Exposure to hyperbaric oxygen leads to increased amount of reactive oxygen species (ROS) that are derived from various sources. After the discovery that ROS can function as signaling molecules, the idea of ROS being hazardous to biological tissues has been challenged. The aim of this study was to examine the changes in oxidative stress parameters in diabetics undergoing hyperbaric oxygen therapy (HBOT) due to foot ulcers. Twenty patients, who received HBOT for diabetic foot ulcers, were included in the study. Blood samples were taken before HBOT and 30 min after exit from the chamber, on the day of the first and the 15th HBOT sessions. They were used for the determinations of malondialdehyde (MDA), 8-isoprostane and advanced oxidation protein products (AOPPs). 8-Isoprostane and AOPP levels were not altered significantly after the first HBOT session, while both were increased on the fifteenth day (p<0.05). MDA was significantly increased only after the first HBOT session, and remained unchanged on the fifteenth day (within-day variations). Plasma AOPP levels were lowered significantly after fifteen consecutive HBOT sessions (between-day variations). Decreased AOPP levels suggest that increased oxygenation of tissues due to HBO therapy may activate some endogenous factors that prevent hazardous effects of the disease itself.

No abstract

In this study, the use of Cu and Ni interlayers have been investigated for functional core-rim composite part production with WC-Co 9 wt-% feedstock/steel. For this purpose, different experiments have been performed and joining condition, shear strength and microstructure of the intermediate region have been examined. It has been found that AISI 4340 insert/WC-Co have been joined and 85.8 MPa shear strength achieved, but high speed steel insert has not joined. Moreover, it has been determined that better results are obtained with Ni interlayer. Under the same conditions, when the 40 µm Ni interlayer has been used between AISI 4340 core and WC-Co rim, shear strength has been increased approximately twice and has been 162.7 MPa.

No abstract

Toz enjeksiyon kalıplama yöntemiyle yüksek yoğunluklu metal, seramik, kompozit ve intermetal malzemelerden geometrik hassasiyete sahip küçük parçaların üretimi yapılabilmektedir. Daha büyük parçalar üretebilmek için insört adı verilen hazır parça kalıp içerisine yerleştirilerek üzerine toz enjeksiyon kalıplama yapılmaktadır. Bu yöntem insörtlü toz enjeksiyon kalıplama (İTEK) olarak adlandırılmaktadır. İTEK yöntemi, daha büyük parçaların üretiminde kullanılmasının yanında farklı malzemelerden parça üretimi için de kullanılabilecek bir yöntemdir. Bu çalışmada nikel ara katman kullanılarak İTEK yöntemiyle WC-Co/HSS kompozit parça üretimi araştırılmıştır. Sinterleme sıcaklığının ve süresinin etkileri, besleme stokunda meydana gelen boyutsal çekme ve ara bölgedeki kesme dayanımı incelenmiştir. Sıcaklık ve süre arttıkça enjekte kısmın boyutsal çekme miktarı artmaktadır. En yüksek boyutsal çekme oranı, 1250 °C ve 360 dakikada sinterlenen numunelerde %15,92 olarak ölçülmüştür. Deneylerde en yüksek kesme mukavemeti 1200 °C sıcaklık ve 120 dakika sinterleme süresiyle, 100 µm Ni ara katman kullanılan numunede 114 MPa olarak elde edilmiştir.