunoreactivity at the stereological level. Results: The MDA level and total oxidant capacity (TOC) in the follicular fluid were higher in Group 1 patients than in the other 2 groups, while the SOD was lower (p<0.05). In Group 2 patients, the MDA level and TOS were higher than those of Group 3, while the SOD level was lower (p<0.05). The total antioxidant capacity (TAC) and GSH levels did not vary significantly according to the number of oocytes (p<0.05). Immunohistochemical staining showed that mTOR and caspase-3 immunoreactivity were more intense in Group 1 than in the other groups. Conclusion: The increase in mTOR expression may activate the caspase-3 pathway, which could lead to oxidative stress. The mTOR pathway may affect the oocyte coun

(1 → 3)-β-d-glucan enhances the toxicity induced by Bortezomib in rat testis

Akaras, Nurhan ( Aksaray, Yazar )We aimed to determine the possible effects of the antioxidant agent (1 → 3)-β-D-glucan on bortezomib-induced rat testis damage. We used five groups of rats; control, (1 → 3)-β-D-glucan (75 mg/kg), bortezomib group, bortezomib + (1 → 3)-β-D-glucan groups (injection of (1 → 3)-β-D-glucan after bortezomib and sacrificed at 48th or 72nd h). The effects of these substances were assessed by measuring the levels of the antioxidant enzymes and LPO, and by performing immunohistochemical analysis with NF-κB. The histology of testis was evaluated using aniline blue staining. (1 → 3)-β-D-glucan leads to significant reductions in the levels of antioxidant enzymes and increased levels of LPO in testes. Moreover, it increased the NF-κB immunopositivity significantly in testis, especially in Bortezomib + (1 → 3)-β-D-glucan group at 48th h. The histological changes were observed in the bortezomib and/or (1 → 3)-β-D-glucan groups. Our results demonstrated that testis damage caused by the treatment with bortezomib was not eliminated by (1 → 3)-β-D-glucan and shockingly it increased the damage. Practical applications: The testis damage caused by the treatment with bortezomib was not eliminated by (1 → 3)-β-D-glucan and as a result, β-1,3-(D)-glucan enhanced the toxicity by leading a decrease in the levels of GSH, SOD, and CAT, thus caused an elevation in the immunoreactivity of NF-κB and altered the histopathological changes by enhancing the toxic effects of bortezomib. The findings of the previous studies about the antioxidative activity of (1 → 3)-β-D-glucan are controversial. So, it is necessary to consider the cytotoxicity of (1 → 3)-β-D-glucan in testis tissue. Thus, more studies on testis tissue are necessary to confirm that (1 → 3)-β-D-glucan is safe as an antioxidant